JP2012009330A - Lithium ion secondary battery - Google Patents

Abstract

An object of the present invention is to provide a lithium ion secondary battery having excellent cycle characteristics in a lithium ion secondary battery including a negative electrode having an alloy active material as a plurality of columns on the surface of a negative electrode current collector. .
A wound electrode group formed by winding a laminate of a negative electrode sheet, a positive electrode sheet, and a microporous insulating sheet, a non-aqueous electrolyte, and a cylindrical shape containing the electrode group and the non-aqueous electrolyte. A battery case and a sealing member that seals the battery case, wherein the negative electrode sheet occludes a negative electrode current collector having a plurality of convex portions formed on the surface and lithium ions supported by the convex portions. And a plurality of columnar bodies made of an alloy-based active material that can be released, and the positive electrode sheet contains a positive electrode current collector and a positive electrode active material that can occlude and release lithium ions stacked on the positive electrode current collector A lithium ion secondary battery including a positive electrode active material layer and having a gas phase space of 1 to 20% by volume with respect to the total volume of the battery case in a discharge state at the initial stage of the charge / discharge cycle is used.
[Selection] Figure 2

Description

  The present invention relates to a lithium ion secondary battery using, as a negative electrode, an alloy-based active material containing silicon or tin that forms an alloy with lithium during lithium ion storage.

  A lithium ion secondary battery is lightweight, has high electromotive force, and high energy density. For this reason, demand is expanding as a driving power source for various portable electronic devices such as mobile phones, digital still cameras, and notebook personal computers.

  A lithium ion secondary battery (hereinafter also simply referred to as a battery) includes a negative electrode including a negative electrode active material capable of inserting and extracting lithium ions and a positive electrode including a positive electrode active material capable of inserting and extracting lithium ions in a battery case. And a separator that separates them and a non-aqueous electrolyte are accommodated. As the negative electrode active material, a so-called alloy-based active material containing silicon (Si) or tin (Sb) that occludes lithium by forming an alloy in recent years, instead of a carbon material such as graphite that has been widely used conventionally. Adoption of substances is widely studied. This is because the alloy-based active material can achieve higher capacity and higher output than the carbon material.

Since the alloy-based active material has a large capacity, it remarkably expands by charging and remarkably shrinks by discharging. For example, when Si is used as the alloy-based active material, when Si absorbs the maximum amount of lithium ions and changes to Li _4.4 Si, the volume increases about four times. Accordingly, in a battery using an alloy-based active material as a negative electrode, large stress is generated at the interface between the alloy-based active material and the negative electrode current collector that supports the alloy-based active material due to expansion of the alloy-based active material due to charging. The generated stress causes deformation such as wrinkles and warpage in the negative electrode current collector, or causes the alloy-based active material to fall from the negative electrode current collector. As a result, the charge / discharge cycle characteristics of the battery may be deteriorated.

  In order to solve such a problem, for example, as disclosed in Patent Document 1 below, a method of forming an alloy-based active material as a plurality of columnar bodies on the surface of a negative electrode current collector is known. According to such a columnar alloy-based active material, the stress generated due to expansion during charging is relieved to some extent by the voids existing between the columnar bodies.

  By the way, for example, in Patent Document 2 below, in a lithium ion secondary battery using a carbon material as a negative electrode active material, a non-aqueous electrolyte is used at a rate of 2.5 μl or more and 4.5 μl or less per 1 mAh of battery discharge capacity. The lithium ion secondary battery provided with this is disclosed.

JP 2007-207663 A Japanese Patent Laid-Open No. 04-206364

  A lithium ion secondary battery (hereinafter also simply referred to as an alloy secondary battery) provided with a negative electrode having a plurality of columnar bodies made of an alloy active material on the surface of the negative electrode current collector has a large volume expansion of the active material. Therefore, when the amount of the non-aqueous electrolyte contained in the battery case is set to the same level as that of a lithium ion secondary battery equipped with a negative electrode using a carbon material such as graphite, the active material at the time of charging Due to the volume expansion of the battery, there is a risk of deformation of the case, leakage of the non-aqueous electrolyte, and malfunction of a CID (Current Interrupt Device) stored in the battery case. Therefore, in general, the amount of non-aqueous electrolyte contained in the battery case of an alloy secondary battery is larger than the amount of lithium ion secondary battery provided with a negative electrode using a carbon material. The amount needed to be small. However, it has been found that the following problems occur according to the setting of the amount of the non-aqueous electrolyte determined by such a standard.

