Lithium secondary battery electrode comprising asymmetric buffer layer

Abstract

One embodiment of the present invention provides a lithium secondary battery electrode comprising a current collector, and an electrode active material layer provided on the current collector, wherein, when a particle size distribution is measured on the upper side of the electrode active material layer, less than 24% of fractured particles having a particle size of less than 40% of the average particle size of electrode active material particles are present. One embodiment of the present invention provides a method for manufacturing a lithium secondary battery electrode and a device for manufacturing a lithium secondary battery electrode by using same, the method comprising the steps of: preparing a current collector; forming an electrode active material layer on the current collector so as to obtain a laminated electrode body; and rolling the electrode active material layer, wherein the rolling allows the laminated electrode body to be passed between a first rolling roller and a second rolling roller, and is performed so that at least a portion of the surface of the first rolling roller or the second rolling roller is coated with a buffer material, and the buffer material makes contact with the electrode active material layer.

Description

Lithium secondary battery electrode including an asymmetric buffer layer

[0001] The present invention relates to a lithium secondary battery electrode and a method for manufacturing the same, and more particularly, to a lithium secondary battery electrode and a method for manufacturing the same, wherein the electrochemical performance is improved by uniformly pressing an electrode body using a rolling roller including a non-woven buffer layer. In addition, the present invention relates to a lithium secondary battery electrode and a method for manufacturing the same, wherein the electrochemical performance is improved by uniformly pressing an electrode body using a device having a buffer material coated on a portion of the surface of a rolling roller.

[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] With the recent rapid development of electronic devices and electric vehicles, demand for secondary batteries is increasing. In particular, the trend toward miniaturization and lightweighting of portable electronic devices is driving the need for high-energy-density secondary batteries capable of meeting these demands.

[0006] Furthermore, secondary batteries are also attracting attention as an energy source for electric and hybrid electric vehicles, which are being proposed as a solution to air pollution problems caused by existing gasoline and diesel vehicles that use fossil fuels. Consequently, the applications that utilize secondary batteries are diversifying significantly due to their advantages, and it is expected that secondary batteries will be applied to a wider range of fields and products in the future.

[0007] These secondary batteries are classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the composition of the electrodes and electrolyte. Among them, the use of lithium-ion polymer batteries is increasing due to their low possibility of electrolyte leakage and ease of manufacturing. In general, secondary batteries are classified into cylindrical batteries and prismatic batteries in which the electrode assembly is housed in a cylindrical or prismatic metal can depending on the shape of the battery case, and pouch-type batteries in which the electrode assembly is housed in a pouch-type case made of aluminum laminate sheet. The electrode assembly housed in the battery case is a power plant capable of charging and discharging, consisting of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode. It is classified into a jelly-roll type in which a separator is interposed between long sheets of positive and negative electrodes coated with an active material and wound up, and a stack type in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked while being interposed between separators.

[0008] These electrodes can be formed by a wet method in which an electrode slurry containing an electrode active material and a solvent is applied onto a current collector to form an electrode active material layer, and a dry method in which an active material, a binder, and a conductive material are mixed in a solid state without a solvent and applied onto a current collector, and then dried, calendared, and rolled as needed to form a final electrode.

[0009] In the case of the calendaring process and the rolling process, the surface of the active material layer is usually pressed. However, in particular, when the active material layer is pressed in the rolling process, the positive electrode active material particles are broken or crumbled, which results in the problem of the electrolyte not being smoothly impregnated when the electrolyte is injected in the subsequent battery assembly process.

[0010] In addition, from the perspective of a dry process, it is classified as having the advantage of being able to form a thick film by forming an active material layer thickly, but there was a problem that when the particles on the surface were broken or fractured during the rolling process, the electrolyte impregnation could not be smoothly performed, so the advantage of manufacturing a thick film electrode could not be utilized.

[0011] If the electrode is not sufficiently impregnated with electrolyte, a dead volume develops within the electrode. In the case of the positive electrode, lithium deintercalation from the active material occurs in areas not impregnated with electrolyte, leading to a charge imbalance in the electrode and low-voltage failure in the battery cell. In the case of the negative electrode, lithium precipitation occurs in areas not impregnated with electrolyte, compromising cell safety.

[0012] Therefore, there is an urgent need to develop a pressing method that can achieve uniform rolling over the entire thickness of the active material layer while allowing good electrolyte impregnation, and to develop a laminated electrode body including the active material layer uniformly pressed in this way.

[0013]

[0014] The present invention has been devised to solve the above-mentioned problem, and one embodiment of the present invention provides a lithium secondary battery electrode.

[0015] In addition, another embodiment of the present invention provides a method for manufacturing a lithium secondary battery electrode.

[0016] In addition, another embodiment of the present invention provides an apparatus for manufacturing a lithium secondary battery electrode.

[0017] 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.

[0018]

[0019] As a technical means for achieving the aforementioned technical task, one aspect of the present invention is,

[0020] A lithium secondary battery electrode is provided, comprising: a current collector; and an electrode active material layer provided on the current collector; and when measuring a particle size distribution on the upper surface of the electrode active material layer, the electrode active material layer is characterized in that less than 24% of broken particles having a particle size of less than 40% of the average particle size of electrode active material particles are present.

[0021] The electrode active material layer includes an upper portion of the active material that is up to 30% of the total thickness in the thickness direction from the top and a lower portion of the active material that is up to 30% of the total thickness in the thickness direction from the current collector, and the upper portion of the active material and the lower portion of the active material may each have different porosities.

[0022] The rolling uniformity defined by the following equation 1 may be greater than 1 and less than or equal to 2:

[0023] [Formula 1]

[0024] (Porosity of the lower part of the active material (%)) / (Porosity of the upper part of the active material (%))

[0025] The porosity of the upper portion of the above active material may be less than 10%.

[0026] The porosity of the lower portion of the above active material may be less than 20%.

[0027] The average particle size of the above electrode active material particles may be 3 to 20 μm.

[0028] The particle size of the above-mentioned broken particles may be 3㎛ or less.

[0029] The above electrode active material layer may be a material of the following general formula 1 or general formula 2:

[0030] [General Formula 1]

[0031] Li 1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0032] 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.

[0033] [General Formula 2]

[0034] Li j M1 k M2 m (PO 4-n )A n

[0035] 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.

[0036]

[0037] Another aspect of the present invention is:

[0038] A method for manufacturing a lithium secondary battery electrode is provided, comprising: a step of preparing a current collector; a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body; and a step of rolling the electrode active material layer; wherein the rolling is performed by passing the laminated electrode body between a soft rolling roller and a hard rolling roller having a higher surface hardness than the soft rolling roller, and wherein asymmetric rolling is performed so that the surface of the soft rolling roller comes into contact with the electrode active material layer.

[0039] The step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2 can proceed under the pressure of.

[0040] A buffer layer is introduced between the soft rolling roller and the electrode active material layer, and the buffer layer may be at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate.

[0041] The step of rolling the electrode active material layer may be characterized by showing a porosity of 20 to 55% compared to the porosity of the electrode active material layer before rolling.

[0042] The step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body can be carried out in a dry manner at room temperature.

[0043] The above-mentioned adhesive buffer layer may be characterized by being adhered to or detached from the surface of the soft rolling roller.

[0044]

[0045] Another aspect of the present invention is:

[0046] The present invention provides a device for manufacturing a lithium secondary battery electrode, comprising: a soft rolling roller positioned at the top; a hard rolling roller positioned below the soft rolling roller, having a surface hardness higher than that of the soft rolling roller and positioned to contact the soft rolling roller; and a conveying means for conveying a laminated electrode body while passing between the rolls of the soft rolling roller and the hard rolling roller; wherein the soft rolling roller is formed on a surface that contacts the laminated electrode body.

[0047] It may further include an unwinding roll for transporting the buffer layer material to be placed between the soft rolling roller and the electrode active material layer; and a rewinding roll for removing and winding the buffer layer material after the laminated electrode body passes between the rolls of the soft rolling roller and the hard rolling roller.

[0048]

[0049] As a technical means for achieving the aforementioned technical task, one aspect of the present invention is,

[0050] A method for manufacturing a lithium secondary battery electrode is provided, comprising: a step of preparing a current collector; a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body; and a step of rolling the electrode active material layer; wherein the rolling is performed by passing the laminated electrode body between a first rolling roller and a second rolling roller, and at least a portion of the surface of the first rolling roller or the second rolling roller is coated with a buffer material, and rolling is performed such that the buffer material comes into contact with the electrode active material layer.

[0051] The step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2 It may be progressing under pressure.

[0052] The above-mentioned buffer material may be at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate.

[0053] Through the step of rolling the electrode active material layer, a porosity of 10 to 25% compared to the porosity before rolling, measured on the upper surface of the electrode active material layer, can be exhibited.

[0054] The electrode active material layer includes an upper portion of the active material that is up to 30% of the total thickness in the thickness direction from the top and a lower portion of the active material that is up to 30% of the total thickness in the thickness direction from the current collector, and the upper portion of the active material and the lower portion of the active material may have different specific surface areas and different average pore sizes, respectively.

[0055] The specific surface area of ​​the upper part of the above active material is 400㎛ 2 It may be less than.

[0056] The specific surface area of ​​the lower part of the above active material is 700㎛ 2 It may be less than.

[0057] The average pore size of the upper portion of the above active material may be less than 4.5 μm.

[0058] The average pore size of the lower portion of the above active material may be less than 7 μm.

[0059] The upper and lower surface area uniformity defined by the following equation 2 may be greater than 1 and less than or equal to 2.

[0060] [Formula 2]

[0061] (Specific surface area of ​​the lower part of the active material (㎛) 2 )) / (Specific surface area of ​​the upper part of the active material (㎛) 2 ))

[0062] The upper and lower pore uniformity defined by the following equation 3 may be greater than 1 and less than or equal to 2.

[0063] [Formula 3]

[0064] (Average pore size (㎛) of the lower part of the active material) / (Average pore size (㎛) of the upper part of the active material)

[0065] The average particle size of the above electrode active material particles may be 3 to 20 μm.

[0066] The above electrode active material layer includes an electrode active material, a conductive material, and a binder, and the electrode active material may be a material of the following general formula 3 or general formula 4.

[0067] [General Formula 3]

[0068] Li1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0069] 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.

[0070] [General Formula 4]

[0071] Li j M1 k M2 m (PO 4-n )A n

[0072] 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.

[0073] A step of rolling the electrode active material layer; after this, the thickness of the electrode active material layer may be 150 μm or less.

[0074] The step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body may be performed in a dry manner at room temperature.

[0075]

[0076] Another aspect of the present invention is:

[0077] The present invention provides an apparatus for manufacturing a lithium secondary battery electrode, comprising: a first rolling roller positioned at the top; a second rolling roller positioned below the first rolling roller and positioned to contact the first rolling roller; and a conveying means for conveying a laminated electrode body while passing between the rolls of the first rolling roller and the second rolling roller; wherein the first rolling roller or the second rolling roller includes a buffer material layer provided on at least a portion of a surface, and the buffer material layer is positioned to contact the electrode active material layer during rolling.

[0078] The thickness of the above buffer material layer may be 10 to 200 μm.

[0079]

[0080] Another aspect of the present invention is:

[0081] A method for manufacturing a lithium secondary battery is provided, comprising: a step of preparing a positive electrode according to the above method; a step of preparing a negative electrode; and a step of stacking the positive electrode, a separator, and the negative electrode and injecting an electrolyte.

[0082]

[0083] Figure 1a is a schematic diagram of a lithium secondary battery electrode manufacturing device according to one embodiment of the present invention.

[0084] Figure 1b is a photograph showing a lithium secondary battery electrode manufacturing device according to one embodiment of the present invention.

[0085] Figure 2 shows the results of visual observation images and SEM images of the surface and cross-section of a laminated electrode body before rolling, a laminated electrode body of a comparative example, and a laminated electrode body of an embodiment, according to one embodiment of the present invention.

[0086] Figure 3 is an image of the upper surface of a laminated electrode body according to one embodiment of the present invention, measured using SEM, and then divided into four regions, A to D.

[0087] Figure 4 shows a particle size distribution diagram on the upper surface of a laminated electrode body according to one embodiment of the present invention.

[0088] FIGS. 5 to 7 are SEM images of cross-sections of electrodes before rolling, examples, and comparative examples, in a laminated electrode body manufactured according to one embodiment of the present invention.

