Processing method for controlling moisture of blade sodium battery

Abstract

The invention discloses a processing method for controlling moisture of a blade sodium battery, and belongs to the technical field of battery processing. The method comprises the following steps: baking a die-cut pole piece for 12-24 hours, laminating to an assembly liquid injection flow line for production, controlling the environment temperature of an assembly workshop to be 23 + / -3 DEG C, controlling the dew point to be less than or equal to-30 DEG C, baking a diaphragm at 70 + / -10 DEG C for 8-12 hours before lamination, and omitting the step of baking after entering a shell. According to the processing method for controlling the moisture of the blade sodium battery, the moisture of the battery cell is controlled by designing the processing technology, the influence of the moisture on the performance of the battery is reduced, and the safety and the cycle performance are improved; and the baking step after shell entering is omitted, so that the manufacturing cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery processing, and in particular relates to a process method for controlling the moisture content of a blade sodium battery. Background Art

[0002] Sodium-ion batteries have great potential as large-scale energy storage devices due to their low cost and similar physical and chemical properties to commercial lithium-ion batteries. Water is a key factor that needs to be strictly controlled during the battery production process. The presence of water can not only lead to the decomposition of salts in the electrolyte and cause certain corrosion damage to the positive and negative electrode materials and current collectors, but also lead to the reduction of battery cycle performance and safety performance: (1) Water reacts with electrolyte salts to generate HF; (2) HF destroys the SEI film, causing secondary film formation, resulting in deterioration of battery performance.

[0003] At present, the battery industry's moisture control process mainly relies on long-term high-temperature negative pressure baking of the battery cell after it is shelled, which comes from the baking process of the earliest cylindrical 18650 battery. The disadvantage of this process is that after the battery cell is shelled, the moisture in the pole piece can only be removed from a very small injection port. At the same time, after winding or stacking the core, the pole piece and the diaphragm are tightly fitted together after hot pressing. The moisture in the battery cell is difficult to bake out, and even if the baking time is extended, the effect is still not ideal. At the same time, the space utilization rate of the finished battery cell is small, the baking oven is large in scale, and consumes more energy. At present, the battery industry has been developing rapidly for many years, and high-efficiency assembly line processes have been popularized. At the same time, blade structure batteries have also been widely popularized. Blade batteries pursue high energy density, thicker and longer cores, and the baking effect after shelling is worse. In view of the current situation, the conventional lithium battery baking process is no longer suitable for industry needs.

[0004] Therefore, how to effectively control the moisture content of blade sodium batteries and improve the overall performance of the batteries is an important technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a process method for controlling the moisture content of a blade sodium battery to solve the problem that the performance of the blade sodium battery is poor due to the presence of moisture.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0008] Bake the die-cut pole pieces; bake the diaphragms before lamination; control the assembly environment, laminate and assemble the baked pole pieces and diaphragms, and directly inject liquid into the battery cells after they are put into the shell.

[0009] As a further solution of the present invention: the baking temperature of the die-cut electrode is 90°C±5°C, and the baking time is 12-24h.

[0010] As a further solution of the present invention: the pole piece is baked in a vacuum drying oven, the vacuum is 0.09-0.1MPa, nitrogen is filled in, and the oven is baked with blast air for 20 minutes, and the cycle is repeated 5-10 times.

[0011] As a further solution of the present invention: the die-cut pole piece is constrained by a fixture for baking to avoid edge warping of the pole piece after baking.

[0012] As a further solution of the present invention: the restraining force of the clamp restraining the pole piece is ≥10kgf.

[0013] As a further solution of the present invention: the baking temperature of the diaphragm is 60-80° C., and the baking time is 8-12 hours.

[0014] As a further solution of the present invention: the temperature of the assembly environment is 23±3°C, and the dew point is ≤-30°C.

[0015] As a further solution of the present invention: stacking to liquid injection is an assembly line production, eliminating the cell baking step, and the cell stacking to liquid injection time is ≤6h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a process method for controlling the moisture content of a blade sodium battery, which fully utilizes the advantages of large-scale assembly line production with fast beats, good control of the workshop environment, short operation time of the battery cell from lamination to liquid injection, and is not easy to absorb water, and the like. The die-cut pole piece is baked, and the moisture in the pole piece is more easily baked out than the core winding, which greatly improves the efficiency of baking and dehydration, improves production efficiency and reduces process costs. At the same time, the diaphragm is pre-baked before lamination, which makes it easier to control the moisture content of the battery cell and improve the overall safety performance and cycle performance of the battery; at the same time, the baking step after shelling is omitted, thereby reducing process costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the battery cycle number after capacity conversion in Example 1 of the present invention;

[0020] Figure 2 is a schematic diagram of the negative electrode interface of the battery after being fully charged after being converted into capacity in Example 1 of the present invention;

[0021] Figure 3 Schematic diagram of the battery cycle number after capacity conversion in Comparative Example 2 of the present invention;

[0022] Figure 4 It is a schematic diagram of the negative electrode interface of the battery after being fully charged after the battery is capacitated in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in 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 creative work are within the scope of protection of the present invention.

[0024] In the following examples and comparative examples, the positive electrode active material of the sodium ion battery is P-phase NaNiFeMnO2, the negative electrode active material is hard carbon, the core length is 341 mm, the core thickness is about 19.5 mm, and the core width is 118 mm.

