A novel method to fabricate nonstoichiometric LiFePO4/C core–shell composites

The nonstoichiometric LiFePO4/C core–shell composites (as microscale LiFePO4 cores coated with 3–5 nm thin carbon shells) are synthesized by a novel solid-state reaction method. All samples show outstanding coulombic efficiency (about 100%) and good battery cyclability, along with high tap density (>1.70 g cm−3). On this basis, the electrochemical properties of two different core–shell composites as Li1.02Fe0.99PO4/C and Li0.98Fe1.01PO4/C are compared. The results show that the rate performance of Li1.02Fe0.99PO4/C is obviously better than the rate performance of Li0.98Fe1.01PO4/C.

► A novel method is reported for the first time to fabricate the nonstoichiometric LiFePO4/C core–shell composites which need less carbon to form the thin carbon shell. This method has both advantages of carbon deposition and liquid N2 quenching measurements. ► The nonstoichiometric LiFePO4/C core–shell composites as microscale LiFePO4 core coated with 3–5 nm thin carbon shell show outstanding coulombic efficiency, good battery cyclability whatever high or low current rates along with high tap density. ► On this basis, Li1.02Fe0.99PO4/C (Li-rich) and Li0.98Fe1.01PO4/C (Fe-rich) were compared with each other as two typical shapes of nonstoichiometric LiFePO4. The results show Li1.02Fe0.99PO4/C core–shell composite performs good rate performance which can meet the high power applications and its electrochemical properties are obviously better than that of Li0.98Fe1.01PO4/C.