RU2103766C1 - Carbon-carrying material for electrodes of chemical sources of electric energy and method of manufacture of porous electrodes from it - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: carbon-carrying material includes electrode-active material, predominantly, fluorocarbon containing 58-67 per cent by mass of fluorine, binder, material increasing conductance of electrode-active material and pore-forming material in which capacity graphite fluoroxide is used. Method of manufacture of porous electrode includes operations of stage by stage mixing of components described above. At first stage graphite fluoroxide and electrode-active material are mixed, then this mixture is modified mainly by impact action to produce intermediate product which is mixed at second stage with binder and material increasing conductance of electrode-active material, later article is formed and thermally treated till pores are formed in structure of the latter without destruction. Electrodes using proposed material and manufactured by given process display increased specific energy characteristics. EFFECT: increased specific energy characteristics. 28 cl, 6 tbl

Description

 The invention relates to the field of chemical current sources (CIT), and more particularly, to a carbon-containing material for ChIT electrodes and a method for manufacturing porous electrodes from it.

 The present invention can be used to create new carbon-containing energy-saturated electrode materials used in chemical current sources (HIT), mainly in lithium HIT half-volt and three-volt systems.

 Currently, in the field of chit with solid-state electrodes, there is a problem of providing high energy intensity of electrodes while ensuring a high operational density of the discharge current. This problem mainly concerns cathodes, since the anodes of chemical current sources based on active metals — lithium, sodium, zinc, and others — are most often used in HIT constructions in their compact state, that is, at their density realized at the anodes as close to or equal to the pycnometric density realized in the crystal lattices of these materials.

 To realize the maximum characteristics of HIT in terms of energy intensity, it is necessary to use electrode-active materials with high specific mass and volume characteristics with the maximum possible filling of the electrode structure with electrode-active material. However, with increasing electrode density due to a more complete filling of the electrode volume with electrode-active material, its surface available for a current-forming reaction simultaneously decreases, while the effective electrode discharge current density as a whole decreases.

 On the other hand, the effective discharge current density of the electrode can be increased by increasing the effective surface of the electrode, for example, by finely grinding its components and adding materials that increase its electrical conductivity to the electrode. This leads to an increase in the porosity of the electrode, but, however, also leads to a decrease in the content of the main component in the electrode — the electrode-active material.

 Therefore, the solution to the problem of creating an energy-intensive ChIT with an increased discharge current density is inevitably associated with a compromise between a decrease in the total energy intensity of the electrode and an increase in its porosity and electrical conductivity with the same electrode volume.

 The electrode of a chemical current source usually consists of a mixed composition consisting of an electrode-active material, a binder and a material that increases electrical conductivity. For the formation of the pore structure in the electrodes, pore-forming materials are used, which are substances and materials that dissolve or volatilize during the physicochemical treatment of the formed electrodes, during which a pore structure is created in the electrode, which is necessary to place the electrolyte in them and deposit solid current-forming products reactions (I.A. Kedrinsky et al., Chemical current sources with a lithium electrode, publishing house of the Krasnoyarsk University, Krasnoyarsk .: 1983, p. 248, p. 144 - 147 [1]).

 Various pore-forming materials are known: graphite expanses (Peter Faber, “Active mass of the positive electrode of the primary element”; USSR Author's Certificate N 488432, H 01 M 13/02, 21/00, publ. 15.10.75, BI N 38 [2]; BK Makarenko et al., “Positive electrode of a chemical current source”, USSR Author's Certificate N 564668, H 01 M 4/98, 6/14, publ. 05.07.77, BI N 25 [3]); organic compounds, for example, camphor (French Patent N 2093287, H 01 M 13/00, 1972 [4]) or soluble inorganic compounds, for example, potassium hexafluorophosphate (NS Lidorenko et al., "A method for manufacturing a porous electrode for a chemical a current source with non-aqueous electrolyte ", USSR Author's Certificate N 527775, H 01 M 4/62, publ. 05.09.76, BI N 33 [5]). For the same purpose, insoluble inorganic compounds and materials with a finished porous structure are also used — zeolites (N. Watanabe et al., "Cell with an Organic Electrolyte", Japanese Patents N 61-264679, 61-264680, 61-264682, 61-264681 , H 01 M 6/16, dated 05.20.85 [6]) or activated alumina (Suezugu Sachiko, "Lithium-fluorocarbon system element", Japan Patent 63-334457, H 01 M 4/06, 12.28.88 [7 ]). When these materials are introduced into the composition, all these materials can improve discharge characteristics, however, the electrode density decreases and, ultimately, the electric capacitance in the current source decreases due to a decrease in the content of electrode-active material.

 Methods for the manufacture of porous cathodes for chit are reduced to a combination of the sequence of procedures for preparing, mixing and processing the starting components, most often all prepared ingredients are mixed in one stage [1-7], including in the presence of water or organic solvents, after which they are isolated, dried and crushed the semi-finished cathode material. Then, the cathodes are formed, equipped with current conductors (for example, by pressing them into the cathode bodies) and the cathodes are subjected to either the washing of the soluble pore-forming material with an appropriate solvent or heat treatment to remove the sublimated pore-forming material from the cathode, while the pore structure necessary for normal operation of the cathode is formed in the cathode [2, 4, 5]. However, porous chitosan cathodes, in which soluble compounds such as camphor [4] or potassium hexafluorophosphate [5] are used as pore formers, are rather difficult to wash from the pore former. This is due to the fact that during the formation of the cathode, blocking (occluding) of the particles of the used blowing agent by a binder or energy carrier occurs, which worsens the properties of the cathode and ChIT based on it. For this reason, to complete the removal of the blowing agent, multiple procedures are used, which is associated with the use of additional quantities of solvents. In addition, when using the indicated materials and methods for the manufacture of electrodes in CITs, the impossibility of realizing in the lithium current source with sufficient porosity (35–50%) of higher energy indices for the CIT working capacity is shown, since porous CIT cathodes in which zeolite are used as porogen [6 ] or activated alumina [7], have a reduced mass and volume energy intensity, that is, such pore formers do not exhibit electrical activity and are ballast.

