JP2012248320A - Electrode manufacturing method, battery manufacturing method, electrode and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode manufacturing method in which a manufacturing process is simplified, a battery manufacturing method, an electrode of which the internal resistance is reduced by reducing materials which are not contributed to capacity, and a battery comprising the electrode.SOLUTION: Powder of an active substance raw material and resin powder is mixed and a mixture is calcined in an inactive atmosphere. An active substance is sintered, a resin is thermally decomposed and voids are generated, thereby generating a porous active substance sintered body 11. Next, the active substance sintered body 11 is immersed in molten aluminum, thereby filling the active substance sintered body 11 with molten aluminum. The active substance sintered body 11 filled with molten aluminum is cooled. Molten aluminum is solidified by cooling, thereby manufacturing a positive electrode (electrode) 1 in which the active substance sintered body 11 is integrated with an aluminum continuum 12 in which solidified metal aluminum is distributed continuously.

Description

  The present invention relates to an electrode manufacturing method, a battery manufacturing method, an electrode, and a battery used in a battery.

In recent years, power generation using natural energy such as sunlight or wind power has been promoted as means for generating electric power without discharging carbon dioxide. In the case of power generation using natural energy, power generation is often affected by natural conditions such as climate or weather, and it is difficult to adjust the power generation to meet the power demand. It becomes. In order to level the power supply by charging and discharging, a high-energy density, high-efficiency, large-capacity storage battery is required.
As such a storage battery, a sodium-sulfur battery disclosed in Patent Document 1 has been developed. A sodium-sulfur battery is usually required to operate at a high temperature of 280 ° C. or higher. On the other hand, development of a storage battery that operates at a room temperature or a relatively low temperature of 130 ° C. or less is underway, and an attempt has been made to use a molten salt that melts at a relatively low temperature in addition to an organic electrolyte as an electrolyte (for example, , See Patent Document 2).

JP 2007-273297 A JP 2007-273362 A

The molten salt battery is a battery using a molten salt as an electrolyte, and operates in a state where the molten salt is melted. From the viewpoint of the electrochemical stability of the electrolyte, it is preferable to use an electrolyte that uses sodium ions such as NaFSA (sodium-bisfluorosulfonylamide) as a charge carrier. The positive electrode of the molten salt battery has a composite oxide such as NaCrO ₂ that exchanges electric charge with an electrolyte as a main component of the active material. A conventional positive electrode is manufactured by adding an organic solvent to an active material produced as a powder to form a paste, applying the pasted active material to a current collector made of a conductive material such as aluminum, and drying the paste. Since the active material is produced as a powder, it is necessary to mix a binder in order to form the active material into the shape of an electrode. In addition, since the active material itself is an insulator, it is necessary to mix a conductive additive in order to ensure conductivity in the positive electrode. Thus, there are many processes in the manufacturing process of the positive electrode, and there is a problem that the manufacturing cost of the positive electrode becomes high.

  Further, since the powdered active material and the conductive aid are mixed in the positive electrode, the contact area between the active material, the conductive aid and the current collector is small, and the internal resistance is large. For this reason, there exists a problem that high-speed charging / discharging becomes difficult. Further, since the conductive assistant and binder contained in the positive electrode do not contribute to the capacity of the battery, there is a problem that the capacity of the battery is reduced by the amount of the mixed conductive assistant and binder.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrode manufacturing method, a battery manufacturing method, and a capacity that simplify a manufacturing process by solidifying an active material with a conductive material. It is an object of the present invention to provide an electrode in which the internal resistance is reduced by reducing substances that do not contribute to the battery, and a battery including the electrode.

  An electrode manufacturing method according to the present invention is a method for manufacturing a battery electrode, wherein a porous sintered body in which an active material is sintered is produced, a liquid conductive material is filled in the sintered body, and the filled conductive material is produced. It is characterized by solidifying the material.

  In the electrode manufacturing method according to the present invention, a sintered body is prepared by compressing a mixture obtained by mixing active material raw material powder and resin powder, and firing the formed body in an inert atmosphere. It is characterized by generating a body.

  The electrode manufacturing method according to the present invention uses a molten metal as a liquid conductive material, immerses the sintered body in the molten metal, fills the sintered body with the molten metal, and fills the sintered metal with the molten metal. It cools in order to solidify a structure, It is characterized by the above-mentioned.

  The electrode manufacturing method according to the present invention is characterized in that the molten metal is molten metallic aluminum.

