JP2005093373A - Energy device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably manufacture an energy device using a lithium thin film as a negative electrode. <P>SOLUTION: The energy device has a solid electrolyte layer 25 and a negative active material layer 24 containing lithium and a second metal, and the concentration of lithium in the negative active material layer 24 is gradually increased toward the interface of the solid electrolyte layer 25 side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an energy device and a manufacturing method thereof. In particular, the present invention relates to a lithium ion secondary battery and a manufacturing method thereof.

  The lithium ion secondary battery includes a negative electrode current collector, a negative electrode active material, an electrolyte, a separator, a positive electrode active material, and a positive electrode current collector as main components. This lithium ion secondary battery literally has lithium ions as the basis of its operating principle, and sufficient care must be taken in handling extremely active materials in its manufacturing method.

  Under such safety efforts, lithium ion secondary batteries play a major role as energy sources for mobile communication devices and various AV devices, and much effort has been made to improve battery characteristics. For example, Patent Document 1 discloses that a high energy density can be realized by using, as a positive electrode active material, an amorphous oxide obtained by heating, melting, and rapidly cooling a mixed powder of a specific transition metal oxide. It is disclosed. Patent Document 2 discloses that a positive electrode active material is a transition metal oxide containing lithium, a compound containing a silicon atom is used as a negative electrode material, and the weight of the positive electrode active material is made larger than the weight of the negative electrode active material. It is disclosed that battery capacity and cycle life can be increased.

In this way, along with the downsizing and high performance of devices, lithium secondary batteries are being made thinner and higher in energy density. In particular, by making the current collector and the active material thin and using a solid electrolyte as the electrolyte, it is expected that a thin and high energy density can be realized, and a separator is unnecessary. Although the development of thin film technology in the energy device field has been delayed compared to general electronic components, significant technological innovation is expected due to progress in material technology and process technology, especially the use of metallic lithium thin film for the negative electrode. This is expected to increase the capacity.
JP-A-8-78002 Japanese Unexamined Patent Publication No. 2000-12092

  As a problem in the case of using a metal lithium thin film as a negative electrode, suppression of reaction with moisture and oxygen is extremely important.

  FIG. 12 shows a general configuration of a lithium ion secondary battery using a solid electrolyte. As shown in the figure, the lithium ion secondary battery has a positive electrode current collector layer 27, a positive electrode active material layer 26, a solid electrolyte layer 25, a negative electrode active material layer 28, and a negative electrode current collector layer 23 stacked on a substrate 22 in this order. Being done.

  The negative electrode active material layer 28 is formed by a vacuum process as shown in FIG. 13, for example. That is, in the vacuum chamber 901, the negative electrode active material layer material is heated and evaporated by the evaporation source 902. The evaporated particles 903 of the negative electrode active material layer material pass through the openings of the mask 904 and adhere to the surface of the substrate 905 to form a thin film 906 that becomes a negative electrode active material layer. Reference numeral 916 denotes a vacuum pump that maintains the vacuum chamber 901 at a predetermined degree of vacuum.

  In industrial mass production, for example, it is manufactured as shown in FIG. A long substrate 915 is unwound from an unwinding roll 911 and wound around a take-up roller 914 through a transport roller 912a, a cylindrical can roller 913, and a transport roller 912b in this order. A positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, or a negative electrode current collector layer is formed on one surface of the substrate 915 in advance. When the substrate 915 is transported on the can roller 913, evaporation particles 903 of the negative electrode active material layer material from the evaporation source 902 are deposited on the surface of the substrate 915 through the opening of the mask 904, and the thin film 906 is continuously formed. It is formed.

  When a lithium thin film is formed as a negative electrode active material layer in such a process, since lithium is extremely active, even when it is wound on a winding roll 914, it becomes white in a very short time when exposed to the atmosphere. Discoloration. Therefore, it is necessary to reduce the moisture in the working atmosphere as much as possible, and work in a so-called dry room with a dew point of minus several tens of degrees or less is necessary. However, in such a dry atmosphere, the dew point easily rises due to the presence of workers, so it is necessary to strictly limit the number of workers and clothes to maintain the dry atmosphere, and it is difficult to improve productivity. It is. Moreover, even when such a dry atmosphere is taken into consideration, there are many cases where the characteristics deteriorate due to moisture absorption and the battery performance varies. Therefore, in order to use a lithium thin film as the negative electrode active material layer, it is necessary to solve these problems.

  The first energy device of the present invention is an energy device having a solid electrolyte layer and a negative electrode active material layer containing lithium and a second metal, wherein the concentration of lithium in the negative electrode active material layer is on the solid electrolyte layer side. It is characterized by gradually increasing toward the interface.

  The second energy device of the present invention is an energy device having a solid electrolyte layer and a negative electrode composite layer containing lithium and a second metal, wherein the second metal is a metal having a work function of 4 eV or more, The lithium concentration in the negative electrode composite layer gradually decreases as the distance from the solid electrolyte layer increases, and the lithium contained in the negative electrode composite layer is at or near the interface opposite to the solid electrolyte layer of the negative electrode composite layer. A region having a ratio of 20 at% or less to the total of lithium and the second metal is present with a thickness of 100 nm or more.

  The method for producing an energy device of the present invention is a method for producing an energy device having a step of forming a negative electrode layer containing lithium and a second metal on a solid electrolyte layer by a vacuum thin film process, in order to laminate the lithium The contribution of the thin film formation from the thin film formation by the first thin film formation source to the thin film formation by the second thin film formation source using the first thin film formation source and the second thin film formation source for laminating the second metal To form the negative electrode layer.

