Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/66—Electroplating: Baths therefor from melts
  • C25D3/665—Electroplating: Baths therefor from melts from ionic liquids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0438—Processes of manufacture in general by electrochemical processing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/386—Silicon or alloys based on silicon
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the invention relates to a method of manufacturing a silicon-based electrode and a silicon-based electrode. It also relates to a lithium battery comprising such an electrode.
• anode materials that are materials capable of integrating lithium in the form of alloys, and in particular silicon alloys. These silicon-based anodes can often incorporate higher amounts of lithium per unit mass relative to the lithium exchanging anodes through the intercalation mechanism.
• the electrodes described herein have relatively low properties of reversibility and efficiency because of their tendency to change volume during lithiation and delithiation cycles. This change in volume may result in the deterioration of the electrical contact between the active material grains of the anode. The deterioration of the electrical contact, in turn, leads to a decrease in the capacitance, that is to say the amount of lithium that can be incorporated per unit mass of the anode active material, throughout the entire period. lifetime of the anode.
• the silicon film is 100 nm thick, with a capacity of 50 ⁇ Ah / cm 2 , which is low. This gives a mass capacity of 3000 mAh / g very important, unusable in lithium-ion batteries that generally have capacities of 320 mAh / g for thicknesses of 300 to 400 microns.
• the first reason is that the morphology and the electrical capacitance of the electrodeposited materials strongly depend on the regime of the deposit.
• a potentiostatic deposit promotes instant nucleation followed by three-dimensional growth (3D Volmer-Weber) with a fairly long deposition time, of the order of 60 to 90 minutes.
• 3D Volmer-Weber three-dimensional growth
• the deposited material is compact and homogeneous, sometimes with a lower surface roughness than that of the support. This leads to less attractive properties for electrochemical applications, particularly in lithium-ion batteries.
• the second reason is that the potentiostatic electrodeposition regime leads to the following reaction on the surface of the support:
• the aim of the invention is to overcome the drawbacks of the prior art methods for preparing electrodes, in particular negative for lithium-ion batteries, and to provide a method for preparing such electrodes for obtaining amorphous silicon base, of nanometric size, having a significant stability of their capacity throughout their lifetime and which does not lead to the presence of chloride ions in the pores of the silicon film.
• the invention proposes a method for manufacturing a silicon-based electrode of the type comprising a step of electrochemical deposition of silicon on a substrate, characterized in that the electrochemical deposition step is an electrochemical deposition step by cyclic voltammetry in a solution comprising at least one ionic liquid and a silicon precursor of formula Si n X2n + 2, in which X is Cl, Br or I and n is equal to 1 or 2.
• the silicon precursor has the formula Si n Cl2n + 2 in which n is 1 or 2.
• the silicon precursor is silicon tetrachloride, of formula SiCl 4.
• the ionic liquid is selected from N - butyl - N - methyl pyrrolidinium bis (trifluoromethanesulfonyl) imide, N - ethyl - N, N - dimethyl - N (2 - methoxyethyl) ammonium bis (thfluoromethanesulfonyl) imide and the N - methyl - N - propyl piperidinium bis (trifluoromethylsulfonyl) imide.
• the substrate is a stable conductive material up to a potential of -4V relative to a saturated KCt (ECS) calomel electrode.
• ECS saturated KCt
• the substrate is of a material selected from the group consisting of copper, nickel, stainless steel, vitreous carbon, graphite, and composite materials based on graphite and / or carbon black and / or or carbon nanotubes. Most preferably, the substrate is a copper substrate.
• the invention also provides an electrode comprising a substrate covered with a silicon film consisting of silicon nanoparticles amorphous, which can in particular be obtained by the method of manufacturing an electrode of the invention.
• FIG. 1 represents the potential scan curve used for the deposition of silicon on the surface of a copper substrate, at a potential sweep rate of 100 mV / s
• FIG. 2 represents the potential sweep curve of a button cell having a counter-electrode lithium metal and as working electrode, the electrode obtained by the potential scan of FIG. 1, at a scanning speed of 0.1mV / s
• FIG. 3 represents the cycling resistance curve of the button cell of FIG. Figure 2 in galvanostatic regime, C / 20, that is to say, the total theoretical capacity is reached in 20 hours, between 0V and 1.5V.
