JP2006179241A - Solid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid battery capable of relaxing strain and stress generated with expansion/contraction of a power generation element caused by charge and discharge. <P>SOLUTION: This solid battery includes the power generation element and a protective layer in contact with a side face of the power generation element. The solid battery is so structured that the power generation element includes a lower electrode layer, an electrolyte layer and an upper layer all of which are sequentially stacked on one another; the protective layer is formed of an electron insulator, and covers side faces and an upper surface peripheral part of the lower electrode layer; and a lower surface peripheral part of the electrolyte layer covers at least a part of the upper surface of the protective layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid state battery including a power generation element having a lower electrode layer, an electrolyte layer, and an upper electrode layer that are sequentially stacked.

  The solid battery has a configuration as shown in FIG. 3, for example. The solid state battery of FIG. 3 includes a substrate 31 and a power generation element 30 provided thereon, and a lower electrode layer 33, an electrolyte layer 34, and an upper electrode layer 35 constituting the power generation element 30 are thin films formed above. The area becomes smaller (see, for example, Patent Document 1). Such a solid battery is manufactured by sequentially forming a thin film-like lower current collecting layer 32, lower electrode layer 33, electrolyte layer 34, upper electrode layer 35, and upper current collecting layer 36, respectively. When the substrate 31 has conductivity, the lower current collecting layer 32 may be omitted.

  A solid battery having a configuration as shown in FIG. 4 has also been proposed. The solid state battery of FIG. 4 includes a substrate 41 and a power generation element 40 provided thereon, and the lower electrode layer 43, the electrolyte layer 44, and the upper electrode layer 45 constituting the power generation element 40 all have the same size. (For example, refer to Patent Document 2). Such a solid battery is also fabricated by sequentially forming a thin film-like lower current collecting layer 42, lower electrode layer 43, electrolyte layer 44, upper electrode layer 45, and upper current collecting layer 46, respectively.

A solid battery having a configuration as shown in FIG. 5 has also been proposed. In the solid state battery of FIG. 5, a lower current collecting layer 52 and an upper electrode current collecting layer 56 are formed on a substrate 51. A lower electrode layer 53 is formed on the upper surface of the lower current collecting layer 52, and the lower electrode layer 53 is covered with an electrolyte layer 54. A part of the lower current collecting layer 52 is exposed, and the exposed portion serves as a connection portion with an external terminal. The upper electrode layer 55 covers the upper surfaces of the electrolyte layer 54 and the upper electrode current collecting layer 56 so as to short-circuit each other (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 10-284130 JP 2002-42863 A US Pat. No. 5,538,625

  In the configuration described in Patent Document 1, since the area becomes smaller as the thin film is formed on the upper side, the reaction area of the lower electrode layer 33 used for charging / discharging becomes as small as the area of the upper electrode layer 35. End up.

  In the configuration described in Patent Document 2, since the lower electrode layer 43, the electrolyte layer 44, and the upper electrode layer 45 have the same size, the side surfaces of the respective layers are aligned. In addition, since the thickness of each layer is as thin as several μm, leakage current along the side surface tends to flow, and there is a possibility that the battery characteristics may be defective.

  In the configuration described in Patent Document 3, the upper surface peripheral portion of the lower electrode layer 53 and the upper electrode layer 55 face each other with the electrolyte layer 54 interposed therebetween. In this state, when the lower electrode layer 53 or the upper electrode layer 55 expands or contracts due to discharge or charge / discharge, strain and stress tend to concentrate on the peripheral edge of the upper surface of the lower electrode layer 53. Therefore, there is a possibility that any of the lower electrode layer 53, the electrolyte layer 54, and the upper electrode layer 55 constituting the power generation element is cracked. In particular, the region surrounded by the broken lines X1 and X2, that is, the peripheral edge of the upper surface of the lower electrode layer 53 and the electrolyte layer 54 adjacent thereto are easily cracked.

  In particular, when the electrolyte layer 54 is cracked, there is a high possibility that the lower electrode layer 53 and the upper electrode layer 55 are short-circuited. Further, since the current collecting layer 56 for the upper electrode layer and the lower current collecting layer 52 are adjacent to each other with the electrolyte layer 54 interposed therebetween, if the electrolyte layer 54 is formed thin in order to improve battery performance, there is a risk of short-circuiting easily. is there.

  The present invention aims to solve these problems, the lower electrode layer and the upper electrode layer have a sufficient facing area, the power generation element is hardly cracked, and the side surface of the power generation element An object of the present invention is to provide a high-performance solid state battery in which leakage current along the line is suppressed.

  The present invention first includes a power generation element and a protective layer in contact with a side surface of the power generation element. The power generation element includes a lower electrode layer, an electrolyte layer, and an upper electrode layer that are sequentially stacked. Further, the present invention relates to a solid state battery that is made of an electronic insulator and covers the side surface and the upper surface peripheral portion of the lower electrode layer, and the lower surface peripheral portion of the electrolyte layer covers at least part of the upper surface of the protective layer.

  The present invention also includes a power generation element and a protective layer in contact with a side surface of the power generation element. The power generation element includes a lower electrode layer, an electrolyte layer, and an upper electrode layer that are sequentially stacked. A solid body made of an electronic insulator and covering the side surface of the lower electrode layer and the side surface and upper surface periphery of the electrolyte layer, and the lower surface periphery of the upper electrode layer covers at least part of the upper surface of the protective layer It relates to batteries.

