Gel-state electrolyte precursor, gel-state electrolyte, preparation method of gel-state electrolyte precursor and gel-state electrolyte, and sodium ion battery

Abstract

The invention provides a gel-state electrolyte precursor, a gel-state electrolyte and a preparation method thereof, and a sodium ion battery, the gel-state electrolyte precursor comprises a sodium salt, a solvent, a first monomer, a second monomer and an initiator, the first monomer comprises a carbon-carbon double bond and a carbon-oxygen bond and / or comprises a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer comprises a carbon-carbon double bond and a carbon-nitrogen bond; the second monomer comprises a carbon-carbon double bond and a fluorocarbon bond. In the application, as the reduction potential of the fluorocarbon bond is higher than that of the carbon-oxygen bond and the carbon-nitrogen bond, after the first monomer and the second monomer are polymerized and during formation, the residual second monomer can be reduced at a negative electrode before the residual first monomer, that is, the F-C bond is broken and is combined with Na < + > in the electrolyte to form NaF, so that a thinner and more compact SEI film can be formed; meanwhile, the reduction of main monomers and solvents can be reduced, so that the DCR (Direct Current Reduction) of the battery can be reduced, and the storage performance and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a gel electrolyte precursor, a gel electrolyte and a preparation method thereof, and a sodium ion battery. Background Art

[0002] Compared with lithium-ion batteries, sodium-ion batteries have + / Na has a higher potential than Li + / Li has a potential 300mV higher, which may cause incomplete reduction of some additives in the electrolyte, thus forming an unstable solid electrolyte interface (SEI) film. A large number of side reactions occur at the negative electrode during the subsequent cycle or storage of the battery, consuming active sodium, especially in the liquid sodium ion system. The problem is more prominent. Gel electrolyte can lock most of the electrolyte, thereby suppressing the side reactions on the negative electrode side to a certain extent. However, the residual monomers in the additives will still be reduced at the negative electrode, forming a thicker SEI, affecting the transmission of sodium ions and causing a significant increase in the battery DC resistance (DCR). Summary of the invention

[0003] The embodiments of the present invention provide a gel electrolyte precursor, a gel electrolyte and a preparation method thereof, and a sodium ion battery, which can improve the problem of excessive battery DCR in existing sodium ion batteries.

[0004] In a first aspect, an embodiment of the present invention provides a gel electrolyte precursor, comprising a sodium salt, a solvent, a first monomer, a second monomer and an initiator, wherein the first monomer comprises a carbon-carbon double bond and a carbon-oxygen bond and / or comprises a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer comprises a carbon-carbon double bond and a fluorine-carbon bond.

[0005] In one embodiment, the first monomer includes one or more of pentaerythritol triacrylate, first vinylene carbonate, acrylonitrile and hydroxyethyl acrylate; and / or

[0006] The second monomer includes one or more of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride; and / or

[0007] The initiator comprises one or more of azobisisobutyronitrile and azobisisoheptanenitrile; and / or

[0008] The sodium salt includes one or more of sodium hexafluorophosphate (NaPF6) and sodium bis(oxalatoborate) (NaBOB); and / or

[0009] The solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC).

[0010] In one embodiment, the mass content of the first monomer in the gel electrolyte precursor is 1%-9%; and / or

[0011] The mass content of the second monomer in the gel electrolyte precursor is 0.3%-3%; and / or

[0012] The mass content of the initiator in the gel electrolyte precursor is 0.01%-0.08%; and / or

[0013] The mass content of the sodium salt in the gel electrolyte precursor is 15%-18%.

[0014] In one embodiment, the gel electrolyte precursor further includes an additive, and the additive includes one or more of a second vinylene carbonate (VC), a fluoroethylene carbonate (FEC), and a second sodium bis(oxalatoborate) (NaBOB).

