JP2014207171A - Method for manufacturing lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a lithium battery by which a lithium battery using metallic lithium as a negative electrode active material can be obtained readily at low cost.SOLUTION: A method for manufacturing a lithium battery comprises: an outer packaging step in which a lithium source electrode 14 including a lithium-ion-releasable lithium source active material 26 other than elemental metallic lithium, a blank electrode 28, a positive electrode 22 including a positive electrode active material 34, and an electrolytic solution are put in a sheath material 12 and sealed up; and a deposition step subsequent to the outer packaging step, in which metallic lithium 30 is deposited on the blank electrode 28 by conducting electricity with the lithium source electrode 14 and the blank electrode 28 in contact with the electrolytic solution. According to this method, a lithium battery 10 including the negative electrode 18 using the metallic lithium 30 as a negative electrode active material, the positive electrode 22, and the electrolytic solution is arranged.

Description

  The present invention relates to a method for manufacturing a lithium battery using metallic lithium as a negative electrode active material.

  It is known that a lithium battery having a high capacity can be obtained by using metal lithium (single substance), which is a metal having the lowest oxidation-reduction potential, as a negative electrode active material. However, when manufacturing such a lithium battery, it is necessary to handle metallic lithium in an environment strictly controlled so as to have an argon gas atmosphere with a relative humidity of 1% or less, for example. This is because metallic lithium is extremely highly chemically active and reacts with moisture, oxygen, carbon dioxide and nitrogen in the atmosphere at room temperature to generate heat and corrosion. Therefore, there has been a problem that the manufacturing process of the lithium battery becomes complicated and the manufacturing cost increases.

  From this viewpoint, Patent Document 1 proposes a method of manufacturing a lithium battery that does not require the above-described strict atmosphere management in a process of assembling a lithium battery after producing a negative electrode from metallic lithium. Specifically, a metal vapor deposition film that is easily alloyed with lithium is formed on the surface of the negative electrode using metallic lithium as an active material. And a lithium battery is assembled in the state which protected the negative electrode with this vapor deposition film.

JP 61-1335060 A

  In the method described in Patent Document 1, it is necessary to prevent the lithium metal from being exposed to the atmosphere until a vapor deposition film is formed on the surface of the negative electrode. That is, even in this method, the above-described strict atmosphere management is not required in all processes from the stage of storing and transporting metallic lithium until the lithium battery is obtained. Therefore, it is difficult to sufficiently suppress the complexity of the manufacturing process of the lithium battery and the increase in manufacturing cost. In addition, since a vapor deposition film is formed on the surface of the negative electrode, there is a concern that the capacity may be reduced or the internal resistance may be increased to deteriorate the performance.

  The present invention has been made to solve the above-described problems, and does not require strict atmosphere management. Therefore, a lithium battery using metallic lithium as a negative electrode active material can be obtained simply and at low cost. An object of the present invention is to provide a method for manufacturing a lithium battery.

To achieve the above object, the present invention provides a method for producing a lithium battery using metallic lithium as a negative electrode active material,
A lithium source electrode containing a lithium source active material capable of releasing lithium ions (excluding metallic lithium), a blank electrode, a positive electrode containing a positive electrode active material, and an electrolyte solution are housed inside the exterior material. An exterior process for sealing;
A deposition step of depositing lithium metal on the blank electrode by energizing the lithium source electrode and the blank electrode in contact with the electrolyte; and
Have
A lithium battery is constituted by a negative electrode using metallic lithium deposited on the blank electrode as a negative electrode active material, the positive electrode, and the electrolyte solution in contact with the negative electrode and the positive electrode.

  In the present invention, the lithium source electrode has an active material capable of electrochemically releasing lithium ions such as lithium metal oxide (excluding single metal lithium). Unlike metallic lithium, this active material can be easily handled without special atmosphere management. Therefore, in the above exterior process, for example, strict atmosphere management such as an argon gas atmosphere having a relative humidity of 1% or less is not required.

