Roll-to-roll dry process for electrodes using rolls having different line velocities to increase

Abstract

The invention relates to a roll-to-roll dry process for electrodes using rollers with different linear speeds to increase binder fibrillation. A system for manufacturing an electrode of a battery cell includes N-1 pairs of rollers configured to press and calender a dry mixed material to form an active material layer of the electrode, where N is an integer greater than 1. The dry mix material includes an active material, a conductive filler, and a binder. At least one of the N-1 pairs of rollers includes a first roller operating at a first linear speed and a second roller operating at a second linear speed different from the first linear speed. And an Nth pair of rollers including a third roller operating at a third linear speed and a fourth roller operating at a fourth linear speed identical to the third linear speed to laminate the active material layer to a current collector.

Description

Technical Field

[0001] The present disclosure relates to battery cells for a battery pack, and more particularly to the manufacture of electrodes for battery cells for a battery pack. Background Art

[0002] The information provided in this section is for a general introduction to the background of the present disclosure. The work of the currently named inventors described in this section, as well as aspects of the specification that may not have been otherwise determined to be prior art at the time of filing, are not expressly or impliedly admitted to be prior art to the present disclosure.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles include one or more electric motors and a battery pack system including one or more battery cells, modules, and / or packs. A power control system is used to control charging and / or discharging of the battery pack system during charging and / or driving.

[0004] A battery cell includes a cathode electrode, an anode electrode, and a separator. The cathode electrode includes a cathode active material layer (including cathode active material) disposed on a cathode current collector. The anode electrode includes an anode active material layer (including anode active material) disposed on an anode current collector. Summary of the Invention

[0005] A system for manufacturing an electrode for a battery cell includes N - 1 pairs of rollers configured to press and calender a dry blend material to form an active material layer of the electrode, where N is an integer greater than 1. The dry blend material includes an active material, a conductive filler, and a binder. At least one pair of the N - 1 pairs of rollers includes a first roller operating at a first linear speed and a second roller operating at a second linear speed different from the first linear speed. A Nth pair of rollers includes a third roller operating at a third linear speed and a fourth roller operating at a fourth linear speed the same as the third linear speed to laminate the active material layer to a current collector.

[0006] In other features, the binder includes polytetrafluoroethylene (PTFE). The first roller and the second roller have the same diameter. The first roller has a larger diameter than the second roller. The ratio of the first linear speed to the second linear speed is from 1.02 to 2.0. The ratio of the first linear speed to the second linear speed is from 1.05 to 1.5. The first roller and the second roller are heated to a temperature of 80°C to 200°C.

[0007] In other features, the electrode includes a cathode electrode. The electrode includes an anode electrode.

[0008] A system for manufacturing an electrode for a battery of a battery pack includes N adjacent rollers that press and calender a dry mixed material N - 1 times to form an active material layer of the electrode, where N is an integer greater than 2. The dry mixed material includes an anode active material, a conductive filler, and a binder. At least two of the N adjacent rollers operate at different linear speeds. The (N - 1)th roller and the Nth roller among the N adjacent rollers operate at the same linear speed to laminate the active material layer onto a current collector.

[0009] Among other features, the binder includes polytetrafluoroethylene (PTFE). At least two of the N adjacent rollers have the same diameter. At least two of the N adjacent rollers have different diameters. The ratio of the different linear speeds is from 1.02 to 2.0. The ratio of the different linear speeds is from 1.05 to 1.5. At least two of the N adjacent rollers are heated to a temperature of 80°C to 200°C.

[0010] Among other features, the electrode includes a cathode electrode. The electrode includes an anode electrode.

[0011] A method for manufacturing an electrode for a battery of a battery pack, which includes a dry mixed material for an active material layer that includes an active material, a conductive filler, and a binder; passing the dry mixed material through N - 1 pairs of rollers to press and calender the dry mixed material to form the active material layer, where N is an integer greater than 1. At least one pair of the N - 1 pairs of rollers includes a first roller operating at a first linear speed and a second roller operating at a second linear speed different from the first linear speed. The method includes passing the active material layer and a current collector through a pair including a third roller operating at a third linear speed and a fourth roller operating at a fourth linear speed the same as the third linear speed to laminate the active material layer onto the current collector.

