High-Performance NiS2 Hollow Nanosphere Cathodes in Magnesium-Ion Batteries Enabled by Tunable Redox Chemistry

Fine nanostructure design of metal chalcogenide conversion-based cathode materials for rechargeable magnesium batteries

Magnesium-ion batteries (MIBs) a strong candidate to set off the second-generation energy storage boom due to their double charge transfer and dendrite-free advantages. However, the strong coulombic force and the huge diffusion energy barrier between Mg2+ and the electrode material have led to need for a cathode material that can enable the rapid and reversible de-insertion of Mg2+. So far, researchers have found that the sulfur-converted cathode materials have a greater application prospect due to the advantages of low price and high specific capacity, etc. Based on these advantages, it is possible to achieve the goal of increasing the magnesium storage capacity and cycling stability by reasonable modification of crystal or morphology. In this review, we focus on the application of a variety of sulfur-converted cathode materials in MIBs in recent years from the perspective of microstructural design, and provide an outlook on current challenges and future development.

Ternary Eutectic Electrolyte-Assisted Formation and Dynamic Breathing Effect of the Solid-Electrolyte Interphase for High-Stability Aqueous Magnesium-Ion Full Batteries

Aqueous rechargeable magnesium batteries hold immense potential for intrinsically safe, cost-effective, and sustainable energy storage. However, their viability is constrained by a narrow voltage range and suboptimal compatibility between the electrolyte and electrodes. Herein, we introduce an innovative ternary deep eutectic Mg-ion electrolyte composed of MgCl2·6H2O, acetamide, and urea in a precisely balanced 1:1:7 molar ratio. This formulation was optimized by leveraging competitive solvation effects between Mg2+ ions and two organic components. The full batteries based on this ternary eutectic electrolyte, Mn-doped sodium vanadate (Mn-NVO) anode, and copper hexacyanoferrate cathode exhibited an elevated voltage plateau and high rate capability and showcased stable cycling performance. Ex-situ characterizations unveiled the Mg2+ storage mechanism of Mn-NVO involving initial extraction of Na+ followed by subsequent Mg2+ intercalation/deintercalation. Detailed spectroscopic analyses illuminated the formation of a pivotal solid-electrolyte interphase on the anode surface. Moreover, the solid-electrolyte interphase demonstrated a dynamic adsorption/desorption behavior, referred to as the "breathing effect", which substantially mitigated undesired dissolution and side reactions of electrode materials. These findings underscore the crucial role of rational electrolyte design in fostering the development of a favorable solid-electrolyte interphase that can significantly enhance compatibility between electrode materials and electrolytes, thus propelling advancements in aqueous multivalent-ion batteries.

Hard-Carbon Negative Electrodes from Biomasses for Sodium-Ion Batteries

With the development of high-performance electrode materials, sodium-ion batteries have been extensively studied and could potentially be applied in various fields to replace the lithium-ion cells, owing to the low cost and natural abundance. As the key anode materials of sodium-ion batteries, hard carbons still face problems, such as poor cycling performance and low initial Coulombic efficiency. Owning to the low synthesis cost and the natural presence of heteroatoms of biomasses, biomasses have positive implications for synthesizing the hard carbons for sodium-ion batteries. This minireview mainly explains the research progress of biomasses used as the precursors to prepare the hard-carbon materials. The storage mechanism of hard carbons, comparisons of the structural properties of hard carbons prepared from different biomasses, and the influence of the preparation conditions on the electrochemical properties of hard carbons are introduced. In addition, the effect of doping atoms is also summarized to provide an in-depth understanding and guidance for the design of high-performance hard carbons for sodium-ion batteries.

A single-crystalline Co3O4 nanoparticle-assembled three-dimensional chain as an ultra-stable magnesium-ion battery cathode at different temperatures

Engineering optimal cathode materials is significant for developing stable magnesium-ion (Mg-ion) batteries. Here, we present a single-crystalline Co₃O₄ nanoparticle-chain three-dimensional (3D) micro/nanostructure as an Mg-ion battery cathode. The hierarchical morphology is composed of radial nanochains self-assembled by single-crystalline nanoparticles, thus significantly facilitating the transfer of electrons and ions. 3D single-crystalline Co₃O₄ as an Mg-ion battery cathode displays a stable capacity of 111.7 mA h g^-1 after 200 cycles with a decay rate per cycle as low as 0.037%. After four rounds of testing, the rate performance remains stable with a tiny decrease from 125.94 to 124.78 mA h g^-1. At temperatures of 45 °C and -5 °C, the cathode still displays good stability and rate-performance. Galvanostatic intermittent titration technique (GITT) results verify a low energy barrier of the Co₃O₄ cathode. It is expected that the single-crystalline nanoparticle-assembled 3D structure and the stable Mg-storage performance will find broad applications for developing other stable energy-storage materials and their batteries.

MoS2/CoS heterostructures grown on carbon cloth as free-standing anodes for high-performance sodium-ion batteries

Heterostructure construction with mixed transition metal sulfides has been recognized as a promising strategy to boost the performance of sodium-ion batteries (SIBs). Herein, a carbon-decorated MoS₂/CoS heterostructure on carbon cloth (MoS₂/CoS@CC) as a free-standing anode for SIBs was synthesized via a facile growth-carbonization strategy. In the composite, the generated built-in electric field at MoS₂ and CoS heterointerfaces is beneficial for elevating the electron conductivity, thus expediting the Na-ion transport rate. Moreover, different redox potentials between MoS₂ and CoS can effectively mitigate the mechanical strain induced by repeated Na⁺ de-/intercalation, thus ensuring the structural integrity. In addition, the carbon skeleton derived from the carbonization of glucose can enhance the conductivity of the electrode and maintain the structural integrity. Consequently, the resulting MoS₂/CoS@CC electrode delivers a reversible capacity of 605 mA h g^-1 at 0.5 A g^-1 after 100 cycles, and prominent rate performance (366 mA h g^-1 at 8.0 A g^-1). Theoretical calculations also confirm that the establishment of a MoS₂/CoS heterojunction can powerfully promote the electron conductivity, thereby enhancing the Na-ion diffusion kinetics.