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Lithium iron silicate, Li2FeSiO4, is a promising cathode material for lithium ion batteries due to its high theoretical specific capacity, earth abundance, low cost, and environmental friendliness.

Li metal has been widely recognized as a promising anode candidate for high-energy-density batteries. However, the inherent limitations of Li metal, that is, the low Coulombic efficiency and dendrite issues, make it still far from practical applications. In short, the low Coulombic efficiency shortens the cycle life of Li metal batteries, while the dendrite issue raises safety concerns. Thanks to the great efforts of the research community, prolific fundamental understanding as well as approaches for mitigating Li metal anode safety have been extensively explored. In this Review, Li electrochemical deposition behaviors have been systematically summarized, and recent progress in electrode design and electrolyte system optimization is reviewed. Finally, we discuss the future directions, opportunities, and challenges of Li metal anodes.

Lithium metal is the most attractive anode material owing to its lowest electrochemical potential and high theoretical specific capacity. However, uncontrolled dendrite growth leads to severe safety issues and poor electrochemical stability, hindering its practical application. Herein, we report a dendrite-free and reversible Li metal anode enabled by graphene aerogel (GA) host with three-dimensional gradient porous structure. The gradient porous structure facilitates reversible Li plating/stripping with high Li/carbon mass ratio (Li/C = 5) and realizes uniform Li distribution on the electrode surface. This approach achieves a stable voltage profile for a long lifespan (1300 h at 2 mA cm−2 for 2 mAh cm−2 and 1000 h at 5 mA cm−2 for 3 mAh cm−2) with superior high symmetric cumulative capacity (2500 mAh cm−2). Coupling the LiGA anode with a LiFePO4 (LFP) cathode, a stable cycling of the full LiGA-LFP cells for 200 cycles at 2 C were achieved, demonstrating the promising practical applications of LiGA in advanced rechargeable batteries.

Direct utilization of Na metal anode, instead of carbon or alloy-based anode, is highly desired in Na-ion batteries mainly because of its lowest operating potential and high capacity. Nevertheless, unstable solid electrolyte interphase and uncontrollable Na dendrite growth during the repetitive Na deposition/stripping process usually lead to the low Coulombic efficiency and safety hazards. Herein, dendrite-free Na deposition/stripping can be achieved via constructing a protective PVDF layer on Cu current collector through a facile and scalable doctor blade coating technique. As a result, PVDF@Cu current collector exhibits a stable cycling lifetime for 1200 h with a small overpotential (∼35 mV) at 1 mA cm−2, which is 6 times longer than the bare Cu current collector (∼200 h). Furthermore, PVDF@Cu current collector delivers a high average CE of 99.91% for 2000 h at 1 mA cm−2. The excellent electrochemical performances of PVDF@Cu current collectors are found to arise from the formation of a stable solid electrolyte interphase consisted of Na2O2 with a high shear modulus and rich NaF with a fast Na ion migration based on the defluorination reaction between PVDF and Na metal anode, which synergistically suppresses Na dendrite growth. This approach provides a new opportunity to stabilize Na metal anode.

