Polymer electrolyte and method for manufacturing the same

Abstract

To provide a polymer electrolyte having high ion conductivity, a battery, and a method for manufacturing the polymer electrolyte.SOLUTION: A polymer electrolyte for a battery is provided, including a polymaleimide copolymer including a first polymaleimide repeating unit according to the formula (I), and a second polymaleimide repeating unit according to the formula (II), wherein the first polymaleimide repeating unit and the second polymaleimide repeating unit are covalently bonded to each other.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to polymer electrolytes, particularly solid state electrolytes. The present invention further relates to batteries containing polymer electrolytes and methods for manufacturing polymer electrolytes.

Background Art

[0002] The importance of batteries and other energy storage devices is increasing rapidly. The rise of e-mobility, particularly electric-driven automobiles and e-scooters, requires high-capacity and reasonably weighted batteries.

[0003] Current research in battery technology focuses on developing new materials to improve battery safety, increase and optimize volumetric energy density and gravimetric energy density.

[0004] Conventional liquid electrolytes, such as those for lithium batteries, are based on mixtures of organic solvents and lithium salts. These electrolytes have high ionic conductivity and are electrochemically stable within the battery's voltage window. However, these liquid electrolytes are highly flammable, volatile, and can leak outside the battery casing. These disadvantages can lead to significant drawbacks of the battery, such as ignition and explosion.

[0005] In recent years, solid electrolytes, polymer electrolytes (such as gel (polymer) electrolytes), and ionic liquid electrolytes have been developed to improve the safety of alkali metal batteries and alkaline earth metal batteries.

[0006] A gel polymer electrolyte is a system in which a liquid electrolyte is encapsulated and impregnated in a cross-linked, typically chemically cross-linked polymer structure. This type of electrolyte provides a relatively high ionic conductivity at a reasonable price and also has high structural, thermal, and mechanical stability over a long period. However, the ionic conductivity is still lower than that of liquid electrolytes because the cross-linked polymer structure tends to impede the movement of metal ions, such as lithium ions in the case of lithium-ion batteries.

[0007] International Publication No. 2022 / 055307 (WO2022 / 055307) discloses a gel polymer electrolyte for a lithium secondary battery obtained from a precursor composition containing two cross-linking agents, one of which is the above cross-linking agent containing at least two thiol functional groups, a lithium salt, and a small amount of an organic solvent.

[0008] U.S. Patent Application Publication No. 2023 / 096123 (US2023096123) discloses a solid polymer electrolyte containing a cross-linked polymer network. The cross-linked polymer network contains a cross-linking group, such as a difunctional polyether group and / or a difunctional ionic group, and a cross-linking polyfunctional cross-linking group, and at least one cross-linking group containing a thioether group. For the solid polymer electrolyte to be conductive, it must further contain a dual-ion conducting salt (such as a metal salt), tethered ionic groups, and / or a liquid electrolyte.

[0009] The disadvantage of the aforementioned electrolytes is that the polyether group is unstable at high voltages (e.g., 4V or higher). A further disadvantage is that there is a risk of polarization in the battery containing these electrolytes, which is due to the use of dual-ion conducting salts and the low lithium transport rate of the electrolyte. As is known, polarization reduces the power density of the battery, thereby limiting the current value that can be used for charging and discharging the battery. In other words, polarization in the battery results in a battery with a performance that rapidly decreases with each charge and discharge cycle. Summary of the Invention

[0010] 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 polymer electrolyte having high ionic conductivity, particularly lithium ion conductivity. A further object is to provide a polymer electrolyte having high structural, electrochemical, thermal and mechanical stability over a long period of time. A further object is to provide a polymer electrolyte that is substantially free of any processing solvent. A further object is to reduce the risk of polarization in the battery, thereby improving the current value that can be used in the battery and, in particular, providing a battery having high performance and a longer life (i.e., a significant reduction or further avoidance of performance degradation) especially during repeated charge / discharge cycles.

[0011] A further object is to provide a method for producing such a polymer electrolyte having high ionic conductivity, high voltage stability up to at least 4 V, as well as thermal and mechanical stability.

[0012] According to a first aspect of the present disclosure, there is provided a polymer electrolyte for a battery as shown in the accompanying claims. The polymer electrolyte comprises a polymaleimide copolymer or consists essentially of a polymaleimide copolymer. The polymaleimide copolymer comprises or consists essentially of a first polymaleimide repeating unit and a second polymaleimide repeating unit, and the first polymaleimide repeating unit and the second polymaleimide repeating unit are covalently bonded to each other.

[0013] The first polymaleimide repeating unit is R 3 (Q) μ wherein μ is, individually, at least 2, preferably 2 to 4. Q is, individually, of formula (I):

Chemical formula

[0014] Preferably, R 2 is methyl, ethyl, propyl, n-butyl, isobutyl, benzyl or styryl.

[0015] Preferably, R 4 is H, methyl, ethyl or propyl.

[0016] R 3 is, individually, C(H) h (C x H 2x+1 ) i ((CH2) ψ ) j (CH2OC(O)(CH2) σ ) k or a polymer, where i is 0-2; j and k are, individually, 0-4; h is 4 - i - j - k; the sum of h and i is 0-2; x is 1-6; ψ is 1-10; and σ is 1-20.

[0017] Preferably, when R 3 is a polyether, the polyether is -(CH2) ω (O(CH2) sigma ) α -, where ω is 0-4, sigma is 1-4, and α is 1-10, preferably 1-5.

