Ultrathin 2D Mesoporous TiO2 /rGO Heterostructure for High-Performance Lithium Storage

Recent Advancements of Graphene-Based Materials for Zinc-Based Batteries: Beyond Lithium-Ion Batteries

Graphene-based materials (GBMs) possess a unique set of properties including tunable interlayer channels, high specific surface area, and good electrical conductivity characteristics, making it a promising material of choice for making electrode in rechargeable batteries. Lithium-ion batteries (LIBs) currently dominate the commercial rechargeable battery market, but their further development has been hampered by limited lithium resources, high lithium costs, and organic electrolyte safety concerns. From the performance, safety, and cost aspects, zinc-based rechargeable batteries have become a promising alternative of rechargeable batteries. This review highlights recent advancements and development of a variety of graphene derivative-based materials and its composites, with a focus on their potential applications in rechargeable batteries such as LIBs, zinc-air batteries (ZABs), zinc-ion batteries (ZIBs), and zinc-iodine batteries (Zn-I2 Bs). Finally, there is an outlook on the challenges and future directions of this great potential research field.

Asymmetric Monolayer Mesoporous Nanosheets of Regularly Arranged Semi-Opened Pores via a Dual-Emulsion-Directed Micelle Assembly

Constructing asymmetric two-dimensional (2D) mesoporous nanomaterials with new pore structure, tunable monolayer architectures, and especially anisotropic surfaces remains a great challenge in materials science. Here, we report a dual-emulsion directed micelle assembly approach to fabricate a novel type of asymmetric monolayer mesoporous organosilica nanosheet for the first time. In this asymmetric 2D structure, numerous quasi-spherical semiopened mesopores (∼20 nm in diameter, 24 nm in opening size) were regularly arranged on a plane, endowing the porous nanosheets (several micrometers in size) with a typical surface anisotropy on two sides. Meanwhile, lots of triangular intervoids (4.0-5.0 nm in size) can also be found among each three semiopened mesopores, enabling the nanosheet to be interconnected. Vitally, such interconnected, anisotropic porous nanosheets exhibit ultrahigh accessible surface area (∼714 m2 g-1) and good lipophilicity properties owing to the abundant semiopened mesopores. Additionally, besides the nanosheet, the configuration of the asymmetric porous structure can also be transformed into a microcapsule when controlling the emulsification size via a facile ultrasonic treatment. As a demonstration, we show that the asymmetric microcapsule shows a high demulsification efficiency (>98%) and cyclic stability (>6 recycle times). Our protocol opens up a new avenue for developing next-generation asymmetric mesoporous materials for various applications.

Recent Advances on Heterojunction-Type Anode Materials for Lithium-/Sodium-Ion Batteries

Rechargeable batteries are key in the field of electrochemical energy storage, and the development of advanced electrode materials is essential to meet the increasing demand of electrochemical energy storage devices with higher density of energy and power. Anode materials are the key components of batteries. However, the anode materials still suffer from several challenges such as low rate capability and poor cycling stability, limiting the development of high-energy and high-power batteries. In recent years, heterojunctions have received increasing attention from researchers as an emerging material, because the constructed heterostructures can significantly improve the rate capability and cycling stability of the materials. Although many research progress has been made in this field, it still lacks review articles that summarize this field in detail. Herein, this review presents the recent research progress of heterojunction-type anode materials, focusing on the application of various types of heterojunctions in lithium/sodium-ion batteries. Finally, the heterojunctions introduced in this review are summarized, and their future development is anticipated.

Titanium dioxide-based anode materials for lithium-ion batteries: structure and synthesis

Lithium-ion batteries (LIBs) have high energy density, long life, good safety, and environmental friendliness, and have been widely used in large-scale energy storage and mobile electronic devices. As a cheap and non-toxic anode material for LIBs, titanium dioxide (TiO₂) has a good application prospect. However, its poor electrical conductivity leads to unsatisfactory electrochemical performance, which limits its large-scale application. In this review, the structure of three TiO₂ polymorphs which are widely investigated are briefly described, then the preparation and electrochemical performance of TiO₂ with different morphologies, such as nanoparticles, nanowires, nanotubes, and nanospheres, and the related research on the TiO₂ composite materials with carbon, silicon, and metal materials are discussed. Finally, the development trend of TiO₂-based anode materials for LIBs has been briefly prospected.

