Test battery and test equipment

Abstract

The application discloses a test battery and a test device, and relates to the technical field of battery processing. The test battery comprises a shell, an electrode assembly and a separator. The electrode assembly is arranged in the shell. The electrode assembly comprises a working electrode and an auxiliary electrode which are oppositely arranged along a first direction. The working electrode is arranged as a metal tab. A surface of the metal tab facing the auxiliary electrode is provided with a plurality of recesses. The separator is arranged between the working electrode and the auxiliary electrode, and is used for soaking electrolyte. According to the technical scheme, the plurality of recesses are arranged on the surface of the metal tab facing the auxiliary electrode, so that the specific surface area of the metal tab is increased. The increase of the specific surface area can provide more growth space for the deposition of lithium ions, and can also reduce the current density in the deposition process and reduce the growth of lithium dendrites. This also means that the metal tab can withstand greater test current, and the rapid measurement of coulomb efficiency is realized.

Description

Technical Field

[0001] This application relates to the field of battery processing technology, and in particular to a test battery and test equipment. Background Technology

[0002] In the field of new energy batteries, the coulombic efficiency of a battery reflects the utilization rate of reversible charge during charge-discharge cycles. Coulombic efficiency is usually used as an important indicator to measure the performance of electrolytes. Currently, the testing of coulombic efficiency takes a long time, which is not conducive to technicians conducting large-scale screening of electrolytes. Utility Model Content

[0003] The main objective of this application is to propose a test battery and test equipment that aims to improve the current problem of long measurement time for battery coulombic efficiency.

[0004] Firstly, the test battery proposed in this application is used to test the effect of electrolyte on coulombic efficiency, said test battery comprising:

[0005] shell;

[0006] An electrode assembly, disposed within a housing, includes a working electrode and an auxiliary electrode disposed opposite each other along a first direction. The working electrode is configured as a metal electrode sheet, and the surface of the metal electrode sheet facing the auxiliary electrode has a plurality of recesses.

[0007] A separating membrane is disposed between the working electrode and the auxiliary electrode, and the separating membrane is used to wet the electrolyte.

[0008] The technical solution provided in this application, since the metal electrode is the working electrode, lithium ions will be deposited on the surface of the metal electrode during the test. Multiple recesses are set on the surface of the metal electrode facing the auxiliary electrode, which can increase the specific surface area of ​​the metal electrode. The increase in specific surface area can provide more growth space for lithium ion deposition on the one hand, and reduce the current density during the deposition process on the other hand, reducing the growth of lithium dendrites. This also means that the metal electrode can withstand a larger test current. Under the premise of ensuring that the lithium ion deposition capacity remains unchanged, a larger test current is beneficial to shorten the test time, realize the rapid measurement of coulombic efficiency, and facilitate technicians to conduct a large number of electrolyte screenings.

[0009] In some embodiments, the metal electrode includes a mesh structure, and the recess includes mesh openings in the mesh structure; and / or,

[0010] The metal electrode sheet comprises a foam structure, and the recess includes foam pores of the foam structure; and / or,

[0011] The metal electrode includes a nanoarray structure, and the recess includes the array gaps of the nanoarray structure.

[0012] In the above technical solutions, the mesh structure can be processed by etching, and the pore size of its mesh is easy to control. Mesh with specific pore size and density can be processed according to actual needs, that is, the specific surface area of ​​the mesh structure is easy to control. The pores of the foam structure are interconnected, allowing lithium ions to flow freely in three-dimensional space. The permeability of lithium ions is good. Moreover, the foam structure can withstand a certain mechanical load while maintaining a low density. The nanoarray structure can provide a large lithium deposition interface, which helps to reduce the current density. At the same time, the array gaps provide vertical channels for lithium ion diffusion, improving the lithium ion kinetic performance.

[0013] In some embodiments, the number of recesses provided per square foot of the metal electrode is between 150 and 250.

[0014] In the above technical solution, the number of recesses per square foot is between 150 and 250. While keeping the processing difficulty of the metal electrode sheet at an appropriate level, it can give the metal electrode sheet a larger specific surface area.

[0015] In some embodiments, the auxiliary electrode is a lithium sheet.

