CN115360340A - Anion-cation functionalized doped modified high-entropy polyanion type positive electrode material, preparation method and application thereof - Google Patents

Anion-cation functionalized doped modified high-entropy polyanion type positive electrode material, preparation method and application thereof Download PDF

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CN115360340A
CN115360340A CN202211167558.XA CN202211167558A CN115360340A CN 115360340 A CN115360340 A CN 115360340A CN 202211167558 A CN202211167558 A CN 202211167558A CN 115360340 A CN115360340 A CN 115360340A
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equal
manganous
sodium
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沈杏
苏岳锋
杨妮
吴丹
蒋晓平
莫俊林
冉艳
刘兴兴
赵勇
王萌
王联
吴锋
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Beijing Institute of Technology BIT
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Abstract

The invention relates to a high-entropy polyanion type positive electrode material modified by anion and cation functionalized doping, a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The cathode material comprises a cathode core and a carbon coating layer, wherein the chemical formula of the cathode core is Na δ A α B β C γ X σ Y m Z n Wherein A is V 3+ And/or Fe 2+ B is Cu 2+ 、Mn 2+ And Cr 3+ C is Ni 2+ And/or Ti 4+ X is PO 4 3‑ And/or P 2 O 7 4‑ Y is SO 4 2‑ 、N 3‑ And F ‑ Z is BO 3 3‑ 、SiO 4 4‑ 、S 2‑ And Cl ‑ The particle size of the high-entropy polyanionic positive electrode material is 10-40 mu m, and the thickness of the carbon coating layer is 5-10 nm. The distribution of transition metal sites and polyanion sites is directionally designed by adopting the synergistic action of anions and cations, a high-entropy structure compatible with anions and cations is constructed, the normalized growth and the directional construction of a crystal phase are controlled, and the synergistic control of the cost advantage, the voltage capacity advantage and the conductivity advantage is realized.

Description

Anion-cation functionalized doped modified high-entropy polyanion type positive electrode material, preparation method and application thereof
Technical Field
The invention relates to a high-entropy polyanion type positive electrode material modified by anion and cation functionalized doping, a preparation method and application thereof, and belongs to the technical field of sodium ion batteries.
Background
With the depletion of fossil energy, the energy crisis is increasingly prominent, and the development of clean and renewable energy is urgent. In the novel energy integration process, a large-scale energy storage technology is needed to realize the efficient utilization and interconnection and grid connection of clean energy. Under the background, the sodium ion battery with the similar working principle as the lithium battery has multiple advantages of rich resources, wide distribution, low price, high safety and the like, and has higher research value and application prospect in the field of secondary energy storage. Compared with lithium ions, the radius of the sodium ions is large, the mass is heavy, and the oriented development of the positive electrode material is the key for improving the comprehensive performance of the sodium ion battery.
Among the reported positive electrode materials, polyanionic phosphates are the most interesting active materials for the development of high-power sodium ion batteries due to their higher operating voltage and excellent structural stability. The material has a highly open framework structure, provides rich diffusion channels for sodium ion migration, and has performance comparable to that of lithium iron phosphate in a lithium ion battery, particularly the vanadium-based phosphate is more prominent. However, the vanadium-based raw material has high cost and certain toxicity, so that the specific cost advantage of the sodium-ion battery is weakened, and the intrinsic conductivity of the positive electrode is poor, so that the material has short plates in the aspects of performance and cost, and the large-scale application of the material is greatly limited. In recent years, ti 3+ /Ti 4+ 、Fe 2+ /Fe 3+ 、Mn 2+ /Mn 3+ 、Ni 2+ /Ni 3+ Isoredox couples have been reported to be studied in a variety of NASICON-type compounds, such as Na 3 VTi(PO 4 ) 3 、Na 4 VFe(PO 4 ) 3 、Na 4 MnV(PO 4 ) 3 、Na 3+ x V x Ni 1-x (PO 4 ) 3 And the like. Compared with a pure vanadium phosphate anode, the novel component materials effectively reduce the cost of raw materials, but the modified materials are difficult to ensure the original capacity and voltage advantages. Aiming at the defect of low electronic conductivity of materials, the current common strategy is mainly carbon coating by various forms of different methods. Although carbon coating can effectively improve the conductivity of the material, and has low cost and simple operation, the coating effect is greatly reduced due to the compatibility difference between the carbon layer and the bulk phase structure and the limitation of the carbon content on the ion migration.
