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（PIB）有望用于下一代低成本储能设备。具有类似于石墨的结构的金属铋（Bi）具有较高的理论体积容量（3763 mA h cm ^-3）和相对较低的工作电势（-2.93 V vs.标准氢电极）。但是，当与钾合金化时，Bi的体积膨胀会导致其容量急剧下降。这项研究报告了一种柔性且独立的Bi纳米片（BiNS）/还原型氧化石墨烯复合膜，其设计孔隙率接近于充电后BiNS的膨胀率。受控的孔结构改善了循环过程中的电子和离子传输，并增强了钾化和去钾化过程中电极的结构稳定性，从而为钾离子存储提供了出色的电化学性能。特别地，其在0.5 A g ^-1的电流密度下提供451 mA h cm ^-3的高可逆体积容量，这比先前报道的市售石墨材料高得多。