Three-electrode battery cell

Abstract

According to the three-electrode battery cell provided by the utility model, the reference pole piece is placed on the outermost side of the roll core, and the reference pole piece corresponds to the negative pole piece without the positive pole, so that the interference of the reference pole piece on electrical performance tests of charging and discharging, HPPC, EIS and the like of a normal battery cell can be effectively reduced, and the influence of the reference pole piece in the normal battery cell is reduced; and the accuracy of an electrical performance test result can be improved. In addition, the three-electrode battery cell disclosed by the invention can be prepared by adding a reference pole piece into the roll core obtained after the winding process or the lamination process, and the three-electrode battery cell has the advantages of convenience and rapidness in operation and low safety risk.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a three-electrode battery cell. Background Technology

[0002] Lithium-ion batteries are widely used in products such as 3C (computer, communication, and consumer electronics), new energy vehicles, and energy storage devices due to their advantages such as high specific energy, low self-discharge, and long lifespan. To improve the safety and performance of lithium-ion batteries, in-situ detection of the internal electrochemical reactions is necessary to monitor and control the changes in the positive and negative electrode potentials during charging and discharging in real time.

[0003] Currently, lithium-ion batteries utilize reference electrodes to achieve in-situ monitoring of the positive electrode potential, negative electrode potential, and impedance within the battery. However, the inventors have discovered that existing reference electrode setups can interfere with the electrical performance testing of the battery cell, thereby reducing the accuracy of the test results. Utility Model Content

[0004] The purpose of this application is to at least address one of the aforementioned technical defects, particularly the technical defect in the prior art that reduces the accuracy of electrical performance test results.

[0005] Some embodiments of this application provide a three-electrode battery cell, including: a wound core and a reference electrode;

[0006] When the core is a wound structure, the core includes a first positive electrode sheet, a first negative electrode sheet, a first separator, and a second separator. The first positive electrode sheet, the first separator, the first negative electrode sheet, and the second separator are stacked sequentially and wound along the winding direction to form the wound structure. The first negative electrode sheet includes a first segment and a second segment continuously arranged along the winding direction. The first segment is disposed opposite to the first positive electrode sheet, and the second segment extends beyond the winding end of the first positive electrode sheet along the winding direction. The reference electrode sheet is disposed on the side of the second segment away from the first positive electrode sheet, and the first active material layer of the reference electrode sheet is disposed opposite to the second segment. The reference electrode sheet and the second segment are separated by the first separator and / or the second separator.

[0007] When the core is a stacked structure, the core includes N+1 layers of second negative electrode sheets and N layers of second positive electrode sheets alternately stacked along a first direction. The core also includes a third separator, with adjacent second negative electrode sheets and second positive electrode sheets separated by the third separator. The reference electrode sheet is disposed on the side of the N+1 layer of second negative electrode sheet away from the second positive electrode sheet, and the first active material layer of the reference electrode sheet is disposed opposite to the N+1 layer of second negative electrode sheet. The reference electrode sheet and the N+1 layer of second negative electrode sheet are separated by the third separator.

[0008] In some embodiments, when the core is the winding structure, when viewed along the axial direction of the winding structure, the winding structure has a first bending region, a first straight region and a second bending region continuously arranged along the winding direction, and the reference electrode has a first end and a second end disposed opposite to each other, the first end and the second end being located in the first straight region.

[0009] In some embodiments, when viewed along the axial direction of the winding structure, the length L4 of the reference electrode satisfies: 0.1L2≤L4≤0.8L2, where L2 is the length of the first straight region;

[0010] The first end is close to the first bending area, the second end is close to the second bending area, and the distance between the first end and the first bending area is equal to the distance between the second end and the second bending area.

[0011] In some embodiments, when the core is the wound structure, when viewed radially along the core, the first negative electrode has a first overhang region and a second overhang region, the first diaphragm has a third overhang region and a fourth overhang region, and the second diaphragm has a fifth overhang region and a sixth overhang region.

[0012] Wherein, the first overhang region is the non-overlapping region of the first negative electrode, the first positive electrode, and the reference electrode in the electrode length direction; the second overhang region is the non-overlapping region of the first negative electrode, the first positive electrode, and the reference electrode in the electrode width direction; the third overhang region is the non-overlapping region of the first separator and the first negative electrode in the electrode length direction; the fourth overhang region is the non-overlapping region of the first separator and the first negative electrode in the electrode width direction; the fifth overhang region is the non-overlapping region of the second separator and the first negative electrode in the electrode length direction; and the sixth overhang region is the non-overlapping region of the second separator and the first negative electrode in the electrode width direction.