[0089] Figure 8 is an image showing the extent to which liquid electrolyte has spread when the electrode body is observed with the naked eye 5 minutes after the electrolyte has been dropped, according to one implementation example of the present invention.

[0090] Figure 9 is an image showing the extent to which liquid electrolyte has spread when the electrode body is observed with the naked eye 3 hours after the electrolyte has been dropped, according to one implementation example of the present invention.

[0091] Figure 10 shows the results of measuring the volume resistance of the laminated electrode body of an example and a comparative example according to one implementation example of the present invention.

[0092] Figure 11 shows the capacity and voltage characteristics of a lithium secondary battery using an electrode according to one embodiment of the present invention.

[0093] Figure 12 is data confirming the capacity retention rate characteristics according to the lifespan of up to 30 cycles of a lithium secondary battery using an electrode according to an embodiment of the present invention.

[0094] Fig. 13 is a photograph showing a lithium secondary battery electrode manufacturing device according to one embodiment of the present invention.

[0095] Figure 14 shows the results of visual observation images and SEM images of the surface and cross-section of a laminated electrode body before rolling, a laminated electrode body of a comparative example, and a laminated electrode body of an embodiment, according to one embodiment of the present invention.

[0096] Figure 15 shows the upper surface of a pre-rolled laminated electrode body according to one embodiment of the present invention, measured using SEM.

[0097] Figure 16 shows the upper surface of a laminated electrode body after rolling according to a comparative example of one embodiment of the present invention, measured using SEM.

[0098] Figure 17 shows the upper surface of a laminated electrode body after rolling according to an embodiment of the present invention, measured using SEM.

[0099] Figures 18 to 20 are SEM images of cross-sections of electrodes before rolling, examples, and comparative examples of laminated electrode bodies manufactured according to one embodiment of the present invention.

[0100] Figure 21 shows the capacity and voltage characteristics of a lithium secondary battery using an electrode according to one embodiment of the present invention.

[0101] Figure 22 is data confirming the capacity retention rate characteristics according to the lifespan of up to 30 cycles of a lithium secondary battery using an electrode according to an embodiment of the present invention.

[0102]

[0103] <First aspect>

[0104] 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.

[0105]

[0106] Example 1: Preparation of a laminated electrode body for a lithium secondary battery cathode

[0107] 1) Preparation of positive electrode slurry

[0108] LiNi as a cathode active material 0.6 Co 0.2 Mn 0.2Using O2, Super-P (Super-P™Li, commercially available from Timcal) and graphite (KS-6, commercially available from Timcal) as positive electrode conductive materials and polyvinylidene fluoride (PVdF 1710, commercially available from Kureha) as positive electrode binder are added to NMP (N-methyl-2-pyrrolidone) as a dispersion medium so that the mass ratio of the positive electrode conductive material and positive electrode binder is 94 / 3 / 3. Thereafter, this mixture is kneaded to prepare a positive electrode mixture slurry.

[0109]

[0110] 2) Manufacturing of laminated electrode body

[0111] The formed cathode mixture slurry is applied to one side of a cathode current collector made of 18 ㎛ thick aluminum foil. The width of the application area is 100 mm, and the length is 200 mm. The typical cathode active material loading weight is 16 mg / cm 2 After that, the electrode is dried and 0.5 ton / cm 2 Calendaring is performed using the pressure of . The typical electrode density is 3.2 g / cm 3 am.

[0112] Afterwards, rolling was performed, and a rolling device as shown in Fig. 1 was configured to perform rolling. Specifically, the laminated electrode body was transferred to the nip between the rolls of the upper and lower rolling rollers and pressed. A polyimide film with a thickness of 0.07 mm was transferred to the nip while positioned on the buffer layer laminated electrode body so as to correspond to the surface in contact with the upper rolling roller, and 0.5 ton / cm 2 Rolling was performed using the pressure of .

[0113] Afterwards, an aluminum plate that serves as a positive electrode current collector tab is arc-welded to the end of the positive electrode.

[0114]

[0115] Comparative Example 1: Manufacturing of a laminated electrode body for a lithium secondary battery cathode

[0116] 1) Preparation of positive electrode slurry

[0117] The positive electrode slurry was prepared using the same method as in the example.

[0118] 2) Manufacturing of laminated electrode body

[0119] A laminated electrode body was manufactured in the same manner as in Example 1, except that the polyimide film was not used as a buffer layer in the rolling process.

[0120]

[0121] Experimental Example 1: Visual observation and scanning electron microscope (SEM) analysis results of laminated electrode bodies

[0122] Figure 2 shows the results of visual observation images and SEM images of the surface and cross-section of a laminated electrode body before rolling, a laminated electrode body of a comparative example, and a laminated electrode body of Example 1, according to one embodiment of the present invention.

[0123] Referring first to the photo of Fig. 2, when the general rolling of Comparative Example 1 was performed, it could be seen that the corner portion of the electrode was rolled up. This phenomenon indicates that when performing the roll-to-roll process, if tension is applied to the laminated electrode body, at least a portion of the electrode active material layer may break or it may be difficult to maintain the shape. On the other hand, in the case of the laminated electrode body of Example 1, it could be confirmed that the curling phenomenon at the corner portion was noticeably reduced even after the rolling process, and therefore, it can be seen as a result showing the excellent processability of the manufacturing method of the present invention.

[0124] Next, looking at the SEM surface results of the middle column of Fig. 2, in the case of the surface of the electrode active material layer of Comparative Example 1, it can be easily seen with the naked eye that the electrode active material particles on the upper surface were broken or crushed due to rolling. On the other hand, when looking at the upper surface of the electrode active material layer of the example, it can be seen that the surface particle shape retention rate was high.

[0125] Lastly, referring to the cross-sectional SEM data in the right column of Fig. 2, it can be confirmed that both the laminated electrode bodies of Example 1 and Comparative Example 1 were densified and thinned through rolling. However, in the case of Comparative Example 1, relatively many pieces of crushed or broken active material particles were observed in an area close to the surface of the active material layer, whereas in the case of Example 1, noticeably fewer broken particles were observed on the surface, and it can be confirmed that uniform rolling was performed in the thickness direction from the current collector.

[0126]

[0127] Experimental Example 2: Analysis of particle size distribution on the surface of the positive electrode active material layer

[0128] In order to confirm the characteristics of the rolled active material layer of the electrode according to one embodiment of the present invention, the degree of particle fracture was confirmed through the particle size distribution on the surface of the active material layer.

[0129] First, as shown in Fig. 3, the upper surface of the laminated electrode body was measured using SEM, and then the image was divided into four zones A to D, and the particle size distribution for each zone was measured. Fig. 4 shows the particle size distribution of the upper surface of the laminated electrode body according to one embodiment of the present invention, in which the first row is before rolling, the second row is the result for the laminated electrode body of Comparative Example 1, and the third row is the result for the laminated electrode body of Example 1, and the results for zones A to D are shown in the order of the columns. In particular, the minimum particle size and average particle size are shown in Table 1 below.

[0130] Based on the above results, the fracture rate (%) of the active material particles was calculated. Here, the “fracture rate” is the ratio of particles with a fracture size of 40% or less of the average particle size of the observed particles, expressed as a percentage of all particles. The results are shown in Table 2 below.

[0131]

[0132] Average particle size Zone A [㎛] Zone B [㎛] Zone C [㎛] Zone D [㎛] Average value [㎛] Before rolling 8.9 3 9.0 4 9.8 4 9.9 8 9.45 Comparative example 17.6 2 7.6 4 11.3 2 11.3 19.47 Example 18.0 5 8.0 2 9.1 0 8.6 8 8.46 Minimum particle size Zone A [㎛] Zone B [㎛] Zone C [㎛] Zone D [㎛] Average value [㎛] Before rolling 3.3 9 4.3 4 5.5 9 5.5 4 4.71 Comparative example 11.0 9 0.9 8 1.0 9 1.8 5 1.25 Example 11.4 9 1.7 0 2.0 1 3.0 3 2.0 6

[0133]

[0134] Zone A[%] Zone B[%] Zone C[%] Zone D[%] Avg. Breakage Rate[0 - 3 ㎛, %] Rolling 00000 Comparative Example 13040242429.5 Example 120128411

[0135]

[0136] First, referring to Table 1, in the case of Comparative Example 1, which performed a general rolling process, it can be confirmed that the average particle size became larger after rolling compared to before rolling. This is an unusual phenomenon in that it is a result after pressing. This can be judged to be because, in the general rolling process, the positive electrode active material particles were often broken or crumbled during the pressing process with a relatively rigid roll, and also, the particle size measured on the surface was observed to be larger when pressed. On the other hand, in the case of the active material layer of Example 1, it was confirmed that it was consistent with the change in the characteristics of the particles that could appear when pressing according to technical common sense, and it was confirmed that the breakage and crumbling of the particles were minimized.

[0137] Referring again to the data related to the minimum particles in Table 1, in the case of Comparative Example 1, the minimum particle size was less than 27% of the value before rolling, which can be judged to be the observation of particles that were finely broken by rolling. On the other hand, in the case of Example 1, it can be confirmed that the minimum particle size was measured to be at a level that was not excessively small, at an average of 43.7% of the value before rolling.

[0138] Next, referring to Table 2, the proportion of particles smaller than 3㎛, which is smaller than the minimum particle size of the active material layer before rolling, in the entire particle size distribution is shown. In the case of Comparative Example 1, it can be confirmed that the proportion is more than 24% overall, so it can be interpreted that about 1 / 4 of the entire particles are broken by rolling.

[0139] On the other hand, in the case of the laminated electrode body of Example 1, the fracture rate is less than 24%, more preferably less than 20%, so it can be confirmed that the fracture is small.

[0140]

[0141] Experimental Example 3: Measurement results of cross-sectional porosity of laminated electrode body

[0142] FIGS. 5 to 7 are SEM images of cross-sections of the electrode before rolling, Example 1, and Comparative Example 1 electrodes manufactured according to one embodiment of the present invention.

[0143] By the rolling process, it is easy to predict that the degree of pressurization between the top (TOP) where direct pressurization is performed and the bottom (Bottom) close to the current collector will be different, and this was confirmed by measuring the porosity. Specifically, the top of the active material layer is defined as up to 30% of the total thickness in the thickness direction from the top of the electrode active material layer, and the bottom of the active material is defined as up to 30% of the total thickness in the thickness direction from the current collector, and the porosity was measured. For reference, the total thickness of the active material layer is 50 to 70 ㎛, and the thickness of the top is designated as 20 ㎛ and the thickness of the bottom is designated as 20 ㎛.

[0144] The porosity of the upper and lower parts was measured and shown in Table 3 below. The change in porosity is expressed as a percentage by dividing the porosity after rolling by the porosity before rolling.

[0145]

[0146] Electrode porosity before rolling (%) Comparative Example 1 Porosity (%) Example 1 Porosity (%) Comparative Example 1 Porosity change (%) Example 1 Porosity change (%) Top 16.4 111.5 27.9 729.8 0 51.43 Bottom 30.6 125.9 115.7 715.3 548.48 Rolling uniformity (Porosity of lower part of active material (%)) / (Porosity of upper part of active material (%)) 1.8 72.2 51.98

[0147]

[0148] Referring to Table 3, it can be seen that the porosity of the upper part of the active material of Example 1 of the present invention has a value of less than 10%, and the porosity of the lower part of the active material has a value of less than 20%, which can be interpreted as meaning that rolling was performed uniformly with the porosity reduced to about 50% regardless of the upper or lower part. On the other hand, in the case of Comparative Example 1, the porosity was reduced to only less than 30%, and the degree of change in the porosity of the lower part was significantly lower than the degree of change in the porosity of the upper part, so it can be confirmed that the rolling itself was performed unevenly over the entire thickness.

[0149] In addition, in terms of the rolling uniformity defined in this application, the value of the porosity (%) of the lower part / porosity (%) of the upper part after rolling was 2 or less, and there was almost no change in the value compared to before rolling, so it can be confirmed that rolling was performed uniformly over the entire thickness of the upper and lower parts.

