A hyperbranched polymer electrolyte and a battery comprising the same

Abstract

The application provides a hyperbranched polymer electrolyte and a battery containing the electrolyte. The raw material of the hyperbranched polymer of the application comprises an electrolyte precursor solution; the electrolyte precursor solution at least comprises a prepolymer solution and an initiator; wherein the prepolymer solution comprises a sodium salt, a plasticizer, a polymer monomer, a crosslinking agent and an additive. The application also provides a high-performance polymer electrolyte and a sodium-ion battery containing the electrolyte, by adjusting the raw material, so as to realize high conductivity at room temperature and improve the cycle performance of the electrolyte in a wide temperature range.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a hyperbranched polymer electrolyte and a battery containing the electrolyte. Background Technology

[0002] Sodium, as the closest analogue to lithium in the periodic table, has attracted widespread interest as a potential substitute. It is hoped that Na... + Sodium-ion batteries can be incorporated into the electrode body at a lower cost, serving as a similar intercalation chemical. They are an alternative for large-scale energy storage and can also be used to store electricity generated by solar cells and wind turbines, representing a green and renewable energy source. However, in practical applications, conventional liquid electrolytes pose a risk of leakage, which significantly threatens battery safety. Solid-state electrolytes offer an effective solution to this problem.

[0003] Solid electrolytes are classified into inorganic, gel polymer, and composite solid electrolytes. Among them, gel polymer electrolytes (GPEs) possess excellent thermal stability, a wide electrochemical window, and flexible design capabilities. GPEs typically consist of polymers, lithium salts, and plasticizers, with the plasticizers often being small-molecule carbonates and ether solvents. GPEs utilize their self-formed polymer network to adsorb liquid electrolytes, which not only solves potential safety issues in sodium-ion batteries such as electrolyte volatility, leakage, and battery combustion, but also ensures good matching between the adsorbed liquid electrolyte and the positive and negative electrodes.

[0004] Currently, most gel polymer electrolytes are still prepared into solid electrolyte films using traditional methods such as solution casting and electrospinning. Solid-state batteries assembled using these solid electrolyte films exhibit significant impedance at the electrode / electrolyte interface, leading to substantial electrochemical polarization and hindering the development of excellent electrochemical performance.

[0005] To address these issues, in-situ solidification technology can create rapid ion transport channels between the electrode / electrolyte and between electrodes / electrolytes, achieving effective contact at the electrode / electrolyte interface, reducing interfacial impedance, and improving electrochemical performance. However, in-situ solidification technology often suffers from difficulties in controlling the degree of polymerization and a lack of matrix structure design, leading to a decline in electrochemical performance. Therefore, solid electrolytes can be prepared by combining polymers with other multi-reactive functional groups to design graft or cross-linked structures, suppressing matrix crystallization. This structural design can enable the prepared solid-state batteries to possess excellent cycle rate performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a hyperbranched polymer electrolyte and a battery containing the electrolyte. By introducing polyacrylate-based esters as crosslinking agents, a hyperbranched polymer is designed to suppress matrix crystallization, improve conductivity, and enable the solid-state battery to have excellent cycle rate performance.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] The application of a hyperbranched polymer in energy storage batteries (e.g., sodium-ion batteries), preferably as a hyperbranched polymer electrolyte.

[0009] According to an embodiment of the present invention, the raw material for the hyperbranched polymer includes an electrolyte precursor liquid; the electrolyte precursor liquid includes at least a prepolymer solution and an initiator; wherein,

[0010] The prepolymer solution includes sodium salt, plasticizer, polymerizing monomer, crosslinking agent, and additives.

[0011] According to an embodiment of the present invention, the sodium salt is selected from sodium salts known in the art, such as at least one selected from sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium trifluoromethanesulfonate (NaOTF), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and sodium bis(fluorosulfonyl)imide (NaFSI).

[0012] According to an embodiment of the present invention, the concentration of the sodium salt in the electrolyte precursor solution is 0.4 to 2 mol / L, for example, 0.6 mol / L or 0.9 mol / L.

[0013] According to embodiments of the present invention, the polymerizing monomer is selected from unsaturated bonded olefin monomers, such as at least one selected from acrylate monomers, carbonate monomers, and modified acrylate monomers. For example, it is at least one of hexafluorobutyl acrylate, 2-hydroxyethyl acrylate, methyl acrylate, ethyl acrylate, 2-ethoxyethyl acrylate, 2-cyanoethyl acrylate, methyl methacrylate, ethyl methacrylate, and tetrahydrofuran methacrylate. Preferably, the acrylate monomer is selected from at least one of hexafluorobutyl acrylate, perfluorobutyl acrylate, methyl acrylate, ethyl acrylate, 2-ethoxyethyl acrylate, 2-cyanoethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and tetrahydrofuran methacrylate.

[0014] Preferably, the carbonate monomer is selected from methyl methacrylate or ethyl methacrylate.

[0015] Preferably, the modified acrylate monomer is selected from 2-ethoxyethyl acrylate or 2-cyanoethyl acrylate.

[0016] According to an embodiment of the present invention, based on the total mass of the electrolyte precursor fluid as 100%, the mass percentage of the polymeric monomer is no more than 30%, preferably 5%-30%, for example 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 25%.

