Molecular Engineering on Solvation Structure of Carbonate Electrolyte toward Durable Sodium Metal Battery at -40 °C.

Carbonate electrolytes have excellent chemical stability and high salt solubility, which are ideally practical choice for achieving high-energy-density sodium (Na) metal battery at room temperature. However, their application at ultra-low temperature (-40 °C) is adversely affected by the instability of solid electrolyte interphase (SEI) formed by electrolyte decomposition and the difficulty of desolvation. Here, we designed a novel low-temperature carbonate electrolyte by molecular engineering on solvation structure. The calculations and experimental results demonstrate that ethylene sulfate (ES) reduces the sodium ion desolvation energy and promotes the forming of more inorganic substances on the Na surface, which promote ion migration and inhibit dendrite growth. At -40 °C, the Na||Na symmetric battery exhibits a stable cycle of 1500 hours, and the Na||Na3 V2 (PO4 )3 (NVP) battery achieves 88.2 % capacity retention after 200 cycles.

Structure Engineering of Vanadium Tetrasulfides for High-Capacity and High-Rate Sodium Storage.

Structure engineering of electrode materials can significantly improve the life cycle and rate capability of the sodium-ion battery (SIB), yet remains a challenging task due to the lack of an effective synthetic strategy. Herein, the microstructure of VS4 hollow spheres is successfully engineered through a facile hydrothermal method. The hollow VS4 microspheres possess rich porosity and are covered with 2D ultrathin nanosheets on the surface. The finite element simulation (FES) reveals that such heterostructures can effectively relieve the stress induced by the sodiation and thereby enhance the structural integrity. The SIB with the hollow VS4 microspheres as anode displays impressively high specific capacity, excellent stability upon ultra-long cycling, and extraordinary rate capacity, e.g., a reversible capacity of ≈378 mA h g-1 at ultra-high 10 A g-1 , while retaining 73.2% capacity after 1000 cycles. The Na storage mechanism is also elucidated through in situ/ex situ characterizations. Moreover, the hollow VS4 microspheres demonstrate reliable rate performance at a low temperature of -40 °C (e.g., the capacity is ≈163 mA h g-1 at 2 A g-1 ). This work provides novel insights toward high-performance SIBs.

Synergistic Function between Phosphorus-Containing Flame Retardant and Multi-Walled Carbon Nanotubes towards Fire Safe Polystyrene Composites with Enhanced Electromagnetic Interference Shielding.

As a universal polymer material, polystyrene (PS) is widely applied in electrical devices and construction. Thus, it is necessary to improve the flame retardancy and electromagnetic shielding properties of PS material. In this work, PS/silicon-wrapped ammonium polyphosphate/Inorganic acid-treated multi-walled carbon nanotubes composites (PS/SiAPP/aMWCNT, abbreviated as PAC) were prepared via methods of filtration-induced assembly and hot-pressing. Morphology and structure characterization demonstrated that SiAPP and aMWCNT had good dispersion in PS and excellent compatibility with the PS matrix. Thermogravimetric analysis revealed that the addition of aMWCNT to PS improved its thermal stability and carbon-forming characteristics. The peak heat release rate, the peak carbon monoxide production rate, and the peak smoke production rate of the PAC10 composite decreased by 53.7%, 41.9%, and 45.5%, respectively, while its electromagnetic shielding effectiveness reached 12 dB. These enhancements were attributed to the reason that SiAPP and aMWCNT synergistically catalyzed the char generation and SiAPP produced free radical scavengers and numbers of incombustible gases, which could decrease the oxygen concentration and retard the combustion reaction. Therefore, the assembled PS/SiAPP/aMWCNT system provides a new pathway to improve the flame retardant and electromagnetic shielding properties of PS.

Architectural Engineering Achieves High-Performance Alloying Anodes for Lithium and Sodium Ion Batteries.