CN202110812852.0 discloses a modified titanium manganese phosphate sodium positive electrode material, which utilizes transition metal elements with high cost performance to replace vanadium, adopts anions with strong electronegativity to replace partial phosphate radicals, adjusts the bond length and the binding energy of a metal-oxygen bond, exerts two platform capacities of the manganese elements, simultaneously changes the electronic arrangement and covalent bond characteristics of a polyanion framework structure, and shows excellent sodium storage performance, but the first week of the material has low coulombic efficiency and low discharge capacity.
Chinese patent application 202111458385.2 discloses a manganese-based polyanionic sodium-ion battery anode material which adopts SiO 4 4- Substituted moiety PO 4 3- The obtained cathode material is hollow and spherical, so that the problems of poor electrochemical activity and low electronic conductivity of the manganese-based phosphate are effectively solved, and the regular morphology characteristics enable the material to have better dispersibility, relieve the agglomeration phenomenon among particles and facilitate the high-efficiency transmission of sodium ions in a solid phase. But the cycling stability and rate capability of the material still have a larger improvement space.
Chinese patent application 202210024348.9 discloses a polyanion type sodium ion battery positive electrode material and a preparation method thereof, wherein a plurality of cheap inactive metals are introduced to stabilize the material structure, so that the cycle performance and the rate capability of the material are effectively improved, but the inactive elements are doped to occupy the crystal structure position but do not play an electrochemical role, so that the discharge capacity of the material is still low even if the material is charged to a higher voltage.
Disclosure of Invention
In view of the above, the present invention aims to provide a high-entropy polyanion-type positive electrode material modified by anion and cation functionalized doping, a preparation method and applications thereof. By introducing various functional anion and cation groups to directionally regulate and control the structural stability, working voltage and electronic conductance of the material, local chemical bonds and electronic distribution are regulated, accurate lattice regulation and control are realized, and the sodium storage performance of the material is improved.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the high-entropy polyanion-type cathode material with anion and cation functionalized doping modification comprises a cathode core and a carbon coating layer, wherein the chemical formula of the cathode core is Na δ A α B β C γ X σ Y m Z n Wherein A is V 3+ And/or Fe 2+ B is Cu 2 + 、Mn 2+ And Cr 3+ C is Ni 2+ And/or Ti 4+ X is PO 4 3- And/or P 2 O 7 4- Y is SO 4 2- 、N 3- And F - Z is BO 3 3- 、SiO 4 4- 、S 2- And Cl - 1.2 is more than or equal to delta is more than or equal to 4.8,0.7 is more than or equal to alpha is more than or equal to 1.4,0.16 is more than or equal to beta is more than or equal to 0.75,0.3 is more than or equal to gamma is more than or equal to 0.8,2.1 is more than or equal to sigma is more than or equal to 2.8,0.15 is more than or equal to m is more than or equal to 0.75,0.15 is more than or equal to n is more than or equal to 0.6; the particle size of the high-entropy polyanionic anode material is 10-40 mu m, and the thickness of the carbon coating layer is 5-10 nm.
Preferably, 2. Ltoreq. Delta. Ltoreq. 3.5,0.8. Ltoreq. Alpha. Ltoreq. 1.2,0.3. Ltoreq. Beta. Ltoreq. 0.6,0.4. Ltoreq. Gamma. Ltoreq 0.6,2.2. Ltoreq. Sigma. Ltoreq. 2.6,0.2. Ltoreq. M.ltoreq. 0.5,0.2. Ltoreq.n.ltoreq.0.4.
