WO2008110558A1

WO2008110558A1 - Electrolytes for electrochemical components

Info

Publication number: WO2008110558A1
Application number: PCT/EP2008/052884
Authority: WO
Inventors: Andreas Wuersig; Peter Gulde; Gerold Neumann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2007-03-12
Filing date: 2008-03-11
Publication date: 2008-09-18
Also published as: DE102007031477A1

Abstract

The invention relates to an electrolyte mixture for use in electrochemical components, the anode of which contains a lithium- and/or titanium-containing material or another anode material with a lithium incorporation potential between 1.0 and 2.0 Volt vs. Li/Li+ and in particular lithium titanate, titanium oxide (anatas), lithium titanate sulfide (LiTiS2), lithium molybdenate sulfide (LiMoS2) or doped derivatives thereof, characterized in that the electrolyte mixture contains a conductor salt dissolved in a mixture of at least one solvent and at least one solvent additive, wherein one or more solvents are used which do not comprise ethylene carbonate, wherein each of said solvents is present at a level of at least 10 percent by volume relative to the total volume of the electrolyte produced, a conductor salt is used that is suitable for use in electrochemical components with lithium ion-conduction, and in that each solvent additive is present in a concentration of up to 10 percent by volume. This electrolyte mixture is particularly suitable for use in an electrochemical component, the negative electrode of which contains lithium titanate, titanium oxide (anatas), lithium titanate sulfide (LiTiS2), lithium molybdenate sulfide (LiMoS2) or doped derivatives thereof, and an electron conducting material, e.g., soot. Accordingly, the invention further relates to a coating compound, for example, in a lithium accumulator, with an anode containing a lithium- and/or titanium-containing material or another anode material with a lithium incorporation potential between 1.0 and 2.0 Volt vs. Li/Li+ and in particular lithium titanate, titanium oxide (anatas), lithium titanate sulfide (LiTiS2), lithium molybdenate sulfide (LiMoS2) or doped derivatives thereof, a positive electrode suitable for use in lithium-ion accumulators, and a separator- or solid electrolyte coating which is saturated with the claimed electrolyte mixture.

Description

Electrolytes for electrochemical devices

The present invention relates to the use of solvents mixed with various additives in lithium-ion transport electrochemical devices, in particular in lithium-titanium-oxide spinel lithium batteries in the negative electrode. Lithium batteries are understood here to mean that the battery body consists of a sequence of individual films, each having the necessary for use in a battery or in an accumulator electrochemical properties (electron-conducting and / or ion-conducting) and in which the charge transport within the cell drains via lithium ions. The ionic conductivity is preferably at least partially produced by impregnation of the films with a conductive salt dissolved in the solvent. In particular, the choice of the solvent is the subject of the present invention.

Producing electrochemical components based on film technology has been practiced since the early seventies. The advantages of producing film technology are obvious: film technology is a very economical production process that offers a high degree of freedom of forming. In addition to the possibility of reeling can be realized without much effort changing other geometries. In addition, this technology ensures a very large contact surface between the layers of different functionality such. B. between electrodes and electrolyte in accumulators with respect to the volume of electrochemically active material used. This results in this application particularly favorable loading and unloading.

The patent literature has described a number of methods for producing such films. US 5,219,680, for example, describes the composition of a carbon / polymer electrode consisting of carbon particles bound in a polymer matrix. In order to produce the ionic conductivity in the anode foil between the carbon particles, this anode with a

Liquid electrolyte filled. This is absorbed in pores or in the polymer. The use of carbon or graphite in the negative electrode of lithium-ion or lithium-polymer accumulators is state of the art today. As a rule, compounds such as LiCoO ₂ or LiMn ₂ O ₄ are used in the positive electrode. These materials are converted into films in a production-like manner as described in US Pat. No. 5,219,680 for the negative electrode. For the electrolyte, various ways of producing have been described. So there is the possibility to gelify liquid electrolytes and to make them so in films. Such a way is z. As described in US 5,009,970. Another Approach is to produce a film with fine-pored sponge structure and to make them ionically conductive after completion of the film composite by impregnation in a liquid electrolyte. This method has been disclosed in US 5,464,000. In addition, DE 198 39 217.6 describes the possibility of incorporating solid-state ion conductors into a polymer matrix and thus producing an electrolyte film.

