Dual Immobilization of SnOx Nanoparticles by N-Doped Carbon and TiO2 for High-Performance Lithium-Ion Battery Anodes

TiO2-modified two-dimensional composite of nitrogen-doped molybdenum trioxide nanosheets as a high-performance anode for lithium-ion batteries

Nitrogen-doped molybdenum trioxide (MoO3/NC) has drawbacks such as volume expansion during long-term charging and discharging cycles, which severely limit its further application. This work proposes the addition of titanium dioxide nanoparticles (TiO2 NPs) for performance improvement of MoO3/NC. TiO2 NPs embedded on the surface of a MoO3/NC nanosheet can alleviate its volume expansion and the accumulation of lithiated products and improve the conductivity of the electrode material. The results show that the MoO3/NC nanosheet decorated with TiO2 NPs (TiO2@MoO3/NC), when used as an electrode material, exhibited a discharge specific capacity of 419 mA h g-1 at a current density of 0.05 A g-1 and retained a discharge specific capacity of 517 mA h g-1 after 600 cycles at a current density of 1 A g-1.

SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.

Boosting the Lithium-Ion Transport Kinetics of Sn-Based Coordination Polymers through Ligand Aromaticity Manipulation

Tin-based compounds are promising anode materials for lithium-ion batteries owing to their low charge/discharge voltage and high theoretical capacity but are plagued by both huge volume expansion during cycling and complex synthetic procedures. Constructing a coordination network between Sn and the lithium-active organic matrix can effectively relieve the volume expansion and increase the lithium storage active site utilization. Herein, we report a facile method to prepare two one-dimensional Sn-based coordination polymers [Sn(Hcta)]n (1) and [Sn(Hbtc)]n (2) (H3cta = 1,3,5-cyclohexanetricarboxylic acid, H3btc = 1,3,5-benzenetricarboxylic acid) for lithium storage, which differ only in the aromaticity of the ligand. 2 with an aromatic ligand provided a reversible capacity of 833 mAh g-1 at 200 mA g-1 over 160 cycles, higher than that of 1 without an aromatic ligand due to the quick charge transfer. The reversible lithium storage reactions of metal centers and organic ligands and the volume expansion rate of Sn-based coordination polymers during cycling were studied by detailed characterization and density functional theory (DFT) calculations. This research revealed that the structural factor of ligand aromaticity in these Sn-based coordination polymers boosted the utilization of active sites and rapid charge transfer, offering a coordination chemistry strategy for the design and synthesis of advanced anode materials.

Freestanding and Flexible Interfacial Layer Enables Bottom-Up Zn Deposition Toward Dendrite-Free Aqueous Zn-Ion Batteries

Aqueous rechargeable zinc ion batteries are regarded as a competitive alternative to lithium-ion batteries because of their distinct advantages of high security, high energy density, low cost, and environmental friendliness. However, deep-seated problems including Zn dendrite and adverse side reactions severely impede the practical application. In this work, we proposed a freestanding Zn-electrolyte interfacial layer composed of multicapsular carbon fibers (MCFs) to regulate the plating/stripping behavior of Zn anodes. The versatile MCFs protective layer can uniformize the electric field and Zn²⁺ flux, meanwhile, reduce the deposition overpotentials, leading to high-quality and rapid Zn deposition kinetics. Furthermore, the bottom-up and uniform deposition of Zn on the Zn-MCFs interface endows long-term and high-capacity plating. Accordingly, the Zn@MCFs symmetric batteries can keep working up to 1500 h with 5 mAh cm^-2. The feasibility of the MCFs interfacial layer is also convinced in Zn@MCFs||MnO₂ batteries. Remarkably, the Zn@MCFs||α-MnO₂ batteries deliver a high specific capacity of 236.1 mAh g^-1 at 1 A g^-1 with excellent stability, and maintain an exhilarating energy density of 154.3 Wh kg^-1 at 33% depth of discharge in pouch batteries.

