DE102004057365B4 - Process for producing a cell composite, cell composite, method for producing a lithium polymer battery and lithium polymer battery - Google Patents

Abstract

Process for the preparation of a cell assembly for a lithium polymer batch with the steps:
Preparing a mixture for an anode and a mixture for a cathode,
Extruding the mixture for the anode and the mixture for the cathode to an anode mass and a cathode mass, wherein at least one of the anode mass and the cathode mass is extruded to supply a mixture of cyclohexanone and methyl ethyl ketone (CM) having a volume ratio of 1: 1 becomes,
parallel laminating the anode mass and the cathode mass to a respective arrester to an anode and a cathode,
Removing the mixture (CM) from the anode and / or the cathode,
Assembly of the anode and the cathode with a separator arranged therebetween.

Description

The This invention relates to a cell composite, a lithium polymer battery with the cell composite and process for their preparation.

Lithium polymer batteries consist of anode, cathode and a polymer electrolyte as a separator. Anode, cathode and separator are merged to form a composite, in which the separator serves as an intermediate layer for anode / cathode. Of the obtained composite is then processed into multiple layers. After this Einhausen and Poland has a lithium-polymer battery.

Details of the preparation and the system are known and can be found in the "Handbook of Battery Materials", eds. JO Besenhard, Verlag VCH, Weinheim, 1899. Special production methods, such as the so-called Bellcore method, are described in "Lithium Ion Batteries ", ed. M. Wakihara and O. Yamamoto, Verlag VCH, Weinheim 1998 p. 235 and 10.9 described. Furthermore, in the "Handbook of Batteries" III Ed., D. Linden, Th. B. Reddy, Mc Graw-Rill 2001, in chapter 35.1-35.9 Li-Ion Batteries are described and in chapter 1.1 - the definition of cell and battery:
In this 3 ^rd edition, the term "cell" will be used when describing the cell component of the term "cell" or "cell" battery and its chemistry. The term "battery" is often used to describe performance characteristics, etc. of the product of the individual cells or a single-cell battery (see Section 3.2.13). "

to Production of lithium polymer batteries are so far different Method used. In a coating process, that for the cathode or anode material required polymer binder solved (eg 5-10% Fluoroelastomer homo- or copolymers in N-methyl-pyrrolidone (NMP)) and the thereby resulting polymer solution with the cathode or anode specific additives such as lithium intercalatable Metal oxides or lithium intercalatable carbons (carbon black, graphite o. a.) is added and dispersed. Then this dispersion is with the film coating technology on current collectors (foils, tapes, nets o. ä.) applied.

A Variant of the coating methods described above is aqueous Polymer dispersions instead of the polymer solutions with organic solvents to use.

The so-called "Bellcore method" is another Variant of the coating methods described. In this procedure is an ingredient in the anode or cathode compound (eg dibutyl phthalate, DBP) incorporated prior to the assembly of anode / cathode / separator in the Bellcore process (see above) removed is sufficient to ensure adequate porosity, d. H. a sufficient receptivity for the conducting salt (Electrolyte), create and migration paths for the anions and cations to have during the loading and unloading process.

The by, these processes contained coatings are after the Drying to prismatic cells or wound cells processed (wound), wherein as a separator, a so-called separator z. From Celgard o. a. with porous Structures is used. The system thus produced is enclosed and before closing with conductive salt solution filled.

Another method is the extrusion of separator (polymer gel electrolyte) and an electrode ( US 4818643 A . EP 0 145 498 B1 or the extrusion of anode, separator and cathode in parallel-connected extruders and subsequent combining of the three components ( DE 100 20 031 A1 ).

DE 100 20 031 A1 discloses an extruder process in which electrolyte and the respective electrode mass are extruded together (electrolyte = aprotic solvent + conductive salt).

The The object of the present invention is an improved lithium polymer cell or an improved cell composite, an improved lithium-polymer battery and to provide improved processes for their production. This object is achieved by a method according to claim 1, a cell network according to claim 10, a method according to claim 11 and a lithium polymer battery solved according to claim 15. Preferred embodiments are in the dependent dependent claims Are defined.

