Influence of a binder on the electrochemical behaviour of Si/RGO composite as negative electrode material for Li-ion batteries

Received: 02.12.2020. Accepted: 21.12.2020. Published:30.12.2020.A composite consisting of silicon nanoparticles and reduced graphene oxide nanosheets (Si/RGO) was studied as a promising material for the negative electrode of lithium-ion batteries. Commonly used polyvinylidene fluoride (PVdF) and carboxymethyl cellulose (CMC) served as a binder. To reveal the influence of the binder on the electrochemical behaviour of the Si/RGO composite, binder-free electrodes were also prepared and examined. Anode half-cells with composites comprising CMC as a binder demonstrated the best properties: capacity over 1200 mAh·g–1, excellent cycling performance and good rate capability up to 1.0C.This work was performed with financial support from the Ministry of Science and Higher Education of Russian Federation, project ID RFMEFI60419X0235

Temperature Dependence of Initial Permeability of NixCo1-xFe2O4 Ferrite System

The aim of this work was to create and study of ferrite nickel-cobalt powders, using sol-gel technology with participation of auto-combustion. Dependence of the initial permeability from the degree of substitution of cobalt cations on nickel cations is obtained. It is revealed that the crystallite size has a significant influence on the magnetic properties of the samples. With decreasing of crystallite size of nickel-cobalt ferrite Curie temperature decreases. It is shown that the smaller the particle size, the greater the thickness of the surface layer with significant violations of magnetic structure. Keywords: sol-gel technology, nickel-cobalt ferrite, initial permeability, Curie temperature

SOLID ELECTROLYTE AND ELECTRODE-ACTIVATED MEMBRANE WITH ITS EMPLOYMENT

FIELD: solid polymer ion conductors, namely, ion-conducting polymer electrolytes which can be used in electrochemical devices, specifically, in electrode-activated membranes. SUBSTANCE: given solid electrolyte contains copolymer based on acrylonitrile and butadiene carrying over 17.0 per cent by mass bonds of acrylonitrile or copolymer based on acrylonitrile and butadiene containing over 17.0 per cent by mass bonds of acrylonitrile and additionally under 5.0 per cent by mass of monomer residue of unsaturated carbonic acid. Solid electrolyte contains cobalt chloride (II) in the capacity of inorganic salt of metal with following proportion of components, molecular per cent,: copolymer of acrylonitrile and butadiene 99.00- 99.80; cobalt chloride (II) 0.20-1.00. Electrode-activated membrane includes layer of solid polymer electrolyte and metal current tap in which layer of solid polymer electrolyte has composition in mole per cent: copolymer of acrylonitrile and butadiene containing over 17.0 per cent by mass bonds of acrylonitrile or copolymer based on acrylonitrile and butadiene containing over 17 per cent by mass bonds of acrylonitrile and additionally containing under 5.0 per cent by mass monomeric residue of unsaturated carbonic acid - 99.00-99.80 and cobalt chloride (II) -0.20-1.00 and is 10- 150 mcm thick. Solid polymer electrolyte of proposed composition has conductance of the order of 10-8Ohm-1cm-1 and cobalt (II) detection limit 10-6mole/l. Proposed solid polymer electrolyte can be utilized in electrode-activated membrane showing good operational characteristics and simple design. EFFECT: development of solid polymer electrolyte to detect ions of cobalt and of electrode-activated membrane with its use. 2 cl, 2 dwg.Изобретение относится к области твердотельных полимерных ионных проводников, а именно к ион-проводящим полимерным электролитам, которые могут быть использованы в электрохимических устройствах, в частности в электродно-активных мембранах. Твердый электролит содержит сополимер на основе акрилонитрила и бутадиена, содержащий не менее 17 мас.% звеньев акрилонитрила, или сополимер на основе акрилонитрила и бутадиена, содержащий не менее 17 мас.% звеньев акрилонитрила, и дополнительно не более 5 мас.% мономерных остатков непредельных карбоновых кислот, в качестве неорганической соли металла - хлорид кобальта II при следующем соотношении компонентов, мол.%: сополимер акрилонитрила и бутадиена 99,00-99,80, хлорид кобальта II 0,20-1,00. Электродно-активная мембрана содержит слой твердого полимерного электролита и металлический токоотвод, в которой слой твердого полимерного электролита имеет состав, моль.%: сополимер акрилонитрила и бутадиена, содержащий не менее 17 мас.% звеньев акрилонитрила, или сополимер на основе акрилонитрила и бутадиена, содержащий не менее 17 мас.% звеньев акрилонитрила и дополнительно содержащий не более 5 мас.% мономерных остатков непредельных карбоновых кислот, 99,00?99,80 и хлорид кобальта II - 0,20?1,00, и имеет толщину 10-150 мкм. Твердый полимерный электролит предлагаемого состава имеет проводимость порядка 10-8 Ом-1•см-1 и предел обнаружения кобальта II 10-6 моль/л. Предлагаемый электролит может быть использован в электродно-активной мембране, обладающей хорошими рабочими характеристиками, простой конструкции. Техническим результатом предложенного изобретения является разработка состава твердого полимерного электролита для обнаружения ионов кобальта, а также электродно-активной мембраны с его использованием простой конструкции. 2 с. п. ф-лы, 2 ил

Evaluation of the main processing parameters influencing the performance of poly(vinylidene fluoride – trifluorethylene) lithium ion battery separators

Poly(vinylidene fluoride – trifluorethylene) membranes are evaluated for lithium ion battery separator applications. Some of the main parameters affecting separator performance such as porosity, dehydration of lithium ions and processing technique (Li-ion uptake versus composite formation) are investigated. The polymer characteristics, as determined by infrared spectroscopy, do not change as a function of porosity, dehydration of lithium ions in the electrolyte solution or processing technique. The electrochemical impedance spectroscopy represented through the Nyquist plot, Bode plot and the ionic conductivity as a function of temperature, strongly depends on the aforementioned paramenters. The membrane that exhibits the highest ionic conductivity is a porous membrane without dehydration of lithium ions and prepared by the uptake technique. The performance of the membrane for battery applications are therefore strongly influenced both by porosity and processing technique.This work is funded by FEDER funds through the "Programa Operacional Factores de Competitividade – COMPETE" and by national funds by FCT- Fundação para a Ciência e a Tecnologia, project references Projects PTDC/CTM/69316/2006, project nºF-COMP-01-0124-FEDER-022716 (refª FCT PEst-C/QUI/UI0686/2011) and NANO/NMed-SD/0156/2007, and grants SFRH/BD/68499/2010 (C.M.C) and SFRH/BPD/63148/2009 (V.S.). The authors thank Celgard, LLC for kindly supplying their high quality membranes. The authors also thank support from the COST Action MP1003, 2010 ‘European Scientific Network for Artificial Muscles’