High-Rate Activation of Organic Superlithiation Anodes

Lithium-ion batteries have achieved commercial success; however, work remains to increase the capacity and safety of both the anode and cathode electrodes. Organic anodes have the potential to replace conventional graphite anodes because they are abundant, safe, and high-capacity materials. Superlithiated organic anodes achieve capacities in excess of 1500 mA h g–1; however, the mechanism of superlithiation and how it relates to different materials is an open question. Here, we disclose a pyrene-fused azaacene polymer that undergoes superlithiation and exhibits a continuous activation process, whereby the capacity increases with the number of cycles, reaching values up to 1775 mA h g–1 (1535 mA h g–1, subtracting the carbon additive contribution). This high performance is attributed to the stability and extended conjugation afforded by the polymer design. Ex situ studies suggest cycling results in deformation of the electrode structure, from an amorphous electrode material to one with increased crystallinity and sp2 character. Importantly, this superlithiated electrode maintains the same capacity across a 10-fold increase in rate during the activation process, showing that the kinetic limitations of superlithiation can be overcome and suggesting that commercial practical superlithiation anodes are within reach.