NaClO4 Salt Research Articles

Improving supercapacitor performance with novel potato starch-PVA solid polymer electrolyte blend modified by sodium perchlorate-glycerol additives

The synthesis and analysis of Solid Polymer Electrolytes (SPEs) derived from a blend of Potato Starch and Poly Vinyl Alcohol (PS-PVA), enhanced with Sodium perchlorate salt (NaClO4) and Glycerol (GCL) are explored in this work. Our focus is on their suitability for Electrical Double-Layer Capacitor (EDLC) devices. GCL, a non-toxic substance, served as the plasticizer, and sodium perchlorate was incorporated to enhance the ionic conductivity of the SPE film. The conductivity at room temperature for pure PS-PVA blend, in the absence of salt and GCL, was found to be 4.16 × 10−8 S cm−1. Upon adding an optimized quantity of NaClO4 salt, the conductivity increased to 1.02 × 10−5 S cm−1. Subsequent plasticization of the salt-polymer blend with GCL induced NaClO4 dissociation, further augmenting the conductivity by one order of magnitude. A conductivity value of 10.35 × 10−5 S cm−1 was achieved for the film with 30 wt% GCL. Morphological, electrical, and structural analyses revealed that synthesized polymer films exhibited favorable characteristics. The suitability of these electrolytes for Electric Double-Layer Capacitors (EDLC) was studied using electrochemical characterizations and cycling tests for 2000 cycles. The findings demonstrate their potential for use in energy storage devices, showcasing excellent performance in specific capacitance, energy, and power densities.

Insight into ion dynamics in a NaClO4-doped polycaprolactone solid polymer electrolyte for solid state batteries.

Employing low Tg polymers has fundamental limitations in providing the desirable ionic conductivity at ambient temperature due to the freezing of chain dynamics. The stiffening of polymer chains and the formation of highly ordered systems due to the crosslinks have influenced the ionic conductivity. Ionic conductivity of 1.02 × 10-5 S cm-1 was attained for the system that presented a quantum mechanical tunnelling mode of ion transport. A Na-ion transference number of 0.31 was achieved for 30 wt% of NaClO4 salt in a polycaprolactone (PCL) matrix with an electrochemical stability window of 3.6 V at 25 °C. High crystallinity and limited availability of free Na+ ions in the electrolyte have resulted in lower ionic conductivity. PCL-NaClO4 exhibited brilliant thermal stability and mechanical properties. The influence of cathode materials MnO2, V2O5 and I2 on the discharge characteristics of an electrochemical cell in the configuration cathode |(70 wt%)PCL-NaClO4(30 wt%)|Na has been studied.

Improving the Electrochemical Properties of Cathode Materials for Sodium Ion Batteries

