Apparatus for manufacturing positive electrodes for lithium secondary batteries and method for manufacturing the same

Abstract

The present invention relates to an apparatus and method for manufacturing a positive electrode for a lithium secondary battery, and more particularly, to an apparatus and method for manufacturing a positive electrode for a lithium secondary battery, which is capable of efficiently controlling a loading amount and porosity of the positive electrode by manufacturing the positive electrode for a lithium secondary battery through a dry process including a step of supplying a powdered positive electrode material onto a positive electrode current collector, and a step of pre-molding, rolling, and bonding the powdered positive electrode material.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2021-0181018 dated December 16, 2021, and all contents disclosed in the documents of the relevant Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an apparatus for manufacturing a positive electrode for a lithium secondary battery and a method for manufacturing the same. [Background technology]

[0003] Recently, with the rapid development of electronic devices and electric vehicles, the demand for secondary batteries has increased. In particular, with the trend toward smaller and lighter portable electronic devices, there is a growing demand for secondary batteries with high energy density that can meet this trend.

[0004] Among secondary batteries, lithium-sulfur secondary batteries use a sulfur-based compound with sulfur-sulfur bonds as the positive electrode active material and a carbon-based material in which the insertion and deintercalation of alkali metals such as lithium or metal ions such as lithium ions occurs, or silicon or tin, which form alloys with lithium, as the negative electrode active material. Specifically, they store and generate electrical energy using an oxidation-reduction reaction in which the sulfur-sulfur bond is broken and the oxidation number of sulfur decreases during discharge, which is a reduction reaction, and the oxidation number of sulfur increases and the sulfur-sulfur bond is reformed during charge, which is an oxidation reaction.

[0005] In particular, sulfur, which is used as the positive electrode active material in lithium-sulfur secondary batteries, has a theoretical energy density of 1,675 mAh / g, which is about five times higher than the theoretical energy density of positive electrode active materials used in existing lithium secondary batteries, making it possible for batteries to achieve high output and high energy density.In addition, sulfur has the advantages of being inexpensive, abundant in reserves, easy to supply and demand, and environmentally friendly, and is therefore attracting attention as an energy source for not only portable electronic devices but also medium- to large-sized devices such as electric vehicles.

[0006] Sulfur has an electrical conductivity of 5 x 10 -30 Since sulfur is an insulator with a low electrical conductivity of S / cm, it is difficult to move electrons generated in electrochemical reactions. Therefore, sulfur is combined with an electrically conductive material such as carbon, which can provide electrochemical reaction sites, to form sulfur-carbon composites.

[0007] To use the sulfur-carbon composite as a positive electrode active material, a method of preparing a slurry together with a conductive material and a binder, and then coating the slurry on a current collector, i.e., a wet process, is commonly used to prepare a positive electrode.

[0008] However, positive electrodes manufactured using such a wet process have problems such as a reduced loading amount of positive electrode active material in the positive electrode due to the conductive material and binder used in preparing the slurry, resulting in a reduced energy density. Furthermore, manufacturing positive electrodes using a wet process can cause problems such as residual moisture in the positive electrode, as well as additional costs associated with mixing, coating, and drying processes.

[0009] On the other hand, when manufacturing a positive electrode using a dry process, the type and content of the binder that can be used are limited because the binder must be fiberized. Furthermore, this requires a pre-mixing process of the positive electrode active material, conductive material, and binder, and a milling process in which high shear force is applied to fiberize the binder, which complicates the process and increases costs and time. Furthermore, the high energy applied during the binder fiberization process can cause the positive electrode active material and conductive material to break down.

[0010] In addition, fiberized binder powder is generally formed through a calendar rolling process, and during this process, the variables of the roll rotation speed and nip distance simultaneously affect the loading and porosity of the positive electrode, making it difficult to independently adjust the process conditions to control the properties of the positive electrode.

