Secondary battery

Abstract

In order to suppress the risk of short-circuiting of an electrolyte layer due to expansion of electrode layers, the present invention comprises: a laminate (11) having a positive electrode that has a positive electrode current collector (114) and a positive electrode layer (111), a negative electrode that has a negative electrode current collector (115) and a negative electrode layer (112), and an electrolyte layer (113) interposed between the positive electrode and the negative electrode; and an exterior resin body (15) composed of a thermosetting resin or a thermoplastic resin and covering the laminate, wherein at least a portion of the outer peripheral edge of the negative electrode current collector (115) has a first protruding part (116) that protrudes from the outer peripheral edge of the negative electrode layer (112) to the exterior resin body (15).

Description

secondary battery

[0001] The present invention relates to a secondary battery.

[0002] A known solid-state battery includes a solid-state battery cell including a laminate having at least one positive electrode having a positive electrode current collector and a positive electrode active material layer, at least one negative electrode having a negative electrode current collector and a negative electrode active material layer, and a solid electrolyte interposed between the positive electrode and the negative electrode, and first elastic members disposed on at least both sides of the laminate in the stacking direction, and an exterior resin part made of a thermosetting resin or a thermoplastic resin that tightly covers the solid-state battery cell (Patent Document 1).

[0003] In this solid-state battery, the first elastic members arranged on both sides of the stack in the stacking direction of the stack can compress the first elastic members in the stacking direction C in accordance with the increase in volume, even if the negative electrode active material layer expands due to charging of the solid-state battery, and the volume of the stack increases. Therefore, even if the volume of the stack increases, the first elastic members compress, so that the volume of the entire solid-state battery cell can be kept constant (paragraph

[0043] of the same document).

[0004] Japanese Patent Application Laid-Open No. 2022-1104492

[0005] However, as the negative electrode active material layer expands during charging, strong tensile stress acts on the exterior resin portion around the negative electrode active material layer, causing the exterior resin portion to rupture. The space created by this rupture of the exterior resin portion becomes a step, and when surface pressure is applied, the solid electrolyte layer ruptures, increasing the risk of short circuiting. As in the above-mentioned conventional technology, even if first elastic members are arranged on both sides of the stacking direction of the laminate, the strong tensile stress acting on the exterior resin portion around the negative electrode active material layer cannot be suppressed.

[0006] The problem to be solved by the present invention is to provide a secondary battery capable of suppressing the risk of short-circuiting of the electrolyte layer due to expansion of the electrode layer.

[0007] The present invention solves the above-mentioned problems in a secondary battery including a laminate having a positive electrode having a positive electrode current collector and a positive electrode layer, a negative electrode having a negative electrode current collector and a negative electrode layer, and an electrolyte layer interposed between the positive electrode and the negative electrode, and an exterior resin body covering the laminate, by making at least a part of the outer periphery of the negative electrode current collector protrude beyond the outer periphery of the negative electrode layer into the exterior resin body.

[0008] According to the present invention, the risk of short-circuiting of the electrolyte layer due to expansion of the electrode layer can be reduced.

[0009] FIG. 1 is a cross-sectional view showing an embodiment of a secondary battery according to the present invention. FIG. 2 is a cross-sectional view showing a laminate and an exterior resin body included in the secondary battery of FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a plan view showing an anode layer and an anode current collector included in the laminate of FIG. 2. FIG. 5 is a plan view showing a cathode layer and an anode current collector included in the laminate of FIG. 2. FIG. 6 is a cross-sectional view showing a laminate and an exterior resin body according to a comparative example for explaining the function of the present invention. FIG. 7 is a cross-sectional view showing a laminate and an exterior resin body according to an example for explaining the function of the present invention. FIG. 8 is a plan view showing another example of an anode layer and an anode current collector included in the laminate of FIG. 2. FIG. 9 is a plan view showing yet another example of an anode layer and an anode current collector included in the laminate of FIG. 2.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing one embodiment of a secondary battery according to the present invention, and Fig. 2 is a cross-sectional view showing a laminate 11 and an exterior resin body 15 included in the secondary battery 1 of Fig. 1. Note that the secondary battery 1 of this embodiment is generally flat overall, but to make it easier to understand the layered structure of the laminate (power generating element) 11 housed therein, Figs. 1 to 3 and 6A and 6B show it stretched in the thickness direction.

