Unlocking the Potential of Iron Sulfides for Sodium-Ion Batteries by Ultrafine Pulverization.

Iron sulfides have attracted tremendous research interest for the anode of sodium-ion batteries due to their high capacity and abundant resource. However, the intrinsic pulverization and aggregation of iron sulfide electrodes induced by the conversion reaction during cycling are considered destructive and undesirable, which often impedes their capacity, rate capability, and long-term cycling stability. Herein, an interesting pulverization phenomenon of ultrathin carbon-coated Fe1- xS nanoplates (Fe1- xS@C) is observed during the first discharge process of sodium-ion batteries, which leads to the formation of Fe1- xS nanoparticles with quantum size (≈5 nm) tightly embedded in the carbon matrix. Surprisingly, no discernible aggregation phenomenon can be detected in subsequent cycles. In/ex situ experiments and theoretical calculations demonstrate that ultrafine pulverization can confer several advantages, including sustaining reversible conversion reactions, reducing the adsorption energies, and diffusion energy barriers of sodium atoms, and preventing the aggregation of Fe1- xS particles by strengthening the adsorption between pulverized Fe1- xS nanoparticles and carbon. As a result, benefiting from the unique ultrafine pulverization, the Fe1- xS@C anode simultaneously exhibits high reversible capacity (610 mAh g-1 at 0.5 A g-1), superior rate capability (427.9 mAh g-1 at 20 A g-1), and ultralong cycling stability (377.9 mAh g-1 after 2500 cycles at 20 A g-1).

Water-Stabilized Vanadyl Phosphate Monohydrate Ultrathin Nanosheets toward High Voltage Al-Ion Batteries.

Al ion batteries (AIBs) are attracting considerable attention owing to high volumetric capacity, low cost, and high safety. However, the strong electrostatic interaction between Al3+ and host lattice leads to discontented cycling life and inferior rate capability. Herein, a new strategy of employing water molecules contained VOPO4 ·H2 O to boost Al3+ migration via the charge shielding effect of water is reported. It is revealed that VOPO4 ·H2 O with water lubrication effect and smaller steric hindrance owns high capacity and fast Al3+ diffusion, while the loss of unstable water upon cycling leads to a rapid performance degradation. To address this problem, ultrathin VOPO4 ·H2 O@MXene nanosheets are fabricated via the formed TiOV bond between VOPO4 ·H2 O and MXene. The MXene aided exfoliation results in enhanced VOwater bond strength between H2 O and VOPO4 that endows the obtained composite with strong water holding ability, contributing to the extraordinary cycling stability. Consequently, the VOPO4 ·H2 O@MXene delivers a high discharge potential of 1.8 V and maintains discharge capacities of 410 and 374.8 mAh g-1 after 420 and 2000 cycles at the current densities of 0.5 and 1.0 A g-1 , respectively. This work provides a new understanding of water-contained AIBs cathodes and vital guidance for developing high-performance AIBs.

Lithium Azides Induced SnS Quantum Dots for Ultra-Fast and Long-Term Sodium Storage.

Tin sulfide (SnS) is an attractive anode for sodium ion batteries (NIBs) because of its high theoretical capacity, while it seriously suffers from the inherently poor conductivity and huge volume variation during the cycling process, leading to inferior lifespan. To intrinsically maximize the sodium storage of SnS, herein, lithium azides (LiN3 )-induced SnS quantum dots (QDs) are first reported using a simple electrospinning strategy, where SnS QDs are uniformly distributed in the carbon fibers. Taking the advantage of LiN3 , which can effectively prevent the growth of crystal nuclei during the thermal treatment, the well-dispersed SnS QDs performs superior Na+ transfer kinetics and pseudocapacitive when used as an anode material for NIBs. The 3D SnS quantum dots embedded uniformly in N-doped nanofibers (SnS QDs@NCF) electrodes display superior long cycling life-span (484.6 mAh g-1 after 5800 cycles at 2 A g-1 and 430.9 mAh g-1 after 7880 cycles at 10 A g-1 ), as well as excellent rate capability (422.3 mAh g-1 at 20 A g-1 ). This fabrication of transition metal sulfides QDs composites provide a feasible strategy to develop NIBs with long life-span and superior rate capability to pave its practical implementation.