[0018] Alternatively, more preferably, R 3 is -(CH2) β -, where β is 1-20 (i.e., h is 2, i is 0, j is 2, and k is 0). Even more alternatively and preferably, R 3is C(CH2CH3)(CH2OC(O)(CH2) σ )3- (i.e., h is 0, i is 1, j is 0, and k is 3). Alternatively and preferably, R 3 is C(CH2OC(O)(CH2) σ )4- (i.e., h is 0, i is 0, j is 0, and k is 4).

[0019] The second polymaleimide repeating unit is of formula (II):

Chemical formula

[0020] Preferably, R 1 is H, methyl, ethyl or propyl.

[0021] Preferably, X is CF3, CH3 or F.

[0022] Preferably, the alkali metal is lithium, sodium or potassium, preferably lithium. In other words, the alkali metal ion is preferably a lithium ion (Li + ), sodium ion (Na + ), or potassium ion (K + ), preferably a lithium ion.

[0023] Preferably, the molar ratio of the first polymer maleimide repeating unit to the second polymer maleimide repeating unit is 5 to 95, preferably 10 to 70, more preferably 20 to 50. The inventors have discovered that when the molar ratio of the first polymer maleimide polymer to the second polymer maleimide polymer is 5 to 95, the polymer electrolyte has excellent ionic conductivity in combination with optimal mechanical properties.

[0024] The polymer electrolyte may further contain a plasticizer. Preferably, the polymer electrolyte contains 0 wt% to 90 wt%, preferably 0 wt% to 80 wt% of the plasticizer based on the total weight of the polymer electrolyte. Preferably, when the polymer electrolyte contains a plasticizer, it contains 0.5 wt% to 90 wt% of the plasticizer, such as 5 wt% to 85 wt%, preferably 10 wt% to 85 wt%, such as 20 wt% to 80 wt%, more preferably 45 wt% to 75 wt%.

[0025] Preferably, the plasticizer is selected from the group consisting of linear carbonates, cyclic carbonates, ethers, and nitriles. Preferably, the plasticizer is a linear carbonate or a cyclic carbonate. Particularly preferred examples of the plasticizer are propylene carbonate and ethylene carbonate. The polymer electrolyte may be two or more plasticizers, each individually selected from the group consisting of linear carbonates, cyclic carbonates, ethers, and nitriles.

[0026] According to a second aspect of the present disclosure, a battery as set forth in the appended claims is provided.

[0027] The battery includes the polymer electrolyte described in the first aspect of the present disclosure. Preferably, the battery is a secondary battery. Preferably, the battery is a lithium metal battery.

[0028] According to a third aspect of the present disclosure, there is provided a method for manufacturing a polymer electrolyte for a battery, as set forth in the appended claims. The polymer electrolyte comprises, or consists essentially of, a polymaleimide copolymer. Preferably, the polymer electrolyte manufactured by the method of the third aspect of the present disclosure is the polymer electrolyte of the first aspect of the present disclosure.

[0029] The method includes a step of preparing a compound including a third polymaleimide repeating unit, a second polymaleimide repeating unit, a free radical initiator, and a thiol-ene reagent. The third polymaleimide repeating unit and the second polymaleimide repeating unit are covalently bonded to each other, that is, as a copolymer they are present in the compound. In other words, the compound includes a copolymer including the third and second polymaleimide repeating units.

[0030] The third polymaleimide repeating unit has the formula (III):

Chemical formula

[0031] The second polymaleimide repeating unit is according to formula (II).

[0032] The thiol-ene reagent contains a thiol group. The number of thiol groups, q, is at least 2, for example 2, 3, 4 or more.

[0033] In the present disclosure, the "thiol group" means the functional group -SH, that is, a sulfur atom covalently bonded to a hydrogen atom.

[0034] The number of third polymaleimide repeating units, n, the number of thiol groups, q, and the number of thiol-ene reagent molecules, a, are

Number

[0035] Optionally, the compound further comprises a processing solvent. The term "processing solvent" is used in the present disclosure with respect to a solvent that is used during the production of the polymer electrolyte but is not present in the polymer electrolyte. Preferably, the optional processing solvent is acetone , dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, or a combination of two or more thereof, or consists essentially of these.

[0036] The inventors have surprisingly found that the compound enables its handling, for example, application to a substrate, and obtains favorable viscosity and handling properties, thereby surprisingly making the presence of the processing solvent in the compound optional without the need for a processing solvent.

[0037] Optionally, the compound further comprises a plasticizer. The optional plasticizer is as described above. Preferably, the compound comprises 0.5 wt% to 90 wt%, for example 5 wt% to 85 wt%, 10 wt% to 85 wt%, preferably 20 wt% to 80 wt%, for example 45 wt% to 60 wt% of the plasticizer based on the total weight of the compound minus the weight of the optional processing solvent.

[0038] In the present disclosure, the term "total weight of the compound minus the weight of the optional processing solvent" is used with respect to the weight of the compound as if the compound does not contain a processing solvent, and the weight of the compound without considering the weight of the processing solvent when the compound contains a processing solvent.

[0039] Preferably, the free radical initiator is capable of initiating a thiol-ene reaction between the third polymaleimide repeating unit and the thiol-ene reagent. Preferably, upon initiation, a sulfur-carbon covalent bond is formed between the third polymaleimide repeating unit and the thiol-ene reagent, leading to a thio-ether linkage.

[0040] Preferably, the compound comprises from 0.05 wt% to 1.5 wt%, preferably from 0.075 wt% to 1.4 wt%, more preferably from 0.1 wt% to 1.25 wt% of a free radical initiator, based on the total weight of the compound minus the weight of any optional processing solvent.

