DE102004057365A1 - Production of lithium polymer cell extrudes anode and cathode mixtures to form electrodes using ketone solvent mixture that is then removed - Google Patents

Abstract

Production process for lithium polymer cells comprises forming anode and cathode mixtures and extruding to electrode forms with at least one extrusion using a 1:1 v:v mixture of cyclohexanone and methylethylketone (CM). These are laminated in parallel on conductors, CM is removed and the cell formed using a separator. An independent claim is also included for: a battery produced as above.

Description

The This invention relates to a lithium polymer cell, a lithium polymer battery with the cell and process for its 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 the 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, 1999. Special manufacturing methods, such as the so-called Bellcore method are described in "Lithium Ion Batteries", eds M. Wakihara and O. Yamamoto, Verlag VCH, Weinheim 1998 p 10.9 described. Furthermore, in the "Handbook of Batteries" III Edit., D. Linden, Th. B. Reddy, Mc Graw-Hill 2001, described in chapter 35.1-35.9 Li-ion batteries 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" The term "battery" is usually used to describe the performance of a battery be different than the performance 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.

at a coating method is that for the cathode or anode material required polymer binder solved (e.g., 5-10% Fluoroelastomer homopolymers or copolymers in N-methyl-pyrrolidone (NMP)) and the resulting polymer solution with the cathode or anode-specific additives such as lithium-intercalatable metal oxides or lithium intercalatable Carbons (soot, Graphite or similar) mixed and dispersed. Then this dispersion with the film coating technique on current collectors (foils, tapes, Nets or similar) 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 (e.g., dibutyl phthalate) in the anode or DBP) incorporated prior to the assembly of anode / cathode / separator in the Bellcore method (s.o.) is dissolved to a sufficient Porosity, d. H. adequate absorption capacity for the electrolyte solution, create and migration paths for the anions and cations to have during the loading and unloading process.

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

One Another method is the extrusion of separator (polymer gel electrolyte) and an electrode (US-A-4818643, EP-B-0 145 498) or extrusion of anode, separator and cathode in parallel extruders and subsequent merging of the three components (DE-A-10020031).

DE-A-10020031 discloses an extruder process in the electrolyte and the respective ones Electrode mass be extruded together (electrolyte = aprotic solvent + Conductive salt).

The The present invention has for its object to provide an improved lithium polymer cell, an improved lithium-polymer battery as well as improved methods to provide for their manufacture. This task through a process according to claim 1, a lithium polymer cell according to claim 14, a method according to claim 15 and a lithium-polymer battery according to claim 19 solved. Preferred embodiments are in the dependent dependent claims Are defined.

In accordance with the foregoing, the present invention relates to a process for producing a lithium polymer cell, comprising the steps of:
Prepare a mixture for an anode and a mixture for the cathode with the addition of 5-30% by weight of a mixture of cyclohexanone and methyl ethyl ketone (Vol 1: 1) (CM).

Extruding the mixture for the anode and the mixture for the cathode to an anode mass and a cathode mass, wherein the anode mass and / or the cathode material prior to extrusion, the above mixture (CM) can be supplied;
separately laminating the anode mass and the cathode mass onto an arrester to form an anode laminate and a cathode laminate,
Removing the mixture (CM) from the anode laminate and / or the cathode laminate,
Calendering the anode laminate and the cathode laminate, and
Assembling the anode laminate and the cathode laminate with a separator therebetween.

The Use of the mixture (CM) allows for improved flow behavior when extruding. Among others, it is in the present invention therefore advantageous to remove the mixture (CM) after extrusion, as a lithium polymer cell, from which the mixture (CM) is removed was better adhered, better fillable with electrolyte and better processing properties contains. By the subsequent Calendering is also the quality of the electrodes by clear Improved reduction of 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 extrusion, 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 further processibility anode and / or cathode material and the latter Filling the Cell with electrolyte to improve, the mixture (CM) in the step removal (i.e. <1 mass%) completely deducted 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 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 lamination e.g. 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 preferred to remove the mixture (CM) by heating at elevated temperatures up to 180 ° C and in vacuo at 10 ^-2 to make 10 ^-1 mm.

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 present invention provides a lithium polymer cell which is obtainable by the method described above.

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

The present invention further relates to a method for producing a lithium-polymer battery, comprising the steps of:
Producing a lithium polymer cell by the method described above, winding the lithium polymer cell,
Disconnecting the wound lithium polymer cell with subsequent contacting, preferably metal spraying.

Housing the contacted lithium polymer cell in a housing and welding the lithium polymer cell to the housing,
Drying the housed and welded lithium polymer cell,
Evacuating the dried lithium polymer cell and filling the evacuated lithium polymer cell with electrolyte,
Closing the filled cell 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 formation takes place over 10-24 h, since on this Make a battery with sufficient capacity and high cycle stability especially can be well preserved. For the same reason it is beneficial that before forming for 1 to 24 h, a storage step is performed.

