KR20000002115A - Lithium polymer secondary battery including cathode made of metal compound cathode material - Google Patents

Abstract

PURPOSE: A solid lithium secondary battery is provided to be used to portable devices, to offer a property of high energy density and superior reversible charge/discharge. CONSTITUTION: A lithium polymer secondary battery including a cathode made of metal compound cathode material comprises: copper and more than 1 of copper compound selected among copper salt in the form of CuXn; a cathode made by applying a compound electrode material composed of high molecule materials to a collecting body; a non-aqueous high molecule electrolyte; an anode composed of lithium, lithium alloy or lithium intercalation.

Description

Lithium polymer secondary battery including a positive electrode made of a metal composite positive electrode material

The present invention relates to a lithium polymer secondary battery including a positive electrode made of a metal composite positive electrode material, and more particularly, a metal composite positive electrode material composed of a polymer compound containing copper metal or copper salt and a basic group. The present invention relates to a solid lithium secondary battery which is composed of a positive electrode, a polymer electrolyte, and a negative electrode, which has high energy density and excellent reversible charge / discharge characteristics.

In modern life, batteries are one of the important components of various electronic devices.

The development of electronic communication and computer equipment has led to the rapid spread of mobile devices, and the small secondary batteries used in mobile devices are not only required to have high capacity and long life, but also to be compact and lightweight. Is required.

In order to meet such demands, efforts have been made to use metals with high theoretical capacity as high capacity cathode materials. In particular, many proposals have been made on secondary batteries using copper metal ions as cathode materials.

For example, US Pat. No. 4,945,012 (Bugga, RV, et al) discloses a cell using copper dichloride (CuCl ₂ ) as the positive electrode and sodium (Na) metal as the negative electrode.

In this case, molten salt containing aluminum chloride salt, which is insoluble in copper dichloride, was used as an electrolyte, and a beta alumina ceramic material was used as the separator.

Theoretical capacity of this battery is very high, 1,190 Wh / kg, but it has a disadvantage of working only at a high temperature of 200 ° C or higher.

In addition, U.S. Patent No. 4,844,993 and Electrochemical Journal (J. Electrochem. Soc. 134, 2383, 1987) disclose a lithium secondary battery using copper dichloride as a cathode material and using a liquid electrolyte.

Here, a mixture of lithium aluminum chloride (LiAlCl ₄ ) and sulfur dioxide was used as the liquid electrolyte. Such a liquid electrolyte has an advantage of providing high electrical conductivity, but since the solvent-based battery is solidified according to the change in the component ratio, the conductivity may be reduced or volatilized to generate pressure.

In order to compensate for these disadvantages, US Patent No. 5,024,906 proposes a method of adding an organic solvent such as ethyl chloroformate or sulfolane to the mixed electrolyte. Since the copper salt used as the ash is dissolved and dispersed in the electrolyte, the capacity gradually decreases, and eventually the life of the secondary battery can be reduced.

As the liquid electrolyte is used, a rigid battery structure is required for the prevention of leakage inevitably generated or the control of the internal pressure of the battery by volatilization of the solvent.

Meanwhile, as an example of a method for miniaturizing a secondary battery using a metal as an anode, US Patent No. 4,714,665 discloses a film-type electrode that can be used in a thin film battery.

Herein, the electrode manufactured in the form of a polymer film is proposed to be lightweight and flexible in combination with the polymer electrolyte layer.

In the case of the battery of the type described above, an organic solvent having good solubility in copper salts is used as a plasticizer to accommodate more copper ions, which are active materials in the positive electrode, to increase capacity and improve dispersibility.

However, when a large amount of a flowable plasticizer is included in the electrode, the organic solvent used as the plasticizer is dispersed in the electrolyte layer during repeated charge and discharge, and copper ions may also melt together with the electrolyte, thereby gradually decreasing the life.

As described above, many secondary batteries using copper ions as a cathode material have been proposed, but much improvement is necessary to realize high capacity and secure charge and discharge stability.

