Electrochemical performance of LiFePO4@C composites with biomorphic porous carbon loading and nano-core-shell structure

Effect of biomorphic porous carbon (BPC) addition on the composition, microstructure, and electrochemical performance of LiFePO4@C/C composites was investigated. Results indicated that network pores of BPC were almost completely filled by LiFePO4@C nanoparticles, which were formed by an olivine structure LiFePO4 core with size that ranged from 58.6 nm to 80.1 nm and an amorphous carbon shell with a thickness of approximately 2 nm. Double electrical conductive networks formed in the composites improved the electrical properties of samples from 2.59×10−6 S cm−1 (sample A-0) to 5.76×10−2 S cm−1 (sample A-20). Synergy effect of electric double layer energy storage produced by BPC and lithium-ion extraction/insertion energy storage by LiFePO4 clearly reduced the capacity reduction rate of composites, and obtained a charge/discharge capacity of 114.2/110.5 mA h g−1 (sample A-5) at 10 C. Moreover, addition of BPC showed a significant advantage in reducing the interfacial resistance of the electrode reaction in composites from 86.72 Ω (sample A-0) to 37.58 Ω (sample A-20). The electrical conductive mechanism of LiFePO4@C/C composites is discussed.