Formation method of secondary battery and secondary battery formed thereby

Abstract

The present disclosure provides a formation method for a secondary battery having an anode reversible capacity of 400 mAh / g or more, which can include the steps of charging the secondary battery to a first state of charge (SOC) of 3% to 10% at a rate of 0.1 to 0.5C, charging the secondary battery from the first SOC to a second SOC of 20% to 40% at a rate of 0.3 to 1.8C, charging the secondary battery from the second SOC to a third SOC of 100% at a rate of 0.05 to 1.8C, and discharging the secondary battery from the third SOC. At least one of the charging to the first SOC, the second SOC, or the third SOC or the discharging step can be performed under a pressure condition of more than 800 kgf / cm 3 and less than or equal to 2000 kgf / cm 3 and / or at a temperature condition of 30 to 70℃.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0173761, filed on November 28, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a method for forming a secondary battery and the secondary battery formed therefrom. Background Technology

[0004] With the rapid development of the electronics, communications, and computer industries, the application of energy storage technology has expanded to cameras, mobile phones, laptops, personal computers (PCs), and even electric vehicles. For such applications, lightweight, long-lasting, and highly reliable high-performance rechargeable batteries are ideal.

[0005] Among currently used rechargeable batteries, lithium-ion batteries, developed in the early 1990s, have higher operating voltages and energy densities than traditional batteries such as nickel-metal hydride, nickel-cadmium, and lead-sulfur batteries that use aqueous electrolyte solutions. Therefore, lithium-ion batteries have been used as a power source for many portable devices.

[0006] Materials including graphite have been widely used as anode active materials in lithium-ion batteries. This is because the average potential of graphite during lithium absorption / release is approximately 0.1 to 0.2 V (based on Li / Li). + Graphite has a relatively flat discharge potential, thus graphite batteries have the advantage of high and constant voltage. However, graphite's disadvantage is its very small theoretical capacity, only 372 mAh / g.

[0007] Therefore, various anode active materials are being researched to further improve the capacity of lithium-ion batteries. Materials that form intermetallic compounds with lithium (such as silicon or tin) are promising anode active materials as high-capacity materials. Silicon, in particular, is an alloy-type anode active material with a theoretical capacity (4200 mAh / g) approximately 10 times that of graphite, and is attracting attention as a next-generation anode active material.

[0008] Typically, after the secondary battery is manufactured, a formation process is performed, during which charging and discharging occur. The battery structure becomes stable and usable through the formation process. The formation process forms a solid electrolyte interface (hereinafter referred to as the "SEI film") on the electrode (specifically, the anode), stabilizing the electrode structure. However, silicon-based anode active materials undergo significant volume changes (approximately 300%) during charging and discharging, which can disrupt and fragment the physical contacts between active materials. As a result, ionic conductivity and electrical conductivity deteriorate rapidly, and lifetime characteristics tend to decrease rapidly.

[0009] Therefore, in secondary batteries with high reversible capacity that use silicon-based materials as anode active materials, there is a need to develop improved formation process technologies that can shorten the process time while ensuring battery performance.

[0010] The matters described in this background section are only intended to enhance the understanding of the background of this disclosure and should not be construed as an admission that they correspond to prior art known to those skilled in the art. Summary of the Invention

[0011] The following summary provides a simplified overview of certain characteristics. This summary is not an exhaustive overview, nor is it intended to identify important or key elements.

[0012] This disclosure describes systems, apparatus, and methods for the formation of secondary batteries. The formation method for a secondary battery with an anode reversible capacity of at least 400 mAh / g may include the following steps: charging the secondary battery to a first state of charge (SOC) of 3% to 10% at a first rate of 0.1 to 0.5C; charging the secondary battery from the first SOC to a second SOC of 20% to 40% at a second rate of 0.3 to 1.8C; charging the secondary battery from the second SOC to a third SOC of 100% at a third rate of 0.05 to 1.8C; and discharging the secondary battery charged to the third SOC.

[0013] The formation method for secondary batteries may include at least one of the following steps: at a concentration exceeding 800 kgf / cm² 3 And less than or equal to 2000 kgf / cm 3 Charging secondary batteries under pressure; or exceeding 800 kgf / cm 3 And less than or equal to 2000 kgf / cm 3 Discharging the secondary battery under pressure.

[0014] The formation method for a secondary battery may include the steps of charging the secondary battery at a temperature of 30°C to 70°C, or discharging the secondary battery at a temperature of 30°C to 70°C.

[0015] Secondary batteries can be formed / prepared using any one or more formation methods disclosed herein.

[0016] These and other features and advantages will be described in more detail below. Detailed Implementation

[0017] The embodiments disclosed in this specification will be described in detail below. Repeated descriptions of the same or similar components may be omitted in the following description.

