JP3719312B2 - Positive electrode sheet and non-aqueous electrolyte secondary battery using the same - Google Patents

Description

【００９７】
第２表の結果から、本発明の正極シートを用いたリチウム二次電池が高い放電容量を示し、かつ繰返しの使用においても高い放電容量を維持することが分る。
【００９８】
【発明の効果】
本発明の正極シートは、放電容量が高く、かつ繰返しの使用においても高い放電容量を維持することのできる非水電解質二次電池の製造を可能にする。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a non-aqueous electrolyte secondary battery using a lithium salt as an electrolyte, that is, a positive electrode sheet suitable for use in a lithium secondary battery, and a non-aqueous electrolyte secondary battery using the positive electrode sheet.
[0002]
[Prior art]
In recent years, lithium secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material capable of occluding and releasing lithium for the negative electrode and LiCoO for the positive electrode.₂ A composite oxide of a transition metal such as lithium and the like is used as an active material, thereby realizing a secondary battery having a high potential and a high discharge capacity.
However, even in the battery having the above-described configuration, there is a decrease in capacity due to charge / discharge cycles and deterioration in battery performance due to self-discharge, and improvement has been desired. For this reason, use of active materials having different functions is described in JP-A-2-297867, JP-A-4-206267, and JP-A-5-151995. I haven't got it.
[0003]
On the other hand, an attempt is made to control the physical properties of the positive electrode active material. In JP-A-4-249073, the specific surface area of the lithium composite oxide positive electrode active material particles is set to 0.01 to 3.0 m.² It is proposed that the specific surface area of the lithium composite oxide positive electrode active material particles be 0.5 to 10 m.² / G is proposed. Furthermore, in JP-A-6-275277, the specific surface area of lithium cobalt composite oxide particles made amorphous by adding phosphorus is 1-1000 m.² / G, and in Japanese Patent Laid-Open No. 7-122262, the specific surface area of the electrode is 4 m.² / G or more is proposed. However, these methods have not yet achieved sufficient cycle characteristics.
[0004]
Japanese Patent Laid-Open No. 9-102321 discloses, as an improvement of a secondary battery using a solid electrolyte, an electrode layer of an electrode sheet such as a positive electrode sheet or a negative electrode sheet, a coating layer containing an electrode material having a small particle size. And a coating layer containing an electrode material having a large particle size are sequentially laminated, and by this method, a gradient is provided so that the particle size of the electrode material increases on the interface side between the electrode layer and the solid electrolyte layer. Thus, a method for improving the contact property at the interface between the solid electrolyte material and the electrode sheet is described.
[0005]
On the other hand, according to the research of the inventors of the present invention, it has been found that as the lithium secondary battery is repeatedly used, the positive electrode surface changes in quality and the cycle life decreases.
[0006]
[Problems to be solved by the invention]
  An object of the present invention is to provide a positive electrode sheet for a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics. Moreover, this invention is providing the high capacity | capacitance and the non-aqueous-electrolyte secondary battery which was excellent in cycling characteristics using this positive electrode sheet.
[0007]
[Means for Solving the Problems]
  The present inventionMade of aluminumA positive electrode sheet comprising a current collector sheet and a positive electrode mixture layer containing positive electrode active material particles and a binder formed on a surface of at least one side of the current collector sheet, the positive electrode mixture layer Is a coating liquid containing positive active material particles having a relatively large specific surface area and a binder, and a coating liquid containing positive active material particles having a relatively small specific surface area and a binder,In such a distribution that the specific surface area is small on the surface side of the positive electrode mixture layer and large on the current collector sheet side.It is a layer formed by the method of applying at the same time and then drying those applied layers at the same time.Yes, the binder addition amount in each positive electrode mixture layer is 1 to 30% by weightIt is characterized by beingFor non-aqueous electrolyte secondary batteriesLocated on the positive electrode sheet.
[0009]
The specific surface area of the positive electrode active material particles in the present invention means an average specific surface area (average surface area average value of a particle aggregate generally called secondary particles), and is generally used as a method for measuring the specific surface area. It means a numerical value measured by the BET method.
By using the positive electrode sheet of the present invention, a non-aqueous lithium secondary battery having a high capacity and excellent cycle characteristics can be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  Although the preferable form of this invention is demonstrated below, this invention is not limited to these.
1)Made of aluminumA positive electrode sheet comprising a current collector sheet and a positive electrode mixture layer containing positive electrode active material particles and a binder formed on a surface of at least one side of the current collector sheet, the positive electrode mixture layer A coating liquid containing positive electrode active material particles having a relatively large specific surface area and a binder, and a coating liquid containing positive electrode active material particles having a relatively small specific surface area and a binder.The distribution is such that the specific surface area is small on the surface side of the positive electrode mixture layer and large on the current collector sheet side.It is a layer formed by the method of applying at the same time and then drying those applied layers at the same time.Yes, the binder addition amount in each positive electrode mixture layer is 1 to 30% by weightIt is characterized by beingFor non-aqueous electrolyte secondary batteriesPositive electrode sheet.
2) The chemical composition of the positive electrode active material particles is the same throughout the positive electrode mixture layer.In item 1DescribedFor non-aqueous electrolyte secondary batteriesPositive electrode sheet.
[0011]
  3) The positive electrode active material particles are Li_xCoO₂, Li_xNiO₂, Li_xMnO₂, Li_xCo_aNi_1-aO₂, Li_xMn₂O₄, And Li_xCo_bV_1-bO_z(However, at least one of x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.9 to 0.98, z = 2.01 to 2.3) Having the chemical composition representedIn item 1 or 2DescribedFor non-aqueous electrolyte secondary batteriesPositive electrode sheet.
4) The positive electrode sheet for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 3, wherein the solvent of the coating solution containing the positive electrode active material particles and the binder is water.
5) A positive electrode sheet, a negative electrode sheet, and a lithium salt-containing electrolyte are accommodated in an airtight container, and the positive electrode sheet is4A non-aqueous electrolyte secondary battery, which is the positive electrode sheet according to any one of the above.
[0012]
The positive electrode sheet of the present invention is a positive electrode sheet comprising a current collector sheet and a positive electrode mixture layer containing positive electrode active material particles and a binder formed on the surface of at least one side of the current collector sheet. The positive electrode active material particles are arranged in such a distribution that the specific surface area is small on the surface side of the positive electrode mixture layer and large on the current collector sheet side, and the binder is at least the positive electrode mixture layer The positive electrode sheet is characterized in that a continuous phase is formed in the thickness direction. The positive electrode sheet of the present invention includes, for example, a coating liquid containing positive electrode active material particles having a relatively large specific surface area and a binder, and positive electrode active material particles and a binder having a relatively small specific surface area. It can form by the method (So-called simultaneous multilayer coating method) which apply | coats a coating liquid simultaneously and then drys those coating layers simultaneously. In carrying out the simultaneous multi-layer coating method, the coating liquid is not limited to two types, and three or more types of coating liquids are used, and an arbitrary number of coating layers are simultaneously formed to obtain a positive electrode mixture layer. You can also.
