WO2012132154A1 - Secondary battery - Google Patents

Abstract

A secondary battery which comprises: a positive electrode; a separator; a negative electrode that is arranged so as to face the positive electrode with the separator being interposed therebetween; an electrolyte solution; and a case that contains the aforementioned components. The negative electrode contains, as negative electrode active materials, a resin component and a metal (a) that can be alloyed with lithium. The resin component contains a resin that has an amide-imide structural unit, which is derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof, or an imide structural unit, which is derived from an aromatic tetracarboxylic acid or a derivative thereof and an aromatic diamine or a derivative thereof. The resin component has a contact angle with water of less than 70˚.

Description

Secondary battery

The present invention relates to a secondary battery.

With the rapid market expansion of notebook computers, mobile phones, electric vehicles, etc., secondary batteries with high energy density are required. Various techniques have been proposed, such as using a negative electrode material having a large capacity in order to increase the energy density, and using a binder having an excellent binding force in order to improve cycle characteristics.

Patent Document 1 describes that a lithium-containing silicon oxide or silicate is used as a negative electrode active material of a nonaqueous electrolyte secondary battery.

Patent Document 2 discloses carbon material particles that can occlude and release lithium ions (eg, graphite), metal particles that can be alloyed with lithium (eg, silicon, aluminum, tin, indium, and zinc), and oxidation that can occlude and release lithium ions. A negative electrode for a secondary battery having an active material layer containing physical particles (for example, silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, phosphoric acid compound, boric acid compound) is described.

Patent Document 3 describes a negative electrode material for a non-aqueous electrolyte secondary battery using a conductive silicon composite in which the surface of particles having a structure in which silicon microcrystals are dispersed in a silicon compound is coated with carbon.

Patent Document 4 describes a negative electrode for a lithium secondary battery including active material particles containing silicon and / or silicon alloy having a specific average particle size and particle size distribution, and polyimide as a binder.

Patent Document 5 describes a negative electrode for a non-aqueous electrolyte secondary battery including an active material containing Si, polyimide and polyacrylic acid as a binder, and a carbon material as a conductive material.

Patent Document 6 discloses a non-aqueous electrolyte secondary battery including active material particles in which a mixture of simple silicon and silicon oxide is coated with carbon (a mixture of amorphous carbon and graphite) and a thermosetting resin as a binder. A negative electrode is described. Examples of the binder include polyimide, polyamide, polyamideimide, and polyacrylic acid resin. Regarding the polyimide and polyacrylic acid resin, a battery using these is prepared and evaluated.

Patent Document 7 discloses the ratio of the adhesion area of the coating film to the surface of the metal foil in a negative electrode for a non-aqueous electrolyte secondary battery in which a coating film made of an electrode active material carrier and a binder component is formed on the surface of the metal foil. In addition, it is described that a polyamide-imide resin is included as a binder component.

Patent Document 8 discloses a polyamideimide excellent in adhesiveness, which contains a 4,4′-diaminodiphenyl ether residue and an m-phenylenediamine residue in a specific ratio and has a specific residual carboxyl group amount and gelling activity. It describes that a resin can be used as a binder for a Li-ion secondary battery.

Patent Document 9 and Patent Document 10 describe resins containing specific aramid structural units and specific amidoimide structural units. Further, Patent Document 9 has these structural units and further structural units in which carboxyl groups remain without ring closure of imide, and has a specific copolymer composition, so that it has excellent adhesiveness and volume expansion due to charge / discharge. It is described that it is possible to provide a resin for a lithium ion secondary battery electrode binder that is excellent in retention of a negative electrode active material having large shrinkage.

In Patent Document 11, an oxide in which the surface of a compound containing Si and O is coated with carbon is used as a negative electrode active material, and polyimide, polyamideimide, or polyamide is used as a binder. A lithium secondary battery is described in which at least one of the agent layers is bonded to the separator. Actually, only a battery using polyimide as a binder is manufactured and a charge test is performed.

Patent Document 12 has an active material layer containing particles of an active material containing Si or Sn, and the surface of the active material layer is a polymer film having a large number of pores containing polyvinylidene fluoride or polyamideimide. A coated negative electrode for a non-aqueous electrolyte secondary battery is described.

JP-A-6-325765 JP 2003-123740 A JP 2004-47404 A Japanese Patent Laid-Open No. 2004-22433 JP 2007-95670 A JP 2008-153117 A JP 2000-149921 A JP 2007-246680 A WO2008 / 105036 JP 2007-84808 A JP 2009-152037 A JP 2009-176703 A

However, in the secondary battery using the silicon oxide described in Patent Document 1 as the negative electrode active material, there is a problem of capacity reduction accompanying the charge / discharge cycle.

Although the negative electrode for a secondary battery described in Patent Document 2 has an effect of relieving stress and strain associated with volume change associated with insertion and extraction of lithium, the characteristics of a secondary battery using such a negative electrode are sufficient. It was not a thing. Moreover, although the negative electrode material for secondary batteries described in Patent Document 3 has an effect of suppressing volume change associated with insertion and extraction of lithium, the characteristics of a secondary battery using such a negative electrode material are sufficient. It wasn't.

In the secondary battery negative electrode described in Patent Document 4 and Patent Document 5, while using a silicon-based active material and polyimide as a binder, the characteristics of the secondary battery using such a negative electrode are sufficient. It was not a thing.

In the negative electrode for secondary battery described in Patent Document 6, while using a silicon-based active material and using a polyimide or a polyacrylic acid-based resin as a binder, an improvement in cycle characteristics is shown, but polyamideimide is used. There is no specific description of the secondary battery. For secondary batteries using such silicon-based negative electrode active materials, further improvements have been demanded.

Patent Documents 7 to 10 describe the use of polyamideimide as a binder, but further improvements have been demanded for secondary batteries using such a binder.

In the lithium secondary battery described in Patent Document 11, a silicon-based active material is used for the negative electrode, polyimide is used as the binder, and the separator is bonded to at least one of the negative electrode mixture layer and the positive electrode mixture layer. Although it has been shown that the volume change of the negative electrode accompanying discharge can be suppressed, there is no specific description of a secondary battery using polyamideimide as a binder. For secondary batteries using such silicon-based negative electrode active materials, further improvements have been demanded.

The negative electrode described in Patent Document 12 covers the surface of an active material layer containing Si-based active material particles with a coating having a large number of pores to prevent the active material from falling off, and there is room for further improvement. there were.

In the laminated laminate type lithium ion secondary battery using a metal that can be alloyed with lithium such as silicon as the negative electrode active material, in addition to the problem due to the volume change of the negative electrode active material due to charge and discharge, The inventors discovered problems that the secondary battery itself swells when charged and discharged in a high temperature environment, and conducted extensive studies to solve these problems.

An object of the present invention is to provide a secondary battery having good cycle characteristics.

A secondary battery according to an aspect of the present invention includes a positive electrode, a separator, a negative electrode disposed to face the positive electrode with the separator interposed therebetween, an electrolytic solution, and an outer package including these.
The negative electrode includes a metal (a) that can be alloyed with lithium as a negative electrode active material, and a resin component.
The resin component includes an amide imide structural unit derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof, or an imide structural unit derived from an aromatic tetracarboxylic acid or a derivative thereof and an aromatic diamine or a derivative thereof. Including resin,
The contact angle of the resin component with water is less than 70 °.