Preferably, the chemical formula of the positive electrode inner core is Na 2.6 VFe 0.2 Mn 0.3 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.4 (BO 3 ) 0.4 、Na 3 VMn 0.5 Ti 0.5 (PO 4 ) 2.4 (SO 4 ) 0.3 (BO 3 ) 0.3 、Na 3.1 V 0.8 Fe 0.4 Mn 0.4 Ti 0.4 (PO 4 ) 2.4 (SO 4 ) 0.3 (BO 3 ) 0.3 、Na 2.4 VCu 0.6 Ti 0.4 (PO 4 ) 2.6 (SO 4 ) 0.2 (BO 3 ) 0.2 、Na 3.5 Fe 0.9 Mn 0.6 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.5 (BO 3 ) 0.3 Or Na 3.3 VFe 0.2 Cu 0.3 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.4 (BO 3 ) 0.4 。
The invention relates to a preparation method of a modified high-entropy polyanion type positive electrode material by anion and cation functionalized doping, which comprises the following steps:
(1) Adding a sodium source, a transition metal A source, a transition metal B source, a transition metal C source, a polyanion X source, a polyanion Y source, a polyanion Z source and a carbon source into a volatile solvent, heating and stirring until the solvent is evaporated to dryness, and obtaining a precursor;
(2) Sintering the precursor in a protective gas atmosphere to obtain a high-entropy polyanion type positive electrode material modified by anion and cation functionalized doping;
wherein, in the step (1), the molar ratio of the sodium source to the total amount of the transition metal source is 0.6-2.4, the molar ratio of the sodium source to the total amount of the polyanion source is 0.4-1.6, and the molar ratio of the carbon source to the total amount of the transition metal source is 1-6:1;
in the step (2), the sintering temperature is 300-800 ℃, and the time is 4-20 h.
Preferably, in the step (1), the molar ratio of the sodium source to the total amount of the transition metal source is 1 to 2:1, the molar ratio of the sodium source to the total amount of the polyanion source is 0.8 to 1.2.
Preferably, in the step (1), the sodium source includes one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium formate, sodium acetate and sodium nitrate.
Preferably, in the step (1), in the transition metal a source, the vanadium source is one or more of vanadium trichloride, vanadium tribromide, vanadium trioxide, vanadium acetylacetonate, vanadium oxychloride, vanadyl sulfate, vanadyl oxalate, vanadium dioxide, vanadyl acetylacetonate, vanadium oxychloride, sodium vanadate, sodium metavanadate, ammonium metavanadate, vanadium pentoxide and metallurgical vanadium slag; the iron source is more than one of ferrous fluoride, ferrous chloride, ferrous bromide, ferrous nitrate, ferrous sulfate, ferrous carbonate, ferrous oxalate, ferrous acetate, ferrous hydroxide, ferrous oxide, ferrous sulfide, ferrous acetylacetonate, ferric trifluoride, ferric chloride, ferric tribromide, ferric nitrate, ferric sulfate, ferric carbonate, ferric oxalate, ferric acetate, ferric hydroxide, ferric oxide, ferroferric oxide and ferric acetylacetonate.
In the transition metal B source, the copper source is more than one of copper fluoride, copper chloride, copper bromide, copper nitrate, copper sulfate, copper carbonate, copper oxalate, copper acetate, basic copper carbonate, copper hydroxide, copper oxide, copper sulfide and copper acetylacetonate; the manganese source is more than one of manganous fluoride, manganous chloride, manganous bromide, manganous nitrate, manganous sulfate, manganous carbonate, manganous oxalate, manganous acetate, manganous hydroxide, manganous oxide, manganous sulfide, manganous acetylacetonate, manganous trifluoride, manganous trichloride, manganous tribromide, manganous nitrate, manganous sulfate, manganous carbonate, manganous oxalate, manganous acetate, manganous hydroxide, manganous trioxide, manganese dioxide and manganous acetylacetonate; the chromium source comprises more than one of chromium trichloride, chromium tribromide, chromium nitrate, chromium sulfate, chromium oxalate, chromium formate, chromium acetate, chromium chromate, chromium lactate, basic chromium sulfate, chromium perchlorate, chromium sesquioxide, chromium hydroxide, chromium acetylacetonate, sodium chromate and sodium dichromate.
In the transition metal C source, the nickel source is more than one of nickelous fluoride, nickelous chloride, nickelous bromide, nickelous nitrate, nickelous sulfate, nickelous carbonate, nickelous oxalate, nickelous acetate, nickelous hydroxide, nickelous oxide, nickelous sulfide and nickelous acetylacetonate; the titanium source is more than one of titanium chloride, titanium bromide, titanium sulfate, titanium nitrate, titanium oxalate, titanium formate, titanium acetate, titanium dioxide, titanium acetylacetonate and tetrabutyl titanate;
when the transition metal exhibits a high valence, a reducing agent is also added.
