Hybrid Aqueous Battery Research Articles

Scalable porous zinc anode to improve the cycling performance of aqueous lithium energy storage systems

Abstract A porous zinc anode is successfully fabricated using a simple, scalable method for use in Rechargeable Hybrid Aqueous Battery (ReHAB) systems. The porous anode provides a higher surface area (2X), roughness, and wettability than the planar one. These properties allow for better contact between the anode surface and the electrolyte, increasing the cycling performance when used in the ReHAB system. ReHABs with the porous anode show an improvement in initial discharge capacity (34%) at 1C, capacity retention after 300 cycles at 1C, rate performance at various C-rates, and float charge current (a 94% decrease). This decrease in float charge current corresponds to the lower levels of gas generated from detrimental side reactions during battery operation. The enhancements in the rate performance as well as minimized gas evolution in both small (1.13 cm2 in 1.15 mAh coin-cell) and large (9 cm2 in 7 mAh big battery) show the promising potential of the porous anode for use in large-scale battery applications. Based on the findings from various characterization techniques, suppression in dendrite growth and side reactions on the porous anode surface during battery operations have been the main reason for the improvement in ReHAB cycling performance.

An expanded clay-coated separator with unique microporous structure for enhancing electrochemical performance of rechargeable hybrid aqueous batteries

In this study, a novel composite separator for rechargeable hybrid aqueous batteries is successfully fabricated by coating porous expanded dickite aqueous slurry using polyacrylic latex as the binder on ES (Ethylene-Propylene Side By Side) nonwoven. The porous expanded dickite is prepared by intercalation and violent chemical reaction, forming porous structure with pore size of 0.3–1.2 μm. The porous morphology of the composite separators could be fine-tuned by varying the content of expanded dickite. The air permeability, porosity, electrolyte uptake, and ionic conductivity of the composite separators gradually improve with the increase of the content of expanded dickite. The improved performance of composite separators helps to improve battery performance, especially at high expanded dickite content. The composite separators with 90 wt.% expanded dickite provide superior cell performance owing to well-tailored pore structure, as compared to a commercialized absorbed glass mat (AGM).

Tuning Microstructures of Graphene to Improve Power Capability of Rechargeable Hybrid Aqueous Batteries.

Low conductivity and structural degradation of LiMn2O4 lead to poor power capability and severe capacity fading of hybrid aqueous Zn/LiMn2O4 battery. Here, we propose an effective strategy by tuning the microstructures of graphene to optimize its electrical and interfacial properties and electrode dynamics of LiMn2O4/graphene cathodes, which successfully prompt significant improvements in electrical conductivity and structural stability, thus essentially leading to a promising electrochemical performance. More importantly, it reveals different electrochemical properties prompted by different conductivity, which mainly depends on the microstructures of graphene. This dependence is due to the influence of electronic channels and conductive paths on the conductivity of LiMn2O4/graphene electrodes. A well-designed mesoporous graphene composed of about two graphene-layers exhibits an excellent high-rate performance; even after 300 cycles, a highly reversible capacity of 75 mAh g-1 is retained at 4C rate. The results of this study suggest that the structural tuning of electronic channels of graphene can be used as an effective means to improve the performance of LiMn2O4 cathodes in hybrid aqueous batteries.

Unveiling Conversion Reaction on Intercalation‐Based Transition Metal Oxides for High Power, High Energy Aqueous Lithium Battery

AbstractAqueous lithium batteries are reaching their energy and power limits partly due to limited capacity from intercalation chemistry. Alternatively, conversion reactions bring added capacity that can significantly increase the capacity ceiling of the cell. However, such reactions can only be realized in organic electrolytes, and similar redox chemistry in aqueous lithium batteries is not reported yet. In this work, it is discovered that a large work function difference (up to 1.78 eV) between crystalline LiMn2O4 (cLMO) and semicrystalline MnO2 (scMO) makes energy bands of MnO2 bend downward toward their interface, resulting in the accumulation of free electrons on scMO and inducing a reversible conversion reaction between scMO and Li+ in aqueous media. Based on this mechanism, a rechargeable hybrid aqueous battery employing hierarchical porous cLMO–scMO composite as a cathode delivers an extremely high cell‐level energy (171 Wh kg−1) and power density (5118 W kg−1) with excellent cycling stability (up to 3000 cycles) in a wide working temperature range (25 to 60 °C). More significantly, similar conversion reactions can also be achieved on LiCoO2, which provides a general design principle to obtain unprecedented energy and power density in commonly used transition metal oxides.

