NL2036529B1

NL2036529B1 - Coffee melanoidin for electrical energy storage device

Info

Publication number: NL2036529B1
Application number: NL2036529A
Authority: NL
Inventors: Akcay Adnan; Medina Juan
Original assignee: Kaffe Bueno Aps
Priority date: 2023-09-26
Filing date: 2023-12-14
Publication date: 2025-04-01
Also published as: NL2036531B1

Abstract

37384 The present disclosure is directed to a storage device comprising coffee melanoidin, preferably extracted from spent coffee grounds. Owing to the abundance presence of polycondensates with polyelectrolyte/ polyampholite behaviour with a polyphenol or quinone—based aromatic core, the melanoidin has large redox capacities making it suitable for use in electrical energy storage devices. A further advantage of using spent coffee grounds is that this material which has been considered waste material in the past is now upcycled to a useful material which even helps to replace relatively scarce raw materials such as for instance transition metal salts for electrolytes, and transition metals, porous carbon and graphite for electrodes.

Description

COFFEE MELANOIDIN FOR ELECTRICAL ENERGY STORAGE DEVICE

Field

The present disclosure is directed to electrical energy storage devices such as flow batteries and superconductors comprising coffee melanoidin.

Background

In recent years, concerns resulting from environmental consequences of exploiting fossil fuels as the main energy sources have led to an increasing prominence of renewable- energy systems (e.g., solar- and wind-based systems). The intermittent nature of such renewable energy sources however makes it difficult to fully integrate these energy sources into electrical power grids and distribution networks. A solution to this problem are large-scale electrical energy storage (EES) systems, which are also vital for the smart grid and distributed power generation development. Another important application of EES is electrification of on-ground transportation, as the replacement of traditional combustion engines with hybrid, plug-in hybrid, and pure electric vehicles (EVs) allows for reduction of carbon emissions and fuel savings.

Four major challenges to the widespread implementation of

EES have been identified: cost, reliability and safety, equitable regulatory environments, and industry acceptance.

The development of novel EES technologies capable of resolving these challenges is critical. Redox-flow batteries (RFBs) -first developed by NASA during the energy crisis of the 1970's and currently entering a period of renaissance- are among the most promising scalable EES technologies. RFBs are electrochemical systems that can repeatedly store and convert electrical energy to chemical 1 energy and vice versa when needed. Redox reactions are employed to store energy in the form of a chemical potential in liquid electrolyte solutions which flow through a battery of electrochemical cells during charge and discharge. The stored electrochemical energy can be converted to electrical energy upon discharge with concomitant reversal of the opposite redox reactions. RFBs usually include a positive electrode (cathode) and a negative electrode (anode) in separated cells and separated by an ion-exchange membrane, and two circulating electrolyte solutions, positive and negative electrolyte flow streams, generally referred to as the “catholyte” and “anolyte”", respectively. Energy conversion between electrical energy and chemical potential occurs instantly at the electrodes, once the electrolyte solutions begin to flow through the cell. During discharge, electrons are released via an oxidation reaction from a high chemical potential state on the anode of the battery and subsequently move through an external circuit. Finally, the electrons are accepted via a reduction reaction at a lower chemical potential state on the cathode of the battery.

Redox -flow batteries can be recharged by inversing the flow of the redox fluids and applying current to the electrochemical reactor.

The capacity and energy of redox flow batteries is determined by the total amount of redox active species for a set system available in the volume of electrolyte solution, whereas their current (power) depends on the number of atoms or molecules of the active chemical species that are reacted within the redox flow battery cell as a function of time. Redox-flow batteries thus have the advantage that their capacity (energy) and their current the (power) can be readily separated, and therefore readily 2 up-scaled. Thus, capacity (energy) can be increased by increasing the number or size of the electrolyte tanks whereas the current (power) is controlled by controlling the number and size of the current collectors. Since energy and power of RFB systems are independent variables, RFBs are inherently well suitable for large applications, since they scale-up in a more cost-effective manner than other batteries. Moreover, RFBs provide a unique design flexibility as the required capacities for any application can be provided using tailor-made energy and power modules.

