Water removal method of solid-state battery and solid-state battery

Abstract

The invention provides a water removal method of a solid-state battery and the solid-state battery, and the water removal method comprises the following steps: repeatedly executing a first operation for multiple times until the water content of the solid-state battery is lower than a preset threshold value; wherein the first operation comprises the steps of vacuumizing a space where the solid-state battery is located, keeping the space at a preset temperature, and applying a preset pressure of a first duration to the solid-state battery; introducing inert gas into the space to enable the pressure of the space to be normal pressure, and applying voltage to the solid-state battery for a first preset number of times; the voltage applying operation comprises the step of applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery. According to the invention, bound water in the solid-state battery can be greatly reduced, and the battery drying efficiency is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a water removal method for a solid-state battery and a solid-state battery. Background Art

[0002] All-solid-state lithium-ion batteries have the advantages of high safety, wide operating temperature range and high energy density. The development of all-solid-state lithium-ion batteries will become a major direction for the future development of lithium-ion batteries.

[0003] The solid-state battery baking process of the existing technology is time-consuming, has average water replacement efficiency and certain limitations. When the electrode coating thickness, compaction density and battery size become larger and larger, the water volatilization path in the battery increases, and the double layer on the electrode surface and the water molecules will form bound water that is difficult to remove, making it difficult to remove water from the battery and increasing production costs. Even if the water removal fails to meet the standards, the battery performance will be reduced. Summary of the invention

[0004] The present invention aims to solve the above-mentioned defects of the prior art and provide a method for dehydrating a solid-state battery, and an all-solid-state battery packaged after baking using the dehydration method.

[0005] In order to solve the above problems, the first aspect of the present invention provides a method for removing water from a solid-state battery, comprising:

[0006] Repeating the first operation multiple times until the water content of the solid-state battery is lower than a preset threshold;

[0007] Wherein, the first operation includes:

[0008] The space where the solid-state battery is located is evacuated and maintained at a preset temperature, and a preset pressure is applied to the solid-state battery for a first period of time;

[0009] Introducing an inert gas into the space so that the pressure of the space is normal pressure, and performing a first preset number of voltage application operations on the solid-state battery;

[0010] The voltage applying operation includes: alternately applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery.

[0011] The present invention also provides a solid-state battery, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte layer, wherein the positive electrode sheet, the electrolyte sheet and the negative electrode sheet are dehydrated by the dehydration method provided in the first aspect.

[0012] The method for removing water from a solid-state battery described in the present invention involves a drying method that applies a periodically variable voltage to the battery during the entire baking process, thereby changing the surface charge of the positive and negative electrodes and causing the internal bound water to continuously move, and involves a drying method that applies pressure to the battery during the entire baking process, thereby gathering moisture from the internal materials of the battery. More importantly, the present invention alternately cycles between pressurizing the battery and applying voltage, while taking into account the traditional drying method of vacuuming and breaking vacuum for ventilation cycles. The present invention can significantly reduce the bound water in the solid-state battery and significantly improve the efficiency of battery drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic flow chart of a method for removing water from a solid-state battery provided in an embodiment of the present invention;

[0014] Figure 2 A schematic flow chart of another method for removing water from a solid-state battery provided in an embodiment of the present invention;

[0015] Figure 3 A schematic flow chart of another method for removing water from a solid-state battery provided in an embodiment of the present invention;

[0016] Figure 4 A schematic flow chart of another method for removing water from a solid-state battery provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] All-solid-state lithium-ion batteries have the advantages of high safety, wide operating temperature range, and high energy density. The development of all-solid-state lithium-ion batteries will become a major direction for the future development of lithium-ion batteries. Among them, sulfide solid electrolytes are considered to be the most likely solid electrolyte materials to achieve commercial applications due to their high electrical conductivity and good processing properties at room temperature.