An insight into failure mechanism of NASICON-structured Na3V2(PO4)3 in hybrid aqueous rechargeable battery

NASICON (Na-super-ionic-conductors)-structured materials have attracted extensive research interest due to their great application potential in secondary batteries. However, the mechanism of capacity fading for NASICON-structured electrode materials has been rarely studied. In this paper, we synthesized the NASICON-structured Na3V2(PO4)3/C composite by simple sol–gel and high-temperature solid-phase method and investigated its electrochemical performance in Na–Zn hybrid aqueous rechargeable batteries. After characterizing the structure, morphology and composition variations as well as the interfacial resistance changes of Na3V2(PO4)3/C cathode during cycling, we propose a mechanical and interfacial degradation mechanism for capacity fading of NASICON-structured Na3V2(PO4)3/C in Na–Zn hybrid aqueous rechargeable batteries. This work will shed light on enhancing the mechanical and interfacial stability of NASICON-structured Na3V2(PO4)3/C in Na–Zn hybrid aqueous rechargeable batteries.

Self-Assembly of Free-Standing LiMn2O4-Graphene Flexible Film for High-Performance Rechargeable Hybrid Aqueous Battery

A novel LiMn2O4-graphene flexible film is successfully prepared by facile vacuum filtration technique. LiMn2O4 nanowires with diameters of 50–100 nm are distributed homogeneously on graphene sheet matrix. Used as cathode in rechargeable hybrid aqueous batteries, the LiMn2O4-graphene film exhibits enhanced electrochemical performance in comparison to LiMn2O4-graphene powder. The LiMn2O4-graphene film shows stable 13.0 mAh g−1 discharge capacity after 200 cycles at 1.0 C, benefitting from the presence of graphene with strong conductivity and large pore area in this free-standing film. This synthetic strategy for a free-standing film can provide a new avenue for other flexible materials and binder-free electrodes.

Pyrosynthesis of Na3 V2 (PO4 )3 @C Cathodes for Safe and Low-Cost Aqueous Hybrid Batteries.

Rechargeable hybrid aqueous batteries (ReHABs) have emerged as promising sustainable energy-storage devices because all components are environmentally benign and abundant. In this study, a carbon-wrapped sponge-like Na3 V2 (PO4 )3 nanoparticle (NVP@C) cathode is prepared by a simple pyrosynthesis for use in the ReHAB system with impressive rate capability and high cyclability. A high-resolution X-ray diffraction study confirmed the formation of pure Na ion superionic conductor (NASICON) NVP with rhombohedral structure. When tested in the ReHAB system, the NVP@C demonstrated high rate capability (66 mAh g-1 at 32 C) and remarkable cyclability over 1000 cycles (about 72 % of the initial capacity is retained at 30 C). Structural transformation and oxidation change studies of the electrode evaluated by using in situ synchrotron X-ray diffraction and ex situ X-ray photoelectron spectroscopy, respectively, confirmed the high reversibility of the NVP@C electrode in the ReHAB system through a two-phase reaction. The combined strategy of nanosizing and carbon-wrapping in the NVP particles is responsible for the remarkable electrochemical properties. The pyrosynthesis technique appears to be a promising and feasible approach to prepare a high-performance electrode for safe and low-cost ReHAB systems as nextgeneration large-scale energy storage devices.

