A method and device for differential modification of both sides of the surface of a solid electrolyte layer

Abstract

The present invention discloses a method and device for differential modification of the surfaces on both sides of a solid electrolyte layer. The method of the present invention uses an argon-oxygen mixed gas to perform micro-oxygen atmosphere pretreatment on the upper and lower surfaces of the solid electrolyte layer respectively under different temperatures and different oxygen volume fractions, and differentially modifies the upper and lower surfaces of the electrolyte layer, thereby meeting the different performance requirements of the positive and negative electrode interfaces of an all-solid-state lithium battery. The device of the present invention controls the surface temperature of the solid electrolyte layer by using a temperature controller, and regulates the temperature on the basis of a certain temperature. At the same time, by using a two-stage or multi-stage gas mixing method and a gas circulation pump to control the oxygen concentration at the surface of the electrolyte layer, the upper and lower surfaces of the electrolyte layer are modified and pretreated under different temperatures and oxygen concentrations. While maintaining good electrochemical stability, the adverse effects of oxygen on ion conductivity are minimized, thereby improving the performance of the solid electrolyte layer after being applied to an all-solid-state lithium battery.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state lithium battery preparation, and in particular to a method and device for differentially modifying the surfaces of both sides of a solid electrolyte layer. Background Art

[0002] All-solid-state lithium batteries use non-flammable solid electrolytes, which fundamentally solve the battery fire problem caused by the organic electrolyte and diaphragm of traditional liquid lithium batteries. They also have higher energy density and longer service life, and are expected to become a key technology for the development of the next generation of power energy. Sulfide solid electrolytes have an ionic conductivity that is similar to or even higher than that of liquid electrolytes, an order of magnitude higher than other types of solid electrolytes, and are one of the solid electrolytes with good prospects due to their relatively tight interface contact and easy preparation. However, the application of sulfide solid electrolytes in all-solid-state lithium batteries still has serious interface problems.

[0003] Interface problems are key issues in the development of all-solid-state lithium batteries. Taking sulfide solid electrolytes as an example, interface problems mainly include: the interface layer produced by chemical reactions at the electrode interface leads to higher impedance, the space charge layer formed at the positive electrode interface due to the electronegativity difference between oxygen and sulfur elements leads to larger interface resistance, and the lithium dendrites formed at the negative electrode interface due to the uneven deposition of lithium metal during charging lead to battery short circuit failure.

[0004] Existing studies have shown that by replacing part of the sulfur in the electrolyte with oxygen during the preparation of sulfide solid electrolyte powder, the electrochemical stability of the solid electrolyte can be effectively improved, thereby improving the performance of all-solid-state lithium batteries. However, the doping of oxygen in the electrolyte will lead to a decrease in its ionic conductivity. Experiments have shown that the oxygen in the Li6PS5Cl electrolyte powder prepared in an atmosphere containing trace oxygen is mainly distributed on the surface of the particles, while maintaining good electrochemical stability, the adverse effects on ionic conductivity are minimized. In addition, existing studies have shown that temperature has a great influence on the interface impedance, critical current density, diffusion properties and mechanical properties of lithium, and cycle stability of lithium negative electrodes in all-solid-state lithium batteries. However, there is still a lack of research on the influence of process temperature during preparation, especially the non-uniform temperature field, on the performance of the pressed solid electrolyte layer. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, one purpose of the present invention is to propose a method for differentiated modification of the surfaces on both sides of a solid-state electrolyte layer. This method modifies the upper and lower surfaces of the solid-state electrolyte layer under different conditions, including different oxygen concentrations and different temperatures, so as to find the optimal temperature and the optimal oxygen concentration for the modification pretreatment of the solid-state electrolyte layer. While improving the electrochemical stability of the solid-state electrolyte layer, the high ionic conductivity inside the electrolyte layer is retained to the greatest extent, so as to achieve a comprehensive improvement in the performance of all-solid-state lithium batteries.

[0007] Another object of the present invention is to provide a device for differentially modifying the surfaces of both sides of a solid electrolyte layer.

[0008] On the one hand, the present invention provides a method for differentially modifying the surfaces of both sides of a solid electrolyte layer, comprising the following steps:

[0009] (1) preparing an argon-oxygen mixed gas with an oxygen volume fraction of less than 10%;

[0010] (2) At a temperature of 450°C-600°C, the positive electrode interface and the negative electrode interface of the solid electrolyte layer are treated respectively using the argon-oxygen mixed gas with different oxygen volume fractions, and the temperature when the positive electrode interface of the solid electrolyte layer is treated is different from the temperature when the negative electrode interface of the solid electrolyte layer is treated, so as to meet the differentiated modification requirements of the positive electrode interface and the negative electrode interface of the solid electrolyte layer, while improving the electrochemical stability of the solid electrolyte layer, retaining the high ionic conductivity inside the electrolyte layer to the greatest extent, and realizing the comprehensive improvement of the performance of the all-solid-state lithium battery.