[0013]
In the positive electrode mixture layer of the positive electrode sheet of the present invention, the specific surface area of the positive electrode active material is arranged so as to have a gradient in the thickness (depth) direction of the positive electrode mixture layer and forms a continuous phase in the thickness direction. The layer state is formed and maintained by the adhesive. For this reason, not only the physical strength of the entire layer is improved, but also in the repeated use of the secondary battery using the positive electrode sheet, the positive electrode mixture layer (that is, the positive electrode layer) of the positive electrode sheet Since lithium ions move smoothly, it is possible to effectively suppress the occurrence of adverse effects such as an increase in overvoltage and a decrease in capacity associated therewith.
[0014]
The positive electrode mixture of the positive electrode sheet used in the present invention contains a particulate positive electrode active material and a binder, and if necessary, a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, and a pressure enhancer. Various additives such as can be included. The positive electrode sheet may be disk-shaped or plate-shaped, but is preferably a flexible sheet.
[0015]
Below, the positive mix used for the positive electrode sheet of this invention is demonstrated.
It is preferable that the positive electrode active material used for manufacture of the positive electrode sheet of this invention is a lithium containing transition metal oxide. The lithium-containing transition metal oxide is an oxide mainly containing at least one transition metal element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Mo, and W and lithium. A compound having a molar ratio of lithium to transition metal of 0.3 to 2.2. More preferable is an oxide mainly containing at least one transition metal element selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, and a molar ratio of lithium to transition metal. It is a compound of 0.3 to 2.2. Note that Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, and B may contain other elements in a range of less than 30 mole percent with respect to the transition metal element that is mainly present.
[0016]
As a specific example of the lithium-containing transition metal oxide preferably used as the positive electrode active material, Li_x CoO₂ , Li_x NiO₂ , Li_x MnO₂ , Li_x Co_a Ni_1-a O₂ , Li_x Co_b V_1-b O_z , Li_x Co_b Fe_1-b O₂ , Li_x Mn₂ O_Four , Li_x Mn_c Co_2-c O_Four , Li_x Mn_c Ni_2-c O_Four , Li_x Mn_c V_2-c O_Four And Li_x Mn_c Fe_2-c O_Four (Where x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.8 to 0.98, c = 1.6 to 1.96, z = 2.1-2. .3). Specific examples of the most preferred lithium-containing transition metal oxide include Li_x CoO₂ , Li_x NiO₂ , Li_x MnO₂ , Li_x Co_a Ni_1-a O₂ , Li_x Mn₂ O_Four , Li_x Co_b V_1-b O_z (X = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.9 to 0.98, z = 2.01 to 2.3). The value of x is a value before the start of charging / discharging and increases / decreases due to charging / discharging.
[0017]
The positive electrode active material used in the present invention can be synthesized by a method in which a lithium compound and a transition metal compound are mixed and fired, or by a solution reaction, and a firing method is particularly preferable.
Details of the firing step for producing the positive electrode active material are described in paragraph [0035] of JP-A-6-60867, JP-A-7-14579, and the like, and these methods can be used. The positive electrode active material obtained by firing may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.
Further, as a method of chemically inserting lithium ions into the transition metal oxide, a method of synthesis by reacting lithium metal, a lithium alloy or butyl lithium with a transition metal oxide may be used.
[0018]
When the positive electrode active material of the present invention is obtained by firing, the firing temperature is preferably 500 to 1500 ° C, more preferably 700 to 1200 ° C, and particularly preferably 750 to 1000 ° C. The firing time is preferably 4 to 30 hours, more preferably 6 to 20 hours, and particularly preferably 6 to 15 hours.
[0019]
The positive electrode active material used for the positive electrode sheet of the present invention is composed of a mixture of two or more kinds of positive electrode active material particles having different specific surface areas, and the mixture of these positive electrode active materials has a smaller specific surface area on the upper side (positive electrode mixture). The specific surface area is inclined along the depth direction (thickness direction) of the positive electrode mixture layer so that the larger specific surface area is on the lower side (current collector sheet side) Yes. In addition, it is preferable that the positive electrode active material used for the positive electrode sheet of this invention exists in a uniform chemical composition over the whole positive mix layer. That is, the positive electrode active material particles used in the present invention are preferably composed of two or more types having the same chemical composition and different specific surface areas.
[0020]
The specific surface area of the positive electrode active material particles is not particularly limited, but is 0.01 to 50 m by the BET method.² / G is preferred, especially 0.2 m² / G-1m² / G is preferred. Then, two or more kinds of particles having a specific surface area in such a range are arranged in a distribution according to the present invention on the upper side and the lower side of the positive electrode mixture layer. For example, the positive electrode active material particles in the lower half region of the positive electrode mixture layer are arranged so that the specific surface area is in the range of 1.2 to 50 times the specific surface area of the positive electrode active material particles in the upper half region. In particular, the positive electrode active material in which the specific surface area of the positive electrode active material particles in the lower half region of the positive electrode mixture layer is in the upper half region with the central portion in the thickness direction of the positive electrode mixture layer as a boundary. It is preferable to arrange so as to be in the range of 1.4 to 5 times the specific surface area of the particles. The specific surface area of the positive electrode active material particles in the lower half region of the positive electrode mixture layer is 0.2 to 10 m.² / G, and the specific surface area of the positive electrode active material particles in the upper half region is 0.05 to 5 m.² / G is preferable.
[0021]
The positive electrode mixture layer of the present invention is prepared by preparing two or more kinds of positive electrode mixture forming coating liquids containing positive electrode active materials having different specific surface areas, and applying these to the collector sheet surface by a simultaneous multilayer coating method. By applying and drying almost simultaneously, when forming the specific surface area distribution of the positive electrode active material particles in the depth direction in the positive electrode mixture layer, the continuity of the distribution in the depth direction can be increased. The binder is formed as a continuous phase in the thickness direction of the positive electrode layer.
[0022]
In the case where the positive electrode mixture layer of the positive electrode sheet of the present invention is composed of two or three positive electrode mixture unit layers, examples of preferable combinations of specific surface areas of the positive electrode active material particles to be introduced into each unit layer The following.
[0023]
[Table 1]
(A) In the case of a two-layer structure (unit: m² / G)
Example of combination          Upper layer (surface side layer)        Lower layer (current collector side)
No. 1 0.1-0.5 0.5-2.0
No. 2 0.1-0.5 1.0-5.0
No. 3 0.1-0.3 0.3-1.0
No. 4 0.1-1.0 1.0-5.0
No. 5 0.1-0.5 0.5-1.0
No. 6 0.1-0.3 0.5-0.8
No. 7 0.1-0.3 0.5-1.0
No. 8 0.1-0.5 1.0-5.0
No. 9 0.1-0.5 0.8-2.0
[0024]
[Table 2]
(B) In the case of a three-layer structure (unit: m² / G)
Example of combination    Upper layer (surface side layer)    Middle class      Lower layer (current collector side)
No. 1 0.1-0.5 0.5-2.0 2.0-5.0
No. 2 0.1-0.5 2.0-5.0 0.5-2.0
No. 3 0.5-2.0 0.1-0.5 2.0-5.0
[0025]
The particle size (average particle size) of the positive electrode active material used in the present invention is not particularly limited, but is preferably in the range of 0.1 to 50 μm, and the volume of particles of 0.5 to 30 μm is 95% or more. Is preferred. More preferably, the volume occupied by a particle group having a particle size of 3 μm or less is 18% or less of the total volume, and the volume occupied by a particle group of 15 μm or more and 25 μm or less is 18% or less of the total volume.
