A particle for use in the manufacture of batteries via electrophotographic deposition

Abstract

A particle for use in the manufacture of batteries via electrophotographic deposition. The application related to a particle, suitable for use in the manufacture of batteries via electrophotographic deposition. The particle comprises a core comprising a battery active material and a shell, the shell at least partially covering the core. The shell is formed of a polymer. The shell is decorated by, and / or contains, one or more toner-additive pendants. A printer medium comprising the particle, a method of manufacturing the particle, and a method of forming a battery electrode is also disclosed.

Description

A PARTICLE FOR USE IN THE MANUFACTURE OF BATTERIES VIA ELECTROPHOTOGRAPHIC DEPOSITION.TECHNICAL FIELD

[0001] The application relates to a particle, suitable for use in the manufacture of batteries via electrophotographic deposition. A printer medium comprising the particle, a method of manufacturing the particle, and a method of forming a battery electrode is also disclosed.BACKGROUND

[0002] Battery electrode deposition is currently performed on a roll-to-roll process where a solvent borne slurry of active materials, carbon black and polymer is spread onto the current collector foils by either slot-die or gravure printing. The layer is then dried through high temperature baking to form the final electrode. This process is very energy intensive and the solvents used are hazardous and with no known suitable substitute.

[0003] Very thick (and therefore high capacity) electrodes are difficult to slurry cast as they can crack during drying. During solvent during drying binder can migrate binder to the active surface which negatively impacts performance.

[0004] Electrodes can be formed in a dry deposition processes. Dry deposition eliminates the solvent required and reduces the energy required to produce an electrode layer. Dry deposition methods include free-standing film, electrostatic spray, scattering and laminating.

[0005] These methods for dry electrode deposition produce continuous electrode coatings and are therefore suitable replacements for slot-die coating. However, none of these methods are able to produced patterned electrode material on current collector foils. No dry process is able to replace gravure printing of battery electrode coatings.SUMMARY OF INVENTION

[0006] According to the disclosure there is presented a particle, suitable for use in the manufacture of batteries via electrophotographic deposition, the particle comprising; a core comprising a battery active material; a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants. The particle is suitable for incorporation into a toner andused as a printer medium. This enables the particle to be deposited via electrographic printing (e.g. Via a standard laser printer). Electrophotography offers an alternative method for dry electrode production with the added feature of pattern control (as the printer can deposit the toner comprising the particle in any desired pattern upon a substrate). Pattern control offers a powerful method for fabrication of cells with designed structures, reduction of process waste and controlled microstructure.

[0007] Preferably, the one or more toner-additive pendants include any of metal oxides, alumina, silica, titania, triboelectric additives. Such additives allow the particle to be susceptible to the triboelectric effect, and therefore be compatible with an electrophotographic apparatus. The toner-additive pendants may be added in the range of of between 0.2%wt and 2%wt relative to the weights of the core and shell.

[0008] Suitably, the core has a size in the range of 1pm to 25pm and / or wherein the battery active material, comprising one or more of lithium iron phosphate, lithium nickel manganese cobalt oxide, lithium manganese iron phosphate. Ensuring the core size range is within the normal parameters of a laser printer toner ensures that the normal printing resolution of the printer may be maintained while printing with a toner comprising the particle. This allows for fine pattern formation (to the ability / tolerance of any given laser printer).

[0009] Appositely, the shell is formed of a polymer, and optionally wherein the polymer comprises poly vinylidene fluoride and / or polytetrafluoroethylene. The shell couples the toneradditive pendants to the core. The toner-additive pendants may adhere to an exterior surface of the shell, be partially embedded, or fully coated by the shell. The shell may completely cover the core, or partially (i.e. Patchy coverage). Complete coverage of the core is not required by the shell in order for its function to be fulfilled (i.e. To provide sufficient toner-additive pendants to allow the particle to be susceptible to electrophotographic deposition).

[0010] Appropriately, the particle further comprising one or more carbon conductive additives. Carbon conductive additives (e.g. Carbon black) assist in the formation of conductive networks in the deposited electrodes thereby improving performance of the final battery electrode.

[0011] Preferably, the shape of the particle describes a sphere, including being spherical, however it will be apparent that the shape of the particle may be any that allows the particle to fulfil its function (deposition in an electrophotographic process).

