Manufacturing method for lithium secondary battery, separator for lithium secondary battery and lithium secondary battery with thereof

Abstract

The present invention relates to a method for manufacturing a lithium secondary battery that can control a specific additive to affect only one of the positive and negative electrodes, or allow different additives to individually affect each electrode, comprising: a) forming a first coating layer with a first additive on one side of a separator and forming a second coating layer with a second additive on the other side of the separator; b) inserting the separator, a positive body, and a negative body into a housing such that the positive body is in contact with one side of the separator and the negative body is in contact with the other side of the separator; c) injecting an electrolyte into the housing and allowing the first additive and the second additive to dissolve in the electrolyte; and d) first charging and discharging the positive body and the negative body to form a film composed of the electrolyte and the first additive on the surface of the positive body and a film composed of the electrolyte and the second additive on the surface of the negative body.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a lithium secondary battery, a separator for a lithium secondary battery, and a lithium secondary battery including the same. Background Technology

[0002] A lithium-ion secondary battery is a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and from the positive electrode to the negative electrode during charging. Lithium-ion secondary batteries are primarily used in commercially available portable electronic devices because they have high energy density, lack the memory effect, and exhibit minimal self-discharge even when not in use.

[0003] A lithium secondary battery can largely consist of a housing, a positive and negative electrode housed within the housing, a separator housed within the housing that separates the positive and negative electrodes and allows only ions to pass through, and an electrolyte housed within the housing. The manufacturing of such lithium secondary batteries was carried out by inserting the positive, negative, and separator into the housing and then injecting the electrolyte into the housing; if necessary, various additives were added to the electrolyte to impart various functions to the positive or negative electrode. However, in this conventional method of adding various additives to the electrolyte and then injecting it into the housing, the electrolyte impregnates the electrodes without distinction between the positive and negative electrodes. Consequently, it is unclear which electrode the additives will impregnate and function on, leading to difficulties for the operator to determine the effect on each electrode, control the effect of a specific additive on either the positive or negative electrode, or control different additives to have individual effects on each electrode. Prior art literature

[0004] Korean Registered Patent Publication No. 10-2053043 (“Lithium battery with improved output characteristics and seismic resistance,” published Dec. 02, 2019) The problem to be solved

[0005] The present invention has been devised to solve the problems described above. The purpose of the method for manufacturing a lithium secondary battery, the separator for a lithium secondary battery, and the lithium secondary battery including the same according to the present invention is to provide a method for manufacturing a lithium secondary battery that can control a specific additive to affect only one of the positive and negative electrodes, or allow different additives to individually affect each electrode. means of solving the problem

[0006] A method for manufacturing a lithium secondary battery according to the present invention to solve the problems described above may include: a) a step of manufacturing a separator by forming a first coating layer containing a first additive on one side of a membrane-shaped separator and forming a second coating layer containing a second additive on the other side of the separator; b) a step of inserting the separator, a positive electrode, and a negative electrode into a housing such that the positive electrode is in contact with one side of the separator and the negative electrode is in contact with the other side of the separator; c) a step of injecting an electrolyte into the housing so that the first additive and the second additive dissolve in the electrolyte and are delivered to the positive electrode and the negative electrode, respectively; and d) a step of forming a film containing the electrolyte and the first additive on the surface of the positive electrode and a film containing the electrolyte and the second additive on the surface of the negative electrode.

[0007] In addition, the first additive and the second additive may be different from each other.

[0008] In addition, step c) above can be performed by inserting the nozzle into the housing and then injecting the electrolyte into the housing using the nozzle.

[0009] Additionally, in step c), the injection end of the nozzle may be positioned to be in contact with or adjacent to the first coating layer and the second coating layer to inject the electrolyte.

[0010] Additionally, in step c), the injection end of the nozzle may be positioned to be in contact with or adjacent to the bottom of the first coating layer and the second coating layer, and then the electrolyte may be injected while moving the nozzle upward.

[0011] Additionally, step a) above may form the first coating layer with a mixture comprising a porous material and the first additive, and form the second coating layer comprising a porous material and the second additive.

[0012] In addition, step a) above may form an internal coating layer on each side of the separation part using a porous material, and form the first coating layer and the second coating layer on the surface of the internal coating layer, respectively.