[0026]
Moreover, it is preferable that the pH of the supernatant liquid when the positive electrode active material particles 5 g are dissolved in 100 mL of distilled water is 7 or more and 12 or less.
[0027]
For the positive electrode mixture of the positive electrode sheet, a binder for holding the active material is used. Examples of the binder include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Preferred binders include starch, carboxymethyl cellulose, cellulose, diacetyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone. Water-soluble polymers such as polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene furo Ride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene (Meth) acrylic acid ester copolymers containing (meth) acrylic acid esters such as ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, (meta ) Acrylic acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluoro rubber, polyethylene oxide, Emulsion (latex) or support of polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, phenol resin, epoxy resin, etc. Penjon can be mentioned. In particular, polyacrylate ester latex, carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride are exemplified. These binders are preferably those obtained by dispersing fine powders in water, more preferably those having an average particle size of 0.01 to 5 μm in the dispersion, and 0.05 to 1 μm. It is particularly preferable to use one.
[0028]
These binders can be used alone or in combination. When the amount of the binder added is small, the holding power and cohesion of the electrode mixture is weak. If the amount is too large, the electrode volume increases and the capacity per electrode unit volume or unit weight decreases. For this reason, the addition amount of the binder is preferably 1 to 30% by weight, and particularly preferably 2 to 10% by weight.
[0029]
Next, the negative electrode sheet used with the positive electrode sheet in the nonaqueous electrolyte secondary battery of the present invention will be described. The negative electrode material used in the negative electrode mixture of the nonaqueous electrolyte secondary battery of the present invention may be a compound that can occlude and release lithium ions. Examples of such negative electrode materials include metallic lithium, lithium alloys, carbonaceous compounds, inorganic oxides, inorganic chalcogen compounds, metal complexes, and organic polymer compounds. These may be used alone or in combination of a plurality of types.
[0030]
In the present invention, an amorphous chalcogen compound or an amorphous oxide mainly containing three or more kinds of atoms selected from Group 1, 2, 13, 14, and 15 atoms of the periodic table is particularly preferably used as the negative electrode material. The term “amorphous” as used herein refers to an X-ray diffraction method using CuKα rays, which has a broad scattering band having a peak at 20 ° to 40 ° with a 2θ value, and has a crystalline diffraction line. Also good. Preferably, the strongest intensity of the crystalline diffraction lines seen at 2θ values from 40 ° to 70 ° is the diffraction line intensity at the apex of the broad scattering band seen from 2 ° values to 20 ° to 40 °. It is preferably 500 times or less, more preferably 100 times or less, particularly preferably 5 times or less, and most preferably no crystalline diffraction line.
[0031]
The chalcogen compound and oxide are composite chalcogen compounds mainly composed of two or more elements of B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi, A composite oxide is more preferable. Particularly preferred are complex chalcogen compounds or oxides mainly composed of two or more elements of B, Al, Si, Ge, Sn, and P. These composite chalcogen compounds and composite oxides mainly contain at least one element selected from elements of Groups 1 to 2 of the periodic table in order to modify the amorphous structure.
[0032]
Among the above negative electrode materials, amorphous composite oxides mainly composed of Sn are preferable, and those represented by the following general formula (1) are particularly preferable.
SnM^Three _cM^Four _dO_t     ... (1)
In the above general formula (1), M^Three Is at least one of Al, B, P, Ge, and M^Four Represents at least one of Group 1 elements and Group 2 elements in the periodic table, c is a number of 0.2 or more and 2 or less, and d is a number of 0.01 or more and 1 or less (provided that 0.2 <C + d <2), and t represents a number of 1 or more and 6 or less.
[0033]
The amorphous composite oxide can employ either a firing method or a solution method, but a firing method is more preferable. In the firing method, it is preferable to obtain an amorphous composite oxide by thoroughly mixing oxides or compounds of the elements described in the general formula (1) and then firing.
[0034]
The firing conditions are preferably 5 ° C. or more and 200 ° C. or less as the rate of temperature rise, the firing temperature is preferably 500 ° C. or more and 1500 ° C. or less, and the firing time is 1 hour or more. And preferably 100 hours or less. In addition, the decreasing temperature rate is 10 at 2 ° C. or more per minute.⁷ It is preferable that it is below ℃. This rate of temperature increase is the average rate of temperature rise from “50% of the firing temperature (indicated in ° C.)” to “80% of the firing temperature (indicated in ° C.)”. It is the average rate of temperature drop from reaching “80% of (° C.)” to “50% of firing temperature (° C.)”.
[0035]
The temperature drop may be cooled in a firing furnace, or may be taken out of the firing furnace and cooled in, for example, water. In addition, a super rapid cooling method such as the gun method, the Hammer-Anvil method, the slap method, the gas atomization method, the plasma spray method, the centrifugal quenching method, or the melt drag method described on page 217 of ceramics processing (Gihodo Publishing, 1987) can also be used. Moreover, you may cool using the single-roller method of a new glass handbook (Maruzen, 1991) 172 pages, and the double roller method. In the case of a material that melts during firing, the fired product may be continuously taken out while supplying raw materials during firing. In the case of a material that melts during firing, it is preferable to stir the melt.
[0036]
The firing gas atmosphere is preferably an atmosphere having an oxygen content of 5% by volume or less, and more preferably an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, krypton, and xenon. The most preferred inert gas is pure argon.
[0037]
The average particle size of the negative electrode material particles in the negative electrode mixture layer is preferably 0.1 to 60 μm. More specifically, it is preferable that the average particle diameter is 0.7 to 25 μm, and 60% or more of the total volume is 0.5 to 30 μm. In the negative electrode material of the present invention, the volume occupied by particle groups having a particle size of 1 μm or less is preferably 30% or less of the total volume, and the volume occupied by particle groups having a particle size of 20 μm or more is preferably 25% or less of the total volume. Needless to say, the particle size of the material used does not exceed the thickness of the negative electrode material layer.
[0038]
To obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet. The average particle diameter is a median diameter of primary particles, and is measured by a laser diffraction type particle size distribution measuring apparatus.
The specific surface area of the negative electrode material particles is 0.1 to 5.0 m as measured by the BET specific surface area measurement method.² / G is preferable.
[0039]
Although the example of the negative electrode material which can be used with the nonaqueous electrolyte secondary battery of this invention is shown below, this invention is not limited to these.
