Chitosan-based Electrolyte Research Articles

Dynamic interfacial pH regulation with chitosan gel electrolyte for enhanced high-temperature Zn anode stability

Aqueous zinc-ion batteries (AZIBs) are promising for high-temperature energy storage due to their high safety, low cost, and energy density. However, their reversibility and cycling stability at elevated temperatures remain challenging. We introduce a novel dynamic interfacial pH regulation strategy specifically designed for high-temperature conditions to mitigate proton and by-product formation on zinc anodes. This strategy involves a chitosan gel electrolyte that not only reduces proton generation from water decomposition but also impedes zinc ion dissociation at elevated temperatures. The amino and hydroxyl groups in chitosan act as proton traps, releasing functional groups that form complexes with zinc ions, thereby reducing zinc ion activity and preventing hydrolysis. Furthermore, chitosan's hydrogen bonding sites decrease free water activity, inhibiting its decomposition and further suppressing proton generation. These unique features work together to enhance the stability and efficiency of zinc plating/stripping, achieving a coulombic efficiency of 99.3 % at 25 °C and 98.5 % at 60 °C. Zn||PANI cells using this chitosan-based electrolyte demonstrated remarkable long-term stability, retaining 68.7 % of their initial capacity after 2000 cycles at 60 °C and 5 A g-1.

Chitosan-based electrolytes containing carbon nanotube-titanium dioxide for energy conversion devices applications

Chitosan-based electrolytes containing carbon nanotube-titanium dioxide for energy conversion devices applications

Performance of phototronically activated chitosan electrolyte in rare-earth doped Bi2Ti2O7 nanostructure based DSSC

Power conversion efficiency (PCE) of piezo-phototronic activated chitosan-based electrolyte is established for pristine and rare-earth (RE) doped Bi2Ti2O7 (BTO) nanoparticles. Addition of 2% Gd in the host BTO reduces the particle size by five-fold. The maximum absorption edge for the pristine BTO is shifted towards a higher wavelength about 10 nm confirming the mid-band states. A small external potential ≤ +0.4 V at the photoanode enhances the mobility of the carrier and hence the PCE of about 20% along with the 26% higher photo-responsivity leading to a maximum PCE of 4.68%.

Flexible oxide neuromorphic transistors with synaptic learning functions

Realization of brain-inspired hardware devices is deemed to be a significant step for constructing a neuromorphic system. Moreover, flexible bioinspired neuromorphic devices have broad applications in bioinspired intelligent electronics. Here, we propose flexible IWO neuromorphic transistors gated with proton-conducting chitosan-based electrolytes. The transistor exhibits a low subthreshold swing of ~112 mV/dec and a high mobility of ~17 cm2 V−1 s−1. Moreover, the transistor exhibits excellent mechanical robustness against mechanical stress. Some crucial synaptic functions in biological synapses are mimicked on the proposed flexible transistor, including excitatory post-synaptic currents, paired-pulse facilitation, post-tetanic potentiation, etc. Most importantly, ‘learning-experience’ behaviors are implemented in the device. The proposed flexible neuromorphic devices have applications in artificial perception learning systems, including electronic skin and personal health monitoring.

Improved performance and stability of solid state electrochromic devices with eco-friendly chitosan-based electrolytes

Development of chitosan (Ch)-based green solid polymer electrolyte was attained with addition of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) using solvent casting method for electrochromic device. In the electrochromic device configuration, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-methylthiophene) (PMeT) were used as counter polymer electrodes. The effect of chitosan/PEDOT:PSS-based electrolyte on PEDOT/PMeT-based electrochromic devices was evaluated. In order to deeply compare all electrochromic devices, electrochemical, transmittance, electrochemical impedance measurements were used. PEDOT:PSS can assist both electronic and ionic conduction leading to reduced charge transfer resistance and better electrochromic performance. Presented electrochromic device with use of PEDOT:PSS displayed higher optical modulation (20.6%/±1 V; 32.2%/±2 V at 650 nm, faster response times (coloration time (tc): 0.1 s/±1 V, 0.24 s/±2 V and bleaching time (tb): 0.11 s/±1 V, 0.52 s/±2 V)). These results signify that the addition of PEDOT:PSS to electrolyte is useful for improved electrochromic characteristics as the electrolyte for the fabrication of electrochromic device.

Fabrications and investigation of physicochemical and electrochemical properties of heteropoly acid-doped sulfonated chitosan-based polymer electrolyte membranes for fuel cell applications

A proton exchange membrane for fuel cell application consists of modified chitosan/PEO doped with different weight percentage of HPA acids cross-linked by sulfosuccinic acid. Modifying the chemical structure of the chitosan by means of sulfonation, which was successfully synthesized by direct sulfonating reagent 1,3-propane sultone, chemical structure and thermal stability of the membrane were characterized by FTIR and TG analysis. Further the membrane was characterized by XRD, SEM, AFM and impedance analysis. The results shows that the structure of the composite membranes becomes more compact compared with undoped membranes due to interaction between the sulfonic acid groups and amine groups. This could lead to increase the conductivity and reduce the excess swelling of the membrane. From all the results, these biodegradable and low-costs composite membrane was tested in the single-cell proton exchange membrane fuel cell and it predicts that chitosan-based electrolytes are promising material for fuel cell application.

