ELECTRODE WITH CURRENT COLLECTION MULTIPLE ARRAY

Abstract

Disclosed is an electrode for an energy storage rechargeable device, including a plurality of electrode material layers and a plurality of porous current collector layers, the electrode material layers and current collector layers being arranged in a specific manner, an energy storage rechargeable device including the electrode, and the uses of the electrode.

Claims

1. An electrode for a rechargeable energy storage device, wherein said electrode comprises two external layers and several internal layers interposed between the two external layers, said internal and external layers comprising several electrode material layers ME and several porous current collector layers CC, said electrode material ME and current collector CC layers being alternated according to the repetition pattern [CCME] and at least one of the two external layers of the electrode is an electrode material layer ME.

2. The electrode according to claim 1, wherein the electrode has a thickness varying from 50 m to 4 mm.

3. The electrode according to claim 1, wherein at least a part or each of the porous current collector layers CC is in the form of a grid, a perforated sheet, a felt, a meshing, a fabric or a foam.

4. The electrode according to claim 1, wherein the porous current collector layers CC, identical or different, are conductive material layers.

5. The electrode according to claim 1, wherein said electrode comprises an external layer that is an electrode material layer ME and an external layer that is a porous current collector layer CC and wherein said electrode is in the form of an assembly of successive layers having the following structure:
[CCME].sub.n wherein ME is an electrode material layer, CC is a porous current collector layer, and 2n8.

6. The electrode according to claim 1, wherein the other external layer of the electrode is an electrode material layer ME and said electrode is in the form of an assembly of successive layers having the following structure:
ME[CCME].sub.p-1 wherein ME is an electrode material layer, CC is a porous current collector layer, and 2p8.

7. The electrode according to claim 1, wherein each of the electrode material layers ME comprises at least one electrode active material.

8. The electrode according to claim 1, wherein said electrode is a zinc-based negative electrode.

9. The electrode according to claim 1, wherein said electrode is intended to be arranged into a rechargeable energy storage device comprising the electrode, a counter-electrode and an electrolyte, the external electrode material layer ME being intended to face an external layer of the counter-layer and intended to be in direct contact with the electrolyte.

10. A rechargeable energy storage device comprising: at least one positive electrode, at least one negative electrode, an electrolyte, wherein in said device, at least one of the positive or negative electrodes is an electrode as defined in claim 1.

11. The device according to claim 10, wherein the electrolyte is in direct contact with the electrode as defined in claim 1, through the external layer that is an electrode material layer ME of said electrode.

12. The device according to claim 10, wherein said device is chosen among an alkaline accumulator, a lithium-ion battery, a lead battery, a nickel-metal hydride battery and a supercapacitor.

13. The device according to claim 10, wherein said device is an alkaline accumulator chosen among a zinc/air battery and a zinc/nickel battery.

14. Method for improving the energy density of a rechargeable energy storage device, comprising providing the electrode as defined in claim 1, and applying the electrode to the energy storage device.

15. The method according to claim 14, wherein the electrode is in an alkaline accumulator.

16. The electrode according to claim 2, wherein at least a part or each of the porous current collector layers CC is in the form of a grid, a perforated sheet, a felt, a meshing, a fabric or a foam.

17. The electrode according to claim 2, wherein the porous current collector layers CC, identical or different, are conductive material layers.

18. The electrode according to claim 3, wherein the porous current collector layers CC, identical or different, are conductive material layers.

19. The electrode according to claim 1, wherein each of the electrode material layers ME comprises at least one electrode active material comprising a polymer binder.

20. The electrode according to claim 1, wherein each of the electrode material layers ME comprises at least one electrode active material comprises an electronic conductivity agent.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0086] The present invention is illustrated by the following examples, to which it is however not limited.

EXAMPLES

[0087] The raw materials used in the examples are listed hereinafter:

[0088] polyvinyl alcohol, Fluka, molar mass M.sub.w=72000,

[0089] titanium nitride, EASYL, purity of 99%,

[0090] nickel-oxide positive electrode recovered from the disassembly of a PKcell-brand NiZn battery),

[0091] nickel hydroxide (II) (Ni(OH).sub.2), of battery grade,

[0092] potassium hydroxide (KOH), Alfa Aesar, purity of 85%,

[0093] lithium hydroxide (LiOH), Normapur, purity of 96%,

[0094] zinc oxide (ZnO), a.m.p.e.r.e. industrie, purity of 99,9%,

[0095] calcium zincate, EASYL, purity of 99%,

[0096] polytetrafluorethylene (PTFE), ROTH, Seal Tape Grade L,

[0097] non-woven, polyolefin-based separator, Viledon, Freudenberg, FS 2203-10,

[0098] polypropylene membrane, Celgard 3401,

[0099] porous current collector layer in the form of a circular copper foam, GoodFellow, CU003804, (thickness reduced to 800 m),

[0100] porous current collector layer in the form of a circular copper grid, Alfa Aesar, with copper wires of diameter 56 m, ref. 46603,

[0101] porous current collector layer consisting of a nickel foam recovered from the disassembly of a PKcell-brand NiZn battery.

