Deepak Prakash Dubal

By immobilizing ionic liquids (ILs) within polymer networks, ionogels offer a route to quasi-solid-state electrolytes with liquid-like ion mobility and solid-like dimensional stability. Their practical performance, however, is not determined by IL content or total ionic conductivity alone. Frequently reported limitations include low Li⁺ transference numbers, polymer–IL demixing, creep, insufficient electrode wetting, and unstable interphases. This review develops a mechanistically informed framework that traces how polymer chemistry and polymer–IL–lithium salt interactions shape process-induced microstructures, which in turn influence ion transport, mechanical response, and electrode interfaces. We examine electrostatic interactions, hydrogen bonding, and competitive Li⁺ coordination across representative polymer–IL systems, and compare fabrication routes in terms of the confinement, phase connectivity, and electrode contact they generate. The routes considered include solution casting, phase inversion and scaffold impregnation, electrospinning, thermal or photoinitiated in situ polymerization, physical self-assembly, interpenetrating-network and multiple-network formation, hybrid sol–gel processing, and thin-film patterning. The review distinguishes structural evidence from Li⁺-specific transport evidence and considers differences in measurement and cell conditions. Load-bearing networks and continuous ion-rich domains can mitigate the transport–mechanical trade-off, but their benefits require verification of Li⁺ transport and interfacial stability under relevant operating conditions. Minimum reporting criteria for meaningful comparison and scale-up are proposed.

Through-thickness Si gradients have been explored to improve the stability of Si/Gr anodes, yet how vertical Si distribution shapes the coupled evolution of transport and structural degradation during prolonged cycling remains unclear. Here, composition-inverted mixed Si/Gr dual-layer electrodes were designed to isolate this positional effect while maintaining the overall composition, areal loading, and electrode density. Reversing only the Si-rich and Si-lean layers produced a pronounced aging-dependent divergence: after 300 cycles at 0.5 C, the lower Si-enriched electrode (LSE) delivered approximately 3.5 times the discharge capacity of the upper Si-enriched electrode (USE). State-resolved impedance analysis further revealed that, during delithiation, the maximum diffusion-related distribution of relaxation times (DRT) intensity of USE was 13–17 times the corresponding intensities of the other electrodes near 50% state of lithiation. This state corresponded to 0.51 V vs. Li/Li⁺, where Si-associated delithiation makes a substantial contribution. Post-cycling characterization showed that this transport deterioration was accompanied by severe cracking, 2.2-fold thickness expansion, distinct surface/interfacial evolution, and the highest residual Li signal in USE, whereas LSE largely preserved its morphology with only 1.5-fold expansion and the lowest residual Li signal. Together, these observations support a coupled position-dependent aging pathway in which repeated deformation of a Si-rich separator-facing region progressively degrades structural and transport continuity, with the electrochemical consequence becoming particularly severe during Si-associated delithiation. These findings establish vertical Si distribution as a critical electrode-level design variable, while providing mechanistic insight into the role of the separator-facing region in long-term degradation of Si/Gr anodes.

Developing electrode materials that combine high electrical conductivity, abundant electroactive sites, and long-term structural stability remains a key challenge for high-performance hybrid supercapacitors. In this study, a hierarchical NH4NiPO4·H2O/Ni3S2/CdIn2S4 (NPO/NCIS) ternary heterostructure was synthesized directly on Ni foam through a two-step hydrothermal process. The Ni foam served as both the conductive substrate and the nickel source, enabling the in-situ formation of interconnected Ni3S2 nanosheets that establish intimate contact between NH4NiPO4·H2O microflakes and CdIn2S4 nanostructures. This unique architecture promotes efficient charge transport and abundant electroactive sites, leading to specific capacity of 174.60 mAh/g at a current density of 1 mA/cm2 while maintaining excellent rate capability. More importantly, the assembled NPO/NCIS//AC hybrid supercapacitor demonstrates outstanding long-term durability, retaining 88% of its initial capacitance after 30,000 charge–discharge cycles, which compares favorably with many reported phosphate- and sulfide-based heterostructured supercapacitors. The device also delivers a maximum energy density of 64 μWh/cm2 at a power density of 610 μW/cm2 and successfully powers light-emitting diodes. The exceptional cycling stability stems from the robust phosphate–sulfide heterointerface through conductive Ni3S2 nanosheet network, which effectively preserve structural integrity during prolonged operation. This work presents an effective strategy for developing long-life phosphate/chalcogenide heterostructures for advanced electrochemical energy-storage applications.

