Method for producing positive and negative electrode pastes for lithium-ion cells, method for producing electrodes using these electrode pastes, and electrodes thus obtained

Abstract

A method for producing an electrode paste for a lithium-ion cell characterised by the fact that the electrode paste contains two solid components, i.e. active material and PEDOT:PSS conductive binder. A method for producing electrodes for a lithium-ion cell characterised in that it uses the electrode mass described above. Lithium-ion cell electrodes produced by the method described above using the electrode pastes described above. The electrodes obtained by the method according to the invention have a specific capacity similar to that of classical lithium-ion cells and, at the same time, have a higher energy density due to the active material content reaching preferably 95.0-97.5% by weight, which allows to produce even lighter batteries. In addition, the electrode pastes according to the invention use only two solid components, as well as a low-cost and non-toxic solvent (preferably DMSO), which makes it possible to simplify the production process and shorten supply chain.

Description

[0001] Method for producing positive and negative electrode pastes for lithium-ion cells, method for producing electrodes using these electrode pastes, and electrodes thus obtained

[0002] The present invention relates to a method for producing positive and negative electrode pastes for lithium-ion cells using non-standard additives for active materials, as well as a method for producing electrodes using these electrode pastes, and electrodes produced by this method.

[0003] Lithium-ion cells (Li-ion) are among the most efficient electrochemical energy sources, in terms of capacity and power per mass unit, currently available on the market. There are other cell types in the research phase, such as sodium and calcium cells, but due to reliability and safety problems they have not yet found a wider commercial application.

[0004] Lithium-ion cells have an energy density (based on entire cell) of up to 250 Wh / kg, which significantly exceeds the capacity of commercially available cells of other types, such as nickelhydrogen cells (55-90 Wh / kg) or lead-acid cells (25-40 Wh / kg). The average voltage of lithium- ion cells is between 3.2 and 3,8 volts, which exceeds those of other types of cells (1.2 V for nickelhydride cells; 2,0 V for lead-acid cells).

[0005] The disadvantage of Li-ion cells is their relatively high price, partly due to the high price of the components of the positive electrode (such as nickel and cobalt) and partly due to the costly procedure of preparing electrode pastes using numerous additives to improve the functioning of the electrodes. For example, amorphous carbon (e.g. carbon black, Vulcan carbon) is used to improve the electrical conductivity of electrodes. In turn, materials such as CIVIC (carboxymethylcellulose) or PVDF (polyvinylidene fluoride) are used to ensure adequate cohesion of the electrodes. CIVIC as a binder is only used as an additive to active materials, such as graphite or silicon, which are resistant to water used here as a solvent. PVDF is also used as a binder for materials sensitive to water contact as it uses organic solvents, mainly NMP (n-methylpyrrolidone). Unfortunately, NMP is toxic, expensive, degrades in contact with humidity and during exposure to light, and its solutions with PVDF also rapidly decompose under these conditions. However, PVDF binder in NMP is currently commercially exploited and serves as a benchmark for possible innovations.

[0006] The use of conductive polymers as additives to electrode pastes in electrochemical cells is known. Unfortunately, due to relatively low chemical and electrochemical resistance, conductive polymers have moderate applications under the potential conditions of lithium-ion cell operation. The commercially available polymeric material PEDOT:PSS is known, consisting of a mixture of two ionomers: positive-charged PEDOT (poly-3, 4-ethylenedioxythiophene) and negative-charged PSS (polystyrenosulfonate) [Synthetic Metals 273 (2021) 116709], PEDOT:PSS, unlike PEDOT and PSS polymers researched individually, is an electric current conductive material and its conductivity results from the interaction of its constituent ionomers. PEDOT:PSS is a chemically and electrochemically resistant material, insensitive to water and exhibiting significant mechanical resistance.