Platinum (Pt) is a critical element in making electrocatalysts for oxygen reduction reaction (ORR) occurring at the cathode of polymer electrolyte membrane fuel cells (PEMFCs). To address the Pt abundance issue and to enhance Pt catalysis, Pt is often alloyed with another transition metal M (i.e. M = Fe, Co, and Ni). Ordered intermetallic PtM alloys are considered as one of the most promising candidates to achieve both high activity and stability in practical fuel cell applications. The transition metals in ordered intermetallic PtM alloys occupy specific sites, and are stabilized by both metallic and ionic bonding. Ordered intermetallic structures are formed via high temperature (>600 °C) annealing of disordered PtM alloys, as the atomic ordering is a thermodynamically driven process. However, the high temperature annealing inevitably leads to the migration and agglomeration of the nanoparticles forming randomly alloyed particles with poor dispersion and broad size distributions, due to weak adhesions to the carbon support under typical processing conditions. To prevent this coalescence during annealing, protective coating of the nanoparticles with inorganic shells or physical barriers has been suggested. However, these studies were limited to the synthesis of intermetallic nanoparticles on carbon supports at low metal loadings, or require an additional step of removing the coating layer from the surface of the nanoparticles to expose the active sites. Thus, it is essential to develop a general approach that can produce highly dispersed, structurally ordered nanoparticles while achieving controls over the size and size distribution. We propose to use the functionalized carbon supports to control PtM alloy nanoparticle size and prevent nanoparticles from aggregating during the high temperature annealing through improving the metal-support interactions. A strong electrostatic attraction between the negative charge from Pt precursor (PtCl6 2 -) and positive charge from the amino groups (C-NH2+) on the surface of the functionalized carbon will be established during the wet impregnation synthesis. Such bonds will help to make the PtM nanoparticle size smaller and more uniformly distributed over the surface of support. The ordered intermetallic 30 wt.% PtCo/KB-NH2 catalyst demonstrated an average size of 2.7 nm and uniform size distribution. In addition, 30 wt.% PtCo/KB-NH2 catalyst exhibited a mass activity of 535 A/gPt (H2/O2) and a rated power density of 1.05 W/cm2 at 0.67 V (H2/air), meeting the DOE targets.

Metal phosphide based anodes for potassium-ion batteries (KIBs) have attracted increasing attention due to their high theoretical capacities and appropriate operating voltages. In this work, monodisperse SnP0.94 nanoplates are synthesized through a facile hot-injection method, followed by the fabrication of a SnP0.94 nanoplates/graphene oxide (SnP0.94@GO) composite. The results show that as-prepared SnP0.94@GO composite can serve as a novel anode for KIBs, and exhibit superior potassium storage performance.

The expanding energy storage market has created a surge of interest in the exploration of high energy density alternatives to Li-ion batteries, and Na metal batteries have received considerable attention due to their abundant reserves and low cost. Similar to Li metal anodes, the unstable plating/stripping behaviors of Na metal anodes upon cycling hinder their practical applications at room temperature. Herein, a superelastic graphene lattice (GL) with hierarchical structures was fabricated via a 3D printing technique on the basis of the direct inkjet writing strategy. This approach enables the precise tailoring of the multiscale graphene bulk structure, from nanometer GO building elements to macroscopic monoliths. Due to the pore-structure design of the GL, the rim regions of the holes demonstrated a highly concentrated current density and could serve as preferred sites for Na deposition. This phenomenon was utilized to regulate the Na deposition; hence, a stable Na metal anode is produced. As a result, ...

Intractable hurdles of low Coulombic efficiency and dendritic Li formation during a repeated deposition/stripping process hinder the commercial use of Li metal anode for next-generation battery systems. Achieving uniform Li nucleation is one of the effective strategies to address these issues, and it is of practical importance to realize this on a commercial Cu current collector that is lithiophobic. Herein, we design a nanostructured Ag lithiophilic layer on a Cu foil via an electroless plating process for a Li metal current collector. The deposition of lithiophilic Ag particles that are homogeneously distributed on the Cu foil can reduce the nucleation overpotential, realizing uniform Li nucleation and subsequently flat Li plating. As a result, a stable cycle stability of up to 360 h (1 mA cm

The increasing demand for high-specific-energy batteries drives researchers to revisit Li metal anode. However, the formation and growth of Li-dendrite possibly leads to short-circuit of the battery, causing safety hazard of Li metal batteries. Therefore, it is quite necessary to regulate the plating/stripping behaviors of Li metal anodes to address this long-standing issue. Herein, we report the regulation of Li plating/striping behavior via manipulating the ratio of oxygen containing groups on reduced graphene oxide papers. It has been revealed that the electrochemical properties are highly dependent on the amount of carbonyl C O groups, which could associate Li+ and serve as a uniform nucleation site to guide Li plating. Furthermore, a high lithium ion diffusion coefficient of ∼2.09 × 10−14 m2 s−1 was enabled, around one magnitude higher than that of the Li lattice self-diffusivity (∼2 × 10−15 m2 s−1). As a result, stable dendrite-free Li metal anode is realized on the reduced graphene oxide paper with high C O group content (8.4%), which exhibits a low and stable overpotential of 50 mV for a long lifetime of 400 h. Our studies provide a fresh insight into the Li ion diffusion and its critical role in the regulation of the Li plating/stripping behaviors.

