Lithium ion battery formation method

Abstract

The invention discloses a lithium ion battery formation method which satisfies the following conditions during formation: P = U * c * alpha / (rho * d * k), P being a negative pressure required during battery formation, and the unit being kpa; u is the voltage during battery formation, and the unit is V; c is the battery capacity, and the unit is Ah; alpha is an influence value brought by other factors in the battery trial-manufacture process; rho is the surface density of the positive pole piece of the battery, and the unit is kg / m < 2 >; d is the compaction density of the positive pole piece of the battery, and the unit is g / cm < 3 >; k is the liquid injection coefficient of the battery, and the unit is g / Ah. The formation method can effectively prevent electrolyte from being sucked out and overflowing due to overlarge negative pressure in the battery formation process, and also can effectively promote gas generated in the battery to be discharged, so that the battery performance is improved.

Description

Technical Field

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

[0002] With the rise of the ion battery industry and the increasing demand for ion batteries year by year, consumers have also put forward higher requirements for the battery performance and service life of ion batteries. In recent years, researchers have also been continuously optimizing the processing and manufacturing process of batteries to continuously improve battery performance.

[0003] In the production process of lithium-ion batteries, formation is an important factor affecting the quality and performance of the final product. In the formation process of existing lithium-ion batteries, the problem of electrolyte being easily sucked out affects the battery performance after formation. Therefore, it is urgent to solve the problem of electrolyte being easily sucked out during the battery formation process to improve battery performance. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a lithium ion battery formation method, which can effectively prevent the electrolyte from being sucked out during the battery formation process and improve the battery performance.

[0005] In the first aspect of the present invention, a lithium ion battery formation method is provided, which satisfies the following conditions during formation: P = U*c*α / (ρ*d*k), wherein P is the negative pressure required during battery formation, in kPa; U is the voltage during battery formation, in V; c is the battery capacity, in Ah; α is the impact value of other factors during battery trial production; ρ is the surface density of the positive electrode sheet of the battery, in kg / m 2 ; d is the compaction density of the positive electrode of the battery, in g / cm 3 ; k is the battery filling coefficient, unit is g / Ah.

[0006] The negative pressure during the battery formation process has a crucial impact on the battery performance. When the battery is formed, the required negative pressure satisfies P=U*c*α / (ρ*d*k). It can be seen from the formula that the negative pressure P required for formation increases as the voltage U gradually increases during formation. In the initial formation stage, the voltage is low and the formation negative pressure is also low. The lower formation negative pressure can effectively prevent the electrolyte in the battery from being sucked out, resulting in poor formation and affecting the battery performance. As the formation proceeds, the voltage gradually increases, and the negative pressure also gradually increases, which helps to discharge the gas generated by the battery during the formation process to the maximum extent. When the voltage reaches the maximum voltage of 2.8V, the gas production inside the battery reaches the maximum at this time, and the formation negative pressure is also the maximum value, and it is maintained until the end of the battery formation, further ensuring that the produced gas is discharged to the maximum extent. In addition, as the formation voltage increases, the formation negative pressure gradually increases, which can also reduce excess energy consumption during the formation process. Therefore, this formation method can effectively prevent the electrolyte from being sucked out and overflowing due to excessive negative pressure during the battery formation process, and can also effectively promote the discharge of gas generated inside the battery, thereby improving battery performance.

[0007] In some embodiments, in the battery formation method, 80≤c*α≤120 is satisfied.

[0008] In some embodiments, U is the voltage of the battery during formation, which is 0 to 2.8V.

[0009] In some embodiments, k is the filling coefficient of the battery, and the filling coefficient is 3 to 3.5 g / Ah.

[0010] In some embodiments, the formation temperature is 45 ± 3 °C.

[0011] In some embodiments, before the chemical formation treatment, a high temperature static treatment is also included; during the high temperature static treatment, the control parameters are:

[0012] (i) The standing temperature is 45±3℃;

[0013] (ii) The standing time is 36 to 48 hours.

[0014] In some embodiments, before the high temperature static treatment, a liquid injection treatment is also included; during the liquid injection treatment, the control parameters are:

[0015] (1) The injection temperature is 25±3℃;

[0016] (2) The dew point temperature is -50±2℃.

[0017] In a second aspect of the present invention, the present invention provides a method for preparing a lithium-ion battery, comprising any formation method of the first aspect.

[0018] Therefore, the preparation method can prevent electrolyte overflow during battery formation, while promoting the discharge of gas generated inside the battery and improving battery performance.

[0019] In the third aspect of the present invention, the present invention provides a lithium ion battery, including a battery obtained by the preparation method of the second aspect, or a battery processed by any formation method of the first aspect.

