All-solid-state battery using an expansion layer to increase lifespan and method of operating the same

Abstract

The present disclosure relates to a solid-state battery with increased lifespan and an operating method thereof. Specifically, the solid-state battery includes: a stack including unit cells, each unit cell including an anode, a cathode, and a solid electrolyte layer interposed between the anode and the cathode; and an expansion layer located on at least one surface of the stack and expanding due to a change in at least one of voltage and temperature.

Description

Technical Field

[0001] The present disclosure relates to a solid-state battery with increased lifespan and an operating method thereof. Background Art

[0002] Rechargeable and dischargeable lithium secondary batteries are used not only in small electronic devices such as mobile phones or laptop computers, but also in large transportation devices such as hybrid vehicles or electric vehicles. Therefore, there is a need to develop secondary batteries with higher stability and energy density.

[0003] Since conventional lithium secondary batteries mainly consist of organic solvents (organic liquid electrolytes) to form a cell, there are limitations in improving stability and energy density.

[0004] Meanwhile, all-solid-state batteries using inorganic solid electrolytes are based on technologies that do not include organic solvents, so safer and simpler cells can be manufactured. Therefore, all-solid-state batteries using inorganic solid electrolytes have recently received much attention.

[0005] However, during charging and discharging, the components of all-solid-state batteries are damaged due to shrinkage and expansion, or the lifespan is shortened due to weakened adhesion between interfaces. One method to prevent damage to the solid electrolyte due to shrinkage and expansion is to add a binder. However, the preventive effect is insufficient, and when manufacturing all-solid-state batteries by a wet process, the range of solvent selection is narrowed due to the type of binder used.

[0006] The above information disclosed in this background art section is only for enhancing the understanding of the background of the present disclosure. Therefore, the above information may include information that does not constitute the prior art known to those skilled in the art. Summary of the Invention

[0007] An object of the present disclosure is to provide an all-solid-state battery and an operating method thereof that do not shorten the lifespan even when charging and discharging are repeatedly performed.

[0008] The object of the present disclosure is not limited to the above object. The object of the present disclosure will become more apparent through the following description and will be achieved by the means and combinations described in the claims.

[0009] An all-solid-state battery according to an embodiment of the present disclosure may include: a stack including unit cells, each unit cell including an anode, a cathode, and a solid electrolyte layer interposed between the anode and the cathode; and an expansion layer located on at least one surface of the stack and expanding due to a change in at least one of voltage and temperature.

[0010] The expansion layer may include a piezoelectric polymer selected from the group consisting of polyvinylidene fluoride-based polymers, fluorine-based polymers, styrene-ethylene-butadiene-styrene (SEBS) terpolymers with or without functional groups, sulfonated poly(styrene-ethylene) (SPSE), and combinations thereof. The polyvinylidene fluoride-based polymers include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), poly(vinylidene fluoride-co-trifluoroethylene), and poly(vinylidene fluoride-co-tetrafluoroethylene). The fluorine-based polymers include at least one of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and fluoroethylenepropylene (FEP).

[0011] The expansion layer may include a thermally expandable polymer selected from the group consisting of polystyrene, polymethylmethacrylate, polyethylene, polypropylene, polymethylpentene, polybutene, polyurethane, ethylene-propylene rubber, and combinations thereof.

[0012] The expansion layer may be located on two surfaces of the stack, and the thicknesses of each expansion layer may be the same or different from each other.

[0013] The stack may have a plurality of unit cells stacked.

[0014] A plurality of stacks may be stacked, and the expansion layer is interposed between the plurality of stacks.

[0015] The thickness (a) and expansion rate (b) of the expansion layer may satisfy the following formula 1:

[0016] Formula 1

[0017]

[0018] Wherein, a refers to the thickness of the expansion layer, b refers to the expansion rate of the expansion layer, m refers to the number of expansion layers included in the all-solid-state battery, c refers to the thickness of a single cell, and n refers to the number of single cells included in the stack, and n is an integer of 1 or greater.

[0019] The thickness of the expansion layer can be from 300 μm to 1000 μm.