[0011] Therefore, in order to prevent problems caused by the binder in the dry process of manufacturing a positive electrode, it is necessary to develop a technology for manufacturing a positive electrode in a dry process without using a binder. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-078497 Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, the present inventors conducted extensive research to solve the above problems. As a result, they found that, in an apparatus for manufacturing a cathode through a dry process, a cathode material supply unit that supplies powdered cathode material and a cathode material molding unit that pressurizes the cathode material are configured to operate independently, and that by simultaneously using pressure and temperature in the cathode material molding unit, a cathode can be molded without using a binder, and that it is easy to control the loading and porosity of the cathode in the cathode manufacturing process, thereby completing the present invention.

[0014] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an apparatus and method for manufacturing a positive electrode for a lithium secondary battery by a dry process without using a binder. [Means for solving the problem]

[0015] In order to achieve the above object, the present invention provides a transport means that moves in one direction; a positive electrode material supply unit that supplies a powdered positive electrode material to one surface of the positive electrode current collector transferred by the transfer means; and a cathode material forming unit that pre-forms, rolls, and bonds the powdered cathode material supplied to one surface of the cathode current collector into a cathode material layer shape, the positive electrode material forming unit includes a preliminary forming roll, a rolling roll, and an adhesive roll arranged in a line, The pre-molding roll, the rolling roll, and the adhesive roll each include a pair of rolls that are symmetrical to each other, and the transport means is transported in one direction between the pair of rolls.

[0016] The present invention also provides a method for manufacturing a positive electrode for a lithium secondary battery, including: (S1) a step of supplying a powdered positive electrode material to one side of a positive electrode current collector transported by a transport means; (S2) a pre-molding step of applying pressure to the powdered positive electrode material transported from (S1) and supplied to one side of the positive electrode current collector to form a layered positive electrode material layer; (S3) a rolling step of applying pressure to the positive electrode current collector having the positive electrode material layer formed on one side thereof to adjust the porosity of the positive electrode material layer; and (S4) a step of heating the positive electrode current collector having the positive electrode material layer formed thereon, which has been rolled in (S3), to bond the positive electrode material layer to the positive electrode current collector.

[0017] After the step (S4), the step (S5) may include recovering the powdery cathode material remaining on the cathode current collector after the bonding to a cathode material supply unit.

[0018] The steps (S1) to (S4) may be repeated twice, and the steps (S1) to (S4) may be performed sequentially. [Effects of the Invention]

[0019] According to the present invention, a positive electrode for a lithium secondary battery can be manufactured by a dry process using an apparatus for manufacturing a positive electrode for a lithium secondary battery without using a binder.

[0020] In addition, the apparatus for manufacturing a positive electrode for a lithium secondary battery includes a powdered positive electrode material supply unit and a positive electrode material molding unit that pre-forms, rolls, and bonds the powdered positive electrode material. These units are configured to operate independently, so that the positive electrode loading amount can be adjusted in the positive electrode material supply unit and the positive electrode porosity can be adjusted in the positive electrode material molding unit. This allows the positive electrode loading amount and porosity to be independently adjusted in the positive electrode manufacturing process.

[0021] Furthermore, since the cathode material forming section applies pressure using a mold in the shape of the cathode, the remaining cathode material powder that is not pressed can be recovered and reused. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of an apparatus for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will now be described in more detail to aid in understanding the invention.

[0024] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his / her invention.

[0025] The term "dry process" as used in the present invention means a process in which no solvent is used.

[0026] (Production equipment for positive electrodes for lithium secondary batteries) The present invention relates to an apparatus for manufacturing a positive electrode for a lithium secondary battery, and more particularly to an apparatus for manufacturing a positive electrode by a dry process without using a binder.

[0027] FIG. 1 is a schematic diagram of an apparatus for manufacturing a positive electrode for a lithium secondary battery according to one embodiment of the present invention.

[0028] Referring to FIG. 1 , the apparatus 1 for manufacturing a positive electrode for a lithium secondary battery includes a cathode material supply unit 10 that supplies powdered cathode material P to one side of a cathode current collector 50 transported by a transport means 30 that moves in one direction, and a cathode material forming unit 20 that pre-forms, rolls, and bonds the powdered cathode material P supplied to the one side of the cathode current collector 50 into the form of a cathode active material layer 52. The cathode material forming unit 20 includes a pre-forming roll 21, a rolling roll 22, and a bonding roll 23 arranged in a line. The pre-forming roll 21, the rolling roll 22, and the bonding roll 23 each include a pair of symmetrical rolls, and the transfer means 30 moves in one direction between the pair of rolls. The apparatus 1 for manufacturing a positive electrode for a lithium secondary battery may further include a cathode material recovery unit 40 that transfers the powdered cathode material P remaining on the cathode current collector 50 after being pre-formed, rolled, and bonded by the cathode material forming unit 20 to the cathode material supply unit 10.

