JP2012069453A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electrolyte battery which is excellent in charge-discharge cycle characteristics and high-temperature continuous charge characteristics.SOLUTION: The nonaqueous electrolyte secondary battery comprises a power-generation element having a separator and positive and negative electrodes including an active material and opposed to each other with the separator placed therebetween, and a nonaqueous electrolyte, which are sealed in an outer sheath. The active material which will be combined with lithium into an alloy, an electrically conducting agent including a carbon material at least partially having a specific surface area of from 50 to 1500 m/g inclusive, an aqueous binder solution including an aqueous solution-base binder dispersed in water so that pH falls between 0.05 and 4 inclusive are wet-mixed and dried into a powder mixture. The powder mixture is used for the negative electrode.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery using, as a negative electrode, an active material that is alloyed with lithium, which is excellent in charge / discharge cycle characteristics and continuous charge characteristics at high temperatures.

  Non-aqueous electrolyte secondary batteries with high voltage and high energy density are used as main power sources for portable electronic devices. Graphite is mainly used as a negative electrode material for the non-aqueous electrolyte secondary battery. This is because the energy density is the highest when lithium metal is used for the negative electrode, but in terms of safety, the dendrite deposited on the surface of the lithium metal during charging grows by repeated charge and discharge and penetrates the separator to cause an internal short circuit. This is because there are problems.

  However, in a non-aqueous electrolyte secondary battery using graphite as a negative electrode material, the theoretical capacity of graphite (372 mAh / g) is considerably smaller than the theoretical capacity of lithium metal (3,860 mAh / g). There is a limit.

  As negative electrode materials replacing graphite, metal materials such as Al, Sb, Pb, and Sn that are alloyed with lithium, Si, Ge, and the like are attracting attention. In particular, Sn and Si that can be alloyed with a lot of lithium have been widely studied recently.

Theoretically, Si can occlude up to 22 lithium atoms per 5 Si atoms, that is, Li ₂₂ Si ₅ . Further, the theoretical capacity of Si is 4,199 mAh / g, which is much larger than the theoretical capacity of graphite, and a high energy density can be achieved.

Similarly to Si, Sn can occlude up to 22 lithium atoms up to 5 Sn atoms, that is, Li ₂₂ Sn ₅ , and the theoretical capacity of Sn is a large value of 994 mAh / g. Indicates. Of Sn and Si, Si is the most promising material from the viewpoint of discharge sustaining voltage and capacity.

  By using a material that forms an alloy with lithium, an internal short circuit due to dendrite during discharge does not occur. However, there is a volume expansion as a problem when a material alloyed with lithium is used as an active material. In particular, when Si is used, the volume expands up to about 4 times. Therefore, when the charge / discharge cycle is repeated, a large internal strain is generated in the Si particles, cracks are generated, the particles are pulverized, and the charge / discharge cycle characteristics are remarkably deteriorated.

  Methods for suppressing charge / discharge cycle characteristics deterioration include a method of pulverizing Si at an early stage, a method of alloying Si with other elements, a method of coating the Si surface with a carbon-based material, Si and graphite particles, etc. Methods such as compounding are being studied.

  Further, by using a negative electrode water dispersion paste having a pH of 5 or more and 10 or less, the dispersibility of the carbon compound as a conductive agent is improved, and the lithium-containing transition metal compound or inorganic oxide is eluted from the negative electrode active material. It is disclosed that charge / discharge characteristics such as discharge potential, discharge capacity, and charge / discharge cycle life of a non-aqueous electrolyte secondary battery are improved by suppressing changes in the surface state (see Patent Document 1).

JP-A-2005-310800

  However, in a non-aqueous electrolyte secondary battery using an active material that is alloyed with lithium for the negative electrode, when an aqueous dispersion paste having a pH of 5 or more and 10 or less is used as in Patent Document 1, the negative electrode active Charge / discharge cycle characteristics and continuous charge characteristics deteriorated due to lithium consumption reaction and organic film formation due to the reaction between the substance and the electrolyte.

  An object of the present invention is to solve the above-mentioned problems and to provide a non-aqueous electrolyte secondary battery using, as a negative electrode, an active material that is alloyed with lithium and has excellent charge / discharge cycle characteristics and continuous charge characteristics.

In order to achieve the above object, the present invention provides a non-aqueous electrolyte secondary battery in which a power generation element in which a positive electrode and a negative electrode containing an active material are opposed to each other via a separator is enclosed in a package together with a non-aqueous electrolyte. An active material that forms an alloy with lithium, a conductive agent containing at least a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less, and an aqueous binder with a pH of 0.05 or more and 4 or less. A non-aqueous electrolyte secondary battery in which a mixture powder obtained by wet-mixing a binder aqueous solution dispersed in water so as to be dried and then drying is used for the negative electrode. .

