A high-current-based sodium-ion battery formation method

Abstract

This invention discloses a sodium-ion battery formation method based on high current, comprising the following steps: S1: obtaining the initial discharge specific capacity Q1, initial coulombic efficiency K, discharge specific capacity Q2 of the sodium-ion battery at voltage ≥ 0.1V, and discharge specific capacity Q3 at voltage 0.05V ≤ voltage < 0.1V for the hard carbon anode material used in the sodium-ion battery; S2: obtaining the amount of hard carbon anode material M in the sodium-ion battery; S3: under a preset first formation temperature and first formation pressure, performing constant current charging on the sodium-ion battery with a preset first charging current I1, with a charging cutoff capacity of Q4, wherein 0.5C < I1 ≤ 5C, (1-K)*M*Q1 ≤ Q4 ≤ M*Q2; S4: continuing constant current charging on the sodium-ion battery with a preset second charging current I2, with a charging cutoff capacity of Q5, wherein 0.2C ≤ I2 ≤ 0.5C, 0 < Q5 + Q4 ≤ (Q2 + Q3)*M. This invention can significantly shorten the formation time, greatly improve the formation efficiency, and the method is easy to operate and can be widely applied.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a sodium-ion battery formation method based on high current. Background Technology

[0002] Sodium-ion batteries, similar in principle to lithium-ion batteries, store and release energy through the reversible insertion and extraction of sodium ions between the positive and negative electrodes. Due to the abundance of sodium resources, fast charging and discharging capabilities, a wide operating temperature range, and superior safety performance, sodium-ion batteries have broad application prospects in new energy storage and small-scale power applications. Formation is a crucial step in sodium-ion battery production. During formation, variations in the formation environment and conditions result in different properties of the SEI film formed on the negative electrode. These differences in SEI film performance further affect the initial capacity, charge / discharge efficiency, and cycle life of the sodium-ion battery.

[0003] To obtain a stable SEI film, existing technologies generally adjust and optimize the formation temperature, charge-discharge regime, and voltage. For example, Chinese patent CN202210712378.9 provides a multi-step charge-discharge regime that strengthens the structure of sodium-ion battery electrode materials through low-temperature pulse charging and high-temperature pulse discharging to stabilize the performance of the SEI film. This process has a small charging current and requires 2-3 repeated cycles, which is time-consuming, inefficient, and requires constant switching between high and low temperature formation environments, making the process complex.

[0004] Furthermore, Chinese patent CN113097557A discloses a sodium-ion battery and its preparation method. This method includes providing a sodium-ion battery to be formed and performing gradient formation on the sodium-ion battery to be formed to obtain the sodium-ion battery. The gradient formation includes multiple charge-discharge steps, charging and discharging the sodium-ion battery to be formed at different temperatures, which is beneficial for forming a stable and dense SEI film and extending the lifespan of the sodium-ion battery. However, this process also has drawbacks such as low formation current, long processing time, and low efficiency. Therefore, the sodium-ion formation process still needs further optimization. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium-ion battery formation method based on high current. This method adopts a formation approach that first charges the sodium-ion battery with a high current and then continues to charge it with a low current. Compared with conventional formation methods based on low current, this method can significantly shorten the formation time while ensuring the formation quality of the battery, greatly improve the formation efficiency, and is easy to operate and promote.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A method for forming a sodium-ion battery based on high current includes the following steps:

[0008] S1: Obtain the initial discharge specific capacity Q1, initial coulombic efficiency K, discharge specific capacity Q2 of the sodium-ion battery at voltage ≥ 0.1V, and discharge specific capacity Q3 at 0.05V ≤ voltage < 0.1V for the hard carbon anode material used in sodium-ion batteries;

[0009] S2: Obtain the amount of coating M for the hard carbon anode in a sodium-ion battery;

[0010] S3: Under the preset first formation temperature and first formation pressure, the sodium-ion battery is charged with a preset first charging current I1 at a constant current, and the charging cutoff capacity is Q4, where 0.5C<I1≤5C, (1-K)*M*Q1≤Q4≤M*Q2;

[0011] S4: Continue to charge the sodium-ion battery with a preset second charging current I2, and the charging cutoff capacity is Q5, where 0.2C≤I2≤0.5C, 0<Q5+Q4≤(Q2+Q3)*M.