According to the embodiment of the present invention, a secondary battery having good cycle characteristics can be provided.

1 is a schematic cross-sectional view showing a structure of a laminated laminate type secondary battery according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.

The secondary battery according to the present embodiment includes a positive electrode, a separator, an electrode stack including a negative electrode disposed to face the positive electrode with the separator interposed therebetween, an electrolyte, and an exterior body that includes them. In one container made of the outer package, the electrode laminate may include one electrode pair of a positive electrode and a negative electrode, or may include two or more electrode pairs.

FIG. 1 is a schematic cross-sectional view showing an example of an electrode laminate of such a laminated secondary battery. In FIG. 1, the exterior body is omitted. The positive electrode 3 and the negative electrode 1 are alternately stacked via the separator 2. The positive electrode current collector 5 of each positive electrode 3 is welded to and electrically connected to each other at an end portion not covered with the positive electrode active material, and the positive electrode terminal 6 is welded to the welded portion. A negative electrode current collector 4 included in each negative electrode 1 is welded to and electrically connected to each other at an end portion not covered with the negative electrode active material, and a negative electrode terminal 7 is welded to the welded portion. This electrode laminate is housed in a container formed of a laminate film as an exterior body, and an electrolyte is injected and sealed.

A laminated laminate type battery using an electrode laminate having such a planar laminate structure has a smaller R portion (for example, a wound type) than a wound battery using an electrode laminate having a wound structure. Since there is no region close to the winding core of the structure or the folded region of the flat wound structure, there is an advantage that it is difficult to be adversely affected by the volume change of the electrode accompanying charge / discharge. At this time, it is desirable that the separator and the electrode are not fixed to each other by adhesion or the like, and stress due to a change in the volume of the electrode can be relieved as compared with the case where the separator is fixed. On the other hand, since the electrode is curved in the wound type battery, the structure is easily distorted when a volume change occurs in the electrode, and in particular, a negative electrode active material having a large volume change due to charge / discharge, such as silicon, is used. It is remarkable in the case. For this reason, it is difficult to prevent a capacity decrease associated with charge / discharge in a wound battery. On the other hand, the laminated laminate type battery is suitable when an active material having a large volume change accompanying charging / discharging is used. In addition, “planar laminated structure” means that each laminated electrode is a sheet-like body, and is laminated in a planar form (laminated with the outer peripheral edge of the sheet-like body being the peripheral edge). Is distinguished from a structure in which the electrode stack is bent or a structure in which the electrode stack is wound.

Even in such a laminated battery, when a negative electrode containing a metal (a) having a large volume change due to charge / discharge, such as silicon, is used, the negative electrode volume change adversely affects the charge / discharge cycle characteristics.

By using a resin component having a contact angle with water of less than 70 °, preferably less than 65 °, more preferably 60 ° or less, the wettability with the negative electrode active material particles is high. As it increases, a negative electrode in which the resin component is uniformly distributed between the negative electrode active material particles can be formed. This is particularly effective when the negative electrode active material particles have a relatively hydrophilic surface such as silicon or silicon oxide.

As such a resin component, an amide imide structure unit derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof, or an imide structure derived from an aromatic tetracarboxylic acid or a derivative thereof and an aromatic diamine or a derivative thereof When a resin containing a unit is used, the mechanical characteristics are excellent, and therefore the deterioration of the cycle characteristics due to the volume change of the negative electrode can be effectively suppressed in combination with the adhesion and the uniform distribution.

The presence of hydrogen-bonding functional groups on the resin surface reduces the contact angle with water, and thus tends to improve the adhesion to the negative electrode active material particles and the uniformity of distribution. The higher the functional group concentration, the smaller the contact angle. The carbonyl moiety of the imide ring of the imide structural unit or the amide imide structural unit can form a hydrogen bond, but the amide group of the amide imide structural unit more easily forms a hydrogen bond. Accordingly, the higher the ratio of trimellitic acid units among the acid component units constituting the resin, the higher the ratio of amide groups, the smaller the contact angle. Moreover, since the ratio of the terminal amino group or the terminal carboxyl group increases as the molecular weight of the resin decreases, the contact angle tends to decrease.

The cause of cycle characteristics deterioration is gas generation in the battery in addition to the volume change of the negative electrode. In particular, in laminated laminated batteries, when gas is generated between the electrodes, the generated gas tends to stay between the electrodes. This is because in the wound battery, the distance between the electrodes is difficult to increase because tension is applied to the electrodes, whereas in the laminated laminate battery, the distance between the electrodes is likely to increase. This problem is particularly noticeable when the outer package is an aluminum laminate film.

Furthermore, when the electrolytic solution contains a carbonate ester solvent or a carboxylic acid ester solvent, this problem becomes more prominent.

By using the resin component containing the specific amideimide structural unit or the imide structural unit in the present embodiment, particularly by using the resin containing the specific polyamideimide structural unit, in combination with the above adhesiveness and uniform distribution, Gas generation can be effectively suppressed. That is, even in a laminated laminate type lithium ion secondary battery using a high energy type negative electrode that easily generates gas, it is possible to perform long-life driving.

Hereinafter, the components of the secondary battery according to the present embodiment will be described in order.

[1] Negative Electrode The negative electrode in the present embodiment includes a negative electrode active material and a resin component, and the resin component includes a polyamideimide resin or a polyimide resin as a main component. The negative electrode active material is preferably covered with the resin component.

The negative electrode can further include a current collector, and a negative electrode active material layer including the negative electrode active material and the resin component can be provided on the current collector. The negative electrode active material can be bound to the current collector by the resin component. Moreover, this resin component can bind between the particles of the negative electrode active material contained in the negative electrode active material layer.

The negative electrode active material in this embodiment includes a metal (a) that can be alloyed with lithium. The negative electrode active material can further include a metal oxide (b) or a carbon material (c) that can occlude and release lithium. The negative electrode active material in the present embodiment preferably contains a metal (a) and a metal oxide (b), and contains a metal (a), a metal oxide (b), and a carbon material (c). More preferred.

As the metal (a), Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, or an alloy containing two or more of these is used. it can. In particular, silicon (Si) or a silicon-containing metal is preferable as the metal (a), and silicon is more preferable.

The content of the metal (a) in the negative electrode active material is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more from the viewpoint of charge / discharge capacity, and charge / discharge. 90 mass% or less is preferable from points, such as cycle life, 80 mass% or less is more preferable, It is more preferable to set it as 50 mass% or less.

As the metal oxide (b), silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, or a composite oxide containing two or more of these can be used. In particular, it is preferable to contain silicon oxide as the metal oxide (b). This is because silicon oxide is relatively stable and hardly reacts with other compounds. In addition, one or more elements selected from nitrogen, boron, and sulfur may be added to the metal oxide (b), for example, 0.1 to 5% by mass. By carrying out like this, the electrical conductivity of a metal oxide (b) can be improved.

The content of the metal oxide (b) in the negative electrode active material is preferably 5% by mass or more, more preferably 15% by mass or more, and further preferably 45% by mass or more from the viewpoint of improving the charge / discharge cycle life. In addition, from the viewpoint of current collection and the like, 90% by mass or less is preferable, 80% by mass or less is more preferable, and 70% by mass or less is more preferable.

