A high-volumetric-capacity bismuth nanosheet/graphene electrode for potassium ion batteries

一种用于钾离子电池的高体积容量铋纳米片/石墨烯复合物电极

Potassium ion batteries(PIBs)with high-volumetric energy densities are promising for next-generation low-cost energy storage devices.Metallic bismuth(Bi)with a structure similar to graphite,is a promising anode material for PIBs due to its high theoretical volumetric capacity(3763 mA h cm^−3)and relatively low working potential(−2.93 V vs.standard hydrogen electrode).However,it experiences severe capacity decay caused by a huge volume expansion of Bi when alloying with potassium.This study reports a flexible and free-standing Bi nanosheet(BiNS)/reduced graphene oxide composite membrane with designed porosity close to the expansion ratio of BiNS after charging.The controlled pore structure improves the electron and ion transport during cycling,and strengthens the structural stability of the electrode during potassiation and depotassiation,leading to excellent electrochemical performance for potassium-ion storage.In particular,it delivers a high reversible volumetric capacity of 451 mA h cm^−3 at the current density of 0.5 A g^−1,which is much higher than the previously reported commercial graphite material.

具有高体积能量密度的钾离子电池有望成为下一代的低成本能源存储设备.金属铋具有较高的理论容量(3763 mA h cm^−3)和相对较低的工作电位(−2.93 Vvs.SHE),是一种很有前途的钾离子电池负极材料.但铋在与钾的合金化过程中,会产生大的体积膨胀,导致电极容量严重衰减.本文报道了一种柔性、自支撑的铋纳米片/石墨烯复合物电极膜,该电极膜具有优化的孔隙率,可满足电极循环过程中的体积膨胀.此外,该电极中优化的孔隙结构改善了循环过程中的电子和离子输运,并提高了电极在钾化和去钾化过程中的结构稳定性,使其具有良好的电化学储钾性能.特别是,在电流密度为0.5 A g^−1的情况下,该电极的体积容量可以达到451 mA h cm^−3,明显优于之前报道的商用石墨材料.