Tremendous efforts have been dedicated to the development of high-performance electrochemical energy storage devices. The development of lithium- and sodium-ion batteries (LIBs and SIBs) with high energy densities is urgently needed to meet the growing demands for portable electronic devices, electric vehicles, and large-scale smart grids. Anode materials with high theoretical capacities that are based on alloying storage mechanisms are at the forefront of research geared towards high-energy-density LIBs or SIBs. However, they often suffer from severe pulverization and rapid capacity decay due to their huge volume change upon cycling. So far, a wide variety of advanced materials and electrode structures are developed to improve the long-term cyclability of alloying-type materials. This review provides fundamentals of anti-pulverization and cutting-edge concepts that aim to achieve high-performance alloying anodes for LIBs/SIBs from the viewpoint of architectural engineering. The recent progress on the effective strategies of nanostructuring, incorporation of carbon, intermetallics design, and binder engineering is systematically summarized. After that, the relationship between architectural design and electrochemical performance as well as the related charge-storage mechanisms is discussed. Finally, challenges and perspectives of alloying-type anode materials for further development in LIB/SIB applications are proposed.

Optimizing the Void Size of Yolk-Shell Bi@Void@C Nanospheres for High-Power-Density Sodium-Ion Batteries.

Bismuth (Bi) has been demonstrated as a promising anode for Na-ion batteries (NIBs) because it has high gravimetry (386 mA h g-1) and volumetric capacity (3800 mA h cm-3). However, Bi suffers from large volume expansion during sodiation, leading to poor electrochemical performance. The construction of a nanostructure with sufficient void space to accommodate the volume change has been proven effective for achieving prolonged cycling stability. However the excessive void space will definitely decrease the volumetric energy density of the battery. Herein, we design optimized Bi@Void@C nanospheres (Bi@Void@C-2) with yolk-shell structure that exhibit the best cycling performance and enhanced volumetric energy density. The optimized void space not only could buffer the volume change of the Bi nanosphere but also could keep the high volumetric energy density of the battery. The Bi@Void@C-2 shows an excellent rate capacity of 173 mA h g-1 at ultrahigh current density of 100 A g-1 and long-cycle life (198 mA h g-1 at 20 A g-1 over 10 000 cycles). The origin of the superior performance is achieved through in-depth fundamental studies during battery operation using in situ X-ray diffraction (XRD) and in situ transmission electron microscope (TEM), complemented by theoretical calculations and ex situ TEM observation. Our rational design provides insights for anode materials with large volume variation, especially for conversion type and alloying type mechanism materials for batteries (i.e., Li-ion batteries, Na-ion batteries).

The Synergetic Effect of Lithium Bisoxalatodifluorophosphate and Fluoroethylene Carbonate on Dendrite Suppression for Fast Charging Lithium Metal Batteries.

Fluorinated solid-electrolyte interphase (SEI) derived from fluoroethylene carbonate (FEC) is particularly favored for dendrite suppression in lithium metal batteries because of the high Young's modulus (≈64.9 Gpa) and low electronic conductivity (10-31 S cm-1 ) of LiF. However, the transportation ability of Li+ in this fluorinated SEI under high current densities is limited by the low ionic conductivity of LiF (≈10-12 S cm-1 ). Herein, by rational design, 0.1 m lithium bisoxalatodifluorophosphate (LiDFBOP) is adopted to modify fluorinated SEI in FEC based electrolyte for fast charging lithium metal batteries. Benefiting from the synergetic effect of LiDFBOP and FEC, a fluorinated SEI rich in LiF and Lix POy Fz species can be yielded, which can further improve the stability and ionic conductivity of SEI for fast Li+ transportation. Meanwhile, the average coulombic efficiency for Li plating/stripping is improved from 92.0% to 96.7%, thus promoting stable cycling of Li||Li symmetrical batteries with dendrite free morphologies, even at high current densities (3.0 mA cm-2 ) and high plating/stripping capacities (3.0 mAh cm-2 ). More attractively, in practical Li||LiNi0.6 Co0.2 Mn0.2 O2 batteries, the cycling life at 1C and rate capacities at 6C are also significantly improved. Therefore, the synergetic effect of LiDFBOP and FEC provides great potential for achieving advanced lithium metal batteries with fast charging ability.

