Inorganic precipitation synthesis of Sn-doped LiTi2(PO4)3 as an anode material for high-performance aqueous lithium-ion batteries

Abstract

Regarding aqueous lithium-ion batteries, LiTi₂(PO₄)₃ (LTP) emerges as a promising candidate, distinguished by its substantial specific capacity and structural integrity. While the conventional precipitation methods predominantly employ Ti(C₄H₉O)₄ as the titanium source, its inherent deficiencies of hydrolysis, compromised storage stability, and considerable cost have significantly impeded widespread application. In order to solve these problems, this paper introduced Ti(SO₄)₂, a chemically stable inorganic material and crucial industrial intermediate in TiO₂ synthesis, as an economically viable and easily accessible source. Through the development of a novel inorganic precipitation method, this study obtained a homogeneous precursor by in-situ coating LiTi₂(PO₄)₃ anode with tannic acid and in-situ doping. The incorporation of Sn(C₄H₉)₄ through in-situ doping effectively addresses the intrinsic electronic conductivity constraints, with the successful integration of Sn conclusively demonstrated through XPS depth profiling analyses. The resultant Sn-doped LiTi₂(PO₄)₃/C exhibits refined particle size and enhanced electrochemical characteristics, showing excellent multiplicative cycle stability with a capacity retention of about 75.4% over 1000 cycles. Additionally, the investigation with density flooding theory facilitated the construction of an independent gradient model, indicating the role of Sn doping in enhancing the structural stability of LTP. The electronically constructed model significantly reduces the band gap to improve the electronic conductivity, providing a theoretical basis and some commercial prospects for the new aqueous lithium-ion battery anode.