Electrolyte‐Regulated Solid‐Electrolyte Interphase Enables Long Cycle Life Performance in Organic Cathodes for Potassium‐Ion Batteries

Abstract

Organic cathode materials as economical and environment‐friendly alternatives to inorganic cathode materials have attracted comprehensive attention in potassium‐ion batteries (KIBs). Nonetheless, active material dissolution and mismatched electrolytes result in insufficient cycle life that definitely hinders their practical applications. Here, a significantly improved cycle life of 1000 cycles (80% capacity retention) on a practically insoluble organic cathode material, anthraquinone‐1,5‐disulfonic acid sodium salt, is realized, in KIBs through a solid‐electrolyte interphase (SEI) regulation strategy by ether‐based electrolytes. Such an excellent performance is attributed to the robust SEI film and fast reaction kinetics. More importantly, the ether‐electrolyte‐derived SEI film has a protective inorganic‐rich inner layer arising from the prior decomposition of potassium salts to solvents, as revealed by X‐ray photoelectron spectroscopy analysis and computational studies on molecular orbital energy levels. The findings shed light on the critical roles of electrolytes and the corresponding SEI films in enhancing performance of organic cathodes in KIBs.

Review on Recent Advances of Cathode Materials for Potassium‐ion Batteries

“…Copyright 2018, Elsevier; d) crystal structure of AQDS. Reproduced with permission . Copyright 2018, John Wiley and Sons.…”

“…The good electrochemical performance is attributed to the low solubility of the AQDS molecules in organic electrolyte. Li et al . used an ether‐based electrolyte to build a high‐quality SEI film to achieve high electrochemical performance of AQDS (Figure d) for PIBs.…”

Novel Insoluble Organic Cathodes for Advanced Organic K‐Ion Batteries

“…[ 4 ] Among them, potassium terephthalate (K 2 TP, 222 mAh g −1 ) and potassium 2,5‐pyridinedicarboxylate (K 2 PC, 221 mAh g −1 ) were initially unveiled as the first organic anodes in 2017; [ 5 ] and 3,4,9,10‐perylene‐tetracarboxylic dianhydride (PTCDA, 131 mAh g −1 ) was the first example of organic cathodes reported in 2015. [ 6 ] Afterward, several organic anodes (e.g., K 2 BPDC, [ 7 ] K 4 PTC, [ 8 ] ADAPTS, [ 9 ] and vitamin K [ 10 ] ) and organic cathodes (e.g., PAQS, [ 11 ] AQDS, [ 12 ] CuTCNQ, [ 13 ] PPTS, [ 14 ] HAT, [ 15 ] PI, [ 16 ] and PTCDI [ 17 ] ) were respectively reported.…”

“…At present, there are two distinct limitations for usage of organic electrodes in PIBs: i) one is that most small‐molecule organic electrodes face serious dissolution problem against liquid electrolytes (poor cycle stability); [ 18 ] ii) the other one is that organic electrodes show relatively fair conductivity (poor rate performance). [ 12,19 ]…”

An Insoluble Anthraquinone Dimer with Near‐Plane Structure as a Cathode Material for Lithium‐Ion Batteries

“…The simplest way is to introduce substituent(s) into AQ to increase the intermolecular van der Waals force or ion interaction (Figure a). Various substituents have been investigated, including phenolic lithium salts ( 1 ), carboxylate ( 2 ), sulfonate ( 3 ), and so on . For example, AQ functionalized with two SO 3 Na groups ( 3 ) displays greatly decreased solubility and enhanced cycling stability .…”