Highly Reversible Mg Insertion in Nanostructured Bi for Mg Ion Batteries

Abstract

Rechargeable magnesium batteries have attracted wide attention for energy storage. Currently, most studies focus on Mg metal as the anode, but this approach is still limited by the properties of the electrolyte and poor control of the Mg plating/stripping processes. This paper reports the synthesis and application of Bi nanotubes as a high-performance anode material for rechargeable Mg ion batteries. The nanostructured Bi anode delivers a high reversible specific capacity (350 mAh/gBi or 3430 mAh/cm(3)Bi), excellent stability, and high Coulombic efficiency (95% initial and very close to 100% afterward). The good performance is attributed to the unique properties of in situ formed, interconnected nanoporous bismuth. Such nanostructures can effectively accommodate the large volume change without losing electric contact and significantly reduce diffusion length for Mg(2+). Significantly, the nanostructured Bi anode can be used with conventional electrolytes which will open new opportunities to study Mg ion battery chemistry and further improve its properties.

Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI)2 in Diglyme: Implications for Multivalent Electrolytes

“…These systems provide a relatively facile delivery of Mg 2+ ions in a chloride-free electrolyte and an 28,30,48,49 in cells with a working Mg electrode. However, these electrolytes suffer from low (≤87%) CE, significant overpotential, destructive incompatibilities with Mg metal resulting in passivation of the anode surface, and parasitic loss of electrolyte due to the electrochemical decomposition of solvent (e.g., AN) mimicking Mg-plating/insertion.…”

Composite Anodes for Secondary Magnesium Ion Batteries Prepared via Electrodeposition of Nanostructured Bismuth on Carbon Nanotube Substrates

“…16 In addition, using 0.4 M Mg(TFSI) 2 in diglyme, ∼60 mAh/g was observed under repeated cycling in a cathode limited cell configuration. 16 Notably, repeated cycling of bismuth electrodes in non-corrosive lithium-free magnesium- * Electrochemical Society Active Member. Carbon nanotubes (CNT) have been reported to function effectively as current collecting electrode substrates, holding several advantages as electrode supports relative to metal foils.…”

“…15 Liu and coworkers reported ∼300 mAh/g capacities for chemically synthesized bismuth nanotubes in special electrolyte consisting of a Mg(BH 4 ) 2 /LiBH 4 mixture. 16 In addition, using 0.4 M Mg(TFSI) 2 in diglyme, ∼60 mAh/g was observed under repeated cycling in a cathode limited cell configuration. 16 Notably, repeated cycling of bismuth electrodes in non-corrosive lithium-free magnesium- * Electrochemical Society Active Member.…”

“…15,16 Assuming six electron equivalents of bismuth oxidation to form magnesium bismuthide, (3Mg 2+ + 2Bi + 6e − Mg 3 Bi 2 ) translates to a theoretical capacity of 385 mAh/g Bi, Figure 1. As bismuth is a dense material (9.8 g/cm 3 ), a significant volume expansion (25-40% increase in Bi-Bi bond length for Mg 3 Bi 2 ) is required to accommodate Mg 2+ insertion and thus loss of contact to the current collecting electrode substrate upon repeated cycling may occur.…”

Principles and Prospects of High-Energy Magnesium-Ion Batteries

“…Whereas commercial microsphere Bi powder undergoes pulverization on cycling in a magnesium cell (Fig. 2), Shao et al 4 at the Pacific Northwest National Laboratory, Washington, demonstrated that bismuth nanotubes could be used in magnesium anodes with fast charge-discharge rates and a capacity of 303 mA h g -1 , even after 200 cycles. Very recently, Parent et al, also at the Pacific Northwest National Laboratory produced a Sb-Sn alloy that was electrochemically conditioned to form Sn-rich nanoparticles 5 ; scanning transmission electron microscopy indicated that these (<40nm) particles would have excellent performance in Mg battery anodes, although electrochemical data have not yet been reported.…”