Study On Interface Of Lithium Titanate Material/Sulfur-based Solid Electrolyte And Its Application In All-solid-state Batteries

Lithium secondary batteries have been used to power laptops,mobile phones,electric cars,etc.because of their high operating voltage,high energy density,and long cycle performance.However,liquid electrolytes make themselves prone to risks of leakage and ignition,which slash the safety,the primary concern to customers,of lithium ion batteries.Recently,the so called “all-solid-state lithium secondary batteries”?ASSLBs?using inorganic solid electrolytes have been recognized as good alternatives due to their high energy density,excellent safety,efficient packing,and versatility in battery geometry.Despite the se great promises,the commercialization of ASSLBs has still many obstacles to overcome,including interface resistance between electrodes?anode and cathode?and electrolytes,ionic conductivity and windows of bulk-type electrolytes,cyclic stability,rate performance,etc.As we all know,the composite electrode should contain active materials and conductive agents as well as solid electrolyte at the same time.The favorable interfaces can be easily prepared by using the liquid-phase method which is a much simpler and cheaper process than other methods.However,the hydrophobous electrode compared with conventional electrolytes makes it an obstacle to achieve the physical contact environment so that we can disperse all these all-solid-state powders.Despite various prepared composite electrodes using only dry mixing methods with an agate mortar,their unsatisfied electrochemical properties are not suitable for further applications.In addition,the nanoparticles are capable agglomerated through the mixture,for instance the Super P which is widely used as conductive agent.Hence,for the uniformly mixture and performance enhancement of the composite electrode,it is crucial to figure out certain liquid-phase method.Here,we successfully prepared anhydrous LPSCl electrolyte and LTO@LPSCl composite to construct Li₄Ti₅O₁₂?LTO?/ Li₆PS₅Cl?LPSCl?/Li ASSLBs with favorable electrode/electrolyte interface and optimized electrochemical performance.Coating of the solid electrolytes on Li₄Ti₅O₁₂ particles was carried out by liquid-phase method using brand-new solvent,200#Paint,so that the uniform interface between electrode and solid electrolyte with a large contact area was formed.The 200#Paint proposed by us firstly has many advantages as a solvent,for instance,a lower distil-off temperature which should be effective in preventing side-reactions between the electrolyte coating layer and electrode particles during heat-treatment for removing the solvent.What's more,this 200#Paint is cheaper and hypotoxic compared with other solvents such as the N-methlyformamide solvent.The ASSLBs were fabricated by cold-press method and further characterized in coin-cells.From the perspective of recent research status,the cell exhib ited superior rate capacity and excellent cycling stability.Additionally,we compared the electrochemical properties of the cell using electrolyte-coated Li₄Ti₅O₁₂ with non-coated Li₄Ti₅O₁₂ to clarify the performance optimization owing to the coating effect.We demonstrated the electrochemical performance at a high temperature of 80 °C.It is difficult for liquid-electrolyte batteries to operate at a temperature of 80 °C because of thermal runaway.Nevertheless,charge-discharge analysis at that temperature is propitious to describe features of all-solid-state batteries.The LiCoO₂ thin film was prepared by radio-frequency magnetron sputtering,and by adjusting the technical parameters during sputtering process,a series of thin film can be obtained.The annealed films under different sputtering parameters have notable difference in its morphology,composition,structure and properties.Through the experiment,the performance of the film after annealing has been greatly improved.And based on it,by changing the sputtering parameters,such as the gas flow rate of argon and oxygen and sputtering time,we can obtained the thin film with relatively good performance.Its capacity exhibits a certain change at 0.05 C,0.1 C,0.2 C,0.5 C.Thus this thin-film electrode material is suitable for thin-film battery which is installed in the device with small current.