Balancing the Ion/Electron Transport of Graphite Anodes by a La-Doped TiNb<sub>2</sub>O<sub>7</sub> Functional Coating for Fast-Charging Li-Ion Batteries.

Sheng, Yeliang; Yue, Xinyang; Hao, Wei; Dong, Yongteng; Liu, Yakun; Liang, Zheng · Nano Lett · 2024

basic_science · Level V

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Abstract

A functional coating layer (FCL) is widely applied in fast-charging lithium-ion batteries to improve the sluggish Li<sup>+</sup> transport kinetics of traditional graphite anodes. However, blindly increasing the Li<sup>+</sup> conductivity for FCL reduces the overall electron conductivity of the anodes. Herein, we decoupled the effect of La-doping on TiNb<sub>2</sub>O<sub>7</sub> (TNO) in terms of the phase evolution, Li<sup>+</sup>/electron transport, and lithiation behavior, and then proposed a promising La<sub>0.1</sub>TNO FCL with balanced Li<sup>+</sup>/electron transport for a fast-charging graphite anode. By optimizing the doping concentration of La, more holes are introduced into the TNO as electron carriers without causing lattice distortion, thus maintaining the fast Li<sup>+</sup> diffusion channel in TNO. As a result, the graphite with La<sub>0.1</sub>TNO FCL delivers an excellent capacity of 220.2 mAh g<sup>-1</sup> (96.3% retention) after 450 cycles at 3 C, nearly twice that of the unmodified one.