Revealing the Magnesium‐Storage Mechanism in Mesoporous Bismuth via Spectroscopy and Ab‐Initio Simulations

Abstract

We present mesoporous bismuth nanosheets as am odel to study the charge-storage mechanism of Mg/Bi systems in magnesium-ion batteries (MIBs). Using asystematic spectroscopyi nvestigation of combined synchrotron-based operando X-ray diffraction, near-edge X-ray absorption fine structure and Raman, we demonstrate ar eversible two-step alloying reaction mechanism Bi$MgBi$Mg 3 Bi 2 .A b-initio simulation methods disclose the formation of aM gBi intermediate and confirm its high electronic conductivity.T his intermediate serves as ab uffer for the significant volume expansion (204 %) and acts to regulate Mg storage kinetics. The mesoporous bismuth nanosheets,a sa ni deal material for the investigation of the Mg charge-storage mechanism, effectively alleviate volume expansion and enable significant electrochemical performance in al ithium-free electrolyte. These findings will benefit mechanistic understandings and advance material designs for MIBs.

Synchrotron X‐ray Spectroscopic Investigations of In‐Situ‐Formed Alloy Anodes for Magnesium Batteries

“…During the charge process, a reversible phase transition from Mg 3 Bi 2 to MgBi occurs as demonstrated in the previous report. [ 15 ] Importantly, approaching the end of the charge process, a new bismuth phase of orthorhombic Bi (o‐Bi) appears at 36.73° with a gradual disappearance of MgBi phase. During the initial alloying/de‐alloying process, the phase transition from m‐Bi to o‐Bi results from the highly efficient alloying/de‐alloying processes owing to the nanosize of the in‐situ‐formed Bi crystals, and similar observations have been reported in tin alloy anode.…”

“…The prototype of reversible alloying/de‐alloying of Mg in Bi was achieved in Mg(N(SO 2 CF 3 ) 2 ) 2 /acetonitrile electrolyte by Arthur et al., [ 6 ] demonstrating the compatibility of Bi with the conventional electrolyte. Bi anodes with various morphologies and components such as Bi nanotubes, [ 7 ] colloidal Bi nanocrystals, [ 8 ] nanocluster Mg 3 Bi 2 alloy, [ 9 ] and mesoporous Bi nanosheets [ 15 ] have been developed to reversibly store Mg 2+ . However, these Bi anodes suffered from severe volume change and limited Mg 2+ diffusion kinetics during alloying/de‐alloying processes, and therefore exhibited poor cycling stability.…”

Efficient Stress Dissipation in Well‐Aligned Pyramidal SbSn Alloy Nanoarrays for Robust Sodium Storage

“…To estimate the electronic conductivity of annealed Sb, Sn, and SbSn anode, the total/partial density of states (TDOS/PDOS) were computed (Figure 5c). It is clear that all three systems are in the metallic state, while SbSn‐SbSnCu has increased DOS at the Fermi level, [ 26 ] corresponding to its highest electron density and thus highest electronic conductivity. Moreover, the d band center of SbSn was significantly shifted to the Fermi level, revealing a reduced anti‐bonding between SbSn‐SbSnCu and other atoms, giving rise to facilitated electrochemical kinetics.…”

Role of binary metal chalcogenides in extending the limits of energy storage systems: Challenges and possible solutions

“…Besides monovalent cation batteries (LIBs/SIBs/PIBs), rechargeable ion batteries based on multivalent cations such as Mg 2+ , Al 3+ , Zn 2+ can be the future energy storage devices due to their high energy density, low cost, and relatively large abundance in the Earth's crust [260][261][262][263]. The working principle of multi-IBs is similar to that of mono-valent ion batteries (LIBs/ SIBs/PIBs) in many ways, except the use of multivalent ion instead of mono-valent ion.…”