[0007] The limited use of PEDOT:PSS in lithium-ion cells is known. The use of PEDOT:PSS usually requires the use of water as a solvent, limiting its use mainly to active materials for negative electrodes (e.g. graphite, silicon) [Energy Technology 4 (2016) 331], The use of PEDOT:PSS material using NMP as a solvent or a co-solvent that is expensive and shows high toxicity is also known [Journal of Alloys and Compounds 939 (2023) 168703],

[0008] A positive electrode containing lithium iron phosphate with PEDOT:PSS added is known, which unfortunately exhibits a much smaller capacity (approx. 110 mAh / g) compared to commercially used cells equipped with NMC positive electrodes containing lithium nickel manganese cobalt oxide (approx. 180 mAh / g) [Journal of the Electrochemical Society 162 4 (2015) A674], The use of PEDOT:PSS as one of the additives to electrode pastes together along with amorphous carbon and non-conductive binder (e.g. CMC, PVDF) is also known, but this complicates the preparation procedure without significantly improving the performance [ChemElectroChem 1 (2014) 1679], There is also known use of PEDOT:PSS as a material constituting a protective layer around the grains of active material which is then conventionally mixed with amorphous carbon to produce electrode paste, but this solution is time-consuming, costly and does not bring significant benefits in terms of increasing cell capacity [Electrochimica Acta 163 (2015) 323-329],

[0009] There is an unmet need for developing a simpler and cheaper procedure for producing electrodes for lithium-ion cells and for developing electrode pastes allowing to optimise the electrochemical parameters of electrodes produced. Essence of the invention.

[0010] A method for producing electrode paste for a lithium-ion cell, consisting of mixing a suitable active material with the addition of PEDOT:PSS polymeric conducting material, acting as a conductive binder to increase mechanical strength and electrical conductivity of electrodes, wherein the mixing of the solid components of the active mass is carried out in the liquid phase to produce a suspension in a solvent neutral in regard to the active material, is characterised in that the electrode paste contains two solid components, i.e. an active material in quantities above 80-98% by weight, preferably 95.0-97.5% by weight, and PEDOT:PSS conductive binder in the amount of 2-20% by weight, preferably 2.5-5.0% by weight, wherein at an initial stage the binder is made a suspension in an anhydrous polar organic solvent, preferably aprotic, most preferably in dimethylsulphoxide (DMSO), with a polymer content of 1-5% by weight, preferably 2.5%, by mechanical stirring for 1 to 48 hours, preferably 48 hours, preferably at a stirring rate of not less than 400 rpm, preferably not less than 1,000 rpm, preferably using ultrasonification by means of an ultrasonic head of 10-500 W, preferably 150 W, for 0.1-2 min / ml of an electrode paste, preferably 0.5 min / ml of an electrode paste, and the suspension thus obtained is mixed with the active material in the desired proportion and subjected to a mechanical homogenisation for 2 to 5 hours, preferably for 4 hours, at a stirring rate of 200 to 500 rpm, preferably 400 rpm, and the homogeneous electrode paste thus obtained is ready for use.

[0011] According to the invention, a positive electrode paste is obtained by mixing PEDOT:PSS conductive binder with positive active material, preferably lithium nickel manganese cobalt oxide (NMC), lithium manganese oxide (LIVIO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP) or lithium nickel manganese oxide (LNMO). A negative electrode paste is obtained by mixing PEDOT:PSS conductive binder with negative active material, preferably lithium titanium oxide (LTO), graphite, silicon or graphite-silicon composite.

[0012] A method for producing electrodes for a lithium-ion cell, consisting of applying a wet electrode paste onto a conductive substrate, leaving it to dry under elevated temperature and reduced pressure, and then compressing it, is characterised in that it uses the electrode mass described above, which is applied, preferably by means of a mechanical applicator, in the form of a thin homogeneous layer with a thickness of 50-400 pm, preferably 200 pm, onto a conductive substrate, preferably for a positive electrode in the form of an aluminium foil with a thickness of 5-50 pm, preferably 20 pm, or for a negative electrode in the form of a copper foil with a thickness of 5-50 pm, preferably 10 pm, then dried under a pressure below 10 mbar at 110-130 °C for 10-15 hours, preferably 12 hours, wherein the electrodes of the desired shape are cut from the dry mass-coated substrate thus obtained, and the electrodes thus obtained have an active material content in the dry electrode mass of 80-98% by weight, preferably 95.0- 97.5% by weight.

