Calculation method for aging time of sodium ion battery after liquid injection

Abstract

The invention discloses a method for calculating aging time after liquid injection of a sodium ion battery. The aging time after liquid injection is T = K * (eta * D) / (gamma * cos theta * epsilon * r), wherein K is an aging temperature compensation coefficient, and the value range of K is 0.15-0.8; eta is the dynamic viscosity of the electrolyte, and gamma is the surface tension of the electrolyte; d is the coating thickness of the pole piece, and epsilon is the porosity of the pole piece; theta is a contact angle between the electrolyte and the pole piece; r is the average pore radius of the pole piece, and the value range of r is as follows: the positive pole is 0.3-0.5, and the negative pole is 0.1-0.3. The method for calculating the aging time of the sodium ion battery after liquid injection has the characteristics of accurate aging time, high production efficiency and good battery batch consistency.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a method for calculating the aging time of sodium-ion batteries after electrolyte injection. Background Technology

[0002] In sodium-ion batteries, the aging process after electrolyte injection involves the electrolyte wetting the electrodes and separators inside the cell. Through capillary action and the aging time, the electrolyte completely penetrates into every tiny pore of the positive and negative electrode materials and the separator, eliminating the "dry areas" of the electrodes and separators. Through aging, the electrolyte and electrode materials are fully integrated and react stably, ensuring that sodium ions flow freely.

[0003] Electrolyte wetting degree (i.e. aging time) is one of the key factors affecting battery performance such as kinetics, cycle life and safety reliability. Good wetting effect can enable the negative electrode surface to undergo a mild initial reaction with the electrolyte, forming a preliminary and stable passivation film (SEI film prototype), reducing the interfacial resistance between the positive and negative electrode materials and the electrolyte, and laying a good foundation for subsequent formation processes.

[0004] In current mass production, the aging process after electrolyte injection typically involves either room temperature aging or high-temperature aging. High-temperature aging takes 24 hours at 45℃-50℃, while room temperature aging takes 72 hours at 25℃. Larger cell volumes require longer aging times. This uniform aging time has significant drawbacks: First, when the electrolyte type changes (e.g., density, viscosity) or the electrode structure (e.g., thickness, porosity) is adjusted, the fixed aging time cannot adapt, potentially leading to insufficient wetting (too short an aging time) or reduced production efficiency (too long an aging time). Second, it cannot effectively address fluctuations caused by batch variations in raw materials, affecting the consistency of battery product performance and yield. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the aging time of sodium-ion batteries after electrolyte injection, which features accurate aging time, high production efficiency, and good batch consistency of batteries.

[0006] This invention can be achieved through the following technical solutions:

[0007] The present invention provides a method for calculating the aging time of sodium-ion batteries after electrolyte injection. The aging time after electrolyte injection is: T = K * (η * D) / (γ * cosθ * ε * r);

[0008] Wherein, K is the aging temperature compensation coefficient, ranging from 0.15 to 0.8; η is the dynamic viscosity of the electrolyte, in mPa·s; γ is the surface tension of the electrolyte, in mN / m; D is the coating thickness of the electrode, in μm, and the maximum value of the positive / negative electrode thickness is taken based on actual measurement to ensure complete battery wetting; ε is the porosity of the electrode, and the minimum value of the porosity of the positive / negative electrode is taken based on parameter calculation to ensure complete battery wetting; θ is the contact angle (°) between the electrolyte and the electrode; r is the average pore radius of the electrode, in μm, and the maximum value of the average pore radius of the positive / negative electrode material is taken based on the material parameter D50 to ensure complete battery wetting. The value range varies depending on the material: 0.3-0.5 for NFPP positive electrode and 0.1-0.3 for hard carbon negative electrode.

[0009] Furthermore, the value of K is taken within the range of 0.15-0.8 based on the temperature of the battery placement area during battery aging. As the aging temperature decreases, the coefficient of K increases. For example, at a high temperature of 45℃, K is taken as 0.15; at a normal temperature of 25℃, K is taken as 0.5; and at a room temperature < 25℃, K is taken as 0.8.

[0010] Furthermore, when the electrolyte is an ester-based electrolyte, the value of θ ranges from 25° to 40° (ester-based electrolytes typically have high viscosity and high surface tension, resulting in greater resistance to spreading on the electrode surface); when the electrolyte is an ether-based electrolyte, the value of θ ranges from 20° to 30°. Ether-based electrolytes typically have lower viscosity and lower surface tension, making it easier to penetrate into the pores of the electrode under capillary action, exhibiting a smaller contact angle and excellent wetting properties.