The use of known active cathode masses in HIT electrodes containing metal oxide (manganese dioxide, lead oxide, or a mixture thereof) as the electrode-active material, and graphite expandate as a material for increasing electrical conductivity [2], also reduces the specific energy consumption of the electrode. The expanded graphite in the cathode material simultaneously serves as a pore-forming agent due to its low density (0.007-0.05 g / cm ³ ), large specific surface area [2] and high porosity. For the manufacture of electrode material, a ready-made graphite expansion of a coral-like structure is used, which is introduced in an amount of up to 25% of the weight of the energy carrier. The coral structure of the graphite expandant is realized by separately thermolysis of various graphite compounds, for example, fluorinated graphite [3]. The introduction of graphite expanders (expanded graphite) into the electrode composite is an inconvenient procedure due to the fact that this material refers to highly "dusty" objects.

 The known electrode of the current source and the method of its manufacture, adopted by us as a prototype (EP Patent N 0146764, H 01 M 4/06, 4/88 [8]). The composition of the electrode material includes: electrode-active material, which is carbon monofluoride, a binder (fluoropolymer), a material that increases the electrical conductivity of the electrode-active material. During its manufacture, a pore-forming material is introduced, which is used as a non-polymer additive (alcohols, hydrocarbons, solutions). The pore-forming material is introduced into the mixture of ingredients when they are mixed at the very beginning of the electrode manufacturing process to prepare a pasty mass and make a ready-made elastic microporous carbon-containing electrode by removing the pore-forming material. The porous structure of the cathode is formed after removal of the pore-forming material by evaporation, and this is carried out after the electrode is manufactured (the procedure of mixing all components with a strong shear force to form a homogeneous fibrous structure in the material and then forming the electrode by extruding or calendaring, pressing, folding the bags to obtain a finished electrode cathode plate for a current source).

The described material and the method of manufacturing an electrode (cathode) from it are quite acceptable for their use in a lithium chemical current source. However, the material and method have the following properties related to the features of the components used in the electrode and the method for manufacturing an electrode for HIT from them:
relatively low energy efficiency, namely the electric capacitance of the obtained carbon-containing cathode material, which is associated with the lack of one of the main components - electrode-active material, which is used carbon monofluoride. In the world market, fluorocarbon materials are usually used for cathodes of fluorocarbon-lithium batteries: carbon monofluoride — C ₂ F and carbon monofluoride — CF _1,0 , containing up to 59 wt.% Fluorine, for example, fluorinated petroleum coke the composition of CF is _0.92-1.0 . The theoretical electrical capacity of carbon monofluoride is 861 mAh / g;
carbon monofluoride also has a relatively low bulk density (about 1.0 g / cm ³ ), which does not allow introducing a larger amount of energy carrier into the real volume of the positive lithium ChIT electrode and, thus, increasing the specific volume energy consumption of the current source;
carbon monofluoride has relatively low operational discharge current densities in standard fluorocarbon cathodes (not more than 0.1 mA / cm ² ) and is characterized by a strong decrease in the initial discharge voltage at higher current loads, which is associated with the phenomenon of deposition of solid lithium fluoride on the cathode surface. This phenomenon is observed due to the fact that the pore volume is not enough in a real current source in such increased current modes to accommodate the required amount of electrolyte to dissolve the resulting diffusion layer of solid lithium fluoride, a reaction product of fluorocarbon with lithium. It is also influenced by the fact that fluorocarbon cathodes have high ohmic resistance and, as a result, a large amount of overvoltage, which is manifested by the cumulative effect - during operation, the current source reduces the value of the current discharge voltage at a nominal load of 30 kOhm to 2.6 - 2.7 V;
when a current source is discharged with a fluorocarbon electrode, its "swelling" often occurs. This effect is taken into account when designing a lithium current source, and as a result, less fluorocarbon is introduced into the electrode to prevent "swelling" of the CIT;
while the simplicity of the procedure for mixing the starting components of the carbon-containing electrode material and the subsequent molding procedures by extruding or calendering, pressing, folding the bags, until a finished porous cathode plate for a current source is obtained, the resulting cathode plate becomes uniform but stiff due to the strong bulk cohesion of the composite a binder material is a fluoropolymer;
in the manufacture of the electrode according to the known method by mixing all the components in one step, and mixing is carried out with a large shear force to provide a fibrous structure of the electrode material, excessive blocking of the particles of the electrode-active material and the material that increases the electrical conductivity of the latter by the binder material (active particles masses often turn out to be coated with a layer of binder material), which leads either to a significant decrease in the electrode delivered a nominal capacitance discharge mode (0.1 mA / cm ²⁾ or to the inability to properly operate such an electrode at high discharge current density in a lithium chemical current source (in the implementation of the discharge current density at 1 mA / cm ² and above a fluorocarbon an electrode paired with lithium gives a voltage below 2V);
the process of pore formation in the cathode by the known method is quite difficult to control during the manufacturing and molding of the finished product (electrode), and the pores in such a carbon-containing electrode are formed due to small droplets of the pore former - liquid non-polymer additives (alcohols, hydrocarbons, solutions) distributed in the cathode composite during mixing and volume cohesion during calendaring due to a binder. Pores are freed from the blowing agent by volatilization of the applied non-polymer liquid;
As a result of such a procedure for manufacturing the electrode mass of a carbon-containing material, the adhesion of the obtained porous cathode rigid plate to the current lead becomes low (with a loose pressing), and with a denser pressing (under a higher pressure), the cathode porosity decreases due to squeezing the liquid from the pores. An intermediate option is chosen for applying such pressure values (or pressing on an additional current collector welded to the cathode cover) at which adhesion is maintained and acceptable cathode porosity is achieved.

