JP6635616B2 - Positive electrode for non-aqueous electrolyte secondary battery and battery using the same - Google Patents

Description

  The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a battery using the same.

  Applications of secondary batteries are expanding from electronic devices to automobiles and large power storage systems, and the market scale is expected to grow to an industry of 10 trillion yen or more. In particular, information communication devices such as smartphones and tablet terminals have been remarkably spread, and the global penetration rate has exceeded 30%.

  In addition, the application range of the secondary battery is expanding to a power source of a next-generation vehicle such as an electric vehicle (EV) and a plug-in hybrid vehicle (PHEV). Also, secondary batteries have been used for home backup power supplies, renewable energy storage, load leveling, and the like in the wake of the Great East Japan Earthquake of 2011, and the use of secondary batteries is expanding. As described above, the secondary battery is indispensable even in the introduction of energy saving technology and new energy technology.

  Conventionally, secondary batteries have been mainly alkaline rechargeable batteries such as nickel-cadmium batteries and nickel-hydrogen batteries.However, due to their small size, light weight, high voltage, and no memory effect, non-aqueous electrolyte secondary batteries, In particular, the use of lithium secondary batteries (lithium ion batteries) is increasing. A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator, an electrolytic solution or electrolyte, and a battery case (storage case).

  Electrodes such as a positive electrode and a negative electrode are composed of an active material, a conductive additive, an organic polymer binder, and a current collector. In general, an electrode is manufactured by mixing an active material, a conductive auxiliary agent, and an organic binder into a solvent to form a slurry, coating the slurry on a current collector, drying it, and rolling it by a roll press or the like. You.

  Rolling after drying the electrode increases the contact area with the conductive assistant and the current collector by shrinking the volume of the active material layer of the electrode, that is, the coating layer composed of the active material, the conductive aid, and the binder. It is to make it. Thereby, the electron conduction network of the active material layer is firmly constructed, and the electron conductivity is improved.

  The binder is used to bind the active material and the active material, the active material and the conductive auxiliary, the active material and the current collector, and the conductive auxiliary and the current collector. Binder precursor is reacted by heat or light with "solution type", which uses liquid form dissolved in solvent, and "dispersion type (emulsion / latex type)", which uses solid content dispersed in solvent. Can be roughly classified into the "reaction type" used.

  Further, the binder can be classified into an aqueous solvent and an organic solvent according to the type of the solvent. For example, polyvinylidene fluoride (PVdF) is a soluble binder, and an organic solvent such as N-methyl-2-pyrrolidone (NMP) is used at the time of preparing the electrode slurry. Styrene butadiene rubber (SBR) is a dispersion type binder, and is used by dispersing SBR fine particles in water. Polyimide (PI) is a reactive binder. A PI precursor is dissolved or dispersed in a solvent such as NMP, and is subjected to heat treatment to promote imidization and a cross-linking reaction to obtain a tough PI.

  Although it differs depending on the molecular weight and the substituent of the binder, the soluble binder includes polyvinylidene fluoride (PVdF) and ethylene-vinyl acetate (EVA). Examples of the dispersion type binder include styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), urethane rubber, polypropylene (PP), polyethylene (PE), polyvinyl acetate (PVAc), and nitrocellulose. Reactive binders include polyimide (PI), polyamide (PA), polyamideimide (PAI), polybenzimidazole (PBI), and polybenzoxazole (PBO).

  In addition, since organic solvent-based binders such as N-methyl-2-pyrrolidone (NMP) are considered to have an adverse effect on the environment, they are required to be collected when the electrodes are dried. This is a factor that increases manufacturing costs. Further, the organic solvent-based binder swells in a high-temperature electrolytic solution to increase the electrode resistance, and thus is difficult to use in a high-temperature environment.

  Aqueous soluble binders are inferior in oxidation resistance or reduction resistance, are often gradually decomposed by repeated charge and discharge, and do not have sufficient life characteristics. Further, since the ion conductivity is low, the output characteristics are lacking. The dispersion type binder has the advantage that water can be used as a solvent, but the dispersion stability is easily impaired by the degree of acid or alkali (pH), the water concentration or the environmental temperature, and segregation, agglomeration, and precipitation during mixing of the electrode slurry. And so on. The binder fine particles dispersed in water have a particle diameter of 1 to 800 nm, and when moisture is vaporized by drying, the particles fuse to form a film. Since this film has neither electrical conductivity nor ionic conductivity, a slight difference in the amount used has a great effect on the output characteristics and life characteristics of the battery.

  As described above, in the case of the dissolving or dispersing type binder, the active material is combined with an active material such as sulfur (S), silicon (Si), tin (Sn), and aluminum (Al) that undergoes a drastic volume change upon charging and discharging. In this case, stable life characteristics cannot be obtained, and the charge / discharge capacity becomes less than half in about several cycles.

  On the other hand, the reactive binder is excellent in all of heat resistance, binding property and chemical resistance. In particular, PI exhibits high heat resistance and binding properties, can provide stable life characteristics even with an active material having a large volume change, and does not easily swell the binder even in a high-temperature electrolytic solution.

  Non-Patent Document 1 discloses that by combining a PI with a high-intensity current collector, the current collector can be prevented from deteriorating, and the life characteristics can be further improved.

Patent Literature 1 discloses that a LiFePO ₄ / SiO-based lithium ion secondary battery using PI for the positive electrode and the negative electrode can be stably charged and discharged even at a high temperature of 120 ° C. On the other hand, when PI is used, the current collector is excellent in binding property, and therefore, when combined with an active material having a large volume change, wrinkles and cracks may occur in the current collector during initial charge and discharge. Therefore, it is necessary to use iron foil or stainless steel foil having high mechanical strength for the current collector.

  There are few reports in the field of non-aqueous electrolyte secondary batteries in addition to the organic binder described above, but Patent Documents 2 to 4 disclose techniques using an inorganic binder for the secondary battery electrode. Patent Literature 2 includes an amorphous carbon material containing an inorganic binder, a conductive agent, a binder, and a solvent, and has a viscosity in a range of 2,000 mPa · s to 10,000 mPa · s, which is an electrode mixture for a non-aqueous electrolyte secondary battery. , Electrodes and non-aqueous electrolyte secondary batteries have been proposed. In addition, it is described that the presence of an inorganic binder can suppress the decomposition reaction of the binder in some cases.

  Patent Literature 3 and Patent Literature 4 provide physically and chemically stable lithium ion batteries using an inorganic binder. On the other hand, as described above, an electrode is generally composed of an active material layer (a layer composed of an active material, a conductive auxiliary agent, and a binder) and a current collector, but is different from the active material layer on the active material layer. In some cases, a layer is provided.

  For example, Patent Document 5 proposes a non-aqueous secondary battery using an electrode sheet having a layer mainly composed of a metal or a metalloid oxide and at least one auxiliary layer containing water-insoluble particles. The auxiliary layer provided on the electrode sheet is composed of water-insoluble conductive particles and a binder, and may further contain particles having substantially no conductivity. The particles having substantially no conductivity are oxides, and an oxide containing a compound that is soluble in both acidic and alkaline is preferable. It is shown that the binder used for forming the electrode mixture can be used as the binder used for the auxiliary layer.

  As such secondary batteries, batteries of various shapes such as a cylindrical type, a square type, and a laminated type are widely used. A relatively small-capacity battery has a cylindrical shape in terms of pressure resistance and ease of sealing, and a relatively large-capacity battery has a rectangular shape for ease of handling.

  In addition, focusing on the electrode structure of the secondary battery, two types, that is, a stacked type and a wound type are generally used. That is, in the stacked battery, an electrode group in which a positive electrode and a negative electrode are alternately stacked via a separator is housed in a battery case. Many of the stacked batteries have a rectangular battery case. On the other hand, a wound-type battery is housed in a battery case in a state where a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween. The wound type battery case includes a cylindrical type and a square type.

Patent 5728721 Patent 5293020 JP-A-11-144736 JP-A-10-523411 WO 1996/027910

Takashi Mukai et al., Development of lithium ion battery active material and electrode material technology, Science & Technology Co., Ltd. 269-311 (2014), ISBN: 978-4-86428-089-1 Masahiro Yanagida et al., Proc. 83rd IEICE Abstracts, 1T28, (2016)

  As described above, Non-Patent Literature 1 and Patent Literature 1 cannot be formed as electrodes because wrinkles and cracks are generated when a thin copper foil or the like is used for the current collector (see FIG. 19). On the other hand, if a high-strength iron foil or stainless steel foil is used for the current collector, wrinkles, cracks, and the like can be suppressed from occurring even if the current collector is thin. However, since the current collector has very high strength and excellent toughness, the step of punching the electrode is difficult, and the active material layer may fall off during cutting, or burrs may be generated on the cut surface.

  Further, PI is so excellent in chemical resistance that it is insoluble in almost all organic solvents. Therefore, in preparing the electrode slurry, a PI precursor such as polyamic acid (polyamic acid) or the like is dissolved in NMP, and is heated at 200 ° C. or higher, and an imidization reaction (dehydration cyclization reaction) is performed to advance the PI. Get. Then, after the imidization reaction, a heat treatment is performed at a higher temperature to cause a crosslinking reaction, and PI having high mechanical strength is obtained. From the viewpoint of the electrode life, it is preferable that the heat treatment is performed at a high temperature until the PI is not carbonized. However, heat treatment at 200 ° C. or higher not only reduces the flexibility of the electrode and makes handling difficult, but also inevitably oxidizes the active material and the surface of the current collector and causes irreversible capacity. In addition, heat treatment at a high temperature also causes an increase in power consumption during electrode production.

  In some cases, there is a PI binder dispersed in a solvent in the state of being imidized to form a PI.However, when a preliminarily imidized one is used at the time of addition to a slurry, an electrode having poor adhesion strength is obtained, resulting in poor life characteristics. Inferior. Further, many reactive binders such as PI occlude alkali metal ions at the time of initial charging, but cannot take them out at the time of discharging, which causes irreversible capacity. For example, depending on the molecular structure, PI has an irreversible capacity of 500-1000 mAh / g. Therefore, the electrode using the reactive binder has a low initial charge / discharge efficiency, and the battery capacity is greatly reduced.

  By the way, a nail penetration test is performed to confirm the safety of the battery. When a nail is inserted into a fully charged battery, heat generation exceeding 600 ° C. may be observed even in a battery having a nominal capacity of 1 Ah class. Non-Patent Document 1 discloses that a battery using a Si-based active material is greatly improved in nail penetration safety of the battery. Further, it has been shown that a battery using a Si-based negative electrode and a heat-resistant nonwoven fabric separator has further improved safety.

  Non-Patent Document 2 discusses this phenomenon. If the electron conductivity of the active material layer of the electrode is high, the heat generation temperature of the battery and the nail at the time of nail penetration increases, and the electron conductivity of the electrode active material layer is low. The results show that the temperature at which the battery and the nail generate heat when the nail is pierced also decreases. That is, the electron conductivity of the electrode active material layer greatly contributes to the safety of the battery in piercing. If the electron conductivity of the active material layer is high, the current value flowing through the nail increases, and the calorific value of the nail and the battery also increases.If the electron conductivity is low, the current value flowing through the nail decreases, The amount of heat generated per unit time is reduced.

  An alloy-based active material improves electron conductivity when alloyed with an alkali metal. For example, Si in a discharged state is a semiconductor and has a low electron conductivity, whereas a LixSi alloy in a charged state (0 <x ≦ 4.4) is a conductor and has a high electron conductivity. That is, in the case of the Si-based negative electrode, it is considered that the internal short-circuit causes the lithium-based active material in the short-circuited portion to be delithiated, the electron conductivity of the electrode to be rapidly reduced, and the current to be cut off, thereby suppressing the battery temperature rise. Can be

  However, in an electrode having a large amount of the conductive additive in the active material layer, or an electrode using a material in which a material having high conductivity is coated or compounded with the active material, the electron conductivity of the active material layer is increased, Even if a Si-based material is used, the above-described current interruption mechanism is difficult to function, and the battery temperature rise cannot be sufficiently suppressed. Therefore, in order to design a battery with an emphasis on safety, an electrode having a low conductivity in the active material layer had to be used. Conversely, an electrode composition that emphasizes safety has a low possibility of producing a low-output battery because of low electron conductivity.

  Even in a battery using an electrode with a low electron conductivity of the active material layer, instantaneous heat generation at the time of internal short circuit cannot be eliminated, so if the binder is carbonized by this heat generation, the electron conductivity of the electrode increases, Security will be compromised. Even organic reactive binders with excellent heat resistance are limited to a heat resistance temperature of about 400 ° C, and if the temperature rise due to internal short circuit exceeds the heat resistance temperature of the binder, carbonization occurs. ing.

In addition, it is generally known that a material having a small volume change exhibits good life characteristics among active materials. For example, in the charge reaction of Si (Si + 4.4Li ++ 4.4e− → Li _4.4 Si), a volume change of about 4 times occurs, and the charge reaction of SiO (SiO + 8.4Li ++ 8.4e− → Li _4.4 Si + Li ₄ SiO _4). In (), since the volume change is about 2.7 times excluding the volume change for the initial generation of Li ₄ SiO ₄ , SiO exhibits excellent life characteristics compared to Si.

  As another example, in a negative electrode using a mixture of Si and alumina, as compared with a pure Si negative electrode, the capacity decreases as the Si ratio decreases, but the life characteristics tend to be improved. Alumina is inactive with Li and does not contribute to the charge / discharge reaction, but serves as a buffer for the volume change of Si, and can reduce the volume change of the entire electrode.

For example, in the charging reaction of the Si negative electrode, due to the reaction of the following formula 1, the volume change occurs about four times as compared to before charging, and the stress applied to the electrode binder also becomes about four times.
_{Si + 4.4Li ++ 4.4e- → Li 4.4} Si ···· ( Equation 1)

In the case of a negative electrode to which Al ₂ O ₃ is added in an equimolar amount to Si, Al ₂ O ₃ is inactive with Li, so that a charging reaction as shown in equation (2) is obtained from a macroscopic viewpoint. With such an electrode, the volume change of the electrode is halved as compared with a pure Si electrode, so that the stress applied to the electrode binder is also halved. Therefore, it is expected that an electrode in which a material whose volume change is smaller than that of Si is mixed, as the Si ratio decreases, the capacity will decrease but the life characteristics will tend to be improved.
_{0.5Si + 0.5Al 2 O 3 + 2.2Li} ++ 2.2e -
→ 0.5Li _4.4 Si + 0.5Al ₂ O ₃ ··· (Equation 2)

  However, in actual life characteristics, although there is a slight life improvement effect, the result is that the deterioration rate of Si in each cycle does not change much. This is because, from a microscopic point of view, since the volume change of the Si particle itself is about four times, the stress applied to the electrode binder is not different from the equation 1, and the stress is eventually concentrated on the binding portion. Particularly, in the case of electrodes in which electrode materials are mutually bonded or the electrode material and the current collector are point-bonded with a binder, the bonded portion is intensively subjected to stress due to a change in volume, the binding property is lost, and the conductive network of the electrodes is lost. Easy to be destroyed.

  On the other hand, if the binder is surface-bonded, the bonding portion uniformly disperses the stress, so that the conductive network is less likely to be broken. However, the output characteristics are degraded because the binder inhibits the movement of ions. Although depending on the type of binder, spot bonding is likely to occur when the amount of binder is small, and surface bonding is likely to occur when the amount of binder is large.

  At present, among the various types of binders, a binder capable of stably charging and discharging the alloy-based active material is limited to a reactive type such as PI. However, the reactive binder uses an organic solvent during the production of the slurry, requires a heat treatment step of 200 ° C. or higher, and the resulting electrode has a large irreversible capacity derived from the binder, and has a limit in terms of safety.

  In addition, it is difficult for the reactive binder alone to exhibit sufficient life characteristics, and it has been necessary to combine it with SiO, a high-strength current collector foil, or the like. Organic substances have a low melting point, are easily soluble in organic solvents, and are flammable, while inorganic substances are known to have a high melting point, are difficult to dissolve in organic solvents, are nonflammable, and have high thermal conductivity. . Therefore, if a binder composed of an inorganic substance can be used, there is a high possibility that an electrode having high heat resistance and excellent in electrolyte resistance and heat dissipation can be obtained.

  However, many inorganic binders have not been adapted for non-aqueous electrolyte secondary battery electrodes. Inorganic binders can be broadly classified into four types: silicate-based, phosphate-based, sol-based, and cement-based. Among them, the present inventors have proposed a silicate-based and phosphate-based, particularly alkali metal silicic acid, which have strong binding properties to all metals, oxides, and carbon and have heat resistance of 1000 ° C. or more. Attention was paid to the acid salt system.

  The silicate type may be a silicate of a guanidine compound or a silicate of an ammonium compound, in addition to the alkali metal silicate. A silicate salt-based inorganic binder is a compound having a silicon (Si) having a siloxane bond (-Si-O-Si-) and oxygen (O) as a main molecular skeleton, and an organic skeleton having a carbon-based skeleton. Different from the binder (see FIG. 21a).

