Sodium-ion battery negative electrode material for self-repairing coated electrode and preparation method of sodium-ion battery negative electrode material

Abstract

The invention discloses a sodium ion battery negative electrode material for a self-repairing coating electrode and a preparation method thereof, the negative electrode material comprises a self-repairing coating layer and an active substance layer, the self-repairing coating layer is composed of a dynamic covalent polymer and a sodium ion conduction agent, the active material layer includes at least one of hard carbon, soft carbon, or a metal oxide. The self-repairing coating layer realizes more than five times of self-repairing at room temperature through a dynamic covalent network, the repairing efficiency exceeds 90%, crack propagation is effectively inhibited, abnormal growth of an SEI film is reduced, and the cycle life of the battery is greatly prolonged; by means of the optimized proportion of the sodium ion conducting agent and the polymer and the design of a thin layer of 1-5 microns, mechanical protection is guaranteed, meanwhile, efficient conduction of sodium ions is guaranteed, and the capacity retention rate at the 10C multiplying power exceeds 70%. And the interlayer spacing and specific surface area parameters of the hard carbon of the active material layer are optimized, so that the sodium storage capacity and the reaction activity are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, in particular to a self-repairing sodium-ion battery negative electrode material for coating electrodes and a preparation method thereof. BACKGROUND

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage due to abundant resources and low cost. At present, hard carbon, soft carbon or metal oxides are mostly used as negative electrode materials of sodium-ion batteries. However, such materials are prone to cracking due to volume expansion during charge and discharge cycles, which leads to shedding of active substances, continuous breaking and regeneration of SEI films, and significantly reduces the cycle life and safety of the battery. In the prior art, the above problems can be alleviated by adding an elastic binder or a carbon coating layer, but active repair cannot be achieved, and an excessively thick protective layer will hinder the conduction of sodium ions, sacrificing the rate performance of the battery. In addition, in the traditional preparation process, the uniformity and interlayer bonding force of the electrode material are difficult to balance, further limiting the improvement of the comprehensive performance of the sodium-ion battery. SUMMARY

[0003] In order to overcome the deficiencies of the prior art, the application provides a self-repairing sodium-ion battery negative electrode material for coating electrodes and a preparation method thereof, which can effectively solve the problems raised in the background art.

[0004] The technical scheme adopted by the application to solve the technical problems is:

[0005] A self-repairing sodium-ion battery negative electrode material for coating electrodes, the negative electrode material comprising a self-repairing coating layer and an active substance layer, the self-repairing coating layer being composed of a dynamic covalent polymer and a sodium ion conductive agent, and the active substance layer containing at least one of hard carbon, soft carbon or metal oxides.

[0006] The dynamic covalent polymer forms a reversible crosslinked network through Diels-Alder reaction or imine bond, the sodium ion conductive agent is NaPF6 or NaBF4, and the mass ratio of the dynamic covalent polymer to the sodium ion conductive agent is 1:0.1-1:0.5.

[0007] As a further description of the above technical scheme, the thickness of the self-repairing coating layer is 1-5 microns, the thickness of the active substance layer is 50-200 microns, and the self-repairing coating layer completely covers the surface of the active substance layer.

[0008] As a further description of the above technical scheme, the dynamic covalent polymer is a furan-maleimide copolymer or an aldehyde-amine copolymer, the glass transition temperature of the furan-maleimide copolymer is 60-80 DEG C, and the pH response range of the aldehyde-amine copolymer is 4-8.

[0009] As a further description of the above technical solution, the content of hard carbon in the active material layer is 60-90wt%, the interlayer spacing of the hard carbon is 0.34-0.38nm, and the specific surface area is 200-500m 2 / g.

[0010] A preparation method of a sodium ion battery negative electrode material, comprising the following steps:

[0011] Step S1: mixing a dynamic covalent polymer precursor, a sodium ion conductive agent and an organic solvent, ultrasonic dispersion for 30-60 minutes to obtain a self-repairing coating liquid;

[0012] Step S2: mixing an active material, a conductive agent and a binder, ball milling for 2-4 hours to obtain an active material slurry;

[0013] Step S3: coating the active material slurry on a current collector, and drying to obtain an active material layer;

[0014] Step S4: coating the self-repairing coating liquid on the surface of the active material layer, and curing at 60-100℃ for 1-3 hours to form a self-repairing coating layer.

[0015] As a further description of the above technical solution, the dynamic covalent polymer precursor is a furan group terminated polyurethane prepolymer and a bismaleimide, or an aldehyde group terminated polyethylene glycol and an amine group terminated polyacrylic acid, and the molar ratio of the furan group terminated polyurethane prepolymer to the bismaleimide is 2:1, and the molar ratio of the aldehyde group terminated polyethylene glycol to the amine group terminated polyacrylic acid is 1:1.

