Apparatus adapted for unwinding of an electrode assembly

Abstract

An apparatus (20) adapted for unwinding of an electrode assembly (1) and separation of layers (2, 3, 4, 5) of the electrode assembly (1). The apparatus (20) comprises a first holder (24) configured to support a wound electrode assembly (1, 6, 8) from which one or more layers (2, 3, 4, 5) are to be separated. The apparatus further comprises a second and a third holder (26, 28), each configured to create a pulling force in a respective layer (2, 4) of the electrode assembly (1) to thereby unwind the electrode assembly from the first holder (24) and to wind up said respective layer (2, 4). The apparatus also comprises a plurality of rotatably arranged separation rollers (36, 37, 38, 39) configured to separate adjacent layers of the electrode assembly from each other as a result of the pulling forces created by the second and third holders (26, 28). A method for separating layers of an electrode assembly using the apparatus, and a method for post-mortem analysis are also described.

Description

[0001] APPARATUS ADAPTED FOR UNWINDING OF AN ELECTRODE ASSEMBLY

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to an apparatus adapted for unwinding of an electrode assembly. The present disclosure also relates in general to a method for separating one or more layers of an electrode assembly. Moreover, the present disclosure relates in general to a method for post-mortem analysis of an electrode layer of an electrode assembly.

[0004] BACKGROUND

[0005] The electrification of vehicles has led to a lot of research being focused on energy storage devices that may be used for powering electrical propulsion units of vehicles. One of the most important issues to consider is the service life of the energy storage device as it directly affects the total life cost of the vehicle.

[0006] Energy storage devices for vehicles require many electrochemical cells to achieve the desired capacity. Energy storage devices for vehicles may for example comprise one or more battery packs. Each battery pack may in turn comprise a plurality of battery modules, and each battery module may comprise a plurality of electrochemical cells, also known as battery cells. The most frequently used electrochemical cells today in energy storage devices for vehicles are secondary lithium-ion electrochemical cells. The electrochemical cells may be classified as cylindrical cells, prismatic cells or pouch cells depending on the geometrical configuration of the electrochemical cells.

[0007] In general, cylindrical cells can be produced faster and therefore at lower cost than prismatic battery cells. However, prismatic cells typically allows for higher capacity and a much more efficient use of space in view of their shape, which are factors that are very important within the automotive industry. Furthermore, prismatic cells have the advantage of higher capacity as they can be stacked up better in their rigid casings compared to pouch cells which have a flexible outer casing. Moreover, the prismatic cells are typically less susceptible to damage caused by high temperatures and humidity compared to pouch cells. Therefore, prismatic battery cells are often used in energy storage devices for vehicles, especially in heavy vehicles. Each electrochemical cell comprises an anode, a cathode and an electrolyte present between the anode and the cathode. The electrolyte is an electrically insulating, but ionically conducting electrolyte enabling ions to move through the electrochemical cell between the anode and cathode. Typically, the electrolyte is a liquid electrolyte, although solid electrolytes are also possible. At least when the electrolyte is a liquid electrolyte, the electrochemical cell further comprises a separator arranged between the anode and cathode. The separator is configured to contain the electrolyte and to prevent short circuit between the anode and the cathode. The anode, the cathode and the separator are typically manufactured into an electrode assembly which for example may be winded to a jelly roll. Thereafter, the jelly roll is arranged in the casing, which is thereafter filled with the electrolyte and sealed to form the battery cell. In case of a cylindrical cell, the jelly roll has a cylindrical configuration. However, in the case of a prismatic cell, the jelly roll may suitably be a prismatic jelly roll.

[0008] The service life of an energy storage device is dependent of the configuration of the energy storage device as such, including for example the selection of constituent materials of the electrochemical cells (such as electroactive materials and electrolyte), the jelly roll configuration, and the relative arrangement of the electrochemical cells and how they are connected within the energy storage device. Moreover, the service life of an energy storage device is affected by how it is operated. For example, the charging / discharging rate as well as temperature conditions during charging / discharging may affect the aging of the electrochemical cells within the energy storage device and thereby the service life.

[0009] To be able to improve the service life of energy storage devices, it is important to understand the aging mechanisms for various electrochemical cells. In practice, the extent of degradation can be distributed very differently throughout the electrode area within a cell. In an automotive Li-ion cell, there may typically be about 1 m2of electrode area for each electrode wound in a package often less than 0.5 liter in volume. Uneven, or heterogeneous, degradation drives increasingly rapid degradation, which results in increasingly rapid loss of capacity and / or power of the cell. The reasons for the heterogenous degradation may be related to manufacturing tolerances as well as gradients in internal or external conditions during operation of the electrochemical cell. Performing post-mortem analysis of electrochemical cells may therefore contribute to a better understanding of the factors affecting the service life.

[0010] To be able to perform post-mortem analysis of electrode layers of an electrochemical cell, the jelly roll needs to be removed from the casing and the electrolyte, unwound and the respective layers of the electrode assembly separated from each other. The unwinding and separation of the layers is a long and tedious process that typically requires an operator to spend an average of 30 minutes (depending on the length of the electrode assembly) of manual work. It requires the operator to work inside a glove box, which makes it more challenging. Furthermore, manual unwinding and separation is prone to electrode and separator tearing, deposition of foreign material on the surface of the layers, and delamination of the electroactive material from the current collector. Therefore, there is a need for a solution that is faster, safer, more consistent and preferably also automated.

[0011] US 2022 / 0344773 Al proposes a method for separating battery components. A battery casing of a battery is cut to uncover a battery cell core, which is then washed to remove an electrolyte therefrom. An outer wrapping layer of the washed battery cell core is cut to form an open loose end, and the open loose end is engaged by first and second rollers to unroll a laminate therefrom. Said laminate includes a cathode layer, an anode layer, a first polymer separator layer, and a second polymer separator layer. The laminate is then separated into the cathode layer, the anode layer, the first polymer separator layer, and the second polymer separator layer by a plurality of rollers, each formed as a hollow cylindrical housing having a plurality of apertures formed therethrough. Negative pressure or vacuum suction is applied within the hollow cylindrical housing of each roller, thus causing the layer of the laminate adjacent the outer surface to be held thereagainst, peeling the closest layer from the remaining layers. However, the use of negative pressure or vacuum suction may risk damaging the surfaces of the layers to be examined, and the proposed method is therefore not suitable when seeking to perform post-mortem analysis. Furthermore, the proposed method is not adapted for unwinding and disassembly of prismatic cells.

