This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0148296 dated November 19, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[2]
The present invention relates to a method for activating a secondary battery, and more particularly, to a method for activating a secondary battery in which the detection power of a low voltage defect is improved by reducing the variation in the voltage drop amount of a good product when a low voltage defect is detected.
background
[3]
In general, a secondary battery means a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used in electronic devices such as mobile phones, notebook computers, camcorders, etc. or electric vehicles. In particular, a lithium secondary battery has a larger capacity than a nickel-cadmium battery or a nickel-water tank battery and has a high energy density per unit weight, so the degree of utilization thereof is rapidly increasing.
[4]
Such a lithium secondary battery mainly uses a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. A lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate to which the positive electrode active material and the negative electrode active material are applied, respectively, are disposed with a separator interposed therebetween, and a casing for sealing and housing the electrode assembly together with an electrolyte.
[5]
On the other hand, depending on the shape of the battery case, the lithium secondary battery may be classified into a can-type secondary battery in which an electrode assembly is embedded in a metal can and a pouch-type secondary battery in which an electrode assembly is embedded in a pouch of an aluminum laminate sheet.
[6]
A secondary battery is generally manufactured through a process in which an electrolyte in a liquid state, ie, an electrolyte, is injected in a state in which the electrode assembly is accommodated in the battery case, and the battery case is sealed.
[7]
Such lithium secondary batteries may have various types of defects due to various causes during a manufacturing process or use. In particular, some of the manufactured secondary batteries exhibit a voltage drop behavior greater than or equal to the self-discharge rate, which is referred to as a low voltage.
[8]
The low voltage failure phenomenon of the secondary battery is typically caused by a metal foreign material located inside the secondary battery. In particular, when a metal foreign material such as iron or copper is present on the positive electrode plate of the secondary battery, the metal foreign material may grow as a dendrite in the negative electrode. In addition, such dendrites may cause an internal short circuit of the secondary battery, which may cause failure or damage to the secondary battery, or, in severe cases, ignition.
[9]
On the other hand, the above-described metal-induced low voltage defect is indicated by a relative increase in voltage drop, and the low voltage defect is detected through the aging process during the activation process of the secondary battery.
[10]
1 is a schematic diagram showing step-by-step process conditions of a conventional activation process. Referring to this, in the related art, a pre-aged battery is primarily charged in a SOC range of 10 to 40%, and the primary charged secondary battery is subjected to high temperature aging. And, after secondary charging of the secondary battery aged at high temperature, the activation process was performed in such a way that aging was performed at room temperature. And by measuring the OCV at two time points selected during the room temperature aging process, comparing the change value (voltage drop amount) of the OCV with the reference value, and determining that the battery with the voltage drop amount is less than the reference value as a good product, low voltage failure has been selected. .
[11]
However, in the above method, there is a region in which the voltage drop amount of the good product and the voltage drop amount of the defective product appear at the same level, so it is difficult to accurately select the low voltage defect. Therefore, in order to improve the low-voltage defect detection power, it is necessary to develop a technique for reducing the voltage drop amount and the deviation thereof.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[12]
An object of the present invention is to solve the above problems, and to provide a method for activating a secondary battery that significantly improves the detection power of low voltage defects by reducing the amount of voltage drop of a good product and improving its dispersion.
[13]
Other objects and advantages of the present invention may be understood by the following description, and will become more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof indicated in the claims.
means of solving the problem
[14]
In the activation method of the present invention for solving the above problems, a secondary battery including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and an electrolyte are aged at room temperature. Aging (Pre-aging) step (S100); a primary charging step (S200) of charging the pre-aged secondary battery to 60% or more of a secondary battery capacity (SOC); A high-temperature aging step of aging the primary charged secondary battery at a high temperature (S300); and a room temperature aging step (S400) of aging the high temperature-aged secondary battery at room temperature, wherein the room temperature aging step includes a resetting process of charging at the same charge rate (SOC) as the primary charging step do.
[15]
In an embodiment of the present invention, during the resetting process, the charging may be performed at a C-rate of 0.01C to 1.0C, and more preferably, a C-rate of 0.05C to 0.4C. can be charged with
[16]
In one embodiment of the present invention, the high temperature aging step (S300) is performed at a temperature of 60 ℃ or higher.
[17]
In one embodiment of the present invention, the high temperature aging step (S300) is performed for 12 hours to 48 hours.
[18]
In one embodiment of the present invention, the primary charging step (S200) includes charging to 65% to 75% of the secondary battery capacity (SOC).