  ADVANTAGE OF THE INVENTION According to this invention, the characteristic deterioration at the time of the continuous charge of a nonaqueous electrolyte secondary battery and a charging / discharging cycle can be suppressed, and long-term storage performance improves remarkably.

  According to the present invention, in a non-aqueous electrolyte secondary battery using an active material that is alloyed with lithium as a negative electrode, it is possible to improve excellent charge / discharge cycle performance and continuous charge characteristics, and for various uses over a long period of time. It can correspond to.

Sectional drawing of the nonaqueous electrolyte secondary battery in one embodiment of this invention

According to a first aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery in which a power generation element in which a positive electrode and a negative electrode containing an active material are opposed to each other via a separator is enclosed in a package together with a non-aqueous electrolyte. The pH of the active material to be alloyed with, a conductive agent containing a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less at least in part, and an aqueous binder is 0.05 or more and 4 or less. Thus, a non-aqueous electrolyte secondary battery in which a mixture powder obtained by wet-mixing a binder aqueous solution dispersed in water and then drying is used for the negative electrode. By setting it as this structure, the non-aqueous-electrolyte secondary battery by which deterioration of the charging / discharging cycling performance and continuous charge characteristic which are the subjects of the active material alloyed with lithium was suppressed is obtained.

An active material that is alloyed with lithium, a conductive agent containing a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less at least in part, and an aqueous binder having a pH of 0.05 or more and 4 or less By wet-mixing the binder aqueous solution dispersed in water so that the active material and the conductive material carbon material constitute a local battery, a short-circuit current flows, and the active material surface has a dense active material. An oxide can be formed. At the same time, the reactivity of the active layer on the surface can be reduced while maintaining the conductivity of the carbon material as the conductive agent. By using the mixture powder obtained by drying this wet mixture as the negative electrode, the reaction with the electrolytic solution at the negative electrode during continuous charging at high temperature can be suppressed. This is due to the fact that a dense oxide is formed on the surface of the active material and the reactivity of the conductive agent is lowered. In addition, with regard to deterioration during charge / discharge cycles, which is an issue with active materials that are alloyed with lithium, the deterioration of the electrode structure is suppressed by the dense oxide layer on the surface, resulting in a lower deterioration rate and cycle performance. Improved significantly.

  When the local battery is constructed, it is important that the pH when the aqueous binder is diluted with water is in the range of 0.05 to 4. The same effect cannot be obtained when a water-soluble binder having an alkaline or neutral pH is used. Although the detailed mechanism is unknown, it is considered that the difference in activity between the layer formed on the active material surface and the carbon material is a factor. In the alkaline region, the active material surface is covered with porous hydroxide or oxyhydroxide, and the activity of the surface of the carbon material remains high. By performing charging and discharging, the hydroxide or oxyhydroxide on the surface of the active material reacts with lithium, causing a decrease in battery capacity due to consumption of lithium. Further, during continuous charging at a high temperature, the electrolytic solution was decomposed due to the reaction between the active material and the carbon material of the active conductive agent, causing deterioration in characteristics. When the pH is 5 to 7, an oxide is formed on the surface of the active material, but the thickness is thin and not completely dense but pinholes are present. Therefore, the effect was insufficient, and the charge / discharge cycle and continuous charge characteristics at high temperature were deteriorated. It seems that the formation of oxide on the active material surface and the decrease in reactivity on the surface of the carbon material are triggered by the smaller the pH value, and the reaction proceeds faster, resulting in a difference in effect. When the pH value is smaller than 0.05, the thickness of the oxide on the active material surface becomes thick, so that the performance is slightly deteriorated in charge / discharge cycle characteristics.

Even when the pH when the aqueous binder is diluted with water is 0.05 or more and 4 or less, the conductive agent contains a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less. If not, the same effect cannot be obtained. The amount of the conductive agent added to the active material is about 40% at maximum with respect to the negative electrode mixture from the viewpoint of capacity, and at least 5% is required from the viewpoint of electric resistance of the negative electrode. In order to efficiently react with the active material during wet mixing with an addition amount of 5 to 40%, it is necessary to increase the reaction area with the active material using a material having a specific surface area within the above range. When the specific surface area is smaller than 50 m ² / g, the reaction efficiency is lowered and oxide formation on the surface of the active material becomes insufficient, and the aimed effect cannot be obtained. In addition, even if the specific surface area is larger than 1500 m ² / g, there is no difference in effect, and the carbon material becomes bulky. If the charge / discharge cycle is repeated, the electrode shape cannot be maintained and the cycle performance is lowered. did.