SnAl_0.4 B_0.5 P_0.5 K_0.1 O_3.65, SnAl_0.4 B_0.5 P_0.5 Na_0.2 O_3.7 , SnAl_0.4 B_0.3 P_0.5 Rb_0.2 O_3.4 , SnAl_0.4 B_0.5 P_0.5 Cs_0.1 O_3.65, SnAl_0.4 B_0.5 P_0.5 K_0.1 Ge_0.05O_3.85, SnAl_0.4 B_0.5 P_0.5 K_0.1 Mg_0.1 Ge_0.02O_3.83, SnAl_0.4 B_0.4 P_0.4 O_3.2 , SnAl_0.3 B_0.5 P_0.2 O_2.7 , SnAl_0.3 B_0.5 P_0.2 O_2.7 , SnAl_0.4 B_0.5 P_0.3 Ba_0.08Mg_0.08O_3.26, SnAl_0.4 B_0.4 P_0.4 Ba_0.08O_3.28, SnAl_0.4 B_0.5 P_0.5 O_3.6 , SnAl_0.4 B_0.5 P_0.5 Mg_0.1 O_3.7 ,
[0040]
SnAl_0.5 B_0.4 P_0.5 Mg_0.1 F_0.2 O_3.65, SnB_0.5 P_0.5 Li_0.1 Mg_0.1 F_0.2 O_3.05, SnB_0.5 P_0.5 K_0.1 Mg_0.1 F_0.2 O_3.05, SnB_0.5 P_0.5 K_0.05Mg_0.05F_0.1 O_3.03, SnB_0.5 P_0.5 K_0.05Mg_0.1 F_0.2 O_3.03, SnAl_0.4 B_0.5 P_0.5 Cs_0.1 Mg_0.1 F_0.2 O_3.65, SnB_0.5 P_0.5 Cs_0.05Mg_0.05F_0.1 O_3.03, SnB_0.5 P_0.5 Mg_0.1 F_0.1 O_3.05, SnB_0.5 P_0.5 Mg_0.1 F_0.2 O_Three , SnB_0.5 P_0.5 Mg_0.1 F_0.06O_3.07, SnB_0.5 P_0.5 Mg_0.1 F_0.14O_3.03, SnPBa_0.08O_3.58, SnPK_0.1 O_3.55, SnPK_0.05Mg_0.05O_3.58, SnPCs_0.1 O_3.55, SnPBa_0.08F_0.08O_3.54, SnPK_0.1 Mg_0.1 F_0.2 O_3.55, SnPK_0.05Mg_0.05F_0.1 O_3.53, SnPCs_0.1 Mg_0.1 F_0.2 O_3.55, SnPCs_0.05Mg_0.05F_0.1 O_3.53,
[0041]
Sn_1.1 Al_0.4 B_0.2 P_0.6 Ba_0.08F_0.08O_3.54, Sn_1.1 Al_0.4 B_0.2 P_0.6 Li_0.1 K_0.1 Ba_0.1 F_0.1 O_3.65, Sn_1.1 Al_0.4 B_0.4 P_0.4 Ba_0.08O_3.34, Sn_1.1 Al_0.4 PCs_0.05O_4.23, Sn_1.1 Al_0.4 PK_0.05O_4.23, Sn_1.2 Al_0.5 B_0.3 P_0.4 Cs_0.2 O_3.5 , Sn_1.2 Al_0.4 B_0.2 P_0.6 Ba_0.08O_3.68, Sn_1.2 Al_0.4 B_0.2 P_0.6 Ba_0.08F_0.08O_3.64, Sn_1.2 Al_0.4 B_0.2 P_0.6 Mg_0.04Ba_0.04O_3.68, Sn_1.2 Al_0.4 B_0.3 P_0.5 Ba_0.08O_3.58, Sn_1.3 Al_0.3 B_0.3 P_0.4 Na_0.2 O_3.3 , Sn_1.3 Al_0.2 B_0.4 P_0.4 Ca_0.2 O_3.4 , Sn_1.3 Al_0.4 B_0.4 P_0.4 Ba_0.2 O_3.6 , Sn_1.4 Al_0.4 PK_0.2 O_4.6 , Sn_1.4 Al_0.2 Ba_0.1 PK_0.2 O_4.45, Sn_1.4 Al_0.2 Ba_0.2 PK_0.2 O_4.6 , Sn_1.4 Al_0.4 Ba_0.2 PK_0.2 Ba_0.1 F_0.2 O_4.9 , Sn_1.4 Al_0.4 PK_0.3 O_4.65, Sn_1.5 Al_0.2 PK_0.2 O_4.4 , Sn_1.5 Al_0.4 PK_0.1 O_4.65, Sn_1.5 Al_0.4 PCs_0.05O_4.63, Sn_1.5 Al_0.4 PCs_0.05Mg_0.1 F_0.2 O_4.63,
[0042]
SnSi_0.5 Al_0.1 B_0.2 P_0.1 Ca_0.4 O_3.1 , SnSi_0.4 Al_0.2 B_0.4 O_2.7 , SnSi_0.5 Al_0.2 B_0.1 P_0.1 Mg_0.1 O_2.8 , SnSi_0.6 Al_0.2 B_0.2 O_2.8 , SnSi_0.5 Al_0.3 B_0.4 P_0.2 O_3.55, SnSi_0.5 Al_0.3 B_0.4 P_0.5 O_4.30, SnSi_0.6 Al_0.1 B_0.1 P_0.3 O_3.25, SnSi_0.6 Al_0.1 B_0.1 P_0.1 Ba_0.2 O_2.95. SnSi_0.6 Al_0.1 B_0.1 P_0.1 Ca_0.2 O_2.95, SnSi_0.6 Al_0.4 B_0.2 Mg_0.1 O_3.2 , SnSi_{0. 6} Al_0.1 B_0.3 P_0.1 O_3.05, SnSi_0.6 Al_0.2 Mg_0.2 O_2.7 , SnSi_0.6 Al_0.2 Ca_0.2 O_2.7 , SnSi_0.6 Al_0.2 P_0.2 O_Three , SnSi_0.6 B_0.2 P_0.2 O_Three , SnSi_0.8 Al_0.2 O_2.9 , SnSi_0.8 Al_0.3 B_0.2 P_0.2 O_3.85, SnSi_0.8 B_0.2 O_2.9 , SnSi_0.8 Ba_0.2 O_2.8 , SnSi_0.8 Mg_0.2 O_2.8 , SnSi_0.8 Ca_0.2 O_2.8 , SnSi_0.8 P_0.2 O_3.1
[0043]
Sn_0.9 Mn_0.3 B_0.4 P_0.4 Ca_0.1 Rb_0.1 O_2.95, Sn_0.9 Fe_0.3 B_0.4 P_0.4 Ca_0.1 Rb_0.1 O_2.95, Sn_0.8 Pb_0.2 Ca_0.1 P_0.9 O_3.35, Sn_0.3 Ge_0.7 Ba_0.1 P_0.9 O_3.35, Sn_0.9 Mn_0.1 Mg_0.1 P_0.9 O_3.35, Sn_0.2 Mn_0.8 Mg_0.1 P_0.9 O_3.35, Sn_0.7 Pb_0.3 Ca_0.1 P_0.9 O_3.35, Sn_0.2 Ge_0.8 Ba_0.1 P_0.9 O_3.35,
[0044]
SnSi_0.8 B_0.2 O_2.9 , SnSi_0.7 B_0.3 O_2.85, SnSi_0.7 B_0.3 Al_0.1 O_3.0 , SnSi_0.5 B_0.3 Al_0.1 Mg_0.1 O_2.7 , Sn_0.8 Si_0.6 B_0.2 Al_0.1 Li_0.1 O_2.5 , Sn_0.8 Si_0.6 B_0.2 Al_0.1 Cs_0.1 O_2.65, Sn_0.8 Si_0.7 B_0.1 P_0.1 Al_0.1 O_2.75, Sn_0.8 Si_0.5 B_0.3 P_0.2 Al_0.1 O_2.9 , Sn_0.8 Si_0.7 B_0.1 P_0.1 Al_0.1 Li_0.05O_2.78, Sn_0.8 Si_0.5 B_0.3 P_0.1 Al_0.1 Li_0.1 O_2.7 , Sn_0.8 Si_0.5 B_0.3 P_0.2 Al_0.1 Cs_0.1 O_2.95, Sn_0.8 Si_0.7 P_0.3 O_2.95, Sn_0.8 Si_0.7 P_0.3 Al_0.1 O_3.1 , SnSi_0.5 B_0.3 Zr_0.1 O_2.65, Sn_0.8 Si_0.6 P_0.2 Zr_0.1 O_2.7 , Sn_0.8 Si_0.6 B_0.2 P_0.1 Zr_0.1 O_2.75.
