Temperature-sensitive polymer, electrode sheet, preparation method therefor and use thereof

Abstract

The present disclosure relates to a polymer solid-state battery. Specifically disclosed are a temperature-sensitive polymer, an electrode sheet, a preparation method therefor, and the use thereof. The temperature-sensitive polymer comprises at least one of a compound represented by formula I and a compound represented by formula II, wherein M1 and M2 are respectively polymer soft segments, R1 and R2 are respectively compound segments linked to temperature-sensitive chemical bonds, A1 and A2 are respectively temperature-sensitive chemical bonds, Z1 and Z2 are respectively plasticizer groups, each of m1 and m2 ranges from 2000 to 20000, and each of n1 and n2 ranges from 200 to 5000.

Description

Temperature-sensitive polymer, electrode sheet and preparation method and application thereof

[0001] Priority information

[0002] The present disclosure claims the priority and benefit of the patent application No. 2024108538336 filed on June 27, 2024 with the China National Intellectual Property Office, and incorporates it herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure belongs to the technical field of polymer solid-state batteries, and particularly relates to a temperature-sensitive polymer, an electrode sheet and a preparation method and application thereof. BACKGROUND

[0004] With the development of electric vehicle technology and the increasing demand for endurance, the improvement of battery energy density has become an urgent problem. The most direct way to improve the battery energy density is to increase the loading of the electrode sheet. Polymer batteries have the advantages of non-flammability, easy processing, and wide source of raw materials, and are the first type of batteries that have been commercialized in the field of solid-state batteries. Unlike liquid electrolytes, solid-state electrolytes have poor wettability, and need to be mixed with active materials, conductive agents, and binders to form a slurry during the preparation of the electrode. In order to ensure that the electrode has a high ionic conductivity, a large amount of electrolyte needs to be added, which will result in poor dispersion ability of the slurry and high solvent content. With the increase of the loading of the electrode sheet, the thick electrode sheet coating is prone to cracking during the baking process. However, the existing methods to solve the problem of cracking of thick electrodes still have various defects and need to be further improved. SUMMARY

[0005] The present disclosure aims to at least partially solve one of the technical problems in the related art. To this end, the purpose of the present disclosure is to propose a temperature-sensitive polymer, an electrode sheet and a preparation method and application thereof. The temperature-sensitive polymer of the present disclosure grafts plasticizers to the polymer main chain. After the electrode sheet is dried, under the action of high temperature triggering, the plasticizer groups of the side chains of the temperature-sensitive polymer are separated from the main chain to form free small molecule plasticizers, thereby optimizing the electrode sheet drying process, ensuring the high ionic conductivity of the electrode sheet, and also inhibiting the cracking tendency of the electrode sheet, which is particularly suitable for thick electrodes.

[0006] In one aspect of the present disclosure, the present disclosure proposes a temperature-sensitive polymer. According to the embodiments of the present disclosure, the temperature-sensitive polymer comprises at least one of a compound as shown in Formula I and a compound as shown in Formula II:

[0007] wherein M1 and M2 are each independently a polymer soft segment;

[0008] R1 and R2 are each independently a compound segment connected by a temperature-sensitive chemical bond.

[0009] A1 and A2 are each independently a temperature-sensitive chemical bond;

[0010] Z1 and Z2 are each independently a plasticizer group;

[0011] m1 and m2 are each independently in the range of 2000-20000;

[0012] n1 and n2 are each independently in the range of 200-5000.

[0013] According to the temperature-sensitive polymer of the embodiments of the present disclosure, the temperature-sensitive polymer is a block copolymer, including soft segments and hard segments, a plasticizer group as a branched chain, and a main chain combined through a temperature-sensitive chemical bond. During the mixing and baking process of the electrode sheet, the structure of the temperature-sensitive polymer can remain stable; under the action of high temperature triggering, the plasticizer group of the side chain of the temperature-sensitive polymer is separated from the main chain to form free small molecule plasticizers, thereby effectively improving the ionic conductivity of the electrode sheet. Thus, when the temperature-sensitive polymer of the present disclosure is used for the electrode sheet, firstly, the use of the temperature-sensitive polymer of the present disclosure enables the electrode sheet to withstand a higher baking temperature, optimizes the manufacturing process of the electrode sheet, shortens the manufacturing time and reduces the manufacturing cost. Secondly, during the baking process of the electrode sheet, the plasticizer group exists in the form of a branched chain of the temperature-sensitive polymer, and there is no problem of the floating of small molecule plasticizers, which uniform the electrode sheet dispersion. Most importantly, there is no free small molecule plasticizer during the mixing and baking process of the electrode sheet to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector, which greatly inhibits the cracking tendency of the electrode sheet while ensuring high ionic conductivity, especially the cracking phenomenon of thick electrodes.

[0014] In addition, the temperature-sensitive polymer according to the above embodiments of the present disclosure can also have the following additional technical features:

[0015] In some embodiments of the present disclosure, the polymer soft segment includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylonitrile, polypropylene carbonate, polyethylene oxide, and ethylene oxide-propylene oxide copolymer.

[0016] In some embodiments of the present disclosure, the temperature-sensitive chemical bond includes at least one of a hydrogen bond, an azo bond, and a disulfide bond.

[0017] In some embodiments of the present disclosure, the compound segment connecting the temperature-sensitive chemical bond includes at least one of an azo compound, a disulfide compound, urea, thiourea, 1,3-propanedioic acid, pyridine, piperidine, tetrahydropyrrole, and tetrahydropyrrole derivatives.

[0018] In some embodiments of the present disclosure, the plasticizer group comprises at least one of linear ether organic, cyclic ether organic and benzene ring organic.

