FR3021810A1 - LEAD-ACID BATTERY, METHOD OF MANUFACTURING SUCH ACCUMULATOR, AND METHOD OF MANUFACTURING ELECTRODE - Google Patents

Abstract

The invention relates to a method of manufacturing an electrochemical cell electrode comprising the following steps: - providing first and second sheets of flattening paper (30a, 30b) and a current collecting sheet (32); depositing on each of the first and second sheets of stripping paper (30a, 30b) a layer of paste of active material (31a, 31b); and - simultaneously gluing, by means of the active material, the first sheet of flattening paper (30a) on a first face of the current collecting sheet (32) and the second sheet of flattening paper (30b) on a second opposite side of the current collecting sheet (32), resulting in a multilayer stack.

Description

TECHNICAL FIELD The present invention relates to a lead-acid storage battery used as an electrochemical energy storage system, particularly in the field of electrochemical energy storage. of the automobile, a method of manufacturing an electrode and a method of manufacturing a lead acid battery. STATE OF THE ART A lead-acid accumulator comprises a positive electrode and a negative electrode immersed in a liquid electrolyte based on sulfuric acid. Each electrode conventionally comprises a lead current collector on which is disposed an active material based on lead, typically porous lead dioxide for the positive electrode and porous lead for the negative electrode. The current collector, for example in the form of a grid or a plate, serves as a mechanical support for the active material and provides the electrical connection between the active material of the electrode and a terminal of the accumulator. The chemical reactions taking place in the discharge accumulator convert the lead dioxide (PbO2) of the positive electrode and the lead (Pb) of the negative electrode into lead sulphate (PbSO4), and conversely into charge.

This type of electrochemical accumulator is particularly robust, but its specific energy density (also called specific energy) is low, of the order of 30 to 40 Wh / kg. This value of the energy density results from the significant weight of lead current collectors and a limited use of active materials. For example, the coefficients of use of the positive and negative active materials in discharge (ie the conversion rates of lead and lead dioxide to lead sulphate) are between 30% and 50% for current collectors in the form of gate and a moderate discharge current (for example Cn / 10h, 3021810 2 where Cn is the nominal capacity of the battery in Ah). In order to increase the utilization coefficients of the active materials, some authors have proposed modifying the geometry of the electrodes, in particular by reducing the thickness of the current collectors and layers of active material covering these collectors. Thus, in the article [RCA Bhardwaj et al., J. of Power Sources 91, pp.51-61, 2000], the positive electrode and the negative electrode each comprise a thin sheet of lead (approximately 50 μm thick) coated on both sides with a layer of active material (approximately 100 μm thick). The positive and negative electrodes are wound spirally, with a glass microfiber separator sheet disposed between the two electrodes. An uncoated web of active material, corresponding to one edge of each lead sheet, protrudes at each end of the spiral winding. Two cylindrical lead connectors, forming the positive and negative terminals of the accumulator, are then molded at both ends of the winding over the entire length of the projecting strips.

In this lead-acid battery, the utilization coefficients of the positive and negative active materials are greater than 80%. However, due to the small thickness of the lead sheets, the life of the accumulator is limited. Indeed, the current collector of the positive electrode is subject to a corrosion phenomenon, the lead gradually becoming lead dioxide. However, the lead dioxide is fragile, which may involve a loss of dimensional stability. In addition, the use of large lead connectors limits the specific energy density of the battery (of the order of 30 Wh / kg). The energy density can be improved by replacing the lead of the positive current collector with a lighter metal such as titanium, nickel, tin or molybdenum. Thus, in US Pat. No. 4,323,017, a titanium grid (250 μm thick) constitutes the current collector of the positive electrode. This grid has an electrical resistance comparable to that of a conventional 302 1 8 10 3 lead grid, but its weight is less. The titanium grid is coated with a protective layer of semiconductor metal oxide (for example fluorine-doped SnO 2) and a dense layer of lead dioxide (PbO 2) before being coated with active material. porous PbO 2 lead oxide, 10 μm to 10 mm thick). The semiconductor metal oxide layer prevents contact between the sulfuric acid electrolyte and the titanium grid. The titanium current collector is thus protected from oxidation and the life of the accumulator is increased. The dense layer of PbO2 connects the active material to the current collector and reduces voltage drop across the electrode.

In combination with this positive electrode, US4326017 discloses two negative electrodes each comprising a lead sheet. Due to the use of lead as a negative current collector, the specific energy of such a lead accumulator is only partially improved.

Furthermore, patent EP2313353 describes a lead-acid battery electrode comprising a flexible carbon sheet, having a thickness of between 60 μm and 180 μm, covered on both sides with a layer of active material of 200 μm to 250 μm. pm thick. The electrode further comprises a tie layer containing lead and tin between the carbon sheet and each layer of active material. Two electrodes of this type are spirally wound to form a lead-acid battery. However, this battery has a limited life because the positive electrode degrades over the charging and discharging cycles. Whatever the geometry proposed and the nature of the electrodes, none of the solutions proposed up to now has made it possible simultaneously to obtain a high density of specific energy and a long lifetime.

Furthermore, US Pat. No. 4,606,982 discloses a method of manufacturing a lead battery electrode. A paste of active material is first deposited on both sides of a lead grid. Then, a sheet of porous material paper is adhered to each face of the dough-covered grid to form a stack of laminated layers. Each sheet of paper adheres to the grid by exerting sufficient pressure for the paste of active material to impregnate the porous material.

To form the battery, the electrode is assembled with one or more other multilayer electrodes of opposite polarity. The two sheets of paper are made of glass microfibers and are stored in the final structure of the battery, where they act as a separator with electrodes of opposite polarity.

SUMMARY OF THE INVENTION There is therefore a need to provide a lead-acid electrochemical accumulator having both a high lifetime and a high specific energy.

According to the invention, there is a tendency to satisfy this requirement by providing a negative electrode comprising: a current collector formed of a carbon sheet having a thickness of between 50 μm and 200 μm and preferably between 130 μm and 200 μm; first and second lead layers respectively covering first and second faces of the carbon sheet; and first and second layers of a lead-containing active material having a thickness of between 100 μm and 500 μm, and preferably between 300 μm and 400 μm, and disposed on either side of the carbon sheet, respectively on the first and second layers of 25 lead; and a positive electrode comprising: a current collector formed from a titanium sheet having a thickness of between 50 μm and 250 μm and preferably between 100 μm and 150 μm; electrically conductive first and second electrically conductive metal layers respectively covering first and second faces of the titanium foil; and first and second layers of a lead-containing active material having a thickness of between 100 μm and 500 μm, and preferably between 130 μm and 200 μm, and disposed on either side of the titanium sheet. respectively on the first and second metal oxide layers.

Preferably, the negative electrode and the positive electrode are separated by at least one sheet of porous electrically insulating material and held together so that the porous material is compressed. In a first embodiment, the negative electrode, the positive electrode and two sheets of porous material form a multilayer stack, said multilayer stack being wound on itself to give the battery a spiral shape. According to a development of this first embodiment, the negative and positive electrodes 15 each comprise projecting collector portions not coated with the first and second layers of active material, the protruding portions of each of the negative and positive electrodes being distributed along a radius of the spiral. In a second embodiment, one of the negative and positive electrodes 20 has a plurality of electrode portions. Two sheets of porous material and the other of negative and positive electrodes form a multilayer stack, said multilayer stack being folded into a coil to receive, under each fold, one of the electrode portions.