  Further, a part of the Si site in the siloxane bond is replaced with a transition metal element such as Al, Zr, Ti, Mg, Mo, Sr, Ca, Zn, Ba, B, W, Ta, Ce, Hf, or Y. May be.

The silicate includes orthosilicate (A ₄ SiO ₄ ), metasilicate (A ₂ SiO ₃ ), pyrosilicate (A ₆ Si ₂ O ₇ ), and disilicate (A ₂ Si ₂ O ₅ ) , Polysilicates such as tetrasilicate (A ₂ Si ₄ O ₉ ), and many types such as A ₂ Si ₂ O ₅ , A ₂ Si ₃ O ₇ , A ₂ Si ₄ O ₉ , These may be hydrates. Further, their structures can be broadly classified into crystalline silicates and amorphous silicates (A = alkali metal element or guanidine compound, ammonium compound). Such a silicate tends to have a lower melting point as the proportion of A in the silicate increases, and at the same time shows solubility in water.

Industrially, silicates can have a continuously varying proportion of A in the silicate, any salt can be adjusted, and the general molecular formula of the silicate is A ₂ O · NSiO represented by ₂ of the form.

  Due to this difference in molecular skeleton, it shows higher heat resistance and oxidation resistance than organic binder, and various fields such as fire retardant, waterproof agent, bleach, detergent, soap, coating agent, sealing agent, civil engineering ground reinforcement, etc. However, there are few reports in the field of non-aqueous electrolyte secondary batteries.

  The phosphate type may be a magnesium phosphate salt or a calcium phosphate salt in addition to the aluminum phosphate salt.

  In the phosphate-based inorganic binder, water is removed from the hydroxyl group by heating to form a covalent bond between phosphorus and oxygen, and a dehydration condensation reaction occurs. This dehydration-condensation reaction can be performed at a maximum of six places per molecule centering on the transition metal (M), and a three-dimensionally polymerized transition metal phosphate can be obtained. That is, it is a compound having phosphorus (P) having an aluminophosphate bond, oxygen (O), and a transition metal (M) as a main molecular skeleton, which is different from an organic binder having a carbon-based skeleton (see FIG. 21B). .

  Some of the transition metal sites are Al, Mg, Ca, Cu, Fe, Ba, Ti, Mn, Mo, Mg, Si, Sr, Ca, Zn, Ba, B, W, Ta, Ce, Hf, It may be substituted with a transition metal element such as Y.

Specifically, aluminum phosphates include aluminum phosphate monobasic (Al (H ₂ PO ₄ ) ₃ ), aluminum hydrogen phosphate (Al ₂ (H ₂ PO ₄ ) ₃ ), and aluminum metaphosphate ( Al (PO ₃ ) ₃ ). Magnesium phosphate salts include magnesium phosphate monobasic (Mg (H ₂ PO ₄ ) ₃ ), magnesium hydrogen phosphate (MgHPO ₄ ), and magnesium metaphosphate (Mg (PO ₃ ) ₂ ). Examples of the calcium phosphate salt include monocalcium phosphate salt (Ca (H ₂ PO ₄ ) ₃ ), calcium hydrogen phosphate (CaHPO ₄ ), tricalcium phosphate (Ca ₃ (H ₂ PO ₄ ) ₂ ), calcium metaphosphate ( Ca (PO ₃ ) ₂ ), which may be hydrates. Their structures can be broadly divided into crystalline phosphates and amorphous phosphates.

Industrially, phosphates can have a continuously varying ratio of M and P in the phosphate, any salt can be adjusted, and the general molecular formula of the phosphate is M - represented by NHxPO ₄ of the form (M = Al or, Mg, Ca).

The sol system is a colloid solution in which fine oxide particles are dispersed in water. The particle size of the oxide is 10 nm or more and 200 nm or less, and a hydroxyl group is present on the surface. For example, when the oxide is SiO ₂ , a siloxane bond is formed by dehydration-condensation, but since the siloxane bond is formed inside the oxide particles, the binding force is weaker than that of a silicate salt. Further, there is a problem that pH control is important and it is difficult to stably maintain a sol state. In the present invention, since the sol-based material hardly penetrates into the active material layer, it is not preferable to use it as a skeleton-forming agent.

Patent Literature 2 discloses that when a binder includes an inorganic binder, a decomposition reaction of the binder may be suppressed in some cases. This is because the carbon material (graphite, soft carbon, hard carbon, etc.) has a charge / discharge plateau potential near 0.1 V (vs. Li + / Li), and the electrode has strong reducing power. It is considered that the decomposition reaction is suppressed by an excellent inorganic binder.

  However, since the alloy-based material is higher than the charge / discharge plateau potential of the carbon material and has a lower reducing power than the carbon-based electrode, the decomposition reaction of the binder hardly occurs. Therefore, even if the decomposition reaction of the binder is suppressed, the life characteristics of the alloy-based electrode are not significantly improved.

  In Patent Document 2, the inorganic binder contains inorganic particles, and the particle diameter of the inorganic particles is preferably from 1 nm to 100 nm, more preferably from 1 nm to 50 nm, and still more preferably from 1 nm to 10 nm. , Is indicated. It is described that a binder having more excellent dispersibility and adhesive strength of the electrode mixture can be obtained by using such a particle size.

  Since the specific gravity of the inorganic particles is larger than that of the carbon material, as the particle size of the inorganic particles increases, the sedimentation speed of the particles increases, and the dispersibility and the adhesive force decrease. Therefore, it is effective to use particles of 100 nm or less. However, at the time of drying after electrode coating, particles having a diameter of 100 nm or less prevent escape of vaporized water, the coating film foams, and the binding property with the current collector is reduced, and it is difficult to obtain a uniform electrode. There is a problem that. In addition, such an electrode does not contain an organic binder having excellent flexibility, and thus is brittle, and is broken when the electrode is bent. Therefore, it is not suitable for a wound type battery.

  On the other hand, alloy-based active materials are known to have higher capacities than conventional carbon-based active materials. For example, a high electric capacity of 2800 to 4000 mAh / g for Si, 1300 to 2000 mAh / g for SiO, 700 to 1000 mAh / g for Sn, and 800 to 1500 mAh / g for S is shown. For this reason, even a small error causes a large variation in the electrode capacitance, which may deteriorate the life characteristics and output characteristics. Further, the viscosity of the electrode slurry is difficult to control because it drastically changes depending on the amount of the solvent used.

Patent Literature 3 and Patent Literature 4 provide physically and chemically stable lithium ion batteries using an inorganic binder. Examples of the electrode include a graphite negative electrode (graphite anode) and a LiCoO ₂ positive electrode (LiCoO ₂ cathode). The graphite negative electrode is composed of 1.0 g of lithium hydroxide, 23.4 g of an inorganic binder (lithium polysilicate), and 45.0 g of graphite powder.

  Therefore, when the total solid content of the active material, the conductive additive, and the binder is 100% by mass, the active material is 64.8% by mass, and the inorganic binder is 33.7% by mass.

The LiCoO ₂ cathode is composed of 1.0 g of lithium hydroxide, 1.9 g of graphite powder, 2.9 g of C-100 carbon black, 24 g of inorganic binder (lithium polysilicate) and 85.6 g of graphite powder. ing.

  Therefore, when the total solid content of the active material, the conductive additive, and the binder is 100% by mass, the active material is 74.2% by mass and the inorganic binder is 20.8% by mass. %. In Patent Document 3 and Patent Document 4, the inorganic binder does not describe the inorganic particles, and the Examples do not include the inorganic particles.

  The above Patent Documents 2 to 4 all attempt to improve the decomposition reaction of the binder and the swelling due to the electrolytic solution, which are difficult to realize with the conventional organic binder. By using an alloy material such as a Si-based or Sn-based material as an active material and a binder that does not easily swell with an electrolytic solution, it is likely that the operating temperature of the electrode can be increased and the capacity can be increased.

  However, since the silicate-based binder is strongly alkaline and the phosphate-based binder is strongly acidic, the alloy-based active material when the electrode slurry is prepared is dissolved, and hydrogen gas is generated to foam the slurry. . In particular, since the temperature becomes high when the electrode is dried, the amount of hydrogen gas generated increases, and even electrode production cannot be maintained. In addition, if a current collector having no resistance to alkali or acid is used, the current collector deteriorates.

For example, when the Si active material comes into contact with the alkali metal silicate system, a reaction of Si + 2OH− + H ₂ O → SiO ₃₂ − + 2H ₂ } occurs. Therefore, at present, there is only an option for an alkali- or acid-resistant active material, that is, a carbon-based material. The binder, which is one of the components of the electrode, is used for binding the active material and the active material, the active material and the conductive auxiliary, the active material and the current collector, and the conductive auxiliary and the current collector. However, since current batteries employ an organic binder such as PVdF or SBR, their thermal conductivity is small compared to inorganic materials such as active materials, conductive aids, and current collectors, and heat is difficult to transfer. . In addition, since the silicate-based or phosphate-based inorganic binder has a higher specific gravity than a conventional organic binder, the amount of the binder used when preparing an electrode is reduced by the solid content of the active material, the conductive additive, and the binder. If the total is 100% by mass, a sufficient binding force will not be exhibited unless the total is not less than 20% by mass. In particular, when a material having a large volume change is used, 30 to 70% by mass is required. Therefore, the ratio of the active material of the electrode decreases, and the electrode energy density decreases.

  As described above, the inventors of the present application initially studied the application of a silicate-based or phosphate-based binder, but when a silicate-based or phosphate-based binder was applied, It has been found that it contains many problems and cannot be realized as a practical electrode. Thus, the inventors have repeated studies to apply a silicate-based or phosphate-based material to an electrode instead of a binder, and have completed the present invention. The present invention can solve the conventional problems described above and the problems newly discovered by the inventors.

  The skeleton-forming agent used in the present invention is a skeleton-forming agent used for an electrode of a non-aqueous electrolyte secondary battery, and a silicate having a siloxane bond as a component, or a phosphate having an aluminophosphate bond as a component. It is characterized by including. According to this configuration, by using a skeleton-forming agent containing silicate or phosphate for the electrode, an electrode having excellent heat resistance, high strength, and improved cycle life characteristics can be obtained.

The skeleton forming agent and the silicate have a crystalline or amorphous structure represented by the general formula A ₂ O.nSiO ₂ , where A is Li, Na, K, a triethanolammonium group, tetramethanol. It is at least one of an ammonium group, a tetraethanol ammonium group, and a granidine group, and n is 0.5 or more and 5.0 or less.

Preferably, in the skeleton forming agent, A in the above general formula is Li or Na, and n is 1.6 or more and 3.9 or less, more preferably 2.0 or more and 3.5 or less. A is preferably Na from the viewpoint of excellent mechanical strength for forming the skeleton, binding properties, and abrasion resistance. Note that Li is excellent in the input / output characteristics of the battery because a skeleton-forming body having high ion conductivity is obtained. However, when the number n of SiO ₂ exceeds 5.0 even with Na, the binding property with the active material layer and the separator is poor, and the volume change of the electrode during charge and discharge and the outside of the nail penetration test etc. Peeling and cracking are likely to occur significantly due to physical factors. Further, the viscosity becomes too low, and the stability of dispersibility with ceramics described later decreases.

  On the other hand, when n is less than 0.5, the viscosity is high, so that it becomes difficult for the skeleton forming agent to penetrate or apply to the electrode active material layer and the separator. Further, when kneading with ceramics, the calorific value increases.

  Preferably, the silicate is amorphous. An amorphous silicate does not crack in a specific direction unlike a crystal, so that the life characteristics of the electrode are improved. In addition, since the resistance to hydrofluoric acid is improved, the collapse of the electrode derived from hydrofluoric acid can be suppressed.

  Usually, amorphous solids consist of disordered molecular arrangements and do not possess a distinguishable crystal lattice. In addition, the solubility of an amorphous solid is higher than that of a crystalline form and does not have a constant melting point. Therefore, the absence of a distinct peak in the powder X-ray diffraction (XRD) pattern and the absence of a melting endothermic peak in a differential thermal analysis (DTA) curve or a differential scanning calorimetry (DSC) curve indicate that the amorphous form is present. Is shown.

  That is, the amorphous silicate does not have a sharp peak characteristic of a crystalline form in XRD, and has a typical diffraction angle (2θ) in the range of 15 ° to 40 ° by Cu-Kα ray. It shows a broad broad peak, the so-called halo pattern. More specifically, it shows essentially the same XRD pattern as FIG.

However, even if a halo pattern is obtained by XRD, not all of them are amorphous. However, it is only the limited condition that the crystal grain is smaller than 5 nm according to the Scherrer equation shown in Equation 3. That is, when the crystal grain size is 5 nm or more, the diffraction line is not wide and the pattern is not similar to that of the amorphous.
D (Å) = 0.9λ / (β × cosθ) (3)
(Where D is the size of the crystal grain, λ is the wavelength of the X-ray tube, β is the spread of the diffraction line due to the size of the crystal grain, and θ is the diffraction angle)

  Further, when the state changes from the amorphous state to the crystalline state, a large amount of heat is generated. Therefore, it is possible to determine the crystalline state of the silicate by measuring this. The amorphous silicate can be obtained by heat-treating the electrode at a rate of 10 ° C./h or more at a temperature of 80 ° C. or more and 600 ° C. or less.

  Preferably, in this skeleton forming agent, the solid content concentration of the silicate is 0.1% by mass or more and 30% by mass or less. More preferably, the content is 0.1% by mass or more and 15% by mass or less.

  This skeleton forming agent further contains a surfactant, and the surfactant is present in an amount of 0.001% by mass or more and 5.0% by mass or less. According to this configuration, the lyophilicity of the skeleton forming agent to the active material layer is improved, and the skeleton forming agent uniformly penetrates the active material layer. Therefore, a uniform skeleton is formed in the active material layer, and the cycle life characteristics are further improved. When the content is less than 0.001% by mass, the skeleton forming agent hardly penetrates into the active material layer containing a large amount of a carbon-based material such as graphite, hard carbon, and a conductive additive. In the absence of a defoaming agent, the surface of the active material layer foams and it is difficult to form a strong skeleton.

  Further, the skeleton forming agent further contains alkali-resistant inorganic particles. According to this configuration, when the skeleton-forming agent is applied to the electrode, the inorganic particles are laminated on the surface of the active material layer of the electrode, and the active material layer is covered with the layer of the inorganic particles. Also inorganic particles enter.

  As a result, a strong skeleton can be formed in the active material layer, peeling and cracking during drying can be suppressed, and pores are formed due to gaps between the inorganic particles, resulting in good electrolysis. The lyophilicity with the liquid is obtained. In addition, the inorganic particle layer provides an electrode having high heat resistance and high strength and excellent wear resistance. In addition, the layer of inorganic particles replaces the separator, and the battery can be configured without using a separate separator.

Preferably, in the skeleton forming agent, the content of the silicate is 5% by mass or more and 80% by mass or less, when the total of the solid content including the silicate and the alkali-resistant inorganic particles is 100% by mass. The content of the alkali-resistant inorganic particles is 20% by mass or more and 95% by mass or less, and the median diameter (D ₅₀ ) of the alkali-resistant inorganic particles is 0.2 μm or more and 20 μm or less.

Here, the median diameter (D ₅₀ ) means a volume-based particle diameter in a laser diffraction / scattering particle diameter distribution measuring method. The laser diffraction / scattering particle size distribution measuring method is a method of measuring the particle size by utilizing a phenomenon that when a laser beam is applied to particles, the light intensity distribution of the diffracted scattered light varies depending on the particle size.

  When the skeleton forming agent contains the alkali-resistant inorganic particles, the skeleton forming agent is less likely to foam when dried at a high temperature. When the skeleton-forming agent foams, the binding property with the active material layer and the separator is reduced, and it is difficult to obtain sufficient strength.

The reason for setting the median diameter (D ₅₀ ) of the alkali-resistant inorganic particles to 0.2 μm or more and 20 μm or less is that pores are formed by gaps between the inorganic particles, and good lyophilicity with an electrolytic solution can be obtained. From the viewpoint of the output characteristics of the battery, the thickness is more preferably 0.25 μm or more and 10 μm or less, and even more preferably 0.3 μm or more and 2 μm or less.

  If the particle size of the inorganic particles is larger than this range, the thixotropy will be low and dilatancy will tend to be exhibited, and the dispersion stability when the inorganic particles are added to the skeleton forming agent will be reduced. Conversely, if the particle size is smaller than this range, when forming a skeleton having a thickness of more than 2 μm, there is no way for moisture vaporized during drying to escape, the coating film foams, and the binding property with the current collector decreases. In addition, it is difficult to obtain a uniform electrode.