[0012] According to an example of the disclosure there is provided a printer medium, suitable for use in electrophotographic deposition, comprising a particle as described above, and further comprising carrier and toner. Incorporating the particle in a printer medium allows the particle to be deposited by a laser printer, and for battery electrodes to be formed by printing (or any suitable electrophotographic apparatus).

[0013] Preferably, the printer medium comprises 30wt% to 70wt% toner and the balance made up with carrier, and optionally wherein the carrier is a ceramic carrier.

[0014] Suitably, the toner comprises 75 - 98 wt% lithium iron phosphate or lithium nickel manganese cobalt oxide.

[0015] According to an example of the disclosure there is provided a method of forming a particle suitable for use in the manufacture of batteries via electrophotographic deposition, the method comprising: in a high-shear mixer, mixing a battery active material having an average particle size distribution greater than 1 pm, with a powdered polymer; adding, and mixing, one or more powdered toner-additives.

[0016] Preferably, the one or more toner-additives include any of metal oxides, alumina, silica, titania, triboelectric additives.

[0017] Suitably, the powdered polymer is an electrochemically stable polymer such as polyvinylidene fluoride or polytetrafluoroethylene.

[0018] According to a further example of the disclosure there is provided a method of forming a battery electrode comprising: supplying electrophotographic apparatus with a printer medium, the printer medium comprising particles, the particles comprising; a core comprising a battery active material; a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants; and depositing the printer medium on a substrate via the electrophotographic apparatus.

[0019] Preferably, the electrophotographic apparatus is a printer, and optionally a laser printer.

[0020] Suitably, the substrate comprises a metal foil, and optionally wherein the metal foil is aluminium, copper or any other current collector foil.

[0021] Appositely, wherein the electrophotographic apparatus has a resolution in the range of one pixel per 22pm to 84pm. Typical print resolutions for laser printing are in the range of 300-1200 DPI which correspond to minimum feature sizes of 8.5pm - 2pm.

[0022] Appropriately, the printer medium is in a solid phase.

[0023] Suitably, the method is solventless. Advantageously, this bypasses the need for hazadous solvents such as N-methyl pyrolidione.

[0024] Preferably, the electrophotographic apparatus deposits the printer medium according to a predetermined layout, and optionally wherein the layout is a pattern. Electrophotographic deposition enables lateral patterning of toners (i.e. In x and y directions). When multiple depositions of toner are performed, the possibility for the creation of structure in the z direction with both thickness and compositional variation possible in addition to the printing of lateral features.

[0025] This also helps to reduce process waste. In some cell designs a continuous film of electrode on current collector is punched or cut to fit into the casing (together with the separator and counter electrode) leaving unused areas of electrode material on current collector. This under utilisation of electrode and current collector can be very large for some cell designs eg. coin cells. By depositing material only where required electrode printing substantially reduces the waste of active material in such processes.

[0026] Patterning is also key to applications in flexible electronics. The ability to accurately place layers opens up opportunities for low cost circuit level integration of batteries to power small and flexible devices for applications in wearable electronics, the internet of things and in packaging.

[0027] Appositely, the particles are any as herein described.

[0028] Appropriately, the substrate is a laminate, and optionally a laminate of metal foil and a non-metallic material. The substrate may be a calendared insulation paper (e.g. Having a dielectric strength in the range 27 to 33 kV) or other synthetic paper or plastic. The substrate may be provided as a continuous belt. Suitably, the method further comprising priming the substrate and / or deposited printer medium with a conventional printer medium.

[0029] Preferably, the method further comprising curing the deposited printer medium, and optionally wherein curing comprises heating the substrate to a cure temperature, and optionally wherein the cure temperature is in excess of 60°C, and optionally, heating the substrate to substantially 180°C, and further optionally, when the substrate is a laminate, the laminate is delaminated into its component layers prior to curing.

[0030] Suitably, the method further comprising consolidating the deposited printer medium, and optionally wherein consolidating comprises compressing and / or calendaring the substrate.

[0031] Appropriately, wherein one or more elements of the method are repeated one or more times.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGSTo easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0032] FIG. 1 illustrates a schematic of a particle.

[0033] FIG. 2 illustrates an SEM of particles.

[0034] FIG. 3 illustrates A) deposited toner on a substrate and B) SEM images of the deposited toner containing the particles on the substrate of Fig. 5A).

