Secondary battery

Abstract

A lithium secondary battery (1) includes: a positive electrode current collector (10); a positive electrode layer (40) provided on the positive electrode current collector; a negative electrode current collector (20); a negative electrode layer (50) provided on the negative electrode current collector and including a lithium metal layer (52); an electrolyte layer (60) interposed between the positive electrode layer and the negative electrode layer and containing a solid electrolyte; and an annular insulating layer (70) provided on the negative electrode current collector and surrounding the periphery of the negative electrode layer and the periphery of the electrolyte layer. The electrolyte layer includes a first base part (61) that is in contact with the insulating layer from the positive electrode layer side and has an outer dimension larger than the inner dimension of the insulating layer, and a first protruding part (62) that protrudes from the first base part so as to enter the inside of the insulating layer. At full charge, the thickness of the lithium metal layer is thinner than the thickness of the insulating layer, and the thickness of the insulating layer is smaller than the sum of the thickness of the electrolyte layer and the thickness of the negative electrode layer at full discharge.

Description

secondary battery

[0001] The present invention relates to a secondary battery containing a solid electrolyte in an electrolyte layer.

[0002] An all-solid-state battery is known in which the first current collector layer, the first active material layer, the second active material layer, the first solid electrolyte layer, and the second solid electrolyte layer extend outward beyond the third active material layer and the fourth active material layer to form an extended portion (see Patent Document 1). An insulating resin layer is also provided continuously over one surface of the first solid electrolyte layer, the side surface of the extended portion, and the other surface of the second solid electrolyte layer (see paragraph

[0043] and FIGS. 2 and 4 of Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-4697

[0004] In the above-mentioned all-solid-state battery, since the volume change when lithium metal is deposited on the negative electrode layer is large, if the side surfaces of each layer are continuously pressed down by an insulating resin layer, the insulating resin layer may not be able to follow the volume change and may break. In this case, there is a problem that lithium ions move outward from the side surfaces of the negative electrode layer, causing lithium metal to deposit, which may cause a short circuit with the positive electrode.

[0005] The problem to be solved by the present invention is to provide a secondary battery capable of appropriately suppressing the migration of lithium ions, thereby suppressing the occurrence of short circuits.

[0006] The present invention solves the above problem by providing an annular insulating layer on the negative electrode current collector and surrounding the periphery of the negative electrode layer or the periphery of the negative electrode layer and the periphery of the electrolyte layer, and by making the thickness of the alkali metal layer contained in the negative electrode layer at full charge thinner than the thickness of the insulating layer and making the thickness of the insulating layer smaller than the sum of the thickness of the electrolyte layer and the thickness of the negative electrode layer at full discharge.

[0007] According to the present invention, the insulating layer can suppress the outward migration of alkali metal ions during deposition of the alkali metal, thereby suppressing the occurrence of short circuits caused by the deposited alkali metal.

[0008] FIG. 1 is a cross-sectional view showing a secondary battery according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of part II in FIG. 1. FIG. 3 is a back view showing a negative electrode current collector, an insulating layer, and an electrolyte layer. FIG. 4 is a cross-sectional view showing a first modified example of the secondary battery according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view showing a second modified example of the secondary battery according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view showing a third modified example of the secondary battery according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view showing a fourth modified example of the secondary battery according to the first embodiment of the present invention. FIG. 8 is a cross-sectional view showing a secondary battery according to a second embodiment of the present invention. FIG. 9 is an enlarged cross-sectional view of part IX in FIG. 8.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] First Embodiment

[0011] Fig. 1 is a cross-sectional view showing a secondary battery 1A according to the first embodiment, and Fig. 2 is an enlarged cross-sectional view of part II in Fig. 1. Fig. 1 shows the secondary battery 1A in a fully discharged state, while Fig. 2 shows the secondary battery 1A in a fully charged state. Fig. 3 is a back view showing the negative electrode current collector 20, the insulating layer 70, and the electrolyte layer 60.

