Systems and control devices for charging and discharging lithium-ion battery, and relevant methods

A system for charging or discharging a lithium-ion battery, comprising:

• a variable frequency triggering oscillation charging/discharging device, which forms an oscillation loop with the lithium-ion battery to generate two or more oscillation currents for charging or discharging the lithium-ion battery;
• and
• a control device that controls the variable frequency triggering oscillation charging/discharging device to supply two or more oscillation currents to the lithium-ion battery according to temperature and a State of Charge (SOC) of the lithium-ion battery of the lithium-ion battery, wherein:
• the variable frequency triggering oscillation charging/discharging device is to be coupled between a first charging device for charging or a load for discharging and the lithium-ion battery;
• and
• the two or more oscillation currents include a first oscillation current and a second oscillation current, and the first oscillation current has a frequency range higher than that of the second oscillation current, wherein:
• the duration T2 of the first oscillation current is adjusted according to a temperature of the lithium-ion battery (a first battery temperature), and determined by the following formula:
• T2=n/fg, wherein:
• n=0 if the first battery temperature ≥a first working temperature desired for the charging or discharging of the lithium-ion battery;
• and
• n=1+INT((the first working temperature−the first battery temperature)x′) if the first battery temperature <the first working temperature, wherein 0.01≤x′≤20, and INT is the integer-valued function;
• and
• the lower limit fcd and upper limit fg of the frequency of the second oscillation current are determined by:
• plotting a line parallel to the horizontal axis and through an intersection of EIS at the first working temperature and the vertical axis in the EIS plots with a first state of charge (SOC) in a frequency range;
• wherein:
• the frequency fcd corresponds to the intersection of the EIS plot at the first battery temperature and the parallel line in the low frequency region;
• and
• the frequency fg corresponds to the intersection of the EIS plot at the first battery temperature and the parallel line in the high frequency region.