Yolk–shell structured SnSe nanoparticles have been investigated as anode materials in Na-ion batteries for the first time. These SnSe nanoparticles can deliver an initial de-sodiation capacity of 355.8 mA h g−1 at 500 mA g−1 with a high capacity retention of 72.5% after 150 cycles and exhibit excellent rate capabilities. The significant capacitive contribution in the total Na+ storage of the SnSe electrode is identified, which should account for its superior rate performance.

Sn-Based materials are considered as promising anode materials for lithium ion batteries due to their high theoretical capacities; however, aggregation of electrochemically active particles and pulverization resulting from huge volume changes during alloying/dealloying severely limit their performance. To solve these problems, nanosized and hollow structures have been proposed. Herein, uniform solid Sn nanoparticles and hollow/amorphous SnOx nanospheres are prepared accordingly and their electrochemical performances as anode materials in lithium ion batteries have been evaluated. Uniform solid Sn nanoparticles deliver a capacity of 416.4 mA h g−1 for 400 cycles at a current of 500 mA g−1, corresponding to a high capacity retention of 81.1%. Furthermore, hollow/amorphous SnOx nanospheres show a high capacity retention of 81.3% for 400 cycles at a current of 500 mA g−1 and exhibit a good rate capability (retains 58.0% of the capacity at 1000 mA g−1 with respect to 100 mA g−1). It is believed that their good electrochemical performances mainly originate from their small sizes (

The irreversible lithium loss due to the formation of solid electrolyte interphase (SEI) in the initial cycle greatly reduced the overall cell energy density of lithium ion batteries. Cathode prelithiation methods have been widely explored to compensate this lithium loss. However, these cathode additives with high lithium contents inevitable lower the active cathode materials loading. Here we report a facile graphite prelithiation method by pre-forming SEI layers on graphite surface (Pre-SEI graphite) in a flow cell. The Li accommodation in graphite anode could be controlled by the operation of the time and current density in flow cell for the electrochemical SEI formation. As a result, we demonstrate a 10% initial Columbic efficiency increase of the LiFePO4 electrode in a full cell configuration with our Pre-SEI graphite. The electrochemical pre-formation of SEI on graphite offers a novel route to offset initial lithium loss without a sacrifice of active cathode loading.

Chondrogenesis and subsequent osteogenesis of mesenchymal stem cells (MSCs) and angiogenesis at injured sites are crucial for bone fracture healing. Amygdalin, a cyanogenic glycoside compound derived from bitter apricot kernel, has been reported to inhibit IL-1β-induced chondrocyte degeneration and to stimulate blood circulation, suggesting a promising role of amygdalin in fracture healing. In this study, tibial fractures in C57BL/6 mice were treated with amygdalin. Fracture calluses were then harvested and subjected to radiographic, histological, and biomechanical testing, as well as angiography and gene expression analyses to evaluate fracture healing. The results showed that amygdalin treatment promoted bone fracture healing. Further experiments using MSC-specific transforming growth factor- (TGF-) β receptor 2 conditional knockout (KO) mice (Tgfbr2Gli1-Cre) and C3H10 T1/2 murine mesenchymal progenitor cells showed that this effect was mediated through TGF-β/Smad signaling. We conclude that amygdalin could be used as an alternative treatment for bone fractures.

