KR20020002858A - Method for manufacturing lithium polymer battery - Google Patents

Abstract

PURPOSE: Provided is a simple process for producing a lithium ion polymer battery, which can increase mechanical properties of a polymer electrolyte and give a low interfacial resistance between electrode plates and the polymer electrolyte and make the lithium ion polymer battery light. CONSTITUTION: The process comprises the steps of: preparing a cathode by spreading cathode slurry comprising a cathode active material such as meso phase carbon microbead(MCMB), a polymer binder such as polyvinylidene fluoride(PVDF), and a solvent on a current collector such as an expanded or punched metal; preparing an anode by spreading anode slurry comprising an anode active material such as a lithium cobalt oxide, a conductive agent, a polymer binder such as the PVDF, and a solvent on a current collector such as the expanded or punched metal; preparing the polymer electrolyte by spreading a gel obtained from a polymer matrix such as the PVDF, a lithium salt such as lithium hexafluoro phosphate, and a plasticizer of the polymer electrolyte, such as ethylene carbonate, on a film; winding or laminating the cathode, the anode, and the polymer electrolyte to make an end-cell; putting the end-cell into a plastic bag.

Description

Lithium ion polymer battery manufacturing method {METHOD FOR MANUFACTURING LITHIUM POLYMER BATTERY}

The present invention relates to a method for manufacturing a lithium ion polymer battery, and in particular, a slurry for a lithium ion battery is applied directly to a current collector to form a pole plate, and a lithium ion polymer battery is made by using a polymer electrolyte integrated with the pole plate and an insulating porous membrane. By increasing the mechanical strength of the polymer electrolyte, low interface resistance between the electrode plate and the polymer electrolyte, the weight of the lithium ion polymer battery, and the manufacturing process of the lithium ion polymer battery can be simplified. .

Due to the rapid proliferation of portable devices such as laptops, hand fishes, and mobile communication terminals, the demand for high capacity, high performance rechargeable secondary batteries is rapidly increasing. The lithium ion polymer battery uses a carbon material (carbon or carbon composite material) that can be absorbed and desorbed as a negative electrode, and a lithium composite oxide capable of charging and discharging lithium ions by structural deformation as a positive electrode. Using a non-aqueous electrolyte in which lithium salt is dissolved in one or more organic solvents, the charge and discharge are made by generating electromotive force when lithium ions are moved between the positive electrode and the negative electrode. However, such lithium ion polymer batteries have high reactivity with water and use excessive electrolytes that are thermally unstable, and thus there is a concern about stability. In addition, by using a metal can or the like as a battery packaging material, not only the energy density is lowered, but also there is a disadvantage in that design freedom for the battery type is not free.

In order to compensate for these problems, various types of battery designs are possible, energy density is high, miniaturization and weight reduction are possible, and research is being actively conducted to provide a lithium ion polymer battery having excellent stability.

The polymer electrolyte is durable in electrode volume change due to the adsorption and desorption of lithium ions into the electrode plate, and is less reactive than the liquid electrolyte due to the properties of the solid and the low liquid content, thereby improving battery cycle characteristics. Compared with the stability is excellent. In particular, a battery core plate of a bellcore type battery using polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a polymer electrolyte has an active material capable of absorbing and desorbing lithium ions, and a PVDF-HFP copolymer as a binder. And it can be prepared by applying a slurry in which dibutyl phthalate dissolved in acetone to lower the resistance of the plate and also serves as a mobile passage of lithium ions to the film. In addition, the electrode having the electrode plate and the polymer electrolyte as described above are laminated in the order of negative electrode / polymer electrolyte / anode to make a single cell, and after extracting dibutyl phthalate, the electrolyte is injected and thermally packaged in a plastic bag to produce a lithium ion polymer battery. You can get it.

The advantage of this lithium ion polymer battery and its manufacturing method is that due to the high ionic conductivity of the PVDF-HFP copolymer, it exhibits the same battery characteristics as that of the lithium ion battery, but also has excellent stability, excellent structural deformation, and ultra-thin film by using a polymer electrolyte. There is an advantage.

However, in spite of the above advantages, in the lithium ion polymer battery and its manufacturing method, acetone having high volatility is used as the solvent, so that the slurry is difficult to apply directly to the current collector. By manufacturing the electrode plate by thermocompression bonding the current collector having a big net structure, the manufacturing process is complicated and productivity is lowered. In addition, in the lamination state of the electrode plate and the polymer electrolyte, there is a problem that the interface resistance is large, which adversely affects the battery characteristics. In addition, according to the quality control of the process of extracting the dibutyl phthalate added to increase the electrolyte impregnation, the battery performance difference is very large, it is difficult to manufacture a battery of uniform performance.

