This application is a national stage application under 35 U.S.C. 371 of International Application No. PCT/GB2019/052033, filed Jul. 19, 2019, which claims the priority of United Kingdom Application No. 1811885.1, filed Jul. 20, 2018, the entire contents of each of which are incorporated herein by reference.
The present disclosure relates to energy storage devices, intermediate structures for manufacture of energy storage devices and methods of manufacturing an energy storage device.
Energy storage devices such as solid-state thin film cells are known. A thin-film battery typically includes a first electrode layer, a second electrode layer, and an electrolyte layer between the first electrode layer and the second electrode layer. A known thin-film battery is susceptible to failures, which can cause the battery to rise rapidly in temperature. This can lead to explosions. For example, the battery may be susceptible to short circuits between the first and second electrode layers or to overcharging.
It is desirable to provide an energy storage device that is safer or more reliable than an existing thin-film battery.
According to some embodiments of the present disclosure, there is provided a thin-film energy storage device comprising:
a substrate;
a first electrode comprising a fuse portion;
a second electrode;
an electrolyte between the first electrode and the second electrode; and
an electrical connector, different from the first electrode, connected to the first electrode by the fuse portion.
A fuse portion for example acts as an electrical safety device, which reduces the risk of thermal runaway. For example, such a fuse portion may be electrically conductive at a current below a predetermined threshold current (which may correspond with a temperature below a predetermined threshold temperature). However, above the predetermined threshold current or predetermined threshold temperature, the fuse portion may cease to conduct electricity. For example, the fuse portion may melt upon exposure to a current or temperature exceeding the predetermined threshold current or temperature, respectively. This may prevent the temperature rising further, which may in turn prevent thermal runaway from occurring. This typically improves the safety of the energy storage device. A fuse portion may be considered sacrificial in that it must be replaced or fixed after fusing has occurred.
For example, a defect in a layer of an energy storage device (such as a short circuit) may cause a rapid discharge of the layer. A single defect may therefore cause a discharge which propagates to other layers of a multi-layer cell of such an energy storage device. However, the fuse portion in the energy storage device according to examples herein may electrically isolate the first electrode from other layers of the energy storage device. Hence, if the first electrode includes a defect, the fuse portion may cease to be electrically conductive (for example, due to a rapid increase in temperature of the fuse portion, which may cause the fuse portion to melt). This may prevent current from flowing to other layers of the energy storage device, thereby electrically isolating the first electrode from the other layers. The other layers of the energy storage device may therefore be unaffected by the faulty layer (in this case, the first electrode). The other layers may therefore continue to function effectively. Hence, the safety and reliability of the energy storage device may be improved compared with other approaches in which individual layers are less effectively isolated from each other.
The fuse portion in these examples is for example an integrated fuse, which is part of a pre-existing component of the energy storage device (namely, the first electrode). Accordingly, the fuse portion may be provided straightforwardly, without increasing the complexity of the energy storage device.
In examples, the first electrode is closer to the substrate than the second electrode and the fuse portion is narrower than a portion of the first electrode overlapped by the second electrode, or the first electrode is further from the substrate than the second electrode and the fuse portion is narrower than a portion of the first electrode which overlaps the second electrode. In such examples, the fuse portion may therefore be a portion of the first electrode which is relatively thin, slim or otherwise narrow compared to a different portion of the first electrode. The relative thinness of the fuse portion for example causes the temperature of the fuse portion to rise more rapidly than a different portion of the first electrode upon exposure to a current exceeding a predetermined threshold current. This therefore causes the fuse portion to melt, and interrupt current flowing through the fuse portion to or from the first electrode.
By providing the fuse portion as a narrower portion of the first electrode, the fuse portion may be formed during formation of the first electrode. This can simplify the manufacture of the energy storage device, as the fuse portion can be provided without adding additional process steps to the manufacturing method. The first electrode may be closer to or further from the substrate than a second electrode. For example, the first electrode may be a cathode or an anode. Hence, either (or both) a cathode or an anode of the energy storage device may be provided with a fuse portion in a simple manner.
In some embodiments, the fuse portion is a protrusion of a first side of the first electrode. With such an arrangement, the fuse portion may be provided more straightforwardly than otherwise. For example, the fuse portion may be shaped during manufacture of the first electrode itself, without adding further processing. For example, the fuse portion may be formed during separation of a first electrode layer into a plurality of portions, with each portion corresponding to a first electrode for a cell of a multi-cell energy storage device, respectively.