[0035] FIG. 4 illustrates A) a pattern to be printed, B) the pattern of FIG. 4A) printed upon a substrate, C) an SEM image of the deposited printer medium and D) a further SEM image of the deposited printer medium.DETAILED DESCRIPTION

[0036] FIG. 1 shows a schematic of a particle 102. The particle 102 comprises a core 104 formed of a battery active material 106. Any suitable battery active material 106 may be used, dependent upon the battery which is intended to be formed. Typical, but non-limiting examples, of a battery active material 106 comprise one or more of lithium iron phosphate, lithium nickel manganese cobalt oxide.

[0037] The core 104 is at least partially coated by a shell 108. The word “shell” is used to describe the exterior of the particle 102 which is formed of a different material to the core 104. It will be apparent that the shell need not be a continuous covering, but could comprise discrete sections or patches which either perfectly or imperfectly cover the core 104. As such the core 104 may or may not be visible, accessible, or otherwise available to the exterior of the particle 102 depending on the coverage of the core 104 by the shell 108. The shell 108 is typically formed of a polymer, suitable polymers comprise, but are not limited to polyvinylidene fluoride and / or polytetrafluoroethylene.

[0038] The particle 102 is shown as spherical in shape, however, this is merely an example and not intended to be limiting. The particle 102 may be of any suitable shape. A host of particles may be of a uniform shape or multiple shapes. The host of particles may comprise size and shape variations according to a distribution or spectrum.

[0039] The shell 108 contains or is otherwise decorated by a plurality of toner-additive pendants 110. The toner-additive pendants 110 are susceptible to the triboelectric effect, and therefore be compatible with an electrophotographic apparatus. Suitable toner-additive pendants 110 comprise, but are not limited to, metal oxides, alumina, silica, titania, triboelectric additives.

[0040] The particle 102 is formed via mechanofusion. A typical method of particle formation comprises mixing the battery active material with powdered polymer and adding one or more toner-additives. The mixture is processed in a high-shear mixer, that is one which possess spinning blades or paddles with a tip speed in excess of lOm / s (or typically in the range 10-30m / s). The blades or paddles may have a close fit with a mixing vessel in which the mixture is processed.

[0041] FIG. 2 shows an SEM of particles 102 formed using the above described method. The particles 102 shown have a nickel manganese cobalt oxide core (micron sized particles in the range 10 to 25 pm) with fumed silica toner-additive pendants 110. The shell 108 is formed of polyvinylidene fluoride powder.

[0042] In the method the components were added together in the following amounts: 88.6wt% nickel manganese cobalt oxide, 10.5wt% poly vinylidene fluoride, and 1% silica.

[0043] The resulting particles 102 were formed into a printer medium by adding 40wt% of particles 102 to 60 wt% carrier (any carrier suitable for use with a laser printer may be used, one non-limiting example of which is an iron based carrier including resin coated ferrite carriers) . A printer medium is a consumable supplied to a printer for use in creating an output (e.g. A deposited print upon a substrate). Amongst other constituents a printer medium may comprise one or more toners. Printer medium may consist of just toner (of one kind or multiple kinds of toners).

[0044] Once formed the printer medium may be deposited on a substrate (such as paper, aluminium foil, or the like) using electrophotographic apparatus (such as a laser printer). A single or multiple depositions may be performed depending on the required amount, thickness,or pattern variation between layers required. The substrate may be a laminate e.g. Of aluminium and paper.

[0045] A primer may be applied to the substrate prior to deposition of the printer medium. The primer may be any suitable printer toner.

[0046] Once deposited, the substrate and deposited printer medium (including the particles), is cured by heating to 190°C resulting in final coat weights of the order of 5.26mg / cm2to 6.3mg / cm2.

[0047] FIG. 3 shows the particle 102 of FIG. 2 deposited on the substrate (Fig. 3A) and then SEM images of the deposited printer medium, including a cross section showing the substrate 302 and the deposited printer medium 304.

[0048] FIG. 4 shows an alternative particle 102 formed with a lithium iron phosphate core and fumed silica toner-additive pendants 110. The shell 108 is formed of poly vinylidene fluoride powder.

[0049] In the method the components were added together in the following amounts: 80wt% lithium iron phosphate (micro particles), 19.5wt% polyvinylidene fluoride powder, and 0.5% fumed silica.

[0050] The resulting particles 102 were formed into a printer medium by adding 30wt% of particles 102 to 70 wt% carrier (any carrier suitable for use with a laser printer may be used, one non-limiting example of which is an iron based carrier including resin coated ferrite carriers).

[0051] The printer medium may be applied to a substrates by any suitable electrophotographic apparatus as described about (including as laser printer). The deposited printer medium is then cured by heating to 180°C for 5 minutes.

