A polymer coating, a method of making the same, a negative current collector, and a sodium-ion battery without negative electrode

Abstract

The application belongs to the field of batteries, and particularly relates to a polymer coating, a preparation method thereof, a negative electrode current collector and a sodium-ion battery without negative electrode. The polymer coating is made of a coating containing a polymer precursor, a photocuring initiator, an electronic conductor, an ionic conductor and a binder, and the chemical structure of the polymer precursor is shown as formula A; in formula A, X is Br, and R is one or more of propenyl, butenyl, propynyl, methyl vinyl ketone, 3-heptene-2-ketone, 5-methyl-3-hexene-2-ketone and 5,5-difluoro-1-hexenyl. The polymer coating provided by the application is introduced into the sodium-ion battery without negative electrode as the surface coating of the negative electrode current collector, and is matched with reasonable electronic and ionic conductors, so that the electronic and ionic transmission capacity at the negative electrode interface can be significantly improved, the growth of sodium dendrites during the cycle can be obviously inhibited, and the electrochemical performance of the battery is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and particularly relates to a polymer coating, its preparation method, a negative electrode current collector, and a negative electrode-free sodium-ion battery. Background Technology

[0002] Due to the scarcity and uneven global distribution of lithium resources, researchers have discovered sodium, an element in the same group, to address the lithium resource problem. Sodium possesses similar physicochemical properties to lithium, and it is not only abundant but also inexpensive. Sodium ions (Na₂O / Na₂O) + The electrode potential of the ion is 0.3V higher than that of lithium ion, resulting in more stable electrochemical performance and higher safety performance.

[0003] Currently, the most commonly used current collector materials for sodium-ion batteries are copper foil or aluminum foil. Copper foil has good conductivity, which can effectively promote the deposition and precipitation of sodium, and it also has high conductivity and mechanical strength. However, the main advantage of sodium-ion batteries is their higher cost-effectiveness. Therefore, in many cases, the lower-priced aluminum foil is used as the negative electrode current collector. Unlike lithium, which easily undergoes an alloying reaction with aluminum-based current collectors at low negative electrode potentials, sodium negative electrodes do not undergo an alloying reaction with aluminum-based current collectors. Therefore, it is necessary to develop new negative electrode material systems to improve the energy density of sodium-ion batteries.

[0004] Currently, sodium-ion batteries mostly use hard carbon as the negative electrode material. However, due to the large specific surface area and numerous surface defects of hard carbon, the initial charge-discharge efficiency of the battery is low. Limited by the low capacity, low compaction, and low initial efficiency of hard carbon, the energy density of sodium-ion batteries is typically below 140 Wh / kg. One solution is to directly use copper or aluminum foil as the negative electrode, utilizing the electroplating deposition and dissolution of sodium ions as the negative electrode reaction to construct a negative electrode-free sodium-ion battery, achieving extremely high energy density. However, the binding energy between traditional aluminum and copper foil and sodium metal ions is low, leading to uneven sodium deposition during charging and low coulombic efficiency. Furthermore, the volume of the negative electrode formed by sodium metal deposition changes during cycling, affecting battery safety and electrochemical performance, thus limiting the practical application of negative electrode-free sodium-ion batteries. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a polymer coating, a method for preparing the same, a negative electrode current collector, and a negative electrode-free sodium-ion battery. By introducing the polymer coating provided by the present invention as a surface coating for the negative electrode current collector into a negative electrode-free sodium-ion battery, the electrochemical performance of the negative electrode-free sodium-ion battery can be significantly improved.

[0006] This invention provides a polymer coating, which is made of a coating containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder. The chemical structure of the polymer precursor is shown in Formula A.

[0007]

[0008] Wherein, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methyl vinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl.

[0009] Preferably, the polymer precursor is at least one of compounds of formulas (I) to (VII):

[0010]

[0011] Preferably, the polymer precursor is prepared according to the following steps:

[0012] a) The aldehyde-containing methylpyrrole monomer of formula a is subjected to a McMurray coupling reaction to obtain the intermediate compound of formula b.

[0013] b) React the intermediate compound of the structure of formula b with the haloolefin of the structure of formula c to obtain the polymer precursor of the structure of formula A;

[0014] XR type c;

[0015]

[0016] Wherein, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methyl vinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl.

[0017] Preferably, the electronic conductor is one or more of graphite, acetylene black, SuperP, SuperS, graphene, carbon fiber, carbon nanotubes, and Ketjen black; the ionic conductor is a sodium solid electrolyte with the structural formula Na. 1+x Zr2Si x P 3- x O 12 , 0≤x≤3.

