Synthesis and characterization of LiFe0.5Mn0.3Co0.2PO4/C composite material for high-voltage Li-ion battery application

Highlights: • The work reports the preparation of LiFe_0.5Mn_0.3Co_0.2PO₄/C by a solid-state method. • Flower-like nano-sized Co₃O₄ is prepared by a hydrothermal process. • The capacity of LFMCP/C with 1%TMB shows 150 mAh g⁻¹ at 0.1C and 120 mAh g⁻¹ at 1C. • XPS and SIMS were used to study the properties of CEI with and without 1%TMB. • We propose a dual layer structure CEI model for LFMCP. A LiFe_0.5Mn_0.3Co_0.2PO₄/C composite cathode material was prepared using a solid-state ball-milling method. The flower-like Co₃O₄ precursor was prepared by hydrothermal method and used to improve the electrochemical properties of composite material. The galvanostatic charge–discharge profile is performed in the potential range of 2–5 V by using different electrolyte compositions with/without 1 wt% trimethyl boroxane (TMB) additive at various C rates. The highest discharge capacities of the composite material were 150.42 mAh g⁻¹ at 0.1C and 120 mAh g⁻¹ at 1C in LiPF₆+1 wt%TMB in EC:EMC (1:2, v/v). In addition, the excellent cycle-life was observed at 0.1C and 1C rate for 30 and 100 cycles with the charge retention of 97.7% and 73%, respectively. These appreciable results were obtained due to the carbon coating layer and highly active composite material. The thickness of cathode electrolyte interphase layer on composite electrode is ca. 3 nm which was measured by secondary ion mass spectroscopy. And also, we found that the B element on interphase layer that acts as F-scavenger to reduce the amount of LiF formation over cathode interphase layer. As a result, it can markedly reduce the charge transfer resistance and improve the electrochemical performance for long-term cycling.