Battery cells and manufacturing processes including stretchable and compressible functional layers

Abstract

The present disclosure relates to a rechargeable battery cell that includes a compressible and stretchable composite material to form one or more of a compressible and stretchable first current collector, a compressible and stretchable positive electrode, a compressible and stretchable solid electrolyte, a compressible and stretchable negative electrode, and a compressible and stretchable second current collector, wherein the compressible and stretchable composite material includes a plurality of compressible pores.

Description

Technical Field

[0001] Technical Field and Background The present disclosure relates to solid-state batteries. In the case of 3D and 2D all-solid-state batteries, the functional layers are usually compactly stacked together as a stack. In normal battery applications, the volume change between the discharged state and the charged state of the battery can be up to about 20%, for example, 1.2 times. Expansion inside the stack, such as swelling, may be caused by the formation of a negative electrode, for example, an electrode layer, during the first charge cycle of a rechargeable battery. In response, during discharge, the volume of the negative electrode may decrease, for example, shrink. In the case of microbatteries, where the amount of active material is very small and thus the volume change during charge and discharge is very small, a design including densely integrated layers may work well. However, when moving to large-scale applications, such as 3D and 2D batteries with higher energy density, this may no longer apply. Expansion with a large volume may lead to the formation of defects, such as the formation and / or propagation of cracks, and / or a decrease in the ionic or electrical conductivity between layers inside the stack. There are several different ways to address the above problems to some extent.

Background Art

[0002] The first approach involves using a 3D-structured porous solid electrolyte on the current collector. Wang CW et al., Nano Lett. 17, 17, 565-571, describe a porous solid ceramic electrolyte compound in which, during charging, the lithium electrode material can fill existing pores in the solid electrolyte. However, this solution is only applicable to 2D batteries because the high sintering temperature required to produce the ceramics damages other components of the 3D structure. Furthermore, the large space occupied by the electrochemically inert ceramic material reduces the energy density of such batteries, e.g., energy per unit volume and energy-to-weight ratio. In addition, the large surface contact area and long diffusion paths through the pores in the lithium plating are undesirable because they can lead to parasitic reactions.

[0003] The second approach involves forming a porous current collector. Polym. Sci. 2014, 39, 486-509 by Antunes M. et al. describes a lithium cell with a porous current collector formed from copper nanowires. During plating, lithium may fill the pores inside the current collector. A disadvantage of using a porous conductive current collector is that it does not provide ionic conductivity and can only be used in combination with a liquid electrolyte. If such a current collector is used in a lithium battery with a solid electrolyte, lithium will only plate at the interface between the current collector and the electrolyte, and will not fill the pores.

[0004] A third approach involves applying external pressure to the functional layer stack (e.g., a stretchable casing or spring at the pouch cell level). U.S. Patent No. 10786418 describes a pouch cell in a stretchable / plastic casing that keeps the stack under continuous pressure. This design reduces the loss of interlayer electrical contact during stack contraction. However, this design does not prevent volume expansion, which can still cause damage to the cell, such as cracking, and is therefore unsuitable for anode-free designs where large volume expansion is expected. Furthermore, plastic deformation of the cell stack is observed very frequently, which leads to battery damage.

[0005] A fourth approach involves providing a battery with a compressible and expandable inert layer. U.S. Patent Application Publication 20170365841 describes the encapsulation of an expandable layer within a cylindrical AAA-type zinc-air battery. In addition to introducing a large amount of electrochemically inert material, such a design cannot be used in lithium batteries because it adds an insulating layer between the functional layers that prevents charge transport across a continuous stack. Furthermore, such an approach results in a large amount of useless volume and mass (the inert portion of the battery), thus reducing the energy density of the battery.

[0006] This disclosure addresses one or more of the above limitations by describing a cell having a functional layer whose volume can be compressed and expanded in order to at least partially compensate for volume changes of other layers of the battery during a charge-discharge cycle. [Overview of the project] [Means for solving the problem]

[0007] overview Aspects of the present disclosure relate to a rechargeable battery cell comprising a compressible and stretchable composite material for forming one or more of a compressible and stretchable first current collector, a compressible and stretchable positive electrode, a compressible and stretchable solid electrolyte, a compressible and stretchable negative electrode, and a compressible and stretchable second current collector, wherein the compressible and stretchable composite material comprises a plurality of compressible pores and is configured to at least partially resist compressive and / or tensile forces within the cell resulting from volume changes of the negative and / or positive electrodes during charging and / or discharging of the rechargeable battery cell.

[0008] The stretchable composite material is preferably robust enough to withstand the compressive and / or tensile forces inside a rechargeable battery cell repeatedly, for example, over the lifespan of the cell, for example, over numerous charge-discharge cycles, without significant degradation. The compressible and stretchable layer is preferably composed of a stretchable base material in order to obtain the desired mechanical properties and elastic behavior of the layer.

[0009] In a preferred embodiment, the compressible pores have a diameter of less than 20% of the thickness of the compressible and stretchable composite material (C) containing the pores, and the total volume of the pores is in the range of 30 to 150%, more preferably 100 to 120%, of the volume change of the negative and / or positive electrodes during charging and / or discharging of the rechargeable battery cell.

[0010] The disclosure can also be advantageously applied to rechargeable battery cells that are particularly susceptible to damage caused by volume changes of the negative and / or positive electrodes. Accordingly, the disclosure is advantageously more relating to rechargeable battery cells, such as a 3D battery cell, which is formed from a conductive base structure including an array of conductive elements spaced apart from each other and extending away from the base, with at least one of electrodes and a solid electrolyte provided between the elements.