[0018] Preferably, the photocuring initiator is one or more of benzoin, benzoin derivatives, benzoyl groups, alkyl phenyl ketones, acyl phosphorus oxides, benzophenones, and thioxanthones; and the binder is one or more of acrylic binders, polyvinyl alcohol, and sodium carboxymethyl cellulose.

[0019] Preferably, the mass ratio of the polymer precursor, photocuring initiator, electronic conductor, ionic conductor and binder is 6:(0.2-2):(0.5-2):(0.5-2):(1-3).

[0020] This invention provides a method for preparing the polymer coating described above, comprising the following steps:

[0021] A polymer coating is obtained by coating a material containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder, followed by baking and UV curing.

[0022] The present invention provides a negative electrode current collector, which includes a negative electrode current collector substrate and a coating coated on the surface of the negative electrode current collector substrate. The coating is a polymer coating as described in the above technical solution or a polymer coating prepared by the preparation method described in the above technical solution.

[0023] Preferably, the negative electrode current collector substrate is made of aluminum.

[0024] This invention provides a negative electrode-free sodium-ion battery, wherein the negative electrode current collector described in the above technical solution is used as the negative electrode.

[0025] Compared with existing technologies, this invention provides a polymer coating, its preparation method, a negative electrode current collector, and a negative electrode-free sodium-ion battery. The polymer coating provided by this invention is made of a coating containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder. The chemical structure of the polymer precursor is shown in Formula A; in Formula A, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methylvinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl. This invention uses a polymer coating with specific components as the surface coating for the negative electrode current collector in a negative electrode-less sodium-ion battery. This polymer coating has a three-dimensional porous structure with conductive material filling the gaps, facilitating both rapid electron and ion transport. Simultaneously, the free bromine anions in the polymer coating readily combine with sodium ions, inducing the formation of a NaBr phase in the SEI layer. NaBr has a low sodium ion diffusion barrier in the SEI layer, thus improving the stability of interfacial ion transport. Furthermore, the anchored cationic groups in the polymer coating, through charge attraction, can enrich more anions in the electrolyte on the negative electrode surface, participating in negative electrode film formation. This increases the NaF component in the SEI film, thereby reducing the overpotential for sodium metal nucleation and constructing a high-speed sodium ion transport channel at the negative electrode interface. This improves the uniformity of sodium ion deposition on the negative electrode surface, enhances the coulombic efficiency of the battery charge / discharge, and avoids dendrite growth caused by insufficient sodium ion diffusion rate. Therefore, introducing the polymer coating provided by this invention as a surface coating for the negative electrode current collector into a negative electrode-free sodium-ion battery can significantly improve the battery's electron and ion transport capabilities, significantly improve the growth of sodium dendrites in the battery, and enhance the battery's cycle performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 This is a comparison chart of the room temperature cycling performance of the battery of Example 9 and the battery of Comparative Example 2 provided by the present invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a polymer coating, which is made by coating, baking and UV curing a paint containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor and a binder. The chemical structure of the polymer precursor is shown in Formula A.

[0030]

[0031] Wherein, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methyl vinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl.

[0032] In the polymer coating provided by the present invention, the polymer precursor in the coating may specifically be at least one of the compounds of formula (I) to (VII):

[0033]

[0034] In the polymer coating provided by the present invention, the polymer precursor is preferably prepared according to the following steps:

[0035] a) The aldehyde-containing methylpyrrole monomer of formula a is subjected to a McMurray coupling reaction to obtain the intermediate compound of formula b.

[0036] b) React the intermediate compound of the structure of formula b with the haloolefin of the structure of formula c to obtain the polymer precursor of the structure of formula A;

[0037] XR type c;

[0038]

[0039] Wherein, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methyl vinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl.