[0017] According to embodiments of the present invention, the plasticizer is selected from at least one of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and phosphate ester solvents. Preferably, the carbonate solvent is selected from methyl ethyl carbonate and propylene carbonate. Preferably, the carboxylic acid ester solvent is selected from propyl acetate, methyl propionate, and methyl acetate. Preferably, the ether solvent is selected from diethylene glycol dimethyl ether and triethylene glycol dimethyl ether. Preferably, the nitrile solvent is selected from succinic anionibacterium and acetonitrile. Preferably, the phosphate ester solvent is selected from trimethyl phosphate and triethyl phosphate.

[0018] According to an embodiment of the present invention, the plasticizer has a mass percentage content of 45%-95%, preferably 60%-95%, based on the total mass of the electrolyte precursor solution as 100%.

[0019] According to an embodiment of the present invention, the crosslinking agent is selected from esters with at least two acrylate groups, wherein the acrylate groups have the following structure:

[0020]

[0021] In this context, * indicates a connection point.

[0022] Preferably, the crosslinking agent is selected from at least one of diallyl phthalate, N,N-methylenebisacrylamide, acrylic anhydride, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, dipropylene glycol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, neopentyl glycol dimethacrylate, pentaerythritol tetraacrylate, ethoxypentaerythritol tetraacrylate, polyethylene glycol dimethacrylate, polydipentaerythritol hexaacrylate, and polydipentaerythritol pentaacrylate. In this invention, the addition of a multi-branched crosslinking agent yields a hyperbranched polymer electrolyte, thereby improving the polymer's antioxidant properties and conductivity.

[0023] According to an embodiment of the present invention, the mass ratio of the crosslinking agent to the polymeric monomer is 3:1 to 1:5, for example, 2:1, 1:2, 1:2, 1:3, or 1:4.

[0024] According to an embodiment of the present invention, based on the total mass of the electrolyte precursor solution as 100%, the mass percentage of the total mass of the crosslinking agent and the polymer monomer is not greater than 30%, for example, 10%, 15%, 18%, or 25%.

[0025] According to embodiments of the present invention, the additive is an electron-withdrawing anionic salt or a nitrile compound. Preferably, the additive is selected from at least one of fluoroethylene carbonate, 1,3-propenesulfonyl lactone, 1,3-propanesulfonyl lactone, sodium difluorooxalate borate, sodium difluorophosphate, tris(trimethylsilyl)phosphate, tetravinylsilane, hexanetrionitrile, vinyl sulfate, and methanedisulfonate, and exemplaryly, two or more of them.

[0026] According to an embodiment of the present invention, the additive has a mass percentage content of 0.01% to 3%, for example, 0.01%, 0.05%, 0.1%, or 2%, based on the total mass of the electrolyte precursor solution as 100%.

[0027] According to an embodiment of the present invention, the initiator is at least one selected from organotin compounds, azo compounds, and peroxide compounds. Preferably, the initiator is selected from any one or a combination of at least two or more of the following: dibutyltin dilaurate, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylamizazoline hydrochloride, potassium persulfate, benzoyl peroxide, benzoyl diperoxide, tert-butyl peroxide-2-ethylhexanoate, benzoyl tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0028] According to an embodiment of the present invention, the initiator has a mass percentage content of 0.01% to 1%, for example, 0.05%, 0.2%, 0.3%, 0.4%, or 0.5%, based on the total mass of the electrolyte precursor solution as 100%.

[0029] According to an embodiment of the present invention, the hyperbranched polymer is obtained by the above-described electrolyte precursor liquid polymerization.

[0030] According to an embodiment of the present invention, the polymerization condition is high-temperature polymerization.

[0031] According to an embodiment of the present invention, the high-temperature polymerization temperature is 55℃~90℃, preferably 50℃~80℃, such as 60℃, 65℃, 70℃, 80℃.

[0032] According to an embodiment of the present invention, the high-temperature polymerization time is not specifically limited, as long as the hyperbranched polymer electrolyte can be obtained, for example, 12h or 24h.

[0033] The present invention also provides a hyperbranched polymer electrolyte, wherein the hyperbranched polymer electrolyte comprises a hyperbranched polymer having the meaning described above.

[0034] The present invention also provides the application of the above-mentioned hyperbranched polymer electrolyte in energy storage batteries.

[0035] The present invention also provides a sodium-ion battery containing the above-mentioned hyperbranched polymer electrolyte.

[0036] According to an embodiment of the present invention, the sodium-ion battery includes a positive electrode, a negative electrode, and the above-described hyperbranched polymer electrolyte.

[0037] According to an embodiment of the present invention, the positive electrode comprises a positive electrode material and a positive electrode current collector. Preferably, the positive electrode material is selected from sodium nickel iron manganese ternary materials and / or sodium iron pyrophosphate (such as Na+). 4 / 3 Fe 3 / 2 (PO4) 2 / 1 At least one of P2O7. Further, the sodium nickel iron manganate ternary material is preferably Na[Ni] 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. Preferably, the positive electrode current collector can be made of materials known in the art, but the present invention does not specifically limit it.

[0038] According to an embodiment of the present invention, the negative electrode is selected from a negative electrode sheet or a negative electrode current collector.

[0039] According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode active layer and a negative electrode current collector.

[0040] According to an embodiment of the present invention, the negative electrode active layer comprises a negative electrode active material, a conductive agent, and a binder. Preferably, the negative electrode active material is selected from at least one of hard carbon, nano-carbon materials, sodium titanate, metals and their alloys (including Sn, Si, In, Bi, Na) anode materials. Preferably, the conductive agent and binder can be materials known in the art, as long as the negative electrode active layer can be obtained; the present invention does not impose specific limitations.

