WO2021116666A1

WO2021116666A1 - Energy storage device

Info

Publication number: WO2021116666A1
Application number: PCT/GB2020/053126
Authority: WO
Inventors: Joseph Howard
Original assignee: Dyson Technology Limited
Priority date: 2019-12-11
Filing date: 2020-12-04
Publication date: 2021-06-17
Also published as: GB2590373B; GB201918201D0; CN114830385A; GB2590373A

Abstract

A method comprising providing a plurality of cells for an energy storage device. Each cell comprises a first and second electrode layer, and an electrolyte layer therebetween. The plurality of cells are stacked to form a cell stack. Exposed edges of the first and second electrode layers and the electrolyte layer of each of the plurality of cells are arranged along a side of the cell stack. A material is deposited on the side of the cell stack to at least partly cover the exposed edges of the first and second electrode layers and the electrolyte layer of each of the plurality of cells, to insulate the first and second electrode layers for each of the plurality of cells.

Description

ENERGY STORAGE DEVICE

Technical Field

The present invention relates to an energy storage device and, more specifically, although not exclusively, to methods and apparatus for manufacturing an energy storage device.

Background

A known method of producing energy storage devices such as solid-state thin film cells comprising layers of electrodes, electrolyte and current collectors is to form a stack on a substrate. The stack comprises a first electrode layer, an electrolyte layer, and a second electrode layer. Grooves are machined through the stack and filled with electrically insulating material to insulate the first electrode layer from the second electrode layer. The stack is then cut into separate sections, through the electrically insulating material, to form individual cells. Electrode layers of multiple cells stacked one on top of another are electrically connected to each other in order to connect the cells together.

Known methods for manufacturing energy storage devices can be complex. It is therefore desirable to provide a method of manufacturing an energy storage device that is more straightforward than known manufacturing methods.

Summary

According to a first aspect of the present disclosure, there is provided a method comprising: providing a plurality of cells for an energy storage device, each cell comprising: a first electrode layer; a second electrode layer; and an electrolyte layer between the first electrode layer and the second electrode layer; stacking the plurality of cells to form a cell stack, wherein an exposed edge of the first electrode layer, an exposed edge of the electrolyte layer, and an exposed edge of the second electrode layer of each of the plurality of cells are arranged along a side of the cell stack; and depositing a material on the side of the cell stack to at least partly cover the exposed edge of the first electrode layer, the exposed edge of the electrolyte layer, and the exposed edge of the second electrode layer of each of the plurality of cells, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

The approach of the first aspect simplifies insulation of the first and second electrode layers compared to an existing approach in which electrically insulating material is provided in narrow channels between neighbouring cells. For example, the side of the cell stack on which the material is deposited typically provides a larger surface area for deposition of the material than deposition within narrow channels. The manufacturing tolerances for deposition of the material may therefore be relaxed, allowing the material to be deposited more straightforwardly and efficiently.

Deposition of the material on the side of the cell stack can improve the coverage of the exposed edges of the first and second electrode layers and the electrolyte layer. This can reduce the risk of short circuits, which may otherwise occur if the first and second electrode layers are not entirely electrically insulated from each other. The efficiency of the manufacturing process may be further improved, by reducing the number of cell stacks that are insufficiently insulated, and which may otherwise be discarded for failing to satisfy quality control requirements.

In examples, the method comprises removing a portion of the material over the exposed edge of the first electrode layer of each of the plurality of cells, respectively. In this way, the exposed edge of the first electrode layer may be revealed or otherwise exposed, so that the first electrode layer of each of the cells may be connected to a further electrical component, e.g. to connect the cells in parallel or series. Although this provides an extra process step compared with applying the precise amount of material for insulation of the first and second electrode layers, the reduction in complexity of the process more than compensates for the additional process step of removing the portion of the material. In particular, the formation of an exposed first electrode layer, which is nevertheless sufficiently insulated from the second electrode layer to avoid or reduce the risk of short circuits, may be more efficient using the methods herein than existing methods. This is for example due to the extra efficiency associated with depositing the material on the side of the cell stack, in combination with the removal of the portion of the material over the exposed edge of the first electrode layer, which itself may be performed in an efficient manner. For example, the portion of the material may be removed straightforwardly by exploiting different material properties of the material and the layers underlying the material (such as the first and second electrode layers and the electrolyte layer).

In these examples, removing the portion of the material may use a laser. In such cases, the material is absorptive for electromagnetic radiation emitted by the laser. Laser removal of material, e.g. using laser ablation, is generally straightforward and easily controllable. This approach therefore typically allows the portion of the material to be removed in an efficient manner.

In examples in which the portion of the material is removed using a laser, the material may be more absorptive for the electromagnetic radiation than at least part of the exposed edge of the first electrode layer of a cell of the plurality of cells. For example, at least part of the first electrode layer of the cell may be at least one of: reflective or transmissive for the electromagnetic radiation. In this way, the different optical properties of these elements may be utilised to simplify the removal of the portion of the material. For example, the portion of the material may be ablated to a greater extent upon exposure to electromagnetic radiation emitted by the laser than at least part of the first electrode layer, as the portion of the material may absorb a greater proportion of the electromagnetic radiation than the part of the first electrode layer. The portion of the material may therefore be selectively removed, e.g. without removing or with removal of a smaller amount of, underlying elements such as the first electrode layer. This further simplifies removal of the portion of the material, and hence revelation of the exposed edge of the first electrode layer for connection to a further electrical component.

In these examples, the material may comprise a black material and a wavelength of the electromagnetic radiation emitted by the laser may at least partly overlap a visible wavelength range of the electromagnetic spectrum. For example, the properties of the material (e.g. such as the wavelengths absorbed by the material) may be selected so that removal of the portion of the material may be effected with an easily available and economic laser. A suitable material is for example a black material.

In these examples, removing the portion of the material using the laser may comprise: generating a laser beam using the laser; directing the laser beam such that the laser beam is incident on a surface of the material; and, while the laser beam is incident on the surface of the material, moving the laser beam relative to the surface of the material according to a raster pattern. This further simplifies removal of the portion of the material. For example, rather than controlling the motion of the laser beam according to a complex pattern to precisely remove a particular portion of the material without removing another portion, the laser beam can be straightforwardly scanned across the surface of the material, in a line-by4ine fashion. Despite this, the portion of the material may be removed without removing the other portion, so that the first and second electrode layers remain electrically insulated from each other. For example, the portion of the material may have a smaller thickness than the other portion of the material, so that the portion of the material is removed without removing an entirety of the other portion of the material. A remaining part of the other portion of the material may continue to insulate the first and second electrode layers from each other after the removal of the portion of the material.

In examples, the method comprises, after removing the portion of the material, depositing an electrical connector material on the side of the cell stack to contact the first electrode layer of each of the plurality of cells. This allows the cells to be connected in parallel in an efficient manner. For example, similarly to the deposition of the first material, the electrical connector material may be deposited straightforwardly on the side of the cell stack. In these examples, depositing the electrical connector material may use thermal spray deposition. This is for example a more efficient deposition method than other approaches for use in depositing materials according to complex patterns.

In examples, the material deposited on the side of the cell stack is a second material, the side of the cell stack is a second side of the cell stack, each cell of the plurality of cells within the cell stack comprises a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell, and the first side of each of the cells is arranged at a first side of the cell stack, opposite to the second side of the cell stack. The first material in this case protects the first side of the cell from exposure to a surrounding environment. This can reduce undesired reactions between the layers of each cell and the environment, which may otherwise occur (e.g. if the first and/or second electrode layers comprise highly reactive materials such as lithium).

In these examples, for each respective cell of the plurality of cells, the exposed portion of the second electrode layer may extend along the first side of the respective cell such that the first material is between the exposed portion of the second electrode layer of the respective cell and the first electrode layer of the respective cell. This can provide a greater contact area for connection of the second electrode layer to a further electrical component. This typically reduces contact resistance between the second electrode layer and the further electrical component, which can improve the performance of the manufactured energy storage device. For example, reducing contact resistance can reduce the risk of failure of the energy storage device and/or reduce unwanted heating of the energy storage device. This can, in turn, improve the safety of the energy storage device. In these examples, an electrical connector material may be deposited on the second side of the cell stack to contact the second electrode layer of each of the plurality of cells. This allows the cells to be connected in parallel in an efficient manner.