[0040] In the polymer precursor preparation steps provided by this invention, step a) preferably includes the following specific process for the McMurray coupling reaction: mixing an aldehyde-containing methylpyrrole monomer of formula a with a solvent, then lowering the temperature of the mixture to below -10°C, then adding titanium tetrachloride to the mixture and reacting for a period of time, then adding zinc powder to the mixture and reacting for a period of time, then raising the temperature of the mixture to above 10°C, continuing the reaction for a period of time, quenching the reaction, and then post-processing the reaction product to obtain an intermediate compound of formula b. The entire McMurray coupling reaction is carried out under a protective gas atmosphere, preferably nitrogen; the solvent is preferably tetrahydrofuran; the temperature below -10°C is preferably -15 to -20°C, more preferably -18°C; the ratio of titanium tetrachloride to the aldehyde-containing methylpyrrole monomer of formula a is preferably (5-8) mL:50 mmol, more preferably 6.5 mL:50 mmol; the reaction time after adding titanium tetrachloride is preferably 20-60 min, more preferably 30 min; the ratio of zinc powder to the aldehyde-containing methylpyrrole monomer of formula a is... The preferred ratio of the aldehyde-containing methylpyrrole monomer is (6-9) g:50 mmol, more preferably 7.8 g:50 mmol; the preferred reaction time after adding the zinc powder is 20-60 min, more preferably 30 min; the preferred temperature above 10°C is 15-35°C, more preferably 25°C (room temperature); the preferred reaction time is 2-6 h, more preferably 4 h; the preferred quenching method is ice-water quenching; the preferred post-treatment method includes sequential extraction, rotary evaporation to remove solvent, and column chromatography.

[0041] In the polymer precursor preparation steps provided by this invention, in step b), the molar ratio of the intermediate compound of formula b to the haloolefin of formula c is preferably 50:(70-130), specifically 50:105; the reaction is preferably carried out in a protective gas atmosphere, preferably nitrogen; the reaction is preferably carried out in an organic solvent, preferably acetonitrile; the reaction temperature is preferably 50-80°C, specifically 60°C; the reaction time is preferably 12-48 h, specifically 24 h; after the reaction, the product is post-treated, and the post-treatment process preferably includes: vacuum distillation, washing, and drying in sequence.

[0042] In the polymer coating provided by the present invention, the photocuring initiator in the coating is preferably one or more of benzoin, benzoin derivatives, benzoyl groups, alkyl phenyl ketones, acyl phosphorus oxides, benzophenones, and thioxanthones, more preferably α-hydroxy ketones, 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide, or 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone.

[0043] In the polymer coating provided by the present invention, the electronic conductor in the coating is preferably one or more of graphite, acetylene black, SuperP, SuperS, graphene, carbon fiber, carbon nanotubes and Ketjen black.

[0044] In the polymer coating provided by this invention, the ionic conductor in the coating is preferably a sodium solid electrolyte with the structural formula Na. 1+x Zr2Si x P 3-x O 12 0≤x≤3, where x can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3; the ionic conductor is a nanoparticle, preferably with a particle size of 300–800 nm, specifically 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, or 800 nm.

[0045] In the polymer coating provided by the present invention, the binder in the coating is preferably one or more of polyacrylic acid, polyvinyl alcohol and sodium carboxymethyl cellulose.

[0046] In the polymer coating provided by this invention, the preferred mass ratio of the polymer precursor, photocuring initiator, electronic conductor, ionic conductor, and binder is 6:(0.2-2):(0.5-2):(0.5-2):(1-3); wherein the specific mass ratio of the polymer precursor to the photocuring initiator can be 6:0.2, 6:0.3, 6:0.4, 6:0.5, 6:0.6, 6:0.7, etc. The mass ratio of the polymer precursor to the electronic conductor can be 6:0.8, 6:0.9, 6:1, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8, 6:1.9, or 6:2; specifically, the mass ratio of the polymer precursor to the electronic conductor can be 6:0.5, 6:0.6, 6:0.7, 6:0.8, 6:0.9, 6:1, 6:1.1, 6:1.2, 6:1.3, or 6:2. The mass ratio of the polymer precursor to the ionic conductor can be 6:0.5, 6:0.6, 6:0.7, 6:0.8, 6:0.9, 6:1, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8, 6:1.9, or 6:2; specifically, the mass ratio of the polymer precursor to the ionic conductor can be 6:0.5, 6:0.6, 6:0.7, 6:0.8, 6:0.9, 6:1, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8, 6:1.9, or 6:2. The mass ratio of the polymer precursor to the binder can be 6:1, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8, 6:1.9, 6:2, 6:2.1, 6:2.2, 6:2.3, 6:2.4, 6:2.5, 6:2.6, 6:2.7, 6:2.8, 6:2.9, or 6:3.

[0047] In the polymer coating provided by the present invention, the coating also contains a solvent, preferably ethanol.

[0048] In the polymer coating provided by the present invention, the solid content of the coating is preferably 10% to 60%, specifically 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%.

[0049] The present invention also provides a method for preparing the polymer coating described above, comprising the following steps:

[0050] A polymer coating is obtained by coating a material containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder, followed by baking and UV curing.

