Secondary batteries and secondary battery stacks

Abstract

The present invention provides a secondary battery and a secondary battery stack that can improve the accuracy of electrode potential measurement using a reference electrode. [Solution] The secondary battery comprises a first current collector 4, a first active material layer 5, an electrolyte layer 6 containing a solid electrolyte, a second active material layer 7, a second current collector 8, and a reference electrode 3 connected to the electrolyte layer 6. The first current collector 4 is formed to be larger in shape than the first active material layer 5, and the electrolyte layer 6 has a main surface portion 61 disposed between the first active material layer 5 and the second active material layer 7, a side portion 62 disposed to cover the side surface of the first active material layer 5, and an outer peripheral portion 63 disposed on the first current collector 4 so as to extend from the side portion 62 in a direction perpendicular to the stacking direction A. The reference electrode 3 comprises an electrode layer 31 disposed on an installation surface 631 of the outer peripheral portion 63 opposite to the surface on which the first current collector 4 is provided, and a metal tab 32 extending outward from the electrode layer 31 along the outer peripheral portion 63.

Description

Technical Field

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

Background Art

[0002] As a secondary battery, one having a configuration in which a positive electrode layer, an electrolyte layer, and a negative electrode layer are laminated in this order is known. In this specification, a laminated structure composed of a positive electrode layer, an electrolyte layer, and a negative electrode layer may be referred to as a power generation element.

[0003] As such a secondary battery, one further provided with a reference electrode is known. Thereby, even after the production of the secondary battery, the electrode potential can be measured.

[0004] In relation to the above, Patent Document 1 discloses a sulfide solid-state battery including a second current collector containing copper, a negative electrode composite material layer disposed on the second current collector and containing a negative electrode active material, and a positive electrode composite material layer containing a positive electrode active material. This sulfide solid-state battery further includes a sulfide solid electrolyte layer sandwiched between the negative electrode composite material layer and the positive electrode composite material layer and having an overhanging portion that protrudes from the peripheral edge of the negative electrode composite material layer and contacts the second current collector, and a reference electrode connected to the overhanging portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By measuring the electrode potential using a reference electrode, for example, it is possible to detect the state and defects inside the battery in the electrode without disassembling the battery. Therefore, the present inventors aim to realize measurement of the electrode potential with high accuracy.

[0007] However, in the invention described in Patent Document 1, the end face of the inner end of the reference electrode only contacts the side surface of the electrolyte layer (protruding portion), resulting in a small contact area between the two, which may hinder stable contact. This may lead to a decrease in the accuracy of electrode potential measurement.

[0008] Therefore, the object of the present invention is to provide a secondary battery and a secondary battery stack that can improve the accuracy of measuring electrode potential using a reference electrode. [Means for solving the problem]

[0009] According to one aspect of the present invention, a secondary battery is provided comprising: a first current collector; a first active material layer disposed on the first current collector; an electrolyte layer containing a solid electrolyte disposed on the first current collector and the first active material layer; a second active material layer disposed on the electrolyte layer; a second current collector disposed on the second active material layer; and a reference electrode connected to the electrolyte layer. The first current collector is formed to be larger in shape than the first active material layer, and the electrolyte layer has a main surface portion disposed between the first active material layer and the second active material layer; a side portion disposed to cover the side surface of the first active material layer; and an outer peripheral portion disposed on the first current collector so as to extend from the side portion in a direction perpendicular to the stacking direction. The reference electrode comprises an electrode layer disposed on the mounting surface of the outer peripheral portion opposite to the surface on which the first current collector is provided, and a metal tab extending outward from the electrode layer along the outer peripheral portion. [Effects of the Invention]

[0010] According to the present invention, by placing the reference electrode on the mounting surface of the outer periphery of the electrolyte layer, stable contact between the reference electrode and the electrolyte layer is achieved, thereby providing a secondary battery and a secondary battery stack that can improve the accuracy of electrode potential measurement by the reference electrode. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a top view of the secondary battery according to this embodiment. [Figure 2] Figure 2 is a cross-sectional view of the XX' section in Figure 1. [Figure 3A] Figure 3A is a diagram illustrating a preferred embodiment of the reference pole. [Figure 3B] Figure 3B is a diagram illustrating a preferred embodiment of the reference pole. [Figure 4] Figure 4 is a cross-sectional view of a secondary battery stack including a secondary battery according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings.