[0041] Preferably, the compound comprises from 0% to 95%, such as from 1 wt% to 95 wt%, from 5 wt% to 92.5 wt%, preferably from 10 wt% to 90 wt%, more preferably from 20 wt% to 90 wt%, such as from 50 wt% to 90 wt% of a processing solvent, based on the total weight of the compound including the weight of the processing solvent.

[0042] In the present disclosure, the term "total weight of the compound including the weight of the processing solvent" is used with respect to the weight of the compound when the compound does not contain a processing solvent (processing solvent in the compound is 0% by weight), and the weight of all components of the compound including the processing solvent when the compound contains a processing solvent.

[0043] Preferably, the compound comprises from 30 wt% to 80 wt% of a plasticizer, from 15 wt% to 70 wt% of the compound, and from 0.05 wt% to 1.5 wt% of a free radical initiator, based on the total weight of the compound minus the weight of any optional processing solvent.

[0044] The method further includes applying a compound to a substrate. The substrate may be any substrate, such as a Teflon sheet or glass, or may be an anode or cathode of a battery. The application of the compound to the substrate may be performed by means known in the art, such as, without limitation, casting, hot pressing or cold pressing, pressing which may or may not involve the application of any pressure, such as by spatula. Preferably, when applying the compound to the substrate, a film of the compound is obtained.

[0045] When the compound contains a processing solvent, the method further includes removing it, whereby a compound substantially free of the processing solvent is obtained.

[0046] The method further includes exposing the compound (substantially free of the processing solvent) to one or more of UV irradiation, IR irradiation or a temperature up to 100 °C. Upon exposure to one or more of UV irradiation, IR irradiation or a temperature up to 100 °C, a thiol-ene reaction of the compound (substantially free of the processing solvent), in particular the thiol-ene reactant and the third poly(maleimide) repeating unit, is initiated, whereby a polymer electrolyte is obtained.

[0047] Preferably, the thiol-ene reaction enables crosslinking of the compound, in particular the third poly(maleimide) repeating unit, whereby a polymer electrolyte is obtained. In particular, a film or sheet of the polymer electrolyte is obtained on the substrate.

[0048] Advantages of the method of the present invention include the possibility of reducing or eliminating the use of a processing solvent, which makes the method more environmentally friendly.

[0049] Advantages of the presence of the second polyimide repeating unit and optional plasticizer in the polymer electrolyte of the present disclosure include high ionic conductivity and high stability over a long period. Advantages of the presence of the first polyimide repeating unit in the polymer electrolyte of the present disclosure include high thermal, structural, and mechanical stability over a long period. Generally, the advantages of the polymer electrolyte of the present disclosure are the ability to resist high voltages, which, in combination with active materials, enables use in operation at high voltages.

[0050] Advantages of the battery of the present invention, i.e., the battery containing the polymer electrolyte of the present invention, include high ionic conductivity and excellent resistance to repeated charge / discharge, thereby having an excellent lifespan.

Brief Description of the Drawings

[0051] Aspects of the present invention will now be described in more detail with reference to the accompanying drawings. In the drawings, the same reference numerals illustrate the same features.

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4A-4B

Figure 5A-5B

Figure 6A-6B

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0052] The polymer electrolyte comprises a polymaleimide copolymer or consists essentially of a polymaleimide copolymer. The polymaleimide copolymer according to the present disclosure preferably contains a first polymaleimide repeating unit, a second polymaleimide repeating unit, and optionally a plasticizer. The first polymaleimide repeating unit and the second polymaleimide repeating unit are preferably covalently bonded to each other through a carbon-carbon bond.

[0053] The first polymaleimide repeating unit is represented by R 3 (Q) μ wherein.

[0054] μ is individually at least 2, preferably from 2 to 4.

[0055] Q is individually of formula (I):

Chemical formula

[0056] Preferably, R 2 is individually C1-C 16 alkyl, preferably C1-C 10 alkyl, more preferably C1-C8 alkyl, most preferably C1-C6 alkyl, such as methyl, ethyl, propyl and butyl. R 2 may be straight-chain or branched-chain.

[0057] Alternatively or additionally, still preferably, R 2 is individually C2-C containing one or more C=C bonds16 Alkenyl, preferably C2-C 10 alkenyl, more preferably C2-C8 alkenyl, most preferably C2-C6 alkenyl. R 2 may be linear or branched.

[0058] Alternatively or further, more preferably, R 2 is, individually, C2-C containing one or more C≡C bonds 16 alkynyl, preferably C2-C 10 alkynyl, more preferably C2-C8 alkynyl, most preferably C2-C6 alkynyl. R 2 may be linear or branched.

[0059] Alternatively or further, more preferably, R 2 is, individually, aryl, such as benzyl or phenyl.

[0060] Preferably, R 4 is H, C1-C 16 alkyl, C2-C 16 alkenyl or C2-C 16 alkynyl, preferably H, C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, most preferably H, C1-C4 alkyl, C2-C4 alkenyl or C2-C4 alkynyl. Alkyl, alkenyl and alkynyl may each be linear or branched.

[0061] Preferred examples of Q are

Chemical formula

[0062] Preferably, Q is covalently bonded to R 3 through the sulfur atom of Q.

[0063] Preferably, R 3Individually, they are polyethers. "Individually" means that the first polymer maleimide repeating units can be different from each other, for example, by including different Rs 3 This means that they can be different from each other by including, for example, different Rs 3 is a polyether by -(CH2) ω (O(CH2) sigma ) α -, where ω is from 0 to 6, preferably from 0 to 4, more preferably from 1 to 4, sigma is from 1 to 4, preferably from 1 to 3, for example 2, and α is from 1 to 10, preferably from 1 to 5, more preferably from 2 to 4.