[0015] In one embodiment, the additive includes a second vinylene carbonate (VC), and the mass content of the second vinylene carbonate (VC) in the gel electrolyte precursor is 1%-4%; and / or

[0016] The additive includes fluoroethylene carbonate (FEC), and the mass content of the fluoroethylene carbonate (FEC) in the gel electrolyte precursor is 0.5%-1%; and / or

[0017] The additive includes a second sodium bis(oxalatoborate) (NaBOB), and the mass content of the second sodium bis(oxalatoborate) (NaBOB) in the gel electrolyte precursor is 0.03%-0.06%.

[0018] In a second aspect, an embodiment of the present invention provides a gel electrolyte obtained by curing the above-mentioned gel electrolyte precursor.

[0019] In one embodiment, the weight average molecular weight of the polymer obtained by curing the first monomer and the second monomer is 17000-19000.

[0020] In a third aspect, an embodiment of the present invention provides a method for preparing a gel electrolyte, comprising the following steps: providing a sodium salt, a solvent, a first monomer, a second monomer and an initiator, mixing them, and performing a curing reaction to obtain a gel electrolyte, wherein the first monomer contains a carbon-carbon double bond and a carbon-oxygen bond and / or contains a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer contains a carbon-carbon double bond and a fluorine-carbon bond.

[0021] In one embodiment, the mixing includes: mixing the sodium salt, the solvent, the first monomer and the second monomer, and then adding the initiator.

[0022] In one embodiment, the mixing further comprises a standing treatment; and / or

[0023] The curing reaction temperature is 20°C to 60°C, and the curing reaction time is 1h to 8h; and / or

[0024] The curing reaction is pressurized curing with a pressure of 5N-30N.

[0025] In a fourth aspect, an embodiment of the present invention provides a sodium ion battery, comprising the above-mentioned gel electrolyte, or a gel electrolyte prepared by the above-mentioned method for preparing the gel electrolyte.

[0026] In the embodiment of the present application, since the reduction potential of the fluorine-carbon bond is higher than that of the carbon-oxygen bond and the carbon-nitrogen bond, after the first monomer and the second monomer are polymerized, during the formation, the residual second monomer can be reduced at the negative electrode before the residual first monomer, that is, the FC bond is broken and reacts with the Na in the electrolyte. + The combination to form NaF is conducive to the formation of a thinner and denser SEI film, which is beneficial to the desolvation of sodium ions. At the same time, it can reduce the reduction of major monomers and solvents, thereby reducing the battery DCR and improving the battery's storage performance and cycle performance. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0028] In the description of this application, the term "including" means "including but not limited to." The terms first, second, third, etc. are used merely as labels and do not impose numerical requirements or establish a sequence.

[0029] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0030] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0031] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0032] The technical solution of this application is as follows:

[0033] In a first aspect, an embodiment of the present application provides a gel electrolyte precursor, comprising a sodium salt, a solvent, a first monomer, a second monomer and an initiator, wherein the first monomer comprises a carbon-carbon double bond and a carbon-oxygen bond and / or comprises a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer comprises a carbon-carbon double bond and a fluorine-carbon bond.

[0034] In the present application, by adding a first monomer and a second monomer to a gel electrolyte precursor, the first monomer and the second monomer have a carbon-carbon double bond, so that they can be efficiently cross-linked in a short time to form a long-chain polymer with a high degree of polymerization, thereby fully encapsulating the sodium salt and the solvent in the polymer to effectively form a gel electrolyte. In addition, the first monomer also contains a carbon-oxygen bond and / or a carbon-nitrogen bond, and the second monomer contains a fluorine-carbon bond. Since the reduction potential of the fluorine-carbon bond is higher than that of the carbon-oxygen bond and the carbon-nitrogen bond, during the formation, the residual second monomer after polymerization can be reduced at the negative electrode before the first monomer, that is, the FC bond is disconnected and reacts with the Na in the sodium salt. + Combining to form NaF can reduce the reduction of main monomers and solvents, which is beneficial to the formation of thinner and denser SEI film and the desolvation of sodium ions, thereby reducing the battery DCR and improving the storage performance and cycle performance of the battery.

