CN115528226A - Layered positive electrode material of sodium-ion battery and application - Google Patents
Layered positive electrode material of sodium-ion battery and application Download PDFInfo
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention discloses a layered positive electrode material of a sodium ion battery and application thereof 2 CO 3 、NaHCO 3 At least one of (a). The alkaline coating layer can effectively enhance the air stability of the cathode material, prevent the performance deterioration caused by the loss of sodium in a body phase, and improve the storage time of the cathode material in an air environment. In addition, the oxalic acid solution is sprayed in the atmosphere rotary furnace to react with the alkaline coating layer, so that the alkaline coating layer can be converted into sodium oxalate, the overall alkalinity of the anode material is reduced, the material has good processing performance, the sodium oxalate can be decomposed in the formation stage of the battery, sodium ions are provided to participate in the generation of an SEI (solid electrolyte interface) film of the cathode, the consumption of the sodium ions in a body phase is reduced, the gram volume exertion of the anode material is improved, and the energy density of the battery is improved.
Description
Technical Field
The invention relates to the technical field of sodium-ion batteries, in particular to a layered positive electrode material of a sodium-ion battery and application thereof.
Background
At present, the large-scale application of the lithium ion battery on the electric automobile can quickly consume the scarce lithium resource, and can seriously hinder the long-term development of the lithium ion battery. Sodium element is abundant in earth crust, low in price and high in energy density, and sodium element and lithium element belong to the same main group element, so that the sodium element and the lithium element have similar physical and chemical properties and working principles. In the long run, sodium ion batteries are expected to be a beneficial complement to lithium ion batteries. Compared with other anode materials, the layered anode material of the sodium-ion battery has the advantages of higher specific capacity and energy density, and is one of the most promising options for being used as the industrialized anode material of the sodium-ion battery.
During the sintering process of the layered positive electrode material of the sodium-ion battery by adopting a high-temperature solid-phase method, after sodium salt and metal oxide form a layered structure through the fracture and recombination of chemical bonds, part of the sodium salt does not enter the bulk structure of the material, but remains on the surface of the material to form an alkaline substance, so that the alkalinity of the material is too strong; in addition, patent CN 111370664A and Nano lett.2019,19 (1), 182-188 all indicate that the air stability of the layered positive electrode material of the sodium ion battery is poor, when the material is stored in an air environment containing water and carbon dioxide, sodium in a bulk phase is easy to be removed to form alkaline substances such as sodium carbonate and sodium hydroxide on the surface of particles, and the capacity of the positive electrode material itself is reduced, which makes such positive electrode material need to be stored in a vacuum or protective atmosphere environment, and the storage cost is high. In addition, in the process of preparing the positive electrode slurry, alkaline substances on the surface of the main material attack the PVDF binder containing fluorine elements in the positive electrode slurry, HF is removed, unstable double bonds are generated, the double bonds are further crosslinked with active points on the surface of positive electrode active material particles, gel is finally formed, the coating consistency is influenced, the slurry is even scrapped and cannot be coated, and in addition, the PVDF is damaged, so that the bonding strength of a positive electrode plate is greatly reduced, and the performance of a battery cell is deteriorated.
At present, the problem of high-alkalinity sodium ion battery anode material slurry gelation is mainly solved by reducing the content of residual alkali in a main material. For example, the alkalinity of the main material is reduced by adopting water washing, alcohol washing or acid washing methods (for example, CN 10880706980 a. In addition, although the residual alkali on the surface of the material can be washed away by a method of water washing, alcohol washing or acid washing, the sodium loss of the part removed from the bulk phase is inevitably caused, the capacity loss of the cathode material is caused, and the consistency of the battery capacity is influenced.
Therefore, for the layered oxide cathode material of the sodium-ion battery, it is of great significance to develop a method which can improve the air stability of the layered cathode material and can improve the energy density of the battery by supplementing sodium.
Disclosure of Invention
In view of the problems in the related art, the present invention aims to provide a layered cathode material of a sodium-ion battery and an application thereof, which can improve the air stability of the layered cathode material and can improve the energy density of the battery by sodium supplement.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect of the present invention, there is provided a layered positive electrode material for a sodium-ion battery, which can be stably stored in air for a long period of time and prevents loss of bulk sodium.