[0052] FIG. 4A shows a desired pattern for printing. Fig. 4B shows the lithium iron phosphate based printer medium deposited on a substrate. Fig. 4C and Fig. 4D show SEM images of the cured printer medium on the substrate. The coat weight of the lithium iron phosphate based printer medium, following depositing 3 layers printed on aluminium foil was 0.256mg / cm2.

[0053] A primer may also be used with this formulation if desired, as described above.

[0054] An ideal target particle size for particles 102 prepared using the methods described herein is in the range 5-15pm, other ranges may be appropriate depending on application, such as 3-30pm.The invention is further described in the below clauses, which are not to be confused with the claims:Clause 1. A particle, suitable for use in the manufacture of batteries via electrophotographic deposition, the particle comprising;a core comprising a battery active material;a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants.Clause 2. The particle of clause 1 wherein the one or more toner-additive pendants include any of metal oxides, alumina, silica, titania, triboelectric additives.Clause 3. The particle of clause 1 or 2 wherein the core has a size in the range of 1 pm to 2 5pm and / or wherein the battery active material, comprises one or more of lithium iron phosphate, lithium nickel manganese cobalt oxide, lithium manganese iron phosphate.Clause 4. The particle of any one of clauses 1 to 3 wherein the shell is formed of a polymer, and optionally wherein the polymer comprises polyvinylidene fluoride and / or polytetrafluoroethylene.Clause 5. The particle of any one of clauses 1 to 4 further comprising one or more carbon conductive additives.Clause 6. The particle of any one of clauses 1 to 5 wherein the shape of the particle describes a sphere.Clause 7. A printer medium, suitable for use in electrophotographic deposition, comprising a particle as recited in any one of clauses 1 to 6, and further comprising carrier and toner.Clause 8. The printer medium of clause 7 comprising 30wt% to 70wt% toner and the balance made up with carrier, and optionally wherein the carrier is a ceramic carrier.Clause 9. The printer medium of clause 7 or 8 wherein the toner comprises 75 to 98 wt% lithium iron phosphate or lithium nickel manganese cobalt oxide.Clause 10. A method of forming a particle suitable for use in the manufacture of batteries via electrophotographic deposition, the method comprising:in a high-shear mixer, mixing a battery active material having an average particle size distribution greater than 1 pm, with a powdered polymer;adding, and mixing, one or more powdered toner-additives.Clause 11. The method of clause 10 wherein the one or more toner-additives include any of metal oxides, alumina, silica, titania, triboelectric additives.Clause 12. The method of clause 10 or 11 wherein the powdered polymer is an electrochemically stable polymer such as polyvinylidene fluoride or polytetrafluoroethylene.Clause 13. A method of forming a battery electrode comprising:supplying electrophotographic apparatus with a printer medium, the printer medium comprising particles,the particles comprising;a core comprising a battery active material;a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants; and depositing the printer medium on a substrate via the electrophotographic apparatus.Clause 14. The method of clause 13, wherein the electrophotographic apparatus is a printer, and optionally a laser printer.Clause 15. The method of clause 13 or 14, wherein the substrate comprises a metal foil, and optionally wherein the metal foil is aluminium, copper or any other current collector foil.Clause 16. The method of any one of clauses 13 to 15, wherein the electrophotographic apparatus has a resolution in the range of one pixel per 22pm to 84pm.Clause 17. The method of any one of clauses 13 to 16, wherein the printer medium is in a solid phase.Clause 18. The method of any one of clauses 13 to 17, wherein the method is solventless.Clause 19. The method of any one of clauses 13 to 18, wherein the electrophotographic apparatus deposits the printer medium according to a predetermined layout, and optionally wherein the layout is a pattern.Clause 20. The method of any one of clauses 13 to 19, wherein the particles are any as recited in any one of clauses 1 to 6.Clause 21. The method of any one of clauses 13 to 20, wherein the substrate is a laminate, and optionally a laminate of metal foil and a non-metallic material and optionally or alternatively, the method further comprising priming the substrate and / or deposited printer medium with a conventional printer medium.Clause 22. The method of any one of clauses 13 to 21, the method further comprising curing the deposited printer medium, and optionally wherein curing comprises heating the substrate to a cure temperature, and optionally wherein the cure temperature is in excess of 60°C, and optionally, heating the substrate to substantially 180°C, and further optionally, when comprising the laminate of clause 21, the laminate is delaminated into its component layers prior to curing.Clause 23. The method of any one of clauses 13 to 21, the method further comprising consolidating the deposited printer medium, and optionally wherein consolidating comprises compressing and / or calendaring the substrate.Clause 24. The method of any one of clauses 13 to 23, wherein one or more elements of the method are repeated one or more times.

