Rapid microwave-enhanced ion exchange process for the synthesis of LiNi0.5Mn0.5O2 and its characterization as the cathode material for lithium batteries

Abstract

An energy- and time-efficient microwave-enhanced ion exchange (MW-IE) process is developed for the synthesis of low-cation-mixed LiNi_0.5Mn_0.5O₂ cathode material. The synthesized MW-IE LiNi_0.5Mn_0.5O₂ shows comparable low cation mixing (∼ 4%) within a short reaction time of 10 min, when comparing with conventional ion exchange processes with a reaction time of 5–10 h. The MW-IE LiNi_0.5Mn_0.5O₂ delivers a higher initial discharge capacity (213 mAh g⁻¹) than that obtained by the sol–gel (SG) method (186 mAh g⁻¹) when charging in the potential range of 2.5–4.6 V. Further electrochemical cycleability of MW-IE LiNi_0.5Mn_0.5O₂ cathode demonstrates excellent capacity retention and rate capability compared to that of the SG LiNi_0.5Mn_0.5O₂ cathode. The results show better Li⁺ ion pathways for MW-IE LiNi_0.5Mn_0.5O₂, where Li⁺ ion transport in SG LiNi_0.5Mn_0.5O₂ would be obstructed by transition metal cations (Ni²⁺, resulting from higher degree of cation mixing). The effective methodology developed could be easily extended to the synthesis of potential layered compounds with less cation-mixing.