Electrolyte composite for all-solid-state battery and all-solid-state battery

Abstract

An electrolyte composite for an all-solid-state battery comprises: a porous body having an electrolyte region for supporting a solid electrolyte; and an insulation frame disposed so as to surround the porous body and joined to an outer peripheral portion of the porous body. The insulating frame is ionically and electronically insulating, and is formed of a separate member from the porous body.

Description

Electrolyte composite for all-solid-state battery and all-solid-state battery

[0001] The present invention relates to an electrolyte composite for an all-solid-state battery and an all-solid-state battery.

[0002] All-solid-state batteries using solid electrolytes are known. Known examples of such all-solid-state batteries include those in which the solid electrolyte is supported on a porous body. Supporting the solid electrolyte on a porous body allows the electrolyte layer to have self-supporting properties, making it possible to handle the electrolyte layer independently.

[0003] In relation to the above, Patent Document 1 (JP 2019-192564 A) discloses an all-solid-state battery including a laminated electrode assembly having a laminated structure including a specific positive electrode, a specific negative electrode, and a separator layer including a porous substrate and solid electrolyte particles held by the substrate. Patent Document 1 describes that the separator layer has a protruding portion that protrudes outward beyond the end of the opposing portion between the positive electrode and the negative electrode, and at least a portion of the protruding portion is formed by a dense structure portion. Patent Document 1 also describes that the dense structure portion prevents problems associated with the detachment of solid electrolyte particles.

[0004] However, performance improvement is required for all-solid-state batteries. In all-solid-state batteries in which a porous body is included in the electrolyte layer, the thickness of the porous body is preferably thin in order to improve ionic conductivity. However, if the porous body is too thin, the strength is insufficient, and the electrolyte layer is easily damaged, especially at the edges.

[0005] Therefore, an object of the present invention is to provide a technique capable of preventing breakage at the edge of an electrolyte layer in an all-solid-state battery using a porous body for the electrolyte layer.

[0006] In one aspect, the present invention relates to an electrolyte composite for an all-solid-state battery. The electrolyte composite for an all-solid-state battery includes a porous body having an electrolyte region supporting a solid electrolyte, and an insulating frame disposed so as to surround the porous body and joined to the outer periphery of the porous body. The insulating frame is ionically and electronically insulating and is formed of a separate member from the porous body.

[0007] In another aspect, the present invention relates to an all-solid-state battery including the above-described electrolyte composite, and a positive electrode active material layer and a negative electrode active material layer disposed so as to sandwich an electrolyte-filled region in the thickness direction.

[0008] Fig. 1 is a schematic cross-sectional view showing an all-solid-state battery according to a first embodiment. Fig. 2 is a plan view showing an electrolyte composite. Fig. 3 is a diagram for explaining the thickness of an insulating frame. Fig. 4 is a schematic cross-sectional view showing a modified example of the first embodiment. Fig. 5 is a schematic cross-sectional view showing another modified example of the first embodiment. Fig. 6 is a schematic view showing an all-solid-state battery according to a second embodiment.

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

[0010] In this specification, the term "all-solid-state battery" refers to a secondary battery in which the electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer are all substantially solid. Each layer may be "substantially" solid, and a small amount of liquid material may be used.

[0011] (1) First Embodiment FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery 1 according to a first embodiment.

[0012] Schematically, the all-solid-state battery 1 includes an electrolyte composite 2, a positive electrode active material layer 3, and a negative electrode active material layer 4. These are stacked in a stacking direction. Specifically, the electrolyte composite 2 is sandwiched between the positive electrode active material layer 3 and the negative electrode active material layer 4. Although not shown, current collectors and the like are further disposed on the outer sides of the positive electrode active material layer 3 and the negative electrode active material layer 4.

[0013] In this all-solid-state battery 1, charging and discharging are performed by the conduction of lithium ions between the positive electrode active material layer 3 and the negative electrode active material layer 4. That is, during charging, lithium ions are conducted from the positive electrode active material layer 3 to the negative electrode active material layer 4 via the electrolyte composite 2. On the other hand, during discharging, lithium ions are conducted from the negative electrode active material layer 4 to the positive electrode active material layer 3 via the electrolyte composite 2.

