Poly(vinylpylrrolidone) as Surfactant in the Sol–Gel Preparation of Lithium Iron Phospate/Carbon Cathodes for Lithium‐Ion Batteries

Abstract Lithium iron phosphate/carbon (LiFePO 4 /C) is synthesized by a modified sol–gel method, in which the nonionic surfactant poly(vinylpyrrolidone) (PVP) is used. PVP plays a dual roles in the preparation of LiFePO 4 /C: it is used as surfactant to prevent the colloid particles and carbon source from aggregating, and is a carbon source. The carbon contents and conductivities of LiFePO 4 /C increase with increasing of PVP. When the ratio of PVP to LiFePO 4 reaches 1 ‰, the conductivity of LiFePO 4 /C reaches its optimal value of 2.67×10 −2 S cm −1 and its discharge capacity at 1 C is 131.0 mAh g −1 . This is because the use of PVP leads particles that are small and have a homogeneous size distribution, which is due to dispersion by PVP. Titanium (Ti 4+ )‐doped samples, obtained from a sol–gel method, possess even better performances. The discharge capacities of this sample is 111.1 mAh g −1 at 5 C and 87.3 mAh g −1 at 8 C. The gap in potential between the oxidative and reductive peaks is as low as 0.2053 V, which shows its reversibility is excellent.