[0011] In some embodiments, the temperature at which the positive electrode interface of the solid electrolyte layer is treated is lower than the temperature at which the negative electrode interface of the solid electrolyte layer is treated.

[0012] In some embodiments, the volume fraction of oxygen in the argon-oxygen mixed gas when the positive electrode interface of the solid electrolyte layer is treated is lower than the volume fraction of oxygen in the argon-oxygen mixed gas when the negative electrode interface of the solid electrolyte layer is treated.

[0013] In some embodiments, when the positive electrode interface of the solid electrolyte layer is treated, the argon-oxygen mixed gas is introduced into the positive electrode interface, and argon is introduced into the negative electrode interface, so that the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the positive electrode interface is lower than the pressure at the negative electrode interface; when the negative electrode interface of the solid electrolyte layer is treated, the argon-oxygen mixed gas is introduced into the negative electrode interface, and argon is introduced into the positive electrode interface, so that the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the negative electrode interface is lower than the pressure at the positive electrode interface.

[0014] In some embodiments, the argon-oxygen mixed gas is prepared by a two-stage or multi-stage gas mixing method.

[0015] In some embodiments, the solid electrolyte layer is formed by pressing solid electrolyte powder.

[0016] In some embodiments, the solid electrolyte layer is a sulfide solid electrolyte layer.

[0017] On the other hand, the present invention provides a device for differentially modifying the surfaces of both sides of a solid electrolyte layer, comprising:

[0018] An atmosphere control module, the atmosphere control module is used to prepare the argon-oxygen mixed gas and control the circulation of the argon-oxygen mixed gas to achieve modification of the positive and negative electrode interfaces of the solid electrolyte layer in atmospheres with different oxygen volume fractions;

[0019] A temperature control module is used to control the surface temperature of the solid electrolyte layer to achieve modification of the positive and negative electrode interfaces of the solid electrolyte layer at different temperatures.

[0020] In some embodiments, the atmosphere control module includes a flow control valve, a gas mixing device, a gas valve, a gas circulation pump and a gas replenishing device, the flow control valve is used to control the gas flow, the gas mixing device is a two-stage or multi-stage gas mixing device, the gas valve is used to control the circulation of the gas, the gas circulation pump provides power for the gas circulation, and the gas replenishing device is used to replenish the consumed oxygen; the temperature control module includes a high-temperature furnace, a sample chamber, a temperature controller and a fixed bracket, the sample chamber is arranged in the high-temperature furnace, the fixed bracket and the temperature controller are both arranged in the sample chamber, the solid electrolyte layer is arranged between the fixed brackets, the solid electrolyte layer divides the sample chamber into a positive electrode chamber and a negative electrode chamber, and the temperature controllers respectively arranged in the positive electrode chamber and the negative electrode chamber are arranged on the fixed bracket and are respectively close to the positive electrode interface and the negative electrode interface of the solid electrolyte layer.

[0021] In some embodiments, when the positive electrode interface of the solid electrolyte layer is processed, the temperature controller disposed at the positive electrode interface is removed, so that the positive electrode interface of the solid electrolyte layer is exposed to the positive electrode chamber, the argon-oxygen mixed gas is introduced into the positive electrode chamber, and argon is introduced into the negative electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are maintained constant by the gas circulation pump and the gas replenishing device, and the positive electrode chamber pressure is lower than the negative electrode chamber pressure; when the negative electrode interface of the solid electrolyte layer is processed, the temperature controller disposed at the negative electrode interface is removed, so that the negative electrode interface of the solid electrolyte layer is exposed to the negative electrode chamber, the argon-oxygen mixed gas is introduced into the negative electrode chamber, and argon is introduced into the positive electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are maintained constant by the gas circulation pump and the gas replenishing device, and the negative electrode chamber pressure is lower than the positive electrode chamber pressure.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The method for differentially modifying the surfaces of both sides of a solid electrolyte layer of the present invention utilizes an argon-oxygen mixed gas to perform micro-oxygen atmosphere pretreatment on the upper and lower surfaces of the solid electrolyte layer respectively under conditions of different temperatures and different oxygen volume fractions, and differentially modifies the upper and lower surfaces of the electrolyte layer, thereby meeting the different performance requirements of the positive and negative electrode interfaces of an all-solid-state lithium battery.

