RECHARGEABLE BATTERY CELL

Abstract

This disclosure relates to a rechargeable battery cell, comprising: an active metal; at least one positive electrode; at least one negative electrode comprising an active material selected from the group consisting of an insertion material made of carbon, an alloy-forming active material, an intercalation material which does not comprise carbon, and a conversion active material; an SO.sub.2 based electrolyte comprising a first conducting salt which has the formula (I),

##STR00001##

wherein: M is a metal selected from the group consisting of alkali metals, alkaline earth metals, metals of group 12 of the periodic table of the elements, and aluminum; x is an integer from 1 to 3; R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are selected independently of one another from the group consisting of C.sub.1-C.sub.10 alkyl, C.sub.2-C.sub.10 alkenyl, C.sub.2-C.sub.10 alkynyl, C.sub.3-C.sub.10 cycloalkyl, C.sub.6-C.sub.14 aryl and C.sub.5-C.sub.14 heteroaryl; and Z is aluminum or boron.

Claims

1. A rechargeable battery cell, comprising: an active metal; at least one positive electrode; at least one negative electrode comprising an active material selected from the group consisting of an insertion material made of carbon, an alloy-forming active material, an intercalation material which does not comprise carbon, and a conversion active material; an SO.sub.2 based electrolyte comprising a first conducting salt which has the formula (I), ##STR00006## wherein: M is a metal selected from the group consisting of alkali metals, alkaline earth metals, metals of group 12 of the periodic table of the elements, and aluminum; x is an integer from 1 to 3; R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are selected independently of one another from the group consisting of C.sub.1-C.sub.10 alkyl, C.sub.2-C.sub.10 alkenyl, C.sub.2-C.sub.10 alkynyl, C.sub.3-C.sub.10 cycloalkyl, C.sub.6-C.sub.14 aryl and C.sub.5-C.sub.14 heteroaryl; and Z is aluminum or boron.

2. The rechargeable battery cell according to claim 1, wherein the insertion material made of carbon is selected from the group consisting of: graphite, natural graphite, synthetic graphite, graphitized mesocarbon microbeads, carbon coated graphite, and amorphous carbon.

3. The rechargeable battery cell according to claim 2, wherein the natural graphite comprises flake-shaped or rounded natural graphite and the synthetic graphite comprises mesophase graphite.

4. The rechargeable battery cell according to claim 1, wherein the alloy-forming active material is selected from the group consisting of lithium-storing metals and metal alloys or from the group consisting of oxides of lithium-storing metals and metal alloys.

5. The rechargeable battery cell according to claim 4, wherein the lithium-storing metals and metal alloys are selected from the group consisting of Si, Ge, Sn, SnCo.sub.xC.sub.y and SnSi.sub.x, and the oxides of lithium-storing metals and metal alloys are selected from the group consisting of SnO.sub.x, SiO.sub.x and oxidic glasses of Sn, Si.

6. The rechargeable battery cell according to claim 1, wherein the alloy-forming active material is formed from silicon or from silicon oxides or from blends of silicon and silicon oxides.

7. The rechargeable battery cell according to claim 1, wherein the negative electrode comprises at least one alloy-forming anode active material.

8. The rechargeable battery cell according to claim 7, wherein the alloy-forming anode active material forms an alloy with lithium, in combination with at least one insertion material made of carbon, combinations of silicon and/or silicon oxides and graphite.

9. The rechargeable battery cell according to claim 1, wherein the intercalation material is a lithium titanate.

10. The rechargeable battery cell according to claim 9, wherein the lithium titanate comprises Li.sub.4Ti.sub.5O.sub.12.

11. The rechargeable battery cell according to claim 1, wherein the conversion active material is selected from: the group consisting of manganese oxides (MnO.sub.x), iron oxides (FeO.sub.x), cobalt oxides (CoO.sub.x), nickel oxides (NiO.sub.x) and copper oxides (CuO.sub.x), or the group consisting of magnesium hydride (MgH.sub.2), titanium hydride (TiH.sub.2), aluminum hydride (AlH.sub.3) and boron-, aluminum- and magnesium-based ternary hydrides.

12. The rechargeable battery cell according to claim 1, wherein the positive electrode comprises as active material at least one compound having the composition A.sub.xM′.sub.yM″.sub.zO.sub.a, wherein: A is at least one metal selected from the group consisting of the alkali metals, the alkaline earth metals, the metals of group 12 of the periodic table, and aluminum; M′ is at least one metal selected from the group consisting of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn; M″ is at least one element selected from the group consisting of the elements of groups 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 of the periodic table of the elements; x and y independently of one another are numbers greater than 0; z is a number greater than or equal to 0; and a is a number greater than 0.

13. The rechargeable battery cell according to claim 12, wherein the compound has the composition Li.sub.xM′.sub.yM″.sub.zO.sub.a, wherein M′ is manganese and M″ is cobalt.

14. The rechargeable battery cell according to claim 13, wherein x, y and z are equal to 1 and a is equal to 4.

15. The rechargeable battery cell according to claim 12, wherein the compound has the composition Li.sub.xM′.sub.yM″.sub.zO.sub.a, wherein M′ comprises nickel and manganese and M″ is cobalt and the composition has the formula Li.sub.xNi.sub.y1Mn.sub.y2Co.sub.zO.sub.a.

16. The rechargeable battery cell according to claim 12, wherein the compound has the composition Li.sub.xM′.sub.yM″.sup.1.sub.z1M″.sup.2.sub.z2O.sub.4, wherein M″.sup.2 is phosphorus and z2 has the value 1.

17. The rechargeable battery cell according to claim 16, wherein the compound has the composition Li.sub.xM′.sub.yM″.sup.1.sub.z1PO.sub.4, wherein M′ is iron and M″.sup.1.sub.z1 is manganese.

18. The rechargeable battery cell according to claim 17, wherein the compound has the composition Li(Fe.sub.0.3Mn.sub.0.7)PO.sub.4.