[0012] A method for manufacturing an electrode for a battery of a battery pack, which includes a dry mixed material for an active material layer that includes an anode active material, a conductive filler, and a binder; passing the dry mixed material through N - 1 times between N adjacent rollers to press and calender the dry mixed material to form an active material layer, where N is an integer greater than 2. At least two of the N adjacent rollers operate at different linear speeds. The method includes passing the active material layer and a current collector between the (N - 1)th roller and the Nth roller among the N adjacent rollers operating at the same linear speed to laminate the active material layer onto the current collector.

[0013] The present invention discloses the following solutions:

[0014] Solution 1. A system for manufacturing an electrode for a battery of a battery pack, which includes:

[0015] N - 1 pairs of rollers configured to press and roll a dry mixture to form the active material layer of the electrode, where N is an integer greater than 1,

[0016] where the dry mixture includes an active material, a conductive filler, and a binder;

[0017] at least one pair of the N - 1 pairs of rollers includes a first roller operating at a first linear speed and a second roller operating at a second linear speed different from the first linear speed; and

[0018] a 10th pair of rollers including a third roller operating at a third linear speed and a fourth roller operating at a fourth linear speed the same as the third linear speed to laminate the active material layer onto the current collector.

[0019] Solution 2. The system according to Solution 1, wherein the binder includes polytetrafluoroethylene (PTFE).

[0020] Solution 3. The system according to Solution 1, wherein the first roller and the second roller have the same diameter.

[0021] Solution 4. The system according to Solution 1, wherein the first roller has a larger diameter than the second roller.

[0022] Solution 5. The system according to Solution 1, wherein the ratio of the first linear speed to the second linear speed is 1.02 to 2.0.

[0023] Solution 6. The system according to Solution 1, wherein the ratio of the first linear speed to the second linear speed is 1.05 to 1.5.

[0024] Solution 7. The system according to Solution 1, wherein the first roller and the second roller are heated to a temperature of 80°C to 200°C.

[0025] Solution 8. The system according to Solution 1, wherein the electrode includes a cathode electrode.

[0026] Solution 9. The system according to Solution 1, wherein the electrode includes an anode electrode.

[0027] Solution 10. A system for manufacturing an electrode of a battery pack cell, comprising:

[0028] N adjacent rollers that press and roll a dry mixture N - 1 times to form the active material layer of the electrode, where N is an integer greater than 2,

[0029] where the dry mixture includes an anode active material, a conductive filler, and a binder;

[0030] at least two of the N adjacent rollers operate at different linear speeds; and

[0031] The (N - 1)th roller and the Nth roller among the N adjacent rollers run at the same linear speed to laminate the active material layer by layer onto the current collector.

[0032] Solution 11. The system according to Solution 10, wherein the binder comprises polytetrafluoroethylene (PTFE).

[0033] Solution 12. The system according to Solution 10, wherein at least two of the N adjacent rollers have the same diameter.

[0034] Solution 13. The system according to Solution 10, wherein at least two of the N adjacent rollers have different diameters.

[0035] Solution 14. The system according to Solution 10, wherein the ratio of the different linear speeds is from 1.02 to 2.0.

[0036] Solution 15. The system according to Solution 10, wherein the ratio of the different linear speeds is from 1.05 to 1.5.

[0037] Solution 16. The system according to Solution 10, wherein at least two of the N adjacent rollers are heated to a temperature of 80°C to 200°C.

[0038] Solution 17. The system according to Solution 10, wherein the electrode comprises a cathode electrode.

[0039] Solution 18. The system according to Solution 10, wherein the electrode comprises an anode electrode.

[0040] Solution 19. A method for manufacturing an electrode for a battery pack cell, comprising:

[0041] A dry mixed material for an active material layer, which contains an active material, a conductive filler, and a binder;

[0042] Passing the dry mixed material through (N - 1) pairs of rollers to press and calender the dry mixed material to form the active material layer, where N is an integer greater than 1,

[0043] wherein at least one pair of the (N - 1) pairs of rollers comprises a first roller running at a first linear speed and a second roller running at a second linear speed different from the first linear speed; and

[0044] Passing the active material layer and the current collector through the Nth pair of rollers comprising a third roller running at a third linear speed and a fourth roller running at a fourth linear speed the same as the third linear speed to laminate the active material layer onto the current collector.