[0020] The expansion rate of the expansion layer can be from 0.01 to 0.05.

[0021] The thickness of the anode can be from 50 μm to 300 μm, the thickness of the cathode can be from 50 μm to 300 μm, and the thickness of the solid electrolyte layer can be from 10 μm to 500 μm.

[0022] The all-solid-state battery can further include an anode current collector on the anode, and the thickness of the anode current collector can be from 5 μm to 15 μm.

[0023] The all-solid-state battery can further include a cathode current collector on the cathode, and the thickness of the cathode current collector can be from 5 μm to 15 μm.

[0024] A method of operating an all-solid-state battery according to the present disclosure can include: changing at least any one of the pressure and temperature applied to the all-solid-state battery.

[0025] Since the all-solid-state battery according to the present disclosure can apply pressure to the single cell from the outside of the single cell, the problem of shortened life due to shrinkage and expansion of components can be effectively solved.

[0026] The effects of the present disclosure are not limited to the above effects. It should be understood that the effects of the present disclosure include all effects that can be inferred from the following description.

[0027] It is understood that as used herein, the term "vehicle" or "vehicular" or other similar terms generally include motor vehicles, such as passenger vehicles including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various ships and boats, airplanes, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other alternative fuel (e.g., fuels derived from resources other than petroleum) vehicles. As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as a gasoline and electric dual-power vehicle Description of the Drawings

[0028] Now referring to the specific exemplary embodiments of the present disclosure shown in the accompanying drawings, the above-described features and other features of the present disclosure will be described in detail. The accompanying drawings are given hereinafter only by way of illustration and thus do not limit the present disclosure. In the drawings:

[0029] Figure 1 is a diagram showing a first embodiment of a all-solid-state battery according to the present disclosure.

[0030] Figure 2 is a diagram showing a second embodiment of a all-solid-state battery according to the present disclosure.

[0031] Figure 3 is a diagram showing a third embodiment of a all-solid-state battery according to the present disclosure.

[0032] Figure 4 is a diagram showing a fourth embodiment of a all-solid-state battery according to the present disclosure.

[0033] Figure 5 is a graph showing the results of the first experimental example below.

[0034] Figure 6 is a graph showing the results of the second experimental example below.

[0035] It should be understood that the accompanying drawings are not necessarily drawn to scale and present somewhat simplified illustrations showing various preferred features illustrating the basic principles of the present disclosure. Specific design features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined respectively by a specific intended application and use environment.

[0036] In the drawings, reference numerals refer to the same or equivalent parts of the present disclosure in multiple drawings. Detailed Description of the Invention

[0037] By the following preferred embodiments associated with the accompanying drawings, the above objects, other objects, features, and advantages according to the present disclosure will be readily understood. However, the present disclosure is not limited to the embodiments described herein and may also be implemented in other forms. On the contrary, the embodiments described herein are provided so that the present disclosure may be thorough and complete, and the spirit of the present disclosure may be fully conveyed to those skilled in the art.

[0038] In this specification, it should be understood that terms such as "including" or "having" are intended to indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, and do not exclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, or plate is referred to as being "on" another part, the part can not only be directly "on" the other part, but there can also be other parts in between. On the contrary, when a part such as a layer, film, region, or plate is referred to as being "under" another part, the part can not only be directly "under" the other part, but there can also be other parts in between.

[0039] Unless otherwise specified, all quantities, values, and / or statements regarding the amounts of ingredients, reaction conditions, polymer compositions, and formulations used herein will be understood to be modified in all cases by the term "about" such that these values are essentially approximate values reflecting the various measurement uncertainties encountered in obtaining these values, etc. In addition, when a numerical range is disclosed herein, the range is continuous and includes every value from the minimum value to the maximum value of the range and including the maximum value, unless otherwise specified. Further, when the range involves integers, every integer from the minimum value to the maximum value and including the maximum value is included, unless otherwise specified.

