Para-Conjugated Dicarboxylates with Extended Aromatic Skeletons as the Highly Advanced Organic Anodes for K-Ion Battery.

A new family of the para-conjugated dicarboxylates embedding in biphenyl skeletons was exploited as the highly advanced organic anodes for K-ion battery. Two members of this family, namely potassium 1,1'-biphenyl-4,4'-dicarboxylate (K2BPDC) and potassium 4,4'-E-stilbenedicarboxylate (K2SBDC), were selectively studied and their detailed redox behaviors in K-ion battery were also clearly unveiled. Both K2BPDC and K2SBDC could exhibit very clear and highly reversible two-electron redox mechanism in K-ion battery, as well as higher potassiation potentials (above 0.3 V vs K+/K) when compared to the inorganic anodes of carbon materials recently reported. Meanwhile, the satisfactory specific and rate capacities could be realized for K2BPDC and K2SBDC. For example, the K2BPDC anode could realize the stable rate capacities of 165/143/135/99 mAh g-1 under the high current densities of 100/200/500/1000 mA g-1, respectively, after its electronic conductivity was improved by mixing a very small amount of graphene. More impressively, the average specific capacities of ∼75 mAh g-1 could be maintained for the K2BPDC anode for 3000 cycles under the high current density of 1 A g-1.