  In the deposition step, the lithium source electrode and the blank electrode brought into contact with the electrolytic solution are energized inside the pre-sealed exterior material, and metallic lithium is deposited on the surface of the blank electrode to produce a negative electrode. That is, metal lithium is deposited in the electrolyte solution in the sealed outer packaging material, and thus it is not necessary to perform the above strict atmosphere management even in the deposition step.

  From the above, it is possible to eliminate the strict atmosphere management described above in all steps of manufacturing a lithium battery using metallic lithium as a negative electrode active material. At this time, it is not necessary to protect the surface of the metallic lithium with a deposited film or the like. Therefore, a lithium battery can be obtained easily and at low cost without deteriorating battery performance such as capacity and output characteristics.

  In the above lithium battery manufacturing method, the positive electrode active material may not contain lithium. As described above, in the production method according to the present invention, a lithium battery using metallic lithium as a negative electrode active material can be obtained simply and at low cost. Thus, a lithium battery using metallic lithium as a negative electrode active material can exhibit good battery characteristics even when the positive electrode active material does not contain lithium. Therefore, the degree of freedom in selecting a material that can be employed as the positive electrode active material is improved, and thus a lithium battery can be manufactured from a suitable material according to the application.

  In the above lithium battery manufacturing method, in the precipitation step, the blank electrode is selectively masked with an insulating material, so that the metallic lithium is deposited only on a portion of the blank electrode exposed from the insulating material. preferable. For example, only the position facing the positive electrode through the electrolytic solution on the surface of the blank electrode is exposed from the insulating material. Thereby, metallic lithium can be efficiently deposited at the above position to form a negative electrode. That is, it is possible to shorten the time required for forming the negative electrode and reduce the amount of metallic lithium used for forming the negative electrode.

  According to the present invention, metallic lithium can be deposited in an electrolytic solution inside a sealed exterior material to produce a negative electrode. Since a lithium battery can be comprised from this negative electrode and the positive electrode and electrolyte solution which were previously accommodated in the exterior material, exact | strict atmosphere management at the time of handling metallic lithium can be made unnecessary. As a result, it becomes possible to manufacture a lithium battery easily and at low cost.

It is a schematic longitudinal cross-sectional view of the lithium battery manufactured by the manufacturing method which concerns on this embodiment. It is a schematic longitudinal cross-sectional view for demonstrating the exterior process of the manufacturing method of the lithium battery which concerns on this embodiment. It is a schematic longitudinal cross-sectional view for demonstrating the precipitation process of the manufacturing method of the lithium battery which concerns on this embodiment.

  Preferred embodiments of a method for producing a lithium battery according to the present invention will be described below in detail with reference to the accompanying drawings.

  First, the lithium battery 10 manufactured by the manufacturing method according to the present embodiment will be described with reference to the schematic longitudinal sectional view of FIG. The lithium battery 10 is a secondary battery using single metal lithium as a negative electrode active material. Specifically, the lithium battery 10 includes a lithium source electrode 14, a first separator 16, a negative electrode 18, a second separator 20, and a positive electrode 22 in a sealed space 12 a formed by the exterior material 12 from below in FIG. 1. It is comprised by accommodating with electrolyte solution in the state laminated | stacked in this order.

  The lithium source electrode 14 includes a current collector 24 and a lithium source active material 26 provided on the surface of the current collector 24 facing the first separator 16. The current collector 24 may be formed in a plate shape from Al, Cu, stainless steel, Ni, W, Au, Pt, or the like, or may be in a mesh shape or a porous shape. Further, an end portion of the current collector 24 where the lithium source active material 26 is not provided is exposed to the outside of the exterior material 12 as an electrode terminal 24a.

The lithium source active material 26 only needs to be an active material capable of electrochemically releasing lithium ions. Specific preferred examples include LiFePO ₄ , LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and Li ₂ FePO _4. F, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , Li ₄ Ti ₅ O _{12 and the} like. However, metallic lithium is excluded from the lithium source active material 26.

