In-situ X-ray diffraction study on the structural reversibility of lithium nickel cobalt oxide in a broad electrochemical window of 1.35–4.3 V

• Published in: Electrochimica acta 2016-02, Vol.190, p.248-257
• Main Authors: Wang, Pengfei, Li, Peng, Yi, Ting-Feng, Yu, Haoxiang, Lin, Xiaoting, Qian, Shangshu, Zhu, Yan-Rong, Shui, Miao, Shu, Jie
• Format: Article
• Language: English
• Subjects: Chemical reactions; Diffraction; Evolution; Lithium; Nickel; Platforms; Transformations; X-rays
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2015.12.200

The overlithiation and delithiation behaviors of sol-gel formed LiNi sub(0.75)Co sub(0.25)O sub(2) are investigated in this work. As an insertion host material, LiNi sub(0.75)Co sub(0.25)O sub(2) is cycled in a broad working potential range of 1.35-4.3 V. It shows two lithiation platforms at 1.75/3.6 V and only one reverse delithiation platform at 3.7 V. The long lithiation platform at 1.75 V is attributed to the overlithiation behavior of LiNi sub(0.75)Co sub(0.25)O sub(2). Although overlithiation reaction takes place below 2.0 V, LiNi sub(0.75)Co sub(0.25)O sub(2) can maintain electrochemical reversibility during the initial 20 cycles. To study the overlithiation/delithiation process, the structural evolution of LiNi sub(0.75)Co sub(0.25)O sub(2) is thoroughly observed by in-situ X-ray diffraction method. It can be found that the electrochemical reaction between LiNi sub(0.75)Co sub(0.25)O sub(2) and Li in 1.35-4.3 V is a reversible process, which is associated with a single-phase transition process above 3.0 V and a two-phase transformation below 2.0 V. This result not only demonstrates the high structural and electrochemical reversibility of LiNi sub(0.75)Co sub(0.25)O sub(2) in 1.35-4.3 V, but also proves the improved structural stability of LiNi sub(0.75)Co sub(0.25)O sub(2) via partial replacement of Ni by Co in layered LiNiO sub(2).