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Realizing practical magnesium-ion batteries (MIBs) is hindered by parasitic formation processes on the surface of the magnesium anode from contaminants typically from the electrolyte. Aiming to address this issue, we investigate the addition of water scavengers like hexamethyldisilazane (HMDS) and 2,2-dimethoxypropane (DMP) into a non-aqueous electrolyte-based magnesium perchlorate. The addition of water scavengers greatly reduces the overpotential of Mg deposition/dissolution, improves the ionic transfer number, and enhances the electrochemical performance of the electrolyte. In addition, a buffer layer interface from ionic conductive polymer–based magnesium chloride and polyvinylidene difluoride (PVDF) was applied between the liquid electrolyte and magnesium anode to protect the surface of the Mg anode from the direct contact with the liquid electrolyte to further inhibit Mg metal corrosion. The Mg symmetric cells deliver low overpotential compared with the liquid electrolytes by introducing the buffer layer, with and without scavengers. The value of the ion transference increased compared with analogs of liquid electrolytes. Mg-S coin cell assembled with an electrolyte-based HMDS can deliver a high initial discharge/charge specific capacity of ~ 520/530 mAhg−1. [ABSTRACT FROM AUTHOR]

• SACs were firstly applied to Mg-S batteries. • Graphene loaded with single atom iron promote the reaction kinetics. • The prepared electrode exhibited high reversible capacity of 892.7 mAh/g at 0.3C. • The catalyst can be easily synthesized through pyrolysis at relatively low temperatures. Magnesium-sulfur battery (MSB) with the advantages of low cost, high theoretical energy density and high security is regarding as a promising energy storage system. However, it suffers from sluggish reaction kinetics, fast capacity fading and poor cycling stability due to the shortage of compatible electrolyte and high performance cathode. Herein, Fe single atom catalyst is introduced to improve the electrochemical performance of MSB for the first time. Fe atoms are uniformly dispersed on graphene support by a facile method to prepare Fe-N-G, which is applied as an effective sulfur host. Benefited from the remarkable catalytic performance of the single-atom Fe, the produced S@ Fe-N-G exhibits a high reversible discharge specific capacity of 962 mA h g−1 at 0.1C, outstanding cycling stability of maintaining 892.7 mA h g−1 at 0.3C after 200 cycles and excellent rate capability. It is expected that this work could promote the development of more high-efficient single-atom catalysts for high performance MSB. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel bifunctional non-nucleophilic magnesium battery electrolyte is proposed. • The electrolyte can react with Mg anode, synthesizing magnesium salt in situ. • The electrolyte can eliminate the existing passive film on Mg anode surface. • Mg anode with the novel electrolyte exhibits low polarization. Magnesium batteries are one of the ideal candidates for next-generation battery systems with high energy density and safety. However, the development of compatible non-nucleophilic electrolytes and the passivation of the Mg anode are the primary obstacles that impede their development. Here, a non-nucleophilic electrolyte is proposed through in-situ reactions between AlCl 3 + InCl 3 /TEG (AI-E) electrolyte and Mg anode, which kills two birds with one stone that magnesium salts with the structures of [MgCl·TEG]+ and [MgCl·2TEG]+ are generated and the passive film on Mg anode is converted into solid electrolyte interphase (SEI). Compared with the Mg(TFSI) 2 electrolyte, the polarization of the Mg anode in the AI-E electrolyte decreases from 2.0 V to 0.08 V for 400 cycles, and the Mg/S battery with the AI-E electrolyte reaches an improved discharge voltage plateau of 1.12 V for 50 cycles. This work expects to provide a one-step method for magnesium salt synthesis and Mg anode passivation. [ABSTRACT FROM AUTHOR]

The true potential of Mg–S batteries is not yet realized despite its great advantages in material cost and safety. This is due to the lethargic reaction kinetics involved in the dissociation of Mg polysulfide (MgPS) on the cathode. Herein, we propose nitrogen–doped mesoporous carbon (N d MC) materials with suitable nitrogen content and surface moieties that can be utilized as catalytic hosts to enhance polysulfide fragmentation and electron access to the redox active sites in Mg–S batteries. In controlled N d MC, the surface nitrogen atoms located at the pyridinic positions can strongly bind MgPS and accelerate the reduction of MgPS to MgS, while the graphitic wall structure facilitates facile electron transport to the reaction sites. This synergic effect enables the composite electrode made of tuned N d MC and sulfur to exhibit an enhanced reversible capacity and good cycling capacity retention in Mg–S batteries. This study offers a new strategy for improving the performance of Mg–S batteries by fine-tuning the structural properties of the carbon hosts. [Display omitted] • N-doped graphitic mesoporous carbon is utilized as a host for S 8 imbibition. • Suitable surface moiety and wall structure of carbon host is proposed. • The pyridinic-N stronly binds MgPS and accelerates its dissociation. • Synergic effect enables an enhanced performance for Mg–S batteries. [ABSTRACT FROM AUTHOR]

The magnesium–sulfur (Mg-S) battery may be a safer alternative for the lithium-sulfur battery because Mg plating usually proceeds without dendrite formation. Here, we correlate the thermal runaway of Mg-S battery with the associated change of electrolyte vapour pressure via battery testing calorimetry. Over-pressure builds up along with the programmed heating of the cell, and as a result, the thermal runaway is triggered at 20–45 K over the electrolyte boiling point, corresponding to 70–150 kPa pressure difference between the cell and the environment. The distinct performance-safety-cost behaviours of three ether type of electrolytes stems from the different CH 2 CH 2 O chain lengths. Such molecular insight will serve as a fundamental guideline in choosing and designing the desired electrolyte that simultaneously achieves a high explosion limit and good electrochemical performance. The safety of the MgS battery is mainly related to the vapour pressure of the electrolyte. The over-pressure builds up along with heating of the cell and triggers the battery explosion. The subsequent exothermic reaction between MgS and H 2 O caused a sudden temperature jump of the battery. A modified DME with higher boiling point will be ideal of the MgS battery. [Display omitted] • A novel method of safety evaluation is introduced to the Mg-S system. • The thermal runaway of Mg-S battery is correlated with the associated change of electrolyte vapour pressure. • The distinct performance-safety-cost relationship of ether electrolytes with different degree of polymerisation. [ABSTRACT FROM AUTHOR]