[0012] SUMMARY

[0013] The object of the present invention is to enable a fast and reliable method for separating one or more layers of a wound electrode assembly with reduced risk for damage of said layers.

[0014] The object is achieved by the subject-matter of the appended independent claim(s).

[0015] The present disclosure provides an apparatus adapted for unwinding of an electrode assembly, said apparatus also adapted for separation of one or more layers of the electrode assembly. The apparatus comprises a rotatably arranged first holder. The first holder is configured to support a wound electrode assembly from which one or more layers are to be separated. The apparatus further comprises a rotatably driven second holder and a rotatably driven third holder. Each of the second and third holders is configured to create a pulling force in a respective layer of the electrode assembly to thereby unwind the electrode assembly from the first holder and to wind up said respective layer when separated from another layer of the electrode assembly. The apparatus further comprises a plurality of rotatably arranged separation rollers configured to separate adjacent layers of the electrode assembly from each other as a result of the pulling forces created by the second and third holders.

[0016] The herein described apparatus enables a fast process for separation of one or more layers of a wound electrode assembly as well as a reduced risk for damaging the layers during said separation. The reduced risk for damage is achieved by the separation being achieved by pulling forces in layers of the electrode assembly, which in turn create a shearing force between adjacent layers of the electrode assembly and thereby separation thereof. Thereby, a layer need not be e.g. scraped off from an adjacent layer, or be subjected to suction forces, which could result in damage of the surface of the relevant layer. Reducing the risk of damage during separation of layers in turn enables more accurate results during post-mortem analysis of the layer(s) of the electrode assembly. The fact that the process for separation is fast also enables a more cost-efficient post-mortem analysis.

[0017] Moreover, the herein described apparatus may also be used for separation of the layers of the electrode assembly for the purpose of recycling. Previous attempts of recycling electrode assemblies of batteries have shown that it is difficult to obtain a sufficiently cost effective method which also allows the different materials of the layers of the electrode assembly to be separated from each other. However, by usage of the herein described apparatus, the different layers of the electrode assembly may reliably be separated from each other in a sufficiently fast process to make it economically feasible.

[0018] The apparatus may further comprise a rotatably driven fourth holder configured to create a tensioning or pulling force in a first separator layer of the electrode assembly during unwinding of the electrode assembly from the first holder and to wind up said first separator layer when separated from adjacent layers of the electrode assembly. The apparatus may optionally also comprise a rotatably driven fifth holder configured to create a tensioning or pulling force in a second separator layer of the electrode assembly or an insulating layer during unwinding of the electrode assembly from the first holder. The fourth and optional fifth holders enables more than one layer of the electrode assembly to be separated simultaneously, which in turn results in a more cost-efficient separation process. The first holder may suitably be a non-driven holder. Thereby, the unwinding of the electrode assembly from the first holder is achieved solely by the pulling forces created in the respective layers of the electrode assembly by the rotatably driven holders.

[0019] Each of the rotatably driven second holder and third holder may be driven by a respective motor. This allows for an accurate control of the pulling forces created in the respective layers of the electrode assembly.

[0020] Moreover, each of the plurality of separation rollers may be a non-driven separation roller. In such a case, the separation rollers are configured to rotate as a result of the pulling forces created in the respective layers of the electrode layers as a layer passing over the surface of a separation roller. The usage of non-driven separation rollers ensures that only the purposively created pulling forces, created by the second and third holders, contribute to the separation of the layers of the electrode assembly and thereby further reduces the risk for damage of the respective layers.

[0021] According to one embodiment, each of the second and third holders comprises two elongated members arranged in parallel and on opposing sides of an axis of rotation of the respective holder. Said two elongated members are configured to support an electrode layer separated from the electrode assembly during the winding of said electrode layer on said holder. Using a holder comprising such elongated members as the second and third holders is particularly advantageous in case of prismatic electrode assemblies since the elongated members can be fitted to the regions of the respective electrode layer which were in the curved portions of the prismatic electrode assembly. This reduces the risk of damaging the electrode layers and the surfaces thereof since the original shape of the electrode layers, when present in the prismatic electrode assembly, may be essentially preserved also when winded up on the second or the third holders. Seeking to preserve the original shape of the electrode layers of a prismatic electrode assembly is important since the electrode layers tend to, at the curved portions, delaminate the electroactive material and the current collector of the electrode layer or the surfaces of the electrode layers disintegrate the more the electrode layers are bent out of their original shape. It is especially important to reduce the risk of damaging the electrode layers when separating the layers of the electrode assembly for the purpose of enabling post-mortem analysis thereon.

[0022] The above described two elongated members may be arranged at an adjustable distance from each other. This has the advantage of allowing adjustment of the relative distance of the elongated members to adapt to different sizes of prismatic electrode assemblies (in terms of distance between the curved portions of a prismatic electrode assembly), thereby avoiding the need for providing numerous second and third holders to meet all possible prismatic electrode assembly sizes.

[0023] The apparatus may further comprise at least one divider configured to align the electrode assembly within the apparatus during unwinding of the electrode assembly. Thereby, the apparatus may be used for unwinding of electrode assemblies having different sizes (in terms of width of the layers of the electrode assembly) without risk for misalignment of the electrode assembly, or layers thereof, during unwinding and separation of layers.

[0024] The apparatus may also comprise a plurality of pin rollers configured to align and guide the layers of the electrode assembly, when separated from the other layers of the electrode assembly, toward the respective holders. This reduces the risk of misalignment of the separated layer(s), which in turn could damage the separated layer(s).

[0025] Each of the first holder, the second holder and the third holder (as well as the fourth holder and fifth holder, if present) may be detachably mounted to a support structure of the apparatus. This allows for removing the holders from the apparatus for the purpose of arranging a would electrode assembly on the first holder and removing the separated layers from the other holders after unwinding.