  Since the energy device of the present invention includes a negative electrode layer containing lithium and a solid electrolyte layer, a small secondary battery having a high energy density can be provided. In addition, since the negative electrode contains lithium and the second metal and the concentration of lithium gradually increases toward the interface on the solid electrolyte layer side, the negative electrode can be manufactured stably with high productivity.

  Moreover, according to the manufacturing method of the energy device of this invention, the energy device of this invention can be manufactured stably with sufficient productivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
An example of a schematic configuration of the energy device according to the first exemplary embodiment of the present invention is shown in FIG. In the energy device of the present embodiment, the battery element 20 is laminated on the substrate 22. In the battery element 20, a positive electrode current collector layer 27, a positive electrode active material layer 26, a solid electrolyte layer 25, a composition gradient negative electrode active material layer 24, and a negative electrode current collector layer 23 are formed in this order. In FIG. 1, the substrate 22 is disposed on the positive electrode current collector layer 27 side of the battery element 20, but may be disposed on the negative electrode current collector layer 23 side.

  Examples of the substrate 22 include polyimide (PI), polyamide (PA), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), other polymer films, stainless metal foil, nickel, copper, aluminum, and other metals. A flexible material such as a metal foil containing an element can be used. Furthermore, various shapes of silicon, glass, ceramic, plastic, and the like can be used, and in the present invention, the material and shape of the substrate are not particularly limited.

  As the positive electrode current collector layer 27, for example, nickel, copper, aluminum, platinum, platinum-palladium, gold, silver, titanium, or a metal represented by ITO (indium-tin oxide) can be used. Depending on the final form of the energy device, when the substrate 22 is disposed on the positive electrode side and a conductive material is used as the substrate 22, the positive electrode current collector layer 27 is omitted and the substrate 22 is used as the positive electrode current collector layer 27. Can also work.

  As the positive electrode active material layer 26, for example, lithium cobaltate, lithium nickelate, or the like can be used. However, the material of the positive electrode active material layer 26 of the present invention is not limited to the above, and other materials can also be used.

As the solid electrolyte layer 25, a material having ion conductivity and small enough to have negligible electronic conductivity can be used. Especially when the energy device is a lithium ion secondary battery, since lithium ions are mobile ions, Li ₃ PO ₄ and, mixed with nitrogen to Li ₃ PO ₄ (or part of the elements of Li ₃ PO ₄ A solid electrolyte made of a material (LiPON: typical composition is Li _2.9 PO _3.3 N _0.36 ) or the like obtained by substituting with nitrogen is preferable because of its excellent lithium ion conductivity. Similarly, a solid electrolyte made of a sulfide such as Li ₂ S—SiS ₂ , Li ₂ S—P ₂ S ₅ , Li ₂ S—B ₂ S ₃ is also effective. Furthermore, solid electrolytes obtained by doping these solid electrolytes with lithium halides such as LiI and lithium oxyacid salts such as Li ₃ PO ₄ are also effective. The material of the solid electrolyte 25 of the present invention is not limited to the above, and other materials can be used as the solid electrolyte layer 25. By using a solid electrolyte as the electrolyte, it is not necessary to take countermeasures against liquid leakage which are essential in the conventional liquid electrolyte, and the energy device can be easily reduced in size and thickness.

  The composition gradient type negative electrode active material layer 24 is made of a lithium compound containing at least lithium and a second metal. This improves the chemical stability of the composition-graded negative electrode active material layer 24 and facilitates production. Further, in the thickness direction (up and down direction in FIG. 1), the composition ratio between lithium and the second metal is not constant, and the lithium concentration gradually increases toward the interface with the solid electrolyte layer 25. Thereby, the negative electrode active material layer 24 can be stably formed without impairing charge / discharge characteristics. The second metal is not particularly limited, but a metal having a work function of 4 eV or more is preferable. This is because such a metal is chemically stable and facilitates efficient film formation of the negative electrode active material layer 24. Examples of metals having a work function of 4 eV or more are aluminum, silicon, vanadium, cobalt, nickel, copper, germanium, zirconium, niobium, molybdenum, silver, rhodium, tin, tantalum, palladium, platinum, gold, tungsten, and the like. . Aluminum is preferable. This is because a thin film having good characteristics can be easily formed. However, it is not limited to these, For example, you may use metals other than the metal illustrated previously and whose work function is 4 eV or more as a 2nd metal. Further, two or more metals having a work function of 4 eV or more may be included.

  As the negative electrode current collector layer 23, similarly to the positive electrode current collector layer 27, for example, a metal typified by nickel, copper, aluminum, platinum, platinum-palladium, gold, silver, ITO (indium-tin oxide) is used. Can be used. Depending on the final form of the energy device, when the substrate 22 is disposed on the negative electrode side and a conductive material is used as the substrate 22, the negative electrode current collector layer 23 may be omitted and the substrate 22 may be used as the negative electrode current collector 23. Can function.

  The lithium ratio Re with respect to the total of lithium and the second metal is preferably 70 at% or more at the interface of the gradient composition negative electrode active material layer 24 on the solid electrolyte layer 25 side or in the vicinity thereof. When the lithium ratio Re at the interface on the solid electrolyte layer 25 side of the composition-graded negative electrode active material layer 24 or in the vicinity thereof is less than 70 at%, the capacity is likely to decrease in the charge / discharge cycle test of the energy device. In particular, the cycle deterioration is remarkable when the charge / discharge rate is 2C or more. This is because when the lithium ratio Re decreases at the solid electrolyte layer 25 side interface of the composition-graded negative electrode active material layer 24, it becomes difficult for Li to enter and exit at the interface, thereby deteriorating charge / discharge cycle characteristics. Seems to be. Preferably, the lithium ratio Re is 80 at% or more. As a result, when the charge / discharge rate is 10 C, cycle characteristics comparable to those when the second metal is not included (that is, Re = 100 at%) are obtained.