In examples, before depositing the material on the side of the cell stack, the side of the cell stack comprises, for each respective cell of the plurality of cells, a protrusion comprising an end portion of the first electrode layer of each respective cell. This for example facilitates straightforward removal of a portion of the material over the end portion of the first electrode layer, to reveal the end portion of the first electrode layer for subsequent connection to a further electrical component. As discussed above, a thickness of the material over the end portion of the first electrode layer may be smaller than that over other portions of the cells, so that a portion of the material over the end portion of the first electrode layer can be removed, e.g. by laser ablation, without entirely removing other portions of the material. If the end portion of the first electrode layer is revealed by removal of the material, the surface area of the end portion of the first electrode layer may be larger than a surface area of an edge surface of the first electrode layer. Hence, the approach of these examples may allow a greater contact area to be formed between the first electrode layer and the further electrical component than if the further electrical component is connected to the first electrode layer via an edge surface of the first electrode layer. This can reduce contact resistance and improve performance of the manufactured energy storage device. In these examples, the protrusion may comprise, for each respective cell of the plurality of cells, an end portion of a substrate on which the end portion of the first electrode layer of each respective cell is arranged. The substrate may improve the stability of the first electrode layer, and reduce the risk of breakages of the end portion of the first electrode layer. Furthermore, the substrate for example provides a suitable surface for initial deposition of the first electrode layer before subsequent processing.

In examples, depositing the material on the side of the cell stack comprises depositing the material with a first thickness over a first portion of a cell of the plurality of cells, the first portion of the cell comprising the first electrode layer of the cell, and a second thickness over a second portion of the cell comprising the electrolyte layer of the cell and the second electrode layer of the cell, the second thickness greater than the first thickness. As discussed above, this for example facilitates the straightforward removal of a first portion of the material with the first thickness, e.g. using laser ablation techniques.

In examples, depositing the material comprises depositing the material using a non-inkjet-printing method. This allows the second material to be deposited using a method which is more straightforward than inkjet printing, including e.g. flood deposition and/or a vapour deposition process such as physical vapour deposition (PVD). In PVD, the material in a condensed phase is vaporised to produce a vapour, which vapour is then condensed onto the side of the cell stack, whereas in flood deposition the side of the cell stack is flooded with liquid material, which is subsequently hardened, e.g. by curing, to form the material on the side of the cell stack. Such methods may be performed without needing to control deposition of the material according to a particular pattern or in a particular location. This allows the material to be deposited straightforwardly and efficiently.

According to a second aspect of the present disclosure, there is provided a method comprising: providing a plurality of cells for an energy storage device, each cell comprising: a first electrode layer; a second electrode layer; an electrolyte layer between the first electrode layer and the second electrode layer; and a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell; stacking the plurality of cells to form a cell stack, with the first side of each of the cells arranged at a first side of the cell stack; and depositing a second material on the second side of the cell stack, opposite to the first side of the cell stack, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

Similarly to the approach of the first aspect, the method of the second aspect simplifies insulation of the first and second electrode layers by depositing the second material on the relatively large surface area provided by the second side of the cell stack. This allows the second material to be deposited straightforwardly and efficiently. The insulation of the first and second electrode layers may be improved, reducing the risk of short circuits.

In examples, depositing the second material comprises depositing the second material to at least partly cover the first electrode layer, the electrolyte layer and the second electrode layer of each cell of the plurality of cells, and the method further comprises removing a portion of the second material over the first electrode layer of each of the plurality of cells, respectively, to provide an exposed portion of the first electrode layer for each of the plurality of cells. As discussed with reference to the first aspect of the present disclosure, this can improve the efficiency of providing an exposed portion of the first electrode layer, which is nevertheless electrically insulated from the second electrode layer.

According to a third aspect of the present disclosure, there is provided an energy storage device formed according to the first or second aspects of the present disclosure. Such an energy storage device may be manufactured straightforwardly and may have a lower risk of short circuits, e.g. due to improved insulation of first and second electrode layers of respective cells of a cell stack. According to a fourth aspect of the present disclosure, there is provided a cell stack for an energy storage device, the cell stack comprising a stack of cells, each cell comprising: a first electrode layer; a second electrode layer; and an electrolyte layer between the first electrode layer and the second electrode layer, wherein an exposed edge of the first electrode layer, an exposed edge of the electrolyte layer, and an exposed edge of the second electrode layer of each of the plurality of cells are arranged along a side of the cell stack; and a material arranged on the side of the cell stack, wherein the material at least partly covers the exposed edge of the first electrode layer, the exposed edge of the electrolyte layer, and the exposed edge of the second electrode layer of each of the plurality of cells, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

Such a cell stack facilitates the straightforward manufacture of an energy storage device. An energy storage device formed from such a cell stack may have a lower risk of short circuits, e.g. due to improved insulation of first and second electrode layers of respective cells of the cell stack.

In examples, the material arranged on the side of the cell stack is a second material, the side of the cell stack is a second side of the cell stack, each cell of the plurality of cells within the cell stack comprises a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell, and the first side of each of the cells is arranged at a first side of the cell stack, opposite to the first side of the cell stack. With this arrangement, the exposed portion of the second electrode layer of each of the cells may be connected straightforwardly to a further electrical component, e.g. to connect the cells in parallel.

Further features will become apparent from the following description, given by way of example only, which is made with reference to the accompanying drawings. Brief Description of the Drawings

Figure 1 is a schematic diagram that shows a cell for an energy storage device according to examples;

Figure 2 is a schematic diagram that shows two cells for an energy storage device according to further examples;

Figures 3a to 3d are schematic diagrams that show features of a method of manufacturing an energy storage device according to examples;

Figure 4 is a schematic diagram that shows a cell for an energy storage device according to further examples; and Figure 5 is a schematic diagram that shows a cell for an energy storage device according to yet further examples.

Detailed Description

Details of methods, structures and devices according to examples will become apparent from the following description, with reference to the Figures. In this description, for the purpose of explanation, numerous specific details of certain examples are set forth. Reference in the specification to “an example” or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples. It should further be noted that certain examples are described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the examples.

Figure 1 shows a cell 100 for an energy storage device according to examples. The cell 100 of Figure 1 may be used as part of a thin film energy storage device having a solid electrolyte, for example.

The cell 100 comprises a substrate 102, a cathode current collector (CC) layer 104, a cathode layer 106, an electrolyte layer 108, an anode layer 110 and an anode CC layer 112. In Figure 1, the anode layer 110 is further from the substrate 102 than the cathode layer 106, and the electrolyte layer 108 is between the cathode layer 106 and the anode layer 110. The substrate 102 contacts the cathode CC layer 104 and supports the cell 100. While in this example the substrate 102 directly contacts the cathode CC layer 104, in other examples there may be additional layers (not shown) in between the substrate 102 and the cathode CC layer 104, or the cathode CC layer may be omitted and the cathode layer 106 may be in contact with the substrate 102. Unless otherwise indicated, reference herein to an element being “on” another element is to be understood as including direct or indirect contact. In other words, an element on another element may be either touching the other element, or not in contact the other element but, instead, generally supported by an intervening element (or elements) but nevertheless located above, or overlapping, the other element.

The substrate 102 of Figure 1 is a polymer, such as polyethylene terephthalate (PET). In other examples, the substrate 102 may be or comprise a different material, such as silicon or a glass. The substrate 102 in Figure 1 is planar and flexible (in this case, sufficiently flexible that the substrate 102 can be wound around a roller as part of a roll-to-roll manufacturing process, sometimes referred to as a reel-to-reel process). In other examples, though, the substrate may be non-planar and/or rigid.

The cathode CC layer 104 acts as a positive current collecting layer and in this case comprises nickel foil, but it will be appreciated that any suitable metal could instead be used, such as aluminium, copper or steel, or a metallised material including metallised plastics such as aluminium on polyethylene terephthalate (PET).