[0016] In the above technical solution, lithium sheet is selected as the auxiliary electrode. Lithium sheet can continuously and stably provide lithium ions, and the reaction of lithium sheet is simple and the potential is stable. In the scenario of testing coulombic efficiency, lithium sheet is an ideal auxiliary electrode material.

[0017] In some embodiments, the metal electrode is made of copper.

[0018] In the above technical solution, copper is electrochemically inert under the potential window of lithium deposition and stripping. This means that copper is difficult to alloy with lithium, and can provide a stable and pure "background". This allows the measurement current to come almost entirely from the lithium deposition and stripping reaction itself, so that the coulombic efficiency can be calculated most accurately.

[0019] In some embodiments, the housing includes two half-shells that are interlocked and insulated from each other along the first direction;

[0020] The metal electrode and the auxiliary electrode are electrically connected to the corresponding half-shell, respectively.

[0021] In the above technical solution, the outer shell is composed of two half-shells that are fastened together. The two half-shells are electrically connected to the metal electrode and the auxiliary electrode, respectively, and the two half-shells are insulated from each other. This is equivalent to limiting the test battery to a button cell structure, which is beneficial for efficiently measuring the performance of the electrolyte.

[0022] In some embodiments, an elastic conductive element is provided between the metal electrode and / or the auxiliary electrode and the corresponding half-shell.

[0023] In the above technical solution, since the metal electrode and the auxiliary electrode are electrically connected to the external circuit through two half-shells, the overall thickness of the metal electrode, the auxiliary electrode and the isolation film is usually smaller than the spacing between the inner surfaces of the two half-shells without affecting the snap-fit ​​assembly of the two half-shells. Based on this, an elastic conductive element is set between the metal electrode or the auxiliary electrode and the corresponding half-shell. The elastic conductive element can not only conduct electricity, but also use its own elastic properties to compensate for the assembly gap between the metal electrode or the auxiliary electrode and the corresponding half-shell, ensuring the stability of the overall structure.

[0024] In some embodiments, the elastic conductive element includes a gasket and a spring, the gasket being disposed abutting against the metal electrode, and the spring being disposed between the gasket and the corresponding half-shell.

[0025] In the above technical solution, considering that the metal electrode sheet is a thin sheet structure, the elastic conductive element is limited to a gasket and a spring sheet. The structural strength of the gasket is usually greater than that of the metal electrode sheet. The spring sheet indirectly abuts against the metal electrode sheet through the gasket. The function of the gasket is to increase the contact area of ​​the metal electrode sheet, thereby reducing the pressure on the metal electrode sheet and also reducing the probability of the elastic conductive element damaging the metal electrode sheet.

[0026] In some embodiments, the isolation membrane includes a membrane body, and at least one side of the membrane body in the thickness direction is provided with a edging structure. The membrane body includes an ion passage region in the middle and an edging region surrounding the ion passage region, and the edging structure is disposed in the edging region.

[0027] The projections of the metal electrode and the auxiliary electrode in the first direction cover the ion passage area.

[0028] In the above technical solution, the separator membrane is positioned between the metal electrode and the auxiliary electrode to prevent short circuits between them. Based on this, the edging structure is set in the edging area on the outer edge of the membrane body, which can define an ion passage area of ​​the target size in the middle of the membrane body. Furthermore, the projections of the metal electrode and the auxiliary electrode in the first direction cover the ion passage area, which means that the reaction area can be defined through the ion passage area, which is beneficial for controlling the test variables.

[0029] In some embodiments, the edging structure is configured as a polyimide film; and / or,

[0030] The membrane body is a polyethylene membrane.

[0031] In the above technical solution, polyimide has excellent insulation properties and can restrict the passage of ions. It is a commonly used material in the battery production field. Setting the edge-wrapping structure as a polyimide film helps to reduce the difficulty and cost of obtaining the edge-wrapping structure. The melting point of polyethylene film is about 135°C. When an abnormality occurs inside the battery (such as overcharging or short circuit) and the temperature rises and approaches the melting point, the polyethylene film will melt and shrink to close the original micropores. The closure of the micropores will block the transmission of lithium ions, thereby greatly increasing the internal resistance of the battery, effectively suppressing the current and preventing further aggravation of thermal runaway.

[0032] Secondly, this application also proposes a testing device, including a test battery. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the structure of an embodiment of the test battery provided in this application;

[0035] Figure 2 for Figure 1 A schematic diagram of the exploded structure of the battery being tested.

