The development of new rechargeable battery systems could fuel various energy applications, from personal electronics to grid storage. Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. However, research efforts over the past 30 years have encountered numerous problems, such as cathode material disintegration, low cell discharge voltage (about 0.55 volts; ref. 5), capacitive behaviour without discharge voltage plateaus (1.1-0.2 volts or 1.8-0.8 volts) and insufficient cycle life (less than 100 cycles) with rapid capacity decay (by 26-85 per cent over 100 cycles). Here we present a rechargeable aluminium battery with high-rate capability that uses an aluminium metal anode and a three-dimensional graphitic-foam cathode. The battery operates through the electrochemical deposition and dissolution of aluminium at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, using a non-flammable ionic liquid electrolyte. The cell exhibits well-defined discharge voltage plateaus near 2 volts, a specific capacity of about 70 mA h g(-1) and a Coulombic efficiency of approximately 98 per cent. The cathode was found to enable fast anion diffusion and intercalation, affording charging times of around one minute with a current density of ~4,000 mA g(-1) (equivalent to ~3,000 W kg(-1)), and to withstand more than 7,500 cycles without capacity decay.

In recent years, impressive advances in harvesting renewable energy have led to a pressing demand for the complimentary energy storage technology. Here, a high Coulombic efficiency (∼99.7%) Al battery is developed using earth-abundant aluminum as the anode, graphite as the cathode, and a cheap ionic liquid analog electrolyte made from a mixture of AlCl 3 and urea in a 1.3:1 molar ratio. The battery displays discharge voltage plateaus around 1.9 and 1.5 V (average discharge = 1.73 V) and yielded a specific cathode capacity of ∼73 mAh g −1 at a current density of 100 mA g −1 (∼1.4 C). High Coulombic efficiency over a range of charge-discharge rates and stability over ∼150-200 cycles was easily demonstrated. In situ Raman spectroscopy clearly showed chloroaluminate anion intercalation/deintercalation of graphite (positive electrode) during charge-discharge and suggested the formation of a stage 2 graphite intercalation compound when fully charged. + cations. This battery is a promising prospect for a future high-performance, low-cost energy storage device.aluminum-ion battery | urea electrolyte | ionicity | ionic liquid | energy storage C heap, high-rate (fast charge/discharge) rechargeable batteries with long cycle lives are urgently needed for grid-scale storage of renewable energy, as it is becoming increasingly important to replace fossil fuels (1). Lithium-ion batteries (LIBs) are expensive and have limited cycle life, which makes them nonideal for grid-scale energy storage. Furthermore, high-rate capability is necessary for use in the grid, under which conditions LIBs become increasingly unsafe due to the flammability of the electrolytes used. Batteries based on aluminum offer a viable alternative due to aluminum's three-electron redox properties (offers potential for high-capacity batteries), stability in the metallic state, and very high natural abundance. Furthermore, the development of these batteries based on nonflammable electrolytes of low toxicity is critical for minimizing safety hazard and environmental impact. Recently, our group developed a secondary Al battery system based on the reversible deposition/stripping of aluminum at the Al negative electrode and reversible intercalation/deintercalation of chloroaluminate anions at the graphite positive electrode in a nonflammable 1-ethyl-3-methylimidazolium chloroaluminate (EMIC-AlCl 3 ) IL electrolyte (7,8). A ratio of AlCl 3 /EMIC = 1.3 by mole was used such that Al 2 Cl 7 − was present in the (acidic) electrolyte to facilitate aluminum deposition (9). During charging, Al 2 Cl 7 − is reduced to deposit aluminum metal, and AlCl 4 − ions intercalate (to maintain neutrality) in graphite as carbon is oxidized. During discharge, this battery exhibited a cathode specific capacity of ∼70 mAh g −1 with a Coulombic efficiency (CE) of 97-98%, and ultrahigh charge/discharge rate (up to 5,000 mA g −1 ) for over 7,000 cycles. However, room for improvement exists as the parameter space for the Al battery remains largely unexplored. The three-electron redox properti...

Recently, interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. Here, an aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of ∼110 mAh g−1 with Coulombic efficiency ∼98%, at a current density of 99 mA g−1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60 mAh g−1 at 6 C, over 6,000 cycles with Coulombic efficiency ∼ 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Finally, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.

A 3D graphitic foam vertically aligned graphitic structure and a low density of defects is derived through chloroaluminate anion intercalation of graphite followed by thermal expansion and electrochemical hydrogen evolution. Such aligned graphitic structure affords excellent Al-ion battery characteristics with a discharge capacity of ≈60 mA h g under a high charge and discharge current density of 12 000 mA g over ≈4000 cycles.

Sodium is a promising anode material for batteries due to its low standard electrode potential, high abundance and low cost. In this work, we report a new rechargeable ~ 3.5 V sodium ion battery using Na anode, amorphous carbon-nanosphere cathode and a starting electrolyte comprised of AlCl 3 in SOCl 2 with uoride-based additives. The battery, exhibiting ultrahigh ~ 2800 mAh/g rst discharge capacity, could cycle with a high reversible capacity up to ~ 1000 mAh/g. Through battery cycling, the electrolyte evolved to contain NaCl, various sulfur and chlorine species that supported anode's Na/Na + redox and cathode's chloride/chlorine redox. Fluoride-rich additives were important in forming a solid-electrolyte interface, affording reversibility of the Na anode for a new class of high capacity secondary Na battery. Main TextDevising new battery concepts is important to meeting society's growing demand of energy storage.Different rechargeable batteries have been developed, including lithium ion batteries (LIBs), sodium ion batteries (SIBs) and aluminum ion batteries (AIBs) [1][2][3][4][5][6][7][8][9] . Prior to the invention of secondary LIBs, a primary Li-metal battery was developed in the 1970's using thionyl chloride (SOCl 2 ) as a catholyte, Li metal as anode and amorphous carbon as the positive electrode [10][11][12][13][14][15][16] . The Li-SOCl 2 battery was attractive due to its high energy density, but did not receive sustained interest due to the lack of rechargeability 17,18 . The battery discharges through Li anode oxidation and catholyte SOCl 2 reduction into sulfur (S), sulfur dioxide (SO 2 ), and chloride ion (Cl -) on the carbon electrode 19,20 . The Clions react with Li + stripped from