Facile Synthesis of Hybrid Anodes with Enhanced Lithium-Storage Performance Realized by a "Synergistic Effect"

Alloying-type anodes including Si- and Sn-based materials are considered the most exploitable anodes for high-performance lithium-ion batteries. However, problems of poor kinetics properties and structural failures such as grain pulverization and coarsening hinder their large-scale application. Herein, SnO₂/Si@graphite hybrid anodes, with nano-SnO₂ and nano-Si thoroughly mixed with each other and loaded onto graphite flakes, have been prepared by a facile ball milling method. Attributed to the "synergistic effect" between SnO₂ and Si, the mechanical stability and kinetics properties can be remarkably enhanced. Furthermore, graphite substrate supplies a fast electrically conductive path and buffers the volume expansion of active particles. Accordingly, SnO₂/Si@graphite delivers 798.9 mAh g^-1 at 200 mA g^-1 and maintains 550.8 mAh g^-1 after 1000 cycles at 1 A g^-1 in half cells. Impressively, a high energy density of 431.4 Wh kg^-1 (based on the mass of anode and cathode) can be obtained in full cells when paired with the NCM622 cathode. This work presents an effective strategy to exploit high-performance alloying-type anodes for LIBs by designing hybrid materials with multiple active components.

Nitrogen-Doped Carbon-Encapsulated Ordered Mesoporous SiOx as Anode for High-Performance Lithium-Ion Batteries

SiO_x (0<x<2) has been broadly investigated as a promising anode in lithium-ion batteries (LIBs) due to its high theoretical capacity, low cost, and proper working voltage. Nevertheless, its practical application is hindered by volume expansion during the lithiation process and low electrical conductivity, resulting in rapid capacity decay. Herein, we designed a core-shell structured nitrogen-doped carbon-encapsulated ordered mesoporous SiO_x composite (SiO_x @NC) using 3-aminophenol-formaldehyde (3-AF) as carbon and nitrogen precursor, tetraethyl orthosilicate (TEOS) as the silica precursor, and cationic surfactant cetyltrimethylammonium bromide (C₁₆ TAB) as the mesoporous template. The obtained composite electrode not only can effectively reduce the volume expansion, but also can effectively improve electronic conductivity and further enhance the charge and ion transfer kinetics. Benefiting from the unique structural merits, the obtained SiO_x @NC-2 delivers a high reversible capacity of 602.4 mAh g^-1 at 0.1 A g^-1 after 100 cycles and long-term cyclability (maintain 426.1 mAh g^-1 over 1000 cycles at 1 A g^-1 ).

Heterostructural Sn/SnO2 microcube powders coated by a nitrogen-doped carbon layer as good-performance anode materials for lithium ion batteries

The nitrogen-doped carbon (NC) coating encapsulating heterostructural Sn/SnO₂ microcube powders (Sn/SnO₂@NC) are successfully fabricated through hydrothermal, polymerization of hydrogel, and carbonization processes, in which the SnO precursor powders exhibit regular microcube structure and uniform size distribution in the presence of optimized N₂H₄·H₂O (3.0 mL of 1.0 mol/L). Interestingly, the precursor powders are easily subjected to a disproportionated reaction to yield the desirable heterostructural Sn/SnO₂@NC microcube powders after being calcined at 600 °C in N₂ atmosphere in the presence of home-made hydrogel. The coin cells assembled with the Sn/SnO₂@NC electrode present a high initial discharge specific capacity (1058 mAh g^-1 at 100 mA g^-1), improved rate capability (an excellent D_Li+ value of 2.82 × 10^-15 cm² s^-1) and enhanced cycling stability (a reversible discharge specific capacity of 486.5 mAh g^-1 after 100 cycles at 100 mA g^-1). The enhanced electrochemical performance can be partly ascribed to the heterostructural microcube that can accelerate the transfer rate of lithium ions by shortening the transmission paths, and be partly to the NC coating that can accommodate the volume effect and contribute to partial lithium storage capacity. Therefore, the strategy may be able to extend the fabrication of Sn/SnO₂ heterostructural microcube powders and further application as promising anode materials in lithium ion batteries.