Boosting the performance of LiTi2(PO4)3/C anode for aqueous lithium ion battery by Sn doping on Ti sites

Highlights: • LiTi_2-xSn_x(PO₄)₃/C anodes for ALIB were synthesized by sol-gel approach. • The performance of LiTi_2-xSn_x(PO₄)₃/C anodes was systematically studied. • The optimal LiTi_1.7Sn_0.3(PO₄)₃/C exhibited superior rate and cycling performance. In this paper, LiTi_2-xSn_x(PO₄)₃/C (x = 0, 0.2, 0.3, 0.4) composites were synthesized by sol-gel approach, and were investigated as anodes for aqueous lithium ion battery. Sn doping with proper content has no obvious influence on phase and morphology of the composite, while excessive dosage of Sn can affect its crystal structure. Sn doping can enhance the electrochemical properties of LiTi₂(PO₄)₃/C (LC). Among LiTi_2-xSn_x(PO₄)₃/C composites, LiTi_1.7Sn_0.3(PO₄)₃/C (LC-Sn-0.3) demonstrates the best electrochemical properties. Most importantly, the rate performance of LC can be improved dramatically by Sn doping on Ti sites. LC-Sn-0.3 delivers a discharge capacity of 118.9, 115.3, and 104.2 mAh g⁻¹ at 0.2, 6, and 20 C (1 C = 150 mA g⁻¹), respectively, with significant increase of 15.2, 27.4, and 41.9 mAh g⁻¹ compare with LC. In addition, LC-Sn-0.3 exhibits superior cycling performance. The capacity retention for LC-Sn-0.3 can keep 76.8% after 1000 cycles at relatively high rate of 10 C, while only 51.7% of initial discharge capacity is retained for LC. Our study reveals that Sn doping on Ti sites is an efficient and facile method to improve the performance of LiTi₂(PO₄)₃/C composite for aqueous lithium ion battery.