WO2021006752A1 - Élément lithium-ion comprenant des collecteurs de courant tridimensionnels et procédé de fabrication d'électrodes pour cet élément - Google Patents

Élément lithium-ion comprenant des collecteurs de courant tridimensionnels et procédé de fabrication d'électrodes pour cet élément Download PDF

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WO2021006752A1
WO2021006752A1 PCT/PL2020/000059 PL2020000059W WO2021006752A1 WO 2021006752 A1 WO2021006752 A1 WO 2021006752A1 PL 2020000059 W PL2020000059 W PL 2020000059W WO 2021006752 A1 WO2021006752 A1 WO 2021006752A1
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Prior art keywords
carbon
current collector
active mass
porous
lithium
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PCT/PL2020/000059
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English (en)
Inventor
Bartosz HAMANKIEWICZ
Maciej RATYŃSKI
Piotr Podsadni
Karol Fijałkowski
Andrzej CZERWlŃlSKI
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Uniwersytet Warszawski
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Priority to EP20780375.0A priority Critical patent/EP3997750A1/fr
Publication of WO2021006752A1 publication Critical patent/WO2021006752A1/fr

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    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
    • 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
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/76—Containers for holding the active material, e.g. tubes, capsules
    • 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

  • a lithium-ion cell comprising three-dimensional current collectors
  • the present invention relates to a lithium-ion cell comprising three-dimensional current collectors, and a method of manufacturing electrodes for this cell.
  • Lithium-ion cells are currently one of the most popular types of electrochemical energy storage devices. Thanks to implementation of lithium oxidation-reduction reaction, which lithium is the lightest metal, Li-ion cells have a very high energy density and specific capacity. Lithium-ion cells reveal a working voltage in the range of 2.5-4.2 V. Due to the utilisation of two- dimensional construction of the electrodes, currently the specific energy of lithium-ion cells is limited to 240 Wh/kg, at most. This results from a limited thickness of the electrode mass covering metallic current collectors, which constitute 20-30% of the mass of the entire electrode.
  • lithium-ion cells which cells comprise different types of electrode materials.
  • Classic designs include a negative electrode (anode during discharge) made of carbon-based material (e.g. lithium intercalated in graphite) and a positive electrode (cathode during discharge) made of transition metal oxides: lithium-cobalt oxide (LCO), lithium-nickel- manganese-cobalt oxide (NMC), iron phosphoolivin (LFP) or lithium-manganese oxide (LMO) having molecular formula LiMn204 ["Lithium Batteries Science and Technology", Springer (2003)].
  • a cell comprising carbon material as the negative electrode and LMO as the positive electrode has a capacity of ca. 100 mAh/g and at room temperature loses ca. 20% of its original capacity after 200 cycles of operation. At elevated temperatures (60°C), the loss is higher than 50% after 100 galvanostatic charge/discharge cycles [Electrochim. Acta, 130 (2014) 778].
  • Electrodes of known lithium-ion cells usually have layered structure, where the active material (e.g. LTO, LMO, graphite) overlays a surface of a current collector, which is usually copper or aluminum foil.
  • the active material e.g. LTO, LMO, graphite
  • a foil of a thickness of ca. 10 pm is used, and the thickness of the active mass usually does not exceed 50 pm, which means that the metal foil, which is only a current collector, makes up about 20% of the electrode's volume.
  • the active layer cannot be too thick because of its low conductivity. Too thick active layer would not be fully used during the charging and discharging of the cell, and besides, it would have a tendency to crack, which would cause irreversible loss of the cell's capacity.
  • production of this type of electrodes requires high precision and care at the stage of manufacture of the electrode material and assembly of the cell.
  • Lithium-ion cells comprising three-dimensional, non-planar current collectors are known. Those collectors allow to deposit larger amount of active mass and without a need to use a multi-layer structure based on thin, flat electrodes. Among them there are metallic and carbon collectors [Adv. Mater., 30 (2016) 1802014.]. Carbon collectors are typically used in cathode construction as they would undergo intercalation with lithium under anodic conditions. In turn, metallic collectors are used in construction of both cathodes and anodes. There are known a three-dimensional metallic current collectors for lithium-ion cells, built of metals resistant to corrosion in the potential range of 2-5 V vs. Li for the cathode (e.g.
  • the anode e.g. copper
  • Metals such as nickel and stainless steel, which are resistant over a wide range of potentials, are also used.
  • the current collector structure is designed to maximise the ratio of pores volume to metal weight while maintaining optimal pore-size.
  • metallic reticulated foams are used, objects with an appropriate nano- or microstructure are created, or the so-called metallic paper of an appropriate thickness is used [Adv. Mater., 30 (2016) 1802014].
  • the use of relatively heavy metal collectors significantly reduces the gravimetric energy density of lithium- ion cells.
  • a lithium-ion cell having at least one three-dimensional carbon current collector wherein the three-dimensional carbon current collector of a thickness of 0.1-3.0 mm, preferably 1.0-2.0 mm, is made of porous conductive carbon with pores' size of 10-200 ppi, preferably 40-80 ppi, in form of a shaped element with the required target geometry, dimensions, shape, spatial architecture, relief and porosity, made in a manner not requiring mechanical treatment of the porous carbon material, which collector is filled with an active mass, preferably mixed with a solid or liquid electrolyte.
