FI127814B

FI127814B - Cellulose-based functional composites, energy storage devices and processes for their preparation

Info

Publication number: FI127814B
Application number: FI20145974A
Authority: FI
Inventors: Vesa Kunnari; Otto-Ville Kaukoniemi
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2014-11-06
Filing date: 2014-11-06
Publication date: 2019-03-15
Also published as: WO2016071573A1; EP3215563A1; EP3215563B1; CA2965436C; EP3215563A4; CA2965436A1; CN107001699A; JP2017533339A; KR20190045319A; US10396328B2; FI20145974A7; US20170346059A1; CN107001699B; KR20170078772A

Abstract

Asiakirja esittää uusia tekniikoita selluloosapohjaisten materiaalien hyödyntämiseksi komposiiteissa ja sähköisesti toiminnallistetuissa rakenteissa, kuten energianvarastolaitteissa. Keksinnön tavoite saadaan käyttäen pitoisuudeltaan runsasta fibrilloitua selluloosaa ja sen kanssa ainakin yhtä toiminnallista lisäainetta. Tämä koostumukseltaan runsas seos prosessoidaan muodon omaavan komposiittirakenteen muodostamiseksi ja kuivataan sitten tai annetaan kuivua.The document presents new techniques for utilizing cellulose-based materials in composites and electrically functionalized structures such as energy storage devices. The object of the invention is achieved by using a high content of fibrillated cellulose and at least one functional additive with it. This high composition blend is processed to form a shape composite structure and then dried or allowed to dry.

Description

CELLULOSE BASED FUNCTIONAL COMPOSITES, ENERGY STORAGE DEVICES AND MANUFACTURING METHODS THEREOF

Technical Field

The present invention relates to manufacture of functional composites containing cellulose based materials as well as such composites and composite structures.

Cellulose based functional composites include electrically functionalised stuctures such as energy storage devices.

Background Art

WO 2010/134868 Al discloses a method of producing a cellulose based paper with enhanced mechanical properties. The method involves providing a suspension of well dispersed modified cellulose at a low concentration. The properties and the chemical structure of the paper make it suitable for in vivo applications such as implant material.

WO 2012/049198 Al discloses a process for the production of a surface coated support material wherein said process comprises contacting a support material with an aqueous dispersion of nanocellulose. The surface coated support material can be used in a composite material.

US 2014/302336 Al discloses a process for manufacturing a composite structure, wherein nanocellulose has been absorbed onto the cellulose surface before fibrillation.

WO 2014/087053 Al discloses nanocellulose composites comprising nanocellulose material mixed with a polymer.

Disclosure of Invention

It is an object of the present invention to create new technologies for utilizing cellulose based materials in composites and electrically functionalised structures, such as energy storage devices.

The object of the invention is achieved by means of high consistency fibrillated cellulose with at least one functional additive. This high consistency mixture is processed to form the composite structure having a shape and then dried or let to dry.

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The invention provides a new technology for utilizing cellulose based materials in composites and electrically functionalised stuctures, such as energy storage devices.

According to embodiments, the invention allows new methods that are energy-efficient.

Other advantages provided by certain embodiments include easier manufacturing and 5 allowing new shapes and dimensions for the structures.

Thus, such mixtures and processes can also be used to make new structures with novel features.

Brief Description of Drawings

For a more complete understanding of the present invention and the advantages thereof, 10 the invention is now described with the aid of the examples and with reference to the following drawings, in which:

Figure 1 presents a method according to an embodiment of the invention; and

Figure 2 presents a method according to another embodiment of the invention.

Modes for Carrying Out the Invention

While the embodiments are applicable in several areas of technology and can be used to manufacture various different articles and components, we will exemplify the embodiments by means of some specific examples.

Fig. 1 describes a method for manufacturing a supercapacitor according to an embodiment. According to Fig. 1, step 11 comprises preparing high consistency 20 fibrillated cellulose. The term “high consistency” means over 20% of dry solids consistency. The fibrillated cellulose comprises microfibrillated cellulose and/or nanofibrillated cellulose. The fibrillated cellulose can be prepared, for example, using methods described in more detail later in this specification.