[0013] The first overhang region has a length of 1mm to 4mm in the length direction of the electrode, the second overhang region has a width of 1mm to 4mm in the width direction of the electrode, the third overhang region has a length of 0.5mm to 4mm in the length direction of the electrode, the fourth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode, the fifth overhang region has a width of 0.5mm to 4mm in the length direction of the electrode, and the sixth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode.

[0014] In some embodiments, when the core is the laminated structure, the cut size of the reference electrode is the same as the cut size of the second positive electrode.

[0015] In some embodiments, when the core is the laminated structure, when viewed along the first direction, the second negative electrode has a seventh overhang region and an eighth overhang region. The seventh overhang region is the non-overlapping region of the second negative electrode, the second positive electrode, and the reference electrode in the electrode length direction, and the eighth overhang region is the non-overlapping region of the second negative electrode, the second positive electrode, and the reference electrode in the electrode width direction.

[0016] Viewed along the first direction, the third diaphragm has a ninth overhang region and a tenth overhang region. The ninth overhang region is the non-overlapping region of the third diaphragm and the second negative electrode in the length direction of the electrode, and the tenth overhang region is the non-overlapping region of the third diaphragm and the second negative electrode in the width direction of the electrode.

[0017] The seventh overhang region has a length of 1mm to 4mm in the length direction of the electrode, and the eighth overhang region has a width of 1mm to 4mm in the width direction of the electrode; the ninth overhang region has a length of 0.5mm to 4mm in the length direction of the electrode, and the tenth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode.

[0018] In some embodiments, the active material of the first active material layer is one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium titanate, and lithium titanium phosphate.

[0019] In some embodiments, the thickness of the active material coating of the first active material layer is 1 μm to 10 μm.

[0020] In some embodiments, when the core is the wound structure, the first positive electrode sheet has a second active material layer and a third active material layer disposed opposite to each other; when the core is the stacked structure, the second positive electrode sheet has a fourth active material layer and a fifth active material layer disposed opposite to each other.

[0021] The active material of the second active material layer is at least one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; the active material of the third active material layer is at least one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; the active material of the fourth active material layer is at least one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; and the active material of the fifth active material layer is at least one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.

[0022] In some embodiments, when the core is the wound structure, the first negative electrode sheet has a sixth active material layer and a seventh active material layer disposed opposite to each other; when the core is the stacked structure, the second negative electrode sheet has an eighth active material layer and a ninth active material layer disposed opposite to each other.

[0023] The active material of the sixth active material layer is at least one of carbon material, silicon-based material, and lithium titanate material; the active material of the seventh active material layer is at least one of carbon material, silicon-based material, and lithium titanate material; the active material of the eighth active material layer is at least one of carbon material, silicon-based material, and lithium titanate material; and the active material of the ninth active material layer is at least one of carbon material, silicon-based material, and lithium titanate material.

[0024] The solution presented in this application has at least the following technical effects:

[0025] Compared to existing solutions that place the reference electrode between the positive and negative electrodes, this application places the reference electrode on the outermost side of the core, so that the reference electrode corresponds to the negative electrode without a corresponding positive electrode. This effectively reduces the interference of the reference electrode on the normal cell's electrical performance tests such as charge and discharge, HPPC (Hybrid Pulse Power Characteristic), and EIS (Electrochemical Impedance Spectroscopy), thereby reducing the influence of the reference electrode in the normal cell and improving the accuracy of electrical performance test results.

[0026] Furthermore, the three-electrode battery cell of this application can be manufactured by adding a reference electrode to the core obtained after the winding or stacking process, which has the advantages of convenient and quick operation and low safety risk. Attached Figure Description

[0027] 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 these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the winding structure along the radial direction in one embodiment;

[0029] Figure 2 This is one of the schematic diagrams of the reference electrode structure in one embodiment;

[0030] Figure 3 This is a second schematic diagram of the reference electrode structure in one embodiment;

[0031] Figure 4 This is a schematic diagram illustrating the arrangement of the reference electrode and the negative electrode in one embodiment;

[0032] Figure 5 This is a schematic diagram of the stacked structure in one embodiment;

[0033] Figure 6 This is a schematic diagram of the dimensions of the winding structure in one embodiment;

[0034] Figure 7 This is a schematic diagram of the overhang region on the width of the negative electrode relative to the positive electrode / reference electrode in one embodiment;

[0035] Figure 8 This is a schematic diagram of the structure of the first positive electrode in one embodiment;

[0036] Figure 9 This is a schematic diagram of the structure of the first negative electrode in one embodiment;

[0037] Figure 10A This is one of the schematic diagrams of a three-electrode battery cell in one embodiment;

[0038] Figure 10B This is a second schematic diagram of the structure of a three-electrode battery cell in one embodiment;

[0039] Figure 10C This is the third schematic diagram of the structure of a three-electrode battery cell in one embodiment.