  The reason that the inorganic particles require alkali resistance is that silicate exhibits strong alkalinity (pH 12 or more). Further, it is desirable that the skeleton-forming agent is inorganic particles that have excellent resistance to dissolution in an electrolytic solution in addition to the alkali resistance.

The inorganic particles satisfying such conditions are selected, for example, from the group consisting of Al, Zr, Ti, Si, Mg, Mo, Sr, Ca, Zn, Ba, B, W, Ta, Ce, Hf and Y. Examples include oxides, hydroxides, nitrides, carbides, carbonates, and sulfates of at least one element. Of these, Al ₂ O ₃ , ZrO ₂ , TiO ₂ ,
SiO ₂ , CaO, MgO, CeO, Y ₂ O ₃ , AlN, WC, SiC, B ₄ C, BN, TaC, TiC, TiB ₂ , HfB ₂ , Si ₃ N ₄ , TiN, CaCO ₃ , MgSO ₄ , Al It preferably contains ₂ (SO ₄ ) ₃ , CaSO ₄ , and ZrSiO ₄ .

In addition, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ , MgO, CeO, Y ₂ O ₃ , WC, SiC, B ₄ C, TaC, TiC , Si ₃ N ₄ , TiN, CaCO ₃ , MgSO ₄ , CaSO ₄ , and ZrSiO ₄ . With these materials, it is possible to have an effect of suppressing a large volume shrinkage of the silicate generated at the time of drying, and to have a sufficient strength even when dried at a low temperature.

On the other hand, the phosphate has a crystalline or amorphous structure represented by the general formula M · nHxPO ₄ , M is at least one of Al, Ca, and Mg, and x is 0 or more and 2 or less. And n is 0.5 or more and 5 or less.

  M is preferably Al from the viewpoint of excellent mechanical strength in forming the skeleton, binding properties, and wear resistance. x is preferably 1 or 2 and more preferably 2 from the viewpoint of excellent skeleton formation binding property. n is preferably from 0.5 to 5.0, more preferably from 2.5 to 3.5, from the viewpoint of excellent mechanical strength for forming the skeleton, binding properties, and abrasion resistance. The phosphate is preferably amorphous as in the case of the silicate.

  Preferably, the skeleton forming agent has a solid content concentration of the phosphate of 0.1% by mass or more and 30% by mass or less. More preferably, the content is 0.1% by mass or more and 15% by mass or less.

  The skeleton forming agent contains a surfactant, and the content of the surfactant is preferably 0.001% by mass or more and 5.0% by mass or less.

  The skeleton forming agent preferably further contains acid-resistant inorganic particles. According to this configuration, when the skeleton-forming agent is applied to the electrode, the inorganic particles are laminated on the surface of the active material layer of the electrode, and the active material layer is covered with the layer of the inorganic particles. Also inorganic particles enter.

  As a result, a strong skeleton can be formed in the active material layer, peeling and cracking during drying can be suppressed, and pores are formed due to gaps between the inorganic particles, resulting in good electrolysis. The lyophilicity with the liquid is obtained. In addition, the inorganic particle layer provides an electrode having high heat resistance and high strength and excellent wear resistance. In addition, the layer of inorganic particles replaces the separator, and the battery can be configured without using a separate separator.

Preferably, the skeleton forming agent has a phosphate content of 5% by mass or more and 80% by mass or less when the total of the solid content including the phosphate and the acid-resistant inorganic particles is 100% by mass. The acid-resistant inorganic particles are at least 20 mass% and at most 95 mass%, and the median diameter (D ₅₀ ) of the acid-resistant inorganic particles is at least 0.2 μm and at most 20 μm.

When the skeleton-forming agent contains the above-mentioned acid-resistant inorganic particles, the skeleton-forming agent hardly foams when dried at a high temperature. When the skeleton-forming agent foams, the binding property with the active material layer and the separator is reduced, and it is difficult to obtain sufficient strength. The median diameter (D ₅₀ ) of the acid-resistant inorganic particles is preferably 0.2 μm or more and 20 μm or less.

  The reason that the inorganic particles require acid resistance is that phosphates show strong acidity (pH 1 to 2). In addition, it is desirable that the skeleton forming agent is inorganic particles that have excellent resistance to dissolution in an electrolytic solution in addition to the acid resistance.

The inorganic particles satisfying such conditions include, for example, at least one or more elements selected from the group consisting of Al, Zr, Ti, Si, Mo, Sr, Ba, B, W, Ta, Ce, Hf, and Y. Oxides, hydroxides, nitrides, carbides, carbonate compounds, sulfate compounds and the like can be mentioned. Among them, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ , CeO, and Y ₂ O ₃ are materials that are hardly oxidatively decomposed or reductively decomposed at the time of charging or discharging of the battery and have a small irreversible capacity. , WC, SiC, B ₄ C, BN, TaC, TiC, TiB ₂ , HfB ₂ , Si ₃ N ₄ , TiN, and ZrSiO ₄ .

In addition, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ , CeO, Y ₂ O ₃ , WC, SiC, B ₄ C, BN, TaC, TiC , Si ₃ N ₄ , TiN, and ZrSiO ₄ . With these materials, it is possible to suppress the large volume shrinkage of the phosphate generated during drying and to have sufficient strength even when dried at a low temperature.

  Among silicates and phosphates, silicates are preferred from the viewpoints of battery life and input / output characteristics, irreversible capacity, moisture absorption resistance, heat resistance and the like.

  The electrode according to the present invention is an electrode for a non-aqueous electrolyte secondary battery, wherein the skeleton forming agent is present at least on the surface of the active material layer. According to this configuration, the skeleton-forming agent containing silicate or phosphate forms the skeleton of the electrode, and the electrode has excellent heat resistance, high strength, and improved cycle life characteristics. When a binder containing silicate or phosphate is not used as an electrode, an electrode having excellent cycle life characteristics can be obtained by attaching a skeleton-forming agent to the surface of the active material layer.

  Here, the non-aqueous electrolyte secondary battery is a secondary battery using an electrolyte not containing water as a main component, such as a lithium secondary battery (lithium ion battery), a sodium battery (sodium ion battery), and a potassium battery ( Potassium ion battery). The electrode is not particularly limited as long as it is an electrode used for a nonaqueous electrolyte secondary battery, and the material and shape of the electrode are not particularly limited.

  The electrodes include a negative electrode and a positive electrode. First, regarding the negative electrode, the negative electrode active material used for the negative electrode is not particularly limited as long as it is a material capable of reversibly storing and releasing alkali metal ions (such as lithium ions, sodium ions, and potassium ions). For example, Li, Na, K, C, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, At least one element selected from the group consisting of Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb and Bi, alloys, composites, oxides, chalcogenides or halogens using these elements Any compound can be used.

  From the viewpoint that the region of the discharge plateau can be observed in the range of 0 to 1 V (vs. Li + / Li), Li, Na, K, C, Mg, Al, Si, Ti, Zn, Ge, Fe, Mn, Ag , Cu, In, Sn and Pb, at least one element selected from the group consisting of these, and allotropes, alloys or oxides using these elements are preferable.

Further, from the viewpoint of energy density, the elements are preferably Al, Si, Zn, Ge, Ag, Sn and the like, and the alloys are Si-Al, Al-Zn, Si-Mg, Si-La, Al-Ge, Si-Ge, Si-Ag, Si-Sn, Si-Ti, Si-Y, Si-Cr, Si-Ni, Si-Zr, Si-V, Si-Nb, Si-Mo, Zn-Sn, Ge- Ag, Ge-Sn, Ge- Sb, Ag-Sn, Ag-Ge, the combination such as Sn-Sb is preferable, as the _{oxide, Fe 2 O 3, CuO,} MnO 2, NiO, Li 4 Ti 5 O ₁₂ , H ₂ Ti ₁₂ O ₂₅ , Na ₂ Ti ₃ O _{7 and the} like are preferable. The alloy may be a solid solution alloy, a eutectic alloy, a hypoeutectic alloy, a hypereutectic alloy, or a peritectic alloy. Further, the surface of the active material particles may be coated with a material having excellent electron conductivity or ceramics. Note that two or more materials capable of reversibly occluding and releasing lithium may be used.

  The shape of the active material particles is not particularly limited, and may be spherical, elliptical, faceted, strip-shaped, fiber-shaped, flake-shaped, donut-shaped, or hollow. Materials that can occlude and release alkali metal ions (lithium ion, sodium ion, and potassium ion) reversibly are substances and solid electrolytes that can occlude and release alkali metal ions during the initial charging process. Compounds that degrade are more preferred.

  The solid electrolyte is not particularly limited as long as it has ion conductivity, but is preferably a solid electrolyte represented by LiαXβYγ. Here, in the formula, 0 <α ≦ 4, 0 ≦ β ≦ 2, and 0 ≦ γ ≦ 5. The solid electrolyte also serves as a buffer material of a material capable of reversibly storing and releasing alkali metal ions.

X is, for example, any one or more of Si, Ti, Mg, Ca, Al, V, Ge, Zr, Mo, and Ni, and Y is O, S, F, Cl, Br, I, P, B _{It is at least one of 2} O ₃ , C ₂ O ₄ , CO ₃ , PO ₄ , S, CF ₃ SO ₃ , and SO ₃ . More specifically, for example, LiF, LiCl, LiBr, LiI , Li 3 N, LiPON, Li 2 C 2 O 4, Li 2 CO 3, LiAlCl 4, Li 2 O, Li 2 S, LiSO 4, Li 2 SO ₄ , Li ₃ PO ₄ , Li ₃ VO ₄ , Li ₄ GeO ₄ , Li ₂ Si ₂ O ₅ , Li ₂ SiO ₃ , Li ₄ SiO ₄ , Li ₄ ZrO ₄ , LiMoO ₄ , LiAlF ₄ , Li ₃ Ni ₂ , LiBF ₄ , LiCF ₃ SO ₃ , NaF, NaCl, NaBr, NaI, Na ₃ N, NaPON, Na ₂ C ₂ O ₄ , Na ₂ CO ₃ , NaAlCl ₄ , Na ₂ O, Na ₂ S, NaSO ₄ , Na ₂ SO ₄ , Na ₃ PO ₄ , Na ₃ VO ₄ , Na ₄ GeO ₄ , Na ₂ Si ₂ O ₅ , Na ₂ SiO ₃ , Na ₄ SiO ₄ , Na ₄ ZrO ₄ , NaMoO ₄ , NaAlF ₄ , Na ₃ Ni ₂ , NaBF _{4, NaCF 3 SO 3, KF} , KCl, KBr, KI, K 3 N, KPON, K 2 C 2 O 4, K 2 CO 3, KAlCl 4, K 2 O, K 2 S, KSO 4, K 2 SO _{4, K 3 PO 4, K} 3 VO 4, K 4 GeO 4, K 2 Si 2 O 5, K 2 SiO 3, K 4 SiO 4, K 4 ZrO 4, KMoO 4, KAlF 4, K 3 Ni 2, Examples thereof include KBF ₄ and KCF ₃ SO ₃ , and one or more of these can be used.

The decomposing compound material and a solid electrolyte capable of occluding and releasing an alkali metal ion, for example, SiO, GeO, GeS, GeS 2, SnO, SnO 2, SnC 2 O 4, SnO-P 2 O 5, _{SnO-B 2 O 3, SnS} , SnS 2, Sb 2 S 3, SnF 2, SnCl 2, SnI 2, SnI 4 and the like, may be used two or more of these. However, it is preferable that the substance capable of inserting and extracting alkali metal ions and the compound decomposing into a solid electrolyte be pre-doped before the battery is assembled because if the pre-doping is not performed beforehand, the battery capacity is extremely reduced. .

  Regarding the method of pre-doping, refer to Patent Literature (Japanese Patent Application Laid-Open No. 2015-088437) and Non-Patent Literature (“Collection of Measurement and Analysis Data of Lithium Secondary Battery Members”, Chapter 3, Section 30, pp. 200-205, Technical Information Association As described in (1), known methods such as an electrochemical method, an alkali metal bonding method, and a mechanical method can be used. Although the reason is not clear, in the present invention, the cycle life improvement is particularly remarkable when the electrode on which the skeleton is formed is Si, a Si alloy, a Si compound, a Si oxide, or a mixture containing at least one of these. The effect is exhibited.

  When the active material powder having a small particle diameter is used as the active material, the collapse of the particles is reduced, and the life characteristics of the electrode tend to be improved. In addition, the specific surface area tends to increase, and the output characteristics tend to be improved. For example, according to Non-Patent Document (Latest Technology Trend of Rare Metal Free Secondary Battery, Chapter 3, Section 1, Section 4, PP.125-135, CMC Publishing, 2013), the particle size of the active material is small. It is described that the initial discharge capacity increases and the cycle life also improves, indicating that the active material particle size has a correlation between the initial charge / discharge efficiency and the cycle life.

  However, nano-order active materials are difficult to handle, so it is preferable to use them after granulation. For example, Patent No. 55250003, polyimide, polybenzimidazole, styrene butadiene rubber, polyvinylidene fluoride, carboxymethylcellulose, nano-granules using one or more granulation binder of polyacrylic acid The negative electrode used is shown. By granulating the nano-order active material, the stress applied to the copper foil due to expansion and contraction of the negative electrode active material is reduced, and the deformation of the copper foil can be prevented.

On the other hand, it is also conceivable to use the skeleton forming agent of the present invention as a binder for granulating the negative electrode active material described above. In that case, the primary particles of the active material preferably have a median diameter (D ₅₀ ) in the range of 0.01 μm to 10 μm, and the granulated active material particles (secondary particles) have a median diameter (D ₅₀ ). It is preferable to be within the range of 1 μm to 100 μm.

  Further, as a method of granulating the active material, a known granulation method can be applied, for example, a fluidized bed granulation method, a stirring granulation method, a tumbling granulation method, a spray drying method, an extrusion granulation method. , A tumbling granulation method, and a coating granulation method. Of these, spray drying and fluidized bed granulation are particularly preferred.

  In the spray drying method, for example, a suspension in which an active material is dispersed in a skeleton forming agent is sprayed from above into a greenhouse heated to 50 to 300 ° C. at 1 to 30 mL / min at an air pressure of 0.01 to 5 MPa. In this way, agglomerated particles are formed and dried to obtain granules.

  In the fluidized bed granulation method, for example, a powder raw material (granulated material precursor) is fluidized by putting a powder raw material into a fluidized bed granulator and sending warm air heated to 50 to 300 ° C. from below. And water mixed with the skeleton forming agent dissolved in the mixed powder material is sprayed from above with a nozzle, and the skeleton forming agent is sprayed uniformly on the powder surface at 1 to 30 mL / min at an air pressure of 0.01 to 5 MPa. In this way, agglomerated particles are formed and dried to obtain granules.

  However, when an active material having poor alkali resistance, such as Si or Sn, is used, it is likely to react with a skeleton-forming agent to generate hydrogen gas and fail as a negative electrode. Therefore, when the skeleton-forming agent of the present invention is used, the skeleton-forming agent is sprayed on the secondary particles previously granulated with the organic binder for granulation, and the skeleton is formed on the granulated product to generate hydrogen gas. Seems to be as small as possible.

  As the organic binder for granulation, a known organic binder can be used. For example, a binder used for the positive electrode and the negative electrode may be used, but from the viewpoints of chemical stability of the granulated material, heat resistance, reduction resistance, and the like, polybenzimidazole, styrene butadiene rubber, polyvinylidene fluoride, carboxymethyl cellulose, Polyvinyl alcohol, polyacrylic acid, cellulose nanofiber, polyimide, polyamide, and polyamideimide are preferred.

  The amount of the binder for granulation is not particularly limited as long as it can bind the active material particles, but is preferably in the range of 0.1 to 30% by mass based on the granulated material. The granulated body may contain a conductive additive for imparting electron conductivity, if necessary, in addition to the active material particles and the granulating binder. It is preferable that the skeleton-forming agent is contained in the range of 0.2 to 30% by mass based on the granule. The granules thus obtained have not only improved cycle life characteristics but also improved slurry coatability.

  The conductive assistant for the negative electrode is not particularly limited as long as it has electron conductivity, and the above-described metals, carbon materials, conductive polymers, conductive glasses, and the like can be used. Specifically, acetylene black (AB), Ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, roller black, disk black, carbon black (CB), carbon fiber (for example, registered Vapor-grown carbon fibers named VGCF, a trademark), carbon nanotubes (CNT), carbon nanohorns, graphite, graphene, glassy carbon, amorphous carbon, and the like. One or more of these may be used.

  When the total of the active material, the binder, and the conductive additive contained in the negative electrode is 100% by mass, the conductive additive is preferably contained in an amount of 0 to 20% by mass. That is, the conductive assistant is contained as needed. If it exceeds 20% by mass, the ratio of the active material in the battery is small, so that the electrode capacity density tends to be low.

