Reducing Mg Anode Overpotential via Ion Conductive Surface Layer Formation by Iodine Additive. Issue 7 (24th October 2017)

• Record Type: Journal Article
• Authors: Li, Xiaogang; Gao, Tao; Han, Fudong; Ma, Zhaohui; Fan, Xiulin; Hou, Singyuk; Eidson, Nico; Li, Weishan; Wang, Chunsheng
• Is Part Of: Advanced energy materials. Volume 8:Issue 7(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-10-24
• Subjects: electrochemistry -- iodine additive -- Mg(TFSI)2‐DME simple salt electrolyte -- reduce overpotential -- sulfur; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201701728
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Electrolytes that are able to reversibly deposit/strip Mg are crucial for rechargeable Mg batteries. The most studied complex electrolytes based on Lewis acid‐base chemistry are expensive, difficult to be synthesized, and show limited anodic stability. Conventional electrolytes using simple salts such as Mg(TFSI)2 can be readily synthesized, but Mg deposition/stripping in these simple salt electrolytes is accompanied by a large overpotential due to the formation of a surface layer on the Mg metal with a low Mg ion conductivity. Here the overpotential for Mg deposition/stripping in a simple salt, Mg(TFSI)2 ‐1, 2‐dimethoxyethane (DME), electrolyte is significantly reduced by adding a small concentration of iodine (≤50 × 10 −3 m ) as an additive. Mechanism studies demonstrate that an Mg ion conductive solid MgI2 layer is formed on the surface of the Mg metal and acts as a solid electrolyte interface. With the Mg(TFSI)2 ‐DME‐I2 electrolyte, a very small voltage hysteresis is achieved in an Mg‐S full cell. Abstract : A solid electrolyte interphase (SEI) layer is formed due to the reaction of iodine with Mg, whose main component is magnesium iodide. This SEI layer dramatically decreases the overpotential of Mg deposition/stripping, hence enabling the usage of simple electrolyte Mg(TFSI)2 ‐1, 2‐dimethoxyethane (DME) in full cells. For the first time, the SEI concept is successfully used in Mg batteries to address the interfacial kinetics problem.