[0036] Figure 3 for Figure 2 Schematic diagram of the structure of the metal electrode sheet;

[0037] Figure 4 for Figure 2 A schematic diagram of the exploded structure of the middle separator membrane.

[0038] Explanation of icon numbers:

[0039] 100. Test the battery;

[0040] 1. Outer shell; 11. Semi-shell; 2. Electrode assembly; 21. Working electrode; 211. Recess; 21a. Metal electrode sheet; 211a. Mesh structure; 2111a. Mesh opening; 22. Auxiliary electrode; 22a. Lithium sheet; 3. Elastic conductive element; 31. Gasket; 32. Spring sheet; 4. Separating membrane; 41. Membrane body; 41a. Ion passage area; 41b. Edge-sealing area; 42. Edge-sealing structure;

[0041] X, the first direction.

[0042] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0043] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0050] In the field of new energy batteries, the coulombic efficiency of a battery reflects the utilization rate of reversible charge during charge-discharge cycles. Coulombic efficiency is usually used as an important indicator to measure the performance of electrolytes. Currently, the main methods for measuring coulombic efficiency are Cycle and Aurbach methods.

[0051] The Cycle method test principle is to deposit a certain capacity of lithium on a metal substrate and then strip it all off, thereby calculating the coulombic efficiency of the electrolyte. Since the deposition and stripping are greatly affected by the metal substrate, the coulombic efficiency fluctuates greatly per cycle. In order to obtain a stable coulombic efficiency, the number of cycles is mostly greater than 100 cycles, and the corresponding test time is greater than 200 hours.

[0052] The Aurbach method is a relatively fast detection method. Its working principle is to use a small capacity for cycling after large-capacity lithium deposition. Since the lithium deposited on the metal substrate is not completely stripped during the cycling process, the cycling process occurs on the surface of the deposited lithium, avoiding the influence of the metal substrate on deposition and stripping. The number of cycles can be reduced accordingly. The commonly used number of cycles is 10 cycles, and the test time is reduced to 66 hours.

[0053] However, even the 66-hour test time in the Aurbach method is still too long for technicians, making it difficult for them to screen a large number of electrolytes. Therefore, those skilled in the art urgently need to improve the existing coulombic efficiency measurement methods in order to shorten the test time.

[0054] For the Aurbach method, the specific testing procedure is as follows: 1. Deposit 4mAh cm⁻¹ -2 2. Complete stripping, cutoff voltage 1V; 3. Deposition of 4mAh cm⁻¹ -2 4. With 0.5mAh cm -2 Deposition and stripping, 10 cycles; 5. Complete stripping, cutoff voltage 1V, total current 0.4mA. -2 .

[0055] Theoretically, while maintaining the same deposition capacity, if the test current is increased from 0.4 mA cm⁻¹ -2Increased to 2.0 mAcm -2 The test time can be shortened from 66 hours to 13.5 hours. However, in the actual verification process, it was found that increasing the test current would cause lithium metal to grow dendrites on the surface of the metal substrate. Lithium dendrites are prone to piercing the isolation film, causing short circuits and test failure. At this point, the problem faced by the technicians became how to suppress the growth of lithium dendrites while ensuring a large test current.

[0056] Analysis revealed that the main reasons for lithium dendrite growth piercing the separator are: 1. Lithium deposition causes a huge volume expansion, and the planar two-dimensional structure of the metal substrate causes the deposited lithium to grow towards the separator; 2. Increasing the test current will cause a corresponding increase in current density, and a large current density will make the deposited lithium more inclined to dendrite growth.

[0057] In view of this, this application provides a test battery in which a metal electrode is used for lithium deposition. The surface of the metal electrode has a recessed structure. On the one hand, the recessed structure can give the metal electrode a certain three-dimensional depth, providing additional growth space for deposited lithium. On the other hand, the recessed structure is conducive to increasing the specific surface area of ​​the metal electrode, thereby reducing the current density and changing the growth direction of deposited lithium. Based on this, the test battery provided by this application can at least improve the problem of the long measurement time of coulombic efficiency.