[0020] Therefore, the battery has excellent electrical properties.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The negative pressure required for battery formation of the present invention satisfies: P=U*c*α / (ρ*d*k), wherein P is the negative pressure required for battery formation, in kPa; U is the voltage during battery formation, in V; c is the battery capacity, in Ah; α is the impact value of other factors during battery trial production; ρ is the surface density of the positive electrode sheet of the battery, in kg / m 2 ; d is the compaction density of the positive electrode of the battery, in g / cm 3 ; k is the battery filling coefficient, in g / Ah. The negative pressure required for formation increases as the voltage gradually increases during formation, which can effectively prevent the electrolyte from being sucked out and overflowing due to excessive negative pressure during the battery formation process, especially in the initial stage, and can also promote the discharge of gas generated inside the battery, thereby improving battery performance.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 The present invention is a flow chart of the battery formation and lithium ion battery preparation method. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0027] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0028] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0029] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0030] Existing lithium-ion battery formation usually adopts constant negative pressure formation. During the formation process, when the negative pressure is too large, it is easy to cause the electrolyte to be sucked out, resulting in abnormal formation. When the negative pressure is too small, the gas generated inside the battery during the formation process cannot be effectively discharged, resulting in bubble-shaped gaps around the pole piece, affecting the final battery performance.

[0031] In the first aspect of the embodiments of the present invention, the present invention proposes a lithium ion battery formation method, which satisfies the following conditions during formation: P = U*c*α / (ρ*d*k), wherein P is the negative pressure required during battery formation, in kPa; U is the voltage during battery formation, in V; c is the battery capacity, in Ah; α is the impact value of other factors during battery trial production; ρ is the surface density of the positive electrode of the battery, in kg / m 2 ; d is the compaction density of the positive electrode of the battery, in g / cm 3 ; k is the battery filling coefficient, unit is g / Ah.

[0032] The negative pressure during the battery formation process has a crucial impact on the battery performance. During the battery formation, the required negative pressure satisfies P=U*c*α / (ρ*d*k). It can be seen from the formula that the negative pressure P required for formation increases as the voltage U gradually increases during formation. At the beginning of formation, the voltage is low and the formation negative pressure is also low. The lower formation negative pressure can effectively prevent the electrolyte in the battery from being sucked out, resulting in poor formation and affecting the battery performance. As the formation proceeds, the voltage gradually increases, and the negative pressure also gradually increases, which helps to discharge the gas generated by the battery during the formation process to the maximum extent. When the voltage reaches the maximum voltage of 2.8V, the gas production inside the battery reaches the maximum, and the formation negative pressure is also the maximum value, and it is maintained until the end of the battery formation, further ensuring that the produced gas is discharged to the maximum extent. In addition, as the formation voltage increases, the formation negative pressure gradually increases, which can also reduce excess energy consumption during the formation process. Therefore, this formation method can effectively prevent the electrolyte from being sucked out and overflowing due to excessive negative pressure during the battery formation process, and can also effectively promote the discharge of gas generated inside the battery, thereby improving battery performance.

[0033] In some embodiments of the present invention, in the battery formation method, the following condition is satisfied: 80≤c*α≤120.

[0034] The change of α is related to the battery capacity. When the battery capacity is determined, the value of α is a range value, and the negative pressure value P calculated within this range meets the negative pressure required for formation. In this way, electrolyte overflow can be effectively prevented during battery formation, while promoting the discharge of gas generated inside the battery and improving battery performance.

[0035] In some embodiments of the present invention, U is the voltage of the battery during formation, which is 0 to 2.8V.

[0036] The voltage during battery formation is controlled within the range of 0 to 2.8V, which can not only ensure that the battery safely and stably forms a solid electrolyte interface (SEI) film and activates the battery, but also avoid battery overcharging and violent internal chemical reactions, thereby ensuring battery performance and life.

[0037] Exemplarily, the voltage is 0, 1V, 1.5V, 2V, 2.5V, 2.8V, etc.

[0038] In some embodiments of the present invention, k is a liquid filling coefficient of the battery, and the liquid filling coefficient is 3 to 3.5 g / Ah.

[0039] When the injection coefficient during battery formation is controlled at 3-3.5g / Ah, it can not only ensure sufficient electrolyte infiltration, but also balance battery performance and cost, ensuring battery safety and service life.

[0040] Exemplarily, the injection coefficient is 3g / Ah, 3.1g / Ah, 3.2g / Ah, 3.3g / Ah, 3.4g / Ah, 3.5g / Ah, etc.

[0041] In some embodiments of the present invention, the formation temperature is 45±3°C.

[0042] The formation temperature of 45±3℃ can effectively balance the formation of solid electrolyte interface film (SEI film) and the maintenance of battery performance.

[0043] In some embodiments of the present invention, before the chemical formation treatment, a high temperature static treatment is also included; during the high temperature static treatment, the control parameters are:

[0044] (i) The standing temperature is 45±3℃;

[0045] (ii) The standing time is 36 to 48 hours.

