WO2018070941A1

WO2018070941A1 - A polymer composition

Info

Publication number: WO2018070941A1
Application number: PCT/SG2017/050515
Authority: WO
Inventors: Yugen Zhang; Jinquan Wang
Original assignee: Agency For Science, Technology And Research
Priority date: 2016-10-14
Filing date: 2017-10-13
Publication date: 2018-04-19

Abstract

The present invention generally relates to a new polymer composition comprising a hexaazatriphenylene (HATN)-type organic framework, which is suitable for use as a cathode in lithium ion batteries. The present invention also relates to a method of preparing of said polymer composition, preferably by condensation between cyclic polyketones and aromatic polyamines.

Description

A Polymer Composition

Technical Field

The present invention generally relates to a polymer composition comprising an organic framework and a method of preparing said polymer composition. The present invention also relates to a cathode material comprising a polymer composition as defined herein and a method of preparing said cathode.

Background Art

Although organic-based electrode materials were conceived as early as their inorganic counterparts, the progress of development of organic-based electrode materials for rechargeable battery applications is relatively slow. Due to the advantages of low-cost and sustainability of naturally abundant elements, environmental benignity, high capacity, excellent structural versatility and flexibility, there has been a resurgence of interest to develop the organic-based electrode materials in view of the current limitations of inorganic cathode materials.

Various types of organic materials, including traditional conducting polymers, organic radical compounds, organodisulfides, carbonyl compounds and carbon/nitrogen compounds, have been investigated as electrode materials. Despite the above-mentioned advantages, the low redox stability, high solubility in electrolytes and low electronic conductivity of the above organic materials are crucial limitations.

There are several important parameters in determining the performance of a solid-state battery electrode: (1) redox potential, (2) redox stability and cycling stability, (3) reaction rate of the redox site, (4) solid-state ion transport, and (5) electronic conduction. The redox reaction rate is an intrinsic property of the redox active moiety. Attaching redox active sites within a porous organic framework could improve the ion diffusion rate, while embedding redox active sites within porous organic conjugated framework could enhance both ion diffusion rate and electronic conductivity.

Theoretically, porous polymer materials are also advantageous as organic cathode material due to their inherent insolubility and attractive porosity. However, efforts towards utilizing porous organic polymers in energy storage applications have been focused more on increasing the capacity by forming electrochemical double- layers. Recently, several examples of using porous organic polymers as organic cathode materials have been reported. However, most of these approaches work towards improving one or two parameters of electrode materials, which, in turn, limits the overall performance of the battery.

HATNA (with its structure reproduced below) is a derivative of hexaazatriphenylene (HAT), which is an electron deficient, rigid, planar, aromatic discotic system. It can be easily synthesized from low-cost chemicals. This type of molecules has been used to build up large conjugated frameworks and themselves have also been studied as energy storage materials in many cases.

HATNA has been studied as organic cathode material in lithium battery; however, due to the high solubility in electrolyte, poor cycling stability was observed. A highly conjugated framework with HATNA core and 1,4-bisethynylbenzene linker was also developed (HATN-CMP) and tested as organic cathode material in lithium-ion battery (LIB). Though these conjugated porous polymers possess high porosity and high electronic conductivity, the cycling stability and rate capacity did not reflect these structure advantages. HATN- CMP exhibits a discharge capacity of 147 mAh g ¹ at 100 mA g ¹ with 71% of theoretical capacity. However, HATN-CMP exhibits 62% capacity retention after 50 cycles, 44% capacity retention at 500 mAh g ¹ as compared to the capacity at 100 mAh g^"1.

Therefore, there is a need to provide an organic cathode material that overcomes, or at least ameliorates, one or more of the disadvantages described above.

Summary

According to a first aspect, there is provided a polymer composition comprising repeat units of Formula (I)

Formula (I);

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from a bond, optionally substituted C_{1 4} alkanediyl and, together with a, a fused poly cyclic heteroaromatic ring structure; and

a is hydrogen or together with linker b form the fused polycyclic heteroaromatic ring structure; or

a monomer of Formula (II)

Formula (II).

Advantageously, polymer compositions as defined herein have moderate porosity and/or conjugating framework. These polymer compositions as defined herein may be used as cathode materials. When used, said cathodes may exhibit high capacity, excellent rate capacity, long- term cycling stability, and/ or near-unity coulombic efficiency.

Therefore, advantageously, the polymer compositions as defined herein have great potential to be used as green cathode materials for high-energy and fast charging storage devices.

In another aspect, there is provided a method of preparing a polymer composition that comprises repeat units of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from the group consisting of a bond, optionally substituted Ci_₄ alkanediyl, and together with a, a fused polycyclic heteroaromatic ring structure; and

a monomer of Formula (II)

Formula (II),

comprising the steps of: a. mixing a cycloketone and an amine in the presence of a solvent and an acid to form a reaction mixture;

b. heating the reaction mixture obtained in step a) to a prescribed reaction temperature for a period of time to produce said polymer composition having repeat units of Formula (I) or monomer of Formula (II).

Advantageously, the process used to prepare the polymer composition as described herein is a wet chemical process under mild and simple conditions. Therefore, said method may be scaled- up in a straightforward manner.

In another aspect, there is provided a cathode comprising a polymer composition that comprises repeat units of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from a bond, optionally substituted Ci_₄ alkanediyl and together with a, a fused poly cyclic heteroaromatic ring structure; and

a is hydrogen or together with linker b form the fused polycyclic heteroaromatic ring structure; or monomer of Formula (II)

Formula (II).

In another aspect, there is provided a method for preparing a cathode comprising the steps of: a) providing an active material comprising a polymer composition that comprises repeat units of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from a bond, optionally substituted Ci_₄ alkanediyl, and together with a, a fused poly cyclic heteroaromatic ring structure; and

a is hydrogen or together with linker b form the fused polycyclic heteroaromatic ring structure; or a monomer of Formula (II)

Formula (II);

mixing a conductive material and optionally a binder with the active material of step a) to form the cathode.