The invention relates to a layered positive electrode material of a sodium ion battery, which comprises a layered positive electrodeThe anode active material comprises an anode active material and an alkaline coating layer coated on the outer surface of the layered anode active material, wherein the alkaline coating layer is NaOH, naO or Na 2 CO 3 、NaHCO 3 At least one of (1).
Preferably, the layered positive electrode active material is an O3, P2 or P3 phase layered positive electrode active material, and has a chemical formula of Na x MO y (ii) a Wherein M is one or more elements of Ni, cu, mn, fe, zn, co, al, cr, zr and Mo; x, y satisfy charge balance; x is more than 0.5 and less than 1.5; y is more than or equal to 2; the elements in the chemical formula satisfy charge balance.
Preferably, the thickness of the alkaline coating layer is 10-100nm.
Preferably, the pH of the layered positive electrode material is 12.5.
In a second aspect according to the present invention, a method is provided for removing and converting an alkaline coating layer of a layered positive electrode material of a sodium-ion battery into a sodium supplement additive.
The invention relates to a method for removing and converting an alkaline coating of a layered positive electrode material of a sodium-ion battery into a sodium supplement additive, which comprises the following steps:
s1, placing a to-be-treated layered positive electrode material with an alkaline coating layer into an atmosphere rotary furnace, heating the material in the furnace to 60 ℃ at a heating rate of 2 ℃/min, and preserving heat;
s2, introducing an oxalic acid solution with the concentration of 20mM-100mM into the furnace at a constant speed for spraying, reacting for 2-6 h at a constant flow rate, removing the oxalic acid spraying device after the reaction is finished, and introducing nitrogen at a constant speed;
and S3, heating the atmosphere rotary furnace to 150 ℃ at the heating rate of 2 ℃/min, preserving the heat for 1-2 h, removing water and redundant oxalic acid in the furnace until the effluent gas is not acidic, finishing the reaction, and cooling to room temperature to obtain the treated layered positive electrode material.
Preferably, in step S2, the constant flow rate is 2mL/min to 10mL/min.
Preferably, in step S2, the mass ratio of the oxalic acid in the oxalic acid solution to the layered positive electrode material is 0.005 to 0.05.
Preferably, in step S3, the pH of the treated layered positive electrode material is 12.
In a third aspect of the present invention, a sodium ion battery positive electrode material containing a sodium supplement additive is provided.
The invention relates to a sodium ion battery anode material, which is obtained by removing an alkaline coating layer of the sodium ion battery layered anode material and converting the alkaline coating layer into a sodium supplement additive.
In a fourth aspect according to the present invention, there is provided a high energy density sodium ion battery comprising a positive electrode material comprising a sodium supplement additive.
The invention relates to a sodium-ion battery, which comprises the positive electrode material of the sodium-ion battery.
The technical scheme provided by the invention can achieve the following beneficial effects:
1) The invention coats amorphous and compact NaOH, naO and Na on the surface of the layered positive electrode material of the sodium-ion battery 2 CO 3 Or NaHCO 3 The alkaline coating layer can be used as a physical barrier to isolate air, effectively enhances the air stability of the cathode material, prevents the performance deterioration caused by the loss of sodium in a body phase, can prolong the storage time of the cathode material in a common air environment, and does not need to be stored under special conditions.
2) The invention can convert the alkaline coating layer into sodium oxalate (Na) by spraying oxalic acid solution in an atmosphere rotary furnace to react with the alkaline coating layer on the surface of the anode material of the layered oxide of the sodium ion battery 2 C 2 O 4 ) The overall alkalinity of the positive electrode material is reduced, the good processing performance of the material is ensured, and the process is simple; and the generated sodium oxalate is remained in the anode material, when the formation voltage is higher than the decomposition potential of the sodium oxalate, the sodium oxalate can be decomposed in the battery formation stage and provide sodium ions to participate in the generation of the SEI film of the cathode, so that the consumption of the sodium ions in the body phase is reduced, the gram capacity exertion of the anode material is improved, and the energy density of the battery is improved.