According to a development of this second embodiment, the negative and positive electrodes each comprise projecting collector portions not coated with the first and second layers of active material, the protruding portions of the negative electrode being aligned on one side. of the serpentine stack and the protruding portions of the negative electrode being aligned on an opposite side of the serpentine stack. The accumulator may also have one or more of the following characteristics, considered individually or in any technically possible combination: the first and second lead-based layers of the negative electrode have a thickness of between 10 μm and 20 μm; the first and second metal oxide layers of the positive electrode 5 have a thickness of between 0.5 μm and 2 μm; each of the first and second active material layers of the negative electrode and of the positive electrode is covered with a sheet of paper made of glass fibers or of cellulose; the negative electrode further comprises first and second copper layers disposed on either side of the carbon sheet, between each of the first and second lead-based layers and the carbon sheet; the positive electrode further comprises first and second lead oxide layers disposed on either side of the titanium foil, respectively between the first metal oxide layer and the first layer of active material, and between the second layer of metal oxide and the second layer of active material; the accumulator further comprises a lead connector electrically connected to a portion of the carbon sheet and a titanium connector electrically connected to a portion of the titanium sheet, the lead and titanium connectors respectively forming the negative terminals. and positive of the accumulator; - The lead and titanium connectors occupy part of only one face of the accumulator; the carbon sheet is a graphite sheet, flexible carbon paper or a carbon fabric; and the titanium sheet is provided with through openings, advantageously of square, round or diamond-shaped section. The invention also relates to a method of manufacturing such a lead acid battery comprising the following steps: forming a negative electrode by successively depositing on each of the two faces of a carbon sheet, with a thickness of between 50 um and 200 μm, a lead-based layer and a lead-containing material layer of thickness between 100 μm and 500 μm; forming a positive electrode by successively depositing on each of the two faces of a titanium sheet, of thickness between 50 μm and 250 μm, an electrically conductive metal oxide layer and a layer of lead-containing active material, thickness between 100 μm and 500 μm; and assembling the negative and positive electrodes with at least one sheet of porous electrically insulating material separating the negative and positive electrodes.

According to a first embodiment, the assembly of the negative and positive electrodes comprises the steps of: bonding, by means of the active material, a sheet of electrically insulating porous material to each of the negative and positive electrodes; Pressing the negative and positive electrodes against each other on which the sheets of porous material are glued, so as to form a multilayer stack; and winding the multilayer stack so as to compress the porous material.

Advantageously, the sheets of porous material are partially impregnated with water during the winding of the multilayer stack. According to a second embodiment, the assembly of the negative and positive electrodes comprises the following steps: bonding, by means of the active material, a sheet of electrically insulating porous material on each of the faces of one of the negative electrodes and positive, from which results a multilayer stack; fold the multilayer stack into several areas; cutting the other of the negative and positive electrodes into a plurality of electrode portions; and disposing an electrode portion under each fold of the multilayer stack.

Preferably, the negative electrode and the positive electrode are, during the assembly step, distributed in the form of continuous and flexible bands, driven by rotary cylinders and shaped in parallel with one of the two. 'other.

Negative and positive electrode shaping may comprise a brushing step and a step of cutting a portion of the carbon sheet and a portion of the titanium foil, so as to form connecting tabs on each of the negative and positive electrodes, said portions being devoid of active material.

Another aspect of the invention relates to a method of manufacturing an electrode, for a lead acid battery or other battery technology. This method comprises the steps of: providing first and second blanking paper sheets and a current collecting sheet; depositing on each of the first and second sheets of stripping paper a layer of paste of active material; and simultaneously adhering, by means of the active material, the first sheet of caliper paper to a first face of the current collecting sheet and the second sheet of caliper paper to a second opposite side of the current collecting sheet from which results a multilayer stack. The method of manufacturing an electrode may also have one or more of the following characteristics, considered individually or in any technically possible combination: the current collecting sheet is in the form of a vertically oriented strip and each of the first and second sheets of pickling paper is brought into contact with the current collecting sheet in a direction perpendicular to the current collecting sheet; the first and second sheets of strapping paper are in the form of strips, each strip being carried by a belt conveyor during the step of depositing the layer of dough; The first and second sheets of flattening paper move at a speed of between 5 cm / s and 1 m / s and preferably between 5 cm / s and 50 cm / s; the first and second sheets of pickling paper are adhered to the current collecting sheet by means of two calendering rolls exerting a pressure on either side of the current collecting sheet; - The multilayer stack is further laminated by means of two rolling rolls disposed on either side of the current collector sheet; the first and second sheets of stripping paper have a thickness of between 20 μm and 200 μm; the layer of active material paste disposed on each of the first and second sheets of stripping paper has a thickness of between 100 μm and 500 μm; the paste of active material is spread on each of the first and second sheets of pickling paper by means of a spreading roll and smoothed by means of a doctor blade; the active material paste is laid in beads on each of the first and second blanking paper sheets by means of a plurality of coating nozzles and spread during the pressing step of said paper sheet flattening against the current collecting sheet; the current collecting sheet is made of carbon or titanium and the paste of active material contains lead; the electrode is configured for a Ni-MH, Ni-Cd, Ni-Zn or Zn-Ag battery or a C / Pb02 supercapacitor.

BRIEF DESCRIPTION OF THE FIGURES Other characteristics and advantages of the invention will emerge clearly from the description which is given below, by way of indication and in no way limitative, with reference to the appended figures, among which: FIG. a cross sectional view of a negative electrode for a lead accumulator according to the invention; FIG. 2 is a cross-sectional view of a positive electrode for a lead-acid accumulator according to the invention; FIGS. 3A and 3B show a first embodiment of a lead-acid accumulator according to the invention, in which the negative and positive electrodes of FIGS. 1 and 2 are wound in a spiral; FIG. 4 is a front view of the negative electrode of FIGS. 3A and 3B, arranged in the form of a strip before its spiral winding; FIG. 5 represents a second embodiment of a lead-acid accumulator according to the invention, in which the negative and positive electrodes of FIGS. 1 and 2 are assembled into a prismatic cell; - Figure 6 shows a front view of the negative electrode and the positive electrode of Figure 5, before they are respectively folded and cut to be assembled in the form of Figure 5; FIGS. 7, 8A and 8B show a first electrical connector fixed to the connection elements projecting from a negative electrode and forming the negative terminal of a lead-acid battery; - Figure 9 shows a second electrical connector, forming the positive terminal of a lead accumulator; FIGS. 10A and 10B show two modes of attachment of the connector of FIG. 9 to the connection elements projecting from a positive electrode; FIG. 11 represents a preferred embodiment of a method for manufacturing an electrode, of the "roll-to-roll" type; FIGS. 12A to 12C show an alternative embodiment of the etching step of the electrode of FIG. 11; and FIG. 13 represents a preferred mode of implementation of the step of assembling a spiral accumulator, of the "roll-to-roll" type. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT FIGS. 1 and 2 respectively represent a negative electrode 1 and a positive electrode 2 of a lead-acid accumulator having an energy density (or specific energy) and a power density ( or specific power).

Each electrode consists of a multilayer stack constructed symmetrically around a current collector in the form of a sheet, i.e., a thin, flexible plate. This sheet constitutes the support of two layers of active material, hereinafter called Negative Active Material (NAM) for the negative electrode and positive active material (PAM) for the active material. positive electrode. A layer of active material covers each side of the sheet.