An Ultra-Stable Electrode-Solid Electrolyte Composite for High-Performance All-Solid-State Li-Ion Batteries.

The low ionic and electronic conductivity between current solid electrolytes and high-capacity anodes limits the long-term cycling performance of all-solid-state lithium-ion batteries (ASSLIBs). Herein, this work reports the fabrication of an ultra-stable electrode-solid electrolyte composite for high-performance ASSLIBs enabled by the homogeneous coverage of ultrathin Mg(BH4 )2 layers on the surface of each MgH2 nanoparticle that are uniformly distributed on graphene. The initial discharge process of Mg(BH4 )2 layers results in uniform coverage of MgH2 nanoparticle with both LiBH4 as the solid electrolyte and Li2 B6 with even higher Li ion conductivity than LiBH4 . Consequently, the Li ion conductivity of graphene-supported MgH2 nanoparticles covered with ultrathin Mg(BH4 )2 layers is two orders of magnitude higher than that without Mg(BH4 )2 layers. Moreover, the thus-formed inactive Li2 B6 with strong adsorption capability toward LiBH4 , acts as a stabilizing framework, which, coupled with the structural support role of graphene, alleviates the volume change of MgH2 nanoparticles and facilitates the intimate contact between LiBH4 and individual MgH2 nanoparticles, leading to the formation of uniform stable interfaces with high ionic and electronic conductivity on each MgH2 nanoparticles. Hence, an ultrahigh specific capacity of 800 mAh g-1 is achieved for MgH2 at 2 A g-1 after 350 cycles.

Stable Aluminum Metal Anode Enabled by Dual-Functional Molybdenum Nanoparticles.

Constructing robust anode with strong aluminophilicity and rapid desolvation kinetics is essential for achieving high utilization, long-term durability, and superior rate performance in Al metal-based energy storage, yet remains largely unexplored. Herein, molybdenum nanoparticles embedded onto nitrogen-doped graphene (Mo@NG) are designed and prepared as Al host to regulate the deposition behavior and achieve homogeneous Al plating/stripping. The monodispersed Mo nanoparticles reduce the desolvation energy barrier and promote the deposition kinetics of Al. Additionally, Mo nanoparticles act as aluminophilic nucleation sites to minimize the Al nucleation overpotential, further guiding uniform and dense Al deposition. As a result, the dual-functional Mo@NG endows Al anodes with low voltage hysteresis, reversible Al plating/stripping with high coulombic efficiency, and excellent high-rate capability under 5 mA cm-2 . Moreover, the as-designed Al metal full batteries deliver a high capacity retention of 92.8% after 3000 cycles at 1 A g-1 . This work provides an effective solution to optimize the electrochemical properties of Al metal anode from the perspective of desolvation and deposition reactions, towards the development of high-safety and long-cycling aluminum-ion batteries.

Designing a hybrid electrode toward high energy density with a staged Li+ and PF6 - deintercalation/intercalation mechanism.

Existing lithium-ion battery technology is struggling to meet our increasing requirements for high energy density, long lifetime, and low-cost energy storage. Here, a hybrid electrode design is developed by a straightforward reengineering of commercial electrode materials, which has revolutionized the "rocking chair" mechanism by unlocking the role of anions in the electrolyte. Our proof-of-concept hybrid LiFePO4 (LFP)/graphite electrode works with a staged deintercalation/intercalation mechanism of Li+ cations and PF6 - anions in a broadened voltage range, which was thoroughly studied by ex situ X-ray diffraction, ex situ Raman spectroscopy, and operando neutron powder diffraction. Introducing graphite into the hybrid electrode accelerates its conductivity, facilitating the rapid extraction/insertion of Li+ from/into the LFP phase in 2.5 to 4.0 V. This charge/discharge process, in turn, triggers the in situ formation of the cathode/electrolyte interphase (CEI) layer, reinforcing the structural integrity of the whole electrode at high voltage. Consequently, this hybrid LFP/graphite-20% electrode displays a high capacity and long-term cycling stability over 3,500 cycles at 10 C, superior to LFP and graphite cathodes. Importantly, the broadened voltage range and high capacity of the hybrid electrode enhance its energy density, which is leveraged further in a full-cell configuration.

