【摘要】 钠离子电池因其成本低、资源丰富等优点而成为新一代储能设备.在各种正极中,隧道型Na_0.44MnO₂因其较大的Na⁺通道,被认为是快速充电电池的合适正极材料,但仍然存在Na⁺动力学缓慢等问题.本文首次提出了一种Na_0.44MnO₂的新型离子交换方法,通过调节合成条件,可以很好地控制K⁺残余量和Na_0.44MnO₂的尺寸.结果表明,Na_0.44MnO₂结构中的残留K⁺扩大了Na⁺的输运通道,小颗粒形貌缩短了Na⁺的迁移距离,且晶体中的带状缺陷界面进一步加速了Na⁺的输运.获得的Na_0.44MnO₂具有本征赝电容特性,在2-4 V和20 C电流下有79.0 mA h g^-1的优异倍率性能.长期循环测试表明,20 C下1000次循环的保持率为98.1%,0.5 C下200次循环的保持率为96.3%.本工作为用于快速充电储能装置的高倍率、高稳定性Na_0.44MnO₂正极的大规模生产提供了一条新途径.更多还原

【Abstract】 Sodium-ion batteries are promising new-generation energy storage devices due to the low cost and rich resource of sodium.Among various cathodes,tunnel-type Na_0.44MnO₂ with large S-shaped Na⁺transport tunnels is considered an appropriate cathode for fast-charging batteries,yet still suffering from sluggish Na⁺kinetics.Herein,a novel ion-exchange method is developed for the first time to synthesize Na_0.44MnO₂ from K_0.5MnO₂ precursor.By precisely adjusting the synthesis condition,the amount of residual K⁺and the size of Na_0.44MnO₂ are well controlled.The presence of trace K⁺in the Na_0.44MnO₂ structure is demonstrated to broaden the Na⁺transport tunnels while the minimized size shortens the Na⁺migration distance.Besides,band-like defects with distorted polyhedrons further promote Na⁺transport.The as-prepared Na_0.44MnO₂ with intrinsic pseudocapacitance characteristic exhibits excellent rate performance of 79.0 mA h g^-1 at 20 C between 2 and 4 V.Long-term cycling tests present superior stability of 98.1% retention after 1000cycles at 20 C and 96.3% retention after 200 cycles at 0.5 C.This work provides a novel way for large-scale production of high-rate and robust Na_0.44MnO₂ cathode for fast-charging energy storage devices.更多还原