Concentration cell device and its applications

Abstract

The application provides a concentration cell device and application thereof, and belongs to the technical field of batteries. The concentration cell device comprises a shell, a liquid storage structure, a limited domain diaphragm and a pole piece assembly are arranged in the shell; the liquid storage structure comprises an annular gasket and a porous material arranged in the annular gasket, the liquid storage structure comprises two groups, the porous material of one group of the liquid storage structure is configured to store a first electrolyte, the porous material of the other group of the liquid storage structure is configured to store a second electrolyte, the electrolytes of the first electrolyte and the second electrolyte are the same, and the concentrations are different; the limited domain diaphragm is arranged between the two groups of liquid storage structures, and the limited domain diaphragm comprises a limited domain ring and a separation film arranged in the limited domain ring. The pole piece assembly comprises a positive pole piece and a negative pole piece, the positive pole piece abuts against one group of the liquid storage structure, and the negative pole piece abuts against the other group of the liquid storage structure. The application can improve the problem of poor consistency when the open circuit voltage is tested by the concentration cell device.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a concentration cell device and its application. Background Technology

[0002] Open-circuit voltage (OCV) is an important parameter for measuring the thermodynamic state of an electrolyte in a battery system. When lithium metal is used as the electrode in a battery system, the OCV reflects the lithium-ion activity on the surface of the lithium metal electrode in the electrolyte. Electrolytes with low lithium-ion activity will produce large concentration polarization during the operation of lithium-ion batteries, resulting in low rate performance, unnecessary side reactions, and aging. Therefore, it is necessary to conduct preliminary testing of the electrolyte.

[0003] The conventional method is to construct a concentration cell and test its open-circuit voltage. However, existing concentration cell structures have poor consistency when testing open-circuit voltage. Summary of the Invention

[0004] In view of the above problems, this application provides a concentration cell device and its application, which aims to improve the problem of poor consistency when testing open-circuit voltage.

[0005] In a first aspect, this application provides a concentration cell device, including a housing, within which are disposed a liquid storage structure, a confining diaphragm, and an electrode assembly. The liquid storage structure includes an annular gasket and a porous material disposed within the annular gasket. The liquid storage structure is provided in two sets, one set of which is configured to store a first electrolyte, and the other set of which is configured to store a second electrolyte. The first and second electrolytes have the same electrolyte but different concentrations. The confining diaphragm is disposed between the two sets of liquid storage structures, and includes a confining ring and a separating membrane disposed within the confining ring. The electrode assembly includes a positive electrode and a negative electrode, the positive electrode abutting against one set of the liquid storage structures, and the negative electrode abutting against the other set of the liquid storage structures.

[0006] In the technical solution of this application embodiment, the first electrolyte and the second electrolyte can be added to a porous material storage system with two sets of liquid storage structures. The first electrolyte and the second electrolyte are separated by a confinement ring and diffuse through a separator membrane. The porous material uniformly adsorbs the electrolyte, reducing local concentration abrupt changes (such as the "liquid bridge" effect) caused by direct contact between droplets and the separator membrane. This allows the electrolyte to diffuse uniformly, helping to form a stable concentration gradient and thus improving measurement consistency. Furthermore, the porous material slows down the free diffusion of the electrolyte through physical confinement and capillary action, delaying the mixing rate of the first and second electrolytes on both sides of the separator membrane, extending the effective measurement time and ensuring a more ample measurement window. The three-dimensional network structure of the porous material promotes uniform distribution of the electrolyte on the electrode surface, avoiding "false concentration differences" caused by uneven wetting and optimizing the electrode-electrolyte interface contact. In other words, the porous material can also improve the accuracy of test measurement data and the repeatability of experiments by physically confining the electrolyte and homogenizing the interface contact.

[0007] In some embodiments, the outer periphery of the porous material is fitted with the inner ring of the annular gasket, and the outer periphery of the separator is fitted with the inner ring of the confinement ring; the inner diameter of the confinement ring is smaller than the inner diameter of the annular gasket.

[0008] In the technical solution of this application embodiment, when the inner diameter of the confinement ring is smaller than the inner diameter of the annular gasket, it means that the size of the separator is smaller than the size of the porous material. The oversized design of the porous material (extending beyond the separator region) forms a physical barrier, which can block the "bypass diffusion" (such as capillary climb or lateral permeation) of the electrolyte through the edge of the separator, so that the concentration gradient is established only in the effective area of ​​the separator, which helps to improve the stability of the concentration gradient. In addition, when the size of the separator is smaller than the size of the porous material, the electrolyte needs to diffuse laterally to the boundary of the separator in the porous material first, forming a quasi-one-dimensional diffusion field, avoiding the uneven concentration distribution caused by three-dimensional diffusion. Therefore, setting the inner diameter of the confinement ring to be smaller than the inner diameter of the annular gasket can help improve the consistency of measurement.

[0009] In some embodiments, the outer diameter of the confinement ring is larger than the outer diameter of the annular gasket; or, the outer diameter of the confinement ring is larger than the inner diameter of the outer shell.

