JP2005100959A - Negative electrode for nonaqueous electrolyte secondary battery, manufacturing method of the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode capable of giving nonaqueous electrolyte secondary batteries that has high capacity, has a long cycle lifetime, and excellent safety, and exhibits an excellent cycle characteristics even if charging/deep-discharging are repeated. <P>SOLUTION: The negative electrode for nonaqueous electrolyte secondary batteries is provided, where it is made of a current collector sheet and an active material layer deposited on the surface, the active material layer is made of SiO<SB>x</SB>satisfying 0.7≤x≤1.3, and does not include a binder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a negative electrode used for a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

  In recent years, information electronic devices such as personal computers, mobile phones, and PDAs, and audiovisual electronic devices such as video camcorders and mini-disc players are rapidly becoming smaller and lighter and cordless. There is an increasing demand for a secondary battery having a high energy density as a power source for driving these electronic devices. Therefore, non-aqueous electrolyte secondary batteries having a high energy density that cannot be achieved by conventional lead storage batteries, nickel cadmium storage batteries, nickel hydride storage batteries, and the like are becoming mainstream as power sources for driving. Among non-aqueous electrolyte secondary batteries, development of lithium ion secondary batteries and lithium ion polymer secondary batteries is progressing.

A non-aqueous electrolyte is selected that can withstand the oxidizing atmosphere of the positive electrode that discharges at a high potential of 3.5 V to 4.0 V and can withstand the reducing atmosphere of the negative electrode that charges and discharges at a potential close to lithium. At present, the mainstream is one in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solvent of ethylene carbonate (EC) having a high dielectric constant and chain carbonate which is a low viscosity solvent. As the chain carbonate, one or more of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like are used. A polymer secondary battery uses a gel electrolyte in which these nonaqueous electrolytes are contained in a polymer component as a plasticizer.

A transition metal oxide having an average discharge potential with respect to lithium in the range of 3.5 V to 4.0 V is mainly used as the positive electrode active material of the nonaqueous electrolyte secondary battery. Examples of transition metal oxides include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and solid solution materials incorporating a plurality of transition metals (LiCo _x Ni _y Mn _z O such as _{2, Li (Co a Ni b} Mn c) 2 O 4) is used. The positive electrode active material is mixed with a conductive agent, a binder or the like and used as a positive electrode mixture. The positive electrode is produced by applying a positive electrode mixture to a current collector sheet made of aluminum foil, or compression molding in a sealing plate or case made of titanium or stainless steel.

  For the negative electrode, a carbon material that mainly stores and releases lithium is used. Examples of carbon materials include artificial graphite, natural graphite, mesophase fired bodies made from coal / petroleum pitch, non-graphitic carbon fired in the presence of oxygen, non-graphitic carbon made from fired oxygen-containing plastics, etc. It is done. The carbon material is mixed with a binder and used as a negative electrode mixture. The negative electrode is produced by applying a negative electrode mixture to a current collector sheet made of copper foil, or compression molding in a sealing plate or case made of iron or nickel.

When a graphite material is used for the negative electrode, the average potential for releasing lithium is about 0.2V. Since this potential is lower than that in the case of using non-graphite carbon, graphite materials are used in fields where high voltage and voltage flatness are desired. However, the graphite material has a small capacity per unit volume of 838 mAh / cm ^3, and no further increase in capacity can be expected.

  On the other hand, as a negative electrode material having a high capacity, a material capable of occluding and releasing lithium such as simple substances such as silicon and tin and oxides thereof is promising (Patent Document 1).

Silicon oxide is represented by the chemical formula SiO _x , and the capacity of lithium that can be stored and released varies depending on the x value. SiO _x is an amorphous material and has a non-stoichiometric composition. Therefore, the x value changes continuously. Usually, the x value is obtained as an average value of the atomic ratio of O to Si by the fundamental parameter method using fluorescent X-ray diffraction.

  However, these materials cause a change in crystal structure when lithium is occluded, and the volume expands. As a result, cracking of the particles, separation from the current collector, and the like are caused, and thus the charge / discharge cycle life is short. In particular, the cracking of the particles increases the reaction between the nonaqueous electrolyte and the active material, so that a film or the like is formed on the particles. This increases the interface resistance, which is a major cause of shortening the charge / discharge cycle life.

  In addition, when using a battery case with low strength, such as an aluminum or iron square case, an exterior material made of aluminum foil (aluminum laminate sheet) having a resin film on both sides, the battery thickness increases due to volume expansion of the negative electrode, There is a risk of damage to embedded devices. In a cylindrical battery using a high-strength battery container, the separator between the positive and negative electrodes is strongly compressed due to the volume expansion of the negative electrode, and a depleted portion of the electrolyte is generated between the positive and negative electrodes, so that the battery life is further shortened.

By incorporating lithium silicide (NiSi ₂ ), zinc, cadmium, or the like that does not occlude lithium or has a small occlusion amount into a material that occludes lithium, expansion per volume of the negative electrode can be reduced. However, since the lithium occlusion amount of the whole electrode plate, that is, the charge acceptance amount is lowered, it is not sufficient as a measure for increasing the capacity.

  Furthermore, when the whole negative electrode expands due to volume expansion or cracking of the particles, there is a problem that the internal pressure of the battery increases and safety is impaired. In the nail penetration test, it is possible to increase the safety to some extent by using a current collector sheet made of a resin core material and a metal layer covering the surface, but if the battery internal pressure increases, It becomes difficult to secure. Further, when a flammable carbon material is used as the negative electrode material, there is a limit to improvement in safety.

  As a method for producing a negative electrode using silicon oxide, a method is known in which silicon oxide, a binder and a liquid component are mixed to prepare a paste, which is applied to a core and then dried ( Patent Document 2). However, in this method, deterioration of the electrode plate due to the volume change of the active material accompanying charge / discharge is still a problem, and the cycle characteristics are insufficient.

