Strategy to Enhance the Cycling Stability of the Metallic Lithium Anode in Li-Metal Batteries.

Based on the analysis of systematic research (density functional theory calculations, physical characterizations, and electrochemical performances), here, we report a novel mixture surface modification layer of LiC6&LiF, which can enhance the lithium-ion diffusion and decrease the local current density. This is beneficial to the improvement of cycling stability. As a result, the Li@LiC6&LiF-5/NCM half-cell possesses an excellent capacity retention of 94% after 100 cycles at 0.1C, with a capacity decay of only 0.06% per cycle. For comparison, the capacity retention of a pristine Li/NCM cell is only 9.3% after 100 cycles. Our study confirms that compositing the high ionic conductivity layer (e.g., LiC6&LiF for the first time) is a promising avenue to stabilize lithium-metal anodes. From this perspective, we concisely review recent discoveries in this field and suggest possible new research directions for further development of Li-metal batteries.

Asymmetric Structure Design of Electrolytes with Flexibility and Lithium Dendrite-Suppression Ability for Solid-State Lithium Batteries.

Solid polymer electrolytes can be used to construct solid-state lithium batteries (SSLBs) using lithium metals as the anode. However, the lifespan and safety problems of SSLBs caused by lithium dendrite growth have hindered their practical application. Here, we have designed and prepared a rigid-flexible asymmetric solid electrolyte (ASE) that is used in building SSLBs. The ASE can inhibit efficiently the growth of lithium dendrites and lead to a long cycle life of SSLBs due to the hierarchical structure of a combination of "polymer-in-ceramic" (i.e., rigid ceramic layer of Li6.4La3Zr1.4Ta0.6O12) and "LiBOB-in-polymer" (i.e., soft polymer-layer of polyethylene oxide and LiBOB components). The results demonstrated that a symmetrical battery with ASE (Li|ASE|Li) can be steadily cycled for more than 2000 h and yielded a flat plating/stripping voltage profile under a current density of 0.1 mA cm-2. As a consequence, the SSLB of LiFePO4|ASE|Li delivered a specific capacity of 155.1 mA h g-1 with a capacity retention rate up to 90.2% after 200 cycles with the Coulombic efficiency over 99.6% per cycle. This asymmetric structure combines the advantages of ceramics and polymers, providing an ingenious solution for building rigid and flexible solid electrolytes.

3D web freestanding RuO2-Co3O4 nanowires on Ni foam as highly efficient cathode catalysts for Li-O2 batteries.

The mechanism of Li-O2 batteries is based on the reactions of lithium ions and oxygen, which hold a theoretical higher energy density of approximately 3500 W h kg-1. In order to improve the practical specific capacity and cycling performance of Li-O2 batteries, a catalytically active mechanically robust air cathode is required. In this work, we synthesized a freestanding catalytic cathode with RuO2 decorated 3D web Co3O4 nanowires on nickel foam. When the specific capacity was limited at 500 mA h g-1, the RuO2-Co3O4/NiF had a stable cycling life of up to 122 times. The outstanding performance can be primarily attributed to the robust freestanding Co3O4 nanowires with RuO2 loading. The unique 3D web nanowire structure provides a large surface for Li2O2 growth and RuO2 nanoparticle loading, and the RuO2 nanoparticles help to promote the round trip deposition and decomposition of Li2O2, therefore enhancing the cycling behavior. This result indicates the superiority of RuO2-Co3O4/NiF as a freestanding highly efficient catalytic cathode for Li-O2 batteries.