[0040] Figure 1 is a view schematically showing a all-solid-state battery according to the present disclosure. The all-solid-state battery 1 includes: a stacked body 10 including unit cells 100, the unit cells 100 including an anode 110, a cathode 120, and a solid electrolyte layer 130 interposed between the anode 110 and the cathode 120; and an expansion layer 20 located on at least one surface of the stacked body 10.

[0041] The present disclosure is characterized in that the expansion layer 20 is applied to the all-solid-state battery 1. In the all-solid-state battery 1, during charging, lithium ions (Li + ) move to the cathode 120 to be stored as lithium metal (Li 0 ). On the contrary, during discharging, lithium metal (Li 0 ) is converted into lithium ions (Li + ) and moves to the anode 110, thereby being stored in the form of lithium oxide (Li2O) or the like. That is, as the all-solid-state battery 1 is charged and discharged, the volumes of the anode 110 and the cathode 120 expand and contract repeatedly, respectively. In this process, solid components such as active materials and solid electrolytes included in the electrodes 110, 120 may be damaged, or the contact between the electrodes 110, 120 and the solid electrolyte layer 130 may become weak.

[0042] The present disclosure may form an expansion layer 20 including a material that expands in volume under specific conditions on the outside of the stack 10 to apply pressure to the stack 10, thereby eliminating the influence of the expansion and contraction of the volume of the electrodes 110 and 120. Hereinafter, the expansion layer 20 will be described in detail.

[0043] The expansion layer 20 includes a material that expands due to a change in at least one of voltage and temperature.

[0044] The expansion layer 20 may include a piezoelectric polymer whose volume expands due to a change in voltage. The piezoelectric polymer may include one selected from the group consisting of polyvinylidene fluoride-based polymers, fluorine-based polymers, styrene-ethylene-butadiene-styrene (SEBS) triblock copolymers with or without functional groups, sulfonated poly(styrene-ethylene) (SPSE), and combinations thereof.

[0045] The polyvinylidene fluoride-based polymer may include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene copolymer), poly(vinylidene fluoride-trifluoroethylene copolymer), and poly(vinylidene fluoride-tetrafluoroethylene copolymer).

[0046] The fluorine-based polymer may include at least one of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), and polyperfluoroethylenepropylene (FEP).

[0047] Meanwhile, the expansion layer 20 may further include a thermally expandable polymer whose volume expands due to a change in temperature. The thermally expandable polymer may include one selected from the group consisting of polystyrene, polymethyl methacrylate, polyethylene, polypropylene, poly(methylpentene), polybutene, polyurethane, ethylene-propylene rubber, and combinations thereof.

[0048] As described above, the expansion layer 20 is used to apply pressure to the stack 10 from the outside of the stack 10. Therefore, if the expansion layer 20 can play this role, the expansion layer 20 can be used in various embodiments. Hereinafter, various embodiments of the stack 10 and the expansion layer 20 will be described with reference to the drawings. However, since this is only illustrative, the shapes, positions, etc. of the stack 10 and the expansion layer 20 should not be understood to be limited to each drawing.

[0049] Referring to Figure 1 , the expansion layer 20 may be located on two surfaces of the stack 10. Here, the all-solid-state battery 1 including the stack 10 and the expansion layer 20 may be disposed in a predetermined space such as a bag or a case.

[0050] Referring to Figure 2 , the expansion layer 20 may be located on one surface of the stack 10. Figure 2It shows that the expansion layer 20 is located on the cathode 120 side, but the expansion layer 20 can also be located on the anode 110 side.

[0051] Figure 3 It shows a all-solid-state battery 1 in the stack 10 including a plurality of unit cells 100. Refer to Figure 3 , the all-solid-state battery 1 can be provided with an expansion layer 20 on both surfaces of the stack 10 including a plurality of unit cells 100. However, as Figure 2 shown, the expansion layer 20 can also be located on one surface of the stack 10.

[0052] Figure 4 It shows a all-solid-state battery 1 in which a plurality of stacks 10 are stacked and the expansion layer 20 is inserted between the plurality of stacks 10. Refer to Figure 4 , the expansion layer 20 can include an expansion layer 20' inserted between the plurality of stacks 10 and an expansion layer 20" located on the outermost of the plurality of stacks 10. However, the expansion layer 20 can also only include the expansion layer 20' inserted between the plurality of stacks 10.