A well-established example of an RFB is the vanadium redox flow battery, which contains redox couples exclusively based on vanadium cations. Nevertheless, there is also a wide range of less commonly used inorganic flow cell chemistries, including the polysulfide- bromide battery (PSB). The wide- scale utilization of RFBs using inorganic redox materials is presently still limited by availability and costs of the redox materials. That holds even more so, whenever the redox materials are based on redox-active transition metals such as vanadium, and/or require precious-metal electrocatalysts. Toxicity (and associated health and environmental risks) of inorganic redox materials (such as vanadium salts or bromine) further limits applicability of inorganic RFBs for energy storage.

That holds in particular when applying distributed, modular energy generation technologies that use (intermittent) „green power", such as wind, photovoltaic, or hydroelectric power. Also, the incorporated materials may constitute overheating, fire or explosion risks.

In view of the disadvantages of RFBs based on inorganic redox species, RFBs were envisaged with different organic compounds. Novel organic redox active species for large- 3 scale use in redox flow batteries should preferably be inexpensive, with high solubility and redox potential, and exhibit fast electrode kinetics. In WO 2014/052682arly a metal-free flow battery based on 9,10-anthraquinone-2,7- disulphonic acid (AQDS) was described. The derivatized anthra- and benzoquinones suggested as electrolytes herein are commercially available. However, costly and elaborate manufacture of any of them severely limits their broad- range, large-scale employment.

WO 2020/035548 discloses lignin-derived compounds and compositions comprising the same and their use as redox flow battery electrolytes. The publication further discloses a method for preparing said compounds and compositions as well as a redox flow battery comprising sald compounds and compositions.

As mentioned-above, sheer volume of needed energy storage demands millions of tons of active materials.

Based on scale and availability, the “ideal" redox flow battery for large-scale deployment should be aqueous and use highly soluble multi- electron (i.e. highly energy dense) redox active species that are readily available and inexpensive as electrolytes.

In addition to the electrolytes, also the scarcity electrode material poses a challenge to the growth of electrical energy storage devices such as RFBs and

Supercapacitors. These electrodes conventionally consist of transition metals, carbon such as graphite or carbon felt or porous carbon or even precious metals. Among these, graphite is the most electrically and thermally conductive of the non-metals and is chemically inert. These properties 4 make graphite desirable for many industrial applications, and both natural and synthetic graphite have industrial uses resulting in a growing need of sustainable material for electrodes in electrical energy storage devices.

For instance, EP 3578512 discloses methods of production of graphite from biomass, char or tar. The publication also provides novel apparatus and catalysts for the production of graphite from carbon-containing materials such as the production of graphite by hydrothermal treatment of biomass to produce tar or hydrochar and graphitisation to produce graphite. However, the preparation of graphite and porous carbon by charring has the disadvantage that this process requires high temperatures and precise process control, which is neither sustainable or cost effective.

Furthermore, the fact that graphite is so inert also poses problems when having to dispose of the electrode material.

Supercapacitors are also electrical energy storage devices beit for slightly different applications. A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor, with a capacitance value much higher than solid- state capacitors but with lower voltage limits. It bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charge and discharge cycles than rechargeable batteries.

Unlike ordinary capacitors, supercapacitors do not use the conventional solid dielectric, but rather, they use electrostatic double-layer capacitance and electrochemical pseudocapacitance, both of which contribute to the total capacitance of the capacitor. 5

Supercapacitors are used in applications requiring many rapid charge/discharge cycles, rather than long-term compact energy storage: in automobiles, buses, trains, cranes and elevators, where they are used for regenerative braking, short-term energy storage, or burst-mode power delivery. [4] Smaller units are used as power backup for static random-access memory (SRAM),

Electrochemical capacitors (supercapacitors) consist of two electrodes separated by an ion-permeable membrane (separator), and an electrolyte ionically connecting both electrodes. When the electrodes are polarized by an applied voltage, ions in the electrolyte form electric double layers of opposite polarity to the electrode's polarity.

For example, positively polarized electrodes will have a layer of negative ions at the electrode/electrolyte interface along with a charge-balancing layer of positive ions adsorbing onto the negative layer. The opposite is true for the negatively polarized electrode.

As with redox flow batteries, there is a need for sustainable, reliable and safe, non-toxic active materials for supercapacitors such as electrolytes and electrodes.