 In General, as a result of the application of the technology according to the known method, the discharge characteristics of the HIT during its operation are reduced.

 The basis of the present invention is the task to create a carbon-containing material with such components and such a method of manufacturing porous electrodes from this material that would allow to increase the specific energy characteristics of the carbon-containing material in the electrode of a chemical current source, including volumetric and mass electrical and energy consumption, to increase operational discharge current density, discharge voltage and simplify the method of manufacturing electrodes.

 The problem is solved by creating a carbon-containing material for the electrodes of chemical current sources containing an electrode-active material, a binder, a material that increases the electrical conductivity of the electrode-active material, and a pore-forming material, which, according to the invention, contains graphite fluoride as a pore-forming material.

 The effect of the use of such a blowing agent is that in the structure of the active mass for the manufacture of a carbon-containing electrode, after mixing and the heat treatment procedure, a sufficient number of pores appears to accommodate a non-aqueous electrolyte in them. In addition, during the heat treatment of graphite fluoride, thermally expanded graphite is formed inside the electrode volume, which is also a material that increases the electrical conductivity of the electrode. At the same time, unification of electrode materials is achieved by using a single blowing agent for various types of HIT half-volt and three-volt systems with different electrode-active materials, the use of which increases the specific energy characteristics of the proposed material in the HIT electrode described above.

Typically, graphite fluoride is assigned the general formula
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 12; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.1-0.5.

(L. L. Gornostaev et al., USSR Author's Certificate N 955654, reg. 04.05.82, "Graphite fluoroxides and a method for their preparation", C 01 B 31/00 [9]). However, the use of a product of this composition as a blowing agent is effective only in fairly expensive cathode masses based on an electrode-active material - fluorocarbon. For use in cathode masses based on metal oxides, sulfides or their mixtures, another, cheaper type of graphite fluoroxide with a modified phase ratio (increased graphite phase content and reduced graphite fluoride phase content), expressed by another general formula, is used as a blowing agent, expressed by another general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 5 - 15; y = 2.2-2.5; z = 0.2 - 2.0 and n = 0.1 - 2.0.

This is due to the fact that graphite fluoride, by known methods of preparation, is almost always a close mixture of three phases in which the phases of graphite oxide (ZC _y O) and graphite fluoride (CF) etched during oxidation are represented in the phase of graphite (C _x ). In accordance with this, the chemical behavior of graphite fluoroxide, and therefore the conditions for its use as a blowing agent, are determined by the ratio and behavior of all three phases at a changing temperature.

In this case, it is advisable to use the cheapest fluoroxide graphite of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01 - 0.5.

 To increase the energy intensity of a carbon-containing material to the maximum possible values in it, it is most expedient to use fluorocarbon containing 58 to 67 wt.% Fluorine as an electrode-active material, since fluorocarbon containing 58 to 67 wt.% Fluorine has more than in known fluorocarbon materials (carbon monofluoride or fluorinated petroleum coke), the amount of fluorine, and therefore contains more energy than the objective of the invention is achieved to increase the specific energy consumption of the electrode and HIT in general.

 It is also advisable to increase the specific energy consumption of the material and the electrode based on it as the electrode-active material to use energy-intensive compounds of transition metals, which can be used metal oxides and sulfides, taken separately or in combination.

 To increase the specific energy consumption of three-volt lithium ChIT, it is advisable to use cheaper manganese dioxide as the electrode-active material.

 The use of graphite fluoroxide is also advisable to combine with one-and-a-half-volt electrode-active materials, namely copper oxide, as well as a mixture of copper oxide with pyrite or copper oxide with chalcopyrite.

 The use of copper oxide as well as a mixture of copper oxide with pyrite and a mixture of copper oxide with chalcopyrite in one and a half-volt chemical current sources gives a good effect in combination with graphite fluoride, a binder and a material that increases electrical conductivity in carbon materials for HIT electrodes.

 Thus, the use of the proposed carbon-containing material for HIT electrodes makes it possible to manufacture a porous electrode for a chemical current source having an increased electric capacity in comparison with known electrodes. This is achieved due to the formation of pores in the structure of the electrode made of the proposed carbon-containing material. Pores in the electrode are necessary to place electrolyte in it. In addition, a close mixture of the products of the thermolysis of graphite fluoroxide with electrode-active material allows the discharge to achieve higher efficiency of the electrode-active material, as shown below.

 The problem is also solved by the creation of a method of manufacturing a porous electrode for chemical current sources, including mixing the electrode-active material, a binder, a material that increases the electrical conductivity of the electrode-active material and a pore-forming material, and molding the finished product, in which, according to the invention, as the pore-forming material and graphite fluoride is used, and the components are mixed in stages, and at the first stage, graphite fluoroxide and elemental are mixed cathode-active material, then this mixture is modified to obtain an intermediate product, which in the second stage is mixed with a binder and a material that increases the electrical conductivity of the electrode-active material, and after molding the finished product, it is heat treated to form pores in the structure of the finished electrode without destroying it .