[19]
In an embodiment of the present invention, the room temperature aging step ( S400 ) includes a process of measuring a change in a voltage value while aging the secondary battery and selecting a secondary battery with low voltage defect from an amount of voltage drop.
[20]
At this time, to measure the change in the voltage value, the voltage value V1 is measured at the start point of the room temperature aging, the voltage value V2 is measured at the end point of the room temperature aging, and the voltage that is the difference between the voltage value of the start point and the end point and determining whether the descent amounts V1-V2 satisfy a reference value range.
[21]
An embodiment of the present invention further includes a secondary charging step of charging the secondary battery at a citrate of 0.1 to 2.0C after the room temperature aging step (S400).
[22]
In an embodiment of the present invention, the pre-aging step (S100) includes aging the secondary battery by leaving it to stand for 0.5 to 72 hours in a temperature environment of 20°C to 30°C.
[23]
The present invention also provides a method for manufacturing a secondary battery including the activation method.
Effects of the Invention
[24]
The activation method of the present invention reduces the voltage drop of a non-defective product by uniformly and stably forming a negative SEI film by primary charging and accelerating SEI film stabilization through high-temperature aging.
[25]
In addition, the activation method of the present invention includes a resetting process of recharging up to the charging rate (SOC) during primary charging, thereby reducing variations in the voltage drop amount of good products, and as a result, has the effect of improving the detection power of low voltage defects.
[26]
Therefore, according to these aspects of the present invention, it is possible to prevent the secondary battery from being distributed or used with a high probability of occurrence of a low voltage failure at an early stage, and failure or damage to the secondary battery during use of the secondary battery. , ignition, etc., can be prevented.
Brief description of the drawing
[27]
1 is a schematic diagram showing a conventional activation method.
[28]
2 is a schematic diagram illustrating an activation method according to an embodiment of the present invention.
[29]
3 is a schematic diagram showing the steps of the activation method of the present invention.
Best mode for carrying out the invention
[30]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention.
[31]
Therefore, the configuration shown in the embodiments and drawings described in this specification is only the most preferred embodiment of the present invention, and does not represent all of the technical spirit of the present invention, so they can be substituted at the time of the present application It should be understood that various equivalents and modifications may be made.
[32]
[33]
FIG. 2 schematically shows step-by-step process conditions of an activation method according to an embodiment of the present invention, and FIG. 3 shows steps of an activation method according to an embodiment of the present invention. Referring to these drawings, in the method for activating a secondary battery of the present invention, a secondary battery including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and an electrolyte are aged at room temperature. a pre-aging step (S100); a primary charging step (S200) of charging the pre-aged secondary battery to 60% or more of a secondary battery capacity (SOC); A high-temperature aging step of aging the primary charged secondary battery at a high temperature (S300); and a room temperature aging step of aging the high temperature aged secondary battery at room temperature (S400); Including, wherein the room temperature aging step includes a resetting step of charging at the same charging rate (SOC) as the primary charging step.
[34]
According to the inventors of the present invention, when the process of charging the secondary battery at the same charging rate as in the primary charging step is included during the room temperature aging process, the voltage drop of the good product in the secondary battery is reduced as well as the deviation thereof. In the present invention, there is an effect of remarkably improving the low-voltage detection power when selecting low-voltage defective batteries.
[35]
First, the pre-aging step ( S100 ) will be described. The pre-aging step ( S100 ) is a step of aging the battery so that the electrolyte solution is sufficiently impregnated in the electrode and the separator after the battery is assembled.
[36]
More specifically, when the secondary battery is charged by electrons traveling to the negative electrode along a conducting wire during charging, lithium ions are intercalated in the negative electrode to achieve charge neutrality. In this case, the lithium ions can be occluded in the region impregnated with the electrolyte, that is, the ion movement path is maintained (wetting area), but it is relatively difficult to occlude in the non-wetting area.
[37]
Accordingly, through the pre-aging step, the battery may be aged for 0.5 to 72 hours at room temperature and atmospheric pressure so that the electrolyte can be well permeated into the positive and negative electrodes. For example, the pre-aging step may be carried out at 20 °C to 30 °C, specifically 22 °C to 28 °C, more specifically 23 °C to 27 °C, even more specifically 25 °C to 27 °C. .
[38]
The activation process of the present invention is performed for a lithium secondary battery. Such a lithium secondary battery is assembled through the following process, and then undergoes the pre-aging step.