Further, a negative electrode is reported in which a second layer made of silicon oxide is formed on a first layer containing carbon as a main component by vapor deposition, CVD, or sputtering (Patent Document 3). However, SiO _x having a composition close to x = 2 has been studied.
JP 2001-220124 A JP 2002-260651 A Japanese Patent No. 3520921

The volume expansion of the negative electrode during charge / discharge as described above becomes more serious especially when the battery is deep discharged. Hereinafter, the deep discharge will be described.
The battery is often left for a long time without being charged in a state where it is set in the device. However, even when the device is not used, a minute dark current flows through the battery set in the device. Therefore, if the device is left for a long period of time, the battery may be discharged to a level equal to or lower than the normal discharge end potential. Even in such a deep discharge state, when the device is used thereafter, it is required from the market that the device operates normally.

  Therefore, the present invention is a non-aqueous electrolyte secondary battery that can be increased in capacity, has a long cycle life, and is excellent in safety, and exhibits excellent cycle characteristics even when charging and deep discharging are repeated. It aims at providing the negative electrode which gives a water electrolyte secondary battery.

  The present invention has been found that if a silicon oxide in the vicinity of x = 1 is used, a battery maintaining excellent cycle characteristics can be obtained even when charge-deep discharge is repeated. It is a thing.

The present invention comprises a current collector sheet and an active material layer carried on the surface thereof, wherein the active material layer is made of SiO _x satisfying 0.7 ≦ x ≦ 1.3 and does not contain a binder. The present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery. A metal foil can be used for the current collector sheet. A current collector sheet made of a resin core material and a metal layer covering the surface thereof can also be used.

The surface of the metal foil can be covered with a layer containing a carbon material. The carbon material is, for example, carbon black or graphite.
The metal for the current collector sheet is preferably composed of at least one selected from the group consisting of gold, silver, copper, iron, nickel, zinc and aluminum.

  The resin core material is preferably made of at least one selected from the group consisting of polyethylene terephthalate, polycarbonate, aramid resin, polyimide resin, phenol resin, polyethersulfone resin, polyetheretherketone resin and polyamide resin.

The thickness of the active material layer is preferably 0.5 μm or more and 20 μm or less.
The present invention also relates to a secondary battery comprising the negative electrode, the positive electrode and a nonaqueous electrolyte.
The present invention also provides a method for producing a negative electrode for a nonaqueous electrolyte secondary battery including a step of depositing SiO _x satisfying 0.7 ≦ x ≦ 1.3 by vapor deposition on a current collector sheet to form an active material layer Regarding the method.

The negative electrode obtained by forming an active material layer made of silicon monoxide SiO _x (0.7 ≦ x ≦ 1.3) and containing no binder on the current collector sheet is bonded to silicon oxide. Compared to a negative electrode obtained by applying a mixture containing an agent to a current collector sheet, expansion / shrinkage associated with charge / discharge is small, and a decrease in current collection due to particle cracking or the like is also suppressed. Therefore, in addition to the high capacity, the charge / discharge cycle life, particularly the cycle life when charging and deep discharge are repeated, is effectively suppressed. Moreover, since the expansion of the negative electrode is suppressed, the battery internal pressure hardly increases, and the safety is improved.

The present invention comprises a current collector sheet and an active material layer carried on the surface thereof, and the active material layer is made of silicon monoxide SiO _x (0.7 ≦ x ≦ 1.3) for a non-aqueous electrolyte secondary battery. It relates to the negative electrode. However, the active material layer according to the present invention does not include a binder. Such an active material layer can be formed by directly depositing silicon monoxide SiO _x (0.7 ≦ x ≦ 1.3) on the current collector sheet.

The thickness of the active material layer made of silicon monoxide SiO _x (0.7 ≦ x ≦ 1.3) is preferably 20 μm or less, and more preferably 10 μm or less. In consideration of the energy density of the battery, the thickness of the active material layer is preferably 0.5 μm or more. However, if the thickness is less than 0.5 μm, the charge / discharge efficiency can be maintained high. Therefore, if the energy density does not need to be increased so much, even if the thickness of the active material layer is less than 0.5 μm, it is sufficiently practical. A simple battery can be manufactured.

Examples of the method for directly depositing silicon monoxide SiO _x (0.7 ≦ x ≦ 1.3) on the current collector sheet include vapor deposition, sputtering, and electrochemical methods. It is preferable to make it. The conditions for vapor deposition may be selected according to the desired thickness of the active material layer, the material of the current collector sheet, and the like.

  For the current collector sheet, for example, a metal foil having a thickness of 0.1 to 100 μm can be used. The metal foil may be three-dimensionally processed or perforated. Moreover, you may coat | cover the surface of metal foil with the layer containing a carbon material from a viewpoint of improving the electroconductivity of a negative electrode.

  When the surface of the metal foil is coated with a layer containing a carbon material, not only the conductivity of the negative electrode is improved, but also the layer containing the carbon material has a more uneven surface than on the metal foil. And the adhesion to the metal foil as a current collector is improved even when the active material layer is repeatedly expanded and contracted. As a result, the cycle characteristics are particularly improved.

  As a carbon material used for a layer containing a carbon material (hereinafter referred to as a carbon layer), acetylene black (hereinafter referred to as AB), ketjen black, graphitized VGCF (vapor phase), which has been conventionally used as a conductive material in a lithium battery or the like. And graphitized grown carbon fiber). Moreover, you may use carbon materials, such as a graphite conventionally used as the negative electrode of a lithium battery. In particular, when graphite or the like is used, since the lithium itself undergoes an insertion / release reaction of lithium, the capacity is improved as compared with the case of using a conductive material.

  The thickness of the carbon layer is preferably 5 μm or less when a conductive material is used. Even if it is thicker than 5 μm, it operates as a battery without any problem, but the charge / discharge capacity per volume of the battery becomes too small, which is disadvantageous in practice. On the other hand, no matter how thin the carbon layer is, there is no problem.

  When a carbon material capable of inserting and extracting lithium is used and a high capacity is intended, the thickness of the carbon layer is desirably 5 μm or less. When such a high capacity is not required, it may be thicker than 5 μm, or may be as thick as the silicon monoxide film.

  The metal foil is preferably made of a transition metal such as gold, copper, or iron that is not alloyed with lithium. However, when the negative electrode potential with respect to the lithium metal potential is 0.4 V or more during charging, the metal foil is made of aluminum, silver, or the like. It is also possible to use a metal foil. When the negative electrode potential is less than 0.4 V with respect to lithium metal, aluminum or silver may be alloyed with lithium to be powdered to reduce electronic conductivity. An alloy containing at least one selected from the group consisting of gold, silver, copper, iron, nickel, zinc, and aluminum can also be used.