  The lithium source electrode 14 is prepared by mixing a powder of the above-described materials as the lithium source active material 26 with a conductive additive and a binder, and attaching the mixture to the current collector 24. Can be formed.

  The 1st separator 16 is an insulator which consists of a nonwoven fabric of glass fiber, a porous resin film, etc., for example, and impregnates electrolyte solution. Since the first separator 16 is interposed between the lithium source electrode 14 and the negative electrode 18, it is possible to avoid a short circuit between the lithium source electrode 14 and the negative electrode 18. Further, the electrolyte solution contacts each of the lithium source electrode 14 and the negative electrode 18.

  The negative electrode 18 includes a current collector 28 (blank electrode) that can be configured in the same manner as the current collector 24, and metal lithium 30 deposited on the surface of the current collector 28. Specifically, the metallic lithium 30 is deposited on a portion of the current collector 28 that is not masked with the insulating material 31 (exposed portion 28a).

The insulating material 31 is not particularly limited as long as it is a material that does not exhibit electronic conductivity, but may be composed of a resin such as polyimide or polypropylene, or an inorganic material such as SiO ₂ or Al ₂ O ₃ .

  Further, the metal lithium 30 reversibly binds to and separates from electrons, thereby changing from lithium ion to metal lithium, or conversely, from metal lithium to lithium ion. This reversible reaction functions as a negative electrode active material. Note that the end of the current collector 28 where the metallic lithium 30 is not deposited is exposed to the outside of the exterior material 12 as the negative electrode terminal 28b.

  The second separator 20 can be configured similarly to the first separator 16. That is, the second separator 20 is interposed between the negative electrode 18 and the positive electrode 22, thereby preventing a short circuit from occurring between the negative electrode 18 and the positive electrode 22. Further, an electrolytic solution is brought into contact with each of the negative electrode 18 and the positive electrode 22.

  The positive electrode 22 includes a current collector 32 that can be configured in the same manner as the current collectors 24 and 28, and a positive electrode active material 34 provided on a surface of the current collector 32 facing the second separator 20. It is configured. Further, the end of the current collector 32 where the positive electrode active material 34 is not provided is exposed to the outside of the exterior material 12 as a positive electrode terminal 32a.

The positive electrode active material 34 is not particularly limited as long as it is an active material capable of electrochemically releasing and storing lithium ions, and may or may not contain lithium. Specific examples of the positive electrode active material 34 in the case of containing lithium include the same materials as the lithium source active material 26 described above. On the other hand, specific examples of the positive electrode active material 34 not containing lithium include FeF ₃ , S, graphite, Si, Ge, Al, Sn, and the like.

  The positive electrode 22 is prepared by mixing a powder of the above-described materials as the positive electrode active material 34 with a conductive additive and a binder, and attaching the composite material to the current collector 32. Can be formed.

The electrolytic solution conducts lithium ions electrically. For example, a lithium salt such as LiPF ₆ , LiBF ₄ , LiClO ₄ or the like in a solvent composed of at least one of ethylene carbonate, diethyl carbonate, dimethyl carbonate, vinylene carbonate, and the like. Can be used.

  The packaging material 12 is not particularly limited as long as it is a substance that is stable with respect to the electrolytic solution. For example, the exterior material 12 can be formed from a laminated film (laminated film) of a metal foil such as Al and a resin, or a metal such as stainless steel, Al, Al alloy, or Mg alloy. From the viewpoint of weight reduction and the like, a laminate film is preferably used. When using a laminate film, the exterior material 12 can be formed by heat-sealing the resin layers to form a sealed and sealed structure.

  In the lithium battery 10 configured as described above, discharging is performed by connecting the negative electrode terminal 28 b and the positive electrode terminal 32 a to the external load 36. Further, charging is performed by connecting the negative terminal 28b and the positive terminal 32a to an external power source (not shown). That is, charging / discharging can be performed by transferring lithium ions between the positive electrode active material 34 of the positive electrode 22 and the metal lithium 30 (negative electrode active material) of the negative electrode 18.