Cover Picture: Engineering Fast Ion Conduction and Selective Cation Channels for a High-Rate and High-Voltage Hybrid Aqueous Battery (Angew. Chem. Int. Ed. 24/2018)

A hybrid aqueous battery based on two electrode materials with fast ion conduction and selective cation channels is reported by M. Xue, R. Li et al. in their Communication on page 7046 ff. Using this strategy for integrating different electrode materials with unique cation selectivities towards metal ions a high-voltage rechargeable aqueous battery is realized with a high capacity, remarkable energy density, and considerable capacity retention at high rate. A hybrid aqueous battery based on two electrode materials with fast ion conduction and selective cation channels is reported by M. Xue, R. Li et al. in their Communication on page 7046 ff. Using this strategy for integrating different electrode materials with unique cation selectivities towards metal ions a high-voltage rechargeable aqueous battery is realized with a high capacity, remarkable energy density, and considerable capacity retention at high rate. Carbon versus Silicon Optogenetics G-Quadruplexes

Engineering Fast Ion Conduction and Selective Cation Channels for a High‐Rate and High‐Voltage Hybrid Aqueous Battery

AbstractThe rechargeable aqueous metal‐ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor‐performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high‐voltage K–Na HAB based on K2FeFe(CN)6 cathode and carbon‐coated NaTi2(PO4)3 (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g−1 at a 0.5 C rate. Considerable capacity retention of 94.3 % is also obtained after 1000 cycles at even 60 C rate. Meanwhile, high energy density of 69.6 Wh kg−1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.

Engineering Fast Ion Conduction and Selective Cation Channels for a High-Rate and High-Voltage Hybrid Aqueous Battery.

The rechargeable aqueous metal-ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor-performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high-voltage K-Na HAB based on K2 FeFe(CN)6 cathode and carbon-coated NaTi2 (PO4 )3 (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g-1 at a 0.5 C rate. Considerable capacity retention of 94.3 % is also obtained after 1000 cycles at even 60 C rate. Meanwhile, high energy density of 69.6 Wh kg-1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.

Controlling the sustainability and shape change of the zinc anode in rechargeable aqueous Zn/LiMn2O4 battery

The use of thixotropic gel electrolytes in the rechargeable hybrid aqueous battery improves the battery performance but it is required to have a corrosion inhibitor in the gel electrolyte. These inhibitors are not always friendly to the environment. In this work, we use lignin – a renewable material – to neutralize strong acid sites of the fumed silica gelling agent prior to gel preparation. Linear polarization, chronoamperometry, and ex-situ scanning electron microscopy examinations show that the new gel electrolyte reduces the corrosion on zinc (up to 43%) and supports planar zinc deposit. In other words, the shape of the zinc surface is controlled and it is further confirmed by the XRD and SEM of post-battery run anodes. Moreover, the battery using this new lignin coated fumed silica based gel electrolyte exhibits a float charge current as low as 0.0025 mA after 24 h of monitoring, which is 30.6% lower than the reference. The capacity retention of gelled battery is as high as 82% after 1000 cycles at 4 C, which is 14% higher than the reference battery using reference liquid electrolyte under the same CC-CV test, complemented by lower self-discharge and higher rate capability. The results lead the team nearer to a commercializable gelled battery system.

Improved performance of the rechargeable hybrid aqueous battery at near full state-of-charge

For the first time, a green lignin/silica nanocomposite (LSC) is introduced to the rechargeable hybrid aqueous Zn/LiMn2O4 battery (ReHAB) as additive in the cathode formulation. Lignin acts as a key role to regulate and control the structure of LSC, intending to enhance the stability of the ReHAB by improving the float charge performance while maintaining other electrochemical performances of the battery. The lignin/silica nanocomposites (LSCs) are characterized by X-ray diffraction, scanning electron microscopy, surface area and porosimetry analyzer, and transmission electron microscopy. The results show that amorphous, uniform and mesoporous LSC-1 is prepared at the mass ratio of 1:2 of lignin to silica. LSC-1 used as the cathode additive improves the float charge performance of ReHAB via decreasing the float charge capacity by 57%. To compensate the loss of conductivity caused by LSC-1 and increase the capacity of the battery, graphene (G) is added. Compared to the reference battery, battery using the cathode containing 3 wt% combined additive of LSC-1 and G at mass ratio of 1:1, has 50% lower float charge capacity, higher rate performance and better cyclability. Up to a discharge capacity of 95 mAh g−1 is still obtained after 300 cycles of 100% depth-of-discharge.

