WO2021006752A1

WO2021006752A1 - A lithium-ion cell comprising three-dimensional current collectors and a method of manufacturing electrodes for this cell

Info

Publication number: WO2021006752A1
Application number: PCT/PL2020/000059
Authority: WO
Inventors: Bartosz HAMANKIEWICZ; Maciej RATYŃSKI; Piotr Podsadni; Karol Fijałkowski; Andrzej CZERWlŃlSKI
Original assignee: Uniwersytet Warszawski
Priority date: 2019-07-08
Filing date: 2020-07-06
Publication date: 2021-01-14
Also published as: EP3997750A1; PL430517A1

Abstract

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. 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 three-dimensional carbon current collector has a cross-linked type morphology or inverse opal type morphology. The three-dimensional carbon current collector is covered with an elastic conductive coating of a thickness of 1-5 pm, preferably made of a nickel, titanium or aluminium alloy for cathode collectors, or made of copper alloy for anode collectors. After being filled with an active mass, the collectors are optionally compressed in order to compact the active mass, to ensure proper contact between the active mass grains and the current collector, to eliminate voids within the electrode, to obtain the optimum pore size of the collector and give it the target shape and size. The cell according to the invention has light, three-dimensional current collectors made of conductive porous carbon, which have an increased mechanical strength, increased electrical conductivity and increased ability to utilise the active mass, and which can be shaped into any desired target spatial shape. In result, the cell according to the invention has an increased energy capacity and is cheaper in production in comparison to classical solutions, and can also have a shape adapted to the requirements determined by specific applications, and additionally also has a lower environmental impact than conventional cells. The cell according to the invention can be easily implemented into existing technological lines.

Description

A lithium-ion cell comprising three-dimensional current collectors

and a method of manufacturing electrodes for this cell

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.

Various types of lithium-ion cells are known, 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. Usually 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. Moreover, 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 (2018) 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. aluminium, titanium) and 0.01-2 V for 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. For this purpose, 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 (2018) 1802014]. Unfortunately, the use of relatively heavy metal collectors significantly reduces the gravimetric energy density of lithium- ion cells.

There are known a three-dimensional carbon current collectors for lithium-ion cells, made of the so-called graphene foam (graphene flakes connected by carbon-carbon bonds), which being filled with LiFeP0₄ cathode material give an electrode capacity of 102 mAh/g, i.e. 23% higher than classic electrode with LiFeP0₄ deposited on aluminium. Moreover, the electrode with a graphene current collector is also able to work at high current densities, while the classic electrode loses its properties under such conditions [Nano Lett., 12 (2012) 2446.]. A method for obtaining graphene foams involves dissolving carbon in nickel matrix at a temperature of 1000°C and slow creation of carbon surface structures while nickel cooling. Then the nickel is dissolved and a carbon structure having porosity of 99.9% by volume is obtained [Nature Mater., 10 (2011) 424.].

There are known three-dimensional carbon current collectors for lithium-ion cells, built of porous carbon materials obtained by pyrolysis of polymer foams [J. Mater. Chem. A, 4 (2016) 8636]. In order to increase the conductivity of the porous carbon matrix, it is possible to dope carbon with nitrogen by carbonisation of a melamine foam [Small, 12 (2016) 6724]. In turn, to increase its mechanical strength, it is surface coated with titanium [J. Mater. Chem. A, 5 (2017) 13168]. Carbon collectors intended for manufacturing anodes are covered with a protective layer of silicon. There is known a lithium-ion cell of a capacity of 479.5 Wh/kg having a carbon- titanium collector and a carbon-silicon collector [J. Mater. Chem. A, 5 (2017) 13168]. Unfortunately, covering the collectors with a layer of titanium increases their mass and reduces the total specific energy of the cell.

There are known three-dimensional carbon current collectors for lithium-ion cells, made of carbon fibres forming so called carbon cloth. Single carbon fibres have a diameter of 5-10 pm, and the carbon cloth is flexible and chemically highly resistant [Adv. Mater., 30 (2018) 1802014]. Unfortunately, a complete electrochemical cell comprising the current collectors of this type is still not known.

There is known a lithium-ion half-cell having a three-dimensional current collector made of carbon cloth filled with carbon particles, creating a three-dimensional space for the active mass of the cell [ACS Energy Lett., 4 (2019) 271]. Such a geometry of current collectors allows for the construction of relatively thick electrodes with an energy density of 140 mAh/g. Unfortunately, a complete electrochemical cell comprising current collectors of this type is still not known. The above-mentioned known prior art solutions using carbon current collectors are characterised by incomplete occupation of the collector's volume by the active mass due to the fact that using classic pasting devices to paste them is not possible. The use of such devices would result in crumbling of the carbon material of the matrix. Moreover, known solutions lead to obtain electrodes with a suboptimal use of an active mass during operation of the cell due to the fact that the porosity of the used materials cannot be fully controlled.

