WO2012005176A1 - Raw-material mixture and alkali-metal/transition-metal complex oxide - Google Patents

Abstract

The disclosed raw-material mixture for an alkali-metal/transition-metal complex oxide contains a flux containing an inorganic salt, an alkali-metal salt containing a compound different from the flux, and a transition-metal compound, and satisfies the following condition: the temperature (Tmp) at which the raw-material mixture starts to melt is higher than the lower limit (Teq) of temperatures at which the alkali-metal/transition-metal complex oxide is produced with higher priority than an oxide consisting only of oxygen and the transition-metal element in the transition metal compound when the mixture is fired.

Description

Raw material mixture and alkali metal-transition metal composite oxide

The present invention relates to a raw material mixture for producing an alkali metal-transition metal composite oxide. Alkali metal-transition metal composite oxides are particularly used as electrode active materials in nonaqueous electrolyte secondary batteries.

Alkali metal-transition metal composite oxides are used as electrode active materials in nonaqueous electrolyte secondary batteries such as lithium secondary batteries. Lithium secondary batteries have already been put into practical use as small power sources for cellular phones and notebook computers. Furthermore, the application of lithium secondary batteries has also been attempted in large power sources such as automobile applications and power storage applications.
Conventionally, an alkali metal-transition metal composite oxide is produced by firing a raw material mixture obtained by mixing an alkali metal raw material and a transition metal compound. As a method for producing a more crystalline alkali metal-transition metal composite oxide, lithium hydroxide monohydrate or lithium carbonate as an alkali metal raw material and nickel-manganese-iron coprecipitate as a transition metal compound ( A method of firing a raw material mixture obtained by mixing transition metal composite hydroxide) and potassium chloride as a flux has been proposed (see, for example, Patent Document 1).
However, in the above method, when lithium hydroxide monohydrate is used as the alkali metal raw material, the portion in contact with air in the lithium hydroxide monohydrate reacts with carbon dioxide or moisture in the air, thereby This decreases the reactivity. This causes a problem that the reactivity of lithium hydroxide monohydrate partially varies, and industrial handling is not easy.
On the other hand, in the above method, when lithium carbonate is used as the alkali metal raw material, the lithium carbonate is stable in the air and thus industrial handling is easy. However, the discharge capacity of the obtained lithium secondary battery is lithium hydroxide. Compared to the case of using a monohydrate, it is not sufficient (see, for example, Patent Document 1).

JP 2010-21134 A

In the production of alkali metal-transition metal composite oxides, the present inventor has a lithium secondary battery discharge capacity obtained when using lithium carbonate, which is an alkali metal salt that is easy to handle industrially as an alkali metal raw material. The cause which was not enough compared with the case where lithium hydroxide monohydrate was used was investigated. As a result, a raw material mixture obtained by mixing lithium carbonate as an alkali metal raw material, nickel-manganese-iron coprecipitate (transition metal composite hydroxide) as a transition metal compound, and potassium chloride as a flux is fired. It was found that the alkali metal-transition metal composite oxide obtained by this contains an oxide composed only of a transition metal element and an oxygen element constituting the transition metal compound. Since this oxide is inactive as a positive electrode active material, it is an undesirable impurity to be contained in the alkali metal-transition metal composite oxide.
An object of the present invention is a raw material mixture for an alkali metal-transition metal composite oxide containing a flux containing an inorganic salt, an alkali metal salt, and a transition metal compound, and exhibits a high discharge capacity. It is providing the raw material mixture for manufacturing the electrode active material which gives a battery.
Means for Solving the Problems The present invention provides the following.
<1> A raw material mixture for an alkali metal-transition metal composite oxide comprising a flux containing an inorganic salt, an alkali metal salt containing a compound different from the flux, and a transition metal compound, and satisfying the following:
Compared to the lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced over the oxide composed only of the transition metal element and oxygen of the transition metal compound during firing of the mixture, the raw material mixture The temperature (Tmp) at the start of melting is high.
<2> The inorganic salt is borate, carbonate, nitrate, phosphate, sulfate, vanadate, tungstate, molybdate, niobate, and halide (where halide is <1> raw material mixture which is at least one salt selected from the group consisting of fluoride, chloride, bromide and iodide.
<3> The raw material of <1> or <2>, wherein the cation constituting the inorganic salt is one or more salts selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba blend.
<4> The alkali metal salt is carbonate, sulfate, nitrate, phosphate, and halide (wherein the halide is selected from the group consisting of fluoride, chloride, bromide, and iodide) The raw material mixture according to any one of <1> to <3>, which is one or more salts selected from the group consisting of:
<5> The raw material mixture according to any one of <1> to <4>, wherein the alkali metal element constituting the alkali metal salt is one or more elements selected from the group consisting of Li, Na and K.
<6> The raw material mixture according to any one of <1> to <5>, wherein the transition metal element constituting the transition metal compound is one or more elements selected from the group consisting of Mn, Fe, Co, and Ni.
<7> The raw material mixture according to any one of <1> to <5>, wherein the transition metal element constituting the transition metal compound is Fe and one or more elements selected from the group consisting of Mn, Co, and Ni .
<8> A method for producing an alkali metal-transition metal composite oxide, wherein the raw material mixture according to any one of <1> to <7> is fired at a temperature higher than a temperature (Tmp) at the start of melting of the raw material mixture.
<9> Alkali metal-transition metal composite oxide produced by the method of <8>.
<10> The alkali metal-transition metal composite oxide according to <9>, wherein the crystal structure is a layered structure.
<11> A positive electrode active material having the alkali metal-transition metal composite oxide of <9> or <10>.
<12> A positive electrode having the positive electrode active material of <11>.
<13> A nonaqueous electrolyte secondary battery having the positive electrode of <12>.
<14> The nonaqueous electrolyte secondary battery according to <13>, further comprising a separator.
<15> The nonaqueous electrolyte secondary battery according to <14>, wherein the separator is a laminated film in which a heat-resistant porous layer and a porous film are laminated to each other.

FIG. 1 shows the temperature dependence of the standard free energy change ΔrG _T ° relating to the equilibrium between an alkali metal-transition metal composite oxide in an alkali metal salt containing lithium and an oxide composed only of a transition metal element and an oxygen element.
FIG. 2 shows the temperature dependence of the standard free energy change ΔrG _T ° relating to the equilibrium between an alkali metal-transition metal composite oxide in an alkali metal salt containing sodium and an oxide composed only of a transition metal element and an oxygen element.

