WO2023096638A1

WO2023096638A1 - Liquid electrophotographic ink compositions and li-ion electrochemical cells

Info

Publication number: WO2023096638A1
Application number: PCT/US2021/060659
Authority: WO
Inventors: Keren GOLDSHTEIN; Rachelle ROSENBERG; Yaron Grinwald; Gleb ROMANTCOV; Getahun BIADGLIN; Diana Golodnitsky; Elazar Cohen; David Stark
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2021-11-23
Filing date: 2021-11-23
Publication date: 2023-06-01

Abstract

Herein is described a liquid electrophotographic ink composition. The composition may comprise a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; a charge adjuvant; and a non-polar, non-aqueous carrier liquid. The liquid electrophotographic composition may be used to electrophotographically print an electrolyte for an Li-cell. Also disclosed herein is a Li-ion cell comprising the electrophotographic ink composition.

Description

Liquid Electrophotographic Ink Compositions and Li-ion Electrochemical Cells Background

[0001] A lithium ion cell comprises an anode, a cathode and an electrolyte. The anode and cathode may each comprise a lithium ion intercalation material. Thus, both the cathode and the anode allow lithium ions to move in and out of their structures in a process by intercalation or de-intercalation. During discharge, the (positive) lithium ions move from the negative electrode to the positive electrode through the electrolyte, while electrons flow through an external circuit. When the cell charges, the reverse occurs with lithium ions and electrons moving back to the negative electrode, again via the electrolyte.

[0002] Lithium ion cells may be used as a power source for a variety of applications.

Brief Description of the Figures

[0003] Figure 1 shows a schematic diagram of two substrates (101), each having printed thereon an example of an electrophotographic ink composition (102), and then pressed together.

[0004] Figures 2A and 2B shows optical images of an example of a solid-state electrolyte, which is an electrophotographic ink composition, coated on an indium tin oxide (ITO) substrate. This is described in more detail in the Examples below.

[0005] Figure 3 shows a Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) surface image of a solid-state electrolyte, which is an electrophotographic ink composition, coated on an indium tin oxide (ITO) substrate. This is described in more detail in the Examples below.

[0006] Figure 4 shows a Nyquist plot for a solid-state electrolyte film, which is an electrophotographic ink composition (measured in a cell described in the Examples) coated on aluminum foil. This is described in more detail in the Examples below.

[0007] Figure 5 shows a Nyquist plot for solid-state electrolyte film, which is an electrophotographic ink composition (measured in in a cell described in the Examples) coated on aluminum foil with a doctor blade. The electrophotographic ink composition on the substrate contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethyleneoxide units in the PEG to Li), 66%, A-C 580 resin and 2% charge adjuvant. This is described in more detail in the Examples below. [0008] Figure 6 shows a Nyquist plot for solid-state electrolyte film, which is an electrophotographic ink composition (measured in in a cell described in the Examples) printed on aluminum and carbon-coated foil, 28 separations. The formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethyleneoxide units in the PEG to Li), 66%, A-C 580 resin and 4% charge adjuvant. This is described in more detail in the Examples below.

[0009] Figure 7 shows a Nyquist plot for solid-state electrolyte film, which is an electrophotographic ink composition, (measured in a cell described in the Examples) printed on aluminum and carbon-coated foil, 28 separations. The formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethyleneoxide units in the PEG to Li), 66%, A-C 580 resin and 4% charge adjuvant. This is described in more detail in the Examples below.

[0010] Figure 8 is a schematic diagram of an example of Li-ion electrochemical cell. It comprises a first material (801) for acting as a Li-ion cell cathode or anode, an electrolyte (803), a second material (802) for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The electrolyte may comprise: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; a charge adjuvant. The electrolyte (803) may have been electrophotographically printed on either the first material (801) or second material (802).

[0011] Figure 9 is a schematic diagram of an example of Li-ion electrochemical cell. It comprises a substrate (804), onto which has been printed, e.g. electrophotographically printed, a first material (801) for acting as a Li-ion cell cathode or anode. In turn, an electrolyte (803) has been printed, e.g. electrophotographically printed, onto the first material, and a second material has been printed, e.g. electrphotographically printed, onto the electrolyte. The second material (802) is for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The first material, second material and electrolyte are as defined in Figure 8. Detailed Description

[0012] Before the present disclosure is disclosed and described, it is to be understood that this disclosure is not limited to the particular process steps and materials disclosed in this disclosure because such process steps and materials may vary. It is also to be understood that the terminology used in this disclosure is used for the purpose of describing particular examples. The terms are not intended to be limiting because the scope is intended to be limited by the appended claims and equivalents thereof.

[0013] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0014] As used in this disclosure, “carrier fluid”, "carrier liquid," "carrier," or "carrier vehicle" refers to the fluid in which polymers, particles, charge directors and other additives can be dispersed to form a liquid electrostatic composition or liquid electrophotographic composition. The carrier liquids may include a mixture of a variety of different agents, such as surfactants, co-solvents, viscosity modifiers, and/or other possible ingredients.

[0015] As used in this disclosure, "electrophotographic composition" or “electrostatic composition” generally refers to a composition, which is suitable for use in an electrophotographic or electrostatic printing process. The electrophotographic composition may comprise chargeable particles of polymer dispersed in a carrier liquid. The composition, once coated on a substrate, can act as an electrolyte. It can form part or all of an electrolyte in a Li-ion cell.

[0016] As used herein, “electrophotographic ink composition”, which may be termed an "electrostatic ink composition", generally refers to an ink composition, which may be in liquid form. The composition is suitable for use in an electrophotographic or electrostatic printing process. The electrophotographic ink composition may include chargeable particles of polymer dispersed in a carrier liquid. The composition may include a colorant that is visible to the eye.

[0017] As used in this disclosure, "co-polymer" refers to a polymer that is polymerized from at least two monomers. The term “terpolymer” refers to a polymer that is polymerized from 3 monomers. [0018] A polymer may be described as comprising a certain weight percentage of monomer. This weight percentage is indicative of the repeating units formed from that monomer in the polymer.

[0019] If a standard test is mentioned in this disclosure, unless otherwise stated, the version of the test to be referred to is the most recent at the time of filing this patent application.

[0020] As used in this disclosure, “electrostatic printing” or "electrophotographic printing" refers to the process that provides an image that is transferred from a photo imaging plate either directly or indirectly via an intermediate transfer member to a print substrate. As such, the image may not be substantially absorbed into the photo imaging substrate on which it is applied. Additionally, "electrophotographic printers" or “electrostatic printers” refer to those printers capable of performing electrophotographic printing or electrostatic printing, as described above. An electrophotographic printing process may involve subjecting the electrophotographic composition to an electric field, e.g. an electric field having a field gradient of 0.5-5V/pm..

[0021] As used in this disclosure, the term "about" is used to provide flexibility to a numerical range endpoint by providing that a given value may be a little above or a little below the endpoint to allow for variation in test methods or apparatus. The degree of flexibility of this term can be dictated by the particular variable and would be within the knowledge of those skilled in the art to determine based on experience and the associated description in this disclosure.

[0022] As used in this disclosure, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.

[0023] Concentrations, amounts, and other numerical data may be expressed or presented in this disclosure in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not just the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of "about 1 wt% to about 5 wt%" should be interpreted to include not just the explicitly recited values of about 1 wt% to about 5 wt%, but also include individual values and subranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3.5, and 4 and subranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting a single numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described.

[0024] As used in this disclosure, weight% (wt%) values are to be taken as referring to a weight-for-weight (w/w) percentage of solids in the composition, and not including the weight of any carrier fluid present.

[0025] Li-ion electrochemical cells, also termed Li-ion batteries, are in common use in many electrical devices. Many Li-cells produced commercially involve the separate production and then mechanical assembly of the cathode, electrolyte and anode. The present disclosure provides a way to make many electrochemical cells very fast by printing the electrolyte onto the cathode or anode. In some examples, the cathode, electrolyte and anode can all be printed. Electrophotographic printing has been found to be particularly successful for the printing of the layers. The printed layers, i.e. the cathode, electrolyte and anode, can be very thin, which is useful in some electrical devices or in objects for which it has been difficult to introduce a power source, in view of the small size or very thin nature of the objects. The printed cell or battery may be used as a power source, for example, to generate light, sound or kinetic energy.

[0026] In some examples, the cathode, electrolyte and anode may be printed onto a packaging substrate to form a lithium-ion cell or battery on the packaging substrate. The resulting packaging may thus include a power source, for example, to generate light, sound or kinetic energy on the packaging. In some examples, the packaging may be provided with e.g. light(s) or speaker(s) that may be powered by the lithium-ion cell printed on the packaging.

[0027] It has been found that, when trying to produce an electrophotographic ink for printing an electrolyte layer for use in a Li-ion battery, sometimes a phase separation can occur during mixing of the components, believed to be, at least in part, due to the polymerLi complex that is used, and its high polarity, compared to the low polarity of some other LEP ink components. It has been found that using PEG, and particularly PEG of about 500,000 g/mol or less, avoids or reduces the phase separation, and allows a high quality printed electrolyte layer to be produced.

[0028] In an aspect, there is provided a liquid electrophotographic ink composition comprising: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; a charge adjuvant; and a non-polar, non-aqueous carrier liquid. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

[0029] In an aspect, there is provided a process for assembling a Li-ion electrochemical cell, said process comprising: providing a first material for acting as a Li-ion cell cathode or anode; electrophotographically printing an liquid electrophotographic ink composition on the first material to form an electrolyte, wherein the electrophotographic ink composition comprises a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant; and a non-polar, non-aqueous carrier liquid; removing the carrier liquid from the electrolyte, and then disposing on the electrolyte a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

[0030] In an aspect, there is provided a Li-ion electrochemical cell comprising: a first material for acting as a Li-ion cell cathode or anode an electrolyte comprising a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; a charge adjuvant; a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The PEG of the PEG:Li complex may have a molecular weight of 500,000 g/mol or less.

[0031] Also provided is a method of making the liquid electrophotographic ink composition, the method comprising: dispersing in a non-polar, non-aqueous carrier liquid: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

PEG:Li complex

[0032] The polyethylene glycol-lithium (PEG:Li) complex may be formed by combining polyethylene glycol with a lithium salt. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less, in some examples about 100,000 g/mol or less, in some examples about 50,000 g/mol or less, in some examples about 20,000 g/mol or less, in some examples about 10,000 g/mol or less. The PEG of the PEG:Li complex may have a molecular weight of from about 50 g/mol to about 500,000 g/mol, in some examples from about 50 g/mol to about 100,000 g/mol, in some examples from about 50 g/mol to about 20,000 g/mol, in some examples from about 50 g/mol to about 10,000 g/mol. The molecular weight may refer to the number average molecular weight, Mn. Polyethylene glycols are sold commercially, sometimes with reference to the molecular weight. For example, PEG400 may refer to PEG having a number average molecular weight of 400. PEG of various molecular weights is available from a number of commercial sources, examples of which are Sigma-Aldrich and Merck Milhpore. The number average molecular weight, Mn, may be measured by any suitable method, such as mass spectrometry.