Preferably, the reducing agent includes one or more of ascorbic acid, oxalic acid, citric acid, charcoal, and hydroxylamine hydrochloride.
Preferably, in step (1), the polyanion X source is PO 4 3- 、P 2 O 7 4- The corresponding acid and/or salt; the polyanion Y source comprises SO 4 2- 、N 3- 、F - The corresponding acid and/or salt; the polyanion Z source is BO 3 3- 、SiO 4 4- 、S 2- 、Cl - SO 4 2- 、N 3- 、F - The corresponding acid and/or salt.
Preferably, in the step (1), the carbon source includes one or more of citric acid, sodium citrate, sodium oleate, oleic acid, polyvinylpyrrolidone, glucose, sucrose, starch, dopamine hydrochloride, starch, graphene, ketjen black and carbon nanotubes.
Preferably, in the step (1), the solvent is one or more of water, ethanol, acetone and ethyl acetate; the heating and stirring temperature is 60-200 ℃, the stirring speed is 300-1000 rpm, and the time is 1-6 h.
Preferably, in the step (2), the sintering temperature is 400-600 ℃, and the time is 6-12 h.
Preferably, in the step (2), the protective gas is nitrogen or inert gas.
The positive electrode material of the sodium-ion battery adopts the anion-cation functionalized doped modified high-entropy polyanion-type positive electrode material.
Advantageous effects
1. The invention provides a cation and anion functionalized doped modified high-entropy polyanion-type cathode material, wherein the distribution of a transition metal position and a polyanion position group is directionally designed by adopting the synergistic action of anions and cations, a transition metal A and a polyanion X are used for constructing a stable structure skeleton, a transition metal B and a polyanion Y are used for increasing the working voltage, and a transition metal C and a polyanion Z are used for adjusting the structure band gap; through the collaborative design of stabilizing a structural frame, improving working voltage and reducing structural band gap, a high-entropy structure compatible with anions and cations is constructed, the normalized growth and the directional construction of a crystalline phase are controlled, and the collaborative control of cost advantage, voltage capacity advantage and conductivity advantage is realized. Compared with the traditional doping coating strategy, the design and synthesis of the high-entropy NASICON material adopt a scheme of functional group matching, and the introduced elements not only do not lose the sodium storage performance of the material, but also can synergistically strengthen the inherent defects of the material; the intrinsic physical properties and substance crystal phases are regulated and controlled from the crystal structure of the material, the local electronic structure is synchronously changed, and the intrinsic electronic conductivity is improved.
2. The invention provides a sodium ion battery assembled by taking the anion-cation functionalized doped and modified high-entropy polyanion type positive electrode material as the positive electrode material, which has higher discharge capacity and the capacity retention rate of up to 98 percent.
Drawings
Fig. 1 is an XRD spectrum of the high-entropy polyanionic cathode material prepared in example 1 of the present invention.
Fig. 2 is a structural model of the high-entropy polyanionic cathode material prepared in example 2 of the present invention.
Fig. 3 is an SEM image of the high-entropy polyanionic positive electrode material prepared in example 2 of the present invention.
FIG. 4 is a charge-discharge curve diagram of the high-entropy polyanionic cathode material prepared in example 3 of the present invention at 0.2C.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1
(1) Adding sodium nitrate, vanadium acetylacetonate, manganese acetate, tetrabutyl titanate, phosphoric acid, ammonium sulfate, boric acid in a molar ratio of 2.4; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace in an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the anion-cation functionalized doped modified high-entropy polyanion-type positive electrode material.
The XRD pattern of the cathode material is shown in figure 1, and as can be seen from figure 1, the diffraction peak and the standard spectrum of the cathode material can be correspondingly assigned, and the crystallinity is good, which indicates that the obtained high-entropy polyanionic cathode material is a pure phase. The crystal structures of the corresponding components are built through a first principle, and as shown in FIG. 2, the results show that stable high-entropy solid solution can be obtained by the design, and the material shows a lower band gap through simulation calculation, so that the advantages of the high-entropy material design are verified.
