Co-authors​ :

 Beatriz MAIA (PORTUGAL), Nuno CORREIA (PORTUGAL), Maria HELENA BRAGA , Raquel SANTOS  

More than ever before, battery research pursues to improve the energy density, charging speed, safety of energy storage devices, and to decrease the cost associated to their manufacturing (1). Lithium iron phosphate (LiFePO4 or LFP) has emerged as a promising cathode alternative in the battery field, owing to its stable performance, exceptional thermal stability, satisfactory theoretical discharge capacity, eco-friendliness, and cost-effectiveness (2). However, a new challenge arose: it is imperative to surpass LFP’s characteristic low ionic and electrical conductivity, hindering its commercial application. Several approaches have been investigated to enhance ionic conductivity, encompassing techniques such as metal doping, surface coatings, ion-exchange processes, heat treatments, and comprehensive optimization of synthesis conditions. Conversely, in fulfilling electrical conductivity prerequisites, typical electrode slurries involve the incorporation of carbon-based materials, emphasizing the significance of conductive carbon black (CB). However, higher loadings of CB are typically required (3-10 wt.%), which can potentially detrimentally impact the electrochemical properties of the final cathode. Owing to their unusual physical properties provided by the high aspect ratio, multiwalled carbon nanotubes (MWCNTs) and graphene, or their combinations, are interesting solutions to replace CB at ultralow contents, as long as a homogeneous and stable dispersion is ensured. To boost the advancement of structural batteries, extensive optimizations have been undertaken to create a safe and efficient cathode for not only this specific application but also for lithium-ion batteries in general. Therefore, in this work, several efforts have been made to develop novel materials with enhanced properties by implementing strategies to disperse the cathode constituents using a three-roll mill. Additionally, MWCNTS at ultralow contents (< 0.1 wt.%) were effectively dispersed and distributed into the polymeric matrix, allowing to improve the mechanical and electrochemical performance of the final battery. By decreasing the active material content from 80 to 75 wt.% in a 24.96 wt.% PVDF solution with MWCNTs, it was possible to obtain approximately 100 mA.h.g-1 of specific discharge capacity at a final C/20 C-rate, with 80% capacity retention and good reversibility between 2.8 and 3.8 V. To the best of our understanding, the utilization of this large-scale production method and the incorporation of an extremely low content of carbon-based nanomaterials represent a novel approach within the scientific community.