Siti Zafirah Zainal Abidin

The development of sustainable solid polymer electrolytes from agricultural waste offers an environmentally friendly alternative to conventional synthetic polymers for energy storage applications. In this study, cellulose and nanocellulose were extracted from coconut shell powder and chemically modified into carboxymethyl cellulose (CMC) and carboxymethyl nanocellulose (CMNC), followed by complexation with NH ₄ NO ₃ through the solvent-casting method. Successful carboxymethylation was confirmed by ¹ H and ¹³ C NMR, where three carboxyl carbon signals at 177.43, 179.61, and 180.96 ppm verified the incorporation of carboxymethyl groups without polymer degradation. ATR-FTIR analysis confirmed the removal of lignin and hemicellulose and the formation of carboxylate groups. FESEM analysis revealed the morphology of coconut shell powder and cellulose. TEM analysis confirmed the nanoscale morphology of nanocellulose, with 54.05% of the particles exhibiting a size distribution within the range of 0–100 nm. Thermogravimetric analysis showed that CMNC exhibited lower thermal stability and degraded at 190°C due to the formation of sulfated amorphous regions during acid hydrolysis. X-ray diffraction analysis demonstrated that carboxymethylation reduced the crystallinity index from 46.40% to 64.27% for cellulose and nanocellulose to 3.54% and 20.45% for CMC and CMNC, respectively. Electrochemical impedance spectroscopy revealed that the CMC electrolyte achieved the highest ionic conductivity of 2.87 × 10 ^-1 S cm ^-1 at 30 wt% NH ₄ NO ₃ , whereas CMNC (2.07 × 10 ^-3 S cm ^-1 ) highlighted its potential as a sustainable proton-conducting electrolyte for proton battery applications.

The electrochemical stability and charge-transport properties of biopolymer blend films are significantly affected by blend composition, as each polymer component contributes uniquely to segmental mobility, bulk resistance, amorphous structure, and interfacial stability. In this study, salt-free agarose:phytagel (AG:PY) biopolymer blend films were fabricated at various weight ratios using the solution-casting method to identify an optimal host matrix for the development of salt-doped electrolytes. Linear voltammetry measurements showed that the 50:50 mass ratio AG:PY mixture has an electrochemical stability window of 3.25 V, indicating substantial resistance to electrochemical decomposition within the tested potential range. Electrochemical impedance spectro­scopy analysis showed that the 50:50 blend achieved the highest room-temperature conductivity of 1.56 mS cm⁻¹, attributed to reduced bulk resistance and indicating more favourable charge-transport characteristics within the polymer host. X-ray diffraction analysis verified this finding, revealing the lowest crystallinity in the 50:50 mass ratio, suggesting increased amorphous content and greater polymer chain flexibility. Fourier-transform infrared spectroscopy spectral shifts confirmed interactions between the functional groups of agarose and phytagel, indicating improved blend compatibility. Collectively, the 50:50 mass ratio AG:PY blend exhibited the most advantageous combination of electrochemical stability, ionic conductivity, amorphous structure, and polymer interaction, establishing it as a promising sustainable host matrix for future salt-doped biopolymer electrolyte applications.

The performance of polymer electrolyte can be improved through various approaches, including the addition of filler and dopant salt, in which has demonstrated significant potential for enhancing performance in electrochemical applications. The purpose of this study was to investigate the ionic conductivity and structural studies of 49% poly (methyl methacrylate) grafted natural rubber (MG49)-graphene oxide (GO) integrated with ammonium triflate (NH ₄ CF ₃ SO ₃ ) based polymer electrolytes. The highest ionic conductivity, 4.42 x 10 ^-6 Scm ^-1 , was achieved with 25 wt.% of NH ₄ CF ₃ SO _3. ATR-FTIR analysis showed a reduction in C=O peak intensity, indicating interaction between the polymer matrix and salt, while optical microscopy (OM) revealed that the 25 wt.% sample had the smoothest surface and the most amorphous structure, correlating with the highest ionic conductivity. These results suggest that nanocomposite polymer electrolytes based on MG30-GO-NH ₄ CF ₃ SO ₃ have potential for energy storage applications.