[0018] In the production process of sulfide solid-state batteries, moisture has a great impact on the performance of the battery. If the internal water content is too high after the battery is packaged, it will cause abnormal conditions such as gas production, poor cycle performance, and excessive internal resistance in the later stage of the battery. Therefore, the internal materials need to be dehydrated before the battery is packaged. The traditional baking process usually heats the battery to a set temperature at normal pressure for a period of time, and then accelerates the drying by continuously cyclically evacuating and filling with nitrogen. The whole process is time-consuming and the water replacement efficiency is average. In addition, this method has limitations. When the electrode coating thickness, compaction density and battery size become larger and larger, the water volatilization path in the battery increases, and the double layer on the surface of the electrode and the water molecules will form bound water that is difficult to remove, resulting in high difficulty in battery dehydration and increased production costs. Even if the dehydration fails to meet the standard, the battery performance will be reduced.

[0019] The traditional baking process is time-consuming, has average water replacement efficiency, and has certain limitations. When the electrode coating thickness, compaction density, and battery size become larger and larger, the water volatilization path in the battery increases, and the double layer on the electrode surface and water molecules form bound water that is difficult to remove, making it difficult to remove water from the battery and increasing production costs. Even if the water removal fails to meet the standards, the battery performance will decrease. Therefore, it is necessary to explore an efficient water removal method suitable for sulfide solid-state batteries.

[0020] Therefore, an embodiment of the present invention provides a method for removing water from a solid-state battery, particularly a method for removing water from a sulfide solid-state battery, which can effectively remove bound water in the solid-state battery.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0023] In addition, the terms "comprising", "including", "containing", and "having" are not restrictive, that is, other steps and other components that do not affect the results can be added. Unless otherwise specified, materials, equipment, and reagents are commercially available.

[0024] In addition, although the present invention describes the various steps in the preparation in the form of S101, S201, S202, etc., this description method is only for ease of understanding, and the form of S101, S201, S202, etc. does not limit the sequence of the steps.

[0025] Combination Figure 1 As shown, a first aspect of an embodiment of the present invention provides a method for removing water from a solid-state battery, comprising:

[0026] S101, repeatedly performing the first operation multiple times until the water content of the solid-state battery is lower than a preset threshold;

[0027] The first operation includes:

[0028] The space where the solid-state battery is located is evacuated and maintained at a preset temperature, and a preset pressure is applied to the solid-state battery for a first period of time;

[0029] Introducing an inert gas into the space so that the pressure of the space is normal pressure, and performing a first preset number of voltage application operations on the solid-state battery;

[0030] The voltage applying operation includes: alternately applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery.

[0031] That is to say, the first operation repeatedly performed in the embodiment of the present application includes two steps: first, the space where the solid-state battery is located (which can be an oven) is evacuated to remove water vapor in the space as much as possible, and the space is maintained at a preset temperature. It should be understood that since the purpose of the present application is to dehydrate the solid-state battery, the preset temperature must be higher than normal temperature. Then, a preset pressure of a first duration is applied to the solid-state battery. On the one hand, the residual moisture on the positive and negative electrodes and the electrolyte sheets of the battery and the moisture inside the active material are gathered by extrusion. On the other hand, the contact between the positive electrode, electrolyte and negative electrode inside the battery is made closer by pressurization, thereby improving the energy density of the battery and having a certain gain effect on the later electrical performance of the battery. Then, an inert gas is introduced into the space to break the vacuum environment. When the space pressure is normal pressure, the voltage application operation is performed on the battery for a first preset number of times. The voltage application operation of the present invention includes two actions: applying a positive voltage for a second duration to the solid-state battery, and applying a negative voltage for a third duration to the solid-state battery. It should be noted that the positive and negative voltages of the embodiments of the present application can be achieved by applying currents in different directions to the battery, wherein applying current in the positive direction means applying a positive voltage, and applying current in the reverse direction means applying a negative voltage. The positive direction of the embodiments of the present application may refer to the direction from the positive electrode to the negative electrode of the solid-state battery, and the negative direction may refer to the direction from the negative electrode to the positive electrode of the solid-state battery. The present invention applies a variable voltage at both ends of the positive and negative electrodes to change the surface charge of the positive and negative electrodes. The water in the battery forms bound water with the double electric layer on the surface of the electrode, which is constantly moved by the attraction of the charge, thereby accelerating the speed of water removal. In the process of performing the first operation each time, the embodiments of the present application need to perform the first preset number of voltage application operations, the purpose of which is to continuously gather and move the bound water, so that the bound water is continuously gathered into a larger amount of bound water through multiple voltage application operations, so that it can be removed more easily.