[0018] Unless otherwise defined, the terms used herein, including technical or scientific terms, may have the meanings commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0019] In this specification, the terms “comprising,” “including,” or “having” indicate the presence of any feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude any feature, number, step, operation, component, part, or combination thereof.

[0020] Unless the context otherwise requires, the singular expressions used herein may include the plural meaning, and this also applies to the singular expressions described in the claims.

[0021] For the purposes of this application and claims, the exemplary phrases “at least one of A; B; or C” or “at least one of A, B, or C” are used, which means “at least one A, or at least one B, or at least one C, or any combination of at least one A, at least one B, and at least one C.” Furthermore, exemplary phrases used herein, such as “A, B, or C,” “at least one of A, B, and C,” “at least one of A, B, or C,” etc., may refer to each listed item or all possible combinations of listed items. For example, “at least one of A or B” may mean (1) at least one A; (2) at least one B; or (3) at least one A and at least one B.

[0022] The term "about" and similar wording used herein in relation to reference values ​​can include the reference value itself and a range of values ​​within ±10% of that reference value. For example, the term "about 10" includes 10 and any quantity between 9 and 11. In some cases, the term "about" in relation to a reference value can also include a range of values ​​within ±10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of that reference value. In some embodiments, "about" in relation to a number or range measured by a particular method indicates that the given value includes values ​​determined by the variability in that method. The values ​​and ranges disclosed herein can include exact values, or values ​​that include or are approximately disclosed.

[0023] Unless the context otherwise requires, the terms “first” or “second” as used herein are used to distinguish one object from another when referring to multiple similar objects, and do not limit their order or importance. For example, multiple chips according to this disclosure can be distinguished from each other by referring to them respectively as “first chip” and “second chip”.

[0024] The expression “based on” as used herein is intended to describe one or more factors that influence the behavior or action of a judgment or decision described in the phrase or sentence that includes the expression, and the expression does not exclude any other factors that influence the behavior or action of a judgment or decision.

[0025] The formation method for secondary batteries according to embodiments of the present disclosure relates to a formation method for secondary batteries having an anode reversible capacity of 400 mAh / g or more. The formation method for secondary batteries according to embodiments of the present disclosure can be applied to secondary batteries having an anode reversible capacity of 400 mAh / g to 600 mAh / g. The formation method for secondary batteries according to embodiments of the present disclosure can be applied to secondary batteries having an anode reversible capacity of 400 mAh / g to 570 mAh / g. The formation method for secondary batteries according to embodiments of the present disclosure can be applied to secondary batteries containing a silicon-based material as the anode active material.

[0026] The formation method for secondary batteries may include a first formation step, a second formation step, a third formation step, and a discharge step.

[0027] The first formation step may include charging the secondary battery to a first state of charge (SOC) of 3% to 10% at a first rate of 0.1C to 0.5C (C-rate; here, 1C represents the rate at which the battery is charged from 0 to its capacity in 1 hour, 0.1C represents the rate at which the battery is charged from 0 to its capacity in 10 hours, and so on). The first formation step may include charging the secondary battery to a first SOC of 3% to 8% at a first rate of 0.1C to 0.4C. The first formation step may include charging the secondary battery to a first SOC of 3% to 7% at a first rate of 0.1C to 0.3C. The first formation step may include charging the secondary battery to a first SOC of 3% to 6% at a first rate of 0.1C to 0.2C. The first formation step may include charging the secondary battery to a first SOC of 4% to 6% at a first rate of 0.1C to 0.2C. The first formation step may include charging the secondary battery to a SOC of 5% at a rate of 0.1C to 0.2C.

[0028] The first formation step can be carried out under high temperature and pressure conditions. The first formation step can be performed at pressures exceeding 800 kgf / cm³. 3 And less than or equal to 2000 kgf / cm 3 The process is carried out under pressure conditions. The first formation step can be performed at 800 kgf / cm². 3 Up to 1800 kgf / cm 3 The process is carried out under pressure conditions. The first formation step can be performed at 1000 kgf / cm². 3 Up to 1800 kgf / cm 3The process is carried out under pressure conditions. The first formation step can be carried out at a temperature of 30 to 70°C. The first formation step can be carried out at a temperature of 40 to 65°C. The first formation step can be carried out at a temperature of 45 to 60°C.

[0029] The second formation step may include charging the secondary battery, which has been charged to a first SOC, to a second SOC of 20% to 40% at a second rate of 0.3C to 1.8C. The second formation step may include charging the secondary battery to a second SOC of 20% to 40% at a second rate of 0.4C to 1.7C. The second formation step may include charging the secondary battery to a second SOC of 20% to 40% at a second rate of 0.5C to 1.5C. The second formation step may include charging the secondary battery to a second SOC of 25% to 35% at a second rate of 0.5C to 1.5C. The second formation step may include charging the secondary battery to a second SOC of 30% at a second rate of 0.5C to 1.5C (C-rate).