[0150]

[0151] Experimental Example 4: Analysis of Electrolyte Impregnation Characteristics

[0152] The electrolyte impregnation characteristics of a laminated electrode assembly manufactured according to one embodiment of the present disclosure were examined. This can serve as an indicator of the uniformity of the rolling process. Furthermore, when manufacturing lithium secondary batteries using the electrodes of the present disclosure, the electrolyte impregnation process time can be shortened or the amount of electrolyte used can be minimized. Therefore, this experimental example demonstrates the effectiveness of the method in terms of process efficiency and energy efficiency during the manufacturing process.

[0153] Circular laminated electrode bodies with a diameter of 14 mm and a thickness of 0.7 mm were prepared. 1 to 2 drops of electrolyte (1 M lithium hexafluorophosphate in ethylene carbonate / diethylene carbonate (3 / 7, v / v)) were dropped onto the surface of the laminated electrode bodies before the rolling process and the electrode bodies of Comparative Example 1 and Example 1, and the spread of the electrolyte into the electrodes was compared.

[0154] Figure 8 is an image showing the extent to which the liquid electrolyte has spread when the electrode body is observed with the naked eye 5 minutes after the electrolyte has been dropped, and Figure 9 is an image showing the extent to which the liquid electrolyte has spread when the electrode body is observed with the naked eye 3 hours after the electrolyte has been dropped.

[0155] Referring to Fig. 8, in the case of the electrode body before rolling, since the porosity of the surface and interior was maintained high, it could be confirmed that the electrolyte was spread over the entire area in less than 5 minutes, and in the case of Comparative Example 1 in which a general rolling process was applied, it could be confirmed that wettability occurred only in some areas centered around the area where the electrolyte was dropped on the electrode body. This can be judged to be because the space for the electrolyte to be impregnated on the surface of the electrode active material layer was reduced by the calendaring process during general rolling, making impregnation difficult. On the other hand, in the case of the electrode body of Example 1, it could be confirmed that the electrolyte was spread over the entire area in less than 5 minutes, like the electrode body before rolling. In other words, it can be seen that the electrode of the present invention has excellent electrolyte wettability from the initial stage.

[0156] Next, referring to Fig. 9, in the case of the electrode body before rolling, since the porosity of the surface and interior was maintained high, it could be confirmed that the entire area and thickness were maintained wet with the electrolyte after a sufficient time of about 3 hours, and in the case of Comparative Example 1 in which a general rolling process was applied, the state of being wet with the electrolyte was maintained only in some areas centered on the part where the electrolyte was dropped on the electrode body, and it could be confirmed that the electrode was not impregnated with the electrolyte even for a long time. This can be judged to be because the space for the electrolyte to be impregnated on the surface of the electrode active material layer during general rolling was reduced by the calendaring process, so it can be judged that it is difficult for impregnation to occur from the surface to the interior. On the other hand, in the case of the electrode body of Example 1, it could be confirmed that the electrolyte was wetted throughout the entire area even after 3 hours. In other words, it can be seen that the electrode of the present application maintains electrolyte wettability even after a long time.

[0157]

[0158] Experimental Example 5: Electrochemical Characteristics Analysis

[0159] 1) Volume resistance measurement

[0160] For the electrode body before rolling, the electrode body of Comparative Example 1 to which a general rolling process was applied, and the electrode body of Example 1, the volume resistance was repeatedly measured using the equipment of a Hioki electrode resistance measuring instrument (RM9004) as a method of measuring electrode resistance.

[0161] The volume resistance results are shown in Table 4 and Fig. 10 below.

[0162]

[0163] Sample complex volume resistivity (ohm / cm 3 )1st 2nd 3rd Standard deviation Rolling before 6.656.926.730.139 Comparative example 13.913.643.850.142 Example 13.473.463.370.055

[0164]

[0165] Referring to Table 4 and Fig. 10, the volume resistance of the electrodes after rolling all showed a tendency to decrease, but compared to Comparative Example 1, the electrode body of Example 1 showed an additional 2.60% to 7.13% decrease in volume resistance. This indicates that when rolling was performed with a buffer layer applied as in the Example, the deviation in resistance within the electrode decreased due to the uniform pressing characteristics of the upper and lower parts of the active material layer.

[0166]

[0167] 2) Initial efficiency and irreversible capacity measurement results

[0168] A lithium secondary battery is manufactured using the positive electrode according to Example 1 of the present invention and the positive electrode of Comparative Example 1.

[0169] The cathode used was a commercially available lithium metal cathode (200 μm). The non-aqueous electrolyte was obtained by dissolving lithium hexafluorophosphate (LiPF6) salt at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 3:7.

[0170] A positive electrode, a negative electrode, and a separator sheet made of a 25 μm thick microporous polymer film (Celgard®2400, commercially available from Celgard) were prepared. Then, the prepared electrodes and separator sheets were assembled into a 2032 coin cell in a glove box (O2 < 0.5 ppm, H2O < 0.5 ppm) to manufacture a coin-type lithium secondary battery.

[0171] Figure 11 shows the capacity and voltage characteristics using an electrode according to one embodiment of the present invention, and Figure 12 shows data confirming the capacity retention characteristics according to the lifespan up to 30 cycles. The results are shown in Table 5 below.

[0172]

[0173] Sample Name Capacity Retention Rate ICE [%] 0.1C Initial Cycle Test Capacity [1 st Cycle, mAh g -1 ]Comparative Example 87.4161.2Embodiment 88.1165.4

[0174]

[0175] Referring to FIGS. 11 and 12 and Table 5, it was confirmed that in the case of the electrode that went through the rolling process of Example 1, the initial irreversible capacity increased by about 3% compared to Comparative Example 1 through effective pressurization of the entire volume of the electrode, and the capacity retention rate according to the progression of the cycle was also better.

[0176]

[0177] <Second aspect>

[0178] 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.

[0179]

[0180] Example 2: Preparation of a laminated electrode body for a lithium secondary battery cathode

[0181] 1) Preparation of positive electrode slurry

[0182] LiNi as a cathode active material 0.6 Co 0.2 Mn 0.2 Using O2, Super-P (Super-P™Li, commercially available from Timcal) and graphite (KS-6, commercially available from Timcal) as positive electrode conductive materials and polyvinylidene fluoride (PVdF 1710, commercially available from Kureha) as positive electrode binder are added to NMP (N-methyl-2-pyrrolidone) as a dispersion medium so that the mass ratio of the positive electrode conductive material and positive electrode binder is 94 / 3 / 3. Thereafter, this mixture is kneaded to prepare a positive electrode mixture slurry.

[0183]

[0184] 2) Manufacturing of laminated electrode body

[0185] The formed cathode mixture slurry is applied to one side of a cathode current collector made of 18 ㎛ thick aluminum foil. The width of the application area is 100 mm, and the length is 200 mm. The typical cathode active material loading weight is 16 mg / cm 2 After that, the electrode is dried and 0.5 ton / cm 2 Calendaring is performed using the pressure of . The typical electrode density is 3.2 g / cm 3 am.

[0186] Afterwards, rolling was performed, and a rolling device as shown in Fig. 13 was configured to perform rolling. Specifically, the laminated electrode body was transferred to the nip between the rolls of the upper and lower rolling rollers and pressed. A polyimide buffer material layer with a thickness of 0.07 mm was coated on the surface of the upper rolling roller to correspond to the surface in contact with the upper rolling roller, and was transferred to the nip while positioned on the laminated electrode body to apply pressure of 0.5 ton / cm. 2 Rolling was performed using the pressure of .

[0187] Afterwards, an aluminum plate that serves as a positive electrode current collector tab is arc-welded to the end of the positive electrode.

[0188]

[0189] Comparative Example 2: Manufacturing of a laminated electrode body for a lithium secondary battery cathode

[0190] 1) Preparation of positive electrode slurry

[0191] The positive electrode slurry was prepared using the same method as in the example.

[0192] 2) Manufacturing of laminated electrode body

[0193] A laminated electrode body was manufactured in the same manner as in Example 2, except that a buffer material layer (polyimide) was not coated on the surface of the upper soft roller in the rolling process.

[0194]

[0195] Experimental Example 6: Visual observation and scanning electron microscope (SEM) analysis results of laminated electrode bodies

[0196] Figure 14 shows the results of visual observation images and SEM images of the surface and cross-section of a laminated electrode body before rolling, a laminated electrode body of Comparative Example 2, and a laminated electrode body of Example 2, according to one embodiment of the present invention.

[0197] Referring first to the photo of Fig. 14, when the general rolling of Comparative Example 2 was performed, it could be seen that the corner portion of the electrode was rolled up. This phenomenon indicates that when performing the roll-to-roll process, if tension is applied to the laminated electrode body, at least a portion of the electrode active material layer may break or it may be difficult to maintain the shape. On the other hand, in the case of the laminated electrode body of Example 2, it could be confirmed that the curling phenomenon at the corner portion was noticeably reduced even after the rolling process, and therefore, it can be seen as a result showing the excellent processability of the manufacturing method of the present invention.

[0198] Next, looking at the SEM surface results of the middle column of Fig. 14, in the case of the surface of the electrode active material layer of Comparative Example 2, it can be easily seen with the naked eye that the electrode active material particles on the upper surface were broken or crushed due to rolling. On the other hand, when looking at the upper surface of the electrode active material layer of Example 2, it can be seen that the surface particle shape retention rate was high.

[0199] Lastly, referring to the cross-sectional SEM data in the right column of Fig. 14, it can be confirmed that both the laminated electrode bodies of Example 2 and Comparative Example 2 were densified and thinned through rolling. However, in the case of the Comparative Example, relatively many pieces of crushed or broken active material particles were observed in an area close to the surface of the active material layer, whereas in the case of Example 2, noticeably fewer broken particles were observed on the surface, and it can be confirmed that uniform rolling was performed in the thickness direction from the current collector.

[0200]

[0201] Experimental Example 7: Porosity measurement results on the upper surface of the positive electrode active material layer

[0202] FIG. 15 is a SEM measurement of the upper surface of a laminated electrode body before rolling according to one embodiment of the present invention, FIG. 16 is a SEM measurement of the upper surface of a laminated electrode body after rolling of Comparative Example 2 according to one embodiment of the present invention, and FIG. 17 is a SEM measurement of the upper surface of a laminated electrode body after rolling of Example 2 according to one embodiment of the present invention.

[0203] In addition, the porosity of the upper surface was measured and shown in Table 6 below.

[0204]

[0205] Porosity (%) Electrode before rolling 44.58 Comparative example 2 (electrode applied with general rolling roll) 12.49 Example 2 (rolling roller applied with buffer material) 10.80

[0206]

[0207] Referring to Table 6, it was confirmed that all electrodes after rolling had a porosity of less than 15% when observed from the top surface. However, when examining the rate of change in porosity compared to before each rolling, it was confirmed that Comparative Example 2 had a decrease in porosity of approximately 72% (i.e., the porosity decreased to about 28%), and Example 2 had a decrease in porosity of approximately 76% (i.e., the porosity changed to less than 25%).

[0208] That is, it was confirmed that the porosity of the upper surface was at a similar level to that of rolling using a general rolling roller, but it was confirmed that the phenomenon of particle pressing, fracture, and deformation due to rolling on the surface was suppressed.

[0209]

[0210] Experimental Example 8: Measurement results of cross-sectional surface area and average pore size of laminated electrode body

[0211] Figures 18 to 20 are SEM images of cross-sections of the electrode before rolling, Example 2, and Comparative Example 2, in a laminated electrode body manufactured according to one embodiment of the present invention.

[0212] By the rolling process, it is easy to predict that the degree of pressurization between the top (TOP) where direct pressurization is performed and the bottom (Bottom) close to the current collector will be different, and this was confirmed by measuring the specific surface area and the average pore size. Specifically, the top of the active material layer is defined as up to 30% of the total thickness in the thickness direction from the top of the electrode active material layer, and the bottom of the active material is defined as up to 30% of the total thickness in the thickness direction from the current collector, and the specific surface area and the average pore size were measured. For reference, the total thickness of the active material layer is 50 to 70 μm, and the thickness of the top is designated as 20 μm and the thickness of the bottom is designated as 20 μm.

[0213] The specific surface area and average pore size of the upper and lower parts were measured and presented in Tables 7 and 8 below. The change in specific surface area and average pore size was calculated by subtracting the specific surface area and average pore size after rolling from the specific surface area and average pore size before rolling and dividing the result by the specific surface area and average pore size before rolling, and expressed as a percentage.