For example, in accordance with the foregoing, the present invention relates to a method of manufacturing a cell composite comprising the steps of:
Preparing a mixture for an anode and a mixture for the cathode and a mixture of cyclohexanone and methyl ethyl ketone (CM), which has a volume ratio of 1: 1.
Extruding the mixture for the anode and the mixture for the cathode to an anode mass and a cathode mass, wherein the anode composition and / or the cathode composition before extrusion, the above mixture (CM) is preferably supplied in a ratio of 5-30 mass% ;
Separate (parallel) lamination of the anode material and the cathode material on each one arrester to an anode and a cathode,
Removing the mixture (CM) from the anode and / or the cathode,
Calendering the anode and the cathode; and assembling the anode and the cathode with a separator therebetween.

The Use of the mixture (CM) allows an improved flow behavior when extruding. Among others, it is in the present invention therefore advantageous to remove the mixture (CM) after extrusion, since a cell composite from which the mixture (CM) has been removed adheres better, better fillable with electrolyte is and contains better processing properties. By the subsequent calendering In addition, the quality of the Improved electrodes by significantly reducing the internal resistance.

It It should be noted that the term "electrode mass" in the present Invention relates to the anode material and / or the cathode material.

to better processability of the mixed with the mixture (CM) material while In extruding, it is preferred that extrusion at temperatures of 80-130 ° C takes place.

Around the fluidity to increase and the electrode mass in a particularly procedural economic and simple way to extrude, it is preferred that the mixture (CM) be from 5 up to 30, more preferred 10 to 25 mass%, is supplied to the anode mass, based on the total mass the anode mass.

Out the same reasons For example, it is preferable that the mixture (CM) is 5 to 30% by mass, more preferably 15 to 25 mass%, is supplied to the cathode mass, based on the total mass the cathode mass.

Around the processability of the anode and / or cathode material and the later one Filling the Cell with electrolyte to improve, the mixture (CM) in the step removing completely (i.e. <1% by mass) withdrawn from the electrode masses.

Around to simplify the lamination step and increased adhesion in this step between the arrester and the electrode mass, the Anode mass and / or the cathode material preferably with a layer thickness extruded from 20-90 microns.

Around an increased stability and thus a better further processability of the extruded electrode material to achieve when the anode mass and also the cathode material respectively preferably extruded onto the arrester film (mesh, grid, fabric).

Regarding it is the adhesion between the arrester and the electrode mass further advantageous that the lamination z. At temperatures from 20 ° C and 80 ° C he follows.

In order to achieve the simplest possible and rapid removal of the mixture (CM), the advantages of which have already been described above, it is preferable to remove the mixture (CM) by heating at elevated temperatures up to 180 ° C and in vacuo at 1.33 to 13 ^-3 Pa.

moreover is it for the production efficiency advantageous when calendering (laminating the anode + separator + cathode, to the trilaminate) z. B. with a Speed of 5-10 m / min.

The The present invention provides a cell composite obtained by the method described above is obtainable.

moreover The present invention relates to a lithium-polymer battery and to a method of manufacturing such a battery. In this case, the cell composite can be both to a wound cell as well to other battery forms, such as flat cells processed become.

The present invention further relates to a method for producing a lithium-polymer battery, comprising the steps of:
Producing a cell composite by the method described above,
Winding the cell composite,
Notching the wound cell composite with subsequent contacting, preferably metal spraying.
Einhausen the contacted cell assembly in a housing and welding the cell assembly to the housing,
Drying of the housed and welded cell composite,
Evacuating the dried cell composite and filling the evacuated cell composite with electrolyte,
Closing the filled cell composite with subsequent forming.

Regarding a simple processing with sufficient safety of the battery it is advantageous that the closure preferably by riveting he follows.

It is also preferred that the forming takes place over 10-24 hours, since in this way a battery with sufficient capacity and high cycle stability can be obtained particularly well. For the same reason it is beneficial that before the For a storage step is carried out for 1-24 h.

