Core–Shell Aluminum@Carbon Nanospheres for Dual‐Ion Batteries with Excellent Cycling Performance under High Rates

Abstract

In a typical DIB, graphite is not only used as the anode material but can also serve as the cathode due to its intrinsic redox amphoteric nature. Thus, both Li + cations and anions such as PF 6 − and BF 4 − can intercalate/deintercalate into/from the graphite layers during the charging and discharging processes. Researchers have continued to make progress in DIBs, including studies on the intercalation of different anions into graphite, different cathode materials (e.g., graphitic carbon, [6] metalorganic frameworks, [7] aromatic amines, [8] etc.), investigation of the anion intercalation process, [9] and so on. Although these DIBs usually exhibit higher working voltages (above 4.5 V) than conventional LIBs (normally 3.7 V), their capacities are much lower (typically below 100 mA h g −1 ), which results in moderate energy densities. Recently, by using Al foil as both the anode and current collector, our group reported an aluminum-graphite DIB (AGDIB), which exhibited decreased dead volume and dead weight for the full cell, thus significantly enhanced the energy density of DIB. [10] However, the cycling stability of this AGDIB is still unsatisfied, partially because Al-Li alloying/dealloying on the Al foil anode during the cycling process caused the Al to crack and pulverize, which has been similarly observed in other alloy-type anodes (e.g., Si, Sn, Ge, etc.). [3,11] This pulverization issue is actually caused by the tendency of Al to experience large volume changes during the alloying/dealloying processes (expanding/shrinking by up to ≈97% for AlLi [12] ). The volume change can cause two failure modes: (1) loss of electrical contact during cycling and (2) repeated breaking and reformation of the solid electrolyte interphase (SEI) layer, causing the active materials to continuously consume the electrolyte. [13,14] These failures lead to large irreversible capacities, as well as rapid capacity fading.Herein, we report core-shell Al and carbon nanospheres (named as nAl@C) as anode materials to optimize the cycling performance of Al-based DIBs. It was found that the nAl@C can accommodate mechanical strain and stress better than flat electrodes, thus inhibiting pulverization. In addition, the conductive carbon layer is beneficial for conducting both Li + ions and electrons, which helps to form the SEI film. The DIB based on nAl@C nanospheres anode exhibited superior long-term cycling stability with a capacity retention of 94.6% after 1000 cycles at a high current rate of 15 C (1 C = 100 mA g −1 ) in the Dual-ion battery (DIB) has been proposed as a novel energy storage device with the merits of high safety, low cost and environmental friendliness. Herein, we have developed core/shell aluminum@carbon nanospheres (nAl@C) as anode material for DIB. The nanoscale framework is composed of an Al nanosphere and an amorphous carbon outer layer that is conductive and protective, facilitating the formation of a stable SEI film during cycling. Owing to the core-shell structural design, the nAl@C nanospheres demonstrate signif...

Strategies towards Low‐Cost Dual‐Ion Batteries with High Performance

“…This integrated DIB exhibited superior long-term cycling stability with capacity retention about 61 % after 1500 cycles at high current rate of 60 C. The integrity of the porous structure of Al anode still maintained very well after long-term cycling without obvious Graphite 106 (at 1 C) ca. 4.2 1500 / 99% at 2 C 85 mAh g À1 at 10 C Carbon-coated Al nanospheres [114] Graphite 105 (at 2 C) 4.2 1000 / 89% at 2 C 100 mAh g À1 at 10 C (87 mAh g À1 at 20 C) pulverization, suggesting the effective volume change accommodation by the porous structure. Moreover, ultrafast charge/ discharge rate up to 120 C was achieved.…”

“…SEM morphologies of a) Al nanospheres (nAl), b) carboncoated Al nanospheres (nAl@C), c) HRTEM images of the nAl@C nanospheres, and d) Long-term cycling stability of the nAl@C-G DIB at a high current rate of 15 C for 1000 cycles. Reproduced from Ref [114]. with permission from WILEY-VCH, copyright 2018.…”

Electrolytes for Batteries with Earth‐Abundant Metal Anodes

“…The process is accomplished inside the cell electrochemically, so that there is no need to worry aboutt he handling of active potassium metal.T he same configuration is also applicable for sodium-ion-based dual-ion cells (Figure 8g). [96][97][98][99] Most recently,b enefiting from the dendrite-free properties and lower platingb arrier,aroom-temperature calcium-based dual-ion battery with tin as the alloy-type anode was first introduced (Figure 8i,j,k). It is known that lithium ions can alloy with aluminum at low po-tentials.T his makes aluminumb oth the current collector and anode material.…”

“…[95] Additionally,m odification of the aluminuma node, separator,o rc ell configuration can also enhancet he performance of aluminum-based dual-ion batteries;t his is beyond the scope of this review. [96][97][98][99] Most recently,b enefiting from the dendrite-free properties and lower platingb arrier,aroom-temperature calcium-based dual-ion battery with tin as the alloy-type anode was first introduced (Figure 8i,j,k). The dual-ion cell showed as pecific capacity of 70 mA h À1 g À1 at ac urrent density of 100 mA g À1 with ac ell voltage of 5V .T he electrolyte for this dual-ion battery was composed of two kinds of carbonates:c yclic carbonates that can dissolve CaPF 6 salts and linear carbonates that reduce the viscosity and increase the ionic conductivity.…”

Microstructure Characteristics of Cathode Materials for Rechargeable Magnesium Batteries

“…Li et al presented a nanostructured rhodizonate salt (Na 2 C 6 O 6 ) as cathode material for Mg–organic battery in a dual‐salt electrolyte. The Mg‐storage behavior of the Mg–organic battery was based on the dual‐ion battery principle . The Mg–organic battery demonstrated a high discharge capacity of 400 mAh g −1 and an operating voltage of ≈2.2 V.…”