Polymer reinforced carbon fiber interfaces for high energy density structural lithium-ion batteries

Here, we show that for battery active materials coated onto carbon fiber current collectors, a thin electroconductive poly acrylonitrile, or PAN, coating applied to the surface of the battery material coated fiber drastically improves adhesion and multifunctional structural energy storage performance. With this electrode design, we demonstrate structural battery composites composed of lithium iron phosphate cathodes and graphite anodes which exhibit a maximum energy density of 58 W h kg−1 considering all combined battery and composite materials that make up both the energy storage unit and structural system framework it powers. These full-cell structural batteries also demonstrate capacity retention over 80% exceeding 100 cycles with an average energy density of 52 W h kg−1. Combined mechanical and electrochemical testing correlates this excellent multifunctional performance to the role of PAN coating that adheres active battery materials to carbon fibers during battery operation and mechanical loading. Our findings demonstrate a structural Li-ion battery with a gravimetric multifunctional advantage for electrically powered systems, and highlights the importance of interface engineering to enable practical structural battery systems.