[0024] The device for differentially modifying the surfaces of both sides of the solid electrolyte layer of the present invention controls the surface temperature of the solid electrolyte layer by using a temperature controller, and regulates the temperature on the basis of a certain high temperature. At the same time, a two-stage or multi-stage gas mixing method and a gas circulation pump are used to control the oxygen concentration at the surface of the electrolyte layer, so as to achieve modification pretreatment of the upper and lower surfaces of the electrolyte layer under different temperature and oxygen concentration conditions. While maintaining good electrochemical stability, the adverse effects of oxygen on ion conductivity are minimized, thereby improving the performance of the solid electrolyte layer after being applied to an all-solid-state lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 The flowchart is a method for differentially modifying the surfaces on both sides of a solid electrolyte layer;

[0027] Figure 2 A flow chart of a method for differentially modifying the surfaces of both sides of a solid electrolyte layer according to an embodiment;

[0028] Figure 3A schematic diagram of gas content and temperature for differential modification of the surfaces on both sides of a sulfide solid electrolyte layer according to an embodiment;

[0029] Figure 4 A schematic diagram of the distribution of oxygen doping amount along the cross section of a modified sulfide solid electrolyte layer according to an embodiment;

[0030] Figure 5 A double-sided lithium polarization test diagram of a Li / / Li6PS5Cl / / Li battery assembled with a modified sulfide solid electrolyte layer and an unmodified sulfide solid electrolyte layer according to an embodiment;

[0031] Figure 6 It is a schematic diagram of the structure of the device for differential modification of the surfaces on both sides of the solid electrolyte layer;

[0032] Figure 7 Schematic diagram of the modular structure of the device for differential surface modification on both sides of the solid electrolyte layer.

[0033] Description of reference numerals:

[0034] Flow control valve 1, gas mixing device 2, gas valve 3, high temperature furnace 4, sample chamber 5, temperature controller 6, fixed bracket 7, solid electrolyte layer 8, gas circulation pump 9, gas replenishing device 10. DETAILED DESCRIPTION

[0035] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0036] Please refer to the attached Figure 1-7 The method and device for differentially modifying the surfaces of both sides of a solid electrolyte layer proposed according to an embodiment of the present invention are described. First, the method for differentially modifying the surfaces of both sides of a solid electrolyte layer proposed according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0037] like Figure 1 As shown, the method for differentially modifying the surfaces of both sides of the solid electrolyte layer of the present invention comprises the following steps:

[0038] (1) preparing an argon-oxygen mixed gas with an oxygen volume fraction of less than 10%;

[0039] (2) At a temperature of 450°C to 600°C, the positive electrode interface and the negative electrode interface of the solid electrolyte layer are treated respectively using argon-oxygen mixed gases with different oxygen volume fractions, and the temperature when the positive electrode interface of the solid electrolyte layer is treated is different from the temperature when the negative electrode interface of the solid electrolyte layer is treated.

[0040] In step (1), the argon-oxygen mixed gas is prepared by a two-stage or multi-stage gas mixing method. It can be understood that the two-stage or multi-stage gas mixing obtains the argon-oxygen mixed gas containing trace amounts of oxygen, and the two-stage or multi-stage mixing is performed so that the oxygen and argon are mixed evenly.

[0041] When assembling an all-solid-state lithium battery, the upper and lower surfaces of the solid electrolyte layer are in contact with the positive electrode and the negative electrode of the battery respectively. The interface where the solid electrolyte layer contacts the positive electrode of the battery is defined as the positive electrode interface, and the interface where the solid electrolyte layer contacts the negative electrode of the battery is defined as the negative electrode interface.

[0042] In step (2), at a temperature of 450°C to 600°C, the positive electrode interface and the negative electrode interface of the solid electrolyte layer are treated respectively using argon-oxygen mixed gases with different oxygen volume fractions, and the temperature when treating the positive electrode interface of the solid electrolyte layer is different from the temperature when treating the negative electrode interface of the solid electrolyte layer. The positive and negative electrode materials of the all-solid-state lithium battery have different requirements for electrolyte stability, and different conditions need to be adjusted when modifying the positive and negative electrode interfaces of the solid electrolyte. The differentiated modification method of the surfaces of both sides of the solid electrolyte layer of the present invention can realize the modification pretreatment of the positive and negative electrode interfaces of the electrolyte layer under different temperatures and oxygen concentrations to adapt to the differentiated modification requirements of the positive and negative electrode interfaces of the solid electrolyte layer, while improving the electrochemical stability of the solid electrolyte layer, retaining the high ionic conductivity inside the electrolyte layer to the greatest extent, and realizing the overall improvement of the performance of the all-solid-state lithium battery.

[0043] In some embodiments, the temperature when the positive electrode interface of the solid electrolyte layer is treated is lower than the temperature when the negative electrode interface of the solid electrolyte layer is treated.

[0044] In some embodiments, the volume fraction of oxygen in the argon-oxygen mixed gas when treating the positive electrode interface of the solid electrolyte layer is lower than the volume fraction of oxygen in the argon-oxygen mixed gas when treating the negative electrode interface of the solid electrolyte layer.

[0045] In some embodiments, the solid electrolyte layer is formed by pressing solid electrolyte powder. It is understood that solid electrolyte layers in other forms are also applicable to the present method.