[0013] In addition, the first additive may include at least one of Lithium difluoro bis-oxalato phosphate and LiPO2F2.

[0014] In addition, the second additive may include at least one of VC, VEC, FEC, PRS, LiBOB, PS, ESA, LiTFSi, LiBF4, and LiFSI.

[0015] Additionally, step a) above may include metal organic frameworks (MOFs) in the first coating layer or the second coating layer.

[0016] A separator for a lithium secondary battery according to the present invention may include a membrane-shaped separator, a first coating layer formed on one side of the separator including a first additive and in contact with the positive electrode of the lithium secondary battery, and a second coating layer formed on the other side of the separator including a second additive different from the first additive and in contact with the negative electrode of the lithium secondary battery.

[0017] In addition, the above-mentioned separator may be any one of a plate shape, a roll shape, and a zigzag wound shape.

[0018] In addition, the first additive may be at least one of Lithium difluoro bis-oxalato phosphate and LiPO2F2.

[0019] In addition, the second additive may be at least one of VC, VEC, FEC, PRS, LiBOB, PS, ESA, LiTFSi, LiBF4, and LiFSI.

[0020] In addition, the mixture containing the first additive or the mixture containing the second additive may include metal organic frameworks (MOFs).

[0021] A lithium secondary battery according to the present invention may include a separator for a lithium secondary battery, a positive electrode disposed to be in contact with a first coating layer formed on one surface of the separator, a negative electrode disposed to be in contact with a second coating layer formed on the other surface of the separator, a housing accommodating the separator for the lithium secondary battery, the positive electrode and the negative electrode, and an electrolyte injected into the housing. Effects of the invention

[0022] According to the method for manufacturing a lithium secondary battery, the separator for a lithium secondary battery, and the lithium secondary battery including the same as described above, by forming a film with a different additive on each of a positive electrode arranged to be in contact with one surface of the separator and a negative electrode arranged to be in contact with the other surface of the separator, and by applying a different additive to each of the positive electrode and the negative electrode, the effect of the additive can be individually applied to different electrodes. Brief explanation of the drawing

[0023] FIG. 1 is a cross-sectional view of a separator after step a) of the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention has been performed. FIG. 2 is a schematic diagram of the process in which step b) of the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention is performed. FIG. 3 is a schematic diagram of the process in which step c) of the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention is performed. FIG. 4 is a schematic cross-sectional view of the process in which step c) of the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention shown in FIG. 3 is performed. FIG. 5 is a cross-sectional view of a separator after step a) of the method for manufacturing a lithium secondary battery according to the second embodiment of the present invention has been performed. Specific details for implementing the invention

[0024] A preferred embodiment of the method for manufacturing a lithium secondary battery according to the present invention will be described in detail below with reference to the attached drawings.

[0025] [First Example]

[0026] A method for manufacturing a lithium secondary battery according to the first embodiment of the present invention may include steps a), b), c), and d).

[0027] a) Step is to manufacture a separation membrane by forming a first coating layer and a second coating layer on each side of a membrane-shaped separation portion.

[0028] FIG. 1 illustrates the separation section (100) after step a) is performed.

[0029] As illustrated in FIG. 1, a first coating layer (110) is formed on one side of the separation part (100) after step a) is performed, and a second coating layer (120) is formed on the other side of the separation part (100). In this embodiment, the first coating layer (110) and the second coating layer (120) are each coating layers formed from a mixture of a coating raw material and an additive, the first coating layer (110) may be formed from a mixture of a coating raw material and a first additive, and the second coating layer (120) may be formed from a mixture of a coating raw material and a second additive. The coating raw material, which is one of the raw materials constituting the first coating layer (110) and the second coating layer (120), may be a porous material as an example, and may be a porous ceramic as an example of a porous material. In addition, in this embodiment, the first additive and the second additive may be different materials. The reason for configuring the first additive and the second additive differently in this embodiment is to ensure that, in the future manufacturing process, regarding the positive body in contact with one side of the separator (100) and the negative body in contact with the other side of the separator (100), the first additive affects only the positive body, and the second additive affects only the negative body. In the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention, the first additive and the second additive may be additives that are generally included in and injected into the electrolyte during the manufacture of the lithium secondary battery. That is, in the present invention, the additives are intended to add additional functions, such as supplementing the insufficient performance of the battery or improving stability, and various types of additives may be used. More specifically, the first additive may include an additive that has a beneficial effect on the positive body, and the second additive may include an additive that has a beneficial effect on the negative body.

