Lithium (Li) metal batteries (LMBs) are promising for high-energy-density rechargeable batteries 1 , 2 , 3 . However, Li dendrites formed by the reaction between highly active Li and non-aqueous electrolytes lead to safety concerns and rapid capacity decay 4 , 5 , 6 , 7 . Developing a reliable solid–electrolyte interphase is critical for realizing high-rate and long-life LMBs, but remains technically challenging 4 , 8 . Here we demonstrate that adding excess m -Li 2 ZrF 6 (monoclinic) nanoparticles to a commercial LiPF 6 -containing carbonate electrolyte of LMBs facilitates the release of abundant ZrF 6 2 – ions into the electrolyte driven by the applied voltage, converting to t -Li 2 ZrF 6 (trigonal) and creating a stable solid–electrolyte interphase in situ with high Li-ion conductivity. Computational and cryogenic transmission electron microscopy studies revealed that the in situ formation of the t -Li 2 ZrF 6 -rich solid–electrolyte interphase markedly enhanced Li-ion transfer and suppressed the growth of Li dendrites. As a result, LMBs assembled with LiFePO 4 cathodes (areal loading, 1.8/2.2 mAh cm −2 ), three-dimensional Li–carbon anodes (50-µm-thick Li) and Li 2 ZrF 6 -based electrolyte displayed greatly improved cycling stability with high capacity retention (>80.0%) after 3,000 cycles (1C/2C rate). This achievement represents leading performance and, thus, delivers a reliable Li 2 ZrF 6 -based electrolyte for durable LMBs under practical high-rate conditions.
Lei Zhang,Luqing Xi,Yuexiao Pan,Yajun Jia,Mingmei Wu,Hongzhou Lian,Jun Lin
A series of red-emitting phosphors composed of Li2ZrF6:Mn4+ (LZF:Mn) have been synthesized via an ionic-exchange reaction route at room temperature. The microstructure and optical characterizations have been investigated according to the detailed experiments. The morphology of the phosphor LZF:Mn changes with the concentration of HF, the reaction time and temperature. The uniform crystals of LZF:Mn with regular hexagonal tablets have been obtained in 30–40 wt% HF solutions by conducting the reaction at room temperature for about 8 h. The influences of reaction parameters on the morphology and photoluminescence properties of LZF:Mn have been systematically investigated. The luminescence intensity of LZF:Mn has been optimized by controlling the synthesis procedure and parameters. The white light-emitting diode (WLED) fabricated with LZF:Mn and Y3Al5O12:Ce3+ (YAG:Ce) on InGaN LED chip displays a warm white light with correlated color temperature (CCT) at 3789.4 K and color rendering index (CRI) of 91.
The application of high-voltage positive electrode materials in sulfide all-solid-state lithium batteries is hindered by the limited oxidation potential of sulfide-based solid-state electrolytes (SSEs). Consequently, surface coating on positive electrode materials is widely applied to alleviate detrimental interfacial reactions. However, most coating layers also react with sulfide-based SSEs, generating electronic conductors and causing gradual interface degradation and capacity fading. To address this, we propose a Li 2 ZrF 6 coating layer on LiCoO 2 , which exhibits minimal reaction with SSEs, and its decomposition products are electron-conductive-free. Furthermore, this coating layer also efficiently mitigates the layered-to-spinel/rock-salt surface structural transformation in LiCoO 2 . As a result, the In-Li|Li 6 PS 5 Cl | Li 2 ZrF 6 -LiCoO 2 all-solid-state cell demonstrates an initial areal capacity of 5.2 mAh cm −2 and a capacity retention of 80.5% after 1500 cycles at 70 mA/g with high LiCoO 2 areal mass loading (30.19 mg cm −2 ) and a cut-off voltage of 3.9 V (corresponding to potential of 4.5 V versus Li + /Li), at 25 °C.
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