Definitions

The following words and terms used herein shall have the meaning indicated:

"Aryl" as a group or part of a group denotes (i) an optionally substituted monocyclic, or fused polycyclic, aromatic carbocycle (ring structure having ring atoms that are all carbon) preferably having from 5 to 12 atoms per ring. Examples of aryl groups include phenyl, naphthyl, and the like; (ii) an optionally substituted partially saturated bicyclic aromatic carbocyclic moiety in which a phenyl and a C5 7 cycloalkyl or C5 7 cycloalkenyl group are fused together to form a cyclic structure, such as tetrahydronaphthyl, indenyl or indanyl. The group may be a terminal group or a bridging group. Typically an aryl group is a C₆-C₁₈ aryl group.

"Repeat unit or repeating unit" used in the present disclosure refers to a part of polymer whose repetition would produce the complete polymer chain (except the end-groups) by linking or binding the repeat units together successively.

"Heteroaryl" either alone or part of a group refers to groups containing an aromatic ring (preferably a 5 or 6 membered aromatic ring) having one or more heteroatoms as ring atoms in the aromatic ring with the remainder of the ring atoms being carbon atoms. Suitable heteroatoms include nitrogen, oxygen and sulphur. Examples of heteroaryl include thiophene, benzothiophene, benzofuran, benzimidazole, benzoxazole, benzothiazole, benzisothiazole, naphtho[2,3-b]thiophene, furan, isoindolizine, xantholene, phenoxatine, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, tetrazole, indole, isoindole, lH-indazole, purine, quinoline, isoquinoline, phthalazine, naphthyridine, quinoxaline, cinnoline, carbazole, phenanthridine, acridine, phenazine, thiazole, isothiazole, phenothiazine, oxazole, isooxazole, furazane, phenoxazine, 2-, 3- or 4- pyridyl, 2-, 3-, 4-, 5-, or 8- quinolyl, 1-, 3-, 4-, or 5- isoquinolinyl 1-, 2-, or 3- indolyl, and 2-, or 3-thienyl. A heteroaryl group is typically a Q-Qg heteroaryl group. A heteroaryl group may comprise 3 to 8 ring atoms. A heteroaryl group may comprise 1 to 3 heteroatoms independently selected from the group consisting of N, O and S. The group may be a terminal group or a bridging group.

The term "alkanediyl" refers to a non-aromatic divalent group, wherein the alkanediyl group is attached with two σ-bonds, with one or two saturated carbon atom(s) as the point(s) of attachment, a linear or branched, cyclo, cyclic or acyclic structure. The term "alkanediyl" as defined herein, does not include carbon-carbon double or triple bonds, and does not have atoms other than carbon and hydrogen. The groups,— CH₂— (methylene), — CH₂CH₂— ,— CH₂C(CH₃) CH₂— ,— CH₂CH₂CH₂— or— CH₂CH₂CH₂CH₂— are non- limiting examples of alkanediyl groups.

"Fused" has the meaning commonly used in organic chemistry. Two carbocyclic and/or heterocyclic rings are fused if they share a common side, as exemplified in the definition of aryl.

The term "optionally substituted" as used herein means the group to which this term refers may be unsubstituted, or may be substituted with one or more groups independently selected from alkyl, alkenyl, alkynyl, halogen, haloalkyl, haloalkenyl, haloalkynyl, alkynyloxy, hydroxyl, hydroxyalkyl, alkyloxy, alky loxy alkyl, aryl, heteroaryl, arylalkyl.

The term "bond" refers to a linkage between atoms in a compound or molecule. The bond may be a single bond, a double bond, or a triple bond.

The term "heteroaromatic ring" as used herein or when a definition is not otherwise provided, refers to a functional group including a heteroatom selected from N, O, and S in a ring in which all atoms in the cyclic functional group have a p-orbital, wherein the p-orbital is conjugated. For example, the heteroaromatic ring may be a C₂ to C₂₀ heteroaryl group.

The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Detailed Disclosure of Embodiments

Exemplary, non-limiting embodiments of a polymer composition having repeat units of Formula (I) or monomer of Formula (II), will now be disclosed.

The polymer composition may comprise repeat units of Formula (I)

Formula (I);

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from the group consisting of a bond, optionally substituted Ci_₄ alkanediyl, and, together with a, a fused polycyclic heteroaromatic ring structure; and

a monomer of Formula (II)

Formula (II).

The polymer composition having 4 repeat units of Formula (I) is represented by structures (la) or (lb) while the polymer composition of Formula (I) having a and linker b forming the hexaazatriphenylene is represented by structure (Ic) shown below with their respective linker to show the connection between a repeat unit and the subsequent repeat units.

(la),

wherein the dashed lines represent points of attachments to another structure (la) ;

(lb),

wherein the dashed lines represent points of attachments to another structure (lb);

(Ic),

wherein the dashed lines represent points of attachments to another structure (Ic).

As can be seen from the above structures, the linker between the repeat units may be a bond as in structure (la) or optionally substituted C_{_₄ alkanediyl (as in structure (lb)). When the linker is the optionally substituted C_{1 4} alkanediyl as in structure (lb), the preferred alkanediyl group is a methylene. Further, from structure (Ic), the polymer composition is a highly conjugated planar two- dimensional structure. Whereas, in the framework structure (la), HATNA cores are linked together via directly cross linking of two phenyl rings. It is a conjugated system; however, due to the twist angle of phenyl rings, the π-π electron conjugation is limited.

With regard to the polymer composition with 4 repeat units of structure (lb), the HATNA cores are linked via a sp³ carbon of methylene group.

When the monomer of formula (II) is used to produce the polymer composition as described herein, the polymer composition with two repeat units of structure (Ila) is shown below.

(Ila)

Exemplary, non-limiting embodiments of a method to produce the polymer composition comprising repeat units of Formula (I) or monomer of Formula (II) as defined herein, will now be disclosed.

