Method for manufacturing lithium secondary battery dry electrode including thermoplastic binder, and lithium secondary battery including same

Abstract

The present invention relates to a positive electrode for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including same. The positive electrode for a lithium secondary battery contains a fluorine-free compound as a binder and is thus eco-friendly, and has the advantage of superior adhesive strength compared to a wet process even when manufactured using a dry process. The present invention relates to a negative electrode for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including same. The negative electrode for a lithium secondary battery contains a fluorine-free compound as a binder and is thus eco-friendly, and has the advantage of superior adhesive strength compared to a wet process even when manufactured using a dry process.

Description

Method for manufacturing a lithium secondary battery dry electrode including a thermoplastic binder, and a lithium secondary battery including the same

[0001] The present invention relates to a positive electrode material for a lithium secondary battery comprising a fluorine-free compound as a binder, a positive electrode for a lithium secondary battery comprising the same, and a method for manufacturing the same. The present invention also relates to a negative electrode for a lithium secondary battery comprising a fluorine-free compound as a binder, a method for manufacturing the same, and a lithium secondary battery comprising the same.

[0002] This study was supported by the National Research Council for Science and Technology (NRST) Creative Convergence Research Project (CAP21044-000) funded by the government (Ministry of Science and ICT) in 2024.

[0003] This research was supported by the National Research Council of Science & Technology (NST) grant by the Korea government (MSIT) (No. CAP21044-000).

[0004]

[0005] The positive and negative electrodes of lithium-ion secondary batteries are manufactured by wet coating and drying an electrode composition including a positive electrode active material (or negative electrode active material), a binder, and a conductive agent on a current collector. Typically, the positive and negative electrodes can be manufactured by coating a slurry containing polyvinylidene difluoride (PVdF) as a binder on a current collector made of an aluminum film, and drying the slurry. PVdF is the most widely used binder for positive electrode active materials (or negative electrode active materials), but it can swell due to the electrolyte in a high temperature and high voltage environment, weakening the bonding force with the positive electrode active material or negative electrode active material, reducing durability, and increasing electrode resistance. In addition, due to the low ionic conductivity of PVdF, there is a problem that it must be additionally mixed with a material having high ionic conductivity, such as a polymer electrolyte.

[0006] In addition, in the process of manufacturing a conventional positive electrode (or negative electrode), a solvent is used to disperse or dissolve a positive electrode active material (or negative electrode active material), a conductive agent, and a binder to manufacture a positive electrode slurry (or negative electrode slurry), and the positive electrode slurry (or negative electrode slurry) is coated on a current collector, dried, and then rolled at high pressure to manufacture a positive electrode (or negative electrode). Therefore, when considering viscosity, etc. suitable for the process of manufacturing a positive electrode (or negative electrode), there is a problem in that there is an upper limit to the content of binder and conductive agent that can be introduced into the solvent and an upper limit to the solid content of the manufactured positive electrode slurry (or negative electrode slurry).

[0007] In addition, when manufacturing a positive electrode (or negative electrode) using a positive electrode slurry (or negative electrode slurry) that uses a solvent, defects such as pinholes or cracks may be induced as the solvent contained in the electrode mixture evaporates during the drying process. In addition, since the inside and outside of the slurry coating layer are not uniformly dried, a powder floating phenomenon due to a difference in the solvent evaporation rate may occur, that is, the powder in the area that dries first may float and form a gap with the area that dries relatively later, which may deteriorate the electrode quality. Accordingly, a drying device that can control the evaporation rate of the solvent while ensuring that the inside and outside of the active layer are uniformly dried is being considered, but such drying devices are expensive and require considerable cost and time to operate, which is disadvantageous in terms of the manufacturing process.

[0008] To solve these problems, a method of manufacturing electrodes without using anode slurry (or cathode slurry) is being proposed.

[0009] Accordingly, there is a growing need for development of a lithium-ion secondary battery cathode binder (negative electrode binder) that is manufactured under dry conditions and has excellent cycle stability and binding strength with lithium metal oxide-based cathode active material (or negative electrode active material) even under high temperatures and high voltages.

[0010] In addition, in the case of fluorinated binders such as PTFE, which are known to be binders that can be used in conventional positive electrode dry processes, when mixed with negative electrode active materials, not only is the electrochemical performance not properly obtained, but considering the global concerns about the environmental side effects of fluorinated compounds, there is a need to discover a binder that is non-fluorinated and can be used in the manufacture of negative electrodes.

[0011]

[0012] The present invention has been devised to solve the above-mentioned problem, and one embodiment of the present invention provides a cathode material for a lithium secondary battery including a fluorine-free compound as a binder, a cathode for a lithium secondary battery including the same, and a method for manufacturing the same.

[0013] In addition, one embodiment of the present invention provides a negative electrode for a lithium secondary battery including a fluorine-free compound as a binder, a method for manufacturing the same, and a lithium secondary battery including the same.

[0014] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0015]

[0016] As a technical means for achieving the aforementioned technical task, one aspect of the present invention is,

[0017] A positive electrode for a lithium secondary battery is provided, comprising a positive electrode current collector; and a positive electrode active material, a conductive material, and a binder, and a positive electrode active material layer formed on the positive electrode current collector, wherein the binder comprises a fluorine-free compound.

[0018] The above positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof, but is not necessarily limited thereto, and any positive electrode active material available in the relevant technical field may be used.

[0019] The above conductive material may include at least one selected from the group consisting of carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, and combinations thereof.

[0020] The above binder can be expressed by the following [chemical formula 1].

[0021] [Chemical Formula 1]

[0022] C n H 2n+2

[0023] (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.)

[0024] The above fluorine-free compound may include at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

[0025] The above binder can undergo a liquid-solid phase transition in a temperature range of 20 to 200°C.

[0026] The above binder may further include a thermoplastic resin.

[0027] The thermoplastic resin may include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

[0028] The positive electrode active material layer may include 80 to 99 wt% of the positive electrode active material; 0.1 to 10 wt% of the conductive material; and 0.1 to 10 wt% of the binder, based on 100 wt% of the positive electrode active material layer.

[0029] The weight ratio of the above-mentioned challenge material and binder may be 1 to 3:1.

[0030] The above positive electrode active material layer is formed by solvent-free dry coating, and the positive electrode may be a dry electrode.