[0030] According to the present embodiment, specific examples of the first additive and the second additive and the resulting effects may be as follows.

[0031] i) First additive

[0032] Lithium difluoro bis-oxalato phosphate: Anode film formation, high-rate charge / discharge improvement

[0033] LiPO2F2: Anode film formation, high-rate charge / discharge improvement

[0034] ii) Second additive

[0035] VC (Vinylene Carbonate): Cathode film formation, improvement of lifespan characteristics

[0036] VEC (Vinyl Ethylene Carbonate): Cathode film formation, improvement of high-temperature performance

[0037] FEC (FluoroEthylene Carbonate): Cathode film formation, lifespan improvement

[0038] PRS (Propensulton): Cathode film formation, improvement of high-temperature characteristics

[0039] LiBOB (Lithium bis(oxalato)borate): Cathode film formation, improvement of swelling characteristics

[0040] PS (Propane Sultone): Cathode film formation, improvement of high-temperature characteristics

[0041] ESA (Ethylene sulfate): Formation of cathode film, improvement of resistance characteristics

[0042] LiTFSi (Lithium bis(trifluoromethane)sulfonamide): Cathode film formation, improvement of high voltage characteristics

[0043] LiFSI (Lithium bis(fluorosulfonyl)imide): Cathode film formation, improvement of high voltage characteristics

[0044] LiBF4 (Lithium Tetrafluoroborate): Cathode film formation, improvement of lifespan characteristics

[0045] The aforementioned first additive has a positive expected effect only on the anode in contact with the additive, and the second additive has a positive expected effect only on the cathode in contact with the additive. This characteristic is manifested because the redox potential of the additive varies completely depending on the design.

[0046] When the first additive comes into contact with the cathode and acts, it can have a negative effect on the cathode, and similarly, when the second additive comes into contact with the anode and acts, it can also have a negative effect on the anode. As explained in the background art, it was difficult to make the additives act individually on the anode and the cathode, respectively, using conventional methods, but the present invention makes it possible to make different additives individually affect the anode and the cathode, respectively, by using steps a), b), c), and d) described below.

[0047] In step a), a separator can be manufactured by forming a first coating layer (110) and a second coating layer (120) on the surface of the separation unit (100) using various methods. Typically, step a) may involve mixing ceramic powder, a water-based binder, and either a first additive or a second additive to create a slurry, and then coating the slurry onto the surface of the separation unit (100). That is, the first coating layer (110) formed on one side of the separation unit (100) may contain ceramic powder, a water-based binder, and a first additive, and the second coating layer (120) formed on the other side of the separation unit (100) may contain ceramic powder, a water-based binder, and a second additive. The first additive may be at least one of the additives listed in the anode additive, and the second additive may be at least one of the additives listed in the cathode additive.

[0048] Step a) may include metal organic frameworks (MOFs) as the material of at least one of the first coating layer (110) and the second coating layer (120) described above. In this embodiment, by controlling the cavity structure and pore size of the metal organic framework included in either the first coating layer (110) or the second coating layer (120), the first coating layer (110) or the second coating layer (120) may be able to adsorb carbon dioxide gas or control the electric current flux. In Step a), the metal organic framework may be included in only one of the first coating layer (110) and the second coating layer (120).

[0049] Figure 2 schematically illustrates the process of performing step b).

[0050] As illustrated in FIG. 2, step b) assembles a semi-finished product by inserting a separator (100), an anode (200), and a cathode (300) into the interior of a housing (10). An anode (200) is positioned to be in contact with one side of the separator (100), and a cathode (300) is positioned to be in contact with the other side of the separator (100), so that a first coating layer containing a first additive formed on one side of the separator (100) is in contact with the anode (200), and a second coating layer (120) containing a second additive formed on the other side of the separator (100) is in contact with the cathode (300). The first additive may be at least one of the anode additives described above, and the second additive may be at least one of the cathode additives described above.

