Electrode structure of battery and battery comprising same

Abstract

The utility model belongs to the technical field of lithium ion batteries, and provides an electrode structure of a battery and a battery comprising the same, the electrode structure comprises a positive pole piece, a reference electrode, a diaphragm and a negative pole piece, the diaphragm is used for separating the positive pole piece from the negative pole piece, the diaphragm comprises a base membrane, the reference electrode is arranged on the surface of the base membrane, and the negative pole piece is arranged on the surface of the base membrane. The diaphragm further comprises an organic coating located on the surfaces of the reference electrode and the base membrane, and the reference electrode further comprises an electric connection part arranged on the outer side of the diaphragm. The organic coating is arranged on the surface of the diaphragm to reduce the gap between the diaphragm and the copper wire, so that the copper wire is in better contact with the diaphragm, the use of the diaphragm is reduced, the diaphragm is saved, the diaphragm containing reference is closer to the surface of a negative electrode, and the test accuracy is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium ion batteries, and in particular relates to a battery electrode structure and a battery containing the same. Background Art

[0002] The current method for preparing three electrodes involves disassembling a prepared bare cell, wrapping a separator around the copper wire, and placing it on the negative electrode surface to recreate the bare cell. This method is cumbersome and costly, resulting in a low success rate for both the cell and the three-electrode process. Furthermore, the separator has a certain thickness, leaving a gap between it and the copper wire. Excessive separators increase the distance between the separator and the negative electrode, reducing test accuracy. Utility Model Content

[0003] In response to the above problems, the present invention proposes an electrode structure of a battery, including a positive electrode sheet, a reference electrode, a diaphragm and a negative electrode sheet, wherein the diaphragm is used to separate the positive electrode sheet and the negative electrode sheet, the diaphragm includes a base film, the reference electrode is arranged on the surface of the base film, the diaphragm also includes an organic coating located on the reference electrode and the surface of the base film, and the reference electrode also includes an electrical connection part arranged on the outside of the diaphragm.

[0004] Furthermore, the organic coating is a PVDF coating.

[0005] Furthermore, an inorganic coating is provided on the surface of the organic coating, and the inorganic coating is a ceramic coating.

[0006] Furthermore, the reference electrode is a copper wire, and the diameter of the copper wire is 200nm-1um.

[0007] Furthermore, the base film is one of polypropylene, polyethylene, polyethylene terephthalate, and polyamide, and the thickness of the base film is 5-15 μm.

[0008] Furthermore, the ratio of the length L1 of the copper wire disposed between the base film and the PVDF coating to the width of the base film is (0.3-0.8).

[0009] Furthermore, the length L1 of the copper wire disposed between the base film and the PVDF coating is 30 mm to 90 mm.

[0010] Furthermore, the length L2 of the electrical connection portion of the copper wire disposed outside the diaphragm is 50-70 mm.

[0011] Furthermore, the thickness of the organic coating is 2-4 μm, and the thickness of the inorganic coating is 1-5 μm.

[0012] The utility model also provides a battery, comprising any one of the battery electrode structures described above.

[0013] The electrode structure of the battery of the present invention and the battery containing the same pre-buries the copper wire in the diaphragm in advance, which reduces the time for later disassembly and placement, improves efficiency and has a high success rate, and has little impact on the performance test of the battery cell; by arranging an organic coating on the surface of the diaphragm to reduce the gap between the diaphragm and the copper wire, the contact between the copper wire and the diaphragm is better, and the use of the diaphragm is reduced, saving the diaphragm, and making the reference diaphragm closer to the negative electrode surface, thereby improving the test accuracy.

[0014] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained by the structures indicated in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A schematic diagram of a cross-sectional structure of a copper wire diaphragm in an embodiment of the present invention is shown;

[0017] Figure 2 A schematic cross-sectional structure diagram of a copper wire diaphragm in an embodiment of the present invention is shown;

[0018] Figure 3 The figure shows a schematic diagram of the battery cell structure in an embodiment of the present utility model. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0020] In order to solve the technical problem in the prior art that there is a gap between the thickness of the battery cell diaphragm and the reference electrode (in this embodiment, the reference electrode is copper wire), which leads to a large distance between the diaphragm and the negative electrode plate and a decrease in test accuracy, a battery electrode structure is provided in this embodiment, including a positive electrode plate, a reference electrode, a diaphragm and a negative electrode plate, the diaphragm is used to separate the positive electrode plate and the negative electrode plate, the diaphragm includes a base membrane, the reference electrode is arranged on the surface of the base membrane, the diaphragm also includes an organic coating located on the surface of the reference electrode and the base membrane, and the reference electrode also includes an electrical connection part arranged on the outside of the diaphragm.

