Electrolyte, method for preparing the same, and use thereof

Abstract

The present application relates to an electrolyte and a preparation method and application thereof. The electrolyte is a gel and comprises a polymer matrix, an organic solvent swelling the polymer matrix and a lithium salt absorbed in the gel; the polymer matrix contains a cyano-modified polymer, the repeating structural unit of the cyano-modified polymer at least comprises a first repeating structural unit containing a cyano group and a second repeating structural unit not containing a cyano group; and the cyano content in the polymer matrix is 80-340 mol% based on the total amount of the repeating structural units of the polymer matrix. The electrolyte containing the cyano-modified polymer can undergo a complexation reaction with metal cations dissolved from the positive electrode material in the battery, so as to fix the metal cations on the skeleton of the electrolyte, avoid the metal cations from reaching the negative electrode region of low potential to react and destroy the negative electrode SEI, and affect the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an electrolyte, its preparation method, and its application. Background Technology

[0002] The dissolution of metal cations from the positive electrode material in a battery can lead to a decrease in battery capacity and affect battery life. Taking lithium manganese oxide, a manganese-based positive electrode material, as an example, lithium manganese oxide boasts good safety performance, thermal stability, overcharge resistance, a high voltage platform, and low cost. Furthermore, its unique spinel structure gives it excellent high-current charge-discharge performance and high / low-temperature charge-discharge performance. However, its poor long-term cycle stability and poor storage resistance hinder its development in power batteries. This is mainly due to the dissolution of manganese ions during charge-discharge and storage. After dissolving, manganese ions pass through the separator to the low-potential negative electrode, where they are reduced and precipitated. This process not only causes continuous loss of lithium manganese oxide but also damages the SEI film of the negative electrode and continuously consumes electrolyte, all of which negatively impact battery life.

[0003] To address this issue, current methods primarily involve treating the cathode material itself through doping and surface coating. These methods place high demands on the material synthesis process and are costly. Furthermore, doping or coating alters the original crystal structure of the cathode material, significantly reducing its inherent advantages in charge-discharge current. Doping also affects the lithium content of the battery, thus decreasing its capacity. Therefore, suppressing the dissolution of metal cations from the cathode material from multiple angles is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide an electrolyte, its preparation method, and its application, so as to solve the battery degradation problem caused by the dissolution of positive electrode metal cations in batteries.

[0005] To achieve the above objectives, a first aspect of the present invention provides an electrolyte, which is a gel and comprises a polymer matrix, an organic solvent that swells the polymer matrix, and a lithium salt adsorbed in the gel; the polymer matrix contains a cyano-modified polymer, wherein the repeating structural units of the cyano-modified polymer include at least a first repeating structural unit containing cyano and a second repeating structural unit not containing cyano; and the cyano content in the polymer matrix is ​​80-340 mol% based on the total amount of repeating structural units in the polymer matrix.

[0006] Optionally, the cyano-modified polymer contains cyano-modified polyethylene oxide; the molecular structure of the cyano-modified polyethylene oxide is shown in Formula 1:

[0007]

[0008] Wherein, R1 and R6 are each independently cyanoethyl or hydrogen; n is the number of repeating polyoxyethylene structural units and is between 20 and 2000; the repeating polyoxyethylene structural units include a first repeating polyoxyethylene structural unit containing cyano groups and a second repeating polyoxyethylene structural unit not containing cyano groups;

[0009] In the first repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a cyanoalkyl, cyano or hydrogen containing 3-20 carbon atoms, and at least one of R2, R3, R4 and R5 is a cyanoalkyl or cyano containing 3-20 carbon atoms.

[0010] In the second repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a hydrocarbon group containing 1-20 carbon atoms, a hydrocarbon group with substituents containing 1-20 carbon atoms, or hydrogen; the substituents are alkoxy, hydroxy, ester, carboxyl, halogen or aromatic groups.

[0011] Optionally, the first repeating polyoxyethylene unit is at least one of 1,1,2,2-tetracyanoethylene oxide, 1-cyanopropylene oxide, 1,1-dicyanopropylene oxide, 1,2-dicyanopropylene oxide, and 1,1,2-tricyanopropylene oxide; and / or, the second repeating polyoxyethylene unit is at least one of ethylene oxide, propylene oxide, benzyloxymethylethylene oxide and methylpropylene oxide, glycidyl, 1,2-epoxybutane, and methoxymethylethylene oxide.