The The present invention also provides a lithium polymer battery powered by the above-described method for producing such Lithium polymer battery available is. This lithium-polymer battery consists of anode, cathode, separator, anode mass and cathode mass are applied to the respective current collectors and wherein the Separator between each anode and the cathode is present and soaked in electrolyte is that of at least one lithium conducting salt and an aprotic solvent contains.

Further For example, it is preferred that in a lithium-polymer battery according to the present invention Li-interkalierbarer Carbon is contained in the anode. It is also preferable that the cathode contains Li-intercalatable heavy metal oxides.

Prefers The anode mass of lithium-polymer battery Li includes intercalatable synthetic and / or natural Carbon materials, in particular in a proportion of 80-95% by mass. moreover For example, it is preferred that the cathode material be Li intercalatable metal oxide comprises, preferably in a proportion of 85-95% by mass.

It It is preferred that in the inventive process, the extruded Electrodes are laminated to metallic conductor foils. Corresponding it is preferred that the extruded electrodes be in a lithium polymer cell or the lithium-polymer battery, which according to the methods of the present Invention were laminated to metallic Ableitfolien are. It is particularly preferred that as a drain for the cathode primer-coated aluminum foils are used while as Arrester for the anode is preferably used copper foils. It is called a primer preferably terfluorprimer THV 220 D o. a. used (as a binder combined with> 25 Mass% of an electrically conductive Carbon compound or carbon black and / or graphite).

The Lithium polymer battery of the present invention is particularly for one cylindrical battery of the so-called bobbin type suitable. exemplary can be duplicated D cells (DD cells) with a length of 60-75 mm to a length from 120-180 specify mm.

in the The following are the attached Figures briefly explained become.

The 1 shows a plot of the specific capacity versus the number of cycles for a lithium-polymer battery according to an embodiment of the present invention.

The 2 Figure 12 shows a plot of discharge capacity versus voltage for one embodiment of the lithium polymer battery of the present invention determined for seven different C rates.

The 3 Figure 12 shows a plot of discharge capacity versus voltage for one embodiment of the lithium polymer battery of the present invention determined at a constant discharge rate of C / 2 for four different temperatures.

The 4 FIG. 12 shows a plot of the ratio between the current and the average voltage during discharge at four different temperatures for an embodiment of the lithium-polymer battery according to the present invention. FIG.

5 shows so-called ragone plots for one embodiment of the lithium-polymer battery according to the present invention at five different temperatures. Ragone plot gives the ratio spec. Energy to spec. Performance.

in the The following is the method for producing a cell composite under the invention Reference to a preferred specific embodiment.

So long Unless otherwise indicated, in the invention "%" refers to "mass%".

1) Preparation of the mixtures for the anode or cathode materials

• a. anode paste The for the production of Anodes or cathode mass used solids were before their use degassed in vacuum 13.3 Pa at 50-60 ° C. It be z. B. 91% graphite (MCMB (Osaka gas, SGB-L (Kropfmühl) weight ratio 1: 1 with 1% carbon black (Ensaco 250, Super P), 8% Dyneon THV 220 with a mixture of cyclohexanone + Methyl ethyl ketone (1: 1 by volume) 10 parts per 100 parts of the above mixture intense - under Argon inert gas - mixed.
• b. cathode material z. For example, 90% Al-doped LiNiCoOx (C.C. Starck, TODA) with 2% carbon black (Ensaco 250, Super P), 8% Dyneon THV 220 and then with the addition of 10 parts of cyclohexanone + Methyl ethyl ketone (vol 1: 1) to 100 parts of the above mixture intensively - under Argon inert gas stirred vigorously.

2) extrusion

When Extruder, for example, a twin-screw extruder (Collin) is used, in which the respective, previously obtained material mixture mixed and kneaded while the mixture (CM) supplied is this by preferably this over a pump (eg 10-20 ° C) is promoted.

The extrusion of the dry mixes obtained above takes place in this embodiment at about 80-120 ° C. Extruded in this case on the metallic or primed Al arrester. The layer thickness is 30-90 microns.
Power: 5 to 50 kg / h

lamination takes place practically parallel to the extrusion d. H. Direct coating.