In some embodiments, the protrusion (which for example corresponds to the fuse portion) protrudes in a direction substantially parallel to a plane of a surface of the substrate. The energy storage device in such examples is more compact than in other cases in which the protrusion of the fuse portion extends in a different direction. For example, a thickness of the energy storage device in a direction perpendicular to the plane of the substrate may be smaller than otherwise. This may therefore allow a larger number of cells to be included in an energy storage device of a predetermined thickness. Hence, the energy density of the energy storage device may be greater than otherwise.
In some embodiments, a first portion of the protrusion is narrower than a second portion of the protrusion further from the electrical connector than the first portion of the protrusion. In such cases, a contact area between the fuse portion and the electrical connector may correspond with a fusing area, at which fusing occurs if a predetermined threshold current is exceeded. For example, the first portion of the protrusion may be an end portion of the protrusion, which contacts the electrical connector. The protrusion may therefore narrow or otherwise decrease in width towards the protrusion. This may therefore provide a relatively small area of contact between the fuse portion and the electrical connector at which fusing may occur. In other examples, though, the protrusion may not progressively or gradually decrease in width towards the protrusion. Nevertheless, the first portion of the protrusion may be narrower than the second portion of the protrusion. By providing a narrower portion of the protrusion (as the first portion, for example), the narrower portion of the protrusion provides a region of the protrusion which melts when exposed to too high a current. This therefore provides the desired fusing effect. A shape, size or other feature of the first portion of the protrusion may be controlled to provide the first electrode with a fuse portion of a predetermined fuse rating.
In some embodiments, the electrical connector contacts the fuse portion without contacting an indented portion of the first side of the first electrode. Fusing may occur at a contact area between the fuse portion and the electrical connector (for example where the fuse portion is narrowest where it contacts the electrical connector). During manufacture of the energy storage device, a size of the contact area may be controlled to control an internal resistance of the first electrode. In turn, this may control the current the first electrode can carry before reaching a sufficiently high temperature for melting of the fuse portion, and fusing, to occur. In this way, an appropriate fuse rating for the fuse portion can be obtained, so that the energy storage device operates effectively and safely.
In some embodiments, the indented portion of the first side of the first electrode is substantially C-shaped, substantially V-shaped, or substantially elongate in plan view. In other words, various different shapes may be used to provide a fuse portion of the first electrode. The shape selected may depend on an intended use of the energy storage device, such as whether the energy storage device is intended to be used in relatively high or relatively low power applications. First electrodes with different shaped fuse portions may therefore be provided, for example to provide fuse portions of different fuse ratings.
In some embodiments, a side of the electrical connector comprises an electrical connector fuse portion in contact with the fuse portion of the first electrode and a further portion not in contact with the first electrode. For example, the further portion of the electrical connector may be indented or otherwise recessed compared to the electrical connector fuse portion. The electrical connector fuse portion may be a protrusion of the side of the electrical connector. In these examples, the electrical connector fuse portion and the fuse portion of the electrode layer may together provide or otherwise correspond with a combined fuse portion. A fuse rating of the combined fuse portion may be controlled by controlling features of the fuse portion of the electrode layer and/or the electrical connector fuse portion, such as its width, length or shape.
In some embodiments, a second side of the first electrode, opposite to the first side, is substantially planar. For example, a sufficient fusing capability may be provided by providing the fuse portion on one side of the first electrode. The other side of the first electrode (e.g. the second side) may hence be planar. This may further simplify manufacture of the energy storage device.
In some embodiments, the thin-film energy storage device comprises a further first electrode comprising a further fuse portion, the further first electrode overlapping the first electrode. In these examples, the electrical connector is connected to the further first electrode by the further fuse portion. In this way, a multi-cell energy storage device may be provided. As the further first electrode in these examples includes the further fuse portion, fusing of the further first electrode may occur independently of fusing of the first electrode. Hence, if the fuse portion of the first electrode melts, for example if the first electrode is defective, the further first electrode may nevertheless continue to operate effectively. In this way, the fuse portion of the first electrode electrically isolates the first electrode from the further first electrode. The further first electrode may itself be protected from excessively high currents due to the further fuse portion. For example, the further fuse portion may, in due course, also melt if the further first electrode is subjected to a current that exceeds a predetermined threshold current. This improves the effectiveness of the energy storage device, by increasing the number of cells (or layers) that continue to operate in the event of a defect in a cell or layer of the energy storage device.