3) The oxalic acid spraying method provided by the invention is simple, low in energy consumption and high in treatment efficiency, and the anode material does not need to be soaked in water/acid solution for a long time, so that the phase structure of the anode material is not affected, and the alkaline coating layer can be effectively and completely converted into a sodium supplement additive; and the production process of the method is clean and environment-friendly, the sprayed redundant oxalic acid solution can be sublimated and recovered, no waste liquid is generated, and the adverse effects of oxalic acid remaining in the anode material on the subsequent processing and the battery performance can be avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic view of the method for removing and converting the alkaline coating layer of the layered cathode material into the sodium supplement additive according to the present invention.
Fig. 2 is an XRD spectrum of the layered cathode material comprising the alkaline coating layer of the present invention.
Fig. 3 is an XRD spectrum of the layered cathode material with the alkaline coating layer removed according to the present invention.
Fig. 4 is an SEM image of the layered positive electrode material including the alkaline coating layer according to the present invention.
Fig. 5 is a second SEM image of the layered cathode material containing an alkaline coating layer according to the present invention.
Fig. 6 is an SEM image of the layered cathode material with the alkaline coating layer removed according to the present invention.
Fig. 7 is a second SEM image of the layered cathode material with the alkaline coating layer removed according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In a first aspect, the invention provides a layered positive electrode material of a sodium-ion battery, which comprises a layered positive electrode active substance and a layered positive electrode active substance coated on the layered positive electrode active substanceAn alkaline coating layer on the outer surface, wherein the alkaline coating layer is amorphous and compact NaOH, naO and Na 2 CO 3 、NaHCO 3 At least one of (1).
Wherein, the alkaline coating layer can not change the surface appearance and the crystal structure of the layered anode material, and can be used as a physical barrier to effectively prevent H in the air 2 O and CO 2 The corrosion to the surface of the layered anode material improves the air stability of the layered anode material and improves the storage capacity of the layered anode material in the air environment.
Wherein, the alkaline coating method can use a solid phase coating method, a liquid phase coating method or a gas phase coating method; the solid phase coating method comprises a mechanochemical method, a solid phase reaction method, a high energy method, a polymer coating method and a microcapsule modification method; the liquid phase coating method comprises a hydrothermal method, a sol-gel method, a precipitation method, a non-uniform nucleation method, a chemical plating method, a micro-emulsion method and a heterogeneous flocculation method; vapor phase coating methods include physical vapor deposition and chemical vapor deposition.
The method is characterized in that an alkaline coating layer is arranged on the surface of the layered positive active material, preferably, a solid-phase reaction method is adopted, and the method specifically comprises the following steps:
1) Mixing sodium salt and a salt solution of metal salt to obtain a precursor mixed solution, wherein the sodium salt and the metal salt are added according to the atom molar ratio of the layered positive electrode active substance, and then adding excessive sodium salt and uniformly mixing;
2) Reacting the precursor mixed solution for 5-20h at the pressure of 5-50MPa and the temperature of 120-200 ℃ to obtain a product;
3) And calcining the resultant to obtain the layered positive electrode material of the sodium-ion battery.
Wherein the metal salt is at least one of sulfate, chloride, nitrate and carbonate of metal elements of Ni, cu, mn, fe, zn, co, al, cr, zr and Mo.
Wherein, the added excessive sodium salt can not enter into the positive active material plastid phase and forms a coating layer outside the positive active material particles.
In one embodiment of the present invention, the layered positive active material is O3, P2 or P3A phase layered positive electrode active material having a chemical formula of Na x MO y (ii) a Wherein M is one or more elements of Ni, cu, mn, fe, zn, co, al, cr, zr and Mo; x and y satisfy charge balance; x is more than 0.5 and less than 1.5; y is more than or equal to 2; the elements in the chemical formula satisfy charge balance.
In an embodiment according to the present invention, the thickness of the alkaline coating layer is 10-100nm, preferably 40-80 nm, and more preferably 60nm.
In one embodiment according to the present invention, the pH of the layered cathode material is 12.5.
In a second aspect according to the present invention, a method is provided for removing and converting an alkaline coating layer of a layered positive electrode material of a sodium-ion battery into a sodium supplement additive.