The cathode layer 106 of Figure 1 forms a positive electrode layer (i.e. that corresponds to a cathode during discharge of a cell of an energy storage device including the stack 100). The cathode layer 106 in the example of Figure 1 comprises a material which is suitable for storing lithium ions by virtue of stable chemical reactions, such as lithium cobalt oxide, lithium iron phosphate or alkali metal polysulphide salts. In the example of Figure 1, the cathode CC layer 104 and the cathode layer 106 together form a first electrode layer 114. In other examples, though, the first electrode layer may comprise solely one of the cathode CC layer or the cathode layer. Indeed, the cathode CC layer may be omitted or may be part of the cathode layer, rather than a separate layer.

The electrolyte layer 108 may include any suitable material which is ionically conductive, but which is also an electrical insulator such as lithium phosphorous oxynitride (LiPON). The electrolyte layer 108 of Figure 1 is a solid layer, and may be referred to as a fast ion conductor. A solid electrolyte layer may have structure which is intermediate between that of a liquid electrolyte, which for example lacks a regular structure and includes ions which may move freely, and that of a crystalline solid. A crystalline material for example has a regular structure, with an ordered arrangement of atoms, which may be arranged as a two-dimensional or three-dimensional lattice. Ions of a crystalline material are typically immobile and may therefore be unable to move freely throughout the material.

The anode layer 110 of Figure 1 forms a negative electrode layer (i.e. that corresponds to an anode during discharge of a cell of the energy storage device including the stack 100). The anode layer 110 in this case comprises lithium. However, in other examples, the anode layer may comprise lithium, graphite, silicon and/or indium tin oxide.

The anode CC layer 112 acts as a negative current collecting layer and in this case comprises copper. However, it will be appreciated that any suitable metal could be used, such as aluminium, nickel foil or steel, or a metallised material including metallised plastics such as aluminium on polyethylene terephthalate (PET). In the example of Figure 1, the anode layer 110 and the anode CC layer 112 together form a second electrode layer 116. In other examples, though, the second electrode layer may comprise solely one of the anode layer or the anode CC layer. Indeed, the anode CC layer may be omitted or may be part of the anode layer, rather than a separate layer.

The cell 100 also includes a first material 118 along a first side 120a of the cell 100 to insulate at least the first electrode layer 114. The first material 118 is electrically insulating. An electrically insulating material may be considered to be electrically non- conductive and may therefore conduct a relatively a small amount of electric current when subjected to an electric field. Typically, an electrically insulating material (sometimes referred to as an insulator) conducts less electric current than semiconducting materials or electrically conductive materials. However, a small amount of electric current may nevertheless flow through an electrically insulating material under the influence of an electric field, as even an insulator may include a small amount of charge carriers for carrying electric current. In examples herein, a material may be considered to be electrically insulating where it is sufficiently electrically insulating to perform the function of an insulator. This function may be performed for example where the material insulates one element from another sufficiently for short circuits to be avoided. Insulation of the first electrode layer 114 by the first material 118 for example refers to arrangement of the first material 118 to cover or otherwise overlap an otherwise exposed portion of the first electrode layer 114. For example, with the first electrode layer 114 insulated by the first material 118, the first material 118 may be between the first electrode layer 114 and at least one other electrically conductive component of the cell 100. This is the case in Figure 1, in which the first material 118 extends along the first side 120a of the cell 100 so that the first material 118 covers the edge of the first electrode layer 114 along the first side 120a of the cell 100 and prevents the first electrode layer 114 from contacting the anode CC layer 112. In this case, the first material 118 encapsulates the edge of the first electrode layer 114. This also prevents the first electrode layer 114 from coming into contact with the anode layer 110 of the second electrode layer 116. In this way, the risk of short circuits between the first electrode layer 114 and the second electrode layer 116 is reduced or eliminated. In Figure 1, the first material 118 also covers the edges of the electrolyte layer 108 and the anode CC layer 110 along the first side 120a of the cell 100, although this need not be the case in other examples.

In Figure 1, there is an exposed portion 112a of the second electrode layer 112 along at least part of the first side 120a of the cell 100 (in this case, along the entire side of the first material 118, although this is merely an example). The first side 120a of the cell 100 in Figure 1 is a short side of the cell 100, which is perpendicular to top and bottom sides of the cell 100 (which may be referred to as top and bottom faces of the cell 100). In Figure 1, the first side 120a is perpendicular to a surface 122 of the substrate 102 on which the first electrode layer 114 is arranged, although in other examples the first side need not be exactly perpendicular to this surface. For example, the first side may be perpendicular to this surface within manufacturing tolerances or measurement uncertainties, or at a sufficient angle to this surface to allow the first material 118 to be deposited along the first side 120a, e.g. to form an angle from 70 degrees to 110 degrees with this surface. The exposed portion 112a of the second electrode layer 112 may be subsequently connected to a further electrical component, e.g. to connect a plurality of cells in parallel, as discussed further with reference to Figure 3d. In Figure 1, a portion 112b of the second electrode layer 112 which is parallel to the surface 122 of the substrate 102 is also exposed. However, this portion 112b of the second electrode layer 112 may not remain exposed after the cell 100 has been stacked with other cells to form a cell stack. In general, this portion 112b of the second electrode layer 112 will be overlapped by other cells within the cell stack (unless the cell is the uppermost cell of the cell stack), and hence is not easily accessible for connection to a further electrical component. However, after stacking of the cell 100 with other cells, the exposed portion 112a of the second electrode layer 112 typically remains exposed, to allow straightforward connection of the cell 100 to other components.

The cell 100 also has a second side 120b opposite to the first side 120a. Exposed edges of the first electrode layer 114, the electrolyte layer 108 and the second electrode layer 116 are arranged on the second side 120b of the cell 100. According to examples herein, insulation is subsequently arranged along the second side 120b to prevent or reduce the risk of short circuits between the first and second electrode layers 114, 116. However, the cathode CC layer 104 is exposed to allow connection of the cell 100 to a further electrical component, e.g. to connect the cell 100 to other cells in parallel. In the example of Figure 1, the cathode CC layer 104 extends beyond the exposed edges of the other layers of the cell 100 towards the second side 120b of the cell 100. Similarly, at the first side 120a of the cell 100, the anode CC layer 112 extends beyond the other layers of the cell 100. In this way, the cathode CC layer 104 overlaps (and in this case contacts) a first portion of the surface 122 of the substrate 102 which is not overlapped by the other layers of the cell 100, and the anode CC layer 112 overlaps (and in this case contacts) a second, different, portion of the surface 122 of the substrate 100, which is also not overlapped by the other layers of the cell 100. The extended portions of the cathode CC layer 104 and the anode CC layer 112 facilitate connection of the cell 100 to a further electrical component, e.g. by providing a greater surface area for connection to the further electrical component. In other examples, though, the first and/or second electrode layers as a whole may be extended similarly (e.g. in cases where the cathode and/or anode CC layers are omitted), or the first and/or second electrode layers need not be extended in this way. The cell 100 of Figure 1 is manufactured by depositing the cathode CC layer 104 on the substrate 102. The cathode layer 106 is subsequently deposited on the cathode CC layer 104, the electrolyte layer 108 is then deposited on the cathode layer 106, and the anode layer 110 is then deposited on the electrolyte layer 108. Each of these layers of the cell 100 may be deposited by flood deposition (sometimes referred to as slot die coating or slit coating), which provides a simple and effective way of producing a highly homogenous layer, although other deposition methods are possible, e.g. a vapour deposition process such as physical vapour deposition (PVD) or chemical vapour deposition (CVD).

A groove is formed through the deposited layers (which may be referred to as a stack), to separate the stack from a neighbouring stack. Laser ablation may be used to form the groove. Laser ablation typically allows the formation of the groove to be controlled in a straightforward and rapid manner. However, in other examples, alternative methods may be used to form the groove, such as photolithographic techniques.

