Towards understanding the functional mechanism and synergistic effects of LiMn2O4 - LiNi0.5Mn0.3Co0.2O2 blended positive electrodes for Lithium-ion batteries

Abstract

Blended positive electrodes consisting of mixtures of LiMn2O4 spinel (LMO) and layered LiNi0.5Mn0.3Co0.2O2 (NMC) have been studied by coupling electrochemical testing to operando synchrotron based X-ray absorption and powder diffraction experiments to shed light on their redox mechanism. Blending NMC with LMO results in enhanced energy density at high rates, with the composition with 25% LMO exhibiting the best electrochemical performance. Tests with a special electrochemical setup detecting the contribution of each blend component indicate that the effective current load on each blend component can be significantly different from the nominal rate and also varies as function of SoC. Operando studies enabled to monitor the evolution of oxidation state and changes in the crystal structure, which are in agreement with the expected behaviour of the individual components considering the material specific electrochemical current loads. These findings should contribute to a deeper mechanistic understanding of blended electrodes to foster a rational driven approach for their design.