[0041] According to an embodiment of the present invention, the negative electrode current collector includes at least one of microporous aluminum foil, high specific surface area embossed foil, carbon-coated aluminum foil, carbon-coated copper foil, and aluminum fluoride current collector, wherein the carbon layer material in the carbon-coated aluminum foil and carbon-coated copper foil is selected from at least one of conductive carbon black, graphite, and graphene-like materials.

[0042] According to an embodiment of the present invention, the sodium-ion battery further includes a separator. Preferably, the separator is disposed between the positive electrode and the negative electrode.

[0043] According to an embodiment of the present invention, the diaphragm is selected from at least one of polyethylene (PE), polypropylene (PP), polyethylene and polypropylene composite diaphragm, and glass fiber diaphragm.

[0044] Compared with existing technical solutions, the present invention has the following advantages:

[0045] This invention provides a high-performance polymer electrolyte and a sodium-ion battery containing the electrolyte. By selecting the type of sodium salt, the type of plasticizer, the type and ratio of polymer monomers, the type and ratio of crosslinking agents, the type of additives, and the type and ratio of initiators, high conductivity at room temperature is achieved, and the cycling performance of the electrolyte is improved over a wide temperature range.

[0046] The sodium-ion battery using the polymer electrolyte of the present invention has the following performance:

[0047] 1) The sodium-ion battery of this invention exhibits excellent room-temperature cycling and rate performance: 2000 cycles at 25°C and 1C / 1C charge / discharge, using sodium nickel iron manganese oxide cathode material (Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 [O2) or polyanionic cathode material (Na) 4 / 3Fe 3 / 2 (PO4) 2 / 1 P2O7) maintains a capacity retention rate of over 80% and 90% respectively, and a 10C discharge capacity retention rate of >70%;

[0048] 2) The sodium-ion battery of this invention exhibits excellent high-temperature cycle performance: 1000 cycles at 55°C using a 1C / 1C charge / discharge cycle, and using sodium nickel iron manganese oxide cathode material (Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 [O2) or polyanionic cathode material (Na) 4 / 3Fe 3 / 2 (PO4) 2 / 1 P2O7) retains more than 80% and 90% of its capacity, respectively;

[0049] 3) The sodium-ion battery of this invention exhibits excellent low-temperature cycling and rate performance: maintaining over 93% and 88% of its room temperature capacity at -10°C and -20°C respectively, and completing 200 charge-discharge cycles at -10°C and 0.2C / 0.2C. It utilizes a ternary material of sodium nickel iron manganese oxide (Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 [O2), maintaining a capacity retention rate of over 80%. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Example 1: Sodium Salts (1-4)

[0053] 1. Prepare the electrolyte precursor solution, following these steps:

[0054] (1) Mix the fully dried sodium salt with the plasticizer, and add the additive after the salt has completely dissolved to obtain solution A;

[0055] (2) After the additives have completely dissolved, add the crosslinking agent and the polymerizing monomer, mix them evenly to obtain a prepolymer solution, which is denoted as solution B.

[0056] (3) The initiator is slowly added to solution B to obtain the electrolyte precursor solution;

[0057] In the electrolyte precursor solution:

[0058] Solution A: The sodium salts are sodium hexafluorophosphate (concentration of 0.6 mol / L) and sodium difluorosulfonamide (concentration of 0.9 mol / L), the plasticizer is ethyl methyl carbonate (EMC), and the additives include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, and 1,3-propanesulfonic acid lactone, with mass percentages of 1%, 0.5%, 0.3%, and 1%, respectively.

[0059] Component B: The monomer for polymerization is methyl methacrylate (MMA), with a mass percentage of 9%, and the crosslinking agent is ethylene glycol dimethacrylate (EDGMA), with a mass percentage of 3%.

[0060] In the electrolyte precursor solution of step (3), the initiator is azobisisobutyronitrile (AIBN), with a mass percentage of 0.3%.

[0061] The above steps (1)-(3) are carried out in an argon atmosphere glove box with a water content of <10ppm. The electrolyte precursor liquid is then prepared for use and can be further polymerized at 60°C for 24h to obtain a polymer electrolyte.

[0062] 2. The above electrolyte precursor solution is used to prepare a sodium-ion battery, wherein the positive electrode active material is Na[Ni] 1 / 3 Fe 1 / 3Mn 1 / 3O2; the negative electrode is hard carbon, and the separator is a composite separator of polyethylene and polypropylene. The preparation method of sodium-ion battery is as follows:

[0063] (A1) Preparation of positive electrode sheet

[0064] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone (NMP) to prepare a 4 wt% solution, and then the positive electrode active material Na[Ni] was added. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 (or

[0065] Na 4 / 3 Fe 3 / 2 (PO4) 2 / 1 P2O7 and conductive carbon black (SP) are thoroughly stirred and mixed to obtain a positive electrode slurry; wherein, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 (or Na) 4 / 3 Fe 3 / 2 (PO4) 2 / 1 The mass ratio of P2O7, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) is 93:3:4. The positive electrode slurry is coated on Al foil, dried, compacted, and cut into sheets to obtain the positive electrode sheet. The drying is carried out in a vacuum drying oven at 120°C for 12 hours.