[0032] It should be understood that in the embodiment of the present application, when an inert gas is introduced into the space and a voltage application operation is performed, the space is still maintained at a preset temperature to promote the movement of each water molecule inside the solid-state battery.

[0033] See also Figure 2 , Figure 2 The schematic diagram of the process of removing water from a solid-state battery in one embodiment of the present application is shown as an example. Figure 2 As shown, including:

[0034] S201, evacuating the space where the solid-state battery is located and maintaining it at a preset temperature, and applying a preset pressure for a first period of time to the solid-state battery;

[0035] S202, introducing an inert gas into the space so that the pressure of the space is at normal pressure;

[0036] S203, determining whether the voltage application operation has been executed for a first preset number of times, if not, executing S204, if it has been reached, executing S206;

[0037] S204, performing a voltage application operation on the solid-state battery, the voltage application operation comprising: alternately applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery;

[0038] S205, adding 1 to the number of times the voltage application operation is performed, and returning to step S203;

[0039] S206, detecting the water content of the solid-state battery. If the water content is lower than a preset threshold, the process is terminated. If the water content is not lower than the preset threshold, the process returns to S201.

[0040] Based on the above embodiment, the first preset number is 8 to 12.

[0041] In this embodiment, by applying voltage for multiple times, bound water can be continuously gathered, making the weight of bound water larger and easier to remove.

[0042] Based on the above embodiments, as an optional embodiment, applying a preset pressure for a first duration to the solid-state battery includes:

[0043] The solid-state battery is mounted on the upper and lower clamping plates;

[0044] A preset pressure of a first duration is applied to the solid-state battery by clamping the upper and lower clamping plates.

[0045] The thickness of the upper and lower clamping plates of the embodiment of the present application is uniform, so that during the process of clamping the upper and lower clamping plates, various parts of the solid-state battery can be subjected to the same pressure to promote the removal and aggregation of moisture.

[0046] Based on the above embodiment, the preset pressure is 2 MPa to 4 MPa; and the first time length is 10 min to 20 min.

[0047] The embodiments of the present application pressurize the solid-state battery within the above-mentioned pressure range, which is not only conducive to the accumulation of moisture inside the solid-state battery, but also makes the contact between the positive electrode, electrolyte and negative electrode inside the battery closer, and can also avoid excessive pressure that affects the interface performance of the solid-state battery.

[0048] Based on the above embodiments, as an optional embodiment, the preset temperature is 100° C. to 120° C.

[0049] Based on the above embodiments, as an optional embodiment, the second duration is 3s to 5s, and the positive voltage is 1V to 2V; the third duration is 3s to 5s, and the negative voltage is -1V to -2V.

[0050] In the embodiments of the present application, by setting the positive voltage and the negative voltage within the above range and alternating the positive voltage and the negative voltage, it is beneficial to change the surface charge of the positive and negative electrodes, which is beneficial to speed up the water removal without affecting the performance of the battery.

[0051] Based on the above embodiments, as an optional embodiment, for each first operation, the voltage application operation is performed on the solid-state battery for a first preset number of times, and then further includes:

[0052] If it is determined that the number of times the first operation is repeatedly performed is not less than a second preset number of times, the water content of the solid-state battery is detected.

