High-power lithium-ion batteries (LIBs) are required for a variety of technological applications, especially in the field of electric vehicles (EVs). Oxides based on niobium, titanium, and tungsten, and having crystallographic shear structures, are considered promising materials for high-rate anodes of LIBs. The unique structures with open channels, multielectron redox processes, and a moderate potential window with a resulting solid electrolyte interface-free interface provide them with rapid Li-ion diffusion pathways, fairly high capacities, and high safety. In this review, the recent advancements in diverse crystallographic shear structure Nb-based oxide anodes for fast Li-ion energy storage are comprehensively presented, with a specific focus on the relationships between the crystal structures and electronic properties, lithiation mechanisms, kinetic properties, and electrochemical performance. The challenges in the design, optimization, and practical application of oxides with crystallographic shear structures are also discussed, together with strategies to overcome these challenges and prospects for the future.

Antimony (Sb) holds a high theoretic capacity and suitable redox potential as a promising anode for aqueous alkaline batteries (AABs). However, the uncontrollable nucleation for SbO2− and promiscuous water-induced side reactions severely degrade the reversibility of Sb anode. Herein, the carbon-anchored Sb nanoparticles are constructed to induce uniform Sb plating/stripping for high-performance AABs. The experimental results reveal that the enhanced interaction between carbon and antimony as well as defective carbon can significantly improve the electrical conductivity and decrease the Sb nucleation overpotential. Accordingly, the as-prepared Sb anode enables preferential plating of Sb rather than parasitic side reactions. As a result, the cycle life of A-Sb/CF is sustained over 500 cycles at 10 mA cm−2/2 mAh cm−2. Even at the high capacity of 4 mAh cm−2, this anode can cycle stably for 225 cycles, which is significantly better than the Sb/CF counterpart. Furthermore, the assembled Ni3S2@Ni(OH)2//A-Sb/CF full battery demonstrates a high capacity of 2.17 mAh cm−2 and a stable cycle life of over 500 cycles.

Silicon (Si)-based anodes have long been viewed as the next promising solution to improve the performance of modern lithium-ion batteries. However, the poor cycling stability of Si-based anodes impedes their application and calls for solutions for further improvements. In the present work, the incorporation of phosphate groups on the surface of an amorphous Si-carbon composite (a-Si/C) has been achieved by a hydrothermal reaction using phosphoric acid and sodium dihydrogen phosphate at pH = 2. Different levels of the surface P-doping have been realized using reaction times (2, 4, and 8 h) at two different phosphate concentrations. The presence of phosphate groups on the particle's surface has been confirmed by energy-dispersive X-ray, infrared, and Raman spectroscopy. The cycling stability of the P-treated a-Si/C composites has been significantly improved when using lithium bis(trifluoromethanesulfonyl)imide as a salt in ether-based solvents mixture compared to a conventional electrolyte for Si-based anodes (LiPF6 in carbonate-based solvents). Coulombic efficiencies as high as 99% have been reached after five charge/discharge cycles for almost all phosphate-treated materials. The 4 h P-treated a-Si/C composite electrode exhibits the best reversible capacity of 1598 mAh g−1 after 200 cycles demonstrated in half-cells using an ether-based electrolyte.

Metal-organic frameworks (MOFs) integrate several advantages such as adjustable pore sizes, large specific surface areas, controllable geometrical morphology, and feasible surface modification. Benefiting from these appealing merits, MOFs have recently been extensively explored in the field of advanced secondary batteries. However, a systematic summarization of the specific functional units that these materials can act as in batteries as well as their related design strategies to underline their functions has not been perceived to date. Motivated by this point, this review dedicates to the elucidation of diverse functions of MOFs for batteries, which involve the electrodes, separators, interface modifiers, and electrolytes. Particularly, the main engineering strategies based on the physical and chemical features to enable their enhanced performance have been highlighted for the individual functions. In addition, perspectives and possible research questions in the future development of these materials have also been outlined. This review captures such progress ranging from fundamental understanding and optimized protocols to multidirectional applications of MOF-based materials in advanced secondary batteries.

