The low ion transport is a major obstacle for low‐temperature (LT) sodium‐ion batteries (SIBs). Herein, a core‐shell structure of bismuth (Bi) nanospheres coated with carbon (Bi@C) is constructed by utilizing a novel Bi‐based complex (1,4,5,8‐naphthalenetetracarboxylic dianhydride as the ligand) as the precursor, which provides an effective template to fabricate Bi‐based anodes. At −40°C, the Bi@C anode achieves a high capacity, which is equivalent to 96% of that at 25°C, benefitting from the core‐shell nanostructured engineering and Na⁺‐ether‐solvent cointercalation process. The special Na⁺‐diglyme cointercalation behavior may effectively reduce the activation energy and accelerate the Na⁺ diffusion kinetics, enabling the excellent low‐temperature performance of the Bi@C electrode. As expected, the fabricated Na₃V₂(PO₄)₃//Bi@C full‐cell delivers impressive rechargeability in the ether‐based electrolyte at −40°C. Density functional theory calculations and electrochemical tests also reveal the fast reaction kinetic mechanism at LT, thanks to a much lower diffusion energy barrier (167 meV) and a lower reaction activation energy (32.2 kJ mol⁻¹) of Bi@C anode in comparison with that of bulk Bi. This work provides a rational design of Bi‐based electrodes for rechargeable SIBs under extreme conditions.

Heteroatom doping is considered to be an efficient strategy to improve the electrochemical performance of carbon-based anode materials for Na-ion batteries (SIBs), due to the introduction of an unbalanced electron atmosphere and increased electrochemical reactive sites of carbon. However, developing green and low-cost approaches to synthesize heteroatom dual-doped carbon with an appropriate porous structure, is still challenging. Here, N/S-co-doped porous carbon sheets, with a main pore size, in the range 1.8–10 nm, has been fabricated through a simple thermal treatment method, using KOH-treated waste bagasse, as a carbon source, and thiourea, as the N and S precursor. The N/S-co-doped carbon sheet electrodes possess significant defects, high specific surface area, enhanced electronic conductivity, improved sodium storage capacity, and long-term cyclability, thereby delivering a high capacity of 223 mA h g⁻¹ at 0.2 A g⁻¹ after 500 cycles and retaining 155 mA h g⁻¹ at 1 A g⁻¹ for 2000 cycles. This work provides a low-cost route to fabricate high-performance dual-doped porous carbonaceous anode materials for SIBs.

Inferior electrical conductivity and large volume variation are two disadvantages of metal selenides. In this work, we have designed a core–shell structure of FeSe ₂ @C composite with low cost using facile hydrothermal method. The FeSe ₂ particles as the ‘core’ and the carbon layer as the ‘shell’ displayed good synergistic effect that attributed to alleviate volume expansion of electrode and improving the electrical conductivity, which achieved the fast potassium storage. The core–shell structural FeSe ₂ @C electrode achieved 286 mA h g ⁻¹ at 1 A g ⁻¹ over 1000 cycles with 99.8% coulombic efficiency and delivered excellent rate capacity with 273 mA h g ⁻¹ at 2 A g ⁻¹ , which was ascribed to dispersed FeSe ₂ particles and the strong carbon shell coating. This work will provide the basis for the further development of the application of metal selenides in the field of flexible electrodes.