Sodium ion cylindrical battery and formation method thereof

Abstract

The invention belongs to the technical field of sodium ion batteries, and particularly relates to a sodium ion cylindrical battery and a formation method thereof. The formation method of the sodium ion cylindrical battery provided by the invention comprises the following steps: (1) carrying out constant-current charging with a first current under a first vacuum degree; (2) under a second vacuum degree, carrying out constant current charging with a second current; (3) under a third vacuum degree, carrying out constant current charging with a second current; the second vacuum degree is greater than the first vacuum degree and less than the third vacuum degree; the second current is greater than the first current and less than the third current. According to the method, on the premise of ensuring a good formation interface, the formation time is greatly shortened, and the energy consumption required by formation is reduced; and meanwhile, the gradient increased vacuum degree is utilized, so that gas generated in the formation process is fully discharged, the influence of the formation gas on the subsequent performance is effectively reduced, and the performance of the battery cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium ion cylindrical battery and a formation method thereof. Background Art

[0002] During the formation process of sodium-ion batteries, a solid electrolyte film (SEI film) will be formed on the surface of the negative electrode. The thickness, composition, density and stability of the SEI film will directly affect the battery's electrochemical properties such as cycle life, safety, thermal stability and self-discharge.

[0003] Unlike the graphite negative electrode used in lithium-ion batteries, sodium-ion batteries usually use hard carbon as the negative electrode material, and the sodium intercalation mechanism of hard carbon is different from the lithium intercalation mechanism of graphite. However, the formation technology of sodium-ion batteries mostly follows that of lithium-ion batteries, that is, a small current charging formation method is used.

[0004] However, in sodium-ion batteries, unidirectional small current charging can easily cause interfacial polarization, which to a certain extent affects the formation of the SEI film and the solubility of SEI in the electrolyte during the later cycle process, and will further affect the cycle life of the sodium-ion battery. On the other hand, the small current formation method is also extremely time-consuming and energy-consuming in practical applications, which is not conducive to the promotion and application of the process.

[0005] CN 117080591 A proposes a formation method for a sodium ion battery based on a large current. Although this method can shorten the formation time and greatly improve the formation efficiency, it is found in experiments that the large current charging method easily causes the battery to generate a large amount of gas during formation. For cylindrical and square shell batteries, if the gas generated during formation cannot be completely discharged from the inside of the pole piece in time, it is easy to cause the sodium ions to be unable to be completely embedded in the negative electrode, thereby causing a small amount of bubble-like sodium precipitation to appear on the negative electrode piece after the battery is formed.

[0006] CN 117039216 A adopts multiple alternating pulse charge and discharge cycles to form sodium ions, strengthens the structure of sodium ion battery electrode materials through low-rate pulse charging and high-rate pulse discharging, and stabilizes the performance of SEI film. However, this method requires 5-10 alternating pulse charge and discharge cycles, which is time-consuming and inefficient. At the same time, there is a certain deviation in the capacity between batches of battery cells in factory production. If the SOC in this method is cut off, it is easy to cause the depth of charge or discharge to fail to reach the required position, thereby causing interface deterioration.

[0007] Therefore, designing a formation method suitable for cylindrical batteries has received increasing attention. Summary of the invention

[0008] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, an embodiment of the present invention provides a sodium ion cylindrical battery formation method, which can shorten the time required for formation while ensuring a good interface and can also ensure the performance of the battery cell.

[0009] The formation method of the sodium ion cylindrical battery of the embodiment of the present invention comprises the following steps:

[0010] (1) performing constant current charging at a first current under a first vacuum degree;

[0011] (2) performing constant current charging with a second current at a second vacuum degree;

[0012] (3) performing constant current charging with a second current at a third vacuum degree;

[0013] The first vacuum degree is less than the second vacuum degree and less than the third vacuum degree;

[0014] The first current is less than the second current and less than the third current.

