In this article, honeycomb-like amorphous VPO₄/C spheres were successfully synthesized via a sol-gel combined hydrothermal route and then tested as anode materials for sodium-ion batteries. After characterized by structure analysis, morphological observation, and composition determination, the prepared VPO₄/C materials exhibit amorphous structure and spherical morphology with honeycomb-like core framework shielded by compact out-layer shell when compared with its crystalline counterpart. As anode material for sodium storage performance, the amorphous VPO₄/C delivers a high discharge capacity of 421.1 mAh g⁻¹ at a current density of 100 mA g⁻¹ and exhibits a good cycling stability upon 100 cycles under 500 mA g⁻¹. The enhancement of electrochemical sodium storage performances can be attributed to the honeycomb-like inner structure facilitating the diffusion of sodium ion and the observable compact out-layer buffering the large volume strains in cycling. Meanwhile, the observed channel-like caves can provide wealthy space for storing richer sodium ion, leading to higher capacity. The proposed viewpoint points out that the synthesis of amorphous architecture is a new strategy to break through the limitation of anode materials for sodium-ion batteries.

中文翻译：

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蜂窝状无定形VPO 4 / C球，具有改善的钠存储性能，作为钠离子电池的负极材料

在本文中，通过溶胶-凝胶结合水热法成功地合成了蜂窝状无定形VPO ₄ / C球，然后将其用作钠离子电池的负极材料。经结构分析，形貌观察和组成确定后，所制得的VPO ₄ / C材料呈现出无定形结构和球形结构，蜂窝状芯骨架被致密的外层壳屏蔽，与结晶态的相比。作为钠储存性能的负极材料，非晶态VPO ₄ / C在100 mA g ^-1的电流密度下可提供421.1 mAh g ^-1的高放电容量并在500 mA g ^-1下100次循环时表现出良好的循环稳定性。电化学钠存储性能的增强可归因于蜂窝状内部结构，促进了钠离子的扩散，并且可观察到的致密外层缓冲了循环中的大体积应变。同时，观察到的通道状洞穴可以提供丰富的空间来储存更丰富的钠离子，从而提高容量。提出的观点指出，非晶结构的合成是突破钠离子电池负极材料局限性的一种新策略。