Cost-effective sodium-ion battery technologies require low-cost, high-performance hard carbon anode materials. Therefore, the employment of sustainable lignocellulose as a precursor offers economic benefits. Herein, an insitu sacrificing templating strategy is proposed, and hard carbon anode materials with high closed-pore volumes are successfully synthesized using lignin as the sustainable precursor. The closed-pore structure and microscopic crystalline structures of hard carbon are regulated through the adsorption of zinc ions by the abundant oxygen containing functional groups in pristine lignin molecules, followed by the in-situ generation of ZnO nanoparticles as sacrificial templates during carbonization. Results demonstrate that the ZnO templates significantly enhance the closed-pore volume (0.258 cm3 g-1) and expand the interlayer spacing (0.374 nm). The optimized hard carbon material (HC-Z-1600) exhibits a high reversible specific capacity of 358 mAh g-1 at 0.05 A g-1. Through combined in-situ Raman spectroscopy and electrode kinetic analyses, the progressive sodium-ion storage mechanism is demonstrated as a mechanism of "surface adsorption, interlayer intercalation, closed-pore filling". This study provides an innovative strategy for the controlled synthesis of sustainable biomass-derived hard carbon materials for high-performance sodium-ion batteries.

Understanding the structural formation mechanism of hard carbon and the relationship between its microstructure and sodium-ion storage performance is critical for the precise fabrication of hard carbon. Herein, lignin-derived hard carbons with tunable microstructures were prepared via one-step carbonization by tuning carbonization temperatures (600 degrees C-1600 degrees C) and time (0-6 h). The graphitic microcrystalline structures in hard carbons become more ordered with increasing carbonization temperature and time, which in turn leads to the reduced interlayer spacing of graphene layers, decreased defect concentration, and increased size and volume of the closed pores. The pseudo-graphitic structures with expanded interlayer spacing and abundant defect structures contribute to enhanced slope-potential capacity, whereas the sodium-ion accessible closed pores with large pore volume contribute to improved plateau-potential capacity. A small closed-pore size is beneficial for enhancing the rate performance. The hard carbons displayed an adsorption/intercalation-dominated to a pore-filling-dominated mechanism with increasing carbonization temperature and time. The optimized hard carbon exhibited a high reversible capacity (322 mAh g-1 at 0.05 A g-1) with a plateau-potential capacity of 246 mAh g-1, and good rate performance. These findings provide fundamental insights for the structural revolution and sodium-ion storage mechanism of hard carbon anodes, which could pave the way for understanding how the structure evolves and how we precisely design high-performance hard carbon anodes.

The design and exploitation of high-property cathode materials and the exploration of their energy storage mechanism have always been research hotspots in the area of zinc-ion hybrid capacitors (ZHCs). In this study, the new RuO2 nanodots/reduced graphene oxide (RuO2 NDs/rGO) composite is designed, and employed as a cathode for ZHC for the first time. Thanks to the synergism of nanoscale design and composite engineering, the RuO2 NDs/rGO//Zn ZHC delivers large specific capacitance (169.5 mAh/g at 0.1 A/g), splendid rate property (74.4 mAh/g at 20 A/g), eminent cyclic property (up to 10,0 0 0 cycles), and high energy and power densities (101.7 Wh/kg and 12 kW/kg). Furthermore, systematic kinetic analyses are used to confirm the rapid ion transport kinetics of the RuO2 NDs/rGO//Zn ZHC. More importantly, systematic ex-situ measurements are employed to illustrate its energy storage mechanism of the coexistence of electric double-layer capacitance (physical adsorption/desorption of SO4 2- ) and pseudocapacitance (insertion/extraction of Zn2 + and H+ and chemical adsorption/desorption between Zn2 + and oxygen-containing functional groups). This study not only offers a good strategy for the design and exploitation of high-performance pseudocapacitive cathode for ZHCs, but also proposes an insight into energy storage mechanism of RuO2 -based pseudocapacitive cathode. (c) 2026 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Particuology engineering could regulate the morphology and microstructure of hard carbon (HC), however, its effect on the microstructure and sodium-ion storage mechanism of HC is rarely explored. Herein, we used hand-grinding and ball-milling methods to pulverize HC particles, to explore the structure and performance of the HC with tuned particle size and morphologies. The microstructure of HC was characterized by a couple of physicochemical methods. These characterizations show that compared with hand-grinded HC, the particle size of ball-milled HC was largely reduced, the graphene interlayer spacing was expanded, and the volume of closed pores decreased. As a result, the enlarged graphene interlayer spacing of ball-milled HC provides more intercalation sites for sodium-ion storage, but the decreased closed-pore volume is not conducive to the sodium-ion filling process. In-situ Raman spectra demonstrate that HC anodes store sodium ions by "adsorption-intercalation" in the slope potential (>0.1 V) region, and sodium ions are stored by pore-filling in the plateau potential (<0.1 V) region. The microstructure of ball-milled HC is conducive to the rapid transport of sodium ions under high current density, which improves the slope-potential capacity and reduces the plateau-potential capacity. This work revealed the critical role of particuology engineering in regulating the structure and the sodium-ion storage behaviors of HC anode materials in the sodium-ion battery industry.