Back Cover: In article number BTE2.20220032, Wenbo Liu and co-workers develop a simple and effective strategy to achieve PANI-modified freestanding 3D dendritic hierarchical porous Cu-Sn nanocomposites, which shows ultrahigh areal capacity and good cycling stability as additive-free thick anodes for LIBs. The Sn content and areal capacity can be tuned easily by changing the dealloying time of initial alloy for 3D tin-based thick anodes with adjustable capacities toward high-performance LIBs.

Anisotropic nanoparticles have attracted extensive attention due to their potential applications in material transport, energy storage, and biopharmaceutical. However, due to the inadequate understanding of microscopic particle formation, controllable asymmetric growth is still a great challenge. Herein, we report a facile emulsion-assisted interfacial polymerization strategy for the synthesis of nitrogen-doped porous carbon particles (NPCPs) with tunable anisotropic/isotropic architectures. During the synthesis process, we can form emulsion droplets with different nanostructures directionally through dual routes, thereby assisting and mediating the polymerization and growth process of the monomer to obtain poly-diaminopyridine nanoparticles with various architectures. The corresponding NPCPs with tunable specific surface area (125–362 m2 g−1), nitrogen content (10%–14%), and diverse morphologies can be acquired by calcination under N2 atmosphere at 700 °C. The synergetic effect of abundant microporous structures and active nitrogen species content contributes to improve the physicochemical properties, while the unique anisotropic architecture increases the charge diffusion efficiency and enhances the high-rate stability. Therefore, the resultant NPCPs electrode exhibits a specific capacitance up to 275 F g−1 at 0.2 A g−1 and surface-area-normalized capacitance of 83.0 μF cm−2, indicating a promising material for high-performance supercapacitors.

Photocatalytic hydrogen production via solar energy is considered one of the most strategic ways to produce renewable energy. However, expensive Pt is normally used as the cocatalyst during photocatalysis, which prevents commercialization. Therefore, extensive research has been performed to seek abundant and low-cost alternative catalysts. In this work, MoS2 quantum dots (QDs) synthesized by a hydrothermal method are incorporated with graphitic carbon nitride to form a heterostructure for photocatalytic hydrogen evolution. MoS2 QDs/g-C3N4 heterostructure containing 5% and 10% MoS2 QDs exhibited a high hydrogen production of 140 and 152 µmol h−1g−1, respectively, demonstrating the potential of MoS2 as an effective economic cocatalyst. Detailed investigations indicate that incorporating MoS2 QDs with carbon nitride to form heterostructure reduces the bandgap, suppresses the recombination, and enhances electron kinetic energy resulting from the anti-Stoke effect, thus leading to better performance for hydrogen evolution.

Developing super stability, high coulomb efficiency, and long-span life of sodium-ion batteries (SIBs) can significantly widen their practical industrial applications. In this study, we report a pine-derived carbon/SnS2@reduced graphene oxide (PDC/SnS2@rGO) film with fast ion/electron transport micro-channel used as a SIB anode, which shows ultrahigh stable stability and long-span life. Functionally, a biomass PDC/SnS2@rGO film with ~30 μm micro carbon channel and ~1.2 μm thick carbon wall can simultaneously provide the fast electron transport path and the Na+ transport channel. Also, the two-dimensional (2D) layered SnS2 particles attached to the carbon wall of PDC can increase more Na+ contact sites and shorten the Na+ transport path in the NaPF6 electrolyte. To avoid the separation of SnS2 from PDC during the sodiation process, rGO with excellent conductivity and flexibility is wrapped in the SnS2 outer layer as an “electronic garment”. A ~650 mA h g−1 high Na+ storage capacity at 0.1 A g−1 and ~99.8% ultrahigh coulomb efficiency after 800 cycles at 5 A g−1 are obtained when PDC/SnS2@rGO film is used as a SIB anode. Furthermore, a SIB full-cell is assembled using PDC/SnS2@rGO film (anode) and Na3V2(PO4)3 (cathode), which exhibits a ~163.9 mA h g−1 high reversible capacity and ~99.7% coulomb efficiency performance. Our work provides a reasonable design strategy for the application of biomass-derived carbon in SIBs, which may inspire more biomass-derived material studies.