[0035] It can be understood that both the first monomer and the second monomer can undergo polymerization reaction to form a polymer under the action of an initiator, but there will be residual monomers after polymerization. Since the first monomer contains CO bonds and / or CN bonds, CO bonds and CN bonds can be used to conduct sodium ions, but the products formed by the reduction at the negative electrode are not dense enough, so they will continue to consume sodium salts and form a thicker SEI film. By adding the second monomer, the second monomer can be reduced before the first monomer, thereby forming a dense and thin SEI film, so that the first monomer lacks a reaction site, and the SEI film can weaken the subsequent interfacial reaction, and the SEI film can always exist stably and will not grow again; since the product formed by solvent reduction is unstable and easily decomposed at high temperature, the formed SEI film is loose and porous, which will aggravate the side reactions at the negative electrode interface, consume the active sodium in the electrolyte, and cause the battery capacity to decay quickly. By adding the second monomer, the second monomer can be better than the solvent reduction, thereby forming a dense and thin SEI film and reducing the reduction of the solvent.

[0036] In some embodiments, the first monomer includes one or more of pentaerythritol triacrylate, first vinylene carbonate, acrylonitrile and hydroxyethyl acrylate, so that a polymer can be effectively formed, thereby forming a gel electrolyte.

[0037] In some embodiments, the second monomer includes one or more of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. In this way, a thin and dense SEI film can be effectively formed.

[0038] In some embodiments, the mass content of the first monomer in the gel electrolyte precursor is 1%-9%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc. In this way, the polymerization degree of the monomer can be controlled, the formation of long-chain polymers with high polymerization degree can be promoted, and the high temperature stability of the gel electrolyte can be improved.

[0039] In some embodiments, the mass content of the second monomer in the gel electrolyte precursor is 0.3%-3%, for example, 0.3%, 0.5%, 0.7%, 1%, 1.7%, 1.5%, 1.7%, 2%, 2.2%, 2.5%, 2.7%, 3%, etc. In this way, it can participate in the curing to form a gel polymer, and the remaining part of the second monomer preferentially participates in the reduction reaction during the battery formation process.

[0040] In some embodiments, the mass content of the initiator in the gel electrolyte precursor is 0.01%-0.08%, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, etc. In this way, the first monomer can be fully polymerized and the second monomer can be partially polymerized. If the initiator is too little, the polymerization time is too long, and if the initiator is too much, the residual initiator will cause serious side reactions and affect the quality of SEI.

[0041] In some embodiments, the initiator includes one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

[0042] In some embodiments, the mass content of sodium salt in the gel electrolyte precursor is 15%-18%, for example, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0043] In some embodiments, the sodium salt includes one or more of sodium hexafluorophosphate (NaPF6) and sodium bis(oxalatoborate) (NaBOB).

[0044] In some embodiments, the gel electrolyte precursor further includes an additive, and the additive includes one or more of a second vinylene carbonate (VC), a fluoroethylene carbonate (FEC), and a second sodium bis(oxalatoborate) (NaBOB).

[0045] In some embodiments, the additive includes a second vinylene carbonate (VC), and the mass content of the second vinylene carbonate (VC) in the gel electrolyte precursor is 1%-4%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc. In this way, the negative electrode interface can be repaired during the battery cycle or storage process.

[0046] In some embodiments, the additive includes fluoroethylene carbonate (FEC), and the mass content of fluoroethylene carbonate (FEC) in the gel electrolyte precursor is 0.5%-1%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0047] In some embodiments, the additive includes a second sodium bis(oxalatoborate) (NaBOB), and the mass content of the second sodium bis(oxalatoborate) (NaBOB) in the gel electrolyte precursor is 0.03%-0.06%, for example, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, etc. In this way, it can help the positive electrode to form a stable film, thereby reducing the battery impedance.