[0064] For example, R 3 is -(CH2)2(O(CH2)2) α -(that is, ω is 2 and sigma is 2), for example -(CH2)2(O(CH2)2)2- (that is, α is 2) or -(CH2)2(O(CH2)2)3- (that is, α is 3).

[0065] Alternatively or furthermore, still preferably, R 3 individually is C(H) h (C x H 2x+1 ) i ((CH2) ψ ) j (CH2OC(O)(CH2) σ ) k is by. Preferably, x is from 1 to 6, preferably from 1 to 4, more preferably 1 or 2. Preferably, ψ is from 1 to 10, preferably from 1 to 8, more preferably from 1 to 6, for example from 1 to 4. Preferably, σ is from 1 to 20, preferably from 1 to 10, for example from 1 to 6, more preferably from 1 to 4. Furthermore, i is from 0 to 2, and j and k are, individually, from 0 to 4. Furthermore, h is 4 - i - j - k. The sum of h and i is from 0 to 2.

[0066] For example, R 3 is -(CH2) β where β is from 1 to 20 (that is, h is 2, i is 0, j is 2, k is 0, and β is equal to 2*ψ + 1).

[0067] For example, R 3 is C(C2H5)(CH2OC(O)(CH2) σ )3- (that is, h is 0, i is 1, j is 0, k is 3, and x is 2).

[0068] For example, R 3 is C(CH2OC(O)(CH2) σ )4- (that is, h is 0, i is 0, j is 0, k is 4, and x is 2).

[0069] The second polymaleimide unit is represented by formula (II) [Chemical formula] wherein R 1 is H, C1-C 16 alkyl, C2-C 16 alkenyl or C2-C 16 alkynyl, m is 1-5, M + is independently an alkali metal ion, X is H, F, C1-C 16 alkyl, C1-C 16 fluoroalkyl.

[0070] Preferably, R 1 is H, C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, preferably H, C1-C4 alkyl, C2-C4 alkenyl or C2-C4 alkynyl. The alkyl, alkenyl and alkynyl may each be straight-chain or branched-chain.

[0071] Preferably, X is H, F, C1-C6 alkyl or C1-C6 fluoroalkyl, preferably H, F, CH3 or CF3. The alkyl and fluoroalkyl may be straight-chain or branched-chain.

[0072] Preferably, the alkali metal is lithium, sodium or potassium. In other words, the alkali metal ion is preferably a lithium ion (Li + ), a sodium ion (Na + ), or a potassium ion (K + ).

[0073] A preferred example of the second polymaleimide repeating unit is the repeating unit represented by Formula IV

Chemical formula

[0074] A non-limiting example of the polymer electrolyte is represented by Formula V

Chemical formula

[0075] Yet another non-limiting example of the polymer electrolyte is shown in Formula VI

Chemical formula

[0076] Yet another non-limiting example of a polymer electrolyte is of formula VII

Chemical Formula

[0077] Preferably, the polymer electrolyte is thermally stable up to at least 75 °C, preferably up to at least 100 °C, or at least up to a temperature of 125 °C.

[0078] Preferably, the polymer electrolyte has an ionic conductivity of at least 0.3 mS / cm, preferably at least 0.4 mS / cm, more preferably at least 0.5 mS / cm at 70 °C.

[0079] Preferably, the polymer electrolyte has an ionic conductivity of at least 0.05 mS / cm, preferably at least 0.1 mS / cm, more preferably at least 0.15 mS / cm at 40 °C.

[0080] Preferably, the polymer electrolyte of the present invention is self-standing. The terms "self-standing" and "self-supporting" are used interchangeably and refer to a film, substrate, product or article that has sufficient mechanical strength to be manipulated, e.g., cut, shaped or handled, without the need for a carrier or support on which the film is placed to avoid damage to the film.

[0081] The polymer electrolyte of the present disclosure is preferably produced (i.e., generated or prepared) by the method of the present disclosure.

[0082] In a first step, a compound is prepared. The compound comprises a third polymaleimide repeating unit, a second polymaleimide repeating unit, a thiol-ene reactant and a free radical initiator.

[0083] Optionally, the compound further comprises a plasticizer. Optionally, the compound further comprises a processing solvent.

[0084] The third polymaleimide repeating unit has a pendant vinyl group and has the formula III:

Chemical formula

[0085] Preferably, the number of third polymaleimide repeating units, n, is from 1 to 9500, preferably from 20 to 3750, more preferably from 100 to 1600.

[0086] The second polymaleimide repeating unit is according to Formula II. Preferably, the number of the second polymaleimide repeating units, p, is from 4 to 8000, preferably from 50 to 6000, more preferably from 250 to 3400.

[0087] The second and third polymaleimide repeating units are preferably covalently bonded to each other through a carbon-carbon bond. In other words, the compound comprises a copolymer of the second and third polymaleimide repeating units.

[0088] A first example of the copolymer is of Formula VIII:

Chemical formula

[0089] A second example of the copolymer is of Formula IX:

Chemical formula

[0090] The thiol-ene reactant contains a thiol group. The number of thiol groups, q, is at least 2, for example 2, 3, 4 or more. Preferably, the thiol-ene reactant is R 3 (SH) μ wherein R 3and μ is as described above in this specification.

[0091] Non-limiting examples of thiol-ene reagents include, without limitation, the formulas X(q=2), XI(q=2), XII(q=3) and XIII(q=4):

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0092] A preferred example of a free radical initiator is 2-hydroxy-2-methylpropiophenone.

