JP2010080203A - Battery - Google Patents

Abstract

To provide a battery with a small expansion of an outer can after charging while ensuring a high battery capacity while having a compact configuration.
In this battery, a battery element in which a positive electrode 21 and a negative electrode 22 are laminated and wound with a separator 23 therebetween is housed in a hollow rectangular parallelepiped outer can 11. The outer can 11 has a rectangular bottom plate 11B, a pair of opposing plates 1A and 1B connected to the long side of the bottom plate 11B and facing each other, and a short side of the bottom plate 11B connected to each other and facing each other and the bottom plate 11B. The opposite edge includes a pair of side plates 2A and 2B that constitute an open end 11K together with the bottom edge 11B and the opposite edge of the pair of opposing plates 1A and 1B. The opposing plates 1A and 1B have, on their outer surfaces, a first recess 3 that crosses in the direction parallel to the bottom plate 11B, and a second that extends from the bottom plate 11B to the first recess 3 in a direction perpendicular to the bottom plate 11B. And the recess 4.
[Selection] Figure 3

Description

  The present invention relates to a battery in which a battery element having a positive electrode and a negative electrode is housed in an outer can.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a notebook computer have appeared, and their size and weight have been reduced. Batteries used as portable power sources for these electronic devices, particularly secondary batteries, are actively used as key devices for research and development aimed at improving energy density. Among them, non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) can provide a larger energy density than conventional lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries. Considerations are being made in various directions.

  As a negative electrode active material used for a lithium ion secondary battery, a carbon material such as non-graphitizable carbon or graphite having a relatively high capacity and good cycle characteristics is widely used. However, considering the recent demand for higher capacity, further increase in capacity of carbon-based materials has become an issue.

  Against this background, a technique for achieving a high capacity with a carbon material by selecting a carbonization raw material and production conditions has been developed (see, for example, Patent Document 1). However, when such a carbon material is used, since the negative electrode discharge potential is 0.8 V to 1.0 V with respect to lithium (Li), the battery discharge voltage when the battery is configured becomes low. No significant improvement is expected in terms of battery energy density. Furthermore, there is a drawback that the charge / discharge curve has a large hysteresis and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high-capacity negative electrode that surpasses carbon materials, research is being conducted on alloy materials that apply the fact that a certain metal is electrochemically alloyed with lithium and is reversibly generated and decomposed. Furthermore, as a method for improving the cycle characteristics, it has been studied to alloy tin (Sn) or silicon (Si) to suppress expansion thereof. For example, it has been proposed to alloy a transition metal such as iron with tin (see Patent Documents 2 to 4 and Non-Patent Documents 1 to 3). In addition, Mg ₂ Si and the like have been proposed (see Non-Patent Document 4).
JP-A-8-315825 Japanese Patent Laid-Open No. 2004-22306 JP 2004-63400 A JP 2005-78999 A “Journal of the Electrochemical Society”, 1999, No. 146, p405 “Journal of the Electrochemical Society”, 1999, No. 146, p414 “Journal of the Electrochemical Society”, 1999, No. 146, p423 “Journal of the Electrochemical Society”, 1999, No. 146, p4401

  However, even when these methods are used, it is difficult to sufficiently suppress the expansion and contraction of the negative electrode during charging and discharging. Therefore, as a result, the actual situation is that the features of the high-capacity negative electrode employing the above alloy material are not fully utilized.

  Specifically, it is as follows. When the battery element including the negative electrode made of the alloy material as described above is sealed and accommodated in a predetermined outer can, the battery element including the negative electrode expands when charged or repeatedly charged and discharged, The pressure inside the outer can rises. Here, when an excessive pressure rise occurs, for example, in a rectangular parallelepiped outer can that is generally used at present, the side wall having the largest surface area swells outward, and the outer dimensions are distorted. . When a battery is mounted on various electronic devices, it is often placed in a very limited space, which causes a problem in mounting. Therefore, in practice, it is necessary to secure an appropriate clearance in advance between the outermost surface of the battery element and the inner surface of the outer can in consideration of the expansion rate of the negative electrode after charging. In this case, a useless space is generated between the battery element and the inner surface of the outer can, and the battery capacity relative to the size of the space occupied by the outer can (the apparent battery capacity per unit volume) is a negative electrode made of a carbon material. It is better than expected, but not as big as expected. Although it is possible to improve the strength of the outer can by increasing the thickness of the side wall of the outer can and prevent distortion of the outer dimensions of the outer can, it is disadvantageous for downsizing due to an increase in weight and size. Therefore, it is not preferable.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a battery with a small expansion of the outer can after charging while ensuring a high battery capacity while having a compact configuration.

  The battery of the present invention includes a battery element having a positive electrode and a negative electrode, and a hollow rectangular outer can that accommodates the battery element. The outer can is connected to the rectangular bottom plate and the long side of the bottom plate, respectively. A pair of opposing plates, and a pair of side plates that are connected to the short sides of the bottom plate and face each other, and an edge opposite to the bottom plate constitutes an open end together with an edge opposite to the bottom plate in the pair of opposing plates And a pair of opposing plates includes, on its outer surface, a first recess that crosses in the direction along the bottom plate, and a second recess that extends from the connecting portion with the bottom plate to at least the first recess. It is what I did.

  In the battery of the present invention, since the first and second recesses intersecting each other are provided on the outer surface of the opposing plate in the hollow square outer can, the first and second recesses are bent or distorted by the opposing plate. It functions as a beam that suppresses and provides excellent mechanical strength.

  According to the battery of the present invention, the counter plate can be effectively reinforced by the first and second recesses provided on the outer surface of the counter plate in the hollow square outer can, while having a compact configuration. Even when the pressure inside the outer can rises due to the expansion of the battery element accompanying charging, the outer can can be prevented from swelling. Therefore, it is suitable for further reducing the clearance between the battery element and the inner surface of the outer can and increasing the capacity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each drawing schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood for each component, and does not necessarily match the actual size.

