(Invited) Beyond Single Cell Characterization: Impacts of Module Configuration on Lithium-Ion Battery Performance and Degradation

Abstract

Batteries are commonly connected in series and parallel to form modules that meet the power and energy requirements of specific applications. However, conclusions about battery performance and degradation under different conditions are often based on single cell cycling results. In this study, we evaluate the performance of lithium-ion eight-cell modules in six different series-parallel configurations over the course of hundreds of cycles. Each cell was individually instrumented for voltage, current, and temperature monitoring. Current data were collected using closed-loop Hall effect sensors to provide accurate measurements of parallel branch currents without the influence of in-circuit shunt sensing elements. This cell-level data collection enabled calculation of the underutilization of individual cells and assessment of differences in energy lost to cell balancing for different configurations. We also evaluated current redistribution in parallel cells, which in some cases yielded transients with peak magnitudes more than twice the average expected cell current value. The capacity and energy fade of the full modules was compared to that of individual cells cycled under the same conditions. This module cycling study, one of the broadest reported to date, allows us to systematically evaluate the performance trade-offs and safety implications of different module configurations.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-5209 A