[0012] Optionally, the first repeating polyoxyethylene unit is tetracyanoethylene oxide, and the second repeating polyoxyethylene unit is ethylene oxide.

[0013] Optionally, R1 and R6 are cyanoethyl.

[0014] Optionally, the content of the organic solvent is 15-65 parts by weight relative to 30-80 parts by weight of the polymer matrix, and the content of the lithium salt is 0.5-5 parts by weight; preferably, the content of the organic solvent is 35-55 parts by weight relative to 40-60 parts by weight of the polymer matrix, and the content of the lithium salt is 0.6-2 parts by weight.

[0015] Optionally, the electrolyte further contains functional additives; the functional additives are one or more selected from acetonitrile, succinic anionyl ether, fluoroethylene carbonate, lithium difluorophosphate dioxane, and lithium difluorooxane borate; the content of the functional additives is 0.1-10 parts by weight relative to 30-80 parts by weight of the polymer matrix; preferably, the content of the functional additives is 0.5-8 parts by weight relative to 40-60 parts by weight of the polymer matrix.

[0016] Optionally, the weight loss rate of the electrolyte after vacuum drying at 60°C for 20-120 min is less than 2%, preferably less than 0.5%.

[0017] Optionally, the electrolyte is formed as a thin film with a thickness of 10-60 μm, preferably 20-40 μm.

[0018] Optionally, the polymer matrix further comprises a supplementary polymer selected from one or more of polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, polyvinyl carbonate, polypropylene carbonate, polyfluoropropylene carbonate, polypyrrolidone, and polyacrylonitrile.

[0019] Optionally, the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, and lithium perchlorate.

[0020] Optionally, the organic solvent is one or more of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate.

[0021] A second aspect of the present invention provides a method for preparing the electrolyte provided in the first aspect of the present invention, the method comprising:

[0022] The polymer matrix is ​​swollen with a swelling agent to obtain a swollen material; the swelling agent contains an organic solvent and a lithium salt; some of the organic solvent is removed from the swollen material.

[0023] Optionally, the swelling agent may also contain functional additives.

[0024] Optionally, the swelling treatment includes: immersing the polymer matrix in the swelling agent for 0.5-12 hours.

[0025] Optionally, removing some of the organic solvent from the swollen material includes: vacuum drying the swollen material; the vacuum drying temperature is 60-80℃ and the time is 1-8h.

[0026] A third aspect of the present invention provides a rechargeable battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte provided in the first aspect of the present invention.

[0027] Optionally, the positive electrode and / or the negative electrode contain at least one of manganese ions, iron ions, cobalt ions, and nickel ions.

[0028] A fourth aspect of the present invention provides a rechargeable electronic product, wherein the electronic product is provided with a rechargeable battery provided in a third aspect of the present invention.

[0029] Through the above technical solution, the polymer matrix of the electrolyte of the present invention contains a cyano-modified polymer. The cyano group can undergo a complexation reaction with the metal cations dissolved from the positive electrode material in the battery, fixing the metal cations on the electrolyte framework. This prevents the metal cations from reaching the low-potential negative electrode region and reacting to damage the negative electrode SEI, thus affecting battery life. The gel-state electrolyte of the present invention ensures normal Li + While improving conductivity, it can also reduce the diffusion of metal cations and isolate the metal cations from the negative electrode.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is an electron microscope image of the electrolyte of this invention. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] A first aspect of the present invention provides an electrolyte, which is a gel and comprises a polymer matrix, an organic solvent that swells the polymer matrix, and a lithium salt adsorbed in the gel; the polymer matrix contains a cyano-modified polymer, wherein the repeating structural units of the cyano-modified polymer include at least a first repeating structural unit containing cyano and a second repeating structural unit not containing cyano; and the cyano content in the polymer matrix is ​​80-340 mol% based on the total amount of repeating structural units in the polymer matrix.

[0035] The polymer matrix of the electrolyte in this invention comprises a cyano-modified polymer. The cyano groups can undergo a complexation reaction with metal cations dissolved from the positive electrode material in the battery, fixing the metal cations onto the electrolyte framework. This prevents the metal cations from reaching the low-potential negative electrode region and reacting, thus avoiding damage to the negative electrode SEI and affecting battery life. The gel-state electrolyte of this invention ensures normal Li... +While improving conductivity, it can also reduce the diffusion of metal cations and isolate the metal cations from the negative electrode.