  1 and 2 show a cross-sectional structure of a secondary battery as an embodiment of the present invention, and FIG. 3 is a perspective view showing an external appearance of an outer can 11 constituting the secondary battery. . The cross section shown in FIG. 1 and the cross section shown in FIG. 2 are in a positional relationship orthogonal to each other. That is, FIG. 2 is a cross-sectional view in the arrow direction along the line II-II shown in FIG. This secondary battery is called a so-called square shape, and a flat battery element 20 is housed inside an outer can 11 having a substantially rectangular parallelepiped shape together with the battery lid 13. Further, this secondary battery is a lithium ion battery in which the capacity of the negative electrode is represented by the capacity based on insertion and extraction of lithium which is an electrode reactant.

  The outer can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and also has a function as a negative electrode terminal. The outer can 11 has a structure in which one end is closed and the other end is opened, and the inside is sealed by attaching an insulating plate 12 and a battery lid 13 to the open end 11K. Specifically, the outer can 11 includes a rectangular bottom plate 11B as shown in FIG. 3, a pair of opposing plates 1A and 1B and a pair of side plates 2A and 2B standing along the periphery of the bottom plate 11B. The portion facing the bottom plate 11B is open. The pair of opposing plates 1A and 1B are connected to the long sides of the bottom plate 11B and face each other, and the pair of side plates 2A and 2B are connected to the short sides of the bottom plate 11B and face each other. The opposing plates 1A and 1B and the side plates 2A and 2B also have a rectangular shape, and the edge of the opposing plates 1A and 1B and the side plates 2A and 2B opposite to the bottom plate 11B constitutes the opening 11K.

  As shown in FIG. 3, the 1st recessed part 3 and the 2nd recessed part 4 are provided in the outer surface of opposing board 1A, 1B, respectively. The first recess 3 extends in parallel along the bottom plate 11B and crosses the opposing plates 1A and 1B so as to connect the side plate 2A and the side plate 2B. The first recess 3 is preferably located between the bottom plate 11B and the open end 11K. On the other hand, the second recess 4 extends from the bottom plate 11B to the first recess 3 in a direction perpendicular to the bottom plate 11B. It is desirable that the second recess extends perpendicular to the bottom plate 11B at an intermediate position in a direction parallel to the bottom plate 11B. Moreover, the cross-sectional shape of the 1st and 2nd recessed parts 3 and 4 is circular arc shape, for example, and the depth of the deepest part is about 1/4 to 1/2 of the thickness of opposing board 1A, 1B. Moreover, the width | variety of the 1st and 2nd recessed parts 3 and 4 is good in it being 0.5 to 300 times the depth of the deepest part, for example. This is because the bending strength of the opposing plates 1A and 1B is further improved. In the present embodiment, one each of the first recess 3 and the second recess 4 is provided, but a plurality of them may be provided. The first recess 3 is preferably parallel to the bottom plate 11B, but is not necessarily parallel. That is, the first recess 3 extends so that one end is located at a connection portion with the side plate 2A in the opposing plates 1A and 1B and the other end is located at a connection portion with the side plate 2B in the opposing plates 1A and 1B. If it is. Similarly, the second recess 4 desirably extends perpendicularly to the bottom plate 11B, but does not necessarily have to be perpendicular. Furthermore, although it is desirable in terms of strength that both the first recess 3 and the second recess 4 extend linearly, they may extend in a curved shape.

  The insulating plate 12 attached to the open end 11K of the outer can 11 is made of polypropylene or the like, and is disposed on the battery element 20 perpendicular to the winding peripheral surface. The battery cover 13 is made of, for example, the same material as that of the outer can 11 and has a function as a negative electrode terminal together with the outer can 11. A terminal plate 14 serving as a positive electrode terminal is disposed outside the battery lid 13. A through hole is provided near the center of the battery lid 13, and a positive electrode pin 15 electrically connected to the terminal plate 14 is inserted into the through hole. The terminal plate 14 and the battery lid 13 are electrically insulated by an insulating case 16, and the positive electrode pin 15 and the battery lid 13 are electrically insulated by a gasket 17. The insulating case 16 is made of, for example, polybutylene terephthalate. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  A cleavage valve 18 and an electrolyte injection hole 19 are provided near the periphery of the battery lid 13. The cleaving valve 18 is electrically connected to the battery lid 13 and is cleaved when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating, thereby suppressing an increase in the internal pressure. . The electrolyte injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.

  In the battery element 20, a positive electrode 21 and a negative electrode 22 are laminated and wound with a separator 23 interposed therebetween, and are formed into a flat shape in accordance with the shape of the outer can 11. The separator 23 is located on the outermost periphery of the battery element 20, and the positive electrode 21 is located immediately inside thereof. In FIG. 2, the laminated structure of the positive electrode 21 and the negative electrode 22 is shown in a simplified manner. Further, the number of windings of the battery element 20 is not limited to that shown in FIGS. 1 and 2 and can be arbitrarily set. A positive electrode lead 24 made of aluminum or the like is connected to an end portion (for example, an inner terminal portion) of the positive electrode 21, and a negative electrode lead 25 made of nickel or the like is connected to the negative electrode 22 (for example, an outer terminal portion). The positive electrode lead 24 is electrically connected to the terminal plate 14 by being welded to the lower end of the positive electrode pin 15, and the negative electrode lead 25 is welded and electrically connected to the outer can 11.

  4 is a developed cross-sectional view of the positive electrode 21 shown in FIGS. This positive electrode 21 is obtained by selectively providing a positive electrode active material layer 21B on both surfaces of a strip-shaped positive electrode current collector 21A. Specifically, the positive electrode current collector 21A is located on both sides of the positive electrode active material layer 21B on the both sides of the positive electrode covering region 21C and the winding center side and the winding outer peripheral side so as to sandwich the positive electrode covering region 21C. Both surfaces of the positive electrode current collector 21A have positive electrode exposed regions 21DS and 21DE in which the positive electrode active material layer 21B is exposed without being present. The positive electrode lead 24 is joined to the positive electrode exposed region 21DS on the winding center side. The positive electrode covering region 21C and the positive electrode exposed regions 21DS and 21DE do not need to coincide on both surfaces of the positive electrode current collector 21A, and there may be a region where the positive electrode active material layer 21B is provided only on one surface. Good.