[0051] In the preparation method provided by this invention, the specific information of each component in the coating has been described above and will not be repeated here.

[0052] In the preparation method provided by the present invention, the coating thickness is preferably 1.5 to 3 μm, specifically 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3 μm.

[0053] In the preparation method provided by the present invention, the baking temperature is preferably 80-120℃, specifically 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃; the baking time is preferably 20-60s, specifically 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0054] In the preparation method provided by the present invention, the ultraviolet lamp used for ultraviolet curing is preferably 10-15 cm away from the coating surface, specifically 10 cm, 11 cm, 12 cm, 13 cm, 14 cm or 15 cm; the power of the ultraviolet lamp is preferably 2-3 kW; the ultraviolet curing time is preferably 10-15 s, specifically 10 s, 11 s, 12 s, 13 s, 14 s or 15 s.

[0055] The present invention also provides a negative electrode current collector, comprising a negative electrode current collector substrate and a coating coated on the surface of the negative electrode current collector substrate, wherein the coating is a polymer coating as described in the above technical solution or a polymer coating prepared by the preparation method described in the above technical solution.

[0056] In the negative electrode current collector provided by the present invention, the material of the negative electrode current collector substrate is preferably aluminum; the coating is preferably applied to both sides of the negative electrode current collector substrate.

[0057] The present invention also provides a method for preparing the negative electrode current collector described in the above technical solution, comprising the following steps:

[0058] A coating containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder is applied to the surface of the negative electrode current collector substrate, baked, and then cured under ultraviolet light to form a coating, thus obtaining the negative electrode current collector. Specific information regarding the components of the coating, coating thickness, baking, and UV curing conditions can be found in the previous text and will not be repeated here.

[0059] The present invention also provides a negative electrode-free sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the negative electrode current collector described in the above technical solution.

[0060] In the negative electrode-free sodium-ion battery provided by the present invention, the positive electrode includes a positive electrode current collector and a positive electrode coating coated on the surface of the positive electrode current collector; the positive electrode current collector includes, but is not limited to, aluminum foil; the components of the positive electrode coating include a positive electrode active material, a conductive agent, and a binder. In the present invention, the positive electrode active material is preferably sodium ferric sulfate, nickel-iron-manganese layered oxide, sodium ferric pyrophosphate, and sodium copper-iron-manganese oxide (Na₂O₃). 0.9 Cu 0.22 Fe 0.30 Mn 0.48 At least one of O2); the conductive agent is preferably carbon nanotubes (CNTs); the binder is preferably polyvinylidene fluoride (PVDF); the mass ratio of the positive electrode active material, the conductive agent and the binder is preferably 97.4:(0.5-3):(0.5-3), more preferably 97.4:1.3:1.3.

[0061] In the negative electrode-free sodium-ion battery provided by the present invention, the separator is preferably a polypropylene separator, a polyethylene separator, or a polyethylene separator coated with alumina on one side, and more preferably a polyethylene separator coated with alumina on one side.

[0062] In the negative electrode-free sodium-ion battery provided by the present invention, the electrolyte is preferably a diethylene glycol dimethyl ether solution of sodium hexafluorophosphate; the content of sodium hexafluorophosphate in the electrolyte is preferably 0.5-2 mol / L, specifically 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L or 2 mol / L.

[0063] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects:

[0064] (1) The free bromide anions in the polymer coating on the surface of the negative electrode current collector provided by the present invention are easily combined with sodium ions to induce the formation of NaBr phase in the SEI layer. NaBr has a low sodium ion diffusion barrier in the SEI layer, which can improve the stability of interfacial ion transport.

[0065] (2) The polymer coating on the surface of the negative electrode current collector provided by the present invention has a three-dimensional structure. The sodium solid electrolyte particles that are preferably filled in the gaps serve as fast ion conductors, which can give sodium ions the ability to be transported quickly in the gaps, effectively avoiding sodium precipitation at the interface due to polarization, thereby improving the safety performance of the negative electrode-free sodium ion battery.

[0066] (3) The polymer coating on the surface of the negative electrode current collector provided by the present invention is anchored with cationic groups. The cationic groups can attract more anions in the electrolyte to participate in the negative electrode film formation through charge attraction, thereby increasing the NaF phase in the SEI film. The NaF phase with high Young's modulus is combined with the NaBr phase with low diffusion barrier, which reduces the overpotential for sodium metal nucleation on the negative electrode surface, improves the uniformity of sodium ion deposition on the negative electrode surface, improves the coulombic efficiency of battery charging and discharging, and avoids dendrite growth caused by insufficient sodium ion diffusion rate.

