JP5414371B2 - Manufacturing method of all-solid-state lithium ion secondary battery - Google Patents

Description

  The present invention relates to a method for producing an all-solid lithium ion secondary battery.

In recent years, there has been a strong demand for a secondary battery that can be used for a long time, is small in size and light in weight, and has high safety, with an increase in functionality of a mobile phone, a PDA, a notebook personal computer, and the like.
However, a lithium secondary battery containing a flammable organic solvent that has been used conventionally has a risk of liquid leakage or ignition during overcharge or abuse. Therefore, ensuring the safety has been an important issue as the energy density of batteries increases.

  Research and development of an all-solid-state lithium ion secondary battery that uses a solid electrolyte that is chemically stable and has no leakage or ignition problems compared to organic electrolytes as a battery to solve these problems. It has been broken.

  By the way, as a manufacturing method of the all-solid-state lithium ion secondary battery, a method of pressurizing powder of a battery constituent material into a pellet form (for example, Patent Document 1) and a battery constituent material mixed in a solvent and applied. A method (for example, Patent Document 2) is known.

JP 2008-257932 A JP 2008-243560 A

  By the way, in the method in which the powder of the material constituting the battery is pressed into a pellet form, only a small area and a thick shape can be manufactured so that the pellet does not crack. There has been a problem that the thinning / upsizing required for increasing the capacity / capacity cannot be realized.

  In addition, in the method of applying the constituent materials of the battery in a solvent, there is a problem that impurities such as a residue or a binder remaining after the solvent is dried impedes ionic conductivity, resulting in hindering improvement in battery performance.

  Therefore, an object of the present invention is to provide a method for producing an all-solid-state lithium ion secondary battery capable of realizing thinning / enlarging necessary for high performance / high capacity of a lithium ion battery.

In order to solve the above-described problem, a manufacturing method of an all-solid-state lithium ion secondary battery according to claim 1 of the present invention includes a lithium ion solid electrolyte disposed between a positive electrode material and a negative electrode material, and each of these electrode materials. A method for producing an all-solid-state lithium ion secondary battery in which current collectors are respectively disposed on outer surfaces,
When the electrode material layer and the solid electrolyte layer are formed by sequentially spraying the electrode material and the solid electrolyte powder material onto the surface of the current collector with the carrier gas, the electrode material and the solid electrolyte powder material are charged. This is a method of spraying.

Moreover, the manufacturing method of the all-solid-state lithium ion secondary battery which concerns on Claim 2 is a method of using inert gas as carrier gas in the manufacturing method of Claim 1.
Moreover, the manufacturing method of the all-solid-state lithium ion secondary battery which concerns on Claim 3 is a method using the inert gas whose dew point is -80 degrees C or less in the manufacturing method of Claim 1 or 2.

  A method for producing an all-solid-state lithium ion secondary battery according to claim 4 is a method using a sulfide-based inorganic solid electrolyte as the solid electrolyte in the production method according to any one of claims 1 to 3.

  Furthermore, the manufacturing method of the all-solid-state lithium ion secondary battery which concerns on Claim 5 is a manufacturing method in any one of Claims 1 thru | or 4. WHEREIN: After formation of an electrode material layer and a solid electrolyte, it is pressurized and charged. Is a method of removing static electricity.

  According to the manufacturing method of claim 1, when the electrode material layer and the solid electrolyte layer are formed by spraying the electrode material and the solid electrolyte powder material onto the surface of the current collector with a carrier gas, Since the electric charge is charged and sprayed on the material and the powder material of the solid electrolyte, a powder layer is formed with a uniform thickness, and the pressure at the time of molding press is applied to the whole, so the pellet molding method Thus, since cracking due to pressurization does not occur, it is possible to reduce the film thickness and increase the size necessary for high performance / high capacity lithium ion secondary batteries. Further, since additives such as a solvent and a binder are unnecessary, battery performance is not deteriorated due to residual impurities.

Furthermore, since the powder material is charged with electric charge and sprayed, the adhesion between the current collector and the electrode material and between the electrode material and the solid electrolyte is increased, and the battery performance can be improved.
Moreover, according to the manufacturing method of Claims 2-4, since it was made to remove | eliminate a water | moisture content so that the dew point might be -80 degrees C or less while using inert gas for conveyance gas, It is possible to prevent the solid electrolyte, for example, the sulfide-based inorganic solid electrolyte material powder from reacting with each other, and thus it is possible to prevent the battery performance from deteriorating. In particular, in an all-solid-state lithium ion secondary battery using a sulfide-based inorganic solid electrolyte in which deterioration of battery performance due to moisture is particularly remarkable, thinning / enlargement necessary for high performance / high capacity is possible.