[0031]

[0032] As a technical means for achieving the aforementioned technical task, another aspect of the present invention is,

[0033] A method for manufacturing a positive electrode for a lithium secondary battery is provided, comprising: a step of mixing a positive electrode active material, a conductive material, and a binder to obtain a mixture; a step of coating the mixture on a positive electrode current collector to form a positive electrode active material layer; and a step of rolling the positive electrode active material layer coated on the positive electrode current collector to manufacture a positive electrode.

[0034] The above mixture can be mixed dry without a solvent.

[0035] The above rolling can be performed at a temperature range of 20 to 200°C.

[0036]

[0037] As a technical means for achieving the aforementioned technical task, another aspect of the present invention is,

[0038] The present invention provides a lithium secondary battery comprising a positive electrode for a lithium secondary battery; a negative electrode; and an electrolyte layer interposed and provided between the positive electrode and the negative electrode.

[0039]

[0040] As a technical means for achieving the aforementioned technical task, one aspect of the present invention is,

[0041] A negative electrode for a lithium secondary battery is provided, comprising: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material including a negative electrode current collector, a conductive material, and a binder; wherein the binder includes a fluorine-free compound.

[0042] The above negative active material may include at least one selected from the group consisting of carbon materials, lithium metal, silicon-based materials, and combinations thereof.

[0043] The above conductive material may include at least one selected from the group consisting of carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, and combinations thereof.

[0044] The above binder can be expressed by the following [chemical formula 2].

[0045] [Chemical Formula 2]

[0046] C n H 2n+2

[0047] (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.)

[0048] The above fluorine-free compound may include at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

[0049] The above binder can undergo a liquid-solid phase transition in a temperature range of 20 to 200°C.

[0050] The above binder may further include a thermoplastic resin.

[0051] The thermoplastic resin may include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

[0052] The negative electrode active material layer may include 80 to 99 wt% of the negative electrode active material; 0.1 to 10 wt% of the conductive material; and 0.1 to 10 wt% of the binder, based on 100 wt% of the negative electrode active material layer.

[0053] The weight ratio of the above-mentioned challenge material and binder may be 1 to 3:1.

[0054] The above negative electrode active material layer is formed by solvent-free dry coating, and the negative electrode may be a dry electrode.

[0055]

[0056] As a technical means for achieving the aforementioned technical task, another aspect of the present invention is,

[0057] A method for manufacturing an anode for a lithium secondary battery is provided, comprising: a step of mixing a negative electrode active material, a conductive material, and a binder to obtain a mixture; a step of coating the mixture on a negative electrode current collector to form a negative electrode active material layer; and a step of rolling the negative electrode active material layer coated on the negative electrode current collector to manufacture an anode.

[0058] The above mixture can be mixed dry without a solvent.

[0059] The above rolling can be performed at a temperature range of 20 to 200°C.

[0060]

[0061] As a technical means for achieving the aforementioned technical task, another aspect of the present invention is,

[0062] A lithium secondary battery is provided, comprising: a positive electrode; an anode for a lithium secondary battery according to the present invention; and an electrolyte layer interposed and provided between the positive electrode and the negative electrode.

[0063]

[0064] Figure 1 is a schematic diagram of a lithium secondary battery according to one embodiment of the present invention.

[0065] Figure 2 shows a process for manufacturing a positive electrode for a lithium secondary battery according to Example 1 of one embodiment of the present invention.

[0066] Figure 3 shows the results of differential scanning calorimetry (DSC) measurement of Example 1 according to one embodiment of the present invention.

[0067] Figure 4 shows the results of thermogravimetric analysis (TGA) measurement of Example 1 according to one embodiment of the present invention.

[0068] Figure 5 shows the results of linear sweep voltammetry (LSV) measurement of Example 1 according to one embodiment of the present invention.

[0069] Figure 6 shows the results of a scanning electron microscope (SEM) measurement of Example 1 according to one embodiment of the present invention.

[0070] Figure 7 shows the results of a scanning electron microscope (SEM) measurement of Example 2 according to one embodiment of the present invention.

[0071] Figure 8 shows the results of adhesive strength measurement of Example 1 according to one embodiment of the present invention.

[0072] Figure 9 is an impedance measurement result of Example 1 according to one embodiment of the present invention.

[0073] Figure 10 shows the results of measuring the charge / discharge profile of Example 2 according to one embodiment of the present invention.

[0074] Figure 11 shows the results of measuring the charge / discharge profile of Example 3 according to one embodiment of the present invention.

[0075] Figure 12 shows the results of measuring the specific capacity values ​​of Examples 2 and 3 according to one embodiment of the present invention.

[0076] Figure 13 shows the manufacturing process of a negative electrode for a lithium secondary battery according to Example 4 of one embodiment of the present invention.

[0077] Figure 14 shows the results of a scanning electron microscope (SEM) measurement of Example 4 according to one embodiment of the present invention.

[0078] Figure 15 shows the results of measuring the charge / discharge profile of Example 5 according to one embodiment of the present invention.

[0079] Figure 16 shows the results of measuring the charge / discharge cycle of Example 5 according to one embodiment of the present invention.

[0080]

[0081] <First aspect>

[0082] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0083]

[0084] Example 1

[0085] LiNi, a cathode active material 0.8 Co 0.1 Mn 0.19.7 g of O2 (NCM811), 0.2 g of Super P as a conductive agent, 0.05 g of paraffin as a binder, and 0.05 g of polyethylene were placed in a blender (weight ratio 97: 2: 1) and mixed at 2000 rpm for 5 minutes to prepare a mixture. Then, the prepared electrode mixture powder was weighed according to the target loading amount and placed in a pellet mold press together with an unprimed current collector to prepare a dry electrode. The dry positive electrode prepared in this way is as shown in Fig. 2.

[0086]

[0087] Example 2

[0088] The cathode was manufactured in the same manner as in Example 1, except that 0.0375 g of carbon black (Super P) and 0.0125 g of MWCNT were used as conductive materials (weight ratio 97: 1.5: 0.5: 1).

[0089]

[0090] Example 3

[0091] The cathode was manufactured in the same manner as in Example 1, except that 0.0375 g of carbon black and 0.0125 g of SWCNT were used as conductive materials (weight ratio 97: 1.5: 0.5: 1).

[0092]

[0093] Experimental Example 1: DSC and TGA Measurements

[0094] To investigate the thermal properties (phase transition), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed in Example 1. The results are shown in Figures 3 and 4.

