Halogen-free polymer binder for positive electrodes

Abstract

To provide a halogen-free polymer binder for battery electrodes that has a low environmental impact. [Solution] The present invention relates to formula (I) Regarding halogen-free polymer binders for cathodes according to TIFF2026057505000015.tif42170, R1 is (CH2) x -R3 is where x is 1 to 20, and R3 is H or CN; R2 is C1 to C 10 Alkyl or C2-C 10 The material is an alkenyl; and n is between 50 and 5000. The present invention further relates to a cathode comprising a halogen-free polymer binder, and a method for producing the halogen-free polymer binder.

Description

[Technical Field]

[0001] This invention relates to a halogen-free polymer binder for a positive electrode. Furthermore, this invention relates to a positive electrode comprising the halogen-free polymer binder, and to a method for producing the halogen-free polymer binder. [Background technology]

[0002] In recent years, the battery industry has begun to move away from fluorine-containing binders, particularly for electrodes and positive electrodes, due to several significant problems and drawbacks. From an environmental perspective, fluorine-based materials such as polyvinylidene fluoride (PVDF) release persistent organic pollutants that are difficult to decompose during manufacturing and disposal, potentially causing long-term damage to ecosystems. These processes are also linked to the massive emission of greenhouse gases, accelerating climate change. Such materials also raise serious health and safety concerns, as workers are exposed to hazardous chemicals during manufacturing and handling. Furthermore, battery fires can release highly toxic gases such as hydrogen fluoride, posing serious dangers to both humans and the environment.

[0003] In terms of performance, the use of fluorine-containing binders such as PVDF necessitates the use of hazardous organic solvents like N-methyl-2-pyrrolidone (NMP) in electrode manufacturing, complicating manufacturing and recycling processes. NMP is not only harmful to human health but also to the environment, making battery recycling difficult and unsustainable. Furthermore, increasing global regulatory pressure, with governments and regulators imposing stricter restrictions on the use of hazardous substances in industrial processes, makes reliance on fluorine-based materials increasingly difficult. All these factors are driving the industry to seek safer and more sustainable alternatives to fluorine-containing binders. [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to overcome one or more of the aforementioned drawbacks. The object of the present invention is to provide a halogen-free polymer binder for battery electrodes, particularly for positive electrodes. The object is to provide an electrode binder that has a low environmental impact by not containing halogens, particularly fluorides. The object is to manufacture such a binder by a process that minimizes the use of harmful solvents or eliminates the need for such solvents, thereby reducing the environmental footprint.

[0005] Furthermore, the aim is to provide electrodes, particularly positive electrodes, containing such halogen-free polymer binders, which have at least equivalent, and in some cases superior, performance to existing positive electrodes containing halogen-containing binders such as PVDF. This performance includes both mechanical properties, i.e., the ease of handling of the positive electrode during assembly into a battery, and the electrochemical performance of the positive electrode within the battery.

[0006] In other words, the present invention aims to provide a halogen-free process and binder, thereby offering a more sustainable process, while ensuring that the performance of the cathode containing this binder is equivalent to that of halogen-containing cathodes well known in the art. [Means for solving the problem]

[0007] A first aspect of the present invention discloses a halogen-free polymer binder for a cathode as described in the appended claims.

[0008] The halogen-free polymer binder is of formula (I)

[0009] TIFF2026057505000002.tif33170

[0010] in accordance with R1 is (CH2) x -R3 is H or CN, where x is 1 to 20, and R3 is either H or CN; R2 is C1~C 10 Alkyl or C2-C 10is alkenyl; and n is from 50 to 5000.

[0011] A first particularly preferred example of the halogen-free polymer binder is a binder in which x is 6, R3 is CN, and R2 is (CH2)2. A second particularly preferred example of the halogen-free polymer binder is a binder in which x is 10, R3 is H, and R2 is (CH2)2.

[0012] A second aspect of the present invention discloses a positive electrode for a battery as described in the appended claims. The positive electrode contains a halogen-free polymer binder according to the first aspect of the present invention.

[0013] Advantageously, the positive electrode contains 75 to 95% by weight, preferably 80 to 95% by weight, more preferably 85 to 92% by weight, for example 90% by weight of an active material based on the total weight of the positive electrode.