[0013] According to the invention, positive electrodes are produced from the positive pastes described above. Negative electrodes are produced from negative pastes described above.

[0014] Lithium-ion cell electrodes, consisting of an electrode mass applied onto a conductive substrate, characterised in that they were produced by the method described above using the electrode pastes described above, wherein they have a layer of electrode mass with a thickness of 50-400 pm, preferably 200 pm, applied onto a conductive substrate, preferably for a positive electrode in the form of an aluminium foil with a thickness of 5-50 pm, preferably 20 pm, or for a negative electrode in the form of a copper foil with a thickness of 5-50 pm, preferably 10 pm, and characterised in that their active material content in the dry electrode mass is in the range 80-98% by weight, preferably 95.0-97.5% by weight.

[0015] According to the invention, positive electrodes are produced from positive pastes described above by the method described above. Negative electrodes are produced from negative pastes described above by the method described above.

[0016] Electrodes obtained by the method according to the invention have a specific capacity comparable to classical lithium-ion cells and, at the same time, have a higher energy density due to an active material content preferably reaching 95.0-97.5%, which allows for the creation of even lighter batteries. In addition, electrode pastes according to the invention use only two solid components (active material and conductive binder) and a solvent. Without the need for many additives to electrode pastes, the production process can be simplified and supply chains shortened. PEDOT:PSS conductive binder used is electrochemically stable and durable in contact with water. The aprotic polar organic solvent used allows electrode pastes to be formed using all known active materials. It is particularly advantageous to use DMSO as a solvent which is nontoxic and repeatedly cheaper than the currently used NMP, while being durable in contact with water and air, and mixable with water, allowing easy recycling of the conductive binder and the solvent itself.

[0017] The method for producing positive and negative electrode pastes for lithium-ion cells, the method for producing electrodes using these electrode pastes, and electrodes thus obtained are described in detail below in embodiments, with reference to the attached drawing in which: Fig. 1 represents photographs of a suspension of PEDOT:PSS in DMSO, prepared in Example 1 (A) and a positive electrode with NMC / PEDOT:PSS electrode paste prepared Example 2: in a general view when cutting off (B) and zoomed in when cut out (C);

[0018] Fig. 2 shows a diagram of the specific capacity and charging efficiency of a test cell prepared and tested cyclically in Example 3 (successive discharging cycles with current 0.1 C, 0.2 C, 0.5 C, 0.1 C, 0.2 C), equipped with an operating positive electrode, prepared in Example 1 and shown in Fig. 1;

[0019] Fig. 3 shows a diagram of the specific charging capacity of the test cell prepared and tested in Example 3 (initial charging cycle with current 0.1 C, further charging cycles with current 0.2 C), equipped with an operating positive electrode, prepared in Example 1 and shown in Fig. 1;

[0020] Fig. 4 shows a diagram of the specific discharging capacity of the test cell prepared and tested in Example 3 (successive charging cycles with current 0.1 C, 0.2 C, 0.5 C, 0.1 C, 0.2 C), equipped with an operating positive electrode, prepared in Example 1 and shown in Fig. 1;

[0021] Fig. 5 presents photographs of a suspension of PEDOT:PSS in DMSO, prepared in Example 1 (A) and a negative electrode with LTO / PEDOT:PSS electrode paste, prepared in Example 4: in the general view during felling (B) and cut in the proximity (C);

[0022] Fig. 6 shows a diagram of the specific capacity and charging efficiency of the test cell prepared and tested cyclically in Example 5 (successive discharging cycles with current 0.1 C, 1 C,

[0023] 2 C, 5 C, 10 C, 1 C), equipped with an operating positive electrode, prepared in Example

[0024] 3 and shown in Fig. 5;

[0025] Fig. 7 shows a diagram of the specific charging capacity of the test cell prepared and tested in Example 5 (charging cycle with current 1 C), equipped with an operating positive electrode, prepared in Example 3 and shown in Fig. 5;

[0026] Fig. 8 shows a diagram of the specific discharging capacity of the test cell prepared and tested in Example 5 (successive charging cycles with current 0.1 C, 1 C, 2 C, 5 C, 10 C, 1 C), equipped with an operating positive electrode, prepared in Example 3 and shown in Fig. 5.