[0095] Referring to Figure 3, the DSC measurement results demonstrate basic thermal characteristics. The presence of a peak indicates an endothermic or exothermic reaction, indicating a phase transition. In other words, it can be confirmed that the binder, paraffin, undergoes a phase transition from solid to liquid, increasing adhesive strength even in a solvent-free dry process.

[0096] Referring to Figure 4, it can be confirmed that paraffin among the binder components undergoes thermal decomposition at 200°C or higher, and polyethylene undergoes thermal decomposition at 373°C or higher.

[0097]

[0098] Experimental Example 2: LSV Measurement

[0099] To determine electrochemical stability, a linear sweep voltammetry (LSV) measurement experiment was conducted in Example 1. The results are shown in Fig. 5.

[0100] Referring to Figure 5, Example 1 using paraffin + PE as a binder has a chemically stable structure and is electrochemically stable as it is not reduced / oxidized at both high and low voltages.

[0101]

[0102] Experimental Example 3: SEM Measurement

[0103] To determine the particle morphology of the positive electrode material, scanning electron microscope (SEM) measurements were conducted in Examples 1 and 2. The results are shown in Figures 6 and 7.

[0104] Referring to Figure 6, in the case of Example 1, it can be confirmed that the positive electrode active material, carbon black conductive material, and binder are uniformly composited.

[0105] Referring to Figure 7, in the case of Example 2, it can be confirmed that the positive electrode active material, carbon black, CNT mixed conductive material, and binder are uniformly composited.

[0106]

[0107] Experimental Example 4: Confirmation of Adhesive Strength Measurement

[0108] To determine the adhesive strength of the anode, an adhesive strength measurement experiment was conducted in Example 1. The results are shown in Fig. 8.

[0109] -measurement method

[0110] The weight ratio of the positive electrode active material, conductive material, and binder was 96:2:2, and the electrode loading was 50 mg / cm. 2 After manufacturing a 2cmX5cm dry electrode, 3M tape was attached and the electrode was peeled at a speed of 100mm per minute in a 180-degree direction.

[0111] Referring to Fig. 8, in the case of Example 1, the adhesive strength of the anode can be about 0.06 kgf / mm on average under the conditions of 25°C, 1 atm, and about 3 mm of peeling. That is, it can be confirmed that the adhesive strength of Example 1 is very good even when manufactured dry.

[0112]

[0113] Experimental Example 5: Electrochemical Impedance Measurement

[0114] To determine the electrochemical properties, an experiment was conducted to measure the impedance of Example 1. The results are shown in Fig. 9.

[0115] Referring to Figure 9, typical charge transfer and ion diffusion behaviors observed in a conventional positive electrode were observed in proportion to the electrode loading. This behavior is related to the electrode mixture layer, indicating that the dry electrode exhibits electrochemical characteristics similar to those of a conventional electrode. On the other hand, the series resistance associated with the current collector and electrolyte resistance was confirmed to occur almost constantly regardless of the electrode loading. This confirms that the paraffin-based dry electrode binder fabrication of the present invention does not affect the remaining electrode characteristics.

[0116]

[0117] Experimental Example 6: Charge-Discharge Profile Measurement

[0118] The lithium secondary batteries according to Examples 2 and 3 were charged and discharged under 0.1C discharge / 0.1C charge conditions. The specific capacity and voltage were measured during charge and discharge, and the results are shown in Figures 10 and 11.

[0119] Referring to Figures 10 and 11, it can be confirmed that not only is the specific capacity of the cathode active material (NCM811) appropriately expressed, but also that satisfactory initial cycle performance is exhibited. This demonstrates that the paraffin-based dry electrode of the present invention possesses electrochemical properties at a typical level.

[0120]

[0121] Experimental Example 7: Lifespan Measurement

[0122] The specific capacity values ​​for the number of cycles measured by changing the charge / discharge voltage ranges of the lithium secondary batteries according to Examples 2 and 3 were measured, and the results are as shown in Fig. 12.

[0123] Referring to Figure 12, it can be confirmed that not only is the specific capacity of the cathode active material appropriately expressed, but also that satisfactory initial cycle performance is achieved. This demonstrates that the paraffin-based dry electrode of the present invention possesses typical electrochemical properties.

[0124]

[0125] <Second aspect>

[0126] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0127]

[0128] Example 4

[0129] Cathode manufacturing

[0130] A mixture was prepared by placing 9.7 g of natural graphite as a negative active material, 0.2 g of Super P as a conductive material, 0.05 g of paraffin as a binder, and 0.05 g of polyethylene in a blender (weight ratio 97: 2: 1) and mixing at 2000 rpm for 5 minutes. Then, the prepared electrode mixture powder was weighed according to the target loading amount and placed in a pellet mold press together with a current collector that was not coated with a primer to prepare a dry electrode. The dry negative electrode prepared in this way is as shown in Fig. 13.

[0131]

[0132] Example 5

[0133] The cathode was manufactured in the same manner as in Example 4, except that 0.0375 g of carbon black (Super P) and 0.0125 g of MWCNT were used as conductive materials (weight ratio 97: 1.5: 0.5: 1).

[0134]

[0135] Example 6

[0136] The cathode was manufactured in the same manner as in Example 4, except that 0.0375 g of carbon black and 0.0125 g of SWCNT were used as conductive materials (weight ratio 97: 1.5: 0.5: 1).

[0137]

[0138] Experimental Example 8: SEM Measurement

[0139] To determine the particle morphology of the cathode material, a scanning electron microscope (SEM) measurement experiment was conducted in Example 4. The results are shown in Fig. 14.

[0140] Referring to Figure 14, in the case of Example 4, it can be confirmed that the negative active material, carbon black conductive material, and binder are uniformly composited.

[0141]

[0142] Experimental Example 9: Charge-Discharge Profile Measurement

[0143] The lithium secondary battery according to Example 5 was charged and discharged under 0.1C discharge / 0.1C charge conditions. The specific capacity and voltage were measured during charge and discharge, and the results are shown in Fig. 15.

[0144] Referring to Figure 15, it can be confirmed that not only is the inherent specific capacity of the negative active material (natural graphite) appropriately expressed, but also that satisfactory initial cycle performance is exhibited. This demonstrates that the paraffin-based dry electrode of the present invention possesses electrochemical properties at a typical level.