[0048] In some embodiments, the solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC).

[0049] In some embodiments, the mass ratio of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) is (20-40):(5-6):(60-80).

[0050] In a second aspect, the embodiments of the present application further provide a gel electrolyte obtained by curing the above-mentioned gel electrolyte precursor.

[0051] In the present application, the sodium salt, solvent and additive are locked in the gel polymer, which can reduce the liquid contact at the interface compared to the liquid electrolyte, thereby reducing the side reactions at the interface and improving the cycle performance of the battery.

[0052] In one embodiment, the weight average molecular weight of the polymer obtained by curing the first monomer and the second monomer is 17000-19000, for example, it can be 17000, 17100, 17200, 17300, 17400, 17500, 17600, 17700, 17800, 17900, 18000, 18100, 18200, 18300, 18400, 18500, 18600, 18700, 18800, 18900, 19000, etc.

[0053] In a third aspect, the present invention also provides a method for preparing a gel electrolyte, comprising the following steps:

[0054] A sodium salt, a solvent, a first monomer, a second monomer and an initiator are provided, mixed, and then subjected to a curing reaction to obtain a gel electrolyte, wherein the first monomer contains a carbon-carbon double bond and a carbon-oxygen bond and / or contains a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer contains a carbon-carbon double bond and a fluorine-carbon bond.

[0055] In the present application, by performing a curing reaction, the first monomer and the second monomer can form a polymer under the action of an initiator, so that the sodium salt and the solvent are encapsulated in the polymer to form a gel electrolyte.

[0056] In some embodiments, the mixing includes: mixing the sodium salt, the solvent, the first monomer and the second monomer, and then adding the initiator. The initiator is unstable, so the probability of the initiator failing due to long storage time can be reduced.

[0057] In some embodiments, the mixing further includes a standing treatment.

[0058] In some embodiments, the standing time is 2 hours to 24 hours, for example, 2 hours, 4 hours, 5 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc. In this way, the uniformity of the mixed solution can be improved.

[0059] In some embodiments, the curing reaction temperature is 20°C to 60°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc., and the curing reaction time is 1h-8h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc. In this way, the degree of polymerization of the polymer in the gel electrolyte can be controlled, and the curing temperature can retain part of the free gel electrolyte precursor, which is conducive to forming a stable negative electrode interface during the formation process, thereby improving the high temperature stability of the negative electrode at low potential.

[0060] In some embodiments, the curing reaction is pressurized curing, and the pressure is 5N-30N, for example, 5N, 10N, 15N, 20N, 25N, 30N, etc. In this way, by applying pressure during curing, the polymer in the gel electrolyte can be confined, thereby reducing the expansion of the polymer, thereby reducing the increase in the distance between the positive and negative electrodes caused by the expansion of the polymer, and improving the contact between the electrode and the electrolyte.

[0061] In the present application, the curing reaction can be completed by high-temperature curing using a fixture, and the fixture can provide pressure, or a chemical forming cabinet can be used for pressurized curing, and the chemical forming can be performed directly after the curing is completed.

[0062] The materials used in the preparation method of the gel electrolyte in the present application are as described above.

[0063] In a fourth aspect, an embodiment of the present application further provides a sodium ion battery, comprising the above-mentioned gel electrolyte.

[0064] The present application is described in detail below by means of specific examples, which are only partial examples of the present application and are not intended to limit the present application. The raw materials used in the following examples are all commercially available products unless otherwise specified.