[0029] In the apparatus 1 for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, a series of processes are continuously performed, in which a positive electrode current collector 50 is transported in one direction by a transport means 30, a powdered positive electrode material P is supplied from a positive electrode material supply unit 10, and then the positive electrode current collector 50 is pre-molded, rolled, and bonded in a positive electrode material forming unit 20 to manufacture a positive electrode for a lithium secondary battery 60. This can improve process efficiency and productivity. The continuous process may also include a process of transporting the remaining powdered positive electrode material P from a positive electrode material recovery unit 40 to the positive electrode material supply unit 10.

[0030] The transfer means 30 may transfer the cathode current collector 50 or the cathode current collector 50 coated with the powdered cathode material P in one direction along a predetermined transfer path, enabling the continuous process described above. For example, the transfer means 30 may form a transfer path for transferring the cathode current collector 50 in the direction of arrow A, and may sequentially pass through the cathode material supply unit 10 and the cathode material forming unit 20 at a constant speed under the control of a driving unit. For example, the transfer means 30 is not particularly limited as long as it is a device known in the art that can transfer an object to be transferred. For example, the transfer means 30 may be a device that enables a roll-to-roll process, which may be performed using an unwinder and a rewinder.

[0031] The positive electrode current collector 50 is not particularly limited as long as it supports the positive electrode active material layer 52, does not induce chemical changes in the battery, and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, or calcined carbon; copper or stainless steel surface-treated with carbon, nickel, or silver; or an aluminum-cadmium alloy may be used. In addition, the positive electrode current collector 50 may have fine irregularities on its surface to strengthen its bonding with the positive electrode active material, and may be in various forms, such as a film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0032] In addition, a primer coating layer 51 containing a binder and a conductive material may be formed on the surface of the positive electrode current collector 50. The primer coating layer 51 may serve to better bind the powdered positive electrode material P to the positive electrode current collector 50.

[0033] The binder is not particularly limited as long as it is a binder commonly used in the industry. For example, the binder may be one or a mixture or copolymer of two or more selected from the group consisting of fluororesin-based binders including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE), rubber-based binders including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber, cellulose-based binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose, polyalcohol-based binders, polyolefin-based binders including polyethylene and polypropylene, polyimide-based binders, polyester-based binders, and silane-based binders.

[0034] In addition, the binder may be included in an amount of 10 wt % to 30 wt % based on the total weight of the primer coating layer 51. Specifically, the binder content may be 10 wt % or more, 12 wt % or more, or 15 wt % or more, and 25 wt % or less, 28 wt % or less, or 30 wt % or less. If the binder content is less than 10 wt %, the adhesive strength of the powdered cathode material P to the cathode current collector 50 may be reduced, and if it exceeds 30 wt %, it may act as a resistor, reducing the performance and lifespan of the battery.

[0035] The conductive material may serve to impart conductivity to the positive electrode.

[0036] The conductive material is not particularly limited as long as it does not induce chemical changes in the battery and can impart conductivity to the positive electrode.

[0037] For example, the conductive material may be graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0038] Furthermore, the conductive material may be included in an amount of 70 wt % to 90 wt % based on the total weight of the primer coating layer. Specifically, the conductive material content may be 70 wt % or more, 72 wt % or more, or 75 wt % or more, and 85 wt % or less, 88 wt % or less, or 90 wt % or less. If the conductive material content is less than 70 wt %, the binder content in the primer coating layer will be relatively high, causing the primer coating layer to act as a resistance layer, which may reduce battery performance and lifespan and may reduce the conductivity of the positive electrode. If the conductive material content is more than 90 wt %, the binder content will be relatively low, which may reduce formability.

