Simulated Crystal Growth of Intermediate Phases Formed during Li and O Extraction of Nano-Li2MnO3 Cathode Material

Abstract

Li2MnO3 is considered as a potential candidate for high capacity (theoretical capacity of 458 mAh/g) lithium ion batteries applicable in electric vehicles owing to its larger number of exploitable Li ions. However, it is vulnerable to degradation originating from complex phenomena such as the oxygen release, phase transformation and Li+ /H+ exchange reaction, but the detailed mechanisms governing these degradation behaviors have not been fully understood yet. In the current work, spontaneous crystal growth of the nano-Li2MnO3 structures via the amorphisation and crystallisation technique is carried out with systematic removal of oxygen and lithium contents in a quest to explore the formation of different intermediate structures/phases. The simulated nano-architectures crystallised into multi-grained (except for Li1.75MnO2.75) and highly defective structures. To study the formation possible phases, the XRD patterns were measured for all intermediate structures and reveal emergence of new Mn3O4 peak at 2Ө~ 29⁰ and strong cubic spinel LiMn2O4 at 2Ө~ 37⁰. Microstructural analysis revealed the formation of layered and spinel-type structures for low lithium and oxygen content nanostructures. These findings shed light towards mechanisms that take place during the cycling of nanostructured high capacity oxide electrodes during lithium and oxygen extraction that will help guide the optimisation of new Li-rich materials for rechargeable lithium batteries.