  In the structure as described above, the protective layer covering the side surface and the upper surface peripheral edge of the lower electrode layer suppresses leakage current, and also prevents distortion and stress generated in the power generation element due to battery discharge or charge / discharge reaction. Relaxation or fracture resistance against strain and stress is suitable.

  For the protective layer, a resin, metal oxide, glass, or the like having electronic insulating properties can be used, but the protective layer is not limited thereto.

  The elastic modulus of the protective layer is preferably smaller than the elastic modulus of the electrolyte layer. This is because when the elastic modulus of the protective layer is controlled in this way, the effect of relieving strain and stress generated in the power generation element is increased. The protective layer is preferably made of a material having rubber elasticity, and it is particularly desirable to use a rubbery polymer. This is because by using a material having rubber elasticity, the effect of relieving strain and stress generated in the power generation element becomes remarkable.

  For the protective layer, an ion conductor having electronic insulating properties can also be used. By using the ionic conductor, ions are exchanged between the upper surface peripheral portion of the lower electrode layer and the lower surface peripheral portion of the upper electrode layer, so that the characteristics of the solid state battery are improved.

  The ionic conductor may be an inorganic ionic conductor, but an organic ionic conductor such as a polymer electrolyte is more preferable because of its low elastic modulus. As the organic ionic conductor, polyethylene oxide and its derivatives are particularly desirable because of their low elastic modulus.

The electrolyte layer may be made of an organic solid electrolyte, but is preferably made of an inorganic solid electrolyte from the viewpoint of easy formation into a thin film having a thickness of several μm or less and easy improvement of energy density. . As the inorganic solid electrolyte, a phosphorus compound containing at least Li, P and O is desirable.
The size of the power generation element, the thickness of the lower electrode layer, the electrolyte layer and the upper electrode layer, the thickness of the protective layer, and the like are not particularly limited.

  According to the present invention, the strain or stress generated in the power generation element, particularly the lower electrode layer accompanying the discharge or charge / discharge reaction of the battery is alleviated by the protective layer, or the fracture resistance due to the strain or stress is improved. Therefore, it is possible to prevent the power generation element, particularly the lower electrode layer and the electrolyte layer from being cracked. Therefore, it is possible to obtain a reliable and high-performance primary solid battery or secondary solid battery excellent in discharge characteristics and charge / discharge cycle characteristics.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
FIG. 1 is a cross-sectional view of a solid state battery 100 having a substrate 11, a power generation element 10 provided thereon, and a protective layer 17 in contact with a side surface of the power generation element 10 according to an embodiment of the present invention. is there. The protective layer 17 is made of an electronic insulator. A thin film-shaped lower current collecting layer 12 is formed on the substrate 11, and a power generation element 10 including a thin film-shaped lower electrode layer 13, an electrolyte layer 14, and an upper electrode layer 15 is formed on the upper surface of the substrate 11. Yes. The size of the lower current collecting layer 12 is formed larger than the size of the lower electrode layer 13, and the lower surface of the protective layer 17 is in contact with the upper surface of the lower current collecting layer 12. The lower current collecting layer 12 may be formed to have a smaller size, and the lower surface of the protective layer 17 may be in contact with the substrate 11.

  The protective layer 17 covers the side surface and the upper surface periphery of the lower electrode layer 13. On the other hand, the lower surface peripheral portion of the electrolyte layer 14 formed on the upper surface of the lower electrode layer 13 covers a part of the upper surface of the protective layer 17. That is, a part of the protective layer 17 made of an electronic insulator is interposed between the upper surface periphery of the lower electrode layer 13 and the lower surface periphery of the electrolyte layer 14. Such a state can be obtained by forming the lower electrode layer 13, forming the protective layer 17, and then forming the electrolyte layer 14.

  In the above structure, even when the upper electrode layer 15 has an area equal to or larger than that of the lower electrode layer 13, the presence of the protective layer 17 made of an electronic insulator suppresses leakage current along the side surface of the power generation element. Is done. Therefore, the upper electrode layer 15 can be formed on the upper surface of the electrolyte layer 14 so that the area facing the lower electrode layer 13 is maximized, and the active material contained in the lower electrode layer 13 can be effectively used. is there.

  In addition, when the solid battery having the above-described structure is discharged or charged / discharged, the lower electrode layer 13 expands or contracts, so that distortion or stress is generated in the power generation element. Such strain and stress tend to concentrate on the side surface and the upper surface peripheral edge of the lower electrode layer 13. However, since the protective layer 17 is disposed so as to cover the side surface and the upper surface periphery of the lower electrode layer 13, the generated strain and stress are alleviated by the protective layer 17. Alternatively, the thickness of the electronic insulator covering the side surface and the upper surface peripheral portion of the lower electrode layer 13 is increased, so that the breakdown strength is increased, so that a short circuit hardly occurs.

  From the viewpoint of enhancing the effect of relieving strain and stress, the elastic modulus of the protective layer 17 is preferably smaller than the elastic modulus of the electrolyte layer 14, and is preferably smaller than 1/2 of the electrolyte layer 14, for example. . By reducing the elastic modulus of the protective layer 17, the concentration of strain and stress on the peripheral edge of the upper surface of the lower electrode layer 53 is greatly suppressed, and the lower electrode layer 53, the electrolyte layer 54, and the upper electrode layer 55 constituting the power generation element. The risk of cracks in either of these is greatly reduced.