  A current collector sheet comprising a resin core material and a metal layer covering the surface thereof can also be used. When such a current collector sheet is used, the surface of the current collector sheet has fine irregularities, so that the contact between silicon monoxide and the metal layer is good, and the electrical resistance can be further reduced. At the same time, safety is greatly improved. The thickness of the resin core material is preferably 3 to 100 μm, and more preferably 3 to 20 μm. The thickness of the metal layer covering the surface of the resin core is preferably 0.1 to 20 μm, but is not particularly limited as long as it does not exceed the thickness of the resin core. The resin core material preferably has a tensile strength of 20 MPa or more.

  As the resin core material, polyethylene terephthalate, polycarbonate, aramid resin, polyimide resin, phenol resin, polyether sulfone resin, polyether ether ketone resin, polyamide resin, or the like can be used. From the viewpoint of obtaining a high-strength resin core material, it is preferable to use a laminate of a plurality of resin films or to include a filler in the resin.

  The nonaqueous electrolyte secondary battery of the present invention can be produced by a method similar to the conventional method except that the above negative electrode is used. Therefore, what is conventionally used for the nonaqueous electrolyte secondary battery can be used for the positive electrode combined with the negative electrode and the nonaqueous electrolyte without any particular limitation.

The present invention can be applied to any type of battery, such as a cylindrical type, a square type, a laminate sheet packaging type, and a coin type. What is necessary is just to change the aspect of a positive electrode and a negative electrode according to the type of battery.
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
Example 1

  FIG. 1 shows a longitudinal sectional view of the nonaqueous electrolyte secondary battery produced in Example 1. FIG. This battery was produced as follows.

(I) Preparation of positive electrode 3 parts by weight of acetylene black as a conductive agent was mixed with 100 parts by weight of lithium cobaltate (LiCoO ₂ ) as an active material, and N of poly (vinylidene fluoride) (PVdF) as a binder was mixed into this mixture. 4 parts by weight of a methyl-2-pyrrolidone (NMP) solution in terms of PVdF was added and kneaded to obtain a paste-like positive electrode mixture. The positive electrode mixture was applied to one side of a current collector sheet 5 made of an aluminum foil having a thickness of 15 μm, and then dried and rolled to form the positive electrode active material layer 4. Next, the current collector sheet carrying the active material layer was cut so that the mixture area was 35 mm × 35 mm, and the positive electrode lead 8 was connected to the lead contact portion made of the exposed portion of the aluminum foil to obtain a positive electrode. . The thickness of the active material layer was 65 μm. The electric capacity of the positive electrode was 73.5 mAh when the capacity per unit weight of LiCoO ₂ was 155 mAh / g.

(Ii) Production of Negative Electrode A current collector sheet 2 made of copper foil having a length of 50 mm, a width of 50 mm, and a thickness of 10 μm was prepared, and this was set on a substrate of a vacuum heating deposition apparatus ED-1500 manufactured by Sunbac Co., Ltd. The inside of the chamber was evacuated to 1 × 10 ⁻⁴ Torr. Next, a silicon monoxide (SiO) powder (SIO05BP, purity 4N) manufactured by Kojundo Chemical Laboratory Co., Ltd. was deposited under the conditions of a deposition rate of 0.7 to 0.9 nm / second and a continuous deposition time of 1 hour. Deposition was carried out several times until a 20 μm silicon monoxide (SiO _x , x = 1) film 3 was obtained. The temperature of the substrate on which the copper foil was placed was controlled by cooling so as not to exceed 200 ° C. A silicon monoxide film having a thickness of 20 μm was also provided on the back surface of the copper foil by the same operation.

  A polyimide tape was affixed to the lead contact portion before vapor deposition, and after vaporizing silicon monoxide, the polyimide tape was peeled off. And the negative electrode lead 7 made from nickel was connected to the exposed part of copper foil, and it fixed with the tape made from a polypropylene from on the lead. The copper foil carrying silicon monoxide was cut so that the area of the silicon monoxide carrying portion was 37 mm × 37 mm to obtain a negative electrode. The electric capacity of the negative electrode was about 82.1 mAh when the capacity per unit weight of silicon monoxide was 1200 mAh / g. However, the capacity of the portion facing the positive electrode was 73.5 mAh.

As a method for depositing silicon monoxide, a vacuum heating vapor deposition method is employed this time. However, a similar film formation can be performed by a sputtering apparatus using a block-shaped silicon monoxide target. Also, a deposited film made of silicon monoxide having a content of components other than SiO of 10% or less can be obtained by using a mixture of Si and SiO ₂ as the silicon monoxide source.

(Iii) Production of Battery The positive electrode and the negative electrode were laminated through a separator 6 made of a polypropylene microporous film (# 2500) manufactured by Celgard with a thickness of 25 μm to constitute an electrode group. Each end of the positive electrode active material layer was disposed 1.0 mm inside from the end of the negative electrode active material layer. Next, the electrode group was dried in a vacuum dryer at 60 ° C. for 12 hours to reduce the amount of water in the electrode group to 50 ppm or less.

  The dried electrode group was accommodated in an exterior material 1 made of a laminate sheet (thickness 50 μm). As the laminate sheet, an aluminum foil having a modified polyethylene resin film on both sides was used. After the nonaqueous electrolyte was vacuum-injected into the exterior material, the lead portions of the negative electrode lead 7 and the positive electrode lead 8 were sealed with the resin 9 to complete the battery.

As the non-aqueous electrolyte, a solution in which LiPF ₆ having a concentration of 1 mol / L was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 3 was used.

