To pursue a higher energy density (>300 Wh kg−1 at the cell level) and a lower cost (<$125 kWh−1 expected at 2022) of Li‐ion batteries for making electric vehicles (EVs) long range and ...cost‐competitive with internal combustion engine vehicles, developing Ni‐rich/Co‐poor layered cathode (LiNi1−x−yCoxMnyO2, x+y ≤ 0.2) is currently one of the most promising strategies because high Ni content is beneficial to high capacity (>200 mAh g−1) while low Co content is favorable to minimize battery cost. Unfortunately, Ni‐rich cathodes suffer from limited structure stability and electrode/electrolyte interface stability in the charged state, leading to electrode degradation and poor cycling performance. To address these problems, various strategies have been employed such as doping, structural optimization design (e.g., core–shell structure, concentration‐gradient structure, etc.), and surface coating. In this review, five key aspects of Ni‐rich/Co‐poor layered cathode materials are explored: energy density, fast charge capability, service life including cycling life and calendar life, cost and element resources, and safety. This enables a comprehensive analysis of current research advances and challenges from the perspective of both academy and industry to help facilitate practical applications for EVs in the future.
Current research advances and challenges in the field of Ni‐rich NCM cathodes for electric vehicles both in academy and industry, along with future perspectives are discussed. Ni‐rich NCM cathodes for automotive applications in five key aspects including energy density, fast charge capability, service life, cost and element resources, and safety are analyzed comprehensively.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The electrochemical nitrogen reduction reaction (NRR) is a very efficient method for sustainable NH3 production, but it requires effective catalysts to expedite the NRR kinetics and inhibit the ...concomitant hydrogen evolution reaction (HER). Two-dimensional (2D)/2D interface engineering is an effective method to design powerful catalysts due to intimate face-to-face contact of two 2D materials that facilitates the strong interfacial electronic interactions. Herein, we explored a 2D/2D MoS2/C3N4 heterostructure as an active and stable NRR catalyst. MoS2/C3N4 exhibited a conspicuously improved NRR performance with an NH3 yield of 18.5 μg h–1 mg–1 and a high Faradaic efficiency (FE) of 17.8% at −0.3 V, far better than those of the individual MoS2 or C3N4 component. Density functional theory calculations revealed that the interfacial charge transport from C3N4 to MoS2 could enhance the NRR activity of MoS2/C3N4 by promoting the stabilization of the key intermediate *N2H on Mo edge sites of MoS2 and concurrently decreasing the reaction energy barrier. Meanwhile, MoS2/C3N4 rendered a more favorable *H adsorption free energy on S edge sites than on Mo edge sites of MoS2, thereby protecting the NRR-active Mo edge sites from the competing HER and leading to a high FE.
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IJS, KILJ, NUK, PNG, UL, UM
The emergence of carbon dots (CDs) has opened up an exciting new field in the science and technology of carbon nanomaterials and has attracted increasing interest in recent years. Due to their ...diverse physicochemical properties and favourable attributes, such as quantum confinement effects and abundant surface defects, CDs and their derived hybrids have shown exciting and indispensable prospects in the energy conversion and storage fields. Considering the latest developments, in this review, we comprehensively summarize the classification and structure of CDs. Three strategies for structural engineering of CDs are presented and analyzed, in terms of the tuning of size and crystallinity, and the methodologies for surface modification and heteroatom doping, with a focus on the relationship among the synthesis methods, structure and properties of the concerned CDs. More importantly, the recent advances in energy-oriented applications of CDs, including photo- and electro-catalysis, light-emitting diodes, photovoltaic cells, lithium/sodium ion batteries and supercapacitors, will be systematically highlighted. Finally, we discuss and outline the remaining major challenges and opportunities for CDs in the future.
Lithium–sulfur (Li–S) batteries have great promise to support the next‐generation energy storage if their sluggish redox kinetics and polysulfide shuttling can be addressed. The rational design of ...sulfur electrodes plays key roles in tacking these problems and achieving high‐efficiency sulfur electrochemistry. Herein, a synergetic defect and architecture engineering strategy to design highly disordered spinel Ni–Co oxide double‐shelled microspheres (NCO‐HS), which consist of defective spinel NiCo2O4–x (x = 0.9 if all nickel is Ni2+ and cobalt is Co2.13+), as the multifunctional sulfur host material is reported. The in situ constructed cation and anion defects endow the NCO‐HS with significantly enhanced electronic conductivity and superior polysulfide adsorbability. Meanwhile, the delicate nanoconstruction offers abundant active interfaces and reduced ion diffusion pathways for efficient Li–S chemistry. Attributed to these synergistic features, the sulfur composite electrode achieves excellent rate performance up to 5 C, remarkable cycling stability over 800 cycles and good areal capacity of 6.3 mAh cm−2 under high sulfur loading. This proposed strategy based on synergy engineering could also inform material engineering in related energy storage and conversion fields.
Defective hollow structured transition metal chalcogenide microspheres are developed as sulfur immobilizers via universal synthesis process. The synergistic combination of defect engineering and a morphological control strategy contributes to superior electrical/ionic conduction, strong polysulfide adsorption, and excellent structural integrity. Thanks to those features, the composite electrode achieves superb rate capability and cycling stability, thus leading to highly efficient lithium‐sulfur battery performance.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this work, unique porous carbon sheets (PCSs) are developed via a facile synthesis. The obtained PCS delivers long‐range conductive framework, abundant active interfaces, rich element doping, and ...notably a high inner porosity that builds up an admirable 3D network for multidirectional ion transfer. Such unique architecture and surface chemistry enable ultrafast sulfur electrochemistry as well as high‐efficiency inhibition on polysulfide shuttling via the dually physical and chemical sulfur confinement. The PCS‐based sulfur electrodes achieve superb rate capability up to 10 C, outstanding cyclability over 1000 cycles, and high areal capacity of 4.8 mA h cm−2. This work offers an appealing model of material engineering for fast and reliable lithium–sulfur batteries, as well as guidance for rational structural design in extended energy storage and conversion systems.