　各化合物の標準生成エンタルピーΔｆＨ_２５℃°から、平衡（１−１）の標準エンタルピー変化ΔｒＨ_２５℃°は式（１）のように計算される。
ΔｒＨ_２５℃°＝２ΔｆＨ_２５℃°（ＬｉＦｅＯ_２）＋ΔｆＨ_２５℃°（ＣＯ_２）
−ΔｆＨ_２５℃°（Ｆｅ_２Ｏ_３）−ΔｆＨ_２５℃°（Ｌｉ_２ＣＯ_３）
＝２×（−７５０）−（−３９４）−（−８２４）−（−１２１６）
＝１４６［ｋＪ／ｍｏｌ］　　　　　　　　　　　　　　　　　　・・・式（１）
　各化合物の標準エントロピーＳ_２５℃°から、平衡（１−１）の標準エントロピー変化Ｓ_２５℃°は式（２）のように計算される。
ΔｒＳ_２５℃°＝２Ｓ_２５℃°（ＬｉＦｅＯ_２）＋Ｓ_２５℃°（ＣＯ_２）
−Ｓ_２５℃°（Ｆｅ_２Ｏ_３）−Ｓ_２５℃°（Ｌｉ_２ＣＯ_３）
＝２×７５＋２１４−８７−９０
＝１８７［Ｊ／℃・ｍｏｌ］　　　　　　　　　　　　　　　　　・・・式（２）
　平衡（１−１）の標準エンタルピー変化ΔｒＨ_２５℃°と標準エントロピー変化ΔｒＳ_２５℃°から、平衡（１−１）の標準自由エネルギー変化ΔｒＧ_Ｔ°を求める。
ΔｒＧ_Ｔ°、ΔｒＨ_２５℃°およびΔｒＳ_２５℃°の間には式（３）の関係がある。
ΔｒＧ_Ｔ°＝ΔｒＨ_２５℃°−（Ｔ＋２７３）×ΔｒＳ_２５℃°／１０００
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　・・・式（３）
　ここで、ΔｒＧ_Ｔ°［ｋＪ／ｍｏｌ］は、Ｔ［℃］における平衡の標準自由エネルギーの変化であり、ΔｒＨ_２５℃°［ｋＪ／ｍｏｌ］は、２５［℃］における平衡の標準エンタルピーの変化であり、ΔｒＳ_２５℃°［Ｊ／℃・ｍｏｌ］は、２５［℃］における平衡の標準エントロピーの変化である。
　ΔｒＧ_Ｔ°＝０となる温度Ｔｅｑは、式（４）で与えられる。
Ｔｅｑ＝（１０００×ΔｒＨ_２５℃°／ΔｒＳ_２５℃°）−２７３・・・式（４）
　式（４）を平衡（１−１）に適用すると式（５）のように計算される。
Ｔｅｑ＝（１０００×ΔｒＨ_２５℃°／ΔｒＳ_２５℃°）−２７３
＝（１０００×１４６／１８７）−２７３
＝５０８［℃］　　　　　　　　　　　　　　　　　　　　　　　・・・式（５）
　上記の計算より、アルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりも優先して生成する温度の下限Ｔｅｑは５０８［℃］である。
　アルカリ金属塩について、遷移金属元素および酸素元素のみからなる酸化物よりもアルカリ金属−遷移金属複合酸化物が優先して生成する温度の下限について、上記の例に従って計算する。アルカリ金属塩としてＬｉ_２ＣＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてのＦｅ_２Ｏ_３と、アルカリ金属−遷移金属複合酸化物としてのＬｉＦｅＯ_２との平衡は、平衡（１−１）で表される。平衡（１−１）の上記の例で計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図１に示す。
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＬｉ_２ＣＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは５０８［℃］である。
　アルカリ金属塩としてＬｉＮＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（１−２）で表される。平衡（１−２）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図１に示す。
Ｆｅ_２Ｏ_３＋２ＬｉＮＯ_３＝２ＬｉＦｅＯ_２＋Ｎ_２Ｏ_５　　・・・平衡（１−２）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＬｉＮＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは９８９［℃］である。
　アルカリ金属塩としてＬｉ_２ＳＯ_４を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（１−３）で表される。平衡（１−３）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図１に示す。
Ｆｅ_２Ｏ_３＋Ｌｉ_２ＳＯ_４＝２ＬｉＦｅＯ_２＋ＳＯ_３　　　・・・平衡（１−３）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＬｉ_２ＳＯ_４を使用する場合には、遷移金属元素および酸素元素のみでからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは１５０７［℃］である。
　アルカリ金属塩であるハロゲン化物の例としてＬｉＣｌを使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（１−５）で表される。平衡（１−５）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図１に示す。
Ｆｅ_２Ｏ_３＋２ＬｉＣｌ＋Ｈ_２Ｏ＝２ＬｉＦｅＯ_２＋２ＨＣｌ
　　　　　　　　　　　　　　　　　　　　　　　　　　　・・・平衡（１−５）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＬｉＣｌを使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは１２５８［℃］である。
　アルカリ金属塩としてＮａ_２ＣＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（２−１）で表される。平衡（２−１）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図２に示す。
Ｆｅ_２Ｏ_３＋Ｎａ_２ＣＯ_３＝２ＮａＦｅＯ_２＋ＣＯ_２　　　・・・平衡（２−１）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＮａ_２ＣＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは７０９［℃］である。
　アルカリ金属塩としてＮａＮＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（２−２）で表される。平衡（２−２）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図２に示す。
Ｆｅ_２Ｏ_３＋２ＮａＮＯ_３＝２ＮａＦｅＯ_２＋Ｎ_２Ｏ_５　　・・・平衡（２−２）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＮａＮＯ_３を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは１４９７［℃］である。
　アルカリ金属塩としてＮａ_２ＳＯ_４を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（２−３）で表される。平衡（２−３）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図２に示す。
Ｆｅ_２Ｏ_３＋Ｎａ_２ＳＯ_４＝２ＮａＦｅＯ_２＋ＳＯ_３　　　・・・平衡（２−３）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＮａ_２ＳＯ_４を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは１９７９［℃］である。
　アルカリ金属塩としてＮａ_３ＰＯ_４を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（２−４）で表される。平衡（２−４）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図２に示す。
１／２Ｆｅ_２Ｏ_３＋１／３Ｎａ_３ＰＯ_４＝ＮａＦｅＯ_２＋１／６Ｐ_２Ｏ_５
　　　　　　　　　　　　　　　　　　　　　　　　　　　・・・平衡（２−４）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＮａ_３ＰＯ_４を使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは３１９６［℃］である。
　アルカリ金属塩であるハロゲン化物の例としてＮａＣｌを使用する場合には、遷移金属元素および酸素元素のみからなる酸化物としてＦｅ_２Ｏ_３とアルカリ金属−遷移金属複合酸化物としてＬｉＦｅＯ_２との平衡は、平衡（２−５）で表される。平衡（２−５）の上記の例に従って計算した標準自由エネルギー変化ΔｒＧ_Ｔ°の温度依存性を図２に示す。
Ｆｅ_２Ｏ_３＋２ＮａＣｌ＋Ｈ_２Ｏ＝２ＮａＦｅＯ_２＋２ＨＣｌ
　　　　　　　　　　　　　　　　　　　　　　　　　　　・・・平衡（２−５）
　ΔｒＧ_Ｔ°＝０となる温度ＴよりＴｅｑを求めることができ、アルカリ金属塩としてＬｉＣｌを使用する場合には、遷移金属元素および酸素元素のみからなる酸化物であるＦｅ_２Ｏ_３よりもアルカリ金属−遷移金属複合酸化物であるＬｉＦｅＯ_２が優先して生成する温度の下限Ｔｅｑは２０９５［℃］である。
＜アルカリ金属−遷移金属複合酸化物用原料混合物の溶融開始時の温度（Ｔｍｐ）＞
　アルカリ金属−遷移金属複合酸化物用原料混合物の溶融開始時の温度（Ｔｍｐ）は、原料混合物の一部が液相になる最も低い温度を示す。アルカリ金属−遷移金属複合酸化物用原料混合物の溶融開始時の温度（Ｔｍｐ）は、示差熱熱重量同時測定装置（ＴＧ／ＤＴＡ）装置や示差走査熱量測定（ＤＳＣ）装置などの熱分析装置を用いた測定により得られる。原料混合物の溶融開始時の温度では、示差熱熱重量同時測定装置（ＴＧ／ＤＴＡ）や示差走査熱量測定（ＤＳＣ）により測定される熱量変化が吸熱のピークを示す。
＜アルカリ金属−遷移金属複合酸化物の製造方法＞
　本発明において、アルカリ金属−遷移金属複合酸化物は、前記原料混合物を焼成することで製造されることが好ましい。
　前記焼成における保持温度は、アルカリ金属−遷移金属複合酸化物用原料混合物の溶融開始時の温度（Ｔｍｐ）よりも高いことが好ましい。
　前記焼成における保持温度は、得られるアルカリ金属−遷移金属複合酸化物の比表面積を調整するために重要な因子である。通常、保持温度が高いほど、比表面積は小さくなる傾向にある。保持温度が低いほど、比表面積は大きくなる傾向にある。保持温度で保持する時間は、通常０．１~２０時間であり、好ましくは０．５~８時間である。保持温度までの昇温速度は、通常５０~４００℃／時間であり、保持温度から室温までの降温速度は、通常１０~４００℃／時間である。また融剤は、アルカリ金属−遷移金属複合酸化物に残留していてもよいし、洗浄、分解、蒸発などにより除去されていてもよい。
　また、焼成後において、得られるアルカリ金属−遷移金属複合酸化物を、ボールミルやジェットミルなどを用いて粉砕してもよい。粉砕によって、アルカリ金属−遷移金属複合酸化物の比表面積を調整することが可能な場合がある。また、焼成と粉砕とを２回以上繰り返してもよい。また、アルカリ金属−遷移金属複合酸化物は必要に応じて洗浄または分級できる。
　本発明の原料混合物を用いて得られるアルカリ金属−遷移金属複合酸化物は、高い出力特性を要する非水電解質二次電池の正極活物質として有用となる。
　本発明の原料混合物を用いて得られるアルカリ金属−遷移金属複合酸化物は、通常０．０５~１μｍの粒径の一次粒子からなる。一次粒子の粒径は、アルカリ金属−遷移金属複合酸化物の電子顕微鏡写真から測定できる。
　本発明の原料混合物を用いて得られるアルカリ金属−遷移金属複合酸化物の結晶構造は、層状構造であることが好ましい。さらに非水電解質二次電池の放電容量を大きくするために、結晶構造はＲ−３ｍまたはＣ２／ｍの空間群に帰属することが好ましい。空間群Ｒ−３ｍは、六方晶型の結晶構造に含まれる。前記六方晶型の結晶構造は、Ｐ３、Ｐ３_１、Ｐ３_２、Ｒ３、Ｐ−３、Ｒ−３、Ｐ３１２、Ｐ３２１、Ｐ３_１１２、Ｐ３_１２１、Ｐ３_２１２、Ｐ３_２２１、Ｒ３２、Ｐ３ｍ１、Ｐ３１ｍ、Ｐ３ｃ１、Ｐ３１ｃ、Ｒ３ｍ、Ｒ３ｃ、Ｐ−３１ｍ、Ｐ−３１ｃ、Ｐ−３ｍ１、Ｐ−３ｃ１、Ｒ−３ｍ、Ｒ−３ｃ、Ｐ６、Ｐ６_１、Ｐ６_５、Ｐ６_２、Ｐ６_４、Ｐ６_３、Ｐ−６、Ｐ６／ｍ、Ｐ６_３／ｍ、Ｐ６２２、Ｐ６_１２２、Ｐ６_５２２、Ｐ６_２２２、Ｐ６_４２２、Ｐ６_３２２、Ｐ６ｍｍ、Ｐ６ｃｃ、Ｐ６_３ｃｍ、Ｐ６_３ｍｃ、Ｐ−６ｍ２、Ｐ−６ｃ２、Ｐ−６２ｍ、Ｐ−６２ｃ、Ｐ６／ｍｍｍ、Ｐ６／ｍｃｃ、Ｐ６_３／ｍｃｍおよびＰ６_３／ｍｍｃからなる群より選ばれるいずれか一つの空間群に帰属する。また、空間群Ｃ２／ｍは、単斜晶型の結晶構造に含まれる。前記単斜晶型の結晶構造は、Ｐ２、Ｐ２_１、Ｃ２、Ｐｍ、Ｐｃ、Ｃｍ、Ｃｃ、Ｐ２／ｍ、Ｐ２_１／ｍ、Ｃ２／ｍ、Ｐ２／ｃ、Ｐ２_１／ｃおよびＣ２／ｃからなる群より選ばれるいずれか一つの空間群に帰属する。なお、アルカリ金属−遷移金属複合酸化物の結晶構造は粉末Ｘ線回折測定により得られる粉末Ｘ線回折図形から同定することができる。粉末Ｘ線回折測定におけるＸ線の線源としてはＣｕＫα線、ＣｏＫα線、ＭｏＫα線およびＷＫα線を用いることができる。
　また、本発明において、アルカリ金属−遷移金属複合酸化物を構成する遷移金属元素が、Ｎｉ、Ｍｎ、ＣｏおよびＦｅからなる群より選ばれる１種以上の遷移金属元素である場合には、本発明の効果を損なわない範囲で、該遷移金属元素の一部を、他元素で置換してもよい。ここで、他元素としては、Ｂ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｍｇ、Ｓｃ、Ｙ、Ｚｒ、Ｈｆ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｒｕ、Ｒｈ、Ｉｒ、Ｐｄ、Ｃｕ、Ａｇ、Ｚｎなどの元素を挙げることができる。
　また、本発明の効果を損なわない範囲で、本発明のアルカリ金属−遷移金属複合酸化物の粒子の表面に、該酸化物とは異なる化合物を付着させてもよい。該化合物としては、Ｂ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｍｇおよび遷移金属元素からからなる群より選ばれる１種以上の元素から構成される化合物であり、好ましくはＢ、Ａｌ、Ｍｇ、Ｇａ、ＩｎおよびＳｎからなる群より選ばれる１種以上の元素から構成される化合物、より好ましくはＡｌの化合物を挙げることができる。前記化合物として具体的には、前記元素の酸化物、水酸化物、オキシ水酸化物、炭酸塩、硝酸塩および有機酸塩を挙げることができ、好ましくは、酸化物、水酸化物およびオキシ水酸化物である。また、これらの化合物を混合して用いてもよい。これら化合物の中でも、特に好ましい化合物はアルミナである。また、付着後に加熱を行ってもよい。
　本発明の方法によって得られるアルカリ金属−遷移金属複合酸化物を有する正極活物質は、非水電解質二次電池に好適である。
＜正極の製造＞
　前記正極活物質を用いて、正極を製造する方法として、非水電解質二次電池用の正極を製造する場合を例に挙げて、次に説明する。
　正極は、正極活物質、導電材およびバインダーを含む正極合剤が正極集電体に担持されることにより製造できる。
　前記導電材としては炭素材料を用いることができ、炭素材料として黒鉛粉末、カーボンブラック（例えば、アセチレンブラック）および繊維状炭素材料を挙げることができる。正極中の導電材の割合を高めることにより、正極の導電性が高くなり、充放電効率およびレート特性を向上させることができる。正極中の導電材の割合が大きすぎると、正極合剤と正極集電体との結着性が低下し、内部抵抗が増大することがある。通常、正極合剤中の導電材の割合は、正極活物質１００重量部に対して５~２０重量部である。
　導電材として黒鉛化炭素繊維、カーボンナノチューブなどの繊維状炭素材料を用いる場合には、この割合を下げることも可能である。またカーボンブラックは、少量を正極合剤中に添加することで、正極内部の導電性を高め、得られる電池の充放電効率およびレート特性を向上させることができる。
　前記バインダーとしては、熱可塑性樹脂が挙げられ、具体的には、ポリフッ化ビニリデン（以下、ＰＶｄＦということがある。）、ポリテトラフルオロエチレン（以下、ＰＴＦＥということがある。）、四フッ化エチレン・六フッ化プロピレン・フッ化ビニリデン系共重合体、六フッ化プロピレン・フッ化ビニリデン系共重合体および四フッ化エチレン・パーフルオロビニルエーテル系共重合体などのフッ素樹脂；ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂；が挙げられる。また、これらの二種以上の熱可塑性樹脂を混合して用いてもよい。また、バインダーとしてフッ素樹脂およびポリオレフィン樹脂を用い、正極合剤１００重量％中の該フッ素樹脂の割合が１~１０重量％、該ポリオレフィン樹脂の割合が０．１~２重量％となるように正極合剤がこれらを含有することによって、正極集電体との結着性に優れた正極合剤を得ることができる。
　前記正極集電体としては、Ａｌ、Ｎｉ、ステンレスなどの導電体を用いることができる。さらに、薄膜に加工しやすく、安価であるという点でＡｌが好ましい。正極集電体に正極合剤を担持させる方法としては、加圧成型する方法；正極合剤ペーストを用いて、正極合剤を正極集電体に固着する方法が挙げられる。
　正極合剤ペーストは、正極活物質と導電材とバインダーと溶媒とを含有する。該正極合剤ペーストを正極集電体に塗工し、乾燥して、得られたシートをプレスして、正極合剤を正極集電体に固着する。
　該溶媒としては、水系溶媒または有機溶媒を用いることができる。溶媒には必要に応じて増粘剤を添加してもよい。該増粘剤の例としては、カルボキシメチルセルロース、ポリアクリル酸ナトリウム、ポリビニルアルコールおよびポリビニルピロリドンが挙げられる。
　該有機溶媒の例としては、Ｎ，Ｎ—ジメチルアミノプロピルアミン、ジエチレントリアミンなどのアミン系溶媒；テトラヒドロフランなどのエーテル系溶媒；メチルエチルケトンなどのケトン系溶媒；酢酸メチルなどのエステル系溶媒；ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン（以下、ＮＭＰということがある）などのアミド系溶媒；が挙げられる。
　正極合剤ペーストを正極集電体へ塗工する方法の例としては、スリットダイ塗工法、スクリーン塗工法、カーテン塗工法、ナイフ塗工法、グラビア塗工法および静電スプレー法が挙げられる。
　以上により、非水電解質二次電池用正極を製造することができる。
＜非水電解質二次電池＞
　前記の正極を用いて、非水電解質二次電池を説明する。例えば、リチウム二次電池は、セパレータ、負極および前記の正極を、積層する、または積層かつ巻回することにより電極群を作製して、該電極群を電池ケース内に収納し、電解液を電池ケース内に注入する方法により、製造できる。
　前記電極群の形状としては、例えば、該電極群を巻回の軸と垂直方向に切断したときの断面が、円、楕円、長方形、角がとれたような長方形などの形状を挙げることができる。また、電池の形状としては、ペーパー型、コイン型、円筒型、角型などの形状を挙げることができる。
＜負極＞
　前記負極は、正極よりも低い電位でリチウムイオンでドープかつ脱ドープされることができる。負極としては、負極活物質を含む負極合剤が負極集電体に担持された電極；負極活物質単独からなる電極を挙げることができる。負極活物質としては、炭素材料、カルコゲン化合物（酸化物、硫化物など）、窒化物、金属または合金のうち、正極よりも低い電位でリチウムイオンでドープかつ脱ドープされることができる材料が挙げられる。これらの負極活物質を混合して用いてもよい。
　前記負極活物質について以下に例示する。
　前記炭素材料の例として、具体的には、天然黒鉛、人造黒鉛などの黒鉛、コークス類、カーボンブラック、熱分解炭素類、炭素繊維および有機高分子化合物焼成体などを挙げることができる。
　前記酸化物の例として、具体的には、ＳｉＯ_２、ＳｉＯなど式ＳｉＯ_ｘ（ここで、ｘは正の実数）で表されるケイ素の酸化物；ＴｉＯ_２、ＴｉＯなど式ＴｉＯ_ｘ（ここで、ｘは正の実数）で表されるチタンの酸化物；Ｖ_２Ｏ_５、ＶＯ_２など式ＶＯ_ｘ（ここで、ｘは正の実数）で表されるバナジウムの酸化物；Ｆｅ_３Ｏ_４、Ｆｅ_２Ｏ_３、ＦｅＯなど式ＦｅＯ_ｘ（ここで、ｘは正の実数）で表される鉄の酸化物；ＳｎＯ_２、ＳｎＯなど式ＳｎＯ_ｘ（ここで、ｘは正の実数）で表されるスズの酸化物；ＷＯ_３、ＷＯ_２など一般式ＷＯ_ｘ（ここで、ｘは正の実数）で表されるタングステンの酸化物；Ｌｉ_４Ｔｉ_５Ｏ_１２、ＬｉＶＯ_２などのリチウムとチタンおよび／またはバナジウムとを含有する複合金属酸化物；を挙げることができる。