Example 2
(2) Adding sodium acetate, ferrous acetylacetonate, copper acetate, nickel nitrate, pyrophosphoric acid, ammonium fluoride, silicic acid in a molar ratio of 4.6 to 1.0.0.2; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 1000rpm at the temperature of 200 ℃, and completely volatilizing the solvent after stirring for 1h to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace in an argon atmosphere, and sintering for 10h at 400 ℃ to obtain the anion-cation functionalized doped modified high-entropy polyanion-type positive electrode material.
The XRD test result of the cathode material shows that the diffraction peak and the standard spectrum of the cathode material can be correspondingly attributed, and the crystallinity is good, which indicates that the obtained high-entropy polyanionic cathode material is a pure phase.
An SEM image of the modified high-entropy polyanionic cathode material is shown in FIG. 3, and as can be seen from FIG. 3, the prepared material has a bulk structure of about 20 μm.
Example 3
(1) Adding sodium formate, ammonium metavanadate, ferrous nitrate, manganese acetate, tetrabutyl titanate, phosphoric acid, ammonium sulfate and boric acid to an ethanol solution containing polyvinylpyrrolidone at a molar ratio of polyvinylpyrrolidone to transition metal salt of 5:1; then placing the mixed solution in a constant temperature heating table, performing magnetic stirring at the speed of 800rpm at the temperature of 100 ℃, and completely volatilizing the solvent after stirring for 1 hour to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace in an argon atmosphere, and sintering for 6h at 600 ℃ to obtain the anion-cation functionalized doped modified high-entropy polyanion-type positive electrode material.
The XRD test result of the cathode material shows that the diffraction peak and the standard spectrum of the cathode material can be correspondingly attributed, and the crystallinity is good, which indicates that the obtained high-entropy polyanionic cathode material is a pure phase.
Comparative example 1
(1) Adding sodium formate, ammonium metavanadate and phosphoric acid into an ethanol solution containing polyvinylpyrrolidone at a molar ratio of 3; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 2
(1) Adding sodium nitrate, vanadium acetylacetonate, tetrabutyl titanate, phosphoric acid, ammonium sulfate and boric acid in a molar ratio of 1.3; then placing the mixed solution in a constant temperature heating table, performing magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 3
(1) Adding sodium nitrate, vanadium acetylacetonate, manganese acetate, tetrabutyl titanate, phosphoric acid, ammonium sulfate in a molar ratio of 1.7; then placing the mixed solution in a constant temperature heating table, performing magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 4
(1) Adding sodium nitrate, vanadium acetylacetonate, manganese acetate, phosphoric acid, boric acid in a molar ratio of 4; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 5
(1) Adding sodium nitrate, vanadium acetylacetonate, aluminum acetate, zinc acetate, phosphoric acid, ammonium sulfate, boric acid in a molar ratio of 2.6; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 6
(1) Adding sodium nitrate, vanadium acetylacetonate, manganese acetate, tetrabutyl titanate, phosphoric acid, ammonium sulfate, boric acid in a molar ratio of 3; then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Comparative example 7
(1) Sodium nitrate, vanadium acetylacetonate, manganese acetate, tetrabutyl titanate, phosphoric acid, ammonium sulfate, boric acid in a molar ratio of 3.1.0. Then placing the mixed solution in a constant temperature heating table, carrying out magnetic stirring at the speed of 300rpm at the temperature of 60 ℃, and completely volatilizing the solvent after stirring for 6 hours to obtain a precursor;
(2) And (3) placing the precursor in a tubular furnace with an argon atmosphere, and sintering for 4h at 800 ℃ to obtain the high-entropy polyanionic anode material.