[0010] In the technical solution of this application embodiment, when the outer diameter of the confinement ring is greater than the outer diameter of the annular gasket or greater than the inner diameter of the shell, the risk of bypass diffusion of the electrolyte can be further reduced.

[0011] In some embodiments, the porous material includes at least one of porous ceramics and polymer fiber membranes; the porosity of the porous material is 10%-50%.

[0012] In the technical solution of this application embodiment, porous materials are used to store electrolyte. When the porosity of the porous material is between 10% and 50%, it can effectively adsorb and store the electrolyte in its pore structure, thereby having a certain physical confinement effect. Porous ceramics and polymer fiber membranes both have high porosity and can effectively store electrolyte.

[0013] In some embodiments, the porosity of the isolation membrane is 10%-50%.

[0014] In the technical solution of this application embodiment, the separator forms a diffusion channel for the electrolyte, and the porosity of the separator is 10%-50%, which is beneficial to the transport of the electrolyte.

[0015] In some embodiments, the housing includes a first housing and a second housing, which are fastened together; the diameter of the housing is 9.5mm-30mm, and the thickness of the housing is 1.5mm-8.0mm.

[0016] In the technical solution of this application embodiment, the outer casing adopts a structure similar to that of a button battery casing. On the one hand, the size of the concentration cell can be reduced, thereby reducing electrolyte loss and lowering costs. On the other hand, the concentration cell device with a structure similar to that of a button battery casing can be adapted to a multi-channel testing device for button batteries, which helps to improve the testing throughput.

[0017] In some embodiments, when the porous material is a flexible material, the annular gasket is a rigid gasket; and / or, the outer diameter of the positive electrode and the negative electrode is larger than the inner diameter of the annular gasket.

[0018] In the technical solutions of this application embodiment, when the porous material is a flexible material, selecting an annular gasket as a rigid gasket, or when the outer diameter of the positive electrode and the negative electrode is larger than the inner diameter of the annular gasket, can reduce the occurrence of electrolyte seepage from the porous material due to the snapping and squeezing of the first shell and the second shell, thereby reducing the impact on the test results.

[0019] In some embodiments, the thickness of the porous material is 50 μm-800 μm; and / or, the diameter of the porous material is 8 mm-12 mm; and / or, the thickness of the separator is 50 μm-100 μm.

[0020] In the technical solution of this application embodiment, when the size of the shell is within the above-defined range, the thickness of the porous material is 50μm-800μm and the diameter is 8mm-12mm, which helps to accumulate a certain amount of electrolyte; the thickness of the separator is 50μm-100μm, which helps the electrolyte diffuse and form a stable ion transport pathway.

[0021] In some embodiments, an elastic element is provided inside the first housing or the second housing, one end of the elastic element abutting against the inner wall of the first housing or the first housing, and the other end abutting against the positive electrode or the negative electrode.

[0022] In the technical solution of this application embodiment, the elastic element can make the components fit tightly together, thereby providing a stable internal clamping force, reducing the occurrence of loosening, and thus helping to improve the stability of the concentration tank device.

[0023] In some embodiments, both the positive and negative electrode plates are lithium plates, and the electrolytes of the first and second electrolytes are both lithium salts.

[0024] In the technical solution of this application embodiment, when both the positive electrode and the negative electrode are lithium sheets, and both the first electrolyte and the second electrolyte are lithium salts, the properties and states of the electrodes can be better controlled during the test, reducing the impact caused by differences in electrode materials. The fact that the positive electrode and the negative electrode are made of the same electrode material also helps to keep the electrolyte in a relatively stable environment, which is beneficial to improving the reliability of the test results.

[0025] Secondly, this application provides the application of any of the above-mentioned concentration cell devices in testing the thermodynamic properties of electrolytes.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the concentration cell device in some embodiments of this application. Attached image description:

[0029] The concentration cell device 100 includes an outer shell 11, a first housing 111, a second housing 112, a first liquid storage structure 12, a first annular gasket 121, a first porous material 122, a second liquid storage structure 13, a second annular gasket 131, a second porous material 132, a confining diaphragm 14, a confining ring 141, a separating membrane 142, an electrode assembly 15, a positive electrode 151, a negative electrode 152, an elastic element 16, and a gasket 17. Detailed Implementation

[0030] The following embodiments are only used to illustrate the technical solutions of this application more clearly, and are therefore only examples and should not be used to limit the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0032] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). The term "at least one" refers to one or more.

[0036] A concentration cell is an electrochemical system consisting of two parts with the same electrolyte but different concentrations. Its open-circuit voltage (OCV) directly reflects the difference in ionic chemical potential in the electrolyte. By measuring the open-circuit voltage, parameters such as the activity coefficient and ion transport number of ions in the electrolyte can be analyzed, thereby enabling the evaluation of the electrolyte.

[0037] Some embodiments of concentration cells include two sets of electrolyte reservoirs and a separator disposed between the two reservoirs. The electrolyte reservoirs are formed by creating circular through-holes in the middle of a plate-like gel sample, and these through-holes are used to store electrolyte. Because the electrolyte is directly filled into the through-holes, the electrolyte on both sides diffuses and mixes rapidly through the separator, and there are localized concentration abrupt changes at the separator, resulting in a large deviation in the open-circuit voltage. It is possible to consider using porous materials to adsorb and store the electrolyte, thereby ensuring uniform electrolyte distribution and slowing down the diffusion time of the electrolyte. This helps stabilize the concentration gradient, extends the measurement window, and improves the measurement accuracy of the open-circuit voltage.

