Study On The Construction And Interface Modulation Of Garnet Electrolyte-based Solid-state Lithium Metal Batteries

As the ideal anode material,Li metal possesses low formal potential and high specific energy.However,the flowing and flammable organic liquid electrolyte used in conventional Li metal batteries not only fails to inhibit the growth of Li dendrites,but also causes safety problems.Thanks to the wide electrochemical windows,superior Li⁺conductivity,high mechanical strength and shear modulus,the employment of inorganic solid-state electrolytes can eliminate the safety issues caused by liquid electrolytes.Also,solid-state lithium metal batteries can match with high-voltage cathode material,or combine with Li-O₂ and Li-S battery technologies,thereby delivering higher energy density.Among various solid-state electrolytes,the garnet-type electrolyte is considered as the most promising solid-state electrolyte due to its chemical stability with Li metal.However,the application of garnet electrolytes has been hampered by severe interface issues,such as high resistance and instability of interface.In this work,Li metal batteries are constructed based on garnet electrolyte,and the researches about interface issues are carried out.（1）A poly-DOL interlayer is formed at electrolyte/electrode interfaces via in-situ polymerization to solve the interfacial issues and suppress lithium dendrite.A flexible,ion-conducting polymer interlayer can effectively improve interfacial contact and alleviate the volume change of the material during charge and discharge.After the introduction of the poly-DOL interlayer,the anode/electrolyte interfacial impedance has decreased from 1875Ωcm² to 185Ωcm²,and the symmetrical battery can stably cycle for 450 h without Li dendrite at the current density of 0.2 m A cm^-2.The all-solid-state Li batteries with poly-DOL interlayer at both sides show significantly enhanced performances.The total resistance of batteries is around 1000Ωcm²,and both of them show good rate and cycle performance.The Li Fe PO₄ batteries can cycle 150 times at a current density of 0.5 C,maintaining a Coulomb efficiency close to 99%.（2）In order to realize a safe and high-performance Li-O₂ battery,we designed a Porous Framework Infiltrating（PFI）Li-O₂ battery based on garnet electrolyte.On the anode side,a lithium alloy is used instead of lithium to optimize the anode/electrolyte interface and adjust the current distribution.When the anode contains 30wt.%Sn,the interfacial resistance drops to 15Ωcm²,and the lithium symmetrical battery can cycle for 200 h with a capacity of 0.4 m A h cm^-2.The surface of the LLZTO facing the cathode side is modified by acidic etching to be porous.This acid etched porous structure exhibits a smooth and clear surface without any Li₂CO₃.After infiltrating a tiny amount of liquid electrolyte,the structure exhibits non-flammable when ignited with fire and considerably low resistance when coated with a cathode plate.The Li-O₂battery can cycle 50 times with a limited capacity of 1000 m A h g^-1,maintaining the energy efficiency close to 70%.XRD,XPS and DEMS tests demonstrate that the electrochemical reactions in the Li-O₂ battery are dominated by the formation and decomposition of Li₂O₂.