The polymer composition described in the disclosure may be prepared by mixing a cycloketone and an amine in the presence of a solvent and an acid to form a reaction mixture. The reaction mixture may then be heated to a prescribed reaction temperature for a period of time to produce the polymer composition comprising repeat units of Formula (I) or monomer of Formula (II). The method as described above may be carried out under a substantially oxygen-free or inert environment.

The cycloketone used in the reaction to produce polymer composition above may be selected from a group consisting of cyclohexanehexone, cyclopentane- l,2,3,4,5-pentone, cyclobutane- l,2,3,4-tetraone and mixtures thereof. The cycloketone used in the reaction may be cyclohexanehexone.

The amine used in the above reaction may be selected from the following amines :

The amount of the above cycloketone and amine added may be in an appropriate mole ratio. The mole ratio between mole of cycloketone and that of amine required for the method above may be in the range of about 1 : 10 to about 10: 1, about 1 :5 to about 10: 1, about 1 :3 to about 10: 1, about 2:3 to about 10: 1, about 1 : 1 to about 10: 1, about 2: 1 to about 10: 1, about 3: 1 to about 10: 1, or about 5: 1 to about 10: 1. In a preferred embodiment the mole ratio above may be 2:3 or 1 : 1. Exemplary conditions (see below) are provided to further illustrate the relationship between adjusting the mole ratio above and the polymer products obtained.

The polymer synthesis described herein may be undertaken in the presence of suitable solvent such as an organic solvent known in the art or a mixture of two or more organic solvents. Non-limiting examples of the organic solvent include acetonitrile, ethanol, 1- butanol, 2-butanol, tert-butyl alcohol, chlorobenzene, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethyl acetate, ethylene glycol, 1-propanol, 2-propanol, N- Methyl-2-pyrrolidone (NMP), toluene and triethylamine. The preferred organic solvent in the above reaction may be NMP.

The polymer synthesis described herein may be carried out in the presence of an acid known in the art or a mixture of two or more acids. The acid used may be organic acid, inorganic acid, weak acid, strong acid, monoprotic acid, polyprotic acid or other suitable acids. Non-limiting examples of such acids include sulphuric acid, hydrochloric acid, acetic acid, nitric acid, formic acid, citric acid, malic acid, lactic acid, and carbonic acid. In a preferred embodiment, the acid used in the above reaction may be sulphuric acid.

When the cycloketone is mixed with amine to form a mixture, the mixture may undergo a deoxygenation step to ensure that the reaction will proceed under substantially oxygen-free or inert environment. Such inert condition may be achieved by introducing a continuous flow of inert gas such as nitrogen, argon, helium or a mixture thereof into the above mixture for a period of time or subjecting the mixture above to an ultrasonication procedure. Prior to the addition of solvent and acid, the mixture may be optionally placed in an ice bath so as to reduce the temperature of the mixture. The solvent and acid are subsequently added to the mixture of cycloketone and amine to form a reaction mixture. The solvent may be added to the mixture of cycloketone and amine prior to, at the same time as or after the addition of the acid. The reaction mixture resulted from the mixing of the above components may be in a homogeneous phase, where all components are substantially miscible to each other i.e. only one phase exists. Hence, the reaction may proceed with a minimum mass-transfer resistance.

Similar as above, the solvent or the mixture of solvents and acid or the mixture of acids used in the polymer synthesis may have to be substantially free of oxygen. This inert condition may be achieved by the method known in the art such as providing a continuous flow of inert gas into the solution. Regardless of the method used, the ultimate objective of this step is to provide an oxygen-free environment.

The temperature of the mixture above may be optionally lowered by indirectly contacting the mixture with a suitable cooling agent or a coolant selected from dry ice, ice, and cold water. The coolant may be optionally mixed with water, a solvent or a mixture of solvent as defined above. The coolant may be further optionally mixed with a salt as defined below when a further lower temperature is desired. When the reaction mixture is placed in an ice bath, the temperature of said mixture may be lowered to a temperature that is below room temperature such as about 0°C to 10°C, about 1°C, about 2°C, about 3°C, about 4°C, about 5°C, about 6°C, about 7°C, about 8°C, about 9°C, or about 10°C. The step of lowering the temperature here is not limited and therefore it may be undertaken during the addition of the solvent and or acid to the mixture of cycloketone and amine or after the addition is completed.

If the temperature of the above mixture is lowered, said mixture may be optionally preheated to room temperature, which is about 20°C to 30°C, about 20°C to 25°C, or 25°C to 30°C, after which it is further heated to attain a prescribed reaction temperature of about 60°C to 220°C, about 60°C to 80°C, about 60°C to 100°C, about 60°C to 120°C, about 60°C to 140°C, about 60°C to 160°C, about 60°C to 180°C, about 60°C to 200°C, about 80°C to 100°C, about 80°C to 120°C, about 80°C to 140°C, about 80°C to 160°C, about 80°C to 180°C, about 80°C to 200°C, about 80°C to 220°C, about 100°C to 120°C, about 100°C to 140°C, about 100°C to 160°C, about 100°C to 180°C, about 100°C to 200°C, about 120°C to 140°C, about 120°C to 160°C, about 120°C to 180°C, about 120°C to 200°C, about 120°C to 220°C, about 140°C to 160°C, about 140°C to 180°C, about 140°C to 200°C, about 140°C to 220°C, about 160°C to 170°C, about 160°C to 180°C, about 160°C to 200°C, about 160°C to 220°C, about 170°C to 180°C, about 180°C to 200°C, about 180°C to 220°C, or about 200°C to 220°C. In an embodiment, the preferred range of prescribed reaction temperature is about 60°C to 170°C.