[0053] This disclosure is not a simple description of the expansion layer 20. The feature of this disclosure is that, according to the thickness of the unit cell 100, both the thickness of the expansion layer 20 and the expansion rate of the expansion layer 20 are considered to apply the expansion layer 20. This will be described in detail below.

[0054] The expansion layer 20 is characterized in that the thickness (a) and the expansion rate (b) of the expansion layer 20 satisfy the following formula 1:

[0055] Formula 1

[0056]

[0057] Wherein, a refers to the thickness of the expansion layer 20, b refers to the expansion rate of the expansion layer 20, and m refers to the number of expansion layers 20 included in the all-solid-state battery 1. Here, if the all-solid-state battery 1 is provided with a plurality of expansion layers 20, the thickness (a) of the expansion layer 20 is the value obtained by adding the thicknesses of all the expansion layers 20. For reference, as described above, the thicknesses of the plurality of expansion layers 20 can be the same or different from each other. The expansion rate (b) can represent the volume expansion rate of the expansion layer 20, and can represent the maximum volume expansion rate when the expansion layer 20 expands due to at least one of voltage and temperature change. The expansion rate (b) is a dimensionless number, and the dimensionless number represents the ratio of the initial volume of the expansion layer 20 to the volume of the expansion layer 20 when it expands due to at least one of voltage and temperature change.

[0058] In addition, c refers to the thickness of the unit cell 100, and n refers to the number of unit cells 100 included in the stack 10, and n is an integer of 1 or greater.

[0059] For example, in the case of the all-solid-state battery 1 as shown in Figure 1 the thickness (a) of the expansion layer 20 is the value obtained by adding the thicknesses of a pair of expansion layers 20 located on the two surfaces of the stacked body 10, and m is 2. In addition, n is 1, and c refers to the thickness of the unit cell 100.

[0060] In the case of the all-solid-state battery 1 as shown in Figure 2 the thickness (a) of the expansion layer 20 is the thickness of the expansion layer 20 located on one surface of the stacked body 10, and m is 1. In addition, n is 1, and c refers to the thickness of the unit cell 100.

[0061] In the case of the all-solid-state battery 1 as shown in Figure 3 the thickness (a) of the expansion layer 20 is the value obtained by adding the thicknesses of a pair of expansion layers 20 located on the two surfaces of the stacked body 10, and m is 2. At the same time, n is 2, and c refers to the thickness of each unit cell 100 included in the stacked body 10. As shown in Figure 3 since a plurality of unit cells 100 are provided in the stacked body 10, the degree of volume expansion and contraction is greater. Therefore, an external force should be strongly applied to the expansion layer 20. This means that the thickness (a) and / or the expansion rate (b) of the expansion layer 20 should be large, and it can be said that n is an indication of this.

[0062] In the case of the all-solid-state battery 1 as shown in Figure 4 the thickness (a) of the expansion layer 20 is the value obtained by adding the thickness of the expansion layer 20' inserted between the stacked bodies 10 and the thickness of the outermost expansion layer 20" of the stacked body 10, and m is 3. At the same time, n is 1, and c refers to the thickness of the unit cell 100. For reference, as shown in Figure 4 as the number of unit cells 100 increases, the number of expansion layers 20 increases simultaneously, so there is no need to correct the formula as in Figure 3 .

[0063] "0.02" in Formula 1 is a coefficient, and represents the relationship that the thickness (a), the expansion rate (b), and the thickness (c) of the unit cell of the expansion layer 20 should have in order to achieve the object of the present disclosure. This is obtained through experiments, and will be described in detail with reference to the embodiments.

[0064] As described above, only when the expansion layer 20 that satisfies Formula 1 is applied, can the adverse effects of the volume expansion and contraction of the electrodes 110 and 120 caused by the charging and discharging of the all-solid-state battery 1 be effectively eliminated.