[0011] Furthermore, in the positive electrode, r is 0.3 when D50 < 5 μm and 0.5 when D50 ≥ 5 μm.

[0012] Furthermore, in the negative electrode, r is 0.1 when D50 < 5 μm and 0.3 when D50 ≥ 5 μm.

[0013] Furthermore, in sodium-ion batteries, the positive electrode is a polyanion-type positive electrode (NFPP).

[0014] Furthermore, in sodium-ion batteries, the negative electrode is hard carbon.

[0015] Furthermore, the sodium-ion battery types include pouch sodium-ion batteries, cylindrical sodium-ion batteries, or aluminum-cased sodium-ion batteries.

[0016] This invention provides a method for calculating the aging time of sodium-ion batteries after electrolyte injection, which has the following beneficial effects:

[0017] First, the aging time is precise. Starting from the physical parameters of aging temperature, raw materials, electrodes, and electrolyte, the shortest time for the electrolyte to completely wet the electrodes is calculated, replacing the "uniform" aging time of the original, and ensuring that the shortest aging time can be obtained for the same batch of batteries produced in mass production.

[0018] Secondly, regarding production efficiency, this invention effectively avoids the excessively long aging time required for rapid battery immersion. By comparing data on pre-formation internal resistance, first-time formation efficiency, and discharge specific capacity at different aging times (as shown in Tables 1 and 2), the aging time is reasonably calculated, and the battery production cycle is shortened to the maximum extent, thereby improving battery production efficiency.

[0019] Third, the battery batch consistency is good. It can effectively avoid fluctuations in parameters of raw materials, electrodes, and electrolytes, and significantly improve the adverse effects caused by poor batch consistency due to incomplete electrode wetting. Attached Figure Description

[0020] Figure 1 This is a comparison of the capacity retention of different embodiments after 300 cycles at 1C in an environment of 25°C. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0022] The present invention provides a method for calculating the aging time of sodium-ion batteries after electrolyte injection. The aging time after electrolyte injection is: T = K * (η * D) / (γ * cosθ * ε * r);

[0023] Wherein, K is the aging temperature compensation coefficient, with a value range of 0.15-0.8; η is the dynamic viscosity of the electrolyte (mPa·s); γ is the surface tension of the electrolyte (mN / m); D is the coating thickness of the electrode (μm, based on actual measurement, taking the maximum value of the positive / negative electrode thickness, considering complete battery wetting); ε is the porosity of the electrode (calculated based on parameters, taking the minimum value of the positive / negative electrode porosity, considering complete battery wetting); θ is the contact angle between the electrolyte and the electrode (°); r is the average pore radius of the electrode (μm, based on the material parameter D50, taking the maximum value of the average pore radius of the positive / negative electrode material, considering complete battery wetting), with a value range of: 0.3-0.5 for NFPP positive electrode and 0.1-0.3 for hard carbon negative electrode.

[0024] Furthermore, the value of K is taken within the temperature range of 0.15-0.8 in the battery placement area during battery aging. As the aging temperature decreases, the coefficient of K increases. (For example, at a high temperature of 45℃, K is taken as 0.15; at a normal temperature of 25℃, K is taken as 0.5; and at a room temperature < 25℃, K is taken as 0.8.)

[0025] Furthermore, when the electrolyte is an ester-based electrolyte, the value of θ ranges from 25° to 40° (ester-based electrolytes typically have high viscosity and high surface tension, resulting in greater resistance to spreading on the electrode surface); when the electrolyte is an ether-based electrolyte, the value of θ ranges from 20° to 30° (ether-based electrolytes typically have low viscosity and low surface tension, making it easier to penetrate into the pores of the electrode under capillary action, exhibiting a smaller contact angle and excellent wetting properties).

[0026] Furthermore, in the positive electrode, r is 0.3 when D50 < 5 μm and 0.5 when D50 ≥ 5 μm.

[0027] Furthermore, in the negative electrode, r is 0.1 when D50 < 5 μm and 0.3 when D50 ≥ 5 μm.

[0028] Furthermore, in sodium-ion batteries, the positive electrode is a polyanion-type positive electrode (NFPP).