In some embodiments, the fuse portion is a first fuse portion, the electrical connector is a first electrical connector, the second electrode comprises a second fuse portion, and the thin-film energy storage device comprises a second electrical connector connected to the second electrode by the second fuse portion. The second fuse portion may be similar to the first fuse portion, but be formed as part of the second electrode rather than the first electrode. The second fuse portion may therefore become electrically non-conductive, for example by melting, if subjected to a current which exceeds a predetermined threshold current. Melting of the second fuse portion, for example, electrically isolates the second electrode from other layers of the energy storage device. In this way, fusing of the first fuse portion of the first electrode may not affect the second electrode, which may continue to operate. Similarly, fusing of the second fuse portion of the second electrode may not affect the first electrode.
In some embodiments, the thin-film energy storage device comprises a stack comprising the first electrode, the second electrode and the electrolyte. In these examples, the first electrical connector extends along a first side of the stack and the second electrical connector extends along a second side of the stack, opposite to the first side of the stack. The first and second electrical connectors may therefore be electrically isolated from each other. This allows multiple cells to be connected in parallel with each other. This can improve the energy storage capacity of the energy storage device. In such cases, the first electrode is connected to the first electrical connector via the first fuse portion and the second electrode is connected to the second electrical connector via the second fuse portion. Hence, if there is a defect in the first or second electrodes, the first or second fuse portions may become electrically non-conductive, preventing current from flowing to other first or second electrodes, e.g. via the first or second electrical connectors. In this way, the other first or second electrodes may continue to function effectively, while the defect is contained within the layer in which it originates (e.g. the first or second electrode).
In some embodiments, the first electrode comprises a plurality of fuse portions each having substantially the same shape as each other, the plurality of fuse portions comprising the fuse portion. The number and shape of the fuse portions may be selected to provide a particular fuse rating of the plurality of fuse portions. It may be more straightforward to accurately control the fuse rating by controlling the number and shape of the fuse portions rather than by attempting to accurately control the shape or size of a single fuse portion. This may allow the energy storage device to be manufactured with a wider range of different fuse ratings.
According to some embodiments of the present disclosure, there is provided a method comprising:
providing a stack for a thin-film energy storage device, the stack comprising an electrode layer;
removing a first portion of the electrode layer corresponding to a first region of the electrode layer, using at least one first pulse of a laser beam, a first shape of the first portion at least partly corresponding to a first cross-section of the laser beam during the at least one first pulse; and
removing a second portion of the electrode layer corresponding to a second region of the electrode layer, using at least one second pulse of the laser beam, a second shape of the second portion at least partly corresponding to a second cross-section of the laser beam during the at least one second pulse, the second region of the electrode layer displaced from the first region of the electrode layer to leave a remaining portion of the electrode layer at least partly between the first region of the electrode layer and the second region of the electrode layer as a fuse portion of the electrode layer.
In some embodiments in accordance with some embodiments of the present disclosure, the removal of the first and second portions of the electrode layer is used to manufacture the fuse portion of the electrode layer. Manufacture of an energy storage device may include removal of portions of the electrode layer in order to provide a channel into which an electrically insulating material may be deposited to insulate the electrode layer from other portions of the stack, such as a further electrode layer. For example, by forming the channel, the electrode layer may be separated into a plurality of portions, each corresponding with a different respective cell of a multi-cell energy storage device. The electrically insulating material may be deposited between neighbouring cells.
In such cases, the removal of the first and second portions of the electrode layer may be performed during formation of the channel in the electrode layer. This allows the fuse portion to be manufactured during existing processing for the manufacture of the energy storage device. In other words, the fuse portion can be provided without adding in further process steps to the manufacturing process. The fuse portion can therefore be provided straightforwardly, without increasing complexity in the manufacturing method. In addition, the shape of the first and second portions of the electrode layer, which are removed, can be controlled straightforwardly by controlling a cross-section of the laser beam during application of the at least one first and second pulse. This allows the shape of the fuse portion to be controlled in an accurate and easy manner.
In some embodiments, methods in accordance with some embodiments may further include:
arranging an electrical connector in contact with the electrode layer;
removing a first portion of the electrical connector corresponding to a first region of the electrical connector, using the at least one first pulse of the laser beam, during removing the first portion of the electrode layer; and
removing a second portion of the electrical connector corresponding to a second region of the electrical connector, using the at least one second pulse of the laser beam, during removing the second portion of the electrode layer, the second region of the electrical connector displaced from the first region of the electrical connector to leave a remaining portion of the electrical connector at least partly between the first region of the electrical connector and the second region of the electrical connector,
wherein the remaining portion of the electrical connector is in contact with the fuse portion of the electrode layer.