　前記硫化物として、具体的には、Ｔｉ_２Ｓ_３、ＴｉＳ_２、ＴｉＳなど式ＴｉＳ_ｘ（ここで、ｘは正の実数）で表されるチタンの硫化物；Ｖ_３Ｓ_４、ＶＳ_２、ＶＳなど式ＶＳ_ｘ（ここで、ｘは正の実数）で表されるバナジウムの硫化物；Ｆｅ_３Ｓ_４、ＦｅＳ_２、ＦｅＳなど式ＦｅＳ_ｘ（ここで、ｘは正の実数）で表される鉄の硫化物；Ｍｏ_２Ｓ_３、ＭｏＳ_２など式ＭｏＳ_ｘ（ここで、ｘは正の実数）で表されるモリブデンの硫化物；ＳｎＳ_２、ＳｎＳなど式ＳｎＳ_ｘ（ここで、ｘは正の実数）で表されるスズの硫化物；ＷＳ_２など式ＷＳ_ｘ（ここで、ｘは正の実数）で表されるタングステンの硫化物；Ｓｂ_２Ｓ_３など式ＳｂＳ_ｘ（ここで、ｘは正の実数）で表されるアンチモンの硫化物；Ｓｅ_５Ｓ_３、ＳｅＳ_２、ＳｅＳなど式ＳｅＳ_ｘ（ここで、ｘは正の実数）で表されるセレンの硫化物；を挙げることができる。
　前記窒化物の例として、具体的には、Ｌｉ_３Ｎ、Ｌｉ_３−ｘＡ_ｘＮ（ここで、ＡはＮｉおよび／またはＣｏであり、０＜ｘ＜３である。）などのリチウム含有窒化物を挙げることができる。
　これらの炭素材料、酸化物、硫化物、窒化物は、２種以上組み合わせて用いてもよく、これらは結晶質または非晶質のいずれでもよい。また、これらの炭素材料、酸化物、硫化物、窒化物は、主に、負極集電体に担持して、電極として用いられる。
　また、前記金属の例として、具体的には、リチウム金属、シリコン金属およびスズ金属が挙げられる。
　また、前記合金の例としては、Ｌｉ−Ａｌ、Ｌｉ−Ｎｉ、Ｌｉ−Ｓｉなどのリチウム合金；Ｓｉ−Ｚｎなどのシリコン合金；Ｓｎ−Ｍｎ、Ｓｎ−Ｃｏ、Ｓｎ−Ｎｉ、Ｓｎ−Ｃｕ、Ｓｎ−Ｌａなどのスズ合金；Ｃｕ_２Ｓｂ、Ｌａ_３Ｎｉ_２Ｓｎ_７などの合金；を挙げることができる。
　前記負極活物質の中で、電位平坦性が良好である、平均放電電位が低い、サイクル性が良いために、天然黒鉛、人造黒鉛などの黒鉛を主成分とする炭素材料が好ましく用いられる。炭素材料の形状としては、例えば天然黒鉛のような薄片状、メソカーボンマイクロビーズのような球状、黒鉛化炭素繊維のような繊維状が挙げられる。炭素材料は微粉末の凝集体でもよい。
　前記負極合剤は、必要に応じて、バインダーを含有してもよい。バインダーとしては、熱可塑性樹脂を挙げることができ、具体的には、ＰＶｄＦ、熱可塑性ポリイミド、カルボキシメチルセルロース、ポリエチレンおよびポリプロピレンを挙げることができる。
　前記負極集電体としては、Ｃｕ、Ｎｉ、ステンレスなどの導電体を挙げることができ、リチウムと合金を作り難い点、薄膜に加工しやすいという点で、Ｃｕが好ましい。
　負極集電体に負極合剤を担持させる方法としては、正極の場合と同様であり、加圧成型する方法；負極合剤ペーストを用いて、負極合剤を負極集電体に固着する方法が挙げられる。
＜セパレータ＞
　前記セパレータとしては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂、フッ素樹脂、含窒素芳香族重合体などの材料からなる、多孔質膜、不織布、織布などの形態を有する部材を用いることができ、セパレータは、２種以上の前記材料からなってもよいし、前記部材が積層された積層セパレータであってもよい。セパレータとしては、例えば特開２０００−３０６８６号公報、特開平１０−３２４７５８号公報などに記載のセパレータを挙げることができる。セパレータの厚みは電池の体積エネルギー密度が上がり、かつ内部抵抗が小さくなるという点で、通常５~２００μｍ程度、好ましくは５~４０μｍ程度である。セパレータは機械的強度が保たれる限り薄いことが好ましい。
　セパレータは、好ましくは、熱可塑性樹脂を含有する多孔質フィルムを有する。非水電解質二次電池において、セパレータは正極と負極の間に配置される。セパレータは、正極−負極間の短絡などが原因で電池内に異常電流が流れた際に、電流を遮断して、過大電流が流れることを阻止する機能（シャットダウン機能）を有することが好ましい。ここで、シャットダウンは、通常の使用温度を越えた場合に、セパレータにおける多孔質フィルムの微細孔を閉塞することによりなされる。そしてシャットダウンした後、ある程度の高温まで電池内の温度が上昇しても、その温度により破膜することなく、シャットダウンした状態を維持することが好ましい。かかるセパレータとしては、耐熱多孔層と多孔質フィルムとが互いに積層された積層フィルムが挙げられ、該フィルムをセパレータとして用いることにより、二次電池の耐熱性がより高められる。耐熱多孔層は、多孔質フィルムの両面に積層されていてもよい。
＜積層フィルム＞
　以下、前記耐熱多孔層と多孔質フィルムとが互いに積層された積層フィルムについて説明する。
　前記積層フィルムにおいて、耐熱多孔層は、多孔質フィルムよりも耐熱性の高い層であり、該耐熱多孔層は、無機粉末から形成されていてもよいし、耐熱樹脂を含有していてもよい。耐熱多孔層が、耐熱樹脂を含有することにより、塗工などの容易な手法で、耐熱多孔層を形成することができる。
　耐熱樹脂としては、ポリアミド、ポリイミド、ポリアミドイミド、ポリカーボネート、ポリアセタール、ポリサルホン、ポリフェニレンサルファイド、ポリエーテルケトン、芳香族ポリエステル、ポリエーテルサルホンおよびポリエーテルイミドを挙げることができる。耐熱性をより高めるためには、ポリアミド、ポリイミド、ポリアミドイミド、ポリエーテルサルホンおよびポリエーテルイミドが好ましい。より好ましくは、ポリアミド、ポリイミドまたはポリアミドイミドである。さらにより好ましくは、芳香族ポリアミド（パラ配向芳香族ポリアミド、メタ配向芳香族ポリアミド）、芳香族ポリイミド、芳香族ポリアミドイミドなどの含窒素芳香族重合体である。とりわけ好ましくは芳香族ポリアミドであり、製造面で、特に好ましいのは、パラ配向芳香族ポリアミド（以下、パラアラミドということがある。）である。
　また、耐熱樹脂として、ポリ−４−メチルペンテン−１、環状オレフィン系重合体を挙げることもできる。これらの耐熱樹脂を用いることにより、積層フィルムの耐熱性、すなわち、積層フィルムの熱破膜温度をより高めることができる。
　前記積層フィルムの熱破膜温度は、耐熱樹脂の種類に依存し、使用場面、使用目的に応じ、選択使用される。より具体的には、耐熱樹脂として、前記含窒素芳香族重合体を用いる場合には４００℃程度に、ポリ−４−メチルペンテン−１を用いる場合には２５０℃程度に、環状オレフィン系重合体を用いる場合には３００℃程度に、夫々、熱破膜温度をコントロールすることができる。また、耐熱多孔層が、無機粉末からなる場合には、熱破膜温度を５００℃以上にコントロールすることも可能である。
　前記パラアラミドは、パラ配向芳香族ジアミンとパラ配向芳香族ジカルボン酸ハライドとの縮重合により得られ、アミド結合が芳香族環のパラ位またはそれに準じた配向位（例えば、ビフェニレンにおける４，４’位、ナフタレンにおける１，５位、ナフタレンにおける２，６位）で結合される繰り返し単位から実質的になるものである。
　パラアラミドの具体例にとしては、ポリ（パラフェニレンテレフタルアミド）、ポリ（パラベンズアミド）、ポリ（４，４’−ベンズアニリドテレフタルアミド）、ポリ（パラフェニレン−４，４’−ビフェニレンジカルボン酸アミド）、ポリ（パラフェニレン−２，６−ナフタレンジカルボン酸アミド）、ポリ（２−クロロ−パラフェニレンテレフタルアミド）、パラフェニレンテレフタルアミド／２，６−ジクロロパラフェニレンテレフタルアミド共重合体などのパラ配向型またはパラ配向型に準じた構造を有するパラアラミドが挙げられる。
　前記芳香族ポリイミドとしては、芳香族の二酸無水物とジアミンの縮重合により製造される全芳香族ポリイミドが好ましい。
　該二酸無水物の具体例としては、ピロメリット酸二無水物、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、２，２’−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパンおよび３，３’，４，４’−ビフェニルテトラカルボン酸二無水物が挙げられる。
　該ジアミンの具体例としては、オキシジアニリン、パラフェニレンジアミン、ベンゾフェノンジアミン、３，３’−メチレンジアニリン、３，３’−ジアミノベンソフェノン、３，３’−ジアミノジフェニルスルフォンおよび１，５−ナフタレンジアミンが挙げられる。
　また、溶媒に可溶なポリイミドが好適に使用できる。このようなポリイミドとしては、例えば、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物と芳香族ジアミンとの重縮合物のポリイミドが挙げられる。
　前記芳香族ポリアミドイミドとしては、芳香族ジカルボン酸および芳香族ジイソシアネートの縮重合により得られるもの、ならびに、芳香族二酸無水物および芳香族ジイソシアネートの縮重合により得られるものが挙げられる。
芳香族ジカルボン酸の具体例としてはイソフタル酸およびテレフタル酸が挙げられる。また芳香族二酸無水物の具体例としては無水トリメリット酸が挙げられる。芳香族ジイソシアネートの具体例としては、４，４’−ジフェニルメタンジイソシアネート、２，４−トリレンジイソシアネート、２，６−トリレンジイソシアネート、オルソトリランジイソシアネートおよびｍ−キシレンジイソシアネートが挙げられる。
　また、イオン透過性をより高めるために、耐熱多孔層の厚みは、好ましくは１~１０μｍ、さらに好ましくは１~５μｍ、特に好ましくは１~４μｍである。また、耐熱多孔層は微細孔を有し、その孔径は、通常３μｍ以下であり、好ましくは１μｍ以下である。
　また、耐熱多孔層が、耐熱樹脂を含有する場合には、耐熱多孔層は後述のフィラーを含有することもできる。
　前記積層フィルムにおいて、多孔質フィルムは、微細孔を有する。多孔質フィルムは、シャットダウン機能を有することが好ましい。この場合、多孔質フィルムは、熱可塑性樹脂を含有する。多孔質フィルムにおける微細孔のサイズ（直径）は通常３μｍ以下であり、好ましくは１μｍ以下である。多孔質フィルムの空孔率は、通常３０~８０体積％、好ましくは４０~７０体積％である。
　熱可塑性樹脂を含有する多孔質フィルムをセパレータとして用いた非水電解質二次電池が通常の使用温度を越えると、熱可塑性樹脂が軟化することにより、多孔質フィルムの微細孔を閉塞する。
　前記熱可塑性樹脂には、非水電解質二次電池における電解液に溶解しないものが選択される。このような熱可塑性樹脂として、具体的には、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂および熱可塑性ポリウレタン樹脂を挙げることができ、２種以上の熱可塑性樹脂を混合して用いてもよい。より低温で軟化してシャットダウンさせるためには、多孔質フィルムはポリエチレンを含有することが好ましい。前記ポリエチレンの具体例としては、低密度ポリエチレン、高密度ポリエチレン、線状ポリエチレンおよび分子量が１００万以上の超高分子量ポリエチレンを挙げることができる。前記多孔質フィルムは、該フィルムの突刺し強度をより高めるために、超高分子量ポリエチレンを含有することが好ましい。また、多孔質フィルムを容易に製造するために、熱可塑性樹脂は、重量平均分子量１万以下の低分子量のポリオレフィンからなるワックスを含有することが好ましい場合もある。
　また、積層フィルムにおける多孔質フィルムの厚みは、通常、３~３０μｍであり、好ましくは３~２５μｍである。また、本発明において、積層フィルムの厚みは、通常４０μｍ以下、好ましくは２０μｍ以下である。また、耐熱多孔層の厚みをＡ（μｍ）、多孔質フィルムの厚みをＢ（μｍ）としたときには、Ａ／Ｂの値が、０．１以上１以下であることが好ましい。
　また、耐熱多孔層に耐熱樹脂を含有する場合には、耐熱多孔層には１種以上のフィラーを含有してもよい。フィラーは、有機粉末、無機粉末またはこれらの混合物のいずれから選ばれてもよい。フィラーを構成する粒子の平均粒子径は０．０１~１μｍであることが好ましい。
　前記有機粉末としては、例えば、スチレン、ビニルケトン、アクリロニトリル、メタクリル酸メチル、メタクリル酸エチル、グリシジルメタクリレート、グリシジルアクリレート、アクリル酸メチルなどの単独または２種類以上の共重合体；ポリテトラフルオロエチレン、４フッ化エチレン−６フッ化プロピレン共重合体、４フッ化エチレン−エチレン共重合体、ＰＶｄＦなどのフッ素系樹脂；メラミン樹脂；尿素樹脂；ポリオレフィン；ポリメタクリレート；が挙げられる。
該有機粉末は、単独で用いてもよいし、２種以上を混合して用いることもできる。これらの有機粉末の中でも、化学的安定性の点で、ポリテトラフルオロエチレン粉末が好ましい。
　前記無機粉末としては、例えば、金属酸化物、金属窒化物、金属炭化物、金属水酸化物、炭酸塩、硫酸塩などの無機物からなる粉末が挙げられる。これらの中でも、導電性の低い無機物からなる粉末が好ましく用いられる。好ましい無機粉末の具体例としては、アルミナ、シリカ、二酸化チタンまたは炭酸カルシウムからなる粉末が挙げられる。無機粉末は、単独で用いてもよいし、２種以上を混合して用いることもできる。これらの無機粉末の中でも、化学的安定性の点で、アルミナ粉末が好ましい。より好ましくは、フィラーがアルミナ粒子のみである。さらに好ましくは、フィラーを構成するアルミナ粒子の一部または全部が略球状であることである。
　耐熱多孔層が無機粉末から構成される場合には、前記例示の無機粉末を用いればよく、必要に応じてバインダーと混ぜて用いればよい。
　フィラーを構成する粒子のすべてがアルミナ粒子である場合には、フィラーの重量の比は、耐熱多孔層の総重量１００重量部に対して、通常５~９５重量部であり、好ましくは、２０~９５重量部であり、より好ましくは３０~９０重量部である。これらの範囲は、フィラーの材質の比重により、適宜設定できる。
　フィラーの形状については、略球状、板状、柱状、針状、ウィスカー状および繊維状が挙げられ、均一な孔を形成しやすいことから、略球状であることが好ましい。略球状粒子としては、粒子のアスペクト比（粒子の長径／粒子の短径）が１~１．５である粒子が挙げられる。粒子のアスペクト比は、電子顕微鏡写真から測定することができる。
　二次電池におけるイオン透過性を高めるために、前記セパレータのガーレー法による透気度は、５０~３００秒／１００ｃｃであることが好ましく、さらに好ましくは、５０~２００秒／１００ｃｃである。また、セパレータの空孔率は、通常３０~８０体積％であり、好ましくは４０~７０体積％である。セパレータは空孔率の異なるセパレータを積層したものであってもよい。
＜電解液および固体電解質＞
　二次電池において、電解液は、通常、電解質および有機溶媒から構成される。電解質の例としては、アルカリ金属をカチオンとする過塩素酸塩、六フッ化リン塩、六フッ化ヒ素塩、六フッ化アンチモン塩、四フッ化ホウ素塩、トリフルオロメタンスルホナート塩、スルホンアミド化合物のトリフルオロメタンスルホン酸塩、ホウ素化合物塩およびホウ酸塩が挙げられる。これらの２種以上の混合物を使用してもよい。
　リチウム塩の例としては、ＬｉＣｌＯ_４、ＬｉＰＦ_６、ＬｉＡｓＦ_６、ＬｉＳｂＦ_６、ＬｉＢＦ_４、ＬｉＣＦ_３ＳＯ_３、ＬｉＮ（ＳＯ_２ＣＦ_３）_２、ＬｉＮ（ＳＯ_２Ｃ_２Ｆ_５）_２、ＬｉＮ（ＳＯ_２ＣＦ_３）（ＣＯＣＦ_３）、Ｌｉ（Ｃ_４Ｆ_９ＳＯ_３）、ＬｉＣ（ＳＯ_２ＣＦ_３）_３、Ｌｉ_２Ｂ_１０Ｃｌ_１０、ＬｉＢＯＢ（ここで、ＢＯＢは、ｂｉｓ（ｏｘａｌａｔｅ）ｂｏｒａｔｅのことである。）、低級脂肪族カルボン酸リチウム塩、ＬｉＡｌＣｌ_４などが挙げられる。通常、これらの中でもＬｉＰＦ_６、ＬｉＡｓＦ_６、ＬｉＳｂＦ_６、ＬｉＢＦ_４、ＬｉＣＦ_３ＳＯ_３、ＬｉＮ（ＳＯ_２ＣＦ_３）_２およびＬｉＣ（ＳＯ_２ＣＦ_３）_３からなる群より選ばれる１種以上のフッ素含有リチウム塩が用いられる。
　また前記電解液において、有機溶媒としては、プロピレンカーボネート、エチレンカーボネート（以下、ＥＣということがある）、ジメチルカーボネート（以下、ＤＭＣということがある）、ジエチルカーボネート、エチルメチルカーボネート（以下、ＥＭＣということがある）、４−トリフルオロメチル−１，３−ジオキソラン−２−オン、１，２−ジ（メトキシカルボニルオキシ）エタンなどのカーボネート類；１，２−ジメトキシエタン、１，３−ジメトキシプロパン、ペンタフルオロプロピルメチルエーテル、２，２，３，３−テトラフルオロプロピルジフルオロメチルエーテル、テトラヒドロフラン、２−メチルテトラヒドロフランなどのエーテル類；ギ酸メチル、酢酸メチル、γ−ブチロラクトンなどのエステル類；アセトニトリル、ブチロニトリルなどのニトリル類；Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミドなどのアミド類；３−メチル−２−オキサゾリドンなどのカーバメート類；スルホラン、ジメチルスルホキシド、１，３−プロパンサルトンなどの含硫黄化合物；が挙げられる。また、前記の有機溶媒にさらにフッ素置換基を導入したものを用いることができる。
　通常は前記有機溶媒のうちの二種以上の有機溶媒が混合された混合溶媒を用いる。中でもカーボネート類を含む混合溶媒が好ましく、環状カーボネートと非環状カーボネートとの混合溶媒、または環状カーボネートとエーテル類との混合溶媒がさらに好ましい。環状カーボネートと非環状カーボネートとの混合溶媒としては、動作温度範囲が広く、負荷特性に優れ、かつ負極の活物質として天然黒鉛、人造黒鉛などの黒鉛材料を用いた場合でも難分解性であるという点で、ＥＣ、ＤＭＣおよびＥＭＣを含む混合溶媒が好ましい。
　また、特に、安全性をより向上する効果があることから、ＬｉＰＦ_６などのフッ素含有アルカリ金属塩およびフッ素置換基を有する有機溶媒を含む電解液を用いることが好ましい。ペンタフルオロプロピルメチルエーテル、２，２，３，３−テトラフルオロプロピルジフルオロメチルエーテルなどのフッ素置換基を有するエーテル類とＤＭＣとを含む混合溶媒は、大電流放電特性にも優れており、さらに好ましい。
　前記の電解液の代わりに固体電解質を用いてもよい。固体電解質としては、例えばポリエチレンオキサイド系の高分子、ポリオルガノシロキサン鎖およびポリオキシアルキレン鎖の少なくとも１種を含む高分子などの有機系高分子電解質を用いることができる。また、高分子に電解液を保持させた、いわゆるゲルタイプのものを用いることもできる。また、Ｌｉ_２Ｓ−ＳｉＳ_２、Ｌｉ_２Ｓ−ＧｅＳ_２、Ｌｉ_２Ｓ−Ｐ_２Ｓ_５、Ｌｉ_２Ｓ−Ｂ_２Ｓ_３、Ｌｉ_２Ｓ−ＳｉＳ_２−Ｌｉ_３ＰＯ_４、Ｌｉ_２Ｓ−ＳｉＳ_２−Ｌｉ_２ＳＯ_４などの硫化物を含む無機系固体電解質を用いてもよい。これら固体電解質を用いて、安全性をより高めることができることがある。また、本発明の非水電解質二次電池において、固体電解質を用いる場合には、固体電解質がセパレータの役割を果たす場合もあり、その場合には、セパレータを必要としないこともある。 <Raw material mixture for alkali metal-transition metal composite oxide>
The raw material mixture for alkali metal-transition metal composite oxide includes a flux containing an inorganic salt, an alkali metal salt containing a compound different from the flux, and a transition metal compound, and satisfies the following requirements:
Compared to the lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced from the oxide consisting only of the transition metal element and oxygen element of the transition metal compound during firing of the mixture, The temperature (Tmp) at the start of melting of the mixture is high.
<Flux containing inorganic salt>
The flux in the present invention refers to a material that is partially or wholly melted at the holding temperature during firing.
Examples of the inorganic salt constituting the flux in the present invention include borate, carbonate, nitrate, phosphate, sulfate, vanadate, tungstate, molybdate, niobate and halide ( Here, examples of the halide include one or more compounds selected from the group consisting of fluoride, chloride, bromide, and iodide.
The cation of the flux is preferably one or more metal elements selected from the group consisting of Li, Na, K, Rb, Cs, Ca, Mg, Sr and Ba.
