N-doped carbon coated LiTi2(PO4)3 as superior anode using PANi as carbon and nitrogen bi-sources for aqueous lithium ion battery

Highlights: • N-doped carbon coated LiTi₂(PO₄)₃ composites were synthesized by using polyaniline as carbon and nitrogen bi-sources.. • High-quality N-doped carbon layer and good dispersion for LiTi₂(PO₄)₃ composite were achieved by this strategy. • LiTi₂(PO₄)₃/C-N composite demonstrated superior rate and cycling performance. N-doped carbon coated LiTi₂(PO₄)₃ composites were synthesized by polyaniline (PANi) as carbon and nitrogen bi-sources, and used as anode for aqueous lithium ion battery (ALIB). High-quality N-doped carbon layers were achieved to modify LiTi₂(PO₄)₃ crystal. ALIB using as-synthesized LiTi₂(PO₄)₃@C-N as anode exhibited superior rate performance. It delivered discharge capacities of 122.4, 105.8, and 95.3 mAh g⁻¹ at rates of 0.2, 10, and 20C, respectively, much higher than those (97.4, 61.1, and 43.9 mAh g⁻¹) of LiTi₂(PO₄)₃/C using sucrose as carbon source. Furthermore, LiTi₂(PO₄)₃@C-N anode demonstrated outstanding cycling performance with a capacity retention of 82.1% after 1000 cycles at 2C, while only 56.3% of capacity retention was kept for that using sucrose as carbon source. The excellent electrochemical performances of LiTi₂(PO₄)₃@C-N are mainly attributed to good dispersion, proper carbon layer, and nitrogen doping, further accelerating the charge transfer and diffusion of Li ions/electrons.