Honglin Yan,Xiaoya Gao,Xiangting Yue,Yuan Ha,Zhimin Li
Ni-rich LiNi 0.80 Co 0.15 Al 0.05 (NCA) cathode material with high energy density always suffers from structural degradation during cycles, resulting in rapid capacity fading and severe voltage decay. In this study, a solid-state electrolyte film of Li 1.8 Sc 0.8 Ti 1.2 (PO 4 ) 3 (LSTP) is constructed on the surface of NCA cathode via a chemical route to enhance the cycling stability of NCA cathode. The Ex-situ XRD, EIS, dQ/dV, and SEM analyses show that the structural degradation of NCA derives mainly from the corrosion of electrolyte rather than H2-H3 phase transition, which gives rise to the extremely weak phase transitions of H1-M−H2−H3 after cycles. Besides the isolation role of LSTP film, it is found that Ti 4+ ions in LSTP incorporate into the subsurface structure of NCA, which can accelerate the Li + diffusion, reduce the Li + /Ni 2+ disorder, reinforce the crystal structure, and enlarge the inter-slab spacing of NCA. Consequently, the coated NCA-2 %LSTP cathode reveals well structural integrity and evident phase transition behavior, delivering stable cycling performance with a superior capacity retention of 96.8 % at 1.0C after 100 cycles. This study not only deeply analyzes the mechanism of the structural degradation of NCA, but also demonstrates an efficient improving approach through LSTP modification.
Gaozhan Liu,Jiamin Shi,Mengting Zhu,Wei Weng,Lin Shen,Jing Yang,Xiayin Yao
All-solid-state lithium batteries with high safety and high energy density are one of the most promising next generation energy storage devices. However, the enhancement of energy density of all-solid-state lithium batteries is generally hindered by the thick and heavy solid electrolyte layer. In this work, a 5 nm thick homogeneous polydopamine layer is coated on the Li 6 PS 5 Cl electrolyte particles in organic alkali solution, resulting in a modified adhesive particle surface. Free-standing polydopamine-coated Li 6 PS 5 Cl thin film with thickness of 35 μm could be achieved by cold pressing. All-solid-state lithium battery with the polydopamine-coated Li 6 PS 5 Cl thin film is assembled and exhibits a discharge capacity of 485.1 mAh g −1 after 100 cycles with a capacity retention of 78.5% at 0.1 C and 25 °C. A high full-cell level energy density of 284.4 Wh kg −1 can be realized with reduced thickness and weight of electrolyte layer.
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