1D ultrafine SnO2 nanorods anchored on 3D graphene aerogels with hierarchical porous structures for high-performance lithium/sodium storage

The role of graphene aerogels in rechargeable batteries

Energy storage systems, particularly rechargeable batteries, play a crucial role in establishing a sustainable energy infrastructure. Today, researchers focus on improving battery energy density, cycling stability, and rate performance. This involves enhancing existing materials or creating new ones with advanced properties for cathodes and anodes to achieve peak battery performance. Graphene aerogels (GAs) possess extraordinary attributes, including a hierarchical porous and lightweight structure, high electrical conductivity, and robust mechanical stability. These qualities facilitate the uniform distribution of active sites within electrodes, mitigate volume changes during repeated cycling, and enhance overall conductivity. When integrated into batteries, GAs expedite electron/ion transport, offer exceptional structural stability, and deliver outstanding cycling performance. This review offers a comprehensive survey of the advancements in the preparation, functionalization, and modification of GAs in the context of battery research. It explores their application as electrodes and hosts for the dispersion of active material nanoparticles, resulting in the creation of hybrid electrodes for a wide range of rechargeable batteries including lithium-ion batteries (LIBs), Li-metal-air batteries, sodium-ion batteries (SIBs), zinc-ion batteries (AZIBs) and zinc-air batteries (ZABs), aluminum-ion batteries (AIBs) and aluminum-air batteries and other.

Construction of Carbon Nanofiber-Wrapped SnO2 Hollow Nanospheres as Flexible Integrated Anode for Half/Full Li-Ion Batteries

SnO2 is deemed a potential candidate for high energy density (1494 mAh g-1) anode materials for Li-ion batteries (LIBs). However, its severe volume variation and low intrinsic electrical conductivity result in poor long-term stability and reversibility, limiting the further development of such materials. Therefore, we propose a novel strategy, that is, to prepare SnO2 hollow nanospheres (SnO2-HNPs) by a template method, and then introduce these SnO2-HNPs into one-dimensional (1D) carbon nanofibers (CNFs) uniformly via electrospinning technology. Such a sugar gourd-like construction effectively addresses the limitations of traditional SnO2 during the charging and discharging processes of LIBs. As a result, the optimized product (denoted SnO2-HNP/CNF), a binder-free integrated electrode for half and full LIBs, displays superior electrochemical performance as an anode material, including high reversible capacity (~735.1 mAh g-1 for half LIBs and ~455.3 mAh g-1 at 0.1 A g-1 for full LIBs) and favorable long-term cycling stability. This work confirms that sugar gourd-like SnO2-HNP/CNF flexible integrated electrodes prepared with this novel strategy can effectively improve battery performance, providing infinite possibilities for the design and development of flexible wearable battery equipment.

3D graphene nanosheets from plastic waste for highly efficient HTM free perovskite solar cells

Herein, we report the first time application of waste plastic derived 3D graphene nanosheets (GNs) for hole transport material (HTM) free perovskite solar cells (PSCs), where 3D GNs have been employed as an electrode dopant material in monolithic carbon electrode based mesoscopic PSCs. Waste plastics were upcycled into high-quality 3D GNs by using two-step pyrolysis processes, where, a nickel (99.99%) metal mesh was taken as the catalytic and degradation template to get an acid free route for the synthesis of 3D GNs. Raman spectroscopy, HRTEM analysis and XRD analysis show the presence of 1-2 graphene layers within the 3D GNs. Further, the optical band gap study has also been performed to analyze the applicability of 3D GNs for PSCs. The optimized device with 3D GNs shows a power conversion efficiency (PCE) of 12.40%, whereas the carbon-based control device shows a PCE of 11.04%. Further, all other device parameters such as short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) have been improved with the addition of 3D GNs. The performance enhancement in 3D GN doped HTM free PSC solar cells is attributed to the enhancement in conductivity and reduced recombination within the device. Further, the photocurrent study shows that the 3D GN device shows better performance as compared to the reference device due to the larger diffusion current. Thus, the upcycling of waste plastics into 3D GNs and their exploitation for application in energy conversion show an effective and potential way to convert waste into energy.