[0067] (4) The negative electrode current collector provided by the present invention has both high electron and ion transport capabilities. When used directly as a negative electrode, it can significantly suppress the growth of sodium dendrites on the negative electrode surface during cycling, thereby improving the cycle performance of the negative electrode-free sodium ion battery.

[0068] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0069] Example 1

[0070] The specific steps for preparing compound (I) are as follows:

[0071] (1) Preparation of intermediate product 1, the chemical reaction formula is shown below:

[0072]

[0073] The preparation process is as follows: Under a nitrogen atmosphere, 100 mL of ultra-dry tetrahydrofuran and 1-methyl-2,5-dihydropyrrole-3-carboxaldehyde (5.55 g, 50.00 mmol) were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. The mixture was then transferred to a cryogenic reactor, the temperature was adjusted to -18 °C, and stirring was started. After the system temperature reached the preset value, titanium tetrachloride (IV) (6.50 mL) was slowly added to the system using a syringe. After the addition was complete, the reaction was stirred for another 30 min. Subsequently, zinc powder (7.50 mL) was added within 30 min. 80g of silica gel powder was added in small, multiple portions. After the addition was complete, the mixture was stirred for 30 minutes, and then the cryogenic reactor was removed. After the reaction system returned to room temperature, the reaction continued for 4 hours, followed by quenching with 100mL of ice water. The mixture was then extracted with dichloromethane (50mL x 3). The organic phases were combined, and half of the solvent was removed by rotary evaporation. Then, 50g of silica gel powder was added, and the remaining solvent was removed by rotary evaporation. The compound was separated by column chromatography using dichloromethane as the eluent. After removing the solvent by rotary evaporation, the target intermediate compound 1 was obtained with a yield of 90.1%. EIMS (m / z): calcd.for C 14 H 20 N4, found 190.20.

[0074] (2) Preparation of compound (I), the chemical reaction formula is shown below:

[0075]

[0076] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 3-bromopropene (12.70 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, the mixture was dried under vacuum to obtain compound (I) with a yield of 94.3%. EIMS (m / z): calcd.for C 18 H 28 N2 2+ ,found 136.32.

[0077] The specific steps for preparing the composite modified current collector sample 1 are as follows:

[0078] The above polymer precursor compound (I) was combined with the photocuring initiator α-hydroxy ketone, the conductive agent acetylene black, and the sodium solid electrolyte (Na3Zr2Si2PO4). 12 Particle size 500nm) and binder polyacrylic acid (PAA) were mixed in a mass ratio of 6:0.5:1:1:1.5, and anhydrous ethanol was added at a solid content of 55%. The mixture was then dispersed evenly using a double planetary mixer to obtain a slurry. The slurry was then coated on both sides of a 13μm aluminum foil with a single-sided coating thickness of 3μm. The foil was baked at 100℃ for 30s to remove the solvent, and then irradiated with a 2kW UV lamp at a distance of 15cm from the coated surface for 15s for photocuring to obtain a composite modified aluminum foil current collector. The prepared composite modified aluminum foil was then stored in a dry room with a dew point of -35℃.

[0079] The specific steps for preparing standard electrolyte samples are as follows:

[0080] Sodium hexafluorophosphate was dissolved in diethylene glycol dimethyl ether in an argon glove box with a water and oxygen content of ≤0.1ppm to obtain a labeled electrolyte sample.

[0081] The specific steps for preparing experimental battery sample 1 are as follows:

[0082] Preparation of the positive electrode: Na 0.9 Cu 0.22 Fe 0.30 Mn 0.48 O2 is the positive electrode material, and Na is the positive electrode material. 0.9 Cu 0.22Fe 0.30 Mn 0.48 O2, carbon nanotubes (CNTs, in a 5% NMP solution) and binder polyvinylidene fluoride (PVDF, in a 5% NMP solution) were weighed and mixed at a mass ratio of 97.4:1.3:1.3 (excluding solvent). After mixing, an appropriate amount of NMP was added to control the theoretical solid content to 65%. The mixture was homogenized using a planetary homogenizer to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a 13μm thick aluminum foil. After drying, rolling, and cutting, a 50mm×70mm positive electrode sheet was obtained.

[0083] Preparation of the diaphragm: A polyethylene diaphragm coated with alumina on one side was used as the isolation membrane and was left to stand in a dry room with a dew point of -35°C for 72 hours before use.