[0013] Figure 1 is a top view of the secondary battery 1 according to this embodiment. As shown in Figure 1, the secondary battery 1 according to this embodiment has a rectangular power generation element 2 housed inside a sheet-like outer casing 9, and is provided as a so-called laminate cell.

[0014] Figure 2 is a cross-sectional view of the XX' section of Figure 1. As shown in Figure 2, the secondary battery 1 has a power generation element 2 and a reference electrode 3. The power generation element 2 comprises a first current collector 4, a first active material layer 5 disposed on the first current collector 4, an electrolyte layer 6 containing a solid electrolyte disposed on the first current collector 4 and the first active material layer 5, a second active material layer 7 disposed on the electrolyte layer 6, and a second current collector 8 disposed on the second active material layer 7. The reference electrode 3 is connected to the electrolyte layer 6. The secondary battery 1 according to this embodiment includes solid batteries such as semi-solid batteries and all-solid batteries.

[0015] In this embodiment, the first current collector 4 and the first active material layer 5 function as a positive electrode current collector and a positive electrode active material layer, respectively. The second current collector 8 and the second active material layer 7 function as a negative electrode current collector and a negative electrode active material layer, respectively.

[0016] The combination of the above-described positive electrode current collector and the positive electrode active material layer may be referred to as a positive electrode layer. Also, the combination of the negative electrode current collector and the negative electrode active material layer may be referred to as a negative electrode layer. That is, in the present embodiment, the positive electrode layer is a layer formed by combining the first current collector 4 and the first active material layer 5, and the negative electrode layer is a layer formed by combining the second current collector 8 and the second active material layer 7.

[0017] Both the first current collector 4 (positive electrode current collector) and the second current collector 8 (negative electrode current collector) are film-like metal foils. As the positive electrode current collector, for example, an aluminum foil or the like can be used. As the negative electrode current collector, for example, thin films such as copper, copper alloy, nickel, and nickel alloy can be used.

[0018] As shown in FIG. 2, the outer shape of the first current collector 4 is formed larger than that of the first active material layer 5. More specifically, when viewed along the stacking direction A, the outer peripheral end of the first current collector 4 is located outside the outer peripheral end of the first active material layer 5.

[0019] Also, as shown in FIG. 2, the electrolyte layer 6 includes a main surface portion 61 disposed between the first active material layer 5 and the second active material layer 7, a side surface portion 62 disposed so as to cover the side surface of the first active material layer 5, and an outer peripheral portion 63 disposed on the first current collector 4 so as to extend from the side surface portion 62 along a direction perpendicular to the stacking direction A (hereinafter referred to as the lateral direction B). That is, it can be said that the electrolyte layer 6 is disposed on the first current collector 4 and the first active material layer 5 so as to surround the entire first active material layer 5.

[0020] Here, the secondary battery 1 includes a reference electrode 3 having an electrode layer 31 disposed on the installation surface 631 of the outer peripheral portion 63 and a metal tab 32 extending outward from the electrode layer 31 along the outer peripheral portion 63. That is, as shown in FIG. 2, the electrode layer 31 of the reference electrode 3 is disposed on the installation surface 631 of the outer peripheral portion 63 of the electrolyte layer 6, and the metal tab 32 connected to the electrode layer 31 extends outward along the outer peripheral portion 63 in the lateral direction B. Note that the metal tab 32 is a metal plate. As the metal tab 32, for example, a nickel plate, a copper alloy plate, or the like can be used.

[0021] In some cases, a reference electrode may be provided in the electrolyte layer for the purpose of measuring the electrode potential of the positive electrode layer or the negative electrode layer after the secondary battery is manufactured. By electrically connecting the reference electrode and the positive electrode layer or the negative electrode layer and measuring the potential difference (voltage) therebetween, the electrode potential can be measured.

