Controllable Preparation Of Lithium Lanthanum Titanate Nanofiberous Material For Li-metal Anode

Li metal is expected to further increase the energy density due the fact that it has the highest specific capacity?3,860 mA h/g?.However,the practical applications of Li-metal anode remain challenged by the high reactivity and the dendrite growth.On the one hand,the continuous reactions could consume electrolyte and cause low Coulombic efficiency.Moreover,the sharp Li-dendrite could pierce separator and cause safety issues.The LLTO ceramic material has a stable chemical structure and high temperature resistance.As a fast Li-ion conductor,it has a high ion conductivity at room temperature,which can achieve rapid Li-ion migration.Compared with pratical,fiberous membrane composed of nanofiber with a 3D network structure not only can regulate the ion flux on the surface of Li-metal anode,but also have certain deformation ability.The size effect and surface effect brought by namometer fiber diameter could give many unique properties for nanofiber materials.Among the technologies for preparing nanofibers,electrospinning,which can produce controllable and continuous nanofibers at low cost,is currently the most promising technology to realize the industrial production of nanofibrous materials.In this paper,polyvinylpyrrolidone?PVP?was selected as polymer template,and the hydrolysis of the metal alkoxide and its interaction with different complexing agents were simultaneously adjusted to obtain a spinnable and stable precursor solution.Using the optimized spinnig process,continuous and defect-free Li_0.33La_0.557TiO₃ nanofibrous membrane were prepared.In order to obtain LLTO nanofibrous membranes with small crystal grains and high ionic conductivity,this research explored the effect of calcination process on the micro-morphology structure and macroscopic properties of LLTO nanofibrous membrane.The results show that by increasing temperature,the fiber would shrink along the length direction,resulting in a larger fiber diameter,and the crystals growth has its suitable temperature.The LLTO ceramic nanofibers prepared in this research constructed a hybrid ionic and electronic conducting interphase due to the spontaneous reaction with Li-metal anode,which ionic conductivity guaranteed long-term rapid ionic conduction and electronic conductivity uniformed surface potential and prevented Li-depositing at the tip.The results showed that the protective battery after 160 h did not increase the interphace impedance,and no obvious dendrite growth was observed under the electron microscope.The Li//Li battery exhibits a stable cycling performance of 450 h and a low polarization voltage of 100 mV at 3 mA/cm².The NCA//Li battery also exhibits stable rate performance at 1 C.In addition,the LLTO was optimized by lithiophilic Al₂O₃ to form hybrid ionic conductive-lithiophilic interface layer.Li//Cu battery exhibited lower nucleation overpotential,while Li//Li battery steadily cycled for 1000 h at 3 mA/cm²,the surface of cycled Li-metal anode was flat and dense and no obvious corrosion and chalking with considerable volume change.More importantly,the NCA//Li battery exhibit a capacity of 147 mA h/g under the high load of the cathode?7.5 mg/cm²?at 1 C,and the capacity remains 85%after 100 cycles.