[0065] Example 1

[0066] A sodium ion battery and a method for preparing the same, comprising the following steps:

[0067] (1) mixing sodium hexafluorophosphate, ethylene carbonate, diethyl carbonate and vinylene carbonate to obtain an electrolyte, wherein the mass ratio of ethylene carbonate, diethyl carbonate and vinylene carbonate is 30:5:65;

[0068] (2) mixing an electrolyte, pentaerythritol triacrylate, hexafluoropropylene and azobisisobutyronitrile to obtain a gel electrolyte precursor, wherein the mass content of sodium hexafluorophosphate is 17%, the mass content of pentaerythritol triacrylate is 5%, the mass content of hexafluoropropylene is 1.5%, and the mass content of azobisisobutyronitrile is 0.05%;

[0069] (3) The gel electrolyte precursor is injected into the battery cell and left to stand at room temperature for 12 hours, and then in-situ cured at 40°C and 20N for 5 hours to form a gel electrolyte. The battery cell is then formed and capacity divided to obtain a sodium ion battery.

[0070] Example 2

[0071] This embodiment is substantially the same as Embodiment 1, except that pentaerythritol triacrylate is replaced by acrylonitrile in this embodiment.

[0072] Example 3

[0073] This embodiment is substantially the same as Embodiment 1, except that pentaerythritol triacrylate is replaced by hydroxyethyl acrylate in this embodiment.

[0074] Example 4

[0075] This embodiment is substantially the same as Embodiment 1, except that the mass content of pentaerythritol triacrylate in the gel electrolyte precursor in this embodiment is 1%.

[0076] Example 5

[0077] This embodiment is substantially the same as Embodiment 1, except that the mass content of pentaerythritol triacrylate in the gel electrolyte precursor in this embodiment is 9%.

[0078] Example 6

[0079] This embodiment is substantially the same as Embodiment 1, except that hexafluoropropylene is replaced by tetrafluoroethylene in this embodiment.

[0080] Example 7

[0081] This embodiment is substantially the same as Embodiment 1, except that hexafluoropropylene is replaced by vinylidene fluoride in this embodiment.

[0082] Example 8

[0083] This embodiment is substantially the same as Embodiment 1, except that the mass content of hexafluoropropylene in the gel electrolyte precursor in this embodiment is 0.3%.

[0084] Example 9

[0085] This embodiment is substantially the same as Embodiment 1, except that the mass content of hexafluoropropylene in the gel electrolyte precursor in this embodiment is 3%.

[0086] Example 10

[0087] This embodiment is substantially the same as Embodiment 1, except that the mass content of azobisisobutyronitrile in the gel electrolyte precursor in this embodiment is 0.01%.

[0088] Embodiment 11

[0089] This embodiment is substantially the same as Embodiment 1, except that the mass content of azobisisobutyronitrile in the gel electrolyte precursor in this embodiment is 0.08%.

[0090] Example 12

[0091] This embodiment is substantially the same as Embodiment 1, except that the in-situ curing temperature in this embodiment is 20°C.

[0092] Embodiment 13

[0093] This embodiment is substantially the same as Embodiment 1, except that the in-situ curing temperature in this embodiment is 60°C.

[0094] Embodiment 14

[0095] This embodiment is substantially the same as Embodiment 1, except that the mass content of hexafluoropropylene in the gel electrolyte precursor in this embodiment is 0.1%.

[0096] Embodiment 15

[0097] This embodiment is substantially the same as Embodiment 1, except that the mass content of hexafluoropropylene in the gel electrolyte precursor in this embodiment is 5%.

[0098] Example 16

[0099] This embodiment is substantially the same as Embodiment 1, except that the mass content of pentaerythritol triacrylate in the gel electrolyte precursor in this embodiment is 15%.

[0100] Embodiment 17

[0101] This embodiment is substantially the same as Embodiment 1, except that the mass content of azobisisobutyronitrile in the gel electrolyte precursor in this embodiment is 0.2%.

[0102] Embodiment 18

[0103] This embodiment is substantially the same as Embodiment 1, except that the in-situ curing temperature in this embodiment is 80°C.

[0104] Embodiment 19

[0105] This embodiment is substantially the same as Embodiment 1, except that the in-situ curing temperature in this embodiment is 10°C.