[0011] In some preferred embodiments, the present disclosure relates to a rechargeable battery cell in which compressible pores are provided at least partially by hollow latex beads. Preferably, the hollow latex beads have a core-to-shell ratio (Vcore / Vshell) in the range of 5 to 0.05. The hollow latex beads preferably have a diameter in the range of 100 nanometers to 5 micrometers.

[0012] This disclosure further relates to a process for manufacturing a rechargeable battery cell comprising a compressible and stretchable composite material. The process includes one or more of the following: providing a compressible and stretchable composite material to form a compressible and stretchable first current collector; providing a compressible and stretchable composite material to form a compressible and stretchable positive electrode; providing a compressible and stretchable composite material to form a compressible and stretchable solid electrolyte; providing a compressible and stretchable composite material to form a compressible and stretchable negative electrode; and providing a compressible and stretchable composite material to form a compressible and stretchable second current collector. Multiple compressible pores are provided in the compressible and stretchable composite material by preparing a mixture comprising one or more pore-forming agents; the formation of a compressible and stretchable solid electrolyte is made possible by adding a solid electrolyte-forming material; the formation of a compressible and stretchable electrode is made possible by adding an electrode material; and the formation of a compressible and stretchable current collector is made possible by adding a current collector material. The pore-forming agent comprises one or more of the following: hollow particles, hollow latex beads, and a blowing agent, a high vapor pressure solvent, or a dissolved gas.

[0013] In some embodiments where the pore-forming agent is hollow latex beads, the process further includes steps for obtaining the aforementioned hollow latex beads. Advantageously, the hollow latex beads can be manufactured in a process starting from core-shell polymer latex beads, where the core comprises an aqueous gel, and the core-shell polymer latex beads are then dried by freeze-drying or by a liquid-gas phase exchange treatment using a dry gas stream. Thus, the disclosure also relates to hollow latex beads obtainable by such a process.

[0014] Brief explanation of the drawing These and other features, aspects, and advantages of the apparatus, systems, and methods of this disclosure will be better understood from the following description, the appended claims, and the appended drawings. [Brief explanation of the drawing]

[0015] [Figure 1A] This diagram shows schematic cross-sectional views of rechargeable battery cells in both the charged and discharged states, illustrating the volume change of the negative electrode between these states. [Figure 1B] This diagram shows a schematic cross-section of a rechargeable battery cell damaged due to crack formation. [Figure 1C] The diagram shows a schematic cross-section of a multi-layered stack, where a compressible and expandable composite material resists volume changes within the stack. [Figure 2A] This shows a schematic cross-sectional view of a rechargeable battery cell containing a compressible and expandable current collector. [Figure 2B] A schematic cross-sectional view of a compressible and expandable current collector, solid electrolyte, and solid electrode is shown. [Figure 3] This diagram shows schematic cross-sectional views of rechargeable 3D battery cells in both charged and discharged states, illustrating a compressible and expandable current collector that counteracts volume changes in the negative electrode. [Figure 4] A schematic cross-sectional view of a hollow latex bead is shown. [Modes for carrying out the invention]

[0016] Detailed explanation The terms used to describe specific embodiments are not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless otherwise specified. The terms “and / or” include any and all combinations of one or more of the items listed in relation. The terms “comprises” and / or “comprising” indicate the presence of the described features, but it will be understood that this does not preclude the presence or addition of one or more other features. Where a particular step of a method is said to occur following another step, it will be further understood that, unless otherwise specified, it may occur immediately after the other aforementioned step or one or more intervening steps may occur before that particular step. Similarly, where a connection between structures or components is described, it will be understood that, unless otherwise specified, this connection may be established directly or through an intervening structure or component.

[0017] In electronic devices, electronic circuits may have current collectors of a type similar to those found in electrochemical devices. For example, an electrochemical device is a battery, such as a rechargeable lithium-ion solid-state battery, which has a non-planar current collector. In discharge mode, the anode becomes the "negative electrode," and a positive current flows toward it from the cathode, which is the "positive electrode." During charging, these functions are reversed. Regardless of the charging mode, the electrochemical relationship can be characterized by the exchange of charge between the negative electrode material and the positive electrode material. The negative electrode material has a lower work function or redox potential than the positive electrode material.

[0018] For example, known negative electrode (anode during battery discharge) materials are Li4Ti5O12 (lithium spinel titanate or LTO), LiC6 (graphite), Li4.4Si (silicon), and Li4.4Ge (germanium). Known positive electrode (cathode) materials are LiCoO2 (lithium cobaltate or LCO), LiCoPO4, (doped) LiMn2O4 (lithium manganese spinel or LMO), LiMnPO4, LiFePO4 (LFP), LiFePO4F (LFPF), or LiCo1 / 3Ni1 / 3Mn1 / 3O2 (LCNMO).

[0019] The positive electrode (cathode) may contain an insertion or conversion base material. Suitable materials can be selected from the group consisting of, for example, metal oxides, silicon, graphite materials, sulfur, phosphates, oxygen, and air. In the case of lithium-ion batteries, it may include, for example, LiCoO2, MnO2, LiMn2O4, LiNiO2, Lix(MnyNi1-y)2-xO2, LiNi1-xCoxO2, LiNixCoyAlzO2, Li(Ni1 / 3Mn1 / 3Co1 / 3)O2, LiFePO4, Li2FePO4F, V2O5, V2O5-TeO2, WO3-V2O5, TiSxOy, MOx, MSx, or Li-V2O. In the case of other ion-insertion batteries, the positive electrode layer may contain, for example, a material similar to those listed above for lithium-ion batteries, but where Li is replaced by other ions. For example, in the case of a sodium-ion battery, the first electrode layer 12 may contain, for example, NaMn2O4; in the case of a magnesium-ion battery, the first electrode layer may contain, for example, MgMn2O4; and in the case of an aluminum-ion battery, the first electrode layer may contain, for example, AlxV2O3, but the disclosure is not limited to these.