An object of the present invention is to solve the shortcomings in a secondary battery using a copper ion as a positive electrode material as described above, including at least one copper metal species selected from a copper metal or copper salt and a polymer compound containing a basic group. The battery can be reversibly charged and discharged by constructing the battery to include the positive electrode manufactured by applying the electrode material to the current collector. Since the battery has a high energy density, the battery can be lightened and it does not contain a liquid electrolyte. There is no problem according to the purpose of providing a lithium polymer secondary battery to enable the production of small and thin batteries according to the use as a solid-type battery.

1 is a graph showing the results of measuring the discharge capacity of each battery manufactured according to Examples 1, 2 and 3 of the present invention,

Figure 2 is a graph showing the results of measuring the discharge capacity according to the number of charge and discharge when the battery prepared according to Example 1 of the present invention at 100% utilization.

Lithium polymer secondary battery comprising a positive electrode made of a metal composite positive electrode material of the present invention for achieving the above object is a copper metal and CuX _n (where X is a halogen anion, sulfur, thiocyanate (SCN) or acid) A positive electrode prepared by applying a composite electrode material composed of at least one copper compound selected from a copper salt of the form and a polymer material containing a basic functional group to a conductive current collector. It is characterized by consisting of an aqueous polymer electrolyte and a negative electrode made of a material selected from lithium metal, lithium alloy (alloy) or a carbon-based material capable of lithium intercalation (intercalation).

The present invention will be described in more detail as follows.

In the present invention, the positive electrode material constituting the positive electrode of the battery is at least one selected from copper salts of copper metal or CuX _n (where X is a halogen anion or a counterbase anion of an acid and n is an integer of 1 or 2). The copper compound is contained as an active material to be reversibly redox.

When the battery is charged, copper metal (Cu) is oxidized to copper ions (Cu ⁺ , Cu ²⁺ ), and when discharged, copper metal is reduced. The potentials at which Cu ⁺ is reduced to copper metal (Cu) and Cu ²⁺ to copper metal (Cu) are 3.57 and 3.39 V (relative to Li / Li ⁺ ) for the lithium electrode, respectively. When using lithium metal species as a negative electrode material can be configured a 3.0V battery. In addition, when the oxidation reaction of the copper metal proceeds to Cu ²⁺ , a theoretical capacity of 843 mAh / g can be expected.

Therefore, the cathode material proposed in the present invention can realize the weight reduction of the lithium secondary battery by adopting copper metal having high energy density as the active material.

On the other hand, the positive electrode material composition of the present invention is a polymer compound having a basic group to be bonded to the copper metal ions generated during the oxidation reaction of the copper metal with the copper metal or copper salt active material as described above to fix the copper metal ions to the electrode It contains.

In other words, the copper metal ions generated by the oxidation of the copper metal during charging are fixed to the electrode by bonding with basic groups contained in the polymer material included in the electrode.

Unlike copper metal, copper metal ions may be dissolved in an organic solvent used in an electrode or an electrolyte, and thus may be dispersed in the electrolyte or released from the conductive material by moving in the electrode, thereby reducing the capacity of the battery when repeated charging and discharging. Can be.

Accordingly, in the present invention, by designing the electrode so that the copper metal or copper salt is dispersed in the polymer matrix containing the basic functional group, the copper metal ion is coordinated to the basic functional group or ions are bonded to the electrode, resulting in dispersion or separation of the active material. It lowers and enables reversible charging and discharging.

In addition, in the case of using a polymer matrix having a basic functional group having affinity with copper metal species, the copper active material may be more contained in the electrode material to maximize the capacity of the electrode, and the copper active material effectively in the electrode material. Can be dispersed.

As a polymer containing a basic functional group capable of forming such a bond, a polymer material containing a functional group including a single or a combination thereof selected from nitrogen, oxygen, sulfur, phosphorus and halogen atoms in the repeating structure of the polymer can be used. have.

More specifically, it contains basic functional groups, such as a halogen, a nitrile, a carboalkoxy, a carbohydroxy, a pyrrolidonyl, a pyridyl group, etc. It is preferable that it is a polymer.

