With the ever‐increasing adaption of large‐scale energy storage systems and electric devices, the energy storage capability of batteries and supercapacitors has faced increased demand and challenges. ...The electrodes of these devices have experienced radical change with the introduction of nano‐scale materials. As new generation materials, heterostructure materials have attracted increasing attention due to their unique interfaces, robust architectures, and synergistic effects, and thus, the ability to enhance the energy/power outputs as well as the lifespan of batteries. In this review, the recent progress in heterostructure from energy storage fields is summarized. Specifically, the fundamental natures of heterostructures, including charge redistribution, built‐in electric field, and associated energy storage mechanisms, are summarized and discussed in detail. Furthermore, various synthesis routes for heterostructures in energy storage fields are roundly reviewed, and their advantages and drawbacks are analyzed. The superiorities and current achievements of heterostructure materials in lithium‐ion batteries (LIBs), sodium‐ion batteries (SIBs), lithium‐sulfur batteries (Li‐S batteries), supercapacitors, and other energy storage devices are discussed. Finally, the authors conclude with the current challenges and perspectives of the heterostructure materials for the fields of energy storage.
Constructing heterostructures is an effective way to enhance the electrochemical performance of active materials due to the unique heterointerface structure and some unrevealed synergistic effects. An overview of the recent advancements in heterostructured materials in terms of enhanced mechanism, synthesis techniques, and electrochemical performance is provided. Future development trends for design of heterostructured electrodes are analyzed.
In response to the change of energy landscape, sodium‐ion batteries (SIBs) are becoming one of the most promising power sources for the post‐lithium‐ion battery (LIB) era due to the cheap and ...abundant nature of sodium, and similar electrochemical properties to LIBs. The electrochemical performance of electrode materials for SIBs is closely bound up with their crystal structures and intrinsic electronic/ionic states. Apart from nanoscale design and conductive composite strategies, heteroatom doping is another effective way to enhance the intrinsic transfer characteristics of sodium ions and electrons in crystal structures to accelerate reaction kinetics and thereby achieve high performance. In this review, the recent advancements in heteroatom doping for sodium ion storage of electrode materials are reviewed. Specifically, different doping strategies including nonmetal element doping (e.g., nitrogen, sulfur, phosphorous, boron, fluorine), metal element doping (magnesium, titanium, iron, aluminum, nickel, copper, etc.), and dual/triple doping (such as N–S, N–P, N–S–P) are reviewed and summarized in detail. Furthermore, various doping methods are introduced and their advantages and disadvantages are discussed. The doping effect on crystal structure and intrinsic electronic/ionic state are illustrated and the relationship with capacity and energy/power density is interrogated. Finally, future development trends in doping strategies for advanced SIBs electrodes are analyzed.
Heteroatom doping is an effective way to enhance the intrinsic transfer characteristics of sodium ions and electrons in crystal structures to accelerate reaction kinetics. Herein, an overview of recent advancements in understanding the heteroatom doping effect on sodium ion storage is presented. Different doping strategies are reviewed and summarized in detail. Future development trends in doping strategies are analyzed.
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•Sludge production in China in 2019 was 39.0 million tons, average 28.1 kg/y per capita.•Higher reginal urbanization rate and GDP led to a higher per capita sludge ...production.•Spatial/temporal trends of sludge treatment/disposal techniques were investigated.•Incineration in East China accounted 31.3% of GHG emission of sludge disposal in 2019.•Discrepancy, challenges and future perspectives of sludge disposal in China was analyzed.
This study statistically reported the current state of sludge treatment/disposal in China from the aspects of sources, technical routes, geographical distribution, and development by using observational data after 1978. By the end of 2019, 5476 municipal wastewater treatment plants were operating in China, leading to an annual sludge productivity of 39.04 million tons (80% water content). Overall, 29.3% of the sludge in China was disposed via land application, followed by incineration (26.7%) and sanitary landfills (20.1%). Incineration, compost, thermal hydrolysis and anerobic digestion were the mainstream technologies for sludge treatment in China, with capacities of 27,122, 11,250, 8342 and 6944 t/d in 2019, respectively. Incineration and drying were preferentially constructed in East China. In contrast, sludge compost was most frequently used in Northeast China (46.5%), East China (22.4%) and Central China (12.8%), while anaerobic digestion in East China, North China and Central China. The capacities of sludge facilities exhibited a sharp increase in 2009–2019, with an overall greenhouse gas emissions in China in 2019 reached 108.18 × 108 kg CO2-equivaient emissions, and the four main technical routes contributed as: incineration (45.11%) > sanitary landfills (23.04%) > land utilization (17.64%) > building materials (14.21%). Challenges and existing problems of sludge disposal in China, including high CO2 emissions, unbalanced regional development, low stabilization and land utilization levels, were discussed. Finally, suggestions regarding potential technical and administrative measures in China, and sustainable sludge management for developing countries, were also given.