In step 12, the high consistency fibrillated cellulose is mixed with at least one additive. 25 In this example, the additive comprises graphite and graphene particles. The mixture contains water up to 80 % of weight and dry solids at least 20 % of weight. The dry solids contain:

Fibrillated cellulose 10-70 % of weight of dry solids

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Carbon based particles 30-90 % of weight of dry solids

Other additives 0-50 % of weight of dry solids

At least 20 %, such as 30-90 % of weight of the carbon based particles are graphite and/or graphene particles.

Possible other additives include additives that can provide or assist electrical properties and/or binding between carbon and fibre material.The mixture is in gel form and can be easily shaped.

In step 13, the mixture is pressed or rolled to form a sheet.

Step 14 is optional. In step 14, the sheet is partially dried in order to reduce water 10 content. This is done for example when the sheet is to be stacked with a layer of another material, which does not withstand moisture.

In step 15, the sheet is stacked with other layers, for example with an electrolyte layer and a second electrode layer. In this case, the sheet forms the basic structure of the first electrode. The structure can also include at least one separator layer made of at least one 15 additive and fibrillated fibre material.

In step 16, a final drying of the product is conducted, if necessary. Thus, also this step is optional.

In step 17, electrical contacts to the electrodes are made. This can be done, for example, by printing or by adding conductive foil, e.g metallic foil. Conducting adhesive, for 20 instance, can be used to improve the electrical contact between the conductive foil and the electrode.

In step 18, the supercapasitor is finished with surfacing layer. This can be done, for example, by encapsulation in plastic foil or metallic foil.

Fig. 2 describes a method for manufacturing a rigid three-dimensional electrode 25 structure. This can be later surfaced with other layers for example by spraying or painting. The three-dimensional structure can form part of a vehicle, for instance. It can be used as a roof structure in a car or in a house or form a support structure for a solar panel, for instance.

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According to Fig. 2, step 21 comprises preparing high consistency fibrillated cellulose, as described above with reference to Fig. 1.

In step 22, the high consistency fibrillated cellulose is mixed with at least one additive.

In this example, the additive comprises graphite and graphene particles. The mixture 5 contains water up to 80 % of weight and dry solids at least 20 % of weight. The dry solids contain:

Fibrillated cellulose 10-70 % of weight of dry solids

Carbon based particles 30-90 % of weight of dry solids

Other additives 1-50 % of weight of dry solids.

At least one of the other additive is a polymer having ability to bind to cellulose fibres and carbon based particles.

Also in this example, at least 20 %, such as 30-90 % of weight of the carbon based particles are graphite and/or graphene particles.

Possible other additives include additives that can provide or assist electrical properties 15 and/or binding between carbon and fibre material.

The mixture is in gel form and can be easily shaped.

In step 23, the mixture is molded to final shape.

In step 24, the mold is dried to the structure its desired rigidity.

Alternatively to the above steps 23 and 24, the mixture can be given an preliminary 20 shape and then dried. After the object to be made has a sufficient hardness, it can be machined to give the final shape. Additionally, a surfacing, such as a film of carbon and fibre material, can be attached or applied on the surface of the made object.

Embdiments offer a new solution for cellulose based energy storage devices such as supercapacitors (later referred as SC) for flexible and wearable devices. Using 25 nanocellulose as both SC separator material and as a binder for electrode material makes it possible to manufacture SC’s in a simple and cost efficient way. Further, it gives technical benefits such as low internal losses because it makes it possible to create

20145974 prh 14-02- 2019 optimal contact between electrodes and separator layer. Fibrillated cellulose containing material is also lightweight material which means that weight of the manufactured SC’s is low. This is beneficial for mobile applications as well as for use in vehicles.