[0051] As illustrated in FIG. 2, in this embodiment, the separator (100) is wound in a zigzag pattern, the positive electrode (200) is located in a space enclosed by one side of the separator (100) wound in a zigzag pattern, and the negative electrode (300) is located in a space enclosed by the other side of the separator (100) wound in a zigzag pattern. The reason for winding a single separator (100) in a zigzag pattern in this manner is to assemble multiple positive electrodes (200) and negative electrodes (300) using a single separator (100). However, the present invention is not limited to the shape of the separator (100) as described above, and the separator may be configured in a plate or roll form, and the positive electrode and negative electrode may also be configured to correspond to the shape of the separator.

[0052] Figure 3 schematically illustrates the process of performing step c).

[0053] Step c) involves injecting an electrolyte into the interior of the housing (10) so that the first additive included in the first coating layer and the second additive included in the second coating layer dissolve in the electrolyte. Although the process of injecting the electrolyte in Step c) can be carried out in various ways, in this embodiment, as shown in FIG. 3, it can be carried out by inserting a nozzle (20) into the interior of the housing (10) and spraying the electrolyte from the nozzle (20). In Step c), the spray end of the nozzle (20) from which the electrolyte is sprayed may be adjacent to or in contact with one of the two ends of the separation part (100).

[0054] FIG. 4 schematically illustrates a cross-section of the state shown in FIG. 3 cut in a plane parallel to the ground, schematically illustrating the state in which the injection end (21) of the nozzle (20) is adjacent to one end of the separation part (100) housed inside the housing (10).

[0055] As illustrated in FIG. 4, in step c), the reason the spray end (21) of the nozzle (20) is adjacent to one end of the separation part (100) housed inside the housing (10) is to allow the electrolyte sprayed from the spray end (21) of the nozzle (20) to be delivered to the first coating layer (110) and the second coating layer (120), which are each composed of a first additive and a second additive. Through step c), the electrolyte that has penetrated into the first coating layer (110) and the second coating layer (120) from the spray end (21) of the nozzle (20) spreads over the entire first coating layer (110) and the second coating layer (120) after a certain period of time has elapsed. In this process, the electrolyte that has penetrated and distributed into the coating layer dissolves the first additive and the second additive, and the electrolyte in which the first additive and the second additive have dissolved is discharged into the housing (10). Since the interior of the housing (10) is primarily partitioned through the separation section (100), the electrolyte in which the first additive is dissolved is located on one side of the separation section (100), and the electrolyte in which the second additive is dissolved is located on the other side of the separation section (100). More specifically, the electrolyte in which the first additive is dissolved is located on the surface of the positive body (200), and the electrolyte in which the second additive is dissolved is located on the surface of the negative body (300).

[0056] c) In step, the spray end (21) of the nozzle (20) is not positioned adjacent to one end of the separation part (100) but is positioned to be in contact with each other, after which the electrolyte can be injected. Additionally, in FIG. 4, the spray end (21) of the nozzle (20) is positioned adjacent to one end of the separation part (100), but the present invention is not limited thereto. There may also be an embodiment in which the electrolyte is injected while the spray end (21) of the nozzle (20) is adjacent to or in contact with the zigzag folded end (part folded to have a curvature) of the separation part (100), and there may also be an embodiment in which the electrolyte is injected while the spray end (21) of the nozzle (20) is adjacent to or in contact with one end of the separation part (100) and the zigzag folded end. Additionally, as described above, the separation part (100) is accommodated inside the housing (10) and divides the internal space of the housing (10) into one side and the other side, so the step c) described above can be performed in the one side space and the other side space respectively, which are divided based on the separation part (100).

[0057] In step c) described above, the nozzle (20) is positioned so that the injection section (21) is adjacent to the lower side of the separation section (100) and the electrolyte is injected while the position is fixed. Since this method involves the nozzle (20) itself being submerged in the electrolyte rising from the housing (10), if the injection speed of the electrolyte is fast, the surface of the electrolyte may slosh due to the nozzle (20), causing the electrolyte to overflow to the other side of the separation section (100). To prevent this, the present invention may raise the nozzle (20) while injecting the electrolyte from the nozzle (20) so that the nozzle (20) is not submerged in the electrolyte. To this end, the present invention may include a lifting and lowering means for controlling the lifting and lowering of the nozzle (20) and a sensing means for detecting the surface of the electrolyte injected from the nozzle (20).

