High density conductive LiFePO4 cathode with enhanced high-rate and high temperature performance

Abstract

Lithium iron phosphate (LiFePO₄) has been extensively investigated as a cathode material for next generation lithium ion batteries, but it faces inherent low electronic conductivity and slow Li⁺ diffusion rate. This leads to poor electrochemical performance at high C-rates and at high temperatures. To solve this, we coat optimally thick, conductive, and conformal TiN films on LiFePO4 particles using atomic layer deposition. The 10 cycles of TiN (10TiN) coated sample delivers an initial capacity of ∼78.8 mAhg⁻¹ at a high rate of 5 C-rate and at a high temperature of 55 °C, while an uncoated sample delivers only ∼ 62.8 mAhg⁻¹ under the same condition. The high electrode density due to ALD thin film coating, optimized pressing, and protective nature of the ultrathin film and increase in conductivity are contributing factors to the improved the high rate performance of the coated samples as compared to the pristine sample at elevated temperature.