Review of metal oxides as anode materials for lithium-ion batteries

Novel nitrogen-doped carbon-coated SnSe2 based on a post-synthetically modified MOF as a high-performance anode material for LIBs and SIBs

SnSe2 with high theoretical capacity has been identified as an emerging anode candidate for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, the rate performance and cycling performance of this material in practical applications are still limited by unavoidable volume expansion and low conductivity. In this work, we designed and synthesized nitrogen-doped carbon-coated SnSe2/C-N composites using 2-aminoterephthalic acid (C8H7NO4) as a nitrogen-containing compound for modification by hydrothermal and vacuum calcination methods to achieve efficient utilization of active sites and optimization of the electronic structure. The carbon skeleton inherited from the Sn-MOF precursor can effectively improve the electronic conduction properties of SnSe2. N-doping in the Sn-MOF can increase the positive and negative electrostatic potential energy regions on the molecular surface to further improve the electrical conductivity, and effectively reduce the binding energy with Li+/Na+ which was determined by Density Functional Theory (DFT) methods. In addition, the N-doped carbon skeleton also introduces a larger space for Li+/Na+ intercalation and enhances the mechanical properties. In particular, the post-synthetically modified MOF-derived SnSe2/C-N materials exhibit excellent cyclability, with a reversible capacity of 695 mA h g-1 for LIBs and 259 mA h g-1 for SIBs after 100 cycles at 100 mA g-1.

An Effective Catholyte for Sulfide-Based All-Solid-State Batteries Utilizing Gas Absorbents

All-solid-state batteries (ASSBs) possess the advantage of ensuring safety while simultaneously maximizing energy density, making them suitable for next-generation battery models. In particular, sulfide solid electrolytes (SSEs) are viewed as promising candidates for ASSB electrolytes due to their excellent ionic conductivity. However, a limitation exists in the form of interfacial side reactions occurring between the SSEs and cathode active materials (CAMs), as well as the generation of sulfide-based gases within the SSE. These issues lead to a reduction in the capacity of CAMs and an increase in internal resistance within the cell. To address these challenges, cathode composite materials incorporating zinc oxide (ZnO) are fabricated, effectively reducing various side reactions occurring in CAMs. Acting as a semiconductor, ZnO helps mitigate the rapid oxidation of the solid electrolyte facilitated by an electronic pathway, thereby minimizing side reactions, while maintaining electron pathways to the active material. Additionally, it absorbs sulfide-based gases, thus protecting the lithium ions within CAMs. In this study, the mass spectrometer is employed to observe gas generation phenomena within the ASSB cell. Furthermore, a clear elucidation of the side reactions occurring at the cathode and the causes of capacity reduction in ASSB are provided through density functional theory calculations.

Advancing lithium-sulfur battery efficiency: utilizing a 2D/2D g-C3N4@MXene heterostructure to enhance sulfur evolution reactions and regulate polysulfides under lean electrolyte conditions

Lithium-sulfur batteries (LSBs) show promise for achieving a high energy density of 500 W h kg-1, despite challenges such as poor cycle life and low energy efficiency due to sluggish redox kinetics of lithium polysulfides (LiPSs) and sulfur's electronic insulating nature. We present a novel 2D Ti3C2 Mxene on a 2D graphitic carbon nitride (g-C3N4) heterostructure designed to enhance LiPS conversion kinetics and adsorption capacity. In a pouch cell configuration with lean electrolyte conditions (∼5 μL mg-1), the g-C3N4-Mx/S cathode exhibited excellent rate performance, delivering ∼1061 mA h g-1 at C/8 and retaining ∼773 mA h g-1 after 190 cycles with a Coulombic efficiency (CE) of 92.7%. The battery maintained a discharge capacity of 680 mA h g-1 even at 1.25 C. It operated reliably at an elevated sulfur loading of 5.9 mg cm-2, with an initial discharge capacity of ∼900 mA h g-1 and a sustained CE of over 83% throughout 190 cycles. Postmortem XPS and EIS analyses elucidated charge-discharge cycle-induced changes, highlighting the potential of this heterostructured cathode for commercial garnet LSB development.

Constructing novel hydrated metal molten salt with high self-healing as the anode material for lithium-ion batteries

Lithium-ion batteries (LIBs) are greatly limited in their practical application because of their poor cycle performance, low conductivity and volume expansion. Herein, molten salts (MSs) FeCl3·6H2O-NMP with low temperature via simple preparation are used as the anode material of LIBs for the first time to break through the bottleneck of LIBs. The good fluidity and high self-healing of FeCl3·6H2O-NMP effectively avoid the collapse and breakage of the structure. Based on this feature, the initial discharge specific capacity reached 770.28 mA h g-1, which was more than twice that of the commercial graphite anode. After 200 cycles at a current density of 100 mA g-1, the specific capacity did not decrease rather it was found to be higher than the initial discharge specific capacity, reaching 867.24 mA h g-1. Besides, the good conductivity of MSs provides convenience for the removal and intercalation of Li+. The active H sites that can combine with lithium ions form LiH and provide capacity for LIBs. Density functional theory (DFT) calculation also provided theoretical proof for the mechanism of LIBs.