  The electrode manufacturing method according to the present invention is characterized in that the active material is sodium chromite.

  The battery manufacturing method according to the present invention is characterized in that a battery is assembled using the electrode manufactured by the electrode manufacturing method according to the present invention as one electrode.

  The electrode according to the present invention is a battery electrode, in which a conductive material is filled in a porous sintered body in which an active material is sintered, and the conductive material forms a continuous body continuously distributed in the sintered body. It is characterized by being.

  The battery according to the present invention includes the electrode according to the present invention.

  The battery according to the present invention is characterized in that a molten salt is used as an electrolyte.

  In the present invention, a porous active material sintered body in which an active material is sintered is filled with a liquid conductive material, and the conductive material is solidified, whereby a continuous body in which the active material sintered body and the conductive material are solidified is obtained. Is manufactured. By integrating the sintered body of the active material and the continuous material of the conductive material, the electrode is formed without a binder.

  In the present invention, the active material raw material powder and the resin powder are mixed and molded, and the molded body is fired in an inert atmosphere so that the active material is sintered, and the resin is thermally decomposed to cause voids. As a result, a porous active material sintered body is generated.

  Further, in the present invention, the active material sintered body is immersed in the molten metal to fill the active material sintered body with the molten metal, and the active material sintered body is cooled, so that the molten metal is solidified and the active material A continuous metal body is produced which is integrated with the sintered body.

  In the present invention, metal aluminum is used as the molten metal, and the electrode is produced at a relatively low temperature.

  In the present invention, sodium chromite having high reduction resistance is used as the active material of the electrode.

  In the present invention, no binder is required for the electrode, and the manufacturing process of the electrode is simplified, so that the manufacturing costs of the electrode and the battery are reduced. In addition, since the contact area between the active material and the conductive material in the electrode is larger than in the conventional case, charging / discharging can be performed at a higher speed than in the conventional case. In addition, the present invention has excellent effects such as an increase in volumetric energy density and an increase in battery capacity as compared with a conventional battery in which a binder is included in the electrode.

It is typical sectional drawing which shows the structural example of the molten salt battery which is an example of the battery of this invention. It is explanatory drawing explaining the manufacturing method of a positive electrode. It is a typical sectional view of an active material sintered compact. It is a typical sectional view of a positive electrode.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a schematic cross-sectional view showing a configuration example of a molten salt battery which is an example of the battery of the present invention. FIG. 1 shows a schematic cross-sectional view of a molten salt battery cut longitudinally. In the molten salt battery, a rectangular plate-shaped positive electrode 1, a sheet-shaped separator 3, and a rectangular plate-shaped negative electrode 2 are arranged side by side in a rectangular parallelepiped box-shaped battery container 51 whose upper surface is open, and a lid portion is placed on the battery container 51. 52 is attached. The battery container 51 and the lid 52 are made of aluminum. The positive electrode 1 and the negative electrode 2 are formed in a rectangular flat plate shape, and the separator 3 is formed in a sheet shape. The separator 3 is interposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the separator 3, and the negative electrode 2 are stacked and arranged vertically with respect to the bottom surface of the battery container 51.

  A spring 41 made of corrugated metal is disposed between the negative electrode 2 and the inner wall of the battery case 51. The spring 41 is made of an aluminum alloy and biases a flat plate-like presser plate 42 having inflexibility to press the negative electrode 2 toward the separator 3 and the positive electrode 1 side. The positive electrode 1 is pressed by the reaction of the spring 41 from the inner wall opposite to the spring 41 to the separator 3 and the negative electrode 2 side. The spring 41 is not limited to a metal spring or the like, and may be an elastic body such as rubber, for example. When the positive electrode 1 or the negative electrode 2 expands or contracts due to charge / discharge, the volume change of the positive electrode 1 or the negative electrode 2 is absorbed by the expansion and contraction of the spring 41.

