Rechargeable Al-ion Batteries Research Articles

Self-healing liquid metal layer as high-capacity and long cycle life anode for Al-ion batteries

Rechargeable Al-ion batteries (AIBs) with high capacity and Earth-abundant metal resources are gaining attention. However, the anode side of AIBs has been overlooked, with most using pure Al foil as the anode. In this study, a simple brush painting technique using eutectic Ga-In (EGaIn) liquid metal (LM) creates a high-performance AIBs anode. The EGaIn@Mo anode allows uniform and reversible plating/stripping of Al for over 10,000 h at 10 mAh cm−2 with 99.6 % average Coulombic efficiency. It enables half-cell operation at an ultrahigh areal capacity of 50 mAh cm−2 for over 1200 h. A full cell with EGaIn@Mo anode and graphite cathode maintains a reversible capacity of 82.8 mAh g−1 after approximately 6000 cycles at a high rate of 2 A g−2, exhibiting an ultralow capacity fading rate of 0.00064 % per cycle. Moreover, an anode-free cell lasts over 800 cycles with a specific capacity of 75.9 mAh g−1. This work demonstrates the potential of EGaIn LM coating for high-capacity AIBs and LM anode application.

Long-chain alkylammonium organic–inorganic hybrid perovskite for high performance rechargeable aluminon-ion battery

Recent advances in the use of organic-inorganic hybrid perovskites have been investigated in a variety of applications, such as solar cells, photodetectors, light-emitting devices, and lasers, because of their outstanding semiconductor properties. Furthermore, the perovskite structure can host extrinsic elements, making it a promising candidate for battery applications. Previous studies have shown that organic-inorganic hybrid perovskites can be suitable anode materials for both lithium- and sodium-ion batteries. However, multivalent rechargeable batteries with perovskite materials have not yet been realized. Herein, we studied the electrochemical performance of three-dimensional (CH3NH3PbI3 (MAPbI3) and long-chain alkylammonium (C4H9NH3)2(CH3NH3)3Pb4I13 ((iBA)2(MA)3Pb4I13) thin films as electrode materials for rechargeable Al-ion batteries. Our results showed that (iBA)2(MA)3Pb4I13 presented a specific capacity of 257 mAh g–1 at a current density of 0.1 A g−1 and delivered 108 mAh g–1 after 250 cycles at a current density of 0.3 A g−1 with a retention of as high as 91 %, demonstrating a crucial role of isobutyl amine (C4H9NH3) due to the unique hydrogen-bonding interaction of isobutyl amine that hinders the shuttle effect of polyiodide. The results open a new direction for the use of organic–inorganic hybrid perovskites for new secondary aluminum ion batteries.

Enabling Al-metal anodes for aqueous electrochemical cells by using low-cost eutectic mixtures as artificial protective interphase

Elemental aluminum is an exciting battery anode material due to its high abundance and volumetric capacity (8040 mAh cm−3). However, it tends to form a stubborn surface oxide layer that blocks ion transport through the electrode–electrolyte interphase and stops battery cyclability. To circumvent this problem, here we engineer an artificial protective barrier layer on metallic Al by using AlCl3 + urea and AlCl3 + triethylamine hydrochloride eutectic coating formulations. We find both coatings provide significantly facile ion migration kinetics at the anode/electrolyte interface, enabling a drastic reduction in anodic electroplating/stripping overpotentials, but AlCl3 + urea is superior. Using depth-profiling XPS spectroscopy and impedance studies, we find that the AlCl3 + urea derived artificial interphase is also stable in ambient air, affording extended protection for metallic Al anodes from air-oxidation in the form of a battery electrode SEI. We demo the eutectic-treated Al anode (UTAl) based on a FeHCF | 2 m AlTFS | UTAl full cell chemistry and obtain a stable battery performance of ∼ 60 Wh kg−1 over 100 cycles. Our study promotes the strategic viability of using facile, inexpensive reagent treatments to enable the application of water-based electrolytes for rechargeable Al-ion batteries, and specifically encourages systematic exploration of analogue coating formulations using our anode enhancement protocol for similar high-capacity metal/alloy battery chemistries.