[0036] According to the present invention, optionally, the cyano-modified polymer is a block copolymer, an alternating copolymer, a random copolymer, or a graft copolymer.

[0037] According to the present invention, optionally, the cyano-modified polymer contains cyano-modified polyethylene oxide; the molecular structure of the cyano-modified polyethylene oxide is shown in Formula 1:

[0038]

[0039] Wherein, R1 and R6 are each independently cyanoethyl or hydrogen; n is the number of repeating polyoxyethylene structural units and is between 20 and 2000; the repeating polyoxyethylene structural units include a first repeating polyoxyethylene structural unit containing cyano groups and a second repeating polyoxyethylene structural unit not containing cyano groups;

[0040] In the first repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a cyanoalkyl, cyano or hydrogen containing 3-20 carbon atoms, and at least one of R2, R3, R4 and R5 is a cyanoalkyl or cyano containing 3-20 carbon atoms.

[0041] In the second repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a hydrocarbon group containing 1-20 carbon atoms, a hydrocarbon group with substituents containing 1-20 carbon atoms, or hydrogen; the substituents are alkoxy, hydroxy, ester, carboxyl, halogen or aromatic groups.

[0042] According to the present invention, optionally, the first repeating structural unit of polyethylene oxide is at least one selected from 1,1,2,2-tetracyanoethylene oxide, 1-cyanopropylene oxide, 1,1-dicyanopropylene oxide, 1,2-dicyanopropylene oxide, and 1,1,2-tricyanopropylene oxide; and / or, the second repeating structural unit of polyethylene oxide is at least one selected from ethylene oxide, propylene oxide, benzyloxymethylethylene oxide and methylpropylene oxide, glycidyl, 1,2-epoxybutane, and methoxymethylethylene oxide.

[0043] According to the present invention, optionally, the first repeating structural unit of the polyethylene oxide is tetracyanoethylene oxide, and the second repeating structural unit of the polyethylene oxide is ethylene oxide. The tetracyanoethylene oxide reacts with ethylene oxide to obtain a cyano-modified polyethylene oxide copolymer, where R1 and R6 are each independently hydrogen, and R2, R3, R4, and R5 are each independently cyano. The cyano group can effectively complex the metal cations dissolved from the positive electrode of the battery into the electrolyte, blocking the harmful effects of the metal cations on the negative electrode, thereby reducing the adverse effects on battery performance.

[0044] According to the present invention, optionally, the copolymer obtained by reacting tetracyanoethylene oxide with ethylene oxide is further reacted with acrylonitrile to end-cap the hydroxyl groups at the ends of the copolymer with cyanoethyl, thus R1 and R6 are cyanoethyl. End-capping the active functional groups of the copolymer with cyanoethyl eliminates the activity of the terminal active functional groups of the hydroxyl groups, thereby stabilizing the copolymer.

[0045] According to the present invention, optionally, the content of the organic solvent is 15-65 parts by weight relative to 30-80 parts by weight of the polymer matrix, and the content of the lithium salt is 0.5-5 parts by weight; preferably, the content of the organic solvent is 35-55 parts by weight relative to 40-60 parts by weight of the polymer matrix, and the content of the lithium salt is 0.6-2 parts by weight. In the present invention, a suitable content of polymer matrix can result in good electrolyte conductivity and stability.

[0046] According to the present invention, optionally, the electrolyte further contains functional additives; the functional additives are one or more selected from acetonitrile, succinic anionyl ether, fluoroethylene carbonate, lithium difluorophosphate bis(oxalate) and lithium difluorooxalate borate; in the present invention, the functional additives can improve the high voltage resistance of the gel electrolyte, enabling it to better match high voltage cathode materials.

[0047] According to the present invention, optionally, the content of the functional additive is 0.1-10 parts by weight relative to 30-80 parts by weight of the polymer matrix; preferably, the content of the functional additive is 0.5-8 parts by weight relative to 40-60 parts by weight of the polymer matrix.

[0048] According to the present invention, optionally, the electrolyte is formed as a thin film, the thickness of which is 10-60 μm, preferably 20-40 μm. In this invention, the thickness of the electrolyte film is within a suitable range, the electrolyte film is uniform, and micropores and cracks are not generated, resulting in high battery energy density and high ionic conductivity, thus improving battery performance.