[0020] Thin film ion batteries, including thin film solid lithium ion batteries, can be prepared from various deposition techniques for manufacturing the anode, cathode, and electrolyte materials that are bonded together to form the battery. Such techniques may typically involve depositing thin films of such materials using vacuum deposition or other techniques that result in similar thin films in order to manufacture a "thin film" battery. Thin film batteries are often used in applications where it is desirable to save space and weight and where a very long cycle life may be desired.

[0021] A 3D battery typically includes a structured current collector formed from a base structure that includes an array of conductive elements spaced apart from each other and extending away from the base. On top of these elements, additional functional layers, such as electrodes and / or electrolytes, are provided in a conformal manner, such that the 3D cell comes to include a larger interfacial area between the functional layers than the corresponding 2D cell and is able to provide a larger current.

[0022] The present invention will be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. In the drawings, the absolute and relative dimensions of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and / or cross-sectional views of idealized embodiments and intermediate structures of the invention in some cases. In the description and the drawings, like numbers refer to like elements throughout. Relative terms and their derivatives should be construed to refer to the orientation being described at that time or shown in the drawing under consideration. These relative terms are for convenience of description and do not require that the system be manufactured or operate in a particular orientation unless otherwise specified.

[0023] Figure 1A schematically shows cross-sectional views of a rechargeable thin-film battery 100 in a fully discharged state 100D (left) and a charged state 100C (right) on the left. The discharged battery cell includes a rigid upper current collector 20, a layer 30 containing positive electrode material, a solid electrolyte layer 40, and a bottom current collector 60 for receiving negative electrode material during charging. During the charging cycle, the ionic negative electrode material is carried toward the bottom current collector, where it is reduced to form a layer 50 of negative electrode material. During the discharging cycle, the deposited negative electrode material can be re-oxidized by releasing electrons into an externally connected circuit and carrying oxide ions toward the positive electrode. Inevitably, these oxidation and reduction processes involve a volume change Δh inside the battery cell. Typically, batteries have a rigid external current collector, for example, in the form of a rigid external casing. As the desired capacity of the battery increases, more electrode material is required, which can lead to larger volume changes. As shown in Figure 1B, volume changes can lead to battery degradation. For example, an increase in volume during a charging cycle can lead to damage or breakage of the battery and / or the rigid layers of the battery. For example, a decrease in volume during a discharge cycle can lead to delamination and / or crack formation within and between layers 99.

[0024] Figure 1C schematically shows a side cross-sectional view of a stack formed from a compressible and expandable composite material C and a reversibly expandable layer E, sandwiched between two rigid layers R. The compressible and expandable composite materials C and C' are formed from continuous phases and contain a plurality of compressible pores P. By providing compressible pores in the compressible material, the composite layer can resist compressive forces within the stack, for example, forces generated due to volume changes in layer E. Rather than distributing the force elsewhere, the compressible and expandable composite material C can also contract advantageously, thus mitigating the overall volume increase of the stack. By providing a compressible composite material layer in the stack, the aforementioned layer can resist compressive forces within the stack. In other words, the compressible composite material C can adapt to compressive forces by reducing its volume by compressing the pores. By providing a compressible and expandable composite material layer in the stack, the aforementioned layer can resist compressive and tensile forces within the stack. In other words, a compressible and stretchable composite material C can adapt to compressive forces by reducing its volume ΔhE through compression ΔhP of the pores, and can adapt to tension by increasing its volume through (re)expansion of the pores.

[0025] Accordingly, this disclosure relates to a rechargeable battery cell comprising a compressible and stretchable composite material C. This compressible and stretchable composite material C can advantageously be combined with one or more functional layers contained within a battery stack. Accordingly, this disclosure relates to a rechargeable battery cell 1 comprising a compressible and stretchable composite material C to form one or more of the following: - Compressible and expandable first current collector 2, - Compressible and stretchable positive electrode 3, - Compressible and stretchable solid electrolyte 4, - Compressible and stretchable negative electrode 5, - A second current collector 6 that is compressible and expandable, Here, the compressible and stretchable composite material C includes a plurality of compressible pores P, and the compressible and stretchable composite material C is configured to at least partially resist the compressive and / or tensile forces within the stack resulting from volume changes of the negative and / or positive electrodes during charging and / or discharging of the rechargeable cell.

[0026] In preferred embodiments, the compressible layer is composed of a stretchable continuous phase, such as a matrix, to obtain the desired mechanical properties and elastic behavior of the layer. In some embodiments, the compressible and stretchable composite material C includes, but is not limited to, stretchable polymers such as polyurethane, spandex, various rubbers, ethylene vinyl acetate, polyisoprene, nitrile butadiene, polybutadiene, polyesters, polycarbonates, polyamides, and silicones. By providing a stretchable polymer in the composite material C, the compressible layer can re-expand when the compressive force is released. Alternatively or in addition to this, the compressible and stretchable composite material C may include copolymers and / or polymer blends containing stretchable polymers, where additional functionality is provided through one or more conductive polymers and ion-conducting polymers. Accordingly, the present disclosure relates to a rechargeable battery cell 1, where the compressible and stretchable composite material C also has electrochemical properties as ion-conductive or electronically conductive. Ion-conductive, compressible, and stretchable composite material C may be provided through compounds containing suitable stretchable / ionic-conductive copolymers, such as poly(ethylene vinyl acetate)-co-polyethylene oxide. Conductive, compressible, and stretchable composite material C may be provided, for example, through blends of stretchable polymers and conductive additives, such as polyurethane polymers with carbon additives.