Sodium ion coin cells assembled from examples and comparative examples: firstly, preparing a positive pole piece: the prepared high-entropy polyanion material serving as a positive electrode active material, conductive Carbon Black (Carbon Black) and a conductive binder PTFE are mixed in an agate mortar according to the mass ratio of 8. Grinding, rolling into 0.8 × 0.8 square pole piece with active material surface density of 8-10mg/cm 2 . And (4) drying the rolled pole piece for 6 hours in vacuum at 120 ℃. Cooling to below 30 deg.C, and placing into glove box. The battery assembling process comprises the following steps: and assembling the button cell by adopting a CR2032 electrode shell according to the order of placing the cathode shell, the metal sodium, the diaphragm, the anode piece, the gasket, the spring piece and the anode shell. The diaphragm is made of glass fiber, the electrolyte is 1.0M sodium perchlorate (NaClO 4) and Propylene Carbonate (PC) solution containing 2% fluoroethylene carbonate (FEC), and the addition amount of the electrolyte is 120 mu L. After assembly, the assembly was encapsulated in a button cell press, and after standing for 6 hours, the assembled cell was subjected to a charge and discharge test at room temperature (25 ℃) using a wuhan blue electric test system, and the assembled button cell of example 1 was tested at 0.2C (1c =110mah g) -1 ) The following charge and discharge curves are shown in fig. 4, and the test results of the examples and comparative examples are shown in table 1:
TABLE 1
Figure BDA0003862018040000111
As can be seen from Table 1, the 0.2C specific discharge capacity of the batteries prepared by the positive electrode materials of the invention in examples 1-3 can reach 110mAh g -1 Above, the 2C specific discharge capacity can reach 105mAh g -1 The capacity retention rate of the capacitor can reach more than 97 percent under the condition of 2C circulation for 100 weeks, and the discharge medium voltage can reach more than 3.455V. Through the cooperative high entropy regulation of anions and cations, the 0.2C specific discharge capacity can reach 117mAh g -1 And the 2C specific discharge capacity can reach 111mAh g -1 The capacity retention rate can reach 98% after circulation for 100 weeks under 2C, and the discharge medium voltage can reach 3.495V.
Compared with the comparative example 1, the method has the advantages that a high-entropy anion-cation collaborative doping strategy is introduced, and the material charging and discharging platform is effectively improved. The invention proves that the anion and cation synergistic doping can effectively reduce the cost of raw materials, adjust local chemical bonds and electron distribution, realize accurate lattice regulation, obviously improve the discharge capacity of the doped material and greatly improve the cycle retention rate.
As can be seen from the comparison between example 1 and comparative example 2, the synergistic design of cations has a significant improvement effect on both the working voltage and the discharge capacity of the material. Only the simultaneous presence of the transition metal source A, B, C can the better electrochemical performance be obtained.
As can be seen from comparison of example 1 and comparative example 3, the synergistic effect of the anions has a significant improvement effect on the cycle stability and discharge capacity of the material. Only when the polyanionic source X, Y, Z exists at the same time can the better sodium storage performance be obtained.
From the comparison between example 1 and comparative example 4, it can be seen that the design of the anionic and cationic synergistic components has a directional effect on the improvement of the overall electrochemical performance of the material. Only the simultaneous existence of the transition metal source A, B, C and the polyanion source X, Y, Z can the structural stability, the working voltage and the conductive property of the material be synergistically regulated and controlled.
As can be seen from the comparison between example 1 and comparative example 5, the effect of improving the sodium storage performance by the directional control structure can be achieved only by selecting the transition metal source. Transition metal sources that are not limited in scope do not have a functional characteristic and cannot achieve good electrochemical performance even if a high entropy structure can be obtained.
As can be seen from the comparison between example 1 and comparative example 6, the effect of improving the sodium storage performance by directionally regulating the structural stability of the crystal structure can be achieved only if the proportion of the transition metal source is proper. High entropy components which are not in the limited range cannot achieve ideal regulation and control effects, and good cycle performance is difficult to obtain.
As can be seen from comparison between example 1 and comparative example 7, the effect of directionally regulating voltage and improving sodium storage performance can be achieved only if the ratio of the polyanion source is proper. High entropy components that are not within the defined range do not achieve the desired operating voltage and it is difficult to obtain higher energy densities. The high-entropy design with the transition metal source and the polyanion source in the limited proportion can not only fully reflect the electrochemical characteristics of each element/group, improve the voltage and the capacity, but also improve the disorder degree of the whole structure, relieve the phase transition of the material in the circulating process and further improve the circulating life of the material.
