Benchmark dataset for the study of the relaxation of commercial NMC-811 and LFP cells

Abstract

Voltage relaxation can be a powerful indicator of lithium-ion battery characteristics, but variations in relaxation times complicate the widespread use of relaxation as an analytical tool. This study investigates the voltage relaxation behavior of commercial lithium-ion batteries, focusing on the impact of depth of discharge, rate, and temperature to gain a better understanding of relaxation and to improve state-of-charge estimation. Most of the data, available in a public dataset, are gathered using a unique protocol derived from intermittent titration techniques with an emphasis on ensuring that every rest is independent of the previous one. The findings demonstrate that relaxation behavior and open-circuit voltage settling times are influenced by depth of discharge, rate, current flow direction, and cell chemistry. In addition, the obtained dataset is used to test the validity of relaxation models to showcase the benefits of having a benchmark relaxation dataset available for validation of future open-circuit voltage forecasting studies.