Accordingly, the present inventors have studied in view of the above problems and have developed a method capable of manufacturing an electrode plate having excellent ion conductivity without adding dibutyl phthalate to the electrode plate and the polymer electrolyte.

The present invention is to apply a slurry for a lithium ion battery directly to the current collector to form a pole plate, and to make a lithium ion polymer battery using the polymer electrolyte integrated with the pole plate and the insulating porous membrane, thereby increasing the mechanical strength of the polymer electrolyte, Low interfacial resistance between electrode plate and polymer electrolyte, light weight of lithium ion polymer battery and high lithium ion

An object of the present invention is to simplify the manufacturing process of a molecular battery.

In order to achieve the above object, the lithium ion polymer battery manufacturing method according to the present invention comprises the steps of preparing a negative electrode by dissolving the negative electrode active material and the polymer binder in a solvent to make a negative electrode slurry and applying it to a current collector to dry hot air; Dissolving a positive electrode active material, a conductive material, and a polymer binder in a solvent to form a positive electrode slurry, and applying the same to a current collector to hot air dry the positive electrode slurry; Making a polymer electrolyte by adding a plasticizer of a polymer electrolyte to the polymer matrix and a lithium salt and applying the melted gel to the film; Winding or stacking the negative electrode, the positive electrode, and the polymer electrolyte in a predetermined combination to form a unit cell; In addition, the single cell is packaged in a plastic bag, characterized in that it comprises a step of making a lithium ion polymer battery.

Other features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

In the method of manufacturing a lithium ion polymer battery according to the present invention, the electrode slurry prepared by dissolving an electrode active material and a polymer binder in a solvent is directly applied to a current collector to prepare an electrode, thereby lowering the interfacial resistance between the current collector and the active material and increasing binding force. It is supposed to be.

That is, the negative electrode manufacturing method in the lithium ion polymer battery manufacturing method according to the present invention is made as follows.

First, the negative electrode active material and the polymer binder are dissolved in a solvent to prepare a negative electrode slurry. And a negative electrode can be manufactured by apply | coating this negative electrode slurry to an electrical power collector, and hot-air drying.

Specifically, as the negative electrode active material, any one selected from the group containing mesophase carbon microbead (MCMB), mesophase carbon fiber (MPCF), and graphite-based carbon, which are coke-based materials, and a combination thereof are used. As a material, polyvinylidene fluoride (PVDF) polymer is used. The negative electrode active material and the polymer binder are mixed, and an NMP solvent is added thereto to melt the negative electrode active material and the polymer binder to form a negative electrode slurry. As a current collector, an expanded metal or a punched metal having a mesh structure is used, and the current collector is applied by hot-air drying by directly applying the negative electrode slurry to one or both surfaces of the current collector. It is possible to obtain a cathode in which a plate is formed on one or both sides of the substrate.

Next, as a method for manufacturing an electrode for a lithium ion polymer battery according to the present invention, a method for producing a cathode is performed as follows.

First, the positive electrode active material, the conductive material, and the polymer binder are dissolved in a solvent to form a positive electrode slurry. The positive electrode slurry can be prepared by applying the positive electrode slurry to a current collector and drying the hot air.

Specifically, a lithium composite oxide of any one or a mixture thereof selected from the group containing lithium cobalt oxide, lithium manganese oxide, or lithium nickel oxide is used as the positive electrode active material. As the polymer binder, polyvinylidene fluoride (PVDF) polymer is used, and a conductive material is added to increase the electron conductivity of the electrode plate. The positive electrode active material, the conductive material and the polymer binder are mixed, and an NMP solvent is added thereto to melt the negative electrode active material, the conductive material and the polymer binder to form a positive electrode slurry, and the bipolar slurry is expanded or expanded to a punched metal. It is possible to obtain a positive electrode having a pole plate formed on one or both sides of the current collector by directly applying it to one or both surfaces of the current collector and hot air drying.

Next, a method for making a polymer electrolyte used to manufacture a lithium ion polymer battery as described above will be described.