The electronic insulator constituting the protective layer 17 is not particularly limited, and examples thereof include resins, nitrides, carbides, sulfides, borides, fluorides, fluorides, and mixed materials thereof. The electronic insulator is desirably a material (particularly a resin) having rubber elasticity.
As the material having rubber elasticity, a rubbery polymer is preferable. As the rubbery polymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, or the like is desirable. One material having rubber elasticity may be used alone, or two or more materials may be used in combination.

  The electronic insulator constituting the protective layer 17 may have ionic conductivity. When the protective layer 17 has ionic conductivity, ions can move even in a part of the protective layer 17 interposed between the upper surface periphery of the lower electrode layer 13 and the lower surface periphery of the electrolyte layer 14. The battery characteristics are improved.

  When an organic ionic conductor such as a polymer electrolyte is used as the protective layer 17, an organic ionic conductor such as polyethylene oxide or a derivative of polyethylene oxide is particularly desirable because of its low elastic modulus. An organic ion conductor may be used individually by 1 type, and may be used in combination of 2 or more type.

  The lower electrode layer 13 and the upper electrode layer 15 include one and the other of a positive electrode active material and a negative electrode active material, respectively. As the positive electrode active material and the negative electrode active material, materials known as active materials for secondary batteries can be used without any particular limitation.

Examples of the positive electrode active material include lithium-containing transition metal oxides, vanadium oxides, chromium oxides, and titanium sulfides. Examples of the lithium-containing transition metal oxide include lithium cobalt oxide (LiCoO ₂ , LiCoPO ₄ F), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnP 0 ₄ , LiMn ₂ O ₄ ), lithium Iron-based oxides (LiFePO ₄ , Li ₂ FePO ₄ F), LiMO ₂ (M is at least two selected from Ni, Co, Fe, Al, Mg, Mn, etc.) are preferable. These may be used alone or in combination of two or more.

Examples of the negative electrode active material include metals or metalloids, oxides, nitrides, oxynitrides, SiB ₃ , Mg ₂ Si, carbon, Cu ₂ P, Fe ₂ S, and FeSb ₂ . As the metal or semimetal, lithium, silicon, amorphous silicon, aluminum, silver, tin, antimony, or the like can be used. As the oxide, SiO, SnB _0.5 P _0.5 O ₃ , SnBPO _{6 , SnO 2, Fe 2 O 3} , CoO, WO 2, Li 2 SrTi 6 O 14, MoO 2, Li 4 Ti 5 O 12, TiO 2, Nb 2 O 5, WO, be used _Ta 2 _{O 5} or _the like As the nitride, Li _2.6 Co _0.4 N, Li ₃ FeN ₂ , Li ₇ MnN ₄ or the like can be used. These may be used alone or in combination of two or more.

The electrolyte layer 14 is not particularly limited, but is preferably made of an inorganic solid electrolyte. As the inorganic solid electrolyte, a phosphorus compound containing at least Li, P and O is desirable. For example, lithium phosphate (Li ₃ PO ₄ ), LiPON obtained by substituting part of oxygen of lithium phosphate with nitrogen, LiPOD (D is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb) , Mo, Ru, Ag, Ta, W, Pt, Au, etc.). LiAON (A is at least one selected from Si, B, Ge, Al, C, Ga and the like) can also be preferably used. These may be used alone or in combination of two or more.

  The lower current collecting layer 12 and the upper current collecting layer 16 can be used without particular limitation as long as they are electronic conductors that are stable at the potential of the adjacent electrodes. For example, a metal, an alloy, a metal oxide, or the like can be used. As the metal or alloy, for example, Au, Pt, Cu, Ni, Co, Ti or the like can be used. As the metal oxide, tin oxide, indium tin oxide, or the like can be used.

  In the structure of FIG. 1, the protective layer 17 covers a region having a width w <b> 1 at the periphery of the upper surface of the lower electrode layer 13. In addition, the electrolyte layer 14 covers a region of the width d1 at the inner peripheral edge of the upper surface of the protective layer 17. Furthermore, the upper surface of the protective layer 17 is positioned above the upper surface of the lower electrode layer 13 by a height h1.

  Here, the width w1 is preferably 0.01 mm to 5 mm. If the width W1 is too small, the effect of suppressing leakage current and cracking of the power generation element is reduced. If the width W1 is too large, the effective use area of the lower electrode layer 13 is reduced. The width d1 is preferably (W1 + 0.01) mm to (W1 + 5) mm. If the width d1 is too small, the effect of suppressing the leakage current is reduced, and if the width d1 is too large, the raw material for the electrolyte layer 14 is wasted. Further, the height h1 is desirably 0.005 mm to 1 mm. If the height h1 is too small, the effect of suppressing leakage current and cracking of the power generation element is reduced, and if the height h1 is too large, the battery capacity is reduced.

  The lower current collecting layer 12, the lower electrode layer 13, the electrolyte layer 14, the upper electrode layer 15, the upper current collecting layer 16 and the protective layer 17 can be easily formed by a normal thick film or thin film forming process, respectively. . As a thick film or thin film forming process applicable to the present invention, HP (hot press), plasma sintering, electric current sintering method, sol-gel method, CVD method (chemical-vapor-deposition), vapor deposition method, Examples thereof include a vacuum forming method such as a sputtering method, a plating technique, a spin coating method, a screen printing method, a coating method using a printing technique such as ink jetting and spraying. As a means for performing desired patterning, a mask method using metal, resin, oil or the like, or photolithography can be used.

