Cycle-Life Evaluation of the 30 Ah Prismatic Li-Ion Secondary Cells for Low Earth Orbit Satellite

Abstract

We performed a cycle test with 25% and 40% depth of discharge (DoD) using 30 Ah prismatic Lithium-Ion secondary cells designed for ground applications. For 25% DoD, we observed adequate cycle performance exceeding 18,000 cycles. For 40% DoD, the end of discharge voltage (EoDV) decreased to 3.0 volt after 10,000 charge-discharge cycles, which enabled us to disassemble the cell and check the reason of performance degradation. Through the analysis, we found that the reduced cell performance mainly caused by capacity loss in the negative electrode, especially in the middle of the cell stack. The positive electrode also degraded slightly, and the impedance of the positive electrode increased. The discharge capacity during the 40% DoD test might not be restored by simulated low Earth orbit cycling because of these degradations.