Metal selenides have received extensive research attention as anode materials for batteries due to their high theoretical capacity. However, their significant volume expansion and slow ion migration rate result in poor cycling stability and suboptimal rate performance. To address these issues, the present work utilized multivalent iron ions to construct fast pathways similar to superionic conductors (Fe-SSC) and introduced corresponding selenium vacancies to enhance its performance. Based on first-principles calculations and molecular dynamics simulations, it is demonstrated that the addition of iron ions and the presence of selenium vacancies reduced the material\'s work function and adsorption energy, lowered migration barriers, and enhances the migration rate of Li+ and Na+. In Li-ion half batteries, this composite material exhibites reversible capacity of 1048.3 mAh g-1 at 0.1 A g-1 after 100 cycles and 483.6 mAh g-1 at 5.0 A g-1 after 1000 cycles. In Na-ion half batteries, it is 687.7 mAh g-1 at 0.1 A g-1 after 200 cycles and 325.9 mAh g-1 at 5.0 A g-1 after 1000 cycles. It is proven that materials based on Fe-SSC and selenium vacancies have great applications in both Li-ion batteries and Na-ion batteries.

Aqueous rechargeable lithium-ion batteries (ARLIBs) are extensively researched due to their inherent safety, typical affordability, and potential high energy density. However, fabricating ARLIBs with both high energy density and power performance remains challenging. Herein, based on cyanoethyl-modified bacterial cellulose nanofibers (CBCNs), a multifunctional fast ion transport framework is developed to construct the flexible free-standing ARLIBs with high areal loading and excellent rate performance. Benefiting from the unique merits of CBCNs, such as ultra-high aspect ratio, excellent toughness, superior adhesion, good lithiophilicity and ideal stability, the flexible free-standing and highly robust electrodes are fabricated and exhibit a long-term stable cycling of 1200 cycles with a high specific capacity of 117 mAh∙g-1 at 15 C. Remarkably, the corresponding full cell with the free-standing high mass loading (45.5 mg∙cm-2) electrodes under the condition of ultra-low addition of battery binder demonstrates a cycle lifespan of over 1000 cycles with a specific capacity of 120 mAh∙g-1 and a capacity decay as low as 0.03% per cycle, which is far superior to those of almost all previous reports. This work provides a strategy for constructing ARLIBs with high energy density and power performance by introducing a unique fast ion transport nanofiber framework.

Here, we demonstrate the production of 2D nanosheets of arsenic disulfide (As2S3) via liquid-phase exfoliation of the naturally occurring mineral, orpiment. The resultant nanosheets had mean lateral dimensions and thicknesses of 400 and 10 nm, and had structures indistinguishable from the bulk. The nanosheets were solution mixed with carbon nanotubes and cast into nanocomposite films for use as anodes in potassium-ion batteries. These anodes exhibited outstanding electrochemical performance, demonstrating an impressive discharge capacity of 619 mAh/g at a current density of 50 mA/g. Even after 1000 cycles at 500 mA/g, the anodes retained an impressive 94% of their capacity. Quantitative analysis of the rate performance yielded a capacity at a very low rate of 838 mAh/g, about two-thirds of the theoretical capacity of As2S3 (1305 mAh/g). However, this analysis also implied As2S3 to have a very small solid-state diffusion coefficient (∼10-17 m2/s), somewhat limiting its potential for high-rate applications.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur batteries owing to its reversible solid-solid conversion for high-energy-density batteries. However, the sluggish reaction kinetics of SPAN cathodes significantly limit their output capacity, especially at high cycling rates. Herein, a CNT-interpenetrating hierarchically porous SPAN electrode is developed by a simple phase-separation method. Flexible self-supporting SPAN cathodes with fast electron/ion pathways are synthesized without additional binders, and exceptional high-rate cycling performances are obtained even with substantial sulfur loading. For batteries assembled with this special cathode, an impressive initial discharge capacity of 1090 mAh g-1 and a retained capacity of 800 mAh g-1 are obtained after 1000 cycles at 1 C with a sulfur loading of 1.5 mg cm-2. Furthermore, by incorporating V2O5 anchored carbon fiber as an interlayer with adsorption and catalysis function, a high initial capacity of 614.8 mAh g-1 and a notable sustained capacity of 500 mAh g-1 after 500 cycles at 5 C are achieved, with an ultralow decay rate of 0.037% per cycle with a sulfur loading of 1.5 mg cm-2. The feasible construction of flexible SPAN electrodes with enhanced cycling performance enlists the current processing as a promising strategy for novel high-rate lithium-sulfur batteries and other emerging battery electrodes.