The metal oxide (b) preferably has an amorphous structure in whole or in part. The metal oxide (b) having an amorphous structure has a large effect of suppressing the volume expansion of the carbon material (c) and the metal (a) which are other negative electrode active material components. Further, it is considered that the metal oxide (b) having an amorphous structure contributes relatively little to non-uniformity such as crystal grain boundaries and defects. It can be confirmed by X-ray diffraction measurement (general XRD measurement) that all or part of the metal oxide (b) has an amorphous structure. Specifically, when the metal oxide (b) does not have an amorphous structure, a peak specific to the metal oxide (b) is observed, but all or part of the metal oxide (b) is amorphous. When it has a structure, a peak specific to the metal oxide (b) is observed as a broad.

It is preferable that all or part of the metal (a) is dispersed in the metal oxide (b). The metal (a) can be dispersed in the amorphous metal oxide (b). By dispersing at least a part of the metal (a) in the metal oxide (b), the volume expansion of the entire negative electrode can be further suppressed. Note that all or part of the metal (a) is dispersed in the metal oxide (b) because of observation with a transmission electron microscope (general TEM observation) and energy dispersive X-ray spectroscopy (general). This can be confirmed by using a combination of a standard EDX measurement. Specifically, the cross section of the sample containing the metal (a) is observed, the oxygen concentration of the particles dispersed in the metal oxide (b) is measured, and the metal (a) constituting the particles is oxidized. It can be confirmed that it is not a thing.

The metal oxide (b) is preferably an oxide of the same kind of metal as the metal (a). For example, the case where the metal (a) is a metal containing silicon and the metal oxide (b) contains a silicon oxide is preferable, the metal (a) is simple silicon (Si), and the metal oxide (b) is In the case of silicon oxide, the metal (a) is an alloy of silicon and tin (Sn), and the metal oxide (b) is silicon oxide or a composite oxide of silicon and tin. In particular, it is preferable that the metal (a) is simple silicon and the metal oxide (b) is silicon oxide.

The mass ratio (a / b) between the metal (a) and the metal oxide (b) in the negative electrode active material is not particularly limited, but is preferably set in the range of 5/95 to 90/10. More preferably, it is set within the range of / 90 to 80/20, and can be set within the range of 30/70 to 60/40.

As the carbon material (c), graphite, amorphous carbon, diamond-like carbon, carbon nanotube, or a composite containing two or more of these can be used. Here, graphite with high crystallinity has high electrical conductivity, and is excellent in adhesiveness and voltage flatness with a positive electrode current collector made of a metal such as copper. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.

The content of the carbon material (c) in the negative electrode active material is preferably 1% by mass or more, more preferably 2% by mass or more, from the viewpoint of improving conductivity and charge / discharge cycle life, and the charge / discharge capacity. Is preferably 50% by mass or less, and more preferably 30% by mass or less, from the viewpoint of sufficiently ensuring the above.

The metal (a), the metal oxide (b), and the carbon material (c) contained in the negative electrode active material are not particularly limited, but can each include particles. By making the negative electrode active material material an aggregate of particles, the restraining force between different kinds of material particles can be maintained moderately, so the occurrence of residual stress and residual strain due to the difference in volume change associated with charge / discharge is suppressed. be able to. Furthermore, the average particle diameter of the metal (a) is preferably smaller than the average particle diameter of the carbon material (c) and the average particle diameter of the metal oxide (b). In this way, the metal (a) having a large volume change during charge / discharge has a relatively small particle size, and the metal oxide (b) and the carbon material (c) having a relatively small volume change are relatively large. Because of the particle size, dendrite formation and alloy pulverization are more effectively suppressed. In addition, during the charge / discharge process, the large particle size and the small particle size alternately occlude and release lithium, whereby the generation of residual stress and residual strain can be more effectively suppressed. The average particle diameter of the metal (a) can be, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and can also be 5 μm or less. Here, the average particle diameter is a 50% cumulative diameter D ₅₀ (median diameter) obtained by particle size distribution measurement by a laser diffraction scattering method.

The negative electrode including metal (a) particles, metal oxide (b) particles, and carbon material (c) particles as a negative electrode active material comprises these particles, a polyamide-imide resin (binder resin if necessary), and a solvent. It can be formed by preparing a slurry containing, applying this onto a current collector, drying and compressing.

As the negative electrode active material, composite particles A can be formed by mechanically milling metal (a) particles, metal oxide (b) particles, and carbon material (c) particles. A slurry containing the composite particles A (negative electrode active material particles), a polyamide-imide resin (binder resin if necessary) and a solvent is prepared, applied to a current collector, dried and compressed to form a negative electrode. Can do. The surface of the composite particle can be coated with a carbon material.

The negative electrode active material can include a composite particle B containing a metal (a) and a metal oxide (b), and a carbon material. The negative electrode active material containing the composite particles B and the carbon material can be obtained by mechanical milling the composite particles B and the carbon material particles, or can be obtained by coating the composite particles B with a carbon material. it can.

The method of coating the composite particle B with carbon includes a method in which the organic compound and the composite particle B are mixed and fired, or a thermal chemical vapor deposition (CVD) by introducing the composite particle B into a gas atmosphere of an organic compound such as methane. The method of performing is mentioned.

The composite particle B containing the metal (a) and the metal oxide (b) can be obtained, for example, by sintering the metal (a) and the metal oxide (b) under high temperature and reduced pressure. Moreover, it can obtain by carrying out mechanical milling of a metal (a) and a metal oxide (b).

In addition, in the composite particle B containing the metal (a) and the metal oxide (b), all or part of the metal oxide (b) has an amorphous structure, and all or part of the metal (a) is metal oxidized. It can take the form which is disperse | distributing in the thing (b). The negative electrode active material in which the composite particles B having such a form are coated with a carbon material can be produced by, for example, a method described in Patent Document 3 (Japanese Patent Laid-Open No. 2004-47404). Specifically, for example, the metal oxide (b) is disproportionated at 900 to 1400 ° C. in a gas atmosphere of an organic compound such as methane, and thermal CVD is performed. Thereby, the metal elements in the metal oxide (b) are nanoclustered in the metal oxide (b) to form composite particles B, and the surface of the composite particles B is covered with the carbon material (c). . As another method, the metal (a) and the amorphous metal oxide (b) can be obtained by mechanical milling.

The specific surface area of the negative electrode active material as a whole (by general BET specific surface area measurement) is preferably 0.2 m ² / g or more, more preferably 1.0 m ² / g or more, and 2.0 m ² / g or more. but more preferably, and is preferably 9.0 m ² / g or less, more preferably 8.0 m ² / g or less, more preferably 7.0 m ² / g or less. If the specific surface area of the negative electrode active material is small, the coating with polyamideimide tends to be uniform, but Li ions are not smoothly inserted and removed, resulting in high resistance and low battery characteristics such as output characteristics. There is. Conversely, when the specific surface area of the negative electrode active material is large, Li ions can be easily removed and inserted, and there is a tendency for low resistance and high output. Gas generation increases and battery characteristics such as life characteristics tend to be lowered.

The average particle diameter of the negative electrode active material is preferably 0.01 μm or more, more preferably 0.1 μm or more, further preferably 0.2 μm or more, and preferably 30 μm or less, more preferably 20 μm or less. It is preferable to set in such a range from the viewpoint of handling at the time of manufacture, easiness of film formation, battery characteristics after manufacture, and the like. Here, the average particle diameter is a 50% cumulative diameter D ₅₀ (median diameter) obtained by particle size distribution measurement by a laser diffraction scattering method.