There is a still unmet need to develop a new type of three-dimensional carbon current collectors with a controlled pore size, as well as optimisation of the active mass volume being used and the method of its insertion.

Summary of the invention

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.

According to the invention the three-dimensional carbon current collector has a cross-linked type morphology. Alternatively, the three-dimensional carbon current collector has a reverse opal type morphology. According to the invention, 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. According to the invention, the three-dimensional carbon current collector, after filling with active mass, is pressed to the desired size and shape. According to the invention, 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.

According to the invention, 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. Alternatively, 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.

According to the invention, 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. According to the invention, 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. According to the invention, 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.

According to the invention, the conductive coating of the cathode current collector is a chromium, nickel, titanium or aluminium alloy layer, and the conductive coating of the anodic current collector is a copper alloy layer, or the conductive coating is a platinum-group metal alloy layer or a conductive polymer layer, preferably polyaniline. According to the invention, 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 LiPF₆. Alternatively, a solid electrolyte is used, preferably Li₇PS₆, and a homogeneous mixture with the active mass is prepared, then a paste is made from the material obtained using the addition of U₇PS₆. According to the invention, the current collectors are filled with active mass, with paste filling machine, preferably flow-type or vibration-type. According to the invention, 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. The lithium-ion cell comprising three-dimensional current collectors and the method of manufacturing the same are described in detail below in the working examples and embodiments, with reference to the attached drawings, in which:

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:

A. a top view of a circular current collector made of conductive porous carbon covered with a copper layer,

B. a top view of a circular silicon electrode having a copper coated cu rrent collector made of conductive porous carbon,

C. a top view of a circular silicon electrode having a copper coated cu rrent collector made of conductive porous carbon, compressed under compression of 0.5 tons;

Fig. 4 shows a Swagelok-type measuring cell comprising two electrodes having current collectors made of conductive porous carbon;

Fig. 5 shows the charge and discharge curves for the LTO/NMC cell, where both electrodes have current collectors made of conducting porous carbon, the limiting electrode is the NMC electrode, charge/discharge current density = C/20;

Fig. 6 shows the charge and discharge curves for the LTO/NMC cell, where both electrodes have current collectors made of conducting porous carbon, the limiting electrode is the NMC electrode, charge/discharge current density = C/10;

Fig. 7 shows the charge and discharge curves for a half-cell constructed of a CPC (conductive porous carbon) collector coated with a copper layer and filled with an active mass containing 60 wt.% of nano-silicon, 25 wt.% of Vulcan carbon, 10 wt.% of binding polymer - CMC and 5 wt.% of a liquid electrolyte salt in form of 1M LiPF₆ solution in the equilibrium concentration of ethylene and dimethyl carbonates; the collector was not compressed and it is shown in Fig. 3B; charge/discharge current density = 1 mA;

Fig. 8 shows the charge and discharge curves for a half-cell constructed of a CPC (conducting porous carbon) collector coated with a copper layer and filled with an active mass containing 60 wt.% of nano-silicon, 25 wt.% of Vulcan carbon, 10 wt.% of binding polymer - CMC and 5 wt.% of a liquid electrolyte salt in form of 1M LiPF₆ solution in the equilibrium concentration of ethylene and dimethyl carbonates; the collector was pressed and is shown in Fig. 3C; charge/discharge current density = 1 mA;

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. Detailed description of the invention

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/dm³), 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 cm³. 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. 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. These parameters are not crucial in designing the KLAB batteries because of their much larger size and due to very good conductivity of its active mass and electrolyte.

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. Such precise control is necessary because of the relatively low conductivity of the active mass and electrolyte used in this type of cell. Therefore, in order to allow effective charge exchange between the mass and the collector, 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 use of a collector with too large pores will cause a part of the active mass remaining unused, because the electric charge will not be able to reach that part. On the other hand, the use of collectors with too small pores will unnecessarily reduce the ratio of active mass to the mass of the collector, thus lowering the energy density of the cell and making difficult introduction of the active mass into the collector.

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. On the other hand, 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.

In order to further increase the mechanical strength and electric conductivity of the current collectors, the shaped elements made of conductive porous carbon are covered with an elastic conductive coating. For this purpose, 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. For special applications, the collectors are coated with platinum-group metals and their alloys.

It is also possible to cover the surface of the current collectors with a coating of suitably selected 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.