[0093] The inventors have found that the presence of a processing solvent in the compound is optional. The advantages of the processing solvent being optional are a reduction in the cost of the compound and the polymer electrolyte, the process for manufacturing the polymer electrolyte becoming less complex (i.e., having fewer processing steps), the unnecessary need for further (processing) solvent recovery and recycling, and a reduction in the environmental impact.

[0094] However, depending on the exact composition of the compound, a processing solvent may be added and its properties optimized in view of the conversion to a polymer electrolyte. Whether to add a processing solvent to the compound thus depends on the type and amount of the third and second polymaleimide repeating units, the thiol-ene reactant, the free radical initiator, and the optional plasticizer.

[0095] If the compound contains a processing solvent, the latter preferably comprises or consists essentially of acetone, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, or a combination of two or more thereof.

[0096] If the compound contains a plasticizer (i.e., a plasticizing agent), the plasticizer is preferably selected from the group consisting of linear carbonates, cyclic carbonates, ethers, and nitriles. Particularly preferred examples of the plasticizer are propylene carbonate and ethylene carbonate. The compound may be two or more plasticizers, each containing two or more plasticizers selected from the group consisting of linear carbonates, cyclic carbonates, ethers, and nitriles.

[0097] Optionally, the compound further contains a crosslinking agent. Non-limiting examples of the crosslinking agent include polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate (PETA), and butyl acrylate (BA).

[0098] Optionally, the compound further contains a metal salt. Preferably, when the compound contains a metal salt, the metal is preferably lithium, sodium, magnesium, or aluminum.

[0099] Preferably, the compound contains 0 wt% to 10 wt% of the metal salt, such as 0.1 wt% to 7.5 wt%, preferably 0.2 wt% to 5 wt%, more preferably 0.5 wt% to 5 wt%, based on the total weight of the compound minus the weight of the optional processing solvent.

[0100] Preferably, the compound is applied to a substrate, thereby obtaining a film of the compound. Preferably, the film has a thickness of 10 μm to 1000 μm, preferably 20 μm to 750 μm, more preferably 25 μm to 500 μm, for example 50 μm to 250 μm. It is understood that the thickness can vary based on the targeted or required thickness of the polymer electrolyte. Preferably, the targeted or required thickness is determined based on the required total cell resistance and the required mechanical properties, such as mechanical strength and flexibility.

[0101] Preferably, when the compound contains a processing solvent, the processing solvent is removed after the compound is applied to the substrate and before the compound (substantially free of the processing solvent) is exposed to UV irradiation, IR irradiation, or a temperature up to 100 °C.

[0102] Preferably, the processing solvent is removed by heating the substrate containing the compound to a temperature of 20 °C to 100 °C, preferably 20 °C to 50 °C.

[0103] Preferably, when the compound contains a plasticizer, the substrate is heated to a temperature below the maximum continuous use temperature of the plasticizer as defined by the Underwriter Laboratory (UL 746B) relative thermal index (RTI), preferably 20 °C to T v - 10 °C, where T v is the maximum continuous use temperature of the plasticizer defined by the Underwriter Laboratory (UL 746B) relative thermal index (RTI). By doing so, evaporation and / or removal of the plasticizer will be avoided.

[0104] Alternatively or additionally, and preferably, the processing solvent is removed by exposing the substrate containing the compound to an atmosphere at a pressure below atmospheric pressure.

[0105] Preferably, when a pressure below atmospheric pressure is applied, the pressure is 975 mbar or less, preferably 950 mbar or less, more preferably 930 mbar or less, for example 900 mbar or less, 750 mbar or less, or 500 mbar or less.

[0106] It will be understood that the optimal temperature and / or pressure for evaporating the processing solvent will depend on the composition of the compound. In particular, when the compound contains a plasticizer, the optimal conditions for evaporating the processing solvent will depend on the plasticizer used, and the conditions are preferably selected to avoid evaporation or decomposition of the plasticizer.

[0107] Preferably, the processing solvent is acetone. Acetone is particularly preferred because it has a relatively low boiling point (i.e., 56 °C at atmospheric pressure) and a relatively high vapor pressure (i.e., 230 mm Hg at 25 °C). This boiling point and vapor pressure allow for the removal of the processing solvent by heating to a moderate temperature, for example about 40 °C to 65 °C at atmospheric pressure, preferably at atmospheric pressure, and / or at a pressure slightly below atmospheric pressure, for example about 950 mbar, to 50 °C to 60 °C.

[0108] Preferably, exposure of the compound (substantially free of processing solvent) to one or more of UV irradiation, IR irradiation, or temperatures up to 100 °C initiates a thiol-ene reaction of the thiol-ene reagent and the third maleimide repeat unit, thereby obtaining the first maleimide repeat unit of formula I.

[0109] In other words, upon exposure to one or more of UV irradiation, IR irradiation, or temperatures up to 100 °C, the compound (substantially free of processing solvent) is converted to a polymer electrolyte, particularly a polymer electrolyte as described hereinabove, i.e., a polymer electrolyte comprising a maleimide copolymer comprising a second maleimide repeat unit of formula II and a first maleimide repeat unit of formula I.

Examples

[0110] Example 1 R 2 is CH2, and R 4 is H, a third polymaleimide repeating unit according to formula III, and R 1 is H, m is 2, M + is Li + and X is CF3, a compound containing a polymaleimide copolymer containing a second polymaleimide repeating unit according to formula II was prepared.

[0111] First, allylamine was

Chemical formula

Chemical formula

[0112] The compound further contained a thiol-ene reagent according to formula XIII.

[0113] The compound further contained propylene carbonate with a molecular weight of 102 Da as a plasticizer, 2-hydroxy-2-methylpropiophenone with a molecular weight of 164 Da as a free radical initiator, and acetone as a processing solvent.