It is the object of the present invention to comply with the above needs.

Melanoidins are a class of brown, hydrophilic nitrogen- containing polymers which are formed during the thermal processing of foods - such as coffee, cocoa, bread, malt, barley, Brewers Spent Grain (RSG), soy, meat, and honey.

During thermal processing of such foods, amino acids and reducing sugars, such as aldose and d-xylose, react to form 6 what are termed initial Maillard reaction products. Under continued heating, melanoidins are formed by cyclizations, dehydrations, retro-aldolizations, rearrangements, isomerizations and condensations of those initial Maillard reaction products. The complexity of the Maillard reaction pathways results in a range of final reaction products, with inter alia the time of heating, type of heating, temperature. initial chemical composition of the system, moisture content, water activity and pH value being determinative of the final composition.

Although the precise structure of melanoidins varies and is unclear, it was found that melanoidins comprise polycondensates with polyelectrolyte/polyampholite behaviour with a polyphenol or quinone-based aromatic core, in which functional side structures contain carboxylic, phenolic, and carbonyl groups, as well as sugar, peptide fragments. The sub entities are connected by various connectors, such as -0- , - CH2- , =CH- , -NH- , -S-S5- , and similar groups. The contained chemical functionality determines its redox capacities as well as interactions and complexation with metals.

We have found that these properties make melanoidin excellent material for use in electrical energy storage devices such as redox flow batteries and super capacitors.

More particularly, melanoidin extracts from roasted coffee were found to have excellent redox capacities which make them very suitable for use in energy storage devices.

Summary

The present disclosure provides a storage device comprising coffee melanoidin. 7

The melanoidin may be a molecular weight (Mw) fraction of melanoidin extracted from spent coffee grounds. The molecular weight (Mw)of the melanoidin fraction is preferably above 10 kDa, more preferably ranging from 10 kDa to 500 kDa, and most preferably between 50 to 200 kDa.

The melanoidin may be present in the electrical energy storage device as an electrolyte.

Preferably a first electrolyte is present comprising melanoidin and a second electrolyte comprising a metal cation dissolved in a solvent.

Said second electrolyte may comprise iron, copper, sodium, vanadium, zinc or potassium cations.

The melanoidin may also be present as a metal chelate. Said metal chelate may comprise iron, copper, sodium, vanadium or potassium ions.

At least one of the electrodes present in the electrical energy storage device preferably has been derived from melanoidin.

Preferably the melanoidin is obtained by alkaline extraction from spent coffee grounds, more preferably by extraction with potassium hydroxide. Optionally the extraction is assisted by ultrasonic treatment.

Especially preferred are melanoidins with a phenolics content of at least 3 wt3, more preferably ranging from 3- 30 wt. % of the total melanoidin, calculated as tyrosol equivalents, most preferably ranging from 5-20 wt&. 8

The electrical energy storage device according to the present disclosure may be flow battery or a superconductor, or a combination thereof.

Detailed Description

The present disclosure provides a storage device comprising coffee melanoidin. Owing to the abundance presence of polycondensates with polyelectrolyte/ polyampholite behaviour with a polyphenol or quinone-based aromatic core, the melanoidin has large redox capacities making it suitable for use in electrical energy storage devices.

Within the context of this disclosure the term melanoidin refers to both melanoidin and derivatives of melanoidins such as salts and chelates thereof. It is believed that upon chelation with metals at least part of the metals are part of an metal organic framework, accounting for its high specific surface area, and porosity.

The use of melanoidin to replace part of the conventionally used toxic and environmentally unfriendly material in electrical energy storage devices is also an advantage with respect to disposal aspects. Because of its biorganic nature, at the end of life or when disposed, the melanoidin can be used as a biostimulant or fertilizer due its organic nature and benefits.

Preferably the melanoidin is a molecular weight (Mw) fraction of melanoidin extracted from spent coffee grounds.

The molecular weight (Mw)of the melanoidin fraction is preferably above 5 kDa, more preferably ranging from 10 kDa to 500 kDa, and most preferably between 50 to 200 kDa. With fractionating the particle size and the electrical density can be controlled. 9

A further advantage of using spent coffee grounds is that this material which has been considered waste material in the past is now upcycled to a useful material which even helps to replace relatively scarce raw materials such as for instance transition metal salts for electrolytes, and transition metals, porous carbon and graphite for electrodes.