Materials sustainability is becoming increasingly important across advanced technologies, driving the development of environmentally friendly electrolyte systems. In this work, biopolymer electrolytes were prepared using Phytagel as the host polymer and varying concentrations of sodium perchlorate (NaClO4) as the dopant salt via the solution-casting method for sodium-ion battery applications. The prepared biopolymer electrolytes were characterised using various techniques to assess changes in their morphology and electrical performance. X-ray diffraction (XRD) confirms the crystalline/amorphous nature of the prepared biopolymer electrolytes, and the membrane with 40 wt.% NaClO4 exhibits a high degree of amorphousness. Peak-deconvoluted XRD analysis confirms that optimal NaClO4 loading (40 wt.%) induces maximum amorphisation in the Phytagel matrix, minimising crystallite size and crystallinity, thereby establishing a structurally favorable pathway for enhanced ionic conductivity. From electrical analysis, the ionic conductivity calculated for pure phytagel is 2.97 × 10–5 S.cm-1, and on addition of salt, the 40 wt.% of NaClO4 exhibits enhanced ionic conductivity of 2.41 × 10−4 S.cm-1 at room temperature. These findings emphasise the importance of optimising salt concentration to achieve an effective balance between structural amorphisation and free-ion availability. This work advances Phytagel-based biopolymer electrolytes as a sustainable and high-performance alternative to conventional polymer electrolytes, offering a viable pathway toward greener battery technologies.

The urgent demand for sustainable energy materials aligned with the United Nations Sustainable Development Goal 7 has intensified interest in biopolymer electrolytes (BPEs). Many non-polysaccharide biopolymers exhibit low ionic conductivity and weak salt dissociation at room temperature, limiting their performance in sodium-ion energy storage devices. Polysaccharides such as guar gum provide abundant coordination sites that can enhance Na+ transport. This study investigates the electrical, structural, and electronic behaviour of guar gum–sodium perchlorate (guar gum–NaClO4) BPEs to establish structure–transport relationships. Biopolymer electrolyte films were prepared via solution casting using guar gum (0.5 g) with NaClO4 at six salt loadings: 0, 10, 20, 30, 40, and 50 wt.%. Electrochemical impedance spectroscopy (EIS) was conducted at room temperature for all compositions and at elevated temperatures (303–343 K) for selected samples (0, 30, and 40 wt.%). Structural properties were examined by X-ray diffraction (XRD), and crystallite size was quantified using the Scherrer equation. Electronic properties, including density of states (DOS) and frontier molecular orbitals, were evaluated using density functional theory (DFT) with the DMol3 module. Ionic conductivity increased from 9.13 × 10−9 S·cm−1 in the unadded salt guar gum sample (0 wt.%) to a maximum of 8.40 × 10−4 S·cm−1 at 40 wt.% NaClO4, attributed to enhanced NaClO4 dissociation and reduced bulk resistance. At 50 wt.%, conductivity decreased to 3.37 × 10−4 S·cm−1, indicating ion pairing. Temperature-dependent EIS confirmed Arrhenius behaviour, with the 40 wt.% sample exhibiting the lowest activation energy (7.61 × 10−20 eV). XRD analysis showed progressive amorphization with crystallite size reducing from 5.05 nm (0 wt.%) to 0.82 nm (40 wt.%), correlating with enhanced ionic mobility. DFT findings revealed strong guar gum–NaClO4 interactions and a significant HOMO–LUMO band-gap reduction from 6.6129 eV (unadded salt guar gum) to 0.3813 eV, suggesting improved electronic flexibility and salt dissociation. The combined EIS, XRD, and DFT analyses demonstrate that guar gum–NaClO4 BPEs exhibit strong structure–transport coupling, with 40 wt.% NaClO4 producing optimal ionic conductivity and molecular stability. These findings identify guar gum as a promising, sustainable host polymer for sodium-based solid electrolytes in next-generation energy storage systems.

The polymer electrolyte membrane functions as both an electrolyte and a separator within an energy storage device. This article provides an analysis of the performance of the manufactured electric double-layer capacitors (EDLC) using plasticized lithium ion conducting poly (lactic acid) (PLA) based solid polymer electrolytes (BPEs). At present, the electrolyte employed in EDLC often consists of aqueous, organic, or liquid salts/ionic liquids. However, these electrolyte options are often accompanied by issues like leakage, self-discharge, corrosion, and bulky design. Therefore, the objective of this work is to explore the potential of Plasticized PLA BPEs as a solid-based form for EDLC application, with the aim of mitigating the issue and evaluating its performance. This study focuses on characterizing the complexes of LiCF3SO3- PLA with varying weight percentages of polypropylene carbonate (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, and 25 wt.%). The high-conducting samples were then utilized for application in EDLC, and the performance of the EDLC was further studied. It is specified that the transference numbers of ions (tion) and electrons (tel) are 0.98 and 0.02, correspondingly. As determined by linear sweep voltammetry (LSV), the potential window is 7.10 V. Electrodes for the EDLC were manufactured utilizing the preferred combination of activated carbon (AC) and carbon black. By sandwiching the Plasticized PLA BPEs between two carbon-based electrodes, cyclic voltammetry (CV) was performed, which disclosed an almost rectangular shape. The EDLC demonstrated average values of 158.89 Ω for equivalent series resistance, 46.5 F/g for specific capacitance and 0.987 Wh/kg for energy density. The initial power density was determined by the EDLC to be 130 W/kg. In conclusion, plasticized lithium ion conducting PLA BPEs were successfully fabricated and employed in EDLC applications.

