K-Doped Li-Rich Molybdenum-Based Oxide with Improved Electrochemical Properties for Lithium-Ion Batteries

Abstract

Li-rich molybdenum-based oxide (\(\hbox {Li}_{2}\hbox {MoO}_{3})\), which owns a layered structure similar to that of \(\hbox {Li}_{2}\hbox {MnO}_{3}\), has caused much attention as a kind of high-energy-density cathode material for Li-ion batteries. Although \(\hbox {Mo}^{4+}\) in the [\(\hbox {Li}\hbox {Mo}_{2}\)] slabs could be oxidized to \(\hbox {Mo}^{5+}/\hbox {Mo}^{6+ }\) easily, the \(\hbox {Li}_{2}\hbox {MoO}_{3 }\) might still suffer from a phase transformation from layered to disordered at a deeply charged state more than 4.4 V (vs. \(\hbox {Li}^{+}/\hbox {Li}\)) in the first cycle, resulting in fast capacity degradation. To resolve these issues, \(\hbox {K}^{+}\) ion is chosen to dope into the \(\hbox {Li}_{2}\hbox {MoO}_{3}\) crystal using a K-doped precursor \(\hbox {K}_{0.1}\hbox {MoO}_{3}\) that prepared by a hydrothermal method. The as-prepared \(\hbox {Li}_{1.9}\hbox {K}_{0.1}\hbox {MoO}_{3}\) sample showed nanobelt morphology and possessed a layered structure. Befitting from the chemical pre-insertion of \(\hbox {K}^{+}\), this doped sample exhibited a stable cycling life and an improved rate capability when operated over the potential range of 1.5–4.4 V (vs. \(\hbox {Li}^{+}/\hbox {Li}\)). The results suggest that chemical pre-insertion of \(\hbox {K}^{+}\) is an effective approach to improve the electrochemical properties of the \(\hbox {Li}_{2}\hbox {MoO}_{3 }\) cathode material.