LFP-based binder-free electrodes produced via fused filament fabrication

Carbon coated-LiFePO4 (LFP) is a strong candidate as lithium-ion battery (LiB) cathode due to the combination of safe operation, stable electrochemical performance and positive environmental impact as does not depend on Co, which is toxic and a critical raw material. In this work, we report the development of binder-free LFP cathodes fabricated by fused filament fabrication (FFF) technology. Several novel carbon-LFP filaments have been developed to 3D-print LiB cathodes, analysing both the carbon to LFP ratio in the formulation and also the impact of the carbon source used as current collector, i.e. glassy carbon (GC) microspheres or carbon black (CB), in the electrochemical performance. LFP remained stable upon debinding and sintering at temperatures as low as 500 °C as determined by x-ray diffraction. The conductivity of 3D printed LFP monoliths was 2.06 × 10−4 S∙cm−1 at 50 °C, which is fairly close to that of LFP produced via conventional processing. This is mainly attributed to the preservation of the carbon coating around the LFP particles after debinding and sintering under controlled Ar atmospheres. The LFP-based electrodes containing CB or GC microspheres as conductive additives exhibited specific capacities of 150 mAh g−1, and over 95% coulombic efficiency after 100 cycles, showing no significant performance losses. These results largely exceed the performances reported for previous LFP-based electrodes produced via FFF as the non-active binder is removed upon fabrication.