Aqueous Sodium-ion Batteries Research Articles

Graphene oxide suspension-based electrolyte promotes the cycling performance of aqueous sodium-ion batteries through the interaction between metal ions, free water molecules and functional groups

Prussian blue analogue (PBA)-based aqueous batteries are promising solutions for large-scale energy storage. However, PBA cathode materials are still facing erosion and dissolution originating from the strong polarity and high proton activity of water leading to the destruction of their frameworks and poor cycling performance. Herein, we developed a new route to protect Sodium Prussian blue analogue (PB–Na, Na0.65Fe[Fe(CN)6]0.91·□0.09·2.7H2O) by introducing graphene oxide (GO) into the aqueous electrolyte, which can in-situ form an ion selectivity membrane on the separator surface. GO can prevent the diffusion of transition metal ions of dissolved PB-Na penetrating the separator to the anode material by the coordination interaction between transition metal ions and the oxygen-containing functional groups (carboxyl, carbonyl, etc). Meanwhile, hydrophilic groups (hydroxyl, carboxyl, etc) of GO can absorb free water molecules by hydrogen bond and electrostatic interaction reducing the dissolution of PB-Na. Thus PB-Na cathode material-based sodium-ion batteries in the low-concentration aqueous electrolyte can still achieve a capacity of 65.5 mAh g−1 and a high capacity retention of 65.1% after 17000 cycles. This strategy can be considered a simple and effective method to protect active materials in the aqueous batteries.

Manganese-based NASICON structured Na1+2xMnxTi2-x(PO4)3 as promising cathode in aqueous sodium ion battery

Herein, a series of manganese-based NASICON structured Na1+2xMnxTi2-x(PO4)3 (x = 1, 1.2, 1.4, denoted as NMTP, NM1.2T0.8P and NM1.4T0.6P) are obtained by sol-gel method and employed as cathodes for an aqueous sodium ion battery (ASIB). There is no obvious difference in structure among these samples, except for a small amount of impurity phase detected in NM1.4T0.6P. Three as-prepared samples exhibit impressive electrochemical performances, thereinto NM1.2T0.8P possesses the best electrochemical performance with the proper operating potential. NM1.2T0.8P delivers a discharge specific capacity of 68.2, 60.3, 52.2, 45.9 mAh g−1 at 1, 2, 5, 10 C, and still maintain 62.8 mAh g−1 when the current density returns to 1 C. Meanwhile, long-term cycling performance test shows that NM1.2T0.8P displays an initial discharge capacity of 46.4 mAh g−1 and still retains a reversible capacity of 39.1 mAh g−1 at 10 C rate after 300 cycles. Cyclic voltammetry demonstrates that both the diffusion and pseudocapacitance determine the sodium-ion (Na-ion) storage mechanism of NM1.2T0.8P and the pseudocapacitance dominates the charge/discharge processes. Besides, a cathode-limited full cell with NM1.2T0.8P cathode and NaTi2(PO4)3 anode was assembled and shows excellent long-term cycling performance with a capacity retention ratio of 81.9 % at 10 C after 200 cycles. This exploration of manganese-based NASICON structured Na1+2xMnxTi2-x(PO4)3 provides an option for cathode materials of ASIB.

Dilute Hybrid Electrolyte for Low-Temperature Aqueous Sodium-Ion Batteries.

A hybrid electrolyte based on low-concentration sodium nitrate with glycerol as an additive was proposed for aqueous sodium-ion batteries (ASIBs) towards low-temperature performance. Based on this dilute hybrid electrolyte and configured by bimetallic Prussian blue analogue (Ni2 ZnHCF) cathode and 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) anode, the full cell demonstrated surprising cycle performance with a specific capacity of 60 mAh g-1 (>800 cycles) and achieved prominent performance at low temperature. Glycerol effectively expanded the electrochemical stability window of the hybrid electrolyte to 2.7 V from formation of strong hydrogen bonds with water molecules and realized the operation of the cell at low temperature, delivering a stable reversible capacity of 40 mAh g-1 at -10 °C. The hybrid electrolyte of glycerol-water provides a new alternative in development of low-cost, long-lifespan, and low-temperature ASIBs and other aqueous battery systems.