[39]
An electrode mixture including an electrode active material and a binder is applied to an electrode current collector to prepare a positive electrode and a negative electrode, respectively, and then, a separator is interposed between the positive electrode and the negative electrode to prepare an electrode assembly.
[40]
After the electrode assembly thus prepared is accommodated in the battery case, the electrolyte is injected, and the battery case is sealed to assemble the battery.
[41]
The step of assembling such a battery is not particularly limited and can be performed according to a known method.
[42]
In addition, the electrode assembly is not particularly limited as long as it has a structure including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, and may be, for example, a jelly-roll type, a stack type, or a stack/folding type.
[43]
The battery case is not particularly limited as long as it is used as an exterior material for battery packaging, and a cylindrical, prismatic, or pouch type may be used.
[44]
The electrolyte includes an organic solvent and a lithium salt, and may optionally further include an additive.
[45]
The organic solvent is not limited as long as decomposition due to oxidation reaction or the like can be minimized during charging and discharging of the battery, and may be, for example, a cyclic carbonate, a linear carbonate, an ester, an ether, or a ketone. These may be used alone, or two or more of them may be used in combination.
[46]
Among the organic solvents, a carbonate-based organic solvent may be preferably used. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and the linear carbonate includes dimethyl carbonate. (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC) are representative.
[47]
The lithium salt is LiPF 6 , LiAsF 6 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiBF 4 , LiBF 6 , LiSbF 6 , LiN(C 2 F 5 SO 2 ) 2 , LiAlO 4 , LiAlCl 4 , LiSO 3 CF 3 and LiClO 4 Lithium salts commonly used in the electrolyte of a lithium secondary battery may be used without limitation, and these may be used alone, or two or more kinds may be used in combination.
[48]
In addition, the electrolyte may optionally further include an additive, for example, as the additive, in order to stably form an SEI film, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sultone, Any one selected from the group consisting of unsaturated sultone, acyclic sulfone, lithium oxalyldifluoroborate (LiODFB), and derivatives thereof or a mixture of two or more thereof may be used, but the present invention is not limited thereto.
[49]
Examples of the cyclic sulfite include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite phite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, 1,3-butylene glycol sulfite, and the like, and saturated sultones include 1,3-propane sultone, 1,4-butane sultone, and the like, and unsaturated sultones include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, 1-methyl-1,3-prop pensulfone and the like, and examples of the acyclic sulfone include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone.
[50]
These additives are added to the electrolyte to improve low-temperature output characteristics by forming a strong SEI film on the anode, suppress decomposition of the anode surface that may occur during high-temperature cycle operation, and prevent oxidation of the electrolyte.
[51]
When the battery case is a pouch type, an aluminum laminated pouch including an aluminum layer may be used. After injecting the electrolyte, the opened portion of the aluminum-laminated pouch may be sealed by heat welding or heat sealing.
[52]
Next, a primary charging step (S200) of charging the pre-aged secondary battery to 60% or more of the secondary battery capacity (SOC) is performed.
[53]
The primary charging step (S200) is a step of forming a SEI (solid electrolyte interface, hereinafter referred to as "SEI") film layer, and in the present invention, the charge amount of the battery is determined by the design capacity (SOC) during primary charging. ) is characterized in that it is charged to 60% or more of.
[54]
In order to improve the detection power of the low-voltage defective battery, it is advantageous to decrease the voltage drop of the good product and increase the voltage drop of the defective product. And in order to reduce the voltage drop of the non-defective secondary battery and improve its deviation, the SEI film of the negative electrode must be uniformly and stably formed, which can be achieved only when the volume of the negative electrode is maximally expanded. In the primary charging stage, if initially charged to 60% or more of the battery design capacity (SOC), the SEI film is formed as uniformly as possible, thereby reducing the voltage drop of the non-defective product. Therefore, in the first charging step, if the charging is performed with an SOC of less than 60%, it may be difficult to achieve the object of the present invention, so it is not preferable.
[55]
In an embodiment of the present invention, the charging amount of the charging step is preferably 65% ​​to 75% of the design capacity (SOC) of the secondary battery.
[56]
Charging may be performed according to conditions known in the art as the charging conditions in the charging step (S200).
[57]
In one embodiment of the present invention, in the first charging step ( S200 ), charging may be performed at a charge termination voltage of 3.0 to 4.0V and a C-rate of 1.0C or less. However, in the case of such a charge termination voltage, it may vary depending on the type or characteristics of the positive electrode active material.