In these examples, the remaining portion of the electrical connector may act as an electrical connector fuse portion. The electrical connector fuse portion and the fuse portion of the electrode layer may together provide or otherwise correspond with a combined fuse portion. A fuse rating of the combined fuse portion may be controlled by controlling formation of the fuse portion of the electrode layer and/or the electrical connector fuse portion, to provide these portions with predetermined features, such as a predetermined width, length and/or shape to provide a given fuse rating.
A plurality of cells can be manufactured on the same substrate and subsequently separated, for example by cutting the stack. This allows a plurality of cells to be formed efficiently, for example using a roll-to-roll manufacturing technique. In such cases, the electrical connector may be provided along a side of the stack, for example after the stack has been cut into individual cell portions. The first and second portions of the electrode layer and the electrical connector may then be removed. By using the at least one first pulse to remove the first portions of both the electrode layer and the electrical connector, the method may be more efficient than other methods in which these portions are removed at different times, for example in different process steps. The efficiency may be further improved by removing the second portions of both the electrode layer and the electrical connector using the at least one second pulse.
In some embodiments, the electrical connector comprises a different material than the electrode layer. This may provide further flexibility for the manufacturing process, by allowing the electrical connector and the electrode layer to be deposited using different processes or at different times from each other. Furthermore, an effectiveness of the energy storage device may be increased by selecting materials for the electrical connector and the electrode layer that are appropriate for their respective functions.
In some embodiments, after removing the first portion of the electrode layer and the second portion of the electrode layer, the electrode layer comprises a first perforation corresponding to the first region of the electrode layer, and a second perforation corresponding to the second region of the electrode layer. The first and second perforations for example correspond with holes in the electrode layer, which may pass partly or entirely through the electrode layer. The remaining portion of the electrode layer for example separates the first perforation from the second perforation. Hence, by controlling the laser beam during formation of the first and second perforations, the shape and size of the fuse portion can also be controlled. This allows the fuse portion to be provided with a particular fuse rating.
In some embodiments, the first perforation and the second perforation are at least one of: substantially the same size as each other, or substantially the same shape as each other. This may simplify manufacture. For example, various characteristics or parameters of the laser beam may remain unchanged between formation of the first perforation (e.g. using the at least one first pulse) and formation of the second perforation (e.g. using the at least one second pulse). Instead, the laser beam and the stack may be moved relative to each other during provision of the at least one first and second pulses, without altering other features of the laser beam.
In some embodiments, the method includes controlling the laser beam to form the first perforation and the second perforation each with least one of: a predetermined size or a predetermined pitch. By controlling the size or pitch of the first and second perforations, a corresponding size or pitch of the fuse portion may also be controlled. This allows the fuse portion to be manufactured with a particular size or pitch. In this way, the fuse portion may be manufactured with a predetermined fuse rating.
In some embodiments, the remaining portion of the electrode layer is a first remaining portion, the fuse portion is a first fuse portion, and the method comprises: removing a third portion of the electrode layer corresponding to a third region of the electrode layer, using at least one third pulse of the laser beam, a third shape of the third portion at least partly corresponding to a third cross-section of the laser beam during the at least one third pulse, the third region displaced from the second region to leave a second remaining portion at least partly between the second region and the third region as a second fuse portion of the electrode layer. In this way, a plurality of fuse portions of the electrode layer may be provided. By controlling the number and shape of the fuse portions, the fusing properties of the electrode layer may be controlled straightforwardly.
In some embodiments, the electrode layer comprises a first section and a second section, the first region of the electrode layer between the first section and the second section, and the second region of the electrode layer between the first section and the second section. In these examples, the fuse portion of the electrode layer connects the first section of the electrode layer to the second section of the electrode layer. This may reduce the amount of the electrode layer which is removed during formation of the fuse portion. This may improve the efficiency of the manufacturing process, and reduce wastage of the material of the electrode layer.
In some embodiments, the electrode layer comprises a first section and a second section, the first region between the first section and the second section, and the second region between the first section and the second section. In these examples, a length of the fuse portion of the electrode layer is less than a distance between the first section and the second section such that the first section of the electrode layer is not connected to the second section of the electrode layer by the fuse portion. This for example allows a greater separation between the first and second sections of the electrode layer to be provided. This may simplify the deposition of an electrically insulating material to insulate the electrode layer from other layers of the stack. For example, the electrically insulating material may be deposited in an elongate channel between the first and second sections of the electrode layer. This may be more straightforward than in other cases in which the fuse portion connects the first and second sections of the electrode layer to each other (and in which the electrically insulating material may be deposited within separate first and second channels formed by removal of the first and second portions of the electrode layer).