  For example, as shown in FIG. 6A, in the discharged state, the volume of the gap S formed between the columnar bodies 2 is increased by the contraction of the columnar bodies 2 by releasing lithium ions. . On the other hand, as shown in FIG. 6B, the columnar bodies 2 on the negative electrode are formed between the columnar bodies 2 when the columnar bodies 2 are expanded by occlusion of a large amount of lithium ions in the charged state. The volume of the gap S to be reduced is small. Since the columnar body 2 is contracted in the discharged state, the liquid level of the non-aqueous electrolyte 15 in the battery case 16 is significantly lower than the liquid level in the charged state. Become. Therefore, when the injection amount of the non-aqueous electrolyte is set in accordance with the conventional general standard, the entire surface of the positive electrode active material layer is immersed in the non-aqueous electrolyte when charging and discharging are repeated. However, it was found that in the discharged state, a part of the positive electrode active material layer was not immersed in the non-aqueous electrolyte solution and could be drained.

  In addition, since the space | gap S formed between the columnar bodies 2 on a negative electrode is a small space, once taking in a non-aqueous electrolyte, it tends to be hard to re-release. Furthermore, since the columnar body is composed of only the active material, it has high affinity with the electrolytic solution. Therefore, the non-aqueous electrolyte tends to be unevenly distributed on the negative electrode side, while the positive electrode side tends to be particularly liable to wither. When liquid withering occurs on the positive electrode side, the portion of the positive electrode active material that has not withered liquid occludes lithium excessively in the discharged state, and as a result, the deterioration of the crystal structure is promoted. Cycle characteristics are degraded. As a result of intensive studies to solve such problems, the present invention has been completed.

  That is, an object of the present invention is to provide a lithium ion secondary battery having excellent cycle characteristics in a lithium ion secondary battery having a negative electrode having an alloy active material as a plurality of columnar bodies on the surface of the negative electrode current collector. And

  One aspect of the present invention is a wound electrode group obtained by winding a laminate of a negative electrode sheet, a positive electrode sheet, a positive electrode sheet, and a microporous insulating sheet interposed between the negative electrode sheet, a non-aqueous electrolyte, A negative electrode current collector having a cylindrical battery case containing an electrode group and a non-aqueous electrolyte, and a sealing member for sealing the battery case, the negative electrode sheet having a plurality of convex portions formed on the surface And a plurality of columnar bodies made of an alloy-based active material that can occlude and release lithium ions supported by the convex portions, and the positive electrode sheet comprises a positive electrode current collector and lithium ions laminated on the positive electrode current collector A positive electrode active material layer containing a positive electrode active material capable of occluding and releasing hydrogen, and in a discharge state at the initial stage of a charge / discharge cycle, 1 to 20% by volume of a gas phase space is present with respect to the total volume of the battery case It is a lithium ion secondary battery. According to such a configuration, even after the volume of the void formed between the columnar bodies of the negative electrode is increased by discharge and a large amount of nonaqueous electrolyte is absorbed in the gap between the columnar bodies, the liquid on the positive electrode side Withering can be suppressed. As a result, even when the charge / discharge cycle is repeated, the positive electrode active material is unlikely to deteriorate, so that a lithium ion secondary battery having excellent cycle characteristics can be obtained.

  In order to maintain a high capacity, when the battery case is a 18650 type cylindrical case, it is preferable that the non-aqueous electrolyte is accommodated in a range of 0.7 to 1.5 mL with respect to the battery capacity 1Ah. . Further, when the battery case is a 14400 type cylindrical case, it is preferable that the non-aqueous electrolyte is accommodated in a range of 1.0 to 2.0 mL with respect to the battery capacity 1Ah.

  According to the present invention, it is possible to provide a lithium ion secondary battery having excellent cycle characteristics in a lithium ion secondary battery including a negative electrode having an alloy active material as a plurality of columnar bodies on the surface of a negative electrode current collector. it can.