Further, the flux may consist of two or more of the above inorganic salts. When the flux is composed of two or more of the inorganic salts, the temperature at the start of melting of the flux is lower than the melting point of each inorganic salt.
Also, the coexisting flux with the alkali metal salt lowers the temperature at the start of melting. A part of the flux may be the same as the alkali metal salt.
As a borate having a cation of Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba, LiBO₂, NaBO₂, KBO₂, RbBO₂, CsBO₂, Mg (BO₂)₂, Ca (BO₂)₂, Sr (BO₂)₂And Ba (BO₂)₂Can be mentioned. Their melting point is LiBO₂(845 ° C), NaBO₂(966 ° C), KBO₂(950 ° C.), Ca (BO₂)₂(1154 ° C.).
As carbonates with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations, Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, Cs₂CO₃, MgCO₃, CaCO₃, SrCO₃And BaCO₃Can be mentioned. These melting points are Li₂CO₃(735 ° C), Na₂CO₃(854 ° C), K₂CO₃(899 ° C), Rb₂CO₃(837 ° C), Cs₂CO₃(793 ° C), MgCO₃(990 ° C), CaCO₃(825 ° C), SrCO₃(1497 ° C), BaCO₃(1380 ° C.).
As a nitrate salt with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations, LiNO₃, NaNO₃, KNO₃, RbNO₃, CsNO₃, Mg (NO₃)₂, Ca (NO₃)₂, Sr (NO₃)₂And Ba (NO₃)₂Can be mentioned. These melting points are LiNO₃(254 ° C), NaNO₃(310 ° C), KNO₃(337 ° C), RbNO₃(316 ° C), CsNO₃(417 ° C), Ca (NO₃)₂(561 ° C), Sr (NO₃)₂(645 ° C), Ba (NO₃)₂(596 ° C.).
Lithium phosphate with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations₃PO₄, Na₃PO₄, K₃PO₄, Rb₃PO₄, Cs₃PO₄, Mg₃(PO₄)₂, Ca₃(PO₄)₂, Sr₃(PO₄)₂And Ba₃(PO₄)₂Can be mentioned. These melting points are Li₃PO₄(857 ° C), K₃PO₄(1340 ° C), Mg₃(PO₄)₂(1184 ° C), Sr₃(PO₄)₂(1727 ° C), Ba₃(PO₄)₂(1767 ° C.).
As the sulfate salt with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations, Li₂SO₄, Na₂SO₄, K₂SO₄, Rb₂SO₄, Cs₂SO₄, CaSO₄, MgSO₄, SrSO₄And BaSO₄Can be mentioned. These melting points are Li₂SO₄(859 ° C), Na₂SO₄(884 ° C), K₂SO₄(1069 ° C), Rb₂SO₄(1066 ° C), Cs₂SO₄(1005 ° C), MgSO₄(1137 ° C), CaSO₄(1460 ° C), SrSO₄(1605 ° C), BaSO₄(1580 ° C.).
バ LiVO as a vanadate salt with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations₃, NaVO₃, KVO₃, RbVO₃, CsVO₃, Mg (VO₃)₂, Ca (VO₃)₂, Sr (VO₃)₂And Ba (VO₃)₂Can be mentioned. These melting points are NaVO₃(630 ° C), Ba (VO₃)₂(Ba₂V₂O₇863 ° C.).
Tungstic acid salts with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations are Li₂WO₄, Na₂WO₄, K₂WO₄, Rb₂WO₄, Cs₂WO₄, MgWO₄, CaWO₄, SrWO₄And BaWO₄Can be mentioned. These melting points are Li₂WO₄(742 ° C), Na₂WO₄(687 ° C), K₂WO₄(926 ° C.).
As the molybdate with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations, Li₂MoO₄, Na₂MoO₄, K₂MoO₄, Rb₂MoO₄, Cs₂MoO₄, MgMoO₄, CaMoO₄, SrMoO₄And BaMoO₄Can be mentioned. These melting points are Li₂MoO₄(705 ° C), Na₂MoO₄(698 ° C), K₂MoO₄(919 ° C), Rb₂MoO₄(958 ° C), Cs₂MoO₄(956 ° C.), MgMoO₄(1060 ° C), CaMoO₄(1520 ° C), SrMoO₄(1040 ° C), BaMoO₄(1460 ° C.).
LiNbO as a niobate salt with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations₃NaNbO₃, KNbO₃, RbNbO₃, CsNbO₃, Mg (NbO₃)₂, Ca (NbO₃)₂, Sr (NbO₃)₂And Ba (NbO₃)₂Can be mentioned. These melting points are LiNbO₃(1255 ° C.), NaNbO₃(1250 ° C), KNbO₃(1050 ° C.).
¡LiCl, NaCl, KCl, RbCl, CsCl, MgCl as chlorides with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba as cations₂, CaCl₂, SrCl₂And BaCl₂Can be mentioned. These melting points are LiCl (605 ° C.), NaCl (801 ° C.), KCl (770 ° C.), RbCl, (718 ° C.), CsCl (645 ° C.), MgCl₂(714 ° C), CaCl₂(782 ° C), SrCl₂(857 ° C), BaCl₂(963 ° C.).
In the present invention, the ratio of the flux containing the inorganic salt in the raw material mixture is usually 0.1 to 1000 parts by weight, preferably 0.5 to 200 parts by weight with respect to 100 parts by weight of the transition metal compound. More preferably, it is 1 to 100 parts by weight.
<Alkali metal salt>
In the present invention, the alkali metal salt containing a compound different from the flux includes alkali metal carbonate, alkali metal nitrate, alkali metal sulfate, alkali metal phosphate, and alkali metal halide ( Here, examples of the halide include one or more compounds selected from the group consisting of fluoride, chloride, bromide, and iodide. These alkali metal salts may be hydrates. Two or more of these alkali metal salts may be used in combination.
Alkali metal carbonates include Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃And Cs₂CO₃Can be mentioned.
ア ル カ リ As the alkali metal nitrate, LiNO₃, NaNO₃, KNO₃, RbNO₃And CsNO₃Can be mentioned.
Alkali metal sulfates include Li₂SO₄, Na₂SO₄, K₂SO₄, Rb₂SO₄And Cs₂SO₄Can be mentioned.
Alkaline metal phosphates include Li₃PO₄, Na₃PO₄, K₃PO₄, Rb₃PO₄And Cs₃PO₄Can be mentioned.
Examples of alkali metal halides include chlorides. Examples of alkali metal chlorides include LiCl, NaCl, KCl, RbCl, and CsCl.
The alkali metal element constituting the alkali metal salt is preferably one or more elements selected from the group consisting of Li, Na and K.
<Transition metal compounds>
In the present invention, transition metal compounds include transition metal oxides, hydroxides (including oxyhydroxides, the same shall apply hereinafter), chlorides, carbonates, sulfates, nitrates, oxalates and acetates. be able to. These transition metal compounds may be hydrates. Two or more of these transition metal compounds may be used in combination.
The transition metal element constituting the transition metal compound is preferably one or more elements selected from the group consisting of Mn, Fe, Co and Ni.
In order to further improve the rate characteristics of the obtained nonaqueous electrolyte secondary battery, the transition metal element constituting the transition metal compound is one or more selected from the group consisting of Fe, Mn, Co, and Ni. It is preferable that More preferably, the transition metal element constituting the transition metal compound has Fe and Ni or Mn.
Preferably, the transition metal compound has Fe as a constituent element. As a preferable amount of Fe, the molar fraction of Fe in the transition metal element is 0.01 to 0.5, and more preferably 0.02 to 0.2.
Suppose that M is a transition metal element, examples of transition metal oxides include MO and M₂O₃And MO₂Can be mentioned.
As a transition metal hydroxide, for example, M (OH)₂And M (OH)₃Can be mentioned. The transition metal hydroxide may be an oxyhydroxide of a transition metal. Examples of transition metal oxyhydroxides include MOOH.
As a transition metal chloride, for example, MCl₂And MCl₃Can be mentioned.
Examples of transition metal carbonates include MCO₃And M₂(CO₃)₃Can be mentioned.
Examples of transition metal sulfates include MSO₄And M₂(SO₄)₃Can be mentioned.
Examples of transition metal nitrates include M (NO₃)₂Can be mentioned.
Examples of transition metal oxalates include MC₂O₄Can be mentioned.
Examples of transition metal acetates include M (CH₃COO)₂Can be mentioned.
The transition metal compound is preferably a hydroxide.
The transition metal compound is preferably composed of a plurality of transition metal elements. The transition metal compound can be obtained by coprecipitation, and is preferably a hydroxide.
<Lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially generated over the oxide composed of only the transition metal element and the oxygen element>
Next, the lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced over the oxide consisting only of the transition metal element and the oxygen element will be described. The lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced over the oxide consisting only of the transition metal element and oxygen element is the standard production enthalpy ΔfH which is thermodynamic data of the substance involved in the equilibrium._T° and standard entropy S_TCalculated from °.
Here, as an example, the alkali metal salt is Li₂CO₃And an oxide composed only of a transition metal element and an oxygen element is Fe₂O₃And the alkali metal-transition metal composite oxide is LiFeO₂Consider the case.
Fe, an oxide consisting only of transition metal elements and oxygen elements₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Shows a method of calculating the lower limit (Teq) of the temperature generated with priority. Fe, which is an oxide consisting only of transition metal elements and oxygen elements₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is the lower limit (Teq) of the temperature that is preferentially generated, the standard free energy change ΔrG of the equilibrium (1-1)_TΔrG at °_TA temperature T at which 0 = 0. That is, ΔrG_Teq° = 0.
Fe₂O₃+ Li₂CO₃= 2LiFeO₂+ CO₂・ ・ ・ Equilibrium (1-1)
The standard free energy change ΔrG ° (T) of equilibrium (1-1) is the standard generation enthalpy ΔfH of each substance involved in equilibrium (1-1)_T° and standard entropy S_TCalculated from °. Standard generation enthalpy ΔfH which is thermodynamic data of each substance_T° and standard entropy S_T° can be examined using a thermodynamic database. As a thermodynamic database and thermodynamic calculation software, for example, MALT2 (copyright holder: Japan Society for Thermal Measurement, Publisher: Science and Technology Co., Ltd.) can be used. Standard free energy change ΔrG of equilibrium (1-1)_TThe values in Table 1 below were used for calculating °.