[0027] The compressible and stretchable composite material C is preferably an elastic material, for example, adapted to repeatedly compensate for volume changes inside a rechargeable battery cell.

[0028] It is preferable that the compressible pores P are uniformly dispersed throughout the compressible and stretchable composite material C. By uniformly distributing the compressible pores P throughout the compressible and stretchable composite material C, it is possible to adapt evenly to compressive and tensile deformations. This makes it possible to avoid local disturbances in the electric field and / or ion diffusion distance, thereby reducing battery degradation.

[0029] In some embodiments, the compressible and stretchable composite material C and the pores P form bubbles, such as sponges, or microfoams, such as microporous structures with voids.

[0030] Figure 2A shows a schematic cross-sectional view of a rechargeable battery cell 1 in discharge state 1D (left) and charge state 1C (right). This cell is formed from a stack of functional layers including a first current collector 2, a positive electrode 3, a solid electrolyte 4, and a compressible and stretchable second current collector 6, 6', which is sandwiched between two rigid external current collectors R. During the charging cycle, a negative electrode 5 is formed on the second current collector 6. In one preferred embodiment, for example, as shown in Figure 2, a compressible and stretchable composite material C forms the compressible and stretchable current collector. During charging, the compressible and stretchable current collector 6 resists the volume change of the battery stack by compression, e.g., volume reduction, which is indicated by the change in the thickness of the compressible and stretchable current collector from an initial thickness h6 to a reduced thickness h6'. Conversely, during discharge, the compressible and expandable current collector re-expands, thereby compensating for the contraction of the negative electrode layer and mitigating the overall volume change of the battery cell.

[0031] The compressible pores preferably have a diameter of less than 20% of the thickness of the compressible and stretchable composite material C containing the pores. Providing small-diameter pores in the compressible and stretchable composite material C allows for a uniform distribution of multiple pores throughout the entire layer containing the pores. By uniformly distributing the multiple pores, compressive and tensile deformations can be absorbed evenly. Using pores with a maximum diameter of 20% of the thickness of the layer containing the pores can reduce the distribution of non-uniform pores. The 20% dimension has been found to be the maximum value that can avoid plastic deformation. The total volume of pores in the compressible and stretchable composite material C is preferably in the range of 30-150%, more preferably 100-120%, of the volume change of the negative and / or positive electrodes during charging and / or discharging of a rechargeable battery cell. The total volume of pores is considered to correspond to the maximum compressibility of the compressible and stretchable composite material C. Providing a large total pore volume in the compressible and stretchable composite material C may allow for the absorption of increased electrode volume changes. By providing the compressible and stretchable composite material C with a total pore volume equivalent to the predicted volume change of the electrode material, the compressible and stretchable composite material C can completely cancel out the aforementioned volume change within the cell. Providing the compressible and stretchable composite material C with a total pore volume exceeding the predicted volume change of the negative and / or positive electrode may not further contribute to canceling out the volume change. The portion of the total pore volume exceeding the predicted volume change of the electrode material may be considered an undesirable, useless volume, e.g., a volume that does not contribute to the performance or integrity of the rechargeable battery cell 1. In a typical battery application, the above limitations on pore dimensions correspond to pores having dimensions between 10 micrometers and 50 nanometers, preferably between 5 micrometers and 100 nanometers, more preferably between 1 micrometer and 100 nm. It will be understood that the maximum thickness relates to the thickness of the compressible and stretchable composite material C layer containing the pores.A thicker layer, for example, a second current collector with a thickness of 50 micrometers, can use larger pores than a thinner layer, for example, a solid electrolyte layer with a thickness of 1 micrometer.

[0032] In another or further embodiment, the compressible pores are at least partially provided by compressible hollow particles 10. These particles preferably include a stretchable shell structure surrounding a hollow core. In particular, in the case of rechargeable battery cells where the compressible and stretchable composite material will be provided in a high aspect ratio structure, such as between the extension elements of a 3D battery, it may be preferable that the pores be provided by compressible hollow particles 20, because controlling the formation and dispersion of pores, which are foams, can be difficult, especially in 3D structures. The compressible hollow particles 10 preferably have a diameter in the range of 10 micrometers to 50 nanometers, preferably between 5 micrometers to 200 nanometers, and more preferably between 1 micrometer to 300 nm. Using smaller compressible hollow particles 10 may allow for the formation of a thin, compressible and stretchable composite functional layer. Using a thin, compressible and stretchable composite functional layer may allow for the manufacture of high-energy-density rechargeable battery cells. It will be understood that, similar to the dimensions of pores, the dimensions of compressible hollow particles depend on the thickness of the layer into which the hollow particles are incorporated. For example, if compressible hollow particles are incorporated into a positive electrode layer with a thickness of 1 micrometer, the diameter of the compressible hollow particles should be at the lower end of the range, e.g., within the range of approximately 50 to 300 nm. If compressible hollow particles are incorporated into a current collector with a thickness of 5 micrometers, the diameter can be larger, e.g., up to a maximum of 2 micrometers. The hollow core preferably contains gas. By providing gas to the hollow particles, the particles can be compressible and expandable. It is thought that by compressing a particle containing a gas-filled core, the gas pressure within the particle may increase during compression. When the external force compressing the particle decreases, the increased gas pressure inside the hollow particle can cause the particle to re-expand, for example, to its original volume. Furthermore, the expansion and contraction properties of the shell may help in the recovery of the original volume.