[0040] Explanation of reference numerals in the attached figures:

[0041] 20: Reference electrode, 21: First active material layer, 22: Current collector of the reference electrode, 110: First positive electrode, 111: Second active material layer, 112: Third active material layer, 113: Current collector of the first positive electrode, 120: First negative electrode, 121: First segment, 122: Second segment, 123: Sixth active material layer, 124: Seventh active material layer, 125: Current collector of the first negative electrode, 130: First separator, 140: Second separator, 150: Second positive electrode, 160: Second negative electrode, 170: Third separator, 40: First tab, 41: Second tab, 42: Third tab, 900: Three-electrode cell, 901: Bare cell, 902: Aluminum-plastic film; A: Axial direction of the wound structure; R: Radial direction of the wound structure. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] In some embodiments, this application provides a three-electrode battery cell 900, including a wound core and a reference electrode 20. The wound core can be manufactured using a winding process or a lamination process. When manufactured using a winding process, the wound core has a wound structure; when manufactured using a lamination process, the wound core has a lamination structure.

[0044] When the core is a wound structure, it may include a first positive electrode 110, a first negative electrode 120, a first separator 130, and a second separator 140. When the core is a stacked structure, it may include a second positive electrode 150, a second negative electrode 160, and a third separator 170. It should be noted that the first positive electrode 110 and the second positive electrode 150 may have the same or different structures, the first negative electrode 120 and the second negative electrode 160 may have the same or different structures, and the first separator 130, the second separator 140, and the third separator 170 may be made of the same or different materials.

[0045] Please see Figure 1 When the core is a wound structure, the first positive electrode 110, the first separator 130, the first negative electrode 120, and the second separator 140 are stacked sequentially and wound along the winding direction to form a wound core. The first negative electrode 120 includes a first segment 121 and a second segment 122 continuously arranged along the winding direction. The first segment 121 is opposite to the first positive electrode 110, and the second segment 122 extends beyond the winding end of the first positive electrode 110 along the winding direction. That is, the second segment 122 is the negative electrode area at the end of the core where there is no corresponding positive electrode.

[0046] The reference electrode 20 may be disposed on the side of the second segment 122 away from the first positive electrode 110, and the first active material layer 21 of the reference electrode 20 is disposed opposite to the second segment 122. In this application, at least one side of the reference electrode 20 is coated with an active material to form the first active material layer 21. For example, such as Figure 2 As shown, when the reference electrode 20 is coated with an active material on one side, the reference electrode 20 has a first active material layer 21. For example, as... Figure 3 As shown, when the reference electrode 20 is coated with active material on both sides, the reference electrode 20 has two first active material layers 21, and the two first active material layers 21 are arranged opposite to each other.

[0047] like Figure 4 As shown, when the reference electrode 20 has a single-sided coating structure, the first active material layer 21 of the reference electrode 20 is positioned opposite to the second segment 122. That is, this application requires that the side of the reference electrode 20 coated with the active material be opposite to the first negative electrode 120. When the reference electrode 20 has a double-sided coating structure, either the first active material layer 21 of the reference electrode 20 is positioned opposite to the second segment 122. The reference electrode 20 and the second segment 122 are separated by a first separator 130 and / or a second separator 140, so as to separate the first active material layer 22 from the first negative electrode 120 and avoid short circuits.

[0048] With the above arrangement, the reference electrode 20 can be placed on the outside of the winding structure, and the film surface of the reference electrode 20 coated with active material is directly opposite the negative electrode at the end of the winding core where there is no positive electrode. The first separator 130 and / or the second separator 140 are used to tightly attach to the second segment 122 of the first negative electrode 120.

[0049] Please see Figure 5 When the core has a laminated structure, it includes a third separator 170, an N+1 layer of second negative electrode sheets 160, and an N layer of second positive electrode sheets 150. The N layer of second positive electrode sheets 150 and the N+1 layer of second negative electrode sheets 160 are alternately stacked along a first direction, and adjacent second negative electrode sheets 160 and second positive electrode sheets 150 in the first direction are separated by the third separator 170. For example, the core is arranged sequentially along the first direction as follows: negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, separator, etc.