In the cell according to the invention, various active masses are used, depending on the needs. For example, as anode materials the following are used: intercalation materials (i.a. graphite, hard carbon, LTO, etc.), alloy materials (i.a. silicon, aluminium, tin, etc.) or 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.). For example, the following are used as 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. Also, a solid electrolyte based on conductive inorganic glasses or ceramics, e.g. Li₇PS₆, or other compounds with high lithium ionic conductivity and high potential window, e.g. LiPF₆, are used. There is also used a liquid electrolyte in form of a commercially used electrolyte containing lithium salts, e.g. LiPF₆, or other lithium conducting liquid electrolytes that are inert towards the electrode masses.

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. In such cases, 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. For example, for button cells, disks of 20 mm in diameter and 1.5 mm thick elements are used. In turn, for AA type cells, 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. When forming shaped elements, 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. It is possible to prepare shaped elements made of porous polymer material (impregnated or not) having any desired shape by machining a single block of the polymer material. It is also possible to produce hybrid shaped elements by machining and merging two or more elements made of polymeric material with the same or different porosity, which are connected together using the solution used for impregnation.

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. In order to provide the shaped elements with a specific, desired target shape, an appropriately shaped holder is used during hardening and carbonisation. During 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.

It is possible to experimentally determine the dependence of the initial dimensions of the shaped elements made of porous polymer material in relation to the final dimensions of the shaped elements made of conductive porous carbon as a function of the impregnation time H, by determining its expansion during impregnation step and subsequent shrinkage during carbonisation process. At the same time, the dependence of the porosity of the shaped elements made of conductive porous carbon on the impregnation time H is experimentally determined. These dependencies are determined separately for each polymeric material, each impregnating agent and the impregnation time, by carrying out a series of control impregnation and carbonisation processes as well as conducting experimental measurements of the material's expansion and contraction.

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. According to the invention, 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. Preferably, 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. The use of 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. Most preferably, 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. Preferably, 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. For example, 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. Preferably, 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.

Solutions of thermosetting resin solutions or solutions of mixtures of thermosetting resins are used as the impregnating agent. Preferably, 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. However, it is possible to use liquid resins without diluting them in a solvent.

Preferably, 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. As additional components of the resin solution, hardeners and resin cross-linkers are used, which undergoes decomposition and/or are released at elevated temperatures. Preferably, the addition of 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. These agents are slowly released during the thermal hardening step and allow for the gradual and equal fixation of the open-pore structure of the shaped elements made of impregnated polymeric material. Preferably a saturated urotropin solution is used. Alternatively, the impregnation is carried out in solutions of thermosetting resin or solutions of mixtures of thermosetting resins without the addition of urotropin. In such a case, however, 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.

It is essential to use spheres made of a polymer that decomposes above the curing temperature of the resin used. Otherwise, the inverse opal structure will collapse. There are used spheres made of a polymer that decomposes to gaseous products at temperature of 150-300°C, preferably 200-250°C. Preferably, 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). 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.

For correct carbonisation it is required to remove traces of solvents that may have remained in the structure of impregnated shaped elements made of porous polymeric material. For this purpose, before starting the carbonisation process, 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. Preferably, 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. Moreover, 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. For this purpose, 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. For special applications, 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].

In the cell according to the invention, all of the above mentioned anodic (intercalating, alloying or conversion materials) and cathodic (intercalating or conversion materials) active masses can be used as needed.

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. Also, solid electrolytes based on conductive inorganic glasses or ceramics, e.g. Li₇PS₆, or other compounds with high lithium ionic conductivity and high potential window, e.g. LiPF₆, are used. A liquid electrolyte in form of a commercially available electrolyte containing lithium salts, e.g. LiPF₆, 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. 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.

In the first stage of the preparation, appropriate amounts of active powder and conductive carbon are mixed. The mixture is then grounded in an agate mortar for 10 minutes. The mixture prepared in this way is transferred to a vial where the binding polymer is added: 5% PVDF solution in NMP or 4% CMC solution in water. The viscosity of the mixture is reduced by adding appropriate amounts of the solvent until it is possible to mix it freely using a magnetic stirrer. The suspension is stirred for 3-18 hours until all components are evenly dispersed.

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. Alternatively, 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.

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.

By applying compression at the last step of the electrode preparation, 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.

In the first stage of the preparation, appropriate amounts of an active powder (300 mg) and a conductive carbon (37.5 mg) were mixed. The mixture was then ground in a n agate mortar for 10 minutes. The mixture thus prepared was transferred to a vial to which the binding polymer: 5% PVDF solution in NMP (1000 mg) was added. The viscosity of the mixture was reduced by addition of an appropriate amount of the NMP solvent (200 mg) until it was possible to mix it freely with a magnetic stirrer. The suspension was stirred for 3 hours until all ingredients were evenly dispersed.