[0022] For example, in the case of a lithium-ion secondary battery, it becomes possible to detect internal states and defects of the battery such as the precipitation of Li metal from the measured electrode potential without disassembling the battery. Therefore, it is preferable that the measurement accuracy of the electrode potential is as high as possible.

[0023] The measurement accuracy of the electrode potential varies depending on, for example, the contact state between the reference electrode and the electrolyte layer. The contact state between the two can vary depending on the size of the contact area between them. That is, when the contact area between the reference electrode and the electrolyte layer is small, such as when only the end face of the inner end portion of the reference electrode contacts the side face of the electrolyte layer, stable contact between the two may be hindered and the contact state may become unstable. As a result, the measurement accuracy of the electrode potential may decrease.

[0024] On the other hand, in the secondary battery 1 according to the present embodiment, the lower surface (flat surface extending in the lateral direction B) of the electrode layer 31 of the reference electrode 3 is in surface contact with the installation surface (631) of the outer peripheral portion 63 of the electrolyte layer 6. Therefore, the contact area between the reference electrode 3 and the electrolyte layer 6 becomes relatively large, and the contact state between the two is stabilized. As a result, the measurement accuracy of the electrode potential by the reference electrode 3 is improved.

[0025] In the present embodiment, as shown in FIG. 2, it is preferable that the thickness of the outer peripheral portion 63 in the stacking direction A is smaller than the total thickness of the first active material layer 5 and the main surface portion 61. [[ID=IS]]

[0026] In this case, it is preferable that the reference electrode 3 is arranged at a distance from the side surface portion 62 of the electrolyte layer 6 in the lateral direction B. That is, in FIG. 2, it is preferable that the reference electrode 3 is arranged such that the right end face of the electrode layer 31 of the reference electrode 3 does not contact the left end face of the side surface portion 62 of the electrolyte layer 6.

[0027] Furthermore, when viewed along the stacking direction A, it is preferable that the outer edge of the second active material layer 7, which is the negative electrode active material layer, is located inward from the outer edge of the first active material layer 5, which is the positive electrode active material layer.

[0028] Furthermore, the length of the outer periphery 63 of the electrolyte layer 6 in the lateral direction B is not particularly limited, as long as it is long enough to stably position the electrode layer 31 of the reference electrode 3. For example, the length of the outer periphery 63 in the lateral direction B is three times or more the length of the electrode layer 31 in the lateral direction B.

[0029] Furthermore, as shown in Figure 1, if the first tab 10 and the second tab 11 protrude side by side from one side of the secondary battery 1 when viewed from above, it is preferable that the metal tab 32 of the reference pole 3 be positioned to protrude from the other side of the secondary battery 1. The first tab 10 and the second tab 11 are connected to the first current collector 4 and the second current collector 8, respectively, and function as input / output terminals that electrically connect an external device to the secondary battery 1.

[0030] Next, we will explain the detailed configuration of reference pole 3.

[0031] If the secondary battery 1 is a lithium-ion secondary battery and the second active material layer 7, which is the negative electrode active material layer, contains an active material including Li, then it is preferable that the electrode layer 31 of the reference electrode 3 is an electrode layer having Li metal or a LiIn alloy.

[0032] In another preferred example, the electrode layer 31 of the reference electrode 3 is arranged to integrally cover the entire end face and outer surface of the inner end of the metal tab 32. For example, as shown in Figure 3A, the electrode layer 31 is in the shape of a flat cap and has an insertion hole 311 extending inward from the side, with the inner end of the metal tab 32 (the end on the side surface 62 in Figure 2) positioned inside the insertion hole 311.

[0033] In this case, as shown in Figure 3B, it is preferable that the resin layer 33 covers the entire circumference of the portion of the metal tab 32 that is not covered by the electrode layer 31 and faces the outer peripheral portion 63 of the electrolyte layer 6. In other words, it is preferable that the entire circumference of the portion of the main body of the metal tab 32 that is not covered by the electrode layer 31 and faces the outer peripheral portion 63 is covered by the resin layer 33. Furthermore, it is even more preferable that the electrode layer 31 and the resin layer 33 are in close contact without any gaps.