[0019] In some embodiments of the present disclosure, the linear ether organic comprises at least one of compounds as shown in Formula III:

[0020] wherein a is equal to 0 or 1; b is equal to 0 or 1; y is in the range of 1-25 and is an integer.

[0021] In some embodiments of the present disclosure, the cyclic ether organic comprises at least one of compounds as shown in Formula IV:

[0022] wherein R3=(CH2)n3X, X is F, Cl or OH, n3 is in the range of 5-80 and is an integer.

[0023] In some embodiments of the present disclosure, the benzene ring organic comprises at least one of compounds as shown in Formula V:

[0024] wherein R4 is H or SH; R5 is OH, NH or O-(CH2) X R6; R6 is CN or ether polymer; x is in the range of 0-10 and is an integer.

[0025] In some embodiments of the present disclosure, at least one of the following compounds is included:

[0026] In a second aspect, the present disclosure provides a pole piece. According to embodiments of the present disclosure, the pole piece comprises a current collector; an active material layer disposed on at least one side of the current collector, the active material layer comprising an active material, a conductive agent, a plasticizer formed by the breakage of the temperature-sensitive chemical bond of the temperature-sensitive polymer and the remaining polymer, and an electrolyte salt. Thus, first, the temperature-sensitive polymer contained in the pole piece of the present disclosure will not decompose at a higher baking temperature, so that the pole piece can withstand a higher baking temperature, thereby optimizing the manufacturing process of the pole piece, shortening the manufacturing time and reducing the manufacturing cost. The conventional plasticizer is prone to decomposition at a higher baking temperature, so the existing pole piece cannot use a higher baking temperature. Second, during the baking process of the pole piece, the plasticizer group exists in the form of a branched chain of the temperature-sensitive polymer, and there is no problem of the plasticizer small molecule floating up, which uniformly disperses the pole piece. Most importantly, there is no free plasticizer small molecule in the mixing and baking process of the pole piece to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector, which greatly suppresses the cracking tendency of the pole piece while ensuring high ionic conductivity, and is particularly suitable for thick electrodes.

[0027] In addition, the pole piece according to the above-mentioned embodiments of the present disclosure can also have the following additional technical features:

[0028] In some embodiments of the present disclosure, the pole piece is a positive pole piece, which comprises a positive current collector; a positive active layer disposed on at least one side of the positive current collector, the positive active layer comprising a positive active material, a positive conductive agent, the temperature-sensitive polymer and an electrolyte salt.

[0029] In some embodiments of the present disclosure, the mass ratio of the positive active material, the conductive agent, the temperature-sensitive polymer and the electrolyte salt is (50-90):(1-10):(10-25):(0-10).

[0030] In some embodiments of the present disclosure, the single-sided loading of the positive active layer is 20 mg / cm 2 -50 mg / cm 2 ; and / or, the single-sided thickness of the positive active layer is 130 μm-300 μm; and / or, the compaction density of the positive active layer is 2.2 g / cm 3 -2.6 g / cm 3 .

[0031] In a third aspect, the present disclosure provides a method for preparing the pole piece of the above-mentioned embodiments. According to embodiments of the present disclosure, the above-mentioned method comprises:

[0032] The active material, the conductive agent, the temperature-sensitive polymer, the electrolyte salt and the solvent are mixed to form a slurry;

[0033] The slurry is coated on at least one side of the current collector, the solvent is removed, and high-temperature heating is performed to obtain the electrode sheet.

[0034] According to the method for preparing the electrode sheet of the embodiments of the present disclosure, the temperature-sensitive polymer does not decompose during the drying process of the electrode sheet, so that the electrode sheet can withstand a higher baking temperature. At the same time, during the baking process of the electrode sheet, the plasticizer groups exist in the form of branched chains of the temperature-sensitive polymer, and there is no problem of the plasticizer small molecules floating up, which uniform the electrode sheet dispersion. Most importantly, there is no free plasticizer small molecule in the slurry mixing and baking process of the electrode sheet to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector, which greatly inhibits the cracking tendency of the electrode sheet while ensuring high ionic conductivity, and is particularly suitable for thick electrodes.

[0035] In addition, the method according to the above embodiments of the present disclosure can also have the following additional technical features:

[0036] In some embodiments of the present disclosure, the removing the solvent includes: vacuum drying at 40-60°C for 1-3h; vacuum drying at 80-120°C for 4-12h.

[0037] In some embodiments of the present disclosure, the high-temperature heating is performed at a temperature of 180-240°C for 10-20min.

[0038] In a fourth aspect of the present disclosure, the present disclosure provides a polymer solid-state battery. According to the embodiments of the present disclosure, the polymer solid-state battery comprises the electrode sheet according to the above embodiments or is prepared by the method according to the above embodiments. Thus, the energy density of the polymer solid-state battery is effectively improved, and the problem of easy cracking of thick electrode coatings during baking is also avoided.

[0039] In a fifth aspect of the present disclosure, the present disclosure provides an electrical equipment. According to the embodiments of the present disclosure, the electrical equipment has the polymer solid-state battery as above. Thus, the electrical equipment has all the advantages of the polymer solid-state battery, which will not be repeated here.

[0040] Additional aspects and advantages of the present disclosure will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0041] The above and / or additional aspects and advantages of the present disclosure will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0042] FIG. 1 is a topographic map of the positive electrode sheet prepared in Example 1;

[0043] FIG. 2 is a topographic map of the positive electrode sheet prepared in Comparative Example 1. DETAILED DESCRIPTION

[0044] Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings, in which the same or similar components have the same or similar designations and functions throughout. The embodiments described below are exemplary and are intended to explain the present disclosure, and are not to be understood as limiting the present disclosure.