[0011] The secondary battery 1 of this embodiment is a secondary battery in which electrodes expand and contract upon charging and discharging, such as an all-solid-state battery or a semi-solid-state battery. The all-solid-state battery in this invention refers to a secondary battery that uses a solid electrolyte as an electrolyte and is capable of being charged and discharged, and all-solid-state batteries also include those that contain a small amount of liquid material in a solid electrolyte. Furthermore, the semi-solid-state battery in this invention refers to a secondary battery that uses a gel electrolyte as an electrolyte and is capable of being charged and discharged. In the following embodiments, the configuration of the secondary battery according to the present invention will be described using the secondary battery 1 made of an all-solid-state battery as an example, but known semi-solid-state batteries may also be used.

[0012] 1, the secondary battery 1 of this embodiment includes a laminate 11 serving as a power generating element, a positive electrode terminal 12, a negative electrode terminal 13, an exterior member 14, and an exterior resin body 15. The laminate 11 and the exterior resin body 15 of FIG. 1 are extracted and shown in FIG. 2.

[0013] As shown in Fig. 2 , the laminate 11 of this embodiment includes a plurality of positive electrode layers 111, a plurality of negative electrode layers 112, a plurality of electrolyte layers 113, a plurality of positive electrode current collectors 114, and a plurality of negative electrode current collectors 115. The laminate 11 of this embodiment is formed by stacking these plurality of positive electrode layers 111, a plurality of negative electrode layers 112, a plurality of electrolyte layers 113, a plurality of positive electrode current collectors 114, and a plurality of negative electrode current collectors 115 in the X-axis direction shown in the figure. The secondary battery 1 shown in Fig. 2 includes four positive electrode layers 111, four negative electrode layers 112, three electrolyte layers 113, three positive electrode current collectors 114, and three negative electrode current collectors 115, but the number of these positive electrode layers 111, negative electrode layers 112, electrolyte layers 113, positive electrode current collectors 114, and negative electrode current collectors 115 and the number of layers are not limited in any way. The laminate according to the present invention functions as a power generating element if it comprises at least one positive electrode layer 111, one negative electrode layer 112, one electrolyte layer 113, one positive electrode current collector 114, and one negative electrode current collector 115.

[0014] A pair of positive electrode layers 111, 111 included in the laminate 11 are respectively formed on both sides of one positive electrode current collector 114. The positive electrode layer 111 according to this embodiment is not particularly limited, but it contains at least a positive electrode active material capable of releasing and absorbing an alkali metal such as lithium (Li), sodium (Na), or potassium (K), and preferably contains a positive electrode active material containing sulfur. The sulfur-containing positive electrode active material may be a substance that utilizes a sulfur oxidation-reduction reaction to release alkali metal ions such as lithium ions during charging and to absorb the alkali metal ions during discharge. The type of sulfur-containing positive electrode active material is not particularly limited, but particles or thin films of elemental sulfur (S), organic sulfur compounds, or inorganic sulfur compounds can be used.

[0015] The organic sulfur compound is not particularly limited, but examples thereof include disulfide compounds, sulfur-modified polyacrylonitrile, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), polycarbon sulfide, etc. The inorganic sulfur compound is not particularly limited, but examples thereof include S-carbon composite, TiS ２ , TiS ３ , TiS ４ , NiS, NiS ２ , CuS, FeS ２ , Li ２ S, MoS ２ , MoS ３ The positive electrode active material may be one that does not contain sulfur.

[0016] A pair of negative electrode layers 112, 112 included in the laminate 11 are formed on both sides of one negative electrode current collector 115, respectively. The negative electrode layer 112 according to this embodiment is formed of a layer containing a negative electrode active material, although it is not particularly limited. The type of negative electrode active material is not particularly limited, but may include a carbon material, a metal oxide, and a metal active material. Examples of the carbon material include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the metal oxide include Nb ２ O ５ , Li ４ Ti５ O １２ Furthermore, examples of the metal active material include metal elements such as In, Al, Si, and Sn, TiSi, La, ３ Ni ２ Sn ７ and other alloys.

[0017] The negative electrode active material may be a metal containing Li. Such a negative electrode active material is not particularly limited as long as it is an active material containing Li, and may be Li metal or a lithium alloy containing Li. Examples of lithium alloys include alloys of lithium and at least one metal selected from gold (Au), magnesium (Mg), aluminum (Al), calcium (Ca), zinc (Zn), tin (Sn), and bismuth (Bi). The lithium alloy may also be an alloy of lithium and two or more of the above-mentioned metals. Specific examples of lithium alloys include lithium-gold alloy (Li-Au), lithium-magnesium alloy (Li-Mg), lithium-aluminum alloy (Li-Al), lithium-calcium alloy (Li-Ca), lithium-zinc alloy (Li-Zn), lithium-tin alloy (Li-Sn), and lithium-bismuth alloy (Li-Bi).

