Diaphragm and lithium ion battery
By setting a coating layer on the surface of the lithium-ion battery separator to form regular or irregular pore channels, the problem of electrical performance loss caused by the improvement of battery safety in the prior art is solved, the uniformity of electrolyte and gas discharge are optimized, and the charging and discharging efficiency and cycling performance of the battery are improved.
Patent Information
- Application Number
- CN202422179188.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-05
- Publication Date
- 2025-07-01
- Estimated Expiration
- 2034-09-05
AI Technical Summary
While improving safety performance, existing lithium-ion battery separators lead to loss of electrical performance, such as reduced charge and discharge efficiency, poor circulation performance, and difficulty in discharging gas during the decomposition process, affecting the thickness and energy density of the battery.
A coating layer is provided on the surface of the diaphragm base film, which includes a mesh coating, a cross mesh coating or a special-shaped coating, forming regular or irregular pores or channels, providing channels for electrolyte infiltration and side-reacting gas discharge.
The electrolyte infiltration time is shortened, the gas discharge during the melting process is optimized, the uniformity and stability of the SEI film are improved, and the charging and discharging efficiency and cycling performance of the battery are improved.
Smart Images
Figure CN223052325U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the field of batteries, and particularly relates to a separator and a lithium-ion battery. Background Art
[0002] In recent years, with the wide application of lithium-ion batteries, the lithium-ion battery industry has achieved rapid growth. Lithium-ion batteries mainly consist of positive and negative electrode materials, electrolyte, separator, etc. Among them, the separator, as one of the key components of lithium-ion batteries, plays an important role in maintaining battery safety and improving battery performance. It mainly isolates the positive and negative electrodes to prevent direct contact between the two poles from causing a short circuit, and allows electrolyte ions to pass through, which is crucial for the electrical and safety performance of lithium-ion batteries.
[0003] The reaction mechanism of lithium-ion batteries is the reversible insertion and extraction process of Li + through the separator between the positive and negative electrode materials. Lithium-ion battery separators have good insulation; high corrosion resistance; high heat resistance and stability; high mechanical strength; sufficient pore size and porosity, allowing lithium ions to pass through while preventing other substances from passing through. However, in actual use, in order to ensure the safety performance of the battery, it often causes losses in the electrical performance of lithium-ion batteries. For example, for high-capacity batteries, the separator thickness is increased to reduce thermal shrinkage, or ceramic is coated on one or both sides, which will lead to a slower Li + transmission speed during charge and discharge, resulting in a decrease in charge and discharge efficiency, poor rate performance and cycling performance, and an increase in battery thickness, thereby causing a loss of energy density. In addition, during the formation of the SEI film in the formation process of lithium-ion batteries, gas is generated, which is likely to cause difficulties in discharging bubbles on the surface of the negative electrode sheet and uneven formation of the SEI film, and there is a risk of failure during the cycling process. Content of the Utility Model
[0004] The purpose of the utility model is to overcome the shortcomings in the prior art and provide a separator and a lithium-ion battery.
[0005] To achieve the above purpose, the technical solution adopted by the utility model is as follows:
[0006] A separator, comprising a separator base film and a coating layer provided on the surface of the separator base film;
[0007] The coating layer includes a reticular coating or a special-shaped coating;
[0008] The reticular coating includes a parallel reticular coating layer or a cross reticular coating layer; the parallel reticular coating layer includes multiple reticular coating lines arranged in parallel; the cross reticular coating layer includes multiple reticular coating lines arranged in a cross;
[0009] The special-shaped coating includes special-shaped coating lines;
[0010] Regular or irregular pores or channels are formed between the reticulated coating lines and the profiled coating lines described above.
[0011] The thickness of the coating layer on one side is t, where 0.1 μm ≤ t ≤ 20 μm, preferably 2 μm.
[0012] The widths of the reticulated coating lines and the profiled coating lines described above are independently m; 0.1 mm ≤ m ≤ 20 mm. The distance between adjacent parallel reticulated lines in the parallel reticulated coating layer is d1, 0.1 mm ≤ d1 ≤ 20 mm; the coating angle is a1, 0° ≤ a1 ≤ 180°. Preferably, 30° ≤ a1 ≤ 60°; m1 = 1 mm; d1 = 2 mm.
