Abstract: For the main second harmonic component of the DC side of the photovoltaic storage system on the impact of energy storage batteries,the paper analyzes the mechanism and law of the influence of different sizes of second harmonic components on the internal and external characteristics of the Li-ion battery through electrochemical modeling,and finds that the main factor affecting the battery life is the average value of the current during the charging and discharging state rather than the effective value of the current. Based on the influence of this factor on the battery life,it is proposed that the second harmonic component of current can be divided into three intervals,which are not significantly affecting the battery life,slowing down the battery life decay and accelerating the battery life decay,and finally these three intervals are verified by simulation and experiment. These three intervals provide a reference for optimizing the safe operation interval of lithium-ion batteries under the influence of interaction between photovoltaic storage system and power grid in engineering applications and reducing the cost of DC-side filters for energy storage.