Embodiments offer new solution for cellulose based energy storage devices for flexible and wearable devices. Previous implementations have been manufactured by laminating or filtrating separate layers on each other. Embodiments provide more efficient method to manufacture supercapacitors and battery structures having optimal contact between electrodes and separator layer. Also manufacturing from fibrillated cellulose containing material, such as enzyme treated cellulose, is simple and cost efficient due to high solids 10 contents of over 25%.

Some prior methods conductive layer has been filtered on nanocellulose sheet. Procedure is time consuming and requires excessive amount of drying energy. The layers in SC stuctures are being combined by laminating.

Supercapacitors are attractive energy storage devices for flexible and wearable devices. 15 Rapid development of such devices has promoted needs for flexible and light weight energy sources. SCs possess high power characteristics, long cycle lifetime, no maintanance or replacement. To successfully manufacture a high-performance flexible supercapacitor, it is good to consider such aspects as physical flexibility, electrochemical properties and mechanical integration of different materials. Fibers are 20 good SC substrates since they are flexible and can be integrated with conductive materials such as CNT's and activated carbon.

When stronger fiber stuctures are desired nanocellulose can be used to make stuctures with superior mechanical properties. Nanocellulose as low consistency suspension may hinder production technologies and commercialization efforts while tightly binded 25 water is difficult to remove as films are formed from the suspension by evaporation of water. Nanocellulose like material can be manufactured using enzymes to break down the fibre structure. Such procedure enables higher solids contents to be used meaning less water is present to be evaporated. Solids up to 35% can be used compared to nanocellulose suspension solids of 2%. The enzyme based fibrillated cellulose can be 30 formed directly to desired shapes using molded pulp-type techniques. Film making from enzyme treated nanocellulose is possible to implement using e.g consecutive rollers to

20145974 prh 14-02- 2019 thin the film to desired thickness level followed by moderate drying. The manufacturing process is much more simpler to implement by using enzyme treatment to make nanocellulose like material.

If solid electrolytes are used manufactured power source structures can also be rigid. In 5 this case they can also be used as structural elements in for example cars where they could be e.g. integrated inside the roof of the car.

One process for manufacturing fibrillated cellulose is described in Finnish patent application No. 20136282, which was filed on 18^th December in 2013 and not made public at the time of filing the first application for the present invention. The whole 10 content of the Finnish patent application No. 20136282 is incorporated herein by reference. The method is also discussed below.

The method is based on the ability of certain cellulases to loosen and fibrillate cellulose structure and use of a tailored enzyme mix, which facilitates fibrillating activity instead of cellulose hydrolysis. The desired fibrillated cellulose is produced by using the 15 enzyme mix, which comprises mainly cellobiohydrolase(s), some endoglucanase(s), and may also contain other enzyme activities, such as β-glucosidase or hemicellulases.

These enzymes are preferably used in a ratio, which minimizes the cellulose degradation, but accelerates production of fibrillated cellulose. This type of action is favored by choosing enzymes with varying thermostability and controlling their activity 20 by process temperature. The loosening of the cellulose fibres is achieved preferably by simultaneous enzymatic and mechanical treatment.

This method has an advantage that the product after treatment has lower moisture content (60-80%) compared to existing methods, which produce nanocellulose at 9799% moisture content. Thus, the material can be used in embodiments, which cannot 25 tolerate large amounts of water associated with the fibrillated cellulose.

According to an embodiment, the method comprises producing fibrillated cellulose in an improved and energy efficient way, which process comprises a fibrillation of the starting cellulose material with enzyme(s) and enhancing the fibrillation mechanically.

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The term “fibrillated cellulose” is here intended to encompass all fibrillated cellulose materials, having typically minimum lateral dimensions of 5-20 nanometers and longitudinal dimensions from 10 nanometers to several microns, even up to 100 pm.