[0066] Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 The compacted density of O2 material is 3.1 ± 0.1 g / cm³. 3 Na 4 / 3 Fe 3 / 2 (PO4) 2 / 1 The compacted density of P2O7 material is 2.0 ± 0.1 g / cm³. 3 The size of the cut piece is 43mm*56mm.

[0067] (A2) Preparation of negative electrode sheet

[0068] The negative electrode slurry is prepared by thoroughly mixing hard carbon, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and conductive carbon black (SP) in a mass ratio of 93:1.5:2.5:3. The CMC is pre-dissolved in deionized water to prepare a 1.2% solution. The negative electrode slurry is coated onto Al foil, dried, compacted, and cut to obtain the negative electrode sheet. Drying is carried out in a vacuum drying oven at 120℃ for 12 hours. The compacted density of the negative electrode is 0.95±0.05 g / cm³. 3 The size of the cut piece is 43mm*56mm.

[0069] (A3) Battery fabrication

[0070] The positive electrode, separator, and negative electrode are placed in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell. The bare cell is first packaged in an aluminum-plastic film bag and dried to remove moisture. The electrolyte precursor solution prepared in step 1 is injected into the dried aluminum-plastic film bag containing the bare cell. After a second packaging, the electrolyte precursor solution is allowed to stand at 60°C to polymerize in situ in the bare cell for 24 hours to obtain a polymer electrolyte. Subsequently, a solid-state battery is formed.

[0071] The transformation steps are as follows:

[0072] Step 1: Charge at 0.05C and 0.1C for 2 hours;

[0073] Step 2: Charge at 0.2C to the cutoff voltage (Na[Ni)). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is charged to 4.0V, Na 4 / 3 Fe 3 / 2 (PO4) 2 / 1 (P2O7 cathode material charged to 3.6V);

[0074] Step 3: Discharge to 1.5V at 0.2C.

[0075] Example 2

[0076] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the concentrations of sodium hexafluorophosphate and sodium difluorosulfonamide in solution A are 0.9 mol / L and 0.6 mol / L, respectively, and other conditions are the same as in Example 1.

[0077] 2. The preparation method of sodium-ion batteries is the same as in Example 1.

[0078] Example 3

[0079] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the concentrations of sodium hexafluorophosphate and sodium difluorosulfonamide in solution A are 0.9 mol / L and 0.3 mol / L, respectively, and other conditions are the same as in Example 1.

[0080] 2. The battery preparation method is the same as in Example 1.

[0081] Example 4

[0082] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the sodium salt in solution A is only sodium hexafluorophosphate with a concentration of 1 mol / L, and other conditions are the same as in Example 1.

[0083] 2. The battery preparation method is the same as in Example 1.

[0084] Examples 5-9 Different Polymer Monomers

[0085] Example 5

[0086] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the monomer used in solution B is ethyl methacrylate, and the other conditions are the same as in Example 1.

[0087] 2. The battery preparation method is the same as in Example 1.

[0088] Example 6

[0089] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the monomer used in solution B is hexafluorobutyl acrylate, and the other conditions are the same as in Example 1.

[0090] 2. The battery preparation method is the same as in Example 1.

[0091] Example 7

[0092] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the monomer used in solution B is ethyl acrylate, and the other conditions are the same as in Example 1.

[0093] 2. The battery preparation method is the same as in Example 1.

[0094] Example 8

[0095] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the monomer used in solution B is 2-ethoxyethyl acrylate, and the other conditions are the same as in Example 1.

[0096] 2. The battery preparation method is the same as in Example 1.

[0097] Example 9

[0098] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the monomer used in solution B is hydroxyethyl methacrylate, and the other conditions are the same as in Example 1.

[0099] 2. The battery preparation method is the same as in Example 1.

[0100] Examples 10-15 Crosslinking Agent

[0101] Example 10

[0102] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is dipropylene glycol diacrylate and N,N-methylenebisacrylamide, the mass percentages of methyl methacrylate (MMA), dipropylene glycol diacrylate and N,N-methylenebisacrylamide are 9%, 2% and 3% respectively, the initiator is dibutyltin dilaurate, and other conditions are the same as in Example 1.

[0103] 2. The battery preparation method is the same as in Example 1, except that the polymerization conditions are adjusted to polymerization at 70°C for 4 hours, while other conditions are the same as in Example 1.

[0104] Example 11

[0105] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is ethylene glycol diacrylate, and the mass percentages of methyl methacrylate (MMA) and ethylene glycol diacrylate are 12% and 5%, respectively. Other conditions are the same as in Example 1.

[0106] 2. The battery preparation method is the same as in Example 1, except that the polymerization conditions are adjusted to polymerization at 55°C for 24 hours, while other conditions are the same as in Example 1.

[0107] Example 12

[0108] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is ethoxylated trimethylolpropane triacrylate, and the mass percentages of methyl methacrylate (MMA) and ethoxylated trimethylolpropane triacrylate are 15% and 4%, respectively, and other conditions are the same as in Example 1.

[0109] 2. The battery preparation method is the same as in Example 1, except that the polymerization conditions are adjusted to polymerization at 70°C for 2 hours, while other conditions are the same as in Example 1.

[0110] Example 13

[0111] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is polyethylene glycol dimethacrylate, and the mass percentages of methyl methacrylate (MMA) and polyethylene glycol dimethacrylate are 10% and 5%, respectively. Other conditions are the same as in Example 1.

