Carbon based nanomaterials with tuned porosity and compositions are of great interest in terms of energy storing materials. Nevertheless, it is still a challenge to produce such nanostructures on a large scale in cost-effective manner. In this work, we demonstrate that carbon nanomaterial (CNM) can be prepared using biogas plant residual waste (BPRW) as the precursor on a bulk scale under the specific two step pyrolysis technique. The optimized process along with the catalyst used is crucial as the simple pyrolysis of precursor can only produce traditional activated carbon with significantly lower specific capacitance values. The spherical structure of silica nanoclusters and graphitic skeleton of synthesized CNM confirmed with the help of FE-SEM, AFM and HR-TEM along with Raman and XRD while EDX, XPS, and FT-IR studies confirm the presence of various functional groups along with their respective percentage composition. These CNMs show mesoporous structure of the nanomaterial. Among three different aqueous electrolytes, the maximum specific capacitance of 371.88 Fg−1 at 0.5 Ag−1 current density in 1 M H2SO4 indicates its suitability for the practical supercapacitor applications. The fabricated symmetric supercapacitor device using CNMs as the electrode material and 1 M H2SO4 as the electrolyte shows very good specific capacitance value with the high energy density of 34.4 Whkg−1 corresponding to 360 Wkg−1 power density along with the good cyclic stability over 10,000 cycles of charge–discharge. This innovative technique paves the way towards upcycling any lignin containing waste material into carbon-based nanomaterial on a bulk scale by an effective method, which can be further used as high-performance electrode material for energy storage applications like in supercapacitors and batteries.

The electrochemical and charge storage performance of a fluorine-free structurally flexible hybrid pyrrolidinium-based ionic liquid electrolyte (HILE) in a symmetric graphite-based supercapacitor is thoroughly investigated. The HILE revealed thermal decomposition at above 230°C, a glass transition (Tg) temperature of below −70°C, and ionic conductivity of 0.16 mS cm−1 at 30°C. The chemical and electrochemical properties are investigated using a systematic variable temperature 1H and 31P NMR spectroscopy and diffusometry, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD). The supercapacitor demonstrated a notable specific capacitance of 186 F g−1 at a scan rate of 1 mV s−1 and a specific capacitance of 122 F g−1 at a current density of 0.5 A g−1. The maximum energy density of 48.8 Wh kg−1, a power density of 450 W kg−1 at a current density of 0.5 A g−1, and a potential window of 4 V were obtained. Altogether, this study demonstrates that the new HILE can be used in symmetric graphite-based supercapacitors over a wide potential window of 4 V and a temperature range from −20°C to 90°C. 

The utilization of metal–organic frameworks (MOFs) in energy storage applications is constrained by their limited electrical conductivity and insufficient chemical robustness, posing various challenges and limitations. Nevertheless, research has demonstrated that MOF structures with exceptional porosity and adaptable architectures yield a wide range of composites, presenting promising prospects for improving their electrochemical performance in energy storage devices. When combined with other advanced materials, MOFs form composite structures overcoming these constraints by exhibiting superior electrical conductivity, electrochemical activity, and stability in comparison to pure MOFs. This article comprehensively overviews the designed chemistry of MOF-composites for metal-ion batteries (MIBs) and metal-ion capacitors (MICs). The synthesis and properties of various composites involving MOFs, including MOF-MXene, MOF-carbon nanomaterials (CNM)/graphene/carbon, MOF-transition metal oxide (TMO), MOF/polymers, MOF-derived layered double hydroxide (LDH), as well as the challenges and mitigation strategies have been discussed. A brief overview of MOF-composites as electrode materials for MIBs, including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (KIBs) is presented. The recent developments in MICs, such as lithium-ion capacitors (LICs), magnesium-ion capacitors (MGICs), zinc-ion capacitors (ZICs), sodium-ion capacitors (SICs), and potassium-ion capacitors (KICs) have also been included. Furthermore, the electrochemical performance of the MOF composites has been assessed using a range of metrics, including output voltage, capacity, cycle stability, energy density (ED), and power density (PD). A comprehensive analysis has also been conducted to identify potential obstacles and possible mitigations to explore future possibilities. Overall, a comprehension of MOF-based materials and potential approaches for enhancing the futuristic progression of MOF-composite materials for MIBs and MICs have been elucidated.

