A Mesoporous Material Based Solid-State Electrolyte With Nanowetted Interfaces

Lithium ion batteries have been widely applied in the areas of portable electronic devices and small power tools,due to its high energy density,light weight,portability,long cycle life and high working voltage.Nevertheless,the application of lithium-ion batteries in electric vehicles（EV）and hybrid electric vehicles（HEV）is still confronted with great challenges.To satisfy the requirements of EV concerning energy density,power density,safety and so on,we need to develop the next generation high-performance lithium-ion batteries.lithium metal is considered as the ideal anode material for next generation lithium-ion batterie,because it has the highest specific capacity of 3860 mA h g^-1,far exceeding the theoretical capacity of graphite(370 mA h g^-1),and the lowest negative electrochemical potential of-3.04 V vs.the standard hydrogen electrode.Unfortunately,the practical application of Li metal anode is hindered by the uncontrollable growth of lithium dendrites.Solid-state electrolytes（SSEs）are currently widely considered as a potential solution to solve the challenges encountered in Li metal batteries due to their inherent advantage in mechanical strength,which can suppress the growth of Li dendrites.Though strong mechanical strength traditional SSEs generally possess,low ionic conductivity at room temperature and large interfacial resistance they have long been suffering from.Composite electrolyte is an effective solution to this challenge.MCM-41,an ordered mesoporous silica material with high specific surface area and large pore volume,was synthesized by sol-gel method.Li-IL@MCM-41 SSE with nanoconfined ionic liquids was prepared through a post-impregnation method.The as-prepared SSE with abundant nanowetted interfaces,which facilitated the ionic conduction of intra-particles,exhibited a high ionic conductivity of 3.98×10^-44 S cm^-11 at room temperature.Li-IL@MCM-41 demonstrates excellent electrochemical stability with a broad electrochemical potential window up to 5.2 V.The mesoporous structure could be retained at high pressure,which prove its high mechanical strength.Li-IL@MCM-41 also has a good thermal stability with thermal decomposition temperature above 350℃.Solid-state batteries（SSBs）were assembled to evaluate the battery performance of Li-IL@MCM-41.The polarization voltage of Li|Li-IL@MCM-41|Li symmetric cell showed negligible fluctuation and remained stable over 1000 h.No short circuit happened and Li tended to deposit in a flaky form in the cells,instead of dendritic form,under the suppression of Li-IL@MCM-41 The solid-state batteries（SSBs）assembled exhibited excellent cycling performance,which delivered capacities of 127 mA h g^-1,163 mA h g^-11 and 138 mA h g^-1after 100 cycles under room temperature with LiCoO₂,LiNi_0.8Co_0.1Mn_0.1O₂ and LiFePO₄cathode materials,respectively.The good battery performance should be ascribed to the homogenously effective three-dimensional ion-conducting and electron-conducting network established by Li-IL@MCM-41 nanocomposites with nanowetted interfaces and acetylene black nanoparticles,which facilitates the electrochemical reaction of cathode active material.