[0065] The thickness and the expansion rate of the expansion layer 20 are not particularly limited as long as they satisfy Formula 1, but preferably, they are not difficult to implement or lose the function as a battery because their range exceeds the general battery specifications.

[0066] For example, the thickness of the expansion layer 20 may be from 300 μm to 1000 μm. In addition, the expansion rate of the expansion layer 20 may be from 0.01 to 0.05. Here, an expansion rate of 0.05 means that the volume of the expansion layer 20 expands by 5% compared to the initial volume due to a change in voltage and / or temperature.

[0067] In addition, the thickness (c) of the unit cell 100 is not particularly limited as long as it satisfies Formula 1, but preferably, it is not difficult to implement or lose the function as a battery because its range exceeds the general battery specifications.

[0068] For example, the thicknesses of the anode 110 and the cathode 120 may be from 50 μm to 300 μm, respectively. The thickness of the solid electrolyte layer 130 may be from 10 μm to 500 μm.

[0069] The unit cell 100 may further include an anode current collector 140 on the anode 110. The thickness of the anode current collector 140 is not particularly limited, but for example, it may be from 5 μm to 15 μm.

[0070] In addition, the unit cell 100 may further include a cathode current collector 150 on the cathode 120. The thickness of the cathode current collector 150 is not particularly limited, but for example, it may be from 5 μm to 15 μm.

[0071] Each configuration of the unit cell 100 is not particularly limited in terms of its components and functions, and any configuration known in the art to which the present disclosure pertains may be used as long as its relationship with the expansion layer 20 satisfies Formula 1.

[0072] Hereinafter, the present disclosure will be described in more detail with reference to specific embodiments. The following embodiments are merely examples for helping to understand the present disclosure, and the scope of the present disclosure is not limited thereto.

[0073] Experimental Example 1

[0074] As Figure 1 shown, a all-solid-state battery 1 in which the expansion layer 20 is applied to both surfaces of the unit cell 100 was fabricated. At this time, poly(vinylidene fluoride-trifluoroethylene copolymer), which is a piezoelectric polymer, was used as the expansion layer. Various types of all-solid-state batteries were fabricated by appropriately adjusting the specific specifications of each configuration, and the details are shown in Table 1 below. The expansion rate of the expansion layer was adjusted as follows by irradiating electrons to the copolymer to form defects in the crystal structure of the polymer.

[0075] Table 1

[0076]

[0077] 1) In Experimental Example 1, m is 2 and n is 1.

[0078] Charge and discharge experiments were performed on all-solid-state batteries according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2. After performing 5 charge and discharge cycles on each all-solid-state battery, the applied voltage was changed to 100 V / μm to cause volume expansion of the expansion layer. Then, when repeating up to 10 charge and discharge cycles, the capacity of each all-solid-state battery was measured. The results are as Figure 5 shown. Referring to Figure 5 , it can be seen that in Example 1 and Example 2 where the expansion layer was applied to satisfy Formula 1, the capacity was restored after changing the voltage.

[0079] Experimental Example 2

[0080] Next, all-solid-state batteries in Table 2 below were prepared. Except for the items in Table 2 below, the all-solid-state batteries were prepared in the same manner as in Experimental Example 1.

[0081] Table 2

[0082]

[0083] 1) In Experimental Example 2, m is 2 and n is 1.

[0084] Charge and discharge experiments were performed on all-solid-state batteries according to Example 3, Comparative Example 3, Comparative Example 4, and Comparative Example 5. After performing 5 charge and discharge cycles on each all-solid-state battery, the applied voltage was changed to 100 V / μm to cause volume expansion of the expansion layer. Then, when repeating up to 10 charge and discharge cycles, the capacity of each all-solid-state battery was measured. The results are as Figure 6 shown. Referring to Figure 6 , it can be seen that only in Example 3 where the expansion layer was applied to satisfy Formula 1, the capacity was restored after changing the voltage.

[0085] As described above, when operating an all-solid-state battery according to the present disclosure, if the expansion layer is expanded by changing at least any one of the pressure and temperature applied to the all-solid-state battery in a state where the all-solid-state battery has been charged and discharged a predetermined number of times, the capacity can be restored again.

