Silicon (Si) anodes are advantageous for application in lithium‐ion batteries in terms of their high theoretical capacity (4200 mAh g−1), appropriate operating voltage (<0.4 V vs Li/Li+), and earth‐abundancy. Nevertheless, a large volume change of Si particles emerges with cycling, triggering unceasing breakage/re‐formation of the solid‐electrolyte interphase (SEI) and thereby the fast capacity degradation in traditional carbonate‐based electrolytes. Herein, it is demonstrated that superior cyclability of Si anode is achievable using a nonflammable ether‐based electrolyte with fluoroethylene carbonate and lithium oxalyldifluoroborate dual additives. By forming a high‐modulus SEI rich in fluoride (F) and boron (B) species, a high initial Coulombic efficiency of 90.2% is attained in Si/Li cells, accompanied with a low capacity‐fading rate of only 0.0615% per cycle (discharge capacity of 2041.9 mAh g−1 after 200 cycles). Full cells pairing the unmodified Si anode with commercial LiFePO4 (≈13.92 mg cm−2) and LiNi0.5Mn0.3Co0.2O2 (≈17.9 mg cm−2) cathodes further show extended service life to 150 and 60 cycles, respectively, demonstrating the superior cathode‐compatibility realized with a thin and F, B‐rich cathode electrolyte interface. This work offers an easily scalable approach in developing high‐performance Si‐based batteries through Si/electrolyte interphase regulation.

Sodium (Na) metal anodes stand out with their remarkable capacity and natural abundance. However, the dendritic Na growth, infinite dimensional changes, and low Coulombic efficiency (CE) present key bottlenecks plaguing practical applications. Here, heteroatom‐doped (nitrogen, sulfur) hollow carbon fibers (D‐HCF) are rationally synthesized as a nucleation‐assisting host to enable a highly reversible Na metal. The “sodiophilic” functional groups introduced by the heteroatom‐doping and large surface area (≈1052 m2 g−1) synchronously contribute to a homogenous plating morphology with dissipated local current density. High “sodiophilicity” of the D‐HCF is confirmed by first‐principle calculations and experimental results, where strong adsorption energy of −3.52 eV with low Na+ nucleation overpotential of 3.2 mV at 0.2 mA cm−2 is realized. As such, highly reversible plating/stripping is achieved at 1.0 mA cm−2 with average CE approximating 99.52% over 600 cycles. The as‐assembled Na@D‐HCF symmetric cells exhibit a prolonged lifetime for 1000 h. A full‐cell paired with Na3V2(PO4)3 cathode further demonstrates stable electrochemical behavior for 200 cycles at 1 C along with excellent rate performance (102 mAh g−1 at 5 C). The results clearly show the effectiveness of the D‐HCF in manipulating Na+ deposition and thus the significance of nucleation control in realizing dendrite‐free metal anodes.

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Rechargeable batteries based on sodium metal anodes (SMAs) are endowed with much higher energy density than traditional sodium-ion batteries. However, the use of SMAs brings intrinsic challenges of dendrite growth and unstable solid/electrolyte interphase (SEI) formation. This situation can be further exacerbated at high temperature (>55 °C, HT). Here, we resolve such "HT-challenge" by formulating a thermally stable sulfolane (SL)-based electrolyte that regulates the electrode/electrolyte interfacial chemistries. Besides rapid Na anode passivation enabled by fluoroethylene carbonate (FEC) molecules, a nitrile-based 1,3,6-hexanetricarbonitrile (HTCN) cosolvent is simultaneously introduced, whose three electron-rich -C≡ N groups interact with the electropositive metal ions of Na 3 V 2 (PO 4 ) 2 O 2 F, shielding away solvent attacks occurring at the cathode interface. As a result, we realize a high capacity retention (91.7% after 500 cycles at 1 C) for the Na/Na 3 V 2 (PO 4 ) 2 O 2 F cell at 60 °C, with a high average carbon equivalent (CE) of ∼99.6%. Even at 80 °C, the cell still delivers ∼89.1% of its initial capacity after 100 cycles, whereas the control sample fails rapidly within 30 cycles.

Supramolecular precursors exhibit unique superiority in preparing functional nanocomposites comprised of ultrasmall active nanoparticles uniformly embedded in carbon. By virtue of the self-assembly of supramolecule MoO4 2––polydopamine (Mo-PDA) on the surface of sulfonated polystyrene microspheres, hierarchical hollow MoO2/nitrogen-doped carbon (H-MoO2/NC) microspheres, which are assembled from ultrathin nanosheets comprising of ultrasmall nanoisland-like MoO2 embedded in nitrogen-doped carbon, are obtained. During the preparation of H-MoO2/NC, the confining effect of the surrounding carbon effectively inhibits the growth of MoO2 nanoparticles and results in the formation of ultrasmall nanoisland-like MoO2. In addition, the nanoisland-like MoO2 is strongly embedded into nitrogen-doped carbon as indicated by the presence of strong Mo–N bond. The strong coupling between MoO2 nanocrystallites and nitrogen-doped carbon results in an enhanced synergistic effect for the electrochemical Li-ion storage. As a result, H-MoO2/NC manifests a high capacity and good long-term stability (1191 mAh g–1 in the 100th cycle at 0.2 C) as well as excellent rate behavior (a capacity of 697 mAh g–1 at 20 C).