  Moreover, it is preferable that lithium ratio Rc with respect to the sum total of lithium and a 2nd metal is 60 at% or less in the interface on the opposite side to the solid electrolyte layer 25 of the composition inclination type negative electrode active material layer 24 or its vicinity. When the lithium ratio Rc at the interface opposite to or near the solid electrolyte 25 of the composition gradient negative electrode active material layer 24 exceeds 60 at%, the composition gradient negative electrode active material layer 24 is exposed to the atmosphere after film formation, Peeling from the negative electrode current collector layer 23 formed thereon and a significant decrease in battery capacity are likely to occur. This is to reduce the lithium ratio Rc at the interface opposite to the solid electrolyte 25 of the composition gradient negative electrode active material layer 24, thereby making the reactivity of the composition gradient negative electrode active material layer 24 with moisture and oxygen low. This seems to be because it can be suppressed. Preferably, the lithium ratio Rc is 40 at% or less. This makes it easy to prevent the battery capacity from being reduced by exposure to the atmosphere, and if the humidity and oxygen concentration of the exposed atmosphere are the same, the exposure time required to reduce the battery capacity to a problem level is increased. Become.

  In the energy device of the present embodiment, the negative electrode current collector layer 23 can be omitted. As described above, the lithium concentration in the composition gradient negative electrode active material layer 24 gradually decreases toward the interface opposite to the solid electrolyte 25. Therefore, a portion having a low lithium ratio Rc at the interface opposite to the solid electrolyte 25 of the composition-graded negative electrode active material layer 24 can be substantially used as the negative electrode current collector layer. In this case, the composition gradient negative electrode active material layer 24 can be considered as a composite layer of the negative electrode active material layer and the negative electrode current collector layer. By omitting the negative electrode current collector layer 23 in this way, the problem of peeling at the interface between the composition-gradient negative electrode active material layer 24 and the negative electrode current collector layer 23 and the decrease in battery capacity caused thereby is eliminated. Is done. Further, the step of separately forming the negative electrode current collector layer 23 becomes unnecessary. When the negative electrode current collector layer 23 is omitted, the lithium ratio Rc with respect to the total of lithium and the second metal is 20 at% at the interface opposite to the solid electrolyte layer 25 of the composition gradient negative electrode active material layer 24 or in the vicinity thereof. The following is preferable. In addition, the portion where the lithium ratio Rc with respect to the total of lithium and the second metal is 20 at% or less at the interface opposite to the solid electrolyte layer 25 of the composition-graded negative electrode active material layer 24 or in the vicinity thereof has a thickness of 100 nm. More preferably, it exists over the above.

  The product form of the energy device is not particularly limited, and various types are conceivable. For example, what laminated | stacked the battery element 20 shown in FIG. 1 on the flexible long board | substrate 22 may be wound by flat form as shown in FIG. At this time, a plate-shaped inner core 11 may be disposed on the inner periphery of the wound body 10.

  FIG. 3 is a perspective view of the flat energy device shown in FIG. In FIG. 3, reference numeral 12 denotes a pair of external electrodes 12 provided at both ends of the wound body 10. As the material of the external electrode 12, various conductive materials such as nickel, zinc, tin, solder alloy, and conductive resin can be used. As the formation method, thermal spraying, plating, coating, or the like can be used. The negative electrode current collector layer 23 is electrically connected to one external electrode 12, the positive electrode current collector layer 27 is electrically bonded to the other external electrode 12, and the pair of external electrodes 12, 12 are The formation regions in the width direction (winding center direction) of the negative electrode current collector layer 23 and the positive electrode current collector layer 27 are patterned so as to be insulated from each other. Thereby, the negative electrode current collector layer 23 and the positive electrode current collector layer 27 are not short-circuited via any one of the external electrodes 12.

  FIG. 4 is a cross-sectional view showing another product form of the energy device. In FIG. 4, reference numeral 15 denotes a pair of external electrodes. A negative electrode current collector layer 23 is electrically connected to one external electrode 15, and a positive electrode current collector layer 27 is electrically connected to the other external electrode 15. Be joined. The material and the formation method are the same as those of the external electrode 12 shown in FIG.

  Reference numeral 16 denotes a fuse portion provided in the vicinity of the connection portion between the negative electrode current collector layer 23 and the external electrode 15 and in the vicinity of the connection portion between the positive electrode current collector layer 27 and the external electrode 15. The fuse section 16 functions as a safety device that prevents the occurrence of ignition or the like by cutting off the overcurrent when the overcurrent flows and causing the ignition. In the present embodiment, the fuse portion 16 is provided in the negative electrode current collector layer 23 and the positive electrode current collector layer 27, but only one of them may be provided. 5A is a plan view showing an example of the fuse portion 16, and FIG. 5B is a cross-sectional view taken along line 5B-5B in FIG. 5A. The fuse portions 16 are formed on the current collector layers 23 and 27 by giving a pattern that narrows the width of the portion where current flows. When an overcurrent flows, the fuse portion 16 generates heat due to Joule heat and melts to cut off the overcurrent. Therefore, it is possible to prevent a serious situation such as ignition from occurring. Note that the configuration of the fuse portion 16 is not limited to FIGS. 5 (A) and 5 (B). For example, the fuse portion 16 may be configured by partially reducing the thickness of the negative electrode current collector layer 23 and the positive electrode current collector layer 27. Or you may form a fuse part in the negative electrode collector layer 23 and the positive electrode collector layer 27 by forming dissimilar material with a large temperature coefficient of electrical resistance with a specific pattern. Since the temperature coefficient of the electric resistance of the dissimilar material is larger than the temperature coefficient of the electric resistance of the negative electrode current collector layer 23 and the positive electrode current collector layer 27, the resistance of the dissimilar material when the temperature of the fuse portion 16 rises slightly during overcurrent. The value increases rapidly. Therefore, as a result of the current flowing in the material of the negative electrode current collector layer 23 and the positive electrode current collector layer 27 other than the dissimilar materials in the fuse part 16, the fuse part 16 generates heat due to Joule heat and melts. Cut off the overcurrent.