  Further, according to the manufacturing method of the fifth aspect, since the electric charge charged after pressurization is removed, the electric resistance of the powder increased by the charging is lowered, so that the battery performance can be improved.

It is a perspective view which shows schematic structure of the lithium ion secondary battery which concerns on the Example of this invention. It is a figure which shows schematic structure of the electrostatic film forming apparatus used for the manufacturing method of the lithium ion secondary battery which concerns on the Example of this invention. It is principal part sectional drawing of the electrostatic film forming apparatus. It is principal part sectional drawing explaining the manufacturing method of the lithium ion secondary battery of this invention. It is the graph which compared the charging / discharging characteristic of the lithium ion secondary battery.

Hereinafter, the manufacturing method of the all-solid-state lithium ion secondary battery which concerns on embodiment of this invention is demonstrated based on the Example specifically shown.
First, the configuration of the all solid lithium ion secondary battery will be described.

The all-solid-state lithium ion secondary battery according to this example is generally composed of a positive and negative current collector, a positive and negative electrode material layer, and a solid electrolyte layer.
As the current collector, a plate-like body or foil-like body made of copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, lithium, tin, or an alloy thereof, or the like Powder or the like is used. In addition to these, films formed from various materials can be used.

  A lithium ion conductive solid material is used as the solid electrolyte. That is, a lithium ion solid electrolyte is used. The lithium ion conductive solid substance is not particularly limited, and for example, a material composed of an organic compound, an inorganic compound, or both an organic / inorganic compound can be used, and a known material in the lithium ion battery field can be used. it can. In particular, it is known that sulfide-based inorganic solid electrolytes have higher ionic conductivity than other inorganic compounds.

Moreover, as a positive electrode material, what is used as a positive electrode active material in the battery field | area can be used. For example, in the oxide system, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and the like. On the other hand, as a negative electrode material, what is used as a negative electrode active material in the battery field | area can be used. For example, natural graphite, artificial graphite, graphite carbon fiber, resin-fired carbon, or the like can be used.

  By the way, in order to improve the ionic conductivity (also ionic conductivity) in addition to the electronic conductivity, the solid electrode material has many particles and contact points between the particles. Thus, it is important to secure more ion conduction paths. Therefore, an electrode mixture obtained by mixing an ion conductive active material such as an electrolyte is used. Therefore, as the electrode material, a material in which a lithium ion solid electrolyte is mixed with an electrode active material (so-called positive electrode mixture, negative electrode mixture) is used. This mixing ratio is appropriately adjusted according to the design of the electrode.

In FIG. 1, the schematic diagram of the all-solid-state lithium ion secondary battery which concerns on a present Example is shown.
In this all solid lithium ion secondary battery (hereinafter, also simply referred to as a secondary battery), a lithium ion solid electrolyte 3 is disposed (laminated) between the negative electrode material 1 and the positive electrode material 2, and the solid of the negative electrode material 1 A negative electrode current collector 4 is disposed (laminated) on the surface opposite to the electrolyte 3, and a positive electrode current collector 5 is disposed on the surface of the positive electrode material 2 opposite to the solid electrolyte 3.

Hereinafter, the manufacturing method of an all-solid-state lithium ion secondary battery is demonstrated.
Briefly explaining this production method, an inert gas [a carrier gas (also referred to as a carrier gas), specifically nitrogen gas is used] which is controlled so that the water content is a dew point of −80 ° C. or lower. Is used for conveying and spraying (spraying) powder material, and on one surface of the negative electrode current collector (or positive electrode current collector), A manufacturing method in which solid electrolyte powder materials are sequentially deposited to form a film, and in brief, a manufacturing method of a battery using an electrostatic method.

Here, the manufacturing method of an all-solid-state lithium ion secondary battery is demonstrated based on drawing.
As described above, this manufacturing method performs film formation using an electrostatic method. First, an electrostatic film forming apparatus for performing an electrostatic method, that is, used in an electrostatic film forming process will be described. .