The dimensions of the obtained battery were 40 mm in width, 40 mm in total height, and 0.5 mm in thickness. The battery was charged at a constant current of up to 4.2 V at a charging current of 7.2 mA at an ambient temperature of 20 ° C., paused for 20 minutes, and then discharged to a final voltage of 3.0 V at a discharge current of 7.2 mA. Charging / discharging was repeated twice. Finally, the battery was charged to a battery voltage of 4.2 V at a charging current of 7.2 mA. This battery was referred to as the battery of Example 1.
Example 2

A negative electrode was obtained by performing the same operation as in Example 1 except that the thickness of the silicon monoxide film was reduced to 10 μm by reducing the number of depositions. Further, in order to match the positive electrode capacity to the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to be half that of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 2.
Example 3

A negative electrode was obtained by performing the same operation as in Example 1 except that the thickness of the silicon monoxide film was changed to 5 μm by reducing the number of times of deposition. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to ¼ of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 3.
Example 4

A negative electrode was obtained by performing the same operation as in Example 1 except that the thickness of the silicon monoxide film was reduced to 3 μm by reducing the number of depositions. Further, in order to match the positive electrode capacity to the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to about 0.15 times those of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 4.
Example 5

A negative electrode was obtained by carrying out the same operation as in Example 1 except that the thickness of the silicon monoxide film was reduced to 0.5 μm by reducing the number of depositions. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to 1/40 of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 5.
Example 6

  The thickness of the silicon monoxide film was reduced to 10 μm by reducing the number of depositions, and a negative electrode was obtained in the same manner as in Example 1 except that a nickel foil having a thickness of 10 μm was used instead of the copper foil. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 6.

Comparative Example 1

  To 100 parts by weight of the carbon material as the active material, 4 parts by weight of an N-methyl-2-pyrrolidone (NMP) solution of poly (vinylidene fluoride) (PVdF) as the binder is converted into PVdF weight and kneaded. A paste-like negative electrode mixture was obtained. This negative electrode mixture was applied to both surfaces of a current collector sheet made of a copper foil having a thickness of 10 μm, dried at 60 ° C. for 8 hours, and rolled to form an active material layer. Next, the current collector sheet carrying the active material layer was cut, and a negative electrode lead was connected to a lead contact portion made of an exposed portion of the copper foil to obtain a negative electrode. The active material packing density was 1.2 g / cc, and the thickness of the negative electrode was 110 μm. The capacity of the carbon material per one side unit area was 3 mAh. A battery was produced in the same manner as in Example 1 except that this negative electrode was used. This battery was referred to as the battery of Comparative Example 1.

Comparative Example 2

To 100 parts by weight of silicon monoxide powder (SIO05BP, 90% particle size (D ₉₀ ) 75 μm) manufactured by Kojundo Chemical Laboratories Co., Ltd., which is an active material, N—of polyvinylidene fluoride (PVdF), which is a binder. 4 parts by weight of methyl-2-pyrrolidone (NMP) solution in terms of PVdF was added and kneaded to obtain a paste-like negative electrode mixture. This negative electrode mixture was applied to both surfaces of a current collector sheet made of a copper foil having a thickness of 10 μm, dried at 60 ° C. for 8 hours, and rolled to form an active material layer. Next, the current collector sheet carrying the active material layer was cut, and a negative electrode lead was connected to a lead contact portion made of an exposed portion of the copper foil to obtain a negative electrode. The capacity of silicon monoxide per unit area on one side was the same as in Example 1. A battery was produced in the same manner as in Example 1 except that this negative electrode was used. This battery was referred to as the battery of Comparative Example 2.
Example 7

A negative electrode was obtained by performing the same operation as in Example 1 except that the thickness of the silicon monoxide film was increased to 30 μm by increasing the number of depositions. Further, in order to match the positive electrode capacity to the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to about 1.5 times that of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 7.
Example 8

A negative electrode was obtained by performing the same operation as in Example 1 except that the thickness of the silicon monoxide film was 10 μm and an aluminum foil having a thickness of 10 μm was used instead of the copper foil. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 1. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 8.
Example 9

As a resin core material, a polyethylene terephthalate (PET) sheet having a length of 50 mm, a width of 50 mm, and a thickness of 10 μm was prepared. A copper vapor deposition film having a thickness of 2 μm was provided on both surfaces of the PET sheet. The vapor deposition conditions were the same as in the formation of the silicon monoxide film of Example 1 except that the target was changed to copper. Thereafter, the target was changed to the above-mentioned silicon monoxide powder (purity 4N), and a silicon monoxide film having a thickness of 20 μm was formed on both surfaces in the same manner as in Example 1. During the vapor deposition of copper and silicon monoxide, the temperature was controlled by cooling so that the substrate on which the resin core material was placed did not exceed 100 ° C. A battery was produced in the same manner as in Example 1 except that this negative electrode was used. This battery was referred to as the battery of Example 9.
Example 10

A negative electrode was obtained by carrying out the same operation as in Example 9 except that the thickness of the silicon monoxide film was reduced to 10 μm by reducing the number of depositions. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 10.
Example 11

A negative electrode was obtained by performing the same operation as in Example 9 except that the thickness of the silicon monoxide film was reduced to 5 μm by reducing the number of depositions. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to ¼ of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 11.
Example 12

A negative electrode was obtained by performing the same operation as in Example 9 except that the thickness of the silicon monoxide film was reduced to 3 μm by reducing the number of times of deposition. Further, in order to match the positive electrode capacity to the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to about 0.15 times those of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 12.
Example 13

A negative electrode was obtained in the same manner as in Example 9 except that the thickness of the silicon monoxide film was reduced to 0.5 μm by reducing the number of times of deposition. Further, in order to match the positive electrode capacity to the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to 1/40 of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 13.
Example 14

A negative electrode was obtained in the same manner as in Example 9 except that a nickel film having a thickness of 5 μm was deposited on the resin core instead of copper and the thickness of the silicon monoxide film was changed to 10 μm. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 14.
Example 15

A negative electrode was obtained in the same manner as in Example 9 except that a polyimide sheet having a thickness of 10 μm was used instead of the PET sheet and the thickness of the silicon monoxide film was changed to 10 μm. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 15.
Example 16

A negative electrode was obtained in the same manner as in Example 9 except that a polypropylene sheet having a thickness of 10 μm was used instead of the PET sheet and the thickness of the silicon monoxide film was changed to 10 μm. Moreover, in order to match the positive electrode capacity with the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were changed to half of Example 9. Using these positive and negative electrodes, a battery was produced in the same manner as in Example 1. This battery was referred to as the battery of Example 16.
Example 17

  First, the carbon layer was apply | coated on both surfaces of the copper core material. That is, to 100 parts by weight of AB, an NMP solution of polyvinylidene fluoride (PVdF) as a binder was added in an amount of 10 parts by weight in terms of PVdF, and kneaded to obtain a paste. This was applied to both sides of a current collector sheet made of a copper foil having a thickness of 10 μm, dried at 60 ° C. for 8 hours, and rolled to form a carbon layer having a thickness of 0.5 μm.