[0050] In some examples, the second positive electrode 150, the second negative electrode 160, and the third separator 170 can be placed on a lamination device for lamination to form a core of a laminated structure.

[0051] The reference electrode 20 can be disposed on the side of the N+1th layer of the second negative electrode 160 away from the second positive electrode. It should be noted that the "N+1th layer of the second negative electrode 160" mentioned in this application refers to the negative electrode located on the outermost side of the core in the N+1th layer of the second negative electrode 160. For example, if the core along the first direction is sequentially composed of negative electrode A, separator, positive electrode A, separator, negative electrode B, separator, positive electrode B, separator, negative electrode C, separator, positive electrode C, separator, negative electrode D, separator, then the N+1th layer of the second negative electrode 160 can be negative electrode D.

[0052] The first active material layer 22 of the reference electrode 20 is positioned opposite to the (N+1)th layer of the second negative electrode 160. For example... Figures 2-4 As shown, at least one side of the reference electrode 20 is coated with an active material to form a first active material layer 21. The first active layer 21 of the reference electrode 20 faces the N+1th layer of the second negative electrode 160, and the reference electrode 20 and the N+1th layer of the second negative electrode 160 are separated by a third separator 170 to separate the first active material layer 21 and the second negative electrode 160 and prevent short circuits. For details regarding the active layer configuration and specific configuration of the reference electrode 20, please refer to the above description; further details are omitted here.

[0053] With the above configuration, the reference electrode 20 can be placed on the outside of the stacked structure and closely attached to the adjacent second negative electrode 160 by the third diaphragm 170, and the membrane surface of the reference electrode 20 coated with active material is directly opposite the negative electrode corresponding to the outside of the stacked structure where there is no positive electrode.

[0054] Compared to existing solutions that place the reference electrode 20 in the middle of the cell, this application chooses to place the reference electrode 20 on the outermost / outermost ring of the core, on the negative electrode side without a corresponding positive electrode. This avoids blocking lithium-ion transport during electrical performance tests such as charge / discharge, HPPC, and EIS, thereby increasing the lithium-ion migration path, expanding test errors, reducing the influence of the reference electrode in the normal cell, effectively reducing the interference of the reference electrode on the electrical performance test of the normal cell, and simultaneously monitoring the potential changes of the positive and negative references during the test.

[0055] In some embodiments, when the core is a wound structure, viewed along the axial direction of the wound structure, the wound structure has a first bending region, a first straight region, and a second bending region continuously arranged along the winding direction. The reference electrode 20 has a first end and a second end disposed opposite to each other, both of which are located in the first straight region. The first straight region can be understood as the projection of the large surface of the core onto the axial direction of the wound structure, and the first bending region and the second bending region can be understood as the projection of the core's radius (R-angle) onto the axial direction of the wound structure.

[0056] In this embodiment, the entire reference electrode 20 is located on the large surface of the cell, avoiding placing part or all of the reference electrode 20 at the radius (R) corner of the cell. This prevents the reference electrode 20 from breaking due to expansion in different directions at the large surface and the radius, thereby increasing the service life of the reference electrode 20 and consequently improving the durability of the three-electrode cell 900.

[0057] When the core is a wound structure, and the distances from the left and right sides of the reference electrode 20 to the R-angle are not equidistant, the lithium-ion concentration at different locations around the reference electrode 20 will vary, thus affecting the accuracy of the positive and negative reference potential tests. To improve the accuracy of the positive and negative reference potential tests, in some embodiments, please refer to... Figure 6 When the core is a wound structure, viewed along the axial direction of the wound structure, the lengths of the first and second bending regions can both be L1, the length of the first straight region can be L2, and the length of the reference electrode 20 can be L4, where 0.1L2≤L4≤0.8L2. The first end of the reference electrode 20 is close to the first bending region, and the second end of the reference electrode 20 is close to the second bending region; therefore, the distance between the first end and the first bending region is equal to the distance between the second end and the second bending region.

[0058] That is, in this embodiment, the length of the reference electrode 20 is 0.1 to 0.8 times the length of the large surface of the core, and the distance L3 between the two sides of the reference electrode 20 and the R-angle satisfies: L3 = (L2 - L4) / 2. In this way, the reference electrode 20 can be placed at the center of the large surface of the cell, thereby improving the accuracy of the positive and negative reference potential tests.

