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To advance the state of structural battery composites, more mechanically robust polymeric materials must be investigated for use as the ionically conductive electrolyte. Currently, the matrices being utilized in solid polymer electrolytes lack mechanical strength, and are often gels, due to their amorphous structure offering increased lithium-ion conductivity. To address the need for more robust, semicrystalline polymer matrices, poly ether ether ketone (PEEK) was selected as a candidate that would offer both ionic conductivity and mechanical reinforcement in these novel multifunctional composite structures. Through a series of functionalization procedures, specifically sulfonation and lithiation of the polymer chains, the PEEK exhibits ionic conductivity and an amorphous microstructure. However, to maintain the structural characteristics required of the matrix, careful functionalization is used to tailor the PEEK electrolytes and strike a balance between the two inversely related properties (ion conductivity and crystallinity). It was found that selective adjusting of the morphology of the solid electrolyte successfully enables the two properties that are most important for this multifunctional application. The discoveries presented from this work provide a foundation to continue progress on thermoplastic structural battery composites. 

Carbon fiber-based structural lithium-ion batteries are attracting significant attention in the automotive and aerospace industries due to their dual capability of energy storage and mechanical load-bearing, leading to weight reduction. These batteries utilize lightweight carbon fiber (CF) composites, which offer excellent stiffness, strength-to-weight ratios, and electrical conductivity. Polyacrylonitrile-based CFs, comprising graphitic and amorphous carbon, are particularly suitable for Li-ion battery applications as they allow the storage of lithium ions. However, integrating lithium iron phosphate (LFP) into CFs poses challenges due to complex lab-scale processes and the use of toxic dispersants, hindering large-scale industrial compatibility. To address this, we investigate the development of water-based LFP-integrated CF structural Li-ion batteries. Homogeneous suspensions are created using cellulose nanocrystals (CNCs) to form hybrid structures. The battery system employs LFP-modified CF as the cathode, unsized CF as the anode, and a water-based electrolyte. The LFP-CNC-graphene nanoplatelet (GNP) hybrids are coated onto CFs through immersion coating. Scanning electron microscopy (SEM) images confirm the well-dispersed and well-adhered LFP-CNC-GNP structures on the CF surface, contributing to their mechanical interlocking and electrochemical performance. The batteries demonstrate a specific energy density of 62.67 Wh/kg and a specific capacity of 72.7 mAh/g. Furthermore, the cyclic voltammetry experiments reveal the stability of the LFP-CNC-GNP-coated CF batteries over 200 cycles without degradation. This research enables the engineering of hybrid nanostructured battery laminates using novel LFP-CNC-GNP-coated CFs, opening avenues for the development of innovative Li-ion structural batteries. 

Abstract Polyimides (PIs), known for their thermal resistance, chemical stability, and mechanical properties, are often considered challenging materials to process, resulting in limited commercial availability of PIs for melt extrusion, injection molding, and fused filament fabrication (FFF). Currently, material and knowledge gaps prevent the ability to rapidly produce parts from PIs that can be used in high strength and elevated temperature applications. To address this, a novel, fully aromatic PI with thermotropic liquid crystalline properties (LCPI) is successfully synthesized. The synthesized LCPI exhibits better solvent tolerance and thermal stability than commercially available counterparts. The LC phase is confirmed by thermal analysis, wide angle X‐ray scattering, and polarized optical microscopy. Rheological behavior clearly demonstrates that the LC phase reduces melt viscosity. These properties enable the LCPI to be processed into both drawn fibers and filaments for FFF, which is demonstrated alongside an injection molding process. The properties of the printed parts rivaled those made with Ultem 1000, exhibiting an average elastic modulus of 4.16 GPa. The injection molding process resulted in tensile moduli as high as 8.59 GPa and tensile strengths as high as 124.70 MPa. The LCPI polymer demonstrates the desired properties required for aerospace applications via melt processing techniques.