Understanding charge storage in Nb2CTx MXene as an anode material for lithium ion batteries

Renfei Cheng; Tao Hu; Zuohua Wang; Jinxing Yang; Ruqiao Dai; Weizhen Wang; Cong Cui; Yan Liang; Chao Zhang; Cuiyu Li; Hailong Wang; Hongxia Lu; Zhiqing Yang; Hongwang Zhang; Xiaohui Wang

doi:10.1039/D1CP03070A

Understanding charge storage in Nb₂CT_x MXene as an anode material for lithium ion batteries†

Renfei Cheng,^ab Tao Hu,

^c Zuohua Wang,^d Jinxing Yang,^ab Ruqiao Dai,^ab Weizhen Wang,^a Cong Cui,^ab Yan Liang,^a Chao Zhang,^a Cuiyu Li,^e Hailong Wang,^f Hongxia Lu,^f Zhiqing Yang,^a Hongwang Zhang^d and Xiaohui Wang

*^a

Author affiliations

* Corresponding authors

^a Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
E-mail: wang@imr.ac.cn

^b School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China

^c Institute of Materials Science and Devices, Suzhou University of Science and Technology, Suzhou 215009, China

^d National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China

^e Advanced Computing East China Sub-center, Suma Technology Company Limited, Kunshan 215300, China

^f School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

Abstract

MXenes represent an emerging family of two-dimensional materials of transition metal carbides/carbonitrides terminated with functional groups like –O, –OH, and –F on the chemically active surface of MX slabs. As a member of the family, Nb₂CT_x exhibits superior lithium storage capacity over most of the other MXenes as anode materials in lithium-ion batteries (LIBs). However, an in-depth understanding of the charge storage mechanism is still lacking so far. Here, through combining complementary experiments and density functional theory calculations, we provide insights into the (de)lithiation process. Specifically, Nb₂CT_x with dominant –O functional groups stores charge as a result of changes in the oxidation states of both transition metals Nb and O, which is supported by Bader charge analysis showing a significant change in the oxidation states of Nb and O upon lithiation. As monitored by ex situ X-ray diffraction, the interlayer spacing of Nb₂CT_x changes slightly upon lithium ion (de)intercalation, corresponding to a volume change of only 2.3% with a near zero-strain feature. By coupling with a LiFePO₄/C cathode, the full cell presents superior rate capability and cycling stability as well. The insights into the charge storage mechanism of Nb₂CT_x in this work provide useful guidance for the rational design of MXene-based anode materials for high-performance LIBs.

Physical Chemistry Chemical Physics

Understanding charge storage in Nb₂CT_x MXene as an anode material for lithium ion batteries†

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Physical Chemistry Chemical Physics