  In FIG. 4, 17 is a protective layer provided for the purpose of mechanical protection, improvement of moisture resistance, prevention of delamination, and the like. Although the material of the protective layer 17 is not specifically limited, For example, surface treatment agents, such as a silane coupling agent, light or a thermosetting resin, a metal, a metal oxide, a metal nitride etc. can be used. As a forming method, a wet process such as coating, dipping (dipping) or spraying, or a dry process such as vapor deposition or sputtering can be employed. Further, the protective layer 17 may be a multilayer composite film made of different or similar materials. The protective layer 17 can be formed on the outer surface of the energy device excluding the external electrode 15. Depending on the material of the substrate 22, the protective layer 17 may not be formed on the surface of the substrate 22 as shown in FIG. 4.

  Furthermore, the energy device may be configured by repeatedly stacking the battery elements 20 as many times as necessary.

  A method for manufacturing the energy device of the present embodiment will be described. FIG. 6 is a schematic configuration diagram illustrating an example of an apparatus for manufacturing an energy device.

  The vacuum film forming apparatus 30 shown in FIG. 3 includes a vacuum chamber 31 that is partitioned vertically by a partition wall 31a. An unwinding roll 32, a cylindrical can roll 33, a winding roll 34, and conveying rolls 35a and 35b are arranged in a room (conveying chamber) 31b above the partition wall 31a. A first thin film formation source 41 and a second thin film formation source 42 are arranged in a room (thin film formation chamber) 31c below the partition wall 31a. An opening 31d is provided at the center of the partition wall 31a, and the lower surface of the can roll 33 is exposed to the thin film forming chamber 31c side. The inside of the vacuum chamber 31 is maintained at a predetermined degree of vacuum by a vacuum pump 37.

  As a method of forming a thin film by the first thin film forming source 41 and the second thin film forming source 42, various vacuum thin films represented by a vapor deposition method, a sputtering method, an ion plating method, a laser ablation method, etc., depending on the type of the thin film. Process can be used. By such a method, a desired thin film can be formed easily and efficiently.

  The long substrate 22 unwound from the unwinding roll 32 is sequentially conveyed by the conveying roll 35a, the can roll 33, and the conveying roll 35b, and is taken up by the winding roll 34. Particles 43 such as atoms, molecules, or clusters generated from the first thin film forming source 41 and the second thin film forming source 42 pass through the opening 31d of the partition wall 31a and travel on the can roll 33. A thin film 45 is formed on the surface.

  A positive electrode current collector layer 27, a positive electrode active material layer 26, and a solid electrolyte layer 25 are formed in advance on the surface of the substrate 22. Lithium particles are generated from the first thin film formation source 41, and second metal particles are generated from the second thin film formation source. Since the first thin film forming source 41 is arranged on the upstream side and the second thin film forming source 42 is arranged on the downstream side along the traveling direction of the base material 22, the lithium thin film formed by the first thin film forming source 41 is arranged. A thin film is formed on the substrate 22 while the contribution of the thin film formation shifts from the formation to the formation of the second metal thin film by the second thin film formation source 42. Therefore, it is possible to form the composition gradient negative electrode active material layer 24 in which the lithium concentration gradually increases toward the interface on the solid electrolyte layer 25 side and the second metal concentration gradually increases toward the opposite side. Thereafter, by forming the negative electrode current collector layer 23 on the composition gradient negative electrode active material layer 24, an energy device having a laminated structure as shown in FIG. 1 can be obtained.

[Example 1, Comparative Example 1]
An example corresponding to the first embodiment will be described.

  As Example 1, the apparatus shown in FIG. 6 was used to evaporate lithium from the first thin film formation source 41 and aluminum from the second thin film formation source 42, respectively, and to have a thickness of 2.5 μm by a two-source evaporation method. The composition gradient type negative electrode active material layer 24 was formed. As the substrate 22, a substrate in which a positive electrode current collector layer 27, a positive electrode active material layer 26, and a solid electrolyte layer 25 were formed on a 25 μm thick polyimide substrate was used. A 0.5 μm thick nickel thin film was used as the positive electrode current collector layer 27, a 4 μm thick lithium cobaltate thin film was used as the positive electrode active material layer 26, and a 2 μm thick lithium phosphate thin film was used as the solid electrolyte layer 25. After forming the composition gradient negative electrode active material layer 24, a nickel thin film was formed to a thickness of 0.5 μm as the negative electrode current collector layer 23, and the energy device shown in FIG. 1 was obtained.

  As Comparative Example 1, an energy device was obtained through the same steps as Example 1 except that a negative electrode active material layer made of a lithium thin film having a thickness of 2.5 μm was used instead of the composition gradient negative electrode active material layer 24.

  In Example 1, after forming the composition-graded negative electrode active material layer 24, exposure to the atmosphere for 30 minutes was performed, and then vacuum evacuation was performed again to prepare the negative electrode current collector layer 23. Similarly, in the comparative example, after forming the negative electrode active material layer, it was exposed to the atmosphere for 30 minutes, and then evacuated again to form the negative electrode current collector layer 23. The humidity of the exposure atmosphere was 20%. In the case of Comparative Example 1, peeling of the negative electrode current collector layer 23 occurred frequently. On the other hand, in the case of Example 1, peeling of the negative electrode current collector layer 23 did not occur.