Synthesis of 2D anatase TiO2 with highly reactive facets by fluorine-free topochemical conversion of 1T-TiS2 nanosheets

Two-dimensional (2D) anatase titanium dioxide (TiO₂) is expected to exhibit different properties as compared to anatase nanocrystallites, due to its highly reactive exposed facets. However, access to 2D anatase TiO₂ is limited by the non-layered nature of the bulk crystal, which does not allow use of top-down chemical exfoliation. Large efforts have been dedicated to the growth of 2D anatase TiO₂ with high reactive facets by bottom-up approaches, which relies on the use of harmful chemical reagents. Here, we demonstrate a novel fluorine-free strategy based on topochemical conversion of 2D 1T-TiS₂ for the production of single crystalline 2D anatase TiO₂, exposing the {001} facet on the top and bottom and {100} at the sides of the nanosheet. The exposure of these faces, with no additional defects or doping, gives rise to a significant activity enhancement in the hydrogen evolution reaction, as compared to commercially available Degussa P25 TiO₂ nanoparticles. Because of the strong potential of TiO₂ in many energy-based applications, our topochemical approach offers a low cost, green and mass scalable route for production of highly crystalline anatase TiO₂ with well controlled and highly reactive exposed facets.

TiO2 as an Anode of High-Performance Lithium-Ion Batteries: A Comprehensive Review towards Practical Application

Lithium-ion batteries (LIBs) are undeniably the most promising system for storing electric energy for both portable and stationary devices. A wide range of materials for anodes is being investigated to mitigate the issues with conventional graphite anodes. Among them, TiO2 has attracted extensive focus as an anode candidate due to its green technology, low volume fluctuations (<4%), safety, and durability. In this review, the fabrication of different TiO2 nanostructures along with their electrochemical performance are presented. Different nanostructured TiO2 materials including 0D, 1D, 2D, and 3D are thoroughly discussed as well. More precisely, the breakthroughs and recent developments in different anodic oxidation processes have been explored to identify in detail the effects of anodization parameters on nanostructure morphology. Clear guidelines on the interconnected nature of electrochemical behaviors, nanostructure morphology, and tunable anodic constraints are provided in this review.

Robust α-Fe2O3@TiO2 Core–Shell Structures With Tunable Buffer Chambers for High-Performance Lithium Storage

α-Fe2O3 has high potential energy storage capacity and can serve as a green and low-cost anode material for lithium-ion batteries. However, α-Fe2O3 suffers large volume expansion and pulverization. Based on DFT calculations, TiO2 can effectively maintain the integrity of the crystal structure during the discharge/charge process. Well-defined cubic α-Fe2O3 is coated with a TiO2 layer using the hydrothermal method with the assistance of oxalic acid surface treatment, and then α-Fe2O3@TiO2 with tunable buffer chambers is obtained by altering the hydrochloric acid etching time. With the joint efforts of the buffer chamber and the robust structure of the TiO2 layer, α-Fe2O3@TiO2 alleviates the expansion of α-Fe2O3 during the discharge/charge process. The optimized sample (FT-1h) achieves good cycling performance. The reversible specific capacity remains at 893.7 mA h g-1, and the Coulombic efficiency still reaches up to 98.47% after 150 cycles at a current density of 100 mA g−1. Furthermore, the reversible specific capacity can return to 555.5 mA h g−1 at 100 mA g−1 after cycling at a high current density. Hence, the buffer chamber and the robust TiO2 layer can effectively improve the cycling stability and rate performance of α-Fe2O3.