In some embodiments, the stack is on a substrate, and the method comprises cutting through the stack in a direction substantially perpendicular to a plane of a surface of the substrate to provide an intermediate structure for manufacture of the thin-film energy storage device. In such examples, a plurality of cells can be manufactured on the same substrate and subsequently separated, for example by cutting the stack. This allows a plurality of cells to be formed efficiently, for example using a roll-to-roll manufacturing technique.
In these examples, the intermediate structure comprises a portion of the substrate, and an electrode formed from the electrode layer. The electrode comprises the fuse portion as a protrusion of a side of the electrode and the protrusion protrudes in a direction substantially parallel to a plane of a surface of the portion of the substrate. The energy storage device in such examples is more compact than in other cases in which the protrusion of the fuse portion extends in a different direction.
In some embodiments, the fuse portion narrows in shape. Such a shape for example allows the fuse portion to act as a fuse. For example, a narrower part of the fuse portion may tend to melt more readily than other parts of the fuse portion (or other parts of the electrode layer), allowing current flow to be interrupted when the current exceeds a predetermined threshold current.
In some embodiments, the stack is on a first side of a substrate and the laser beam is directed towards the first side of the substrate during the at least one first pulse and the at least one second pulse. This may simplify the removal of the first and second portions of the electrode layer compared to other cases in which there are laser beams on both sides of the stack or in which the laser beam is moved from the first side to a different side in between removal of the first portion and the second portion of the electrode layer.
In some embodiments, the method comprises moving one of the laser beam and the electrode layer relative to the other of the laser beam and the electrode layer after applying the at least one first laser pulse of the laser beam to the electrode layer and before applying the at least one second laser pulse of the laser beam to the electrode layer. In this way, the fuse portion can be generated in a particular position, and with a given shape and/or size, by moving the laser beam and the electrode layer relative to each other. This may be more straightforward than other ways of controlling features of the fuse portion during manufacture.
In some embodiments, the first cross-section of the laser beam overlaps a first region of the stack during the at least one first pulse, and the second cross-section of the laser beam overlaps a second region of the stack during the at least one second pulse, the second region of the stack partly overlapping the first region of the stack. In such examples, the laser spot of the laser beam may not be entirely overlapping during removal of the first and second portions of the electrode layer. An extent of overlap of the first and second regions of the stack (overlapped by the first and second cross-sections of the laser beam) may be controlled to controlled various features of the fuse portion, which in turn may be used to control a fuse rating of the fuse portion in a straightforward manner.
In some embodiments, the method comprises determining a pulse timing scheme for using the at least one first pulse of the laser beam for removing the first portion of the electrode layer and the at least one second pulse of the laser beam for removing the second portion of the electrode layer, without removing the remaining portion of the electrode layer. In these examples, the method may further comprise controlling a timing of the at least one first pulse of the laser beam and the at least one second pulse of the laser beam in accordance with the pulse timing scheme. In this way, the at least one first and second pulses can be applied at appropriate times to produce a fuse portion with a given shape and/or size. This allows the fuse portion to be manufactured simply, and with particular properties.
In some embodiments, the method comprises controlling the laser beam to remove the first portion of the electrode layer and the second portion of the electrode layer so that the fuse portion has a predetermined fuse rating. The fuse rating may be selected based on the intended use of the energy storage device. This allows the method to be adapted to manufacture various different energy storage devices, with different intended uses. Accordingly, the method may be more flexible than other methods, which may be suitable for manufacturing energy storage devices with a more limited range of applications.
Further features will become apparent from the following description, given by way of example only, which is made with reference to the accompanying drawings.
Details of methods, structures and devices according to examples/embodiments 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/embodiments are set forth. Reference in the specification to “an example,” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the example/embodiment is included in at least that one example/embodiment, but not necessarily in other examples/embodiments. It should further be noted that certain examples/embodiments are described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the examples/embodiments.
The stack 100 is on a substrate 102 in
The stack 100 of
The first electrode layer 104 may act as a positive current collector layer. In such embodiments, the first electrode layer 104 may form a positive electrode layer (which may correspond with a cathode during discharge of a cell of the energy storage device including the stack 100). The first electrode layer 104 may include 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 alternative embodiments, there may be a separate positive current collector layer, which may be located between the first electrode layer 104 and the substrate 102. In these embodiments, the separate positive current collector layer may include nickel foil, but it is to be appreciated that any suitable metal could be used, such as aluminium, copper or steel, or a metalised material including metalised plastics such as aluminium on polyethylene terephthalate (PET).