[0058] To facilitate understanding of the test battery provided in this application, the following description is provided in conjunction with the accompanying drawings. Figure 1 A schematic diagram of the structure of an embodiment of the test battery provided in this application; Figure 2 for Figure 1 A schematic diagram of the exploded structure of the battery being tested. Figure 3 for Figure 2 Schematic diagram of the structure of the metal electrode sheet; Figure 4 for Figure 2 A schematic diagram of the exploded structure of the middle separator membrane.

[0059] Please see Figures 1 to 3 In some embodiments, the test battery 100 is used to test the effect of electrolyte on coulombic efficiency. The test battery 100 includes a housing 1, an electrode assembly 2, and a separator 4. The electrode assembly 2 is disposed inside the housing 1 and includes a working electrode 21 and an auxiliary electrode 22 disposed opposite to each other along a first direction X. The working electrode 21 is configured as a metal electrode 21a, and the surface of the metal electrode 21a facing the auxiliary electrode 22 is provided with a plurality of recesses 211. The separator 4 is disposed between the working electrode 21 and the auxiliary electrode 22 and is used to wet the electrolyte.

[0060] It should be noted that the electrode assembly 2 is disposed inside the housing 1, and its electrical connection with the external circuit can be the same as that of the aluminum-cased battery cell. It is connected to the electrode assembly 2 through the electrode terminals disposed on the housing 1, and connected to the external circuit through the electrode terminals. At this time, the material of the housing 1 can be a non-metallic material. This embodiment does not limit the connection method between the electrode assembly 2 and the external circuit.

[0061] Electrode assembly 2 consists of a working electrode 21 and an auxiliary electrode 22, wherein the working electrode 21 is set as a metal electrode 21a. Based on this, the test battery 100 belongs to a half-cell structure. In the coulombic efficiency test, the surface of the metal electrode 21a facing the auxiliary electrode 22 is the surface for lithium-ion deposition. The surface for lithium-ion deposition on the conventional metal electrode 21a is usually a two-dimensional plane. This embodiment improves this aspect by providing a plurality of recesses 211 on the surface of the metal electrode 21a facing the auxiliary electrode 22. The recesses 211 can be grooves or through holes extending along the first direction X. The cross-sectional shape of the recesses 211 can be a regular geometric shape such as square, circle, or triangle, or it can be an irregular geometric shape. Regardless of the shape of the cross-section of the recesses 211, it can at least increase the specific surface area of ​​the metal electrode 21a. "Specific surface area" refers to the total surface area of ​​a substance per unit mass or unit volume. When the metal electrode 21a is subjected to the same test current, the increase in specific surface area means the decrease in current density.

[0062] The "isolation membrane 4" is disposed between the working electrode 21 and the auxiliary electrode 22. It can block the passage of electrons and is intended to prevent short-circuit contact between the working electrode 21 and the auxiliary electrode 22. At the same time, the isolation membrane 4 can also allow lithium ions to pass through, which is intended to allow lithium ions on the auxiliary electrode 22 to pass through the isolation membrane 4 and be deposited on the metal electrode 21a. In this embodiment, the material and structure of the isolation membrane 4 are not limited.

[0063] The technical solution provided in this application, since the metal electrode 21a is the working electrode 21, lithium ions will be deposited on the surface of the metal electrode 21a during the test. Multiple recesses 211 are provided on the surface of the metal electrode 21a facing the auxiliary electrode 22, which can increase the specific surface area of ​​the metal electrode 21a. The increase in specific surface area can provide more growth space for lithium ion deposition on the one hand, and reduce the current density during the deposition process on the other hand, reducing the growth of lithium dendrites. This also means that the metal electrode 21a can withstand a larger test current. Under the premise of ensuring that the lithium ion deposition capacity remains unchanged, a larger test current is beneficial to shorten the test time, realize the rapid measurement of coulombic efficiency, and facilitate technicians to conduct a large number of electrolyte screenings.

[0064] Please see Figure 3In some embodiments, the metal electrode 21a includes a mesh structure 211a, and the recess 211 includes mesh openings 2111a of the mesh structure 211a.

[0065] "Mesh structure 211a" is a two-dimensional interwoven mesh or sieve structure, which usually has a densely distributed number of mesh holes 2111a. The metal mesh structure 211a is usually formed by etching, which means that the pore size and density of the mesh holes 2111a of the mesh structure 211a can be artificially controlled. The mesh structure 211a has advantages such as high flexibility, uniform distribution of mesh holes 2111a, and low cost.