When the protective layer 17 is made of a material having rubber elasticity such as polytetrafluoroethylene, a thick film or thin film forming method such as a sputtering method, or polytetrafluoroethylene previously formed into a sheet shape is heat-sealed. The protective layer 17 can be provided by sticking by a method. However, it is not necessarily limited to these methods.
Further, when the protective layer 17 is made of an organic ionic conductor such as polyethylene oxide, it is mixed with a solvent in advance and formed on the lower electrode to a desired thickness by using a coating method such as a dispenser, coater, blade method or the like. The protective layer 17 can be provided by drying the solvent or attaching polyethylene oxide formed in a sheet shape in advance by a thermal fusion method. However, it is not necessarily limited to these methods.

  In FIG. 1, a thin-film upper current collecting layer 16 is formed on the upper surface of the upper electrode layer 15, but the upper current collecting layer 16 is not essential, and the upper electrode layer 15 also serves as the upper current collecting layer. May be. Further, when the substrate 11 is a conductor, the lower current collecting layer 12 is not necessarily required. Further, when the lower current collecting layer 12 is formed on the substrate 11, the substrate 11 may be removed for thinning after the solid battery having the structure of FIG. 1 is formed.

Note that as the substrate 11, a metal, a resin, a semiconductor, glass, an oxide, a ceramic material, or the like can be used, but the substrate 11 is not limited thereto. Examples of metals that can be used include Al, Cu, Ti, stainless steel (SUS), and Kovar. Examples of resins that can be used include polyimide, polyethylene terephthalate (PET), polyamide, polyimide amide, and polyethylene naphthalate (PEN). Etc., and Si, SiO ₂ , MgO, NaCl, strontium titanate, alumina, sapphire substrates, and the like can be used as the semiconductor and other substrates. In particular, when a metal substrate is used, a reaction preventing film such as an oxide, fluoride, or nitride may be formed on the surface of the substrate in order to prevent a reaction between the active material and the substrate. Each substrate desirably has a smooth surface, and more preferably has a surface roughness Ra of about 5 μm or less.

Embodiment 2
FIG. 2 is a cross-sectional view of a solid state battery 200 having a substrate 21, a power generation element 20 provided thereon, and a protective layer 27 in contact with a side surface of the power generation element 20 according to an embodiment of the present invention. is there. The protective layer 27 is made of an electronic insulator. A thin-film lower current collecting layer 12 is formed on the substrate 21, and a power generation element 20 including a thin-film lower electrode layer 23, an electrolyte layer 24, and an upper electrode layer 25 is formed on the upper surface of the substrate 21. Yes. The size of the lower current collecting layer 22 is formed larger than the size of the lower electrode layer 23, and the lower surface of the protective layer 27 is in contact with the upper surface of the lower current collecting layer 22. Note that the size of the lower current collecting layer 22 may be formed smaller, and the lower surface of the protective layer 27 may be in contact with the substrate 21.

  The protective layer 27 covers the side surface of the lower electrode layer 23, the side surface of the electrolyte layer 24, and the peripheral edge of the upper surface. On the other hand, the lower surface peripheral portion of the upper electrode layer 25 formed on the upper surface of the electrolyte layer 24 covers a part of the upper surface of the protective layer 27. That is, a part of the protective layer 27 made of an electronic insulator is interposed between the upper surface periphery of the electrolyte layer 24 and the lower surface periphery of the upper electrode layer 25. Such a state can be obtained by forming the electrolyte layer 24, forming the protective layer 27, and then forming the upper electrode layer 25.

  In the structure of FIG. 2, the protective layer 27 covers a region of the width w <b> 2 at the peripheral edge of the upper surface of the electrolyte layer 24. Further, the upper electrode layer 25 covers a region having a width d2 at the inner peripheral edge of the upper surface of the protective layer 27. Furthermore, the upper surface of the protective layer 27 is positioned above the upper surface of the electrolyte layer 24 by a height h1.

  Here, the width w2 is preferably 0.01 mm to 5 mm. If the width W2 is too small, the effect of suppressing leakage current and cracking of the power generation element is reduced. If the width W2 is too large, the effective use area of the lower electrode layer 23 is reduced. The width d2 is preferably (W2 + 0.01) mm to (W2 + 5) mm. If the width d2 is too small, the effect of suppressing the leakage current is reduced, and if the width d2 is too large, the raw material of the upper electrode layer 25 is wasted. Further, the height h2 is desirably 0.05 mm to 1 mm. If the height h2 is too small, the effect of suppressing leakage current and cracking of the power generation element is reduced, and if the height h2 is too large, the battery capacity is reduced.

  In the solid state battery having the above-described configuration, the electrolyte layer 24 is affected by the strain and stress generated in the lower electrode layer 23, but the protective layer 27 has the side surface of the lower electrode layer 23 and the side surface and upper surface periphery of the electrolyte layer 24. Since the portion is covered, strain and stress are alleviated. Therefore, the risk of cracks in the electrolyte layer 24 is reduced as in other parts of the power generation element.

  Further, the upper electrode layer 25 can be formed on the upper surface of the electrolyte layer 24 so that the area facing the lower electrode layer 23 is maximized, and the active material contained in the lower electrode layer 23 can be effectively used. is there.