  According to a second aspect of the present invention, in the first aspect of the invention, there is provided a non-aqueous electrolyte secondary battery using a metal-based active material or silicon as an active material alloyed with lithium. As the metal-based active material, aluminum, an aluminum alloy, tin or the like is preferable. Even when a metal oxide is used, it reaches the point where it is alloyed with lithium, but it is not preferable because the battery capacity becomes small due to the formation of lithium oxide or the structural change of the active material layer.

  As for Si, a P-type or N-type semiconductor, or a mixture of both P-type and N-type is preferable. The P type is preferably Si doped with B, and the N type is preferably doped with at least one of P or Sb.

  In addition, when an amorphous material of Si and a crystalline alloy phase of Si obtained by mixing a metal that can be alloyed with Si into a semiconductor Si and performing mechanical alloying are used as an active material, Discharge cycle performance is greatly improved. The mechanical alloying method is a method in which a raw material mixture is mechanically stirred and mixed using a ball mill, and energy is given to the raw material mixture to produce an alloy powder by a solid phase reaction. Examples of the ball mill used in the mechanical alloying method include a rolling ball mill, a vibration ball mill, and a planetary ball mill.

  The Si amorphous phase obtained by the mechanical alloying method has no diffraction peak on the Si (111) plane in the X-ray diffraction image obtained by the wide-angle X-ray diffraction method, and the maximum crystallite size is 200 nm. An excellent charge / discharge cycle performance can be obtained by using the following.

Ti, Co, Ni, Cu, Mg, Zr, V, Mo, W, Mn, and Fe can be used as a metal that can be alloyed with Si. From the viewpoint of electrical conductivity of the negative electrode, a crystalline alloy phase of Si and Ti having high electron conductivity is preferable, and an intermetallic compound phase represented by the composition formula TiSi ₂ is particularly preferable.

  The mass ratio (M / Si) between the metal element M and Si to be alloyed is preferably 10:90 to 40:60. For the ternary alloy, the mass ratio of Si, the alloying element M1 and the alloying element M2 is 10:90 (the mass ratio of M1 and M2 is arbitrary) to 40:60 (the mass ratio of M1 and M2 is (Optional).

As the conductive agent, a negative electrode for a non-aqueous electrolyte secondary battery composed of a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g and metal Ni that does not alloy with graphite or lithium can be used. If only a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less, structural change occurs inside the electrode due to expansion and contraction during the actual charge / discharge cycle, the conductive path inside the electrode is blocked, and the resistance value As a result, the charge / discharge performance at a high load is reduced. By adding Ni, which is a metal that does not alloy with graphite or lithium, as a conductive agent, it is possible to suppress blocking of the conductive path inside the electrode and an increase in resistance value, and to maintain charge / discharge performance under high load. it can.

  When a material comprising the active material, the conductive agent and the water-soluble binder is used as the negative electrode, the same effect can be obtained regardless of whether it is formed into a pellet or formed on a current collector. Copper is the most suitable base material for the current collector.

  Hereinafter, preferred embodiments of the present invention will be described. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  FIG. 1 is a cross-sectional structure diagram of a coin-type lithium secondary battery which is an example of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

  The coin-type battery case container that houses the power generation element has a function of insulating the positive electrode can 1 made of stainless steel with excellent corrosion resistance, the stainless steel negative electrode can 2, and the positive electrode can 1 and the negative electrode can 2. In addition, it has a gasket 3 for physically sealing the power generation element in the battery container.

  For the gasket 3 interposed between the positive electrode can 1 and the negative electrode can 2, a material made of engineering plastics such as polypropylene resin, polyphenylene sulfide, polyether ether ketone, or fluororesin can be used. A sealant (not shown) is formed between the gasket 3 and the positive electrode can 1 and between the negative electrode can 2 and the gasket 3. As the sealant, for example, a sealant made of a butyl rubber film can be formed by applying a solution obtained by diluting butyl rubber with toluene and evaporating the toluene.

  The positive electrode 4 contains a transition metal oxide as an active material. The negative electrode 5 is a negative electrode material of the present invention. A separator 6 disposed between the positive electrode 4 and the negative electrode 5 is filled with a non-aqueous electrolyte (not shown). The positive electrode current collector 7 is formed by applying a carbon paint on the inner surface of the positive electrode can 1.

