Material for an electrode of an organic battery comprising benzene-bis(dithioic) acid derivatives

Abstract

The present invention concerns the use, as an active electrode material, of compounds comprising at least one entity of formula (I): in which the phenyl group is substituted with one to four identical or different substituent(s) R, chosen from a hydrogen atom, a halogen atom chosen from fluorine, chlorine, bromine or iodine, a C(S)SC+ group, an OC+ group, an SC+ group, C+ being an alkali cation chosen from Li+, Na+ and K+, a (C1-C12) alkyl radical, a (C2-C12) alkenyl radical, a (C6-C14) aryl or heteroaryl radical; or two vicinal substituents R that can, if appropriate, be linked to each other to together form a 3- to 7-membered ring optionally including another heteroatom chosen from N, O or S; in the base or salt form; and the tautomeric forms of same. It also concerns an electrode material, an electrode and a lithium, sodium or potassium secondary battery, obtained from these compounds.

Claims

1. An electrode active material comprising at least one compound of formula (IIa): ##STR00007## in which: at least one of the substituents R.sub.1, R.sub.2, R.sub.3, R.sub.4 or R.sub.5 represents a C(S)SLi group, the others, which are identical or different, representing a substituent R selected from the group consisting of a hydrogen atom, a halogen atom chosen from chlorine, bromine or iodine, a C(S)SLi group, an OLi group, an SLi group, a (C.sub.1-C.sub.12)alkyl radical, a (C.sub.2-C.sub.12)alkenyl radical or a (C.sub.6-C.sub.14)aryl or -heteroaryl radical or it being possible for two vicinal substituents R, if appropriate, to be bonded to one another in order to together form a 3- to 7-membered ring optionally including another heteroatom chosen from N, O or S; or base, salt, or tautomeric forms thereof.

2. The electrode active material as claimed in claim 1, which is provided in the form of a dispersed powder or in solution in said conducting additive or binder.

3. The electrode active material as claimed in claim 1, wherein R.sub.3 in formula (IIa) represents a C(S)SLi group, and R.sub.1, R.sub.2, R.sub.4 and R.sub.5, which are identical or different, represent a substituent R as defined above.

4. The electrode active material as claimed in claim 1, wherein the compound is bislithium 1,4-benzenebisdithioate of formula: ##STR00008## or its tautomeric form.

5. An electrode formed in all or part of an electrode active material and at least one electron-conducting additive, said electrode active material comprising at least one compound of formula (IIa): ##STR00009## in which: at least one of the substituents R.sub.1, R.sub.2, R.sub.3, R.sub.4 or R.sub.5 represents a C(S)SLi group, the others, which are identical or different, representing a substituent R selected from the group consisting of a hydrogen atom, a halogen atom chosen from chlorine, bromine or iodine, a C(S)SLi group, an OLi group, an SLi group, a (C.sub.1-C.sub.12)alkyl radical, a (C.sub.2-C.sub.12)alkenyl radical or a (C.sub.6-C.sub.14)aryl or -heteroaryl radical or it being possible for two vicinal substituents R, if appropriate, to be bonded to one another in order to together form a 3- to 7-membered ring optionally including another heteroatom chosen from N, O or S; or base, salt, or tautomeric forms thereof.

6. The electrode as claimed in claim 5, said electron-conducting additive(s) being selected from the group consisting of carbon fibers, carbon black, carbon nanotubes, graphene and their analogues.

7. The electrode as claimed in claim 5, additionally comprising at least one binder.

8. The electrode as claimed in claim 7, said binder(s) being selected from the group consisting of fluorinated binders, polymers derived from carboxymethyl cellulose, polysaccharides and latexes.

9. The electrode as claimed in claim 5, wherein the compound is bislithium 1,4-benzenebisdithioate of formula: ##STR00010## or its tautomeric form.