[0027] A detailed description of the invention.

[0028] The invention relates to the method for producing electrode pastes for lithium-ion cells and the method for producing electrodes for cells of this type, consisting of the use of PEDOT:PSS conductive binder, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, as the only additive to active material (positive or negative one), which ensures good electrical conductivity in electrode mass and mechanical strength of the electrode while maintaining a correspondingly high lithium ion intercalation capacity of this electrode. The electrodes thus obtained can be used in most types of lithium-ion cells.

[0029] The procedure for preparing electrode pastes and lithium-ion cell electrodes according to the invention is easily adaptable in industry due to its low degree of complexity in terms of process stages and the necessary equipment. The advantage of the method for preparing positive electrodes according to the invention is the exclusion of the need for other conductive additives (such as amorphous carbon, acetylene black, Vulcan carbon, etc.) to be used in electrode mass, which enables the production process to be simplified. In addition, an anhydrous polar organic solvent is used, preferably a protic (anhydrous ethanol or isopropanol) or an aprotic one (DMSO, tetrahydrofuran, acetone or acetonitrile), preferably a DMSO, which is insensitive to oxygen and water, cheaper and less toxic than that NMP (N-methylpyrrolidone) commonly used in industry for the production of conventional composition electrodes. Electrodes obtained by the method according to the invention exhibit favourable performance parameters, i.e. high specific capacity and cyclic stability, with a higher active material content in the electrode mass than currently available constructions, which allows to achieve higher energy density and gravimetric capacities of these electrodes, and as a result translates into the capability to produce lighter batteries while maintaining unchanged capacity.

[0030] Method for producing electrode pastes. According to the invention, the first step in the production of electrode pastes is to prepare a suspension of PEDOT:PSS conductive binder in the solvent. For this purpose, the dry mass of PEDOT:PSS binder is mixed with the solvent, then the suspension of the conductive binder is mixed with the active material and homogenised to form electrode pastes. An organic polar anhydrous solvent is used, either a protic or an aprotic solvent, preferably stable in the presence of moisture and atmospheric oxygen. The lack of water is crucial to ensure the stability of active materials, while polarity of the solvent is necessary to dissolve PEDOT:PSS conductive binder. Among the protic solvents, anhydrous ethanol or anhydrous isopropanol are advantageously used, the acidity of which does not endanger the stability of the active materials. Aprotic solvents are safer for active materials because they cannot be dissociated with the release of a proton. Among the aprotic solvents, anhydrous DMSO, tetrahydrofuran, acetone and acetonitrile are preferably used. Finding a replacement for the toxic NMP used so far was a key step in developing the present invention. Unexpectedly, particularly preferable has proved the use of dimethylsulphoxide (DMSO), which excellently disperses PEDOT:PSS, forming stable suspensions with an appropriate concentration of conductive binder, is also stable in contact with water and atmospheric air, non-toxic and cheap, and is also mixable with water, allowing to develop a recycling method. According to the invention, anhydrous mixtures of the above-mentioned solvents or other solvents may also be used if they have similar properties as DMSO and dissolve PEDOT:PSS conductive binder.