[0039] The primer coating layer 51 may be formed by adding the binder and the conductive material to a solvent and then applying the mixture to one or both surfaces of the positive electrode current collector 50 .

[0040] In this case, the solvent may be water or an organic solvent. When the binder is an aqueous binder, water may be used as the solvent, and when the binder is a non-aqueous binder, an organic solvent may be used.

[0041] The organic solvent is not particularly limited as long as it is one commonly used in the art. For example, the organic solvent may be any one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, tetraethylene glycol dimethyl ether (TEGDME), dioxolane (DOL), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran, or a mixture of two or more thereof.

[0042] In the present invention, the powdered cathode material P contains a sulfur-carbon composite composed of 50% to 90% by weight of sulfur and 10% to 50% by weight of a porous carbon material.

[0043] The powdered cathode material contains 90% to 100% by weight, preferably 95% to 100% by weight, more preferably 97% to 100% by weight of the sulfur-carbon composite based on the weight of the entire cathode material.

[0044] The sulfur-carbon composite refers to a form in which sulfur is supported on the porous carbon material. For example, the sulfur-carbon composite may be in a state in which sulfur is attached to or coated on the surface of the porous carbon material. Furthermore, the sulfur-carbon composite may be in a state in which sulfur is attached to, filled in, or coated on the internal pores of the porous carbon material, or in a state in which sulfur penetrates and attaches to the interior of the porous carbon material.

[0045] That is, the lithium secondary battery according to the present invention may be a lithium-sulfur secondary battery containing the sulfur-carbon composite as a cathode material.

[0046] The cathode material supply unit 10 supplies powdered cathode material P to one side of the cathode current collector 50 transferred by the transfer means 30, and its configuration, device, etc. are not particularly limited. For example, the cathode material supply unit 10 may include an ultrasonic sieve machine, a vibratory feeder, a rotary feeder, etc. to remove coarse particles from the powdered cathode material P.

[0047] In addition, the cathode material supply unit 10 can easily adjust the loading amount of the powdered cathode material P according to the purpose, and can also improve the deviation of the loading amount. As a result, the loading amount of the final cathode can be easily adjusted according to the application, thereby improving the reliability of the manufacturing process.

[0048] The cathode material forming unit 20 preliminarily forms the powder-type cathode material P, which is supplied to one side of the cathode current collector 50 via the cathode material supply unit 10, into a layer-type cathode active material layer 52, applies pressure to roll it to adjust the porosity, and then applies a constant temperature to bond the cathode current collector 50 and the cathode active material layer 52 together, thereby manufacturing a cathode. The configuration, apparatus, etc. of the cathode material forming unit 20 are not particularly limited.

[0049] The cathode material forming section 20 includes a provisional forming roll 21, a rolling roll 22, and an adhesive roll 23, which are arranged in a row. The direction in which these are arranged is the same as the direction in which the transfer means 30 moves.

[0050] The pre-forming roll 21 includes a pair of rollers symmetrically arranged to each other, and a cathode current collector 50 supplied with powdered cathode material P is transferred in one direction between the pair of rollers. Pressure is applied to the top and bottom of the cathode current collector 50 supplied with the powdered cathode material P using the pair of rollers, and the powdered cathode material P is subjected to pressure to form a layer-shaped cathode active material layer 52. When the cathode active material layer 52 is formed, the powder is stabilized, preventing fluidization of the powder.

[0051] Hereinafter, the positive electrode current collector 50 and the positive electrode active material layer 52 formed on one surface of the positive electrode current collector 50 will be referred to as a positive electrode laminate.

[0052] The thickness of the positive electrode active material layer 52 after passing through the temporary forming roll 21 may have a thickness ratio of 0.6 or more, specifically 0.6 or more, 0.7 or more, or 0.8 or more, based on the thickness of the positive electrode active material layer 52 before passing through the temporary forming roll 21, i.e., the thickness of the powder-form positive electrode material P. The upper limit is not particularly limited, but may be 0.9 or less. If the thickness ratio α of the positive electrode active material layer 52 before and after passing through the temporary forming roll 21 is less than 0.6, the structure of the supplied powder-form positive electrode material is likely to collapse, and if a large force is applied locally to the current collector, there is a problem of breakage. If the thickness ratio α exceeds 0.9, the layer-form positive electrode active material layer 52 cannot be properly formed, and the powder may not be completely stabilized, resulting in chipping.