[0015] The advantages and technical effects brought by the formation method of the sodium ion cylindrical battery of the embodiment of the present invention are as follows: 1. The method of the embodiment of the present invention formulates a corresponding voltage cut-off formation process according to the charge and discharge curve, DQ / DV curve and the characteristics of the formation gas production when the sodium ion layered oxide is formed, which greatly shortens the formation time and reduces the energy consumption required for the formation while ensuring a good formation interface; 2. The method of the embodiment of the present invention adopts a gradient increase in the vacuum degree to fully discharge the gas generated during the formation process, effectively reducing the influence of the formation gas production on the subsequent performance, thereby further improving the performance of the battery cell.

[0016] In some embodiments, the first vacuum degree is 30±2 kPa, the second vacuum degree is 40±2 KPa, and the third vacuum degree is 50±2 KPa.

[0017] In some embodiments, the first current is 0.01C to 0.03C, the second current is 0.1C to 0.2C, and the third current is 0.3C to 0.5C.

[0018] In some embodiments, in step (1), the constant current charging is performed to 1.5-1.7V.

[0019] In some embodiments, in step (2), the constant current charging is performed to 2.0-2.2V.

[0020] In some embodiments, in step (3), the constant current charging is performed to 3.0-3.2V.

[0021] In some embodiments, in step (1) and / or step (2) and / or step (3), the constant current charging temperature is 45±2°C.

[0022] In some embodiments, in step (1) and / or step (2) and / or step (3), the constant current charging is left alone for 5 to 15 minutes after completion.

[0023] In some embodiments, the mixture is allowed to stand for 5 to 15 minutes before step (1).

[0024] The embodiment of the present invention further provides a sodium ion cylindrical battery, which is formed by the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is an interface photo of Example 1;

[0026] Figure 2 is an interface photo of Example 2;

[0027] Figure 3 is an interface photo of Example 3;

[0028] Figure 4 This is a photo of the interface of Comparative Example 1;

[0029] Figure 5 This is a photo of the interface of Example 2;

[0030] Figure 6 This is a photo of the interface of Example 3;

[0031] Figure 7 This is a photo of the interface of Example 4. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0033] The formation method of the sodium ion cylindrical battery of the embodiment of the present invention comprises the following steps:

[0034] (1) performing constant current charging at a first current under a first vacuum degree;

[0035] (2) performing constant current charging with a second current at a second vacuum degree;

[0036] (3) performing constant current charging with a second current at a third vacuum degree;

[0037] The first vacuum degree is less than the second vacuum degree and less than the third vacuum degree;

[0038] The first current is less than the second current and less than the third current.

[0039] The formation method of the sodium ion cylindrical battery in the embodiment of the present invention specifies a corresponding voltage cut-off formation process according to the charge and discharge curve, DQ / DV curve and the characteristics of the formation gas production when the sodium ion layered oxide is formed, thereby greatly shortening the formation time and reducing the energy consumption required for the formation while ensuring a good formation interface; in the embodiment of the present invention, a gradient-increasing vacuum degree is adopted to fully discharge the gas generated during the formation process, effectively reducing the influence of the formation gas production on the subsequent performance, thereby further improving the performance of the battery cell.

[0040] In some embodiments, preferably, the first vacuum degree is 30±2 kPa, the second vacuum degree is 40±2 KPa, and the third vacuum degree is 50±2 KPa.

[0041] In the embodiment of the present invention, the value of vacuum degree is preferably selected, and the vacuum degree range is conducive to the discharge of gas generated inside the battery cell. If the vacuum degree is too low, the gas generated inside the battery cell is difficult to discharge; if the vacuum degree is too high, although it is conducive to gas discharge, it has high requirements on equipment and also increases unnecessary energy consumption.

[0042] In some embodiments, preferably, the first current is 0.01C to 0.03C, the second current is 0.1C to 0.2C, and the third current is 0.3C to 0.5C.

[0043] In some embodiments, preferably, in step (1), constant current charging is performed to 1.5-1.7V.

[0044] In some embodiments, preferably, in step (2), constant current charging is performed to 2.0-2.2V.

[0045] In some embodiments, preferably, in step (3), constant current charging is performed to 3.0-3.2V.

[0046] In some embodiments, preferably, in step (1) and / or step (2) and / or step (3), the constant current charging temperature is 45±2°C.

[0047] In the embodiment of the present invention, the temperature for constant temperature charging is preferably selected. This temperature range can accelerate the reaction and reduce the reaction energy consumption. If the temperature is low, the formation reaction progresses slowly and there is a risk of incomplete reaction. If the temperature is high, the electrolyte is prone to side reactions, affecting the formation effect.