  The binder for the negative electrode is a commonly used one, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, aramid, polyacryl, styrene butadiene rubber (SBR) , Ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), chitansan gum, polyvinyl alcohol (PVA), ethylene vinyl alcohol, polyvinyl butyral (PVB), Ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, Methyl acrylate, polyethyl acrylate, polyacrylate, polyacrylate, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea Resin, melamine resin, phenol resin, latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2 -Propenoic acid, cyanoacrylic acid, methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate , Alginic acid, starch, to sell, sucrose, glue, casein, may also be an organic material such as cellulose nanofibers alone or in combination of two or more thereof.

  Further, a mixture of these organic binder and inorganic binder may be used. The inorganic binder may be a silicate type, a phosphate type, a sol type, a cement type or the like. For example, lithium silicate, sodium silicate, potassium silicate, cesium silicate, guanidine silicate, ammonium silicate, fluorosilicate, borate, lithium aluminate, sodium aluminate, potassium Aluminate, aluminosilicate, lithium aluminate, sodium aluminate, potassium aluminate, polyaluminum chloride, polyaluminum sulfate, polyaluminum silicate, aluminum sulfate, aluminum nitrate, ammonium alum, lithium alum, sodium alum, potassium Alum, chrome alum, iron alum, manganese alum, nickel ammonium sulfate, diatomaceous earth, polyzirconoxane, polytantaloxane, mullite, white carbon, silica sol, colloidal Rica, fumed silica, alumina sol, colloidal alumina, fumed alumina, zirconia sol, colloidal zirconia, fumed zirconia, magnesia sol, colloidal magnesia, fumed magnesia, calcia sol, colloidal calcia, fumed calcia, titania sol, colloidal titania, fume Dotitania, zeolite, silicoaluminophosphate zeolite, sepiolite, montmorillonite, kaolin, saponite, aluminum phosphate, magnesium phosphate, calcium phosphate, iron phosphate, copper phosphate, zinc phosphate, titanium phosphate Salt, manganese phosphate, barium phosphate, tin phosphate, low melting glass, plaster, gypsum, magnesium cement, litharge cement, Portland Instruments, blast furnace cement, fly ash cement, silica cement, phosphate cement, concrete, inorganic material of the solid electrolyte and the like may be used singly, and may be used in combination of two or more thereof.

  Among these, lithium silicate, sodium silicate, potassium silicate, guanidine silicate, ammonium silicate, Inorganic materials such as fluorosilicates, aluminosilicates, aluminum phosphates, magnesium phosphates and calcium phosphates are preferred.

  However, when a negative electrode is manufactured using an inorganic binder, the specific energy of the inorganic binder is large, so that the electrode energy density per weight tends to be low. In addition, in the case of an inorganic binder having a strong acid or alkali, when an active material having poor chemical resistance such as Si or Sn is contained, hydrogen gas is generated during mixing of the slurry, which not only makes electrode coating difficult, but also heat-drys. Foaming in the step (1) and a uniform electrode cannot be produced. In addition, when a current collector having poor chemical resistance is used, the current collector deteriorates.

  For the binder for the negative electrode, conventionally, when an alloy-based negative electrode active material is used, for example, PI has been considered to be preferable from the viewpoint of suppressing the volume change of the active material due to charge and discharge and improving the cycle life characteristics of the battery. However, in the present invention, since the change in volume can be suppressed by the skeleton-forming agent, all of the above-mentioned commonly used compounds can be used.

  When the total of the active material, the binder, and the conductive additive contained in the negative electrode is 100% by mass, the binder preferably contains 0.1 to 60% by mass, and more preferably 0.5 to 30% by mass. .

  When the binder is less than 0.1% by mass, the mechanical strength of the electrode is low, so that the active material is likely to fall off when forming the skeleton, and the cycle life characteristics of the battery may be deteriorated. On the other hand, when it exceeds 60% by mass, the ion conductivity is low, the electric resistance is high, and the ratio of the active material as a battery is small, so that the electrode capacity density tends to be low.

  The current collector used for the negative electrode is not particularly limited as long as it has electronic conductivity and can conduct electricity to the held negative electrode active material. For example, conductive materials such as C, Ti, Cr, Ni, Cu, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Al, and Au, and alloys containing two or more of these conductive materials ( For example, stainless steel) may be used. When a material other than the above-mentioned conductive material is used, for example, a multilayer structure of a dissimilar metal such as iron coated with Cu or Ni may be used.

  From the viewpoint of high electrical conductivity and good stability in the electrolyte, the current collector is preferably C, Ti, Cr, Au, Fe, Cu, Ni, stainless steel, or the like. From the viewpoint, C, Cu, Ni, stainless steel and the like are preferable. When iron is used as the current collecting base material, it is preferable that the current collecting base material be coated with Ni or Cu in order to prevent oxidation of the surface of the current collecting base material. In addition, since the conventional alloy-based negative electrode has a large change in the volume of the negative electrode material due to charge and discharge, it has been considered that the current collecting base material is preferably stainless steel or iron. Can be alleviated, so that all the above-mentioned commonly used ones can be used.

  The current collector has a linear, rod, plate, foil, or porous shape.The porous material has a high packing density, and the skeleton-forming agent easily penetrates the active material layer. It may be. Examples of the porous shape include a mesh, a woven fabric, a nonwoven fabric, an embossed body, a punched body, an expanded body, a foamed body, and the like. The body is preferred.

  Next, regarding the positive electrode, the active material used for the positive electrode is not particularly limited as long as it is a positive electrode active material used in a nonaqueous electrolyte secondary battery. Known electrodes including alkali metal transition metal oxides, vanadiums, sulfurs, solid solutions (lithium excess, sodium excess, potassium excess), carbons, organic materials and the like are used.

The alkali metal transition metal oxides include, for example, LiCoO ₂ , Li _0.9 Na _0.1 CoO ₂ , LiNiO ₂ , LiNi _0.5 Co _0.5 O ₂ , LiNi _0.33 Mn _0.33 Co _0.33 O ₂ , LiNi _0.5 Mn _0.2 Co _0.3 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , Li (Ni, Co, Al) O ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFe _0.5 Mn _0.5 PO ₄ , LiMnPO ₄ , Li ₂ MnSiO ₄ , Li ₂ FeSiO ₄ , Li ₂ (Mn, Fe) SiO ₄ , Li ₂ CoSiO ₄ , Li ₂ MgSiO ₄ , Li ₂ CaSiO ₄ , Li ₂ ZnSiO ₄ , LiNb ₂ O ₅ , LiNbO ₂ , LiFeO _{2 , LiMgO 2, LiCaO 2, LiTiO} 2, LiTiS 2, LiCrO 2, LiRuO 2, LiCuO 2, LiZ _{O 2, LiMoO 2, LiMoS 2} , LiTaO 2, LiWO 2, NaCoO 2, NaNiO 2, NaNi 0.33 Mn 0.33 Co 0.33 O 2, NaMnO 2, NaMn 2 O 4, NaFePO 4, NaFe 0.5 Mn 0.5 PO 4, NaMnPO 4 _{, Na 2 MnSiO 4, Na 2} FeSiO 4, Na 2 (Mn, Fe) SiO 4, Na 2 CoSiO 4, Na 2 MgSiO 4, Na 2 CaSiO 4, Na 2 ZnSiO 4, NaNb 2 O 5, NaNbO 2, NaFeO _{2, NaMgO 2, NaCaO 2,} NaTiO 2, NaTiS 2, NaCrO 2, NaRuO 2, NaCuO 2, NaZnO 2, NaMoO 2, NaMoS 2, NaTaO 2, NaWO 2, KCoO 2, KNiO 2, kNi 0.33 Mn 0.33 Co 0.33 _{O 2, KMnO 2, KMn 2} O 4, KFePO 4 _{KFe 0.5 Mn 0.5 PO 4, KMnPO} 4, K 2 MnSiO 4, K 2 FeSiO 4, K 2 (Mn, Fe) SiO 4, K 2 CoSiO 4, K 2 MgSiO 4, K 2 CaSiO 4, K 2 ZnSiO 4, KNb ₂ O ₅ , KNbO ₂ , KFeO ₂ , KMgO ₂ , KCaO ₂ , KTiO ₂ , KTiS ₂ , KCrO ₂ , KRuO ₂ , KCuO ₂ , KZnO ₂ , KMoO ₂ , KMoS ₂ , KTaO ₂ , KWO _2, etc. .

The vanadium-based materials include, for example, LiV ₂ O ₅ , LiVO ₂ , Li ₃ VO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , NaV ₂ O ₅ , NaVO ₂ , Na ₃ VO ₄ , Na ₃ V ₂ (PO ₄ ) ₃ , KV ₂ O ₅ , KVO ₂ , K ₃ VO ₄ , K ₃ V ₂ (PO ₄ ) _{3 and the} like. Examples of the sulfur type include sulfur, carbon sulfide, polysulfide, carbon polysulfide, sulfur-modified polyacrylonitrile, disulfide compounds, sulfur-modified rubber, sulfur-modified pitch, sulfur-modified anthracene, and metal sulfide. The solid solution system, for _{example, Li 2 MnO 3 -LiNiO 2,} Li 2 MnO 3 -LiMnO 2, Li 2 MnO 3 -LiCoO 2, Li 2 MnO 3 -Li (Ni, Mn) O 2, Li 2 MnO 3 - _{Li (Ni, Co) O 2} , Li 2 MnO 3 -Li (Mn, Co) O 2, Li 2 MnO 3 -Li (Ni, Mn, Co) O 2, Na 2 MnO 3 -NaNiO 2, Na 2 MnO _{3 -NaMnO 2, Na 2 MnO 3} -NaCoO 2, Na 2 MnO 3 -Na (Ni, Mn) O 2, Na 2 MnO 3 -Na (Ni, Co) O 2, Na 2 MnO 3 -Na (Mn, _{Co) O 2, Na 2 MnO} 3 -Na (Ni, Mn, Co) O 2, K 2 MnO 3 -KNiO 2, K 2 MnO 3 -KMnO 2, K 2 MnO 3 -KCoO 2, K 2 MnO 3 - _{K (Ni, Mn) O 2} , K 2 MnO 3 -K ( _{i, Co) O 2, K} 2 MnO 3 -K (Mn, Co) O 2, K 2 MnO 3 -K (Ni, Mn, Co) O 2, include like.

  Examples of the carbon-based material include graphite, soft carbon, hard carbon, and glassy carbon. Organic compounds include rubeanic acid, tetracyanoquinodimethane, triquinoxalinylene, phenazine dioxide, trioxotriangulene, indigo carmine, nitronyl nitroxide radical compound, radialene compound, aliphatic cyclic nitroxyl radicals, And benzoquinones.

One of the above-described positive electrode active materials may be used alone, or two or more may be used in combination. However, from the viewpoint of energy density, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFe _0.5 Mn _{0.5 PO 4, LiMnPO 4, LiNi 0.33} Mn 0.33 Co 0.33 O 2, LiNi 0.5 Mn 0.2 Co 0.3 O 2 ,, LiNi 0.6 Mn 0.2 Co 0.2 O 2 ,, LiNi 0.8 Mn 0.1 Co 0.1 O 2, Li (Ni, Co, Al) O ₂ , a solid solution system, a vanadium system, and a sulfur system are preferable. The shape of the active material particles is not particularly limited, and may be spherical, elliptical, faceted, strip-shaped, fiber-shaped, flake-shaped, donut-shaped, or hollow.

On the other hand, as in the case of the negative electrode, the skeleton forming agent of the present invention may be used as a binder for granulating the positive electrode active material described above. In that case, the primary particles of the active material preferably have a median diameter (D ₅₀ ) in the range of 0.01 μm to 10 μm, and the granulated active material particles (secondary particles) have a median diameter (D ₅₀ ). It is preferable to be within the range of 1 μm to 100 μm. The granulation method of the active material is substantially the same as the granulation method of the negative electrode active material, and a known granulation method can be applied.

  The conductive auxiliary agent is not particularly limited as long as it has electron conductivity, and examples thereof include a metal, a carbon material, a conductive polymer, and a conductive glass. In light of the above, a carbon material is preferable. Specifically, acetylene black (AB), Ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, roller black, disk black, carbon black (CB), carbon fiber (for example, registered Vapor-grown carbon fibers named VGCF, a trademark), carbon nanotubes (CNT), carbon nanohorns, graphite, graphene, glassy carbon, amorphous carbon, and the like. One or more of these may be used.

  When the total of the active material, the binder, and the conductive additive contained in the positive electrode is 100% by mass, the conductive additive is preferably contained in an amount of 0 to 20% by mass. That is, the conductive assistant is contained as needed. If it exceeds 20% by mass, the ratio of the active material in the battery is small, so that the electrode capacity density tends to be low.

  As the binder for the positive electrode, those commonly used, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, polyacryl, styrene butadiene rubber (SBR), ethylene -Vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethylcellulose (CMC), chitansan gum, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), ethylene vinyl alcohol, polyethylene ( PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethyl acrylate, polyacrylic acid Chill, polyacrylic amine, polyacrylate, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine resin, phenol resin , Latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-propenoic acid, cyanoacrylic acid , Methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate, polyacetal, alginic acid, den Emissions, sucrose, to sell, glue, casein, may also be an organic material such as cellulose nanofibers alone or in combination of two or more thereof. Further, a mixture of the organic binder and the inorganic binder may be used.

  The inorganic binder may be, for example, a silicate type, a phosphate type, a sol type, a cement type, or the like. However, when a positive electrode is manufactured using only an inorganic binder, the specific gravity of the inorganic binder is large, and thus the electrode energy density per weight tends to be low.

  Conventionally, when a sulfur-based, vanadium-based, or solid-solution-based positive electrode active material is used as the positive electrode binder, high binding is required from the viewpoint of suppressing the volume change of the active material due to charge and discharge and improving the cycle life characteristics of the battery. Although a binder having an acidic property is considered to be preferable, in the present invention, since it is possible to suppress a change in volume with a skeleton-forming agent, all the above-mentioned commonly used substances can be used.

  Assuming that the total of the active material, the binder, and the conductive additive contained in the positive electrode is 100% by mass, the binder preferably contains 0.1 to 60% by mass. When the binder is less than 0.1% by mass, the mechanical strength of the electrode is low, so that the active material is likely to fall off when forming the skeleton, and the cycle life characteristics of the battery may be deteriorated. On the other hand, when it exceeds 60% by mass, the ion conductivity is low, the electric resistance is high, and the ratio of the active material as a battery is small, so that the electrode capacity density tends to be low.

  The current collector used for the positive electrode is not particularly limited as long as it has electron conductivity and can conduct electricity to the held positive electrode active material. For example, conductive materials such as C, Ti, Cr, Ni, Cu, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Al, and alloys containing two or more of these conductive materials ( For example, stainless steel) may be used. When a material other than the above-described conductive material is used, for example, a multilayer structure of a different metal such as iron coated with Al may be used. From the viewpoint of high electric conductivity and good stability in the electrolytic solution, the current collector is preferably C, Ti, Cr, Au, Al, stainless steel, or the like. Further, from the viewpoint of oxidation resistance and material cost, C, Al, stainless steel, etc. are preferred. More preferably, carbon-coated Al and carbon-coated stainless steel are preferable.

  The current collector has a linear, rod, plate, foil, or porous shape.The porous material has a high packing density, and the skeleton-forming agent easily penetrates the active material layer. It may be. Porous, mesh, woven fabric, non-woven fabric, embossed body, punched body, expanded, or foam, etc., among them, the shape of the current-collecting base material, embossed body because of good output characteristics, or Foams are preferred.

  Further, this electrode is an electrode for a non-aqueous electrolyte secondary battery, and is a skeleton forming agent used for forming a skeleton of an active material layer in an electrode of the non-aqueous electrolyte secondary battery. A skeleton forming agent containing a phosphate having a phosphate or a phosphate bond, an active material capable of alloying with an alkali metal or an active material capable of occluding an alkali metal ion, and a binder, The skeleton forming agent is present at least on the surface of the active material layer. According to this configuration, by applying a skeleton forming agent to the electrode, the skeleton forming agent permeates the active material layer, and forms a strong skeleton in the active material layer. Thereby, the volume change of the electrode is reduced, and the insulating property of the electrode surface is improved.

  In this electrode, the skeleton forming agent exists in the active material layer, and a gap exists between the active materials in the active material layer. According to this configuration, by applying the skeleton forming agent to the electrode, etc., the skeleton forming agent permeates the active material layer, so that the gap between the active materials in the active material layer is not completely filled with the skeleton forming agent, Gaps between the active materials remain. This allows expansion and contraction of the active material during charge and discharge, and suppresses the occurrence of wrinkles and cracks in the current collector of the electrode.

  This electrode has a layer containing the alkali-resistant inorganic particles on the surface of the layer of the silicate-based skeleton-forming agent. According to this configuration, by providing the layer of inorganic particles, a strong skeleton can be formed, and peeling and cracking during drying can be suppressed. In addition, the layer of inorganic particles replaces the separator, so that the battery can be configured without using a separate separator. When the skeleton-forming agent is a phosphate-based agent, the layer is a layer containing acid-resistant inorganic particles.

