Interfacial Manipulation via In Situ Constructed Fast Ion Transport Channels toward an Ultrahigh Rate and Practical Li Metal Anode.

The successful substitution of Li metal for the conventional intercalation anode can promote a significant increase in the cell energy density. However, the practical application of the Li metal anode has long been fettered by the unstable solid electrolyte interface (SEI) layer on the Li metal surface and notorious dendritic Li growth. Herein, a stabilized SEI layer with in situ constructed fast ion transport channels has successfully been achieved by a robust In2S3-cemented poly(vinyl alcohol) coating. The modified Li metal demonstrates significantly enhanced Coulombic efficiency, high rate performance (10 mA cm-2), and ultralong life cycling stability (∼4900 cycles). The Li|LiCoO2 (LCO) cell presents an ultralong-term stable operation over 500 cycles at 1 C with an extremely low capacity decay rate (∼0.018% per cycle). And the Li|LCO full cell with the ultrahigh loading cathode (∼25 mg cm-2) and ultrathin Li foil (∼40 µm) also reveals a prolonged cycling performance under the low negative-to-positive capacity ratio of 2.2. Furthermore, the Li|LCO pouch cell with a commercial cathode and ultrathin Li foil still manifests excellent cycling performance even under the harsh conditions of limited Li metal and lean electrolyte. This work provides a cost-effective and scalable strategy toward high performance practical Li metal batteries.

TiFeNb10O29-δ anode for high-power and durable lithium-ion batteries.

A new Fe-substituted TiFeNb10O29-δ (TFNO) anode is proposed. TFNO possesses a defective and polycrystalline ReO3 Roth-Wadsley shear structure with a slightly larger lattice volume. Electrochemical behavior results and density functional theory (DFT) calculations show that TFNO can facilitate the kinetics of electron/Li+ transportation and demonstrates pseudocapacitive behavior. Consequently, TFNO exhibits superior high rate capacity and cycling stability compared to pristine TNO, offering 100 mA h g-1 at an ultrahigh rate of 50C and a high capacity retention of 86.7% over 1000 cycles at 10C. This work reveals that TFNO could be a promising anode material for fast-charging, stable, and safe LIBs.

In Situ Trapping Strategy Enables a High-Loading Ni Single-Atom Catalyst as a Separator Modifier for a High-Performance Li-S Battery.

The poor electrochemical reaction kinetics of Li polysulfides is a key barrier that prevents the Li-S batteries from widespread applications. Ni single atoms dispersed on carbon matrixes derived from ZIF-8 are a promising type of catalyst for accelerating the conversion of active sulfur species. However, Ni favors a square-planar coordination that can only be doped on the external surface of ZIF-8, leading to a low loading amount of Ni single atoms after pyrolysis. Herein, we demonstrate an in situ trapping strategy to synthesize Ni and melamine-codoped ZIF-8 precursor (Ni-ZIF-8-MA) by simultaneously introducing melamine and Ni during the synthesis of ZIF-8, which can remarkably decrease the particle size of ZIF-8 and further anchor Ni via Ni-N6 coordination. Consequently, a novel high-loading Ni single-atom (3.3 wt %) catalyst implanted in an N-doped nanocarbon matrix (Ni@NNC) is obtained after high-temperature pyrolysis. This catalyst as a separator modifier shows a superior catalytic effect on the electrochemical transitions of Li polysulfides, which endows the corresponding Li-S batteries with a high specific capacity of 1232.4 mA h g-1 at 0.3 C and an excellent rate capability of 814.9 mA h g-1 at 3 C. Furthermore, a superior areal capacity of 4.6 mA h cm-2 with stable cycling over 160 cycles can be achieved under a critical condition with a low electrolyte/sulfur ratio (8.4 µL mg-1) and high sulfur loading (4.85 mg cm-2). The outstanding electrochemical performances can be attributed to the strong adsorption and fast conversion of Li polysulfides on the highly dense active sites of Ni@NNC. This intriguing work provides new inspirations for designing high-loading single-atom catalysts applied in Li-S batteries.

Uniform and Anisotropic Solid Electrolyte Membrane Enables Superior Solid-State Li Metal Batteries.