[0033] PEG, as used in some Li-ion battery electrolytes, can be of very high molecular weight, e.g. 1 ,000,000 g per mol. However, such high MW PEG was found to encounter difficulties when used to produce liquid electrostatic printing compositions. Sometimes, a phase separation was seen to occur on mixing with the copolymer and the charge adjuvant in the non-polar liquid. However, it was found that using lower molecular weight PEG, e.g. of about 500,000 g/mol or less, particularly when in liquid form when being mixed with the other components, was found to avoid or mitigate the phase separation issue. Accordingly, the electrolyte could be printed more successfully. This is shown in the Examples.

[0034] The PEG (before forming the Li complex) may be in a liquid form at 20 °C and standard pressure (100 kPa).

[0035] The lithium salt may be selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium nitrate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium bis(oxalate) borate and lithium trifluoromethanesulphonate.

[0036] The molar ratio of polyethylene oxide units in the PEG to Li in the PEG:Li complex may be n:1 . n may be about 0.5 or more, in some examples about 1 or more, n may be from about 1 to about 20, in some examples from about 1 to about 15, in some examples about 2 to about 15, in some examples about 3 to about 15, in some examples about 3 to about 10. n may be about 2 to about 5. n may be about 6 to about 12.

[0037] The PEG:Li complex may be present in the electrophotographic printing composition in an amount of about 5 wt% to about 50 wt%, in some examples about 10 wt% to about 40 wt%, in some examples about 20 wt% to about 40 wt%, in some examples about 25 wt% to about 40 wt% of the total weight of solids in the electrophotographic electrolyte composition. Copolymer

[0038] The liquid electrophotographic ink composition described herein comprises a copolymer. The copolymer may be a thermoplastic polymer. A thermoplastic polymer is a polymer that becomes pliable or moldable when heated to an appropriate temperature and solidifies on cooling, and then, when heated to the appropriate temperature again becomes pliable or moldable, and again solidifies on cooling.

[0039] The copolymer may be copolymer of an olefin and a monomer having a carboncarbon double bond and a -CO₂X group, and wherein X is H or Li. The olefin of the copolymer may be selected from ethylene and propylene.

[0040] The monomer having a carbon-carbon double bond and a -CO₂X group may be selected from acrylic acid, methacrylic acid, the lithium acrylate and lithium methacrylate. The monomer having a carbon-carbon double bond and a -CO₂X group may be termed the CO₂X group monomer for brevity herein. The CO₂X group monomer content of the copolymer may be about 5 to about 30 weight %, for example, about 10 to about 25 weight % or about 12 to about 20 weight % of the total weight of the copolymer. The CO₂X group monomer content of the copolymer may be about 15 to about 18 weight % of the total weight of the copolymer. In some examples, the olefin of the copolymer is ethylene. In some examples, the monomer having a carboncarbon double bond is acrylic acid. In some examples, the olefin of the copolymer is ethylene and the monomer having a carbon-carbon double bond is acrylic acid. In some examples, the copolymer is an ethylene acrylic acid copolymer. In some examples, the copolymer is an ethylene acrylic acid copolymer comprising about 15 weight % of units derived from acrylic acid. An example of a suitable copolymer is an ethylene acrylic acid copolymer comprising about 15 weight % of units derived from acrylic acid sold under the trademark Honeywell ® AC-5120. The copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is Li, may be formed from a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H (such as an ethylene-acryhc acid co-monomer) and converting at least some of the free carboxylic acid groups (CO₂H groups) to lithium salts there of (i.e. CO₂Li groups).

[0041] In one example, copolymer is a copolymer of an olefin monomer (e.g. ethylene) and at least one monomer selected from an acrylic or acrylate monomer, for instance, methacrylic acid, acrylic acid, acrylate and methacrylate. An olefin monomer (termed an olefin herein for brevity) may be defined as a hydrocarbon monomer having a carbon-carbon double bond. The olefin may be selected from ethylene and propylene. The copolymer may comprise at least about 80 weight % olefin (e.g. ethylene), for example, about 80 to about 90 weight% olefin (e.g. ethylene). The copolymer may include about 10 to about 20 weight % of an acrylic or acrylate monomer, for example, at least one of methacrylic acid, acrylic acid, acrylate and methacrylate.

[0042] In one example, the copolymer is a polymer of an olefin (e.g. ethylene) and at least one monomer selected from an acrylic or acrylate monomer, for instance, methacrylic acid, acrylic acid, acrylate and methacrylate. The copolymer may comprise at least about 80 weight % olefin (e.g. ethylene), for example, about 80 to about 90 weight% olefin (e.g. ethylene). The copolymer may include about 10 to about 20 weight % of an acrylic or acrylate monomer, for example, at least one of methacrylic acid, acrylic acid, acrylate and methacrylate.

[0043] The copolymer may have a melting point of less than about 110 degrees C or less than about 100 degrees C. In one example, the polymer may have a melting point of about 50 to up to about 110 degrees C, for example, about 60 to about 100 degrees C. Where a polymer mixture is present, the polymer mixture may have a melting point of less than about 110 degrees C or less than about 100 degrees C. In one example, the polymer mixture may have a melting point of about 50 to up to about 110 degrees C, for example, about 60 to about 100 degrees C.

[0044] In one example, the copolymer is a polymer of an olefin (e.g. ethylene) and an acrylic acid (e.g. acrylic acid or methacrylic acid) or acrylate (e.g. acrylate or methacrylate) having a melting point of less than about 110 degrees C or less than about 100 degrees C. In one example, the polymer is a polymer of an olefin (e.g. ethylene) and an acrylic acid (e.g. acrylic acid or methacrylic acid) or acrylate (e.g. acrylate or methacrylate) having a melting point of about 50 to up to about 110 degrees C, for example, about 60 to about 100 degrees C or about 70 to about 95 degrees C. Where the electrophotographic composition comprises a mixture of two or more polymers, at least about 50 weight %, at least about 60 weight %, at least about 70 weight %, at least about 80 weight % or at least about 90 weight % of the polymer mixture may be formed of polymer(s) having melting points of less than about 110 degrees C or less than about 100 degrees C. In one example, at least about 50 weight % at least about 60 weight %, at least about 70 weight %, at least about 80 weight % or at least about 90 weight % of the polymer mixture may be formed of polymer(s) having melting points of about 50 to up to about 110 degrees C, for example, about 60 to about 100 degrees C.

[0045] In one example, the copolymer is a polymer of an olefin (e.g. ethylene) and at least one monomer selected from an acrylic or acrylate monomer, for instance, methacrylic acid, acrylic acid, acrylate and methacrylate. The copolymer may comprise at least about 80 weight % olefin (e.g. ethylene), for example, about 80 to about 90 weight% olefin (e.g. ethylene). The copolymer may include about 10 to about 20 weight % of an acrylic or acrylate monomer, for example, at least one of methacrylic acid, acrylic acid, acrylate and methacrylate.

[0046] In one example, the copolymer is a polymer of an olefin (e.g. ethylene) and methacrylic acid. The polymer may include about 80 to about 90 weight % ethylene and about 10 to about 20 weight % methacrylic acid. The copolymer may include about 85 weight % ethylene and the remainder methacrylic acid. In one example, the polymer is or comprises a polymer sold under the trademark Nucrel ® 925, available from Dow Inc.

[0047] In one example, the copolymer is a polymer of an olefin (e.g. ethylene) and acrylic acid. The copolymer may include about 80 to about 90 weight % ethylene and about 10 to about 20 weight % acrylic acid. The copolymer may include 82 weight % ethylene and the remainder acrylic acid. In one example, the copolymer is or comprises a polymer sold under the trademark Nucrel ® 2806, available from Dow Inc.

[0048] In one example, the copolymer resin may include more than type of copolymer. In an example, the copolymer resin may include 2 or 3 copolymers. In one example, the copolymer comprises a polymer of an olefin (e.g. ethylene) and acrylic acid and a polymer of an olefin (e.g. ethylene) and methacrylic acid. For example, the copolymer resin may include a first resin formed of about 80 to about 90 weight % ethylene and about 10 to about 20 weight % methacrylic acid, and a second resin formed of about 80 to about 90 weight % ethylene and about 10 to about 20 weight % acrylic acid. Where the copolymer resin contains a first resin and a second resin, the amount of the first resin may be about 60 to about 80 weight %, for example, about 65 to about 75 weight % of the polymer resin mixture. The amount of second resin may be about 15 to about 25 weight %, for example, about 17 to about 22 weight % of the polymer resin mixture. The weight ratio the first resin to the second resin may be about 2:1 to about 5:1 , for example, about 3:1 to 4:1.

[0049] In one example, the copolymer resin includes a first resin formed of about 85 weight % ethylene and the remainder methacrylic acid, and a second resin formed of about 82 weight % ethylene and the remainder acrylic acid. In one example, the polymer resin includes a mixture of a polymer sold under the trademark Nucrel ®925 and a polymer sold under the trademark Nucrel®2806, available from Dow Inc.

[0050] The electrophotographic ink composition may comprise a terpolymer. The terpolymer may be a terpolymer of a) an olefin (e.g. ethylene), b) an acrylic acid (e.g. acrylic acid or methacrylic acid) or an acrylate (e.g. acrylate or methacrylate) and c) a polar monomer. The olefin (e.g. ethylene) may form about 60 to about 78 weight % of the terpolymer, for example, about 65 to about 70 weight % of the terpolymer. The acrylic acid (e.g. acrylic acid or methacrylic acid) or acrylate (e.g. acrylate or methyl acrylate) may form about 20 to about 35 weight % of the terpolymer, for example, about 22 to about 30 weight % of the terpolymer. The acrylic acid may be in free form or a salt thereof, e.g. a lithium salt thereof. The polar monomer may form the remainder of the terpolymer. Examples of suitable polar monomers include monomers containing amine, amide, ester, ether and/or anhydride functional groups. In one example, the polar monomer contains amide, amine, groups, anhydride groups or both ester and ether groups. In an example, the polar monomer is selected from maleic anhydride or glycidyl methacrylate.

[0051] In one example, the terpolymer is a terpolymer of ethylene, methacrylic acid and glycidyl methacrylate. The methacrylic acid may be in free form or a salt thereof, e.g. a lithium salt thereof. The amount of ethylene may be about 60 to about 78 weight % of the polymer, for example, about 65 to about 70 weight % of the terpolymer. The amount of methacrylic acid may range from about 20 to about 35 weight % of the terpolymer, for example, about 22 to about 30 weight % of the terpolymer. The remainder of the polymer may be derived from glycidyl methacrylate. In one example, the terpolymer comprises 68 weight % ethylene, 24 weight % methacrylic acid and 8 weight % glycidyl methacrylate. The terpolymer may be one sold under the trademark Lotader ® AX8900. The terpolymer may be used in combination with a copolymer of ethylene and methacrylic acid or acrylic acid. For example, such terpolymers (for instance one sold under the trademark Lotader® AX8900) may be employed in combination with polymers sold under the trademark Nucrel®925.