[0046] In some embodiments, the solid electrolyte layer is a sulfide solid electrolyte layer. It is understood that the solid electrolyte can be a sulfide solid electrolyte, but is not limited to a sulfide solid electrolyte.

[0047] In some embodiments, when the positive electrode interface of the solid electrolyte layer is treated, an argon-oxygen mixed gas is introduced into the positive electrode interface, and argon is introduced into the negative electrode interface, and the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the positive electrode interface is lower than the pressure at the negative electrode interface; when the negative electrode interface of the solid electrolyte layer is treated, an argon-oxygen mixed gas is introduced into the negative electrode interface, and argon is introduced into the positive electrode interface, and the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the negative electrode interface is lower than the pressure at the positive electrode interface. It can be understood that when the positive electrode interface of the solid electrolyte layer is treated, the pressure at the positive electrode interface is kept lower than the pressure at the negative electrode interface to prevent oxygen from penetrating through the solid electrolyte layer to the negative electrode interface; when the negative electrode interface of the solid electrolyte layer is treated, the pressure at the negative electrode interface is kept lower than the pressure at the positive electrode interface to prevent oxygen from penetrating through the solid electrolyte layer to the positive electrode interface.

[0048] like Figure 6 As shown, the device for differentially modifying the surfaces of both sides of the solid electrolyte layer of the present invention includes an atmosphere control module and a temperature control module, wherein the atmosphere control module is used to prepare an argon-oxygen mixed gas and control the circulation of the argon-oxygen mixed gas; the temperature control module is used to control the surface temperature of the solid electrolyte layer.

[0049] In some embodiments, the atmosphere control module includes a flow control valve 1, a gas mixing device 2, a gas valve 3, a gas circulation pump 9 and a gas replenishing device 10, the flow control valve 1 is used to control the gas flow, the gas mixing device 2 is a two-stage or multi-stage gas mixing device, the gas valve 3 is used to control the circulation of the gas, the gas circulation pump 9 provides power for the gas circulation, and the gas replenishing device 10 is used to replenish the consumed oxygen.

[0050] Specifically, an oxygen gas source and an argon gas source provide oxygen and argon gas for the device for differentially modifying the surfaces of both sides of the solid electrolyte layer of the present invention. A flow control valve 1 arranged downstream of the oxygen gas source and the argon gas source is used to control the flow rates of oxygen and argon gas to adapt to different oxygen content requirements. A flow control valve 1 arranged downstream of the gas mixing device 2 is used to control the flow rate of the argon-oxygen mixed gas to adapt to different pressure requirements. Oxygen and argon gas are evenly mixed in the gas mixing device 2. The flow control valve 1 and the gas mixing device 2 can obtain a mixed gas with any argon-oxygen ratio, and prepare a corresponding mixed gas according to the modification requirements. It can be understood that the gas mixing device 2 can be a two-stage or multi-stage mixing device; the gas valve 3 is used to control the flow of gas; the gas circulation pump 9 provides power for gas circulation, and the gas circulation pump 9 realizes the gas flow in the sample chamber 5, and realizes the recycling of residual gas, thereby reducing the cost of using the device; the gas replenishing device 10 is arranged downstream of the gas mixing device 2, and the gas replenishing device 10 is used to replenish the oxygen consumed in the modification process. It can be understood that the gas replenishing device 10 has an oxygen detector, and the argon-oxygen mixed gas replenishes the oxygen lost in the modification process through the gas replenishing device 10 under the action of the gas circulation pump 9 and re-enters the sample chamber 5, thereby ensuring that the oxygen content on the surface of the solid electrolyte layer remains unchanged. The flow control valve 1 and the gas mixing device 2 provide a mixed gas containing trace oxygen, and the gas circulation pump 9 and the gas replenishing device 10 are used in combination to accurately control the oxygen content in the sample chamber, and the dual gas circulation loop realizes the control of the oxygen concentration of the positive and negative electrode chambers respectively, thereby realizing the differential modification of the atmosphere at the positive and negative electrode interfaces of the solid electrolyte layer.

[0051] In some embodiments, the temperature control module includes a high-temperature furnace 4, a sample chamber 5, a temperature controller 6 and a fixed bracket 7. The sample chamber 5 is arranged in the high-temperature furnace 4. The fixed bracket 7 and the temperature controller 6 are both arranged in the sample chamber 5. The solid electrolyte layer 8 is arranged between the fixed brackets 7. The solid electrolyte layer 8 divides the sample chamber 5 into a positive electrode chamber and a negative electrode chamber. The temperature controllers 6 respectively arranged in the positive electrode chamber and the negative electrode chamber are arranged on the fixed bracket 7 and are respectively close to the positive electrode interface and the negative electrode interface of the solid electrolyte layer 8.