Self-Formed Electronic/Ionic Conductive Fe3 S4  @ S @ 0.9Na3 SbS4 ⋠0.1NaI Composite for High-Performance Room-Temperature All-Solid-State Sodium-Sulfur Battery.

Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode is prepared through one-step wet-mechanochemical milling procedure. During milling process, ionic conduction pathway is self-formed in the composite due to the formation of 0.9Na3 SbS4 ⋅0.1NaI electrolyte without further annealing treatment. Meanwhile, the introduction of Fe3 S4 can increase the electronic conductivity of the composite cathode by one order of magnitude and nearly double enhance the ionic conductivities. Besides, the aggregation of sulfur is effectively suppressed in the obtained Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite, which will enhance the contact between sulfur and 0.9Na3 SbS4 ⋅0.1NaI electrolyte, leading to a decreased interfacial resistance and improving the electrochemical kinetics of sulfur. Therefore, the resultant all-solid-state sodium-sulfur battery employing Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode shows discharge capacity of 808.7 mAh g-1 based on Fe3 S4 @S and a normalized discharge capacity of 1040.5 mAh g-1 for element S at 100 mA g-1 for 30 cycles at room temperature. Moreover, the battery also exhibits excellent cycling stability with a reversible capacity of 410 mAh g-1 at 500 mA g-1 for 50 cycles, and superior rate capability with capacities of 952.4, 796.7, 513.7, and 445.6 mAh g-1 at 50, 100, 200, and 500 mA g-1 , respectively. This facile strategy for sulfur-based composite cathode is attractive for achieving room-temperature sodium-sulfur batteries with superior electrochemical performance.

A High-Temperature Na-Ion Battery: Boosting the Rate Capability and Cycle Life by Structure Engineering.

High-temperature sodium ion batteries (SIBs) have drawn significant heed recently for large-scale energy storage. Yet, conventional SIBs are in the depths of inferior charge/discharge efficiency and cyclability at elevated temperatures. Rational structure design is highly desirable. Hence, a 3D hierarchical flower architecture self-assembled by carbon-coated Na3 V2 (PO4 )3 (NVP) nanosheets (NVP@C-NS-FL) is fabricated via a microwave-assisted glycerol-mediated hydrothermal reaction combined with a post heat-treatment. The growth mechanism of NVP@C-NS-FL is systematically investigated, by forming a microspherical glycerol/polyglycerol-NVP complex initially and then converting into flower-like architecture during the subsequent annealing at a low temperature ramping rate. Benefiting from the integrated structure, fast Na+ transportation, and highly effective heat transfer, the as-obtained NVP@C-NS-FL exhibits an excellent high-temperature SIB performance, e.g., 65 mAh g-1 (100 C) after 1000 cycles under 60 °C. When coupled with NaTi2 (PO4 )3 anode, the full cell can still display superior power capability of 1.4 kW kg-1 and long-term cyclability (2000 cycles) under 60 °C.

Three-Dimensional Ordered Macroporous Metal-Organic Framework Single Crystal-Derived Nitrogen-Doped Hierarchical Porous Carbon for High-Performance Potassium-Ion Batteries.

The biggest challenge of potassium-ion batteries (KIBs) application is to develop high-performance electrode materials to accommodate the potassium ions large size. Herein, by rational design, we carbonize three-dimensional (3D) ordered macroporous ZIF-8 to fabricate 3D interconnected nitrogen-doped hierarchical porous carbon (N-HPC) that shows excellent rate performance (94 mAh g-1 at 10.0 A g-1), unprecedented cycle stability (157 mA g-1 after 12000 cycles at 2.0 A g-1), and superior reversible capacity (292 mAh g-1 at 0.1 A g-1). The 3D hierarchical porous structure diminishes the diffusion distance for both ions/electrons, while N-doping improves the reactivity and electronic conductivity via producing more defects. In addition, the bicontinuous structure possesses a large specific surface area, decreasing the current density, again improving the rate performance. In situ Raman spectra analysis confirms the potassiation and depotassiation in the N-HPC are highly reversible processes. The galvanostatic intermittent titration measurement and first-principles calculations reveal that the interconnected macropores are more beneficial to the diffusion of the K+. This 3D interpenetrating structure demonstrates a superiority for energy storage applications.