[0112] 2. The battery preparation method is the same as in Example 1, except that the polymerization conditions are adjusted to polymerization at 45°C for 24 hours, while other conditions are the same as in Example 1.

[0113] Example 14

[0114] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is polydipentaerythritol hexaacrylate, and the mass percentages of methyl methacrylate (MMA) and polydipentaerythritol hexaacrylate are 9% and 4%, respectively. Other conditions are the same as in Example 1.

[0115] 2. The battery preparation method is the same as in Example 1.

[0116] Example 15

[0117] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the crosslinking agent in solution B is polydipentaerythritol pentaacrylate, and the mass percentages of methyl methacrylate (MMA) and polydipentaerythritol pentaacrylate are 15% and 5%, respectively, and other conditions are the same as in Example 1.

[0118] 2. The battery preparation method is the same as in Example 1.

[0119] Examples 16-23 Plasticizers

[0120] Example 16

[0121] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the plasticizer in solution A is methyl propionate and ethyl methyl carbonate in a mass ratio of 2:3, and other conditions are the same as in Example 1.

[0122] 2. The battery preparation method is the same as in Example 1.

[0123] Example 17

[0124] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the plasticizer in solution A is ethyl difluoroacetate and ethyl methyl carbonate in a mass ratio of 1:4, and other conditions are the same as in Example 1.

[0125] 2. The battery preparation method is the same as in Example 1.

[0126] Example 18

[0127] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the plasticizer in solution A is diethylene glycol dimethyl ether and methyl ethyl carbonate in a mass ratio of 2:3, and other conditions are the same as in Example 1.

[0128] 2. The battery preparation method is the same as in Example 1.

[0129] Example 19

[0130] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the plasticizer in solution A is trimethyl phosphate and methyl ethyl carbonate in a mass ratio of 1:4, and other conditions are the same as in Example 1.

[0131] 2. The battery preparation method is the same as in Example 1.

[0132] Example 20

[0133] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the plasticizer in solution A is triethyl phosphate and methyl ethyl carbonate in a mass ratio of 1:4, and other conditions are the same as in Example 1.

[0134] 2. The battery preparation method is the same as in Example 1.

[0135] Example 21

[0136] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the sodium salt in solution A is sodium hexafluorophosphate (concentration of 0.2 mol / L) and sodium bis(trifluoromethanesulfonyl)imide (concentration of 0.8 mol / L), the plasticizer is succinic anionyl, and other conditions are the same as in Example 1.

[0137] 2. The battery preparation method is the same as in Example 1.

[0138] Example 22

[0139] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the sodium salt in solution A is sodium hexafluorophosphate (concentration of 0.2 mol / L) and sodium bis(trifluoromethanesulfonyl)imide (concentration of 0.8 mol / L), the plasticizer is succinate and ethyl propionate, and their mass ratio is 1:1. Other conditions are the same as in Example 1.

[0140] 2. The battery preparation method is the same as in Example 1.

[0141] Example 23

[0142] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the sodium salt in solution A is sodium hexafluorophosphate (concentration of 0.2 mol / L) and sodium bis(trifluoromethanesulfonyl)imide (concentration of 0.8 mol / L), the plasticizer is succinic acid and diethyl carbonate, and their mass ratio is 1:1. Other conditions are the same as in Example 1.

[0143] 2. The battery preparation method is the same as in Example 1.

[0144] Examples 24-28 Additives

[0145] Example 24

[0146] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the additives in solution A include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, ethylene sulfate, (ethoxy)pentafluorocyclotriphosphazene and 1,3-propanesulfonic acid lactone, with a mass percentage of 1%, 0.5%, 0.3%, 0.5%, 4% and 0.8%, respectively, and other conditions are the same as in Example 1.

[0147] 2. The battery preparation method is the same as in Example 1.

[0148] Example 25

[0149] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the additives in solution A include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, ethylene sulfate, (trifluoroethoxy)pentafluorocyclotriphosphazene and 1,3-propanesulfonic acid lactone, with mass percentages of 1%, 0.5%, 0.3%, 0.5%, 4% and 0.8%, respectively, and other conditions are the same as in Example 1.

[0150] 2. The battery preparation method is the same as in Example 1.

[0151] Example 26

[0152] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the additives in solution A include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, ethylene sulfate and 1,3-propanesulfonic acid lactone, with mass percentages of 1%, 0.5%, 0.3%, 0.5% and 0.8%, respectively, and other conditions are the same as in Example 1.

[0153] 2. The battery preparation method is the same as in Example 1.

[0154] Example 27

[0155] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the additives in solution A include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, ethylene sulfate, tetravinylsilane and 1,3-propanesulfonic acid lactone, with mass percentages of 1%, 0.5%, 0.3%, 0.5%, 0.5% and 0.8%, respectively, and other conditions are the same as in Example 1.

[0156] 2. The battery preparation method is the same as in Example 1.

[0157] Example 28

[0158] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that: the additives in solution A include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, ethylene sulfate, and 1,3-propanesulfonic acid lactone, with mass percentages of 1%, 0.5%, 0.3%, 0.5%, and 0.8%, respectively, and other conditions are the same as in Example 1.

[0159] 2. The battery preparation method is the same as in Example 1.

[0160] Example 29

[0161] 1. The method for preparing the electrolyte precursor solution in this embodiment is the same as in Example 1.