Light-Driven Reversible Hydrogen Storage in Light-Weight Metal Hydrides Enabled by Photothermal Effect.

Requiring high temperature for hydrogen storage is the main feature impeding practical application of light metal hydrides. Herein, to lift the restrictions associated with traditional electric heating, light is used as an alternative energy input, and a light-mediated catalytic strategy coupling photothermal and catalytic effects is proposed. With NaAlH4 as the initial target material, TiO2 nanoparticles uniformly distribute on carbon nanosheets (TiO2 @C), which couples the catalytic effect of TiO2 and photothermal property of C, is constructed to drive reversible hydrogen storage in NaAlH4 under light irradiation. Under the catalysis of TiO2 @C, complete hydrogen release from NaAlH4 is achieved within 7 min under a light intensity of 10 sun. Furthermore, owing to the stable catalytic and photothermal effect of TiO2 @C, NaAlH4 delivers a reversible capacity of 4 wt% after 10 cycles with a capacity retention of 85% under light irradiation only. The proposed strategy is also applicable to other light metal hydrides such as LiAlH4 and MgH2 , validating its universality. The concept of light-driven hydrogen storage provides an alternative approach to electric heating, and the light-mediated catalytic strategy proposed herein paves the way to the design of reversible high-density hydrogen storage systems that do not rely on artificial energy.

The Chemistry of Sustainable Energy Conversion and Storage.

The long-term environmental side-effects and finite supply of fossil fuels, which dominate the energy resources in our daily lives, require a transition to renewable and clean energy resources [...].

Hierarchical 3D Cuprous Sulfide Nanoporous Cluster Arrays Self-Assembled on Copper Foam as a Binder-Free Cathode for Hybrid Magnesium-Based Batteries.

On account of easy accessibility, high theoretical volumetric capacity and dendrite-free magnesium (Mg) anode, Mg battery has a great promise to be next generation rechargeable batteries, yet still remains a challenging task in acquiring fast Mg2+ kinetics and effective cathode materials. Herein, hierarchical 3D cuprous sulfide porous nanosheet decorated nanowire cluster arrays with robust adhesion on copper foam (Cu2 S HP/CF), which is employed as a binder-free conversion cathode material for magnesium/lithium hybrid battery, delivering impressively initial and reversible specific capacity of 383 and 311 mAh g-1 at 100 mA g-1 , respectively, which are obviously outperformed corresponding powder cathode in a traditional method by using polymer binder, is reported. Intriguingly, benefiting from the hierarchical nanoporous array architecture and self-assembly feature, Cu2 S HP/CF cathode shows a remarkable cycling stability with a high capacity of 129 mAh g-1 at 300 mA g-1 over 500 cycles. This work not only highlights a guide for designing hierarchical nanoporous materials derived from metal-organic frameworks, but also provides a novel strategy of in situ formation to fabricate binder-free cathodes.

Porous Carbon Nanofibers Encapsulated with Peapod-Like Hematite Nanoparticles for High-Rate and Long-Life Battery Anodes.

Fe2 O3 is regarded as a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe2 O3 anodes, leading to rapid fading of the capacity. Herein, a novel peapod-like nanostructured material, consisting of Fe2 O3 nanoparticles homogeneously encapsulated in the hollow interior of N-doped porous carbon nanofibers, as a high-performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea-like Fe2 O3 nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na-ions. As a consequence, this peapod-like structure exhibits a stable discharge capacity of 1434 mAh g-1 (at 100 mA g-1 ) and 806 mAh g-1 (at 200 mA g-1 ) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g-1 after 1000 cycles and 396 mAh g-1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g-1 . This study provides a promising strategy for developing long-cycle-life LIBs and SIBs.

In Situ Construction of Interface with Photothermal and Mutual Catalytic Effect for Efficient Solar-Driven Reversible Hydrogen Storage of MgH2.

