Realizing Compact Lithium Deposition via Elaborative Nucleation and Growth Regulation for Stable Lithium-Metal Batteries.

Metallic lithium (Li) has been regarded as an ideal candidate for anode materials in next-generation high-energy-density batteries. However, a ubiquitous spongy Li deposition results in low reversibility, huge interfacial impedance, and even safety issues, hindering its practical application. Herein, we proposed a bifunctional electrolyte (BiFE) to avoid the spongy Li deposition, in which lithium nitrate (LiNO3) facilitates a uniform granular Li nucleation via forming a kinetically favorable solid electrolyte interphase and silicon dioxide (SiO2) adsorbs anions to stabilize the electric field distribution near the electrode surface. Such a BiFE provides an even Li+ ion flux for the subsequent growth of electrochemical Li deposition, which was verified by ζ potential, Raman spectra, and specific capacitance characterizations, thus realizing a compact and uniform Li deposition via elaborative nucleation and growth regulation. An improved Li Coulombic efficiency of 99.1% can be achieved within BiFE. When used in Cu∥Li half-cells and Li∥Li symmetric cells, the high Li utilization prolonged the cycling life span to above 300 cycles and 1200 h, respectively. The compact Li deposition also resisted the corrosion of polysulfides to enhance the cycling performance of Li∥S full cells.

Improving the Interfacial Stability between Lithium and Solid-State Electrolyte via Dipole-Structured Lithium Layer Deposited on Graphene Oxide.

Utilization of lithium (Li) metal anode in solid-state batteries (SSBs) with sulfide solid-state electrolyte (SSE) is hindered by the instable Li/SSE interface. A general solution to solve this problem is to place an expensive indium (In) foil between the SSE and Li, while it decreases the output voltage and thus the energy density of the battery. In this work, an alternative strategy is demonstrated to boost the cycling performances of SSB by wrapping a graphene oxide (GO) layer on the anode. According to density functional theory results, initial deposition of a thin Li layer on the defective GO sheets leads to the formation of a dipole structure, due to the electron-withdrawing ability of GO acting on Li. By incorporating GO sheets in a nanocomposite of copper-cuprous oxide-GO (Cu-Cu2O-GO, CCG), a composite Li anode enables a high coulombic efficiency above 99.5% over 120 cycles for an SSB using Li10GeP2S12 SSE and LiCoO2 cathode, and the sulfide SSE is not chemically decomposed after cycling. The highest occupied molecule orbital/lowest unoccupied molecular orbital energy gap of this Li/GO dipole structure likely stretches over those of Li and sulfide SSE, enabling stabilized Li/SSE interface that can replace the expensive In layer as Li protective structure in SSBs.

Transplantable Carbonaceous Li+ Filtrating Membrane for Lithium Metal Protection.

Utilization of the lithium (Li) metal anode is seriously prevented by the undesirable side reactions with electrolyte solvents due to their mismatched energy gaps and easily lacerated SEI layer. In this work, we develop a transplantable carbonaceous membrane with a particular ability of filtrating Li+ ions by blocking organic solvents and use it as an independent protective component to isolate lithium metal anode from the electrolytes. This graphene-supported N-doped membrane (GNM) can separate organic carbonates of dimethyl carbonate (DMC) and diethyl carbonate (DEC) from H2O-DMC/DEC mixtures by holding back the organic solvents. When this membrane is used in a Li-Cu cell, a high Li Coulombic efficiency (CE) of 98.5% is maintained in carbonate electrolyte over 400 cycles. Application of GNM in Li-O2 full cell provides a sustainable use of Li metal for more than 200 cycles (2000 h) by keeping its shiny metal luster. Our results demonstrate that the use of an independent component with Li+ filtrating ability, such as the transplantable membrane of GNM developed in this work, should be a feasible remedy to protect Li metal anode in practical Li metal batteries.

Suppressing Sponge-Like Li Deposition via AlN-Modified Substrate for Stable Li Metal Anode.

Sponge-like lithium (Li) deposition results in high-surface-area morphology that harmfully accelerates the side reactions between Li and electrolyte, arousing serious safety issues of next high energy density Li metal batteries (LMBs). Herein, we propose a strategy to suppress the sponge-like Li deposition by plating Li metal on aluminum nitride (AlN)-modified substrates. For a practical Li deposition of 4 mAh cm-2 on a AlN-modified copper (Cu) electrode, the roughness and thickness of the as-deposited Li layer are only ∼10% and ∼50% of those for the Li layer deposited on bare Cu. Only based on the compacted Li deposition layer without any other protective remedies, the AlN-modified Cu electrode could provide a Li cycling life of 5 times longer than that on bare Cu, and an AlN-modified carbon felt was proved as an efficient interlayer to boost the cycling stability of Li||LiFePO4 batteries. These results demonstrate the high importance of suppressing the sponge-like Li deposition for high energy density LMBs.

Nearly full-dense and fine-grained AZO:Y ceramics sintered from the corresponding nanoparticles.

Aluminum-doped zinc oxide ceramics with yttria doping (AZO:Y) ranging from 0 to 0.2 wt.% were fabricated by pressureless sintering yttria-modified nanoparticles in air at 1,300°C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, a physical property measurement system, and a densimeter were employed to characterize the precursor nanoparticles and the sintered AZO ceramics. It was shown that a small amount of yttria doping can remarkably retard the growth of the as-received precursor nanoparticles, further improve the microstructure, refine the grain size, and enhance the density for the sintered ceramic. Increasing the yttria doping to 0.2 wt.%, the AZO:Y nanoparticles synthetized by a coprecipitation process have a nearly sphere-shaped morphology and a mean particle diameter of 15.1 nm. Using the same amount of yttria, a fully dense AZO ceramic (99.98% of theoretical density) with a grain size of 2.2 µm and a bulk resistivity of 4.6 × 10-3 Ω·cm can be achieved. This kind of AZO:Y ceramic has a potential to be used as a high-quality sputtering target to deposit ZnO-based transparent conductive films with better optical and electrical properties.