[0162] 2. The battery preparation method is basically the same as in Example 1. The positive electrode active material in the sodium-ion battery provided in this comparative example is Na. 4 / 3 Fe 3 / 2 (PO4) 2 / 1 P2O7, other conditions are the same as in Example 1.

[0163] Example 30

[0164] 1. The method for preparing the electrolyte precursor solution in this embodiment is the same as in Example 5.

[0165] 2. The battery preparation method is basically the same as in Example 1. The positive electrode active material in the sodium-ion battery provided in this example is Na. 4 / 3 Fe 3 / 2 (PO4) 2 / 1 P2O7, other conditions are the same as in Example 1.

[0166] Example 31

[0167] 1. The method for preparing the electrolyte precursor solution in this embodiment is the same as in Example 14.

[0168] 2. The battery preparation method is basically the same as in Example 1. The positive electrode active material in the sodium-ion battery provided in this example is Na. 4 / 3 Fe 3 / 2 (PO4) 2 / 1 P2O7, other conditions are the same as in Example 1.

[0169] Comparative Example 1

[0170] Electrolyte preparation: The sodium salt is sodium hexafluorophosphate (concentration of 1 mol / L), the solvent is a mixed solvent of PC (propylene carbonate) / EMC (methyl ethyl carbonate) (mass ratio of 3:5), and the additives include fluoroethylene carbonate, ethylene sulfate and 1,3-propanesulfonic acid lactone, with mass percentages of 1.5%, 0.5% and 1.0%, respectively.

[0171] Sodium-ion batteries are prepared using the above-mentioned electrolyte. The preparation method of sodium-ion batteries includes: placing the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide separation, and then winding them to obtain a bare cell; packaging the bare cell in an aluminum-plastic film bag and drying it to remove moisture; injecting the prepared electrolyte into the dried aluminum-plastic film bag containing the bare cell; repackaging the bag; and then directly forming the battery.

[0172] In this comparative example, the positive electrode, separator, and negative electrode are basically the same as in Example 1, except that the positive electrode active material is Na[Ni]. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0173] Comparative Example 2

[0174] Electrolyte preparation: The sodium salt is sodium hexafluorophosphate (concentration of 1 mol / L), the solvent is a mixed solvent of PC (propylene carbonate) / EMC (methyl ethyl carbonate) / DEC (diethyl carbonate) (mass ratio of 3:5), and the additives include fluoroethylene carbonate, 1,3-propanesulfonate lactone and 1,3-propenesulfonate lactone, with a mass percentage of 1%, 1% and 1%, respectively.

[0175] Sodium-ion batteries were prepared using the electrolyte described above. The preparation method of this comparative battery is the same as that of Comparative Example 1, except that the positive electrode active material is Na. 4 / 3 Fe 3 / 2 (PO4) 2 / 1 P2O7.

[0176] Comparative Example 3

[0177] 1. The method for preparing electrolyte precursor solution in this comparative example is basically the same as in Example 1, except that: no cross-linking agent is added to solution B, only the polymeric monomer methyl methacrylate (MMA) is added, with a mass percentage of 12%, and other conditions are the same as in Example 1.

[0178] 2. The battery preparation method is the same as in Example 1, and other conditions are the same as in Example 1.

[0179] Comparative Example 4

[0180] 1. The method for preparing electrolyte precursor solution in this comparative example is basically the same as in Example 1, except that: the mass percentage of methyl methacrylate (MMA) in solution B is 22%, the mass percentage of ethylene glycol dimethacrylate (EDGMA) is 9%, and other conditions are the same as in Example 1.

[0181] 2. The battery preparation method is the same as in Example 1, and other conditions are the same as in Example 1.

[0182] Comparative Example 5

[0183] 1. The method for preparing electrolyte precursor solution in this comparative example is basically the same as in Example 1, except that: the mass percentage of methyl methacrylate (MMA) in solution B is 27%, the mass percentage of ethylene glycol dimethacrylate (EDGMA) is 9%, and other conditions are the same as in Example 1.

[0184] 2. The battery preparation method is the same as in Example 1, and other conditions are the same as in Example 1.

[0185] Example 32

[0186] 1. The method for preparing the electrolyte precursor solution in this embodiment is basically the same as in Example 1, except that the additive in solution A only contains fluoroethylene carbonate, with a mass percentage of 1%, and other conditions are the same as in Example 1.

[0187] 2. The battery preparation method is the same as in Example 1, and other conditions are the same as in Example 1.

[0188] Test Example 1

[0189] The batteries prepared in Examples 1-31 and the comparative examples were subjected to the following tests:

[0190] (1) Cyclic performance test: At 25 / 55℃, the sodium-ion batteries in Examples 1-31 and the comparative examples were charged with a constant current of 0.1C to the cutoff voltage, then charged with a constant voltage to 0.05C, and then discharged with a constant current of 0.1C to 1.5V. After this charge / discharge cycle twice, they were charged with a constant current of 1C to the cutoff voltage, charged with a constant voltage to 0.05C, and then discharged with a constant current of 1C to 1.5V. This charge / discharge cycle was repeated 500 times. The capacity retention rate was calculated.

[0191] The formula for calculating capacity retention rate is as follows: Capacity retention rate = Discharge capacity of the corresponding cycle / Discharge capacity of the first cycle × 100%, and the results are shown in Table 1.