The first material 118 is deposited within the groove, e.g. using inkjet printing, which typically allows flexible, efficient, and/or reliable deposition of the first material 118. A second material (for forming the anode CC layer 112) is then deposited over the stack of previously-deposited layers and over the first material 118, so that the first material 118 insulates the anode CC layer 112 from the first electrode layer 114 and the electrolyte layer 108. The second material may be deposited using a non-inkjet-printing method, which is a deposition method that does not involve inkjet printing techniques. Such methods may be more straightforward and economic than inkjet printing. Suitable methods include vapour deposition methods such as PVD or CVD, or flood deposition. The deposition of the second material over the cell 100 generally increases a contact area between the second material and the anode layer 110 compared to other cases in which an anode or anode CC is connected to a further electrical component, such as an electrical connector, along an exposed side edge of the anode or anode CC. For example, a side edge of such an anode or anode CC for connection to an electrical connector typically has a much smaller area than an area of a surface of the anode layer 110 on which the second material is deposited in Figure 1. For example, a thickness of the anode or anode CC layers may be of the order of nanometres, whereas a width of an upper surface of the cell 100 may be of the order of millimetres. Increasing the contact area typically reduces the contact resistance at the interface between the second material and the anode layer 110, which improves the performance of the manufactured energy storage device. In examples such as that of Figure 1, the second material is deposited over the stack for forming the cell 100, as well as over other stacks for forming other cells. This further improves the efficiency of deposition of the second material compared with depositing the second material over each stack individually. A plurality of grooves may be formed through the cathode CC 104, cathode 106, electrolyte 108 and anode layers 110, to separate the deposited layers into a plurality of stacks (each for forming a different respective cell for an energy storage device). After deposition of the first material 118 along the first side 120a of each stack (and hence, along the first side 120a of each cell), the second material is deposited across a surface of the plurality of stacks (opposite to the surface 122 of the substrate 102 on which the cathode CC layer 104 is arranged). This further simplifies deposition of the second material and hence formation of the anode CC layer 112 of a plurality of cells.

In some cases, double-sided processing may be performed, in which a plurality of layers is deposited on opposite sides of the same substrate, i.e. so that both sides of the substrate include a plurality of layers thereon. An example of two cells 200, 200’ formed by double-sided processing is shown schematically in Figure 2. The cell 200 of Figure 2 is the same as the cell 100 of Figure 1, and is referred to herein as a first cell 200. Features of the first cell 200 of Figure 2 that are the same as corresponding features of the cell 100 of Figure 1 are labelled with the same reference numeral but incremented by 100. Corresponding descriptions are to be taken to apply.

The first cell 200 is arranged on the surface 222 of the substrate 202, which in this example is a first surface 222 of the substrate 202. The substrate 202 also includes a second surface 222’, which is opposite to the first surface 222. A second cell 200’ is arranged on the second surface 222’ of the substrate 202. The second cell 200’ is otherwise the same as the first cell 200, but is arranged on the second surface 222’ instead of the first surface 222 of the substrate 200. The first and second cells 200, 200’ of Figure 2 are formed in the same ways as the cell 100 of Figure 1, although this need not be the case in other examples. Each layer of the second cell 200’ is the same as a corresponding layer of the first cell 200 and is labelled with the same reference numeral but appended with a prime. Corresponding descriptions are to be taken to apply.

By depositing layers on either side of the substrate 202, the efficiency of the manufacturing process may be further improved. For example, the number of laser cutting processes for separating the layers into cells may be reduced, as each cut may pass through a greater number of layers. Although in Figure 2, the first and second cells 200’, 200 are the same as each other except for their location on the substrate 202, this may not be the case in other cases.

In examples herein, cells similar to or the same as the cell 100 of Figure 1 or the cells 200, 200’ of Figure 2 undergo processing to manufacture an energy storage device. Figures 3a to 3d are schematic diagrams that show features of a method of manufacturing an energy storage device according to examples. Features of Figures 3a to 3d that are similar to corresponding features of Figure 1 are labelled with the same reference numeral but incremented by 200. Corresponding descriptions are to be taken to apply.

Figures 3a to 3d show the processing of a double-sided arrangement, in which cells are arranged on opposite sides of the same substrate 302. However, it is to be appreciated that processing that is otherwise the same as that shown in Figures 3a to 3d may equally be applied to single-sided arrangements, in which cells are arranged solely on one side of a substrate. The processing of Figures 3a to 3d is performed sequentially (i.e. with the processing of Figure 3a performed before that of Figure 3b and so forth). However, this is merely an example.

Prior to Figure 3a, a plurality of cells for an energy storage device is provided. Figure 3a illustrates a first cell 300a, a second cell 300a’, a third cell 300b, and a fourth cell 300b’ (collectively referred to with the reference numeral 300), although it is to be appreciated that, in practice, many more cells may be provided than those shown. Each of the cells 300 of Figure 3 a is the same as the cell 100 of Figure 1. However, in other cases, some of the cells may be different from each other and/or may be different from the cell 100 of Figure 1.

In Figure 3a, the first and second cells 300a, 300a’ are arranged on opposite sides of a first substrate 302a, and the third and fourth cells 300b, 300b’ are arranged on opposite sides of a second substrate 302b. Each of the cells 300 includes a first electrode layer, a second electrode layer and an electrolyte layer between the first and second electrode layers. For ease of illustration, these layers are not individually shown in Figures 3a to 3d (but are shown in the cell 100 of Figure 1, which is the same as each of the cells 300 of Figures 3a to 3d). Instead, Figures 3a to 3d merely illustrate the cathode CC layers 304a, 304a’, 304b, 304b’, the anode CC layers 312a, 312a’, 312b, 312b’, and the first material 318a, 318a’, 318b, 318b’of the first, second, third and fourth cells 300a, 300a’, 300b, 300b’, respectively. The cathode CC layers (collectively referred to as 304) form part of the first electrode layer and the anode CC layers (collectively referred to as 318) form part of the second electrode layer of each respective cell. Figures 3a to 3d also show schematically intermediate layers 324a, 324a’, 324b, 324b’ of the first, second, third and fourth cells 300a, 300a’, 300b, 300b’, respectively, which are between the cathode CC layer 304 and the anode CC layer 312 of each cell. The intermediate layer (collectively referred to as 324) of each of the cells 300 includes a cathode layer, an electrolyte layer and an anode layer in this example. The cathode and cathode CC layers 304 together form the first electrode layer, and the anode and anode CC layers 312 together form the second electrode layer.

The plurality of cells 300 is stacked in Figure 3a to form a cell stack 326. In the example of Figure 3a, each of the cells 300 is provided on the same substrate 302, which has subsequently undergone a stacking procedure to obtain the cell stack 326 of Figure 3a. In Figure 3a, the stacking procedure used to obtain the cell stack 326 is a reel-to- reel process, in which a reel of substrate 302 on which layers corresponding to respective cells is provided (prior to the separation of the layers into cells). A web of the substrate 302 is fed from the reel to a drum. During transfer of the web of substrate 302, the substrate 302 (on which the layers have previously been deposited) is cut into ribbons along the direction of travel of the web, so that the cells (after separation from each other) are of an appropriate width for the energy storage device. Winding the substrate on to the drum involves wrapping the substrate 302 repeatedly around the drum, so as to provide a stack of cells. The stack of cells are then clamped together and undergo a singulation process to separate respective cells from each other so as to provide a plurality of cell stacks, including the cell stack 326 of Figure 3a. Performing singulation of the stack of cells in this way is typically more efficient than individually singulating each cell. In Figure 3a, the first substrate 302a and the second substrate 302b are different respective portions of the same substrate, after the cells 300 have been stacked and the stack of cells have been separated into a plurality of cell stacks. In this case, the first substrate 302a corresponds to a portion of the substrate 302 associated with winding the web of substrate around the drum for a first time, whereas the second substrate 302b corresponds to a different portion of the substrate 302, associated with winding the web of substrate around the drum for a second, subsequent time. In other words, after winding the web of substrate around the drum, the second substrate 302b overlaps the first substrate 302a. The cell stack 326 of Figure 3a is illustrated after separation of the stack of cells (formed by winding the web of substrate around the drum) into different respective cell stacks. Each of the cell stacks 326 (which are for example clamped together prior to the singulation process) is then removed from the drum and processed as shown further in Figures 3b to 3d. Processing of the cell stack 326 rather than individual cells 300 further improves the efficiency of manufacturing the energy storage device.