Rational structure design is a successful approach to develop high-performance composite solid electrolytes (CSEs) for solid-state Li metal batteries. Herein, a novel CSE membrane is proposed, that consists of interwoven garnet/polyethylene oxide-Li bis(trifluoromethylsulphonyl)imide (LLZO/PEO-LiTFSI) microfibers. This CSE exhibits high Li-ion conductivity and exceptional Li dendrite suppression capability, which can be attributed to the uniform LLZO dispersion in PEO-LiTFSI and the vertical/horizontal anisotropic Li-ion conduction in the CSE. The uniform LLZO particles can generate large interaction regions between LLZO and PEO-LiTFSI, which thus form continuous Li-ion transfer pathways, retard the interfacial side reactions and strengthen the deformation resistance. More importantly, the anisotropic Li-ion conduction, that is, Li-ion transfers much faster along the microfibers than across the microfibers, can effectively homogenize the electric field distribution in the CSE during cycling, which thus prevents the excessive concentration of Li-ion flux. Finally, solid-state Li||LiFePO4 cells based on this CSE show excellent electrochemical performances. This work enriches the structure design strategy of high-performance CSEs and may be helpful for further pushing the solid-state Li metal batteries towards practical applications.

Li2(BH4)(NH2) Nanoconfined in SBA-15 as Solid-State Electrolyte for Lithium Batteries.

Solid electrolytes with high Li-ion conductivity and electrochemical stability are very important for developing high-performance all-solid-state batteries. In this work, Li2(BH4)(NH2) is nanoconfined in the mesoporous silica molecule sieve (SBA-15) using a melting-infiltration approach. This electrolyte exhibits excellent Li-ion conduction properties, achieving a Li-ion conductivity of 5.0 × 10-3 S cm-1 at 55 °C, an electrochemical stability window of 0 to 3.2 V and a Li-ion transference number of 0.97. In addition, this electrolyte can enable the stable cycling of Li|Li2(BH4)(NH2)@SBA-15|TiS2 cells, which exhibit a reversible specific capacity of 150 mAh g-1 with a Coulombic efficiency of 96% after 55 cycles.

Highly Lithiophilic Copper-Reinforced Scaffold Enables Stable Li Metal Anode.

Lithium (Li) metal is regarded as one of the most prospective electrodes for next-generation rechargeable batteries. However, its widespread usage has been fettered by low coulombic efficiency (CE), poor cycling stability, and serious safety concerns, mainly arising from huge volumetric variation, inhomogeneous Li deposition, and dendrite growth during repeated Li plating/stripping cycles. Herein, we propose a facile one-pot electrospinning-derived highly lithiophilic nanocopper-reinforced three-dimensional-structured carbon nanofiber (Cu-CNF) as functional scaffold to stabilize the Li metal. The Cu-CNF scaffolded Li metal demonstrates homogeneous nanoplate-like Li deposition, enhanced CE, and ultrastable long lifespan cycling. As coupled with LiNi0.8Co0.1Mn0.1O2 (NCM811), the cell possesses a remarkably stable high capacity retention of 93% over 300 cycles at 0.2 C. Furthermore, the cells paired with a thick LiFePO4 (LFP) electrode (∼12 mg cm-2) still can deliver a superior cycling performance even under the harsh conditions of an extremely low negative/positive electrode capacity (N/P) ratio (∼1.5) and lean electrolyte. Density functional theory calculations are performed to disclose the mechanism of the enhanced electrochemical performance of Cu-CNF scaffolded Li. This work provides a handy and cost-effective method to design superior performance Li metal anodes for practical applications.

Enabling a Stable Room-Temperature Sodium-Sulfur Battery Cathode by Building Heterostructures in Multichannel Carbon Fibers.

Room-temperature sodium-sulfur (RT Na-S) batteries are widely considered as one of the alternative energy-storage systems with low cost and high energy density. However, the both poor cycle stability and capacity are two critical issues arising from low conversion kinetics and sodium polysulfides (NaPSs) dissolution for sulfur cathodes during the charge/discharge process. Herein, we report a highly stable RT Na-S battery cathode via building heterostructures in multichannel carbon fibers. The TiN-TiO2@MCCFs, fabricated by electrospinning and nitriding techniques, are loaded with the active material S, forming S/TiN-TiO2@MCCFs as the cathode in a RT Na-S battery. At 0.1 A g-1, the cathode produces the capacity of more than 640 mAh g-1 within 100 cycles with a high Coulombic efficiency of nearly 100%. Even at 5 A g-1, the battery still exhibites a capacity of 257.1 mAh g-1 after 1000 cycles. Combining structural and electrochemical analyses with the first-principles calculations reveals that the incorporation of the highly electrocatalytic activity of TiN with the powerful chemisorption of TiO2 well stabilizes S and also alleviates the shuttle effects of polysulfides. This work with simple processes and low cost is expected to promote the further development and application of metal-S batteries.