  • the three-dimensional carbon current collector has a cross-linked type morphology.
  • the three-dimensional carbon current collector has a reverse opal type morphology.
  • the three-dimensional carbon current collector is covered with a flexible conductive coating with a thickness of 1-20 pm, preferably 2-5 pm, preferably made of a chromium, nickel, titanium or aluminium alloy for cathode collectors, or made of a copper alloy for anode collectors, or made of platinum-group metals alloys or made of a conductive polymer, preferably polyaniline.
  • the three-dimensional carbon current collector after filling with active mass, is pressed to the desired size and shape.
  • the cell has both electrodes comprising three-dimensional carbon current collectors.
  • a method of manufacturing electrodes for a lithium-ion cell based on the use of three-dimensional carbon current collectors wherein the three-dimensional carbon current collector is produced in form of a porous conductive carbon shaped element with the required target the geometry, dimensions, shape, spatial architecture, relief and porosity, in a manner not requiring mechanical treatment of the porous carbon material, where the shaped elements have a porosity of 10-200 ppi, preferably 40-80 ppi, and the shaped elements are filled with an active mass, preferably mixed with a solid or liquid electrolyte.
  • the shaped elements made of porous conductive carbon with a cross-linked structure are made of a porous polymeric material, mechanically shaped, impregnated with a resin or a mixture of resins, and thermally hardened under controlled conditions using a graphite, carbon, ceramic or metal holder, and then carbonised at high temperature.
  • the shaped elements made of porous conductive carbon having a structure of a type of inverted opal are made of resin or a mixture of resins, mixed with polymeric spheres insoluble in this resin, with a diameter of 0.1-1.0 mm, preferably 0.4-0.6 mm, made of a polymer decomposing exclusively towards gaseous products at a temperature of 150-300°C, preferably 200-250°C, preferably made of polystyrene, constituting a spatial matrix of opal structure, which mixture is thermally hardened under controlled conditions using a graphite, carbon, ceramic or metal holder, followed by gasification of the spatial matrix and then carbonisation at high temperature.
  • the holder has a suitably shaped internal surface with a shape corresponding to the target shape of the shaped elements made of conductive porous carbon, preferably having indentations, lugs or wedges shaping the relief and spatial architecture of the shaped elements made of porous conductive carbon, in which holder the impregnated shaped element made of porous polymeric material is held during carbonisation, which shaped element made of impregnated polymeric preferably has the dimensions larger than the target dimensions of the shaped element made of porous conductive carbon, taking into account the experimentally determined shrinkage of the polymeric material observed during its carbonisation.
  • the shaped elements made of porous conductive carbon are made inside a carbonisation chamber under an oxygen-free atmosphere provided by the presence of a protective, carbon-rich, oxygen-scavenging backfill, preferably containing hard coal, fine coal, brown coal, charcoal, coke, granulated activated carbon, powdered activated carbon, carbon black or biomass, preferably wood or sawdust, and additionally by the use of a protective or reducing atmosphere, preferably in the form of nitrogen, argon, carbon monoxide, hydrogen, helium, neon, krypton or xenon.
  • the shaped elements made of porous conductive carbon are covered with a flexible conductive coating with a thickness of 1-20 pm, preferably 2-5 pm.
  • the conductive coating of the cathode current collector is a chromium, nickel, titanium or aluminium alloy layer
  • the conductive coating of the anodic current collector is a copper alloy layer
  • the conductive coating is a platinum-group metal alloy layer or a conductive polymer layer, preferably polyaniline.
  • a liquid electrolyte is used, preferably a 1 M LiPF6 solution dissolved in the equilibrium concentration of ethylene and dimethyl carbonates, and a homogeneous mixture with the active mass is prepared, then a paste is made from the material obtained using an addition of LiPF 6 .
  • the current collectors are filled with active mass, with paste filling machine, preferably flow-type or vibration-type.
  • the current collectors covered with a conductive coating after filling with active mass, are pressed to tamp the active mass, to ensure a proper contact between the active mass and the current collector, to eliminate voids within the electrode, to obtain an optimal pore size and to form the collector to the desired shape and size.
  • Fig. 1 shows a top view photograph of conductive porous carbon circular sha ped elements, prepared for manufacturing current collectors
  • Fig. 2 shows a side view photograph of a conductive porous carbon circular shaped element, prepared for manufacturing a current collector
  • Fig. 3 shows the photographs of:
  • Fig. 4 shows a Swagelok-type measuring cell comprising two electrodes having current collectors made of conductive porous carbon
  • Fig. 9 shows the charge and discharge curves for an LTO half-cell having CPC (conducting porous carbon) current collectors; charge/discharge current densities used: 1 mA, 3 mA and 5 mA;
  • Fig. 10 shows the specific capacities measured during charge and discharge for an LTO half-cell having CPC (conductive porous carbon) current collectors; the charge/discharge current densities used: 1 mA, 3 mA and 5 mA.
