High-strength polyethylene oxide composite solid electrolyte membrane and preparation method thereof

Abstract

The present application provides a high-strength polyethylene oxide composite solid electrolyte membrane and a preparation method thereof. The above-mentioned preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane includes the following steps: mixing an amino-hydroxy inorganic solid electrolyte, a diisocyanate, and a part of N-methylpyrrolidone to obtain a modified cross-linking agent; heating and mixing polyethylene oxide, the remaining N-methylpyrrolidone, and the modified cross-linking agent to obtain a cross-linked polyethylene oxide dispersion; mixing and molding the cross-linked polyethylene oxide dispersion and a lithium salt to obtain a high-strength polyethylene oxide composite solid electrolyte membrane. The above-mentioned preparation method of the polyethylene oxide composite solid electrolyte membrane forms a polymer coating layer containing amino-isocyanate on the surface of the inorganic solid electrolyte, thereby improving the mechanical strength, thermal stability, and ionic conductivity of the polyethylene oxide solid electrolyte membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state lithium battery processing, and in particular to a high-strength polyethylene oxide composite solid electrolyte membrane and a preparation method thereof. Background Art

[0002] At present, lithium-ion batteries have been widely used due to their high specific energy, high working voltage, long cycle life, low self-discharge rate, and environmental friendliness. However, traditional liquid lithium-ion batteries contain organic carbonate-based liquid electrolytes, which have poor thermal stability and are flammable. When the battery is abused and heated, there are safety hazards such as liquid leakage, fire, and explosion. Compared with traditional liquid lithium-ion batteries, solid-state lithium batteries have become a research hotspot in the field of lithium batteries due to their higher energy density and higher safety.

[0003] Typical solid electrolytes are divided into inorganic solid electrolytes, polymer solid electrolytes, and organic-inorganic composite solid electrolytes. Among them, inorganic solid electrolytes generally have high ionic conductivity and wide electrochemical windows, but they are brittle, which greatly hinders their processing performance. Moreover, a relatively thick thickness is required to maintain a complete structure, which is limited in improving the energy density. At the same time, their contact with the electrode sheet is a solid-solid contact, and the contact is not tight enough, resulting in a large interfacial impedance between the electrolyte / electrode sheet, which greatly affects the electrical performance of the battery. Polymer solid electrolytes are light in weight and easy to form films, and have good processability and interfacial wettability. Among them, polyethylene oxide is the most commonly used, but its mechanical strength is average and its ionic conductivity is low, which seriously affects the electrical performance of the battery. The organic-inorganic composite solid electrolyte combines the advantages of inorganic solid electrolytes and polymer solid electrolytes, and is an effective way to prepare solid-state lithium batteries. Therefore, how to prepare an organic-inorganic composite solid electrolyte with high structural strength and good conductivity is an urgent problem to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a high-strength polyethylene oxide composite solid electrolyte membrane with high structural strength and good conductivity and a preparation method thereof.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A preparation method of a high-strength polyethylene oxide composite solid electrolyte membrane includes the following steps:

[0007] Obtain polyethylene oxide, an amino-hydroxy-containing inorganic solid electrolyte, a diisocyanate, a lithium salt, and N-methylpyrrolidone respectively;

[0008] Mix the amino-hydroxy-containing inorganic solid electrolyte, the diisocyanate, and a part of the N-methylpyrrolidone to obtain a modified crosslinking agent;

[0009] The polyethylene oxide, the remaining N-methylpyrrolidone and the modified cross-linking agent are heated and mixed to obtain a cross-linked polyethylene oxide dispersion;

[0010] The cross-linked polyethylene oxide dispersion and lithium salt are mixed and molded to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0011] In one embodiment, the mass ratio of the amino-hydroxyl inorganic solid electrolyte, the diisocyanate, the N-methylpyrrolidone, the polyethylene oxide and the lithium salt is (5-30): (15-35): (60-90): (50-90): (5-20).

[0012] In one embodiment, the diisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylxylylene diisocyanate and hexamethylene diisocyanate.

[0013] In one embodiment, the amino-hydroxyl-containing inorganic solid electrolyte is obtained by the following preparation method, which comprises the following steps:

[0014] Obtaining inorganic solid electrolytes, dopamine, and buffers;

[0015] Mixing the inorganic solid electrolyte, the dopamine and the buffer to obtain a premix containing an amino-hydroxy inorganic solid electrolyte;

[0016] The premix is ​​filtered and washed to obtain the amino-hydroxyl-containing inorganic solid electrolyte.