[0034] The type of resin used to form the resin layer 33 is not particularly limited, as long as it can prevent the metal tab 32 from coming into contact with the installation surface 631. Examples of resins that can be used to form the resin layer 33 include rubber and thermoplastic resins. Examples of rubbers include chloropyrene rubber. Examples of thermoplastic resins include polyolefin resins, rigid polyvinyl chloride resins, polystyrene, ABS resins, acetal resins, acrylic resins, fluororesins, methylpentene resins, polycarbonate, and nylon. In particular, from the viewpoint of the moldability of the resin layer 33, it is preferable to use polyolefin resins. Examples of polyolefin resins include polyethylene and polypropylene.

[0035] Furthermore, the preferred embodiments of the reference pole 3 described above are not independent of each other, but can be combined within a non-contradictory range.

[0036] The following describes the effects and benefits of the secondary battery 1 according to this embodiment.

[0037] The secondary battery 1 according to this embodiment includes a reference electrode 3, the reference electrode 3 comprising an electrode layer 31 positioned on the mounting surface 631 of the outer peripheral portion 63 of the electrolyte layer 6, and a metal tab 32 extending outward from the electrode layer 31 along the outer peripheral portion 63.

[0038] This configuration improves the accuracy of electrode potential measurement using the reference electrode 3. More specifically, since the lower surface of the electrode layer 31 of the reference electrode 3 is in surface contact with the mounting surface 631 of the outer peripheral portion 63 of the electrolyte layer 6, the contact area between the reference electrode 3 and the electrolyte layer 6 is larger compared to cases where only the end face of the inner end of the reference electrode 3 and the side portion 62 of the electrolyte layer 6 are in contact. As a result, the contact state between the two is stabilized, enabling highly accurate measurement of electrode potential.

[0039] Furthermore, in the secondary battery 1 according to this embodiment, the thickness of the outer peripheral portion 63 of the electrolyte layer 6 in the stacking direction A is thinner than the combined thickness of the first active material layer 5 and the main surface portion 61 of the electrolyte layer 6.

[0040] If the thickness of the outer periphery 63 is greater than the combined thickness of the first active material layer 5 and the main surface 61, then when subjected to some external force such as vibration, the reference pole 3 may unintentionally come into contact with the second active material layer 7 or the second current collector 8, potentially causing a short circuit. In contrast, with the above configuration, as shown in Figure 2, the reference pole 3 is positioned in a location surrounded by the side portion 62 and the outer periphery 63, thus suppressing unintentional contact with the second active material layer 7 or the second current collector 8. This suppresses the occurrence of short circuits.

[0041] Furthermore, in the secondary battery 1 according to this embodiment, the reference electrode 3 is positioned spaced apart from the side surface 62 of the electrolyte layer 6 in a direction perpendicular to the stacking direction A.

[0042] With this configuration, it is possible to prevent the end of the reference electrode 3 from contacting the side portion 62 and damaging the side portion 62 when subjected to some external force. This improves the accuracy of electrode potential measurement by the reference electrode 3.

[0043] Furthermore, in this embodiment, if the second active material layer 7, which is the negative electrode active material layer, contains an active material including Li, the electrode layer 31 of the reference electrode 3 has Li metal or a LiIn alloy.

[0044] With this configuration, when the secondary battery 1 is a so-called lithium-ion secondary battery in which the negative electrode active material layer (second active material layer 7) contains a Li-containing active material, the electrode potential can be easily calculated.

[0045] In addition, since Li metal and LiIn alloy have excellent adhesion to the electrolyte layer 6, the contact state between the electrode layer 31 of the reference electrode 3 and the electrolyte layer 6 is stable. This enables highly accurate measurement of electrode potential.

[0046] Furthermore, LiIn alloys have lower reactivity compared to Li metal. That is, when the electrode layer 31 contains a LiIn alloy, it is possible to suppress unintended reactions between the electrode layer 31 and the electrolyte layer 6. Also, even if impurities are unintentionally present inside the secondary battery 1, it is possible to suppress reactions between the impurities and the electrode layer 31.

[0047] Furthermore, in the secondary battery 1 according to this embodiment, the electrode layer 31 of the reference electrode 3 is arranged to cover the entire end face of the inner end and the outer surface of the metal tab 32.

