自模板法构筑中空纳米结构CoP-C复合微球及其电化学储钠性能

Self-sacrificing Template Approach for Hollow Nanostructured CoP-C Composite Microspheres and Their Electrochemical Sodium Storage Properties

过渡金属磷化物因具有合适的电压平台和较大的理论容量,是一种理想的钠离子电池负极材料。然而,由于过渡金属磷化物导电性差且与钠离子反应过程中体积膨胀严重,导致其倍率和循环性能较差。本研究以磷化钴为研究对象,采用自牺牲模板法,以钴-甘油微米球(Co-gly)为前驱体,通过气相磷化法构筑了中空纳米结构CoP-C复合微球(CoP-C HS)。通过XRD、SEM、TEM和HRTEM等分析技术对所制备的材料进行了结构表征。将该材料用作钠离子电池负极材料时,相较块状CoP,CoP-C HS的储钠性能得到显著提升:在200 mA·g^(-1)的电流密度下循环1000圈后比容量仍然保持在112 mAh·g^(-1);在1 A·g^(-1)的大电流密度下可逆充放电容量达到了126 mAh·g^(-1)。中空纳米结构为电化学反应提供了更多活性位点并能够有效缓解脱钠/嵌钠过程中的体积膨胀,而与碳复合能提高材料的导电性并有效抑制材料循环过程中的结构破坏。

Transition metal phosphides are promising anode materials for sodium-ion batteries(SIBs)considering their appropriate discharge plateau and high theoretical capacity.However,most transition metal phosphides exhibit inferior rate capability and cycling stability due to their poor conductivity and large volume expansion during sodiation/desodiation.Taking CoP as an example,by employing cobalt-glycerate(Co-gly)microspheres as precursor,a self-sacrificing template route is developed to synthesize hollow nanostructured CoP-C hybrid microspheres(CoP-C HS)via a gas-phase phosphorization method in this work.The microstructure of the materials is investigated by XRD,SEM,TEM and HRTEM.When evaluated as anode material for SIBs,compared with bulk CoP,CoP-C HS remarkably enhances the sodium storage performance:a specific capacity of 112 mAh·g^(-1)at 200 mA·g^(-1)after 1000 cycles and a reversible capacity of 126 mAh·g^(-1)at 1 A·g^(-1)can be achieved.The hollow nanostructure provides more active sites for electrochemical reactions and can effectively accommodate the volume change during sodiation/desodiation,while compositing with carbon can improve the conductivity and suppress the structural degradation during the cycling process.