The extruded electrode masses are z. B. at 80-90 ° C on metallic Ableitfolien laminated on both sides. For the anodes, for example a copper foil (Gould, thickness 10-20 μm) used. For the production The cathodes are for example with Dyneon THV 220 D as a binder in the primer primer coated aluminum foil (Togo, thickness 20 μm). The electrodes are dried after lamination. The surface temperature is thereby preferably 120-180 ° C on the film. The removal of the mixture (CM) to be better able to fill the wound cells.

3) calandry ren the single electrode

The Speed of calendering is z. B. 4-5 m / min, which gives 150 m / h Anode or 150 m / h cathode, corresponding to 50 DD cells / h.

4) Join

In this embodiment be the both sides coated anode (Cu) and the two sides coated cathode (Al) together with separator (eg Celgard) assembled by winding, so that there is always a sequence of anode-separator-cathode-separator anode etc. results.

The The following refers to a preferred specific embodiment the method according to the invention for producing a lithium polymer battery with the above obtained cell composite.

5) Contact

In this embodiment the cell coil or cell composite on the front side is preferably through Metal syringes contacted with a Ableiterpol.

6) Housing and welding

The Einhausen and welding takes place in accordance with known Method.

7) Dry in vacuo

Of the received encased and welded cell composite is in this Case dried in vacuum. (Capacity 80 dd cells / d)

8) Evacuate and fill with electrolyte in vacuum as well Closing. (12-20 DD cells / h)

In this embodiment will follow evacuated the cell composite, filled with electrolyte in vacuo and then closed. The closure is done by riveting.

9) Forming

The Cell is z. B. over 10-24 h, wherein prior to forming a storage step from 1 to 24 h can be done.

• 1. Herstellung der Mischungen
• 2. Extrusion + Lamination und Trocknung Die Wickellänge pro Zelle beträgt in diesem Fall 3 m. Mit einer Geschwindigkeit von beispielsweise V = 30 mm/s ergibt sich für die Anode oder Kathode eine Laminierung von 108 m/h, bzw. 54 m/h für die Anode und 54 m/h Kathode.
• 3. Kalandrieren Mit der oben erwähnten bevorzugten Geschwindigkeit von V 4–5 m/min ergibt sich für einmaliges Kalandrieren eine Leistung von 300 m verarbeitetes Laminat pro Stunde, mit der Aufteilung 150 m/h Anode und 150 m/h Kathode lassen sich so 50 Zellen je h herstellen.
• 4. Wickeln In der vorstehend beschriebenen Ausführungsform können 8–10 Zellen je h gewickelt werden.
• 5. Kontaktieren durch Metallspritzen In der vorstehend beschriebenen Ausführungsform können 10–30 Zellen je Arbeitskraft je Stunde hergestellt werden.
• 6. Einhausen + Verschweißen In der vorstehend beschriebenen Ausführungsform können 8–10 Zellen je Arbeitskraft je h ohne Rüstzeiten und bei genau passenden Teilen eingehaust und verschweißt werden.
• 7. Trocknen im Vakuum Die Trockenzeit beträgt im Fall der vorstehenden Ausführungsform 12 h, wobei die Kapazität der Trocknungsvorrichtung bei 80 Zellen liegt.
• 8. Evakuieren und Befüllen Wenn die Zellen zum Verschließen beispielsweise vernietet werden, ergibt sich eine Produktionsleistung von 12 Zellen je h, wobei Celgard als Separator verwendet werden kann.

For the sequence of the individual method steps of the method according to the invention according to the concrete embodiments described above:

• 1. Preparation of the mixtures
• 2. Extrusion + Lamination and Drying The winding length per cell in this case is 3 m. At a speed of, for example, V = 30 mm / s, the anode or cathode results in a lamination of 108 m / h, or 54 m / h for the anode and 54 m / h cathode.
• 3. Calendering With the above-mentioned preferred speed of V 4-5 m / min, a one-time calendering produces an output of 300 m of processed laminate per hour, with the division of 150 m / h anode and 150 m / h cathode 50 Make cells each h.
• 4. Winding In the embodiment described above, 8-10 cells per hour can be wound.
• 5. Contact by metal spraying In the embodiment described above, 10-30 cells per worker per hour can be made.
• 6. Housing + Welding In the embodiment described above, 8-10 cells per worker per hour can be housed and welded without set-up times and with just the right parts.
• 7. Drying in Vacuum The drying time in the case of the above embodiment is 12 hours, with the capacity of the drying apparatus being 80 cells.
• 8. Evacuation and filling For example, when the cells are riveted for sealing, there is a production output of 12 cells per hour, with Celgard being used as a separator.