[0214]

[0215] Electrode surface area before rolling (㎛) 2 ) Comparative Example 2 Surface area (㎛) 2 )Example 2 Surface area (㎛) 2 ) Comparative Example 2 Change in specific surface area (%) Example 2 Change in specific surface area (%) Upper part 70 35 78 36 7 17.78 47.80 Lower part 15 40 13 15 6 6 5 14.6 15 6.82 Uniformity of specific surface area of ​​upper and lower parts (specific surface area of ​​lower part of active material (㎛) 2 )) / (Specific surface area of ​​the upper part of the active material (㎛) 2 ))2.192.281.81

[0216]

[0217] Rolling Average pore size (㎛) Comparative Example 2 Average pore size ((㎛) Example 2 Average pore size (㎛) Comparative Example 2 Average pore size change (%) Example 2 Average pore size change (%) Upper part 6.76 5.19 4.03 23.22 40.38 Lower part 17.9 110.5 26.79 41.26 62.09 Upper and lower pore uniformity (Average pore size of the lower part of the active material ( 2 )) / (Average pore size (㎛) of the top of the active material)2.652.031.68

[0218]

[0219] Referring to Table 7, the specific surface area of ​​the upper part of the active material of Example 2 of the present invention is 400 μm. 2 It shows a value below, and the specific surface area of ​​the lower part of the active material is 700㎛. 2It can be seen that the values ​​are below. This can be seen as a relatively small difference in the specific surface area of ​​the upper and lower parts, and it can be interpreted that the rolling was performed uniformly. On the other hand, in the case of Comparative Example 2, it can be seen that the specific surface area of ​​the lower part is more than twice as large as that of the upper part, so it can be confirmed that the rolling was performed mainly at the upper part, and compared to before rolling, the specific surface area change rate of the upper part is less than 18%, and the lower part is less than 15%, so it can be confirmed that the degree of rolling was not sufficient.

[0220] Referring to Table 4, it can be seen that the average pore size of the upper part of the active material of Example 2 of the present invention is less than 4.5㎛, and the average pore size of the lower part of the active material is less than 6.8㎛. This can be seen as a relatively small difference in the pore sizes of the upper part and the lower part, and can be interpreted as meaning that the rolling was performed uniformly. On the other hand, in the case of Comparative Example 2, it can be seen that the pore size of the lower part is about twice as large as the pore size of the upper part, so it can be confirmed that the rolling was performed mainly at the upper part, and compared to before rolling, the pore size change rate of the upper part was less than 24%, and the lower part was less than 42%, so it can be confirmed that the degree of rolling was not sufficient.

[0221] In addition, in terms of the upper and lower surface area uniformity and upper and lower pore uniformity defined in this application, the lower surface area (㎛) is 2 ) / Specific surface area of ​​the upper part (㎛) 2 ) and the average pore size (㎛) of the lower part / average pore size (㎛) of the upper part are 2 or less, and since there is almost no difference in the specific surface area and average pore size values ​​of the upper part and the lower part, it can be confirmed that rolling is performed uniformly over the entire thickness of the upper part and the lower part.

[0222]

[0223] Experimental Example 9: Electrochemical Characteristics Analysis

[0224] Initial efficiency and irreversible capacity measurement results

[0225] A lithium secondary battery is manufactured using the positive electrode according to Example 2 of the present invention and the positive electrode of Comparative Example 2.

[0226] The cathode used was a commercially available lithium metal cathode (200 μm). The non-aqueous electrolyte was obtained by dissolving lithium hexafluorophosphate (LiPF6) salt at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 3:7.

[0227] A positive electrode, a negative electrode, and a separator sheet made of a 25 μm thick microporous polymer film (Celgard®2400, commercially available from Celgard) were prepared. Then, the prepared electrodes and separator sheets were assembled into a 2032 coin cell in a glove box (O2 < 0.5 ppm, H2O < 0.5 ppm) to manufacture a coin-type lithium secondary battery.

[0228] Figure 21 shows the capacity and voltage characteristics using an electrode according to one embodiment of the present invention, and Figure 22 shows data confirming the capacity retention characteristics according to the lifespan up to 30 cycles. The results are shown in Table 9 below.

[0229]

[0230] Sample Name Capacity Retention Rate ICE [%] 0.1C Initial Cycle Test Capacity [1 st Cycle, mAh g -1 ]Comparative Example 287.4161.2Embodiment 288.3167.9

[0231]

[0232] Referring to FIGS. 21 and 22 and Table 9, in the case of the electrode that went through the rolling process of Example 2, the initial irreversible capacity increased by about 4% or more compared to Comparative Example 2 through effective pressurization of the entire volume of the electrode, and it was confirmed that the capacity retention rate according to the progression of the cycle was also better.

[0233]

[0234] 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.

[0235] 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.

[0236]

[0237] Hereinafter, the present invention will be described in more detail. However, the present invention may be implemented in various different forms, and the present invention is not limited to the embodiments described herein, but is defined only by the claims set forth below.

[0238] 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.

[0239] Throughout the specification, when a part is said to be "connected (connected, contacted, joined)" 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 mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0240] The terminology used in this specification 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.

[0241]

[0242] <First aspect>

[0243] The first aspect of this article is,

[0244] A lithium secondary battery electrode is provided, comprising: a current collector; and an electrode active material layer provided on the current collector; and when measuring a particle size distribution on the upper surface of the electrode active material layer, the electrode active material layer is characterized in that less than 24% of the particles have a particle size of less than 40% of the average particle size of the electrode active material particles.

[0245] Hereinafter, a lithium secondary battery electrode according to the first aspect of the present invention will be described in detail.

[0246] In one embodiment of the present invention, the current collector may be a conductive metal or non-metal material, and may preferably be a foil of copper or a copper alloy, but this is only a non-limiting example.

[0247] In one embodiment of the present invention, the electrode may include an electrode active material layer and / or a current collector. The electrode active material layer may include an electrode active material, an electrode binder, and / or a conductive material. The electrode active material layer may be formed on one or both sides of the current collector. Preferably, when performing a dry process, the active material layer may be formed on one side of the current collector.

[0248] In the case of a lithium secondary battery electrode according to an embodiment of the present invention, an active material layer is laminated in the form of a sheet on a current collector, and the fracture or crumbling of particles is controlled on the upper surface (surface) where rolling is performed, thereby obtaining unique characteristics. These characteristics are described below.

[0249] In the lithium secondary battery electrode according to one embodiment of the present invention, the active material particles that have “broken” mean particles that have a particle size of less than 50%, preferably less than 40%, based on the average particle size value due to the active material particles used in electrode manufacturing being broken by rolling (pressure), and if the proportion of such particles is high in the particle size distribution, it can be seen that a relatively large number of particles have broken.

[0250] In one embodiment of the present invention, when measuring the particle size distribution on the upper surface (surface) of the electrode active material layer, the broken particles having a particle size of less than 40% of the average particle size of the electrode active material particles may be present at less than 24%, preferably 23% or less, more preferably 22% or less, and even more preferably 20% or less. If the above range is exceeded, the fraction of broken particles may become excessively high, and the impregnation of the electrolyte may not occur properly in the subsequent battery manufacturing process. Here, the “upper surface” of the electrode active material layer where the particle size distribution is observed may mean a space viewed from above, having a depth equal to one or more particle sizes in the thickness direction from the upper end.

[0251] In one embodiment of the present invention, the average particle size of the electrode active material particles may be a non-limiting average particle size of active material particles commonly used in the art, for example, 1 to 50 μm, preferably 2 to 30 μm, and more preferably 3 to 20 μm. In addition, the minimum particle size of the particles measured on the upper surface of the electrode active material layer may be 5 μm or less, preferably 3 μm or less. A small minimum particle size of the active material particles does not necessarily mean that the particles are “broken”, and as described above, whether or not they are broken can be confirmed by the relative relationship with the average particle size of the particles introduced during manufacturing. In one embodiment of the present invention, the particle size of the broken particles may be 3 μm or less.

[0252] In one embodiment of the present invention, the electrode active material layer may include an upper portion of the active material that extends from the top to 30% of the total thickness in the thickness direction and a lower portion of the active material that extends from the current collector to 30% of the total thickness in the thickness direction. By classifying the upper portion of the active material and the lower portion of the active material and calculating the porosity, it is possible to determine whether rolling is performed uniformly throughout the electrode active material layer.

[0253] In one embodiment of the present invention, the thickness of the electrode active material layer can be freely laminated in consideration of the capacity to be implemented when manufacturing a lithium secondary battery. However, when forming an electrode through a typical wet process, it is impossible to form a thick thickness in a single lamination process, so it can be seen that there is a limit to the thickness. In the case of a dry process for forming an active material layer by a dry method, it can be seen that a thicker film can be formed. From this perspective, the electrode active material layer may have a thickness of 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, or 180 μm or less. In addition, the upper part of the active material may have a thickness of 150 µm or less, 120 µm or less, 90 µm or less, 60 µm or less, or 30 µm or less in the thickness direction from the upper part of the active material layer, and the lower part of the active material may have a thickness of 150 µm or less, 120 µm or less, 90 µm or less, 60 µm or less, or 30 µm or less in the thickness direction from the current collector.

[0254] In one embodiment of the present invention, the upper part of the active material and the lower part of the active material may have the same, similar, or different porosities depending on the uniformity of the rolling. Here, the porosity can be measured by observing the cross-section of the active material layer, dividing it into sections by thickness, and then measuring it, and the uniformity of the rolling process can be measured by this method. If neither the calendaring process nor the rolling process is performed, the porosities of the upper part of the active material and the lower part may be relatively similar. However, if the calendaring process or the rolling process is performed, the porosity of the upper part of the active material may be smaller than the porosity of the lower part of the active material.

[0255] In one embodiment of the present disclosure, the porosity of the upper part of the active material may be 40% or less, 35% or less, or 32% or less if the rolling and calendaring processes are not performed, and the porosity may be 25% or less, 23% or less, 20% or less, or 18% or less before rolling after the calendaring process. The porosity of the upper part of the active material of the electrode active material layer according to one embodiment of the present disclosure refers to a value measured after the rolling process, and may be 11% or less, preferably less than 10%. If the porosity of the upper part of the active material exceeds 10% even after the rolling process, it is difficult to view the rolling as being performed efficiently.

[0256] In one embodiment of the present disclosure, the porosity of the lower part of the active material may be 40% or less, 35% or less, or 32% or less if the rolling and calendaring processes are not performed, and may be 32% or less, or 31% or less, before rolling after the calendaring process. The porosity of the lower part of the active material of the electrode active material layer according to one embodiment of the present disclosure refers to a value measured after the rolling process, and may be 25% or less, less than 20%, or preferably less than 18%. If the porosity of the lower part of the active material exceeds 25% even after the rolling process, it is difficult to regard uniform rolling as having been performed, and therefore, the degree of impregnation of the electrolyte in the subsequent process will be significantly different from that of the upper part.

[0257] In one embodiment of the present invention, the rolling uniformity defined by the following equation 1 may be greater than 1 and less than or equal to 2.

[0258] [Formula 1]

[0259] (Porosity of the lower part of the active material (%)) / (Porosity of the upper part of the active material (%))

[0260] The above “rolling uniformity” is a measure of how uniformly rolling is performed in the thickness direction from the surface of the electrode active material layer to the current collector. If the active material layer is properly and uniformly rolled, low volume resistance, etc. can be formed in all areas of the upper and lower parts of the active material. If the rolling uniformity is 1, it means that no calendaring or rolling process was performed at all, and if the rolling uniformity is less than 1, it means that the rolling of the upper part was pressed more than the lower part, and therefore, it may be different from the concept of the laminated electrode body according to one embodiment of the present application. On the other hand, if the rolling uniformity exceeds 2, it means that the rolling of the upper and lower parts of the active material is uneven, and in particular, the effect of rolling is concentrated only on the upper part, and therefore, when manufacturing a lithium secondary battery, it may cause the adverse effect of increasing resistance.

[0261] In one embodiment of the present invention, the post-rolling porosity relative to the pre-rolling porosity of the upper or lower portion of the active material may range from 20 to 65%, preferably from 25 to 55%. Exceeding the above-mentioned range may indicate that the rolling has not been sufficiently performed, which may be detrimental to maximizing energy density.

