Improving Li3V2(PO4)3 cathode performance by Mn2+ doping for high-rate aqueous zinc ion hybrid batteries

Li3V2-xMnx(PO4)(3) (x = 0, 0.02, 0.04, 0.06 and 0.1) cathode materials for aqueous zinc-ion hybrid batteries (AZHBs) have been synthesized by freeze-drying-assisted sol-gel method. The effects of Mn2+ dopping content on the structure, morphology, and electrochemical performance of the samples were investigated. XRD results indicated that the Li3V2-xMnx(PO4)(3) products belong to the Li3V2(PO4)(3) structure (P2(1)/n). XPS results indicate that Mn2p(1/2) and Mn2p(2/3) are located at 653.94 eV and 642.46 eV, respectively, with trace amounts of Mn doping in the material. SEM images show that Li3V1.94Mn0.06(PO4)(3) sample has more dispersed and smaller particle size in morphology, and the uniform distribution of elements of Li3V1.94Mn0.06(PO4)(3) sample (V, Mn, P, O) in the precursor composites was confirmed by EDAX. The Zn// Li3V1.94Mn0.06(PO4)(3) battery delivers a superior initial capacity of 106.5 mAh g(-1) at the current density of 2 C (200 mA g(-1)), remarkable cycle stability (98% capacity retention for 50(th) cycles) and superior rate capability (when current density reaches up to 20 C, the reversible capacities are 98mAh g(-1)). The results of CV indicated that the diffusion coefficient of zinc ion in Li3V1.94Mn0.06(PO4)(3) electrode is 1.30 x 10(-12) cm(2) s(-1), which is larger than the other four electrodes. The result of EIS demonstrated that the R-ct value. of Li3V1.94Mn0.06(PO4)(3) is the lowest (243.5 omega), which is in good agreement with rate capability and cyclic results. ex situ XRD results demonstrate that Li+ ion can be inserted or de-inserted reversibly during charge and discharge.

Automated summary

Li3V2-xMnx(PO4)(3) materials with different Mn2+ doping contents were synthesized and their structure and electrochemical performance were investigated. The Li3V1.94Mn0.06(PO4)(3) sample exhibited improved morphology, cycle stability, and rate capability.