  The positive electrode current collector 21A has, for example, a thickness of about 5 μm to 50 μm and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive material and a binder such as polyvinylidene fluoride may be included. As a cathode material capable of inserting and extracting lithium, for example, lithium cobalt oxide, lithium nickel oxide or a solid solution containing them _{(Li (Ni x Co y Mn} z) O 2; x, the values of y and z 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1), lithium manganate having a spinel structure (LiMn ₂ O ₄ ) or a solid solution thereof (Li (Mn _{2− v} Ni _v ) O ₄ ; the value of v is v <2.) and the like. As the cathode material, for example, a phosphate compound having an olivine structure such as lithium iron phosphate (LiFePO ₄₎ can be cited. This is because a high energy density can be obtained. In addition to the above, the positive electrode material includes, for example, oxides such as titanium oxide, vanadium oxide or manganese dioxide, disulfides such as iron disulfide, titanium disulfide or molybdenum sulfide, sulfur, polyaniline or polythiophene, etc. The conductive polymer may be used.

  FIG. 5 is a developed cross-sectional view of the negative electrode 22 shown in FIGS. 1 and 2. The negative electrode 22 is one in which a negative electrode active material layer 22B is selectively provided on both surfaces of a strip-shaped negative electrode current collector 22A. Specifically, the negative electrode covering region 22C where the negative electrode active material layer 22B exists on both surfaces of the negative electrode current collector 22A, and the winding center side and the winding outer peripheral side so as to sandwich the negative electrode covering region 22C, Both surfaces of the negative electrode current collector 22A have positive electrode exposed regions 22DS and 22DE that are exposed without the negative electrode active material layer 22B. The negative electrode lead 25 is joined to the negative electrode exposed region 22DE on the winding outer periphery side. Note that the negative electrode covering region 22D and the negative electrode exposed regions 22DS and 22DE do not need to coincide on both surfaces of the negative electrode current collector 22A, and there may be a region where the negative electrode active material layer 22B is provided only on one surface. Good.

  The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The thickness of the negative electrode current collector 22A is, for example, 5 μm to 50 μm.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material, and a binder as necessary. Or a conductive agent.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and having at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained. Such a negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, and may have one or two or more phases thereof at least in part. In addition, in addition to what consists of 2 or more types of metal elements, the alloy here also contains what contains 1 or more types of metal elements and 1 or more types of metalloid elements. The alloy may contain a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or one in which two or more of them coexist.

  Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), Examples thereof include bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt). Among these, at least one of silicon and tin is preferable, and silicon is more preferable. This is because a high energy density can be obtained because the ability to occlude and release lithium is large.

  Examples of the negative electrode material having at least one of silicon and tin include at least a part of a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or one or two or more phases thereof. The material which has in is mentioned. These may be single and multiple types may be mixed.

  Examples of the negative electrode material having a simple substance of silicon include a material mainly having a simple substance of silicon. The negative electrode active material layer 22B including the negative electrode material has, for example, a structure in which a second constituent element other than silicon and oxygen are present between the silicon simple substance layers. The total content of silicon and oxygen in the anode active material layer 22B is preferably 50% by mass or more, and particularly preferably the content of silicon alone is 50% by mass or more. Examples of the second constituent element other than silicon include titanium (Ti), chromium, manganese (Mn), iron, cobalt (Co), nickel, copper, zinc, indium, silver, magnesium, aluminum, germanium, tin, Bismuth or antimony (Sb) can be used. The negative electrode active material layer 22B containing a material mainly composed of a simple substance of silicon can be formed, for example, by co-evaporation of silicon and other constituent elements.

As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing which has at least 1 sort (s) of these is mentioned. Examples of the silicon compound include those having oxygen or carbon (C), and may contain the second constituent element described above in addition to silicon. Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi. ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2) or LiSiO.

As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing which has at least 1 sort (s) of these is mentioned. Examples of the tin compound include those having oxygen or carbon, and may contain the above-described second constituent element in addition to tin. Examples of tin alloys or compounds include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.

  In particular, as the negative electrode material having at least one of silicon and tin, for example, a material having tin and the second constituent element in addition to tin as the first constituent element is preferable. The second constituent element is cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum (Mo), silver, indium, cerium ( Ce), hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). It is because excellent cycle characteristics can be obtained by having these second and third constituent elements.

  Among them, it has tin, cobalt and carbon as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) Is preferably an SnCoC-containing material having a content of 30% by mass or more and 70% by mass or less. This is because in such a composition range, high energy density and high cycle characteristics can be obtained.

  This SnCoC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like are preferable, and two or more of them may be included. Good. This is because energy density and cycle characteristics are further improved.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase is preferably a low crystalline or amorphous phase. This phase is a reaction phase capable of reacting with lithium, whereby excellent cycle characteristics can be obtained. The half-value width of the diffraction peak obtained by X-ray diffraction of this phase is 1.0 ° or more at a diffraction angle 2θ when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min. Is preferred. This is because lithium is more smoothly inserted and extracted, and the reactivity with the electrolytic solution is reduced when the negative electrode is used in an electrochemical device such as a secondary battery equipped with the electrolytic solution.

  Whether or not the diffraction peak obtained by X-ray diffraction corresponds to a reaction phase capable of reacting with lithium can be easily determined by comparing X-ray diffraction charts before and after electrochemical reaction with lithium. can do. For example, if the position of the diffraction peak changes before and after the electrochemical reaction with lithium, it corresponds to a reaction phase capable of reacting with lithium. In this case, for example, a diffraction peak of a low crystalline or amorphous reaction phase is observed between 2θ = 20 ° and 50 °. This low crystalline or amorphous reaction phase contains, for example, each of the above-described constituent elements, and is considered to be mainly low-crystallized or amorphous due to carbon.