[0045] Further applicable fields of the present disclosure will be apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples are only intended to illustrate and are not intended to limit the scope of the present disclosure. Description of the Drawings

[0046] The present disclosure will be more fully understood from the detailed description and the accompanying drawings, wherein:

[0047] Figure 1 is a side cross-sectional view of an example of a battery cell of a battery pack including an anode electrode, a cathode electrode, and a separator;

[0048] Figure 2 is a side cross-sectional view of an example of a cathode electrode including a cathode active material layer having a fibrillated binder according to the present disclosure;

[0049] Figure 3 is a side cross-sectional view of an example of an anode electrode including an anode active material layer having a fibrillated binder according to the present disclosure;

[0050] Figure 4 shows an example of rollers having the same diameter and the same linear velocity for pressing and heating an active material layer of an electrode;

[0051] Figure 5A shows an example of rollers having the same diameter for pressing and heating an active material layer of an electrode operating at different linear velocities according to the present disclosure;

[0052] Figure 5B shows an example of rollers having different diameters for pressing and heating an active material layer of an electrode operating at different linear velocities according to the present disclosure;

[0053] Figure 6 shows an example of a roll-to-roll manufacturing method of an electrode including a pair of rollers having the same diameter operating at different linear velocities according to the present disclosure;

[0054] Figure 7 shows an example of a roll-to-roll manufacturing method of an electrode including a pair of rollers having different diameters operating at different linear velocities according to the present disclosure;

[0055] Figure 8 shows an example of a roll-to-roll manufacturing method of an electrode including a continuous set of rollers having the same diameter operating at different linear velocities according to the present disclosure;

[0056] Figure 9 shows an example of a roll-to-roll manufacturing method of an electrode including a continuous set of adjacent rollers having different diameters operating at different linear velocities according to the present disclosure; and

[0057] Figure 10It is a flowchart of an example of a method for manufacturing an electrode according to the present disclosure.

[0058] In the drawings, reference numerals may be reused to designate similar and / or identical elements. Detailed Description

[0059] Although the battery cells of the battery pack according to the present disclosure are described herein in the context of a vehicle, the battery cells of the battery pack can be used in other applications such as stationary applications.

[0060] An electrode, such as a cathode or anode electrode, includes an active material layer disposed on one or both sides of a current collector. The active material layer can be manufactured by mixing an anode active material, a conductive filler, and a binder. In the wet method, a solvent is added to the mixture of materials forming the active material layer. After casting the active material layer onto the current collector, the electrode can be heated through a drying stage after casting to remove the solvent. The use of the drying stage increases the manufacturing cost and manufacturing footprint of the roll-to-roll equipment. The use of solvents may be associated with environmental issues.

[0061] A dry method that does not add a solvent to the active material layer can also be used. In the dry method, a binder (such as polytetrafluoroethylene (PTFE)) is fibrillated by dry mixing and applying pressure to the active material layer using one or more pairs of calendering rolls having the same diameter and running at the same linear speed. When using typical pairs of rolls having the same diameter and running at the same speed, the active material layer is mainly subjected to pressure transverse to the plane including the active material layer.

[0062] Sufficient fibrillation of the binder is important for a scalable, high-quality dry electrode manufacturing method. Generally, the processing of the raw materials forming the active material layer includes dry powder mixing, powder-to-film calendaring, and laminating the active material layer onto the current collector to form an electrode. One or more calendering / rolling steps are used to control thickness uniformity. However, due to the poor fluidity of the dry powder, it is prone to over-pressing certain areas of the active material layer, which results in electrode thickness variation and thickness limitations.

[0063] The present disclosure relates to a dry manufacturing method of an electrode using calendering rolls with different linear speeds. For example, the active material layer is pressed and heated between pairs of rolls having the same diameter and different linear speeds or pairs of rolls having different diameters and different linear speeds.