[0012] 1, the secondary battery 1A in this embodiment includes a positive electrode current collector 10, a negative electrode current collector 20, a power generating element 30, and an insulating layer 70. Although not specifically shown, the secondary battery 1A may also include a positive electrode tab, a negative electrode tab, an exterior body (laminate film), and the like.

[0013] The positive electrode current collector 10 is a conductive plate-like (or foil-like) member and is made of, for example, a metal or a conductive resin, although it is not particularly limited thereto. Examples of metals that can be used include aluminum, nickel, iron, stainless steel, titanium, and copper. Alternatively, a clad material of nickel and aluminum, or a clad material of copper and aluminum may also be used. Examples of conductive resins include resins in which a conductive filler is added to a non-conductive polymer material.

[0014] The negative electrode current collector 20, like the positive electrode current collector 10, is a conductive plate-like (or foil-like) member and is made of, for example, a metal or a conductive resin, without any particular limitation. Examples of metals that can be used include aluminum, nickel, iron, stainless steel, titanium, and copper. Alternatively, a clad material of nickel and aluminum, or a clad material of copper and aluminum, may also be used. Examples of conductive resins include resins in which a conductive filler is added to a non-conductive polymer material. The material constituting the positive electrode current collector 10 and the material constituting the negative electrode current collector 20 may be the same material or different materials.

[0015] The power generating element 30 is sandwiched between the positive electrode current collector 10 and the negative electrode current collector 20. The power generating element 30 is an element that contributes to the charging and discharging of the lithium secondary battery 1. The power generating element 30 includes a positive electrode layer 40, a negative electrode layer 50, and an electrolyte layer 60.

[0016] The positive electrode layer 40 is formed on the main surface 101 of the positive electrode current collector 10. Although not particularly limited, the positive electrode layer 40 can be formed by applying a paste containing a positive electrode active material and a binder to the main surface 105 of the positive electrode current collector 10 and drying the paste. In the present embodiment, the positive electrode layer 40 has a rectangular cross section, but is not limited to this. The positive electrode layer 40 may have a tapered shape that narrows from the positive electrode current collector 10 toward the negative electrode current collector 20, and thus the positive electrode layer 40 may have a trapezoidal cross section.

[0017] The negative electrode layer 50 is formed on the main surface 201 of the negative electrode current collector 20. The negative electrode layer 50 in this embodiment has a rectangular cross section, but is not limited thereto, and may have a trapezoidal cross section like the positive electrode layer 40.

[0018] 1 illustrates the anode layer 50 of the secondary battery 1A in a fully discharged state. The anode layer 50 includes an intermediate layer 51. The intermediate layer 51 has a flat plate shape. The intermediate layer 51 is a layer for assisting the deposition of an alkali metal layer composed of lithium, sodium, potassium, or the like, and contains a material capable of absorbing and releasing alkali metal ions.

[0019] 2 illustrates the anode layer 50 of the secondary battery 1A in a fully charged state. The anode layer 50 includes a lithium metal layer 52 in addition to an intermediate layer 51. In this embodiment, the lithium metal layer 52 is composed of lithium metal deposited on the main surface 201 of the anode current collector 20. The volume of the lithium metal layer 52 increases as the lithium metal deposits during charging of the secondary battery 1A, but decreases as the lithium metal disappears (moves toward the cathode layer 40) during discharging. The lithium metal layer 52 may be deposited between the intermediate layer 51 and the anode current collector 20, or between the intermediate layer 51 and the electrolyte layer 60.

[0020] The lithium metal layer 52 may be a layer of another alkali metal such as potassium or sodium, but lithium has a higher melting point than potassium or sodium and is therefore less likely to flow. Therefore, by forming the lithium metal layer 52 as in this embodiment, the deposited lithium metal is less likely to flow, making it less likely for the lithium metal layer 52 to short-circuit with the positive electrode layer 40.

[0021] 1, the electrolyte layer 60 is interposed between the positive electrode layer 40 and the negative electrode layer 50. The electrolyte layer 60 may include a solid electrolyte made of a material with low electronic conductivity. For example, a sulfide solid electrolyte or an oxide solid electrolyte can be used as the solid electrolyte, but it is preferable to use a sulfide solid electrolyte.

