A universal strategy towards high–energy aqueous multivalent–ion batteries

Abstract

Rechargeable multivalent metal (e.g., Ca, Mg or, Al) batteries are ideal candidates for large–scale electrochemical energy storage due to their intrinsic low cost. However, their practical application is hampered by the low electrochemical reversibility, dendrite growth at the metal anodes, sluggish multivalent–ion kinetics in metal oxide cathodes and, poor electrode compatibility with non–aqueous organic–based electrolytes. To circumvent these issues, here we report various aqueous multivalent–ion batteries comprising of concentrated aqueous gel electrolytes, sulfur–containing anodes and, high-voltage metal oxide cathodes as alternative systems to the non–aqueous multivalent metal batteries. This rationally designed aqueous battery chemistry enables satisfactory specific energy, favorable reversibility and improved safety. As a demonstration model, we report a room–temperature calcium-ion/sulfur| |metal oxide full cell with a specific energy of 110 Wh kg–1 and remarkable cycling stability. Molecular dynamics modeling and experimental investigations reveal that the side reactions could be significantly restrained through the suppressed water activity and formation of a protective inorganic solid electrolyte interphase. The unique redox chemistry of the multivalent–ion system is also demonstrated for aqueous magnesium–ion/sulfur||metal oxide and aluminum–ion/sulfur||metal oxide full cells.

Aluminum-copper alloy anode materials for high-energy aqueous aluminum batteries

“…15b ), the characteristic peak at the binding energy of 75.0 eV is attributed to the pre-intercalated Al 3+ cations that are engaged into the MnO 6 sheets to adjust the chemical states of Mn 3+ and Mn 4+ (Supplementary Fig. 15c ) 12 , 15 . O 1 s XPS analysis demonstrates that there mainly exist three oxygen-containing species, i.e., the O 2 − in MnO 6 lattice, the OH − and the H 2 O, to correspond to the peaks at the binding energies of 529.8, 530.9, and 533.0 eV (Supplementary Fig.…”

“…Although 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 (Mg 2+ 8 , 9 , Al 3+ 10 – 13 , Ca 2+ 15 , Zn 2+ 16 – 20 ) cations as charge carriers in low-cost and safe water-based electrolytes 21 , 22 . Among these post-lithium energy storage devices, aqueous rechargeable aluminum-metal batteries (AR-AMBs) hold great promise as safe power sources for transportation and viable solutions for grid-level energy storage because of metallic aluminum (Al) offering high volumetric/gravimetric capacities (8056 mAh cm −3 and 2981 mAh g −1 ) by a three-electron redox reaction 10 , 13 , 21 , 23 – 26 , in addition to its low cost and high Earth abundance 10 , 21 .…”

“…Among these post-lithium energy storage devices, aqueous rechargeable aluminum-metal batteries (AR-AMBs) hold great promise as safe power sources for transportation and viable solutions for grid-level energy storage because of metallic aluminum (Al) offering high volumetric/gravimetric capacities (8056 mAh cm −3 and 2981 mAh g −1 ) by a three-electron redox reaction 10 , 13 , 21 , 23 – 26 , in addition to its low cost and high Earth abundance 10 , 21 . 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 Al 3+ 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 Al 3+ transportation for subsequent Al stripping/plating 10 , 11 , 22 – 25 , 34 .…”

Current Status and Challenges of Calcium Metal Batteries

“…[50] Ca 0.4 MnO 2 and Mg 0.15 MnO 2 obtained from ion exchange reactions are also promising good intercalation/deintercalation cathodes for Ca-storage. [4,51]…”

A rechargeable aqueous manganese-ion battery based on intercalation chemistry

“…Among various aqueous rechargeable batteries, those that pair metal anodes with various cathode materials are usually competitive in energy density because metal anodes provide much higher capacity and lower reduction potential than intercalation anodes. Up to now, Zn, Fe, and Al have been directly utilized as the anodes of aqueous rechargeable batteries since they are stable in aqueous electrolytes and possess high theoretical specific capacity 6 – 10 . Whereas the reduction potentials vs. standard hydrogen electrode (SHE) of Zn and Fe (Zn: −0.76 V, and Fe: −0.44 V) are high (Fig.…”