[0017] In one embodiment, the inorganic solid electrolyte includes Li 3.3 La 0.56 TiO 3 , Li 7 Ln3Z 2 O 12 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , Li 1.4 ZnGe 4 O 16 , Li 3 P 3 S 11 , Li 2 P 2 S 6 and Li 10 G 2 S12 at least one of

[0018] In one embodiment, in the step of mixing and molding the crosslinked polyethylene oxide dispersion liquid and the lithium salt, the following specific steps are included:

[0019] Pour the mixed solution of the crosslinked polyethylene oxide dispersion liquid and the lithium salt into a mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0020] In one embodiment, the molecular weight of the polyethylene oxide is 150,000 g / mol to 800,000 g / mol.

[0021] In one embodiment, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluoromethylsulfonylimide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0022] In one embodiment, the conditions for heating and mixing are: temperature 50°C to 100°C, time 3 h to 12 h.

[0023] A high-strength polyethylene oxide composite solid electrolyte membrane is prepared by using the preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane described in any one of the above.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] In the above-mentioned preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane, since the amino-hydroxy inorganic solid electrolyte contains both amino-hydroxy two active functional groups, the amino-hydroxy can polymerize with the diisocyanate to form a polymer coating layer containing urethane on the surface of the inorganic solid electrolyte to obtain a modified crosslinking agent, effectively improving the dispersion of the traditional inorganic solid electrolyte in the polymer. When the modified crosslinking agent is mixed with polyethylene oxide, the modified crosslinking agent and polyethylene oxide can form a crosslinked network structure by combining with urethane covalent bonds and hydrogen bonds, thereby reducing the regularity of the arrangement of polyethylene oxide molecular chains, significantly improving the mechanical strength and thermal stability of the polyethylene oxide solid electrolyte membrane, and at the same time the crystallinity conductivity of the crosslinked polyethylene oxide. In addition, by introducing an inorganic solid electrolyte into polyethylene oxide, the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane can be further improved and its electrochemical window can be broadened. Description of the Drawings

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of a preparation method of a high-strength polyethylene oxide composite solid electrolyte membrane according to an embodiment of the present invention;

[0028] Figure 2 It is the chemical structure diagrams of three substances of diisocyanate. a is the chemical structure diagram of 2,5-toluene diisocyanate, b is the chemical structure diagram of 1,5-naphthalene diisocyanate, and C is the chemical structure diagram of diphenylmethane diisocyanate. Detailed implementation manners

[0029] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0030] It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] The present application provides a method for preparing a high-strength polyethylene oxide composite solid electrolyte membrane, which includes the following steps: obtaining polyethylene oxide, an amino-hydroxy inorganic solid electrolyte, a diisocyanate, a lithium salt, and N-methylpyrrolidone respectively; performing a mixing operation on the amino-hydroxy inorganic solid electrolyte, the diisocyanate, and a part of the N-methylpyrrolidone to obtain a modified crosslinking agent; heating and mixing the polyethylene oxide, the remaining N-methylpyrrolidone, and the modified crosslinking agent to obtain a crosslinked polyethylene oxide dispersion; performing a mixing and forming operation on the crosslinked polyethylene oxide dispersion and the lithium salt to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0033] In the above method for preparing a high-strength polyethylene oxide composite solid electrolyte membrane, since the amino-hydroxy inorganic solid electrolyte contains two active functional groups, namely amino and hydroxy, the amino and hydroxy can undergo a polymerization reaction with the diisocyanate to form a polymer coating layer containing urethane on the surface of the inorganic solid electrolyte, so as to obtain a modified crosslinking agent, effectively improving the dispersion of the traditional inorganic solid electrolyte in the polymer. When the modified crosslinking agent is mixed with polyethylene oxide, the modified crosslinking agent and polyethylene oxide can form a crosslinked network structure by combining with urethane covalent bonds and hydrogen bonds, thereby reducing the regularity of the arrangement of polyethylene oxide molecular chains, significantly improving the mechanical strength and thermal stability of the polyethylene oxide solid electrolyte membrane, and at the same time, the crystallinity and conductivity of the crosslinked polyethylene oxide. In addition, by introducing an inorganic solid electrolyte into polyethylene oxide, the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane can be further improved and its electrochemical window can be broadened.

[0034] Please refer to Figure 1 , to better understand the technical solutions and beneficial effects of the present application, the following further details the present application with specific embodiments. The method for preparing a high-strength polyethylene oxide composite solid electrolyte membrane in one embodiment includes some or all of the following steps:

[0035] S110. Obtain polyethylene oxide, an amino-hydroxy inorganic solid electrolyte, a diisocyanate, a lithium salt, and N-methylpyrrolidone respectively for standby.

[0036] S120. Perform a mixing operation on the amino-hydroxy inorganic solid electrolyte, the diisocyanate, and a part of the N-methylpyrrolidone to obtain a modified crosslinking agent.