[0029] Furthermore, in sodium-ion batteries, the negative electrode is hard carbon.

[0030] Furthermore, the sodium-ion battery type is a soft-pack sodium-ion battery, a cylindrical sodium-ion battery, or an aluminum-cased sodium-ion battery.

[0031] Application Example 1

[0032] Taking the 604480 polyanionic sodium-ion soft-pack battery cell (positive electrode material: NFPP, negative electrode material: hard carbon, electrolyte: ester) as an example, calculate the aging time after electrolyte injection.

[0033] Aging temperature: High temperature 45℃;

[0034] Positive electrode material NFPP: D50=5μm, positive electrode thickness D: 120μm, true density: 2.95-3.0g / cm³;

[0035] Positive electrode compaction: 2.0 g / cm³; Electrode porosity = (1 - compaction density / true density) × 100%;

[0036] The positive electrode ε = 0.325;

[0037] Anode material: hard carbon; D50: 5μm; Anode sheet thickness: D: 90μm; True density: 1.5-1.7g / cm³.

[0038] Negative electrode compaction: 1.0 g / cm³; Electrode porosity = (1 - compacted density / true density) × 100%; Negative electrode ε = 0.375;

[0039] Electrolyte: dynamic viscosity η: 2.8 mPa·s, surface tension γ: 25 mN / m;

[0040] Contact angle: θ = 37°;

[0041] Average pore radius of the electrode: r = 0.5 μm

[0042] According to the calculation formula: T = K * (η * D) / (γ * cosθ * ε * r), we can calculate:

[0043] T =0.15*(2.8*120) / (25*0.8*0.325*0.5)≈15.51h.

[0044] Application Example 2

[0045] Taking the 604480 polyanionic sodium-ion soft-pack battery cell (positive electrode material: NFPP, negative electrode material: hard carbon, electrolyte: ester) as an example, calculate the aging time after electrolyte injection.

[0046] Aging temperature: 25℃ (room temperature);

[0047] Positive electrode material NFPP: D50=5μm, positive electrode thickness D: 120μm, true density: 2.95-3.0g / cm³;

[0048] Positive electrode compaction: 2.0 g / cm³; Electrode porosity = (1 - compaction density / true density) × 100%; Positive electrode ε = 0.325;

[0049] Anode material: hard carbon; D50: 5μm; Anode thickness: D: 90μm; True density: 1.5-1.7g / cm³; Anode compaction: 1.0 g / cm³; Anode porosity: (1 - compaction density / true density) × 100%; Anode ε: 0.375;

[0050] Electrolyte: dynamic viscosity η: 2.8 mPa·s, surface tension γ: 25 mN / m;

[0051] Contact angle: θ = 37°;

[0052] Average pore radius of the electrode: r = 0.5 μm;

[0053] The aging time is calculated using the formula: T = K * (η * D) / (γ * cosθ * ε * r).

[0054] T =0.5*(2.8*120) / (25*0.8*0.325*0.5)≈51.7h.

[0055] Application Example 3

[0056] Taking the 604480 polyanionic sodium ion soft-pack battery cell (positive electrode material: NFPP, negative electrode material: hard carbon, electrolyte: ether) as an example, calculate the aging time after electrolyte injection.

[0057] Aging temperature: room temperature 25℃;

[0058] Positive electrode material NFPP: D50=5μm, positive electrode thickness D: 100μm, true density: 2.95-3.0g / cm³; positive electrode compaction: 2.0 g / cm³; electrode porosity = (1 - compaction density / true density) × 100%; positive electrode ε=0.325;

[0059] Anode material: hard carbon; D50: 5μm; Anode thickness: D: 75μm; True density: 1.5-1.7g / cm³; Anode compaction: 1.0 g / cm³; Anode porosity: (1 - compaction density / true density) × 100%; Anode ε: 0.375;

[0060] Electrolyte: dynamic viscosity η: 3 mPa·s, surface tension γ: 30 mN / m;

[0061] Contact angle: θ = 30°;

[0062] Average pore radius of the electrode: r = 0.5 μm;

[0063] The aging time is calculated using the formula: T = K * (η * D) / (γ * cosθ * ε * r).

[0064] T =0.5*(3*100) / (30*0.866*0.325*0.5)≈35.5h.