[0030] The second formation step can be performed in one go to the target SOC (e.g., the second SOC). Alternatively, the second formation step can be performed in multiple steps. The second formation step can be performed 1 to 5 times from the first SOC to the target SOC (e.g., performed over 1 to 5 charging periods from the first SOC to the second SOC). The second formation step can be performed 1 to 3 times from the first SOC to the target SOC. For example, if the first formation step achieves a first SOC of 5%, and the second formation step achieves a second SOC of 30%, the process can be divided into segments charging to 5% to 10% SOC, segments charging to 10% to 20% SOC, and segments charging to 20% to 30% SOC. Charging can be paused between segments and / or the rate of charge in each segment can be changed between segments. The rates of charge in each segment can be the same or different from each other. When the rates of charge in each segment are different, the rate of charge in the last segment can be the highest. The individual rates can be within the range of the second rate described above.

[0031] The second formation step can be carried out under high temperature and pressure conditions. The second formation step can be performed at pressures exceeding 800 kgf / cm³. 3 And less than or equal to 2000 kgf / cm 3 The second formation step can be carried out under pressure conditions of 800 kgf / cm³. 3 Up to 1800 kgf / cm 3 The second formation step can be carried out under pressure conditions of 1000 kgf / cm³. 3 Up to 1800 kgf / cm 3The second formation step can be carried out under pressure conditions. The second formation step can be carried out at temperatures ranging from 30 to 70°C. The second formation step can be carried out at temperatures ranging from 40 to 65°C. The second formation step can be carried out at temperatures ranging from 45 to 60°C.

[0032] The third formation step may include charging the secondary battery, which has been charged to the second SOC, to 100% of the third SOC at a third rate of 0.05C to 1.8C. The third formation step may also include charging the secondary battery to 100% of the third SOC at a third rate of 0.1C to 1.7C (C-rate). The third formation step may further include charging the secondary battery to 100% of the third SOC at a third rate of 0.1C to 1.6C. Finally, the third formation step may include charging the secondary battery to 100% of the third SOC at a third rate of 0.1C to 1.5C.

[0033] The maximum rate of the third formation step can be from 0.4C to 1.7C (e.g., the maximum third rate of battery charging during the third formation step). The maximum rate of the third formation step can be from 0.5C to 1.6C. The maximum rate of the third formation step can be from 0.5C to 1.6C. The maximum rate of the third formation step can be from 0.5C to 1.5C.

[0034] The third formation step can be carried out under high temperature and pressure conditions. The third formation step can be performed at temperatures exceeding 800 kgf / cm³. 3 And less than or equal to 2000 kgf / cm 3 The third formation step can be carried out under pressure conditions of 800 kgf / cm³. 3 Up to 1800 kgf / cm 3 The third formation step can be carried out under pressure conditions of 1000 kgf / cm³. 3 Up to 1800 kgf / cm 3 The process is carried out under pressure conditions. The third formation step can be carried out at a temperature of 30 to 70°C. The third formation step can be carried out at a temperature of 40 to 65°C. The third formation step can be carried out at a temperature of 45 to 60°C.

[0035] The discharge step may include discharging the secondary battery from a third SOC. The discharge step may be performed at a discharge rate (C-rate, where 1C corresponds to the discharge rate that fully discharges the battery from 100% SOC to 0% SOC in 1 hour). The discharge step may include discharging to 0 to 70% SOC at a rate of 0.05C to 1.8C. The discharge step may include discharging to 0 to 70% SOC at a rate of 0.1C to 1.7C. The discharge step may include discharging to 0 to 70% SOC at a rate of 0.1C to 1.6C. The discharge step may include discharging to 0 to 70% SOC at a rate of 0.1C to 1.5C. The discharge step may include discharging to 30 to 70% SOC at a rate of 0.05C to 1.8C. The discharge step may include discharging to 40 to 70% SOC at a rate of 0.1C to 1.7C. The discharge step may include discharging at a rate of 0.1C to 1.6C to 50% to 70% of the state of charge (SOC). The discharge step may also include discharging at a rate of 0.1C to 1.5C to 60% of the SOC.

[0036] The discharge rate (i.e., the discharge ratio) can be equal to the maximum rate in the third formation step. For example, the discharge rate can be from 0.4C to 1.7C. The discharge rate can be from 0.5C to 1.6C. The discharge rate can be from 0.5C to 1.6C. The discharge rate can be from 0.5C to 1.5C.