  As shown in FIG. 2 and FIG. 3, the electrostatic film forming apparatus 11 has a material supply passage 12a through which a powder material can be supplied and a material ejection nozzle (also called a spray nozzle) whose tip is narrowed. 12), a material supply device 14 connected to the ejection nozzle 12 via a material supply pipe 13, and a carrier gas via a gas supply pipe 15 in the middle of the material supply device 14 and the material supply pipe 13. A gas supply device (for example, a gas holder) 16 for supplying the inert gas G to the injection nozzle 12 with the powder material supplied from the blowing material supply device 14 and the injection nozzle 12 inserted therein. The needle-like electrode 17, the plate-like counter electrode 18 provided at a position facing the tip opening 12 b of the ejection nozzle 12 and at a predetermined distance, and both of these electrodes High voltage between 17 and 18, for example, and a DC power source 19. for applying a DC electric 20～100KV (range). In addition, the supply location of the inert gas G is made into the two places of the inlet side of the material supply apparatus 14, and an exit side so that supply of a powder material can be performed reliably.

Next, a more specific manufacturing method of the all solid lithium ion secondary battery will be described with reference to FIG.
First, as shown in FIG. 4A, a mask material for disposing any electrode current collector, for example, the negative electrode current collector 4 on the upper surface of the counter electrode 18 and forming the negative electrode material 1 on the upper surface. 21 is arranged.

  A high-voltage direct current electricity of 20 to 100 kV is applied between the counter electrode 18 and the needle electrode 17 by a direct current power source 19, and the powder negative electrode material 1 is formed by the material supply device 14 and the gas supply device 16. Is guided to the ejection nozzle 12 by the inert gas G and ejected from the tip opening 12b onto the surface of the negative electrode current collector 4 (if sprayed), the negative electrode material is generated by corona discharge generated between the electrodes 17 and 18. 1 is charged with a charge (positive charge), and the negative electrode material 1 adheres to the surface of the negative electrode current collector 4 due to the Coulomb force acting on the charged charge. As shown in FIG. A negative electrode material 1 having a predetermined thickness is formed on the surface of the current collector 4. That is, the negative electrode material 1 is formed by the electrostatic method, that is, the principle of electrostatic coating.

  In other words, the tip of the needle electrode 17 in the ejection nozzle 12 and the counter electrode 18 are sufficiently separated from each other, so that they are supplied into the ejection nozzle 12 by corona discharge generated between the electrodes 17 and 18. The charged powder material is charged, and the charged powder material is attracted to the counter electrode 18 by the Coulomb force, so that the powder material is formed on the counter electrode 18 side. Note that the counter electrode 18 itself may be a negative electrode current collector (or a positive electrode current collector).

  Next, the laminate in which the negative electrode material 1 is formed on the negative electrode current collector 4 is moved to the next step, and lithium ion fixation is performed on the surface of the negative electrode material 1 by the electrostatic film forming apparatus similar to that described above. The electrolyte 3 is formed.

  That is, as shown in FIG. 4C, after disposing the mask material 22 for forming the solid electrolyte 3 on the upper surface of the negative electrode material 1, the solid electrolyte supplied from the material supply device of the electrostatic film forming apparatus. The rim ion solid electrolyte 3 having a predetermined film thickness is formed by an electrostatic method.

  Next, as shown in FIG. 4 (d), the laminate in which the lithium ion solid electrolyte 3 is formed on the upper surfaces of the negative electrode current collector 4 and the negative electrode material 1 is moved to the next step, and the above-described one is also used. The positive electrode material 2 is formed on the surface of the solid electrolyte 3 by the same electrostatic film forming apparatus.

  That is, as shown in FIG. 4 (e), after the mask material 23 for forming the positive electrode material 2 as the other electrode is disposed on the upper surface of the solid electrolyte 3, the material supply device of the electrostatic film-forming apparatus is not used. The powder material of the positive electrode material 2 supplied by the active gas is ejected from the ejection nozzle 12, and the positive electrode material 2 having a predetermined film thickness is formed by an electrostatic method.

  Next, the laminate (shown in FIG. 4 (f)) in which the negative electrode material 1, the lithium ion solid electrolyte 3 and the positive electrode material 2 are sequentially formed on the upper surface of the negative electrode current collector 4 is moved to the next press molding step. Then, the surface is pressed with a predetermined pressure by, for example, a single-action press (or a roll press). By this press molding, the contact property between powders (particles) is enhanced, and the electron / ion conductivity is improved.

