Dry electrode and manufacturing method thereof

Abstract

A method of manufacturing a dry electrode includes forming a protective layer on a surface of an electrode active material, and mixing the electrode active material, a conductive material, and a binder.

Description

Technical Field

[0001] The present disclosure relates to a dry electrode for a battery and a method for manufacturing the dry electrode. Background Art

[0002] In recent years, the application of rechargeable secondary batteries is expanding in various fields from small electronic devices to large energy storage systems. In particular, due to the rapid growth of the electric vehicle market, research and development of secondary batteries is being actively carried out.

[0003] Electrodes for secondary batteries are usually manufactured by a wet process. In the wet process, a slurry is produced by dissolving the electrode active material, binder, and conductive material contained in the electrode with a solvent. However, in recent years, a dry process has received great attention because, compared with a wet process, the dry process can increase the energy density of the battery without using a solvent required by a wet process.

[0004] In the dry process of the electrode, the dry electrode film is formed by mixing the electrode active material, the conductive material and the binder without using a solvent to form a mixture, and then forming a film by a pressing or calendaring method. Then, the electrode can be manufactured by bonding the formed dry electrode film to a current collector.

[0005] Compared with the wet electrode manufacturing process, the dry electrode manufacturing process can reduce the manufacturing time and cost because it does not use solvents and can control the film thickness, thereby obtaining a dry electrode film with high energy density.

[0006] However, since no solvent is used in the dry process, a binder different from the binder used in the wet process is required, which can connect the electrode materials. Summary of the invention

[0007] The present disclosure is directed to solving the above problems and provides an electrochemically stable dry electrode and a method for manufacturing the same.

[0008] The objects of the present disclosure are not limited to the above objects, and a person skilled in the art to which the present disclosure belongs should be able to clearly understand other objects not mentioned from the following description.

[0009] In order to achieve the purposes of the present disclosure described below and perform the characteristic functions of the present disclosure, the features of the present disclosure are as follows.

[0010] According to one embodiment of the present disclosure, a method of manufacturing a dry electrode includes forming a protective layer on a surface of an electrode active material, and mixing the electrode active material on which the protective layer is formed, a conductive material, and a binder.

[0011] According to another embodiment of the present disclosure, a dry electrode mix includes an electrode active material having a protective layer formed on a surface thereof, a binder, and a conductive material.

[0012] According to the present disclosure, an electrochemically stable dry electrode and a method for manufacturing the same are provided.

[0013] The effects of the present disclosure are not limited to the above-mentioned effects, and a person of ordinary skill in the art should be able to clearly understand other effects not mentioned from the following description.

[0014] It should be understood that the terms "vehicle," "vehicle-like," or other similar terms as used herein generally include motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various boats and ships, aircraft, etc., and include hybrid cars, electric cars, plug-in hybrid cars, hydrogen-powered cars, and other alternative fuel cars (e.g., fuels derived from sources other than petroleum). As used herein, a hybrid car is a car that has two or more sources of power, for example, a car that is powered by both gasoline and electricity.

[0015] The above and other features of the present disclosure are discussed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above-mentioned features and other features of the present disclosure will now be described in detail with reference to some examples of the present disclosure shown in the accompanying drawings, which are provided for illustration only and thus do not limit the present disclosure, wherein:

[0017] Figure 1A and 1B is a scanning electron microscope (SEM) image of the dry-process negative electrode film;

[0018] Figure 1C is a schematic diagram showing a dry-process negative electrode membrane;

[0019] Figure 2 is a diagram showing the change in capacity of a dry-process negative electrode film during charge and discharge cycles;

[0020] Figure 3 is a schematic diagram showing a dry-process negative electrode membrane according to the present disclosure;

[0021] Figure 4 is a view showing a protective layer forming apparatus for manufacturing a dry-process negative electrode film according to an embodiment of the present disclosure;

[0022] Figure 5 is a view showing a manufacturing flow chart of a dry-process negative electrode film according to an embodiment of the present disclosure;

[0023] Figure 6 It is shown Figure 1C A magnified view of the middle area V1;

[0024] Fig. 7A and Figure 7B is a view showing a transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS) image of a comparative example of a dry-process negative electrode film according to the present disclosure;

[0025] Figure 7C It is shown Figure 7B A view of the surface scan (mapping) image of each element in;

[0026] Fig. 8A and Figure 8B is a view showing a TEM-EDS image of a dry-process negative electrode film according to the present disclosure;

[0027] Figure 8C It is shown Figure 8B a view of a face scan image of each element in the image; and

[0028] Fig. 9 is a view showing the presence of a peak of decomposition of polytetrafluoroethylene (PTFE) of a dry-process negative electrode membrane according to the present disclosure.