[0026] The apparatus may further comprise a removable arranged image capturing device configured to capture an image of at least one surface of a layer separated from the electrode assembly. Thereby, an image of the at least one surface of the layer may be obtained in said apparatus while said layer passes the image capturing device during transfer from one holder to another, allowing for postmortem analysis through digital image analysis of the captured image. This allows for a fast postmortem analysis of the surface over substantially the entire longitudinal extension thereof, which results in a more cost efficient post-mortem analysis compared to previously known methods therefore, such as manually investigating the surface portion by portion.

[0027] The apparatus may further comprise a control device configured to control rotational speed of each of the second and third holders (and if present, of the fourth and fifth holders).

[0028] The present disclosure also provides a method for separating one or more layers from a wound electrode assembly using the apparatus described above. The method comprises arranging the wound electrode assembly on the first holder. The method further comprises inserting an unwound portion of the electrode assembly between a first pair of the separation rollers and guiding two adjacent layers of the unwound portion of the electrode assembly over a respective separation roller of the first pair of separation rollers. The method further comprises attaching or fastening an end portion of each one of said adjacent layers of the unwound portion of the electrode assembly to a respective rotatably driven holder of the second and third holders. Thereafter, the method comprises rotating each of the second and third holders so as to wind the layer whose end portion is attached or fastened thereto onto the holder, thereby creating a pulling force in said layer causing the electrode assembly to unwind from the first holder and said layer to be separated from an adjacent layer of the electrode assembly when passing over the separation rollers.

[0029] The method provides the same advantages as described above with regard to the herein described apparatus.

[0030] The present disclosure further provides a method for post-mortem analysis of an electrode layer of an electrode assembly, the method comprising separating the electrode layer from the electrode assembly using the apparatus as described above and capturing an image of at least one of the surfaces of the electrode layer using an image capturing device. By using the above described apparatus for separation of the electrode layer from the electrode assembly, there is less risk of damaging the electrode layer during separation. This in turn allows for more accurate results of the post-mortem analysis. Moreover, the separation process is considerably faster when using the apparatus described above compared to previously known methods which may enable more costefficient post-mortem analysis.

[0031] The method for post-mortem analysis of the electrode layer may further comprise performing digital image analysis of the captured image.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 schematically illustrates a cross-sectional view of a first example of an electrode assembly;

[0034] Fig. 2 schematically illustrates a cross-sectional view of a second example of an electrode assembly; Fig. 3 schematically illustrates a perspective view of an example of a cylindrical jelly roll;

[0035] Fig. 4 schematically illustrates a cross sectional view of an example of a prismatic jelly roll;

[0036] Fig. 5 schematically illustrates a typical appearance of a degraded electrode layer separated from a prismatic jelly roll of a battery;

[0037] Fig. 6a illustrates a perspective view of a first exemplifying embodiment of the herein described apparatus;

[0038] Fig. 6b illustrates a side view of the first exemplifying embodiment of the herein described apparatus;

[0039] Fig. 6c illustrates a side view of a second or third holder of the first exemplifying embodiment of the herein described apparatus;

[0040] Fig. 7a illustrates a perspective view of a second exemplifying embodiment of the herein described apparatus;

[0041] Fig. 7b illustrates a side view of the second exemplifying embodiment of the herein described apparatus; and

[0042] Fig. 8 schematically illustrates the unwinding and separation process which may be performed in the herein described apparatus.

[0043] DETAILED DESCRIPTION

[0044] The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and / or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof. The term "jelly roll" is in the present disclosure considered to mean a structure wherein a plurality of layers are wound together. A jelly roll may also sometimes be referred to in the art as a Swiss roll. The jelly roll may comprise or consist of an electrode assembly comprising said plurality of layers. In such a case, the electrode assembly is wound to the jelly roll structure. A jelly roll may have a cylindrical configuration, in which case the jelly roll is described herein as a cylindrical jelly roll. A cylindrical jelly roll has an essentially circular cross section, seen in a plane transversal to a center axis thereof. The center axis is here considered to mean the axis about which the electrode assembly is wound. Alternatively, a jelly roll may have a prismatic configuration, in which case the jelly roll is described herein as a prismatic jelly roll. A prismatic jelly roll has a substantially oval cross section, such as an elliptic or oblong cross section, seen in a plane transversal to the center axis thereof.

[0045] In the present disclosure, any term relating to an orientation, such as "vertical" or "horizontal", is herein used to describe the orientation relative to a surface on which the apparatus in arranged.

[0046] It should be noted that although the herein described apparatus has primarily been developed for the purpose of facilitating post-mortem analysis of electrochemical cells, it may also advantageously be used for separation of the layers of the electrode assembly during recycling of an electrochemical cell of a battery.

[0047] The present disclosure provides an apparatus adapted for unwinding of a wound electrode assembly and for separation of one or more layers of the electrode assembly from an adjacent layer of the electrode assembly. The apparatus comprises a rotatably arranged first holder. The first holder is configured to support a wound electrode assembly from which one or more layers are to be separated. The apparatus further comprises a rotatably driven second holder and a rotatably driven third holder. Each of said second and third holders is configured to create a pulling force in a respective layer of the electrode assembly in a longitudinal direction of said layer. More specifically, the second and third holders may each be configured to create a pulling force in an electrode layer of the electrode assembly. The pulling force is created by the layer being attached to the holder and thereafter rotating said holder, this also resulting in the layer being winded on the holder. The pulling forces in the respective layers, achieved by the second and third holders respectively, cause the electrode assembly to unwind from the first holder, which in turn enables separation of one or more layers therefrom. The apparatus may suitably further comprise a rotatably driven fourth holder and a rotatably driven fifth holder, wherein the fourth holder is configured to create a tensioning or pulling force in a first separator layer of the electrode assembly in a longitudinal direction of said layer. Said tensioning or pulling force is created in essentially the same way as the pulling forces in the electrode layers, i.e. by attaching the relevant layer to the holder and rotating the holder so as to wind the relevant layer on the holder. Similarly, the fifth holder may be configured to create a tensioning or pulling force in a fourth layer of the electrode assembly during unwinding of the electrode assembly from the first holder, wherein said fourth layer may be a second separator layer of the electrode assembly, an insulating layer of the electrode assembly, or an insulating layer arranged between adjacent turns of the wound electrode assembly. The apparatus further comprises a plurality of rotatably arranged separation rollers configured to separate adjacent layers of the electrode assembly from each other as a result of the pulling forces created by the second and third holders. More specifically, adjacent layers of the electrode assembly are arranged to pass over a respective separation roller of a pair of separation rollers. Each separation roller rotates as a result of the pulling force to which the adjacent layers are subjected, causing the separation rollers of the pair of separation rollers having opposite rotational directions. Moreover, in view of the separation rollers being configured to rotate as a result of the pulling forces in the respective layers, the risk of damaging the surface of the layers is reduced since the surface of the separation rollers follows the movement of the layer being in contact therewith.