A silicon monoxide film having a thickness of 10 μm was produced on this sheet in the same manner as in Example 9 with the number of depositions reduced. In order to match the positive electrode capacity and the negative electrode capacity, the thickness and the active material weight of the positive electrode active material layer were halved in Example 9.
A battery was produced in the same manner as in Example 1 using these positive electrode and negative electrode. This battery was referred to as the battery of Example 17.
Example 18

A battery was produced in the same manner as in Example 17 except that the thickness of the layer containing AB (carbon layer) was changed to 1 μm by changing the coating thickness, and Example 18 was obtained.
Example 19

A battery was produced in the same manner as in Example 17 except that the thickness of the layer containing AB (carbon layer) was changed to 2 μm by changing the coating thickness, and Example 19 was obtained.
Example 20

A battery was produced in the same manner as in Example 17 except that the thickness of the layer containing AB (carbon layer) was changed to 5 μm by changing the coating thickness, and Example 20 was obtained.
<< Example 21 >>

A battery was produced in the same manner as in Example 17 except that the thickness of the layer containing AB (carbon layer) was changed to 10 μm by changing the coating thickness, and Example 21 was obtained.
Example 22

The battery was fabricated in the same manner as in Example 17 except that VGCF (graphite-grown carbon fiber graphitized at 2800 ° C., average fiber diameter 0.5 μm) was used as the carbon material, and the carbon layer thickness was 2 μm. This was produced as Example 22.
<< Examples 23 to 26 >>

As the carbon material, several types of graphite with different particle shapes were studied.
Here, scaly graphite (FG), spherical graphite, massive graphite (MAG) and fibrous graphite were used. As the spherical graphite, graphitized mesocarbon microbeads (hereinafter referred to as MCMB) were used, and as the fibrous graphite, graphitized mesocarbon fiber (hereinafter referred to as MCF) having a fiber diameter of 2 μm was used. As the scaly, spherical and massive graphite, those having an average particle diameter of 1 to 3 μm were used.

To 100 parts by weight of graphite, an NMP solution of polyvinylidene fluoride (PVdF) as a binder was added in an amount of 4 parts by weight in terms of PVdF and kneaded to obtain a paste. This was applied to both sides of a current collector sheet made of a copper foil having a thickness of 10 μm, dried at 60 ° C. for 8 hours, and rolled to form a carbon layer having a thickness of 2 μm. The graphite packing density at this time was 1.2 g / cc, and the thickness was 5 μm.
A silicon monoxide film having a thickness of 10 μm was produced on this sheet in the same manner as in Example 9 with the number of depositions reduced. A battery was produced in the same manner as in Example 17, except that the thus obtained negative electrode was used.
Example 27

  A battery was fabricated in the same manner as in Example 23, except that the binder of Example 23 was changed to SBR (styrene butadiene rubber), which is one type of rubber-based binder.

Comparative Example 3

Silicon monoxide powder (SIO05BP, 90% particle size (D ₉₀ ) 75 μm) manufactured by Kojundo Chemical Laboratory Co., Ltd. was pulverized by a ball mill using zirconia beads.
First, after coarsely pulverizing with beads having a diameter of 5 mm, further pulverizing with beads having a diameter of 2 mm. As a result, a SiO powder having a particle size D ₉₀ of 10 μm was obtained. A battery was produced in the same manner as in Comparative Example 2 except that the above powder was used.

Comparative Examples 4-5

  A battery was fabricated in the same manner as in Comparative Example 2, except that a nickel foil or aluminum foil having a thickness of 10 μm was used instead of the copper foil as the negative electrode current collector sheet.

[Battery evaluation]
(A) Charge / Discharge Cycle Life Under an environment of 20 ° C., a constant current charge is performed to a battery voltage of 4.2 V at a charge current of 7.2 mA, and after resting for 20 minutes, a discharge current of 7.2 mA and a final voltage of 3. Charging / discharging for discharging to 0V was repeated. The discharge capacity at the second cycle was defined as the initial capacity of the battery. The charge / discharge cycle was repeated 100 cycles, and the maintenance ratio of the discharge capacity to the initial capacity at the 101st cycle was calculated.

(B) Safety Under a 20 ° C. environment, charge current is 7.2 mA at a constant current to a battery voltage of 4.2 V. After a 20-minute pause, the discharge current is 7.2 mA and the end voltage is 3.0 V. Charging / discharging for discharging was repeated twice. The battery was removed from the charging / discharging device in the state where the third cycle charge was performed and the battery voltage reached 4.2 V (full charge state). An alumel-chromel thermocouple was fixed with glass tape at a position 5 mm away from the center of the side surface of the fully charged battery, and connected to a recorder. The battery to which the thermocouple was fixed was placed on an insulating board made of alumina board, and a nail having a diameter of 1 mm was passed through substantially the center of the side surface of the battery. Then, the battery side surface temperature was observed with the above-mentioned recorder, and the highest temperature reached was determined.

  Tables 1 to 3 show the initial capacity, the volume energy density, the capacity retention rate after 100 cycles, and the maximum temperature reached on the battery side surface in the safety test.

(C) High rate characteristic About the battery of Examples 17-27, the high rate characteristic was evaluated. The high-rate characteristics were calculated as a ratio of “discharge capacity when discharged at a current value of 36 mA (equivalent to 0.5 C)” to “discharge capacity when discharged at a current value of 7.2 mA (equivalent to 0.1 C)”. .

  In the case of Example 1, the initial capacity should theoretically be 73.5 mAh, but in the case of a battery using silicon monoxide, the capacity is reduced by about 40%. Since both the charge and discharge currents are equivalent to 0.1 C with respect to the battery capacity, and the current is sufficiently small with respect to the electrode thickness and the amount of active material, the capacity reduction is considered to depend on the irreversible capacity of silicon monoxide. However, it can be seen that the energy density is still higher than that of the battery of Comparative Example 1 using the carbon material as the negative electrode material.

