Figure 1 (a) Illustration of the preparation process of carbon-supported Li-Si alloy electrodes. (Reproduced from ref.[47], with permission from Copyright © 2018 The Royal Society of Chemistry.) (b) Scheme illustrating the high-energy ball-milling process using Li grains and Si powders as precursors. (Reproduced from ref.[49], with permission from Copyright © 2014 American Chemical Society.) (c) Hybrid anodes based on facile and fast Sn deposition on reactive metals produced by ion exchange in a common used aprotic liquid lithium electrolyte, 1 M LiPF6 in an ethylene carbonate-dimethyl carbonate (EC/DMC) solvent blend containing a second salt. (Reproduced from ref.[59], with permission from Copyright © 2019 Elsevier Ltd..) Surface morphology and elemental distribution of the cycled (d) Li metal and (e) Li-Mg alloy anode retrieved from the cells after 100 cycles. (Reproduced from ref.[76], with permission from Copyright © 2019 WILEY-VCH.)
Even the theoretical of Li-Zn alloy is not as high as Li-Si, Li-Sn, Li-Ge, Li-Sb alloys, etc., the volume expansion of Li-Zn alloys is not obvious when used in Li storage[82]. Chen et al. reported a Li-Zn alloy synthesized by depositing Li on the Zn substrate precursor at a constant current density of 0.05 mA·cm−2 until the potential reached 0 V (vs. Li/Li+)[82]. The efficiency of Li deposition/stripping on the Li-Zn alloy anode remained high at 96.7% after 400 cycles at a current density of 0.1 mA·cm−2 and 250 cycles at the current density of 0.2 mA·cm−2.
Different from the Si and Sn that experienced reconstitution reaction with lithium to form alloys, Au and Ag, as two typical noble metals, involve solid-solution reaction with Li to form LiAux and LiAgxalloys[83, 84]. The solid-solution reaction involves much less structure change than its counterpart (e.g. Si and Sn) in the lithiation-delithiation process, therefore can take place with a low charge-discharge voltage hysteresis at a potential that is very close to that of Li/Li+ redox couple and eliminate the nucleation barriers[83]. For example, in 2016, Cui’s group has found Au, Ag, Zn and Mg with good solubility in Li, once fully lithiated, exhibited zero overpotential during deposition of Li as shown in Figure 2a[84]. For materials Al and Pt have relatively small solubility in Li metal and show small but observable overpotential for Li nucleation (5 mV for Al, 8 mV for Pt); For materials showing no solubility (Cu, Ni, C, Sn, Si) in lithium were also tested, as shown in Figure 2b, all five materials show a clear overpotential for Li metal nucleation. According to this vital findings, they designed Au nano particles distributed inside the hollow carbon spheres to selectively nucleate and grow Li metal inside carbon nanoshells during electrochemical deposition, as shown in Figure 2c.