[0012] Furthermore, the first formation temperature is between room temperature and 90°C.

[0013] Furthermore, the first formation pressure is between 0.02 and 3 MPa.

[0014] Furthermore, the positive electrode active material of the sodium-ion battery is a material in which sodium ions can be reversibly inserted and removed.

[0015] Furthermore, the positive electrode active material of the sodium-ion battery adopts any one of the following materials: vanadium-based, iron-based polyanionic positive electrode material containing sodium, Prussian white positive electrode material, Prussian blue positive electrode material, and layered oxide positive electrode material.

[0016] Furthermore, the negative electrode active material of the sodium-ion battery is a soft or hard carbon material.

[0017] Furthermore, the negative electrode active material of the sodium-ion battery is a soft or hard carbon material.

[0018] By adopting the above solution, the beneficial effects of the present invention are:

[0019] This method employs a formation process that first charges the sodium-ion battery with a high current and then continues to charge it with a low current. Compared to conventional formation methods based on low current, this method can significantly shorten the formation time while ensuring the formation quality of the battery, greatly improving the formation efficiency. Furthermore, the method is easy to operate and readily applicable. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention;

[0021] Figure 2 This is a charge-discharge curve of the hard carbon negative electrode used in Embodiment 1 of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Reference Figures 1 to 2 As shown, this invention provides a method for forming a sodium-ion battery based on high current, comprising the following steps:

[0024] S1: Obtain the initial discharge specific capacity Q1, initial coulombic efficiency K, discharge specific capacity Q2 of the sodium-ion battery at voltage ≥ 0.1V (vs Na / Na+), and discharge specific capacity Q3 at 0.05V ≤ voltage < 0.1V (vs Na / Na+) for the hard carbon anode material used in sodium-ion batteries.

[0025] S2: Obtain the amount of coating M for the hard carbon anode in a sodium-ion battery;

[0026] S3: Under the preset first formation temperature and first formation pressure, the sodium-ion battery is charged with a preset first charging current I1 at a constant current, and the charging cutoff capacity is Q4, where 0.5C<I1≤5C, (1-K)*M*Q1≤Q4≤M*Q2;

[0027] S4: Continue to charge the sodium-ion battery with a preset second charging current I2, and the charging cutoff capacity is Q5, where 0.2C≤I2≤0.5C, 0<Q5+Q4≤(Q2+Q3)*M.

[0028] The Q1, Q2, Q3 and K values ​​mentioned above can be obtained by testing the coin cell capacity of the material, or by using industry standard testing methods or testing methods provided by the material supplier. The first formation temperature is not selected. In a preferred embodiment, the first formation temperature is between room temperature and 90°C. The first formation pressure is also not limited. In a preferred embodiment, the first formation pressure is between 0.02 and 3 MPa.

[0029] Furthermore, the positive electrode active material of the sodium-ion battery is a material in which sodium ions can be reversibly inserted and removed. In a preferred embodiment, the positive electrode active material of the sodium-ion battery is any one of the following materials: vanadium-based material containing sodium, iron-based polyanionic positive electrode material, Prussian white positive electrode material, Prussian blue positive electrode material, and layered oxide positive electrode material. Meanwhile, the negative electrode active material of the sodium-ion battery is a soft or hard carbon material.

[0030] Compared with existing sodium-ion battery formation methods, this invention controls the cutoff capacity during the first charge of the sodium-ion battery. At this time, the potential of the hard carbon negative electrode is controlled above 0.1V (vs Na / Na+), and sodium ions undergo an adsorption reaction on the hard carbon surface. The adsorption rate is fast, and there is no risk of sodium precipitation. At the same time, increasing the formation current is beneficial to the formation of an SEI film rich in inorganic substances.