[0033] In some preferred embodiments, the hollow, compressible particles 10 are hollow latex beads 11. The hollow latex beads preferably have a core-to-shell ratio (Vcore / Vshell) in the range of 5 to 0.05 in volume, and have a diameter in the range of 50 nanometers to 5 micrometers, preferably in the range of 200 to 1000 nanometers. Beads with larger pores can be compressed to a greater extent. Beads with thicker shells may be more elastic and more stretchable. It will be understood that, as with pore dimensions, beads with smaller dimensions relative to the thickness of the layer containing the beads can be dispersed more evenly. Homogeneity of the beads results in a more uniform compressible and stretchable layer, which may be able to evenly adapt to the expansion / contraction of electrodes during the operation of a rechargeable battery cell.

[0034] The compressible and stretchable composite material C may be included in any one or more of the multiple functional layers within the battery stack.

[0035] Figure 2B shows a schematic cross-sectional view of an exemplary embodiment of a compressible and stretchable second current collector 2 comprising a compressible and stretchable first current collector 2, a compressible and stretchable solid electrolyte 4, a compressible and stretchable positive electrode 3, and a conductive capping layer 8.

[0036] As described above, one aspect of the present disclosure is to provide a rechargeable battery cell in which one or more of the functional layers in the stack forming the cell are made of a compressible and stretchable composite material C such that they at least partially counteract the compressive and / or tensile forces inside the stack arising from the volume changes of the negative and / or positive electrodes during charging and / or discharging of the rechargeable battery cell.

[0037] Accordingly, this disclosure relates to a rechargeable battery cell, wherein one or more of the first and second current collectors 2, 6 comprise a compressible and stretchable composite material C and a conductive material to form a compressible and stretchable current collector. In one embodiment, as shown, for example, in Figure 2B, the compressible and stretchable composite material C comprises hollow compressible particles 10. The conductive material comprises one or more of carbon black powder, carbon nanotubes, graphene, carbon fibers, graphite, conductive particles, metal particles, conductive nanowires, and conductive polymers, such as polyaniline and polythiophene, and / or conductive copolymers. Alternatively or in addition thereto, the compressible and stretchable composite material C may comprise a conductive polymer. In some preferred embodiments, the compressible and stretchable composite material C comprises hollow latex beads 11. In some of these embodiments, the stretchability may be provided by the hollow latex beads. Alternatively or in addition thereto, the hollow latex beads 11 are conductive.

[0038] This disclosure further relates to rechargeable battery cells, wherein the solid electrolyte 4 comprises a compressible and stretchable composite material C formed from a solid electrolyte material for forming a compressible and stretchable solid electrolyte. In one embodiment, as illustrated, for example, the compressible and stretchable composite material C comprises hollow compressible particles. The solid electrolyte comprises an ion-conducting polymer and one or more salts. Typically, the ion-conducting polymer can be a polyether polymer, such as one or more glycols including polyethylene glycol, polypropylene glycol, and copolymers. The salts preferably comprise non-coordinating anions and metal cations corresponding to the metal used in the negative electrode. For example, in the case of a lithium-ion battery, the solid electrolyte may comprise a lithium salt and polyethylene glycol. In some preferred embodiments, the compressible and stretchable composite material C comprises hollow latex beads 11. In some of these embodiments, the stretchability may be provided by the hollow latex beads. Alternatively, or in addition to this, the hollow latex beads are coated with an ion-conducting coating. By applying an ion-conductive coating to hollow latex beads, the ion conductivity of the entire compressible and stretchable solid electrolyte may be improved, and / or the compatibility between the coated hollow latex beads and the solid electrolyte material may be improved. Alternatively, or in addition to this, the solid electrolyte layer may include a layer of lithium-affinity metal oxide to improve wetting at the interface between the electrolyte layer and the lithium metal electrode. Alternatively, or in addition to this, the compressible and stretchable solid electrolyte layer current collector layer may include a layer of lithium-affinity metal oxide at the interface with the negative electrode to improve wetting at the interface between the current collector layer and the lithium metal electrode, thereby reducing the plating of the non-uniform electrode material and further reducing the formation of dendritic crystals. The lithium-affinity metal oxide is preferably selected from the group consisting of ZnO, Al2O3, Fe2O3, CoO2, MnO2, V2O5, and TiO2.

[0039] This disclosure further relates to a rechargeable battery cell, wherein the positive electrode 3 comprises a compressible and stretchable composite material C, formed from a positive electrode material, an ion-conducting material, and an electronically conductive material dispersed throughout the compressible and stretchable composite material C, thereby forming a compressible and stretchable positive electrode. In one embodiment, for example as shown, the positive electrode comprises hollow compressible particles 10. The conductive material comprises one or more of the following: carbon black powder, carbon nanotubes, graphene, carbon fibers, graphite, conductive particles, metal particles, conductive nanowires, and conductive polymers, such as polyaniline and polythiophene. Dispersion additives may be added to form a homogeneous mixture, and binder materials may be used to manufacture the electrode. In some preferred embodiments, the compressible and stretchable composite material C comprises hollow latex beads 11. In some of these embodiments, the stretchability may be provided by the hollow latex beads. Alternatively, or in addition to this, the hollow latex beads are coated with a conductive coating. By applying a conductive coating to hollow latex beads, conductivity can be improved throughout the compressible and stretchable positive electrode. Alternatively, or in addition to this, the hollow latex beads may be coated with an ion-conductive coating. By applying an ion-conductive coating to hollow latex beads, ion conductivity can be improved throughout the compressible and stretchable positive electrode.