[0014] Advantageously, the positive electrode contains 1 to 15% by weight, preferably 2 to 12% by weight, more preferably 5 to 10% by weight of a conductive compound based on the total weight of the positive electrode.

[0015] Advantageously, the positive electrode contains 1 to 15% by weight, preferably 2 to 12% by weight, more preferably 5 to 10% by weight of the halogen-free polymer binder according to the first aspect of the present invention based on the total weight of the positive electrode.

[0016] Advantageously, the positive electrode contains 75 to 95% by weight of an active material, 1 to 15% by weight of a conductive compound, and 1 to 15% by weight of the halogen-free polymer binder according to the first aspect of the present invention based on the total weight of the positive electrode.

[0017] Advantageously, the total weight percentage of the active material, the conductive compound, and the halogen-free polymer binder of the present invention in the positive electrode is 100%, that is, the positive electrode advantageously consists of an active material, a conductive compound, and the halogen-free polymer binder of the present invention. As those skilled in the art will understand, when the total of these three components reaches 100%, in order to reach 100%, the positive electrode contains a conductive compound of more than 1% by weight and a binder of the present invention of more than 1% by weight, for example, 75% by weight of the active material and 12.5% by weight each of the conductive compound and the binder of the present invention, or 90% by weight of the active material, 3% by weight of the conductive compound, and 7% by weight of the binder of the present invention.

[0018] Advantageously, the positive electrode has a porosity of at least 20%, preferably at least 25%, more preferably at least 30%, for example at least 40%. The porosity is expressed as the ratio of the density of the positive electrode to the theoretical density of the positive electrode, and the theoretical density of the positive electrode is calculated from the composition of the positive electrode and the density of each compound in the positive electrode.

[0019] Advantageously, the active material contains one or more of lithium nickel cobalt manganese oxide (NMC), LiFePO4, and V2O5, or consists essentially of these. Preferred examples of NMC include LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811) and LiNi 0.6 Mn 0.2 Co 0.2 O2 (NMC622).

[0020] Advantageously, the conductive compound contains carbon. The carbon may exist in a form well known in the art such as carbon nanotubes or carbon black.

[0021] A non-limiting example of the positive electrode of the present invention is a positive electrode containing 85 to 95% by weight of NMC, 2 to 10% of a conductive compound containing carbon black, and 2 to 10% by weight of the halogen-free polymer binder of the first aspect with respect to the total weight of the positive electrode.

[0022] Advantageously, the positive electrode consists of NMC, a carbon black-containing conductive compound, and the halogen-free binder of the present invention, i.e., the positive electrode contains no further components (additives), and the sum of the weight percent of these three components is advantageously 100%. A particularly preferred example of such a positive electrode is one consisting of 90 wt% NMC, 5 wt% carbon black-containing conductive compound, and 5 wt% of the halogen-free binder of the present invention.

[0023] A more non-limiting example of the positive electrode of the present invention is a positive electrode comprising 75-85% by weight of LiFePO4 (LFP), 5-15% of a carbon black-containing conductive compound, and 5-15% by weight of a halogen-free polymer binder of the first embodiment, based on the total weight of the positive electrode.

[0024] Advantageously, the positive electrode consists of LFP, a carbon black-containing conductive compound, and the halogen-free binder of the present invention, i.e., the positive electrode contains no further components (additives), and the sum of the weight percent of these three components is advantageously 100%. A particularly preferred example of such a positive electrode is one consisting of 80 wt% LFP, 10 wt% carbon black-containing conductive compound, and 10 wt% halogen-free binder of the present invention.

[0025] A third aspect of the present invention discloses a method for producing the halogen-free polymer binder described in the appended claims. The halogen-free polymer binder conforms to the first aspect of the present invention.

[0026] The method involves using an amino derivative according to H2N-R1,

[0027] TIFF2026057505000003.tif23170

[0028] This involves reacting with R1 as described above, and R2 and n as described above.

[0029] The reaction is carried out in the presence of dimethylformamide.

[0030] The reaction is carried out at a temperature T1 of 15-80°C, more preferably 20-60°C, for example, room temperature or 50°C.