Sodium decavanadate encapsulated Mn-BTC POM@MOF as high-capacity cathode material for aqueous sodium-ion batteries

Aqueous sodium-ion batteries are the promising candidates for large scale energy storage applications owing to their cost effectiveness and environmental safety. However, the development of a stable cathode material with high capacity is still a challenging task for the commercial viability of aqueous electrolyte-based sodium-ion batteries. This work demonstrates the development of a hierarchically nanostructured high-capacity cathode material by encapsulating sodium decavanadate Na6V10O28 (NaDV) in the scaffold of manganese-based metal-organic framework Mn-BTC (where BTC is 1,3,5-benzenetricarboxylic acid) by an in situ synthesis. The uniform distribution of NaDV in the pores of Mn-BTC enables the multielectron redox properties of NaDV whereas the diverse 3D diffusion channels, high surface area, and flexible architecture of Mn-BTC ensure high intercalation capacity by suppressing the agglomeration and providing faster ionic diffusion kinetics in the NaDV@Mn-BTC nano-hybrid cathode material. The Mn-BTC framework not only ensures the stabilization of NaDV but also enhances sodium storage capacity by the involvement of Mn in the redox process. The NaDV@Mn-BTC cathode material exhibits high reversible capacity of 137 mAh/g at 1 C rate. High capacity of this cathode material suggests that the development of these nano-hybrid materials is a feasible approach to design high energy cathode materials for aqueous batteries.

Aqueous Rechargeable Sodium-Ion Batteries: From Liquid to Hydrogel

Sodium-ion batteries stand out as a promising technology for developing a new generation of energy storage devices because of their apparent advantages in terms of costs and resources. Aqueous electrolytes, which are flame-resistant, inexpensive, and environmentally acceptable, are receiving a lot of attention in light of the present environmental and electronic equipment safety concerns. In recent decades, numerous improvements have been made to the performance of aqueous sodium-ion batteries (ASIBs). One particular development has been the transition from liquid to hydrogel electrolytes, whose durability, flexibility, and leakproof properties are eagerly anticipated in the next generation of flexible wearable electronics. The current review examines the most recent developments in the investigation and development of the electrolytes and associated electrode materials of ASIBs. An overview of new discoveries based on cycle stability, electrochemical performance, and morphology is presented along with previously published data. Additionally, the main milestones, applications, and challenges of this field are briefly discussed.

Anion Selection Criteria for Water-in-Salt Electrolytes

Water-in-salt electrolytes have enabled the development of novel high-voltage aqueous lithium-ion batteries due to their wide electrochemical stability window. Here, we explore why analogous sodium electrolytes have struggled to reach the same level of electrochemical stability and compare solution structure and electrochemical stability for eleven sodium salts, selected among the major classes of salts proposed for highly concentrated electrolytes.[1-3] We relate the water environment established for each anion to its position in the Hofmeister series, finding a strong correlation between the chaotropicity of the anion and the resulting electrochemical stability of the electrolyte. We discuss the importance of the solid-electrolyte interphase for stable battery performance, how it relates to the choice of anion, and further show that the search for suitable sodium salts is complicated by the fact that higher salt concentrations are needed than for their lithium equivalents.[4] Reaching such a high concentration of 25 to 30 mol/kg with one or a combination of multiple sodium salts that have the desired properties remains a major challenge. We conclude that alternative approaches such as mixed water/organic solvent or dual-cation electrolytes should be pursued to enable the development of high-voltage aqueous sodium-ion batteries. We demonstrate the potential of the mixed-solvent approach by showing that the water solubility of NaTFSI can be increased from 8 to 30 mol/kg in the presence of ionic liquids. Such a ternary electrolyte, based on highly chaotropic anions, enables stable cycling of a 2 V-class sodium-ion battery based on the NaTi2(PO4)3/Na2Mn[Fe(CN)6] electrode couple for 300 cycles at 1C with a Coulombic efficiency of >99.5%.[5]