Enhanced Fire Safety of Rigid Polyurethane Foam via Synergistic Effect of Phosphorus/Nitrogen Compounds and Expandable Graphite.

In order to explore highly efficient flame-retardant rigid polyurethane foam (RPUF), phosphorus/nitrogen compounds and expandable graphite (EG) were successfully incorporated into RPUF by a free one-spot method. The combustion results showed that the fire safety of the RPUF samples was remarkably improved by the addition of phosphoric/nitrogen compounds and EG. With the incorporation of 22.4 wt.% phosphorus/nitrogen compounds and 3.2 wt.% EG, the RPUF composites achieved UL-94 V-0 rating. Besides, the total heat release and total smoke release of RPUF composites were reduced by 29.6% and 32.4% respectively, compared to those of the pure RPUF sample. PO• and PO2• together with nonflammable gaseous products were evolved from phosphoric/nitrogen compounds in the gas phase, which quenched the flammable free radicals in the matrix and diluted the concentration of combustible gaseous products generated from PRUF during combustion. The compact char residues which acted as excellent physical barriers were formed by catalysis of EG and phosphoric/nitrogen compounds in the condense phase. The fire hazard of RPUF was significantly reduced by the synergistic effect of phosphorus-nitrogen compounds and EG. This work provides a promising strategy to enhance the fire safety of RPUF.

RuO2 Particles Anchored on Brush-Like 3D Carbon Cloth Guide Homogenous Li/Na Nucleation Framework for Stable Li/Na Anode.

Lithium (sodium)-metal batteries are the most promising batteries for next-generation electrical energy storage due to their high volumetric energy density and gravimetric energy density. However, their applications have been prevented by uncontrollable dendrite growth and large volume expansion during the stripping/plating process. To address this issue, the key strategy is to realize uniform lithium (sodium) deposition during the stripping/plating process. Herein, a thin lithiophilic layer consisting of RuO2 particles anchored on brush-like 3D carbon cloth (RuO2 @CC) is prepared by a simple solution-based method. After infusion of Li, the RuO2 @CC transfers to Li-Ru@CC. Ru nanoparticles not only play a role in leading Li+ (Na+ ) to plate on the 3D carbon framework, but also lower local current density because of the good electrical conductivity. Furthermore, density functional theory calculations demonstrate that Ru metal, the reaction product of alkali metal and Ru, can lead Li+ to plate evenly around carbon fiber owing to the strong binding energy with Li+ . The Li-Ru@CC anode shows ultralong cycle life (1500 h at 5 mA cm-2 ). The full cell of Li-Ru@CC|LiFePO4 exhibits lower polarization (90% capacity retention after 650 cycles). In addition, sodium metal batteries based on Na-Ru@CC anodes can achieve similar improvement.

Reinforcing and toughening bacterial cellulose/MXene films assisted by interfacial multiple cross-linking for electromagnetic interference shielding and photothermal response.

Ultrathin MXene composite films, with their flexibility, metal-level conductivity, and multifunction compatibility, are an ideal choice for electromagnetic interference (EMI) shielding materials in future developments. Nonetheless, the dilemma between electrical conductivity and robustness in these composite films remains a challenge. Herein, an ammonium polyphosphate (APP) assisted interfacial multiple cross-linking strategy, achieved via simple solution blending and filtration, was employed to reinforce and toughen the "brick-mortar" layered MXene/bacterial cellulose (MBCA) films without compromising their conductivity and EMI shielding ability. The introduction of a small amount of APP leads to multiple interfacial interactions between MXene and bacterial cellulose, resulting in significant enhancements in mechanical strength (360.8 MPa), Young's modulus (2.8 GPa), fracture strain (17.3%), and toughness (34.1 MJ/m3). Concurrently, the MBCA film displayed satisfactory conductivity values of 306.7 S/cm and an EMI SE value of 41 dB upon optimizing the MXene content. Additionally, the MBCA film demonstrated a consistent, rapid-response photothermal conversion capability, achieving a photothermal conversion temperature of 97 °C under a light intensity of 200 mW/m2. Consequently, this tough and multifunctional EMI shielding film holds substantial promise for protecting electronic equipment.