The positive electrode 1 includes an active material sintered body 11 obtained by sintering a positive electrode active material containing NaCrO ₂ (sodium chromite) as a component and an aluminum continuous body 12 in which metallic aluminum is continuously distributed. ing. The positive electrode 1 is an electrode of the present invention. A detailed manufacturing method of the positive electrode 1 will be described later. In the negative electrode 2, a negative electrode material 22 containing a negative electrode active material such as tin is formed on a rectangular plate-shaped negative electrode current collector 21 made of aluminum by plating. When the negative electrode material 22 is plated on the negative electrode current collector 21, tin plating is performed after zinc is plated on the base as a zincate treatment. The negative electrode active material is not limited to tin. For example, tin may be replaced with metallic sodium, carbon, silicon, or indium. The negative electrode material 22 may be formed, for example, by applying a binder to a negative electrode active material powder and applying the powder onto the negative electrode current collector 21. The separator 3 is an insulating material such as silicate glass or resin, and is formed in a shape capable of holding an electrolyte therein and allowing sodium ions to pass therethrough. The separator 3 is a resin formed in, for example, a glass cloth or a porous shape.

  In the battery container 51, the positive electrode 1 and the negative electrode material 22 face each other, and the separator 3 is interposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the negative electrode 2, and the separator 3 are impregnated with an electrolyte made of a molten salt. In order to prevent a short circuit between the positive electrode 1 and the negative electrode 2, the inner surface of the battery container 51 has an insulating structure by a method such as coating with an insulating resin. A positive terminal 53 and a negative terminal 54 for connecting to the outside are provided on the outside of the lid 52. The positive electrode terminal 53 and the negative electrode terminal 54 are insulated from each other, and the portion of the lid 52 facing the inside of the battery container 51 is also insulated by an insulating film or the like. One end of the positive electrode 1 is connected to the positive electrode terminal 53 with a lead wire 55, and one end of the negative electrode current collector 21 is connected to the negative electrode terminal 54 with a lead wire 56. The lead wires 55 and 56 are insulated from the lid portion 52. The lid 52 is attached to the battery container 51 by welding.

  The electrolyte is a molten salt that becomes a conductive liquid in a molten state. At a temperature equal to or higher than the melting point of the molten salt, the molten salt melts into an electrolytic solution, and the molten salt battery operates as a secondary battery. In order to lower the melting point, it is desirable that the electrolyte is a mixture of a plurality of types of molten salts. For example, the electrolyte is a mixed salt of NaFSA using sodium ion as a cation and FSA (bisfluorosulfonylamide) as an anion and KFSA using potassium ion as a cation and FSA as an anion. The molten salt that is an electrolyte may contain other anions such as TFSA (bistrifluoromethylsulfonylamide) or FTA (fluorotrifluoromethylsulfonylamide) and other cations such as organic ions. Also good. In this form, sodium ions serve as charge carriers in the electrolyte. Moreover, the structure of the molten salt battery shown in FIG. 1 is a schematic structure, and the molten salt battery may include other components (not shown) such as a heater for heating the inside or a temperature sensor. Good. Moreover, although the form provided with one pair of the positive electrode 1 and the negative electrode 2 was shown in FIG. 1, the molten salt battery of this invention is a form with which the some positive electrode 1 and the negative electrode 2 were piled up alternately via the separator 3. There may be.

FIG. 2 is an explanatory diagram for explaining a method of manufacturing the positive electrode 1. A powder of Cr ₂ O ₃ (III) and Na ₂ CO ₃ that are raw materials of the positive electrode active material and a resin powder such as ethyl cellulose are mixed, and the mixture is compression-molded to form a rectangular plate. At this stage, a molded body of a mixture of the raw material powder of the positive electrode active material and the resin powder is produced. A molded body of a mixture of the raw material powder of the positive electrode active material and the resin powder is fired at a temperature of 850 ° C. or higher in an argon atmosphere. By firing, Cr ₂ O ₃ (III) reacts with Na ₂ CO ₃ , the generated CO ₂ is released, and NaCrO ₂ is generated. At this time, place reaction sintering powders of NaCrO ₂ in parallel with chemical reactions NaCrO ₂ is generated by sintering. Further, the resin powder contained in the molded body is thermally decomposed. The Cr ₂ O ₃ (III) and Na ₂ CO ₃ parts in the molded body become a sintered body of NaCrO ₂ , and the resin part is thermally decomposed into cavities, and as a result, a positive electrode containing NaCrO ₂ as a component. The active material is sintered, and a porous active material sintered body 11 having voids therein is generated.

FIG. 3 is a schematic cross-sectional view of the active material sintered body 11. Cr ₂ O ₃ (III) and Na ₂ CO ₃ react to produce NaCrO ₂ particles, and the NaCrO ₂ particles are sintered to form a sintered body. The particle size of the NaCrO ₂ particles is about 0.5 μm. Corresponding to the cavity in which the resin is thermally decomposed, voids exist inside the active material sintered body 11, and a large number of holes exist on the surface of the active material sintered body 11.