Energetic-Materials-Driven Synthesis of Graphene-Encapsulated Tin Oxide Nanoparticles for Sodium-Ion Batteries

By evenly mixing polytetrafluoroethylene-silicon energetic materials (PTFE-Si EMs) with tin oxide (SnO₂) particles, we demonstrate a direct synthesis of graphene-encapsulated SnO₂ (Gr-SnO₂) nanoparticles through the self-propagated exothermic reaction of the EMs. The highly exothermic reaction of the PTFE-Si EMs released a huge amount of heat that induced an instantaneous temperature rise at the reaction zone, and the rapid expansion of the gaseous SiF₄ product provided a high-speed gas flow for dispersing the molten particles into finer nanoscale particles. Furthermore, the reaction of the PTFE-NPs with Si resulted in a simultaneous synthesis of graphene that encapsulated the SnO₂ nanoparticles in order to form the core-shell nanostructure. As sodium storage material, the graphene-encapsulated SnO₂ nanoparticles exhibit a good cycling performance, superior rate capability, and a high initial Coulombic efficiency of 85.3%. This proves the effectiveness of our approach for the scalable synthesis of core-shell-structured graphene-encapsulated nanomaterials.

MOF derived double-carbon layers boosted the lithium/sodium storage performance of SnO2nanoparticles

Tin oxide (SnO₂) was considered as a promising alternative to commonly used graphite anode in energy storage devices thanks to its superior specific capacity. However, its electrochemical property was severely limited due to the inherent poor conductivity and drastic volume variation during the charging/discharging process. To overcome this disadvantage, we grew Sn-MOF directly on graphene oxide (GO) layers to synthesize a double carbon conductive network-encapsulated SnO₂nanoparticles (SnO₂/C/rGO) via a facile solvothermal method. During the process, Sn-MOF skeleton transformed into porous carbon shells, in which nanosized SnO₂particles (~8nm) were embedded, while GO template was reduced to highly conductive rGO layer tightly wrapping the SnO₂/C particles. This double-carbon structure endowed SnO₂/C/rGO anode with enhanced specific capacity and rate property both in lithium ion batteries (LIB) and sodium ion batteries (SIB). The SnO₂/C/rGO anode showed a highly reversible specific capacity of 1038.3 mAh g^-1at 100 mA g^-1, and maintained a stable capacity of 720.2 mAh g^-1(70.1%) under 500 mA g^-1after 150 cycles in LIBs. Similarly, highly reversible capacity of 350.7 mAh g^-1(81.1%) under 100 mA g^-1after 150 cycles was also achieved in SIBs. This work provided a promising strategy in improving the electrochemical properties of SnO₂nanoparticles (NPs), as well as other potential anode materials suffering from huge volume change and poor conductivity.

3D Graphene Materials: From Understanding to Design and Synthesis Control

Carbon materials, with their diverse allotropes, have played significant roles in our daily life and the development of material science. Following 0D C₆₀ and 1D carbon nanotube, 2D graphene materials, with their distinctively fascinating properties, have been receiving tremendous attention since 2004. To fulfill the efficient utilization of 2D graphene sheets in applications such as energy storage and conversion, electrochemical catalysis, and environmental remediation, 3D structures constructed by graphene sheets have been attempted over the past decade, giving birth to a new generation of graphene materials called 3D graphene materials. This review starts with the definition, classifications, brief history, and basic synthesis chemistries of 3D graphene materials. Then a critical discussion on the design considerations of 3D graphene materials for diverse applications is provided. Subsequently, after emphasizing the importance of normalized property characterization for the 3D structures, approaches for 3D graphene material synthesis from three major types of carbon sources (GO, hydrocarbons and inorganic carbon compounds) based on GO chemistry, hydrocarbon chemistry, and new alkali-metal chemistry, respectively, are comprehensively reviewed with a focus on their synthesis mechanisms, controllable aspects, and scalability. At last, current challenges and future perspectives for the development of 3D graphene materials are addressed.