When the components are mixed in stages and the modification is applied at the first mixing stage, close mixing of the electrode-active material with the pore-forming material is achieved, accompanied by additional grinding of the components and an increase in the bulk density of the mixture of electrode-active material and graphite fluoride and obtaining an intermediate product. In this intermediate product, a significantly higher volume concentration of paramagnetic centers is realized, which increases the electrical conductivity of the electrode. Phased mixing makes it possible to avoid excessive blocking of the binder particles of the electrode-active material and the material that increases the electrical conductivity of the latter. In addition, such phased mixing makes it possible to control the final density and porosity of the electrode material by adjusting the mixing mode in the second stage to obtain an elastic active mass. The presence of an elastic mass obtained after the second stage of the final mixing of all components facilitates the procedure of forming the electrode and controlling its density. The effect of this method of manufacturing a porous electrode lies in the possibility of realizing an increased energy intensity in the electrode at the nominal mode (0.1 mA / cm ² ) due to a combination of several newly arising effects:
the placement in the electrode volume of a sufficiently large amount of any of the listed electrode-active materials that have been modified in a mixture with a pore-forming material makes it possible to achieve significantly higher specific energy consumption from such electrodes than for the best of the known lithium CITs, one-and-a-half and three-volt systems;
the use of the proposed pore-forming material — graphite fluoroxide, and the electrode manufacturing method in the electrode makes it possible to achieve an increased density of the continuous discharge current (0.75 - 1.0 mA / cm ² or more) while maintaining a high electric capacity, which is achieved by heat treatment of the finished product, since during the thermal decomposition of graphite fluoroxide, pores are formed from it in the electrode volume without destroying the latter, as well as thermally expanded graphite uniformly distributed in the electrode material, the presence of which allows t increase the electrical conductivity of the electrode material and, hence, reduce the magnitude of the voltage drop due to the internal resistance of the current source as a whole.

As graphite fluoride, any of the known graphite fluoroxides can be used, but it is advisable to use graphite fluoroxide of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01 - 0.5.

 It is advisable to use the most energy-intensive substances, such as fluorocarbon and manganese dioxide, to create three-volt cathodes of lithium ChIT, oxides and sulfides of transition metals, in particular, copper oxide, pyrite, chalcopyrite, taken as electrode active materials to achieve increased specific energy consumption of electrodes and ChIT individually or in a mixture.

 The use of each of the indicated electrode-active materials as components of the electrode masses for lithium ChITs, in combination with the other components of the carbon-containing material, allows the creation of electrodes of lithium ChITs with increased specific energy consumption.

 It is desirable to mix the electrode-active material and graphite fluoride in a mass ratio of from 8: 1 to 40: 1, respectively. The proposed ratio of these materials is established empirically. The lower limit of the ratio is determined by the fact that when the content of graphite fluoroxide in the composition is less than 40: 1, the effect of introducing a pore-forming material becomes insignificant and practically does not manifest itself in an increase in energy intensity and achieved operational discharge current density. The upper limit of the ratio is determined by the fact that when the content of graphite fluoride in the composition is more than 8: 1, the electrode is highly porous, but the content of electrode-active material is reduced in it, which leads to a decrease in the output electric capacity of lithium ChIT.

 Advantageously, in the second mixing step, a diluent is introduced into the mixture until a paste is obtained. This allows you to get a homogeneous elastic pasty material.

 It is advisable to use a fluoroplastic suspension as a binder, which makes it possible to obtain a sufficiently strong elastic and homogeneous material, which is easily rolled on rollers.

Heat treatment is preferably carried out at a temperature of 150 - 350 ^o C.

 This temperature range is characteristic of the thermolysis of graphite fluoride of the indicated composition and this range is sufficient for uniform flow of the complete thermolysis of graphite fluoride and the formation of pores in the structure of the carbon-containing electrode without destroying its shape.

It is advisable to modify by impact. The most effective is the impact with the acceleration of impact bodies from 10 _g to 75 _g , where g is the acceleration of gravity. As a result of this treatment, fluorocarbon materials are modified, that is, the changes described above, in particular, the bulk density increases, the concentration of paramagnetic centers increases, the sizes of crystallites or particles decrease, which is accompanied by a decrease in the regions of coherent scattering. This leads to an increase in the discharge characteristics of fluorocarbon materials and an increase in the energy intensity of the cathode materials obtained from them. The average interplanar spacing (according to X-ray diffraction data) also decreases somewhat due to a sharp decrease in the number of mixed-layer structures.

It is desirable to carry out the impact in the presence of water or a boiling organic solvent in an amount of from 0.1 (the level of natural humidity of the electrode-active material) to 5 wt.% In the mixture. In this case, the impact is advantageously carried out until an intermediate product having a bulk density of from 1.0 to 1.5 g / cm ^{3 is} obtained.

The presence of water or a low boiling organic solvent during mechanical processing of a mixture of fluorocarbon with graphite fluoride gives an additional effect due to the fact that in the presence of 0.1 - 5 wt.% Water or a low boiling organic solvent, the material becomes non-dusty, retains flowability, and the required density of the intermediate product (1.0 - 1.5 g / cm ³ ) during impact machining is achieved faster than without the introduction of a liquid additive.

It is advisable at the second stage to carry out the mixing in the presence of water, ethyl alcohol, a mixture of water and alcohol or a low-boiling hydrocarbon with a boiling point up to 100 ^o C. This provides the possibility of obtaining a pasty mass, which is easily molded into electrode tapes and finished electrodes, and is also easily pressed onto current leads when forming electrodes.

Thus, the inventive carbon-containing material for electrodes of chemical current sources and a method for manufacturing porous electrodes from it make it possible to achieve the following in a current source, mainly lithium,:
increased specific volumetric (and mass) energy intensity of the carbon-containing electrode, which is achieved by combining an increase in the efficiency of the electrode-active material with a sufficiently high content of the latter in the volume of the electrode;
increasing the maximum operational density of the electrode discharge current in the CIT achieved by creating a porous electrode, as well as by applying a modification of a mixture of electrode-active material with a pore-forming material to obtain an intermediate product and the subsequent manufacture of a porous electrode;
unification of the procedure for manufacturing electrodes with increased energy intensity using a wide range of electrode-active materials to create efficient lithium chemical current sources of various electrochemical systems, both three-volt and one-and-a-half volt ranges.