[0045]
The chemical formula of the compound obtained by firing can be calculated from the weight difference between the powders before and after firing as an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method.
[0046]
The negative electrode material of the present invention can be used by inserting a light metal, particularly lithium. Examples of the insertion method in the case of using lithium include an electrochemical method, a chemical method, and a thermal method. Particularly preferred is an electrochemical method. For example, a small piece of lithium-based metal is pasted on the non-coated portion of the negative electrode mixture of the current collector or the negative electrode mixture layer, and inserted by contacting with an electrolytic solution. it can. In particular, a method of electrochemically inserting lithium in the battery is preferable. It is preferable that the metal piece mainly composed of lithium is pasted in the form of a strip having a thickness of 5 to 200 μm.
[0047]
Lithium can be inserted up to 0.01V, more preferably up to 0.05V when lithium is used as a counter electrode. A particularly preferable method is a method of partially inserting lithium in order to compensate for the irreversible capacity of the negative electrode material, and a method of inserting up to 0.3 V when lithium is used as a counter electrode.
[0048]
More specifically, the amount of lithium inserted is 0.005 g to 0.5 g, more preferably 0.03 g to 0.2 g, and particularly preferably 0.06 g to 0.15 g per 1 g of the negative electrode material. When the negative electrode material is a metal oxide, the equivalent per mole of metal oxide is 0.5 to 4.0 equivalent, more preferably 1 to 3.5 equivalent, and particularly preferably 1.2 to 3 .2 equivalents. When lithium less than 1.2 equivalents is preliminarily inserted into the negative electrode material, the battery capacity is low, and when more than 3.2 equivalents of lithium is preliminarily inserted, cycle performance is deteriorated.
[0049]
The amount of lithium inserted can be arbitrarily controlled by the amount of lithium superimposed on the negative electrode sheet. As the metal mainly composed of lithium, lithium metal is preferably used, but a metal having a purity of 90% by weight or more is preferable, and a metal having a purity of 98% by weight or more is particularly preferable. As the overlapping pattern of lithium on the negative electrode sheet, it is preferable to overlap the entire surface of the sheet, but since lithium preliminarily inserted into the negative electrode material gradually diffuses into the negative electrode material due to aging, it is not a full sheet, but a stripe, frame shape Also, any partial overlap of disk-like is preferable. The term “lamination” as used herein means that a metal foil mainly composed of lithium is directly bonded onto a sheet having a negative electrode mixture and an auxiliary layer.
[0050]
The coverage of the metal foil overlapping in the negative electrode sheet is preferably 10 to 100%, more preferably 15 to 100%, and particularly preferably 20 to 100%. When it is 20% or less, the preliminary insertion of lithium may become uneven, which is not preferable. Further, from the viewpoint of uniformity, the thickness of the metal foil mainly composed of lithium is preferably 5 to 150 μm, more preferably 5 to 100 μm, and particularly preferably 10 to 75 μm.
[0051]
The handling atmosphere such as cutting and sticking of the metal foil mainly composed of lithium is preferably a dry air or argon gas atmosphere having a dew point of −30 ° C. or lower and −80 ° C. or higher. In the case of dry air, −40 ° C. or lower and −80 ° C. or higher is more preferable. Carbon dioxide gas may be used in combination during handling. Particularly in the case of an argon gas atmosphere, it is preferable to use carbon dioxide in combination.
[0052]
Next, various materials and additives that can be arbitrarily introduced into each mixture layer of the negative electrode sheet used in combination with the positive electrode sheet in the positive electrode sheet and the nonaqueous electrolyte secondary battery of the present invention will be described.
[0053]
The conductive agent used in combination with the electrode mixture is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the constituted battery. Specific examples thereof include natural graphite such as scaly graphite, scaly graphite, and earthy graphite, high-temperature fired bodies such as petroleum coke, coal coke, celluloses, saccharides, and mesophase pitch, and artificial graphite such as vapor-grown graphite. Graphite, carbon black such as acetylene black, furnace black, ketjen black, channel black, lamp black, thermal black, etc., carbon materials such as asphalt pitch, coal tar, activated carbon, mesofuse pitch, polyacene, etc. Examples thereof include conductive fibers, metal powders such as copper, nickel, aluminum and silver, conductive whiskers such as zinc oxide and potassium titanate, and conductive metal oxides such as titanium oxide. Among these, graphite and carbon black are preferable, and the particle size is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.02 μm or more and 10 μm or less. These may be used singly or as a mixture.
The amount of the conductive agent added to the mixture layer is preferably 6 to 50% by weight, particularly 6 to 30% by weight, based on the negative electrode material or the positive electrode material. In the case of carbon black or graphite, the content is particularly preferably 6 to 20% by weight.
[0054]
For the negative electrode mixture, a binder for holding the active material is usually used in the same manner as the positive electrode mixture. As examples of the binder, various binders as described regarding the positive electrode mixture can be arbitrarily used.
[0055]
Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0 to 30 weight% is preferable.
As the ionic conductive agent, materials known as inorganic and organic solid electrolytes can be used, and details are described in the section of the electrolytic solution.
A pressure enhancer is a compound that increases the internal pressure of a battery, and carbonates such as lithium carbonate are typical examples.
[0056]
The collector sheet that can be used in the positive electrode sheet and the negative electrode sheet of the non-aqueous electrolyte secondary battery of the present invention is aluminum, stainless steel, nickel, titanium, or an alloy thereof for the positive electrode, copper for the negative electrode, Stainless steel, nickel, titanium, or an alloy thereof is used. The form of the current collector is foil, expanded metal, punching metal, or wire mesh. In particular, an aluminum foil is preferable for the current collector sheet for the positive electrode, and a copper foil is preferable for the current collector sheet for the negative electrode.
[0057]
Next, the structure of the positive / negative electrode sheet in a nonaqueous electrolyte secondary battery is demonstrated. The positive and negative electrode sheets are preferably in a form in which an electrode mixture is applied to both surfaces of the current collector sheet. In this case, the number of layers per side may be one or may be composed of two or more layers. When the number of layers per side is two or more, the positive electrode active material (or material) -containing layer may be two or more layers. A particularly preferable configuration is a case where the layer is composed of a layer containing a positive electrode active material (or negative electrode material) and a layer not containing a positive electrode active material (or negative electrode material).
[0058]
The layer not containing the positive electrode active material (or negative electrode material) includes a protective layer for protecting the layer (electrode mixture layer) containing the positive electrode active material (or negative electrode material), a divided positive electrode active material (or negative electrode) Material) an intermediate layer between the containing layers, an undercoat layer between the positive electrode active material (or negative electrode material) containing layer and the current collector sheet. In the present invention, these are collectively referred to as an auxiliary layer. .