H-MoO3/AlCl3-Urea/Al: High performance and low-cost rechargeable Al-ion battery

A completely functional rechargeable aluminium – ion battery (AIB) operating at room temperature based on hexagonal molybdenum oxide (h-MoO3) as positive electrode active material and AlCl3-Urea as electrolyte has been developed. This is the first demonstration of the compatibility between a metal oxide and a urea based electrolyte in an AIB. Our battery shows a good electrochemical performance by using this low-cost, eco-friendly, positive electrode - electrolyte system with low corrosion properties. Thanks to an exhaustive study carried out by using different characterization techniques (XRD, micro-Raman, CV), it has been observed that h-MoO3 is capable of efficiently inserting and de-inserting the redox active species in its crystalline structure by means of controlled diffusion processes. When combined with a suitable amount of carbon nanotubes, the capacitive properties of this material are enhanced, obtaining batteries with a pseudo-capacitive behaviour. This battery reaches specific capacity values ∼100 mA h g−1 at current densities of 100 mA g−1 and ∼45 mA h g−1 at current densities of 500 mA g−1, always with efficiencies higher than 90%. The obtained results pave the way for the commercialisation of these energy storage devices, providing a promising and simple strategy for the development of high performance, low-cost and non-corrosive AIBs.

Rechargeable Al-ion batteries

Aluminum (Al) is the most abundant metal element in earth crust, together with low cost and high safety. Al-ion batteries (AIBs) have been regarded as potential alternatives to lithium-ion batteries (LIBs) in large scale applications and attracted much attention in current days. In this review, recent developments of AIBs including the electrolyte exploration, electrode design and Al protection are summarized. Both aqueous and non-aqueous electrolytes exhibit important benefits for AIBs, especially ionic liquid electrolytes with high stripping/plating efficiency, which are preferentially discussed here. Furthermore, we highlight the design principles and electrochemical mechanism for carbons, metal compounds as well as new-type positive electrode materials for high-performance AIBs. Besides, we focus on the negative electrode protection with suitable coating layers to reduce dendrite formation and improve electrochemical activation of Al negative electrodes. The accessible characterization techniques that promote the development of AIBs are discussed. Finally, prospects and outlooks of AIBs towards theoretical investigations and practical applications are provided.

Quasi-2D Organic–Inorganic Hybrid Perovskite for High Performance Rechargeable Aluminon-Ion Battery

Recent advances in the use of organic–inorganic hybrid perovskites have been investigated in a variety of applications, such as solar cells, photodetector, light emitting devices (LEDs), and lasers because of their outstanding semiconductor properties. Furthermore, the perovskite structure has the ability to host extrinsic elements, making it a promising candidate for battery field. Previous studies have shown that organic–inorganic hybrid perovskites can be a suitable anode material for both lithium- and sodium-ion batteries. However, the multivalent rechargeable batteries with perovskite material have not yet been realized. Herein, we studied the electrochemical performance of three-dimensional (3D) CH3NH3PbI3 and quasi-two dimensional (C4H9NH3)2(CH3NH3)3Pb4I13 thin films as electrode materials for rechargeable Al-ion batteries. In this work, these electrodes were successfully synthesis on carbon cloth through a feasible solution process. The (C4H9NH3)2(CH3NH3)3Pb4I13 electrode yield a specific capacity of 210 mAh g–1 at the current density of 50mA g−1 . It still delivered 81 mAh g–1 after 250 cycles at the current density of 200mA g−1 with a retention of as high as 95%, indicating a long cycling stability. Compared with the CH3NH3PbI3, the (C4H9NH3)2(CH3NH3)3Pb4I13 presented higher initial capacities, better reversibility, and more excellent high-rate capabilities, all demonstrating the vitally prominent role of isobutyl amine (C4H9NH3). which can be attributed to the unique hydrogen-bonding interaction of isobutyl amine could effectively hinder the shuttle effect of polyiodide. We anticipate that these results open a new direction for the use of organic–inorganic hybrid perovskites for new secondary aluminum ion batteries.

Al homogeneous deposition induced by N-containing functional groups for enhanced cycling stability of Al-ion battery negative electrode

Rechargeable Al-ion batteries (AIBs) are considered as one of the most fascinating energy storage systems due to abundant Al resource and low cost. However, the cycling stability is subjected to critical problems for using Al foil as negative electrode, including Al dendrites, corrosion and pulverization. For addressing these problems, here a lightweight self-supporting N-doped carbon rod array (NCRA) is demonstrated for a long-life negative electrode in AIBs. Experimental analysis and first-principle calculations reveal the storage mechanism involving the induced deposition of N-containing function groups to Al as well as the ideal skeleton of the NCRA matrix for Al plating/stripping, which is favorable for regulating Al nucleation and suppressing dendrites growth. Compared with the Al foil, the NCRA exhibits lower areal mass density (∼ 72% of Al foil), smaller thickness (40% of Al foil), but much longer cycle life (> 4 times of Al foil). Benefiting from the remarkable stability of the array structure, symmetric cells show excellent cycling stability with small voltage hysteresis (∼ 80 mV) and meanwhile there are no corrosion and pulverization problems even after cycled for 120 hours. Besides, full cells also manifest long lifespan (1,500 cycles) and increased Coulombic efficiency (100±1%).