[0262] In one embodiment of the present invention, the electrode active material layer may be composed of a material of the following general formula 1 or general formula 2:

[0263] [General Formula 1]

[0264] Li 1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0265] 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.

[0266] [General Formula 2]

[0267] Li j M1 k M2 m (PO 4-n )A n

[0268] 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.

[0269]

[0270] The second aspect of the original text is,

[0271] A method for manufacturing a lithium secondary battery electrode is provided, comprising: a step of preparing a current collector; a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body; and a step of rolling the electrode active material layer; wherein the rolling is performed by passing the laminated electrode body between a soft rolling roller and a hard rolling roller having a higher surface hardness than the soft rolling roller, and wherein asymmetric rolling is performed so that the surface of the soft rolling roller comes into contact with the electrode active material layer.

[0272]

[0273] 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.

[0274]

[0275] Hereinafter, a method for manufacturing a lithium secondary battery electrode according to the second aspect of the present invention will be described in detail.

[0276]

[0277] First, in one embodiment of the present invention, a step of preparing a collector may be included. Specific details regarding the collector are described in the first aspect of the present invention, and thus, detailed descriptions are omitted.

[0278] Next, in one embodiment of the present invention, a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body may be included.

[0279] In one embodiment of the present invention, the electrode active material layer may include electrode active material particles, a conductive material, and a binder.

[0280] In one embodiment of the present invention, the conductive material is not particularly limited as long as it is a conductive material. Examples of such conductive materials include carbonaceous materials; metals; and conductive ceramics. Examples of the carbonaceous material include graphite and carbon black. Examples of carbon black include furnace black, acetylene black, and Ketjen black. Among these, carbonaceous materials are preferable from the viewpoint of conductivity and processability. Among these, acetylene black and Ketjen black are preferable. Examples of the conductive material shape include powder, sheet, and fiber. The conductive material may typically be added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material.

[0281] In one embodiment of the present invention, the binder may be, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used. The above binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and can be added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material.

[0282] In one embodiment of the present invention, an electrode slurry may be prepared as a precursor of an electrode active material layer, and this may be prepared by dissolving an electrode active material, a conductive material, a binder, etc. in a solvent. There is no particular limitation on the type of the solvent as long as it can disperse the electrode active material, etc., and both aqueous solvents and non-aqueous solvents may be used. For example, the solvent may be a solvent commonly used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these may be used alone or as a mixture of two or more. The amount of the solvent used is not particularly limited as long as the slurry can be adjusted to have an appropriate viscosity in consideration of the coating thickness of the slurry, manufacturing yield, workability, etc. The solvent may be removed during the drying process.

[0283] In addition, in another embodiment of the present invention, the step of forming an electrode active material layer on the current collector to obtain a laminated electrode body can be performed by a dry process. Without a separate solvent, the conductive material, the active material, and the binder are all provided in a powder or solid state. In this case, a primer coating layer may be formed in advance so that the powder-phase electrode active material mixture forms a layer on the current collector, if necessary. In the case of such a dry process, it can be performed at room temperature, but if necessary, it can be performed by increasing the temperature to a relatively high temperature from the viewpoint of inducing fibrillation or fiberization of the binder.

[0284] Next, in one embodiment of the present invention, a step of rolling the electrode active material layer may be included. Fig. 1a is a schematic diagram of a lithium secondary battery electrode manufacturing apparatus according to one embodiment of the present invention. As shown in Fig. 1a, in the lithium secondary battery manufacturing method according to one embodiment of the present invention, the rolling process is performed by asymmetric rolling using an asymmetric buffer layer. Here, “asymmetric” may mean rolling by applying the buffer layer only to one side that comes into contact with the electrode active material layer. Referring to the right side of Fig. 1a, according to the experimental results according to one embodiment of the present invention, in the case of rolling with the buffer layer applied to both sides, it could be seen that the current collector or electrode was crumpled or its shape was not maintained (upper right photo), whereas in the case of applying the asymmetric buffer layer, it could be confirmed that the pressing was performed uniformly and with an appropriate strength, and the shape of the electrode was well maintained.

[0285] In one embodiment of the present invention, the rolling may be performed by applying pressure between a relatively soft material and a relatively hard material. When utilizing a press roll method, the rolling may be performed by passing the laminated electrode body between a soft rolling roller and a hard rolling roller. In addition, the rolling may be performed using a flat material such as a soft rolling roller and a hard material conveyor belt. Preferably, the rolling may be performed in a form in which a buffer layer is introduced between the soft rolling roller and the electrode active material layer.

[0286] In one embodiment of the present invention, the surface of the soft rolling roller that comes into contact with the electrode active material layer may have a buffer layer formed thereon. The buffer layer may have an adhesive layer formed on the surface facing the soft rolling roller in order to temporarily or permanently adhere to the surface of the soft rolling roller. However, if the buffer layer can be supplied in accordance with the rotation speed when in contact with the surface of the soft rolling roller, the adhesive layer may not be present on both sides of the buffer layer. However, in order to avoid causing the adverse effect of unnecessarily detaching active material particles on the surface (upper surface) of the active material layer, the surface of the buffer layer that comes into contact with the electrode active material layer may essentially have to be free of adhesive components.

[0287] In one embodiment of the present invention, the buffer layer may be at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate; however, other materials may also be used without limitation as long as they satisfy the surface characteristics of the electrode according to the first aspect of the present invention described above.

[0288] In one embodiment of the present invention, the step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2It can be carried out under pressure. If it is below the above-mentioned range, the densification of the active material layer does not occur, so the energy density does not increase, and if it exceeds the above-mentioned range, the pressure is excessively applied, so it may not be possible to prevent the breakage and crumbling of the active material particles despite the presence of a buffer layer.

[0289] In one embodiment of the present invention, the step of rolling the electrode active material layer may result in a porosity of 20 to 55% compared to the porosity of the electrode active material layer before rolling. Since the change in porosity has been described above, detailed descriptions will be omitted.

[0290] In one embodiment of the present invention, the adhesive buffer layer may be adhered or detached from the surface of the soft rolling roller. This may mean that it is adhered temporarily or permanently, as described above.

[0291]

[0292] The third aspect of this foundation is,

[0293] The present invention provides a device for manufacturing a lithium secondary battery electrode, comprising: a soft rolling roller positioned at the top; a hard rolling roller positioned below the soft rolling roller, having a surface hardness higher than that of the soft rolling roller and positioned to contact the soft rolling roller; and a conveying means for conveying a laminated electrode body while passing between the rolls of the soft rolling roller and the hard rolling roller; wherein the soft rolling roller is formed on a surface that contacts the laminated electrode body.

[0294]

[0295] Detailed descriptions of overlapping parts with the first and second aspects of the present application have been omitted, but the contents described for the first and second aspects of the present application may be equally applied even if the description is omitted for the third aspect.

[0296]

[0297] Hereinafter, a manufacturing device for a lithium secondary battery electrode according to the third aspect of the present invention will be described in detail.

[0298]

[0299] In one embodiment of the present invention, the rolling rollers are composed of a pair of soft rolling rollers positioned on the upper surface of the laminated electrode body to roll the laminated electrode body, and hard rolling rollers positioned on the lower surface (the surface in contact with the current collector when the active material layer is formed only on the cross-section) of the laminated electrode body. In the lithium secondary battery manufacturing device according to one embodiment of the present invention, two or more pairs of soft / hard rolling rollers may be included, and the total number of rolling rollers may be appropriately designed by a person skilled in the art. The laminated electrode body may be introduced into the space between the soft rolling roller and the lower hard rolling roller.

[0300] In one embodiment of the present invention, a manufacturing device for a lithium secondary battery electrode can provide a buffer layer to a laminated electrode body. The buffer layer is placed between rolling rollers together with the laminated electrode body and rolled together with the laminated electrode body by the rolling rollers. The buffer layer can change the surface condition of the laminated electrode body, particularly the active material layer, due to the rolling, as it is separated from the laminated electrode body after rolling.

[0301] In one embodiment of the present invention, the buffer layer may include a substrate and an adhesive layer formed on one surface of the substrate. In this case, the types of the substrate and adhesive layer constituting the buffer layer can be appropriately designed by a person skilled in the art.

[0302] In one embodiment of the present invention, during the rolling process, a buffer layer is interposed between the laminated electrode body and the rolling roller, thereby preventing electrode active material particles, binder powder, conductive material, etc. from attaching to the rolling roller and acting as contaminants.

[0303] In one embodiment of the present invention, the method may further include an unwinding roll for transporting a buffer layer material to be unwound and arranged between the soft rolling roller and the electrode active material layer, and a rewinding roll for removing and winding the buffer layer material after the laminated electrode body passes between the rolls of the soft rolling roller and the hard rolling roller. The unwinding roll is a roll on which a pre-prepared buffer layer is wound, and the buffer layer can be unwound and introduced together with the electrode during rolling. In addition, the rewinding roll performs the function of separating and recovering the buffer layer located on the electrode surface by rolling and winding it. At this time, one side of the buffer layer may be wound on the unwinding roll, and the other side may be wound on the rewinding roll. In this state, when the laminated electrode body is introduced, the buffer layer can be rolled together with the electrode while traveling at the same speed as the traveling speed of the electrode by the rotation of the unwinding roll and the rewinding roll. The buffer layer rolled together with the electrode can be automatically separated from the electrode as it is wound on the rewinding roll. At this time, the buffer layer, the unwinding roll, and the rewinding roll may be formed on one or both sides of the laminated electrode body.

[0304]

[0305] The fourth aspect of this foundation is,

[0306] A lithium secondary battery is provided, which includes a positive electrode, a negative electrode, and an electrolyte positioned between the positive electrode and the negative electrode, including the above lithium secondary battery electrode.

[0307]

[0308] Detailed descriptions of overlapping parts with the first to third aspects of the present application have been omitted, but the contents described with respect to the first to third aspects of the present application may be equally applied even if the description is omitted in the fourth aspect.

[0309]

[0310] Hereinafter, a lithium secondary battery according to the fourth aspect of the present invention will be described in detail.

[0311]

[0312] In one embodiment of the present invention, the lithium secondary battery may include an electrode. The matters relating to the electrode may be equally applicable to the aforementioned electrode and / or electrode manufacturing method. The electrode may be, for example, a positive electrode or a negative electrode.

[0313] In one embodiment of the present invention, the positive electrode may be the positive electrode for a lithium secondary battery described above.

[0314] In one embodiment of the present invention, the negative electrode active material is typically a material capable of absorbing and releasing lithium ions. Specific examples of the negative electrode active material include lithium alloys, metals or semimetals or alloys such as Sn, metal oxides or semimetal oxides such as Sn oxide, silicon-based active materials, polyphosphate compounds, carbon materials such as graphite, and non-graphitizing carbon (graphitizable carbon or non-graphitizable carbon).

[0315] In one embodiment of the present invention, for example, the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, and the like.

[0316] In addition, in one embodiment of the present invention, for example, the carbon-based active material may include crystalline carbon, amorphous carbon, a carbon composite, carbon fiber, etc. For example, the amorphous carbon may include hard carbon, coke, mesocarbon microbeads, mesophase pitch-based carbon fiber, etc. For example, the crystalline carbon may include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0317] In one embodiment of the present invention, for example, the silicon-based active material is Si, SiO x (0 <x<2), Si / C, SiO / C, Si-Metal 등을 포함할 수 있다.

[0318] In another embodiment of the present invention, the area of ​​the negative electrode may be larger than that of the positive electrode. Accordingly, lithium ions generated from the positive electrode can smoothly move to the negative electrode without being precipitated in the middle.

[0319] In another embodiment of the present invention, the positive and negative electrodes may be alternately and repeatedly arranged to form an electrode assembly.

[0320] In one embodiment of the present invention, an electrolyte may be additionally included. The electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of secondary batteries.

[0321] In one embodiment of the present invention, a separator may be interposed between the positive and negative electrodes. The separator may include a porous polymer film made of a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer. Furthermore, for example, the separator may include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, or the like.

[0322] In one embodiment of the present invention, a lithium secondary battery may include a positive electrode lead connected to a positive electrode and protruding outward from a case; and a negative electrode lead connected to a negative electrode and protruding outward from a case. For example, the positive electrode and the positive electrode lead may be electrically connected. Similarly, the negative electrode and the negative electrode lead may be electrically connected. For example, the positive electrode lead may be electrically connected to a positive electrode current collector. Additionally, the negative electrode lead may be electrically connected to a negative electrode current collector.