In the negative electrode 1 of Figure 1, the current collector 10 is carbon-based. It is preferably formed of a glassy carbon or graphite sheet, as opposed to carbon foams which generally contain a large volume of pores. Alternatively, it may be made of carbon or graphite fibers, in the form of a flexible paper (ie the fibers are cut and held by a binder - they are not woven) or of a fabric (ie the fibers are woven). The thickness of the carbon collector 10 is between 50 μm and 200 μm, and preferably between 130 μm and 200 μm. By way of example, a graphite foil (known under the Anglo-Saxon term "graphite foil") can have a density of the order of 1 g.cm-3 to 2 g.cm-3. The carbon sheet 10 also has a thermal conductivity ten times greater than that of lead, which allows the use of the battery in high power applications. The carbon sheet 10 comprises two main and parallel faces 10a and 10b, each coated with a thin layer of lead or a lead alloy (eg lead and tin). A first lead-based layer 11a is thus disposed on the face 10a and a second lead-based layer 11b is disposed on the face 10b. The layers 11a and 11b allow a better grip of the negative active material, also based on lead, on the current collector 10. In addition, they improve the electrical conductivity and the mechanical strength of the collector 10 in carbon. Preferably, the layers 11a and 11b cover the entire carbon sheet surface 10 and their thickness is between 10 μm and 20 μm, so that they are devoid of holes.

The negative electrode 1 of FIG. 1 further comprises two layers of negative active material (NAM) 12a and 12b respectively arranged on the lead layers 11a and 11b. The NAM layers 12a and 12b have a thickness of between 100 μm and 500 μm, and preferably between 300 μm and 400 μm. Thicker layers 12a and 12b would make the electrode less flexible and complicate its assembly with the positive electrode to form an electrochemical cell, while a lower thickness would cause less use of the active material. The negative active material is preferably porous lead.

Two paper sheets 13a and 13b made of fiberglass (about 100 μm thick) or cellulose-based (about 50 μm thick) can be placed on either side of the sheet. the carbon sheet 10 on the layers of active material 12a and 12b. The sheets 13a and 13b prevent the layers of active materials 12a and 12b from cracking during assembly of the electrodes and flaking during operation of the accumulator. Advantageously, the negative electrode 1 comprises two intermediate copper layers 14a and 14b, preferably having a thickness of between 5 .mu.m and 10 .mu.m, and disposed on either side of the carbon sheet 10, between each of the 20 layers. 11a-11b lead and carbon sheet 10. These copper layers 14a, 14b significantly improve the electrical conductivity of the carbon sheet 10, with a minimum of additional weight given their small thickness.

The positive electrode 2, shown in FIG. 2, comprises a sheet of titanium having a thickness of between 50 μm and 250 μm, and preferably between 100 μm and 150 μm. This sheet 20 may be solid (i.e. not pierced) or provided with through openings, for example of square, round or diamond-shaped section (in the latter case, it is called expanded titanium, "expanded foil"). The size of the openings (i.e. their side or diameter) is advantageously between 50 pm and 250 pm (for the diamond-shaped section, the average of the two diagonals of the diamond is considered). The titanium constituting the sheet 20 is preferably more than 99% pure (class 1 and / or class 2). It is thus soft and ductile, facilitating its implementation in the lead accumulator as a current collector of the positive electrode. Each of the two faces 20a and 20b of the titanium foil 20 is coated with an electrically conductive metal oxide layer, 21a and 21b respectively, for example tin dioxide SnO 2. The layers 21a and 21b preferably cover the current collector 20 in their entirety. They constitute artificial corrosion layers and protect the titanium from oxidation, thus avoiding the formation of an electrically resistive TiO2 titanium oxide that is poorly soluble in the electrolyte. Thus, the titanium current collector 20 with positive potentials can withstand the electrolyte longer. The metal oxide is preferably a semiconductor doped with fluorine (F), antimony (Sb) or transition metal ions to increase its electrical conductivity. Its thickness in the layers 21a and 21b is advantageously between 0.5 pm and 2 pm, so that they contain a minimum of defects. Two layers of positive active material (PAM) 22a and 22b are disposed on each side of the titanium foil 20 coated with the semiconductor metal oxide 21a-21b. The layer 22a covers the layer 21a of metal oxide and the layer 22b, located on the other side of the electrode with respect to the titanium sheet 20, covers the layer 21b. Like the NAM layers 12a and 12b, the PAM layers 22a and 22b have a thickness of between 100 μm and 500 μm, and preferably between 130 μm and 200 μm. The positive active material of the layers 22a and 22b is preferably porous lead dioxide (PbO 2). Like the negative electrode 1, each of the layers 22a and 22b in Pb02 of the positive electrode 2 can be covered with a sheet of paper made of glass fiber or cellulose. These layers bear respectively the references 23a and 23b in FIG. 2. Finally, the positive electrode 2 advantageously comprises two dense layers of lead dioxide 24a and 24b (ie without pores, unlike the PAM layers). . These layers 24a and 24b of PbO 2, whose thickness is between 5 .mu.m and 20 .mu.m, are arranged on either side of the titanium foil 20, respectively between the semiconductor metal oxide layer 21a and the layer PAM 22a, 5 and between the semiconductor metal oxide layer 21b and the PAM layer 22b. With these layers 24a and 24b, the PAM material adheres better to the titanium current collector 20 (covered with artificial corrosion layers 21a-21b).

Thus, the negative electrode comprises a current collector formed of a carbon sheet, coated on each of its two faces with a lead-based layer, then with a layer of a lead-containing active material having a thickness of between 100 μm and 500 μm. Similarly, the positive electrode is formed of a titanium foil successively coated on both sides with an electrically conductive metal oxide layer and a layer of a lead containing active material having a thickness of between 100. um and 500 μm. Thanks to these particular configurations of electrodes, the coefficients of use of the positive and negative active materials are particularly high, of the order of 90%.

This is due in part to the low occupancy rates of the active materials on the current collectors (expressed as mass of active material per unit area). In fact, given the thicknesses of the active material layers and the geometry of the current collectors, this occupancy rate, also called coefficient y, is less than 0.5 g / cm 2 for each of the positive and negative electrodes. In addition, the mass ratio of the active material on the current collector is high, between 3 and 7 for each of the electrodes. The aforementioned utilization coefficients and mass ratios provide, after assembly of the negative and positive electrodes, high values of mass densities of energy and power, respectively from 60 Wh / kg to about 90 Wh / kg and 1 kW. kg to about 10 kW / kg. By way of comparison, the energy density of an accumulator comprising thin lead collectors, as described in the article ["Lead acid battery with thin metal film technology for high power 3021810 applications", RC Bhardwaj et al. , J. of Power Sources 91, pp.51-61, 2000], is less than 30 Wh / kg. Furthermore, each of the electrodes is designed to resist corrosion by the electrolyte. The negative carbon current collector is insensitive to the sulfuric acid electrolyte at negative potentials while the positive current collector is protected over its entire surface in contact with the electrolyte by the semiconductor metal oxide layers. . This ensures a long life to the lead accumulator comprising these two electrodes.

