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

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.