Despite their promised safety and mechanical flexibility, solvent‐free polymer electrolytes suffer from low Li‐ion conductivities due to poor dissociation of conducting salts and low Li+‐transference numbers due to Li+‐trapping by ether‐linkages. In this work, the authors found that oxygen vacancies carried by nanosized Al2O3 fillers preferentially promotes Li+‐conduction in poly(ethylene oxide) (PEO). These vacancies and free electrons therein, whose concentration can be tuned, effectively break up the ion pairs by weakening the Coulombic attraction within them, while simultaneously interacting with the anions, thus preferentially constraining the movement of anions. This synergistic dissociation‐and‐trapping effect leads to the significant and selective improvement in Li‐ion conductivity. Solid state batteries built on such PEO‐based electrolytes exhibits superior performance at high current density. This discovery reveals a molecular‐level rationale for the long‐observed phenomenon that certain inorganic nano‐fillers improve ion conduction in PEO, and provides a universal approach to tailor superior polymer‐based electrolytes for the next generation solid‐state batteries.

Despite exhibiting high specific capacities, Si‐based anode materials suffer from poor cycle life as their volume change leads to the collapse of conductive network within the electrode. For this reason, the challenge lies in retaining the conductive network during electrochemical processes. Herein, to address this prominent issue, a cross‐linked conductive binder (CCB) is designed for commercially available silicon oxides (SiOx) anode to construct a resilient hierarchical conductive network from two aspects: on the one hand, exhibiting high electronic conductivity, CCB serves as an adaptive secondary conductive network in addition to the stiff primary conductive network (e.g., conductive carbon), facilitating faster interfacial charge transfer processes for SiOx in molecular level; on the other hand, the cross‐linked structure of CCB shows resilient mechanical properties, which maintains the integrity of the primary conductive network by preventing electrode deformation during prolonged cycling. With the aid of CCB, untreated micro‐sized SiOx anode material delivers an areal capacity of 2.1 mAh cm−2 after 250 cycles at 0.8 A g−1. The binder design strategy, as well as, the relevant concepts proposed herein, provide a new perspective toward promoting the cycling stability of high‐capacity Si‐based anodes.

High-surface-area carbon (HSAC) has been regarded as one of the most promising anode materials for sodium-ion batteries. However, it generally suffers from low initial Coulombic efficiency (ICE), which is closely related to the formation process of a solid electrolyte interface (SEI). Herein, the impact of different electrolyte salts on the electrochemical performance and SEI formation of a commercial HSAC anode is studied. It is found that the use of NaCF3SO3 enables much higher ICE (69.28%) and reversible capacity (283 mA h g–1) of the HSAC anode compared with the NaPF6 electrolyte (59.65%, 243 mA h g–1). Through comprehensive characterizations, the improvement in electrochemical performance facilitated by NaCF3SO3 could be attributed to the reduced amount of Na x C and the thinner SEI formed on the surface of HSAC during the initial cycle, which not only provides extra active sites for Na+ storage but also contributes to the promoted ICE. This work not only provides a deeper understanding of the role of electrolyte salt in SEI formation in the HSAC anode but also proposes a new method to further promote the ICE of the HSAC anode in sodium-ion batteries.