Polyvinylpyrrolidone assisted transformation of Cu-MOF into N/P-co-doped Octahedron carbon encapsulated CuP nanoparticles as high performance anode for lithium ion batteries.

The large volume expansion and poor electrical conductivity of copper phosphide (CuP) during the cycle limit their further application as anode of lithium-ion batteries. Therefore, polyvinylpyrrolidone (PVP) modified Cu(BTC)-derived (BTC = 1, 3, 5-Benzentricarboxylic acid) in-situ N/P-co-doped Octahedron carbon encapsulated CuP nanoparticles (CuP@NPC) are successfully prepared through a two-step process of carbonization and phosphating. The N/P-co-doped Octahedron carbon matrix improves the conductivity of CuP and moderates the volume expansion during the lithiation/delithiation process. Meanwhile, the interaction between the CuP and the doped carbon matrix is methodically explored by using density functional theory (DFT). Through the analysis of the partial charge density, the density of states and the Bader charge, and the calculation results verify the correctness of the experimental observation results, that is, CuP@NPC has good electrochemical performance. The results show that CuP@NPC, as the anode of Lithium-ion batteries, has excellent electrochemical performance: it exhibits satisfactory rate performance (251.9 mAh g at 5.0 A g) and excellent cycle performance (336.4 mAh g at 1 A g over 1000 cycles). This article provides an effective strategy for the encapsulation of metal phosphide nanoparticles in a doped carbon matrix.