[0086] That is, when the number of charge and discharge cycles of the all-solid-state battery according to the present disclosure is the same as that of a conventional battery, the all-solid-state battery according to the present disclosure has a high charge and discharge capacity and a capacity retention rate. This means that the all-solid-state battery according to the present disclosure has a longer lifespan.

[0087] As described above, although the embodiments of the present disclosure have been described with reference to the accompanying drawings, those skilled in the art to which the present disclosure pertains can understand that the present disclosure can be implemented in other specific forms without changing the technical idea or basic features of the present disclosure. Therefore, it should be understood that the above embodiments are completely exemplary and not restrictive.

Claims

1. A all-solid-state battery, comprising: A stack including unit cells, each unit cell including an anode, a cathode, and a solid electrolyte layer interposed between the anode and the cathode; The stack has a top surface and a bottom surface, and the unit cell further includes at least one of an anode current collector on an outer surface of the anode and a cathode current collector on an outer surface of the cathode, and An expansion layer located horizontally on at least one of the top surface and the bottom surface of the stack, and expanding due to a change in at least one of voltage and temperature, Wherein the expansion layer is located on at least one of the anode current collector and the cathode current collector, The thickness a and expansion rate b of the expansion layer satisfy the following formula: In the formula, a refers to the thickness of the expansion layer, b refers to the expansion rate of the expansion layer, m refers to the number of the expansion layers included in the all-solid-state battery, c refers to the thickness of the unit cell, and n refers to the number of the unit cells included in the stack, and n is an integer of 1 or greater.

2. The all-solid-state battery according to claim 1, wherein, The expansion layer includes a piezoelectric polymer selected from the group consisting of polyvinylidene fluoride-based polymers, fluorine-based polymers, styrene-ethylene-butadiene-styrene triblock copolymers with or without functional groups, sulfonated poly(styrene-ethylene), and combinations thereof. The polyvinylidene fluoride-based polymers include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene copolymer), poly(vinylidene fluoride-trifluoroethylene copolymer), and poly(vinylidene fluoride-tetrafluoroethylene copolymer). The fluorine-based polymers include at least one of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, and polyperfluoroethylenepropylene.

3. The all-solid-state battery according to claim 1, wherein, The expansion layer includes a thermally expandable polymer selected from the group consisting of polystyrene, polymethyl methacrylate, polyethylene, polypropylene, poly(methylpentene), polybutene, polyurethane, ethylene-propylene rubber, and combinations thereof.

4. The all-solid-state battery according to claim 1, wherein, The expansion layer is located on two surfaces of the stack, and the thicknesses of each expansion layer are the same or different from each other.

5. The all-solid-state battery according to claim 1, wherein, The stack has a plurality of the unit cells stacked.

6. The all-solid-state battery according to claim 1, wherein, A plurality of the stacks are stacked, and the expansion layer is interposed between the plurality of stacks.

7. The all-solid-state battery according to claim 1, wherein, The thickness of the expansion layer is 300 μm to 1000 μm.

8. The all-solid-state battery according to claim 1, wherein, The expansion rate of the expansion layer is 0.01 to 0.

05.

9. The all-solid-state battery according to claim 1, wherein, The thickness of the anode is 50 μm to 300 μm.

10. The all-solid-state battery according to claim 1, wherein, The thickness of the cathode is 50 μm to 300 μm.

11. The all-solid-state battery according to claim 1, wherein, the thickness of the solid electrolyte layer is from 10 μm to 500 μm.

12. The all-solid-state battery according to claim 1, wherein, the unit cell includes the anode current collector, and the thickness of the anode current collector is from 5 μm to 15 μm.

13. The all-solid-state battery according to claim 1, wherein, the unit cell includes the cathode current collector, and the thickness of the cathode current collector is from 5 μm to 15 μm.

14. A method of operating an all-solid-state battery, comprising: operating the all-solid-state battery according to claim 1; and changing at least one of the pressure and temperature applied to the all-solid-state battery.

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