Fluorine-Doped Tin Oxide Nanocrystal/Reduced Graphene Oxide Composites as Lithium Ion Battery Anode Material with High Capacity and Cycling Stability

Identifying Current Collectors that Enable Light-Battery Interactions

In recent years, there has been an increased focus on studying light-battery interactions in the context of operando optical studies and integrated photoelectrochemical energy harvesting. However, there has been little insight into identifying suitable "light-accepting" current collectors for this class of batteries. In this study, fluorine-doped tin oxide, indium-tin oxide, and silver nanowire-graphene films are analyzed along with carbon paper, carbon nanotube paper, and stainless-steel mesh as current collectors for optical batteries. They are categorized into two classes - transmissive and non-transmissive, based on the orientation of the light-electrode interaction. Various methods to prepare the electrode are highlighted, including drop casting and the fabrication of free-standing electrodes. The optical and electrical properties of these current collectors as well as their electrochemical stability are measured using linear sweep voltammetry against zinc and lithium anodes. Finally, the rate performance and long-term cycling stability of lithium manganese oxide (LiMn2O4) cathodes are measured against lithium anodes with these current collectors and their performance is compared. These results show which current collector to choose depends on the application and cell chemistry. These guidelines will assist in the design of future optical cells for in-situ measurements and photoelectrochemical energy storage.

Light Rechargeable Lithium-Ion Batteries Using V2O5 Cathodes

Solar energy is one of the most actively pursued renewable energy sources, but like many other sustainable energy sources, its intermittent character means solar cells have to be connected to an energy storage system to balance production and demand. To improve the efficiency of this energy conversion and storage process, photobatteries have recently been proposed where one of the battery electrodes is made from a photoactive material that can directly be charged by light without using solar cells. Here, we present photorechargeable lithium-ion batteries (Photo-LIBs) using photocathodes based on vanadium pentoxide nanofibers mixed with P3HT and rGO additives. These photocathodes support the photocharge separation and transportation process needed to recharge. The proposed Photo-LIBs show capacity enhancements of more than 57% under illumination and can be charged to ∼2.82 V using light and achieve conversion efficiencies of ∼2.6% for 455 nm illumination and ∼0.22% for 1 sun illumination.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Porous SnO2 nanostructure with a high specific surface area for improved electrochemical performance

Tin oxide (SnO₂) has been attractive as an alternative to carbon-based anode materials because of its fairly high theoretical capacity during cycling. However, SnO₂ has critical drawbacks, such as poor cycle stability caused by a large volumetric variation during the alloying/de-alloying reaction and low capacity at a high current density due to its low electrical conductivity. In this study, we synthesized a porous SnO₂ nanostructure (n-SnO₂) that has a high specific surface area as an anode active material using the Adams fusion method. From the Brunauer–Emmett–Teller analysis and transmission electron microscopy, the as-prepared SnO₂ sample was found to have a mesoporous structure with a fairly high surface area of 122 m² g⁻¹ consisting of highly-crystalline nanoparticles with an average particle size of 5.5 nm. Compared to a commercial SnO₂, n-SnO₂ showed significantly improved electrochemical performance because of its increased specific surface area and short Li⁺ ion pathway. Furthermore, during 50 cycles at a high current density of 800 mA g⁻¹, n-SnO₂ exhibited a high initial capacity of 1024 mA h g⁻¹ and enhanced retention of 53.6% compared to c-SnO₂ (496 mA h g⁻¹ and 23.5%).

A porous SnO₂ nanostructure as an anode active material showed significantly improved electrochemical performance.

Recent Advances and Perspectives of Carbon-Based Nanostructures as Anode Materials for Li-ion Batteries

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge cycles. One important approach to ensure the electrodes' integrity is by increasing the storage capacity of cathode and anode materials. This could be achieved using nanoscale-sized electrode materials. In the article, we review the recent advances and perspectives of carbon nanomaterials as anode material for Lithium-ion battery applications. The first section of the review presents the general introduction, industrial use, and working principles of Li-ion batteries. It also demonstrates the advantages and disadvantages of nanomaterials and challenges to utilize nanomaterials for Li-ion battery applications. The second section of the review describes the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications. The last section presents the conclusion and future directions.

