RESUMO
Nickel-rich layered oxide cathodes, such as LiNi0.5Co0.2Mn0.3O2 (NCM523), are prevalent in high-power batteries owing to their high energy density. However, these cathodes suffer from undesirable side reactions occurring at the cathode/liquid electrolyte interface, leading to inferior interface stability and poor cycle life. To address these issues, herein, an amphiphilic diblock copolymer poly(dimethylsiloxane)-block-poly(acrylic acid) (PDMS-b-PAA) along with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is utilized for modifying the electrode surface. This modification causes a thin and stable cathode-electrolyte interface (CEI) on the surface of NCM523 particles, as evidenced by XPS, TEM, and EIS analysis. The introduction of this modified interface successfully suppresses the capacity fading of NCM523. After 200 cycles at a rate of 1.0 C, the capacity of the modified NCM523 cathode is 108.7 mAh g-1, with a capacity retention of 82.8%, while the control samples without the polymer modification display a capacity retention of 72.7%. These results outline the distinct advantage of electrode surface modification with diblock copolymers/LiTFSI for the stabilization of Ni-rich layered oxide cathodes.
RESUMO
Lithium-ion batteries (LIBs) have been widely applied and studied as an effective energy supplement for a variety of electronic devices. Titanium dioxide (TiO2 ), with a high theoretical capacity (335 mAh g-1 ) and low volume expansion ratio upon lithiation, has been considered as one of the most promising anode materials for LIBs. However, the application of TiO2 is hindered by its low electrical conductivity and slow ionic diffusion rate. Herein, a 2D ultrathin mesoporous TiO2 /reduced graphene (rGO) heterostructure is fabricated via a layer-by-layer assembly process. The synergistic effect of ultrathin mesoporous TiO2 and the rGO nanosheets significantly enhances the ionic diffusion and electron conductivity of the composite. The introduced 2D mesoporous heterostructure delivers a significantly improved capacity of 350 mAh g-1 at a current density of 200 mA g-1 and excellent cycling stability, with a capacity of 245 mAh g-1 maintained over 1000 cycles at a high current density of 1 A g-1 . The in situ transmission electron microscopy analysis indicates that the volume of the as-prepared 2D heterostructures changes slightly upon the insertion and extraction of Li+ , thus contributing to the enhanced long-cycle performance.
RESUMO
Dendritic copper offers a highly effective method for synthesizing porous copper anodes due to its intricate branching structure. This morphology results in an elevated surface area-to-volume ratio, facilitating shortened electron pathways during aqueous and electrolyte permeation. Here, we demonstrate a procedure for a time- and cost-efficient synthesis routine of fern-like copper microstructures as a host for polymer-templated Si/Ge/C thin films. Dissolvable Zintl clusters and sol-gel chemistry are used to synthesize nanoporous coating as the anode. Cyclic voltammetry (CV) with KOH as the electrolyte is used to estimate the surface area increase in the dendritic copper current collectors (CCs). Half cells are assembled and tested with battery-related techniques such as CV, galvanostatic cycling, and electrochemical impedance spectroscopy, showing a capacity increase in the dendritic copper cells. Energy-dispersive X-ray spectroscopy is used to estimate the removal of K in the bulk after oxidizing the Zintl phase K12Si8Ge9 in the polymer/precursor blend with SiCl4. Furthermore, scanning electron microscopy images are provided to depict the thin films after synthesis and track the degradation of the half cells after cycling, revealing that the morphological degradation through alloying/dealloying is reduced for the dendritic Cu CC anodes as compared with the bare reference. Finally, we highlight this time- and cost-efficient routine for synthesizing this capacity-boosting material for low-mobility and high-capacity anode coatings.
RESUMO
Poly(ethylene oxide) (PEO)-based composite electrolytes (PCEs) are considered as promising candidates for next-generation lithium-metal batteries (LMBs) due to their high safety, easy fabrication, and good electrochemical stability. Here, we utilize operando grazing-incidence small-angle and wide-angle X-ray scattering to probe the correlation of electrochemically induced changes and the buried morphology and crystalline structure of the PCE. Results show that the two irreversible reactions, PEO-Li+ reduction and TFSI- decomposition, cause changes in the crystalline structure, array orientation, and morphology of the PCE. In addition, the reversible Li plating/stripping process alters the inner morphology, especially the PEO-LiTFSI domain radius and distance between PEO-LiTFSI domains, rather than causing crystalline structure and orientation changes. This work provides a new path to monitor a working battery in real time and to a detailed understanding of the Li+ diffusion mechanism, which is essential for developing highly transferable and interface-stable PCE-based LMBs.
RESUMO
Pattern fabrication by self-assembly of diblock copolymers is of significant interest due to the simplicity in fabricating complex structures. In particular, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) is a fascinating base material as it forms an ordered micellar structure on silicon surfaces. In this work, silver (Ag) is applied using direct current magnetron sputter deposition and high-power impulse magnetron sputter deposition on an ordered micellar PS-b-P4VP layer. The fabricated hybrid materials are structurally analyzed by field emission scanning electron microscopy, atomic force microscopy, and grazing incidence small angle X-ray scattering. When applying simple aqueous posttreatment, the pattern is stable and reinforced by Ag clusters, making micellar PS-b-P4VP ordered layers ideal candidates for lithography.
RESUMO
The Ni-rich cathode holds great promise for high energy density lithium-ion batteries because of its high capacity and operating voltage. However, crucial problems such as cation disorder, structural degradation, side reactions, and microcracks become serious with increasing nickel content. Herein, a novel and facile sol/antisolvent coating modification of Ni-rich layered oxide LiNi0.85Co0.1Mn0.05O2 (NCM) is developed where we use ethanol to disperse the nanosized LiBO2 to form the sol and adopt tetrahydrofuran (THF) as antisolvent to prepare the cluster of nanoparticles to be coated on the surface of NCM. The coating thickness can be tuned through the THF addition amount. The LiBO2 nanorod deposition is formed as well over the crack of the NCM cathode, likely acting as a patch to repair the original defect of the intrinsic crack. The uniform LiBO2 nanospherical particle coating together with LiBO2 nanorod wrapping provides a double protection against electrolytes. Compared with the raw material, LiBO2-coated LiNi0.85Co0.1Mn0.05O2 (LiBO2-coated NCM) exhibits a high initial Coulombic efficiency of 90.3% at 0.2 C between 2.8 and 4.3 V vs Li+/Li, a superior rate capability, enhanced fast charge property at 3 C, and restricted microcrack formation. This simple in-site modification and repairing technology guarantees a good mechanical integrity of the polycrystalline Ni-rich cathode.
RESUMO
Antimony (Sb) has been regarded as one of the most promising anode materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) and attracted much attention in recent years. Alleviating the volumetric effect of Sb during charge and discharge processes is the key point to promote Sb-based anodes to practical applications. Carbon dioxide (CO2) activation is applied to improve the rate performance of the Sb/C nanohybrid anodes caused by the limited diffusion of Li/Na ions in excessive carbon components. Based on the reaction between CO2 and carbon, CO2 activation can not only reduce the excess carbon content of the Sb/C nanohybrid but also create abundant mesopores inside the carbon matrix, leading to enhanced rate performance. Additionally, CO2 activation is also a fast and facile method, which is perfectly suitable for the fabrication system we proposed. As a result, after CO2 activation, the average capacity of the Sb/C nanohybrid LIB anode is increased by about 18 times (from 9 mA h g-1 to 160 mA h g-1) at a current density of 3300 mA g-1. Moreover, the application of the CO2-activated Sb/C nanohybrid as a SIB anode is also demonstrated, showing good electrochemical performance.