【作者】 刘志亮； 杨飘萍； 郑捷； 李星国；

【Author】 Zhiliang Liu;Piaoping Yang;Jie Zheng;Xingguo Li;Harbin Engineering University;Peking University;

【机构】 哈尔滨工程大学； 北京大学；

【摘要】 金属磷化物在电催化,光催化,超级电容器以及锂/钠离子电池等领域具有广泛的应用前景,因此近年来受到很大的关注。然而,传统的合成方法直接利用剧毒的PH₃气体磷化金属前驱体,或者利用NaH₂PO₂加热释放出PH3气体实现磷化。为了使反应物完全磷化,通常需要消耗极大过量的磷源。因此过量的剧毒磷源的使用限制了过渡金属磷化物进一步研究和应用。本文通过发展报道了一种新型熔融盐还原磷化方法^[1],在250℃的低温NaCl-KCl-AlCl₃熔融盐中,利用低毒的等化学计量比的PCl₃作为磷源,Mg为还原剂,磷化Co@C合成了豆荚状CoP@C纳米材料。该方法不仅反应条件温和,而且具有磷源毒性低和利用率高的优点。机理研究表明,熔融盐不仅提供了液态反应环境,而且通过A13+/Al氧化还原电子对实现了对活性电子的有效传递。并且该方法能进一步拓展用于合成纳米Ni2P、蜂巢状CuP₂等其它金属磷化物^[2],实现磷含量、纳米结构和形貌的有效调控。将豆荚状CoP@C用作锂离子电池负极材料,其纳米结构具有周期性空隙,能够有效缓冲电化学嵌锂和脱锂过程中的体积变化,并且在脱嵌Li⁺过程中能够实现结构和物相的可逆变化。在1.0 A/g的电流密度下循环800圈,豆荚状CoP@C容量仍能保持在500 mAh/g。含磷量更高的峰巢状CuP₂@C具有更高的首次可逆储锂容量,达1146 mAh/g。并且经过600次循环后,其容量稳定在720 mAh/g。因此本方法制备的豆荚状CoP@C、峰巢状CuP₂@C均是优秀的储锂负极材料。更多还原

【Abstract】 Metal phosphides（MP_s） have intriguing applications in energy conversion and storage,such as electrocatalysis,photocatalysis,supercapacities,lithium-ion and sodium-ion batteries,thus attracting a great deal of attention in recent years.However,current synthesis methods of MPs usually requires either harsh conditions or large excess of hypertoxic phosphorus source such as PH₃ or NaH₂ PO₂,which severely limits the further study and application of MPs.In this work,a mild molten-salt reduction phosphorization method is developed to phosphorize CoP@C and synthesize peapod-liked CoP@C nanomaterials by using PCl₃ as the phosphorus source and Mg as the reductant in NaCl-KCl-AlCl₃ molten salts at 250℃.This method holds multiple advantages,including mild phosphorizaion condition,low toxicity and high efficiency of the phosphorous source.The molten NaCl-KCl-AlCl₃ system not only provides a liquid environment for reaction but also participate in the electron transport by A13+/Al redox couple.In addition,the molten-salt reduction phosphorization method is extended to synthesize honeycomb-like CuP₂@C nanostructures through phosphorizing MOFs derived Cu@C in ZnCl₂ molten salt at 300℃,which achieves the synthesis of phosphorus-rich transition metal phosphide at low temperature.The obtained peapod CoP@C nanostructure has periodic voids,which can effectively buffer volume change during lithiation/delithiation process.Moreover,the CoP@C electrode exhibits good structure and phase conversion reversibility,delivering a stable capacity of 500 mAh/g after 800 cycles at 1.0 A/g.Moreover,the honeycomb-like CuP₂@C serves as a good material for lithium storage with high capacity and excellent cycling stability,retaining 720 mAh/g after 600 cycles at 1.0 A/g.更多还原