[0045] The present application is proposed by the inventors based on the following problems:

[0046] With the increase of the electrode loading, the thickness of the electrode increases, the unit absolute content of the solvent also increases, and the volatilization amount per unit time becomes larger, so a large amount of solvent small molecules further reduces the adhesion of the polymer, thereby causing the thick electrode sheet coating to be prone to cracking during the baking process.

[0047] To solve the problem of easy cracking of thick electrodes, on the one hand, the idea of in-situ polymerization of electrolyte to form a solid electrolyte can be adopted from the perspective of baking process, so as to realize zero volatilization of solvent and thereby avoid the problem of electrode sheet cracking caused by solvent volatilization, but this method brings the problems of reduced processability of the electrode, difficulty in ensuring the internal polymerization degree and polymerization uniformity, and the existence of solvent residues in the electrode. On the other hand, the active particles can be filled into a porous ordered electrolyte structure as a skeleton to prepare a thick electrode from the perspective of electrode sheet structure, which can improve the loading while ensuring the morphology, but has the problems of uneven dispersion of active particles, large interface impedance between active particles and porous skeleton, difficulty in skeleton forming process, and poor structural stability.

[0048] For a polymer solid-state battery, in the case of no additional binder addition, there are mainly two reasons for the cracking of thick electrodes, one is that the solvent volatilization amount is too large during the baking process, and the other is that the adhesion of the polymer itself is insufficient. Adding a plasticizer can reduce the viscosity of the slurry and thereby reduce the solvent content, but when the content of the solid-state polymer electrolyte (SPE) in the electrode sheet is low (less than 13%), the plasticizer has little effect on the viscosity of the slurry, but greatly reduces the crystallinity of the solid-state polymer electrolyte and its adhesion to the active particles. The inventors have found that the plasticizer is one of the main reasons for the cracking of thick electrodes, and when the contents of other formulations are controlled to be the same, the higher the content of the plasticizer, the greater the degree of cracking of the electrode sheet. No one has started from the perspective of the plasticizer to solve the problem of cracking of thick electrodes.

[0049] Therefore, in one aspect of the present disclosure, a temperature-sensitive polymer is provided. According to embodiments of the present disclosure, the temperature-sensitive polymer comprises at least one of a compound as shown in Formula I and a compound as shown in Formula II:

[0050] wherein M1 and M2 are each independently a polymer soft segment; As the polymer hard segment, R1 and R2 are each independently a compound segment connected by a temperature-sensitive chemical bond; A1 and A2 are each independently a temperature-sensitive chemical bond; Z1 and Z2 are each independently a plasticizer group; m1 and m2 are each independently in the range of 2000-20000; and n1 and n2 are each independently in the range of 200-5000. The temperature-sensitive polymer provided by the present disclosure is described in detail as follows:

[0051] The temperature-sensitive polymer provided by the present disclosure is a block copolymer comprising a soft segment and a hard segment, wherein the soft segment is a conventional polymer for solid-state batteries, and the hard segment is a polypropylene-based polymer grafted with a plasticizer. The plasticizer group is a branched chain connected to the main chain by a temperature-sensitive chemical bond. During the mixing and baking processes of the electrode sheet, the structure of the temperature-sensitive polymer can remain stable; under the action of high temperature triggering, the plasticizer group of the side chain of the temperature-sensitive polymer is separated from the main chain to form free small molecule plasticizers, thereby effectively reducing the crystallinity of the polymer, improving the flow of the polymer itself, and further improving the migration rate of lithium ions dissolved in the polymer, thereby improving the ionic conductivity of the electrode sheet. Therefore, when the temperature-sensitive polymer of the present disclosure is used in the electrode sheet, firstly, the temperature-sensitive polymer of the present disclosure will not decompose at a higher baking temperature, so that the electrode sheet can withstand a higher baking temperature. The conventional plasticizer is easy to decompose at a higher baking temperature, so the existing electrode sheet cannot use a higher baking temperature. Therefore, the use of the temperature-sensitive polymer enables the electrode sheet to withstand a higher baking temperature, optimizes the manufacturing process of the electrode sheet, shortens the manufacturing time and reduces the manufacturing cost. Secondly, during the baking process of the electrode sheet, the plasticizer group exists in the form of a branched chain of the temperature-sensitive polymer, and there is no problem of floating of the small molecule plasticizer, and the electrode sheet is uniformly dispersed. Most importantly, there is no free small molecule plasticizer to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector during the mixing and baking processes of the electrode sheet, which greatly inhibits the cracking tendency of the electrode sheet while ensuring high ionic conductivity, and is particularly suitable for thick electrodes.

[0052] In the embodiments of the present disclosure, each of M1 and M2 is independently a polymer soft segment, and the specific type of the polymer soft segment is not particularly limited, and as some preferred solutions, the polymer soft segment includes at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyethylene oxide (PEO), and ethylene oxide-propylene oxide copolymer (PEO-PO). When the polymer soft segment is an ether polymer such as polyethylene oxide (PEO) or ethylene oxide-propylene oxide copolymer (PEO-PO), the general formula of the formed temperature-sensitive polymer is Formula II, otherwise the general formula of the formed temperature-sensitive polymer is Formula I.

[0053] In the embodiments of the present disclosure, the temperature-sensitive chemical bond refers to a bond that is easily broken under the triggering of high temperature.

[0054] In the embodiments of the present disclosure, the plasticizer is grafted on the main chain through a temperature-sensitive chemical bond, and as some preferred solutions, the temperature-sensitive chemical bond includes at least one of a hydrogen bond, an azo bond, and a disulfide bond, so that the temperature-sensitive chemical bond of the above-mentioned type is easily broken under the triggering of high temperature, so that the plasticizer group of the temperature-sensitive polymer side chain can easily separate from the main chain due to the breaking of the temperature-sensitive chemical bond, and form a free small molecule plasticizer. Among them, the azo bond and the disulfide bond both belong to covalent bonds, and the hydrogen bond (also known as van der Waals force) belongs to non-covalent bond, and the molecules are connected through the mutual attraction of force. Moreover, the hydrogen bond can be represented by a dashed line X----Y, such as OH----O, OH----Cl, etc., wherein the dashed line represents the hydrogen bond.