  In addition to the low crystalline or amorphous phase, the SnCoC-containing material may have a phase containing a simple substance or a part of each constituent element.

  In particular, in the SnCoC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a metalloid element as another constituent element. This is because aggregation or crystallization of tin or the like is suppressed.

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. This XPS irradiates the sample surface with soft X-rays (Al-Kα ray or Mg-Kα ray is used in a commercial apparatus), and measures the kinetic energy of photoelectrons jumping out of the sample surface. To elemental composition in the region of several nanometers and the bonding state of the elements.

  The binding energy of the core orbital electrons of the element changes in a first approximation in correlation with the charge density on the element. For example, when the charge density of the carbon element decreases due to an interaction with an element present in the vicinity, the outer electrons such as 2p electrons decrease, so the 1s electron of the carbon element exerts a strong binding force from the shell. Will receive. That is, the binding energy increases as the charge density of the element decreases. In XPS, when the binding energy increases, the peak shifts to a high energy region.

  In XPS, if the peak of carbon 1s orbital (C1s) is graphite, it appears at 284.5 eV in an energy calibrated apparatus so that the peak of 4f orbital (Au4f) of gold atom is obtained at 84.0 eV. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when it is bonded to an element more positive than carbon, the C1s peak appears in a region lower than 284.5 eV. That is, when at least a part of carbon contained in the SnCoC-containing material is bonded to a metal element or a metalloid element that is another constituent element, the peak of the synthetic wave of C1s obtained for the SnCoC-containing material is 284. Appears in a region lower than 5 eV.

  When performing XPS measurement, it is preferable that the surface is lightly sputtered with an argon ion gun attached to the XPS apparatus when the surface is covered with surface-contaminated carbon. In addition, when a negative electrode having a SnCoC-containing material to be measured is present in an electrochemical device such as a secondary battery provided with an electrolytic solution, the electrochemical device is disassembled and the negative electrode is taken out, and then dimethyl carbonate, etc. It is good to wash with a volatile solvent. This is for removing the low-volatile solvent and the electrolyte salt present on the negative electrode surface. These samplings are preferably performed under an inert atmosphere.

  In XPS measurement, for example, the peak of C1s is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface of the substance, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, and this is used as an energy standard. In XPS measurement, the waveform of the peak of C1s is obtained as a form including the surface contamination carbon peak and the carbon peak in the SnCoC-containing material. For example, by analyzing using commercially available software, The surface contamination carbon peak is separated from the carbon peak in the SnCoC-containing material. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  This SnCoC-containing material can be formed by, for example, a method in which a mixture obtained by mixing raw materials of each constituent element is melted in an electric furnace, a high-frequency induction furnace, an arc melting furnace or the like and then solidified. Also, various atomizing methods such as gas atomization or water atomization, methods using various mechanochemical reactions such as various roll methods, mechanical alloying methods, and mechanical milling methods may be used. Among these, a method using a mechanochemical reaction is preferable. This is because the SnCoC-containing material has a low crystalline or amorphous structure. In the method using the mechanochemical reaction, for example, a manufacturing apparatus such as a planetary ball mill or an attritor can be used.

  The raw material may be a mixture of individual constituent elements, but it is preferable to use an alloy for some of the constituent elements other than carbon. This is because, by adding carbon to such an alloy and synthesizing it by a method using a mechanical alloying method, a low crystalline or amorphous structure is obtained, and the reaction time is shortened. The raw material may be in the form of powder or a block.

  In addition to this SnCoC-containing material, an SnCoFeC-containing material having tin, cobalt, iron and carbon as constituent elements is also preferable. The composition of the SnCoFeC-containing material can be arbitrarily set. For example, as the composition when the iron content is set to be small, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the iron content is 0.3 mass% or more and 5.9 weight% %, And the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is preferably 30% by mass or more and 70% by mass or less. In addition, for example, as a composition when the content of iron is set to be large, the content of carbon is 11.9 mass% or more and 29.7 mass% or less, and cobalt and iron with respect to the total of tin, cobalt, and iron The total ratio of (Co + Fe) / (Sn + Co + Fe)) is 26.4 mass% to 48.5 mass%, and the ratio of cobalt to the total of cobalt and iron (Co / (Co + Fe)) is 9.9 mass% It is preferable that it is 79.5 mass% or more. This is because a high energy density can be obtained in such a composition range. The crystallinity of the SnCoFeC-containing material, the method for measuring the bonding state of elements, the formation method, and the like are the same as those of the above-described SnCoC-containing material.

  As a negative electrode material capable of inserting and extracting lithium, a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or a material having one or more phases thereof at least in part. The used negative electrode active material layer 22B is formed by using, for example, a gas phase method, a liquid phase method, a thermal spraying method, a coating method or a firing method, or two or more of these methods. In this case, it is preferable that the anode current collector 22A and the anode active material layer 22B are alloyed at least at a part of the interface. Specifically, the constituent element of the negative electrode current collector 22A may be diffused into the negative electrode active material layer 22B at the interface between them, or the constituent element of the negative electrode active material layer 22B is diffused into the negative electrode current collector 22A. These constituent elements may be diffused with each other. This is because breakage due to expansion and contraction of the negative electrode active material layer 22B during charging and discharging is suppressed, and electron conductivity between the negative electrode current collector 22A and the negative electrode active material layer 22B is improved.