Investigation on Fabrication of Reduced Graphene Oxide-Sulfur Composite Cathodes for Li-S Battery via Hydrothermal and Thermal Reduction Methods.

Lithium-sulfur (Li-S) battery is considered one of the possible alternatives for next-generation high energy batteries. However, its practical applications are still facing great challenges because of poor electronic conductivity, large volume change, and polysulfides dissolution inducing "shuttle reaction" for the S cathode. Many strategies have been explored to alleviate the aforementioned concerns. The most common approach is to embed S into carbonaceous matrix for constructing C-S composite cathodes. Herein, we fabricate the C-S cathode reduced graphene oxide-S (rGO-S) composites via one step hydrothermal and in-situ thermal reduction methods. The structural features and electrochemical properties in Li-S cells of the two type rGO-S composites are studied systematically. The rGO-S composites prepared by one step hydrothermal method (rGO-S-HT) show relatively better comprehensive performance as compared with the ones by in-situ thermal reduction method (rGO-S-T). For instance, with a current density of 100 mA g-1, the rGO-S-HT composite cathodes possess an initial capacity of 1290 mAh g-1 and simultaneously exhibit stable cycling capability. In particular, as increasing the current density to 1.0 A g-1, the rGO-S-HT cathode retains a reversible capacity of 582 mAh g-1 even after 200 cycles. The enhanced electrochemical properties can be attributed to small S particles uniformly distributed on rGO sheets enabling to significantly improve the conductivity of S and effectively buffer large volume change during lithiation/delithiation.

Highly Stable and Ultrahigh-Rate Li Metal Anode Enabled by Fluorinated Carbon Fibers.

The advanced energy storage of an Li metal substituted for graphite anode can provide a significant enhancement in a battery's energy density. Nevertheless, the practical implementation of metallic Li has seriously been fettered by the notorious Li dendrite growth and the huge volumetric variation of Li metal inducing poor cycling performance and safety concerns. In this regard, constructing a robust SEI layer combined with a 3D host to stabilize the Li metal is strongly in demand. Herein, a highly stable hosted Li with an LiF dominated SEI has successfully been achieved through metal-free fluorinated carbon fibers (FCF) with strong lithiophilicity. The metal-free design is cost-effective and can retain the energy density of the Li metal, minimizing the unnecessary energy sacrifice from the extra high gravimetric density lithiophilic sites. The FCF hosted Li delivers a promoted high Coulombic efficiency, homogeneous Li deposition, and ultrahigh rate stable cycling over 1000 cycles at 20 mA cm-2 with a much lower voltage polarization (≈220 mV). Moreover, half cells coupled with LiNi0.8 Co0.1 Mn0.1 O2 , sulfur or even thick LiCoO2 cathode demonstrate superior rate performances and enhanced cycling stability even under a lean electrolyte. This work proves the feasibility of FCF hosted Li for practical usage and provides a novel approach toward cost-effective and high performance lithium metal batteries.

Molten Salt Synthesis of High-Performance, Nanostructured La0.6Sr0.4FeO3-δ Oxygen Electrode of a Reversible Solid Oxide Cell.

Nanoscale perovskite oxides with enhanced electrocatalytic activities have been widely used as oxygen electrodes of reversible solid oxide cells (RSOC). Here, La0.6Sr0.4FeO3-δ (LSF) nanoscale powder is synthesized via a novel molten salt method using chlorides as the reaction medium and fired at 850 °C for 5 h after removing the additives. A direct assembly method is employed to fabricate the LSF electrode without a pre-sintering process at high temperature. The microstructure characterization ensures that the direct assembly process will not damage the porosity of LSF. When operating as a solid oxide fuel cell (SOFC), the LSF cell exhibits a peak power density of 1.36, 1.07 and 0.7 W/cm2 at 800, 750 and 700 °C, respectively, while in solid oxide electrolysis cell (SOEC) mode, the electrolysis current density reaches 1.52, 0.98 and 0.53 A/cm2 under an electrolysis voltage of 1.3 V, respectively. Thus, it indicates that the molten salt routine is a promising method for the synthesis of highly active perovskite LSF powders for directly assembled oxygen electrodes of RSOC.