[0059] In some embodiments, when the core is a wound structure, the width of the reference electrode 20 is the same as the width of the first positive electrode 110. In both the length and width directions of the electrode, the first negative electrode 120 has an overhang region compared to both the first positive electrode 110 and the reference electrode 20, with the overhang region value ranging from 1 mm to 4 mm. In both the length and width directions of the electrode, the separator (including the first separator 130 and the second separator 140) has an overhang region compared to the first negative electrode 120, with the overhang region value ranging from 0.5 mm to 4 mm.

[0060] Specifically, please refer to Figure 7When the core is a wound structure, viewed radially along the core (i.e., projected radially), the first negative electrode 120 has a first overhang region and a second overhang region, the first separator 130 has a third overhang region and a fourth overhang region, and the second separator 140 has a fifth overhang region and a sixth overhang region. The first overhang region is the non-overlapping region of the first negative electrode 120 with the first positive electrode 110 and the reference electrode 20 along the length of the electrode. The second overhang region is the non-overlapping region of the first negative electrode 120 with the first positive electrode 110 and the reference electrode 20 along the width of the electrode. The length of the first overhang region along the length of the electrode is 1mm to 4mm, and the width of the second overhang region along the width of the electrode is 1mm to 4mm.

[0061] The third overhang region is the non-overlapping region of the first separator 130 and the first negative electrode 120 in the electrode length direction; the fourth overhang region is the non-overlapping region of the first separator 130 and the first negative electrode 120 in the electrode width direction; the fifth overhang region is the non-overlapping region of the second separator 140 and the first negative electrode 120 in the electrode length direction; and the sixth overhang region is the non-overlapping region of the second separator 140 and the first negative electrode 120 in the electrode width direction.

[0062] Specifically, the third overhang region has a length of 0.5mm to 4mm along the electrode length direction, the fourth overhang region has a width of 0.5mm to 4mm along the electrode width direction, the fifth overhang region has a width of 0.5mm to 4mm along the electrode length direction, and the sixth overhang region has a width of 0.5mm to 4mm along the electrode width direction. This design improves the safety of the three-electrode cell 900 and enhances battery performance.

[0063] When the core has a stacked structure, if the area of ​​the reference electrode 20 is too large, it will increase the difficulty of matching the negative electrode and reduce the accuracy of the overhang, causing uneven local lithium-ion concentration, which may lead to lithium plating or even short circuit. If the area of ​​the reference electrode 20 is too small, it will affect the uneven expansion of the corresponding positive and negative electrodes in this area and the positive and negative electrodes in other areas, which may cause wrinkling of the electrode or separator and reduce the electrochemical performance of the cell.

[0064] To overcome the above problems, in some embodiments, the cutting size of the reference electrode 20 is the same as that of the second positive electrode 150, that is, the cutting sizes of the reference electrode 20 and the second positive electrode 150 are kept consistent during the die-cutting stage. In this way, lithium plating and short circuits caused by uneven local lithium ion concentration can be avoided, and the electrochemical performance of the cell can be guaranteed.

[0065] In some embodiments, when the core is a laminated structure, the second negative electrode 160 has an overhang region compared to both the second positive electrode 150 and the reference electrode 20 in both the length and width directions, and the overhang region value is between 1 mm and 4 mm. The third diaphragm 170 also has an overhang region compared to the second negative electrode 160 in both the length and width directions, and the overhang region value is between 0.5 mm and 4 mm.

[0066] Specifically, please refer to Figure 5 When the core is a laminated structure, viewed along the first direction (i.e., the lamination direction), i.e., the projection along the first direction, the second negative electrode 160 has a seventh overhang region and an eighth overhang region. The seventh overhang region is the non-overlapping region of the second negative electrode 160 with the second positive electrode 150 and the reference electrode 20 along the electrode length direction. The eighth overhang region is the non-overlapping region of the second negative electrode 160 with the second positive electrode 150 and the reference electrode 20 along the electrode width direction. The length of the seventh overhang region along the electrode length direction is 1mm to 4mm, and the width of the eighth overhang region along the electrode width direction is 1mm to 4mm. Viewed along the first direction, the third separator 170 has a ninth overhang region and a tenth overhang region. The ninth overhang region is the non-overlapping area between the third separator 170 and the second negative electrode 160 in the length direction of the electrode, and the tenth overhang region is the non-overlapping area between the third separator 170 and the second negative electrode 160 in the width direction of the electrode. The length of the ninth overhang region in the length direction of the electrode is 0.5mm to 4mm, and the width of the tenth overhang region in the width direction of the electrode is 0.5mm to 4mm. This improves the safety of the three-electrode cell 900 and enhances battery performance.