In this article, by composing three functional constituents into a multilayered structure with well-bonded interfaces, a conductive graphene-papers (GPs)/glass-fibers (GFs) reinforced epoxy composite (GPs-GE) with outstanding mechanical robustness, high electrical conductivity and sensitive stimuli-responsive performance is highlighted. Thereinto, GPs serves as a stimuli-responsive and Joule heating chip due to its superiorities on both of mechanical and electrical properties, while GFs possessing mechanically protective and strengthening functionality. The stimuli-responsive characterizations by electrical resistance change reveal the synchronous sensing properties of GPs-GE to different stimuli inputs such as mechanical deformation, temperature fluctuation and humidity. Subsequently, Joule heating and de-icing/anti-icing properties of GPs-GE are investigated symmetrically, indicating its large heating rate, high efficiency of energy conversion and low cost. Such superior performance of GPs-GE confirms that the design of multilayer microstructure to achieve multi-functionalization paves a novel way to scale-up fabrication of advanced graphene composites, indicating promising applications as mechanically reinforcing elements, stimuli-responsive sensors and electrical Joule heating chips in intelligent engineering monitoring and icing-induced disaster prevention at low-temperature environment.

A fluoroalkyl-silane (FS)-modified three-dimensional (3D) graphene foam (GF) composite (FS-GF) with a hierarchical porous microstructure was fabricated via a nickel foam template chemical vapor deposition and followed modification. The 3D GF, as an electrically conductive framework and hydrophobic porous substrate, was grafted with FS to further improve the hydrophobicity due to its long non-polar molecular chains and numerous fluoric/silicon functional groups. Porous FS-GF with high electrical conductivity (~650 S/m) is functionalized as a Joule-heating mesh for airflow, which synchronously demonstrates rapid heating rates, high conversion efficiencies, and uniform temperature distributions. Moreover, FS-GF exhibits self-cleaning and anti-icing properties that are superior to metallic and inorganic coatings. The outstanding performances of FS-GF suggest the potential for functionalizing 3D graphene composites using hierarchical structures at the multi-scale and chemical modifications of functional molecular groups.

We report a mild synthetic method to access Sn nanocrystals with tunable diameter and narrow size distribution (6–8%). The self-templated formation of various types of Sn chalcogenide hollow nanostructures including oxides, sulfides, selenides, and tellurides is also demonstrated for the first time. The use of air-stable tungsten hexacarbonyl that produces carbon monoxide at elevated temperature to reduce the SnCl2 precursor and coordinate the nanoparticle surface is thought to play an essential role in this method. This synthesis method is likely to be extended to other metal systems and could find potential applications including battery anodes and catalysts.

The proton conduction within a catalyst layer is one of the critical factors affecting the performance of membrane electrode assembly in polymer electrolyte fuel cells. In this work, a simple and effective approach for providing surface proton conduction over carbon supports was developed utilizing chemically grafting SO3H and COOH groups covalently bonded onto carbon surface. A method for accurately measuring the proton conductivity within a catalyst layer was also developed which physically excluded the conductivity contribution from the membrane. This method has several advantages: 1) providing easy sample preparation with high reproducibility, 2) allowing the control of measurement conditions such as gas flow rate, relative humidity and temperature to mimic the exact fuel cell operating conditions. The proton and electron conductivities of the catalyst layers made with and without functional groups at different relative humidifies were characterized with a specially designed 4-probe cell using the AC impedance spectroscopy technique. The results clearly demonstrated that the introduction of functional groups (i.e., SO3H and COOH) did result in a significant improved surface proton conduction over carbon surface and the resulted conductivity depends on the relative humidity, temperature and porosimetry of the carbon blacks.

In this article, thin flexible sandwiched graphite-PET sheets (GPSs) with 10 μm thick graphite interlayer as self-heating element are developed and reveal a desirable electrical resistance and an excellent mechanical flexibility. Employing these promising properties, a GPS-based self-snow-thawing pavement system is proposed with GPSs adopted as a high efficient electro-heating element. Powered by the alternative energies (grid power or solar energy), the snow-thawing experiments are implemented at the outdoor site under the impacts of multi-parameters (ambient temperature, wind speed, snow density and thickness and input power). The temperature distributions of pavement, feasibility, time/energy efficiency and economic cost are systematically evaluated through snow-thawing experiments. With advantages of desirable feasibility, high efficiency, long-term stability, low economic cost and environmental protection, the GPS-based self-snow-thawing pavement is verified promising potential in snow-thawing applications.