[0021] Specifically, in this embodiment, in order to improve the affinity between the electrode and the electrolyte and increase the electrolyte retention, the organic coating is a PVDF (polyvinylidene fluoride) coating. After the PVDF layer on the surface of the base film dries, it can fix the copper wire; secondly, during the hot pressing process, PVDF bonds the electrode and the diaphragm, eliminates the air in the internal gap, increases the hardness of the battery cell, and maintains the consistency of the battery cell thickness.

[0022] Specifically, in this embodiment, in order to further strengthen the fixation of the copper wire, improve the high temperature resistance and heat shrinkage resistance of the base film, and enhance the mechanical strength of the diaphragm, thereby improving the safety performance of the battery, an inorganic coating is also provided on the surface of the organic coating. The inorganic coating is a ceramic coating. The ceramic layer has a rich pore structure and good electrolyte wettability, which enhances the liquid absorption and retention capacity of the diaphragm and improves the service life of the battery.

[0023] Copper wire is a material with excellent electrical and mechanical properties, which improves production convenience and efficiency, allowing for large-scale production. Furthermore, the lithium foil layer on the copper surface has a stable electrode potential, which improves test accuracy. Thinner copper wire is more likely to break, making implantation difficult and reducing subsequent usability. Thicker copper wire has a greater impact on battery performance, leading to increased self-discharge. In this example, copper wire is used as the reference electrode, and the diameter of the copper wire is further limited to 200nm-1um. Figure 1 The cross-sectional structure diagram of the copper wire diaphragm in the embodiment of the present invention is shown. Figure 1 In the process, the copper wire is placed on the surface of the base film, which is in a wet film state. After the copper wire is placed, the liquid on the surface of the base film is in contact with the solid copper wire. The PVDF coating and the ceramic layer are sprayed on the surface of the copper wire in sequence. After drying, the copper wire can be fixed.

[0024] In this embodiment, the type of base film is also limited and described. The base film is one of PP (polypropylene), PE (polyethylene), PET (polyethylene glycolterephthalate), PA (polyamide), and PI (polyimide). In this embodiment, the thickness of the base film is also limited and described. The thinner the base film is, the smaller the resistance to blocking the electrolyte is, the lower the internal resistance is, and the faster the ion transmission rate is, so that the discharge rate of the battery is faster and the cycle performance is improved. However, if the base film is too thin, its strength will be reduced, the isolation performance will be reduced, and it may even cause a short circuit; the thicker the base film is, the greater the resistance to blocking the electrolyte is, the slower the ion transmission rate is, the internal resistance is increased, the battery performance is deteriorated, the safety performance is improved, and the cycle performance is reduced. In this embodiment, the thickness of the base film is selected to be 5-15um, which can better improve the battery performance.

[0025] Figure 2 The cross-sectional structure diagram of the copper wire diaphragm in the embodiment of the present invention is shown. Figure 2 In the width direction of the base film, the length of the copper wire set between the base film and the PVDF coating is represented by L1, and the length of the electrical connection part of the copper wire set on the outside of the diaphragm is represented by L2. In this embodiment, considering the difficulty of placing the copper wire and the safety performance of the electrode diaphragm, the ratio of the length L1 of the copper wire set between the base film and the PVDF coating to the width of the base film is (0.3-0.8). Specifically, the length L1 of the copper wire set between the base film and the PVDF coating is 30mm-90mm, and the length L2 of the electrical connection part of the copper wire set on the outside of the diaphragm is 50-70mm.

[0026] Specifically, in this embodiment, the thickness of the organic coating is 2-4 um, and the thickness of the inorganic coating is 1-5 um.

[0027] This embodiment also provides a battery, including the above electrode structure.

[0028] In this embodiment, the preparation method of the electrode structure and the battery assembly is also described in detail:

[0029] First, the pretreatment of the reference electrode is described. In this embodiment, the reference electrode is a copper wire. A copper wire with a diameter R of 300 nm and a length of 100 mm is selected and soaked in concentrated acid for a period of time to remove the oxide layer on the surface. In this embodiment, concentrated sulfuric acid is selected as the concentrated acid. It should be noted that this embodiment does not limit the type of concentrated acid and the soaking time of the reference electrode. Without departing from the concept of the present invention, they are all within the protection scope of the present invention.