[0031] During the second charge, the potential of the hard carbon anode is above 0.05V (vs Na / Na+), and sodium ions will embed into the hard carbon anode. At this time, the charging current is appropriately reduced to avoid sodium deposition on the anode surface and to limit the capacity, preventing sodium ions from depositing in the micropores, preventing the generation of gas during formation, and preventing the electrolyte from reacting with active sodium, thereby reducing irreversible losses. Through the above formation steps, an inorganic-rich SEI film can be constructed on the surface of the battery anode. The SEI film has high ionic conductivity and good stability, which can reduce irreversible losses and improve the cycle stability of the battery anode. In addition, this method adopts a formation method of first charging the sodium-ion battery with a large current and then continuing to charge it with a small current. Compared with the conventional method based on small current formation, this method can significantly shorten the formation time while ensuring the formation quality of the battery, greatly improving the formation efficiency. Moreover, the method is easy to operate and easy to promote and apply.

[0032] The following comparison uses specific examples:

[0033] Example 1:

[0034] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M was 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0035] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 45℃, the first formation pressure is set to 0.5Mpa, and the first charging current is set to 1C (current 5A). It performs constant current charging on the sodium-ion battery, and the charging cutoff capacity Q4 = 450mAh (19.2*355*(1-0.934)).

[0036] Second step of charging: Adjust the current to 0.2C (current 1A), cut off capacity Q5 = 1000mAh;

[0037] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0038] Comparative Example 1:

[0039] The same materials were used as in Example 1, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 1) was used to charge the product to the same capacity as in Example 1.

[0040] Example 2:

[0041] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M = 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0042] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 45℃ and the first formation pressure is set to 0.5Mpa, and the first charging current is set to 1.5C (6A current). The sodium-ion battery is charged with constant current, and the charging cutoff capacity Q4 = 1728mAh (19.2*90).

[0043] Second charging step: Adjust the current to 0.2C (current 1A), cut-off capacity Q5 = 1382.4mAh (19.2*72);

[0044] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0045] Comparative Example 2:

[0046] The same materials were used as in Example 2, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 2) was used to charge the product to the same capacity as in Example 2.

[0047] Example 3:

[0048] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M was 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0049] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 60℃, the first formation pressure is set to 0.8Mpa, and the first charging current is set to 1C (current 5A). It performs constant current charging on the sodium-ion battery, and the charging cutoff capacity Q4 = 450mAh (19.2*355*(1-0.934)).

[0050] Second step of charging: Adjust the current to 0.4C (current 2A), cut off capacity 2000mAh;

[0051] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0052] Comparative Example 3:

[0053] The same materials were used as in Example 3, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 3) was used to charge the product to the same capacity as in Example 3.

[0054] Example 4:

[0055] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M was 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0056] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 70℃, the first formation pressure is set to 1.0Mpa, and the first charging current is set to 2C (current 10A). It performs constant current charging on the sodium-ion battery, and the charging cut-off capacity is 1000mAh.

[0057] Second step of charging: Adjust the current to 0.5C (current 2.5A), cut off capacity 1500mAh;

[0058] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0059] Comparative Example 4:

[0060] The same materials were used as in Example 4, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 4) was used to charge the product to the same capacity as in Example 4.

[0061] Example 5:

[0062] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M was 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0063] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 80℃, the first formation pressure is set to 1.5Mpa, and the first charging current is set to 4C (current 20A). It performs constant current charging on the sodium-ion battery, and the charging cut-off capacity is 1500mAh.

[0064] Second step of charging: Adjust the current to 0.5C (current 2.5A), cut off capacity 1250mAh;

[0065] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0066] Comparative Example 5:

[0067] The same materials were used as in Example 5, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 5) was used to charge the product to the same capacity as in Example 5.

[0068] Example 6:

[0069] Using layered ternary materials NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 (NFM) as the positive electrode and hard carbon as the negative electrode, a sodium-ion battery cell with a designed capacity of 5Ah was prepared. The cell had the following properties: Q1 = 355mAh / g, K = 93.4%, Q2 = 90mAh / g, Q3 = 72mAh / g, and the amount of hard carbon coating M was 19.2g. The cell was injected with liquid at a rate of 7g / Ah, aged at 45°C for 24 hours, and then formed and charged.