Electrochemical Performance of Graphitic Multi-walled Carbon Nanotubes with Different Aspect Ratios as Cathode Materials for Aluminum-ion Batteries.

Graphitic multi‐walled carbon nanotubes (MWCNTs) can function as high‐performance cathode materials for rechargeable Al‐ion batteries with well‐defined discharging plateaus and reasonable charge/discharge C‐rates. However, the main intercalation/deintercalation or adsorption/desorption path of AlCl4 − anions into or onto G‐MWCNTs has not been elucidated. Herein, we used battery cells comprised of G‐MWCNTs with different aspect ratios, Al metal, and AlCl3/1‐ethyl‐3‐methylimidazolium chloride ionic liquid as the cathode, anode, and electrolyte, respectively. The electrochemical performance of the Al||G‐MWCNT cell increased as the aspect ratio of the G‐MWCNT cathode increased (i. e., longer and thinner). The degree of defects of the G‐MWCNTs was similar (0.15–0.22); hence, the results confirm that the main and alternate paths for the AlCl4 − intercalation/de‐intercalation or adsorption/desorption into/from or onto/from the G‐MWCNT are the basal and edge planes, respectively. The step‐like structures of defects on the basal plane provide the main reaction site for AlCl4 − anions.

Electrochemical activity of Samarium on starch-derived porous carbon: rechargeable Li- and Al-ion batteries

Rechargeable metal-ion batteries are considered promising electric storage systems to meet the emerging demand from electric vehicles, electronics, and electric grids. Thus far, secondary Li-ion batteries (LIBs) have seen great advances in terms of both their energy and their power density. However, safety issues remain a challenge. Therefore, rechargeable Al-ion batteries (AIBs) with a highly reliable safety advantage and active electrochemical performances have gathered intensive attention. However, the common issue for these two metal-ion batteries is the lack of cathode materials. Many advanced electrode materials reported provide greatly enhanced electrochemical properties. However, their inherent disadvantages—such as complicated fabrication procedures, restricted manufacturing parameters, and the requirement of expensive instruments—limits their potential for further applications. In this work, we demonstrate the high electrochemical activity of the lanthanide element, Sm, towards storing charges when used in both LIBs and AIBs. Lanthanide elements are often overlooked; however, they generally have attractive electrochemical properties owing to their unpaired electrons. We employed starch as both a low-cost carbon source and as a three-dimensional support for Sm metal nanoparticles. The composite product is fabricated using a one-pot wet-chemical method, followed by a simultaneous carbonization process. As a result, highly improved electrochemical properties are obtained when it is used as a cathode material for both LIBs and AIBs when compared to bare starch-derived C. Our results may introduce a new avenue toward the design of high-performance electrode materials for LIBs and AIBs.

Graphitic multi-walled carbon nanotube cathodes for rechargeable Al-ion batteries with well-defined discharge plateaus

One-dimensional multi-walled carbon nanotubes (MWCNTs) are promising electrode materials for rechargeable batteries. This paper reports that graphitic MWCNT (G-MWCNT) can serve as a cathode material for a rechargeable Al-ion battery and exhibits well-defined discharging plateaus at around 2 V. AlCl4−intercalates and de-intercalates into/from the graphitic MWCNT rather than simply adsorbing on the surfaces. Hence, the Al||G-MWCNT cell exhibits good electrochemical performance with a specific capacity of 64 mA h g−1 at a current density of 200 mA g−1. The discharge capacity is almost unattenuated and maintained at about 58 mA h g−1 (Coulombic efficiency: 99.5%) after 1000 charge/discharge cycles, which indicates that the Al||G-MWCNT cell has excellent cycling stability. In addition, the low self-discharging rate (~0.4% over 72 h of rest) suggests that the intercalated AlCl4− is stable in the spaces between the graphene layers of G-MWCNT. This work reveals that Al||G-MWCNT cells exhibit diffusion-controlled faradaic process rather than capacitor behavior, which may boost the development of aluminum batteries.

