In†Situ Electropolymerization Enables Ultrafast Long Cycle Life and High-Voltage Organic Cathodes for Lithium Batteries.

Organic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4',4''-Tris(carbazol-9-yl)-triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high-voltage redox-active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g-1 , and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries.

Bismuth Nanoparticle@Carbon Composite Anodes for Ultralong Cycle Life and High-Rate Sodium-Ion Batteries.

Bismuth has emerged as a promising anode material for sodium-ion batteries (SIBs), owing to its high capacity and suitable operating potential. However, large volume changes during alloying/dealloying processes lead to poor cycling performance. Herein, bismuth nanoparticle@carbon (Bi@C) composite is prepared via a facile annealing method using a commercial coordination compound precursor of bismuth citrate. The composite has a uniform structure with Bi nanoparticles embedded within a carbon framework. The nanosized structure ensures a fast kinetics and efficient alleviation of stress/strain caused by the volume change, and the resilient and conductive carbon matrix provides an interconnected electron transportation pathway. The Bi@C composite delivers outstanding sodium-storage performance with an ultralong cycle life of 30 000 cycles at a high current density of 8 A g-1 and an excellent rate capability of 71% capacity retention at an ultrahigh current rate of 60 A g-1 . Even at a high mass loading of 11.5 mg cm-2 , a stable reversible capacity of 280 mA h g-1 can be obtained after 200 cycles. More importantly, full SIBs by pairing with a Na3 V2 (PO4 )3 cathode demonstrates superior performance. Combining the facile synthesis and the commercial precursor, the exceptional performance makes the Bi@C composite very promising for practical large-scale applications.