Ultrafine aramid nanofibers prepared by high-efficiency wet ball-milling-assisted deprotonation for high-performance nanopaper.

Aramid nanofibers (ANFs) with a nanoscale diameter, large aspect ratio, and exposed electronegative surface, as well as ultrahigh thermal/chemical inertness and extreme mechanical properties, provide promising applications in many emerging fields, but these are greatly limited by the low preparation efficiency and broad diameter distribution. Herein, we put forward a high-efficiency wet ball milling-assisted deprotonation (BMAD) strategy to rapidly prepare ANFs with an ultrafine diameter. The strong shear and collision forces from ball-milling induced stripping and splitting effects on the macroscopic fibers, which promoted the penetration and expanded the contact interfaces between reactants, thus accelerating the deprotonation reaction and refining the ANF diameter. As a result, ultrafine ANFs with a diameter of only 2.09 nm and high concentration (1 wt%) were successfully achieved within 30 min. This BMAD strategy represents a vastly advantageous approach compared to the existing reported ANF preparation approaches in terms of efficiency (20 g L-1 h-1) and fiber diameter. The ultrafine microstructure leads to the corresponding ANF nanopaper having more compact stacking and fewer defects, thus exhibiting extraordinary mechanical properties including tensile strength (271.7 MPa) and toughness (33.1 MJ m-3). This work achieves significant progress toward high-efficiency production of ultrafine ANFs, bringing about appreciable prospects in preparing promising multifunctional ANF-based materials.

Transparent and Stretchable Electromagnetic Interference Shielding Film with Fence-like Aligned Silver Nanowire Conductive Network.

Flexible transparent conductive electrodes (TCEs) that can be used as electromagnetic interference (EMI) shielding materials have a great potential for use as electronic components in optical window and display applications. However, development of TCEs that display high shielding effectiveness (SE) and good stretchability for flexible electronic device applications has proven challenging. Herein, this study describes a stretchable polydimethylsiloxane (PDMS)/silver nanowire (AgNW) TCE with a fence-like aligned conductive network that is fabricated via pre-stretching method. The fence-like AgNW network endowed the PDMS/AgNW film with excellent optoelectronic properties, i.e., low sheet resistance of 7.68 Ω sq-1 at 73.7% optical transmittance, thus causing an effective EMI SE of 32.2 dB at X-band. More importantly, the fence-like aligned AgNW conductive network reveals a high stability toward tensile deformation, thus gives the PDMS/AgNW film stretch-stable conductivity and EMI shielding property in the strain range of 0-100%. Typically, the film can reserve ≈70% or 80% of its initial EMI SE when stretching at 100% strain or stretching/releasing (50% strain) for 128 cycles, respectively. Additionally, the film exhibits a low-voltage driven and stretchable Joule heating performance. With these overall performances, the PDMS/AgNW film should be well suited for use in flexible and stretchable optical electronic devices.

Architecting fire safe hierarchical polymer nanocomposite films with excellent electromagnetic interference shielding via interface engineering.