  Next, a method for manufacturing the lithium battery 10 will be described with reference to FIGS. In the following description, the direction of the arrow a shown in FIGS.

  In this manufacturing method, the lithium battery 10 is obtained by performing an exterior process and a deposition process. In the exterior process according to the present embodiment, the exterior material 12 is formed from a laminate film. In this case, first, the lithium source electrode 14 is placed on the laminate film with the lithium source active material 26 facing upward. Furthermore, the 1st separator 16 and the electrical power collector 28 (blank electrode) in which the metal lithium 30 is not deposited on the lithium source electrode 14 are piled up in order.

  The current collector 28 is selectively masked with an insulating material 31 so that when the lithium battery 10 is assembled, the position facing the positive electrode 22 via the electrolytic solution becomes the exposed portion 28a. The current collector 28 is placed on the first separator 16 with the exposed portion 28a facing upward. Further, the second separator 20 and the positive electrode 22 with the positive electrode active material 34 facing downward are superimposed in order above the current collector 28.

  As described above, the superimposed body 38 in which the lithium source electrode 14, the first separator 16, the current collector 28, the second separator 20, and the positive electrode 22 are superimposed in this order from below is formed on the laminate film. Can do.

  Next, an electrolytic solution is injected into the first separator 16 and the second separator 20. The amount of the electrolyte to be injected is adjusted so that the electrolyte sufficiently penetrates into the porous structures of the first separator 16 and the second separator 20.

  Next, the superposed body 38 is further covered with a laminate film from the current collector 32 of the positive electrode 22. At this time, the other end side of the laminate film in which one end side is disposed under the superposed body 38 may be folded back and the superposed body 38 may be covered with the other end side. Alternatively, two laminated films may be prepared, and one of the laminated films may be disposed under the superimposing body 38 as described above, and the other may cover the superimposing body 38.

  Next, the outer peripheral edge portions of the laminate films are heat-sealed while evacuating the laminate films arranged above and below with the superimposed body 38 interposed therebetween. Thereby, as shown in FIG. 2, the exterior material 12 is formed, and the sealed space 12 a is formed therein. At the same time, the superposed body 38 and the electrolytic solution are accommodated in the sealed space 12a.

  By performing the exterior process in this manner, each component of the superimposed body 38 including the lithium source active material 26 and the exposed portion 28a of the current collector 28 can be brought into contact with the electrolytic solution in the sealed space 12a. In the exterior process, the electrode material 24a, the negative electrode terminal 28b, and the positive electrode terminal 32a can be exposed to the outside of the sealed space 12a by removing the exterior material 12 partially.

Next, a deposition step for depositing metallic lithium 30 on the exposed portion 28 a of the current collector 28 is performed. Specifically, as shown in FIG. 3, first, the electrode terminal 24 a and the negative electrode terminal 28 b are connected to the external power source 40. Then, the voltage of the electrode terminal 24 a and the negative electrode terminal 28 b is set to be higher than the potential (vsLi / Li ⁺ ) of the lithium source active material 26, and a current flows from the lithium source electrode 14 to the current collector 28. . As a result, the lithium ions released from the lithium source active material 26 move through the electrolyte and receive electrons at the exposed portion 28 a of the current collector 28, so that the metal lithium 30 is deposited on the exposed portion 28 a of the current collector 28. . Note that the voltage, current, and energization time of the external power supply 40 may be adjusted so that a desired amount of the lithium metal 30 is deposited electrochemically.

  As a result, the negative electrode 18 containing the metal lithium 30 as the negative electrode active material can be formed. Therefore, the lithium battery 10 including the negative electrode 18 obtained in the sealed space 12a, the positive electrode 22 and the electrolytic solution previously accommodated in the sealed space 12a can be configured. Then, instead of connecting the electrode terminal 24a and the negative electrode terminal 28b via the external power source 40, the lithium battery 10 is connected by connecting the negative electrode terminal 28b and the positive electrode terminal 32a to the external load 36 as shown in FIG. Makes it possible to obtain power.