[0029] It should be understood that the drawings are not necessarily drawn to scale and thus represent only a slightly simplified representation of various features illustrating the basic principles of the present disclosure. The specific design features of the present disclosure disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, should be determined in part by the specific intended application and use environment.

[0030] In the drawings, like reference numerals refer to the same or equivalent parts of the present disclosure throughout the several figures of the drawing. DETAILED DESCRIPTION

[0031] The specific structure or function description is presented in the embodiments of the present disclosure, which is only for the purpose of illustrating the embodiments according to the concepts of the present disclosure, and the embodiments according to the concepts of the present disclosure can be implemented in various forms. In addition, the present disclosure should not be interpreted as being limited to the embodiments described in the present disclosure, and it should be understood that the present disclosure includes all modifications, equivalents or substitutes within the spirit and technical scope of the present disclosure.

[0032] Meanwhile, in the present disclosure, terms such as first and / or second may be used to describe various components, but the components are not limited by the terms. Without departing from the scope of the present disclosure according to the concepts of the present disclosure, the above terms are only used, for example, to distinguish one component from another component. A first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

[0033] When a certain component is described as being “connected” or “coupled” to another component, it should be understood that the certain component may be directly connected or coupled to the other component, or the other component may be arranged therebetween. On the other hand, when a certain component is described as being “directly connected” or “directly coupled” to another component, it should be understood that the other component is not arranged therebetween. Other expressions describing the relationship between components, such as “between” and “directly between” or “adjacent to” and “directly adjacent to”, should be understood in the same manner.

[0034] In the present disclosure, the same reference numerals represent the same or equivalent parts. At the same time, the terms used in the present disclosure are used to describe the embodiments and are not used to limit the present disclosure. In the present disclosure, unless otherwise specified in the expression, the singular form also includes the plural form. As used herein, "include" and / or "comprise" means that the parts, steps, operations and / or elements do not exclude the existence or addition of one or more other parts, steps, operations and / or elements.

[0035] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings.

[0036] Dry electrodes can be made from a dry electrode mixture and a current collector without the use of a solvent. The dry electrode mixture is a mixture of electrode active materials, conductive materials, and a binder. The dry electrode mixture can be made into a dry electrode film through a series of film-forming processes that apply heat and pressure. The dry electrode film can be made into a dry electrode by laminating it with a current collector.

[0037] The dry electrode can be a positive electrode or a negative electrode. In some embodiments, when the positive electrode is manufactured, the electrode active material includes a positive electrode active material. As a non-limiting example, the positive electrode active material can be a nickel manganese cobalt (NMC) series, lithium iron phosphate (LFP), lithium cobalt (LCO) or sulfur. For example, the positive electrode active material can include lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ) layered compound, a compound substituted by one or more transition metals; the chemical formula is Li 1+x Mn 2-x O 4 (Here, x ranges from 0 to 0.33), such as LiMnO 3 、LiMn 2 O 3 and LiMnO 2 Lithium manganese oxide; lithium copper oxide (Li 2 CuO 2 ); such as LiV 3 O 8 、LiFe 3 O 4, V 2 O 5 and Cu 2 V 2 O 7 vanadium oxides; expressed as the chemical formula LiNi 1-x M x O 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and the range of x is from 0.01 to 0.3) nickel-site lithium nickel oxides; expressed as the chemical formula LiMn 2-x M x O 2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and the range of x is from 0.01 to 0.1) or Li 2 Mn 3 MO 8 (where M = Fe, Co, Ni, Cu or Zn) lithium manganese composite oxides; LiMn in which part of Li in the chemical formula is replaced by alkaline earth metal ions 2 O 4 ; lithium metal phosphide LiMPO 4 (where M = Fe, CO, Ni or Mn), disulfide; Fe 2 (MoO 4 ) 3 etc. However, the positive electrode active material is not limited to the above examples.

