CN115939336A - Positive electrode material of sodium ion battery, positive plate and secondary battery - Google Patents
Positive electrode material of sodium ion battery, positive plate and secondary battery Download PDFInfo
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Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode material of a sodium-ion battery, which comprises a manganese-based layered oxide material and a coating layer coated on the manganese-based layered oxide material, wherein the chemical general formula of the manganese-based layered oxide material is Na n Mn 1‑x‑ y M x A y O 2 Wherein M is at least one of Li, mg, cu, ni, ca, zn, fe, cr and Al, A is at least one of Ta, mo, W, nb, si, sn and V, wherein x is more than or equal to 0.4 and less than or equal to 0.8,0 is added into the alloy<y is not less than 0.1, n is not less than 0.85 and not more than 1, and the coating layer comprises polyanion material. The sodium ion battery anode material inhibits harmful phases in the charge and discharge process by lattice dopingAnd the surface coating modification is combined, so that the lattice stability is improved, the stability in the air is improved, and the surface alkalinity is reduced, thereby prolonging the cycle life of the material and inhibiting the flatulence of the battery.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode material of a sodium ion battery, a positive plate and a secondary battery.
Background
With the rapid development of automobile electromotion, the demand for lithium ion power batteries is increasing, so that the supply of lithium resources is increasingly tense, and the price is high. Since lithium ion batteries dominate in energy storage, rapid development of the energy storage industry also aggravates rapid consumption of lithium resources and imbalance of supply and demand. Therefore, the development of new energy storage batteries based on non-lithium ion batteries is imminent. The sodium ion battery has the remarkable advantages of low cost, abundant resources, good safety, environmental friendliness and the like, and is suitable for large-scale energy storage. For sodium ion batteries, the development of suitable cathode materials is critical. The manganese-based layered material has the advantages of high capacity, good rate capability, long cycle life and the like, and is suitable for being used as the positive electrode of the sodium-ion battery.
Compared with the layered anode material of the lithium ion battery, the layered material for the sodium ion battery is more complex, is easy to generate phase change and lattice oxygen loss under lower charging voltage, and is easy to absorb water and carbon dioxide in the air to generate side reaction to cause strong surface alkalinity. At present, the layered material used for the positive electrode of the sodium ion battery generally takes Mn element as a basic framework, and active elements such as Ni, fe, cu and the like are doped to contribute to capacity and inactive elements are doped to stabilize crystal lattices. Among manganese-based layered cathode materials, the O3-type material has the advantage of high capacity, but is prone to phase change during cycling, causing lattice distortion and resulting in poor cycling performance. In addition, the layered material is unstable in air, resulting in strong surface alkalinity, thereby causing gelation of the slurry, and swelling of the battery.
Therefore, a technical solution to the above problems is needed.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the sodium-ion battery anode material has good structural stability, good electrochemical performance and good cycling stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
sodium ionThe battery anode material comprises a manganese-based layered oxide material and a coating layer coated on the manganese-based layered oxide material, wherein the chemical general formula of the manganese-based layered oxide material is Na n Mn 1-x-y M x A y O 2 Wherein M is at least one of Li, mg, cu, ni, ca, zn, fe, cr and Al, A is at least one of Ta, mo, W, nb, si, sn and V, wherein x is more than or equal to 0.4 and less than or equal to 0.8<y is not less than 0.1, n is not less than 0.85 and not more than 1, and the coating layer comprises polyanion material.
Preferably, the positive electrode material of the sodium-ion battery is of a single crystal structure, and the particle size of the positive electrode material of the sodium-ion battery is 2-10 microns.
Preferably, the manganese-based layered oxide material is an O3 phase.
Preferably, the thickness of the coating layer is 10 to 200nm.
Preferably, the mass ratio of the manganese-based layered oxide material to the coating layer is 90 to 110:1 to 10.
Preferably, the preparation method of the polyanion material comprises the steps of mixing the metal source material and the material containing the anionic group, carrying out solid-phase reaction to obtain the polyanion material, wherein the solid-phase reaction temperature is 500-1000 ℃, the reaction time is 1-10 hours, and the reaction atmosphere is reducing atmosphere.
Preferably, the preparation method of the polyanion material further comprises modification treatment, wherein the modification treatment specifically comprises mixing the prepared polyanion material and an oxidant in a solvent, grinding, centrifuging, and drying in vacuum to obtain the modified polyanion material.
Preferably, the weight part ratio of the polyanion material to the oxidant is 0.1-10.
The second purpose of the invention is: aiming at the defects of the prior art, the positive plate is provided, and has good electrochemical performance and cycling stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
a positive plate comprises the positive electrode material of the sodium-ion battery.
The third purpose of the invention is that: aiming at the defects of the prior art, the secondary battery is provided, and has good electrochemical performance and cycling stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the positive plate.