Organic/inorganic hybrid low-voltage flexible oxide transistor gated with biodegradable electrolyte

Abstract Eco-friendly “green” electronics are attracting increasing interests in recent years. Here, biodegradable organic/inorganic hybrid indium-tin-oxide electric double layer (EDL) transistors were fabricated on plastic substrates. Solution processed chitosan based polysaccharide films were used as gate dielectrics. Due to extremely high EDL capacitances of the chitosan-based electrolytes, the oxide EDL transistors exhibit good performances. Resistor loaded inverters were also built, exhibiting full-swing characteristics and high voltage gains at low operation voltages. Wave-type conversions were realized including conversions from sinusoid waves into rectangular waves and from noise signals into two-bit outputs. Furthermore, the organic/inorganic hybrid transistors can be dissolved in water easily. The proposed organic/inorganic hybrid oxide transistors may have potential applications in “green” portable devices.

Bio-inspired coplanar-gate-coupled ITO-free oxide-based transistors employing natural nontoxic bio-polymer electrolyte

Bio-inspired coplanar-gate-coupled indium-tin-oxide (ITO)-free thin-film transistors (TFTs) are demonstrated by employing natural nontoxic bio-polymer electrolyte. Effective coplanar-gate coupling is realized through bottom-conducting fluorine-tin-oxide layer due to the strong electric-double-layer (EDL) effect in chitosan-based electrolyte dielectric. The optimized channel thickness (∼30 nm) gives the best performance with a low subthreshold swing of 0.22 V/dec, a high on-off ratio of 104, and a field-effect mobility of 3.53 cm2/V. Furthermore, the mechanism of coplanar multi-gate coupling in such TFTs is proposed by using an equivalent circuit composed of multiple paralleling EDL capacitors in series with an additional EDL capacitor. These results present a great step toward the potential applications for the next-generation green bio-compatible low-cost transparent coplanar-gate-integrated electronics.

Investigation of transport properties of chitosan-based electrolytes utilizing impedance spectroscopy

A method based on impedance spectroscopy has been utilized to obtain values of transport parameters such as number density, mobility and diffusion coefficient of mobile ions of solid polymer electrolytes (SPEs). SPE membranes consisting of chitosan and various amounts of oxalic acid (C2O4H2) from 10 to 50 wt% have been prepared by the solution casting method. The Nyquist plots of all electrolytes have been fitted using the impedance equations based on equivalent circuits, and the parameters involved have been evaluated by trial and error. Number density, mobility and diffusion coefficient of mobile ions were calculated based on the parameters obtained. The values obtained from the proposed electrical impedance spectroscopy method are in reasonable agreement with those calculated using the percentage of mobile ions obtained from Fourier transform infrared (FTIR) measurements. The results were further compared with the results obtained using broadband dielectric response or Bandara-Mellander approach. The findings were confirmed by repeating the measurements and calculations on a glycerol-chitosan-oxalic acid-based electrolyte.

Protonic/electronic hybrid oxide transistor gated by chitosan and its full-swing low voltage inverter applications

Modulation of charge carrier density in condensed materials based on ionic/electronic interaction has attracted much attention. Here, protonic/electronic hybrid indium-zinc-oxide (IZO) transistors gated by chitosan based electrolyte were obtained. The chitosan-based electrolyte illustrates a high proton conductivity and an extremely strong proton gating behavior. The transistor illustrates good electrical performances at a low operating voltage of ∼1.0 V such as on/off ratio of ∼3 × 107, subthreshold swing of ∼65 mV/dec, threshold voltage of ∼0.3 V, and mobility of ∼7 cm2/V s. Good positive gate bias stress stabilities are obtained. Furthermore, a low voltage driven resistor-loaded inverter was built by using an IZO transistor in series with a load resistor, exhibiting a linear relationship between the voltage gain and the supplied voltage. The inverter is also used for decreasing noises of input signals. The protonic/electronic hybrid IZO transistors have potential applications in biochemical sensors and portable electronics.