  • the invention relates to lithium-ion cells having lightweight, three-dimensional current collectors made of conductive porous carbon. These collectors have an increased mechanical strength, increased electrical conductivity and increased ability to utilise an active mass filling the collector in comparison to the prior art three-dimensional current collectors dedicated to lithium-ion cells. Moreover, in comparison to the classic layered lithium-ion cells, the cell according to the present invention has a maximised ratio of the active mass to the mass of the current collector, which results in an overall increase of the energy density stored by this cell.
  • the cell according to the invention has an increased energy density in comparison to classical solutions. According to the invention, it is possible to manufacture a cell having a specific energy of up to ca. 300 Wh/kg (700 Wh/dm 3 ), that is 30-130% higher than that of known cells available on the market. The availability of the cells having so high specific energy will allow construction of lighter, smaller and more capacious energy stores. This will result, for example, in increase of operation time of electronic devices, or increase of the range of electric vehicles.
  • the cell according to the invention utilise the current collectors, which can be given any desired shape, and thus it is possible to manufacture lithium-ion cells of any desired geometric parameters, adapted to the spatial requirements determined by specific applications. It is estimated that according to the invention, it is possible to construct a single cell having a volume in the range of 5-5000 cm 3 . Such cells may be used in all areas of energy storage, from microelectronics and medical devices, through electric vehicles, to stationary energy storage facilities.
  • the cell according to the invention may also be cheaper in manufacturing, because it does not use expensive metal foils (copper and aluminium foils), the price of which is estimated to be at average ca. 10% of the total price of the known cells. It is estimated that the production cost of the cell according to the invention will be 5-8% lower compared to the standard cells.
  • the cell according to the invention has a lower negative impact on the environment than conventional cells, because it does not contain aluminium foil.
  • the aluminium collector According to the LCA [Life Cycle Assessment, Dr. Denise Ott, LCA EU-685716] analyses of all battery components, the aluminium collector has the greatest environmental impact. It is estimated that the implementation of the cells according to the invention will reduce the environmental burden of the battery production process by ca. 10%.
  • the cell according to the invention may be easily implemented into the existing technological lines without the need to introduce significant changes, which means that the costs related to implementation of such cells are negligible.
  • the only modification will relate to the method of inserting the electrode masses into the volume of current collectors, while the method of preparing the masses, the way of electrode placement, filling with electrolyte and sealing in the cell housing will remain the same.
  • Table 1 Comparison of the properties of the standard current collector, the three-dimensional porous carbon collector according to the invention and the three-dimensional porous carbon collector overlaid with copper according to the invention
  • the lithium-ion cell according to the invention employs three-dimensional current collectors made of conductive porous carbon shaped elements having increased mechanical strength and conductivity.
  • the conductive porous carbon used for production of the collectors has the proper macroscopic structure, low mass, high specific surface area and satisfactory electrical conductivity.
  • the solution according to the present invention allows for the use of conductive porous carbon shaped elements produced by a method similar to the method disclosed in the Polish patent application No. P.423253 that covers KLAB-type composite lead-acid battery.
  • the method described therein allows to produce carbon shaped elements with full control of their geometry, dimensions, shape, spatial architecture, relief and porosity, without any need for mechanical processing (machining) of the carbon material.
  • the difference between the method presented in the Polish patent application No. P.423253 and the method according to the present invention is that in the case of lithium-ion cells it is necessary to control the porosity of the material and the degree of filling the current collector with an active mass more precisely.
  • the present lithium-ion cell requires that much greater porosity of the three- dimensional current collectors is ensured in the range of 10-200 ppi, preferably 40-80 ppi, which means that a pore size should be in the range of 0.13-2.5 mm, preferably 0.3-0, 6 mm.
  • a sufficient "thickness" of the active mass the thickness being defined as half diameter of the collector's pores must be ensured, the range of which is ca. 0.15-0.30 mm.
  • the present cell comprises current collectors made of conductive porous carbon produced in the designated shape, without the need for their subsequent mechanical treatment, thus increasing their strength and excluding possibilities of cracks in the carbon material, which in turn would reduce electrical conductivity of the collectors.
  • the shaped elements are obtained in a way that ensures their required geometry, dimensions, shape, spatial architecture, relief and porosity, thanks to use of special holders ensuring their target shape.
  • Two types of shaped elements made of conductive porous carbon are used: with a cross- linked type morphology or an inverse opal type morphology.
  • the CPC shaped elements with cross-linked type morphology have lower density, but their pores are poorly defined.
  • the shaped elements with an inverse opal type morphology have a very well-defined pores' shape and size, but they are denser and more expensive to manufacture.
  • the shaped elements made of conductive porous carbon are covered with an elastic conductive coating.
  • an elastic conductive coating 1-5 pm thick metallic layers are used, preferably made of a chromium, nickel, titanium or aluminium alloy in case of cathode collectors, or made of a copper alloy in case of anode collectors.
  • the collectors are coated with platinum-group metals and their alloys.
  • conductive polymers such as, for example, polyaniline [Synthetic Metals, 121 (2001) 1401; PL.197961].
  • the polymer coating will increase the conductivity of the material and simultaneously will make it more mechanically resistant.