[0022] Examples of sulfide solid electrolytes include LiI-Li ２ S-SiS ２ , LiI-Li ２ S-P ２ O ５ , LiI-Li ３ P.O. ４ -P ２ S ５ , Li ２ S-P ２ S ５ , LiI-Li ３ P.S. ４ , LiI-LiBr-Li ３ P.S. ４ , Li ３ P.S.４ , Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ , Li ２ S-SiS ２ - LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ｎ (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -Li ｘ MO ｙ (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In). ２ S-P ２ S ５ " The statement Li ２ S and P ２ S ５The same applies to the other descriptions above. Alternatively, sulfide glass or the like may be used as the sulfide solid electrolyte.

[0023] As the oxide solid electrolyte, for example, a compound having a NASICON structure can be used. Examples of the compound having a NASICON structure include compounds represented by the general formula Li １＋ｘ Al ｘ Ge ２－ｘ (P.O. ４ ) ３ (0≦x≦2) (LAGP), a compound represented by the general formula Li １＋ｘ Al ｘ Ti ２－ｘ (P.O. ４ ) ３ (0≦x≦2) (LATP) and the like can be used. In addition, other oxide solid electrolytes include LiLaTiO (for example, Li ０．３４ La ０．５１ TiO ３ ), LiPON (e.g., Li ２．９ P.O. ３．３ N ０．４６ ), LiLaZrO (e.g., Li ７ La ３ Zr ２ O １２ ) etc. can be used.

[0024] Although not particularly limited, this electrolyte layer 60 is formed by transferring the negative electrode layer 50 and the insulating layer 70 while applying pressure. The electrolyte layer 60 may contain a non-solid electrolyte, and may contain, for example, a polymer electrolyte or a liquid electrolyte in addition to a solid electrolyte.

[0025] The electrolyte layer 60 has a first base 61 and a first protrusion 62. The first base 61 is a plate-shaped portion and is in direct contact with the positive electrode layer 40. The first base 61 is also in direct contact with the insulating layer 70 in the Z direction in the figure. This prevents damage to the electrolyte layer 60 due to contact between the insulating layer 70 and the electrolyte layer 60, thereby preventing lithium from being deposited in cracks or the like caused by damage to the electrolyte layer 60 and short-circuiting the deposited lithium with the positive electrode layer 40.

[0026] 2 , the first base 61 may be separated from the insulating layer 70 when the secondary battery 1A is charged. The first base 61 may be separated from the insulating layer 70 when lithium metal is deposited on the negative electrode current collector 20 due to charging, causing an increase in the volume of the lithium metal layer 52 of the negative electrode layer 50.

[0027] 1 , a first protrusion 62 protrudes from the first base 61 toward the negative electrode current collector 20. In this embodiment, the first protrusion 62 protrudes from near the center of the first base 61 and is narrower than the first base 61. The first protrusion 62 is sandwiched between the first base 61 and the negative electrode layer 50, and at least a portion of the first protrusion 62 is housed inside the insulating layer 70.

[0028] As shown in FIGS. 1 to 3 , the insulating layer 70 has a rectangular ring shape that surrounds the periphery of the first protrusion 62 of the electrolyte layer 60. The insulating layer 70 may have a circular or polygonal ring shape other than a rectangle. The insulating layer 70 in this embodiment has electrical insulation properties. Furthermore, the insulating layer 70 is non-Li ion conductive and does not conduct lithium ions or suppresses the conduction of lithium ions.

[0029] The material for forming such insulating layer 70 is not particularly limited, but may be, for example, metal oxide particles such as alumina or zirconia, a resin material, etc. Although not particularly limited, insulating layer 70 can be formed by applying a paste in which the above-mentioned metal oxide particles, a binder, etc. are mixed onto negative electrode current collector 20 so as to cover negative electrode layer 50, and then drying the paste.

[0030] As shown in FIGS. 1 and 3, the outer dimension W of the first base portion 61 is １ is the inner dimension W of this insulating layer 70 ３ As a result, the outer peripheral portion of the first base 61 is interposed between the insulating layer 70 and the positive electrode layer 40, and this outer peripheral portion can prevent lithium deposited along the surface of the insulating layer 70 from short-circuiting with the positive electrode layer 40.