[0067] In existing technologies, reference electrode 20 is mostly made of lithium metal sheets / foils. However, considering that elemental lithium metal is sensitive to oxygen and moisture and cannot be exposed to air, the cell / battery needs to be assembled in an inert and dry environment, which is cumbersome. To solve the aforementioned problems, in some embodiments, the active material of the first active material layer 21 can be any one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium titanate, and lithium titanium phosphate. By using lithium oxide as the active material of the reference electrode 20, this embodiment can reduce the environmental requirements of the reference electrode 20 during the assembly process and simplify the assembly operation of the reference electrode 20.

[0068] In existing technologies, the reference electrode 20 can also be achieved by in-situ electrodeposition of lithium on the surface of a copper wire. However, using copper, silver, or platinum wire as the reference electrode requires lithium plating under a small current to serve as a reference potential, which leads to distortion of the positive electrode potential. Furthermore, the exposed metal wire within the cell can interfere with the electrical signal in the electrolyte. Additionally, the lithium plating on the metal wire reference electrode is relatively thin, resulting in a short lifespan. To address these issues, in some embodiments, the current collector 22 of the reference electrode can be aluminum foil, with at least one side of the aluminum foil forming a first active material layer 21. Compared to the copper wire lithium plating solution, the reference electrode 20 provided in this embodiment does not affect the cell performance, does not interfere with the test signal, and eliminates the need for repeated lithium plating (load adjustment), saving time.

[0069] In some embodiments, the thickness of the active material coating of the first active material layer 21 can be 1 μm to 10 μm. For example, the coating thickness of the first active material layer 21 can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0070] Specifically, if the coating of the reference electrode 20 is too thick, it will cause uneven expansion between the positive and negative electrodes in that area and those in other areas, leading to wrinkling of the electrode or separator and reducing electrochemical performance. If the coating of the reference electrode 20 is too thin, it indicates insufficient active material, affecting reference lifetime and potentially exposing the foil, causing reference electrode failure. In this embodiment, by controlling the coating thickness of the reference electrode 20 to be between 1 μm and 10 μm, both reference lifetime and electrochemical performance of the cell can be improved.

[0071] In some embodiments, the positive electrode sheet of the core can be coated with active material on both sides, and the positive electrode material of the cell can be one or more of lithium-rich oxides such as NCM ternary material, LFP lithium iron phosphate, LMFP lithium manganese iron phosphate, and LCO lithium cobalt oxide.

[0072] Specifically, please refer to Figure 8When the core is a wound structure, the first positive electrode 110 has a second active material layer 111 and a third active material layer 112 disposed opposite to each other. The active material of the second active material layer 111 is at least one selected from ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide. The active material of the third active material layer 112 is at least one selected from ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide. Further, in some examples, the second active material layer 111 and the third active material layer 112 are made of the same active material.

[0073] Similarly, when the core is a laminated structure, the second positive electrode 150 has a fourth active material layer and a fifth active material layer disposed opposite to each other. The active material of the fourth active material layer is at least one selected from ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide. The active material of the fifth active material layer is at least one selected from ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide. Further, in some examples, the fourth and fifth active material layers are made of the same active material.

[0074] In some embodiments, the current collector 113 of the first positive electrode may be aluminum foil, and the current collector of the second positive electrode 150 may be aluminum foil.

[0075] In some embodiments, the negative electrode sheet of the winding core can be coated with active material on both sides, and the negative electrode material of the battery cell can be one or more of carbon materials such as graphite, hard carbon, and soft carbon, silicon-based materials, and lithium titanate materials.

[0076] Specifically, please refer to Figure 9 When the core is a wound structure, the first negative electrode 120 has a sixth active material layer 123 and a seventh active material layer 124 disposed opposite to each other. The active material of the sixth active material layer 123 is at least one selected from carbon materials, silicon-based materials, and lithium titanate materials. The active material of the seventh active material layer 124 is at least one selected from carbon materials, silicon-based materials, and lithium titanate materials. Further, in some examples, the sixth active material layer 123 and the seventh active material layer 124 are made of the same active material.

[0077] Similarly, when the core is a laminated structure, the second negative electrode 160 has an eighth active material layer and a ninth active material layer disposed opposite to each other. The active material of the eighth active material layer is at least one of carbon material, silicon-based material, and lithium titanate material. The active material of the ninth active material layer is at least one of carbon material, silicon-based material, and lithium titanate material. Further, in some examples, the eighth and ninth active material layers are made of the same active material.