[0031] According to the invention, a suspension of PEDOT:PSS conductive binder in DMSO is prepared by stirring using a magnetic stirrer, a mechanical stirrer at a stirring rate of not less than 400 rpm, preferably at a rate of not less than 1,000 rpm, for 1 to 48 h, preferably for 48 h, or by means of a planetary mixer, preferably at a rate of not less than 3000 rpm, for 20 to 30 minutes, preferably 30 minutes. The suspension thus obtained is ultrasonified using an ultrasonic head of 10 to 500 W, preferably 150 W, for 0.1-2 min / ml of the polymer suspension, preferably 0.5 min / ml of the polymer suspension to ensure its homogeneity. Percentage of PEDOT:PSS in suspension is 1-5% by weight, preferably 2.5% by weight. PEDOT:PSS content in suspension significantly influences its viscosity. Suspensions with a PEDOT:PSS content of less than 1% by weight exhibit an insufficient viscosity to ensure the homogeneity of the electrode paste when applied onto a conductive substrate. Suspensions with a PEDOT:PSS content of more than 5% by weight exhibit viscosity too high to allow complete and homogeneous dissolution of the conductive binder in solvent. Optimal PEDOT:PSS content in suspension is 2.5% by weight, due to the viscosity of the resulting mixture preferable in terms of further obtaining wet electrode pastes capable of remaining homogeneity when being applied onto a conductive substrate, while maximising the PEDOT:PSS content in suspension, which minimizes solvent consumption.

[0032] PEDOT:PSS suspension in solvent, most preferably in DMSO, prepared according to the invention, is ready for use in the process of preparation of electrode pastes, and retains its properties for at least 10 minutes, including in contact with moisture and atmospheric air. Preferably, a suspension of the conductive binder is produced immediately before use to produce electrode paste and used without undue delay.

[0033] For electrode pastes, PEDOT:PSS suspension described above is used and any known electrochemically active material (capable of lithium ion intercalation and oxidation-reduction reaction) used for producing positive and negative electrodes of the lithium-ion cell, preferably material with high specific capacity and high specific energy. Percentage of active material in the dry mass of electrode paste (i.e. based the active material mass) may be arbitrary, but for optimum parameters it amounts to 80-98% by weight, preferably 95-97.5% by weight. The active material is mixed with a solvent suspension of the conductive binder in relation to dry active material by mass to dry conductive binder in the range of 80:20-98:2, preferably in the range of 95.0:5.0-97.5:2.5. The electrode paste is homogenised by stirring using a magnetic stirrer, a mechanical stirrer at 200 to 500 rpm, preferably 400 rpm, or a planetary mixer, preferably above 3000 rpm.

[0034] The electrode paste thus obtained is then used to produce electrodes for lithium-ion cells. Electrode paste according to the invention retains its properties for at least 30 minutes, and with chemically inertial electrode materials used also in contact with humidity and atmospheric air. Preferably, the electrode paste is produced immediately before use to produce lithium-ion cell electrodes and is used without undue delay.

[0035] Method for producing electrodes. According to the invention, a conductive substrate is used as a current collector for electrode mass produced according to the method described above. Preferably, a metal substrate is used, preferably in the form of an aluminium foil for a positive electrode or of copper or aluminium foil for a negative electrode. In the case of the negative electrode, the choice of the material of which the current collector foil is made (copper, aluminium) depends on the electrode material chosen, wherein for materials working in the range of potentials higher than the potential formation of a lithium aluminium alloy (e.g. LTO), the formation of which results in pulverisation of the substrate and destruction of the negative electrode, preferably aluminium foil is used (which decreases the cost and dead weight of the cell), while for materials working in a lower range of potentials, such as graphite or silicon, preferably copper foil is used which does not form a lithium alloy, thus remaining inert when a negative electrode is working with such active materials. This foil must have mechanical properties allowing manual or machine operations and must therefore not be too thin (less than 5 pm) as it would be susceptible to rupture during treatment. The foil must also not be too thick (over 50 pm) as it would constitute a dead weight in the finished cell and would unnecessarily reduce the cell energy density. The optimal thickness of the foil for this application is 20 pm.

