Advanced Nano-Structured Materials for Energy Storage Devices

Boosted by the increasing demand for clean and portable energy resources, there have been tremendous efforts being made in the energy harvesting and energy storage materials and devices, such as solar cells, fuel cells, Li-ion batteries etc. Since its first commercial debut in 1991, Li-ion battery has achieved significant progress in energy storage performances. The development of nanostructured electrode material is regarded as one of the key potentials for the further advancement in Li-ion batteries. This paper highlights our recent studies in the synthesis and characterization of nanostructured electrode materials for high-performance Li-ion batteries. The main focuses are on the binder-less and additive-free vanadium oxide films and lithium iron phosphate - carbon nanocomposite films via sol-gel processing. Enhanced Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> intercalation capacities, improved rate capabilities and better cyclic stability were achieved by architecting micro- or nanostructure, controlling materials crystallinity and introducing desired defects on surface and/or in bulk.

Different advanced nanostructured carbon materials, such as carbon nanocoils, carbon nanofibers, graphitized ordered mesoporous carbons and carbon xerogels, presenting interesting features such as high electrical conductivity and extensively developed porous structure were synthesized and used as supports in the preparation of electrocatalysts for direct methanol fuel cells (DMFCs). The main advantage of these supports is that their physical properties and surface chemistry can be tailored to adapt the carbonaceous material to the catalytic requirements. Moreover, all of them present a highly mesoporous structure, diminishing diffusion problems, and both graphitic character and surface area can be conveniently modified. In the present work, the influence of the particular features of each material on the catalytic activity and stability was analyzed. Results have been compared with those obtained for commercial catalysts supported on Vulcan XC-72R, Pt/C and PtRu/C (ETEK). Both a highly ordered graphitic and mesopore-enriched structure of these advanced nanostructured materials resulted in an improved electrochemical performance in comparison to the commercial catalysts assayed, both towards CO and alcohol oxidation.

Carbon and silicon materials are two of the most important materials involved in the history of the science and technology development. In the last two decades, C and Si nanoscale materials, e.g., carbon nanotubes, graphene, and silicon nanowires, and quantum dots, have also emerged as the most interesting nanomaterials in nanoscience and nanotechnology for their myriad promising applications such as for electronics, sensors, biotechnology, etc. In particular, carbon and silicon nanostructures are being utilized in energy-related applications such as catalysis, batteries, solar cells, etc., with significant advances. Understanding of the nature of surface and electronic structures of nanostructures plays a key role in the development and improvement of energy conversion and storage nanosystems. Synchrotron soft X-ray absorption spectroscopy (XAS) and related techniques, such as X-ray emission spectroscopy (XES) and scanning transmission X-ray microscopy (STXM), show unique capability in revealing the surface and electronic structures of C and Si nanomaterials. In this review, XAS is demonstrated as a powerful technique for probing chemical bonding, the electronic structure, and the surface chemistry of carbon and silicon nanomaterials, which can greatly enhance the fundamental understanding and also applicability of these nanomaterials in energy applications. The focus is on the unique advantages of XAS as a complementary tool to conventional microscopy and spectroscopy for effectively providing chemical and structural information about carbon and silicon nanostructures. The employment of XAS for in situ, real-time study of property evolution of C and Si nanostructures to elucidate the mechanisms in energy conversion or storage processes is also discussed.

Heterogeneous based functionalized nanocomposite materials have attracted considerable attention in both energy storage and conversion process, due to their fast electron transfer process and their ling-life cycles. Herein, the review briefly discussed different kinds of techniques, which are used for the fabrication of carbon based nanocomposites like sol-gel, hydrothermal (HT), in situ polymerization and electrochemical methods, etc In particularly, functionalized carbon decorated nanocomposites have been focused on the designing and development of rational candidate for future energy technologies. Especially, the highlighted nanocomposites have become more attention in the area of energy technologies mainly caused by their larger electrode surface area, high mechanical strength, excellent electrochemical properties, and rapid electrochemical redox behaviour. Considerable advancements in the combinations of nanoscale based composite devices have the platforms to develop new energy storage technology to fulfill the global energy demands. Finally, it summarizes the recent advantages of carbon supported composite, which significantly enhanced their electrochemical energy storage devices properties like high capacitance and boosted specific capacitive values.

