CHARGE STATE ESTIMATION METHOD FOR LITHIUM ION BATTERY AND CHARGE STATE ESTIMATION DEVICE FOR LITHIUM ION BATTERY

摘要

Provided is a method for estimating the charge state on the basis of the voltage change rate in a lithium ion battery that uses, in the positive electrode, a lithium phosphate compound having an olivine crystal structure, and in the negative electrode, an active substance in which the electric potential is not varied by a lithium insertion/extraction reaction, the method comprising: a first step for storing a map indicating the correspondence between the voltage change rate and the charge state at a plurality of charge/discharge rates; a second step for determining present charge state candidates by referring to the map, using measured voltage change rates calculated on the basis of values measured during charging/discharging; and a third step for determining the present charge state by comparing a charge state candidate determined during charging with a charge state candidate determined during discharging.