[0052] Specifically, considering that the solid electrolyte preparation temperature is usually above 500°C, the temperature controller 6 does not have the ability to heat to this temperature. Therefore, the high-temperature furnace 4 is used to heat the ambient temperature to about 450°C, and the surface temperature of the solid electrolyte layer 8 is regulated by the temperature controller 6 on this basis; the sample chamber 5 is arranged in the high-temperature furnace 4, the fixed bracket 7 and the temperature controller 6 are both arranged in the sample chamber 5, the solid electrolyte layer 8 is arranged between the fixed brackets 7, and the solid electrolyte layer 8 divides the sample chamber 5 into a positive electrode chamber and a negative electrode chamber. It can be understood that the side of the solid electrolyte layer 8 exposed to the positive electrode chamber is the positive electrode interface, and the side of the solid electrolyte layer 8 exposed to the negative electrode chamber is the negative electrode interface; the temperature controller 6 is arranged on the fixed bracket 7 and is close to the interface of the solid electrolyte layer 8. It can be understood that the temperature controller 6 arranged in the positive electrode chamber is close to the positive electrode interface of the solid electrolyte layer 8, and the temperature controller 6 arranged in the negative electrode chamber is close to the negative electrode interface of the solid electrolyte layer 8.

[0053] In some embodiments, when the positive electrode interface of the solid electrolyte layer 8 is processed, the temperature controller 6 disposed at the positive electrode interface is removed, so that the positive electrode interface of the solid electrolyte layer 8 is exposed to the positive electrode chamber, an argon-oxygen mixture is introduced into the positive electrode chamber, and argon is introduced into the negative electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are maintained constant by a gas circulation pump 9 and a gas replenishing device 10, and the positive electrode chamber pressure is lower than the negative electrode chamber pressure; when the negative electrode interface of the solid electrolyte layer 8 is processed, the temperature controller 6 disposed at the negative electrode interface is removed, so that the negative electrode interface of the solid electrolyte layer 8 is exposed to the negative electrode chamber, an argon-oxygen mixture is introduced into the negative electrode chamber, and argon is introduced into the positive electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are maintained constant by a gas circulation pump 9 and a gas replenishing device 10, and the negative electrode chamber pressure is lower than the positive electrode chamber pressure. The temperature controller 6 can control the positive and negative electrode interfaces of the solid electrolyte layer to be at different temperatures during modification, thereby achieving differential modification of the positive and negative electrode interface temperatures of the solid electrolyte layer.

[0054] It can be understood that when the positive electrode interface of the solid electrolyte layer 8 is treated, the positive electrode chamber pressure and the negative electrode chamber pressure are kept unchanged by the gas circulation pump 9 and the gas replenishing device 10, and the positive electrode chamber pressure is lower than the negative electrode chamber pressure. At this time, the pressure at the positive electrode interface is lower than the pressure at the negative electrode cross section, preventing oxygen from penetrating through the solid electrolyte layer 8 to the negative electrode interface; when the negative electrode interface of the solid electrolyte layer 8 is treated, the positive electrode chamber pressure and the negative electrode chamber pressure are kept unchanged by the gas circulation pump 9 and the gas replenishing device 10, and the negative electrode chamber pressure is lower than the positive electrode chamber pressure. At this time, the pressure at the negative electrode interface is lower than the pressure at the positive electrode interface, preventing oxygen from penetrating through the solid electrolyte layer 8 to the positive electrode interface.

[0055] like Figure 2As shown, using the device and method of the present invention to differentially modify the surfaces of both sides of the sulfide electrolyte layer includes the following steps:

[0056] S1: Pressing the solid electrolyte powder into a solid electrolyte layer through a mold, placing the solid electrolyte layer in a sample cavity, and preparing an argon-oxygen mixed gas with a certain volume fraction of oxygen through a two-stage or multi-stage gas mixing method;

[0057] S2: The gas content in the positive electrode chamber and the negative electrode chamber is kept constant by the flow control valve and the gas circulation pump, and when the positive electrode interface is processed, the positive electrode chamber pressure is lower than the negative electrode chamber pressure, and when the negative electrode interface is processed, the negative electrode chamber pressure is lower than the positive electrode chamber pressure;

[0058] S3: Heating to a certain ambient temperature through a high temperature furnace, and controlling the temperature of the solid electrolyte layer through a temperature controller 6 based on the ambient temperature.

[0059] In step S1, an argon-oxygen mixed gas with a certain volume fraction of oxygen is prepared by a two-stage or multi-stage gas mixing method.

[0060] Among them, the purpose of multi-stage gas mixing is to obtain an argon-oxygen mixed gas containing trace oxygen. The reason is that the sulfide solid electrolyte is very sensitive to water oxygen. Only a small amount of oxygen is needed to treat the sulfide solid electrolyte. Through the multi-stage mixing method and the flow control valve 1, a mixed gas containing trace oxygen can be accurately obtained, and the oxygen content is controlled to be 10% or less. When the positive electrode interface and the negative electrode interface of the solid electrolyte layer are treated respectively, the oxygen volume fraction at the negative electrode interface of the solid electrolyte layer is controlled to be higher than the oxygen volume fraction at the positive electrode interface.