[0031] The reaction forms an intermediate polymer. Advantageously, the intermediate polymer does not contain ring closures, particularly imide rings, in its molecular structure.

[0032] The imide ring-closing of the intermediate polymer is performed, thereby forming a halogen-free polymer binder. The imide ring-closing step can be carried out by heating the intermediate polymer to a temperature T2 of 100-250°C, preferably 125-200°C, more preferably 150-180°C. Alternatively, the imide ring-closing step can be carried out at T1 in the presence of a catalyst. In other words, when a catalyst is used for imide ring-closing, it is not necessary to heat the intermediate polymer to T2.

[0033] Advantageously, when the intermediate polymer is heated to T2 to close the imide ring, the heating step includes heating to an intermediate temperature T3, where T3 is higher than T1 and lower than T2. ​​Advantageously, T3 is T1 + 5°C or higher, preferably T1 + 10°C or higher, more preferably T1 + 20°C or higher. Advantageously, T3 is T2 - 5°C or lower, preferably T2 - 10°C or lower, more preferably T2 - 20°C or lower.

[0034] Advantageously, T3 is 30-80°C, preferably 40-70°C, and more preferably 50-60°C.

[0035] According to the first embodiment, x is 6, R3 is CN, R2 is (CH2)2, T1 is 40-60°C, and T2 is 150-180°C.

[0036] According to the second embodiment, x is 10, R3 is H, R2 is (CH2)2, T1 is 15-30°C, T3 is 50-60°C, and T2 is 150-180°C.

[0037] Advantageously, when the imide ring is closed in the presence of a catalyst, the catalyst contains or substantially consists of carbonyldiimidazole.

[0038] This disclosure further relates to the use of a halogen-free polymer binder according to the first embodiment in a slurry for manufacturing a cathode according to the second embodiment.

[0039] The embodiments of the invention will be described in more detail below with reference to the attached drawings. The same reference numerals indicate the same features. [Brief explanation of the drawing]

[0040] [Figure 1] This figure shows the 1H nuclear magnetic resonance (1H-NMR) spectrum of the first halogen-free polymer binder of the present invention. [Figure 2] This figure shows the Fourier transform infrared (FTIR) spectrum of the first halogen-free polymer binder. [Figure 3] This figure shows the TGA analysis of the first binder. [Figure 4] This figure shows the DSC analysis of the first binder. [Figure 5] This figure shows the LSV analysis of the first binder. [Figure 6] This figure shows the H-NMR spectrum of the second halogen-free polymer binder of the present invention. [Figure 7] This figure shows the FTIR spectrum of the second binder. [Figure 8] This figure shows the TGA analysis of the second binder. [Figure 9] This figure shows the DSC analysis of the second binder. [Figure 10] This figure shows the LSV analysis of the second binder. [Figure 11] This figure shows the porosity of the two positive electrodes and the reference positive electrode of the present invention. [Figure 12] This figure shows the discharge capacity and Coulomb efficiency of a first battery cell including a positive electrode obtained using the first binder. [Figure 13] This figure shows the voltage as a function of the specific capacity of the first battery cell. [Figure 14]This figure shows the discharge capacity and Coulomb efficiency of a second battery cell containing a positive electrode obtained using a second binder. [Figure 15] This figure shows the voltage as a function of the specific capacity of the second battery cell. [Modes for carrying out the invention]

[0041] The halogen-free polymer binder is of formula (I)

[0042] TIFF2026057505000004.tif33170

[0043] in accordance with R1 is (CH2) x -R3 is H or CN, x is 1 to 20, preferably 2 to 15, more preferably 4 to 10, and R3 is H or CN; R2 is C1~C 10 Alkyl or C2-C 10 It is Alkenil.

[0044] Advantageously, n is 50 to 5000, preferably 75 to 4500, and more preferably 100 to 4000.

[0045] Advantageously, the halogen-free polymer binder has a molecular weight of 200 to 1500 kDa, preferably 250 to 1400 kDa, more preferably 300 to 1300 kDa, and most preferably 350 to 1200 kDa.

[0046] R1 can be a straight chain or branched, i.e., (CH2) x The chain can be straight or branched. Favorably, R1, i.e., (CH2) x The chain is a straight chain.