In summary, the invention includes but is not limited to the above embodiments, and any equivalent replacement or local modification made under the spirit and principle of the invention should be considered as being within the protection scope of the invention.

Claims (10)

1. A high-entropy polyanion type cathode material modified by anion and cation functionalized doping is characterized in that: the cathode material comprises a cathode core and a carbon coating layer, wherein the chemical formula of the cathode core is Na δ A α B β C γ X σ Y m Z n Wherein A is V 3+ And/or Fe 2+ B is Cu 2+ 、Mn 2+ And Cr 3+ C is Ni 2+ And/or Ti 4+ X is PO 4 3- And/or P 2 O 7 4- Y is SO 4 2- 、N 3- And F - Z is BO 3 3- 、SiO 4 4- 、S 2- And Cl - More than one of the above, 1.2 is more than or equal to delta and less than or equal to 4.8,0.7 is more than or equal to alpha and less than or equal to 1.4,0.16 is more than or equal to beta and less than or equal to 0.75,0.3 is more than or equal to gamma and less than or equal to 0.8,2.1 is more than or equal to sigma and less than or equal to 2.8,0.15 is more than or equal to m and less than or equal to 0.75,0.15 is more than or equal to 0.6; the particle size of the high-entropy polyanionic anode material is 10-40 mu m, and the thickness of the carbon coating layer is 5-10 nm.
2. The anion-cation functionalized doped modified high-entropy polyanionic positive electrode material of claim 1, which is characterized in that: 2 is more than or equal to delta and less than or equal to 3.5,0.8 is more than or equal to alpha and less than or equal to 1.2,0.3 is more than or equal to beta and less than or equal to 0.6,0.4 is more than or equal to gamma and less than or equal to 0.6,2.2 is more than or equal to sigma and less than or equal to 2.6,0.2 is more than or equal to m and less than or equal to 0.5,0.2 and less than or equal to 0.4.
3. The anion-cation functionalized doped modified high-entropy polyanionic positive electrode material of claim 1, which is characterized in that: the chemical formula of the anode core is
Na 2.6 VFe 0.2 Mn 0.3 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.4 (BO 3 ) 0.4 、Na 3 VMn 0.5 Ti 0.5 (PO 4 ) 2.4 (SO 4 ) 0.3 (BO 3 ) 0.3 、Na 3.1 V 0.8 Fe 0.4 Mn 0.4 Ti 0.4 (PO 4 ) 2.4 (SO 4 ) 0.3 (BO 3 ) 0.3 、
Na 2.4 VCu 0.6 Ti 0.4 (PO 4 ) 2.6 (SO 4 ) 0.2 (BO 3 ) 0.2 、Na 3.5 Fe 0.9 Mn 0.6 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.5 (BO 3 ) 0.3 Or Na 3.3 VFe 0.2 Cu 0.3 Ti 0.5 (PO 4 ) 2.2 (SO 4 ) 0.4 (BO 3 ) 0.4 。
4. A method for preparing the anion-cation functionalized doped modified high-entropy polyanionic positive electrode material according to any one of claims 1 to 3, which is characterized in that: the method comprises the following steps:
(1) Adding a sodium source, a transition metal A source, a transition metal B source, a transition metal C source, a polyanion X source, a polyanion Y source, a polyanion Z source and a carbon source into a volatile solvent, heating and stirring until the solvent is evaporated to dryness, and obtaining a precursor;
(2) Sintering the precursor in a protective gas atmosphere to obtain a high-entropy polyanion type positive electrode material modified by anion and cation functionalized doping;
wherein, in the step (1), the molar ratio of the sodium source to the total amount of the transition metal source is 0.6-2.4, the molar ratio of the sodium source to the total amount of the polyanion source is 0.4-1.6, and the molar ratio of the carbon source to the total amount of the transition metal source is 1-6:1;
in the step (2), the sintering temperature is 300-800 ℃, and the time is 4-20 h.
5. The preparation method of the anion-cation functionalized doped modified high-entropy polyanionic positive electrode material according to claim 4, characterized in that: in the step (1), the molar ratio of the sodium source to the total amount of the transition metal source is 1-2:1, the molar ratio of the sodium source to the total amount of the polyanion source is 0.8-1.2, and the molar ratio of the carbon source to the total amount of the transition metal source is 3-6:1.