[0061] In step S2, the gas content in the positive electrode chamber and the negative electrode chamber is kept unchanged by the flow control valve 1 and the gas circulation pump 9, and when the positive electrode interface is processed, the positive electrode chamber pressure is lower than the negative electrode chamber pressure, and when the negative electrode interface is processed, the negative electrode chamber pressure is lower than the positive electrode chamber pressure.

[0062] Specifically, when the positive electrode interface of the sulfide solid electrolyte layer is subjected to a micro-oxygen atmosphere treatment, pure argon is introduced into the negative electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 5% is introduced into the positive electrode chamber, and the gas pressure in the positive electrode chamber is slightly lower than the pressure in the negative electrode chamber to prevent oxygen from penetrating into the negative electrode chamber through the solid electrolyte layer, and a gas circulation pump 9 and a gas replenishing device 10 are used to further ensure that the gas content at the surface of the solid electrolyte layer in the two chambers remains unchanged; when the negative electrode interface of the sulfide solid electrolyte layer is subjected to a micro-oxygen atmosphere treatment, pure argon is introduced into the positive electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 10% is introduced into the negative electrode chamber, and the gas pressure in the negative electrode chamber is slightly lower than the pressure in the positive electrode chamber to prevent oxygen from penetrating into the positive electrode chamber through the solid electrolyte layer, and a gas circulation pump 9 and a gas replenishing device 10 are used to further ensure that the gas content at the surface of the solid electrolyte layer in the two chambers remains basically unchanged.

[0063] In step S3, the high temperature furnace 4 is used to heat the solid electrolyte layer to a certain ambient temperature, and the temperature of the solid electrolyte layer is controlled by the temperature controller 6 based on the ambient temperature.

[0064] The high temperature furnace 4 is used to heat the environment to a temperature of 450° C., and the surface temperature of the solid electrolyte layer is regulated by the temperature controller 6 based on this temperature.

[0065] It should be noted that, since the positive and negative electrode materials of all-solid-state lithium batteries have different requirements for electrolyte stability, different conditions need to be adjusted for the modification of the positive and negative electrode interfaces of sulfide solid electrolytes. For example, the positive electrode material can be coated with some special materials to improve the interface stability of the battery, while the use of lithium metal as the electrode material for the negative electrode will lead to serious lithium dendrite growth and interface reaction problems. Therefore, a higher oxygen concentration is required to improve the chemical stability of the negative electrode interface of the solid electrolyte layer, while the positive electrode interface requires relatively less oxygen incorporation to reduce unnecessary effects on ionic conductivity. In practical applications, there are a variety of options for positive and negative electrode materials used in all-solid-state lithium batteries. According to the stability of the material, the appropriate oxygen concentration is selected to modify the positive and negative interface layers of the sulfide solid electrolyte layer.

[0066] In some embodiments, when the negative electrode interface of the solid electrolyte layer is subjected to a micro-oxygen atmosphere treatment, the temperature controller 6 placed in the negative electrode chamber is removed so that the argon-oxygen mixture is in full contact with the negative electrode interface, and the temperature of the electrolyte layer is regulated to 550°C by regulating the temperature controller 6 in close contact with the positive electrode interface. At the same time, pure argon is introduced into the positive electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 10% is introduced into the negative electrode chamber; when the positive electrode interface of the solid electrolyte layer is subjected to a micro-oxygen atmosphere treatment, the temperature controller 6 placed in the positive electrode chamber is removed so that the argon-oxygen mixture is in full contact with the positive electrode interface, and the temperature of the electrolyte layer is regulated to 500°C by regulating the temperature controller 6 in close contact with the negative electrode interface. At the same time, pure argon is introduced into the negative electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 5% is introduced into the positive electrode chamber.

[0067] It can be understood that the present invention can obtain a solid electrolyte layer modified under different conditions by changing the oxygen volume fraction in the argon-oxygen mixture and the temperature of the surface of the solid electrolyte layer, and explore the optimal modification atmosphere and temperature to prepare a sulfide solid electrolyte layer with better performance.

[0068] The method for differentially modifying the surfaces of both sides of the sulfide solid electrolyte layer is further described below through a specific example.