[0059]
In the present invention, a particularly preferable configuration of the electrode sheet is a configuration having a protective layer on the surface. It is preferable that a protective layer exists in either the positive / negative electrode sheet or either positive / negative electrode sheet. In particular, in the negative electrode sheet, when lithium is inserted into the negative electrode mixture layer in the battery, the negative electrode sheet desirably has a protective layer. The protective layer is composed of at least one layer, and may be composed of multiple layers of the same type or different types. Moreover, the form which has a protective layer only in the single side | surface of the electrode mixture layers of both surfaces of a collector sheet may be sufficient. These protective layers are composed of water-insoluble particles and a binder. The binder used when forming the above-mentioned electrode mixture layer can be used as the binder. As the water-insoluble particles, various conductive particles and organic and inorganic particles having substantially no conductivity can be used. The solubility of water-insoluble particles in water is 100 ppm or less, preferably insoluble.
[0060]
The proportion of the particles contained in the protective layer is preferably 2.5% by weight or more and 96% by weight or less, more preferably 5% by weight or more and 95% by weight or less, and particularly preferably 10% by weight or more and 93% by weight or less. preferable.
Next, a material for forming the protective layer will be described.
[0061]
Examples of water-insoluble conductive particles include carbon particles such as metals, metal oxides, metal fibers, carbon fibers, carbon black, and graphite. Among these water-insoluble conductive particles, those having low reactivity with alkali metals, particularly lithium, are preferred, and metal powders and carbon particles are more preferred. The electrical resistivity at 20 ° C. of the elements constituting the particles is 5 × 10⁹ Ω · m or less is preferable.
[0062]
The metal powder is preferably a metal that has low reactivity with lithium, that is, a metal powder that is difficult to form a lithium alloy, and specifically, copper, nickel, iron, chromium, molybdenum, titanium, tungsten, and tantalum powders are preferred. . The shape of these metal powders may be any of acicular, columnar, plate-like, and massive shapes, and the maximum diameter is preferably 0.02 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less. These metal powders are preferably those whose surfaces are not excessively oxidized, and when oxidized, heat treatment is preferably performed in a reducing atmosphere.
[0063]
As the carbon particles, known carbon materials that are conventionally used as conductive materials that are used in combination when the electrode active material is not conductive can be used. Specifically, a conductive agent used for making an electrode mixture is used.
[0064]
Examples of water-insoluble particles having substantially no electrical conductivity include fine powders of tetrafluoroethylene, SiC, aluminum nitride, alumina, zirconia, magnesia, mullite, forsterite, steatite and the like. These particles may be used in combination with conductive particles, and are preferably used in an amount of 0.01 to 10 times that of the conductive particles.
[0065]
The positive (negative) electrode sheet can be prepared by applying a positive (negative) electrode mixture onto a current collector sheet, drying, and compressing.
The mixture is prepared by mixing a positive electrode active material (or negative electrode active material) and a conductive agent, adding a binder (suspension or emulsion of resin powder), and a dispersion medium, and kneading and mixing. In addition, it can be carried out by dispersing with a mixer / disperser such as a mixer, homogenizer, dissolver, planetary mixer, paint shaker or sand mill. As the dispersion medium, water or an organic solvent is used, but water is preferable. In addition, various additives such as a filler, an ionic conductive agent, and a pressure enhancer may be added as appropriate. The pH of the dispersion is preferably 5 to 10 for the negative electrode and 7 to 12 for the positive electrode.
[0066]
As described above, the formation of the positive electrode mixture layer for the production of the positive electrode sheet preferably uses a simultaneous multilayer coating layer.
Application of the mixture coating solution (mixture paste) for forming the negative electrode mixture layer of the negative electrode sheet can be performed by various methods. Examples thereof include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a slide method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. A method using an extrusion die and a method using a slide coater are particularly preferred. The application is preferably performed at a speed of 0.1 to 100 m / min. Under the present circumstances, the surface state of a favorable application layer can be obtained by selecting the said application | coating method suitably according to the liquid physical property and dryness of a mixture paste. When the electrode layer is a plurality of layers, it is preferable to apply the plurality of layers at the same time from the viewpoint of uniform electrode production, production cost, and the like. The thickness, length and width of the coating layer are determined by the size of the battery. The thickness of a typical coating layer is 10 to 1000 μm in a compressed state after drying.
[0067]
The electrode sheet after application is dried and dehydrated by the action of hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air. These methods can be used alone or in combination. The drying temperature is preferably in the range of 80 to 350 ° C, particularly preferably in the range of 100 to 250 ° C. The water content after drying is preferably 2000 ppm or less, and more preferably 500 ppm or less.
[0068]
For the compression of the electrode sheet, a generally employed pressing method can be used, but a die pressing method and a calendar pressing method are particularly preferable. The press pressure is not particularly limited, but is 10 kg / cm.² ~ 3t / cm² Is preferred. The press speed of the calendar press method is preferably 0.1 to 50 m / min. The pressing temperature is preferably room temperature to 200 ° C.
[0069]
The separator that can be used in the secondary battery of the present invention only needs to have a large ion permeability, a predetermined mechanical strength, and an insulating thin film. As a material, an olefin polymer, a fluorine polymer, a cellulose polymer, Polyimide, nylon, glass fiber, and alumina fiber are used, and as a form, a nonwoven fabric, a woven fabric, and a microporous film are used. In particular, polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and tetrafluoroethylene, and a mixture of polyethylene and Teflon are preferred as the material, and a form of a microporous film is preferred. In particular, a microporous film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable. These microporous films may be a single film or a composite film composed of two or more layers having different properties such as the shape, density, and material of the micropores. For example, the composite film which bonded the polyethylene film and the polypropylene film can be mentioned.
[0070]
The electrolytic solution is generally composed of a supporting salt and a solvent. Lithium salt is mainly used as the supporting salt in the lithium secondary battery.
Examples of lithium salts that can be used in the present invention include LiClO._Four , LiBF_Four , LiPF₆ , LiCF_Three SO_Three , LiCF_Three CO₂ , LiAsF₆ , LiSbF₆ , LiB_TenCl_Ten, Lower aliphatic lithium carboxylate, LiAlCl_Four Li salts such as LiCl, LiBr, LiI, chloroborane lithium and lithium tetraphenylborate can be used, and one of these can be used alone, or two or more can be used in combination. Above all, LiBF_Four And / or LiPF₆ What melt | dissolved is preferable.
The concentration of the supporting salt in the electrolytic solution is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.
[0071]
Solvents of the electrolytic solution that can be used in the present invention include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, dioxane, acetonitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, Such as sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, etc. Can be exemplified ton organic solvent, mixed and used alone or in combination. Among these, carbonate-based solvents are preferable, and it is particularly preferable to use a mixture of a cyclic carbonate and an acyclic carbonate. As the cyclic carbonate, ethylene carbonate and propylene carbonate are preferable. Moreover, as an acyclic carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate are preferable.
[0072]
As an electrolytic solution that can be used in the present invention, LiCF is added to an electrolytic solution in which ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate or diethyl carbonate is appropriately mixed._Three SO_Three LiClO_Four , LiBF_Four And / or LiPF₆ An electrolytic solution containing is preferable. In particular, in a mixed solvent of at least one of propylene carbonate or ethylene carbonate and at least one of dimethyl carbonate or diethyl carbonate, LiCF_Three SO_Three LiClO_Four Or LiBF_Four At least one salt selected from LiPF and LiPF₆ An electrolytic solution containing is preferable. The amount of the electrolyte added to the battery is not particularly limited, and can be used according to the amount of the positive electrode mixture or the negative electrode mixture and the size of the battery.