[0114] Then, the compound containing acetone was applied to a Teflon substrate by solvent casting, and then the Teflon substrate containing the compound was placed in an argon box, and acetone was removed by supplying an argon stream to the substrate at room temperature and atmospheric pressure for 24 hours.

[0115] Next, a substantially processing-solvent-free compound was exposed to UV irradiation, thereby stimulating the thiol-ene reaction, which led to a polymer electrolyte film having a thickness of 150 - 200 μm. The film was self-supporting.

[0116] Example 2 Two compounds were prepared that contained the same components but in different amounts. Table 1 shows the weight % of each component for both compounds. For each compound,

Number

[0117] The compound contains a third polymaleimide repeating unit of formula III, where R 2 is CH2. The third polymaleimide repeating unit (the "third" in Table 1) had a molecular weight between 152 kDa.

[0118] The compound contains a second polymaleimide repeating unit of formula II (the "second" in Table 1), where R 1 is H, m is 2, M + is Li + and X is CF3, and the molecular weight of this repeating unit was 357 kDa.

[0119] The thiol-ene reagent (the "4SH" in Table 1) contains four thiol groups and, according to formula XIII, where η, θ, λ, and ξ are 1, and the molecular weight is 489 Da.

[0120] The plasticizer (the "PC" in Table 1) is propylene carbonate having a molecular weight of 102 Da, and the free radical initiator (the "Ini" in Table 1) is 2-hydroxy-2-methylpropiophenone having a molecular weight of 164 Da.

Table 1

[0121] Acetone as a processing solvent was added to the two compounds in Table 1 in an amount such that the compounds contained 86 wt% acetone based on the total weight of the compounds including the weight of acetone. The compound containing acetone was then applied to a Teflon substrate by casting, more specifically solvent casting.

[0122] The Teflon substrate containing the compound was placed in an argon box, and acetone was removed by supplying an argon stream to the substrate at room temperature and atmospheric pressure for 24 hours.

[0123] Next, the substantially solvent-free compound was exposed to UV irradiation, thereby stimulating the thiol-ene reaction, which led to a polymer electrolyte film having a thickness of 150 - 200 μm. The films were self-standing. In other words, these had sufficient mechanical strength to be manipulated without further requiring a Teflon substrate as a support material (see Figure 1).

[0124] Four reference polymer electrolytes were also prepared.

[0125] R 1 is H, m is 2, M + is Li + and X is CF3. The first reference electrolyte was prepared from a compound containing a second maleimide repeating unit according to formula II, and the average molecular weight was 250 kDa - 1500 kDa.

[0126] The compound for the first reference electrolyte further included the same plasticizer as the two compounds of the present invention, as well as polyethylene glycol diacrylate (PEGDA, number average molecular weight 700 g / mol) as a crosslinking agent, and polyvinylidene difluoride - hexafluoropropylene copolymer (PVdF - HFP) as a mechanical support agent. The reference compound was then polymerized by radical polymerization. The resulting polymer electrolyte contained 7.3 wt% of the second polymaleimide polymer, 5 wt% of the PVdF - HFP copolymer, 17.6 wt% of PEGDA, and 70.1 wt% of the plasticizer, based on the total weight of the electrolyte.

[0127] Three further reference electrolytes contained the second polymaleimide polymer of the first reference electrolyte and polyethylene glycol dimethyl ether, Mw 500 (PEGDME) as a plasticizer in 5M polyethylene oxide (PEO) powder in an acetonitrile solution. All three had a ratio of 20 ethylene oxide units to lithium ions, and weight ratios of PEO to PEGDME of 20 / 80, 30 / 70, and 40 / 60, respectively.

[0128] Example 3 The ionic conductivities of two polymer electrolytes, as well as four reference polymer electrolytes (all as prepared in Example 1) and 100% polyethylene oxide (PEO) as a benchmark, were measured by alternating current (AC) impedance spectroscopy using a BT Laboratories potentiostat (Bio - Logic Science Instruments). The measurements were carried out at temperatures varying from 25 °C to 70 °C in a frequency range from 10 kHz to 0.1 Hz. Ionic conductivity is a measure of the suitability of the polymer electrolyte to be used in a battery.

[0129] Figure 2A shows the Arrhenius plot of ionic conductivity (S / cm) for two polymer electrolytes of the present invention. Figure 2B shows the Arrhenius plot of ionic conductivity for the first reference electrolyte. Figure 2C shows the Arrhenius plots of ionic conductivity for the second to fourth reference electrolytes (samples 20 / 80, 30 / 70, and 40 / 60) together with the PEO benchmark (sample 100 / 0), respectively.

[0130] From Figures 2B and 2C, it is clear that all four reference electrolytes show reasonable or excellent ionic conductivity values, while the values for the 100% PEO sample are very low and below acceptable values, which was as expected. The ionic conductivity values of the four reference electrolytes varied from 2*10 -7 S / cm to 1.5*10 -5 S / cm at 25°C and from 2*10 -5 S / cm to 4*10 -5 S / cm at 70°C.

[0131] Both electrolytes of the present invention (Figure 2A) showed high ionic conductivity, which was several orders of magnitude higher than the ionic conductivity of the reference electrolyte at that temperature at all temperatures. The ionic conductivity values of the electrolytes of the present invention varied from 0.8*10 -5 S / cm to 10 -4 S / cm at 25°C and from 4*10 -4 S / cm to 5*10 -4 S / cm at 70°C.