It is a schematic cross section which shows typically the structure of the negative electrode 10 of this embodiment. It is a schematic cross section which shows the lithium ion secondary battery 20 of this embodiment. It is a top view which shows a state when the winding of the electrode group 14 of this embodiment is removed. FIG. 3 is an explanatory diagram for explaining a change in liquid level in a battery case when a columnar body expands and contracts before and after charging / discharging of the lithium ion secondary battery. It is side surface perspective drawing of the electron beam type vacuum evaporation system 40 used in the Example. It is a cross-sectional schematic diagram for demonstrating the volume change accompanying charging / discharging of the columnar body which consists of an alloy type active material of a negative electrode sheet.

  An embodiment of a lithium ion secondary battery of the present invention will be described with reference to the drawings.

First, a negative electrode sheet 10 having an alloy active material as a plurality of columnar bodies on the surface of a negative electrode current collector will be described in detail with reference to FIG.
FIG. 1 is a schematic cross-sectional view schematically showing the structure of the negative electrode sheet 10 in the present embodiment. In FIG. 1, 1 is a negative electrode current collector having a convex portion 1a formed on the surface, 2 is a columnar body made of an alloy-based active material capable of inserting and extracting lithium ions supported by the convex portion 1a, and S is a columnar body. It is the space | gap formed between two.

  The negative electrode sheet 10 includes a strip-shaped negative electrode current collector 1 having a plurality of convex portions 1a on the surface, and a columnar body 2 made of a negative electrode active material that is an alloy-based active material supported on the surface of the convex portions 1a. A space S is formed between the columnar bodies 2. The voids S become smaller as the columnar body 2 expands as the lithium ions are occluded, and the gap S increases as the columnar body 2 contracts as the lithium ions are released.

The negative electrode current collector 1 is a strip-shaped metal foil made of a metal material such as copper, copper alloy, stainless steel, or nickel, and has a plurality of convex portions 1a. The dimension of each convex part 1a is about 3-15 micrometers in height, for example, and it is preferable that it is about 25-10000 micrometers ^{2 of} bottom areas. Moreover, the density of the convex part 1a is about 10,000 to 10 million pieces / cm < ² >, for example. Moreover, it is preferable that the distance between the axis lines of the adjacent convex part 1a is about 10-100 micrometers, for example. The negative electrode current collector 1 is formed, for example, by roll pressing a metal foil with a roller having a plurality of recesses formed on the surface.

  Each convex part 1a on the surface of the negative electrode current collector 1 supports a plurality of columnar bodies 2 made of an alloy-based active material on the surface.

  The alloy-based active material is a material that occludes lithium by alloying with lithium and reversibly occludes and releases lithium ions under a negative electrode potential. As the alloy-based active material, a silicon-based active material or a tin-based active material is preferably used.

Specific examples of the silicon-based active material include, for example, silicon alone, silicon oxide represented by the formula SiO _a (0.05 <a <1.95), and formula SiC _b (0 <b <1). Silicon carbide, silicon nitride represented by the formula SiN _c (0 <c <4/3), an alloy of silicon and a different element (A), and the like. Specific examples of the different element (A) include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, and the like.

Specific examples of the tin-based active material include, for example, tin alone, tin oxide represented by the formula SnO _d (0 <d <2), tin dioxide (SnO ₂ ), tin nitride, Ni—Sn alloy, Mg -Tin alloys such as -Sn alloy, Fe-Sn alloy, Cu-Sn alloy, Ti-Sn alloy, and tin compounds such as SnSiO ₃ , Ni ₂ Sn ₄ , Mg ₂ Sn, and the like.

  The columnar body 2 is grown on the surface of the convex portion 1a by using, for example, vacuum deposition, sputtering, ion plating, laser ablation, chemical vapor deposition, plasma chemical vapor deposition, thermal spraying, or the like. Can be formed.

  For example, the columnar body 2 preferably has a multilayer structure in which a plurality of unit layers made of an alloy-based active material are sequentially stacked from the surface of the convex portion 1a. Moreover, it is preferable that the average height from the surface of the convex part 1a of the columnar body 2 is 5-30 micrometers, Furthermore, it is about 8-20 micrometers. Moreover, it is preferable that the average maximum width of the cross section of the columnar body 2 is about 5-100 micrometers.

  Next, a cylindrical lithium ion secondary battery 20 of this embodiment provided with the above-described negative electrode sheet 10 as a negative electrode will be described with reference to the schematic cross-sectional view of FIG.

