Lithium ion secondary battery and charging method therefor
View Patent ↗A method for charging a lithium ion secondary battery including at least a positive electrode, a negative electrode provided with a negative electrode active material layer that includes carbon as a negative electrode active material, an electrolytic solution, and a sheathing material that encloses the positive electrode, the negative electrode and the electrolytic solution; the negative electrode active material layer including carboxymethyl cellulose and the electrolytic solution including an additive that can be decomposed at a predetermined voltage includes: preliminary charging including constant-current charging in which charging is performed at a fixed current value and, following the constant-current charging, constant-voltage charging in which charging is performed at a fixed voltage; degassing in which gas is removed from within the sheathing material after the preliminary charging; and main charging that follows the degassing in which the lithium ion secondary battery is charged. The fixed voltage during the constant-voltage charging is at least 3.3 V per cell.
1. A charging method of a lithium ion secondary battery that comprises at least a positive electrode, a negative electrode that is provided with a negative electrode active material layer that contains carbon as a negative electrode active material, an electrolytic solution, and a sheathing material that encapsulates said positive electrode, said negative electrode and said electrolytic solution; wherein said negative electrode active material layer contains carboxymethyl cellulose and said electrolytic solution contains an additive that can be decomposed at a predetermined voltage; the charging method comprising:
preliminary charging that includes constant-current charging in which charging is carried out at a fixed current and, following the constant-current charging, constant-voltage charging in which charging is carried out at a fixed voltage;
degassing that extracts gas from an interior of said sheathing material following said preliminary charging; and
main charging that charges said lithium ion secondary battery after said degassing,
wherein said fixed voltage in said constant-voltage charging is at least 3.3 V per cell.
2. The charging method as set forth in claim 1 , wherein charging capacity per unit mass of said negative electrode active material in said preliminary charging is 17 mAh/g or more.
3. The charging method as set forth in claim 1 , wherein specific surface area of said negative electrode active material is 1.6 m 2 /g or more.
4. The charging method as set forth in claim 1 , wherein said negative electrode active material layer contains 95.5 mass percent or more of simple substance carbon.
5. The charging method as set forth in claim 1 , wherein a surface of said negative electrode active material is covered by 0.2 to 7 parts by mass of amorphous carbon with respect to 100 parts by mass of said negative electrode active material.
6. The charging method as set forth in claim 1 , wherein an area of sites in which precipitate is present on a surface of said negative electrode active material layer is no greater than 0.5% with respect to an area of the surface of said negative electrode active material layer at the time of completion of said main charging.
7. The charging method as set forth in claim 2 , wherein specific surface area of said negative electrode active material is 1.6 m 2 /g or more.
8. The charging method as set forth in claim 2 , wherein said negative electrode active material layer contains 95.5 mass percent or more of simple substance carbon.
9. The charging method as set forth in claim 2 , wherein a surface of said negative electrode active material is covered by 0.2 to 7 parts by mass of amorphous carbon with respect to 100 parts by mass of said negative electrode active material.
10. The charging method as set forth in claim 2 , wherein an area of sites in which precipitate is present on a surface of said negative electrode active material layer is no greater than 0.5% with respect to an area of the surface of said negative electrode active material layer at the time of completion of said main charging.
11. A charging method of a lithium ion secondary battery that comprises at least a positive electrode, a negative electrode that is provided with a negative electrode active material layer that contains carbon as a negative electrode active material, an electrolytic solution, and a sheathing material that encapsulates said positive electrode, said negative electrode and said electrolytic solution; wherein said negative electrode active material layer contains carboxymethyl cellulose and said electrolytic solution contains an additive that can be decomposed at a predetermined voltage; the charging method comprising:
preliminary charging that includes constant-current charging in which charging is carried out at a fixed current and, following the constant-current charging, constant-voltage charging in which charging is carried out at a fixed voltage;
degassing that extracts gas from an interior of said sheathing material following said preliminary charging; and
main charging that charges said lithium ion secondary battery after said degassing,
wherein charging capacity per unit mass of said negative electrode active material in said preliminary charging is at least 17 mAh/g.
12. The charging method as set forth in claim 11 , wherein specific surface area of said negative electrode active material is 1.6 m 2 /g or more.
13. The charging method as set forth in claim 11 , wherein said negative electrode active material layer contains 95.5 mass percent or more of simple substance carbon.
14. The charging method as set forth in claim 11 , wherein a surface of said negative electrode active material is covered by 0.2 to 7 parts by mass of amorphous carbon with respect to 100 parts by mass of said negative electrode active material.
15. The charging method as set forth in claim 11 , wherein an area of sites in which precipitate is present on a surface of said negative electrode active material layer is no greater than 0.5% with respect to an area of the surface of said negative electrode active material layer at the time of completion of said main charging.
16. A lithium ion secondary battery comprising at least:
a positive electrode;
a negative electrode that is provided with a negative electrode active material layer that contains carbon as a negative electrode active material;
an electrolytic solution; and
a sheathing material that encapsulates said positive electrode, said negative electrode and said electrolytic solution,
wherein said negative electrode active material layer contains carboxymethyl cellulose and said electrolytic solution contains an additive that can be decomposed at a predetermined voltage, and
wherein an area of sites on which a precipitate is present on a surface of said negative electrode active material layer after being discharged to 3 V after having been fully charged is no greater than 0.5% of an area of the surface of said negative electrode active material layer,
wherein the lithium ion secondary battery is charged, in a process of the lithium ion secondary battery, by means of a charging method comprising:
preliminary charging that includes constant-current charging in which charging is carried out at a fixed current and, following the constant-current charging, constant-voltage charging in which charging is carried out at a fixed voltage;
degassing that extracts gas from an interior of said sheathing material following said preliminary charging; and
main charging that charges said lithium ion secondary battery after said degassing,
wherein the preliminary charging satisfies at least one of conditions of (a) said fixed voltage in said constant-voltage charging being at least 3.3 V per cell; and (b) charging capacity per unit mass of said negative electrode active material being at least 17 mAh/g.