[0084] Preparation of negative electrode sheet: The composite modified aluminum foil current collector prepared above is used directly as the negative electrode, and a negative electrode sheet of 52mm×72mm is obtained by cutting.

[0085] Battery fabrication: The battery was fabricated in a dry room with an ambient dew point ≤ -35℃. The separator was folded in a Z-shape, with the positive and negative electrodes placed on opposite sides. There were 12 layers of positive electrode and 13 layers of negative electrode. The positive electrode, separator, and negative electrode were stacked in sequence and aligned. The positive electrode was coated with an alumina-coated separator to obtain the electrode assembly. The electrode assembly was then fixed with polyimide tape and the tabs were welded. The battery was then placed in an aluminum-plastic film and vacuum-baked at 90℃ for 12 hours. After cooling, the prepared standard electrolyte was injected at an injection coefficient of 4.0 g / Ah. Finally, after vacuum sealing, high-temperature wetting, formation, aging, secondary sealing, and capacity testing, an experimental battery 1 with a capacity of approximately 2.5Ah was obtained.

[0086] Example 2

[0087] The specific steps for preparing compound (II) are as follows:

[0088] (1) Intermediate product 1 was prepared according to the method of Example 1.

[0089] (2) Preparation of compound (II), the chemical reaction formula is shown below:

[0090]

[0091] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 3-bromobutene (14.07 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, after vacuum drying, compound (II) was obtained, with a yield of 93.9%. EIMS (m / z): calcd.for C 20 H 32 N2 2+ ,found 150.22.

[0092] The composite modified aluminum foil 2 sample and the experimental battery 2 were prepared according to the method of Example 1, except that the polymer precursor compound (II) was used in the composite modified aluminum foil 2 sample.

[0093] Example 3

[0094] The specific steps for preparing compound (III) are as follows:

[0095] (1) Intermediate product 1 was prepared according to the method of Example 1.

[0096] (2) Preparation of compound (III), the chemical reaction formula is shown below:

[0097]

[0098] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 3-bromopropyne (12.49 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, after vacuum drying, compound (III) was obtained with a yield of 90.7%. EIMS (m / z): calcd.for C 18 H 24 N2 2+ ,found 134.17.

[0099] The composite modified aluminum foil 3 sample and the experimental battery 3 were prepared according to the method of Example 1, the difference being that the polymer precursor compound (III) was used in the composite modified aluminum foil 3 sample.

[0100] Example 4

[0101] The specific steps for preparing compound (IV) are as follows:

[0102] (1) Intermediate product 1 was prepared according to the method of Example 1.

[0103] (2) Preparation of compound (IV), the chemical reaction formula is shown below:

[0104]

[0105] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 1-bromo-2-one-3-butene (15.64 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, the mixture was dried under vacuum to obtain compound (IV) in a yield of 91.5%. EIMS (m / z): calcd.for C 20 H 28 N2O2 2+ ,found 164.25.

[0106] The composite modified aluminum foil sample 4 and experimental battery 4 were prepared according to the method of Example 1. The difference was that the composite modified aluminum foil sample 4 used a polymer precursor compound (IV), a photocuring initiator of 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO), and a binder of sodium carboxymethyl cellulose (CMC). The polymer precursor compound (IV), the photocuring initiator TPO, the conductive agent SuperP, and the sodium solid electrolyte (Na3Zr2Si2PO4) were used. 12 The particle size is 500nm), the binder CMC mass ratio is 6:0.2:2:2:3, the single-sided coating thickness of the coating slurry is 1.5μm, the baking temperature is 80℃, and the baking time is 60s.

[0107] Example 5

[0108] The specific steps for preparing compound (V) are as follows:

[0109] (1) Intermediate product 1 was prepared according to the method of Example 1.

[0110] (2) Prepare compound (V) using the following chemical reaction formula:

[0111]

[0112] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 1-bromo-2-one-3-heptene (19.95 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, the mixture was dried under vacuum to obtain compound (V) in 92.0% yield. EIMS (m / z): calcd.for C 26 H 40 N2O2 2+ ,found 206.33.

[0113] The composite modified aluminum foil 5 sample and experimental battery 5 were prepared according to the method of Example 1, the difference being that the polymer precursor compound (V) was used in the composite modified aluminum foil 5 sample.

[0114] Example 6

[0115] The specific steps for preparing compound (VI) are as follows:

[0116] (1) Intermediate product 1 was prepared according to the method of Example 1.

