Toward the commercialisation of LiNi0.5Mn1.5O4 for a diversified battery supply chain : revealing key properties for enhanced performance

Murdock, Beth and Tapia Ruiz, Nuria and Toghill, Kathryn (2024) Toward the commercialisation of LiNi0.5Mn1.5O4 for a diversified battery supply chain : revealing key properties for enhanced performance. PhD thesis, Lancaster University.

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Abstract

Lithium-ion batteries (LIBs) have become a vital technology within modern society. With the increasing demand for LIBs, however, comes a drastic increase in demand for the materials inside of them—particularly the cathode material, which is typically high in critical metal content. This PhD thesis aims to advance cathode development toward a more diverse battery supply chain to alleviate supply risk, by providing a deep understanding of their structureproperty-performance relationships. Initially, an evaluation of the criticality and sustainability of state-of-the-art and advanced cathode materials was performed to identify a material that could diversify the demand for battery metals. It was found that current NMC materials pose a future supply risk due to high Ni demand. LNMO emerged as a promising candidate with low Co, Li, and Ni content, alongside benefits such as high energy density and good rate performance. However, commercialisation of LNMO is limited by its poor capacity retention. Subsequent chapters focused on improving LNMO’s capacity retention through cationic substitution, where Fe and Mg were chosen as earth-abundant substituents. Structural investigations revealed that Fe and Mg substitution led to an increasing concentration of Lisite defects, with Mg showing a distinct preference for the Li sites. The increased Mn3+ content did not significantly impact rate performance or cycling stability, although high Fe and Mg concentrations led to capacity loss. At elevated temperatures, Mg-substituted LNMO demonstrated improved cycling stability due to the formation of a corrosion-resistant surface layer rich in C–O functionality. The findings highlight that Mg-substituted LNMO can achieve better capacity retention through the presence of MgLi defects and a stable surface layer. The similarity in structure and morphology of unsubstituted and Fe-substituted LNMO meant that Fe offered little improvement to the electrochemical performance.