Graphical Everyday I'm shuttling : A functional lithiated Nafion-decorated separator (Li-Nafion@PE) exhibits a good inhibition for redox shuttling in LiI-containing Li-O 2 batteries. The fabrication combines the wide universality, easy operation, and suitability for mass production. A cell with as-prepared Li-Nafion@PE exhibits considerable cycling stability and good reversibility associated with desired Li 2 O 2 generation and degradation. Although the employment of redox mediator (RM) is an effective strategy to reduce the overpotential by avoiding the direct electrochemical oxidization of Li 2 O 2 during charging, an unexpected redox shuttling in Li-O 2 system leads to RM degradation and continuous deterioration of Li anode, finally resulting in a limited cycling stability. Here, a functional lithiated Nafion-modified separator was firstly introduced to inhibit the shuttle effect by coulombic/electrostatic interactions in RM-involved Li-O 2 batteries. The fabrication of the separator involved easily accessible raw materials and an easy-to-operate process, which made it suitable for large-scale production. The enhancement of lithiated process on electrochemical properties was systematically investigated. In addition, the influence of decorated amount on cycling stability was also studied. Furthermore, the functional contribution of lithiated Nafion on inhibition of redox shuttling and the working mechanism for cells with and without as-prepared separators were proposed. This work can give an insight into the development of functional separator ( i . e ., activity issue) and the suppression of parasitic reactions ( i . e ., selectivity issue) in Li-O 2 batteries.
Due to flexible property and light weight, the lithiated Nafion membrane swollen with PC (PC-Li-Nafion) has been employed as both solid-state electrolyte and separator to fabricate solid-state Li-S cells. The electrochemical measurements of PC-Li-Nafion membrane show that its Li-ion transference number is 0.928, ionic conductivity of 2.1 × 10 −4 S cm −1 can be achieved at 70 °C and its electrochemical window is 0 ∼ +4.1 V vs. Li + /Li. It is observed that the Li dendrites are suppressed by using PC-Li-Nafion membrane due to its single-ion conducting property. The amounts of Li-Nafion resin binder and conductive carbon in the cathode are optimized as 40% and 10% respectively to make a balance of ionic and electronic conductivities . A thin-layer Li-Nafion resin with a thickness of around 2 μm is fabricated between the cathode and PC-Li-Nafion membrane to improve the interfacial contact and further enhance the specific capacity of the cell. When measured at 70 °C, the Li-S cell delivers a reversible specific capacity of 1072.8 mAh g −1 (S) at 0.05 C and 895 mAh g −1 (S) at 1 C. The capacity retention at 1 C is 89% after 100 cycles. These results suggest that high-performance solid-state Li-S cells can be fabricated with the Li-Nafion polymer electrolyte .
The low cycling efficiency and uncontrolled dendrite growth resulting from an unstable and heterogeneous lithium–electrolyte interface have largely hindered the practical application of lithium metal batteries. In this study, a robust all-organic interfacial protective layer has been developed to achieve a highly efficient and dendrite-free lithium metal anode by the rational integration of porous polymer-based molecular brushes (poly(oligo(ethylene glycol) methyl ether methacrylate)-grafted, hypercrosslinked poly(4‐chloromethylstyrene) nanospheres, denoted as x PCMS- g -PEGMA) with single-ion-conductive lithiated Nafion. The porous x PCMS inner cores with rigid hypercrosslinked skeletons substantially increase mechanical robustness and provide adequate channels for rapid ionic conduction, while the flexible PEGMA and lithiated Nafion polymers enable the formation of a structurally stable artificial protective layer with uniform Li + diffusion and high Li + transference number. With such artificial solid electrolyte interphases, ultralong-term stable cycling at an ultrahigh current density of 10 mA cm −2 for over 9,100 h (>1 year) and unprecedented reversible lithium plating/stripping (over 2,800 h) at a large areal capacity (10 mAh cm −2 ) have been achieved for lithium metal anodes. Moreover, the protected anodes also show excellent cell stability when paired with high-loading cathodes (~4 mAh cm −2 ), demonstrating great prospects for the practical application of lithium metal batteries.
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