[0055] In the embodiments of the present disclosure, the compound segments R1 and R2 connected by the temperature-sensitive chemical bond are condensed on the side chain of to form a polymer hard segment. As some preferred solutions, the compound segment connected by the temperature-sensitive chemical bond includes at least one of an azo compound, a disulfide compound, urea, thiourea, 1,3-propanedioic acid, pyridine, piperidine, tetrahydropyrrole, and tetrahydropyrrole derivatives. Therefore, the compound segments of the above-mentioned types can all form temperature-sensitive chemical bonds between the plasticizer groups, which are easily broken under the triggering of high temperature, so that the plasticizer group of the temperature-sensitive polymer side chain can easily separate from the main chain due to the breaking of the temperature-sensitive chemical bond, and form a free small molecule plasticizer.

[0056] In the embodiments of the present disclosure, the plasticizer group includes at least one of a linear ether organic compound, a cyclic ether organic compound, and a benzene ring organic compound. According to some specific embodiments of the present disclosure, the linear ether organic compound includes at least one of the compounds as shown in Formula III:

[0057] wherein a is equal to 0 or 1, indicating the number of methyl groups here; b is equal to 0 or 1, indicating the number of methyl groups here; y ranges from 1 to 25 and is an integer. The linear ether plasticizer of the structure shown in the above Formula III is combined with the main chain as a branch chain through a temperature-sensitive chemical bond to form a plasticizer group. During the mixing and baking process of the electrode sheet, the structure of the temperature-sensitive polymer containing the above plasticizer group can remain stable; under the action of high temperature triggering, the plasticizer group of the side chain of the temperature-sensitive polymer can be separated from the main chain to form a free small molecule plasticizer.

[0058] According to still some specific embodiments of the present disclosure, the above-mentioned cyclic ether organic matter includes at least one of the compounds as shown in Formula IV:

[0059] wherein R3=(CH2)n3X, X is F, Cl or OH, n3 ranges from 5 to 80 and is an integer. The cyclic ether plasticizer of the structure shown in the above Formula IV is combined with the main chain as a branch chain through a temperature-sensitive chemical bond to form a plasticizer group. During the mixing and baking process of the electrode sheet, the structure of the temperature-sensitive polymer containing the above plasticizer group can remain stable; under the action of high temperature triggering, the plasticizer group of the side chain of the temperature-sensitive polymer can be separated from the main chain to form a free small molecule plasticizer.

[0060] According to still some specific embodiments of the present disclosure, the above-mentioned cyclic ether organic matter includes at least one of the compounds as shown in Formula IV:

[0061] wherein R4 is H or SH; R5 is OH, NH or O-(CH2) X R6; R6 is CN or an ether polymer; x ranges from 0 to 10 and is an integer. The cyclic ether plasticizer of the structure shown in the above Formula V is combined with the main chain as a branch chain through a temperature-sensitive chemical bond to form a plasticizer group. During the mixing and baking process of the electrode sheet, the structure of the temperature-sensitive polymer containing the above plasticizer group can remain stable; under the action of high temperature triggering, the plasticizer group of the side chain of the temperature-sensitive polymer can be separated from the main chain to form a free small molecule plasticizer.

[0062] In the embodiments of the present disclosure, the specific type of the above-mentioned temperature-sensitive polymer is not particularly limited, and as some preferred solutions, the above-mentioned temperature-sensitive polymer includes at least one of the following compounds:

[0063] The above-mentioned temperature-sensitive polymers are all block copolymers, and all include soft segments and hard segments. The structures of the above-mentioned temperature-sensitive polymers have good stability during the mixing and baking of the electrode sheet; under the action of high temperature triggering, the plasticizer groups of the side chains of the above-mentioned temperature-sensitive polymers can all be separated from the main chain to form free small molecule plasticizers, thereby effectively improving the ionic conductivity of the electrode sheet.

[0064] In the embodiments of the present disclosure, the preparation method of the above-mentioned temperature-sensitive polymer is not particularly limited, and as a specific example, the preparation method of the above-mentioned temperature-sensitive polymer is as follows:

[0065] The main chain of the temperature-sensitive polymer is prepared by free radical polymerization reaction of the polymer soft segment and the polymer hard segment with hydroxyethyl isobromobutyrate (ATRP) as an initiator;

[0066] The above-mentioned temperature-sensitive polymer is obtained by condensation reaction of the active functional groups such as carboxyl, amino and hydroxyl on the plasticizer of the temperature-sensitive chemical bond chain and the carboxylic acid on the hard segment under the catalysis of metals such as antimony.

[0067] In the second aspect of the present disclosure, the present disclosure provides an electrode sheet. According to the embodiments of the present disclosure, the electrode sheet includes a current collector; an active material layer, the active material layer is arranged on at least one side of the current collector, and the active material layer includes an active substance, a conductive agent, a plasticizer and a remaining polymer formed by the breaking of the temperature-sensitive chemical bond of the above-mentioned temperature-sensitive polymer, and an electrolyte salt. Therefore, first, the temperature-sensitive polymer contained in the electrode sheet of the present disclosure will not decompose at a higher baking temperature, so that the electrode sheet can withstand a higher baking temperature, thereby optimizing the manufacturing process of the electrode sheet, shortening the manufacturing time and reducing the manufacturing cost. The conventional plasticizer is easy to decompose at a higher baking temperature, so the existing electrode sheet cannot use a higher baking temperature. Secondly, during the baking process of the electrode sheet, the plasticizer groups exist in the form of side chains of the temperature-sensitive polymer, and there is no problem of floating of small molecule plasticizers, and the electrode sheet is uniformly dispersed. Most importantly, there is no free small molecule plasticizer to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector during the mixing and baking process of the electrode sheet, which greatly inhibits the cracking tendency of the electrode sheet while ensuring high ionic conductivity, and is particularly suitable for thick electrodes.

