Synthesis of KVPO<sub>4</sub>F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries.

Liao, Jiaying; Zhang, Xinxin; Zhang, Qinghua; Hu, Qiao; Li, Yafei; Du, Yichen; Xu, Jianzhi; Gu, Lin et al. · Nano Lett · 2022

basic_science · Level V

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Abstract

With high theoretical capacity and operating voltage, KVPO<sub>4</sub>F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium-oxalate-phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO<sub>4</sub>F nanoplates. It is found that the V-F-C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO<sub>4</sub>F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO<sub>4</sub>F. The as-synthesized KVPO<sub>4</sub>F/C cathode delivers a reversible capacity of 106.5 mAh g<sup>-1</sup> at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g<sup>-1</sup> at the ultrahigh current density of 100 C. In addition, a KVPO<sub>4</sub>F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg<sup>-1</sup>.