Abstract
Aqueous aluminum batteries are promising post-lithium battery technologies for large-scale energy storage applications because of the raw materials abundance, low costs, safety and high theoretical capacity. However, their development is hindered by the unsatisfactory electrochemical behaviour of the Al metal electrode due to the presence of an oxide layer and hydrogen side reaction. To circumvent these issues, we report aluminum-copper alloy lamellar heterostructures as anode active materials. These alloys improve the Al-ion electrochemical reversibility (e.g., achieving dendrite-free Al deposition during stripping/plating cycles) by using periodic galvanic couplings of alternating anodic α-aluminum and cathodic intermetallic Al2Cu nanometric lamellas. In symmetric cell configuration with a low oxygen concentration (i.e., 0.13 mg L−1) aqueous electrolyte solution, the lamella-nanostructured eutectic Al82Cu18 alloy electrode allows Al stripping/plating for 2000 h with an overpotential lower than ±53 mV. When the Al82Cu18 anode is tested in combination with an AlxMnO2 cathode material, the aqueous full cell delivers specific energy of ~670 Wh kg−1 at 100 mA g−1 and an initial discharge capacity of ~400 mAh g−1 at 500 mA g−1 with a capacity retention of 83% after 400 cycles.
Highlights
Aqueous aluminum batteries are promising post-lithium battery technologies for large-scale energy storage applications because of the raw materials abundance, low costs, safety and high theoretical capacity
We demonstrate that eutectic engineering of Al-based alloy anodes improves their Al reversibility in aqueous electrolyte, based on eutectic Al82Cu18 alloy (E-Al82Cu18) with a lamellar nanostructure consisting of alternating α-Al and intermetallic
The optical micrograph of E-Al82Cu18 alloy sheets reveals that the eutectic solidification produces an ordered lamellar nanostructure of alternating α-Al and intermetallic Al2Cu lamellas with thicknesses of ~150 nm and ~270 nm (Fig. 1e and Supplementary Fig. 1), i.e., the lamellar spacing of ~420 nm
Summary
Aqueous aluminum batteries are promising post-lithium battery technologies for large-scale energy storage applications because of the raw materials abundance, low costs, safety and high theoretical capacity. Lithium-ion batteries (LIBs) dominate the present energy-storage landscape, they are far from meeting the needs of large-scale energy storage due to their inherent issues such as high cost and scarcity of lithium resources, as well as safety problems associated with highly toxic and flammable organic electrolytes[2–4] This dilemma has led to the recent boom in the development of alternative battery technologies[2,5], especially aqueous rechargeable batteries that use monovalent (Na+6, K+ 7) or multivalent (Mg2+8,9, Al3+10–13, Ca2+15, Zn2+16–20) cations as charge carriers in low-cost and safe water-based electrolytes[21,22]. Despite various cathode materials including titanium oxides[27,28], bismuth oxides[29], vanadium oxides[30], aluminum manganese oxides[12,15,22,31], and Prussian blue analogues[32,33] have been explored for reversible Al3+ storage/delivery in aqueous electrolytes via intercalation or conversion reaction mechanisms[10,13,22], these AR-AMBs generally exhibit low Coulombic efficiency and inadequate cycling stability, even in water-in-salt aluminum trifluoromethanesulfonate (Al(OTF)3) electrolytes[10–12,22–25] Their poor rechargeability primarily results from irreversibility of Al anode due to inherent formation of the insulating and passivating aluminum oxide (alumina) layer that substantially limits Al3+ transportation for subsequent Al stripping/plating[10,11,22–25,34]. Such nanostructure enlists the E-Al82Cu18 electrode to have periodically localized galvanic couples of anodic α-
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