 The use of graphite fluoride as a pore-forming material makes it possible to use a fluorocarbon (and cheaper) containing less than 61.29 wt.% (As is necessary for carbon monofluoride composition CF 1, for the manufacture of an electrode of a chemical current source of increased energy intensity) 0), and only 58 wt.%, (Which corresponds to the composition of CF 0.87), which allows to expand the range of used electrode-active materials.

 To implement the invention using the following starting materials. As electrode-active materials use fluorocarbons with a fluorine content of 58 - 67 wt.%, Or transition metal compounds - oxides and sulfides, taken separately, or in a mixture, for example, copper oxide, a mixture of copper oxide with pyrite, a mixture of copper oxide with chalcopyrite .

 The use of fluorocarbon materials with a fluorine content of less than 58 wt. % is ineffective, since electrodes and chemical current sources with a lower energy intensity are obtained than the known and achieved for the fluorocarbon-lithium electrochemical system. The use of fluorocarbon materials with a fluorine content of more than 67 wt.%, For example a fluoroplastic containing 76 wt.% Fluorine, as an electrode-active material is not effective, since such fluorine-rich materials are electrochemically inactive. Fluorocarbon containing 65 to 67% by weight of fluorine is commonly used.

 As a binder, a fluoroplastic suspension can be used.

As pore-forming material using graphite fluoride of the General formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01 - 0.5.

 It is possible, in principle, the use of graphite fluoroxides obtained by known methods and having a different composition, however, the methods for their preparation are very complex, and therefore, other fluoroxides are more expensive and, therefore, less effective products. In addition, there is no significant advantage in the energy intensity achieved and in the discharge current density from the use of graphite fluoroxides of a different composition in the electrode of a chemical current source.

 The minimum parameter - x = 1.5 - in the general formula of graphite fluoroxide is due to the experimental possibilities of obtaining this material by the method [8], as well as the fact that with an x value of less than 1.5, it is not possible to select an electrode composition such that during heat treatment it does not electrode destruction would occur due to the turbulent nature of the thermolysis process of such graphite fluoroxide.

 The maximum parameter, x = 15, in the general formula of graphite fluoroxide was chosen because its further increase, i.e., an increase in the amount of graphite phase in the mass of graphite fluoroxide, does not lead to a significant pore-forming effect and does not further increase the discharge characteristics of the electrode in CIT.

 Typically, graphite fluoroxide with a parameter of x = 12-15 is used as the cheapest pore-forming material.

 As a material that increases the electrical conductivity of the electrode-active material (and the electrode as a whole), acetylene carbon black is usually used.

Usually they take 78 - 85 wt.% Electrode-active material, for example, fluorocarbon material with a fluorine content of 58 - 67 wt.%, With its natural moisture content of 0.1 - 1.0 wt.%, Mix it directly in the drum of the mechanochemical activator ( for example, S. I. Golosov, Centrifugal drum mill, USSR Author's Certificate N 101874, BI 1955, N 11, [11]) with graphite fluoride of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01 - 0.5 with their mass ratio from 8: 1 to 40: 1, water or a low boiling organic solvent (alcohol, acetone, volatile hydrocarbon) are added to the resulting mixture values of 1.0 - 5.0 wt.% and carry out at the first stage of mixing modification by impact mechanical treatment of such a mixture to obtain an intermediate product having a bulk density of 1.0 - 1.5 g / cm ³ , for example, in planetary friction A unit with an acceleration of 10 - 75g, (usually a processing time of 2.5 minutes is required). The minimum acceleration value of 10g (g is the gravitational acceleration) was obtained empirically by checking the absence of a significant effect on fluorocarbon material in various aggregates (in particular, the effects described in example 2 with acceleration 10g occur with prolonged impact and, accordingly, with high energy and processing time). The maximum acceleration used is 75g. Above this limit, energy consumption is growing significantly, design requirements for apparatus parts necessary for this material are becoming more complicated (significant metal grinding into cathode masses must not be allowed), without leading to further significant modification of the properties of fluorocarbon materials.

It is difficult to achieve the desired effects of increasing the number of paramagnetic centers and changing other important properties of electrode-active material by conventional mechanical processing — the widely known grinding of materials in traditional grinders (when accelerating impact grinding bodies from 1 to 5g, for example, in ball mills or disk grinders). It is possible, however, the use of other methods of modification by mechanical shock using other devices that provide the specified shock mode - from 10 to 75g. It is also possible to use chemical methods for modifying the surface of an electrode-active material, for example, by treating fluorocarbon materials in a controlled gas environment at an elevated temperature (more than 350 ^o C), however, their use in relation to a mixture of graphite fluoroxide with electrode-active material can cause premature " swelling of the intermediate product due to the thermolysis of graphite fluoride and its unsuitability for the further manufacture of a carbon-containing porous electrode for a chemical source ika increased power consumption current.

It has been experimentally established that the best range of density values for the resulting intermediate product (a modified mixture of graphite fluoroxide with fluorocarbon material) is a density of 1.0-1.5 g / cm ³ . At lower densities of the intermediate product, the finished electrode produced is highly porous, but has a lower volumetric energy intensity than is necessary for CIT. Higher density values are, in principle, achievable during the modification process, however, an intermediate product is obtained from which it is difficult to obtain the elastic pasty material necessary for a successful electrode forming procedure. In addition, when trying to achieve a higher density of the intermediate product, a strong consumption of the material of the impacting bodies is observed, which leads to the presence of foreign impurities in the electrode and, ultimately, worsens the preservation of the properties of the electrode and the ChIT itself over time.