The material of the negative electrode 5 of the present invention includes an active material that is alloyed with lithium, a conductive agent containing at least a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less, and an aqueous binder. Wet mixing was performed with a binder aqueous solution dispersed in water so that the pH was 0.05 or more and 4 or less, and then water was removed by drying to obtain a mixture powder. The mixture powder was molded into a pellet shape to produce a negative electrode 5.

  As the graphite of the conductive agent of the negative electrode 5, it is preferable to use at least one of natural graphite, artificial graphite, and non-graphitizable carbon.

  As the aqueous solution binder for the negative electrode 5, polyacrylic acid, ethylene / methacrylic acid copolymer, fluororesin, or the like is used, and ion exchange water is used so that the aqueous solution binder has a pH of 0.05 or more and 4 or less. The binder aqueous solution diluted with water and dispersed in water was wet mixed.

  Examples of the material for the separator 6 as the porous insulator include olefin polymers such as polypropylene and polyethylene, engineering plastics such as polybutylene terephthalate, polyphenylene sulfide, and polyether ether ketone, and glass separators made of inorganic glass fibers. Can be used. It is also possible to use a separator such as a nonwoven fabric or a film.

Solutes constituting the non-aqueous electrolyte include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN ( A single component such as CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) or a mixture of a plurality of components can be used.

  Further, as a solvent constituting the non-aqueous electrolyte, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, sulfolane, dimethoxyethane, diethoxyethane, tetrahydrofuran, dioxolane, γ-butyrolactone However, the present invention is not limited to this.

  1 to 10% by mass of ethylene sulfide, 1,3 propane sultone, 1,4 butane sultone, sulfolene, vinylene carbonate and vinyl ethylene carbonate can be added to the organic electrolyte.

  As the material of the positive electrode 4, a transition metal oxide containing lithium used for battery reaction, a transition metal oxide containing lithium not used for battery reaction, or a transition metal oxide not containing lithium can be used.

Examples of the transition metal oxide containing lithium used in the battery reaction include LiCoO ₂ , LiNiO ₂ , LiNi _x Co _1-X O ₂ (0 <X <1), LiCo _1/3 Ni _1/3 Mn _{1 / 3} O ₂ , spinel-type Li _{1 + X} Mn _2−X O ₄ (0 ≦ X ≦ 0.33) or spinel-type manganese partially substituted with a different element Li _{1 + X} Mn _2−X−y AO ₄ (A Cr, Ni, Co, Fe, Al, B, 0 ≦ X ≦ 0.33, 0 <y ≦ 0.25) and LiFePO ₄ .

The transition metal oxide containing lithium is not used in the cell _{reaction, Li 0.33 MnO 2, LiMnO 2} , Li 1.33 Ti 1.67 O 4, etc. LiFeO ₂ and the like. The transition metal oxide containing no _lithium, and the like _{V 2 O 5, Nb 2 O} 5, TiO 2, M O O 3.

The conductive agent for the positive electrode 4 is preferably at least one selected from the group consisting of carbon black, acetylene black, and denka black. In addition, natural graphite, artificial graphite and the like can be mixed and used. As a compounding quantity of a electrically conductive material, it is the range of 3-10 mass%. As the binder for the positive electrode 4, polytetrafluoroethylene is preferable, and the blending amount thereof is 5 to 1.
It is in the range of 0% by mass.

  By setting it as the battery of the said structure, it can provide the non-aqueous-electrolyte secondary battery which has the outstanding charging / discharging cycling performance and high rate discharge characteristic, and is stable also at the time of continuous charge at high temperature.

  Hereinafter, preferred embodiments of the present invention will be described.

Example 1
FIG. 1 is a cross-sectional view of a secondary battery having a thickness of 1.4 mm and a diameter of 6.8 mm used in an example of the present invention.

The positive electrode 4 has a lithium-containing manganese oxide obtained by firing lithium hydroxide and manganese dioxide at 400 ° C. for 10 hours as an active material, a carbo black having a specific surface area of 800 m ² / g as a conductive agent, and a binder. After mixing an aqueous binder in which a fluororesin powder having a pH value of 8 was dispersed, the moisture was dried to obtain a positive electrode mixture. As a mixture, an active material, a conductive agent, and a fluororesin were mixed at a mass ratio of 85: 7: 8. 20 mg of this mixture was molded into a pellet having a diameter of 4 mm and a thickness of 0.7 mm, and then dried at 250 ° C. for 12 hours. The obtained pellet-like positive electrode material is in contact with the positive electrode current collector 7 formed by applying a carbon paint on the inner surface of the positive electrode can 1.