Fast and Stable Batteries with High Capacity Enabled by Germanium-Phosphorus Binary Nanoparticles Embedded in a Porous Carbon Matrix via Metallothermic Reduction.

Lithium-alloyable materials such as Ge and P have attracted considerable attention as promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity. However, these materials inevitably undergo capacity attenuation caused by large volume expansion in repeated electrochemical processes. Herein, we propose a facile strategy to synthesize germanium-phosphorus binary nanoparticles embedded in porous carbon (GPBN/C) via metallothermic reduction. As an LIB anode, the GPBN/C electrode exhibits outstanding rate performance (368 mAh g-1 at 40 A g-1) and remarkable long-term cycling ability (541 mAh g-1 at 1.0 A g-1 after 1000 cycles). Besides, the GPBN/C composite electrode presents an outstanding cycling performance at wide temperature ranges, showing reversible capacities of 1030 and 696 mAh g-1 at 60 and 0 °C, respectively. Attributed to the formation of highly dispersed Ge-P nanoparticles in a porous carbon matrix, the GPBN/C electrode shows exceptional electrochemical performance. Importantly, our strategy provides an effective way to explore alloy-type electrodes to develop fast and stable high-capacity batteries.

Homologous Strategy to Construct High-Performance Coupling Electrodes for Advanced Potassium-Ion Hybrid Capacitors.

Potassium-ion hybrid capacitors (PIHCs) have been considered as promising potentials in mid- to large-scale storage system applications owing to their high energy and power density. However, the process involving the intercalation of K+ into the carbonaceous anode is a sluggish reaction, while the adsorption of anions onto the cathode surface is relatively faster, resulting in an inability to exploit the advantage of high energy. To achieve a high-performance PIHC, it is critical to promote the K+ insertion/desertion in anodic materials and design suitable cathodic materials matching the anodes. In this study, we propose a facile "homologous strategy" to construct suitable anode and cathode for high-performance PIHCs, that is, unique multichannel carbon fiber (MCCF)-based anode and cathode materials are firstly prepared by electrospinning, and then followed by sulfur doping and KOH activation treatment, respectively. Owing to a multichannel structure with a large interlayer spacing for introducing S in the sulfur-doped multichannel carbon fiber (S-MCCF) composite, it presents high capacity, super rate capability, and long cycle stability as an anode in potassium-ion cells. The cathode composite of activated multichannel carbon fiber (aMCCF) has a considerably high specific surface area of 1445 m2 g-1 and exhibits outstanding capacitive performance. In particular, benefiting from advantages of the fabricated S-MCCF anode and aMCCF cathode by homologous strategy, PIHCs assembled with the unique MCCF-based anode and cathode show outstanding electrochemical performance, which can deliver high energy and power densities (100 Wh kg-1 at 200 W kg-1, and 58.3 Wh kg-1 at 10,000 W kg-1) and simultaneously exhibit superior cycling stability (90% capacity retention over 7000 cycles at 1.0 A g-1). The excellent electrochemical performance of the MCCF-based composites for PIHC electrodes combined with their simple construction renders such materials attractive for further in-depth investigations of alkali-ion battery and capacitor applications.

Rational Construction of a Binder-Free and Universal Electrode for Stable and Fast Alkali-Ion Storage.

Na-ion batteries (SIBs) and K-ion batteries (PIBs) are considered as promising alternatives to Li-ion batteries (LIBs) for large-scale electrical-energy-storage applications. Thus, developing an advanced anodic material with appropriate structure for both SIBs and PIBs is urgently desirable but remains an eager challenge because of the relatively large ionic radius of Na+ or K+. Herein, we rationally design a sulfur-mediated three-dimensional graphene aerogel (SMGA) with plant cell wall structure as a binder-free anodic material for SIBs and PIBs as well as LIBs, exhibiting high capacity and excellent rate capability along with long cycling stability. For instance, at 0.1 A g-1, the SMGA anodes can deliver a high capacity of 320 mAh g-1 in PIBs after 500 cycles and 304 mAh g-1 in SIBs and 690 mAh g-1 in LIBs after 200 cycles. Furthermore, a detailed electrochemical kinetic calculation manifests that the Li/Na/K-ion storage capability is mainly ascribed to the introduction of sulfur in graphene aerogel (GA) to enlarge the interlayer distance, the three-dimensional interconnected network with porous structure providing sufficient space to accommodate volumetric expansion, and a short transport pathway for electrons/alkali-ions. Our results demonstrate the advanced performance of alkali-ion batteries, thus making it possible to develop a universal electrode for applications of cost-effective next-generation rechargeable batteries.