High-rate NaMo0.05Ti1.95(PO4)3 for aqueous sodium-ion battery anode material

High-rate NaMo0.05Ti1.95(PO4)3 for aqueous sodium-ion battery anode material

Common ion effect enhanced cobalt hexacyanoferrate for aqueous Na-ion battery

Given the merits of rich reserves, high ion conductivity and non-combustion property, aqueous sodium ion batteries (SIBs) were once considered as high-quality substitutes for organic lithium ion batteries. However, due to the large radius of carrier sodium ion and unstable structure of electrode materials, the practical implementation of aqueous SIBs is seriously impeded. In this work, a reliable aqueous SIB is constructed by employing Na2Co[Fe(CN)6] as cathode, which is synthesized by co-precipitation assisted electrochemical synthesis. As a Prussian blue analogue (PBA), Na2Co[Fe(CN)6] inherits open framework structure, ion insertion stability and electrochemical tunability. Benefitting from common ion effect, Na2Co[Fe(CN)6] can maintain stable host structure in the SIBs with CoSO4 as an additive of electrolyte, and exhibits an exceptional cycling stability without capacity decay over 2000 cycles and outstanding rate performance. By further exploring the changes in crystal structure, elemental valence states and ion storage kinetics, it fully explains the structural and electrochemical stability of Na2Co[Fe(CN)6] as the cathode for aqueous SIBs and the mechanism of Na+ insertion/extraction during cycling process. This work provides a pathway to settle the problems of large carrier ion and structural instability in aqueous SIBs, and greatly broadens the path of its research and development.

Unravelling capacity fading mechanisms in sodium vanadyl phosphate for aqueous sodium-ion batteries

Na3V2(PO4)3 (NVP), which is known as a sodium superionic conductor (NASICON), has been successfully developed as an excellent cathode material for sodium-ion batteries (SIBs). However, the capacity of NVP quickly fades when used in an aqueous electrolyte. Herein, the charge storage and capacity attenuation mechanisms of carbon-coated NVP (NVP@C) were carefully investigated by systematic material characterization and density functional theory (DFT) calculations. According to the results, protons in the aqueous electrolyte diffuse into the surface of NVP@C to occupy the sodium site and attack the nearby phosphates during the charge–discharge cycles, leading to the deformation and breakage of the POV bond. The distorted phosphates on the surface of NVP@C gradually dissolve into the electrolyte, causing a decrease in capacity. To stabilize the phosphates on the surface of NVP, DFT calculations suggest that iron doping of NVP can effectively relieve the deformation of the POV bond and suppress the capacity decay. The as-prepared Na3V1.5Fe0.5(PO4)3@C (NV1.5Fe0.5P@C) has a capacity retention of 95% in the first ten cycles, while NVP@C retains only 55% of the initial capacity in the same number of cycles.

Promoting the performances of NaTi2(PO4)3@C porous composite as novel anode materials for application in sodium ion battery

Rechargeable aqueous sodium-ion batteries (SIBs) are urgently pursued as a low-cost candidate for grid-scale storage of intermittent renewable energies. NASICON-type NaTi2(PO4)3 holds great promises as anode material for aqueous SIBs owing to the high theoretical capacity and low redox potential, but being severely challenged by poor cycling performance and low reaction kinetics. In this study, a porous carbon-decorated NaTi2(PO4)3 composite was made using a simple sol-gel method and then thermally treated. The NaTi2(PO4)3 particles are adhered to the surface of carbon sheets uniformly. The NTP@C electrode delivers a reversible capacity of 198.1 mAhg−1 at 0.2 C, which is much higher than NTP (125.5 mAhg−1). Atta 50 cycle, a capacity of 196.5 mAhg−1 can be obtained for the NTP@C composite, which in about 99.1% of its initial capacity. From the EIS, RCT value of NTP@C was estimated to be 51.32 Ὠ which is lower than that of bar NTP (78.2 Ὠ). Carbon greatly improves the cell's performance, particularly the cycle lifetime at high charge-discharge rates of NTP electrodes. The increased structural stability and electron/Na + ion transfer kinetics of the NTP@C anode material are responsible for its exceptional electrochemical properties and long cycle lifespan.