Preferably, in this electrode, the skeleton-forming agent per unit area of the electrode coated on one side is 0.01 mg / cm ² or more and 3 mg / cm ² or less, or the unit area of the electrode coated on both sides is used. the skeleton-forming agent per are, at 0.02 mg / cm ² or more 6 mg / cm ² or less. More preferably, the skeleton forming agent per unit area of the electrode coated on one side is 0.05 mg / cm ² or more and 3 mg / cm ² or less, or the skeleton forming agent per unit area of the electrode coated on both sides is used. The skeletal forming agent is at least 0.1 mg / cm ^{2 and at most} 6 mg / cm ² .

  The electrode includes an active material capable of alloying with an alkali metal or an active material capable of absorbing alkali metal ions, an organic binder, and the skeleton forming agent.

  Preferably, in this electrode, when the total solid content of the active material, the conductive auxiliary agent, the binder, and the skeleton-forming agent is 100% by mass, the skeleton-forming agent is preferably from 0.1% by mass to 30% by mass, and more preferably. Is from 0.2% by mass to 20% by mass, more preferably from 0.5% by mass to 10% by mass.

  Further, as a separator for a non-aqueous electrolyte secondary battery, a configuration in which the skeleton forming agent is present at least on the surface may be employed.

  According to this configuration, the separator has high strength, excellent heat resistance, and improved cycle life characteristics. Here, a separator generally used for a non-aqueous electrolyte secondary battery can be used. The material of the separator is not particularly limited. The separator may be coated or filled with a ceramic layer so as not to melt down due to local heat generation during a short circuit. The shape of the separator includes a microporous membrane, a woven fabric, a nonwoven fabric, and a compact, and the shape is not particularly limited.

  By applying the skeleton forming agent to the separator, it is possible to suppress the short circuit of the battery due to the meltdown of the separator substrate due to local heat generation at the time of short circuit. In addition, when the battery is charged, oxidation of the separator on the positive electrode side can be suppressed, so that self-discharge of the battery is suppressed. In addition, since the heat resistance of the separator is improved, the safety of nail penetration and overcharge is improved.

  Further, the silicate-based skeleton forming agent may contain inorganic particles such as ceramics having alkali resistance. In this case, the particle size of the ceramic is preferably in the range of 0.2 to 20 μm, and more preferably in the range of 0.25 to 10 μm. However, phosphate-based materials may contain inorganic particles such as acid-resistant ceramics. In that case, it is the same as the silicate type.

  Alternatively, a separator in which a skeleton forming agent is applied to and filled in a ceramic layer of an existing ceramic coat separator to improve heat resistance may be used.

  The porosity of the separator is preferably 30% or more, and more preferably 40% or more and 90% or less from the viewpoint of alkali metal ion conductivity and dendrite resistance. The air permeability obtained by the Gurley test method is preferably 3000 seconds / 100 cc or less. Here, the porosity was calculated from the apparent density of the separator and the true density of the solids of the constituent materials by the formula: porosity (%) = 100− (apparent density of separator / true density of material solids) × 100. Value. The Gurley air permeability is the air resistance measured by the Gurley tester method specified in JIS P8117.

Preferably, the skeleton forming agent per unit area of the separator coated on one side is 0.01 mg / cm ² or more and 3 mg / cm ² or less, or the unit area of the separator coated on both sides is preferable. the skeleton-forming agent per are, at 0.02 mg / cm ² or more 6 mg / cm ² or less.

  Further, as a method of manufacturing an electrode, a method of manufacturing an electrode of a non-aqueous electrolyte secondary battery, a skeleton forming agent containing a silicate having a siloxane bond in the component, or a skeleton forming agent containing a phosphate, A step A of attaching the electrode to the surface of the active material layer and a step B of drying the electrode may be provided. According to this configuration, by using the skeleton-forming agent in the production of the electrode, an electrode having excellent heat resistance, high strength, and improved cycle life characteristics can be produced.

  In the method for manufacturing an electrode, in the step A, the skeleton forming agent permeates from the surface of the active material layer to the inside.

  In the method for manufacturing an electrode, the step A is a step of impregnating the electrode in a tank containing the skeleton forming agent.

  Preferably, in the method for producing an electrode, the solid content concentration of the silicate or the phosphate in the skeleton forming agent is 0.1 to 30 parts by mass, and the step B is performed at a temperature of 60 ° C. or more. This is the step of heat treatment. If the drying is performed at a temperature lower than 60 ° C., the bonding strength between the electrode and the separator is low, and the moisture cannot be sufficiently removed, so that it is difficult to obtain a stable life characteristic when the battery is assembled.

  Here, the manufacturing method of the electrode is, for example, an active material, a binder, and a conductive auxiliary agent added as necessary, and a slurry is applied to the current collector, and then temporarily dried, The electrode is obtained by filling the active material layer with water in which the skeleton forming agent is dissolved, and performing heat treatment at 60 ° C. or higher. That is, the electrode obtained by the slurry coating method is filled with the skeleton forming agent in the active material layer and heat-treated to obtain the electrode. The temporary drying is not particularly limited as long as the solvent in the slurry can be volatilized and removed. For example, a method of performing heat treatment in a temperature atmosphere of 50 to 200 ° C. in the air can be used.

  In addition, this heat treatment is preferably performed at a temperature of at least 80 ° C., more preferably at least 100 ° C., and preferably at least 110 ° C., since the heat treatment time can be shortened at a high temperature and the strength of the skeleton forming agent is improved. ° C or higher. The upper limit temperature of the heat treatment is not particularly limited as long as the current collector does not melt. For example, the temperature may be increased to about 1000 ° C., which is the melting point of copper. In the case of a conventional electrode, the upper limit temperature was estimated to be much lower than 1000 ° C. because the electrode binder was carbonized and the current collector was sometimes softened. Since the agent exhibits excellent heat resistance and is stronger than the strength of the current collector, the upper limit of the temperature is 1000 ° C.

  Further, the heat treatment can be performed by maintaining the time for 0.5 to 100 hours. The atmosphere for the heat treatment may be in the air, but it is preferable to perform the treatment in a non-oxidizing atmosphere in order to prevent oxidation of the current collector. The non-oxidizing atmosphere means an environment in which the amount of oxygen gas is smaller than in air. For example, a reduced pressure environment, a vacuum environment, a hydrogen gas atmosphere, a nitrogen gas atmosphere, a rare gas atmosphere, or the like may be used.

  In the case of an electrode using a material having an irreversible capacity, it is preferable that the irreversible capacity be canceled by lithium doping. The method of lithium doping is not particularly limited. For example, (i) metal lithium is attached to a portion of the electrode current collector where no active material layer is provided, and a liquid is injected to form a local cell. A method of doping lithium into the active material layer; (ii) a method of applying metallic lithium on the active material layer on the electrode current collector and injecting and forcibly short-circuiting the active material layer to dope the active material layer with lithium; (iii) A) a method in which metallic lithium is deposited on the active material layer by vapor deposition or sputtering, and lithium is doped into the electrode active material by a solid-phase reaction. Examples include a method of doping lithium, and a method of (v) adding lithium metal to an active material powder and mixing the active material powder to dope lithium into the active material.

  In addition, as a method for manufacturing an electrode, for example, an active material or an active material precursor is formed by forming an active material layer on a current collector by using a chemical plating method, a sputtering method, an evaporation method, a gas deposition method, or the like. Although a method of integration may be used, a slurry coating method is preferred from the viewpoint of the lyophilicity of the skeleton forming agent and the electrode manufacturing cost.

  Further, by using this electrode for a battery, a battery having excellent cycle life characteristics and good safety can be obtained.

  For example, in the case of a battery using the above-mentioned electrode (positive electrode or negative electrode), a battery structure in which the positive electrode and the negative electrode are joined via a separator and sealed in a state of being immersed in an electrolytic solution can be considered. The structure of the battery is not limited to this, and can be applied to existing battery forms and structures such as a stacked battery and a wound battery.

  The electrolyte used in this battery may be any liquid or solid capable of moving alkali metal ions from the positive electrode to the negative electrode or from the negative electrode to the positive electrode, and may be the same as the electrolyte used in known nonaqueous electrolyte secondary batteries. Can be used. For example, there are an electrolyte, a gel electrolyte, a solid electrolyte, an ionic liquid, and a molten salt. Here, the electrolyte refers to a solution in which the electrolyte is dissolved in a solvent.

As the electrolyte, since it is necessary to contain an alkali metal ion, the electrolyte salt is not particularly limited as long as it is used in a non-aqueous electrolyte secondary battery, such as a lithium salt, a sodium salt, and a potassium salt. Alkali metal salts are preferred. Examples of the alkali metal salt include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₄ ), and lithium bistrioxide. trifluoromethanesulfonyl imide _{(LiN (SO 2 CF 3)} 2), lithium bis pentafluoroethane imide _{(LiN (SO 2 C 2 F} 5) 2), lithium bis (oxalato) borate (LiBC ₄ O ₈₎ ,, hexafluoro Sodium phosphate, sodium perchlorate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate and sodium trifluoromethanesulfonimide, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate It is possible to use at least one or more selected from the group consisting of trifluoromethane sulfonic acid and potassium trifluoromethanesulfonate imide potassium.

Examples of the solvent for the electrolyte include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (GBL), and methyl-γ-. Butyrolactone, methyl lactone, 2-methyltetrahydrofuran, 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, furan, dimethyl Furan, tetrahydrofuran (T
HF), methyltetrahydrofuran (MeTHF), tetrahydroplan (THP), dioxane (DIOX), crown ether, dimethoxymethane (DMM), dimethoxyethane (DME), diglyme, triglyme, tetraglyme, methyl acetate (MA), Ethyl acetate (EA), propyl acetate, isopropyl acetate, butyl acetate, methyl fluoroacetate, ethyl trifluoroacetate, methyl propionate, ethyl propionate, propyl propionate, methyl formate, ethyl formate, propyl formate, ethyl butyrate, propyl butyrate , Methyl propylate, vinyl acetate, methyl cyanoacetate, γ-valerolactone, σ-valerolactone, ε-caprolactone, γ-hexalactone, γ-undecalactone, trimethyl phosphate (TMP), phosphorus Triethyl (TEP), tri-n-propyl phosphate, trioctyl phosphate, triphenyl phosphate, N, N-dimethylformamide (DMF), ethylenediamine, pyridine, N-methylimidazole, dimethyl sulfate, dimethyl sulfate, diphenyl Propyl sulfite, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, diphenyl sulfone, sulfolane, methyl sulfolane, methyl methane sulfonate, methyl benzene sulfonate, methyl trifluoromethane sulfonate, propane sulfone, butane sulfone, dimethyl sulfoxide, diphenyl disulfide , Dimethyl sulfide, diethyl sulfide, acetonitrile, propanenitrile, adiponitrile, valeronitrile, glutanitrile, malo Nonitrile, succinonitrile, pimeronitrile, suberonitrile, isobutyronitrile, biphenyl, succinic anhydride, t-butylbenzene, naphthalene, cyclohexylbenzene, benzotriazole, thiophene, toluene, methyl ethyl ketone, benzene, fluorobenzene, hexafluorobenzene, nitromethane , N, N-dimethylformamide, dimethyl sulfoxide, vinylene carbonate (VC), vinyl ethylene carbonate (EVC), fluoroethylene carbonate (FEC), and ethylene sulfite (ES). Can be.

  Ionic liquids and molten salts are classified into pyridines, alicyclic amines, and aliphatic amines, depending on the type of cation (cation). By selecting the type of anion (anion) to be combined with this, various ionic liquids or molten salts can be synthesized. Examples of the cation include ammonium ions such as imidazolium salts and pyridinium salts, phosphonium ions, and inorganic ions. Examples of anions include halogen ions such as bromide ions and triflate, boron ions such as tetraphenylborate, and hexafluoro ions. Phosphorus such as phosphate.

Ionic liquids and molten salts include, for example, cations such as imidazolinium, and Br ⁻ , Cl ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ , and FeCl _4. ^- in combination with anions such as it can be obtained by known synthetic methods, such as to configure. An ionic liquid or a molten salt can function as an electrolyte without adding an electrolyte.

  Further, an electric device including a battery using the electrode may be used.

  Examples of electrical equipment include irons, whisks, integrated personal computers, clothes dryers, medical equipment, intercoms, wearable terminals, video equipment, air conditioners, air circulators, horticultural machinery, motorcycles, ovens, music players, music recorders , Hot air heaters, toys, car components, flashlights, loudspeakers, car navigation systems, cassette stoves, home storage batteries, nursing care equipment, humidifiers, dryers, refuelers, water supplies, suction machines, safes, glue guns, mobile phones, Portable information devices, air purifiers, air conditioning clothes, game machines, fluorescent lights, pill removers, cordless phones, coffee makers, coffee warmers, ice scrapers, kotatsu, copiers, haircuts, shavers, lawn mowers, automobiles, Lighting equipment, dehumidifier, sealer, shredder, automatic external defibrillator, rice cooker, stereo, strike , Speaker, trouser press, smartphone, rice mill, washing machine, toilet seat with washing function, sensor, fan, submarine, blower, vacuum cleaner, tablet, body fat scale, fishing gear, digital camera, television, television receiver, television Games, displays, disc changers, desktop personal computers, railways, televisions, electric carpets, desk lamps, electric stoves, electric pots, electric blankets, calculators, electric carts, electric wheelchairs, electric tools, electric vehicles, electric brushes, electric toothbrushes, Telephone, electric bicycle, electric shock insect, electromagnetic cooker, electronic organizer, electronic musical instrument, electronic lock, electronic card, microwave oven, electronic mosquito catcher, electronic cigarette, telephone, toaster, dryer, transceiver, clock, drone, garbage disposal , Laptop, incandescent bulb, soldering iron, panel heater Heaters, halogen heaters, fermenters, baking machines, hybrid vehicles, personal computers, personal computer peripherals, clippers, panel heaters, video cameras, VCRs, airplanes, emergency lights, emergency storage batteries, ships, beauty equipment, printers, copiers , Crusher, sprayer, facsimile, forklift, plug-in hybrid vehicle, projector, hair dryer, hair iron, headphones, disaster prevention equipment, security equipment, home theater, hot sand maker, hot plate, pump, fragrance machine, massage machine, mixer, mill , Movie player, monitor, mochi, water heater, floor heating panel, radio, radio cassette, lantern, radio control, laminator, remote control, range, water cooler, refrigerator, cooler, cool fan, cooling device, robot, work Professional, GPS, and the like.

  When the skeleton forming agent according to the present invention is used for an electrode, unlike the case where the skeleton forming agent is used as a binder, generation of wrinkles and cracks can be suppressed. Further, better life characteristics than in the past can be obtained. Further, even when the electron conductivity of the active material layer is high, heat generation due to an internal short circuit can be reduced.

It is a figure showing the section of the electrode which applied the skeleton formation agent concerning one embodiment of the present invention. It is a figure showing an example of application of a skeleton former concerning one embodiment of the present invention. It is a figure showing an example of a manufacturing process of an electrode concerning one embodiment of the present invention. FIG. 3 is a diagram showing cycle life characteristics of an electrode according to one embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between a skeletal density and a discharge capacity of an electrode according to an embodiment of the present invention. FIG. 3 is a diagram showing cycle life characteristics of an electrode according to one embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between a skeletal density and a discharge capacity of an electrode according to an embodiment of the present invention. FIG. 3 is a diagram showing cycle life characteristics of an electrode according to one embodiment of the present invention. FIG. 3 is a view showing cycle life characteristics of an electrode to which a skeleton forming agent containing a surfactant according to one embodiment of the present invention is applied. FIG. 4 is a diagram comparing cycle life characteristics of an electrode coated with a skeleton-forming agent according to an embodiment of the present invention and an electrode not coated with the skeleton forming agent. FIG. 4 is a diagram comparing cycle life characteristics of an electrode coated with a skeleton-forming agent according to an embodiment of the present invention and an electrode not coated with the skeleton forming agent. It is a figure showing the section of the electrode which applied the skeleton former containing inorganic particles concerning one embodiment of the present invention. FIG. 4 is a diagram showing an initial charge / discharge curve of a battery without using a separator according to one embodiment of the present invention. FIG. 2 is a diagram showing an SEM image of a Si granule to which a skeleton forming agent according to one embodiment of the present invention has been applied. It is a figure showing the charge and discharge curve in each rate concerning one embodiment of the present invention. It is a figure showing the result of the exfoliation test which compared the electrode which applied the skeleton formation agent concerning one embodiment of the present invention, and the electrode which was not applied. Silicate (Na ₂ O · nSiO ₂₎ shows an X-ray diffraction (XRD) patterns of the powder. It is a diagram showing the cycle life characteristics and after 200 cycles of the electrodes of the electrode of reference example containing an alkali metal silicate _{(Li 0.05 Na 1.95 O · 2.8SiO} 2) as a binder. It is a copy of the photograph which shows the current collector in the conventional Si negative electrode. It is a figure which shows the glow discharge optical emission spectroscopy analysis result which compared the electrode impregnated with the skeleton forming agent with the electrode which did not impregnate. It is a figure which shows a silicate type molecular formula and a phosphate type molecular formula.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment. Particularly, in the present embodiment, an electrode of a lithium secondary battery (lithium ion battery) will be described as an example, but the present invention is not limited to this. In addition, as an example of the skeleton forming agent, an alkali metal silicate aqueous solution containing Na ₂ O.3SiO ₂ will be described as an example, but is not limited thereto.