  As shown in Table 1, when the thickness of the silicon monoxide film is up to 20 μm, the capacity retention rate after 100 cycles is equivalent to that of the battery of Comparative Example 1 using the carbon material. However, when the film thickness is larger than that, the capacity retention rate is greatly reduced. This is presumably because small pores increase in the active material layer due to the volume expansion of the silicon monoxide film accompanying charge / discharge, and the amount of non-aqueous electrolyte is insufficient. This can be inferred from the fact that when the battery internal resistance at the initial stage and after 100 cycles was measured, the internal resistance, particularly the resistance of the imaginary part increased.

  When the thickness of the silicon monoxide film is less than 10 μm, the volume energy density is extremely reduced, because the ratio of battery components not related to the electric capacity with respect to the amount of active material is increased. Here, since the battery capacity retention rate is focused, the thickness of the resin core is fixed at 10 μm. However, when a thin resin core of, for example, 5 μm or less is used, a negative electrode made of a carbon material is used. It can be improved to the same level as the battery of Comparative Example 1.

  As shown in Table 1, the capacity retention rate of the battery increases as the thickness of the silicon monoxide film decreases. Here, the thickness of the silicon monoxide film is set to a minimum of 0.5 μm, but it is clear that a sufficient cycle life can be obtained even with a silicon monoxide film of less than 0.5 μm. If it exists, even if it is a silicon monoxide film | membrane less than 0.5 micrometer, it is thought that it can fully apply.

In Comparative Example 2, since the silicon monoxide powder having a particle diameter D ₉₀ of 75 μm is used instead of the silicon monoxide deposited film, the cycle life is greatly deteriorated. This is thought to be because the particles that make up the powder are much larger than the particles that make up the deposited film, and the particles are distorted by the expansion and contraction of the particles that accompany charge and discharge, resulting in particle cracking and reduced current collection. . On the other hand, in Comparative Example 3 in which the particle diameter D ₉₀ of the SiO powder was reduced to 10 μm, the initial capacity and volumetric energy density were slightly reduced, and the maintenance factor and the maximum temperature were slightly higher than in Comparative Example 2. It was. The reason why the initial capacity and the volume energy density are decreased is considered to be that the filling property of the SiO powder into the negative electrode is decreased due to the small particle diameter. In addition, the reason why the maintenance ratio and the maximum temperature were increased is thought to be that the specific surface area of the SiO powder was increased. In any case, the result of Comparative Example 3 was not much different from that of Comparative Example 2 as a whole.

  Next, the result of Comparative Example 4 in which Ni was used instead of Cu as the current collector sheet was almost the same as the case where Cu was used. On the other hand, in Comparative Example 5 in which Al was used instead of Cu, the battery characteristics were generally lowered. This is the same tendency as in Example 8, and it is considered that Al was alloyed with lithium during charging and powdered to increase resistance.

  Even when polyimide having a higher strength than the PET sheet was used as the resin core material, the capacity retention rate did not improve much, but conversely, in Example 16 using polypropylene having a lower strength, the capacity retention rate was lowered. . This is because polypropylene has insufficient resistance to expansion and contraction associated with charging and discharging of silicon monoxide, and the resin core material expands and contracts, resulting in damage to the copper vapor deposition film serving as a current collector. Conceivable. Therefore, it is desirable to select a material having a high tensile strength as the resin core material. A resin core material having a tensile strength of 20 MPa or more can be particularly preferably used because the electronic conductivity between the active materials is not impaired by the flexibility of the resin. The improvement effect of the capacity retention rate by the resin core material that can follow the expansion and contraction of the active material can also be confirmed from the comparison of Examples 10, 15, and 16.

  In the negative electrode current collector sheet, the best capacity retention rate is obtained when copper is used, and relatively good capacity maintenance rates are also obtained in Example 6 and Example 14 in which nickel is used. ing. On the other hand, in Example 8 using aluminum, the capacity retention rate is greatly reduced. This is presumably because Al was alloyed with lithium during charging and powdered to increase resistance. However, Al can be used for the current collector sheet of the negative electrode as long as the charging is completed up to a potential of 0.4 V or more with respect to lithium.

  From the result of the safety test, it can be seen that the safety of the battery using the deposited film of silicon monoxide is greatly improved as compared with the battery using the powdered silicon monoxide. If the battery capacity is the same, the maximum temperature at the side of the battery is lower when the resin core material is used than when the resin core material is not used. Moreover, compared with the comparative example 1, the battery of an Example has the low ultimate temperature of 10 degreeC or more, and it turns out that all are excellent in safety | security. In the nail penetration test, since the short-circuit current between the positive and negative electrodes continues to flow, the heat of chemical reaction and Joule heat accumulates and the battery temperature rises. This is considered to be due to dissolution and loss of electronic conductivity, which suppresses further heat generation.

Comparing Table 2 and Table 3, the following can be understood.
(A) When the carbon layer is provided, the rate characteristics are greatly improved as compared with the case where the carbon layer is not provided.
(B) The rate characteristics improve as the thickness of the carbon layer containing AB increases (Examples 17 to 21).
(C) When it has a carbon layer, the cycle maintenance factor improves as a whole. This is presumably because the adhesion between the carbon layer and the current collector is good and the contact resistance between SiO and the current collector is reduced. Usually, when a charge / discharge cycle is repeated over a long period of time, the electrode plate repeatedly expands and contracts along with charge / discharge, which causes peeling from the current collector, but this is considered to be reduced.

(D) When graphite is used, the capacity itself increases because it itself participates in charging and discharging of lithium. In addition, when graphite is used, the cycle retention ratio is slightly inferior to that when a conductive material such as AB is used, but is within an allowable range.

(E) The cycle maintenance rate is improved by using SBR compared to PVdF. Although details are unknown, it can be seen that a rubber-based binder is preferable to PVdF as a binder for the carbon layer (Examples 23 to 27).
Next, the value of x of SiO _x was examined.
<< Examples 28 to 29 >>

  Example 1 except that instead of SiO powder alone, Si powder (SIE13PB, average particle diameter (diameter) 10 μm or less, purity 4N) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used in combination with SiO powder as a raw material. A negative electrode was produced in the same manner as described above.

