The relatively narrowe lectrochemical steady windowa nd low ionic conductivity are two critical challenges for Li + -conducting solid polymer electrolytes (SPE). Here,afamily of poly-oxalate(POE) structures were prepared as SPE; among them, POEs composed from diols with an odd number of carbons show higher ionic conductivity than those composed from diols with an even number of carbons,a nd the POE composed from propanediol (C5-POE) has the highest Li + conductivity.T he HOMO (highest occupied molecular orbital) electrons of POE were found located on the terminal units.W hen using trifluoroacetate as the terminating unit (POE-F), not only does the HOMO become more negative, but also the HOMO electrons shift to the middle oxalate units, improving the antioxidative capability.F urthermore,t he interfacial compatibility across the Li-metal/POE-F is also improved by the generation of aL iF-based solid-electrolyteinterlayer(SEI). With the trifluoroacetate-terminated C5-POE (C5-POE-F) as the electrolyte and Li + -conducting binder in the cathode,t he all-solid-state Li/LiNi 0.8 Mn 0.1 Co 0.1 O 2 -(NMC811) cells showed significantly improved stability than the counterpart with poly-ether,p roviding ap romising candidate for the forthcoming all-solid-state high-voltage Li-metal batteries.

The critical challenges for lithium-ion batteries today are how to improve the energy densities and solve the safety issues, which can be addressed through the construction of solid-state lithium metal batteries with solid polymer electrolytes (SPEs). Significant efforts have been devoted to the design and synthesis of SPEs, in which their electrochemical windows and corresponding compatibilities with both electrodes are crucial, particularly when taking high-voltage transition metal oxides as cathodes. In this review, the SPEs with different electrochemical windows are summarized and categorized, including (i) anode stable SPEs with good lithium metal compatibilities, (ii) cathode stable SPEs with good oxidation resistances, (iii) multilayer SPEs simultaneously withstanding reduction of a lithium anode and oxidation at high voltage. The impacts of polymer molecular structures and compositions on the SPE properties and performance are discussed. The development of high-performance SPEs that can stabilize or form stable interfacial passivation layers with both cathodes and anodes simultaneously is the desired candidate of future applications.

The application of solid polymer electrolytes (SPEs) in all‐solid‐state(ASS) batteries is hindered by lower Li+‐conductivity and narrower electrochemical window. Here, three families of ester‐based F‐modified SPEs of poly‐carbonate (PCE), poly‐oxalate (POE) and poly‐malonate (PME) were investigated. The Li+‐conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li+, the Li+‐conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl‐units are observed more effective than −O−CH2−CF2−CF2−CH2−O− during the in situ passivation of Li‐metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li‐metal and high‐voltage‐cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi0.6Co0.2Mn0.2O2 (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl‐group in malonate and the suppression of enol isomerization. The coordinating capability with Li+, molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.

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The relatively narrow electrochemical steady window and low ionic conductivity are two critical challenges for Li+‐conducting solid polymer electrolytes (SPE). Here, a family of poly‐oxalate(POE) structures were prepared as SPE; among them, POEs composed from diols with an odd number of carbons show higher ionic conductivity than those composed from diols with an even number of carbons, and the POE composed from propanediol (C5‐POE) has the highest Li+ conductivity. The HOMO (highest occupied molecular orbital) electrons of POE were found located on the terminal units. When using trifluoroacetate as the terminating unit (POE‐F), not only does the HOMO become more negative, but also the HOMO electrons shift to the middle oxalate units, improving the antioxidative capability. Furthermore, the interfacial compatibility across the Li‐metal/POE‐F is also improved by the generation of a LiF‐based solid‐electrolyte‐interlayer(SEI). With the trifluoroacetate‐terminated C5‐POE (C5‐POE‐F) as the electrolyte and Li+‐conducting binder in the cathode, the all‐solid‐state Li/LiNi0.8Mn0.1Co0.1O2(NMC811) cells showed significantly improved stability than the counterpart with poly‐ether, providing a promising candidate for the forthcoming all‐solid‐state high‐voltage Li‐metal batteries.