[0038] In some embodiments, when manufacturing the negative electrode, the electrode active material includes a negative electrode active material. As a non-limiting example, the negative electrode active material is a graphite series and may include silicon. For example, the negative electrode active material may include carbons such as non-graphitized carbon and graphitized carbon; such as Li x Fe 2 O 3 (0 ≤ x ≤ 1), Li x WO 2 (0 ≤ x ≤ 1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge, Me': Al, B, P, Si, Group 1, Group 2 and Group 3 elements in the periodic table, halogens, 0 < x ≤ 1, 1 ≤ y ≤ 3, 1 ≤ z ≤ 8) metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; silicon-based oxides such as SiO, SiO / C and SiO 2 ; silicon-based oxides such as SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 、GeO、GeO 2 、Bi 2 O 3 、Bi 2 O 4 and Bi 2 O 5 Metal oxides; conductive polymers such as polyacetylene; Li-Co-Ni based materials, etc.

[0039] The conductive material may include a carbon-based material. For example, the conductive material may include various carbon-based materials such as Super P, Ketjen Black, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). In addition, when manufacturing a dry electrode for a solid-state battery, the dry electrode mixture may also include a polyethylene oxide (PEO)-based polymer, an oxide, and a sulfide-based solid electrolyte.

[0040] The binder may be a material having a CF bond, a mixture of carbon and fluorine, such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). Alternatively, the binder may include styrene butadiene rubber (SBR) / carboxymethyl cellulose (CMC) or polyacrylonitrile (PAN).

[0041] Generally, the negative electrode manufactured by the wet process includes a negative electrode active material such as graphite, a conductive material and a binder. The negative electrode can be manufactured by dissolving and dispersing the negative electrode active material, the conductive material and the binder in an aqueous solvent, and then coating the mixture on a current collector such as copper foil. In the wet process, SBR and CMC are mainly used as binders.

[0042] Figure 1A is a view showing a scanning electron microscope (SEM) image of a dry-process negative electrode film F, Figure 1B It is shown Figure 1A A partial magnified view of the image in Figure 1C Schematic diagram showing a dry-process negative electrode film F. Figure 1A , 1B 1C, the dry-process negative electrode includes a negative electrode active material 10, a conductive material 20, and a binder 30. In the illustrated example, the negative electrode active material 10 and the conductive material 20 are uniformly mixed, and the binder 30 such as PTFE is fiberized into a skein shape. Therefore, the dry-process negative electrode can maintain the form of a free-standing film.

[0043] As mentioned above, the dry negative electrode can use the same negative electrode active material and conductive material as the wet negative electrode. However, because no solvent is used in the dry process, the binder in the wet process cannot be used. On the contrary, in the dry process, a binder that connects the electrode material in a network form by fibrosis should be used. For example, PTFE can be used as a binder for the dry electrode. By mixing the electrode materials and pressing the mixture by a roller press, an unsupported dry negative electrode film can be obtained with PTFE. As shown in the example, it can be seen that PTFE is fibrosis to keep the electrode material in a film form.

[0044] PTFE is a binder that can be used to make dry electrodes. When PTFE is used for the negative electrode, an irreversible chemical reaction as shown in Chemical Formula 1 occurs at the reduction potential of the electrode.

[0045] [Chemical formula 1]

[0046] (C 2 F 4 ) n +2n Li→nC(amorphous)+2nLiF

[0047] Here, C 2 F 4 is the chemical formula of PTFE, n is an integer, C is carbon, Li is lithium, and F is fluorine.

[0048] like Figure 2 As shown, when the charge-discharge cycle is repeated, the decomposed PTFE may not be able to function as a binder to hold the electrode active material due to volume changes during charge-discharge. A continuous decrease in capacity is observed, which has a negative impact on the deterioration of battery characteristics.

[0049] Therefore, the present disclosure aims to provide an electrochemically stable dry-process negative electrode by forming a protective layer on the surface of a negative electrode active material.