[0053] The pre-forming roll 21 may apply pressure so that the layer-shaped positive electrode active material layer 52 is well formed and the thickness ratio α of the positive electrode active material layer 52 before and after passing through the pre-forming roll 21 is in the range of 0.6 or greater. The pressure to satisfy this thickness ratio may be appropriately adjusted during the process. For example, a pressure of 100 kPa to 500 kPa may be applied to the top and bottom of the positive electrode current collector 50 to which the powder-state positive electrode material P is supplied. Specifically, the pressure may be 100 kPa or greater, 150 kPa or greater, or 200 kPa or greater, and may be 400 kPa or less, 450 kPa or less, or 500 kPa or less. If the pressure is less than 100 kPa, the layer shape may not be properly formed, and the powder may not be completely stabilized, resulting in chipping. If the pressure is greater than 500 kPa, the electrode may break.

[0054] The rolling rolls 22 include a pair of rollers symmetrical to each other, and the positive electrode laminate is transferred in one direction between the pair of rollers. The positive electrode laminate includes a positive electrode current collector 50 and a positive electrode active material layer 52 that have passed through the preliminary forming rolls 21.

[0055] The thickness ratio of the positive electrode active material layer 52 after passing through the rolling rolls 22 to the thickness of the positive electrode active material layer 52 before passing through the rolling rolls 22, i.e., the thickness of the positive electrode active material layer 52 after passing through the preliminary forming roll 21, may be 0.5 or less, specifically 0.5 or less, 0.4 or less, or 0.3 or less, and the lower limit may be 0.1 or more, although not particularly limited. If the thickness ratio β of the positive electrode active material layer 52 before and after passing through the rolling rolls 22 exceeds 0.5, the process of forming a positive electrode active material layer with the final porosity may become longer, and if it is less than 0.1, excessive rolling may cause the current collector to break.

[0056] The pressure applied by the pressure rolls 22 may be such that the layered positive electrode active material layer 52 is well formed and the thickness ratio β of the positive electrode active material layer 52 before and after passing through the pressure rolls 22 is 0.5 or less. The pressure to satisfy this thickness ratio may be appropriately adjusted during the process. For example, a pressure of 1 MPa to 5 MPa may be applied to the upper and lower portions of the positive electrode laminate including the positive electrode current collector 50 and the positive electrode active material layer 52. Specifically, the pressure may be 1 MPa or more, 1.5 MPa or more, or 2 MPa or more, and may be 4 MPa or less, 4.5 MPa or less, or 5 MPa or less. If the pressure is less than 1 MPa, the resulting positive electrode may have high porosity, resulting in reduced durability, or may not be completely stabilized, resulting in chipping. If the pressure is greater than 5 MPa, the electrode may break.

[0057] The adhesive roll 23 includes a pair of rollers symmetrically arranged, and the positive electrode laminate is transferred in one direction between the pair of rollers. The positive electrode laminate includes a positive electrode current collector 50 and a positive electrode active material layer 52 that have passed through a rolling roll 22.

[0058] The adhesive roll 23 can apply an appropriate temperature and slight pressure to ensure good adhesion between the positive electrode current collector 50 and the positive electrode active material layer 52. The adhesive roll 23 can be a rubber roll or a roll that is several μm thinner than the thickness of the electrode, allowing adhesion to proceed with a gap of several μm.

[0059] The temperature may be 50° C. to 130° C., and specifically, the temperature may be 50° C. or higher, 55° C. or higher, or 60° C. or higher, and 110° C., 120° C. or lower, or 130° C. or lower. If the temperature is lower than 50° C., the adhesive strength of the positive electrode active material layer 52 to the positive electrode current collector 50 may decrease, and if the temperature exceeds 130° C., the sulfur content in the powder may fall outside the appropriate range, resulting in a decrease in battery performance.