Compared with the prior art, the invention has the beneficial effects that: the layered positive electrode material takes Mn element as a basic frame, inhibits harmful phase change in the charge-discharge process by lattice doping, forms a coating layer by combining surface coating modification, further stabilizes the lattice of the material in the charge-discharge process, improves the stability in the air, reduces the surface alkalinity, prolongs the cycle life of the material, improves the processing performance of an electrode and inhibits the gas expansion of a battery.
Drawings
Fig. 1 is an XRD pattern of the positive electrode material for sodium-ion battery prepared in example 1 of the present invention.
Fig. 2 is a low-power scanning electron microscope image of the positive electrode material of the sodium-ion battery prepared in example 1 of the present invention.
Fig. 3 is a high-power scanning electron microscope image of the positive electrode material of the sodium-ion battery prepared in example 1 of the present invention.
Fig. 4 is a spectral plot of the positive electrode material and V element of the sodium-ion battery prepared in example 1 of the present invention.
Fig. 5 is a charge-discharge curve diagram of the positive electrode material of the sodium-ion battery prepared in example 1 of the present invention.
Fig. 6 is a cycle life diagram of the positive electrode material of the sodium ion battery prepared in example 1 of the present invention.
Fig. 7 is a cycle life diagram of the layered cathode material prepared in comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the present invention is not limited thereto.
The positive electrode material of the sodium-ion battery comprises a manganese-based layered oxide material and a coating layer coated on the manganese-based layered oxide material, wherein the manganeseThe chemical general formula of the base layer oxide material is Na n Mn 1-x-y M x A y O 2 Wherein M is at least one of Li, mg, cu, ni, ca, zn, fe, cr and Al, A is at least one of Ta, mo, W, nb, si, sn and V, wherein x is more than or equal to 0.4 and less than or equal to 0.8,0 is added into the alloy<y is not less than 0.1, n is not less than 0.85 and not more than 1, and the coating layer comprises polyanion material.
In the formula of the positive electrode material of the sodium-ion battery, mn plays a role of a basic framework, preferably, M contains at least one electrochemical active element, the electrochemical active elements comprise Cu, ni, fe and Cr, and the electrochemical activity means that the capacity can be contributed through valence change, and preferably, the element M is uniformly doped. More preferably, M contains at least one electrochemically inactive element, wherein the electrochemically inactive element comprises Li, mg, cu, ca, zn and Al, and the electrochemically inactive element means that capacity cannot be contributed through valence change and only plays a role in stabilizing crystal lattices; more preferably, the inactive element contains Li element, and the low-valence Li doping is beneficial to improving the valence state of manganese, the content of sodium and the capacity of the material. In the formula of the positive electrode material of the sodium-ion battery, A is a high-valence inactive element, preferably, A is selected from at least one of Ta, mo, W, nb, si, sn and V, and preferably, the element A is uniformly doped. Research shows that the doping of the element A can not only improve the lattice stability, but also improve the working voltage of the battery and reduce the surface alkalinity of the material; research also shows that co-doping of inactive elements in a and M can produce a synergistic effect, serving to stabilize the crystal lattice and increase the operating voltage.
In the present invention, for Na n Mn 1-x-y M x AyO 2 The particles are subjected to surface coating modification, and through surface coating, the stability of the layered material in the air can be improved, the surface alkalinity of the layered material can be reduced, and the gelatinization of slurry and the flatulence of the battery can be inhibited; in addition, the surface coating can also improve Na n Mn 1-x-y M x A y O 2 The interface stability with the electrolyte, the surface lattice distortion is inhibited, and the material circulation stability is improved.
Preferably, the material of the coating layerThe material is sodium-based polyanionic material which has air stability, hydrophobicity and carbon dioxide repellency, thereby reducing or eliminating Na n Mn 1-x-y M x A y O 2 The alkalinity of the surface; in addition, the polyanionic material is a sodium storage material and a sodium ion conductor, and the coating of the polyanionic material does not influence the specific capacity of the material and the diffusion of sodium ions.
Preferably, the polyanionic material is selected from, but not limited to, naffepo 4 、NaTi 2 PO 4 、Na 3 V 2 (PO 4 ) 3 、Na 3 V 2 (PO 4 ) 2 F 3 、Na 3 (VOPO 4 ) 2 F、Na 4 MnV(PO 4 ) 3 、NaFeSO 4 F
Na 3 Fe 2 (PO 4 )P 2 O 7 、Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 )、Na 2 Fe 2 (SO 4 ) 3 、NaVPO 4 F、Na 2 FePO 4 F、NaFe 2 PO 4 (SO 4 ) 2 (ii) a The polyanionic material also comprises derivatives thereof, wherein the derivatives comprise dopants of an F position, an Mn position, a V position and an Fe position, and the doping amount is 0.5-10%.
Preferably, the polyanion material is selected from surface sodium-deficient polyanion materials, the sodium deficiency is 5-30%, and sodium deficiency is favorable for spontaneously absorbing residual sodium on the surface of the layered positive electrode, so that the surface alkalinity is further reduced.
Further preferably, the polyanionic material is subjected to sanding treatment, after sanding, the particle size is reduced to 10-200 nanometers, and the sanded nanoscale polyanionic material is easier to completely and uniformly coat the layered material.