[0145]

[0146] Experimental Example 10: Lifespan Measurement

[0147] The specific capacity value for the number of cycles measured by varying the charge / discharge voltage range of the lithium secondary battery according to Example 5 was measured, and the results are as shown in Fig. 16.

[0148] Referring to Figure 16, it can be confirmed that not only is the inherent specific capacity of the negative active material appropriately expressed, but also that satisfactory initial cycle performance is exhibited. This demonstrates that the paraffin-based dry electrode of the present invention possesses electrochemical properties at a typical level.

[0149]

[0150] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0151] The scope of the present invention is indicated by the claims set forth below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0152]

[0153] Hereinafter, the present invention will be described in more detail. However, the present invention may be implemented in many different forms, and the present invention is not limited to the embodiments described herein, but is defined solely by the claims set forth below.

[0154] Additionally, the terminology used herein is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. Throughout the specification of the present invention, the term "including" or "comprising" a component does not exclude other components, but rather implies the inclusion of other components, unless specifically stated otherwise.

[0155] Throughout the specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another part in between. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that it may include other components, unless otherwise specifically stated.

[0156] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0157]

[0158] <First aspect>

[0159] The first aspect of this article is,

[0160] A lithium secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode.

[0161] Hereinafter, with reference to Fig. 1, a lithium secondary battery according to the first aspect of the present invention will be described in detail.

[0162] In one embodiment of the present disclosure, the lithium secondary battery (10) may include a positive electrode (100), an electrolyte layer (200), and an anode (300). The electrolyte layer (200) may be provided on the positive electrode (100). The positive electrode (100) and the anode (300) may be separated from each other by the electrolyte layer (200). Although not illustrated, the lithium secondary battery (10) according to one embodiment of the present disclosure may further include a separator.

[0163] In one embodiment of the present invention, the positive electrode (100) may include a positive electrode current collector (110) and a positive electrode active material layer (120) formed on the positive electrode current collector (110).

[0164] The positive electrode current collector (110) may be made of a material having high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used. In the case of aluminum or stainless steel, a material surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector (110) may have fine unevenness formed on its surface to increase the adhesive strength of the positive electrode active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0165] The above positive electrode active material layer (120) may include a positive electrode material for a lithium secondary battery.

[0166] The above-mentioned positive electrode material for a lithium secondary battery may include a positive electrode active material, a conductive material, and a binder.

[0167] The above positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof, but is not necessarily limited thereto, and any positive electrode active material available in the relevant technical field may be used.

[0168] The above positive electrode active material can be expressed by the following [general formula 1] or [general formula 2].

[0169] [General Formula 1]

[0170] Li 1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0171] In the general formula 1 above, M is at least one element from the Mn, Zr, and Ti groups, M' is at least one element from the Al, B, and Co groups, M" is a dopant different from M and M', x, a, b, and c are expressed in moles (mol), and -0.02≤x≤0.02, 0≤c≤0.05, 0.10≤(a+b)≤0.65, and 0≤z≤0.05.

[0172] [General Formula 2]

[0173] Li j M1 k M2 m (PO 4-n )A n

[0174] In the general formula 2 above, M1 is at least one selected from the group consisting of Fe, Co, Ni, and Mn, M2 is at least one selected from the group consisting of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Z, A is at least one selected from the group consisting of N, S, and F, and 0.5≤j≤1.5, 0.5≤k≤1, 0≤m≤0.5, 0≤n≤1.

[0175] The conductive agent lowers the interfacial resistance of the adhesion reinforcing composition, and may be included without particular limitation as long as it does not cause a chemical change and has electronic conductivity. Specifically, the conductive agent may include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these may be used alone or a mixture of two or more may be used.

[0176] The above-mentioned conductive material may include, for example, at least one selected from the group consisting of carbon black (Super P), multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT), and combinations thereof, and when two types are included, they may be included in a ratio of 1:0.5 to 5.

[0177] Typically, lithium secondary battery cathodes use polyvinylidene fluoride (PVDF) as a wet binder or polytetrafluoroethylene (PTFE) as a dry binder. However, when PTFE is used as a dry electrode binder, lumps form after kneading, necessitating processing into thin sheets.

[0178] In addition, PTFE is a perfluorinated compound, so it has low liquid electrolyte impregnation properties, and it does not adhere unless a primer is applied to the current collector, and it is not environmentally friendly.

[0179] To overcome the problems of such conventional binders, in one embodiment of the present invention, the binder may include a fluorine-free compound.

[0180] The above binder is a saturated hydrocarbon or an alkane (C n H 2n+2 ) may be a binder based.

[0181] The above binder can be expressed by the following [chemical formula 1].

[0182] [Chemical Formula 1]

[0183] C n H 2n+2

[0184] (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.)

[0185] The above binder is composed only of carbon and hydrogen and is therefore very low in toxicity.

[0186] The above binder may include at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

[0187] The above binder can undergo a phase transition between liquid and solid phases in a temperature range of 20 to 200°C.

[0188] The melting point of the above binder is in the temperature range of 20 to 200°C, and when temperature is applied, it undergoes a phase transition from a solid form (powder) to a liquid form, so that even when the electrode is manufactured dry without a solvent, the liquid electrolyte impregnation property is good, and it can be easily adhered to a current collector without a primer coating.

[0189] The above binder may further include a thermoplastic resin. By further including a thermoplastic resin, the binder can achieve the effect of having a chemically stable structure without reduction or oxidation under high and low voltage conditions.

[0190] The thermoplastic resin may include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

[0191] The binder may contain 0.1 to 100 wt% of the fluorine-free compound and 0 to 99.9 wt% of the thermoplastic resin, based on 100 wt% of the total binder. For example, the fluorine-free compound may be 10 to 90 wt%, or 20 to 80 wt%, or 30 to 70 wt%, or 40 to 60 wt%, and the thermoplastic resin may be 10 to 90 wt%, or 20 to 80 wt%, or 30 to 70 wt%, or 40 to 60 wt%. If the above content range is not satisfied, problems such as detachment of the electrode or reduction in capacity and output expression may occur.

[0192] The above cathode material may include 80 to 99 wt% of the cathode active material; 0.1 to 10 wt% of the conductive agent; and 0.1 to 10 wt% of the binder, based on 100 wt% of the cathode material. If the above content range is not satisfied, problems such as electrode detachment or reduced capacity and output expression may occur.