In the combination of the above-mentioned electrode materials, accumulators are obtained which, according to their position in the electrochemical series, provide quiescent voltages of approximately 4 V and, under load, an average voltage of approximately 3.65 V. They have a high energy density compared to lead, nickel cadmium or Nickelmetallhydridakkumulatoren and are therefore used in many applications, especially in portable electronic systems. The voltage provided also fits quite well with the operating voltage requirements of modern microelectronic circuits, as e.g. Mobile phones are installed.

However, the use of carbon or graphite in the negative electrode of lithium-ion / lithium-polymer batteries entails three material-related disadvantages.

(1) Carbons / graphites undergo a significant volume change during the intercalation and deintercalation of lithium ions, which is on the order of several percent. This permanent expansion and contraction in the operation of the accumulator leads to the loss of contacts between the carbon particles within the anode so that an increasing number of carbon particles can no longer contribute to the storage of lithium ions as they lose contact with the matrix. In addition, the contact with the Ableitgitter deteriorated. These effects affect the outside in the form of a decreasing capacity and in an increase of the internal resistance.

(2) In particular, in the initial charging of a lithium battery with carbon-based anode and including a liquid electrolyte, which is also referred to as formation, builds on the surface of the carbon particles from a cover layer, which in the literature with the name Solid Electrolyte Interface (SEI) occupied is. This forms from a chemical decomposition of the solvents involving lithium ions. In the case of an unfavorable choice of solvents, this covering layer continues to grow with each charge / discharge cycle and impedes the migration of the lithium ions during the deposition and removal from the carbon particles. In addition, the Volume change in the carbon during the installation and removal of lithium ions lead to a rupture of the cover layer, with the result that the cover layer continues to grow continuously. In addition to the unavoidable loss of lithium at least during the formation of an increase in the internal resistance (penetration resistance in the outer layers) and in further growth of the

Overlay layers continuously loss of capacity occur. All the effects that lead to capacity losses in the battery are summarized under the generic term "fading." Today, in good commercially available lithium-ion or lithium polymer accumulators, after 500 charge / discharge cycles, 80% of the capacity is still present after the forming step ,

When forming, capacity losses between 5% and 10% of the theoretically expected capacity are common. For this purpose, according to current knowledge, primarily the carbon in the anode is responsible. (3) Carbon-based electrodes pose a safety risk, since due to the potential ratios to metallic lithium very quickly to

Deposition of finely divided, metallic lithium can come, z. B. overload.

Also, the standard used in lithium-ion batteries electrolytes based on ethylene carbonate (EC) are associated with some disadvantages. Since this organic solvent already passes into a solid state of matter just above room temperature and also has a high viscosity and thus low ionic conductivity even at temperatures below that, it must be mixed with a viscosity reducer. For this purpose, dimethyl carbonate (DMC) is often used. But this combination is only limited

Temperature range (about -10 ° to about +60 ⁰ C) used. Table 1 represents the Schmelzbzw. Compared with boiling temperatures of various solvents. Particularly noteworthy is the significantly extended temperature range of gamma-butyrolactone (GBL) or propylene carbonate (PC) compared to the solvents that are currently used as standard in lithium accumulators.

Table 1 The combination of carbons as active negative electrode material with standard electrolytes, however, does not guarantee the robust SEI with pure GBL or PC, which is necessary for permanent cycle stability under standard operating conditions.

In applications with special requirements, in particular with regard to high and low temperature resistance, it is therefore preferable to use an alternative material for the combination of carbon / graphite with EC-based electrolytes.

US Pat. No. 6,929,885 B2 reports the problems of various solvent compositions in lithium secondary batteries with carbon as a negative electrode and a lithium oxide or mixed oxide as a positive electrode. Although γ-butyrolactone (GBL) as a solvent leads to good charge-discharge characteristics; However, the Zykeleigenschaften are not satisfactory. In addition, when ethylene carbonate (EC) and vinylene carbonate (VC) are added, the cycling properties are good; however, gas formation is observed at higher temperatures. Improved properties are obtained, however, when a mixture of EC and GBL is used as the main component with VC and vinyl ethylene carbonate.