Selective ion transport in assembled graphene oxide-modified separator and the novel intra-series architecture for improved aqueous batteries

Aqueous batteries, as one of the most promising candidates in large-scale energy storage, have attracted comprehensive attention owing to their high safety and low cost. Nevertheless, their poor lives are mainly caused by undesired side reactions and carrier transport due to the high solvent power and high proton activity of water. Herein, a strategy based on the separator design is developed to enhance the cycling stability of aqueous batteries. In this way, an assembled graphene oxide (GO) film is introduced to modify glass fiber separator, which can only allow alkali metal ions to pass through with the intercept of multivalent cations. Based on the design, the dissolution and destruction of sodium Prussian blue (PB-Na) are suppressed for achieving the long-life aqueous sodium-ion batteries (SIBs), providing a high capacity retention of 78.76% after 10,000 cycles at a current density of 2.0 A/g. Furthermore, the assembled GO film also enables a novel intra-series architecture with the combined mechanism of bipolar plate capacitor and battery for providing the extra capacity of electric double layer capacitor (EDLC). Independent from the optimization of electrode and electrolyte, the strategy based on the separator design would provide a new perspective for improving the performance of electrochemical energy storage system.

Performance and Lifetime of Battery Desalination Cells Based on Nickel Hexacyanoferrate

Prussian blue analogs, e.g., nickel hexacyanoferrate, NiFe(CN)6 or NiHCF, are promising candidates as low-cost and high-rate intercalation materials for secondary batteries.1–4 Recently, this material class has been shown to possess tremendous potential for a novel energy-efficient water desalination approach.5–8 Rising water demands are exacerbating water scarcity in many world regions. It is estimated that 60% of the global population will face severe water scarcity by 2025.9 The growing water demand necessitates new desalination technologies with high energy efficiency, low capital and operating cost and high freshwater output. In this work, we assess the performance and lifetime of electrochemical water desalination cells based on sodium intercalation into nickel hexacyanoferrate.10–12 The battery desalination cells feature a symmetric design, with two NiHCF electrodes at opposite state-of-charge (SOC), capable of intercalating Na+-ions into their crystal structure. The electrodes are separated by an anion exchange membrane, a porous functionalized polyether ether ketone (PEEK) membrane, that only permits negatively charged ions, e.g., Cl--ions, to pass. Two feed water streams with 20 mM NaCl enter the symmetric cell on either side (see Figure 1a). During charge of the symmetric cell, incoming Na+-ions are removed from one water stream and intercalated into the NiHCF electrode at low SOC. Simultaneously, Na+-ions are deintercalated from the opposite NiHCF electrode at high SOC. In order to maintain charge neutrality, Cl--ions cross the anion exchange membrane. Thus, during every charge/discharge cycle, one water stream is desalinated forming a freshwater stream, while the other is enriched in NaCl forming a brine waste stream (see Figure 1b).In order to quantify performance and lifetime of the novel battery-type water desalination cells, we define and measure objective metrics. We see that energy consumption (Wh/l) and productivity (l/h/m2) of NiHCF/NiHCF cells are superior to cells based on membrane capacity deionization (mCDI). Stable charge/discharge cycling of NiHCF/NiHCF cells can be achieved for over 500 cycles with NaCl feed water, but rapid aging is observed with CaCl2 feeds. Synchrotron-based characterization of NiHCF/NiHCF cells is used to elucidate the reason for capacity fade. X-ray absorption spectroscopy and X-ray fluorescence spectroscopy reveal Fe dissolution from the NiHCF active material as a primary aging mode with CaCl2 water feeds. References Wessells, C. D., Peddada, S. V., Huggins, R. A. & Cui, Y. Nickel hexacyanoferrate nanoparticle electrodes for aqueous sodium and potassium ion batteries. Nano Lett. 11, 5421–5425 (2011).Wessells, C. D. et al. Tunable reaction potentials in open framework nanoparticle battery electrodes for grid-scale energy storage. ACS Nano 6, 1688–1694 (2012).Pasta, M. et al. Full open-framework batteries for stationary energy storage. Nat. Commun. 5, 1–9 (2014).Firouzi, A. et al. Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries. Nat. Commun. 9, (2018).Pasta, M., Wessells, C. D., Cui, Y. & La Mantia, F. A desalination battery. Nano Lett. 12, 839–843 (2012).Lee, J., Kim, S. & Yoon, J. Rocking Chair Desalination Battery Based on Prussian Blue Electrodes. ACS Omega 2, 1653–1659 (2017).Kim, T., Gorski, C. A. & Logan, B. E. Low Energy Desalination Using Battery Electrode Deionization. Environ. Sci. Technol. Lett. 4, 444–449 (2017).Porada, S., Shrivastava, A., Bukowska, P., Biesheuvel, P. M. & Smith, K. C. Nickel Hexacyanoferrate Electrodes for Continuous Cation Intercalation Desalination of Brackish Water. Electrochim. Acta 255, 369–378 (2017).Jones, E., Qadir, M., van Vliet, M. T. H., Smakhtin, V. & Kang, S. mu. The state of desalination and brine production: A global outlook. Sci. Total Environ. 657, 1343–1356 (2019).Metzger, M. et al. Techno-economic analysis of capacitive and intercalative water deionization. Energy Environ. Sci. 13, 1544–1560 (2020).Sebti, E. et al. Removal of Na+ and Ca2+ with Prussian blue analogue electrodes for brackish water desalination. Desalination 487, (2020).Besli, M. M. et al. Performance and lifetime of intercalative water deionization cells for mono- and divalent ion removal. Desalination 517, 115218 (2021). Figure 1. (a) Battery-type water desalination approach in symmetric NiHCF/NiHCF cells with two salt water streams entering the cell and a brine stream and freshwater stream exiting the cell. (b) During galvanostatic charge/discharge cycling the salt concentrations of brine and freshwater stream can be monitored with microfluidic operando conductivity probes to determine important performance metrics. Figure 1