10. A lithium, sodium or potassium storage battery, comprising an electrode formed in all or part of an electrode active material, said electrode active material comprising at least one compound of formula (IIa): ##STR00011## in which: at least one of the substituents R.sub.1, R.sub.2, R.sub.3, R.sub.4 or R.sub.5 represents a C(S)SLi group, the others, which are identical or different, representing a substituent R selected from the group consisting of a hydrogen atom, a halogen atom chosen from chlorine, bromine or iodine, a C(S)SLi group, an OLi group, an SLi group, a (C.sub.1-C.sub.12)alkyl radical, a (C.sub.2-C.sub.12)alkenyl radical or a (C.sub.6-C.sub.14)aryl or -heteroaryl radical or it being possible for two vicinal substituents R, if appropriate, to be bonded to one another in order to together form a 3- to 7-membered ring optionally including another heteroatom chosen from N, O or S; or base, salt, or tautomeric forms thereof.

11. The battery as claimed in claim 10, being a lithium storage battery.

12. The battery as claimed in claim 10, wherein the compound is bislithium 1,4-benzenebisdithioate of formula: ##STR00012## or its tautomeric form.

13. A process for the preparation of an electrode as defined according to claim 5, comprising at least the stages of: (i) having available a mixture formed: of at least one of said electrode active material, of a liquid phase, of one or more electron-conducting additive(s), and optionally of one or more binder(s); and (ii) depositing said mixture from stage (i) by coating or by a printing technique on a base substrate or by extrusion or by corolling.

14. The process as claimed in claim 13, said base substrate being a polymeric film of polyethylene or polypropylene type, said process comprising a subsequent stage (iii) of detaching said polymeric film, in order to form a self-supported electrode.

15. A process for the preparation of an electrode according to claim 5, comprising the formation of a polymer by in situ electropolymerization on a current collector of monomers functionalized by entities of formula (IIa).

16. The process as claimed in claim 15, comprising at least the stages of: (i) introducing said monomers functionalized by entities of the formula (IIa) in the powder form into the electrolyte of a lithium, sodium or potassium electrochemical cell or dissolving said functionalized monomers in the electrolyte of a lithium, sodium or potassium electrochemical cell; and (ii) carrying out at least one charging cycle of the cell in order to form a positive electrode or at least one discharging cycle of the cell in order to form a negative electrode.

Description

FIGURES

(1) FIG. 1: Cyclic voltammetry curves of BBDTLi.sub.2: in solution on Pt electrode (2 mm) (FIG. 1A) and on glassy carbon (3 mm) (FIG. 1B)

(2) FIG. 2: Cyclic voltammetry curves of BBDTPLi.sub.2 in a button cell

(3) FIG. 3: Capacity-potential curves of BBDTLi.sub.2 in a button cell

(4) FIGS. 4 to 6: Cyclic curves of BBDTLi.sub.2 under different conditions

(5) FIG. 7: UV-visible spectrum recorded during the electrolysis of BBDTLi.sub.2

(6) FIG. 8: Capacity-potential curves of TPLi.sub.2 (not in accordance with the invention) in a button cell

(7) FIGS. 9 and 10: Cyclic curves of TPLi.sub.2 (not in accordance with the invention) under different conditions

(8) FIG. 11: Comparison of the capacity under C/10 conditions for BBDTLi.sub.2 and TPLi.sub.2

(9) FIG. 12: Comparison of the capacity as a function of the number of cycles for BBDTLi.sub.2 (C/10 conditions) and TPLi.sub.2 (C/50 conditions).

EXAMPLES

Example 1

Preparation of bislithium 1,4-benzenebisdithioate (BBDTLi2)

(10) A solution of lithium ethoxide is prepared by addition of 10 mL of anhydrous ethanol to 0.16 g of lithium metal in a dropping funnel.

(11) This solution is subsequently added dropwise to 5.86 g of crystalline sulfur in 90 mL of anhydrous ethanol.

(12) The reaction mixture is maintained at reflux for approximately 2 hours.

(13) One equivalent of ,-dichloro-p-xylene (1 g) is subsequently added in the solid form to the reaction mixture and brought to reflux for 20 hours.

(14) After cooling to ambient temperature, the crude mixture is filtered, in order to remove the excess sulfur, and then the filtrate is concentrated under reduced pressure and again filtered.

(15) The solution is subsequently evaporated to dryness in order to give a red solid.

(16) The solid is copiously washed with toluene, cyclohexane and dichloromethane.