[0069] Use Figure 6 The structure shown in the figure is used to perform a modification pretreatment experiment on the pressed Li6PS5Cl solid electrolyte layer. First, the negative electrode interface of the solid electrolyte layer is treated with a micro-oxygen atmosphere, the solid electrolyte layer is fixed on a fixed bracket 7, and a temperature controller 6 is installed at the positive electrode interface of the solid electrolyte layer. The negative electrode interface is in contact with the ambient gas, pure argon is introduced into the positive electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 10% is introduced into the negative electrode chamber. The air pressure in the negative electrode chamber is slightly lower than that in the positive electrode chamber. The sample chamber 5 is placed in a high-temperature furnace 4, and the high-temperature furnace 4 heats the ambient temperature to 450°C. The temperature controller 6 at the positive electrode interface regulates the electrolyte layer. The temperature reaches 550°C, maintained for 6 hours and then returned to room temperature; then the positive electrode interface is treated with a micro-oxygen atmosphere, the temperature controller 6 at the positive electrode interface is removed, and the temperature controller 6 is installed at the negative electrode interface. After vacuuming, pure argon is introduced into the negative electrode chamber, and an argon-oxygen mixture with an oxygen volume fraction of 5% is introduced into the positive electrode chamber, and the air pressure in the positive electrode chamber is slightly lower than that in the negative electrode chamber. The high-temperature furnace 4 heats the temperature to 450°C, and the temperature controller 6 at the negative electrode interface adjusts the temperature of the electrolyte layer to 500°C, maintained for 6 hours and then returned to room temperature. During the modification process, the gas content and temperature of the two chambers are as follows: Figure 3 shown.

[0070] The oxygen doping amount of the modified sulfide solid electrolyte layer is distributed along its cross section as follows: Figure 4As shown by Figure 4 It can be seen that the oxygen content at the negative electrode interface is higher than that at the positive electrode interface, and the oxygen content on both sides gradually decreases from the surface of the electrolyte layer to the middle. No oxygen is introduced into the middle of the electrolyte layer, that is, the oxygen content in the middle of the electrolyte layer is zero. The different oxygen contents at the positive and negative electrode interfaces make the electrolyte layer have different adaptability to the positive and negative electrode materials, thereby improving the interface stability while reducing the adverse effects on ionic conductivity.

[0071] The double-sided lithium polarization test diagram of the Li / / Li6PS5Cl / / Li battery assembled using the unmodified Li6PS5Cl solid electrolyte layer and the Li6PS5Cl solid electrolyte layer modified by the above method is shown in the figure. Figure 5 As shown. Among them, Figure 5 (a) is a double-sided lithium polarization test diagram of a Li / / Li6PS5Cl / / Li battery assembled using an unmodified Li6PS5Cl solid electrolyte layer. Figure 5 (b) is a double-sided lithium polarization test diagram of a Li / / Li6PS5Cl / / Li battery assembled using the Li6PS5Cl solid electrolyte layer modified by the above method. Figure 5 It can be seen that the voltage of the Li / / Li6PS5Cl / / Li battery assembled with the unmodified electrolyte layer suddenly dropped at about 1.5 hours, indicating that a short circuit occurred inside the battery at this time, and the battery cycle life was about 1.5 hours; the voltage of the Li / / Li6PS5Cl / / Li battery assembled with the modified electrolyte layer remained basically unchanged within 10 hours, and the battery was significantly more stable than when it was not modified. The battery life after modification was increased to 10 hours. In addition, the polarization voltage of the battery after modification did not increase significantly compared with that before modification, indicating that the micro-oxygen modification treatment at the interface has little effect on the ion transport capacity of the electrolyte layer. The embodiment shows that the electrochemical performance of the solid electrolyte layer obtained by this design method is more stable, and the battery life is effectively improved.

[0072] The present invention is not limited to the above-mentioned specific embodiments. The modification method of the solid electrolyte layer mentioned in the present invention can be widely applied to this field and other related fields, and the present invention can be implemented in various other specific embodiments. For example, based on the design concept of modifying the surface of the sulfide solid electrolyte layer, this principle is applied to other solid electrolyte layers or unpressed solid electrolyte powders, and the electrolyte is modified under an adjustable gas atmosphere and temperature field. Therefore, any design that adopts the design concept of the present invention and makes some simple changes or modifications belongs to the scope of protection of the present invention.

[0073] In summary, the embodiments of the present invention effectively improve the electrochemical stability of the sulfide solid electrolyte, thereby improving the battery life of the all-solid-state lithium battery prepared therefrom, and by using a gas mixing device to obtain a mixed gas with a certain ratio of argon and oxygen to circulate in the chamber and a temperature controller to control the temperature, the surface of the solid electrolyte layer is modified, thereby improving the interface performance of the solid electrolyte layer. The sulfide solid electrolyte layer modification method designed based on this method can improve the electrochemical stability of the sulfide solid electrolyte layer without causing much impact on the ionic conductivity of the electrolyte.