Probably due to a relatively strong and sustained reductive degradation of GBL at potentials typically achieved in graphite-based lithium batteries, therefore, stable cycling in such batteries using GBL as the major component is not possible. In general, a strong fading of the discharge capacity can be observed.

It is an object of the present invention to provide a battery or accumulator system whose electrode and electrolyte materials are adjusted to one another in such a way that the aforementioned disadvantages are avoided.

This object is achieved by the choice of specifically matched materials for the negative electrode and the electrolyte solvent. In particular, the object is achieved by providing an anode comprising a lithium- and / or titanium-containing material such as lithium titanate, titanium oxide (anatase), lithium titanium sulfide (LiTiS2), lithium molybdenum sulfide (UM0S2) or doped derivatives thereof or any other anode material having a lithium insertion potential between 1 , 0 and 2.0 volts vs. Li / Li ⁺ contains, as well as an especially suitable for this electrolyte mixture. According to the invention, it has been found that it is favorable, as an anode material, a lithium- and / or titanium-containing material such as lithium titanate, titanium oxide (anatase), lithium titanium sulfide (LiTiS 2), lithium molybdenum sulfide (UMOS 2) or doped derivatives thereof, provided that suitable solvents are chosen or any other anode material having a lithium storage potential between 1, 0, and 2.0 volts. Li / Li ⁺ lithium titanate (Li ₄ Ti ₅ Oi ₂ ) to use. By doping is meant the targeted displacement of the materials with foreign atoms (foreign ions). These are usually added in only minimal proportions of molar amounts (eg in the ppm range), but in special cases may be up to about 1 mol% or more, based on the other cations or anions of the Materials, be present.

To increase the electronic conductivity of the said anode material is usually added an electron conductor, such as a (conductivity) soot. In particular, lithium titanate (Li ₄ Ti ₅ Oi ₂ ), but also the other aforementioned substances offer as negative electrode material compared to graphite some decisive advantages. For example, lithium titanate has a voltage of 2.3 V versus positive electrodes with LiCoO ₂ or LiMn ₂ O ₄ , but at about 160 Ah / kg has a lower energy density than carbon-based negative electrodes. However, it largely avoids the above-mentioned disadvantages. The volume expansion or contraction during loading and unloading is less than 1% and is thus negligible. A brief summary of the properties of lithium titanates can be found in JO Besenhard (Ed.), Handbook of Battery Materials, Wiley-VCH, 1999, pp. 316-317.

The tendency for the formation of cover layers and the risk of metallic lithium deposition is significantly lower, because the Lithiumeinlagerungspotential of the lithium titanate as well as the other materials mentioned in the invention is significantly more positive compared to graphite / carbon-based anode materials. The reduced rest voltage in cells with lithium titanate in the negative electrode also advantageously takes into account the requirements of many electronic systems that are either now or will operate at lower voltages and in which at high operating voltages, the voltage would have to be transformed down under power loss.

Lithium titanate is proposed in US Pat. No. 5,766,796 as a material for an allegedly cover-free anode. This anode is made of electroactive lithium titanate formed in situ from TiO ₂ and Li ₂ CO ₃ , a high surface area carbon material such as acetylene black, as an electron-conducting additive, and a polymer electrolyte. The polymer electrolyte It consists of polyacrylonitrile, ethylene carbonate (EC), propylene carbonate (PC) and LiPF ₆ . It is combined with LiMn ₂ O ₄ or the like as a cathode and an electrolyte layer made of polyacrylonitrile, which in turn is filled with EC and PC in which a lithium salt such as LiPF _{6 is} dissolved.

Whether an accumulator of the aforementioned materials is actually topcoat-free, may be doubted. The increase in resistance from 3 Ω to 3.2 Ω after 150 cycles is certainly no proof of this. Because there are quite good ion-conductive cover layers; it is extremely difficult to track down or even analyze. Regardless, however, the use of EC, at least in larger proportions, as a solvent for the electrolyte for the above reasons unsuitable.