Hydrogen storage in MgH2 is an ideal solution for realizing the safe storage of hydrogen. High operating temperature, however, is required for hydrogen storage of MgH2 induced by high thermodynamic stability and kinetic barrier. Herein, flower-like microspheres uniformly constructed by N-doped TiO2 nanosheets coated with TiN nanoparticles are fabricated to integrate the light absorber and thermo-chemical catalysts at a nanometer scale for driving hydrogen storage of MgH2 using solar energy. N-doped TiO2 is in situ transformed into TiNxOy and Ti/TiH2 uniformly distributed inside of TiN matrix during cycling, in which TiN and Ti/TiHx pairs serve as light absorbers that exhibit strong localized surface plasmon resonance effect with full-spectrum light absorbance capability. On the other hand, it is theoretically and experimentally demonstrated that the intimate interface between TiH2 and MgH2 can not only thermodynamically and kinetically promote H2 desorption from MgH2 but also simultaneously weaken Ti─H bonds and hence in turn improve H2 desorption from the combination of weakened Ti─H and Ti─H bonds. The uniform integration of photothermal and catalytic effect leads to the direct action of localized heat generated from TiN on initiating the catalytic effect in realizing hydrogen storage of MgH2 with a capacity of 6.1 wt.% under 27 sun.

Atomic reconstruction for realizing stable solar-driven reversible hydrogen storage of magnesium hydride.

Reversible solid-state hydrogen storage of magnesium hydride, traditionally driven by external heating, is constrained by massive energy input and low systematic energy density. Herein, a single phase of Mg2Ni(Cu) alloy is designed via atomic reconstruction to achieve the ideal integration of photothermal and catalytic effects for stable solar-driven hydrogen storage of MgH2. With the intra/inter-band transitions of Mg2Ni(Cu) and its hydrogenated state, over 85% absorption in the entire spectrum is achieved, resulting in the temperature up to 261.8 °C under 2.6 W cm-2. Moreover, the hydrogen storage reaction of Mg2Ni(Cu) is thermodynamically and kinetically favored, and the imbalanced distribution of the light-induced hot electrons within CuNi and Mg2Ni(Cu) facilitates the weakening of Mg-H bonds of MgH2, enhancing the "hydrogen pump" effect of Mg2Ni(Cu)/Mg2Ni(Cu)H4. The reversible generation of Mg2Ni(Cu) upon repeated dehydrogenation process enables the continuous integration of photothermal and catalytic roles stably, ensuring the direct action of localized heat on the catalytic sites without any heat loss, thereby achieving a 6.1 wt.% H2 reversible capacity with 95% retention under 3.5 W cm-2.

Solar-Driven Reversible Hydrogen Storage.

The lack of safe and efficient hydrogen storage is a major bottleneck for large-scale application of hydrogen energy. Reversible hydrogen storage of light-weight metal hydrides with high theoretical gravimetric and volumetric hydrogen density is one ideal solution but requires extremely high operating temperature with large energy input. Herein, taking MgH2 as an example, a concept is demonstrated to achieve solar-driven reversible hydrogen storage of metal hydrides via coupling the photothermal effect and catalytic role of Cu nanoparticles uniformly distributed on the surface of MXene nanosheets (Cu@MXene). The photothermal effect of Cu@MXene, coupled with the "heat isolator" role of MgH2 indued by its poor thermal conductivity, effectively elevates the temperature of MgH2 upon solar irradiation. The "hydrogen pump" effect of Ti and TiHx species that are in situ formed on the surface of MXene from the reduction of MgH2 , on the other hand, plays a catalytic role in effectively alleviating the kinetic barrier and hence decreasing the operating temperature required for reversible hydrogen adsorption and desorption of MgH2 . Based on the combination of photothermal and catalytic effect of Cu@MXene, a reversible hydrogen storage capacity of 5.9 wt% is achieved for MgH2 after 30 cycles using solar irradiation as the only energy source.

Size-Controllable Nickel Sulfide Nanoparticles Embedded in Carbon Nanofibers as High-Rate Conversion Cathodes for Hybrid Mg-Based Battery.