[0014] As shown in FIG. 1, the electrolyte composite 2 includes a porous body 5 and an insulating frame 6 .

[0015] The porous body 5 is sheet-shaped and is provided to support the solid electrolyte. That is, the porous body 5 is provided with an electrolyte region 5-1, which is a region where the solid electrolyte is supported. In the electrolyte region 5-1, the pores of the porous body 5 are filled with the solid electrolyte. The electrolyte region 5-1 is sandwiched between the positive electrode active material layer 3 and the negative electrode active material layer 4 in the stacking direction. The electrolyte region 5-1 is a portion that functions as an electrolyte layer in the all-solid-state battery 1. During charge and discharge, lithium ions move between the positive electrode active material layer 3 and the negative electrode active material layer 4 via this electrolyte region 5-1.

[0016] Furthermore, the porous body 5 is provided with a non-electrolyte region 5-2. The non-electrolyte region 5-2 is a region lacking a solid electrolyte. The non-electrolyte region 5-2 is provided on the outer periphery of the porous body 5 and surrounds the electrolyte region 5-1. When viewed along the stacking direction, the non-electrolyte region 5-2 is located outside the electrode layers (the positive electrode active material layer 3 and the negative electrode active material layer 4).

[0017] The insulating frame 6 is provided to ensure strength at the ends of the electrolyte composite 2. FIG. 2 is a plan view showing the electrolyte composite 2. As shown in FIGS. 1 and 2, the insulating frame 6 is arranged to surround the porous body 5. The insulating frame 6 is joined to the outer periphery of the porous body 5. Specifically, the insulating frame 6 is joined to the non-electrolyte region 5-2 of the porous body 5. The insulating frame 6 sandwiches the non-electrolyte region 5-2 at its inner ends from both sides in the stacking direction. The insulating frame 6 is ionically and electronically insulating. The insulating frame 6 is formed from a member separate from the porous body 5. The insulating frame 6 is dense.

[0018] The above is a schematic configuration of the all-solid-state battery 1 according to this embodiment.

[0019] According to this embodiment, the insulating frame 6, which is a separate member from the porous body 5, is joined to the outer periphery of the porous body 5. Therefore, it is possible to adopt a configuration for the insulating frame 6 that has a high strength that cannot be achieved by the porous body 5 alone. This increases the strength of the ends of the electrolyte composite 2. Therefore, even if the thickness of the porous body 5 is thin, breakage of the ends can be prevented, and short circuits at the ends are prevented. Furthermore, because the ends are less likely to be broken, the electrolyte composite 2 is easy to handle during production. Furthermore, because the porous body 5 can be made thinner, the resistance related to ion conduction in the electrolyte region 5-1 can be reduced. This also makes it easy to improve the characteristics of the secondary battery.

[0020] Furthermore, in this embodiment, the insulating frame 6 sandwiches the porous body 5 (non-electrolyte region 5-2 in FIG. 1) at its inner end from both sides in the stacking direction. This configuration can increase the bonding strength between the insulating frame 6 and the porous body 5. The insulating frame 6 having this configuration can be formed, for example, by using a pair of resin films. That is, a pair of frame-shaped resin films are arranged so as to sandwich the outer periphery of the porous body 5 at the inner end. Next, the pair of frame-shaped resin films are integrated by thermal welding or the like. This allows the insulating frame 6 having the configuration shown in FIG. 1 to be obtained.

[0021] On the other hand, the insulating frame 6 does not necessarily have to sandwich the outer periphery of the porous body 5 from both sides in the stacking direction. For example, the insulating frame 6 may be provided only on one side of the porous body 5 in the stacking direction. Alternatively, the inner peripheral end face of the insulating frame 6 and the outer peripheral end face of the porous body 5 may face each other in the planar direction (direction perpendicular to the stacking direction), and the two may be joined at their end faces. Even when these configurations are adopted, the use of the insulating frame 6 makes it possible to ensure the strength of the end of the electrolyte composite 2.

[0022] In this embodiment, the porous body 5 has the non-electrolyte region 5-2 in addition to the electrolyte region 5-1. With this configuration, no conduction path for lithium ions is formed in the non-electrolyte region 5-2. This is preferable because it is possible to suppress the growth of lithium dendrites at the edge.