  Electrodes were extracted from the positive and negative current collector layers 23 and 27 of the energy device having the configuration shown in FIG. 1, and a charge / discharge test was conducted at a charge / discharge rate of 0.2C. In Comparative Example 1, only 3% of the theoretical capacity expected from the positive electrode active material amount could be confirmed, but in Example 1, the battery capacity of 98% of the theoretical capacity could be confirmed.

  Under the same conditions as in Example 1, the composition gradient negative electrode active material layer 24 and the negative electrode current collector layer 23 were formed on the silicon substrate, and the distribution of lithium, aluminum, oxygen, nickel, and silicon in the film thickness direction was examined. . The results are shown in FIG. In addition, a negative electrode active material layer and a negative electrode current collector layer 23 were formed on a silicon substrate under the same conditions as in Comparative Example 1, and the distribution of lithium, oxygen, nickel, and silicon in the film thickness direction was examined. The results are shown in FIG. The element distribution was measured by a technique of spectroscopic analysis of the sample while plasma etching from the film surface, and the composition data was obtained by calibrating the detection signal intensity with the data of the standard sample.

  In FIG. 8 corresponding to Comparative Example 1, oxygen was detected at a high level at the interface between the negative electrode active material layer and the negative electrode current collector layer 23 (point where the etching depth was about 0.5 μm). In FIG. 7 corresponding to FIG. 7, the oxygen detection level at the interface between the composition-gradient negative electrode active material layer 24 and the negative electrode current collector layer 23 (point where the etching depth is about 0.5 μm) was low.

  In FIG. 7 corresponding to Example 1, the lithium distribution curve and the aluminum distribution curve of the composition gradient negative electrode active material layer 24 are extended to the negative electrode current collector layer 23 side. The element concentrations indicated by the lithium extension line and the aluminum extension line at the position where the oxygen concentration peaks near the interface with the negative electrode current collector layer 23 (point where the etching depth is about 0.5 μm) are respectively Lic. And Alc. Accordingly, the lithium ratio Rc (= Lic / (Lic + Alc) × 100) on the negative electrode current collector layer 23 side of the composition gradient negative electrode active material layer 24 is 50 at%, and the lithium ratio Rc is a preferable numerical range. Rc ≦ 60 at% was satisfied. Therefore, in the energy device of Example 1, peeling of the negative electrode current collector layer 23 and a significant decrease in battery capacity were not recognized.

  In FIG. 7 corresponding to Example 1, the lithium distribution curve and the aluminum distribution curve of the composition-graded negative electrode active material layer 24 are extended to the silicon substrate side (corresponding to the solid electrolyte layer 25 side in the energy device). To do. The element concentrations indicated by the extension line of lithium and the extension line of aluminum at the position where the oxygen concentration peaks near the interface with the silicon substrate (point where the etching depth is about 3 μm) are set to Lie and Ale, respectively. Accordingly, the lithium ratio Re (= Lie / (Lie + Ale) × 100) on the silicon substrate side of the composition-graded negative electrode active material layer 24 is 90 at%, and the lithium ratio Re is a preferable numerical range, Re ≧ 70 at%. Was satisfied. Therefore, the energy device of Example 1 had good charge / discharge cycle characteristics.

(Embodiment 2)
An example of a schematic configuration of the energy device according to the second embodiment of the present invention is shown in FIG. In the energy device of the present embodiment, the battery element 20 is laminated on the substrate 22. In the battery element 20, a positive electrode current collector layer 27, a positive electrode active material layer 26, a solid electrolyte layer 25, and a negative electrode composite layer 29 are formed in this order. In FIG. 9, the substrate 22 is disposed on the positive electrode current collector layer 27 side of the battery element 20, but may be disposed on the negative electrode composite layer 29 side.

  Examples of the substrate 22 include polyimide (PI), polyamide (PA), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), other polymer films, stainless metal foil, nickel, copper, aluminum, and other metals. A flexible material such as a metal foil containing an element can be used. Furthermore, various shapes of silicon, glass, ceramic, plastic, and the like can be used, and in the present invention, the material and shape of the substrate are not particularly limited.

  As the positive electrode current collector layer 27, for example, nickel, copper, aluminum, platinum, platinum-palladium, gold, silver, titanium, or a metal represented by ITO (indium-tin oxide) can be used. Depending on the final form of the energy device, when the substrate 22 is disposed on the positive electrode side and a conductive material is used as the substrate 22, the positive electrode current collector layer 27 is omitted and the substrate 22 is used as the positive electrode current collector layer 27. Can also work.

  As the positive electrode active material layer 26, for example, lithium cobaltate, lithium nickelate, or the like can be used. However, the material of the positive electrode active material layer 26 of the present invention is not limited to the above, and other materials can also be used.

As the solid electrolyte layer 25, a material having ion conductivity and small enough to have negligible electronic conductivity can be used. Especially when the energy device is a lithium ion secondary battery, since lithium ions are mobile ions, Li ₃ PO ₄ and, mixed with nitrogen to Li ₃ PO ₄ (or part of the elements of Li ₃ PO ₄ A solid electrolyte made of a material (LiPON: typical composition is Li _2.9 PO _3.3 N _0.36 ) or the like obtained by substituting with nitrogen is preferable because of its excellent lithium ion conductivity. Similarly, a solid electrolyte made of a sulfide such as Li ₂ S—SiS ₂ , Li ₂ S—P ₂ S ₅ , Li ₂ S—B ₂ S ₃ is also effective. Furthermore, solid electrolytes obtained by doping these solid electrolytes with lithium halides such as LiI and lithium oxyacid salts such as Li ₃ PO ₄ are also effective. The material of the solid electrolyte 25 of the present invention is not limited to the above, and other materials can be used as the solid electrolyte layer 25. By using a solid electrolyte as the electrolyte, it is not necessary to take countermeasures against liquid leakage which are essential in the conventional liquid electrolyte, and the energy device can be easily reduced in size and thickness.