Representative examples of the polymer having a basic functional group include polyacrylate, poly (acrylic acid), polymethyl methacrylate, polyvinylpyrrolidone, poly Acrylonitrile, acrylonitrile-methyl acrylate copolymer, polyvinylidene fluoride (poly (vinylidene fluoride)) having a fluorine group, polyvinylidene chloride ( poly (vinylidene chloride)), polyvinylidene fluoride-hexafluoropropylene copolymer (poly (vinylidenefluoride-co-hexafluoropropylene)) and the like.

In addition, a polymer including an ether, imine, sulfide, and sulfone bond in the polymer main chain may be used as a polymer having a basic functional group. Representative examples of polymers having such basic functional groups include polyethylene oxide, polypropylene oxide, polyethylene imine, polyphenylene sulfide, and polysulfone resin. (polysulfone resin) and the like.

In addition, a conductive polymer compound having electrical conductivity and containing nitrogen, oxygen, or sulfur atoms in the repeating structure of the polymer may be used as the polymer compound having a basic functional group. Such conductive polymers enhance the electron transfer effect on the active material by disposing a copper metal active material around the polymer chain by affinity with the copper metal and forming a conductive network in the electrode material. Representative examples of such conductive polymer materials include polyaniline, polypyrrole, polythiophene, and the like.

In addition, a high molecular compound having an ionic end group can be used. Specifically, there is a metal salt of polystyrene-p-sulfonate.

In addition, in order to complete the cathode material used in the battery, the conductive material may contain conductive carbon black such as acetylene black, and a binder material for producing a polymer film, and an organic solvent may be added to disperse or dissolve the electrode material. Can be. In this case, as the polymer material used as the binder of the cathode material, it is preferable to use a material of the same kind as the host polymer material used in the polymer electrolyte, but a ratio such as EPDM and styrene-butadiene rubber (SBR) is preferable. Ion conductive polymer materials may also be used.

The organic solvent to be added may vary depending on the type of the matrix polymer or the binder, but aprotic solvents may be generally used. Such organic solvents include organic carbonate solvents such as N-methyl-2-pyrrolidone or propylene carbonate and ethylene carbonate.

The positive electrode material mixture prepared according to the above composition is coated on various metal current collectors to prepare a positive electrode. First, the positive electrode material mixture is dispersed by using strong mechanical agitation or ultrasonic agitation in order to improve dispersibility. The positive electrode material mixture is applied on various metal current collectors in paste form.

As the coating method, a mechanical coating method such as simple painting, spin coating, or bar coating may be used. And when an anode material is apply | coated on an electrical power collector, it is preferable to maintain an inert gas atmosphere.

As the current collector of the positive electrode, a conductive support of metal or carbon material may be used, but a current collector made of copper metal or copper alloy is preferably used.

The current collector made of copper metal or copper alloy used in the present invention fixes the voltage below the oxidation potential of the copper metal during charging of the battery, thereby preventing excessive voltage rise, thereby allowing each element of the battery to maintain stability.

When a metal current collector having a lower oxidation potential than that of a copper metal as an active material is used, the metal constituting the current collector may be ionized prior to the copper metal during charging, resulting in a decrease in discharge capacity along with current loss.

The current collector may be used in the form of a thin film, a gauze, a mesh, etc. according to the battery structure.

Therefore, the new positive electrode material composed of a polymer matrix containing a copper metal species and a basic functional group as in the present invention is judged to be useful for a lithium secondary battery at present, but the present invention is not limited to a specific type of battery and, of course, also for a primary battery. Can be used.

The lithium polymer secondary battery of the present invention is composed of a material selected from a cathode, a non-aqueous polymer electrolyte containing a lithium salt, and a material capable of lithium intercalation such as lithium metal, lithium alloy, carbon, and graphite. It consists of a cathode.