[0038] Based on the above considerations, this application provides a concentration cell device 100, with reference to... Figure 1 As shown, the device includes a housing 11, within which are disposed a first liquid storage structure 12, a second liquid storage structure 13, a confining diaphragm 14, and an electrode assembly 15. The first liquid storage structure 12 includes a first annular gasket 121 and a first porous material 122 disposed within the first annular gasket 121. The second liquid storage structure 13 includes a second annular gasket 131 and a second porous material 132 disposed within the second annular gasket 131. One of the first porous material 122 and the second porous material 132 is configured to store a first electrolyte, and the other of the first porous material 122 and the second porous material 132 is configured to store a second electrolyte. The first electrolyte and the second electrolyte have the same electrolyte but different concentrations. The confining diaphragm 14 is disposed between the first liquid storage structure 12 and the second liquid storage structure 13. The confining diaphragm 14 includes a confining ring 141 and a separating membrane 142 disposed within the confining ring 141. The electrode assembly 15 includes a positive electrode 151 and a negative electrode 152. The positive electrode 151 abuts against one of the first liquid storage structure 12 and the second liquid storage structure 13, and the negative electrode 152 abuts against the other of the first liquid storage structure 12 and the second liquid storage structure 13.

[0039] The housing 11 provides a space for accommodating the first liquid storage structure 12, the second liquid storage structure 13, the confining diaphragm 14, and the electrode assembly 1, as shown in the reference. Figure 1As shown, the outer shell 11 of this application can be cylindrical, but its shape is not limited to this; it can also be set as a cuboid or other shapes, as long as it meets the sealing structure requirements. This application does not impose specific restrictions on the material of the outer shell 11, as long as it has high stability in the electrolyte. For example, the material of the outer shell 11 can be one of fluorinated polymers, thermoplastic resins, glass, metal-ceramic composites, and stainless steel. Fluorinated polymers refer to polymeric compounds containing fluorine atoms in their molecular structure. The fluorine atoms can be located on the main chain and / or side chains of the polymeric compound. For example, fluorinated polymers can be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy polymers (PFA), tetrafluoroethylene-ethylene copolymers (ETFE), or tetrafluoroethylene-hexafluoropropylene copolymers (FEP). Thermoplastic resins refer to polymeric materials that soften upon heating and harden upon cooling. Examples of thermoplastic resins include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polycarbonate (PC), polyamide (PA), or polyester (PET, PBT). Glass is an amorphous inorganic non-metallic material whose main raw materials are various inorganic minerals such as quartz sand, soda ash, limestone, and feldspar. Its main component is silicon dioxide and other oxides. Metal-ceramic composite materials refer to composite materials with a ceramic layer coated on a metal surface.

[0040] The first annular gasket 121 and the second annular gasket 131 provide a space for accommodating the porous material. (Reference) Figure 1 As described above, both the first annular gasket 121 and the second annular gasket 131 in this application are annular, but their shapes are not limited to this and can match the shape of the outer casing 11. Regarding the material of the first annular gasket 121 and the second annular gasket 131, since they will come into contact with the electrolyte, it is necessary to select a material that is stable to the electrolyte.

[0041] In some embodiments, the materials of the first annular gasket 121 and the second annular gasket 131 can also be selected from fluorinated polymers, thermoplastic resins, glass, ceramic materials, etc. Since the electrolyte reacts with trace amounts of water to generate hydrofluoric acid, and the aforementioned materials have corrosion resistance to hydrofluoric acid; furthermore, under test conditions, the aforementioned materials do not react with the electrode in the presence of the electrolyte. Therefore, selecting the aforementioned materials for the annular gaskets not only ensures mechanical strength but also helps improve the stability of the concentration cell device.

[0042] The first porous material 122 and the second porous material 132 are used to store the electrolyte. (Reference) Figure 1As shown, the first porous material 122 is disposed in the central cavity of the first annular gasket 121. Both ends of the first porous material 122 can be flush with both ends of the first annular gasket 121, or the end of the first porous material 122 that contacts the separator 142 can be flush with the first annular gasket 121. The second porous material 132 is disposed similarly. This application does not limit the shape of the first porous material 122 and the second porous material 132, as long as they match the inner ring shape of the first annular gasket 121 and the second annular gasket 131.

[0043] Porous materials, with pores ranging from 1 nm to 100 μm in size, can adsorb electrolyte, reducing localized concentration abrupt changes (such as the "liquid bridge" effect) caused by direct contact between droplets and the separator 142. This allows for uniform electrolyte diffusion, contributing to a stable concentration gradient and improving measurement consistency. Furthermore, the porous material slows down the free diffusion of the electrolyte through physical confinement and capillary action, delaying the mixing rate of the first and second electrolytes on both sides of the separator 142, extending the effective measurement time and ensuring a more ample measurement window. The three-dimensional network structure of the porous material promotes uniform electrolyte distribution on the electrode surface, avoiding "false concentration differences" caused by uneven wetting and optimizing the electrode-electrolyte interface contact. In short, porous materials can also improve the accuracy and repeatability of test measurement data by physically confining the electrolyte and homogenizing the interface contact.