[0023] On the other hand, the non-electrolyte region 5-2 does not necessarily have to be provided. That is, the entire region of the porous body 5 may be the electrolyte region 5-1. Even in such a case, by joining the insulating frame 6 to the outer periphery of the porous body 5, it is possible to increase the strength of the end portion of the electrolyte composite 2.

[0024] When the non-electrolyte region 5-2 is provided, the pores in the non-electrolyte region 5-2 may be filled with the same material as that of the insulating frame 6, or with an adhesive. This configuration is preferable because it allows the insulating frame 6 to be more firmly bonded to the porous body 5. It also makes it possible to more reliably prevent the growth of lithium dendrites at the end portions.

[0025] Next, a description will be given of the thickness of the insulating frame 6. Fig. 3 is a diagram for explaining the thickness of the insulating frame 6, and is a schematic cross-sectional view showing an example of the all-solid-state battery 1.

[0026] In the example shown in FIG. 3 , the thickness x of the insulating frame 6 is greater than the thickness A of the electrolyte region 5-1. With this configuration, the insulating frame 6 is thick, making it easier to ensure the strength of the insulating frame 6. Therefore, it is easier to ensure the necessary strength at the end portion while reducing the thickness of the electrolyte region 5-1. In this specification, the thickness A of the electrolyte region refers to the thickness of the portion where the solid electrolyte is present. That is, in the electrolyte region 5-1, the solid electrolyte may be present not only in the pores of the porous body 5 but also on the surface of the porous body 5. As a result, the thickness of the portion where the solid electrolyte is present may be greater than the thickness of the porous body 5 itself. In such cases, the "thickness A of the electrolyte region 5-1" does not refer to the thickness of the porous body 5, but rather to the thickness of the portion where the solid electrolyte is present (which may also be called the electrolyte layer), as shown in FIG. 3 .

[0027] On the other hand, as shown in FIG. 3 , the thickness x of the insulating frame 6 is preferably smaller than the total thickness B of the electrolyte region 5-1, the positive electrode active material layer 3, and the negative electrode active material layer 4. In an all-solid-state battery, the electrolyte layer and the electrode layer must be firmly bonded to each other to obtain desired characteristics. Therefore, the all-solid-state battery 1 is usually compressed. Here, if the thickness x is smaller than the total thickness B, the insulating frame 6 does not interfere with the compression. In other words, a compressive force can be easily applied in the stacking direction to the laminate consisting of the electrolyte region 5-1, the positive electrode active material layer 3, and the negative electrode active material layer 4. This can improve battery characteristics. It can also reduce dendrite formation.

[0028] In the all-solid-state battery 1, the thickness of the positive electrode active material layer 3 or the negative electrode active material layer 4 may change with charge and discharge. That is, the total thickness B may change with charge and discharge. In such a case, it is preferable that the thickness x of the insulating frame 6 is smaller than the minimum value of the total thickness B. This always prevents the insulating frame 6 from interfering with pressure application, regardless of the charge and discharge state.

[0029] The specific thickness of the insulating frame 6 is not particularly limited, but may be, for example, 30 to 200 μm.

[0030] There are no particular limitations on the frame width of the insulating frame 6. In order to ensure the necessary strength at the end portions, it is preferable that the frame width of the insulating frame 6 be determined according to the size of the porous body 5. For example, the frame width of the insulating frame 6 can be set to 5 to 30% when the width of the porous body 5 is taken as 100%.

[0031] Next, the position of the insulating frame 6 in the stacking direction will be described. In the examples shown in Figures 1 and 3, the center position of the insulating frame 6 in the stacking direction is aligned with the center position of the porous body 5. However, these do not necessarily have to be aligned. This point will be described below with reference to modified examples.

[0032] 4 is a schematic cross-sectional view showing a modified example of this embodiment. In the example shown in Fig. 4, the center position a of the insulating frame 6 in the stacking direction is shifted from the center position b of the porous body 5. Specifically, the surface of the electrolyte region 5-1 on the side of the negative electrode active material layer 4 is generally aligned with the surface of the insulating frame 6.

[0033] 5 is a schematic cross-sectional view showing another modified example of this embodiment. In the example shown in Fig. 5, similar to the example shown in Fig. 4, the center position a of the insulating frame 6 in the stacking direction is shifted from the center position b of the porous body 5. Specifically, the surface of the electrolyte region 5-1 on the side of the positive electrode active material layer 3 is generally aligned with the surface of the insulating frame 6.