Reduced graphene oxide wrap buffering volume expansion of Mn2SnO4 anodes for enhanced stability in lithium-ion batteries

MSnO4 (M = Mn, Zn, Co, Mg, etc.) has been widely investigated as an anode material for lithium-ion batteries in recent years, but its practical applications are limited by serious capacity loss caused by severe volume expansion during Li+ insertion/extraction. So far, hollow structures, carbon coating, and encapsulation by reduced graphene oxide have been introduced to improve the electrochemical properties of MSnO4. In this study, Mn2SnO4 nanoparticles@reduced graphene oxide (Mn2SnO4@rGO) composites were prepared using simple steps and applied as anode materials for lithium-ion batteries. The rGO sheet encapsulated Mn2SnO4 nanoparticles show improved electrochemical properties. The first discharge capacity of Mn2SnO4@rGO reaches 1223.5 mAh g-1 and remains at 542.0 mAh g-1 after 100 cycles at a current density of 0.1 A g-1. The electrochemical properties were significantly improved compared to those of pure Mn2SnO4 nanoparticles.

Heterostructural Graphene Quantum Dot/MnO2 Nanosheets toward High-Potential Window Electrodes for High-Performance Supercapacitors

The potential window of aqueous supercapacitors is limited by the theoretical value (≈1.23 V) and is usually lower than ≈1 V, which hinders further improvements for energy density. Here, a simple and scalable method is developed to fabricate unique graphene quantum dot (GQD)/MnO2 heterostructural electrodes to extend the potential window to 0-1.3 V for high-performance aqueous supercapacitor. The GQD/MnO2 heterostructural electrode is fabricated by GQDs in situ formed on the surface of MnO2 nanosheet arrays with good interface bonding by the formation of Mn-O-C bonds. Further, it is interesting to find that the potential window can be extended to 1.3 V by a potential drop in the built-in electric field of the GQD/MnO2 heterostructural region. Additionally, the specific capacitance up to 1170 F g-1 at a scan rate of 5 mV s-1 (1094 F g-1 at 0-1 V) and cycle performance (92.7%@10 000 cycles) between 0 and 1.3 V are observed. A 2.3 V aqueous GQD/MnO2-3//nitrogen-doped graphene ASC is assembled, which exhibits the high energy density of 118 Wh kg-1 at the power density of 923 W kg-1. This work opens new opportunities for developing high-voltage aqueous supercapacitors using in situ formed heterostructures to further increase energy density.

Highly reversible and fast sodium storage boosted by improved interfacial and surface charge transfer derived from the synergistic effect of heterostructures and pseudocapacitance in SnO2-based anodes

Sodium-ion batteries have attracted worldwide attention as potential alternatives for large scale stationary energy storage due to the rich reserves and low cost of sodium resources. However, the practical application of sodium-ion batteries is restricted by unsatisfying capacity and poor rate capability. Herein, a novel mechanism of improving both interfacial and surface charge transfer is proposed by fabricating a graphene oxide/SnO₂/Co₃O₄ nanocomposite through a simple hydrothermal method. The formation of heterostructures between ultrafine SnO₂ and Co₃O₄ could enhance the charge transfer of interfaces owing to the internal electric field. The pseudocapacitive effect, which is led by the high specific area and the existence of ultrafine nanoparticles, takes on a feature of fast faradaic surface charge-transfer. Benefiting from the synergistic advantages of the heterostructures and the pseudocapacitive effect, the as-prepared graphene oxide/SnO₂/Co₃O₄ anode achieved a high reversible capacity of 461 mA h g^-1 after 80 cycles at a current density of 0.1 A g^-1. Additionally, at a high current density of 1 A g^-1, a high reversible capacity of 241 mA h g^-1 after 500 cycles is obtained. A full cell coupled by the as-prepared graphene oxide/SnO₂/Co₃O₄ anode and the Na₃V₂(PO₄)₃ cathode was also constructed, which exhibited a reversible capacity of 310.3 mA h g^-1 after 100 cycles at a current density of 1 A g^-1. This method of improving both interfacial and surface charge transfer may pave the way for the development of high performance sodium-ion batteries.

Superior Potassium Ion Storage via Vertical MoS2 "Nano-Rose" with Expanded Interlayers on Graphene

Potassium has its unique advantages over lithium or sodium as a charge carrier in rechargeable batteries. However, progresses in K-ion battery (KIB) chemistry have so far been hindered by lacking suitable electrode materials to host the relatively large K⁺ ions compared to its Li⁺ and Na⁺ counterparts. Herein, molybdenum disulfide (MoS₂ ) "roses" grown on reduced graphene oxide sheets (MoS₂ @rGO) are synthesized via a two-step solvothermal route. The as-synthesized MoS₂ @rGO composite, with expanded interlayer spacing of MoS₂ , chemically bonded between MoS₂ and rGO, and a unique nano-architecture, displays the one of the best electrochemical performances to date as an anode material for nonaqueous KIBs. More importantly, a combined K⁺ storage mechanism of intercalation and conversion reaction is also revealed. The findings presented indicate the enormous potential of layered metal dichalcogenides as advanced electrode materials for high-performance KIBs and also provide new insights and understanding of K⁺ storage mechanism.