[0193] The weight ratio of the above-mentioned challenge material and binder may be 1 to 3:1.

[0194] The above positive electrode active material layer is formed by solvent-free dry coating, and the positive electrode may be a dry electrode.

[0195] In the case of existing dry electrodes, when there is no primer adhesive layer on the current collector, the adhesion of the active material layer to the current collector is not smooth due to the limitations of the binder material. In addition, since the primer coating is performed as a wet process, this causes the environmental advantages of the dry electrode to be diluted. To overcome this problem, the present invention includes a fluorine-free compound as a binder, and can have the effect of improving adhesion even without a primer adhesive layer.

[0196] When the peeling force of the positive electrode active material layer is measured for the positive electrode current collector, the maximum peeling force is shown in a peeling distance range of about 3 mm, and may be about 0.01 to 0.1 kgf / mm on average, for example, 0.02 to 0.09 kgf / mm, or 0.03 to 0.08 kgf / mm, or 0.04 to 0.07 kgf / mm, and preferably, may be characterized by having an adhesive force of 0.06 kgf / mm.

[0197] The above adhesive peel strength layering conditions can be performed under temperature and pressure conditions such as 25 degrees and 1 atm.

[0198] What is meant by the above adhesive peel strength showing a maximum value is that "the adhesive force between the two bonded materials is resisting the most strongly at this point, which may indicate that the adhesive is most strongly attached, or that more force is required to peel at a particular point due to defects or irregularities in the bonding surfaces."

[0199] The positive electrode for a lithium secondary battery comprising the fluorine-free binder of the present invention, which has overcome these problems, has a maximum adhesive peel strength in a peeling distance range of about 3 mm, and may be about 0.01 to 0.1 kgf / mm on average, for example, 0.02 to 0.09 kgf / mm, or 0.03 to 0.08 kgf / mm, or 0.04 to 0.07 kgf / mm, and preferably has an adhesive peel strength of 0.06 kgf / mm. Referring to the fact that the adhesive strength when a conventional binder is used is at the level of 0.056 N / mm under the same conditions, it can be confirmed that the adhesive strength of the composite layer is very good even when manufactured as a dry electrode without a primer coating layer.

[0200] In one embodiment of the present invention, the electrolyte layer (200) may include a lithium salt and a solvent.

[0201] The above lithium salts are LiPF6, LiBF4, LiClO4, LiCl, LiBr, LiI, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiC4F9SO3, LiB(C6H5)4, LiB(C2O4)2, LiPO2F2, Li(SO2F)2N, (LiFSI), (CF3SO2)2Nli and combinations thereof, but is not necessarily limited thereto, and all lithium salts available in the art can be used.

[0202] The above solvent may include at least one selected from the group consisting of carbonate solvents, ester solvents, ether solvents, ketone solvents, and combinations thereof, but is not necessarily limited thereto, and any solvent available in the relevant technical field may be used.

[0203] In one embodiment of the present invention, the negative electrode (300) may include a negative electrode current collector (310) and a negative electrode active material layer (320) formed on the negative electrode current collector (310).

[0204] In one embodiment of the present invention, the negative electrode current collector (310) is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0205] The negative electrode current collector (310) may typically have a thickness of 3 μm to 500 μm, and, like the positive electrode current collector (110), may have fine irregularities formed on the surface of the current collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0206] In one embodiment of the present invention, the negative electrode active material layer (320) may optionally include a binder and a conductive material together with the negative electrode active material.

[0207] In one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0208] In one embodiment of the present invention, the binder of the negative electrode active material layer (320) is a component that assists in bonding between the conductive material, the active material, and the current collector, and examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0209] In one embodiment of the present invention, the conductive material of the negative electrode active material layer (320) is a component for further improving the conductivity of the negative electrode active material (320), and is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black; conductive fiber such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0210] The above lithium secondary battery (10) may further include a separator (not shown).

[0211] The separator prevents short circuits between the positive electrode (100) and the negative electrode (300) and provides a passage for lithium ions. The separator may be a polyolefin polymer film such as polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, polypropylene / polyethylene / polypropylene, or a multi-film thereof, a microporous film, a woven fabric, or a non-woven fabric, as known in the art. In addition, a film coated with a resin having excellent stability on a porous polyolefin film may be used.

[0212] In one embodiment of the present invention, a lithium secondary battery (10) including a positive electrode (100) according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0213] There is no particular limitation on the external shape of the lithium secondary battery (10) according to one embodiment of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0214] A lithium secondary battery (10) according to one embodiment of the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0215] Accordingly, in one embodiment of the present invention, a battery module including the lithium secondary battery (10) as a unit cell and a battery pack including the same are provided.

[0216] In one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0217]

[0218] The second aspect of this article is,

[0219] A method for manufacturing a positive electrode for a lithium secondary battery is provided, comprising: a step (S1) of mixing a positive electrode active material, a conductive material, and a binder to obtain a mixture; a step (S2) of coating the mixture on a positive electrode current collector to obtain an active material layer; and a step (S3) of rolling the active material layer coated on the positive electrode current collector to manufacture a positive electrode.

[0220]

[0221] Detailed explanations of parts that overlap with the first aspect of the present application have been omitted, but the explanations of the first aspect of the present application may be applied equally even if the explanations are omitted in the second aspect.

[0222]

[0223] In one embodiment of the present invention, the S1 may be a step of obtaining a mixture that is a positive electrode material.

[0224] The positive electrode active material, conductive material, and binder are the same as those described above, and the mixture may be dry-mixed without a solvent. However, a case may also be included in which a solvent is used to ensure uniform mixing and then dried to obtain dry electrode composite particles.

[0225] In general, the above mixture mixing process is a process of mixing a coating material for forming an electrode active layer where an actual electrochemical reaction occurs on the electrode, and specifically, it is a process of mixing an electrode active material, which is an essential element of the electrode, and other additives such as a conductive material, a binder for interparticle bonding and adhesion to a current collector, a solvent, etc., to manufacture a slurry having fluidity. Thereafter, an electrode coating process of applying the mixture onto a positive electrode current collector and a drying process to remove the solvent contained in the electrode mixture are performed, and additionally, the electrode is rolled to manufacture a predetermined thickness.

