Positive electrode sheet for improving low-temperature performance of lithium iron phosphate, battery cell structure and manufacturing method

Abstract

The application discloses an anode sheet for improving low-temperature performance of lithium iron phosphate, a battery structure and a manufacturing method, and belongs to the field of novel battery structure design, comprising a lithium iron phosphate anode sheet, and sodium ion anode sheets are arranged at the upper end and the lower end of the lithium iron phosphate anode sheet respectively. Through the mixed collocation of the lithium iron phosphate and the sodium ion anode sheets, the high energy density of the lithium iron phosphate battery and the excellent low-temperature performance of the sodium ion battery are comprehensively combined. Meanwhile, the mixed structure of the application also improves the SOC precision of the lithium iron phosphate battery, and improves the lithium precipitation problem at the edge of the lithium iron phosphate battery anode sheet.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of novel battery cell structure design, and particularly relates to a positive electrode sheet for improving low-temperature performance of lithium iron phosphate, a battery cell structure and a manufacturing method. BACKGROUND

[0002] The lithium iron phosphate battery cell has low ion and electron conductivity at low temperature due to the intrinsic characteristics of the limited material, and has poor low-temperature performance. The above technical problems are mainly solved by doping and coating of lithium iron phosphate material, and by adding an external heating device. The doping and coating of lithium iron phosphate material cannot fundamentally solve the intrinsic defects of the material, and the doping and coating will increase the production cost of the material. The external heating method also increases the manufacturing cost of the entire battery pack, and the design is also relatively complex. The technical solution recorded in patent publication No. CN103107332A and patent name A lithium iron phosphate positive electrode material with excellent low-temperature performance and a preparation method thereof has the disadvantages of complex material production process and uncontrollable product coating consistency. The technical solution recorded in patent application No. CN202210908456.2 and patent name A thermal management system for improving the low-temperature performance of a lithium iron phosphate battery has the disadvantage of high product cost. SUMMARY

[0003] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a positive electrode sheet for improving the low-temperature performance of lithium iron phosphate, a battery cell structure and a manufacturing method, so as to solve the disadvantages of complex material production process and increased product cost in the prior art.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] A positive electrode sheet for improving the low-temperature performance of lithium iron phosphate, comprising a lithium iron phosphate positive electrode sheet, and sodium ion positive electrode sheets arranged at the upper and lower ends of the lithium iron phosphate positive electrode sheet.

[0006] The application also discloses a manufacturing method of the positive electrode sheet for improving the low-temperature performance of lithium iron phosphate, comprising:

[0007] The middle layer of the electrode sheet is coated with lithium iron phosphate slurry to form a lithium iron phosphate positive electrode sheet;

[0008] Sodium ion positive electrode sheets are coated at the upper and lower ends of the lithium iron phosphate positive electrode sheet;

[0009] The coated electrode sheet is dried, rolled and cut to form a finished positive electrode sheet.

[0010] Preferably, the lithium iron phosphate positive electrode sheet is coated by means of doctor blade, spraying or rolling.

[0011] Preferably, the sodium ion positive electrode plate is coated by means of doctor blade, spraying or rolling.

[0012] Preferably, the drying conditions of the coated electrode plate are as follows: drying temperature is 100-130 DEG C, and drying time is 5-10 min.

[0013] An improved lithium iron phosphate low-temperature performance battery structure comprises the positive electrode plate prepared by the method for preparing an improved lithium iron phosphate low-temperature performance positive electrode plate.

[0014] Preferably, the positive electrode plate and the negative electrode plate are separated by a diaphragm.

[0015] The application also discloses a method for preparing an improved lithium iron phosphate low-temperature performance battery structure, comprising the following steps:

[0016] The middle layer of the electrode plate is coated with lithium iron phosphate slurry to form a lithium iron phosphate positive electrode plate.

[0017] The upper and lower ends of the lithium iron phosphate positive electrode plate are coated with sodium ion positive electrode plates.

[0018] The coated electrode plate is dried, rolled and cut to form a finished positive electrode plate.

[0019] The positive electrode plate and the negative electrode plate are separated by a diaphragm to form a battery.

[0020] Preferably, after the positive electrode plate and the negative electrode plate are separated by a diaphragm, a battery is formed by winding.

[0021] Preferably, after the positive electrode plate and the negative electrode plate are separated by a diaphragm, a battery is formed in the form of a laminated sheet.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] The application combines the high energy density of the lithium iron phosphate battery and the excellent low-temperature performance of the sodium ion battery through the mixed arrangement of the lithium iron phosphate and the sodium ion positive electrode plate.

[0024] ①The new battery structure combines the high energy density of the lithium iron phosphate battery and the excellent low-temperature performance of the sodium ion battery, and can exhibit more excellent performance at low temperature.