Electrochemical capacitors bridge the energy gap between conventional dielectric capacitors and batteries. The energy storage mechanism relies on purely physical electrical double-layer charging (EDL) and the faradaic process involving fast electrochemical redox reactions. These processes are strongly influenced by the surface area, porosity, electrical conductivity of the electrode materials, and the operating potential window of the electrolyte used. Carbonaceous materials play enormous roles in delivering outstanding electrochemical performance in electrochemical supercapacitors (ESCs) due to attractive material features suitable for high charge storage and release. However, due to the purely EDL-based charge storage mechanism in only carbon-based ESCs, the achievable energy density is low and hardly meets the high energy density demanding applications. Therefore, various carbon structures such as activated carbon, carbon nanotubes, graphene, and so on are designed and integrated with other hetero atoms or combined with transition metal oxides and polymer components to induce the pseudo-capacitive contributions via the electrochemical faradaic reaction. Thus, promoting the electrochemical performance of ESC based on the hybrid/composite material attributed to synergistic capacitances from EDLC and pseudocapacitance. Therefore, this review overviews the general perspective of the ESCs based on nanocarbons with various forms trending the progressive research contributions in developing high-performance ESCs.

Hard carbons are widely studied as anode materials for sodium-ion batteries (SIBs) due to their high Na-storage capacity, long cycle life, and low cost. However, the low initial coulombic efficiency (ICE) and poor cycle performance remain bottleneck concerns that necessitate a comprehensive material engineering solution. Herein, we propose a facile strategy to synthesize amorphous carbons with pseudo-graphitic dominated crystalline, expanded interlayer spacing, and reduced surface defects via carbonization of the cross-linking network of phenolic resin and sucrose. An elaborate structural and electrochemical characteristics analysis has been investigated against different sucrose contents and carbonization temperatures. The representative PF-S-55-1200 with the optimum cross-linking degree as well as carbonization temperature realizes a high reversible Na-storage capacity of 323.0 mAh g−1 with an ICE as high as 86.4%, much superior to the pristine phenolic resin pyrolytic carbon with a capacity of 267.1 mAh g−1 and an ICE of 46.3%. The hybrid hard carbons also exhibit robust structural stability with a prolonged cycle lifespan evidenced by a retained capacity of 238.3 mAh g−1 at a current density of 200 mA g−1 over 1500 cycles. The proposed route promises low-cost and high-performance hybrid hard carbons with optimized structural configuration for advanced SIBs.

To follow up on the performance of lithium-ion batteries (LIBs), transition metal sulfides (TMSs) have been developed as promising carbon alternatives for sodium-ion batteries (SIBs). Although attractive, it is still a great challenge to fulfill their capacity utilization with high cycling performance. Herein, a nanoemulsion-directed method has been developed to control the spherical arrangement of ZnS@C units with both penetrating macropores from the center to the surface and inner mesopores distributed among the bulks. With respect to ion diffusion, the penetrating macropores could serve as the built-in ion-buffer reservoirs to keep a steady flow of electrolyte, while the inner mesopores facilitate the ion diffusion across the whole bulks. In terms of stability, the radical porous structure could work as self-supported vertical bones to accommodate the volume change from both lateral and vertical sides. Besides, the localized carbon distributed among the ZnS nanoparticles not only acts as binding agents to join the numerous ZnS nanoparticles but also endows the radical bones with effective electron transmission capability. As a proof of concept, such hydrangea-like ZnS@C nanospheres deliver sodium storage performance with high-rate and long-cycling capability. This nanoemulsion-directed approach is anticipated for other TMSs with penetrating pores for post-lithium-ion batteries applications.

Front Cover: In article number BTE2.20220034, Sunggi Lee, Yong Min Lee, and co-works successfully designed a functional electrolyte with new fluorinated linear carbonate, Ethyl 2-(2-fluoroethoxy)ethyl carbonate (EFEEC). The new EFEEC additive can function at both electrode surfaces, which forms stable CEI and SEI on the surface, resulting in suppressing the parasitic reactions between electrolyte and electrode, such as HF, gas generation, and Li dendrite growth.