[0060] The positive electrode laminate that has passed through the adhesive roll 23 is manufactured as a positive electrode 60 for a lithium secondary battery including a positive electrode current collector 50 and a positive electrode active material layer 52 formed on one surface of the positive electrode current collector 50, and can be wound up on a winding roll 70.

[0061] The cathode material recovery unit 40 can recover the powdered cathode material P from the cathode current collector 50 to the cathode material supply unit 10 in order to reuse the powdered cathode material P remaining on the cathode current collector 50 after the cathode active material layer 52 is formed on the cathode current collector 50 in the cathode material molding unit 20.

[0062] There are no particular limitations on the positive electrode material recovery unit 40 as long as it is a device that can recover powder with little adhesive force. For example, the positive electrode material recovery unit 40 may be a scraper, an air gun, or the like.

[0063] In addition, the cathode material recovery unit 40 may be installed at a position corresponding to the cathode manufactured through the cathode material forming unit 30 before the cathode is wound around the winding roll 70 .

[0064] Furthermore, the manufactured positive electrode that has passed through the positive electrode material forming section 20 can be wound up on a winding roll 70.

[0065] (Method of manufacturing a positive electrode for a lithium secondary battery) The present invention relates to a method for manufacturing a positive electrode for a lithium secondary battery, the method including: (S1) supplying a powdered positive electrode material to one side of a positive electrode current collector transported by a transport means; (S2) applying pressure to the powdered positive electrode material transported from (S1) and supplied to one side of the positive electrode current collector to form a layered positive electrode material layer; (S3) applying pressure to the positive electrode current collector having the positive electrode material layer formed on one side thereof to adjust the porosity of the positive electrode material layer; and (S4) heating the rolled positive electrode current collector having the positive electrode material layer formed thereon in (S3) to bond the positive electrode material layer to the positive electrode current collector, and may further include (S5) recovering the powdered positive electrode material remaining on the positive electrode current collector after the bonding to the positive electrode material supply unit.

[0066] Hereinafter, each step of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention will be described in more detail.

[0067] In step (S1) of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, a powdered positive electrode material may be supplied to one surface of a positive electrode current collector transferred by a transfer means.

[0068] The step (S1) is performed in the cathode material supply unit as described above, and the details of the transfer means, cathode current collector, and powdered cathode material are the same as those described above.

[0069] In step (S2) of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, pressure may be applied to the powdery positive electrode material transferred from step (S1) and supplied to one surface of the positive electrode current collector to pre-form the positive electrode material layer in a layer form.

[0070] The step (S2) is performed in the pre-forming roll of the cathode material forming unit as described above, and the device and pressure conditions of the pre-forming roll are the same as those described above.

[0071] In step (S3) of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, pressure may be applied to the positive electrode current collector having the positive electrode material layer formed on one surface thereof to adjust the porosity of the positive electrode material layer.

[0072] The step (S3) is performed in the pressure roll of the cathode material forming unit as described above, and the device and pressure conditions of the pressure roll are the same as those described above.

[0073] In step (S4) of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, the positive electrode current collector having the positive electrode material layer formed thereon, which has been rolled in step (S3), may be heated to bond the positive electrode material layer and the positive electrode current collector together.

[0074] The step (S4) is performed in the adhesive roll of the cathode material forming unit as described above, and the details of the device and pressure conditions provided in the rolling roll are as described above.

[0075] In step (S5) of the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, the powder-state positive electrode material remaining on the positive electrode current collector after the bonding may be collected in the positive electrode material supply unit.

[0076] The step (S5) is performed using a cathode material recovery unit, and the cathode material recovery unit is as described above.

[0077] In the method for manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present invention, steps (S1) to (S4) may be repeated twice, or steps (S1) to (S4) may be performed sequentially.

[0078] After steps (S1) to (S4) are performed once, a positive electrode having a positive electrode active material layer formed on one surface of a positive electrode current collector can be manufactured.

[0079] Thereafter, the steps (S1) to (S4) are performed once more, and then repeated two times in total, to manufacture a positive electrode in which positive electrode active material layers are formed on both sides of the positive electrode current collector.