[0018] The negative electrode active material layer may contain a lithium alloy, and its configuration is not particularly limited. For example, when the metal other than lithium constituting the lithium alloy is "Me," the negative electrode active material layer may take any of the following forms (1) to (3): (1) A single layer consisting of only a lithium alloy (i.e., a Li-Me layer). (2) A layer comprising a layer of lithium metal and a layer of a lithium alloy (i.e., a Li layer / Li-Me layer). (3) A layer comprising a layer of lithium metal, a layer of a lithium alloy, and a layer of a metal other than lithium (i.e., a Li layer / Li-Me layer / Me layer).

[0019] The electrolyte layer 113 included in the laminate 11 is interposed between the positive electrode layer 111 and the negative electrode layer 112, and the front and back principal surfaces thereof are in contact with the positive electrode layer 111 and the negative electrode layer 112, respectively. The electrolyte layer 113 of this embodiment is made of a solid electrolyte or a semi-solid electrolyte.

[0020] As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used, and it is preferable to use a sulfide solid electrolyte. As the sulfide solid electrolyte, for example, 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 -LixMOy (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 ５ The same applies to the other descriptions above. In addition, sulfide glass or the like may be used as the sulfide solid electrolyte.

[0021] 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 N０．４６ ), LiLaZrO (e.g., Li ７ La ３ Zr ２ O １２ ) etc. can be used.

[0022] The positive electrode current collector 114 and the negative electrode current collector 115 included in the laminate 11 are conductive plate- or foil-shaped members, and are made of, for example, a metal or a conductive resin, although there is no 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 be used. Examples of conductive resins include resins in which a conductive filler is added to a non-conductive polymer material.

[0023] The positive electrode current collector 114 according to this embodiment has a main body portion 114a on both sides of which a pair of positive electrode layers 111 are formed, a connection portion 114b extending from this main body portion toward the positive electrode terminal 12, and a second protrusion portion 117 protruding outward from the outer periphery of the main body portion 114a. Similarly, the negative electrode current collector 115 according to this embodiment has a main body portion 115a on both sides of which a pair of negative electrode layers 112 are formed, a connection portion 115b extending from this main body portion toward the negative electrode terminal 13, and a first protrusion portion 116 protruding outward from the outer periphery of the main body portion 115a. Details of the first protrusion portion 116 formed on the negative electrode current collector 115 and the second protrusion portion 117 formed on the positive electrode current collector 114 will be described later.

[0024] The exterior resin body 15 of this embodiment is made of a thermosetting resin or a thermoplastic resin, and tightly covers the entire laminate 11. That is, the exterior resin body 15 covers four side surfaces of the laminate 11 along the stacking direction X and two upper and lower surfaces perpendicular to the stacking direction X. Although not particularly limited, when comparing the coating lengths L5, L6 (lengths L5, L6 shown in the cross-sectional view of FIG. 2 ) of the exterior resin body 15 on the four side surfaces along the stacking direction X of the laminate 11 to which the positive electrode terminal 12 and the negative electrode terminal 13 are connected as shown in FIG. 1 with the coating lengths L7, L8 (lengths L7, L8 shown in the cross-sectional view of FIG. 3 ) of the exterior resin body 15 on the other side surfaces, the coating lengths L7, L8 of the exterior resin body 15 on the side surfaces to which the positive electrode terminal 12 and the negative electrode terminal 13 are not connected are set shorter than the coating lengths L5, L6 of the exterior resin body 15 on the side surfaces to which the positive electrode terminal 12 and the negative electrode terminal 13 are connected (L7, L8 < L5, L6). This is because, since heat is conducted to the exterior resin body 15 by the conduction of current through the first protrusion 116 and the second protrusion 117, the exterior resin body 15 itself should be made as small as possible to suppress temperature rise.

[0025] Furthermore, the exterior resin body 15 of this embodiment may cover two upper and lower surfaces perpendicular to the stacking direction X, with covering lengths L9 and L10. This is because, when surface pressure is applied to the stack 11 along the stacking direction X during use of the secondary battery 1, the presence of the exterior resin body 15 on the two upper and lower surfaces perpendicular to the stacking direction X allows the surface pressure to be applied evenly.

[0026] The resin used as the exterior resin body 15 of this embodiment preferably has a melting point that does not affect the positive electrode active material, negative electrode active material, and solid electrolyte of the secondary battery 1 of this embodiment, and for example, the melting point is less than 200° C. Examples of types of resin include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polystyrene (PS), acrylonitrile-styrene resin (AS), acrylonitrile-butadiene-styrene resin (ABS), polyethylene (PE), ethylene vinyl acetate (EVA), polystyrene (PP), polyacetal (POM), acrylic resin (PMMA), methyl methacrylate-styrene copolymer (MS), polycarbonate (PC), polyurethane (PU), and polyvinylidene fluoride (PVDF).