[0323] In one embodiment of the present invention, the positive electrode collector may include a positive electrode tab protruding on one side. A positive electrode active material layer may not be formed on the positive electrode tab. The positive electrode tab may be integral with the positive electrode collector, or may be connected by welding or the like. The positive electrode collector and the positive electrode lead may be electrically connected through the positive electrode tab. For example, the negative electrode collector may include a negative electrode tab protruding on one side. A negative electrode active material layer may not be formed on the negative electrode tab. The negative electrode tab may be integral with the negative electrode collector, or may be connected by welding or the like. The negative electrode collector and the negative electrode lead may be electrically connected through the negative electrode tab.

[0324] In one embodiment of the present invention, the electrode assembly may include a plurality of anodes and a plurality of cathodes. For example, the plurality of anodes may each include a cathode tab. For example, the plurality of cathodes may each include a cathode tab. For example, the anode tabs (or cathode tabs) may be laminated, pressed, and welded to form a cathode tab laminate (or cathode tab laminate). For example, the cathode tab laminate may be electrically connected to a cathode lead. For example, the cathode tab laminate may be electrically connected to a cathode lead.

[0325] In one embodiment of the present invention, for example, the electrode assembly and the above-described electrolyte may be housed together in a case to form a lithium secondary battery. For example, the lithium secondary battery may be manufactured in a cylindrical, square, pouch, or coin shape.

[0326] In one embodiment of the present invention, the electrolyte may include a lithium salt. The lithium salt may include Li + X - can be expressed as, for example, the above X - is F - , Cl - , Br- , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - ,　 CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - ,SCN - and (CF3CF2SO2)2N - It can be any one of them. For example, the lithium salt may include LiBF4, LiPF6, etc.

[0327] In one embodiment of the present invention, the electrolyte may include an organic solvent. For example, the organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, etc.

[0328] In one embodiment of the present invention, for example, the carbonate solvent may include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), etc.

[0329] In one embodiment of the present invention, the ester solvent may include methyl propionate, ethyl propionate, propyl acetate, butyl acetate, ethyl acetate, butyrolactone, caprolactone, valerolactone, and the like.

[0330] In one embodiment of the present invention, the ether solvent may include dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0331] In one embodiment of the present invention, the ketone solvent may include cyclohexanone or the like.

[0332] In one embodiment of the present invention, the alcohol solvent may include ethyl alcohol, isopropyl alcohol, and the like.

[0333] In one embodiment of the present invention, the aprotic solvent may include a nitrile solvent, an amide solvent (e.g., dimethylformamide), a dioxolane solvent (e.g., 1,3-dioxolane), a sulfolane solvent, etc.

[0334]

[0335] <Second aspect>

[0336] The first aspect of this article is,

[0337] A method for manufacturing a lithium secondary battery electrode is provided, comprising: a step of preparing a current collector; a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body; and a step of rolling the electrode active material layer; wherein the rolling is performed by passing the laminated electrode body between a first rolling roller and a second rolling roller, and at least a portion of the surface of the first rolling roller or the second rolling roller is coated with a buffer material, and rolling is performed such that the buffer material comes into contact with the electrode active material layer.

[0338]

[0339] Hereinafter, a method for manufacturing a lithium secondary battery electrode according to the first aspect of the present invention will be described in detail.

[0340]

[0341] First, in one embodiment of the present invention, a step of preparing the entire body may be included.

[0342] In one embodiment of the present invention, the current collector may be a conductive metal or non-metal material, and may preferably be a foil of copper or a copper alloy, but this is only a non-limiting example.

[0343] Next, in one embodiment of the present invention, a step of forming an electrode active material layer on the current collector to obtain a laminated electrode body may be included.

[0344] In one embodiment of the present invention, the electrode may include an electrode active material layer and / or a current collector. The electrode active material layer may include an electrode active material, an electrode binder, and / or a conductive material. The electrode active material layer may be formed on one or both sides of the current collector. Preferably, when performing a dry process, the active material layer may be formed on one side of the current collector. Preferably, the electrode active material layer may include electrode active material particles, a conductive material, and a binder.

[0345] In the case of a lithium secondary battery electrode according to an embodiment of the present invention, an active material layer is laminated in the form of a sheet on a current collector, and the fracture or crumbling of particles is controlled on the upper surface (surface) where rolling is performed, thereby obtaining unique characteristics. These characteristics are described below.

[0346] In the lithium secondary battery electrode according to one embodiment of the present invention, the active material particles that have “broken” mean particles that have a particle size of less than 50%, preferably less than 40%, based on the average particle size value due to the active material particles used in electrode manufacturing being broken by rolling (pressure), and if the proportion of such particles is high in the particle size distribution, it can be seen that a relatively large number of particles have broken.

[0347] In one embodiment of the present invention, when measuring the particle size distribution on the upper surface (surface) of the electrode active material layer, the broken particles having a particle size of less than 40% of the average particle size of the electrode active material particles may be present at less than 24%, preferably 23% or less, more preferably 22% or less, and even more preferably 20% or less. If the above range is exceeded, the fraction of broken particles may become excessively high, and the impregnation of the electrolyte may not occur properly in the subsequent battery manufacturing process. Here, the “upper surface” of the electrode active material layer where the particle size distribution is observed may mean a space viewed from above, having a depth equal to one or more particle sizes in the thickness direction from the upper end.

[0348] In one embodiment of the present invention, the average particle size of the electrode active material particles may be a non-limiting average particle size of active material particles commonly used in the art, for example, 1 to 50 μm, preferably 2 to 30 μm, and more preferably 3 to 20 μm. In addition, the minimum particle size of the particles measured on the upper surface of the electrode active material layer may be 5 μm or less, preferably 3 μm or less. A small minimum particle size of the active material particles does not necessarily mean that the particles are “broken”, and as described above, whether or not they are broken can be confirmed by the relative relationship with the average particle size of the particles introduced during manufacturing. In one embodiment of the present invention, the particle size of the broken particles may be 3 μm or less.

[0349] In one embodiment of the present invention, the electrode active material layer may include an upper portion of the active material that extends from the top to 30% of the total thickness in the thickness direction and a lower portion of the active material that extends from the current collector to 30% of the total thickness in the thickness direction. By classifying the upper portion of the active material and the lower portion of the active material and calculating the specific surface area and average pore size, it is possible to determine whether rolling is performed uniformly throughout the electrode active material layer.

[0350] In one embodiment of the present invention, the thickness of the electrode active material layer can be freely laminated in consideration of the capacity to be implemented when manufacturing a lithium secondary battery. However, when forming an electrode through a typical wet process, it is impossible to form a thick thickness in a single lamination process, so it can be seen that there is a limit to the thickness. In the case of a dry process for forming an active material layer by a dry method, it can be seen that a thicker film can be formed. From this perspective, the electrode active material layer may have a thickness of 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, or 180 μm or less. In addition, the upper part of the active material may have a thickness of 150 µm or less, 120 µm or less, 90 µm or less, 60 µm or less, or 30 µm or less in the thickness direction from the upper part of the active material layer, and the lower part of the active material may have a thickness of 150 µm or less, 120 µm or less, 90 µm or less, 60 µm or less, or 30 µm or less in the thickness direction from the current collector.

[0351] In one embodiment of the present invention, the upper part of the active material and the lower part of the active material may have the same, similar, or different specific surface areas and average pore sizes, respectively, depending on the uniformity of the upper and lower specific surface areas and the uniformity of the upper and lower pores. Here, the measurement of the specific surface area and the average pore size may be performed by measuring the specific surface area and the pore size of the surface of the active material layer by adsorbing a gas on the active material layer, and the uniformity of the upper and lower specific surface areas and the uniformity of the upper and lower pores may be measured by this method. When neither the calendering process nor the rolling process is performed, the specific surface area and the average pore size of the upper part of the active material may be relatively similar. However, when the calendering process or the rolling process is performed, the specific surface area and the average pore size of the upper part of the active material may be smaller than those of the lower part of the active material.

[0352] In one embodiment of the present invention, the specific surface area of ​​the upper part of the active material is 2000㎛ when not subjected to the rolling and calendaring processes. 2 Below, 1800㎛ 2 Below, or 1600㎛ 2 It may be less than 1100㎛ in surface area before rolling after the calendaring process. 2 Below, 1000㎛ 2 Below, 900㎛ 2 or less, or 800㎛ 2 It may be as follows. The specific surface area of ​​the upper part of the active material of the electrode active material layer according to one embodiment of the present invention refers to the value measured after the rolling process, and is 500㎛. 2 Below, preferably 400㎛ 2 It may be less than 400㎛. Even after the rolling process, the specific surface area of ​​the upper part of the active material 2 If it exceeds , it is difficult to see that the rolling is done efficiently.

[0353] In one embodiment of the present invention, the specific surface area of ​​the lower part of the active material is 2000㎛ when not subjected to the rolling and calendaring processes. 2 Below, 1800㎛ 2 Below, or 1600㎛ 2 It may be less than 1600㎛ in surface area before rolling after the calendaring process. 2 Below, or 1550㎛ 2 It may be as follows. The specific surface area of ​​the lower part of the active material of the electrode active material layer according to one embodiment of the present invention refers to the value measured after the rolling process, and is 1000㎛. 2 Below 800㎛ 2 Less than, or preferably less than, 700㎛ 2 It may be less than 1000㎛. Even after the rolling process, the specific surface area of ​​the lower part of the active material 2 If it exceeds , it is difficult to see that uniform rolling has been achieved, and therefore, the degree of electrolyte impregnation in the subsequent process will be significantly different from that of the upper part.

[0354] In one embodiment of the present disclosure, the average pore size of the upper portion of the active material may be 24 μm or less, 21 μm or less, or 19 μm or less when not subjected to the rolling and calendaring processes, and may be 13 μm or less, 11 μm or less, 9 μm or less, or 7 μm or less before rolling after the calendaring process. The average pore size of the upper portion of the active material of the electrode active material layer according to one embodiment of the present disclosure refers to a value measured after the rolling process, and may be 5 μm or less, preferably less than 4.5 μm. If the average pore size of the upper portion of the active material exceeds 4.5 μm even after the rolling process, it is difficult to regard the rolling as being performed efficiently.

[0355] In one embodiment of the present disclosure, the average pore size of the lower part of the active material may be 24 μm or less, 21 μm or less, or 19 μm or less if the rolling and calendaring processes are not performed, and the average pore size may be 20 μm or less, or 18 μm or less before rolling after the calendaring process. The average pore size of the lower part of the active material of the electrode active material layer according to one embodiment of the present disclosure refers to a value measured after the rolling process, and may be 10 μm or less, less than 8 μm, or preferably less than 7 μm. If the average pore size of the lower part of the active material exceeds 10 μm even after the rolling process, it is difficult to regard uniform rolling as having been performed, and therefore, the degree of impregnation of the electrolyte in the subsequent process will be significantly different from that of the upper part.

[0356] In one embodiment of the present invention, the upper and lower surface area uniformity defined by the following equation 2 may be greater than 1 and less than or equal to 2.

[0357] [Formula 2]

[0358] (Specific surface area of ​​the lower part of the active material (㎛) 2 )) / (Specific surface area of ​​the upper part of the active material (㎛) 2 ))

[0359] In one embodiment of the present invention, the upper and lower pore uniformity defined by the following equation 3 may be greater than 1 and less than or equal to 2.

[0360] [Formula 3]

[0361] (Average pore size (㎛) of the lower part of the active material) / (Average pore size (㎛) of the upper part of the active material)

[0362] The above “upper and lower specific surface area uniformity” and “upper and lower pore uniformity” are measures that can be used to check how much rolling is uniformly performed in the thickness direction from the surface of the electrode active material layer to the current collector. If the active material layer is properly and uniformly rolled, low volume resistance, etc. can be formed in all regions of the upper and lower parts of the active material. When the upper and lower specific surface area uniformity and the upper and lower pore uniformity are 1, it means that no calendaring or rolling process was performed at all, and when the upper and lower specific surface area uniformity and the upper and lower pore uniformity are less than 1, it means that the rolling of the lower part was pressurized more than the upper part, and therefore, it may be different from the concept of the laminated electrode body according to one embodiment of the present application. On the other hand, if the uniformity of the upper and lower surface areas and the uniformity of the upper and lower pores exceed 2, it means that the rolling of the upper and lower parts of the active material is uneven, and in particular, the effect of the rolling is concentrated only on the upper part, which may cause the side effect of increasing resistance when manufacturing a lithium secondary battery.