As a starting material pulp, unbleached pulp or native biomass of different origin (e.g.

wood, annual plants, crop residues) can be used. Pulp material can be for example bleached pine pulp. Particularly, “slurry” is used, which is here intended to mean a starting material, e.g. wood pulp, which comprises the cellulose fibres that are processed in an aqueous dispersion. The starting consistency of the slurry is preferably higher than 10%, such as higher than 15% by weight. Slurry consistency may be even 10 over 30%. The starting material i.e. pulp or biomass can also be in a grinded form.

In prior art technology fibrillation is generally carried out by grinding or high-pressure homogenizing, possibly with the help of chemical pre-treatments such as strong acid hydrolysis or chemical oxidation. In the present method, it is possible to use an enzymatic fibrillation in conjunction with low energy mixing, i.e. a procedure including 15 at least one enzymatic treatment of the fibres. Suitable machinery includes any equipment enabling adequate mixing in high consistency without having an excessive high shear or cutting action upon fibres. These include e.g. mixers, compounders, extruders or kneaders. This enzymatic fibrillation can be enhanced by using a mechanical treatment to further disintegrate the fibres, which mechanical treatment for 20 example can be carried out by using a homogenizer, grinder or fluidizer.

Said combination of mechanical treatment and enzymatic treatment results in a more efficient production process for fibrillated cellulose compared to the simultaneous procedure used in the prior art. The increased efficiency is due to the synergistic effect of this combined treatment. The mechanical treatment carried out in high consistency 25 conditions in conjunction with the enzymatic treatment will open and unravel fibre cell wall allowing the enzymes to have easier access to the fibre matrix. Enzymes will then attack to uncovered fibre surfaces and further disintegrate fibre structure. Because of the combined treatment, the enzymes are distributed more thoroughly and homogeneously throughout the slurry and they will find more suitable places to attach to, thus making 30 the fibrillation more efficient. High consistency promotes gentle fibre-fibre friction which enhances the fibrillating effect of the treatment. Since the enzymatic treatment

20145974 prh 14-02- 2019 loosens up the fibres, mechanical treatment can be performed in a softer manner and in milder reaction conditions.

An advantage of this method is that fibrillated cellulose is produced enzymatically, i.e. gently, by using a low energy demanding mechanical mixer. Another advantage is that 5 it is possible to enhance the fibrillation in a desired and controlled way, without too high degradation, thus producing fibrillated material of a controlled quality. Enzymes are used so that the cellulose degradation compared to the produced fibrillated material is as low as possible. Sugars that are produced into the end-product may also be furthermore exploited. Researchers have shown that these sugars can be fermented to 10 for example ethanol by common yeast.

In the method, the fibrillation is carried out by using an enzyme mix having mainly a cellobiohydrolase (CBH) activity and a low endoglucanase (EG) activity, wherein the endoglucanase activity is very low, but sufficient enough to create new chain ends for CBH action. In addition, it is preferred to use an enzyme mix and reaction conditions, 15 wherein the cellobiohydrolase activity is more thermostable than the endoglucanase activity. The enzyme mix may optionally contain assisting carbohydrate active enzymes such as β-glucosidases, hemicellulases, pectinases or lytic polysaccharide monooxygenases, or their combinations.

Cellobiohydrolases (CBHs) have been shown to act processively and unidirectionally 20 along cellulose fibre starting either from reducing or non-reducing chain end and liberating cellobiose as the main product. Characteristic for CBHs are that DP (degree of polymerization) of cellulose is affected only slightly. Endoglucanases attack randomly along cellulose chain creating new sites for CBHs to act. The extent of new chain ends created by endoglucanases can be controlled by enzyme dosage, treatment 25 time and temperature profile or their combinations. The role of β-glucosidase is to hydrolyze arising cello-oligomers to glucose and to prevent end-product inhibition of CBHs.

The reaction temperature of the process is chosen according to the enzymes that are used. In an embodiment, the fibrillation is carried out in two stages: selecting such 30 reaction temperature, which allows both cellobiohydrolase and endoglucanase to be active in a first stage and inactivating the endoglucanase activity by increasing the

20145974 prh 14-02- 2019 reaction temperature in a second stage. Then, the temperatures used can be between 050 °C in the first stage and between 50-80 °C in the second stage, for instance. After treatment, when necessary, inactivation of enzyme activity can be performed by heating up the material to 100 °C for 15-30 min e.g. by steam. Alternatively, inactivation can 5 also be carried out by pH adjustment outside pH optima of the enzymes.

