K doping on Li site enables LiTi2(PO4)3/C excellent lithium storage performance

Abstract

LiTi2(PO4)3 as anode for aqueous lithium ion battery shows promising prospect in energy storage and electronic products owing to stable structure and suitable intercalation/deintercalation voltage of Li ions. However, the performance of LiTi2(PO4)3 needs to be further improved to meet their higher requirements. Herein, K-doped LiTi2(PO4)3/C on Li site was synthesized by sol-gel method combined with heat-treatment. And synthesized sample was used as anode for aqueous lithium ion battery. The main lattice structure and morphology of LiTi2(PO4)3 are not affected by K doping on Li site. And electrochemical property of LiTi2(PO4)3 is obviously improved by K doping. Performance changing trend is in order of Li0.97K0.03Ti2 (PO4)3/C (LCK-3) > Li0.99K0.01Ti2(PO4)3/C (LCK-1) > Li0.95K0.05Ti2(PO4)3/C (LCK-5) > LiTi2(PO4)3/C (LC), which is consistent with the changing trend of lattice volume. LCK-3 demonstrates superb electrochemical property. LCK-3 delivers the discharge capacities of 104.4, 88.9, and 73.1 mAh g−1 at 0.5, 7.0, and 15 C, respectively, 26.7, 42.9, and 53.0 mAh g−1 higher than these of original LC. Moreover, capacity retention of 78.8% for LCK-3 is retained at 6 C even after 1000 cycles, which is much larger than that for LC (60.6%). It is attributed to that K with proper content can widen the pathway for Li ions, which is confirmed by XRD measurement. This can further accelerate the transfer of Li ions in crystal. This work demonstrates that K doping on Li site is a valid method to ameliorate electrochemical performance of LiTi2(PO4)3 in aqueous lithium ion battery.