Electric power steering (EPS) systems have become the dominant steering solution in modern vehicles due to their advantages in energy efficiency and driving convenience. Among EPS configurations, rack-type EPS(R-EPS) is widely adopted in mid-to-large vehicles for its direct and responsive steering characteristics. However, conventional slotted motors used in R-EPS suffer from cogging torque and torque ripple caused by periodic reluctance variation in the stator tooth structure, resulting in vibration and noise directly perceived by the driver. This article proposes a slotless Surface Permanent Magnet Synchronous Motor (SPMSM) employing a Bar-Type magnet with a double-bridge rotor structure for R-EPS applications. By eliminating stator teeth, the proposed design achieves a uniform reluctance distribution during rotor rotation, theoretically reducing cogging torque to zero. The absence of stator tooth magnetic saturation further enables the use of high-remanence permanent magnets, improving gravimetric power density and enabling motor miniaturization. The proposed motor was designed and verified through finite element analysis (FEA). Compared to the conventional Arc-Type motor, the optimized design achieves a torque ripple reduction of 64.7% (from 5.07% to 1.79%) through Bar-Type magnet shaping combined with a 5 mm edge filet. The optimized design achieved an output power of 359.9 W, a gravimetric power density of 276.85 W/kg based on an active part weight of 1.30 kg, and a structural safety factor of 1146, demonstrating the effectiveness of the proposed double-bridge slotless motor for R-EPS applications.

The accumulation of non‐biodegradable thermocol (expanded polystyrene, EPS) waste presents a critical environmental challenge and an untapped resource for sustainable energy technologies. In this work, we demonstrate a waste‐to‐functional‐material strategy by transforming discarded thermocol into electrospun EPS nanofibers and employing them as an efficient tribonegative layer in a triboelectric nanogenerator (TENG). Unlike conventional polymer films, the nanofibrous EPS architecture introduces high surface roughness and electrospinning‐induced dipole alignment, leading to markedly enhanced charge generation. The resulting TENG delivers an open‐circuit voltage of ∼159 V, a short‐circuit current of ∼22 µA, and a maximum output powerdensity of 2083 mW/m ² , outperforming widely used triboelectric polymers such as PTFE and PET. The device further exhibits excellent mechanical durability, long‐term stability over six months, and robust performance under varying humidity and temperature conditions. Beyond energy harvesting, the TENG is implemented as a self‐powered intelligent switching interface, where machine‐learning‐assisted signal processing enables reliable operation of a digital elevator system. This study establishes recycled EPS nanofibers as a high‐performance triboelectric material and demonstrates their potential for sustainable, intelligent, and self‐powered electronic systems.

3D perovskite nanocrystals have emerged as promising fillers incorporated into PVDF films for flexible piezoelectric nanogenerators (PENGs). Nevertheless, their stability issues, such as moisture sensitivity and thermal degradation, cause reduced long‐term reliability and durability of perovskite‐based PENGs, hindering their practical application. Herein, we demonstrate the high‐performance PENGs using in situ grown 2D perovskite (PEA ₂ MA ₂ Pb ₃ Br ₁₀ ) nanocrystals (2D PSK NCs) in the PVDF matrix. The interaction between 2D PSK NCs and PVDF dipoles enhances the electroactive phase content to 86.35% and the piezoelectric coefficient to 35.16 pm/V of the composite films. Therefore, the unpolarized 17.3 wt.% 2D PSK NCS@PVDF‐based PENG demonstrates outstanding piezoelectric outputs with an ultra‐high voltage of 66.54 V and a decent current density of 1.166 µA/cm ² under periodic vertical impact, corresponding to 2.74‐ and 7.29‐fold increases over the pure PVDF‐based device. Notably, the PENG also performs under different light conditions. The addition of 2D PSK NCs absorbed photons leads to enhanced piezoelectric output in sunlight. Additionally, the composite films display remarkable hydrophobicity and mechanical durability, sustaining stable operation for over 12000 continuous impact cycles. The energy generated from the PENG can charge capacitors and power small electrical devices, such as a calculator and commercial light–emitting diodes.

Potassium‐ion batteries (KIBs) require cathodes that combine structural robustness with fast K ⁺ transport and scalable manufacturing. Here, P2‐type KMO is developed using fast and efficient microwave heating process with controlled crystallite sizes (≈30–60 nm) and high crystallinity for Anode‐Free K‐ion batteries. In situ X‐ray powder diffraction (XRD) and Raman track reversible ‘breathing’ of the layered framework‐00l reflections shift smoothly to lower 2 θ on charge (c ≈ 12.6 → 12.8 Å) and return on discharge, with no persistent new phases‐evidence for mainly solid‐solution K ⁺ (de)intercalation. In K‐ion half‐cells, the cathode delivers 91.3 mAh g ⁻¹ with good rate capability; galvanostatic intermittent titration technique (GITT) (10 ⁻¹¹ –10 ⁻⁹ cm ² s ⁻¹ ) and electrochemical impedance spectroscopy (EIS) confirm favorable K ⁺ kinetics. Importantly, the material is further evaluated in an anode‐free K‐ion battery using carbon cloth as the current collector, achieving 83.5 mAh g ⁻¹ initially and 73.6% retention after 50 cycles with >99% Coulombic efficiency. The modest performance gap relative to half‐cells is attributed to limited K inventory and interfacial losses, indicating clear avenues for optimization. Microwave synthesis thus offers an efficient route to KMO compatible with both conventional and anode‐free operation.