The resin component of the negative electrode is derived from a resin containing an amide-imide structural unit derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof, or from an aromatic tetracarboxylic acid or a derivative thereof and an aromatic diamine or a derivative thereof. Includes resins containing imide structural units.

As one of the resin components, a resin containing an amide imide structural unit derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof (hereinafter referred to as “polyamide imide resin”) has excellent electrolytic solution resistance and heat resistance. In addition to having excellent properties as a binder, it can have a function of suppressing gas generation caused by the negative electrode active material and the solvent of the electrolytic solution.

Such a polyamideimide resin includes trimellitic acid or a derivative thereof (such as trimellitic anhydride or acid chloride thereof) (hereinafter collectively referred to as “aromatic tricarboxylic acid component”), an aromatic diamine. Alternatively, it can be obtained by a reaction with a derivative thereof (aromatic diisocyanate, substituted product having a substituent on an aromatic ring, etc.) (hereinafter collectively referred to as “aromatic diamine component”). For example, it can be obtained by reaction of trimellitic anhydride and aromatic diamine, reaction of trimellitic anhydride and aromatic diisocyanate, reaction of trimellitic anhydride chloride and aromatic diamine. Although it does not specifically limit as a manufacturing method of a polyamidoimide resin, It can manufacture by a normal melt polymerization method or solution polymerization method. At that time, the acid component and the diamine component are usually mixed in an equimolar amount, but if necessary, one component may be excessively mixed.

A part of the aromatic tricarboxylic acid component unit of this polyamide-imide resin is a part of pyromellitic acid, biphenyl-3,3 ′, 4,4′-tetracarboxylic acid, diphenylmethane-3,3 ′, 4,4 ′. -Tetracarboxylic acid, diphenyl ether-3,3 ', 4,4'-tetracarboxylic acid, diphenylthioether-3,3', 4,4'-tetracarboxylic acid, benzophenone-3,3 ', 4,4'- It may be replaced with a unit of an aromatic polyvalent carboxylic acid component such as tetracarboxylic acid (including derivatives such as acid anhydrides, acid chlorides, and substituents having aromatic substituents). These aromatic polyvalent carboxylic acid components can be used alone or in combination of two or more. In this case, from the viewpoint of not damaging the desired properties, the replacement ratio of the aromatic polycarboxylic acid component unit to the aromatic tricarboxylic acid component unit of the polyamideimide resin before replacement is preferably less than 40 mol%, 30 Less than mol% is more preferable, and less than 20 mol% is more preferable. That is, the ratio of the unit of the aromatic tricarboxylic acid component to the unit of the total acid component (the total of the aromatic tricarboxylic acid component and the aromatic polycarboxylic acid component) is preferably 60 mol% or more, more preferably 70 mol% or more. Preferably, 80 mol% or more is more preferable.

In addition, the polyamideimide resin in the present embodiment is a polyvalent carboxylic acid other than the aromatic polycarboxylic acid component described above, with a part of the unit of the aromatic tricarboxylic acid component within a range that does not impair the desired characteristics. It may be replaced with the unit of the component. Other polyvalent carboxylic acid components include aliphatic dicarboxylic acids (or acid anhydrides and acid chlorides thereof) such as adipic acid, sebacic acid and azelaic acid; aromatic dicarboxylic acids such as isophthalic acid and terephthalic acid (or acids thereof) Anhydrides, acid chlorides); aliphatic polycarboxylic acids (or acid anhydrides, acid chlorides thereof) such as butane-1,2,3,4-tetracarboxylic acid. In this case, from the viewpoint of not impairing desired properties, the replacement ratio of other polycarboxylic acid component units to the aromatic tricarboxylic acid component units of the polyamideimide resin before replacement is preferably less than 10 mol%. Less than mol% is more preferable. As other polyvalent carboxylic acid components, aromatic carboxylic acid components are preferable.

The unit of the aromatic tricarboxylic acid component in the unit of the total acid component (total of aromatic tricarboxylic acid component, aromatic polyvalent carboxylic acid component and other polyvalent carboxylic acid component) contained in the polyamideimide resin in the present embodiment The ratio is preferably 60 mol% or more, more preferably 70 mol% or more, and further preferably 80 mol% or more. That is, the ratio of the amide-imide structural unit of the aromatic tricarboxylic acid component and the aromatic diamine component to the whole condensation structural unit of the acid component and the diamine component is preferably 60 mol% or more, more preferably 70 mol% or more, 80 mol% or more is more preferable. As for the polyamideimide resin in this embodiment, it is especially preferable that all the units of the acid component are units of an aromatic carboxylic acid component.

Examples of the aromatic diamine component used in the polyamideimide resin in the present embodiment include 1,3-phenylenediamine, 1,4-phenylenediamine and other phenylenediamine; biphenyl-4,4′-diamine, biphenyl-3,4 ′ -Biphenyldiamine (diaminobiphenyl) such as diamine, biphenyl-3,3'-diamine, biphenyl-2,2'-diamine; 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether such as diaminodiphenyl ether; diaminodiphenylmethane such as 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane; 4,4′-diaminodiphenylethane, 3,4′-diaminodi Diaminodiphenylethanes such as phenylethane, 3,3′-diaminodiphenylethane; diaminodiphenylpropanes such as 4,4′-diaminodiphenylpropane, 3,4′-diaminodiphenylpropane, 3,3′-diaminodiphenylpropane; Diaminobenzophenones such as 4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone; 4,4'-diaminodiphenylthioether, 3,4'-diaminodiphenylthioether, 3,3'-diamino Diaminodiphenylthioethers such as diphenylthioether; 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4 -Screw (3 Aminophenoxy) bis aminophenoxy benzene such as benzene, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and a diaminodiphenyl sulfone such as 3,4'-diaminodiphenyl sulfone. The aromatic ring of these aromatic diamine components may have a substituent, and examples of the substituent include an alkyl group having 1 to 4 carbon atoms such as a methyl group and an ethyl group. Moreover, the diisocyanate which substituted the amino group of these aromatic diamine components with the isocyanate group is mentioned. Among these, aromatic diamines selected from phenylenediamine, biphenyldiamine (diaminobiphenyl), diaminodiphenylmethane, diaminodiphenyl ether, diaminobenzophenone, diaminodiphenylthioether, and bisaminophenoxybenzene are preferable, and phenylenediamine, biphenyldiamine, diaminodiphenylmethane, and diamino An aromatic diamine selected from diphenyl ether, diaminobenzophenone and diaminodiphenyl thioether is more preferable, and an aromatic diamine selected from phenylenediamine, biphenyldiamine, diaminodiphenylmethane, diaminodiphenyl ether and diaminobenzophenone is more preferable, and phenylenediamine, biphenyldiamine and diaminodiphenyl. Meta , Aromatic diamines selected from diaminodiphenyl ether is particularly preferable. Aromatic diamines may be used alone or in combination of two or more. In the production of the resin, diisocyanate in which the amino group of these aromatic diamine components is replaced with an isocyanate group can be used.

