Additive Manufacturing and Characterization of Micro-Architected LiFePO₄/C Composite Electrodes for Li Ion Batteries

Electrodes with 3D architected structures hold the potential to disrupt the trade-off between high energy density and power density in commercial 2D slurry batteries. 3D electrodes offer the advance of a large interphase area between the electrode and the electrolyte and allow for a greater active material mass loading without increasing the ion diffusion distance in electrode compared with slurry electrodes.<br/>We design, synthesize, and characterize a 3D LiFePO₄ (LFP)/C composite electrode with tilted cubic architecture and 150μm beam diameter. In this additive manufacturing (AM) process, a polymer scaffold is first printed via vat photopolymerization (VP)-based additive manufacturing technique, which provides a high resolution of 50μm and flexibility in structural design. Then ion precursors are infused into the hydrogel scaffolds and calcined at 800°C under inert atmosphere to produce LFP/C composite micro-lattices with a porous surface and 500nm LPF particles formed in the micro-lattices. The chemical composition is tuned by the ion precursor concentrations and optimized for electrochemical performance. The concomitant formation of carbon within the lattice provides a pathway for electron transport and reduces the internal resistance of the electrode. X-ray powder diffraction and thermogravimetric analysis were applied to determine the chemical composition of the LFP/C micro-lattice. The uniform distribution of C, O, P, and Fe elements is revealed through energy dispersive X-ray (EDX) mapping. To characterize its electrochemical properties, the LFP/C electrode was assembled into a coin cell against Li foil. The formation of electrochemical active LFP was confirmed by the cyclic voltammetry (CV) curve. This method is amenable to printing a wide range of electrode materials and offers the advantages of 3D architecture on the overall cell electrochemical performance.