Earth-abundant potassium is a promising alternative to lithium in energy-storage systems, but a pivotal limitation of potassium-ion batteries (KIBs) is their relatively low capacity and inferior cycle stability. Here we report the first synthesis of ultrathin metallic V₅Se₈ nanosheets embedded in porous carbon (graphene-like V₅Se₈@C) as a superior anode for KIBs, which achieves a high reversible depotassiation capacity along with unprecedented rate performance and outstanding cycling stability (a reversible depotassiation capacity of 145 mAh g^–1 after 800 cycles at 4 A g^–1 with 82.9% capacity retention). The impressive performances achieved are attributed to the synergistic contributions of the NiAs-type superstructure, ultrathin nanosheet architecture, sufficient accessible active sites, multi-dimensional electronic/ionic transport pathways and significant pseudocapacitive behaviors. Combined experimental analysis and first-principles calculations reveal fast reaction kinetics, high ionic/electronic conductivity and low diffusion barriers of K-ion in graphene-like V₅Se₈@C hybrid. Ex-situ characterizations confirm that V₅Se₈@C electrode undergo a reversible phase-evolution by the sequential intercalation and conversion reactions with synergistic K⁺-storage mechanisms. Furthermore, by coupling with pre-treated K_0.5MnO₂ cathode, the full-cell is demonstrated to exhibit large energy density of 160.2 Wh kg^–1 with average discharge voltage of 2.2 V and capacity retention of 86% over 200 cycles. These desirable findings demonstrate graphene-like V₅Se₈@C nanosheets hold great practical application in future grid-scale energy storage.

在储能系统中，富含地球的钾是锂的有前途的替代品，但是钾离子电池（KIB）的一个关键限制是其相对较低的容量和较差的循环稳定性。在这里，我们报道了首次合成的超薄金属V ₅ Se ₈纳米片，其嵌入在多孔碳中（类石墨烯的V ₅ Se ₈ @C）作为KIBs的优良阳极，实现了高可逆的失活能力以及空前的速率性能和出色的的145毫安克的循环稳定性（可逆容量depotassiation ^-1之后，在4 A G 800次循环^-1容量保留率为82.9％）。取得的令人印象深刻的性能归因于NiAs型超结构，超薄纳米片结构，足够的可利用活性位点，多维电子/离子传输途径和重要的假电容行为的协同作用。结合实验分析和第一性原理计算，揭示了类似石墨烯的V ₅ Se ₈ @C杂化物中K离子的快速反应动力学，高离子/电子电导率和低扩散势垒。异位表征证实，V ₅ Se ₈ @C电极通过具有协同K ⁺的顺序嵌入和转化反应经历了可逆的相演化。存储机制。此外，通过与预处理的K _0.5 MnO ₂阴极耦合，该全电池被证明具有160.2 Wh kg ^–1的大能量密度，平均放电电压为2.2 V，在200个循环中的容量保持率为86％。这些令人满意的发现表明，类似石墨烯的V ₅ Se ₈ @C纳米片在未来的网格规模储能中具有巨大的实际应用。