Further, when the electronic insulator constituting the protective layer 27 has ionic conductivity, even a part of the protective layer 27 interposed between the upper surface periphery of the lower electrode layer 23 and the lower surface periphery of the electrolyte layer 24. Since ions can be moved, the characteristics of the solid state battery are improved.
Therefore, even the solid battery having the structure shown in FIG. 2 can obtain substantially the same effect as that of the solid battery of the first embodiment.

The substrate 21, the lower current collecting layer 22, the lower electrode layer 23, the electrolyte layer 24, the upper electrode layer 25, the upper current collecting layer 26, and the protective layer 27 according to the second embodiment are the same as those described in the first embodiment. The lower current collecting layer 12, the lower electrode layer 13, the electrolyte layer 14, the upper electrode layer 15, the upper current collecting layer 16, and the protective layer 17 can be formed by using the same material and by the same method.
Specific examples of the present invention will be described below.

(I) Production of Substrate A 3 μm thick SiO ₂ film was formed on both surfaces of a stainless steel substrate (SUS304 substrate) (size 60 mm × 60 mm × 0.01 mm). Then, one cell of the structure shown in FIG. 1 was produced on both sides of the substrate having the SiO ₂ film. This double-sided, 2-cell battery was taken as 1 unit, and a total of 5 units (10 cells) were produced.

(Ii) Formation of the lower current collecting layer As a first step, a metal mask having an opening of 45 mm × 45 mm is attached to the substrate, and a 1 μm-thickness is formed on the SiO ₂ film by sputtering using a Ti target and an Au target. A lower current collecting layer made of a laminated film of a Ti layer and a 2 μm thick Au layer was formed. Ar was used as a sputtering discharge gas, and the gas pressure was 8 mTorr.

(Iii) Formation of the lower electrode layer As a second step, a metal mask having an opening of 20 mm × 20 mm is attached in alignment with the center of the lower current collecting layer, and the lower current collecting is performed by vapor deposition using Li and Co as an evaporation source. A 7 μm-thick lower electrode layer made of LiCoO ₂ was formed on the layer. Li was evaporated by resistance heating, and Co was evaporated by an electron beam and supplied onto the lower current collecting layer. Further, oxygen gas was circulated at 80 sccm in the film forming atmosphere, and the substrate temperature was 450 ° C.

(Iv) Formation of protective layer As a third step, a lithium salt LiTFSI (lithium trifluoromethanesulfonylimide), polyethylene oxide (PEO), and a solution of acetonitrile as a solvent are mixed using a dispenser. The protective layer was formed by coating and vacuum drying so as to cover the side surface and the upper surface peripheral edge of the lower electrode layer. The thickness of the protective layer containing PEO after drying was 10 μm, h1 was 3 μm, and the width was 5 mm. Further, the width (W1) of the upper surface peripheral portion of the lower electrode layer covered with the protective layer was 0.5 mm, and a 19 mm × 19 mm region at the center of the upper surface of the lower electrode layer was exposed.

  The protective layer thus obtained is an ionic conductor made of PEO containing a lithium salt and has lithium ion conductivity.

(V) Formation of electrolyte layer As a fourth step, a lower electrode layer and a 30 mm × 30 mm metal mask are fitted together with the center of the lower electrode layer, and a sputtering method using a target obtained by sintering LiSiPO is used. An electrolyte layer made of Li _3.5 Si _0.5 P _0.5 O ₄ and having a thickness of 2 μm was formed on the protective layer. As a result, the 19 mm × 19 mm region in the center of the upper surface of the lower electrode layer and the protective layer made of PEO were completely covered with the electrolyte layer. A sputtering gas used was a mixed gas of Ar and O _2, and the gas pressure was 10 mTorr. The flow ratio of Ar to O ₂ in the mixed gas was Ar: O ₂ = 90: 10.

(Vi) Formation of upper current collecting layer and upper current collecting layer As a fifth step, a resistance heating vapor deposition method using a metal mask having an opening of 25 mm × 25 mm aligned with the center of the electrolyte layer and using Li as an evaporation source As a result, a 4 μm thick upper electrode layer and upper current collecting layer made of Li were formed on the electrolyte layer.

(I) Production of substrate A 3 μm thick SiO ₂ film was formed on both surfaces of a stainless steel substrate (SUS304 substrate) (size 60 mm × 60 mm × 0.01 mm). Then, one cell of the structure shown in FIG. 2 was formed on both sides of the substrate having the SiO ₂ film. This double-sided, 2-cell battery was taken as 1 unit, and a total of 5 units (10 cells) were produced.

(Ii) Formation of lower current collecting layer As a first step, a metal mask having an opening of 45 mm × 45 mm is mounted on a substrate, and a Ti film having a thickness of 1 μm is formed on the SiO ₂ film by sputtering using Ti and Au targets. A lower current collecting layer made of a laminated film of a layer and an Au layer having a thickness of 2 μm was formed. Ar was used as a sputtering discharge gas, and the gas pressure was 8 mTorr.

(Iii) Formation of the lower electrode layer As a second step, a metal mask having an opening of 20 mm × 20 mm is attached in alignment with the center of the lower current collecting layer, and the lower current collecting is performed by vapor deposition using Li and Co as an evaporation source. A 7 μm-thick lower electrode layer made of LiCoO ₂ was formed on the layer. Li was evaporated by resistance heating, and Co was evaporated by an electron beam and supplied onto the lower current collecting layer. Further, oxygen gas was circulated at 80 sccm in the film forming atmosphere, and the substrate temperature was 450 ° C.