[0058] Step d) involves initially charging and discharging the positive body (200) and the negative body (300) to form a film on the surface of the positive body (200) and the negative body (300). Step d) is a step generally referred to as a formation process, and through step d), a film is formed on the surface of the positive body (200) with an electrolyte containing a first additive, and a film is formed on the surface of the negative body (300) with an electrolyte containing a second additive. The additives included in the films formed on the surfaces of the positive body (200) and the negative body (300) through step d) act individually on the positive body (200) and the negative body (300), thereby affecting each electrode. That is, the operator performing the manufacturing method according to the present embodiment can determine the first additive and the second additive in advance to cause individual effects on the positive body (200) and the negative body (300), respectively.

[0059] As described above, step d) can be performed after a predetermined amount of time has elapsed following the performance of step c), in order to secure sufficient time for the additive contained throughout the coating layer to dissolve in the electrolyte injected through one side of the separation unit (100). However, since the separation unit (100) contained within the housing (10) does not perfectly seal and partition the space inside the housing (10), if too much time elapses after the performance of step c), the electrolytes containing the first additive and the second additive located on each side of the separation unit (100) may be mixed with each other, and may affect the electrode body with an effect other than the effect desired by the operator. In order to prevent this, the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention may limit the predetermined time between the execution of step c) and step d) to within a certain time, and the limited reference time may be calculated through repeated experiments in a specific environment, and as an example of the predetermined time between the execution of step c) and step d), it may be 12 to 24 hours.

[0060] [2nd Example]

[0061] A method for manufacturing a lithium secondary battery according to the second embodiment of the present invention will be described in detail below with reference to the attached drawings.

[0062] The part where the method for manufacturing a lithium secondary battery according to the second embodiment of the present invention and the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention described above differ is step a), and since the other steps are identical between the first and second embodiments, only step a), which is the part that differs, will be explained.

[0063] In this embodiment, step a) involves forming an internal coating layer on the surface of the separation part using a coating material, and forming a first coating layer and a second coating layer on the surface of the internal coating layer using a first additive and a second additive, respectively.

[0064] FIG. 5 illustrates a separation unit (100) after step a) of the method for manufacturing a lithium secondary battery according to the second embodiment of the present invention has been performed.

[0065] As illustrated in FIG. 5, after step a) is performed in the method for manufacturing a lithium secondary battery according to the second embodiment of the present invention, an internal coating layer (130) is formed on each of the one side and the other side of the separator (100). The internal coating layer (130) is a layer formed solely from the coating raw material that forms the first coating layer or the second coating layer in the method for manufacturing a lithium secondary battery according to the first embodiment of the present invention described above. That is, the internal coating layer (130) can be formed from a porous material, and specifically, it can be formed from a material including a porous ceramic. A first coating layer (110) and a second coating layer (120) are formed on each of the one side and the other side of the internal coating layer (130), wherein the first coating layer (110) is formed from a first additive and the second coating layer (120) is formed from a second additive. When the separation unit (100) has a structure as shown in FIG. 5, in step c) to be performed later, the spraying end (21) of the nozzle (20) is positioned adjacent to the inner coating layer (130), and then an electrolyte is injected from the spraying end (21). The electrolyte can spread along the inner coating layer (130) and leak out onto the surface of the inner coating layer (130), thereby dissolving the first coating layer (110) and the second coating layer (120), respectively, and through step d), a film containing the first additive and the second additive can be formed on the anode (200) and the cathode (300), respectively, in the same manner as in the first embodiment.