[58]
Also, the first charging step ( S200 ) may have a three-step process instead of a one-step process. That is, it consists of a first charging section up to 10% of the secondary battery capacity (SOC), a second charging section up to 40% of the secondary battery capacity (SOC), and a third charging section of a subsequent section, and the three sections Charging may be performed by setting different charging conditions for each. In this case, the charging rate in the second charging section is preferably 0.5C or less.
[59]
In a preferred embodiment of the present invention, the charging seed rate in the second charging section is preferably higher than the charging seed rate in the first charging section and the charging seed rate in the third charging section. In this case, it is more preferable that a ratio of the charging seed rate in the first charging section to the charging seed rate in the third charging section is 2:3 to 3:2.
[60]
For example, in the first charging step (S200), a citrate of 0.2C up to 10% of the secondary battery capacity (SOC), a cirate of 0.25C up to 40% of the secondary battery capacity (SOC), the secondary battery capacity ( Up to 65% of SOC) can be charged with a citrate of 0.2C.
[61]
In addition, the charging step (S200) may be carried out at 20 °C to 30 °C, specifically 22 °C to 28 °C, more specifically 23 °C to 27 °C.
[62]
Thereafter, a high-temperature aging step (S300) of aging the primary charged battery in a high-temperature environment is performed.
[63]
The high-temperature aging step (S300) is a step of stabilizing the SEI film formed in the previous charging step, and the stabilization of the SEI film is further accelerated through high-temperature aging, thereby reducing the voltage drop of a good product in the defective inspection aging section to be described later.
[64]
In particular, in the present invention, this high-temperature aging step is carried out at a high temperature of 60°C or higher, preferably 65°C to 75°C to accelerate SEI film stabilization, thereby reducing the amount of self-discharge of non-defective products, thereby improving low voltage detection. do. When the high-temperature aging is performed at a temperature of less than 60° C., it is difficult to achieve the object of the present invention, and when the temperature is too high, there is a problem in that battery performance, such as capacity and lifespan, are reduced.
[65]
In one embodiment of the present invention, the high temperature aging step may be performed for 12 hours to 48 hours, more preferably 18 hours to 36 hours. When the high-temperature aging time is less than 12 hours, it may be difficult to achieve the object of the present invention because the stabilization of the SEI film is not sufficient.
[66]
Thereafter, a room temperature aging step (S400) of aging the high temperature aged secondary battery at room temperature is performed. The room temperature aging step may be carried out at 2 °C to 30 °C, specifically 22 °C to 28 °C, more specifically 23 °C to 27 °C, even more specifically 25 °C to 27 °C.
[67]
The present invention includes a process of recharging the battery to the same charging rate (SOC) as in primary charging in the room temperature aging step ( S400 ) in order to minimize the variation in the voltage drop due to self-discharge of the non-defective product. For convenience, this is referred to as resetting charging.
[68]
The resetting charging may be performed simultaneously with starting the aging at room temperature, or may be performed within 12 hours from the time at which room temperature aging is started.
[69]
The reset charging is charging at a C-rate of 0.01C to 1.0C or less, preferably at a C-rate of 0.05C to 0.4C. In the case of charging at a seed rate exceeding 1.0C, the effect of reducing the variation in the voltage drop amount is insignificant, which is not preferable.
[70]
In addition, the room temperature aging step ( S400 ) may include measuring a change in a voltage value while aging the secondary battery. This may be configured in the form of determining whether the low voltage of the secondary battery is defective by using the open circuit voltage (OCV) measured at a plurality of different time points. For example, by storing a high-temperature-aged secondary battery at room temperature, measuring the OCV at at least two time points, and comparing the difference value between each OCV with a reference value stored in advance in the memory unit, etc., whether the secondary battery has low voltage failure or not can be selected.
[71]
In one embodiment of the present invention, the selection of whether the secondary battery is defective in low voltage is by measuring the voltage value V1 at the start point of the room temperature aging and measuring the voltage value V2 at the end point of the room temperature aging, and the voltage at the start point and the end point The content is to determine whether the voltage drop amount (V1-V2), which is the difference in values, satisfies the reference value range.
[72]
More specifically, when the measured voltage drop amount of the secondary battery to be inspected is 20 mV and the reference value of the voltage drop amount of the non-defective product is 10 mV, the measured voltage drop is greater than the reference value. have.
[73]
The activation method of the present invention may further include a secondary charging step of charging the secondary battery at a citrate of 0.1 to 2.0C after the room temperature aging step (S400).