The negative electrode 5 is an aqueous solution system comprising a Ti—Si alloy as an active material, carbo black having a specific surface area of 800 m ² / g as a conductive material and natural graphite having a specific surface area of 10 m ² / g, and polyacrylic acid as a binder. Pure water was added to the binder, and the aqueous solution was wet-mixed at a pH of 1. Then, the water was dried to obtain a negative electrode mixture. The mixture was a mixture of 80: 4: 8: 8 in mass ratio of the active material, the conductive agent carbon black, natural graphite, and polyacrylic acid. 8 mg of the negative electrode mixture was formed into a pellet having a diameter of 4 mm and a thickness of 0.3 mm, and then dried at 150 ° C. for 12 hours to obtain the negative electrode 5.

The Ti-Si alloy as an active material was obtained by pulverizing a Si wafer doped with 1 × 10 ¹⁸ P atoms per 1 cm ³ of Si by a mother alloy doping method in a mortar to obtain a powder having an average particle diameter of 1 mm. Further, a Si wafer doped with 1 × 10 ¹⁸ B atoms per 1 cm ³ of Si by a mother alloy doping method was crushed in a mortar to obtain a powder having an average particle diameter of 1 mm.

  1.5 kg of this N-type semiconductor and P-type semiconductor Si powder mixed at a mass ratio of 10:90, 1 kg of Ti powder with an average particle size of 0.5 mm, and 300 kg of 1-inch diameter stainless steel balls, The container was put in a container of a stainless steel vibrating ball mill (product code: FV-30, manufactured by Chuo Kaoki Co., Ltd.) having an internal volume of 95 liters and covered.

  The inside of the container was depressurized, and Ar gas was introduced until the inside of the container reached 1 atm. Next, the amplitude of the vibration ball mill was set to 8 mm and the rotational speed of the drive motor was set to 1200 rpm, respectively, and mechanical alloying was performed for 20 hours to produce a Ti 37 wt% -Si 63 wt% alloy powder used as a negative electrode active material.

  Using a wide angle X-ray diffractometer (product code: RINT-2500, manufactured by Rigaku Corporation) using a CuKα ray having a wavelength of 1.5405 mm as a radiation source, the diffraction intensity in a range of diffraction angle 2θ = 10 ° -80 ° is measured did. When the presence or absence of a peak near the diffraction angle attributed to the (111) plane of Si was examined, no peak was present.

Moreover, when the obtained alloy powder was observed using TEM (transmission electron microscope), the maximum crystallite size was 40 nm and the average crystallite size was 10 nm. An active material comprising an amorphous phase of Si and an alloy phase of Ti and Si was obtained.

  A sheet of lithium metal having a thickness of 0.20 mm was punched out to 3.7 mm and pressed onto the surface of the negative electrode 5 pellet. The surface of the pellet of the negative electrode 5 to which the lithium metal is pressure-bonded is disposed on the separator 6 side.

  When the battery is assembled, by injecting a non-aqueous electrolyte, lithium and the negative electrode 5 are short-circuited, and lithium is occluded electrochemically in the amorphous phase Si of the negative electrode 5. A Li—Si alloy was obtained by this reaction. The separator 6 disposed between the positive electrode 4 and the negative electrode 5 was made of a polypropylene nonwoven fabric, a polypropylene film, and a polypropylene nonwoven fabric.

1 mol of LiN (CF ₃ SO ₂ ) ₂ was dissolved as a solute in a mixed solvent having a volume ratio of propylene carbonate (PC), ethylene carbonate (EC) and 1,2 · dimethoxyethane (DME) of 3: 2: 5. A non-aqueous electrolyte was used. A volume of 8 μ1 is filled in the separator 6 in the battery container composed of the positive electrode can 1, the negative electrode can 2, and the gasket 3.

  The nonaqueous electrolyte secondary battery thus obtained was designated as an inventive battery 1 according to Example 1.

  Inventive battery 2 having the same configuration was prepared except that an aqueous solution-based binder composed of polyacrylic acid having a diluted aqueous solution pH of 2 was used instead of the aqueous solution-based binder of inventive battery 1.

  Inventive battery 3 having the same configuration was prepared except that an aqueous solution-based binder composed of polyacrylic acid having a diluted aqueous solution pH of 3 was used instead of the aqueous solution-based binder of inventive battery 1.

  Inventive battery 4 having the same configuration was prepared except that an aqueous solution-based binder composed of polyacrylic acid having a pH of 4 after dilution was used instead of the aqueous solution-based binder of inventive battery 1.