[0106] Comparative Example 1

[0107] This comparative example is substantially the same as Example 1, except that hexafluoropropylene, pentaerythritol triacrylate and azobisisobutyronitrile are not added in this comparative example.

[0108] Comparative Example 2

[0109] This comparative example is substantially the same as Example 1, except that hexafluoropropylene is not added in this comparative example.

[0110] Comparative Example 3

[0111] This comparative example is substantially the same as Example 1, except that hexafluoropropylene is replaced by methyl acrylate in this comparative example.

[0112] Test example:

[0113] The sodium ion batteries obtained in the examples and comparative examples were tested, and the test results are shown in Table 1 below.

[0114] (1) Weight average molecular weight test: The gel electrolyte in the sodium ion battery is taken and the weight average molecular weight is measured by gel chromatography.

[0115] (2) Cyclic performance test of sodium ion batteries at 25°C: At 25°C, the sodium ion battery was charged to 3.5V at 1C constant current and constant voltage, left for 30 min, and then discharged to 2.0V at 1C constant current. This cycle was repeated 500 times to obtain the capacity retention rate after 500 cycles at 25°C.

[0116] Cycling performance test of sodium ion battery at 45℃: The method is the same as the cycling performance test of sodium ion battery at 25℃, except that the temperature is changed from 25℃ to 45℃.

[0117] The capacity retention rate (%) of the sodium ion battery after N cycles = (discharge capacity of the Nth cycle / first discharge capacity) × 100%, where N is the number of cycles of the sodium ion battery.

[0118] (3) Discharge DC resistance (DCR) test of sodium ion battery at 25°C: The battery was charged to 50% SOC at 0.2C at 25°C, left for 30 minutes, and then charged at 0.2C current I for 30 seconds, followed by 1C current I for 5 seconds. The voltage V1 at 0.2C charging at 30 seconds and the sampled voltage V2 at 1C charging at 5 seconds were recorded. The DCR test was performed once for the first cycle and every 100 cycles.

[0119] DCR=(V2-V1) / (I2-I1)

[0120] Sodium ion battery discharge DC impedance (DCR) test at 45°C: The method is the same as the sodium ion battery discharge DC impedance (DCR) test at 25°C, except that the temperature needs to be changed from 25°C to 45°C.

[0121] Table 1

[0122]

[0123]

[0124] From Table 1 we can see that:

[0125] Compared with Examples 1 to 3, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the weight average molecular weight of the gel electrolyte affects the performance of the battery.

[0126] Compared with Example 1, Example 4, Example 5 and Example 16, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the content of the first monomer affects the weight average molecular weight of the gel electrolyte and the performance of the battery.

[0127] Compared with Example 1, Example 6 and Example 7, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the type of the second monomer affects the weight average molecular weight of the gel electrolyte and the performance of the battery.

[0128] Compared with Example 1, Example 8, Example 9, Example 14 and Example 15, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the content of the second monomer affects the weight average molecular weight of the gel electrolyte and the performance of the battery.

[0129] Compared with Example 1, Example 10, Example 11 and Example 17, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the content of the initiator affects the weight average molecular weight of the gel electrolyte and the performance of the battery.

[0130] Compared with Example 1, Example 12 and Example 13, the weight average molecular weight of the gel electrolyte of the sodium ion battery of Example 1 is larger, the first cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the curing temperature affects the weight average molecular weight of the gel electrolyte and the performance of the battery.

[0131] Compared with Comparative Example 1, the capacity retention rate of the sodium ion battery of the embodiment after 500 cycles at 25°C and 45°C is higher. It can be seen that the gel electrolyte of the present application has better cycle performance than the liquid electrolyte.

[0132] Compared with Comparative Example 2, the weight-average molecular weight of the gel electrolyte of the sodium ion battery of the embodiment is larger, the first-cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the present application can reduce the battery DCR and improve the battery cycle performance by adding the second monomer.