[0050] According to the present disclosure, Figure 3 As shown, the dry process negative electrode includes a protective layer 40. The protective layer 40 may have conductivity. The protective layer 40 may be formed particularly on the surface of the negative electrode active material 10 of the dry process negative electrode. In one embodiment, the protective layer 40 formed on the negative electrode active material 10 may be preformed before manufacturing the dry process electrode mixture.

[0051] like Figure 4 As shown, according to one embodiment of the present disclosure, a protective layer forming apparatus 100 for forming a protective layer 40 on a negative electrode active material 10 may be prepared.

[0052] The protective layer forming device 100 includes a container 110. The material of the container 110 is not limited. As a non-limiting example, the container 110 can be formed of stainless steel, acrylic, etc. In one embodiment, the inner surface of the container 110 is made of a material that is stable to the reduction reaction. For example, the inner surface of the container 110 can be made of copper, nickel, gold, or an alloy of these materials for the current collector of the negative electrode. In other words, the outer surface of the container 110 can be made of any material, but the inner surface of the container 110, that is, the surface in contact with the electrolyte, is made of a material that is stable to the reduction reaction.

[0053] The container 110 is filled with an electrolyte 120. The electrolyte 120 may be an electrolyte having the same composition as that used in the battery. The reason is to make the solid electrolyte interface (SEI) layer formed in the battery system the same or similar. The SEI layer is a thin film that is formed on the surface of the negative electrode when the manufactured battery is charged for the first time. In some examples, the electrolyte used in the protective layer forming apparatus 100, i.e., the electrolyte participating in the electrochemical reaction, can be reused in the next process.

[0054] The electrolyte 120 in the container 110 includes an additive. Here, the electrolyte 120 may be the same as a known electrolyte commonly used in a battery. The electrolyte 120 may be a single-component solvent electrolyte or a multi-component solvent electrolyte. For example, a lithium salt LiPF 6 It can be dissolved in a carbonate-based single-component solvent, or a two-component solvent EC / DEC (1:1 v / v%) and EC / DMC (1:1 v / v%), or a three-component solvent EC / DMC / DEC (1:1:1 v / v / v%). Lithium salts can be used differently depending on the application, such as LiBF 4 、LiASF 6 、LiClO 4 、LiCF 3 SO 3 and LiTFSI, and may be used alone or in combination. Depending on the system, the concentration of the lithium salt may also vary, such as 0.01M to 10M. The additive may include fluoroethylene carbonate (FEC), vinylene carbonate (VC), or a combination thereof. Depending on the amount of electrolyte 120 in container 110, the amount of FEC added may be within 20wt%. When the amount of FEC added exceeds 20wt%, the effect of protective layer 40 is reduced. According to the present disclosure, by using an additive to form a protective layer 40 before the SEI layer is formed when the battery is first charged, the decomposition reaction of PTFE can be prevented.

[0055] The negative electrode active material 10 is contained in a container 110 filled with an electrolyte 120. The negative electrode active material 10 is a material for a dry process electrode.

[0056] The protective layer forming apparatus 100 further includes a working electrode 130 and a counter electrode / reference electrode 140. In one embodiment, as the working electrode 130, copper, nickel, gold, or an alloy of these materials, which is a material forming the inner surface of the container 110, can be used. The container 110 itself can be used as the working electrode 130. The counter electrode / reference electrode 140 can be suspended on the container 110 so that at least a portion of it is immersed in the electrolyte 120 in the container 110. For example, the counter electrode / reference electrode 140 can be a lithium metal plate.

[0057] The working electrode 130 and the counter electrode / reference electrode 140 are connected to the potentiostat 160 through conductors 150a and 150b, respectively. The negative active material 10 in the container 110 can be charged and discharged through the working electrode 130, the counter electrode / reference electrode 140, and the potentiostat 160.

[0058] refer to Figure 5 According to some embodiments of the present disclosure, the protection layer 40 may be formed on the negative electrode active material 10 by the protection layer forming apparatus 100 .