(17) The crude residual solid is purified by slow recrystallization at ambient temperature from an ether/cyclohexane mixture.

(18) The structure of the bislithium 1,4-benzenebisdithioate compound obtained is characterized by single-crystal X-ray diffraction. The crystal data obtained are given in detail in table 1 below.

(19) TABLE-US-00001 TABLE 1 Compound Bislithium 1,4-benzenebisdithioate (BBDTLi.sub.2) Empirical formula C.sub.8H.sub.16Li.sub.2O.sub.6S.sub.4 Atomic weight 350.33 Temperature 150(2) K Wavelength 0.71073 A Crystal system Monoclinic Space group P 1 21/c 1 Unit cell dimensions a = 8.0373(5) A alpha = 90 b = 16.5938(11) A beta = 104.367(8) c = 6.0809(6) A gamma = 90 Volume, Z 785.65(10) A.sup.3, 2 Density (calculated) 1.481 g/cm.sup.3 Absorption coefficient 0.618 mm.sup.1 F(000) 364 Size of the crystal 0.40 0.05 0.02 mm

Example 2

(20) Cyclic Voltammetry of the BBDTLi.sub.2 in Solution

(21) A 1 mM solution of bislithium 1,4-benzenebisdithioate in acetonitrile (AN) containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF.sub.6) is prepared. The cyclic voltammetry curves are measured by scanning the potential between 1 and 4 V vs Li.sup.+/Li.sup.0 at a rate of 0.1 V/s.

(22) The variation in the electrical potential applied to the platinum or glassy carbon electrode is measured (FIGS. 1A and 1B respectively).

(23) With regard to the platinum electrode (2 mm) (FIG. 1A), the process of reversible reduction of the bislithium 1,4-benzenebisdithioate is observed at a potential of 1.25 V vs Li.sup.+/Li.sup.0 (solid line curve) and then the appearance of a new redox process in the 2.sup.nd scan (dotted line curve) is detected at 1.99 V.

(24) With regard to the glassy carbon electrode (3 mm) (FIG. 1B), the irreversible reduction of the bislithium 1,4-benzenebisdithioate is measured at a potential of 1.09 V vs Li.sup.+/Li.sup.0 (solid line curve). With regard to this electrode, the electrogeneration of a new product in the 2.sup.nd scan (dotted line curve) is observed at a potential of 1.93 V vs Li.sup.+/Li.sup.0.

Example 3

(25) Preparation of an Electrode

(26) An electrode having the composition BBDTLi.sub.2:SuperP:Binder=40:40:20 (as % by weight) is prepared according to the following stages.

(27) 40% of BBDTLi.sub.2 and 40% of SuperP are ground in the presence of cyclohexane. The cyclohexane is subsequently evaporated at ambient temperature for 30 minutes.

(28) 20% of polyvinylidene difluoride binder (12% PVDF solution) and N-methylpyrrolidone (NMP) are subsequently added in order to form an ink.

(29) This ink is coated with a thickness of 200 vim onto a copper current collector and is then dried in an oven at 55 C. for 24 hours.

(30) Electrodes with a diameter of 14 mm are cutout using a hollow punch and then dried in a Bchi oven at 80 C. for 48 hours.

Example 4

(31) Manufacture of a Button Half-Cell

(32) In order to determine the electrochemical performance of the electrode material according to the invention, a battery of button cell type is produced with: a lithium metal negative electrode (1 M LiTFSI in TEGDME:diox=1:1 (% by volume)); a positive electrode composed of a BBDTLi.sub.2:SuperP:Binder=40:40:20 (% by weight) composition, comprising the compound of the invention prepared according to example 1 deposited on copper; and two separators based on polyolefins.

(33) The variation in the electrical potential during the cycles is measured (FIG. 2A (1.sup.st and 2.sup.nd scans) and FIG. 2B (from the 6.sup.th to the 8.sup.th scan)).

(34) In the first scan, the existence of several reduction processes is observed between 1.2 and 1.8 V vs Li.sup.+/Li.sup.0 and, from the 2.sup.nd cycle, the appearance is observed of new electrochemical signatures, for subsequently generating a very stable system (FIG. 2B), characterized by a reduction process at a potential of 1.64 V vs Li.sup.+/Li.sup.0 and two oxidation processes at 1.86 and 2.23 V vs Li.sup.+/Li.sup.0.