[0034] 4 and 5 , the center position of the insulating frame 6 does not necessarily have to coincide with the center position of the porous body 5. By independently setting the center positions of the insulating frame 6 and the porous body 5, the thicknesses of the positive electrode active material layer 3 and the negative electrode active material layer 4 can be set arbitrarily. This makes it possible to design the stack structure of the all-solid-state battery 1 while taking into consideration the stress applied to the electrolyte composite 2.

[0035] Next, the materials of each member will be described.

[0036] There are no particular limitations on the material of the insulating frame 6. For example, the insulating frame 6 can be made of resin.

[0037] The material of the porous body 5 is not particularly limited. For example, a resin nonwoven fabric can be used as the porous body 5. Examples of nonwoven fabric include polyester nonwoven fabric, polyethylene nonwoven fabric, and cellulose fiber nonwoven fabric. The thickness of the porous body 5 (thickness when not supporting the solid electrolyte) is, for example, 5 to 100 μm, preferably 20 to 60 μm.

[0038] The specific material of the solid electrolyte is not particularly limited. Preferably, the solid electrolyte includes an inorganic electrolyte. For example, a sulfide-based solid electrolyte can be used as the solid electrolyte. The solid electrolyte may be supported by the porous body 5 together with a polymer binder.

[0039] The positive electrode active material layer 3 may be configured to absorb lithium during discharge and release lithium as lithium ions during charge. The positive electrode active material layer 3 is formed, for example, from a material containing a resin binder and a positive electrode active material dispersed in the resin binder. The positive electrode active material may be, for example, a lithium metal composite oxide. The thickness of the positive electrode active material layer 3 is, for example, 30 to 1000 μm, preferably 10 to 500 μm.

[0040] The negative electrode active material layer 4 is configured to absorb lithium during charging and release lithium as lithium ions during discharging. For example, the negative electrode active material layer 4 can be formed from a material including a resin binder and a negative electrode active material dispersed in the resin binder. Alternatively, the negative electrode active material layer 4 may be realized by metallic lithium that precipitates between the electrolyte region 5-1 and the current collector during charging. That is, the all-solid-state battery 1 may be a so-called lithium deposition type secondary battery. In such a lithium deposition type secondary battery, there may be almost no metallic lithium present as the negative electrode active material layer 4 in a fully discharged state. However, at least the metallic lithium that precipitates during charging functions as the negative electrode active material layer 4, and therefore the all-solid-state battery 1 according to this embodiment is included.

[0041] The method for manufacturing the all-solid-state battery 1 according to this embodiment is not particularly limited. For example, first, a resin nonwoven fabric is prepared as the raw material for the porous body 5. Then, a slurry containing a solid electrolyte, a polymer binder, and the like is prepared, and the prepared slurry is applied to the nonwoven fabric and dried. This results in a porous body 5 having an electrolyte region 5-1. Thereafter, as described above, a pair of resin films or the like is placed on the outer periphery of the porous body 5 and bonded by thermal welding or the like. This results in an electrolyte composite 2 in which the insulating frame 6 is bonded to the porous body 5. Thereafter, electrode layers (positive electrode active material layer 3 and negative electrode active material layer 4) and the like are laminated on the electrolyte composite 2. This results in an all-solid-state battery 1.

[0042] (2) Second Embodiment Next, a second embodiment will be described. Note that detailed description of the second embodiment will be omitted for the fact that the same configuration as the first embodiment can be adopted.

[0043] Fig. 6 is a schematic diagram showing the all-solid-state battery 1 according to this embodiment. Fig. 6 shows a cross-sectional view and a plan view.

[0044] In this embodiment, the size of the positive electrode active material layer 3 is different from the size of the negative electrode active material layer 4. Accordingly, the size of the opening of the insulating frame 6 is different between the positive electrode side and the negative electrode side in the stacking direction.

[0045] Specifically, the size of the opening of the insulating frame 6 is larger on the negative electrode side than on the positive electrode side. That is, when viewed along the stacking direction, the outer peripheral edge of the opening of the insulating frame 6 on the positive electrode side is located more inward than the outer peripheral edge of the opening of the insulating frame 6 on the negative electrode side.