Standard generation enthalpy of each compound ΔfH_{25 ° C}From the standard enthalpy change ΔrH of equilibrium (1-1)_{25 ° C}° is calculated as in equation (1).
ΔrH_{25 ° C}° = 2ΔfH_{25 ° C}° (LiFeO₂) + ΔfH_{25 ° C}° (CO₂)
-ΔfH_{25 ° C}° (Fe₂O₃) -ΔfH_{25 ° C}° (Li₂CO₃)
= 2 × (−750) − (− 394) − (− 824) − (− 1216)
= 146 [kJ / mol] (1) Formula (1)
Standard entropy S for each compound_{25 ° C}From the standard entropy change S of equilibrium (1-1)_{25 ° C}° is calculated as in equation (2).
ΔrS_{25 ° C}° = 2S_{25 ° C}° (LiFeO₂) + S_{25 ° C}° (CO₂)
-S_{25 ° C}° (Fe₂O₃-S_{25 ° C}° (Li₂CO₃)
= 2 × 75 + 214−87−90
= 187 [J / ° C · mol] .... Formula (2)
Equilibrium (1-1) standard enthalpy change ΔrH_{25 ° C}° and standard entropy change ΔrS_{25 ° C}From the standard free energy change ΔrG of equilibrium (1-1)_TAsk for °.
ΔrG_T°, ΔrH_{25 ° C}° and ΔrS_{25 ° C}There is a relationship of Equation (3) between °.
ΔrG_T° = ΔrH_{25 ° C}°-(T + 273) × ΔrS_{25 ° C}° / 1000
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2015, 2015, 2015 (1),,,,,,,,,,,,,,,, (,,, (),,,,,,, (),,,,,,,, (),, (),, (),,,,,,,,,,,,,,,,,,,,,, 2015, and (, for example, (3) Expression: (3)
Where ΔrG_T° [kJ / mol] is the change in the standard free energy of equilibrium at T [° C], and ΔrH_{25 ° C}° [kJ / mol] is the change in the standard enthalpy of equilibrium at 25 [° C] and ΔrS_{25 ° C}° [J / ° C · mol] is the change in the standard entropy of equilibrium at 25 [° C].
ΔrG_TThe temperature Teq at which 0 is 0 is given by Equation (4).
Teq = (1000 × ΔrH_{25 ° C}° / ΔrS_{25 ° C}°) -273 ... Formula (4)
When equation (4) is applied to equilibrium (1-1), it is calculated as equation (5).
Teq = (1000 × ΔrH_{25 ° C}° / ΔrS_{25 ° C}°) -273
= (1000 × 146/187) -273
= 508 [° C] Sr ... Formula (5)
From the above calculation, LiFeO is an alkali metal-transition metal composite oxide₂Fe is an oxide consisting only of transition metal elements and oxygen elements₂O₃The lower limit Teq of the temperature generated with higher priority is 508 [° C.].
For the alkali metal salt, the lower limit of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced over the oxide consisting only of the transition metal element and oxygen element is calculated according to the above example. Li as the alkali metal salt₂CO₃When Fe is used, Fe as an oxide composed only of a transition metal element and an oxygen element is used.₂O₃LiFeO as an alkali metal-transition metal composite oxide₂Is represented by equilibrium (1-1). Standard free energy change ΔrG calculated in the above example of equilibrium (1-1)_TThe temperature dependence of ° is shown in FIG.
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and Li can be obtained as an alkali metal salt.₂CO₃When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 508 [° C.].
LiNO as alkali metal salt₃In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (1-2). Standard free energy change ΔrG calculated according to the above example of equilibrium (1-2)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ 2LiNO₃= 2LiFeO₂+ N₂O₅... Equilibrium (1-2)
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and LiNO as an alkali metal salt₃When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 989 [° C.].
Li as alkali metal salt₂SO₄In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (1-3). Standard free energy change ΔrG calculated according to the above example of equilibrium (1-3)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ Li₂SO₄= 2LiFeO₂+ SO₃・ ・ ・ Equilibrium (1-3)
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and Li can be obtained as an alkali metal salt.₂SO₄When Fe is used, Fe that is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is the lower limit Teq of 1507 [° C.].
When LiCl is used as an example of a halide that is an alkali metal salt, Fe as an oxide consisting only of a transition metal element and an oxygen element₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (1-5). Standard free energy change ΔrG calculated according to the above example of equilibrium (1-5)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ 2LiCl + H₂O = 2LiFeO₂+ 2HCl
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ``, `` 8s ,,, 5, ",,,,,,, 5 ,,,,,,,,,,,,,,,,,,,, ()), (,), EX balanced, (1-5), are hereby:
ΔrG_TTeq can be determined from the temperature T at which 0 = 0, and when LiCl is used as the alkali metal salt, Fe, which is an oxide composed only of a transition metal element and an oxygen element, is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 1258 [° C.].
Na as alkali metal salt₂CO₃In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (2-1). Standard free energy change ΔrG calculated according to the above example of equilibrium (2-1)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ Na₂CO₃= 2NaFeO₂+ CO₂・ ・ ・ Equilibrium (2-1)
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and Na can be used as an alkali metal salt.₂CO₃When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 709 [° C.].
NaNO as alkali metal salt₃In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (2-2). Standard free energy change ΔrG calculated according to the above example of equilibrium (2-2)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ 2NaNO₃= 2NaFeO₂+ N₂O₅... Equilibrium (2-2)
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and NaNO as an alkali metal salt₃When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 1497 [° C.].
Na as alkali metal salt₂SO₄In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (2-3). Standard free energy change ΔrG calculated according to the above example of equilibrium (2-3)_TThe temperature dependence of ° is shown in FIG.
Fe₂O₃+ Na₂SO₄= 2NaFeO₂+ SO₃・ ・ ・ Equilibrium (2-3)
ΔrG_TTeq can be obtained from the temperature T at which 0 = 0, and Na can be used as an alkali metal salt.₂SO₄When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 1979 [° C.].
Na as alkali metal salt₃PO₄In the case of using Fe, as an oxide consisting only of a transition metal element and an oxygen element, Fe₂O₃And LiFeO as alkali metal-transition metal composite oxide₂Is represented by equilibrium (2-4). Standard free energy change ΔrG calculated according to the above example of equilibrium (2-4)_TThe temperature dependence of ° is shown in FIG.
1 / 2Fe₂O₃+ 1 / 3Na₃PO₄= NaFeO₂+ 1 / 6P₂O₅
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,, ``, `` ``, ``) `` Worms) '' ... Balance (2-4)
ΔrG<sub>T</sub>Teq can be obtained from the temperature T at which 0 = 0, and Na can be used as an alkali metal salt.<sub>3</sub>PO<sub>4</sub>When Fe is used, Fe which is an oxide composed of only a transition metal element and an oxygen element is used.<sub>2</sub>O<sub>3</sub>LiFeO which is an alkali metal-transition metal composite oxide than<sub>2</sub>Is a lower limit Teq of 3196 [° C.].
When NaCl is used as an example of a halide that is an alkali metal salt, Fe is used as an oxide composed only of a transition metal element and an oxygen element.<sub>2</sub>O<sub>3</sub>And LiFeO as alkali metal-transition metal composite oxide<sub>2</sub>Is represented by equilibrium (2-5). Standard free energy change ΔrG calculated according to the above example of equilibrium (2-5)<sub>T</sub>The temperature dependence of ° is shown in FIG.
Fe<sub>2</sub>O<sub>3</sub>+ 2NaCl + H<sub>2</sub>O = 2NaFeO<sub>2</sub>+ 2HCl
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, parts, `` `` or ": This time (2-5): Equilibrium (2-5)
ΔrG_TTeq can be determined from the temperature T at which 0 = 0, and when LiCl is used as the alkali metal salt, Fe, which is an oxide composed only of a transition metal element and an oxygen element, is used.₂O₃LiFeO which is an alkali metal-transition metal composite oxide than₂Is a lower limit Teq of 2095 [° C.].
<Temperature at start of melting of raw material mixture for alkali metal-transition metal composite oxide (Tmp)>
The temperature (Tmp) at the start of melting of the raw material mixture for the alkali metal-transition metal composite oxide indicates the lowest temperature at which a part of the raw material mixture becomes a liquid phase. The temperature (Tmp) at the start of melting of the raw material mixture for the alkali metal-transition metal composite oxide is determined by a thermal analyzer such as a differential thermothermal gravimetric simultaneous measurement device (TG / DTA) device or a differential scanning calorimetry (DSC) device. Obtained by the measurement used. At the temperature at the start of melting of the raw material mixture, the change in calorie measured by the differential thermothermal gravimetric simultaneous measurement device (TG / DTA) or differential scanning calorimetry (DSC) shows the endothermic peak.
<Method for producing alkali metal-transition metal composite oxide>
In the present invention, the alkali metal-transition metal composite oxide is preferably produced by firing the raw material mixture.
The holding temperature in the firing is preferably higher than the temperature (Tmp) at the start of melting of the alkali metal-transition metal composite oxide raw material mixture.
The holding temperature in the firing is an important factor for adjusting the specific surface area of the obtained alkali metal-transition metal composite oxide. Usually, the higher the holding temperature, the smaller the specific surface area. The specific surface area tends to increase as the holding temperature decreases. The holding time at the holding temperature is usually 0.1 to 20 hours, preferably 0.5 to 8 hours. The rate of temperature rise to the holding temperature is usually 50 to 400 ° C./hour, and the rate of temperature drop from the holding temperature to room temperature is usually 10 to 400 ° C./hour. The flux may remain in the alkali metal-transition metal composite oxide or may be removed by washing, decomposition, evaporation, or the like.
Further, after firing, the obtained alkali metal-transition metal composite oxide may be pulverized using a ball mill, a jet mill or the like. It may be possible to adjust the specific surface area of the alkali metal-transition metal composite oxide by grinding. Moreover, you may repeat baking and grinding | pulverization twice or more. Further, the alkali metal-transition metal composite oxide can be washed or classified as necessary.
The alkali metal-transition metal composite oxide obtained using the raw material mixture of the present invention is useful as a positive electrode active material for non-aqueous electrolyte secondary batteries that require high output characteristics.
The alkali metal-transition metal composite oxide obtained using the raw material mixture of the present invention is usually composed of primary particles having a particle size of 0.05 to 1 μm. The particle size of the primary particles can be measured from an electron micrograph of an alkali metal-transition metal composite oxide.
The crystal structure of the alkali metal-transition metal composite oxide obtained using the raw material mixture of the present invention is preferably a layered structure. Furthermore, in order to increase the discharge capacity of the nonaqueous electrolyte secondary battery, it is preferable that the crystal structure belongs to the R-3m or C2 / m space group. The space group R-3m is included in the hexagonal crystal structure. The hexagonal crystal structure is P3, P3₁, P3₂, R3, P-3, R-3, P312, P321, P3₁12, P3₁21, P3₂12, P3₂21, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6₁, P6₅, P6₂, P6₄, P6₃, P-6, P6 / m, P6₃/ M, P622, P6₁22, P6₅22, P6₂22, P6₄22, P6₃22, P6mm, P6cc, P6₃cm, P6₃mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6₃/ Mcm and P6₃It belongs to any one space group selected from the group consisting of / mmc. The space group C2 / m is included in the monoclinic crystal structure. The monoclinic crystal structure is P2, P2₁, C2, Pm, Pc, Cm, Cc, P2 / m, P2₁/ M, C2 / m, P2 / c, P2₁It belongs to any one space group selected from the group consisting of / c and C2 / c. The crystal structure of the alkali metal-transition metal composite oxide can be identified from a powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement. CuKα rays, CoKα rays, MoKα rays and WKα rays can be used as the X-ray source in the powder X-ray diffraction measurement.
In the present invention, when the transition metal element constituting the alkali metal-transition metal composite oxide is one or more transition metal elements selected from the group consisting of Ni, Mn, Co and Fe, the present invention A part of the transition metal element may be substituted with another element as long as the above effect is not impaired. Here, as other elements, B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Zr, Hf, Nb, Ta, Cr, Mo, W, Ru, Rh, Ir, Pd, Examples of the element include Cu, Ag, and Zn.
In addition, a compound different from the oxide may be attached to the surface of the particles of the alkali metal-transition metal composite oxide of the present invention as long as the effects of the present invention are not impaired. The compound is a compound composed of one or more elements selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg and a transition metal element, preferably B, Al, A compound composed of one or more elements selected from the group consisting of Mg, Ga, In and Sn, more preferably an Al compound. Specific examples of the compound include oxides, hydroxides, oxyhydroxides, carbonates, nitrates, and organic acid salts of the above elements, preferably oxides, hydroxides, and oxyhydroxides. It is a thing. Moreover, you may use these compounds in mixture. Among these compounds, a particularly preferred compound is alumina. Moreover, you may heat after adhesion.
The positive electrode active material having an alkali metal-transition metal composite oxide obtained by the method of the present invention is suitable for a non-aqueous electrolyte secondary battery.
<Production of positive electrode>
Next, as a method for producing a positive electrode using the positive electrode active material, a case of producing a positive electrode for a non-aqueous electrolyte secondary battery will be described as an example.
The positive electrode can be produced by supporting a positive electrode mixture containing a positive electrode active material, a conductive material and a binder on a positive electrode current collector.
A carbon material can be used as the conductive material, and examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and fibrous carbon material. By increasing the proportion of the conductive material in the positive electrode, the conductivity of the positive electrode is increased, and charge / discharge efficiency and rate characteristics can be improved. If the proportion of the conductive material in the positive electrode is too large, the binding property between the positive electrode mixture and the positive electrode current collector may decrease, and the internal resistance may increase. Usually, the proportion of the conductive material in the positive electrode mixture is 5 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material.
When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered. Moreover, carbon black can add the small amount in a positive electrode mixture, can improve the electroconductivity inside a positive electrode, and can improve the charging / discharging efficiency and rate characteristic of the battery obtained.
Examples of the binder include thermoplastic resins, and specifically, polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), and tetrafluoroethylene.・ Fluorine resin such as hexafluoropropylene / vinylidene fluoride copolymer, hexafluoropropylene / vinylidene fluoride copolymer and tetrafluoroethylene / perfluorovinyl ether copolymer; polyolefin such as polyethylene and polypropylene Resin; Moreover, you may mix and use these 2 or more types of thermoplastic resins. In addition, a fluorine resin and a polyolefin resin are used as a binder, and the positive electrode mixture has a ratio of 1 to 10% by weight of the fluororesin in 100% by weight of the positive electrode mixture and 0.1 to 2% by weight of the polyolefin resin. When the mixture contains these, a positive electrode mixture having excellent binding properties with the positive electrode current collector can be obtained.
As the positive electrode current collector, a conductor such as Al, Ni, or stainless steel can be used. Furthermore, Al is preferable because it is easy to process into a thin film and is inexpensive. Examples of the method of supporting the positive electrode mixture on the positive electrode current collector include a method of pressure molding; a method of fixing the positive electrode mixture to the positive electrode current collector using a positive electrode mixture paste.
The positive electrode mixture paste contains a positive electrode active material, a conductive material, a binder, and a solvent. The positive electrode mixture paste is applied to the positive electrode current collector, dried, and the obtained sheet is pressed to fix the positive electrode mixture to the positive electrode current collector.
As the solvent, an aqueous solvent or an organic solvent can be used. You may add a thickener to a solvent as needed. Examples of the thickener include carboxymethyl cellulose, sodium polyacrylate, polyvinyl alcohol and polyvinyl pyrrolidone.
Examples of the organic solvent include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; dimethylacetamide, N And amide solvents such as methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).
Examples of the method of applying the positive electrode mixture paste to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method.
As described above, a positive electrode for a non-aqueous electrolyte secondary battery can be manufactured.
<Nonaqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery will be described using the positive electrode. For example, in a lithium secondary battery, an electrode group is produced by laminating or laminating and winding a separator, a negative electrode, and the positive electrode, and the electrode group is accommodated in a battery case, and an electrolytic solution is stored in the battery. It can manufacture by the method of inject | pouring in a case.