[0064] When using pairs of rolls running at different linear speeds, due to the different linear speeds, the active material layer is subjected to a squeezing force transverse to the plane including the active material layer and a shear force parallel to the direction of the active material layer. The shear force increases the fibrillation of PTFE and overcomes the problem of over-pressing in local areas of the active material layer.

[0065] Now refer to Figure 1 , the battery cell 10 of the battery pack includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a predetermined order in the battery cell stack 12 of the battery pack, where C, S, and A are integers greater than zero. The battery cell stack 12 is arranged in the housing 50. The C cathode electrodes 20-1, 20-2,..., and 20-C include cathode active material layers 24 arranged on one or both sides of the cathode current collector 26.

[0066] In some examples, the A anode electrodes 40 and the C cathode electrodes 20 exchange lithium ions during charging / discharging. The A anode electrodes 40-1, 40-2,..., and 40-A include anode active material layers 42 arranged on one or both sides of the anode current collector 46. In some examples, one or both of the cathode active material layer 24 and / or the anode active material layer 42 include a dry coating that contains one or more active materials, one or more conductive additives, and / or one or more binder materials applied to the current collector. The binder material includes at least one fibrillatable binder (such as PTFE).

[0067] In some examples, the cathode current collector 26 and / or the anode current collector 46 include metal foil, metal mesh, perforated metal, three-dimensional (3D) metal foam, and / or expanded metal. In some examples, the current collector is made of one or more materials selected from copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys. The external tabs 28 and 48 are respectively connected to the current collectors of the cathode electrode and the anode electrode, and can be arranged on the same side or different sides of the battery cell stack 12. The external tabs 28 and 48 are connected to the terminals of the battery cell of the battery pack.

[0068] Now refer to Figure 2 and Figure 3 , examples of the cathode electrode and the anode electrode are shown. In Figure 2 , one of the C cathode electrodes 20 is shown in further detail. The cathode active material layer 24 of the C cathode electrodes 20 contains a cathode active material 62, a conductive additive 64, and a fibrillatable binder 66. In some examples, the binder 66 includes PTFE. In Figure 3 , one of the A anode electrodes 40 is shown in further detail. The anode active material layer 42 of the anode electrode 40 contains an anode active material 72, a conductive additive 74, and a fibrillatable binder 76. In some examples, the binder 76 includes PTFE.

[0069] Now refer to Figure 4, an active material layer (e.g., a cathode or anode active material layer) is manufactured by dry-mixing active materials, conductive additives, and binders. Generally, the mixture 108 is pressed and / or heated between a pair of rollers 110 and 112. In Figure 4 , the rollers 110 and 112 have the same diameter and the same linear speed (e.g., L1 and L2).

[0070] When the rollers operate at the same linear speed, problems may occur. The rollers mainly provide pressure in one direction (e.g., perpendicular to the active material layer). The rollers may get stuck due to the non-uniformity of the supplied dry powder mixture, resulting in local over-pressing on the electrode film (e.g., causing cracks or failures). Changes in electrode thickness and / or insufficient fibrillation may occur, resulting in low mechanical strength of the electrode.

[0071] In Figure 5A , during the manufacture of the electrode according to the present disclosure, the roll-to-roll method utilizes one or more pairs of rollers having the same diameter and different linear speeds L1 and L2, where L1≠L2. The different linear speeds can be achieved using two different drive motors that drive the rollers at different speeds or a single motor that drives at least one roller via gears with different transmission ratios. Due to the speed difference, the rollers apply a pressure perpendicular to the active material layer and a shear force parallel to the active material layer. In Figure 5B , one or more pairs of rollers with different diameters can also be used to provide different linear speeds L1 and L2, where L1≠L2.

[0072] Now refer to Figure 6 , the manufacturing method according to the present disclosure uses rollers with different linear speeds to generate sufficient shear force to promote PTFE fibrillation by enhancing the frictional movement between particles. The mixture 215 for the active material layer is supplied between a pair of rollers 214-11 and 214-12 (with linear speeds R1 and r1 respectively) at 210. After being pressed and / or heated, the mixture 215 is supplied around one or more guide rollers 216 between the rollers 214-21 and 214-22 (with linear speeds R2 and r2 respectively).