Synthesis of multi-cavity mesoporous carbon nanospheres through solvent-induced self-assembly: Anode material for sodium-ion batteries with long-term cycle stability

Mesoporous carbon nanospheres (MCSs) are extensively employed in energy storage applications due to their ordered pore size, large specific surface area (SSA), and abundant active sites, resulting in excellent electrochemical performance for sodium storage. However, challenges persist in achieving precise structural control and stable synthesis reactions for these MCSs. Additionally, employing MCSs with a larger SSA in sodium storage applications can lead to increased side reactions and potential structural instability. To address these issues, we propose a solvent-induced self-assembly method for obtaining high nitrogen-containing multi-cavity MCSs with reduced SSA. The morphology and SSA of the nanospheres can be precisely adjusted by regulating the reaction time. Introducing an amine-phenol bridging structure into the polymer system significantly bolsters the structural and morphological stability of the mesoporous materials. The performance of these novel nanospheres in sodium-ion batteries (SIBs) is remarkable, exhibiting excellent sodium storage capability and exceptional ultra-long cycle stability. At a rate of 0.1 A g-1, the nanospheres achieved a high reversible capacity of 252 mAh g-1, and even after 20,000 cycles at 5 A g-1, a specific capacity of 136 mAh g-1 was retained. In summary, our study presents a novel approach for synthesizing mesoporous carbon materials and offers valuable insights for sodium storage research, opening new possibilities for enhancing energy storage applications.

Design and Construction of Carbon-Coated Fe3 O4 /Cr2 O3 Heterostructures Nanoparticles as High-Performance Anodes for Lithium Storage

Transition metal oxides, highly motivated anodes for lithium-ion batteries due to high theoretical capacity, typically afflict by inferior conductivity and significant volume variation. Architecting heterogeneous structures with distinctive interfacial features can effectively regulate the electronic structure to favor electrochemical properties. Herein, an engineered carbon-coated nanosized Fe3 O4 /Cr2 O3 heterostructure with multiple interfaces is synthesized by a facile sol-gel method and subsequent heat treatment. Such ingenious components and structural design deliver rapid Li+ migration and facilitate charge transfer at the heterogeneous interface. Simultaneously, the strong coupling synergistic interactions between Fe3 O4 , Cr2 O3 , and carbon layers establish multiple interface structures and built-in electric fields, which accelerate ion/electron transport and effectively eliminate volume expansion. As a result, the multi-interface heterostructure, as a lithium-ion battery anode, exhibits superior cycling stability maintaining a reversible capacity of 651.2 mAh g-1 for 600 cycles at 2 C. The density functionaltheory calculations not only unravel the electronic structure of the modulation but also illustrate favorable lithium-ion adsorption kinetics. This multi-interface heterostructure strategy offers a pathway for the development of advanced alkali metal-ion batteries.

Nanotubular Fe2O3 and Mn3O4 with hierarchical porosity as high-performance anode materials for lithium-ion batteries

Developing eco-friendly and low-cost advanced anode materials, such as Fe2O3 and Mn3O4, is fundamental to improve the electrochemical performance of lithium-ion batteries (LIBs). The rational engineering of the microstructure of Fe2O3 and Mn3O4 to endow it with one-dimensionally and hierarchically porous architecture is a feasible way to further improve and optimize the electrochemical performance of the anode materials. Herein, we demonstrate a facile strategy to prepare nanotubular Fe2O3 and Mn3O4 as advanced anode materials for high-performance LIBs. By combining the merits of the one-dimensionally nanotubular morphology and hierarchically porous structure, limitations in the lithiation activity of Mn3O4 and Fe2O3 anode materials, such as low electrical conductivity, large volume expansion, and sluggish lithium-ion diffusion within the materials, have been effectively overcome. When used as anode materials, t-Fe2O3 and t-Mn3O4 exhibited outstanding electrochemical performances, including a high reversible discharge capacity (859.7 and 901.4 mA h g-1 for t-Fe2O3 and t-Mn3O4, respectively), excellent rate performance, and ultra-stable cycling stability. Such superior electrochemical performances proved the exceptional potential of the materials for the real-world application in LIBs.