 The intermediate product obtained after modification, consisting of a close mixture of graphite fluoroxide with an electrode-active material, is mixed in a separate container with a binder material (usually a fluoroplastic suspension is used) and with a material that increases the electrical conductivity of the electrode-active material (acetylene carbon black is usually used ) The amount of binder introduced is usually 5 - 10 wt.%, And the amount of material that increases the electrical conductivity of the electrode-active material and a carbon-containing electrode, for CHIT, is usually 5 - 10 wt.% Of the total weight of the material and mixed, for example, on a standard propeller ( or another) mixer to obtain a homogeneous mass of carbon-containing material for electrodes of HIT.

A two- to five-fold volume of water, alcohol, or a volatile hydrocarbon (hexane, heptane, gasoline) can be added to the mixture obtained in the second stage to improve the mixing procedure and mix, for example, using a standard propeller mixer to obtain a paste-like mass. After separating the pasty mass, the carbon-containing material for the electrodes of the Chit electrodes is dried, for example, at 100 - 150 ^o C to remove the main amount of moisture or diluent.

The obtained carbon-containing material for HIT electrodes is moistened with alcohol or heptane, for example, according to the standard procedure described in [1] and the resulting pasty electrode mass is rolled on rollers to obtain an electrode strip preform. After that, carbon-containing electrodes are cut from the tape and pressed onto current leads, for example, onto metal housings of disk current sources or onto metal grids for coil current sources; or they are pressed, for example, into metal cylindrical cases of printed-type chemical current sources, which also serve as down conductors. The electrode blanks together with the down conductors are subjected to heat treatment, for example, in a vacuum oven at 150 - 350 ^o C, while choosing such a rate of temperature rise and holding time in the oven that do not destroy the finished electrodes and quantitative removal of volatile products (water, organic solvents and products of thermolysis of graphite fluoride) with the formation of pore structures inside the electrodes. After that, chemical current sources, for example, lithium HIT of a disk or cylindrical design, are collected.

 For a better understanding of the invention below are specific examples of its implementation.

 Example 1

According to the technology described above, porous electrodes were manufactured at specific given parameters. From these electrodes disc lithium ChITs were collected using a standard 1M LiClO ₄ electrolyte in a mixture of propylene carbonate and dimethoxyethane. The assembly was carried out in sizes BR2325 (electrochemical system "fluorocarbon-lithium) and CR2325 (electrochemical system" manganese dioxide-lithium). They were discharged at room temperature for a load of 30 kOhm. The test results are summarized in Table 1.

 The following are further examples of various embodiments of the present invention using various materials for the manufacture of porous lithium HIT electrodes.

 Example 2

 Fluorocarbon materials in the form of powders containing 63 - 67 wt.% Fluorine, as well as crushed fluorinated fabric with a content of 58 - 61 wt.% Fluorine (in the form of pieces of fluorinated fabric and dust formed during its cutting into pieces), were subjected to mechanical processing in standard ball mills for 8 to 20 hours with a rotation speed of 2 to 20 rpm. In this case, the acceleration of the falling grinding body - the ball is almost equal to the Earth's acceleration of gravity. With this treatment, the bulk density of the obtained ground fluorocarbon materials slightly increases compared to the original: for a material with 65 - 67 wt.% Fluorine - by 3 - 7 wt.%, For a material with a fluorine content of 63 - 65 wt.% Fluorine - by 10 - 15 wt.%, And for crushed fluorinated tissue - by 10 - 15%. The concentration of paramagnetic centers for all types of fluorinated carbons practically does not change (within the sensitivity of the electron paramagnetic resonance method - EPR). The size of the coherent scattering regions (i.e., the size of microparticles of fluorocarbon materials), within the error of the X-ray diffraction method, also remains the same. Only the particle size distribution (established by sieve analysis) changes significantly, in particular, for the first two described materials, the average size of the macroparticles (microparticle agglomerates) decreases by two to four times. The fluorine content, within the accuracy of the analysis, in the crushed fluorocarbon materials remains the same as in the starting materials.

Carbon-containing electrodes made of crushed fluorocarbon materials by the standard mixing procedure with acetylene black and a binder - fluoroplastic suspension - in the same formulations (80 wt.% Fluorocarbon powder, 10 wt.% Carbon black and 10 wt.% Fluoroplastic suspension) and prepared according to the scheme the known method (except for the use of strong shear forces) were tested in lithium HIT packets of frame size BR2325. The following results were obtained on the electric capacity of lithium ChIT at a discharge current density of 0.1 mA / cm ² for the first material - 190 + 13 mAh, for the second material 160 + 15 mAh and for powder fluorocarbon obtained by grinding fluorinated fabric - 140 + 20 mAh . At a discharge current density of 1.0 mA / cm ^{2, the} results of measuring the electric capacitance were approximately 20-60% lower, with the worst results being shown by CIT based on the second and third material.

 The number of manufactured HIT and electrical measurements in each series for each material is not less than ten.

 For comparison, under the same conditions, CIs were tested on the basis of fluorocarbon cathodes of the same composition, obtained from unmilled materials (first and second). The following results were obtained on the electric capacitance after the first shock mechanical treatment (Table 2).

Processing conditions - acceleration 10 - 75g, processing time - 3 - 5 min, discharge current density 0.1 mA / cm ² : for FS - 165 + 35 mAh, for FT - 150 + 35 mAh.

 From the above examples, it follows that for powdered fluorocarbon materials, the standardly used grinding in ball mills practically does not increase the maximum electric capacity in lithium HIT, but affects only the standard deviation with an overall average decrease in capacity in a series. The role of treating fluorocarbon material by mechanical action in a ball mill, therefore, is reduced only to the production of fine powders without a noticeable change in their properties.