[0059] At S500, the negative electrode active material 10 is contained in a container 110 filled with a prepared electrolyte 120 including an additive. At S510, a current is applied to the counter electrode / reference electrode 140 and the working electrode 130 connected to the potentiostat 160 to produce an electrochemical reaction. In other words, the negative electrode active material 10 in the container 110 can be charged and discharged once. Taking graphite as an example, graphene has a layered structure of graphite. Lithium ions are inserted between the graphene layers, and the lithium ions are charged or intercalated. Therefore, when the electrolyte and the additive decompose, an SEI layer can be formed. After the SEI layer is formed, the lithium ions inserted between the graphene layers are removed by discharge or deintercalation. Therefore, graphite induced to form a protective layer 40 can be obtained.

[0060] The electrochemical reaction conditions, i.e., the charge and discharge conditions of the negative electrode active material 10, can be determined based on the mass (e.g., in grams) and theoretical capacity (e.g., in milliampere hours per gram (mAh / g)) of the negative electrode active material 10 put into the container 110. The capacity of the negative electrode active material 10 put in can be determined by multiplying the mass of the negative electrode active material 10 put in by the theoretical capacity. For example, the theoretical capacity of the negative electrode active material graphite put in is 372 mAh / g. When 1 g is input, the capacity is 372 mAh.

[0061] The C rate, which represents the charge and discharge speed, can be applied as a value between 0.05C (capacity) and 1C. Within this range, the negative electrode active material 10 can maintain a stable protective layer. The C rate is expressed as the inverse of the application time. For example, 0.1C means 10 hours, and 1C means 1 hour. In the above example, when the C rate is selected as 1C, this means applying a constant current of 372mA for 1 hour. When the C rate is selected as 0.1C, this means applying a constant current of 37.2mA for 10 hours. At the same time, the voltage is terminated in the range of 0.01V to 0.05V during charging and in the range of 1 to 2.5V during discharging, and the electrochemical reaction is completed.

[0062] After charging and discharging are completed, at S520, the negative electrode active material 10 is rinsed. Rinsing is performed to remove lithium salts, electrolytes, contaminants, etc. that may remain on the surface of the negative electrode active material 10. The negative electrode active material 10 can be rinsed using a low viscosity solvent in the electrolyte 120 solvent. For example, when the electrolyte 120 is a two-component solvent electrolyte (the solvent is ethylene carbonate (EC) / diethyl carbonate (DEC)), the negative electrode active material is rinsed with DEC. This is to minimize the impact of the electrolyte. Due to the relationship between the dielectric constant and the viscosity, the solvent of the electrolyte is generally formed by a mixture of cyclic carbonates and linear carbonates. In order to rinse the negative electrode active material, a low viscosity linear carbonate can be used, which can minimize the impact on the protective layer 40 that has been formed. In some examples, an ether-based solvent can be used to rinse a battery system using an ether-based electrolyte. Flushing can be configured so that the electrolyte flows to the negative electrode active material without applying external energy.

[0063] After the rinsing process, at S530, the negative electrode active material 10 is dried. The drying temperature may be room temperature. In some examples, the maximum temperature at which the drying may be performed may be lower than about 60 degrees Celsius. This is because the protective layer 40 may be affected when the temperature exceeds about 60 degrees Celsius. In some examples, the drying may be performed in a dry room atmosphere or an argon atmosphere, and may be performed using a vacuum.

[0064] Therefore, the protective layer 40 may be formed on the negative electrode active material 10. The negative electrode active material 10 having the protective layer 40 formed on the surface thereof may be used to manufacture a dry process electrode.

[0065] The dry negative electrode mixture can be made into a dry negative electrode film F (S540) by a series of film-forming processes that apply heat and pressure. The dry negative electrode mixture is obtained by mixing the negative electrode active material 10, the conductive material 20 and the binder 30 on which the protective layer 40 is formed. The dry negative electrode mixture can be mixed by a mixer at a preset time and speed. As a non-limiting example, the dry electrode mixture can be prepared by using a rotating high shear mixer or a fluid mixer using air. The preset time and speed can be adjusted by changing the rotation speed and working time of the mixer.

[0066] At S550, the prepared dry negative electrode mixture is transported to a film forming process and formed into a film. One or more roller presses may be used in the film forming process. For example, the mixed dry negative electrode mixture may be initially pressed by a primary roller press and formed into a film. Subsequently, the film-forming dry negative electrode mixture may be pressed again by a secondary roller press, wherein the thickness thereof is adjusted by pressing. Thus, the dry negative electrode mixture may be formed into a dry negative electrode film F.