[0226] Meanwhile, during the drying process, the solvent contained in the electrode mixture may evaporate, causing defects such as pinholes or cracks in the already formed electrode active layer. Furthermore, since the inside and outside of the active layer are not uniformly dried, differences in solvent evaporation rates can lead to particle floating, i.e., particles in areas that dry first may float to the surface, forming gaps with areas that dry relatively later, which can degrade electrode quality. This presents a critical drawback: making the manufacture of thick-film electrodes difficult.

[0227] Accordingly, to solve the above problems, drying devices capable of controlling the evaporation rate of the solvent while ensuring uniform drying of the inside and outside of the active layer have been considered. However, such drying devices are very expensive and require considerable operating costs and time, which poses a disadvantage in terms of manufacturing process efficiency. Therefore, the present invention prevents the above problems from occurring by mixing the mixture in a dry manner without a solvent.

[0228] In one embodiment of the present invention, the S2 may be a step of manufacturing a positive electrode.

[0229] The mixture resulting from the above step S1 is in a powder state without using a solvent, and can be rolled onto a positive electrode current collector to manufacture a positive electrode.

[0230] The above rolling can be performed at a temperature range of 20 to 200°C. If the temperature is outside the above range, as described above, the phase transition of the binder does not occur, and thus, there may be a problem of poor adhesion.

[0231]

[0232] <Second aspect>

[0233] The first aspect of this article is,

[0234] A lithium secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode.

[0235] Hereinafter, with reference to FIG. 13, a lithium secondary battery according to the first aspect of the present invention will be described in detail.

[0236]

[0237] In one embodiment of the present disclosure, the lithium secondary battery (10) may include a positive electrode (100), an electrolyte layer (200), and an anode (300). The electrolyte layer (200) may be provided on the positive electrode (100). The positive electrode (100) and the anode (300) may be separated from each other by the electrolyte layer (200). Although not illustrated, the lithium secondary battery (10) according to one embodiment of the present disclosure may further include a separator.

[0238] In one embodiment of the present invention, the positive electrode (100) may include a positive electrode current collector (110) and a positive electrode active material layer (120) formed on the positive electrode current collector (110).

[0239] The positive electrode current collector (110) may be made of a material having high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used. In the case of aluminum or stainless steel, a material surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector (110) may have fine unevenness formed on its surface to increase the adhesive strength of the positive electrode active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0240] The above positive electrode active material layer (120) may include a positive electrode material for a lithium secondary battery.

[0241] The above-mentioned positive electrode material for a lithium secondary battery may include a positive electrode active material, a conductive material, and a binder.

[0242] The above-mentioned positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof, but is not necessarily limited thereto, and any positive electrode active material available in the relevant technical field may be used. The above-mentioned positive electrode active material may be expressed by the following [General Formula 3] or [General Formula 4].

[0243] [General Formula 3]

[0244] Li 1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0245] In the above general formula 3, M is at least one element from the Mn, Zr, and Ti groups, M' is at least one element from the Al, B, and Co groups, M" is a dopant different from M and M', x, a, b, and c are expressed in moles (mol), and -0.02≤x≤0.02, 0≤c≤0.05, 0.10≤(a+b)≤0.65, and 0≤z≤0.05.

[0246] [General Formula 4]

[0247] Li j M1 k M2 m (PO 4-n )A n

[0248] In the general formula 4 above, M1 is at least one selected from the group consisting of Fe, Co, Ni, and Mn, M2 is at least one selected from the group consisting of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Z, A is at least one selected from the group consisting of N, S, and F, and 0.5≤j≤1.5, 0.5≤k≤1, 0≤m≤0.5, 0≤n≤1.

[0249] The conductive agent lowers the interfacial resistance of the adhesion reinforcing composition, and may be included without particular limitation as long as it does not cause a chemical change and has electronic conductivity. Specifically, the conductive agent may include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these may be used alone or a mixture of two or more may be used.

[0250] The above-mentioned conductive material may include, for example, at least one selected from the group consisting of carbon black (Super P), multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT), and combinations thereof, and when two types are included, they may be included in a ratio of 1:0.5 to 5.

[0251] The binder may include, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, nitrocellulose, etc., but is not particularly limited as long as it can bind the positive electrode material onto the positive electrode current collector (110). In one embodiment of the present invention, the electrolyte layer (200) may include a lithium salt and a solvent.

[0252] The above lithium salts are LiPF6, LiBF4, LiClO4, LiCl, LiBr, LiI, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiC4F9SO3, LiB(C6H5)4, LiB(C2O4)2, LiPO2F2, Li(SO2F)2N, (LiFSI), (CF3SO2)2Nli and combinations thereof, but is not necessarily limited thereto, and all lithium salts available in the art can be used.

[0253] The above solvent may include at least one selected from the group consisting of carbonate solvents, ester solvents, ether solvents, ketone solvents, and combinations thereof, but is not necessarily limited thereto, and any solvent available in the relevant technical field may be used.

[0254] In one embodiment of the present invention, the negative electrode (300) may include a negative electrode current collector (310) and a negative electrode active material layer (320) formed on the negative electrode current collector (310).

[0255] In one embodiment of the present invention, the negative electrode current collector (310) is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0256] The negative electrode current collector (310) may typically have a thickness of 3 μm to 500 μm, and, like the positive electrode current collector (110), may have fine irregularities formed on the surface of the current collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0257] In one embodiment of the present invention, the negative electrode active material layer (320) may optionally include a binder and a conductive material together with the negative electrode active material.

[0258] The above negative electrode active material layer (320) may include a negative electrode material for a lithium secondary battery.

[0259] The above-mentioned negative electrode material for a lithium secondary battery may include a negative electrode active material, a conductive material, and a binder.

[0260] In one embodiment of the present invention, the negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. The negative electrode active material may include at least one selected from the group consisting of carbonaceous materials, lithium metal, silicon-based materials, and combinations thereof. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as carbon materials. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. The negative electrode active material may be characterized by being at least one selected from the group consisting of graphite-based materials.

[0261] In one embodiment of the present invention, the conductive material of the negative electrode active material layer (320) is a component for further improving the conductivity of the negative electrode active material (320), and is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black; conductive fiber such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0262] Typically, negative electrodes for lithium secondary batteries use styrene-butadiene rubber (SB) polymers and carboxymethylcellulose (CMC) as wet binders. However, when used as a dry electrode binder, these polymers form lumps after kneading, requiring processing into thin sheets.