Energy storage systems made from abundant materials are essential for the transition to a more sustainable economy. Although today lithium-ion batteries (LIBs) are the most popular battery technology, the growing demand and low availability of lithium, as well as the use of cobalt and other rare metals raise questions about the sustainability and long-term viability of LIB as the only energy storage solution. The high abundance of sodium content and relative similarity to LIBs, allows the sodium ion batteries (SIBs) to be considered as alternative for stationary energy storage [1]. However, the widespread adoption of SIB technology is hampered by many challenges, including the relatively low energy density compared to LIB. Lower energy density electrodes, such as Na2FeP2O7, are generally stable during cycling [2], while many higher energy density electrodes, such as NaxMnO2, have had a shorter cycle life [3]. In this work we show several possible solutions how to improve the electrochemical properties of the SIBs made of these cathode materials.The promising cathode material Na2FeP2O7 was studied to improve its electrical conductivity, which is often low in the case of sodium pyrophosphates. Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for sodium-ion batteries, using glucose as a carbon source. While the pristine Na2FeP2O7 displays capacity of only 45 mAh/g due to the relatively large grain size, the addition of carbon increases the capacity to up to 92 mAh/g (95% of the theoretical 97 mAh/g capacity) with excellent rate capability, as 44 mAh/g capacity is still retained even at 20 C (1.94 A/g) current. The optimal content of carbon was found to be 4.8%. The initial capacity of 81 mAh/g is fully retained after 500 cycles at 1 C, indicating excellent cycle life of Na2FeP2O7/C. Electrochemical measurements were carried out in 1 M NaClO4 salt in propylene carbonate as electrolyte and show that the addition of 5 wt.% fluoroethylene carbonate solid electrolyte interphase stabilizing additive greatly benefits the rate and cycling performance of Na2FeP2O7/C as measured in half-cells [4].Na0,67MnO2 is another compound that is widely studied as cathode materials in sodium ion batteries. Currently polyvinylidene fluoride (PVDF) is the most popular binder choice. In our study, a novel tetrabutylammonium (TBA) alginate binder is used to prepare a Na0,67MnO2 electrode for sodium-ion batteries with improved electrochemical performance. The ageing of the electrodes has been characterized. TBA alginate-based electrodes are compared to PVDF and Na alginate-based electrodes and show favorable electrochemical performance, with gravimetric capacity values of up to 164 mAh/g, which is 6% higher than measured for the electrode prepared with PVDF binder. TBA alginate-based Na0,67MnO2 electrodes also display good rate capability and improved cyclability and their solid–electrolyte interface is similar to that of PVDF-based electrodes. As the only salt of alginic acid soluble in non-aqueous solvents, TBA alginate emerges as a good alternative to PVDF binder in battery applications where the water-based processing of electrode slurries is not feasible, such as the demonstrated case with Na0,67MnO2 [5].Overall, we have shown that binder and electrolyte selection can significantly improve the electrochemical properties of electrode materials for SIBs.The financial support of projects No. 1.1.1.2/VIAA/1/16/166 “Advanced materials for sodium Ion batteries” and No. lzp-2020/1-0391 “Advanced polymer – ionic liquid composites for sodium-ion polymer batteries” is greatly acknowledged. Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01–2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2. Vaalma, C.; Buchholz, D.; Weil, M.; Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 2018, 3, 18013.Jin, T.; Li, H.; Zhu, K.; Wang, P.-F.; Liu, P.; Jiao, L. Polyanion-type cathode materials for sodium-ion batteries. Chem. Soc. Rev. 2020, 49, 2342.Lyu, Y.; Liu, Y.; Yu, Z.-E.; Su, N.; Liu, Y.; Li, W.; Li, Q.; Guo, B.; Liu, B. Recent advances in high energy-density cathode materials for sodium-ion batteries. Sustain. Mater. Technol. 2019, 21, e00098.Kucinskis, G.; Nesterova, I.; Sarakovskis, A.; Bikse, L.; Hodakovska, J.; Bajars, G. Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive. J. Alloys Compd. 2022, 895, 162656.Kucinskis, G.; Kruze, B.; Korde, P.; Sarakovskis, A.; Viksna, A.; Hodakovska, J.; Bajars, G. Enhanced Electrochemical Properties of Na67MnO2 Cathode for Na-Ion Batteries Prepared with Novel Tetrabutylammonium Alginate Binder. Batteries 2022, 8, 6. Figure 1

Effects of sodium salts on compatibility between Na2Ti3O7@C anode and electrolyte for sodium-ion batteries

A non-carbonaceous titanium-based materials of Na2Ti3O7 have been considered as an attractive anode material for sodium ion battery (SIBs), due to its low charge potential and high energy density. However, the selection of preferred sodium salts in liquid electrolyte is still a challenge to improve battery performance. Herein, the compatibility of Na2Ti3O7 @C anode material with sodium perchlorate (NaClO4)-based and sodium trifluoromethyl sulfonate (NaCF3SO3)-based electrolytes are studied, respectively. The results show that solid electrolyte interphase (SEI) film formed by NaCF3SO3-based electrolyte is thin, compact and uniform, which can effectively reduce the transmission energy barrier of Na+. Different from that, the SEI film derived in NaClO4-based electrolyte contains more Na2CO3 and NaF, caused by the continuous decomposition of NaClO4 salt in carbonate solvent. It makes the SEI film thicker and the interface impedance larger, which results in the decline of battery cycle performance. In addition, more sulfur-containing compounds with good sodium conductivity and stability are generated due to the decomposed of NaCF3SO3 salt in carbonate solvent, which improves interfacial transport performance of materials, and inhibits the increase of the SEI film thickness and thus improves the cycling and rate performance of batteries. This study provides a reference method for designing advanced SIBs.

