Phase transitions and related electrochemical performances of Li-Rich layered cathode materials for high-energy lithium ion batteries

Highlights: • Ion exchanges of H⁺-Li⁺ and TBA⁺-H⁺ are performed on Li-rich layered oxides. • Layered-to-spinel phase transition of Li-rich layered oxides has been realized. • The converted spinel phase has a Li₄Mn₅O₁₂-type spinel structure. • Electrochemical performances of Li-rich layered cathodes are manipulated. • The resulting spinel cathode delivers a capacity higher than 300 mAh/g at 0.1 C. The present work systematically probes and tracks the phase transition of Li-rich layered Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ (marked as LMNCO) by using an ex-situ chemical activation that is realized through ion-exchange and post-annealing processes, in order to understand related electrochemical performances of Li-rich cathode materials for advanced lithium-ion batteries. Ion exchanges of H⁺-Li⁺ and subsequent TBA⁺-H⁺ (TBA: tetrabutylammonium) in LMNCO are carried out, resulting in its layered-to-spinel phase transition after optimal heat treatments. The resultant compound shows a Li₄Mn₅O₁₂-type spinel structure. This converted spinel cathode material can deliver discharge capacities higher than 300 mAh/g at 0.1 C and 200 mAh/g at 1 C (1 C = 250 mA/g), respectively, and also exhibits better cycling stability and rate capability in comparison with pristine layered LMNCO and other derivatives. This work offers a feasible route to study all changes of morphologies, crystal structures, chemical compositions, surface areas and related electrochemical lithium storage behaviors during phase transitions of Li-rich layered cathode materials, and thus provides insights on optimizing electrochemical performances for high-energy and high-power lithium ion batteries.