The integration of highly-safe Mg anode and fast Li+ kinetics endows hybrid Mg2+ /Li+ batteries (MLIBs) a promising future, but the practical application is circumvented by the lack of appropriate cathodes that enable the realization of an enough participation of Mg2+ in the reactions, resulting in a high dependence on Li+ . Herein, the authors develop a series of size-controllable nickel sulfide nanoparticles embedded in carbon nanofibers (NiS@C) with synergistic effect of particle diameter and carbon content as the cathode material for MLIBs. The optimized particle size is designed to maximize the utilization of the active material and remit internal stress, and appropriate carbon encapsulation efficiently inhibiting the pulverization of particles and accelerates the ability of conducting ions and electrons. In consequence, the representative NiS@C delivers superior electrochemical performance with a highest discharge capacity of 435 mAh g-1 at 50 mA g-1 . Such conversion cathode also exhibits excellent rate performance and remarkable cycle life. Significantly, the conversion mechanism of NiS in MLIBs is unambiguously demonstrated for the first time, affirming the corporate involvement of both Mg2+ and Li+ at the cathodic side. This work underlines a guide for developing conversion-type materials with high rate capability and cyclic performance for energy storage applications.

Identifying the positive role of lithium hydride in stabilizing Li metal anodes.

Lithium hydride has been widely identified as the major component of the solid-electrolyte interphase of Li metal batteries (LMBs), but is often regarded as being detrimental to the stabilization of LMBs. Here, we identify the positive and important role of LiH in promoting fast diffusion of Li ions by building a unique three-dimensional (3D) Li metal anode composed of LiMg alloys uniformly confined into graphene-supported LiH nanoparticles. The built-in electric field at the interface between LiH with high Li ion conductivity and LiMg alloys effectively boosts Li diffusion kinetics toward favorable Li plating into lithiophilic LiMg alloys through the surface of LiH. Therefore, the diffusion coefficient of Li ions of the thus-formed 3D structured Li metal anode is 10 times higher than the identical anode without the presence of LiH, and it exhibits a long cycle life of over 1200 hours at 3 mA cm-2 under 5 mA hour cm-2.

Co-Construction of Solid Solution Phase and Void Space in Yolk-Shell Fe0.4Co0.6S@N-Doped Carbon to Enhance Cycling Capacity and Rate Capability for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs), using low-cost and inherent safety Al metal anodes, are regarded as promising energy storage devices next to lithium-ion batteries. Currently, one of the greatest challenges for AIBs is to explore cathodes suitable for feasible Al3+ insertion/extraction with high structure stability. Herein, a facile co-engineering on solid solution phase and cavity structure is developed via Prussian blue analogues by a simple and facile sulfidation strategy. The obtained uniform yolk-shell Fe0.4Co0.6S@N-doped carbon nanocages (y-s Fe0.4Co0.6S@NC) display a high reversible capacity of 141.3 mA h g-1 at 500 mA g-1 after 100 cycles and a good rate capability of 100.9 mA h g-1 at 1000 mA g-1. The improved performance can be mainly ascribed to the dual merits of the composite; that is, more negative Al3+ formation energy and improved Al3+ diffusion kinetics favored by the solid solution phase and Al3+ insertion/extraction accommodable space stemmed from the yolk-shell structure. Moreover, the reaction mechanism study discloses that the reaction involves the intercalation of Al3+ ions into Fe0.4Co0.6S to generate AllFemConS and elemental Fe and Co.

Metal Hydrides with In Situ Built Electron/Ion Dual-Conductive Framework for Stable All-Solid-State Li-Ion Batteries.

Due to their high theoretical specific capacity, metal hydrides are considered to be one of the most promising anode material for all-solid-state Li-ion batteries. Their practical application suffers, however, from the poor cycling stability and sluggish kinetics. Herein, we report the in situ fabrication of MgH2 and Mg2NiH4 that are uniformly space-confined by inactive Nd2H5 frameworks with high Li-ion and electron conductivity through facile hydrogenation of single-phase Nd4Mg80Ni8 alloys. The formation of MgH2 and Mg2NiH4 nanocrystals could not only shorten Li-ion and electron diffusion pathways of the whole electrode but also relieve the induced stress upon volume changes. Additionally, the robust frameworks constructed by homogeneous distribution of inactive Nd2H5 based on a molecular level could effectively alleviate the volume expansion and phase separation of thus-confined MgH2 and Mg2NiH4. More importantly, it is theoretically and experimentally verified that the uniform distribution of Nd2H5, which is an electronic conductor with a Li-ion diffusion barrier that is much lower than that of MgH2 and Mg2NiH4, could further facilitate the electron and Li-ion transfer of MgH2 and Mg2NiH4. Consequently, the space-confined MgH2 and Mg2NiH4 deliver a reversible capacity of 997 mAh g-1 at 2038 mA g-1 after 100 cycles.

