Wu Min, Zhao Hongshun, Zhou Bo, Ding Zhengping, Liang Kang, Wei Peng, Qin Shaopan, Li Jianbin, Huang Xiaobing, Zhang Zhi, Ma Jianmin, Ren Yurong
School of Materials Science and Engineering, Jiangsu Province Engineering Research Center of Intelligent Manufacturing Technology for the New Energy Vehicle Power Battery, Changzhou Key Laboratory of Intelligent Manufacturing and Advanced Technology for Power Battery, Changzhou University, Changzhou, 213164, China.
College of Chemistry and Materials Engineering, Hunan University of Arts and Science, Changde, 415000, China.
Small. 2024 Jun;20(25):e2309871. doi: 10.1002/smll.202309871. Epub 2024 Feb 1.
Owing to the outstanding comprehensive properties of high energy density, excellent cycling ability, and reasonable cost, Ni-rich layered oxides (NCM) are the most promising cathode for lithium-ion batteries (LIBs). To further enhance the specific capacity of Ni-rich layered oxides, it is necessary to increase the cut-off voltage to a higher level. However, a higher cut-off voltage can lead to substantial structural changes and trigger interface side reactions, presenting significant challenges for practical applications (cycle life and safety). Herein, to solve above issues, tris(hexafluoroisopropyl)borate (TFPB) is introduced as a high voltage electrolyte additive for LiNiCoMnO cathode. Based on detail in situ/ex situ characterization, this study proves that TFPB forms a protective solid-state interphase (SEI) layer on the Li-anode. Additionally, derivatives of TFPB are easily oxidatively decomposed to create a dense cathode electrolyte interphase (CEI) film on the cathode. This CEI film effectively prevents the continuous oxidation of the electrolyte and mitigates the adverse effects of HF on the battery. Benefit from the protective SEI and CEI layer, the LiNiCoMnO||Li battery with a TFPB-containing electrolyte maintains an unprecedented level of performance, with a capacity retention of 89.1% after 100 cycles under the ultrahigh cut-off voltage of 4.6 V (vs Li/Li).
由于具有高能量密度、出色的循环能力和合理成本等优异综合性能，富镍层状氧化物（NCM）是锂离子电池（LIBs）最具前景的正极材料。为进一步提高富镍层状氧化物的比容量，有必要将截止电压提高到更高水平。然而，较高的截止电压会导致大量结构变化并引发界面副反应，给实际应用（循环寿命和安全性）带来重大挑战。在此，为解决上述问题，引入三（六氟异丙基）硼酸酯（TFPB）作为LiNiCoMnO正极的高电压电解质添加剂。基于详细的原位/非原位表征，本研究证明TFPB在锂负极上形成了一层保护性固态界面（SEI）层。此外，TFPB的衍生物易于氧化分解，在正极上形成致密的正极电解质界面（CEI）膜。该CEI膜有效防止了电解质的持续氧化，并减轻了HF对电池的不利影响。受益于保护性的SEI和CEI层，含TFPB电解质的LiNiCoMnO||Li电池保持了前所未有的性能水平，在4.6 V（相对于Li/Li）的超高截止电压下循环100次后容量保持率为89.1%。