[0046] The outer peripheral ends of the positive electrode active material layer 3 and the negative electrode active material layer 4 are each located inside the inner peripheral end of the insulating frame 6. Specifically, the outer peripheral end of the positive electrode active material layer 3 is located inside the inner peripheral end of the insulating frame 6 on the positive electrode side (in the example shown in FIG. 6, both are located at approximately the same position). Similarly, the outer peripheral end of the negative electrode active material layer 4 is located inside the inner peripheral end of the insulating frame 6 on the negative electrode side (in the example shown in FIG. 6, both are located at approximately the same position). When viewed along the stacking direction, the outer peripheral end of the negative electrode active material layer 4 is located outside the outer peripheral end of the positive electrode active material layer 3.

[0047] According to this embodiment, the outer peripheral edge of the negative electrode active material layer 4 is located further outward than the outer peripheral edge of the positive electrode active material layer 3, which makes it possible to prevent the growth of lithium dendrites at the edge of the electrolyte region 5-1. That is, the strength of the edge of the electrolyte composite 2 can be ensured while preventing the growth of lithium dendrites.

[0048] The present invention has been described above with reference to the first and second embodiments. Note that the above-described embodiments and modifications are not independent of each other, and can be implemented in combination as long as there is no contradiction.

[0049] The following is a summary of the representative configurations of the present invention and their effects as appendices.

[0050] (Supplementary Note 1) An electrolyte composite for an all-solid-state battery, comprising: a porous body (5) having an electrolyte region (5-1) that supports a solid electrolyte; and an insulating frame (6) that is arranged to surround the porous body (5) and is joined to the outer periphery of the porous body (5), wherein the insulating frame (6) is ionically and electronically insulating and is formed of a separate member from the porous body (5).

[0051] According to this configuration, a structure having high strength can be adopted for the insulating frame 6. As a result, the strength of the end portions of the electrolyte composite can be increased, and damage to the end portions can be prevented.

[0052] (Supplementary Note 2) The electrolyte composite according to Supplementary Note 1, wherein the solid electrolyte includes an inorganic electrolyte.

[0053] (Supplementary Note 3) The electrolyte composite according to Supplementary Note 1 or 2, wherein the solid electrolyte includes a sulfide-based solid electrolyte.

[0054] (Appendix 4) The electrolyte composite according to any one of Appendices 1 to 3, wherein the solid electrolyte is supported by a porous body together with a polymer binder.

[0055] (Supplementary Note 5) The electrolyte composite according to any one of Supplementary Notes 1 to 4, wherein the porous body 5 further has a non-electrolyte region 5-2 that is provided around the electrolyte region 5-1 and is a region where the solid electrolyte is not supported, and the porous body 5 is joined to the insulating frame 6 at the non-electrolyte region 5-2.

[0056] With this configuration, no ion conduction path is formed outside the electrolyte region 5-1, so that the generation of lithium dendrites at the end portions can be suppressed.

[0057] (Supplementary Note 6) The electrolyte composite according to Supplementary Note 5, wherein the non-electrolyte region 5-2 is filled with the same material as that constituting the insulating frame 6, or with an adhesive.

[0058] With this configuration, the insulating frame 6 and the porous body 5 can be firmly joined together.

[0059] (Supplementary Note 7) The electrolyte composite according to any one of Supplementary Notes 1 to 6, wherein the thickness of the insulating frame 6 is greater than the thickness of the electrolyte region 5-1.

[0060] With this configuration, the strength of the insulating frame 6 is ensured, and damage to the ends of the electrolyte composite 2 is more reliably prevented.

[0061] (Supplementary Note 8) An all-solid-state battery comprising the electrolyte composite 2 according to any one of Supplementary Notes 1 to 7, and a positive electrode active material layer 3 and a negative electrode active material layer 4 arranged to sandwich an electrolyte region 5-1 in the stacking direction.

[0062] According to this configuration, an all-solid-state battery using the electrolyte composite 2 is realized.

[0063] (Appendix 9) The all-solid-state battery according to appendix 8, wherein the thickness of the insulating frame 6 is smaller than the total thickness of the electrolyte region 5-1, the positive electrode active material layer 3, and the negative electrode active material layer 4.