Nanomaterials have emerged as a cornerstone in advancing energy conversion technologies, offering unparalleled potential for improving efficiency and sustainability. Their unique properties—such as high surface area, tunable electronic structure, and quantum effects—enable superior performance in applications like solar cells, fuel cells, thermoelectric devices, and batteries. By manipulating nanoscale architectures, researchers can enhance energy harvesting, storage, and conversion processes. This study explores the role of nanomaterials in energy conversion, focusing on their design, synthesis, and application in cutting-edge technologies. The integration of nanomaterials with advanced energy systems has shown significant potential to address challenges such as limited energy resources and environmental concerns. Special emphasis is placed on nanostructured semiconductors, quantum dots, and graphene-based materials for their contributions to photovoltaic and catalytic processes. Despite their advantages, challenges remain, including scalability, stability, and cost-efficiency. This research aims to provide a comprehensive overview of recent advancements, evaluate existing challenges, and highlight future directions for nanomaterials in energy conversion, ultimately contributing to a sustainable energy future.

Charging up Stationary Energy Storage

Heterogeneous nanostructure array for electrochemical energy conversion and storage

In a society that increasingly relies on mobile electronics, demand is rapidly growing for both primary and rechargeable batteries that power devices from cell phones to vehicles. Existing batteries utilize lightweight active materials that use electrochemical reactions of ions such as H(+), OH(-) and Li(+)/Mg(2+) to facilitate energy storage and conversion. Ideal batteries should be inexpensive, have high energy density, and be made from environmentally friendly materials; batteries based on bulk active materials do not meet these requirements. Because of slow electrode process kinetics and low-rate ionic diffusion/migration, most conventional batteries demonstrate huge gaps between their theoretical and practical performance. Therefore, efforts are underway to improve existing battery technologies and develop new electrode reactions for the next generation of electrochemical devices. Advances in electrochemistry, surface science, and materials chemistry are leading to the use of nanomaterials for efficient energy storage and conversion. Nanostructures offer advantages over comparable bulk materials in improving battery performance. This Account summarizes our progress in battery development using a combination of lightweight elements and nanostructured materials. We highlight the benefits of nanostructured active materials for primary zinc-manganese dioxide (Zn-Mn), lithium-manganese dioxide (Li-Mn), and metal (Mg, Al, Zn)-air batteries, as well as rechargeable lithium ion (Li-ion) and nickel-metal hydride (Ni-MH) batteries. Through selected examples, we illustrate the effect of structure, shape, and size on the electrochemical properties of electrode materials. Because of their numerous active sites and facile electronic/ionic transfer and diffusion, nanostructures can improve battery efficiency. In particular, we demonstrate the properties of nanostructured active materials including Mg, Al, Si, Zn, MnO(2), CuV(2)O(6), LiNi(0.8)Co(0.2)O(2), LiFePO(4), Fe(2)O(3), Co(3)O(4), TiS(2), and Ni(OH)(2) in battery applications. Electrochemical investigations reveal that we generally attain larger capacities and improved kinetics for electrode materials as their average particle size decreases. Novel nanostructures such as nanowires, nanotubes, nanourchins, and porous nanospheres show lower activation energy, enhanced reactivity, improved high-rate charge/discharge capability, and more controlled structural flexibility than their bulk counterparts. In particular, anode materials such as Si nanospheres and Fe(2)O(3) nanotubes can deliver reversible capacity exceeding 500 mA.h/g. (Graphite used commercially has a theoretical capacity of 372 mA x h/g.) Nanocomposite cathode materials such as NiP-doped LiFePO(4) and metal hydroxide-coated Ni(OH)(2) nanotubes allow us to integrate functional components, which enhance electrical conductivity and suppress volume expansion. Therefore, shifting from bulk to nanostructured electrode materials could offer a revolutionary opportunity to develop advanced green batteries with large capacity, high energy and power density, and long cycle life.