(Iv) Formation of Electrolyte Layer As a third step, Li _3.5 Si _{0.5 is formed} on the lower electrode layer by sputtering using a LiSiPO sintered target with a metal mask having an opening of 20 mm × 20 mm attached. An electrolyte layer having a thickness of 2 μm made of P _0.5 O ₄ was formed. As a result, the upper surface of the lower electrode layer was completely covered with the electrolyte layer. A sputtering gas used was a mixed gas of Ar and O _2, and the gas pressure was 10 mTorr. The flow ratio of Ar to O ₂ in the mixed gas was Ar: O ₂ = 90: 10.

(V) Formation of protective layer As a fourth step, a solution obtained by mixing LiTFSI (lithium trifluoromethanesulfonylimide) which is a lithium salt, polyethylene oxide (PEO), and acetonitrile as a solvent is used with a dispenser. The protective layer was formed by coating and vacuum drying so as to cover the side surface of the lower electrode layer and the peripheral edge of the upper surface of the electrolyte layer. The thickness of the protective layer made of PEO after drying was 10 μm, h2 was 10−9 = 1 μm, and the width was 5 mm. Moreover, the width (W2) of the upper surface periphery of the electrolyte layer covered with the protective layer was 0.5 mm, and a 19 mm × 19 mm region at the center of the upper surface of the electrolyte layer was exposed.

  The protective layer thus obtained is an ionic conductor made of PEO containing a lithium salt and has lithium ion conductivity.

(Vi) Formation of upper current collecting layer and upper current collecting layer As a fifth step, a resistance heating vapor deposition method using a metal mask having an opening of 25 mm × 25 mm aligned with the center of the electrolyte layer and using Li as an evaporation source As a result, a 4 μm thick upper electrode layer and an upper current collecting layer made of Li were formed on the electrolyte layer and the protective layer. As a result, the 19 mm × 19 mm region in the center of the upper surface of the electrolyte layer and the protective layer made of PEO were completely covered by the upper current collecting layer.

<< Comparative Example 1 >>
(I) Production of substrate A 3 μm thick SiO ₂ film was formed on both surfaces of a stainless steel substrate (SUS304 substrate) (size 60 mm × 60 mm × 0.01 mm). Then, one cell of the structure shown in FIG. 3 was formed on both sides of the substrate having the SiO ₂ film. This double-sided, 2-cell battery was taken as 1 unit, and a total of 5 units (10 cells) were produced.

(Ii) Formation of lower current collecting layer As a first step, a metal mask having an opening of 45 mm × 45 mm is mounted on a substrate, and a Ti film having a thickness of 1 μm is formed on the SiO ₂ film by sputtering using Ti and Au targets. A lower current collecting layer made of a laminated film of a layer and an Au layer having a thickness of 2 μm was formed. Ar was used as a sputtering discharge gas, and the gas pressure was 8 mTorr.

(Iii) Formation of the lower electrode layer As a second step, a metal mask having an opening of 20 mm × 20 mm is attached in alignment with the center of the lower current collecting layer, and the lower current collecting is performed by vapor deposition using Li and Co as an evaporation source. A 7 μm-thick lower electrode layer made of LiCoO ₂ was formed on the layer. Li was evaporated by resistance heating, and Co was evaporated by an electron beam and supplied onto the lower current collecting layer. Further, oxygen gas was circulated at 80 sccm in the film forming atmosphere, and the substrate temperature was 450 ° C.

(Iv) Formation of electrolyte layer As a third step, a metal mask having an opening of 19 mm × 19 mm is mounted in alignment with the center of the lower electrode layer, and the lower electrode layer is formed by sputtering using a target obtained by sintering LiSiPO. Then, an electrolyte layer having a thickness of 2 μm made of Li _3.5 Si _0.5 P _0.5 O ₄ was formed. A sputtering gas used was a mixed gas of Ar and O _2, and the gas pressure was 10 mTorr. The flow ratio of Ar to O ₂ in the mixed gas was Ar: O ₂ = 90: 10.

(V) Formation of upper current collecting layer and upper current collecting layer As a fourth step, a resistance heating vapor deposition method using a metal mask having an opening of 18 mm × 18 mm aligned with the center of the electrolyte layer and using Li as an evaporation source As a result, a 4 μm thick upper electrode layer and upper current collecting layer made of Li were formed on the electrolyte layer.

<< Comparative Example 2 >>
(I) Production of substrate A 3 μm thick SiO ₂ film was formed on both surfaces of a stainless steel substrate (SUS304 substrate) (size 60 mm × 60 mm × 0.01 mm). Then, one cell of the structure shown in FIG. 2 was formed on both sides of the substrate having the SiO ₂ film. This double-sided, 2-cell battery was taken as 1 unit, and a total of 5 units (10 cells) were produced.

(Ii) Formation of lower current collecting layer As a first step, a metal mask having an opening of 45 mm × 45 mm is mounted on a substrate, and a Ti film having a thickness of 1 μm is formed on the SiO ₂ film by sputtering using Ti and Au targets. A lower current collecting layer made of a laminated film of a layer and an Au layer having a thickness of 2 μm was formed. Ar was used as a sputtering discharge gas, and the gas pressure was 8 mTorr.