[0052] In one example, the terpolymer is a terpolymer of ethylene, ethyl acrylate and maleic anhydride. The amount of ethylene may be about 60 to about 80 weight % of the terpolymer, for example, about 65 to about 70 weight % of the terpolymer. The amount of ethyl acrylate may range from about 19 to about 35 weight % of the terpolymer, for example, about 20 to about 30 weight % of the terpolymer. The remainder of the terpolymer may be derived from maleic anhydride. In one example, the amount of maleic anhydride may be about 0.1 to about 5 weight %, for example, 1 to 3 weight %. In one example, the terpolymer comprises 70 weight % ethylene, 29 weight % ethyl acrylate and 1 .3 weight % maleic anhydride. The terpolymer may be used in combination with a copolymer of ethylene and methacrylic acid or acrylic acid. The terpolymer may be sold under the trademark Lotader ® 4700. Alternatively, the polymer B may be one or more polymers sold under the trademark Lotader ® 5500, Lotader ® 4503 and Lotader ® 4720, available from the SKFP Group. Such terpolymers (for instance one sold under the trademark Lotader ® 4700) may be employed in combination with polymers sold under the trademark Nucrel®925.

[0053] Where a terpolymer is employed, the terpolymer may form about 1 to about 50 weight % of the polymer resin. In some examples, the terpolymer forms about 1 to about 20 weight %, for instance about 5 to about 15 weight % of the polymer resin. Where a copolymer of an olefin (e.g.) and an acrylic or acrylate (e.g. methacrylic acid, acrylic acid, methacrylate or acrylate) is employed, the copolymer may form about 50 to about O weight %, for example, about 70 to about 99 weight %, for instance, about 80 or about 85 to about 95 weight % of the polymer resin.

[0054] The copolymer in the electrophotographic composition may have a melting point of less than about 110 degrees C, for example, less than about 100 degrees C. [0055] The copolymer may have (or may contain a polymer having) an acidity of about 50 mg KOH/g or more, in some examples an acidity of about 60 mg KOH/g or more, in some examples an acidity of about 70 mg KOH/g or more, in some examples an acidity of about 80 mg KOH/g or more, in some examples an acidity of about 90 mg KOH/g or more, in some examples an acidity of about 100 mg KOH/g or more, in some examples an acidity of about 105 mg KOH/g or more, in some examples about 110 mg KOH/g or more, in some examples about 115 mg KOH/g or more. The copolymer may have an acidity of about 200 mg KOH/g or less, in some examples about 190 mg or less, in some examples about 180 mg or less, in some examples about 130 mg KOH/g or less, in some examples about 120 mg KOH/g or less. Acidity of a polymer, as measured in mg KOH/g can be measured using standard procedures known in the art, for example using the procedure described in ASTM D1386.

[0056] The copolymer may have a melt flow rate of less than about 70 g/10 minutes, in some examples about 60 g/10 minutes or less, in some examples about 50 g/10 minutes or less, in some examples about 40 g/10 minutes or less, in some examples about 30 g/10 minutes or less, in some examples about 20 g/10 minutes or less, in some examples about 10 g/10 minutes or less. In some examples, if a plurality of copolymers are present, each copolymer individually has a melt flow rate of less than about 90 g/10 minutes, about 80 g/10 minutes or less, in some examples about 80 g/10 minutes or less, in some examples about 70 g/10 minutes or less, in some examples about 70 g/10 minutes or less, in some examples about 60 g/10 minutes or less.

[0057] The copolymer may have a melt flow rate of about 10 g/10 minutes to about 120 g/10 minutes, in some examples about 10 g/10 minutes to about 70 g/10 minutes, in some examples about 10 g/10 minutes to 40 g/10 minutes, in some examples 20 g/10 minutes to 30 g/10 minutes. The copolymer may have a melt flow rate of, in some examples, about 50 g/10 minutes to about 120 g/10 minutes, in some examples 60 g/10 minutes to about 100 g/10 minutes. The melt flow rate can be measured using standard procedures known in the art, for example as described in ASTM D1238.

[0058] Where a terpolymer is present, this may have a melt index of about 1 to about 20 g/10min, for instance, about 1 to about 9g/10min or about 10g/10min. In another example, the terpolymer has a melt index of about 3 to about 8g/1 Omin, for instance, about 4 to about 7g/1 Omin. [0059] Where a copolymer of an olefin (e.g. ethylene) and an acrylic or acrylate (e.g. methacrylic acid, acrylic acid, methacrylate or acrylate) is employed, the copolymer may have a melt index of about 20 to about 200g/10min, for example, about 25 to about 70g/10min. In one example, the copolymer has a melt index of about 25 to about 35 g/10min. This copolymer may be used in combination with another copolymer of an olefin (e.g.) and an acrylic or acrylate (e.g. methacrylic acid, acrylic acid, methacrylate or acrylate) having a melt index of about 50 to about 70 g/1 Omin.

[0060] The acidic side groups (i.e. the CO₂X groups) may be in free acid form or may be in the form of an anion and associated with one or more counterions, which may be metal counterions, e.g. a metal selected from the alkali metals, such as lithium, sodium and potassium, alkali earth metals, such as magnesium or calcium, and transition metals, such as zinc. The polymer having acidic sides groups can be selected from resins such as co-polymers of ethylene and an ethylenically unsaturated acid of either acrylic acid or methacrylic acid; and ionomers thereof, such as methacrylic acid and ethylene-acrylic or methacrylic acid co-polymers which are at least partially neutralized with metal ions (e.g. Zn, Na, Li) such as ionomers sold under the trademark SURLYN ®. The copolymer can be a co-polymer of ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid, where the ethylenically unsaturated acid of either acrylic or methacrylic acid constitute from about 5 wt% to about 25 wt% of the co-polymer, in some examples from about 10 wt% to about 20 wt% of the co-polymer.

[0061] The composition may comprise two different polymers having acidic side groups. The two polymers having acidic side groups may have different acidities, which may fall within the ranges mentioned above. The resin may comprise a first polymer having acidic side groups that has an acidity of from about 10 mg KOH/g to about 110 mg KOH/g, in some examples about 20 mg KOH/g to about 110 mg KOH/g, in some examples about 30 mg KOH/g to about 110 mg KOH/g, in some examples about 50 mg KOH/g to about 110 mg KOH/g, and a second polymer having acidic side groups that has an acidity of about 110 mg KOH/g to about 130 mg KOH/g.

[0062] The composition may comprise two different polymers having acidic side groups: a first polymer having acidic side groups that has a melt flow rate of about 10 g/10 minutes to about 50 g/10 minutes and an acidity of from about 10 mg KOH/g to about 110 mg KOH/g, in some examples about 20 mg KOH/g to about 110 mg KOH/g, in some examples about 30 mg KOH/g to about 110 mg KOH/g, in some examples about 50 mg KOH/g to about 110 mg KOH/g, and a second polymer having acidic side groups that has a melt flow rate of about about 50 g/10 minutes to about about 120 g/10 minutes and an acidity of about 110 mg KOH/g to about 130 mg KOH/g. The first and second polymers may be absent of ester groups.

[0063] The ratio of the first polymer having acidic side groups to the second polymer having acidic side groups can be from about 10:1 to about 2:1. The ratio can be from about 6:1 to about 3:1 , in some examples about 4:1.

[0064] The composition may comprise a copolymer having a melt viscosity of about 15000 poise or less, in some examples a melt viscosity of about 10000 poise or less, in some examples about 1000 poise or less, in some examples about 100 poise or less, in some examples about 50 poise or less, in some examples about 10 poise or less; said polymer may be a polymer having acidic side groups as described in this disclosure. The resin may comprise a first polymer having a melt viscosity of about 15000 poise or more, in some examples about 20000 poise or more, in some examples about 50000 poise or more, in some examples about 70000 poise or more; and in some examples, the resin may comprise a second polymer having a melt viscosity less than the first polymer, in some examples a melt viscosity of about 15000 poise or less, in some examples a melt viscosity of about 10000 poise or less, in some examples about 1000 poise or less, in some examples about 100 poise or less, in some examples about 50 poise or less, in some examples about 10 poise or less. The composition may comprise a first copolymer having a melt viscosity of more than about 60000 poise, in some examples from about 60000 poise to about 100000 poise, in some examples from about 65000 poise to about 85000 poise; a second copolymer having a melt viscosity of from about 15000 poise to about 40000 poise, in some examples about 20000 poise to about 30000 poise, and a third copolymer having a melt viscosity of about 15000 poise or less, in some examples a melt viscosity of about 10000 poise or less, in some examples about 1000 poise or less, in some examples about 100 poise or less, in some examples about 50 poise or less, in some examples about 10 poise or less. The melt viscosity can be measured using a rheometer, e.g. a commercially available AR-2000 Rheometer from Thermal Analysis Instruments, using the geometry of: 25mm steel plate-standard steel parallel plate, and finding the plate over plate rheometry isotherm at 120°C, 0.01 hz shear rate. [0065] If the electrophotographic composition comprises a single type of copolymer, the polymer (excluding any other components of the electrophotographic composition) may have a melt viscosity of about 6000 poise or more, in some examples a melt viscosity of about 8000 poise or more, in some examples a melt viscosity of about 10000 poise or more, in some examples a melt viscosity of about 12000 poise or more. If the resin comprises a plurality of polymers all the polymers of the resin may together form a mixture (excluding any other components of the electrostatic composition) that has a melt viscosity of about 6000 poise or more, in some examples a melt viscosity of about 8000 poise or more, in some examples a melt viscosity of about 10000 poise or more, in some examples a melt viscosity of about 12000 poise or more. Melt viscosity can be measured using standard techniques. The melt viscosity can be measured using a rheometer, e.g. a commercially available AR-2000 Rheometer from Thermal Analysis Instruments, using the geometry of: 25mm steel plate-standard steel parallel plate, and finding the plate over plate rheometry isotherm at 120°C, 0.01 Hz shear rate.

[0066] The copolymer can constitute about about 5 to up to about 100 weight %, in some examples about about 50 to about 99 %, by weight of the solids of the liquid electrophotographic composition. The resin can constitute about about 60 to about 95 %, in some examples about about 70 to about 95 %, by weight of the solids of the liquid electrophotographic composition.

[0067] For the avoidance of doubt, the polymer or polymer mixture used in the electrophotographic ink composition may be the same or different to the polymer or polymer mixture used in the electrophotographic electrolyte ink composition. It may be possible to use the same or different polymer in the electrophotographic cathode ink composition, electrophotographic anode ink composition and/or electrophotographic electrolyte ink composition.

[0068] As used in this disclosure, “melt index” and "melt flow rate" are used interchangeably. The “melt index” or “melt flow rate” refers to the extrusion rate of a resin through an orifice of defined dimensions at a specified temperature and load, reported as temperature/load, e.g. 190°C/2.16 kg. In the present disclosure, "melt flow rate" or “melt index” is measured per ASTM D1238-04c Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer. If a melt flow rate of a particular polymer is specified, unless otherwise stated, it is the melt flow rate for that polymer alone, in the absence of any of the other components of the electrostatic composition.