Adsorption of Hydrophilic Silica Nanoparticles at Oil-Water Interfaces with Reversible Emulsion Stabilization by Ion Partitioning.

Adsorption of particles at oil-water interfaces is the basis of Pickering emulsions, which are common in nature and industry. For hydrophilic anionic particles, electrostatic repulsion and the absence of wetting inhibit spontaneous adsorption and limit the scope of materials that can be used in emulsion-based applications. Here, we explore how adding ions that selectively partition in the two fluid phases changes the interfacial electric potential and drives particle adsorption. We add oil-soluble tetrabutyl ammonium perchlorate (TBAP) to the nonpolar phase and Ludox silica nanoparticles or silica microparticles to the aqueous phase. We find a well-defined threshold TBAP concentration, above which emulsions are stable for months. This threshold increases with the particle concentration and with the oil's dielectric constant. Adding NaClO4 salt to water increases the threshold and causes spontaneous particle desorption and droplet coalescence even without agitation. The results are explained by a model based on the Poisson-Boltzmann theory, which predicts that the perchlorate anions (ClO4-) migrate into the water phase and leave behind a net positive charge in the oil. Our results show how a large class of inorganic hydrophilic, anionic nanoparticles can be used to stabilize emulsions in a reversible and stimulus-responsive way, without surface modifications.

INVESTIGATION OF PMMA AND PVdF-HFP WITH NaClO4POLYMER BLEND ELECTROLYTE SYSTEM– APPLICATION TO AN ELECTROCHEMICAL CELL

A solution-cast process was used to prepare pure poly (methyl methacrylate) (PMMA), and pure poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), their blend, and different weight percentages of sodium per chlorate (NaClO4) salt added to PMMA: PVdF-HFP polymer blend electrolyte thin films. The polymer electrolyte film was prepared using the solution cast process, which involves combining sodium per chlorate (NaClO4) ionic slat with poly (methyl methacrylate) (PMMA) and pure poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) blended polymer. These films have been characterized systematically using different experimental techniques to investigate structural, morphological, thermal, and conductivity properties. The degree of crystallinity and porous microstructure of all the thin films were determined by XRD and SEM data and revealed that higher content of the amorphous nature was noticed at higher NaClO4 salt concentration in PMMA:PVdF-HFP polymer blend. When NaClO4 salt was added to a PMMA:PVdF-HFP polymer blend, fair complexation/interaction between polymers and salt was observed.In DSC curves of PMMA and PVdF-HFP polymers, a sharp melting temperature (Tm) was seen, which diminished when NaClO4 salt was added, showing that its amorphous nature had risen to prominence. The ionic conductivity of NaClO4 salt added PMMA:PVdF-HFP polymer blend electrolyte has been investigated, with an optimal value found to be1.55382 x 10-4S/cm at 40% NaClO4 salt. Electrochemical cells have been fabricated and investigated its characteristics in the configuration of Na/[PMMA:PVdF-HFP: NaClO4]/(I2:C).

Optical properties of PMMA and PVDF-HFP blend with NaClO4 salt

The poly(methyl methacrylate) (PMMA), pure poly(vinylidene fluoride) (PVDF-HFP), and NaClO4 salt were used to prepare the blend thin films by solution casting procedure. By using the UV–Visible spectrophotometer optical absorption properties of this prepared film were recorded. The direct and indirect optical energy gaps for these thin films were estimated using Tauc's plots from the UV–visible spectra and found that increasing NaClO4 salt content in PMMA + PVDF-HFP blend the absorption edge and indirect band gap energy values were found to be decreased.