Integrating high flame retardancy and excellent electromagnetic interference (EMI) shielding into polymetric materials is extremely necessary, and well dispersing conductive fillers into polymeric materials is still a great challenge because of incompatible interfacial polarity between polymer matrix and conductive fillers. Therefore, under the premise of maintaining integral conductive films in the process of hot compression, constructing a novel EMI shielding polymer nanocomposites where conductive films closely adhere to polymer nanocmposites layers should be a fascinating stratety. In this work, salicylaldehyde-modified chitosan decorated titanium carbide nanohybrid (Ti3C2Tx-SCS) was combined with piperazine-modified ammonium polyphosphate (PA-APP) to fabricate thermoplastic polyurethane (TPU) nanocomposites, which were used for construction of hierarchical nanocomposite films by inserting reduced graphene oxide (rGO) films into TPU/PA-APP/Ti3C2Tx-SCS nanocomposite layers through our self-developed air assisted hot pressing technique. The total heat release, total smoke release and total carbon monoxide yield for TPU nanocomposite containing 4.0 wt% Ti3C2Tx-SCS nanohybrid were 58.0%, 58.4% and 75.8% lower than those of pristine TPU, respectively. Besides, the hierarchical TPU nanocomposite film containing 1.0 wt% Ti3C2Tx-SCS presented an averaged EMI shielding effectiveness of 21.3 dB in X band. This work provides a promising strategy for fabricating fire safe and EMI shielding polymer nanocomposites.

Tunable construction of fire safe and mechanically strong hierarchical composites towards electromagnetic interference shielding.

Cotton fabric composites were designed to be protected by fire safe thermoplastic polyurethane (TPU) composites for developing electromagnetic interference (EMI) shielding polymer composites with superior mechanical properties. Herein, the as-prepared MXene was coated onto the fiber surface of cotton and then thermally compressed with TPU composites, which were filled with the sodium dodecyl sulfate modified layered double hydroxides functionalized the short carbon fiber hybrids through melt blending method. Then, a series of highly fire safe cotton/TPU hierarchical composites were constructed by a designed thermal compression technique. For instance, the obtained cotton/TPU hierarchical sample showed greatly reduced peak of heat release rate, peak of carbon monoxide production rate and peak of carbon dioxide production rate of TPU by 50.1%, 52.1% and 55.4%, respectively. Furthermore, the cotton/TPU hierarchical composites possessed the EMI shielding effectiveness of 40.0 dB in the X band and 54.6 dB in the K band. The mechanical property of the cotton/TPU hierarchical composites was also reinforced, where the elongation at break and toughness values of the TPU/SCF/mLDH1/C2 hierarchical composite were 21.47 and 18.30 times higher than those of pure TPU, respectively. These mechanically strong hierarchical composites have brought a promising attempt to broaden their practical application, removing the fire hazards and electromagnetic waves radiation from the environment.

Multifunctional magnetic sponge with outstanding solar/electro-thermal performance for high-efficiency and all-day continuous cleanup of crude oil spills.

The high-efficient, eco-friendly and low-energy cleanup of viscous crude oil spills is still a global challenge. Emerging absorbents with self-heating function are promising candidates due to that they can significantly decrease crude oil viscosity via in-situ heat transfer so as to accelerate remediation. Herein we developed a novel multifunctional magnetic sponge (P-MXene/Fe3O4@MS) with outstanding solar/electro-thermal performance by facilely coating Ti3C2TX MXene, nano-Fe3O4 and polydimethylsiloxane onto melamine sponge for fast crude oil recovery. Superior hydrophobicity (water contact angle of 147°) and magnetic responsivity allowed P-MXene/Fe3O4@MS to be magnetically driven for oil/water separation and easy recycling. Owing to excellent full-solar-spectrum absorption (average absorptivity of 96.5 %), effective photothermal conversion and high conductivity (resistance of 300 Ω), P-MXene/Fe3O4@MS possessed remarkable solar/Joule heating capability. The maximum surface temperature of P-MXene/Fe3O4@MS could quickly reach 84 °C under a solar irradiation of 1.0 kW/m2 and 100 °C after applying a voltage of 20 V. The generated heat induced a significant decrease of crude oil viscosity, enabling the composite sponge to absorb more than 27 times its weight of crude oil within 2 min (1.0 kW/m2 irradiation). More importantly, by means of the synergistic effect of Joule heating and solar heating, a pump-assisted absorption device based on P-MXene/Fe3O4@MS was able to realize the high-efficiency and all-day continuous separation of high-viscosity oil on water surface (crude oil flux = 710 kg m-2 h-1). The new-typed multifunctional sponge provides a competitive approach for dealing with large-area crude oil pollution.