[0117] (2) Preparation of compound (VI), the chemical reaction formula is shown below:

[0118]

[0119] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 1-bromo-2-one-5-methyl-3-hexene (19.95 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, the mixture was dried under vacuum to obtain compound (VI) in a yield of 90.4%. EIMS (m / z): calcd.for C 26 H 40 N2O2 2+ ,found206.28.

[0120] The composite modified aluminum foil 6 sample and the experimental battery 6 were prepared according to the method of Example 1, except that the polymer precursor compound (VI) was used in the composite modified aluminum foil 6 sample.

[0121] Example 7

[0122] The specific steps for preparing compound (VII) are as follows:

[0123] (1) Prepare intermediate product 1 according to the method of Example 1

[0124] (2) Prepare compound (VII) using the following chemical reaction:

[0125]

[0126] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 1 (9.51 g, 50.00 mmol) and 150 mL of anhydrous acetonitrile were added to a clean, dry 250 mL three-necked flask equipped with a magnetic rotor. Stirring was started, followed by the slow addition of 1-bromo-2,2-difluoro-5-hexene (20.79 g, 105.00 mmol). After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was completed, acetonitrile was removed by vacuum distillation, and the mixture was washed three times with ethyl acetate (3 × 20 mL). Finally, after vacuum drying, compound (VII) was obtained, with a yield of 89.5%. EIMS (m / z): calcd.for C 24 H 36 F4N2 2+ ,found 214.27.

[0127] The composite modified aluminum foil 7 sample and the experimental battery 7 were prepared according to the method of Example 1, except that the polymer precursor compound (VII) was used in the composite modified aluminum foil 7 sample.

[0128] Example 8

[0129] The composite modified aluminum foil 8 sample and experimental battery 8 were prepared according to the method of Example 1. The difference is that the composite modified aluminum foil 8 sample used a polymer precursor compound (VII), the coating and baking temperature was 120°C, the baking time was 20s, the UV lamp power was 3kW, the distance from the coating surface was 10cm, and the curing time was 10s.

[0130] Example 9

[0131] The composite modified aluminum foil 9 sample and experimental battery 9 were prepared according to the method of Example 1. The difference is that the composite modified aluminum foil 9 sample used a polymerization precursor compound (VII), the photocuring initiator used was 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionylphenyl)benzyl)-2-methyl-1-propanone, and the conductive agent was carbon nanotubes.

[0132] Comparative Example 1

[0133] Experimental battery 10 was prepared according to the method of Example 1, except that the negative electrode current collector of experimental battery 10 sample used commercially available 13μm carbon-coated aluminum foil, without composite modification.

[0134] Comparative Example 2

[0135] Experimental battery 11 was prepared according to the method of Example 1, except that the preparation process of the negative electrode of experimental battery 11 was as follows: the negative electrode material was hard carbon (specific capacity 300mAh g) -1 The following agents were mixed in a mass ratio of 94.5:2:1.5:2: conductive agent SuperP, thickener sodium carboxymethyl cellulose (CMC, 1.5% solids content deionized aqueous solution), and binder styrene-butadiene rubber (SBR, 48% solids content deionized aqueous solution). After mixing, deionized water was added to control the theoretical solids content at 40%. The mixture was homogenized using a planetary homogenizer to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a 17μm thick copper foil. After drying, rolling, and cutting, a 52mm×72mm negative electrode sheet was obtained. The N / P ratio of the positive and negative electrodes was 1.1.

[0136] Performance Evaluation

[0137] The sodium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to long-cycle performance tests and high-temperature cycle tests, respectively, under the following test conditions:

[0138] (1) Battery long-cycle test:

[0139] The prepared sodium-ion battery was placed in a constant temperature chamber at 25℃ and charged at a constant current and voltage of 1C and 4.0V until the cutoff current was 0.05C. Then, it was discharged at a constant current of 1C until the voltage was 2V. The cycle was repeated 1000 times, and the capacity retention rate was recorded. The capacity retention rate (%) of the nth cycle was calculated as (discharge capacity of the nth cycle / discharge capacity of the first cycle) × 100%. The test sample consisted of 5 cells, and the average value of the results was taken.

[0140] (2) High-temperature cycling test:

[0141] The prepared sodium-ion battery was placed in a high-temperature explosion-proof chamber at an ambient temperature of 45℃ and charged under constant current and constant voltage at a current of 1C and a voltage of 4.0V until the cutoff current was 0.05C. Then, it was discharged under constant current at 1C until the voltage was 2V. The cycle was repeated 1000 times, and the capacity retention rate was recorded. The capacity retention rate (%) of the nth cycle was calculated as (discharge capacity of the nth cycle / discharge capacity of the first cycle) × 100%. The test sample consisted of 5 cells, and the average value of the results was taken.

