Vanchiappan Aravindan

Lithium–ion capacitors (LICs) are modern electrochemical energy storage devices that combine two energy storage mechanisms in a single device, bridging the gap between Li‐ion batteries (LIBs) & supercapacitors to achieve a high‐power, high‐energy system. This work utilizes Sn‐containing CuO (Sn‐CuO) as an anode material for the LIC, synthesized by the precipitation method at low temperature, without a calcination step or high‐temperature furnace. The electrochemical examination revealed that the Li/Sn‐CuO half‐cell exhibited a reversible specific capacity of 644 mAh g ⁻¹ and better stability over long cycles. The LIC fabricated by pairing prelithiated Sn‐CuO and mass‐balanced activated carbon (AC) as a counter electrode has a high energy density of ∼80.3 Wh kg ⁻¹ and displayed high cycling performance for over 2500 cycles. The working conditions and adaptability of the LIC were also tested across a range of temperatures, from −10 to 50°C, yielding interesting results.

A high‐voltage Li‐rich LiCoMnO ₄ (LCMO) cathode is successfully prepared using the co‐precipitation technique and then tuned with varying concentrations of AlPO ₄ coating (1, 3, 5, and 10 wt.%). Among these, the LCMO@AlPO ₄ _3 wt.% shows excellent electrochemical performance with a specific capacity of 103 mAh g ⁻¹ and 71% capacity retention. This is significantly better than the pristine sample, which has a specific capacity of 91 mAh g ⁻¹ and 60% capacity retention after 100 cycles. Additionally, the Li‐diffusion coefficient is computed using electrochemical impedance spectroscopy, and the optimized coated sample exhibited a higher diffusion value. To realize the practical feasibility of such an AlPO ₄ ‐modified cathode, the full‐cell is fabricated using an Li ₄ Ti ₅ O ₁₂ anode under balanced loading conditions. At ambient temperature conditions, the full cell offered an energy density of 227 Wh kg ⁻¹ . To produce high‐energy next‐generation cathodes for lithium‐ion batteries, this research offers the concept of surface modification with inexpensive Li‐rich materials

In this work, we explore the possibility of utilizing lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ or LNMO) as a cathode material for developing a stable and safe Li‐ion battery (LIB). The full‐cell configuration is assembled by pairing LNMO with coprecipitated SnS, a high‐capacity alloy‐type anode material that surpasses conventional anode materials, such as graphite. While LNMO is typically operated in the high‐voltage region (~4.8 V vs. Li) utilizing the Ni ^2+/4+ couple associated with tetrahedral insertion, such operation often leads to severe electrolyte degradation and parasitic reactions. To overcome this, we employ a lower‐voltage (~2.8 V vs. Li) approach that utilizes the Mn ^4+/3+ redox couple corresponding to octahedral insertion, enhancing safety and stability. However, conventionally synthesized (i.e., bulk) LNMO often fails to facilitate this insertion, prompting us to adopt the electrospinning technique to produce nanostructured LNMO with improved Li‐ion kinetics and ionic transport that supports octahedral insertion. Our work also demonstrates the importance of nanostructuring, which facilitates octahedral insertion and enables us to incorporate a low‐voltage application without compromising safety. The electrospun (E‐spun) LNMO can exhibit a higher discharge capacity and superior cycling stability in both high‐ and low‐voltage regions; however, we will focus on low‐voltage applications. This hybrid configuration, integrating a fast Li‐ion diffusion spinel cathode and a high‐capacity alloy anode, enables efficient ion transport and enhanced electrode compatibility. By narrowing the voltage window to 2–3 V versus Li, the system exhibits stable cycling performance, along with improved safety, which facilitates the development of next‐generation LIBs with balanced performance and durability.