Here, Si powder and SiO powder were set in separate boats in the chamber, and each was heated independently and deposited at the same time. The heating temperature of each boat was controlled so that a deposited film composed of SiO _x having an average x value of 0.7 or 0.9 was obtained. The x value was calculated using fluorescent X-ray diffraction and the fundamental parameter method.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.
<< Examples 30 to 31 >>

A negative electrode was produced in the same manner as in Example 28 except that a slight amount of oxygen gas was allowed to flow into the chamber during vacuum deposition while maintaining the degree of vacuum in the chamber at 10 ⁻⁴ Torr.
Here, the heating temperature and oxygen gas flow rate of each boat were controlled so that a deposited film made of SiO _x having an average x value of 1.1 or 1.3 was obtained. The x value was calculated using fluorescent X-ray diffraction and the fundamental parameter method.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Examples 6-7

A negative electrode was produced in the same manner as in Example 28 except that the heating temperature of each boat was controlled so that a deposited film composed of SiO _x having an average x value of 0.3 or 0.5 was obtained. The value of x was calculated using a fundamental parameter method using fluorescent X-ray diffraction.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Examples 8-9

A negative electrode was produced in the same manner as in Example 30 except that the heating temperature and oxygen gas flow rate of each boat were controlled so that a deposited film made of SiO _x having an average x value of 1.5 or 1.7 was obtained. Went. The value of x was calculated using a fundamental parameter method using fluorescent X-ray diffraction.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 10

In place of the SiO powder alone as a raw material, a negative electrode comprising a Si thin film was produced in the same manner as in Example 1 except that Si powder (SIE13PB, purity 4N) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used alone. Fabrication was performed.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 11

The same method as in Example 1 except that instead of SiO powder alone, SiO ₂ powder (SIO13PB, average particle diameter (diameter) 600 μm or less, purity 5N) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used as the raw material. Thus, a negative electrode made of a SiO ₂ thin film was produced.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 12

Comparative example except that Si powder (SIE13PB, purity 4N) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used instead of silicon monoxide powder (SIO05BP, 90% particle size (D ₉₀ ) 75 μm) as the active material. In the same manner as in No. 2, a negative electrode was produced. A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 13

A deposition film made of SiO _x having an average x value of 0.5 was prepared in the same manner as in Comparative Example 7, and the process of scraping the thin film from the copper foil was repeated to obtain the required amount of SiO _0.5 powder. . This SiO _0.5 powder was pulverized with a ball mill, and a negative electrode was produced in the same manner as in Comparative Example 2 using the pulverized powder.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 14

Instead of the silicon monoxide powder as an active material (SIO05BP, 90% particle size (D ₉₀₎ 75 [mu] m), except for using (Ltd.) by Kojundo Chemical Laboratory of SiO powder (SIO15PB, average particle size of about 10 [mu] m) A negative electrode was prepared in the same manner as in Comparative Example 2. A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 15

In the same manner as in Comparative Example 8, a deposited film made of SiO _x having an average x value of 1.5 was prepared, and the process of scraping the thin film from the copper foil was repeated to obtain a required amount of SiO _1.5 powder. . This SiO _1.5 powder was pulverized with a ball mill, and a negative electrode was produced in the same manner as in Comparative Example 2 using the pulverized powder.
A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

Comparative Example 16

In place of silicon monoxide powder (SIO05BP, 90% particle size (D ₉₀ ) 75 μm) as an active material, SiO ₂ powder (SiO14PB, average particle size of about 1 μm) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used. A negative electrode was produced in the same manner as in Comparative Example 2 except for the above. A battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode was used.

The batteries of Examples 28 to 31 and Comparative Examples 6 to 16 were evaluated in the same manner as Example 1.
Tables 4 and 5 show the initial capacity, the volume energy density, the capacity retention rate after 100 cycles, the maximum temperature reached on the side surface of the battery in the safety test, and the high rate characteristics.

Furthermore, the deep discharge characteristics of each battery were evaluated in the following manner. Here, in order to clarify the characteristics of the deposited film made of SiO _x, model batteries using the negative electrodes produced in Examples 28 to 31 and Comparative Examples 6 to 16 as working electrodes were produced. As the counter electrode of the working electrode, a 37 mm × 37 mm lithium foil (thickness 150 μm) stuck on a copper plate was used. A nickel lead was previously connected to the exposed portion of the copper plate.

A model battery was produced in the same manner as in Example 1 except that the working electrode and the counter electrode were opposed to each other via a separator.
In the evaluation of the deep discharge characteristics, the following charge / discharge was repeated.
First, at an ambient temperature of 20 ° C., the battery is charged with a constant current at a current of 7.2 mA until the battery voltage reaches 0 V, pauses for 20 minutes, and then at a current of 7.2 mA until the battery voltage reaches 1.5 V. Discharged. This charge / discharge was repeated three times.

Charging here refers to the case where Li moves to the working electrode, and the potential of the working electrode becomes lower due to charging.
Thereafter, the ambient temperature and the charging / discharging current were the same as described above, and charging / discharging for charging up to the battery voltage 0V and discharging up to the battery voltage 3.0V was repeated 50 times. The maintenance ratio of the discharge capacity at the 50th cycle to the discharge capacity at the first cycle was defined as the deep discharge characteristics. The results are shown in Tables 4 and 5.

In Tables 4 and 5, no initial capacity was obtained when SiO ₂ was used. Therefore, the capacity retention rate after 100 cycles, the maximum temperature reached on the side of the battery in the safety test, the high rate characteristics, and the deep discharge characteristics were not evaluated.

As is clear from Table 4, when SiO _x having an x value of 0.7 to 1.3, particularly 0.9 to 1.3 is used, the deep discharge characteristics are particularly excellent and both are maintained at a high level. Showed the rate. On the other hand, when the x value was smaller than 0.7 and larger than 1.3, the deep discharge characteristics were greatly lowered and the maintenance rate was lowered. This result shows that a battery having specifically excellent deep discharge characteristics can be obtained by using SiO _x in the region where the x value is 0.7 to 1.3, particularly 0.9 to 1.3. Show.

This result is probably due to the following reasons.
When the x value of SiO _x is 0.7 to 1.3, it is considered that in the charged state in which Li is inserted into SiO _x , O—Li bonds are formed in addition to Si—O bonds. It is done. Among the bonds, the O—Li bond is relatively strong, and even if deep discharge is performed until the SiO _x becomes 3.0 V with respect to the metal Li, it is difficult for Li to escape from the O—Li bond. Therefore, even when charge-deep discharge is repeated, the degree of expansion and contraction is not so different from that of normal charge / discharge, and the cycle characteristics are relatively good.