  As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, vacuum deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD) Or plasma chemical vapor deposition. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. The application method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and then dispersed in a solvent and applied. The baking method is, for example, a method in which a heat treatment is performed at a temperature higher than the melting point of a binder or the like after being applied by a coating method. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

  In addition to the above, examples of the anode material capable of inserting and extracting lithium include a carbon material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less. It is. More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks. The cokes include pitch coke, needle coke, petroleum coke and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. Since carbon materials undergo very little change in crystal structure due to insertion and extraction of electrode reactants, for example, when used together with other negative electrode materials, high energy density can be obtained, and the negative electrode can be used for secondary batteries, etc. When used in an electrochemical device, excellent cycle characteristics can be obtained, and it also functions as a conductive agent, which is preferable. The shape of the carbon material may be any of fibrous, spherical, granular or scale-like.

  Further, examples of the negative electrode material capable of inserting and extracting lithium include metal oxides and polymer compounds capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Of course, the negative electrode material capable of inserting and extracting lithium may be other than the above. Further, two or more kinds of the above series of negative electrode materials may be mixed in any combination.

  Examples of the binder for the positive electrode 21 and the negative electrode 22 include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be used alone or in combination of two or more. However, as shown in FIG. 1, when the positive electrode 21 and the negative electrode 22 are wound, it is preferable to use a styrene butadiene rubber or a fluorine rubber having high flexibility.

  Moreover, as a electrically conductive agent of the positive electrode 21 and the negative electrode 22, carbon materials, such as graphite, carbon black, or ketjen black, are mentioned, for example. These may be used alone or in combination of two or more. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  In this secondary battery, the charge capacity of the negative electrode active material is larger than the charge capacity of the positive electrode active material by adjusting the amount between the positive electrode active material and the negative electrode active material. This prevents lithium metal from being deposited on the negative electrode 22 even during full charge.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows ions of the electrode reactant to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, a porous film made of ceramic, or the like, and these two or more kinds of porous films are laminated. It may be what was done. Among these, a porous film made of polyolefin is preferable because it has an excellent short-circuit prevention effect and can improve the safety of the secondary battery due to the shutdown effect. In particular, polyethylene is preferable because a shutdown effect can be obtained at 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and other resins having chemical stability may be copolymerized with polyethylene or polypropylene, or may be blended.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent contained in the electrolytic solution, various high dielectric constant solvents and low viscosity solvents can be used. For example, as a high dielectric constant solvent, in addition to ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate), 4-chloro-1,3-dioxolane Cyclic carbonates such as 2-one (chloroethylene carbonate) and trifluoromethylethylene carbonate are preferably used. As the high dielectric constant solvent, a lactone such as γ-butyrolactone, γ-valerolactone, δ-valerolactone or ε-caprolactone, N-methylpyrrolidone, etc., instead of or in combination with the above cyclic carbonate Lactam, cyclic carbamates such as N-methyloxazolidinone, and sulfone compounds such as tetramethylene sulfone can also be used. On the other hand, as low-viscosity solvents, in addition to diethyl carbonate, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, Chain carboxylic acid esters such as methyl trimethylacetate and ethyl trimethylacetate, chain amides such as N, N-dimethylacetamide, chain carbamic acid such as methyl N, N-diethylcarbamate and ethyl N, N-diethylcarbamate Esters and ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran and 1,3-dioxolane can be used.

  In addition, as a solvent, 1 type in the above-mentioned high-dielectric-constant solvent and low-viscosity solvent can be used individually, or 2 or more types can be arbitrarily mixed, but 20-50 mass% cyclic carbonate can be used. And a low-viscosity solvent of 50 to 80% by mass are preferable, and a low-viscosity solvent including a chain carbonate having a boiling point of 130 ° C. or less is particularly preferable. By using such a solvent, the polymer compound can be swelled satisfactorily with a small amount of electrolytic solution, and it is possible to achieve both suppression of battery swelling and prevention of leakage and high ion conductivity. Here, if the content of the low-viscosity solvent occupying the electrolytic solution is too high, the dielectric constant will be lowered, and if the content of the low-viscosity solvent is too low, the viscosity will be lowered. Ionic conductivity may not be obtained, and good battery characteristics may not be obtained.

Any electrolyte salt may be used as long as it dissolves in a solvent to generate ions, and one kind may be used alone, or two or more kinds may be mixed and used. For example, if the lithium salt, lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ Inorganic lithium salts such as lithium perchlorate (LiClO ₄ ) and lithium tetrachloride aluminum oxide (LiAlCl ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis (trifluoromethanesulfone) imide (LiN (CF ₃ SO _2
2 ), perfluoroalkanes such as lithium bis (pentafluoromethanesulfone) imide (LiN (C ₂ F ₅ SO ₂ ) ₂ ) and lithium tris (trifluoromethanesulfone) methide (LiC (CF ₃ SO ₂ ) ₃ ) Lithium salts of sulfonic acid derivatives can be used. Of these, lithium hexafluorophosphate and lithium tetrafluoroborate are preferable from the viewpoint of oxidation stability.

  The content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because higher ion conductivity can be obtained in such a range.

  The electrolytic solution may contain various additives along with the solvent and the electrolyte salt. This is because the chemical stability of the electrolytic solution is further improved.

  Examples of the additive include sultone (cyclic sulfonic acid ester). This sultone is, for example, propane sultone or propene sultone, among which propene sultone is preferable. These may be single and multiple types may be mixed.

  Moreover, as an additive, an acid anhydride is mentioned, for example. Examples of the acid anhydride include carboxylic acid anhydrides such as succinic acid anhydride, glutaric acid anhydride and maleic acid anhydride, disulfonic acid anhydrides such as ethanedisulfonic acid anhydride and propanedisulfonic acid anhydride, Examples thereof include carboxylic acid and sulfonic acid anhydrides such as benzoic acid anhydride, sulfopropionic acid anhydride and sulfobutyric acid anhydride, among which sulfobenzoic acid anhydride and sulfopropionic acid anhydride are preferable. These may be single and multiple types may be mixed.

  This secondary battery is manufactured by the following procedure, for example.

