Plum pudding model inspired KVPO4F@3DC as high-voltage and hyperstable cathode for potassium ion batteries

Abstract

The investigation on the cathode material of potassium ion batteries (PIBs), one of the most promising alternatives to lithium ion batteries, is of great significance. Potassium vanadium fluorophosphate (KVPO4F) with a high working voltage is an appealing cathode candidate for PIBs, while the poor cycling performance and low electronic conductivity dramatically hinder the application. Herein, a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite (KVPO4F@3DC) is successfully designed in this study to tackle these problems. In the composite, KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by cross-linked large area carbon sheets. As the cathode for PIBs, the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g−1 at 20 mA g−1. An excellent long cycle stability with a capacity retention of 85.4% over 550 cycles at 500 mA g−1 is achieved. In addition, it maintains 83.6% of its initial capacity at 50 mA g−1 after 100 cycles at 55 °C. The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode, successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.