Effect of EC plasticizer on Na+ ion based PMMA:PEO blend solid polymer electrolyte system

Solution casting method was used to prepare the Ethylene Carbonate (EC) doped in NaClO4 salt added PMMA:PEO blend polymer electrolyte thin films. Different characterization techniques such as XRD, SEM, DSC and FTIR were employed to study the effect on structural properties of these prepared thin films. The XRD, SEM and DSC results revealed the dominant presence of amorphous content in PMMA based polymer blend with the addition of PEO, NaClO4 and EC, which functions to enhance in ionic conductivity. FTIR spectra results elucidated that the vibrational band peaks corresponds to PMMA shifted towards lower or higher wave number side in presence of PEO, NaClO4 and EC, which confirms the interaction/complexation between PMMA, PEO polymers with NaClO4 salt and EC plasticizer.

Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive

Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for sodium-ion batteries, using glucose as a carbon source. While the pristine Na2FeP2O7 displays capacity of only 45 mAh/g due to the relatively large grain size, the addition of carbon increases the capacity to up to 92 mAh/g (95% of the theoretical 97 mAh/g capacity) with excellent rate capability, as 44 mAh/g capacity is still retained even at 20 C (1.94 A/g) current. The optimal content of carbon was found to be 4.8%. The initial capacity of 81 mAh/g is fully retained after 500 cycles at 1 C, indicating excellent cycle life. Measurements were carried out in 1 M NaClO4 salt in propylene carbonate as electrolyte and show that the addition of 5 wt% fluoroethylene carbonate solid electrolyte interphase stabilizing additive greatly benefits the rate and cycling performance of Na2FeP2O7/C as measured in half-cells.

Investigation of morphology and transport properties of Na+ ion conducting PMMA:PEO hybrid polymer electrolyte

Abstract The aim of this research work is to examine the modification of structure, morphology and conductivity properties of PMMA: PEO blend hybrid polymer electrolyte system complexed with NaClO4 salt. Solution-cast procedure was adopted in preparation of these films. These films were characterized with XRD, SEM, DSC, and DC conductivity for the evaluation of modified properties. Peaks have disappeared and broadened in the XRD pattern of PMMA for higher concentration of PEO polymer and salt presented films, which indicated that attaining of higher amorphous phase in these polymer electrolyte films. Almost smooth surface morphology with fewer pores was observed in 20 wt. % of PEO and NaClO4 salt present PMMA films of SEM image. This establishes a dominant presence of amorphous content in these NaClO4 complexed PMMA:PEO hybrid electrolyte films when compared to pure PMMA and PEO. Disappearance of melting temperature was observed in all concentrations of NaClO4 salt and PEO polymer added PMMA polymer films, which suggests a decrease of crystalline and an increase of amorphous nature. Enhancing of DC conductivity with temperature was observed in all the films but higher conductivity was exhibited at higher concentration of NaClO4 salt present films.

Fast and Large Shrinking of Thermoresponsive Hydrogels with Phase-Separated Structures.

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been attracting attention in a variety of functional materials, such as biomaterials, because they exhibit a volume phase transition phenomenon near physiological temperatures. However, the slow kinetics and small volume shrinkage of bulk PNIPAAm hydrogels upon heating greatly limit their practical application. Here, we report PNIPAAm hydrogels with phase-separated structures that exhibited ultrafast shrinking upon heating. The phase separation into a PNIPAAm-rich phase and a water-rich phase was formed through aqueous polymerization in the presence of NaClO4 salt. Through structural analysis of the hydrogels, a topologically heterogeneous and porous structure was observed, which was highly dependent on the NaClO4 concentration in the polymerization step. Compared to conventional PNIPAAm hydrogels, the phase-separated hydrogels exhibited much faster and larger shrinkage upon heating. Simultaneously, the hydrogels quickly released a large amount of water owing to the effective water channels inside them. The present method can be widely applied to general hydrogels, and it can address the numerous limitations of hydrogels in terms of operating programmability and deformation efficiency.