  • intercalation materials i.a. graphite, hard carbon, LTO, etc.
  • alloy materials i.a. silicon, aluminium, tin, etc.
  • conversion materials i.a. oxides and nitrides of metals such as tin and aluminium and nonmetals such as silicon, silicon materials of natural and synthetic origin, etc.
  • cathode materials intercalation materials (i.a.
  • NMC nickel-manganese-cobalt oxides in various metal ratios LFP lithium-iron phosphate, LCO lithium-cobalt oxide, LMO lithium- manganese oxide, lithium silicates containing manganese, iron and aluminium at various mass ratios LFS or LMS etc., nickel-manganese-aluminium oxide NCA, etc.) or conversion materials (i.a. chlorides and fluorides of transition metals such as iron and tin, etc.).
  • the cell according to the invention comprises an active mass mixed with an electrolyte, either solid or liquid, before being introduced into the collector.
  • the addition of the electrolyte to the active mass increases the electrode's ability to efficiently exchange lithium ions with the electrolyte, which is crucial in the case of electrodes of considerable thickness.
  • a slight decrease in the ratio of the active mass to the mass of the current collector is compensated by the increase in the contact surface of the active mass and electrolyte.
  • a solid electrolyte based on lithium ion conducting polymers such as polyethylene and its derivatives or polyurethane and its derivatives is used.
  • a solid electrolyte based on conductive inorganic glasses or ceramics e.g.
  • Li 7 PS 6 or other compounds with high lithium ionic conductivity and high potential window, e.g. LiPF 6 , are used.
  • the cell according to the invention may also comprise compressed electrodes, preferably when using current collectors coated with an elastic sheath and an active mass with an addition of an electrolyte.
  • compression increases the electrical contact between the active mass grains and the collector material, without damaging the collector structure and without hindering the penetration of the electrolyte in the active mass. Compression of the electrode also increases its volumetric specific energy.
  • the method of producing electrodes for use in a lithium-ion cell according to the invention consists in the appropriate preparation of current collectors comprising shaped elements made of conductive porous carbon.
  • Conductive porous carbon shaped elements are manufactured in the desired target shape without any need for their subsequent mechanical processing (machining), which increases their strength and excludes the possibility of the carbon material cracking. The presence of cracks would reduce their electrical conductivity. These shaped elements are obtained in a way that ensures their target geometry, dimensions, shape, spatial architecture and relief, and porosity, thanks of the use of special holders shaping them to the target shape.
  • Two methods are used to manufacture shaped elements made of conductive porous carbon, that lead to materials with a cross-linked type morphology or inverse opal type morphology.
  • the shaped elements with cross-linked morphology are usually produced using standard shaped elements made of porous polymeric material with appropriately selected dimensions and porosity.
  • standard shaped elements made of porous polymeric material with appropriately selected dimensions and porosity.
  • button cells disks of 20 mm in diameter and 1.5 mm thick elements are used.
  • hollow cylindrical elements with an outer diameter of 5 mm, an inner diameter of 3 mm and a thickness of 30 mm, and cylindrical shapes with an outer diameter of 0.2 mm and a thickness of 30 mm are used.
  • the shape and size of the shaped elements are selected according to the specific application of the cells being built (e.g. for button cells - disks, for cylindrical cells - hollow and closed cylinders, for prismatic cells— cuboids).
  • the shape of the current collector can be freely modified.
  • the porous polymer material is subjected to preliminary machining, which considers cutting out the shaped element of appropriate dimensions and geometry.
  • Cutting a porous polymer material is simple and does not require the use of specialised equipment, because the material has high flexibility and is easy to cut, and its cutting does not cause its crushing, deformation or structural degradation.
  • the shaped elements made of porous polymeric material are then impregnated with a solution of thermosetting resin or a mixture of thermosetting resins and then left to dry. During the impregnation, the material expands and its mass, volume and density increase.
  • the impregnated, shaped elements made of porous polymeric material remain flexible and can be further shaped without damaging their structure.
  • the impregnated porous polymeric material shaped elements are thermally hardened at a temperature range of 70-180°C, preferably 120-160°C, followed by carbonisation at a temperature above 200°C, preferably 200-1600°C, most preferably 700-1100°C.
  • an appropriately shaped holder is used during hardening and carbonisation.
  • the material shrinks and its mass, volume and density decrease.
  • the product of the carbonisation process are shaped elements made of conductive porous carbon with an open-cell structure reflecting the similar structure of starting porous polymeric material.
  • a holder In order to ensure the precise shape and dimensions of the shaped elements made of conductive porous carbon, a holder is used, in which the impregnated shaped elements made of polymeric material are placed for hardening and carbonisation.
  • the holder provides an accurate representation of the target shape of the shaped elements, which otherwise could undergo irreversible, uncontrolled deformations (e.g. surface undulations) in the carbonisation chamber as a result of softening and flowing of the resin material during the first carbonisation steps, i.e. below the temperature of ca. 400°C. Even those shaped elements which have been previously thermally or chemically hardened undergo such deformation.
