Lithium-silver alloys in anode-less batteries: comparison in liquid- and solid-electrolytes.

This study comprehensively investigates the phase evolution of silver-carbon composite (Ag/C) layers in anode-less batteries with both liquid and solid electrolytes. The results of in situ X-ray diffraction and cross-sectional electron microscopy analyses reveal that the alloying reaction of Ag and Li is more homogeneous in solid-electrolyte-based cells compared to liquid-electrolyte-based cells. This homogeneity is attributed to diffusional Coble creep across the heterogeneous interfaces of Ag/C layers and solid electrolytes.

Designing 3D Anode Based on Pore-Size-Dependent Li Deposition Behavior for Reversible Li-Free All-Solid-State Batteries.

Li-free all-solid-state batteries can achieve high energy density and safety. However, separation of the current collector/solid electrolyte interface during Li deposition increases interfacial resistance, which deteriorates safety and reversibility. In this study, a reversible 3D porous anode is designed based on Li deposition behavior that depends on the pore size of the anode. More Li deposits are accommodated within the smaller pores of the Li hosting anode composed of Ni particles with a granular piling structure; this implies the Li movement into the anode is achieved via diffusional Coble creep. Surface modification of Ni with a carbon coating layer and Ag nanoparticles further increases the Li hosting capacity and enables Li deposition without anode/solid electrolyte interface separation. A Li-free all-solid-state full cell with a LiNi0.8 Mn0.1 Co0.1 O2 cathode shows an areal capacity of 2 mAh cm-2 for retaining a Coulombic efficiency of 99.46% for 100 cycles at 30 °C.

Energy-Density Improvement in Li-Ion Rechargeable Batteries Based on LiCoO2 + LiV3O8 and Graphite + Li-Metal Hybrid Electrodes.

We developed a novel battery system consisting of a hybrid (LiCoO2 + LiV3O8) cathode in a cell with a hybrid (graphite + Li-metal) anode and compared it with currently used systems. The hybrid cathode was synthesized using various ratios of LiCoO2:LiV3O8, where the 80:20 wt% ratio yielded the best electrochemical performance. The graphite and Li-metal hybrid anode, the composition of which was calculated based on the amount of non-lithiated cathode material (LiV3O8), was used to synthesize a full cell. With the addition of LiV3O8, the discharge capacity of the LiCoO2 + LiV3O8 hybrid cathode increased from 142.03 to 182.88 mA h g-1 (a 28.76% improvement). The energy density of this cathode also increased significantly, from 545.96 to 629.24 W h kg-1 (a 15.21% improvement). The LiCoO2 + LiV3O8 hybrid cathode was characterized through X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Its electrochemical performance was analyzed using a battery-testing system and electrochemical impedance spectroscopy. We expect that optimized synthesis conditions will enable the development of a novel battery system with an increase in energy density and discharge capacity.

Electrochemical Behaviors of a Vapor-Phase Polymerized Conductive Polymer Coated on LiV3O8 in Li-Metal Rechargeable Batteries.

A new coating method called vapor-phase polymerization (VPP) is used to coat a conductive polymer on LiV3O8 (LVO) surfaces for the first time in lithium-metal secondary batteries to protect the interface layer and enhance the electrochemical properties of the cathode. The VPP method can be used to coat an appropriate amount of the polymer and homogeneously coat the LVO active material surfaces because of the use of vapor-phase monomers. The presence of the coating layer was confirmed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Polymer coating of LVO by VPP results in enhanced cyclic stability and rate capability at various C-rates. At 0.2 C-rate, it has high specific capacities of 254.7 and 272.2 mA h g-1 in the first and second cycles, respectively. Further, the capacity retention is 94.6% from the 2nd cycle to the 100th cycle. The improved electrochemical performance is attributed to the homogeneously conductive polymer formed by VPP, which can improve the electrical conductivity of the active material and inhibit dissolution by preventing direct contact with the electrolyte.

Dendrite Suppression by Synergistic Combination of Solid Polymer Electrolyte Crosslinked with Natural Terpenes and Lithium-Powder Anode for Lithium-Metal Batteries.

Lithium-metal anode has fundamental problems concerning formation and growth of lithium dendrites, which prevents practical applications of next generation of high-capacity lithium-metal batteries. The synergistic combination of solid polymer electrolyte (SPE) crosslinked with naturally occurring terpenes and lithium-powder anode is promising solution to resolve the dendrite issues by substituting conventional liquid electrolyte/separator and lithium-foil anode system. A series of SPEs based on polysiloxane crosslinked with natural terpenes are prepared by facile thiol-ene click reaction under mild condition and the structural effect of terpene crosslinkers on electrochemical properties is studied. Lithium powder with large surface area is prepared by droplet emulsion technique (DET) and used as anode material. The effect of the physical state of electrolyte (solid/liquid) and morphology of lithium-metal anode (powder/foil) on dendrite growth behavior is systematically studied. The synergistic combination of SPE and lithium-powder anode suggests an effective solution to suppress the dendrite growth owing to the formation of a stable solid-electrolyte interface (SEI) layer and delocalized current density.

Solid Polymer Electrolytes Based on Functionalized Tannic Acids from Natural Resources for All-Solid-State Lithium-Ion Batteries.

Solid polymer electrolytes (SPEs) for all-solid-state lithium-ion batteries are prepared by simple one-pot polymerization induced by ultraviolet (UV) light using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as an ion-conducting monomeric unit and tannic acid (TA)-based crosslinking agent and plasticizer. The crosslinking agent and plasticizer based on natural resources are obtained from the reaction of TA with glycidyl methacrylate and glycidyl poly(ethylene glycol), respectively. Dimensionally stable free-standing SPE having a large ionic conductivity of 5.6×10(-4)  Scm(-1) at room temperature can be obtained by the polymerization of PEGMA into P(PEGMA) with a very small amount (0.1 wt %) of the crosslinking agent and 2.0 wt % of the plasticizer. The ionic conductivity value of SPE with a crosslinked structure is one order of magnitude larger than that of linear P(PEGMA) in the waxy state.

Germanium-tin alloy nanocrystals for high-performance lithium ion batteries.

Germanium-tin (Ge(1-x)Sn(x)) alloy nanocrystals were synthesized using a gas-phase laser photolysis reaction of tetramethyl germanium and tetramethyl tin. A composition tuning was achieved using the partial pressure of precursors in a closed reactor. For x < 0.1, cubic phase alloy nanocrystals were exclusively produced without separation of the tetragonal phase Sn metal. In the range of x = 0.1-0.4, unique Ge(1-x)Sn(x)-Sn alloy-metal hetero-junction nanocrystals were synthesized, where the Sn metal domain becomes dominant with x. Thin graphitic carbon layers usually sheathed the nanocrystals. We investigated the composition-dependent electrochemical properties of these nanocrystals as anode materials of lithium ion batteries. Incorporation of Sn (x = 0.05) significantly increased the capacities (1010 mA h g(-1) after 50 cycles) and rate capabilities, which promises excellent electrode materials for the development of high-performance lithium batteries.