COF-based single Li^(+)solid electrolyte accelerates the ion diffusionandrestrains dendritegrowthin quasi-solid-state organic batteries

A solid-state electrolyte(SSE),which is a solid ionic conductor and electroninsulating material,is known to play a crucial role in adapting a lithium metal anode to a high-capacity cathode in a solid-state battery.Among the various SSEs,the single Li-ion conductor has advantages in terms of enhancing the ion conductivity,eliminating interfacial side reactions,and broadening the electrochemical window.Covalent organic frameworks(COFs)are optimal platforms for achieving single Li-ion conduction behavior because of wellordered one-dimensional channels and precise chemical modification features.Herein,we study in depth three types of Li-carboxylate COFs(denoted LiOOC-COFn,n=1,2,and 3)as single Li-ion conducting SSEs.Benefiting from well-ordered directional ion channels,the single Li-ion conductor LiOOC-COF3 shows an exceptional ion conductivity of 1.36×10^(-5) S cm^(-1) at room temperature and a high transference number of 0.91.Moreover,it shows excellent electrochemical performance with long-term cycling,high-capacity output,and no dendrites in the quasi-solid-state organic battery,with the organic small molecule cyclohexanehexone(C_(6)O_(6))as the cathode and the Li metal as the anode,and enables effectively avoiding dissolution of the organic electrode by the liquid electrolyte.

SINGLE IONIC CONDUCTI0N OF POLYSILOXANE CONTAINING PROPYLENE CARBONATE GROUP AND LITHIUM POLYMERIC SALTS

The polysiloxane containing propylene carbonate side group and several lithium poly-meric salts were synthesized. The structure were confirmed by IR, NMR and XPS. Theblending systems of polysiloxane containing propylene carbonate group with different lithiumpolymeric salts were studied by ion conductivity XPS and DSC. Different lithium poly-meric salts in the blending system lead to conductivity arranged in the following sequence:poly(lithium ethylenebenzene sulfonate methylsiloxane)>poly(lithium propionate methyl-siloxane)>poly(lithium propylsulfonate methylsiloxane)>poly(lithium styrenesulfonate).In the blending system the best single ion conductivity was close to 10^(-5) Scm^(-1) at roomtemperature. XPS showed that at low lithium salt concentration the conductivity increasedwith the increasing content of lithium salt, in consequence of the increase of free ion andsolvent separated ion pair. At high lithium salt concentration the free ion was absent andthe solvent-separated ion pair functioned as carrier.

Ion transport and structural design of lithium-ion conductive solid polymer electrolytes:a perspective

Solid polymer electrolytes(SPEs)possess several merits including no leakage,ease in process,and suppressing lithium dendrites growth.These features are beneficial for improving the cycle life and safety performance of rechargeable lithium metal batteries(LMBs),as compared to conventional non-aqueous liquid electrolytes.Particularly,the superior elasticity of polymeric material enables the employment of SPEs in building ultra-thin and flexible batteries,which could further expand the application scenarios of high-energy rechargeable LMBs.In this perspective,recent progresses on ion transport mechanism of SPEs and structural designs of electrolyte components(e.g.conductive lithium salts,polymer matrices)are scrutinized.In addition,key achievements in the field of single lithium-ion conductive SPEs are also outlined,aiming to provide the status quo in those SPEs with high selectivity in cationic transport.Finally,possible strategies for improving the performance of SPEs and their rechargeable LMBs are also discussed.