The second electrode layer 108 may act as a negative current collector layer. The second electrode layer 108 in such cases may form a negative electrode layer (which may correspond with an anode during discharge of a cell of an energy storage device including the stack 100). The second electrode layer 108 may include a lithium metal, graphite, silicon or indium tin oxide (ITO). As for the first electrode layer 104, in other embodiments, the stack 100 may include a separate negative current collector layer, which may be on the second electrode layer 108, with the second electrode layer 108 between the negative current collector layer and the substrate 102. In some embodiments in which the negative current collector layer is a separate layer, the negative current collector layer may include nickel foil. It is to be appreciated, though, that any suitable metal could be used for the negative current collector layer, such as aluminium, copper or steel, or a metalised material including metalised plastics such as aluminium on polyethylene terephthalate (PET).
The first and second electrode layers 104, 108 are typically electrically conductive. Electrical current may therefore flow through the first and second electrode layers 104, 108 due to the flow of ions or electrons through the first and second electrode layers 104, 108.
The electrolyte layer 106 may include any suitable material which is ionically conductive, but which is also an electrical insulator, such as lithium phosphorous oxynitride (LiPON). As explained above, the electrolyte layer 106 is for example 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 stack 100 may for example be manufactured by depositing the first electrode layer 104 on the substrate 102. The electrolyte layer 106 is subsequently deposited on the first electrode layer 104, and the second electrode layer 108 is then deposited on the electrolyte layer 106. Each layer of the stack 100 may be deposited by flood deposition, which provides a simple and effective way of producing a highly homogenous layer, although other deposition methods are possible.
The stack 100 of
In
In the example of
After formation of the grooves, electrically insulating material may be deposited in at least some of the grooves using a material deposition system 118. The material deposition system 118 for example fills at least some of the grooves with a liquid 120 such as an organic suspended liquid material. The liquid 120 may then be cured in the grooves to form electrically insulating plugs in the grooves. 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 some embodiments 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.
Referring to
In
Although not shown in
After cutting the cells, electrical connectors can be provided along opposite sides of a cell, such that a first electrical connector on one side of the cell contacts the first electrode layer 104 (which may be considered to form a first electrode after the cell has been separated from the remainder of the intermediate structure 110), but is prevented from contacting the other layers by the electrically insulating material. Similarly, a second electrical connector on an opposite side of the cell can be arranged in contact with the second electrode layer 108 (which may be considered to form a second electrode after the cell has been separated from the remainder of the intermediate structure 110), but is prevented from contacting the other layers by the insulating material. The insulating material may therefore reduce the risk of a short circuit between the first and second electrode layers 104, 108 and the other layers in each cell. The first and second electrical connectors may, for example, be a metallic material that is applied to the edges of the stack (or to the edges of the intermediate structure 110) by sputtering. The cells can therefore be joined in parallel simply and easily.
The energy storage device 126 of
The energy storage device 126 includes the first electrode 104, the second electrode 108 and the electrolyte 106 between the first and second electrodes 104, 108. The first electrode 104 includes a fuse portion 130a. In
The fuse portion 130a may be any portion of the first electrode 104 with a characteristic (such as a shape and/or size) that is appropriate for the fuse portion 130a to act as a fuse. The fuse portion 130a may therefore allow current to flow between the first electrode 104 and the electrical connector 128 up to a particular predetermined threshold current, which is below a threshold current that may otherwise flow through the bulk of the electrode. However, above this threshold current, the temperature of the fuse portion 130a may rise (for example due to an intrinsic resistance of the fuse portion 130a) sufficiently that the fuse portion 130a melts and prevents current from flowing between the first electrode 104 and the electrical connector 128.
The fuse portion 130a in
In order to provide a fuse portion 130a as a narrower portion of the first electrode 104, for connection to the electrical connector 128, the fuse portion 130a may be a protrusion of a first side 132 of the first electrode 104.
The fuse portion 130a may have a variety of different shapes. In
In the example of
With the arrangement of
The indented portion 134a may have various different shapes, depending on an intended use of the energy storage device 126. In
A second side 138 of the first electrode 104, opposite to the first side 132, may be substantially planar. A substantially planar side of an electrode is for example flat within manufacturing tolerances, or with height variations of less than 20%, 15%, 10%, 5% or less of a thickness of the electrode in a direction perpendicular to a surface of the side.
In some embodiments such as
Where there are a plurality of fuse portions 130, the plurality of fuse portions 130 may provide the first electrode 104 with a patterned or otherwise non-planar or non-straight first side 132. This is shown in
In
The electrical connector fuse portion 135 of the electrical connector 228 may for example act as a fuse portion of the electrical connector 228, and may have similar or the same features as the fuse portion 230a of the first electrode 204. In
In
In
However, in
In the example of
The second fuse portions 140 of
In some embodiments, an energy storage device includes a plurality of cells.