[0048] It should be noted that in case there is no need to separate all of the layers from the electrode assembly from each other, e.g. if only desiring to perform post-mortem analysis on one of the electrode layers, the apparatus need not comprise the fourth and fifth holders. In such a case, one of the second and third holders is used to create the pulling force, and to wind up, the single layer to be separated from the electrode assembly, whereas the other one of the second and third holders is used to create a pulling force in the other layers of the electrode assembly (i.e. the layers which need not be separated from each other). Similarly, it may in some situations be desired to be able to separate the electrode layers and the separator layer, interposed between said electrode layers, from each other while being acceptable to leave a second separator layer or an insulating layer attached to one of the electrode layers. In such cases, the apparatus need to comprise the fourth holder, but not the fifth holder. Thus, the number of rotatably driven holders in the apparatus depend on the number of layers to be separated from the electrode assembly.

[0049] The above described second, third, fourth and fifth holders may each be configured to be rotatably driven by a respective electrical motor. This allows for an accurate control of the rotational speed of the holders, which in turn also allows for controlling the forces created by the holders in the respective layers of the electrode assembly. The first holder need however not be a driven holder since the pulling forces created by the second and third holders will naturally also cause a pulling force in the electrode assembly, this causing the first holder to automatically rotate as the electrode assembly is pulled therefrom.

[0050] The herein described apparatus may be used for unwinding and separation of one or more layers of an electrode assembly having a prismatic configuration. In such a case, the second and third holders may suitably each comprise two rod shaped elongated members onto which a layer separated from the electrode assembly may be winded. The two elongated members are arranged in parallel and on opposing sides of an axis of rotation of the holder. The two elongated members each comprises a free end and an opposing end mounted to a mounting member which in turn is mounted to a connection member configured to be connected to a motor for the purpose of driving the holder. If desired, the two elongated members may be slidably mounted to the mounting member such that the distance between the two elongated members may be adjusted.

[0051] Alternatively, the herein described apparatus may be used for unwinding and separation of one or more layers of an electrode assembly having a cylindrical configuration. In such a case, the second and third holders may suitably each have a cylindrical envelope surface on which layer, separated from the electrode assembly, is to be winded.

[0052] The herein described apparatus has a compact size allowing it to be arranged inside a glove box such that the electrode assembly and the layers thereof may be subjected to a controlled atmosphere during unwinding and separation of the layers.

[0053] Furthermore, the herein described apparatus also allows for post-mortem analysis to be performed inside the same glove box without having to remove a separated layer from the controlled atmosphere prior to the post-mortem analysis. The post-mortem analysis may be performed by an image capturing device configured to capture an image of a surface of layer separated from the electrode assembly. For the purpose of obtaining an image of said surface over substantially the entire longitudinal extension thereof, the image may be captured as the layer is transferred from one holder to another holder while passing the image capturing device.

[0054] Figure 1 schematically illustrates a cross-sectional view of a first example of an electrode assembly 1. The electrode assembly 1 comprises a plurality of layers that may be laminated or otherwise attached to each other so as to form a sandwich structure. More specifically, the electrode assembly 1 according to the first example comprises or consists of, a first electrode layer 2, a first separator layer 3, and a second electrode layer 4. The separator layer 3 is arranged between the first electrode layer 2 and the second electrode layer 4. The first electrode layer 2 may for example be an anode, and the second electrode layer 4 may for example be a cathode.

[0055] The first electrode layer 2 comprises a first sub-layer 2a bonded to a second sub-layer 2b. The first sub-layer 2a comprises a first electroactive material. The second sub-layer 2b constitutes a current collector. Similarly, the second electrode layer 4 comprises a first sub-layer 4a comprising a second electroactive material. The second electrode layer 4 further comprises a second sub-layer 4b bonded to the first sub-layer 4a. The second sub-layer 4b of the second electrode layer constitutes a current collector. The first and second electrode layers 2, 4 are arranged within the electrode assembly 1 such that their respective first sub-layers 2a, 4a are facing the separator layer 3.

[0056] The electrode assembly 1 according to the first example as shown in Figure 1 may be winded into a jelly roll. In order to prevent short-circuiting between the electrode layers of adjacent turns electrode assembly in the jelly roll, at least one insulating sheet or layer is arranged between adjacent turns of the electrode assembly in the jelly roll. According to one alternative, the insulating sheet or layer may be attached to one of the first electrode layer 2 and the second electrode layer 4. If so, the insulating sheet or layer constitutes a part of the electrode assembly 1 and is arranged such that it constitutes an outermost layer of the electrode assembly 1. Naturally, it is also possible that the electrode assembly comprises a first insulating sheet or layer attached to the first electrode layer 2 and a second insulating sheet or layer attached to the second electrode layer 4. If so, the first and second insulating sheets or layers constitutes the outermost layers of the electrode assembly. According to another alternative, the insulating layer or sheet is not a part of the electrode assembly 1 as such, but a separate constituent component of the jelly roll.

[0057] Figure 2 schematically illustrates a cross-sectional view of a second example of an electrode assembly 1, comprising a plurality of layers that may be laminated or otherwise attached to each other so as to form a sandwich structure. According to this example, the electrode assembly 1 comprises or consist of a first electrode layer 2, a first separator layer 3, a second electrode layer 4 and a second separator layer 5. The first electrode layer 2 may for example be an anode, and the second electrode layer 4 may for example be a cathode. The first separator layer 3 is arranged between the first electrode layer 2 and the second electrode layer 4. As shown in the figure, the second separator layer 5 may be arranged in the electrode assembly 1 outwardly of the second electrode layer 4. In other words, the second electrode layer 4 may be arranged between the first separator layer 3 and the second separator layer 5. Alternatively, the second separator layer 5 may be arranged outwardly of the first electrode layer 2 such that the first electrode layer 2 is arranged between the first separator layer 3 and the second separator layer 5.