[0075]
Further, other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine, pyrroline, pyrrole, triphenylamine, phenylcarbazole, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N , N′-substituted imidazolidinone, ethylene glycol dialkyl ether, quaternary ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, AlCl_Three , Conductive polymer electrode active material monomers, triethylene phosphoramide, trialkylphosphine, morpholine, aryl compounds having a carbonyl group, crown ethers such as 12-crown-4, hexamethylphosphoric triamide and 4-alkyl Examples thereof include morpholine, bicyclic tertiary amine, oil, quaternary phosphonium salt, and tertiary sulfonium salt. Particularly preferred is a case where triphenylamine and phenylcarbazole are used alone or in combination.
[0076]
In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte. In addition, carbon dioxide gas can be included in the electrolyte in order to make it suitable for high-temperature storage.
[0077]
It is desirable that the electrolytic solution contains as little water and free acid as possible. For this reason, the raw material of the electrolytic solution is preferably one that has been sufficiently dehydrated and purified. The electrolyte solution is preferably prepared in dry air having a dew point of -30 ° C or lower, or in an inert gas. The amount of water and free acid content in the electrolyte is 0.1 to 500 ppm, more preferably 0.2 to 100 ppm.
[0078]
The entire amount of the electrolytic solution may be injected at one time, but it is preferable to inject it in two or more times. When injecting in two or more times, each solution may have the same composition but a different composition (for example, a non-aqueous solvent or a non-aqueous solvent having a higher viscosity than the solvent after injecting a solution of a lithium salt dissolved in the non-aqueous solvent). Or a solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent may be injected). In order to shorten the time for injecting the electrolyte, etc., the battery can may be decompressed, or centrifugal force or ultrasonic waves may be applied to the battery can.
[0079]
Battery cans and battery lids that can be used in the present invention are nickel-plated steel plates, stainless steel plates (SUS304, SUS304L, SUS304N, SUS316, SUS316L, SUS430, SUS444, etc.), nickel-plated stainless steel plates (same as above) , Aluminum or an alloy thereof, nickel, titanium, and copper, and the shapes are a true circular cylinder, an elliptical cylinder, a square cylinder, and a rectangular cylinder. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate and a nickel-plated steel plate are preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum, or an alloy thereof is preferable. The shape of the battery can may be any of buttons, coins, sheets, cylinders, and corners. As a countermeasure against an increase in the internal pressure of the battery can, a safety valve can be attached to the sealing plate. In addition, a method of cutting a member such as a battery can or a gasket can be used. In addition, various conventionally known safety elements (for example, fuses, bimetals, PTC elements, etc. as overcurrent prevention elements) may be provided.
[0080]
For the lead plate used in the present invention, a metal having electrical conductivity (for example, iron, nickel, titanium, chromium, molybdenum, copper, aluminum, etc.) or an alloy thereof can be used. As a welding method for the battery lid, battery can, electrode sheet, and lead plate, a known method (eg, direct current or alternating current electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.
[0081]
Gaskets that can be used in the present invention are olefin polymers, fluoropolymers, cellulosic polymers, polyimides, and polyamides as materials. Olefin polymers are preferred from the viewpoint of organic solvent resistance and low moisture permeability, and are mainly composed of propylene. Polymers are preferred. Furthermore, a block copolymer of propylene and ethylene is preferable.
[0082]
The secondary battery assembled as described above is preferably subjected to an aging treatment. The aging treatment includes pre-treatment, activation treatment, post-treatment, and the like, whereby a battery with high charge / discharge capacity and excellent cycleability can be produced. The pretreatment is a treatment for homogenizing the distribution of lithium in the electrode. For example, control of lithium dissolution, temperature control to make the lithium distribution uniform, oscillation and / or rotation treatment, optional charging / discharging A combination is made. The activation process is a process for inserting lithium into the negative electrode of the battery body, and it is preferable to insert 50 to 120% of the amount of lithium inserted during actual use charging of the battery. The post-processing is processing for sufficient activation processing, and includes storage processing for uniform battery reaction and charge / discharge processing for determination, which can be arbitrarily combined.
[0083]
The battery of the present invention is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, and a plastic case. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be known.
[0084]
A plurality of the batteries of the present invention are assembled in series and / or in parallel as needed, and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, temperature fuses, fuses and / or current interrupting elements, the battery pack also requires safety circuits (monitoring the voltage, temperature, current, etc. of each battery and / or the entire battery pack) In this case, a circuit having a function of interrupting current may be provided. In addition to the positive and negative terminals of the entire assembled battery, the battery pack should be provided with the positive and negative terminals of each battery, the entire assembled battery, the temperature detection terminal of each battery, the current detection terminal of the entire assembled battery, etc. as external terminals. You can also. The battery pack may incorporate a voltage conversion circuit (such as a DC-DC converter). The connection of each battery may be fixed by welding a lead plate, or may be fixed so that it can be easily attached and detached with a socket or the like. Further, the battery pack may be provided with display functions such as the remaining battery capacity, the presence / absence of charging, and the number of uses.
[0085]
The battery of the present invention is used in various devices. In particular, video movies, portable video decks with built-in monitors, movie cameras with built-in monitors, compact cameras, single-lens reflex cameras, film with lenses, notebook computers, notebook word processors, electronic notebooks, mobile phones, cordless phones, whiskers, electric tools, It is preferably used for electric mixers, automobiles and the like.
[0086]
【Example】
The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.
[0087]
[Example 1]
1) Preparation of positive electrode mixture coating liquid (paste) A
Cathode active material; LiCoO₂ (A mixture of lithium carbonate and tricobalt tetroxide in a molar ratio of 3: 2 is placed in an alumina crucible, heated to 750 ° C. at 2 ° C./min in the air, calcined for 4 hours, and then 2 min / min. The temperature was raised to 900 ° C. at a rate of 0 ° C., baked and pulverized at that temperature for 8 hours, and the electrical conductivity of the dispersion liquid was 0.6 mS / m when the center particle size was 5 μm and the washing product was dispersed in 100 ml of water. , PH is 10.1, specific surface area by nitrogen adsorption method is 0.42m² / G)
200 g of the positive electrode active material and 10 g of acetylene black were mixed with a homogenizer, and then an aqueous dispersion of a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile (solid content concentration 50% by weight) was used as a binder. 60 g of a carboxymethyl cellulose aqueous solution having a concentration of 8 g and 2 wt% was added and kneaded and mixed, 50 g of water was further added, and the mixture was stirred and mixed with a homogenizer to prepare a positive electrode mixture paste A.
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2) Preparation of positive electrode mixture coating liquid (paste) B
By the same method as above, the specific surface area in the nitrogen adsorption method is 0.89 m.² / G positive electrode active material (LiCoO₂ The positive electrode mixture paste B was prepared in the same manner.