Polyvinylidene fluoride (PVDF), polyacrylonitrile as polymer matrix

(PAN), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyvinyl chloride

At least one of a polymer made of (PVC), polystyrene (PS) or a copolymer is prepared. Lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiCIO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroassenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ And a lithium salt containing at least one of these mixtures. In addition, ethylene carbonate (EC), propylene carbonate

(PC), butylene carbonate (BC), Prepare a plasticizer of a polymer electrolyte comprising at least one of butyrolactone (GBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF) and mixtures thereof Then, the plasticizer is added to the polymer matrix and the lithium salt to dissolve them, and in the gel solution state, the gel solution is then applied onto the film to prepare a polymer electrolyte. The film preferably functions as a separator of a lithium ion polymer battery, and is preferably in the form of a porous membrane. As described above, a polymer electrolyte is prepared using an insulating porous membrane to maintain a constant mechanical strength of the polymer electrolyte, and a film of the porous membrane is used. This allows the movement of lithium ions through the pores.

Next, the negative electrode, the positive electrode, and the polymer electrolyte prepared by the above-described manufacturing methods are wound or laminated in a predetermined combination, for example, negative electrode / polymer electrolyte / anode, to form a single cell.

In addition, the single cell is heat-packed in a plastic bag to complete the production of a lithium ion polymer battery.

The lithium ion polymer battery manufactured according to the present invention has been tested with charge and discharge characteristics, compared with a conventional lithium ion polymer battery using electrodes made by compressing a pole plate slurry coated on a glass plate or a film onto a grid as a current collector. It was found that the ionic conductivity was excellent without adding dibutyl phthalate to the electrode plate and the polymer electrolyte, the interfacial resistance between the current collector and the electrode plate was low, and the binding force was increased, thereby providing excellent cycle characteristics and high rate characteristics of the lithium ion polymer battery.

<Example 1>

92 wt% of MCMB as a negative electrode active material and 8 wt% of poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)) copolymer as a polymer binder were dissolved in NMP solvent to form a negative electrode slurry. The slurry was applied directly to a current collector made of Cu, followed by hot air drying to form a negative electrode.

Further, LiCoO ₂ as the positive electrode active material, acetylene black as the conductive material, and poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)) as the polymer binder had a weight ratio of 90: 6: 4. A positive electrode slurry was prepared by dissolving in an acetone solvent to prepare a positive electrode slurry. The positive electrode slurry was directly applied to a current collector made of Al, followed by hot air drying to make a positive electrode.

Meanwhile, the poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)) copolymer and silica were dissolved in an electrolyte solution in which LiPF ₆ was dissolved in a mixed solvent of EC and EMC in the same volume ratio. A slurry was made and the slurry was applied to a PE film as a separator to prepare a polymer electrolyte.

In addition, the negative electrode, the positive electrode, and the polymer electrolyte obtained as described above are combined in the order of positive electrode / polymer electrolyte / cathode / polymer electrolyte / anode to make a single cell, and the unit cell is placed in a plastic bag and thermally packaged to obtain lithium ions. Production of the polymer battery was completed.

Table 1 shows the results of testing the charge / discharge characteristics of the battery by applying a current of 1 mA / cm 2 in the range of 4.2 to 3.0 V. As shown in Table 1, the lithium ion polymer battery according to Example 1 was found to increase the cycle number of the battery and excellent charge and discharge efficiency.

<Example 2>

The negative electrode and the positive electrode were prepared in the same manner as in Example 1.

The polymer electrolyte was prepared using a mixed solvent in which EC and DEC were mixed at the same volume ratio, and the rest were prepared in the same manner as in Example 1, and the anode and cathode polymer electrolytes were prepared in the same manner as in Example 1. To prepare, as shown in Table 1, the results of testing the charge and discharge characteristics are shown in Table 1. As shown in Table 1, it was found that the lithium ion polymer battery of Example 2 was slightly inferior in cycle characteristics to the lithium ion polymer battery of Example 1.

Comparative Example

75 wt% of MCMB as a negative electrode active material, 8 wt% of poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)) copolymer and 17 wt% of dibutylphthalate as a polymer binder were dissolved in acetone. The slurry was applied to PET to make an electrode plate, and then the electrode plate was pressed by applying a constant pressure and temperature to a current collector made of Cu.

In addition, 75 wt% of lithium cobalt oxide as the positive electrode active material, 5 wt% of acetylene black as the 1111 conductive material, and poly (vinylidene fluoride-co-hexafluoropropylene) as the polymer binder.

(P (VDF-HFP)) 6 wt% and 14 wt% dibutyl phthalate are dissolved in acetone solvent to make a positive electrode slurry, and this slurry is applied to PET to make a pole plate. And pressure was applied to form a positive electrode.

Meanwhile, a slurry obtained by mixing 40 wt% of poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)), 30 wt% of silica, and 30 wt% of dibutylphthalate in acetone was added to a PET film as a separator. It was applied to prepare a polymer electrolyte.