[0040] This disclosure further relates to a rechargeable battery cell, wherein the anode 5 comprises a compressible and stretchable composite material C formed from an anode material, an ion-conducting material, and a conductive material, thereby forming the compressible and stretchable anode 5. The conductive material includes one or more of the following: carbon black powder, carbon nanotubes, graphene, carbon fibers, graphite, conductive particles, metal particles, conductive nanowires, and conductive polymers, such as polyaniline and polythiophene. Dispersion additives may be added to form a homogeneous mixture, and binder materials may be used to manufacture the electrode. In some preferred embodiments, the compressible and stretchable composite material C comprises hollow latex beads 11. In some of these embodiments, the stretchability may be provided by the hollow latex beads. Alternatively, or in addition to this, the hollow latex beads are coated with a conductive coating. By coating the hollow latex beads with a conductive coating, conductivity may be improved throughout the compressible and stretchable anode.

[0041] In other or further embodiments, a rechargeable battery cell is provided, in which one or more of the first and second compressible and stretchable current collectors are provided with an electrically conductive capping at the interface for connection to the negative or positive electrode. Preferably, the capping layer has a higher modulus of elasticity than the electrode in contact with the capping layer. Having a capping layer that is harder than the electrode in contact with the capping layer allows for more uniform pressure distribution, e.g., uniform compression along the layer, and thus mitigates mechanical degradation of the compressed layer. In embodiments in which the capping layer is in contact with a lithium metal electrode, preferably the modulus of elasticity of the capping layer is greater than 4.9 GPa. Having a capping layer with a modulus of elasticity greater than 4.9 GPa can further prevent the formation of lithium dendritic crystals. Alternatively or in addition to this, the stretchable current collector layer for collecting electrons from the negative lithium electrode may include a layer of lithium-affinity metal oxide to improve wetting at the interface between the current collector layer and the lithium metal electrode, thereby reducing the plating of the non-uniform electrode material and further reducing the formation of dendritic crystals. The lithium-affinity metal oxide is preferably selected from the group consisting of ZnO, Al2O3, Fe2O3, CoO2, MnO2, V2O5, and TiO2.

[0042] In other or further embodiments, a rechargeable battery cell is provided, in which one or more of the first and second compressible and stretchable current collectors comprises at least partially a conductive metal layer to improve the spatial conductivity of the compressible and stretchable current collector. The metal layer may be provided as a foil or mesh and may be embedded in the current collector or provided on the surface. Alternatively or in addition to this, the compressible and stretchable current collector may be sandwiched between two metal foils, metal meshes, or a combination thereof. Providing good high spatial conductivity is particularly important at the interface for connection with the negative electrode. For example, in a rechargeable lithium metal battery, non-uniform spatial conductivity may lead to the formation of a non-uniform electric field during the charging cycle, which may lead to the deposition and / or plating of non-uniform electrode material, which may lead to the formation of dendritic crystals. Accordingly, the present disclosure relates to a compressible and stretchable current collector, in which the compressible and stretchable current collector comprises a metal film at the interface for connection with the negative electrode material. The compressible and stretchable current collector for connecting to the positive electrode material preferably has a metal mesh, because uniform spatial conductivity is not very important at these interfaces. Providing a metal mesh in the compressible and stretchable current collector for connecting to the positive electrode material can make it possible to manufacture rechargeable battery cells with improved energy density by weight, for example, rechargeable battery cells with improved energy output per unit mass of the cell compared to similar cells with a metal film instead of a mesh. Alternatively or in addition to this, the compressible and stretchable current collector for collecting electrons from the negative lithium electrode may be a hybrid laminate formed using a metal grid inside the current collector layer, where the stretchable current collector includes a capping layer facing the lithium electrode to prevent the formation of dendritic crystals, and this capping layer also includes a conductive material dispersed throughout the capping layer to form a conductive network throughout the capping layer.

[0043] This disclosure further relates to a rechargeable battery cell as described in any of the prior claims, wherein the stack of functional layers forms a substantially planar structure. In other words, the stack forms a so-called 2D structure, for example in a battery pouch layout. Other cells comprising a number of such stacks, such as battery cells formed from stacks of cells, and cells having non-planar geometries, such as a cylindrical geometry in which the stacks are wound around a central axis, are also contemplated.

[0044] In some embodiments, as shown in Figure 3, for example, the present disclosure relates to a rechargeable battery cell 1, which is formed from a conductive base structure 16 including an array of conductive elements 17 spaced apart from each other and extending away from the base, with at least an electrolyte and one of a positive electrode and a negative electrode provided between the aforementioned extending elements. Such a cell may be described as a 3D cell. By providing a 3D structured cell, batteries may be manufactured with increased energy output. Figure 3 schematically shows cross-sectional views of a rechargeable battery cell 1 in a discharged state 1D (top) and a charged state 1C (bottom). The 3D cell includes a bottom current collector formed from the base structure 16 and the array of conductive elements 17, with a positive electrode material 3 and a solid electrolyte 4 provided as layers tracing the bottom current collector in a conformal manner. In embodiments as shown, a compressible and expandable upper current collector 2, 2' is provided in the remaining space between the upper and the coated 3D current collector. The entire cell is sandwiched between a rigid upper current collector 15 and a bottom current collector 16. By providing a compressible and stretchable layer between the elongating conductive elements 15 in the 3D rechargeable battery cell, a cell is provided that can absorb lateral volume changes, for example, at the negative electrode 5.