According to the invention - and completely surprisingly - it has been found that other solvents previously used in combination with other anode materials then lead to excellent cycle behavior of electrochemical components such as lithium batteries - and in particular of such electrochemical components with lithium titanate as part of the anode - with very good temperature stability when a solvent mixture is used, in which at least one solvent component in a proportion of at most 10 vol .-%, based on the volume of the finished electrolyte, is present. This solvent will be referred to hereinafter as an additive or solvent additive. Preferably, one or more such additives are present in amounts of no more than 5% each by volume, even more preferably at most 2% by volume, and most preferably at most 1% by volume, each based on the volume of the final electrolyte , The total amount of the additives should not exceed 15% by volume, preferably 10% by volume, more preferably 5% by volume and most preferably 2% by volume. In general, an additive is sufficient; if appropriate, however, it is also possible to add two or even more additives. The major component (s) of the solvent is / are not critical or limited except for the fact that ethylene carbonate should not be used. All other carbonates and especially cyclic carbonates such as PC or symmetrical or asymmetric, optionally disubstituted carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) or ethyl methyl carbonate (EMC) may be used, as well as other solvents such as lactones, ie cyclic esters, including in particular γ-butyrolactone, and so-called ionic liquids, ie salts which are liquid at room temperature. The major component may be only a solvent, for example (and preferably) GBL. But it can also be 2 or even 3 or more solvents mixed together, z. GBL and PC or GBL and DMC and DEC, or PC and EMC. In these mixtures, the components are contained in equal (weight) proportions or in any proportion, with the proviso that the proportion of none of the solvents meets the criteria for the additive.

When gamma-butyrolactone is used as the solvent, the significantly higher lithium incorporation voltage compared to graphite is of decisive advantage with lithium titanate. This prevents from the outset a pronounced electrolyte decomposition. By adding at least one additive to the GBL, however, a further improvement in the Zykelverhaltens could surprisingly be achieved, although initially no top layer formation on the surface of the negative electrode material was expected. The same applies when using solvents other than GBL. This ensures a highly stable charge / discharge behavior even at high cycle numbers.

Particularly suitable additives are the following compounds: vinylene carbonate, ethylene sulfite, acrylonitrile, vinyl ethylene carbonate. However, other common solvents could be used, including EC, which is not considered according to the invention as the main solvent component (when EC is used in small amounts, its negative properties are more than compensated by corresponding positive properties of the solvent used). Special advantages are the uncomplicated admixture of flame retardant solvents or

Additives such as fluorinated organic carbonates. Furthermore, there is the possibility of admixing additives to prevent overcharging, which operate according to a so-called "shuttle" mechanism, which are compounds that are able to transport electrons between the anode and the cathode by means of redox reactions : 2,4-difluoroanisole, biphenyl, 3-chlorothiophene or furan.

A further improvement in cycle stability could be achieved by replacing the LiPF ₆ LiBF ₄ used by default in lithium-ion batteries as conductive salt. Further useful conductive salts are LiCIO ₄ , lithium [bis (oxalato) borate] ("LiBOB") or lithium trifluoromethanesulfonate A particular advantage of using a combination of GBL with LiBF ₄ is the economics of these electrolytes GBL is easy to synthesize and is used in the Chemicals have long been used as solvents, and conductive salts are also much cheaper than the most widely used LiPF ₆ .

A particular challenge is the processing of lithium titanate in foil batteries. Lithium titanate is both an electronic insulator and a poor ion conductor. The embedding in the polymer matrix must therefore over the Matrix to ensure the required conductivities. The electronic conductivity can be achieved by the addition of conductive carbon blacks. The ionic conductivity of the matrix can be produced in two ways: (1) The film is produced, for example, from a pasty mass with the setting of a high degree of micropores, which are then - after solidification of the mass - impregnated with a solution dissolved in a solvent Soak up lithium salt to produce ionic conductivity. (2) A suitable binder such as polyvinylidene fluoride (PVDF) develops sufficient ionic conductivity after being impregnated with a suitable solution of a lithium salt. A combination of options (1) and (2) can also be effective.