In particular, when the x value is 0.9 to 1.3, the cycle characteristics when charging and deep discharging are repeated are good. This is presumably because there are many O-Li bonds.
On the other hand, when the x value of SiO _x is smaller than 0.7, since the amount of O is small, O—Li bonds are relatively reduced, and Li is easily removed. In particular, when x = 0, that is, when Si is used, no O—Li bond exists. Therefore, if charge-deep discharge is repeated, the active material expands and contracts more intensely than during normal charge / discharge, causing the deposited film to collapse and the like, resulting in considerably poor cycle characteristics.

In addition, when the x value of SiO _x is larger than 1.3, the Si—O bond is very strong, so that the Li—O bond is not easily formed, and even if formed, the bond is very weak. It is considered to be. Therefore, when Li is easily removed from SiO _x and charge-deep discharge is repeated, the expansion and contraction of the active material becomes more intense than in normal charge and discharge as in the case where the x value is smaller than 0.7. Incidentally, at the SiO _2, Li-O bond is presumed to hardly formed.

  Next, in the case of an active material layer formed by preparing a paste containing an active material powder and a binder, applying this to a copper foil, and then drying, the cycle characteristics when charging and deep discharging are repeated are: Overall, it was lower than in the case of the deposited film. Moreover, even if the x value of the active material powder changed, the cycle characteristics when charging and deep discharging were repeated did not change so much.

This is because, in the case of an electrode using an active material powder, the particles are cracked or collapsed due to expansion and contraction during charge and discharge, or the adhesion between the particles within the active material layer is weakened, and the electric resistance of the electrode It is thought to increase. Moreover, this tendency is also observed in a normal charge / discharge cycle, and is not unique when charge-deep discharge is repeated. Therefore, even if the x value of the active material powder changes, it is considered that no significant change was observed in the cycle characteristics when the charge-deep discharge was repeated. From the above, it can be seen that the x value of SiO _x greatly affects the characteristics of the deposited film, and such an effect is unique to the deposited film.

  By applying the present invention to a negative electrode for a non-aqueous electrolyte secondary battery comprising a current collector sheet and an active material layer carried on the surface of the current collector sheet, the active material layer does not contain a binder, a high capacity, cycle A non-aqueous electrolyte secondary battery having a long life, excellent safety, and excellent cycle characteristics even when repeated charge-deep discharge is obtained.

It is a longitudinal cross-sectional view of an example of the nonaqueous electrolyte secondary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exterior material 2 Current collector sheet made of copper foil 3 SiO _x film 4 Positive electrode active material layer 5 Current collector sheet made of aluminum foil 6 Separator 7 Negative electrode lead 8 Positive electrode lead 9 Resin

Claims (25)

It consists of a current collector sheet and an active material layer carried on the surface thereof,
The negative electrode for a non-aqueous electrolyte secondary battery, wherein the active material layer is made of SiO _x satisfying 0.7 ≦ x ≦ 1.3 and does not contain a binder.   The negative electrode according to claim 1, wherein the current collector sheet is made of a metal foil.   The negative electrode according to claim 2, wherein the surface of the metal foil is coated with a layer containing a carbon material.   The negative electrode according to claim 3, wherein the carbon material is at least one selected from the group consisting of carbon black and graphite.   The negative electrode according to claim 4, wherein the carbon black is at least one selected from the group consisting of acetylene black and ketjen black.   The negative electrode according to claim 4, wherein the graphite is at least one selected from the group consisting of flaky graphite, spherical graphite, massive graphite, and fibrous graphite.   The negative electrode according to claim 1, wherein the current collector sheet comprises a resin core material and a metal layer covering the surface thereof.   The negative electrode according to claim 2 or 7, wherein the metal is at least one selected from the group consisting of gold, silver, copper, iron, nickel, zinc, and aluminum.   The said resin core material consists of at least 1 sort (s) chosen from the group which consists of a polyethylene terephthalate, a polycarbonate, an aramid resin, a polyimide resin, a phenol resin, a polyether sulfone resin, a polyether ether ketone resin, and a polyamide resin. Negative electrode.   The negative electrode according to claim 7 or 9, wherein the resin core material has a tensile strength of 20 MPa or more.   The negative electrode according to claim 7 or 9, wherein the resin core material has a thickness of 3 to 100 µm.   The negative electrode according to claim 1, wherein the active material layer has a thickness of 0.5 μm or more and 20 μm or less.   The secondary battery which consists of a negative electrode in any one of Claims 1-12, a positive electrode, and a nonaqueous electrolyte. A method for producing a negative electrode for a nonaqueous electrolyte secondary battery, comprising a step of depositing SiO _x satisfying 0.7 ≦ x ≦ 1.3 by vapor deposition on a current collector sheet to form an active material layer.   The manufacturing method according to claim 14, wherein the current collector sheet is made of a metal foil.   The manufacturing method according to claim 15, wherein the surface of the metal foil is coated with a layer containing a carbon material.   The production method according to claim 16, wherein the carbon material is at least one selected from the group consisting of carbon black and graphite.   The production method according to claim 17, wherein the carbon black is at least one selected from the group consisting of acetylene black and ketjen black.   The production method according to claim 17, wherein the graphite is at least one selected from the group consisting of flaky graphite, spherical graphite, massive graphite, and fibrous graphite.   The manufacturing method according to claim 14, wherein the current collector sheet includes a resin core material and a metal layer covering the surface thereof.   The manufacturing method according to claim 15 or 20, wherein the metal is at least one selected from the group consisting of gold, silver, copper, iron, nickel, zinc, and aluminum.   The said resin core material consists of at least 1 sort (s) chosen from the group which consists of a polyethylene terephthalate, a polycarbonate, an aramid resin, a polyimide resin, a phenol resin, a polyether sulfone resin, a polyether ether ketone resin, and a polyamide resin. Production method.   The manufacturing method according to claim 20 or 22, wherein the resin core material has a tensile strength of 20 MPa or more.   The manufacturing method according to claim 20 or 22, wherein the resin core material has a thickness of 3 to 100 µm.   The manufacturing method according to any one of claims 14 to 20, wherein the active material layer has a thickness of 0.5 µm or more and 20 µm or less.

Images