Vanadium fluorophosphates: advanced cathode materials for next-generation secondary batteries.

Next-generation secondary batteries including sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are considered the most promising candidates for application to large-scale energy storage systems due to their abundant, evenly distributed and cost-effective sodium/potassium raw materials. The electrochemical performance of SIBs (PIBs) significantly depends on the inherent characteristics of the cathode material. Among the wide variety of cathode materials, sodium/potassium vanadium fluorophosphate (denoted as MVPF, M = Na and K) composites are widely investigated due to their fast ion transportation and robust structure. However, their poor electron conductivity leads to low specific capacity and poor rate capacity, limiting the further application of MVPF cathodes in large-scale energy storage. Accordingly, several modification strategies have been proposed to improve the performance of MVPF such as conductive coating, morphological regulation, and heteroatomic doping, which boost the electronic conductivity of these cathodes and enhance Na (K) ion transportation. Furthermore, the development and application of MVPF cathodes in SIBs at low temperatures are also outlined. Finally, we present a brief summary of the remaining challenges and corresponding strategies for the future development of MVPF cathodes.

A Multifunctional Interphase Layer Enabling Superior Sodium-Metal Batteries under Ambient Temperature and -40 °C.

The sodium (Na)-metal anode with high theoretical capacity and low cost is promising for construction of high-energy-density metal batteries. However, the unsatisfactory interface between Na and the liquid electrolyte induces tardy ion transfer kinetics and dendritic Na growth, especially at ultralow temperature (-40 °C). Herein, an artificial heterogeneous interphase consisting of disodium selenide (Na2 Se) and metal vanadium (V) is produced on the surface of Na (Na@Na2 Se/V) via an in situ spontaneous chemical reaction. Such interphase layer possesses high sodiophilicity, excellent ionic conductivity, and high Young's modulus, which can promote Na-ion adsorption and transport, realizing homogenous Na deposition without dendrites. The symmetric Na@Na2 Se/V cell exhibits outstanding cycling life span of over 1790 h (0.5 mA cm-2 /1 mAh cm-2 ) in carbonate-based electrolyte. More remarkably, ab initio molecular dynamics simulations reveal that the artificial Na2 Se/V hybrid interphase can accelerate the desolvation of solvated Na+ at -40 °C. The Na@Na2 Se/V electrode thus exhibits exceptional electrochemical performance in symmetric cell (over 1500 h at 0.5 mA cm-2 /0.5 mAh cm-2 ) and full cell (over 700 cycles at 0.5 C) at -40 °C. This work provides an avenue to design artificial heterogeneous interphase layers for superior high-energy-density metal batteries at ambient and ultralow temperatures.

Functional MXene-Based Materials for Next-Generation Rechargeable Batteries.

MXenes are seen as an exceptional candidate to reshape the future of energy with their viable surface chemistry, ultrathin 2D structure, and excellent electronic conductivity. The extensive research efforts bring about rapid expansion of the MXene families with enriched functionalities, which significantly boost performance of the existing energy-storage devices. In this review, the strategies that are developed to functionalize the MXene-based materials, including tailoring their microstructure by ions/molecules/polymers-initiated interaction or self-assembly, surface/interface engineering with dopants or functional groups, constructing heterostructures from MXenes with various materials, and transforming them into a series of derivatives inheriting the merits of the MXene precursors are highlighted. Their applications in emerging battery technologies are demonstrated and discussed. With delicate functionalization and structural engineering, MXene-based electrode materials exhibit improved specific capacity and rate capability, and their presence further suppresses and even eliminates dendrite formation on the metal anodes, which lengthens the lifespan of the rechargeable batteries. Meanwhile, MXenes serve as additives for electrolytes, separators, and current collectors. Finally, some future directions worth of exploration to address the remaining challenging issues of MXene-based materials and achieve the next-generation high-power and low-cost rechargeable batteries are proposed.