Tin–Germanium Alloys as Anode Materials for Sodium-Ion Batteries

Abstract

The sodium electrochemistry of evaporatively deposited tin, germanium, and alloys of the two elements is reported. Limiting the sodium stripping voltage window to 0.75 V versus Na/Na+ improves the stability of the tin and tin-rich compositions on repeated sodiation/desodiation cycles, whereas the germanium and germanium-rich alloys were stable up to 1.5 V. The stability of the electrodes could be correlated to the surface mobility of the alloy species during deposition suggesting that tin must be effectively immobilized in order to be successfully utilized as a stable electrode. While the stability of the alloys is greatly increased by the presence of germanium, the specific Coulombic capacity of the alloy decreases with increasing germanium content due to the lower Coulombic capacity of germanium. Additionally, the presence of germanium in the alloy suppresses the formation of intermediate phases present in the electrochemical sodiation of tin. Four-point probe resistivity measurements of the different compositions show that electrical resistivity increases with germanium content. Pure germanium is the most resistive yet exhibited the best electrochemical performance at high current densities which indicates that electrical resistivity is not rate limiting for any of the tested compositions.

A review of carbon materials and their composites with alloy metals for sodium ion battery anodes

“…Yu et al have synthesized a carbon coated NVP embedded in a porous carbon matrix [211]. Mai's group also demonstrated similar work by studying the effect of carbon matrix dimensions on the electrochemical properties of NVP [53].…”

“…However, large volume expansion/contraction associated with alkaline ion insertion-extraction is known to generate tremendous damage to electrodes, leding to the loss of electrical contact and subsequently rapid capacity fading [52]. Considering such factors that hinders metal oxide-based anode, someworth attention were given to the development of elements that can alloy with Na named "Alloy Materials" [53][54][55][56]. For example, many elements of Group IVA and VA of the periodic table, such as Ge, Sn, Sb, P etc.…”

“…can alloy with Na to form rich alloy phases such as NaGe, Na 3.75 Sn, Na 3 Sb, and Na 3 P and high capacity Na-storage were realized [53][54][55][56]. Such an alloying reaction was able to attain large capacities to a great extent but obstacles, accompanied with huge volume expansion of the host materials due to the continuous pulverization of the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 6 electrode materials, still posed a basic dilemma.…”

Metallic Sn‐Based Anode Materials: Application in High‐Performance Lithium‐Ion and Sodium‐Ion Batteries

“…Benefiting from these synergistic effects, the Sn‐based alloys usually exhibit merits of both high specific capacity and long cycling life 103, 104. Up to now, many Sn‐based compounds alloyed with active elements have been investigated as potential anode materials, including Ge‐Sn,105, 106, 107 Sb–Sn,108, 109, 110, 111, 112 Ag–Sn,113, 114, 115 Mg–Sn,116, 117, 118 etc.…”

The electrochemical reactions of SnO2 with Li and Na: A study using thin films and mesoporous carbons

“…4 Co-Sn alloys [28,29], Ge [30][31][32][33] and In [34]. Tin [7][8][9][10][11][12] and antimony [15][16][17][18] are particularly interesting since they can store up to 3.75 and 3 Na/M (M=Sn, Sb), corresponding to large expected storage capacities of 847 and 660 mAh g -1 , respectively.…”