[0053] In order to further improve the water removal efficiency, the embodiment of the present application takes into account that when the first operation is executed a small number of times, the solid-state battery often does not meet expectations. Therefore, there is no need to detect the water content when the first operation is executed for the first few times. The water content of the solid-state battery is only detected when the first operation is repeated for no less than a second preset number of times.

[0054] Based on the above embodiment, the second preset number is 4 to 6. In some embodiments, for example, when the production environment, production process or production raw materials of the solid-state battery are relatively dry, the second preset number can be 1, which means that the water content needs to be detected after each execution of the first operation, so that the present application can be used as a way to measure whether the production environment, production process or production raw materials are qualified.

[0055] See also Figure 3 , Figure 3 A schematic diagram of a process for removing water from a solid-state battery according to another embodiment of the present application is shown as an example. Figure 3 As shown, including:

[0056] S301, evacuating the space where the solid-state battery is located and maintaining it at a preset temperature, and applying a preset pressure for a first period of time to the solid-state battery;

[0057] S302, introducing an inert gas into the space so that the pressure of the space is at normal pressure;

[0058] S303, determining whether the voltage application operation has been executed for a first preset number of times, if not, executing S304, if it has been reached, executing S306;

[0059] S304, performing a voltage application operation on the solid-state battery, the voltage application operation comprising: applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery;

[0060] S305, adding 1 to the number of executions of the voltage application operation, and returning to execute S203;

[0061] S306, adding 1 to the number of executions of the first operation;

[0062] S307, determining whether the number of the first operation (i.e., steps S301 to S306) is less than a second preset number of times, if not less than the second preset number of times, executing S308, if less than the second preset number of times, returning to executing S301;

[0063] S308, detecting the water content of the solid-state battery. If the water content is lower than a preset threshold, the process is terminated. If the water content is not lower than the preset threshold, the process returns to S301.

[0064] Based on the above embodiments, as an optional embodiment, the first operation is performed for the first time, and before that, the following steps are also included:

[0065] After evacuating the space, an inert gas is introduced to the space until the pressure reaches normal pressure;

[0066] The temperature of the space is adjusted to the preset temperature for a fourth time period.

[0067] The present application first evacuates the space to remove moisture inside the oven, and then introduces inert gas to normal pressure in order to break the vacuum, and further adjusts the temperature of the space to a preset temperature for a fourth period of time, thereby significantly reducing the water content of the internal components of the battery.

[0068] Based on the above embodiments, as an optional embodiment, the fourth duration is 60 minutes to 90 minutes.

[0069] Based on the above embodiments, as an optional embodiment, adjusting the temperature of the space to the preset temperature further includes:

[0070] Air is blown in the space.

[0071] In the embodiment of the present application, air blowing can speed up the gas circulation in the space, which can not only make the solid-state battery heat up evenly, but also effectively improve the moisture dissipation efficiency.

[0072] Based on the above embodiments, as an optional embodiment, after the water content of the solid-state battery is lower than a preset threshold, the method further includes:

[0073] The solid-state battery is packaged.

[0074] See also Figure 4 , Figure 4 A schematic diagram of a process for removing water from a solid-state battery according to another embodiment of the present application is shown as an example. Figure 4 As shown, including:

[0075] S401, evacuating the space and introducing an inert gas to normal pressure;

[0076] S402, adjusting the temperature of the space to the preset temperature, and performing air blowing in the space for a fourth time period;

[0077] S403, evacuating the space where the solid-state battery is located and maintaining it at a preset temperature, and applying a preset pressure for a first period of time to the solid-state battery;

[0078] S404, introducing an inert gas into the space so that the pressure of the space is at normal pressure;

[0079] S405, determining whether the voltage application operation has reached a first preset number of times, if not, executing S406, if reached, executing S408;

[0080] S406, performing a voltage application operation on the solid-state battery, the voltage application operation comprising: applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery;

[0081] S407, adding 1 to the number of executions of the voltage application operation, and returning to execute S405;

[0082] S408, adding 1 to the number of executions of the first operation;

[0083] S409, determining whether the number of the first operation (i.e., steps S401 to S406) is less than a second preset number of times, if not less than the second preset number of times, executing S410, if less than the second preset number of times, returning to executing S403;

[0084] S410, detecting the water content of the solid-state battery, if the water content is lower than a preset threshold, executing S411, if the water content is not lower than the preset threshold, returning to execute S403;

[0085] S411, encapsulate the solid-state battery and end the process.