In one embodiment the temperature is kept low (below or about 50 °C) in the beginning of the reaction and then raised up to about 70 °C for the remaining reaction time. Enzyme products usually always contain minor traces of side activities. Herein low temperature first allows the enzymes to co-operate, after which high temperature 10 inactivates the remaining side activities allowing cellobiohydrolase work alone on the fibre.

Based on the above described temperature and/or pH controlling, in one embodiment the reaction is carried out by having only endoglucanase activity in a first stage and only cellobiohydrolase activity in a second stage (i.e. CBH addition and EG inactivation in a 15 second stage) or by using an enzyme mix comprising said enzymes with high initial endoglucanase activity, which is correspondingly inactivated e.g. by increasing the temperature in a second stage.

CBH I and CBH II tend to hydrolyze cellulose from chain ends, whereas endoglucanase attacks randomly cellulose chain with concomitant decrease of DP. It is thereby good to 20 use an enzyme mix, which has at least small traces of endoglucanase activity, because cellobiohydrolases can utilize chain ends that are provided by endoglucanase. Sufficient amount of endoglucanase is dependent on endoglucanase in question, since specific activity of endoglucanases varies greatly and some of them are very difficult to analyze even with the most sensitive methods (e.g. CMC viscosity method). Therefore proper 25 amount of endoglucanase activity can even exist as a contaminant side activity in the preparation. Higher endoglucanase activities, however, work synergistically with CBH releasing a lot of soluble oligo-saccharides causing yield losses.

The treatment time can vary between 15 minutes and 25 hours, for instance, According to an embodiment, the treatment time is from 1 hour to 6 hours. Enzymes are added 30 before or during the mechanical treatment, for example by spraying. It is noteworthy, that by using enzymes and low energy demanding mechanical mixing together, also

20145974 prh 14-02- 2019 longer treatments lead to a more energy efficient process, compared to traditional processing, such as grinding and high-pressure homogenizing.

According to one embodiment, mechanical agitation is carried out without using grinding forces that cause excessive degradation of the fibres and consumption of 5 energy. An example of a suitable mechanical mixer to be used in the process is a nonrefining mixer such as a plough share mixer, a screw mixer, kneader, compounder or an extruder. Usually it is good to keep mixing speed rather low, such as around 100 rpm. In addition, according to a further embodiment, the fibrillation may be enhanced by a posttreatment step such as a grinding or a high shear treatment in an extruder, homogenizer 10 orfluidizer.

The above-described methods can be used to manufacture fibrillated cellulose material, which has lower moisture content (60-80%) compared to existing methods, which produce nanocellulose at 97-99% moisture content.

As is apparent from the above discussion, there is provided a method of making a 15 composite structure, the method comprising:

obtaining a mixture containing solids and water, the solids content of the mixture being at least 20 % of the weight of the mixture, the solids containing at least cellulose and at least one functional additive, wherein at least a portion of the cellulose is fibrillated cellulose;

processing the mixture having the solids content of at least 20 % of the weight to form the composite structure having a shape; and reducing the water content of the mixture to solidify the formed composite structure.

Particularly, the method of making a composite structure of the invention comprises 25 obtaining a mixture in gel form, the mixture containing cellulose, at least a portion of which is enzyme-treated fibrillated cellulose.

The mixture in gel form is obtained by steps comprising a step of preparing a mixture comprising fibrillated cellulose and water such that the solids content of the mixture is at least 20 % of the weight of the mixture; and

20145974 prh 14-02- 2019 a step of mixing the mixture obtained from the preparation step with at least one additive and thereby obtaining the mixture in gel form, the solids content of the gel being at least 20 % of the weight of the gel; and using said gel as the mixture in the step of processing to form the composite 5 structure having the shape.