[0067] In S560 , the dry-process negative electrode film F may be completed as a dry-process negative electrode through a lamination process with a current collector.

[0068] refer to Figure 6 As described above, the dry negative electrode film F includes a negative electrode active material 10, a conductive material 20 and a binder 30. The negative electrode active material 10 and the conductive material 20 are uniformly mixed. PTFE as a binder is fiberized into a twisted shape to maintain the form of an unsupported film.

[0069] As described above, in the dry-process negative electrode film including PTFE, due to the decomposition of PTFE, the characteristics as a binder are lost. The negative electrode active material 10 is separated from the current collector, resulting in a decrease in electrode capacity. When describing the phenomenon occurring in the negative electrode during this process, it can be seen that the binder (position P1) in contact with the surface of the negative electrode active material 10 is decomposed, but the binder (position P2) not in contact with the negative electrode active material 10 does not participate in the decomposition reaction.

[0070] Based on this observation, according to the present disclosure, the surface of the negative electrode active material is protected by a protective layer 40 having conductivity. As another method, a fine structure can be grown on the negative electrode active material by coating a conductive polymer having an ethylene oxide unit on the negative electrode active material, or by a process such as atomic layer deposition (ALD) or chemical vapor deposition (CVD). However, in this case, there is a difficulty in that the coating is thick, which leads to a loss of electrode energy density and a high process cost.

[0071] Without using this process, according to the present disclosure, the SEI layer formation mechanism of the battery can be used to solve the above-mentioned problems and prevent the electrode capacity from decreasing.

[0072] like Fig. 7A , 7B 8A and 8B, it can be seen that the protective layer 40 is formed on the negative electrode active material 10 according to the present disclosure. Fig. 7A is a view showing a transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS) image of a negative electrode active material which is subjected to washing and drying without applying an electric current to the negative electrode active material put into the container 110 through the regulator 160 in the protective layer forming apparatus 100. Fig. 8A is a view showing a TEM-EDS image of the negative electrode active material 10. Fig. 7A The same conditions are applied by charging and discharging current. Fig. 7A In the figure, no structure is visible on the surface of the negative electrode active material 10 (see Figure 7B and 7C ), and Fig. 8A In the graphite structure of the negative electrode active material 10, an amorphous layer can be seen (see Figure 8B ). In addition, through face scanning (mapping), we can also see that it contains C, F and O (see Figure 8C This is the LiF-containing layer (containing LiF and -CHF-OCO 2 -compounds, etc.), which are formed by FEC (which is an additive). It can be seen that the thickness of the formed protection layer 40 is in the range of several nanometers to tens of nanometers.

[0073] Fig. 9 : is a view showing data about a dry-process negative electrode film made of graphite including a protective layer 40 according to the present disclosure. In the experiment related to this data, the negative electrode active material 10 is graphite, the binder 30 is PTFE, and the weight ratio of the negative electrode active material 10 to the binder 30 is 98.5:1.5. After the dry-process negative electrode is manufactured, the manufactured dry-process negative electrode film is laminated on a copper foil. Then, an electrode punched into a circle with a diameter of 10 mm is used. By using the dry-process negative electrode film as the working electrode, lithium metal is used as the counter electrode / reference electrode, and 1 molar concentration (M) of LiPF 6 Half-cells were fabricated in EC / DEC (EC:DEC volume ratio of 1:1) as electrolyte and 10 wt% FEC as additive. The charge and discharge conditions of the half-cells were: discharge at 0.1C in constant current (CC) / constant voltage (CV) mode and terminated at 0.01V / 0.05C; and charge at 0.1C in CC mode and terminated at 1.5V.

[0074] At the initial 0.1C, it can be seen that the PTFE decomposition reaction peak of the first cycle in which lithium ions are inserted into graphite. The dotted line graph represents a dry-process negative electrode membrane without forming a protective layer 40, and a peak due to PTFE decomposition can be seen. The PTFE decomposition peak is observed between 0.5 and 0.1V. The solid line graph relates to a dry-process negative electrode membrane according to the present disclosure, on which a protective layer 40 is formed, and it can be seen that no peak due to PTFE decomposition is observed.