Improvement in cycling stability of Prussian blue analog-based aqueous sodium-ion batteries by ligand substitution and electrolyte optimization

In this study, we investigated the effects of ligand substitution in Prussian blue analog (PBA) cathode materials on the performance of aqueous sodium-ion batteries. NaCu[Fe(CN)6] (NaCuHCF) and ligand-modified PBAs, NaxCu[Fe(CN)5(C6H4N2)] (NaxCuCNPFe), and NaxCu[Fe(CN)5(CH3C6H4NH2)] (NaxCuTolFe) were tested in different electrolytes. The NaxCuCNPFe and NaxCuTolFe cathodes exhibited the best capacity retention of ∼50% after 2000 cycles in 1 M Na2SO4, which is much higher than that of the NaCuHCF cathode (0% capacity remained after 2000 cycles). To understand the charge–discharge mechanism of PBA cathodes, in situ synchrotron X-ray absorption spectroscopy and X-ray diffraction were performed. To demonstrate practical energy storage applications, PBAs were tested in full-cell configurations with an anode made of sodium titanium phosphate (NTP) coated with reduced graphene oxide and carbon (NTP@C@RGO). The NaxCuCNPFe//NTP@C@RGO and NaxCuTolFe//NTP@C@RGO full cells in 17 m NaClO4 aqueous electrolyte exhibited high power densities of up to 4338 W kg−1 (with an energy density of 18.11 Wh kg−1) and 4742 W kg−1 (with an energy density of 11.87 Wh kg−1), respectively. Our study demonstrates the potential of optimizing organic ligands in PBAs and electrolytes for the improvement of the cycling stability of high-power aqueous sodium-ion batteries.

Effect of Al doping on electrochemical performance of NaTi2(PO4)3/C anode for aqueous sodium ion battery

Effect of Al doping on electrochemical performance of NaTi2(PO4)3/C anode for aqueous sodium ion battery

Synthesis of NaNiF3 and its composite with multi-walled carbon nanotubes as cathode materials for aqueous sodium-ion battery

Synthesis of NaNiF3 and its composite with multi-walled carbon nanotubes as cathode materials for aqueous sodium-ion battery

Transparent aqueous rechargeable sodium-ion battery

Aqueous sodium-ion battery is a sustainable, non-toxic, non-flammable, and low-cost alternative to lithium-ion batteries, while transparency is a growing requisite of modern and integrated devices that batteries have yet to fulfill. In this work we present the preparation of a transparent and rechargeable aqueous Na-ion battery, assembled with different thin films of carbon/cobalt-based nanomaterials as electrodes. Cobalt-filled carbon nanotubes and cobalt/cobalt oxide encapsulated carbon nanoparticles are simultaneously synthesized in one single experimental procedure and deposited as thin and transparent films through the liquid/liquid interfacial route. The former is used for the electrosynthesis of a Prussian blue analogue, yielding carbon nanotubes/cobalt hexacyanoferrate thin film nanocomposite used as cathodes, while the cobalt/cobalt oxide/carbon nanoparticles thin film is used as the anode. The transparent device is prepared using a diluted aqueous solution of NaCl as the electrolyte, reaching capacities of 22 mAh•g−1 at 2 A•g−1 that remains stable after 2000 charge/discharge cycles, and energy density of 19.2 Wh•kg−1 at 1.4 kW•kg−1.