Na0.44MnO2/Polyimide Aqueous Na-ion Batteries for Large Energy Storage Applications

Aqueous salt batteries with high concentrations of salt or water in salt aqueous systems have received considerable attention with focus on improving working voltage range and energy density. Here, the effect of NaClO4 salt concentration on the electrochemical performance and stability of tunnel-type Na0.44MnO2 (NMO) cathodes and organic polyimide (PI) derivative anodes was studied. High capacity retention and 100% coulombic efficiency were shown for NMO/PI full cell in saturated NaClO4 electrolyte. A high, stable capacity of 115 mAh/g was achieved for the PI anode material, and the full cell showed a stable capacity of 41 mAh/g at 2C rate for 430 cycles (calculated for the weight of NMO cathode). Even at a fast 5C rate, a discharge capacity of 33 mAh/g was maintained for 2,400 prolonged cycles with nearly 100% efficiency. The full cell device can achieve an average voltage of 1 V with energy density of 24 Wh/kg. This study highlights concentrated sodium perchlorate as a promising electrolyte solution for stabilization of electrodes and enhancement of electrochemical performance in aqueous media.

Preparation, characterization and impedance spectroscopic studies of Na+ ion conducting PEO + PVDF-blended polymer electrolytes

The films of poly (ethylene oxide) (PEO) and poly (vinylidene fluoride) (PVDF)-based blended polymer electrolyte films complexed with sodium perchlorate (NaClO4) salt were prepared using the solution casting method. The complexation of NaClO4 salt with the blend of polymers PEO and PVDF was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The melting temperatures were measured by differential scanning calorimetry (DSC). The surface morphology was examined by scanning electron microscopy (SEM). The prepared films were subjected to electrical impedance spectroscopy (EIS) to investigate ionic conductivity, dielectric and electrical modulus studies. It was observed that adding a small amount of PVDF to the PEO host polymer improves the interaction between the ions and the polymer and results in more ionic dissociation. Consequently, the number of active mobile carriers in the polymer matrix increases. The ionic conductivity studies have shown the maximum conductivity 2.84 × 10−6 S/cm at 303 K for the polymer blend 0.8PEO + 0.2PVDF complexed with 5 wt% NaClO4 and it is attributed to a decrease in crystallinity. Ionic transport numbers of various prepared samples were measured using Wagner’s polarization technique.

Increasing the ionic conductivity of solid state polymer electrolyte using fly ash as a filler

Polymer electrolytes film based on polyethylene oxide (PEO) complexes with NaClO4 salt with a ratio of EO: Na = 20:1 and fly ash as filler has been prepared by solution casting technique. The crystallinity of the solid polymer electrolyte was characterized by X-Ray Diffraction (XRD). The interaction between PEO and Na-ions confirmed by Fourier Transform Infra Red (FTIR) analysis. The ionic conductivity of the solid polymer electrolyte was investigated by impedance analysis from 1 MHz to 1 Hz at a varied temperature of 50°C, 60°C, 70°C, 80°C, and 90°C. The maximum ionic conductivity of EO: Na = 20 was 5.31 x 10-5 S cm-1 and increases to 2.13 x 10-4 S cm-1 by the addition of fly ash 5% at the temperature of 60°C.