The pre-heating process above may be undertaken for about 1 hour to 6 hours, about 1 hour to 2 hours, about 1 hour to 3 hours, about 1 hour to 4 hours, about 1 hour to 4 hours, about 1 hour to 5 hours, about 2 hours to 3 hours, about 2 hours to 4 hours, about 2 hours to 4 hours, about 2 hours to 5 hours, about 2 hours to 6 hours, about 3 hours to 4 hours, about 3 hours to 4 hours, about 3 hours to 5 hours, about 3 hours to 6 hours, 4 hours to 5 hours, about 4 hours to 6 hours, or about 5 hours to 6 hours. Once the reaction temperature above is attained, the reaction may proceed for about 6 hours to 36 hours, about 6 hours to 12 hours, 6 hours to 14 hours, about 6 hours to 16 hours, about 6 hours to 18 hours, about 6 hours to 20 hours, about 6 hours to 22 hours, about 6 hours to 24 hours, about 6 hours to 28 hours, about 6 hours to 32 hours, about 6 hours to 36 hours, about 12 hours to 14 hours, about 12 hours to 16 hours, about 12 hours to 18 hours, about 12 hours to 20 hours, about 12 hours to 22 hours, about 12 hours to 24 hours, about 12 hours to 28 hours, about 12 hours to 32 hours, about 12 hours to 36 hours, about 14 hours to 16 hours, about 14 hours to 18 hours, about 14 hours to 20 hours, about 14 hours to 22 hours, about 14 hours to 24 hours, about 14 hours to 28 hours, about 14 hours to 32 hours, about 14 hours to 36 hours, about 18 hours to 20 hours, about 18 hours to 22 hours, about 18 hours to 24 hours, about 18 hours to 28 hours, about 18 hours to 32 hours, about 18 hours to 36 hours, about 20 hours to 24 hours, about 20 hours to 28 hours, about 20 hours to 32 hours, about 20 hours to 36 hours, about 24 hours to 28 hours, about 24 hours to 32 hours, about 24 hours to 36 hours, about 28 hours to 32 hours, about 28 hours to 36 hours, or about 32 hours to 36 hours.

Upon completion of reaction, the reaction mixture may be cooled down to the room temperature as defined above followed by the addition of a suitable solution or solvent to initiate a precipitation process. Such solvent may be an aqueous or an organic solvent known in the art as long as it is able to initiate the precipitation process. Non-limiting examples of such solvent include water, a salt solution and the organic solvent as defined above.

Non-limiting examples of salt solution above includes neutral, basic and acidic salts such as sodium chloride, potassium chloride, sodium carbonate, sodium bicarbonate, sodium acetate, or ammonium chloride solution.

Solid form of the polymer composition obtained from the precipitation procedure above may be separated from the reaction mixture via a suitable separation technique known in the art. Non-limiting examples of such separation technique include filtration, centrifugation, extraction and decantation. The resulting solid product may be optionally subjected to drying at about 50°C to about 80°C, about 50°C to about 60°C, about 50°C to about 70°C, about 60°C to about 70°C, about 60°C to about 80°C, or about 70°C to about 80°C.

The drying above may be undertaken optionally under vacuum for a period of about 8 hours to 16 hours, about 8 hours to 10 hours, about 8 hours to 12 hours, about 8 hours to 14 hours, about 10 hours to 12 hours, about 10 hours to 14 hours, about 10 hours to 16 hours, about 12 hours to 14 hours, about 12 hours to 16 hours, or about 14 hours to 16 hours.

Once the polymer composition above is recovered, the polymer composition may be subjected for material characterization. The non-limiting examples of such characterization include Fourier Transform Infrared (FT-IR), solid state Nuclear Magnetic Resonance (NMR), X-ray powder diffraction (XRD), and suitable methods to evaluate the electrochemical properties of the composition described herein.

In the present disclosure, there is provided the exemplary conditions for preparing the polymer composition as defined above. The exemplary conditions are provided for illustration purposes only and it is to be understood that the conditions are not limited to these exemplary conditions.

Exemplary condition 1

When cyclohexanehexone and ¾N

are mixed at a mole ratio of 2:3, in the presence of NMP and sulphuric acid, followed by heating the resulting mixture to 170°C for about 12 hours, a polymer with a and linker b forming the hexaazatriphenylene may be formed and may be re resented by the following structure (Ic):

(ic) ;

Exemplary condition 2

Cyclohexanehexone and

are mixed at a mole ratio of 2:3, in the presence of NMP and sulphuric acid, followed by heating the resulting mixture to 60 °C for about 12 hours, a polymer having 4 repeat units of Formula (I) represented by structure (la) below may be formed.

(la);

wherein the dashed lines represent points of attachments to another structure (la).

Exemplary condition 3

Cyclohexanehexone and ^Ν¾ ^Ν¾ are mixed at a mole ratio of 2:3, in the presence of NMP and sulphuric acid, followed by heating the resulting mixture to 60 °C for about 12 hours, a polymer having 4 repeat units of Formula (I) represented by structure (lb) below may be formed.

(lb);

wherein the dashed lines represent points of attachments to another structure (lb).

Exemplary condition 4

Cyclohexanehexone and

are mixed at a mole ratio of 1 : 1, in the presence of NMP and sulphuric acid, followed by heating the resulting mixture to 60 °C for about 12 hours, a polymer having two repeat units of Formula (II) represented by structure (Ila) below may be formed.

wherein the dashed lines represent points of attachments to another structure (Ila).

As can be seen from the exemplary conditions and the examples provided in the present disclosure, the process for preparing the polymer composition as described herein is undertaken using mild and simple conditions. Hence, this method may be scaled-up in a straightforward manner. Exemplary, non-limiting embodiments of a cathode comprising the polymer composition disclosed herein and method of making said cathode, will now be disclosed.

There is provided a cathode comprising the polymer composition that comprises repeat units of Formula (I) or monomer of Formula (II) as described herein.

The cathode comprising the polymer composition that comprises repeat units of Formula (I) or monomer Formula (II) may be prepared by mixing the active material with a conductive material that may include graphene oxide, graphite oxide, or other conductive carbon materials and a binder in an appropriate ratio. It may be desirable that a higher polymer (active material) ratio is used.