[0102] Unless otherwise mentioned, all the materials have been used as received from the manufacturers.

Example 1: Preparation of Electrode E-A not in Accordance with the Invention and of Two Electrodes E-1 and E-2 in Accordance with the Invention

[0103] An electrode material ink comprising 900 mg of calcium zincate as an active material, 42 mg of bismuth oxide and 144 mg of titanium nitride as conductive additives, 66 mg of polyvinyl alcohol as a polymer binder and 1.90 ml of water has been prepared.

[0104] The calcium zincate has been synthetized by a hydro-micromechanical method as described in the International Application WO 2016/156749 A1. The size distribution of the calcium zincate particles, measured by LASER granulometry (liquid process), was such that d.sub.50=102 m.

[0105] This ink has thereafter been applied to one of the main faces of an 800 m-thick porous current collector layer consisting of a circular copper foam to form a circular electrode E-A. The obtained circular electrode E-A has then been dried at about 50 C. in an oven, placed into a PTFE ring and squeezed until reaching a thickness of about 0.5 mm. The PTFE ring protected the circular edges of the electrode, while always leaving a central electrolyteelectrode contact surface.

[0106] The circular electrode E-A comprised a current collector layer CC and an electrode material layer ME deposited on the current collector layer CC. It was hence in the form of an assembly of successive layers having the following structure:

[CCME]

[0107] An electrode material ink comprising 450 mg of calcium zincate as an active material, 21 mg of bismuth oxide and 72 mg of titanium nitride as conductive additives, 33 mg of polyvinyl alcohol as a polymer binder and 1.90 ml of water has been prepared.

[0108] A first deposit using the ink as prepared hereinabove has then been applied to a first 100 m-thick porous current collector layer CC consisting of a circular copper grid.

[0109] A second deposit using the ink as prepared hereinabove has been applied to a second 100 m-thick porous current collector layer CC consisting of a circular copper grid having a diameter higher than the deposit. The two porous current collector layers CC, each covered with an electrode material ink, have then been dried at about 50 C. in an over, and assembled so as to place the first electrode material layer ME into contact with the second current collector layer CC, to form a circular electrode E-1. According to FIG. 1, it can be noted that the current collector CC 1 having a diameter higher than the deposit and used in the second deposit is folded over the first current collector CC 1, used for the first deposit, so that these two latter ones are in contact. The obtained circular electrode 3 E-1 has then been placed into a PTFE ring 2 and squeezed until reaching the thickness of about 0.5 mm. The PTFE ring 2 protected the circular edges of the electrode, while always leaving a central electrolyteelectrode contact surface 4.

[0110] The circular electrode E-1 comprised successively a first porous current collector layer CC 1, a first electrode material layer ME 5, a second porous current collector layer CC 1 connected to the first porous current collector layer CC 1 and a second electrode material layer ME 5. The second electrode material layer ME 5 being intended to be in contact with the electrolyte and the first porous current collector layer 1 being intended to ensure the electrical connection of the electrode 3 with the external circuit (not shown). The electrode 3 was hence in the form of an assembly of successive layers having the following structure:

[CCME].sub.2

[0111] An electrode material ink comprising 300 mg of calcium zincate as an active material, 14 mg of bismuth oxide and 48 mg of titanium nitride as conductive additives, 22 mg of polyvinyl alcohol as a polymer binder and 1.90 ml of water has been prepared.

[0112] The calcium zincate has been synthetized by a method as described hereinabove.

[0113] A first deposit using the ink as prepared hereinabove has then been applied to a first 100 m-thick porous current collector layer CC consisting of a circular copper grid.

[0114] A second deposit using the ink as prepared hereinabove has been applied to a second 100 m-thick porous current collector layer CC consisting of a circular copper grid having a diameter higher than the deposit.