The positive electrode material of the sodium-ion battery comprises a layered material synthesis method and a surface modification method. The preparation of the layered material comprises a direct solid-phase reaction method, a coprecipitation method and a sol-gel method. The direct solid-phase reaction method refers to the direct high-temperature solid-phase reactionPreparation of Na n Mn 1xy M x A y O 2 In the synthesis process, compounds containing Na, mn, M and A are uniformly mixed by ball milling, sand milling, high-speed mixing or other processes, and then solid-phase reaction is carried out, wherein the compounds are selected from nitrate, acetate, carbonate, oxalate, oxide, hydroxide, oxyhydroxide and the like containing the elements. Preferably, the solid-phase reaction temperature is 600-1000 ℃, the reaction time is 5-20 hours, the reaction atmosphere is selected from air, oxygen or compressed air, and the reaction equipment is selected from a box furnace, a roller kiln, a rotary kiln and the like. After high-temperature roasting, the steps of crushing, sorting, iron removal and the like are also needed, wherein the crushing comprises ball milling, airflow crushing and the like.
The coprecipitation method refers to the synthesis of Na n Mn 1xy M x A y O 2 In the process, soluble salt containing Mn and M is dissolved in deionized water to prepare a salt solution, then a coprecipitation reaction is used under the action of a precipitator and a complexing agent to obtain a solid precursor, and the solid precursor is mixed with a sodium-containing compound to synthesize a final product through a solid-phase reaction. Preferably, the salt solution is selected from chloride, sulfate, nitrate and the like, and the complexing agent is selected from ammonia water, sodium citrate, sodium ethylene diamine tetracetate and the like; the precipitant is selected from sodium hydroxide, potassium hydroxide, sodium oxalate, potassium oxalate, sodium carbonate, potassium carbonate and the like; the sodium-containing compound is selected from sodium carbonate, sodium bicarbonate, sodium nitrate, sodium oxalate, sodium hydroxide, sodium acetate and the like. Wherein, when the elements M and A are easy to coprecipitate, the elements M and A are introduced as precursors, and when the elements M and A are difficult to coprecipitate, the elements M and A are introduced together with the sodium-containing compound. Preferably, the coprecipitation reaction temperature is 40-70 ℃, the solid phase reaction temperature is 600-1000 ℃, the reaction time is 5-20 hours, the reaction atmosphere is air, oxygen or compressed air, and the reaction equipment is selected from a box furnace, a roller kiln, a rotary kiln and the like. After high-temperature roasting, the steps of crushing, sorting, iron removal and the like are also needed, wherein the crushing comprises ball milling, airflow crushing and the like.
The sol-gel method refers to the synthesis of Na n Mn 1-x-y M x A y O 2 In the process, nitrate, sulfate or organic salt containing Na, mn, M and A is dissolved in water, sol is formed after mixing, then complexing agent such as citric acid is added, gel is obtained after stirring at a certain temperature, and then the final product is obtained through solid phase reaction. Preferably, the stirring temperature is 50-90 ℃, the solid phase reaction temperature is 600-1000 ℃, the reaction time is 5-20 hours, the reaction atmosphere is air, oxygen or compressed air, and the reaction equipment is selected from a box furnace, a roller kiln, a rotary kiln and the like. After high-temperature roasting, the steps of crushing, sorting, iron removal and the like are also needed, wherein the crushing comprises ball milling, airflow crushing and the like.
After coating, heat treatment is needed, preferably, the heat treatment temperature is 500-800 ℃, the heat treatment time is 0.5-5 hours, and the heat treatment atmosphere is inert atmosphere or reducing atmosphere. After heat treatment, the residual sodium on the surface of the layered material can be implanted into the polyanion material with the surface being sodium-deficient, so that the alkalinity of the surface of the material can be reduced.
The invention also discloses a preparation method of the surface sodium-deficient nano polyanion material, which comprises the following steps:
(1) By containing Na + 、Fe 2+ Or Fe 3+ 、Mn 2+ Or Mn 3+ 、Ti 4+ 、V 3+ Or V 4+ Or V 5+ 、PO 4 3- 、SO 4 2- 、F - The polyanionic material is synthesized by a solid-phase reaction. Preferably, the solid-phase reaction temperature is 500-1000 ℃, the reaction time is 1-10 hours, and the reaction atmosphere is a reducing atmosphere;
(2) Mixing the polyanion material and an oxidant in deionized water, and performing sanding treatment, wherein the sanding time is preferably 5 minutes to 5 hours, the oxidant is preferably ammonium persulfate, sodium persulfate, tetrafluoroboric nitric acid, potassium dichromate and sodium dichromate, and the molar ratio of the polyanion material to the oxidant is preferably 0.1 to 10:1 to 3;
(3) And carrying out centrifugal separation and vacuum drying on the sand-ground product to obtain the polyanion material with the surface lacking sodium and the nanometer level, wherein the preferable drying temperature is 80-120 ℃.