[0078] In some embodiments, the current collector 125 of the first negative electrode may be copper foil, and the current collector of the second negative electrode 160 may be copper foil.

[0079] In some embodiments, such as Figure 10A , Figure 10B and Figure 10C As shown, the positive electrode, negative electrode, and reference electrode 20 of the battery can respectively form a positive tab, a negative tab, and a reference tab in the area of ​​the current collector not coated with active material. Further, the positive tab and the first aluminum tab can be connected by ultrasonic welding, and the aluminum tab connected to the positive tab is the first tab 40. The negative tab and the copper-plated nickel tab can be connected by ultrasonic welding, and the copper-plated nickel tab connected to the negative tab can be the second tab 41. The reference tab and the second aluminum tab can be connected by ultrasonic welding, and the aluminum tab connected to the reference tab is the third tab 42.

[0080] In some examples, the first tab 40, the second tab 41, and the third tab 42 are all provided with tab adhesive.

[0081] In some embodiments, this application also provides a pouch battery, including: an electrolyte, an aluminum-plastic film 902 shell, and a three-electrode cell 900 as described in any of the above embodiments, wherein the aluminum-plastic film 902 shell is in close contact with the three-electrode cell 900.

[0082] Furthermore, this application can prepare a pouch cell by winding or stacking the reference electrode 20 and the core to form a bare cell 901 (i.e., bare JR) with a reference electrode, and then preparing it into a pouch cell through steps such as liquid injection, encapsulation, and formation.

[0083] In some embodiments, this application also provides a reference electrode usage method, which calculates the capacity of the reference electrode based on design information and connects the reference electrode tab and the negative electrode tab. A constant current charging method is used to adjust the state of charge (SOC) of the reference electrode. The charging rate is 0.1~1C, and the charging time is 0.1~10h.

[0084] Furthermore, the reference electrode only needs to be connected to the charging and discharging equipment together with the negative electrode for constant current charging, without the need for double-sided lithium plating like metal wires.

[0085] Furthermore, the reference electrode SOC is 20%~80%. Too low or too high SOC will cause the reference electrode potential to be unstable, making it impossible to accurately monitor the changes in the positive and negative reference potentials.

[0086] Furthermore, the charging rate is preferably 0.1~0.5C. Excessively high charging rates can cause polarization of the reference electrode, affecting its lifespan.

[0087] The reference electrode provided in the above embodiments has an excellent service life after being adjusted for load, and the reference potential maintains good stability after long-term electrical performance testing.

[0088] Finally, it should be noted that in the description of this application, the 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 used only for the convenience of describing this application and simplifying the description, and do not 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 this application.

[0089] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0090] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., 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, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0091] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0092] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0093] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0094] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-electrode battery cell, characterized in that, include: Core and reference electrode; When the core is a wound structure, the core includes a first positive electrode sheet, a first negative electrode sheet, a first separator, and a second separator. The first positive electrode sheet, the first separator, the first negative electrode sheet, and the second separator are stacked sequentially and wound along the winding direction to form the wound structure. The first negative electrode sheet includes a first segment and a second segment continuously arranged along the winding direction. The first segment is disposed opposite to the first positive electrode sheet, and the second segment extends beyond the winding end of the first positive electrode sheet along the winding direction. The reference electrode sheet is disposed on the side of the second segment away from the first positive electrode sheet, and the first active material layer of the reference electrode sheet is disposed opposite to the second segment. The reference electrode sheet and the second segment are separated by the first separator and / or the second separator. When the core is a stacked structure, the core includes N+1 layers of second negative electrode sheets and N layers of second positive electrode sheets alternately stacked along a first direction. The core also includes a third separator, with adjacent second negative electrode sheets and second positive electrode sheets separated by the third separator. The reference electrode sheet is disposed on the side of the N+1 layer of second negative electrode sheet away from the second positive electrode sheet, and the first active material layer of the reference electrode sheet is disposed opposite to the N+1 layer of second negative electrode sheet. The reference electrode sheet and the N+1 layer of second negative electrode sheet are separated by the third separator.

2. The three-electrode battery cell according to claim 1, characterized in that, When the core is the winding structure, when viewed along the axial direction of the winding structure, the winding structure has a first bending area, a first straight area and a second bending area continuously arranged along the winding direction, and the reference electrode has a first end and a second end arranged opposite to each other, with the first end and the second end both located in the first straight area.