In other examples, a cell stack which is the same as or similar to the cell stack 326 of Figure 3a may be formed using a folding procedure involving folding the substrate back on itself to create a z-fold arrangement with each of the cells aligned with each other. This is merely an example, though, and other methods may be used to form the cell stack in other examples. For example, each of the cells 300 may be provided on a different respective substrate, and then stacked together to form the cell stack 326.

In Figure 3a, the first material 318 of each of the cells 300 is arranged along a first side of each of the cells (which first side is illustrated in Figure 1 for the cell 100). The first side of each of the cells is arranged at a first side 328a of the cell stack 326 (which is a lower side of the cell stack 326 in the orientation of Figure 3a). In Figure 3 a, an exposed portion of the second electrode layer of each cell 300 (which in this case is an exposed portion of the anode CC layer 312 of each cell 300, as discussed further with reference to the cell 100 of Figure 1) extends along the first side of the respective cell such that the first material 318 is between the exposed portion of the anode CC layer 312 and the first electrode layer of the respective cell. The first material 318 electrically insulates the exposed portion of the second electrode layer (in this case, the exposed portion of the anode CC layer 312) from the first electrode layer, to prevent or reduce the risk of short circuits. The exposed portion of the anode CC layer 312 extending along the first side of each cell (and, hence, along the first side 328a of the cell stack 326) provides a greater surface area for connection of the anode CC layer 312 to a further electrical component. This can reduce contact resistance at an interface between the anode CC layer 312 and the further electrical component, and therefore improve performance of the energy storage device. In Figure 3 a, the exposed portion of the anode CC layer 312 extends in a plane perpendicular to a plane of the substrate 302a, 302b and therefore has a greater surface area in this plane than if the exposed portion of the anode CC layer 312 is not extended in this plane. The second electrode layer may be considered to extend along the first side of a respective cell where at least a portion of the second electrode layer is elongate along the first side 328a of the cell stack 326, even if other portions of the second electrode layer do not extend in this way. This is the case in Figure 3a, in which the anode CC layer 312 of the second electrode layer includes an exposed portion that extends along the first side 328a of the cell stack 326 but in which the anode layer of the second electrode layer does not extend in this direction.

Exposed edges of the first electrode layer, the electrolyte layer and the second electrode layer are arranged along a second side 328b of the cell stack 326, which is opposite to the first side 328a and is an upper side of the cell stack 326 in the orientation of Figure 3a. It is to be appreciated that exposure of at least part of the first electrode layer, the electrolyte layer and the second electrode layer along the second side 328b of the cell stack 326 is to be considered to correspond to an exposed edge of the first electrode layer, the electrolyte layer and the second electrode layer, respectively. For example, although in Figure 3a, the entire edge of the first electrode layer (including edges of the cathode CC layer 304 and the cathode layer) and the entire edge of the second electrode layer (including edges pf the anode CC layer 312 and the anode layer) of each of the cells 300 is exposed along the second side 328b, this is merely an example. In other cases, the first electrode layer is considered to have an exposed edge where at least part of an edge of the cathode layer and/or at least part of an edge of the cathode CC layer is exposed along the second side 328b. Similarly, in further examples, the second electrode layer is considered to have an exposed edge where at least part of an edge of the anode layer and/or at least part of an edge of the anode CC layer is exposed along the second side 328b. By arranging the exposed edges, which are to be insulated subsequently, on the same side of the cell stack 326, subsequent deposition of an insulating material is simplified.

Deposition of a material 330 to insulate the first electrode layer and the second electrode layer for each of the plurality of cells 300 is shown schematically in Figure 3b. The material 330 is electrically insulating, to prevent or reduce the risk of short circuits between the first and second electrode layers during use of the manufactured energy storage device. The material 330 may be referred to as a second material, to distinguish it from the first material 118 (shown for the cell 100 of Figure 1), which is arranged along the first side of each respective cell to insulate at least the first electrode layer of the cell and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell). In examples, however, the first material 118 and the material 330 may be or comprise the same material as each other, as each of these materials is intended to perform the function of insulating an electrically conductive component. For example, the first material 118 and the material 330 may each be a dielectric ink such as DM-INI-7003, available from Dycotec Materials Ltd., Unit 12 Star West, Westmead Industrial Estate, Westlea, Swindon, SN5 7SW, United Kingdom. A dielectric ink is for example an electrical insulator which may be polarized upon application of an electric field, and which typically has a low electrical conductivity. In other cases, though, a different deposition method than inkjet printing may be used to deposit the first material. In such cases, the first material may be or comprise a different material than a dielectric ink. In other examples, though, the first material 118 and the material 330 may be or comprise different materials than each other.

The material 330 is deposited on the second side 328b of the cell stack 326 to insulate the first electrode layer and the second electrode layer for each of the plurality of cells 300. The material 330 is deposited to at least partly cover the exposed edge of the first electrode layer, the exposed edge of the electrolyte layer, and the exposed edge of the second electrode layer of each of the plurality of cells 300. In Figure 3b, the material 330 entirely covers the exposed edges of the first and second electrode layers and the electrolyte layer. Depositing the material 330 on the second side 328b of the cell stack 326 (which is an upper side in the orientation of Figure 3b) for example improves the efficiency with which the material 330 is deposited, e.g. as the material 330 may be deposited with the aid of gravity.

Deposition of the material 330 on the second side 328b of the cell stack 326 simplifies the insulation of the first and second electrode layers of the cells 300 compared with other manufacturing processes that involve filling narrow channels with insulating material. Insulation of the first and second electrode layers may in turn be improved, by improved coverage of the exposed edges of the first and second electrode layers by the deposited material 330.

In the examples such as that of Figure 3b, the material 330 is deposited to cover substantially all of the second side 328b of the cell stack 326. It is to be appreciated that deposition of the material 330 to cover substantially all of a given surface for example refers to the material 330 being deposited to cover all of the given surface, all of the given surface within manufacturing tolerances or measurement tolerances or a substantial part of the given surface, such as more than 80% of the given surface. Deposition of the material 330 to cover substantially all of the second side 328b of the cell stack 326 further simplifies deposition of the material 330 and improves insulation of the first and second electrode layers by the material 330. Deposition of the material 330 in this way for example involves encapsulating the second side 328b of the cell stack 326 using the material 330. This protects the exposed edges of the layers of the cells 300 by reducing contact between these exposed edges and a surrounding environment, e.g. due to the arrangement of the material 330 as a barrier between the exposed edges and the environment. The material 330 therefore protects the exposed edges from potential damage or interaction with an ambient environment, while also insulating the exposed edges to reduce the risk of short circuits.

The material 330 may be deposited using any suitable method. For example, the material 330 may be deposited using a non-inkjet-printing method, such as flood deposition or vapour, which are typically more straightforward than inkjet printing. In other cases, though, the material 330 may be deposited using inkjet printing techniques. Inkjet printing may be performed at relatively low (e.g. ambient) temperatures and/or pressures, for example as compared to thermal spray coating, and hence may allow for economic and/or efficient deposition and hence energy storage device production. In Figure 3b, the second side 328b of the cell stack 326 includes, for each cell of the plurality of cells 300, a protrusion comprising an end portion 332a, 332a’, 332b, 332b’ (collectively referred to as 332) of the first electrode layer of each respective cell. In Figure 3b, the end portions 332 of the first electrode layer of each of the cells 300 is an end portion of the cathode CC layer 304 of the respective first electrode layer, although in other cases, the end portion may be of a different component or other portion of the first electrode layer, or of the entirety of the first electrode layer.

A protrusion for example refers to a portion of a component which extends or otherwise projects beyond at least one other component of the cell stack 326 or cell 300. In Figure 3b, the end portion 332 of the cathode CC layer 304 juts upwardly (in the sense of Figure 3b), and hence extends beyond a plane of the exposed edges of the other layers of each of the cells 300. The end portion 332 of the cathode CC layer 304 therefore forms part of a protrusion in this case.