(35) The specific capacity as a function of the electrical potential is also measured (FIG. 3). In the first cycle, a capacity of 320 mAh.Math.g.sup.1, which is greater than the theoretical capacity of BBDTLi.sub.2 (Q.sub.th=221 mAh.Math.g.sup.), is measured. The specific capacity then decreases and stabilizes at 200 mAh.Math.g.sup.1 after five cycles (FIG. 4).

(36) The cycling behavior of the electrogenerated material was measured under various conditions, either, on the one hand, by changing the solvent (FIG. 5, from 1 to 1.8 V), or by replacing the mixture of ethers with carbonate mixtures, or, on the other hand, in different potential ranges (FIG. 6).

(37) In order to understand the nature of the material electrogenerated in situ during the cycling of the BBDTLi.sub.2, spectroelectrochemical studies were carried out (FIG. 7).

(38) The exhaustive electrolysis of the BBDTLi.sub.2 in 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile (TBAPF.sub.6/AN), monitored by UV-visible spectroscopy, results in major spectroscopic changes, such as the decrease in intensity of the band at 340 nm, accompanied by the emergence of new bands in the near IR.

Example 5

(39) Comparison of the Performance of BBDTLi.sub.2 with Dilithium Terephthalate TPLi.sub.2 (not in Accordance)

(40) Preparation of Dilithium Terephthalate (TPLi.sub.2)

(41) 1 g of terephthalic acid is dispersed in 50 mL of a 1/1 by volume ethanol/water mixture and then 0.44 g of lithium carbonate is added.

(42) The solution is heated in an autoclave at 110 C. for 48 hours. The precipite is subsequently separated by centrifuging, washed with ethanol and then dried at 50 C. 1 g of white powder is obtained.

(43) Electrochemical Performance of TPLi.sub.2

(44) The electrochemical characterization of TPLi.sub.2 is carried out according to the procedure described in the preceding examples 3 and 4, except for the fact that the electrolyte used is a solution of LiPF.sub.6 (1M) in a carbonate mixture and that the charging conditions are C/50.

(45) FIG. 8 shows the change in the potential as a function of the specific capacity during the first two cycles under C/50 conditions. These curves show a very significant decrease in the capacity during the first two cycles.

(46) The measurement of the specific capacity as a function of the number of cycles, under C/50 conditions (FIG. 9), shows a constant decrease in the capacity with the number of cycles. Furthermore, it may be noted, from FIG. 10, which represents the specific capacity as a function of the number of cycles, under discharging conditions, that the capacities under C/50 conditions are greater than those under C/10 conditions.

(47) Comparison of the Performances of BBDTLi.sub.2 and TPLi.sub.2

(48) The change in the potential as a function of the specific capacity, during the 11.sup.th cycle under C/10 conditions, for BBDTLi.sub.2 and TPLi.sub.2, is represented in FIG. 11.

(49) Likewise, in FIG. 12, the curves and respectively represent the change in the specific capacity, as a function of the number of cycles, under discharging conditions, for the battery with TPLi.sub.2 and the battery with BBDTLi.sub.2, under C/50 conditions for the first and under C/10 conditions for the second.

(50) The performances of the batteries employing BBDTLi.sub.2 in accordance with the invention and TPLi.sub.2 as active material of the positive electrode are summarized in the following table 1.

(51) TABLE-US-00002 TABLE 1 Active material Capacity Irreversible of the positive Voltage.sup.(1) under C/10 Cycling loss electrode (V vs Li.sup.+/Li) conditions.sup.(2) behavior (%).sup.(3) BBDTLi.sub.2 2 220 Stable 35 (according to the invention) TPLi.sub.2 (prepared 0.8 80 Loss in 60 by the inventors) perfor- mance at each cycle .sup.(1)discharge voltage (mean voltage value over the 11.sup.th cycle); .sup.(2)capacity in the 11.sup.th cycle (C/10 conditions); .sup.(3)loss in discharging/charging capacity in the 1.sup.st cycle.