• Electrochemical deposition by cyclic voltammetry also called electrochemical deposition in potential sweep, is a deposition technique for imposing a linear sweep of potential as a function of time.
• the silicon nucleation mechanism is complex, resembling the growth mechanism "layer by layer with growth of the islands" (3D Stranski - Krastanov).
• the potential sweep facilitates the nucleation of the silicon on the surface of the support, which makes it possible to reach a large deposition area without loss of roughness relative to the support. Therefore, the highest values of specific capacity and cycling stability of conductive or semiconductor materials deposited in this way are obtained when the deposition is performed by electrochemical deposition by cyclic voltammetry.
• the process for preparing a silicon-based electrode for obtaining nanoparticulate and amorphous silicon used in the invention is the electrochemical deposition by cyclic voltammetry in a solution of an ionic liquid or a mixture of liquids. ionic, this solution further containing a silicon precursor of formula Si n X2n + 2 wherein X is Cl, Br or I, most preferably Cl, and n is 1 or 2, preferably n is 1.
• the method of electrochemical deposition by cyclic voltammetry makes it possible to deposit the semiconductor, in this case silicon, at the potential of reducing the precursor, in this case SiCl 4 , and then to sweep potential towards the positive potentials in order to evacuate the chlorides by releasing the chlorine.
• SiCl 4 the reaction that occurs is as follows:
• the potential scan curve used in the method of the invention is shown in Figure 1.
• the silicon reduction currents and oxidation CI ions "increases from one cycle to the another, because the surface of electrodeposited silicon is increasingly important because each cycle is deposited a new atomic layer of silicon.
• the ionic liquid used in the invention may be any of the known ionic liquids containing a cation associated with an anion. In other words, the whole family of ionic liquids can be used in the invention. Among these ionic liquids, mention may be made of ionic liquids containing quaternary ammonium ions such as 1-ethyl-3-methylimidazolium, 1-methyl-3-propylimidazolium, 1-methyl-3-isopropylimidazolium, 1-butyl-3 methyl imidazolium, 1 - ethyl - 2,3 - dimethylimidazolium, 1 - ethyl - 3,4 - dimethylimidazolium, N - propylpyridinium, N - butylpyridinium, N - tert - butylpyridinium, N - tert - butanol pentylpyridinium, N - methyl - N - prop
• ionic liquids containing ammonium ions such as butyl ions - N - N 1 N 1 N - trimethyl ammonium, N - ethyl - N 1 N - dimethyl - N - propyl ammonium chloride, N - butyl - N - ethyl - N, N - dimethyl ammonium, butyl and N - N1 N - dimethyl - N - propyl ammonium, associated with any anion such as the anion group consisting of a tetrafluoroborate (BF 4), hexafluorophosphate (PF 6 ), a bis (trifluoromethanesulfonyl) amide (TFSI) or anions bis (trifluorosulfonyl) amides (FSI).
• BF 4 tetrafluoroborate
• PF 6 hexafluorophosphate
• TFSI bis (trifluoromethanesulf
• the ionic liquid is preferably N - butyl - N methyl pyrrolidinium bis (trifluoromethanesulfonyl) imide or N - ethyl - N 1 N - dimethyl - N (2methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide or N methyl - N - propyl piperidinium bis (trifluoromethylsulfonyl) imide.
• the silicon is deposited by electrochemical deposition by cyclic voltammetry on a substrate which acts as a working electrode during the deposition of silicon and as a support for the silicon film formed in the electrode obtained by the invention.
• the materials for the substrate may be selected in a non-exhaustive manner from copper, nickel, stainless steel, graphite, or carbon black, or glassy carbon or composite materials with or without a graphite-based binder and / or carbon black, such as for example a carbon black coated copper foil or carbon nanotubes.
• the bottom line is that the substrate is a stable conductive material up to a potential of -4V versus a saturated KCt calomel electrode.
• the substrate will have a large surface area on the side on which the silicon is electrodeposited, this specific surface being either natural or artificially obtained, for example using abrasive paper.