Scrupulous design and smart hybridization of bespoke electrode materials are of great importance for the advancement of sodium ion batteries (SIBs). Graphene‐based nanocomposites are regarded as one ...of the most promising electrode materials for SIBs due to the outstanding physicochemical properties of graphene and positive synergetic effects between graphene and the introduced active phase. In this review, the recent progress in graphene‐based electrode materials for SIBs with an emphasis on the electrode design principle, different preparation methods, and mechanism, characterization, synergistic effects, and their detailed electrochemical performance is summarized. General design rules for fabrication of advanced SIB materials are also proposed. Additionally, the merits and drawbacks of different fabrication methods for graphene‐based materials are briefly discussed and summarized. Furthermore, multiscale forms of graphene are evaluated to optimize electrochemical performance of SIBs, ranging from 0D graphene quantum dots, 2D vertical graphene and reduced graphene oxide sheets, to 3D graphene aerogel and graphene foam networks. To conclude, the challenges and future perspectives on the development of graphene‐based materials for SIBs are also presented.
The recent progress of multiscale graphene‐based electrode materials for application in sodium ion batteries in respect of electrode design principle, preparation methods, characterization, synergistic effects, and electrochemical performance is reviewed, and future challenges and prospects of the field are presented.
Tailored construction of advanced flexible supercapacitors (SCs) is of great importance to the development of high‐performance wearable modern electronics. Herein, a facile combined wet chemical ...method to fabricate novel mesoporous vanadium nitride (VN) composite arrays coupled with poly(3,4‐ethylenedioxythiophene) (PEDOT) as flexible electrodes for all‐solid‐state SCs is reported. The mesoporous VN nanosheets arrays prepared by the hydrothermal–nitridation method are composed of cross‐linked nanoparticles of 10–50 nm. To enhance electrochemical stability, the VN is further coupled with electrodeposited PEDOT shell to form high‐quality VN/PEDOT flexible arrays. Benefiting from high intrinsic reactivity and enhanced structural stability, the designed VN/PEDOT flexible arrays exhibit a high specific capacitance of 226.2 F g−1 at 1 A g−1 and an excellent cycle stability with 91.5% capacity retention after 5000 cycles at 10 A g−1. In addition, high energy/power density (48.36 Wh kg−1 at 2 A g−1 and 4 kW kg−1 at 5 A g−1) and notable cycling life (91.6% retention over 10 000 cycles) are also achieved in the assembled asymmetric flexible supercapacitor cell with commercial nickel–cobalt–aluminum ternary oxides cathode and VN/PEDOT anode. This research opens up a way for construction of advanced hybrid organic–inorganic electrodes for flexible energy storage.
Mesoporous vanadium nitride arrays coupled with poly(3,4‐ethylenedioxythiophene) (PEDOT) as an integrated electrode for all‐solid‐state flexible supercapacitors show excellent cycling stability and high energy densities. High‐performance capacitive behavior is contributed by the effect of surface‐controlled process and PEDOT coating protection.
Sodium-ion batteries are a potentially low-cost and safe alternative to the prevailing lithium-ion battery technology. However, it is a great challenge to achieve fast charging and high power density ...for most sodium-ion electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate sodium-ion anode based on ultrathin layered tin(II) sulfide nanostructures, in which a maximized extrinsic pseudocapacitance contribution is identified and verified by kinetics analysis. The graphene foam supported tin(II) sulfide nanoarray anode delivers a high reversible capacity of ∼1,100 mAh g(-1) at 30 mA g(-1) and ∼420 mAh g(-1) at 30 A g(-1), which even outperforms its lithium-ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin tin(II) sulfide nanostructures may also work in other layered materials for high-performance sodium-ion storage.