[0025] Example 1

[0026] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0027] Place the die-cut electrode in a vacuum drying oven, constrain with a clamp, and set the constraint force to 30kgf. Evacuate to 0.09-0.1MPa, fill with nitrogen, and bake with blast for 20 minutes. Set the baking temperature to 90℃, cycle 5 times, and then lower the nitrogen environment to room temperature (25-30℃).

[0028] Bake the diaphragm at 60°C for 8 hours;

[0029] In an environment with a temperature of 23±3℃ and a dew point ≤-30℃, the baked pole pieces and diaphragms are stacked, assembled and injected on an assembly line. The battery cells are not baked before injection, and the time from stacking to injection is 4.5h.

[0030] Comparative Example 1

[0031] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0032] In an environment with a temperature of 23±3℃ and a dew point ≤-30℃, the die-cut pole pieces and diaphragms are directly stacked and assembled;

[0033] Place the assembled battery cell in a vacuum drying oven, evacuate to 0.09-0.1MPa, fill with nitrogen, set the baking temperature to 90℃, and bake with forced air for 20min. Repeat 5 times until the nitrogen environment drops to room temperature.

[0034] The baked battery cell is then injected with liquid.

[0035] Comparative Example 2

[0036] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0037] In an environment with a temperature of 23±3℃ and a dew point ≤-30℃, the die-cut pole pieces and diaphragms are directly stacked and assembled;

[0038] Place the assembled battery cell in a vacuum drying oven, evacuate to 0.09-0.1MPa, fill with nitrogen, set the baking temperature to 90℃, and bake with blast for 72h. Break the vacuum with nitrogen, and drop the nitrogen environment to room temperature.

[0039] The baked battery cell is then injected with liquid.

[0040] Comparative Example 3

[0041] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0042] Place the die-cut electrode in a vacuum drying oven, constrain with a clamp with a restraining force of 30kgf, evacuate to 0.09-0.1MPa, fill with nitrogen, and bake with blast for 20 minutes at a baking temperature of 90°C. Repeat 5 times until the nitrogen environment drops to room temperature.

[0043] In an environment with a temperature of 23±3℃ and a dew point ≤-30℃, the diaphragm and the baked pole pieces are produced on a stacking-assembly-injection process line. The battery cells are not baked before injection, and the time from stacking to injection is 4.5h.

[0044] Comparative Example 4

[0045] A process for controlling the moisture content of a blade sodium battery comprises the following steps:

[0046] Bake the diaphragm at 60°C for 8 hours;

[0047] In an environment with a temperature of 23±3℃ and a dew point ≤-30℃, the pole pieces and the baked diaphragms are stacked, assembled and injected on an assembly line. The battery cells are not baked before injection, and the time from stacking to injection is 4.5h.

[0048] The moisture content of the positive electrode sheets and the negative electrode sheets of the battery cells before liquid injection in Example 1 and Comparative Examples 1-4 were randomly sampled and tested at a test temperature of 180° C. The test results of the battery cell moisture content are shown in Table 1.

[0049] Table 1

[0050] Moisture content of positive electrode before injection Moisture content of negative electrode before injection Example 1 108ppm 389ppm Comparative Example 1 480ppm 1557ppm Comparative Example 2 280ppm 600ppm Comparative Example 3 260ppm 478ppm Comparative Example 4 350ppm 872ppm

[0051] At room temperature, the cycle number and capacity retention rate of the battery after capacity conversion in Example 1 are as follows: Figure 1As shown (tested twice in parallel), the negative electrode interface after the battery is fully charged is as follows Figure 2 As shown by Figure 1 and Figure 2 It can be seen that due to the effective control of the moisture in the blade sodium battery, there is no sodium precipitation at the negative electrode interface of the battery, and the number of cycles is >1500.

[0052] The battery cycle number and capacity retention rate after the battery was converted into capacity in Comparative Example 2 are as follows: Figure 3 As shown in Figure 2, the negative electrode interface of the battery after full charge is as follows: Figure 4 As shown by Figure 3 and Figure 4 It can be seen that the traditional method of baking battery cells cannot completely control the moisture content of the blade sodium battery, sodium precipitation will occur at the negative electrode interface of the battery, and the battery cycle number will be less than 160 cycles.

[0053] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process method for controlling the moisture content of a blade sodium battery, characterized in that: The method comprises the following steps: baking the die-cut pole pieces; baking the diaphragms before lamination; controlling the assembly environment, laminating and assembling the baked pole pieces and diaphragms, and directly injecting liquid into the battery cells after they are placed in the shells.

2. A process method for controlling moisture in blade sodium batteries according to claim 1, characterized in that: The baking temperature of the die-cut electrode is 90℃±5℃, and the baking time is 12-24h.

3. A process method for controlling moisture in blade sodium batteries according to claim 1, characterized in that: The electrode is baked in a vacuum drying oven, evacuated to 0.09-0.1MPa, filled with nitrogen, and baked with blast air for 20 minutes, repeating 5-10 times.

4. A process for controlling moisture in blade sodium batteries according to claim 1, characterized in that: The electrode baking is restrained by a clamp, and the clamp restraint force is ≥10kgf.

5. The process method for controlling moisture in blade sodium battery according to claim 1, characterized in that: The baking temperature of the diaphragm is 60-80°C, and the baking time is 8-12h.

6. A process for controlling moisture in blade sodium batteries according to claim 1, characterized in that: The assembly environment temperature is 23±3℃, dew point ≤-30℃.

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