[0069] As used in this disclosure, "acidity," "acid number," or "acid value" refers to the mass of potassium hydroxide (KOH) in milligrams that neutralizes one gram of a substance. The acidity of a polymer can be measured according to standard techniques, for example as described in ASTM D1386. If the acidity of a particular polymer is specified, unless otherwise stated, it is the acidity for that polymer alone, in the absence of any of the other components of the liquid toner composition.

[0070] As used in this disclosure, "melt viscosity" generally refers to the ratio of shear stress to shear rate at a given shear stress or shear rate. Testing may be performed using a capillary rheometer. A plastic charge is heated in the rheometer barrel and is forced through a die with a plunger. The plunger is pushed either by a constant force or at constant rate depending on the equipment. Measurements are taken once the system has reached steady-state operation. One method used is measuring Brookfield viscosity @ 140°C, units are mPa-s or ePoise, as known in the art. Alternatively, the melt viscosity can be measured using a rheometer, e.g. a commercially available AR- 2000 Rheometer from Thermal Analysis Instruments, using the geometry of: 25mm steel plate-standard steel parallel plate, and finding the plate over plate rheometry isotherm at 120°C, 0.01 Hz shear rate. If the melt viscosity of a particular polymer is specified, unless otherwise stated, it is the melt viscosity for that polymer alone, in the absence of any of the other components of the electrostatic composition.

Charge adjuvant

[0071] As mentioned above, the electrophotographic composition can include a charge adjuvant. A charge adjuvant may be present with a charge director, and may be different to the charge director, and act to increase and/or stabilise the charge on particles, e.g. resin-containing particles, of an electrostatic composition. Resin herein may refer to the copolymer(s) in the composition. The charge adjuvant may be selected from a salt of a fatty acid, a petronate, a salt of naphthenic acid, and a resinate. The charge adjuvant may be selected from barium petronate, calcium petronate, Co salts of naphthenic acid, Ca salts of naphthenic acid, Cu salts of naphthenic acid, Mn salts of naphthenic acid, Ni salts of naphthenic acid, Zn salts of naphthenic acid, Fe salts of naphthenic acid, Ba salts of stearic acid, Co salts of stearic acid, Pb salts of stearic acid, Zn salts of stearic acid, Al salts of stearic acid, Cu salts of stearic acid, Fe salts of stearic acid, metal carboxylates (e.g. Al tristearate, Al octanoate, Li heptanoate, Fe stearate, Fe distearate, Ba stearate, Cr stearate, Mg octanoate, Ca stearate, Fe naphthenate, Zn naphthenate, Mn heptanoate, Zn heptanoate, Ba octanoate, Al octanoate, Co octanoate, Mn octanoate, and Zn octanoate), Co lineolates, Mn lineolates, Pb lineolates, Zn lineolates, Ca oleates, Co oleates, Zn palmirate, Ca resinates, Co resinates, Mn resinates, Pb resinates, Zn resinates, AB diblock co-polymers of 2- ethylhexyl methacrylate-co-methacrylic acid calcium, and ammonium salts, co-polymers of an alkyl acrylamidoglycolate alkyl ether (e.g. methyl acrylamidoglycolate methyl ether-co-vinyl acetate), and hydroxy bis(3,5-di- tert- butyl salicylic) aluminate monohydrate. In some examples, the charge adjuvant is aluminium di and/or tristearate and/or aluminium di and/or tripalmitate.

[0072] The charge adjuvant can constitute about 0.1 to about 5 % by weight of the solids of the liquid electrophotographic composition. The charge adjuvant can constitute about 0.5 to about 4 % by weight of the solids of the liquid electrophotographic composition. The charge adjuvant can constitute about 2 to about 4 % by weight of the solids of the liquid electrophotographic composition. The charge adjuvant can constitute about 1 to about 3 % by weight of the solids of the liquid electrophotographic composition.

Charge Director

[0073] As an optional component, a charge director may be added to the electrophotographic composition. In some examples, the charge director may be selected from metal salts of sulfo-succinates, metal salts of oxyphosphates, metal salts of alkyl-benzenesulfonic acid, metal salts of aromatic carboxylic acids or sulfonic acids, polyoxyethylated alkylamines, lecithin, polyvinylpyrrolidone and organic acid esters of polyvalent alcohols. In some examples, the charge director is selected from petroleum sulfonates (e.g. neutral calcium petronate, neutral barium petronate and basic barium petronate), polybutylene succinimides (e.g. OLOA™ 1200 and Amoco 575), and glyceride salts (e.g. sodium salts of phosphated mono- and diglycerides with unsaturated and saturated acid substituents), sulfonic acid salts including, but not limited to, barium, sodium, calcium, and aluminum salts of sulfonic acid. In some examples, the charge director may be selected from sulfonic acids, including, but not limited to, alkyl sulfonic acids, aryl sulfonic acids, and sulfonic acids of alkyl succinates.

[0074] In some examples, the charge director comprises nanoparticles of a simple salt and a salt of the general formula MA_n, wherein M is a barium, n is 2, and A is an ion of the general formula [R₁-O-C(O)CH₂CH(SO₃')C(O)-O-R₂], where each of RT and R₂ is an alkyl group e.g. as discussed above.

[0075] The sulfosuccinate salt of the general formula MA_r is an example of a micelle forming salt. The charge director may be substantially free or free of an acid of the general formula HA, where A is as described above. The charge director may comprise micelles of said sulfosuccinate salt enclosing at least some of the nanoparticles. The charge director may comprise at least some nanoparticles having a size of about 10 nm or less, in some examples about 2 nm or more (e.g. about 4 to about 6 nm).

[0076] The simple salt may comprise a cation selected from Mg , Ca , Ba , NH₄ , tertbutyl ammonium, Li⁺, and Al⁺³, or from any sub-group thereof. In one example, the simple salt is an inorganic salt, for instance, a barium salt. The simple salt may comprise an anion selected from SO₄ ²', PO³', NO₃', HPO₄ ²', CO₃ ²', acetate, trifluoroacetate (TFA), Cl', Bf, F', CIO₄', and TiO₃ ⁴', or from any sub-group thereof. In some examples, the simple salt comprises a hydrogen phosphate anion.

[0077] The simple salt may be selected from CaCO₃, Ba₂TiO₃, AI₂(SO₄)₃, AI(NO₃)₃, Ca₃(PO₄)₂, BaSO₄, BaHPO₄, Ba₂(PO₄)₃, CaSO₄, (NH₄)₂CO₃, (NH₄)₂SO₄, NH₄OAc, Tertbutyl ammonium bromide, NH₄NO₃, LiTFA, AI₂(SO₄)₃, l_iCIO₄ and LiBF₄ or any subgroup thereof. In one example, the simple salt may be BaHPO₄.

[0078] In the formula [Ri-O-C(O)CH₂CH(SO₃')C(O)-O-R₂], in some examples, each of R, and R₂ is an aliphatic alkyl group. In some examples, each of Ri and R₂ independently is a C_6.25 alkyl. In some examples, said aliphatic alkyl group is linear. In some examples, said aliphatic alkyl group is branched. In some examples, said aliphatic alkyl group includes a linear chain of more than 6 carbon atoms. In some examples, RT and R₂ are the same. In some examples, at least one of RT and R₂ is CI₃H₂7.

[0079] The charge director may comprise one of or all of (i) soya lecithin, (ii) a barium sulfonate salt, such as basic barium petronate (BPP), and (iii) an isopropyl amine sulfonate salt. Basic barium petronate is a barium sulfonate salt of a 21-26 hydrocarbon alkyl, and can be obtained, for example, from Chemtura.

[0080] In an electrophotographic composition, the charge director can constitute about 0.001% to about 20%, in some examples about 0.01 to about 20% by weight, in some examples about 0.01 to about 10% by weight, in some examples about 0.01 to about 1 % by weight of the solids of the electrostatic composition. The charge director can constitute about about 0.001 to about 0.15 % by weight of the solids of the liquid electrophotographic composition, in some examples about 0.001 to about 0.15 %, in some examples about 0.001 to about 0.02 % by weight of the solids of the liquid electrophotographic composition. In some example, the charge director is present in an amount of at least 10 mg of charge director per gram of solids of the electrophotographic composition (mg/g for brevity), in some examples at least about 20 mg/g, in some examples from about 10 mg/g to about 100 mg/g, in some examples from about 20 mg/g to about 80 mg/g. In some examples, the charge director imparts a negative charge on the electrostatic composition. The particle conductivity may range from about 50 to about 500 pmho/cm, in some examples from about 200 to about 350 pmho/cm.

Non-polar, non-aqueous carrier liquid

[0081] The electrophotographic composition may be printed in liquid form. The nonpolar, non-aqueous carrier liquid may comprise any liquid suitable for dispersing charged particles and allowing electrophoresis to occur to allow the particles to move and adhere to charged rollers of an electrophotographic printing apparatus. Generally, the carrier liquid for the liquid electrophotographic composition can act as a dispersing medium for the other components in the electrostatic composition. For example, the carrier liquid can comprise or be a liquid selected from a hydrocarbon, a silicone oil and a vegetable oil. The carrier liquid can include, but is not limited to, an insulating, nonpolar, non-aqueous liquid that can be used as a medium for toner particles. The carrier liquid can include compounds that have a resistivity in excess of about 10⁹ ohm-cm. The carrier liquid may have a dielectric constant below about 5, in some examples below about 3. The carrier liquid can include, but is not limited to, hydrocarbons. The hydrocarbon can include, but is not limited to, an aliphatic hydrocarbon, an isomerized aliphatic hydrocarbon, branched chain aliphatic hydrocarbons, aromatic hydrocarbons, and combinations thereof. Examples of the carrier liquids include, but are not limited to, aliphatic hydrocarbons, isoparaffinic compounds, paraffinic compounds, dearomatized hydrocarbon compounds, and the like. In some examples, the carrier liquid is an isoparaffinic liquid. In particular, the carrier liquids can include, but are not limited to liquids sold under the trademarks, Isopar-G™, Isopar-H™, Isopar-L™, Isopar-M™, Isopar-K™, Isopar-V™, Norpar 12™, Norpar 13™, Norpar 15™, Exxol D40™, Exxol D80™, Exxol D100™, Exxol D130™, and Exxol DUO™ (each sold by EXXON CORPORATION); Teclen N-16™, Teclen N-20™, Teclen N-22™, Nisseki Naphthesol L™, Nisseki Naphthesol M™, Nisseki Naphthesol H™, #0 Solvent L™, #0 Solvent M™, #0 Solvent H™, Nisseki Isosol 300™, Nisseki Isosol 400™, AF-4™, AF-5™, AF- 6™ and AF-7™ (each sold by NIPPON OIL CORPORATION); IP Solvent 1620™ and IP Solvent 2028™ (each sold by IDEMITSU PETROCHEMICAL CO., LTD.); Amsco OMS™ and Amsco 460™ (each sold by AMERICAN MINERAL SPIRITS CORP.); and Electron, Positron, New II, Purogen HF (100% synthetic terpenes) (sold by ECOLINK™).