[0068] In the embodiments of the present disclosure, the above-mentioned temperature-sensitive polymer can be applied to both positive electrode sheets and negative electrode sheets. The above-mentioned temperature-sensitive polymer can achieve the above-mentioned technical effects whether it is applied to a positive electrode sheet or a negative electrode sheet. According to some specific embodiments of the present disclosure, the above-mentioned electrode sheet is a positive electrode sheet, and the positive electrode sheet includes a positive electrode current collector; a positive electrode active layer, the positive electrode active layer is arranged on at least one side of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active substance, a positive electrode conductive agent, a temperature-sensitive polymer and an electrolyte salt.

[0069] In embodiments of the present disclosure, the material of the positive electrode current collector is not particularly limited, and as some preferred solutions, the positive electrode current collector includes at least one of an aluminum foil, a foamed aluminum, a carbon-coated aluminum foil, a carbon mesh, and a carbon cloth.

[0070] According to some embodiments of the present disclosure, the thickness of the positive electrode current collector can be 8 μm to 25 μm.

[0071] According to still some embodiments of the present disclosure, the mass ratio of the positive electrode active material, the positive electrode conductive agent, the temperature-sensitive polymer, and the electrolyte salt is (50-90):(1-10):(10-25):(0-10), and the content of the electrolyte salt is greater than 0. By limiting the mass ratio of each component within the above range, it is further ensured that the electrode tab can withstand a higher baking temperature, thereby optimizing the manufacturing process of the electrode tab, shortening the manufacturing time and reducing the manufacturing cost; at the same time, the problem of floating of the plasticizer small molecules is further avoided; it is further ensured that the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector are reduced in the entire process of the electrode tab, the high ionic conductivity is ensured, and the cracking tendency of the electrode tab is greatly inhibited, which is particularly suitable for thick electrodes.

[0072] In embodiments of the present disclosure, the specific type of the positive electrode active material is not particularly limited, and a person skilled in the art can select it according to actual needs, and as some preferred solutions, the positive electrode active material includes lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2(wherein, A is selected from one of Co, Mn, and 0 m B n C (1-m-n) O2(wherein, B, C are independently selected from at least one of Co, Al, Mn, and B and C are not the same, 0

[0073] In embodiments of the present disclosure, the specific type of the positive electrode conductive agent is not particularly limited, and a person skilled in the art can select it according to actual needs, and as some preferred solutions, the positive electrode conductive agent includes at least one of acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube, and Ketjen black.

[0074] In the embodiments of the present disclosure, the specific type of the electrolyte salt is not particularly limited, and can be selected by those skilled in the art according to actual needs. For example, when the electrode sheet is applied to a lithium ion battery, the electrolyte salt is selected to be a lithium salt, and correspondingly, when the electrode sheet is applied to a sodium ion battery, the electrolyte salt is selected to be a sodium salt. As some specific examples, when the electrolyte salt is a lithium salt, the lithium salt can be at least one of an organic lithium salt, an inorganic lithium salt, for example, LiPF6, LiBF4, LiClO4, LiAsF6, LiTFSI, LiFSI, LiBOB, LiDFOB, LiTFOP.

[0075] According to still some specific embodiments of the present disclosure, the single-side loading of the positive electrode active layer is 20 mg / cm 2 ~ 50 mg / cm 2 Thereby, the positive electrode active layer can have high ionic conductivity and high loading, and the cracking tendency of the electrode sheet is greatly inhibited.

[0076] According to still some specific embodiments of the present disclosure, the single-side thickness of the positive electrode active layer is 130 μm ~ 300 μm, thereby the positive electrode active layer can have high ionic conductivity and high loading, and the cracking tendency of the electrode sheet is greatly inhibited.

[0077] According to still some specific embodiments of the present disclosure, the compaction density of the positive electrode active layer is 2.2 g / cm 3 ~ 2.6 g / cm 3 Thereby, the positive electrode active layer can have high ionic conductivity and high loading, and the cracking tendency of the electrode sheet is greatly inhibited.

[0078] In a third aspect of the present disclosure, a method for preparing the electrode sheet of the above embodiments is provided. According to the embodiments of the present disclosure, the method comprises:

[0079] S100: forming a slurry

[0080] In this step, the active material, the conductive agent, the temperature-sensitive polymer, the electrolyte salt and the organic solvent are mixed to form a slurry.

[0081] According to some specific embodiments of the present disclosure, the solid content of the slurry can be 30 wt% ~ 55 wt%, preferably 40 wt% ~ 45 wt%.

[0082] S200: coating the slurry on at least one side of the current collector, removing the solvent, and heating at high temperature

[0083] In this step, the slurry is coated on at least one side of the current collector, the solvent is removed, and high-temperature heating is performed to obtain the electrode sheet. As a specific example, the slurry can be uniformly coated on the current collector by using a doctor blade method.

[0084] According to some embodiments of the present disclosure, the removal of the solvent includes vacuum drying at 40-60°C for 1-3h to remove a large amount of solvent, and vacuum drying at 80-120°C for 4-12h to remove residual solvent. By using gradient drying, the solvent in the slurry coated on the current collector can be effectively removed, and the temperature-sensitive polymer of the present disclosure will not decompose at the above drying temperature, so that the electrode sheet can withstand a higher baking temperature. At the same time, during the above drying process, the plasticizer groups exist in the form of branched chains of the temperature-sensitive polymer, and there is no problem of floating of small molecule plasticizers, and the electrode sheet dispersion is uniform.