[0066] In the above technical solution, the mesh structure 211a can be processed by etching, and the aperture of its mesh 2111a is easy to control. Mesh 2111a with specific aperture and density can be processed according to actual needs, that is, the specific surface area of ​​the mesh structure 211a is easy to control.

[0067] In some embodiments, the metal electrode 21a includes a foam structure, and the recess 211 includes foam pores of the foam structure.

[0068] "Foam structure" typically has an interconnected three-dimensional pore structure. The molding methods of metal foam structure usually include electrodeposition, powder sintering, casting, etc. The embodiments of this application do not limit this. Foam structure also has the advantages of high porosity, excellent electrical conductivity, and good mechanical strength.

[0069] In the above technical solution, the pores of the foam structure are interconnected, allowing lithium ions to flow freely in three-dimensional space. The permeability of lithium ions is good. Moreover, the foam structure can withstand a certain mechanical load while maintaining a low density.

[0070] In some embodiments, the metal electrode 21a includes a nanoarray structure, and the recess 211 includes an array gap of the nanoarray structure.

[0071] The "nanoarray structure" is usually composed of a substrate and multiple nanotubes. The multiple nanotubes are distributed in an array on the substrate and grow perpendicular to the substrate. There are usually array gaps between adjacent nanotubes. The presence of array gaps can also increase the specific surface area of ​​the metal electrode 21a. The forming methods of metal nanoarray structures usually include template method, electrochemical deposition method, chemical vapor deposition method, etc. The embodiments of this application are not limited to these. The nanoarray structure also has characteristics such as high specific surface area and ordered ion channels.

[0072] In the above technical solution, the nanoarray structure can provide a larger lithium deposition interface, which helps to reduce the current density. At the same time, the array gaps provide a vertical channel for lithium ion diffusion, improving the lithium ion kinetic performance.

[0073] It should be noted that the above three parallel technical features, "metal electrode 21a includes a mesh structure 211a", "metal electrode 21a includes a foam structure" and "metal electrode 21a includes a nanoarray structure", can be selected as one of them (for example, the metal electrode 21a is completely set as a mesh structure 211a, a foam structure or a nanoarray structure), two of them can be selected (for example, the metal electrode 21a includes two regions, and the two regions are respectively composed of two of the mesh structure 211a, the foam structure and the nanoarray structure), or all of them can be set (for example, the metal electrode 21a includes three regions, and the three regions are respectively composed of the mesh structure 211a, the foam structure and the nanoarray structure). This embodiment does not comment on the advantages and disadvantages of the three setting methods.

[0074] In one specific embodiment, the metal electrode 21a includes a first region, a second region, and a third region distributed from the center outwards. The second region is arranged around the first region, and the third region is arranged around the second region. The first region of the metal electrode 21a is a mesh structure 211a, the second region of the metal electrode 21a is a foam structure, and the third region of the metal electrode 21a is a nanoarray structure.

[0075] In some embodiments, the number of recesses 211 provided per square foot of metal electrode 21a is between 150 and 250.

[0076] It should be noted that this embodiment limits the number of recesses 211 per square foot, that is, the density of recesses 211. Generally speaking, the higher the density of recesses 211, the more significant the increase in the specific surface area of ​​the metal electrode 21a, and the higher the processing difficulty. Within the range of metal electrode 21a per square foot, the number of recesses 211 can be arbitrarily selected between 150 and 250, for example, 150 / square foot, 150 / square foot, 175 / square foot, 200 / square foot, 225 / square foot, 250 / square foot, etc. This embodiment does not limit the specific density of recesses 211.

[0077] In the above technical solution, the number of recesses 211 per square foot is between 150 and 250. While keeping the processing difficulty of the metal electrode 21a at an appropriate level, the metal electrode 21a can be given a larger specific surface area.

[0078] For the metal electrode 21a with a mesh structure 211a, the number of recesses 211 per square foot of the metal electrode 21a is between 150 and 250. This can also be understood as the mesh count of the mesh structure 211a being between 150 and 250. Specifically, the mesh count of the mesh structure 211a is 200. Combined with the shape of the mesh openings 2111a, the specific surface area of ​​the metal electrode 21a can be increased to 5 times its original value. Tests have shown that when the test current increases from 0.4 mA cm⁻¹... -2 Increased to 2mA cm -2 At that time, the test time was reduced from 66h to 13.5h, and there was basically no lithium dendrite formation on the surface of the metal electrode 21a.