(Iii) Formation of the lower electrode layer As a second step, a metal mask having an opening of 20 mm × 20 mm is attached in alignment with the center of the lower current collecting layer, and the lower current collecting is performed by vapor deposition using Li and Co as an evaporation source. A 7 μm-thick lower electrode layer made of LiCoO ₂ was formed on the layer. Li was evaporated by resistance heating, and Co was evaporated by an electron beam and supplied onto the lower current collecting layer. Further, oxygen gas was circulated at 80 sccm in the film forming atmosphere, and the substrate temperature was 450 ° C.

(Iv) Formation of Electrolyte Layer As a third step, Li _3.5 Si _{0.5 is formed} on the lower electrode layer by sputtering using a LiSiPO sintered target with a metal mask having an opening of 20 mm × 20 mm attached. An electrolyte layer having a thickness of 2 μm made of P _0.5 O ₄ was formed. As a result, the upper surface of the lower electrode layer was completely covered with the electrolyte layer. A sputtering gas used was a mixed gas of Ar and O _2, and the gas pressure was 10 mTorr. The flow ratio of Ar to O ₂ in the mixed gas was Ar: O ₂ = 90: 10.

(V) Formation of upper current collecting layer and upper current collecting layer As a fourth step, with a metal mask having an opening of 20 mm × 20 mm attached, a resistance heating vapor deposition method using Li as an evaporation source is performed on the electrolyte layer. An upper electrode layer and an upper current collecting layer made of Li and having a thickness of 4 μm were formed.

<< Comparative Example 3 >>
(I) Production of Substrate A 3 μm thick SiO ₂ film was formed on both surfaces of a stainless steel substrate (SUS304 substrate) (size 60 mm × 60 mm × 0.01 mm). Then, cells each having the structure shown in FIG. 5 were formed on both sides of the substrate having the SiO ₂ film. This double-sided, 2-cell battery was taken as 1 unit, and a total of 5 units (10 cells) were produced.

(Ii) Formation of the lower current collecting layer As a first step, a metal mask having an opening 30 mm × 30 mm for the lower current collecting layer and an opening 20 mm × 20 mm for the current collecting layer for the upper electrode layer is attached to the substrate, A lower current collecting layer composed of a laminated film of a Ti layer having a thickness of 1 μm and an Au layer having a thickness of 2 μm was formed on the SiO ₂ film by a sputtering method using a Ti and Au target. Ar was used as a sputtering discharge gas, and the gas pressure was 8 mTorr.

(Iii) Formation of the lower electrode layer As a second step, a metal mask having an opening of 20 mm × 20 mm is attached in alignment with the center of the lower current collecting layer, and the lower current collecting is performed by vapor deposition using Li and Co as an evaporation source. A 7 μm-thick lower electrode layer made of LiCoO ₂ was formed on the layer. Li was evaporated by resistance heating, and Co was evaporated by an electron beam and supplied onto the lower current collecting layer. Further, oxygen gas was circulated at 80 sccm in the film forming atmosphere, and the substrate temperature was 450 ° C.

(Iv) Formation of electrolyte layer As a third step, a metal mask having an opening of 40 mm × 40 mm is mounted so that the entire lower electrode layer, a part of the lower current collecting layer, and a part of the SiO ₂ film enter the opening. did. Then, Li _3.5 Si _0.5 P is covered so as to cover a part of the lower current collecting layer, all of the lower electrode layer, and part of the SiO ₂ film by sputtering using a target obtained by sintering LiSiPO. An electrolyte layer made of _0.5 O ₄ and having a thickness of 2 μm was formed. A sputtering gas used was a mixed gas of Ar and O _2, and the gas pressure was 10 mTorr. The flow ratio of Ar to O ₂ in the mixed gas was Ar: O ₂ = 90: 10.

(V) Formation of upper current collecting layer and upper current collecting layer As a fourth step, a metal mask having an opening of 45 mm × 25 mm is used, and the entire lower electrode layer and a part of the current collecting layer for the upper electrode layer are placed in the opening. Installed to enter. Then, a 4 μm-thick upper electrode layer and upper current collecting layer made of Li were formed on the electrolyte layer and the upper electrode current collecting layer by a resistance heating vapor deposition method using Li as an evaporation source. As a result, the entire surface of the lower electrode layer was opposed to the upper electrode layer through the electrolyte layer.

  A charge / discharge cycle test was conducted on the five types of batteries having the structure shown in FIGS. The upper limit of the charging potential was 4.3 V, the lower limit of the discharging potential was 3 V, and the cell characteristics after 50 cycles were measured. One cycle was measured at 0.2C.

  The ratio of the discharge capacity after 50 cycles to the initial discharge capacity is obtained as an average value of 10 cells and is shown in Table 1 as a percentage. Table 1 also shows whether or not a short circuit occurs. When a short circuit occurred, the number of short circuit occurrence cycles of the cell having the shortest lifetime among the five cells was shown. In Comparative Examples 2 and 3, since all 10 cells were short-circuited, the ratio of the discharge capacity after 50 cycles to the initial discharge capacity could not be measured.

  As shown in Table 1, the solid batteries of Examples 1 and 2 having the structures shown in FIGS. 1 and 2 have a large ratio of the discharge capacity after 50 cycles to the initial discharge capacity, and are deteriorated due to the charge / discharge cycle. Was small. In addition, no short circuit occurred.