The polyamide-imide resin in the present embodiment may replace a part of the unit of the aromatic diamine component with the unit of another diamine component as long as the desired characteristics are not impaired. In this case, the replacement ratio of the units of the other diamine component with respect to the units of the aromatic diamine component of the polyamideimide resin before replacement is preferably less than 10 mol%, and more preferably less than 5 mol%. That is, the ratio of the aromatic diamine component units to the total diamine component units contained in the polyamide resin in the present embodiment is preferably 90 mol% or more, more preferably 95 mol% or more. As for the polyamideimide resin in this embodiment, it is especially preferable that all the units of the diamine component are units of an aromatic diamine component. That is, in the polyamideimide resin in the present embodiment, the content ratio of the aromatic condensation unit derived from the aromatic polyvalent carboxylic acid component and the aromatic diamine component (including the amideimide structural unit) is preferably 90 mol% or more, 95 mol% or more is more preferable, and 100 mol% is further more preferable.

When metal (a) such as silicon is used as the negative electrode active material, gas is generated from the negative electrode due to the charge / discharge cycle, and particularly in a laminated laminate type secondary battery, gas accumulates between the electrodes and the entire battery expands. There is a problem that the capacity decreases due to poor contact or the like. By uniformly distributing the negative electrode active material causing such a problem in the negative electrode so as to be coated with polyamideimide, generation of gas such as CO ₂ due to reductive decomposition of the electrolytic solution can be suppressed. Such a gas generation suppression effect is not seen when using normal polyimide or polyamic acid which is a precursor of polyimide. Polyamide having no imide group has low solubility in a solvent such as water or N-methylpyrrolidone, and it is difficult to produce a negative electrode. On the other hand, polyamideimide has high solubility in a solvent such as water or N-methylpyrrolidone, and a negative electrode in which polyamideimide is uniformly distributed in the negative electrode can be easily formed. Furthermore, since polyamideimide has high mechanical strength like polyimide, it can also function as a binder. Therefore, the gas generation suppression effect can be obtained without significantly increasing the amount of the resin component in the negative electrode (that is, without significantly reducing the energy density).

Although the mechanism of the gas generation suppression effect by polyamideimide is not clear, it is presumed that the hydrogen atom present in the amide bond functions as a negative catalyst during the reductive decomposition of the electrolytic solution. In particular, when a negative electrode active material containing silicon is used as the metal (a), it is presumed that active dangling bonds generated on the silicon surface by the oxidation-reduction reaction are inactivated. In addition, as the negative electrode active material, silicon (or silicon-containing metal) of metal (a), silicon oxide of metal oxide (b), and silicon (silicon-containing metal) that is metal (a), and The use of the carbon material (c) is preferable from the viewpoint of suppressing gas generation. Further, it is preferable that all or part of the metal oxide (b) is amorphous from the viewpoint of suppressing gas generation. Furthermore, it is preferable from the viewpoint of gas generation suppression that all or part of the metal (a) is dispersed in the metal oxide (b).

On the other hand, as a resin component of the negative electrode, instead of the polyamide-imide resin, a resin containing an imide structural unit derived from an aromatic tetracarboxylic acid or derivative thereof and an aromatic diamine or derivative thereof (hereinafter referred to as “polyimide resin”). Can be used.

Examples of the aromatic tetracarboxylic acid include pyromellitic acid, biphenyl-3,3 ′, 4,4′-tetracarboxylic acid, diphenylmethane-3,3 ′, 4,4′-tetracarboxylic acid, and diphenylether-3,3. One or two selected from ', 4,4'-tetracarboxylic acid, diphenylthioether-3,3', 4,4'-tetracarboxylic acid, benzophenone-3,3 ', 4,4'-tetracarboxylic acid The above can be used.

Derivatives of aromatic tetracarboxylic acids include acid anhydrides, acid chlorides, and substituents having substituents on the aromatic ring (the substituents include alkyl groups having 1 to 4 carbon atoms such as methyl and ethyl groups) ).

As the aromatic diamine or derivative thereof, the aromatic diamine component used in the above-mentioned aromatic polyamideimide resin can be used. In particular, one or more aromatic diamines selected from phenylenediamine, biphenyldiamine (diaminobiphenyl), diaminodiphenylmethane, diaminodiphenyl ether, diaminobenzophenone, diaminodiphenylthioether, and bisaminophenoxybenzene, or derivatives thereof (diisocyanate, aromatic ring) Can be used.

The mass ratio of the resin component to the negative electrode active material (mass ratio Mb / Mc of the amount Mb of the resin component to the amount Mc (100 parts by mass) of the negative electrode active material) is preferably 7/100 or more, more preferably 8/100 or more. More preferably, 11/100 or more is more preferable, 25/100 or less is preferable, 20/100 or less is more preferable, and 15/100 or less is more preferable. If the resin component is too small, the resin is unevenly distributed, the effect of improving the cycle characteristics cannot be sufficiently obtained, and the gas generation suppressing effect and the binding effect are also lowered. When there are too many resin components, energy density will become low.

As the polyamideimide resin and the polyimide resin in the present embodiment, those having a number average molecular weight (Mn) in the range of, for example, 5000 to 100,000 can be used, and those having a number average molecular weight in the range of 5000 to 70000 are preferable. Those within the range are more preferred. This number average molecular weight (standard polystyrene conversion) can be measured by gel permeation chromatography (GPC). If the molecular weight is too low, the film forming property and the binding force are lowered, and if the molecular weight is too large, it becomes difficult to form the active material layer or it is difficult to form a homogeneous active material layer.

The ratio of the polyamideimide resin and the polyimide resin to the total resin component in the negative electrode is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more. When the polyamideimide resin and the polyimide resin are used in combination, the total ratio of these resins to the total resin components in the negative electrode is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more. . In the case where the gas generation suppression effect by the polyamideimide resin is particularly emphasized, the ratio of the polyamideimide resin can be 100% by mass, and even in this case, sufficient binding properties can be ensured.

When the polyamideimide resin and the polyimide resin are used in combination, it is possible to obtain both a gas generation suppressing effect and a cycle characteristic deterioration preventing effect due to a negative electrode volume change at a high level. From the viewpoint of emphasizing the gas generation suppression effect, it is preferable to increase the amount of the polyamideimide resin, and the mass ratio (PAI / PI) of the polyamideimide resin (PAI) to the polyimide resin (PI) is 60/40 to 90 / A range of 10 can be set.

The resin component in the negative electrode can contain other resins than the above polyamideimide resin and polyimide resin as long as the desired effect is not impaired. As the other resin, a normal negative electrode binder can be used, for example, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer. Rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyamideimide other than the above, polyimide other than the above, and the like can be used.

As the negative electrode current collector, it is preferable to use a material selected from aluminum, nickel, copper, silver, and alloys thereof from the viewpoint of electrochemical stability. Examples of the shape include foil, flat plate, and mesh. As the negative electrode current collector, a copper foil is particularly preferable.

The negative electrode can be formed, for example, as follows. A negative electrode current material is prepared by preparing a negative electrode slurry containing a negative electrode active material, a polyamide-imide resin, and other resins (binders) and a solvent as required. The negative electrode slurry is applied onto a negative electrode current collector and dried. A negative electrode active material layer can be formed on the body. The obtained electrode can be compressed by a method such as a roll press and adjusted to an appropriate density.

As the solvent, polar solvents such as N-methyl-2-pyrrolidone, γ-butyrolactone, water, aromatic hydrocarbons such as xylene, ketones such as cyclohexanone, N-methyl-2-pyrrolidone, water, etc. can be used. Is preferred.

Examples of the method for applying the negative electrode material include a doctor blade method, a die coater method, and a dip coating method. After forming the negative electrode active material layer in advance, a metal thin film such as aluminum, nickel, or an alloy thereof may be formed on the negative electrode active material layer by a method such as vapor deposition or sputtering, and the negative electrode current collector may be used.