[0027] The method for forming the exterior resin body 15 of this embodiment is not particularly limited, and a known method can be used. For example, the laminate 11 is housed in an exterior member 14 described below, the interior of this exterior member 14 is filled with a liquid thermosetting resin or thermoplastic resin at a temperature below its melting point, the exterior member is sealed by vacuum degassing, and the resin is then heated and cured to form the exterior resin body 15. Alternatively, the laminate 11 may be set in an insert molding die, the die is filled with a liquid thermosetting resin or thermoplastic resin at a temperature below its melting point, and the resin is then heated and cured to form the exterior resin body 15.

[0028] As shown in FIG. 1 , the positive electrode terminal 12 of this embodiment is connected to the connection portions 114b of three positive electrode collectors 114. The positive electrode terminal 12 is a conductive plate-shaped member made of metal or conductive resin. Although not particularly limited, the positive electrode terminal 12 may be made of the same material as the positive electrode collectors 114. The positive electrode terminal 12 may also be made of a material having a thermal conductivity of 10 W / m·K or more. This allows the positive electrode terminal 12 to improve the cooling efficiency of the all-solid-state battery or semi-solid-state battery.

[0029] The negative electrode terminal 13 of this embodiment is connected to the connection portions 115b of the three negative electrode current collectors 115 as shown in FIG. 1 . The negative electrode terminal 13 is a conductive plate-shaped member, and like the positive electrode terminal 12, is made of a metal or a conductive resin. Furthermore, although not particularly limited, the negative electrode terminal 13 may be made of the same material as the negative electrode current collectors 115. Furthermore, the negative electrode terminal 13 may be made of a material having a thermal conductivity of 10 W / m·K or more. This allows the negative electrode terminal 13 to improve the cooling efficiency of the all-solid-state battery or semi-solid battery.

[0030] The exterior member 14 is a casing for housing the laminate 11 therein, and may be made of a laminate film or the like. Although not particularly limited, the interior of the exterior member 14 is evacuated to a vacuum, so that almost no gas is present inside the exterior member 14.

[0031] In the secondary battery 1 of this embodiment, as shown in FIG. 1 , the positive electrode terminal 12 extends from one of the four sides of the rectangular exterior member 14, and the negative electrode terminal 13 extends from the opposite side. Note that this embodiment illustrates a so-called unipolar secondary battery 1 in which a positive electrode layer 111 is formed on each side of the main body 114a of one positive electrode current collector 114 and a negative electrode layer 112 is formed on each side of the main body 115a of one negative electrode current collector 115. However, a so-called bipolar secondary battery may also be used in which a positive electrode layer is formed on one side of one current collector and a negative electrode layer is formed on the other side. Furthermore, this embodiment illustrates a secondary battery 1 in which the positive electrode terminal 12 and the negative electrode terminal 13 extend from different sides of the exterior member 14. However, a secondary battery 1 in which the positive electrode terminal 12 and the negative electrode terminal 13 extend from the same side of the exterior member 14 may also be used.

[0032] In the secondary battery 1 of the present embodiment described above, the positive electrode layer 111 and the negative electrode layer 112 expand and contract during charging and discharging. The expansion and contraction of the negative electrode layer 112 is particularly significant compared to the positive electrode layer 111. FIG. 6A is a cross-sectional view showing the laminate 11 and the exterior resin body 15 according to a comparative example for illustrating the operation of the present invention. When the negative electrode layer 112 expands during charging, a strong tensile stress, indicated by the black arrows in the figure, acts on the exterior resin body 15 around the negative electrode layer 112. This tensile stress causes the exterior resin body 15 to break in the portion in contact with the negative electrode layer 112. The resulting space S creates a step, and the application of surface pressure can cause the electrolyte layer 113 to break, increasing the risk of a short circuit.

[0033] Therefore, in the secondary battery 1 of this embodiment, a first protrusion 116 is formed on each of the four sides of the rectangular negative electrode current collector 115, protruding from the corresponding side of the negative electrode layer 112 toward the exterior resin body 15, and a second protrusion 117 is formed on each of the four sides of the rectangular positive electrode current collector 114, protruding from the corresponding side of the positive electrode layer 111 toward the exterior resin body 15. Fig. 4 is a plan view (viewed in the X direction) showing the negative electrode layer 112 and the negative electrode current collector 115 included in the laminate 11, and Fig. 5 is a plan view (viewed in the X direction) showing the positive electrode layer 111 and the positive electrode current collector 114 included in the laminate 11.

