High-rate, long-life magnesium-sulfur battery system: Benefit from MOF derived carbon carriers and lithium salt regulators
Electric vehicles and smart grid in areas such as battery energy density, safety requirements continue to increase, the development of low-cost, high energy density, safety of the new secondary batteries more pressing.In many new battery systems, magnesium batteries due to the volume ratio of negative electrode capacity (3833mAh / cm3), rich in resources, not easy to form dendrites during deposition / stripping, etc. However, due to its small volume, large charge density and strong polarization, Price of magnesium ion reversible release of the positive electrode material selection.Due to the lack of high potential of the positive electrode structure and electrolyte formulation prototype, through the development of high potential embedded magnesium battery research has been slow.In addition, there is a viable path is to build a moderate potential Magnesium-based battery systems based on bulk conversion reactions, such as Mg-S batteries (theoretical energy density up to 1722 Wh / kg), but successful strategies in Li-S batteries can not simply be replicated into Mg-S systems. Battery potential polarization, rate and cycle performance is still poor.
In order to avoid the problem of slow intragranular migration of divalent magnesium ions, Li Qilin team from Shanghai Institute of Ceramics, Chinese Academy of Sciences, has developed a large capacity double-salt magnesium-based battery (Adv Funct. Mater. 2015, 25). At the same time, a magnesium-based battery system with an anion embedded activation and an exposed reaction center was proposed (Adv. Funct. Mater. 2015, 25). Recently, The researchers made a metal-organic framework compound ZIF67 as a precursor to prepare a Co, N heterogeneous co-doped graded porous carbon as a sulfur host material to achieve magnesium sulfur battery capacity and cycle performance Significantly improved at 1C rate, the magnesium sulfur battery showed excellent cycle stability, the first discharge capacity up to 600mAh / g, after 200 cycles capacity remained at 400mAh / g or so.At higher 5C rate, The cells still have a reversible capacity of 300-400 mAh / g To continue to improve the electrochemical performance, researchers use reduced graphene modified membranes to optimize the cell architecture, further limiting the Sulfide shuttle, the battery can operate at 0.1C current density for more than 250 cycles, significantly improving the cycle stability of magnesium-sulfur battery. Magnesium sulfur battery excellent electrochemical performance benefits from synergies such as heterogeneous Miscellaneous conducive magnesium sulfur battery charging and discharging in the process of polysulfide adsorption and catalytic decomposition of non-nucleophilic magnesium electrolyte solution added lithium salt and chloride ions is conducive to inhibit the magnesium anode surface passivation and improve electrolyte activity, charge Discharge mode adjustment and membrane modification help to reduce and control the loss of polysulfides, inhibit the shuttle effect.
Relevant research results were published in "Advanced Materials." The research has received funding from the National Key Research and Development Program, the National Natural Science Foundation, the Chinese Academy of Sciences' Hundred Talents Program, and the Shanghai 'Thousand Talents Program'.