• composite materials will be preferred because they naturally have a significant specific surface area of the order of 2m 2 / g, which is sufficient to obtain satisfactory deposits of specific surface area.
• This large surface area of the substrate thus makes it possible to obtain a deposit of a large active surface, which leads to a large area of deposited materials.
• the method of electrochemical deposition of silicon by cyclic voltammetry makes it possible to obtain a homogeneous deposition of silicon over a large area, and therefore a large capacity.
• the specific surface area of a composite is calculated from the specific surfaces of the elementary components, for example those provided by the TIMCAL Company.
• the substrate was a 4cm 2 copper foil.
• the deposition solution consisted of an ionic liquid which was N - butyl - N methyl pyrrolidinium bis (trifluoromethanesulfonyl) imide reference P14TFSI, marketed by Solvionic, with a purity of 99.99%, saturated with pure SiCl 4 . 99.9% marketed by Aldrich.
• the deposition of the silicon on the substrate was carried out in a three-electrode glass cell, with a platinum wire as a counter-electrode and a platinum wire in the ionic liquid placed in a compartment separated by a fried glass, as the electrode of almost reference.
• the potential of the ferrocene / ferricenium redox pair, denoted Fc / Fc + in the solution of the ionic liquid with respect to this electrode is 55OmV.
• This ferrocene / ferricenium redox pair is also used as a reference when it is not possible to use a calomel electrode saturated with KC. It has a potential of 0.4V compared to ECS. All the manipulations were carried out in a glove box containing less than 1 ppm of O 2 and H 2 O. The ionic liquid was dried under vacuum at 80 ° C. for 12 h and then the electrochemical deposition by cyclic voltammetry was carried out. using a scan speed of 50 mV / s starting at OV and then down to -3.2V, then sweeping to the positive potential up to 0.3V. The VoltaLab 50 potentiostat (PST050) was used to monitor the potential.
• the silicon film prepared in this manner was rinsed several times with isopropanol to remove residual ionic liquid and silicon tetrachloride. It was then dried under vacuum at room temperature for one hour.
• the copper foil coated with the silicon film having a thickness of 30 nm was cut into pellets with a diameter of 14 mm, ie a surface of 1.54 cm 2 .
• a silicon-based electrode made of a substrate coated with a 30 nm silicon film was obtained.
• Electrochemical cells of the "button cell” type were assembled with lithium metal as a negative electrode, a microporous separator, which is a commercial Celgard ® polymer, using as the electrolyte the ionic liquid N - butyl - N - methyl pyrrolidinium bis (trifluoromethanesulfonyl) ) imide used for the deposition of silicon, plus lithium bis (trifluoromethanesulfonyl) imide, LiTFSI, and copper foil with its deposited silicon film, as a positive electrode.
• LiTFSI had a purity of 99%, and was marketed by 3M. This system has been tested in cyclic voltammetry using the multipotentiostat (VMP System, Biology). The scanning speed was 0.1 mV / s.
• Figure 2 shows the potential scan curve obtained with this button cell.
• the electrochemical behavior is very stable.
• the two characteristic peaks of lithium de-insertion at the anode do not change during cycling.
• the cycling resistance curve of the button cell obtained in this example is shown in FIG. 3. As can be seen in FIG. 3, the capacity of the button cell obtained is constant both in charge and in discharge for more than fifteen cycles. .
• the substrate was a 4 cm 2 copper foil that was used as a working electrode for silicon deposition.
• Silicon deposition was performed by cyclic voltammetry in a three electrode glass cell, with a platinum wire as the counter electrode and a platinum wire in the ionic liquid which consisted of N - ethyl - N, N - dimethyl - N (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide (EDMMEATFSI, Solvionic, purity 99.99%) and which contained, as precursor of silicon, SiCl 4 silicon tetrachloride with a purity of 99.9%, marketed by Aldrich .
• the platinum wire in the ionic liquid EDMMEATFSI was placed in the separate compartment by a fried glass as a quasi-reference electrode.
• the potential of Fc / Fc + in the solution of the ionic liquid with respect to this electrode is 55OmV.