Effect of fumed silica concentration and separator type on the electrochemical performance of gel electrolyte in the rechargeable hybrid aqueous battery

The rechargeable hybrid aqueous battery (ReHAB) has been developed as one of the commercial substitutions for the lead-acid battery thanks to its utilization of environmentally benign materials (hence lower toxicity) and higher energy storage capability. The system consists of a LiMn2O4 composite cathode and a zinc metal anode, separated by a porous separator containing a mixed aqueous solution of Li2SO4 and ZnSO4. Fumed silica, a gelling agent, is dispersed in the aqueous electrolyte, and physical and electrochemical characteristics of the newly formed gel electrolytes are investigated. Although the presence of Li2SO4 enhances the gel formation and ZnSO4 promotes the reverse, the gel strength and gelling time depend on the molar ratio between ZnSO4 and Li2SO4. Incorporation of fumed silica into the liquid electrolyte enhances the charge-discharge and the cyclability significantly. After 300 charge-discharge cycles at 4 C, discharge capacity retention of the cells with the gel electrolyte is over 10% higher than that of cells with the liquid electrolyte. Moreover, the absorbed glass mat separator (AGM) provides better stability at high C-rates than filter paper separator, thanks to the superior water retention ability of the AGM.

Effect of poly (vinylidene fluoride)/poly (vinyl acetate) blend composition as cathode binder on electrochemical performances of aqueous Li-ion battery

In this study, the effect of poly (vinylidene fluoride)/poly (vinyl acetate) (PVDF/PVAc) ratio in the cathode binder of the LiMn2O4 (LMO) electrode on the electrochemical performance of a rechargeable hybrid aqueous battery (ReHAB) is investigated. The miscibility of two polymers is confirmed by Furrier transform infrared (FTIR) and differential scanning calorimetry (DSC) measurements. The binary blends with different PVDF/PVAc ratios (100/0, 75/25, 50/50, 25/75 and 0/100) are used as binder for the LMO cathode preparation. It is found that incorporation of PVAc in the blend decreases the crystallinity of PVDF and increases the cathode hydrophilicity, leading to better wetting by the aqueous electrolyte. The morphology and electrochemical properties of the cathode are also studied. Electrochemical cyclic voltammogram, discharge capacity, capacity retention, electrochemical impedance and rate capability are investigated. It is concluded that the blend with a PVDF/PVAc ratio of 25/75 has the best cycle performance (80% capacity retention after 100 cycles at the rate of 1 °C), with 0.2 °C discharge capacity (110 mAh gr−1) and the best rate capability.

Acrylonitrile copolymer/graphene skinned cathode for long cycle life rechargeable hybrid aqueous batteries at high-temperature

For aqueous rechargeable lithium battery (ARLB), excellent cycling stability at elevated temperature is highly desirable in its application of electric vehicles (EVs). However, most state-of-art ARLBs show poor durability under high-temperature operation. Herein, we demonstrate a facile coating approach that can construct a thin acrylonitrile copolymer (ANC)/graphene skin on the top-surface of the LiMn2O4 (LMO) cathode in a rechargeable hybrid aqueous lithium battery (ReHAB). Featuring the continuous coverage and the facile electron transport, the ANC/graphene skinned cathode shows a capacity retention of 61% after 300 cycles at 60 °C, two times larger than the battery without the skin. In the cathode, ANC helps to suppress unwanted interfacial side reactions, and graphene renders a robust ion diffusion framework. Quantitative analysis of Mn suggests that the ANC/graphene skin can greatly suppress dissolution of Mn from the LMO into the aqueous electrolyte, while maintaining the charge transfer kinetics. The polymer-based nanocomposite skin on small (1.15 mAh cell) and large (7 mAh cell) cathodes show similar electrochemical improvement, indicting good scale-up potentials.

A low-cost Mg2+/Na+ hybrid aqueous battery

A Mg2+/Na+ hybrid aqueous battery with high energy density is constructed using commercial Mn3O4 as a cathode and NaTi2(PO4)3 as an anode.

Highly Sustainable Zinc Anodes for a Rechargeable Hybrid Aqueous Battery.