19. The rechargeable battery cell according to claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are selected independently of one another from the group consisting of: C.sub.1-C.sub.6 alkyl; C.sub.2-C.sub.6 alkenyl; C.sub.2-C.sub.6 alkynyl; C.sub.3-C.sub.6 cycloalkyl; phenyl; and C.sub.5-C.sub.7 heteroaryl.

20. The rechargeable battery cell according to claim 19, wherein: the C.sub.1-C.sub.6 alkyl comprises C.sub.2-C.sub.4 alkyl; the C.sub.2-C.sub.6 alkenyl comprises C.sub.2-C.sub.4 alkenyl; and the C.sub.2-C.sub.6 alkynyl comprises C.sub.2-C.sub.4 alkynyl.

21. The rechargeable battery cell according to claim 20, wherein: the C.sub.2-C.sub.4 alkyl is selected from the group consisting of 2-propyl, methyl and ethyl; and the C.sub.2-C.sub.4 alkenyl is selected from the group consisting of ethenyl and propenyl.

22. The rechargeable battery cell according to claim 1, wherein at least one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is substituted by at least one fluorine atom and/or by at least one chemical group, wherein the chemical group is selected from the group consisting of C.sub.1-C.sub.4 alkyl, C.sub.2-C.sub.4 alkenyl, C.sub.2-C.sub.4 alkynyl, phenyl and benzyl.

23. The rechargeable battery cell according to claim 1, wherein at least one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is a CF.sub.3 group or an OSO.sub.2CF.sub.3 group.

24. The rechargeable battery cell according to claim 1, wherein the first conducting salt is selected from the group consisting of: ##STR00007##

25. The rechargeable battery cell according to claim 1, wherein the electrolyte comprises a second conducting salt different from the first conducting salt.

26. The rechargeable battery cell according to claim 25, wherein the second conducting salt is an alkali metal compound.

27. The rechargeable battery cell according to claim 26, wherein the alkali metal compound is a lithium compound selected from the group consisting of an aluminate, a halide, an oxalate, a borate, a phosphate, an arsenate and a gallate.

28. The rechargeable battery cell according to claim 25, wherein the second conducting salt is a lithium tetrahaloaluminate.

29. The rechargeable battery cell according to claim 28, wherein the lithium tetrahaloaluminate is lithium tetrachloroaluminate.

30. The rechargeable battery cell according to claim 1, wherein the electrolyte comprises at least one additive.

31. The rechargeable battery cell according to claim 30, wherein the additive of the electrolyte is selected from the group consisting of vinylene carbonate and its derivatives, vinylethylene carbonate and its derivatives, methylethylene carbonate and its derivatives, lithium (bisoxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium oxalate, 2-vinylpyridine, 4-vinylpyridine, cyclic exomethylene carbonates, sultones, cyclic and acyclic sulfonates, acyclic sulfites, cyclic and acyclic sulfinates, organic esters, inorganic acids, acyclic and cyclic alkanes, which acyclic and cyclic alkanes have a boiling point of at least 36° C. at 1 bar, aromatic compounds, halogenated cyclic and acyclic sulfonylimides, halogenated cyclic and acyclic phosphate esters, halogenated cyclic and acyclic phosphines, halogenated cyclic and acyclic phosphites, halogenated cyclic and acyclic phosphazenes, halogenated cyclic and acyclic silylamines, halogenated cyclic and acyclic halogenated esters, halogenated cyclic and acyclic amides, halogenated cyclic and acyclic anhydrides, and halogenated organic heterocycles.

32. The rechargeable battery cell according to claim 1, wherein the electrolyte comprises: (i) 5 to 99.4% by weight sulfur dioxide; (ii) 0.6 to 95% by weight of the first conducting salt; (iii) 0 to 25% by weight of the second conducting salt; and (iv) 0 to 10% by weight of the additive; based on the total weight of the electrolyte composition.

33. The rechargeable battery cell according to claim 1, wherein the molar concentration of the first conducting salt is in the range selected from the group consisting of from 0.01 mol/L to 10 mol/L, from 0.05 mol/L to 10 mol/L, from 0.1 mol/L to 6 mol/L and from 0.2 mol/L to 3.5 mol/L, based on the total volume of the electrolyte.

34. The rechargeable battery cell according to claim 1, wherein the electrolyte has a molar concentration of SO.sub.2 per mole of conducting salt selected from the group consisting of at least 0.1 mol SO.sub.2, at least 1 mol SO.sub.2, at least 5 mol SO.sub.2, at least 10 mol SO.sub.2 and at least 20 mol SO.sub.2.

35. The rechargeable battery cell according to claim 1, wherein the active metal comprises: an alkali metal; an alkaline earth metal; a metal from group 12 of the periodic table; or aluminum.

36. The rechargeable battery cell according to claim 35, wherein the alkali metal is lithium or sodium, the alkaline earth metal is calcium, and the metal from group 12 of the periodic table is zinc.

37. The rechargeable battery cell according to claim 1, wherein the positive electrode comprises at least one metal compound selected from the group consisting of a metal oxide, a metal halide and a metal phosphate.

38. The rechargeable battery cell according to claim 37, wherein the metal of the metal compound is a transition metal of atomic numbers 22 to 28 of the periodic table of the elements.

39. The rechargeable battery cell according to claim 38, wherein the metal of the metal compound is cobalt, nickel, manganese or iron.

40. The rechargeable battery cell according to claim 1, wherein the positive electrode comprises at least one metal compound having the chemical structure of a spinel, a layered oxide, a conversion compound or a polyanionic compound.

41. The rechargeable battery cell according to claim 1, wherein the positive electrode and/or the negative electrode have a discharge element, which is formed (i) planar in the form of a metal sheet or a metal foil, or (ii) three-dimensional in the form of a porous metal structure.