The method of mixing the active material i.e. polymer composition defined herein with the conductive material and the binder stated above may be adopted from the method known in the art. These materials may be further mixed in the presence of a solvent, and the thus-obtained paste may be coated on a metal sheet such as aluminum sheet using a coater. The solvent may be then removed under vacuum at about 60°C, about 65°C, about 70°C, about 75°C, about 80°C, about 85°C, about 90°C, about 95°C, about 100°C, about 105°C, about 110°C, or about 115°C for about 6 to 16 hours, about 6 to 9 hours, about 6 to 12 hours, about 9 to 12 hours, about 9 to 16 hours, preferably for about 12 hours.

The cathode material as described herein may be assembled in a hermetically sealed two- electrode cell or system and this cell is used for electrochemical experiments to further evaluate the electrochemical performance of the cathode comprising the polymer composition as described herein. The cathode may be separated from the lithium anode by a film known in the art such as polyethylene porous film imbibed with an equimolar LiCF₃S0₃/G4 (tetraglyme) salt. The layers obtained from the assembly above may be pressed between two current collectors, one in contact with the cathodic material and the other in contact with a lithium disk. All cells are preferably assembled in a substantially free-oxygen environment such as argon-filled glovebox.

As mentioned above, when used, the cathodes comprising the polymer composition as described above may exhibit high capacity, excellent rate capacity, long- term cycling stability, and/ or near-unity coulombic efficiency. Therefore, advantageously, the polymer compositions as defined herein may potentially be used as green cathode materials for high-energy and fast charging storage devices.

Brief Description of Drawings

The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig.l [Fig. 1] is a Fourier Transform Infrared (FT-IR) spectra obtained from characterization of the polymer composition synthesized in examples 1, 2, 3 and 4. HATNA-1 indicates the polymer composition of example 1 ; HATNA-2 indicates the polymer composition of example 2; HATNA-3 indicates the polymer composition of example 3; and PTAPQ indicates the polymer composition of example 4.

Fig.2

[Fig. 2] is a solid-state ¹³C nuclear magnetic resonance (NMR) spectra obtained from characterization of the polymer composition synthesized in examples 1, 2, 3 and 4. (A) shows the solid- state ¹³C NMR spectra for the polymer composition of example 1 ; (B) shows the solid- state ¹³C NMR spectra for the polymer composition of example 2; (C) shows the solid- state ¹³C NMR spectra for the polymer composition of example 3; and (D) shows the solid- state ¹³C NMR spectra for the polymer composition of example 4.

Fig.3

[Fig. 3] is a number of Nitrogen adsorption-desorption isotherms curves obtained from porosity characterization of the polymer composition synthesized in examples 1, 2, and 3. (A) shows the Nitrogen adsorption-desorption isotherms curve for the polymer composition of example 1; (B) depicts the Nitrogen adsorption-desorption isotherms curve for the polymer composition of example 2; (C) shows the Nitrogen adsorption-desorption isotherms curve for the polymer composition of example 3.

Fig.4

[Fig. 4] is a number of voltage profile curves obtained from the polymer composition synthesized in examples 1, 2, 3, and 4. (A) shows the voltage profile curve (voltage vs. specific capacity) for the polymer composition of example 1 ; (B) depicts the voltage profile curve (voltage vs. specific capacity) for the polymer composition of example 2; (C) shows the voltage profile curve (voltage vs. specific capacity) for the polymer composition of example 3; (D) shows the voltage profile curve (voltage vs. specific capacity) for the polymer composition of example 4.

Fig.5

[Fig. 5] is a number of specific capacity vs. cycle number curves to evaluate the rate capacities of the polymer composition synthesized in examples 2, 3, and 4. (A) shows the specific capacity vs. cycle number curve for the polymer composition of example 2; (B) depicts the specific capacity vs. cycle number curve for the polymer composition of example 3; (C) shows the specific capacity vs. cycle number curve for the polymer composition of example 4.

Fig.6

[Fig. 6] is a number of Nyquist plots to depict the electrochemical impedance spectroscopy (EIS) of the cathodes comprising the polymer composition synthesized in examples 1, 2, 3, and 4. (A) shows the electrochemical impedance spectroscopy (EIS) for the polymer composition of example 1 ; (B) depicts the electrochemical impedance spectroscopy (EIS) for the polymer composition of example 2; (C) shows the electrochemical impedance spectroscopy (EIS) for the polymer composition of example 3; (D) shows the electrochemical impedance spectroscopy (EIS) for the polymer composition of example 4.

Fig.7

[Fig. 7] is a number of specific capacity vs. cycling number curves to evaluate the cycling stability and coulombic efficiency of these polymer cathodes at a current density of 500 mAh g Voltage profile curve obtained from the polymer composition synthesized in examples 1, 2, 3, and 4. (A) shows the specific capacity vs. cycling number curve for the cathode comprising polymer composition of example 1 ; (B) depicts the specific capacity vs. cycling number curve for the cathode comprising the polymer composition of example 2; (C) shows the specific capacity vs. cycling number curve for the cathode comprising the polymer composition of example 3; (D) shows the specific capacity vs. cycling number curve for the cathode comprising polymer composition of example 4.

Examples

Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1: Preparation of HATNA-1

Cyclohexanehexone octahydrate (0.193 g, 0.6 mmol, purchased from ACROS organics of New Jersey of the United States of America) and 1,2,4,5-benzenetetramine tetrahydrochloride (0.269 g, 0.9 mmol, purchased from BEPHARM Limited of Shanghai of China) were charged in a 20 mL two -necked flask under argon gas and placed in an ice bath. 5-mL of deoxygenated N-Methyl-2-pyrrolidone (NMP, purchased from Tedia of Fairfield- Ohio of the United States of America) with two drops of sulfuric acid was slowly added. The reaction mixture was warmed up to room temperature for 3 hours. The ice bath was replaced with oil bath and heated to 170°C for overnight. The flask was then cooled to room temperature (such as 25°C) and water was added. The solid product that precipitated was collected by centrifugation. The resultant dark solid was further Soxhlet extracted with methanol, and dried at 60°C under vacuum oven for 12 hours to give HATNA-1 in 90% yield (refer to the reaction scheme provided below) .

