The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation. Herein, we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders (e.g., sodium alginate (SA) and carboxymethyl cellulose (CMC)) by reacting with an inorganic crosslinker (sodium metaborate hydrate (SMH)) upon vacuum drying. The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability, which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li⁺ ion transfer. SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g⁻¹ of specific capacity at 100 mA g⁻¹ after 200 cycles, which is 5 times higher than that fabricated with SA binder alone (293 mAh g⁻¹). Nearly, no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g⁻¹. The new binders also dramatically improved the performance of Fe₂O₃, Fe₃O₄, NiO, and Si electrodes, indicating the excellent applicability. This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.

Critical limitations in applying MgH₂ as a hydrogen-storage medium include the high H₂ desorption temperature and slow reaction kinetics. In this study, we synthesized hierarchical porous TiNb₂O₇ spheres in micrometer scale built with 20-50 nm nanospheres, which showed stable activity to catalyze hydrogen storage in MgH₂ as precursors. The addition of 7 wt.% TiNb₂O₇ in MgH₂ reduced the dehydrogenation onset temperature from 300 to 177 °C. At 250 °C, approximately 5.5 wt.% H₂ was rapidly released in 10 min. Hydrogen uptake was detected even at room temperature under 50 bar hydrogen; 4.5 wt.% H₂ was absorbed in 3 min at 150 °C, exhibiting a superior low-temperature hydrogenation performance. Moreover, nearly constant capacity was observed from the second cycle onward, demonstrating stable cyclability. During the ball milling and initial de/hydrogenation process, the high-valent Ti and Nb of TiNb₂O₇ were reduced to the lower-valent species or even zero-valent metal, which in situ created multivalent multielement catalytic surroundings. A strong synergistic effect was obtained for hybrid oxides of Nb and Ti by density functional theory (DFT) calculations, which largely weakens the Mg-H bonding and results in a large reduction in kinetic barriers for hydrogen storage reactions of MgH₂. Our findings may guide the further design and development of high-performance complex catalysts for the reversible hydrogen storage of hydrides.

Adding a small amount of nanocrystalline TiO₂@C (TiO₂ supported on nanoporous carbon) composite dramatically decreases the operating temperatures and improves the reaction kinetics for hydrogen storage in NaAlH₄. The nanocrystalline TiO₂@C composite synthesized at 900 ℃ (referred as TiO₂@C-900) exhibits superior catalytic activity to other catalyst-containing samples. The onset dehydrogenation temperature of the TiO₂@C-900-containing sample is lowered to 90 ℃; this is 65 ℃ lower than that of the pristine sample. The dehydrogenated sample is completely hydrogenated at 115 ℃ and 100 bar of hydrogen pressure with a hydrogen capacity of 4.5 wt.%. Structural analyses reveal that the Ti undergoes a reduction process of Ti⁴⁺→Ti³⁺→Ti²⁺→Ti during the ball milling and heating processes, and further converts to Ti hydrides or forms Ti-Al species after rehydrogenation. The catalytic activities of Ti-based catalytic species decrease in the order Al-Ti-species > TiH_0.71 > TiH₂ > TiO₂. This understanding guides further improvement in hydrogen storage properties of metal alanates using nanocrystalline transition metal-based additives.