  • a holder of an appropriately defined size and shape is used, ensuring and maintaining the desired shape of the element during the process of its carbonisation. Moreover, the shaped elements placed in the holders are not exposed to any mechanical factors that could lead to their deformation. At the same time, the use of holders separates the carbonised shaped elements from each other and eliminates the risk of their sticking together during carbonisation.
  • the holder may have a closed form, then it consists of a vessel with a base, side walls, and a lid that closes the vessel from the top.
  • the holder of such design is used for carbonisation of shaped elements of a complex shape and architecture.
  • the inner space of the holder has the shape and dimensions identical with the target shape and dimensions of the shaped elements made of conductive porous carbon.
  • the impregnated shaped element made of porous polymeric material is placed inside the vessel which is then closed with the lid.
  • shaped elements having dimensions larger than the target dimensions of shaped elements made of conductive porous carbon are inserted into the vessel, taking into account the experimentally determined contraction of the material.
  • a shaped elements with dimensions larger than it would be suggested from the contraction of the material is advantageous because the edges of the shaped elements are smoothed and the porosity of the elements near the edges is locally increased.
  • shaped elements made of impregnated polymer material having dimensions 101-200% larger than the target dimensions of porous conductive carbon elements are used, taking into account the experimentally determined material contraction.
  • the holder has an additional inner space at one of its edges for formation of protrusions of the shaped elements made of porous conductive carbon. This space is thinner than the rest of the holder, preferably by 2-3 mm, so that the formed protrusion has a locally increa sed porosity in comparison with other parts of the shaped element. This space can also form a relief on the protrusion, which is used to attach additional parts.
  • the inner planes of the holder which are in contact with the shaped elements made of impregnated porous polymeric material during carbonisation, may have indentations, protrusions or wedges forming reliefs on the surface of the shaped elements made of conductive porous carbon.
  • the shape of these indentations and protrusions is transferred in an inverse form on the surface of the shaped elements made of conductive porous carbon. This gives the possibility to design the shaped elements for possible deposition of additional ele ments on their surface at the post-production stage.
  • the holder may be made of any material resistant to high temperature inside the carbonisation chamber during carbonisation.
  • the holder may be metal or ceramic. It is advantageous to use a holder made of carbon (graphite), because such a holder additionally has a protective function, eliminating oxygen inside the carbonisation chamber, thus preventing corrosion of the formed shaped elements made of conductive porous carbon.
  • Polymer foams capable of absorbing the impregnating solutions are used as a porous polymer material for production of the shaped elements made of conductive porous carbon.
  • porous polyurethane foams are used.
  • Polyurethane foams are easily available, cheap to produce, flexible and easy to shape.
  • the open-cell structure of polyurethane foams is 100% reproduced in the structure of conductive porous carbon resulting from carbonisation process.
  • thermosetting resin solutions or solutions of mixtures of thermosetting resins are used as the impregnating agent.
  • solutions of phenol-formaldehyde resin are used, since they allow to remain the initial structure of the porous polyurethane foam and to increase carbon content in the produced polymer blend prepared for carbonisation.
  • Carbonisation of non-impregnated polyurethane foam leads to an amorphous carbon powder which does not retain the macroscopic structure of the starting foam.
  • liquid resins without diluting them in a solvent.
  • an ethanol solution of phenol-formaldehyde resin is used as it allows to control the degree of impregnation of the porous polyurethane foam, allows the foam to be homogeneously saturated with the resin, and prevents clogging of the open pores thank to the lower viscosity of the liquid.
  • Commercial, liquid, unhardened phenol-formaldehyde resins need to be diluted with a solvent, because they are characterised by high viscosity, which prevents homogeneous and isotropic penetration of the resin into the hollow structure of the porous polyurethane foam. Additionally, the use of liquid and undiluted phenol-formaldehyde resins leads to clogging of the polyurethane foam.
  • opening the pores of the impregnated polyurethane foam is tedious and time-consuming, as it requires, for example, compression of the impregnated foam, purging or vacuuming.
  • hardeners and resin cross-linkers are used, which undergoes decomposition and/or are released at elevated temperatures.
  • urotropin is used, which releases ammonia and formaldehyde during its thermal decomposition.
  • Ammonia is the hardening agent and formaldehyde is the cross- linking agent with respect to phenol-formaldehyde resins.
  • a saturated urotropin solution is used.
  • the impregnation is carried out in solutions of thermosetting resin or solutions of mixtures of thermosetting resins without the addition of urotropin.
  • the shaped elements made of impregnated porous polymer are additionally soaked in an urotropin solution, preferably in a saturated urotropin solution, immediately before the beginning of hardening and further carbonisation.
  • the thermal hardening of the shaped elements made of impregnated polymeric material is carried out at a temperature of 70-180°C, preferably 120-160°C. It is preferably carried out in a carbonisation chamber, where subsequent carbonisation will take place. Most preferably, the hardening step is the initial step of the carbonisation process of the impregnated shaped elements made of porous polymeric material.
  • the shaped elements with inverse opal morphology are prepared using the above described resin or resin blend.
  • a mixture of the resin and polymer spheres made of material insoluble in the resin is formed, where the spheres have a diameter of 0.1-1.0 mm, preferably 0.4-0.6 mm, and will constitute a three-dimensional matrix of the opal structure.