The melanoidin may be present in the electrical energy storage device as an electrolyte. To this end both melanoidins or melanoidin salts can be used. The melanoidin can be present in the electrical energy storage device as an aqueous solution or as a solution in a suitable solvent such as ionic liquids or deep eutectic solvents, with aqueous solutions being preferred both from environmental and cost perspective.

Electrical energy storage device according to the disclosure may comprise a first electrolyte comprising melanoidin and a second electrolyte comprising a metal cation dissolved in a solvent. It was found that the melanoidin has a higher energy density than for instance vanadium based electrolytes. It was found that with the melanoidin highly effective electrolyte pairs can be created. Especially electrical energy storage devices wherein the second electrolyte comprises iron, copper, sodium, vanadium, zinc or potassium cations were found effective.

Owing to the abundance presence of polycondensates with polyelectrolyte/polyampholyte behavior with a polyphenol or quinone-based aromatic core, the melanoidin has high metal chelating capacities. This increases the versatility of 10 creating electrical energy storage devices with specific redox activities, since metal melanoidin chelates can be used in (aqueous) solutions as electrolyte or as solid electrode material. Suitable metal chelates comprise for instance iron, copper, sodium, vanadium, zinc or potassium.

The general procedure to prepare metal melanoidin chelates comprises: -preparing an aqueous solution Preparation: Metal ions and coffee melanoidins are dissolved in an aqueous solvent to create a reaction mixture conducive to chelation; — Chelation Reaction: Coffee melanoidins selectively coordinate with metal ions, forming stable complexes through shared electron pairs. This process enhances the solubility and electrochemical properties of the resulting complexes; - Complex Stabilization and Purification: The formed metal- melanoidin complexes undergo stabilization and purification steps to ensure homogeneity and purity, suitable for integration into RFB electrolytes; - Filtration: The chelation reaction mixture undergoes filtration to remove larger particulate matter or insoluble residues, separating any undissolved materials or impurities from the complex solution. Filtration methods such as gravity filtration or vacuum filtration can be employed for this purpose; - Centrifugation: After filtration, the solution undergoes centrifugation, subjecting it to high-speed rotation to induce sedimentation of smaller particles or impurities that may not have been captured during filtration. This step aids in further separating solid impurities from the solution; - Decantation or Supernatant Removal: The supernatant, containing the desired metal-melanoidin complexes, is 11 carefully separated from the sedimented impurities or precipitates generated during centrifugation. The clear supernatant is retained for subsequent purification steps; - Purification by Column Chromatography: The supernatant, containing the metal-melancidin complexes, can undergo purification via column chromatography. This technique separates individual components based on their different affinities for the stationary phase within the column, refining the complexes by removing any remaining impurities or unbound species; — Optional, re-suspension and Concentration: The purified metal-melanoidin complexes are re-suspended in a suitable solvent to maintain their stability and enhance their concentration. This step ensures a homogeneous and potent solution ready for integration into RFB electrolytes.

As mentioned above solid metal melanoidin chelates can suitably be used as electrode material. These metal melanoidin chelates per se may formed to solid electrodes, or the metal melanoidin chelates may be coated or precipitated on other electrode material such as graphite, porous carbon or metal electrodes. The metal melanoidin chelate can suitably serve as electrode material to replace (part of) the conventional graphite and porous carbon.

Since the metal melanoidin may be prepared using mild reaction conditions compared to the high temperature usually necessary to prepare graphite or porous carbon electrode material, this has advantages from both economic and environmental aspects.

Also melanoidin-coated metal or carbon electrodes may be prepared by using the chelating properties of melanoidin. 12

Preferably the electrical energy storage device according to the disclosure comprises one or more electrodes that has been derived from melanoidin. Since char or tar can also be prepared from melanoidin and this char and tar may be converted into graphite or porous carbon, also the electrodes may be derived from melanoidin. This adds to the sustainability and affordability of the devices. However, as explained above the melanoidin- comprising electrode material is preferred because its preparation is more environmentally friendly.

The melanoidins can suitably be used to replace the conventional carbon or graphite electrodes that act as anodes in for instance lithium, sodium and potassium batteries and in Solid-state and rechargeable batteries.