[0037] It can be understood that since the amino-hydroxy inorganic solid electrolyte contains two active functional groups, namely amino and hydroxy, the amino-hydroxy can react with diisocyanate to form a polymer coating layer containing urethane on the surface of the inorganic solid electrolyte, effectively improving the dispersion of the traditional inorganic solid electrolyte in the polymer. Moreover, the added N-methylpyrrolidone has good hygroscopicity and can effectively remove the moisture in the inorganic solid electrolyte, thereby reducing the water content of the polyethylene oxide composite solid electrolyte membrane. In addition, N-methylpyrrolidone has good solubility and can dissolve both diisocyanate and inorganic solid electrolyte, ensuring that diisocyanate can well form a polymer coating layer of urethane on the surface of the inorganic solid electrolyte, that is, a modified crosslinking agent is obtained for subsequent crosslinking reaction with polyethylene oxide.

[0038] It should be noted that since the chemical formula of diisocyanate is O=C=N-R-N=C=O, that is, it contains two NCOs, it can better crosslink with the hydroxy group of the amino-hydroxy inorganic solid electrolyte to form a network structure with good density and good strength, ensuring that a good structural form is maintained after multiple cycles. Compared with a single isocyanate, the network density formed by the crosslinking of 1 NCO is relatively loose and has high flexibility, so that deformation is likely to occur after multiple cycles. For polyisocyanates, since the number of NCOs is greater than two, a network structure with high density and high strength is easily formed after crosslinking, but high density is likely to hinder the passage of ions, that is, the ionic conductivity is relatively low. Therefore, in this application, by using diisocyanate containing two NCOs, while ensuring good strength, high ionic conductivity is also ensured, and further optimizing the network structure of the polymer coating layer coated on the surface of the inorganic solid electrolyte, so that a relatively good structural form can be maintained after multiple cycles of use.

[0039] In one embodiment, the diisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylxylylene diisocyanate, and hexamethylene diisocyanate.

[0040] It can be understood that since toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylxylylene diisocyanate, and hexamethylene diisocyanate all contain two NCOs, they provide raw materials for diisocyanate.

[0041] In one embodiment, the diisocyanate is a mixture of 2,5-toluene diisocyanate, 1,5-naphthalene diisocyanate, and diphenylmethane diisocyanate. Please refer to Figure 2, By utilizing the two symmetric NCO groups in 2,5-toluene diisocyanate, 1,5-naphthalene diisocyanate, and diphenylmethane diisocyanate, it is beneficial for crosslinking to form a more perfect network structure, that is, a continuous and complete network structure can be formed during crosslinking to ensure the formation of a continuous and complete network structure with good density and moderate strength on the surface of the amino-hydroxy inorganic solid electrolyte, so as to ensure that the polyethylene oxide composite solid electrolyte membrane maintains a good structural morphology after multiple cycles. In addition, 2,5-toluene diisocyanate, 1,5-naphthalene diisocyanate, and diphenylmethane diisocyanate are all of low toxicity, ensuring the safety of the human body during the preparation process and ensuring that the prepared lithium battery has low toxicity, improving the safety of use. That is, under the condition of ensuring a continuous and complete network structure with good density and moderate strength, the safety of use is also improved.

[0042] In one of the embodiments, the mass ratio of the 2,5-toluene diisocyanate, the 1,5-naphthalene diisocyanate, and the diphenylmethane diisocyanate is 1:1:0.5. It can be understood that, referring to Figure 2 , Since there is a linear structure between the double benzene rings of diphenylmethane diisocyanate, therefore, by using 2,5-toluene diisocyanate, 1,5-naphthalene diisocyanate, and diphenylmethane diisocyanate in a ratio of 1:1:0.5 in this application, it can ensure that the crosslinked network structure has certain gaps for ions to pass through better, thereby further optimizing the network structure and improving the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane.

[0043] S130. Heat and mix the polyethylene oxide, the remaining N-methylpyrrolidone, and the modified crosslinking agent to obtain a crosslinked polyethylene oxide dispersion. It can be understood that since the modified crosslinking agent contains N-methylpyrrolidone, the added N-methylpyrrolidone can be quickly dispersed in the modified crosslinking agent. Also, due to the high compatibility of N-methylpyrrolidone with polyethylene oxide, polyethylene oxide can be quickly dispersed in N-methylpyrrolidone, thereby improving the dispersibility of polyethylene oxide and the modified crosslinking agent. In addition, due to the good hygroscopicity of N-methylpyrrolidone, it can well adsorb the moisture in polyethylene oxide and the modified crosslinking agent, so that the water content of the crosslinked polyethylene oxide composite solid electrolyte membrane is less, ensuring a higher ionic conductivity of the polyethylene oxide composite solid electrolyte membrane.