[0016] As a further description of the above technical solution, the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide, the conductive agent is carbon nanotube or graphene, and the binder is sodium carboxymethyl cellulose or butadiene styrene rubber.

[0017] As a further description of the above technical solution, in the step S3, the coating adopts doctor blade coating or slot extrusion coating, the coating speed is 5-20m / min, the drying temperature is 80-120℃, and the drying time is 1-2 hours.

[0018] As a further description of the above technical solution, in the step S4, the curing is carried out in a nitrogen or argon atmosphere, and the self-repairing coating layer after curing can realize more than 5 times of self-repairing at room temperature, and the repair efficiency is greater than 90%.

[0019] A sodium ion battery, comprising a negative electrode material, a negative electrode shell, a positive electrode material, a positive electrode shell, an electrolyte and a separator, the positive electrode material is a layered oxide or a polyanion compound, the electrolyte is a carbonate solution containing NaPF6, and the separator is a polypropylene or polyethylene microporous membrane.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The self-repairing coated sodium-ion battery negative electrode material and the preparation method thereof have at least one of the following beneficial effects in use:

[0022] The self-repairing coating layer realizes more than 5 times of self-repair at room temperature through a dynamic covalent network, the repair efficiency is more than 90%, crack propagation is effectively inhibited, abnormal growth of the SEI film is reduced, and the cycle life of the battery is greatly improved; the optimized ratio of the sodium ion conductive agent and the polymer and the 1-5 mu thin layer design ensure efficient sodium ion conduction while ensuring mechanical protection, the capacity retention rate is more than 70% at 10C rate. The interlayer spacing and specific surface area parameters of the active material layer of hard carbon are optimized to improve the sodium storage capacity and reaction activity. The preparation process is compatible with existing lithium battery equipment, the raw material cost is low, and the process can be scaled up to reduce the whole life cycle cost; and the sodium dendrite growth is inhibited, the battery safety is enhanced, and the comprehensive performance is better than that of the traditional negative electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 The figure is a negative electrode material structure schematic diagram of the self-repairing coated sodium-ion battery negative electrode material and the preparation method thereof.

[0024] Fig. 2 The figure is a preparation method process flow diagram of the self-repairing coated sodium-ion battery negative electrode material and the preparation method thereof.

[0025] Fig. 3 The figure is a sodium-ion battery structure diagram of the self-repairing coated sodium-ion battery negative electrode material and the preparation method thereof.

[0026] Figure label:

[0027] 1, self-repairing coating layer; 2, active material layer; 3, current collector; 4, positive electrode shell; 5, positive electrode material; 6, separator; 7, negative electrode shell; 8, negative electrode material; 9, electrolyte. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] As Figs. 1-3As shown, the present application provides a self-repairing coated sodium-ion battery negative electrode material 8, which comprises a self-repairing coating layer 1 and an active material layer 2, the self-repairing coating layer 1 is composed of a dynamic covalent polymer and a sodium ion conductive agent, and the active material layer 2 contains at least one of hard carbon, soft carbon or metal oxide.

[0030] The dynamic covalent polymer (such as furan-maleimide copolymer or aldehyde-amine copolymer) in this embodiment forms a reversible cross-linked network through Diels-Alder reaction or imine bond. During the battery cycle, when the electrode material cracks due to volume change, a slight change in temperature (such as 60-80℃, close to the glass transition temperature) or pH value (4-8) will trigger the breakage and recombination of reversible bonds, making the polymer network flow and fill the cracks, achieving "self-repairing".

[0031] The dynamic covalent polymer forms a reversible cross-linked network through Diels-Alder reaction or imine bond, the sodium ion conductive agent is NaPF6 or NaBF4, and the mass ratio of the dynamic covalent polymer to the sodium ion conductive agent is 1:0.1-1:0.5.

[0032] NaPF6 or NaBF4 in the self-repairing coating layer 1 acts as a conductive agent, forming ion channels in the polymer network to ensure efficient transmission of sodium ions between the active material layer 2 and the electrolyte 9. The design of mass ratio 1:0.1-1:0.5 balances the mechanical strength and ion conductivity.

[0033] Hard carbon has an interlayer spacing of 0.34-0.38 nm (larger than the 0.335 nm of graphite), which is suitable for the intercalation / deintercalation of sodium ions; a high specific surface area of 200-500 m 2 / g provides more reaction sites to improve the charging and discharging efficiency.