[0037] The discharge step can be performed under high temperature and pressure conditions. The discharge step can be performed at pressures exceeding 800 kgf / cm². 3 And less than or equal to 2000 kgf / cm 3 The discharge step can be performed under pressure conditions exceeding 800 kgf / cm². 3 And less than or equal to 1800 kgf / cm 3 The discharge process can be carried out under pressure conditions exceeding 1000 kgf / cm². 3 And less than or equal to 1800 kgf / cm 3 The discharge process is carried out under pressure conditions. The discharge step can be performed at temperatures ranging from 30 to 70°C. The discharge step can be performed at temperatures ranging from 40 to 65°C. The discharge step can be performed at temperatures ranging from 45 to 60°C.

[0038] The formation method for secondary batteries according to embodiments of the present disclosure may exclude the initialization step of charging at a fourth rate to a fourth state of charge (SOC) of less than 3%. That is, the formation method for secondary batteries according to embodiments of the present disclosure may exclude another formation step before the first formation step. The formation method for secondary batteries according to embodiments of the present disclosure may omit the initialization step. The formation method for secondary batteries according to one embodiment of the present disclosure, for example, by omitting the initialization step, can ensure excellent battery performance while reducing process time.

[0039] The formation method for secondary batteries according to embodiments of this disclosure can reduce anode volume expansion. When applied to secondary batteries having an anode reversible capacity of 400 mAh / g or more, the formation method for secondary batteries disclosed herein can form a dense interface. The formation method for secondary batteries according to embodiments of this disclosure can improve the battery appearance and / or durability of secondary batteries having an anode reversible capacity of 400 mAh / g or more. The formation method for secondary batteries according to embodiments of this disclosure can ensure the battery performance of secondary batteries having an anode reversible capacity of 400 mAh / g or more.

[0040] The formation method for secondary batteries according to embodiments of the present disclosure can reduce anode volume expansion and form a dense interface when applied to secondary batteries containing silicon-based materials as anode active materials. The formation method for secondary batteries according to embodiments of the present disclosure can improve the battery appearance and durability of secondary batteries containing silicon-based materials as anode active materials. The formation method for secondary batteries according to embodiments of the present disclosure can ensure the battery performance of secondary batteries containing silicon-based materials as anode active materials. The formation method for secondary batteries according to embodiments of the present disclosure can suppress initial silicon volume expansion and improve electrode interface uniformity.

[0041] The formation method for secondary batteries according to the embodiments of this disclosure can greatly reduce process time and is beneficial for the large-scale production of secondary batteries.

[0042] The secondary battery according to embodiments of this disclosure can be formed by the formation method described herein.

[0043] The anode of the secondary battery according to various embodiments of the present disclosure may include silicon (Si) as the anode active material. Si may account for 5 wt% to 15 wt% of the total composition of the anode. The anode of the secondary battery according to various embodiments of the present disclosure may also include graphite as the anode active material. The anode of the secondary battery according to various embodiments of the present disclosure may include at least one other anode active material besides graphite (e.g., not only graphite as the anode active material).

[0044] The anode of the secondary battery according to various embodiments of this disclosure may also include a conductive material, a binder, and / or a thickener.

[0045] Conductive materials may include at least any one selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fibers, fluorocarbons, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, polyphenylene derivatives, carbon nanotubes, plate graphite, graphene, graphene oxide, and graphite sheets.

[0046] The adhesive and / or thickener may each independently comprise at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluoroelastomers and polyacrylic acid, and may also include various copolymers thereof.

[0047] The secondary battery according to various embodiments of this disclosure may include a cathode. The cathode may include a cathode active material, a conductive material, and a binder. The cathode active material may include at least one selected from, for example, nickel cobalt manganese (NCM), nickel cobalt aluminum (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), and lithium iron phosphate (LFP). Preferably, the cathode active material may include NCM.

[0048] Conductive materials may include at least any one selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fibers, fluorocarbons, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, polyphenylene derivatives, carbon nanotubes, plate graphite, graphene, graphene oxide, and graphite sheets.

[0049] The adhesive may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluoroelastomers, and polyacrylic acid. The adhesive may also include, or alternatively may include, various copolymers from the group above.

[0050] The secondary battery according to various embodiments of the present disclosure may include a separator and an electrolyte located between the cathode and the anode.

[0051] The separator can separate the anode and cathode and provide a channel for lithium ions to move. The separator can include a porous polymer membrane, such as a porous polymer membrane made of polyolefin polymers (e.g., any one or more of ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), or a laminated structure of two or more layers thereof. Alternatively or additionally, the separator can include a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0052] Electrolytes can include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc.

