Xiaochuan Duan

Polymer electrolytes are promising for all‐climate rechargeable batteries due to their safety and compatibility with high‐energy‐density battery systems. However, topological traps induced by chain entanglement become a major transport bottleneck limiting continuous ion motion and interfacial charge transfer as temperature and liquid‐phase content decrease. Here, we unveil that temperature‐dependent ion‐traps in the entangled gel polymer are a key factor for slow Na ⁺ transport at low temperatures. Specifically, we propose a low‐temperature‐tolerant gel polymer electrolyte, denoted as non‐entangled poly(1,3‐dioxolane) (NPDOL), which promotes sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) dissociation and provides homogeneous coordination sites for continuous Na ⁺ transport. Meanwhile, the non‐entangled, high‐entropy polymer framework decreases chain relaxation time and expands free volume, thereby reducing the density of ion‐traps and enhancing Na ⁺ diffusion kinetics. Furthermore, reduced ion‐trap density improves the Na ⁺ transference number ( t _Na+ = 0.85), resulting in a thin and uniform solid electrolyte interphase (SEI) with improved interfacial Na ⁺ charge‐transfer. The NPDOL electrolyte exhibits high ionic conductivity ( σ ) of 0.25 mS cm ⁻¹ at ‐50°C, enabling Na//NPDOL//Na ₃ V ₂ (PO ₄ ) ₃ full cells to deliver nearly 100% capacity retention at ‐40°C. This strategy of reducing chain entanglement to suppress Na ⁺ traps widens the low‐temperature operational window of batteries, paving the way for high‐performance energy storage systems.

Polymer electrolytes are promising for all‐climate rechargeable batteries due to their safety and compatibility with high‐energy‐density battery systems. However, topological traps induced by chain entanglement become a major transport bottleneck limiting continuous ion motion and interfacial charge transfer as temperature and liquid‐phase content decrease. Here, we unveil that temperature‐dependent ion‐traps in the entangled gel polymer are a key factor for slow Na ⁺ transport at low temperatures. Specifically, we propose a low‐temperature‐tolerant gel polymer electrolyte, denoted as non‐entangled poly(1,3‐dioxolane) (NPDOL), which promotes sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) dissociation and provides homogeneous coordination sites for continuous Na ⁺ transport. Meanwhile, the non‐entangled, high‐entropy polymer framework decreases chain relaxation time and expands free volume, thereby reducing the density of ion‐traps and enhancing Na ⁺ diffusion kinetics. Furthermore, reduced ion‐trap density improves the Na ⁺ transference number ( t _Na+ = 0.85), resulting in a thin and uniform solid electrolyte interphase (SEI) with improved interfacial Na ⁺ charge‐transfer. The NPDOL electrolyte exhibits high ionic conductivity ( σ ) of 0.25 mS cm ⁻¹ at ‐50°C, enabling Na//NPDOL//Na ₃ V ₂ (PO ₄ ) ₃ full cells to deliver nearly 100% capacity retention at ‐40°C. This strategy of reducing chain entanglement to suppress Na ⁺ traps widens the low‐temperature operational window of batteries, paving the way for high‐performance energy storage systems.

Compared with other metal anodes such as lithium, sodium and potassium, carbon materials exhibit low redox potential, enhanced safety, significant low‐cost advantages and decent electrochemical performance for large‐scale metal‐ion batteries and supercapacitors. Among the various carbon precursors, low‐cost coal and coal derivatives are preferred due to their unique carbon structure with high carbon content. A variety of coal‐derived carbon materials have been constructed using different strategies and have been investigated for diverse electrochemical energy storage due to their specific microstructures. In the short term, the electrochemical performance of coal‐derived carbon materials is normal. However, it is imperative to develop low‐cost and high‐performance coal‐derived carbon materials in order to reduce the cost of energy storage systems. Therefore, this review focuses on the microstructure modulation strategies for coal‐based derived carbon materials to further enhance their electrochemical performance through heteroatom doping, defect engineering, interlayer engineering, crystallinity regulation, pore regulation and multi‐strategy synergy. In addition, this review summarizes the enhancement mechanisms for modification strategies and analyses their limitations. Furthermore, current challenges and future research directions for the development of high‐performance coal‐based derived carbon materials are proposed in this review. It is anticipated that through novel modification strategies, coal‐derived carbon materials will exhibit electrochemical performance comparable to that of carbon materials prepared from other precursors.

