Research On The Preparation And Performance Of Solid Lithium-air Batteries Based On Composite Electrolytes

Compared with lithium-ion batteries,lithium-air batteries have a higher theoretical specific capacity,which can meet people's requirements for energy storage systems in the fields of electric vehicles,military,and aviation.It is a very promising new energy storage technology.However,most lithium-air batteries currently use organic electrolytes,which are susceptible to nucleophilic attack by active oxides generated during the charging and discharging process,causing side reactions,causing by-products to accumulate,and reducing the cycle performance of the battery.In addition,the organic electrolyte is flammable,it has potential safety hazards,and it cannot suppress lithium dendrites well.It is easy to cause short circuit and thermal runaway of the battery,and serious safety problems occur.A composite polymer electrolyte?CPE?composed of a polymer electrolyte,a lithium salt,and an inorganic filler has better stability,can resist the corrosion of active oxygen species,suppress lithium dendrites,and avoid safety issues.Moreover,CPE has good flexibility,which can reduce the interface resistance between the electrolyte/electrode very well.In this paper,a polyvinylidene fluoride?PVDF?and Li₇La₃Zr₂O₁₂?LLZO?composite solid electrolyte?CPE?were prepared,and their morphology and electrochemical performance were systematically studied.First tested the electrical conductivity of PVDF electrolyte and CPE doped with different content of LLZO at different temperatures.The performance of CPE doped with 10wt%LLZO is the best.The ionic conductivity at room temperature is 1.17×10^-6 S cm^-1.which is 1 to 3 orders of magnitude higher than other electrolytes.Full charge and discharge tests and equal-capacity charge-discharge tests were performed on lithium-air batteries assembled using CPE.The discharge capacity of10wt%doped CPE in the first cycle is 2953.6 m Ah g^-1.Under the controlled capacity of300 m Ah g^-1,the battery assembled with 10wt%doped CPE can run for 30discharge/charge cycles stably.The first discharge voltage plateau is 2.65V,and the first charge plateau is 3.6V.It has a small overpotential.A long life cycle of the battery can be achieved.In this paper,a three-dimensional?3D?macro-porous LLZO is also prepared and added as interconnected inorganic fillers for polyethylene oxide?PEO?-based CPEs.The3D LLZO network-based CPE?denoted as 3D-CPE?with a high filler content of 65 wt%achieves high electrochemical stability up to 5.0 V owing to the superior stability of LLZO,and total conductivity of 9.2 x 10^-5 S cm^-1 at room temperature,which overwhelmingly surpass its counterpart with ordinary LLZO particles?denoted as o-CPE?.The integrated structure of 3D LLZO network offers an interconnected network which is conducive to lithium ion conduction through.The solid-state lithium-air battery using3D-CPE delivers the initial discharge capacity of 2485 m Ah g^-1 in ambient air.Under the limited capacity of 300 m Ah g^-1,the battery achieves a high-efficiency cycle performance in ambient air without significant fading,having all discharge voltages above 2.0 V and charge voltages below 4.5 V for 50 cycles.In contrast,the LAB with o-CPE only gives23 cycles with rapid attenuation until battery dies.Composite solid electrolyte based on three-dimensional LLZO framework is a very promising electrolyte material,especially for the use in LAB.