[0045] This disclosure also relates to a process for manufacturing a rechargeable battery cell 1 comprising a compressible and stretchable composite material C. This process comprises one or more of the following: providing a compressible and stretchable composite material C to form a compressible and stretchable first current collector 2; providing a compressible and stretchable composite material C to form a compressible and stretchable positive electrode 3; providing a compressible and stretchable composite material C to form a compressible and stretchable solid electrolyte 4; providing a compressible and stretchable composite material C to form a compressible and stretchable negative electrode 5; and providing a compressible and stretchable composite material C to form a compressible and stretchable second current collector 6, wherein a plurality of compressible pores P are provided to the compressible and stretchable composite material C by preparing a mixture comprising one or more pore-forming agents. By adding a solid electrolyte forming material to this mixture, a compressible and expandable solid electrolyte can be formed; by adding an electrode material, a compressible and expandable electrode can be formed; and by adding a current collector material, a compressible and expandable current collector can be formed. The pore-forming agent comprises one or more of the following: hollow particles 10, hollow latex beads 11, a blowing agent, a solvent, and a dissolved gas. Examples of suitable blowing organic and inorganic agents include NaHCO3, NH4HCO3, NaNO2, NH4NO2, azodicarbonamide, oxybis(benzenesulfonyl hydrazide), p-toluenesulfonyl hydrazide, toluenesulfonyl semicarbazide, and 5-phenyltetrazole. Alternatively, a solvent such as H2O may be used as a blowing agent.

[0046] The current collector-forming material in a mixture for forming a compressible and stretchable current collector further comprises a conductive material selected from one or more of the following: carbon black powder, carbon nanotubes, graphene, carbon fibers, graphite, conductive particles, metal particles, conductive nanowires, and conductive polymers, such as polyaniline and polythiophene; and a dispersant for dispersing one or more of the conductive material and compressible porous particles. The electrolyte material in a mixture for forming a compressible and stretchable solid electrolyte comprises an ion-conducting polymer and one or more salts. For example, the solid electrolyte may include a lithium salt, as well as a polyether polymer, such as one or more of the following glycols: polyethylene glycol, polypropylene glycol, and copolymers. Alternatively or in addition to this, the solid electrolyte layer may include a thin, 5-10 nm thick, lithium-affinity metal oxide layer to improve wetting at the interface between the electrolyte layer and the lithium metal electrode.

[0047] Electrode materials in a mixture for forming a compressible and stretchable positive electrode include a positive electrode material, an ion-conducting material, and an electronically conductive material. Dispersion additives may be added to form a homogeneous mixture, and binder materials may be used to manufacture the electrode. Electrode materials in a mixture for forming a compressible and stretchable negative electrode include a negative electrode material, an ion-conducting material, and an electrically conductive material. Electrically conductive materials contained in one or more mixtures for forming the electrode include one or more of carbon black powder, carbon nanotubes, graphene, carbon fibers, graphite, conductive particles, metal particles, conductive nanowires, and conductive polymers, such as polyaniline and polythiophene.

[0048] The compressible functional layer may preferably be cast directly onto any of the functional layers contained in the rechargeable battery cell, for example, a compressible electrolyte layer may be overlaid on a functional layer containing the cathode material. Alternatively, a mixture for forming a compressible and stretchable layer may be cast onto one or more of a carrier substrate, metal foil, or mesh. In embodiments in which the mixture contains monomers, the aforementioned monomer polymerization step follows the casting of the mixture. In embodiments in which one or more pore-forming agents contain a foaming agent, a solvent, and a dissolved gas, this process includes activating the aforementioned pore-forming agents to form a plurality of pores, where the aforementioned activation is performed by applying low pressure and / or high temperature for a time and temperature sufficient to activate the pore-forming agents. Following the activation, an exchange step is preferably performed, in which the released gas and / or vapor is exchanged with argon or nitrogen by applying one or more of the respective gas suction cycles of argon or nitrogen. When using lithium metal materials, argon is preferred because it does not react with lithium.

[0049] In embodiments where a 3D rechargeable battery cell is formed, the mixture may be cast onto a rigid 3D structure by vacuum impregnation. In embodiments where the resulting component mixture is molten, a molten extrusion process may be used for casting.

[0050] In preferred embodiments, the pore-forming agent comprises hollow particles, more preferably hollow latex beads 11. In contrast to foaming agents, pores formed by hollow particles and / or latex beads can be provided with greater control over pore size and pore distribution.

[0051] In some preferred embodiments, a process for producing a rechargeable battery cell 1 comprising a compressible and stretchable composite material C comprises providing hollow latex beads to a mixture, the hollow latex beads 11 being obtained by acquiring core-shell polymer latex beads, the core comprising an aqueous gel, and drying the core-shell polymer latex beads comprising freeze-drying or a liquid-gas phase exchange treatment using a dry gas flow. Optionally, a process for providing hollow latex beads comprises applying a conductive coating 18 to the dried conductive hollow latex beads. A suitable conductive coating is preferably selected from the group consisting of carbonaceous materials (e.g., carbon black, graphene, carbon nanotubes), metals, metal oxides, conductive polymers, e.g., polyaniline, polyethylenedioxythiophene (PEDOT)).