[0049] According to the present invention, optionally, the weight loss rate of the electrolyte after vacuum drying at 60°C for 20-120 min is less than 2%, preferably less than 0.5%.

[0050] According to the present invention, optionally, the polymer matrix further comprises a supplementary polymer selected from one or more of polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, polyvinyl carbonate, polypropylene carbonate, polyfluoropropylene carbonate, polypyrrolidone, and polyacrylonitrile.

[0051] According to the present invention, optionally, the lithium salt is one or more selected from lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, and lithium perchlorate.

[0052] According to the present invention, optionally, the organic solvent is one or more selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0053] A second aspect of the present invention provides a method for preparing the electrolyte provided in the first aspect of the present invention, the method comprising:

[0054] The polymer matrix is ​​swollen with a swelling agent to obtain a swollen material; the swelling agent contains an organic solvent and a lithium salt; some of the organic solvent is removed from the swollen material.

[0055] In the swelling process of this invention, the solubilizing polymer contained in the polymer matrix absorbs a portion of the swelling agent in the swelling agent solution due to the solvation effect of the polymer chains, thus undergoing volume expansion until saturation is reached. Then, excess organic solvent in the swollen material is removed by vacuum drying at 60°C for 1 hour to obtain a gel-state electrolyte. The 60°C temperature treatment gives the gel-state electrolyte good stability.

[0056] According to the present invention, optionally, the swelling agent further comprises functional additives.

[0057] According to the present invention, optionally, the swelling treatment includes: immersing the polymer matrix in the swelling agent for 0.5-12 hours.

[0058] According to the present invention, optionally, removing part of the organic solvent from the swollen material includes: vacuum drying the swollen material; the vacuum drying temperature is 60-80°C and the time is 20-120 min.

[0059] A third aspect of this invention provides a rechargeable battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte provided in the first aspect of this invention. Taking a lithium manganese oxide battery as an example, the electrolyte in the lithium manganese oxide battery contains a cyano group, which possesses the ability to complex manganese ions at the positive electrode and to prevent manganese ions from migrating to the negative electrode. The cyano group (-C=N) is a strongly electrophilic ligand. The outer 3d orbital of the paramagnetic metal ion Mn(II) coordinates with the lone pair electron of N in -C=N, forming a stable organically bound Mn metal-supramolecular polymer through complexation or chelation. Simultaneously, a small amount of lithium ions are adsorbed in the electrolyte and transported along the polymer backbone during battery charging and discharging, reducing the lithium ion transport impedance. This reduces manganese ion diffusion while ensuring normal lithium ion conductivity, thus isolating manganese ions from affecting the negative electrode.

[0060] According to the present invention, optionally, the positive electrode and / or the negative electrode contains at least one of manganese ions, iron ions, cobalt ions, and nickel ions. For example, it can be at least one of lithium manganese oxide, lithium iron manganese, lithium-rich manganese-based oxide, lithium cobalt oxide, lithium iron phosphate, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium-rich ternary materials, sodium manganate, and sodium cobalt oxide; it can also be Prussian blue and its homologues; it can also be at least one of transition metal layered oxides containing sodium ions such as Fe, Mn, and Cu, sodium vanadate, lithium vanadate, zinc vanadate, calcium vanadate, magnesium vanadate, and potassium vanadate.

[0061] A fourth aspect of the present invention provides a rechargeable electronic product, wherein the electronic product is provided with a rechargeable battery as described in the third aspect of the present invention. For example, the rechargeable electronic product can be a car, an electric vehicle, a computer, a Bluetooth headset, a smartwatch, etc.

[0062] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0063] Preparation Example 1

[0064] The polymer matrix is ​​a copolymer of tetracyanoethylene oxide and ethylene oxide, and the specific preparation includes the following steps:

[0065] 0.2 mol of 1,1,2,2-tetracyanoethylene oxide monomer was mixed with 200 mL of DMF in a 1 L three-necked round-bottom flask, followed by the introduction of 0.2 mol of ethylene oxide gas; the molar ratio of ethylene oxide gas to 1,1,2,2-tetracyanoethylene oxide was 1:1. The mixture was stirred thoroughly under Ar protection, and then 20 mL of 1 M NaOH solution was slowly added, with stirring continued for 30 mins. The flask was then placed in an oil bath and reacted at 100 °C for 12 h. After the reaction was complete, the DMF solvent was removed by vacuum distillation, and the resulting gelatinous polymer was filtered out and repeatedly washed with deionized water until pH = 7. The resulting gelatinous polymer was dried in a vacuum oven at 60 °C to obtain the polymer matrix, in which the cyano content was 200 mol%.

