No abstract

A 3D porous Al foil coated with a uniform carbon layer (pAl/C) is prepared and used as the anode and current collector in a dual-ion battery (DIB). The pAl/C-graphite DIB demonstrates superior cycling stability and high rate performance, achieving a highly reversible capacity of 93 mAh g after 1000 cycles at 2 C over the voltage range of 3.0-4.95 V. In addition, the DIB could achieve an energy density of ≈204 Wh kg at a high power density of 3084 W kg .

imperative to develop new-generation batteries with high energy densities as well as long cycle lives and good safety. [4][5][6][7][8] These demands trigger intense research leading to various intelligent designs of novel device structures in LIB technology. [9][10][11][12][13][14][15] Dual-ion battery (DIB), typically dualgraphite battery, has been proposed as a novel energy storage device with unconventional architecture which has the merits of high safety and environmental friendliness over conventional LIBs. [16,17] The main difference of working mechanism between DIB and LIB is that both cations (typically Li + ) and anion (such as PF 6 − ) are involved in such DIB for charge transportation and storage, while conventional LIB involves only Li + ion. In 1994, Carlin et al. pioneered the concept of a novel DIB which works via intercalation/ deintercalation of PF 6 − and EMI + at a graphite cathode and a graphite anode, respectively. [18] Consequently, several related works have been reported on DIBs based on different anions, including PF 6 − , BF 4 − , and ClO 4 − , [19][20][21] with high cut-off voltages (4.5-5.2 V vs Li + /Li) and specific capacity up to ≈90 mA h g −1 . [22] For instance, Read et al. reported a dual-graphite battery based on an organic electrolyte containing LiPF 6 , which exhibits a specific capacity of 60 mA h g −1 and a ≈62% capacity retention at C/7 rate after 50 cycles. [22] As these anions intercalate into the graphite cathode typically at potentials up to ≈5 V versus Li + /Li, energy densities of these DIBs are usually higher than those of the conventional LIBs. Generally, most of reported DIBs used carbon materials as cathode, and carbon, [16][17][18][19][20]22] Li, [21] Si, [23] or metal oxide [24][25][26][27] as anode. Recently, we reported a novel DIB using an aluminum foil as anode which also enables the elimination of additional metal current collector and leads to further energy density enhancement and cost saving. [28] However, similar to most of DIBs, its cycling stability is still limited by decomposition of the organic electrolyte due to the high working voltages of DIBs. Additionally, organic solvents in the electrolyte can also cointercalate into the graphite cathode forming Cn + (solv) y X − , [29] resulting in graphite exfoliation upon cycling. Thus, developing appropriate electrolytes with good stability at high voltage is a key challenge for enhancing the cycling stability of DIBs.Ionic liquids (ILs), composed of liquid-state molten salts at room temperature, show good potential in electrochemistry as A novel dual-ion battery constructed with aluminum foil anode and mesocarbon microbead (MCMB) cathode based on a lithium-salt containing ionic liquid electrolyte is prepared. The working mechanism of this Al-MCMB dualion battery is demonstrated to be intercalation/deintercalation of anions into/ from the MCMB cathode and AlLi alloying/dealloying at the Al anode. Owing to the good stability of ionic liquid at high working voltage and the protection of fluoroethylene carb...