[0070] First step of charging: The cell is placed on the cabinet, the first formation temperature is set to 25℃, the first formation pressure is set to 0.4Mpa, and the first charging current is set to 0.6C (current 3A). It performs constant current charging on the sodium-ion battery, and the charging cut-off capacity is 900mAh.

[0071] Second step of charging: Adjust the current to 0.2C (1A), cut off capacity 1250mAh;

[0072] After formation is complete, the sodium-ion battery manufacturing process is carried out according to existing technology.

[0073] Comparative Example 6:

[0074] The same materials were used as in Example 6, but the formation process was different. Specifically, the same small current (the charging current in the second step of Example 6) was used to charge the product to the same capacity as in Example 6.

[0075] The sodium-ion batteries obtained in Examples 1-6 and Comparative Examples 1-6 were tested using the following methods. The initial efficiency, charge-discharge specific capacity, and capacity retention rate after 200 cycles are shown in Table 1 below.

[0076] 1) Test its first-efficiency and charge-discharge capacity under a voltage range of 1.5 to 4.0V and a discharge current density of 0.1C;

[0077] 2) A discharge test was performed at a voltage range of 1.5 to 4.0 V and a current density of 0.5 C for 200 cycles to obtain the capacity retention rate after 200 cycles.

[0078]

[0079]

[0080] Table 1. Comparison of battery performance between various embodiments and comparative examples.

[0081] As shown in Table 1, the sodium-ion battery prepared by the present invention is formed by first forming with a large current and then with a small current. It has high initial efficiency and is conducive to the formation of a stable SEI film with high conductivity. This results in a relatively low internal resistance of the prepared sodium-ion battery and a high capacity retention rate after 200 cycles, thereby extending the life of the sodium-ion battery.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming a sodium-ion battery based on high current, characterized in that, Includes the following steps: S1: Obtain the initial discharge specific capacity Q1, initial coulombic efficiency K, discharge specific capacity Q2 of the sodium-ion battery at voltage ≥ 0.1V, and discharge specific capacity Q3 at 0.05V ≤ voltage < 0.1V for the hard carbon anode material used in sodium-ion batteries; S2: Obtain the amount of coating M for the hard carbon anode in a sodium-ion battery; S3: Under the preset first formation temperature and first formation pressure, the sodium-ion battery is charged with a preset first charging current I1 at a constant current, and the charging cutoff capacity is Q4, where 0.5C<I1≤5C, (1-K)*M*Q1≤Q4≤M*Q2; S4: Continue to charge the sodium-ion battery with a preset second charging current I2, and the charging cutoff capacity is Q5, where 0.2C≤I2≤0.5C, 0<Q5+Q4≤(Q2+Q3)*M.

2. The sodium-ion battery formation method based on high current according to claim 1, characterized in that, The first formation temperature is between room temperature and 90°C.

3. The sodium-ion battery formation method based on high current according to claim 1, characterized in that, The first formation pressure is between 0.02 and 3 MPa.

4. The sodium-ion battery formation method based on high current according to claim 1, characterized in that, The positive electrode active material of the sodium-ion battery is a material in which sodium ions can be reversibly inserted and removed.

5. The sodium-ion battery formation method based on high current according to any one of claims 1 to 4, characterized in that, The positive electrode active material of the sodium-ion battery is any one of the following materials: vanadium-based or iron-based polyanionic positive electrode materials containing sodium, Prussian white positive electrode materials, Prussian blue positive electrode materials, or layered oxide positive electrode materials.

6. The method for forming a sodium-ion battery based on high current according to any one of claims 1 to 4, characterized in that, The negative electrode active material of the sodium-ion battery is hard carbon material.

7. The sodium-ion battery formation method based on high current according to claim 5, characterized in that, The negative electrode active material of the sodium-ion battery is hard carbon material.

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