42. The rechargeable battery cell according to claim 41, wherein the porous metal structure comprises a metal foam.

43. The rechargeable battery cell according to claim 1, wherein the positive electrode and/or the negative electrode comprises at least one binder, the binder comprising: a fluorinated binder, or a polymer which is built up from monomeric structural units of a conjugated carboxylic acid or from the alkali, alkaline earth or ammonium salt of said conjugated carboxylic acid or from a combination thereof, or a polymer based on monomeric styrene and butadiene structural units, or a binder from the group of carboxymethyl celluloses, wherein the binder is present in a concentration by weight selected from the group consisting of at most 20%, at most 15%, at most 10%, at most 7%, at most 5% and at most 2% based on the total positive electrode weight.

44. The rechargeable battery cell according to claim 43, wherein the fluorinated binder is a polyvinylidene fluoride and/or a terpolymer made of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride.

45. The rechargeable battery cell according to claim 1, wherein the at least one positive electrode comprises a plurality of electrodes and the at least one negative electrode comprises a plurality of negative electrodes, wherein the positive and negative electrodes are stacked alternately in the housing.

46. The rechargeable battery cell according to claim 45, wherein the positive and negative electrodes are separated from one another by separators.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0147] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0148] FIG. 1 shows a first embodiment of a rechargeable battery cell according to this disclosure in a cross-sectional illustration;

[0149] FIG. 2 shows an electron microscope image of the three-dimensional porous structure of the metal foam of the first embodiment from FIG. 1 as a detailed illustration;

[0150] FIG. 3 shows a second embodiment of a rechargeable battery cell according to this disclosure in a cross-sectional illustration;

[0151] FIG. 4 shows a detail of the second embodiment from FIG. 3;

[0152] FIG. 5 shows a third embodiment of the rechargeable battery cell according to this disclosure in an exploded illustration;

[0153] FIG. 6 shows the potential in [V] of four test full cells when charging the negative electrodes with graphite 1, graphite 2, graphite 3 and graphite 4 as active electrode material as a function of capacity, during formation of a coating layer on the negative electrode;

[0154] FIG. 7 shows the discharge capacity as a function of the cycle number of three test full cells which comprise graphite 1, graphite 2 and graphite 3 as the active electrode material of the negative electrode;

[0155] FIG. 8 shows the potential in [V] of two test full cells when charging the negative electrodes with graphite 1 as the active electrode material as a function of capacity, during formation of a coating layer on the negative electrode, wherein one reference test full cell is filled with the reference electrolyte and one test full cell is filled with electrolyte 1;

[0156] FIG. 9 shows the discharge capacity as a function of the number of cycles of two test full cells which comprise graphite 1 as the active electrode material of the negative electrode, wherein one reference test full cell is filled with the reference electrolyte and one test full cell is filled with electrolyte 1;

[0157] FIG. 10 shows the potential in [V] of three half-cells when charging the negative electrodes with graphite 2, graphite 3 and graphite 4 as active electrode materials as a function of capacity, during formation of a coating layer on the negative electrode, wherein the half-cells are filled with the reference electrolyte;

[0158] FIG. 11 shows the potential in [V] of two test full cells when charging the negative electrodes with graphite 1 as the active electrode material as a function of capacity, during formation of a coating layer on the negative electrode, wherein one test full cell is filled with electrolyte 3 and one test full cell is filled with electrolyte 4;

[0159] FIG. 12 shows the potential in [V] during discharge as a function of the percentage charge of three test full cells which comprise graphite 1 as the active electrode material of the negative electrode and were filled with electrolytes 1, 3 and 4;

[0160] FIG. 13 shows the potential in [V] of three test full cells when charging the negative electrodes with blends of SiO.sub.x 5.0%/graphite 3, SiO.sub.x 17.3%/graphite 3 and SiO.sub.x 24.0%/graphite 3 as electrode active materials as a function of capacity, during formation of a coating layer on the negative electrode;

[0161] FIG. 14 shows the discharge capacity of the first ten cycles during discharge as a function of the number of cycles of three test full cells which comprise blends of SiO.sub.x 5.0%/graphite 3, SiO.sub.x 17.3%/graphite 3 and SiO.sub.x 24.0%/graphite 3 as the negative electrode active material;

[0162] FIG. 15 shows the potential in [V] of four test full cells when charging the negative electrodes with a blend of nano-silicon (5% by weight) and graphite 3 (95% by weight), a blend of nano-silicon (2.5% by weight) and graphite 1 (97.5% by weight), a blend of nano-silicon (5.0% by weight) and graphite 1 (95.0% by weight) and a blend of nano-silicon (10% by weight) and graphite 1 (90% by weight) as active electrode materials as a function of capacity, during formation of a coating layer on the negative electrode;

[0163] FIG. 16 shows the discharge capacity of the first ten cycles during discharge as a function of the number of cycles of four test full cells comprising a blend of nano-silicon (5% by weight) and graphite 3 (95% by weight), a blend of nano-silicon (2.5% by weight) and graphite 1 (97.5% by weight), a blend of nano-silicon (5.0% by weight) and graphite 1 (95.0% by weight) and a blend of nano-silicon (10% by weight) and graphite 1 (90% by weight) as the active electrode material of the negative electrode;

[0164] FIG. 17 shows the conductivity in [mS/cm] of electrolyte 1 as a function of the concentration;

[0165] FIG. 18 shows the conductivity in [mS/cm] of electrolyte 3 as a function of the concentration; and

[0166] FIG. 19 shows the conductivity in [mS/cm] of electrolyte 4 as a function of the concentration.