Rapid preparation of ultra-fine and well-dispersed SnO2 nanoparticles via a double hydrolysis reaction for lithium storage

An efficient and rapid method is reported for preparing ultra-fine and well-dispersed SnO₂ nanoparticles in a large scale. A simple double hydrolysis reaction between SnO₃^2- and Fe³⁺ ions was masterly used to form a stable colloid system, in which colloidal particles of H₂SnO₃ with negative charges and Fe(OH)₃ with positive charges electrostatically interact with each other and form honeycomb-like "core-shell" units. Through the hydrothermal reaction, the units are easily transformed into SnO₂@FeO(OH) structures. Ultra-fine and well-dispersed SnO₂ particles with less than 6 nm diameter were finally obtained with a high yield by further etching using hydrochloric acid. When used as anode materials for lithium ion batteries, the ultra-fine SnO₂ particles can be easily dispersed into the carbon networks originating from the carbon source of glucose during the hydrothermal reaction. Electrochemical tests confirmed that these ultra-fine SnO₂/C materials were endowed with excellent cyclic stability and C-rate performance. Even at a 1.56 A g^-1 (2C) high current density, the reversible capacity could be maintained at 710 mA h g^-1 after 100 cycles owing to the ultra-fine particle size of SnO₂ and the rich carbon networks.

Environmentally Friendly and Cost-Effective Synthesis of Carbonaceous Particles for Preparing Hollow SnO2 Nanospheres and their Bifunctional Li-Storage and Gas-Sensing Properties

The templated preparation of hollow nanomaterials has received broad attention. However, many templates are expansive, environmentally-harmful, along with involving a complicated preparation process. Herein, we present a cost-effective, environmentally friendly and simple approach for making carbonaceous particles which have been demonstrated as efficient templates for preparing hollow nanospheres. Natural biomass, such as wheat or corn, is used as the source only, and thus other chemicals are not needed. The carbonaceous particles possess abundant hydroxyl and carboxyl groups, enabling them to efficiently adsorb metal ions in solution. The prepared SnO2 hollow spheres were used in a lithium-ion (Li-ion) battery anode, and as the sensing layer of a gas sensor, respectively. After charge–discharge for 200 times at a rate of 1 C, the anodes exhibit a stable capacity of 500 mAh g−1, and a Coulombic efficiency as high as 99%. In addition, the gas sensor based on the SnO2 hollow spheres shows a high sensing performance towards ethanol gas. It is expected that the presented natural biomass-derived particles and their green preparation method will find more applications for broad research fields, including energy-storage and sensors.

Molybdenum-doped tin oxide nanoflake arrays anchored on carbon foam as flexible anodes for sodium-ion batteries

Tin oxide (SnO₂) has been widely used as an anode material for sodium-ion storage because of its high theoretical capacity. However, it suffers from large volume expansion and poor conductivity. To overcome these limitations, in this study, we have designed and prepared Mo-doped SnO₂ nanoflake arrays anchored on carbon foam (Mo-SnO₂@C-foam with 38.41 wt% SnO₂ and 3.7 wt% Mo content) by a facile hydrothermal method. The carbon foam serves as a three-dimensional conductive network and a buffer skeleton, contributing to improved rate performance and cycling stability. In addition, Mo doping enhances the kinetics of sodium-ion transfer, and the interlaced SnO₂ nanoflake arrays is beneficial to promote the conversion reactions during the charge/discharge process. The as-prepared composite with a unique structure demonstrate a high initial capacity of 1017.1 mAh g^-1 at 0.1 A g^-1, with a capacity retention over three times higher than that of the control sample (SnO₂@C-foam) at 1 A g^-1, indicating a remarkable rate performance.