Here, the non-aqueous polymer electrolyte is an ion conductive polymer electrolyte, and contains a lithium salt in the form of LiY (where Y is a counterbase anion of an acid) so that Li ⁺ cation precipitates as a metal on the negative electrode during charging or intercalates on the negative electrode material. It can be a migration. In addition, the charge balance of the anode is achieved by supplying or absorbing ions depending on the oxidation state of the anode during charge and discharge.

In the lithium secondary battery of the present invention, an ion conductive non-aqueous polymer electrolyte is used as the electrolyte.

According to the present invention, the non-aqueous polymer electrolyte receives Li ⁺ from the negative electrode and the negative electrode from the positive electrode when the battery is discharged to form a LiY-type lithium salt, and when charged, Li ⁺ moves to the negative electrode again and the Y ⁻ anion It must contain LiY type lithium salt to move to the anode.

These ion conductive non-aqueous polymer electrolytes are composed of lithium salts, polymer compounds, and organic solvents used as plasticizers.

At this time, the lithium salt used is LiBF ₄ , LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiAsCl ₆ . LiSbCl ₆ , LiSbF ₆ or LiN (SO ₂ CH ₃ ) ₂ .

The host polymer material constituting the polymer electrolyte includes polyethylene (poly (ethylene oxide)) and polypropylene oxide (poly (ethylene oxide)) having a functional group containing oxygen, nitrogen, sulfur, etc. to have a chemical affinity for lithium ions. oxide)), polyacrylate, polyacrylonitrile, acrylonitrile-methyl acrylate copolymer (poly (acrylonitrile-co-methyl acrylate)) and fluorinated polyvinylidene fluoride ( poly (vinylidene fluoride)), polyvinylidene fluoride-hexafluoropropylene copolymer (poly (vinylidene fluoride-co-hexafluoropropylene)) and the like.

The amount of lithium salt contained in the non-aqueous polymer electrolyte is controlled so that the ratio of Li ions per monomer of the polymer (Li ⁺ / monomer) is 5 to 50 mol%.

The organic solvent added as a plasticizer contains a carbonate group in a highly polar solvent. Examples thereof include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Etc., It can select from these solvent and can use individually or in combination of 2 or more.

The amount of plasticizer added is preferably 20 to 90% by weight of the total nonaqueous polymer electrolyte.

Finally, a metal material of lithium metal or a lithium alloy may be used as a negative electrode constituting the lithium polymer secondary battery of the present invention. In addition, a carbon-based material such as carbon or graphite capable of intercalating lithium ions may be used. .

In the case of using a lithium metal, lithium ions supplied from the electrolyte are reduced during charging to form lithium metal. In the case of using a carbon-based negative electrode, intercalation of lithium ions occurs during charging. During discharge, lithium ions are generated from the cathode by an oxidation reaction.

Lithium polymer secondary battery according to the present invention has no problem due to leakage due to the solid state of the battery content, and can be used for portable electronic devices used for mobile use because it is light and easy to select an external form according to the use because the simple sealed packaging is possible. The following is advantageous.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

(Manufacture of positive electrode)

1 g of polyvinylpyrrolidone (PVP), 1 g of polyvinylidene fluoride (poly) and 1 g of polyvinylpyrrolidone (PVP) in N-methyl-2-pyrrolidone solvent After adding and melting, 1 g of polyaniline (Versicon, Allied Signal Corp.), 7 g of copper salt powder (CuSCN), and 2 g of acetylene black were added thereto.

Then, the resulting mixture was stirred for 2 days or more to sufficiently mix.

The cathode material mixture thus obtained was applied on a copper metal thin film current collector in an argon gas atmosphere, and then dried under vacuum at 60 to 80 ° C. to prepare a positive electrode. The copper salt content was 58.3% in the total composition of the positive electrode.

(Preparation of negative electrode)

Lithium metal plate (battery grade) having a thickness of 150 ~ 700㎛ is used as a negative electrode stored in an argon gas atmosphere without further purification process.