The sodium-deficient polyanionic material is a surface sodium-deficient polyanionic material, and the surface sodium deficiency can absorb the surface residual alkali of the layered material more easily.
Preferably, the Na is n Mn 1-x-y M x A y O 2 The grain size is 2-10 microns. Within the particle size range, the method is favorable for improving the compaction density of the electrode, reducing the exposed area of air or electrolyte, reducing the surface alkalinity, improving the processing performance of the electrode, and improving the interface stability of materials and electrolyte, thereby improving the cycle life.
Preferably, the surface coating method is selected from the group consisting of an atomic layer deposition method, a sol-gel method, a magnetron sputtering method, and a mechanofusion method; preferably, the surface coating method is selected from a mechanofusion method, the mechanofusion method can realize uniform and complete coating, the process is simple, the cost is low, and large-scale production can be realized.
In some embodiments, the sodium-ion battery cathode material has a single crystal structure, and the particle size of the sodium-ion battery cathode material is 2-10 μm. Within the particle size range, the method is favorable for improving the compaction density of the electrode, reducing the exposed area of air or electrolyte, reducing the surface alkalinity, improving the processing performance of the electrode, and improving the interface stability of materials and electrolyte, thereby improving the cycle life.
In some embodiments, the manganese-based layered oxide material is an O3 phase. Among manganese-based layered positive electrode materials, the O3-type material has an advantage of high capacity, but is easily subjected to phase transition during cycling, and therefore, it is necessary to perform doping and coating layer structure treatment on the O3 phase.
In some embodiments, the cladding layer has a thickness of 10 to 200nm. Specifically, the coating layer has a thickness of 10nm, 20nm, 40nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, or 200nm.
In some embodiments, the mass ratio of the manganese-based layered oxide material to the coating layer is 90 to 110:1 to 10. The mass ratio of the manganese-based layered oxide material to the coating layer is 90.
In some embodiments, the polyanionic material is prepared by mixing a metal source material and a material containing an anionic group, and performing a solid-phase reaction to obtain the polyanionic material, wherein the solid-phase reaction temperature is 500-1000 ℃, the reaction time is 1-10 hours, and the reaction atmosphere is a reducing atmosphere. Preferably, the solid phase reaction temperature is 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 1000 ℃; the reaction time was 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours.
In some embodiments, the preparation method of the polyanionic material further comprises a modification treatment, wherein the modification treatment is specifically to mix the prepared polyanionic material and an oxidant in a solvent, grind, centrifuge and dry in vacuum to obtain the modified polyanionic material.
In some embodiments, the weight part ratio of the polyanionic material to the oxidant is 0.1-10. The weight ratio of the polyanionic material to the oxidant is 0.1.
A positive plate comprises the positive electrode material of the sodium-ion battery. The positive plate has good electrochemical performance and cycling stability.
A secondary battery comprises the positive plate. A secondary battery may be a sodium ion battery, a lithium ion battery, a magnesium ion battery, a calcium ion battery, a potassium ion battery, or the like. Preferably, the following secondary battery is exemplified by a sodium ion battery, which includes a positive plate, a negative plate, a separator, an electrolyte, and a case, wherein the separator separates the positive plate from the negative plate, and the case is used for installing the positive plate, the negative plate, the separator, and the electrolyte. The secondary battery of the invention has good electrochemical performance and cycling stability.
The positive electrode sheet adopts the above positive electrode sheet, wherein the positive electrode current collector is generally a structure or a part for collecting current, and the positive electrode current collector may be any material suitable for serving as a positive electrode current collector of a sodium ion battery in the art, for example, the positive electrode current collector may be a metal foil or the like, and more specifically, the positive electrode current collector may be an aluminum foil or the like.
The negative electrode sheet includes a negative electrode current collector, which is generally a structure or part that collects current, and a negative electrode active material, which may be various materials suitable for use as a negative electrode current collector of a sodium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, etc., and more particularly, may include, but is not limited to, an aluminum foil, etc. The anode active material includes soft carbon, hard carbon, metal oxide, and the like.
The sodium ion battery also comprises an electrolyte, and an organic solution containing an organic solvent, a sodium salt and an additive is used as the organic electrolyte. The sodium salt comprises at least one of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonylimide, sodium bifluorosulfonylimide, sodium tetrafluoroborate and sodium bisoxalato. The organic solvent comprises at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate and methyl ethyl carbonate.
The separator may be any material suitable for a sodium ion battery separator in the art, and for example, may be a combination including, but not limited to, one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.
Preferably, the material of the shell is one of stainless steel, an aluminum shell and an aluminum-plastic film.