In examples such as Figure 3b, the protrusion comprises, for each respective cell of the plurality of cells 300, an end portion 334a, 334b (collectively referred to as 334) of the substrate 302a, 302b on which the end portion of the first electrode layer of each respective cell is arranged. The delimitation of the end portions 334 of the substrate are illustrated by a dashed line in Figure 3b. By arranging the end portions 332 of the first electrode layers on the end portions 334 of the substrate, the robustness of the first electrode layers is improved, reducing the risk of breaking or otherwise damaging the protruding end portions 332 of the first electrode layers. In Figure 3b, the end portions 332a, 332a’ of the first and second cells 300a, 300a’ are arranged on opposite sides of the same substrate end portion 334a (which in this case, is of the first substrate 302a). Similarly, the end portions 332b, 332b’ of the third and fourth cells 300b, 300b’ are arranged on opposite sides of the same substrate end portion 334b (which in this case, is of the second substrate 302b). In other words, the same substrate end portion may form part of a protrusion associated with different respective cells. In other cases, though, the end portion of the first electrode layer of each of the cells may be arranged on different respective substrate end portions.

In Figure 3b, the material 330 is deposited with a first thickness ti over a first portion of each of the cells 300, which first portion comprises the first electrode layer of the respective cell (in this case, the cathode CC layer 304 of the first electrode layer). In Figure 3b, in which the material 300 entirely overlaps the first side 328a of the cell stack 326, the first portion of the material 330 (with the first thickness ti) overlaps the cathode CC layer 304 of each of the cells 300 and the substrate 302a, 302b. The material 300 has a second thickness ti over a second portion of each of the cells 300, which second portion comprises the electrolyte and second electrode layers of the respective cell. In Figure 3b, the second portion of the material 330 (with the second thickness h) overlaps the intermediate layers 324 and the anode CC layers 312 of each of the cells 300. The second thickness h is greater than the first thickness ti.

Deposition of the material 330 with a varying thickness, e.g. as shown in Figure 3b, can simplify the subsequent removal of the material 330 (if desired). For example, the first portion of the material 330 may be removed upon exposure to a smaller amount of laser energy than the second portion of the material 330 (such as by application of a laser beam for a shorter amount of team, or with a lower intensity). This simplifies selective removal of the first portion of the material 330 without entirely removing the second portion of the material 330. This is merely an example, though, and in other cases the material 330 may be deposited with a uniform or substantially uniform thickness.

In Figure 3c, a portion of the material 330 over the exposed edge of the first electrode layer of each of the cells 300 is removed. In this way, the first electrode layer of each of the cells 300 is at least partially revealed or otherwise exposed, to allow the first electrode layer to be connected to a further electrical component. Another portion of the material 330, which in Figure 3c overlaps the intermediate layers 324 and the anode CC layer 312 at the second side 328b of the cell stack 326, is not entirely removed. This remaining portion of material 330 continues to insulate the first and second electrode layers from each other. In Figure 3c, the portion of the material 330 over the cathode CC layers 304 of the first electrode layer of each of the cells 300 is removed, but the remainder of the first electrode layer remains covered by the material 330. This is merely an example, though. In other cases, a portion of the material 330 overlapping a different part of the first electrode layer, or overlapping an entirety of the first electrode layer, of each of the cells 300 may be removed. Deposition and subsequent removal of the material 330 as shown in Figures 3b and 3c is typically more efficient that selective deposition of the material 330, e.g. to provide the arrangement shown in Figure 3c. This is due to the relative ease of the deposition and removal of the material 330 according to the methods of Figures 3b and 3c, compared to the difficulty of selectively depositing the material 330 according to a complex pattern.

The material 330 may be removed using various different techniques. In the example of Figure 3c, the material 330 is removed using a laser 336, e.g. using laser ablation. Laser ablation typically involves irradiating the material 330 with a laser beam 338 produced by the laser 336. Although Figure 3c illustrates the laser 336 and the laser beam 338, it is to be appreciated that the removal of the material 330 is almost complete in the example of Figure 3c, to illustrate the cell stack 326 after removal of substantially all of the material 330 to be removed.

In this case, the material 330 is absorptive for electromagnetic (EM) radiation emitted by the laser 336. Absorption of the EM radiation by portions of the material 330 causes such portions to evaporate, sublimate or be converted to a plasma and therefore be removed. Laser ablation is easily controllable and therefore allows the material 330 to be removed efficiently and economically. For example, the material 330 for insulating the first and second electrode layers may be selected based on its sensitivity to EM radiation. The material 330 selected may be sensitive to ablation by exposure to EM radiation of a particular range of wavelengths that can be easily produced by an economic and readily-available laser. It is to be appreciated that the material 330 may be considered absorptive for the EM radiation emitted by the laser where the material 330 absorbs at least some of at least one wavelength of the EM radiation to a sufficient degree to allow for laser ablation of the material 330 by exposure to the EM radiation. The material 330 need not, however, absorb all or all the wavelengths of the EM radiation emitted by the laser.

In Figure 3c, the material 330 is more absorptive for the EM radiation than at least part of the exposed edge of the first electrode layer of the cells 300. In this case, the material 330 is more absorptive for the EM radiation than the exposed edge of the cathode CC layer 304 of each of the cells 300, although in other cases, the material 330 may be more absorptive than other parts of the exposed edge of the first electrode layer than the cathode CC layer 304 (which other parts may or may not include the cathode CC layer 304). In this way, the material 330 may be ablated to a greater extent than at least part of the first electrode layer upon exposure to the EM radiation. The material 330 may therefore be removed from the at least part of the first electrode layer in a straightforward manner, without damaging and/or removing the underlying first electrode layer. In this way, the differing optical properties of the various layers of the cell stack 326 can be exploited to selectively remove particular portions of the material 330 in a simple way. In Figure 3c, this therefore provides laser ablation of the portion of the material 330 which previously covered the cathode CC layer 304, but without removing the underlying cathode CC layer 304.

At least part of the first electrode layer of each cell 300 may be reflective and/or transmissive for the EM radiation. For example, the at least part of the first electrode layer may reflect a portion of the EM radiation and transmit a different portion of the EM radiation. Other portions of the cell 300 (apart from the material 330) are typically also reflective and/or transmissive for the EM radiation. For example, the substrate 302a, 302b is typically transparent (i.e. transmissive) for the EM radiation, whereas the first and second electrode layers and the electrolyte layer are typically reflective for the EM radiation. In contrast, the material 330 absorbs a greater extent of the EM radiation than at least part of these other portions of the cell 300.

In Figure 3c, the material 330 comprises a black material (which absorbs visible light) and a wavelength of the EM radiation emitted by the laser at least partly overlaps a visible wavelength of the EM spectrum (which is typically considered to include wavelengths from around 380 nanometres to 740 nanometres), although this is merely an example. In this case, the black material also absorbs EM radiation in the infrared (IR) wavelength range of the EM spectrum (which is typically considered to include wavelengths from around 700 nanometres to around 1 millimetre). The laser emits at least some IR radiation, which is absorbed by the material 330, causing ablation of the material 330. However, the underlying layers of the cell 300, which are beneath the material 330, absorb a smaller proportion of the IR radiation emitted by the laser (and are typically reflective and/or transmissive for the IR radiation). These underlying layers are therefore not ablated by the laser or are ablated to a less extent.

The removed portion of material 330 in Figure 3c corresponds to the first portion of material 330 discussed with reference to Figure 3b, which has a smaller thickness than the second portion of the material 330 (which is not entirely removed in the example of Figure 3c). In this way, the exposed edges of the cathode CC layer 304 of each of the cells 300 and the first and second substrate 302a, 302b are revealed by the removal of the first portion of material 330. The first portion of material 330 is removed before the entirety of the second portion of the material 330 is removed, due to the smaller thickness of the first portion of material 330. In this way, the first portion of material 330 is selectively removed in a straightforward manner, due to the varying thickness of the material 330, without having to precisely control an intensity of the laser beam. In other examples, though, the intensity of the laser beam may be varied or a speed of scanning the laser beam across the second side 328b during exposure of different respective portions of the material 330 to the laser beam, to remove greater quantities of the material 330 in some regions than in others.