[0034] When the active material layer 2 contains multiple materials (such as hard carbon and metal oxide composite), the synergistic effect of different materials can alleviate the volume expansion (such as the buffering effect of metal oxide), and improve the cycle stability.

[0035] Further, the thickness of the self-repairing coating layer 1 is 1-5 μm, the thickness of the active material layer 2 is 50-200 μm, and the self-repairing coating layer 1 completely covers the surface of the active material layer 2. The thickness of the self-repairing coating layer 1 of 1-5 μm has little effect on the diffusion resistance of sodium ions, while the active material layer 2 of 50-200 μm provides sufficient sodium storage space to ensure the energy density of the battery. The sodium ion conductive agent forms a continuous channel in the self-repairing layer,

[0036] Further, the dynamic covalent polymer is a furan-maleimide copolymer or an aldehyde-amine copolymer, the glass transition temperature of the furan-maleimide copolymer is 60-80℃, and the pH response range of the aldehyde-amine copolymer is 4-8. The glass transition temperature (60-80℃) of the furan-maleimide copolymer is close to the normal working temperature of the battery, which ensures the sensitivity of the self-repairing reaction; the pH response of the aldehyde-amine copolymer matches the chemical environment of the carbonate electrolyte 9.

[0037] Further, the content of the hard carbon in the active material layer 2 is 60-90wt%, the interlayer spacing of the hard carbon is 0.34-0.38nm, and the specific surface area is 200-500m 2 / g. Combined with the high specific surface area of the hard carbon, the battery still maintains good rate performance (such as capacity retention rate > 70% at 10C charging and discharging) at high current density.

[0038] A preparation method of a sodium ion battery negative electrode material 8, comprising the following steps:

[0039] Step S1: mixing a dynamic covalent polymer precursor, a sodium ion conductive agent and an organic solvent, ultrasonic dispersion for 30-60 minutes to obtain a self-repairing coating liquid;

[0040] Step S2: mixing an active material, a conductive agent and a binder, ball milling for 2-4 hours to obtain an active material slurry;

[0041] Step S3: coating the active material slurry on the current collector 3, and drying to obtain an active material layer 2;

[0042] Step S4: coating the self-repairing coating liquid on the surface of the active material layer 2, and curing at 60-100℃ for 1-3 hours to form a self-repairing coating layer 1.

[0043] Using doctor blade coating or slot extrusion coating (speed 5-20m / min), combined with 80-120℃ drying and 60-100℃ curing, it is compatible with existing lithium battery production equipment and easy to scale up production. The prices of raw materials such as hard carbon and NaPF6 are lower than those of lithium electrode materials (such as graphite and LiPF6), and the self-repairing layer can reduce the frequency of battery failure and reduce the total life cycle cost.

[0044] The self-repairing coating layer 1 can realize more than 5 times of self-repairing at room temperature, with a repair efficiency of more than 90%, effectively inhibiting crack propagation, reducing direct contact between the active material and the electrolyte 9, and reducing the continuous growth of the SEI film and the increase of the battery internal resistance.

[0045] If the self-repairing layer is too thick (>5 μm), the ion diffusion resistance will increase, and if it is too thin (<1 μm), the active material layer 2 cannot be effectively protected; the thickness of the active material layer 2 needs to be balanced in the range of 50-200 μm to balance the energy density and ion transmission efficiency. If the self-repairing layer has defects or is not completely covered, the active material is exposed to the electrolyte 9, which will cause the SEI film to be unstable and shorten the battery life.

[0046] Further, the dynamic covalent polymer precursor is furan-terminated polyurethane prepolymer and bismaleimide, or aldehyde-terminated polyethylene glycol and amine-terminated polyacrylic acid, and the molar ratio of the furan-terminated polyurethane prepolymer to the bismaleimide is 2:1, and the molar ratio of the aldehyde-terminated polyethylene glycol to the amine-terminated polyacrylic acid is 1:1.

[0047] Further, the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide, the conductive agent is carbon nanotube or graphene, and the binder is sodium carboxymethyl cellulose or butadiene-styrene rubber.

[0048] Further, the coating in step S3 adopts knife coating or slot extrusion coating, the coating speed is 5-20 m / min, the drying temperature is 80-120℃, and the drying time is 1-2 hours.

[0049] Further, the curing in step S4 is carried out in a nitrogen or argon atmosphere, and the self-repairing coating layer 1 after curing can realize more than 5 times of self-repair at room temperature, and the repair efficiency is greater than 90%.