[0082] Before printing, the carrier liquid can constitute about 20% to about 99.5% by weight of the electrostatic composition, in some examples about 50% to about 99.5% by weight of the electrophotographic composition. Before printing, the carrier liquid may constitute about about 40 to about 90 % by weight of the electrophotographic composition. Before printing, the carrier liquid may constitute about about 60% to about 80% by weight of the electrophotographic composition. Before printing, the carrier liquid may constitute about about 90% to about 99.5% by weight of the electrophotographic composition, in some examples about 95% to about 99% by weight of the electrophotographic composition.

[0083] The electrophotographic ink composition, when printed on a substrate, may be substantially free from carrier liquid. In an electrophotographic printing process and/or afterwards, the carrier liquid may be removed, e.g. by an electrophoresis processes during printing and/or evaporation, such that substantially just solids are transferred to the substrate. Substantially free from carrier liquid may indicate that the ink printed on the print substrate contains less than about 5 wt% carrier liquid, in some examples, less than about 2 wt% carrier liquid, in some examples less than about 1 wt% carrier liquid, in some examples less than about 0.5 wt% carrier liquid. In some examples, the ink printed on the print substrate is free from carrier liquid.

Li-ion electrochemical cell, Printing Process, and Print Substrate [0084] In some examples, the electrophotographic composition as described in this disclosure is printed onto a substrate using a liquid electrophotographic printer. The first or second material may be disposed on the substrate and the electrophotographic composition may be printed on the first or second material to form an electrolyte on the first or second material. A layered structure can be formed, comprising the first material, the second material, with the electrophotographic composition as described herein disposed between the first and second material to act as an electrolyte. The first and/or second material may be printed, e.g. electrophotographically printed onto the substrate before the electrophotographic ink composition is printed onto the first or second material to form the electrolyte, and then the other of the first and/or second material can be printed, e.g. electrophotographically printed, onto the electrolyte. This can form the Li-ion electrochemical cell.

[0085] In the liquid electrophotographic printer, an image is first created on a photoconductive surface or photo imaging plate (PIP). The image that is formed on the photoconductive surface is a latent electrostatic image having image and background areas with different potentials. When an electrophotographic composition containing charged toner particles is brought into contact with the selectively charged photoconductive surface, the charged toner particles adhere to the image areas of the latent image while the background areas remain clean. The image is then transferred to a print substrate either directly or by first being transferred to an intermediate transfer member (e.g. a soft swelling blanket) and then to the print substrate. The intermediate transfer member, if present, may be a rotating flexible member, which may be heated, e.g. to a temperature of from about 80 to about 105 degrees C.

[0086] In the case of the liquid electrophotographic ink compositions of the present disclosure for acting as an electrolyte, the toner particles include the copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; and a polyethylene glycol-lithium (PEG:Li) complex. The copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; and the polyethylene glycol-lithium (PEG:Li) complex may therefore be printed together onto a substrate. The toner particles may further comprise the charge adjuvant.

[0087] The substrate, which may be termed a print substrate, may be any suitable substrate. The substrate may be any suitable substrate capable of having the first or second material and/or the electrolyte printed therein. The substrate may include a material selected from an organic or inorganic material. The material may include a natural polymeric material, e.g. cellulose. The material may include a synthetic polymeric material, e.g. a polymer formed from alkylene monomers, including, but not limited to, polyethylene and polypropylene, and co-polymers such as styrenepolybutadiene. The polypropylene may, in some examples, be biaxially orientated polypropylene. The material may include a metal, which may be in sheet form. The metal may be selected from or made from, for instance, aluminium (Al), silver (Ag), tin (Sn), copper (Cu), mixtures thereof. The material of the print substrate may be electrically conductive, for example comprising a metal or carbon or an electrically conductive compound such as indium tin oxide; in some embodiments the metal substrate may have a non-electrically conductive layer, e.g. comprising a polymer or a cellulosic paper, and a conductive layer, e.g. comprising an electrically conductive material selected from a metal, carbon and an electrically conductive compound such as indium tin oxide; and the first and/or second material, and/or the electrophotographic ink composition for forming an electrolyte may be disposed on the electrically conductive layer, and in some examples the other of the first and/or second material and the electrophotographic composition form further layers therein, for example to form the Li-ion electrochemical cell. In an example, the substrate includes a cellulosic paper. In an example, the cellulosic paper is coated with a polymeric material, e.g. a polymer formed from styrene-butadiene resin. In some examples, the cellulosic paper has an inorganic material bound to its surface (before printing with ink) with a polymeric material, wherein the inorganic material may be selected from, for example, kaolinite or calcium carbonate. The substrate is, in some examples, a cellulosic print substrate such as paper. The cellulosic print substrate is, in some examples, a coated cellulosic print. In some examples, a primer may be coated onto the print substrate, before the electrophotographic composition is printed onto the print substrate.

[0088] The present disclosure further provides a process for assembling a Li-ion electrochemical cell. The process may comprise: providing a first material for acting as a Li-ion cell cathode or anode and electrophotographically printing a liquid electrophotographic ink composition on the first material to form an electrolyte, wherein the electrophotographic ink composition comprises a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO2X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant; and a non-polar, non-aqueous carrier liquid.

The carrier liquid is then removed from the electrolyte (e.g. by allowing it to evaporate). A second material is then disposed on the electrolyte; the second material is for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

[0089] Herein is also provided a Li-ion electrochemical cell comprising: a first material for acting as a Li-ion cell cathode or anode an electrolyte comprising a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; a charge adjuvant; a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

[0090] The first material may be a print substrate or be a material on a print substrate. The first material may have been printed on a print substrate, for example by any suitable printing technique, e.g. a printing technique selected from ink-jet printing, electrophotographic printing, which may be with liquid toner or dry toner, 3D printing, offset lithography, screen printing, flexography. According, the method may involve printing the first material on a print substrate, for example using any of the printing techniques described. The first material may have been electrophotographically printed on a print substrate.

[0091] The process may comprise electrophotographically printing a cathode on a substrate using a liquid electrophotographic cathode ink composition comprising a copolymer of an olefin and acrylic acid or methacrylic acid; a cathodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier. The electrolyte may then be printed on the cathode. An anode may then be printed on the electrolyte. An anode may also printed on the electrolyte using a liquid electrophotographic anode ink composition comprising a copolymer of an olefin and acrylic acid or methacrylic acid; an anodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier.

[0092] Alternatively, the anode may be printed onto the substrate first, followed by the electrolyte and then the cathode. The process may comprise electrophotographically printing an anode on a substrate using a liquid electrophotographic anodic ink composition comprising a copolymer of an olefin and acrylic acid or methacrylic acid; a anodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier. The electrolyte may then be printed on the anode. A cathode may then be printed on the electrolyte. A cathode may also be printed on the electrolyte using a liquid electrophotographic anode ink composition comprising a copolymer of an olefin and acrylic acid or methacrylic acid; a cathodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier.

[0093] Herein is also provided a Li-ion electrochemical cell comprising: a first material for acting as a Li-ion cell cathode or anode an electrolyte comprising a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; a charge adjuvant; a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less. The first material may or may not be a printed material. The second material may or may not be a printed material. The electrolyte may or may not have been printed. While the electrophotographic printing composition described herein for producing an electrolyte may be electrophotographically printed onto the first or second material, it may alternatively be coated onto the material using another technique, such as spreading (e.g. using a doctor blade), spraying or electroplating. The first or second material may be disposed on a substrate, e.g. a print substrate, which may be as described herein. If either the first or the second material is for acting as a cathode, then it may include any suitable Li-ion cathodic material. The cathodic material may be a lithium intercalation material selected from transition metal oxides, for example, lithium-containing transition metal oxides. Other examples of cathodic materials include lithium iron phosphate (LFP). Suitable transition metal oxides include lithium cobalt oxide (LCO - LiCo0₂), lithium cobalt aluminium oxide (NCA - LiCoAI0₂), lithium manganese oxide spinel (LMO - LiMn₂O₄), and lithium nickel cobalt manganese oxide (NCM - Li Ni_xCo_yMn_z0₂, where x+y+z=1 , 0^y<1 , 0^z<1 and O^x<1).0ther examples include lithium manganate (Li_1+xMn_2-xO₄, where x=0 to 0.33), Li_1+xMn_2-x-yMyO₄ (where M contains at least one species of metal selected from Ni, Co, Cr, Cu, Fe, Al and Mg, x=0 to 0.33, y=0 to 1.0 and 2-x-y>0), LiMnO₃, LiMn₂O₃, LiMnO₂, LiMn_2-xMxO₂ (where M contains at least one species of metal selected from Co, Ni, Fe, Cr, Zn and Ta, and x=0.01 to 0.1), Li₂Mn₃MO₃ (where M contains at least one species of metal selected from Fe, Co, Ni, Cu and Zn), copper-lithium oxide (Li₂CuO₂), and vanadium oxide (e.g., LiV₃O₃, LiFe₃O₄, V₂O or Cu₂V₂O₇). If either the first or second material is to act as an anode, it may include any suitable Li-ion anodic material, which may be selected from a graphitic material, lithium titanate, hard carbon, alloys of tin and cobalt, silicon/carbon composites.

[0094] In the Li-ion electrochemical cell, the first material may be an electrophotographically printed ink comprising: a copolymer; a cathodic material comprising a lithium intercalation material; and a charge adjuvant. The copolymer may be a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO2X group, and wherein X is H or Li. The copolymer may be as defined for the electrolyte. The copolymer may be a copolymer of an olefin (e.g. ethylene) and acrylic acid. The copolymer in the first material may be the same as or different to the copolymer of the electrolyte. The charge adjuvant may be as defined for the electrolyte.

[0095] In the process for assembling a Li-ion electrochemical cell the providing of a first material for acting as a Li-ion cell cathode or anode may involve printing a cathodic electrophotographic print composition to form a cathode or printing an anodic electrophotographic print composition to form an anode, respectively.

[0096] If a cathodic electrophotographic print composition is used to print the first material, an anodic electrophotographic print composition may be used to print the second material. If an anodic electrophotographic print composition is used to print the first material, a cathodic electrophotographic print composition may be used to print the second material. The anodic electrophotographic print composition may be for forming the first material if the first material is for acting as a Li-ion cell anode. The cathodic electrophotographic print composition may be for forming the first material if the first material is for acting as a Li-ion cell cathode.

[0097] The cathodic electrophotographic print composition may comprise a copolymer; a cathodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier. In the cathodic electrophotographic print composition, the copolymer; the cathodic material comprising a lithium intercalation material; and the charge adjuvant may be as defined for the cathodic material. The liquid carrier may be as defined for the electrolyte, i.e. a non-polar, non-aqueous carrier liquid, which may be as defined herein.