Further, the positive electrode current collector 5 is placed on the upper surface of the positive electrode material 2 of the laminate obtained as described above to obtain a substantially completed battery.
Finally, the substantially completed secondary battery is inserted into a thermocompression-bonded laminate film and sealed while sucking the internal gas, whereby a finished product of the secondary battery is obtained. By this sealing, the compactness at the time of charging / discharging is enhanced, and a solid electrolyte, for example, a sulfide-based solid electrolyte that changes by reacting with moisture is protected from the atmosphere. In addition, since a very small amount of gas in the constituent material is discharged to the outside by the applied pressure, it is desirable to pressurize in the direction perpendicular to the laminate film when the gas in the laminate film is sucked.

  Note that the openings of the mask material are sequentially sized so that a predetermined upper layer portion can be formed on the upper surface of the lower layer portion. For example, the opening of the mask material 21 that forms the negative electrode material 1 is made smaller than the negative electrode current collector 4, and the mask that forms the solid electrolyte layer 3 that conducts lithium ions and electrically separates the positive electrode and the negative electrode. The opening of the material 22 is made slightly larger than the negative electrode material 1, and the opening of the mask material 23 forming the positive electrode material 2 is made smaller than the solid electrolyte 3 and the same size as the negative electrode material 1. .

  By the way, in the said manufacturing process, although the press-molding process which press-forms after forming the positive electrode material 2 into a film is arrange | positioned, in other words, in the state which match | combined the three layers of the negative electrode material 1, the solid electrolyte 3, and the positive electrode material 2. Although described as performing press molding, after film formation for each layer, that is, after the negative electrode material 1 is formed on the negative electrode current collector 4 and after the solid electrolyte 3 is formed on the negative electrode material 1, Each may be provided with a pressure forming step.

  As described above, an inert gas such as nitrogen gas is used as the carrier gas for supplying the powder material in order to prevent alteration of the film forming material, and a sulfide solid electrolyte is used as the solid electrolyte. In this case, the sulfur component contained is very easy to react with moisture, and since the contact with the carrier gas is particularly large, it is necessary to limit the moisture contained in the carrier gas to a trace amount as much as possible. It is made to become -80 degrees C or less.

Furthermore, when transporting a mixture of two or more types of materials, for example, materials having different particle diameters, shapes, specific gravity, and the like, using a carrier gas, a material supply device that is a mixing unit and an ejection nozzle If the distance between them is long, a predetermined mixing ratio may not be obtained, or the mixing ratio may be different between the upper part and the lower part of the film forming layer. For this reason, the tetrafluoroethylene resin ( Teflon : registered trademark) is used instead of the material supply tube having flexibility as used in electrostatic coating while keeping the material supply device and the ejection nozzle as close as possible. It is necessary to use a hard tube or piping with good fluidity.

  Furthermore, the voltage applied during electrostatic film formation is generally 20 to 100 kV, and the higher the voltage, the greater the charge applied to the powder material and the greater the adhesion. On the other hand, when the voltage is low, the adhesive force is reduced, so that the material adhered by the carrier gas discharged at the same time is removed from a certain film thickness. For this reason, in the film formation of the same material using the same carrier gas and opposite height, the film thickness that can be formed can be controlled by the magnitude (height) of the applied voltage.

  In general spray-type electrostatic film coating for the purpose of rust prevention and aesthetics, the required performance does not vary greatly depending on the difference in film thickness. It has a big impact.

Therefore, the film thickness can be controlled more precisely than before by the following method.
That is, when a certain film is formed (when a single layer is formed), the film forming process is performed twice, and the film thickness is measured as an intermediate process. If it demonstrates concretely, film-forming will be performed on the conditions that predetermined | prescribed film thickness of 80 to 90% is obtained by film-forming of the 1st time. Since the film thickness can be controlled with an accuracy of about ± 10% with respect to a predetermined film thickness in one film formation, the film thickness measurement performed after the first film formation is received for the second time. By performing the film formation, the finally obtained film thickness accuracy is ± 1 to 2% with respect to a predetermined one.

Here, the result of comparing the performance of the secondary battery according to this example and the conventional pellet type secondary battery will be described.
The pellet type secondary battery requires about 475 μm in total thickness of the solid electrolyte and the positive electrode material (which is a positive electrode mixture) in order to stably operate as a battery without cracking, and its size is large. Also, about φ10 is required.

