Bifunctional nitrile-borate based electrolyte additive enables excellent electrochemical stability of lithium metal batteries with single-crystal Ni-rich cathode at 4.7 V

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-04, Vol.434, p.134745, Article 134745
• Main Authors: Liu, Fangyan, Zhang, Zhi, Yu, Ziyang, Fan, Xinming, Yi, Maoyi, Bai, Maohui, Song, Ying, Mao, Qiuyun, Hong, Bo, Zhang, Zhian, Lai, Yanqing
• Format: Article
• Language: English
• Subjects: Cycling stability; High-voltage lithium metal battery; Single-crystal LiNi0.88Co0.09Mn0.03O2; Tris(2-cyanoethyl) borate
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.134745

An in-situ-formed a nitrile and boron-rich interface, which is derived by the tris(2-cyanoethyl) borate (TCEB), on single crystal LiNi0.88Co0.09Mn0.03O2 cathode is pioneeringly demonstrated to against severe electrolyte decomposition and structure degradation of the cathode at an ultrahigh charge cut-off voltage of 4.7 V. This protective film significantly improves the electrochemical performance of LiNi0.88Co0.09Mn0.03O2 cathode with a high reversible capacity of 158.7 mAh g−1 after 150 cycles at 4.7 V (versus Li/Li+) and 1C. This work highlights the interface engineering method by regulating the composition of electrolytes to stabilize high-energy single-crystal LiNi0.88Co0.09Mn0.03O2 cathode. The high-energy and cycling stability of a single-crystal LiNi0.88Co0.09Mn0.03O2 cathode with a robust and thin protective CEI film provides a prospective choice for next-generation Li metal batteries. [Display omitted] •Designing a bifunctional nitrile-borate molecule tris(2-cyanoethyl) borate (TCEB) as a high-voltage electrolyte additive is proposed.•TCEB-derived CEI film effectively mitigates high-voltage induced irreversible interfacial parasitic reactions.•This strategy maintains an excellent capacity retention of the single-crystal NCM88||Li metal battery at 4.7 V. The high-voltage lithium metal battery (HVLMB) with the Ni-rich cathode is one of the most promising next-generation energy storage systems due to its significantly high energy density (>500 Wh kg−1). Nevertheless, the real application of HVLMB is limited by the unstable electrode/electrolyte interface and the heterogeneous reaction of polycrystalline Ni-rich layered oxide ternary cathode. To overcome these challenges, an effective strategy is proposed utilizing a high-voltage bifunctional nitrile-borate molecule, tris(2-cyanoethyl) borate, as a film-forming additive and the robust single-crystal LiNi0.88Co0.09Mn0.03O2 (SC-NCM) cathode as a feasible alternative cathode: a high voltage stable protective film improves the electrode/electrolyte interface, and the outstanding chemo-mechanical of micro-sized particles effectively suppress the localized overutilization of active material. The TCEB derived CEI layer not only enlarges the electrochemical oxidation window of the electrolyte but also protects the cathode from notorious interfacial side reactions. With this strategy, the cycling stability of SC-NCM||Li-metal battery is significantly improved at an ultrahigh cut-off voltage of 4.7 V, exhibitin