The graphitic porous carbons derived from coir pith are activated (C‐900) and systematically investigated as a potential electrode material for Li‐ion and Na‐ion capacitors (LICs and NICs), coupled with pre‐lithiated or pre‐sodiated commercial hard carbon (HC) as the battery‐type counter electrode. The C‐900 exhibits outstanding charge‐storage performance in Li/Na half‐cells, which is attributed to its high specific surface area (2086 m ² g ⁻¹ ). The HC is pre‐lithiated (LHC) or pre‐sodiated (NHC) before LIC/NIC assembly, and the mass loading of C‐900 is adjusted based on the performance of HC. The C‐900/HC devices deliver maximum energy densities of ∼153 and ∼128 Wh kg ⁻¹ for LIC and NIC, respectively. The temperature‐dependent performance of both LIC and NIC is evaluated, revealing excellent adaptability with capacity retention exceeding 95 and 85%, respectively, across a wide temperature range from –10 to 50 °C. The LIC maintains electrochemical stability over 2,500 cycles, while the NIC remains stable for 1,000 cycles. These results demonstrate that the high‐surface‐area, graphene‐like carbon derived from coir pith serves as a promising positive electrode for next‐generation energy storage devices, offering excellent energy and power performance.

Li-sulfur (Li-S) batteries are considered highly promising next-generation energy storage systems because of their exceptionally high theoretical energy density (2500-2600 Wh kg–1). However, their practical application is significantly limited by Li-dendrite formation, parasitic side reactions at the Li-metal anode, and the inherent instability of sulfur cathodes. Sulfurized polyacrylonitrile (SPAN) has gained considerable attention as a sulfur host due to its polysulfide-free redox mechanism, which effectively mitigates the shuttle effect. In this study, the electrochemical performance of SPAN electrodes is systematically enhanced by examining the impact of various binders in a conventional electrolyte (1 M LiPF6 in EC/DEC with 5 wt.% LiBOB) using Li-metal half-cells. Amongst, the water-based polyacrylic acid (PAA) binder demonstrates the best performance, delivering a high initial specific capacity of 1438 mAh g–1 and achieving 97% capacity retention after 200 cycles. Moreover, a full-cell configuration is assembled by coupling the optimized SPAN electrode with a commercial layered LiNi1/3Mn1/3Co1/3O2 (NMC111) cathode. The assembled full cell provides an initial capacity of 1155 mAh g–1 and maintains 88% of its capacity after 100 cycles at a current density of 0.5 A g–1 under ambient conditions. Overall, this work demonstrates that binder engineering is an effective approach to fully exploit the potential of SPAN electrodes for practical high-energy Li-based batteries.

The rapid development of energy storage technologies has increased the demand for lithium‐based solutions due to their superior efficiency and scalability. Simultaneously, the growing global population and heavy reliance on electronic devices have resulted in substantial e‐waste generation. This study focuses on converting e‐waste, specifically spent battery components, into active materials for lithium‐ion capacitors (LICs). Through a straightforward wet‐chemical process, copper foil and graphite are recovered and converted into CuO‐NiO hybrid nanostructures and reduced graphene oxide (rGO), respectively. These materials are subsequently used as the negative and positive electrodes, respectively, in the LIC assembly. The fabricated half‐cell (Li/CuO‐NiO) demonstrated a reversible specific capacity of approximately 657 mAh g ⁻¹ . Prior to the LIC assembly with the rGO electrode, the hybrid nanostructures were pre‐lithiated (Cu ⁰ +Ni ⁰ +xLi ₂ O). The assembled rGOǁ(Cu ⁰ +Ni ⁰ +xLi ₂ O) LIC exhibited an energy density of 57.8 Wh kg ⁻¹ and a power density of 6.6 kW kg ⁻¹ , along with long cyclic stability. This approach emphasises the recycling of discarded battery components into functional active materials for LICs, presenting a sustainable pathway to convert e‐waste into high‐performance, value‐added products for next‐generation energy storage.

