Selective Doping to Controllably Tailor Maximum Unit-Cell-Volume Change of Intercalating Li+ -Storage Materials: A Case Study of γ Phase Li3 VO4.

Abstract

Capacity decay of an intercalating Li+‐storage material is mainly due to the its particle microcracks from stress‐causing volume change. To extend its cycle life, its unit‐cell‐volume change has to be minimized as much as possible. Here, based on a γ‐Li3VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit‐cell‐volume change, then clarify the relationship between its crystal‐structure openness and maximum unit‐cell‐volume change, and finally demonstrate the superiority of “zero‐strain” materials within 25–60 °C (especially at 60 °C). With increasing the large‐sized Ge4+ dopant, the unit‐cell volume of γ‐Li3+ x Ge x V1− x O4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit‐cell‐volume change. In contrast, the doping with small‐sized Si4+ shows a reverse trend. The tailoring reveals that γ‐Li3.09Ge0.09V0.91O4 owns the smallest maximum unit‐cell‐volume change of 0.016% in the research field of intercalating Li+‐storage materials. Consequently, γ‐Li3.09Ge0.09V0.91O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity‐retention percentages after 1800/1500 cycles at 2 A g−1. This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long‐life lithium‐ion batteries.