Examples:

In In the following examples, the term "μm" always refers to the thickness the respective films or films.

Example 1: Preparation of the mixtures

1.1 cathode (25 kg batch size)

In a vacuum mixing dryer, a mixture of 23.75 kg of lithium cobalt oxide, 1 kg of terpolymer Dyneon THV ^® 220 is homogenized and 0.25 kg of acetylene black Ensaco ^® for 12 hours at 120 ° C and then degassed in a vacuum at 1.33 Pa.

1.2 anode (25 kg batch size)

In In a vacuum mixer, a mixture of 23.5 kg MCMB (Meso Carbon Micro Beads) and 1.5 kg of Dyneon THV 220 terpolymer for 12 hours at 120 ° C homogenized and dried and degassed as in 1.1.

Example 2: Extrusion

The The mixture prepared in Example 1 is prepared by adding 15% by weight. Mixture (CM) cyclohexanone / methyl ethyl ketone, which has a volume ratio of 1: 1, (anode) at 100 ° C in a twin-screw extruder to a thermoplastic film worked up and through a nozzle pressed and laminated to the respective arrester foil and indeed with a layer thickness of 35-45 μm each. As arrester for the anode mass serves a Gould Cu foil 12 microns strong and for the cathode material is a primed Al foil, laminated on both sides. Before the electrodes are wound, the mixture (CM) is placed in a drying unit thermally removed.

Example 3: Cell Composite and Battery Production

The produced cells are wound, so that a cell composite is obtained. This cell composite is contacted by metal spraying with the poles, housed, evacuated and filled with electrolyte, so that still to be formed lithium polymer batteries are obtained. The electrolyte used is 1 M LiBF ₆ in diethyl carbonate, alternatively suitable as conductive salts z. B. Li organoborates and as aprotic solvent z. As dimethyl glycol, propylene carbonate o. Ä.

in the Following are the physical and electrical properties listed lithium polymer batteries listed. In doing so, the corresponding Measurements were performed on each of the above-described formed cells.

Physical Properties:

• Diameter: 32 mm
• height (without ends): 150 mm
• Weight: 290 g
• Volume (without ends): 115 cm ³
• Housing material: stainless steel

Electrical Properties:

• Specific power (30 s impulse discharge): 1600 W / kg
• Power density (30 s impulse discharge): 3800 W / l
• Nominal voltage: 3.6V
• nominal capacity at 0.3 C: 6 Ah
• Specific energy: 75-80 Wh / kg
• Energy density 190-200 Wh / l

Example 4: Formation

The Formation of the batteries takes place with a constant current of 0.60 A up to a potential of 4.2V and then at constant potential from 4.2V until the current reaches <0.12 A has fallen (CCCV = constant current constant voltage). The discharge takes place at 0.60 A up to the lower voltage limit of 3.0V. Following are for quality assurance and capacity determination two more cycles performed. The charge happens with 1.8 A to 4.2 V and at constant potential until the current has fallen below 0.18A. The discharge takes place with 1.8 A to the final voltage of 3.0 V.

Example 5: Cyclic data

To measure the cycle stability of the battery formed in Example 4, it is charged at 3 A to 4.2 V, then recharged at 4.2 V in a constant potential phase until the current has fallen below 0.3 A. The discharge takes place at 4.8 A. The lower cut-off voltage is 3.0 V. The 1 shows a plot of the specific capacity versus the number of cycles. How out 1 As can be seen, the battery obtained according to the present invention is characterized by a high cycle stability, ie the specific capacity decreases only insignificantly even over large numbers of cycles.