[0048] With this configuration, since the inner end of the metal tab 32 is surrounded by the electrode layer 31, contact between the inner end of the metal tab 32 and the outer periphery 63 can be suppressed. This suppresses damage to the outer periphery 63.

[0049] Furthermore, in the secondary battery 1 according to this embodiment, the reference electrode 3 has a resin layer 33. The resin layer 33 is arranged to cover the entire circumference of the portion of the metal tab 32 that is not covered by the electrode layer 31 and faces the outer peripheral portion 63.

[0050] With this configuration, contact between the main body and outer peripheral portion 63 of the metal tab 32, which is not covered by the electrode layer 31, can be suppressed. This prevents unintended reactions from occurring between the metal tab 32 and the outer peripheral portion 63, thereby improving the accuracy of electrode potential measurement by the reference electrode 3.

[0051] Furthermore, when the reference electrode 3 has a resin layer 33, the electrode layer 31 and the resin layer 33 are in close contact without any gaps.

[0052] With this configuration, contact between the metal tab 32 and the outer periphery 63 can be more reliably suppressed.

[0053] Furthermore, in the secondary battery 1 according to this embodiment, when the first tab 10 and the second tab 11 protrude side by side from one side of the secondary battery 1 in a top view, the metal tab 32 of the reference pole 3 protrudes from the other side of the secondary battery 1.

[0054] With this configuration, it is possible to prevent the metal tab 32 of the reference pole 3 from coming into contact with the first tab 10 or the second tab 11. This prevents short circuits from occurring between the tabs.

[0055] The secondary battery 1 according to this embodiment has been described above. Next, the secondary battery stack 100 including the secondary battery 1 according to this embodiment will be described. Details will be omitted regarding aspects where the same configuration as described above can be adopted.

[0056] Figure 4 is a cross-sectional view of a secondary battery stack 100 including a secondary battery 1 according to this embodiment. As shown in Figure 4, the secondary battery stack 100 is a stacked battery in which two or more secondary batteries 1 are stacked in the stacking direction A. Therefore, the secondary battery stack 100 is equipped with a plurality of reference poles 3.

[0057] Here, the multiple reference poles 3 are arranged so as to protrude from both sides of the secondary battery stack 100, one end and the other end, in a cross-sectional view. More specifically, if the poles protruding from one end of the secondary battery stack 100 are designated as the first reference pole 101, and the poles protruding from the other end are designated as the second reference pole 102, then the first reference pole 101 and the second reference pole 102 are arranged alternately along the stacking direction A.

[0058] If multiple reference electrodes 3 are arranged on the same side of the secondary battery stack 100, or if they are not arranged alternately along the stacking direction A, there is a risk that the metal tabs 32 of the reference electrodes 3 may come into contact with each other. If contact occurs, the accuracy of electrode potential measurement will decrease. In contrast, with the above configuration, contact between the metal tabs 32 of the reference electrodes 3 can be suppressed. This makes it possible to measure electrode potential with high accuracy.

[0059] Although embodiments of the present invention have been described above, the configurations described above represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0060] In the embodiments described above, the first current collector 4 and the first active material layer 5 were described as a positive electrode current collector and a positive electrode active material layer, respectively, and the second current collector 8 and the second active material layer 7 were described as a negative electrode current collector and a negative electrode active material layer, respectively. However, the invention is not limited to this configuration. That is, the first current collector 4 and the first active material layer 5 may be a negative electrode current collector and a negative electrode active material layer, respectively, and the second current collector 8 and the second active material layer 7 may be a positive electrode current collector and a positive electrode active material layer, respectively.

[0061] In this case, it is preferable that, when viewed along the stacking direction A, the outer edge of the first active material layer 5, which is the negative electrode active material layer, is located inward from the outer edge of the second active material layer 7, which is the positive electrode active material layer.

[0062] Furthermore, if the negative electrode active material layer of the secondary battery 1 contains an active material containing Na, it is preferable that the electrode layer 31 of the reference electrode 3 contains Na. Moreover, if the negative electrode active material layer of the secondary battery 1 contains an active material containing Mg, it is preferable that the electrode layer 31 of the reference electrode 3 contains Mg.