[0034] 4 , the negative electrode current collector 115 of this embodiment has a main body portion 115a on both sides of which a pair of negative electrode layers 112 are formed, and a connection portion 115b extending from the main body portion toward the negative electrode terminal 13. The negative electrode current collector 115 further has first protrusions 116 protruding outward from the outer peripheral edges of three sides of the main body portion 115a. As shown in FIG. 4 , the negative electrode current collector 115 of this embodiment is formed in a rectangular shape having long and short sides. The protrusion length L2 of the first protrusions 116 on the long sides is set shorter than the protrusion length L1 of the first protrusions 116 on the short sides (L2<L1). The first protrusions 116 mitigate breakage of the exterior resin body 15 due to expansion of the negative electrode layers 112. However, when current is applied, heat from the first protrusions 116 is transferred to the exterior resin body 15, causing thermal degradation of the exterior resin body 15. Therefore, the contact area between the first protrusion 116 on the long side and the exterior resin body 15 is made as small as possible, or made close to the contact area between the first protrusion 116 on the short side and the exterior resin body 15, thereby suppressing deterioration of the exterior resin body 15 due to heat.

[0035] 5 , the positive electrode current collector 114 of this embodiment has a main body portion 114a having a pair of positive electrode layers 111 formed on each of its two surfaces, and a connection portion 114b extending from the main body portion toward the positive electrode terminal 12. The positive electrode current collector 114 further has second protrusions 117 protruding outward from the outer peripheral edges of three sides of the main body portion 114a. As shown in the figure, the positive electrode current collector 114 of this embodiment is formed in a rectangular shape having long and short sides. The protrusion length L4 of the second protrusions 117 on the long sides is set shorter than the protrusion length L3 of the second protrusions 117 on the short sides (L4<L3). The second protrusions 117 mitigate breakage of the exterior resin body 15 due to expansion of the positive electrode layer 111. However, when current is applied, heat from the second protrusions 117 is transferred to the exterior resin body 15, causing thermal degradation of the exterior resin body 15. Therefore, the contact area between the second protrusion 117 on the long side and the exterior resin body 15 is made as small as possible, or made close to the contact area between the second protrusion 117 on the short side and the exterior resin body 15, thereby suppressing deterioration of the exterior resin body 15 due to heat.

[0036] Furthermore, in this embodiment, the protrusion lengths L3, L4 of the second protrusions 117 included in the positive electrode current collector 114 are set to be shorter than the protrusion lengths L1, L2 of the first protrusions 116 included in the negative electrode current collector 115 (L3, L4<L1, L2). As described above, the first protrusions 116 and the second protrusions 117 transfer heat generated by current flow to the exterior resin body 15. Therefore, for the positive electrode layer 111 in which expansion of the electrode layer is relatively small, the contact area between the second protrusions 117 and the exterior resin body 15 is made as small as possible to suppress deterioration of the exterior resin body 15 due to heat.

[0037] Next, the operation will be described. FIG. 6B is a cross-sectional view showing the laminate 11 and the exterior resin body 15 according to an embodiment for illustrating the operation of the present invention. When the negative electrode layer 112 expands during charging, a strong tensile stress, indicated by the solid arrows in FIG. 6B, acts on the exterior resin body 15 around the negative electrode layer 112. However, this tensile stress is alleviated by the first protrusion 116 protruding from the exterior resin body 15, thereby preventing fracture of the portion of the exterior resin body 15 in contact with the negative electrode layer 112. Similarly, when the positive electrode layer 111 expands during discharging, a somewhat strong tensile stress, indicated by the solid arrows in FIG. 6B, acts on the exterior resin body 15 around the positive electrode layer 111. However, this tensile stress is alleviated by the second protrusion 117 protruding from the exterior resin body 15, preventing fracture of the portion of the exterior resin body 15 in contact with the positive electrode layer 111. As a result, fracture of the exterior resin body 15 is prevented from leading to fracture of the electrolyte layer 113, thereby reducing the risk of short-circuiting.

[0038] 1 to 5, the negative electrode current collector 115 and the negative electrode layer 112 are formed into a rectangular shape having four sides in a plan view, and the first protrusion 116 is provided on three sides other than the connection portion 115b connected to the negative electrode terminal 13, but the secondary battery of the present invention is not limited to this, and the first protrusion 116 may be provided on at least one of the three sides other than the connection portion 115b connected to the negative electrode terminal 13. Fig. 7 is a plan view showing another example of the negative electrode layer 112 and the negative electrode current collector 115 included in the laminate 11 of Fig. 2, and in this example, the first protrusion 116 is provided only on the short side of the main body portion 115a of the negative electrode current collector 115, and the first protrusion 116 is not provided on the long side of the main body portion 115a.