[0142] The test results are shown in Table 1:

[0143] Table 1. Negative electrode current collectors and corresponding battery performance for each embodiment and comparative example.

[0144]

[0145] The performance test results of the sodium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 are shown in Table 1. The room temperature long-cycle performance graphs of Example 9 and Comparative Example 2 are shown in Table 1. Figure 1 As shown, the anode-free sodium-ion battery made with the composite modified aluminum foil of this invention exhibits significantly improved long-cycle performance at both room temperature and high temperature compared to anode-free sodium-ion batteries made with unmodified base aluminum foil. Furthermore, compared to sodium-ion batteries with conventional hard carbon anodes, it also demonstrates significantly enhanced long-cycle performance at both room temperature and high temperature. It is evident that the three-dimensional porous composite modified fast-ion conductor polymer layer proposed in this invention, constructed on the surface of the anode current collector, can simultaneously facilitate the rapid transport of electrons and ions, while inducing the formation of more NaBr components in the SEI layer. This results in a lower diffusion barrier for interfacial charge transfer, thereby improving the stability of interfacial ion transport. Simultaneously, the anchored cationic groups in the polymer coating can attract more anions from the electrolyte to accumulate on the anode surface, thus participating in anode film formation. This increases the NaF component in the SEI film, thereby reducing the overpotential for sodium metal nucleation, improving the uniformity of sodium ion deposition on the anode surface, enhancing the coulombic efficiency of the battery's charge and discharge, and preventing dendrite growth due to insufficient sodium ion diffusion rate. Therefore, when the composite modified current collector provided by this invention is used as the negative electrode of a negative electrode-free sodium-ion battery, the interface stability of the negative electrode-free sodium-ion battery can be significantly improved, and the long-cycle performance at room temperature and high temperature of the negative electrode-free sodium-ion battery can be significantly enhanced.

[0146] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polymer coating, characterized in that, The polymer coating is made of a paint containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder; The polymer precursor is at least one of the compounds of formula (I) to (VII): 。 2. The polymer coating according to claim 1, characterized in that, The polymer precursor is prepared according to the following steps: a) The aldehyde-containing methylpyrrole monomer of formula a is subjected to a McMurray coupling reaction to obtain the intermediate compound of formula b. b) React the intermediate compound of the formula b with the haloolefin of the formula c to obtain the polymer precursor of the formula A; Formula a; Formula b; XR Formula c; Formula A; Wherein, X is Br, and R is one or more of the following: propenyl, butenyl, propynyl, methyl vinyl ketone, 3-hepten-2-one, 5-methyl-3-hexen-2-one, and 5,5-difluoro-1-hexenyl.

3. The polymer coating according to claim 1, characterized in that, The electronic conductor is one or more of graphite, acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotubes, and Ketjen black; the ionic conductor is a sodium solid electrolyte with the structural formula Na. 1+x Zr2Si x P 3-x O 12 , 0≤x≤3.

4. The polymer coating according to claim 1, characterized in that, The photocuring initiator is one or more of benzoin, benzoin derivatives, benzoyl groups, alkyl phenyl ketones, acyl phosphorus oxides, benzophenones, and thioxanthones; the binder is one or more of acrylic binders, polyvinyl alcohol, and sodium carboxymethyl cellulose.

5. The polymer coating according to claim 1, characterized in that, The mass ratio of the polymer precursor, photocuring initiator, electronic conductor, ionic conductor and binder is 6:(0.2~2):(0.5~2):(0.5~2):(1~3).

6. A method for preparing the polymer coating according to any one of claims 1 to 5, characterized in that, Includes the following steps: A polymer coating is obtained by coating a material containing a polymer precursor, a photocurable initiator, an electronic conductor, an ionic conductor, and a binder, followed by baking and UV curing.

7. A negative electrode current collector, characterized in that, The negative electrode current collector includes a negative electrode current collector substrate and a coating coated on the surface of the negative electrode current collector substrate. The coating is a polymer coating as described in any one of claims 1 to 5 or a polymer coating prepared by the preparation method described in claim 6.

8. The negative electrode current collector according to claim 7, characterized in that, The substrate of the negative electrode current collector is made of aluminum.

9. A sodium-ion battery without a negative electrode, characterized in that, The negative electrode-free sodium-ion battery uses the negative electrode current collector as described in claim 7 or 8 as the negative electrode.

Images