In addition, the charge acceptance (synonymous with charge efficiency) and the high current discharge capacity of the battery are high because the positive and negative electrodes are thin compared to those of conventional lead-acid batteries. These high electrical performances are mainly due to rapid diffusion of the sulfate ions through the layers of active material and low electrical resistance of the active material layers. Preferably, the total thickness of the electrodes does not exceed 0.8 mm. To form a lead accumulator, the negative and positive electrodes of FIGS. 1 and 2 are joined by interposing at least one sheet of an electrically insulating porous material between them. This porous material is intended to contain the electrolyte of the accumulator, typically sulfuric acid, and to electrically isolate the two electrodes.

The electrodes are advantageously assembled such that the porous material of the separator sheet is compressed. This compression is measured by a reduction in the thickness of the separator sheet of about 20%. It can further increase the life of the battery, the active materials are less likely to soften and flake over time. Several forms of assembly of the negative and positive electrodes can be envisaged. According to a first embodiment shown in FIGS. 3A and 3B, respectively in plan view and in perspective view, the negative and positive electrodes 2 2 are stacked with two separator sheets 3 formed of the porous and insulating material. This multilayer stack is wound on itself to give the accumulator a spiral shape.

The sheets 3 are arranged so that at any point of the winding, one of them separates the negative electrodes 1 and positive 2. Thus, no short circuit between the electrodes 1 and 2 is possible and the utilization coefficient of the electrolyte is maximum. The two separator sheets 3 are for example disposed on either side of the positive electrode 2 in FIG. 3A.

The separator sheets 3 are preferably AGM ("Adsorptive Glass Mat"), that is, microporous glass fiber layers. This type of separator is commonly employed in Valve-Regulated Lead-Acid (VRLA) batteries to store the electrolyte and keep the active material on the electrodes. The sheets 3 preferably have a thickness (before compression) of the order of 2 mm for a battery of high energy density. For a battery of high power density, the thickness of the sheets 3 is advantageously between 0.8 mm and 1 mm. In both cases, the separator sheets 3 can store an electrolyte volume sufficient to achieve active material utilization coefficients (positive and negative) of about 90%. The spiral accumulator of FIGS. 3A and 3B further comprises two sets of projecting connecting tabs, for example on the upper side of the stack. Each series of tongues allows the attachment of an electrical connector, preferably metal. The tongues 15 belong to the negative electrode 1 (FIG. 3A) and are fixed to a connector 16 (FIG. 3B), whereas the tongues 25 belong to the positive electrode 2 and are fixed to a connector 26. Thus, Each of the connectors 16, 26 connect the connection tongues 15, 25 electrically in parallel. The connectors 16 and 26 respectively form the negative and positive terminals, which extend to the outside of the accumulator. They will be described in detail in relation to 3021810 17 with FIGS. 7, 8A-8B, 9 and 10A-10B. The connection tongues of each electrode ensure the transport of the electric current between the collector of this electrode and the corresponding electrical terminal 5 of the accumulator. They are advantageously aligned and distributed along a radius of the spiral, as shown in FIG. 3A. This configuration of the tabs simplifies the geometry of the connectors 16, 26 and facilitates their attachment to the spiral stack.

FIG. 4 shows an arrangement of the connecting tabs 15 of the negative electrode 1 prior to its assembly with the positive electrode 2. Preferably, the tabs 15 each consist of a projecting portion of the carbon sheet coated with the lead-based layers 11a and 11b. They extend on the same side of the electrode 1 and, unlike the rest of the electrode, they are not covered with the layers of active material 12a and 12b. The connecting tabs 15 are advantageously spaced two by two by a distance that varies by increasing (looking from left to right in Figure 4). More specifically, the spacing between the tongues 15 is chosen so that after winding the electrode 1 with the electrode 2 and the separators 3, the tongues 15 are aligned. In addition, the length L of the tongues 15 increases as one moves away from the center of the spiral (FIG. 3), at the same time as the increase in their spacing (FIG. It is thus intended to obtain a positioning of the tongues in a cone, which has the highest angle possible, for example 90 °. This makes it possible to obtain a ratio between the sum of the lengths L of the tongues 15 and the total width of the electrode much greater than that of a prismatic configuration, which results in a higher current injection and therefore a higher power ( at least 3 times higher than that of a prismatic cell).

In the embodiment shown in FIGS. 3A, 3B and 4, the spacing of the tongues 15 is such that each tongue is positioned centrally on the same radius of the spiral, at each spiral turn. This arrangement of the tongues 15 is particularly suitable for high power electrochemical cells, which require a large number of these connection elements 7) in order to better distribute the current. In an alternative embodiment (not shown) for the lower current density accumulators, it is desired that one tab appear only every second turn and the spacing may be chosen accordingly. The connecting tabs 25 of the positive electrode 2 each consist of a portion of the titanium current collector covered with the metal oxide layers, but not coated with active material. They are preferably arranged in the same way as the tongues 15. By way of example, the lead accumulator comprises a negative electrode of the type of FIG. 1 and a positive electrode of the type of FIG. 2, stacked with two AGM separators 2 mm thick. The electrodes have, regardless of the connection tabs, a rectangular surface equal to 10 cm x 150 cm. Each electrode therefore exposes a surface of active material of the order of 3000 cm 2. The wound stack occupies a cylinder 10.5 cm in diameter and 10 cm high, which corresponds approximately to 8 turns of winding. The number of tongues of each electrode is 7. The winding of electrodes and separators is arranged in a cylindrical housing, about 11 cm in diameter and 12 cm in height, closed by a cover. Housing and cover, both made of polypropylene, have walls approximately 2.5 mm thick. A lead connector and a titanium connector respectively form the negative and positive terminals of the accumulator. The remaining volume of the cylindrical housing is filled with a solution having a concentration of sulfuric acid (in the fully charged state) of 5 mol / L and a density of 1.285 g / mL. Table 1 below lists the components of this spiral accumulator and gives, for each of them, its thickness and weight. It should be noted that the thickness values indicated in the table concern the thickness of a single copy of the component, and not the cumulative thickness of several copies of the same component (if several copies exist). On the other hand, the weight values 302 1 8 10 19 represent the total weight of all the copies of the same component. These remarks are valid for the layers of NAM, PAM, Pb, Pb02 and AGM (2 copies each). Component Thickness Weight Utilization Capacity (Ah) Energy (Wh) NAM 300 μm 360 g 90% 83.9 168 PAM 350 μm 441 g 85% 84.0 5M H2SO4 - 892 g 90% 83.7 Ti sheet 50 μm 34 g Total area: 3000 cm2 Coating PbO 2 15 μm 43 g On both sides 100 μm graphite sheet 18 g Total surface: 3000 cm2 Pb coating 15 μm 51 g On both sides Housing + lid 2.5 mm 124 g Polypropylene; 0 = 11 cm / h = 12 cm Ti connector - 22 g On 7 connection tabs Pb connector - 187 g On 7 AGM connection tabs [400g / m2] 2.2 mm * 120 g 2 mm AGM + 2x0.1 mm fiber paper of glass Total weight 2292 g 73 Wh / kg Cell volume 1140 mL 147 Wh / L 5 Table 1 For the negative electrode, the current collector is a graphite sheet of 100 μm thickness and its density is of the order of 1.2 g / cm3. The active negative material (NAM) layers consist of pure lead (4 g / cm3) and have a thickness of 300 μm. The galvanic lead coatings on the carbon collector have a thickness of 15 μm and the paper layers have a thickness of 100 μm (the paper layers are assimilated to AGM in Table 1). For this negative electrode, the occupancy rate of the negative active material yNAM is equal to approximately 0.12 g / cm 2 (compared with values ranging from 2 to 2.5 g / cm 2 for the prior art grid collectors) and the ratio of the mass of NAM to the mass of the collector is about 7: 1. The details concerning the positive electrode are as follows: a sheet of titanium 50 μm thick (density equal to 4.5 g / cm 3); Two layers of antimony-doped SnO 2 of 2 μm thickness; Two fluorine doped PbO 2 layers each having a thickness of 15 μm; two layers of PAM (PbO 2) of 350 μm thickness (density equal to 4.2 g / cm 3); 5 - two sheets of fiberglass paper 100 μm thick; The occupancy level of the positive active material yPAM is about 0.15 g / cm 2 and the mass ratio PAM / collector is about 7: 1. In addition to the coefficients of use of the negative and positive active materials, Table 1 above gives the capacities (expressed in Ah) relative to each active material and to the electrolyte, as well as the energy (expressed in Wh) developed. by their combination. The latter is, in the last lines of Table 1, relative to the total weight and the volume of the cell to give respectively the mass energy density and the density of energy density.