 The industrial applicability of the invention is confirmed by the following examples.

 Example 3

 Fluorocarbon materials in the form of powders or pieces of fluorinated fabric (filaments) containing 0.1 wt.% Water (natural moisture of materials) were loaded into the drums of a friction planetary grinder of any type (APF-3, APF-7 and APF-8 aggregates were used, and other laboratory devices that allow acceleration of the striking body 10–75 g) and were processed by the method of impact mechanical impact, for example, using special grinding bodies (bolters or balls) for 3–5 min. In this case, the following changes occurred in the treated fluorocarbon materials (Table 2).

 From the data of table 2 it follows that the impact machining allows you to achieve changes in the properties of fluorocarbon materials that have a positive effect on the solution of the problem of the invention is to increase specific energy consumption.

 Note: During impact machining of fluorocarbon materials in lithium ChIT, the average voltage increases by 0.15 - 0.2 V on an open circuit, and the maximum achievable discharge current densities increase by about three to five times, up to 5 mA / sq.cm, which indicates a decrease in overvoltage in a fluorocarbon-lithium current source. The indicated increase in the specific energy consumption of the electrode in lithium HIT allows even fluorocarbon with a relatively low fluorine content to be used - a powdery material obtained by impact mechanical treatment of fluorocarbon tissue containing 58 wt.% Fluorine, i.e. lower than that contained in carbon monofluoride in the known method.

 Example 4

 Percussion mechanical treatment of fluorocarbon materials with a content of 58 - 67 wt.% Fluorine in the presence of 1 wt.% Water (increased humidity of materials that occurred during storage in a humid atmosphere) for 2 to 3 minutes. The obtained modified fluorocarbon materials had the same characteristics as shown in table 2 for processing materials with a moisture level of 0.1 wt. % Similar results on the properties were obtained for the fluorocarbon materials being processed with their moistening of 1-5 wt.%, Used in the technology of cathode masses of organic solvents - alcohol, acetone and liquid hydrocarbons (hexane, heptane and decane). However, this reduces to 1 - 2 min the time of the necessary processing and the material becomes low-dust.

 Note: The method described in this example is especially convenient for working with such a "dusty" fluorocarbon material (with a relatively low bulk density) such as fluorinated carbon black with a fluorine content of 63 - 65 wt.%.

 Example 5

By the above-described methods, test series of fluorocarbon cathode materials were made, which included 78 - 85 wt.% Fluorocarbon material of the three types indicated in Example 2, 5 - 10 wt.% Binder, 3 - 10 wt.% Graphite fluoroxide of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01-0.5, as well as 5 - 15 wt.% acetylene black. Usually use the average values of the given ranges of the content of the components of the electrode. Positive electrodes (cathodes) are made (formed) from these cathode masses. From molded cathodes, BR2325 type fluorocarbon-lithium ChIT with standard electrolyte 1M LiC104 in a mixture of propylene carbonate and dimethoxyethane were collected, and then their discharge tests were carried out at room temperature for a load of 30 kOhm. The test results depending on the characteristics and composition of the cathodes are summarized in table 3. The lower and upper limits of the contents of the binder and the material that increases the electrical conductivity of the electrode-active material and the electrode as a whole are shown in the first two and four last rows of the table. 3 for powdered fluorocarbon material with a fluorine content of 65 to 67 wt.%. For comparison, the same table shows data on a chemical current source of the BR2325 type manufactured by Matsushita Electric (11, New in the technology of fluorine compounds, edited by N. Isikawa, Moscow: Mir, 1984, p. 592, 149) .

 The results of electrical tests of carbon-containing electrodes in HIT BR2325 (load 10 kOhm, room temperature), galvanostatic mode, final voltage - 2.0V, are summarized in table. 4.

 Example 6

 HIT system "manganese dioxide-lithium".

Cathode masses containing 80 wt.% Manganese dioxide, 5 - 7 wt.% Fluoroplastic suspension, 3 - 5 wt.% Acetylene black, and 2, 5 and 10 wt.% Graphite fluoride of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.2 - 2.0 and n = 0.1-2.0.

 Positive electrodes (cathodes) of 0.9 g mass were made from these cathode masses, and lithium disk CITs of the CR2325 type were assembled in a known manner. To compare the properties, lithium ChITs of the CR2325 type were also produced, containing 80 wt.% Manganese dioxide, 10 wt. % fluoroplastic suspension and 10 wt.% acetylene black. In both series, the same electrolyte was used - a 1M solution of lithium perchlorate in a mixture of propylene carbonate and dimethoxyethane. Discharge tests were carried out at load resistances of 5.6 and 10 kOhm at room temperature. As a result of the tests, it was established that in both series the following electrical parameters of the CRIT CR2325 were implemented (see table 5).

 Example 7

 HIT of the system "copper oxide-pyrite-lithium" and the system "copper oxide-chalcopyrite-lithium".

Cathode masses containing 80 wt.% A mixture of transition metal compounds consisting of 60 wt.% Copper oxide and 40 wt.% Pyrite, 5 - 7 wt.% Fluoroplastic suspension, 3 - 5 wt.% Acetylene black, and also 2, 5 and 10 wt.% Graphite fluoroxide of the general formula:
C _x • zC _y O • nH ₂ O • CF,
where x = 1.5 to 15; y = 2.2-2.5; z = 0.5 - 1.4 and n = 0.01-0.5.

 The positive electrodes (cathodes) of the roll type are made from these cathode masses and lithium coil chit type GR6P is assembled in a known manner. To compare the properties, roll chitters of the GR6P type were also made, containing in positive electrodes weighing 80 wt.% A mixture of transition metal compounds consisting of 60 wt.% Copper oxide and 40 wt.% Pyrite, 10 wt.% Fluoroplastic suspension, 10 wt. % acetylene black (without blowing agent). In both series, the same electrolyte was used - a 1M solution of lithium perchlorate in a mixture of propylene carbonate and dimethoxyethane.