Hard carbon (HC) attracts significant attention as an auspicious anode material for commercial sodium-ion batteries. However, the relationship between the pore architecture and the kinetics and cycling stability of sodium-ion storage of HC remains poorly understood. Based on the construction of HC anodes with distinct pore architectures through multi-dimensional structure regulation of the lignin precursors, we systematically investigated the correlation between the pore architecture and the kinetics and cycling stability of sodium-ion storage. HCs with smaller pore sizes and abundant pores exhibit lower formation energy of sodium clusters, faster charge transfer rates, and more abundant diffusion networks for sodium ions. These properties enable HC to exhibit fast sodium-ion storage kinetics, thereby demonstrating superior rate capability and sodium-ion storage capacity at low operation temperatures. During high-current cycling, the graphene nanodomains of HC, rich in sp3-hybridized carbon content and large pore size, are prone to being destroyed. This leads to increased disorder in the graphene layer structure and decreased pore volume, accelerating the decay of the plateau potential capacity of HC. Moreover, the disordered graphene layer structure hinders sodium ion diffusion between interlayers, thus lowering the formation potential of sodium clusters and increasing the risk of sodium dendrite formation.

Lignocellulose biomass is an ideal precursor for the preparation of hard carbon (HC) due to its abundant resource and low-cost advantages. However, the structure of HC prepared by direct carbonization of lignocellulosic biomass has a small closed-pore volume and large pore size, resulting in low capacity and poor rate capability. Herein, we propose a low-corrosive aqueous maleic acid hydrothermal pretreatment strategy, which effectively and efficiently removes hemicellulose from coconut shell tissues, while also recovering the liquid products of xylose and furfural. After high-temperature carbonization of the obtained precursor rich in lignin and cellulose, the closed-pore size of the HC decreased from 2.297 to 1.640 nm, and the closed-pore volume increased from 0.202 to 0.236 cm3 g-1. A small closed-pore size and a large-pore volume are beneficial for the filling of sodium ions in the closed pores. The optimized HC provides a reversible specific capacity of 365 mAh g-1 and excellent rate performance (the capacity retention rate was 69% at a high current density of 5.0 A g-1). This study achieves the high-value utilization of all the components of lignocellulosic biomass, and provides a new path for the preparation of HC anode in high-performance sodium-ion batteries.

Hard carbon materials have emerged as a crucial anode choice for commercial sodium-ion batteries (SIBs), owing to their inherent abundance in porosity and the adaptability in adjusting interlayer spacing. However, the low capacity below 1 V and sluggish transportation kinetics respectively hinders the output voltage and rate performance. In this work, a one-step polymerization technique has been proposed to synthesize interconnected three-dimensional N/S-rich molecules via a methylene (-CH2-) bridge. During the subsequent carbonization process, the in-situ elimination of-CH2- bridge and partial heteroatoms facilitated the formation of intrinsic defects within the carbon layers, yielding an N/S co-doping hard carbon with intrinsic defect structures. This innovative approach provides a remarkable reversible capacity of 238mAh g- 1 at voltages below 1 V, a high-rate capability of 150mAh g- 1 at 5 A/g, along with exceptional cyclic stability of nearly 100 % capacity extension after 2000 cycles. This obviously enhancement in low-voltage sodium storage capacity and rate performance is attributed to the enhanced effect through N/S co-doping with intrinsic defect structures. This work highlights the critical role of defect engineering in carbon materials for efficient low-voltage sodium ions storage, offering a promising anode material with superior rate and cyclic stability.

