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

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.

Automated summary

By coupling electrochemical testing to operando synchrotron based X-ray absorption and powder diffraction experiments, blended positive electrodes consisting of LiMn2O4 spinel (LMO) and layered LiNi0.5Mn0.3Co0.2O2 (NMC) were studied to understand their redox mechanism. It was found that blending NMC with LMO can enhance energy density at high rates, with the blend containing 25% LMO showing the best performance. Testing with a special electrochemical setup revealed that the effective current load on each blend component can vary significantly from the nominal rate and also changes with SoC. Operando studies allowed monitoring of the oxidation state evolution and changes in crystal structure, in line with the expected behavior of individual components considering their electrochemical current loads.