Chengliang Lin,Jiaxuan Yin,Shengrui Cui,Xiang Huang,Wei Liu,Yongcheng Jin
High-voltage spinel LiNi0.5Mn1.5O4 (LNMO), which has the advantages of high energy density, low cost, environmental friendliness, and being cobalt-free, is considered one of the most promising cathode materials for the next generation of power lithium-ion batteries. However, the side reaction at the interface between the LNMO cathode material and electrolyte usually causes a low specific capacity, poor rate, and poor cycling performance. In this work, we propose a facilitated method to build a well-tuned dual structure of LiF coating and F– doping LNMO cathode material via simple calcination of LNMO with LiF at low temperatures. The experimental results and DFT analysis demonstrated that the powerful interface protection due to the LiF coating and the higher lithium diffusion coefficient caused by F– doping effectively improved the electrochemical performance of LNMO. The optimized LNMO-1.3LiF cathode material presents a high discharge capacity of 140.3 mA h g–1 at 1 C and 118.7 mA h g–1 at 10 C. Furthermore, the capacity is retained at 75.4% after the 1000th cycle at 1 C. Our research provides a concrete guidance on how to effectively boost the electrochemical performance of LNMO cathode materials.
Lan Zhang,Kaihang Zhang,Zhaohui Shi,Suojiang Zhang
Li4Ti5O12 (LTO) is a promising anode material for electric vehicles (EVs) and electrochemical energy storage applications because of its safety, good rate capability, and long cycle life. At elevated temperature, such as 60 °C, it always shows poor cycle performance because of the instability between the electrode material and electrolyte, which may also lead to a serious gassing issue. In this article, a facile hydrothermal method is adopted to coat the LTO powder with a thin LiF layer, in which the LiF acts as an artificial solid electrolyte interface (SEI) layer to prevent the direct contact of LTO and electrolyte, thus improving the high-temperature cycle performance. Electrochemical tests prove that the LiF coating layer has no influence on the kinetics at ambient temperature and greatly enhances the high-temperature cycle stability, and the LTO@LiF composite material keeps 87% of its initial discharge capacity in 300 1C cycles at 60 °C. Moreover, the LiF coating layer exhibits a special self-driven reforming process during the initial cycles, which makes it uniform and more effective at enhancing the stability between electrode/electrolyte interfaces.
Shijun Tang,Guiwei Chen,Fucheng Ren,Hongchun Wang,Wu Yang,Chenxi Zheng,Zhengliang Gong,Yong Yang
The electronic conductivity of solid electrolytes, which plays an important role in inducing Li dendrite deposition, is a key obstacle to the practical application of Li metal in all-solid-state lithium metal batteries. Herein, an ultrathin insulating LiF coating with controllable thickness is proposed as an electronic isolation layer to inhibit the formation of Li dendrites. The homogeneous LiF interfacial layer can effectively facilitate the physical contact of the Li metal and LLZTO electrolyte and promote uniform Li plating/stripping. In contrast to the inhomogeneous lithium nucleation and dendritic lithium growth in an unmodified LLZTO electrolyte induced by electron beam irradiation, dendritic Li deposition is efficiently inhibited on LiF coated LLZTO. The Li|0.5LF-LLZTO|Li symmetric cell exhibits a low interfacial impedance of 12.7 ohm cm2 and stable Li plating/stripping without lithium penetration, over 1500 hours at 0.2 mA cm−2 and 300 hours at 0.4 mA cm−2. Besides, the Li|0.5LF-LLZTO|LiCoO2 full cell also shows excellent long-term cycling stability with a high capacity retention of 76.8% after 2500 cycles at 1C. Our results reveal the importance of tuning the interface modification layer properties to guide the uniform lithium plating toward suppressing Li dendrite formation in solid electrolytes.
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