[0031] As shown in FIG. 3, the outer dimension W ２ is the outer dimension W of the first base portion 61 of the electrolyte layer 60 １ In this way, the outer dimension W of the insulating layer 70 is larger than ２ is the outer dimension W of the first base portion 61 １ Since the distance between the insulating layer 70 and the first base portion 61 is larger than the distance between the insulating layer 70 and the first base portion 61, it is easy to grasp the relative positional relationship between the insulating layer 70 and the first base portion 61 in a dimensional inspection using a camera. This makes it easy to inspect the dimensions, thereby improving manufacturability.

[0032] As shown in FIG. 2, the thickness T １ is the thickness T of the insulating layer 70 ２ In this way, since the insulating layer 70 is thicker than the anode layer 50 in a fully charged state, the insulating layer 70 can suppress the migration of lithium from the anode layer 50 in the X and Y directions in the figure, and therefore it is possible to suppress the deposited lithium from short-circuiting with the cathode layer 40. Note that the thickness T １ is the thickness T of the intermediate layer 51 ３ and the thickness T of the lithium metal layer 52 ４ It is the sum of and.

[0033] In this embodiment, the thickness T of the negative electrode layer 50 when fully charged １ However, the thickness T of the insulating layer 70 ２ Although the thickness of the lithium metal layer 52 is thinner, ４ However, the thickness T of the insulating layer 70 ２ A thinner layer can limit lithium migration and reduce the short circuiting mentioned above.

[0034] As shown in FIG. 2, the thickness T １is the thickness T of the intermediate layer 51 ３ and the thickness T of the electrolyte layer 60 ５ Tonowa T ６ It should be noted that the thickness T of the intermediate layer 51 in FIG. ３ is the thickness of the negative electrode layer 50 at the time of full discharge. By satisfying this thickness relationship, the outer peripheral portion of the first base 61 is interposed between the insulating layer 70 and the positive electrode layer 40 even at the time of full discharge, and therefore, it is possible to prevent lithium deposited by the outer peripheral portion from short-circuiting with the positive electrode layer 40.

[0035] In the secondary battery 1A as described above, the first base portion 61 of the electrolyte layer 60 can suppress the occurrence of a short circuit between the deposited metallic lithium (lithium metal layer 52) and the positive electrode layer 40.

[0036] In the above embodiment, the electrolyte layer 60 is not formed outside the insulating layer 70, but the electrolyte layer 60 may be formed outside the insulating layer 70. Fig. 4 is a cross-sectional view showing a first modified example of the secondary battery in the first embodiment.

[0037] 4 , the electrolyte layer 60 of the secondary battery 1B includes an extension portion 63 in addition to a first base portion 61 and a first protrusion portion 62. The extension portion 63 extends from the first base portion 61 in a direction substantially parallel to the main surface 201 of the negative electrode current collector 20. In this embodiment, the extension portion 63 has a ring shape that covers the outer periphery of the first base portion 61.

[0038] In this first modified example, the thickness T of the extension portion ７ is the distance d between the insulating layer 70 and the positive electrode layer 40 in the Z direction １ By forming such extension portion 63, it is possible to suppress the movement of lithium along the surface direction of insulating layer 70, and therefore it is possible to suppress a short circuit between the deposited lithium and positive electrode layer 40.

[0039] In addition, in the above embodiment, the outer dimensions of the anode layer 50 are smaller than those of the cathode layer 40, but the outer dimensions of the anode layer 50 may be larger than those of the cathode layer 40. Fig. 5 is a cross-sectional view showing a second modified example of the secondary battery in the first embodiment.

[0040] As shown in FIG. 5, the outer dimension W ４ is the outer dimension W of the positive electrode layer 40 ５ By adopting such a width relationship, the position of lithium deposition can be concentrated in the center of the negative electrode layer 50, thereby suppressing the outflow of lithium in the X and Y directions. This makes it possible to suppress a short circuit between the deposited lithium and the positive electrode layer 40.