A unique porous carbon sheet (PCS) material is developed through a facile synthesis by using phosphorus pentoxide as a single template. When employed as advanced sulfur host for lithium–sulfur batteries, the as‐developed PCS delivers multidirectional inner ion pathways and dually physical and chemical sulfur confinements, thus enabling admirably fast sulfur electrochemistry and excellent battery durability.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Oxygen‐related electrocatalysis, including those used for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), play a central role in green‐energy related technologies. Rational ...fabrication of effective oxygen electrocatalysts is crucial for the development of oxygen related energy devices, such as fuel cells and rechargeable metal–air batteries. Recently, owing to their tunable compositions and microstructures, metal–organic frameworks (MOFs) based materials have drawn extensive attention as nonprecious oxygen electrocatalysts. Various strategies have been developed to fabricate MOF‐based electrocatalysts and regulate their active sites, such as heterometal doping, defect engineering, morphology tuning, heterostructure construction, and hybridization. In this review, by focusing on various modulation strategies aiming at active sites, the recent advances of MOF‐based electrocatalysts are summarized. The synthetic methods used to synthesize various MOF‐based oxygen electrocatalysts are discussed, followed by the underlying engineering mechanisms required to allow performance enhancement, and finally some existing challenges that hinder for their practical applications are discussed alongside a perspective on their possible future.
Recent advances in active sites engineering strategies on metal–organic framework (MOF) based oxygen electrocatalysts are summarized, including secondary metal doping, coordination optimization, defect engineering, structure optimization, heterostructure construction, and hybridization. The fundamental understanding for these strategies and the synthetic methods are provided. Some existing challenges and possible solutions to the issues facing MOF‐based oxygen electrocatalysts are presented.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Recent fruitful studies on rechargeable zinc-air battery have led to emergence of various bifunctional oxygen electrocatalysts, especially metal-based materials. However, their electrocatalytic ...configuration and evolution pathway during battery operation are rarely spotlighted. Herein, to depict the underlying behaviors, a concept named dynamic electrocatalyst is proposed. By selecting a bimetal nitride as representation, a current-driven "shell-bulk" configuration is visualized via time-resolved X-ray and electron spectroscopy analyses. A dynamic picture sketching the generation and maturation of nanoscale oxyhydroxide shell is presented, and periodic valence swings of performance-dominant element are observed. Upon maturation, zinc-air battery experiences a near two-fold enlargement in power density to 234 mW cm
, a gradual narrowing of voltage gap to 0.85 V at 30 mA cm
, followed by stable cycling for hundreds of hours. The revealed configuration can serve as the basis to construct future blueprints for metal-based electrocatalysts, and push zinc-air battery toward practical application.
Boron nitride nanosheets were dispersed in polymers to give composite films with excellent thermal transport performances approaching the record values found in polymer/graphene nanocomposites. ...Similarly high performance at lower BN loadings was achieved by aligning the nanosheets in poly(vinyl alcohol) matrix by simple mechanical stretching (see picture).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Direct growth of electrocatalysts on conductive substrates is an emerging strategy to prepare air electrodes for flexible Zn‐air batteries (FZABs). However, electrocatalysts grown on conductive ...substrates usually suffer from disorder and are densely packed with “prohibited zones”, in which internal blockages shut off the active sites from catalyzing the oxygen reaction. Herein, to minimize the “prohibited zones”, an ordered multidimensional array assembled by 1D carbon nanotubes and 2D carbon nanoridges decorated with 0D cobalt nanoparticles (referred as MPZ‐CC@CNT) is constructed on nickel foam. When the MPZ‐CC@CNT is directly applied as a self‐supported electrode for FZAB, it delivers a marginal voltage fading rate of 0.006 mV cycle−1 over 1800 cycles (600 h) at a current density of 50 mA cm−2 and an impressive energy density of 946 Wh kg−1. Electrochemical impedance spectroscopy reveals that minimal internal resistance and electrochemical polarization, which is beneficial for the flash reactant shuttling among the triphase (i.e., oxygen, electrolyte, and catalyst) are offered by the open and ordered architecture. This advanced electrode design provides great potential to boost the electrochemical performance of other rechargeable battery systems.
An ordered multidimensional air electrode assembled by one‐dimensional carbon nanotube and two‐dimensional carbon nanoridge decorated with zero‐dimensional cobalt nanoparticles is developed for application in flexible Zn‐air batteries. This unique architecture enables ample gas‐solid‐liquid triphasic interfaces and flash reactant shuttling. High energy‐density and minimal low voltage gap increasement are delivered by flexible Zn‐air batteries, showing promise in wearable devices.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Electrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a ...combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation‐energy barrier for stabilization of *N2H, which is the rate‐limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 μg h−1 mg−1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2SO4 at −0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.
ZnO/RGO can fix it: A hybrid material, in which ZnO quantum dots are supported on reduced graphene oxide (ZnO/RGO), was synthesized by a facile, one‐step, microwave‐assisted solvothermal method and found to be a highly active and stable catalyst for the electrochemical reduction of dinitrogen to ammonia (see figure) under ambient conditions, which is a promising method for artificial nitrogen fixation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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