[0066] Preparation Example 2

[0067] The tetracyanoethylene oxide and ethylene oxide copolymer prepared in Example 1 were further reacted with acrylonitrile to cap the hydroxyl groups at the ends of the copolymer with cyanoethyl groups. The specific preparation method includes the following steps:

[0068] 0.2 mol of the tetracyanoethylene oxide and ethylene oxide copolymer prepared in Example 1 was dissolved in 200 mL of DMF solvent, and 0.005 mol of the catalyst hydrotalcite Mg6Al2(OH) was added. 16 CO3·4H2O was added, followed by the addition of 0.2 mol of acrylonitrile. The mixture was stirred and reacted at 25-40℃ for 12 h. After the reaction was completed, the resulting gelatinous polymer was collected and repeatedly washed with deionized water. The resulting gelatinous polymer was then dried in a vacuum oven at 60℃ to obtain a cyanoethyl-terminated polymer matrix.

[0069] Example 1

[0070] The electrolyte in this embodiment includes a polymer matrix, an organic solvent that swells the polymer matrix, and lithium salts and functional additives adsorbed in the gel. The preparation method of the electrolyte includes the following steps:

[0071] 50 parts by weight of the polymer matrix obtained in Example 1 were added to 50 parts by weight of a swelling agent and soaked for 6 hours to induce swelling, resulting in a swollen material. The swelling agent contained 44 parts by weight of an organic solvent (EC:EMC:DMC = 1:1:1 vol%), 1 part by weight of a lithium salt (LiPF6), and 5 parts by weight of the functional additive acetonitrile (AN). The swollen material was then vacuum-dried at 60°C for 1 hour to remove some of the organic solvent, yielding an electrolyte, such as... Figure 1 As shown, the electrolyte is formed as a thin film with a thickness of 30 μm.

[0072] The process involves soaking the polymer matrix for 6 hours, after which the polymer matrix swells and adsorbs a portion of the swelling agent, reaching saturation. The main purpose of vacuum drying the swollen material at 60°C for 1 hour is twofold: firstly, to ensure more uniform dispersion of the swelling agent within the polymer matrix; and secondly, to dry some of the organic solvents in the swollen material, thereby increasing the electrolyte strength and preventing subsequent battery short circuits.

[0073] Example 2

[0074] The preparation method of this embodiment is the same as that of Embodiment 1, except that the electrolyte is prepared as follows: 40 parts by weight of the polymer matrix are added to 60 parts by weight of the swelling agent and soaked for 6 hours for swelling treatment to obtain the swollen material; wherein, the swelling agent contains 50 parts by weight of organic solvent (EC:EMC:DMC=1:1:1vol%), 2 parts by weight of lithium salt (LiPF6) and 8 parts by weight of functional additive acetonitrile (AN); then the swollen material is vacuum dried at 60°C for 1 hour to remove part of the organic solvent in the swollen material to obtain the electrolyte, which is formed into a thin film with a thickness of 20 μm.

[0075] Example 3

[0076] The preparation method of this embodiment is the same as that of Embodiment 1, except that the electrolyte is prepared as follows: 60 parts by weight of the polymer matrix are added to 40 parts by weight of the swelling agent and soaked for 6 hours to undergo swelling treatment, thereby obtaining the swollen material; wherein, the swelling agent contains 35 parts by weight of organic solvent (EC:EMC:DMC=1:1:1vol%), 1 part by weight of lithium salt (LiPF6) and 4 parts by weight of functional additive acetonitrile (AN); then the swollen material is vacuum dried at 60°C for 1 hour to remove some of the organic solvent in the swollen material, thereby obtaining the electrolyte, which is formed into a thin film with a thickness of 40 μm.