• the deposition solution consisted of the ionic liquid saturated with SiCl 4 . All the manipulations were carried out in a glove box in an atmosphere containing less than 1 ppm O 2 and H 2 O. The ionic liquid was dried under vacuum at 80 ° C. for 12 hours before the electrochemical deposition.
• the electrochemical deposition was carried out using the cyclic voltammetry technique, with a scanning speed of 50mV / s, a scan start at 0V and then a descent at -3.2V, then a scan towards the positive potential up to 0.3V.
• the VoltaLab 50 potentiostat (PST050) was used to monitor the potential. To obtain a deposit of a silicon film of about 30 nm, fifteen scanning cycles were necessary. The silicon film prepared in this manner was rinsed several times with isopropanol to remove the residual ionic liquid and silicon tetrachloride, and then dried under vacuum at room temperature for 1 h.
• the copper foil has been cut into pellets of a diameter of
• Electrochemical cells of the "button cell” type were assembled with lithium metal as negative electrode, a microporous separator, an LP100 electrolyte.
• the LP100 electrolyte is a Merck commercial electrolyte, consisting of LiPF 6 (lithium hexafluorophosphate)
• the substrate is a plate made of a composite material made of: graphite MCMB2528 "Mesocarbon microbeads" which is a material made of natural and artificial graphite and carbon fibers used by the lithium batteries supplied by the Osaka Gas Company, carboxymethyl cellulose (CMC), NBR, i.e. the aqueous solution of Perbunan - N - Latex, supplied by Polymer Latex GmH, as a binder, and
• TIMCAL company as electronic conductor coated on a copper sheet.
• This plate served as a working electrode for depositing silicon to form the electrode according to the invention.
• the geometric area of the plate used for the deposit was 4cm 2 .
• the working electrode made of composite material described above was dried under vacuum for 24 hours at 80 ° C. before silicon deposition.
• Silicon deposition was performed in a three-electrode glass cell, with a platinum wire as the counter-electrode and a platinum wire in the ionic liquid which was N-ethyl-N, N-dimethyl-N (2).
• -methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide (EDMMEATFSI, Solvionic, 99.99%) placed in the separated compartment by the fried glass as a quasi-reference electrode.
• the Fc / Fc + potential in the ionic liquid solution with respect to this electrode is 55OmV.
• the deposition solution consisted of SiCI 4 saturated ionic liquid (99.9%, Aldrich). All manipulations related to the deposition of silicon and the preparation of electrochemical cells of the button cell type were made in a glove box containing an atmosphere containing less than 1 ppm of O 2 and H 2 O. The ionic liquid was dried under vacuum at 80 ° C. for 12 hours before electrodeposition. Silicon deposition was carried out in this cell by electrochemical deposition by cyclic voltammetry, with a scanning speed of 20mV / s, with a start of scanning at OV then descent at -3.2V and then scanning towards the positive potential up to 0.3V. The VoltaLab 50 potentiostat (PST050) was used to monitor the potential.
• the capacity of the button cell obtained is still constant and stable, as in the previous examples.
• the deposition method of the invention makes it possible to deposit a controlled thickness of a material which maintains the same properties throughout its thickness, in particular its amorphous nature, which allows this great reversibility of the material during the course of operation. battery.
• the method of preparing an anode according to the invention makes it possible to prepare silicon-based electrodes having a good life, and a constant capacity during its lifetime.
• the electrode of the invention therefore consists of a support coated with an amorphous silicon film having a large specific surface area. It has a stable capacity of about 2300 mAh / g.
• the electrode of the invention is particularly suitable for the manufacture of lithium batteries.
• silicon tetrachloride has been used as silicon precursor
• any other silicon precursor of formula Si n X 2n + 2 in which X represents a halogen such as chlorine, iodine or bromine and n is 1 or 2 may be used.

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• 2008
  • 2008-02-26 FR FR0801032A patent/FR2928036B1/fr not_active Expired - Fee Related
• 2009
  • 2009-02-11 EP EP09718818A patent/EP2260526A2/de not_active Withdrawn
  • 2009-02-11 CN CN2009801066060A patent/CN101981731A/zh active Pending
  • 2009-02-11 US US12/919,298 patent/US20110183205A1/en not_active Abandoned
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