  Next, the active material sintered body 11 is filled with molten aluminum by immersing the active material sintered body 11 in liquid molten aluminum in a molten aluminum obtained by melting metal aluminum. Molten aluminum permeates into the active material sintered body 11 immersed in the molten aluminum, and the voids in the active material sintered body 11 are filled with the molten aluminum. Next, the active material sintered body 11 is taken out from the molten aluminum and cooled to a temperature lower than the melting point of the metal aluminum. Since the molten aluminum is solidified by cooling, the molten aluminum in the active material sintered body 11 is solidified, and the active material sintered body 11 and the aluminum continuous body 12 in which the molten aluminum is solidified are integrated. Next, the positive electrode 1 is manufactured by shaping the integrated body of the active material sintered body 11 and the aluminum continuous body 12 by a shaping method such as cutting.

FIG. 4 is a schematic cross-sectional view of the positive electrode 1. The positive electrode 1 is composed of an active material sintered body 11 containing NaCrO ₂ as a component and an aluminum continuous body 12 in which metallic aluminum is continuously distributed. The active material sintered body 11 is filled with an aluminum continuous body 12, and the aluminum continuous body 12 is continuously connected in the active material sintered body 11. An aluminum continuum 12 is buried between NaCrO ₂ particles constituting the active material sintered body 11, and the NaCrO ₂ particles are connected to each other via the aluminum continuum 12. Since the active material sintered body 11 and the aluminum continuous body 12 are integrated, the shape of the positive electrode 1 is maintained without a binder. Metal aluminum is a conductive material, and conductivity within the positive electrode 1 is ensured by the aluminum continuum 12. Conduction is performed through the aluminum continuum 12 between NaCrO ₂ particles as the positive electrode active material.

  Next, a method for manufacturing a molten salt battery using the manufactured positive electrode 1 will be described. The manufactured positive electrode 1, separator 3 and negative electrode 2 are stacked in a battery container 51 as shown in FIG. 1, and the positive electrode 1, the negative electrode 2 and the separator 3 are impregnated with a molten salt used as an electrolyte of a molten salt battery. . The impregnation step is performed at a temperature equal to or higher than the melting point of the molten salt impregnated in the positive electrode 1, the negative electrode 2, and the separator 3. Next, the molten salt battery is manufactured by assembling the molten salt battery by adding other necessary components.

  As described above in detail, in the method of manufacturing positive electrode 1 according to the present embodiment, the step of pasting the active material produced as powder, the step of applying the pasted active material to the current collector, and drying The process is unnecessary. For this reason, the method of manufacturing the positive electrode 1 and the method of manufacturing the molten salt battery are simplified, and the manufacturing costs of the positive electrode 1 and the molten salt battery are reduced. Moreover, the positive electrode 1 manufactured in the present embodiment is composed of an active material sintered body 11 and an aluminum continuous body 12, and does not require a binder and a current collector. For this reason, since the cost of the material of the positive electrode 1 can be reduced, the manufacturing cost of the positive electrode 1 and the molten salt battery is further reduced. Moreover, since the aluminum continuum 12 filled in the active material sintered body 11 is obtained by solidifying molten aluminum, compared to a conventional electrode in which a powdered active material and a conductive additive are mixed, The contact area between the positive electrode active material and the conductive material is increased. For this reason, the internal resistance of the positive electrode 1 is reduced, and charging / discharging can be performed at a higher speed than in the prior art. Furthermore, since the positive electrode 1 does not contain a binder that does not contribute to the capacity of the battery, the molten salt battery according to the present embodiment has an improved volume energy density compared to a conventional battery in which a binder is contained in the electrode, Capacity is improved.