[0363] In one embodiment of the present invention, through the step of rolling the electrode active material layer, a porosity measured on the upper surface of the electrode active material layer may be 10 to 25%, preferably 12 to 25%, compared to the porosity before rolling. If the above range is exceeded, it may mean that the rolling has not been performed sufficiently, and may be disadvantageous in terms of maximizing energy density.

[0364] In one embodiment of the present invention, the electrode active material layer may be composed of a material of the following general formula 3 or general formula 4:

[0365] [General Formula 3]

[0366] Li 1+x [Ni 1-a-b-c M a M' b M" c ] 1-x O 2-z

[0367] 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.

[0368] [General Formula 4]

[0369] Li j M1 k M2 m (PO 4-n )A n

[0370] 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.

[0371] In one embodiment of the present invention, the conductive material is not particularly limited as long as it is a conductive material. Examples of such conductive materials include carbonaceous materials; metals; and conductive ceramics. Examples of the carbonaceous material include graphite and carbon black. Examples of carbon black include furnace black, acetylene black, and Ketjen black. Among these, carbonaceous materials are preferable from the viewpoint of conductivity and processability. Among these, acetylene black and Ketjen black are preferable. Examples of the conductive material shape include powder, sheet, and fiber. The conductive material may typically be added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material.

[0372] In one embodiment of the present invention, the binder may be, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used. The above binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and can be added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material.

[0373] In one embodiment of the present invention, an electrode slurry may be prepared as a precursor of an electrode active material layer, and this may be prepared by dissolving an electrode active material, a conductive material, a binder, etc. in a solvent. There is no particular limitation on the type of the solvent as long as it can disperse the electrode active material, etc., and both aqueous solvents and non-aqueous solvents may be used. For example, the solvent may be a solvent commonly used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these may be used alone or as a mixture of two or more. The amount of the solvent used is not particularly limited as long as the slurry can be adjusted to have an appropriate viscosity in consideration of the coating thickness of the slurry, manufacturing yield, workability, etc. The solvent may be removed during the drying process.

[0374] In addition, in another embodiment of the present invention, the step of forming an electrode active material layer on the current collector to obtain a laminated electrode body can be performed by a dry process. Without a separate solvent, the conductive material, the active material, and the binder are all provided in a powder or solid state. In this case, a primer coating layer may be formed in advance so that the powder-phase electrode active material mixture forms a layer on the current collector, if necessary. In the case of such a dry process, it can be performed at room temperature, but if necessary, it can be performed by increasing the temperature to a relatively high temperature from the viewpoint of inducing fibrillation or fiberization of the binder.

[0375] Next, in one embodiment of the present invention, a step of rolling the electrode active material layer may be included. Fig. 13 is a photographic image of a lithium secondary battery electrode manufacturing apparatus according to one embodiment of the present invention. As shown in Fig. 13, in the lithium secondary battery manufacturing method according to one embodiment of the present invention, the rolling process is performed by asymmetric rolling using an asymmetric buffer layer. Here, “asymmetric” may mean that the buffer layer is applied only to one surface that is in contact with the electrode active material layer and then rolled.

[0376] In one embodiment of the present invention, the rolling may be performed by applying pressure between a relatively soft material and a relatively hard material, and when utilizing a press roll method, at least a portion of the surface of the first rolling roller or the second rolling roller may be coated with a buffer material in the rolling process, and rolling may be performed such that the buffer material comes into contact with the electrode active material layer. Specifically, the rolling may be performed by passing the laminated electrode body between a soft rolling roller (the first or second rolling roller) and a hard rolling roller (the second or first rolling roller). In addition, it may be rolling with a flat material such as a conveyor belt made of a soft rolling roller and a hard material. Preferably, it may be characterized in that at least a portion of the surface of the soft rolling roller is coated with a buffer material, and rolling is performed such that the buffer material comes into contact with the electrode active material layer.

[0377] In one embodiment of the present invention, the surface of the soft rolling roller that comes into contact with the electrode active material layer may have a buffer layer formed thereon coated with a buffer material. The buffer layer may be temporarily or permanently adhered to the surface of the soft rolling roller; however, in order to avoid the adverse effect of unnecessarily detaching active material particles on the surface (upper surface) of the active material layer, the surface of the buffer layer that comes into contact with the electrode active material layer must be free of adhesive components.

[0378] In one embodiment of the present invention, the adhesive buffer layer may be adhered or detached from the surface of the soft rolling roller. This may mean that it is adhered temporarily or permanently, as described above.

[0379] In one embodiment of the present invention, the buffer material may be at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate; however, other materials may also be used without limitation as long as they satisfy the surface properties of the electrode.

[0380] In one embodiment of the present invention, the step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2 It can be carried out under pressure. If it is below the above-mentioned range, the densification of the active material layer does not occur, so the energy density does not increase, and if it exceeds the above-mentioned range, the pressure is excessively applied, so it may not be possible to prevent the breakage and crumbling of the active material particles despite the presence of a buffer layer.

[0381]

[0382] The second aspect of the original text is,

[0383] The present invention provides an apparatus for manufacturing a lithium secondary battery electrode, comprising: a first rolling roller positioned at the top; a second rolling roller positioned below the first rolling roller and positioned to contact the first rolling roller; and a conveying means for conveying a laminated electrode body while passing between the rolls of the first rolling roller and the second rolling roller; wherein the first rolling roller or the second rolling roller includes a buffer material layer provided on at least a portion of a surface, and the buffer material layer is positioned to contact the electrode active material layer during rolling.

[0384]

[0385] 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.

[0386]

[0387] Hereinafter, a manufacturing device for a lithium secondary battery electrode according to the second aspect of the present invention will be described in detail.

[0388]

[0389] In one embodiment of the present invention, the rolling rollers are composed of a pair of soft rolling rollers positioned on the upper surface of the laminated electrode body to roll the laminated electrode body, and hard rolling rollers positioned on the lower surface (the surface in contact with the current collector when the active material layer is formed only on the cross-section) of the laminated electrode body. In the lithium secondary battery manufacturing device according to one embodiment of the present invention, two or more pairs of soft / hard rolling rollers may be included, and the total number of rolling rollers may be appropriately designed by a person skilled in the art. The laminated electrode body may be introduced into the space between the soft rolling roller and the lower hard rolling roller.

[0390] In one embodiment of the present invention, a device for manufacturing a lithium secondary battery electrode may provide a buffer material on the surface of a first or second rolling roller. The buffer material is introduced between the rolling rollers in contact with the laminated electrode body and rolled by the rolling roller. The surface condition of the laminated electrode body, particularly the active material layer, resulting from the rolling may be changed by the buffer material.

[0391] In one embodiment of the present invention, during the rolling process, the buffer material acts as a buffer layer during the rolling process of the laminated electrode body, thereby achieving uniform pressure, and at the same time, electrode active material particles, binder powder, conductive material, etc. are prevented from adhering to the surface of the first or second rolling roller, thereby preventing them from acting as contaminants.

[0392] In one embodiment of the present invention, the thickness of the buffer material layer may be 10 to 200 μm. If it is less than the above-described range, it may be difficult to function as a buffer layer during rolling, and if it exceeds the above-described range, the thickness of the buffer layer becomes excessively thick, so that rolling itself may not be performed properly.

[0393]

[0394] The third aspect of this foundation is,

[0395] A method for manufacturing a lithium secondary battery is provided, comprising: a step of preparing a positive electrode according to the above method; a step of preparing a negative electrode; and a step of stacking the positive electrode, a separator, and the negative electrode and injecting an electrolyte.

[0396]

[0397] Detailed descriptions of overlapping parts with the first and second aspects of the present application have been omitted, but the contents described with respect to the first and second aspects of the present application may be equally applied even if the description is omitted with respect to the third aspect.

[0398]

[0399] Hereinafter, a method for manufacturing a lithium secondary battery according to the third aspect of the present invention will be described in detail.

[0400]

[0401] In one embodiment of the present invention, the lithium secondary battery may include an electrode. The matters relating to the electrode may be equally applicable to the aforementioned electrode and / or electrode manufacturing method. The electrode may be, for example, a positive electrode or a negative electrode.

[0402] In one embodiment of the present invention, the positive electrode may be the positive electrode for a lithium secondary battery described above.

[0403] In one embodiment of the present invention, the negative electrode active material is typically a material capable of absorbing and releasing lithium ions. Specific examples of the negative electrode active material include lithium metal, lithium alloy, metals or semimetals or alloys such as Sn, metal oxides or semimetal oxides such as Sn oxide, silicon-based active materials, polyphosphate compounds, carbon materials such as graphite, and non-graphitizing carbon (graphitizable carbon or non-graphitizable carbon).

[0404] In one embodiment of the present invention, for example, the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, and the like.

[0405] In addition, in one embodiment of the present invention, for example, the carbon-based active material may include crystalline carbon, amorphous carbon, a carbon composite, carbon fiber, etc. For example, the amorphous carbon may include hard carbon, coke, mesocarbon microbeads, mesophase pitch-based carbon fiber, etc. For example, the crystalline carbon may include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0406] In one embodiment of the present invention, for example, the silicon-based active material is Si, SiO x (0 <x<2), Si / C, SiO / C, Si-Metal 등을 포함할 수 있다.

[0407] In another embodiment of the present invention, the area of ​​the negative electrode may be larger than that of the positive electrode. Accordingly, lithium ions generated from the positive electrode can smoothly move to the negative electrode without being precipitated in the middle.

[0408] In another embodiment of the present invention, the positive and negative electrodes may be alternately and repeatedly arranged to form an electrode assembly.

[0409] In one embodiment of the present invention, an electrolyte may be additionally included. The electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of secondary batteries.

[0410] In one embodiment of the present invention, a separator may be interposed between the positive and negative electrodes. The separator may include a porous polymer film made of a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer. Furthermore, for example, the separator may include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, or the like.

[0411] In one embodiment of the present invention, a lithium secondary battery may include a positive electrode lead connected to a positive electrode and protruding outward from a case; and a negative electrode lead connected to a negative electrode and protruding outward from a case. For example, the positive electrode and the positive electrode lead may be electrically connected. Similarly, the negative electrode and the negative electrode lead may be electrically connected. For example, the positive electrode lead may be electrically connected to a positive electrode current collector. Additionally, the negative electrode lead may be electrically connected to a negative electrode current collector.

[0412] In one embodiment of the present invention, the positive electrode collector may include a positive electrode tab protruding on one side. A positive electrode active material layer may not be formed on the positive electrode tab. The positive electrode tab may be integral with the positive electrode collector, or may be connected by welding or the like. The positive electrode collector and the positive electrode lead may be electrically connected through the positive electrode tab. For example, the negative electrode collector may include a negative electrode tab protruding on one side. A negative electrode active material layer may not be formed on the negative electrode tab. The negative electrode tab may be integral with the negative electrode collector, or may be connected by welding or the like. The negative electrode collector and the negative electrode lead may be electrically connected through the negative electrode tab.

[0413] In one embodiment of the present invention, the electrode assembly may include a plurality of anodes and a plurality of cathodes. For example, the plurality of anodes may each include a cathode tab. For example, the plurality of cathodes may each include a cathode tab. For example, the anode tabs (or cathode tabs) may be laminated, pressed, and welded to form a cathode tab laminate (or cathode tab laminate). For example, the cathode tab laminate may be electrically connected to a cathode lead. For example, the cathode tab laminate may be electrically connected to a cathode lead.

[0414] In one embodiment of the present invention, for example, the electrode assembly and the above-described electrolyte may be housed together in a case to form a lithium secondary battery. For example, the lithium secondary battery may be manufactured in a cylindrical, square, pouch, or coin shape.

[0415] In one embodiment of the present invention, the electrolyte may include a lithium salt. The lithium salt may include Li + X - can be expressed as, for example, the above X - is F - , Cl - , Br- , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - ,　 CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - ,SCN - and (CF3CF2SO2)2N - It can be any one of them. For example, the lithium salt may include LiBF4, LiPF6, etc.

[0416] In one embodiment of the present invention, the electrolyte may include an organic solvent. For example, the organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, etc.