The invention relates to a method for removing and converting an alkaline coating of a layered cathode material of a sodium-ion battery into a sodium supplement additive, which comprises the following steps of:
s1, placing a to-be-treated layered positive electrode material with an alkaline coating layer into an atmosphere rotary furnace, heating the material in the furnace to 60 ℃ at a heating rate of 2 ℃/min, and preserving heat;
s2, introducing an oxalic acid solution with the concentration of 20mM-100mM into the furnace at a constant speed for spraying, reacting for 2-6 h at a constant flow rate, removing the oxalic acid spraying device after the reaction is finished, and introducing nitrogen at a constant speed; wherein, the reaction time can be determined according to the content of alkaline coating substances in the layered anode material and the corresponding concentration of oxalic acid solution spray;
and S3, heating the atmosphere rotary furnace to 150 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 1-2 h, removing water and redundant oxalic acid in the furnace until the effluent gas is not acidic, finishing the reaction, and cooling to room temperature to obtain the well-treated layered anode material.
The weak acidic oxalic acid solution spray and an alkaline coating layer on the surface of the layered positive electrode material are subjected to acid-base neutralization reaction to remove alkaline substances on the particle surface of the layered positive electrode material, the reaction product is sodium oxalate, and after the reaction is finished, the residual oxalic acid in the furnace is sublimated and volatilized (the oxalic acid is quickly sublimated at 125 ℃ and is greatly sublimated at 150 ℃), and then enters an oxalic acid water solution collecting bottle along with nitrogen flow.
The method comprises the steps of reacting alkaline substances coated on the surface of a layered positive electrode material under the action of oxalic acid to convert the alkaline substances into sodium oxalate; sodium oxalate remains in the anode material, can be decomposed in the battery formation stage and provides sodium ions to participate in the generation of the cathode SEI film, so that the consumption of the sodium ions in the bulk phase is reduced, the gram capacity exertion of the anode material is improved, and the energy density of the battery is improved.
In an embodiment according to the present invention, in step S2, the constant flow rate is 2mL/min to 10mL/min, preferably 5 to 8mL/min.
In one embodiment according to the present invention, in the step S2, the mass ratio of the oxalic acid in the oxalic acid solution to the layered positive electrode material is 0.005 to 0.05, preferably 0.01 to 0.02.
In an embodiment according to the present invention, in step S3, the pH of the treated layered cathode material is 12.
In a third aspect of the present invention, a sodium-ion battery positive electrode material containing a sodium supplement additive is provided.
The invention relates to a sodium ion battery anode material, which is obtained by removing an alkaline coating layer of the sodium ion battery layered anode material and converting the alkaline coating layer into a sodium supplement additive.
In a fourth aspect according to the present invention, there is provided a high energy density sodium ion battery comprising a positive electrode material comprising a sodium supplement additive.
The invention relates to a sodium-ion battery, which comprises the sodium-ion battery cathode material. According to the invention, the alkaline coating layer is converted into sodium oxalate serving as a sodium supplement additive, and the sodium oxalate can be decomposed in the battery formation stage and provide sodium ions to participate in the generation of the negative electrode SEI film, so that the consumption of the sodium ions in the bulk phase is reduced, the gram capacity exertion of the positive electrode material is improved, and the energy density of the battery is improved.
As an example, a sodium ion battery includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte. Stacking the positive pole piece, the isolating film and the negative pole piece in sequence, so that the isolating film is positioned between the positive pole piece and the negative pole piece to play an isolating role, and obtaining the battery cell, or obtaining the battery cell after winding; and (4) placing the battery core in a packaging shell, injecting electrolyte and sealing to obtain the sodium ion battery.
The positive pole piece comprises a positive current collector and a positive active substance layer stacked on the positive current collector, and the positive active substance layer comprises the positive material. For example, the positive electrode current collector includes two opposite surfaces, and the positive electrode active material layer is stacked on either or both of the two surfaces of the positive electrode current collector.
The positive electrode active material layer may further include a binder and/or a conductive agent. The kind of the binder and the conductive agent is not particularly limited, and those skilled in the art can select them according to actual needs. As an example, the binder for the positive electrode sheet may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin (water-based acrylic resin), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA); the conductive agent may be one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers.
The positive electrode current collector can be made of metal foil, carbon-coated metal foil or porous metal plate, and preferably is made of aluminum foil.
The positive electrode sheet can be prepared according to a conventional method in the art. The positive electrode material, and optionally a conductive agent and a binder are generally dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector and subjected to drying, rolling, and the like to obtain a positive electrode sheet.