The The present invention also provides a lithium polymer battery prepared by the method of preparation described above Such a lithium-polymer battery is available. This lithium-polymer battery consists of anode, cathode, separator (where 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 with Electrolyte soaked which is at least one lithium conducting salt and an aprotic solvent contains.

Further it is preferred that in a lithium polymer battery according to the present Invention Li-intercalatable carbon contained in the anode is. In addition, it is preferred that the cathode be Li-intercalatable Contains 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 prefers terfluorprimer THV 220 D or similar used (combined as a binder with> 25 mass% of an electrical 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 as they e.g. is described in. By way of example, double D cells can be used (DD cells) with a length from 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 process for producing a lithium polymer cell according to the invention with reference to a preferred specific embodiment explained in more detail.

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

1) Preparation of the mixtures for the Anode or cathode masses

a. anode paste

The solids used to make the anode or cathode mass were degassed at 50-60 ° C prior to their use in vacuo at 10 ^-1 torr.

For example, 91% graphite (MCMB (Osaka Gas, SGB-L (Kropfmühl) weight ratio 1: 1 with 1% Leitruß (Ensaco 250, Super P), 8% Dyneon THV 220 with a mixture of cyclohexanone + methyl + ethyl ketone (Vol 1: 1) 10 parts 100 parts of the above mixture intensively - under argon, inert gas - mixed.

b. cathode material

For example, 90% Al-doped LiNiCoOx (H.C. Starck, TODA) with 2% carbon black (Ensaco250, SuperP), 8% Dyneon THV220 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, in addition to this preferably over a pump (e.g., 10-20 ° C) is conveyed.

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 on both sides (Toyo, Dicke 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) calendering of the single electrode

The Speed of calendering is e.g. 4-5 m / min, that 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) are used together with separator (e.g., Celgard) assembled by winding, so that always results in a sequence of anode-separator-cathode-separator anode, etc.

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 lithium polymer cell.

5) Contact

In this embodiment the cell winding on the front side is preferably by metal spraying 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 wraps is in this Case dried in vacuum. (Capacity 80 dd cells / d)

8) evacuate and fill with Electrolyte in vacuum and sealing. (12-20 DD cells / h)

In this embodiment will follow the cell coil evacuated, 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 = 30mm/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 lamination is 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 a capacity of 300 m processed laminate per hour, with the division of 150 m / h anode and 150 m / h cathode can be so Make 50 cells per hour.
• 4. Wrap 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 If the cells are riveted, for example, for sealing purposes, this results in a production capacity of 12 cells per h, whereby Celgard can be used as a separator.

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 and 0.25 kg of acetylene black Ensaco ^® for 12 hours at 120 ° C is homogenized and then degassed under vacuum ei 10 ^-2 Torr.

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 Vol 1: 1 (anode) at 100 ° C in a Twin screw extruder worked up to a thermoplastic film 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 and battery manufacturing

The prepared cells are wound so that a lithium polymer cell is obtained. This lithium polymer cell is contacted by metal spraying with the poles, housed, evacuated and filled with electrolyte, so that still formative 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 or 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 against 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 takes place with 6 A to 4.2 V, in a constant potential phase is at 4.2 V is charged until the current has fallen below 0.6A. The discharge takes place at different currents between 6 (1C) and 126A (21C). The lower cut-off voltage is 2.7 V.

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 contents (Ragone plots) ratio 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 producing a lithium polymer cell with the steps: Make a mixture for the 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 + methyl ethyl ketone Vol 1: 1 extruded becomes and parallel Laminating the anode mass and the cathode mass on an arrester to an anode and a cathode (anode ground + Arrester gives the anode, analogous cathode material + arrester results the cathode). Removing the mixture (CM) from the anode and / or the cathode, Put together the anode and the cathode with a separator disposed therebetween. Method according to claim 1, characterized in that that the extrusion takes place at temperatures of 80-120 ° C. Method according to one of the preceding claims, characterized characterized in that the mixture (CM) to 15 to 35% 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 anode mass to 15 to 35% by mass, based on the total mass of the anode mass. Method according to one of the preceding claims, characterized characterized in that the mixture (CM) is removed in the drying step becomes. Method according to claim 5, characterized in that that the mixture (CM) in the drying step to 0.01 to 0.1% Will get removed. Method according to one of the preceding claims, characterized in that the anode mass and / or the cathode mass are with a layer thickness of 20-80 microns extruded becomes. Method according to one of the preceding Claims, characterized in that the anode and / or cathode material on Cu arrester (for the anode) and primed Al arrester (for the cathode) are coated. 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. Lithium polymer cell, obtainable by a process according to one of the claims 1 to 9. Process for producing a lithium-polymer battery with the steps: Making a lithium polymer cell by a method according to any one of claims 1 to 9, Wrap the Lithium-polymer cell, Contacting the wound lithium polymer cell Metal spraying, Enclosing the contacted lithium polymer cell in a housing and welding the lithium-polymer cell with the housing, Dry the housed and welded Lithium-polymer cell, Evacuate the dried lithium polymer cell and fill the evacuated lithium polymer cell with electrolyte, Closing the filled Cell followed by forming. 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.