A Novel Solid Solution Mn_1-xV_xP Anode with Tunable Alloying/Insertion Hybrid Electrochemical Reaction for High Performance Lithium Ion Batteries

The substitutional solid solution Mn_1-xV_xP compounds are proposed as a high performance anode for lithium ion batteries (LIBs) through a novel alloying/insertion hybrid electrochemical reaction concept by combining alloying reaction-type MnP and insertion reaction-type VP. The solid solution series of Mn_1-xV_xP are successfully synthesized via a facile high energy mechanical milling. Their electrochemical properties as an anode for LIBs are systematically studied and compared with those of MnP/VP mixture, particularly focusing on the verification of simultaneous alloying/insertion hybrid electrochemical reaction in the solid solution compounds. The Mn_0.75V_0.25P solid solution electrode shows the excellent high rate cyclability delivering the reversible capacity of 321 mAh g⁻¹ after 5000 cycles at a high current density of 1.0 A g⁻¹, resulting from the synergistic effects of two reaction mechanisms. The homogeneously substituted vanadium ions enable the alloying/insertion hybrid electrochemical reaction in a Mn_1-xV_xP single phase, which can effectively reduce the rate of volume change, hinder the pulverization and agglomeration of alloying reaction-type Li-Mn-P crystallite during cycling, and ensure the fast electron and ion transport. This simple, yet innovative, solid solution design with the consideration of structural relationships and electrochemical properties inspires the development of advanced ternary or multi-component compound electrode materials for LIBs or other energy storage devices.