  A lithium ion secondary battery 20 shown in FIG. 2 includes an electrode group 14 and a nonaqueous electrolyte solution 15 accommodated in a battery case 16, and the battery case 16 is sealed with a sealing plate 25. The electrode group 14 is formed by winding a negative electrode sheet 10 and a positive electrode sheet 11 via a separator 12 that is a microporous insulating sheet. The positive electrode lead 21 is drawn from the positive electrode sheet 11 and connected to the positive electrode terminal 26, and the negative electrode lead 22 is drawn from the negative electrode sheet 10 and connected to the bottom of the battery case 16. Insulating rings 27 and 28 are provided on the upper and lower portions of the electrode group 14, respectively. The electrode group 14 and the non-aqueous electrolyte 15 accommodated in the battery case 16 are sealed with a sealing plate 25 provided with a safety valve 29.

  As the battery case 16, for example, an aluminum case, an iron case whose inner surface is nickel-plated, a case made of an aluminum laminate film, or the like can be used. The shape of the battery case may be any shape such as a cylindrical shape or a square shape. From the viewpoint of versatility, a so-called 18650 type cylindrical case (diameter: about 18 mm, height: about 65 mm) and 14400 type cylindrical case (diameter: about 14 mm, height: about 40 mm) are preferable.

  As the positive electrode sheet 11, a positive electrode mixture in which, for example, a positive electrode active material and, if necessary, various conductive agents and a binder are dispersed in an appropriate dispersion medium on the surface of a belt-shaped positive electrode current collector. Are coated, dried and rolled to form a positive electrode active material layer.

  Specific examples of the positive electrode active material include, for example, lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (partially replacing nickel with cobalt). And composite oxides such as lithium manganate and modified products thereof.

  Specific examples of the conductive agent include carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and various graphites. Specific examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, rubber particles having an acrylate unit, and the like. These may be used alone or in combination of two or more.

  The separator 12, the nonaqueous electrolyte solution 15, the battery case 16, and the like are not particularly limited, and various materials known in this field can be used.

  The separator 12 is disposed between the negative electrode sheet 10 and the positive electrode sheet 11. Specifically, for example, a porous sheet of polyolefin such as polyethylene or polypropylene is used. The thickness of the separator 12 is not particularly limited, but is preferably about 10 to 300 μm, more preferably about 10 to 40 μm.

  FIG. 3 is a schematic explanatory diagram when viewed from the positive electrode sheet 11 side when the winding of the electrode group 14 shown in FIG. 1 is unwound. The negative electrode sheet 10, the positive electrode sheet 11, and the separator 12 have a width in the winding axis direction of the separator 12> the negative electrode sheet 10> the positive electrode sheet 11, and the center lines H in the width direction overlap each other. Repeatedly beaten up. By making the width of the separator 12 the largest, a short circuit between the peripheral edge of the negative electrode sheet 10 and the peripheral edge of the positive electrode sheet 11 can be reliably suppressed. Further, by making the relationship of the negative electrode sheet 10> the positive electrode sheet 11, the lithium ions supplied from the positive electrode sheet 11 at the time of charging are formed on the surface of the region where the columnar body 2 of the negative electrode current collector 1 is not formed. It is possible to suppress the formation of so-called dendrites that are precipitated as

  The non-aqueous electrolyte includes a solute (supporting salt) and a non-aqueous solvent, and further includes various additives as necessary. Solutes usually dissolve in non-aqueous solvents.

  Specific examples of the non-aqueous solvent include, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate; chain carbonates such as diethyl carbonate, ethylmethyl carbonate, and dimethyl carbonate; and cyclic carboxyls such as γ-butyrolactone and γ-valerolactone. Examples include acid esters. These may be used alone or in combination of two or more.

Specific examples of the solute include, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate , LiCl, LiBr, LiI, LiBCl ₄ , borates, imide salts and the like. These may be used alone or in combination of two or more. The amount of solute dissolved in 1 liter of nonaqueous solvent is preferably about 0.5 to 2 mol.

  Such a lithium ion secondary battery 20 is assembled by a method similar to a conventionally known method of assembling a lithium ion secondary battery.

  In the lithium ion secondary battery 20 of the present embodiment, the electrode group 14 and the non-aqueous electrolyte 15 are housed in a cylindrical battery case 16, and insulating rings 27 and 28 are disposed on the upper and lower parts of the electrode group 14, respectively. It is formed by sealing with a sealing plate 25.