[0039] In the embodiment shown in FIGS. 1 to 5 , the negative electrode current collector 115 and the negative electrode layer 112 are formed into a rectangle having four sides in a plan view, but the secondary battery of the present invention is not limited to this. The negative electrode current collector 115 may be formed into a shape other than a rectangle having four sides in a plan view, and a first protrusion 116 that protrudes from the outer periphery of the negative electrode layer 112 toward the exterior resin body 15 may be provided on at least a part of the outer periphery of the negative electrode current collector 115.

[0040] In addition, in the embodiment shown in Figures 1 to 5, the negative electrode current collector 115 is provided with the first protrusion 116 and the positive electrode current collector 114 is provided with the second protrusion 117, but the secondary battery of the present invention is not limited to this, and it is also possible to only provide the negative electrode current collector 115 with the first protrusion 116.

[0041] 8 is a plan view showing yet another example of the negative electrode layer 112 and the negative electrode current collector 115 included in the laminate 11 of FIG. 2. In this example, the first protrusions 116 provided on three sides of the negative electrode current collector 115 are insulated. The insulation treatment in this example is not particularly limited, but for example, tape 16 made of an insulating material is attached to both sides of the first protrusions 116. This is to prevent the negative electrode current collector 115 from coming into contact with the positive electrode current collector 114 or another negative electrode current collector 115 when the laminate 11 is formed by providing the first protrusions 116.

[0042] Although not shown in the figures, the second protrusions 117 provided on the three sides of the positive electrode current collector 114 may also be insulated, for example, by attaching tape 16 made of an insulating material to both surfaces of the second protrusions 117, similar to the negative electrode current collector 115 shown in FIG.

[0043] As described above, the secondary battery 1 of this embodiment includes a laminate 11 including a positive electrode having a positive electrode current collector 114 and a positive electrode layer 111, a negative electrode having a negative electrode current collector 115 and a negative electrode layer 112, and an electrolyte layer 113 interposed between the positive electrode and the negative electrode, and an exterior resin body 15 made of a thermosetting resin or a thermoplastic resin and covering the laminate 11. At least a part of the outer periphery of the negative electrode current collector 115 has a first protrusion 116 that protrudes from the outer periphery of the negative electrode layer 112 into the exterior resin body 15. Therefore, even if the negative electrode layer 112 expands during charging and tensile stress acts on the exterior resin body 15, the first protrusion 116 protruding into the exterior resin body 15 relieves this tensile stress. As a result, fracture of the exterior resin body 15 at the portion in contact with the negative electrode layer 112 is suppressed, thereby reducing the risk of short circuiting.

[0044] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 and the negative electrode layer 112 are formed into a rectangle having four sides in a plan view, and at least one of the three sides of the negative electrode current collector 115 other than the connection portion 115b has the first protrusion 116 that protrudes from the corresponding side of the negative electrode layer 112 toward the exterior resin body 15. Therefore, even if the negative electrode layer 112 expands during charging and tensile stress acts on the exterior resin body 15, the first protrusion 116 protruding from the exterior resin body 15 relieves this tensile stress. As a result, fracture of the exterior resin body 15 at the portion in contact with the negative electrode layer 112 is suppressed, and the risk of short circuiting is reduced.

[0045] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 has, on all three sides other than the connection portion 115b, the first protrusions 116 that protrude from the corresponding sides of the negative electrode layer 112 toward the exterior resin body 15. Therefore, even if the negative electrode layer 112 expands during charging and tensile stress acts on the exterior resin body 15, the first protrusions 116 that protrude toward the exterior resin body 15 relieve this tensile stress. As a result, breakage of the exterior resin body 15 at the portion in contact with the negative electrode layer 112 is suppressed, and the risk of short circuiting is reduced.

[0046] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 and the negative electrode layer 112 are formed into a rectangle having long sides and short sides in a plan view, and the length L2 of the first protrusion 116 on the long side of the negative electrode current collector 115 is shorter than the length L1 of the first protrusion 116 on the short side of the negative electrode current collector 115, so that deterioration of the exterior resin body 15 due to heat can be suppressed.