[0048] In some embodiments, preferably, in step (1) and / or step (2) and / or step (3), the constant current charging is left for 5 to 15 minutes after completion. Leaving after the constant current charging is completed and leaving after each charge can effectively reduce the occurrence of polarization reaction of the battery cell and ensure the stable formation of the SEI film during the formation process.

[0049] In some embodiments, preferably, the battery is left standing for 5 to 15 minutes before step (1). The battery is left standing before constant current charging and before charging to ensure that the battery is in the same state before formation, and if there is any abnormality in the battery, there is time to deal with it in time.

[0050] The embodiment of the present invention also provides a sodium ion cylindrical battery, which is obtained by using the above method.

[0051] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and drawings.

[0052] Example 1

[0053] 1. Preparation of semi-finished battery cells

[0054] (1) The sodium ion layered oxide material and PVDF, SP, and CNT were dissolved in the solvent NMP in a ratio of 96:2:1:1 and stirred evenly, and then evenly coated on a 12 μm plain aluminum foil to obtain a surface density of 390 g / m 2 The positive electrode;

[0055] (2) Hard carbon, SP, CMC, and SBR were mixed in a ratio of 96.0:1:1:2 and evenly coated on a 13 μm aluminum foil to obtain a surface density of 197.4 g / m 2 The negative electrode;

[0056] (3) The positive electrode sheet, the separator, and the negative electrode sheet are wound, assembled, injected, and aged at high temperature for 48 hours in a constant temperature room at 45° C. to obtain a cylindrical battery with a capacity of 16 Ah;

[0057] 2. Place the cylindrical battery after high temperature standing on the formation cabinet, set the formation temperature to 45±2℃; then perform the formation according to the following steps:

[0058] (1) Leave for 10 minutes;

[0059] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.01 C, and leave for 10 minutes;

[0060] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds; charge to 2.0 V at a constant current of 0.1 C; leave for 10 minutes;

[0061] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.5 C, and leave for 10 minutes;

[0062] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0063] Example 2

[0064] The processing method of this embodiment is the same as that of embodiment 1, except that the formation process is:

[0065] (1) Leave for 10 minutes;

[0066] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.03 C, and leave for 10 minutes;

[0067] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds, charge to 2.0 V at a constant current of 0.1 C, and leave for 10 minutes;

[0068] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.3 C, and leave for 10 minutes;

[0069] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0070] Example 3

[0071] The processing method of this embodiment is the same as that of embodiment 1, except that the formation process is:

[0072] (1) Leave for 10 minutes;

[0073] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.03 C, and leave for 10 minutes;

[0074] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds, charge to 2.0 V at a constant current of 0.2 C, and leave for 10 minutes;

[0075] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.5 C, and leave for 10 minutes;

[0076] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0077] Comparative Example 1 (Different Vacuum Degrees)

[0078] The processing method of this comparative example is the same as that of Example 1, except that the formation process is:

[0079] (1) Leave for 10 minutes;

[0080] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.01 C, and leave for 10 minutes;

[0081] (3) Charge to 2.0 V at a constant current of 0.1 C and leave for 10 min;

[0082] (4) Charge to 3.0 V at a constant current of 0.3 C and leave for 10 min;

[0083] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0084] Comparative Example 2 (Small Rate Charging)

[0085] The processing method of this comparative example is the same as that of Example 1, except that the formation process is:

[0086] (1) Leave for 10 minutes;

[0087] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.01 C, and leave for 10 minutes;

[0088] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds; charge to 2.0 V at a constant current of 0.01 C; leave for 10 minutes;

[0089] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.01 C, and leave for 10 minutes;

[0090] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0091] Comparative Example 3 (High Rate Charging)

[0092] The processing method of this comparative example is the same as that of Example 1, except that the formation process is:

[0093] (1) Leave for 10 minutes;

[0094] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.5 C, and leave for 10 minutes;

[0095] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds; charge to 2.0 V at a constant current of 0.5 C; leave for 10 minutes;

[0096] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.5 C, and leave for 10 minutes;