  • the volume ratio of the spheres to the resin should be ca. 1:1 with a slight excess of the volume of the spheres, which ratio allows the mixture to self-organize in such a way that the spheres arrange themselves to form the opal structure, and the resin fills the spaces between them. At the top the resin will not close the porous structure of the formed material.
  • the mixture is poured into the holder having the above described structure, and then, after self-arrangement of the spheres at the bottom of the vessel, the resin is hardened. The self-arrangement of the spheres can be accelerated by ultrasonication.
  • spheres made of a polymer that decomposes above the curing temperature of the resin used are used.
  • polystyrene spheres are used. After hardening of the resin as described above, the material obtained is subjected to carbonisation.
  • the carbonisation process is carried out in the same way for both types of shaped elements with a cross-linked morphology and those of inverse opal morphology, the only difference being that in the case of shaped elements of inverse opal morphology, the process of a spatial polymer matrix gasification takes place during carbonisation.
  • Carbonisation is carried out by heating the polymeric material under anaerobic conditions in a closed carbonisation chamber by heating at a variable temperature, which increases during the carbonisation process in the temperature range of 200-1600°C, preferably in the temperature range of 700-1100°C. It is possible to carry out heating at different rates of temperature rise in the range of 0.1-15°C/min. Use of different temperature regimes lead to obtain porous conductive carbon of the desired physical and chemical properties.
  • the carbonisation process is carried out in a closed carbonisation chamber in which the polymeric material is placed.
  • Oxygen may be removed from the carbonisation chamber in any manner, for example by surrounding the carbonised polymer material with a tight layer of protective powder and/or by using a protective atmosphere of inert or reducing gas or mixtures of such gases (e.g. nitrogen, argon, carbon monoxide, hydrogen).
  • a protective atmosphere of inert or reducing gas or mixtures of such gases e.g. nitrogen, argon, carbon monoxide, hydrogen.
  • the heating of the polymeric material begins after the carbonisation chamber is closed.
  • the carbonisation chamber can be additionally equipped with an installation for the flow of protective gas.
  • the shaped elements are isothermally heated at a temperature of 50-100°C, preferably 80°C.
  • the heating duration is 1-5 hours, preferably 2 hours.
  • the heating aiming to strip the solvent is an initial step in the carbonisation process.
  • the resulting shaped elements made of conductive porous carbon have a well-defined, desired target geometry, dimensions, shape, spatial architecture, relief and porosity, and can be used to build lithium-ion cells without further machining, thus reducing the risk of carbon structure cracking.
  • the shaped elements have smooth external surfaces and edges, so there is no risk of puncturing the separator during the assembly and further operation of the cell.
  • Shaped elements made of conductive porous carbon can be used directly as current collectors or after additional coating with an elastic layer of conductive material in order to increase their mechanical strength and electrical conductivity.
  • metallic layers 1-5 pm thick are used, preferably made of chromium, nickel, titanium or aluminium alloys in case of cathodic collectors, or made of copper alloys in case of anodic collectors.
  • the collectors are overlaid with a coating made of platinum group metals and their alloys. It is also possible to cover the surface of the current collectors with a coating made of suitably selected conductive polymers, such as for example, polyaniline [Synthetic Metals, 121 (2001) 1401; PL.197961].
  • the active mass is mixed with the solid or liquid electrolyte, before its introduction into the collector, in order to increase the electrode's ability to efficiently exchange lithium ions with the electrolyte, which ability is crucial in the case of electrodes of large thickness. Slight decrease of the ratio of active mass to mass of the current collector is compensated by the increase of the contact surface of the active mass and electrolyte.
  • a solid electrolyte based on lithium ion conducting polymers such as polyethylene and its derivatives or polyurethane and its derivatives is used.
  • solid electrolytes based on conductive inorganic glasses or ceramics e.g. Li 7 PS 6 , or other compounds with high lithium ionic conductivity and high potential window, e.g. LiPF 6
  • a liquid electrolyte in form of a commercially available electrolyte containing lithium salts, e.g. LiPF 6 may be used as well, so as other liquid lithium conducting electrolytes inert against the electrode masses.
  • the electrode mass is prepared by forming a slurry containing 60-95 wt.% of active powder (silicon, LTO, NMC, graphite), 3-25 wt.% of Vulcan carbon and 2-15 wt.% of binder polymer (PVDF or CMC).
  • the dispersant medium is n-methylpyrrolidone (NMP) - when PVDF is used, or deionized water when CMC is used.
  • NMP n-methylpyrrolidone
  • the addition of conductive carbon aims to improve the electron conductivity of the electrode by improving the electrical contact between the active material grains.
  • the addition of the polymer aims to improve the mechanical properties of the electrode by means of mechanical bonding of all components.
  • the active mass is introduced into the current collector by means of a flow or vibrating pasting device. It is important not to apply direct mechanical pressure to the current collector when introducing the paste, especially if it is not coated with an elastic conductive layer, as it could cause cracking of its carbon structure and thus reduce conductivity.
  • Flow pasting devices are used, wherein empty current collectors are placed in a closed space through which the active mass in the form of a paste is pressed. In the flow pasting device, the current collectors are not affected by a direct mechanical pressure, but only a constant, slight and even pressure of the flowing paste.