[0044] It should be noted that since a polymer coating layer containing urethane is formed on the surface of the modified crosslinking agent, when the modified crosslinking agent is mixed with polyethylene oxide, the modified crosslinking agent and polyethylene oxide can form a crosslinked network structure by combining with urethane covalent bonds and hydrogen bonds. Due to the linear and regular helical structure of polyethylene oxide, after adding the modified crosslinking agent, the regularity of the arrangement of polyethylene oxide molecular chains can be effectively reduced, the mechanical strength and thermal stability of the polyethylene oxide solid electrolyte membrane can be significantly improved, and at the same time, the crystallinity of the crosslinked polyethylene oxide is significantly reduced, further improving the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane. Further, in one embodiment, the conditions for the heating and mixing are: temperature 50°C to 100°C, time 3h to 12h, to ensure a uniformly mixed crosslinked polyethylene oxide dispersion is obtained.

[0045] S140. Perform a mixing and molding operation on the crosslinked polyethylene oxide dispersion and the lithium salt to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0046] In one embodiment, the mass ratio of the amino-hydroxy inorganic solid electrolyte, the diisocyanate, the N-methylpyrrolidone, the polyethylene oxide, and the lithium salt is (5 to 30):(15 to 35):(60 to 90):(50 to 90):(5 to 20). It can be understood that since the covalent bond between the modified crosslinking agent and polyethylene oxide is urethane, that is, it is mainly obtained by the reaction of the amino-hydroxy inorganic solid electrolyte and isocyanate. Therefore, to ensure the full and comprehensive reaction of the modified crosslinking agent, polyethylene oxide, and lithium salt. In this application, by controlling the mass ratio of the amino-hydroxy inorganic solid electrolyte, the diisocyanate, the N-methylpyrrolidone, the polyethylene oxide, and the lithium salt to be (5 to 30):(15 to 35):(60 to 90):(50 to 90):(5 to 20), it is ensured that the amino-hydroxy inorganic solid electrolyte, diisocyanate, N-methylpyrrolidone, polyethylene oxide, and lithium salt can react fully and comprehensively, so as to ensure a high-strength and high-ionic conductivity polyethylene oxide composite solid electrolyte membrane is obtained.

[0047] In one embodiment, the amino-hydroxy inorganic solid electrolyte is obtained by the following preparation method, and the preparation method includes the following steps: Obtain an inorganic solid electrolyte, dopamine, and a buffer solution; mix the inorganic solid electrolyte, the dopamine, and the buffer solution to obtain a premix of the amino-hydroxy inorganic solid electrolyte; filter and wash the premix to obtain the amino-hydroxy inorganic solid electrolyte.

[0048] It can be understood that by mixing an inorganic solid electrolyte, dopamine, and a buffer solution, since dopamine contains amino-hydroxy active functional groups, it can undergo self-polymerization on the surface of the inorganic solid electrolyte under buffer solution conditions to form a polymer coating layer with amino-hydroxy active functional groups on the surface of the inorganic solid electrolyte.

[0049] It should be noted that since the chemical structure of dopamine is benzene ring-amino-hydroxy, where the number of hydroxyl groups is two, the two hydroxyl groups are adjacent and directly connected to the carbon on the benzene ring, while the amino group is indirectly linearly connected to the carbon on the benzene ring. Thus, when dopamine undergoes self-polymerization, it can form a network with a relatively moderate density and continuity on the surface of the inorganic solid electrolyte to achieve the coating of the surface of the inorganic solid electrolyte and improve the dispersion of the inorganic solid electrolyte in polyethylene oxide.

[0050] It is worth mentioning that when the amino-hydroxy-containing inorganic solid electrolyte obtained by coating the inorganic solid electrolyte with dopamine reacts with diisocyanate, the two hydroxyl groups on dopamine can polymerize with the two NCOs of diisocyanate to form a larger continuous network structure on the surface of the solid electrolyte to obtain a polymer coating layer containing urethane, further optimizing the network structure of the inorganic solid electrolyte. In addition, the indirect linear connection of the amino group to the carbon on the benzene ring makes the gap between the amino group and the hydrogen bond of polyethylene oxide relatively large. Thus, the cross-linked network structure has a certain gap for the passage of ions, thereby improving the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane.

[0051] In one embodiment, the inorganic solid electrolyte includes Li 3.3 La 0.56 TiO 3 , Li 7 La 3 Zr 2 O 12 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , Li 1.4 ZnGe 4 O 16 , Li 3 P 3 S 11 , Li 2 P 2 S 6 and Li 10 GeP 2 S 12 at least one of.

[0052] In one embodiment, the mass parts of the inorganic solid electrolyte, the dopamine, and the buffer solution are 1 part to 15 parts, 0.1 part to 1 part, and 90 parts to 100 parts respectively. It can be understood that by compounding the inorganic solid electrolyte, dopamine, and buffer solution in the amounts of 1 part to 15 parts, 0.1 part to 1 part, and 90 parts to 100 parts, an amino-hydroxy inorganic solid electrolyte can be ensured to be obtained. Further, the buffer solution is a tris(hydroxymethyl)aminomethane buffer solution with a pH value of 7.5 to 8. Further, the premix is used to ensure that self-polymerization of dopamine occurs on the surface of the inorganic solid electrolyte.

