| Summary: | 碩士 === 明志科技大學 === 化學工程系碩士班 === 107 === The LiFe1/3Mn1/3Co1/3PO4/C (denoted as LFMCP/C) composite cathode material with olivine structure was prepared by a solid-state ball-milled method. The citric acid is a reducing agent and sucrose is used as the carbon sources. The properties of the as-synthesized LFMCP/C composite materials were examined by XRD, SEM, EA, and DLS, etc. The CR2032 coin-type cell was assembled to study the electrochemical performance of the LFMCP/C composite materials. The galvanostatic charge/discharge test was conducted in the potential range of 2.0 – 5.0 V at various C-rates, i.e., at 0.1 – 10C.
The result was found that the dual-time ball milled LFMCP/C cathode material with 30 wt.% citric acids, 5 wt.% sucrose, and further coating with 2 wt.% LATP@pSP filler (LATP : porous super P = 3:7, wt.%) (denoted as Dual-BM-LFMCP-C30S5/LATP@pSP) shows the best electrochemical performance. In order to overcome serious electrolyte decomposition problem of LFMCP cathode at 5.0 V high charge potential, a 1 wt.% Propane Sultone (PS) additive was added in the 1 M LiPF6 in EC/EMC (1:2, v/v) for high voltage electrolyte (denoted as SH-Electrolyte) in this study. According to our charge/discharge test results, the discharge capacity of the dual-time ball milled LFMCP-C30S5/LATP composite with SH-Electrolyte is around 151.87 mAh g-1 at 0.1C rate; 123.52 mAh g-1 for 1C rate. It was found that the discharge capacity retention is achieved around 92.20%, after 30 cycles at 0.1C/0.1C. Besides, it is around 81.01% for 100 cycles at 1C/1C. It was revealed that the excellent cycling performance of LiFe1/3Mn1/3Co1/3PO4 composite material with SH-Electrolyte was archived with the improved interfacial stability at LFMCP/C electrolyte interface. It was demonstrated that LiFe1/3Mn1/3Co1/3PO4 composite material with organic electrolyte additive and further coating with 2 wt.% LATP@pSP filler can be a good candidate for the high voltage and energy density of Li-ion power battery.
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