Example 1
According to Na 0.92 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 Stoichiometric ratio, using direct solid phase reaction method to prepare the material. Firstly, adding Na according to the stoichiometric ratio 2 CO 3 ，MnO 2 、MgO、Fe 2 O 3 、NiO、Li 2 CO 3 、Nb 2 O 5 Uniformly mixing, ball-milling to obtain a precursor, wherein the ball-milling time is 15 hours, the rotating speed is 350rpm, then placing the precursor in a muffle furnace, roasting for 15 hours at 850 ℃ in air atmosphere to obtain O3 Na 0.92 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 The layered material, the product, was analyzed by XRD to be O3 phase, see fig. 1. Preparing Na with a surface sodium-deficient type and a particle size of 100 nanometers by adopting a solid phase method and combining sanding treatment in a sodium persulfate environment 3-x V 2 (PO 4 ) 3 . Mixing the above layered material with Na with sodium-deficient surface 3-x V 2 (PO 4 ) 3 Mixing, and mechanically fusing with a fusing machine to obtain Na 0.92 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 With Na 3-x V 2 (PO 4 ) 3 The weight ratio of (A) to (B) is 100:1. the particle size of the coated product was 210 microns by SEM analysis, na 3-x V 2 (PO 4 ) 3 Mixing Na 0.92 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 Uniform, complete coating, see fig. 2-4. The pH of the product was 9.1. The layered material prepared in the example was used as a positive electrode, sodium metal as a negative electrode, glass fiber as a separator, naPF 6 The Propylene Carbonate (PC)/Ethyl Methyl Carbonate (EMC) solution is used as an electrolyte, fluorinated Ethylene Carbonate (FEC) with the weight of 4% of that of the electrolyte is added, a button cell is assembled, and a charge-discharge test is carried out, wherein the current density is 75mA/g, the voltage range is 1.9-4.1V, the charge-discharge curve is shown in figure 5, the specific capacity is 133.5mAh/g, the median voltage is 3.14V, and the capacity retention ratio of the material is 95.8% after 100 cycles, which is shown in figure 6. After the above charge-discharge cycle, the battery did not swell.
Example 2
According to Na 0.88 [Li 0.03 Mg 0.03 Ni 0.22 Fe 0.31 Mn 0.40 Mo 0.01 ]O 2 Stoichiometry ofIn comparison, a coprecipitation method is used for preparing a precursor, and a high-temperature solid-phase reaction method is combined for preparing the material. Firstly, according to the proportion of Ni: fe: mn =0.22:0.31:0.40 metering ratio, niSO 4 、FeSO 4 、MnSO 4 Mixing the solution, obtaining a coprecipitation precursor by a coprecipitation method, and then mixing the coprecipitation precursor with Na 2 CO 3 ，Li 2 CO 3 、MgO、MoO 3 Mixing the materials, placing the mixture in a muffle furnace after high-speed mixing, and roasting the mixture for 15 hours at 840 ℃ in air atmosphere to obtain O3 type Na 0.88 [Li 0.03 Mg 0.03 Ni 0.22 Fe 0.31 Mn 0.40 Mo 0.01 ]O 2 The layered material and the product are analyzed by XRD and are O3 phase. Adopts a solid phase method and combines with sanding treatment under the potassium persulfate environment to prepare Na with a surface sodium-deficient type and a particle size of 100 nanometers 3-x V 2 (PO 4 ) 2 F 3 . Mixing the above layered material with Na with sodium-deficient surface 3-x V 2 (PO 4 ) 2 F 3 Mixing, and mechanically fusing with a fusing machine, wherein Na is 0.88 [Li 0.03 Mg 0.03 Ni 0.22 Fe 0.31 Mn 0.40 Mo 0.01 ]O 2 With Na 3-x V 2 (PO 4 ) 2 F 3 The weight ratio of (A) to (B) is 100:1.5. the particle size of the coated product is 2-10 microns and Na by SEM analysis 3-x V 2 (PO 4 ) 2 F 3 Mixing Na 0.88 [Li 0.03 Mg 0.03 Ni 0.22 Fe 0.31 Mn 0.40 Mo 0.01 ]O 2 Uniform and complete coating. The pH of the product was 9.3. The layered material prepared in the example was used as a positive electrode, sodium metal as a negative electrode, glass fiber as a separator, naPF 6 The PC/EMC solution is taken as electrolyte, FEC with the weight of 4% of the electrolyte is added, a button cell is assembled, and a charge-discharge test is carried out, wherein the current density is 75mA/g, the voltage range is 1.9-4.1V, the specific capacity is 135.1mAh/g, the median voltage is 3.15V, and the capacity retention ratio of the material is 94.5% after 100 cycles. After the above charge-discharge cycle, the battery did not swell.