The negative electrode sheet may be a metal sodium sheet, and may include a negative electrode current collector and a negative electrode active material layer stacked on the negative electrode current collector. For example, the negative electrode current collector includes two opposite surfaces, and the negative electrode active material layer is stacked on either or both of the two surfaces of the negative electrode current collector.
The anode active material layer generally includes an anode active material and optionally a conductive agent, a binder, and a thickener.
As an example, the negative active material may be one or more of natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, and soft carbon, preferably hard carbon.
The conductive agent may be one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers.
The binder may be one or more of Styrene Butadiene Rubber (SBR), water-based acrylic resin (water-based acrylic resin), and carboxymethyl cellulose (CMC), and the thickener may be carboxymethyl cellulose (CMC).
However, the present invention is not limited to these materials, and other materials that can be used as a negative electrode active material, a conductive agent, a binder, and a thickener for a sodium ion battery can be used.
The negative electrode current collector may be made of metal foil, carbon-coated metal foil, or porous metal plate, and preferably is made of aluminum foil.
The above negative electrode sheet may be prepared according to a conventional method in the art. Generally, a negative electrode active material and optional conductive agents, binders and thickeners are dispersed in a solvent, wherein the solvent can be deionized water, so as to form uniform negative electrode slurry, the negative electrode slurry is coated on a negative electrode current collector, and the negative electrode plate is obtained through the procedures of drying, cold pressing and the like.
The sodium ion battery provided by the invention has no particular limitation on the separation membrane, and can be any known separation membrane with a porous structure and electrochemical stability and chemical stability, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
The electrolyte of the sodium ion battery provided by the invention can comprise an organic solvent and an electrolyte sodium salt. As an example, the organic solvent may be one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC); the sodium salt of the electrolyte may be NaPF 6 、NaClO 4 、NaBCl 4 、NaSO 3 CF 3 And Na (CH) 3 )C 6 H 4 SO 3 One or more of (a).
The present disclosure is more particularly described in the following examples that are intended as illustrations only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Furthermore, all reagents used in the examples are commercially available or synthesized according to a conventional method, and can be used as they are without further treatment, and the instruments used in the examples are commercially available.
Examples
Preparation of layered positive electrode material containing alkaline coating layer：
1) Mixing sodium carbonate (Na) 2 CO 3 ) Copper sulfate (CuSO) 4 ) Iron chloride (FeCl) 3 ) And manganese carbonate (MnCO) 3 ) According to the mol ratio of Na 2 CO 3 :CuSO 4 :FeCl 3 :MnCO 3 0.22, 0.48, and an excess of Na was added 2 CO 3 Uniformly mixing to obtain precursor mixed liquor;
2) Reacting the precursor mixed solution for 10 hours at the pressure of 20MPa and the temperature of 180 ℃ to obtain a product;
3) And calcining the resultant at 800 ℃ for 8 hours to obtain the layered positive electrode material containing the alkaline coating layer.
Wherein, the XRD pattern of the prepared laminar anode material is shown in figure 2; the SEM spectra of the obtained layered positive electrode material are shown in fig. 4 to 5, and it can be observed that the surface of the layered positive electrode material has a layer of obvious coating layer.
The pH value of the prepared layered positive electrode material is 12.5, the layered positive electrode material is still 12.5 after being exposed in the air for 15 days, which shows that the coating layer effectively isolates the air, prevents the layered positive electrode material from reacting with water and carbon dioxide in the air, and effectively improves the storage time of the layered positive electrode material in the air without special measures for protection.
Removal of alkaline coating and positive electrode material containing sodium supplement additivePreparation of：
S1, referring to figure 1, 500g of sodium ion battery layered positive electrode material Na with sodium carbonate coating layer to be treated 0.9 Cu 0.22 Fe 0.30 Mn 0.48 O 2 (pH = 12.5) is placed in the position of an atmosphere rotary furnace, the atmosphere rotary furnace rotates at a constant speed, and the temperature is raised to 60 ℃ at the temperature raising rate of 2 ℃/min;
s2, introducing an oxalic acid solution with the concentration of 50mM into the furnace at a constant speed at 60 ℃ for spraying, wherein the flow rate is 8mL/min, the reaction time is 2 hours, removing an oxalic acid spraying device after the reaction is finished, and introducing nitrogen at a constant speed;
and S3, heating the atmosphere rotary furnace to 150 ℃ at the heating rate of 2 ℃/min, preserving the temperature, removing water in the furnace and removing redundant oxalic acid until effluent gas is not acidic, finishing the reaction, and cooling to room temperature to obtain the processed laminar anode material.