Lithium-air batteries (LABs) have aroused worldwide interest due to their high energy density as a promising next-generation battery technology. From a practical standpoint, one of the most pressing issues currently in LABs is their poor rate performance. Accelerating the mass transfer rate within LABs is a crucial aspect for enhancing their rate capability. In this Perspective, we have meticulously analyzed the ion and oxygen transport processes to provide readers with a comprehensive understanding of the mass transfer within LABs. Following this, we have discussed potential misconceptions in the existing literature and propose our recommendations for improving the rate performance of LABs. This Perspective provides a deep insight into the mass transfer process in LABs and offers promising strategies for developing other high-rate metal-O2 batteries.

Exploring robust electrode materials which could permit fast and reversible insertion/extraction of large K+ is a crucial challenge for potassium-ion batteries (PIBs). Smart interfacial design could facilitate electron/ion transport as well as assure the integrity of electrode. Herein, Cetyltrimethylammonium bromide (CTAB) was found to play bifunctional roles in construction of Nb2CTx@MoSe2 heterostructure. Firstly, functionalization of CTAB on the surface of Nb2CTx could influence the subsequent growth of MoSe2 by electrostatic effect, stereochemical effect and the synergetic Lewis acid-base interaction, leading to the formation of Nb2CTx@MoSe2 with tiled heterostructure. Secondly, the interlayer spacing of Nb2CTx was expanded from 0.77 to 1.21 nm owing to the pillar effect of CTAB. As excepted, the capacity retention was 80 % from 100 mA g-1 (406 mA h g-1) to 1000 mA g-1 concerning rate capability and the specific capacity maintained at 240 mA h g-1 (at 2000 mA g-1) over 300 cycles. The calculated DK values from Galvanostatic intermittent titration technique (GITT) measurement of the titled C-T-Nb2CTx@MoSe2@C electrode is two orders of magnitude larger than the traditional T-Nb2CTx@MoSe2@C electrode, further confirming intimate interface between MoSe2 and Nb2CTx could provide convenient potassium-ion transport channels and fast diffusion kinetics. Finally, ex-situ characterizations at different charging and discharging voltage stages, including ex-situ XRD/Raman/HRTEM/XPS have been carried out to reveal the potassium storage mechanism. This work provides a facile strategy for the regulation of interface engineering by the assist of CTAB which could extend to other MXenes-TMDs (Transition metal dichalcogenides) hybrid electrodes.

The bismuth anode has garnered significant attention due to its high theoretical Na-storage capacity (386 mAh g-1). There have been numerous research reports on the stable solid electrolyte interphase (SEI) facilitated by electrolytes utilizing ether solvents. In this contribution, cyclic tetrahydrofuran (THF) and 2-methyltetrahydrofuran (MeTHF) ethers are employed as solvents to investigate the sodium-ion storage properties of bismuth anodes. A series of detailed characterizations are utilized to analyze the impact of electrolyte solvation structure and SEI chemical composition on the kinetics of sodium-ion storage. The findings reveal that bismuth anodes in both THF and MeTHF-based electrolytes exhibit exceptional rate performance at low current densities, but in THF-based electrolytes, the reversible capacity is higher at high current densities (316.7 mAh g-1 in THF compared to 9.7 mAh g-1 in MeTHF at 50 A g-1). This stark difference is attributed to the formation of an inorganic-rich, thin, and uniform SEI derived from THF-based electrolyte. Although the SEI derived from MeTHF-based electrolyte also consists predominantly of inorganic components, it is thicker and contains more organic species compared to the THF-derived SEI, impeding charge transfer and ion diffusion. This study offers valuable insights into the utilization of cyclic ether electrolytes for Na-ion batteries.