Example 3
According to Na 0.88 [Cu 0.02 Mg 0.02 Ni 0.22 Fe 0.32 Mn 0.40 Ta 0.02 ]O 2 Preparing a precursor by a sol-gel method according to a stoichiometric ratio, and preparing the material by combining a high-temperature solid-phase reaction. Firstly, according to the stoichiometric ratio, adding NaNO 3 、Mn(NO 3 ) 2 、Ni(NO 3 ) 2 、Cu(NO 3 ) 2 、Mg(NO 3 ) 2 、Fe(NO 3 ) 2 、C 10 H 25 O 5 Ta is mixed in deionized water, sol is obtained through stirring, citric acid is added, gel precursors are obtained through full stirring at 70 ℃, the precursors are placed in a muffle furnace after full drying and ball milling crushing, and O3 type Na is obtained after roasting for 12 hours at 855 ℃ in air atmosphere 0.88 [Cu 0.02 Mg 0.02 Ni 0.22 Fe 0.32 Mn 0.40 Ta 0.02 ]O 2 The layered material and the product are analyzed by XRD and are O3 phase. Adopting a solid phase method, combining with sanding treatment in a sodium persulfate environment to prepare Na with a surface sodium-deficient type and a particle size of 100 nanometers 3-x (VOPO 4 ) 2 F. Mixing the above layered material with Na-deficient Na 3-x (VOPO 4 ) 2 F, mixing uniformly, and mechanically fusing by using a fusing machine, wherein Na is 0.88 [Cu 0.02 Mg 0.02 Ni 0.22 Fe 0.32 Mn 0.40 Ta 0.02 ]O 2 With Na 3-x (VOPO 4 ) 2 The weight ratio of F is 100:2. the particle size of the coated product is 2-10 microns and Na by SEM analysis 3-x (VOPO 4 ) 2 F is Na 0.88 [Cu 0.02 Mg 0.02 Ni 0.22 Fe 0.32 Mn 0.40 Ta 0.02 ]O 2 Uniform and complete coating. The pH of the product was 9.5. The layered material prepared in the example was used as a positive electrode, sodium metal as a negative electrode, glass fiber as a separator, naPF 6 The PC/EMC solution is taken as electrolyte, FEC with the weight of 4% of the electrolyte is added, a button cell is assembled, and a charge-discharge test is carried out, wherein the current density is 75mA/g, the voltage range is 1.9-4.1V, and the specific volume isThe amount is 134.1mAh/g, the median voltage is 3.12V, and the capacity retention ratio of the material is 92.7 percent after 100 cycles. After the above charge-discharge cycle, the battery did not swell.
Example 4
According to Na 0.89 [Al 0.01 Mg 0.04 Ni 0.23 Fe 0.32 Mn 0.39 Sn 0.01 ]O 2 Stoichiometric ratio, using direct solid phase reaction method to prepare the material. Firstly, adding Na according to the stoichiometric ratio 2 CO 3 ，Mn 2 O 3 、Fe 2 O 3 、NiO、MgO、Al 2 O 3 、SnO 2 Uniformly mixing, ball-milling to obtain a precursor, wherein the ball-milling time is 15 hours, the rotating speed is 350rpm, then placing the precursor in a muffle furnace, roasting at 850 ℃ for 12 hours in an air atmosphere to obtain O3 Na 0.89 [Al 0.01 Mg 0.04 Ni 0.23 Fe 0.32 Mn 0.39 Sn 0.01 ]O 2 The layered material and the product are analyzed by XRD and are O3 phase. Adopting a solid phase method, combining sand grinding treatment in a tetrafluoroborate nitric acid environment to prepare Na with a surface sodium-deficient type and a particle size of 100 nanometers 3-x Fe 2 (PO 4 )P 2 O 7 . Mixing the above layered material with Na with sodium-deficient surface 3-x Fe 2 (PO 4 )P 2 O 7 Mixing, and mechanically fusing with a fusing machine, wherein Na is 0.89 [Al 0.01 Mg 0.04 Ni 0.23 Fe 0.32 Mn 0.39 Sn 0.01 ]O 2 With Na 3-x Fe 2 (PO 4 )P 2 O 7 The weight ratio of (A) to (B) is 100:1. the particle size of the coated product is 2-10 microns and Na is analyzed by SEM 3* x Fe 2 (PO 4 )P 2 O 7 Mixing Na 0.89 [Al 0.01 Mg 0.04 Ni 0.23 Fe 0.32 Mn 0.39 Sn 0.01 ]O 2 Uniform and complete coating. The pH of the product was 9.4. The layered material prepared in the example was used as a positive electrode, sodium metal as a negative electrode, glass fiber as a separator, naPF 6 The PC/EMC solution is taken as electrolyte, and is addedThe electrolyte is FEC with the weight of 4%, a button battery is assembled, charging and discharging tests are carried out, the current density is 75mA/g, the voltage range is 1.9-4.1V, the specific capacity is 136.2mAh/g, the median voltage is 3.14V, and after 100 cycles, the capacity retention rate of the material is 93.1%. After the above charge-discharge cycle, the battery did not swell.
Example 5
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 97.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 90.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 96.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 102.
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 104.