[0036] According to the invention, a wet electrode mass is applied onto a conductive substrate. Preferably, it is applied onto a conductive substrate in such a way as to ensure an even distribution of the mass, most preferably by means of an automatic applicator with an adjustable aperture enabling the thickness of the applied wet layer to be controlled, wherein the thickness of the wet layer of electrode mass is 50-400 pm, preferably 200 pm. Thin layers perfectly bind with the ground and are stable at high current, but insufficient mass thickness reduces the capacity of the electrode. On the other hand, although too thick layers provide more electrochemical capacity, they tend to break. The electrode mass thickness of 200 pm is an optimum ensuring both a high capacity and a high stability of the electrode.

[0037] Electrode in the form of a conductive substrate coated with the layer of a wet electrode mass is dried under a pressure below 10 mbar at 110 to 130 °C for 12 hours. The method for preparing electrodes presented above is simple and eliminates the need for active material homogenisation with a conductive additive (e.g. amorphous carbon, acetylene black) that is present in prior art known solutions. The procedure used can be easily rescaled to an industrial scale by an appropriate magnification of the device homogenising the active material and the binder.

[0038] The method for producing positive and negative electrode pastes for lithium-ion cells, the method for producing electrodes using these electrode pastes and electrodes thus obtained are described below in embodiments.

[0039] Example 1. A suspension of PEDOT:PSS in DMSO was prepared by the method according to the invention using a commercially available PEDOT:PSS polymer in the form of pellets and anhydrous DMSO as a solvent. 50,0 mg of PEDOT:PSS polymer and 1,950 g of DMSO were weighed, then the weighed portions were mixed altogether and after that mixed using a planetary mixer at a rate of 3500 rpm for 30 minutes. The suspension thus formed was then ultrasonified with an adjustable-power ultrasonic head for 1 minute with a power setting of 150 W. The prepared PEDOT:PSS suspension with a concentration of 2.5% by weight in DMSO and a volume of approx. 2.2 ml is shown in Fig. 1A and Fig. 5A. The resulting suspension was used to produce electrode pastes in Examples 2 and 4.

[0040] Example 2. A positive electrode was produced for the lithium-ion cell by the method according to the invention, using an addition of a conductive binder to an electrochemically active material. The active material used was the commercially available positive electrode active material: lithium nickel manganese cobalt oxide (NMC) presented by the formula of LiNi0.6Mn0.2Co0.2O2. PEDOT:PSS was used as a conductive binder. Positive electrode paste was prepared by mixing 200 mg of NMC and 205.1 mg of PEDOT:PSS suspension in DMSO containing 5.13 mg of PEDOT:PSS (suspension concentration: 2.5% by weight) produced in Example 1. Positive electrode paste with a weight of 405.1 mg was obtained with a ratio of active material (NMC) weight to conductive binder (PEDOT:PSS) weight of 97.5:2.5 (binder content in the electrode mass: 2.5% by weight). The positive electrode paste was homogenised for 4 hours using a magnetic stirrer at a stirring rate of 400 rpm. The resulting wet electrode paste was applied onto a conductive substrate in the form of an aluminium foil with a thickness of 20 pm by means of an automatic applicator with an adjustable aperture, wherein the thickness of the wet layer amounted to 200 pm. The foil coated with a wet positive electrode paste was dried for 12 hours at 120 °C under reduced pressure below 10 mbar to remove the solvent completely (DMSO). A dried foil coated with electrode foil is shown in Fig. IB. From the obtained dried foil circular electrodes with a diameter of 9 mm were cut out by means of a manual cutter. Electrodes were then compressed for 60 seconds under a pressure of 200 bar by means of a hydraulic press (pressure of 6 tonnes). The packaging of the electrode material on the finished electrodes amounted to 1.0-1.5 mg / cm2. A finished electrode is shown in Fig. 1C.