[0047] R2 can be a straight chain or branched. Advantageously, R2 is (CH2) y C1~C according to 10 It is an alkyl group, where y is 1 to 10, preferably 1 to 4, more preferably 1 or 2, i.e., CH2 or (CH2)2.

[0048] An example of a halogen-free polymer binder is formula (II)

[0049] TIFF2026057505000005.tif46170

[0050] This is a binder according to the formula, where x is 6, R3 is CN, and R2 is (CH2)2.

[0051] Another example of a halogen-free polymer binder is formula (III)

[0052] TIFF2026057505000006.tif52170

[0053] This is a binder according to the formula, where x is 10, R3 is H, and R2 is (CH2)2.

[0054] According to a first preferred embodiment of the present disclosure, a halogen-free binder according to formula (I) contains an amino derivative according to H2N-R1,

[0055] TIFF2026057505000007.tif23170

[0056] It is prepared by reacting with, where R1 and x are as described above, and R2 and n are as described above.

[0057] The reaction is carried out at a temperature T1 of 15–80°C in the presence of dimethylformamide (DMF) as the solvent.

[0058] The reaction yields equation (IV)

[0059] TIFF2026057505000008.tif34170

[0060] An intermediate polymer having a structure according to the above is formed, and R1 and R2 are structures that do not contain cyclic structures such as imide rings, as described above.

[0061] For example, if x is 6, R3 is CN, and R2 is (CH2)2, the intermediate polymer is given by formula (V)

[0062] TIFF2026057505000009.tif52170

[0063] It has a structure that conforms to [the following].

[0064] For example, if x is 10, R3 is H, and R2 is (CH2)2, the intermediate polymer is given by formula (VI)

[0065] TIFF2026057505000010.tif52170

[0066] It has a structure that conforms to [the following].

[0067] Next, the intermediate polymer is subjected to an imide ring-closing step, in which the -OH and -NH- groups of the intermediate polymer react, thereby closing the ring and obtaining a halogen-free polymer binder of formula (I). Water is formed as a byproduct.

[0068] According to the first embodiment of the imide ring-closing step, imide ring-closing is performed by heating the intermediate polymer to a temperature higher than T1, preferably 100 to 250°C, for example, 150 to 180°C.

[0069] According to a second embodiment of the imide ring-closing step, the imide ring-closing is carried out at T1 in the presence of a catalyst, but is not limited to, carbonyldiimidazole.

[0070] Advantageously, the halogen-free polymer binder material of the present invention has high heat resistance, meaning it can withstand temperatures of at least 300°C, preferably at least 350°C, and more preferably at least 400°C, as measured by thermogravimetric analysis (TGA) at 10°C / min under an argon flow rate of 60 mL / min.

[0071] Advantageously, the halogen-free polymer binder material of the present invention has a glass transition temperature of 25 to 100°C, preferably 30 to 80°C, more preferably 40 to 60°C, for example, 42 to 55°C. This temperature is measured by performing two cycles of differential scanning calorimetry (DSC) in an argon atmosphere from -80°C to over 200°C at a heating / cooling rate of 10°C / min. By adopting the results of the second cycle to ensure that the thermal history of the polymer is reliably erased, a reliable and reproducible glass transition temperature value is ensured.

[0072] The positive electrode according to the present invention comprises, or consists of, an active compound and a conductive material in addition to the halogen-free polymer binder of the present invention.

[0073] The active material can be any cathode active material well known in the art. The cathode is understood to contain two or more active materials. A non-limiting example of a suitable active material is LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811) and LiNi 0.6 Mn 0.2 Co 0.2 Lithium nickel cobalt manganese oxide (NMC), such as O2 (NMC622), LiFePO4, LiMn x Fe 1-x PO4(LMFP), LiMn 1.5 Ni 0.5 There are O(LMNO) and V2O5.

[0074] The conductive compound may be any conductive compound well known in the art. Advantageously, the conductive compound contains carbon or is substantially composed of carbon. Non-limiting examples of suitable conductive materials include carbon-containing compounds such as carbon black (e.g., C-65), carbon nanotubes (CNTs), graphene, and vapor-grown carbon fibers (VGCFs).