[0053] In one embodiment, in the step of mixing and molding the crosslinked polyethylene oxide dispersion and the lithium salt, the following specific steps are included: pouring the mixed solution of the crosslinked polyethylene oxide dispersion and the lithium salt into a mold and drying it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane. Further, the mold is a polytetrafluoroethylene mold. It can be understood that since the polytetrafluoroethylene mold is made of polytetrafluoroethylene resin, and since polytetrafluoroethylene has good self-lubricity and non-stickiness, it is beneficial for the high-strength polyethylene oxide composite solid electrolyte membrane to be quickly and completely demolded, so as to ensure that a high-strength polyethylene oxide composite solid electrolyte membrane with a relatively high flatness is obtained.

[0054] It is worth mentioning that since the crosslinked polyethylene oxide dispersion has a certain adhesiveness, and the non-stickiness of polytetrafluoroethylene can effectively avoid the phenomenon of adhesion. In addition, the self-lubricity of polytetrafluoroethylene helps to reduce the friction between the high-strength polyethylene oxide composite solid electrolyte membrane and the mold during demolding, so as to reduce the wear between the mold and the contact surface of the high-strength polyethylene oxide composite solid electrolyte membrane, and ensure that a high-strength polyethylene oxide composite solid electrolyte membrane with high flatness and integrity is obtained.

[0055] It should be further noted that since both the crosslinked polyethylene oxide dispersion and polytetrafluoroethylene are compatible with organic substances, that is to say, the urethane covalent bonds in the mixed solution of the crosslinked polyethylene oxide dispersion and lithium salt poured into the mold can combine with the hydrogen bonds in the polytetrafluoroethylene, so as to adhere and spread flat on the surface of the mold better, thereby effectively reducing the stress between the mixed solution of the crosslinked polyethylene oxide dispersion and lithium salt and the mold surface, so that the mixed solution of the crosslinked polyethylene oxide dispersion and lithium salt can be laid flat on the surface of the mold. When the laid flat mixed solution is dried, the non-stickiness and self-lubricity of the polytetrafluoroethylene mold are conducive to the rapid demolding of the high-strength polyethylene oxide composite solid electrolyte membrane from the mold under the condition of ensuring that the high-strength polyethylene oxide composite solid electrolyte membrane has high flatness and integrity, thus improving the production efficiency. Further, since the diisocyanate crosslinks with the amino-hydroxy inorganic solid electrolyte to form a continuous and complete network structure with good density and moderate strength, it is possible to achieve faster demolding of the high-strength polyethylene oxide composite solid electrolyte membrane, and it is not easy to appear adhesion or fracture phenomena.

[0056] In one of the embodiments, the molecular weight of the polyethylene oxide is 150,000 g / mol to 800,000 g / mol. Since the polyethylene oxide with a molecular weight of 150,000 g / mol to 800,000 g / mol has good adhesiveness, it can ensure a relatively firm combination with the amino-hydroxy inorganic solid electrolyte.

[0057] In one of the embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluoromethylsulfonylimide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0058] This application also provides a high-strength polyethylene oxide composite solid electrolyte membrane, which is prepared by using the preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane described in any one of the above. It can be understood that since the high-strength polyethylene oxide composite solid electrolyte membrane prepared by this application has high flatness, high ionic conductivity, good mechanical strength and thermal stability, it can improve the mechanical strength and thermal stability of the polyethylene oxide solid electrolyte membrane, the ionic conductivity, and broaden its electrochemical window.

[0059] Compared with the prior art, the present invention has at least the following advantages:

[0060] The above-mentioned preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane. Since the amino-hydroxy inorganic solid electrolyte contains two active functional groups, namely amino and hydroxy, the amino-hydroxy can undergo a polymerization reaction with diisocyanate to form a polymer coating layer containing urethane on the surface of the inorganic solid electrolyte, so as to obtain a modified cross-linking agent, effectively improving the dispersion of the traditional inorganic solid electrolyte in the polymer. When the modified cross-linking agent is mixed with polyethylene oxide, the modified cross-linking agent and polyethylene oxide can form a cross-linked network structure by combining urethane covalent bonds and hydrogen bonds, thereby reducing the regularity of the arrangement of polyethylene oxide molecular chains, significantly improving the mechanical strength and thermal stability of the polyethylene oxide solid electrolyte membrane. At the same time, the crystallinity of the cross-linked polyethylene oxide is significantly reduced, further improving the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane. In addition, by introducing an inorganic solid electrolyte into polyethylene oxide, the ionic conductivity of the polyethylene oxide composite solid electrolyte membrane can be further improved and its electrochemical window can be broadened.