[0192] (2) Low-temperature cycling performance test: At 25°C, the sodium-ion batteries in Examples 1-31 and the comparative examples were charged to the cutoff voltage at a constant current of 0.1C, and then discharged to 1.5V at a constant current of 0.1C. After this charge / discharge cycle twice, they were placed at -10°C for 12 hours, and then charged to the cutoff voltage at a constant current of 0.2C, and then discharged to 1.5V at a constant current of 0.2C. This charge / discharge cycle was repeated 200 times. The capacity retention rate was calculated.

[0193] Among them, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and Na 4 / 3 Fe 3 / 2(PO4) 2 / 1 The charging cutoff voltages of the P2O7 cathode material are 4.0V and 3.6V, respectively. The formula for calculating the low-temperature discharge capacity retention rate is: Low-temperature discharge capacity retention rate = Discharge capacity of the corresponding cycle / Discharge capacity at 25℃ × 100%, and the results are shown in Table 1.

[0194] Table 1

[0195]

[0196]

[0197] According to the test results of Examples 1-4, when different sodium salts and their combinations are used in the polymer electrolyte, the capacity retention rate of the battery with NFM as the positive electrode material at -10℃ and -20℃ (-10℃, greater than 90%; -20℃, greater than 88%, VS room temperature) is higher than that of the commercial liquid electrolyte (Comparative Example 1). The capacity retention rate after cycling at 25℃ (2000 cycles) and 55℃ (1000 cycles) is greater than 80%. The polymer electrolyte using sodium hexafluorophosphate (concentration of 0.6 mol / L) and sodium bis(trifluoromethanesulfonyl)imide (concentration of 0.9 mol / L) has the best overall performance, with a capacity retention rate of 81.5% after cycling at -10℃ for 200 cycles, which is far better than that of the commercial liquid electrolyte (Comparative Example 1). Similar results were obtained when NFPP material was used as the positive electrode (Example 29 and Comparative Example 2).

[0198] According to the test results of Examples 1 and 5-9, when polymer electrolytes are polymerized using different monomers, the battery with NFM as the positive electrode material has a capacity retention rate of more than 78% after cycling at 25°C (2000 cycles) and 55°C (1000 cycles). The polymer electrolyte polymerized with ethyl methacrylate as the monomer has the best overall performance, with a capacity retention rate of 83.6% after cycling at -10°C for 200 cycles, which is far superior to the commercial liquid electrolyte (Comparative Example 1). Similar results were obtained when NFPP material was used as the positive electrode (Example 30 and Comparative Example 2).

[0199] Based on the test results of Examples 1 and 10-15, it can be seen that when polymer electrolytes are polymerized using different crosslinking agents, the battery with NFM as the positive electrode material exhibits the following capacity retention rates at -10℃ and -20℃ (-10℃, greater than 85%; -20℃, greater than 78%, VS room temperature), and the capacity retention rate after cycling at 25℃ (2000 cycles) and 55℃ (1000 cycles) is greater than 78%. The polymer electrolyte polymerized using polydipentaerythritol hexaacrylate as the crosslinking agent has the best overall performance, with a capacity retention rate of 85.1% after 200 cycles at -10℃, which is far superior to commercial liquid electrolytes (Comparative Example 1). Similar results were obtained when using NFPP material as the positive electrode (Example 31 and Comparative Example 2).

[0200] Based on the test results of Examples 1 and 16-23, it can be seen that when the polymer electrolyte is polymerized with different plasticizers, the battery using NFM as the positive electrode material retains more than 79% of its capacity after cycling at 25°C (2000 cycles) and 55°C (1000 cycles). The polymer electrolyte plasticized with methyl propionate (Example 16), ethyl difluoroacetate (Example 17), and diethylene glycol dimethyl ether (Example 18) in combination with methyl ethyl carbonate shows significantly improved low-temperature capacity retention and cycling performance. The high-temperature and room-temperature cycling performance decreases slightly, but is still far superior to the commercial liquid electrolyte (Comparative Example 1). When flame-retardant phosphoric acid solvents (Examples 19 and 20) and nitrile solvents are used for plasticization (Examples 21-23), the polymer electrolyte maintains good high and low temperature cycling performance, and its cycling performance at all three temperatures is superior to that of the commercial liquid electrolyte (Comparative Example 1).

[0201] Based on the test results of Examples 1 and 24-28, it can be seen that when different additive combinations are used in polymer electrolytes, the additive combination in Example 1 has the best performance (the additives include fluoroethylene carbonate, sodium difluorooxalate borate, sodium difluorophosphate, and 1,3-propanesulfonic acid lactone, with percentage contents of 1%, 0.5%, 0.3%, and 1%, respectively). After cycling at 25°C (2000 cycles) and 55°C (1000 cycles), the capacity retention rates are 85.6% and 83.8%, respectively, and after cycling at -10°C (200 cycles), the capacity retention rate reaches 81.5%, all of which are superior to commercial liquid electrolytes (such as Comparative Example 1).

[0202] According to the test results of Example 1 and Comparative Example 3, the crosslinking agent has a significant effect on improving the performance of polymer electrolytes. The performance of the hyperbranched polymer electrolyte formed after crosslinking is better than that of the electrolyte formed by pure monomer polymerization.