[0080] Alternatively, the cathode material supply unit and cathode material molding unit may be configured as two layers, and then the cathode material may be simultaneously supplied to both sides of the cathode current collector, thereby manufacturing a cathode having cathode active material layers formed on both sides in a single operation. In this case, the cathode active material layer on the upper surface of the cathode current collector may be formed in the same manner as steps (S1) to (S4), and the cathode active material layer on the lower surface of the cathode current collector may be formed by transferring a foil instead of a foil cathode current collector and then transferring it to the cathode current collector in the cathode material molding unit. In other words, the cathode material in powder form is not separately supplied to the lower surface of the cathode current collector from the cathode material supply unit, but is transferred in foil form. [Explanation of symbols]

[0081] 1: Lithium secondary battery positive electrode manufacturing equipment 10: Cathode material supply section 20: Cathode material molding section 21: Pre-forming roll 22: Rolling mill 23: Adhesive roll 30:Transportation means 40: Cathode material recovery unit 50: Positive electrode current collector 51: Primer coating layer 52: Positive electrode active material layer 60: Positive electrode 70: Winding roll P: Positive electrode material in powder form

Claims

1. a positive electrode material supply unit that supplies a powdered positive electrode material not containing a binder to one surface of the positive electrode current collector that is transported by a transport means that moves in one direction; a cathode material forming unit that pre-forms, rolls, and bonds the powdered cathode material supplied to one surface of the cathode current collector into a cathode material layer shape, the positive electrode material forming unit includes a preliminary forming roll, a rolling roll, and an adhesive roll arranged in a line, the preliminary forming roll, the rolling roll, and the adhesive roll each include a pair of rolls that are symmetrical to each other, and the transfer means is transferred in one direction between the pair of rolls; The adhesive roll applies a temperature of 50°C to 130°C to bond the positive electrode current collector and the positive electrode material layer together, The apparatus for manufacturing a positive electrode for a lithium secondary battery, wherein only the adhesive roll is heated among the provisional forming roll, the rolling roll, and the adhesive roll.

2. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the provisional forming roll applies pressure so that the thickness ratio of the positive electrode material layer after passing through the provisional forming roll compared to the thickness before passing through the provisional forming roll is 0.6 or more.

3. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the pressure roll applies pressure so that the thickness ratio of the positive electrode material layer after passing through the pressure roll compared to before passing through the pressure roll is 0.5 or less.

4. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the positive electrode material supply unit comprises an ultrasonic sieve machine, a vibratory feeder, or a rotary feeder.

5. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein a primer coating layer containing a binder is formed on one surface of the positive electrode current collector.

6. 6. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 5, wherein the binder comprises at least one selected from the group consisting of: a fluororesin-based binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber-based binder including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; a cellulose-based binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder; a polyolefin-based binder including polyethylene and polypropylene; a polyimide-based binder; a polyester-based binder; and a silane-based binder.

7. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the powdered positive electrode material comprises a sulfur-carbon composite containing 50 to 90 wt % of sulfur and 10 to 50 wt % of a porous carbon material.

8. (S1) supplying a powdered cathode material containing no binder onto one surface of a cathode current collector transferred by a transfer means; (S2) a pre-molding step of applying pressure to the powdery cathode material transferred from the step (S1) and supplied to one surface of the cathode current collector to form a layer-shaped cathode material layer; (S3) a rolling step of applying pressure to the positive electrode current collector having the positive electrode material layer formed on one surface thereof to adjust the porosity of the positive electrode material layer; and (S4) heating the rolled cathode current collector having the cathode material layer formed thereon in the (S3) step to bond the cathode material layer and the cathode current collector together, The heating in step (S4) is performed at a temperature of 50°C to 130°C, A method for manufacturing a positive electrode for a lithium secondary battery, wherein only step (S4) is heated among steps (S2), (S3), and (S4).

9. 9. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 8, further comprising, after step (S4), (S5) recovering the powdery positive electrode material remaining on the positive electrode current collector after the bonding to a positive electrode material supply unit.

10. 9. The method of claim 8, wherein steps (S1) to (S4) are repeated twice, and steps (S1) to (S4) are performed sequentially.

11. 2. The apparatus for manufacturing a positive electrode for a lithium secondary battery according to claim 1, wherein the adhesive roll is a rubber roll.

Images