According to Table 1, this example of a spiral accumulator shows utilization coefficients of NAM and PAM respectively of 90% and 85%, which results in an energy density of 73Wh / kg (mass) or 147 Wh / L (volumetric), more than twice as much as the accumulators of the prior art. In addition, when the accumulator is discharged with a current equal to 30 ° C./h (where Cn is the nominal capacity of the accumulator in Ah), the power density delivered by the accumulator is close to 2 kW / kg (or 4 kW / L). Figure 5 shows, in top view, a second embodiment of a lead accumulator, in which the electrodes 1 and 2 are assembled in an undulating form, in the manner of a coil. The electrochemical accumulator thus configured resembles a prismatic cell, where the positive (s) and negative (s) electrodes are arranged parallel to each other in a parallelepipedal housing.

One of the positive and negative electrodes, here the negative electrode 1, is disposed between two layers of separators 3, preferably of the AGM type. The multilayer stack thus obtained is folded into a serpentine shape, that is to say, repeatedly and in opposite directions of a fold 4 to another. Under each fold 4 is disposed a portion 2 'of positive electrode. These portions 2 'are for example obtained after cutting a positive electrode 2 of larger dimensions.

The electrodes of the accumulator also have, in this second embodiment, tongues or connecting elements 15 and 25 protruding. These tongues extend in a direction parallel to the bends of the negative electrode 1, perpendicular to the plane of FIG. 5.

The tabs of each electrode can be, here too, aligned to facilitate the design and placement of the connectors (not shown). For example, the tongues 15 of the continuous negative electrode 1 extend above the folding zones 5 of the stack 3-1-3, these zones 5 being located on the same side of the coil assembly. . The tabs 25 of the positive electrode, which is "exploded" into several portions 2 ', are located on the opposite side of the assembly, in the immediate vicinity of the folding zones 6. The zones 6 result from the folding of the stack in a direction contrary to that of the zones 5. Of course, the configuration of FIG. 5 can be reversed. The positive electrode 2 is then stacked with the AGM separators 3, then folded, and the negative electrode 1 is subdivided into a plurality of portions arranged under the folds of the positive electrode 2. FIG. 2 before assembly in the form of Figure 5, and more particularly the arrangement of their connecting tongues 15 and 25. The electrodes 1 and 2 are strip-shaped, that is to say, long and narrow. Their composition is identical to that described with reference to FIG. 1 or 2. As previously mentioned, the tabs 15 and 25 are formed of portions of the current collector (respectively made of carbon and titanium), projecting from the same side of the electrode and not covered by the layers of active material (NAM and PAM respectively). Thus, with respect to the configuration of the electrodes in FIG. 4, only the spacing and the dimensions of the tongues 15 and 25 differ. On the negative electrode 1, the tongues 15 are located at the fold zones 5 of the electrode, shown schematically by dashed lines in FIG. 6.

They are preferably centered on these fold lines 5. In addition, two successive tongues 15 are separated by a folding zone 6, also reduced to a dashed line. In other words, there are no tongues 15 in the folding zones 6, as is also visible in FIG. 5.

The positive electrode 2 is shown in FIG. 6 before being cut into portions 2 '. The electrode portions 2 'are delimited by cutting lines 7. Preferably, they are the same size and each have a connecting tab 25.

In this second embodiment, the tabs 15 of the negative electrode 1 on the one hand, and the tongues 25 of the negative electrode 2 on the other hand, are regularly spaced along the strips 1 and 2 (as the fold lines 5 and 6). All the tongues 15 of the negative electrode 1 have the same size, unlike those of FIG. 4. Similarly, the positive electrode tongues 20 are all identical, their area being for example equal to half that of a negative electrode tab. Compared with a spiral accumulator, the prismatic accumulator has the advantage of being more compact (the density of energy is slightly higher). However, maintaining compression in this configuration requires a casing with mechanically reinforced sidewalls, which makes it heavier (hence lower mass density of energy than in the spiral accumulator).

Figures 7 and 9 show preferred embodiments of the electrical connectors 16 and 26, respectively forming the negative and positive terminals of the accumulator. These terminals connect the negative and positive electrodes (and more particularly their current collector) to an external electrical circuit, for example a load to supply energy. The connectors 16 and 26, which are described in connection with these figures, are compatible with the lead accumulator according to the invention regardless of its configuration - for example spiral or prismatic. Their composition and processing technique vary, because the nature of the current collector to which they are attached differs depending on whether this collector belongs to the positive electrode or the negative electrode.

The negative connector 16 of FIG. 7 is preferably formed of a single piece of lead obtained by a molding process around the connection tabs 15 of the negative electrode ("Cast-On-Strap" process). COS). The choice of lead as a material ensures a secure attachment of the connector 16 to the connecting tabs 15, which are also covered with lead (layers 11a-11b).

During this "COS" process, the cylindrical accumulator is turned over so that the connecting tongues 15, arranged projecting parallel to one another, are placed in a mold. The mold is filled with a molten metal, here lead, then cooled to release the molded part. The mold contains the final shape 20 of the negative connector 16, shown in FIG. 7. FIGS. 8A and 8B are other views of the negative connector 16 of FIG. 7, taken from the front and from the side, and making the tabs more clearly visible. connection 15 of the negative electrode.

The connector 16 comprises a first flat portion 16a molded around the tongues 15 and a second flat portion 16b, in the extension of the first portion 16a. As is apparent in Figures 8A and 8B, the tabs 15 extend perpendicularly to the plane of the portion 16a. The thickness of the portion 16a is advantageously between 5 mm and 20 mm. The second flat portion 16b also extends in a direction perpendicular to the plane of the portion 16a, but in a direction opposite to that of the tongues 15. Its thickness is advantageously between 5 mm and 15 mm. In the finalized accumulator, the portion 16b of the connector 16 leaves the housing and constitutes the negative terminal of the accumulator. Advantageously, the connecting tongues 15 each comprise a hole 15 ', so that during the molding step, the latter is filled with lead. This reinforces the mechanical and electrical connections between the tongues 15 and the connector 16. The current collector of the positive electrode being made of titanium, the positive connector 26 of FIG. 9 is advantageously made of titanium, ideally of the same quality (class 1 and / or 2). The connector 26 is, for example, obtained by punching a titanium sheet having a thickness of between 0.5 mm and 3 mm, depending on the power of the accumulator (a high thickness is provided in the case of a strong electrical capacity and a high electrical power, and vice versa).