Nonfullerene acceptors (NFAs) lead the continuous development of organic solar cells (OSCs) with competitive efficiency over 19%. Design and synthesis of novel photovoltaic materials are effective methods to improve the OSCs performance, which can regulate the optoelectric properties, such as energy level, absorption spectra, charge transport, and so on. So far, hundreds of NFAs have been reported. Meanwhile, it has been demonstrated that intrinsic morphology of active layer is partially determined by the chemical structures of NFAs. Hence, only in-depth understanding of the relationship between different structures of NFAs and morphology can guide the molecular design of NFAs for highly efficient OSCs. Herein, we review some state-of-the-art NFAs according to their functional moieties, that is, arene core, end group and side chain, and discuss the relationship between molecular structure, morphology and device parameter. Additionally, the challenges and prospects for further development of OSCs based on NFAs are briefly considered. This review brings a unique insight into structure–function correlation in this field, which may help to rapidly develop efficient OSCs.

Layered Co-free Ni-rich cathodes are the most cost-effective for high-energy-density Li-ion batteries (LIBs), yet the structural instability and interfacial side reactions seriously hamper their commercial applications versus the Co-contained counterpart. Herein, a synchronous Ge-doping and Li4GeO4-coating of the Co-free Ni-rich cathodes have been realized to tackle these limitations during high-temperature lithiation of the corresponding hydroxide precursors. The nonmagnetic Ge4+ doping effectively relieves the magnetic frustration and the lattice oxygen loss with reduced cation mixing and gas emission. The Li-ion conductive and anti-erosive Li4GeO4 coatings contribute to enhance the surface chemistry stability and Li-ion migration interface kinetics. Consequently, the resulting Co-free Ni-rich cathodes delivers a high reversable capacity of 223.3 mAh g−1 at 0.1 C and maintains 127.5 mAh g−1 even at 10C within 2.7–4.4 V. More impressively, it displays high-capacity retention of 90.5% in coin-type half-cell after 150 cycles and 80.5% in pouch-type full-cell after 500 cycles at 3C, demonstrating a long-term cycle life.

Porous carbons with advanced nanostructures and volumetric performance are particularly attractive and essential for miniature supercapacitors to access high energy densities and capacitances, both for portable electronics and massive electrical equipments. However, the electrochemical performances and the pore structure are closely bound up, both restricted by pore volume and pore density. Herein, the wood slice (~0.7 mm) with the periodic porous structure is chosen as the basic framework with rich macropores and the graphene nanotube array (GNTA) with mesopores is used as an intermediate structure in situ synthesized to form the substructure in macropores; therefore, the biomass and nanotube array together construct a porous carbon with hierarchical pores and large surface area. On this basis, Cu-Co oxides are coated on the surface of the pores, to increase the capacitance of electrodes for supercapacitor applications. Because of the GNTA, the specific surface area increases from 38.2 to 1086.0 m2 g−1, which is quite helpful for the deposition of Cu-Co oxide nanosheets and effectively alleviates their typical self-stacking phenomenon. Meanwhile, the GNTA creates multiscale pores that served as channels for the rapid electron transfer and ion shuttling; as a result, the resistance obviously induces and capacitance increased by 131% (from 323.4 to 747.5 mF cm−2). For the assembled all-wood asymmetric supercapacitor, the specific capacitance is 151.2 F g−1 (1 A g−1), the energy density is 53.8 Wh kg−1 with a power density of 900 W kg−1, and the specific capacitance remains extremely stable during the cycling. Our work provides a practical structure–design strategy for high-performance supercapacitors.

Electrochemical batteries with organic electrode materials have attracted worldwide attention due to their high safety, low cost, renewability, low contamination, and easiness of recycling. However, the practical application of such system is limited by low density, low electronic/ionic conductivity, and the dissolution of organic electrode materials in conventional liquid electrolytes. Herein, a novel battery configuration is proposed to replace liquid electrolyte/solid organic cathode with solid electrolyte/liquid organic cathode to ultimately solve the shuttle effect and dissolution problem of organic cathodes. More importantly, this configuration combines room-temperature high-safety liquid lithium metal anode Li-BP-DME that can essentially inhibit lithium dendrite nucleation/growth and sulfide SE with ultrahigh room-temperature ionic conductivity for facilitated ion-conduction.