In
The first electrically insulating material 144a insulates the first electrode 404a from the second electrode 408a, while revealing a side of the first electrode 404a for connection to the first electrical connector 428. The side of the first electrode 404a in contact with the first electrical connector 428 is the first side, which for example includes one or more fuse portions as illustrated in
Similarly, the second electrically insulating material 146a insulates the first electrode 404a from the second electrode 408a, while revealing a side of the second electrode 408a for connection to the second electrical connector 442. The side of the second electrode 408a in contact with the second electrical connector 442 is the first side, which for example includes one or more fuse portions as illustrated in
A lateral extent of the fuse portions of the first electrode 404a is indicated with the dotted line 431 in
In some embodiments such as
In the example of
In some embodiments, a plurality of the first cell may be manufactured on the first side of the substrate 402 and a plurality of the second cell may be manufactured on the second side of the substrate 402, for example as part of a roll-to-roll manufacturing process. In such cases, the substrate 402 may be folded so as to stack a plurality of cells on top of each other. This therefore allows an energy storage device including a plurality of cells connected in parallel to be produced.
For example, the first electrode 404b of the second cell of the energy storage device 426 of
The energy storage device 526 of
Features of
The first electrode layer 604, the electrolyte layer 606 and the second electrode layer 608 may be provided for example by a vapour deposition process such as physical vapour deposition (PVD) or chemical vapour deposition (CVD), or by a coating process for use with a roll-to-roll system such as slot die coating (sometimes referred to as slit coating). Each of these layers may be provided sequentially. However, in other examples, the substrate 602 may be provided partially assembled. For example, a stack including the first electrode layer 604, the electrolyte layer 606, and the second electrode layer 608 (or a subset of these layers) may already be arranged on the substrate 602 before the substrate 602 is provided. In other words, the substrate 602 may be provided with the stack 600 (or part of the stack 600) already arranged thereon.
Methods in accordance with
In
In
The laser ablation system 148 is arranged to produce at least one first pulse of a laser beam 150. In
In some embodiments in accordance with
In
Formation of the groove in the second electrode layer 608 includes removal of a first portion 154a of the second electrode layer 608. A second portion 154b of the second electrode layer 608 is removed using at least one second pulse of the laser beam 150 (in this example, a series of second pulses, although solely one second pulse is possible in other examples). The second portion 154b of the second electrode layer 608 corresponds to a second region of the second electrode layer 608. The second region is displaced from the first region to leave a remaining portion 158a of the second electrode layer 608 at least partly between the first region and the second region, as a fuse portion of the second electrode layer 608. The fuse portion may be similar to the fuse portion described herein with reference to
As will be appreciated from
In the example of
The shape of the first and second portions 154a, 154b of the second electrode layer 608 that are removed by the laser beam 150 each have a shape at least partly corresponding to a cross-section of the laser beam 150 during the first and second pulses, respectively. In this example, the second electrode layer 608 has a substantially straight first side 160 before removal of the first and second portions 154a, 154b. However, by removing the first and second portions 154a, 154b of the second electrode layer 608, the first side 160 of the second electrode layer 608 is patterned so it is no longer straight. By patterning the first side 160 of the second electrode layer 608, the second electrode layer 608 is provided with fuse portions. The first and second portions 154a, 154b in
In some embodiments in accordance with
By controlling the time and duration of application of pulses of the laser beam 150, a shape of a removed portion of an electrode layer (such as the second electrode layer 608) can be controlled. In this way, a remaining portion of the electrode layer can be produced, as a fuse portion. A fuse rating of the fuse portion may depend on a shape and/or size of the fuse portion. Hence, a shape and/or size of the fuse portion (e.g. by controlling the first and second portions of the electrode layer removed by the laser beam 150) can be controlled so that the fuse portion has a predetermined fuse rating.
In
As can be seen in
In some embodiments such as this, the laser beam 150 may be moved from one position to another while the stack 600 remains stationary. Conversely, the laser beam 150 may remain stationary while the stack 600 is moved from one position to another. In yet further examples, both of the laser beam 150 and the stack 600 may be moved, so as to alter a position of the laser beam 150 relative to a position of the stack 600. The stack 600 may be moved for example by moving the substrate 602 on which the stack 600 is arranged. For example, the substrate 602 may be arranged on rollers or on a moveable belt, in order to translate the substrate 602 (and hence the stack 600) beneath the laser beam 150, or beneath the laser ablation system 148. The laser beam 150 may be moved by altering an optical element of the laser ablation system 148, such as a mirror or other reflector, to deflect the laser beam 150 to alter a position at which the laser beam 150 intersects a surface of the stack 600. In such cases, a laser which produces the laser beam 150 may remain still. In other cases, though, the laser itself may be moved using any suitable actuator.