[0041] Example 3. The electrodes obtained in Example 2 were subjected to a standard assessment of the intercalation properties against the Li+ions. Measurements were made of galvanostatic charging and discharging a lithium-ion cell in which the positive operating electrode was that produced in Example 2. The counter and reference electrodes were made of metallic lithium. Liquid electrolyte was used in the cell in the form of 1 M LiPFg solution in a mixture of solvents ethylene carbonate and dimethyl carbonate in a ratio of 1:1 by weight. Polypropylene separator Celgard 2325 was used. The whole has been placed in a three-electrode Swagelok’ housing. Measurements were made with a multichannel potentiostat / galvanostat Atlas 0961 equipped with a digital recorder of the charging and discharge curves. The charging current used was 0.2 °C (55.2 mA / g) and the discharging current intensities, alternating in successive operating cycles of the cell, were as follows: 0.1 C (27.6 mA / g), 0.2 C (55.2 mA / g), 0.5 C (138 mA / g) and 1 C (276 mA / g). The operating cycle included galvanostatic charging and discharging in the potential range of 2, 9-4, 3 V relative to the reference electrode. The result of the test measurements is shown in Figs. 2-4.

[0042] Example 4. A negative electrode for the lithium-ion cell was produced by the method according to the invention, using an addition of a conductive binder to an electrochemically active material. Lithium titanium oxide (LTO) with spinel structure having the sum formula Li4Ti50i2 was used as an active material. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was used as a polymeric conductive binder. The negative mass was prepared by mixing 200 mg of LTO and 421.2 mg of PEDOT:PSS polymer suspension in dimethylsulphoxide (DMSO) containing 10.53 mg of PEDOT:PSS polymer (concentration by weight of a suspension: 2.5%), produced in Example 1. A negative mass of 621.2 mg was obtained with a ratio of active material weight (LTO) to polymer binder weight of 95.0:5.0 (binder content in the electrode mass: 5.0% by weight). The negative electrode mass was homogenised for 4 hours using a magnetic stirrer at a stirring rate of 400 rpm. The resulting wet mass was applied onto a conductive substrate in the form of an aluminium foil with a thickness of 20 pm by means of an automatic applicator with an adjustable aperture, wherein the thickness of a wet layer amounted to 200 pm. The foil covered with a wet negative mass was dried for 12 hours at 120 °C under a pressure below 10 mbar. The foil coated with electrode paste after drying is shown in Fig. 5B. From the obtained dried foil circular electrodes with a diameter of 9 mm were cut out by means of a manual cutter. Electrodes were compressed for 60 seconds at 200 bar by a hydraulic press (pressure 6 tonnes). The packaging of the electrode material on the finished electrodes amounted to 1.5 and 2,0 mg / cm2. A finished electrode is shown in Fig. 5C. Example 5. The electrodes obtained in Example 4 were subjected to a standard assessment of the intercalation properties against the Li+ions. Measurements were made of galvanostatic charging and discharging of a lithium-ion cell in which the negative operating electrode was that produced in Example 4. The counter and reference electrodes were made of metallic lithium. Liquid electrolyte was used in the cell in the form of 1 M LiPFg solution in a mixture of solvents ethylene carbonate and dimethyl carbonate in a ratio of 1:1 by weight.

[0043] Polypropylene separator Celgard 2325 was used. The whole has been placed in a three-electrode Swagelok’ housing. Measurements were made with a multichannel potentiostat / galvanostat Atlas 0961 equipped with a digital recorder of the charging and discharge curves. There was used a charging current intensity amounting to 1 C (175 mA / g), while in the successive cell operation cycles there were used alternating discharging intensities amounting to: 0.1 C (17.5 mA / g), 1 C (175 mA / g), 2 C (350 mA / g), 5 C (875 mA / g) and 10 C (1,750 mA / g). The operating cycle included galvanostatic charging and discharging in the potential range of 1, 0-3,0 V relative to the reference electrode. The result of the test measurements is shown in Fig drawings. 6-8.