A novel natural drying (ND) strategy for low-cost and simple fabrication of graphene aerogels (GAs) is highlighted. The as-formed NDGAs exhibit ultralarge reversible compressibility (99%) and tunable Poisson's ratio behaviors (-0.30 < ν < 0.46), which suggests promising applications in soft actuators, soft robots, sensors, deformable electronic devices, drug release, thermal insulator, and protective materials.

Using dc magnetron sputtering, Fe/Pt/Au multilayer films were prepared, and the effects of Au layer thickness and annealing temperature on structure and magnetic properties of the Fe/Pt/Au multilayer films were investigated. The as-deposited Fe/Pt/Au multilayer films have good periodic structure with composition modulation along the growth direction. The stress stored in the as-deposited films promoted the ordering of the films annealed at 400 °C. When the films were annealed at 500 °C, the thicker Au layer could restrain the order–disorder transformation region volume and lead to the decrease of the ordered volume fraction with Au layer thickness increasing.

FePt (20 nm) films with AgCu (20 nm) underlayer were prepared on thermally oxidized Si (0 0 1) substrates at room temperature by using dc magnetron sputtering, and the films annealed at different temperature to examine the disorder–order transformation of the FePt films. It is found that the ordered L 1 0 FePt phase can form at low annealing temperature. Even after annealing at 300 °C, the in-plane coercivity of 5.2 kOe can be obtained in the film. With increase in annealing temperature, both the ordering degree and coercivity of the films increase. The low-temperature ordering of the films may result from the dynamic stress produced by phase separation in AgCu underlayer and Cu diffusion into FePt phase during annealing.

A hyperbolically patterned 3D graphene metamaterial (GM) with negative Poisson's ratio and superelasticity is highlighted. It is synthesized by a modified hydrothermal approach and subsequent oriented freeze-casting strategy. GM presents a tunable Poisson's ratio by adjusting the structural porosity, macroscopic aspect ratio (L/D), and freeze-casting conditions. Such a GM suggests promising applications as soft actuators, sensors, robust shock absorbers, and environmental remediation.

Conduction of pressurized water through two-dimensional (2D) layers in monolithic folded-graphene aerogels (FGA) is investigated experimentally. The synthesized FGA has a regular layered structure with a uniform d-spacing around 20 nm. Compared with one-dimensional nanofluidics in carbon nanotube arrays that have a similar characteristic length scale, the conduction pressure of FGA is much lower by nearly 2/3. The reduction in pressure may be attributed to the more energetically favourable molecular configurations in the 2D nanoenvironment, associated with the relaxation of lateral constraints of water molecules. The water conduction pressure through FGA rises exponentially with the sample thickness, due to the interlayer resistance. This finding may find wide applications in nanotransportation, nanofiltration, and nanofluidic energy management.

Using dc magnetron sputtering, FePt/Au multilayer films were prepared, and the effects of Au thickness and annealing temperature on structure and magnetic properties of the FePt/Au films were investigated. The as-deposited FePt/Au multilayer films with a thicker Au layer show a superlattice structure. The interatomic layer spacing d(2 2 0) in face centered cubic (fcc) FePt lattice increases with increase in Au thickness. Accordingly, the strain energy stored in the fcc FePt lattice increases. After annealing at 300 °C, ordered FePt films were obtained, and the in-plane and out-of-plane coercivities of the films were found to increase with the increase in the Au layer thickness. When the Au layer thickness is 3.5 nm, the in-plane and out-of-plane coercivities of the films can reach 2.08 kOe and 1.56 kOe, respectively. The strain energy stored in fcc FePt lattice is responsible for the lower temperature ordering of FePt phase. For the films annealed at high temperature, the thicker Au layer in the films restrained the ordering of the FePt phase, which leads to the decrease in the coercivities of the films with increasing Au thickness.