-First Embodiment-
[1. Electrode manufacturing method]
First, as an example of the present embodiment, a method for manufacturing an electrode of a lithium secondary battery will be described. Note that the electrodes include a negative electrode and a positive electrode, and the negative electrode and the positive electrode have the same manufacturing method except that the current collector and the active material are different. Therefore, the method for manufacturing the negative electrode will be described, and the method for manufacturing the positive electrode will be appropriately omitted.

  The negative electrode is manufactured by applying an electrode material to a copper foil. First, a rolled copper foil having a thickness of, for example, 10 μm is manufactured, and a copper foil wound in a roll shape in advance is prepared. The electrode material of the negative electrode is prepared by baking a carbon precursor and graphitizing artificial graphite and mixing it with a binder, a conductive additive, and the like to form a paste. In the present embodiment, as an example, PVdF is used as a binder, and acetylene black (AB) is used as a conductive additive. Then, an electrode material is applied to the surface of the copper foil, dried, and then subjected to a pressure regulation process to complete a negative electrode body.

  The positive electrode is manufactured by applying an electrode material to an aluminum foil. In addition, as the electrode material of the positive electrode, a lithium-transition metal oxide is mixed with a binder, a conductive additive, or the like to form a paste. In the present embodiment, as an example, PVdF is used as a binder and AB is used as a conductive additive. Hereinafter, the positive electrode body and the negative electrode body may be collectively referred to as an electrode body, the copper foil and the aluminum foil may be collectively referred to as a current collector, and the electrode material applied to the current collector may be referred to as an active material layer.

On the other hand, in the present embodiment, a skeleton forming agent used for the electrode body is prepared in advance. The skeleton-forming agent is produced by purifying Na ₂ O · 3SiO ₂ , which is an alkali metal silicate having a siloxane bond, by a dry or wet method, and adjusting the water to prepare the skeleton-forming agent. For example, the following equation 4 is used for the dry type, and the following equation 5 is used for the wet type. At this time, a surfactant is mixed. As an example of the skeleton forming agent of the present embodiment, the solid content concentration of Na ₂ O · 3SiO _{2 in} the skeleton forming agent is 5% by mass, and the surfactant is 0.04% by mass.
Na ₂ CO ₃ + 3SiO ₂ → Na ₂ O · 3SiO ₂ + CO ₂ ↑ (Formula 4)
2NaOH + 3SiO ₂ → Na ₂ O · 3SiO ₂ + H ₂ O (Equation 5)

  Then, a skeleton-forming agent is applied to the surface of each electrode body to coat the active material layer. The method of applying the skeleton forming agent includes a method of impregnating the electrode body in a tank storing the skeleton forming agent, a method of dropping or applying the skeleton forming agent on the surface of the electrode body, spray coating, screen printing, a curtain method, a spin method. Coating, gravure coating, die coating and the like are performed. The skeleton-forming agent applied to the surface of the electrode body penetrates into the active material layer and enters a gap between the active material and the conductive assistant. Then, the electrode body is dried by hot air at 110 ° C. to 160 ° C., heating, or the like to cure the skeleton forming agent. Thereby, the skeleton forming agent forms the skeleton of the active material layer.

  Finally, each electrode body, that is, the negative electrode body and the positive electrode body are cut into desired sizes, respectively, to complete the skeleton-formed electrodes.

  Further, the above-described electrode manufacturing method can be realized by a manufacturing apparatus. The current collector wound in a roll is sent out, the current collector is coated with an electrode material in an active material layer coating device, the electrode material is dried in a first drying device with warm air, and a skeleton forming agent is formed. The skeleton-forming agent is applied to the surface of the electrode body in the coating device, the skeleton-forming agent is dried and cured by warm air in the second drying device, and is wound up again in a roll. Finally, the electrode wound into a roll is cut into a desired size.

  According to the above-described electrode manufacturing method, an electrode having high strength, excellent heat resistance, and improved cycle life characteristics can be continuously manufactured. In addition, by using a silicate having a siloxane bond as a binder and not as a skeleton forming agent, the copper foil does not generate wrinkles or cracks, and the active material layer cracks and warps, and expansion due to generated gas also occurs. Instead, it can be used as an electrode.

  Further, the positive electrode and the negative electrode obtained as described above are joined to each other with a separator interposed therebetween, and sealed in a state of being immersed in the electrolytic solution to obtain a lithium secondary battery. According to the lithium secondary battery having this structure, it can function as a lithium secondary battery having good safety. The structure of the lithium secondary battery is not particularly limited, and can be applied to existing battery forms and structures such as a stacked battery and a wound battery.

[2. Configuration of Electrodes]
The negative electrode for a non-aqueous electrolyte secondary battery manufactured by the above manufacturing process includes a current collector made of a copper foil, and an active material layer including an active material, a conductive additive, and a binder on the surface thereof. Further, the surface of the active material layer is coated with the cured skeleton forming agent, and the cured skeleton forming agent also exists inside the active material layer. The skeleton forming agent inside the active material layer is present in these gaps so as to cover the active material, the conductive additive, and the binder. The density of the skeleton-forming agent of the active material layer is 0.7 mg / cm ² as an example, it is preferable in the range of 0.1mg~3mg / cm ^2.

Further, the positive electrode includes a current collector made of an aluminum foil, and an active material layer including an active material, a conductive additive, and a binder on the surface thereof. Further, the surface of the active material layer is coated with the cured skeleton forming agent, and the cured skeleton forming agent also exists inside the active material layer. The skeleton forming agent inside the active material layer is present in these gaps so as to cover the active material, the conductive additive, and the binder. The density of the skeleton-forming agent of the active material layer is 0.5 mg / cm ² as an example, it is preferable that the 0.1mg~3mg / cm ^2.

  The electrode of the present embodiment has high strength, excellent heat resistance, and improved cycle life characteristics. In addition, as shown in the results of a nail penetration test described later, nail penetration safety is also improved. In addition, since the skeleton forming agent is applied from the surface of the electrode by application or impregnation, the skeleton forming agent is present in the gap inside the active material layer so as to cover the active material, the conductive additive, and the binder. . That is, when the skeleton-forming agent is kneaded with the binder and used, the skeleton-forming agent exists in the active material layer with almost no gap, but in the electrode of the present embodiment, a certain gap exists in the active material layer. It will be. Thereby, expansion and contraction of the electrode is allowed, and generation of wrinkles and cracks of the current collector can be suppressed.

[3. Structure of skeleton forming agent]
As described above, the skeleton forming agent of the present embodiment has a solid content concentration of Na ₂ O · 3SiO ₂ , which is an alkali metal silicate having a siloxane bond, of 7.5% by mass and a surfactant of 0.09%. In mass%, the balance is water. Although a surfactant is not essential, lyophilicity to the active material layer is improved, and the skeleton forming agent uniformly penetrates the active material layer.

In addition, the skeleton forming agent of the present embodiment uses alkali metal sodium silicate Na ₂ O · 3SiO ₂ as a silicate, but is not limited thereto. Instead of Na, Li, K, triethanol ammonium And a tetramethanol ammonium group, a tetraethanol ammonium group, and a granidine group.

  The reason why Na is used is that Na has high strength and excellent cycle life characteristics. In addition, Na and Li can be used in combination, and the use of Li improves ionic conductivity. In this case, it is preferable to satisfy Li <Na. In this case, a skeleton forming agent that maintains a certain strength and has good ion conductivity is obtained. More specifically, when the total of Na and Li is 100 mol%, it is preferable that Na is within a range of 51 to 99% and Li is within a range of 1 to 49%. More preferably, it is in the range of 2 to 30%.

Further, the skeleton forming agent of the present embodiment has a coefficient of SiO ₂ of 3, but is not limited to this, and may be 0.5 to 5.0, preferably 2.0 to 4.5. More preferably, it is 2.2 or more and 3.8 or less.

  Further, the skeleton forming agent of the present embodiment can also be used for coating an existing electrode. In this case, an electrode having high strength, excellent heat resistance, and improved cycle life characteristics can be obtained.

  Further, the skeleton forming agent of the present embodiment can be used by coating on the surface of the separator. By doing so, a separator having high strength, excellent heat resistance, and improved cycle life characteristics can be obtained.

[4. Example]
Hereinafter, in the present embodiment, examples in which the solid content concentration and the skeleton density of the skeleton forming agent are variously changed, and their tests, results, and effects will be described.

<Study of n number and skeletal density in Na ₂ O · nSiO ₂ >
(Examples 1 to 18 and Comparative Example 1)
Using a Si—C granule as an electrode active material, under conditions of 0.2 C-rate, a cutoff potential of 0.01 V to 1.2 V (vs. Li ⁺ / Li), and 30 ° C., This is a test on cycle life characteristics when the solid content concentration of Na ₂ O · nSiO ₂ is changed from 0% by mass to 20% by mass and the value of n is changed to 2.0, 2.5, and 3.0. The Si—C granules (D ₅₀ = 9.8 μm) are composed of Si (D ₅₀ = 1.1 μm) and artificial graphite (D ₅₀ = 1 μm) (Si: artificial graphite = 29: 71% by mass) and granulated It was prepared by spray-drying a suspension composed of an auxiliary agent under the conditions of a liquid sending rate of 6 g / min, a spray pressure of 0.1 MPa, and a drying temperature of 80 to 180 ° C.

As the granulation assistant, polyvinyl alcohol (PVA, Poval 1400) was used. PVA is contained in an amount of 1% by mass with respect to 100% by mass of a solid content of Si, artificial graphite, and PVA. Note that the value of D ₅₀ indicates the median diameter by a laser diffraction-scattering particle size distribution measurement method.

The test electrode (1.4 mAh / cm ² ) was a slurry (solid content ratio: 85: 3: 1: 1 :) of Si—C granules, AB, vapor grown carbon fiber (VGCF), copper flake, and PVdF. (10% by mass) was applied to a copper foil, pressure-adjusted, immersed in an aqueous solution in which a predetermined skeleton-forming agent was dissolved, and then heat-treated at 160 ° C. As a counter electrode, a metal lithium foil was used. As the separator, a glass non-woven fabric (manufactured by Toyo Rokko Co., Ltd., GA-100) and a microporous polyethylene (PE) film (20 μm) were used. As the electrolyte, 1.0 M LiPF ₆ / (EC: DEC = 50: 50 vol%, +1 mass% of vinylene carbonate) was used.

Table 1 shows the solid content concentrations of the skeleton-forming agents of Examples 1 to 18 and Comparative Example 1 and the value of n of Na ₂ O · nSiO ₂ . The inorganic skeleton-forming agent was prepared by mixing a mixture of Na ₂ CO ₃ and SiO _{2 so as} to have a composition shown in Table 1 below, heating and melting the mixture to 1000 ° C. or higher, cooling, and then dissolving in water. Produced.

FIG. 4 is a graph showing cycle life characteristics of Examples 1 to 18 and Comparative Example 1. As is clear from FIG. 4, the negative electrode coated with the skeleton-forming agent (Examples 1 to 18) has significantly improved life characteristics as compared with the negative electrode not coated (Comparative Example 1). Among them, the solid content concentration of Na ₂ O.nSiO ₂ in the range of 2 to 10% by mass showed particularly excellent cycle life characteristics. As for the value of n in Na ₂ O · nSiO ₂ , 3.0 showed particularly excellent cycle life characteristics.

FIG. 5 is a graph showing the relationship between the density (skeleton density) of the skeleton forming bodies of Examples 1 to 18 and Comparative Example 1 and the discharge capacity at each cycle. As is clear from FIG. 5, in the electrode using the Si—C granules (Si: artificial graphite = 29: 71 mass%) as the active material, the skeleton density is 0.04 to 3.15 mg / cm ^2. It can be seen that a sufficient discharge capacity can be obtained in the case of. More preferably, the skeleton density is 0.1 to 2.5 mg / cm ² .

(Examples 19 to 36 and Comparative Example 2)
In Examples 19 to 36 and Comparative Example 2, as active materials, the composition of the Si—C granules was changed from Si: artificial graphite = 29: 71 mass% to 46:54 mass%, and the capacity density of the test electrode was changed. Was changed to 1.2 mAh / cm ^2, and the same as the previous tests (Examples 1 to 18 and Comparative Example 1). Table 2 shows the solid content concentrations of the skeleton forming agents of Examples 19 to 36 and Comparative Example 2, and the value of n of Na ₂ O · nSiO ₂ .

FIG. 6 is a graph showing cycle life characteristics of Examples 19 to 36 and Comparative Example 2. As is clear from FIG. 6, the negative electrode (Examples 19 to 36) coated with the skeleton-forming agent has significantly improved life characteristics as compared with the negative electrode not coated (Comparative Example 2). Among them, the solid content concentration of Na ₂ O.nSiO ₂ in the range of 2 to 10% by mass showed particularly excellent cycle life characteristics. As for the value of n in Na ₂ O · nSiO ₂ , 3.0 showed particularly excellent cycle life characteristics.

FIG. 7 is a graph showing the relationship between the density (skeleton density) of the skeleton forming bodies of Examples 19 to 36 and Comparative Example 2 and the discharge capacity at each cycle. As is clear from FIG. 7, in the electrode using the Si—C granules (Si: artificial graphite = 46: 54 mass%) as the active material, the skeletal density is 0.03 to 3.45 mg / cm ^2. It can be seen that a sufficient discharge capacity can be obtained in the case of. More preferably, the skeleton density is 0.1 to 2.5 mg / cm ² .

(Examples 37 to 40 and Comparative Example 3)
Examples 37-40, the active material is Si (D ₅₀ = 1.1μm), skeleton-forming agent is _{Li 0.05 Na 1.95 O · 3SiO 2} , the capacity density of the test electrodes to 3.0 mAh / cm ^2, charge-discharge test Is the same as in the previous tests (Examples 1 to 18 and Comparative Example 1) except that the conditions were 0.1 C-rate and a cutoff potential of 0.01 V to 1.4 V (vs. Li ⁺ / Li). . Table 3 shows the solid content concentrations of the skeleton-forming agents of Examples 37 to 40 and Comparative Example 3, and the skeleton density of the electrodes, respectively. The inorganic skeleton-forming agent was prepared by mixing a mixture of Li ₂ CO ₃ , Na ₂ CO ₃ , and SiO _{2 so as} to have a composition shown in Table 3, heating and melting at 1000 ° C. or higher, cooling, and then adding water. Was prepared by dissolving the same.

FIG. 8 is a graph showing cycle life characteristics of Examples 37 to 40 and Comparative Example 3. As is clear from FIG. 8, the negative electrode coated with the skeleton forming agent (Examples 37 to 40) has an initial discharge capacity exceeding 1800 mAh / g, but the negative electrode not coated (Comparative Example 3) The discharge capacity was 56.7 mAh / g. As can be seen by comparing the negative electrode coated with the skeleton-forming agent (Examples 37 to 40) and the negative electrode not coated (Comparative Example 3), a dramatic improvement in cycle life characteristics was shown. Among them, Li _0.05 Na _1.95 O.3SiO ₂ showed particularly excellent cycle life characteristics when the solid concentration was in the range of 0.5 to 2.5% by mass. It was found that in the electrode using Si as the active material, a discharge capacity exceeding 2000 mAh / g was obtained when the skeleton density was 0.12 to 0.90 mg / cm ² .

  Next, the batteries after charge and discharge (after 20 cycles) of Examples 37 to 40 and Comparative Example 3 were disassembled, and the test electrodes were observed. In Comparative Example 3, the active material layer was peeled off from the current collector. On the other hand, in Examples 37 to 40, the current collector did not peel off, and no wrinkles or cracks were found in the current collector. From this result, it was revealed that the electrode coated and filled with the skeleton-forming agent had improved adhesion between the active material layer and the current collector, and improved electrode performance.

<Examination of surfactant>
(Example 41 and Example 42)
In Example 41, an Si—C granule (Si: artificial graphite = 29: 71 mass%) was used as an electrode active material, and the solid content concentration of Na ₂ O · nSiO ₂ was 6 mass% as a skeleton forming agent. , N were adjusted to 2.5, and the skeleton density was adjusted to 0.84 mg / cm ² , and other conditions were the same as in Example 10.

  Example 42 is the same as Example 41 except that 0.05% by mass of a nonionic surfactant (registered trademark: Triton X-100) was added as a skeleton-forming agent.