Surface and interface engineering of anatase TiO2 anode for sodium-ion batteries through Al2O3 surface modification and wise electrolyte selection

In the present study, Al2O3 is utilized for the first time as coating agent on nanostructured anatase TiO2 in order to investigate its effect on sodium-ion batteries performance. Our results show that the Al2O3 coating, introduced by a facile two-step approach, provides beneficial effects to the TiO2-based anodes. However, the coated TiO2 still suffers of capacity fading upon cycling when using 1.0 M of NaClO4 in propylene carbonate (PC) as electrolyte. To address this issue, the influence of different electrolytes (NaClO4 salt in various solvents) is further studied. It is found that the modified TiO2 exhibits significant improvements in cycling performance using binary ethylene carbonate (EC) and PC solvent mixture without the need of the commonly used fluoroethylene carbonate (FEC) additive. Under the best configuration, our battery could deliver a high reversible capacity of 188.1 mAh g−1 at 0.1C after 50 cycles, good rate capability up to 5C, and remarkable long-term cycling stability at 1C rate for 650 cycles. This excellent performance can be ascribed to the synergistic effects of surface and interface engineering enabling the formation of a stable and highly ionic conductive interface layer in EC:PC based electrolyte which combines the native SEI film and an ‘artificial’ SEI layer of irreversibly formed Na−Al−O.

Poly(AN-co-PEGMA)/hBN/NaClO4 composite electrolytes for sodium ion battery

AbstractPolymer electrolytes composed of an acrylonitrile and polyethylene glycol methacrylate copolymer poly(AN-co-PEGMA) with addition of NaClO4 are studied by impedance spectroscopy, differential scanning calorimetry (DSC), fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Hexagonal boron nitride (hBN) particles are having increasing interest owing to mechanical properties, thermal stability, chemical stability and good lubrication property. In this study, hBN was used as an inorganic filler. FTIR spectroscopy was used to examine the interactions between the host polymer and both NaClO4 salt and nano hBN particles. The thermal properties of the composites were studied using TGA and DSC tests. TGA results showed that all the composites membranes were thermally stable till 300°C with one step degradation. Surface morphology of the films was examined with SEM which also reveals the homogeneous dispersion of nano hBN in the polymer matrix. Ionic conductivity was studied with impedance spectroscopy, the results showed that the ionic conductivity increases with increasing PEGMA ratio. ANcoPEGMA 11 20Na (EO:Na ratio=20) sample showed maximum ion conductivity of approximately 3.6×10−4 S cm−1 at 100°C. This is because ANcoPEGMA 11 20Na has highest percentage of PEGMA and highest number of Na+ ion per EO groups.

Effect of NaClO4 concentration on electrolytic behaviour of corn starch film for supercapacitor application

Polymer electrolyte has seen tremendous growth after works of Fenton & Armand, and energy devices are being produced at commercial level. Today’s social lifestyle needs miniaturized energy devices at every step of life; consequently, they add up to chemical garbage of the world. The sustainable development in the field needs eco-friendly energy devices. Hence, starch (being at low cost, abundant in nature and eco-friendly) has received great scientific attention. In recent past, many attempts have been made to modify the various starches to get fast ion-conducting materials. In our laboratory, also, wheat, potato, rice and arrowroot starches have been modified with different sodium salts, and in each case, considerably high-conducting (>10−3 S/cm) films have been found. In present case, also, a high-conducting transparent film (10−2 S/cm) is obtained with corn starch and NaClO4 salt after being crosslinked with glutaraldehyde (GA). Bode plots (both phase and magnitude), capacitive-response plot, capacitive-frequency plots and linear sweep voltammetry curves are analysed to explain the possibility of using the prepared electrolyte in capacitive device. The larger electrochemical stability window (ESW) ~ 2.4 V and smaller ion relaxation time ~ 65 μs make it a potential candidate for device fabrication. The equivalent series resistance is ~6.252 Ω for 0.8-mm-thick sample.

