Gels in Motion: Recent Advancements in Energy Applications.

Gels are attracting materials for energy storage technologies. The strategic development of hydrogels with enhanced physicochemical properties, such as superior mechanical strength, flexibility, and charge transport capabilities, introduces novel prospects for advancing next-generation batteries, fuel cells, and supercapacitors. Through a refined comprehension of gelation chemistry, researchers have achieved notable progress in fabricating hydrogels endowed with stimuli-responsive, self-healing, and highly stretchable characteristics. This mini-review delineates the integration of hydrogels into batteries, fuel cells, and supercapacitors, showcasing compelling instances that underscore the versatility of hydrogels, including tailorable architectures, conductive nanostructures, 3D frameworks, and multifunctionalities. The ongoing application of creative and combinatorial approaches in functional hydrogel design is poised to yield materials with immense potential within the domain of energy storage.

Achieving Order in Disorder: Stabilizing Red Light-Emitting α-Phase Formamidinium Lead Iodide.

While formamidinium lead iodide (FAPbI3) halide perovskite (HP) exhibits improved thermal stability and a wide band gap, its practical applicability is chained due to its room temperature phase transition from pure black (α-phase) to a non-perovskite yellow (δ-phase) when exposed to humidity. This phase transition is due to the fragile ionic bonding between the cationic and anionic parts of HPs during their formation. Herein, we report the synthesis of water-stable, red-light-emitting α-phase FAPbI3 nanocrystals (NCs) using five different amines to overcome these intrinsic phase instabilities. The structural, morphological, and electronic characterization were obtained using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS), respectively. The photoluminescence (PL) emission and single-particle imaging bear the signature of dual emission in several amines, indicating a self-trapped excited state. Our simple strategy to stabilize the α-phase using various amine interfacial interactions could provide a better understanding and pave the way for a novel approach for the stabilization of perovskites for prolonged durations and their multifunctional applications.

Polymer Backbone Stabilized Methylammonium Lead Bromide Perovskite Nano Islands.

Organic-inorganic hybrid perovskite materials continue to attract significant interest due to their optoelectronic application. However, the degradation phenomenon associated with hybrid structures remains a challenging aspect of commercialization. To overcome the stability issue, we have assembled the methylammonium lead bromide nano islands (MNIs) on the backbone of poly-3-dodecyl-thiophene (PDT) for the first time. The structural and morphological properties of the MNI-PDT composite were confirmed with the aid of X-ray diffraction (XRD) studies, Field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The optical properties, namely absorption studies, were carried out by ultraviolet-visible spectroscopy. The fluorescent behavior is determined by photoluminescence (PL) spectroscopy. The emission peak for the MNI-PDT was observed at 536 nm. The morphology studies supported by FESEM indicated that the nano islands are completely covered on the surface of the polymer backbone, making the hybrid (MNI-PDT) stable under environmental conditions for three months. The interfacial interaction strategy developed in the present work will provide a new approach for the stabilization of hybrids for a longer time duration.

Decoding the puzzle: recent breakthroughs in understanding degradation mechanisms of Li-ion batteries.

Lithium-ion batteries (LIBs) remain at the forefront of energy research due to their capability to deliver high energy density. Understanding their degradation mechanism has been essential due to their rapid engagement in modern electric vehicles (EVs), where battery failure may incur huge losses to human life and property. The literature on this intimidating issue is rapidly growing and often very complex. This review strives to succinctly present current knowledge contributing to a more comprehensible understanding of the degradation mechanism. First, this review explains the fundamentals of LIBs and various degradation mechanisms. Then, the degradation mechanism of novel Li-rich cathodes, advanced characterization techniques for identifying it, and various theoretical models are presented and discussed. We emphasize that the degradation process is not only tied to the charge-discharge cycles; synthesis-induced stress also plays a vital role in catalyzing the degradation. Finally, we propose further studies on advanced battery materials that can potentially replace the layered cathodes.

Self-Assembly of Copper Oxide Interfaced MnO2 for Oxygen Evolution Reaction.

Designing efficient electrocatalytic systems through facile synthesis remains a formidable task. To address this issue, this paper presents the design of a combination material comprising two transition metal oxides (copper oxide and manganese oxide (CuO/MnO2)), synthesized using a conventional microwave technique to efficiently engage as an active oxygen evolution reaction (OER) catalyst. The structural and morphological properties of the composite were confirmed by the aid of X-ray diffraction (XRD) studies, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive spectrometry (EDS). FESEM clearly indicated well-aligned interlacing of CuO with MnO2. The OER performance was carried out in 1 M KOH. The assembled CuO/MnO2 delivered a benchmark current density (j = 10 mA cm-2) at a minimal overpotential (η = 294 mV), while pristine CuO required a high η (316 mV). Additionally, the CuO/MnO2 electrocatalyst exhibited stability for more than 15 h. These enhanced electrochemical performances were attributed to the large volume and expanded diameter of the pores, which offer ample surface area for catalytic reactions to boost OER. Furthermore, the rate kinetics of the OER are favored in composite due to low Tafel slope (77 mV/dec) compared to CuO (80 mV/dec).