[0074] The method for differentially modifying the surfaces of both sides of the sulfide solid electrolyte layer of the example of the present invention controls the oxygen concentration at the surface of the electrolyte layer by using a two-stage or multi-stage gas mixing method and gas circulation. At the same time, the surface temperature of the sulfide solid electrolyte layer is controlled by using a temperature controller. The temperature is regulated on a certain high temperature basis to achieve modification pretreatment of the upper and lower surfaces of the electrolyte layer under different temperatures and oxygen concentrations, so that oxygen replaces part of the sulfur on the surface of the electrolyte layer. While maintaining good electrochemical stability, the adverse effects of oxygen on ionic conductivity are minimized, thereby improving the performance of the sulfide solid electrolyte after being applied to an all-solid-state lithium battery.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0076] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0077] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for differentially modifying the surfaces of both sides of a solid electrolyte layer, characterized in that: The following steps are involved: (1) preparing an argon-oxygen mixed gas having an oxygen volume fraction of less than 10%; (2) at a temperature of 450° C. to 600° C., the positive electrode interface and the negative electrode interface of the solid electrolyte layer are treated respectively using the argon-oxygen mixed gas with different oxygen volume fractions, and the temperature when the positive electrode interface of the solid electrolyte layer is treated is different from the temperature when the negative electrode interface of the solid electrolyte layer is treated, The temperature when the positive electrode interface of the solid electrolyte layer is treated is lower than the temperature when the negative electrode interface of the solid electrolyte layer is treated, the volume fraction of oxygen in the argon-oxygen mixed gas when the positive electrode interface of the solid electrolyte layer is treated is lower than the volume fraction of oxygen in the argon-oxygen mixed gas when the negative electrode interface of the solid electrolyte layer is treated, and the solid electrolyte layer is a sulfide solid electrolyte layer.

2. The method according to claim 1, characterized in that When the positive electrode interface of the solid electrolyte layer is treated, the argon-oxygen mixed gas is introduced into the positive electrode interface, and argon is introduced into the negative electrode interface, so that the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the positive electrode interface is lower than the pressure at the negative electrode interface; when the negative electrode interface of the solid electrolyte layer is treated, the argon-oxygen mixed gas is introduced into the negative electrode interface, and argon is introduced into the positive electrode interface, so that the pressure at the positive electrode interface and the pressure at the negative electrode interface are kept constant, and the pressure at the negative electrode interface is lower than the pressure at the positive electrode interface.

3. The method according to claim 1, characterized in that The argon-oxygen mixed gas is prepared by a two-stage or multi-stage gas mixing method.

4. The method according to claim 1, characterized in that The solid electrolyte layer is formed by pressing solid electrolyte powder.

5. A device for differentially modifying the surfaces of both sides of a solid electrolyte layer, characterized in that: The method according to any one of claims 1 to 4 comprises: An atmosphere control module, which is used to prepare the argon-oxygen mixed gas and control the circulation of the argon-oxygen mixed gas to achieve modification of the positive electrode interface and the negative electrode interface of the solid electrolyte layer in atmospheres with different oxygen volume fractions; A temperature control module is used to control the surface temperature of the solid electrolyte layer so as to modify the positive electrode interface and the negative electrode interface of the solid electrolyte layer at different temperatures.

6. The device according to claim 5, characterized in that The atmosphere control module includes a flow control valve, a gas mixing device, a gas valve, a gas circulation pump and a gas replenishing device, wherein the flow control valve is used to control the gas flow, the gas mixing device is a two-stage or multi-stage gas mixing device, the gas valve is used to control the circulation of the gas, the gas circulation pump provides power for the gas circulation, and the gas replenishing device is used to replenish the consumed oxygen; the temperature control module includes a high-temperature furnace, a sample chamber, a temperature controller and a fixed bracket, the sample chamber is arranged in the high-temperature furnace, the fixed bracket and the temperature controller are both arranged in the sample chamber, the solid electrolyte layer is arranged between the fixed brackets, the solid electrolyte layer divides the sample chamber into a positive electrode chamber and a negative electrode chamber, and the temperature controllers respectively arranged in the positive electrode chamber and the negative electrode chamber are arranged on the fixed bracket and are respectively close to the positive electrode interface and the negative electrode interface of the solid electrolyte layer.

7. The device according to claim 6, characterized in that When the positive electrode interface of the solid electrolyte layer is processed, the temperature controller arranged at the positive electrode interface is removed, so that the positive electrode interface of the solid electrolyte layer is exposed to the positive electrode chamber, the argon-oxygen mixed gas is introduced into the positive electrode chamber, and argon is introduced into the negative electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are kept unchanged by the gas circulation pump and the gas replenishing device, and the positive electrode chamber pressure is lower than the negative electrode chamber pressure; when the negative electrode interface of the solid electrolyte layer is processed, the temperature controller arranged at the negative electrode interface is removed, so that the negative electrode interface of the solid electrolyte layer is exposed to the negative electrode chamber, the argon-oxygen mixed gas is introduced into the negative electrode chamber, and argon is introduced into the positive electrode chamber, and the positive electrode chamber pressure and the negative electrode chamber pressure are kept unchanged by the gas circulation pump and the gas replenishing device, and the negative electrode chamber pressure is lower than the positive electrode chamber pressure.

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