Enabling the Transport Dynamics and Interfacial Stability of Porous Si Anode Via Rigid and Flexible Carbon Encapsulation for High-Energy Lithium Storage.

The stable electrode/electrolyte interface and fast electron/ion transport channel play important roles in boosting the rate performance and cycling life of lithium-ion batteries. Herein, a porous silicon/carbon composite (pSi@PC@MC) is presented by integrating hollow porous silicon (pSi) with pitch-derived carbon (PC) and dopamine-derived mesoporous carbon (MC), employing microporous zeolite as the silicon source. The finite element simulation first reveals the stress release effect of rigid and flexible carbon encapsulation on the hollow Si anode for lithium-ion storage. In situ and ex situ characterization results further elucidate that hybrid sp2/sp3 carbon coating greatly enhances the liquid/solid interface stability and the compatibility with the electrolyte, as well as facilitates the electron/ion transmission dynamics, achieving a uniform, stable, and LiF-rich SEI film, ultimately improving the lithium storage performance. As expected, the as-designed pSi@PC@MC anode delivers an impressive rate capability (756.6 mAh g-1 at 6 A g-1) and excellent cycling stability with a capacity of 1650 mAh g-1 after 300 cycles at 0.2 A g-1. Meanwhile, the pSi@PC@MC//NCM811 full-cell exhibits an outstanding cycling stability (75.8% capacity retention after 100 cycles). This study highlights the significance of rational porous design and effective hybrid carbon encapsulation for the development of fast-charging Si/carbon anodes.

Flexible, Mechanically Robust, Solid-State Electrolyte Membrane with Conducting Oxide-Enhanced 3D Nanofiber Networks for Lithium Batteries.

Using a three-dimensional (3D) Li-ion conducting ceramic network, such as Li7La3Zr2O12 (LLZO) garnet-type oxide conductor, has proved to be a promising strategy to form continuous Li ion transfer paths in a polymer-based composite. However, the 3D network produced by brittle ceramic conductor nanofibers fails to provide sufficient mechanical adaptability. In this manuscript, we reported a new 3D ion-conducting network, which is synthesized from highly loaded LLZO nanoparticles reinforced conducting polymer nanofibers, by creating a lightweight continuous and interconnected LLZO-enhanced 3D network to outperform conducting heavy and brittle ceramic nanofibers to offer a new design principle of composite electrolyte membrane featuring all-round properties in mechanical robustness, structural flexibility, high ionic conductivity, lightweight, and high surface area. This composite-nanofiber design overcomes the issues of using ceramic-only nanoparticles, nanowires, or nanofibers in polymer composite electrolyte, and our work can be considered as a new generation of composite electrolyte membrane in composite electrolyte development.

Porous hybrid encapsulation enables high-rate lithium storage for a micron-sized SiO anode.

Establishing a durable interfacial layer between an electrode and electrolyte to enable micron-sized silicon-based lithium-ion battery (LIB) anodes to achieve superior electrochemical performance is highly desired. Recent studies have shown that heterogeneous encapsulation with enhanced ion/electron transport is an effective strategy. However, the structural design of the existing hetero-coated interface lacks a reasonable ion/electron transport channel, resulting in high interfacial impedance. Herein, we designed a heterogenous MXene-mesoporous polypyrrole (mPPy) encapsulation layer onto micron-sized SiO particles. The MXene coating layer functions as a bridging interface that can build a strong chemical link to internal SiO via covalent bonding, thus reinforcing interfacial charge transfer rate. Meanwhile, it forms a dynamic connection with the outer mPPy through hydrogen bonding, which contributes to high interfacial Li+ concentration and ion/electron coupling transport rate. Accordingly, the as-prepared SiO@MXene@mPPy anode delivers a boosted specific capacity of 673.9 mA h g-1 at 2 A g-1 after 1000 cycles and high-rate capability of 777.4 mA h g-1 at 5 A g-1. Further, electrochemical kinetic analysis indicates that the MXene@mPPy coating layer shows a pseudocapacitance controlled Li storage mechanism, thereby displaying improved high-rate capability. This porous hybrid encapsulation strategy offers new possibilities for a micron-sized SiO anode to achieve an excellent performance.

Dual structure engineering of SiOx-acrylic yarn derived carbon nanofiber based foldable Si anodes for low-cost lithium-ion batteries.

Silicon (Si) is attracted much attention due to its outstanding theoretical capacity (4200 mAh/g) as the anode of lithium-ion batteries (LIBs). However, the large volume change and low electron/ion conductivity during the charge and discharge process limit the electrochemical performance of Si-based anodes. Here we demonstrate a foldable acrylic yarn-based composite carbon nanofiber embedded by Si@SiOx particles (Si@SiOx-CACNFs) as the anode material. Since the amorphous SiOx and carbon (C) coating on the outside of the Si particles can provide a double buffer for volume expansion while reducing the contact between the Si core and the electrolyte to form a thin and stable solid electrolyte interface (SEI) film. Simultaneous in-situ electrochemical impedance spectroscopy (in-situ EIS) and galvanostatic intermittent titration technique (GITT) tests show that SiOx and C have higher ion/electron transport rates, and in addition, using acrylic fiber yarn and Zn(Ac)2 as raw materials reduces the manufacturing cost and enhanced mechanical properties. Therefore, the half-cell can achieve a high initial Coulombic efficiency (ICE) of 82.3% and a reversible capacity of 1358.2 mAh/g after 180 cycles. It can return to its original shape and remain intact after four consecutive folds, and the soft-pack full battery can also light up LED lights under different bending conditions.

Excimer ultraviolet-irradiated exfoliated graphite loaded with carbon-coated SnOx small nanoparticles as advanced anodes for high-rate-capacity lithium-ion batteries.

This paper reports a fast and efficient excimer ultraviolet (EUV) radiation method to prepare carbon-coated mixed tin oxide-loaded exfoliated graphite (SnOx@C-G) nanocomposites. The SnOx small nanoparticles (SNPs) are isolated using oxidized sucrose and uniformly deposited onto mildly oxidized exfoliated graphite during the 20-minute EUV radiation process. XPS and ESR analyses suggest the existence of abundant oxygen vacancies in the SnOx SNPs. The electrochemical kinetics of SnOx@C-G, which are determined by in situ electrochemical impedance analysis, demonstrated a high reversible capacity of approximately 740 mA h g-1 after 250 cycles at a current density of 1.6 A g-1, and an impressive reversible rate performance exceeding 450 mA h g-1 can be obtained even at a high current density of 3.2 A g-1 when applied as an anode for lithium storage. This improved cycling stability and rate capability benefit from the carbon coating, which not only buffers the volume change of SnOx SNPs but also provides a path for electron transport on the surface of the SnOx SNPs during the electrochemical process. Furthermore, the oxygen vacancies in SnOx SNPs result in a large capacitive contribution to capacity. The EUV radiation method used to synthesize SnOx@C-graphite nanosheets is universally applicable to prepare a high-performance SNPs/carbon-based anode for lithium-ion batteries.