Effect of sintering and C65 conductive additive on the performance of full-ceramic 3D-LiFePO4 thick electrodes produced by direct ink writing

Thick ceramic LiFePO₄ electrodes (800 µm thickness, ∼104 mg/cm² mass loading) are fabricated by direct ink writing using a sustainable aqueous-based suspension. This approach enables the formation of three-dimensional electrodes with a controlled porous architecture that enhances electrode/electrolyte wettability and mitigates ion and charge transport limitations typically associated with thick electrodes. The effects of debinding and sintering conditions on the microstructure and electrochemical performance are systematically investigated. In addition, the role of a super conductive carbon black (C65) additive is evaluated as a strategy to enhance electronic conductivity while preserving the ceramic nature of the electrodes. After optimization, fully ceramic binder-free electrodes are obtained. When assembled in full cells with Li₄Ti₅O₁₂ as the negative electrode and LP30 electrolyte, the optimized electrodes deliver areal capacities from 8.1 mAh/cm² at C/4 up to 14.4 mAh/cm² at C/25, retaining 5.9 mAh/cm² at 1 C.