[0085] According to still some embodiments of the present disclosure, the high-temperature heating temperature is 180-240°C, and the high-temperature heating time is 10-20min, so as to ensure that under the above high-temperature triggering action, the plasticizer groups of the side chain of the temperature-sensitive polymer in the electrode sheet are separated from the main chain to form free small molecule plasticizers, thereby effectively reducing the crystallinity of the polymer, improving the flow of itself, and further improving the migration rate of lithium ions dissolved in the polymer, and improving the ionic conductivity of the electrode sheet.

[0086] Further, the above method further includes:

[0087] Rolling the above electrode sheet at 30-60°C can obtain a positive electrode sheet with high ionic conductivity, high loading, and no cracking.

[0088] According to the method for preparing the electrode sheet according to the embodiments of the present disclosure, the temperature-sensitive polymer will not decompose during the drying process of the electrode sheet, so that the electrode sheet can withstand a higher baking temperature. At the same time, during the baking process of the electrode sheet, the plasticizer groups exist in the form of branched chains of the temperature-sensitive polymer, and there is no problem of floating of small molecule plasticizers, and the electrode sheet dispersion is uniform. Most importantly, there is no free small molecule plasticizer in the slurry mixing and baking process of the electrode sheet to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector, which greatly inhibits the cracking tendency of the electrode sheet while ensuring high ionic conductivity, and is particularly suitable for thick electrodes.

[0089] In a fourth aspect of the present disclosure, a polymer solid-state battery is provided. According to the embodiments of the present disclosure, the polymer solid-state battery includes the electrode sheet described in the above embodiments or the electrode sheet prepared by the method described in the above embodiments. Thus, the energy density of the polymer solid-state battery is effectively improved, and the problem of easy cracking of the thick electrode coating during the baking process is also avoided.

[0090] In a fifth aspect of the present disclosure, a power consuming device is provided. According to embodiments of the present disclosure, the power consuming device has the polymer solid-state battery as described above. Thus, the power consuming device has all the advantages of the polymer solid-state battery, which are not repeated here.

[0091] Specifically, the power consuming device can include lighting elements, display elements, mobile devices, etc., and can specifically include street lamps, signal indicator lights, insect killing lamps, electric fans, electric toys, electric tools, electric vehicles, electric cars, ships, spacecraft, etc., wherein the electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric plane toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc. The photovoltaic power generation system can include large-scale ground photovoltaic power generation systems, distributed photovoltaic power generation systems, and building-integrated photovoltaic power generation systems, etc.

[0092] Embodiments of the present disclosure are described in detail below. It should be noted that the embodiments described below are exemplary and are used to explain the present disclosure only, and should not be construed as limiting the present disclosure. In addition, if not specifically stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also readily available to those skilled in the art.

[0093] Example 1

[0094] (1) Lithium iron phosphate was selected as the positive active material, Super P was selected as the conductive agent, and lithium bis(trifluoromethanesulfonyl)imide was selected as the lithium salt. The positive electrode slurry was prepared by dissolving the above-mentioned positive active material, conductive agent, temperature-sensitive polymer, and lithium salt in N,N-dimethylformamide. The solid content of the positive electrode slurry was 42 wt.%. The mass ratio of the above-mentioned positive active material, conductive agent, temperature-sensitive polymer, and lithium salt was 80:2:13.5:4.5.

[0095] The temperature-sensitive polymer has the following structure:

[0096] The polyethylene oxide is the soft segment, the polyacrylate condensed with 1,3-propanedioic acid is the hard segment, and the ethylene glycol-1-methyl ether is the plasticizer, which is grafted to the main chain through hydrogen bonds.

[0097] (2) The positive electrode slurry was uniformly coated on the current collector by using a doctor blade method.

[0098] (3) The gradient baking method was used, i.e., vacuum drying at 50°C for 2h, vacuum drying at 100°C for 10h, and finally high-temperature heating at 180°C for 20min, so as to promote the plasticizer of the polymer side chain to separate from the main chain under the action of heat, forming free small molecules.

[0099] (4) The above electrode sheet is rolled at 60°C to obtain a positive electrode sheet. The single-sided loading of the positive electrode active layer formed on the positive electrode sheet is about 40 mg / cm 2 ; and the thickness of the single-sided positive electrode material layer is 160 μm.

[0100] Example 2

[0101] The preparation method of Example 2 is basically the same as that of Example 1, except that:

[0102] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula II-2:

[0103] wherein polyethylene oxide is the soft segment, polyacrylate condensed with 1,3-propanedioic acid in the side chain is the hard segment, and 2-ethylchloro-dioxolane is the plasticizer grafted to the main chain through hydrogen bond.

[0104] Example 3

[0105] The preparation method of Example 3 is basically the same as that of Example 1, except that:

[0106] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula II-3:

[0107] wherein polyethylene oxide is the soft segment, polyacrylate condensed with phenyl-dithio-1-phenol in the side chain is the hard segment, and 1-thiol-phenyl is the plasticizer grafted to the main chain through disulfide bond.

[0108] Example 4

[0109] The preparation method of Example 4 is basically the same as that of Example 1, except that:

[0110] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula II-4:

[0111] wherein polyethylene oxide is the soft segment, polyacrylamide condensed with azobisaminobenzene in the side chain is hard segment A, polyacrylate condensed with 1,3-propanedioic acid in the side chain is hard segment B, 1,3-aminobenzene and 2-ethylchloro-dioxolane are the plasticizers grafted to the main chain through azo bond and hydrogen bond.

[0112] Example 5

[0113] The preparation method of Example 5 is basically the same as that of Example 1, except that:

[0114] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula I-1:

[0115] wherein polyvinylidene fluoride is the soft segment, and other structures are the same as in Example 1.