The viscosity of the negative electrode slurry is preferably in the range of 1000 to 20000 mPa · s (cP) as measured by a rotary viscometer at a rotor rotational speed of 10 rpm. At that time, it is preferable to use a negative electrode active material having a BET specific surface area in the range of 0.2 to 9.0 m ² / g. By using a negative electrode slurry in such a viscosity range, a negative electrode active material layer in which the resin component is uniformly distributed with respect to the negative electrode active material particles can be formed, and as a result, gas generation is suppressed and cycle characteristics are improved. An excellent secondary battery can be obtained. If the viscosity of the negative electrode slurry is too low, the formation of the negative electrode active material layer itself becomes difficult.

The viscosity of the negative electrode slurry is measured at room temperature using a Brookfield Digital Viscometer III Ultra (LVDV-III Ultra, RVDV-III Ultra, HADV-III Ultra, HBDV-III Ultra) manufactured in the United States. can do.

[2] Positive Electrode As the positive electrode, for example, a positive electrode active material layer including a positive electrode active material and a binder provided on a positive electrode current collector can be used.

As the positive electrode active material, an active material capable of occluding and releasing lithium ions can be used. As the positive electrode active material, various lithium metal oxides can be used. For example, lithium manganate having a layered structure or spinel structure such as LiMnO ₂ , Li _x Mn ₂ O ₄ (0 <x <2); Lithium metal oxide in which part of Mn of lithium acid is replaced with other metal; LiCoO ₂ , LiNiO ₂ , lithium metal oxide in which part of these transition metals (Co, Ni) is replaced with other metal; LiNi Lithium transition metal oxides in which specific transition metals such as _1/3 Co _1/3 Mn _1/3 O ₂ do not exceed half of the total number of transition metals (atomic ratio); stoichiometric composition in these lithium metal oxides And lithium metal oxide containing Li in excess. Among these, as a positive electrode active material suitable for the present embodiment, Li _α Ni _β Co _γ Al _δ O ₂ (0.8 ≦ α ≦ 1.2, β + γ + δ = 1, 0.5 <β, 0 <γ, 0 <δ), or Li _α Ni _β Co _γ Mn _δ O ₂ (0.8 ≦ α ≦ 1.2, β + γ + δ = 1, 0.5 <β, 0 <γ, 0 <δ) can be used. In these lithium metal oxides, γ ≧ 0.1 can be set, and δ ≧ 0.01 can be set. In particular, Li _α Ni _β Co _γ Al _δ O ₂ (1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0.2), or Li _α Ni _β Co _γ Mn _δ O ₂ ( 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6, γ ≦ 0.2) are preferable. A positive electrode active material can be used individually by 1 type or in combination of 2 or more types.

As the positive electrode binder, the same negative electrode binder as that of a normal negative electrode can be used. Among these, polyvinylidene fluoride is preferable from the viewpoint of versatility and low cost. The amount of the positive electrode binder to be used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoint of the binding effect and energy density which are in a trade-off relationship.

As the positive electrode current collector, the same one as the negative electrode current collector can be used as long as the potential is stable, but an aluminum foil is particularly preferable.

A conductive auxiliary material may be added to the positive electrode active material layer containing the positive electrode active material for the purpose of reducing impedance. Examples of the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.

The positive electrode can be formed as follows, for example. A positive electrode active material, a binder, a solvent, and, if necessary, a positive electrode slurry containing a conductive auxiliary agent is prepared, and this positive electrode slurry is applied on the positive electrode current collector and dried to obtain a positive electrode active material on the positive electrode current collector A layer can be formed. The obtained electrode can be compressed by a method such as a roll press and adjusted to an appropriate density. As the solvent, for example, N-methyl-2-pyrrolidone can be used.

[3] Electrolytic Solution As the electrolytic solution used in the present embodiment, a nonaqueous electrolytic solution containing a lithium salt (supporting salt) and a nonaqueous solvent that dissolves the supporting salt can be used.

As the non-aqueous solvent, an aprotic organic solvent such as carbonate ester (chain or cyclic carbonate) or carboxylic acid ester (chain or cyclic carboxylic acid ester) can be used.

Examples of the carbonate solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC); dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate. (EMC), chain carbonates such as dipropyl carbonate (DPC); and propylene carbonate derivatives.

Examples of the carboxylic acid ester solvent include aliphatic carboxylic acid esters such as methyl formate, methyl acetate, and ethyl propionate; and lactones such as γ-butyrolactone.

Among these, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), dipropyl carbonate Carbonic acid esters (cyclic or chain carbonates) such as (DPC) are preferred.

Non-aqueous solvents can be used alone or in combination of two or more.

The nonaqueous electrolytic solution preferably further contains a fluorinated ether compound. The fluorinated ether compound has a high affinity with the metal (a) (particularly Si), and can improve cycle characteristics (particularly capacity retention rate). The fluorinated ether compound may be a fluorinated chain ether compound obtained by substituting a part of hydrogen of a non-fluorinated chain ether compound with fluorine, or a part of hydrogen of a non-fluorinated cyclic ether compound with fluorine. It may be a substituted fluorinated cyclic ether compound. In particular, a fluorinated chain ether compound having higher stability is preferable. As the fluorinated chain ether compound, the following formula (1):
H- (CX ¹ X ² -CX ³ X ⁴ ) _n -CH ₂ O-CX ⁵ X ⁶ -CX ⁷ X ⁸ -H (1)
(In the formula, n is 1, 2, 3 or 4, and X ¹ to X ⁸ are each independently a fluorine atom or a hydrogen atom, provided that at least one of X ¹ to X ⁴ is a fluorine atom, At least one of X ⁵ to X ⁸ is a fluorine atom, the atomic ratio of fluorine atoms to hydrogen atoms bonded to the fluorinated chain ether compound (total number of fluorine atoms / total number of hydrogen atoms) ≧ 1 .)
A compound represented by the following formula (2):
H— (CF ₂ —CF ₂ ) n—CH ₂ O—CF ₂ —CF ₂ —H (2)
(In the formula, n is 1 or 2.)
The compound represented by these is more preferable.

The content of such a fluorinated ether compound is preferably 10 vol% or more, more preferably 15 vol% or more with respect to the total amount of the nonaqueous solvent (100 vol%) from the viewpoint of obtaining a sufficient addition effect within a range not impairing the battery characteristics. Is more preferable, 75 vol% or less is preferable, 70 vol% or less is more preferable, and 50 vol% or less is more preferable.

Examples of the supporting salt in the present embodiment include LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ , LiN ( CF ₃ SO _{2) 2} normal lithium salt which can be used in lithium ion batteries or the like can be used. The supporting salt can be used alone or in combination of two or more.

[4] Separator As the separator in the present embodiment, a porous film or nonwoven fabric made of polyolefin such as polypropylene or polyethylene, a fluororesin, or the like can be used. Moreover, what laminated | stacked them can also be used as a separator.

[5] Exterior Body As the exterior body in the present embodiment, a laminate film that is stable in an electrolytic solution and has a sufficient water vapor barrier property can be used. For example, a laminate film such as polypropylene or polyethylene coated with aluminum or silica can be used as such an exterior body. In particular, it is preferable to use an aluminum laminate film from the viewpoint of suppressing volume expansion.