The connector 26 has a first portion 26a and a second portion 26b, which, after folding the titanium foil along the axis 260 shown in broken lines, extends perpendicular to the portion 26a. The portion 26a includes notches 261 for receiving the connection tabs of the positive electrode.

For this purpose, the notches 261 have a width denoted "I" slightly greater than the thickness of the tongues and their length "L '" substantially corresponds to the length "L" of the tongues (Fig.4). Their shape may be rectilinear, as shown in FIG. 9 or in an arc of a circle, in the case of the spiral accumulator for example (the radius of curvature of the notches 261 then corresponds to the radius of curvature of each tongue, see Figs.3A-3B). The notches 261 are preferably arranged parallel to each other in the portion 26a. Figures 10A and 10B show two modes of attachment of the positive connector 26 on the connection tabs 25 of the positive electrode.

According to a first embodiment shown in FIG. 10A, the tongues 25 of the positive electrode are inserted into the slots 261 of the connector 26, and then folded so that their free end is pressed against the surface of the portion 26a. Then, each tongue end 25 is attached to connector portion 26a by a plurality of resistance weld points 262 distributed along each slot 261. In a second embodiment shown in FIG. 10B, tabs 25 are inserted. in the slots 261, then cut so that they do not exceed the surface of the portion 26a. Then, each tab 25 is welded to the portion 26a of the titanium connector over the entire length of the edge inserted into the slots 261. This welding is performed by a laser under an atmosphere comprising a shielding gas, for example argon .

Both of these welding techniques, by resistance by spot ("resistance spot welding") or by laser ("laser welding"), are fast and inexpensive, especially because they can be automated or semi-automated.

In the example of FIGS. 7 and 9, the portion 16a of the negative connector 16 and the portion 26a of the positive connector 26 have a trapezoidal shape adapted to connection tongues of variable length. This shape is therefore more particularly suitable for connecting tongues of the spiral accumulator (see Figs.3A-3B). Alternatively, the portions 16a and 26a may have a rectangular shape, more adapted to connecting tongues of the same length (the slots 261 of the connector 26 are in this case the same length). Unlike the connectors of the prior art, the connectors 16 and 26 of FIGS. 7 to 10 are designed to occupy only a portion of the upper face of the accumulator (FIGS. 3B and 5). Their negative impact on the specific energy and the specific power of the accumulator is thus limited. Of course, other forms of connectors 16 and 26 than those shown in FIGS. 7 and 9 can be envisaged. For example, the outer edge of connector portions 16a and 26a may be rounded, rather than straight, and so coincide with the cylindrical housing of the spiral accumulator. A method of manufacturing a lead accumulator according to the invention will now be described. This process comprises the steps of: forming a negative electrode from a carbon sheet (Fig.1); the formation of a positive electrode from a titanium foil (FIG. and the assembly of the negative and positive electrodes with at least one insulating and porous material sheet separating them, for example in a spiral (FIG. 3A-3B) or in a prismatic form (FIG. To form the negative electrode 1 of Figure 1, is deposited successively on each of the two faces 10a and 10b of the carbon sheet 10, a lead-based layer (layers 11a-11b) and a layer of active material containing lead 10 (layers 12a-12b). The lead-based layers 11a and 11b may be formed by electrodeposition of lead or a lead alloy on the surface of the carbon current collector, for example by applying the operating conditions described in EP2313353. Optionally, the copper layers 14a and 14b are electro-deposited on the surface of the carbon sheet 10, before the deposition of the lead layers 11a and 11b, according to a procedure also described herein.

Advantageously, the carbon sheet 10 undergoes, prior to the deposition of the lead layers 11a and 11b, a treatment aimed at increasing its surface roughness. Indeed, a high roughness guarantees a better grip of the layers 11a and 11b made of lead. This treatment can be carried out mechanically, by polishing, brushing or sanding, chemically by thermal treatment with oxygen or by immersion in an oxidizing solution, or electro-chemically by anodic etching (by dipping the carbon sheet in an electrolyte and applying a positive potential). Then, a paste of negative active material (NAM) is spread on each of the faces of the lead-coated carbon sheet (so-called "pasting" step). The paste of NAM preferably contains lead oxide (PbO), water, sulfuric acid and one or more additives, for example known under the name Anglo-Saxon "expander" and formed of lignosulfonates, BaSO4 or fine carbon particles. Finally, the carbon sheet coated with the layers of dough 12a-12b can be laminated with the two sheets of paper 13a and 13b made of glass fiber or cellulose. The dough layers 12a and 12b having a low viscosity can be partially dried before the step of rolling the paper sheets 13a-13b. For a high viscosity paste, such a drying step is not necessary because the paper sheets 13a and 13b absorb excess moisture in the dough. Pastes of active material are thixotropic mixtures whose viscosity depends on the mixing speed, between 0.5 and 5 revolutions / s, for example 1 turn / s. The formation of the positive electrode 2 comprises successively, on each of the faces 20a-20b of the titanium foil 20 (FIG. 2), the deposition of a semiconductor metal oxide layer (layers 21a-21b), then possibly the deposition of a dense layer of lead oxide PbO2 (layers 24a-24b) and finally the deposition of a layer of active material containing lead (layers 22a-22b).

Preferably, the titanium foil 20 is treated to increase its surface roughness, before receiving the semiconductor metal oxide layers 21a-21b. This treatment can be carried out mechanically, by sandblasting or brushing, and / or chemically by immersion in a solution of hydrochloric acid or oxalic acid (for example for 2 minutes to 5 minutes in a boiling solution of 10% hydrochloric acid). % or for 30 min to 60 min in a boiling solution of 10-15% oxalic acid). The deposition of the semiconductor metal oxide layers 21a-21b can be carried out in various ways, in particular by spray-pyrolysis. For example, the solution sprayed onto the substrate (heated to 400-500 ° C) contains a solution of SnCl2 at 0.5 mol / L, a solution of SbCl3 at 0.05 mol / L and a solution of 0.1 mol / l HCl in a mixture of ethanol and water (40% ethanol, 60% water).

The layers 24a-24b of lead oxide PbO 2 are preferably formed by electrodeposition, by mixing a source of dopants in the plating bath, for example NaF for fluorine doping. By way of example, the galvanic bath comprises a 0.1-1 mol / L solution of lead methanesulphonate (II), a solution of 0.1-0.2 mol / L methane sulphonic acid, a solution containing a cetrimonium salt (bromide, chloride or cetrimonium tosylate) at 0.05 mol / L and a NaF solution at 0.01 mol / L. These three preliminary stages of preparation of the titanium current collector 10 prevent the formation of a superficial and highly resistive TiO 2 titanium oxide prior to the application of the positive active material (PAM) paste layers. PAM paste conventionally comprises lead oxide (PbO), water and sulfuric acid. It is spread on both sides of the titanium sheet covered with SnO2 and PbO2 layers, for example by squeegee.

Finally, two sheets of paper 23a and 23b of fiberglass or of cellulose are advantageously laminated on the two active material paste layers 22a and 22b.