Applications of organic compounds-based electrodes in aqueous zinc-ion batteries (AZIBs) at low temperatures are severely restricted by the freezing of aqueous electrolytes and the inferior dynamic behavior of organic electrodes below zero. Herein, tetracyanoquinodimethane (TCNQ) was purified by the sublimation method and used as a cathode in AZIBs to investigate electrochemical Zn storage performance in comparison with nonpurified TCNQ at a temperature range of 25°C to −40°C. Nuclear magnetic resonance and elemental analysis prove increased purity in purified TCNQ (p-TCNQ), whereas scanning electron microscope and Brunner−Emmet−Teller data verify reduced particle size and increased surface area of p-TCNQ. Kinetic analysis demonstrates that p-TCNQ is a more surface-controlled electrode process than TCNQ and offers much higher ionic diffusivity than the latter at various temperatures. Molecular dynamics simulation validates that the existence of impurity increases the absorption energy of TCNQ in a TCNQ//Zn system that is unfavorable to Zn migration. Comprehensive analysis, including ex situ X-ray diffraction, Fourier transform infrared, Raman, and electron spin-resonance spectroscopy characterization confirm the high reversibility of transformation between C≡N and −C═N groups in p-TCNQ. This work provides a simple, environmentally friendly strategy to fabricate a high-performance AZIB at low temperatures while offering fundamental chemistry insight into organic electrode performance, thus possessing universal significance.

Cell design is effective to improve the performances of lithium-ion batteries (LIBs). For identifying the bottleneck of a full battery used for high-rate charging/discharging, we developed a simple method, by a reference electrode in practical pouch cells, to quick obtain the polarizations of the cathode and the anode. For a Li(Ni0.6Co0.2Mn0.2)O2/graphite full cell, 63.9% and 97.0% of the polarizations originate from the anode at 50% state of charge (SOC) during 2.0 C charging and discharging rates, respectively. While for LiFePO4/graphite system, 62.5% and 55.8% of the polarizations originate from the anode at the same charging and discharging conditions. These indicate that the anode is the limitation during fast charging/discharging, which is consistent with the common understanding but in contrary to the results obtained by coin cells reported previously. While the rate limitation from anode in LiFePO4/graphite system during fast charging/discharging is significantly changed to both cathode and anode compared with Li(Ni0.6Co0.2Mn0.2)O2/graphite. Besides, graphite anodes in LiFePO4/graphite cells more readily dive to the Li-metal plating potential at high charging rate. This leads to safety concerns of LiFePO4/graphite cells during fast charging. This is a facile strategy for fast distinguishing polarizations from cathodes and anodes of high-rate LIBs.

Solid-state Li–air batteries with ultrahigh energy density and safety are promising for long-range electric vehicles and special electronics. However, the challenging issues of developing Li–air battery-oriented solid-state electrolytes (SSEs) with high ionic conductivity, interfacial compatibility, and stability to boost reversibility, increase stable triple-phase boundaries, and protect the Li anode in an open system substantially impede their applications. Herein, we systematically summarize the recent progress achieved in terms of SSEs for Li–air batteries, and describe in detail the basic characteristics of SSE|air cathode interfaces and SSE|Li anode interfaces. First, the major characteristics of SSEs in Li–air batteries in terms of ionic/electronic conductivity, chemical/electrochemical/thermal stability, mechanical strength, and interfacial compatibility are briefly introduced according to three types of SSEs: inorganic, organic, and hybrid SSEs. Second, key strategies of integrating catalytic sites, porous structures, and electronic conductors with SSEs to enhance triple-phase boundaries at the SSE|air cathode for improving Coulombic efficiency are described in detail. Moreover, the protection of Li metal from H2O, CO2, O2, and redox mediators at the SSE|Li anode to ensure safety is elaborately overviewed. Finally, future opportunities and perspectives on three important topics of three-dimensional structural integration, external field assistance, and operando characterizations are proposed for advanced solid-state Li–air batteries.

Front Cover: Developing super stability and long-span life of sodium ion batteries (SIBs) can significantly widen their practical applications. However, the low specific Na+ storage performance and poor cycle stability at large current density are still unsatisfactory. In article number BTE.20220046, Sun et al. reported a pine-derived carbon/SnS2@reduced graphene oxide film with fast ion/electron transport micro-channel, which was used as a SIB anode and cycled 800 times at 5 A g−1. This work provides a novel design strategy for the application of biomass-derived carbon in energy storage.