  4 (a) and 4 (b) are models for explaining the change in the liquid level when the columnar body 2 expands and contracts before and after charging and discharging of the lithium ion secondary battery 20 shown in FIG. It is explanatory drawing and shows a mode when the winding of the electrode group 14 is solved. FIG. 4B is a schematic view showing only the positive electrode sheet 11 of FIG. 4A in an enlarged manner. The positive electrode sheet 11 has a positive electrode active material layer 11b formed on the surface of a positive electrode current collector 11a.

  The lithium ion secondary battery 20 shown in FIG. 2 has a discharge state at the beginning of a charge / discharge cycle when the cylindrical battery case is upright, with reference to the schematic explanatory diagrams of FIGS. 4 (a) and 4 (b). It is preferable that the liquid level of the non-aqueous electrolyte solution 15 is positioned at a height higher than the height at which the upper end surface L1 of the positive electrode active material layer 11b of the positive electrode sheet 11 in the electrode group 14 is immersed. In the charged state, the columnar body 2 of the negative electrode sheet 10 expands to increase the volume, and the liquid level of the nonaqueous electrolytic solution 15 further increases to L2. Thus, in the discharge state at the initial stage of the charge / discharge cycle, by storing the nonaqueous electrolyte solution 15 in the battery case 16 in such an amount that the entire positive electrode active material layer 11b is immersed in the battery case 16, even if the charge / discharge cycle is repeated, the positive electrode side It is difficult for liquid to dry out. Here, the initial charge / discharge cycle means a charge / discharge cycle of up to 10 cycles after the assembly of the lithium ion secondary battery 20.

  The amount of the non-aqueous electrolyte 15 stored in the battery case 16 is such that 1 to 20% by volume of the gas phase space S is left with respect to the total volume of the battery case 16 in the discharge state at the beginning of the charge / discharge cycle. The amount is preferably such that the gas phase space S of 5 to 15% by volume is left. When the gas phase space S is too small, there is a tendency that the deformation such as the deformation of the case and the reliability such as the CID operation cannot be sufficiently secured, and when the gas phase space S is too much, the electrolyte is insufficient. It tends to be difficult to ensure sufficient battery capacity and cycle characteristics.

  In order to ensure both the reliability and the battery characteristics of the lithium ion secondary battery 20, when the battery case is an 18650 type cylindrical case, the nonaqueous electrolyte is 0.7 to 0.7 with respect to the battery capacity 1 Ah. It is preferable to be accommodated in the range of 1.5 mL, and further 0.8 to 1.2 mL. Further, when the battery case is a 14400 type cylindrical case, the nonaqueous electrolyte solution is accommodated in the range of 1.0 to 2.0 mL, and further 1.1 to 1.5 mL with respect to the battery capacity 1Ah. Is preferred.

  Next, the present invention will be described more specifically with reference to examples. The scope of the present invention is not limited by the examples.

[Example 1]
<Creation of negative electrode>
(1) Formation of negative electrode current collector Two forged steel rollers having a plurality of concave portions arranged in a staggered pattern on the surface were brought into pressure contact with each other in parallel to form a nip portion. The shape of the opening of the concave portion on the roller surface was approximately rhombus.

  Both surfaces of a 26 μm-thick alloy copper foil (trade name: HCL02Z, manufactured by Hitachi Cable Ltd.) were subjected to surface roughening by electrolytic plating to form a plurality of copper particles (particle size: about 1 μm). The surface roughness Rz of the alloy copper foil after the roughening treatment was 1.5 μm. By passing this copper foil through the nip formed by the two forged steel rollers at a linear pressure of 1000 N / cm, a negative electrode current collector sheet 51 having a plurality of convex portions formed on both surfaces is produced. did.

  The plurality of convex portions had an average height of 8 μm and were arranged in a staggered pattern. Further, the tip portion of the convex portion was a plane substantially parallel to the surface of the negative electrode current collector sheet 51. Moreover, in the orthographic projection figure from the perpendicular direction upper direction of the negative electrode collector sheet | seat 51, the shape of the convex part was a substantially rhombus. The distance between the axes of the protrusions was 25 μm in the longitudinal direction of the negative electrode current collector and 20 μm in the width direction.