[0047] Furthermore, according to the secondary battery 1 of this embodiment, the positive electrode current collector 114 and the positive electrode layer 111 are formed into a rectangle having four sides in a plan view, and all three sides of the positive electrode current collector 114 other than the connection portion 114b have second protrusions 117 that protrude from the corresponding sides of the positive electrode layer 111 toward the exterior resin body 15. Therefore, even if the positive electrode layer 111 expands during discharge and tensile stress acts on the exterior resin body 15, the second protrusions 117 protruding from the exterior resin body 15 relieve this tensile stress. As a result, fracture of the exterior resin body 15 at the portion in contact with the positive electrode layer 111 is suppressed, and the risk of short circuiting is reduced.

[0048] Furthermore, according to the secondary battery 1 of this embodiment, the positive electrode current collector 114 and the positive electrode layer 111 are formed into a rectangle having long sides and short sides in a plan view, and the length L4 of the second protrusion 117 on the long side of the positive electrode current collector 114 is shorter than the length L3 of the second protrusion 117 on the short side of the positive electrode current collector 114, so that deterioration of the exterior resin body 15 due to heat can be suppressed.

[0049] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 is formed in a rectangular shape having four sides in a plan view, with the negative electrode terminal 13 connected to one of the four sides, and the positive electrode current collector 114 is formed in a rectangular shape having four sides in a plan view, with the positive electrode terminal 12 connected to one of the four sides. Since the coating lengths L7 and L8 of the exterior resin body 15 on the side other than the side to which the negative electrode terminal 13 or the positive electrode terminal 12 is connected are shorter than the coating lengths L5 and L6 of the exterior resin body 15 on the side to which the negative electrode terminal 13 or the positive electrode terminal 12 is connected, a temperature rise in the exterior resin body 15 can be suppressed.

[0050] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 is formed in a rectangular shape having four sides in a plan view, and the negative electrode terminal 13 is connected to one of the four sides, and the positive electrode current collector 114 is formed in a rectangular shape having four sides in a plan view, and the positive electrode terminal 12 is connected to one of the four sides, and lengths L3 and L4 of the second protrusions 117 on three sides of the positive electrode current collector 114 other than the side to which the positive electrode terminal 12 is connected are shorter than lengths L1 and L2 of the first protrusions 116 on three sides of the negative electrode current collector 115 other than the side to which the negative electrode terminal 13 is connected, so that deterioration of the exterior resin body 15 due to heat can be suppressed.

[0051] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode current collector 115 is formed in a rectangular shape having four sides in a plan view, and the negative electrode terminal 13 is connected to one of the four sides. The first protrusions 116 on the three sides of the negative electrode current collector 115 other than the side to which the negative electrode terminal 13 is connected are insulated, thereby reducing the risk of short circuiting.

[0052] Furthermore, according to the secondary battery 1 of this embodiment, the positive electrode current collector 114 and the positive electrode layer 111 are formed into a rectangle having four sides in a plan view, and a positive electrode terminal 12 is connected to one of the four sides. All three sides of the positive electrode current collector 114 other than the side to which the positive electrode terminal 12 is connected have second protrusions 117 that protrude from the corresponding sides of the positive electrode layer 111 toward the exterior resin body 15, and the second protrusions 117 on the three sides of the positive electrode current collector 114 other than the side to which the positive electrode terminal 12 is connected are insulated, thereby reducing the risk of short circuiting.

[0053] Furthermore, according to the secondary battery 1 of this embodiment, the exterior resin body 15 covers both sides of the stack 11 in the stacking direction, so that a uniform surface pressure can be applied during use.

[0054] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode layer 112 contains lithium metal, lithium alloy, or silicon as an active material, so even if the negative electrode layer 112 expands during charging and tensile stress acts on the exterior resin body 15, the first protrusion 116 protruding from the exterior resin body 15 relieves this tensile stress. As a result, breakage of the portion of the exterior resin body 15 in contact with the negative electrode layer 112 is suppressed, and the risk of short circuiting is reduced.

[0055] Furthermore, according to the secondary battery 1 of this embodiment, the negative electrode layer contains lithium metal or a lithium alloy as the active material, so even if the negative electrode layer 112 expands during charging and tensile stress acts on the exterior resin body 15, the first protrusion 116 protruding from the exterior resin body 15 relieves this tensile stress. As a result, fracture of the portion of the exterior resin body 15 in contact with the negative electrode layer 112 is suppressed, and the risk of short circuiting is reduced.