DESCRIPTION

[0167] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0168] FIG. 1 shows a first embodiment of a rechargeable battery cell 2 according to this disclosure in a cross-sectional illustration. Said rechargeable battery cell 2 is designed as a prismatic cell and has a housing 1, among other things. Said housing 1 encloses an electrode array 3 which comprises three positive electrodes 4 and four negative electrodes 5. The positive electrodes 4 and the negative electrodes 5 are stacked alternately in the electrode array 3. The housing 1 can, however, also accommodate more positive electrodes 4 and/or negative electrodes 5. In general, it is preferred when the number of negative electrodes 5 is one greater than the number of positive electrodes 4. This has the consequence of the outer end faces of the electrode stack being formed by the electrode surfaces of the negative electrodes 5. The electrodes 4, 5 are connected to corresponding contacts 9, 10 of the rechargeable battery cell 2 via electrode connections 6, 7. The rechargeable battery cell 2 is filled with an SO.sub.2-based electrolyte such that the electrolyte penetrates as completely as possible into all pores or cavities, in particular within the electrodes 4, 5. The electrolyte is not visible in FIG. 1. In the present embodiment, the positive electrodes 4 comprise an intercalation compound as an active material. This intercalation compound is LiCoMnO.sub.4.

[0169] The electrodes 4, 5 are designed flat in the present embodiment, that is, as layers having a thickness that is smaller in relation to their surface area. They are each separated from one another by separators 11. The housing 1 of the rechargeable battery cell 2 is essentially designed cuboid, wherein the electrodes 4, 5 and the walls of the housing 1 shown in a sectional illustration extend perpendicular to the plane of the drawing and are essentially straight and flat. The rechargeable battery cell 2 can, however, also be designed as a winding cell in which the electrodes consist of thin layers that are wound up together with a separator material. The separators 11, on the one hand, separate the positive electrode 4 and the negative electrode 5 spatially and electrically and, on the other hand, are permeable to the ions of the active metal, among other things. In this way, large electrochemically effective surfaces are created, which enable a correspondingly high current yield.

[0170] The electrodes 4, 5 also have a discharge element which serves to enable the required electronically conductive connection of the active material of the respective electrode. Said discharge element is in contact with the active material involved in the electrode reaction of the respective electrode 4, 5 (not depicted in FIG. 1). The discharge element is designed in the form of a porous metal foam 18. The metal foam 18 extends over the thickness dimension of the electrodes 4, 5. The active material of the positive electrodes 4 and the negative electrodes 5 is incorporated into the pores of said metal foam 18 so that it fills its pores uniformly over the entire thickness of the metal structure. The positive electrodes 4 comprise a binder to improve the mechanical strength. This binder is a fluoropolymer. The negative electrodes 5 comprise carbon as an active material in a form suitable as an insertion material for the absorption of lithium ions. The structure of the negative electrode 5 is similar to that of the positive electrode 4.

[0171] FIG. 2 shows an electron microscope image of the three-dimensional porous structure of the metal foam 18 of the first embodiment from FIG. 1. On the basis of the specified scale, it can be seen that the pores P have an average diameter of more than 100 μm, that is, are relatively large. This metal foam is a metal foam made of nickel.

[0172] FIG. 3 shows a second embodiment of a rechargeable battery cell 20 according to this disclosure in a cross-sectional illustration. Said second embodiment differs from the first embodiment shown in FIG. 1 in that the electrode array comprises a positive electrode 23 and two negative electrodes 22. They are each separated from one another by separators 21 and surrounded by a housing 28. The positive electrode 23 has a discharge element 26 in the form of a planar metal foil, to which the active material 24 of the positive electrode 23 is applied on both sides. The negative electrodes 22 also comprise a discharge element 27 in the form of a planar metal foil, to which the active material 25 of the negative electrode 22 is applied on both sides. Alternatively, the planar discharge elements of the edge electrodes, that is, of the electrodes that close off the electrode stack, can only be coated with active material on one side. The non-coated side faces the wall of the housing 28. The electrodes 22, 23 are connected to corresponding contacts 31, 32 of the rechargeable battery cell 20 via electrode connections 29, 30.

[0173] FIG. 4 shows the planar metal foil which serves as a discharge element 26, 27 for the positive electrodes 23 and the negative electrodes 22 in the second embodiment from FIG. 3. This metal foil has a perforated or mesh-like structure having a thickness of 20 μm.

[0174] FIG. 5 shows a third embodiment of a rechargeable battery cell 40 according to this disclosure in an exploded illustration. This third embodiment differs from the two embodiments explained above in that the positive electrode 44 is enveloped by a sheath 13. In this case, a surface area of the sheath 13 is greater than a surface area of the positive electrode 44, the boundary 14 of which is shown in FIG. 5 as a dashed line. Two layers 15, 16 of the sheath 13 that cover the positive electrode 44 on both sides are connected to one another at the circumferential edge of the positive electrode 44 by an edge connection 17. The two negative electrodes 45 are not enveloped. The electrodes 44 and 45 can be contacted via the electrode connections 46 and 47.

EXAMPLE 1

Preparation of a Reference Electrolyte

[0175] A reference electrolyte used for the examples described below was produced according to the method described in patent specification EP 2 954 588 B1 (hereinafter referred to as [V2]). First, lithium chloride (LiCl) was dried under vacuum at 120° C. for three days. Aluminum particles (Al) were dried under vacuum for two days at 450° C. LiCl, aluminum chloride (AlCl.sub.3) and Al were mixed together in an AlCl.sub.3:LiCl:Al molar ratio of 1:1.06:0.35 in a glass bottle having an opening to allow gas to escape. This blend was thereafter heat-treated in stages to produce a molten salt. After cooling, the salt melt formed was filtered, then cooled to room temperature and finally SO.sub.2 was added until the desired molar ratio of SO.sub.2 to LiAlCl.sub.4 was formed. The reference electrolyte thus formed had the composition LiAlCl.sub.4*x SO.sub.2, wherein x is dependent on the amount of SO.sub.2 supplied.