[0073] After being pressed and / or heated, the mixture 215 is supplied around one or more guide rollers 216 between the rollers 214-31 and 214-32 (R3 and r3 respectively). After being pressed and / or heated, the mixture 215 is supplied around one or more guide rollers 216 between the rollers 214-N1 and 214-N2 (R N and r N) The mixture 215 is supplied around one or more guide rollers 216 between them, where N1 and N2 are integers greater than 1. The substrate 222 (e.g., a current collector with an adhesive coating) is supplied from the roller 220 between the rollers 214-N1 and 214-N2 to laminate the active material layer and the current collector to form the electrode 224. The electrode 224 is collected on the roller 326.

[0074] R N and r N The linear velocities of are defined as L N and l N . L N-1 ≠l N-1 and L N =l N (where N≥2). At least two sets of rollers (R N =r N , N≥2) are used to roll the dry powder mixture into an active material layer and laminate the active material layer onto the current collector. In some instances, at least 1 pair and at most N-1 pairs of rollers have different linear velocities, where the ratio of L N-1 / l N-1 is from 1.05 to 2, and the ratio of L N / l N =1.0. In some instances, at least 1 pair and at most N-1 pairs of rollers have different linear velocities, where the ratio of L N-1 / l N-1 is from 1.02 to 1.5. All the rollers can be heated to a temperature of 40°C to 200°C. The rollers in each pair are on a paired basis or all the rollers have the same diameter.

[0075] Now refer to Figure 7 , the mixture 315 for the active material layer is supplied between a pair of rollers 314-11 and 314-12 at 310. After being pressed and / or heated, the mixture 315 is supplied around one or more guide rollers 316 between the rollers 314-31 and 314-22. After being pressed and / or heated, the mixture 315 is supplied around one or more guide rollers 316 between the rollers 314-31 and 314-32. After being pressed and / or heated, the mixture 315 is supplied around one or more guide rollers 316 between the rollers 314-N1 and 314-N2, where N1 and N2 are integers greater than 1. The substrate 322 (e.g., a current collector with an adhesive coating) is supplied from the roller 320 between the rollers 314-N1 and 314-N2 to form the electrode 324. The electrode 324 is collected on the roller 326.

[0076] R N and r N The linear velocities of are defined as L N and l N。R N-1 ≠r N-1 and R N =r N (where N≥2) and L N-1 ≠l N-1 and L N =l N (where N≥2). At least two pairs of rollers are used, with at least 1 and at most N - 1 pairs of rollers having different roller diameters to achieve different linear speeds, where the ratio of L N-1 / l N-1 is from 1.05 to 2.0, and L N / l N =1.0. It can be understood that one control motor can be used for each pair of rollers to reduce costs. All rollers can be heated to a temperature of 40°C to 200°C.

[0077] Now referring to Figure 8 and Figure 9 , a continuous roller set can be controlled at different linear speeds (e.g., having the same or different diameters). The different linear speed / roller diameter design of adjacent roller sets is applied so that additional shear forces can promote PTFE fibrillation. A dry powder mixture is supplied between adjacent pairs of rollers. In other words, the dry powder mixture is supplied between the first and second rollers, the second and third rollers, etc. The opposite sides of each roller are used to press and / or heat the active material layer twice (e.g., once between the roller and the adjacent roller on one side, and then between the roller and the adjacent roller on the opposite side).

[0078] In Figure 8 , the dry powder mixture is supplied between rollers 414 - 1 and 414 - 2 and between rollers 414 - 3, 414 - 4, …, and 414 - N. In some examples, a doctor blade 415 can be used to bias the active material layer towards the downstream roller. A substrate 422 is supplied between rollers 414 - N - 1 and 414 - N to produce an electrode 424 collected on roller 426. All rollers 414 - 1, 414 - 2, …, and 414 - N have the same diameter. The linear speed of R N is defined as L N , where L N-1 =l N (where N≥2) is used for lamination, and at least one adjacent roller set (from 1 to N - 1) has a different linear speed.