  On the other hand, in the solid batteries of Comparative Examples 2 and 3 having the structures of FIGS. 4 and 5, a short circuit occurred during initial charge and discharge. When the location where the short circuit occurred was analyzed, it was found that in the solid state battery of Comparative Example 2 having the structure of FIG. 4, a leak current flows on the side surface of the power generation element. Further, in the solid state battery of Comparative Example 3 having the structure of FIG. 5, the upper surface edge portion of the lower electrode layer (in the region indicated by the broken line X1 in FIG. 5) and the upper surface edge portion of the lower current collecting layer (broken line in FIG. 5) In the region indicated by X2, the upper electrode layer and the lower electrode layer were short-circuited.

  The short circuit within the broken line X1 is considered to be due to the destruction of the electrolyte layer due to the expansion and contraction of the lower electrode layer accompanying charge / discharge. In addition, the short circuit within the broken line X2 is considered to be caused by dielectric breakdown in the electrolyte layer having a thickness of 2 μm interposed between the upper electrode layer and the lower electrode layer.

Further, in the solid battery of Comparative Example 1 having the structure of FIG. 3, the discharge capacity after 50 cycles with respect to the initial discharge capacity is higher than that of the solid batteries of Examples 1 and 2 having the structure of FIGS. The deterioration due to the charge / discharge cycle was large. This is because the ratio of the area of the upper electrode layer facing the lower electrode layer is smaller in the structure of FIG. 3 than in the structure of FIGS. This is considered to be due to the occurrence of heterogeneous potential and a mixed potential. That is, when charging / discharging to a predetermined voltage, Li diffusion in the lower electrode layer is not fast enough, so in a part of the lower electrode layer, overcharging until the potential becomes a predetermined value or more (extraction of Li atoms), Or it is thought that deterioration of a positive electrode was accelerated | stimulated by carrying out overdischarge (insertion of Li ion) until it becomes below a predetermined value.
In the above examples, the protective layer was produced using PEO. For example, when polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer or the like is used, polytetrafluoroethylene or tetrafluoroethylene is used. An ethylene-hexafluoropropylene copolymer may be used as a target, and this may be formed on the protective film by sputtering using a vacuum process.
For example, in the third step of Example 1, a first metal mask is disposed so as to cover a 19 mm × 19 mm region in the center of the upper surface of the lower electrode layer, and the opening is 29 × 29 mm with the lower electrode layer as the center. It has been confirmed that a battery substantially similar to that of Example 1 can be manufactured by arranging a second metal mask and performing sputtering as described above.

  The present invention can be applied to a device that requires a small and highly reliable solid battery, and is particularly preferably applied to a small thin film solid battery mounted on a substrate such as a semiconductor substrate. Moreover, although this invention is suitable for the solid battery using lithium as an active material, the kind of solid battery is not restricted to this.

It is sectional drawing of the solid battery which concerns on Embodiment 1 of this invention. It is sectional drawing of the solid battery which concerns on Embodiment 2 of this invention. It is sectional drawing of the conventional solid battery. It is sectional drawing of another conventional solid battery. It is sectional drawing of another conventional solid battery.

Explanation of symbols

100, 200, 300, 400, 500 Solid battery 10, 20, 30, 40, 50 Power generation element 11, 21, 31, 41, 51 Substrate 12, 22, 32, 42, 52 Lower current collecting layer 13, 23, 33 , 43, 53 Lower electrode layer 14, 24, 34, 44, 54 Electrolyte layer 15, 25, 35, 45, 55 Upper electrode layer 16, 26, 36, 46 Upper current collecting layer 56 Current collecting layer 17 for upper electrode layer 27 Protective layer

Claims (9)

A power generation element, and a protective layer in contact with a side surface of the power generation element,
The power generating element has a lower electrode layer, an electrolyte layer, and an upper electrode layer that are sequentially stacked,
The protective layer is made of an electronic insulator, and covers the side surface and the upper surface periphery of the lower electrode layer,
The lower surface peripheral part of the said electrolyte layer is a solid battery which coat | covers at least one part of the upper surface of the said protective layer. A power generation element, and a protective layer in contact with a side surface of the power generation element,
The power generating element has a lower electrode layer, an electrolyte layer, and an upper electrode layer that are sequentially stacked,
The protective layer is made of an electronic insulator, and covers the side surface of the lower electrode layer and the side surface and upper surface periphery of the electrolyte layer,
A solid state battery in which a lower surface peripheral portion of the upper electrode layer covers at least a part of an upper surface of the protective layer.   The solid battery according to claim 1, wherein an elastic modulus of the protective layer is smaller than an elastic modulus of the electrolyte layer.   The solid battery according to claim 3, wherein the protective layer has rubber elasticity.   The solid battery according to claim 3, wherein the protective layer is made of an organic ion conductor.   The solid state battery according to claim 4, wherein the protective film having rubber elasticity includes at least one selected from the group consisting of a tetrafluoroethylene-hexafluoropropylene copolymer and polytetrafluoroethylene.   The solid state battery according to claim 5, wherein the organic ionic conductor includes at least one selected from the group consisting of polyethylene oxide and derivatives thereof.   The solid battery according to claim 1, wherein the electrolyte layer is made of an inorganic solid electrolyte.   The solid battery according to claim 8, wherein the inorganic solid electrolyte is made of a phosphorus compound containing at least Li, P, and O.

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