A high-performance flexible aqueous Al ion rechargeable battery with long cycle life

With the increasing development of flexible and wearable electronic devices, exploration of advanced power supplies with excellent electrochemical performance, safety and flexibility is highly urgent. In light of natural abundance as well as three-electron redox properties, rechargeable Al ion batteries (AIBs) draw much attention while they still face great challenge of limited Al3+ storage material as well as poorly ionic conductive electrolyte. In our work, an intercalation MoO3 anode and VOPO4 cathode are proposed and mechanically robust gelatin-polyacrylamide hydrogel electrolyte is utilized to fabricate a safe and flexible high-performance rechargeable AIB. The as-assembled AIB exhibits high rate capability of 6 A g−1, high discharge capacity of 88 mAh g−1 and long cyclic stability of 86.2% capacity retention even after 2800 cycles. Besides, the AIB possesses high safety and mechanical flexibility properties, which could serve as reliable power source when even being bent, punctured or cut. Additionally, the aqueous AIB could power 1 m long and 100 cm2 electroluminescent panels, demonstrating their good Al storage property. Considering their favourable electrochemical performance, robustness and safety, the flexible aqueous AIB in our work is believed to open up new avenue in flexible and wearable energy.

Reversible Intercalation of Multivalent Al3+ Ions into Potassium-Rich Cryptomelane Nanowires for Aqueous Rechargeable Al-Ion Batteries.

The development of new battery technology that utilizes abundant electrode materials that are environmentally benign is an important area of research. To alleviate the reliance on Li-ion batteries new energy storage mechanisms are urgently needed. To address these issues, MnO2 nanowires were investigated as a possible electrode material for use in rechargeable Al ion batteries that can operate in aqueous conditions. The use of this type of material and an aqueous electrolyte ensures safe operation as well as easy recycling of spent batteries. A potassium-rich cryptomelane structure was presented, and a new mechanism of electrochemical energy storage was elucidated based on the intercalation and deintercalation of small-radius Al3+ ions interchanging with larger K+ ions in the cryptomelane MnO2 nanowires, which was supported by DFT calculations. This first-time use of a cryptomelane MnO2 cathode for an aqueous Al ion system yielded a discharge capacity of 109 mAh g-1 , which indicates the potential commercial viability of rechargeable aqueous Al-ion batteries.

Insights into dynamic molecular intercalation mechanism for Al[sbnd]C battery by operando synchrotron X-ray techniques

Recently, a novel rechargeable Al ion battery (AIB) with high performance has been developed. Owing to its low cost, high-rate capability, excellent cyclability, and non-flammability, AIB provides a safe alternative to many commercial batteries used in the energy storage system. To improve its performance, identifying molecular structure and arrangement of chloroaluminate anion (AlCl4−) intercalated in the graphite layer remains a great challenge. In this work, operando analysis of X-ray diffraction (XRD) measurement and X-ray absorption (XAS) spectroscopy were performed to investigate the intercalation of AlCl4− anion and related molecular arrangement in the graphite layers. The intercalated stage and intercalant gallery height of graphite cathode electrode during AIB battery operation were observed to be stage 3 and 9.22 Å, respectively. Furthermore, the spectral evolution from ex-situ XAS at the Al and Cl K-edge was associated with closely packed intercalation of AlCl4− molecules. With density functional theory (DFT) calculation, three simulated models of intercalated AlCl4− molecules in the graphite layer were revealed successfully, which explained possible molecular structures at different charging states. This analytical methodology paves the way for better understanding the structural transformation of molecular ions de-/intercalation in graphite layers.

Cu-Al Composite as the Negative Electrode for Long-life Al-Ion Batteries

Rechargeable Al-ion batteries have attracted great interest due to their advantages in high anode capacity, high safety, etc. However, conventional Al foil negative electrode has critical problems in corrosion and pulverization. Here, we propose a novel Cu-Al composite, which is prepared by a facile electrochemical plating approach, as the negative electrode for addressing above challenges. Remarkably, the plated Cu foil negative electrode delivers excellent stability and long cycle life compared with the Al foil negative electrode, although its thickness and areal mass density are only 30% and ∼76% of that of the Al foil negative electrode, respectively. The essential pulverization problem in bare Al negative electrode would be dramatically reduced attributing to excellent corrosion resistance of Cu foil. Besides, the plated Al is still attached to the Cu foil during repeated charge-discharge processes, resulting in a nearly 100% Coulombic efficiency even after long-term cycling. More importantly, the plated Cu foil negative electrode is convenient for the large-scale practical applications. In view of our results, this work opens an effective approach for configuring low-cost, high energy density, long cycle life and scalable negative electrode of Al-ion batteries.