Then, the negative electrode, the positive electrode, and the polymer electrolyte obtained as described above are combined in the order of positive electrode / polymer electrolyte / cathode / polymer electrolyte / anode to be laminated by applying heat and pressure to extract a dibutyl phthalate from the cell. After the electrolyte injection process, the single cell was heat-packed in a plastic bag to complete the production of a lithium ion polymer battery.

Table 1 shows the results of testing the charge / discharge characteristics of the lithium ion polymer battery thus prepared under the same conditions as in Example 1. As shown in Table 1, the lithium ion polymer battery of the comparative example is a general form of the lithium polymer battery of the core core, and due to the high interfacial resistance between the electrode plate and the polymer electrolyte, the capacity deteriorates with the cycle and the cycle characteristics are deteriorated. .

Charge and discharge efficiency (%) Cycles (times) Capacity deterioration rate (mAh / cycle) Example 1 99.8 530 0.18 Example 2 99.6 485 0.23 Comparative example 99.1 380 0.56

As described above, in the present invention, a slurry prepared by dissolving an active material and a polymer electrolyte in a solvent is applied directly to a current collector to make an electrode, and a lithium ion polymer battery is manufactured by using the electrode. Low interfacial resistance and low electrode resistance facilitate charge / discharge of lithium ions, thereby increasing the charge and discharge efficiency of the battery, thereby extending the life of the lithium ion polymer battery.

In addition, by reducing the thickness of the electrode plate, the movement path of lithium ions is shortened to increase the ion conductivity of the electrode plate, and by applying the polymer electrolyte to the film of the insulating porous membrane, the mechanical strength of the polymer electrolyte is increased and the ion conductivity is further increased. The interface resistance between the electrode plate and the polymer electrolyte is also lowered.

In addition, the dibutyl phthalate extraction process is eliminated, and the electrode plate is laminated on the current collector by applying slurry, instead of making the electrode plate and pressing the current collector, thereby reducing the man-hour and productivity of the lithium ion polymer battery electrode. In addition to lowering the manufacturing cost of the lithium ion polymer battery, it is possible to manufacture a lithium ion polymer battery with uniform performance.

The present invention is also effective in lithium ion polymer batteries in which polyacrylonitrile resins, polyether resins, polyester resins or polyvinyl resins are applicable as polymers of polymer electrolytes.

Claims (4)

Preparing a negative electrode by dissolving a negative electrode active material and a polymeric binder in a solvent to form a negative electrode slurry and applying the same to a current collector for hot air drying; Dissolving a positive electrode active material, a conductive material, and a polymer binder in a solvent to form a positive electrode slurry, and applying the same to a current collector to hot air dry the positive electrode slurry; Making a polymer electrolyte by adding a plasticizer of a polymer electrolyte to the polymer matrix and a lithium salt and applying the melted gel to the film; Winding or stacking the negative electrode, the positive electrode, and the polymer electrolyte in a predetermined combination to form a unit cell; And, The method of manufacturing a lithium ion polymer battery comprising the step of packaging the unit cell in a plastic bag to make a lithium ion polymer battery. The method of claim 1, Mesophase carbon microbeads made of coke as the negative electrode active material (MCMB), mesophase carbon fiber (MPCF), and any one selected from the group containing graphite carbon, or a combination thereof, and a polyvinylidene fluoride (PVDF) polymer is used as the polymer binder. The manufacturing method of the lithium ion polymer battery characterized by manufacturing a negative electrode using the expanded metal or punched metal of a net structure as a whole. The method of claim 1, The positive electrode active material is a lithium composite oxide of any one or a mixture thereof selected from the group consisting of lithium cobalt oxide, lithium manganese oxide or lithium nickel oxide, and a polyvinylidene fluoride (PVDF) polymer as a polymer binder. Using a lithium ion polymer battery, characterized in that for producing a positive electrode, using an expanded metal or punched metal as a current collector. The method of claim 1, Polyvinylidene fluoride (PVDF), polyacrylonitrile as the polymer matrix (PAN), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), at least one of a polymer made of polystyrene (PS) or a copolymer is used, and lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate as a lithium salt (LiCIO ₄ ), Lithium tetrafluoroborate (LiBF ₄ ), Lithium hexafluoroassenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ) and mixtures thereof containing at least one of them, ethylene carbonate as a plasticizer of the polymer electrolyte (EC), propylene carbonate (PC), butylene carbonate (BC), -But include at least one of butyrolactone (GBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF) and mixtures thereof, The plasticizer is added to a polymer matrix and a lithium salt, and the gel solution dissolved therein is coated on a film in the form of a porous membrane to prepare a polymer electrolyte.