Lignocellulosic biomass-derived hard carbon has gained prominence as a promising anode material for commercial sodium-ion batteries owing to its tunable microstructure, cost-effectiveness, and sustainability. However, the intrinsic heterogeneity and structural complexity of lignocellulosic biomass pose significant challenges to the large-scale deployment of its derived hard carbons. This perspective summarizes recent advances in laboratory-scale research, highlights the key obstacles hindering commercial application, and outlines guiding principles for structural design. Finally, we discuss future development pathways to enable the production of low-cost, high-performance hard carbon anodes, thereby accelerating the commercialization of sodium-ion batteries

Dual-carbon sodium-ion capacitors (SICs) represent cost-effective, high-energy-density alternatives to traditional electrochemical double-layer capacitors (EDLCs). Previous studies have been limited by the inability to tailor anode and cathode properties from a single precursor. In this work, a straightforward precursor regulation strategy is developed, synthesizing phenol-furfural resins with tunable crosslinking degrees to simultaneously fabricate optimized hard carbon anodes and porous carbon cathodes for SICs. For the anode, highly crosslinked precursors demonstrate inherent advantages: the larger interlayer spacing in graphitic microdomains and greater volume of closed micropores, which enable the derived hard carbon 24H1400 to achieve a specific capacity of 337.8 mAh g(-1) at 0.05 A g(-1), along with superior rate capability compared to low-crosslinking-derived anodes. As for the cathode, although low-crosslinking-derived porous carbons exhibit a higher specific surface area, this parameter proves irrelevant to electrochemical performance. Instead, the cathode A15H750 derived from moderately crosslinked precursors achieves optimal properties: a high microporosity ratio and abundant surface oxygen functional groups. This design delivers an exceptional specific capacity of 206.5 mAh g(-1) at 0.1 A g(-1), coupled with satisfactory cycle and rate performance. Benefiting from optimal precursors regulation, the assembled SIC full cell 24H1400//A15H750 demonstrates exceptional performance, including reliable operational capability across an extended temperature range from -10 to 50 degrees C.

Soft carbon has been recognized as a promising anode material for potassium-ion batteries (PIBs), due to low cost, high conductivity and low voltage platform. However, their practical application is hampered by slow storage kinetics and unsatisfactory cycle life. In this work, pitch-derived needle coke, a typical soft carbon, was incorporated with oxygenated functional groups through liquid phase oxidation by using H 2 O 2 oxidant. When used as anode materials for PIBs, the oxidized needle coke delivers a high reversible capacity of 322.7 mAh g −1 , significantly superior to that of the needle coke (237.9 mAh g −1 ). The enhanced electrochemical performance can be attributed to the abundant oxygenated functional groups and resultant defects on the surface of oxidized needle coke, which not only serve as extra active sites for potassium storage, but also provide sufficient pathways for K + migration across the adjacent carbon layers. Moreover, the expanded interlayer spacing derived from H 2 O 2 oxidation facilitates rapid K + intercalation and deintercalation. This work offers an effective modification strategy for the fabrication of high-performance pitch-based soft carbon anodes for PIBs. Graphical Abstract

The design and development of energy storage device with high energy/power density has become a research hotspot. Zinc-ion hybrid capacitors (ZHCs) are considered as one of the most promising candidates. However, the application of ZHCs is hindered by their low energy density at high power density due to the unsatisfactory cathode material. In this study, a novel 3D phosphorus-doped carbon nanotube/reduced graphene oxide (P-CNT/rGO) aerogel cathode is synthesized through a synergistic modification strategy of CNT insertion and P doping modification combined with 3D porous design. The as-obtained P-CNT/rGO aerogel cathode manifests significantly increased surface aera, expanded interlayer spacing, and enhanced pseudocapacitance behavior, thus leading to significantly enhanced specific capacitance and superb ions transport performance. The as-assembled ZHC based on P-CNT/rGO cathode delivers a superior energy density of 42.2 Wh/kg at an extreme-high power density of 80 kW/kg and excellent cycle life. In-depth kinetic analyses are undertaken to prove the enhanced pseudocapacitance behavior and exceptional power output capability of ZHCs. Furthermore, the reaction mechanism of physical and chemical adsorption/desorption of electrolyte ions on the P-CNT/rGO cathode is revealed by systematic ex-situ characterizations. This work can provide a valuable reference for developing advanced graphene-based cathode for high energy/power density ZHCs.

