Particle-Scale Path-Dependent Behavior of Li x Ni 0.5 Mn 1.5 O 4 Electrode in Li-Ion Batteries: Part I

The voltage behavior of the Li_xNi_0.5Mn_1.5O₄ (LNMO) electrode was studied in this work. A thin-layer LNMO electrode was prepared for testing in a coin cell format where lithium metal was used as the counter electrode. A series of charge and discharge cycling experiment was designed to investigate LNMO rate performance and voltage behavior. Our results indicated that a phase transformation process in the LNMO electrode has significant influence on its voltage behavior. Results also showed that the LNMO electrode has path-dependent behavior on both discharge and charge, which is due to the lithium transport inside the LNMO electrode. Experiments revealed that this path-dependent behavior depends on the state of charge (SOC), and may result from limited phase transformation rates. Relaxation experiments were also conducted at different SOC conditions. Results showed that the voltage behavior of the LNMO electrode is time-dependent, where long relaxation can lead to the vanishing of the electrode path-dependent behavior.