Introducing nonvolatile liquid acids into porous solids is a promising solution to construct anhydrous proton-conducting electrolytes, but due to weak coordination or covalent bonds building these solids, they often suffer from structural instability in acidic environments. Herein, we report a series of steady conjugated microporous polymers (CMPs) linked by robust alkynyl bonds and functionalized with perfluoroalkyl groups and incorporate them with phosphoric acid. The resulting composite electrolyte exhibits high anhydrous proton conductivity at 30−120 °C (up to 4.39 × 10 −3 S cm −1 ), and the activation energy is less than 0.4 eV. The excellent proton conductivity is attributed to the hydrophobic pores that provide nanospace for continuous proton transport, and the hydrogen bonding between phosphoric acid and perfluoroalkyl chains of CMPs promotes short-distance proton hopping from one side to the other.
Although covalent organic frameworks (COFs) with agraphene-like structure present unique chemical and physical properties,t hey are essentially insoluble and infusible crystalline powders with poor processability,h indering their further practical applications.H ow to improve the processability of COF materials is am ajor challenge in this field. In this contribution, we proposed ag eneral side-chain engineering strategy to construct ag el-state COF with high processability. This method takes advantages of large and soft branched alkyl side chains as internal plasticizers to achieve the gelation of the COF.W es ystematically studied the influence of the length of the side chain on the COF gel formation. Benefitting from their machinability and flexibility,this novel COF gel can be easily processed into gel-type electrolytes with specific shape and thickness,w hich were further applied to assemble lithium-ion batteries that exhibited high cycling stability.
Although covalent organic frameworks (COFs) with agraphene-like structure present unique chemical and physical properties,t hey are essentially insoluble and infusible crystalline powders with poor processability,h indering their further practical applications.H ow to improve the processability of COF materials is am ajor challenge in this field. In this contribution, we proposed ag eneral side-chain engineering strategy to construct ag el-state COF with high processability. This method takes advantages of large and soft branched alkyl side chains as internal plasticizers to achieve the gelation of the COF.W es ystematically studied the influence of the length of the side chain on the COF gel formation. Benefitting from their machinability and flexibility,this novel COF gel can be easily processed into gel-type electrolytes with specific shape and thickness,w hich were further applied to assemble lithium-ion batteries that exhibited high cycling stability.
An anhydrous proton conductor represents a key material for the manufacture of high-energy electrical devices. Incorporation of proton carriers into the vacancies of the porous solid provides an effective method for their preparation, but the weak or even no interactions between the ion carriers and the porous solids causing a serious leaking of ion carriers result in trade-off of long-term conductivity. In this term, we developed a host−guest supramolecular chemistry-induced strategy to assemble hydrogen bond networks along the 1D nanochannels of covalent organic frameworks (COFs) for ultrafast and anhydrous proton transfer (1.33 × 10 −2 S cm −1 at 140 °C). Solid-state NMR was applied to explore guest interaction between protic ionic liquids (PILs) and the COFs to investigate the proton transport mechanism. This work presents an excellent example of accumulation of PILs into the nanochannels of COFs for anhydrous proton conduction at high temperature, demonstrating great advantages of COFs to serve as a supramolecular host for holding/transiting ions in the solid state.
Poly(ethylene
glycol) (PEG)-derived electrolytes can promote not
only conduction of lithium ions but also that of anions. To avoid
anion conduction and increase the Li-ion transference number, we propose
a new concept that utilizes crowded space to restrict anion movement.
Branched PEG chains with different lengths were covalently grafted
into the pore surface of covalent organic frameworks (COFs) and construct
crowded nanochannels. After incorporating LiTFSI, the COF with longer
PEG chains achieves an ionic conductivity of 1.5 × 10–3 S cm–1 at 200 °C and an activation energy
of 0.60 eV. It also inhibits anion movement in a certain direction
and obtains a higher transference number than other COFs with shorter
PEG chains. The full cell is further assembled, finally obtaining
a specific discharge capacity of 153 mAh g–1 after
60 cycles at 100 °C.
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