[0075] Advantageously, the positive electrode includes a positive electrode current collector. The positive electrode current collector may be any positive electrode current collector known in the art, such as aluminum foil, which may optionally include a carbon-containing coating layer. If the positive electrode includes a positive electrode current collector, the positive electrode may preferably include a layer comprising an active material, a conductive compound, and the aforementioned binder, the layer being in contact with the positive electrode current collector, and preferably adhering to or attached to the positive electrode current collector.

[0076] A non-limiting example of the positive electrode of the present invention is a positive electrode comprising a positive electrode current collector and a layer comprising 85-95% by weight of NMC, 2-10% of a carbon black-containing conductive compound, and 2-10% by weight of the halogen-free polymer binder of the present invention, relative to the total weight of the layer. Advantageously, the layer consists of NMC, a carbon black-containing conductive compound, and the halogen-free binder of the present invention, i.e., the sum of these by weight percentages in the layer is 100%.

[0077] A more non-limiting example of the positive electrode of the present invention is a positive electrode comprising a positive electrode current collector and a layer comprising 75-85% by weight of LiFePO4, 5-15% of a carbon black-containing conductive compound, and 5-15% by weight of the halogen-free polymer binder of the present invention, relative to the total weight of the layer. Advantageously, the layer consists of LiFePO4, a carbon black-containing conductive compound, and the halogen-free binder of the present invention, i.e., the sum of these by weight percentages in the layer is 100%.

[0078] The positive electrode according to the present invention can be manufactured by methods well known in the art. A preferred method includes preparing a slurry containing the halogen-free polymer binder, active material, and the conductive compound described above in a solvent, and tape-casting the slurry onto a positive electrode current collector.

[0079] Advantageously, the slurry contains 25-75% by weight, preferably 30-70% by weight, more preferably 35-65% by weight, and most preferably 40-60% by weight, for example, 45-55% by weight, of the total weight of the slurry.

[0080] Advantageously, the solids content of the slurry comprises 75-95% by weight of active material, 1-10% by weight of conductive compound, and 1-10% by weight of halogen-free polymer binder.

[0081] Advantageously, the solvent is selected from the group consisting of N-methyl-2-pyrrolidone (NMP), acetonitrile, methyltetrahydrofuran, cyclohexanone, DMF, and propylene carbonate (PC).

[0082] Advantageously, the positive electrode has an adhesive strength to the positive electrode current collector that, as measured according to the ISO-8510-1 standard, is at least 20 N / m, preferably at least 25 N / m, more preferably at least 30 N / m, and most preferably at least 40 N / m. [Examples]

[0083] HO-(CH2)6-NH2 was reacted with di-tert-butyl dicarbonate in the presence of tetrahydrofuran at room temperature for 15 hours. After removing the solvent, the reaction product was placed in diethyl ether and washed with acetic acid and aqueous sodium bicarbonate. The solvent was removed under vacuum. The resulting reaction product was then reacted with methanesulfonyl chloride / triethylamine in the presence of dichloromethane (DCM) at room temperature for 3 hours. The mixture was then washed with aqueous sodium bicarbonate. After removing the dichloromethane, the resulting product was reacted with KCN at 80°C for 18 hours in the presence of DCM as the solvent. The reaction product was then placed in a mixture of ethyl acetate and water and washed with water and brine. The organic matter was recovered and the solvent was removed under vacuum. The resulting reaction product was then reacted with HCl in 1,4-dioxane at a temperature between 0°C and room temperature for 5 hours. The reaction was quenched with sodium bicarbonate, the product was extracted with dichloromethane, and treated with sodium hydroxide to obtain H2N-(CH2)6-CN ("amino derivative").

[0084] Next, the amino derivative was incubated at 50°C for 24 hours in the presence of DMF.

[0085] TIFF2026057505000011.tif24170

[0086] The reaction was carried out with n ranging from 100 to 4000. The resulting reaction product followed formula (V) and was further reacted in the presence of DMF at 170°C for 16 hours. Figures 1 and 2 show the 1H nuclear magnetic resonance (1H-NMR) and Fourier transform infrared (FTIR) spectra of the obtained halogen-free polymer binder, respectively.