[0058] Furthermore, the first electrode layer 2 comprises a second sub-layer 2b which is arranged between two first sub-layers 2a. Each of the two first sub-layers 2a comprises a first electroactive material and the second sub-layer 2b constitutes a current collector. Similarly, the second electrode layer 4 comprises a second sublayer 4b, constituting a current collector, arranged between two first sublayers 4a. Each of the two second sub-layers 4a of the second electrode layer 4 comprises a second electroactive material.

[0059] The electrode assembly 1 shown in Figure 2 may be winded to a jelly roll such that the second separator layer 5 is brought into contact with an electrode layer of an adjacent turn of the jelly roll. Thus, when the second separator layer 5 is arranged in the electrode assembly 1 outwardly of the second electrode layer 4 as shown in the figure, the second separator layer 5 would in the jelly roll also be in contact with the first electrode layer 2.

[0060] Figure 3 schematically illustrates a perspective view of a cylindrical jelly roll 6. The cylindrical jelly roll 6 comprises an electrode assembly 1 (such as shown in Figures 1 or 2) winded around a center axis A. The jelly roll 6 thus has a substantially cylindrical cross section in a plane transversal to the center axis A. The height of the cylindrical jelly roll corresponds to the width of the electrode assembly and the layers thereof, respectively.

[0061] Figure 4 schematically illustrates a cross-sectional view of a prismatic jelly roll 8. Similar to the cylindrical jelly roll 6 shown in Figure 3, the prismatic jelly roll 8 comprises an electrode assembly 1 (such as shown in Figures 1 or 2) wound around a center axis A in a plurality of turns. However, the prismatic jelly roll 8 has a substantially oval cross section seen in a plane transversal to the center axis A. The prismatic jelly roll 8 may for example be produced by pressing a cylindrical jelly roll 6 as shown in Figure 3, or by using an oval mandrel during winding of the electrode assembly 1. As shown in Figure 4, a prismatic jelly roll 8 comprises a curved portion 9 in which the electrode assembly has a considerably lower radius than in other portions of the jelly roll.

[0062] The extent of degradation (caused by for example loss of active material and / or formation of solid electrolyte interface on the surface of an electrode layer) of an electrode layer of the electrode assembly during use thereof in a battery can be distributed differently over the surface area of the electrode layer. Figure 5 schematically illustrates a typically appearance of a degraded electrode layer 2' separated from a prismatic jelly roll of a battery, for example at the end of the service life of the battery. In the figure, the degraded electrode layer 2' is shown in a top view, such that the surface shown is the one which faced the opposing electrode layer before separation from the jelly roll. As seen from the figure, the surface of the degraded electrode layer 2' may comprise highly degraded regions 11, medium degraded regions 12, and regions 13 where the degradation is relatively low. The different regions 11, 12, 13 may be distinguished from each other for example by differing from each other in color when the surface of the electrode layer is visually inspected. The regions 13 having the lowest degradation are typically present between the regions which was in the curved portions 9 (see Figure 4) of the prismatic electrode assembly before unwinding. The highly degraded regions 11 are typically present at the regions which was in the curved portions 9 before unwinding. The part of the curved portions 9 with the lowest radius is in Figure 5 illustrated by the dashed lines 9'.

[0063] When desiring to perform post-mortem analysis of an electrode layer, such as the degraded electrode layer 2' shown in Figure 5, it is important to be able to separate said electrode layer from the electrode assembly with as low damage as possible to the surface of the electrode layer. This is an important factor to be able to study the heterogeneity of the degradation over the surface as well as the primary mechanisms for the degradation. For a prismatic jelly roll, the highest degradation of the electrode layers typically occurs at the curved portions as described above. However, these portions also have the highest risk of being damaged since bending too much from the original shape, i.e. the shape of the electrode layers when present in the prismatic jelly roll, may lead to disintegration of the surfaces thereof and even delamination of the electroactive material from the current collector.

[0064] Figure 6a illustrates a perspective view of a first exemplifying embodiment of the herein described apparatus 20. Furthermore, Figure 6b illustrates a side view of the apparatus shown in Figure 6a. The apparatus according to the first exemplifying embodiment is especially suitable for unwinding of prismatic jelly rolls, i.e. prismatic electrode assemblies, as will be explained in further detail below.

[0065] The apparatus 20 comprises a plurality of rotatably arranged holders and a support structure 21 configured to support said holders. The plurality of holders are arranged in the apparatus 20 such that their respective rotational axes are parallel to each other. The support structure 21 may comprise a first support frame 22 and a second support frame 23. The first and second support frames 21, 23 may be arranged in parallel and extending substantially vertically. The apparatus 20 may also comprise an outer housing. Such a housing has however been omitted in the figures in order to clearly show the details of the apparatus. The housing may suitably comprise at least one door to allow easy access to the constituent components of the apparatus arranged inside the housing.

[0066] The plurality of rotatably arranged holders comprises a first holder 24. The first holder 24 is removably and rotatably arranged in the apparatus 20. More specifically, the first holder 24 may, at a first longitudinal end thereof, be rotatably supported by the first support frame 22, and, at a second longitudinal end thereof, be rotatably supported by the second support frame 23 as shown in the figure. The first holder 24 may suitably be arranged in the apparatus 20 such that its rotational axis B extends substantially horizontally. The first holder 24 is configured to support a wound electrode assembly during unwinding thereof. The first holder 24 may suitably be a non-driven holder. A nondriven holder is in the present disclosure considered to mean a holder that is not directly driven by a motor or the like for the purpose of rotation of said holder. Instead, the first holder 24 may be configured to rotate as a result of a pulling force to which a wound electrode assembly, supported by the first holder 24, is subjected.