In the step of etching the electrodes, an edge of the carbon sheet and an edge of the titanium foil are not covered with the paste of active material. These edges are intended to form the connecting tongues of each electrode. Advantageously, the negative and positive electrodes are in the form of long continuous and flexible bands and are manufactured by a "roll-to-roll" process from a current collecting sheet (e.g. carbon or titanium) stored as a coil. This type of process is particularly well suited to the formation of thin film battery electrodes and achieves a high production efficiency.

FIG. 11 shows a preferred embodiment of this electrode manufacturing method, in which a sheet of paper, serving as a support for the active material of the electrode, is carried on each of the faces of the sheet 302. 8 10 29 current collector. Two sheets of paper 30a and 30b are, independently of one another, coated with a paste of active material (PAM or NAM depending on the nature of the electrode to be manufactured).

The paper of the sheets 30a and 30b is commonly referred to as calving paper because it is suitable for depositing a paste of active material. It is preferably formed of glass fibers, with a structure identical to that of the AGM separators used in lead batteries. Alternatively, it may be formed of fibers of a material other than glass (cellulose, polyester) or a mixture of glass fibers 10 and fibers of this other material. The paper sheets 30a and 30b preferably have a thickness of between 50 μm and 200 μm. The steps of squatting the sheets of paper 30a and 30b are preferably carried out simultaneously using two belt-pressing machines. Thus, the strip-shaped sheets 30a and 30b are each carried by a belt conveyor during the deposition of the active material paste. The paper web 30a from a roll 300a is driven by a belt conveyor 40a and covered with a dough layer 31a by means of a coating device 41a. In the same way, the paper web 30b from the roll 300b is driven by a belt conveyor 40b and covered with a dough layer 31b by means of a coating device 41b. The movement of the belts 40a-40b has the effect of progressively unrolling the paper rolls 300a-300b. The dough layers 31a and 31b preferably have a thickness of between 100 μm and 500 μm.

The sheets of paper 30a and 30b are then glued on either side of the current collection sheet 32, by means of the paste of active material. In other words, the layers 31a and 31b act as glue for respectively fixing the paper sheet 30a on a first face of the sheet 32 and the paper sheet 30b on a second opposite face of the sheet 32. A pressure can be exerted on the 30 sheets of paper 30a-30b to reinforce this bonding, for example by passing the sheets 30a, 30b and 32 between two calendering rolls 42a-42b. The cylinders 42a-42b rotate in opposite directions.

Advantageously, the sheets of paper 30a-30b are (on one side only) completely covered with paste of active material and have a width smaller than that of the current collecting sheet 32. Thus, an edge of the sheet 32 is without active material paste (on both sides) and will serve to form the 5 connection tongues of the electrode. The current collecting sheet 32 may be formed of different materials and possibly covered with adhesion and / or anticorrosive layers. Its thickness is preferably between 20 μm and 200 μm. For example, in the case of a lead accumulator electrode, the sheet 32 is preferably carbon (negative electrode) or titanium (positive electrode), and the active material paste contains lead. In the preferred embodiment shown in Fig. 11, the current collecting sheet 32 is a continuous flexible strip from a coil 301 and oriented vertically. The sheets of paper 30a-30b coated with paste are brought into contact with the sheet 32, in a direction perpendicular to the sheet 32. This arrangement makes it possible to exert an identical pressure on either side of the sheet 32. Thus, the paste layers 31a and 31b have after bonding substantially the same thickness. The sheets of paper 30a-30b thus move toward the sheet 32 in opposite directions. The speed of movement of the sheet 30a on the conveyor 40a is preferably equal to that of the sheet 30b on the conveyor 40b and between 5 cm / s and 1 m / s, preferably between 5 cm / s and 50 cm / s. The sheet 32 is driven at the same speed of movement by the paper strips 30a and 30b. After the gluing operation, the stack of sheets 30a-31a-32-31b-30b constitutes a multilayer electrode strip, ready for assembly in an accumulator.

This stack is advantageously laminated, passing it between another pair of cylinders 43a-43b disposed on either side of the current collecting sheet 32. This operation is carried out if it is desired to reduce the thickness of the electrode strip, for example when the pressure exerted by the cylinders 42a-42b is not sufficient to achieve the desired thickness. Thus, it is easier to adjust the thickness of the electrode and perfect the adhesion between the different layers of the stack.

Another optional step of the manufacturing process is to glue a separator sheet 33 against the multilayer electrode strip in preparation for the assembly of the positive and negative electrodes of the accumulator. The separator sheet 33 is preferably an AGM-type strip from a roll 302. It is pressed against the electrode strip by means of a pair of calendering rolls 44a-44b. To facilitate its packaging, the electrode strip (with or without AGM separator 33) can also be wound into a coil 303 immediately after its manufacture.

Once the electrode coil 303 is locked or immobilized, it can be rolled up with an adhesive, then put in an oven at 60-120 ° C for 12-24 hours in order to dry and bake the paste of active material.

This electrode manufacturing method makes it possible to deposit, quickly and with good accuracy (+ 1-50 μm), two layers of active material paste on either side of a current collecting sheet. Thus, large battery electrodes having a total thickness of between 100 μm and 1000 μm, and preferably between 200 μm and 600 μm, can be produced in large quantities and at low cost. Using the sheets of stripping paper as a support for the active material paste, rather than the current collector, makes the step of the stripping easier and allows better control of the thickness of the layers of active material. Thus, compared to the prior art electrode manufacturing methods, especially that described in US Pat. No. 4,606,982, it is easier to achieve layers of paste of identical thickness on both sides of the current collector, and therefore to obtain a better use of the active material. Finally, the fact of working simultaneously with both faces of the electrode allows a gain in terms of productivity. In FIG. 11, each coating device 41a-41b comprises a dough tank 410, a spreading cylinder 411 and at least one mixer 412 disposed in the tank 410. In addition, a squeegee 413 is disposed at the outlet of the coating device for adjusting the thickness of the layer of dough deposited on the moving paper sheet. The paste of active material is, in this embodiment of the etching step, spread on each of the paper sheets 30a and 30b by means of the spreading roller 411 and smoothed by means of the doctor blade 413.

In an alternative embodiment shown in Figs. 12A-12C, the active material paste is deposited on the strapping paper sheets 30a-30b in the form of rectilinear strands 31 '. For this purpose, the coating devices 41a-41b comprise a plurality of coating nozzles 414, instead of the spreading roll 411 and the doctor blade 413. Preferably, the nozzles 414 are aligned perpendicular to the direction of movement of the rollers 414. strips of paper 30a-30b, symbolized by the arrows 45, so that the dough strips 31 'are parallel to each other. The nozzles 414 are fed with paste of active material through the tank 410.

In the step of gluing the sheets of paper 30a-30b to the manifold 32, pressure is exerted on each sheet of paper (by means of the calendering rolls 42a-42b) (see Figs.12B-12C). Then, the dough strands 31 'spread and join to form the dough layers 31a-31b.