[0087] Figure 3 shows the TGA analysis of the binder, demonstrating high heat resistance exceeding 400°C. Figure 4 shows the DSC analysis of the binder, indicating a glass transition temperature of 52°C. Figure 5 shows the linear sweep voltammetry (LSV) analysis of the polymer binder in a propylene carbonate (PC) solution, demonstrating high oxidation stability. [Examples]

[0088] H2N-(CH2)9-CH3 as an amino derivative was incubated in the presence of DMF at room temperature for 16 hours.

[0089] TIFF2026057505000012.tif24170

[0090] The reaction was carried out with n ranging from 100 to 4000. The resulting reaction product was further reacted according to formula (VI) at 50°C for 8 hours in the presence of DMF, and then at 170°C for 16 hours in the presence of DMF. Figures 6 and 7 show the H-NMR and FTIR spectra of the obtained halogen-free polymer binder, respectively.

[0091] Figure 8 shows the TGA analysis of the binder, demonstrating high heat resistance exceeding 400°C. Figure 9 shows the DSC analysis of the binder, indicating a glass transition temperature of 44°C. Figure 10 shows the LSV analysis of the polymer binder in PC solution, demonstrating high oxidation stability. [Examples]

[0092] Next, cathodes were manufactured using the halogen-free polymer binders of Examples 1 and 2. A first slurry was prepared using the binder of Example 1, which had a solid content of 49-52% by weight, and a second slurry was prepared using the binder of Example 2, which had a solid content of 46-49% by weight. NMP was used as the solvent for both slurries. The solid content of each slurry contained 90% by weight of NMC622 as the active material, 5% by weight of carbon black (C-65) as the conductive compound, and 5% by weight of each halogen-free polymer binder. As a result, the loading of the active material in the slurry was 3-4 mAh cm⁻¹. -2 That's what happened.

[0093] Next, the slurry was cast onto carbon-coated aluminum foil, which served as the positive electrode current collector, using the doctor blade method (doctor blade coating technology), thereby obtaining the positive electrode. In other words, the positive electrode consisted of a positive electrode current collector and layers made of NMC622, C-65, and a halogen-free polymer binder.

[0094] The reference cathode was also prepared by casting a slurry with similar solid content and loading using the doctor blade method. The solid content consisted of 90% by weight of NMC622 as the active material, 5% by weight of carbon black (C-65) as the conductive compound, and 5% by weight of polyvinylidene fluoride (PVdF) as the binder.

[0095] The porosity of all three positive electrodes, more specifically the porosity of the layer on the current collector, was measured by dividing the density of the positive electrode by the theoretical density. Figure 11 shows that the porosity of the positive electrode of the present invention is the same as that of the reference positive electrode.

[0096] The peel strength, expressed as adhesive strength and determined according to ISO-8510-1, was also measured. The adhesive strength of the positive electrode obtained using the binder of Example 1 was 58 N / m, the adhesive strength of the positive electrode obtained using the binder of Example 2 was 42 N / m, and the adhesive strength of the reference positive electrode containing PVdF was 41 N / m. In other words, the adhesive strength of the halogen-free positive electrode of the present invention was at least equivalent to and greater than that of the reference fluoride-containing positive electrode. [Examples]

[0097] Three coin cells were assembled using the positive electrode of the present invention in Example 3. Lithium metal was used as the negative electrode, and the electrolyte was a liquid electrolyte containing 1 M LiPF6 in a solvent mixture containing ethylene carbonate and dimethyl carbonate in a 1:1 volume ratio.

[0098] Two of the coin cells were cycled at 25°C for at least 30 cycles at various current rates, namely C / 20, C / 10, C / 5, C / 2, and 1C, without any problems. Figure 12 shows the discharge capacity and Coulomb efficiency of both coin cells, including the positive electrode of Example 3, obtained using the binder of Example 1. Despite the harsh test conditions, it can be seen that excellent rate characteristics and high discharge capacity are obtained, in addition to a very high Coulomb efficiency close to 100%. This indicates that the halogen-free polymer binder provides excellent adhesion and enables the cycle characteristics of the cells. Furthermore, the results for both coin cells are very similar, indicating that the behavior of the positive electrode of the present invention, and by extension the halogen-free polymer binder, is very stable and reproducible. Figure 13 shows the voltage as a function of specific capacity.