The present invention creates a NaCrO ₂ of the positive electrode active material in advance, may be in the form of manufacturing an active material sintered body 11 by sintering the powder of NaCrO ₂ created. Moreover, in this invention, if it is a conductive material which can be utilized for a battery, you may use conductive materials other than metal aluminum, such as another metal, an alloy, or a conductive resin. However, as in this embodiment, it is preferable to use a method of manufacturing the active material sintered body 11 by firing the raw material of the active material, and it is preferable to use metal aluminum as the conductive material. When the method of manufacturing the active material sintered body 11 from the positive electrode active material powder is used, the space in the active material sintered body 11 is completely filled with the conductive material and the positive electrode 1 is impregnated with the electrolyte. There is a risk that the transfer of ions may be difficult between the positive electrode active material and the electrolyte. In addition, the molten conductive material and the positive electrode active material may react to deteriorate the characteristics of the positive electrode active material during battery operation. In the present embodiment, the active material raw materials Cr ₂ O ₃ (III) and Na ₂ CO ₃ are fired to simultaneously generate and sinter NaCrO ₂ of the positive electrode active material. Fine holes are generated in the active material sintered body 11 by CO ₂ . Therefore, voids that are difficult to be filled with the conductive material are generated in the active material sintered body 11, and a space in which the electrolyte is impregnated in the positive electrode 1 is secured. In the present embodiment, since the resin powder is mixed with the raw material powder of the positive electrode active material and fired, voids to be filled with the conductive material are generated by thermal decomposition of the resin, and a part of the resin is formed. Carbonizes and remains on the surface of the positive electrode active material. The carbonized resin remaining on the surface of the positive electrode active material suppresses the reaction between the positive electrode active material and the molten conductive material, and the deterioration of the characteristics of the positive electrode active material is suppressed. Metal aluminum has a melting point of 660 ° C. and a lower melting point than other metals such as copper or nickel. For this reason, in this Embodiment, reaction with a positive electrode active material and the fuse | melted electrically conductive material is suppressed more compared with the case where the electrically conductive material whose melting | fusing point is higher than metal aluminum, such as copper or nickel.

Further, the present invention may be in a form in which a substance other than NaCrO ₂ is used as the positive electrode active material. For example, the present invention may be in a form in which the component of the positive electrode active material is LiCoO ₂ . Similarly, an active material sintered body containing LiCoO ₂ as a component can be manufactured by mixing powders of Co ₂ O ₃ and Li ₂ CO ₃ and performing reactive sintering. For example, the present invention may be in a form in which the component of the positive electrode active material is LiMn ₂ O ₄ . Similarly, an active material sintered body containing LiMn ₂ O ₄ as a component can be produced by performing reactive sintering by mixing MnO ₂ and Li ₂ CO ₃ powders. However, when the component of the positive electrode active material is NaCrO ₂ , the reaction between the positive electrode active material and the molten conductive material is relatively suppressed, so that the component of the positive electrode active material is NaCrO ₂ as in the present embodiment. It is preferable to do. This effect is attributed to the relatively high reduction resistance of the chromium element among the transition metal elements.

Moreover, in this Embodiment, although the battery of this invention showed the form which is a molten salt battery, the battery of this invention is not restricted to this, Other batteries may be sufficient. For example, the battery of the present invention may be a lithium ion battery in which the positive electrode active material component is NaCrO ₂ . Moreover, the shape of the battery according to the present invention is not limited to the shape of a rectangular parallelepiped, and may be other shapes such as a columnar shape. Moreover, although the electrode of this invention showed the form which is the positive electrode 1 in the above embodiment, the battery using the electrode of this invention as a negative electrode may be sufficient as the battery of this invention. The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Active material sintered compact 12 Aluminum continuum 2 Negative electrode 21 Negative electrode collector 22 Negative electrode material 3 Separator

Claims (9)

In a method of manufacturing a battery electrode,
Producing a porous sintered body in which the active material is sintered,
An electrode manufacturing method comprising filling the sintered body with a liquid conductive material and solidifying the filled conductive material. Compressing a mixture of active material raw material powder and resin powder to produce a molded body,
The electrode manufacturing method according to claim 1, wherein the sintered body is produced by firing the produced molded body in an inert atmosphere. Using molten metal as a liquid conductive material,
By immersing the sintered body in the molten metal, the sintered body is filled with the molten metal,
The electrode manufacturing method according to claim 1, wherein the sintered body filled with the molten metal is cooled to be solidified.   The electrode manufacturing method according to claim 3, wherein the molten metal is molten metal aluminum.   5. The electrode manufacturing method according to claim 1, wherein the active material is sodium chromite.   A battery manufacturing method comprising assembling a battery using the electrode manufactured by the electrode manufacturing method according to claim 1 as one electrode. In the battery electrode,
A porous sintered body in which the active material is sintered is filled with a conductive material,
The electrode is characterized in that the conductive material forms a continuous body distributed continuously in the sintered body.   A battery comprising the electrode according to claim 7.   The battery according to claim 8, wherein the molten salt is an electrolyte.

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