Fast Lithium Ionic Conductivity in Complex Hydride-Sulfide Electrolytes by Double Anions Substitution.

Hydride-based solid-state electrolytes (SSEs) can maintain their stability against Li metal and exhibit high compatibility with a Li metal anode owing to their reducing property and flexible character. However, poor ionic conductivity at room temperature is a major challenge for hydride materials used as SSEs in a lithium ion battery. In this work, a room-temperature fast lithium-ion conductor is explored in response to double anion substitution, (100-x)(3LiBH4 -LiI)-xP2 S5 (LLPx, 0 ≤ x ≤ 50). Among these samples, LLP20 respectively delivers an ionic conductivity up to 3.77 × 10-4 S cm-1 at 30 °C and 1.0 × 10-2 S cm-1 at 100 °C, with a stable electrochemical window of 0-5 V. A Li plating/stripping test has been conducted under a current density of 1.0 mA cm-2 , which exhibits an excellent stability even after 1000 h. Moreover, the all solid-state cell exhibits a remarkable electrochemical performance in a wide temperature range including high reversible capacity, good rate capability, and long cycling durability. These outstanding performances present a practical strategy for developing ambient-temperature, fast ionic conductors for all solid-state batteries in near future.

Amminelithium amidoborane Li(NH3)NH2BH3: a new coordination compound with favorable dehydrogenation characteristics.

The monoammoniate of lithium amidoborane, Li(NH(3))NH(2)BH(3), was synthesized by treatment of LiNH(2)BH(3) with ammonia at room temperature. This compound exists in the amorphous state at room temperature, but at -20 degrees C crystallizes in the orthorhombic space group Pbca with lattice parameters of a = 9.711(4), b = 8.7027(5), c = 7.1999(1) A, and V = 608.51 A(3). The thermal decomposition behavior of this compound under argon and under ammonia was investigated. Through a series of experiments we have demonstrated that Li(NH(3))NH(2)BH(3) is able to absorb/desorb ammonia reversibly at room temperature. In the temperature range of 40-70 degrees C, this compound showed favorable dehydrogenation characteristics. Specifically, under ammonia this material was able to release 3.0 equiv hydrogen (11.18 wt %) rapidly at 60 degrees C, which represents a significant advantage over LiNH(2)BH(3). It has been found that the formation of the coordination bond between ammonia and Li(+) in LiNH(2)BH(3) plays a crucial role in promoting the combination of hydridic B-H bonds and protic N-H bonds, leading to dehydrogenation at low temperature.

Heterostructures Built in Metal Hydrides for Advanced Hydrogen Storage Reversibility.

Hydrogen storage is a vital technology for developing on-board hydrogen fuel cells. While Mg(BH4 )2 is widely regarded as a promising hydrogen storage material owing to its extremely high gravimetric and volumetric capacity, its poor reversibility poses a major bottleneck inhibiting its practical applications. Herein, a facile strategy to effectively improve the reversible hydrogen storage performance of Mg(BH4 )2 via building heterostructures uniformly inside MgH2 nanoparticles is reported. The in situ reaction between MgH2 nanoparticles and B2 H6 not only forms homogeneous heterostructures with controllable particle size but also simultaneously decreases the particle size of the MgH2 nanoparticles inside, which effectively reduces the kinetic barrier that inhibits the reversible hydrogen storage in both Mg(BH4 )2 and MgH2 . More importantly, density functional theory coupled with ab initio molecular dynamics calculations clearly demonstrates that MgH2 in this heterostructure can act as a hydrogen pump, which drastically changes the enthalpy for the initial formation of BH bonds by breaking stable BB bonds from endothermic to exothermic and hence thermodynamically improves the reversibility of Mg(BH4 )2 . It is believed that building heterostructures provides a window of opportunity for discovering high-performance hydrogen storage materials for on-board applications.