Effects of Salt Concentration on the Water and Ion Self-Diffusion Coefficients of a Model Aqueous Sodium-Ion Battery Electrolyte.

The aqueous sodium-ion battery is a promising alternative to the well-known lithium-ion battery owing to the large abundance of sodium ion resources. Although it is safer than the lithium-ion battery, the voltage window of the sodium-ion battery is narrower than that of the lithium-ion battery, thus limiting its practical implementation. Therefore, a highly concentrated electrolyte is required to address this issue. In the present work, the effect of the salt concentration on the transport properties of water molecules is investigated via theoretical analyses at the quantum mechanical level. A molecular dynamics simulation at the quantum mechanical level revealed that as the salt concentration increases, the ion-water interactions became stronger, leading to a lower diffusivity and a lower electronic band gap. These imply that the superconcentrated aqueous-based electrolytes have high potentials for the sodium-ion battery applications.

Inorganic Electrolyte for Low-Temperature Aqueous Sodium Ion Batteries.

Aqueous sodium ion batteries have received widespread attention due to their great application potential and high safety. However, the serious capacity fading under low temperature dramatically restricts their practical application. Compared to flammable and toxic organic antifreezing additives, addition of common cheap inorganic inert additives to improve low-temperature performance is of interest scientifically. Herein, low-cost calcium chloride is served as antifreezing additive in 1 m NaClO4 aqueous electrolyte due to its strong interaction with water molecules. The freezing point of the optimized electrolyte is significantly reduced to below -50 °C with an ultrahigh ionic conductivity (7.13 mS cm-1 ) at -50 °C. All pure inorganic composition of the full battery delivers a high capacity of 74.5 mAh g-1 under 1 C (1 C = 150mA g-1 ) at -30 °C. More importantly, when tested under 10 C at -30 °C, the battery can achieve an ultralong cycling stability of 6000 cycles with no obvious capacity decay, indicating fast Na+ transport under low temperature. Significantly, this work provides an easy-to-operate strategy by adding cheap inorganic salt to develop high-performance low-temperature aqueous batteries.

Electrolyte Effects on the Stabilization of Prussian Blue Analogue Electrodes in Aqueous Sodium-Ion Batteries.

Aqueous sodium-ion batteries based on Prussian Blue Analogues (PBA) are considered as promising and scalable candidates for stationary energy storage systems, where longevity and cycling stability are assigned utmost importance to maintain economic viability. Although degradation due to active material dissolution is a common issue of battery electrodes, it is hardly observable directly due to a lack of in operando techniques, making it challenging to optimize the performance of electrodes. By operating Na2Ni[Fe(CN)6] and Na2Co[Fe(CN)6] model electrodes in a flow-cell setup connected to an inductively coupled plasma mass spectrometer, in this work, the dynamics of constituent transition-metal dissolution during the charge-discharge cycles was monitored in real time. At neutral pHs, the extraction of nickel and cobalt was found to drive the degradation process during charge-discharge cycles. It was also found that the nature of anions present in the electrolytes has a significant impact on the degradation rate, determining the order ClO4- > NO3- > Cl- > SO42- with decreasing stability from the perchlorate to sulfate electrolytes. It is proposed that the dissolution process is initiated by detrimental specific adsorption of anions during the electrode oxidation, therefore scaling with their respective chemisorption affinity. This study involves an entire comparison of the effectiveness of common stabilization strategies for PBAs under very fast (dis)charging conditions at 300C, emphasizing the superiority of highly concentrated NaClO4 with almost no capacity loss after 10 000 cycles for Na2Ni[Fe(CN)6].

Aqueous Sodium Ion Batteries with Ultra-Long Cycle Life at -50℃

Aqueous Sodium Ion Batteries with Ultra-Long Cycle Life at -50℃