[0098] The anodic electrophotographic print composition may be for forming the first material if the first material is for acting as a Li-ion cell anode. The anodic electrophotographic print composition may comprise a copolymer; an anodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier. In the anodic electrophotographic print composition, the copolymer; the anodic material comprising a lithium intercalation material; and the charge adjuvant may be as defined for the cathodic material. The liquid carrier may be as defined for the electrolyte, i.e. a non-polar, non-aqueous carrier liquid, which may be as defined herein. Cathodic electrophotographic print compositions

[0099] The cathodic electrophotographic print composition is for forming a Li-ion cathode by electrophotographically printing the cathodic electrophotographic print composition. The electrophotographic composition for forming the electrolyte may be printed onto the cathodic electrophotographic composition. In the cathodic electrophotographic print compositions, or the first or second material if acting as a cathode, a lithium intercalation material be selected from transition metal oxides, for example, lithium-containing transition metal oxides. Other examples of cathodic materials include lithium iron phosphate (LFP). Suitable transition metal oxides include lithium cobalt oxide (LCO - LiCoO₂), lithium cobalt aluminium oxide (NCA - LiCoAI0₂), lithium manganese oxide spinel (LMO - LiMn₂O₄), and lithium nickel cobalt manganese oxide (NCM - Li Ni_xCo_yMn_z0₂, where x+y+z=1 , 0^y<1 , 0^z<1 and O^xd).

[00100] Other examples include lithium manganate (Li_1+xMn_2-xO₄, where x=0 to 0.33), Li_1+xMn_2-x-yMyO₄ (where M contains at least one species of metal selected from Ni, Co, Cr, Ou, Fe, Al and Mg, x=0 to 0.33, y=0 to 1.0 and 2-x-y>0), LiMnO₃, LiMn₂O₃, LiMnO₂, LiMn_2-xMxO₂ (where M contains at least one species of metal selected from Co, Ni, Fe, Cr, Zn and Ta, and x=0.01 to 0.1), Li₂Mn₃MO₃ (where M contains at least one species of metal selected from Fe, Co, Ni, Cu and Zn), copper-lithium oxide (Li₂CuO₂), and vanadium oxide (e.g., LiV₃O₃, LiFe₃O₄, V₂O or Cu₂V₂0₇).

[00101] The cathodic material may be present in the cathodic electrophotographic print compositions, or first or second materials as appropriate, in an amount of about 5 to about 80 weight %, for example, about 10 to about 60 weight % or about 15 to about 50 weight % based on the total weight of solids in the composition. In some examples, the cathodic material may be present in the cathodic electrophotographic print compositions, or first or second materials as appropriate, in an amount of about 5 to about 40 weight %, for example, about 8 to about 35 weight % or about 10 to about 30 weight % of the total weight of solids present in the liquid electrophotographic cathode composition. In some examples, the cathodic material may be present in the cathodic electrophotographic print composition, or first or second materials as appropriate, in an amount of about 12 to about 25 weight % or about 15 to about 20 weight % of the total weight of solids in the composition.

[00102] An electrically conductive material may be used in combination with the cathodic material to facilitate charge transfer to and from the cathodic material. Examples of suitable materials include electroconductive carbon materials. For instance, graphite, carbon black, graphene and/or carbon nanotubes (CNT) may be used. The electrically conductive material (e.g. carbon material) may be present in an amount of about 1 to about 60 or about 40 weight %, for example, about 5 to about 30 weight % or about 10 to about 20 weight % of the total weight of solids in the composition.

[00103] In some examples, the weight ratio of electroconductive material to cathodic material may be about 1 :5 to about 5 : 1 , for instance about 1 :2 to about 2: 1.

[00104] In some examples, the total weight of electroconductive material and cathodic material in the composition may be about 10 to about 60 weight %, for example, about 15 to about 50 weight % or about 20 to about 40 weight % of the total weight of solids in the electrophotographic cathode composition. In some example, the total weight of electroconductive material and cathodic material in the composition may be about 25 to about 35 weight %, for instance, about 30 weight % of the total weight of solids in the composition.

[00105] The electrophotographic cathode composition may additionally include an electrolyte. The electrolyte may include a lithium salt and/or a solid polymer electrolyte. Suitable lithium salts include lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium nitrate, lithium perchlorate, lithium bis(trifluoromethane) sulfonimide, lithium bis(oxalate) borate, and lithium trifluoromethanesulphonate.

[00106] Where used, the lithium salt may be present in an amount of about 1 to about 20 weight %, for example, about 5 to about 15 weight % of the total weight of solids in the composition. In some examples, the lithium salt may be present in an amount of about 6 to about 12 weight %, for instance about 8 to about 10 weight of the total weight of solids in the electrophotographic cathode composition.

[00107] Suitable solid polymer electrolytes include polyethylene oxide (PEO). Other examples of solid polymer electrolytes include polymers having monomer units derived from at least one of ethylene oxide, propylene oxide, oxymethylene, epichlorohydran, bis-(methoxyethoxyethoxy) phosphazene, oxetane, tetrahydrofuran, 1 ,3-dioxolane, ethylene imine, ethylene succinate, ethylene sulfide, propylene sulfide, (oxyethylene) methacrylate, (oxyethylene) oxymethylene, (oxyethylene) cyclotrisphosphazene, 2-(4- carboxyhexafluorobutanoyloxy) ethylmethacrylate and derivatives thereof. [00108] When present, the polymer electrolyte may be present in an amount of about 1 to about 40 weight %, for example, about 5 to about 35 weight % of the total weight of solids in the electrophotographic ink composition. The polymer electrolyte may be present in an amount of about 8 to about 30 weight %, for instance, about 10 to about 25 weight % of the total weight of solids in the electrophotographic cathode composition.

[00109] The electrophotographic cathode composition also includes a charge adjuvant as described in further detail below. The charge adjuvant may be present in an amount of about 1 to about 10 weight %, for instance about 2 to about 8 weight % or about 3 to about 5 weight % of the total weight of solids in the electrophotographic cathode composition.

Anodic electrophotographic print composition

[00110] The anodic electrophotographic print composition is for forming a Li-ion anode by electrophotographically printing the cathodic electrophotographic print composition. The electrophotographic composition for forming the electrolyte may be printed onto the anodic electrophotographic composition. As described above, the anodic electrophotographic print composition is for printing a material suitable for acting as a Li-ion battery anode.

[00111] The anodic electrophotographic print composition may comprises a copolymer; an anodic material comprising a lithium intercalation material; a charge adjuvant, and a liquid carrier. The copolymer may be as defined for the cathodic electrophotographic print composition and/or the electrolyte. The copolymer may be a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO2X group, and wherein X is H or Li. The copolymer may be a copolymer of an olefin (e.g. ethylene) and acrylic acid. The copolymer in the anodic electrophotographic print composition may be the same as or different to the copolymer of the electrolyte. The charge adjuvant may be as defined for the electrolyte.

[00112] The copolymer may be a copolymer of an olefin (e.g. ethylene) and acrylic acid. The acrylic acid moieties may, at least in certain examples, facilitate Li ion transport to enhance ionic conductivity. The copolymer may comprise about 10 to about 30 weight % of units derived from acrylic acid, for example, about 12 to about 25 weight % of about 15 to about 20 weight %.

[00113] The copolymer may be present in the liquid electrophotographic anodic ink composition in an amount of about 10 to about 90 weight % based on the total weight of solids in the composition. In some examples, the copolymer may be present in an amount of about 15 to about 80 weight %, for instance, about 20 to about 70 weight % or of the total weight of solids in the composition. In some examples, copolymer may be present in an amount of about 25 to about 60 weight % or about 30 to about 55 weight % based on the total weight of solids in the composition.

[00114] The copolymer in the liquid electrophotographic anodic ink composition may be the same as that used in the liquid electrophotographic cathodic ink composition described herein.

[00115] The anodic material may be an electrically conductive material capable of intercalating lithium. In some examples, the electrically conductive material (e.g. carbon material) is the same as the electrically conductive material (e.g. carbon material) employed in some examples of the liquid electrophotographic cathode ink composition described above. However, the amount of electrically conductive material (e.g. carbon material) in the liquid electrophotographic cathode ink composition is less than the amount of electrically conductive material (e.g. carbon material) in the liquid electrophotographic anode ink composition.

[00116] Examples of the electrically conductive materials capable of intercalating lithium include electroconductive carbon materials. For instance, graphite, carbon black, graphene and/or carbon nanotubes (CNT) may be used. In some examples, silicon-based materials may be used. The electrically conductive material (e.g. carbon material) may be present in an amount of about 1 to about 60 weight %, for example, about 10 to about 50 weight % or about 20 to about 40 weight % of the total weight of solids in the composition.

[00117] The liquid electrophotographic anode composition may additionally include an electrolyte. The electrolyte may include a lithium salt and/or a solid polymer electrolyte. Suitable lithium salts include lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium nitrate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium bis(oxalate) borate and lithium trifluoromethanesulphonate. [00118] Where used, the lithium salt may be present in an amount about 1 to about 20 weight % or about 5 to about 15 weight % of the total weight of solids in the electrophotographic anode composition. In some examples, the lithium salt may be present in an amount of about 6 to about 12 weight %, for instance about 8 to about 10 weight of the total weight of solids in the electrophotographic anode composition.

[00119] Suitable solid polymer electrolytes include polyethylene oxide (PEO). When present, the solid polymer electrolyte may be present in an amount of about 1 to about 40 weight %, for example, about 5 to about 35 weight % of the total weight of solids in the electrophotographic anode composition. The solid polymer electrolyte may be present in an amount of about 5 to about 35 weight % or about 5 to about 30 weight %, for instance, 8 to 15 weight % of the total weight of solids in the electrophotographic anode composition.

[00120] The liquid electrophotographic anodic composition also includes a charge adjuvant as described in further detail below. The charge adjuvant may be present in an amount of about 1 to about 10 weight %, for instance about 2 to about 8 weight % or about 3 to about 5 weight % of the total weight of solids in the liquid electrophotographic anodic composition.

[00121] Herein is also provided a Li-ion electrochemical cell. A Li-ion electrochemical cell may also be termed a Li-ion battery and is one that can generate electricity through the flow of lithium ions through the cell, as the cell is discharged. In generating the electricity, the lithium ions may flow from the cathode (sometimes termed the negative electrode) to the anode (sometimes termed the positive electrode) through the electrolyte. The cell may be charged by reversing the flow of lithium ions by applying a suitable potential across the cell. The electrochemical cell may comprise: a first material for acting as a Li-ion cell cathode or anode, wherein the first material comprises a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a cathodic or anodic material comprising a lithium intercalation material; and a charge adjuvant; an electrolyte comprising a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; a charge adjuvant; a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the second material comprises a copolymer of an olefin and a monomer having a carboncarbon double bond and a -CO₂X group, and wherein X is H or Li; a cathodic or anodic material comprising a lithium intercalation material; and a charge adjuvant.

[00122] The copolymers of the first material, electrolyte and second material may be the same as each other or different from each other. They each may independently be as defined as above for the electrolyte. The charge adjuvants of the first material, electrolyte and second material may be the same as each other or different from each other. They each may independently be as defined as above for the electrolyte.

[00123] The present disclosure further provides a process for assembling a Li-ion electrochemical cell, said process comprising: electrophotographically printing a cathodic or anodic electrophotographic print composition on a substrate to form a first material for acting as a Li-ion cell cathode or anode, respectively; electrophotographically printing a liquid electrophotographic ink composition on the first material to form an electrolyte, wherein the electrophotographic ink composition comprises a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO2X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant; and a non-polar, non-aqueous carrier liquid; removing the carrier liquid from the electrolyte, and then electrophotographically printing an anodic or cathodic electrophotographic print composition on the electrolyte to form the second material for acting as a Li-ion cell anode or cathode, respectively, wherein the second material is for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less.