[0067] The plurality of rotatably arranged holders further comprises a second holder 26 and a third holder 28. The second holder 26 has a rotational axis C arranged in parallel with a rotational axis D of the third holder 28. The second and third holders 26, 28 may be arranged such that the rotational axes C and D extend substantially horizontally. Like the first holder 24, each one of the second holder 26 and the third holder 28 is removably arranged in the apparatus 20 by being detachably mounted to the support structure 21.

[0068] Each one of the second holder 26 and the third holder 28 is a rotatably driven holder. More specifically, the second holder 26 may be configured to be rotatably driven by a first electrical motor 27. Similarly, the third holder 28 may be configured to be rotatably driven by a second electrical motor 29. The first and second electrical motors 27, 29 may each be mounted to the support structure 21, for example at the first support frame 22, and releasably connected to the respective holder of the second and third holders 26, 28.

[0069] The second and third holders 26, 28 are each configured to create a pulling force in a respective layer of the electrode assembly to thereby unwind the electrode assembly from the first holder 24. Said pulling force in a respective layer of the electrode assembly is created as a result of the rotation of the second and third holders 26, 28, respectively. The rotation of the second and third holders 26, 28 also leads to winding of a respective layer of the electrode assembly onto each of said holders. More specifically, the second holder 26 may be configured to create a pulling force in, and to wind up, a first electrode layer of the electrode assembly, and the second holder 28 may be configured to create a pulling force in, and to wind up, a second electrode layer of the electrode assembly. The second holder 26 and the third holder 28 have essentially the same configuration, which will be described in more detail with reference to Figure 6c.

[0070] The apparatus 20 may suitably further comprise a fourth holder 30 and a fifth holder 32, each removably arranged in the apparatus 20. Each of the fourth holder 30 and the fifth holder 32 is a rotatably driven holder. The fourth holder 30 may be rotatably driven by a third electrical motor 31 and the fifth holder 32 may be driven by a fourth electrical motor 33. The third and fourth electrical motors 31, 33 may, like the first and second electrical motors 27, 29, each be mounted to the support structure 21, for example at the first support frame 22, and releasably connected to the respective holder.

[0071] The fourth holder 30 is configured to create a tensioning force or a pulling force in a layer of the electrode assembly, more specifically a separator layer of the electrode assembly, during unwinding of the electrode assembly. A tensioning force is here considered to mean a force which, in itself, is not sufficient for unwinding the electrode assembly from the first folder 24 but which is sufficient for keeping a tension in the separator layer sufficient to allow separation of an electrode layer from the separator layer. The fifth holder 32 may be configured to create a tensioning force or a pulling force in a second separator layer of the electrode assembly, if present, during unwinding. In case the electrode assembly does not comprise two separator layers, the fifth holder 32 may instead be configured to create a tensioning force or a pulling force in an insulating layer or sheet providing electrical insulation between adjacent turns of the wound electrode assembly. Said insulating layer or sheet may be a constituent component of the electrode assembly or be a self-standing constituent component of the jelly roll.

[0072] The apparatus 20 further comprises a plurality of separation rollers configured to separate adjacent layers of the electrode assembly from each other as a result of pulling forces created by the second and third holders 26, 28 and the tensioning / pulling forces created by the fourth and fifth holders 30, 32. Each separation roller of the plurality of separation rollers is rotatably arranged in the apparatus and may be supported by the support structure 21. The separation rollers are arranged in the apparatus 20 such that their axes of rotation are parallel with each other as well as parallel to the rotational axes B, C and D of the holders 24, 26, 28. Moreover, each of the separation rollers may suitably have a smooth, cylindrical, envelope surface in order to reduce the risk of damage of a surface of a layer of the electrode assembly when said layer is brought into contact with the separation roller. A smooth envelope surface is here considered to mean an envelope surface which is a continuous surface free from intentional holes and protrusions. The envelope surface should suitably a surface roughness which does not risk to unduly damage the surface of a layer of the electrode assembly passing over said separation roller.

[0073] The plurality of separation rollers may comprise a first separation roller 36, a second separation roller 37, a third separation roller 38 and a fourth separation roller 39. The first separation roller 36 and the second separation roller 37 are arranged so as to achieve a first separation, in which the electrode assembly is separated into a first half-assembly, comprising the first electrode layer and a first separator layer, and a second half-assembly comprising the second electrode layer and a second separator layer or an insulating layer / sheet. Thus, the first separation roller 36 and the second separation roller 37 may be regarded to constitute a first pair of separation rollers configured to perform the first separation of adjacent layers of the electrode assembly. The second separation roller 37 and the third separation roller 38 are arranged so as to achieve a second separation, in which layers of the first-half assembly are separated from each other. In other words, the second separation roller 37 and the third separation roller 38 are arranged so as to separate the first electrode layer from the first separator layer. Similarly, the first separation roller 36 and the fourth separation roller 39 are arranged so as to achieve a third separation, in which the layers of the second half-assembly are separated. In other words, the first separation roller 36 and the fourth separation roller 39 are arranged so as to separate the second electrode layer from the second separator layer or, where applicable, the insulating sheet or layer.

[0074] As the layers of the electrode assembly pass over the separation rollers, a shearing force between adjacent layers of the electrode assembly is created as a result of the pulling forces achieved by the first and second holders 26, 28. Thereby, no scraping blade or the like is necessary for the purpose of separating adjacent layers of the electrode assembly. Hence, the risk of damaging the surface of the different layers of the electrode assembly is reduced.

[0075] The apparatus 20 further comprises a set 42 of pin rollers configured to guide and align the electrode assembly as it passes from the first holder 24 towards the first and second separation rollers 36, 37. In other words, the set 42 of pin rollers is configured to guide and align the electrode assembly before any layer has been separated therefrom. Each pin roll of the set 42 is arranged such that its rotational axis is parallel to the rotational axis B of the first holder 24. Furthermore, the pin rollers of the set 42 of pin rollers are suitably arranged in two parallel rows as shown in Figures 6a and 6b. Furthermore, the apparatus may comprise additional pin rollers 43-50 (see Figure 8) configured to guide and align the layers of the electrode assembly towards the corresponding holder after having been separated from the electrode assembly. In Figure 6a, the pin rollers 43, 44, 45, 46 and 47 are visible.