[0013] The crossing angle of the reticulated coating lines in the cross - reticulated coating layer is a2; 0° ≤ a2 ≤ 180°. Regular pores are formed between the crossing reticulated coating lines; the length of the pores is d2, 0.1 mm ≤ d2 ≤ 20 mm.
[0014] Preferably, 30° ≤ a2 ≤ 60°; m2 = 1 mm; d2 = 2 mm.
[0015] The gaps formed between the profiled coating lines are one of triangles or polygons.
[0016] As one form, the gap formed between the profiled coating lines is a "convex" dodecagon structure; the distance between the head and the tail of the "convex" - shaped structure is d3, 0.1 mm ≤ d3 ≤ 20 mm.
[0017] Preferably, d3 = 6 mm.
[0018] A dot - shaped coating layer is provided on one side of the coating layer close to the edge of the separator; the width of the dot - shaped coating layer is c, c ≥ (b - s) / 2; where b is the width of the separator and s is the width of the positive electrode plate.
[0019] Preferably, c = 1.5 mm.
[0020] The dot - shaped coating layer is a high - temperature - resistant and high - strength separator coating layer; preferably, the dot - shaped coating layer is an aramid coating; preferably, the thickness of the dot - shaped coating layer is 0.1 - 5 μm; preferably 1 μm. The present utility model also includes a lithium - ion battery, including the separator; the positive and negative electrodes and the separator are assembled into lithium - ion batteries with different structures by winding or laminating methods.
[0021] Compared with the prior art, the beneficial effects of the present utility model are:
[0022] In the solution of this application, a functional coating layer is coated on the separator, and at least regular or irregular pores or channels are provided in the coating layer; the pores or channels provide an electrolyte infiltration channel and a side reaction gas discharge channel, which can not only shorten the infiltration time after liquid injection, but also improve the uniformity, density and stability of the surface SEI film by optimizing the electrolyte infiltration uniformity and timely discharging the gas generated by side reactions during the formation process, thereby improving the charge and discharge efficiency and cycle performance of the battery, etc. Description of the Drawings
[0023] Figure 1 It is a schematic structural diagram of the separator of Example 1;
[0024] Figure 2 It is a schematic structural diagram of the separator of Example 2;
[0025] Figure 3 It is a schematic structural diagram of the separator of Example 3;
[0026] Figure 4 It is a schematic structural diagram of the separator of Example 4. Detailed Description of the Invention
[0027] In order to enable those skilled in the art of this technology to better understand the technical solution of this utility model, the following further detailed description of this utility model is provided in conjunction with the drawings and the best embodiments.
[0028] A separator includes a separator base film 001 and a coating layer 002 provided on the surface of the separator base film;
[0029] The coating layer includes a reticulated coating or a special-shaped coating;
[0030] The reticulated coating includes a parallel reticulated coating layer or a cross reticulated coating layer; the parallel reticulated coating layer includes a plurality of reticulated coating lines arranged in parallel; the cross reticulated coating layer includes a plurality of reticulated coating lines arranged in a cross;
[0031] The special-shaped coating includes special-shaped coating lines;
[0032] Regular or irregular pores or channels are formed between the reticulated coating lines and the special-shaped coating lines.
[0033] The thickness of the coating layer on one side is t, 0.1um ≤ t ≤ 20um, specifically it can be 0.1μm, 4μm, 10μm, etc., and preferably it is 2μm.
[0034] The widths of the reticulated coating lines and the special-shaped coating lines are independently m; 0.1mm ≤ m ≤ 20mm. Specifically, it can be 0.1mm, 4mm, 10mm, etc., and preferably it is 1mm.
[0035] The distance between adjacent parallel reticulation lines in the parallel reticulation coating layer is d1, where 0.1 mm ≤ d1 ≤ 20 mm; the coating angle is a1, where 0° ≤ a1 ≤ 180°. Preferably, 30° ≤ a1 ≤ 60°; m1 = 1 mm; d1 = 2 mm.