[0061] The following are some specific examples. If "% " is mentioned, it means by weight percentage. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial channels without special instructions.

[0062] Example 1

[0063] Mix 0.5 kg of amino-hydroxy inorganic solid electrolyte, 1.5 kg of toluene diisocyanate and 2 kg of N-methylpyrrolidone for 3 h to obtain a modified cross-linking agent; heat and mix 5 kg of polyethylene oxide with a molecular weight of 150,000 g / mol, 4 kg of N-methylpyrrolidone and the modified cross-linking agent under the conditions of: temperature 50 °C, time 3 h to obtain a cross-linked polyethylene oxide dispersion;

[0064] Pour the mixture of the cross-linked polyethylene oxide dispersion and 0.5 kg of lithium hexafluorophosphate into a polytetrafluoroethylene mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0065] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte: Add 0.1 kg of Li 3.3 La 0.56 TiO 3 and 0.01 kg of dopamine into 9 kg of tris(hydroxymethyl)aminomethane buffer solution with a pH value of 7.5 and mix and stir for 2 h to obtain a premix of the amino-hydroxy inorganic solid electrolyte; filter and wash the premix to obtain the amino-hydroxy inorganic solid electrolyte.

[0066] Example 2

[0067] Mix 1.75 kg of amino-hydroxy inorganic solid electrolyte, 2.5 kg of diphenylmethane diisocyanate, and 2.5 kg of N-methylpyrrolidone for 4 h to obtain a modified crosslinking agent; heat and mix 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 4.5 kg of N-methylpyrrolidone, and the modified crosslinking agent under the conditions of a temperature of 75 °C and a time of 5 h to obtain a crosslinked polyethylene oxide dispersion;

[0068] Pour the mixture of the crosslinked polyethylene oxide dispersion and 1.25 kg of lithium bis(trifluoromethylsulfonyl)imide into a polytetrafluoroethylene mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0069] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte: Add 0.8 kg of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 and 0.055 kg of dopamine into 9.5 kg of tris(hydroxymethyl)aminomethane buffer solution with a pH value of 8, mix and stir for 2 h to obtain a premix of the amino-hydroxy inorganic solid electrolyte; filter and wash the premix to obtain the amino-hydroxy inorganic solid electrolyte.

[0070] Example 3

[0071] . Mix 3 kg of amino-hydroxy inorganic solid electrolyte, 3.5 kg of isophorone diisocyanate, and 3.5 kg of N-methylpyrrolidone for 6 h to obtain a modified crosslinking agent; heat and mix 7.5 kg of polyethylene oxide with a molecular weight of 800,000 g / mol, 5.5 kg of N-methylpyrrolidone, and the modified crosslinking agent under the conditions of a temperature of 100 °C and a time of 12 h to obtain a crosslinked polyethylene oxide dispersion;

[0072] Pour the mixture of the crosslinked polyethylene oxide dispersion and 2 kg of lithium difluoromethylsulfonylimide into a polytetrafluoroethylene mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0073] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte: Add 1.5 kg of Li7La3Zr 2 O 12, 0.1 kg of dopamine was added to 10 kg of tris(hydroxymethyl)aminomethane buffer solution with a pH value of 7.2 and mixed and stirred for 2 h to obtain a premix containing amino-hydroxy inorganic solid electrolyte; the premix was filtered and washed to obtain the amino-hydroxy inorganic solid electrolyte.

[0074] Example 4

[0075] . 1.75 kg of amino-hydroxy inorganic solid electrolyte, 1.5 kg of diphenylmethane diisocyanate, 1.0 kg of naphthalene diisocyanate and 2.5 kg of N-methylpyrrolidone were mixed for 4 h to obtain a modified crosslinking agent; 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 4.5 kg of N-methylpyrrolidone and the modified crosslinking agent were heated and mixed under the conditions of: temperature 75 °C, time 5 h to obtain a crosslinked polyethylene oxide dispersion;

[0076] The crosslinked polyethylene oxide dispersion and a mixed solution of 1.0 kg of lithium bis(trifluoromethylsulfonyl)imide and 0.25 kg of lithium tetrafluoroborate were poured into a polytetrafluoroethylene mold and dried to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0077] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte was the same as that in Example 2.

[0078] Example 5

[0079] . 1.75 kg of amino-hydroxy inorganic solid electrolyte, 1.5 kg of diphenylmethane diisocyanate, 1.0 kg of hexamethylene diisocyanate and 2.5 kg of N-methylpyrrolidone were mixed for 4 h to obtain a modified crosslinking agent; 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 4.5 kg of N-methylpyrrolidone and the modified crosslinking agent were heated and mixed under the conditions of: temperature 75 °C, time 5 h to obtain a crosslinked polyethylene oxide dispersion;

[0080] The crosslinked polyethylene oxide dispersion and a mixed solution of 1.0 kg of lithium bis(trifluoromethylsulfonyl)imide and 0.25 kg of lithium tetrafluoroborate were poured into a polytetrafluoroethylene mold and dried to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0081] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte was the same as that in Example 2.