The energy demand cannot be fully accomplished as the rate of increasing worldwide population is larger than the production of energy. The increasing population also leads to the development of more electrical components, which need a lot of energy to store, so energy storing devices are the need of the hour. Batteries and supercapacitors are the main class of such energy storage devices. Graphene is a 2D nanomaterial suitable for energy storage devices as electrode material due to its remarkable properties like high theoretical specific surface area and high electrical conductivity. Still, scientific works are underway to optimize the synthesis and applicability of graphene and its derivative materials in energy storage systems. This chapter discusses graphene and its derivatives for supercapacitor applications. Further, the electrochemistry behind storing energy in storage devices is discussed. This in-depth examination of graphene-based materials for energy storage may help researchers better comprehend the advantages and the most promising outcomes of such materials.

This work combined gold colloid probe atomic force microscopy (AFM) with a quartz crystal microbalance (QCM) to accurately quantify the molecular interactions of fluorine-free phosphonium-based ionic liquids (ILs) with gold electrode surfaces. First, the interactions of ILs with the gold electrode per unit area (𝐹′A𝐹A′, N/m2) were obtained via the force–distance curves measured by gold probe AFM. Second, a QCM was employed to detect the IL amount to acquire the equilibrium number of IL molecules adsorbed onto the gold electrode per unit area (NIL, Num/m2). Finally, the quantified molecular interactions of ILs with the gold electrode (F0, nN/Num) were estimated. F0 is closely related to the IL composition, in which the IL with the same anion but a longer phosphonium cation exhibits a stronger molecular interaction. The changes in the quantified interactions of gold with different ILs are consistent with the interactions predicted by the extended Derjaguin–Landau–Verwey–Overbeek theory, and the van der Waals interaction was identified as the major contribution of the overall interaction. The quantified molecular interaction is expected to enable the direct experimental-derived interaction parameters for molecular simulations and provide the virtual design of novel ILs for energy storage applications.

We here present four new fluorine-free ionic liquids (ILs) based on the non-nutritive sweetener saccharinate (Sac) anion coupled with pyrrolidinium, imidazolium, and phosphonium cations and their thermal, physicochemical, and electrochemical properties. The pyrrolidinium cation-based material is a solid at room temperature, whereas the other three materials are room-temperature ionic liquids (RTILs). By infrared spectroscopy, we find the ionic interactions to be controlled by the distinct conformers of the Sac anion, which in turn are cation-dependent. (P4444)(Sac) shows the lowest glass transition temperature, (Tg), the highest thermal stability and ionic conductivity, and the widest electrochemical stability window, up to 6 V. As an electrolyte in a symmetric supercapacitor, it enabled a specific capacitance of 204 F g–1 at 1 mV s–1, an energy density of 53 Wh kg–1 and a power density of 300 W kg–1 at a current density of 0.1 A g–1, and the capacitor retained 81% of its initial capacitance after 10,000 cycles at 60 °C. Altogether, these fluorine-free electrolytes have electrochemical properties promising for application in supercapacitors operating at elevated temperatures over a wide voltage range. 

Due to their intriguing electronic properties and structural composition, transition metal oxides (TMOs) such as AOx, AxOx, and AxB3-xOx; A, B = Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, etc., and their designed composites have tremendous potential in energy storage devices such as supercapacitors (SCs) and metal ion batteries (MIBs). Some outstanding properties of TMOs and their composites for applications as electrode materials in energy storage devices include their high conductivity, charge storage characteristics, doping potential, and composite forming propensity. The significant interactions of TMOs with heteroatoms, conductive polymers, and carbon nanomaterials (CNMs) drastically change the reactive parameters and electrical characteristics. This review covers the most recent advances in TMO research and development, ranging from mechanism design to device performance, with a main focus on essentials such as design, synthesis, manufacturing, and energy-storing properties. The electrochemical pyrolysis, in-situ preparation, solvothermal/hydrothermal approach, and other critical approaches and their implications are also discussed. The synergetic improvement of designed TMO/graphene, TMO/rGO, TMO/heteroatoms, TMO/polymers, TMO/halide/hydride, TMO/Chalcogens through ionic interactions, and investigation of the electrode–electrolyte interfaces have been discussed in detail. In addition, the effect of electrolytes, surface behavior, and performance evaluation parameters on the SC device performance have been included. Furthermore, parameters and models, reliability design and profile lifetime, common mistakes in performance evaluation of SC, and other obstacles and mitigation have been described in depth. Altogether, a well-grasped overview and potential strategies extended from the overall analysis of electrode materials and electrolytes are offered to lift advancement in developing futuristic materials for energy storage applications.