[0077] Example 4

[0078] The preparation method of this embodiment is the same as that of Embodiment 1, except that the electrolyte is prepared as follows: 10 parts by weight of the polymer matrix are added to 90 parts by weight of the swelling agent and soaked for 6 hours to undergo swelling treatment, thereby obtaining the swollen material; wherein, the swelling agent contains 70 parts by weight of organic solvent (EC:EMC:DMC=1:1:1vol%), 8 parts by weight of lithium salt (LiPF6) and 12 parts by weight of functional additive acetonitrile (AN); then the swollen material is vacuum dried at 60°C for 1 hour to remove some of the organic solvent in the swollen material, thereby obtaining the electrolyte, which is formed into a thin film with a thickness of 5 μm.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is the use of a liquid electrolyte. The liquid electrolyte is a mixed solution of 1 mol / L LiPF6 and EC:EMC:DMC = 1:1:1 vol%.

[0081] Comparative Example 2

[0082] The preparation method of this comparative example is the same as that of Example 1, except that the polymer matrix is ​​a polymer without cyano modification. Specifically, 50 parts by weight of polyethylene oxide are added to 50 parts by weight of a swelling agent and soaked for 6 hours for swelling treatment. The swelling agent formulation is the same as that of Example 1, and the swollen material is obtained. The swollen material is then vacuum dried at 60°C for 1 hour to remove some of the organic solvent in the swollen material, and electrolyte is obtained.

[0083] Test case

[0084] Taking lithium manganese oxide battery as an example, the preparation of lithium manganese oxide battery is as follows: CR2025 coin cell battery is assembled in a glove box filled with argon gas (content: O2≤0.5ppm, H2O≤0.5ppm), wherein the positive electrode is a lithium manganese oxide electrode, the negative electrode is a 25μm lithium foil, and the electrolyte is the electrolyte in Examples 1-4 and Comparative Examples 1-2.

[0085] Cycle life tests were conducted on the batteries obtained in Examples 1-4 and Comparative Examples 1-2. The test method is as follows: Ten batteries from each example and comparative example were taken and subjected to charge-discharge cycle tests at 0.5C on a LAND CT 2001C secondary battery performance testing device at 25±1℃. The steps are as follows: rest for 5 minutes, then charge at a constant current to 4.2V and cut off; rest for 5 minutes, then discharge at a constant current to 3V, which constitutes one cycle. This step was repeated. During the cycle, the cycle was terminated when the battery capacity was lower than 80% of the initial discharge capacity. The number of cycles is the cycle life of the battery.

[0086] Table 1

[0087]

[0088] The test results are shown in Table 1. The battery prepared in Example 1 cycled 438 times; the battery prepared in Example 2 cycled 378 times; the battery prepared in Example 3 cycled 424 times; the battery prepared in Example 4 cycled 341 times; the battery prepared in Comparative Example 1 cycled 326 times; and the battery prepared in Comparative Example 2 cycled 334 times. Therefore, it can be seen that when the electrolytes of Examples 1-3 of this invention are assembled into lithium manganese oxide batteries, the electrolyte film thickness is moderate and uniform, and the cyano-modified polymer and Mn... 2+ A complexation reaction occurred, which reduced Mn 2+ The diffusion of Mn isolated 2+The electrolyte in Example 4, when assembled into a battery, has a thin and uneven electrolyte film, which is prone to cracking, causing short circuits and affecting the battery's cycle life. In Comparative Examples 1 and 2, when the electrolytes are assembled into batteries, manganese ions dissolve during charging and discharging, causing continuous loss of lithium manganese oxide and reducing the battery's cycle life.

[0089] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0091] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte is a gel and comprises a polymer matrix, an organic solvent that swells the polymer matrix, and a lithium salt adsorbed in the gel; the polymer matrix contains a cyano-modified polymer, wherein the repeating structural units of the cyano-modified polymer include at least a first repeating structural unit containing cyano groups and a second repeating structural unit without cyano groups; based on the total amount of repeating structural units in the polymer matrix, the cyano content in the polymer matrix is ​​80-340 mol%; the cyano-modified polymer contains cyano-modified polyethylene oxide; the molecular structure of the cyano-modified polyethylene oxide is shown in Formula 1: Formula 1 Wherein, R1 and R6 are each independently cyanoethyl or hydrogen; n is the number of repeating polyoxyethylene structural units and is between 20 and 2000; the repeating polyoxyethylene structural units include a first repeating polyoxyethylene structural unit containing cyano groups and a second repeating polyoxyethylene structural unit not containing cyano groups; In the first repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a cyanoalkyl, cyano or hydrogen containing 3-20 carbon atoms, and at least one of R2, R3, R4 and R5 is a cyanoalkyl or cyano containing 3-20 carbon atoms. In the second repeating polyoxyethylene structural unit, R2, R3, R4 and R5 are each independently a hydrocarbon group containing 1-20 carbon atoms, a hydrocarbon group with substituents containing 1-20 carbon atoms, or hydrogen; the substituents are alkoxy, hydroxy, ester, carboxyl, halogen or aromatic groups. The electrolyte also contains functional additives; the functional additives are one or more of acetonitrile, succinic acid, fluoroethylene carbonate, lithium difluorophosphate bis(oxalate) and lithium difluorooxalate borate. The content of the functional additive is 0.1-10 parts by weight relative to 30-80 parts by weight of the polymer matrix.