Metal–organic framework (MOF)/polymer-based composites are frequently utilized in solid-state electrolytes because of because of the high interfacial compatibility of polymers and the ion-screening ability of MOFs. They are alse often combined with ionic liquids (ILs) to form composite solid-state electrolytes (CSEs). However, the conventional method of combining these components sacrifices some of their individual excellent properties. In this work, the HKUST-1 (Cu) and polyacrylonitrile (PAN) polymer were efficiently combined to create pore-exposed HKUST-1/PAN fibers. Subsequently, the Li-IL@HKUST-1/PAN CSE was obtained by introducing ILs containing lithium salt (Li-IL) into the pores of HKUST-1. At 25 °C, the synthesized CSE exhibited an ionic conductivity of 2.40 × 10⁻³ S cm⁻¹ and a lithium-ion mobility number of 0.698. Furthermore, this CSE enables the assembly of LiFePO₄/Li solid-state batteries with outstanding cycling performance and multiplicity ranging from 0.1C to 5C at room temperature, with a stable reversible capacity of 67.5 mA h g⁻¹ after 100 cycles at a high current density of 5C (25 °C) with a capacity retention of 94.1%. The electrochemical performance of Li-IL@HKUST-1/PAN is significantly superior to that of the conventional Li-IL/HKUST-1/PAN, which can be attributed to the effective combination of HKUST-1, PAN and Li-IL. This combination allows each component to fully exhibit its advantages and synergistically enhances the overall performance, facilitating the selective and rapid transport of lithium ions. This study presents new opportunities for multi-component composite solid-state electrolytes with high performance.

The effect of partial substitution of Mg for Ni on a high‐sodium and lithium‐free layered P2‐type Na _45/54 Mg _6/54 Ni _12/54 Mn _34/54 O ₂ cathode with high initial Coulombic efficiency and excellent cyclic stability has been investigated in this study. Based on the crystal structural analysis, the Mg doping can retain the P2 structure up to 4.3 V, thus restraining the detrimental phase transformation of P2–O2 during the Na‐ion intercalation/deintercalation process. Therefore, the obtained Mg‐doped P2‐type cathode exhibits a reversible specific capacity of 109 mAh·g ⁻¹ at 0.1C between 2.0 and 4.3 V and a retention rate of 81.5% after 200 cycles at 1C. In addition, the full cell consisting of Mg‐doped P2‐type cathode and hard carbon anode shows a capacity retention rate of 85.6% after 100 cycles. This study provides new insight into the development of durable cathode materials for sodium‐ion batteries.

High‐capacity O3‐type layered sodium oxides are considered one of the most promising cathode materials for the next generation of Na‐ion batteries (NIBs). However, these cathodes usually suffer from low high‐rate capacity and poor cycling stability due to structure deformation, native air sensitivity, and interfacial side reactions. Herein, a multi‐site substituted strategy is employed to enhance the stability of O3‐type NaNi_0.5Mn_0.5O₂. Simulations indicate that the Ti substitution decreases the charge density of Ni ions and improves the antioxidative capability of the material. In addition, the synergistic effect of K⁺ and Ti⁴⁺ significantly reduces the formation energy of Na⁺ vacancy and delivers an ultra‐low lattice strain during the repeated Na⁺ extraction/insertion. In situ characterizations verify that the complicated phase transformation is mitigated during the charge/discharge process, resulting in greatly improved structure stability. The co‐substituted cathode delivers a high‐rate capacity of 97 mAh g⁻¹ at 5 C and excellent capacity retention of 81% after 400 cycles at 0.5 C. The full cell paired with commercial hard carbon anode also exhibits high capacity and long cycling life. This dual‐ion substitution strategy will provide a universal approach for the new rational design of high‐capacity cathode materials for NIBs.

O3‐type Fe/Mn‐based layered oxide cathode materials with abundant reserves have a promising prospect in sodium‐ion batteries. However, the electrochemical reversibility of most O3‐type Fe/Mn‐based oxide cathode materials is still not high enough. Herein, the effect of different Cu contents on the electrochemical properties of O3‐NaFe_0.50Mn_0.50O₂ materials is systematically investigated. The as‐prepared NaFe_0.30Mn_0.50Cu_0.20O₂ cathode achieves the synergistic optimization of the interface and bulk phase. It shows superior electrochemical performance, with an initial discharge specific capacity of 114 mAh g⁻¹ at 0.1 C, a capacity retention rate of 94 % after 100 cycles at 0.5 C, and excellent chemical stability in air and water. In addition, the sodium ion full battery based on NaFe_0.30Mn_0.50Cu_0.20O₂ cathode and hard carbon anode has a capacity retention rate of 81 % after 100 cycles. This research provides a useful approach for the preparation of low‐cost and high‐performance O3‐type layered cathode materials.

Ammonium phosphate ((NH₄)₃PO₄) has been first used as a surface treatment reagent for Li-rich cathode materials. Compared to the conventional surface treatment, the samples treated with (NH₄)₃PO₄ exhibit an ultra-high initial Coulomb efficiency of 98.0% and excellent cycling stability. This is mainly attributed to the simultaneous construction of surface integrated structures, including oxygen vacancies, spinel phases, and Li₃PO₄ coating. This study demonstrates the effectiveness of ammonium phosphate surface treatment and provides a new idea for designing other cathode materials.