  Inventive battery 5 having the same configuration was prepared except that an aqueous solution-based binder composed of polyacrylic acid having a pH of 0.5 after dilution was used instead of the aqueous solution-based binder of inventive battery 1.

  Inventive battery 6 having the same configuration was prepared, except that an aqueous solution-based binder composed of polyacrylic acid having a pH of 0.1 after dilution was used instead of the aqueous solution-based binder of inventive battery 1.

  Inventive battery 7 having the same configuration was prepared except that an aqueous solution-based binder composed of polyacrylic acid having a pH of 0.05 after dilution was used instead of the aqueous solution-based binder of inventive battery 1.

  A comparative battery A having the same configuration was prepared except that an aqueous solution binder composed of polyacrylic acid having a pH of 0.01 after dilution was used instead of the aqueous solution binder of Invention Battery 1.

  A comparative battery B having the same configuration was prepared except that an aqueous solution binder made of polyacrylic acid having a pH of 5 after dilution was used instead of the aqueous solution binder of Invention Battery 1.

  A comparative battery C having the same configuration was prepared except that an aqueous solution binder composed of polyacrylic acid whose pH of the diluted aqueous solution was 7 was used instead of the aqueous solution binder of Invention Battery 1.

  A comparative battery D having the same configuration was prepared except that an aqueous solution binder made of polyacrylic acid having a pH of 9 after dilution was used instead of the aqueous solution binder of Invention Battery 1.

  A comparative battery E having the same configuration was prepared except that an aqueous solution binder made of polyacrylic acid having a pH of 11 after dilution was used instead of the aqueous solution binder of Invention Battery 1.

  A comparative battery F having the same configuration was prepared except that an aqueous solution binder made of polyacrylic acid having a pH of 13 after dilution was used instead of the aqueous solution binder of Invention Battery 1.

  The difference in pH of polyacrylic acid was prepared by replacing hydrogen of acrylic acid with Na.

  Inventive batteries 1 to 7 and comparative batteries A to F were evaluated for charge / discharge cycle characteristics and continuous charge characteristics at high temperatures.

  The charge / discharge cycle characteristics were charged / discharged at a charge / discharge voltage range of 3.3 V to 2.0 V and a constant current of 0.1 mA, and the discharge capacity maintenance rate at the 100th cycle was defined as the charge / discharge cycle characteristics.

  The continuous charge characteristic at high temperature was determined by taking the capacity obtained by continuously applying a voltage of 3.3 V in a dry atmosphere at 60 ° C. for 100 days and then discharging to 20 V at 0.1 mA to 2 V as the discharge maintenance ratio. . The discharge maintenance rate was calculated with the value obtained by discharging the battery before evaluation at 20 ° C. to 2 V with a constant current of 0.1 mA. The results are shown in (Table 1).

As shown in (Table 1), the inventive batteries 1 to 7 were excellent in charge / discharge cycle characteristics and continuous charge characteristics. For the comparative batteries A to F, the deterioration rate increased.
In invention batteries 1 to 7, the surface of Si, which is an active material, is uniformly covered with SiO _2, and the reaction between Si of the active material and the electrolyte during charging / discharging and continuous charging can be suppressed, and the electrode during cycling The performance was improved because the deterioration of the structure was suppressed. In the comparative battery A, the acidity of the pH is very high. Therefore, it is considered that the thickness of the SiO ₂ is very thick, and the cycle characteristics are deteriorated due to some influence on the conductive agent carbon black and natural graphite.

On the other hand, in Comparative batteries B and C, since SiO ₂ was not completely covered, the reaction between the active material Si and the electrolytic solution progressed, resulting in performance degradation. In comparison batteries D to F, the surface of Si, which is an active material, is covered with porous SiOH, SiOOH, etc., and the capacity is reduced by consuming lithium used for battery reaction during charge / discharge and continuous charge. It was. In addition, degradation caused by decomposition of the electrolytic solution by reacting with SiOH, SiOOH and the electrolytic solution also occurred.

(Example 2)
Inventive battery 8 having the same configuration was prepared except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer having a pH of 1 after dilution was used instead of the aqueous solution-based binder of inventive battery 1. .
Inventive battery 9 having the same configuration except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer having a pH of 2.5 after dilution was used instead of the aqueous solution-based binder of inventive battery 8. Produced.

  Inventive battery 10 having the same structure was prepared except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer having a pH of 4 after dilution was used instead of the aqueous solution-based binder of inventive battery 8. .