[0025] 2) The voltage platform region of the lithium iron phosphate material is relatively long, the error of the SOC and voltage corresponding relationship is large, the estimation accuracy of the battery system SOC is high, and the SOC and voltage corresponding relationship of the sodium ion positive material is accurate, so that the consistency of the lithium iron phosphate battery cell can be effectively improved, and the estimation accuracy of the battery system SOC is improved;

[0026] 3) The edge current density of the battery cell pole piece is the largest, the lithium ion migration rate of the lithium iron phosphate battery cell is slow, especially at low temperature, the lithium precipitation is prone to occur at the edge of the pole piece, and the excellent low-temperature characteristics of the sodium ion positive material can fundamentally improve the problem of lithium precipitation at the edge of the pole piece.

[0027] 4) The sodium ion positive material has low cost, and the use of the lithium iron phosphate and the sodium ion positive material can further reduce the cost of the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 FIG. 1 is a schematic diagram of the battery cell structure of the present application;

[0029] Figure 2 FIG. 2 is a schematic diagram of the positive pole piece of the present application.

[0030] 1-sodium ion positive pole piece; 2-lithium iron phosphate positive pole piece. DETAILED DESCRIPTION

[0031] In order to enable the personnel in the technical field to better understand the present application scheme, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the personnel in the field without creative labor should belong to the protection scope of the present application.

[0032] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0033] The present application will be described in further detail below in combination with the drawings:

[0034] Referring to Figure 2 The application discloses a positive electrode sheet for improving low-temperature performance of lithium iron phosphate, comprising a lithium iron phosphate positive electrode sheet 2, and sodium ion positive electrode sheets 1 arranged at the upper and lower ends of the lithium iron phosphate positive electrode sheet 2 respectively. Through the mixed arrangement of the lithium iron phosphate and the sodium ion positive electrode sheet, the high energy density of the lithium iron phosphate battery and the excellent low-temperature performance of the sodium ion battery are comprehensively combined. Meanwhile, the mixed structure of the application also improves the SOC accuracy of the lithium iron phosphate battery and solves the problem of lithium precipitation at the edges of the lithium iron phosphate battery cell sheet.

[0035] The application further discloses a manufacturing method of the positive electrode sheet for improving the low-temperature performance of lithium iron phosphate, comprising:

[0036] S1: using lithium iron phosphate slurry to coat the middle layer of the sheet to form a lithium iron phosphate positive electrode sheet 2;

[0037] S2: coating sodium ion positive electrode sheets 1 at the upper and lower ends of the lithium iron phosphate positive electrode sheet 2 respectively;

[0038] S3: drying, rolling and cutting the coated sheet to form a finished positive electrode sheet.

[0039] In some embodiments, the lithium iron phosphate positive electrode sheet 2 is coated by means of a doctor blade, spraying or rolling.

[0040] In some embodiments, the drying conditions of the coated sheet are as follows: the drying temperature is 100-130 DEG C, and the drying time is 5-10 min.

[0041] Referring to Figure 1 The application further discloses a battery cell structure for improving the low-temperature performance of lithium iron phosphate, comprising the positive electrode sheet manufactured by the manufacturing method of the positive electrode sheet for improving the low-temperature performance of lithium iron phosphate.

[0042] In some embodiments, the positive electrode sheet and the negative electrode sheet are arranged by a separator, and the sheets are assembled in a winding or stacking manner.

[0043] The application further discloses a manufacturing method of the battery cell structure for improving the low-temperature performance of lithium iron phosphate, comprising:

[0044] S4: using lithium iron phosphate slurry to coat the middle layer of the sheet to form a lithium iron phosphate positive electrode sheet 2;

[0045] S5: coating sodium ion positive electrode sheets 1 at the upper and lower ends of the lithium iron phosphate positive electrode sheet 2 respectively;

[0046] S6: drying, rolling and cutting the coated sheet to form a finished positive electrode sheet.

[0047] S7: After the positive electrode sheet and the negative electrode sheet are separated by the separator, the battery cell is formed by winding.

[0048] In some embodiments, after the positive electrode sheet and the negative electrode sheet are separated by the separator, the battery cell is formed in the form of a stack.

[0049] [Example 1]

[0050] The electrode sheet is coated according to the design requirement size during production. A specially designed gasket is used during coating, which separates the two sides and the middle area, and different material slurries can be coated. The proportion of the area can be adjusted by gasket design. The middle layer of the electrode sheet is coated with lithium iron phosphate slurry, and the upper and lower ends of the electrode sheet are coated with sodium ion positive electrode slurry. After the coated electrode sheet is dried at 100°C for 8 minutes, it is rolled, cut, and other processes to form the final composition of the finished battery cell. The positive and negative electrode sheets of the battery cell are separated by a separator, and the battery cell is formed by winding.