Fully reversible lithium storage of tin oxide enabled by self-doping and partial amorphization.

SnO2 has a high theoretical capacity of 1493 mA h g-1 as an anode material for Li-ion batteries, but its full reversibility is difficult to achieve upon cycling due to the sluggish kinetics. We for the first time demonstrate a fully reversible SnO2 anode for Li-ion batteries enabled by self-doping and partial amorphization by anchoring its nanoparticles on a graphene/single walled carbon nanotube hybrid framework. The uniquely structured nanocomposite containing 74% SnO2 exhibits high reversible capacities together with good rate and cycling capabilities. For instance, the composite anode retains an overall capacity of 1215 mA h g-1 (1425 mA h g-1 for SnO2) after 200 cycles at 0.1 A g-1, which is very close to its theoretical capacity. Moreover, an overall capacity of 947 mA h g-1 (1062 mA h g-1 for SnO2) can be delivered at a higher rate (1 A g-1) with 98% capacity retention over 350 cycles. This exceptional performance can be attributed to the formation of highly dispersed metallic Sn in the Li2O matrix during cycling, which is caused by the unique two-step lithiation mechanism of the self-doped and partially amorphous SnO2 nanoparticles. A similar strategy can also be applied to develop other high-performance electrodes with conversion reactions.

In Situ Formed Li-B-H Complex with High Li-Ion Conductivity as a Potential Solid Electrolyte for Li Batteries.

Li-B-H complexes facilely prepared via partial dehydrogenation of LiBH4 are presented in this study as solid electrolytes for Li batteries. An exceptionally high Li-ion conductivity is found for the Li-B-H complex with 7.5 wt % H2 desorption under 3 bar H2 pressure, which reaches 2.7 × 10-4 S cm-1 at 35 °C, more than 4 orders higher than that of LiBH4. In-depth characterizations show that LiH and [Li2B12H11+1/ n] n are in situ formed in the LiBH4 matrix and the interface layer between [Li2B12H11+1/ n] n and LiBH4 is believed to be responsible for the high Li-ion conductivity. Moreover, this Li-B-H complex also exhibits excellent electrochemical stability, which enables the stable cycling of all-solid-state batteries at room temperature.

Sulfur encapsulated in thermally reduced graphite oxide as a cathode for Li-S batteries.

Rechargeable Li-S batteries are receiving ever-increasing attention due to their high theoretical energy density and inexpensive raw sulfur materials. However, their practical applications have been hindered by short cycle life and limited power density owing to the poor electronic conductivity of sulfur species, diffusion of soluble polysulfide intermediates (Li2S n , n = 4-8) and the large volume change of the S cathode during charge/discharge. Optimizing the carbon framework is considered as an effective approach for constructing high performance S/carbon cathodes because the microstructure of the carbon host plays an important role in stabilizing S and restricting the "shuttle reaction" of polysulfides in Li-S batteries. In this work, reduced graphite oxide (rGO) materials with different oxidation degree were investigated as the matrix to load the active material by an in situ thermally reducing graphite oxide (GO) and intercalation strategy under vacuum at 600 °C. It has been found that the loaded amount of S embedded in the rGO layer for the S/carbon cathode and its electrochemical performance strongly depended on the oxidation degree of GO. In particular, on undergoing CS2 treatment, the rGO-S cathode exhibits extraordinary performances in Li-S batteries. For instance, at a current density of 0.2 A g-1, the optimized rGO-S cathode shows a columbic efficiency close to 100% and retains a capacity of around 750 mA h g-1 with progressive cycling up to over 250 cycles.

Red Phosphorus-Embedded Cross-Link-Structural Carbon Films as Flexible Anodes for Highly Reversible Li-Ion Storage.

