Short carbon fiber reinforced epoxy-ionic liquid electrolyte enabled structural battery via vacuum bagging process

Carbon fiber-based structural batteries with the functions of load bearing and energy storage simultaneously are highly attractive in aviation and automobile industry. In this work, a structural battery with LiFePO4 coated carbon fiber woven fabric (CFWF) as cathode, graphite coated CFWF as anode, and acidified short carbon fiber (ASCF) reinforced epoxy-ionic liquid (EI) as electrolyte was fabricated with a vacuum bagging process, which demonstrates a high tensile strength of 201 MPa and an energy density of 89.8 Wh/kg. Here, the key for successfully achieving the high performance of structural battery is employing ASCF/EI as electrolyte and matrix simultaneously, which enables the battery to free inactive packaging materials and use fabrication technique compatible with conventional composite manufacturing process. In particular, the ASCF/EI electrolyte prepared shows excellent mechanical properties including the tensile strength of 22.6 MPa and the Young's modulus of 1.08 GPa, as well as an impressive ionic conductivity of 9.46 x 10(-5) S/cm, due to the prominent enhancement effectiveness of ASCF with large aspect ratios and oxygen containing function groups. Moreover, while the discharge capacity of structural battery under loading decreases slightly with increasing the external loading, its capacity recovers after unloading. Finite element analysis results indicate that the mechanical performances of structural battery under tensile and bending are dominated by the CFWF, while its electrochemical performances under compressive loading are determined by the mechanical performance of ASCF/EI electrolyte. The ASCF/EI electrolyte with excellent mechanical, electrochemical, and processing properties simultaneously is particularly suitable for large-scale fabrication of structural battery.