[0097] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0098] Comparative Example 4 (Charge at a high rate first and then at a low rate)

[0099] The processing method of this comparative example is the same as that of Example 1, except that the formation process is:

[0100] (1) Leave for 10 minutes;

[0101] (2) Control the vacuum degree to 30 kPa, wait for 10 seconds, charge to 1.5 V at a constant current of 0.5 C, and leave for 10 minutes;

[0102] (3) Control the vacuum degree to 40 kPa, wait for 10 seconds, charge to 2.0 V at a constant current of 0.1 C, and leave for 10 minutes;

[0103] (4) Control the vacuum degree to 50 kPa, wait for 10 seconds, charge to 3.0 V at a constant current of 0.01 C, and leave for 10 minutes;

[0104] (5) Release the vacuum to 0 KPa, leave for 5 minutes, and then end.

[0105] The cylindrical batteries after the formation treatment of Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to capacity division. The operation of the capacity division treatment is as follows:

[0106] The formed battery is aged in a constant temperature room at 45℃ for 48h. After the second injection, the sealing pins are welded and the capacity is divided. The capacity division process is as follows:

[0107] (1) Leave it for 10 minutes, charge it to 3.95V at a constant current and constant voltage of 0.33C, and leave it for 10 minutes;

[0108] (2) Discharge at a constant current of 0.33C to 1.5V and leave for 10 minutes;

[0109] (3) Charge to 3.95V at 1.0C constant current and constant voltage, and leave for 10 minutes;

[0110] (4) Discharge at a constant current of 1.0C to 1.5V and leave for 10 minutes;

[0111] (5) Repeat the above steps for 2 cycles.

[0112] The cylindrical battery after capacity division is charged to 3.95V at a constant current of 0.5C, then fully charged and disassembled to observe the negative electrode interface. The results are as follows: Figures 1 to 7shown.

[0113] from Figures 1 to 3 It can be seen that the negative electrode interfaces obtained after the formation treatment in Examples 1 to 3 are good; the interface obtained in Comparative Example 1 has a small amount of point-like sodium precipitation; the interface obtained in Comparative Example 2 has a small amount of sodium precipitation; the interface obtained in Comparative Example 3 has a large amount of bubble-like sodium precipitation; and the interface obtained in Comparative Example 4 has a large amount of sodium precipitation.

[0114] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0115] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A formation method for a sodium ion cylindrical battery, characterized in that: The following steps are involved: (1) performing constant current charging at a first current under a first vacuum degree; (2) performing constant current charging with a second current at a second vacuum degree; (3) performing constant current charging with a second current at a third vacuum degree; The first vacuum degree is less than the second vacuum degree and less than the third vacuum degree; The first current is less than the second current and less than the third current.

2. The formation method of sodium ion cylindrical battery according to claim 1, characterized in that: The first vacuum degree is 30±2 kPa, the second vacuum degree is 40±2 kPa, and the third vacuum degree is 50±2 kPa.

3. The formation method of sodium ion cylindrical battery according to claim 1 or 2, characterized in that: The first current is 0.01C to 0.03C, the second current is 0.1C to 0.2C, and the third current is 0.3C to 0.5C.

4. The sodium ion battery formation method according to claim 1, characterized in that: In step (1), the constant current charging is performed to 1.5-1.7V.

5. The sodium ion battery formation method according to claim 1, characterized in that: In step (2), the constant current charging is performed to 2.0-2.2V.

6. The sodium ion battery formation method according to claim 1, characterized in that: In step (3), the constant current charging is performed to 3.0-3.2V.

7. The formation method of sodium ion cylindrical battery according to claim 1, characterized in that: In step (1) and / or step (2) and / or step (3), the temperature of the constant current charging is 45±2°C.

8. The formation method of sodium ion cylindrical battery according to claim 1, characterized in that: In step (1) and / or step (2) and / or step (3), the constant current charging is left for 5 to 15 minutes after completion.

9. The formation method of sodium ion cylindrical battery according to claim 1, characterized in that: Let stand for 5 to 15 minutes before proceeding to step (1).

10. A sodium ion cylindrical battery, characterized in that: The method according to any one of claims 1 to 9 is used to obtain the product.

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