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Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) due to its high Li+ conductivity and stability against lithium metal. However, wide research and application of LLZO are hampered by the difficulty in sintering highly conductive LLZO ceramics, which is mainly attributed to its poor sinterability and the hardship of controlling the Li2O atmosphere at a high sintering temperature (∼1200 °C). Herein, an efficient mutual-compensating Li-loss (MCLL) method is proposed to effectively control the Li2O atmosphere during the sintering process for highly conductive LLZO ceramics. The Li6.5La3Zr1.5Ta0.5O12 (LLZTO) ceramic SSEs sintered by the MCLL method own high relative density (96%), high Li content (5.54%), high conductivity (7.19 × 10–4 S cm–1), and large critical current density (0.85 mA cm–2), equating those sintered by a hot-pressing technique. The assembled Li–Li symmetric battery and a Li-metal solid-state battery (LMSSB) show that the as-prepared LLZTO can achieve a small interfacial resistance (17 Ω cm2) with Li metal, exhibits high electrochemical stability against Li metal, and has broad potential in the application of LMSSBs. In addition, this method can also improve the sintering efficiency, avoid the use of mother powder, and reduce raw-material cost, and thus it may promote the large-scale preparation and wide application of LLZO ceramic SSE.

Due to the advantages of high safety and high energy density, solid-state lithium batteries (SSLBs) are promising competitors for next-generation batteries. Unfortunately, the growth of Li dendrites and irreversible capacity loss caused by the Li metal anode/solid electrolyte interfacial incompatibility remain challenges. Herein, an in situ formed artificial protective layer between the lithium metal anode and solid electrolyte Li 6 PS 5 Cl (LPSC) is introduced. A stable solid electrolyte interface (SEI) is in situ formed in the Li/Li 6 PS 5 Cl interface via the electrochemical reduction of the liquid electrolyte LiTFSI/tetraethylene glycol dimethyl ether (Li(G4)TFSI), which is beneficial for the improvement of the stability of interfacial chemistry and homogeneous lithium deposition behavior. The assembled Li/Li(G4)TFSI-assisted Li 6 PS 5 Cl/Li symmetric cells enable stable cycles for 850 and 400 h at a current density of 0.1 and 0.2 mA/cm 2 , respectively. Moreover, the LiNi 0.6 Co 0.1 Mn 0.3 O 2 (NCM613)/Li(G4)TFSI-assisted Li 6 PS 5 Cl/Li SSLBs can achieve prominent cycling stability at room temperature. This work provides a new insight into the interfacial modification to design SSLBs with high energy density.

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The safety issue of lithium batteries based on liquid electrolytes has become the focus of attention, especially when the batteries are exposed to mechanical, thermal, or electrical abuse conditions. To address this issue, gel polymer electrolytes (GPEs) have attracted widespread interest due to the property of solid–liquid coexistence with higher ionic conductivity, flexibility, and safety. In this work, a poly­(vinylidene-fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly­(methyl methacrylate) (PMMA) matrix GPE, containing bis­(trifluoromethane)­sulfonimide lithium salt (LiTFSI) and spherical zirconium dioxide (ZrO2) nanoparticles, is successfully designed and synthesized by a simple one-step solution-casting route. It has been found that the obtained PVDF-HFP/PMMA-ZrO2-6% (PPZ-6%) electrolyte film possesses an excellent tensile strength of 37.7 MPa. Moreover, the PPZ-6% GPE not only has a high ionic conductivity of 1.46 × 10–3 S cm–1 at 25 °C but also presents excellent interface compatibility in an Li||Li symmetrical battery. The LiFePO4||Li cell assembled with the PPZ-6% GPE exhibits good cyclic stability at room temperature, e.g., a high discharge specific capacity of 153.0 mAh g–1, and a high Coulombic efficiency of 99% after 200 cycles at 0.5 C. Therefore, this organic–inorganic hybrid GPE modified with spherical ZrO2 nanoparticles reveals a good application prospect for high-performance lithium metal batteries (LMBs).