Examples of the shape of the electrode group include a circle, an ellipse, a rectangle, and a rectangle with rounded corners when the electrode group is cut in a direction perpendicular to the winding axis. . Further, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.
<Negative electrode>
The negative electrode can be doped and dedoped with lithium ions at a lower potential than the positive electrode. Examples of the negative electrode include an electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector; an electrode made of a negative electrode active material alone. Examples of the negative electrode active material include carbon materials, chalcogen compounds (oxides, sulfides, and the like), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. It is done. You may mix and use these negative electrode active materials.
The negative electrode active material is exemplified below.
Specific examples of the carbon material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds.
As an example of the oxide, specifically, SiO₂, SiO etc. formula SiO_x(Wherein x is a positive real number) silicon oxide represented by: TiO₂TiO, formula TiO_x(Where x is a positive real number) titanium oxide; V₂O₅, VO₂Etc. VO_x(Where x is a positive real number) oxide of vanadium; Fe₃O₄, Fe₂O₃FeO and other formulas FeO_x(Where x is a positive real number) iron oxide; SnO₂, SnO etc. formula SnO_x(Where x is a positive real number) tin oxide represented by WO₃, WO₂General formula WO_x(Where x is a positive real number)₄Ti₅O₁₂, LiVO₂And a composite metal oxide containing lithium and titanium and / or vanadium.
As the sulfide, specifically, Ti₂S₃TiS₂TiS and other formula TiS_x(Where x is a positive real number) titanium sulfide; V₃S₄, VS_2,VS and other expressions VS_x(Where x is a positive real number) Vanadium sulfide; Fe₃S₄, FeS₂FeS and other formulas_x(Where x is a positive real number) iron sulfide; Mo₂S₃, MoS₂Etc. MoS_x(Where x is a positive real number) molybdenum sulfide represented by SnS_2,SnS etc. formula SnS_x(Where x is a positive real number) tin sulfide represented by WS₂Formula WS_x(Where x is a positive real number) tungsten sulfide represented by: Sb₂S₃Etc. SbS_x(Where x is a positive real number) antimony sulfide; Se₅S₃, SeS₂, SeS etc. formula SeS_xSelenium sulfide represented by (where x is a positive real number).
As an example of the nitride, specifically, Li₃N, Li_3-xA_xA lithium-containing nitride such as N (where A is Ni and / or Co and 0 <x <3) can be used.
These carbon materials, oxides, sulfides and nitrides may be used in combination of two or more, and these may be either crystalline or amorphous. Further, these carbon materials, oxides, sulfides and nitrides are mainly carried on the negative electrode current collector and used as electrodes.
Also, specific examples of the metal include lithium metal, silicon metal, and tin metal.
Examples of the alloy include lithium alloys such as Li—Al, Li—Ni, and Li—Si; silicon alloys such as Si—Zn; Sn—Mn, Sn—Co, Sn—Ni, Sn—Cu, and Sn. -Tin alloys such as La; Cu₂Sb, La₃Ni₂Sn₇And alloys thereof.
Among the negative electrode active materials, carbon materials containing graphite as a main component such as natural graphite and artificial graphite are preferably used because of good potential flatness, low average discharge potential, and good cycleability. Examples of the shape of the carbon material include flakes such as natural graphite, spheres such as mesocarbon microbeads, and fibers such as graphitized carbon fibers. The carbon material may be a fine powder aggregate.
The negative electrode mixture may contain a binder as necessary. Examples of the binder include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.
Examples of the negative electrode current collector include Cu, Ni, stainless steel and the like, and Cu is preferable because it is difficult to form an alloy with lithium and it can be easily processed into a thin film.
The method of supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode, and is a method of pressure molding; a method of fixing the negative electrode mixture to the negative electrode current collector using a negative electrode mixture paste. Can be mentioned.
<Separator>
As the separator, for example, a member made of a material such as a polyolefin resin such as polyethylene or polypropylene, a fluororesin, a nitrogen-containing aromatic polymer, or the like having a form such as a porous membrane, a nonwoven fabric, or a woven fabric can be used. The separator may be made of two or more kinds of the materials, or may be a laminated separator in which the members are laminated. Examples of the separator include separators described in JP 2000-30686 A, JP 10-324758 A, and the like. The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 40 μm, in that the volume energy density of the battery is increased and the internal resistance is reduced. The separator is preferably thin as long as the mechanical strength is maintained.
The separator preferably has a porous film containing a thermoplastic resin. In the nonaqueous electrolyte secondary battery, the separator is disposed between the positive electrode and the negative electrode. The separator preferably has a function (shutdown function) that blocks an electric current and prevents an excessive current from flowing when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode. Here, the shutdown is performed by closing the micropores of the porous film in the separator when the normal use temperature is exceeded. After the shutdown, even if the temperature in the battery rises to a certain high temperature, it is preferable to maintain the shutdown state without breaking the film due to the temperature. Examples of such a separator include a laminated film in which a heat-resistant porous layer and a porous film are laminated with each other. By using the film as a separator, the heat resistance of the secondary battery is further improved. The heat resistant porous layer may be laminated on both surfaces of the porous film.
<Laminated film>
Hereinafter, a laminated film in which the heat resistant porous layer and the porous film are laminated to each other will be described.
In the laminated film, the heat resistant porous layer is a layer having higher heat resistance than the porous film, and the heat resistant porous layer may be formed of an inorganic powder or may contain a heat resistant resin. When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can be formed by an easy technique such as coating.
Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyetherketone, aromatic polyester, polyethersulfone and polyetherimide. In order to further improve the heat resistance, polyamide, polyimide, polyamideimide, polyethersulfone and polyetherimide are preferable. More preferably, it is polyamide, polyimide or polyamideimide. Even more preferred are nitrogen-containing aromatic polymers such as aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides), aromatic polyimides, and aromatic polyamideimides. Particularly preferred is an aromatic polyamide, and in terms of production, para-oriented aromatic polyamide (hereinafter sometimes referred to as para-aramid) is particularly preferred.
Also, examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. By using these heat resistant resins, the heat resistance of the laminated film, that is, the thermal film breaking temperature of the laminated film can be further increased.
The thermal film breaking temperature of the laminated film depends on the type of heat-resistant resin and is selected and used according to the use scene and purpose of use. More specifically, as the heat-resistant resin, when the nitrogen-containing aromatic polymer is used, the cyclic olefin polymer is about 400 ° C., and when poly-4-methylpentene-1 is used, the temperature is about 250 ° C. When using, the thermal film breaking temperature can be controlled to about 300 ° C., respectively. Further, when the heat resistant porous layer is made of inorganic powder, the thermal film breaking temperature can be controlled to 500 ° C. or higher.
The para-aramid is obtained by polycondensation of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide. , 1 and 5 positions in naphthalene, and 2 and 6 positions in naphthalene).
Specific examples of para-aramid include poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide) , Poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, etc. Or the para-aramid which has a structure according to a para orientation type is mentioned.
The aromatic polyimide is preferably a wholly aromatic polyimide produced by condensation polymerization of an aromatic dianhydride and a diamine.
Specific examples of the dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic Examples include acid dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride.
Specific examples of the diamine include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobenzophenone, 3,3′-diaminodiphenylsulfone and 1,5. -Naphthalenediamine.
Also, a solvent-soluble polyimide can be preferably used. Examples of such a polyimide include a polycondensate polyimide of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.
Examples of the aromatic polyamideimide include those obtained by condensation polymerization of aromatic dicarboxylic acid and aromatic diisocyanate, and those obtained by condensation polymerization of aromatic diacid anhydride and aromatic diisocyanate.
Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. A specific example of the aromatic dianhydride is trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, orthotolylane diisocyanate, and m-xylene diisocyanate.
In order to further enhance the ion permeability, the thickness of the heat resistant porous layer is preferably 1 to 10 μm, more preferably 1 to 5 μm, and particularly preferably 1 to 4 μm. The heat-resistant porous layer has fine pores, and the pore diameter is usually 3 μm or less, preferably 1 μm or less.
In addition, when the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can also contain a filler described later.
In the laminated film, the porous film has fine pores. The porous film preferably has a shutdown function. In this case, the porous film contains a thermoplastic resin. The size (diameter) of the micropores in the porous film is usually 3 μm or less, preferably 1 μm or less. The porosity of the porous film is usually 30 to 80% by volume, preferably 40 to 70% by volume.
When a non-aqueous electrolyte secondary battery using a porous film containing a thermoplastic resin as a separator exceeds the normal use temperature, the thermoplastic resin softens and closes the micropores of the porous film.
As the thermoplastic resin, one that does not dissolve in the electrolyte solution in the nonaqueous electrolyte secondary battery is selected. Specific examples of such a thermoplastic resin include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins, and two or more thermoplastic resins may be mixed and used. In order to soften and shut down at a lower temperature, the porous film preferably contains polyethylene. Specific examples of the polyethylene include low density polyethylene, high density polyethylene, linear polyethylene, and ultrahigh molecular weight polyethylene having a molecular weight of 1,000,000 or more. The porous film preferably contains ultra high molecular weight polyethylene in order to further increase the piercing strength of the film. In order to easily produce a porous film, the thermoplastic resin may preferably contain a wax composed of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less.
In addition, the thickness of the porous film in the laminated film is usually 3 to 30 μm, preferably 3 to 25 μm. In the present invention, the thickness of the laminated film is usually 40 μm or less, preferably 20 μm or less. Moreover, when the thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1 or less.
When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer may contain one or more fillers. The filler may be selected from any of organic powder, inorganic powder, or a mixture thereof. The average particle diameter of the particles constituting the filler is preferably 0.01 to 1 μm.
Examples of the organic powder include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or a copolymer of two or more types; polytetrafluoroethylene, 4 fluorine, and the like. Fluorinated resins such as fluorinated ethylene-6propylene copolymer, tetrafluoroethylene-ethylene copolymer, PVdF; melamine resin; urea resin; polyolefin;
The organic powder may be used alone or in combination of two or more. Among these organic powders, polytetrafluoroethylene powder is preferable from the viewpoint of chemical stability.
Examples of the inorganic powder include powders made of inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates and sulfates. Among these, powder made of an inorganic material having low conductivity is preferably used. Specific examples of preferred inorganic powders include powders made of alumina, silica, titanium dioxide or calcium carbonate. An inorganic powder may be used independently and can also be used in mixture of 2 or more types. Among these inorganic powders, alumina powder is preferable from the viewpoint of chemical stability. More preferably, the filler is only alumina particles. More preferably, some or all of the alumina particles constituting the filler are substantially spherical.
When the heat-resistant porous layer is composed of an inorganic powder, the inorganic powder exemplified above may be used, and may be mixed with a binder as necessary.
When all the particles constituting the filler are alumina particles, the filler weight ratio is usually 5 to 95 parts by weight with respect to 100 parts by weight of the total heat-resistant porous layer, preferably 20 to The amount is 95 parts by weight, more preferably 30 to 90 parts by weight. These ranges can be appropriately set depending on the specific gravity of the filler material.
As the shape of the filler, there are a substantially spherical shape, a plate shape, a columnar shape, a needle shape, a whisker shape and a fiber shape, and since it is easy to form a uniform hole, a substantially spherical shape is preferable. Examples of the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) of 1 to 1.5. The aspect ratio of the particles can be measured from an electron micrograph.
In order to enhance ion permeability in the secondary battery, the air permeability of the separator by the Gurley method is preferably 50 to 300 seconds / 100 cc, and more preferably 50 to 200 seconds / 100 cc. Further, the porosity of the separator is usually 30 to 80% by volume, preferably 40 to 70% by volume. The separator may be a laminate of separators having different porosity.
<Electrolytic solution and solid electrolyte>
In a secondary battery, the electrolytic solution is usually composed of an electrolyte and an organic solvent. Examples of electrolytes include perchlorates with alkali metal cations, phosphorus hexafluoride salts, arsenic hexafluoride salts, antimony hexafluoride salts, boron tetrafluoride salts, trifluoromethanesulfonate salts, sulfonamide compounds Trifluoromethanesulfonate, boron compound salt and borate. A mixture of two or more of these may be used.
As an example of lithium salt, LiClO₄, LiPF₆, LiAsF₆, LiSbF₆, LiBF₄, LiCF₃SO₃, LiN (SO₂CF₃)₂, LiN (SO₂C₂F₅)₂, LiN (SO₂CF₃) (COCF₃), Li (C₄F₉SO₃), LiC (SO₂CF₃)₃, Li₂B₁₀Cl₁₀, LiBOB (where BOB is bis (oxalate) boreate), lower aliphatic carboxylic acid lithium salt, LiAlCl₄Etc. Usually, among these, LiPF₆, LiAsF₆, LiSbF₆, LiBF₄, LiCF₃SO₃, LiN (SO₂CF₃)₂And LiC (SO₂CF₃)₃One or more fluorine-containing lithium salts selected from the group consisting of:
In the electrolytic solution, as an organic solvent, propylene carbonate, ethylene carbonate (hereinafter sometimes referred to as EC), dimethyl carbonate (hereinafter sometimes referred to as DMC), diethyl carbonate, ethyl methyl carbonate (hereinafter referred to as EMC). Carbonates such as 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, Ethers such as pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; Nitriles such as ril and butyronitrile; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidone; Sulfolane, dimethyl sulfoxide and 1,3-propane sultone And sulfur-containing compounds such as Moreover, what introduce | transduced the fluorine substituent further into the said organic solvent can be used.
Usually, a mixed solvent in which two or more of the organic solvents are mixed is used. Among these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate or a mixed solvent of cyclic carbonate and ethers is more preferable. As a mixed solvent of cyclic carbonate and non-cyclic carbonate, it has a wide operating temperature range, excellent load characteristics, and is hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. In this respect, a mixed solvent containing EC, DMC and EMC is preferable.
Also, since it has the effect of improving safety in particular, LiPF₆It is preferable to use an electrolytic solution containing a fluorine-containing alkali metal salt such as an organic solvent having a fluorine substituent. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and DMC is excellent in large current discharge characteristics, and more preferable. .
A solid electrolyte may be used instead of the electrolytic solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer, a polymer containing at least one of a polyorganosiloxane chain and a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained electrolyte solution to the polymer | macromolecule can also be used. Li₂S-SiS₂, Li₂S-GeS₂, Li₂SP₂S₅, Li₂SB₂S₃, Li₂S-SiS₂-Li₃PO₄, Li₂S-SiS₂-Li₂SO₄An inorganic solid electrolyte containing a sulfide such as may be used. Using these solid electrolytes, safety may be further improved. In the nonaqueous electrolyte secondary battery of the present invention, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