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from example 1 is that: the mass ratio of the manganese-based layered oxide material to the coating layer is 110.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
The difference from example 1 is that: no Na was carried out 2.5 V 2 (PO 4 ) 3 And (4) coating. The pH of the material was 12.1, the capacity retention rate was 85.1% through 100 cycles under the same test conditions as in example 1, see FIG. 7, and the battery was inflated
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 2
The difference from example 1 is that: no sodium persulfate is added in the sanding process, namely the layered material is subjected to non-sodium-deficiency Na 3 V 2 (PO 4 ) 3 And (4) coating. The pH of the material was 10.3, the capacity retention rate was 91.1% and the battery was inflated under the same test conditions as in example 1 over 100 cycles.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 3
The difference from example 1 is that: the coating material is a common oxide V 2 O 3 Instead of Na 2.5 V 2 (PO 4 ) 3 . The pH of the material was 11.4, the capacity retention rate was 87.2% after 100 cycles under the same test conditions as in example 1, and the battery was inflated.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 4
The difference from example 1 is that: li is not doped in the preparation process, and part of Li is replaced by Mg element to obtain Na 0.88 [Mg 0.08 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 The pH of the material was 9.8. Under the same test conditions as example 1, the specific capacity is 121.4mAh/g, the median voltage is 3.10V, the capacity retention rate is 85.3 percent after 100 cycles, and the battery does not swell.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 5
The difference from example 1 is that: no Nb is doped in the preparation process, and the Nb part is replaced by the element Mn to obtain Na 0.93 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.40 ]O 2 pH of the materialThe value was 10.2. Under the same test conditions as in example 1, the median voltage was 3.06V, the capacity retention ratio was 87.6% after 100 cycles, and the battery was inflated.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 6
The difference from example 1 is that: no Nb is doped in the preparation process, and the Nb part is replaced by trivalent element Co to obtain Na 0.94 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Co 0.01 ]O 2 The pH of the material was 9.7. Under the same test conditions as in example 1, the median voltage was 3.03V, the capacity retention ratio was 86.4% through 100 cycles, and the battery was inflated.
The rest is the same as embodiment 1, and the description is omitted here.
And (4) performance test, wherein the manufactured secondary battery is subjected to performance test, and the test result is recorded in table 1.
TABLE 1
As can be seen from table 1 above, the secondary batteries prepared according to the present invention have better performance and capacity retention rate as high as 95.8% compared to the secondary batteries of comparative examples 1 to 6. From the comparison of examples 1 to 4, it is shown that when the group M element is doped with Li, mg, ni, fe and the group A element is doped with Nb and as Na 0.92 [Li 0.05 Mg 0.03 Ni 0.20 Fe 0.32 Mn 0.39 Nb 0.01 ]O 2 The secondary battery prepared by the stoichiometric ratio has better performance, and the capacity retention rate reaches 95.8 percent.
Compared with the embodiment 1 and the comparative example 1, when the positive electrode layered material is coated by the coating layer, the stability is effectively improved, the capacity retention rate is improved, the capacity protection rate is improved from 85.1% to 95.8%, and the battery flatulence is avoided. This is because the polyanionic material in the coating layer has air stability, hydrophobicity and carbon dioxide repellencyThereby reducing or eliminating Na n Mn 1-x-y M x A y O 2 The alkalinity of the surface improves the stability of the layered material in the air, inhibits the surface lattice distortion, and inhibits the gelatinization of slurry and the flatulence of the battery.
From the comparison between example 1 and comparative example 2, it can be seen that when the material surface of the coating layer is sodium-deficient polyanionic material, the surface alkalinity can be further reduced, because the sodium deficiency is favorable for spontaneously absorbing residual sodium on the surface of the layered positive electrode, thereby further reducing the surface alkalinity, and preferably, the sodium deficiency is 5-30%.
From comparison of example 1 with comparative example 3, it can be seen that when the material of the clad layer is a conventional oxide such as oxide V 2 O 3 In the process, the structural stability of the positive electrode material of the core is not greatly improved by the coating layer, and the battery still has the phenomenon of gas expansion, so that the polyanion material can effectively improve the structural stability of the positive electrode material, harmful phase change can not occur under multiple charge-discharge cycles of the positive electrode material, and the cycle performance of the battery is improved.
From comparison between example 1 and comparative example 4, when doping is performed using Li in the doping element in the layered substance of the positive electrode, the lower-valent Li doping is advantageous in improving the valence state of manganese, the content of sodium, and the capacity of the material. Meanwhile, the lithium doping can also improve the cycling stability of the battery and avoid the battery from expanding.
Compared with the comparative example 5, the comparison between the example 1 and the comparative example 5 shows that when no Nb element is doped in the positive electrode layered substance, and the Nb element is replaced by the Mn element, namely only M elements are doped, the capacity retention rate of the prepared positive electrode material is low, and the battery is easy to swell. The A-type elements are high-valence inactive elements, and the doping of the element A can improve the lattice stability, improve the working voltage of the battery and reduce the surface alkalinity of the material; and meanwhile, the A-type element and the M-type element are co-doped to generate a synergistic effect, so that the effects of stabilizing crystal lattices and improving working voltage are achieved.