[0046] Before formation, the battery is left standing at 45±3℃ for 36 to 48 hours, which helps the electrolyte to better penetrate into the pores of the electrode material, increase the contact area and reaction activity between the electrolyte and the electrode, and promote the formation of a stable solid electrolyte interface film (SEI film) on the surface of the battery's negative electrode, thereby improving battery performance.

[0047] Exemplarily, the standing time is 36h, 38h, 40h, 42h, 44h, 46h, 48h, etc.

[0048] In some embodiments of the present invention, before the high temperature static treatment, a liquid injection treatment is also included; during the liquid injection treatment, the control parameters are:

[0049] (1) The injection temperature is 25±3℃;

[0050] (2) The dew point temperature is -50±2℃.

[0051] During the injection process, strict requirements are placed on the temperature and humidity of the environment to ensure battery performance and safety. When the injection temperature is 25±3℃, the solvent volatilization or lithium salt decomposition in the electrolyte can be reduced, and the chemical stability of the electrolyte can be maintained; when the dew point temperature is -50±2℃, the moisture content of the air can be effectively controlled to prevent the battery material from absorbing too much moisture, which will affect the battery performance and life.

[0052] In a second aspect of the embodiments of the present invention, the present invention provides a method for preparing a lithium-ion battery, comprising any formation method of the first aspect.

[0053] Therefore, the preparation method can prevent electrolyte overflow during battery formation, while promoting the discharge of gas generated inside the battery and improving battery performance.

[0054] In some embodiments of the present invention, the method for preparing a battery further comprises:

[0055] S1000. Battery assembly.

[0056] The positive electrode sheets, battery separators and negative electrode sheets are stacked, then hot pressed, welded and shelled to make dry cells, which are then baked.

[0057] S2000. Battery filling.

[0058] The battery is filled with liquid using the liquid filling method proposed in the first aspect of the embodiment of the present invention.

[0059] S3000. High temperature standing.

[0060] High temperature standing is performed by the high temperature standing method proposed in the first aspect of the embodiment of the present invention.

[0061] S4000. Battery formation.

[0062] The battery formation is performed according to the battery formation method proposed in the first aspect of the embodiment of the present invention.

[0063] S5000. Other processes, including aging and capacity separation.

[0064] After formation, an aging process is carried out, and finally a conventional capacity separation process is carried out to produce a finished battery ( Figure 1 ).

[0065] In a third aspect of the embodiments of the present invention, the present invention provides a lithium-ion battery, including a battery obtained by the preparation method of the second aspect, or a battery processed by any formation method of the first aspect.

[0066] Therefore, the battery has excellent electrical properties.

[0067] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0068] Embodiment 1:

[0069] Take an aluminum shell lithium-ion battery with a capacity of 100Ah for formation treatment, the steps are as follows:

[0070] (1) Control the ambient temperature to 25±3℃ and the dew point temperature to -50±2℃, and inject liquid into the battery.

[0071] (2) Place the battery after the injection in an environment of 45±3°C for 48 hours.

[0072] (3) The rested batteries are placed in an environment of 45±3°C for formation.

[0073] The capacity c of the aluminum shell lithium-ion battery is 100Ah. The influence value α of other factors in the battery trial production process is 0.8≤α≤1.2. The double-sided surface density ρ of the positive electrode sheet is 0.4kg / m 2 The compaction density d of the positive electrode is 2.51 g / cm 3 , the battery filling coefficient k is 3.2g / Ah; according to the formula P=U*c*α / (ρ*d*k)(α=1), the negative pressure required for formation is calculated. When the formation voltage reaches the maximum value of 2.8V, the formation negative pressure P is -87.15kpa and remains unchanged until the formation is completed.

[0074] Embodiment 2:

[0075] The difference between Example 2 and Example 1: α in Example 2 is 0.8.

[0076] Embodiment 3:

[0077] The difference between Example 3 and Example 1: α in Example 3 is 1.2.

[0078] Embodiment 4:

[0079] The difference between Example 4 and Example 1: α in Example 4 is 0.9.

[0080] Comparative Example 1:

[0081] The difference between Comparative Example 1 and Example 1: α of Comparative Example 1 is 0.7.

[0082] Comparative Example 2:

[0083] The difference between Comparative Example 2 and Example 1: α of Comparative Example 2 is 1.3.

[0084] Comparative Example 3:

[0085] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 adopts constant negative pressure formation, and the negative pressure is kept constant from the beginning of formation to the end of formation, and the negative pressure is -85 kPa.

[0086] Battery appearance and performance test:

[0087] For all the examples and comparative examples, three batteries were selected for full-charge disassembly, performance and appearance tests. During the full-charge disassembly, the appearance and surface state of the negative electrode were focused on. The performance tests included liquid retention, first efficiency, first discharge capacity and capacity retention rate after 500 cycles of 1C charge and discharge cycles.