[0056] DESCRIPTION OF SYMBOLS 1 Secondary battery 11 Laminated body 111 Positive electrode layer 112 Negative electrode layer 113 Electrolyte layer 114 Positive electrode current collector 114a Main body 114b Connection portion 115 Negative electrode current collector 115a Main body 115b Connection portion 116 First protrusion 117 Second protrusion 12 Positive electrode terminal 13 Negative electrode terminal 14 Exterior member 15 Exterior resin body 16 Tape (insulated)

Claims

1. A secondary battery comprising: a laminate including a positive electrode having a positive electrode current collector and a positive electrode layer, a negative electrode having a negative electrode current collector and a negative electrode layer, and an electrolyte layer interposed between the positive electrode and the negative electrode; and an exterior resin body made of a thermosetting resin or a thermoplastic resin that covers the laminate, wherein at least a part of the outer periphery of the negative electrode current collector has a first protrusion that protrudes from the outer periphery of the negative electrode layer toward the exterior resin body.

2. The secondary battery according to claim 1, wherein the negative electrode current collector and the negative electrode layer are formed in a rectangular shape having four sides in a plan view, a negative electrode terminal is connected to one of the four sides, and at least one of three sides of the negative electrode current collector other than the side to which the negative electrode terminal is connected has the first protrusion that protrudes from the side of the negative electrode layer corresponding to said side toward the exterior resin body.

3. The secondary battery according to claim 2, wherein the negative electrode current collector has, on all three sides other than the side to which the negative electrode terminal is connected, the first protrusions that protrude from the sides of the negative electrode layer corresponding to each of the three sides toward the exterior resin body.

4. The secondary battery according to any one of claims 1 to 3, wherein the negative electrode current collector and the negative electrode layer are formed in a rectangular shape having long sides and short sides in a plan view, and the length of the first protrusion on the long side of the negative electrode current collector is shorter than the length of the first protrusion on the short side of the negative electrode current collector.

5. The secondary battery according to any one of claims 1 to 4, wherein the positive electrode current collector and the positive electrode layer are formed into a rectangle having four sides in a plan view, a positive electrode terminal is connected to one of the four sides, and second protrusions are provided on all three sides of the positive electrode current collector other than the side to which the positive electrode terminal is connected, the second protrusions protruding from the sides of the positive electrode layer corresponding to the three sides toward the exterior resin body.

6. The secondary battery according to claim 5, wherein the positive electrode current collector and the positive electrode layer are formed in a rectangular shape having long and short sides in a plan view, and the length of the second protrusion on the long side of the positive electrode current collector is shorter than the length of the second protrusion on the short side of the positive electrode current collector.

7. The secondary battery according to any one of claims 1 to 6, wherein the negative electrode current collector is formed in a rectangular shape having four sides in a plan view, and a negative electrode terminal is connected to one of the four sides; the positive electrode current collector is formed in a rectangular shape having four sides in a plan view, and a positive electrode terminal is connected to one of the four sides; and the length of the coating of the exterior resin body on the side other than the side to which the negative electrode terminal or the positive electrode terminal is connected is shorter than the length of the coating of the exterior resin body on the side to which the negative electrode terminal or the positive electrode terminal is connected.

8. The secondary battery according to claim 5 or 6, wherein the negative electrode current collector is formed in a rectangular shape having four sides in a plan view, and a negative electrode terminal is connected to one of the four sides; the positive electrode current collector is formed in a rectangular shape having four sides in a plan view, and a positive electrode terminal is connected to one of the four sides; and the length of the second protrusions on three sides of the positive electrode current collector other than the side to which the positive electrode terminal is connected is shorter than the length of the first protrusions on three sides of the negative electrode current collector other than the side to which the negative electrode terminal is connected.

9. The secondary battery according to any one of claims 1 to 8, wherein the negative electrode current collector is formed in a rectangular shape having four sides in a plan view, a negative electrode terminal is connected to one of the four sides, and the first protrusions on the three sides of the negative electrode current collector other than the side to which the negative electrode terminal is connected are insulated.

10. The secondary battery according to claim 9, wherein the positive electrode current collector and the positive electrode layer are formed into a rectangle having four sides in a plan view, and a positive electrode terminal is connected to one of the four sides, and each of three sides of the positive electrode current collector other than the side to which the positive electrode terminal is connected has a second protrusion that protrudes from the side of the positive electrode layer corresponding to each of the three sides toward the exterior resin body, and the second protrusions on the three sides of the positive electrode current collector other than the side to which the positive electrode terminal is connected are insulated.

11. The secondary battery according to any one of claims 1 to 10, wherein the exterior resin body covers both sides of the laminate in the stacking direction.

12. The secondary battery according to any one of claims 1 to 11, wherein the negative electrode layer contains lithium metal, a lithium alloy, or silicon as an active material.

13. The secondary battery according to claim 12, wherein the negative electrode layer contains lithium metal or a lithium alloy as an active material.

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