The individual battery or accumulator layers or foils are often made from pastes. The composition of a paste as starting material for the production of films for the negative electrode in lithium batteries with an inventively proposed anode material as Interkalationsmatehal is therefore to be chosen as follows due to the above considerations: the said anode material, an electron-conducting material such as conductivity soot, if necessary, a ( preferably non-conductive ionic) polymer binder. These materials are blended with a suitable solvent (often chosen from solvents without plasticizing properties, e.g., acetone). This produces a paste that must be stirred very carefully to achieve a highly uniform distribution of the components without sedimentation or streaking occurring. After stirring and spreading the pastes on a substrate or carrier fabric and allowing the solvent to dry off / evaporate (actively or passively), a supported or preferably self-supporting film is obtained which, with the counter electrode and separator / electrolyte films, becomes a film accumulator can be further processed. As an alternative to a non-conductive polymer binder, it is of course possible to use an ion-conducting polymer binder or a non-ion-conducting polymer binder in combination with electrolyte liquid for the preparation of the paste.

Materials for the positive electrode are known to the person skilled in the art, examples being:

LiF, Li _x NiVO ₄ , Li _x Mn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiNio, ₅ Co ₀ , 5O ₂ , LiNio, ₈ Co ₀ , ₂ O ₂ , V ₂ O ₅ , Li _x V ₆ Oi ₃ , LiFePO ₄ .

Suitable materials for the discharge electrodes are for the positive electrode: Al, Cu, Pt, Au, C. For the negative electrode z. B. Al, Cu, Mo, W, Ti, V, Cr, Ni. In general, lithium polymer accumulators are, if they were prepared using an ionically non-conductive polymer matrix, which forms a separator between the electrodes, but possibly also in the electrode films, by impregnation in a liquid electrolyte mixture consisting of a or more solvents and a lithium salt, activated to ensure the required ion transport between the electrodes. This liquid decisively determines the structure of the cover layers on the anode material. Graphite has a lithium activity close to 1 at a voltage around 0 V against lithium, while lithium titanate at a voltage of about 1, 5 V against lithium only a small

Has lithium activity. As already described, this has the consequence that the construction of cover layers, which must behave like a solid electrolyte, will be different. Thus, the starting point for the choice of electrolyte mixtures for titanium cells and the like. A completely different than that for the choice in graphite / carbon-based systems. In graphite-based systems, despite its disadvantages in terms of useful temperature range, ethylene carbonate is an indispensable component of the activating solution because it is required for the stabilization of the SEI on the graphite. LiBF ₄ dissolved in GBL is an example of a much simpler mixture for use in lithium titanate based accumulators. Another significant advantage that results is the resulting good low temperature and high temperature performance.

The low sensitivity of lithium titanate-based cells to light overcharge allows a much simpler series connection of several cells to achieve elevated voltages than 2.3 V. Production-related fluctuations in capacity in the production of single cells require in graphite-based cells for safety reasons when loading a single cell monitoring. This sensitivity is not present in lithium titanate-based cells, so that a complex single-cell monitoring can be omitted, it is sufficient if necessary, a simple Zener diode.

Examples

Cells were prepared with lithium titanate in the negative electrode as well as with gamma-butyrolactone-based electrolyte and tested for cycle behavior, charge factor, capacity loss on formation. 1 . Positive electrode

For preparation PVDF were dissolved as a binder (Kynar LBG 2) in acetone. Lithium cobalt oxide powder, graphite and acetylene black 5 were then added to this solution, and the mixture was intimately mixed with a stirrer and made into a viscous, uniform paste. This paste was then drawn with a squeegee on a glass plate and the solvent evaporated. The film thus produced had a thickness of about 0.1 mm.

lo 2. Negative electrode

The same binder PVDF (Kynar LBG 2) was dissolved in acetone. Thereafter, Li ₄ Ti ₅ O ₃ , graphite and acetylene black were added and then intimately mixed. This paste was then drawn with a squeegee on a glass plate and the solvent evaporated. The film produced in this way had a thickness i5 of approx. 0.1 mm.