In the example of
Due to the different position of the laser beam 150 with respect to the stacks 600, 700 in
After formation of the fuse portions in the second electrode layer 608 of
In
The removed portions of the first electrode layer 604 are labelled with the reference numerals 168a-168e, and are collectively referred to with the reference numeral 168. The same pulse timing sequence may be used to remove the portions of the first electrode layer 604 as that used to remove the portions of the second electrode layer 608. However, in other examples, different pulse timing schemes may be used for each. In such cases, a size, shape or number of removed portions of the first electrode layer 604 may be different from that of the second electrode layer 608. Similarly, a size, shape or number of fuse portions of the first electrode layer 604 may be different from that of the second electrode layer 608.
Removal of the first electrode layer 604 creates a plurality of remaining portions of the first electrode layer 604, which are labelled with reference numerals 170a-170e (collectively referred to with the reference numeral 170). As in
In the example of
Due to formation of the groove in the stack 600, the first electrode layer 604 includes a first section 604a and a second section 604b, separated by the groove. Similarly, the electrolyte layer 606 includes a first section 606a and a second section 606b, separated by the groove. The second electrode layer 608 also includes a first section 608a and a second section 608b, separated by the groove. The removed portions of the first and second electrode layers 604, 608 are between the first and second sections of the first electrode layer 604a, 406b and the second electrode layer 608a, 608b.
In
The stack 600 of
Such an intermediate structure for example includes a portion of the substrate 602 and an electrode formed from an electrode layer of the stack 600 (such as one of the first and second electrode layers 604, 608). Such an electrode for example includes a fuse portion as a protrusion of a side of the electrode, which protrudes in a direction substantially parallel to a plane of a surface of the portion of the substrate. Although not visible from
In the embodiments of
In
The use of the laser beam may be as described with reference to
The second electrode layer 808 may subsequently be cut into two, to provide two separate sections of the second electrode layer 808, which would otherwise be joined along an axis 178. The axis 178 along which the second electrode layer 808 may be cut for example corresponds to an intersection between a plane perpendicular to a plane of a surface of a substrate on which a stack including the second electrode layer 808 is arranged, and the surface itself. The axis 178 for example passes through the perforations 174 of the second electrode layer 808. In this case, the perforations 174 are aligned along a central axis, and the axis 178 corresponds with the central axis of the perforations 174. However, in other examples, the axis 178 may be off-centre with respect to the perforations 174.
The portion of the second electrode layer 808 which remains after removal of the first and second regions of the second electrode layer 808 (and formation of the first and second perforations 174, 174b) for example corresponds to a fuse portion. In the example of
While
The above examples are to be understood as illustrative examples. Further examples are envisaged. In examples described herein, the first electrode is a cathode, which is closer to the substrate than the second electrode (an anode). However, in other examples, the first electrode (which for example includes a fuse portion) may be further from the substrate than the second electrode. In such cases, the first electrode may be an anode and the second electrode may be a cathode. The fuse portion of the first electrode in these examples may be narrower than a portion of the first electrode which overlaps the second electrode. However, the first electrode may otherwise be similar to the first electrode described above (other than its position with respect to the second electrode and hence its function as an anode rather than a cathode).
In examples such as
In such cases, the first cross-section of the laser beam may overlap the first regions of both the electrode layer and the electrical connector. Similarly, the second cross-section of the laser beam may overlap the second regions of both the electrode layer and the electrical connector. In this way, a combined first portion of the electrode layer and the electrical connector, which is removed by the at least one first pulse, may have a shape which corresponds to the first cross-section of the laser beam. Similarly, a combined second portion of the electrode layer and the electrical connector, which is removed by the at least one second pulse, may have a shape which corresponds to the second cross-section of the laser beam. For example, as shown in
It is to be appreciated that, in yet further examples, the electrical connector may include an electrical connector fuse portion and the electrode layer may not include a fuse portion. In such cases, a side of the electrode layer closest to the electrical connector fuse portion may be planar.
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 without departing from the scope of the accompanying claims.
Number | Date | Country | Kind |
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1811885.1 | Jul 2018 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/GB2019/052033 | 7/19/2019 | WO | 00 |