[0050] A sodium ion battery includes a negative electrode material 8, a negative electrode shell 7, a positive electrode material 5, a positive electrode shell 4, an electrolyte 9, and a separator 6, the positive electrode material 5 is a layered oxide or a polyanion compound, the electrolyte 9 is a carbonate solution containing NaPF6, and the separator 6 is a polypropylene or polyethylene microporous membrane.

[0051] Sodium ions are released from the positive electrode material 5 (layered oxide or polyanion compound), pass through the electrolyte 9, the separator 6, and the self-repairing coating layer 1, and are embedded into the negative electrode active material layer 2 (such as hard carbon); electrons flow to the negative electrode current collector 3 through the external circuit. Sodium ions are de-embedded from the negative electrode active material layer 2, pass through the self-repairing coating layer 1 and the electrolyte 9, and return to the positive electrode; electrons flow to the positive electrode through the external circuit, forming an electric current.

[0052] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims with respect to the figures of the patent document.

Claims

1. A sodium-ion battery anode material for self-healing coated electrodes, characterized in that: The negative electrode material includes a self-healing coating layer and an active material layer. The self-healing coating layer is composed of a dynamic covalent polymer and a sodium ion conductor. The active material layer contains at least one of hard carbon, soft carbon, or metal oxide. The dynamic covalent polymer forms a reversible crosslinked network through Diels-Alder reaction or imine bonds, the sodium ion conductor is NaPF6 or NaBF4, and the mass ratio of the dynamic covalent polymer to the sodium ion conductor is 1:0.1-1:0.

5.

2. The sodium-ion battery anode material for self-healing coated electrodes according to claim 1, characterized in that: The thickness of the self-healing coating layer is 1-5 μm, the thickness of the active material layer is 50-200 μm, and the self-healing coating layer completely covers the surface of the active material layer.

3. The sodium-ion battery anode material for self-healing coated electrodes according to claim 1, characterized in that: The dynamic covalent polymer is a furanyl-maleimide copolymer or an aldehyde-amine copolymer, wherein the glass transition temperature of the furanyl-maleimide copolymer is 60-80℃ and the pH response range of the aldehyde-amine copolymer is 4-8.

4. The sodium-ion battery negative electrode material for self-healing coated electrodes according to claim 1, characterized in that: The active material layer contains 60-90 wt% hard carbon, the interlayer spacing of the hard carbon is 0.34-0.38 nm, and the specific surface area is 200-500 m². 2 / g.

5. A method for preparing a sodium-ion battery negative electrode material as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Mix the dynamic covalent polymer precursor, sodium ion conductor and organic solvent, and ultrasonically disperse for 30-60 minutes to obtain the self-healing coating solution; Step S2: Mix the active material, conductive agent and binder, and ball mill for 2-4 hours to obtain an active material slurry; Step S3: The active material slurry is coated onto the current collector and dried to obtain an active material layer; Step S4: Apply the self-healing coating liquid to the surface of the active material layer and cure it at 60-100℃ for 1-3 hours to form a self-healing coating layer.

6. The method for preparing the sodium-ion battery negative electrode material according to claim 5, characterized in that: The dynamic covalent polymer precursor is a furan-terminated polyurethane prepolymer and bismaleimide, or an aldehyde-terminated polyethylene glycol and an amino-terminated polyacrylic acid, wherein the molar ratio of the furan-terminated polyurethane prepolymer to the bismaleimide is 2:1, and the molar ratio of the aldehyde-terminated polyethylene glycol to the amino-terminated polyacrylic acid is 1:

1.

7. The method for preparing the sodium-ion battery negative electrode material according to claim 5, characterized in that: The organic solvent is N,N-dimethylformamide or dimethyl sulfoxide, the conductive agent is carbon nanotubes or graphene, and the binder is sodium carboxymethyl cellulose or styrene-butadiene rubber.

8. The method for preparing the sodium-ion battery negative electrode material according to claim 5, characterized in that: In step S3, the coating is applied by blade coating or slot extrusion coating, with a coating speed of 5-20 m / min, a drying temperature of 80-120℃, and a drying time of 1-2 hours.

9. The method for preparing the sodium-ion battery negative electrode material according to claim 5, characterized in that: In step S4, curing is carried out under a nitrogen or argon atmosphere. The cured self-healing coating can achieve more than 5 self-healing cycles at room temperature, with a repair efficiency of more than 90%.

10. A sodium-ion battery, characterized in that: The invention includes the negative electrode material, negative electrode shell, positive electrode material, positive electrode shell, electrolyte, and separator as described in any one of claims 1-4, wherein the positive electrode material is a layered oxide or a polyanionic compound, the electrolyte is a carbonate solution containing NaPF6, and the separator is a polypropylene or polyethylene microporous membrane.

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