EXAMPLE 2

Preparation of Four Embodiments 1, 2, 3 and 4 of an SO.SUB.2.-Based Electrolyte for a Battery Cell

[0176] Four embodiments 1, 2, 3 and 4 of the SO.sub.2-based electrolyte were prepared for the experiments described below (hereinafter referred to as electrolytes 1, 2, 3 and 4). For this purpose, four different first conducting salts according to formula (I) were initially prepared using a manufacturing process described in the following documents [V3], [V4] and [V5]: [0177] [V3] “I. Krossing, Chem. Eur. 1 2001, 7, 490; [0178] [V4] S. M. Ivanova et al., Chem. Eur. 1 2001, 7, 503; [0179] [V5] Tsujioka et al., J. Electrochem. Soc., 2004, 151, A1418”

[0180] These four different, first conducting salts according to formula (I) are referred to below as compounds 1, 2, 3 and 4. They come from the family of polyfluoroalkoxyaluminates and were prepared in hexane according to the following reaction equation, starting from LiAlH.sub.4 and the corresponding alcohol R—OH with R.sup.1=R.sup.2=R.sup.3=R.sup.4.

##STR00004##

[0181] As a result, compounds 1, 2, 3 and 4 shown below were formed using the sum and structural formulas:

##STR00005##

[0182] Compounds 1, 2, 3 and 4 were first recrystallized for purification. As a result, residues of the educt LiAlH.sub.4 were removed from the first conducting salt, since said educt could possibly lead to the formation of sparks with possibly existing traces of water in SO.sub.2.

[0183] Compounds 1, 2, 3 and 4 were then dissolved in SO.sub.2. It was found that compounds 1, 2, 3 and 4 dissolve well in SO.sub.2.

[0184] The preparation of electrolytes 1, 2, 3 and 4 was performed at low temperature or under pressure according to process steps 1 to 4 listed below: [0185] 1) receiving of the respective compound 1, 2, 3 and 4 in a pressure piston each with a riser pipe, [0186] 2) evacuation of the pressure pistons, [0187] 3) inflow of liquid SO.sub.2, and [0188] 4) repetition of steps 2+3 until the target amount of SO.sub.2 was added.

[0189] The respective concentration of compounds 1, 2, 3 and 4 in electrolytes 1, 2, 3 and 4 was 0.6 mol/L (molar concentration based on 1 liter of the electrolyte), unless otherwise described in the description of the experiment. The experiments described below were performed using electrolytes 1, 2, 3 and 4 and the reference electrolyte.

EXAMPLE 3

Production of Test Full Cells

[0190] The test full cells used in the experiments described below are rechargeable battery cells having two negative electrodes and one positive electrode, each separated by a separator. The positive electrodes had an active material (named in the respective experiment), a conductivity mediator and a binder.

[0191] The examined negative electrodes comprised an active material, which is named in the respective experiment description. The negative electrodes can also comprise a binder and/or a conductivity additive. The discharge element of the positive and negative electrodes was made of nickel. Tables 3a and 3b show which active materials were examined for the negative electrodes.

TABLE-US-00003 TABLE 3a Investigated Graphites as Negative Electrode Active Materials Mean Grain Size Spec. Surface Name Type D50 [μm] [m.sup.2/g] Graphite 1 Synthetic graphite 22.4 3.7 Graphite 2 Synthetic graphite 20.2 1.8 Graphite 3 Synthetic graphite 17.0 1.8 Graphite 4 Synthetic graphite 22.1 5.4

TABLE-US-00004 TABLE 3b Investigated Blends Comprising Silicon as Active Materials of the Negative Electrode Name Type SiOx 5.0%/graphite 3 Blend of SiOx (5% by weight) and graphite 3 (95% by weight) SiOx 17.3%/graphite 3 Blend of SiOx (17.3% by weight)/ graphite 3 (82.7% by weight) SiOx 24%/graphite 3 Blend of SiOx (24% by weight)/ graphite 3 (76% by weight) Nano-Si 5.0%/graphite 3 Blend of nano-silicon (5% by weight) and graphite 3 (95% by weight Si) Nano-Si 2.5%/graphite 1 Blend of nano-silicon (2.5% by weight) and graphite 1 (97.5% by weight) Nano-Si 5.0%/graphite 1 Blend of nano-silicon (5% by weight) and graphite 1 (95% by weight) Nano-Si 10%/graphite 1 Blend of nano-silicon (10% by weight) and graphite 1 (90% by weight)

[0192] The test full cells were each filled with the electrolyte required for the experiments, that is, either with the reference electrolyte or electrolytes 1, 2, 3 or 4.

[0193] Several, that is, two to four, identical test whole cells were produced for each experiment. The results presented in the experiments are each mean values from the measured values obtained for the identical test full cells.

EXAMPLE 4

Measurement in Test Full Cells

Coating Layer Capacity:

[0194] The capacity consumed in the first cycle to form a coating layer on the negative electrode is an important criterion for the quality of a battery cell. This coating layer is formed on the negative electrode when the test full cell is charged for the first time. Lithium ions are irreversibly consumed for this formation of a coating layer (coating layer capacity), so that the test full cell has less cyclic capacity available for the subsequent cycles. The coating layer capacity in % of the theory that was used to form the coating layer on the negative electrode is calculated according to the following formula:

Coating layer capacity [in % of the theory]=(Q.sub.lad(xmAh)−Q.sub.ent(ymAh))/Q.sub.NEL

[0195] Q.sub.lad describes the amount of charge specified in the respective experiment in mAh; Q.sub.ent describes the amount of charge in mAh that was obtained when the test full cell was subsequently discharged. Q.sub.NEL is the theoretical capacity of the negative electrode used. The theoretical capacity is calculated, for example, in the case of graphite, to a value of 372 mAh/g.

[0196] The nominal capacity is obtained by subtracting the coating layer capacity (=Q.sub.lad(x mAh)−Q.sub.ent (y mAh)) from the theoretical capacity of the positive electrode.

Discharge Capacity:

[0197] For measurements in test full cells, for example, the discharge capacity is determined from the number of cycles. For this purpose, the test full cells are charged with a certain charge current intensity up to a certain upper potential. The corresponding upper potential is held until the charge current has dropped to a certain value. The discharge then takes place with a certain discharge current intensity up to a certain discharge potential. This charging method is called I/U charging. This process is repeated depending on the desired number of cycles.