[0079] In some embodiments, the auxiliary electrode 22 is configured as a lithium sheet 22a.

[0080] "Lithium sheet 22a" is usually composed of a current collector layer and a lithium metal layer. The lithium metal layer is made of high-purity lithium metal. Overall, lithium sheet 22a is a thin sheet structure.

[0081] In the above technical solution, lithium sheet 22a is selected as auxiliary electrode 22. Lithium sheet 22a can continuously and stably provide lithium ions, and the reaction of lithium sheet 22a is simple and the potential is stable. In the scenario of testing coulombic efficiency, lithium sheet 22a is an ideal auxiliary electrode material 22.

[0082] In some embodiments, the metal electrode 21a is made of copper.

[0083] In the above technical solution, copper is electrochemically inert under the potential window of lithium deposition and stripping. This means that copper is difficult to alloy with lithium, and can provide a stable and pure "background". This allows the measurement current to come almost entirely from the lithium deposition and stripping reaction itself, so that the coulombic efficiency can be calculated most accurately.

[0084] Depending on the test scenario, the metal electrode 21a may also be made of aluminum, nickel, stainless steel, or a metal alloy composed of the above metals in different proportions.

[0085] Please see Figure 1 and Figure 2 In some embodiments, the outer casing 1 includes two half-shells 11, which are interlocked and insulated from each other along a first direction X; the metal electrode 21a and the auxiliary electrode 22 are electrically connected to the corresponding half-shells 11 respectively.

[0086] "The two half-shells 11 are interlocked along the first direction X" means that the two half-shells 11 have interlocking parts and mating parts respectively. Considering the sealing requirements, the interlocking parts and mating parts are usually annular protrusions and annular grooves provided at the opening edges of the corresponding half-shells 11, but are not limited to this. Since the metal electrode 21a and the auxiliary electrode 22 are electrically connected to the corresponding half-shells 11 respectively, in this embodiment, the two half-shells 11 are used as the positive and negative electrodes of the test battery 100 respectively. Therefore, the two half-shells 11 need to be insulated from each other. For example, the interlocking parts and mating parts of the two half-shells 11 are made of insulating material, or the surfaces of the interlocking parts and mating parts are provided with an insulating layer.

[0087] In the above technical solution, the outer shell 1 is composed of two half-shells 11 fastened together. The two half-shells 11 are electrically connected to the metal electrode 21a and the auxiliary electrode 22 respectively, and the two half-shells 11 are insulated from each other. This is equivalent to limiting the test battery 100 to a button cell structure, which is beneficial for efficiently measuring the performance of the electrolyte.

[0088] Please see Figure 2 In some embodiments, an elastic conductive element 3 is provided between the metal electrode 21a and / or the auxiliary electrode 22 and the corresponding half-shell 11.

[0089] The "elastic conductive element 3" can be disposed only between the metal electrode 21a and the corresponding half-shell 11, or only between the auxiliary electrode 22 and the corresponding half-shell 11. Alternatively, the elastic conductive element 3 can be disposed between the metal electrode 21a and the auxiliary electrode 22 and the corresponding half-shell 11 respectively. The "elastic conductive element 3" has at least elastic deformation properties and conductive properties along the first direction X. For example, the elastic conductive element 3 can be conductive foam.

[0090] Since the metal electrode 21a and the auxiliary electrode 22 are electrically connected to the external circuit through the two half-shells 11, the overall thickness of the metal electrode 21a, the auxiliary electrode 22 and the isolation membrane 4 is usually smaller than the spacing between the inner surfaces of the two half-shells 11 without affecting the snap-fit ​​assembly of the two half-shells 11.

[0091] In the above technical solution, an elastic conductive element 3 is provided between the metal electrode 21a or the auxiliary electrode 22 and the corresponding half-shell 11. The elastic conductive element 3 can not only conduct electricity, but also use its own elastic properties to compensate for the assembly gap between the metal electrode 21a or the auxiliary electrode 22 and the corresponding half-shell 11, so as to ensure the stability of the overall structure.