[0082] Example 6

[0083] .Mix 1.75 kg of amino-hydroxy inorganic solid electrolyte, 0.5 kg of diphenylmethane diisocyanate, 1.0 kg of 1,5-naphthalene diisocyanate, 1.0 kg of 2,5-toluene diisocyanate, and 2.5 kg of N-methylpyrrolidone for 4 h to obtain a modified crosslinking agent; heat and mix 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 4.5 kg of N-methylpyrrolidone, and the modified crosslinking agent under the conditions of a temperature of 75 °C and a time of 5 h to obtain a crosslinked polyethylene oxide dispersion;

[0084] Pour the mixture of the crosslinked polyethylene oxide dispersion, 1.0 kg of lithium bis(trifluoromethylsulfonyl)imide, and 0.25 kg of lithium tetrafluoroborate into a polytetrafluoroethylene mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0085] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte is the same as that in Example 2.

[0086] Example 7

[0087] . Mix 1.75 kg of amino-hydroxy inorganic solid electrolyte, 1.05 kg of diphenylmethane diisocyanate, 0.95 kg of 1,5-naphthalene diisocyanate, 0.5 kg of 2,5-toluene diisocyanate, and 2.5 kg of N-methylpyrrolidone for 4 h to obtain a modified crosslinking agent; heat and mix 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 4.5 kg of N-methylpyrrolidone, and the modified crosslinking agent under the conditions of a temperature of 75 °C and a time of 5 h to obtain a crosslinked polyethylene oxide dispersion;

[0088] Pour the mixture of the crosslinked polyethylene oxide dispersion, 1.0 kg of lithium bis(trifluoromethylsulfonyl)imide, and 0.25 kg of lithium tetrafluoroborate into a polytetrafluoroethylene mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0089] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte is the same as that in Example 2.

[0090] Comparative Example 1

[0091] Mix 1.75 kg of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3, 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol and 6 kg of N-methylpyrrolidone are heated and mixed. The conditions for heating and mixing are: temperature 75 °C, time 5 h, to obtain a cross-linked polyethylene oxide dispersion;

[0092] The mixture of the cross-linked polyethylene oxide dispersion and 1.25 kg of lithium bis(trifluoromethylsulfonyl)imide is poured into a polytetrafluoroethylene mold and dried to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0093] Comparative Example 2

[0094] 1.75 kg of amino-hydroxy inorganic solid electrolyte, 7.5 kg of polyethylene oxide with a molecular weight of 600,000 g / mol, 6 kg of N-methylpyrrolidone and the modified cross-linking agent are heated and mixed. The conditions for heating and mixing are: temperature 75 °C, time 5 h, to obtain a cross-linked polyethylene oxide dispersion;

[0095] The mixture of the cross-linked polyethylene oxide dispersion and 1.25 kg of lithium bis(trifluoromethylsulfonyl)imide is poured into a polytetrafluoroethylene mold and dried to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

[0096] Among them, the preparation of the amino-hydroxy inorganic solid electrolyte is the same as that in Example 2.

[0097] Test method:

[0098] Tensile strength test method: Refer to the GB / T36363-2018 standard, and the tensile strength of the composite solid electrolyte membrane is tested at a rate of 10 mm / min on a universal tensile testing machine.

[0099] Ionic conductivity test: The ionic conductivity of the electrolyte is measured by assembling a symmetric cell with steel sheets as blocking electrodes on an electrochemical workstation in the frequency range of 0.1 Hz to 10 6 Hz. The ionic conductivity is calculated according to the following formula: σ = L / (R*S), where σ is the ionic conductivity of the composite solid electrolyte membrane, L is the thickness of the composite solid electrolyte membrane, S is the area of the composite solid electrolyte membrane, and R is the bulk resistance of the composite solid electrolyte membrane. The test results are shown in the following table:

[0100] Item Tensile strength (MPa) Ionic conductivity at 25°C (*10-5 S / cm) Example 1 11.9 6.75 Example 2 12.3 5.95 Example 3 13.6 6.63 Example 4 20.2 6.95 Example 5 14.1 7.10 Example 6 23.6 8.90 Example 7 17.9 8.10 Comparative Example 1 2.25 3.10 Comparative Example 2 4.65 4.55

[0101] As can be seen from the table, by comparing Examples 1-3 with Comparative Examples 1-2, it can be known that in Examples 1-3, the inclusion of amino-hydroxy inorganic solid electrolytes and the introduction of diisocyanates can effectively improve the mechanical strength and ionic conductivity of the inorganic solid electrolytes. That is, the tensile strength reaches 11.9 Mpa - 13.6 Mpa, and the ionic conductivity is 5.95*10 -5 S / cm - 6.75*10 -5 S / cm, which is obviously better than that of Comparative Examples 1-2;