3. Separator (solid-state ion conductor)

For the Separatorlage 75 wt.% Lii _{, 3} Alo _{, 3} Tii _{, 7} (PO ₄ ) ₃ powder were intimately mixed with dissolved in acetone PVDF (25 wt.%) And pulled to a film, with a thickness of 20 50 μm.

4. Electrolyte (comparative example)

As a reference, a standard electrolyte mixture LP30 (1 M LiPF ₆ in EC / DMC) was used in test cells.

25

5. electrolyte

A 1 M solution of the conductive salt LiPF ₆ in gamma-butyrolactone was prepared.

so 6. electrolyte

In another variant, the LiPF _{6 was} replaced by LiBF ₄ , which was also prepared as a 1 M solution in GBL.

7. Electrolyte with additive

35 To the electrolyte mixture mentioned in Example 6, an additive was added, here 1 volume percent vinylene carbonate (VC). 8. Activation

The positive electrode, separator / solid electrolyte and negative electrode were respectively laminated to film bodies, which were impregnated with electrolytes according to Examples 5 4 to 7. Subsequently, the cells were sealed in a plastic-coated aluminum foil and annealed at temperatures of 60 ⁰ C for several hours.

Cells were built in these technology variants with identical electrodes or lo separator according to Examples 1 to 3. These were then with

Electrolyte mixtures according to Examples 4 to 7 soaked and compared in terms of their electrical properties out. First, a test cell with the electrolyte according to Example 4 was realized. In this case, a very good Zykestestigkeit showed, however, a limited temperature range of use of the cells. Below i5 -10 ⁰ C, the removable capacity drops markedly, while at temperatures above 70 ° C increased gas formation is observed in the cell. Next, a test cell was prepared with the electrolyte mixture according to Example 5. Figure 2 shows that this cell has unsatisfactory Zykelverhalten. After replacing the electrolyte salt according to Example 6, there was already a significant improvement, which also

20 is shown in Figure 2. The addition of 1% by volume of VC according to Example 7 to the electrolyte mixture gave a very good cycle behavior at room temperature, which corresponds to that with the use of LP30. However, the use of GBL as the major solvent greatly extends the temperature range of use of the cells. In Figure 3 and Figure 4 are Zykelresultate at -30 ⁰ C or at

25 temperatures between + 60 ° C and 85 ° C shown. Both at low temperatures and at high temperatures, a stable cycle with acceptable or very good discharge capacities is possible. In addition, a surprisingly close to 1 lying charge factor is found, indicating that the electronic leakage currents or irreversible lithium losses in these cells are negligible. Also at

Of more aggressive cycles with one charge / discharge per hour (1 C), the decrease relative to the theoretical capacity is relatively small, reaching 84% and more of the theoretical capacity. Results of individual cells are shown in Table 2. The loading / unloading with C / 10 means that this process is carried out for every 10 hours.

Table 2

Figure 1 shows the charge and discharge curve at 1C of a cell with lithium titanate in the negative electrode and a mixture of GBL with 1 M LiBF ₄ and 1 vol .-% VC as the electrolyte. The charge / discharge curve is highly symmetrical in terms of charge / discharge capacity, with very little irreversible loss (0.08%).

Figure 2 shows the Zykelverhalten of cells that have undergone 300 charge / discharge cycles. The residual capacity is still 87% of the initial capacity at 1 C after using an electrolyte of GBL with 1 M LiBF ₄ and 1% by volume VC after 300 cycles. The reference cell with standard electrolyte LP30 is almost identical to its cycle curve.

Figure 3 shows a Zykelexperiment at a temperature of -30 ⁰ C with an electrolyte mixture according to Example 5. At the level of about 11% of the capacity at room temperature, a stable Zyklen with C / 2 is observed.

Figure 4 shows Zykelergebnisse at gradually elevated temperatures between +60 ⁰ C and + 80 ° C with an electrolyte mixture according to Example 5. There are only small capacity losses can be seen and the cells show no gas formation even at 80 ⁰ C.

Figure 5 cells with an electrolyte mixture according to Example 5 were temporarily (between 1 and 5 hours) heated to a temperature of 100 ° C and then weitergezykelt at room temperature. The temperature treatment results in only small capacity losses.