2. The electrolyte according to claim 1, wherein, The first repeating polyoxyethylene structural unit is at least one selected from 1,1,2,2-tetracyanoethylene oxide, 1-cyanopropylene oxide, 1,1-dicyanopropylene oxide, 1,2-dicyanopropylene oxide, and 1,1,2-tricyanopropylene oxide; and / or, The second repeating structural unit of the polyethylene oxide is at least one of ethylene oxide, propylene oxide, benzyloxymethylethylene oxide and methylpropylene oxide, glycidyl, 1,2-epoxybutane and methoxymethylethylene oxide.

3. The electrolyte according to claim 1, wherein, The first repeating structural unit of the polyethylene oxide is 1,1,2,2-tetracyanoethylene oxide, and the second repeating structural unit of the polyethylene oxide is ethylene oxide.

4. The electrolyte according to claim 3, wherein, R1 and R6 are cyanoethyl.

5. The electrolyte according to claim 1, wherein, The content of the organic solvent is 15-65 parts by weight relative to 30-80 parts by weight of the polymer matrix, and the content of the lithium salt is 0.5-5 parts by weight.

6. The electrolyte according to claim 5, wherein, The content of the organic solvent is 35-55 parts by weight relative to 40-60 parts by weight of the polymer matrix, and the content of the lithium salt is 0.6-2 parts by weight.

7. The electrolyte according to claim 1, wherein, The content of the functional additive is 0.5-8 parts by weight relative to 40-60 parts by weight of the polymer matrix.

8. The electrolyte according to claim 1, wherein, The weight loss rate of the electrolyte after vacuum drying at 60°C for 1 hour is less than 2%.

9. The electrolyte according to claim 8, wherein, The weight loss rate of the electrolyte after vacuum drying at 60°C for 1 hour is less than 0.5%.

10. The electrolyte according to claim 1, wherein, The electrolyte is formed as a thin film with a thickness of 10-60 μm.

11. The electrolyte according to claim 10, wherein, The electrolyte is formed as a thin film with a thickness of 20-40 μm.

12. The electrolyte according to claim 1, wherein, The polymer matrix further contains a supplementary polymer selected from one or more of polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, polyvinyl carbonate, polypropylene carbonate, polyfluoropropylene carbonate, polypyrrolidone, and polyacrylonitrile.

13. The electrolyte according to claim 1, wherein, The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, and lithium perchlorate.

14. The electrolyte according to claim 1, wherein, The organic solvent is one or more of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate.

15. A method for preparing the electrolyte according to any one of claims 1-14, characterized in that, The preparation method includes: The polymer matrix is ​​swollen with a swelling agent to obtain a swollen material; the swelling agent contains an organic solvent and a lithium salt. Remove some of the organic solvent from the material after the swelling treatment.

16. The preparation method according to claim 15, wherein, The swelling agent also contains functional additives.

17. The preparation method according to claim 15, wherein, The swelling treatment includes: immersing the polymer matrix in the swelling agent; The soaking time is 0.5-12 hours.

18. The preparation method according to claim 15, wherein, Removing some of the organic solvent from the swollen material includes: vacuum drying the swollen material. The vacuum drying temperature is 60-80℃, and the time is 20-120 min.

19. A rechargeable battery, characterized in that, The battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte described in any one of claims 1-14.

20. The rechargeable battery according to claim 19, wherein, The positive electrode and / or the negative electrode contain at least one of manganese ions, iron ions, cobalt ions, and nickel ions.

21. A rechargeable electronic product, characterized in that, The electronic product is provided with the rechargeable battery as described in claim 19 or 20.

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