[00124] The present disclosure further provides a process for assembling a Li-ion electrochemical cell, said process comprising: electrophotographically printing a cathodic or anodic electrophotographic print composition on a substrate to form a first material for acting as a Li-ion cell cathode or anode, respectively, wherein the cathodic or anodic electrophotographic print composition comprises a copolymer of an olefin and a monomer having a carboncarbon double bond and a -CO2X group, and wherein X is H or Li; a cathodic or anodic material comprising a lithium intercalation material; a charge adjuvant; and a non-polar, non-aqueous carrier liquid; electrophotographically printing a liquid electrophotographic ink composition on the first material to form an electrolyte, wherein the electrophotographic ink composition comprises; a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO2X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant; and a non-polar, non-aqueous carrier liquid; removing the carrier liquid from the electrolyte, and then electrophotographically printing an anodic or cathodic electrophotographic print composition on the electrolyte to form the second material for acting as a Li-ion cell anode or cathode, respectively, wherein the second material is for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The PEG of the PEG:Li complex may have a molecular weight of about 500,000 g/mol or less. The copolymer, the charge carrier, and the non-polar, non-aqueous carrier liquid the of the electrophotographic print compositions for forming the first material and second material may be as defined above for the electrolyte. The copolymer, the charge carrier, and the non-polar, non-aqueous carrier liquid the of the electrophotographic print compositions for forming the first material may be the same as or different from the second material and/or the electrolyte.

[00125] Also provided is a method of making the liquid electrophotographic ink composition, the method comprising: dispersing in a non-polar, non-aqueous carrier liquid: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a - CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex; and a charge adjuvant. The PEG of the PEG:Li complex may have a molecular weight of 500,000 g/mol or less.

The formation of the PEG:Li complex may involve the mixing the PEG and a lithium salt, which may be as described herein, until a single phase is achieved. The mixing may involve heating the PEG and the lithium salt, e.g. such that the PEG is liquified or made less viscous and allows dissolution of the lithium salt in the PEG. The heating may involve heating the PEG and lithium salt to a temperature of from about 30 °C to about 100 °C, in some examples with agitation, such as stirring, of the PEG and lithium salt.

The PEG:Li complex may be combined with the copolymer and the charge adjuvant, and the non-polar, non-aqueous carrier liquid by mixing the components vigorously, e.g. by high-shear mixing of the components. The PEG:Li complex may be in liquid form and combined with copolymer and the charge adjuvant, and the non-polar, nonaqueous carrier liquid by dripping or pouring the PEG:Li complex into a mixture of the copolymer and the charge adjuvant, and the non-polar, non-aqueous carrier liquid, and mixing the components vigorously, e.g. by high-shear mixing of the components.

[00126] The dispersing may involve grinding of the copolymer, the PEG:Li complex and the charge adjuvant in the non-polar, non-aqueous carrier liquid. The grinding may form particles comprising the copolymer, the PEG:Li complex and the charge adjuvant, wherein the particles are dispersed in the non-polar, non-aqueous carrier liquid. The grinding may be carried out in a mill, e.g. a ball mill. The grinding in a mill may be carried out by rotating the mixture such that the RPM of the rotations is at least about 100 RPM, in some examples at least about 200 RPM, in some examples at least about 250 RPM, in some examples from about 100 RPM to about 500 RPM, in some examples from about 200 RPM to about 300 RPM, in some examples about about 250 RPM ; and in some examples the grinding may be carried out for a period of at least about 1 hour, in some examples about 2 hours, in some examples about 3 hours, in some examples about 4 hours, in some examples about 1 to about 15 hours, in some examples about 4 to about 15 hours, in some examples about 5 to about 15 hours, in some examples about 8 to about 12 hours. The temperature during grinding may be at least about 20 °C, in some examples at least about 25 °C, in some examples at least about 30 °C. A suitable grinding mill is a ball mill or attritor. A commercially available attritor is available from Union Process, such as a Union S1 - attritor.

[00127] As used in this disclosure, “alkyl”, or similar expressions such as “alk” in alkaryl, may refer to a branched, unbranched, or cyclic saturated hydrocarbon group, which may, in some examples, contain from about 1 to about 50 carbon atoms, or 1 to about 40 carbon atoms, or 1 to about 30 carbon atoms, or 1 to about 10 carbon atoms, or 1 to about 5 carbon atoms, for example.

[00128] The term “aryl” may refer to a group containing a single aromatic ring or multiple aromatic rings that are fused together, directly linked, or indirectly linked (such that the different aromatic rings are bound to a common group such as a methylene or ethylene moiety). Aryl groups described in this disclosure may contain, but are not limited to, from 5 to about 50 carbon atoms, or 5 to about 40 carbon atoms, or 5 to 30 carbon atoms or more, and may be selected from, phenyl and naphthyl.

[00129] Unless the context dictates otherwise, the terms “acrylic” and “acrylate” refer to any acrylic or acrylate compound. For example, the term “acrylic” includes acrylic and methacrylic compounds unless the context dictates otherwise. Similarly, the term “acrylate” includes acrylate and methacrylate compounds unless the context dictates otherwise.

[00130] Figure 8 is a schematic diagram of an example of a Li-ion electrochemical cell. It comprises a first material (801) for acting as a Li-ion cell cathode or anode, an electrolyte (803), a second material (802) for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The electrolyte may comprise: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO2X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; a charge adjuvant. The electrolyte (803) may have been electrophotographically printed on either the first material (801) or second material (802).

[00131] Figure 9 is a schematic diagram of an example of Li-ion electrochemical cell. It comprises a substrate (804), onto which has been printed, e.g. electrophotographically printed, a first material (801) for acting as a Li-ion cell cathode or anode. In turn, an electrolyte (803) has been printed, e.g. electrophotographically printed, onto the first material, and a second material has been printed, e.g. electrphotographically printed, onto the electrolyte. The second material (802) is for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode. The first material, second material and electrolyte are as defined in Figure 8.

[00132] The printing of the various layers and the materials for each may be as described above.

Examples

Production and testing of an electrophotographic ink composition for use as an electrolyte

Table 1: Material list

[00133] A preliminary composition, termed a paste herein, was first prepared by mixing the copolymer (i.e. the EAA or lithium ionomer of ethylene acrylic acid copolymer) and the isopar. Paste preparation: The lithium ionomer 1163-x or A-C 580 was mixed with

Isopar L in 25-40% solids. The resin was heated to 100°C-120°C until a clear single phase was obtained. After obtaining a clear single phase, the solution was cooled to give a swelled resin as a paste.

[00134] PEG:Li complex preparation - Lithium salt such as LiTFSI or LiTf was dissolved in PEG200 or PEG 500 overnight on hot plate (45-55°C) until clear single phase was produced. This was performed in an argon-controlled atmosphere dry-box having humidity content below 10 ppm. PEG:Li complexes were prepared with a molar ratio of polyethylene oxide units in the PEG to Li of 3: 1 , 10:1 and 20: 1.

[00135] Ink preparation - PEG:Li complex was added by gentle drip and high shear mixture to the paste (40%), VCA and Isopar-L solution. The solution was mixed in Isopar to give dispersion of 10Ogr at 5%-10% NVS. To the glass container 80gr of 0.9 ZrO ceramic media were added. The system was put for high power shaker grinding tool (Fast and fluid shaker) and was ground for 8-12 hours at 500 RPM. The result is solid electrolyte based El formulation at 5% NVS.

[00136] The resultant ink formulation comprised:

Complex PEG:Li - 32wt% of the solids

Resin (copolymer) - 64-66wt% of the solids

VCA (charge adjuvant) - 2-4 wt% of the solids

Total non-volatile solids (NVS) - 5-10%

Deposition onto aluminium plates

[00137] As a preliminary test, the ink composition was coated onto aluminium substrates by two different methods: plating and using a doctor blade.

1 . Plating - the electrophotographic ink composition for forming the electrolyte was electroplated on an aluminum substrate with 0.8-1.2mg/cm². (one and a half drops of NCD (0.7% NVS) charged the dispersion before plating). The film was fused and dried on hot plate of 90° for couple of minutes. 2. Doctor blade - the electrophotographic ink composition for forming the electrolyte was coated on aluminum substrate using blade with a vertical distance separating the blade from the substrate and controls the thickness of the wet ink. %NVS of the solution was 12-16%. The coated film was fused and dried on hot plate of 90° for couple of minutes.

Film thickness of ~10-12pm was evaluated with confocal microscope.

[00138] Building a cell - In order to perform ionic conductivity tests a symmetric cell configuration was made using aluminum foils having the electrolyte therebetween (this is shown schematically in Figure 1 , showing the aluminium substrates (101), each having thereon an ink layer (102), with the two ink layers from each aluminium substrate then brought into contact to form the sandwich structure shown in the figure). This was hermetically sealed in a coin cell construction. The cell assembling was executed in an argon-controlled-atmosphere dry-box humidity content below 10 ppm. Aluminum foils with solid electrolyte film were vacuum dried at 50°C for 24hrs.

[00139] EIS characterization - Electrochemical Impedance spectroscopy (EIS) method represents an approach for the determination of the electrical properties of polymer electrolyte. By this method, using a Nyquist plot, one can determine the electrolyte properties, such as the electrolyte resistance and conductivity.

[00140] Measurement conditions: Biologic sp300 Potentiostat, PEIS, amplitude 100mV, frequency of 7MHz-1 KHz. All measurements were performed after first fusing to 70° for better contact between two "sandwiched" layers.

[00141] Figures 2A and 2B shows optical images of solid-state electrolyte El film coated on an indium tin oxide (ITO) substrate. Formulation contains: 32% PEG200:LiTf 3:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, Lithium ionomer resin and 2% charging adjuvant. More specifically, Figures 2A and 2B show a surface image of the solid-state electrolyte El film coated on an ITO substrate. One can see particles which look like bubbles, trapped in second phase. It is considered that the particles are the PEG200:Li complex, and the second phase around the particles is the resin. This is also supported by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurement. According to ToF-SIMS images (Figure 3), the presence of the Lithium salt and the PEG 200 appears to be in the particle's areas, and the presence of the resin is around the particles.

[00142] Figure 3 shows Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) images of solid-state electrolyte El film. Formulation contains: 32% PEG200:LiTf 3:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, Lithium ionomer resin and 2% charging adjuvant.

[00143] Figure 4 shows a Nyquist plot for solid-state electrolyte film (measured in the sandwiched cell) coated on aluminum foil with doctor blade. Formulation contains: 32% PEG200:LiTf 3:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, Lithium ionomer resin and 2% charging adjuvant. Electrolyte resistant according the Nyquist plot is 8100[Q], and the ionic conductivity is 1.09 • 10^-7[^j.