[0041] Furthermore, in this second modified example, because the width of the positive electrode layer 40 is reduced, the outer periphery of the first base 61 of the electrolyte layer 60 is not in contact with the positive electrode layer 40. A support layer 80 is formed to support the outer periphery of the first base 61. This support layer 80 is provided around the positive electrode layer 40 and has a ring shape that covers the side surface of the positive electrode layer 40. Although not particularly limited, the support layer 80 may be made of the same material as the insulating layer 70 described above.

[0042] By providing such a support layer 80, the electrolyte layer 60 is less likely to deform when the power generating element 30 expands and contracts during charge and discharge, and cracks and the like are less likely to occur in the electrolyte layer 60. Therefore, by suppressing the movement of lithium caused by the cracks, it is possible to suppress a short circuit between the deposited lithium and the positive electrode layer 40.

[0043] 1, in the above embodiment, the first base 61 and the insulating layer 70 are in contact with each other when the secondary battery 1A is fully discharged, but the first base 61 and the insulating layer 70 may be spaced apart. Fig. 6 is a cross-sectional view showing a third modified example of the secondary battery of the first embodiment.

[0044] 6 , in a secondary battery 1D in a fully discharged state, the first base 61 of the electrolyte layer 60 is separated from the insulating layer 70 in the Z direction. By separating the first base 61 from the insulating layer 70 in this manner, damage to the electrolyte layer 60 due to contact with the insulating layer 70 can be suppressed. This makes it possible to suppress lithium deposition in cracks in the damaged portion of the electrolyte layer 60 and short-circuiting with the positive electrode layer 40.

[0045] In the above embodiment, the contact interface between the electrolyte layer 60 and the insulating layer 70 is flat, but may be curved. Fig. 7 is a cross-sectional view showing a fourth modified example of the secondary battery of the first embodiment.

[0046] As shown in FIG. 7 , in a fully discharged secondary battery 1E, the contact interfaces 90A and 90B between the electrolyte layer 60 and the insulating layer 70 are curved. The shape of these curved surfaces is not particularly limited, and may be a circular arc like the contact interface 90A, or a curved surface other than an arc like the contact interface 90B. Such curved contact interfaces 90A and 90B can prevent damage to the electrolyte layer 60 due to contact with the insulating layer 70. This can prevent lithium from being deposited in cracks in the damaged portion of the electrolyte layer 60, which could lead to a short circuit with the positive electrode layer 40.

[0047] Second Embodiment

[0048] Fig. 8 is a cross-sectional view showing a secondary battery 1F in the second embodiment, and Fig. 9 is an enlarged cross-sectional view of part IX in Fig. 8. However, Fig. 8 shows a state in which the secondary battery 1F is fully discharged, and Fig. 9 shows a state in which the secondary battery 1F is fully charged.

[0049] This embodiment differs from the first embodiment in that the negative electrode layer 50 includes a second base portion 53 and a second protruding portion 54, and the electrolyte layer 60 does not include a first protruding portion 62. Only the differences between the second embodiment and the first embodiment will be described below for the secondary battery 1F in the second embodiment, and parts having the same configuration as those in the first embodiment will be denoted by the same reference numerals and will not be described again.

[0050] The negative electrode layer 50 in the second embodiment includes a second base portion 53 and a second protruding portion 54. The second base portion 53 and the second protruding portion 54 are formed from the intermediate layer 51 described above.

[0051] The second base portion 53 is a portion having a flat plate shape and is in direct contact with the electrolyte layer 60. The second base portion 53 is also in direct contact with the insulating layer 70 in the Z direction in the drawing. The outer dimension W of the second base portion 53 is ４ is the inner dimension W of the insulating layer 70 ３ It is larger than that.

[0052] A second protrusion 54 protrudes from the second base 53 toward the negative electrode current collector 20. In this embodiment, the second protrusion 54 protrudes from near the center of the second base 53 and is narrower than the second base 53. The second protrusion 54 is sandwiched between the second base 53 and the negative electrode current collector 20, and is housed inside the insulating layer 70.