HATNA-1

The representative structure of HATNA- 1 having repeat units of Formula (I) with linker b forming the hexaazatriphenylene is depicted in structure (Ic) below.

(Ic)

Example 2: Preparation of HATNA-2

Cyclohexanehexone octahydrate (0.193 g, 0.6 mmol purchased from ACROS Organics of New Jersey of the United States of America) and 3, 3'-diaminobenzidine (0.195 g, 0.9 mmol purchased from Sigma-Aldrich of Saint Louis, Missouri of the United States of America) were charged in a 20 mL two-necked flask under argon gas and placed in ice bath. Deoxygenated NMP (purchased from Tedia of Fairfield-Ohio of the United States of America) (5 mL) with two drops of sulfuric acid was slowly added. The reaction mixture was warmed up to room temperature (such as 25°C) for 3 hours. The ice bath was subsequently replaced with oil bath and heated to 60°C for overnight. Then, the flask was cooled to room temperature and water was added. The solid product that precipitated was collected by centrifugation. The resultant dark solid was further Soxhlet extracted with methanol, and dried at 60°C under vacuum oven for 12 hours to give HATNA-2 in quantitative yield (refer to the reaction scheme below) .

J I * HATNA-2.

The representative structure of HATNA-2 having 4 repeat units of Formula (I) is depicted in structure (la) below.

(Ia)

wherein the dashed lines represent points of attachments to another structure (Ia) .

Example 3: Preparation of HATNA-3

Cyclohexanehexone octahydrate (0.193 g, 0.6 mmol purchased from ACROS organics of New Jersey of the United States of America) and 4, 4'- methylenebisbenzene-l,2-diamine (0.205 g, 0.9 mmol, which was synthesized from nitro-2-aminobenzene (purchased from Sigma-Aldrich of Saint Louis, Missouri of the United States of America)) were charged in a 20 mL two- necked flask under argon gas and placed in ice bath. Deoxygenated NMP (purchased from Tedia of Fairfield-Ohio of the United States of America) (5 mL) with two drops of sulfuric acid was slowly added. The reaction mixture was warmed up to room temperature (such as 25°C) for 3 hours. The ice bath was replaced with oil bath and heated to 60°C for overnight. The flask was subsequently cooled to room temperature and water was added. The solid product that precipitated was collected by centrifugation. The resultant dark solid was further Soxhlet extracted with methanol, and dried at 60°C under vacuum oven for 12 hours to give HATNA-3 in quantitative yield. The reaction above is depicted by the reaction scheme below.

HATNA-3

The representative structure of HATNA-3 having 4 repeat units of Formula (I) is depicted in structure (lb) below.

Example 4: Preparation of PTAPAQ

Cyclohexanehexone octahydrate (0.312 g, 1 mmol, purchased from ACROS organics of New Jersey of the United States of America) and 3, 3'-diaminobenzidine (0.214 g, 1 mmol, purchased from Sigma-Aldrich of Saint Louis, Missouri of the United States of America) were charged in a 20 mL two-necked flask under argon gas and placed in ice bath. Deoxygenated NMP (purchased from Tedia of Fairfield-Ohio of the United States of America) (5 mL) with two drops of sulfuric acid was slowly added. The reaction mixture was warmed up to room temperature (such as 25°C) for 3 hours. The ice bath was replaced with oil bath and heated to 170°C for overnight. Then, the flask was cooled to room temperature and water was added. The solid product that precipitated was collected by centrifugation. The resultant dark solid was further Soxhlet extracted with methanol, and dried at 60°C under vacuum oven for 12 hours to give PTAPAQ in quantitative yield. The synthesis above is summarized in the reaction scheme below.

The representative structure of PTAPAQ having 2 repeat units of Formula (II) is depicted in structure (Ila) below.

(Ila)

Example 5: Materials Characterization a. FTIR

The polymers of examples 1, 2, 3, and 4 were characterized by Fourier Transform Infrared (FTIR, performed on a PerkinElmer Spectrum 100 FT-IR) (Fig. 1) and solid-state NMR (performed on a Bruker AV400 NMR spectrometer) (Fig. 2). In FTIR spectra, the strong peak around 1495 cm ¹ can be assigned to C=N stretching. The broad peaks observed in the range of 3300 to 3700 cm^"1 for HATNA-1, HATNA-2 and HATNA-3 suggest that the reaction was incomplete, thereby leaving a significant amount of amine terminal groups in the polymer materials. A much weaker peak was observed in the same range of 3300 to 3700 cm ¹ for PTAPAQ which corresponds to the minor amine terminal group in the structure. b. Solid-state NMR

For solid- state ¹³C NMR, peaks from 110 to 150 ppm correspond to the aromatic carbon in benzene ring and aza rings. There is a very weak peak observed at 175 ppm in HATNA-1, HATNA-2 and HATNA-3 indicating small amount of terminal C=0 bond. For PTAPAQ, there is a relatively much stronger peak observed at 176 ppm which corresponds to the C=0 bonds in the linear polymer structure.

c. Porosity Analysis

The porosity of the synthesized polymers was evaluated by Nitrogen adsorption-desorption isotherms (Fig. 3). The Brunauer-Emmett-Teller (BET) surface areas for HATNA-1, HATNA- 2 and HATNA-3 are about 43, 384 and 288 m²/g. The total pore volumes are about 0.10, 0.27 and 0.20 cm³/g, respectively, suggesting that HATNA-2 and HATNA-3 have better porosity and more complete framework than HATNA-1. The porosity analysis was performed on a Micromeritics ASAP 2020.