Example 6: Stress test at room temperature

The charge of the formed battery obtained in Example 5 is 6 A to 4.2 V, in a constant potential phase is recharged at 4.2 V until the current has fallen below 0.6 A. Discharge occurs at different currents between 6 (1C) and 126A (21C). The lower cut-off voltage is 2.7V.

The 2 shows a plot of the discharge capacity versus the voltage, in which example a discharge capacity / voltage characteristic was determined for seven different C-rates. It shows over a wide range of discharge capacity for batteries desired extremely low drop in the voltage value.

Example 7: unloading at different temperatures

This test was carried out analogously to Example 6, wherein discharge profiles for different operating temperatures at a constant discharge rate of C / 2 were measured. The results are in 3 shown. As in Example 6, the batteries according to the invention show excellent voltage characteristics even at very low and comparatively high temperatures.

Example 8: Stress test

For the batteries according to the present invention as prepared above, the ratio between the current on the one hand and the average voltage during the discharge on the other hand was determined for different temperatures. In the 4 The results shown illustrate the excellent characteristics of the batteries according to the invention with respect to a high voltage over a wide range of the current value, only slightly changing average voltage.

Example 9: Available Energy Content (Ragone Plots) relationship specif. Energy / specif. power

For the high energy cells, ie for the batteries obtained as above, of the present invention, so-called ragone plots were determined. These are in 5 illustrated. In the lower part of the specific energy only a pulse discharge over a few seconds is possible. The ragone plots show the specific energy dependence (in Wh / kg) of the specific power (in W / kg), ie specific energy (Wh / kg) / specific power (W / kg). In this context, V _low indicates the lower cut-off voltage.

Claims (15)

Process for the preparation of a cell composite for a lithium polymer batch with the steps: Making a mixture for an anode and a mix for a cathode, Extrude the mixture for the anode and the mixture for the Cathode to an anode material and a cathode material, wherein at least one of the anode mass and the cathode mass with feeding a mixture of cyclohexanone and methyl ethyl ketone (CM) containing a volume ratio of 1: 1, extruded, parallel lamination of the Anode ground and the cathode ground on each one arrester to one Anode and a cathode, Remove the mixture (CM) from the Anode and / or the cathode, Assembly of the anode and the cathode with a separator arranged therebetween. Method according to claim 1, characterized in that that the extrusion takes place at temperatures of 80-130 ° C. Method according to one of the preceding claims, characterized characterized in that the mixture (CM) to 5 to 30% by mass to the Anode mass supplied is based on the total mass of the anode mass. Method according to claim 3, characterized that the mixture (CM) is supplied to the cathode mass at 5 to 30% by mass, based on the total mass of the cathode material. Method according to one of the preceding claims, characterized characterized in that the mixture (CM) up to a residual concentration from 0.01 to 0.1 mass% based on the corresponding electrode mass Will get removed. Method according to one of the preceding claims, characterized in that the anode mass and / or the cathode mass extruded with a layer thickness of 20-90 microns becomes. Method according to one of the preceding claims, characterized in that the anode material is applied to a Cu arrester becomes. Method according to one of the preceding claims, characterized characterized in that the cathode material on a primed Al arrester is applied. Method according to one of the preceding claims, characterized characterized in that the removal of the mixture (CM) by heating at temperatures of 120-180 ° C takes place. Cell composite, available by a method according to any one of claims 1 to 9. Process for producing a lithium-polymer battery comprising the steps of: Producing a cell assembly by a method according to one of claims 1 to 9, winding the cell composite, contacting the wound cell composite, preferably by metal spraying, Einhausen the contacted cell assembly in a housing and welding the cell assembly to the housing, drying the housed and welded cell composite, evacuation of the dried cell composite, filling the evacuated cell composite with electrolyte and closing the filled cell composite with subsequent formation. Method according to claim 11, characterized in that that closing done by riveting. Method according to claim 11 or 12, characterized that the formation takes place over 10-24 h. Method according to one of claims 11 to 13, characterized that before forming for 1 to 24 h, a storage step is performed. Lithium polymer battery available through a process according to one of the claims 11 to 14.