  The negative electrode composite layer 29 has both a role as a negative electrode active material layer and a role as a negative electrode current collector layer, and is made of a lithium compound containing at least lithium and a second metal. This improves the chemical stability of the negative electrode composite layer 24 and facilitates production.

  The second metal is a metal having a work function of 4 eV or more. This is because such a metal is chemically stable and facilitates efficient film formation of the negative electrode composite layer 29. Examples of metals having a work function of 4 eV or more are aluminum, silicon, vanadium, cobalt, nickel, copper, germanium, zirconium, niobium, molybdenum, silver, rhodium, tin, tantalum, palladium, platinum, gold, tungsten, and the like. . Aluminum is preferable. This is because a thin film having good characteristics can be easily formed. However, it is not limited to these, For example, you may use metals other than the metal illustrated previously and whose work function is 4 eV or more as a 2nd metal. Further, two or more metals having a work function of 4 eV or more may be included.

  In the thickness direction of the negative electrode composite layer 29 (the vertical direction in FIG. 9), the composition ratio of lithium and the second metal is not constant, and the lithium concentration gradually increases toward the interface with the solid electrolyte layer 25. In other words, the lithium concentration gradually decreases as the distance from the solid electrolyte layer 25 increases. Thereby, the negative electrode composite layer 29 can be stably formed without impairing the charge / discharge characteristics.

  At the interface of the negative electrode composite layer 29 on the side opposite to the solid electrolyte layer 25, the lithium concentration is preferably reduced and is substantially composed of the second metal. Specifically, a portion where the lithium ratio Rc with respect to the total of lithium and the second metal is 20 at% or less exists at or near the interface opposite to the solid electrolyte layer 25 of the negative electrode composite layer 29, and Rc The thickness T of the portion of ≦ 20 at% is 100 nm or more. The thickness T is preferably 200 nm or more, more preferably 500 nm or more. Further, the lithium ratio Rc with respect to the total of lithium and the second metal is preferably 10 at% or less, preferably 5 at% or less, at or near the interface of the negative electrode composite layer 29 opposite to the solid electrolyte layer 25. Is more preferable. Due to the large thickness T and the small lithium ratio Rc, the reactivity of the negative electrode composite layer 29 with moisture and oxygen is suppressed on the surface of the negative electrode composite layer 29 opposite to the solid electrolyte layer 25. I can do it. In particular, when Rc / T is 200 (at% / μm) or less, significant discoloration of the surface of the negative electrode composite layer 29 when the energy device is left in a high humidity atmosphere can be prevented. Further, when Rc / T is 10 (at% / μm) or less, the storage characteristics of the energy device in a high humidity atmosphere and the battery characteristics in the charge / discharge cycle are remarkably improved.

  It is preferable that the lithium ratio Re with respect to the total of lithium and the second metal is 70 at% or more at the interface or the vicinity thereof on the solid electrolyte layer 25 side of the negative electrode composite layer 29. When the lithium ratio Re at the interface of the negative electrode composite layer 29 on the solid electrolyte layer 25 side or in the vicinity thereof is less than 70 at%, the capacity is likely to decrease in the charge / discharge cycle test of the energy device. In particular, the cycle deterioration is remarkable when the charge / discharge rate is 2C or more. This is because when the lithium ratio Re decreases at the solid electrolyte layer 25 side interface of the negative electrode composite layer 29, it becomes difficult for Li to enter and exit at the interface, thereby deteriorating charge / discharge cycle characteristics. . Preferably, the lithium ratio Re is 80 at% or more. As a result, when the charge / discharge rate is 10 C, cycle characteristics comparable to those when the second metal is not included (that is, Re = 100 at%) are obtained.

  Since the negative electrode composite layer 29 has both a role as a negative electrode active material layer and a role as a negative electrode current collector layer, in the energy device of the present embodiment, the negative electrode current collector layer is not provided on the surface of the negative electrode composite layer 29. May be. As described above, the negative electrode composite layer 29 has a portion having a thickness of 100 nm or more and a lithium ratio Rc of 20 at% or less at the interface or the vicinity thereof opposite to the solid electrolyte 25. This portion can function as a negative electrode current collector layer. Omission of the negative electrode current collector layer that is separate from the negative electrode composite layer 29 causes peeling at the interface between the negative electrode active material layer and the negative electrode current collector layer, which has been a problem in conventional energy devices. This eliminates the problem of reduced battery capacity. Moreover, the process of forming a negative electrode collector layer separately becomes unnecessary.

  The product form of the energy device is not particularly limited, and various types are conceivable. For example, it may be a flat wound body as shown in FIG. 2 described in the first embodiment, or may be a laminate structure as shown in FIG. Since it is the same as that of Embodiment 1 except the structure of the battery element 20 differing, these description is abbreviate | omitted.

  A method for manufacturing the energy device of the present embodiment will be described. FIG. 10 is a schematic configuration diagram illustrating an example of an apparatus for manufacturing an energy device.

  The vacuum film forming apparatus 50 shown in FIG. 10 includes a vacuum chamber 51 that is partitioned vertically by a partition wall 51a. An unwinding roll 52, cylindrical first and second can rolls 53a and 53b, a take-up roll 54, and transport rolls 55a, 55b, 55c, and 55d are disposed in a room (transport chamber) 51b above the partition wall 51a. The First to fifth thin film forming sources 61 to 65 and a plasma gun 67 are arranged in a room (thin film forming chamber) 51c below the partition wall 51a. The partition wall 51a is provided with first to fourth openings 58a to 58d. The outer peripheral surface of the first can roll 53a is opposed to the first thin film forming source 61 through the first opening 58a, and is opposed to the second thin film forming source 62 through the second opening 58b. The outer peripheral surface of the second can roll 53b faces the third thin film forming source 63 through the third opening 58c, and faces the fourth thin film forming source 64 and the fifth thin film forming source 65 through the fourth opening 58d. ing. The plasma gun 67 is arranged so that the plasma flow 67a from now on irradiates the outer peripheral surface of the first can roll 53a through the second opening 58b. The inside of the vacuum chamber 51 is maintained at a predetermined degree of vacuum by the first and second vacuum pumps 57a and 57b. The relative positional relationship between the plasma gun 67 and the first to fifth thin film forming sources 61 to 65 and the substrate 22 is not limited to that shown in FIG. 10, and can be changed according to individual circumstances of the process equipment.