3. The three-electrode battery cell according to claim 2, characterized in that, Viewed along the axial direction of the winding structure, the length L4 of the reference electrode satisfies: 0.1L2≤L4≤0.8L2, where L2 is the length of the first straight region; The first end is close to the first bending area, the second end is close to the second bending area, and the distance between the first end and the first bending area is equal to the distance between the second end and the second bending area.

4. The three-electrode battery cell according to any one of claims 1 to 3, characterized in that, When the core is the wound structure, viewed radially along the core, the first negative electrode has a first overhang region and a second overhang region, the first separator has a third overhang region and a fourth overhang region, and the second separator has a fifth overhang region and a sixth overhang region; wherein, the first overhang region is the non-overlapping region of the first negative electrode, the first positive electrode, and the reference electrode in the electrode length direction, the second overhang region is the non-overlapping region of the first negative electrode, the first positive electrode, and the reference electrode in the electrode width direction; the third overhang region is the non-overlapping region of the first separator and the first negative electrode in the electrode length direction, the fourth overhang region is the non-overlapping region of the first separator and the first negative electrode in the electrode width direction, the fifth overhang region is the non-overlapping region of the second separator and the first negative electrode in the electrode length direction, and the sixth overhang region is the non-overlapping region of the second separator and the first negative electrode in the electrode width direction; The first overhang region has a length of 1mm to 4mm in the length direction of the electrode, the second overhang region has a width of 1mm to 4mm in the width direction of the electrode, the third overhang region has a length of 0.5mm to 4mm in the length direction of the electrode, the fourth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode, the fifth overhang region has a width of 0.5mm to 4mm in the length direction of the electrode, and the sixth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode.

5. The three-electrode cell according to claim 1, characterized in that, When the core is the stacked structure, the cutting size of the reference electrode is the same as the cutting size of the second positive electrode.

6. The three-electrode cell according to claim 1 or 5, characterized in that, When the core is the laminated structure, viewed along the first direction, the second negative electrode has a seventh overhang region and an eighth overhang region. The seventh overhang region is the non-overlapping region of the second negative electrode, the second positive electrode, and the reference electrode in the electrode length direction, and the eighth overhang region is the non-overlapping region of the second negative electrode, the second positive electrode, and the reference electrode in the electrode width direction. Viewed along the first direction, the third separator has a ninth overhang region and a tenth overhang region. The ninth overhang region is the non-overlapping region of the third separator and the second negative electrode in the electrode length direction, and the tenth overhang region is the non-overlapping region of the third separator and the second negative electrode in the electrode width direction. The seventh overhang region has a length of 1mm to 4mm in the length direction of the electrode, and the eighth overhang region has a width of 1mm to 4mm in the width direction of the electrode; the ninth overhang region has a length of 0.5mm to 4mm in the length direction of the electrode, and the tenth overhang region has a width of 0.5mm to 4mm in the width direction of the electrode.

7. The three-electrode battery cell according to any one of claims 1 to 3 and 5, characterized in that, The active material in the first active material layer is one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium titanate, and lithium titanium phosphate.

8. The three-electrode cell according to claim 7, characterized in that, The thickness of the active material coating of the first active material layer is 1μm~10μm.

9. The three-electrode battery cell according to any one of claims 1 to 3 and 5, characterized in that, When the core is the wound structure, the first positive electrode sheet has a second active material layer and a third active material layer disposed opposite to each other; when the core is the stacked structure, the second positive electrode sheet has a fourth active material layer and a fifth active material layer disposed opposite to each other. The active material of the second active material layer is one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; the active material of the third active material layer is one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; the active material of the fourth active material layer is one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide; and the active material of the fifth active material layer is one of ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.

10. The three-electrode battery cell according to any one of claims 1 to 3 and 5, characterized in that, When the core is the wound structure, the first negative electrode sheet has a sixth active material layer and a seventh active material layer disposed opposite to each other; when the core is the stacked structure, the second negative electrode sheet has an eighth active material layer and a ninth active material layer disposed opposite to each other. The active material of the sixth active material layer is one of carbon material, silicon-based material, and lithium titanate material; the active material of the seventh active material layer is one of carbon material, silicon-based material, and lithium titanate material; the active material of the eighth active material layer is one of carbon material, silicon-based material, and lithium titanate material; and the active material of the ninth active material layer is one of carbon material, silicon-based material, and lithium titanate material.

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