Solid–Solution-Based Metal Alloy Phase for Highly Reversible Lithium Metal Anode

Abstract

Lithium metal batteries (LMB) are vital devices for high-energy-density energy storage, but Li metal anode is highly reactive with electrolyte and forms uncontrolled dendrite that can cause undesirable parasitic reactions thus poor cycling stability and raise safety concerns. Despite remarkable progress made to partly solve these issues, the Li metal still plate at the electrode/electrolyte interface where the parasitic reactions and dendrite formation invariably occur. Here we demonstrate the inwardgrowth plating of Li into a metal foil while avoiding surface deposition, which is driven by the reversible solid-solution based alloy phase change. Lithiation of the solid solution alloy phase facilitates the freshly generated Li atoms at the surface to sink into the foil, while the reversible alloy phase change is companied by the dealloying reaction during delithiation, which extracts Li atoms from inside of the foil. The yielded dendrite free Li anode produces an enhanced Coulombic efficiency of 99.5  0.2% with a reversible capacity of 1660 mA h g -1 (3.3 mA h cm -2 ).

Structural Evolution upon Delithiation/Lithiation in Prelithiated Foil Anodes: A Case Study of AgLi Alloys with High Li Utilization and Marginal Volume Variation

“…Figure 4g illustrates the schematic diagram of the cross‐section morphology evolutions with the marginal volume variation. As compared to reported anodes in literatures, [ 5a,11a,22 ] NPAgLi electrode with a high theoretical capacity (AgLi‐10%, ≈1420 mAh g −1 ) exhibits a unique ability to inhibit volume change, which is a very attractive character for practical applications (Figure 4h).…”

“…Very recently, foil anodes composed of Li‐rich alloys have been proposed as a family of novel anodes with high capacities. [ 5 ] In comparison to Li‐free metals, such anodes provide necessary shuttling ions when coupled with sulfur/oxygen cathodes, which are also of vital importance for the essentially high efficiencies and stable cycling of cells. Furthermore, the Li‐M components serve as functional skeletons to mitigate volume variation and regulate Li deposition patterns, while Li is the sacrificial element as Ag in Au‐Ag precursors.…”

“…[ 1a ] It was found external electrical current had great impacts on dealloyed morphologies, and the Li dissolution process was highly associated with compositions and particle sizes of pristine materials, a sharp contrast to the free corrosion model of Au‐Ag. [ 10 ] As discussed above, Li‐rich alloy composite anodes have demonstrated great potentials in battery applications, [ 5 ] but most of the delithiated electrodes have random structures and morphologies and few publications discuss this class of electrodes from the dealloying perspective to explore structural evolution. Previous research experiences suggest the typical bicontinuous nanoporosity is more preferable for efficient mass/charge transfer within electrodes.…”

“…[ 12 ] More importantly, the topotactic solid‐solution reactions between Ag and Li afford minor phase or structural changes during the Li alloying process and thereby only small activation energy is required to realize low charge–discharge voltage hysteresis. [ 5a ] Also, the consecutive compositional variation of Li‐Ag solid‐solution phases takes place at similar thermodynamic redox potentials below 0.2 V versus Li/Li + at a wide Li‐Ag composition range, [ 12h ] which is different from the intermetallic phases such as the lithiation of Sn electrodes. [ 1a ] Thus, Li‐Ag is a suitable model to perform studies on structure and morphology upon electrochemical dealloying.…”

Li‐containing alloys beneficial for stabilizing lithium anode: A review

“…Si and Sn) in the lithiation-delithiation process, and can therefore take place with a low charge-discharge voltage hysteresis at a potential that is very close to that of the Li/Li + redox couple and eliminate the nucleation barriers. 82 For example, in 2016, Cui's group has found that Au, Ag, Zn, and Mg have good solubility in Li, and once fully lithiated, exhibited zero overpotential during deposition of Li as shown in Figure 2A. 51 The 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); Materials showing no solubility (Cu, Ni, C, Sn, Si) in lithium were also tested.…”