  Inventive battery 11 having the same configuration except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer whose pH of the diluted aqueous solution is 0.5 is used instead of the aqueous solution-based binder of inventive battery 8. Produced.

  Inventive battery 12 having the same configuration except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer having a pH of 0.1 after dilution was used instead of the aqueous solution-based binder of inventive battery 8. Produced.

  Inventive battery 13 having the same configuration except that an aqueous solution-based binder composed of an ethylene / methacrylic acid copolymer having a pH of 0.05 after dilution was used instead of the aqueous solution-based binder of inventive battery 8. Produced.

  A comparative battery G having the same structure except that an aqueous solution binder composed of an ethylene / methacrylic acid copolymer having a pH of 0.01 after dilution was used instead of the aqueous solution binder of Invention Battery 8 Produced.

  A comparative battery H having the same configuration was prepared except that an aqueous solution binder composed of an ethylene / methacrylic acid copolymer having a pH of 5 after dilution was used instead of the aqueous solution binder of Invention Battery 8. .

  A comparative battery I having the same configuration was prepared except that an aqueous solution binder composed of an ethylene / methacrylic acid copolymer having a pH of 7 after dilution was used instead of the aqueous solution binder of Invention Battery 8. .

  A comparative battery J having the same configuration was prepared except that an aqueous solution binder composed of an ethylene / methacrylic acid copolymer having a pH of 9 after dilution was used instead of the aqueous solution binder of Invention Battery 8. .

  The difference in pH of the ethylene / methacrylic acid copolymer was prepared by replacing hydrogen of methacrylic acid with Na.

  In the same manner as in Example 1, the inventive batteries 8 to 13 and the comparative batteries G to J were evaluated for charge / discharge cycle characteristics and continuous charge characteristics at high temperatures.

  As shown in (Table 2), as in the results of Example 1, the inventive batteries 8 to 13 were excellent in charge / discharge cycle characteristics and continuous charge characteristics. For the comparative batteries G to J, the deterioration rate increased. Similar to Example 1, a difference in performance was observed due to the difference in the layers formed on the Si surface of the active material.

(Example 3)
Inventive battery 14 having the same configuration was produced except that Sn powder having a particle size of 10 μm was used instead of the Ti—Si alloy as the active material of inventive battery 1.

  Inventive battery 15 having the same configuration was prepared except that the aqueous solution-based binder powder made of polyacrylic acid having a pH of 2.5 after dilution was used instead of the aqueous solution-based binder of inventive battery 14.

  Inventive battery 16 having the same structure was prepared except that the aqueous solution binder powder made of polyacrylic acid having a pH of 4 after dilution was used instead of the aqueous solution binder of inventive battery 14.

  Inventive battery 17 having the same configuration was prepared except that an aqueous aqueous binder powder made of polyacrylic acid having a pH of 0.5 after dilution was used instead of the aqueous aqueous binder of inventive battery 14.

  Inventive battery 18 having the same structure was prepared except that an aqueous solution-based binder powder made of polyacrylic acid having a pH of 0.1 after dilution was used instead of the aqueous solution-based binder of inventive battery 14.

  Inventive battery 19 having the same structure was prepared except that an aqueous solution-based binder powder made of polyacrylic acid having a pH of 0.05 after dilution was used instead of the aqueous solution-based binder of inventive battery 14.

  A comparative battery K having the same structure was prepared except that the aqueous solution binder powder made of polyacrylic acid having a pH of 0.01 after dilution was used instead of the aqueous solution binder of Invention Battery 14.

  A comparative battery L having the same configuration was prepared except that the aqueous solution binder powder made of polyacrylic acid having a pH of 5 after dilution was used instead of the aqueous solution binder of Invention Battery 14.

  A comparative battery M having the same configuration was prepared except that an aqueous solution-based binder powder made of polyacrylic acid having a pH of 7 after dilution was used instead of the aqueous solution-based binder of Invention Battery 14.

  A comparative battery N having the same configuration was prepared except that an aqueous solution-type binder powder made of polyacrylic acid having a pH of 9 after dilution was used instead of the aqueous solution-type binder of Invention Battery 14.

  In the same manner as in Example 1, the inventive batteries 14 to 19 and the comparative batteries K to N were evaluated for charge / discharge cycle characteristics and continuous charge characteristics at high temperatures.

Even when Sn powder having a particle size of 10 μm is used instead of the Ti—Si alloy as the active material, the performance difference is greatly caused by the difference in the layer formed by the pH of the aqueous binder used in the same manner as in Example 1. There was a difference. It is considered that the SnO ₂ layer is neutral on the Sn surface of the active material in the acidic region, and the SnOH and SnOOH layers are formed in the alkaline region.