Ternary composite of PANI, CuO and ZnO in its standardized weight composition of PANI54.55%:CuO36.36%:ZnO9.09% (PCZ9) was synthesized by in-situ single-step chemical method to study the supercapacitance of it and its binary composites. An aqueous supercapacitor cell of PCZ9 provided specific energy (E) higher than that of vanadium flow batteries and as close as to that of Pb-acid batteries, which is 27 W h kg^-1 with the specific power (P) of 0.6 kW kg^-1 at 1 A g^-1, mainly inflicted by H⁺/[Formula: see text] ions co-intercalation/de-intercalation. While, an organic asymmetric supercapacitor cell made up of an binary composite of PCZ9, which is CuO80%:ZnO20% (CZ) provided E higher than that of Pb-acid batteries, Ni-Cd batteries, Ni-MH batteries, Na-metal chloride batteries and Na-S batteries, which is 71 W h kg^-1 with the P of 0.232 kW kg^-1 at 0.1 A g^-1. Most importantly, the organic asymmetric supercapacitor continued to provide higher E up to the current density of 2 A g^-1, as a trait of its excellent rate capability. In addition, both the aqueous symmetric and organic asymmetric supercapacitors exhibited promising durability by retaining 58.11 and ~ 75% of their initial energy up to 5000 cycles and 2500 cycles , respectively, when subjected to durability test at 0.4 V s^-1 and 1 A g^-1 (at different temperatures), respectively. The high E of the aqueous symmetric supercapacitor cell of PCZ9 was demonstrated by making it to exhibit its power backup ability, when, the PCZ9 symmetrice cell provided 1 min. and 30 sec. of power backup for 1 min. of charging using the 1.5 V AA battery of Duracell, establishing its high energy character.

Recycled Cu- foil from spent LIBs is repurposed to synthesize copper vanadate anodes for sustainable LICs. The device achieves 120.36 Wh kg ⁻¹ energy density, 8.36 kW kg ⁻¹ power density with wide temperature operation from −10 to 50 °C.

A series of PANI/VO ₂ /Ni(OH) ₂ (PVN) nanocomposites with different weight compositions was synthesized by a single‐step chemical method to determine the best weight composition and, in turn, to study their supercapacitive behavior. A composite with a weight composition of PANI58.33%:VO ₂ 25.00%:Ni(OH) ₂ 16.67% (PVN16) provided superior performance as a symmetric supercapacitor cell among the PVN composites synthesized. The obtained performances of PVN16 are a specific capacity ( Q ) of 60.44 C g ^‒1 , a specific energy ( E ) of 10.07 W h kg ^‒1 , a specific power ( P ) of 0.6 kW kg ^‒1 , and a coulombic efficiency ( ƞ ) of 98.18%. In addition, this symmetric device exhibited no reduction in its Q up to 5000 cycles at 0.4 V s ^‒1 . The asymmetric supercapacitor cells of the PVN16 were fabricated using activated carbon in the presence of two different aqueous electrolytes, which are 1 M H ₂ SO ₄ and a liquid by‐product that was obtained after the synthesis of PANI (SLP). The asymmetric cell in the presence (ITP) of SLP provided electrochemical stability up to 1.55 V, better performance, and the E comparable with vanadium redox flow batteries (VRFB). The obtained higher energy storage the parameters of a Q of 102.8 C g ^‒1 , an E of 22.13 W h kg ^‒1 , a P of 0.775 kW kg ^‒1 , and a ƞ of 70.44%. The asymmetric devices exhibited 95% and 73.88% retention of their initial Q up to 5000 cycles at 0.4 V s ^‒1 ITP of 1 M H ₂ SO ₄ and SLP, respectively. The symmetric and asymmetric devices exhibited 15.75% and 22.33% retention of their initial Q up to 17 and 30 A g ^‒1 , respectively, ITP of H ₂ SO ₄ exhibiting their promising rate capability. Since, the PVN16 asymmetric cells ITP of SLP provide higher energy than those of the VRFB, they could be used to fabricate real‐time hybrid supercapacitor devices at desirable working voltages for real applications as energy storage and conversion devices, where both high E and P are required.