Rechargeable Hybrid Aqueous Battery Research Articles

A True Non-Newtonian Electrolyte for Rechargeable Hybrid Aqueous Battery

The rechargeable aqueous hybrid battery is a unique system in which the Li-ion mechanism dominates the cathode while the first-order metal reaction of stripping/depositing regulates the anode. This battery inherits the advantages of the low-cost anode while possessing the capability of the Li-ion cathode. One of the major challenges is to design a proper electrolyte to nourish such strengths and alleviate the downsides, because two different mechanisms are functioning separately at the node–electrolyte and the cathode–electrolyte interfaces. In this work, we design a non-Newtonian electrolyte which offers many advantages for a Zn/LiMn2O4 battery. The corrosion is kept low while almost non-dendritic zinc deposition is confirmed by chronoamperometry and ex situ microscopy. The gel strength and gelling duration of such non-Newtonian electrolytes can be controlled. The ionic conductivity of such gels can reach 60 mS⋅cm−1. The battery exhibits reduced self-discharge, 6–10% higher specific discharge capacity than the aqueous reference battery, high rate capability, nearly 80% capacity retention after 1000 cycles, and about 100 mAh⋅g−1 of specific discharge capacity at cycle No. 1000th. Negligible amorphization on the cathode surface and no passivation on the anode surface are observed after 1000 cycles, evidenced by X-ray diffraction and scanning electron microscopy on the post-run battery electrodes.

Na-containing manganese-based cathode materials synthesized by sol-gel method for zinc-based rechargeable aqueous battery

Zinc-based rechargeable aqueous batteries are regarded as one of the most safe and inexpensive energy storage systems compared to the conventional rechargeable batteries with organic electrolytes. However, the limited cathode materials and the problem of associated metal ion dissolution restrict its practical application. Herein, the inexpensive novel cathode materials of Na-containing manganese-based composite of Na0.44MnO2/Mn2O3 and Na2/3Fe1/2Mn1/2O2 are designed and synthesized correspondingly by sol-gel methods combined with freeze-drying technique, and are applied in the zinc-based aqueous batteries for the first time. The secondary particles of Na0.44MnO2/Mn2O3 composite with a cubic box and the molecular sieve configurations are composed of nano primary particles with about 150–300 nm, and the obtained O3–Na2/3Fe1/2Mn1/2O2 at 850 °C (O3-NFM-850) appears to homogenous distribution with 3D solid block structure and platelet-shaped particles, while the spherical core-shell structure of P2–Na2/3Fe1/2Mn1/2O2 at 850 °C (P3-NFM-850-PVA) after dispersed by poly (vinyl alcohol) are linked to each other by amorphous carbon. Finally, the cathode of Na0.44MnO2/Mn2O3 and P3-NFM-850-PVA deliver the reversible capacities of 68.3 mAh g−1 and 42 mAh g−1 even after 200 cycles at 0.4 A/g respectively without capacity fading. Compared to the reported Na0.44MnO2, the increased capacity of Na0.44MnO2/Mn2O3 composite is attributed to the possible co-insertion of sodium ion and zinc ion for Na0.44MnO2 and the zinc ion insertion for Mn2O3 as well, indicating the synergetic energy storage for rechargeable hybrid aqueous battery and aqueous zinc ion battery. While the improved cyclic performance of Na2/3Fe1/2Mn1/2O2 is ascribed to the structural stability by Fe-doping and carbon-coating.

Hybrids of LiMn2O4 nanoparticles anchored on carbon nanotubes/graphene sheets as long-cycle-life cathode material for rechargeable hybrid aqueous batteries

A hybrid LiMn2O4-graphene-carbon nanotubes (LMO-GN-CNT) material is synthesized successfully by a facile hydrothermal method. The 15-nm-nanosized LiMn2O4 (LMO) particles anchor uniformly in the cross-linked conductive graphene (GN) and carbon nanotubes (CNT) matrix in the LMO-GN-CNT composite. Rechargeable hybrid aqueous batteries (ReHABs) are assembled by using LMO-based materials as cathodes and zinc metal as anodes. Galvanostatic charging/discharging cycles of the LMO-GN-CNT composite are performed in rechargeable hybrid aqueous batteries (ReHABs) in comparison of LMO-GN composite and pristine LMO material. Electrochemical measurements indicate that the LMO-GN-CNT composite exhibits superior rate capability and cycle ability. The initial discharge capacity of 129 and 100 mAh g−1 can be delivered at 0.2 and 5.0 C. The discharge capacity is still above 93 mAh g−1, and capacity retention of over 82.1% is obtained after 600 cycles at 2.0 C. The satisfactory electrochemical properties can be ascribed to the little aggregation and good dispersion of the nanosized LMO particles and the introduction of GN and CNT, which can enhance the conductivity, shorten the diffusion length of electrolyte, and provide a large specific surface area for lithium storage.

Electrolyte engineering for a highly stable, rechargeable hybrid aqueous battery

Abstract The zinc electrode in secondary zinc batteries suffers from many side reactions, namely corrosion, hydrogen evolution, passivation, and dendrite formation. This electrode also suffers from changes in surface textures, mechanical properties, and volume increases due to the formation and growth of porous space inside the zinc electrode. Keeping the zinc electrode from deterioration is a major challenge because one must address multiple problems at a time. In this study, we introduce a three-functional electrolyte based on ethylene glycol oligomers and aqueous components. When in contact with this electrolyte, the corrosion current density decreases by 37%, which means that corrosion and hydrogen evolution are partially mitigated. The chronoamperometry current density decreases by 77.5%, complemented by a nearly flat and layered zinc deposit (confirmed by SEM and ex situ XRD). Applying this concept to a typical Zn/LiMn2O4 battery with 2 M Li2SO4 and 1 M ZnSO4 mixed electrolyte, the capacity retention is up to 80.2% after 1000 charge-discharge cycles at 4 C rate. This is approximately 12% higher than that of the reference battery using an aqueous electrolyte. Furthermore, the float charge current under constant voltage (2.1 V) dramatically decreases by approximately 36% versus the float charge current of the reference battery, and the rate capability is nearly maintained.

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.

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.

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.

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.

Suppression of Dendrite Formation and Corrosion on Zinc Anode of Secondary Aqueous Batteries.

Novel zinc anodes are synthesized via electroplating with organic additives in the plating solution. The selected organic additives are cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene-glycol (PEG-8000), and thiourea (TU). The synthesized zinc anode materials, namely, Zn-CTAB, Zn-SDS, Zn-PEG, and Zn-TU, are characterized by powder X-ray diffraction and scanning electron microscopy. The results show that each additive produces distinctively different crystallographic orientation and surface texture. The surface electrochemical activity is characterized by linear polarization when the zinc is in contact with the battery's electrolyte. Tafel fitting on the linear polarization data reveals that the synthetic zinc materials using organic additives all exhibit 6-30 times lower corrosion currents. When using Zn-SDS as the anode in the rechargeable hybrid aqueous battery, the float current decreases as much as 2.5 times. The batteries with Zn-SDS, Zn-PEG, and Zn-TU anodes display the capacity retention of 79%, 76%, and 80% after 1000 cycles of charge-discharge at 4C rate, whereas only 67% obtained from the batteries using the anode prepared from commercial zinc foil. Among these electroplated anodes, Zn-SDS is the most suitable for aqueous batteries thanks to its low corrosion rate, low dendrite formation, low float current, and high capacity retention after 1000 cycles.