新能源电池领域导电剂技术的研究与产业化

二次电池已经被广泛开发并应用于各种领域,如大规模储能、便携式电子设备和电动汽车。作为锂离子电池的重要组成部分,主要通过构建导电网络来增加和保持电极的电子导电性,从而有效改善电池的电化学性能。导电剂虽然在锂离子电池成本的占比较小(2%左右),但相比于数十万亿级别的锂离子电池产业,导电剂也随之成为了千亿级别的产业。目前,主流导电剂为炭黑类、导电石墨类、气相生长碳纤维(VGCF)、碳纳米管和石墨烯。其中,炭黑类、导电石墨类和VGCF作为传统导电剂,其在活性物质间可形成点、线接触式导电网络;碳纳米管和石墨烯属于新型导电剂材料,其可分别形成线、面接触式导电网络。相对于单一导电剂,复合导电剂可使不同导电剂之间产生协同效应,从而表现出更优异的性能,因此新型导电剂与传统导电剂是高度统一的关系,在成本及性能的综合考量下,未来导电剂体系将逐步从单一化走向多元复合化。此外,我国导电剂长期依赖进口,近年来一些优秀企业在制备方法和分散技术方面逐步打破工艺壁垒,加速国产化进程。本工作将讨论碳纳米材料作为导电剂用于电池领域并改善电池电化学性能的相关工作,并进一步讨论导电剂的产业化现状前景。要点:(1)总结了导电剂对锂离子电池性能的影响。(2)介绍了导电剂的分散技术。(3)归纳了导电剂的制备方法。(4)讨论了导电剂的产业化现状和前景。

Effects of deformation processes on morphology,microstructure and corrosion resistance of LDHs films on magnesium alloy AZ31

Highly oriented Mg-Al layered double hydroxide(LDHs)films were deposited on magnesium alloy AZ31 with different deformation processes by an easy in-situ growth method.The characteristics of the films were investigated by optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM),and electrochemical,immersion and hydrogen evolution tests.The corrosion protection performance ranked the LDHs films as the increasing series:CS-LDHs(as-cast sample with LDHs)<AE-LDHs(asymmetric extrusion sample with LDHs)<SE-LDHs(symmetric extrusion sample with LDHs)<RS-LDHs(rolled sample with LDHs).A thicker and more compact LDH conversion coating was formed on the RS sample,and had the best corrosion protection performance.

Doublely-doped Mg-Al-Ce-V_(2)O_(7)^(4-)LDH composite film on magnesium alloy AZ31 for anticorrosion

A doublely-doped layered double hydroxide(LDH)film was produced on an anodized magnesium alloy AZ31.The Ce-doped Mg-Al LDH film was prepared by in-situ hydrothermal treatment method,and the intercalation of vanadate was realized by ion-exchange reaction.The structure,morphology and composition of as-prepared LDH film were investigated by X-ray diffractometer,field-emission scanning electronic microscope and energy dispersive spectrometry.Results indicated that a uniform and compact LDH film was formed and the intercalation of Ce^(3+)and vanadate would change the crystal structure of LDHs.The results of the potentiodynamic polarization,electrochemical impedance spectra,hydrogen evolution and corrosion weight loss tests showed the Ce^(3+)and vanadate anions significantly improve the impedance of LDH film,and the active double-doped LDH film could effectively protect the magnesium substrate from corrosion.

Enhanced protective coatings on Ti-10V-2Fe-3Al alloy through anodizing and post-sealing with layered double hydroxides

Anodic oxidation is a prevalent technique to introduce superior corrosion and wear resistance upon the surface of titanium(Ti)alloys,in which the selection of appropriate electrolytes and defect-sealing strategies is a key.This study aims to address such issues through anodizing Ti-10V-2Fe-3Al alloy in malic acid,followed by a post-sealing treatment with Mg-Al layered double hydroxides(LDHs).The characteristics of the samples were investigated using scanning electron microscopy(SEM),atomic force microscopy(AFM),glow discharge optical emission spectroscopy(GDOES),X-ray diffraction(XRD)and energy-dispersive X-ray spectroscopy(EDS).SEM micrographs reveals that the anodic coating had a surface full of bulges and cracks,and was almost sealed by the following LDHs treatment.XRD pattern indicate that the anodic coating was mainly consisted of amorphous TiO2 with a small fraction of anatase,but its crystallization degree was increased through the post-sealing.Moreover,electrochemical and tribological measurements demonstrate that corrosion current density was 2.8×10-6,2.0×10-7,5.9×10-9A cm-2,and wear rate was 1.45×10-3,1.30×10-4 and 6.90×10-5 mm3 N-1 m-1 for respective bare Ti-10V-2Fe-3Al alloy substrate,anodized specimens without and with the LDHs post treatment.Finally,a plausible wear mechanism was proposed.

Influences of pulse frequency on formation and properties of composite anodic oxide films on Ti-10V-2Fe-3Al alloy

A thick composite anodic oxide film was fabricated in an environmentally friendly malic acid electrolyte containing Poly Tetra Fluoro Ethylene(PTFE)nanoparticles on Ti-10V-2Fe-3Al alloys.The influence of pulse frequency on the morphology,microstructure and composition of composite anodic oxide films containing PTFE nanoparticles was investigated using Field Emission Scanning Electron Microscopy(FE-SEM)equipped with Energy Dispersive Spectroscopy(EDS),Atomic Force Microscopy(AFM)and Raman spectroscopy.The tribological properties in terms of the friction coefficient,wear loss and morphology of worn surfaces were measured by ball-ondisc tests.The electrochemical property was evaluated by potentiodynamic polarization.The results indicated that the titanium dioxide of composite anodic oxide films transformed from anatase to rutile with the change of pulse frequency,which could result from the electrochemical dynamic equilibrium.The combination of PTFE nanoparticles and malic acid electrolyte molecules can influence the energy fluctuation of electrochemical equilibrium and formation of composite anodic oxide films.Moreover,composite anodic oxide films fabricated under the condition of 1.0–2.0 Hz exhibited the best wear resistance and corrosion property.The schematic diagram of the film formation and PTFE nanoparticles spreading process under different frequencies was elucidated.