[0044] The confinement membrane 14 refers to a component that restricts the diffusion channel of the electrolyte. The confinement ring 141 stably separates the first and second electrolytes, while the separator 142 allows the first and second electrolytes to diffuse through. The separator 142 has good wettability to the electrolyte and a uniform diffusion path, enabling effective ion transport and facilitating the formation of a stable concentration gradient, thereby improving measurement accuracy. For the purpose of the confinement ring 141, its material must prevent electrolyte passage. In some embodiments, the material of the confinement ring 141 can be at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyetheretherketone, perfluoroalkyl ether, and fluorinated ethylene propylene copolymer. The separator can be any known porous structure separator with good chemical and mechanical stability. In some embodiments, the separator material can be at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0045] The positive electrode 151 abuts against one of the first electrolyte storage structures 12 and the second electrolyte storage structure 13, while the negative electrode 152 abuts against the other of the first electrolyte storage structures 12 and the second electrolyte storage structure 13. This means that the abutment of the positive electrode 151 and the negative electrode 152 needs to be determined based on the concentration of the electrolyte in the first electrolyte storage structure 12 and the second electrolyte storage structure 13. When the concentration of the first electrolyte in the first electrolyte storage structure 12 is higher than the concentration of the second electrolyte in the second electrolyte storage structure 13, the positive electrode 151 abuts against the first electrolyte storage structure 12, and the negative electrode 152 abuts against the first electrolyte storage structure 12. That is, the positive electrode 151 is in contact with the electrolyte storage structure with a high electrolyte concentration, and the negative electrode 152 is in contact with the electrolyte storage structure with a low electrolyte concentration.

[0046] According to some embodiments of this application, the outer periphery of the first porous material 122 is bonded to the inner ring of the first annular gasket 121, the outer periphery of the second porous material 132 is bonded to the inner ring of the second annular gasket 131, and the outer periphery of the separator 142 is bonded to the inner ring of the confinement ring 141; the inner diameter of the confinement ring 141 is smaller than the inner diameters of the first annular gasket 121 and the second annular gasket 131.

[0047] The outer periphery of the first porous material 122 is fitted to the inner ring of the first annular gasket 121, meaning that the shape and size of the first porous material 122 match the shape and size of the inner ring of the first annular gasket 121. This allows the electrolyte to be almost completely stored within the pores of the first porous material 122, reducing electrolyte diffusion from the gap between the first porous material 122 and the first annular gasket 121, thus helping to stabilize the concentration gradient. The same principle applies when the outer periphery of the second porous material 132 is fitted to the inner ring of the second annular gasket 131.

[0048] Based on the bonding arrangement of the porous material and the annular gasket, when the inner diameter of the confinement ring 141 is smaller than the inner diameters of the first annular gasket 121 and the second annular gasket 131, it means that the size of the separator 142 is smaller than the size of the first porous material 122 and the second porous material 132. The oversized design of the first porous material 122 and the second porous material 132 (extending beyond the area of ​​the separator 142) forms a physical barrier, which can block the "bypass diffusion" (such as capillary climb or lateral permeation) of the electrolyte through the edge of the separator 420, so that the concentration gradient is established only in the effective area of ​​the separator 142, which helps to improve the stability of the concentration gradient. In addition, when the size of the separator 142 is smaller than the size of the first porous material 122 and the second porous material 132, the electrolyte needs to diffuse laterally in the first porous material 122 and the second porous material 132 to the boundary of the separator 142, forming a quasi-one-dimensional diffusion field, avoiding uneven concentration distribution caused by three-dimensional diffusion. Therefore, setting the inner diameter of the limiting ring 141 to be smaller than the inner diameters of the first annular gasket 121 and the second annular gasket 131 helps to improve the consistency of measurements.

[0049] According to some embodiments of this application, the outer diameter of the confinement ring 141 is larger than the outer diameters of the first annular gasket 121 and the second annular gasket 131; or, the outer diameter of the confinement ring 141 is larger than the inner diameter of the outer shell 11. When the outer diameter of the confinement ring 141 is larger than the outer diameters of the first annular gasket 121 and the second annular gasket 131 or larger than the inner diameter of the outer shell 11, the risk of electrolyte bypass diffusion can be further reduced.

[0050] According to some embodiments of this application, the first porous material 122 and the second porous material 132 each comprise at least one of porous ceramics and polymer fiber membranes; the porosity of the first porous material 122 and the second porous material 132 is 10%-50%.

[0051] Porous ceramics refer to ceramic materials containing a large number of pores. These pores vary in size, ranging from micropores (pore size less than 2 nm), mesopores (pore size between 2 nm and 50 nm) to macropores (pore size greater than 50 nm), with porosity typically between 30% and 90%. Polymer fiber membranes possess a unique fibrous structure; these fibers can be randomly or directionally arranged, forming a porous network structure. Therefore, porous ceramics and polymer fiber membranes can meet the requirements for adsorption and storage of electrolytes. In some embodiments, the polymer fiber membrane includes at least one of polyethylene membranes, polypropylene membranes, and polyvinylidene fluoride membranes.