[0116] Example 6

[0117] The preparation method of Example 6 is basically the same as that of Example 1, except that:

[0118] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula I-2:

[0119] wherein polytetrafluoroethylene is the soft segment, and other structures are the same as in Example 1.

[0120] Example 7

[0121] The preparation method of Example 7 is basically the same as that of Example 1, except that:

[0122] The temperature-sensitive polymer represented by Formula II-1 in Example 1 is replaced by a temperature-sensitive polymer represented by Formula I-3:

[0123] wherein polyacrylonitrile is the soft segment, and other structures are the same as in Example 1.

[0124] Example 8

[0125] The preparation method of Example 8 is basically the same as that of Example 1, except that:

[0126] The mass ratio of the positive active material, the conductive agent, the temperature-sensitive polymer, and the lithium salt is 83.5:2:10:4.5.

[0127] Example 9

[0128] The preparation method of Example 9 is basically the same as that of Example 1, except that:

[0129] The mass ratio of the positive active material, the conductive agent, the temperature-sensitive polymer, and the lithium salt is 78.5:2:15:4.5.

[0130] Example 10

[0131] The preparation method of Example 10 is basically the same as that of Example 1, except that:

[0132] The mass ratio of the positive active material, the conductive agent, the temperature-sensitive polymer, and the lithium salt is 73.5:2:20:4.5.

[0133] Example 11

[0134] The preparation method of Example 11 is substantially the same as that of Example 1, except that:

[0135] The mass ratio of the positive electrode active material, the conductive agent, the temperature-sensitive polymer, and the lithium salt is 68.5:2:25:4.5.

[0136] Example 12

[0137] The preparation method of Example 12 is substantially the same as that of Example 1, except that:

[0138] The single-side loading of the positive electrode active layer formed on the positive electrode sheet is about 20 mg / cm 2 ; and the single-side positive electrode material layer thickness is 80 μm.

[0139] Example 13

[0140] The preparation method of Example 13 is substantially the same as that of Example 1, except that:

[0141] The single-side loading of the positive electrode active layer formed on the positive electrode sheet is about 50 mg / cm 2 ; and the single-side positive electrode material layer thickness is 200 μm.

[0142] Example 14

[0143] The preparation method of Example 14 is substantially the same as that of Example 1, except that:

[0144] (3) Finally, high-temperature heating at 210°C for 15 min, to promote the plasticizer of the polymer side chain to separate from the main chain under the action of heat, forming a free small molecule.

[0145] Example 15

[0146] The preparation method of Example 15 is substantially the same as that of Example 1, except that:

[0147] (3) Finally, high-temperature heating at 240°C for 10 min, to promote the plasticizer of the polymer side chain to separate from the main chain under the action of heat, forming a free small molecule.

[0148] Comparative Example 1

[0149] (1) Selecting lithium iron phosphate as the positive active material, Super P as the conductive agent, lithium bis-trifluoromethanesulfonimide as the lithium salt, 1,3-aminobenzene as the plasticizer, and polyethylene oxide-polyacrylamide as the polymer, they are dissolved in N,N-dimethylformamide to prepare a positive electrode slurry, and the solid content of the positive electrode slurry is 42wt%. The mass ratio of the above-mentioned positive active material, conductive agent, polymer, plasticizer, and lithium salt is 80:2:9:4.5:4.5.

[0150] (2) The positive electrode slurry is uniformly coated on the current collector by using the doctor blade method.

[0151] (3) The initial electrode sheet is obtained by using the gradient baking method, i.e., vacuum drying at 50°C for 2h, and then vacuum drying at 100°C for 10h.

[0152] (4) The initial electrode sheet is rolled at 60°C to obtain the positive electrode sheet. The single-sided loading of the positive active layer formed on the positive electrode sheet is about 40mg / cm 2 ; and the thickness of the single-sided positive electrode material layer is 160μm.

[0153] The appearance of the positive electrode sheets prepared in Examples 1-15 and Comparative Example 1 is captured by using a common camera on the market, and the results are shown in Table 1. FIG. 1 is a morphology diagram of the positive electrode sheet prepared in Example 1. FIG. 2 is a morphology diagram of the positive electrode sheet prepared in Comparative Example 1.

[0154] The ionic conductivity of the positive electrode sheets prepared in Examples 1-15 and Comparative Example 1 is tested by using an electrochemical workstation, and the results are shown in Table 1.

[0155] The soft pack batteries are assembled by using the positive electrode sheets prepared in Examples 1-15 and Comparative Example 1. The positive electrode is the positive electrode sheet prepared in Examples 1-15 and Comparative Example 1, the negative electrode is lithium metal, the electrolyte is polyethylene oxide (PEO, the relative atomic mass Mn=6*10 5 g / mol), the lithium salt is lithium bis-trifluoromethylsulfonimide (LiTFSI), and the plasticizer is acetonitrile. The mass ratio of PEO, lithium salt, and acetonitrile is 0.5:0.25:0.25. The soft pack batteries of Examples 1-15 and Comparative Example 1 are respectively subjected to conventional electrochemical performance tests. The test voltage is 2.5V-3.8V, and the charge-discharge rate is 0.5C. The test results are shown in Table 1.

[0156] Table 1

[0157] As can be seen from Table 1, the pole piece of Comparative Example 1 is seriously cracked, while the pole pieces of Examples 1-15 of the present disclosure are uniform and not cracked, which shows that Examples 1-15 of the present disclosure can greatly inhibit the cracking tendency of the pole piece by introducing the temperature-sensitive polymer in the preparation process of the pole piece, so as to reduce the adhesion between the polymer and the active particles and the adhesion between the polymer and the current collector in the whole process of the pole piece, while ensuring high ionic conductivity.

