Battery, method of charging and discharging the battery and charge-discharge control device for the battery

Abstract

Provided is a battery capable of improving cycle characteristics through reducing a structural fracture according to charge and discharge of an anode and a reaction of the with an electrolyte. An anode active material layer includes at least one kind selected from the group consisting of a simple substance and alloys of Si capable of forming an alloy with Li. A cathode and an anode are formed so that the molar ratio Li / Si in the anode at the time of charge is 4.0 or the potential of the anode vs. Li is 0.04 V or more through adjusting, for example, a ratio between a cathode active material and an anode active material. Moreover, the cathode and the anode are formed so that the molar ratio Li / Si in the anode at the time of discharge is 0.4 or more, or the potential of the anode vs. Li is 1.4 V or less.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a battery comprising an anode which includes silicon (Si) as an element and is capable of inserting and extracting lithium (Li), a method of charging and discharging the battery, and a charge-discharge control device for the battery. [0003] 2. Description of the Related Art [0004] In recent years, as mobile devices have become more sophisticated and multifunctional, a demand for higher capacity of secondary batteries as power sources for the mobile devices has been made. As a secondary battery which meets the demand, a lithium secondary battery is cited. However, in a currently typical lithium secondary battery which uses lithium cobalt oxide for a cathode and graphite for an anode, its battery capacity has reached the saturation point, so it is extremely difficult to significantly increase its capacity. Therefore, using lithium metal for an anode has been considered since a long tim...

AI Technical Summary

Benefits of technology

[0007] In view of the foregoing, it is an object of the invention to provide a battery capable of improving cycle characteristics through reducing a structural fracture of an anode according to charge and discharge and reactivity with an electrolyte, a method of charging and discharging the battery, and a charge-discharge control device for the battery.

[0014] In the first battery, the first method of charging and discharging a battery, and the first charge-discharge control device according to the invention, the molar ratio of lithium atoms to silicon atoms (Li / Si) in the anode is 4.0 or less, or in the second battery, the second method of charging and discharging a battery, and the second charge-discharge control device according to the invention, the potential of the anode vs. lithium metal as a reference potential is 0.04 V or more, so an overreaction between the anode and the electrolyte and a structural fracture of the anode due to expansion and shrinkage of the anode can be prevented. Therefore, cycle characteristics can be improved.

[0015] In particular, when the molar ratio of lithium atoms to silicon atoms (Li / Si) in the anode is 0.4 or more, or when the potential of the anode vs. lithium metal as a reference potential is 1.4 V or less, the cycle characteristics can be further improved.

[0016] Moreover, when the electrolyte include at least one kind selected from the group consisting of a cyclic carbonate having an unsaturated bond and a carbonate derivative containing a halogen atom, the cycle characteristics can be further improved, and storage characteristics and the like can be improved.

Problems solved by technology

However, in a currently typical lithium secondary battery which uses lithium cobalt oxide for a cathode and graphite for an anode, its battery capacity has reached the saturation point, so it is extremely difficult to significantly increase its capacity.

However, when charge and discharge are repeated, the anode with a high capacity is broken into small pieces due to severe expansion and shrinkage of an active material, thereby a current collecting property declines, and the decomposition of an electrolyte solution is accelerated due to an increase in a surface area, so cycle characteristics are extremely poor.

However, even in the anode, cycle characteristics are not sufficient, because the active material falls off due to expansion and shrinkage of the active material according to charge and discharge.

Moreover, reactivity with an electrolyte is still high, so a reaction of the anode with the electrolyte according to charge and discharge causes a decline in the capacity of the battery.

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