[74]
In addition, in the activation method of the present invention, since the side reaction gas generated inside the secondary battery by the charging step and the high temperature aging step may cause swelling of the battery, degassing for removing the side reaction gas ) may further include a process.
[75]
In this degassing process, various degassing techniques known at the time of filing of the present invention may be employed. For example, the degassing process may be performed in a pouch-type secondary battery in which one side is elongated, by cutting the extended portion and sealing the incised portion. However, since such a degassing technique is widely known to those skilled in the art, a more detailed description thereof will be omitted.
[76]
[77]
Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.
[78]
[79]
production example
[80]
Li[Ni 0.6 Mn 0.2 Co 0.2 ]O 2 96.7 parts by weight serving as a positive electrode active material , 1.3 parts by weight of graphite functioning as a conductive material, and 2.0 parts by weight of polyvinylidene fluoride (PVdF) functioning as a binder, A positive electrode mixture was prepared. A positive electrode mixture slurry was prepared by dispersing the obtained positive electrode mixture in 1-methyl-2-pyrrolidone serving as a solvent. This slurry was coated on both sides of an aluminum foil having a thickness of 20 μm, dried, and pressed to prepare a positive electrode.
[81]
97.6 parts by weight of artificial graphite and natural graphite (weight ratio: 90:10) functioning as an anode active material, 1.2 parts by weight of styrene-butadiene rubber (SBR) functioning as a binder, 1.2 parts by weight of carboxymethyl cellulose (CMC) , a negative electrode mixture was prepared. A negative electrode mixture slurry was prepared by dispersing this negative electrode mixture in ion-exchanged water serving as a solvent. This slurry was coated on both sides of a copper foil having a thickness of 20 μm, dried and pressed to prepare a negative electrode.
[82]
In an organic solvent mixed with ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) in a composition of 3:3:4 (volume ratio), LiPF 6 was dissolved to a concentration of 1.0M to obtain a non-aqueous electrolyte solution. prepared.
[83]
A lithium secondary battery was prepared by stacking a separator of porous polyethylene between the prepared positive electrode and the negative electrode, and storing it in a pouch, and then injecting the electrolyte.
[84]
[85]
Example 1
[86]
20 secondary batteries of Preparation Example were prepared, aged at room temperature of 25° C. for 24 hours, and pre-aged, and the pre-aged secondary batteries were charged with a citrate of 0.2 C up to SOC 65% to complete primary charging. . The primary charged battery was subjected to high temperature aging at a temperature of 60° C. for 24 hours, and then subjected to room temperature aging at a room temperature of 25° C. for 4 days. At this time, after 3 hours from the start of the aging at room temperature, a resetting process was performed in which the SOC was recharged to 65% at a C-rate of 0.1C.
[87]
[88]
Example 2
[89]
In Example 1, the activation process was performed in the same manner as in Example 1, except that the seed rate during the resetting process was changed to 0.3C.
[90]
[91]
Example 3
[92]
In Example 1, the activation process was performed in the same manner as in Example 1, except that the seed rate during the resetting process was changed to 0.5C.
[93]
[94]
Example 4
[95]
In Example 1, the activation process was performed in the same manner as in Example 1, except that the seed rate during the resetting process was changed to 0.7C.
[96]
[97]
Example 5
[98]
In Example 1, the activation process was performed in the same manner as in Example 1, except that the seed rate during the resetting process was changed to 1.0C.
[99]
[100]
Comparative Example 1
[101]
Twenty secondary batteries of Preparation Example were prepared, aged at room temperature of 25° C. for 24 hours, and pre-aged, and the pre-aged secondary batteries were charged with a citrate of 0.2 C up to SOC 17% to complete primary charging. Afterwards, high-temperature aging was performed at a temperature of 65° C. for 24 hours, secondary charging was performed with a citrate of 0.2 C up to SOC 100%, and then, room temperature aging was performed at room temperature of 25° C. for 48 hours.
[102]
[103]
Comparative Example 2
[104]
The activation process was performed in the same manner as in Example 1, except that the resetting process was not performed during the aging at room temperature in Example 1.
[105]
[106]
experimental example; Measurement of voltage drop
[107]
In the case of Examples 1 to 5, the open circuit voltage (V1) of the secondary battery is measured when the resetting process is completed, and the open circuit voltage (V2) of the secondary battery is measured when the room temperature aging is completed. (ΔOCV = V1-V2) was derived. In addition, the average and standard deviation of the voltage drops of each of the 20 batteries were calculated and the results are shown in Table 1.