  • vibrating and vibration-gravity pasting devices are used, wherein the active mass is placed on top of the collector and allowed to spontaneously spread throughout the collector's volume. The process is accelerated by the applied vibrations of appropriately selected frequency.
  • the whole electrode When using current collectors covered with an elastic coating and filled with active mass containing an addition of an electrolyte, the whole electrode is additionally compressed in order to increase the electrical contact between the active mass grains and the collector material, without damaging the collector structure and without hindering the electrolyte penetration in the active mass.
  • the electrode can also be brought to a specific target size and shape, for example providing an embossing or a relief. Possible cracks in the carbon structure of the current collector are irrelevant, because the flexible conductive coating does not undergo deterioration under these conditions and ensures proper conductivity of the collector.
  • the pore size of the current collector can also be optimised, which is particularly advantageous when using a high-viscosity paste. Therefore, it is possible to manufacture current collectors with larger pores, which facilitates introduction of the active mass, and then such electrodes can be compressed in such a way that the pores reach the optimum size.
  • a lithium-ion cell comprising three-dimensional current collectors and the method of its manufacture is described below in the working examples.
  • Example 1 Shaped elements made of conductive porous carbon in the form of discs with a diameter of 10 mm and a thickness of 1.5 mm were produced by ca rbonisation of polyurethane foam impregnated with resin. The shaped elements made of conductive porous carbon are shown in Fig. 1 and Fig. 2.
  • the electrode mass was prepared by forming a thick slurry containing 80 wt.% of active powder (LTO or NMC), 10 wt.% of Vulcan carbon and 10 wt.% of the binding polymer: PVDF.
  • n-Methylpyrrolidone (NMP) was used as the dispersion medium.
  • the current collector was covered with a standard anode electrode paste containing: LTO (lithium titanium oxide) + Vulcan carbon + PVDF in the proportions 8/1/1, or a cathode paste containing: NMC (lithium nickel manganese cobalt oxide) + Vulcan carbon + PVDF in proportions 8/1/1.
  • LTO lithium titanium oxide
  • NMC lithium nickel manganese cobalt oxide
  • Example 2 Shaped elements made of conductive porous carbon were produced according to the procedure described in Example 1. The elements were electrochemically coated with a copper layer of a thickness of ca. 15 pm from a mixture of copper(ll) sulfate pentahydrate (50 g/dm 3 ), sulfuric(VI) acid (10 g/dm 3 ), hydrochloric acid (0.01 g/dm 3 ) and commercially available organic additives. The deposition of copper was carried out at a temperature of 25°C with a current density of 20 mA/cm 2 for 48 minutes. As a counter electrode, a copper sheet with addition of phosphorus was used (MIR type). Prior to deposition, the carbon foam underwent a two-stage purification.
  • MIR type copper sheet with addition of phosphorus
  • the first step was a chemical purification in hot (80°C) NaOH solution for 60 minutes.
  • anodic electrochemical cleaning was used - evolution of hydrogen in a solution of NaOH, NaC03 and surfactants against steel cathodes for 2 minutes.
  • Such obtained collector is shown in Fig. 3.A.
  • the electrode mass was prepared by forming a slurry containing 60 wt.% of an active powder (nano-silicon), 25 wt.% of Vulcan carbon, 10 wt.% of binding polymer - CMC and 5 wt.% of liquid electrolyte salt - 1M LiPF 6 solution in the equal by weight mixture of ethylene and dimethyl carbonates.
  • the dispersion medium was deionised water.
  • the copper-coated current collector was covered with a standard electrode paste consisting of nano-silicon + Vulcan carbon + PVDF + electrolyte in the proportions 6/2.5/1.0/0.5. After applying the electrode mass to the current collector, the whole was placed on a vibrating table for 2 minutes in order to allow the mass to flow into the collector. Subsequently, the electrodes were dried on a hotplate at 50°C under an inert atmosphere until pre-evaporation, and then heated in a vacuum oven at 120°C until all traces of solvent removed. The obtained electrode is shown in Fig. 3.B. The electrode was then compressed under a pressure of 0.5 tons in order to ensure better contact of the active mass with the current collector. The obtained compressed electrode is shown in Fig. 3.C.
  • Example 3 Shaped elements made of conductive porous carbon were produced according to the procedure described in Example 1.
  • the electrode mass was prepared by forming a slurry containing 80 wt.% of active powder (LTO), 10 wt.% of Vulcan carbon, 5 wt.% of binding polymer - PVDF and 5 wt.% of solid electrolyte salt - Li 7 PS 6 .
  • n-Methyl-2-pyrrolidone (NMP) was used as a dispersion medium.
  • the copper-coated current collector was covered with a standard electrode paste consisting of LTO + Vulcan carbon + PVDF + electrolyte in the proportions 8.0/1.0/0.5/0.5. After applying the electrode mass to the current collector, the whole was placed on a vibrating table for 2 minutes in order to allow the mass to flow into the collector. Subsequently, the electrodes were dried on a hotplate at 50°C under an inert atmosphere until pre-evaporation, and then in a vacuum oven at 120°C until all traces of solvent removed. Electrochemical experiments were carried out in a Swagelok type cell (Fig.