Electrochemical energy storage devices (EES) such as batteries and supercapacitors depend significantly on electrolytes, which have properties that significantly impact their energy capacity, rate performance, cyclability, and safety. Agarose–Mg(ClO4)2–based polymer electrolyte was prepared using the solution casting method by incorporating various amounts of Mg(ClO4)2 from 0 – 35 wt%. The presence of Mg(ClO4)2 as the dopant in agarose-matrix enhanced the ionic conductivity of the system from 1.796 × 10-8 S∙cm-1 to 6.247 × 10-4 S∙cm−1 in the composition of 30 wt% Mg(ClO4)2 due to the production of free ions. This system obeys the Arrhenius rule as it records the conductivity increment when temperature increases. This increment shows the amorphous nature of electrolytes, which XRD analyses by determining the crystallite size and degree of crystallinity of agarose–Mg(ClO4)2 polymer electrolyte. High ionic conductivity at room temperature has increased attention to this polymer electrolyte based on agarose–Mg(ClO4)2.

The exponential concern about environmental concerns has heavily driven the development of green technology. In light of these needs, Deep Eutectic Solvent (DES) emerged as a green solvent and additive due to its minimal toxicity and volatility, biodegradability, biocompatibility, simplicity of synthesis, high yields and purity, and the availability of its precursors. This review is intended to summarise and discuss polymer electrolytes based on DES for better insight into the potential of replacing conventional organic solvents or ionic liquids for energy storage applications in the aspect of their electrical and structural properties. Therefore, an examination of dielectric studies is conducted as they hold significance in establishing a correlation between the rise in ionic conductivity and the augmentation of freely movable ions, thereby highlighting the importance of investigating the dielectric properties of an electrolyte. Besides, XRD and morphological studies in this work can show how ionic conductivities can influence the size of pores in DES-based polymer electrolytes.

Solid polymer electrolyte was prepared by blending two different polymers to improve their mechanical properties using solution casting method. The conductivity of films was measured by electrical impendence spectroscopy (EIS) and showed a highest conductivity when 10 wt.% of NaCl incorporated with blending polymer of potato starch and chitosan at 4.82 × 10−6 S.cm−1. This phenomenon is best clarified as the dissociation of ion is higher at this rate and the energy barrier is lowered leads to increase the conductivities. The plot of log σ versus 1000/T for all systems follow the Vogel-Tamman- Fulcher (VTF) rule. ATR-FTIR studies the interaction after addition of salt, shows the shifted band of carboxamide and amine group due to the interaction of salt (Na+ ion and Cl− ion). From the X- Ray diffraction analysis, the blending 50 wt.% starch and 50 wt.% chitosan is the most amorphous blend exhibit to the higher conductivity of addition of 10 wt.% of NaCl into the blending system. The morphology of the systems was observed using scanning electron microscope (SEM). The morphology of highest conductivity film shows the roughness and pores in the systems indicate the space for the ions to moves and increase the conductivities compared the morphology of films beyond 10 wt.% of NaCl. It was showed that the crystalline structure and the movement of ions were inhibited and decreased the conductivity of films.

Solid polymer electrolyte (SPE) based on Ch-g-PMMA – Magnesium Triflate (MgTf) incorporating with Ethylene Carbonate (EC) as plasticizers has been prepared. SPE was first prepared by dissolving polymer Ch-g-PMMA with magnesium triflate (MgTf) (10-50 wt.%) with 1% acetic acid. A different weight percentage (10-50 wt.%) of ethylene carbonate (EC) was added to the best conductivity of Ch-g-PMMA with 40 wt.% MgTf. Ionic conductivity values were calculated from the bulk resistance obtained from impedance plotted at frequency range of 100 Hz to 1 MHz. The ionic conductivity increases as weight percentage of EC increases. The highest conductivity obtained was 1.07×10−3 S.cm-1 at 50 wt.% of EC. This ionic conductivity is studied at the 298 K (room temperature). Molecular interaction between components in each electrolyte system were analyzed through Fourier Transform Infrared Spectroscopy (FTIR). The complexations between the materials used in electrolyte systems are based on shifting of the bands, changes in intensity, shape and existence of some new peaks in FTIR spectra. X-Ray Diffraction (XRD) was used to investigate the crystallographic structure and chemical composition of all samples. The intensity of XRD peaks decreased as more EC added into the system reducing the crystallinity. The Ch-g-PMMA–40 wt.% MgTf–50 wt.% EC are believing as the best system for this study.