[108]
In the case of Comparative Examples 1 and 2, the open circuit voltage (V1) of the secondary battery was measured at the time when room temperature aging was started, and the open circuit voltage (V2) of the secondary battery was measured when the room temperature aging was completed, and the voltage The amount of descent (ΔOCV = V1-V2) was derived. In addition, the average and standard deviation of the voltage drops of each of the 20 batteries were calculated and the results are shown in Table 1.
[109]
[Table 1]
Voltage drop (mV)
average Standard Deviation
Example 1 6.74 0.10
Example 2 6.65 0.13
Example 3 6.52 0.47
Example 4 6.76 0.44
Example 5 6.65 0.43
Comparative Example 1 57.74 1.71
Comparative Example 2 6.64 0.75
[110]
Referring to Table 1, when the batteries manufactured by the activation method according to the embodiment of the present invention and the batteries manufactured by the activation method according to Comparative Example 1 were compared, the voltage drop of the batteries of the Examples was that of the batteries of Comparative Example 1. It is much smaller than the voltage drop, and the standard deviation of the voltage drop of the good product is also much smaller, confirming that the dispersion is improved.
[111]
In addition, when the batteries manufactured by the activation method according to the embodiment of the present invention were compared with the batteries of Comparative Example 2 in which the resetting process was not performed, the voltage drop amount of both was found to be at a similar level, but the standard of the voltage drop amount It can be seen that the deviation is larger in the battery of Comparative Example 2. Accordingly, it will be demonstrated that the activation method of the present invention including the resetting process is excellent in the effect of improving the distribution of the voltage drop. In addition, in the resetting process, Examples 1 to 2 charged with a citrate of 0.3 C or lower showed better voltage drop distribution than Examples 3 to 5 charged with a citrate of 0.5 C or higher. Therefore, in the activation method of the present invention, it can be evaluated that it is more preferable to charge at a seed rate of less than 0.5C during the resetting process.
[112]
[113]
As described above, preferred embodiments of the present invention have been disclosed in the present specification and drawings, and although specific terms are used, these are only used in a general sense to easily explain the technical content of the present invention and help the understanding of the present invention. , it is not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims

[Claim 1]A method for activating a secondary battery, wherein the secondary battery including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and an electrolyte are aged at room temperature (Pre-aging) step (S100); a primary charging step (S200) of charging the pre-aged secondary battery to 60% or more of a secondary battery capacity (SOC); A high-temperature aging step of aging the primary charged secondary battery at a high temperature (S300); and a room temperature aging step of aging the high temperature aged secondary battery at room temperature (S400); and wherein the aging at room temperature comprises a resetting process of charging at the same charging rate as the charging rate (SOC) of the primary charging stage.
[Claim 2]
The method of claim 1 , wherein the resetting process comprises charging at a C-rate of 0.01 C to 1.0 C or less.
[Claim 3]
The method according to claim 1, wherein the resetting process comprises charging at a C-rate of 0.05C to 0.4C.
[Claim 4]
The method of claim 1, wherein in the high-temperature aging step (S300), the battery is aged at a temperature of 60° C. or higher.
[Claim 5]
The method of claim 1, wherein in the high-temperature aging step (S300), the battery is aged for 12 to 48 hours.
[Claim 6]
The method of claim 1, wherein in the primary charging step (S200), the secondary battery is charged to 65% to 75% of the secondary battery capacity (SOC).
[Claim 7]
The method according to claim 1, wherein in the room temperature aging step (S400), a secondary battery having a low voltage defect is selected from a voltage drop amount by measuring a change in a voltage value while the secondary battery is aging.
[Claim 8]
The method of claim 7, wherein measuring the change in the voltage value comprises measuring the voltage value (V1) at the start point of the room temperature aging and measuring the voltage value (V2) at the end point of the room temperature aging, and the voltage values ​​at the start and end points A method of activating a secondary battery, comprising determining whether a voltage drop amount (V1-V2), which is a difference between , satisfies a reference value range.
[Claim 9]
The method of claim 1, further comprising a secondary charging step of charging the secondary battery at a citrate of 0.1 to 2.0C after the room temperature aging step (S400).
[Claim 10]
The method of claim 1, wherein the pre-aging step (S100) comprises aging the secondary battery by leaving it to stand for 0.5 to 72 hours in a temperature environment of 20°C to 30°C.
[Claim 11]
A method of manufacturing a secondary battery comprising the activation method of claim 1.