[0063] Furthermore, although the electrode layer 31 of the reference electrode 3 of the secondary battery 1 according to this embodiment has been described as being arranged to cover the entire end face and outer surface of the inner end of the metal tab 32, it is not limited to this configuration. That is, as long as contact between the end of the metal tab 32 and the outer surface 63 of the electrolyte layer 6 can be suppressed, a configuration in which a flat electrode layer 31 is arranged only between the metal tab 32 and the mounting surface 631 is also possible.

[0064] Furthermore, although the resin layer 33 of the reference electrode 3 of the secondary battery 1 according to this embodiment has been described as being arranged to cover the entire circumference of the portion of the metal tab 32 that is not covered by the electrode layer 31 and faces the outer peripheral portion 63 of the electrolyte layer 6, it is not limited to this. That is, as long as contact between the main body portion and the outer peripheral portion 63 of the metal tab 32 that is not covered by the electrode layer 31 can be suppressed, the resin layer 33 may be provided only between the metal tab 32 and the outer peripheral portion 63. [Explanation of Symbols]

[0065] 1: Secondary battery, 2: Power generation element, 3: Reference electrode, 31: Electrode layer, 311: Insertion hole, 32: Metal tab, 33: Resin layer, 4: First current collector, 5: First active material layer, 6: Electrolyte layer, 61: Main surface, 62: Side surface, 63: Outer periphery, 631: Installation surface, 7: Second current collector, 8: Second active material layer, 9: Outer casing, 10: First tab, 11: Second tab, 100: Secondary battery stack, 101: First reference electrode, 102: Second reference electrode

Claims

1. The first current collector and, A first active material layer disposed on the first current collector, An electrolyte layer containing a solid electrolyte is disposed on the first current collector and the first active material layer, A second active material layer disposed on the electrolyte layer, A second current collector disposed on the second active material layer, The electrolyte layer comprises a reference electrode connected to the electrolyte layer, The first current collector is formed with an outer shape larger than that of the first active material layer. The aforementioned electrolyte layer is A main surface portion disposed between the first active material layer and the second active material layer, A side portion arranged to cover the side surface of the first active material layer, It has an outer peripheral portion that is arranged on the first current collector so as to extend from the side portion in a direction perpendicular to the stacking direction, The reference electrode comprises an electrode layer positioned on the mounting surface of the outer circumference opposite to the surface on which the first current collector is provided, and a metal tab extending outward from the electrode layer along the outer circumference. Secondary battery.

2. A secondary battery according to claim 1, The thickness of the outer periphery in the stacking direction is thinner than the combined thickness of the first active material layer and the main surface. Secondary battery.

3. A secondary battery according to claim 2, The reference pole is positioned spaced apart from the side portion in a direction perpendicular to the stacking direction. Secondary battery.

4. A secondary battery according to claim 1 or 2, The electrode layer of the reference electrode is made of Li metal or LiIn alloy. Secondary battery.

5. A secondary battery according to claim 1 or 2, The electrode layer of the reference electrode is positioned to cover the entire end face and outer surface of the inner end of the metal tab. Secondary battery.

6. A secondary battery according to claim 5, The aforementioned reference electrode further comprises a resin layer, The resin layer is arranged to cover the entire circumference of the portion of the metal tab that is not covered by the electrode layer and faces the outer periphery. Secondary battery.

7. A secondary battery according to claim 6, The electrode layer and the resin layer are in close contact without any gaps. Secondary battery.

8. A secondary battery according to claim 1 or 2, When the first tab connected to the first current collector and the second tab connected to the second current collector protrude side by side from one side of the secondary battery in a top view, the metal tab of the reference electrode protrudes from the other side of the secondary battery. Secondary battery.

9. A secondary battery stack having a configuration in which multiple secondary batteries are stacked, The plurality of secondary batteries include at least two secondary batteries described in claim 1 or 2, The plurality of reference electrodes include a first reference electrode located on one end of the secondary battery stack and a second reference electrode located on the other end of the secondary battery stack. The first reference pole and the second reference pole are arranged alternately along the stacking direction. Stacked secondary battery.

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