[0115] A second deposit using the ink as prepared hereinabove has been applied to a third 100 m-thick porous current collector layer CC consisting of a circular copper grid having a diameter higher than the deposit. The three porous current collector layers CC, each covered with an electrode material ink, have then been dried at about 50 C. in an oven, and assembled so as to place the first electrode material layer ME into contact with the second porous current collector layer CC and the second electrode material layer ME with the third porous current collector layer CC, to form an electrode E-2. According to FIG. 2, it can be noted that the current collectors CC having a diameter higher than the deposit 1, 1 are folded over the first current collector CC 1, used for the first deposit, so that these three latter ones are in contact. The obtained electrode 3 E-2 has then been placed into a PTFE ring 2 and squeezed until reaching the thickness of about 0.5 mm. The PTFE ring 2 protected the circular edges of the electrode, while always leaving a central electrolyteelectrode contact surface 4.

[0116] The circular electrode E-2 3 comprised successively a first porous current collector layer CC 1, a first electrode material layer ME 5, a second porous current collector layer CC 1, a second electrode material layer ME 5, a third porous current collector layer CC 1 and a third electrode material layer ME 5, the third electrode material layer 5 being intended to be in contact with the electrolyte and the first porous current collector layer 1 being intended to ensure the electrical connection of the electrode 3 with the external circuit (not shown). The electrode 3 was hence in the form of an assembly of successive layers having the following structure:

[CCME].sub.3

[0117] Three zinc/nickel alkaline accumulators have then been manufactured by assembling:

[0118] one of the zinc-based negative electrodes E-A, E-1 or E-2,

[0119] a nickel-based positive electrode recovered from a PKcell-brand NiZn battery of the market, comprising an electrode material layer comprising NiOOH and Ni(OH).sub.2, deposited on a porous current collector layer consisting of a nickel foam,

[0120] a polyolefin-based non-woven separator and a polypropylene membrane interposed between the negative and positive electrodes, the separator facing the negative electrode, and the membrane facing the positive electrode, and

[0121] an electrolyte comprising an aqueous solution comprising KOH 7 M and 10 g/l of LiOH, said aqueous solution being saturated in ZnO.

[0122] FIG. 3.a. shows the zinc-based negative electrodes E-A (FIG. 3.a.), E-1 (FIG. 3.b.) and E-2 (FIG. 3.c.) as prepared hereinabove.

[0123] FIG. 3.b. shows an accumulator 6 as manufactured hereinabove, comprising a zinc-based negative electrode 3, a nickel-based positive electrode 7, a polyolefin-based non-woven separator 8 and a polypropylene membrane 9 interposed between the negative 3 and positive 7 electrodes, the separator 8 facing the negative electrode 3, and the membrane 9 facing the positive electrode 7, and an electrolyte 10.

[0124] The accumulator also comprises two glassy carbon layers 11, 11 at its two ends, allowing the direct electrical contact with the external porous current collector layers, as well as a security system that is permeable to the gases but not to the liquid electrolyte 12 in order to avoid a potential overpressure in case of gassing.

[0125] The assembly of the electrode 3 provided with its PTFE ring 2 to the external current collector allows avoiding the direct contact with the external porous current collector layer of the negative electrode and the electrolyte.

[0126] Galvanostatic charge and discharge tests (with constant current) at C/3 (i.e. 3 h of charge and 3 h of discharge with a current of 1.33 mA) with a cut-off voltage of 1.93 V in charge and an end-of-discharge voltage of 1.40 V have then been carried out, i.e. with a practical capacity of 4 mAh that corresponds to 40% of the theoretical capacity. The tests have been carried out at ambient temperature with a potentiostat-galvanostat sold under the commercial name OGF500 by the Origalys Company. Previously to the cycling at C/3, 3 cycles of charge at C/10 and discharge at C/5 have been carried out.

[0127] FIG. 4.a., FIG. 5.a. and FIG. 6.a. show curves of the accumulator voltage (in volts, V) as a function of time (in minutes, min) after 4 cycles (i.e. after the 3 formation cycles +1 cycle at C/3) (full line curve), after 10 cycles (long-dash line curve) and after 20 cycles (short-dash line curve) when the accumulator comprises the electrode E-A (FIG. 4.a.), the electrode E-1 (FIG. 5.a.) or the electrode E-2 (FIG. 6.a), as a negative electrode.

[0128] FIG. 4.b., FIG. 5.b. and FIG. 6.b. show the evolution of the accumulator practical capacity (in milliampere hour, mAh) as a function of the number of cycles when the accumulator comprises the electrode E-A (FIG. 4.b.), the electrode E-1 (FIG. 5.b.) or the electrode E-2 (FIG. 6.b), as a negative electrode.