A critical perspective on rechargeable Al-ion battery technology.

The development of rechargeable aluminum-ion batteries (AIBs) has recently attracted much scientific attention due to the low cost and high specific capacity of Al. Most efforts are being concentrated on enhancing the specific charge capacity of active materials for the positive electrode, while other important issues for commercial deployment of this technology have often been overlooked. The aim of this frontier article is not to systematically review the recent advances in the literature, but to bring under the spotlight the critical aspects requiring intensive research activity for paving the way toward the commercialization of AIBs. After a brief revision of the fundaments of an Al-ion battery, the discussion is classified into 5 sections: energy density, specific power, cost, cycle life and safety. Finally, a performance comparison among Al-ion, Li-ion and lead-acid battery technologies on the basis of these 5 primary parameters summarizes the strengths and limitations of Al-ion batteries.

Imaging the diffusion pathway of Al3+ ion in NASICON-type (Al0.2Zr0.8)20/19Nb(PO4)3 as electrolyte for rechargeable solid-state Al batteries**Project supported by the National Natural Science Foundation of China (Grant Nos. 51672029, 51372271, and 51172275) and the National Key Research and Development Project from the Ministry of Science and Technology, China (Grant No. 2016YFA0202702).

Among all-solid-state batteries, rechargeable Al-ion batteries have attracted most attention because they involve three-electron-redox reactions with high theoretic specific capacity. However, the solid Al-ion conductor electrolytes are less studied. Here, the microscopic path of Al3+-ion conduction of NASICON-type (Al0.2Zr0.8)20/19Nb(PO4)3 oxide is identified by temperature-dependent neutron powder diffraction and aberration-corrected scanning transmission electron microscopy experiments. (Al0.2Zr0.8)20/19Nb(PO4)3 shows a rhombohedral structure consisting of a framework of (Zr,Nb)O6 octahedra sharing corners with (PO4) tetrahedra; the Al occupy trigonal antiprisms exhibiting extremely large displacement factors. This suggests a strong displacement of Al ions along the c axis of the unit cell as they diffuse across the structure by a vacancy mechanism. Negative thermal expansion behavior is also identified along a and b axes, due to folding of the framework as temperature increases.

Synthesis and Characterization Electro Catalytic Al-Ni and Nano Graphite Electrodes for Rechargeable Al Ion Battery

Synthesis and Characterization Electro Catalytic Al-Ni and Nano Graphite Electrodes for Rechargeable Al Ion Battery

Rechargeable Aluminum-Ion Battery Based on MoS2 Microsphere Cathode.

In recent years, a rechargeable aluminum-ion battery based on ionic liquid electrolyte is being extensively explored due to three-electron electrochemical reactions, rich resources, and safety. Herein, a rechargeable Al-ion battery composed of MoS2 microsphere cathode, aluminum anode, and ionic liquid electrolyte has been fabricated for the first time. It can be found that Al3+ intercalates into the MoS2 during the electrochemical reaction, whereas the storage mechanisms of the electrode material interface and internal are quite different. This result is confirmed by ex situ X-ray photoelectron spectroscopy and X-ray diffraction etching techniques. Meanwhile, this aluminum-ion battery also shows excellent electrochemical performance, such as a discharge specific capacity of 253.6 mA h g-1 at a current density of 20 mA g-1 and a discharge capacity of 66.7 mA h g-1 at a current density of 40 mA g-1 after 100 cycles. This will lay a solid foundation for the commercialization of aluminum-ion batteries.

Intercalated Chevrel Phase Mo6S8 as a Janus Material for Energy Generation and Storage

An approach to designing solar absorber materials based on an intercalation-induced metal-to-semiconductor transition has been proposed. Using a hybrid density functional calculation, Al-intercalated Chevrel phase Mo6S8 with end product Al4/3Mo6S8 is predicted to be a semiconductor with a 1.18 eV indirect band gap. Compared with GaAs and Si, Al4/3Mo6S8 shows significantly higher optical absorption over the solar spectrum as a result of the parallel bands across the band gap with direct transitions around 1.35 eV, nearly ideal for an absorber material in a solar cell. Chevrel phase Mo6S8 has recently been explored as a cathode material in rechargeable Al-ion batteries. Thus, Al4/3Mo6S8 is a potential dual-function (or Janus) material for both energy generation and storage. A possible device structure utilizing this unique property has been proposed.