[0076] The apparatus 20 may also comprise a divider 40. The divider may be a plate-like member and be configured to extend substantially vertically. The divider 40 is configured to align the electrode assembly, and the layers thereof, as they pass within the apparatus 20 during unwinding and separation of layers of the electrode assembly. Furthermore, the divider 40 is suitably slidably movable relative to the separation rollers 36-38 and the set 42 of pin rollers to adapt to different possible widths of the electrode assembly.

[0077] As previously mentioned, the second holder 26 and the third holder 28 have the same configuration which will be described in more detail with reference to Figure 6c. Figure 6c illustrates a side view of the second holder 26, or the third holder 28, of the apparatus 20 shown in Figures 6a and 6b.

[0078] Each of the second and third holders 26, 28 comprises a first elongated member 51 / 61 and a second elongated member 52 / 62 onto which an electrode layer from the electrode assembly is to be winded. The first and second elongated members 51 / 61, 52 / 62 may suitably be substantially rod shaped. Moreover, the first and second elongated members 51 / 61, 52 / 62 are each arranged to extend longitudinally substantially parallel to, and on opposing sides of, the rotational axis C / D of the holder. Each of the second and third holders 26, 28 may further comprise a third elongated member 53 / 63 arranged coaxially with the rotational axis C / D allowing the holder to be rotatably mounted to both of the support frames 22 and 23 (shown by dashed lines in the figure). Said third elongated member 53 / 63 may also be rod-shaped.

[0079] Each of the first and second elongated members 51 / 61, 52 / 62 comprises a free end 51a / 61a, 52a / 62a and is, at the opposing longitudinal end, connected to a mounting member 54 / 64 of the holder. The mounting member 54 / 64 is configured to allow connection of the first and second elongated members to a connection member 55 / 65 of the holder, such that the first and second elongated members will rotate about the rotational axis C / D as a result of the rotation of the connection member 55 / 65. Said connection member 55 / 65 is arranged coaxially with the rotational axis C / D and is configured to be connected to an electrical motor 27 / 29 for the purpose of rotationally driving the holder. The mounting member 54 / 64 extends substantially transversal to the longitudinal extension of the elongated members such as essentially forming a U-shape together with the first and second elongated members.

[0080] Suitably, the first and second elongated members 51 / 61, 52 / 62 may each be slidably mounted to the mounting member 54 / 64 such that the distance between the first and second elongated members may be adjusted. This may be achieved by the first and second elongated members 51 / 61, 52 / 62 each being attached to a respective body 56, 57 which is slidably arranged in a recess 58 (see Figure 6a) of the mounting member 54 / 64.

[0081] Using a holder comprising the above described first and second elongated members 51 / 61, 52 / 62 as the second and third holders 26, 28 is particularly advantageous in case of prismatic electrode assemblies since the elongated members can be fitted to the region of the respective electrode layer which was in the curved portion 9 (compare with Figures 4 and 5) of the prismatic electrode assembly. Thereby, the original shape the electrode layers, i.e. the shape of the electrode layers when present in the prismatic electrode assembly before unwinding, may be essentially preserved when winding up said layers on the respective holders, which in turn reduces the risk of damaging the electrode layers.

[0082] The apparatus 20 shown in Figures 6a and 6b may further comprise a removably arranged image capturing device 35 (see Figure 6b) configured to capture an image of at least one surface layer separated from the electrode assembly. Said image capturing device may for example be introduced into the apparatus via an opening 25 in the support frame 23 and / or the support frame 22. Thereby, an image of the at least one surface of the layer may be obtained in said apparatus while said layer passes the image capturing device during transfer from one holder to another, allowing for postmortem analysis through digital image analysis of the captured image.

[0083] For the purpose of capturing an image of a surface of an electrode layer separated from an electrode assembly after the unwinding and separation process has been completed, the holders with their respective layers winded thereon may be removed from their position during the unwinding process and disconnected from their respective motors. Thereafter, one of the holders comprising a winded separated electrode layer (i.e. one of the second holder 26 and third holder 28) may be arranged at the position held by the first holder 24 during the unwinding and separation process. A new rotatably driven holder is thereafter placed at the position held by the second holder 26 or the third holder 28 during the unwinding and separation process. Thereafter, the free end of the electrode layer is moved through the apparatus, such that the surface of the electrode layer passes the image capturing device, and attached to the new holder. By rotatably driving the new holder, the electrode layer will unwind from holder onto which it was winded during the separation process and the surface of the electrode layer will pass the image capturing device such that an image thereof may be captured.

[0084] Figure 7a illustrates a perspective view of, and Figure 7b illustrates a side view of, a second exemplifying embodiment of the herein described apparatus. The second exemplifying embodiment corresponds to the first exemplifying embodiment described above and shown in Figures 6a and 6b, except that the second and third holders 26, 28 are cylindrical holders. Each of the second holder 26 and the third holder 28 may be in the form of solid cylinders, as shown in Figures 7a and 7b, or in the form of hollow cylinders.

[0085] Figure 8 schematically illustrates the unwinding and separation process which may be performed in the herein described apparatus. For ease of illustration, the second and third holders are shown as cylindrical holders. It should however be noted that said holders may alternatively have the configuration shown in Figures 6a-6c. In the figure, the arrows illustrates the rotational directions of the different holders and separator rollers. Moreover, the unwinding and separation process is illustrated for an electrode assembly having the configuration as shown in Figure 2, i.e. comprising a first electrode layer 2, a first separator layer 3, a second electrode layer 4, and a second separator layer 5.

[0086] As shown in Figure 8, the electrode assembly 1 is unwinded from the first holder 24 and passes through the set 42 of pin rollers configured to guide and align the electrode assembly towards the first and second separator rollers 36, 37. The electrode assembly 1 is separated into a first halfassembly 11 following the surface of the first separation roller 36, and a second half-assembly 12 following the surface of the second separation roller 37. The first half-assembly 11 comprises the second electrode layer 4 and the second separator layer 5. The second half-assembly 12 comprises the first electrode layer 2 and the first separator layer 3.