[0053] By applying an optimized formation process to a secondary battery containing silicon-based materials as the anode active material, the secondary batteries according to various embodiments of this disclosure can ensure excellent performance.

[0054] Preparation example: Preparation of secondary batteries

[0055] A cathode containing NCM cathode active material and an anode containing Si anode active material were prepared. Several embodiments were prepared in which the prepared anodes had reversible capacities of 405 mAh / g, 484 mAh / g, and 561 mAh / g by adjusting the Si content. An electrode assembly was fabricated by placing a separator between the cathode and the anode, and the electrode assembly was inserted into a battery case, followed by injection of an electrolyte solution to prepare a secondary battery.

[0056] Experiment Example 1: Verifying the relationship between process time and battery performance in high-temperature pressurization process

[0057] The lithium secondary battery with an anode reversible capacity of 405 mAh / g prepared in the preparation example was subjected to a formation process.

[0058] Comparative Example 1 additionally includes an initialization step of charging to less than 3% SOC, and a third formation step of charging to 100% SOC using a room temperature, non-pressurized (e.g., atmospheric pressure) process instead of a high-temperature pressurized process.

[0059] Comparative Example 2 uses a room temperature, non-pressurized process instead of a high temperature pressurized process to perform the discharge step.

[0060] Comparative Example 3 additionally performs an initialization step of charging to less than 3% SOC at 5 kgf / cm². 3 The first and second formation steps are performed at a certain speed, and the third formation step, charging to 100% SOC, is performed using a room temperature, non-pressurized process instead of a high-temperature pressurized process.

[0061] Comparative Example 4 uses a room temperature, non-pressurized process instead of a high temperature pressurized process to perform the second formation step.

[0062] In other words, Example 1 does not include the initialization step of charging to less than 3% of the fourth SOC, and 45°C and 1800 kgf / cm² are applied to the first, second, third, and discharge steps. 3 The high-temperature and high-pressure process.

[0063] Meanwhile, the SOC, C-rate, temperature, and pressure conditions for each formation step are shown in Table 1 below.

[0064] [Table 1]

[0065]

[0066] For Comparative Examples 1 to 4 and Example 1, the results of total formation process time, maximum power discharge (15s, SOC40), maximum power charge (15s, SOC70), power density discharge (15s, SOC40), and power density charge (15s, SOC40) are shown in Table 2 below.

[0067] [Table 2]

[0068]

[0069] Referring to Table 2 above, it is confirmed that the process time of Example 1 was reduced by 10 times compared with Comparative Example 1, Comparative Example 3 and Comparative Example 4.

[0070] Furthermore, it was confirmed that the values ​​of maximum power discharge (15s, SOC40), maximum power charge (15s, SOC70), power density discharge (15s, SOC40), and power density charge (15s, SOC40) of Example 1 were superior to those of Comparative Examples 1 to 4. In other words, it can be seen that the output value and durability performance of Example 1 are superior to any of the comparative examples.

[0071] This confirms that, except for the initialization step of charging to below 3% SOC, when at 45°C and 1800 kgf / cm², 3 When the high-temperature and high-pressure process is applied to all steps of the first formation step, the second formation step, the third formation step, and the discharge step, the battery performance is excellent.

[0072] Experiment Example 2: Verifying Battery Performance Based on Changes in C-Rate and Temperature

[0073] The lithium secondary battery with an anode reversible capacity of 484 mAh / g prepared in the preparation example was subjected to a formation process. Experimental Example 1 above confirmed that when 45°C and 1800 kgf / cm² were used… 3 When the high-temperature, high-pressure process is applied to all steps of the first, second, and third formation processes, as well as the discharge process, the battery performance is excellent. In this experimental example, the battery performance was verified by varying the C-rate and temperature at each step. In this experimental example, we confirmed that excellent battery performance can be ensured even when the process time is shortened by changing the C-rate and temperature.

[0074] Example 2 only changed the temperature of Example 1. That is, except that the temperature was raised to 60°C, Example 2 was performed in the same manner as Example 1.

[0075] Example 3 modifies the C-rate and temperature of Example 1. That is, Example 3 is performed by reducing the C-rate of the first formation step in Example 1 from 0.2C to 0.1C, subdividing the second formation step to increase the C-rate range to 1.5C, increasing the C-rate of the third formation step and the discharge step to 1.5C, and increasing the temperature to 60°C.

[0076] Example 4 is performed by simply changing the C-rate of Example 1. That is, Example 4 is performed by subdividing the second formation step in Example 1 to increase the C-rate to 1.5C, and increasing the C-rate of the third formation step and the discharge step to 1.5C.

[0077] Example 5 is performed by simply changing the C-rate of Example 1. That is, Example 5 is performed by reducing the C-rate of the first formation step in Example 1 from 0.2C to 0.1C, subdividing the second formation step to increase the C-rate range to 0.33C and 1.5C, and increasing the C-rate of the third formation step and the discharge step to 1.5C.