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3) Preparation of negative electrode mixture coating liquid (paste)
Negative electrode material; SnGe_0.1 B_0.5 P_0.58Mg_0.1 K_0.1 O_3.35(6.7 g of tin monoxide, 10.3 g of tin pyrophosphate, 1.7 g of diboron trioxide, 0.7 g of potassium carbonate, 0.4 g of magnesium oxide, and 1.0 g of germanium dioxide were dry-mixed and placed in an alumina crucible. The temperature was raised to 1000 ° C. at 15 ° C./min in an argon atmosphere, baked at 1100 ° C. for 12 hours, cooled to room temperature at 10 ° C./min, collected from the baking furnace, and pulverized with a jet mill In the X-ray diffraction method using an average particle diameter of 4.5 μm and CuKα ray, the material has a broad peak having a peak at around 28 ° with a 2θ value, and the crystallinity at a 2θ value of 40 ° to 70 ° No diffraction line was seen.)
200 g of the negative electrode material, 30 g of a conductive agent (artificial graphite) and a homogenizer are mixed, and 50 g of a 2% by weight carboxymethylcellulose aqueous solution and 10 g of polyvinylidene fluoride are mixed as a binder, and 30 g of water is added. The mixture was kneaded and mixed to prepare a negative electrode mixture paste.
[0090]
4) Preparation of positive electrode sheet
The positive electrode mixture paste A and the positive electrode mixture paste B prepared above were each applied in the order described in Table 1 using the simultaneous multilayer coating method, and the total coating amount was 400 g / g on both surfaces of the 20 μm thick aluminum foil current collector. m² The film was applied so that the total thickness of the compressed sheet was 280 μm, dried, and then compression-molded with a roller press and cut into a predetermined size to prepare a belt-like positive electrode sheet. Further, it was sufficiently dehydrated and dried with a far-infrared heater in a dry box (dew point: dry air of −50 ° C. or lower) to prepare five types of positive electrode sheets (No. 1 to No. 5). In addition, a sequential coating method in which the mixture paste B is first applied to both surfaces of an aluminum foil current collector having a thickness of 20 μm, the coating layer is dried, and then the mixture paste A is coated and dried on the surface of the dried coating layer. Except for the points used, no. A mixture layer composed of the mixture A and the mixture B was formed in the same manner at the same coating amount ratio as in Example 1 to obtain a positive electrode sheet (No. 6).
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[Table 3]
Table 1
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Positive electrode sheet sample number Lower layer Upper layer Coating amount ratio (upper layer / lower layer)
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No. 1 (Product of the present invention) Mixture B Mixture A 1/1 (Simultaneous multilayer coating)
No. 2 (Invention product) Mixture B Mixture A 1/3 (simultaneous multilayer coating)
No. 3 (Comparative Example) Mixture A Mixture A 1/1 (simultaneous multilayer coating)
No. 4 (Comparative example) Mixture B Mixture B 1/1 (simultaneous multilayer coating)
No. 5 (Comparative Example) Mixture A Mixture B 1/1 (simultaneous multilayer coating)
No. 6 (Comparative Example) Mixture B Mixture A 1/1 (Sequential application)
────────────────────────────────────
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5) Preparation of negative electrode sheet
Similarly, the negative electrode mixture paste was applied to a 20 μm copper foil current collector, and the coating amount was 70 g / m in the same manner as in the preparation of the positive electrode sheet.² A negative electrode sheet having a thickness of 90 μm after compression was prepared.
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6) Preparation of electrolyte
In an argon atmosphere, 65.3 g of diethyl carbonate was placed in a 200 mL narrow-neck polypropylene container, and 22.2 g of ethylene carbonate was dissolved little by little while taking care that the liquid temperature did not exceed 30 ° C. Next, 0.4 g of LiBF_Four , 12.1 g LiPF₆ Were dissolved in small amounts in the polypropylene container in order, taking care that the liquid temperature did not exceed 30 ° C. The obtained electrolyte was a colorless and transparent liquid with a specific gravity of 1.135. Moisture content is 18ppm (Kyoto Electronics, trade name MKC-210 model Karl Fischer moisture measuring device), free acid content is 24ppm (bromthymol blue is used as an indicator, neutralized titration with 0.1N NaOH aqueous solution. Measured).
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7) Creation of cylinder battery
A positive electrode sheet, a microporous polyethylene / polypropylene film separator, a negative electrode sheet and a separator were laminated in this order, and this was wound in a spiral shape. This wound body is housed in a nickel-plated iron-bottomed cylindrical battery can that also serves as a negative electrode terminal, then an electrolyte is injected into the battery can, and the battery lid having the positive electrode terminal is caulked through a gasket. A cylindrical battery (cylinder battery) was prepared.
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8) Evaluation of cylinder battery
Ten cylinder batteries were prepared for each positive electrode sheet sample, and each battery had a current of 1 mA / cm at room temperature.² The battery was charged to 4.2 V and then discharged to 2.6 V, and the discharge capacity was measured. Then, the average discharge capacity (initial average discharge capacity) was determined by averaging the discharge capacity of 10 cylinder batteries using each positive electrode sheet. Then, for these batteries, the above charge and discharge cycle was repeated 300 times, and when the repetition was completed, the average discharge capacity (average discharge capacity after cycle) was determined in the same manner. Then, the ratio of the average post-cycle discharge capacity to the initial average discharge capacity was calculated to obtain the cycle maintenance ratio. The results obtained in these tests are shown in Table 2.
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[Table 4]

[0097]
From the results in Table 2, it can be seen that the lithium secondary battery using the positive electrode sheet of the present invention exhibits a high discharge capacity and maintains a high discharge capacity even after repeated use.
[0098]
【The invention's effect】
The positive electrode sheet of the present invention makes it possible to produce a nonaqueous electrolyte secondary battery that has a high discharge capacity and can maintain a high discharge capacity even during repeated use.

Claims (5)

A positive electrode sheet comprising a current collector sheet made of aluminum and a positive electrode mixture layer containing positive electrode active material particles and a binder formed on the surface of at least one side of the current collector sheet, the positive electrode The mixture layer includes a coating liquid containing positive active material particles having a relatively large specific surface area and a binder, and a coating liquid containing positive active material particles having a relatively small specific surface area and a binder , It is a layer formed by a method in which the specific surface area is simultaneously applied in such a distribution that it is small on the surface side of the positive electrode mixture layer and large on the side of the current collector sheet , and then the applied layers are simultaneously dried . A positive electrode sheet for a non-aqueous electrolyte secondary battery, wherein the amount of binder added in each positive electrode mixture layer is 1 to 30% by weight . The positive electrode sheet for a non-aqueous electrolyte secondary battery according to claim 1, wherein the chemical composition of the positive electrode active material particles is the same throughout the positive electrode mixture layer. The positive electrode active material _{particles, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co a Ni 1-a O 2, Li x Mn 2 O 4, and _{Li x Co b V 1-b} O _z (where x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.9 to 0.98, z = 2.01 to 2.3) The positive electrode sheet for non-aqueous electrolyte secondary batteries according to claim 1 or 2, which has a chemical composition represented by :   The positive electrode sheet for nonaqueous electrolyte secondary batteries according to any one of claims 1 to 3, wherein the solvent of the coating liquid containing the positive electrode active material particles and the binder is water. A positive electrode sheet, a negative electrode sheet, and a lithium salt-containing electrolyte are accommodated in an airtight container, and the positive electrode sheet is the positive electrode sheet according to any one of claims 1 to 4. Non-aqueous electrolyte secondary battery.