We report a rational design of solid-state dry polymer electrolytes with high conductivity, high mechanical strength, and improved cation transference number. Thiol–ene click chemistry provided orthogonal control over the type and number of end groups in poly­(styrene-b-ethylene oxide) (PS-b-PEO) block copolymers. This approach permitted the synthesis of PEO chains with reduced crystallinity, reminiscent of PEO oligomers, thereby playing a key role in improving the room temperature conductivity. Intriguingly, the incorporation of diol or dicarboxylic acid end groups in PS-b-PEO produced a well-defined gyroid structure, leading to order of magnitude improvements in the storage modulus. Out of the various samples examined, the electrolytes bearing terminal diol displayed the highest ionic conductivity and a 2-fold increase in lithium transference number. The improvements in performance are attributed to the reduced interchain aggregation and the anion stabilization mediated by the terminal diol group. The fact that the dramatic changes in ion transport and mechanical properties of PS-b-PEO samples were brought about solely by the modification of single terminal group of the PEO unit confirmed end-group chemistry as a powerful tool for the design of efficient solid-state polymer electrolytes. This work should find applications in various emerging electrochemical technologies, namely those employed in energy storage and conversion.

Increasing the ionic conductivity has for decades been an overriding goal in the development of solid polymer electrolytes. According to fundamental theories on ion transport mechanisms in polymers, the ionic conductivity is strongly correlated to free volume and segmental mobility of the polymer for the conventional transport processes. Therefore, incorporating plasticizing side chains onto the main chain of the polymer host often appears as a clear-cut strategy to improve the ionic conductivity of the system through lowering of the glass transition temperature (T g ). This intended correlation between T g and ionic conductivity is, however, not consistently observed in practice. The aim of this study is therefore to elucidate this interplay between segmental mobility and polymer structure in polymer electrolyte systems comprising plasticizing side chains. To this end, we utilize the synthetic versatility of the ion-conductive poly(trimethylene carbonate) (PTMC) platform. Two types of host polymers with side chains added to a PTMC backbone are employed, and the resulting electrolytes are investigated together with the side chainfree analogue both by experiment and with molecular dynamics (MD) simulations. The results show that while added side chains do indeed lead to a lower T g , the total ionic conductivity is highest in the host matrix without side chains. It was seen in the MD simulations that while side chains promote ionic mobility associated with the polymer chain, the more efficient interchain hopping transport mechanism occurs with a higher probability in the system without side chains. This is connected to a significantly higher solvation site diversity for the Li + ions in the side-chain-free system, providing better conduction paths. These results strongly indicate that the side chains in fact restrict the mobility of the Li + ions in the polymer hosts.

Silicon is a highly promising electrode material for Li-ion batteries because of its high theoretical capacity, but severe volume changes during cycling leads to pulverization and rapid capacity fading. The use of alternative and water-soluble polymer binders such as poly­(vinyl alcohol) (PVA) or poly­(acrylic acid) (PAA) can improve the cycling performance of Si-based Li-ion batteries. Here, we investigate the effect of the substitution of the hydroxyl groups of PVA chains by carboxylic acid and acetate groups on the electrochemical performance of Si anodes in Li-ion batteries. Using modified PVAs, a model system is created spanning the chemical space between PVA and PAA, and the role of different Si-adhering functionalities is investigated. When comparing the electrochemical performance of Li-ion battery cells using Si anodes and the investigated binder systems, PVA with the highest degree of hydrolysis exhibits a superior performance (100 cycles with 1019 mAh g–1) compared to modified PVAs and PAA as a binder for Si anodes. An increased degree of hydrolysis of PVA is also seen to be beneficial for high capacity retention. These effects can be largely explained by the crystallinity of the binder system, which renders an improved electrode integrity during cycling and less swelling of the Si particles.

This investigation reports a facile synthetic route for the preparation of tailor-made polymers bearing reactive pendant bicyclo-alkenyl functionality via selective atom transfer radical polymerization at ambient temperature (AT-ATRP). In this case dicyclopentenyloxyethyl methacrylate (DCPMA) was polymerized at ambient temperature (30 C) using CuBr or CuCl as the catalyst in combination with different ligands, such as N,N,N 0 ,N 00 ,N 00 -pentamethyldiethylenetriamine (PMDETA) and 4,4 0 -di(5-nonyl)-2,2 0 -bipyridine (dNbpy). The polymerization was very fast and very high conversion ($90%) was achieved in 2 min. 1 H NMR and MALDI-TOF-MS analysis confirmed the presence of a bicyclic alkenyl pendant group in the polymer prepared by ATRP. This alkenyl functionality was successfully modified by the 'thiol-ene' reaction, as evidenced by 1 H NMR and FT-IR analysis.

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