The electrolyte mixture described above is independent of whether it is present as such or in conjunction with an electrode, in particular an electrode of the type proposed according to the invention, a composite layer, which has the properties of an electrochemical device, or a electrochemical device as such, for example a lithium battery, is used, in all cases preferably characterized as follows:

Electrolyte mixture, characterized in that a conductive salt is dissolved in a mixture of at least one solvent and at least one additive, wherein

(a) one or more solvents are used which do not comprise ethylene carbonate,

(b) employing a conducting salt suitable for use in lithium ion-conducting electrochemical devices, and (c) each additive in a concentration of at most 10

Volume percent is present.

In this electrolyte composition, the solvent or the solvent mixture preferably has a melting point of below 25 ° C, more preferably below 0 ⁰ C, and even more preferably less than -15 ° C and / or has a boiling point preferably above 100 ⁰ C, more preferably above 150 ⁰ C and most preferably from about 200 ° C or above. In this electrolyte mixture, the conductive salt may be a lithium salt whose anion is the anion of an acid, eg LiPF ₆ , this anion being selected in particular from lithium tetrafluoroborate, lithium perchlorate, lithium [bis (oxalato) borate] ("LiBOB") or lithium trifluoromethanesulfonate or mixtures of at least two of these salts.

In this electrolyte mixture, the one or more solvents may be selected from organic carbonates and lactones. Preferably, one of the solvents is γ-butyrolactone.

In this electrolyte mixture, at least one additive may be selected from vinylene carbonate, ethylene sulfite, acrylonitrile and vinyl ethylene carbonate. Vinylene carbonate is particularly preferred.

The abovementioned electrolyte mixture as such or in its optional, highlighted or preferred embodiments can be used in an electrochemical component which preferably has a lithium titanium-containing negative electrode, which in particular also contains an electron-conducting material. This material may be a conductive carbon material, such as carbon black.

Claims

Claims:

1 . Layer composite intended for electrochemical components, comprising:

(a) a positive electrode with a material suitable for use in the positive electrode of lithium batteries,

(b) a negative electrode comprising a lithium and / or titanium containing material or other anode material having a lithium storage potential between 1, 0 and 2.0 volts. Contains Li / Li ⁺ ,

(c) a separating layer between positive and negative electrodes as a separator layer or solid electrolyte layer

(d) an electrolyte mixture comprising a conductive salt dissolved in a mixture of at least one solvent and at least one solvent additive, wherein

(i) this electrolyte mixture contains one or more solvents which do not comprise ethylene carbonate, each of these solvents being in an amount of at least 10% by volume, based on the

Total volume of the finished electrolyte, is present (ii) a conductive salt is suitable, which is suitable for use in electrochemical devices with lithium ion conduction 20, and

(iii) any solvent additive in a concentration of at most

10 volume percent, based on the total volume of the finished electrolyte, is present.

2. A composite film according to claim 1, wherein the negative electrode contains lithium titanate, titanium oxide, especially in the crystal structure of the anatase, lithium titanium sulfide (LiTiS2), lithium molybdenum sulfide (UMOS2) or doped derivatives thereof.

The layered composite according to claim 1 or 2, wherein either the positive electrode and / or the release layer and / or the negative electrode is a self-supporting or non-self-supporting foil.

4. Laminate according to one of the preceding claims, wherein the solvent 35 or the mixture of the plurality of solvents of the electrolyte mixture a

Melting point of below 25 ° C, preferably below 0 ⁰ C and more preferably below -15 ° C and / or has a boiling point of about 100 ⁰ C, preferably of about 150 ⁰ C and most preferably of about 200 ° C. or above.

5. Laminate according to one of the preceding claims, characterized in that the conductive salt of the electrolyte mixture is a lithium salt whose anion is the anion of an acid, in particular selected from

5 Lithium tetrafluoroborate, lithium perchlorate, lithium [bis (oxalato) borate] ("LIBOB") or lithium trifluoromethanesulfonate or mixtures of at least two of these salts.

6. A laminate according to any one of the preceding claims, wherein the one or more of the plurality of solvents of the electrolyte mixture is / are selected from organic carbonates and lactones, and in particular γ-butyrolactone.

