Electrochemical Properties of LiMn2O4-Li7La3Zr2O12 Composite Film Electrode Fabricated By Aerosol Deposition Method

LiMn₂O₄ (LMO)-Li₇La₃Zr₂O₁₂ (LLZO) composite film electrode was successfully fabricated without any heat treatments by using aerosol deposition (AD) method. Mixture of 75wt%-LMO and 25wt%-LLZO powders with the averaged particle sizes around 1 μm was directly used as raw material. The mixed LMO and LLZO powders were sprayed onto a stainless steel substrate in deposition chamber evacuated to a low vacuum state below 10 Pa with N₂ carrier gas for several 10 minutes. Mass flow of N₂ carrier gas was set to be 20 L min^-1 to form LMO-LLZ composite film via room temperature impact consolidation (RTIC). From both SEM observation and XRD measurement, it was found that as-deposited film has very dense structure without pores and is consisted from fractured LMO and LLZO crystalline particles with the sizes of several 10-100 nm. The thickness of composite film is 4 μm and LLZO content in the film was estimated to be around 21wt%. LMO-LLZO composite film electrode showed good electrochemical property in liquid electrolyte and higher discharge capacity than LMO film without including LLZO. The discharge capacities reduced by the weight of LMO-LLZO composite film electrode was 70 mAh g^-1, 62 mAh g^-1 and 55 mAh g^-1 at different discharge current rates of 0.07C, 0.7C and 3C (1C = 0.11 mA cm^-2). They are corresponding to the specific capacity per LMO in the film of 90 mAh g^-1, 80 mAh g^-1 and 71 mAh g^-1, respectively. In addition, the LMO-LLZO composite film electrode showed good capacity retention during cycle testing, which is attributed to strong adhesion between the composite film and substrate by AD. The present results suggest that AD method can potentially be used for electrode layer composed of active material and solid electrolyte for all-solid state lithium-ion battery.