过渡金属磷化物电位低且比容量高, 是有发展前景的锂离子电池(LIBs)负极材料. 其中, ZnP₂属于双活性负极材料, Zn与P都能与Li⁺发生反应, 储Li⁺性能更具有竞争力. 但是, 对于ZnP₂的锂化机理及产物尚不明确. 采用第一性原理计算和电化学测试方法研究了ZnP₂的电子性质和电化学性能, 通过理论计算和实验测试相结合阐述了ZnP₂的锂化机制. 首先, 以密度泛函理论(DFT)计算揭示了ZnP₂的锂化机理、Li⁺扩散路径、势垒和理论比容量(1477 mAh/g). 其次, 通过直流电弧等离子体法及固相烧结法合成ZnP₂, 并测试其首圈放电曲线, 显示放电容量为1439 mAh/g, 与理论计算结果相近. 此外, 薄膜X射线衍射(XRD)检测最终产物成分为LiZn和Li₃P, 与DFT计算结果一致.

Transition metal phosphides are promising anode materials for lithium ion batteries (LIBS) because of their low potential and high specific capacity. Among them, ZnP₂ is a dual active anode material, and both Zn and P can react with Li, which is more competitive in capacity. However, the lithiation mechanism and the reaction products of ZnP₂ are still unclear. In this work, the electronic and electrochemical properties of ZnP₂ were studied by first-principle calculations and electrochemical measurement. The combination of theoretical calculations and experimental tests demonstrated the lithiation mechanism of ZnP₂. Firstly, density functional theory (DFT) calculations revealed the lithiation reaction products, lithium diffusion path, diffusion barrier and theoretical lithium storage capacity (1477 mAh/g) of ZnP₂. The calculation of the binding energy proved that the formation energies of LiZn and Li₃P were thermodynamically lower than that of Li_nZnP₂. The charge density difference analysis showed that the Zn—P bonds and P—P bonds were gradually broken during the Li⁺ insertion process, which was accompanied by the formation of Li—P bonds and Li—Zn bonds, and these all confirmed the conversion reaction occurred after Li⁺ was inserted into ZnP₂. The calculation result of the density of states proved that ZnP₂ changed from a semiconductor to a conductor with the insertion of Li⁺. The diffusion energy barrier was higher than that of general layered materials, which will reduce the rate performance of LIBs. Secondly, ZnP₂ nanosheets were synthesized by the direct current (DC) arc plasma and solid phase sintering method. The electrochemical test showed that the rate performance and cycle performance were slightly worse, which proved the correctness of the diffusion barrier results. The discharge curve showed that the discharge capacity of the first cycle is similar to the theoretical calculation result, which is 1439 mAh/g. Finally, the components of the discharge products detected by the thin film X-ray diffraction (XRD) were LiZn and Li₃P, which were consistent with the DFT calculation results.