[0079] In Figure 9In [the context], a dry powder mixture is supplied between rollers 514-1 and 514-2 and between rollers 514-3, 514-4, …, and 514-N. A substrate 522 is supplied between rollers 514-N-1 and 514-N to produce an electrode 524 collected on roller 526. All rollers 514-1, 514-2, …, and 514-N have the same diameter. Roller size R N-1 = R N (where N ≥ 2) is for lamination, and at least one adjacent roller group (from 1 to N-1) has a different roller diameter.

[0080] Now refer to Figure 10 , which shows a method for manufacturing an electrode. At 610, the dry powder mixture contains a mixed active material and a conductive additive. At 614, a PTFE binder is added to the mixture. At 618, the mixture is fibrillated with high shear force. At 622, the dry mixture is passed through at least a pair of rollers with different linear speeds to generate a shear force to fibrillate the binder. At 626, the mixture is laminated onto a current collector to form an electrode.

[0081] The foregoing description is merely exemplary and is in no way intended to limit the present disclosure, its application, or uses. The broad teachings of the present disclosure may be implemented in a variety of forms. Thus, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited because other modifications will become apparent after studying the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be implemented in a different order (or simultaneously) without changing the principles of the present disclosure. Additionally, although the various embodiments are described above as having certain features, any one or more of the features described with respect to any one embodiment of the present disclosure may be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and a mutual substitution of one or more embodiments is still within the scope of the present disclosure.

[0082] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "joined," "coupled," "adjacent," "next to," "on top of," "on," "under," and "disposed." Unless explicitly described as "direct," when the relationship between a first element and a second element is described in the foregoing disclosure, the relationship can be a direct relationship in which no other intervening element exists between the first element and the second element, or an indirect relationship in which one or more intervening elements exist between the first element and the second element (spatially or functionally). The phrase "at least one of A, B, and C" as used herein shall be construed to mean a logical (A or B or C) using non-exclusive logical OR and shall not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0083] In the drawings, the direction of an arrow as indicated by the arrow generally shows the information flow (such as data or instructions) of interest in the illustration. For example, when elements A and B exchange various information but the information sent from element A to element B is relevant to the illustration, the arrow can point from element A to element B. Such a unidirectional arrow does not mean that no other information is sent from element B to element A. In addition, for the information transmitted from element A to element B, element B can send a request for the information or receive an acknowledgment to element A.

Claims

1. A system for manufacturing an electrode of a battery pack, comprising: N - 1 pairs of rollers configured to press and calender a dry mixture to form an active material layer of the electrode, where N is an integer greater than 1, wherein the dry mixture contains an active material, a conductive filler, and a binder; at least one pair of the N - 1 pairs of rollers includes a first roller running at a first linear speed and a second roller running at a second linear speed different from the first linear speed; and the Nth pair of rollers includes a third roller running at a third linear speed and a fourth roller running at a fourth linear speed the same as the third linear speed to laminate the active material layer onto a current collector.

2. The system according to claim 1, wherein the binder includes polytetrafluoroethylene (PTFE).

3. The system according to claim 1, wherein the first roller and the second roller have the same diameter.

4. The system according to claim 1, wherein the first roller has a larger diameter than the second roller.

5. The system according to claim 1, wherein the ratio of the first linear speed to the second linear speed is from 1.02 to 2.

0.

6. The system according to claim 1, wherein the ratio of the first linear speed to the second linear speed is from 1.05 to 1.

5.

7. The system according to claim 1, wherein the first roller and the second roller are heated to a temperature of 80°C to 200°C.

8. The system according to claim 1, wherein the electrode includes a cathode electrode.

9. The system according to claim 1, wherein the electrode includes an anode electrode.

10. A system for manufacturing an electrode of a battery pack, comprising: N adjacent rollers that press and calender the dry mixture N - 1 times to form an active material layer of the electrode, where N is an integer greater than 2, wherein the dry mixture contains an anode active material, a conductive filler, and a binder; at least two of the N adjacent rollers run at different linear speeds; and the (N - 1)th roller and the Nth roller of the N adjacent rollers run at the same linear speed to laminate the active material layer onto a current collector.

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