The XRD pattern of the treated layered anode material is shown in figure 3, the crystal structure of the anode material is not changed after oxalic acid spraying treatment, and the XRD pattern shows that the reaction of removing the surface alkaline coating layer by oxalic acid spraying in an atmosphere rotary furnace can not damage the bulk phase of the anode material by controlling the concentration, flow rate and reaction time of oxalic acid spraying, and in addition, the XRD diffraction peak of sodium oxalate is added in the pattern, which shows that the sodium carbonate coated on the surface is converted into sodium oxalate through reaction; the obtained SEM atlas of the anode material is shown in FIGS. 6-7, and observation shows that the surface of the anode material becomes smooth after oxalic acid spraying treatment, the coating layer on the surface is removed, and the bulk phase of the anode material has no any damaged trace; and the pH of the positive electrode material was lowered to 12.0.
Preparation of sodium ion battery
The processed layered positive electrode material is used as a positive electrode material, the conductive agent is acetylene black (SP), graphene, carbon quantum dots and Carbon Nano Tubes (CNT), the adhesive is polyvinylidene fluoride (PVDF), and the weight ratio of the positive electrode material to the conductive agent is SP: CNT: graphene: carbon quantum dots: PVDF =95, 0.5; the specific operation is as follows: adding PVDF; adding conductive agent, stirring at high speed of 1500rpm for 30-60min to disperse uniformly as much as possible; adding the anode material for 2-3 times, and stirring at high speed of 1500rpm for 60-120min until the slurry is uniformly dispersed; reducing the rotating speed to 500rpm, vacuumizing for about 30-60min, and removing bubbles in the slurry; adjusting the viscosity of the slurry to be 6000-10000 mPa.s; filtering the discharged slurry by a 150-mesh screen to prepare final slurry; then uniformly coating the slurry on a carbon-coated aluminum foil by using a 200-micrometer scraper, and drying and slicing to obtain a positive pole piece; the positive pole piece is matched with a hard carbon negative pole, a diaphragm and electrolyte to manufacture the full cell, and the charge-discharge capacity of the full cell is tested.
Comparative example
The positive electrode material is a conventional positive electrode material without a coating layer, the pH value of the prepared positive electrode material is 12.2, the positive electrode material is exposed in the air for 15 days, the pH value of the positive electrode material is increased to 12.8, it is shown that alkaline substances are precipitated from the positive electrode material stored in the air, the positive electrode material is also prepared into slurry and a positive electrode piece, and a hard carbon negative electrode, a diaphragm and electrolyte are matched to prepare a full battery, and the charge-discharge capacity of the full battery is tested.
Wherein, the performance test is respectively carried out on the examples and the comparative examples, and the test results are as follows:
example and comparative example pastes and pole piece conditions are given in the following table (viscosity units: mPas):
| viscosity of discharged material | Standing for 12h to obtain a viscosity | Standing for 24h to obtain viscosity | Pole piece meterState of face | |
| Examples | 7865 | 8025 | 9066 | Is good |
| Comparative example | 13656 | 38689 | Gel | The occurrence of scratches |
As can be seen from the above table, the comparative example slurry has high residual alkali content, high discharge viscosity, and gelation phenomenon after discharge, and is easy to scratch during coating, and the gelation condition is aggravated after standing for a period of time; the discharging fluidity of the slurry is proper, the viscosity is normal, the slurry is stable after being placed for 24 hours, and the state of a coated pole piece is good.