A TiSe monolayer as a superior anode for applications of Li/Na/K-ion batteries

Using density functional theory (DFT), we investigated the energy-storage capabilities of a two-dimensional TiSe monolayer for applications of the anode material of Li/Na/K-ion batteries. The TiSe monolayer showed high thermodynamic stability at 800 K according to ab initio molecular dynamics (AIMD) simulation. The ion-diffusion barrier was estimated to be 0.29/0.36/0.33 eV for Li/Na/K, respectively, indicating the high-rate capacity of this material. The theoretical specific capacity was 422.63 mA h g-1 for Li/Na/K, with an energy density of 1000.19, 802.30, and 802.41 mW h g-1, respectively. Fully charged TiSe was mechanically stable according to the calculated elastic constants. Our results show that the TiSe monolayer could be used as an excellent anode material for Li/Na/K-ion batteries.

Metal-organic framework derived inverse opal type 3D graphitic carbon for highly stable lithium-ion batteries

Graphitic carbon-based anodes for lithium-ion batteries have seen remarkable development and commercial acceptance during the past three decades. Still, the performance of these materials is limited due to the low surface area, stacking of layers, poor porosity, and meager conductivity. To overcome these limitations, we propose using polystyrene as a core and small-sized zeolitic imidazolate framework-67 (ZIF-67) particles as decorators to develop a highly porous three-dimensional graphitic carbon material. The developed material is optimized with the carbonization temperature for the best anodic performance of LIBs. The pyridinic nitrogen content in the material carbonized at 700 °C makes it high performing and more stable than the samples treated at 600, 800, and 900 °C. The packed coin cell exhibited an initial discharge capacity of 775 mA h g-1 at a current density of 50 mA g-1, which increases to 806 mA h g-1 after testing the material at different current densities for 55 cycles. The packed half-cell exhibited a highly stable performance of about 96% even after testing for 2000 cycles at 1 A g-1.

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.

Silicon nanoparticles encapsulated in Si3N4/carbon sheaths as an anode material for lithium-ion batteries

Novel composite materials comprising of silicon nanoparticles (SiNPs) encapsulated with thin layers of silicon nitride and reduced graphene oxide shells (Si@Si₃N₄@rGO) are prepared using a simple and scalable method. The composite exhibits significantly improved cycling stability and rate capability compared to bare SiNPs. The presence of inactiveαandβphases of Si₃N₄increases the mechanical endurance of SiNPs. Amorphous SiN_x, which is possibly present with Si₃N₄, also contributes to high capacity and Li-ion migration. The rGO sheath enhances the electronic conduction and improves the rate capability. 15-Si@Si₃N₄@rGO, which is prepared by sintering SiNPs for 15 min at 1300 °C, spontaneous-coating GO on Si@Si₃N₄, and reducing GO to rGO, delivers the highest specific capacity of 1396 mAh g^-1after 100 cycles at a current density of 0.5 A g^-1. The improved electrochemical performance of 15-Si@Si₃N₄@rGO is attributed to the unique combination of positive effects by Si₃N₄and rGO shells, in which Si₃N₄mitigates the issue of large volume changes of Si during charge/discharge, and rGO provides efficient electron conduction pathways. Si@Si₃N₄@rGO composites are likely to have great potential for a high-performance anode in lithium-ion batteries.

NiFe-LDH/MXene nano-array hybrid architecture for exceptional capacitive lithium storage

Layered double hydroxides (LDHs) have great advantages in the domain of energy storage because of their exchangeable anions and large specific surface area. Nevertheless, the shortcomings of their poor electrical conductivity, easy stacking of nanosheets, and large volume variation in the cycling processes lead to unsatisfactory cycling stability and rate performance, which severely limits their further application. Therefore, we generated homogeneous nanoarrays of NiFe-LDH on the surface of Ti₃C₂T_x-MXene by a refluxing process. The resulting NiFe-LDH/MXene-500 hybrid material was applied as an anode of a lithium-ion battery (LIB) and exhibited a discharge capacity of 894.8 mA h g^-1 at 200 mA g^-1 (over 300 cycles) and could maintain a reversible capacity of 547.1 mA h g^-1 even at 1 A g^-1. With the addition of MXene, the volume increases of the NiFe-LDH/MXene hybrid materials were also significantly alleviated. The thickness of the NiFe-LDH/MXene-500 electrode only increased by 31% after 50 cycles, which was far better than the prepared NiFe-LDH electrode. On the hand, the synergistic interaction of NiFe-LDH and MXene could stabilize the structure, reduce the activation barrier of ion/electron diffusion, and promote electron transfer in the electrode. MXene with high conductivity can be used as electrical and ionic conductance media to promote the transformation reaction of NiFe-LDH. According to the detailed kinetic analysis, the capacitance control behavior is the main electrochemical reaction of NiFe-LDH/MXene electrodes.