  First, the positive electrode 21 is produced. Specifically, a positive electrode active material, a binder, and a conductive agent are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A using a doctor blade or a bar coater, and then dried. Finally, the cathode active material layer 21B is formed by compression molding using a roll press or the like while heating as necessary. In this case, compression molding may be repeated a plurality of times.

  Next, the negative electrode 22 is produced. Specifically, for example, a negative electrode active material and a binder are mixed to form a negative electrode mixture, and then dispersed in an organic solvent to obtain a paste-like negative electrode mixture slurry. After that, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and then compression molded to form the negative electrode active material layer 22B. Here, when the negative electrode active material layer 22B is formed of a negative electrode active material containing silicon, tin, or lithium, the negative electrode current collector 22A and the negative electrode active material are subjected to compression molding or annealing treatment as necessary. It is desirable to improve the adhesion with the layer 22B. By doing so, peeling of the negative electrode active material layer 22B from the negative electrode current collector 22A is suppressed, and good cycle characteristics can be obtained.

  Alternatively, in the case of forming the negative electrode active material layer 22B containing a negative electrode active material containing silicon or tin as a constituent element, a vapor phase method, a liquid phase method, a thermal spraying method or a firing method, or two or more methods thereof are arbitrarily selected. You may make it use. As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, vacuum vapor deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD; Chemical Vapor Deposition) Or plasma chemical vapor deposition. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and dispersed in a solvent and then heat treated at a temperature higher than the melting point of the binder. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

  Next, the positive electrode lead 24 and the negative electrode lead 25 are attached to predetermined positions of the positive electrode current collector 21A and the negative electrode current collector 22A, respectively, by welding or the like. Subsequently, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween, and after being wound a plurality of times, the battery element 20 having a flat shape is obtained.

  On the other hand, an outer can 11 is prepared in which first and second recesses 3 and 4 are provided on the opposing plates 1A and 1B. Specifically, the first and second recesses 3 and 4 are formed on the outer surfaces of the opposing plates 1A and 1B by laser irradiation, electron beam irradiation, cutting, or pressing.

  Finally, the secondary battery is assembled as follows. First, after the battery element 20 is housed in the outer can 11 provided with the first and second recesses 3 and 4, the insulating plate 12 is disposed on the battery element 20. Subsequently, the positive electrode lead 24 is connected to the positive electrode pin 15 and the negative electrode lead 25 is connected to the outer can 11 by welding or the like, and then the battery lid 13 is fixed to the open end 11K of the outer can 11 by laser welding or the like. Further, after injecting the electrolyte into the outer can 11 from the injection hole 19 and impregnating the separator 23, the injection hole 19 is closed with a sealing member 19 </ b> A. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution.

  As described above, in the present embodiment, in the hollow rectangular outer case 11 that houses the battery element 20, the outer surfaces of the opposing plates 1A and 1B connected to the long sides of the bottom plate 11B are crossed along the bottom plate 11B. Since the first concave portion 3 and the second concave portion 4 extending from the bottom plate 11B to the first concave portion 3 are provided, the first and second concave portions 3 and 4 are provided on the opposing plate 1A, It functions as a beam that suppresses the bending and distortion of 1B, and an excellent mechanical strength can be obtained without increasing the thickness of the outer can 11. Therefore, even if the internal pressure of the outer can 11 is increased due to the expansion of the battery element 20 due to charging, etc., the expansion of the outer can 11 can be suppressed while having a compact configuration. Therefore, it is suitable for reducing the clearance between the battery element 20 and the inner surface of the outer can 11 and increasing the capacity.

(Modification)
Hereinafter, some modifications of the outer can 11 in the above embodiment will be exemplified. FIG. 6 schematically shows a planar configuration of the facing plate 11A of the outer can 111 as a first modification (modification 1) in the present embodiment. In the present modification, the second recess 4 penetrates the first recess 3 from the bottom plate 11B and further extends to the open end 11K.

  FIG. 7 schematically illustrates a planar configuration of the facing plate 11A of the outer can 112 as a second modification (modification 2) in the present embodiment. In this modification, the second recess 4 extends through the first recess 3 from the bottom plate 11B and further extends to the middle of the open end 11K. That is, the end of the second recess 4 opposite to the bottom plate 11B is in a state of being separated from the open end 11K.

  FIG. 8 schematically shows a planar configuration of the facing plate 11A of the outer can 113 as a third modification (modification 3) in the present embodiment. In this modification, two second recesses 4A and 4B are provided. Note that three or more second recesses may be provided.

  In each of the above modifications, the same effect as in the above embodiment can be obtained.

  Next, specific examples of the present invention will be described in detail.

(Experimental Example 1-1)
A secondary battery corresponding to FIGS. 1 and 2 described in the above embodiment was manufactured. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio), and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material was obtained. Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Subsequently, the positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of the positive electrode current collector 21A made of an aluminum alloy foil having a thickness of 15 μm and dried. The positive electrode 21 was produced by compression molding with a roll press to form a positive electrode active material layer 21B having a thickness of 145 μm. Subsequently, the positive electrode lead 24 made of aluminum was attached to one end of the positive electrode current collector 21A in the positive electrode exposed region 21DS by welding.

  Next, the negative electrode 22 was produced. Specifically, after an amorphous silicon thin film containing, for example, 4 atomic% oxygen is deposited on both surfaces of the negative electrode current collector 22A made of electrolytic copper foil to a thickness of 5 μm by an electron beam evaporation method. Then, the negative electrode active material layer 22B was formed by performing a heat treatment for 12 hours at a temperature of 250 ° C. in an argon atmosphere. Here, an electrolytic copper foil having a thickness of 15 μm and a surface roughness of Ra value of 3.5 μm was used. Furthermore, a negative electrode lead 25 made of nickel was attached to one end of the negative electrode current collector 21A in the negative electrode exposed region 22DE by welding.