  FIG. 9 is a graph comparing the cycle life characteristics of an electrode in which a surfactant was not added to the skeleton-forming agent (Example 41) and an electrode in which a surfactant was added to the skeleton-forming agent (Example 42). It is. As is apparent from FIG. 9, the cycle life characteristics are improved by adding the surfactant. This is because the surfactant improves the lyophilicity of the skeleton forming agent to the active material layer, and forms a uniform skeleton in the active material layer. In addition, the surfactant of the present embodiment uses a nonionic surfactant, but is not limited thereto, and may be an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a nonionic surfactant. .

<Safety for nail penetration>
(Example 43 and Comparative Example 4)
A test was conducted on the safety of the battery to which the negative electrode using the skeleton forming agent was applied. The test method is based on a nail piercing test in which a battery model is pierced with a nail and the state of smoke and ignition of the battery model is examined. For the test, a 1.1 Ah battery model in which a plurality of negative electrodes, separators, and positive electrodes were laminated on an aluminum laminate casing and an electrolyte was sealed was used. The positive electrode (4.2 mAh / cm ² ) was produced by applying a slurry composed of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , AB, and PVdF to an aluminum foil (20 μm), adjusting the pressure, and then performing a heat treatment at 160 ° C. The negative electrode (4.6 mAh / cm ² ) is produced by applying a slurry composed of artificial graphite (D ₅₀ = 20 μm), AB, and an acrylic binder to a copper foil (10 μm), adjusting the pressure, and then performing a heat treatment at 160 ° C. Was.

Example 43 was produced by immersing the negative electrode in an aqueous solution in which a skeleton forming agent was dissolved and then performing a heat treatment at 150 ° C., as shown in FIG. The skeleton forming agent is an aqueous solution comprising Na ₂ O · 3SiO ₂ and a nonionic surfactant (registered trademark: Triton X-100). The solid content concentration of Na ₂ O · 3SiO ₂ is 6% by mass, and the surfactant is used. Used had a solid content of 0.05% by mass. The skeletal density of the electrode is 0.9 mg / cm ² per side. In this test, since the positive electrode and the negative electrode were prepared by coating on both sides, the skeletal density on both sides is 1.8 mg / cm ² . A battery using the negative electrode to which the skeleton forming agent was not applied was referred to as Comparative Example 4.

The electrolyte used was 1 M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol%, and 1 mass% of vinylene carbonate. As the separator, a microporous polypropylene (PP) film (23 μm) was used. In the nail penetration test, the battery model was charged to 4.2 V at 0.1 C-rate, and then pierced into the center of the battery under a 25 ° C. environment at a speed of 1 mm / sec at a speed of 1 mm / sec. The battery voltage, nail temperature, and casing temperature were measured.

  In the conventional battery model using the negative electrode without the skeleton-forming agent (Comparative Example 4), when nailing was performed, the battery voltage was reduced to 0 V, and a large amount of smoke was generated. This is because the separator was melted down due to heat generated when a short circuit occurred inside the battery model.

  On the other hand, the battery model using the artificial graphite negative electrode using the skeleton-forming agent (Example 43) maintains a voltage of 3 V or more even when nailing is performed, does not generate smoke, and has a temperature of the casing and nails. The temperature was also 50 ° C. or less, and heat generation due to a short circuit hardly occurred. This is presumably because the skeleton existing inside the active material layer of the negative electrode coats the active material and the like to block the movement of electrons and suppress a short circuit.

<Electrode peel test>
(Example 43 and Comparative Example 4)
A peel test of the negative electrode used in the batteries of Example 43 and Comparative Example 4 was performed. The peeling test is based on JIS K685, and pressure-sensitive adhesive tape (Scotch, No. 845, Book Tape) is pressure-bonded to the negative electrode active material layer with a 1 kg roller, and under a 25 ° C. environment, a tensile speed of 300 mm / min and an angle of 180 °. The condition was evaluated. FIG. 16 shows photographs of the negative electrode and the pressure-sensitive adhesive tape of Example 43 and Comparative Example 4 after the peel test. As is clear from FIG. 16, the negative electrode of Comparative Example 4 in which the skeleton forming agent was not used had the peeled active material layer adhered to the pressure-sensitive adhesive tape. The active material layer is hardly adhered to the adhesive tape. It was shown that the peel strength was improved.

<Examination of negative electrode active material>
(Examples 44 to 59 and Comparative Examples 5 to 20)
Using the various negative electrode active materials shown in Table 4, the effect in the presence or absence of the skeleton forming agent was compared. In Examples 44 to 59, a slurry composed of the negative electrode active material, AB, and PVdF shown in Table 4 was applied to a copper foil (10 μm), pressure-adjusted, and the active material layer was impregnated with the skeleton forming agent using a spray gun. Then, it was produced by heat treatment at 160 ° C. The solid content ratio of the electrode slurry was 88% by mass of the electrode active material, 4% by mass of AB, and 8% by mass of PVdF.

The skeleton forming agent is an aqueous solution comprising Li _0.05 Na _1.95 O.3SiO ₂ and a nonionic surfactant (registered trademark: Triton X-100), and the solid content concentration of Li _0.05 Na _1.95 O.3SiO ₂ is 7.5. %, And a surfactant having a solid content of 0.03% by mass. In this test, the test electrode is manufactured by one-side coating.

The test battery used lithium metal as a counter electrode, and 1M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol%, and 1 mass% of vinylene carbonate as an electrolytic solution. As the separator, a polypropylene (PP / PE / PP) three-layer microporous membrane (25 μm) was used. In the charge / discharge test, the current density was 0.1 mA / cm ² , the test environment temperature was 30 ° C., and the cutoff potential, the active material density of the electrode (one side), the electrode thickness, and the skeleton density (one side) were as shown in Table 4. is there.

Table 5 is a table showing the cycle life characteristic test results of each electrode having the skeleton formation (Examples 44 to 59). Table 6 is a table showing the cycle life characteristic test results of each electrode (Comparative Examples 5 to 20) in which a skeleton was not formed as a comparison. As is clear from comparison of Tables 5 and 6, the electrodes using Si, SiO, Ge, In, and Fe ₂ O ₃ as the active materials show excellent cycle life characteristics by using the skeleton forming agent. Was. Among them, the electrodes using Si as the active material (Example 56 and Comparative Example 17) showed a particularly remarkable difference. This seems to be due to the fact that a strong skeleton forming agent was built in the active material layer, thereby suppressing the destruction of the electron conductive network due to the volume change.

On the other hand, in the case of Ag, Ag ₂ O, Sb, Sb ₂ S ₃ , SnO ₂ , CuO, NiO, artificial graphite, and hard carbon, there was no significant difference in cycle life characteristics depending on the presence or absence of the skeleton forming agent. Since these active materials have smaller volume changes than Si, SiO, Ge, In, and Fe ₂ O ₃ , it is considered that no clear difference was shown under the present test conditions.

  However, in the case of Sn, the cycle life characteristics deteriorated when the skeleton forming agent was used. This is presumably because Sn had a higher dissolution rate than the skeleton-forming agent and could not maintain the shape of the active material, so that the capacity was deteriorated.

<Study of Si and graphite mixing ratio>
(Examples 60 to 63 and Comparative Examples 21 to 24)
Electrodes using a mixture of Si (1 μm) and artificial graphite (19 μm) as a negative electrode active material were compared for the effect of skeleton formation. In Examples 60 to 63, a slurry composed of the negative electrode active material, AB, and PVdF shown in Table 7 was applied to a copper foil (10 μm), pressure-adjusted, and the active material layer was impregnated with the skeleton forming agent using a spray gun. Then, it was produced by heat treatment at 160 ° C.

In addition, for comparison, electrodes that were not coated and impregnated with the skeleton-forming agent were produced (Comparative Examples 21 to 24). The solid content ratio of the electrode slurry was 88% by mass of the electrode active material, 4% by mass of AB, and 8% by mass of PVdF. The skeleton forming agent is an aqueous solution comprising Li _0.05 Na _1.95 O.3SiO ₂ and a nonionic surfactant (registered trademark: Triton X-100), and the solid content concentration of Li _0.05 Na _1.95 O.3SiO ₂ is 7.5. %, And a surfactant having a solid content of 0.03% by mass. In this test, the test electrode is manufactured by one-side coating.

The test battery used lithium metal as a counter electrode, and 1M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol%, and 1 mass% of vinylene carbonate as an electrolytic solution. As the separator, a polypropylene (PP / PE / PP) three-layer microporous membrane (25 μm) was used. In the charge / discharge test, the current density was 0.1 C-rate, the test environment temperature was 30 ° C., and the cutoff potential was 0.0 to 1.4 V (vs. Li ⁺ / Li). Table 8 shows the skeleton density (one side). The capacity density of the test electrode was 3.0 mAh / cm ² .

  FIG. 10 is a graph comparing cycle life characteristics of Examples 60 to 63 where the skeleton forming agent was applied and Comparative Examples 21 to 24 where the skeleton forming agent was not applied. As is clear from FIG. 10, when the total amount of the active material contained in the negative electrode is 100% by mass, an electrode containing 10% by mass or less of Si (Example 60, Example 61, Comparative Example 21, Comparative Example 22). No significant change was observed, but the electrodes (Example 62, Example 63, Comparative Example 23, Comparative Example 24) in which the amount of Si was 20% by mass or more had clearly improved life characteristics. I understand. In particular, in the case of the electrode having an Si content of 50% by mass (Example 63 and Comparative Example 24), the overwhelming improvement of the life characteristics was exhibited by forming the skeleton.

<Examination of various cathode materials>
Using each positive electrode active material, the effect on the application amount of the skeleton forming agent was compared. The test electrode was prepared by applying a slurry composed of the positive electrode active material, AB, and PVdF shown in Table 9 to an aluminum foil (20 μm), adjusting the pressure, and impregnating the active material layer with a skeleton forming agent using a spray gun. It was produced by heat treatment with. The electrode slurry had a solid content ratio of 90% by mass of the electrode active material, 5% by mass of AB, and 5% by mass of PVdF.

The skeleton forming agent used in Examples 64 to 72 is an aqueous solution composed of Na ₂ O · 2.8 SiO ₂ and a nonionic surfactant (registered trademark: Triton X-100), and is a solid solution of Na ₂ O · 3SiO ₂ . A surfactant having a concentration of 5.5% by mass and a surfactant having a solid concentration of 0.03% by mass was used.
The skeleton forming agent used in Examples 73 to 81 was an aqueous solution composed of Na ₂ O · 2.8 SiO ₂ and a nonionic surfactant (registered trademark: Triton X-100), and was a solid solution of Na ₂ O · 3SiO ₂ . A surfactant having a concentration of 1.1% by mass and a solid content of a surfactant of 0.03% by mass was used.

  Table 9 shows the skeleton density per one surface of the electrode and the cutoff potential of Examples 64 to 81. However, in Example 72 and Example 81, only the first charging was performed up to 4.6V.

In this test, the test electrode was prepared by one-side coating so that the electrode capacity was 2.0 mAh / cm ² . In the test battery, lithium metal was used as a counter electrode, and 1M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol% was used as an electrolyte. As the separator, a polypropylene (PP / PE / PP) three-layer microporous membrane (25 μm) was used. The charge / discharge test was performed at a test environment temperature of 30 ° C. and a charge / discharge rate of 0.1 C-rate from 1 to 10 cycles.

Table 10 is a table showing the cycle life characteristic test results of Examples 64 to 81. As apparent from Table 10, the positive electrode (Examples 64 to 72) having a skeletal density of greater than 0.5 mg / cm ^2, the positive electrode having a skeleton density of 0.5 mg / cm ² or less (Examples 73 to 81) It can be seen that the discharge capacity is smaller than that of. In the positive electrode, it was found that the skeleton density (one side) was preferably 0.5 mg / cm ² or less.

<High temperature durability of positive electrode>
(Examples 82 to 84 and Comparative Examples 21 to 23)
Example 82 is the same as Example 74, except that the electrode capacity was changed to 1.0 mAh / cm ² and the skeleton density was changed to 0.06 mg / cm ² . Example 83 is the same as Example 76 except that the electrode capacity was changed to 1.0 mAh / cm ² and the skeleton density was changed to 0.07 mg / cm ² . Example 84 is the same as Example 81, except that the electrode capacity was changed to 1.0 mAh / cm ² and the skeleton density was changed to 0.11 mg / cm ² . Comparative Example 21 is the same as Example 74, except that the electrode capacity was 1.0 mAh / cm ² and the skeleton forming body was not provided. Comparative Example 22 was the same as Example 76 except that the electrode capacity was 1.0 mAh / cm ² and the skeleton forming body was not provided. Comparative Example 23 is the same as Example 81 except that the electrode capacity was 1.0 mAh / cm ² and the skeleton forming body was not provided.

All the batteries were manufactured using the positive electrodes of Examples 82 to 84 and Comparative Examples 21 to 23. The negative electrode ( ² mAh / cm ² ) was produced by applying a slurry composed of SiO, AB, and polyimide (PI) to a copper foil (40 μm), adjusting the pressure, and then performing a heat treatment at 300 ° C. The solid content ratio of the negative electrode slurry was 79% by mass of the electrode active material, 3% by mass of AB, and 18% by mass of PI. The negative electrode is electrochemically supplemented with Li for an irreversible capacity before assembling the battery.

The test battery used 1 M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol%, and 1 mass% of vinylene carbonate as an electrolytic solution. As the separator, a glass nonwoven fabric (GA-100, manufactured by Toyo Rokko Co., Ltd.) was used. In the charge / discharge test, the test environment temperature was set to 80 ° C., and charge / discharge was repeated for 10 cycles at a current density of 0.1 C-rate, and thereafter, charge / discharge was performed for 30 cycles at 1 C-rate. The cut-off potential was 4.15 V to 2.0 V for Example 82 and Comparative Example 21, 4.15 to 2.0 V for Example 83 and Comparative Example 22, and 4.25 V to 2 for Example 84 and Comparative Example 23. 0.0V.

  FIG. 11 is a graph comparing cycle life characteristics of Examples 82 to 84 in which the skeleton forming agent was applied and Comparative Examples 21 to 23 in which the skeleton forming agent was not applied. As is clear from FIG. 11, the cycle life characteristics of Examples 82 to 84 to which the skeleton forming agent was applied were improved as compared with Comparative Examples 21 to 23. When the PVdF binder is exposed to a high-temperature electrolytic solution, it absorbs the electrolytic solution and swells to increase the electrode resistance. However, an electrode coated with a skeleton forming agent having excellent swelling resistance (Examples 82 to 84). Thus, it is considered that the swelling of the binder was suppressed even in the electrolytic solution as high as 80 ° C. In addition, it is considered that the application of the skeleton-forming agent to the positive electrode active material layer suppressed the decomposition of the electrolytic solution and contributed to the effect of improving the cycle life characteristics.

[5. Effects of the present embodiment]
According to the above-described embodiment, the following effects can be obtained.
By using a skeleton forming agent containing A ₂ O.3SiO ₂ (A = Na, Li) for the electrode, an electrode having excellent heat resistance, high strength, and improved cycle life characteristics can be obtained. In addition, a tough current collector is not essential, and generation of wrinkles, cracks, and the like in the current collector can be suppressed. Further, it is not necessary to use a binder having a large irreversible capacity. Further, even when the electron conductivity of the active material layer is high, heat generation due to an internal short circuit can be reduced. In addition, it has heat resistance exceeding 1000 ° C., and the skeleton forming agent does not carbonize. Good life characteristics can be obtained even with an electrode using an alloy material whose volume changes drastically and a binder having low adhesive strength. Further, the swelling of the active material layer is small even when the active material layer comes into contact with a high-temperature electrolytic solution.

-Second Embodiment-
[1. Structure of skeleton forming agent and electrode]
Next, a second embodiment of the present invention will be described. The difference between the second embodiment and the first embodiment is that ceramics are mainly contained in the skeleton forming agent. FIG. 12 shows an image of an electrode cross section of the second embodiment. The skeleton forming agent of the second embodiment includes a ceramic powder or a solid electrolyte powder having excellent alkali resistance.

  FIG. 3 shows an example of the manufacturing process. By applying the skeleton forming agent of the second embodiment to the surface of the electrode main body, alumina in the skeleton forming agent is laminated on the surface of the active material layer, and the electrical conduction is performed. An insulating ceramic layer or a solid electrolyte layer is formed on the substrate, and a skeleton forming agent permeates into the active material layer.

  As a result, a strong skeleton can be formed, peeling and cracking during drying can be suppressed, and pores are formed due to gaps between the inorganic particles, and good affinity with the electrolytic solution can be obtained. A liquid property is obtained. In addition, the ceramic layer serves as a separator, and a battery can be configured without using a separate separator.

[2. Example]
Next, examples in which the composition of the skeleton forming agent and the like are variously changed in the second embodiment will be described.

