Electrode composition, electrode, and battery

[0097] Example 1

[0098]Under nitrogen ambient atmosphere, 674.9 parts of deionized water, 7.1 parts of 28% sodium lauryl sulfate aqueous solution, and 0.8 parts of sodium tripolyphosphate were supplied to the reactor equipped with a stirrer and a condenser. The contents of the reactor were then heated to 75°C while stirring. Then, 82 parts of 2.44% ammonium persulfate aqueous solution was added to the reactor as an aqueous initiator solution, and then 400 parts of monomer compositions having the composition shown in Table 1 were added to the reactor at a constant rate over 2 hours. After the addition, the reaction temperature was kept at 80°C and the reaction was continued for 3 hours to obtain a copolymer latex. The polymerization conversion rate was 99%, and the composition ratio of the polymer coincided with that of the monomer composition. Ammonia water was added to this latex to adjust the pH to 7, and then concentrated under reduced pressure to remove residual monomers, and the solid content concentration was 40%.

[0099] Then, according to the method described in Japanese Patent Laid-Open No. 2003-36889, an olivine-structured LiFePO containing 1.6% of carbon and having a 50% volume cumulative diameter of 2.9 μm was produced. 4 as a positive electrode active material. That is, put LiH 2 PO 4 and FeC 2 o 4 2H 2 O and acetylene black were mixed with a sand mixer at a molar ratio of Li:Fe:C=1:1:0.4, and the mixture was calcined at 650° C. for 6 hours in an argon flow, and then pulverized to produce the positive electrode active material.

[0100] Add 7.5 parts of latex prepared above (3 parts of copolymer (P) component, 4.5 parts of water), and 75 parts of a 2% aqueous solution of carboxymethylcellulose (Selogen WSC, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) as a thickener , 100 parts of the above-mentioned positive electrode active material, 10 parts of acetylene black as a conductive material and water, so that the solid content is 60%, use a bead mill to mix for 45 minutes at a speed of 750 rpm at room temperature, and obtain an electrode composition slurry material.

[0101] The prepared electrode composition slurry was evenly coated on an aluminum foil with a thickness of 20 μm by a doctor blade method, and dried at 120° C. using a dryer for 15 minutes. Table 1 shows the results of measuring the surface roughness (Ra) of the obtained electrodes. Next, it was compressed using a 2-axis roll press, and then dried under reduced pressure at 0.6 kPa and 250° C. for 10 hours using a vacuum dryer to obtain an electrode for positive electrodes with an active material layer thickness of 110 μm. Table 1 shows the results of evaluating the peel strength and flexibility of the obtained pressurized positive electrode.

[0102] Then, the obtained electrode for a positive electrode was cut into a circle having a diameter of 15 mm. On the active material layer side of the electrode, a separator made of a circular polypropylene porous membrane with a diameter of 18 mm and a thickness of 25 μm, metal lithium used as a negative electrode, and expanded metal were sequentially stacked, and then accommodated in a polypropylene gasket. In a coin-shaped outer container made of stainless steel (diameter 20mm, height 1.8mm, stainless steel thickness 0.25mm). The electrolyte solution was injected into the container so that no air remained, and a stainless steel cover with a thickness of 0.2 mm was fixed on the outer container through a polypropylene gasket, and the battery can was sealed to manufacture a coin-shaped battery with a diameter of 20 mm and a thickness of about 2 mm. As an electrolyte solution, dissolve ethylene carbonate (EC) and diethyl carbonate (DEC) at a concentration of 1 mol/liter in a mixed solvent of EC:DEC=1:2 (volume ratio at 20°C). Make LiPF 6 The solution. Table 1 shows the results of measuring various characteristics of the produced batteries.

[0103] Table 1

[0104] Example

[0105] * 1. Composition of the monomer composition (values ​​in parentheses are % by weight)

[0106] Example 1 2EHA(74)/BA(20)/AN(5)/EDMA(1)

[0107] Example 2 2EHA(64)/BA(20)/AN(15)/EDMA(1)

[0123] Example 3

[0124] Except using a monomer combination comprising 296 parts of 2-ethylhexyl acrylate (2EHA), 80 parts of butyl acrylate (BA), 20 parts of acrylonitrile (AN) and 4 parts of ethylene glycol dimethacrylate (EDMA) A copolymer latex having a solid content concentration of 40% was obtained in the same manner as in Example 1 except that the monomer composition was used as the monomer composition. Further, a carbon containing 1.6% was produced in the same manner as in Example 1 from this copolymer latex. LiFePO with an olivine structure with a 50% volume cumulative diameter of 2.9 μm 4 as a positive electrode active material.

[0125] Using the obtained positive electrode active material, an electrode having an active material layer thickness of 120 μm was produced in the same manner as in Example 1. Table 2 shows the results of measuring the surface roughness (Ra) of the prepared electrodes.

[0126] In addition, this electrode was compressed and dried under reduced pressure in the same manner as in Example 1 to prepare an electrode for positive electrodes having an active material layer having a thickness of 100 μm. Table 2 shows the results of evaluating the peel strength and flexibility of the obtained compressed positive electrode.

[0127] Next, a battery was produced in the same manner as in Example 1 from the obtained positive electrode. Table 2 shows the results of measuring various characteristics of the produced batteries.

[0128] Table 2

[0129] Example