[0132] Example 4 For the polymer electrolyte of Example 2, as well as for four reference polymer electrolytes, the lithium transference number and lithium conductivity were measured. The Li transference number was measured by a combined measurement of AC impedance and DC polarization method described in “Electrochemical measurement of transference numbers in polymer electrolytes”, Evans et al., Polymer Volume 28, Issue 13 (1987), 2324 - 2328. A lithium symmetric cell having a polymer electrolyte as the electrolyte was used for this purpose. The temperature of the cell was controlled by a temperature chamber at 70 °C. The lithium transference number was calculated by Equation 1.

Equation

[0133] The Li conductivity was calculated by multiplying the total ionic conductivity of the electrolyte and the lithium transference number. The lithium transference number is defined as the ratio of the current derived from lithium cations in the polymer electrolyte to the total current. When the lithium transference number is close to 1, it indicates that the ionic conduction performance in the polymer electrolyte is mainly achieved by lithium cations. Table 2 provides the calculated lithium transference numbers for the two polymer electrolytes of the present invention and four reference electrolytes tested.

Table 2

[0134] Since a value of at least 0.5 is considered high in the art, it can be seen from Table 2 that the two polymer electrolytes and the reference electrolyte described in the present invention exhibit a high lithium transport rate.

[0135] Lithium conductivity is a measured value regarding the conductivity achieved by lithium cations. In other words, a higher lithium transport rate indicates that the difference between the ionic conductivity (measured in Example 2) and the lithium conductivity is smaller.

[0136] The mechanical stability was also tested for the polymer electrolytes obtained from Compound Nos. 1 and 2 of Example 2 by measuring the elongation at break. The polymer electrolytes obtained from Compound Nos. 1 and 2 had elongations at break of 328.59 ± 70.82% and 342.02 ± 7.900%, respectively, while the reference polymer electrolyte had only an elongation at break of 42.13%, i.e., one order of magnitude lower. This improved elongation at break indicates that the electrolyte is more flexible and less brittle. A more flexible electrolyte can better accommodate any volume changes during cycling (repeated charging / discharging of the battery containing the electrolyte) as well as the tensile deformation applied during the processing of the electrolyte and the battery.

[0137] Example 5 The thermal stability of the two polymer electrolytes of the present invention of Example 2 was tested by measuring the mass loss during thermogravimetric analysis (TGA) using a thermogravimetric analyzer. TGA was performed with an argon flow of 0 mL / min and a heating rate of 10 °C / min. Both electrolytes of the present invention showed an initial mass loss at 150 °C due to the evaporation of the plasticizer, as a result of which the polymer decomposition was shifted to 350 °C (Figure 3). In other words, the polymer electrolytes of the present invention have excellent thermal stability with respect to temperatures up to at least 120 °C.

[0138] The electrochemical anodic stability was tested by linear sweep voltammetry at 40 °C using a VMP3 potentiostat. A two-electrode setup was used, with lithium foil serving as the reference and counter electrodes. For this purpose, a CR2032 coin cell was prepared with a lithium foil as the reference and counter electrodes and stainless steel as the working electrode. The polymer electrolyte used in the coin cell was the electrolyte obtained from Compound Nos. 1 and 2 of Example 2. All other components of the CR2032 coin cell were as typically used in the art. The coin cell was assembled in an argon glove box.

[0139] Linear sweep voltammetry was performed at a scan rate of 1 mV / s starting from an open circuit voltage (OCV) of up to 6.0 V with respect to Li + / Li.

[0140] Figures 4A and 4B show the current density as a function of potential as measured for coin cells containing the polymer electrolytes obtained from Compound Nos. 1 and 2, respectively. It is noted that for both polymer electrolytes of the present invention, the onset of the first oxidation of the system occurs at approximately 4.0 V, which is the main oxidation, meaning that for battery applications, the polymer electrolyte can be used in combination with or coupled to an active material operating at a voltage up to 4.0 V.

[0141] A limiting current density test was also conducted using a VMP3 potentiostat. For this purpose, two CR2032 coin cells (i.e., symmetric coin cells) each having a lithium foil as the cathode and anode were prepared. As the electrolyte, the polymer electrolytes obtained from Compound Nos. 1 and 2 were used (one electrolyte per coin cell). All other components of the CR2032 coin cells were as typically used. The coin cells were assembled in an argon glove box.

[0142] with a total capacity of 1.0 mAh / cm 2While maintaining it constant, 0.1 mA / cm 2 ~5 mA / cm 2 The limiting current density test was conducted by cyclically charging and discharging a coin cell galvanostatically at a variable current density of.

[0143] Figures 5A and 5B show the voltage as a function of capacity as measured for coin cells containing the polymer electrolytes obtained from Compound Nos. 1 and 2, respectively, and the measurements were made at 40 °C. The stable profile was observed up to a current density of C / 3 = 0.33 mA / cm at 40 °C. 2 was observed.

[0144] Additional CR2032-type symmetric coin cells (one electrolyte per coin cell) containing the polymer electrolytes obtained from Compound Nos. 1 and 2 were tested by repetitive charge / discharge (cycle test) at a constant current density of 0.33 mA / cm at 40 °C while maintaining the total capacity constant at 1.0 mAh / cm. 2 While maintaining it constant, 0.33 mA / cm at 40 °C 2 at a constant current density of was tested.

[0145] Figures 6A and 6B show the voltage as a function of time as measured for coin cells containing the polymer electrolytes obtained from Compound Nos. 1 and 2, respectively. It is clear from Figures 6A and 6B that both cells exhibit stable cycling for longer than 600 hours without any signs of short circuit.