[0086] The embodiments of the present application also provide an all-solid-state battery, including a positive electrode sheet, a negative electrode sheet and an electrolyte layer, and the positive electrode sheet, the electrolyte sheet and the negative electrode sheet are dehydrated by the methods described in the above embodiments.

[0087] The all-solid-state battery provided in the embodiments of the present application is dehydrated by the dehydration methods provided in the above embodiments, which not only increases the energy density of the battery but also reduces the content of bound water.

[0088] In order to further explain the present invention in detail, the present invention will be further explained in conjunction with specific examples. The experimental methods used in the examples of the present invention are conventional methods unless otherwise specified; the materials, reagents, etc. used in the examples of the present invention are purchased from the market unless otherwise specified.

[0089] Example 1

[0090] This embodiment provides a method for removing water from a solid-state battery, comprising:

[0091] (1) Place a solid-state battery with a standard capacity of 1Ah in a designated position of the oven, and place the battery between two stainless steel clamps. However, the two stainless steel clamps do not apply pressure to the solid-state battery. The positive and negative ears of the solid-state battery are clamped by charging clamps, respectively, so as to apply pressure and voltage to the solid-state battery during the dehydration process. Evacuate the interior of the oven to -100kPa, maintain for 5 minutes, and then introduce inert gas (helium, nitrogen or argon) into the oven to normal pressure and maintain for 5 minutes.

[0092] (2) The oven is heated to 100° C. under normal pressure, and the blower in the oven is turned on to blow air into the oven for 90 minutes.

[0093] (3) The inside of the oven was evacuated to -100 kPa, the temperature inside the oven was maintained at 100 °C, and a pressure of 2 MPa was applied to the solid-state battery through two stainless steel clamps for 10 min; then, an inert gas was introduced into the oven to make the pressure inside the oven normal pressure, and a positive voltage of a second duration and a negative voltage of a third duration were alternately applied to the solid-state battery, wherein the positive voltage was 1 V, the second duration was 3 s, the negative voltage was -1 V, the third duration was 3 s, and the positive voltage and the negative voltage were alternately cycled 10 times;

[0094] (4) Repeat step (3) five times to detect the water content of the solid-state battery.

[0095] Example 2

[0096] This embodiment provides a method for removing water from a solid-state battery. The method for removing water from the solid-state battery is the same as that in Embodiment 1, except that: the standard capacity of the solid-state battery is 10 Ah.

[0097] Example 3

[0098] This embodiment provides a method for removing water from a solid-state battery. The method for removing water from the solid-state battery is the same as that in Embodiment 1, except that: the standard capacity of the solid-state battery is 20 Ah.

[0099] Comparative Example 1:

[0100] This comparative example provides a method for removing water from a solid-state battery, comprising:

[0101] (1) Place a solid-state battery with a standard capacity of 1Ah in a designated position of an oven, evacuate the interior of the oven to -100kPa, maintain the vacuum for 5 minutes, then introduce an inert gas (helium, nitrogen or argon) into the oven to normal pressure and maintain the vacuum for 5 minutes.

[0102] (2) The oven is heated to 100° C. under normal pressure, and the blower in the oven is turned on to blow air into the oven for 180 minutes.

[0103] (3) The interior of the oven was evacuated to -100 kPa, and the temperature inside the oven was maintained at 100°C for 30 minutes. Then, at the temperature inside the oven of 100°C, an inert gas was introduced into the oven to normal pressure, and the temperature and pressure inside the oven were maintained for 30 minutes.