[0053] As shown in FIG. 8, the thickness T ４ is the thickness T of the insulating layer 70 ２ In this way, since the insulating layer 70 is thicker than the lithium metal layer 52 in a fully charged state, the insulating layer 70 can suppress the migration of lithium from the lithium metal layer 52 in the X and Y directions in the figure, and therefore it is possible to suppress the deposited lithium from shorting with the positive electrode layer 40. Note that the thickness T １ is the thickness T of the intermediate layer 51 ３ and the thickness T of the lithium metal layer 52 ４ It is the sum of and.

[0054] The thickness T of the insulating layer 70 １ is the thickness T of the intermediate layer 51 ３ and the thickness T of the electrolyte layer 60 ４ Tonowa T ５ It should be noted that the thickness T of the intermediate layer 51 in FIG. ３ is the thickness of the negative electrode layer 50 at the time of full discharge. By satisfying this thickness relationship, even at the time of full discharge, the outer periphery of the second base and the electrolyte layer 60 are interposed between the insulating layer 70 and the positive electrode layer 40, and therefore, it is possible to prevent lithium deposited along the surface of the insulating layer 70 from short-circuiting with the positive electrode layer 40.

[0055] In the secondary battery 1A as described above, the first base portion 61 of the electrolyte layer 60 can suppress the occurrence of a short circuit between the deposited metallic lithium (lithium metal layer 52) and the positive electrode layer 40.

[0056] 1A to 1F... Secondary battery 10... Positive electrode current collector 20... Negative electrode current collector 30... Power generating element 40... Positive electrode layer 50... Negative electrode layer 60... Electrolyte layer 70... Insulating layer

Claims

a positive electrode current collector; a positive electrode layer provided on the positive electrode current collector; a negative electrode current collector; a negative electrode layer provided on the negative electrode current collector and including an alkali metal layer; an electrolyte layer interposed between the positive electrode layer and the negative electrode layer and including a solid electrolyte; and an annular insulating layer provided on the negative electrode current collector and surrounding the periphery of the negative electrode layer or the periphery of the negative electrode layer and the periphery of the electrolyte layer, wherein the electrolyte layer includes a first base portion interposed between the positive electrode layer and the insulating layer and having outer dimensions larger than the inner dimensions of the insulating layer, and a first protrusion portion protruding from the first base portion to penetrate into the inside of the insulating layer, or wherein the negative electrode layer includes a second base portion interposed between the electrolyte layer and the insulating layer and having outer dimensions larger than the inner dimensions of the insulating layer, and a second protrusion portion protruding from the second base portion to penetrate into the inside of the insulating layer, wherein the thickness of the alkali metal layer when fully charged is thinner than the thickness of the insulating layer, A secondary battery in which the thickness of the insulating layer is smaller than the sum of the thickness of the electrolyte layer and the thickness of the negative electrode layer when fully discharged.

2. A secondary battery according to claim 1, wherein the electrolyte layer includes the first base portion, the first protrusion portion, and an extension portion extending from the first base portion in a direction substantially parallel to the main surface of the negative electrode current collector, and the thickness of the extension portion is greater than the distance between the insulating layer and the positive electrode layer.

3. The secondary battery according to claim 1 or 2, wherein the outer dimensions of the negative electrode layer are larger than the outer dimensions of the positive electrode layer.

4. The secondary battery according to claim 3, further comprising a support layer provided around the positive electrode layer and supporting the electrolyte layer.

5. The secondary battery according to any one of claims 1 to 4, wherein the outer dimensions of the insulating layer are larger than the outer dimensions of the electrolyte layer.

6. A secondary battery according to any one of claims 1 to 5, wherein the insulating layer is spaced apart from the first base portion of the electrolyte layer when fully discharged.

7. A secondary battery according to any one of claims 1 to 5, wherein the insulating layer and the first base portion of the electrolyte layer are in contact with each other during full discharge, and the contact interface between the insulating layer and the first base portion is curved.

8. A secondary battery according to any one of claims 1 to 7, wherein the alkali metal layer is made of lithium metal.

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