[0067] The technical concept of the present invention should not be interpreted as being limited to the above-described embodiments. Not only is the scope of application diverse, but various modifications are possible at the level of a person skilled in the art without departing from the essence of the invention claimed in the claims. Accordingly, such improvements and modifications fall within the scope of protection of the present invention insofar as they are obvious to a person skilled in the art. Explanation of the symbols

[0068] 10 : Housing 20: Nozzle 21 : Partition 100 : Separator 110 : First coating layer 120 : Second coating layer 130: Internal coating layer 200 : Anode 300 : Cathode

Claims

Claim 1 a) A first coating layer comprising a first additive configured to form a film advantageous for anode reaction characteristics on the surface of an anode body on one side of a membrane-shaped separator, and a coating layer configured to form a film advantageous for cathodic reaction characteristics on the surface of a cathodic body on the other side of the separator. a) a step of manufacturing a separator by forming a second coating layer containing a second additive; b) a step of inserting the separator, an anode, and a cathode into a housing such that the anode is in contact with one side of the separator and the cathode is in contact with the other side of the separator; c) a step of injecting an electrolyte into the housing so that the first additive and the second additive dissolve in the electrolyte and are delivered to the anode and the cathode, respectively. and d) a step of selectively forming a film corresponding to each electrode surface on the surface of the positive body and the surface of the negative body; wherein the film formed on the surface of the positive body is formed with an electrolyte containing the first additive, and the film formed on the surface of the negative body is formed with an electrolyte containing the second additive, and the first additive and the second additive are configured to act individually on the positive body and the negative body to exert different effects on each electrode body, and the interior of the housing is partitioned by the separator, and in step c), the electrolyte in which the first additive is dissolved is located on one side of the separator, and the electrolyte in which the second additive is dissolved is located on the other side of the separator. A method for manufacturing a lithium secondary battery. Claim 2 In claim 1, the first additive and the second additive are different methods for manufacturing a lithium secondary battery. Claim 3 A method for manufacturing a lithium secondary battery according to claim 1, wherein step c) involves inserting a nozzle into the housing and then injecting an electrolyte into the housing using the nozzle. Claim 4 In paragraph 3, the above step c) is a method for manufacturing a lithium secondary battery in which an electrolyte is injected by positioning the injection end of the nozzle to be in contact with or adjacent to the first coating layer and the second coating layer. Claim 5 In paragraph 3, the above step c) is a method for manufacturing a lithium secondary battery in which the injection end of the nozzle is positioned to be in contact with or adjacent to the bottom of the first coating layer and the second coating layer, and then the electrolyte is injected while moving the nozzle upward. Claim 6 A method for manufacturing a lithium secondary battery according to claim 1, wherein step a) comprises forming a first coating layer with a mixture comprising a porous material and a first additive, and forming a second coating layer comprising a porous material and a second additive. Claim 7 A method for manufacturing a lithium secondary battery according to claim 1, wherein step a) involves forming an internal coating layer on each side of the separator using a porous material, and forming the first coating layer and the second coating layer on the surface of the internal coating layer. Claim 8 A method for manufacturing a lithium secondary battery according to claim 1, wherein the first additive comprises at least one of Lithium difluoro bis-oxalato phosphate and LiPO2F2. Claim 9 A method for manufacturing a lithium secondary battery according to claim 1, wherein the second additive comprises at least one of VC, VEC, FEC, PRS, LiBOB, PS, ESA, LiTFSi, LiBF4, and LiFSI. Claim 10 A method for manufacturing a lithium secondary battery according to claim 6, wherein the mixture containing the first additive or the mixture containing the second additive comprises metal organic frameworks (MOFs). Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 A lithium secondary battery comprising: a separator having a membrane shape, a first coating layer formed on one side of the separator, and a second coating layer formed on the other side of the separator; an anode disposed to be in contact with the first coating layer; a cathode disposed to be in contact with the second coating layer; a housing accommodating the separator, the anode, and the cathode; and an electrolyte injected into the housing, wherein the first coating layer comprises a first additive configured to form a film advantageous for anode reaction characteristics on the surface of the anode, and the second coating layer comprises a second additive configured to form a film advantageous for cathode reaction characteristics on the surface of the cathode, and wherein the first additive and the second additive are configured to act individually on the anode and the cathode to exert different effects on each electrode, and the interior of the housing is partitioned by the separator, wherein an electrolyte in which the first additive is dissolved is located on one side of the separator, and an electrolyte in which the second additive is dissolved is located on the other side of the separator.

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