[0052] Accordingly, this disclosure relates to hollow latex beads, as shown in Figure 4, which can be obtained as an intermediate product by a process for manufacturing rechargeable battery cells, the process being limited to obtaining core-shell polymer latex beads, the core comprising an aqueous gel, and comprising drying the core-shell polymer latex beads by freeze-drying or by a liquid-gas phase exchange treatment using a continuous dry gas flow. This disclosure further relates to conductive hollow latex beads, which can be obtained as an intermediate product by a process for manufacturing rechargeable battery cells, the process being limited to obtaining core-shell 21 polymer latex beads, the core comprising an aqueous gel, and comprising drying the core-shell polymer latex beads by freeze-drying or by a liquid-gas phase exchange treatment using a continuous dry gas flow, the coating being obtained by a solution treatment using an aqueous emulsion, or by a drying treatment using fluidized bead ALD, PLD, CVD treatment. The coating 22 is preferably selected from one or more of the group consisting of carbonaceous materials (e.g., carbon black, graphene, carbon nanotubes), metals, metal oxides, and conductive polymers, such as polyaniline (PEDOT). Core-shell polymer latex beads containing an aqueous gel core can be commercially available in diameters in the range of 100 to 1000 nanometers. It will be understood that other sources of core-shell polymer latex beads and core-shell polymer latex beads of different diameters may also be applicable.

[0053] In some embodiments, compressible and expandable current collectors may be manufactured by casting a polymer composite solution containing conductive additives and porosinating agents, as well as one or more of molten polymers and monomer compositions. In embodiments containing monomer compositions, polymerization at the site follows casting. In the case of films containing a foaming agent, the cast film is further heat-treated to activate the foaming agent. The resulting reactive gas is exchanged for argon or nitrogen by applying an suction gas cycle in the case of lithium metal. When using lithium metal materials, argon is preferred because argon reacts with lithium.

Claims

1. A rechargeable solid battery cell (1), - A first current collector (2) that is compressible and expandable, - A compressible and stretchable solid electrolyte (4), - A second current collector (6) that is compressible and expandable, The material includes a compressible and stretchable material (C) to form one or more functional layers, The compressible and stretchable material (C) comprises a plurality of compressible pores (P), and is configured to at least partially resist the compressive and / or tensile forces within the rechargeable solid battery cell resulting from volume changes of the negative and / or positive electrodes during charging and / or discharging of the cell. The compressible pores are provided by hollow latex beads (11) having a core-to-shell ratio (Vcore / Vshell) in the range of 5 to 0.05 in volume, and the hollow latex beads have a diameter in the range of 50 nanometers to 1 micrometer. A rechargeable solid battery cell (1) wherein the compressible pores have a diameter less than 20% of the thickness of the functional layer, which is made of the compressible and stretchable material (C) containing the pores.

2. The rechargeable solid battery cell (1) according to claim 1, wherein the hollow latex beads have a diameter in the range of 200 to 1000 nanometers.

3. The rechargeable solid battery cell (1) according to claim 1 or 2, wherein one or more of the first and second compressible and stretchable current collectors (2, 6) comprises the compressible and stretchable material (C) and an electronically conductive material to form the compressible and stretchable current collector.

4. The rechargeable solid battery cell (1) according to claim 1 or 2, wherein the compressible and stretchable solid electrolyte (4) comprises the compressible and stretchable material (C) and the solid electrolyte material to form the compressible and stretchable solid electrolyte.

5. The rechargeable solid battery cell (1) according to claim 3, wherein one or more of the first and second compressible and stretchable current collectors are provided with a conductive capping (8).

6. The rechargeable solid battery cell (1) according to claim 3, wherein one or more of the first and second compressible and stretchable current collectors are at least partially provided with a conductive metal film to improve the uniform conductivity of the current collector along the interface with the electrode material.

7. The stack of functional layers forms a substantially planar structure, or the cell is formed from a base current collector structure (16) including an array of conductive elements (17) spaced apart from each other and extending away from the base, and at least one of the electrodes and the solid electrolyte is provided between the elements, the rechargeable solid battery cell (1) according to any one of claims 1 to 6.

8. A process for manufacturing a rechargeable solid battery cell (1) comprising a compressible and stretchable material (C), wherein the process is: - To provide a compressible and stretchable material (C) to form a compressible and stretchable first current collector (2), - To provide a compressible and stretchable material (C) to form a compressible and stretchable solid electrolyte (4), - Providing a compressible and stretchable material (C) to form a compressible and stretchable second current collector (6), and one or more of the above, By preparing a mixture comprising a stretchable continuous phase and one or more pore-forming agents, multiple compressible pores (P) are introduced into the compressible and stretchable material (C). By adding a solid electrolyte forming material, it becomes possible to form a compressible and expandable solid electrolyte, and by adding a current collector material, it becomes possible to form a compressible and expandable current collector. The compressible pores are provided by hollow latex beads (11) having a core-to-shell ratio (Vcore / Vshell) in the range of 5 to 0.05 in volume, and the hollow latex beads have a diameter in the range of 50 nanometers to 1 micrometer. The process wherein the compressible pores have a diameter of less than 20% of the thickness of the layer of the compressible and stretchable material (C).

9. The process according to claim 8, wherein the stretchable continuous phase comprises a stretchable polymer.

10. The hollow latex beads (11) are - Obtaining core-shell polymer latex beads in which the core contains an aqueous gel, - Drying the core-shell polymer latex beads by freeze-drying or by liquid-gas phase exchange treatment using a continuous dry gas flow, and optionally thereafter, The process according to claim 8 or 9, which is provided by applying a conductive coating (22) to the dried conductive hollow latex beads to form conductive hollow latex beads.

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