[0078] Example 6 modifies the C-rate and temperature of Example 1. That is, Example 6 is performed by subdividing the second formation step in Example 1 to increase the C-rate to 1.5C, increasing the C-rate of the third formation step and the discharge step to 1.5C, and increasing the temperature to 60°C.

[0079] Example 7 is performed by simply changing the C-rate of Example 1. That is, Example 7 is performed by reducing the C-rate of the first formation step in Example 1 from 0.2C to 0.1C, subdividing the second formation step to increase the C-rate segment to 1.5C, and increasing the C-rate of the third formation step and the discharge step to 1.5C.

[0080] The SOC, C-rate, temperature, and pressure conditions for each formation step are shown in Table 3 below.

[0081] [Table 3]

[0082]

[0083] The results of confirming the ratio of anode energy density to weight (weight E / D), the ratio of anode energy density to volume (volume E / D), and discharge power of the above embodiments 2 to 7 are shown in Table 4 below.

[0084] [Table 4]

[0085]

[0086] In Example 2, it can be seen that the discharge power is optimal when the temperature rises to 60°C, but the process time is most unfavorable.

[0087] In order to reduce process time and increase the C-rate of the second formation step, the third formation step and the discharge step while maintaining the same level of battery performance, it was found advantageous to perform the first formation step at a rate of 0.1C, referring to Examples 3 and 6.

[0088] On the other hand, in the case of Example 7, it was carried out at 45°C, but the C-rate of the second formation step, the third formation step and the discharge step were increased, which confirmed that the process time was very short. However, compared with other examples, the weight E / D and volume E / D were optimal, and the room temperature impedance and discharge power were at the same level as in Example 2.

[0089] Therefore, it was confirmed that performing the first formation step at a lower rate of 0.1C at temperatures of 45°C and 60°C is beneficial to battery performance, but performing the second, third, and discharge steps at a higher rate of 1.5C is beneficial.

[0090] Experiment Example 3: Verifying Battery Performance Based on Pressure Changes

[0091] The lithium secondary battery with an anode reversible capacity of 561 mAh / g prepared in the preparation example was subjected to a formation process. Through Experiment 2 above, it was confirmed that Example 7 exhibited optimal performance regarding process time, wherein the first, second, and third formation steps and the discharge step were all performed at 45°C and 1800 kgf / cm². 3 The process is carried out under high temperature and pressure conditions. The C-rate of the first formation step is reduced from 0.2C to 0.1C. The second formation step is subdivided to increase the C-rate to 1.5C. The C-rate of the third formation step and the discharge step is increased to 1.5C.

[0092] In this experimental example, battery performance was confirmed by changing the pressure.

[0093] Example 8 only changed the pressure in Example 7 above. That is, except that the pressure was reduced to 1000 kgf / cm². 3 Otherwise, Example 8 is performed in the same manner as Example 7.

[0094] Comparative Example 5 only changed the pressure in Example 7 above. That is, except for reducing the pressure to 800 kgf / cm². 3 Comparative Example 5 was performed in the same manner as in Example 7.

[0095] Meanwhile, the SOC, C-rate, temperature, and pressure conditions for each formation step are shown in Table 5 below.

[0096] [Table 5]

[0097]

[0098] The results of confirming the room temperature power performance and low temperature power performance of Examples 7 and 8 and Comparative Example 5 are shown in Table 6 below.

[0099] [Table 6]

[0100]

[0101] Referring to Table 6 above, it is confirmed that the pressure is 1800 kgf / cm². 3 Reduced to 1000 kgf / cm 3 Example 8 showed performance comparable to Example 7. This confirmed that performance was achieved even with pressure reduced to 800 kgf / cm². 3 In Comparative Example 5, the room temperature power performance was similar to that of the Example, but the low-temperature power performance was significantly reduced. Therefore, it can be confirmed that the power performance exceeds 800 kgf / cm². 3 And less than or equal to 1800 kgf / cm 3 The pressure conditions are optimal.

[0102] Through the above experimental examples 1 to 3, it was confirmed that, excluding the initialization step of charging to less than 3% SOC, and if 45-60℃ and 1000-1800 kgf / cm² are applied to all steps in the first, second, third, and discharge steps, the results are satisfactory. 3 Under high temperature and pressure conditions, a secondary battery with an anode reversible capacity of over 400 mAh / g and favorable battery performance was formed. In particular, it was demonstrated that if the first formation step is carried out at 0.1 to 0.2C, but the second, third, and discharge steps are carried out at a higher rate of 0.5 to 1.5C, the process time and battery performance are improved compared to the comparative example.