[0129] It can be observed that, when a negative electrode not in accordance with the invention E-A is used, an overvoltage is observed at the 10.sup.th cycle, leading the battery to reach the cut-off voltage in less than 100 min of charge and at the 20.sup.th cycle in less than 50 min of charge (FIG. 4.a.). This also results in a high drop of the practical capacity (FIG. 4.b.) right from the first cycles. The average practical capacity of this electrode E-A for the first 50 cycles was of 1.27 mAh, which represents only 32% of the initial practical capacity of 4 mAh.

[0130] In FIG. 5.a., the electrochemical performances are improved. Hence, with a negative electrode in accordance with the invention E-1 in which two porous current collector layers are used, the overvoltage at the 10.sup.th and the 20.sup.th cycles is less pronounced. A very moderate reduction of the practical capacity is also observed (FIG. 5.b.). The average practical capacity of this electrode E-1 for the first 50 cycles was of 2.3 mAh, which represents 58% of the initial practical capacity of 4 mAh.

[0131] The electrochemical performances are further improved when the number of porous current collector layers increases. Hence, with a negative electrode in accordance with the invention E-3 in which three porous current collector layers are used, the overvoltage at the 10.sup.th and the 20.sup.th cycles is low (FIG. 6.a.). A very low reduction of the practical capacity is also observed (FIG. 6.a.). Indeed, the average practical capacity of this electrode E-3 for the first 50 cycles was of 3.68 mAh, which represents 92% of the initial practical capacity of 4 mAh.

[0132] Morphological analyses by scanning electron microscopy of the electrodes E-A, E-1 and E-2, after cycling, have allowed showing that the use of a current collection multiple array internal to the electrode allows favouring the uniform zinc redistribution during the formation thereof within the electrode during the successive cycles.

Example 2: Preparation of an Electrode E-B not in Accordance with the Invention

[0133] An electrode material ink comprising 450 mg of calcium zincate as an active material, 21 mg of bismuth oxide and 72 mg of titanium nitride as conductive additives, 33 mg of polyvinyl alcohol as a polymer binder and 1.90 ml of water has been prepared.

[0134] The calcium zincate has been synthetized by a method as described hereinabove.

[0135] A first deposit using the ink as prepared hereinabove has then been applied to a first 100 m-thick porous current collector layer CC consisting of a circular copper grid.

[0136] A second deposit using the ink as prepared hereinabove has been applied to a second 100 m-thick porous current collector layer CC consisting of a circular copper grid having a diameter higher than the deposit. The two porous current collector layers CC, each covered with an electrode material ink, have then been dried at about 50 C. in an oven, and assembled so as to place the first electrode material layer ME into contact with the second current collector layer CC. A third porous current collector layer CC, having a diameter higher than the second electrode material layer ME, has been applied to the second electrode material layer ME, to form a circular electrode E-B. According to the appended FIG. 7, it can be noted that the current collectors CC having higher diameters than the deposit 1, 1 are folded over the first current collector CC 1, so that these three latter ones are in contact. The obtained circular electrode 3 E-B has then been placed into a PTFE ring 2 and squeezed until reaching the thickness of about 0.5 mm. The PTFE ring 2 protected the circular edges of the electrode 3, while always leaving a central surface 4 of contact with the electrolyte. In this case, the porous current collector layer CC is in direct contact with the electrolyte.

[0137] The circular electrode E-B comprised successively a first porous current collector layer CC 1, a first electrode material layer ME 5, a second porous current collector layer CC 1 connected to the first porous current collector layer CC 1, a second electrode material layer ME 5 and a third porous current collector layer CC 1 connected to the first porous current collector layer CC 1. The third porous current collector layer CC 1 being intended to be in contact with the electrolyte and the first porous current collector layer 1 being intended to ensure the electrical connection of the electrode 3 with the external circuit. The electrode 3 was hence in the form of an assembly of successive layers having the following structure:

[CCME].sub.2CC

[0138] A zinc/nickel alkaline accumulator has then been manufactured by assembling:

[0139] the zinc-based negative electrode E-B,

[0140] a positive electrode of the market, recovered from a PKcell-brand Ni-Zn battery of the market, comprising an electrode material layer comprising NiOOH and Ni(OH).sub.2, deposited on a porous current collector layer consisting of a nickel foam,

[0141] a polyolefin-based non-woven separator and a polypropylene membrane interposed between the negative and positive electrodes, the separator facing the negative electrode, and the membrane facing the positive electrode, and

[0142] an electrolyte comprising an aqueous solution comprising KOH 7M and 10 g/l of LiOH, said aqueous solution being saturated in ZnO.