[0030] Preparation of a reference electrode-containing diaphragm: A treated copper wire is placed on the surface of the diaphragm base film. In this example, the diaphragm is a 9µm thick polypropylene base film. The treated copper wire is placed on this surface, with a length of 50mm. A 3µm thick PVDF layer is sprayed on this surface, followed by a 3µm thick ceramic layer by gravure coating, to form the reference electrode-containing diaphragm. In this example, the composition and thickness of the diaphragm are conventionally chosen by those skilled in the art and are not specifically limited here.

[0031] Preparation of positive electrode slurry: In this embodiment, the positive electrode active material is prepared by using lithium iron, lithium iron manganese, ternary, lithium titanate, lithium iron phosphate, etc.

[0032] Specifically, lithium iron phosphate is used as the positive electrode active material, and the positive electrode active material, conductive agent, and binder are mixed in a ratio of 95:2:3. After the slurry is mixed, N-methylpyrrolidone (NMP) is added and stirred into a uniform and stable positive electrode slurry.

[0033] It should be noted that, in this embodiment, the conductive agent is selected from one of carbon black, conductive polymers, and metal conductive agents. The conductive polymer is, for example, polyaniline (PANI), and the metal conductive agent is, for example, some metal particles or nanomaterials, such as copper particles, silver particles, etc.; the binder is selected from any one of polytetrafluoroethylene (PTFE), polypropylene (PVDF), carboxymethyl cellulose (CMC), and thermoplastic polymers. In this embodiment, the selection of the type and ratio of the conductive agent and the binder is only an adaptability description and does not impose specific limitations on the content.

[0034] Preparation of positive electrode sheets: The mixed slurry is applied to the positive electrode collector by transfer coating, and the positive electrode roll is obtained after drying; the positive electrode roll is rolled to obtain the positive electrode sheet. In this embodiment, the positive electrode sheet is one of single-layer, double-layer or multi-layer, and there is no specific limitation on the number of positive electrode sheets.

[0035] Preparation of negative electrode slurry: In this embodiment, the negative electrode active material is prepared using hard carbon, soft carbon, natural graphite, artificial graphite, silicon and silicon carbon, etc. Without departing from the concept of the present invention, the components of the negative electrode active material are not limited.

[0036] Specifically, the negative electrode active material, conductive agent, and binder are mixed in a ratio of 95.5:2.5:2, and then deionized water is added and stirred to form a uniform and stable top layer of negative electrode slurry. In this embodiment, the selection of the conductive agent and binder in the negative electrode slurry is the same as that for the preparation of the positive electrode slurry and will not be repeated here.

[0037] Preparation of negative electrode sheets: The mixed slurry is applied to the negative electrode current collector by transfer coating, and a negative electrode roll is obtained after drying; the negative electrode roll is rolled to obtain a negative electrode sheet. In this embodiment, the negative electrode sheet is one of single-layer, double-layer or multi-layer, and there is no specific limitation on the number of negative electrode sheets.

[0038] This embodiment also describes the assembly process of the battery cell: the positive electrode sheet, the reference electrode separator, and the negative electrode sheet are arranged in sequence and wound to form a battery cell. Figure 3 As shown, Figure 3 Figure 3 The figure shows a schematic diagram of the battery cell structure in an embodiment of the present utility model.

[0039] This embodiment also specifically describes the preparation of the battery: the electrolyte is lithium hexafluorophosphate (LiPF6) dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a ratio of 1.5:1:0.5, with a concentration of 1.2 mol / L. The electrolyte is injected into the dry battery cell, and a lithium-ion soft-pack battery is obtained after formation and volume separation.

[0040] In this embodiment, the components, proportions, and concentrations of the electrolyte are all conventional technical choices made by those skilled in the art and are not limited here.

[0041] In this embodiment, the functions such as positive and negative electrode voltage monitoring of the electrode structure involved in the utility model are also explained by setting a comparative example. In this embodiment, the positive and negative electrode voltage monitoring includes capacity testing, the voltage difference between the positive electrode and the reference electrode, and the voltage difference between the negative electrode and the reference electrode.

[0042] In this embodiment, specific test methods for capacity test, voltage difference between the positive electrode and the reference electrode, voltage difference between the negative electrode and the reference electrode, etc. are also described:

[0043] Capacity test: In a 25°C incubator, charge the battery to 3.65V at a constant current rate of 0.33C, charge the battery at a constant voltage of 3.65V to a current cutoff of 0.05C, let it stand for 30 minutes, then discharge the battery to 2.5V at a constant current of 0.33C, let it stand, and cycle the battery for three weeks. The capacity in the last week is the actual capacity C0 of the battery.