A Review on Recent Advances for Boosting Initial Coulombic Efficiency of Silicon Anodic Lithium Ion batteries

Rechargeable silicon anode lithium ion batteries (SLIBs) have attracted tremendous attention because of their merits, including a high theoretical capacity, low working potential, and abundant natural sources. The past decade has witnessed significant developments in terms of extending the lifespan and maintaining high capacities of SLIBs. However, the detrimental issue of low initial Coulombic efficiency (ICE) toward SLIBs is causing more and more attention in recent years because ICE value is a core index in full battery design that profoundly determines the utilization of active materials and the weight of an assembled battery. Herein, a comprehensive review is presented of recent advances in solutions for improving ICE of SLIBs. From design perspectives, the strategies for boosting ICE of silicon anodes are systematically categorized into several aspects covering structure regulation, prelithiation, interfacial design, binder design, and electrolyte additives. The merits and challenges of various approaches are highlighted and discussed in detail, which provides valuable insights into the rational design and development of state-of-the-art techniques to deal with the deteriorative issue of low ICE of SLIBs. Furthermore, conclusions and future promising research prospects for lifting ICE of SLIBs are proposed at the end of the review.

Synergetic Advantages of Atomically Coupled 2D Inorganic and Graphene Nanosheets as Versatile Building Blocks for Diverse Functional Nanohybrids

2D nanostructured materials, including inorganic and graphene nanosheets, have evoked plenty of scientific research activity due to their intriguing properties and excellent functionalities. The complementary advantages and common 2D crystal shapes of inorganic and graphene nanosheets render their homogenous mixtures powerful building blocks for novel high-performance functional hybrid materials. The nanometer-level thickness of 2D inorganic/graphene nanosheets allows the achievement of unusually strong electronic couplings between sheets, leading to a remarkable improvement in preexisting functionalities and the creation of unexpected properties. The synergetic merits of atomically coupled 2D inorganic-graphene nanosheets are presented here in the exploration of novel heterogeneous functional materials, with an emphasis on their critical roles as hybridization building blocks, interstratified sheets, additives, substrates, and deposited monolayers. The great flexibility and controllability of the elemental compositions, defect structures, and surface natures of inorganic-graphene nanosheets provide valuable opportunities for exploring high-performance nanohybrids applicable as electrodes for supercapacitors and rechargeable batteries, electrocatalysts, photocatalysts, and water purification agents, to give some examples. An outlook on future research perspectives for the exploitation of emerging 2D nanosheet-based hybrid materials is also presented along with novel synthetic strategies to maximize the synergetic advantage of atomically mixed 2D inorganic-graphene nanosheets.

Immobilizing Polysulfide by In Situ Topochemical Oxidation Derivative TiC@Carbon-Included TiO2 Core-Shell Sulfur Hosts for Advanced Lithium-Sulfur Batteries

The performance of lithium-sulfur (Li-S) batteries is greatly hindered by the notorious shuttle effect of lithium polysulfides (LiPSs). To address this issue, in situ topochemical oxidation derivative TiC@carbon-included TiO₂ (TiC@C-TiO₂ ) core-shell composite is designed and proposed as a multifunctional sulfur host, which integrates the merits of conductive TiC core to facilitate the redox reaction kinetics of sulfur species, and porous C-TiO₂ shell to suppress the dissolution and shuttling of LiPSs through chemisorption. A unique dual chemical mediation mechanism is demonstrated for the proposed TiC@C-TiO₂ composite that synergistically entraps LiPSs through thiosulfate/polythionate conversion coupled with strong polar-polar interaction. The morphological characterization reveals that the TiC@C-TiO₂ -based cathode can well regulate the distribution of electrode materials to retard their accumulation inside the electrode, ensuring effective contact between the active materials and electrolyte. Based on its unique function and structure, the cathode delivers an improved capacity of 1256 mAh g^-1 at 0.2C, a remarkable rate capability of 643 mAh g^-1 , and an ultralow capacity decay rate of 0.065% per cycle at 2C over 900 cycles. This work not only demonstrates a dual chemical mediation mechanism to immobilize LiPSs, but also provides a universal strategy to construct multifunctional sulfur hosts for advanced Li-S batteries.