  As a method of forming a thin film by the first to fifth thin film forming sources 61 to 65, various vacuum thin film processes represented by a vapor deposition method, a sputtering method, an ion plating method, a laser ablation method and the like are used according to the type of the thin film. Can be used. By such a method, a desired thin film can be formed easily and efficiently.

  The long substrate 22 unwound from the unwinding roll 52 is sequentially transported by the transporting roll 55a, the first can roll 53a, the transporting roll 55b, the transporting roll 55c, the second can roll 53b, and the transporting roll 55d. It is wound on a roll 54. In this process, particles such as atoms, molecules, or clusters generated from the first to fifth thin film forming sources 61 to 65 are sequentially deposited on the surface of the substrate 22 to form a thin film.

  First, the material of the positive electrode current collector layer 27 is deposited on the substrate 22 through the first opening 58a by the first thin film forming source 61, and the positive electrode current collector layer 27 is formed. Next, the material of the positive electrode active material layer 26 is deposited on the substrate 22 through the second opening 58b by the second thin film formation source 62, and the positive electrode active material layer 26 is formed. At this time, the plasma flow 67 a from the plasma gun 67 imparts energy to the material particles of the positive electrode active material layer 26 from the second thin film formation source 62. Next, the material of the solid electrolyte layer 25 adheres on the substrate 22 through the third opening 58c by the third thin film formation source 63, and the solid electrolyte layer 25 is formed. Finally, lithium particles from the fourth thin film formation source 64 and second metal particles from the fifth thin film formation source 65 adhere to the substrate 22 through the fourth openings 58d, and the negative electrode composite layer 29 is formed. Since the fourth thin film forming source 64 is arranged on the upstream side and the fifth thin film forming source 65 is arranged on the downstream side along the traveling direction of the base material 22, the lithium thin film formed by the fourth thin film forming source 64 is arranged. A thin film is formed on the base material 22 while the contribution of the thin film formation shifts from the formation to the formation of the second metal thin film by the fifth thin film formation source 65. Therefore, the negative electrode composite layer 29 in which the lithium concentration gradually increases toward the interface on the solid electrolyte layer 25 side and the second metal concentration gradually increases toward the opposite side can be formed. Thus, an energy device having a laminated structure as shown in FIG. 9 can be obtained.

[Example 2]
An example corresponding to the second embodiment will be described.

  As Example 2, the apparatus shown in FIG. 10 was used, and a 20 μm-thick polyimide substrate was used as the substrate 22. On the substrate 22, a nickel thin film having a thickness of 0.5 μm is formed as the positive electrode current collector layer 27 by the first thin film forming source 61, and a lithium cobalt oxide thin film having a thickness of 4 μm is formed as the positive electrode active material layer 26 by the second thin film forming source 62. 2 μm thick lithium phosphate thin films were sequentially formed as the solid electrolyte layer 25 by the third thin film forming source 63. Further, lithium was evaporated from the fourth thin film forming source 64 and aluminum was evaporated from the fifth thin film forming source 65, respectively, and the negative electrode composite layer 29 having a thickness of 3 μm was formed by a two-source vapor deposition method. Thus, the energy device shown in FIG. 9 was obtained.

  Electrodes were extracted from the positive electrode current collector layer 27 and the negative electrode composite layer 29 of the energy device having the configuration shown in FIG. 9, and a charge / discharge test was performed at a charge / discharge rate of 0.2C. As a result, a battery capacity of 97% of the theoretical capacity expected from the amount of the positive electrode active material was confirmed.

  Under the same conditions as in Example 2, only the negative electrode composite layer 29 was formed on the silicon substrate, and the distribution of lithium, aluminum, oxygen, and silicon in the film thickness direction was examined. The results are shown in FIG. The element distribution was measured by a technique of spectroscopic analysis of the sample while plasma etching from the film surface, and the composition data was obtained by calibrating the detection signal intensity with the data of the standard sample.

  From the composition distribution in the film thickness direction of FIG. 11, it was found that in the energy device of Example 2, the Li concentration was low in the vicinity of the surface of the negative electrode composite layer 29.

  In FIG. 11, the lithium ratio Rc (= Lic / (Lic + Alc) × 100) is 0 at% when the lithium concentration Lic and the aluminum concentration Alc at or near the surface of the negative electrode composite layer 29 are used. The thickness T of the portion satisfying Rc ≦ 20 at% is 500 nm. Rc / T = 0 (at% / μm). The energy device of Example 2 had no discoloration on the surface of the negative electrode composite layer 29 when left in a high humidity atmosphere, and was excellent in battery characteristics in a charge / discharge cycle.

  In FIG. 11, the lithium distribution curve and the aluminum distribution curve of the negative electrode composite layer 29 are extended to the silicon substrate side (corresponding to the solid electrolyte layer 25 side in the energy device). The element concentrations indicated by the extension line of lithium and the extension line of aluminum at the position where the oxygen concentration peaks near the interface with the silicon substrate (point where the etching depth is about 3 μm) are set to Lie and Ale, respectively. Accordingly, the lithium ratio Re (= Lie / (Lie + Ale) × 100) on the silicon substrate side of the negative electrode composite layer 29 is 90 at%, and the lithium ratio Re satisfies a preferable numerical range of Re ≧ 70 at%. It was. Therefore, the energy device of Example 2 had good charge / discharge cycle characteristics.