When the gas is generated in the battery, in the case of the secondary battery using the laminate film as the outer package, the distortion of the electrode becomes very large compared to the secondary battery using the metal can as the outer package. This is because the laminate film is more easily deformed by the internal pressure of the secondary battery than the metal can. Furthermore, when sealing a secondary battery using a laminate film as an exterior body, the internal pressure of the battery is usually lower than atmospheric pressure and there is no extra space inside, so when gas is generated in the battery In this case, battery volume changes and electrode deformation are likely to occur immediately. According to the present embodiment, gas generation in the battery can be suppressed, so that such a problem can be solved. Laminated laminate type lithium ion secondary battery is excellent in heat dissipation, can be provided at low cost, has a high degree of freedom in cell capacity design (cell capacity can be changed depending on the number of laminated layers), and is a wound type using a metal can Although it has various advantageous characteristics with respect to the battery, the cycle characteristics of such a laminated laminate type lithium ion secondary battery can be improved.

[6] Method for Manufacturing Secondary Battery The secondary battery according to the present embodiment can be manufactured according to a normal method. For example, a laminated laminate type lithium ion secondary battery can be manufactured as follows.

First, as described above, a positive electrode having a positive electrode active material layer provided on a positive electrode current collector and a negative electrode having a negative electrode active material layer provided on a negative electrode current collector are prepared.

Next, in dry air or an inert atmosphere, the positive electrode and the negative electrode are arranged to face each other via a separator to form an electrode pair, and an electrode stack having the number of layers corresponding to a predetermined capacity is formed. This electrode laminated body has a positive electrode terminal connected to the positive electrode current collector and a negative electrode terminal connected to the negative electrode current collector.

Next, this electrode laminate is accommodated in an exterior body (container), a nonaqueous electrolyte is injected, and then sealed.

Hereinafter, the present embodiment will be specifically described by way of examples.

Example 1
90 parts by mass of silicon having an average particle diameter of 5 μm as the metal (a) and 10 parts by mass of graphite having an average particle diameter of 30 μm as the carbon material (c) are mixed by mechanical milling for 24 hours to form a negative electrode active material To do. The average particle diameter _{D 50} of the negative electrode active material is 5 [mu] m, BET specific surface area is ^{5 m} 2 / g.

A negative electrode slurry containing this negative electrode active material, the following polyamic acid and N-methyl-2-pyrrolidone (NMP) and having a mass ratio of the negative electrode active material and polyimide of 90:10 is formed. The negative electrode slurry is applied to a copper foil having a thickness of 10 μm, dried, and further subjected to a heat treatment in a nitrogen atmosphere at 300 ° C. to form a negative electrode.

The polyimide in the negative electrode (BPDA-ODA) is represented by the following formula, and the polyamic acid for forming this polyimide is prepared as follows.

0.3 mol of 4,4′-oxydiphenylenediamine (4,4′-diaminodiphenyl ether) is dissolved in 1700 g of N-methyl-2-pyrrolidone (NMP), and then powdered biphenyltetracarboxylic dianhydride (BPDA) ) Add 0.3 mole slowly with vigorous stirring. The polymerization mixture is stirred for 24-48 hours. A mixture with a final polymer concentration of 7% by weight is obtained, and the number average molecular weight of the polyamic acid is 40,000.

90 parts by mass of composite lithium nickelate (LiNi _0.80 Co _0.15 Al _0.05 O ₂ ) as a positive electrode active material, 5 parts by mass of carbon black as a conductive auxiliary, and polyvinylidene fluoride as a positive electrode binder 5 parts by weight are mixed with N-methylpyrrolidone to form a positive electrode slurry.

The positive electrode slurry is applied to an aluminum foil having a thickness of 20 μm, dried, and further pressed to form a positive electrode.

The obtained three layers of positive electrode and four layers of negative electrode are alternately laminated through a polypropylene porous film as a separator to form an electrode laminate. The ends of the positive electrode current collector not covered with the positive electrode active material are welded to each other, the positive electrode terminal made of aluminum is welded to the welded portion, and the ends of the negative electrode current collector not covered with the negative electrode active material And a negative electrode terminal made of nickel is welded to the welded portion.

On the other hand, a carbonate-based non-aqueous electrolyte consisting of EC / PC / DMC / EMC / DEC = 20/20/20/20/20 (volume ratio) was prepared, and LiPF ₆ as a supporting salt was further added at 1 mol / l. To form an electrolyte solution.

The electrode laminate is wrapped with an aluminum laminate film as an outer package, and an electrolyte is poured into the interior, and then sealed while reducing pressure to 0.1 atm to produce a secondary battery.

For the secondary battery thus obtained, the capacity retention rate and the swelling rate after the charge / discharge cycle obtained by the measurement method described later are shown in the table.

Example 2
A secondary battery is formed in the same manner as in Example 1 except that polyimide (BPDA-PDA) represented by the following formula is used as the resin component of the negative electrode. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

The polyamic acid for forming this polyimide is prepared as follows. 0.3 mol of paraphenylenediamine (1,4-phenylenediamine) is dissolved in 1400 g of N-methyl-2-pyrrolidone (NMP), and then 0.3 mol of powdered biphenyltetracarboxylic dianhydride (BPDA) is added. Add slowly with vigorous stirring. The polymerization mixture is stirred for 24-48 hours. A mixture with a final polymer concentration of 7% by weight is obtained, and the number average molecular weight of the polyamic acid is 60,000.

Example 3
A secondary battery is formed in the same manner as in Example 1 except that, in the negative electrode slurry, instead of polyamic acid, polyamideimide (TMA-MDA) represented by the following formula is used. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

This polyamideimide is prepared as follows. A flask is charged with 0.3 mol of 4,4′-diphenylmethane diisocyanate, 0.3 mol of trimellitic anhydride (TMA) and 1400 g of N-methyl-2-pyrrolidone (NMP), and the temperature is increased to 120 with stirring for about 3 hours. The temperature is raised to 0 ° C. and kept at this temperature for 5 hours. A solution of polyamideimide resin (number average molecular weight 42,000) with a final polymer concentration of 7% by mass is obtained.

Example 4
In the negative electrode slurry, a secondary battery is formed in the same manner as in Example 1 except that instead of polyamic acid, polyamideimide (TMA-ODA) represented by the following formula is used. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

This polyamideimide is prepared as follows. A flask was charged with 0.3 mol of 4,4′-oxybis (phenylisocyanate), 0.3 mol of trimellitic anhydride (TMA) and 1400 g of N-methyl-2-pyrrolidone (NMP) and stirred for about 3 hours. The temperature is raised to 120 ° C. and kept at this temperature for 5 hours. A solution of polyamideimide resin (number average molecular weight 42,000) with a final polymer concentration of 7% by mass is obtained.

Example 5
In the negative electrode slurry, a secondary battery is formed in the same manner as in Example 1 except that instead of polyamic acid, polyamideimide (TMA-PDA) represented by the following formula is used. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

This polyamideimide is prepared as follows. Charge 0.4 mol of 1,4-phenylene diisocyanate, 0.4 mol of trimellitic anhydride (TMA) and 1400 g of N-methyl-2-pyrrolidone (NMP) to a flask at a temperature of 120 ° C. for about 3 hours with stirring. And kept at this temperature for 5 hours. A solution of polyamideimide resin (number average molecular weight 41,000) with a final polymer concentration of 7% by mass is obtained.