[0143] The so-obtained negative electrode 3 E-B has hence been placed into an accumulator according to the same assembly as that shown in the appended FIG. 3.d.

[0144] Galvanostatic charge and discharge tests (with constant current) at C/3 (i.e. 3 h of charge and 3 h of discharge with a current of 1.3 mA) with a cut-off voltage of 1.93 V in charge and an end-of-discharge voltage of 1.40 V have then been carried out, with a practical capacity of 4 mAh that corresponds to 40% of the theoretical capacity. The tests have been carried out at ambient temperature with a potentiostat-galvanostat sold under the commercial name OGF500 by the Origalys Company. Previously to the cycling at C/3, 3 cycles of charge at C/10 and discharge at C/5 have been carried out.

[0145] FIG. 8.a. shows the curves of the accumulator voltage (in volts, V) as a function of time (in minutes, min) after 4 cycles (full line curve), after 10 cycles (long-dash line curve) and after 20 cycles (short-dash line curve) when the accumulator comprises the electrode E-B as a negative electrode. The accumulator voltage curves over the first 20 cycles show no overvoltage, which is a result similar to that of the electrode E-2 having the same number of porous current collector layers CC.

[0146] FIG. 8.b. shows the evolution of the accumulator practical capacity (in milliampere hour, mAh) as a function of the number of cycles when the accumulator comprises the electrode E-B as a negative electrode.

[0147] It can be observed that, when a negative electrode not in accordance with the invention E-B is used, a drastic drop of the capacity has been observed from the 35.sup.th cycle.

[0148] The average practical capacity of this electrode E-A for the first 50 cycles was of 2.88 mAh, which represents only 72% of the initial practical capacity of 4 mAh.

[0149] Although the accumulator voltage curves measured up to the 20.sup.th cycle do not alone explain the performance losses of an electrode not in accordance with the invention E-B, the morphological analyses by scanning electron microscopy of the electrodes E-B, after cycling, have allowed showing that the use of an internal current collection multiple array allows favouring the uniform zinc redistribution during the formation thereof within the electrode during the successive cycles but that the external porous current collector layer CC, in direct contact with the electrolyte, is harmful for the good electrochemical performances, leading to the formation of a resistive layer of calcium hydroxide at the surface.

Example 3: Preparation of an Electrode E-3 in Accordance with the Invention

[0150] An electrode material ink comprising 300 mg of calcium zincate as an active material, 14 mg of bismuth oxide and 48 mg of titanium nitride as conductive additives, 22 mg of polyvinyl alcohol as a polymer binder and 1.90 ml of water has been prepared.

[0151] The calcium zincate has been synthetized by a method as described hereinabove.

[0152] According to the appended Fig.9, a first deposit 5 using the ink as prepared hereinabove has then been applied to a first 100 m-thick porous current collector layer CC 1 consisting of a circular copper grid having a diameter higher than the deposit.

[0153] A second deposit 5 using the ink as prepared hereinabove has been applied to a non-adhesive surface 13 in order to use it without any porous current collector layer CC.

[0154] A third deposit 5 using the ink as prepared hereinabove has been applied to a 100 pm-thick third porous current collector layer CC 1 consisting of a circular copper grid comprising an upper extension 13 as illustrated in FIG. 9.

[0155] A fourth deposit 5 using the ink as prepared hereinabove has been applied to a non-adhesive support.

[0156] The three porous current collector layers CC 1, 1 and 1, each covered with an electrode material ink 5, 5 and 5, as well as the non-adhesive surface 14 covered with an electrode material ink 5 have then been dried at about 50 C. in an oven, and assembled so as to place the first porous current collector layer CC 1 of the first deposit 5 into contact with the electrode material layer ME 5 without current collector, the latter being in contact with the porous current collector layer CC 1 of the third deposit, the electrode material layer ME 5 of the third deposit being in contact with the porous current collector layer 1 of the fourth deposit 5 to form a circular electrode 3 E-3. It can be noted that the current collectors CC 1, 1, having diameters higher than the deposits, are folded over the first current collector CC 1, so that these three latter ones 1, 1 and 1 are in contact. As shown in the appended FIG. 10, the obtained circular electrode 3 E-3 has then been placed into two PTFE rings 2 and squeezed until reaching the thickness of 800 m. The two PTFE rings 2 protected the circular edges of the electrode 3, while always leaving two central electrolyteelectrode contact surfaces 4, 4.

