Self-assembled porous structures were manufactured directly onto current collectors based on layer-by-layer spray printing of TiO2(B) nanotubes. The through-thickness porous channels in the electrode structures enabled the efficient penetration of the liquid Li-ion electrolyte into the resulting coral-like electrode, leading to an improvement in thickness-dependent power capability.

A spray printing manufacturing approach to lithium-ion batteries was investigated with a focus on minimizing inactive fractions and maximizing energy and power densities of printable electrodes. Using a lithium titanate based anode initially and comparing with conventional electrodes, the effects of conductivity enhancer and binder fractions, post-calendaring effects, different electrode manufacturing methods, conductivity enhancer types and electrode thicknesses were explored, and optimum electrode structures were identified. These insights were then applied to a lithium iron phosphate based cathode, and full spray printed lithium titanate/lithium iron phosphate cell configurations were investigated. Notably, the full-cell battery with a 1:1 capacity ratio of lithium titanate to lithium iron phosphate had a stable specific energy density of ~ 300 Wh/kg and a power density of ~ 2500 W/kg, showing the promise of layer-by-layer spray printing to realize fully the intrinsic properties of electrode materials in lithium-ion battery cells.

Directional, micron-scale honeycomb pores in Li-ion battery electrodes were fabricated using a layer-by-layer, self-assembly approach based on spray-printing of carbon nanofibers. By controlling the drying behavior of each printed electrode layer through optimization of (i) the volume ratio of fugitive bisolvent carriers in the suspension and (ii) the substrate temperature during printing, self-assembled, honeycomb pore channels through the electrode were created spontaneously and reliably on current collector areas larger than 20 cm × 15 cm. The honeycomb pore structure promoted efficient Li-ion dynamics at high charge/discharge current densities. Incorporating an optimum fraction (2.5 wt %) of high-energy-density Si particulate into the honeycomb electrodes provided a 4-fold increase in deliverable discharge capacity at 8000 mA/g. The spray-printed, honeycomb pore electrodes were then investigated as negative electrodes coupled with similar spray-printed LiFePO4 positive electrodes in a full Li-ion cell configuration, providing an approximately 50% improvement in rate capacity retention over half-cell configurations of identical electrodes at 4000 mA/g.

Heterogeneous, multi-layered electrodes based on high power Li 4 Ti 5 O 12 interleaved with a smaller fraction of high capacity Si were fabricated using layer-by-layer spray printing, with the goal of achieving a balance of power and capacity for Li-ion storage technologies. The faradaic charge/discharge behavior of the multi-layered hybrid electrodes was investigated as a function of (i) the thickness of the discrete Si layer within the multilayered electrode, and (ii) the location of the Si layer within the electrode: on the top of the Li 4 Ti 5 O 12 (closest to the separator), between two layers of Li 4 Ti 5 O 12 (sandwich configuration) or at the Li 4 Ti 5 O 12 base (next to the current collector but furthest from the separator). The optimum arrangement of Si spray printed on Li 4 Ti 5 O 12 offered outstanding electrochemical performance at high current densities of 4000 mA/g and after 500 cycles when in a full Li-ion battery configuration coupled with a spray printed LiFePO 4 cathode. The optimized multilayered electrode was reliably reproduced as a double-sided coating over large area current collectors (≥20 cm × 15 cm). Sprayed printed electrodes were also readily patterned in-plane as well as through-thickness, offering the prospect for selective additions of high capacity Si or other active or inactive electrode components at specific locations to provide new Li-ion battery performance characteristics.

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