Bulk-Type All-Solid-State Lithium-Ion Batteries: Remarkable Performances of a Carbon Nanofiber-Supported MgH2 Composite Electrode

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.

High capacity all-solid-state lithium battery enabled by in situ formation of an ionic conduction path by lithiation of MgH2

All-solid-state Li batteries have attracted significant attention because of their high energy density and high level of safety. In a solid-state Li-ion battery, the electrodes contain a solid electrolyte that does not contribute directly to the capacity. Therefore, a battery that does not require a solid electrolyte in its electrode mixture should exhibit a higher energy density. In this study, a MgH2 electrode was used as the negative electrode material without a solid electrolyte in its mixture. The resultant battery demonstrated excellent performance because of the formation of an ionic conduction path based on LiH in the electrode mixture. LiH and Mg clearly formed upon lithiation and returned to MgH2 upon delithiation as revealed by TEM-EELS analysis. This mechanism of in situ electrolyte formation enables the development of a solid-state battery with a high energy density.

A Review of the MSCA ITN ECOSTORE—Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.

Hydrangea-Shaped 3D Hierarchical Porous Magnesium Hydride-Carbon Framework with High Rate Performance for Lithium Storage

Magnesium hydride (MgH₂) is a promising anode material for lithium-ion batteries (LIBs) by virtue of its high theoretical specific capacity, suitable potential, and abundant source. However, the electrochemical performance of the MgH₂ electrode is still far from satisfactory due to its poor electronic conductivity and fast capacity decay. In this paper, a hydrangea-shaped three-dimensional (3D) hierarchical magnesium hydride-carbon framework (MH@HyC) comprising MgH₂ nanoparticles (NPs) uniformly self-assembled on hierarchical porous carbon (HyC) is fabricated for advanced lithium storage. Featuring high surface area and a well-defined macro-meso-micropore structure, HyC plays an ideal structure-directing role for the growth of MgH₂ NPs with size control, high loading, and a hydrangea-shape array. Taking advantage of the robust 3D hierarchical porous structure and the derived interactions, MH@HyC not only provides sufficient electrochemically active sites and enhances the electronic conductivity and channels for rapid transfer of electrons/Li ions but also relieves the agglomeration and accommodates the volumetric effects during cycling, leading to high capacity utilization, fast electrochemical kinetics, and well-sustained structural integrity. As a result, MH@HyC delivers a high reversible capacity of 554 mAh g^-1 after 1000 cycles at a high current rate of 2 A g^-1, enabling it a potential anode candidate for LIBs.

Highly efficient & stable Bi & Sb anodes using lithium borohydride as solid electrolyte in Li-ion batteries

All solid-state Li-ion batteries using commercial Bi and Sb as negative electrodes with a high coulombic efficiency (90–99%) and high capacity retention of 82 and 95%, respectively.

Borohydride-Scaffolded Li/Na/Mg Fast Ionic Conductors for Promising Solid-State Electrolytes

Borohydride solid-state electrolytes with room-temperature ionic conductivity up to ≈70 mS cm^-1 have achieved impressive progress and quickly taken their place among the superionic conductive solid-state electrolytes. Here, the focus is on state-of-the-art developments in borohydride solid-state electrolytes, including their competitive ionic-conductive performance, current limitations for practical applications in solid-state batteries, and the strategies to address their problems. To open, fast Li/Na/Mg ionic conductivity in electrolytes with BH₄ ^- groups, approaches to engineering borohydrides with enhanced ionic conductivity, and later on the superionic conductivity of polyhedral borohydrides, their correlated conductive kinetics/thermodynamics, and the theoretically predicted high conductive derivatives are discussed. Furthermore, the validity of borohydride pairing with coated oxides, sulfur, organic electrodes, MgH₂ , TiS₂ , Li₄ Ti₅ O₁₂ , electrode materials, etc., is surveyed in solid-state batteries. From the viewpoint of compatible cathodes, the stable electrochemical windows of borohydride solid-state electrolytes, the electrode/electrolyte interface behavior and battery device design, and the performance optimization of borohydride-based solid-state batteries are also discussed in detail. A comprehensive coverage of emerging trends in borohydride solid-state electrolytes is provided and future maps to promote better performance of borohydride SSEs are sketched out, which will pave the way for their further development in the field of energy storage.

Synergism of Rare Earth Trihydrides and Graphite in Lithium Storage: Evidence of Hydrogen-Enhanced Lithiation

The lithium storage capacity of graphite can be significantly promoted by rare earth trihydrides (REH₃ , RE = Y, La, and Gd) through a synergetic mechanism. High reversible capacity of 720 mA h g^-1 after 250 cycles is achieved in YH₃ -graphite nanocomposite, far exceeding the total contribution from the individual components and the effect of ball milling. Comparative study on LaH₃ -graphite and GdH₃ -graphite composites suggests that the enhancement factor is 3.1-3.4 Li per active H in REH₃ , almost independent of the RE metal, which is evident of a hydrogen-enhanced lithium storage mechanism. Theoretical calculation suggests that the active H from REH₃ can enhance the Li⁺ binding to the graphene layer by introducing negatively charged sites, leading to energetically favorable lithiation up to a composition Li₅ C₁₆ H instead of LiC₆ for conventional graphite anode.

MgH2–CoO: a conversion-type composite electrode for LiBH4-based all-solid-state lithium ion batteries

Several studies have demonstrated that MgH₂ is a promising conversion-type anode toward Li. A major obstacle is the reversible capacity during cycling. Electrochemical co-existence of a mixed metal hydride-oxide conversion type anode is demonstrated for lithium ion batteries using a solid-state electrolyte. 75MgH₂·25CoO anodes are obtained from optimized mixing conditions avoiding reactions occurring during high-energy ball-milling. Electrochemical tests are carried out to investigate the cycling capability and reversibility of the on-going conversion reactions. The cycling led to formation of a single-plateau nanocomposite electrode with higher reversibility yield, lowered discharge–charge hysteresis and mitigated kinetic effect at high C-rate compared to MgH₂ anodes. It is believed that reduced diffusion pathways and less polarized electrodes are the origin of the improved properties. The designed composite-electrode shows good preservation and suitability with LiBH₄ solid electrolyte as revealed from electron microscopy analyses and X-ray photoelectron spectroscopy.

The findings point to a means of guided formation of MgH₂–CoO conversion-type nanocomposite electrode for all-solid-state Li-ion batteries.