[0417] In one embodiment of the present invention, for example, the carbonate solvent may include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), etc.

[0418] In one embodiment of the present invention, the ester solvent may include methyl propionate, ethyl propionate, propyl acetate, butyl acetate, ethyl acetate, butyrolactone, caprolactone, valerolactone, and the like.

[0419] In one embodiment of the present invention, the ether solvent may include dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0420] In one embodiment of the present invention, the ketone solvent may include cyclohexanone or the like.

[0421] In one embodiment of the present invention, the alcohol solvent may include ethyl alcohol, isopropyl alcohol, and the like.

[0422] In one embodiment of the present invention, the aprotic solvent may include a nitrile solvent, an amide solvent (e.g., dimethylformamide), a dioxolane solvent (e.g., 1,3-dioxolane), a sulfolane solvent, etc.

[0423]

[0424] The fourth aspect of this foundation is,

[0425] A lithium secondary battery is provided, which includes a positive electrode, a negative electrode, and an electrolyte positioned between the positive electrode and the negative electrode, including the above lithium secondary battery electrode.

[0426]

[0427] Detailed descriptions of overlapping parts with the first to third aspects of the present application have been omitted, but the contents described with respect to the first to third aspects of the present application may be equally applied even if the description is omitted in the fourth aspect.

[0428]

[0429] According to an embodiment of the present invention, a lithium secondary battery electrode can be provided in which uniform rolling is performed over the entire thickness of an active material layer, thereby allowing good electrolyte impregnation, and a method for manufacturing a lithium secondary battery electrode can be provided in which breakage of active material particles, which can cause unnecessary electrochemical performance degradation through uniform pressing throughout the wet and dry electrode manufacturing processes, is suppressed, and further, when a dry process is applied, a high-capacity battery can be manufactured through thickening of the electrode, and contamination of a pressurizing means that may occur during the rolling process during the process can be suppressed, so that it can be considered to have industrial applicability.

[0430] According to an embodiment of the present invention, a lithium secondary battery electrode can be provided in which uniform rolling is performed over the entire thickness of an active material layer, thereby allowing good electrolyte impregnation, and a method for manufacturing a lithium secondary battery electrode can be provided in which breakage of active material particles, which can cause unnecessary electrochemical performance degradation through uniform pressing throughout the wet and dry electrode manufacturing processes, is suppressed, and further, when a dry process is applied, a high-capacity battery can be manufactured through thickening of the electrode, and contamination of a pressurizing means that may occur during the rolling process during the process can be suppressed, so that it can be considered to have industrial applicability.

Claims

1. The entire house; and An electrode active material layer provided on the above-mentioned collector; Including, When measuring the particle size distribution on the upper surface of the electrode active material layer, A lithium secondary battery electrode characterized in that less than 24% of the particles have a particle size of less than 40% of the average particle size of electrode active material particles.

2. In paragraph 1, The above electrode active material layer includes an upper portion of the active material up to 30% of the total thickness in the thickness direction from the top and a lower portion of the active material up to 30% of the total thickness in the thickness direction from the current collector, A lithium secondary battery electrode, characterized in that the upper part of the active material and the lower part of the active material each have different porosities.

3. In paragraph 2, A lithium secondary battery electrode characterized in that the rolling uniformity defined by the following equation 1 is greater than 1 and less than or equal to 2: [Formula 1] (Porosity of the lower part of the active material (%)) / (Porosity of the upper part of the active material (%)) 4. In paragraph 2, A lithium secondary battery electrode, characterized in that the porosity of the upper portion of the active material is less than 10%.

5. In paragraph 2, A lithium secondary battery electrode, characterized in that the porosity of the lower part of the active material is less than 20%.

6. In paragraph 1, A lithium secondary battery electrode, characterized in that the average particle size of the electrode active material particles is 3 to 20㎛.

7. In paragraph 1, A lithium secondary battery electrode, characterized in that the particle size of the above-mentioned broken particles is 3㎛ or less.

8. In paragraph 1, A lithium secondary battery electrode, characterized in that the electrode active material layer is a material of the following general formula 1 or general formula 2: [General Formula 1] Li 1+x [Ni 1-a-b-c M a m' b M" c ] 1-x O 2-z (In the above general formula 1, M is one or more elements of the Mn, Zr and Ti groups, M' is one or more elements of the groups Al, B and Co, M" is a dopant different from M and M', x, a, b and c are expressed in moles (mol), -0.02≤x≤0.02, 0≤c≤0.05, 0.10≤(a+b)≤0.65, and 0≤z≤0.05) [General Formula 2] <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> j <h2 style=";text-align:left;direction:ltr"> M1<h2 style=";text-align:left;direction:ltr"> k <h2 style=";text-align:left;direction:ltr"> M2<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr"> (PO<h2 style=";text-align:left;direction:ltr"> 4-n <h2 style=";text-align:left;direction:ltr"> A)<h2 style=";text-align:left;direction:ltr"> n (In the above general formula 2, 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, 0.5≤j≤1.5, 0.5≤k≤1, 0≤m≤0.5, 0≤n≤1) 9. Steps to prepare the entire house; A step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body; and A step of rolling the electrode active material layer; Including, The above rolling is to pass the laminated electrode body between a soft rolling roller and a hard rolling roller having a higher surface hardness than the soft rolling roller, A method for manufacturing a lithium secondary battery electrode, characterized in that asymmetric rolling is performed so that the surface of the soft rolling roller comes into contact with the electrode active material layer.

10. In paragraph 9, The step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2 A method for manufacturing a lithium secondary battery electrode, characterized in that the process is carried out under pressure.

11. In paragraph 9, A buffer layer is introduced between the above soft rolling roller and the electrode active material layer, A method for manufacturing a lithium secondary battery electrode, characterized in that the buffer layer is at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate.

12. In paragraph 9, Through the step of rolling the above electrode active material layer; A method for manufacturing a lithium secondary battery electrode, characterized in that the electrode active material layer exhibits a porosity of 20 to 55% compared to the porosity before rolling.

13. In paragraph 9, A step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body; A method for manufacturing a lithium secondary battery electrode, characterized in that it is carried out in a dry manner at room temperature.

14. Soft rolling roller located at the top; A hard rolling roller positioned below the soft rolling roller, having a higher surface hardness than the soft rolling roller, and positioned to be in contact with the soft rolling roller; and A transport means for transporting a laminated electrode body while passing between the rolls of the soft rolling roller and the hard rolling roller; A device for manufacturing a lithium secondary battery electrode, characterized in that the above soft rolling roller is formed on a surface that comes into contact with a laminated electrode body.

15. In paragraph 14, An unwinding roll for transporting the buffer layer material so as to be placed between the soft rolling roller and the electrode active material layer; and A rewinding roll that removes and winds the buffer layer material after the laminated electrode body passes between the rolls of the soft rolling roller and the hard rolling roller; A manufacturing device for a lithium secondary battery electrode, further comprising:

16. Steps to prepare the entire house; A step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body; and A step of rolling the electrode active material layer; Including, The above rolling is to pass the laminated electrode body between the first rolling roller and the second rolling roller, At least a portion of the surface of the first rolling roller or the second rolling roller is coated with a buffer material, A method for manufacturing a lithium secondary battery electrode, characterized in that the above-mentioned buffer material is rolled so that the above-mentioned electrode active material layer comes into contact with it.

17. In paragraph 16, The step of rolling the electrode active material layer is 0.1 to 5 ton / cm 2 A method for manufacturing a lithium secondary battery electrode, characterized in that the process is carried out under pressure.

18. In paragraph 16, A method for manufacturing a lithium secondary battery electrode, characterized in that the above-mentioned buffer material is at least one material selected from silicone rubber, polyimide, polytetrafluoroethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene terephthalate.

19. In paragraph 16, Through the step of rolling the above electrode active material layer; A method for manufacturing a lithium secondary battery electrode, characterized in that the electrode active material layer exhibits a porosity of 10 to 25% compared to the porosity before rolling, as measured on the upper surface of the electrode active material layer.

20. In paragraph 16, The above electrode active material layer includes an upper portion of the active material up to 30% of the total thickness in the thickness direction from the top and a lower portion of the active material up to 30% of the total thickness in the thickness direction from the current collector, A method for manufacturing a lithium secondary battery electrode, characterized in that the upper part of the active material and the lower part of the active material have different specific surface areas and average pore sizes, respectively.

21. In paragraph 20, The specific surface area of ​​the upper part of the above active material is 400㎛ 2 A method for manufacturing a lithium secondary battery electrode, characterized by being less than:

22. In paragraph 20, The specific surface area of ​​the lower part of the above active material is 700㎛ 2 A method for manufacturing a lithium secondary battery electrode, characterized by being less than:

23. In paragraph 20, A method for manufacturing a lithium secondary battery electrode, characterized in that the average pore size of the upper portion of the active material is less than 4.5㎛.

24. In paragraph 20, A method for manufacturing a lithium secondary battery electrode, characterized in that the average pore size of the lower portion of the active material is less than 7㎛.

25. In paragraph 20, A method for manufacturing a lithium secondary battery electrode, characterized in that the upper and lower surface area uniformity defined by the following equation 2 is greater than 1 and less than or equal to 2: [Formula 2] (Specific surface area of ​​the lower part of the active material (㎛- 2 )) / (Specific surface area of ​​the upper part of the active material (㎛- 2 )) 26. In paragraph 20, A method for manufacturing a lithium secondary battery electrode, characterized in that the upper and lower pore uniformity defined by the following equation 3 is greater than 1 and less than or equal to 2: [Formula 3] (Average pore size (㎛) of the lower part of the active material) / (Average pore size (㎛) of the upper part of the active material) 27. In paragraph 16, A method for manufacturing a lithium secondary battery electrode, characterized in that the average particle size of the electrode active material particles is 3 to 20㎛.

28. In paragraph 16, The above electrode active material layer includes an electrode active material, a conductive material, and a binder, A method for manufacturing a lithium secondary battery electrode, wherein the electrode active material is a material of the following general formula 3 or general formula 4: [General Formula 3] Li 1+x [Ni 1-a-b-c M a m' b M" c ] 1-x O 2-z (In the above general formula 3, M is one or more elements of the Mn, Zr and Ti groups, M' is one or more elements of the groups Al, B and Co, M" is a dopant different from M and M', x, a, b and c are expressed in moles (mol), -0.02≤x≤0.02, 0≤c≤0.05, 0.10≤(a+b)≤0.65, and 0≤z≤0.05) [General Formula 4] <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> j <h2 style=";text-align:left;direction:ltr"> M1<h2 style=";text-align:left;direction:ltr"> k <h2 style=";text-align:left;direction:ltr"> M2<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr"> (PO<h2 style=";text-align:left;direction:ltr"> 4-n <h2 style=";text-align:left;direction:ltr"> A)<h2 style=";text-align:left;direction:ltr"> n (In the above general formula 4, 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, 0.5≤j≤1.5, 0.5≤k≤1, 0≤m≤0.5, 0≤n≤1) 29. In paragraph 16, A method for manufacturing a lithium secondary battery electrode, comprising: a step of rolling the electrode active material layer; and a method for manufacturing a lithium secondary battery electrode, characterized in that the thickness of the electrode active material layer is 150㎛ or less.

30. In paragraph 16, A step of forming an electrode active material layer on the above-mentioned collector to obtain a laminated electrode body; A method for manufacturing a lithium secondary battery electrode, characterized in that it is carried out in a dry manner at room temperature.

31. First rolling roller located at the top; A second rolling roller positioned below the first rolling roller and positioned to be in contact with the first rolling roller; and A transport means for transporting a laminated electrode body while passing between the rolls of the first rolling roller and the second rolling roller; The first rolling roller or the second rolling roller includes a buffer material layer provided on at least a portion of the surface, A lithium secondary battery electrode manufacturing device, characterized in that the buffer material layer is positioned so that the electrode active material layer comes into contact with it during rolling.

32. In paragraph 31, A device for manufacturing a lithium secondary battery electrode, characterized in that the thickness of the buffer material layer is 10 to 200㎛.

33. A step of preparing an anode according to the method of Article 16; Step of preparing the cathode; and A step of laminating the positive electrode, the separator, and the negative electrode and injecting an electrolyte; A method for manufacturing a lithium secondary battery, comprising:

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