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. 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 for pre-evaporation, and then in a vacuum oven at 120°C until all traces of solvent were removed.

Electrochemical experiments were carried out in a Swagelok type cell (Fig. 4), using 1 M solution of LiPFe dissolved in an equal by weight mixture of ethylene and dimethyl carbonates as electrolyte, and a Celgard2325 membrane as a separator. The tests of cell charging and discharging were carried out using the current density C/20 and C/10. The test results are shown in Fig. 5 and Fig. 6.

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/dm³), sulfuric(VI) acid (10 g/dm³), hydrochloric acid (0.01 g/dm³) 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/cm² 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. The first step was a chemical purification in hot (80°C) NaOH solution for 60 minutes. In the second stage, 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 LiPF₆ solution in the equal by weight mixture of ethylene and dimethyl carbonates. The dispersion medium was deionised water.

In the first stage of preparation, the appropriate amounts of active powder (300 mg) and conductive carbon (125 mg) were mixed. The mixture was then ground in an agate mortar for 10 minutes. The mixture thus prepared was transferred to a vial where the binding polymer was added - 5% solution of CMC in deionized water (1000 mg) and 5% solid electrolyte salt

- U₇PS₆ (24 mg). The viscosity of the mixture was reduced by addition of 30 mg of the solvent

- deionized water, until it was possible to mix it freely with a magnetic stirrer. The suspension was stirred for 18 hours until all ingredients were evenly dispersed.

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.

Electrochemical experiments were carried out in a Swagelok type cell (Fig. 4), using 1 M solution of LiPF₆ dissolved in an equal by weight mixture of ethylene and dimethyl carbonates as electrolyte and a Celgard2325 membrane as a separator. The tests of cell charging and discharging were carried out using the current density C/20 and C/10. The test results are shown in Fig. 7 and Fig. 8.

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 - Li₇PS₆. n-Methyl-2-pyrrolidone (NMP) was used as a dispersion medium.

In the first stage of preparation, appropriate amounts of active LTO powder (300 mg) and conductive carbon (37.5 mg) were mixed. The mixture was then ground in an agate mortar for 10 minutes. The mixture thus prepared was transferred to a vial where the binding polymer was added - 5% PVDF solution in NMP (375 mg) and 5% of solid electrolyte salt - Li₇PS₆ (18.8 mg). The viscosity of the mixture was reduced by addition of 30 mg of the NMP solvent until it was possible to mix it freely with a magnetic stirrer. The suspension was stirred for 5 hours until all ingredients were evenly dispersed.

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. 4), using a 1 M solution of LiPF₆ dissolved in an equal by weight mixture of ethylene and dimethyl carbonates as electrolyte, and a Celgard2325 membrane as a separator. The cell charging and discharging tests were carried out using the current of 1, 3 and 5 mA. The test results are shown in Fig. 9 and Fig. 10.

Claims

1. 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.

2. The lithium-ion cell according to claim 1, wherein the three-dimensional carbon current collector has a cross-linked type morphology

3. The lithium-ion cell according to claim 1, wherein the three-dimensional carbon current collector has a reverse opal type morphology.

4. The lithium-ion cell according to claim 1, wherein 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.

5. The lithium-ion cell according to claim 4, wherein the three-dimensional carbon current collector, after filling with active mass, is pressed to the desired size and shape.

6. The lithium-ion cell according to claim 1, wherein it has both electrodes comprising three- dimensional carbon current collectors.

7. 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.

8. The method according to claim 7, wherein 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.

9. The method according to claim 7, wherein 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.

10. The method according to claim 7, wherein the holder has a suitably shaped i nternal 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.

11. The method according to claim 7, wherein 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.

12. The method according to claim 7, wherein 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.

13. The method according to claim 12, wherein the conductive coating of the cathode current collector is a chromium, nickel, titanium or aluminium alloy layer, and the conductive coating of the anodic current collector is a copper alloy layer, or the conductive coating is a platinum-group metal alloy layer or a conductive polymer layer, preferably polyaniline.

14. The method according to claim 7, wherein 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 LiPFe.

15. The method according to claim 7, wherein a solid electrolyte is used, preferably LbPSe, and a homogeneous mixture with the active mass is prepared, then a paste is made from the material obtained using the addition of Li₇PS₆.

16. The method according to claim 7, wherein current collectors are filled with active mass, with paste filling machine, preferably flow-type or vibration-type.

17. The method according to claim 7, wherein 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.