[0099] Figure 14 shows the discharge capacity and Coulomb efficiency of three coin cells, including the positive electrode of Example 3, obtained using the binder of Example 1. Despite the harsh test conditions, it can be seen that excellent rate characteristics and high discharge capacity are obtained, in addition to a very high Coulomb efficiency of nearly 100%. This indicates that the halogen-free polymer binder provides excellent adhesion and enables the cell's cycle characteristics. Furthermore, the results for all coin cells are very similar, indicating that the behavior of the positive electrode and, consequently, the halogen-free polymer binder of the present invention is very stable. Figure 15 shows the voltage as a function of specific capacity.

Claims

1. Equation (I) A halogen-free polymer binder for positive electrodes, in accordance with the following: R １ (CH ２ ) ｘ -R ３ And x is 1 to 20, and R ３ is H or CN; R ２ is C １ to C １０ alkyl or C ２ to C １０ alkenyl; and n is between 50 and 5000. Halogen-free polymer binder.

2. x is 6, R ３ CN and R ２ (CH ２ ) ２ The halogen-free polymer binder according to claim 1.

3. x is 10, R ３ H and R ２ (CH ２ ) ２ The halogen-free polymer binder according to claim 1.

4. A positive electrode comprising the halogen-free polymer binder described in claim 1.

5. The positive electrode according to claim 4, comprising 75 to 95% by weight of an active material, 1 to 15% by weight of a conductive compound, and 1 to 15% by weight of the halogen-free polymer binder, based on the total weight of the positive electrode.

6. The positive electrode according to claim 4 or 5, wherein the porosity is at least 20%.

7. The active material is lithium nickel cobalt manganese oxide (NMC), preferably NMC811 or NMC622, LiFePO ４ , and V ２ O ５ The positive electrode according to claim 5, comprising one or more of the above.

8. The positive electrode according to claim 5, wherein the conductive compound comprises carbon black.

9. The positive electrode according to claim 4, comprising 85 to 95% by weight of NMC, 2 to 10% of a carbon black-containing conductive compound, and 2 to 10% by weight of the halogen-free polymer binder according to claim 1, based on the total weight of the positive electrode.

10. 75 to 85% by weight of LiFePO4 relative to the total weight of the positive electrode ４ The positive electrode according to claim 4, comprising 5 to 15% of a carbon black-containing conductive compound and 5 to 15% by weight of the halogen-free polymer binder according to claim 1.

11. A method for producing a halogen-free polymer binder according to claim 1, - H ２ N-R １ Amino derivatives according to This is a step that causes a reaction, R １ (CH ２ ) ｘ -R ３ And x is 1 to 20, and R ３ is H or CN; R ２ is C １ ~C １０ Alkyl or C ２ ~C １０ It is an alkenyl; and n is between 50 and 5000. Temperature T of 15–80°C in the presence of dimethylformamide １ The step of performing this, thereby forming an intermediate polymer; and - A step of closing the imide ring of the intermediate polymer, thereby forming the halogen-free polymer binder, The ring closure of the imide ring is performed by the intermediate polymer at a temperature of 100 to 250°C T ２ By heating, or in the presence of a catalyst, T １ Steps to be performed A method that includes this.

12. The imide ring comprises the intermediate polymer T ２ By heating, the ring is closed, T ２ Heating to an intermediate temperature T ３ This includes heating to T ３ is T １ Higher than and T ２ Lower than, preferably, T ３ The temperature is 30-80°C, followed by T ３ From T ２ The method according to claim 11, wherein heating is performed.

13. x is 6, R ３ CN and R ２ (CH ２ ) ２ And, T １ The temperature range is 40-60°C, and T ２ The method according to claim 11, wherein the temperature is 150 to 180°C.

14. x is 10, R ３ H and R ２ (CH ２ ) ２ And, T １ The temperature is 15-30°C. ３ The temperature is 50-60°C, and T ２ The method according to claim 12, wherein the temperature is 150 to 180°C.

15. The aforementioned imide ring is T in the presence of a catalyst. １ The method according to claim 11, wherein the ring is closed and the catalyst comprises carbonyldiimidazole.

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