Example 6: Preparation of Cathode

The synthesized polymer materials were evaluated as cathode for lithium battery. Cathodes were prepared by mixing active material such as the polymer composition synthesized in examples 1, 2, 3 and 4 with graphene oxide (sheet, Sigma- Aldrich of Saint Louis, Missouri of the United States of America) and poly(vinylidene fluoride (PVDF) (purchased from Solvay of Houston, Texas of the United States of America) as a binder (ratio: 4/5/1 wt %). These materials were mixed with (N-methyl-2-pyrrolidone) NMP (purchased from Tedia of Fairfield-Ohio of the United States of America) as a solvent, and the thus-obtained paste was coated on aluminum sheet using a coater. NMP was then removed under vacuum at 80°C for 12 hours. Hermetically sealed two-electrode cells were used for electro-chemical experiments. The cathode was separated from the lithium anode by the polyethylene porous film (purchased from Celgard of Charlotte, North Carolina of the United States of America) imbibed with an equimolar LiCF₃S0₃/G4 (tetraglyme) salt. The three layers were pressed between two current collectors, one in contact with the cathodic material and the other in contact with a lithium disk. All cells were assembled in an argon-filled glovebox. The cyclic voltammetry (CV) experiments were undertaken using a CHI 760C electrochemical workstation (purchased from CH Instruments, Inc., Texas of the United States of America). The battery testing system (CT2001A, purchased from Wuhan LAND electronics Co. Ltd. of China) was used to evaluate the electrochemical performance.

Example 7: Electrochemical Performance

a. Voltage Profile

The voltage profiles of synthesized polymers were measured as shown in Fig. 4. HATNA-1 exhibits sloping charge and discharge curves at about 2.6 eV and the reversible discharge capacity reaches 34 mAh g ¹ at 50 niA g^"1. This value is only about 8% of its theoretical capacity (476 mAh g^"1) which may be due to the incomplete network structure. Interestingly, porous polymer HATNA-2 exhibits very high initial charge capacity of 831 mAh g^"1. However, this capacity is irreversible with the first discharge capacity of 563 mAh g^"1. The discharge capacity decreases gradually and becomes reversible and stable at 10^th cycle with the value of 333 mAh g ¹ which is 79.5% of theoretical capacity.

The irreversible high capacities of initial runs may be due to the defects of the organic porous framework. Since the porous polymer material was synthesized with wet chemical process under relatively mild conditions, there is significant amount of defects in the framework which can be seen from its poor crystalline property (XRD) and moderate surface area (384 m² /g). Similarly, HATNA-3 also exhibits very high initial charge capacity of 498 mAh g ¹ and an irreversible discharge capacity of 350 mAh g^"1. The reversible discharge capacity at 10^th cycle is 171 mAh g ¹ which is about 42.3% of its theoretical capacity.

Linear polymer PTAPAQ exhibits initial charge capacity of 589 mAh g ¹ and an irreversible discharge capacity of 451 mAh g^"1. The reversible discharge capacity at 10^th cycle is 283 mAh g ¹ which is 52.1% of its theoretical capacity. All three new polymer cathode materials exhibit very high initial charge/discharge capacities, discharge potentials at about 2.4 eV and also high reversible discharge capacities among 171 to 333 mAh g^"1. b. Rate Capacity

The rate capacities of three polymer cathodes (polymer composition of examples 1, 2 and 3) were investigated by cycling at various high current densities (Fig. 5). As the current density increased from 50 mA g ¹ to 4000 mA g \ the capacities of all three polymer cathodes decreased slowly. All three polymer cathodes exhibited very good high rate capacities. When batteries were charged and discharged at current density of 2 A g \ capacities of HATNA-2, HATNA-3 and PTAPAQ cathodes are 174, 112 and 141 mAh g which correspond to 65%, 56% and 62% of capacity retention of charged and discharged at current density of 100 mA g^"1. The high capacities were rebounded back as the current density was reduced from 4000 mA g ¹ to 100 mA g^"1. This result indicates that these polymer cathodes enable a quick charge and discharge process. Batteries with these polymer cathodes can therefore be potentially charged and discharged within minutes with high capacities. c. Impedance

It is known in the art that factors determining rate capacity are mainly due to electronic conductivity and solid-state ion transportation for similar redox materials. The electrochemical impedance spectroscopy (EIS) results for HATNA-1, HATNA-2, HATNA- 3 and PTAPAQ are shown in the form of Nyquist plots in Fig. 6. From the diameters of semicircles at high-to- medium frequency region and the straight tails at the low frequency region, it can be concluded that the order of the resistance of ion transportation and charge transfer for tested four polymer cathodes is HATNA-1 < HATNA-2 < PTAPAQ < HATNA-3.

The low charge transfer resistance and diffusion resistance are related to the highly conductive and porous polymer network, which are in accordance with the excellent rate capacity (Fig. 5) and indicated good cycling property (Fig. 7).

Herein, HATNA-1 possesses a highly conjugated 2D framework which corresponds to its low resistance. The 2D framework of HATNA-2 is also partially conjugated with twisted phenyl rings. PTAPAQ is a conjugated linear polymer, while HATNA-3 is a non-conjugated porous polymer network. The non-conjugated network structure of HATNA-3 determines its high resistance and relatively low rate capacity. In fact, HATNA-3 exhibits rather similar rate capacity, especially for the high current density capacity (Fig. 5), as compared with HATNA-2 and PTAPAQ. This result may be due to the partially reducing -CH₂- during redox reaction which will enhance the electron conductivity of the polymer framework. d. Cycling stability and coulombic efficiency

Fig. 7 shows the long-term cycling stability and coulombic efficiency of these polymer cathodes at a current density of 500 mAh g^"1. HATNA-1 exhibits excellent cycling stability with no capacity lost during 120 cycles although at very low capacity. The capacity of HATNA-2 attenuates quickly in the first 20 cycles due to the irreversible reactions and the formation of SEI (solid electrolyte interface) film, and then the capacity is generally stable with slow decay and finally stabilizes at 165 mAh g ¹ from 800 to 1200 cycles, which is 92% of capacity retention compared with the stabilized capacity after 20 cycles. The capacity of HATNA-3 also attenuates quickly in the first 20 cycles (153 mAh g^"1) and then the capacity is slowly decaying and finally stabilizing at 144 mAh g \ which is 94% of capacity retention compared with the stabilized capacity after 20 cycles.