  The field of application of the energy device of the present invention is not particularly limited, but it can be used as a secondary battery for a thin, lightweight, small portable device, for example.

It is a schematic sectional drawing which shows an example of the laminated structure of the energy device concerning Embodiment 1 of this invention. It is a schematic sectional drawing of an example of the product form of the energy device concerning Embodiment 1 of this invention. It is a schematic perspective view of the product form of the energy device shown in FIG. It is a schematic sectional drawing of another example of the product form of the energy device concerning Embodiment 1 of this invention. FIG. 5A is a plan view showing an example of the fuse portion in the energy device of the present invention, and FIG. 5B is a cross-sectional view taken along line 5B-5B in FIG. 5A. It is a schematic sectional drawing of an example of the manufacturing apparatus concerning Embodiment 1 of the energy device of this invention. 4 is an element distribution diagram in the thickness direction of a negative electrode current collector layer and a composition gradient negative electrode active material layer corresponding to Example 1. FIG. 6 is an element distribution diagram in the thickness direction of a negative electrode current collector layer and a negative electrode active material layer corresponding to Comparative Example 1. FIG. It is a schematic sectional drawing which shows an example of the laminated structure of the energy device concerning Embodiment 2 of this invention. It is a schematic sectional drawing of an example of the manufacturing apparatus concerning Embodiment 2 of the energy device of this invention. 5 is an element distribution diagram in the thickness direction of a negative electrode composite layer corresponding to Example 2. FIG. It is sectional drawing which shows the general structure of the lithium ion secondary battery using a solid electrolyte. It is a schematic sectional drawing which shows an example of the conventional formation method of a negative electrode active material layer. It is a schematic sectional drawing which shows an example of the conventional mass-production formation method of a negative electrode active material layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Rolled body 11 ... Inner core 12 ... External electrode 15 ... External electrode 16 ... Fuse part 17 ... Protective layer 20 ... Battery element 22 ... Substrate 23- ··· Negative electrode current collector layer 24 ··· Composition gradient negative electrode active material layer 25 ··· Solid electrolyte layer 26 ··· Positive electrode active material layer 27 ··· Positive electrode current collector layer 29 ··· Negative electrode composite layer 30 ... Vacuum film forming apparatus 31 ... Vacuum chamber 31a ... Branch 31b ... Transfer chamber 31c ... Thin film forming chamber 31d ... Opening 32 ... Unwinding roll 33 ... Can roll 34 ... take-up rolls 35a, 35b ... transport roll 37 ... vacuum pump 41 ... first thin film forming source 42 ... second thin film forming source 43 ... particles 45 ... thin film 50 ..Vacuum film forming apparatus 51 ... Vacuum chamber 51a ... Partition wall 51b ... Transfer chamber 51c ... Thin Forming chamber 52 ... Unwinding rolls 53a, 53b ... Can roll 54 ... Winding rolls 55a, 55b, 55c, 55d ... Conveying rolls 58a-58d ... Openings 57a, 57b ... Vacuum Pump 61 ... First thin film formation source 62 ... Second thin film formation source 63 ... Third thin film formation source 63 ... Fourth thin film formation source 65 ... Fifth thin film formation source 67 ... Plasma gun

Claims (11)

An energy device having a solid electrolyte layer and a negative electrode active material layer containing lithium and a second metal,
An energy device, wherein a concentration of lithium in the negative electrode active material layer gradually increases toward an interface on the solid electrolyte layer side.   The energy device according to claim 1, wherein the second metal is a metal having a work function of 4 eV or more.   2. The energy device according to claim 1, wherein a ratio of lithium contained in the negative electrode active material layer to the total of lithium and the second metal is 70 at% or more at or near the interface on the solid electrolyte side.   2. The energy device according to claim 1, wherein a ratio of lithium contained in the negative electrode active material layer to the total of lithium and the second metal is 60 at% or less at an interface opposite to the solid electrolyte or in the vicinity thereof. .   The energy device according to claim 1, wherein the second metal is aluminum.   The energy device according to claim 1, wherein a current collector layer is not formed on a surface of the negative electrode active material layer opposite to the solid electrolyte. An energy device having a solid electrolyte layer and a negative electrode composite layer containing lithium and a second metal,
The second metal is a metal having a work function of 4 eV or more,
The lithium concentration in the negative electrode composite layer gradually decreases as the distance from the solid electrolyte layer increases.
The region where the ratio of lithium contained in the negative electrode composite layer to the total of lithium and the second metal is 20 at% or less is thick at the interface or the vicinity thereof opposite to the solid electrolyte layer of the negative electrode composite layer. An energy device characterized by being present at 100 nm or more.   8. The energy device according to claim 7, wherein a ratio of lithium contained in the negative electrode composite layer to the total of lithium and the second metal is 70 at% or more at the interface on the solid electrolyte side or in the vicinity thereof.   The energy device according to claim 7, wherein the second metal is aluminum.   The energy device according to claim 7, wherein a current collector layer is not formed on a surface of the negative electrode composite layer opposite to the solid electrolyte. A method for producing an energy device comprising a step of forming a negative electrode layer containing lithium and a second metal on a solid electrolyte layer by a vacuum thin film process,
Using a first thin film forming source for laminating the lithium and a second thin film forming source for laminating the second metal,
A method of manufacturing an energy device, wherein the negative electrode layer is formed by shifting the contribution of thin film formation from thin film formation by the first thin film formation source to thin film formation by the second thin film formation source.

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