支柱策略增强离子传输和结构稳定性的KVPO4F用于超稳定的钾离子电池正极

Pillar strategy enhanced ion transport and structural stability toward ultra-stable KVPO4F cathode for practical potassium-ion batteries

近年来,由于丰富的钾资源储量和低廉的价格,钾离子电池在大规模储能领域表现出极大的应用前景.开发具有高安全性、高能量密度、低成本、长寿命的正极材料是推动钾离子电池实用化的关键.KVPO4F(KVPF)因其工作电压高、能量密度高、热稳定性好,被认为是一种很有前途的钾离子电池正极材料.然而,由于大半径的钾离子反复脱出/嵌入导致较慢的动力学和大的体积变化,从而影响材料循环稳定性.本文通过将大半径铯离子引入KVPF结构中的“支柱”策略,可有效提高材料的离子传导特性,并改善充放电过程中材料的结构稳定性,从而实现铯掺杂的KVPF正极优异的储钾性能.同时,高循环稳定性的KVPF//石墨全电池也展示了其在钾离子电池中巨大的实际应用潜力.

KVPO4F(KVPF)is a promising cathode material for potassium-ion batteries(PIBs)because of its high operating voltage,high energy density,and excellent thermal stability.Nevertheless,the low kinetics and large volume change have been the major hurdles causing irreversible structural damage,high inner resistance,and poor cycle stability.Herein,a pillar strategy of Cs+doping in KVPO4F is introduced to reduce the energy barrier for ion diffusion and volume change during potassiation/depotassiation,which significantly enhances the K+diffusion coefficient and stabilizes the crystal structure of the material.Consequently,the K_(0.95)Cs_(0.05)VPO_(4)F(Cs-5-KVPF)cathode exhibits an excellent discharge capacity of 104.5 m Ah g^(-1)at 20 mA g^(-1) and a capacity retention rate of 87.9%after 800 cycles at 500 mA g^(-1).Importantly,Cs-5-KVPF//graphite full cells attain an energy density of 220 Wh kg^(-1)(based on the cath-ode and anode weight)with a high operating voltage of 3.93 V and 79.1%capacity retention after 2000 cycles at 300 mA g^(-1).The Cs-doped KVPO4F cathode successfully innovates the ultra-durable and high-performance cathode materials for PIBs,demonstrating its considerable potential for practical applications.