(Production of non-aqueous polymer electrolyte)

3.0 g of acrylonitrile-methyl acrylate copolymer (94: 6) and 2.3 g of LiBF ₄ were heated to 120 to 140 ° C. under nitrogen or argon gas atmosphere to obtain propylene carbonate and ethylene carbonate. After dissolving in a mixed solvent (10.5: 7.9 weight ratio), the product was cast on a glass plate and heated to 60 to 80 ° C to prepare a film.

The ion conductivity of the prepared polymer electrolyte membrane was 10 ^-3 to 10 ^-4 S / cm as a result of impedance measurement.

(Assembly of measurement battery)

Using the cathode material, the polymer electrolyte membrane, the lithium thin film negative electrode, the current collector for the positive electrode of the copper metal thin film, and the current collector for the nickel metal mesh negative electrode, the stacked measurement cell without liquid electrolyte was constructed. .

Example 2

0.5 g of polysulfone resin (PSR), 0.5 g of poly (vinylidene fluoride), and 0.5 g of polysulfone resin (PSR) in N-methyl-2-pyrrolidone solvent After melting, 0.5 g of polyaniline (Versicon, Allied Signal Corp.), 3.5 g of copper salt powder (CuSCN), and 1 g of acetylene black were added.

Then, the resulting mixture was stirred for 2 days or more to sufficiently mix.

The cathode material mixture thus obtained was applied onto a copper metal thin film current collector in an argon gas atmosphere, and then dried under vacuum at 60 to 80 ° C. to prepare a positive electrode. The copper salt content is 58.3% of the total anode composition.

Using the positive electrode thus obtained, a stacked measurement battery was constructed through the same assembly process as in Example 1 above.

Example 3

0.5 g of polyethylene oxide (PEO), 0.5 g of poly (vinylidene fluoride), N-methyl-2-pyrrolidone solvent After dissolving in the mixture, 0.5 g of polyaniline (Versicon, Allied Signal Corp.), 3.5 g of copper salt powder (CuSCN), and 1 g of acetylene black were added thereto.

Then, the resulting mixture was stirred for 2 days or more to sufficiently mix.

The cathode material mixture thus obtained was applied onto a copper metal thin film current collector in an argon gas atmosphere, and then dried under vacuum at 60 to 80 ° C. to prepare a positive electrode. The copper salt content was 58.3% in the total composition of the positive electrode.

Using the positive electrode thus obtained, a stacked measurement battery was constructed through the same assembly process as in Example 1.

Experimental Example

The stacked batteries assembled according to Examples 1, 2, and 3 were stored under argon gas atmosphere, and charged and discharged by setting a potential window of 1.8 to 4.5 V (for Li / Li ⁺ ) at a constant current / voltage condition at room temperature. Was done.

Charge and discharge curves of the battery prepared in Example 1 and the batteries prepared in Examples 2 and 3 are shown in FIG. 1.

Specifically, FIG. 1 illustrates discharge curves of the cathode active materials included in the composite cathode material composition of the battery manufactured through the examples after being charged at a utilization rate of 50% based on the theoretical capacity.

It can be seen from FIG. 1 that all of the batteries manufactured through the examples show almost similar discharge curve shapes, discharge capacities, and discharge voltages.

In FIG. 2, the charge and discharge curves that appear when the battery manufactured according to Example 1 is charged at 100% of the utilization rate with respect to the theoretical capacity of the cathode active material (CuSCN) are shown by the number of charge and discharge cycles.

Even when the utilization rate for the copper metal active material is 100%, the charge and discharge efficiency reaches about 90% or more, and shows a stable charge and discharge curve without significant change even after repeated charge and discharge.

In addition, the discharge average potential was 2.8 V, and the discharge capacity and the energy density were 240 mAh / g-cathode and 680 mWh / g-cathode, respectively.

As the results of Figs. 1 and 2 illustrate, in the case of including high molecular compounds such as polyvinylpyrrolidone, polysulfone resin or polyethylene oxide having a basic functional group in the cathode material together with a copper salt, It can be seen that the electrode has a very high reversibility and reproducibility during repeated charging and discharging, and the high-density discharge capacity of the active material is ensured.