[0075] According to the present disclosure, when PTFE is used as a binder, side reactions may be controlled by inducing formation of a protective layer on a negative electrode active material.

[0076] The present disclosure is not limited to the above-mentioned embodiments and drawings, and a person skilled in the art in the technical field to which the present disclosure belongs may make various substitutions, modifications and changes without departing from the technical spirit and scope of the present disclosure.

Claims

1. A method for manufacturing a dry electrode, the method comprising the following steps: forming a protective layer on the surface of the electrode active material; as well as The electrode active material on which the protective layer is formed, a conductive material, and a binder are mixed.

2. The method according to claim 1, wherein: The steps of forming the protective layer include: disposing an electrode active material in an electrolyte contained in a container, wherein the electrolyte includes an additive; and The electrode active material is charged and discharged.

3. The method according to claim 2, wherein: The steps of charging and discharging the electrode active material are performed by applying a voltage through a working electrode and a counter / reference electrode operably associated with the container.

4. The method according to claim 2, further comprising the steps of: The electrode active material is rinsed after charging and discharging the electrode active material.

5. The method according to claim 4, wherein: The electrolyte is a single-component solvent electrolyte or a multi-component solvent electrolyte, and in the case of a multi-component solvent electrolyte, the washing is performed with a solvent with the lowest viscosity among the solvents of the multi-component solvent electrolyte.

6. The method according to claim 4, further comprising the steps of: The electrode active material is dried after rinsing.

7. The method according to claim 2, wherein: The additive is fluoroethylene carbonate FEC, vinylene carbonate VC, or a combination thereof.

8. The method according to claim 2, wherein: The conditions for charging and discharging the electrode active material are determined according to the mass and theoretical capacity of the electrode active material.

9. The method according to claim 1, further comprising the step of forming a film of a dry electrode mixture in which an electrode active material having the protective layer formed thereon, a conductive material, and a binder are mixed.

10. The method according to claim 1, wherein: The electrode active material is a negative electrode active material, and the binder is made of polytetrafluoroethylene (PTFE).

11. A dry electrode mixture comprising: An electrode active material, wherein a protective layer is formed on the surface of the electrode active material; Binder; and Conductive material.

12. The dry electrode mixture according to claim 11, wherein: The protective layer is formed by a protective layer forming device, and the protective layer forming device includes: a container having a working electrode and configured to receive the electrode active material; an electrolyte contained in the container and having an additive; a counter electrode / reference electrode at least partially immersed in the electrolyte; and A potentiostat is connected to the working electrode and the counter / reference electrode and is configured to apply a voltage to the working electrode and the counter / reference electrode.

13. The dry electrode mixture according to claim 12, wherein: The additive is fluoroethylene carbonate FEC, vinylene carbonate VC, or a combination thereof.

14. The dry electrode mixture according to claim 12, wherein: The working electrode is made of copper, nickel, gold, or alloys thereof, and the counter electrode / reference electrode is made of lithium metal.

15. The dry electrode mixture according to claim 11, wherein: The electrode active material is a negative electrode active material, and the binder is made of polytetrafluoroethylene (PTFE).

16. The dry electrode mixture according to claim 11, wherein: The protective layer is formed before manufacturing the dry electrode mix prepared by mixing the electrode active material, the binder, and the conductive material.

17. A protective layer forming device, comprising: a container having a working electrode and configured to receive an electrode active material of a dry electrode mixture; an electrolyte contained in the container and having an additive; a counter electrode / reference electrode at least partially immersed in the electrolyte; as well as A potentiostat is connected to the working electrode and the counter / reference electrode and is configured to apply a voltage to the working electrode and the counter / reference electrode.

18. The protective layer forming apparatus according to claim 17, wherein: The additive is fluoroethylene carbonate FEC, vinylene carbonate VC, or a combination thereof.

19. The protective layer forming apparatus according to claim 17, wherein: The working electrode is made of copper, nickel, gold, or alloys thereof, and the counter electrode / reference electrode is made of lithium metal.

20. The protective layer forming apparatus according to claim 17, wherein: The electrode active material is a negative electrode active material.

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