Example 4
Inventive battery 20 having the same configuration was prepared except that carbo black having a specific surface area of 50 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 1.

Inventive battery 21 having the same configuration was produced except that carbo black having a specific surface area of 100 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 1.

Inventive battery 22 having the same configuration was prepared except that carbo black having a specific surface area of 400 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 1.

Inventive battery 23 having the same configuration was prepared except that carbo black having a specific surface area of 1,200 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 1.

Inventive battery 24 having the same configuration was prepared except that carbo black having a specific surface area of 1,500 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 1.

Inventive battery 25 having the same configuration was prepared except that carbo black having a specific surface area of 50 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 26 having the same configuration was prepared except that carbo black having a specific surface area of 100 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 27 having the same configuration was produced except that carbo black having a specific surface area of 400 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 28 having the same configuration was prepared except that carbo black having a specific surface area of 1,200 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 29 having the same configuration was produced except that carbo black having a specific surface area of 1,500 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 30 having the same configuration was prepared except that carbo black having a specific surface area of 50 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 7.

Inventive battery 31 having the same configuration was prepared except that carbo black having a specific surface area of 100 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 7.

Inventive battery 32 having the same configuration was prepared except that carbo black having a specific surface area of 400 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 7.

Inventive battery 33 having the same configuration was produced except that carbo black having a specific surface area of 1,200 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

Inventive battery 34 having the same configuration was prepared except that carbo black having a specific surface area of 1,500 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of inventive battery 4.

A comparative battery O having the same configuration was prepared except that carbo black having a specific surface area of 40 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 1.

A comparative battery P having the same configuration was prepared except that carbo black having a specific surface area of 1,600 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 1.

A comparative battery Q having the same configuration was prepared except that natural graphite having a specific surface area of 10 m ² / g was used instead of the carbon black having a specific surface area of 800 m ² / g of the conductive agent of the inventive battery 1.

A comparative battery R having the same configuration was prepared except that carbo black having a specific surface area of 40 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 4.

A comparative battery S having the same configuration was prepared except that carbo black having a specific surface area of 1,600 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 4.

A comparative battery T having the same configuration was produced except that natural graphite having a specific surface area of 10 m ² / g was used instead of the carbon black having a specific surface area of 800 m ² / g of the conductive agent of the inventive battery 4.

A comparative battery U having the same configuration was prepared except that carbo black having a specific surface area of 40 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 7.

A comparative battery V having the same configuration was prepared except that carbo black having a specific surface area of 1,600 m ² / g was used instead of carbo black having a specific surface area of 800 m ² / g of the conductive agent of Invention Battery 7.

A comparative battery W having the same configuration was prepared except that natural graphite having a specific surface area of 10 m ² / g was used instead of the carbon black having a specific surface area of 800 m ² / g of the conductive agent of the inventive battery 7.

  In the same manner as in Example 1, the inventive batteries 1, 4, 7, 20 to 34 and the comparative batteries O to W were evaluated for charge / discharge cycle characteristics and continuous charge characteristics at high temperatures.

  Inventive batteries 1, 4, 7, and 20 to 34 were excellent in charge / discharge cycle characteristics and continuous charge characteristics. Comparative batteries O to W deteriorated. In particular, when natural graphite having a small specific surface area is used, the characteristic deterioration becomes extremely large. Since the specific surface area of the carbon material used for the conductive agent is reduced, the contact area with the active material is reduced and the reactivity is lowered, so that the thickness of the formed oxide layer becomes insufficient and the characteristics are considered deteriorated. It is done.

  By providing a non-aqueous electrolyte secondary battery that has excellent charge / discharge cycle performance and is stable even during continuous charging at high temperatures, it can be used for various applications over a long period of time. Very expensive.

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

Claims (2)

In a non-aqueous electrolyte secondary battery in which a power generation element in which a positive electrode and a negative electrode containing an active material are arranged to face each other through a separator is enclosed in a package together with a non-aqueous electrolyte,
An active material that is alloyed with lithium, a conductive agent containing a carbon material having a specific surface area of 50 m ² / g or more and 1500 m ² / g or less at least in part, and an aqueous binder having a pH of 0.05 or more and 4 or less A non-aqueous electrolyte secondary battery comprising, as a negative electrode, a mixture powder obtained by wet-mixing a binder aqueous solution dispersed in water so as to be dried. The non-aqueous electrolyte secondary battery according to claim 1, wherein a metal-based active material or Si is used as the active material to be alloyed with lithium.