[0103] The embodiments disclosed herein are illustrative and are not limited to the embodiments described above.

[0104] One aspect of the present invention is to provide a formation method for a secondary battery and a secondary battery formed therefrom.

[0105] According to one embodiment of the present invention, a formation method for a secondary battery with an anode reversible capacity of 400 mAh / g or more may include the following steps: a first formation step, charging the secondary battery to 3% to 10% SOC at a rate of 0.1 to 0.5C (C-rate); a second formation step, charging the secondary battery after the first formation step to 20% to 40% SOC at a rate of 0.3 to 1.8C; a third formation step, charging the secondary battery after the second formation step to 100% SOC at a rate of 0.05 to 1.8C; and discharging the secondary battery after the third formation step.

[0106] In the formation method for a secondary battery according to embodiments of the present disclosure, the initialization step of charging to less than 3% SOC may be omitted.

[0107] In the formation method for a secondary battery according to embodiments of the present disclosure, the first formation step, the second formation step, the third formation step, and the discharge step can exceed 800 kgf / cm². 3 And less than or equal to 2000 kgf / cm 3 It is carried out under pressure conditions.

[0108] In the formation method for a secondary battery according to embodiments of the present disclosure, the first formation step, the second formation step, the third formation step, and the discharge step can be performed at a temperature of 30 to 70°C.

[0109] In the formation method for a secondary battery according to an embodiment of the present disclosure, the C-rate of the discharge step may be the same as the maximum rate in the third formation step.

[0110] In the formation method for a secondary battery according to embodiments of the present disclosure, the anode reversible capacity of the secondary battery can be 400 mAh / g or higher.

[0111] In the formation method for a secondary battery according to embodiments of the present disclosure, the secondary battery may include a silicon-based material as the anode active material.

[0112] In the formation method for secondary batteries according to embodiments of the present disclosure, a flow rate exceeding 800 kgf / cm² can be achieved. 3 And less than or equal to 2000 kgf / cm 3 Perform at least one step under pressure conditions.

[0113] In the formation method for secondary batteries according to embodiments of the present disclosure, at least any one of the steps can be performed at a temperature of 30 to 70°C.

[0114] In the formation method for a secondary battery according to embodiments of the present disclosure, the anode reversible capacity of the secondary battery can be 400 mAh / g or higher.

[0115] In the formation method for secondary batteries according to embodiments of the present disclosure, at least any one of the steps can be performed at a temperature of 30 to 70°C.

[0116] In the formation method for secondary batteries according to embodiments of the present disclosure, a flow rate exceeding 800 kgf / cm² can be achieved. 3 And less than or equal to 2000 kgf / cm 3 Perform at least one step under pressure conditions.

[0117] According to another embodiment of this disclosure, a secondary battery can be formed by the above-described formation method.

[0118] According to one aspect of this disclosure, the formation method for secondary batteries can omit the initialization step of charging to less than 3% SOC.

[0119] According to another aspect of the present invention, when the formation method for secondary batteries is applied to a secondary battery with an anode reversible capacity of 400 mAh / g or more, the volume expansion of the anode can be reduced and a dense interface can be formed. The formation method for secondary batteries according to embodiments of the present disclosure can improve the battery appearance and durability of secondary batteries with an anode reversible capacity of 400 mAh / g or more. The formation method for secondary batteries according to embodiments of the present disclosure can ensure the battery performance of secondary batteries with an anode reversible capacity of 400 mAh / g or more.

[0120] In another aspect of this disclosure, when the formation method for secondary batteries is applied to a secondary battery containing silicon-based materials as the anode active material, the volume expansion of the anode can be reduced and a dense interface can be formed. The formation method for secondary batteries according to embodiments of this disclosure can improve the battery appearance and durability of secondary batteries containing silicon-based materials as the anode active material. The formation method for secondary batteries according to embodiments of this disclosure can ensure the battery performance of secondary batteries containing silicon-based materials as the anode active material. The formation method for secondary batteries according to embodiments of this disclosure can suppress the initial volume expansion of silicon and improve the uniformity of the electrode interface.

[0121] The formation method for secondary batteries according to the embodiments of this disclosure can greatly reduce the process time and is beneficial for the large-scale production of secondary batteries.

[0122] The effects of this disclosure are not limited to those described above; those skilled in the art can clearly understand other unmentioned effects based on the above description.

[0123] It will be apparent to those skilled in the art that modifications can be made to this disclosure within the scope of the disclosed technical concept. The described embodiments should be considered part of this disclosure, and the scope of this disclosure should not be limited to the described embodiments.