Energy devices are having an increasing technological impact on our society and have become an essential part of our daily lives. Printing technology has been used to manufacture a wide range of energy storage and conversion devices, including solar cells, supercapacitors, lithium-ion batteries, zinc-ion batteries, nanogenerators, etc. High-resolution screen-printing technology is widely used in the fabrication of commercial solar cells. The development of flexible energy devices is a key part of the realization of wearable electronics, and printing technology has unique advantages. In this chapter, the structure and mechanisms of conventional printed energy storage and conversion devices and manufacturing strategy are illustrated.

Highly efficient IR detectors and photo-voltaic solar cells that incorporate nanotechnology composed of nanostructures and nanoparticles (including quantum dots) will play an important role in advanced photonic space applications. While the development of Si-based solar cells has successfully evolved into an efficient and economical technology these devices are predicted to soon reach their theoretical 29% limit efficiency. Alternative organic/polymer solar cells and IR detectors incorporating quantum dots and various nanoparticle or nanostructure materials are emerging which are expected to eventually outperform current state-of-the-art detectors and solar cell devices. By tailoring the QD design wavelength-optimized detectors and detector arrays operating over the UV-IR range can be realized. Specific examples for achieving near-IR photovoltaic and photoconductive detectors with high quantum efficiencies are presented along with brief examples of empirical data reported for assessing the radiation resistance of QD nanocrystalline devices for application in space environments.

Chapter 6 - MXenes and their composites for energy storage and conversion

Integrated energy conversion and storage devices: Interfacing solar cells, batteries and supercapacitors

Review: 341 refs.

The lithium-ion battery (LIB) has emerged as a key energy storage device for a wide range of applications, from consumer electronics to transportation. While LIBs have made key advancements in these areas, limitations remain for Li-ion batteries with respect to affordability, performance, and reliability. These challenges have encouraged the exploration for more advanced materials and novel chemistries to mitigate these limitations. The continued development of Li-ion and other advanced batteries is an inherently multiscale problem that couples electrochemistry, transport phenomena, mechanics, microstructural morphology, and device architecture. Observing the internal structure of batteries, both ex situ and during operation, provides a critical capability for further advancement of energy storage technology. X-ray imaging has been implemented to provide further insight into the mechanisms governing Li-ion batteries through several 2D and 3D techniques. Ex situ imaging has yielded microstructural data from both anode and cathode materials, providing insight into mesoscale structure and composition. Furthermore, since X-ray imaging is a nondestructive process studies have been conducted in situ and in operando to observe the mechanisms of operation as they occur. Data obtained with these methods has also been integrated into multiphysics models to predict and analyze electrode behavior. The following paper provides a brief review of X-ray imaging work related to Li-ion batteries and the opportunities these methods provide for the direct observation and analysis of the multiphysics behavior of battery materials.

Herein, an integrated device that comprises inorganic kesterite solar cells and Li-ion batteries (LIBs) has been proposed for application in fast photo-charging power systems. LiFePO4 and Li4Ti5O12 were selected as the battery electrode materials and six kesterite solar cells connected in series were fabricated to satisfy the charging voltage required for LIBs. Photo-charging was conducted at the rate of 1C (1.790 mAh g−1) at 2.1 V. An energy conversion and storage efficiency of 3.87% was acquired in the integrated device, and a storage efficiency of over 70% was observed in LIBs. Furthermore, by synchronizing the charging voltage of the solar cell and LIB, over 70% of the capacity was obtained at the rate of 1C, while preventing overvoltage during long-term charging.