[0044] Positive / negative and reference electrode voltage difference: Charge the battery to 100% remaining capacity (State of Charge, SOC) at 0.33C0 constant current and constant voltage, and monitor the voltage difference between the positive and reference electrodes, the voltage difference between the negative and reference electrodes, and the voltage difference between the positive and negative electrodes.

[0045] Comparative Example 1:

[0046] The reference electrode in Comparative Example 1 is a copper wire with a diameter of 300 nm. The copper wire is placed between two layers of diaphragms, and the length L1 between the diaphragms on both sides is 50 mm. The two layers of diaphragms with copper wire are placed on the surface of the negative electrode.

[0047] Example 1:

[0048] The reference electrode in Example 1 is a copper wire with a diameter of 300 nm. The copper wire is placed on the surface of the base film. A 2 μm thick PVDF coating and a 3 μm thick ceramic coating are sequentially provided on the copper wire and the surface of the base film. The length L1 of the copper wire between the base film and the PVDF coating is 50 mm. The base film on which the copper wire is placed is placed on the surface of the negative electrode.

[0049] In this embodiment, except for the different way of setting the copper wire, the rest of the preparation of the positive electrode sheet, the preparation of the negative electrode sheet, the preparation method of the battery cell, the selection of the electrolyte, etc. are the same. The preparation content has been explained above and will not be repeated here.

[0050] In this embodiment, the functions of monitoring the positive and negative voltages of the electrode structure involved in the present invention are described by setting Examples 2 to 12, as shown in the following table:

[0051] Table 1

[0052]

[0053]

[0054] Comparing Example 1 with Comparative Example 1, the actual capacity of the battery after the test of the three-electrode structure of the present invention is greater than the actual capacity of the battery after the test in Comparative Example 1, and by comparing the voltage difference between the positive electrode and the reference electrode, and the voltage difference ratio between the negative electrode and the reference electrode in Example 2 and Example 12, and by observing the voltages of the positive electrode and the reference electrode relative to the SOC curve and the voltages of the negative electrode and the reference electrode relative to the SOC curve, the fluctuation range is small, and the performance of the three-electrode structure of the present invention is stable.

[0055] The electrode structure of the battery of the present invention and the battery containing the same pre-buries the copper wire in the diaphragm in advance, which reduces the time for later disassembly and placement, improves efficiency and has a high success rate, and has little impact on the performance test of the battery cell; by arranging an organic coating on the surface of the diaphragm to reduce the gap between the diaphragm and the copper wire, the contact between the copper wire and the diaphragm is better, and the use of the diaphragm is reduced, saving the diaphragm, and making the reference diaphragm closer to the negative electrode surface, thereby improving the test accuracy.

[0056] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A battery electrode structure, characterized in that: It includes a positive electrode sheet, a reference electrode, a diaphragm and a negative electrode sheet, the diaphragm is used to separate the positive electrode sheet and the negative electrode sheet, the diaphragm includes a base film, the reference electrode is arranged on the surface of the base film, the diaphragm also includes an organic coating located on the reference electrode and the surface of the base film, and the reference electrode also includes an electrical connection part arranged on the outside of the diaphragm.

2. The battery electrode structure according to claim 1, characterized in that: The organic coating is a PVDF coating.

3. The battery electrode structure according to claim 2, characterized in that: An inorganic coating is also provided on the surface of the organic coating, and the inorganic coating is a ceramic coating.

4. The battery electrode structure according to claim 3, characterized in that: The reference electrode is a copper wire with a diameter of 200nm-1um.

5. The battery electrode structure according to claim 1, characterized in that: The base film is one of polypropylene, polyethylene, polyethylene terephthalate, and polyamide, and the thickness of the base film is 5-15 μm.

6. The battery electrode structure according to claim 4, characterized in that: The ratio of the length L1 of the copper wire disposed between the base film and the PVDF coating to the width of the base film is (0.3-0.8).

7. The battery electrode structure according to claim 6, characterized in that: The length L1 of the copper wire disposed between the base film and the PVDF coating is 30 mm to 90 mm.

8. The battery electrode structure according to claim 6, characterized in that: The length L2 of the electrical connection portion of the copper wire disposed outside the diaphragm is 50-70 mm.

9. The battery electrode structure according to claim 3, characterized in that: The thickness of the organic coating is 2-4 μm, and the thickness of the inorganic coating is 1-5 μm.

10. A battery, characterized in that: An electrode structure comprising a battery according to any one of claims 1 to 9.

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