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Abstract

L'invention concerne un élément lithium-ion comprenant au moins un collecteur de courant carboné tridimensionnel, ce collecteur de courant carboné tridimensionnel d'une épaisseur de 0,1 à 3,0 mm, de préférence de 1,0 à 2,0 mm, étant constitué de carbone conducteur poreux ayant une taille de pores de 10 à 200 ppi, de préférence de 40 à 80 ppi, sous la forme d'un élément façonné ayant les caractéristiques cibles requises en termes de géométrie, dimensions, forme, architecture spatiale, relief et porosité, fabriqué d'une manière ne nécessitant pas de traitement mécanique du matériau carboné poreux, lequel collecteur est rempli d'une masse active, de préférence mélangée à un électrolyte solide ou liquide. L'invention concerne également un procédé de fabrication d'électrodes pour un élément lithium-ion reposant sur l'utilisation de collecteurs de courant carbonés tridimensionnels, le collecteur de courant carboné tridimensionnel étant réalisé sous la forme d'un élément façonné de carbone conducteur poreux ayant les caractéristiques cibles requises en termes de géométrie, dimensions, forme, architecture spatiale, relief et porosité, d'une manière ne nécessitant pas de traitement mécanique du matériau carboné poreux, les éléments façonnés ayant une porosité de 10 à 200 ppi, de préférence de 40 à 80 ppi, et étant remplis d'une masse active, de préférence mélangée à un électrolyte solide ou liquide. Le collecteur de courant carboné tridimensionnel a une morphologie de type réticulé ou une morphologie de type opale inverse. Le collecteur de courant carboné tridimensionnel est recouvert d'un revêtement conducteur élastique d'une épaisseur de 1 à 5 pm, de préférence en alliage de nickel, de titane ou d'aluminium pour collecteurs cathodiques, ou en alliage de cuivre pour collecteurs anodiques. Après avoit été remplis d'une masse active, les collecteurs sont éventuellement comprimés pour que la masse active soit compactée, pour assurer un contact approprié entre les grains de masse active et le collecteur de courant et éliminer les vides à l'intérieur de l'électrode, de manière à obtenir la taille de pore optimale pour le collecteur et lui donner la forme et la taille cibles. L'élément selon l'invention comprend des collecteurs de courant tridimensionnels légers constitués de carbone poreux conducteur, qui ont une résistance mécanique accrue, une conductivité électrique accrue et une capacité accrue à utiliser la masse active et qui peuvent être façonnés sous n'importe quelle forme spatiale cible souhaitée. L'élément selon l'invention présente ainsi une capacité énergétique accrue et un coût de production réduit par rapport aux solutions classiques et peut également avoir une forme adaptée aux exigences déterminées par les applications spécifiques, et présente en outre un impact environnemental plus faible que les éléments classiques. L'élément selon l'invention peut être facilement mis en oeuvre dans des lignes technologiques existantes.
PCT/PL2020/000059 2019-07-08 2020-07-06 Élément lithium-ion comprenant des collecteurs de courant tridimensionnels et procédé de fabrication d'électrodes pour cet élément WO2021006752A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114031157A (zh) * 2021-11-18 2022-02-11 中国科学院生态环境研究中心 一种利用多孔三维木基电极去除和回收水中重金属的方法
CN114464816A (zh) * 2022-04-12 2022-05-10 瑞浦能源有限公司 一种具有造孔功能涂层的集流体、极片以及锂离子电池

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EP1091841A1 (fr) * 1998-06-29 2001-04-18 Eltech Systems Corporation Production d'une mousse poreuse pour electrodes de batterie
CN103682368A (zh) * 2012-09-20 2014-03-26 中国科学院金属研究所 一种快充的柔性锂离子电池及其电极的制备方法
US20170365851A1 (en) * 2014-12-17 2017-12-21 Leibniz-Institut Für Polymerforschung Dresden E.V. Cathodes for li-s batteries
CN105609783B (zh) * 2016-03-29 2018-05-29 中国科学技术大学 一种碳结构集流体、电池负极、电池正极和锂电池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1091841A1 (fr) * 1998-06-29 2001-04-18 Eltech Systems Corporation Production d'une mousse poreuse pour electrodes de batterie
CN103682368A (zh) * 2012-09-20 2014-03-26 中国科学院金属研究所 一种快充的柔性锂离子电池及其电极的制备方法
US20170365851A1 (en) * 2014-12-17 2017-12-21 Leibniz-Institut Für Polymerforschung Dresden E.V. Cathodes for li-s batteries
CN105609783B (zh) * 2016-03-29 2018-05-29 中国科学技术大学 一种碳结构集流体、电池负极、电池正极和锂电池

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114031157A (zh) * 2021-11-18 2022-02-11 中国科学院生态环境研究中心 一种利用多孔三维木基电极去除和回收水中重金属的方法
CN114464816A (zh) * 2022-04-12 2022-05-10 瑞浦能源有限公司 一种具有造孔功能涂层的集流体、极片以及锂离子电池

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