In addition, by adopting the copper metal as the current collector for the positive electrode to fix the voltage below the oxidation potential of the copper metal during the charging of the battery to prevent excessive voltage rise, each element of the battery can maintain the stability.

As described in detail above, according to the present invention, a composite electrode material composed of a copper metal or a copper salt and a polymer material containing a basic group is prepared to include a positive electrode formed by applying a current collector made of copper metal or a copper alloy. Lithium secondary battery has good reversibility during charging and discharging and has high energy density so that it is possible to reduce the weight of the battery. Since it does not contain liquid electrolyte, there is no problem due to leakage. There are advantages such as thin battery manufacturing.

Claims (11)

At least one copper compound selected from a copper salt in the form of a copper metal and CuX _n (where X is a halogen anion, sulfur, thiocyanate (SCN) or a counter-anion of an acid and n is an integer of 1, 2); A positive electrode manufactured by applying a composite electrode material composed of a polymer material containing a basic functional group in a repeating structure to a current collector, Non-aqueous polymer electrolyte, and Lithium polymer secondary battery comprising a positive electrode made of a metal composite positive electrode material consisting of a negative electrode made of a material selected from lithium metal, lithium alloy (alloy) or lithium intercalation (carbon-based material). 2. The lithium battery of claim 1, wherein the basic functional group is selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a halogen atom, or a combination of atoms thereof. Polymer secondary battery. The method of claim 1, wherein the basic functional group is a halogen, nitrile, carboalkoxy, carbohydroxy, pyrrolidonyl and pyridyl groups Lithium polymer secondary battery comprising a positive electrode made of a metal composite positive electrode material, characterized in that selected from the group. According to claim 1 or 3, wherein the polymer compound containing a basic functional group is polyacrylate (polyacrylate), poly (acrylic acid), polymethyl methacrylate (poly (methyl methacrylate)), polyvinyl Pyrrolidone (polyvinylpyrrolidone), polyacrylonitrile, acrylonitrile-methyl acrylate (poly (acrylonitrile-co-methyl acrylate)), polyvinylidene fluoride (poly) A positive electrode made of a composite metal cathode material, characterized in that selected from the group consisting of poly (vinylidene chloride) and polyvinylidene fluoride-hexafluoropropylene copolymer (poly (vinylidene fluoride-co-hexafluoropropylene)) Lithium polymer secondary battery containing. The lithium polymer of claim 1, wherein the basic functional group is selected from the group consisting of ether, imine, sulfide, and sulfone. Secondary battery. According to claim 1 or 5, wherein the polymer compound containing a basic functional group is polyethylene (poly (ethylene oxide), polypropylene oxide (poly (propylene oxide), polyethylene imine (poly (ethylene imine)), poly Lithium polymer secondary battery comprising a positive electrode made of a metal composite cathode material, characterized in that selected from the group consisting of phenylene sulfide (poly (phenylene sulfide)) and polysulfone resin (poly (sulfone resin)). According to claim 1, wherein the polymer compound containing a basic functional group is lithium containing a positive electrode made of a metal composite cathode material, characterized in that selected from the group consisting of polyaniline (polyaniline), polypyrrole (polypyrrole) and polythiophene (polythiophene) Polymer secondary battery. The lithium polymer secondary battery of claim 1, wherein the high molecular compound including the basic functional group is a metal salt of polystyrene-p-sulfonate. The lithium polymer secondary battery of claim 1, wherein the conductive current collector is made of a copper metal or a copper alloy. The method of claim 1, wherein the non-aqueous polymer electrolyte is a lithium containing lithium anode (wherein Y is a counter-anion of an acid), a lithium compound comprising a positive electrode made of a metal composite cathode material, characterized in that consisting of a high molecular compound and an organic solvent Polymer secondary battery. The lithium polymer secondary battery of claim 1, wherein the lithium-based intercalation-based carbon-based material is carbon or graphite.