Needle coke has attracted much attention as soft carbon anode material for potassium-ion batteries (PIBs) owing to its high crystallinity and conductivity. However, limited research has been conducted on the storage mechanism and the functional and structural evolution of the solid electrolyte interphase (SEI) in ester and ether based electrolytes. This work investigates the potassium ion storage mechanisms of soft carbon anodes in three electrolytes: KPF6 EC/DEC, KPF6 DME, and KFSI DME, and reveals that K+ stored in the KPF6 EC/DEC electrolyte could be through an “adsorption-intercalation” mechanism. Whereas K+ stored in the DME-based electrolytes is believed to undergo a “co-intercalation/adsorption-intercalation” process. Interfacial analyses indicate that the SEI formed in the EC/DEC electrolyte inhibits co-intercalation of potassium ion and solvent, which preserves sufficient space to accommodate potassium ion. Conversely, the [K-DME]+ solvation co-intercalation in DME-based electrolytes compromises the structural integrity, and results in a persistent capacity decline. This work offers novel insights into potassium ion storage in ester and ether-based electrolytes, and provides theoretical support for the fabrication of high-performance soft carbon anodes.

Red phosphorus has been well-recognized as promising anode materials for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs) due to its extremely high theoretical capacity and low cost. However, the huge volume change and poor electric conductivity severely limit its further practical application. Herein, the nanoscale ultrafine red phosphorus has been successfully confined in a three-dimensional pitch-based porous carbon skeleton composed of well-interconnected carbon nanosheets through the vaporization-condensation method. Except for the traditional requirement of high electric conductivity and stable mechanical stability, the micropores and small mesopores in the porous carbon matrix centered at 1 to 3 nm and the abundant amount of oxygen-containing functional groups are also beneficial for the high loading and dispersion of red phosphorus. As anode for LIBs, the composite exhibits high reversible discharge capacities of 968 mAh g−1, excellent rate capabilities of 593 mAh g−1 at 2 A g−1, and long cycle performance of 557 mAh g−1 at 2 A g−1. More impressively, as the anode for PIBs, the composite presents a high reversible capacity of 661 mAh g−1 and a stable capacity of 312 mAh g−1 at 0.5 A g−1 for 500 cycles with a capacity retention up to 84.3%. This work not only sheds light on the structure design of carbon hosts with specific pore structure but also open an avenue for high value-added utilization of coal tar pitch.

在不借助模板的情况下,以中温煤沥青为原料,在表面活性剂和分散介质辅助下,结合预氧化和乳化法成功制备了氧化沥青微球.探究了乳化温度对微球形貌的影响规律,并确定了280℃为最佳的乳化温度.制备的氧化沥青碳微球负极展现出良好的电化学性能.在0.05A/g下的初始放电比容量为310mAh/g,2A/g时的容量为102mAh/g,在1 A/g下经过1000次长循环,容量仍剩余108 mAh/g.其优异的储钾性能得益于低温预氧化形成的交联结构可以实现有序到无序的结构演变.此外,引入的含氧基团不仅使前驱体实现空间层面的交联,确保了材料在电化学脱嵌时的结构稳定性,而且还产生了丰富的空位和缺陷,从而增加储钾位点.

As prospective energy storage devices,zinc-ion hybrid capacitors(ZHCs)still suffer from unsatisfactory cathode materials.Herein,the three dimensional(3D)N,B dual-doped carbon quantum dots/reduced graphene oxide(N,B-CQDs/rGO)composite aerogel is prepared via a one-pot hydrothermal method.Thanks to the synergism of CQDs modification and N,B dual-doping,the resultant N,B-CQDs/rGO composite aerogel delivers superior electro-chemical properties.Furthermore,the as-obtained N,B-CQDs/rGO composite aerogel is served as a cathode for aqueous and flexible quasi-solid-state ZHCs for the first time.Impressively,the aqueous N,B-CQDs/rGO//Zn ZHC manifests a large energy density of 96.2 Wh·kg-1 at 80 W·kg-1 and still remains a high energy density of 54.7 Wh·kg-1 at a superb power density of 80 kW·kg-1.Meanwhile,kinetic analyses are employed to elucidate the prominent power performance,and various ex situ tests are undertaken to explore the energy storage mechanism of aqueous ZHC.More notably,the flexible quasi-solid-state N,B-CQDs/rGO//Zn ZHC displays a desirable energy density(89.1 μWh·cm-2),a superior power density(96,000 μW·cm-2)and exceptional flexible performance.The present study offers a valuable reference for designing and developing advanced cathode materials for aqueous and flexible quasi-solid-state ZHCs.