[0052] Porosity refers to the percentage of pore mass to the total mass of a material. When the porous material is a polymer fiber membrane, the porosity of the first porous material 122 can be tested by the liquid absorption method. The test method includes: first, accurately weighing the dry membrane mass of the separator using a high-precision balance, and recording it as μ0; completely immersing the weighed separator in anhydrous ethanol, ensuring sufficient soaking time so that the anhydrous ethanol can fully fill the pores of the separator. The soaking time should be reasonably set according to factors such as the material, thickness, and pore characteristics of the separator to ensure the best wetting effect; after soaking, quickly remove the separator from the anhydrous ethanol, and then gently wipe the surface of the separator with filter paper to remove the excess anhydrous ethanol. The wiping process should be done with extra care to avoid affecting the structure of the separator itself and the amount of ethanol adsorbed; after wiping, weigh the wet membrane mass again using the same high-precision balance, and record it as μ; finally, calculate the porosity ε according to formula (I).

[0053]

[0054] Where ρ is the density of the membrane material, ρ0 is the density of anhydrous ethanol, and V is the total volume of the membrane (which can be calculated by measuring the length, width, and thickness of the membrane). The porosity test of the second porous material 132 is similar.

[0055] Porous materials are used to store electrolytes. For example, the porosity of the porous material can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. When the porosity of the porous material is between 10% and 50%, the electrolyte can be effectively adsorbed and stored in its pore structure, thereby having a certain physical confinement effect.

[0056] According to some embodiments of this application, the porosity of the separator 142 is 10%-50%.

[0057] For example, the porosity of the separator 142 can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. The separator 142 forms diffusion channels for the electrolyte, and a porosity of 10%-50% is beneficial for electrolyte transport. The method for testing the porosity of the separator 142 is the same as that for the first porous material 122.

[0058] In some embodiments, the material of the separator 142 includes at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0059] Based on some embodiments of this application, continue to refer to Figure 1As shown, the outer shell 11 includes a first shell 111 and a second shell 112, which are fastened together; the diameter of the outer shell 11 is 9.5mm-30mm, and the thickness of the outer shell 11 is 1.5mm-8.0mm.

[0060] When the first housing 111 and the second housing 112 are fastened together, the inner diameter of the first housing 111 may be larger than the inner diameter of the second housing 112, and the first housing 111 may be fastened to the outside of the second housing 112; or the inner diameter of the second housing 112 may be larger than the outer diameter of the first housing 111, and the second housing 112 may be fastened to the outside of the first housing 111.

[0061] When the outer casing 11 is configured as described above, it has a structure similar to that of a button battery casing. In this case, the first casing 111 and the second casing 112 correspond to the positive electrode casing and the negative electrode casing, respectively, and are made of stainless steel. In some embodiments, the outer casing 11 has a diameter of 9.5 mm and a thickness of 2.7 mm; or, a diameter of 10 mm and a thickness of 2.5 mm; or, a diameter of 12.5 mm and a thickness of 2 mm; or, a diameter of 16 mm and a thickness of 1.6 mm, 2 mm, or 3.2 mm; or, a diameter of 20 mm and a thickness of 1.6 mm, 2.5 mm, or 3.2 mm; or, a diameter of 23 mm and a thickness of 2 mm, 3 mm, 3.5 mm, or 5.4 mm; or, a diameter of 24.5 mm and a thickness of 3 mm, 5 mm, or 7.7 mm; or, a diameter of 30 mm and a thickness of 3.2 mm.

[0062] When the casing 11 adopts a button cell casing structure, on the one hand, the size of the concentration cell can be reduced, thereby reducing electrolyte loss and lowering costs; on the other hand, the concentration cell device with the button cell casing structure can be adapted to multi-channel testing devices for button cells, which helps to improve test throughput.

[0063] According to some embodiments of this application, under the condition that the first porous material 122 and the second porous material 132 are flexible materials, the first annular gasket 121 and the second annular gasket 131 are rigid gaskets; and / or, the outer diameter of the positive electrode 151 and the negative electrode 152 is greater than the inner diameter of the first annular gasket 121 and the second annular gasket 131.

[0064] When the first porous material 122 and the second porous material 132 are flexible materials, the electrolyte can easily seep out from them when the first housing 111 and the second housing 112 are fastened together under pressure, thus affecting the test results. Therefore, when the first annular gasket 121 and the second annular gasket 131 are rigid gaskets, they can withstand the pressure when the first housing 111 and the second housing 112 are fastened together, thereby reducing the possibility of electrolyte seepage from the porous materials due to compression. When the outer diameter of the positive electrode 151 and the negative electrode 152 is larger than the inner diameter of the first annular gasket 121 and the second annular gasket 131, the positive electrode 151 and the negative electrode 152 will not enter the inner ring of the annular gasket under pressure, thereby reducing the compression of the porous materials and further reducing the possibility of electrolyte seepage from the porous materials.