[0051] [Example 2]

[0052] The electrode sheet is coated according to the design requirement size during production. A specially designed gasket is used during coating, which separates the two sides and the middle area, and different material slurries can be coated. The proportion of the area can be adjusted by gasket design. The middle layer of the electrode sheet is coated with lithium iron phosphate slurry, and the upper and lower ends of the electrode sheet are coated with sodium ion positive electrode slurry. After the coated electrode sheet is dried at 115°C for 6 minutes, it is rolled, cut, and other processes to form the final composition of the finished battery cell. The positive and negative electrode sheets of the battery cell are separated by a separator, and the battery cell is formed by winding.

[0053] [Example 3]

[0054] The electrode sheet is coated according to the design requirement size during production. A specially designed gasket is used during coating, which separates the two sides and the middle area, and different material slurries can be coated. The proportion of the area can be adjusted by gasket design. The middle layer of the electrode sheet is coated with lithium iron phosphate slurry, and the upper and lower ends of the electrode sheet are coated with sodium ion positive electrode slurry. After the coated electrode sheet is dried at 120°C for 5 minutes, it is rolled, cut, and other processes to form the final composition of the finished battery cell. The positive and negative electrode sheets of the battery cell are separated by a separator, and the battery cell is formed by winding.

[0055] [Example 4]

[0056] The pole piece is coated according to the design requirement size during production, a specially designed gasket is used during coating, the two sides and the middle area are separated, different material slurries can be coated, and the proportion of the area can be adjusted through the gasket design; the middle layer of the pole piece is coated with lithium iron phosphate slurry, the upper and lower ends of the pole piece are coated with sodium ion positive electrode slurry, and the coated pole piece is finally composed of a finished battery cell after drying at 130 DEG C for 5 min, rolling, slitting and other processes. The positive and negative pole pieces of the battery cell are separated by a separator, and the battery cell is formed by winding.

[0057]

Example 5

[0058] The pole piece is coated according to the design requirement size during production, a specially designed gasket is used during coating, the two sides and the middle area are separated, different material slurries can be coated, and the proportion of the area can be adjusted through the gasket design; the middle layer of the pole piece is coated with lithium iron phosphate slurry, the upper and lower ends of the pole piece are coated with sodium ion positive electrode slurry, and the coated pole piece is finally composed of a finished battery cell after drying at 108 DEG C for 9 min, rolling, slitting and other processes. The positive and negative pole pieces of the battery cell are separated by a separator, and the battery cell is formed by winding.

[0059] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A positive electrode sheet for improving low-temperature performance of lithium iron phosphate, characterized by, The lithium iron phosphate positive electrode plate (2) is coated with sodium ion positive electrode plate (1) at the upper and lower ends. The improved lithium iron phosphate positive electrode plate is prepared by the following steps: The middle layer of the electrode plate is coated with lithium iron phosphate slurry to form the lithium iron phosphate positive electrode plate (2). The lithium iron phosphate positive electrode plate (2) is coated with sodium ion positive electrode plate (1) at the upper and lower ends. The coated electrode plate is dried, rolled and cut to form the finished positive electrode plate.

2. The positive electrode sheet for improving low-temperature performance of lithium iron phosphate according to claim 1, characterized by, The lithium iron phosphate positive electrode plate (2) is coated by means of doctor blade, spraying or rolling.

3. The positive electrode sheet for improving low-temperature performance of lithium iron phosphate according to claim 1, characterized by, The sodium ion positive electrode plate (1) is coated by means of doctor blade, spraying or rolling.

4. The positive electrode sheet for improving low-temperature performance of lithium iron phosphate according to claim 1, characterized by, The drying conditions of the coated electrode plate are as follows: drying temperature is 100-130°C, and drying time is 5-10 min.

5. An improved cell structure for improving low temperature performance of lithium iron phosphate, characterized in that, The improved lithium iron phosphate positive electrode plate of any one of claims 1-4.

6. The battery cell structure for improving low temperature performance of lithium iron phosphate according to claim 5, wherein The positive electrode plate and the negative electrode plate are separated by a separator.

7. A method for manufacturing an electrode structure for improving low-temperature performance of lithium iron phosphate, characterized in that, It comprises: The middle layer of the electrode plate is coated with lithium iron phosphate slurry to form the lithium iron phosphate positive electrode plate (2). The lithium iron phosphate positive electrode plate (2) is coated with sodium ion positive electrode plate (1) at the upper and lower ends. The coated electrode plate is dried, rolled and cut to form the finished positive electrode plate. The positive electrode plate and the negative electrode plate are separated by a separator to form the battery cell.

8. The method for manufacturing the structure of the battery cell for improving the low-temperature performance of lithium-iron-phosphate battery according to claim 7, wherein, After the positive electrode plate and the negative electrode plate are separated by a separator, the battery cell is formed by winding.

9. The method of claim 7, wherein the method further comprises: coating the surface of the lithium iron phosphate with a coating material. After the positive electrode plate and the negative electrode plate are separated by a separator, the battery cell is formed by stacking.

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