[0157] According to the appended Fig.10, the circular electrode 3 E-3 comprised successively a first electrode material layer ME 5, a first porous current collector layer CC 1 connected to the second porous current collector layer CC 1, a second electrode material layer ME 5, a second porous current collector layer CC 1 provided with an upper extension 13 intended to ensure the electrical connection of the electrode 3 with the external circuit, a third electrode material layer ME 5, a third porous current collector layer CC 1 connected to the second porous current collector layer CC 1, a fourth electrode material layer ME 5. The first electrode material layer ME 5 as well as the fourth electrode material layer ME 5 are intended to be in contact with the electrolyte. The electrode 3 was hence in the form of an assembly of successive layers having the following structure:

ME[CCME].sub.3

[0158] A zinc/nickel alkaline accumulator 6 has then been manufactured, according to FIG. 11, by assembling:

[0159] the zinc-based negative electrode 3 E-3,

[0160] two nickel-based positive electrodes 7, 7, recovered from a PKcell-brand NiZn battery of the market, comprising an electrode material layer comprising NiOOH and Ni(OH).sub.2, deposited on a porous current collector layer consisting of a nickel foam, [0161] two polyolefin-based non-woven separators 8, 8 and two polypropylene membranes 9, 9 interposed between the positive electrodes 7, 7 and the negative electrode 3, the separators 8, 8 facing the negative electrode 3, and the membranes 9, 9 facing the positive electrodes 7, 7, and

[0162] an electrolyte comprising an aqueous solution comprising KOH 7M and 10 g/l of LiOH, said aqueous solution being saturated in ZnO.

[0163] FIG. 11 shows the accumulator 6 as manufactured hereinabove, comprising a zinc-based negative electrode 3, two nickel-based positive electrodes 7, 7, two polyolefin-based non-woven separators 8, 8 and two polypropylene membranes 9, 9 interposed between the negative 3 and the positive 7, 7 electrodes, the separators 8, 8 facing the negative electrode 3, and the membranes 9, 9 facing the positive electrodes 7, 7.

[0164] The accumulator also comprises, at its two ends, two polychlorotrifluoroethylene tips (Kel-F) 15, 15 provided with glassy carbon rods 16, 16 allowing the direct electrical contact with the two nickel-based positive electrodes 7, 7.

[0165] The negative electrode 3 is connected to the external current collector by the extension 13 of this current collector.

[0166] Galvanostatic charge and discharge tests (with constant current) at C/3 (i.e. 3 h of charge and 3 h of discharge with a current of 1.3 mA) with a cut-off voltage of 1.93 V in charge and an end-of-discharge voltage of 1.40 V have then been carried out, i.e. with a practical capacity of 4 mAh that corresponds to 40% of the theoretical capacity. The tests have been carried out at ambient temperature with a potentiostat-galvanostat sold under the commercial name OGF500 by the Origalys Company. Previously to the cycling at C/3, 3 cycles of charge at C/10 and discharge at C/5 have been carried out.

[0167] FIG. 12.a. shows curves of the accumulator voltage (in volts, V) as a function of time (in minutes, min) after 4 cycles (full line curve), after 10 cycles (long-dash line curve) and after 20 cycles (short-dash line curve) when the accumulator comprises the electrode E-3 as a negative electrode.

[0168] FIG. 12.b. shows curves of the evolution of the accumulator practical capacity (in milliampere hour, mAh) as a function of the number of cycles when the accumulator comprises the electrode E-3 as a negative electrode.

[0169] It may be observed that, when a negative electrode in accordance with the invention E-3 is used, the accumulator voltage curves reveal no overvoltage at the 4.sup.th, 10.sup.th and 20.sup.th cycles.

[0170] It may be observed that, when a negative electrode in accordance with the invention E-3 is used, the practical capacity is held constant over the 50 cycles performed.

[0171] The practical practical capacity of this electrode E-3 for the first 50 cycles was of 3.70 mAh, which represents 93% of the initial practical capacity of 4 mAh.

[0172] Morphological analyses by scanning electron microscopy of the electrode E-3, after cycling, have allowed showing that the use of an internal current collection multiple array allows favouring the uniform zinc redistribution during the formation thereof within the electrode during the successive cycles.