[0087] The second half-assembly 12 passes between the second separation roller 37 and the third separation roller 38 and is thereafter separated into the first electrode layer 2 and the first separator layer 3. The first electrode layer is guided by a pin roller 43 towards the second holder 26, and thereafter winded up on the second holder 26. The first separator layer 3 is guided by pin rollers 44 and 45 towards the fourth holder 30 and is thereafter winded up on the fourth holder 30. The first half-assembly 11 passes between the first separation roller 36 and the fourth separation roller 39 and is thereafter separated into the second electrode layer 4 and the second separator layer 5. The second electrode layer 4 is guided by pin rollers 48, 49 and 50 towards the third holder 28, and thereafter winded up on the third holder 28. The second separator layer 5 is guided by pin rollers 46 and 47 toward the fifth holder 32 and thereafter winded up on the fifth holder 32.

[0088] The rotation of the second holder 26 creates a pulling force in the first electrode layer 2 in the longitudinal direction thereof, and hence also in the second half-assembly 12. Moreover, the rotation of the third holder 28 creates a pulling force in the second electrode layer 4 in the longitudinal direction thereof, and hence also in the first half-assembly 11. These pulling forces causes the electrode assembly 1 to be unwinded from the first holder 24 as well as separation of the layers of the electrode assembly as it passes the separation rollers as described above. Moreover, the fourth holder 30 and the fifth holder 32, respectively, may also be configured to create a pulling force in the first separator layer 3 and the second separator layer 5, and thereby contribute to the unwinding of the electrode assembly 1 from the first holder. Alternatively, the fourth holder 30 and the fifth holder 32 are only configured to create a tensioning force sufficient to separate the respective electrode layer from the adjacent separator layer.

Claims

CLAIMS1. An apparatus (20) adapted for unwinding of an electrode assembly (1) and for separation of one or more layers (2, 3, 4, 5) of the electrode assembly (1), the apparatus (20) comprising: a rotatably arranged first holder (24) configured to support a wound electrode assembly (1, 6, 8) from which one or more layers (2, 3, 4, 5) are to be separated; a rotatably driven second holder (26) and a rotatably driven third holder (28), each of the second holder (26) and the third holder (28) being configured to create a pulling force in a respective layer (2, 4) of the electrode assembly (1) to thereby unwind the electrode assembly (1) from the first holder (24) and to wind up said respective layer (2, 4) when separated from another layer of the electrode assembly (1); a plurality of rotatably arranged separation rollers (36, 37, 38, 39) configured to separate adjacent layers of the electrode assembly (1) from each other as a result of the pulling forces created by the second and third holders (26, 28).

2. The apparatus (20) according to claim 1, further comprising: a rotatably driven fourth holder (30) configured to create a tensioning or pulling force in a first separator layer (3) of the electrode assembly (1) during unwinding of the electrode assembly (1) from the first holder (24) and to wind up said first separator layer (3) when separated from adjacent layers of the electrode assembly (1); and optionally a rotatably driven fifth holder (32) configured to create a tensioning or pulling force in a second separator layer (5) of the electrode assembly (1) or an insulating layer during unwinding of the electrode assembly (1) from the first holder (24).

3. The apparatus (20) according to any one of claims 1 or 2, wherein the first holder (24) is a non-driven holder.

4. The apparatus (20) according to any one of the preceding claims, wherein each one of the rotatably driven second and third holders (26, 28) is driven by a respective motor (27, 29).

5. The apparatus (20 according to any one of the preceding claims, wherein each of the plurality of separation rollers (36, 37, 38, 39) is a non-driven separation roller.

6. The apparatus (20) according to any one of the preceding claims, wherein each of the second holder (26) and the third holder (28) comprises two elongated members (51, 52, 61, 62) arranged in parallel and on opposing sides of an axis of rotation (C, D) of the holder, said two elongated members (51, 52, 61, 62) configured to support an electrode layer (2, 4) of the electrode assembly (1) during wind up thereon.

7. The apparatus (20) according to claim 6, wherein the two elongated members (51, 52, 61, 62) are arranged at an adjustable distance from each other.

8. The apparatus (20) according to any one of the preceding claims, further comprising at least one divider (40) configured to align the electrode assembly (1) within the apparatus (20) during unwinding of the electrode assembly (1).

9. The apparatus (20) according to any one of the preceding claims, further comprising a plurality of pin rollers (43-50) configured to align and guide the layers (2, 3, 4, 5) of the electrode assembly (1), when separated from the other layers of the electrode assembly (1), toward the respective holders.

10. The apparatus (20) according to any one of the preceding claims, wherein each of the first holder (24), the second holder (26) and the third holder (28) is detachably mounted to a support structure (21) of the apparatus (20).

11. The apparatus (20) according to any one of the preceding claims, further comprising a removably arranged image capturing device (35) configured to capture an image of at least one surface of a layer (2, 4) separated from the electrode assembly (1).

12. The apparatus (20) according to any one of the preceding claims, further comprising a control device configured to control rotational speed of each of the second and third holders (26, 28).

13. A method for separating one or more layers (2, 3, 4, 5) from a wound electrode assembly (1, 6, 8) using the apparatus (20) according to any one of the preceding claims, the method comprising: arranging the wound electrode assembly (6, 8) on the first holder (24),inserting an unwound portion of the electrode assembly (1) between a first pair of the separation rollers (36, 37, 38, 39) and guiding two adjacent layers of the unwound portion of the electrode assembly (1) over a respective separation roller (36, 37) of the first pair of separation rollers (36, 37), attaching or fastening an end portion of each of said adjacent layers of the unwound portion of the electrode assembly (1) to a respective rotatably driven holder of the second and third holders (26, 28), rotating each of the second and third holders (26, 28) so as to wind the layer whose end portion is attached or fastened thereto onto the holder, thereby creating a pulling force in said layer causing the electrode assembly (1) to unwind from the first holder (24) and said layer to be separated from an adjacent layer of the electrode assembly when passing over the separation rollers (36, 37).

14. A method for post-mortem analysis of an electrode layer (2, 4) of an electrode assembly (1) of a battery, the method comprising: separating the electrode layer (2, 4) from the electrode assembly (1) using the apparatus (20) according to any one of claims 1 to 12, and capturing an image of at least one of the surfaces of the electrode layer (2, 4) using an image capturing device (35).

15. The method according to claim 14, further comprising performing digital image analysis of the captured image.

Images