Investigation of In-Situ Carbon Coated LiFePO4 as a Superior Cathode Material for Lithium Ion Batteries

In the present study, we have developed a simple and cost-effective approach for the synthesis of carbon coated LiFePO4 wherein different carbon precursors were used to find out the suitable precursor for carbon coating. Initially, the appropriate amount of Li, Fe, and P precursors and carbon source (glucose/sucrose/fructose) were dissolved in ethanol solution followed by hydrothermal treatment at 180 degrees C to obtain carbon coated LiFePO4. The structure and morphological analysis of in-situ carbon coated LiFePO4 revealed the formation of thin and homogeneous carbon layer on crystalline single-phase LiFePO4 particles with fructose used as carbon precursor. Raman analysis confirms the presence of more ordered graphitic carbon and the I-D/I-G ratio is 1.01, 0.69 and 0.87 for C-LFP-S, C-LFP-F and C-LFP-G respectively, indicating that fructose assisted in-situ carbon coating leads to the formation of more ordered carbon coating on LiFePO4 with high graphitization degree in comparison with carbon coating by glucose and sucrose. HR-TEM results revealed the presence of uniform carbon distribution, which encapsulates the crystalline LiFePO4 particles forming a core-shell structure in the presence of fructose as carbon precursor. C-LFP-S delivered a capacity of 125 mAh/g at 0.1 C rate but then due to non-uniform carbon layer distribution, the capacity faded out completely when tested at higher C-rates. Whereas C-LFP-F delivered a discharge capacity of 98 mAh/g at 0.1 C and 48 mAh/g at 1 C, which is promising compared to the LiFePO4 carbon coated using sucrose and glucose. It is concluded that LiFePO4 carbon coated using monosacrides as carbon precursors showed better electro-chemical performance in terms of capacity and cyclic stability when compared to LiFePO4 carbon coated using dissacrides, attributing that uniform, thin layer, and highly ordered graphitic carbon coverage on nano sized LiFePO4 particles greatly reduces the polarization resistance and hence improving the electrochemical performance of C-LFP-F.