Pitch-based soft carbons, with tunable microstructure and low cost, hold great potential as anodes for potassium-ion batteries (PIBs). However, the sluggish storage kinetics and unsatisfying cycle life hinder their practical applications. In addition, low softening point pitch has been seldom used to fabricate carbon microspheres due to its thermoplasticity. Herein, P and O enriched pitch-based carbon micro spheres were directly synthesized via coordinated emulsification and pre-oxidation, and followed carbonized with NaH2PO2. This template-free method can avoid the coalescence of the coal tar pitch without extra post-stabilization. And NaH2PO2 acts as a P doping source and generates modest mesopores. The prepared P and O enriched carbon microspheres manifest a high P content of 4.0 at%, expanded interlayer distance of 0.401 nm, and abundant reversible K+ storage sites. As a result, it delivers considerable discharge capacity of 352 mAh g(-1), impressive rate capacity of 114 mAh g(-1) at 5 A g(-1), and long lifespan of 181 mAh g(-1) at 1 A g(-1) after 1000 cycles. The present work develops a new avenue for heteroatoms doped carbon microspheres to innovative potassium storage and beyond. (c) 2022 Elsevier Ltd. All rights reserved.

Transition metal selenides (TMSs), as a novel type of battery-type electrode material for high-performance supercapacitors, have gradually attracted growing attention in recent years. Herein, the new three-dimensional interconnected ultrathin CoSe nanosheets decorated ZnSe nanoparticles-assembled microspheres hybrid was prepared through a simple one-pot hydrothermal method and employed as battery-type supercapacitor cathode materials for the first time. Benefiting from the unique intertwined structure with a high surface area, mesopore/macropore-rich hierarchical structure as well as superior electrical conductivity, compared with the pure monometallic ZnSe electrode, the as-prepared CoSe/ZnSe hybrid electrode presents significantly boosted electrochemical performances with a high specific capacity of 92.0 mAh g− 1 at 1 A g− 1, admirable rate property with 46.5% of capacity retention at 50 A g− 1 and superior cycle performance with 88.2% of capacity retention after 5000 cycles at 10 A g− 1. These intriguing data imply that the resultant CoSe/ZnSe hybrid can be seen as a promising cathode material for battery-type supercapacitors.

A graphene aerogel-based composite has recently been deemed as a prospective electrode material for advanced energy storage devices. Here, carbon quantum dots (CQDs) are simultaneously utilized as the conductive agents, intercalators, and stable links to boost the electrochemical property of graphene composite aerogels due to their many natural advantages. The threedimensional (3D) N, S dual-doped CQDs/reduced graphene oxide (rGO)/NiCo2S4 composite aerogel (N,S-CQDs/rGO/NiCo2S4) is first fabricated through a one-pot hydrothermal way and utilized as a supercapacitor cathode, exhibiting a large specific capacity of 162.6 mA h g(-1) at 1 A splendid rate property with 77.3% capacity retention at 50 A g(-1), and good cyclic stability with 87.5% capacity retention after 5000 cycles, which originates from the synergistic interaction of the 3D reticulation N,S-CQDs/rGO aerogel framework with excellent conductivity and structural stability and NiCo2S4 nanoparticles with abundant Faradaic redox reactions. Further, the resulting N,S-CQDs/rGO/NiCo2S4 cathode is coupled with the prepared N,S-CQDs/rGO anode to assemble a hybrid supercapacitor (HSC) device, manifesting a superior energy density (51.0 W h kg(-1)), an ultrahigh power density (14.4 kW kg(-1)), and good cyclic stability with 82.9% capacitance retention after 10,000 cycles. The present study offers a good strategy for designing and exploiting superior energy storage systems by utilizing the CQDs/rGO composite aerogel simultaneously as both the cathode and anode.