  As described above, the lithium source electrode 14 is configured to include the lithium source active material 26 (excluding single metal lithium) capable of electrochemically releasing lithium ions, such as lithium metal oxide. . The lithium source active material 26 can be easily handled without special atmosphere management, unlike single metallic lithium. Therefore, in the exterior process, for example, strictly controlling the atmosphere such as an argon gas atmosphere having a relative humidity of 1% or less can be eliminated.

  Then, in the deposition step, the lithium source electrode 14 and the current collector 28 brought into contact with the electrolytic solution are energized inside the pre-sealed exterior member 12 to deposit the metal lithium 30 to produce the negative electrode 18. . That is, since the metal lithium 30 is deposited in the electrolyte solution inside the exterior material 12, it is not necessary to perform the above strict atmosphere management even in the deposition step.

  Therefore, in the manufacturing method of the lithium battery 10 according to the present embodiment, it is not necessary to strictly manage the atmosphere when handling a single metal lithium in all steps of manufacturing the lithium battery 10 using the metal lithium 30 as the negative electrode active material. can do. Furthermore, it is not necessary to cover the surface of the metallic lithium 30 as the negative electrode active material with a vapor deposition film or the like. Therefore, the lithium battery 10 can be obtained easily and at low cost without reducing the battery performance such as the capacity and output characteristics of the lithium metal 30.

  In the lithium battery 10 thus obtained, since the metal lithium 30 can be used as the negative electrode active material, good battery characteristics can be exhibited even when the positive electrode active material 34 does not contain lithium. . Therefore, the materials listed above can be employed as the positive electrode active material 34, and the lithium battery 10 can be manufactured from a suitable material according to the application.

  Further, as described above, the position facing the positive electrode 22 through the electrolytic solution of the current collector 28 is the exposed portion 28 a, and other portions are masked with the insulating material 31. Thus, the negative electrode 18 can be formed by efficiently depositing the metal lithium 30 on the exposed portion 28 a of the current collector 28. That is, it is possible to shorten the time required for forming the negative electrode 18 and reduce the amount of metallic lithium 30 used for forming the negative electrode 18.

  The present invention is not particularly limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, the lithium source active material 26 and the positive electrode active material 34 are not limited to those provided as a binder from a composite material, and may be formed by sputtering or the like.

  The lithium battery obtained by the manufacturing method according to the present invention may be other than a secondary battery. Furthermore, the analysis is carried out in general using an analytical instrument using an electron beam such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), laser light such as Raman spectroscopy or infrared spectroscopy, or visible light such as an optical microscope. It may be an analytical battery used in the case.

  Furthermore, in the above embodiment, the lithium source electrode 14, the first separator 16, the current collector 28, the second separator 20, and the positive electrode 22 are superposed in this order from below, and inside the exterior material 12 The negative electrode 18 was formed to obtain the lithium battery 10. However, the stacking order of the components in the exterior material 12 is not limited to the above order.

<Production of lithium source electrode>
(1) LiCoO ₂ particles that are a lithium source active material, ketjen black that is a conductive auxiliary agent, and carboxymethyl cellulose (CMC) that is a binder so as to have a weight ratio of 85: 5: 10, A slurry was prepared by dissolving in water as a solvent. Next, after applying the slurry to one surface of an Al foil having a thickness of 15 μm as a current collector using a bar coater, the solvent was evaporated by drying at 80 ° C. for 1 hour. Further, heat treatment was performed in a vacuum state at 120 ° C. for 2 hours in a vacuum drying furnace. Thus, a lithium source electrode having a lithium source active material on one surface was produced.