(2) Formation of Negative Electrode Active Material Layer FIG. 5 is a side perspective view schematically showing the configuration of a vacuum vapor deposition apparatus 40 (hereinafter referred to as “vapor deposition apparatus 40”). Using the vapor deposition apparatus 40, the columnar body 52 was formed in the surface of the some convex part of the negative electrode collector sheet 51 obtained above, and the negative electrode sheet 50 was produced.

  The vapor deposition apparatus 40 includes a feed roller 41 around which the negative electrode current collector sheet 51 is wound in advance, and conveyance rollers 42a, 42b, 42c, 42d, 42e, and 42f that guide the negative electrode current collector sheet 51 to the take-up roller 44, Vapor deposition sources 43a and 43b for housing the raw material of the alloy-based active material, a winding roller 44 for winding the negative electrode current collector sheet 51 having a surface deposited with the alloy-based active material, and a negative electrode current collector for the vapor of the alloy-based active material A pair of shielding plates 45a and 45b for regulating a supply area to the surface of the electric sheet 51, oxygen nozzles 46a and 46b for supplying oxygen, a chamber 47 for accommodating these, and a vacuum pump for reducing the pressure in the chamber 47 48 and electron beam irradiation for irradiating the raw material of the alloy active material accommodated in the vapor deposition sources 43a and 43b with an electron beam to generate a vapor of the raw material of the alloy active material It includes a location (not shown), a.

  In the vapor deposition apparatus 40, the 1st vapor deposition area | region 50a is formed between the sending-out roller 41 and the conveyance roller 42a, the 2nd vapor deposition area | region 50b is formed between the conveyance roller 42a and the conveyance roller 42b, and it conveys with the conveyance roller 42e. A third vapor deposition region 50 c is formed between the roller 42 f and a fourth vapor deposition region 50 d is formed between the transport roller 42 f and the take-up roller 44.

First, as an alloy-based active material raw material, silicon single crystal (purity 99.9999%, manufactured by Shin-Etsu Chemical Co., Ltd.) was used and accommodated in evaporation sources 43a and 43b. After the chamber 47 was evacuated to 5 × 10 ⁻³ Pa by the vacuum pump 48, oxygen was supplied from the oxygen nozzles 46 a and 46 b into the chamber 47 to create an oxygen atmosphere with a pressure of 3.5 Pa. Next, the scrap silicon accommodated in the evaporation sources 43a and 43b was irradiated with an electron beam (acceleration voltage: 10 kV, emission: 500 mA) to generate silicon vapor. In the middle of the rise of silicon vapor, it mixed with oxygen to generate a mixed gas of silicon vapor and oxygen.

  On the other hand, the negative electrode current collector sheet 51 is fed from the feed roller 41 at a feeding speed of 2 cm / min, and a mixture of silicon vapor and oxygen is deposited on the convex surface of the negative electrode current collector sheet 51 running in the vapor deposition region 50a. First layer was formed. Next, the second layer was formed on the surface of the convex portion of the negative electrode current collector sheet 51 running in the vapor deposition region 50b and the surface of the first layer. Subsequently, the first and second layers were similarly formed on the back surface. Next, the rotation direction of the winding roller 44 and the feeding roller 41 was reversed, and the feeding direction of the negative electrode current collector sheet 51 was reversed, and vapor deposition was performed in the same manner as described above. Such a reciprocating vapor deposition process was repeated several times. Thereby, the columnar body 52 which is a laminated body made of an alloy-based active material was formed, and the negative electrode sheet 50 was obtained.

The columnar body 52 was supported by the surface of the convex portion and grew to extend outward from the negative electrode current collector sheet 51. One columnar body 52 was formed on one convex portion. The columnar body 52 had a substantially cylindrical solid shape. The columnar body 52 had an average height of 16 μm and an average width of 30 μm. Further, when the amount of oxygen contained in the columnar body 52 was quantified by the combustion method, the composition of the columnar body was SiO _0.4 .

  The plurality of columnar bodies 52 of the negative electrode sheet 50 thus obtained were supplemented with lithium for an irreversible capacity using a resistance heating vacuum deposition apparatus. Note that the vapor deposition of lithium was performed on both surfaces of the negative electrode sheet 50. The negative electrode sheet 50 thus obtained was cut to a size that can be accommodated in a battery case of a 18650 cylindrical battery.