This variant embodiment is more suitable for high viscosity pastes than the so-called "Doctor Blade" method shown in FIG. 11. As the speed of travel of the sheets of paper 30a-30b and the flow of paste in the nozzles 414 are constant, one can precisely control the dough load (ie the basis weight per unit area) deposited on each sheet. In addition, this technique makes it easier to interrupt, that is to say at any time, the deposition of active material paste. This is particularly advantageous when it is desired that one end of the paper sheets, and therefore of the electrode strip, is not covered with paste. For example, in a spiral electrode assembly 3021810 33 (see FIG. 3A), it is unnecessary to deposit material on the face of the electrode turned towards the outside of the winding, since this surface (belonging to at the positive electrode 2 in the example shown) faces the cylindrical housing (not shown) of the accumulator, rather than the opposite polarity electrode. Active material on this surface would not participate in the electrochemical reactions. It should therefore not be deposited, for the sake of economy and not to unnecessarily burden the spiral accumulator. The step of assembling the positive and negative electrodes consists in pressing the electrodes against each other, separating them from at least one sheet of porous and electrically insulating material, and shaping the stack which As a result of this plating, for example by folding, cutting, winding ... During this assembly step, it is also possible to shape the connection elements of the electrode. All these operations can also be performed within the same assembly equipment. FIG. 12 shows a preferred embodiment of the step of assembling a spiral accumulator, in which the negative electrode 1 and the positive electrode 2 have the form of continuous and flexible bands, respectively provided by storage coils 303 and 303 '. The coils 303 and 303 ', which are loaded into the equipment, each contain a winding of a single electrode, positive or negative. For example, the lower coil 303 contains the negative electrode strip 1, while the upper coil 303 'contains the positive electrode strip 2. The negative electrode coil 303 and the positive electrode coil 303' have Preferably, it has been produced in the step of FIG. 11. A separator sheet 3 is adhered to each electrode by means of the active material of the electrode. This bonding may have been carried out immediately after the manufacture of the electrode, as mentioned previously in connection with FIG. 11. The separator sheets 3 are then contained in the coils 303 and 303 '. An alternative is to provide four coils (instead of two): two coils containing only the positive and negative electrode strips and two additional coils for the separator sheets. The four coils are unwound simultaneously in pairs, each separator sheet being laminated on an electrode strip.

As the coils 303 and 303 'are unwound, the electrode strips 1 and 2 progress in the assembly machine and are processed in parallel with each other. This treatment comprises in particular the brushing and cutting of the electrode portions devoid of active material, to form the connection tabs on each of the electrodes. Each electrode-separator pair may optionally pass between a pair of rolling rolls 45, in order to reduce its thickness.

Then, the electrode strips 1 and 2 are pressed against each other, interposing between them one of the two sheets 3 of porous material. In order to do this, the electrode strips 1-2 and their associated separator sheets 3 are introduced between two calendering rolls 46.

Finally, the stack of electrodes 1-2 and separator sheets 3 is wound on itself, so as to compress the porous material. During this operation, the porous material of the sheet 3 disposed between the two electrode strips 1-2 impregnates positive and negative active materials, which definitively binds the two electrodes. Advantageously, the sheets 3 of porous material are partially impregnated with water during this step. This makes it possible to achieve a high level of compression - and thus to improve the life of the accumulator - because the porous material is less elastic while being wet. Finally, to preserve the compression of the porous material, the stack can be held firmly wrapped by an adhesive tape or a plastic film, before being placed in a cylindrical housing. To assemble a lead-acid accumulator in prismatic form, it is possible to proceed analogously with electrode strips according to a "roll-toroll" method, except for bonding the two sheets of porous material on either side of a same electrode, for example the negative electrode. Then, instead of pressing the electrodes against each other, the stack of the negative electrode and the separators is repeatedly bent while the positive electrode is cut into several portions. Each positive electrode portion is then disposed under a fold of the stack. Compression of the porous material of the separators occurs when the positive and negative electrodes thus assembled are introduced into the housing, this time in the shape of a rectangular parallelepiped.

The electrode manufacturing method of FIG. 11 and the assembly step of FIG. 12 are obviously applicable to the lead accumulator technology described in connection with FIGS. 1 to 6, in particular by using a collector sheet. titanium for the positive electrode and a carbon collector foil for the negative electrode. It then follows an electrode activation step, where the NAM paste and the PbO-based PAM paste are converted to lead sulfate PbSO4, after which the accumulator can be used normally (starting with a Training Officer).

It will be appreciated, however, that the manufacturing method of FIG. 11 can be used to form other types of electrodes. Among the examples of possible batteries, mention may be made of: Ni-MH with a nickel oxide paste and suspension based on a multi-component powdery alloy; Ni-Cd with nickel oxide or hydroxide on one side and Cd (OH) 2 on the other side - Ni-Zn with nickel oxide or hydroxide on one side and zinc oxide on the other side; and Zn-Ag with powdered silver and zinc oxide; The current collector sheets are copper, nickel, steel, lead or aluminum depending on the applications. The process of FIG. 11 also allows the formation of electrodes for supercapacitors, such as C / PbO 2 ("supercapacitor hybrid") with carbon suspension and PbO 2, H 2 SO 4 and water paste.

Claims (12)

REVENDICATIONS1. A method of manufacturing an electrochemical cell electrode comprising the steps of: - providing first and second wadding paper sheets (30a, 30b) and a current collecting sheet (32); depositing on each of the first and second sheets of stripping paper (30a, 30b) a layer of paste of active material (31a, 31b); and - simultaneously gluing, by means of the active material, the first sheet of flattening paper (30a) on a first face of the current collecting sheet (32) and the second sheet of flattening paper (30b) on a second opposite side of the current collecting sheet (32), resulting in a multilayer stack. The method according to claim 1, wherein the current collecting sheet (32) is in the form of a vertically oriented strip and wherein each of the first and second sheets of stripping paper (30a, 30b) is brought into contact with the current collecting sheet (32) in a direction perpendicular to the current collecting sheet (32). 3. Method according to one of claims 1 and 2, wherein the first and second sheets of strapping paper (30a, 30b) are strip-shaped, each strip being carried by a belt conveyor (40a, 40b). during the deposition step of the dough layer (31a, 31b). A method according to claim 3, wherein the first and second sheets of strapping paper (30a, 30b) move at a speed of between 5 cm / s and 1 m / s and preferably between 5 cm / s and 50 cm / s. A method according to any one of claims 1 to 4, wherein the first and second blanking paper sheets (30a, 30b) are adhered to the current collection sheet (32) by means of two rolls of calendering (42a, 42b) exerting a pressure on either side of the current collecting sheet (32). 3021810 38 6. A method according to any one of claims 1 to 5, wherein the multilayer stack is further laminated by means of two rolling rolls (43a, 43b) disposed on either side of the current collector sheet 5 (32). The method of any one of claims 1 to 6, wherein the first and second wadding paper sheets (30a, 30b) have a thickness of between 20 μm and 200 μm. 10 A process according to any one of claims 1 to 7, wherein the active material paste layer (31a, 31b) disposed on each of the first and second wadding paper sheets (30a, 30b) has a thickness of between 100 pm and 500 pm. 15 A method according to any one of claims 1 to 8, wherein the active material paste is spread on each of the first and second blanking paper sheets (30a, 30b) by means of a spreading cylinder ( 411) and smoothed by means of a squeegee (413). 20 A method according to any one of claims 1 to 8, wherein the active material paste is laid in cords on each of the first and second wadding sheets (30a, 30b) by means of a plurality of nozzles coating (414) and spread during the step of pressure-bonding said sheet of scuffing paper (30a, 30b) against the current-collecting sheet (32). The method of any one of claims 1 to 10, wherein the current collecting sheet (32) is carbon or titanium and wherein the active material paste contains lead. 30 The method of any of claims 1 to 10, wherein the electrode is configured for a Ni-MH, Ni-Cd, Ni-Zn, Zn-Ag or C / Pb02 supercapacitor battery.