Claims

CLAIMS1. A printer medium, suitable for use in electrophotographic deposition, the printer medium comprising:a carrier;a toner; anda particle, suitable for use in the manufacture of batteries via electrophotographic deposition, the particle comprising;a core comprising a battery active material;a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants.

2. The printer medium of claim 1 wherein the one or more toner-additive pendants include any of metal oxides, alumina, silica, titania, triboelectric additives.

3. The printer medium of claim 1 or 2 wherein the core has a size in the range of 1pm to 25pm and / or wherein the battery active material, comprises one or more of lithium iron phosphate, lithium nickel manganese cobalt oxide, lithium manganese iron phosphate.

4. The printer medium of any one of claims 1 to 3 wherein the shell is formed of a polymer, and optionally wherein the polymer comprises poly vinylidene fluoride and / or polytetrafluoroethylene.

5. The printer medium of any one of claims 1 to 4 further comprising one or more carbon conductive additives.

6. The printer medium of any one of claims 1 to 5 wherein the shape of the particle describes a sphere.

7. The printer medium of any one of claims 1 to 6 comprising 30wt% to 70wt% toner and the balance made up with carrier, and optionally wherein the carrier is a ceramic carrier.

8. The printer medium of any one of claims 1 to 7 wherein the toner comprises 75 to 98 wt% lithium iron phosphate or lithium nickel manganese cobalt oxide.

9. A method of forming a printer medium, comprising providing:a carrier;a toner; anda particle suitable for use in the manufacture of batteries via electrophotographic deposition, the particle formed by:in a high-shear mixer, mixing a battery active material having an average particle size distribution greater than 1 pm, with a powdered polymer;adding, and mixing, one or more powdered toner-additives.

10. The method of claim 9 wherein the one or more toner-additives include any of metal oxides, alumina, silica, titania, triboelectric additives.

11. The method of claim 9 or 10 wherein the powdered polymer is an electrochemically stable polymer such as polyvinylidene fluoride or polytetrafluoroethylene.

12. A method of forming a battery electrode comprising:supplying electrophotographic apparatus with a printer medium, the printer medium comprising particles,the particles comprising;a core comprising a battery active material;a shell, the shell at least partially covering the core, wherein the shell is formed of a polymer; wherein the shell is decorated by, and / or contains, one or more toner-additive pendants; and depositing the printer medium on a substrate via the electrophotographic apparatus.

13. The method of claim 12, wherein the electrophotographic apparatus is a printer, and optionally a laser printer.

14. The method of claim 12 or 13, wherein the substrate comprises a metal foil, and optionally wherein the metal foil is aluminium, copper or any other current collector foil.

15. The method of any one of claims 12 to 14, wherein the electrophotographic apparatus has a resolution in the range of one pixel per 22pm to 84pm.

16. The method of any one of claims 12 to 15, wherein the printer medium is in a solid phase.

17. The method of any one of claims 12 to 16, wherein the method is solventless.

18. The method of any one of claims 12 to 17, wherein the electrophotographic apparatus deposits the printer medium according to a predetermined layout, and optionally wherein the layout is a pattern.

19. The method of any one of claims 12 to 18, wherein the printer medium is any as claimed in any one of claims 1 to 8.

20. The method of any one of claims 12 to 19, wherein the substrate is a laminate, and optionally a laminate of metal foil and a non-metallic material and optionally or alternatively, the method further comprising priming the substrate and / or deposited printer medium with a conventional printer medium.

21. The method of any one of claims 12 to 20, the method further comprising curing the deposited printer medium, and optionally wherein curing comprises heating the substrate to a cure temperature, and optionally wherein the cure temperature is in excess of 60°C, and optionally, heating the substrate to substantially 180°C, and further optionally, when comprising the laminate of claim 21, the laminate is delaminated into its component layers prior to curing.

22. The method of any one of claims 12 to 21, the method further comprising consolidating the deposited printer medium, and optionally wherein consolidating comprises compressing and / or calendaring the substrate.

23. The method of any one of claims 12 to 22, wherein one or more elements of the method are repeated one or more times.

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