[0203] According to the test results of Example 1 and Comparative Examples 4-5, the total mass content of polymeric monomers and crosslinking agents has a significant impact on the performance of polymer electrolytes, and the proportion of the total mass of the two should be less than 30%.

[0204] According to the test results of Examples 1 and 32, compared with the use of 1% fluoroethylene carbonate alone, the combined additive can significantly improve the high and low temperature cycling performance.

[0205] In summary, the polymer electrolyte provided by this invention, when used in sodium-ion batteries, enables sodium-ion batteries to exhibit good capacity retention and cycle performance at high temperatures, room temperatures, and low temperatures.

[0206] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An application of a hyperbranched polymer in energy storage batteries, characterized in that, The raw materials for the hyperbranched polymer include an electrolyte precursor solution; the electrolyte precursor solution includes at least a prepolymer solution and an initiator; wherein... The prepolymer solution includes sodium salt, plasticizer, polymerizing monomer, crosslinking agent, and additives.

2. The application according to claim 1, characterized in that, The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, and sodium difluorosulfonylimide. Preferably, the concentration of the sodium salt in the electrolyte precursor solution is 0.4 to 2 mol / L.

3. The application according to claim 1 or 2, characterized in that, The polymerizing monomer is selected from unsaturated bonded olefin monomers, such as at least one selected from acrylate monomers, carbonate monomers, and modified acrylate monomers. Preferably, the acrylate monomer is selected from at least one of hexafluorobutyl acrylate, perfluorobutyl acrylate, methyl acrylate, ethyl acrylate, 2-ethoxyethyl acrylate, 2-cyanoethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, and tetrahydrofuran methacrylate. Preferably, the carbonate monomer is selected from methyl methacrylate and ethyl methacrylate. Preferably, the modified acrylate monomer is selected from 2-ethoxyethyl acrylate and 2-cyanoethyl acrylate. Preferably, the mass percentage of the polymeric monomer is no more than 30% based on the total mass of the electrolyte precursor solution (100%). Preferably, the plasticizer is selected from at least one of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and phosphate ester solvents. Preferably, the carbonate solvent is selected from methyl ethyl carbonate and propylene carbonate. Preferably, the carboxylic acid ester solvent is selected from propyl acetate, methyl propionate, and methyl acetate. Preferably, the ether solvent is selected from diethylene glycol dimethyl ether and triethylene glycol dimethyl ether. Preferably, the nitrile solvent is selected from succinic anionibacterium and acetonitrile. Preferably, the phosphate ester solvent is selected from trimethyl phosphate and triethyl phosphate. Preferably, the plasticizer has a mass percentage content of 45%-95% based on the total mass of the electrolyte precursor solution of 100%.

4. The application according to any one of claims 1-3, characterized in that, The crosslinking agent is selected from esters having at least two acrylate groups, wherein the acrylate groups have the following structure: In this context, * indicates a connection point. Preferably, the crosslinking agent is selected from at least one of diallyl phthalate, N,N-methylenebisacrylamide, acrylic anhydride, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, dipropylene glycol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, neopentyl glycol dimethacrylate, pentaerythritol tetraacrylate, ethoxypentaerythritol tetraacrylate, polyethylene glycol dimethacrylate, polydipentaerythritol hexaacrylate, and polydipentaerythritol pentaacrylate.

5. The application according to any one of claims 1-4, characterized in that, Based on the total mass of the electrolyte precursor liquid as 100%, the mass ratio of the crosslinking agent to the polymer monomer is 3:1 to 1:

5. Preferably, based on the total mass of the electrolyte precursor solution as 100%, the mass percentage of the total mass of the crosslinking agent and the polymer monomer is not greater than 30%.

6. The application according to any one of claims 1-5, characterized in that, The additive is an electron-withdrawing anionic salt or a nitrile compound. Preferably, the additive is selected from at least one of fluoroethylene carbonate, 1,3-propenesulfonyl lactone, 1,3-propanesulfonyl lactone, sodium difluorooxalate borate, sodium difluorophosphate, tris(trimethylsilyl)phosphate, tetravinylsilane, hexanetrionitrile, vinyl sulfate, and methylene disulfonate. Preferably, the additive has a mass percentage content of 0.01% to 3% based on the total mass of the electrolyte precursor solution as 100%. Preferably, the initiator is at least one of organotin compounds, azo compounds, and peroxide compounds. Preferably, the initiator is selected from any one or a combination of at least two or more of the following: dibutyltin dilaurate, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylamizazoline hydrochloride, potassium persulfate, benzoyl peroxide, benzoyl diperoxide, tert-butyl peroxide-2-ethylhexanoate, benzoyl tert-butyl peroxide, and methyl ethyl ketone peroxide. Preferably, the initiator has a mass percentage content of 0.01% to 1% based on the total mass of the electrolyte precursor solution of 100%.

7. The application according to any one of claims 1-6, characterized in that, The hyperbranched polymer is obtained by polymerization of the electrolyte precursor liquid. Preferably, the polymerization is carried out under high-temperature conditions. Preferably, the high-temperature polymerization temperature is 55℃~90℃.

8. A hyperbranched polymer electrolyte, said hyperbranched polymer electrolyte comprising the hyperbranched polymer as described in any one of claims 1-7.

9. The application of the hyperbranched polymer electrolyte according to claim 8 in energy storage batteries.

10. A sodium-ion battery, characterized in that, The sodium-ion battery contains the hyperbranched polymer electrolyte as described in claim 8.

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