[00144] Figure 5 shows a Nyquist plot for solid-state electrolyte film (measured in the sandwiched cell) coated on aluminum foil by electroplating. Formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, A-C 580 resin and 2% charging adjuvant. An adjustment of electrolyte resistance (R_e) can be observed in this figure. EIS measurements were performed for both coating methods. Electrolyte resistance of -300 [Q] was determined for the doctor blade coated film, whereas electrolyte resistance of -747 [Q] was determined for the film coated by electrodeposition plating. The ionic conductivity is 1.18 • 10^-5

[00145] Figure 6 shows a Nyquist plot for solid-state electrolyte film (measured in the the sandwiched cell) printed on aluminum and carbon-coated foil, 28 separations. The formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, A-C 580 resin and 4% charging adjuvant

^[001461 Figure 7 shows a Nyquist plot for solid-state electrolyte film (measured in the sandwiched cell) printed on aluminum and carbon-coated foil, 28 separations. The formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, A-C 580 resin and 4% charging adjuvant. After first heating to 55°C for 48hrs (for better contact between the film layers), the electrolyte resistance of ~1800[Q] is 1.76 W⁷.

[ooi47] p_rjnt_eC| fj|_m thickness of ~4.5pm was evaluated with confocal microscope. In the sandwiched cell configuration, the solid-state electrolyte film thickness is ~9 pm.

[00148] The test results above illustrate the suitability of the electrophotographic ink compositions for use as an electrolyte in a Li-ion cell, on the basis of the conductivity and resistivity measurements.

Printing test

[00149] Table 2 exhibits LF (low field), PC (particle charge), DC and HF (high field) for a working dispersion with 2% of NVS charged with a charge director (NCD) (NVS 20%) to 60mg/gr. NCD refers to a natural charge director having the components: (i) natural soya lecithin (6.6 wt%) (ii) basic barium petronate (9.8 wt%) and (Hi) Isopropyl amine dodecyl benzene sulphonic acid (3.6wt%) in Isopar (80 wt%). When a weight of this NCD is referred to in the later Examples and the Figures, it refers to the combined weight of (i) natural soya lecithin (ii) basic barium petronate and (Hi) dodecyl benzene sulphonic acid per gram of solids in the ink composition. A stable PC was observed over 24hrs.

Table 2- LF, PC, DC and HF values for solid-state electrolyte working dispersion. Formulation contains: 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 66%, A-C 580 resin and 4% charging adjuvant.

The values for the LF, PC, DC and HF illustrate the suitability of the liquid compositions for use in a liquid electrophotographic printing apparatus.

[00150] Electrophotographic printing test: The first print was performed on an liquid electrophotographic printing apparatus (a HP Indigo 7000 series printer) on standard A3 sheet fed machine configuration. The solid-state electrolyte formulation contained 32% PEG500:LiTf 10:1 molar ratio (i.e. molar ratio of polyethylene oxide units in the PEG to Li), 64%, A-C 580 resin and 4% charging adjuvant. Working dispersion of 2% NVS was charged with NOD (NVS 20%) to lOmg/gr.

[00151] The printing was performed on three different foils.

1. Aluminum foil

2. Aluminum and carbon coated foil

3. PET

Foils 1 and 2 were pasted on a condat substrate with tape in the printing direction.

[00152] Ink transferability to the substrate (sometimes termed the second transfer in electrophotographic printing, when there is a first transfer to the intermediate transfer roller) was good to all substrates, this is may be due to the polarity of the polyethylene glycol. The solid-state electrolyte El was successfully printed with 1 ,4,8,16, 24 and 28 separations.

[00153] Figure 7 shows Nyquist plots for two solid-state electrolyte films printed on aluminum with carbon coated foil with 28 separations. Two cells were prepared: Cell 1 and Cell 2. After first heating to 55°C for 48hrs (for better contact between the film layers), electrolyte resistance of ~7000[Q] for cell 1 , and -4000 for cell 2 [O] were measured.

[00154] Printed film thickness of ~4.5pm was evaluated with confocal microscope. In the sandwiched cell configuration, the solid-state electrolyte film thickness is -9 pm.

[00155] Printed film thickness of -4.5pm was evaluated with confocal microscope. In the sandwiched cell configuration, the solid-state electrolyte film thickness is -9 pm.

Li-ion Electrochemical Cell

[00156] An example of a Li-ion electrochemical cell, as shown schematically in Figure 9, may be produced in an example method as follows.

[00157] Materials for the anodic and cathodic liquid electrophotographic printing compositions:

- A-C 5120 (supplied by Honeywell®) - a thermoplastic resin component - Lithium trifluoromethanesulfonate (lithium salt)

- Lithium Manganese Oxide - LiMnO2 (LMO) as electroactive cathode material

- Multi-walled carbon nanotubes - (MWCNT) as electroconductive carbon material

[00158] An initial paste can be produced as follows, which can then be used to produce the cathodic and anodic electrophotographic ink compositions.

[00159] In this method, resin A-C 5120 at 50-57 %NVS can be inserted in Ross tool and then melted under 50rpm mixing at 130 °C over 60 minutes. After 60 minutes the mixing velocity is raised to 70 rpm to enhance melting and to produce a paste. This can be continued for 90 minutes. Then, the paste is cooled to 25 °C under constant mixing at 50rpm. The cooling can take place over 3 - 4 hours.

Liquid Electrophotographic Anodic Ink Composition:

[00160] The paste produced above (-55% non-volatile solids (NVS) in iso-paraffin (lsopar®-L (Sol-L)), Lithium Manganese Oxide, MWCNT, Lithium salt, PEO and charging adjuvant can be loaded into an Attritor containing metal grinding balls in the amounts shown in Table 3 below. The grinding process is performed at ~43°C (mixing speed of 250 rpm) for 5 hrs ). After reaching a desired particle size (e.g. below 8 micron), the ink is diluted with iso-paraffin (lsopar®-L, Sol-L) and mixed for 15 minutes before being discharged to a receiving container. The %NVS of the obtained ink is in the range of 3-10% NVS.

[00161] Table 3

Liquid Electrophotographic Cathode Ink Composition:

[00162] The paste produced above (~55% non-volatile solids (NVS) in iso-paraffin (lsopar®-L (Sol-L)), MWCNT, Lithium salt, PEO and charging adjuvant are loaded into an Attritor containing metal grinding balls in the amounts shown in Table 4 below. The grinding process can be performed at ~43°C (mixing speed of 250 rpm) for 5 hrs ). After reaching a desired particle size (e.g. below 8 micron), the ink is diluted with isoparaffin (lsopar®-L, Sol-L) and mixed for 15 minutes before being discharged to a receiving container. The %NVS of the obtained ink is in the range of 3-10% NVS.

[00163] Table 4

Working dispersion preparation:

[00164] Before the electrophotographic anodic and cathodic inks above are printed, they can be diluted to form working dispersions. To do this, 3.5 KG of ink 2% NVS can be prepared by diluting the inks with iso-paraffin (lsopar®-L, Sol-L). A charge director (NCD) can be added until a low field charge of 70 pmho is reached and the dispersion mixed in a shaker (200 rpm) for 24 h to reach sufficient charging, homogenization and stabilisation.

[00165] An example electrophotographic ink composition for use as an electrolyte is also prepared as describe above (i.e. as described under the heading ‘Production and testing of an electrophotographic ink composition for use as an electrolyte’). Cell assembly

A substrate is provided and then the electrophotographic cathodic composition can be electrophotographically printed onto the substrate to form a cathode on the substrate. The electrophotographic composition for acting as an electrolyte can then be printed on the cathode to form an electrolyte on the cathode. The anodic electrohotographic composition can then be electrophotographically printed on the electrolyte, to form an anode on the electrolyte. The cathode may, for example, be electrically conductive, e.g. an aluminium foil, or non-electrically conductive, e.g. paper or a plastic film, although, if the substrate is not electrically conductive, electrical connections can be made with other electrically conductive materials, which are contacted with the anode and cathode, and then optionally to other electrical components, to complete the circuit. The cell may be charged and tested for voltage, using suitable equipment, e.g. using a Fluke® voltage tester.

Claims

1 . A liquid electrophotographic ink composition comprising: a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; a charge adjuvant; and a non-polar, non-aqueous carrier liquid.

2. The liquid electrophotographic ink composition according to claim 1 , wherein the PEG of the PEG:Li complex has a molecular weight of 100,000 g/mol or less.

3. The liquid electrophotographic ink composition according to claim 1 , wherein the PEG of the PEG:Li complex has a molecular weight of 50 g/mol to 10,000 g/mol.

4. The liquid electrophotographic ink composition according to claim 1 , wherein a molar ratio of polyethyleneoxide units in the PEG to Li in the PEG:Li complex is n:1 , wherein n is 0.5 or more.

5. The liquid electrophotographic ink composition according to claim 1 , wherein a molar ratio of polyethyleneoxide units in the PEG to Li in the PEG:Li complex is n:1 , wherein n is 3 to 10.

6. The liquid electrophotographic ink composition according to claim 1 , wherein the olefin of the copolymer is ethylene and the monomer having a carboncarbon double bond is acrylic acid.

7. A process for assembling a Li-ion electrochemical cell, said process comprising: providing a first material for acting as a Li-ion cell cathode or anode;

49 electrophotographically printing the liquid electrophotographic ink composition on the first material to form an electrolyte, wherein the electrophotographic ink composition comprises

- a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li;

- a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; and

- a charge adjuvant; and

- a non-polar, non-aqueous carrier liquid; and removing the carrier liquid from the electrolyte, and then disposing on the electrolyte a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode.

8. The process according to claim 7, wherein the PEG of the PEG:Li complex has a molecular weight of 50 g/mol to 10,000 g/mol.

9. The process according to claim 7, wherein the process involves electrophotographically printing the first material on to a substrate, and then electrophotographically printing the liquid electrophotographic ink composition on the first material to form an electrolyte.

10. The process according to claim 7, wherein the process involves electrophotographically printing the second material on the electrolyte or on a substrate and bringing it into contact directly or indirectly with the electrolyte.

11. The process according to claim 7, wherein the charge adjuvant is a salt of a fatty acid.

12. The process according to claim 7, further comprising adding a charge director, different to the charge adjuvant, to the electrophotographic ink composition before it is electrophotographically printed.

50 A Li-ion electrochemical cell comprising: a first material for acting as a Li-ion cell cathode or anode; an electrolyte comprising a copolymer of an olefin and a monomer having a carbon-carbon double bond and a -CO₂X group, and wherein X is H or Li; a polyethylene glycol-lithium (PEG:Li) complex, wherein the PEG of the PEG:Li complex has a molecular weight of 500,000 g/mol or less; and a charge adjuvant; and a second material for acting either as an anode, if the first material is for acting as a cathode, or as a cathode if the first material is for acting as an anode, wherein the electrolyte is disposed between the first and second materials. The Li-ion electrochemical cell according to claim 13, wherein the PEG of the PEG:Li complex has a molecular weight of 50 g/mol to 10,000 g/mol. The Li-ion electrochemical cell according to claim 13, wherein the first and second material each comprises a copolymer of an olefin and acrylic acid or methacrylic acid; a material comprising a lithium intercalation material; and a charge adjuvant.

51