The synthesis of novel zinc electrodes has been successfully implemented by using the electroplating method with the aid of inorganic additives in the electroplating solution. The selected inorganic additives are indium sulfate, tin oxide, and boric acid. From X-ray diffraction results, these synthesized zinc electrodes prefer (002) and/or (103) crystallographic orientations, representing basal morphology and high resistance to dendrite growth. The corrosion rates of these electroplated zinc samples decrease as much as 11 times smaller than the corrosion rate on zinc foil when the zinc materials are in contact with the aqueous electrolyte of a rechargeable hybrid aqueous battery (ReHAB). The ReHABs employing these anodes exhibit up to a threefold decrease in float charge current density after a seven-day constant-voltage charging at 2.1 V versus Zn2+ /Zn. Furthermore, the capacity retention is up to 15 % higher than the performance of battery containing commercial Zn after 1000 cycles of charge-discharge. The significant advancements are attributed to the careful preparation of the anode, which contains appropriate crystallographic orientation and morphology.

Novel Carbon Materials in the Cathode Formulation for High Rate Rechargeable Hybrid Aqueous Batteries

Novel carbon materials, carbon nanotubes (CNTs) and porous graphene (PG), were exploited and used as conductive additives to improve the rate performance of LiMn2O4 cathode for the rechargeable aqueous Zn/LiMn2O4 battery, namely the rechargeable hybrid aqueous battery (ReHAB). Thanks to the long-range conductivity and stable conductive network provided by CNTs, the rate and cycling performances of LiMn2O4 cathode in ReHAB are highly improved—up to about 100 mAh·g−1 capacity is observed at 10 C (1 C = 120 mAh·g−1). Except for CNTs, porous graphene (PG) with a high surface area, an abundant porous structure, and an excellent electrical conductivity facilitates the transportation of Li ions and electrons, which can also obviously enhance the rate capability of the ReHAB. This is important because the ReHAB could be charged/discharged in a few minutes, and this leads to potential application of the ReHAB in automobile industry.

Flexible free-standing Na4Mn9O18/reduced graphene oxide composite film as a cathode for sodium rechargeable hybrid aqueous battery

A novel free-standing Na4Mn9O18/reduced graphene oxide (NMO-RGO) composite was successfully prepared by a facile vacuum filtration technique. Scanning and transmission electron microscopy studies revealed formation of a film with needle-like Na4Mn9O18 homogeneously distributed and anchored on the RGO matrix. A sodium rechargeable hybrid aqueous battery with this novel cathode and zinc anode was first investigated and reported. The NMO-RGO film delivered a reversible discharge capacity of about 83 mAh g−1 when cycled galvanostatically at a current density of 0.1 A g−1, which was for about 78% higher than that of Na4Mn9O18 prepared by a slurry casting technique. This significant enhancement of electrochemical properties of NMO-RGO was due to the presence of graphene sheets in this free-standing composite cathode. These sheets form an agile substrate with a high conductivity to guarantee a successive electronic conduction channels in the electrode. In the same time, such composition and structure enables accommodation of the volume changes of Na4Mn9O18 during sodium insertion-extraction.

Sustainable gel electrolyte containing Pb2+ as corrosion inhibitor and dendrite suppressor for the zinc anode in the rechargeable hybrid aqueous battery

Dendrite formation and corrosion are two major problems occurring on the zinc electrode of the rechargeable hybrid aqueous battery (ReHAB). In this work, we have designed a gel electrolyte containing fumed silica (FS) as the gelling agent and Pb2+ as the dendrite suppressor and also the corrosion inhibitor in aqueous liquid media. Both Pb2+ and fumed silica can inhibit dendrite formation, evidenced by chronoamperometry results and ex-situ scanning electron microscopy images. Furthermore, linear polarization results reveal that corrosion current density on the Zn anode when in contact with the PbSO4 doped 5%FS gel electrolyte is 20% smaller than that of the Zn when in contact with the reference aqueous electrolyte. The ReHAB using the Pb2+ containing gel electrolyte exhibits higher cyclability (75% capacity retention after 300 cycles at 1 C rate) than the ReHAB using the reference aqueous electrolyte (60% capacity retention at the same condition). Self-discharge is massively reduced, represented by an 18% smaller loss of open-circuit voltage after monitoring for 24 h. Float charge current density is reduced significantly up to 35% after 24-h of constant charging the batteries at 2.1 V vs. Zn2+/Zn. The results suggest that battery performance improves when both corrosion current density and dendrite formation are suppressed.