[0088] Test results:

[0089] The results of fully charged battery disassembly and appearance testing of all embodiments and comparative examples are shown in Table 1.

[0090] Table 1 Appearance of lithium-ion battery after formation and disassembly test results of full charge

[0091] Battery Appearance Negative electrode Electrolyte Example 1 No abnormality Uniform golden yellow There is residual electrolyte Example 2 No abnormality Uniform golden yellow There is residual electrolyte Example 3 No abnormality Uniform golden yellow There is residual electrolyte Example 4 No abnormality Uniform golden yellow There is residual electrolyte Comparative Example 1 Slight swelling Lots of black spots There is residual electrolyte Comparative Example 2 Battery is dented and leaking Lots of black spots No electrolyte Comparative Example 3 Some discharge Slight spots Some batteries have no electrolyte

[0092] The battery performance test results of all embodiments and comparative examples are shown in Table 2.

[0093] Table 2 Battery performance test results after lithium-ion battery formation

[0094]

[0095] As can be seen from Table 1, the appearance of the batteries of Examples 1-4 all remain in good condition, no electrolyte is sucked out and overflowed on the surface of the battery, and there is no abnormality in appearance. After the battery is disassembled, the negative electrode plate remains uniformly golden yellow, there is residual electrolyte, and there is no obvious abnormality inside the battery. Comparative Examples 1-3 all have battery problems to varying degrees. In Comparative Example 1, due to insufficient negative pressure during the formation process, the gas inside the battery cannot be effectively discharged, and there are bubbles between the pole pieces, resulting in slight swelling of the battery appearance and black spots on the battery. In Comparative Example 2, due to excessive negative pressure during the formation process, the appearance of the battery is deformed, the battery is concave, the electrolyte is sucked out, and it cannot be completely infiltrated, resulting in black spots on the pole pieces. In Comparative Example 3, since the negative pressure during the formation process is a constant pressure, the constant pressure value is relatively large at the initial stage of formation, which leads to the problem of electrolyte being sucked out of some batteries and spots on the pole pieces.

[0096] It can be seen from Table 2 that the electrical performance of the batteries of Examples 1-4 and Comparative Example 3 is better than that of the battery of Comparative Example 1-2. However, in combination with Table 1, it can be seen that part of the battery electrolyte of Comparative Example 3 is sucked out and the negative electrode plate has spots. Therefore, the overall performance of the battery of Comparative Example 3 is poorer than that of Examples 1-4.

[0097] It can be seen that the battery formation method of the present invention can effectively prevent the electrolyte from being sucked out during the formation process, effectively promote the electrolyte to enter the surrounding of the active material, increase the battery liquid retention, and thus improve the battery performance. In addition, as the formation voltage increases, the formation negative pressure gradually increases, which can also reduce the redundant energy consumption during the formation process.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 specific features, structures, materials or characteristics described 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.

[0099] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A lithium ion battery formation method, characterized in that: When formed, it satisfies: P = U*c*α / (ρ*d*k), Among them, P is the negative pressure required for battery formation, in kPa; U is the voltage during battery formation, in V; c is the battery capacity, in Ah; α is the impact value of other factors during battery trial production; ρ is the surface density of the positive electrode of the battery, in kg / m 2 ; d is the compaction density of the positive electrode of the battery, in g / cm 3 ; k is the battery filling coefficient, unit is g / Ah.

2. The lithium ion battery formation method according to claim 1, characterized in that: In the battery formation method, the following condition is satisfied: 80≤c*α≤120.

3. The lithium ion battery formation method according to claim 1 or 2, characterized in that: The U is the voltage of the battery during formation, which is 0-2.8V.

4. The lithium ion battery formation method according to claim 1 or 2, characterized in that: The k is the liquid filling coefficient of the battery, and the liquid filling coefficient is 3 to 3.5 g / Ah.

5. The lithium ion battery formation method according to claim 1 or 2, characterized in that: In the battery formation method, the formation temperature is 45±3°C.

6. The lithium ion battery formation method according to claim 1 or 2, characterized in that: Before the chemical formation treatment, a high temperature static treatment is also included; during the high temperature static treatment, the control parameters are: (i) The standing temperature is 45±3℃; (ii) The standing time is 36 to 48 hours.

7. The lithium ion battery formation method according to claim 6, characterized in that: Before the high temperature static treatment, a liquid injection treatment is also included; during the liquid injection treatment, the control parameters are: (1) The injection temperature is 25±3℃; (2) The dew point temperature is -50±2℃.

8. A method for preparing a lithium ion battery, characterized in that: The method comprises the chemical formation method according to any one of claims 1 to 7.

9. A lithium ion battery, characterized in that: A battery obtained by the preparation method of claim 8, or a battery treated by the formation method of any one of claims 1 to 7.

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