Enhanced Cycling Performance of Bilayered Vanadium Oxide Cathode in Li-Ion Batteries via Dual Metal Ion Preintercalation

Abstract

Chemical preintercalation of Li+ or Mg2+ ions has showcased the capability to improve either specific capacity or cycling stability, respectively, of the bilayered vanadium oxide (BVO) electrode in Li-ion cells. However, advancing both properties in a single material via chemical preintercalation of both Li+ and Mg2+ ions has never been reported. Herein, we experimentally demonstrate that by simultaneously preintercalating electrochemically active Li+ ions and structure stabilizing Mg2+ ions, the specific capacity and cycling stability of BVO electrodes in lithium-ion cells can be synergistically improved. Additionally, we revealed the role of interlayer structural water in the charge storage and degradation mechanisms of dual metal ions preintercalated BVO electrodes. With the simultaneous preintercalation of 0.19 Li+ ions and 0.10 Mg2+ ions into the interlayer structure of BVO, the LMVO electrode demonstrated the specific capacity of ~245 mAh g-1 in a potential window of 2.0-4.0 V (vs. Li/Li+) with a capacity retention of 58% after 50 cycles. Low-temperature vacuum-drying at 200 °C reduced the hydration degree (n in δ-Li0.19Mg0.10V2O5·nH2O) of LMVO, denoted as LMVO-200, from 0.85 to 0.67 per V2O5 without phase transformation, altered the charge storage mechanism from surface-controlled to diffusion-limited, and demonstrated further enhanced capacity retention of ~66% after 100 cycles. Additionally, via GITT experiments, we demonstrate that the dual metal ion preintercalation and vacuum-drying treatment lead to facilitated diffusion of Li+ ions. Ex-situ XRD and ATR FTIR analyses of the LMVO-200 electrodes reveal their reversible bulk and local structure evolution during electrochemical operation, enabling excellent cycling stability in Li-ion cells. This work demonstrates a general strategy to synergistically enhance the specific capacity and cycling stability of layered oxide electrode materials for intercalation batteries.