[0092] Please continue reading. Figure 2 In some embodiments, the elastic conductive element 3 includes a gasket 31 and a spring 32. The gasket 31 is disposed abutting against the metal electrode 21a, and the spring 32 is disposed between the gasket 31 and the corresponding half-shell 11.

[0093] In the elastic conductive element 3, the "spring piece 32" is usually in a compressed state, and its function is to apply a supporting force to the half shell 11 and the metal electrode 21a.

[0094] In the above technical solution, considering that the metal electrode 21a is a thin sheet structure, the elastic conductive element 3 is limited to be composed of a gasket 31 and a spring 32. The structural strength of the gasket 31 is usually greater than that of the metal electrode 21a. The spring 32 is indirectly connected to the metal electrode 21a through the gasket 31. The function of the gasket 31 is to increase the contact area of ​​the metal electrode 21a, thereby reducing the pressure on the metal electrode 21a and reducing the probability of the elastic conductive element 3 damaging the metal electrode 21a.

[0095] Please see Figure 2 and Figure 4 In some embodiments, the separator 4 includes a membrane body 41, and at least one side of the membrane body 41 in the thickness direction is provided with a rimming structure 42. The membrane body 41 includes an ion passage region 41a in the middle and a rimming region 41b surrounding the ion passage region 41a. The rimming structure 42 is disposed in the rimming region 41b. The metal electrode 21a and the auxiliary electrode 22 are disposed in the projection of the first direction X covering the ion passage region 41a.

[0096] "The thickness direction of the membrane body 41" also refers to the first direction X. At least one side of the membrane body 41 is provided with an edge-sealing structure 42. The edge-sealing structure 42 can be provided on any one side or on both sides. The "edge-sealing structure 42" can usually be provided in the edge-sealing area 41b of the membrane body 41 by adhesive bonding, but it is also possible that it is positioned in the edge-sealing area 41b of the membrane body 41 by other limiting structures. In terms of performance, the edge-sealing structure 42 has at least the characteristic of blocking lithium ion permeation. Therefore, lithium ions can only pass through the ion passage area 41a of the membrane body 41 to pass through the separator membrane 4.

[0097] In the above technical solution, the separator 4 is positioned between the metal electrode 21a and the auxiliary electrode 22 to prevent short circuits between them. Based on this, the edge-sealing structure 42 is provided in the edge-sealing area 41b on the outer edge of the membrane body 41, which can define an ion passage area 41a of the target size in the middle of the membrane body 41. The projections of the metal electrode 21a and the auxiliary electrode 22 in the first direction X cover the ion passage area 41a. In other words, the reaction area can be defined by the ion passage area 41a, which is beneficial for controlling the test variables.

[0098] In some embodiments, the edging structure 42 is configured as a polyimide film.

[0099] "Polyimide film" is also commonly known as blue film. Polyimide has excellent high temperature resistance, excellent insulation properties, and good chemical stability.

[0100] In the above technical solution, the polyimide film has excellent insulation properties and can restrict the passage of ions. It is a material commonly used in the battery production field. Setting the edge-sealing structure 42 as a polyimide film is beneficial to reducing the difficulty and cost of obtaining the edge-sealing structure 42.

[0101] It should be noted that there are various material options for the membrane body 41 of the separator 4, among which the more common ones are polyolefin separator 4, ceramic coated separator 4, non-woven fabric separator 4, etc. In some embodiments, the membrane body 41 is set as a polyethylene film.

[0102] In the above technical solution, the melting point of the polyethylene film is about 135°C. When an abnormality occurs inside the battery (such as overcharging or short circuit) causing the temperature to rise and approach the melting point, the polyethylene film will melt and shrink to close the original micropores. The closure of the micropores will block the transport of lithium ions, thereby greatly increasing the internal resistance of the battery, effectively suppressing the current and preventing further aggravation of thermal runaway.

[0103] It should be noted that the two parallel technical features mentioned above, "the edge-wrapping structure 42 is set as a polyimide film" and "the film body 41 is set as a polyethylene film", can be set as one of them or both of them.

[0104] This application also proposes a testing device, which includes a test battery 100. The specific structure of the test battery 100 is as described in the above embodiments. Since this testing device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here. In addition to the test battery 100, the testing device usually also includes a test circuit, which is electrically connected to the working electrode 21 and auxiliary electrode 22 of the test battery 100 to provide a stable test current and test voltage.