[0198] The upper potentials or the discharge potential and the respective charge or discharge current intensities are given in the experiments. The value to which the charge current must have dropped is also described in the experiments.

[0199] The term “upper potential” is used as a synonym for the terms “charge potential,” “charge voltage,” “end-of-charge voltage” and “upper potential limit.” The terms denote the voltage/potential up to which a cell or battery is charged with the aid of a battery charger.

[0200] The battery is preferably charged at a current rate of C/2 and at a temperature of 22° C. With a charge or discharge rate of 1 C, by definition, the nominal capacity of a cell is charged or discharged in one hour. A charge rate of C/2 means a charge time of 2 hours.

[0201] The term “discharge potential” is used synonymously with the term “lower cell voltage.” This describes the voltage/potential up to which a cell or battery is discharged with the aid of a battery charger.

[0202] The battery is preferably discharged at a current rate of C/2 and at a temperature of 22° C.

[0203] The discharge capacity is obtained from the discharge current and the time until the criteria for ending the discharge are fulfilled. The associated figures show mean values for the discharge capacities as a function of the number of cycles. These mean values of the discharge capacities are often normalized to the maximum capacity that was achieved in the respective experiment and expressed in percent of the nominal capacity.

Experiment 1: Test Full Cells Having Different Graphites as the Positive Electrode Active Material

[0204] Experiments in test full cells according to Example 3 were performed using various graphites as active materials of the negative electrode. On the one hand, the coating layer capacities (graphite 1, 2, 3 and 4) and, on the other hand, the discharge capacities (graphite 1, 2 and 3) were determined. The test full cells were filled with electrolyte 1 described in Example 2.

[0205] The test full cells comprised negative electrodes having the synthetic graphites described in Table 3a, that is, using graphite 1, graphite 2, graphite 3 or graphite 4 as an active material. The positive electrodes comprised lithium nickel manganese cobalt oxide (NMC622) (graphite 1, 2 and 3) and lithium iron phosphate (graphite 4) as the active material.

[0206] FIG. 6 shows the potential in volts of the test full cells when charging the negative electrode as a function of capacity, which is related to the theoretical capacity of the negative electrode. The four curves depicted show averaged results of several experiments with the test whole cells described above. The curve of the test full cell having graphite 4 is at slightly lower potentials due to the different active material of the positive electrode. First, the test full cells were charged with a current of 15 mA until a capacity of 125 mAh (Q.sub.lad) was reached. The test full cells were then discharged at 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Q.sub.ent) was determined.

[0207] The determined coating layer capacities [in % of the theoretical capacity of the negative electrode] are 6.58% for graphite 1, 4.29% for graphite 2, 5.32% for graphite 3 and 7.27% for graphite 4. These are excellent values compared to existing systems in organic electrolytes.

[0208] The discharge capacity was determined in further cycles using the test full cells comprising graphite 1, 2 and 3. To determine the discharge capacities (see Example 4), the test full cells were charged with a current intensity of 100 mA up to an upper potential of 4.4 volts. The corresponding upper potential was held until the charge current had dropped to 40 mA. The discharge then took place with a current intensity of 100 mA up to a discharge potential of 2.5 volts.

[0209] FIG. 7 shows mean values for the discharge capacities normalized to 100% of the starting capacity of the three test full cells as a function of the number of cycles. These mean values of the discharge capacities are expressed as a percentage of the nominal capacity. The test full cells having different graphites show a very stable behavior of the discharge capacities over the number of cycles. 96% of the discharge capacity is still achieved in cycle 250 in the test full cells having graphite 1 and graphite 3. The test full cell having graphite 2 still achieved 93%.

Experiment 2: Graphite 1 as the Active Material of the Negative Electrode in Test Full Cells Using Electrolyte 1 and, in Comparison, in Test Full Cells Using Reference Electrolyte

[0210] Experiments in two test full cells according to Example 3 were performed using graphite 1 as the anode material. The one test full cell was filled with electrolyte 1 described in Example 2, the other test full cell comprised a reference electrolyte having the composition LiAlCl.sub.4×6SO.sub.2. The positive electrodes comprised lithium nickel manganese cobalt oxide (NMC622) as an active material.

[0211] On the one hand, the coating layer capacities and on the other hand, the discharge capacities were determined.

[0212] FIG. 8 shows the potential in volts of the test full cells when charging the negative electrode as a function of capacity, which is related to the theoretical capacity of the negative electrode. The two curves depicted show averaged results of several experiments with the test whole cells described above. First, the test full cells were charged with a current of 15 mA until a capacity of 125 mAh (Q.sub.lad) was reached. The test full cells were then discharged at 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Q.sub.ent) was determined.

[0213] The coating layer capacities determined [in % of the theoretical capacity of the negative electrode] are 6.58% for graphite 1 in the test full cell using electrolyte 1 and 8.30% for graphite 1 in the test full cell using the reference electrolyte. The advantage of electrolyte 1 in combination with graphite 1 is shown in a significantly reduced coating layer capacity.

[0214] The discharge capacities were determined in further cycles using the same test full cells. To determine the discharge capacities (see Example 4), the test full cells were charged with a current intensity of 100 mA up to an upper potential of 4.4 volts. The corresponding upper potential was held until the charge current had dropped to 40 mA. The discharge then took place with a current intensity of 100 mA up to a discharge potential of 2.5 volts.

[0215] FIG. 9 shows mean values for the discharge capacities normalized to 100% of the starting capacity of the two test full cells as a function of the number of cycles. These mean values of the discharge capacities are expressed as a percentage of the nominal capacity.