[0146] Example 6 A lithium metal battery was assembled using the polymer electrolyte obtained from Compound No. 2 of Example 2. The cathode contained 80 wt% LiFePO4 (LFP), 10 wt% binder material, and 10 wt% carbon black based on the total weight of the cathode. The active material loading was such that the theoretical capacity of the battery approached 1 mAh / cm. It is known that the voltage window for LFP is 2.7 V to 3.8 V. The anode was a copper foil coated with lithium metal having 0.3 wt% aluminum doping. 2 was.

[0147] The lithium metal battery was tested by repeated charge / discharge cycles at 40 °C, demonstrating stable capacity retention and 100% Coulomb efficiency up to a maximum of 40 cycles (Figure 7).

Claims

1. R 3 (Q) μ (wherein, R 3 is, individually, C(H) h (C x H 2x+1 ) i ((CH 2 ) ψ ) j (CH 2 OC(O)(CH 2 ) σ ) k or a polyether (where i is from 0 to 2; j and k are, individually, from 0 to 4; h is 4 - i - j - k; the sum of h and i is from 0 to 2; x is from 1 to 6; ψ is from 1 to 10; σ is from 1 to 20); μ is individually at least 2, preferably 2 - 4, Q is individually of formula (I) 【Chemical 1】 (wherein, R 2 is, individually, C 1 to C 16 alkyl, C 2 to C 16 alkenyl, C 2 to C 16 alkynyl or aryl, and R 4 is, individually, H, C 1 to C 16 alkyl, C 2 to C 16 alkenyl, C 2 to C 16 alkynyl, and Q is covalently bonded to R through the sulfur atom of Q 3 by (which is by) a first polymerimide repeating unit according to, formula (II) 【Chemical Formula 2】 (wherein, R 1 is, individually, H, C 1 to C 16 alkyl, C 2 to C 16 alkenyl, C 2 to C 16 alkynyl, and m is individually 1 - 5, M + is independently an alkali metal ion, X is, independently, H, F, C 1 ~C 16 alkyl, C 1 ~C 16 fluoroalkyl) a second polymerimide repeating unit according to, comprises, the first polymerimide repeating unit and the second polymerimide repeating unit are covalently bonded to each other, a polymer electrolyte for a battery, comprising a polymerimide copolymer.

2. The polymer electrolyte according to claim 1, wherein the molar ratio of the first polymerimide repeating unit to the second polymerimide repeating unit is 5 - 95, preferably 20 - 50.

3. R 2 The polymer electrolyte according to claim 1, wherein R is methyl, ethyl, propyl, n-butyl, isobutyl, benzyl, or styryl.

4. The polymer electrolyte according to claim 1, wherein the alkali metal ion is a lithium ion.

5. X is CF 3 , CH 3 or F, the polymer electrolyte according to claim 1.

6. R 3 is a polyether represented by -(CH 2 ) ω (O(CH 2 ) sigma ) α , where ω is from 0 to 4, sigma is from 1 to 4, and α is from 1 to 10, the polymer electrolyte according to claim 1.

7. R 3 is -(CH 2 ) β -, C(CH 2 CH 3 )(CH 2 OC(O)(CH 2 ) σ ) 3 - or C(CH 2 OC(O)(CH 2 ) σ ) 4 -, where β is from 1 to 20 and σ is from 1 to 20, the polymer electrolyte according to claim 1.

8. The polymer electrolyte according to claim 1, further comprising 0.5 wt% - 90 wt%, preferably 30 wt% - 80 wt% of a plasticizer based on the total weight of the polymer electrolyte.

9. The polymer electrolyte according to claim 8, wherein the plasticizer is selected from the group consisting of linear carbonates, cyclic carbonates, ethers, and nitriles.

10. A battery comprising the polymer electrolyte according to claim 1.

11. A method for manufacturing a polymer electrolyte for a battery, wherein the polymer electrolyte comprises a polymerimide copolymer, and the method comprises: - a third polymerimide repeating unit according to formula (III) 【Number】 (wherein, R 2 is, individually, C 1 to C 16 alkyl, C 2 to C 16 alkenyl, C 2 to C 16 alkynyl or aryl, and R 4 is, individually, H, C 1 to C 16 alkyl, C 2 to C 16 alkenyl, C 2 to C 16 alkynyl) a second polymerimide repeating unit according to formula (II), a thiol - ene reactant containing q thiol groups, where q is at least 2, a free radical initiator, optionally a processing solvent, comprising, and preparing a compound in which the third polymerimide repeating unit and the second polymerimide repeating unit are covalently bonded to each other, - applying the compound to a substrate, - when the compound contains a processing solvent, removing the processing solvent to thereby obtain a compound substantially free of the processing solvent. ​ - exposing the (substantially processing-solvent-free) compound to one or more of UV irradiation, IR irradiation, or a temperature up to 100 °C to initiate a thiol-ene reaction of the thiol-ene reagent and the third polymaleimide repeating unit, thereby obtaining the polymer electrolyte comprising 【Number 1】 wherein a is the number of thiol-ene reagent molecules and n is the number of third polymaleimide repeating units in the compound, characterized in that method **Claim 12** The method according to claim 11, wherein the compound further comprises a plasticizer **Claim 13** The method according to claim 11, wherein the compound comprises 0 wt% to 80 wt% plasticizer, 15 wt% to 70 wt% of the compound, and 0.05 wt% to 1.5 wt% of the free radical initiator, based on the total weight of the compound minus the weight of the optional solvent **Claim 14** The method according to claim 11, wherein the optional processing solvent comprises acetone, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, or a combination of two or more thereof **Claim 15** The method according to claim 11, wherein the compound comprises 0 wt% to 95 wt%, preferably 10 wt% to 90 wt% of the processing solvent, based on the total weight of the compound including the weight of the processing solvent

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