In the example of Figure 3c, removing the portion of the material 330 using the laser 336 includes generating the laser beam 338 using the laser 336 and directing the laser beam 338 such that the laser beam 338 is incident on a surface 340 of the material 330 (which in this case is the surface 340 of the material 340 at the second side 328b of the cell stack 326). While the laser beam 338 is incident on the surface 340 of the material 330, the laser beam 338 is moved relative to the surface 340 according to a raster pattern. Such relative movement may be achieved by moving the laser beam 338 across the surface 340 of a stationary cell stack 326, by keeping the laser beam 338 stationary and moving the cell stack 326 relative to the laser beam 338 or by moving both the laser beam 338 and the cell stack 326. A raster pattern for example refers to a line-by-line pattern. For example, the laser beam 338 may be scanned across a first stripe of the surface 340 (in plan view) before being moved to a position corresponding to a start of the first stripe but offset in a direction perpendicular to an extent of the first stripe. The laser beam 338 may then be subsequently scanned across a second stripe of the surface 340 (in plan view), and so on, until the entire surface 340 (or a portion of the surface 340 to be processed) has been exposed to the laser beam 338.

Raster scanning of the laser 336 in this way is simple to control and therefore reduces the complexity of the removal of the material 330 compared to other approaches in which the scanning pattern of the laser 336 is more complex. This takes advantage of the variation in thickness of the material 330 across the second side 328b of the cell stack 326 in the example of Figure 3c. Although the first and second portions of the material 330 may be (sequentially) subjected to the laser beam 338 for the same amount of time and at the same intensity, the first portion is removed and the second portion is not entirely removed, as the first portion has a smaller thickness than the second portion. The speed of the scanning of the laser 336 and the intensity of the laser beam 338 are appropriately controlled to ensure removal of the first portion of the material 330, to reveal at least a portion of the first electrode layer. In this way, an exposed portion of the first electrode layer (which in this case, is a portion of the cathode CC layer 304) is provided for each of the cells 300.

In other cases, the raster scanning need not rely on variations in a thickness of the material 330 to selectively remove portions of the material 330. For example, at least part of the material 330 may instead be removed by protecting at least one portion of the material 330 that is not to be removed (or that is to be removed to a lesser extent) using a suitable mask and exposing the at least part of the material 330 that is to be removed, during raster scanning of the material 330 with the laser 336.

After removing a portion of the material 330 over the exposed edge of the first electrode layer as shown in Figure 3c, an electrical connector material is deposited. This is shown schematically in Figure 3d. Figure 3d shows the deposition of a first electrical connector material 342a at the first side 328a of the cell stack 326 and a second electrical connector material 342b at the second side 328b of the cell stack 326. The first electrical connector material 342a contacts the second electrode layer of each of the cells 300. The second electrical connector material 342b contacts the first electrode layer of each of the cells 300. In Figure 3d, the first and second electrical connector materials 342a, 342b contact the anode and cathode CC layers 312, 304 of each of the cells 300. This is merely an example, though, and in other examples the first and second electrical connector materials may contact a different part of the first and second electrode layers, respectively, which may or may not include anode and cathode layers. The first and second electrical connector materials 342a, 342b allow the cells 300 to be connected in parallel in a straightforward manner.

In Figure 3d, the first and second electrical connector materials 342a, 342b are electrically conductive materials, such as metallic materials. For example, at least one of the first and second electrical connector materials 342a, 342b may comprise at least one of: zinc, a zinc alloy or carbon, which are readily available. Zinc can react with lithium (which may form part of the anode or cathode layers). However, the first material 330 protects the underlying anode and cathode layers from contact with the first and second electrical connector materials 342a, 342b, reducing the risk of unwanted reactions between the first and second electrical connector materials 342a, 342b and the anode or cathode layers. The first and second electrical connector materials 342a, 342b are the same in Figure 3d, although this need not be the case in other examples.

In examples such as that of Figure 3d, the first and second electrical connector materials 342a, 342b are deposited over substantially all (and in Figure 3d, all) of the first and second sides 328a, 328b of the cell stack 326. This simplifies deposition of the first and second electrical connector materials 342a, 342b, allowing these materials to be deposited using various straightforward methods. One suitable method is thermal spray deposition, which provides a simple and efficient way to deposit these materials. This is merely an example, though.

By depositing the first and second electrical connector materials 342a, 342b to overlap the first and second sides 328a, 328b of the cell stack 326, a contact area between these materials and exposed portions of the first and second electrode layers is increased. For example, in Figure 3d, the exposed portion of the first electrode layer includes part of the end portion of the cathode CC layer 304, which extends into the first electrical connector material 342a, providing an elongate interface between the cathode CC layer 304 and the first electrical connector 342a. The exposed portion of the second electrode layer is the portion of the anode CC layer 312 that extends along the second side 328a of the cell stack 326. This elongate portion of the anode CC layer 312 similarly provides an elongate surface for contact with the second electrical connector 342b, increasing the contact area therebetween.

It is to be appreciated that the manufacturing method of Figures 3a to 3d may be used to form an energy storage device from cells of a different structure than the cell 100 shown in Figure 1 (which has the same structure as the cells 300 of Figures 3a to 3d). Figure 4 illustrates a further example of a cell 400 that may be stacked and processed as shown in Figures 3a to 3d. Features of the cell 400 of Figure 4 that are the same as corresponding features of the cell 100 of Figure 1 are labelled with the same reference numeral but incremented by 300. Corresponding descriptions are to be taken to apply. The cell 400 is the same as the cell 100 of Figure 1, except for the anode CC layer 412 and the first material 418. In the cell 400 of Figure 4, a cathode CC layer 404 is arranged on a substrate 402, a cathode layer 406 is arranged on the cathode CC layer 404, an electrolyte layer 408 is arranged on the cathode layer 406, an anode layer 410 is arranged on the electrolyte layer 408 and an anode CC layer 412 is arranged on the anode layer 410. The cathode CC layer 404 and the cathode layer 406 together form a first electrode layer 414. The anode layer 410 and the anode CC layer 412 together form a second electrode layer 416. In this case, a first material 418 is arranged along a first side 420a of the cell 400 (opposite to a second side 420b of the cell 400). The first material 418 insulates exposed edges of the first and second electrode layers 414, 416 and the electrolyte layer 408. The anode CC layer 412 does not, however, overlap the first material 418 in this case. Instead, the anode CC layer 412 is aligned with, and has an extent corresponding to, the anode layer 410.

The cell 400 may be formed by depositing the cathode CC layer 404, the cathode layer 406, the electrolyte layer 408, the anode layer 410 and the anode CC layer 412 successively, one on top of each other, e.g. using flood deposition or vapour deposition. Grooves may be formed through these layers, e.g. using laser ablation, and the first material 418 deposited within the grooves, e.g. using inkjet printing. The cell 400 may then be singulated from neighbouring cells by cutting through the first material 418 within the groove.

In examples, a plurality of the cell 400 are stacked on top of each other to form a cell stack. The first side 420a of each of the cells in these examples is arranged at the first side of the cell stack, and the second side 420b of each of the cells is arranged at the second side of the cell stack, which is opposite to the first side. The cell stack is then processed as shown in Figure 3a to 3b, to provide an energy storage device comprising a plurality of the cells 400 connected in parallel, in these examples.

Figure 5 illustrates a still further example of a cell 500 that may be stacked and processed as shown in Figures 3a to 3d. Features of the cell 500 of Figure 5 that are the same as corresponding features of the cell 100 of Figure 1 are labelled with the same reference numeral but incremented by 400. Corresponding descriptions are to be taken to apply. The cell 400 is the same as the cell 100 of Figure 1, except that the anode CC layer includes a first anode CC layer 512’ which is deposited on the anode layer 510 before deposition of the first material 518 along the first side 520a of the cell 500. In the cell 500 of Figure 5, a cathode CC layer 504 is arranged on a substrate 502, a cathode layer 506 is arranged on the cathode CC layer 504, an electrolyte layer 508 is arranged on the cathode layer 506, an anode layer 510 is arranged on the electrolyte layer 508 and a first anode CC layer 512’ is arranged on the anode layer 510. In this case, a first material 518 is arranged along a first side 520a of the cell 500 (opposite to a second side 520b of the cell 500). A second anode CC layer 512 is deposited on the first anode CC layer 512 and over the first material 518. The cathode CC layer 504 and the cathode layer 506 together form a first electrode layer 514. The anode layer 510 and the first and second anode CC layers 512, 512’ together form a second electrode layer 516. The first material 518 insulates exposed edges of the first and second electrode layers 514, 516 and the electrolyte layer 508.