  While producing the positive electrode 21 and the negative electrode 22, the outer can 11 having the first recess 3 and the second recess 4 was prepared. As the outer can 11, one having outer dimensions of 36 mm in height, 33 mm in width, and 5.5 mm in thickness was used. Height refers to the dimension in the direction orthogonal to the bottom plate 11B (X-axis direction), and width refers to the dimension in the direction orthogonal to the height direction (Y-axis direction) on the surface where the opposing plates 1A and 1B extend, The thickness means a dimension in a direction (Z-axis direction) orthogonal to both the bottom plate 11B and the opposing plates 1A and 1B. The first and second recesses 3 and 4 have a width of 1 mm at the position shown in FIG. 9 by laser irradiation (the width here means a dimension in a direction perpendicular to each extending direction). , And a maximum depth of 0.09 mm. That is, the first recess 3 is formed so as to cross the center position in the height direction (extends in the width direction), and the second recess 4 extends in the height direction at the center position in the width direction. The first recess 3 and the bottom plate 11B are connected to each other. FIG. 9 is a plan view of the outer can 11 viewed from the direction of the arrow III shown in FIG.

  Subsequently, a separator 23 made of a microporous polyethylene film having a thickness of 16 μm is prepared, and a positive electrode 21, a separator 23, a negative electrode 22, and a separator 23 are laminated in this order to form a laminate, and then the laminate is wound 20 times. The battery element 20 having a flat shape was produced by pressure molding.

Further, after the battery element 20 is accommodated in the outer can 11, the insulating plate 12 is disposed on the battery element 20, the negative electrode lead 25 is welded to the outer can 11, and the positive electrode lead 24 is connected to the lower end of the positive electrode pin 15. The battery lid 13 was fixed to the open end of the outer can 11 by laser welding. After that, an electrolytic solution was injected into the outer can 11 from the injection hole 19. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt at a concentration of 1 mol / dm ³ in a solvent in which 30% by volume of ethylene carbonate and 70% by volume of diethyl carbonate were mixed was used. Finally, the injection hole 19 was closed with a sealing member 19A to obtain a square secondary battery. For this secondary battery, by adjusting the thickness of the positive electrode active material layer 21B so that the charge / discharge capacity of the negative electrode 22 is larger than the charge / discharge capacity of the positive electrode 21, lithium metal is deposited on the negative electrode 22 during full charge. I tried not to.

  As experimental examples 1-2 to 1-7, except that the first and second recesses 3 and 4 are provided at the positions shown in FIGS. Thus, a secondary battery was produced. Further, as Experimental Example 1-8, except that the second concave portion 4 is not provided and only the two first concave portions 3A and 3B are provided at the positions shown in FIG. In the same manner as in Example 1, a secondary battery was produced.

  Further, as Experimental Example 1-9, except that the negative electrode active material layer 22B was formed as follows and the first and second recesses 3 and 4 were provided at the positions shown in FIG. Produced a secondary battery in the same manner as in Experimental Example 1-1. Regarding the negative electrode active material layer 22B, a tin thin film was deposited on both surfaces of the negative electrode current collector 22A by an electron beam evaporation method so as to have a thickness of 5 μm, and then for 12 hours at a temperature of 250 ° C. in an argon atmosphere. Obtained by heat treatment.

  Further, as Experimental Example 1-10, except that the negative electrode active material layer 22B was formed as follows and the first and second recesses 3 and 4 were provided at the positions shown in FIG. Produced a secondary battery in the same manner as in Experimental Example 1-1. The negative electrode active material layer 22B was produced as follows. First, 80:20 mass of silicon powder having an average particle diameter of 2 μm as a negative electrode active material and a polyamic acid solution using N-methyl-2-pyrrolidone (NMP) and N, N-dimethylacetamide (DMAC) as a solvent. After mixing at a ratio, the mixture was further diluted with NMP to obtain a negative electrode mixture slurry. Next, the obtained negative electrode mixture slurry was uniformly applied to the negative electrode coating region 22C of the negative electrode current collector 22A and dried. Thereafter, a heat treatment at 550 ° C. for 6 hours in a vacuum atmosphere was performed to obtain a negative electrode active material layer 22B containing sintered silicon as a negative electrode active material and polyimide as a binder.

  Further, as experimental examples 1-1 to 1-13, except that the first and second recesses 3 and 4 were not provided in the outer can 11, the other examples were experimental examples 1-1, 1-9, and 1-10. A secondary battery was fabricated in the same manner.

  About the obtained secondary battery of each experiment example, first, the first charging / discharging process was implemented as follows. That is, constant current charging is performed until the battery voltage reaches 4.25V while maintaining a current density of 0.2C, and then constant voltage charging is performed at a constant voltage of 4.25V, and the current density reaches 0.01C. Stopped at the time. Subsequently, constant current discharge was performed until the battery voltage reached 2.7 V while maintaining a constant current density of 0.2C. Here, “0.2 C” is the current density at which the theoretical capacity can be discharged in 5 hours, and “0.01 C” is the current density at which the theoretical capacity can be discharged in 100 hours.

  About the secondary battery of each experimental example in which the first charge / discharge treatment was completed, charge / discharge cycle treatment was further performed as follows. That is, for charging, constant current charging is performed until the battery voltage reaches 4.2 V while maintaining a current density of 1 C, and then constant voltage charging is performed at a constant voltage of 4.2 V, and the current density is 0.05 C. It stopped when it reached. Regarding the discharge, constant current discharge was performed until the battery voltage reached 2.7 V while maintaining the current density of 1 C constant. 100 cycles of charging / discharging were repeated with this combination of charging and discharging as one cycle. Here, “1C” is the current density at which the theoretical capacity can be discharged in one hour, and “0.05C” is the current density at which the theoretical capacity can be discharged in 20 hours.

  The thickness of the secondary battery of each experimental example subjected to the charge / discharge cycle treatment as described above was measured. Here, the maximum value of the thickness is obtained by sandwiching the secondary battery with two phenol resin plates (bakelite plates) opposed in parallel, and the rate of change relative to the original thickness of 5.5 mm (thickness after charge / discharge cycle). (Increment / initial thickness). The results are shown in Table 1.