[0036] In the cross - reticulation coating layer, the cross - angle of the reticulation coating lines is a2; 0° ≤ a2 ≤ 180°, and regular pores are formed between the cross - reticulation coating lines; the length of the pores is d2, where 0.1 mm ≤ d2 ≤ 20 mm.
[0037] Preferably, 30° ≤ a2 ≤ 60°; d2 = 2 mm.
[0038] The gap formed between the special - shaped coating lines is one of a triangle or a polygon.
[0039] As one form, the gap formed between the special - shaped coating lines is a "convex" dodecagon structure; the distance between the head and the tail of the "convex" - shaped structure is d3, where 0.1 mm ≤ d3 ≤ 20 mm.
[0040] Preferably, d3 = 6 mm.
[0041] A dot - shaped coating layer is provided on one side of the coating layer close to the edge of the separator; the width of the dot - shaped coating layer is c, c ≥ (b - s) / 2; where b is the width of the separator and s is the width of the positive electrode sheet.
[0042] Preferably, c = 1.5 mm.
[0043] The dot - shaped coating layer is a high - temperature - resistant and high - strength separator coating layer; preferably, the dot - shaped coating layer is an aramid coating; preferably, the thickness of the dot - shaped coating layer is 0.1 - 5 μm; preferably 1 μm.
[0044] The following is illustrated by specific examples. Figure 1 Shows a form of a separator in Examples 1 and 2. The coating layer is a reticulation coating in the pore coating layer; the coating angle is a1; the distance between adjacent parallel reticulation lines is d1, and the width of the reticulation coating line is m; a1 = 30°, m = 1 mm, d1 = 2 mm (Example 1), a1 = 30°, m = 1 mm; d1 = 6 mm (Example 2).
[0045] Figure 2 Shows a form of a separator in Example 3. The coating layer is a cross - reticulation coating in the pore coating layer; the cross - angle of the reticulation coating lines in the cross - reticulation coating layer is a2; a2 = 45°; regular pores are formed between the cross - reticulation; the length of the pores is d2; d2 = 2 mm.
[0046] Figure 3 Shows a form of a separator in Example 4, where the coating layer is a form of a special-shaped coating layer in the porous coating layer; the gap formed between the special-shaped coating lines is a "convex" dodecagon structure; the distance between the head and tail of the "convex" character structure is d3, and d3 = 6 mm.
[0047] Figure 4 Shows a form of a separator in Example 5, where a dot-shaped coating layer is provided on one side of the coating layer close to the edge of the separator; the width of the dot-shaped coating layer is c, and c ≥ (b - s) / 2; where b is the width of the separator and s is the width of the positive electrode sheet. As one form, c = 1.5 mm.
[0048] The material of the separator base film is one or a combination of PP, PE, PP, PE, PI, or PEEK; the coating method is one of gravure roll coating, dip coating, narrow coating, or spraying;
[0049] The coating layer includes a binder and an insulating material; the binder is one or a mixture of polyvinylidene fluoride, polyethylene oxide, polyether, polymethyl methacrylate, polyacrylonitrile, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinylidene fluoride, and polyethylene glycol;
[0050] The insulating material is one or a mixture of Al2O3, AlOOH, γ - AlOOH, SiO2, TiO2, ZrO2, SnO2, MgO, ZnO, CaO, CeO2, Y2O3, BaTiO3, SrTiO3, LAGP. In this application, a mixture with a mass ratio of MgO to Al2O3 of 1:1 as the insulating material and PVDF as the binder is used as a preferred example for illustration.
[0051] The separator materials in Examples 1 - 4 were prepared in the following manner: A mixture of MgO and Al2O3 was added to an aqueous solution containing PVDF (wt 7.5%) and stirred to obtain a uniform coating slurry. The slurry was coated on the surface of a PE base film (material from Zhuhai Enjie, thickness: 5 μm) using a roll coating method with a coater, and then vacuum dried at 60°C for 12 h to obtain a separator with a coating layer.