[0065] According to some embodiments of this application, the thickness of the first porous material 122 and the second porous material 132 is 50μm-800μm; and / or, the diameter of the first porous material 122 and the second porous material 132 is 8mm-12mm; and / or, the thickness of the separator 142 is 50μm-100μm.

[0066] Based on the size range of the housing 11 described above, the diameters and thicknesses of the first porous material 122 and the second porous material 132, as well as the thickness of the separator 142, are further defined. For example, the thicknesses of the first porous material 122 and the second porous material 132 can be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, or 800 μm; the diameters of the first porous material 122 and the second porous material 132 can be 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm, or 12 mm; when the thicknesses of the first porous material 122 and the second porous material 132 are between 50 μm and 800 μm, and the diameters are between 8 mm and 12 mm, it helps to accumulate a certain amount of electrolyte. The thickness of the separator 142 can be 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm. When the thickness of the separator 142 is between 50μm and 100μm, it helps the electrolyte to diffuse and form a stable ion transport pathway.

[0067] Based on some embodiments of this application, continue to refer to Figure 1 As shown, an elastic element 16 is provided inside the first housing 111 or the second housing 112. One end of the elastic element 16 abuts against the inner wall of the first housing 111 or the first housing 112, and the other end abuts against the positive electrode plate 151 or the negative electrode plate 152.

[0068] by Figure 1 For example, one end of the elastic element 16 abuts against the inner wall of the first housing 111, and the other end abuts against the negative electrode plate 152. The elastic element 16 can make the components fit tightly together, thereby providing a stable internal clamping force, reducing the occurrence of loosening, and thus helping to improve the stability of the concentration cell device.

[0069] In some embodiments, the elastic element 16 is a stainless steel spring sheet. The stainless steel spring sheet has good elasticity and can provide a certain pressure to ensure a good electrical connection between the first housing 111, the second housing 112, and the positive electrode 151 and the negative electrode 152. At this time, a gasket 17 is also provided between the elastic element 16 and the negative electrode 152. The gasket 17 is made of insulating material and plays the role of insulation and isolation.

[0070] According to some embodiments of this application, both the positive electrode 151 and the negative electrode 152 are lithium sheets, and both the first electrolyte and the second electrolyte are lithium salts.

[0071] When both the positive electrode 151 and the negative electrode 152 are lithium sheets, the electrolytes of both the first and second electrolytes are lithium salts. This allows for better control of the electrode properties and states during testing, reducing the impact of differences in electrode materials. The fact that the positive electrode 151 and the negative electrode 152 are made of the same electrode material also helps to keep the electrolyte in a relatively stable environment, which is beneficial to improving the reliability of the test results.

[0072] In some embodiments, the electrolyte lithium salt of the first electrolyte and the second electrolyte may be one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0073] According to some embodiments of this application, this application also provides the application of any of the above concentration cell devices in testing the thermodynamic properties of electrolytes.

[0074] In some embodiments, the thermodynamic properties of the electrolyte can be balanced by testing the open-circuit voltage of any of the concentration cell devices described above. The testing process for the open-circuit voltage of the concentration cell device includes: connecting the concentration cell device 100 to a voltage detector, and obtaining the voltage signal during the stable phase as the open-circuit voltage U of the concentration cell device 100. cc .

[0075] In some embodiments, the activity coefficient and thermodynamic factor of the electrolyte can also be tested using any of the concentration cell devices described above. The testing method includes connecting the concentration cell device 100 to a voltage detector and taking the voltage signal during the stable phase as the open-circuit voltage U of the concentration cell device 100. cc ; Test the open-circuit voltage U of concentration cell device 100 corresponding to n different concentration gradients. cc According to n groups of U cc ln(c 第二 / c 第一 Data fitting yields U cc With ln(c 第二 / c 第一 The relationship curve is obtained to obtain the activity coefficient value and thermodynamic factor value.

[0076] Among them, c 第一 c is the concentration of the first electrolyte. 第二 The concentration of the second electrolyte is given. The concentration of the first electrolyte, c, is given under different concentration gradients. 第一 Both are c0, and the concentration of the second electrolyte is c. 第二 They are c1, c2, c3, c4…c n Or, the concentration c of the first electrolyte at different concentration gradients. 第一 They are c0, c1, c2, c3…c n-1 The concentration c of the second electrolyte 第二 Corresponding to c1, c2, c3, c4…c n The concentration difference between the first and second electrolytes |c 第二 -c 第一 |=0.25mol / L-2mol / L.

[0077] According to U cc With ln(c 第二 / c 第一 The relationship curves for determining the activity coefficient and / or thermodynamic factor values ​​are based on the following equations (II) and (III):

[0078]

[0079] Among them, U cc : Open-circuit voltage of the concentration cell device; f ± Mean activity coefficient; Migration number; C: electrolyte concentration; R: gas constant; T: temperature; F: Faraday constant.