<Creation of positive electrode sheet>
93 g of lithium nickel-containing composite oxide (average particle size of secondary particles: 10 μm) having a composition represented by LiNi _0.80 Co _0.15 Al _0.05 O ₂ , 3 g of acetylene black (conductive agent), polyvinylidene fluoride powder (binder) ) 4 g and 50 ml of N-methyl-2-pyrrolidone (NMP) were mixed to prepare a positive electrode mixture slurry. This positive electrode mixture slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, dried, and rolled to form a positive electrode active material layer having a thickness of 128 μm. The positive electrode sheet thus obtained was cut into a size that can be accommodated in a battery case of a 18650 cylindrical battery.

<Creation of lithium ion secondary battery>
A wound electrode group is fabricated by winding a strip separator polyethylene microporous membrane, trade name: Hypore, thickness 20 μm, manufactured by Asahi Kasei Co., Ltd., between the prepared negative electrode sheet and positive electrode sheet. did. At this time, it wound so that the center line of the width | variety of the winding axis direction of a negative electrode sheet, a positive electrode sheet, and a separator might overlap. Then, one end of the aluminum lead was connected to the positive electrode sheet, and one end of the nickel lead was connected to the negative electrode sheet. Next, an upper insulating plate and a lower insulating plate made of polypropylene were respectively attached to both ends in the longitudinal direction of the wound electrode group. The wound electrode group is housed in a battery case of an 18650 cylindrical battery having an internal volume of 15.2 ml, the other end of the aluminum lead is connected to a stainless steel sealing plate, and the other end of the nickel lead is connected to the battery case. Connected to the inner surface of the bottom.

  And 3.1 mL of nonaqueous electrolyte solution was inject | poured inside the battery case by the pressure reduction system. And the gasket made from a polypropylene was mounted | worn with the peripheral part of the sealing board which has a safety valve, and the sealing board was mounted | worn with the opening of the battery case in this state. The battery case was hermetically sealed by caulking the open end of the battery case toward the sealing plate. Thus, a 18650 cylindrical lithium ion secondary battery A having an outer diameter of 18 mm and a height of 65 mm was produced.

<Evaluation of lithium ion secondary battery>
The obtained lithium ion secondary battery A was evaluated for battery capacity, high rate characteristics, and capacity retention after 100 cycles of charge / discharge according to the following methods.

[Battery capacity]
With respect to the prepared lithium ion secondary battery A, the charge / discharge cycle was repeated three times under the following conditions, and the third discharge capacity was determined.
Constant current charging: 0.3 C, final voltage 4.15V.
Constant voltage charging: 4.15V 0.05C, downtime 20 minutes.
Constant current discharge: 0.2 C, final voltage 2.0 V, rest time 20 minutes.

[High rate characteristics]
The manufactured lithium ion secondary battery A was subjected to a charge / discharge test under the following conditions to obtain the high rate characteristics of the battery.
Constant current charging: 0.3 C, final voltage 4.15V.
Constant voltage charging: 4.15V 0.05C, downtime 20 minutes.
Constant current discharge: 1.0 C, end voltage 2.0 V, rest time 20 minutes [capacity maintenance rate after 100 cycles of charge / discharge]
For the prepared lithium ion secondary battery A, constant current charging, constant current charging, and constant current discharging were repeated 100 cycles under the above-described conditions. Note that the discharge capacity at the first cycle was the initial discharge capacity, and the current value at the time of this discharge was 1C. Then, the percentage of the discharge capacity after 100 cycles with respect to the initial discharge capacity was determined as the capacity maintenance ratio (%).

[Reliability evaluation]
The battery reliability evaluation results were the presence or absence of battery deformation after charging and discharging and the presence or absence of CID operation during charging and discharging.

The above evaluation results are shown in Table 1 below.

[Example 2]
A lithium ion secondary battery B was prepared and evaluated in the same manner as in Example 1 except that 4.0 mL of nonaqueous electrolyte was injected into the battery case. The results are shown in Table 1.

[Example 3]
A lithium ion secondary battery C was prepared and evaluated in the same manner as in Example 1 except that 4.6 mL of the nonaqueous electrolytic solution was injected into the battery case. The results are shown in Table 1.

[Example 4]
Instead of using 18650 type battery case, use 14400 type battery case, cut negative electrode sheet, separator and positive electrode sheet into a size that can be accommodated in battery case of 14400 cylindrical battery, and add 1.4 mL of non-aqueous electrolyte. A lithium ion secondary battery E was prepared and evaluated in the same manner as in Example 1 except that the liquid was used. The results are shown in Table 1.