[0065] Comparative Example 1

[0066] Model 604480 polyanionic sodium-ion soft-pack battery cells were injected with the same and equal amounts of electrolyte and left to stand at 45°C for 24 hours. The following tests were conducted: internal resistance (mΩ) before formation (see Table 1), initial formation efficiency (%), discharge specific capacity (mAh / g) (see Table 2), and capacity retention after 300 cycles at 1C at 25°C. Figure 1 ).

[0067] Comparative Example 2

[0068] Model 604480 polyanionic sodium-ion soft-pack battery cells were injected with the same and equal amounts of electrolyte and left to stand at room temperature (25℃) for 72 hours. The following tests were conducted: internal resistance (mΩ) before formation (Table 1), initial formation efficiency (%), discharge specific capacity (mAh / g) (Table 2), and capacity retention after 300 cycles at 1C at 25℃ (see details). Figure 1 ).

[0069] Table 1. Internal resistance test results before formation for different embodiments

[0070] Example Class Aging temperature (°C) Aging time (H) Internal resistance before conversion (mΩ) Application Example 1 45 15.5 6.53 Application Example 2 25 51.7 6.49 Comparative Example 1 45 24 6.47 Comparative Example 2 25 72 6.42

[0071] Table 2 Chemical performance test results of different embodiments

[0072] Example Class Aging temperature (°C) Aging time (H) First-effect conversion (%) Discharge specific capacity (mAh / g) Application Example 1 45 15.5 88.67 96.75 Application Example 2 25 51.7 88.71 96.81 Comparative Example 1 45 24 88.69 96.78 Comparative Example 2 25 72 88.73 96.85

[0073] From Table 1, the internal resistance test results before formation, and Table 2, the chemical performance test results... Figure 1 Comparative observations of capacity retention rates after 300 cycles at 1C (room temperature 25℃) revealed that: In Application Example 1 and Comparative Example 1, at the same aging temperature (high temperature 45℃) but different aging times, the calculated aging time and the empirical aging time showed almost no difference in pre-formation internal resistance, first-time formation effect, discharge specific capacity, and capacity retention rate. This indicates that the electrolyte in the calculated aging time method completely wetted the electrode. Blindly relying on empirical values ​​for prolonged high-temperature aging not only increases production costs but also reduces production efficiency. Similarly, in Application Example 2 and Comparative Example 2, at the same aging temperature (room temperature 25℃) but different aging times, the calculated aging time and the empirical aging time showed almost no difference in pre-formation internal resistance, first-time formation effect, discharge specific capacity, and capacity retention rate. This indicates that the electrolyte had achieved a good wetting effect. The calculated aging time saves 20 hours compared to the empirical aging time, effectively improving production efficiency.

[0074] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for calculating the aging time of a sodium-ion battery after electrolyte injection, characterized in that: The aging time after injection is: T = K * (η * D) / (γ * cosθ * ε * r); Wherein, K is the aging temperature compensation coefficient, with a value range of 0.15-0.8; η is the dynamic viscosity of the electrolyte; γ is the surface tension of the electrolyte; D is the coating thickness of the electrode; ε is the porosity of the electrode; θ is the contact angle between the electrolyte and the electrode; and r is the average pore radius of the electrode, with a value range of 0.3-0.5 for the positive electrode and 0.1-0.3 for the negative electrode.

2. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: At a high temperature of 45℃, K is 0.15; at a normal temperature of 25℃, K is 0.5; and at a room temperature < 25℃, K is 0.

8.

3. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: When the electrolyte is an ester-based electrolyte, the value of θ ranges from 25° to 40°; when the electrolyte is an ether-based electrolyte, the value of θ ranges from 20° to 30°.

4. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: In the positive electrode, r takes a value of 0.3 when D50 < 5 μm and r takes a value of 0.5 when D50 ≥ 5 μm.

5. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: In the negative electrode, r takes a value of 0.1 when D50 < 5 μm and r takes a value of 0.3 when D50 ≥ 5 μm.

6. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: In sodium-ion batteries, the positive electrode is a polyanion-type positive electrode.

7. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: In sodium-ion batteries, the negative electrode is hard carbon.

8. The method for calculating the aging time of a sodium-ion battery after electrolyte injection according to claim 1, characterized in that: The sodium-ion battery type is a pouch sodium-ion battery, a cylindrical sodium-ion battery, or an aluminum-cased sodium-ion battery.

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