[0080] Example

[0081] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0082] Example 1

[0083] [Concentration chamber apparatus]

[0084] refer to Figure 1 As shown, the concentration cell device 100 of this embodiment has a button cell housing structure. The concentration cell device 100 includes, from bottom to top, a positive electrode shell (first shell 111), a lithium sheet (positive electrode 151), a first liquid storage structure 12, a confining membrane 14, a second liquid storage structure 13, a lithium sheet (negative electrode 152), a gasket 17, a spring sheet (elastic element 16), and a negative electrode shell (second shell 112). The positive electrode shell, lithium sheet, first liquid storage structure 12, confining membrane 14, second liquid storage structure 13, lithium sheet, gasket 17, spring sheet, and negative electrode shell are centrally arranged.

[0085] The first shell 111 and the second shell 112 both have circular cross-sections and are made of stainless steel. The overall diameter of the outer shell 11 formed by the first shell 111 and the second shell 112 after being fastened together is 24.5 mm and the thickness is 5 mm.

[0086] The first liquid storage structure 12 includes a first annular gasket 121 and a first porous material 122 disposed within the cavity of the first annular gasket 121. The second liquid storage structure 13 includes a second annular gasket 131 and a second porous material 132 disposed within the cavity of the second annular gasket 131. The first annular gasket 121 is a circular gasket with an inner diameter of 10 mm and a thickness of 50 μm. The material of the first annular gasket 121 is a fluorinated polymer. The second annular gasket 131 has the same structure as the first annular gasket 121. The first porous material 122 is a disc with a diameter of 10 mm and a thickness of 50 μm. The first porous material 122 is made of polypropylene fiber membrane. The second porous material 132 has the same structure as the first porous material 122.

[0087] The confinement diaphragm 14 includes a confinement ring 141 and a separator 142 disposed in the annular cavity of the confinement ring 141. The confinement ring 141 is annular in shape, made of polytetrafluoroethylene, with an inner diameter of 5 mm and a thickness of 50 μm. The separator 142 is disc-shaped, with a diameter of 5 mm and a thickness of 50 μm, and is made of polypropylene.

[0088] The positive electrode 151, the negative electrode 152, the first annular gasket 121, and the second annular gasket 131 have the same diameter, while the outer diameter of the limiting ring 141 is larger than the outer diameter of the above components.

[0089] The elastic element 16 is a stainless steel spring sheet, which can provide a stable internal clamping force. The gasket 17 is an insulating gasket.

[0090] Assembly of the concentration cell device

[0091] In a glove box or dry room environment, take the first housing 111 (positive electrode housing) and add the positive electrode 151 (lithium sheet). Completely cover the positive electrode 151 with the first annular gasket 121. Place the first porous material 122 in the cavity of the first annular gasket 121. Add 20 μl of the first electrolyte (high-concentration electrolyte) to the first porous material 122. Cover the first annular gasket 121 with the confinement membrane 14. Place the second annular gasket 131 centrally on the confinement membrane 14. Place the second porous material 132 in the cavity of the second annular gasket 131. Add 20 μl of the second electrolyte (low-concentration electrolyte) to the second porous material 132. Place the negative electrode 152 (lithium sheet) on the second annular gasket 131. This constitutes the positive electrode housing component. Place the elastic spring 16 (stainless steel spring) and the gasket 17 in the second housing 112 (negative electrode housing) to constitute the negative electrode housing component. The positive electrode shell and the negative electrode shell are pressed together using a packaging machine to obtain a concentration cell device.

[0092] Example 2

[0093] Unlike Example 1, in this example, the thickness of the first porous material 122 and the second porous material 132 is 400 μm, and the thickness of the first annular gasket 121 and the second annular gasket 131 is adjusted accordingly.

[0094] Example 3

[0095] Unlike Example 1, in this example, the thickness of the first porous material 122 and the second porous material 132 is 800 μm, and the thickness of the first annular gasket 121 and the second annular gasket 131 is adjusted accordingly.

[0096] Example 4

[0097] Unlike Example 1, in this example, the thickness of the isolation membrane 142 is 80 μm, and the thickness of the confinement ring 141 is adjusted accordingly.

[0098] Example 5

[0099] Unlike Example 1, in this example, the thickness of the isolation membrane 142 is 100 μm, and the thickness of the confinement ring 141 is adjusted accordingly.

[0100] Example 6

[0101] Unlike Example 1, in this example, the diameter of the isolation membrane 142 is 3mm, and the inner diameter of the confinement ring 141 is adjusted accordingly.

[0102] Example 7

[0103] Unlike Example 1, in this example, the diameter of the isolation membrane 142 is 8 mm, and the inner diameter of the confinement ring 141 is adjusted accordingly.

[0104] Comparative Example 1

[0105] Unlike Example 1, this comparative example does not provide a first porous material 122 in the first annular gasket 121, nor does it provide a second porous material 132 in the second annular gasket 131. The electrolyte is directly dripped into the cavity of the annular gasket.

[0106] Comparative Example 2

[0107] Unlike Example 1, this comparative example has an isolation membrane directly disposed between the first liquid storage structure 12 and the second liquid storage structure 13 to allow electrolyte diffusion.