Claims

Patent claims1. A method for producing electrode paste for a lithium-ion cell consisting of mixing suitable active material with the addition of PEDOT:PSS polymeric conductive material, acting as a conductive binder, increasing the mechanical strength and electrical conductivity of the electrode, wherein the mixing of the solid components of the active mass is carried out in the liquid phase to produce a suspension in a solvent that is neutral relative to the active material, characterised in that the electrode paste contains two solid components, i.e. the active material in quantities above 80-98% by weight, preferably 95.0-97.5% by weight, and PEDOT:PSS conductive binder in the amount of 2-20% by weight, preferably 2.5-5.0% by weight, wherein at an initial stage the form of a binder is made a suspension in an anhydrous polar organic solvent, preferably aprotic one, most preferably in dimethylsulphoxide (DMSO), with a polymer content of 1-5% by weight, preferably 2.5% by weight, by mechanical stirring for 1-48 hours, preferably 48 hours, preferably at a stirring rate of not less than 400 rpm, preferably not less than 1,000 rpm, preferably using ultrasonification by means of an ultrasonic head of 10-500 W, preferably 150 W, for 0.1-2 min / ml of an electrode paste, preferably 0.5 min / ml of an electrode paste, and the suspension thus obtained is mixed with the active material in the desired proportion and subjected to a mechanical homogenisation for 2-5 hours, preferably 4 hours, at a stirring rate of 200 to 500 rpm, preferably 400 rpm, and the homogeneous electrode paste thus obtained is ready for use.

2. The method for producing electrode paste according to claim 1, characterised in that a positive electrode paste is obtained by mixing PEDOT:PSS conductive binder with a positive active material, preferably lithium nickel manganese cobalt oxide (NMC), lithium manganese oxide (LIVIO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP) or lithium nickel manganese oxide (LNMO).

3. The method for producing electrode paste according to claim 1, characterised in that a negative electrode paste is obtained by mixing PEDOT:PSS conductive binder with a negative active material, preferably lithium titanium oxide (LTO), graphite, silicon or graphite-silicone composite.

4. The method for producing electrodes for a lithium-ion cell, consisting of applying a wet electrode paste onto a conductive substrate, leaving it to dry under elevated temperature and pressure, and then compressing, characterised in that it uses the electrode mass described in claims 1-3, which is applied, preferably by means of a mechanical applicator, in the form of a thin homogeneous layer with a thickness of 50-400 pm, preferably 200 pm, onto a conductive substrate, preferably for a positive electrode in the form of an aluminium foil with a thickness of 5-50 pm, preferably 20 pm, or for a negative electrode in the formof a copper foil with a thickness of 5-50 pm, preferably 10 pm, then dried under a pressure below 10 mbar at 110-130 °C for 10-15 hours, preferably 12 hours, wherein from the substrate thus obtained covered with a dry mass electrodes of the desired shape are cut out and compressed for 60 seconds under a pressure of 200 bar, and the electrodes thus obtained have an active material content in the dry electrode mass in the range of 80-98% by weight, preferably 95.0-97.5% by weight.

5. The method for producing electrodes according to claim 4, characterised in that positive electrodes are produced from the positive pastes described in claims 1 and 2.

6. The method for producing electrodes according to claim 4, characterised in that negative electrodes are produced from negative pastes described in claims 1 and 3.

7. Lithium-ion cell electrodes, consisting of an electrode mass applied onto a conductive substrate, characterised in that they are produced by the method described in claims 4-6 using electrode pastes described in claims 1-3, wherein they have a layer of electrode mass with a thickness of 50-400 pm, preferably 200 pm, applied onto a conductive substrate, preferably for a positive electrode in the form of an aluminium foil with a thickness of 5-50 pm, preferably 20 pm, or for a negative electrode in the form of a copper foil with a thickness of 5-50 pm, preferably 10 pm, and they are characterised in that they have an active material content in the dry electrode mass amounting to 80-98% by weight, preferably 95.0-97.5% by weight.

8. The electrodes according to claim 7, characterised in that the positive electrodes are produced from the positive pastes described in claims 1 and 2 by the method described in claims 4 and 5.

9. The electrodes according to claim 7, characterised in that the negative electrodes are produced from the negative pastes described in claims 1 and 3 by the method described in claims 4 and 6.

Images