The method for extracting melanoidins from spent coffee grounds is known from for instance WO 2012/130349 and WO 2022/268898 which have been incorporated by reference herein for this purpose.

Preferably, the melanoidin is obtained by alkaline extraction from spent coffee grounds. It was found that alkaline extraction ensures high yields of melanoidin without destroying the various useful compounds present in roasted coffee. Especially the use of KOH is desired because of its significant influence on the specific surface area and specific capacitance of the material

Optionally the extraction process is assisted by ultrasonic treatment. Generally the extraction can be performed at a temperature between 100 and 140 °C and a pressure of between 1 and 8 bar. 13

It was found that ultrasonic treatment assisted in the extraction by creating increased melanoidin yield with higher phenolic and guinone content. Without wishing to be bound to any theory it is thought that the ultrasonic mechanism for the fragmentation of coffee and melanoidins particles partition occurs under ultrasound in two ways, pitting of the defatted coffee grounds surface to produce fines and crack formations, which are further widened and deepened upon prolonged ultrasound exposure, releasing the melanoidins and assisting in the formation phenolic structures within the melanoidin polymers.

The ultrasonic treatment may be conducted at increased temperature of between 20-100°C.

It was found that when the extraction is conducted with assistance of ultrasonic treatment, the melanoidin obtained has a very high phenolics content and also a very high quinone content. With phenolics being part of the polymer structure of the melanoidin and also being a precursor of quinone, both the phenolic content and the quinone content itself is thought to attribute to the suitability of the use of the coffee melanoidins in energy storage devices.

The melanoidins used in the device according to the disclosure was found to have high concentrations of phenolic compounds. Especially preferred are the melanoidins having a phenolics content of at least 3 wt%, more preferably ranging from 3-30 wt? of the total melanoidin, calculated as tyrosol equivalents, most preferably ranging from 5-20 wt2.

The melanoidin used in the devices according to the disclosure was also found to have a relatively high amount 14 of guinone, which is also attributed to the redox capacities of the melanoidin. The quinone content may be as high as at least 3 wt%, or at least 5 wt%, or even at least 10 wt® based on the total weight of the melanoidin.

After extraction the melanoidin may either be dried and particulated directly, for instance by spray drying, ball milling or any other conventional particulation method. It is also possible to co-spray dry the melanoidin and metal salt to create the metal melanoidin chelate. The resulting particle size may be adjusted to the desired final surface area from nano size (i.e below 100 nm) to as much as 500 micrometer particles. The melanoidin may also be converted into so-called nano-fluids. The method for particulation of the melanoidin is known from for instance WO 2012/130349 and WO 2022/268898 which have been incorporated by reference herein for this purpose.

The Electrical energy storage device according to the disclosure preferably is a (redox flow) battery or a superconductor, or a combination thereof.

The present disclosure is further elucidated by an example which merely serves for illustrative purposes and cannot be considered to restrict the present disclosure.

EXAMPLES

Example 1

Utilizing CR2025-type coin cells, an experimental setup featured lithium metal as the counter electrode and a polyvinylidene fluoride (PVDF) membrane as the separator was made. The electrolyte solution was a mix of 1.3 mol :L°%- 1 LiPF 6 in a solvent combination of propylene carbonate 15

(PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a 1:1:1 volume ratio. The anode composition was innovatively designed with 75 wt% melanoidin chelates, complemented by 15 wt® Super P conductive carbon and 10 wt? polytetrafluoroethylene (PTFE) as a binder. Aluminum discs with a diameter of 15 mm were employed as the current collectors. Prior to cell assembly, the electrodes were thoroughly dried at 110 °C for 12 hours to remove any residual solvent.

For electrochemical evaluation, the charge-discharge cycles were conducted using a High Precision Battery Test System, within a voltage range of 0.02 V to 3.0 V against Li/Li"+.

The tests were carried out at a controlled room temperature. Cyclic voltammetry (CV) was performed in a scanning range from 0.02 V to 3.0 V (scan rate: 0.05 mV-s"- 1) on a VoltLab Electrochemical Analyzer. The cycling stability and rate capability of the melanoidin chelates were further evaluated using a s battery cycling system, the PowerTest Series.