Electrical Studies on Chitosan Based Proton Conductors and Application in Capacitors

Ionic conductivity of four chitosan based electrolyte systems viz., chitosan–H3PO4, chitosan–H3PO4–Al2SiO5, chitosan–H3PO4–NH4NO3 and chitosan–H3PO4–NH4NO3–Al2SiO5 were studied by impedance spectroscopy in the frequency range from 50 Hz to 1 MHz and varying temperatures from 293 K to 373 K. The sample 0.62 chitosan − 0.38 H3PO4 has the highest room temperature conductivity of (5.36 ± 1.32) × 10−5 S cm−1. The sample 0.615 chitosan-0.377 H3PO4-0.008 Al2SiO5 exhibits the highest ambient conductivity of (1.12 ± 0.18) × 10−4 S cm−1 in the ternary system with filler. In the ternary system with salt but without filler, 0.56 chitosan-0.34 H3PO4–0.10 NH4NO3 has the highest ambient conductivity of (1.16 ± 0.35) × 10−4 S cm−1. The quarternary sample 0.5572 chitosan-0.3383 H3PO4–0.0995 NH4NO3–0.0005 Al2SiO5 has the highest conductivity of (1.82 ± 0.10) × 10−4 S cm−1. All compositions are in weight fraction. The conductivity-temperature relationship is Arrhenian. Results were analyzed using the Rice and Roth model, Joncher's universal power law, σ = σDC + Aωs and models based on polarons. The frequency dependence conductivity plot shows a frequency independent plateau at low frequency and a high frequency dispersive region, which is dominant at lower temperatures. From the plot of s versus T, it has been shown that the conductivity for Al2SiO5 containing chitosan-based electrolyte occurs by way of the overlapping large polaron tunneling model (OLPT) and for the binary chitosan-phosphoric acid system, conduction mechanism may be explained by the quantum mechanical tunneling (QMT) model. The best conducting sample in each system was used as electrolyte in an electric double layer capacitor. From the charge-discharge profile, a small ohmic voltage drop was observed for each 1 mA constant current discharge curve. The specific discharge capacitance of the best EDLC was found to be ∼220 mF g−1 for 100 cycles.

Transport properties of hexanoyl chitosan-based gel electrolyte

Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizer on the transport properties of hexanoyl chitosan:lithium trifluoromethanesulfonate (LiCF3SO3) electrolytes have been investigated. The plasticizer used was ethylene carbonate (EC). The highest room temperature conductivity achieved in the EC-plasticized hexanoyl chitosan-based electrolytes is 2.75×10−5 S cm−1. The Rice and Roth model was used to explain the variations in the dc conductivity observed. The exponent, s, in Jonscher’s universal power law equation σ(ω)=σdc+Aωs, was analyzed as a function of temperature for the sample containing 30 wt% of EC. The analysis suggests that the conduction mechanism follows that proposed by the overlapping large polaron tunneling model.

Performance characteristics of LiMn 2O 4/polymer/carbon electrochemical cells

This paper discusses the performance characteristics of two types of cells of configuration LiMn 2O 4/chitosan/C. LiMn 2O 4 was prepared by the sol–gel method. The precursor obtained was heated at different temperatures to form LiMn 2O 4. The performance of the LiMn 2O 4 compound prepared at different temperatures was investigated by studying the discharge characteristics of the LiMn 2O 4/LiClO 4–EC-DMC/C cells. It was found that the cell utilising LiMn 2O 4 obtained by heating the precursor at 600°C, for 6 h gave the best performance. The LiMn 2O 4 compound was then used to fabricate cells using a chitosan-based electrolyte. In one of the cells, the chitosan polymer was doped with 32% salt to represent a salt-in-polymer electrolyte and in the other, the polymer was doped with 75% salt to form a polymer-in-salt electrolyte. The room temperature conductivity for the salt-in-polymer electrolyte was 1.3×10 −5 S cm −1 and that of the polymer-in-salt electrolyte was 3.9×10 −3 S cm −1. The cathode of all cells consists 80% active material 10% binder and 10% carbon by weight. The characteristics of the cells were measured and analysed.

Chitosan-based electrolyte for secondary lithium cells

The system chitosan : ethylene carbonate : LiCF3SO3 was prepared by the solution cast technique. To verify that the conductivity of the material is due to the salt, the electrical conductivity at room temperature of the chitosan acetate film and that of the chitosan acetate films containing different amounts of ethylene carbonate added to it were measured. The order of magnitude of the electrical conductivity was 10−10 S cm−1. Films containing fixed content of chitosan and plasticizer but different amounts of salt were then prepared in the same manner and the highest electrical conductivity obtained was 1.3 × 10−5 S cm−1 at room temperature. These results indicate that the conductivity is due to the salt. Conductivity-temperature studies show that the ln σ T versus 103/T graphs obey Arrhenius rule implying that the conductivity occurs by way of some thermally assisted mechanism. Polarization current measurement shows that the lithium ion transference number is ∼0.09. A LiMn2O4/chitosan-LiCF3SO3/C cell was fabricated which cycled between 1.5 to 2.5 V with fading capacity. This could be the result of LiF formation due to interaction between the salt and the fluorine in the binding agent.