The discharge characteristics of lithium one-and-a-half-volt HIT of a roll construction in size GR6P for two electrochemical systems were investigated:
"Li - FeS ₂ -CuO" (OM-P) and "Li - CuO-CuFeS ₂ " (OM-CP).

 In mixed cathodes with chalcopyrite and pyrite, positive electrodes obtained by various methods were tested (with the addition of graphite fluoroxide in the table, these compositions are marked with the letter m).

At various current loads in continuous mode, a comparison was made of the effectiveness of various positive electrodes of the HIT GR6S experimental series using an electrolyte of a 1M LiClO ₄ solution in PC + DME. The discharges were carried out at room temperature using an automatic stand to a final voltage of 0.9 V. The averaged samples of preliminary tests for the experimental series of lithium HIT GR6S are summarized in table. 6.

 According to the operational characteristics achieved in the experimental series in the HIT GR6P, the highest discharge characteristics are exhibited by positive electrodes made using graphite fluoroxide.

 Thus, the use of a carbon-containing cathode material and a method for producing a porous electrode for chemical current sources makes it possible to increase the volume and mass energy intensity of electrode-active additives, and hence the discharge and capacitance characteristics of lithium ChIT electrodes of various electrochemical systems.

Claims (28)

 1. Carbon-containing material for electrodes of chemical current sources, containing an electrode-active material, a binder, a material that increases the electrical conductivity of the electrode-active material, and a pore-forming material, characterized in that it contains graphite fluoride as a pore-forming material. 2. The material according to claim 1, characterized in that as graphite fluoroxide it contains graphite fluoroxide of the general formula
C _x • ZCyO • nH ₂ O • CF,
where x 1.5 15;
y 2.2 2.5;
Z 0.5 1.4;
n 0.01 0.5.  3. The material according to claim 1, characterized in that as the electrode-active material it contains fluorocarbon containing 58 to 67 wt. fluoride.  4. The material according to claim 1, characterized in that as the electrode-active material it contains transition metal compounds, taken separately or in combination.  5. The material according to claim 4, characterized in that it contains manganese dioxide as transition metal compounds.  6. The material according to claim 4, characterized in that it contains copper oxide as transition metal compounds.  7. The material according to claim 4, characterized in that it contains pyrite or chalcopyrite as compounds of transition metals.  8. The material according to claim 4, characterized in that as a mixture of transition metal compounds it contains a mixture of copper oxide and pyrite.  9. The material according to claim 4, characterized in that as a mixture of transition metal compounds it contains a mixture of copper oxide and chalcopyrite.  10. A porous electrode of a chemical current source based on a carbon-containing material, characterized in that it is made of the material described in any one of claims 1 to 9.  11. A method of manufacturing a porous electrode for chemical current sources, mainly lithium, comprising mixing an electrode-active material, a binder, a material that increases the electrical conductivity of the electrode-active material, and a pore-forming material and molding the finished product, characterized in that use as a pore-forming material graphite fluoride, and the components are mixed in stages: at the first stage, graphite fluoroxide and electrode-active material are mixed, then the mixture is modified to obtain an intermediate product, which at the second stage is mixed with a binder and a material that increases electrical conductivity, and after forming the product, it is heat treated to form pores in the structure of the latter without destroying it. 12. The method according to claim 11, characterized in that graphite fluoroxide of the general formula is used as graphite fluoroxide
C _x • ZC _y O • n H ₂ O • CF,
where x 1.5 15;
y 2.2 2.5;
Z 0.5 1.4;
n 0.01 0.5.  13. The method according to claim 11, characterized in that as the electrode-active material using fluorocarbon containing 58 to 67 wt. fluoride.  14. The method according to claim 11, characterized in that as the electrode-active material using compounds of transition metals, taken separately or in combination.  15. The method according to claim 11, characterized in that manganese dioxide is used as the electrode-active material.  16. The method according to claim 11, characterized in that copper oxide is used as the electrode-active material.  17. The method according to claim 11, characterized in that pyrite or chalcopyrite is used as the electrode-active material.  18. The method according to claim 11, characterized in that a mixture of copper oxide and pyrite is used as the electrode-active material.  19. The method according to claim 11, characterized in that a mixture of copper oxide and chalcopyrite is used as the electrode-active material.  20. The method according to any one of the preceding claims 12 to 19, characterized in that the powdered electrode-active material and graphite fluoride are mixed in a mass ratio of from 8 1 to 40 1, respectively.  21. The method according to p. 20, characterized in that at the second stage of mixing the diluent is introduced into the mixture until a paste is obtained.  22. The method according to claim 11, characterized in that a fluoropast suspension is used as a binder. 23. The method according to claim 11, characterized in that the heat treatment is carried out at 150 350 ^o C.  24. The method according to claim 11, characterized in that the modification is carried out by impact on the mixture of the two named components.  25. The method according to paragraph 24, wherein the impact is carried out with the acceleration of the impact bodies from 10 to 75 g, where g is the acceleration of gravity.  26. The method according A.25, characterized in that the impact is carried out in the presence of water or a boiling organic solvent in an amount of 0.1 to 5 wt. 27. The method according to any one of paragraphs.24 to 26, characterized in that the impact is carried out until the density of the intermediate product is from 1.0 to 1.5 g / cm ³ . 28. The method according to claim 11, characterized in that the second stage of mixing uses water, ethyl alcohol, a mixture of water with ethyl alcohol or a low-boiling hydrocarbon with a boiling point up to 100 ^o C.

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