[0158] As can be further seen from Table 1, compared with Examples 1-3, the 60°C pole piece ionic conductivity and the corresponding number of turns of the 0.2C / 80% capacity retention of Example 4 are further improved, and the 0.1C polarization of Example 4 is further reduced. It can be seen that increasing the types of plasticizers in the temperature-sensitive polymer can slightly improve the rate and cycle performance of the battery, and it is possible that the multiple types of plasticizers play a synergistic role in optimizing the microstructure of the pole piece.

[0159] As can be seen by comparing Comparative Example 1, Examples 5-6, the soft segment structure has no obvious effect on the ionic conductivity of the pole piece, but it will affect the adhesion inside the pole piece, and then affect the cycle performance of the battery.

[0160] As can be seen by comparing Comparative Example 1, Examples 8-11, the higher the proportion of active material in the composite positive electrode formula, the greater the polarization, and the higher the electrolyte content, the easier it is to form a complete ion conduction path, thereby improving the ionic conductivity of the pole piece.

[0161] As can be seen by comparing Comparative Example 1, Examples 12-13, the higher the active material loading in the composite positive electrode formula, the greater the polarization of the battery, resulting in a decline in the overall performance of the battery.

[0162] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present specification, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and modified by those skilled in the art without contradiction.

[0163] Although the embodiments of the present disclosure have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A thermosensitive polymer, wherein, Including at least one of the compounds shown in Formula I and the compounds shown in Formula II: Among them, M1 and M2 are each independently polymer soft segments; R1 and R2 are each independently compound segments that connect temperature-sensitive chemical bonds; A1 and A2 are each independently thermosensitive chemical bonds; Z1 and Z2 are each an independent plasticizer group; The ranges of m1 and m2 are each independently 2000 to 20000; The ranges of n1 and n2 are each independent, from 200 to 5000.

2. The thermosensitive polymer according to claim 1, wherein, The polymer soft segment includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylonitrile, polypropylene carbonate, polyethylene oxide, and ethylene oxide-propylene oxide copolymer.

3. The thermosensitive polymer according to claim 1 or 2, wherein, The temperature-sensitive chemical bond includes at least one of hydrogen bond, azo bond, and disulfide bond.

4. The thermosensitive polymer according to any one of claims 1 to 3, wherein, The compound segment connecting the thermosensitive chemical bond includes at least one of azo compounds, disulfide compounds, urea, thiourea, 1,3-malonic acid, pyridine, piperidine, tetrahydropyrrole, and tetrahydropyrrole derivatives.

5. The thermosensitive polymer according to any one of claims 1 to 4, wherein, The plasticizer group includes at least one of linear ether organic compounds, cyclic ether organic compounds, and benzene ring organic compounds.

6. The thermosensitive polymer according to claim 5, wherein, The linear ether organic compounds include at least one of the compounds shown in Formula III: Where a equals 0 or 1; b equals 0 or 1; and y ranges from 1 to 25 and is an integer.

7. The thermosensitive polymer according to claim 5 or 6, wherein, The cyclic ether organic compounds include at least one of the compounds shown in Formula IV: Where R3 = (CH2)n3X, X is F, Cl or OH, and n3 is in the range of 5 to 80 and is an integer.

8. The thermosensitive polymer according to any one of claims 5 to 7, wherein, The benzene ring organic compounds include at least one of the compounds shown in Formula V: Where R4 is H or SH; R5 is OH, NH or O-(CH2). X -R6; R6 is a CN or ether polymer; x ranges from 0 to 10 and is an integer.

9. The thermosensitive polymer according to any one of claims 1 to 8, wherein, Includes at least one of the following compounds:

10. An electrode sheet, wherein, include: current collector; An active material layer is disposed on at least one side of the current collector, the active material layer comprising an active substance, a conductive agent, a plasticizer formed by the breaking of thermosensitive chemical bonds of the thermosensitive polymer according to any one of claims 1 to 9, the remaining polymer, and an electrolyte salt.

11. The electrode according to claim 10, wherein, The electrode is a positive electrode, and the positive electrode includes a positive current collector; A positive electrode active layer is disposed on at least one side of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material, a positive electrode conductive agent, the temperature-sensitive polymer, and an electrolyte salt.

12. The electrode according to claim 11, wherein, The mass ratio of the positive electrode active material, the conductive agent, the thermosensitive polymer and the electrolyte salt is (50-90):(1-10):(10-25):(0-10).

13. The electrode according to claim 11 or 12, wherein, The single-sided loading of the positive electrode active layer is 20 mg / cm³. 2 ~50mg / cm 2 ; And / or, the thickness of one side of the positive electrode active layer is 130μm to 300μm; And / or, the compaction density of the positive electrode active layer is 2.2 g / cm³. 3 ~2.6g / cm 3 .

14. A method for preparing an electrode sheet according to any one of claims 10 to 13, comprising: An active substance, a conductive agent, a thermosensitive polymer as described in any one of claims 1 to 9, an electrolyte salt, and a solvent are mixed to form a slurry; The slurry is coated onto at least one side of the current collector, the solvent is removed, and the mixture is heated at high temperature to obtain an electrode.

15. The method according to claim 14, wherein, The removal of the solvent includes: Vacuum dry at 40℃~60℃ for 1h~3h; Vacuum dry at 80℃~120℃ for 4h~12h.

16. The method according to claim 14 or 15, wherein, The high-temperature heating temperature is 180℃~240℃, and the high-temperature heating time is 10min~20min.

17. A polymer solid-state battery, wherein, The electrode includes any one of claims 10 to 13 or the electrode obtained by the method described in any one of claims 14 to 16.

18. An electrical appliance, wherein, The polymer solid-state battery of claim 17.

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