Exploring advanced battery materials with fast charging/discharging capability is of great significance to the development of modern electric transportation. Herein we report a powerful synergistic ...engineering of carbon and deficiency to construct high-quality three/two-dimensional cross-linked Ti
Nb
O
@C composites at primary grain level with conformal and thickness-adjustable boundary carbon. Such exquisite boundary architecture is demonstrated to be capable of regulating the mechanical stress and concentration of oxygen deficiency for desired performance. Consequently, significantly improved electronic conductivity and enlarged lithium ion diffusion path, shortened activation process and better structural stability are realized in the designed Ti
Nb
O
@C composites. The optimized Ti
Nb
O
@C composite electrode shows fast charging/discharging capability with a high capacity of 197 mA h g
at 20 C (∼3 min) and excellent long-term durability with 98.7% electron and Li capacity retention over 500 cycles. Most importantly, the greatest applicability of our approach has been demonstrated by various other metal oxides, with tunable morphology, structure and composition.
The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step ...solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co(3)O(4) or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The "oriented attachment" and "self-assembly" crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co(3)O(4)/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.
Defect engineering (doping and vacancy) has emerged as a positive strategy to boost the intrinsic electrochemical reactivity and structural stability of MnO2‐based cathodes of rechargeable aqueous ...zinc ion batteries (RAZIBs). Currently, there is no report on the nonmetal element doped MnO2 cathode with concomitant oxygen vacancies, because of its low thermal stability with easy phase transformation from MnO2 to Mn3O4 (≥300 °C). Herein, for the first time, novel N‐doped MnO2–x (N‐MnO2–x) branch arrays with abundant oxygen vacancies fabricated by a facile low‐temperature (200 °C) NH3 treatment technology are reported. Meanwhile, to further enhance the high‐rate capability, highly conductive TiC/C nanorods are used as the core support for a N‐MnO2–x branch, forming high‐quality N‐MnO2–x@TiC/C core/branch arrays. The introduced N dopants and oxygen vacancies in MnO2 are demonstrated by synchrotron radiation technology. By virtue of an integrated conductive framework, enhanced electron density, and increased surface capacitive contribution, the designed N‐MnO2–x@TiC/C arrays are endowed with faster reaction kinetics, higher capacity (285 mAh g−1 at 0.2 A g−1) and better long‐term cycles (85.7% retention after 1000 cycles at 1 A g−1) than other MnO2‐based counterparts (55.6%). The low‐temperature defect engineering sheds light on construction of advanced cathodes for aqueous RAZIBs.
With a facile hydrothermal process and subsequent low‐temperature (200 °C) NH3 treatment, N‐doped MnO2–x (N‐MnO2–x) branch arrays with concomitant oxygen vacancies are fabricated on conductive TiC/C backbones to form N‐MnO2–x@TiC/C core/branch arrays. By virtue of an integrated conductive framework, enhanced electron density, and increased surface capacitive contribution, the designed N‐MnO2–x@TiC/C arrays cathode exhibits excellent electrochemical performance in zinc ion batteries.
Lithium (Li) metal is considered as one of the most promising anode materials for next‐generation high‐energy‐density storage systems. However, the practical application of Li metal anode is hindered ...by interfacial instability and air instability due to the highly reactivity of Li metal. Unstable interface in Li metal batteries (LMBs) directly dictates Li dendrite growth, “dead Li” and low Coulombic efficiency, resulting in inferior electrochemical performance of LMBs and even safety issues. In addition, its sensitivity to ambient air leads to the severe corrosion of Li metal anode, high requirements of production and storage, and increased manufacturing cost. Plenty of efforts in recent years have overcome many bottlenecks in these fields and hastened the practical applications of high‐energy‐density LMBs. In this review, we focus on emerging methods of these two aspects to fulfill a stable and low cost electrode. In this perspective, design artificial solid electrolyte interphase (SEI) layers, construct three‐dimensional conductive current collectors, optimize electrolytes, employ solid‐state electrolytes, and modify separators are summarized to be propitious to ameliorate interfacial stability. Meanwhile, ex situ/in situ formed protective layers are highlighted in favor of heightening air stability. Finally, several possible directions for the future research on advanced Li metal anode are addressed.
In this review, we summarize the feasible strategies of ameliorating interfacial stability and air stability of lithium metal anode to make it more suitable for practical applications in high‐energy‐density storage systems. Meanwhile, we propose the challenges and perspectives for the future research of lithium metal anode in high‐energy batteries.
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