Compared with the comparative example 6, the comparison between the example 1 and the comparative example 6 shows that when the Nb element in the positive electrode layered substance is replaced by the Co element, the capacity retention rate of the prepared positive electrode material is low, and the battery is easy to swell. According to the invention, nb is selected from the A-type elements for doping, so that the prepared anode material has good stability, and the battery is prevented from swelling.
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 improvement, replacement or modification made by those skilled in the art based on the present invention is 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. The positive electrode material of the sodium-ion battery is characterized by comprising a manganese-based layered oxide material and a coating layer coated on the manganese-based layered oxide material, wherein the chemical general formula of the manganese-based layered oxide material is Na n Mn 1-x-y M x A y O 2 Wherein M is at least one of Li, mg, cu, ni, ca, zn, fe, cr and Al, A is at least one of Ta, mo, W, nb, si, sn and V, wherein x is more than or equal to 0.4 and less than or equal to 0.8,0 is added into the alloy<y is not less than 0.1, n is not less than 0.85 and not more than 1, and the coating layer comprises polyanion materials.
2. The positive electrode material for sodium-ion batteries according to claim 1, wherein the positive electrode material for sodium-ion batteries has a single crystal structure, and the particle diameter of the positive electrode material for sodium-ion batteries is 2 to 10 μm.
3. The positive electrode material for sodium-ion batteries according to claim 1, wherein said manganese-based layered oxide material is an O3 phase.
4. The positive electrode material for sodium-ion batteries according to claim 1, wherein the thickness of said coating layer is 10 to 200nm.
5. The positive electrode material for sodium-ion batteries according to any one of claims 1 to 4, wherein the mass ratio of the manganese-based layered oxide material to the coating layer is from 90 to 110:1 to 10.
6. The positive electrode material of the sodium-ion battery of claim 5, wherein the polyanionic material is prepared by mixing a metal source material and a material containing an anionic group, and carrying out a solid-phase reaction at a temperature of 500-1000 ℃ for 1-10 hours in a reducing atmosphere to obtain the polyanionic material.
7. The positive electrode material of the sodium-ion battery as claimed in claim 6, wherein the preparation method of the polyanion material further comprises a modification treatment, and the modification treatment is specifically to mix the prepared polyanion material with an oxidant in a solvent, grind, centrifuge, and dry in vacuum to obtain the modified polyanion material.
8. The positive electrode material for the sodium-ion battery according to claim 7, wherein the weight part ratio of the polyanionic material to the oxidant is 0.1-10.
9. A positive electrode sheet comprising the positive electrode material for sodium-ion batteries according to any one of claims 1 to 8.
10. A secondary battery comprising the positive electrode sheet according to claim 9.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116417617A (en) * | 2023-05-26 | 2023-07-11 | 宁德新能源科技有限公司 | Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device |
| CN116544405A (en) * | 2023-06-26 | 2023-08-04 | 宁德时代新能源科技股份有限公司 | Positive electrode active material, preparation method, positive electrode plate, battery and electric equipment |
| CN116581274A (en) * | 2023-06-15 | 2023-08-11 | 中国科学院深圳先进技术研究院 | Sodium ion battery positive electrode material and preparation method and application thereof |
| CN117276551A (en) * | 2023-11-23 | 2023-12-22 | 兰钧新能源科技有限公司 | Sodium-electricity layered oxide positive electrode material, preparation method thereof and sodium-ion battery |
| CN117285087A (en) * | 2023-11-24 | 2023-12-26 | 北京中科海钠科技有限责任公司 | Layered oxide, preparation method thereof and sodium battery |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116417617A (en) * | 2023-05-26 | 2023-07-11 | 宁德新能源科技有限公司 | Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device |
| CN116417617B (en) * | 2023-05-26 | 2023-10-24 | 宁德新能源科技有限公司 | Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device |
| CN116581274A (en) * | 2023-06-15 | 2023-08-11 | 中国科学院深圳先进技术研究院 | Sodium ion battery positive electrode material and preparation method and application thereof |
| CN116581274B (en) * | 2023-06-15 | 2024-08-13 | 中国科学院深圳先进技术研究院 | Sodium ion battery positive electrode material and preparation method and application thereof |
| CN116544405A (en) * | 2023-06-26 | 2023-08-04 | 宁德时代新能源科技股份有限公司 | Positive electrode active material, preparation method, positive electrode plate, battery and electric equipment |
| CN117276551A (en) * | 2023-11-23 | 2023-12-22 | 兰钧新能源科技有限公司 | Sodium-electricity layered oxide positive electrode material, preparation method thereof and sodium-ion battery |
| CN117276551B (en) * | 2023-11-23 | 2024-03-19 | 兰钧新能源科技有限公司 | Sodium-electricity layered oxide positive electrode material, preparation method thereof and sodium-ion battery |
| CN117285087A (en) * | 2023-11-24 | 2023-12-26 | 北京中科海钠科技有限责任公司 | Layered oxide, preparation method thereof and sodium battery |
| CN117285087B (en) * | 2023-11-24 | 2024-04-23 | 北京中科海钠科技有限责任公司 | Layered oxide, preparation method thereof and sodium battery |
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