According to an embodiment, the shape is a film-shape such as the manufactured structure or object is a film.

According to an embodiment, the solids content of the mixture is at least 20 % of the weight of the mixture during said processing. According to another embodiment, the 10 solids content of the mixture is at least 25 % of the weight of the mixture during said processing.

According to an embodiment, the at least one functional additive comprises at least one electrically conductive additive, such as carbon nanotubes (CNTs), single-walled nanotubes (SWNTs), multi-walled nanotubes (MWNTs), activated carbon (AC), or 15 graphene.

According to an embodiment, the at least one functional additive comprises at least one cathode chemical and/or anode chemical, such as lithium or lithium based chemicals.

According to another embodiment, the at least one functional additive comprises at least one electrolyte. Electrolytes can include, for example, dry polymer electrolytes, gel 20 electrolytes, water-soluble salts, acids, and/or synthetic polymers.According to an embodiment, the at least one functional additive comprises at least one carbon component, the at least one carbon component being one of activated carbon, graphite, graphene and carbon nanotubes.

According to a further embodiment, the content of the at least one carbon component in 25 the solids of the mixture is 50-95 %, such as 55-90 %, such as 60-85 % of weight of the solids.

According to an even further embodiment, the total content of the cellulose and carbon components in the solids of the mixture is at least 75 %, such at least 90 %, such as at least 95 % of weight of the solids.

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According to an embodiment, the at least one functional additive comprises at least one of silicon and lithium.

According to an embodiment, the fibrillated cellulose comprises cellulose fibres having diameters less than 10 nanometers.

According to a further embodiment, the the portion of cellulose fibres having diameters less than 10 nanometers is at least 5 %, such as at least 10 %, such as at least 25 % of the weight of the fibrillated cellulose.

According to another embodiment, the fibrillated cellulose comprises cellulose fibres having diameters less than 20 nanometers.

According to a further embodiment, the the portion of cellulose fibres having diameters less than 20 nanometers is at least 5 %, such as at least 10 %, such as at least 25 % of the weight of the fibrillated cellulose.

According to an embodiment, the content of the cellulose in the solids of the mixture is 5-50 %, such as 10-45%, such as 15-40 % of weight of the solids.

According to an embodiment, the processing comprises moulding the mixture.

According to another embodiment, the the processing comprises using a roller or a press to form the composite structure in the shape of a film.

According to another aspect, there is provided a method of manufacturing an energy storage device, the method comprising providing a first electrode, a second electrode 20 and a separator layer between and in contact with the first electrode and the second electrode. In the method, at least one of the first electrode, the second electrode and the separator layer is made by a method according to one of the above-described embodiment.

According to an embodiment, the method comprises:

making the first electrode by processing a first mixture containing solids and water, where the solids content of the mixture is at least 20 % of the weight of the mixture and the solids contain at least cellulose and at least one electrically conductive additive;

20145974 prh 14-02- 2019 making the separator layer by processing a second mixture containing solids and water, where the solids content of the mixture is at least 20 % of the weight of the mixture and the solids contain at least cellulose and at least one electrolyte; and applying compressive force to bind the first electrode and the separator layer 5 together.

According to a further embodiment, the method comprises:

making the first electrode and the second electrode by processing a first mixture containing solids and water, where the solids content of the mixture is at least 20 % of the weight of the mixture and the solids contain at least cellulose and at least one 10 electrically conductive additive;

making a separator layer by processing a second mixture containing solids and water, where the solids content of the mixture is at least 20 % of the weight of the mixture and the solids contain at least cellulose and at least one electrolyte; and applying compressive force to bind together the first electrode, the separator layer 15 and the second electrode.

According to an aspect, there is provided a mixture for use in the method according embodiements described above. The mixture contains solids and water, the solids content of the mixture being at least 20 % of the weight of the mixture, the solids containing at least cellulose and at least one functional additive, at least a portion of the 20 cellulose being fibrillated cellulose.