<Examination of the ratio of Na ₂ O · 3SiO ₂ and α-Al ₂ O ₃ >
(Examples 85 to 87 and Comparative Example 23)
Table 11 shows the solid content composition of the skeleton-forming agent used in Examples 85 to 87. Further, an electrode using polyimide (PI) as a skeleton forming agent was produced (Comparative Example 23). As α-Al ₂ O ₃ , a powder having a median diameter (D ₅₀ ) of 0.95 μm as measured by a laser diffraction / scattering particle size distribution measuring method was used. The solid content of the skeleton forming agent, when the solid content of Na ₂ O · 3SiO ₂ and α-Al ₂ O ₃ is 100 mass%, and 10 mass%.

The negative electrode (4.0 mAh / cm ² ) was prepared by applying a slurry composed of SiO, carbon black (CB), and an acrylic binder to a copper foil (10 μm), adjusting the pressure, and then using a spray gun to form a skeleton forming agent as shown in Table 11. To an active material layer, and heat-treated at 160 ° C. The skeleton density of the electrode is 3.0 mg / cm ² per side. The solid content ratio of the negative electrode slurry was 90% by mass of SiO, 5% by mass of CB, and 5% by mass of an acrylic binder. The negative electrode is electrochemically supplemented with Li for an irreversible capacity before assembling the battery.

The positive electrode (2.0 mAh / cm ² ) was produced by applying a slurry composed of LiFePO ₄ , CB, and an acrylic binder to an aluminum foil (20 μm), adjusting the pressure, and then performing a heat treatment at 160 ° C. The solid content ratio of the positive electrode slurry was 91% by mass of LiFePO ₄ , 5% by mass of CB, and 4% by mass of an acrylic binder. The test battery used 1 M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol%, and 1 mass% of vinylene carbonate as an electrolytic solution.

  In this test, no separator was used. In the charge / discharge test, the test environment temperature was 60 ° C., and the charge / discharge was performed at a current density of 0.1 C-rate. The cut-off potential was 4.0 V to 2.5 V.

  FIG. 13 shows initial charge / discharge curves of the test batteries of Examples 85 to 87. It turns out that it functions as a battery without using a separator. In Comparative Example 23, a battery test was not performed. The reason is that the coating of the active material layer with PI increases the electrode resistance, making it impossible to electrochemically dope Li ions.

<Examination of alkali-resistant ceramic particle size>
As shown in Table 12, the skeleton forming agent was applied to the surface of the electrode body and dried by changing the particle diameter of α-Al ₂ O ₃ , and the coating property, lyophilic property, binding property, foaming state, and aggregation The state and the sedimentation state were observed. The skeleton-forming agent is an aqueous solution composed of Li _0.05 Na _1.95 O · 3SiO ₂ and α-Al ₂ O ₃ . The solid content concentration of the skeleton forming agent is 25% by mass when the solid content of Li _0.05 Na _1.95 O.3SiO ₂ and α-Al ₂ O ₃ is 100% by mass. The particle diameter of the inorganic particles shown in Table 12 means a median diameter (D ₅₀ ) measured by a laser diffraction / scattering particle diameter distribution measuring method. As shown in Table 12, in the second embodiment, it is understood that the particle diameter of the ceramic is preferably in the range of 0.2 to 20 μm.

[3. Effects of the present embodiment]
According to the above-described embodiment, the following effects can be obtained. A strong skeleton can be formed in the active material layer by applying the skeleton forming agent used in the first embodiment and the powder having excellent alkali resistance (D ₅₀ = 0.2 to 20 μm) to the electrode surface. In addition, the occurrence of peeling and cracking during drying can be suppressed, and pores are formed by the gaps between the inorganic particles, so that good lyophilicity with the electrolytic solution can be obtained. In addition, the ceramic layer serves as a separator, and a battery can be configured without using a separate separator.

-Other embodiments-
<Skeleton formation of active material granules>
(Examples 88 to 93)
It is a test about the manufacturing method of the Si granule which applied the skeleton forming agent.
The Si granules are sprayed with a suspension composed of Si (D ₅₀ = 1 μm), AB, VGCF and PI at a liquid sending rate of 5 g / min, a spray pressure of 0.1 MPa, and a drying temperature of 80 to 180 ° C. It was dried and prepared so that D ₅₀ = 5 to 8 μm. The solid content ratio of the suspension is as shown in Table 13.

Next, as for the Si granules to which the skeleton forming agent was applied, the granules obtained by spray drying were transferred into a fluidized bed, and the skeleton forming agent (Li _0.2 Na _1.8 O · nSiO ₂ ). The skeleton-forming agent was adjusted to be 1% by mass when the mass of the granules obtained by spray drying and the skeleton-forming agent was 100% by mass.

  FIG. 14 shows SEM images of Si granules (Examples 88 to 93) to which the obtained skeleton forming agent was applied. In Example 88, the amount of PI contained in the suspension was small, and it was difficult to obtain spherical granules, but it was found that spherical granules were more likely to be obtained as the amount of PI increased. It was also found that the addition of fibrous particles such as VGCF easily formed sea urchin-like granules.

<Aluminum phosphate skeleton forming agent (Example 94)>
The test electrode (4.0 mAh / cm ² ) is prepared by applying a slurry composed of Si (1 μm), CB, and PVdF binder to a copper foil (40 μm), adjusting the pressure, and then using a spray gun to apply a skeleton forming agent to the active material layer. It was prepared by impregnating the coating and heat-treating at 300 ° C. As a skeleton forming agent, aluminum phosphate (Al ₂ O ₃ .3P ₂ O ₅ ) was dissolved in water and adjusted to have a solid content of 5% by mass. The skeleton density of the electrode is 2.0 mg / cm ² per side. Regarding the solid content ratio of the negative electrode slurry, Si was 90% by mass, CB was 4% by mass, and PVdF binder was 8% by mass.

The test battery used metal Li as a counter electrode, and used 1 M LiPF ₆ / ethylene carbonate (EC): diethyl carbonate (DEC) = 50: 50 vol% and 1 mass% of vinylene carbonate as an electrolytic solution. As the separator, a glass non-woven fabric (GA-100, manufactured by Toyo Rokko Co., Ltd.) was used. In the charge / discharge test, the test environment temperature was 30 ° C., and charge / discharge was performed at current densities of 0.1 C-rate, 0.5 C-rate, and 1.0 C-rate. The cut-off potential was 1.0 V to 0.01 V. FIG. 15 shows a charge / discharge curve at each rate in Example 94. It was found that even when aluminum phosphate (Al ₂ O ₃ .3P ₂ O ₅ ) was used as the skeleton-forming agent, a stable reversible capacity was exhibited.

<Evaluation as a binder>
(Comparative Example 24)
This is a test using a skeleton-forming agent as a binder.
The binder was adjusted by adding water so that the solid concentration of the alkali metal silicate (Li _0.05 Na _1.95 O · 2.8 SiO ₂ ) was 40% by mass. For the test negative electrode ( ² mAh / cm ² ), a slurry composed of Si (D ₅₀ = 1 μm), carbon black, and an inorganic binder was applied to a copper foil (10 μm) and heat-treated at 150 ° C. The solid content ratio of the electrode slurry was 19% by mass of Si, 4% by mass of CB, and 76% by mass of a binder.

(Comparative Example 25)
Comparative Example 25 is the same as Comparative Example 24, except that the binder was changed from an alkali metal silicate to an aluminum phosphate monobasic salt (Al ₂ O ₃ .3P ₂ O ₅ ). As the aluminum phosphate, a commercially available reagent (manufactured by Aesar) was used.

(Reference Example 1)
As a binder, an alkali metal silicate (Li _0.05 Na _1.95 O · 2.8 SiO ₂ ) and α-Al ₂ O ₃ (D ₅₀ = 3 μm) were mixed so as to be 50:50 mass%, and the mixture was mixed. Water was added to adjust the solid content to 40% by mass. Other conditions are the same as in Comparative Example 24.

(Reference Example 2)
As a binder, aluminum phosphate salt (Al ₂ O ₃ .3P ₂ O ₅ ) and α-Al ₂ O ₃ (D ₅₀ = 3 μm) were mixed so as to be 50:50 mass%, and the solid content of the mixture was determined. Water was added to adjust the concentration to 40% by mass. Other conditions are the same as in Comparative Example 25.

  In Comparative Example 25, when the slurry was mixed, Si and the alkali metal silicate reacted, generating hydrogen gas and foaming the slurry. In Comparative Examples 25 and 26, when the preliminary drying was performed at 80 ° C., the active material layer expanded, and a uniform electrode could not be obtained. Further, when the electrodes of Comparative Examples 25 and 26 were heat-treated at 150 ° C., the active material layer contracted significantly, cracking occurred in the active material layer, and dropped off from the current collector.

  On the other hand, in Reference Example 1, when the slurry was mixed, Si and the alkali metal silicate reacted to generate hydrogen gas and foamed the slurry, but the active material layer did not expand due to temporary drying at 80 ° C. Was. Further, when this electrode was heat-treated at 150 ° C., the volume shrinkage was suppressed and the crack of the active material layer and the phenomenon of falling off from the current collector were eliminated as compared with Comparative Example 25.

  In Reference Example 2, since no hydrogen gas was generated during the mixing of the slurry, the slurry did not foam, and the active material layer did not expand even when it was temporarily dried at 80 ° C. Further, when this electrode was heat-treated at 150 ° C., cracks in the active material layer and a phenomenon of falling off from the current collector were eliminated as compared with Comparative Example 25.

  In Comparative Examples 25 and 26, the reason why the active material layer expanded at 80 ° C. was that when the slurry was dried, the vaporized gas (water vapor) was confined in the active material layer and the active material layer expanded. Seem. Further, at 150 ° C., it is considered that the active material layer was cracked due to a large volume shrinkage derived from the alkali metal silicate or the aluminum phosphate salt, and the active material layer was dropped from the current collector.

On the other hand, in Reference Example 1 and Reference Example 2, Al ₂ O ₃ having no binding property was contained as a binder, and gas was discharged from between the particles of Al ₂ O ₃ and Al ₂ O ₃ when the electrode was dried. It is considered that the active material layer did not expand. Furthermore, at 150 ° C., it is considered that Al ₂ O ₃ suppressed the volume shrinkage of the alkali metal silicate and the aluminum phosphate, and prevented the active material layer from cracking and falling off the current collector.

  These phenomena, for example, when the rice cake is heated, the water vapor inside is trapped in the rice cake and expands, but in the cookie where flour is the main component, the water vapor can be released from the gap of the flour, so that it is like rice cake This is the same as making expansion less likely.

A charge / discharge test was performed using the electrodes of Reference Examples 1 and 2. The battery was manufactured using 1 M LiPF ₆ / EC: DEC = 50: 50 vol. %, + VC1% by mass), a separator in which a polyolefin microporous membrane (20 μm) and a glass nonwoven fabric (GA-100) were stacked as a separator, and a half cell using metal Li as a counter electrode were produced. The charge / discharge test was performed at an environmental temperature of 30 ° C., a current density of 0.25 C-rate, and a cutoff potential of 1.5 V to 0.01 V.

  Comparing the initial charge and discharge efficiencies, the alkali metal silicate type (Reference Example 1) was 71%, the aluminum phosphate salt type (Reference Example 2) was 67%, and the alkali metal silicate type had a lower initial charge / discharge efficiency. The result was good charge / discharge efficiency. This means that the alkali metal silicate has a smaller irreversible capacity than aluminum phosphate.

  FIG. 18 shows the cycle life characteristics of Reference Example 1 and an electrode photograph (current collector side) after 200 cycles. The capacity retention after 100 cycles was 78% with respect to the initial discharge capacity of 2609 mAh / g. It is considered that the formation of the strong inorganic binder (alkali metal silicate) skeleton in the active material layer made it difficult for the conductive network to be broken by the expansion and contraction of Si, and exhibited an excellent capacity retention rate. . The reason why the thin copper foil could be used without causing distortion is considered to be that the strength of the inorganic binder (alkali metal silicate) is higher than that of copper.

<Confirmation analysis of inorganic skeleton forming agent>
(Reference Example 3)
This is a test for confirming whether the skeleton-forming agent has penetrated the electrode. The simulated electrode was prepared by applying a slurry composed of Al ₂ O ₃ (D ₅₀ = 9 μm), AB and PVdF binder to a copper foil (10 μm), adjusting the pressure, and then impregnating the active material layer with a skeleton forming agent using a spray gun. Then, it was produced by heat treatment at 150 ° C. As a skeleton forming agent, an alkali metal silicate (Na ₂ O · 3SiO) was dissolved in water and adjusted to have a solid content of 8% by mass. No surfactant was added. The solid content ratio of the simulated electrode slurry was such that α-Al ₂ O ₃ was 85% by mass, CB was 5% by mass, and PVdF binder was 10% by mass.

(Reference Example 4)
Reference Example 4 is the same as Reference Example 3 except that an electrode was not impregnated with a skeleton-forming agent for comparison. FIG. 20 shows the results of glow discharge emission spectroscopy (GDS) of Reference Examples 3 and 4. The GDS measurement conditions were a measurement diameter of 4 mmφ and a Ne gas pressure of 2000 Pa. The measurement wavelength was 121 nm for H, 685 nm for F, 130 nm for O, 156 nm for C, 396 nm for Al, and 251 nm for Si. The time on the horizontal axis is the time of the sputter treatment and is an index corresponding to the depth direction of the active material layer (the direction from the electrode surface to the current collector). The intensity on the vertical axis is the emission intensity, which is an index corresponding to the content of the element. As is clear from FIG. 20, the presence of Si cannot be confirmed in Reference Example 4, whereas in Reference Example 3, although the presence of Si is not constant from the surface to the inside, Si exists in a deep layer. Was confirmed. From this result, it was proved that the skeleton-forming agent could penetrate into the active material layer by applying the skeleton-forming agent to the electrode surface.

As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, various additions, changes, or deletions can be made without departing from the spirit of the present invention. For example, various concentrations and ratios such as the solid concentration of the alkali metal silicate as the skeleton forming agent are not limited to the numerical values of the above-described embodiment. Further, in the above-described embodiment is not limited to an alkali metal silicate _{A 2 O · 3SiO 2 (A} = Li, Na) Li or Na, also factor of SiO ₂ is not limited to two or three. Further, the skeleton forming agent is not limited to aluminum phosphate monobasic (Al ₂ O ₃ · 3P ₂ O ₅ ) as a phosphate, and the coefficient of P ₂ O ₅ is not limited to 3. Therefore, such is also included in the scope of the present invention.

Claims (11)

A skeleton forming agent used for forming a skeleton of an active material layer in an electrode of a nonaqueous electrolyte secondary battery, the skeleton forming agent including a silicate having a siloxane bond or a phosphate having a phosphate bond as a component, and an alkali. An active material capable of absorbing an alkali metal ion or an active material capable of being alloyed with a metal, and a binder,
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the skeleton forming agent is present at least on the surface of the active material layer. A skeleton-forming agent used for forming a skeleton of an active material layer in an electrode of a nonaqueous electrolyte secondary battery, the skeleton-forming agent including a silicate having a siloxane bond or a phosphate having a phosphate bond as a component, and an alkali metal And an active material capable of alloying and an active material capable of absorbing alkali metal ions, and a binder,
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the skeleton forming agent is present at least in an active material layer. The active material is a sulfur-based material,
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1. The sulfur-based material is at least one of sulfur, carbon sulfide, polysulfide, carbon polysulfide, sulfur-modified polyacrylonitrile, disulfide compound, sulfur-modified rubber, sulfur-modified pitch, sulfur-modified anthracene, and metal sulfide.
A positive electrode for a non-aqueous electrolyte secondary battery according to claim 3. The skeleton forming agent is present in the active material layer,
In the active material layer, there is a gap between the active materials,
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1. On the surface of the layer of the skeleton forming agent, having a layer containing alkali-resistant inorganic particles,
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1. The skeleton forming agent per unit area of the electrode coated on one side is 0.01 mg / cm ² or more and 3 mg / cm ² or less, or the skeleton forming agent per unit area of the electrode coated on both sides is is 0.02 mg / cm ² or more 6 mg / cm ² or less,
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1. When the total solid content of the active material, the conductive auxiliary agent, the binder, and the skeleton forming agent is 100% by mass, the skeleton forming agent is 0.1% by mass or more and 30% by mass or less.
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1. The silicate is
A crystalline or amorphous structure represented by the general formula A ₂ O.nSiO ₂ ,
A is at least one of Li, Na, K, a triethanolammonium group, a tetramethanolammonium group, a tetraethanolammonium group, and a granidine group, and n is 1.6 to 3.9.
A positive electrode for a non-aqueous electrolyte secondary battery according to claim 1.   A non-aqueous electrolyte secondary battery comprising the positive electrode according to claim 1.   An electric device comprising the nonaqueous electrolyte secondary battery according to claim 10.