[0102] By comparing Examples 1-3 with Examples 4-7, it can be known that in Examples 4-7, the inclusion of amino-hydroxy inorganic solid electrolytes and the introduction of various different types of diisocyanates for compound use can further improve the mechanical strength and ionic conductivity of the inorganic solid electrolytes. That is, the tensile strength reaches 14.1 Mpa - 23.6 Mpa, and the ionic conductivity is 6.95*10 -5 S / cm - 8.90*10 -5 S / cm, which is obviously better than that of Examples 1-3. Among them, the tensile strength in Example 5 is relatively low, mainly because the diisocyanate used is a compound of diphenylmethane diisocyanate and hexamethylene diisocyanate, and the added hexamethylene diisocyanate has a linear structure without a benzene ring, which will reduce the structural strength of the polymer coating layer covering the amino-isocyanate, thus affecting the tensile strength of the polyethylene oxide composite solid electrolyte membrane. Examples 4 and 6 show relatively excellent mechanical strength and ionic conductivity, mainly because the diisocyanates added in Examples 4 and 6 are both linear structures containing benzene rings, which helps to crosslink with polyethylene oxide to form a network structure with good density and moderate strength, that is, the tensile strength reaches more than 20.2 Mpa, and the ionic conductivity reaches more than 6.95*10 -5 S / cm;

[0103] Furthermore, by comparing Examples 6 and 7, it can be known that the test results of Example 6 are better than those of Example 7, mainly because the compounding ratios of diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate and toluene diisocyanate in the two are different, resulting in differences in their tensile strength and ionic conductivity. Especially in Example 6, the mass ratio of 2,5-toluene diisocyanate, 1,5-naphthalene diisocyanate and diphenylmethane diisocyanate is 1:1:0.5, showing excellent mechanical strength, that is, the tensile strength reaches 23.6 Mpa, and the ionic conductivity reaches 8.90*10 -5 S / cm.

[0104] To better understand the technical solutions and beneficial effects of this application, the following further elaborates on this application with specific examples:

[0105] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a high-strength polyethylene oxide composite solid electrolyte membrane, characterized in that, it includes the following steps: Obtain polyethylene oxide, amino-hydroxy inorganic solid electrolyte, diisocyanate, lithium salt and N-methylpyrrolidone respectively; Mix the amino-hydroxy inorganic solid electrolyte, the diisocyanate and part of the N-methylpyrrolidone to obtain a modified crosslinking agent; Among them, the diisocyanate includes multiple of toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and tetramethylbenzene diisocyanate; The amino-hydroxy inorganic solid electrolyte is obtained by the following preparation method, and the preparation method includes the following steps: Obtain an inorganic solid electrolyte, dopamine and a buffer solution; Mix the inorganic solid electrolyte, the dopamine and the buffer solution to obtain a premix of the amino-hydroxy inorganic solid electrolyte; Filter and wash the premix to obtain the amino-hydroxy inorganic solid electrolyte; Heat and mix the polyethylene oxide, the remaining N-methylpyrrolidone and the modified crosslinking agent to obtain a crosslinked polyethylene oxide dispersion; Perform a mixing and molding operation on the crosslinked polyethylene oxide dispersion and the lithium salt to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

2. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, The mass ratio of the amino-hydroxy inorganic solid electrolyte, the diisocyanate, the N-methylpyrrolidone, the polyethylene oxide and the lithium salt is (5~30):(15~35):(60~90):(50~90):(5~20).

3. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, c includes Li 3.3 La 0.56 TiO 3 、Li 7 La3Zr 2 O 12 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 1.4 ZnGe 4 O 16 、Li 3 P 3 S 11 、Li 2 P 2 S 6 and Li 10 GeP 2 S 12 and at least one of them 4. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, In the step of performing the mixing and molding operation on the crosslinked polyethylene oxide dispersion and the lithium salt, it includes the following specific steps: Pour the mixed solution of the crosslinked polyethylene oxide dispersion and the lithium salt into a mold and dry it to obtain a high-strength polyethylene oxide composite solid electrolyte membrane.

5. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, The molecular weight of the polyethylene oxide is 150000 g / mol to 800000 g / mol.

6. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluoromethylsulfonylimide, lithium perchlorate, lithium tetrafluoroborate and lithium bis(oxalato)borate.

7. The preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane according to claim 1, characterized in that, The conditions for the heat mixing are: temperature 50°C to 100°C, time 3h to 12h.

8. A high-strength polyethylene oxide composite solid electrolyte membrane, characterized in that, Prepared by using the preparation method of the high-strength polyethylene oxide composite solid electrolyte membrane described in any one of claims 1 to 7.

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