EXAMPLE 2

A cost comparison between the costs per kWh of the various electrical energy storage devices has been compiled in

TABLE T.

TABLE I

16

In TABLE II the cost per kWh of different redox flow battery and supercapacitor pairs has been compiled, demonstrating the cost-effectiveness of the electrical energy devices according to the invention.

TABLE IT:

Redox Theoretica Cost

Redox Flow Battery |Potentia |1 Cell Electrolyte [per and Supercapacitor |l (V vs. Voltage Concentratio kWh

Pair SHE) (V) n (M) (3) 0.1-1 M, 531.9 0.1-1 M, 5985.2 155.7

Melanoidin/Potassiu 146.0

Table III gives an overview of typical Materials in electrical energy devices and with their costs, advantages, and disadvantages.

TABLE III

17

Cost ee re [mee]

Graphite $10 - - High electrical - Limited

S20 conductivity specific energy. - requires high temperatures in preparation, - not readily soluble and as such not suitable as electrolyte and also difficult to recycle

Carbon Felt 520 - - Good electrochemical|- Limited $40 performance specific energy - not readily soluble and as such not suitable as electrolyte and also difficult to recycle

Porous Carbon [$20 - - High surface area - Limited

S50 for electrochemical specific energy reactions - not readily soluble and as such not suitable as electrolyte and also difficult to recycle 18

Titanium 520 - - Excellent corrosion | Relatively $40 resistance high cost, - scarce

Platinum $30 - - High catalytic - Very high 560 activity cost, - scarece

Spent Coffee $0 - S1|- Renewable and - Lower

Grounds sustainable electrochemical performance

Cathode

DC]

Vanadium 58 - — High electrochemicallk Limited i

Iron $1 - S5|- Abundant and low - Lower cost electrochemical reactivity

Chromium 55 - - Good electrochemical|- Toxic and i Vel

Zinc 52 — S6|- Relatively low cost | Limited

OT iten

Nickel s15 - - Good electrochemical| High cost and 525 performance potential toxicity

Iodine $10 - — High energy density | Limited $20 cycling stability 19

Claims

CONCLUSIONS

1. Device for electrical energy storage, comprising coffee melancidin.

2. An electrical energy storage device according to claim 1, wherein the melanoidin is a molecular weight fraction (Mw) of melanoidin extracted from spent coffee grounds.

3. An electrical energy storage device according to any one of the preceding claims, wherein the melanoidin is present as an electrolyte in the electrical energy storage device.

4. An electrical energy storage device according to any preceding claim, wherein a first electrolyte comprises melanoidin and a second electrolyte comprises a metal cation dissolved in a solvent.

5. An electrical energy storage device according to claim 4, wherein the second electrolyte comprises iron, copper, sodium, zinc, vanadium or potassium cation.

6. An electrical energy storage device according to any preceding claim, wherein the melanoidin is present as a metal chelate.

7. An electrical energy storage device according to claim 6, wherein the melanoidin is present as a metal chelate, the metal being iron, copper, sodium, zinc, vanadium or potassium.

8. An electrical energy storage device according to any preceding claim, wherein an electrode present in the device is derived from melanoidin.

9. An electrical energy storage device according to any preceding claim, wherein an electrode present in the device comprises melanoidin present as a metal chelate.

10. An electrical energy storage device according to claim 9, wherein the melancidin is present as a metal chelate, the metal being iron, copper, sodium, zinc, vanadium or potassium.

11. Electrical energy storage device according to any one of the preceding claims, wherein the melanoidin is obtained by alkaline extraction from coffee grounds, optionally supported by ultrasonic treatment

12. An electrical energy storage device according to any preceding claim, wherein the melanoidins have a quinone content of at least 3 wt%, more preferably at least 5 wt% of the total melanoidin, most preferably at least 10 wt%. 21

13. An electrical energy storage device according to any preceding claim, wherein the melanoidins have a phenol content of at least 3 wt.%, more preferably ranging from 3-30 wt.% of the total melanoidin, calculated as tyrosole equivalents, most preferably ranging from 10-20 wt.%.

14. An electrical energy storage device according to claim 1, wherein the electrical energy storage device is a redox flow battery or a superconductor, or a combination thereof. 22