Comparative Example 1
A secondary battery is formed in the same manner as in Example 1 except that polyimide (6FDA-ODA) represented by the following formula is used as the resin component of the negative electrode. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

The polyamic acid for forming this polyimide is prepared as follows. 0.24 mol of 4,4′-oxydiphenylenediamine (4,4′-diaminodiphenyl ether) is dissolved in 1500 g of N-methyl-2-pyrrolidone (NMP), and then powdered 2,2-bis (3,4) -0.2 mol of dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) is slowly added with vigorous stirring. The polymerization mixture is stirred for 24-48 hours. A mixture with a final polymer concentration of 7% by weight is obtained, and the number average molecular weight of the polyamic acid is 35,000.

Comparative Example 2
A secondary battery is formed in the same manner as in Example 1 except that polyimide (6FDA-PDA) represented by the following formula is used as the resin component of the negative electrode. About the secondary battery obtained in this way, the capacity | capacitance maintenance factor and swelling rate after a charging / discharging cycle obtained by the below-mentioned measuring method are shown in a table | surface.

The polyamic acid for forming this polyimide is prepared as follows. 0.3 mol of paraphenylenediamine (1,4-phenylenediamine) is dissolved in 1400 g of N-methyl-2-pyrrolidone (NMP), and then powdered 2,2-bis (3,4-dicarboxyphenyl) hexafluoro 0.2 mol of propane dianhydride (6FDA) is slowly added with vigorous stirring. The polymerization mixture is stirred for 24-48 hours. A mixture with a final polymer concentration of 7% by weight is obtained, and the number average molecular weight of the polyamic acid is 50,000.

(Evaluation method of cycle characteristics)
About the secondary battery of an Example and a comparative example, a high temperature cycling characteristic is evaluated as follows.

First, in a constant temperature atmosphere of 20 ° C., the battery is charged to 0.05 V at a 0.05 C rate, then discharged to 2.5 V at a 1 C rate, and the discharge capacity (initial discharge capacity) at that time is measured. Next, in a constant temperature atmosphere of 60 ° C., charging up to 4.1 V and discharging up to 2.5 V are repeated 50 times at 1C rate, and the discharge capacity at the 50th cycle is measured.

The ratio (%) of the discharge capacity at the 50th cycle to the initial discharge capacity is calculated as the capacity maintenance rate. Further, the ratio of the volume increase amount at the 50th cycle to the volume of the battery before the start of charge / discharge is calculated as the swelling rate (%) (volume change rate). This volume increase is measured by the Archimedes method. The volume can be calculated from the decrease in mass when the battery is suspended on a scale and submerged in deionized water.

(Measurement method of contact angle)
The resin solution is coated on a glass plate with a doctor blade (thickness: 100 μm), dried roughly at 150 ° C., and then heat-treated at 200 ° C. for 10 minutes, 250 ° C. for 10 minutes, and 300 ° C. for 20 minutes. Form. After sufficiently cooling to room temperature, 10 μL of pure water is dropped from a height of 5 cm onto this resin film using a syringe, and a photograph is taken from the side. The droplet on the resin film photographed in the photograph is drawn by the θ / 2 method to obtain θ / 2, and θ is the contact angle.

 

As mentioned above, although this invention was demonstrated with reference to embodiment and an Example, this invention is not limited to the said embodiment and Example. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2011-070903 filed on Mar. 28, 2011, the entire disclosure of which is incorporated herein.

The secondary battery according to the present embodiment can be used in all industrial fields that require a power source and industrial fields related to transportation, storage, and supply of electrical energy. Specifically, for example, power sources for mobile devices such as mobile phones and notebook computers; power sources for mobile vehicles such as electric vehicles, hybrid cars, electric motorcycles, electric assist bicycles, electric trains such as trains, satellites, and submarines A backup power source such as a UPS (uninterruptible power supply); a power storage facility for storing power generated by solar power generation, wind power generation, or the like.

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Separator 3 Positive electrode 4 Negative electrode collector 5 Positive electrode collector 6 Positive electrode terminal 7 Negative electrode terminal

Claims (16)

1. A secondary battery including a positive electrode, a separator, a negative electrode disposed opposite to the positive electrode with the separator interposed therebetween, an electrolyte, and an outer package containing these,
   The negative electrode includes a metal (a) that can be alloyed with lithium as a negative electrode active material, and a resin component.
   The resin component includes an amide imide structural unit derived from trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof, or an imide structural unit derived from an aromatic tetracarboxylic acid or a derivative thereof and an aromatic diamine or a derivative thereof. Including resin,
   The secondary battery whose contact angle with the water of the said resin component is less than 70 degrees.
2. The secondary battery according to claim 1, wherein the resin component includes polyimide composed of the imide structural unit as the resin.
3. The aromatic tetracarboxylic acid includes pyromellitic acid, biphenyl-3,3 ′, 4,4′-tetracarboxylic acid, diphenylmethane-3,3 ′, 4,4′-tetracarboxylic acid, diphenylether-3,3 ′. , 4,4′-tetracarboxylic acid, diphenylthioether-3,3 ′, 4,4′-tetracarboxylic acid, benzophenone-3,3 ′, 4,4′-tetracarboxylic acid The secondary battery according to claim 2, wherein
4. The resin component includes, as the resin, a polyamideimide composed of a condensation unit derived from an aromatic polyvalent carboxylic acid containing at least trimellitic acid or a derivative thereof and an aromatic diamine or a derivative thereof. The secondary battery as described.
5. 2. The secondary battery according to claim 1, wherein the resin component includes a polyamideimide composed of the amideimide structural unit as the resin.
6. The said aromatic diamine is at least one selected from the group consisting of phenylenediamine, biphenyldiamine, diaminodiphenylmethane, diaminodiphenyl ether, diaminobenzophenone, diaminodiphenylthioether, and bisaminophenoxybenzene. Secondary battery described in 1.
7. The secondary battery according to any one of claims 1 to 6, wherein a mass ratio Mb / Mc of the amount Mb of the resin component to the amount Mc of the negative electrode active material is in a range of 7/100 to 25/100. .
8. The secondary battery according to any one of claims 1 to 7, wherein the negative electrode further includes a current collector, and the negative electrode active material is bound to the current collector by the resin component.
9. The secondary battery according to any one of claims 1 to 8, comprising silicon or a silicon-containing metal as the metal (a).
10. The secondary battery according to any one of claims 1 to 9, wherein the negative electrode further includes a metal oxide (b) as a negative electrode active material.
11. The secondary battery according to claim 10, wherein the metal (a) includes silicon or a silicon-containing metal, and the metal oxide (b) includes silicon oxide.
12. The secondary battery according to any one of claims 1 to 11, wherein the negative electrode further includes a carbon material (c) capable of occluding and releasing lithium ions as a negative electrode active material.
13. The secondary battery according to any one of claims 1 to 12, wherein the negative electrode active material has a BET specific surface area in the range of 0.2 to 9.0 m ² / g.
14. The secondary battery according to any one of claims 1 to 13, wherein the electrolytic solution includes a carbonate ester solvent or a carboxylic acid ester solvent.
15. The secondary battery according to any one of claims 1 to 14, which has a stacked structure in which a plurality of electrode pairs of the positive electrode and the negative electrode are stacked.
16. The secondary battery according to any one of claims 1 to 15, wherein the exterior body is made of a laminate film.

Images