According to an embodiment, the at least one functional additive comprises at least one of electrically conductive additive, cathode chemical and anode chemical.

According to an embodiment, the at least one functional additive comprises at least one electrolyte.

According to an embodiment, the at least one functional additive comprises at least one carbon component.

According to an embodiment, the at least one carbon component comprises activated carbon, graphite, graphene and/or carbon nanotubes.

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According to an embodiment, the content of the at least one carbon component in the solids of the mixture is 50-95 %, such as 55-90%, such as 60-85 % of weight of the solids.

According to an embodiment, the at least one functional additive comprises at least one 5 of silicon and lithium. Lithium additive can be in the form of lithium containing chemicals. Also silicon can be in the form of a silicon containing chemical.

According to an embodiment, the fibrillated cellulose comprises nanocellulose.

According to another embodiment, nanocellulose comprises cellulose fibres having diameters less than 20 nanometers.

According to an aspect, there is provided a composite structure made by one of the embodiments described above and comprising nanocellulose and at least one electrically 15 conductive additive.

According to an embodiment, the composite structure has a three-dimensional shape.

According to an embodiment, the term three-dimensional shape refers to a shape that has portions of substantial curvature, thickness variation, apertures, protrusions or similar non-planar portions.

A three-dimensional shape can be achieved by moulding and/or machining, for instance.

According to an embodiment, the composite structure can have two or three layers, or more generally a plurality of layers. These layers can be made of the above-discussed mixtures. Additionally, also other mixtures or substances can be used in the composite structure. When making two or more layers of the above-disclosed mixtures, the 25 mixtures used for each of these layers can be mutually same or different. For example, one layer can be made using a first functional additive and another layer using a second functional additive different from the first functional additive. Similarly, a further layer can be made using a third functional additive.

According to an embodiment, the at least one electrically conductive additive comprises at least one carbon component, the at least one carbon component being one of activated carbon, graphite, graphene and carbon nanotubes, wherein the content of the at least one carbon component in the solids of the composite structure is 50-95 %, such as 55-90%, 5 such as 60-85 % of weight of the solids, and the content of the cellulose in the solids of the composite structure is 5-50 %, such as 10-45 %, such as 15-40 % of weight of the solids.

The above description is only to exemplify the invention and is not intended to limit the scope of protection offered by the claims. The claims are also intended to cover the 10 equivalents thereof and not to be construed literally.

Claims

Claims:

A method of making a composite structure comprising:

providing a mixture of solids and water, wherein the solids content is at least 20% by weight of the mixture and the solids contain at least cellulose and at least one functional additive, and wherein at least a portion of the cellulose is fibrillated cellulose;

processing a mixture containing solids of at least 20% by weight to form a composite structure having a shape, and reducing the water content of the mixture to solidify the formed composite structure,

Characterized in that the mixture obtained is in gel form, the fibrillated cellulose is enzyme-treated fibrillated cellulose, and the step of obtaining the mixture comprises:

the step of preparing (11; 21) a mixture comprising fibrillated cellulose and water so that the solids content of the mixture is at least 20% by weight of the mixture

A step of mixing (12; 22) at least one additive from a preparation step (11; 21) to form a gel composition having a solids content of at least 20% of the gel presser used as a mixture in the processing step to form a composite structure.

20

The method of claim 1, wherein the gel has a solids content of at least

20%, such as at least 25% of the weight of the gel, during said processing.

The method of claim 1 or 2, wherein the at least one functional additive comprises at least either an electrically conductive additive, a cathode chemical or an anode chemical.

25

The method of any one of claims 1 to 3, wherein the at least one functional additive comprises at least one electrolyte.

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The method of any one of claims 1 to 4, wherein the at least one functional additive comprises at least one carbon component selected from the group consisting of activated carbon, graphite, graphene, and carbon nanotubes.

The method of claim 5, wherein the at least one carbon component in the solids of the gel 5 is 50-95%, such as 55-90%, such as 60-85% by weight of the solids.