[0064] With this configuration, pressure applied to the electrolyte region 5-1 is less likely to be hindered by the insulating frame 6. The electrolyte region 5-1 can be pressurized so as to obtain desired characteristics.

[0065] (Supplementary Note 10) The all-solid-state battery according to Supplementary Note 8 or 9, wherein the size of the opening of the insulating frame 6 is different between the positive electrode side and the negative electrode side in the stacking direction.

[0066] According to this configuration, even if the size of the opening of the insulating frame 6 varies in the stacking direction, the strength of the end portion can be increased by using the insulating frame 6 .

[0067] (Supplementary Note 11) The all-solid-state battery according to Supplementary Note 10, wherein, when viewed along the stacking direction, an outer peripheral edge of the opening on the positive electrode side of the insulating frame 6 is located more inward than an outer peripheral edge of the opening on the negative electrode side of the insulating frame 6.

[0068] With this configuration, the outer peripheral edge of the positive electrode active material layer 3 can be positioned more inward than the negative electrode active material layer 4, making it possible to suppress the growth of lithium dendrites at the edge.

[0069] (Appendix 12) The all-solid-state battery according to any one of Appendices 8 to 11, wherein an outer peripheral edge of the positive electrode active material layer 3 and / or the negative electrode active material layer 4 is located inside an inner peripheral edge of the insulating frame 6.

[0070] With this configuration, even when the outer peripheral edges of the positive electrode active material layer 3 and / or the negative electrode active material layer 4 are located inside the insulating frame 6, the insulating frame 6 can increase the strength of the edges.

[0071] (Supplementary Note 13) The all-solid-state battery according to any one of Supplementary Notes 8 to 12, wherein the center position of the insulating frame 6 in the stacking direction is shifted from the center position of the porous body 5.

[0072] With this configuration, the thicknesses of the positive electrode active material layer 3 and the negative electrode active material layer 4 can be set as desired.

Claims

1. An electrolyte composite for an all-solid-state battery, comprising: a porous body having an electrolyte region that supports a solid electrolyte; and an insulating frame that is disposed so as to surround the porous body and is joined to the outer periphery of the porous body, wherein the insulating frame is ionically and electronically insulating and is formed of a separate material from the porous body.

2. The electrolyte complex according to claim 1, wherein the solid electrolyte comprises an inorganic electrolyte.

3. The electrolyte composite according to claim 1 or 2, wherein the solid electrolyte comprises a sulfide-based solid electrolyte.

4. An electrolyte complex according to claim 1 or 2, wherein the solid electrolyte is supported by the porous body together with a polymer binder.

5. An electrolyte complex as claimed in claim 1 or 2, wherein the porous body further has a non-electrolyte region provided around the electrolyte region and being a region in which the solid electrolyte is not supported, and the porous body is joined to the insulating frame in the non-electrolyte region.

6. An electrolyte complex according to claim 5, wherein the non-electrolyte region is filled with the same material as that constituting the insulating frame, or with an adhesive.

7. An electrolyte complex according to claim 1 or 2, wherein the thickness of the insulating frame is greater than the thickness of the electrolyte region.

8. An all-solid-state battery comprising: the electrolyte composite according to claim 1 or 2; and a positive electrode active material layer and a negative electrode active material layer arranged to sandwich the electrolyte region in the stacking direction.

9. The all-solid-state battery according to claim 8, wherein the thickness of the insulating frame is smaller than the total thickness of the electrolyte region, the positive electrode active material layer, and the negative electrode active material layer.

10. An all-solid-state battery according to claim 8, wherein the size of the opening of the insulating frame is different between the positive electrode side and the negative electrode side in the stacking direction.

11. An all-solid-state battery as described in claim 10, wherein, when viewed along the stacking direction, the outer peripheral edge of the opening on the positive electrode side of the insulating frame is located more inward than the outer peripheral edge of the opening on the negative electrode side of the insulating frame.

12. An all-solid-state battery according to claim 8, wherein an outer peripheral edge of the positive electrode active material layer and / or the negative electrode active material layer is located inside an inner peripheral edge of the insulating frame.

13. An all-solid-state battery according to claim 8, wherein the center position of the insulating frame in the stacking direction is offset from the center position of the porous body.

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