Synthesis, Characterization, Electrochemistry, and In Situ X-ray Diffraction Investigation of Ni3(PO4)2as a Negative Electrode Material for Lithium-Ion Batteries

Nickel orthophosphate, Ni-3(PO4)(2), was successfully synthesized using solid-state reaction at 900 degrees C. The effect of the calcination temperature on the material purity was investigated at different temperatures (700-900 degrees C). XRD analysis has shown that Ni-3(PO4)(2)crystallizes in a monoclinic system withP2(1)/a space group. The electrochemical performances of carbon-coated Ni-3(PO4)(2)were investigated for the first time versus Li+/Li and improved by the optimization of the cut-off voltage, the carbon-coating source, and the binder used. The best performance was delivered when using 0.01 V cut-off voltage, sucrose for C-coating, and carboxymethyl cellulose (CMC) binder. A reversible capacity of 249 mAh g(-1)and a capacity retention around 74-79 % after 90 cycles with a good coulombic efficiency of 98 % were obtained at C/5 current rate. In situ XRD measurements demonstrated the irreversible amorphization of the Ni-3(PO4)(2)crystal structure during the first discharge process, confirming that this phosphate exhibits a pure conversion mechanism.