Examples and comparative examples the full cell charge and discharge test data are given in the following table (capacity units: mAh):
as can be seen from the above table, the discharge capacity of the battery in the embodiment of the present invention is effectively improved, and the first effect and the stability are also improved, because sodium oxalate can be decomposed in the battery formation stage and provide sodium ions to participate in the generation of the negative electrode SEI film, the consumption of sodium ions in the bulk phase is reduced, the gram capacity exertion of the positive electrode material is improved, and the energy density of the battery is improved.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious modifications, substitutions or alterations based on the present invention will fall within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. A sodium ion battery layered positive electrode material is characterized in that: comprises a layered positive active substance and an alkaline coating layer coated on the outer surface of the layered positive active substance, wherein the alkaline coating layer is NaOH, naO and Na 2 CO 3 、NaHCO 3 At least one of (a).
2. The layered positive electrode material for a sodium-ion battery according to claim 1, wherein: the layered positive active material is O3, P2 or P3 phase layered positive active material with a chemical formula of Na x MO y (ii) a Wherein M is one or more elements of Ni, cu, mn, fe, zn, co, al, cr, zr and Mo; x and y satisfy charge balance; x is more than 0.5 and less than 1.5; y is more than or equal to 2; the elements in the chemical formula satisfy charge balance.
3. The layered positive electrode material for a sodium-ion battery according to claim 1, wherein: the thickness of the alkaline coating layer is 10-100nm.
4. The layered positive electrode material for a sodium-ion battery according to claim 1, wherein: the pH of the layered positive electrode material is 12.5.
5. A method for removing and converting the alkaline coating layer of the layered positive electrode material of the sodium-ion battery into a sodium supplement additive according to any one of claims 1 to 4, which is characterized by comprising the following steps:
s1, placing a to-be-treated layered positive electrode material with an alkaline coating layer into an atmosphere rotary furnace, heating the material in the furnace to 60 ℃ at a heating rate of 2 ℃/min, and preserving heat;
s2, introducing an oxalic acid solution with the concentration of 20mM-100mM into the furnace at a constant speed for spraying, reacting for 2-6 h at a constant flow rate, removing the oxalic acid spraying device after the reaction is finished, and introducing nitrogen at a constant speed;
and S3, heating the atmosphere rotary furnace to 150 ℃ at the heating rate of 2 ℃/min, preserving the heat for 1-2 h, removing water and redundant oxalic acid in the furnace until the effluent gas is not acidic, finishing the reaction, and cooling to room temperature to obtain the treated layered positive electrode material.
6. The method for removing and converting the alkaline coating of the layered positive electrode material of the sodium-ion battery into the sodium supplement additive according to claim 5, wherein the method comprises the following steps: in step S2, the constant flow rate is 2mL/min to 10mL/min.
7. The method for removing the alkaline coating layer of the sodium-ion battery layered cathode material and converting the alkaline coating layer into the sodium supplement additive according to claim 5, wherein the method comprises the following steps: in the step S2, the mass ratio of the oxalic acid in the oxalic acid solution to the layered cathode material is 0.005-0.05.
8. The method for removing the alkaline coating layer of the sodium-ion battery layered cathode material and converting the alkaline coating layer into the sodium supplement additive according to claim 5, wherein the method comprises the following steps: in step S3, the pH of the treated layered positive electrode material is 12.
9. A positive electrode material of a sodium-ion battery is characterized in that: the alkaline coating of the layered positive electrode material of the sodium-ion battery of any one of claims 5 to 8 is removed and converted into a sodium supplement additive.
10. A sodium-ion battery, characterized in that the sodium-ion battery comprises the positive electrode material for sodium-ion battery according to claim 9.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116730408A (en) * | 2023-08-12 | 2023-09-12 | 河南科隆新能源股份有限公司 | Preparation method and application of modified sodium ion positive electrode material |
| CN116914123A (en) * | 2023-09-11 | 2023-10-20 | 浙江华宇钠电新能源科技有限公司 | High-stability layered positive electrode material of battery for vehicle and preparation method thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116730408A (en) * | 2023-08-12 | 2023-09-12 | 河南科隆新能源股份有限公司 | Preparation method and application of modified sodium ion positive electrode material |
| CN116914123A (en) * | 2023-09-11 | 2023-10-20 | 浙江华宇钠电新能源科技有限公司 | High-stability layered positive electrode material of battery for vehicle and preparation method thereof |
| CN116914123B (en) * | 2023-09-11 | 2023-12-15 | 浙江华宇钠电新能源科技有限公司 | High-stability layered positive electrode material of battery for vehicle and preparation method thereof |
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