[0133] Compared with Comparative Example 3, the weight-average molecular weight of the gel electrolyte of the sodium ion battery of the embodiment is larger, the first-cycle DCR and the DCR after 500 cycles at 25°C and 45°C are smaller, and the capacity retention rate after 500 cycles is higher. It can be seen that the second monomer added in the present application can reduce the battery DCR and improve the battery cycle performance.

[0134] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A gel electrolyte precursor, characterized in that: The invention comprises a sodium salt, a solvent, a first monomer, a second monomer and an initiator, wherein the first monomer comprises a carbon-carbon double bond and a carbon-oxygen bond and / or comprises a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer comprises a carbon-carbon double bond and a fluorine-carbon bond.

2. The gel electrolyte precursor according to claim 1, characterized in that: The first monomer includes one or more of pentaerythritol triacrylate, first vinylene carbonate, acrylonitrile and hydroxyethyl acrylate; and / or The second monomer includes one or more of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride; and / or The initiator comprises one or more of azobisisobutyronitrile and azobisisoheptanenitrile; and / or The sodium salt comprises one or more of sodium hexafluorophosphate and first sodium bis(oxalatoborate); and / or The solvent includes one or more of ethylene carbonate, propylene carbonate and diethyl carbonate.

3. The gel electrolyte precursor according to claim 1, characterized in that: The mass content of the first monomer in the gel electrolyte precursor is 1%-9%; and / or The mass content of the second monomer in the gel electrolyte precursor is 0.3%-3%; and / or The mass content of the initiator in the gel electrolyte precursor is 0.01%-0.08%; and / or The mass content of the sodium salt in the gel electrolyte precursor is 15%-18%.

4. The gel electrolyte precursor according to claim 1, characterized in that: The gel electrolyte precursor further includes additives, which include one or more of a second vinylene carbonate, a fluoroethylene carbonate, and a second sodium bis(oxalatoborate).

5. The gel electrolyte precursor according to claim 4, characterized in that: The additive comprises a second vinylene carbonate, and the mass content of the second vinylene carbonate in the gel electrolyte precursor is 1%-4%; and / or The additive comprises fluoroethylene carbonate, and the mass content of the fluoroethylene carbonate in the gel electrolyte precursor is 0.5%-1%; and / or The additive includes a second sodium bis(oxalatoborate), and the mass content of the second sodium bis(oxalatoborate) in the gel electrolyte precursor is 0.03%-0.06%.

6. A gel electrolyte, characterized in that: The gel electrolyte precursor is obtained by curing the gel electrolyte precursor as described in any one of claims 1 to 5.

7. The gel electrolyte according to claim 6, characterized in that: The weight average molecular weight of the polymer obtained by curing the first monomer and the second monomer is 17000-19000.

8. A method for preparing a gel electrolyte, characterized in that: The following steps are involved: A sodium salt, a solvent, a first monomer, a second monomer and an initiator are provided, mixed, and then subjected to a curing reaction to obtain a gel electrolyte, wherein the first monomer contains a carbon-carbon double bond and a carbon-oxygen bond and / or contains a carbon-carbon double bond and a carbon-nitrogen bond, and the second monomer contains a carbon-carbon double bond and a fluorine-carbon bond.

9. The method for preparing a gel electrolyte according to claim 8, wherein: The mixing includes: mixing the sodium salt, the solvent, the first monomer and the second monomer, and then adding the initiator.

10. The method for preparing a gel electrolyte according to claim 8, characterized in that: The mixing further includes a standing treatment; and / or The curing reaction temperature is 20°C to 60°C, and the curing reaction time is 1h to 8h; and / or The curing reaction is pressurized curing with a pressure of 5N-30N.

11. A sodium ion battery, characterized in that: The invention comprises the gel electrolyte as claimed in claim 6 or 7, or the gel electrolyte prepared by the method for preparing the gel electrolyte as claimed in any one of claims 8 to 10.

Images