[0216] The test full cells having the different electrolytes show a different behavior of the discharge capacities over the number of cycles. In the test full cells with graphite 1 in electrolyte 1, 98.4% of the discharge capacity is still reached in cycle 280 with an almost horizontal profile. The test full cell with graphite 1 in reference electrolyte still achieved 96.8% with a slightly further downward trend.

Experiment 3: Cover Layer Formation on Graphite 2, Graphite 3 and Graphite 4 in Half-Cells Using Reference Electrolyte

[0217] For preliminary tests to investigate the coating layer capacity, half-cell experiments were performed at room temperature both with negative electrodes which comprised graphite 2 and graphite 3 as active material, and with a negative electrode, which comprised graphite 4 as an active material. The half-cells were filled with a reference electrolyte of the composition LiAlCl.sub.4×1.5 SO.sub.2 and had a lithium electrode as the reference electrode. Such electrochemical half-cell experiments are standard experiments for testing the performance data of electrodes due to their simple structure and the associated low experimental effort.

[0218] The half-cells were charged and discharged a plurality of times with a current intensity of 10 mA (corresponding to 1 C to the practical capacity). The coating layer capacity was calculated from the capacity loss of the first three cycles.

[0219] FIG. 10 shows the coating layer curves and the associated coating layer capacities of the two half-cell experiments. The coating layer capacity in the reference electrolyte is 12.1% for the half-cell having graphite 2, 10.3% for graphite 3 and 15.5% for graphite 4 of the theoretical capacity of the negative electrode. These values are significantly higher than the data determined in Experiment 1 for the same graphites in electrolyte 1.

[0220] Experiment 4: Graphite 1 as the Active Material of the Negative Electrode in Test Full Cells Using Electrolyte 1, Electrolyte 3 and Electrolyte 4

[0221] Various experiments were performed to investigate electrolytes 1, 3 and 4 in combination with graphite 1 as the active material of the negative electrode. On the one hand, the coating layer capacities of electrolytes 3 and 4 were determined and, on the other hand, discharge capacities in all three electrolytes 1, 3 and 4 were determined.

[0222] Two test full cells were filled with electrolytes 3 and 4 described in Example 2 to determine the coating layer capacity. The two test full cells comprised graphite 1 as the active material of the negative electrode. The positive electrodes had lithium nickel manganese cobalt oxide (NMC622) as an active material.

[0223] FIG. 11 shows the potential in volts of the test full cells when charging the negative electrode as a function of capacity, which is related to the theoretical capacity of the negative electrode. The two curves depicted show averaged results of several experiments with the test whole cells described above. First, the test full cells were charged with a current of 15 mA until a capacity of 125 mAh (Q.sub.lad) was reached. The test full cells were then discharged at 15 mA until a potential of 2.5 volts was reached. The discharge capacity (Q.sub.ent) was determined.

[0224] The coating layer capacities determined [in % of the theoretical capacity of the negative electrode] are 17.77% in electrolyte 3 and 20.02% in electrolyte 4. Very good operation of a battery cell having these electrolytes is also possible with the somewhat higher values of the coating layer capacity in electrolytes 3 and 4.

[0225] For the discharge experiments, three test full cells according to Example 3 were filled with electrolytes 1, 3 and 4 described in Example 2. The test full cells had lithium nickel manganese cobalt oxide (NMC) as the active material of the positive electrode and graphite 1 as the active material of the negative electrode. To determine the discharge capacities (see example 4), the test full cells were charged with a current intensity of 15 mA up to a capacity of 125 mAh. The discharge then took place with a current intensity of 15 mA up to a discharge potential of 2.5 volts.

[0226] FIG. 12 shows the potential profile during the discharge over the discharged amount of charge in % [% of the maximum charge (discharge)]. All test full cells show a flat discharge curve, which is necessary for good operation of a battery cell.

Experiment 5: Test Full Cells Having Blends of SiO.sub.x 5.0%/Graphite 3, SiO.sub.x 17.3%/Graphite 3 and SiO.sub.x 24.0%/Graphite 3 as Active Materials of the Negative Electrode

[0227] As can be seen in Table 3b, the term SiO.sub.x 5%/graphite 3 denotes blends of SiO.sub.x (5% by weight) and graphite 3 (95% by weight), wherein SiO.sub.x consists of a blend of the components Si, SiO and SiO.sub.2. The further described SiOx/graphite 3 blends have an SiO content of 17.3% by weight SiO or 24.0% by weight SiO and the corresponding amounts of graphite 3.

[0228] The three different blends were used in three test full cells according to Example 3 as the active material of the negative electrode, and experiments were performed. On the one hand, the coating layer capacities and on the other hand, the discharge capacities were determined. The test full cells were filled with electrolyte 1 described in Example 2. The positive electrodes comprised lithium nickel manganese cobalt oxide as an active material.

[0229] FIG. 13 shows the potential in volts of the three test full cells when charging the negative electrode as a function of capacity, which is related to the theoretical capacity of the negative electrode. The curves depicted show averaged results of several experiments with the test whole cells described above. First, the test full cells were charged with a current of 15 mA until a capacity of 125 mAh (Q.sub.lad) was reached. The test full cells were then discharged at 15 mA until a potential of 2.8 volts was reached. The discharge capacity (Q.sub.ent) was determined.

[0230] The coating layer capacities determined [in % of the theoretical capacity of the negative electrode] are 12.69% for the SiO.sub.x 5.0%/graphite 3 blend, 15.29% for the SiO.sub.x 17.3%/graphite 3 blend and 14.41% for the SiO.sub.x 24.0%/graphite 3 blend.

[0231] The discharge capacity was determined in ten further cycles using the same test full cells. To determine the discharge capacities (see Example 4), the test full cells were charged with a current intensity of 40 mA up to an upper potential of 4.4 volts. The discharge then took place with a current intensity of 40 mA up to a discharge potential of 2.8 volts. FIG. 14 shows mean values for the discharge capacities for the 10 cycles normalized to 100% of the starting capacity of the test full cells as a function of the number of cycles. These mean values of the discharge capacities are expressed as a percentage of the nominal capacity. All three cells show a flat profile of the discharge capacity.