[0263] In addition, PTFE is a perfluorinated compound, so it has low liquid electrolyte impregnation properties, and it does not adhere unless a primer is applied to the current collector, and it is not environmentally friendly.

[0264] To overcome the problems of such conventional binders, in one embodiment of the present invention, the binder may include a fluorine-free compound.

[0265] The above binder is a saturated hydrocarbon or an alkane (C n H 2n+2 ) may be a binder based.

[0266] The above binder can be expressed by the following [chemical formula 2].

[0267] [Chemical Formula 2]

[0268] C n H 2n+2

[0269] (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.)

[0270] The above binder is composed only of carbon and hydrogen and is therefore very low in toxicity.

[0271] The above binder may include at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

[0272] The above binder can undergo a phase transition between liquid and solid phases in a temperature range of 20 to 200°C.

[0273] The melting point of the above binder is in the temperature range of 20 to 200°C, and when temperature is applied, it undergoes a phase transition from a solid form (powder) to a liquid form, so that even when the electrode is manufactured dry without a solvent, the liquid electrolyte impregnation property is good, and it can be easily adhered to a current collector without a primer coating.

[0274] The above binder may further include a thermoplastic resin. By further including a thermoplastic resin, the binder can achieve the effect of having a chemically stable structure without reduction or oxidation under high and low voltage conditions.

[0275] The thermoplastic resin may include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

[0276] The binder may contain 0.1 to 100 wt% of the fluorine-free compound and 0 to 99.9 wt% of the thermoplastic resin, based on 100 wt% of the total binder. For example, the fluorine-free compound may be 10 to 90 wt%, or 20 to 80 wt%, or 30 to 70 wt%, or 40 to 60 wt%, and the thermoplastic resin may be 10 to 90 wt%, or 20 to 80 wt%, or 30 to 70 wt%, or 40 to 60 wt%. If the above content range is not satisfied, problems such as detachment of the electrode or reduction in capacity and output expression may occur.

[0277] The above-mentioned negative electrode material may include 80 to 99 wt% of the negative electrode active material; 0.1 to 10 wt% of the conductive agent; and 0.1 to 10 wt% of the binder, based on 100 wt% of the negative electrode material. If the above content range is not satisfied, problems such as electrode detachment or reduced capacity and output expression may occur.

[0278] The weight ratio of the above-mentioned challenge material and binder may be 1 to 3:1.

[0279] The above negative electrode active material layer is formed by solvent-free dry coating, and the negative electrode may be a dry electrode.

[0280] In the case of existing dry electrodes, when there is no primer adhesive layer on the current collector, the adhesion of the active material layer to the current collector is not smooth due to the limitations of the binder material. In addition, since the primer coating is performed as a wet process, this causes the environmental advantages of the dry electrode to be diluted. To overcome this problem, the present invention includes a fluorine-free compound as a binder, and can have the effect of improving adhesion even without a primer adhesive layer.

[0281] The above lithium secondary battery (10) may further include a separator (not shown).

[0282] The separator prevents short circuits between the positive electrode (100) and the negative electrode (300) and provides a passage for lithium ions. The separator may be a polyolefin polymer film such as polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, polypropylene / polyethylene / polypropylene, or a multi-film thereof, a microporous film, a woven fabric, or a non-woven fabric, as known in the art. In addition, a film coated with a resin having excellent stability on a porous polyolefin film may be used.

[0283] In one embodiment of the present invention, a lithium secondary battery (10) including a negative electrode (300) according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0284] There is no particular limitation on the external shape of the lithium secondary battery (10) according to one embodiment of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0285] A lithium secondary battery (10) according to one embodiment of the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0286] Accordingly, in one embodiment of the present invention, a battery module including the lithium secondary battery (10) as a unit cell and a battery pack including the same are provided.

[0287] In one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0288]

[0289] The second aspect of this article is,

[0290] A method for manufacturing an anode for a lithium secondary battery is provided, comprising: a step (S1) of mixing a cathode active material, a conductive material, and a binder to obtain a mixture; a step (S2) of coating the mixture on a cathode current collector to obtain a cathode active material layer; and a step (S3) of rolling the cathode active material layer coated on the cathode current collector to manufacture a cathode.

[0291]

[0292] Detailed explanations of parts that overlap with the first aspect of the present application have been omitted, but the explanations of the first aspect of the present application may be applied equally even if the explanations are omitted in the second aspect.

[0293]

[0294] In one embodiment of the present invention, the S1 may be a step of obtaining a mixture that is a negative electrode material.

[0295] The negative active material, conductive material, and binder are the same as those described above, and the mixture may be dry-mixed without a solvent. However, a case may also be included in which a solvent is used to ensure uniform mixing and then dried to obtain dry electrode composite particles.

[0296] In general, the above mixture mixing process is a process of mixing a coating material for forming an electrode active layer where an actual electrochemical reaction occurs on the electrode. Specifically, it is a process of mixing an electrode active material, which is an essential element of the electrode, and other additives such as a conductive material, a binder for interparticle bonding and adhesion to a current collector, a solvent, etc. to manufacture a slurry having fluidity. Thereafter, an electrode coating process of applying the mixture onto a negative electrode current collector and a drying process to remove the solvent contained in the electrode mixture are performed, and additionally, the electrode is rolled to manufacture a predetermined thickness.

[0297] Meanwhile, during the drying process, the solvent contained in the electrode mixture may evaporate, causing defects such as pinholes or cracks in the already formed electrode active layer. Furthermore, since the inside and outside of the active layer are not uniformly dried, differences in solvent evaporation rates can lead to particle floating, i.e., particles in areas that dry first may float to the surface, forming gaps with areas that dry relatively later, which can degrade electrode quality. This presents a critical drawback: making the manufacture of thick-film electrodes difficult.

[0298] Accordingly, to solve the above problems, drying devices capable of controlling the evaporation rate of the solvent while ensuring uniform drying of the inside and outside of the active layer have been considered. However, such drying devices are very expensive and require considerable operating costs and time, which poses a disadvantage in terms of manufacturing process efficiency. Therefore, the present invention prevents the above problems from occurring by mixing the mixture in a dry manner without a solvent.

[0299] In one embodiment of the present invention, the S2 may be a step of manufacturing a cathode.

[0300] The mixture resulting from the above step S1 is in a dry mixed powder state without using a solvent, and can be rolled onto a negative electrode current collector to manufacture a negative electrode.