Next, the present invention will be described in more detail with reference to examples. The measurement of the physical properties of the alkali metal-transition metal composite oxide and the charge / discharge test using the battery using the alkali metal-transition metal composite oxide as the positive electrode active material were performed as follows.
<Charge / Discharge Test with Battery Using Alkali Metal-Transition Metal Composite Oxide as Positive Electrode Active Material>
1. Charge / Discharge Test A positive electrode active material, a conductive material, and a binder solution were prepared. The weight ratio of positive electrode active material: conductive material: binder was 87: 10: 3, respectively. These were kneaded using an agate mortar to prepare a positive electrode mixture paste. Here, the conductive material used was a mixture of acetylene black and graphite in a weight ratio of 1: 9. As the binder solution, an NMP solution in which PVdF (binder) was dissolved was used. The positive electrode mixture paste was applied to an Al foil current collector and then vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode.
The obtained positive electrode, electrolytic solution, separator, and negative electrode were combined to produce a nonaqueous electrolyte secondary battery (coin type battery R2032). The battery was assembled in a glove box in an argon atmosphere. As a solvent in the electrolytic solution, a mixed solvent in which EC, DMC, and EMC were each in a volume ratio of 30:35:35 was used. LiPF ₆ was used as the electrolyte. An electrolytic solution was produced by dissolving the electrolyte in a mixed solvent. The electrolyte concentration was adjusted to 1 mol / liter. A laminated film separator in which a heat resistant porous layer was laminated on a polyethylene porous film was used as a separator. Moreover, metallic lithium was used as the negative electrode.
Using the coin-type battery, a charge / discharge test was performed under the conditions shown below while maintaining at 25 ° C. In the charge / discharge test, the discharge capacity was measured by changing the discharge current during discharge.
Charging conditions:
Maximum charging voltage 4.3 V, charging time 8 hours, charging current 0.2 mA / cm ²
Discharge conditions:
During discharge, the minimum discharge voltage was kept constant at 2.5 V, and the discharge current in each cycle was changed as follows to perform discharge. It shows that a high output characteristic is acquired, so that the discharge capacity in 10C is large.
First cycle discharge (0.2 C): discharge current 0.2 mA / cm ²
Second cycle discharge (0.2 C): discharge current 0.2 mA / cm ²
3rd cycle discharge (1C): discharge current 1.0 mA / cm ²
4th cycle discharge (2C): discharge current 2.0 mA / cm ²
Discharge at the fifth cycle (5C): discharge current 5.0 mA / cm ²
<Measurement of physical properties of alkali metal-transition metal composite oxide>
2. Powder X-ray diffraction measurement of alkali metal-transition metal composite oxide RINT2500TTR type manufactured by Rigaku Corporation was used for powder X-ray diffraction measurement of alkali metal-transition metal composite oxide. A CuKα radiation source was used as the X-ray radiation source. An alkali metal-transition metal composite oxide was filled in a dedicated holder, and the diffraction angle was 2θ = 10 to 90 ° to obtain a powder X-ray diffraction pattern.
3. Measurement of specific surface area of alkali metal-transition metal composite oxide After drying 0.5 g of alkali metal-transition metal composite oxide in a nitrogen atmosphere at 150 ° C. for 15 minutes, the BET specific surface area was measured using Micromerix Flowsorb II2300. Was measured. The BET specific surface area measured by the above method was defined as the specific surface area of the alkali metal-transition metal composite oxide.
4). Measurement of the temperature at the start of melting of the raw material mixture using a differential thermothermal gravimetric simultaneous measurement device (SII Nano Technology Co., Ltd., TG / DTA6000) was used. About 5 mg of the raw material mixture was put in a platinum pan and installed in the apparatus. In an air atmosphere, a range from room temperature to 1000 ° C. was measured at a rate of temperature increase of 10 ° C./min. The temperature at the start of melting was judged from the endothermic peak appearing in the differential heat measurement.
Example 1
<Production of transition metal compound>
In a polypropylene beaker, potassium hydroxide was added to distilled water so as to be 10% by weight. Furthermore, it stirred and potassium hydroxide was dissolved completely and potassium hydroxide aqueous solution was prepared as alkaline aqueous solution. In a glass beaker, manganese (II) sulfate monohydrate in 200 ml of distilled water so that the nickel (II) sulfate hexahydrate is 10 wt% based on the target nickel-manganese-iron mixed aqueous solution. Iron (II) sulfate heptahydrate was further added to 1 wt% so that the sum was 7 wt%. Further, the transition metal salt was completely dissolved by stirring to obtain a nickel-manganese-iron mixed aqueous solution. While stirring the potassium hydroxide aqueous solution, the nickel-manganese-iron mixed aqueous solution was added dropwise thereto. A coprecipitate was formed in the aqueous solution to obtain a coprecipitate slurry. Next, the coprecipitate slurry was filtered and washed with distilled water, and dried at 120 ° C. to obtain a coprecipitate.
<Preparation of raw material mixture for alkali metal-transition metal composite oxide>
When the total amount of transition metal elements (nickel, manganese, iron) constituting the transition metal compound is 100 moles, lithium in the alkali metal salt is prepared to be 130 moles. It adjusted so that it might become a mole.
A coprecipitate as a transition metal compound, lithium carbonate as an alkali metal salt, and potassium sulfate as a flux composed of an inorganic salt were dry-mixed using an agate mortar to obtain a raw material mixture A ^M1 .
<Temperature at the start of melting of raw material mixture for alkali metal-transition metal composite oxide>
Temperature at the melting start of the differential thermogravimetric simultaneous analysis device A ^M1 was determined by (Tmp) was 577 ° C.. Melting starting temperature A ^M1 (Tmp = 577 ℃) are alkali metal than the oxide consisting only of transition metal elements and oxygen elements when using lithium carbonate as the alkali metal salts - transition metal composite oxide is preferentially Thus, the temperature was higher than the lower limit of the temperature to be generated (Teq = 508 ° C.).
<Preparation of alkali metal-transition metal composite oxide by firing>
10 g of the mixture was placed in an alumina firing container and placed in an electric furnace. In the electric furnace in which the air was circulated at a rate of 5 L / min, the mixture was heated to 870 ° C. and kept at that temperature for 6 hours for firing. Then, it cooled to room temperature and obtained the baked product. It was ground, washed with distilled water by decantation, filtered and dried for 8 hours at 100 ° C., an alkali metal - was obtained A ¹ as the transition metal complex oxide.
<Physical Properties of Alkali Metal-Transition Metal Composite Oxide and Charge / Discharge Test Using the Oxide as Positive Electrode Active Material>
And the specific surface area of A ^1, and the crystal structure and a discharge capacity measured in the charge and discharge test by a coin type battery in which the A ¹ and the positive electrode active material shown in Table 2. Comparing the discharge capacity at 5C, than the value of the coin-type battery in which a positive electrode active material B ² in B ¹ and Comparative Example 2 in Comparative Example 1 below, respectively, the coin-type battery in which the A ¹ and the positive electrode active material The value was larger.
Example 2
<Production of transition metal compound>
A coprecipitate was obtained in the same manner as in Example 1.
<Preparation of raw material mixture for alkali metal-transition metal composite oxide>
When the total amount of transition metal elements (nickel, manganese, iron) constituting the transition metal compound is 100 moles, lithium in the alkali metal salt is prepared to be 130 moles. It adjusted so that it might become a mole. A coprecipitate as a transition metal compound, lithium carbonate as an alkali metal salt, and potassium sulfate as a flux composed of an inorganic salt were dry-mixed using an agate mortar to obtain a raw material mixture ^AM2 .
<Temperature at the start of melting of raw material mixture for alkali metal-transition metal composite oxide>
Differential thermogravimetric simultaneous measurement device with the temperature at the melting start of the measured A ^M2 (Tmp) was 577 ° C.. Temperature at the melting start of A ^M2 (Tmp = 577 ℃) are alkali metal than the oxide consisting only of transition metal elements and oxygen elements when using lithium carbonate as the alkali metal salts - transition metal composite oxide is preferentially Thus, the temperature was higher than the lower limit of the temperature to be generated (Teq = 508 ° C.).
<Preparation of alkali metal-transition metal composite oxide by firing>
10 g of the mixture was placed in an alumina firing container and placed in an electric furnace. In the electric furnace in which air was circulated at a rate of 5 L / min, the mixture was heated to 850 ° C. and held at that temperature for 6 hours for firing. Then, it cooled to room temperature and obtained the baked product. This was pulverized, washed with decantation with distilled water, filtered, and dried at 100 ° C. for 8 hours to obtain A ² as an alkali metal-transition metal composite oxide.
<Physical Properties of Alkali Metal-Transition Metal Composite Oxide and Charge / Discharge Test Using the Oxide as Positive Electrode Active Material>
And a specific surface area of A ^2, and the crystal structure and a discharge capacity measured in the charge and discharge test by a coin type battery in which the A ² as a positive electrode active material shown in Table 2. Comparing the discharge capacity at 5C, than the value of the coin-type battery in which a positive electrode active material B ² in B ¹ and Comparative Example 2 in Comparative Example 1 below, respectively, the coin-type battery in which the A ² as a positive electrode active material The value was larger.
Comparative Example 1
<Production of transition metal compound>
A coprecipitate was obtained in the same manner as in Example 1.
<Preparation of raw material mixture for alkali metal-transition metal composite oxide>
When the total amount of transition metal elements (nickel, manganese, iron) constituting the transition metal compound is 100 moles, lithium in the alkali metal salt is prepared to be 130 moles. It adjusted so that it might become a mole. A coprecipitate as a transition metal compound, lithium carbonate as an alkali metal salt, and potassium carbonate as a flux composed of an inorganic salt were dry-mixed using an agate mortar to obtain a raw material mixture B ^M1 .
<Temperature at the start of melting of raw material mixture for alkali metal-transition metal composite oxide>
Differential thermogravimetric simultaneous measurement device with the temperature at the melting start of the measured B ^M1 (Tmp) was 490 ° C.. As for the temperature at the start of melting of B ^M1 (Tmp = 490 ° C.), the alkali metal-transition metal composite oxide has priority over the oxide composed only of the transition metal element and oxygen element when lithium carbonate is used as the alkali metal salt. Thus, the temperature was lower than the lower limit of the temperature to be generated (Teq = 508 ° C.).
<Preparation of alkali metal-transition metal composite oxide by firing>
Then, fired under the same conditions as in Example 1, after grinding, washing, the process of drying, the alkali metal - was obtained B ¹ as the transition metal complex oxide.
<Physical Properties of Alkali Metal-Transition Metal Composite Oxide and Charge / Discharge Test Using the Oxide as Positive Electrode Active Material>
And the specific surface area of B ^1, and the crystal structure, the B ¹ and the discharge capacity measured in the charge and discharge test by a coin type battery was a positive electrode active material shown in Table 2.
Comparative Example 2
<Production of transition metal compound>
In a polypropylene beaker, potassium hydroxide was added to distilled water at 30% by weight. Furthermore, it stirred and potassium hydroxide was dissolved completely and potassium hydroxide aqueous solution was prepared as alkaline aqueous solution. In a glass beaker, 200 ml of distilled water is mixed with manganese (II) chloride tetrahydrate so that nickel chloride (II) hexahydrate is 7% by weight based on the target nickel-manganese-iron mixed aqueous solution. Iron (II) chloride heptahydrate was further added to 1 wt% so that the sum was 6 wt%. Further, the transition metal salt was completely dissolved by stirring to obtain a nickel-manganese-iron mixed aqueous solution. While stirring the potassium hydroxide aqueous solution, the nickel-manganese-iron mixed aqueous solution was added dropwise thereto. A coprecipitate was formed in the aqueous solution to obtain a coprecipitate slurry. Next, the coprecipitate slurry was filtered and washed with distilled water, and dried at 100 ° C. to obtain a coprecipitate.
<Preparation of raw material mixture for alkali metal-transition metal composite oxide>
When the total amount of transition metal elements (nickel, manganese, iron) constituting the transition metal compound is 100 moles, lithium in the alkali metal salt is prepared to be 130 moles. It prepared so that it might become a mole. A coprecipitate as a transition metal compound, lithium carbonate as an alkali metal salt, and potassium carbonate and potassium sulfate as a flux composed of an inorganic salt were dry-mixed using an agate mortar to obtain a raw material mixture ^BM2 .
<Temperature at the start of melting of raw material mixture for alkali metal-transition metal composite oxide>
Differential thermogravimetric simultaneous measurement device with the temperature at the melting start of the measured B ^M2 (Tmp) was 470 ° C.. Temperature at the melting start of B ^M2 (Tmp = 470 ℃) are alkali metal when using lithium carbonate as the alkali metal salts - priority of an oxide transition metal composite oxide composed only of transition metal element and oxygen element Thus, the temperature was lower than the lower limit of the temperature to be generated (Teq = 508 ° C.).
<Preparation of alkali metal-transition metal composite oxide by firing>
10 g of the mixture was placed in an alumina firing container and placed in an electric furnace. In the electric furnace in which air was circulated at a rate of 5 L / min, the mixture was heated to 850 ° C. and held at that temperature for 6 hours for firing. Then, it cooled to room temperature and obtained the baked product. This was pulverized, washed with decantation with distilled water, filtered, and dried at 100 ° C. for 8 hours to obtain B ² as an alkali metal-transition metal composite oxide.
<Physical Properties of Alkali Metal-Transition Metal Composite Oxide and Charge / Discharge Test Using the Oxide as Positive Electrode Active Material>
Table 2 shows the specific surface area of B ² , the crystal structure, and the discharge capacity measured in the charge / discharge test using a coin-type battery using B ² as the positive electrode active material. However, in the charge / discharge test of Comparative Example 2, the measurement of the discharge capacity at 2C was not performed.
Production Example 1 (Production of laminated film)
(1) Production of Coating Slurry After 272.7 g of calcium chloride was dissolved in 4200 g of NMP, 132.9 g of paraphenylenediamine was added thereto and completely dissolved. To the obtained solution, 243.3 g of terephthalic acid dichloride was gradually added for polymerization to obtain para-aramid, and further diluted with NMP to obtain a para-aramid solution (A) having a concentration of 2.0% by weight. To 100 g of the obtained para-aramid solution, 2 g of alumina powder (a) (manufactured by Nippon Aerosil Co., Ltd., alumina C, average particle size 0.02 μm) and 2 g of alumina powder (b) (Sumitomo Chemical Co., Ltd. Sumiko Random, AA03, average particles) 4 g in total as a filler was added and mixed, treated three times with a nanomizer, further filtered through a 1000 mesh wire net and degassed under reduced pressure to produce a coating slurry (B). The weight of alumina powder (filler) in the total weight of para-aramid and alumina powder is 67% by weight.
(2) Manufacture and Evaluation of Laminated Film As the porous film, a polyethylene porous film (film thickness 12 μm, air permeability 140 seconds / 100 cc, average pore diameter 0.1 μm, porosity 50%) was used. The polyethylene porous film was fixed on a PET film having a thickness of 100 μm, and the coating slurry (B) was applied onto the porous film with a bar coater manufactured by Tester Sangyo Co., Ltd. The PET film and the coated porous film are integrated into one piece and immersed in water to precipitate a para-aramid porous film (heat resistant porous layer), and then the solvent is dried, and the PET film is peeled off. A laminated film 1 in which the heat-resistant porous layer and the porous film were laminated was obtained. The thickness of the laminated film 1 was 16 μm, and the thickness of the para-aramid porous film (heat resistant porous layer) was 4 μm. The air permeability of the laminated film 1 was 180 seconds / 100 cc, and the porosity was 50%. When the cross section of the heat-resistant porous layer in the laminated film 1 was observed with a scanning electron microscope (SEM), relatively small micropores of about 0.03 to 0.06 μm and relatively large micropores of about 0.1 to 1 μm were observed. It was found to have The laminated film was evaluated by the following method.
<Evaluation of laminated film>
(I) Thickness measurement The thickness of the laminated film and the thickness of the porous film were measured in accordance with JIS standards (K7130-1992). Moreover, as the thickness of the heat resistant porous layer, a value obtained by subtracting the thickness of the porous film from the thickness of the laminated film was used.
(Ii) Measurement of air permeability by Gurley method The air permeability of the laminated film was measured with a digital timer type Gurley type densometer manufactured by Yasuda Seiki Seisakusho Co., Ltd. based on JIS P8117.
(Iii) Porosity A sample of the obtained laminated film was cut into a 10 cm long square, and the weight W (g) and the thickness D (cm) were measured. The weight of each layer in the sample (Wi (g); i is an integer from 1 to n) is determined, and the true specific gravity (true specific gravity i (g / cm ³ )) of the material of each layer is determined. The volume of the layer was determined, and the porosity (volume%) was determined from the following formula.
Porosity (volume%) = 100 × {1− (W1 / true specific gravity 1 + W2 / true specific gravity 2 + ·· + Wn / true specific gravity n) / (10 × 10 × D)}