Role of ZrO2 on physico‐chemical properties of PVA/NaClO4 composites for energy storage applications

A novel polymer nano composite electrolyte composed of PVA polymer matrix with ZrO2 ceramic filler and NaClO4 salt was prepared by a solution casting. The characteristic properties of PVA/NaClO4 polymer composite electrolytes with ZrO2 filler were studied using FTIR, X‐ray diffractometer (XRD), FESEM, DSC, AFM, AC impedance method, and cyclic voltammeter. The sample containing 3 wt% ZrO2 exhibits good mechanical strength, high conductivity, high dielectric constant and good electrochemical response at room temperature. The conduction mechanism of the composite can be represented by the correlated barrier hopping (CBH) model and the obtained frequency dependent S parameter obeys Almond—West Universal power law. Using Williams–Landel–Ferry (WLF) and Vogel Fulcher Tamman (VTF) equations equivalence correlated the dynamic fragility (m) and activation energy (Eg) with Tg of polymer composites. Transport parameters were calculated using Rice and Roth model. The cyclic voltamograms shows that the prepared films were Pseudo‐capacitive in nature. POLYM. COMPOS., 39:1273–1282, 2018. © 2016 Society of Plastics Engineers

In silico Based Rank-Order Determination and Experiments on Non-Aqueous Electrolytes for Li-Ion Batteries and Beyond

Electrolytes are an important component of electrochemical energy storage systems and their optimization is critical for emerging beyond lithium ion technologies. Here, an integrated computational-experimental approach is used to rank-order and aid the selection of suitable electrolytes for a Na-ion battery. We present an in silico strategy based on both thermodynamic and kinetic descriptors derived from molecular dynamics simulations to rationally arrive at optimal electrolytes for Na-ion batteries. We benchmarked various electrolytes (pure and binary mixtures of cyclic and acyclic carbonates with NaClO4 salt) to identify appropriate formulations with the overarching goal of simultaneously enhancing cell performance while meeting safety norms. Fundamental insights from computationally derived thermodynamic and kinetic data considerations coupled with atomistic-level description of the solvation dynamics is used to rank order the various electrolytes. Thermodynamic considerations based on free energy evaluation indicate EC:PC as a top electrolyte formulation under equilibrium conditions. However, kinetic descriptors which are important factors dictating the rate capability and power performance suggest EC:DMC and EC:EMC to be amongst the best formulations. Experimental verification of these optimized formulations was carried out by examining the electrochemical performance of various electrolytes in Na/TiO2 nanotubes half cells with NaClO4 salt. Our rate capability studies confirm that EC:DMC and EC:EMC to be the best formulations. These optimized formulations have reversible specific capacities ~180-240 mAh/g whereas the lower ranked electrolytes (EC:DEC) have capacities ~100 mAh/g. The various electrolytes are also evaluated from a safety perspective. Such results suggest encouraging prospects for this approach in the a priori prediction of optimal sodium ion systems with possible screening implications for novel battery formulations.

Electrical and structural characterization of PVA/PEG polymer blend electrolyte films doped with NaClO4

A solid polymer blend electrolyte system based on polyvinyl alcohol (PVA) and polyethylene glycol (PEG) complexed with NaClO4 was prepared using solution cast technique. The structural properties of these electrolyte films were examined by X-ray diffractrometry (XRD) studies. The XRD data revealed that the amorphous domains of polymer blend matrix increased with increase of sodium salt concentration. The complexation of the salt with the polymer blend was confirmed by Fourier transform infrared (FTIR) studies. DC conductivity of the films was measured in the temperature range 303–398 K. The electrical conductivity increased with increasing dopant concentration, which is attributed to the formation of charge transfer complexes. The electrolyte exhibited the highest room temperature conductivity 2.41 × 10−6 S cm−1 at 30 % of NaClO4 salt concentration. The polymer complexes exhibited Arrhenius-type dependence of conductivity with temperature. In the temperature range studied, two regions with different activation energies were observed. Electrochemical cells of configuration Na/(PVA + PEG + NaClO4)/(I2 + C + electrolyte) were fabricated and the discharge characteristics of these cells were studied under a constant load of 100 K. Several cell parameters associated with the cells were evaluated and compared with earlier reports. UV-VIS absorption spectra in wavelength region 200–600 nm were used to evaluate the optical properties like direct band gap, indirect band gap and absorption edge. The optical band gaps decreased with increasing sodium ion concentration. This suggests that NaClO4 is a good dopant to improve the electrical properties of PVA + PEG polymer blend electrolytes.