[0105] In a specific embodiment of this application, the test battery 100 includes a casing 1, an electrode assembly 2, and a separator 4. The casing 1 includes two half-shells 11, which are interlocked and insulated from each other along a first direction X. The electrode assembly 2 is disposed inside the casing 1 and includes a working electrode 21 and an auxiliary electrode 22 disposed opposite to each other along the first direction X. The separator 4 is disposed between the working electrode 21 and the auxiliary electrode 22 and is used to wet the electrolyte to be tested. The auxiliary electrode 22 is a lithium sheet 22a, and the working electrode 21 is a metal electrode 21a made of copper. The surface of the metal electrode 21a facing the auxiliary electrode 22 has a plurality of recesses 211. The number of recesses 211 per square foot of the metal electrode 21a is 200. The metal electrode 21a includes a mesh structure 211a, and the recesses 211 include a mesh structure. The mesh 2111a of 211a; the auxiliary electrode 22 is electrically abutted to one of the half-shells 11, wherein an elastic conductive element 3 is provided between the other half-shell 11 and the metal electrode 21a, the elastic conductive element 3 includes a gasket 31 and a spring 32, the gasket 31 is abutted against the metal electrode 21a, and the spring 32 is provided between the gasket 31 and the corresponding half-shell 11; the separator 4 includes a membrane body 41, at least one side of the membrane body 41 in the thickness direction is provided with a edging structure 42, the membrane body 41 includes an ion passage region 41a in the middle and an edging region 41b surrounding the ion passage region 41a, the edging structure 42 is provided in the edging region 41b, the projection of the metal electrode 21a and the auxiliary electrode 22 in the first direction X covers the ion passage region 41a, wherein the edging structure 42 is a polyimide film and the membrane body 41 is a polyethylene film.

[0106] 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 test battery for testing the effect of electrolyte on coulombic efficiency, characterized in that, The test battery includes: shell; An electrode assembly, disposed within a housing, includes a working electrode and an auxiliary electrode disposed opposite to each other along a first direction. The working electrode is configured as a metal electrode sheet, and the surface of the metal electrode sheet facing the auxiliary electrode has a plurality of recesses. A separating membrane is disposed between the working electrode and the auxiliary electrode, and the separating membrane is used to wet the electrolyte.

2. The test battery as described in claim 1, characterized in that, The metal electrode sheet includes a mesh structure, and the recess includes mesh openings in the mesh structure; and / or, The metal electrode sheet comprises a foam structure, and the recess includes foam pores of the foam structure; and / or, The metal electrode includes a nanoarray structure, and the recess includes the array gaps of the nanoarray structure.

3. The test battery as described in claim 1, characterized in that, The number of recesses is between 150 and 250 per square foot of the metal electrode sheet.

4. The test battery as described in claim 1, characterized in that, The auxiliary electrode is a lithium sheet.

5. The test battery as described in claim 1, characterized in that, The metal electrode is made of copper.

6. The test battery as described in any one of claims 1 to 5, characterized in that, The outer casing includes two half-shells, which are interlocked and insulated from each other along the first direction. The metal electrode and the auxiliary electrode are electrically connected to the corresponding half-shell, respectively.

7. The test battery as described in claim 6, characterized in that, An elastic conductive element is provided between the metal electrode and / or the auxiliary electrode and the corresponding semi-shell.

8. The test battery as described in claim 7, characterized in that, The elastic conductive element includes a gasket and a spring, the gasket being disposed against the metal electrode, and the spring being disposed between the gasket and the corresponding half-shell.

9. The test battery as described in any one of claims 1 to 5, characterized in that, The isolation membrane includes a membrane body, and at least one side of the membrane body in the thickness direction is provided with a edging structure. The membrane body includes an ion passage region in the middle and an edging region surrounding the ion passage region. The edging structure is disposed in the edging region. The projections of the metal electrode and the auxiliary electrode in the first direction cover the ion passage area.

10. The test battery as described in claim 9, characterized in that, The edging structure is configured as a polyimide film; and / or, The membrane body is a polyethylene membrane.

11. A testing device, characterized in that, Includes the test battery as described in any one of claims 1 to 10.

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