Red phosphorus (P) is considered to be one of the most attractive anodic materials for lithium-ion batteries (LIBs) due to its high theoretical capacity of 2596 mAh g-1. However, intrinsic characteristics such as the poor electronic conductivity and large volume expansion at lithiation impede the development of red P. Here, we design a new strategy to embed red P particles into a cross-link-structural carbon film (P-C film), in order to improve the electronic conductivity and accommodate the volume expansion. The red P/carbon film is synthesized via vapor phase polymerization (VPP) followed by the pyrolysis process, working as a flexible binder-free anode for LIBs. High cycle stability and good rate capability are achieved by the P-C film anode. With 21% P content in the film, it displays a capacity of 903 mAh g-1 after 640 cycles at a current density of 100 mA g-1 and a capacity of 460 mAh g-1 after 1000 cycles at 2.0 A g-1. Additionally, the Coulombic efficiency reaches almost 100% for each cycle. The superior properties of the P-C films together with their facile fabrication make this material attractive for further flexible and high energy density LIB applications.

Composition-Dependent Reaction Pathways and Hydrogen Storage Properties of LiBH4/Mg(AlH4)2 Composites.

Herein, an initial attempt to understand the relationships between hydrogen storage properties, reaction pathways, and material compositions in LiBH4-x Mg(AlH4)2 composites is demonstrated. The hydrogen storage properties and the reaction pathways for hydrogen release from LiBH4-x Mg(AlH4)2 composites with x=1/6, 1/4, and 1/2 were systematically investigated. All of the composites exhibit a four-step dehydrogenation event upon heating, but the pathways for hydrogen desorption/absorption are varied with decreasing LiBH4/Mg(AlH4)2 molar ratios. Thermodynamic and kinetic investigations reveal that different x values lead to different enthalpy changes for the third and fourth dehydrogenation steps and varied apparent activation energies for the first, second, and third dehydrogenation steps. Thermodynamic and kinetic destabilization caused by the presence of Mg(AlH4)2 is likely to be responsible for the different hydrogen desorption/absorption performances of the LiBH4-x Mg(AlH4)2 composites.

A mechanical-force-driven physical vapour deposition approach to fabricating complex hydride nanostructures.

Nanoscale hydrides desorb and absorb hydrogen at faster rates and lower temperatures than bulk hydrides because of their high surface areas, abundant grain boundaries and short diffusion distances. No current methods exist for the direct fabrication of nanoscale complex hydrides (for example, alanates, borohydrides) with unique morphologies because of their extremely high reducibility, relatively low thermodynamic stability and complicated elemental composition. Here, we demonstrate a mechanical-force-driven physical vapour deposition procedure for preparing nanoscale complex hydrides without scaffolds or supports. Magnesium alanate nanorods measuring 20-40 nm in diameter and lithium borohydride nanobelts measuring 10-40 nm in width are successfully synthesised on the basis of the one-dimensional structure of the corresponding organic coordination polymers. The dehydrogenation kinetics of the magnesium alanate nanorods are improved, and the nanorod morphology persists through the dehydrogenation-hydrogenation process. Our findings may facilitate the fabrication of such hydrides with improved hydrogen storage properties for practical applications.

Compositional effects on the hydrogen storage properties of Mg(NH2)2-2LiH-xKH and the activity of KH during dehydrogenation reactions.

Potassium hydride (KH) was directly added to a Mg(NH2)2-2LiH system to improve the hydrogen storage properties; the corresponding mechanisms were elucidated. The Mg(NH2)2-2LiH-0.08KH composite displays optimized hydrogen-storage properties, reversibly storing approximately 5.2 wt% hydrogen through a two-stage reaction and a dehydrogenation onset at 70 °C. The 0.08KH-added sample fully dehydrogenated at 130 °C begins to absorb hydrogen at 50 °C, and takes up approximately 5.1 wt% of hydrogen at 140 °C. Adding KH significantly enhances the de-/hydrogenation kinetic properties; however, an overly rapid hydrogenation rate enlarges the particle size and raises the dehydrogenation temperature. A cycling evaluation reveals that the KH-added Mg(NH2)2-2LiH system possesses good reversible hydrogen storage abilities, although the operational temperatures for de-/hydrogenation increase during cycling. Detailed mechanistic investigations indicate that adding KH catalytically decreases the activation energy of the first dehydrogenation step and reduces the enthalpy of desorption during the second dehydrogenation step as a reactant, significantly improving the hydrogen storage properties of Mg(NH2)2-2LiH.