7. Laminate according to one of the preceding claims, wherein the at least one solvent additive of the electrolyte mixture is selected from i5 vinylene carbonate, ethylene sulfite, acrylonitrile and vinyl ethylene carbonate and in particular vinylene carbonate.

8. Use of a layer composite according to one of the preceding claims in a lithium accumulator, which is preferably connected to lead-off electrodes,

20 wherein the laminate is sealed in a housing, from the

Sticking tongues out.

9. A method for producing a composite layer according to any one of claims 1 to 7, comprising the steps

25 - Providing a negative electrode containing a lithium and / or titanium containing

Material or other anode material with a lithium storage potential between 1, 0 and 2.0 volts. Li / Li ⁺ contains, providing a separator layer or solid electrolyte layer, providing a positive electrode,

30 - laminating said two electrodes and the separator layer or

Solid electrolyte layer such that the last one lies between the two electrode layers, forming a laminate, impregnating the laminate with an electrolyte mixture as defined in any one of claims 1 and 4 to 7.

35

10. Negative electrode for use in a composite layer as defined in any one of claims 1 to 7 or in a lithium secondary battery as defined in claim 8 or in a method as defined in claim 9, wherein the negative electrode consists of the following components:

5 (a) a lithium- and / or titanium-containing material or another

Anode material with a lithium storage potential between 1, 0 and 2.0 volts. Li / Li ⁺ lithium titanate,

(b) an electron-conducting additive

(c) an ionically non-conductive polymer binder.

10

1 1. Negative electrode according to claim 10, characterized in that the lithium and / or titanium-containing material or other anode material with a lithium storage potential between 1, 0 and 2.0 volts. Li / Li ^{+ is} selected from lithium titanate, titanium oxide, in particular the crystal structure of anatase, lithium lithium titanulphide (LiTiS ₂ ), lithium molybdenum sulphide (UMOS ₂ ) or doped

Descendants of it.

12. Use of an electrolyte mixture comprising a conductive salt which is dissolved in a mixture of at least one solvent and at least one solvent

20 additive is dissolved, wherein

(i) the electrolyte mixture contains one or more solvents that are not

Ethylene carbonate, each of these solvents being present in an amount of at least 10% by volume, based on the total volume of the finished electrolyte, of (ii) an electrolyte salt suitable for use in electrochemical

Lithium ion conductive devices, and (iii) any solvent additive in a concentration of at most

10% by volume, based on the total volume of the finished electrolyte, is present,

30 in an electrochemical device having a negative electrode comprising a lithium and / or titanium containing material or other anode material having a lithium insertion potential between 1, 0 and 2.0 volts. Li / Li ⁺ contains.

13. Use according to claim 12, wherein the lithium- and / or titanium-containing material 35 or the other anode material with a lithium storage potential between 1, 0 and 2.0 volts. Li / Li ^{+ is} selected from lithium titanate, titanium oxide, especially in the crystal structure of anatase, lithium titanium sulfide (LiTiS 2), lithium molybdenum sulfide (UMOS 2) or doped derivatives thereof.

14. Use according to claim 12 or 13, wherein the solvent or the mixture of the plurality of solvents has a melting point of below 25 ° C, preferably below 0 ⁰ C and more preferably below -15 ° C and / or a

5 boiling point of about 100 ⁰ C, preferably of about 150 ⁰ C and most preferably of about 200 ° C or above.

15. Use according to one of claims 12 to 14, characterized in that the conductive salt is a lithium salt whose anion is the anion of an acid, lo is in particular selected from lithium tetrafluoroborate, lithium perchlorate,

Lithium [bis (oxalato) borate] ("LiBOB") or Lithiumtrifluormethansulfonat or mixtures of at least two of these salts.

Use according to any one of claims 12 to 15, wherein the one or more solvents are selected from organic carbonates and

Lactones are and in particular γ-butyrolactone.

17. Use according to any one of claims 12 to 16, wherein the at least one solvent additive is selected from vinylene carbonate, ethylene sulfite, acrylonitrile

20 and vinyl ethylene carbonate and especially vinylene carbonate.