In the alkali metal-transition metal composite oxide produced using the alkali metal-transition metal composite oxide raw material mixture shown in the present invention, the transition metal element and oxygen element which are inert impurities as the positive electrode active material are used. It contains almost no oxide. If the alkali metal-transition metal composite oxide of the present invention is used, a nonaqueous electrolyte secondary battery having a high discharge capacity and high output characteristics can be provided. The secondary battery is particularly useful for non-aqueous electrolyte secondary batteries for applications requiring high output characteristics, for example, power tools such as automobiles and electric tools.

Claims (15)

A raw material mixture for an alkali metal-transition metal composite oxide containing a flux containing an inorganic salt, an alkali metal salt containing a compound different from the flux, and a transition metal compound, and satisfying the following:
Compared to the lower limit (Teq) of the temperature at which the alkali metal-transition metal composite oxide is preferentially produced over the oxide composed only of the transition metal element and oxygen of the transition metal compound during firing of the mixture, the raw material mixture The temperature (Tmp) at the start of melting is high. The inorganic salt is borate, carbonate, nitrate, phosphate, sulfate, vanadate, tungstate, molybdate, niobate and halide (where halide is fluoride, The raw material mixture according to claim 1, which is at least one salt selected from the group consisting of a compound consisting of chloride, bromide and iodide. The raw material mixture according to claim 1 or 2, wherein the cation constituting the inorganic salt is one or more salts selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba. The alkali metal salt is carbonate, sulfate, nitrate, phosphate, and halide (wherein the halide is selected from the group consisting of fluoride, chloride, bromide, and iodide) The raw material mixture according to any one of claims 1 to 3, which is one or more salts selected from the group consisting of: 5. The raw material mixture according to claim 1, wherein the alkali metal element constituting the alkali metal salt is one or more elements selected from the group consisting of Li, Na and K. 6. The raw material mixture according to claim 1, wherein the transition metal element constituting the transition metal compound is one or more elements selected from the group consisting of Mn, Fe, Co, and Ni. 6. The raw material mixture according to claim 1, wherein the transition metal element constituting the transition metal compound is Fe and one or more elements selected from the group consisting of Mn, Co and Ni. A method for producing an alkali metal-transition metal composite oxide, wherein the raw material mixture according to any one of claims 1 to 7 is fired at a temperature higher than a temperature (Tmp) at the start of melting of the raw material mixture. An alkali metal-transition metal composite oxide produced by the method according to claim 8. The alkali metal-transition metal composite oxide according to claim 9, wherein the crystal structure is a layered structure. A positive electrode active material comprising the alkali metal-transition metal composite oxide according to claim 9 or 10. A positive electrode comprising the positive electrode active material according to claim 11. A nonaqueous electrolyte secondary battery having the positive electrode according to claim 12. The nonaqueous electrolyte secondary battery according to claim 13, further comprising a separator. The non-aqueous electrolyte secondary battery according to claim 14, wherein the separator is a laminated film in which a heat-resistant porous layer and a porous film are laminated with each other.

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