[0108] Performance testing

[0109] Consistency of open-circuit voltage testing: Electrolytes with different concentration gradients were set up, with three concentration gradients: 0.1 mol / L-0.5 mol / L, 0.5 mol / L-1 mol / L, and 1 mol / L-1.5 mol / L. Concentration cell devices were constructed using these three concentration gradients. Open-circuit voltage tests were performed on the three concentration cell devices, and the voltage signal in the stable range was taken as the electrochemical potential difference of the concentration cell device. Each concentration cell device was tested six times repeatedly, and the consistency of the test was represented by the standard deviation of the six test results.

[0110] Test Results

[0111] The test results of Examples 1-7 and Comparative Examples 1-2 are shown in Tables 1-9, respectively.

[0112] Table 1. Test results of open-circuit voltage in Example 1

[0113]

[0114] Table 2 shows the test results of the open-circuit voltage in Example 2.

[0115]

[0116] Table 3 shows the test results of the open-circuit voltage in Example 3.

[0117]

[0118] Table 4 shows the test results of the open-circuit voltage in Example 4.

[0119]

[0120] Table 5. Test results of open-circuit voltage in Example 5

[0121]

[0122]

[0123] Table 6 shows the test results of the open-circuit voltage in Example 6.

[0124]

[0125] Table 7 shows the test results of the open-circuit voltage in Example 7.

[0126]

[0127] Table 8 shows the test results of the open-circuit voltage in Comparative Example 1.

[0128]

[0129] Table 9 shows the test results of the open-circuit voltage in Comparative Example 2.

[0130]

[0131] Table 10 shows a comparison table of the test results in Examples 1-7 and Comparative Examples 1-2.

[0132] Table 10 shows the test results of open-circuit voltage in Examples 1-7 and Comparative Examples 1-2.

[0133]

[0134] As can be seen from Table 10, the concentration cell devices in the embodiments of this application all have small standard deviations when testing open-circuit voltage, indicating that the concentration cell devices in the embodiments of this application have high repeatability and can improve the consistency of testing.

[0135] Compared to Comparative Example 1, this application significantly improves the consistency of the test structure by absorbing and storing the electrolyte through a first porous material and a second porous material. Furthermore, this application confines the electrolyte transport channel to a smaller area using a confinement ring, resulting in higher test consistency compared to the direct transport via the isolation membrane in Comparative Example 2.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A concentration cell device, characterized in that, Includes a housing, and the housing contains: The liquid storage structure includes an annular gasket and a porous material disposed within the annular gasket. The liquid storage structure is provided in two sets, one set of which is configured to store a first electrolyte and the other set of which is configured to store a second electrolyte. The first electrolyte and the second electrolyte have the same electrolyte but different concentrations. A confining diaphragm is disposed between the two sets of the liquid storage structures, and the confining diaphragm includes a confining ring and an isolation membrane disposed within the confining ring; An electrode assembly includes a positive electrode and a negative electrode, wherein the positive electrode abuts against one set of the liquid storage structures and the negative electrode abuts against another set of the liquid storage structures.

2. The concentration cell apparatus as described in claim 1, characterized in that, The outer periphery of the porous material is bonded to the inner ring of the annular gasket, and the outer periphery of the separator is bonded to the inner ring of the confinement ring; The inner diameter of the confinement ring is smaller than the inner diameter of the annular gasket.

3. The concentration cell apparatus as described in claim 2, characterized in that, The outer diameter of the confinement ring is greater than the outer diameter of the annular gasket; or, the outer diameter of the confinement ring is greater than the inner diameter of the outer shell.

4. The concentration cell apparatus according to any one of claims 1 to 3, characterized in that, The porous material includes at least one of porous ceramics and polymer fiber membranes; The porosity of the porous material is 10%-50%.

5. The concentration cell apparatus according to any one of claims 1 to 3, characterized in that, The porosity of the isolation membrane is 10%-50%.

6. The concentration cell apparatus according to any one of claims 1 to 5, characterized in that, The outer casing includes a first casing and a second casing, which are fastened together. The diameter of the outer shell is 9.5mm-30mm, and the thickness of the outer shell is 1.5mm-8.0mm.

7. The concentration cell apparatus as described in claim 6, characterized in that, When the porous material is a flexible material, the annular gasket is a rigid gasket; and / or, The outer diameter of the positive electrode and the negative electrode is larger than the inner diameter of the annular gasket.

8. The concentration cell apparatus as described in claim 6, characterized in that, The thickness of the porous material is 50μm-800μm; and / or the diameter of the porous material is 8mm-12mm; and / or the thickness of the separator is 50μm-100μm.

9. The concentration cell apparatus according to any one of claims 6 to 8, characterized in that, An elastic element is provided inside the first housing or the second housing. One end of the elastic element abuts against the inner wall of the first housing or the first housing, and the other end abuts against the positive electrode or the negative electrode.

10. The concentration cell apparatus according to any one of claims 1 to 9, characterized in that, Both the positive and negative electrode sheets are lithium sheets, and the electrolytes of the first and second electrolytes are lithium salts.

11. The application of a concentration cell apparatus as described in any one of claims 1 to 10 in testing the thermodynamic properties of electrolytes.

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