Yao Liu

Bio: Yao Liu is an academic researcher from University of Washington. The author has contributed to research in topics: Carbon & Lithium. The author has an hindex of 1, co-authored 1 publications receiving 1 citations.

Systematic Evaluation of Carbon Hosts for High-Energy Rechargeable Lithium-Metal Batteries

Abstract: Rechargeable lithium (Li)-metal batteries have great potential for high energy and low cost, but poor Li anode stability remains a challenge. Carbon host structures have been widely studied; howeve...

A Quasi‐Double‐Layer Solid Electrolyte with Adjustable Interphases Enabling High‐Voltage Solid‐State Batteries

Abstract: Increasing the energy density and long-term cycling stability of lithium-ion batteries necessitates the stability of electrolytes under high/low voltage application and stable electrode/electrolyte interfacial contact. However, neither a single polymer nor liquid electrolyte can realize this due to their limited internal energy gap, which cannot avoid lithium-metal deposition and electrolyte oxidation simultaneously. Herein, a novel type of quasi-double-layer composite polymer electrolytes (QDL-CPEs) is proposed by using plasticizers with high oxidation stability (propylene carbonate) and high reduction stability (diethylene glycol dimethyl ether) in a poly(vinylidene fluoride) (PVDF)-based electrolyte composites. In-situ-polymerized propylene carbonate can function as a cathode electrolyte interface (CEI) film, which can enhance the antioxidant ability. The nucleophilic substitution reaction between diethylene glycol dimethyl ether and PVDF increases the reduction stability of the electrolyte on the anodic side, without the formation of lithium dendrites. The QDL-CPEs has high ionic conductivity, an enhanced electrochemical reaction window, adjustable electrode/electrolyte interphases, and no additional electrolyte-electrolyte interfacial resistance. Thus, this ingenious design of the QDL-CPEs improves the cycling performance of a fabricated LiNi0.8 Co0.1 Mn0.1 O2 (NCM811)//QDL-CPEs//hard carbon full cell at room temperature, paving a new way for designing solid-state battery systems accessible for practical applications.

Lithium Oxalate as a Lifespan Extender for Anode-Free Lithium Metal Batteries.

Abstract: Anode-free lithium metal batteries (AFLMBs) have been extensively studied due to their intrinsic high energy and safety without a metallic Li anode in cell design. Yet, the dendrite and dead-Li buildup continuously consumes the active Li upon cycling, leading to the poor lifespan of AFLMBs. Here, we introduce lithium oxalate into the cathode as an electrode additive providing a Li reservoir to extend the lifespan of AFLMBs. The AFLMB using 20% lithium oxalate and a LiNi0.3Co0.3Mn0.3O2 composite cathode exhibits >80 and 40% capacity retention after 50 and 100 cycles, respectively, outperforming the poor cycle life of fewer than 20 cycles obtained from the cell using a pure LiNi0.3Co0.3Mn0.3O2 cathode. Surprisingly, the average Coulombic efficiency of AFLMBs is found to improve as the amount of lithium oxalate increases in the composite cathode. This abnormal phenomenon could be attributed to the as-formed carbon dioxide after the first activation cycle forming a Li2CO3-rich solid-electrolyte interphase and improving the Li deposition and stripping efficiency. The findings in this work provide a new strategy to delay the capacity roll-over of AFLMBs from an electrode engineering perspective, which can be coupled with other approaches such as functional electrolytes synergistically to further improve the cycle life of AFLMBs for practical application.

Room‐Temperature Anode‐Less All‐Solid‐State Batteries via the Conversion Reaction of Metal Fluorides

Abstract: All‐solid‐state batteries (ASSBs) that employ anode‐less electrodes have drawn attention from across the battery community because they offer competitive energy densities and a markedly improved cycle life. Nevertheless, the composite matrices of anode‐less electrodes impose a substantial barrier for lithium‐ion diffusion and inhibit operation at room temperature. To overcome this drawback, here, the conversion reaction of metal fluorides is exploited because metallic nanodomains formed during this reaction induce an alloying reaction with lithium ions for uniform and sustainable lithium (de)plating. Lithium fluoride (LiF), another product of the conversion reaction, prevents the agglomeration of the metallic nanodomains and also protects the electrode from fatal lithium dendrite growth. A systematic analysis identifies silver (I) fluoride (AgF) as the most suitable metal fluoride because the silver nanodomains can accommodate the solid‐solution mechanism with a low nucleation overpotential. AgF‐based full cells attain reliable cycling at 25 °C even with an exceptionally high areal capacity of 9.7 mAh cm−2 (areal loading of LiNi0.8Co0.1Mn0.1O2 = 50 mg cm–2). These results offer useful insights into designing materials for anode‐less electrodes for sulfide‐based ASSBs.

High Utilization of Composite Magnesium Metal Anodes Enabled by a Magnesiophilic Coating.

Abstract: Metallic magnesium is a promising high-capacity anode material for energy storage technologies beyond lithium-ion batteries. However, most reported Mg metal anodes are only cyclable under shallow cycling (≤1 mAh cm-2) and thus poor Mg utilization (<3%) conditions, significantly compromising their energy-dense characteristic. Herein, composite Mg metal anodes with high capacity utilization of 75% are achieved by coating magnesiophilic gold nanoparticles on copper foils for the first time. Benefiting from homogeneous ionic flux and uniform deposition morphology, the Mg-plated Au-Cu electrode exhibits high average Coulombic efficiency of 99.16% over 170 h cycling at 75% Mg utilization. Moreover, the full cell based on Mg-plated Au-Cu anode and Mo6S8 cathode achieves superior capacity retention of 80% after 300 cycles at a low negative/positive ratio of 1.33. This work provides a simple yet effective general strategy to enhance Mg utilization and reversibility, which can be extended to other metal anodes as well.

Mechanically Resilient Graphene Assembly Microspheres with Interlocked N‐Doped Graphene Nanostructures Grown In Situ for Highly Stable Lithium Metal Anodes

Abstract: Li metal is considered the most attractive anode material for high‐energy Li batteries. However, the uncontrollable growth of Li dendrites and severe volume changes during Li plating and stripping inhibit the practical application of Li metal anodes. Herein, a synergistic strategy is developed not only to suppress Li dendrite growth but also to withstand repeated volume changes during long‐term cycling. Specifically, mechanically resilient graphene assembly microspheres with interlocked Ni/N‐doped lithiophilic graphene nanostructures grown in situ are developed as stable 3D graphene hosts for Li‐metal anodes. Importantly, the approach provides a novel strategy to control radial distribution of lithiophilic Ni nanocatalysts in the graphene assembly. These 3D graphene hosts can repeatedly guide the uniform deposition of Li owing to the high lithiophilicity of Ni nanocatalysts and the N‐doped graphene nanostructures. Furthermore, graphene nanoshell forms in situ between the graphene layers in the inner part of the graphene assembly, creating strong contacts between rGO layers and providing the 3D graphene host with high structural integrity. Notably, the approach emphasizes mechanical resilience of the 3D graphene host, which retains its initial morphology after repeated Li plating/stripping cycles. Consequently, the 3D graphene host maintains a highly stable coulombic efficiency of 99% over 500 cycles.