[Comparative Example 1]
A lithium ion secondary battery D was prepared and evaluated in the same manner as in Example 1 except that 5.8 mL of the nonaqueous electrolyte was injected into the battery case. The results are shown in Table 1.

[Comparative Example 2]
A lithium ion secondary battery F was prepared and evaluated in the same manner as in Example 1 except that 2.4 mL of the non-aqueous electrolyte was injected into the battery case. The results are shown in Table 1.

[Comparative Example 3]
A lithium ion secondary battery G was prepared and evaluated in the same manner as in Example 4 except that 0.7 mL of nonaqueous electrolyte was injected into the battery case. The results are shown in Table 1.

  In the lithium ion secondary batteries A to D of Examples 1 to 4 according to the present invention, the battery capacity as designed could be charged and discharged, and the high rate characteristics were also good. Furthermore, even when charging / discharging was repeated 100 cycles, the decrease in discharge capacity was small. This is presumably because the necessary amount of the electrolyte was secured and the non-uniform battery reaction was suppressed, so that the deterioration of the positive electrode active material was suppressed. On the other hand, in the lithium ion secondary batteries F and G of Comparative Examples 2 and 3, the charge / discharge capacity was lower than the design capacity and the high rate discharge characteristics were also lowered. Furthermore, the discharge capacity decreased when charging and discharging were repeated 100 cycles. This is presumably because when the charge / discharge cycle was repeated, the positive electrode active material layer had a portion that was not impregnated with the non-aqueous electrolyte solution, and thus the deterioration of a part of the positive electrode active material was promoted.

  Moreover, in the lithium ion secondary battery D of the comparative example 1 with the low volume ratio of the gaseous phase in a battery case, the bottom part of the case is swollen compared with the lithium ion secondary batteries AC of Examples 1-4. It was. The CID was also activated.

  In the lithium ion secondary battery using the negative electrode of the present invention, while maintaining the high charge / discharge capacity that is characteristic of an alloy-based active material, dropping of the active material caused by repeated charging / discharging of the current collector is suppressed. ing. Therefore, it can be preferably used as a power source for driving electronic devices that require a high capacity and a long life, and as a power source for a hybrid vehicle or an electric vehicle.

  DESCRIPTION OF SYMBOLS 1 ... Negative electrode collector, 10 ... Negative electrode sheet, 11 ... Positive electrode sheet, 12 ... Separator, 14 ... Electrode group, 15 ... Nonaqueous electrolyte, 16 ... Battery case, 1a ... Projection part, 2,52 ... Columnar body, DESCRIPTION OF SYMBOLS 20 ... Lithium ion secondary battery, 21 ... Positive electrode lead, 22 ... Negative electrode lead, 25 ... Sealing plate, 26 ... Positive electrode terminal, 27 ... Insulating ring, 40 ... Vacuum deposition apparatus, 50 ... Negative electrode sheet, 51 ... Negative electrode collector Sheet, S ... Gas phase space

Claims (3)

A wound electrode group formed by winding a laminate of a negative electrode sheet, a positive electrode sheet, the positive electrode sheet, and a microporous insulating sheet interposed between the negative electrode sheet, a non-aqueous electrolyte, the electrode group, and the A battery comprising a cylindrical battery case containing a non-aqueous electrolyte and a sealing member for sealing the battery case,
The negative electrode sheet includes a negative electrode current collector having a plurality of convex portions formed on a surface thereof, and a plurality of columnar bodies made of an alloy-based active material capable of inserting and extracting lithium ions supported by the convex portions,
The positive electrode sheet includes a positive electrode current collector, and a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium ions laminated on the positive electrode current collector,
A lithium ion secondary battery, wherein a gas phase space of 1 to 20% by volume is present with respect to the total volume of the battery case in a discharge state at an initial stage of a charge / discharge cycle.   2. The lithium ion secondary battery according to claim 1, wherein the battery case is an 18650 type cylindrical case, and the non-aqueous electrolyte is accommodated in a range of 0.7 to 1.5 mL with respect to a battery capacity of 1 Ah. The lithium ion secondary battery according to claim 1 or 2, wherein the battery case is a 14400 type cylindrical case, and the non-aqueous electrolyte is accommodated in a range of 1.0 to 2.0 mL with respect to a battery capacity of 1 Ah. .

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