A Sodium-Aluminum Hybrid Battery

To effectively harvest the energy from renewable sources such as solar and wind, cheap and long-lasting electric energy storage (EES) devices are essential.1 Among various EES technologies, lithium ion batteries (LIBs) are the most mature technologies with high energy density, high coulombic efficiency and long cycle life. Unfortunately, their high cost and the unevenly distributed global lithium source are major concerns. 2 Thus, beyond lithium technologies based on cheap and naturally abundant elements such as sodium (Na), magnesium (Mg), and aluminum (Al) ion batteries 3, 4 have been intensively studied during the last few years. Among different metals, Al is one of the most earth abundant elements, only second to silicon, resulting in its low price of $0.52/kg, 100 times lower than Li. In addition, Al with three electrons redox couple has distinct advantage over one electron redox couple such as Li and Na and two electrons redox couple such as Mg and Ca, providing a high theoretical specific capacity of 2980 mAh g-1 and a high volumetric capacity of 8040 mAh cm-3. The development of rechargeable Al ion batteries has been hampered by the electrolyte and cathode materials. Due to the low reduction potential of Al (-1.68 V vs. SHE), aqueous electrolytes cannot be used when Al is being used as the anode, since hydrogen will be released before Al can be plated during the reduction process. As an alternative, ambient room temperature ionic liquids with high ionic conductivity and wide electrochemical windows are good candidates for rechargeable Al batteries. Currently, the ionic liquids used for Al deposition are still based on mixtures of anhydrous AlCl3 and organic halide salts.5 It is well-known that only the acidic mixtures show reversible Al deposition/stripping, which poses stringent requirement for the hardwares of the Al batteries.6 To avoid the corrosion issue, pouch cell and special cell configuration have been used.7 Besides electrolytes, Al batteries also face challenges from the cathodes due to the high charge density of the Al3+ ion, making its insertion/extraction into/from the cathode host very difficult. An alternative way to take advantage of metallic Al anode but bypasses the need for efficient Al insertion cathodes is hybrid Al battery.7 It was demonstrated that high voltage and high capacity were possible in a hybrid Al battery with LiFePO4 as the cathode in an acidic ionic liquid electrolyte.7 However, a switch to the more earth-abundant sodium chemistry is more desirable due to the limited Li resources. In this presentation, we report a new hybrid battery using earth-abundant Na and Al chemistry, that is, Al as the anode, Na3V2(PO4)3 (NVP) as the cathode and NaAlCl4 dissolved in acidic ionic liquid as the electrolyte.8 The hybrid battery exhibits a discharge voltage of 1.25 V and a cathodic capacity of 99 mAh g-1 under a current rate of C/10. In addition, the hybrid battery exhibits good rate performance and long cycling stability while maintaining a high coulombic efficiency of 98 %. It is also demonstrated that increasing salt concentration can further enhance the cycling performance of the hybrid battery. X-ray diffraction analysis of the NVP electrodes under different conditions confirms that the main cathode reaction is indeed the Na extraction/insertion. 1. B. Dunn, H. Kamath and J. M. Tarascon, Science, 2011, 334, 928-935. 2. H. L. Pan, Y. S. Hu and L. Q. Chen, Energy Environ. Sci. , 2013, 6, 2338-2360. 3. G. A. Elia, K. Marquardt, K. Hoeppner, S. Fantini, R. Y. Lin, E. Knipping, W. Peters, J. F. Drillet, S. Passerini and R. Hahn, Adv. Mater. , 2016, 28, 7564-7579. 4. T. Gao, X. G. Li, X. W. Wang, J. K. Hu, F. D. Han, X. L. Fan, L. M. Suo, A. J. Pearse, S. B. Lee, G. W. Rubloff, K. J. Gaskell, M. Noked and C. S. Wang, Angew. Chem. Int. Ed. , 2016, 55, 9898-9901. 5. J. S. Wilkes, J. A. Levisky, R. A. Wilson and C. L. Hussey, Inorg. Chem. , 1982, 21, 1263-1264. 6. L. D. Reed and E. Menke, J. Electrochem. Soc., 2013, 160, A915−A917. 7. X. G. Sun, Z. H. Bi, H. S. Liu, Y. X. Fang, C. A. Bridges, M. P. Paranthaman, S. Dai and G. M. Brown, Chem. Commun., 2016, 52, 1713-1716. 8. X. G. Sun, Z. Z. Zhang, H. Y. Guan, C. A. Bridges, Y. X. Fang, Y.-S. Hu, G. M. Veith and S. Dai, J. Mater. Chem. A, 2017, 5, 6589-6596. Figure 1