[0104] (4) Repeat step (3) three times to detect the water content of the solid-state battery.

[0105] Comparative Example 2

[0106] This comparative example provides a method for removing water from a solid-state battery. The method for removing water from the solid-state battery is the same as that in comparative example 1, except that: the standard capacity of the solid-state battery is 10Ah.

[0107] Comparative Example 3

[0108] This comparative example provides a method for removing water from a solid-state battery. The method for removing water from the solid-state battery is the same as that in comparative example 1, except that: the standard capacity of the solid-state battery is 20Ah.

[0109] The moisture contents of the positive electrode sheets, negative electrode sheets, and electrolyte sheets in the solid-state batteries in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively detected, and the results shown in Table 1 were obtained.

[0110] Table 1

[0111]

[0112] The solid-state battery is required to have a water content of ≤400ppm in the positive electrode sheet, ≤300ppm in the electrolyte sheet, and ≤250ppm in the negative electrode sheet after dehydration. It can be seen from Table 1 that the solid-state batteries in Examples 1 to 3 meet the above requirements after dehydration, while the solid-state batteries in Comparative Examples 1 to 3 do not meet the above requirements after dehydration. This shows that the dehydration method for solid-state batteries provided by the present invention alternately cycles between battery pressurization and voltage application, while taking into account the traditional drying method of vacuuming and breaking vacuum ventilation cycles, which can significantly reduce the bound water in the solid-state battery and improve the quality of the solid-state battery.

[0113] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for removing water from a solid-state battery, characterized in that: include: Repeating the first operation multiple times until the water content of the solid-state battery is lower than a preset threshold; The first operation includes: The space where the solid-state battery is located is evacuated and maintained at a preset temperature, and a preset pressure is applied to the solid-state battery for a first period of time; Introducing an inert gas into the space so that the pressure of the space is normal pressure, and performing a first preset number of voltage application operations on the solid-state battery; The voltage applying operation includes: alternately applying a positive voltage of a second duration and a negative voltage of a third duration to the solid-state battery.

2. The water removal method according to claim 1, characterized in that: The step of applying a preset pressure for a first time period to the solid-state battery includes: The solid-state battery is mounted on the upper and lower clamping plates; A preset pressure of a first duration is applied to the solid-state battery by clamping the upper and lower clamping plates.

3. The water removal method according to claim 1, characterized in that: The preset pressure is 2 MPa to 4 MPa; the first time length is 10 min to 20 min.

4. The water removal method according to claim 1, characterized in that: The preset temperature is 100°C to 120°C.

5. The water removal method according to claim 1, characterized in that: The second duration is 3s to 5s, and the positive voltage is 1V to 2V; the third duration is 3s to 5s, and the negative voltage is -1V to -2V.

6. The water removal method according to claim 1, characterized in that: For each first operation, the voltage application operation is performed on the solid-state battery for a first preset number of times, and then further includes: If it is determined that the number of times the first operation is repeatedly performed is not less than a second preset number of times, the water content of the solid-state battery is detected.

7. The water removal method according to any one of claims 1 to 6, characterized in that: The first operation is performed for the first time, and the operation also includes: After evacuating the space, an inert gas is introduced to the space until the pressure reaches normal pressure; The temperature of the space is adjusted to the preset temperature for a fourth time period.

8. The water removal method according to claim 7, characterized in that: The step of adjusting the temperature of the space to the preset temperature further comprises: Air is blown in the space.

9. The water removal method according to claim 7, characterized in that: After the water content of the solid-state battery is lower than a preset threshold, the method further includes: The solid-state battery is packaged.

10. A solid-state battery, characterized in that: It comprises a positive electrode sheet, an electrolyte sheet and a negative electrode sheet, wherein the positive electrode sheet, the electrolyte sheet and the negative electrode sheet are dehydrated by the dehydration method according to any one of claims 1 to 9.

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