  By the way, in the lithium ion secondary battery, it is important to make the positive and negative electrodes as close as possible in order for lithium ions to move in the battery (in a battery using a normal organic electrolyte, it is about 200 μm). .

  On the other hand, in an all-solid-state lithium ion battery using a solid electrolyte as a lithium ion conductor, the ionic conductivity is lower than that of a liquid battery. Therefore, it is necessary to further reduce the distance between positive and negative electrodes as compared with a liquid battery.

Hereinafter, a comparison between a thin battery manufactured by the manufacturing method of this example and a battery by the above-described pellet molding method will be described.
In the battery according to this example, both the solid electrolyte layer and the positive electrode material layer are formed by the electrostatic method, whereas the pellet method battery does not use the electrostatic method, but the thickness of the solid electrolyte layer Other than that, the battery has the same configuration as that of the battery according to this example. And here, the battery performance by the thickness of a solid electrolyte layer is compared.

In both of these performance tests, an indium foil having a thickness of 100 μm was used as a negative electrode, and the indium foil as a negative electrode was placed on a stainless steel plate having a negative electrode current collector, and a solid electrolyte powder was formed thereon by an electrostatic method. To do. The thickness of the solid electrolyte at this time is 79 μm after pressure molding. Then, a positive electrode material is formed thereon by an electrostatic method. The thickness of the positive electrode material at this time was 43 μm after pressure molding. In the battery by the pellet molding method, the thickness of the solid electrolyte is 405 μm, and the thickness of the positive electrode material is 43 μm (same as the battery according to this example). Further, the pressure molding force at this time is the same as 255 MPa (2.6 t / cm ² ). Both are governed by a pressure jig, and a charge / discharge test is performed in a state where a pressure of 78.5 MPa (800 kg / cm ² ) is applied, and the capacities are compared. FIG. 5 shows the results when the charging current is 0.5 mA / cm ² and the discharging current is 2.0 mA / cm ² .

  As shown in FIG. 5, the pellet molded battery had a capacity per positive electrode weight of about 97 mAh / g, whereas the battery of this example (the product of the present invention) achieved a capacity of 120 mAh / g. . That is, it can be clearly seen that the battery performance is improved.

  In the above embodiment, the negative electrode material, the solid electrolyte, and the positive electrode material are formed in this order on the negative electrode current collector. On the contrary, the positive electrode material and the solid material are formed on the positive electrode current collector. The electrolyte may be formed in the order of the negative electrode material, and the polarity of the DC power source applied to the powder material may be reversed during manufacture (in the drawing, the needle electrode side is connected to the positive electrode of the power source). Or may be connected to the negative electrode).

DESCRIPTION OF SYMBOLS 1 Negative electrode material 2 Positive electrode material 3 Solid electrolyte 4 Negative electrode collector 5 Positive electrode collector 11 Electrostatic film-forming apparatus 12 Nozzle 13 for ejection 13 Material supply piping 14 Material supply device 15 Gas supply piping 16 Gas supply device 17 Needle-shaped electrode 18 Counter electrode 19 DC power supply

Claims (5)

A method for producing an all-solid-state lithium ion secondary battery in which a lithium ion solid electrolyte is disposed between a positive electrode material and a negative electrode material, and a current collector is disposed on the outer surface of each of these electrode materials,
When the electrode material layer and the solid electrolyte layer are formed by sequentially spraying the electrode material and the solid electrolyte powder material onto the surface of the current collector with the carrier gas, the electrode material and the solid electrolyte powder material are charged. A method for producing an all-solid-state lithium ion secondary battery, characterized by being sprayed.   2. The method for producing an all-solid-state lithium ion secondary battery according to claim 1, wherein an inert gas is used as the carrier gas.   The method for producing an all-solid-state lithium ion secondary battery according to claim 1, wherein an inert gas having a dew point of −80 ° C. or lower is used.   The method for producing an all-solid-state lithium ion secondary battery according to any one of claims 1 to 3, wherein a sulfide-based inorganic solid electrolyte is used as the solid electrolyte.   5. The method for producing an all-solid-state lithium ion secondary battery according to claim 1, wherein after forming the electrode material layer and the solid electrolyte layer, pressure is applied and the charged electric charge is removed.

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