[0124] The scope of this disclosure should be determined by the technical concept defined in the claims. Furthermore, even if the actions or effects resulting from this configuration are not explicitly described in the description of embodiments of this disclosure, it is obvious that actions or results foreseeable through this configuration should be considered part of this disclosure.

Claims

1. A formation method for a secondary battery with an anode reversible capacity of at least 400 mAh / g, the method comprising the following steps: The secondary battery is charged to a first SOC of 3% to 10% at a first rate of 0.1 to 0.5C, where SOC represents the state of charge. The secondary battery is charged from the first SOC to a second SOC of 20% to 40% at a second rate of 0.3 to 1.8C. The secondary battery is charged from the second SOC to a third SOC at a third rate of 0.05 to 1.8C. as well as Discharge the secondary battery that has been charged to the third SOC.

2. The formation method according to claim 1, wherein, The step of charging the secondary battery to the first SOC is not performed after the step of charging the secondary battery to a fourth SOC of less than 3% at a fourth rate.

3. The formation method according to claim 1, wherein, The steps of charging the secondary battery to the first SOC, charging the secondary battery to the second SOC, charging the secondary battery to the third SOC, and discharging the secondary battery exceed 800 kgf / cm². 3 And less than or equal to 2000 kgf / cm 3 Executed under pressure conditions.

4. The formation method according to claim 1, wherein, The steps of charging the secondary battery to the first SOC, charging the secondary battery to the second SOC, charging the secondary battery to the third SOC, and discharging the secondary battery exceed 1000 kgf / cm². 3 And less than or equal to 1800 kgf / cm 3 Executed under pressure conditions.

5. The formation method according to claim 1, wherein, The steps of charging the secondary battery to the first SOC, charging the secondary battery to the second SOC, charging the secondary battery to the third SOC, and discharging the secondary battery are performed at a temperature of 30 to 70°C.

6. The formation method according to claim 1, wherein, The steps of charging the secondary battery to the first SOC, charging the secondary battery to the second SOC, charging the secondary battery to the third SOC, and discharging the secondary battery are performed at a temperature of 45 to 60°C.

7. The formation method according to claim 1, wherein, The discharge rate is the same as the maximum value of the third rate.

8. The formation method according to claim 1, wherein, The secondary battery includes silicon-based materials as the anode active material.

9. The formation method according to claim 1, wherein, The third multiplier is 1.5C.

10. A formation method for a secondary battery, the formation method comprising at least one of the following: In areas exceeding 800 kgf / cm 3 And less than or equal to 2000 kgf / cm 3 The step of charging the secondary battery under pressure; or In areas exceeding 800 kgf / cm 3 And less than or equal to 2000 kgf / cm 3 The step of discharging the secondary battery under pressure.

11. The formation method according to claim 10, wherein, At least one of the charging or discharging steps is performed at a temperature of 30 to 70°C.

12. The formation method according to claim 10, wherein, The reversible capacity of the anode of the secondary battery is above 400 mAh / g.

13. The formation method according to claim 10, wherein, The formation method includes the step of charging the secondary battery under a defined pressure, wherein the step of charging the secondary battery includes the following steps: The secondary battery is charged to a first SOC of 3% to 10% at a first rate of 0.1C to 0.5C, where SOC represents the state of charge. The secondary battery is charged from the first SOC to a second SOC of 20% to 40% at a second rate of 0.3C to 1.8C; and The secondary battery is charged from the second SOC to a third SOC at a third rate of 0.05C to 1.8C.

14. A formation method for a secondary battery, the formation method comprising at least one of the following: The step of charging the secondary battery at a temperature of 30 to 70°C; or The step of discharging the secondary battery at a temperature of 30 to 70°C.

15. The formation method according to claim 14, wherein, At least one of the charging or discharging steps exceeds 800 kgf / cm 3 And less than or equal to 2000 kgf / cm 3 It was carried out under pressure.

16. The formation method according to claim 14, wherein, The reversible capacity of the anode of the secondary battery is above 400 mAh / g.

17. The formation method according to claim 14, wherein, The formation method includes the step of charging the secondary battery at a defined temperature, wherein the step of charging the secondary battery includes the following steps: The secondary battery is charged to a first SOC of 3% to 10% at a first rate of 0.1C to 0.5C, where SOC represents the state of charge. The secondary battery is charged to a second SOC of 20% to 40% at a second rate of 0.3C to 1.8C; and The secondary battery is charged to 100% of its third state of charge at a third rate of 0.05C to 1.8C.

18. A secondary battery formed by the formation method of claim 1.

19. The secondary battery according to claim 18, wherein, The secondary battery includes an anode, and the anode includes: Silicon is used as an anode active material.

20. The secondary battery according to claim 18, wherein, The anode also includes: Conductive materials; Adhesives; and Thickener.

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