Spontaneous In Situ Formation of Lithium Metal Nitride in the Interface of Garnet-Type Solid-State Electrolyte by Tuning of Molten Lithium

A Stable Matrix Assisting Highly Compatible and Maintainable Lithium-Garnet Interface for Solid-State Batteries

Solid-state Li metal batteries (SSLMBs) are attractive due to their capability to simultaneously offer high energy density and high-level safety when combining Li metal anodes, solid-state electrolytes (SSEs), and high-voltage cathodes together. However, SSLMBs may well incur short circuits caused by Li dendrites penetrations, which mainly originate from the instability and poor contact between Li metal and SSEs. Herein, by taking full advantage of the reaction products of Li and Li1.3Al0.3Ti1.7(PO4)3 (LATP), a lithium-LATP composite anode (Li-LATP) is obtained, in which a stable matrix is formed to enhance the contact between Li and the garnet-type SSEs, alleviating the volume change and preserving an intact interface during the charge/discharge process. Consequently, the Li-LATP/garnet/Li-LATP symmetric cell displays a fairly low interfacial resistance of 6 Ω cm2 and stable cycling performance for over 2500 h with a low overpotential. Furthermore, the LiCoO2/garnet/Li-LATP full cell also shows a high discharge capacity of 159 mAh g-1 and great cycling performance.

A Lithium Intrusion-Blocking Interfacial Shield for Wide-Pressure-Range Solid-State Lithium Metal Batteries

Lithium garnets are considered as promising solid-state electrolytes for next-generation solid-state Li metal batteries (SSLBs). However, the Li intrusion driven by external stack pressure triggers premature of Li metal batteries. Herein, for the first time, an in situ constructed interfacial shield is reported to efficiently inhibit the pressure-induced Li intrusion in SSLBs. Theoretical modeling and experimental investigations reveal that high-hardness metallic Mo nanocrystals inside the shield effectively suppress Li dendrite growth without alloy hardening-derived interfacial contact deterioration. Meanwhile the electrically insulated Li2 S as a shield component considerably promotes interfacial wettability and hinders Li dendrite penetration into the bulk of garnet electrolyte. Interfacial shield-protected Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO)-based cells exhibit significantly enhanced cyclability without short circuits under conventional pressures of ≈0.2 MPa and even at high pressure of up to 70 MPa; which is the highest endurable stack pressure reported for SSLBs using garnet electrolytes. These key findings are expected to promote the wide-pressure-range applications of SSLBs.

In Situ and Low-Cost Improvement of the Lithium Anode Interface in Garnet-Type Solid-State Electrolytes

In recent years, the development of electric vehicles and environmental concerns have made necessary improvements in the energy density and safety of lithium-ion batteries. Therefore, the development of all-solid-state lithium-ion batteries (ASSLIBs) has become imperative. One advantage of ASSLIBs is their potential for downsizing with the use of lithium metal as the anode. However, in this study, a garnet-type solid electrolyte (Li6.75La3Zr1.75Ta0.25O12) was used, which has low reactivity with lithium metal. Thus, interface modification using CaCl2 was employed to form a Li-Ca-Cl composite anode. The interfacial resistance was remarkably reduced to 7 Ω cm2, and the symmetric cell exhibited stable cycling for 1200 h at room temperature and a current density of 0.1 mA cm-2. The voltage ranged from ±15 to ±16 mV. The full cell demonstrated a high initial discharge capacity of 149.2 mA h g-1 and a Coulombic efficiency of 98.0% while maintaining a discharge capacity retention of 91.3% after 100 cycles. These findings lay a solid foundation for future commercial applications as interface modification was achieved through a simple spin-coating process using low-cost CaCl2 (0.7 USD g-1).