The method of claim 6, wherein the total content of cellulose and carbon components in the gel solids is at least 75 percent, such as at least 90 percent, such as at least 95 percent by weight of the solids.

10

The method of any one of claims 1 to 7, wherein the at least one functional additive comprises at least either silicon or lithium.

The method of any one of claims 1 to 8, wherein the fibrillated cellulose comprises cellulose fibers less than 20 nanometers in diameter.

The method of claim 9, wherein the proportion of cellulosic fibers of less than 20 nanometers in diameter is at least 5 percent, such as at least 10 percent, such as at least

25% by weight of fibrillated cellulose.

The process according to any one of claims 1 to 10, wherein the gel has a solids content of 5-50%, such as 10-45%, such as 15-40% by weight of the solids.

20

The method according to any one of claims 1 to 11, wherein the processing comprises gel forming and / or machining.

The method of any one of claims 1 to 11, wherein the processing comprises using a roller or press to form a composite structure in the form of a film.

A method of making an energy storage device, the method comprising:

Providing a first electrode, a second electrode, and a separation layer between and in contact with the first electrode and the second electrode;

characterized in that

20145974 prh 14-02-20199 is made of at least either a first electrode, a second electrode, or a separation layer by a method according to any one of claims 1-13.

The method of claim 14, comprising:

making a first electrode by processing solids and water

The first gel having a solids content of at least 20% by weight of the gel and wherein the solids contain at least cellulose and at least one electrically conductive additive;

subjecting the separating layer to processing a second solid and water containing gel, wherein the solids content is at least 20% by weight of the gel and wherein the solids 10 comprise at least cellulose and at least one electrolyte; and applying a clamping force to bond the first electrode and the separation layer.

The method of claim 14, comprising:

making a first electrode and a second electrode by processing the first

A gel comprising solids and water, wherein the solids content is at least 20% by weight of the gel and wherein the solids contain at least cellulose and at least one electrically conductive additive;

providing a separation layer by processing the second solid and water containing gel, wherein the solids content is at least 20% by weight of the gel and wherein the solids 20 comprise at least cellulose and at least one electrolyte; and applying a clamping force to bond the first electrode, the separation layer, and the second electrode.

A composition for use in a process according to any one of claims 1 to 13, wherein the composition is in the form of a gel containing solids and water, wherein the composition is a

The solids content is at least 20% by weight of the mixture, the solids comprising at least cellulose and at least one functional additive, and wherein at least a portion of the cellulose is enzyme-treated fibrillated cellulose.

The composition of claim 17, wherein the at least one functional additive comprises at least either an electrically conductive additive, a cathode chemical or an anode chemical.

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The composition of claim 17 or 18, wherein the at least one functional additive comprises at least one electrolyte.

The composition of claims 17-18, wherein the at least one functional additive comprises at least one carbon component which is either activated carbon, graphite, graphene or

5 carbon nanotubes.

Mixture according to claim 20, wherein the content of at least one carbon component in the solids of the mixture is 50-95%, such as 55-90%, such as 60-85% by weight of solids.

A composition according to any one of claims 17 to 21, wherein the at least one is functional

The additive comprises at least either silicon or lithium.

The composition of any one of claims 17 to 21, wherein the fibrillated cellulose comprises nanocellulose.

A composite structure made by the process of any one of claims 1 to 13, wherein the composite structure comprises nanocellulose and at least one electrically

15 leading additives.

The composite structure of claim 24, wherein the at least one electrically conductive additive comprises at least one carbon component which is either activated carbon, graphite, graphene or carbon nanotubes, wherein the content of at least one carbon component in the solids of the composite structure is 50-95%, such as 55-90% 60

85% by weight of solids, and the cellulose content in the solids of the composite structure is 5 to 50%, such as 10 to 45%, such as 15 to 40% by weight of solids.

The composite structure of claim 24 or 25, wherein the composite structure has a three-dimensional shape.