Experiment 6: Test Full Cells Having Nano-Silicon/Graphite as the Active Material of the Negative Electrode

[0232] Experiments in test full cells according to Example 3 were performed using the nano-silicon/graphite blends mentioned in Table 3b as active materials of the negative electrode. On the one hand, the coating layer capacities and on the other hand, the discharge capacities were determined. The test full cells were filled with electrolyte 1 described in Example 2.

[0233] The four test full cells comprised negative electrodes having either a blend of nano-silicon (5% by weight) and graphite 3 (95% by weight) or a blend of nano-silicon (2.5% by weight) and graphite 1 (97.5% by weight) or a blend of nano-silicon (5.0% by weight) and graphite 1 (95.0% by weight) or a blend of nano-silicon (10% by weight) and graphite 1 (90% by weight). The positive electrodes comprised lithium nickel manganese cobalt oxide as an active material.

[0234] FIG. 15 shows the potential in volts of the test full cells when charging the negative electrode as a function of capacity, which is related to the theoretical capacity of the negative electrode. The four curves depicted show averaged results of several experiments with the test whole cells described above. First, the test full cells were charged with a current of 15 mA until a capacity of 125 mAh (Q.sub.lad) was reached. The test full cells were then discharged at 15 mA until a potential of 2.8 volts was reached. The discharge capacity (Q.sub.ent) was determined.

[0235] The coating layer capacities determined [in % of the theoretical capacity of the negative electrode] are 12.47% for the blend of nano-silicon (5% by weight) and graphite 3 (95% by weight), 9.91% for the blend of nano-silicon (2.5% by weight) and graphite 1 (97.5% by weight), 11.63% for the blend of nano-silicon (5.0% by weight) and graphite 1 (95.0% by weight) and 14.77% for the blend of nano-silicon (10% by weight) and graphite 1 (90% by weight).

[0236] The discharge capacities were determined in further ten cycles using the same test full cells. To determine the discharge capacities (see Example 4), the test full cells were charged with a current intensity of 40 mA up to an upper potential of 4.4 volts. The discharge then took place with a current intensity of 40 mA up to a discharge potential of 2.8 volts. FIG. 16 shows mean values for the discharge capacities for the 10 cycles of the three test full cells as a function of the number of cycles. These mean values of the discharge capacities are expressed as a percentage of the nominal capacity. All four cells show a flat profile of the discharge capacity.

Experiment 7: Determination of the Conductivities of Electrolytes 1, 3 and 4

[0237] To determine the conductivity, electrolytes 1, 3 and 4 were prepared using different concentrations of compounds 1, 3 and 4. The conductivities of the electrolytes were determined using a conductive measurement method for each concentration of the various compounds. After temperature control, a two-electrode sensor was held touching in the solution and measured in a measuring range of 0-50 mS/cm. During the measurements, it was noted that the sensor can react with the SO.sub.2-comprising electrolyte solution.

[0238] FIG. 17 shows the conductivity of electrolyte 1 as a function of the concentration of compound 1. A maximum of the conductivity can be seen at a concentration of compound 1 of 0.6 mol/L-0.7 mol/L having a value of approx. 37.9 mS/cm. In comparison, the organic electrolytes known from the prior art, such as LP30 (1 M LiPF.sub.6/EC-DMC (1:1 weight)) have a conductivity of only approx. 10 mS/cm.

[0239] FIGS. 18 (electrolyte 3) and 19 (electrolyte 4) show the conductivity values for electrolytes 3 and 4 determined for the different concentrations.

[0240] With electrolyte 4, a maximum of 18 mS/cm is achieved at a conducting salt concentration of 1 mol/L. Electrolyte 3 shows its highest conductivity of 0.5 mS/cm at a conducting salt concentration of 0.6 mol/L. Although electrolyte 3 shows a lower conductivity, as in experiment 4, charging or discharging of a test full cell is quite possible.

Experiment 8: Low Temperature Behavior

[0241] Two test full cells according to example 3 were produced in order to determine the low-temperature behavior of electrolyte 1 in comparison to the reference electrolyte. One test full cell was filled with reference electrolyte of the composition LiAlCl.sub.4*6SO.sub.2 and the other test full cell with electrolyte 1. The test full cell having the reference electrolyte comprised lithium iron phosphate (LEP) as the active material, the test cell having electrolyte 1 comprised lithium nickel manganese cobalt oxide (NMC) as the active material of the positive electrode. Both test full cells comprised graphite 1 as the active material of the negative electrode. The test full cells were charged to 3.6 volts (LEP) or 4.4 volts (NMC) at 20° C. and discharged again to 2.5 volts at the respective temperature to be investigated. The discharge capacity reached at 20° C. was rated as 100%. The temperature for the discharge was lowered in temperature steps of 10° K. The discharge capacity obtained was described in % of the discharge capacity at 20° C. Since the low-temperature discharges are almost independent of the active materials used for the positive and negative electrodes, the results can be transferred to all combinations of active materials. Table 4 shows the results.

TABLE-US-00005 TABLE 4 Discharge Capacities as a Function of the Temperature Discharge Capacity Discharge Capacity of Temperature of Electrolyte 1 the Reference Electrolyte 20° C. 100%  100%  10° C. 99% 99% 0° C. 95% 46% −10° C. 89% 21% −20° C. 82% n/a −30° C. 73% n/a −35° C. 68% n/a −40° C. 61% n/a

[0242] The test full cell having electrolyte 1 shows very good low-temperature behavior. At −20° C., 82% of the capacity is reached, at −30° C., 73%. Even at a temperature of −40° C., 61% of the capacity can still be discharged. In contrast, the test full cell having the reference electrolyte only shows a discharge capacity down to −10° C. A capacity of 21% is achieved here. The cell having the reference electrolyte can no longer be discharged at lower temperatures.

[0243] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.