The cell 500 may be formed by depositing the cathode CC layer 504, the cathode layer 506, the electrolyte layer 508, the anode layer 510 and the first anode CC layer 512’ successively, one on top of each other, e.g. using flood deposition or vapour deposition. Grooves may be formed through these layers, e.g. using laser ablation, and the first material 518 deposited within the grooves, e.g. using inkjet printing. The second anode CC layer 512 may then be deposited on the first anode CC layer 512’ and over the first material 518, e.g. by flood deposition or vapour deposition. The first anode CC layer 512’ protects the underlying layers of the cell 500, e.g. including the anode layer 510, which typically includes reactive materials such as lithium, during the deposition of the first material 518. This typically improves the contact between the anode layer 510 and the first anode CC layer 512’ (e.g. which may be deposited in a vacuum before subsequently breaking the vacuum to deposit the first material 518), and reduces unwanted interactions between the anode layer 510 and an ambient environment. The cell 500 may then be singulated from neighbouring cells by cutting through the second layer of the anode CC layer 512 within the groove.

In examples, a plurality of the cell 500 are stacked on top of each other to form a cell stack. The first side 520a of each of the cells in these examples is arranged at the first side of the cell stack, and the second side 520b of each of the cells is arranged at the second side of the cell stack, which is opposite to the first side. The cell stack is then processed as shown in Figure 3a to 3b, to provide an energy storage device comprising a plurality of the cells 500 connected in parallel, in these examples.

The above embodiments are to be understood as illustrative examples. Further examples are envisaged.

For example, the above-described Figures illustrate cells with a separate cathode and cathode CC layer and a separate anode and anode CC layer. In other examples, which are otherwise the same as the above-described examples, at least one of the CC layers may be omitted. In the examples above, the cathode is closer to the substrate than the anode. In other examples that are otherwise the same as the above-discussed examples, the anode may be closer to the substrate than the cathode. For example, the first electrode layer may comprise an anode layer and an anode CC layer (if present) and the second electrode layer may comprise a cathode layer and a cathode CC layer (if present). It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed within the scope of the accompanying claims.

Claims

1. A method comprising: providing a plurality of cells for an energy storage device, each cell comprising: a first electrode layer; a second electrode layer; and an electrolyte layer between the first electrode layer and the second electrode layer; stacking the plurality of cells to form a cell stack, wherein an exposed edge of the first electrode layer, an exposed edge of the electrolyte layer, and an exposed edge of the second electrode layer of each of the plurality of cells are arranged along a side of the cell stack; and depositing a material on the side of the cell stack to at least partly cover the exposed edge of the first electrode layer, the exposed edge of the electrolyte layer, and the exposed edge of the second electrode layer of each of the plurality of cells, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

2. The method according to claim 1 , comprising removing a portion of the material over the exposed edge of the first electrode layer of each of the plurality of cells, respectively.

3. The method according to claim 2, comprising removing the portion of the material using a laser, wherein the material is absorptive for electromagnetic radiation emitted by the laser.

4. The method according to claim 3, wherein the material is more absorptive for the electromagnetic radiation than at least part of the exposed edge of the first electrode layer of a cell of the plurality of cells, wherein optionally at least part of the first electrode layer of the cell is at least one of: reflective or transmissive for the electromagnetic radiation.

5. The method according to claim 3 or claim 4, wherein the material comprises a black material and a wavelength of the electromagnetic radiation emitted by the laser at least partly overlaps a visible wavelength range of the electromagnetic spectrum.

6. The method according to any one of claims 3 to 5, wherein removing the portion of the material using the laser comprises: generating a laser beam using the laser; directing the laser beam such that the laser beam is incident on a surface of the material; and while the laser beam is incident on the surface of the material, moving the laser beam relative to the surface of the material according to a raster pattern.

7. The method according to any one of claims 2 to 6, comprising, after removing the portion of the material, depositing an electrical connector material on the side of the cell stack to contact the first electrode layer of each of the plurality of cells.

8. The method according to claim 7, comprising depositing the electrical connector material using thermal spray deposition.

9. The method according to any one of claims 1 to 8, wherein: the material deposited on the side of the cell stack is a second material, the side of the cell stack is a second side of the cell stack, each cell of the plurality of cells within the cell stack comprises a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell, and the first side of each of the cells is arranged at a first side of the cell stack, opposite to the second side of the cell stack.

10. The method according to claim 9, wherein, for each respective cell of the plurality of cells, the exposed portion of the second electrode layer extends along the first side of the respective cell such that the first material is between the exposed portion of the second electrode layer of the respective cell and the first electrode layer of the respective cell.

11. The method according to claim 9 or claim 10, comprising depositing an electrical connector material on the second side of the cell stack to contact the second electrode layer of each of the plurality of cells.

12. The method according to any one of claims 1 to 11, wherein, before depositing the material on the side of the cell stack, the side of the cell stack comprises, for each respective cell of the plurality of cells, a protrusion comprising an end portion of the first electrode layer of each respective cell.

13. The method according to claim 12, wherein the protrusion comprises, for each respective cell of the plurality of cells, an end portion of a substrate on which the end portion of the first electrode layer of each respective cell is arranged.

14. The method according to any one of claims 1 to 13, wherein depositing the material on the side of the cell stack comprises depositing the material with a first thickness over a first portion of a cell of the plurality of cells, the first portion of the cell comprising the first electrode layer of the cell, and a second thickness over a second portion of the cell comprising the electrolyte layer of the cell and the second electrode layer of the cell, the second thickness greater than the first thickness.

15. The method according to any one of claims 1 to 14, wherein depositing the material comprises depositing the material using a non-inkjet-printing method, wherein optionally the non-inkjet-printing method comprises at least one of: flood deposition or vapour deposition.

16. A method comprising: providing a plurality of cells for an energy storage device, each cell comprising: a first electrode layer; a second electrode layer; an electrolyte layer between the first electrode layer and the second electrode layer; and a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell; stacking the plurality of cells to form a cell stack, with the first side of each of the cells arranged at a first side of the cell stack; and depositing a second material on the second side of the cell stack, opposite to the first side of the cell stack, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

17. The method according to claim 16, wherein: depositing the second material comprises depositing the second material to at least partly cover the first electrode layer, the electrolyte layer and the second electrode layer of each cell of the plurality of cells; and the method further comprises removing a portion of the second material over the first electrode layer of each of the plurality of cells, respectively, to provide an exposed portion of the first electrode layer for each of the plurality of cells.

18. An energy storage device formed according to the method of any one of claims 1 to 17.

19. A cell stack for an energy storage device, the cell stack comprising a stack of cells, each cell comprising: a first electrode layer; a second electrode layer; and an electrolyte layer between the first electrode layer and the second electrode layer, wherein an exposed edge of the first electrode layer, an exposed edge of the electrolyte layer, and an exposed edge of the second electrode layer of each of the plurality of cells are arranged along a side of the cell stack; and a material arranged on the side of the cell stack, wherein the material at least partly covers the exposed edge of the first electrode layer, the exposed edge of the electrolyte layer, and the exposed edge of the second electrode layer of each of the plurality of cells, to insulate the first electrode layer and the second electrode layer for each of the plurality of cells.

20. The cell stack according to claim 19, wherein the material arranged on the side of the cell stack is a second material, the side of the cell stack is a second side of the cell stack, each cell of the plurality of cells within the cell stack comprises a first material along a first side of the cell to insulate at least the first electrode layer and such that there is an exposed portion of the second electrode layer along at least part of the first side of the cell, and the first side of each of the cells is arranged at a first side of the cell stack, opposite to the first side of the cell stack