[0052] The separator material in Example 5 was prepared in the following manner: First, the overall gravure coating part was the same as the separator preparation method in Example 3. Then, an aramid coating layer needed to be coated on the top as the dot-shaped coating layer. The coating material for the aramid coating layer was prepared as follows: An oily solvent NMP and PMIA with a mass ratio of 8:2 were heated and stirred (80°C, 30 min) and then coated on the above-mentioned gravure ceramic coating layer with a coating width of c = 1.5 mm and a thickness of 1 μm to obtain a separator with a 1.5 mm high-temperature and high-strength coating layer on the top.
[0053] The positive electrode plate is prepared in the following manner: The positive electrode active material LiCoO2, the conductive agent CNT, and the binder PVDF are mixed uniformly according to a mass ratio of 97.5:1.5:1, and the solvent NMP is added and stirred in a vacuum mixer to obtain a uniform positive electrode active paste; the positive electrode active paste is coated on the current collector Al foil and dried, rolled, and sheared to obtain the positive electrode plate.
[0054] The negative electrode plate is prepared in the following manner: The negative electrode active material graphite, the conductive agent Super P, the thickening agent CMC, and the binder SBR are mixed uniformly according to a mass ratio of 97.5:0.5:0.9:1.1, and the solvent deionized water is added and stirred in a vacuum mixer to obtain a uniform negative electrode active paste; the negative electrode active paste is coated on the current collector Cu foil and dried, rolled, and sheared to obtain the negative electrode plate.
[0055] The prefabricated positive electrode plate, negative electrode plate, and the separator obtained in Examples 1-5 are used to separately fabricate lithium-ion battery cells in a winding manner, and after processes such as aluminum-plastic shell encapsulation, drying, liquid injection, standing, jig forming, and grading, lithium-ion batteries are obtained.
[0056] Table 1 shows the preparation parameters of the separators in different examples, with the fully coated separator as the comparative example.
[0057] Table 1
[0058]
[0059] The liquid retention amount, initial voltage, and electrical performance of the lithium-ion batteries assembled with the separators described in the above Examples 1 to 5 and the comparative example are tested as follows:
[0060] Liquid retention amount and initial voltage test: The batteries filled with the same electrolyte are separately left standing at 40°C for 24 h, 36 h, and 48 h, and the initial voltage of the battery cells in different examples at different times is recorded. Generally, the initial voltage of the unformed charged battery reflects the electrolyte infiltration situation, and the stable voltage indicates complete electrolyte infiltration.
[0061] Capacity test: At 25°C, the battery is charged at a constant current of 0.2Cmin to 4.45V, and then charged at a constant voltage of 4.45V until the current drops to 0.05Cmin to obtain the charging capacity; after the battery rests for 10 min, it is discharged at a constant current of 0.2Cmin to 3.0V to obtain the discharge capacity.
[0062] K value: At 25 °C, the battery is charged at a constant current of 0.2C min until 3.9V, then charged at a constant voltage of 3.9V until the current drops to 0.05C min. After standing for 24 ± 12h, the battery voltage is tested with an electrochemical workstation to obtain the battery voltage OCV1. After continuing to stand for T (72 ± 12h), the voltage is tested with an electrochemical workstation to obtain OCV2. K value = (OCV1 - OCV2) / T
[0063] Cyclic test: At 25 °C, the battery is charged at a constant current of 1C min until 4.45V, and then charged at a constant voltage of 4.45V until the current drops to 0.05C min to obtain the charging capacity; after the battery sleeps for 10 min, it is discharged at a constant current of 0.5C min to 3.0V. The above steps of charge and discharge are repeated for the battery, and the number of cycles when the capacity ≥ 80% of the capacity is recorded.
[0064] Hot box test: At 25 °C, the battery is charged at a constant current of 1C min until 4.45V, and then charged at a constant voltage of 4.45V until the current drops to 0.05C min; the battery is placed in a normal temperature oven and heated at a rate of 5 °C per minute until the oven temperature reaches 130 °C and is maintained for 0.5h, and the highest temperature on the battery surface is recorded.