<Production of blank electrode>
(2) A polyimide resin as an insulating material was applied to the surface of a copper foil having a thickness of 35 μm as a current collector so that a portion where metal lithium was deposited was exposed, and heat treatment was performed in a vacuum state at 350 ° C. for 2 hours. . Thus, a blank electrode was produced in which the portion excluding the exposed portion of the current collector showed insulating properties.

<Preparation of positive electrode>
(3) A positive electrode was produced in the same manner as the lithium source electrode produced in (1) above, except that LiFePO ₄ particles as a positive electrode active material were used instead of the lithium source active material in (1). .

<Preparation of electrolyte>
(4) LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 so that the concentration would be 1 mol / l to prepare an electrolytic solution.

<Exterior process>
(5) On the laminate film, the lithium source electrode produced in (1), the glass nonwoven fabric as the first separator, the blank electrode produced in (2), the glass nonwoven fabric as the second separator, A superimposed body was fabricated by superimposing the positive electrode fabricated in (3). At this time, the surface of the lithium source electrode on the lithium source active material side was up, and the surface of the positive electrode on the positive electrode active material side was down.

  Next, the electrolyte prepared in (4) was sufficiently injected into the first separator and the second separator of the superposed body. Thereafter, a laminate film prepared separately from the laminate film was placed on the positive electrode. Under the present circumstances, the edge part of each collector which comprises a lithium source electrode, a blank electrode, and a positive electrode was exposed outside the laminate film as an electrode terminal, a negative electrode terminal, and a positive electrode terminal, respectively. Then, the outer peripheral edge of the laminate film was heat-sealed while evacuating between the laminate films with the superposed body sandwiched between a pair of laminate films.

<Production of negative electrode>
(6) In the step (5), the electrode terminal exposed to the outside of the laminate film and the negative electrode terminal were connected to an external power source, and the voltage of the electrode terminal with respect to the negative electrode terminal was set to 4.2V. As a result, a current of 0.1 A was passed from the lithium source electrode to the blank electrode for 1 hour, and metallic lithium was deposited to a thickness of 10 μm on the exposed portion of the blank electrode that did not exhibit insulation. did. That is, a negative electrode having metallic lithium as a negative electrode active material was produced.

  Through the above steps, a lithium battery including a positive electrode, a negative electrode using metal lithium as a negative electrode active material, and an electrolytic solution inside an exterior material is obtained without performing strict atmosphere management for handling single metal lithium. I was able to.

DESCRIPTION OF SYMBOLS 10 ... Lithium battery 12 ... Exterior material 12a ... Sealed space 14 ... Lithium source electrode 16 ... 1st separator 18 ... Negative electrode 20 ... 2nd separator 22 ... Positive electrode 24, 28, 32 ... Current collector 24a ... Electrode terminal 26 ... Lithium source Active material 28a ... exposed portion 28b ... negative electrode terminal 30 ... metallic lithium 31 ... insulating material 32a ... positive electrode terminal 34 ... positive electrode active material 36 ... external load 38 ... superposed body 40 ... external power source

Claims (3)

A method for producing a lithium battery using metallic lithium as a negative electrode active material,
A lithium source electrode containing a lithium source active material capable of releasing lithium ions (excluding metallic lithium), a blank electrode, a positive electrode containing a positive electrode active material, and an electrolyte solution are housed inside the exterior material. An exterior process for sealing;
A deposition step of depositing lithium metal on the blank electrode by energizing the lithium source electrode and the blank electrode in contact with the electrolyte; and
Have
A lithium battery is produced by forming a lithium battery by using a negative electrode using metallic lithium deposited on the blank electrode as a negative electrode active material, the positive electrode, and the electrolyte solution in contact with the negative electrode and the positive electrode. Method.   2. The method of manufacturing a lithium battery according to claim 1, wherein the positive electrode active material does not contain lithium.   3. The method for manufacturing a lithium battery according to claim 1, wherein in the deposition step, the blank electrode is selectively masked with an insulating material, so that the metallic lithium is exposed only to a portion of the blank electrode exposed from the insulating material. A method for producing a lithium battery, wherein

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