The ultrathin insulating LiF coating with controllable thickness is proposed as an interfacial layer for garnet electrolytes to inhibit the formation of Li dendrites, and promote uniform Li plating/stripping.

The surface chemistry of garnet electrolyte is sensitive to air exposure. The poor LLZO/Li interface caused by Li2CO3/LiOH contaminants on garnet electrolyte surface easily induces large interfacial resistance resulting in the growth of Li dendrites. Herein, a versatile modification strategy is designed to convert the contaminants on Li6.4La3Zr1.4Ta0.6O12 (LLZTO) surface into a LiF and Li2PO3F‐rich lithiophilic interface by targeted chemical reactions at the interface between LiPO2F2 and Li2CO3/LiOH. The newly formed LiF‐Li2PO3F interfacial layer not only facilitates the interface wettability between Li and LLZTO, but also helps to resist corrosion of the LLZTO surface by moisture in the air. The Li|LiF&Li2PO3F‐LLZTO|Li symmetric cell exhibits a low interfacial resistance of 5.1 Ω cm2 and ultrastable galvanostatic cycling, over 1500 h at 0.6 mA cm−2 and over 70 h at 1.0 mA cm−2. In addition, LiCoO2|LiF&Li2PO3F‐LLZTO|Li hybrid solid‐state full cells display high initial specific capacity of 192 mAh g−1 at 0.1 C, and excellent cycling stability with a capacity retention over 76% even after 1000 cycles at 0.5 C at a high cut‐off voltage of 4.5 V. This study provides a simple and practical strategy for the feasibility of the application of high‐voltage cathodes in this modified garnet all‐solid‐state batteries.

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Garnet-type solid-state electrolytes (SSEs) are particularly attractive in the construction of all-solid-state lithium (Li) batteries due to their high ionic conductivity, wide electrochemical window and remarkable (electro)chemical stability. However, the intractable issues of poor cathode/garnet interface and general low cathode loading hinder their practical application. Herein, we demonstrate the construction of a reinforced cathode/garnet interface by spark plasma sintering, via co-sintering Li6.5La3Zr1.5Ta0.5O12 (LLZTO) electrolyte powder and LiCoO2/LLZTO composite cathode powder directly into a dense dual-layer with 5 wt% Li3BO3 as sintering additive. The bulk composite cathode with LiCoO2/LLZTO cross-linked structure is firmly welded to the LLZTO layer, which optimizes both Li-ion and electron transport. Therefore, the one-step integrated sintering process implements an ultra-low cathode/garnet interfacial resistance of 3.9 Ω cm2 (100 ℃) and a high cathode loading up to 2.02 mAh cm-2. Moreover, the Li3BO3 reinforced LiCoO2/LLZTO interface also effectively mitigates the strain/stress of LiCoO2, which facilitates the achieving of superior cycling stability. The bulk-type Li | LLZTO | LiCoO2-LLZTO full cell with areal capacity of 0.73 mAh cm-2 delivers capacity retention of 81.7% after 50 cycles at 100 μA cm-2. Furthermore, we reveal that the non-uniform Li plating/stripping leads to the formation of gaps and finally results in the separation of Li and LLZTO electrolyte during long-term cycling, which becomes the dominant capacity decay mechanism in high-capacity full cells. This work provides insight to the degradation of Li/SSE interface and a strategy to radically improve the electrochemical performance of garnet-based all-solid-state Li batteries.

All-solid-state Li metal batteries (ASSLBs) are currently regarded as one of the most promising next-generation energy storage technologies because of their great potential in realizing both high energy density and safety. However, the development of high performance ASSLBs is still restricted by the large interfacial resistance and Li dendrite propagation within solid electrolytes. Herein, a simple and efficient interfacial modification strategy is proposed to improve the interfacial contact between Li and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) by introducing a uniform and thin Li2Se buffer layer. The Li2Se buffer layer formed by an in situ conversion reaction can not only enhance the wettability of lithium metal toward LLZTO electrolyte but also facilitate uniform lithium plating/stripping. As a result, the interfacial resistance of Li/LLZTO decreased from 270.5 to 5.1 Ω cm2, and the lithium symmetric cell can cycle stably for 350 h at a current density of 0.5 mA cm–2. Meanwhile, the Li|LLZTO-Li2Se|LiNi0.8Co0.1Mn0.1O2 full cells exhibit a high initial capacity of 162.3 mAh g–1 and good cycling stability with a capacity retention of 84.3% after 100 cycles at 0.2 C. These results prove the effectiveness of this modification method and provide new design strategies for the development of high performance ASSLBs.

All-solid-state lithium−sulfur batteries (ASSLSBs) are considered to be a promising solution for the next generation of energy storage systems due to their high theoretical energy density and improved safety. However, the practical application of ASSLSBs is hindered by several critical challenges, including the poor electrode/electrolyte interface, sluggish electrochemical kinetics of solid−solid conversion between S and Li 2 S in the cathode, and big volume changes during cycling. Herein, the 85(92Li 2 S-8P 2 S 5 )-15AB composite cathode featuring an integrated structure of a Li 2 S active material and Li 3 PS 4 solid electrolyte is developed by in situ generating a Li 3 PS 4 glassy electrolyte on Li 2 S active materials, resulting from a reaction between Li 2 S and P 2 S 5 . The wellestablished composite cathode structure with an enhanced electrode/electrolyte interfacial contact and highly efficient ion/electron transport networks enables a significant enhancement of redox kinetics and an areal Li 2 S loading for ASSLSBs. The 85(92Li 2 S-8P 2 S 5 )-15AB composite demonstrates superior electrochemical performance, exhibiting 98% high utilization of Li 2 S (1141.7 mAh g (Li2S)−1) with both a high Li 2 S active material content of 44 wt % and corresponding areal loading of 6 mg cm −2 . Moreover, the excellent electrochemical activity can be maintained even at an ultrahigh areal Li 2 S loading of 12 mg cm −2 with a high reversible capacity of 880.3 mAh g −1 , corresponding to an areal capacity of 10.6 mAh cm −2 . This study provides a simple and facile strategy to a rational design for the composite cathode structure achieving fast Li−S reaction kinetics for high-performance ASSLSBs.

Aqueous zinc‐ion batteries (AZIBs) are expected to be an attractive alternative in advanced energy storage devices due to large abundance and dependable security. Nevertheless, the undesirable energy density and operating voltage still hinder the development of AZIBs, which is intimately associated with the fundamental properties of the cathode. In this work, polyvinylpyrrolidone (PVP) intercalated Mn0.07VOx (PVP‐MnVO) with a large interlayer spacing of 13.5 Å (against 12.5 Å for MnVO) synthesized by a facile hydrothermal method is adopted for the cathode in AZIBs. The experimental results demonstrate that PVP‐MnVO with expanded interlayer spacing provides beneficial channels for the rapid diffusion of Zn2+, resulting in a high discharge capacity of 402 mAh g−1 at 0.1 A g−1, superior to that of MnVO (275 mAh g−1 at 0.1 A g−1). Meanwhile, the PVP molecule remains in the layer structure as a binder/pillar, which can maintain its structural integrity well during the charging/discharging process. Consequently, PVP‐MnVO cathode exhibits superior rate capability and cycling stability (89% retention after 4300 cycles at 10 A g−1) compared to that of MnVO (≈51% retention over 500 cycles at 2 A g−1). This work proposes a new approach to optimize the performance of vanadium‐based electrode materials in AZIBs.