Prussian blue analogues receive tremendous attention owing to their spacious three-dimensional skeleton, high theoretical specific capacity, facile synthesis procedure, and high cost-effectiveness as among the most promising candidates for cathode materials in sodium-ion batteries (SIBs). Nonetheless, the practical specific capacity, especially under high current, is particularly frail due to the sluggish ion diffusion. In this study, the strategy of Ni substitution and formation of water-coordinated Fe is applied to lower the crystal field energy and elevate the active low-spin (LS) Fe content, which leads to a capacitive sodium storage mechanism, resulting in a substantial specific capacity under high current density. The delivered specific capacity of PW-325@2NiFe-55 is 95 mAh g-1 at 50 C, which is 72.5% capacity retention of the one at 0.5 C. Also, it maintains 80.2% of its initial specific capacity after 500 cycles at 5 C. Furthermore, a hypothesis of a joint diffusion-controlled and capacitive mechanism for high-spin (HS) Fe and a mere capacitive mechanism for LS Fe is put forward and verified through potentiastatic tests, operando 57Fe Mössbauer spectroscopy, and ex situ XRD, which provides a new horizon to enhance the electrochemical performance for SIBs.

Quasi solid-state polymer electrolytes (QSPEs) are particularly attractive due to their high ionic conductivity and excellent safety for lithium metal batteries (LMBs). However, it is still a great challenge for QSPEs to achieve strong mechanical strength and high electrochemical performance simultaneously. Herein, a QSPE (SCOF-PEP-PEA) using a covalent organic framework (COF) containing abundant allyl groups (SCOF) as a rigid porous filler as well as a cross-linker to reinforce the polymer network is reported. Benefitting from the unique 3D nanonetwork structure and abundant lithiophilic functional groups, SCOF-PEP-PEA QSPE exhibits high ionic conductivity (4.0 × 10-4 S cm-1) and high lithium-ion transference number (0.82) at room temperature. Moreover, SCOF-PEP-PEA QSPE displays much improved mechanical strength compared to PEP-PEA QSPE (AFM Young\'s modulus: 453 vs 36 MPa). As a result, the Li/LFP full cell with SCOF-PEP-PEA QSPE shows great rate performance of 141 mAh g-1 at 1C and delivers a high specific capacity retention of 92% after 220 cycles at 0.5 C (60 °C). This work provides a new strategy to design and prepare high-performance QSPEs with COFs as porous organic filler, and further expand the application of COFs for energy storage applications.

Li-rich Mn-based layered oxides (LMLOs) are expected to be the most promising high-capacity cathodes for the next generation of lithium-ion batteries (LIBs). However, the poor cycling stability and kinetics performance of polycrystalline LMLOs restrict their practical applications due to the anisotropic lattice stress and crack propagation during cycling. Herein, B-doped micron-sized single-crystal Co-free LMLOs were obtained by molten-salt (LiNO3 and H3BO3)-assisted sintering. The results reveal that the low-melting-point molten salt can serve as liquid-phase media to improve the efficiency of atomic mass transfer and crystal nucleation and growth. The modified single-crystal LMLO cathodes can resist the accumulation of anisotropic stress and strain during the cycling and reduce interface side reactions, thus achieving excellent high-voltage stability and kinetics performance. The reversible specific capacity of the single crystals is 210.8 mAh g-1 at 1C with a voltage decay rate of 1.95 mV/cycle and up to 161.1 mAh g-1 at 10C with a capacity retention of 81.06% after 200 cycles.