Stable 1T-MoSe2 and Carbon Nanotube Hybridized Flexible Film: Binder-Free and High-Performance Li-Ion Anode

Two-dimensional stable metallic 1T-MoSe₂ with expanded interlayer spacing of 10.0 Å in situ grown on SWCNTs film is fabricated via a one-step solvothermal method. Combined with X-ray absorption near-edge structures, our characterization reveals that such 1T-MoSe₂ and single-walled carbon nanotubes (abbreviated as 1T-MoSe₂/SWCNTs) hybridized structure can provide strong electrical and chemical coupling between 1T-MoSe₂ nanosheets and SWCNT film in a form of C-O-Mo bonding, which significantly benefits a high-efficiency electron/ion transport pathway and structural stability, thus directly enabling high-performance lithium storage properties. In particular, as a flexible and binder-free Li-ion anode, the 1T-MoSe₂/SWCNTs electrode exhibits excellent rate capacity, which delivers a capacity of 630 mAh/g at 3000 mA/g. Meanwhile, the strong C-O-Mo bonding of 1T-MoSe₂/SWCNTs accommodates volume alteration during the repeated charge/discharge process, which gives rise to 89% capacity retention and a capacity of 971 mAh/g at 300 mA/g after 100 cycles. This synthetic route of a multifunctional MoSe₂/SWCNTs hybrid might be extended to fabricate other 2D layer-based flexible and light electrodes for various applications such as electronics, optics, and catalysts.

Vertical 1T-MoS2 nanosheets with expanded interlayer spacing edged on a graphene frame for high rate lithium-ion batteries

Vertical 1T-MoS₂ nanosheets with an expanded interlayer spacing of 9.8 Å were successfully grown on a graphene surface via a one-step solvothermal method. Such unique hybridized structures provided strong electrical and chemical coupling between the vertical nanosheets and graphene layers by means of C-O-Mo bonding. The merits are very beneficial for a high-efficiency electron/ion transport pathway and structural stability. As a proof of concept, the lithium ion battery with the as-obtained hybrid's electrode exhibited excellent rate performance with a 666 mA h g^-1 capacity at a high current density of 3500 mA g^-1. We can extend this method to produce various metallic 1T-MX₂ (M = transition metal; X = chalcogen) vertically edged on a graphene frame as one of the promising hetero-structures for several specific applications in the fields of electronics, optics and catalysis.

MoS2 Nanosheets Vertically Grown on Graphene Sheets for Lithium-Ion Battery Anodes

A designed nanostructure with MoS2 nanosheets (NSs) perpendicularly grown on graphene sheets (MoS2/G) is achieved by a facile and scalable hydrothermal method, which involves adsorption of Mo7O24(6-) on a graphene oxide (GO) surface, due to the electrostatic attraction, followed by in situ growth of MoS2. These results give an explicit proof that the presence of oxygen-containing groups and pH of the solution are crucial factors enabling formation of a lamellar structure with MoS2 NSs uniformly decorated on graphene sheets. The direct coupling of edge Mo of MoS2 with the oxygen from functional groups on GO (C-O-Mo bond) is proposed. The interfacial interaction of the C-O-Mo bonds can enhance electron transport rate and structural stability of the MoS2/G electrode, which is beneficial for the improvement of rate performance and long cycle life. The graphene sheets improve the electrical conductivity of the composite and, at the same time, act not only as a substrate to disperse active MoS2 NSs homogeneously but also as a buffer to accommodate the volume changes during cycling. As an anode material for lithium-ion batteries, the manufactured MoS2/G electrode manifests a stable cycling performance (1077 mAh g(-1) at 100 mA g(-1) after 150 cycles), excellent rate capability, and a long cycle life (907 mAh g(-1) at 1000 mA g(-1) after 400 cycles).

Controllable synthesis of rod-like SnO2 nanoparticles with tunable length anchored onto graphene nanosheets for improved lithium storage capability

Rod-like SnO₂ nanoparticles with tunable length have been anchored onto graphene nanosheets as high performance lithium-ion battery anodes.

Graphene oxide: strategies for synthesis, reduction and frontier applications

In this review article, we describe a general introduction to GO, its synthesis, reduction and some selected frontier applications. Its low cost and potential for mass production make GO a promising building block for functional hybrid materials.