Remarkably Enhanced Lattice Oxygen Participation in Perovskites to Boost Oxygen Evolution Reaction.

Enhancing the participation of the lattice oxygen mechanism (LOM) in several perovskites to significantly boost the oxygen evolution reaction (OER) is daunting. With the rapid decline in fossil fuels, energy research is turning toward water splitting to produce usable hydrogen by significantly reducing overpotential for other half-cells' OER. Recent studies have shown that in addition to the conventional adsorbate evolution mechanism (AEM), participation of LOM can overcome their prevalent scaling relationship limitations. Here, we report the acid treatment strategy and bypass the cation/anion doping strategy to significantly enhance LOM participation. Our perovskite demonstrated a current density of 10 mA cm-2 at an overpotential of 380 mV and a low Tafel slope (65 mV dec-1) much lower than IrO2 (73 mV dec-1). We propose that the presence of nitric acid-induced defects regulates the electronic structure and thereby lowers oxygen binding energy, allowing enhanced LOM participation to boost OER significantly.

MoO3@MoS2 Core-Shell Structured Hybrid Anode Materials for Lithium-Ion Batteries.

We explore a phase engineering strategy to improve the electrochemical performance of transition metal sulfides (TMSs) in anode materials for lithium-ion batteries (LIBs). A one-pot hydrothermal approach has been employed to synthesize MoS2 nanostructures. MoS2 and MoO3 phases can be readily controlled by straightforward calcination in the (200-300) °C temperature range. An optimized temperature of 250 °C yields a phase-engineered MoO3@MoS2 hybrid, while 200 and 300 °C produce single MoS2 and MoO3 phases. When tested in LIBs anode, the optimized MoO3@MoS2 hybrid outperforms the pristine MoS2 and MoO3 counterparts. With above 99% Coulombic efficiency (CE), the hybrid anode retains its capacity of 564 mAh g-1 after 100 cycles, and maintains a capacity of 278 mAh g-1 at 700 mA g-1 current density. These favorable characteristics are attributed to the formation of MoO3 passivation surface layer on MoS2 and reactive interfaces between the two phases, which facilitate the Li-ion insertion/extraction, successively improving MoO3@MoS2 anode performance.

Reduced Potential Barrier of Sodium-Substituted Disordered Rocksalt Cathode for Oxygen Evolution Electrocatalysts.

Cation-disordered rocksalt (DRX) cathodes have been viewed as next-generation high-energy density materials surpassing conventional layered cathodes for lithium-ion battery (LIB) technology. Utilizing the opportunity of a better cation mixing facility in DRX, we synthesize Na-doped DRX as an efficient electrocatalyst toward oxygen evolution reaction (OER). This novel OER electrocatalyst generates a current density of 10 mA cm−2 at an overpotential (η) of 270 mV, Tafel slope of 67.5 mV dec−1, and long-term stability >5.5 days' superior to benchmark IrO2 (η = 330 mV with Tafel slope = 74.8 mV dec−1). This superior electrochemical behavior is well supported by experiment and sparse Gaussian process potential (SGPP) machine learning-based search for minimum energy structure. Moreover, as oxygen binding energy (OBE) on the surface closely relates to OER activity, our density functional theory (DFT) calculations reveal that Na-doping assists in facile O2 evolution (OBE = 5.45 eV) compared with pristine-DRX (6.51 eV).

Na/Al Codoped Layered Cathode with Defects as Bifunctional Electrocatalyst for High-Performance Li-Ion Battery and Oxygen Evolution Reaction.

The rational design of bifunctional electrocatalyst through simple synthesis with high activity remains a challenging task. Herein, Na/Al codoped Li-excess Li-Ru-Ni-O layered electrodes are demonstrated with defects/dislocations as an efficient bifunctional electrocatalyst toward lithium-ion battery (LIB) and oxygen evolution reaction (OER). Toward LIB cathode, specific capacity of 173 mAh g-1 (0.2C-rate), cyclability (>95.0%), high Columbic efficiency (99.2%), and energy efficiency (90.7%) are achieved. The codoped electrocatalyst has exhibited OER activity at a low onset potential (270 mV@10 mA cm-2 ), with a Tafel slope 69.3 mV dec-1 , and long-term stability over 36 h superior to the undoped and many other OER electrocatalysts including the benchmark IrO2 . The concurrent doping resides in the crystal lattice (where Na shows the pillaring effect to improve facile Li diffusion), Al improves the stabilization of the layered structure, and defective structures provide abundant active sites to accelerate OER reactions.