The columbic efficiency also keeps stable at 100% during 1200 cycles for all samples. Both the stability and the capacity of HATNA-2 and HATNA-3 are much higher than HATN-CMP cathode, where the stability and capacity of HATN-CMP are 62% after 50 cycles and 44% capacity retention at 500 mAh g \ respectively. In comparison to HATN, the capacity of HATNA-2 and HATNA-3 are also much higher than HATN-based cathode, whereas the capacity retentions for HATN-based cathode are 50% and 30% after 50 and 100 cycles, respectively. Similarly, PTAPAQ cathode also suffers initial capacity lost in first 20 cycles, and then the capacity is more stable with slow decay within 680 cycles and finally stabilizes at 153 mAh g ¹ from 680 to 1200 cycles (90% of capacity retention compared with the stabilized capacity after 20 cycles) with constant 100% columbic efficiency.

Industrial Applicability

The polymer compositions described in the present disclosure can be used as cathode materials. Since, these polymers are shown to exhibit high capacity, excellent rate capacity, long- term cycling stability, and or a near-unity coulombic efficiency, they therefore allow a broader application of lithium-ion battery using the cathode comprising the polymer composition as described herein. The application of the present technology will allow the use of lithium-ion battery in many applications such as electronics (including communication, healthcare and transportation). In addition, these new polymer compositions have great potential as green cathode materials for high-energy and fast charging storage devices.

The lithium-ion batteries that use the cathode comprising the polymer composition as described in the present disclosure may be used as high density power sources for a wide variety of applications for example in automobile (electric vehicles including electric cars, hybrid vehicles, electric bicycles, personal transporters and advanced electric wheelchairs , radio-controlled models, model aircraft, aircraft), portable devices (mobile phone/smartphone, laptops, tablets, digital cameras and camcorders), in power tools (including cordless drills, sanders, and saws), or in healthcare (portable medical equipment such as monitoring devices, ultrasound equipment, and infusion pumps).

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

A polymer composition comprising repeat units of Formula (I)

Formula (I);

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from the group consisting of a bond, optionally substituted Ci_₄ alkanediyl and, together with a, a fused polycyclic heteroaromatic ring structure; and

a monomer of Formula (II)

Formula (II).

2. The polymer composition according to claim 1, where in Formula (I), a is hydrogen and linker b is bond.

3. The polymer composition according to claim 1, where in Formula (I), a is hydrogen and linker b is C_{1 4} alkanediyl.

4. The polymer composition according to claim 3, wherein linker b is Q alkanediyl.

5. The polymer composition according to claim 1, where in Formula (I), the fused polycyclic heteroaromatic ring structure is a hexaazatriphenylene.

6. The polymer composition according to claim 1 or 2, wherein the polymer having 4 repeat units of Formula (I) is represented by the following structure (la)

(la),

wherein the dashed lines represent points of attachments to another structure (la) .

7. The polymer composition according to any one of claims 1, 3 or 4, wherein the polymer having 4 repeat units of Formula (I) is represented by the following structure

(lb),

8. The polymer composition according to claim 1 or 5, wherein the polymer with a and linker b forming the hexaazatriphenylene is represented by the following structure (Ic)

(Ic),

9. The polymer composition according to claim 1, where in Formula (II), the polymer having two repeat units of Formula (II) is represented by the following structure (Ila)

o

(Ila),

wherein the dashed lines represent points of attachments to another structure (Ila) .

10. A method of preparing a polymer composition comprising a monomer of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from the group consisting of a bond, optionally substituted Ci_₄ alkanediyl and together with a, a fused polycyclic heteroaromatic ring structure; and

a is hydrogen or together with linker b, form the fused polycyclic ring structure;

or monomer of Formula (II)

Formula (II),

b. heating the reaction mixture obtained in step a) to a prescribed reaction temperature for a period of time to produce said polymer composition of Formula (I) or Formula (II).

11. The method according to claim 10, wherein the cycloketone is selected from a group consisting of cyclohexanehexone, cyclopentane-l,2,3,4,5-pentone, cyclobutane-l,2,3,4-tetraone and mixtures thereof.

12. The method according to claim 10 or 11 , wherein the amine is selected from the group consisting of

13. The method according to any one of claims 10 to 12, wherein the solvent is acetonitrile, ethanol, 1-butanol, 2-butanol, teri-butyl alcohol, chlorobenzene, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethyl acetate, ethylene glycol, 1-propanol, 2-propanol, N-Methyl- 2-pyrrolidone (NMP), toluene, triethylamine or the combination thereof.

14. The method according to any one of claims 10 to 13, wherein the acid is sulphuric acid, hydrochloric acid, acetic acid, nitric acid, formic acid, citric acid, malic acid, lactic acid, carbonic acid or the combination thereof.

15. The method according to any one of claims 10 to 14, wherein said method further comprises the step of:

c. lowering the temperature of the reaction mixture to below room temperature.

16. The method according to claim 15, wherein the method further comprises, before step (b), the step of:

al . pre-heating the reaction mixture to room temperature.

17. The method according to any one of claims 10 to 16, wherein the prescribed reaction temperature is from 60°C to 220°C.

18. The method according to any one of claims 10 to 17, wherein the period of time during heating of the reaction mixture is from 6 hours to 36 hours.

19. A cathode comprising a polymer composition that comprises repeat units of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein b is selected from a bond, optionally substituted Ci_₄ alkanediyl and together with a, a fused polycyclic heteroaromatic ring structure; and

Formula (II).

20. A method for preparing a cathode comprising the steps of:

a. providing an active material comprising a polymer composition that comprises repeat units of Formula (I)

Formula (I)

wherein the repeat units of Formula (I) are bonded to each other by a linker b, wherein linker b is selected from a bond, optionally substituted Ci_₄ alkanediyl and, together with a, a fused polycyclic heteroaromatic ring structure; and

Formula (II)

b. mixing a conductive material and optionally a binder with the active material of step a) to form the cathode.