A comprehensive review of current developments in artificial buffer layer-modified electrode–electrolyte interfaces for solid-state Li-ion batteries.

All‐solid‐state lithium batteries (ASSBs) have the potential to trigger a battery revolution for electric vehicles due to their advantages in safety and energy density. Screening of various possible solid electrolytes for ASSBs has revealed that garnet electrolytes are promising due to their high ionic conductivity and superior (electro)chemical stabilities. However, a major challenge of garnet electrolytes is poor contact with Li‐metal anodes, resulting in an extremely large interfacial impedance and severe Li dendrite propagation. Herein, an innovative surface tension modification method is proposed to create an intimate Li | garnet interface by tuning molten Li with a trace amount of Si3N4 (1 wt%). The resultant Li‐Si‐N melt can not only convert the Li | garnet interface from point‐to‐point contact to consecutive face‐to‐face contact but also homogenize the electric‐field distribution during the Li stripping/depositing process, thereby significantly decreasing its interfacial impedance (1 Ω cm2 at 25 °C) and improving its cycle stability (1000 h at 0.4 mA cm−2) and critical current density (1.8 mA cm−2). Specifically, the all‐solid‐state full cell paired with a LiFePO4 cathode delivered a high capacity of 145 mAh g−1 at 2 C and maintained 97% of the initial capacity after 100 cycles at 1 C.

Garnet‐based solid‐state Li‐metal batteries (GSSBs) have the merits of high energy density and high safety. However, the realization of a stable and well‐matched Li|garnet interface for GSSBs remains challenging due to electron leakage and lithiophobic Li2CO3 impurity. To address these issues, herein, new surface chemistry is reported that converts the undesired Li2CO3 contaminant into an ultra‐thin lithium polyphosphate (Li‐PPA) layer through anhydrous polyphosphoric acid ‐induced in situ substitution reaction without damaging the water‐sensitive garnet electrolyte. In particular, the Li‐PPA interlayer not only facilitates the homogenous spreading of molten Li but also creates a robust electron‐blocking shield to suppress Li dendrite formation. As a result, the assembled Li symmetric cell exhibits a low interfacial impedance (4 Ω cm2) and high critical current density (1.8 mA cm−2) at 25 °C, which enables the cell to continuously cycle over 2500 h at 0.2 mA cm−2. Furthermore, the GSSBs paired with LiFePO4 deliver a high capacity of 149.3 mAh g−1 at 1 C and maintain 92.3% of the initial capacity after 500 cycles and can be used for solar energy storage, suggesting the feasibility of this interfacial engineering strategy for GSSBs.

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The cycling performance of lithium–sulfur (Li–S) batteries, which is a major parameter determining the practical application of such an advanced high-energy-density battery system (1675 mA h g–1), is strongly affected by the properties of the cathodic sulfur hosts. As a desirable sulfur host, it should possess high surface area, good electronic conductivity, and superior physisorption and chemisorption to polysulfides. Here, by taking advantage of the magnesiothermic denitriding technology, the graphitic carbon nitride (GCN) with a tunable nitrogen content, surface area, and pore volume has been designed as a sulfur host for high-performance Li–S batteries. With a nitrogen content of ∼6%, a surface area of 594 m2 g–1, and a pore volume of about 2 cm3 g–1, the GCN-based host can retain sulfur and allow its reversible convention within cathodic region, thereby delivering a high capacity of 852.2 mA h g–1 at 0.5 C with a low capacity decay of 0.12% per cycle within 300 cycles. This work provides a feasible way to design nitrogen-doped carbon materials with tunable nitrogen content and enlightens the host material design for practical Li–S batteries.