Affiliation:
1. University of Shanghai for Science and Technology, School of
2. Tsinghua University, School of Vehicle and Mobility
Abstract
<div class="section abstract"><div class="htmlview paragraph">The turning point in the process of nonlinear aging is a key feature to identify
the nonlinear aging behavior of lithium-ion batteries. In order to identify the
knee-point online, this paper studies the capacity “diving” phenomenon of the
battery during the experiment and the regulation of the appearance of the
turning point during the nonlinear aging process. Then, a knee-point
identification method based on constant voltage charging capacity is proposed,
and the linear and nonlinear stages of battery decay are redefined. Based on the
change of constant voltage charging capacity in the constant current and
constant voltage charging strategy, the method defines the aging process in
which the constant voltage charging capacity remains invariant as the linear
decay stage of the battery, and the aging process in which the constant voltage
charging capacity rises rapidly as the nonlinear decay stage. The intersection
of linear and nonlinear decay is the knee-point of the battery’s aging
trajectory. This method is tested on nickel manganese cobalt oxide (NCM) and
LiFePO<sub>4</sub> batteries, and both achieve the knee-point identification
very well. The method can achieve online capacity estimation without obtaining
complete battery aging data.</div></div>