Incorporation of Azo-Linkage to Elevate the Redox Potential of Triphenylamine-Based Porous Organic Polymer Cathodes for Li-Ion Batteries

Porous organic polymers with triphenylamine (TPA) subunits have attracted a lot of attention as advanced electrodes for Li-ion batteries (LIBs) but with poor rate performance and low stability. In this work, azo-linkage has been incorporated into TPA-based porous organic polymers to increase the redox potential while maintaining the capacity of TPA. The cathodes based on azo-linked porous organic polymers (Azo-POP-10, Azo-POP-11, and Azo-POP-12) exhibited a high redox potential of 3.8 V and can be charged up to 4.5 V. A stable electrochemical performance is observed and our designed cathodes retain 84% (Azo-POP-10), 87% (Azo-POP-11), and 75% (Azo-POP-12) of their initial capacities at a current density of 1000 mAg –1 . Over 60% capacity retention is observed even after 1000 charge–discharge cycles. Moreover, the cathodes still delivered a stable capacity even at a very high current density of 20,000 mAg –1, showing excellent stability under fast charging conditions. A cutoff potential of 4.5 V and a current density of 20,000 mAg –1 are the highest parameters for TPA-based materials to date. The unique material design is mainly responsible for this excellent performance, and we believe that this report can inspire the further development of organic cathodes with fast charging and better stability.