Hybrid Organic-Inorganic Fast-Charging Structural Batteries

As lithium-ion battery specific energy and power nears its ceiling, other approaches must be taken to increase the system-level specific energy. One such approach is structural batteries, batteries which can bear mechanical load and can thus be used as body panels of UAVs, cars, or satellites. In this goal, carbon-fibers are coated with a cathode slurry to make a carbon-fiber composite cathode. The cathode slurry contains a mixture of an organic active material and an inorganic active material. Organic radical polymers – such as PTMA (poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate)) – are a promising cathode material due to their straightforward synthesis, availability of raw materials, and fast kinetics. However, they fall short of inorganic materials in their specific capacity. To solve this issue, a hybrid organic-inorganic cathode using PTMA and LFP (lithium iron phosphate) was investigated due to their similar reaction potential. Using this hybrid system, the capacity of the cathode was greatly increased and maintained much of the fast-charging capability due to a beneficial charge-transfer reaction between the PTMA and LFP. This system demonstrates capacity of up to 105 mAh/g at 1 C-rate and 25 °C – a 57% improvement over the pure PTMA system. In addition to this, the mechanical properties of the carbon fiber are not deteriorated by the cathode coating, enabling a high specific modulus. The combination of high specific power and high specific modulus make this hybrid system a promising evolution in structural batteries.