  As shown in Table 1, in Experimental Examples 1-1 to 1-3 in which the silicon thin film formed by the electron beam evaporation method was used as the negative electrode active material, compared with Experimental Examples 1-4 to 1-8 and 1-11. The rate of change in thickness could be significantly reduced. In addition, in Experimental Examples 1-9 and 1-10 in which the negative electrode active materials are different, a rate of change in thickness that is substantially equivalent to that of Experimental Example 1-3 was obtained. Therefore, it was confirmed that the battery of the present invention can suppress the swelling of the outer can more effectively and is suitable for further increasing the capacity.

(Experimental examples 2-1 to 2-5)
Next, except for changing the positions of the first and second recesses 3 and 4 shown in FIG. 17, that is, the distances A and B from the edge as shown in Table 2, other examples are experimental examples. A secondary battery was produced in the same manner as in 1-3. Similarly to these experimental examples 2-1 to 2-5, after performing the initial charge / discharge treatment and the charge / discharge cycle treatment, the thickness was measured and the rate of change was calculated. The results are shown in Table 2.

  As shown in Table 2, it has been found that the rate of change in thickness can be reduced most when the first recess 3 and the second recess 4 intersect each other at the center position of the opposing plate 1A.

(Experimental examples 3-1 to 3-6, 4-1 to 4-4)
Next, except that the width of each of the first and second recesses 3 and 4 (the dimension in the direction orthogonal to the extending direction) was changed as shown in Table 3, the others were experimental example 1- In the same manner as in Example 3, a secondary battery was produced. Further, a secondary battery was fabricated in the same manner as in Experimental Example 1-3, except that the maximum depth of the first and second recesses 3 and 4 was changed as shown in Table 4. For these Experimental Examples 3-1 to 3-6 and 4-1 to 4-4, after the initial charge / discharge treatment and the charge / discharge cycle treatment were performed in the same manner, the thickness was measured and the rate of change was calculated. The results are shown in Tables 3 and 4, respectively.

  As shown in Tables 3 and 4, it was found that the rate of change in thickness varies depending on the dimensions of the first and second recesses 3 and 4.

  In the above examples, the case where a simple substance of silicon and a simple substance of tin are used as the negative electrode active material is exemplified. However, the alloy and compound of silicon and the alloy and compound of tin mentioned in the above embodiment are used as the negative electrode active material. Even when used as a substance, it was confirmed that the same tendency as in the above Examples was observed.

  The present invention has been described with reference to some embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where the liquid electrolyte is used as it is as an electrolyte has been described. However, a gel electrolyte in which the electrolyte is held in a polymer compound can also be used. Alternatively, other types of electrolytes may be used. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolyte, or a mixture of another inorganic compound and an electrolyte. Or a mixture of these inorganic compounds and a gel electrolyte.

  Further, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described, but other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or magnesium Alternatively, the present invention can be applied to the case where a Group 2 element in a long-period periodic table such as calcium (Ca), another light metal such as aluminum, lithium, or an alloy thereof is used, and similar effects are obtained. Can be obtained. At that time, a negative electrode active material, a positive electrode active material, a solvent, or the like that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is sectional drawing showing the structure of the secondary battery as one embodiment in this invention. It is sectional drawing showing the structure along the II-II line of the secondary battery shown in FIG. It is a perspective view showing the external appearance of the outer can of the secondary battery shown in FIG. It is sectional drawing which expand | deployed the positive electrode shown in FIG. It is sectional drawing which expand | deployed the negative electrode shown in FIG. It is a top view showing the structure of the armored can as a 1st modification in the secondary battery shown in FIG. It is a top view showing the structure of the armored can as a 2nd modification in the secondary battery shown in FIG. It is a top view showing the structure of the armored can as a 3rd modification in the secondary battery shown in FIG. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-1) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-2) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-3) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-4) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-5) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-6) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-7) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experiment example 1-8) of this invention. It is a top view showing the structure of the armored can in the secondary battery as an experiment example (experimental examples 2-1 to 2-5) of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Outer can, 1A, 1B ... Opposite plate, 11B ... Bottom plate, 11K ... Open end, 2 ... Side plate, 3 ... 1st recessed part, 4 ... 2nd recessed part, 12 ... Insulating plate, 13 ... Battery cover, 14 DESCRIPTION OF SYMBOLS ... Terminal board, 15 ... Positive electrode pin, 16 ... Insulation case, 17 ... Gasket, 18 ... Cleavage valve, 19 ... Injection hole, 19A ... Sealing member, 20 ... Battery element, 21 ... Positive electrode, 21A ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode active material layer, 23 ... Separator, 24 ... Positive electrode lead, 25 ... Negative electrode lead.

Claims (5)

A battery element having a positive electrode and a negative electrode, and a hollow rectangular outer can that accommodates the battery element,
The outer can is
A rectangular bottom plate;
A pair of opposing plates connected to the long sides of the bottom plate and facing each other;
A pair of side plates that are respectively connected to the short sides of the bottom plate and face each other, and an end edge opposite to the bottom plate forms an open end together with an edge opposite to the bottom plate in the pair of opposing plates;
The pair of opposing plates are on the outer surface thereof,
A first recess traversing in a direction along the bottom plate;
A battery including a second recess extending from the connecting portion with the bottom plate to at least the first recess.   The battery according to claim 1, wherein the second recess extends from a connection portion with the bottom plate to the open end.   The battery according to claim 1, wherein the first recess extends in parallel with the bottom plate at an intermediate position between the bottom plate and the open end.   The battery according to claim 1, wherein the second recess extends perpendicularly to the bottom plate at an intermediate position in a direction parallel to the bottom plate.   The battery according to claim 1, wherein the negative electrode includes at least one selected from the group consisting of a simple substance, an alloy and a compound of silicon (Si), and a simple substance, an alloy and a compound of tin (Sn) as an active material.

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