[0065] Table 2 shows the data test results of Examples 1-5 and the comparative example.
[0066] Table 2
[0067]
[0068] The above test results show that: By comparing Examples 1-5 and the comparative example, it can be seen that when the liquid retention amount is at the same level, the standing time required is shorter after the diaphragm coating is subjected to twill, reticular and combined coating, which can be shortened by more than 12h, and the higher the capacity and the more the number of cyclic capacity under the same standing time when using the diaphragm of this utility model, and the K value of the battery is not affected; It is proved that the diaphragm described in this utility model can not only shorten the infiltration time after injection, but also improve the uniformity, compactness and stability of the surface SEI film by optimizing the electrolyte infiltration uniformity and discharging the gas generated by side reactions in time during the formation process, thereby improving the battery cycle performance, etc. Among them, coating the insulating layer on the diaphragm can also ensure the safety and electrical performance of the lithium-ion battery by changing the coating material.
[0069] It should be noted that the ceramic insulating layer or other functional coatings coated on the diaphragm can be single-sided coating or double-sided coating, and the coating material can be optimized according to the battery performance, specifically manifested in Figure 4Among them, the contact range between the separator and the positive and negative electrode plates can be coated with functional materials such as ceramic glue to ensure the electrochemical performance of the battery. The non-contact top position can be coated with an insulating material with better thermal stability or higher strength to reduce the risk of thermal failure of the battery.
[0070] In summary, in the solution of this application, a functional coating layer is coated on the separator, and at least regular or irregular pores or channels are provided in the coating layer; the pores or channels provide electrolyte infiltration channels and by-product gas discharge channels, which can not only shorten the infiltration time after liquid injection, but also improve the uniformity, compactness and stability of the surface SEI film by optimizing the electrolyte infiltration uniformity and timely discharging the gas generated by side reactions during the formation process, thereby improving the charge and discharge efficiency and cycle performance of the battery.
[0071] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.
Claims
1. A diaphragm, characterized in that: It includes a diaphragm base film and a coating layer disposed on the surface of the diaphragm base film; The coating layer includes a mesh coating or a profile coating; The textured coating comprises a parallel textured coating layer or a cross textured coating layer; the parallel textured coating layer comprises a plurality of parallel textured coating lines; the cross textured coating layer comprises a plurality of cross textured coating lines; The profiled coating includes a profiled coating line; Regular or irregular pores or channels are formed between the mesh coating line and the special-shaped coating line.
2. The diaphragm according to claim 1, characterized in that The thickness of the coating layer on one side is t, 0.1um≤t≤20um.
3. The diaphragm according to claim 1, characterized in that The width of the mesh coating line and the special-shaped coating line are independently m; 0.1 mm≤m≤20 mm.
4. The diaphragm according to claim 1, characterized in that The distance between adjacent parallel mesh lines in the parallel mesh coating layer is d1, 0.1mm≤d1≤20mm; the coating angle is a1, 0°≤a1≤180°.
5. The diaphragm according to claim 1, characterized in that The crossing angle of the mesh coating line in the cross mesh coating layer is a2; 0°≤a2≤180°, and regular pores are formed between the cross mesh coating lines; the said pore length is d2, 0.1mm≤d2≤20mm.
6. The diaphragm according to claim 1, characterized in that The gap formed between the special-shaped coating lines is a kind of triangle or polygon.
7. The diaphragm according to claim 6, characterized in that The gap formed between the special-shaped coating lines is a "convex" twelve-side structure; the distance between the head and tail of the "convex" font-shaped structure is d3, 0.1mm≤d3≤20mm.
8. The diaphragm of claim 1, characterized in that The dot-shaped coating layer is provided on one side near the edge of the diaphragm; the width of the dot-shaped coating layer is c, c≥(bs) / 2; wherein b is the width of the diaphragm and s is the width of the positive electrode sheet.
9. The diaphragm of claim 8, characterized in that The thickness of the dot-shaped coating layer is 0.1-5 μm.
10. A lithium ion battery, characterized in that: The diaphragm comprises the diaphragm according to any one of claims 1 to 8.