[0301] The above rolling can be performed at a temperature range of 20 to 200°C. If the temperature is outside the above range, as described above, the phase transition of the binder does not occur, and thus, there may be a problem of poor adhesion.

[0302]

[0303] According to one embodiment of the present invention, the cathode material for a lithium secondary battery is environmentally friendly because it includes a fluorine-free compound as a binder, and has the advantage of superior adhesiveness compared to a wet process even when manufactured through a dry process, so it can be considered to have industrial applicability.

[0304] According to one embodiment of the present invention, the negative electrode material for a lithium secondary battery is environmentally friendly because it includes a fluorine-free compound as a binder, has the advantage of superior adhesiveness compared to a wet process even when manufactured by a dry process, and has excellent compatibility with a negative electrode active material, so that when an electrode is manufactured by a dry process, the electrochemical performance thereof is superior, and therefore, it can be considered to have industrial applicability.

Claims

1. Anode current collector; and A cathode active material layer comprising a cathode active material, a conductive material, and a binder, and formed on the cathode current collector; A positive electrode for a lithium secondary battery, wherein the binder comprises a fluorine-free compound.

2. In paragraph 1, A positive electrode for a lithium secondary battery, wherein the positive electrode active material comprises at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof.

3. In paragraph 1, A positive electrode for a lithium secondary battery, wherein the conductive material comprises at least one selected from the group consisting of carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, and combinations thereof.

4. In paragraph 1, The above binder is a positive electrode for a lithium secondary battery, represented by the following [chemical formula 1]. [Chemical Formula 1] C n H 2n+2 (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.) 5. In paragraph 1, A positive electrode for a lithium secondary battery, wherein the fluorine-free compound comprises at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

6. In paragraph 1, The above binder is a positive electrode for a lithium secondary battery, wherein a liquid-solid phase transition occurs in a temperature range of 20 to 200°C.

7. In paragraph 1, A positive electrode for a lithium secondary battery, wherein the binder further comprises a thermoplastic resin.

8. In paragraph 7, A cathode for a lithium secondary battery, wherein the thermoplastic resin comprises at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

9. In paragraph 1, The above positive electrode active material layer is, based on 100% by weight of the positive electrode active material layer, 80 to 99 wt% of the positive electrode active material; 0.1 to 10 wt% of the above-mentioned conductive agent; and A positive electrode for a lithium secondary battery, comprising 0.1 to 10 wt% of the above binder.

10. In paragraph 1, A positive electrode for a lithium secondary battery, wherein the weight ratio of the above-mentioned conductive material and binder is 1 to 3:

1.

11. In paragraph 1, The above positive electrode active material layer is formed by solvent-free dry coating, The above positive electrode is a dry electrode, a positive electrode for a lithium secondary battery.

12. A step of obtaining a mixture by mixing a positive electrode active material, a conductive agent, and a binder; A step of coating the mixture on a positive electrode current collector to form a positive electrode active material layer; and A step of manufacturing a positive electrode by rolling a positive electrode active material layer coated on the positive electrode current collector; A method for manufacturing a positive electrode for a lithium secondary battery, wherein the binder comprises a fluorine-free compound.

13. In paragraph 12, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the above mixture is mixed dry without a solvent.

14. In paragraph 12, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the above rolling is performed at a temperature range of 20 to 200°C.

15. Anode for lithium secondary battery according to Article 1; cathode; and A lithium secondary battery, comprising an electrolyte layer interposed between the positive electrode and the negative electrode.

16. Negative current collector; and A negative electrode active material layer including a negative electrode active material, a conductive material, and a binder, and formed on the negative electrode current collector; A negative electrode for a lithium secondary battery, wherein the binder comprises a fluorine-free compound.

17. In paragraph 16, A negative electrode for a lithium secondary battery, wherein the negative electrode active material comprises at least one selected from the group consisting of carbon materials, lithium metal, silicon-based materials, and combinations thereof.

18. In paragraph 16, A negative electrode for a lithium secondary battery, wherein the conductive material comprises at least one selected from the group consisting of carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, and combinations thereof.

19. In paragraph 16, The above binder is a negative electrode for a lithium secondary battery, represented by the following [chemical formula 2]. [Chemical Formula 2] C n H 2n+2 (At this time, if n is 3 or more, it includes an isomer structure including linear, branched, and cyclic forms.) 20. In paragraph 16, A negative electrode for a lithium secondary battery, wherein the fluorine-free compound comprises at least one selected from the group consisting of paraffin, chlorinated paraffin, and combinations thereof.

21. In paragraph 16, The above binder is a negative electrode for a lithium secondary battery, wherein a liquid-solid phase transition occurs in a temperature range of 20 to 200°C.

22. In paragraph 16, A negative electrode for a lithium secondary battery, wherein the binder further comprises a thermoplastic resin.

23. In paragraph 22, A negative electrode for a lithium secondary battery, wherein the thermoplastic resin comprises at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), and combinations thereof.

24. In paragraph 16, The above negative electrode active material layer is, based on 100% by weight of the entire negative electrode active material layer, 80 to 99 wt% of the above negative active material; 0.1 to 10 wt% of the above-mentioned conductive agent; and A negative electrode for a lithium secondary battery, comprising 0.1 to 10 wt% of the above binder.

25. In paragraph 16, A negative electrode for a lithium secondary battery, wherein the weight ratio of the above-mentioned conductive material and binder is 1 to 3:

1.

26. In paragraph 16, The above negative active material layer is formed by solvent-free dry coating, The above negative electrode is a dry electrode, a negative electrode for a lithium secondary battery.

27. A step of obtaining a mixture by mixing a negative electrode active material, a conductive material, and a binder; A step of forming a negative electrode active material layer by coating the above mixture on a negative electrode current collector; and A step of manufacturing a negative electrode by rolling a negative electrode active material layer coated on the negative electrode current collector; A method for manufacturing a negative electrode for a lithium secondary battery, wherein the binder comprises a fluorine-free compound.

28. In paragraph 27, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the above mixture is mixed dry without a solvent.

29. In paragraph 27, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the above rolling is performed at a temperature range of 20 to 200°C.

30. Bipolar; A negative electrode for a lithium secondary battery according to Article 13; and A lithium secondary battery, comprising an electrolyte layer interposed between the positive electrode and the negative electrode.

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