6. The preparation method of the anion-cation functionalized doping modified high-entropy polyanion-type cathode material according to claim 4, characterized in that: in the step (1), the sodium source comprises more than one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium formate, sodium acetate and sodium nitrate;
in the step (1), in the transition metal A source, the vanadium source is more than one of vanadium trichloride, vanadium tribromide, vanadium trioxide, vanadium acetylacetonate, vanadium oxychloride, vanadyl sulfate, vanadyl oxalate, vanadium dioxide, vanadyl acetylacetonate, vanadium trichloride, sodium vanadate, sodium metavanadate, ammonium metavanadate, vanadium pentoxide and metallurgical vanadium slag; the iron source is more than one of ferrous fluoride, ferrous chloride, ferrous bromide, ferrous nitrate, ferrous sulfate, ferrous carbonate, ferrous oxalate, ferrous acetate, ferrous hydroxide, ferrous oxide, ferrous sulfide, ferrous acetylacetonate, ferric trifluoride, ferric chloride, ferric tribromide, ferric nitrate, ferric sulfate, ferric carbonate, ferric oxalate, ferric acetate, ferric hydroxide, ferric oxide, ferroferric oxide and ferric acetylacetonate;
in the transition metal B source, the copper source is more than one of copper fluoride, copper chloride, copper bromide, copper nitrate, copper sulfate, copper carbonate, copper oxalate, copper acetate, basic copper carbonate, copper hydroxide, copper oxide, copper sulfide and copper acetylacetonate; the manganese source is more than one of manganous fluoride, manganous chloride, manganous bromide, manganous nitrate, manganous sulfate, manganous carbonate, manganous oxalate, manganous acetate, manganous hydroxide, manganous oxide, manganous sulfide, manganous acetylacetonate, manganous trifluoride, manganous trichloride, manganous tribromide, manganous nitrate, manganous sulfate, manganous carbonate, manganous oxalate, manganous acetate, manganous hydroxide, manganous oxide, manganese dioxide and manganous acetylacetonate; the chromium source comprises more than one of chromium trichloride, chromium tribromide, chromium nitrate, chromium sulfate, chromium oxalate, chromium formate, chromium acetate, chromium chromate, chromium lactate, basic chromium sulfate, chromium perchlorate, chromium sesquioxide, chromium hydroxide, chromium acetylacetonate, sodium chromate and sodium dichromate;
in the transition metal C source, the nickel source is more than one of nickelous fluoride, nickelous chloride, nickelous bromide, nickelous nitrate, nickelous sulfate, nickelous carbonate, nickelous oxalate, nickelous acetate, nickelous hydroxide, nickelous oxide, nickelous sulfide and nickelous acetylacetonate; the titanium source is more than one of titanium chloride, titanium bromide, titanium sulfate, titanium nitrate, titanium oxalate, titanium formate, titanium acetate, titanium dioxide, titanium acetylacetonate and tetrabutyl titanate;
when the transition metal presents high valence, a reducing agent is also added;
in the step (1), the polyanion X source is PO 4 3- 、P 2 O 7 4- The corresponding acid and/or salt; said polyanion Y source comprises SO 4 2- 、N 3- 、F - The corresponding acid and/or salt; the polyanionic Z source is BO 3 3- 、SiO 4 4- 、S 2- 、Cl - SO 4 2- 、N 3- 、F - The corresponding acid and/or salt;
in the step (1), the carbon source comprises more than one of citric acid, sodium citrate, sodium oleate, oleic acid, polyvinylpyrrolidone, glucose, sucrose, starch, dopamine hydrochloride, starch, graphene, ketjen black and carbon nanotubes.
7. The preparation method of the anion-cation functionalized doped modified high-entropy polyanionic positive electrode material according to claim 6, which is characterized in that: the reducing agent comprises more than one of ascorbic acid, oxalic acid, citric acid, charcoal and hydroxylamine hydrochloride.
8. The preparation method of the anion-cation functionalized doped modified high-entropy polyanionic positive electrode material according to claim 6, which is characterized in that: in the step (1), the solvent is more than one of water, ethanol, acetone and ethyl acetate; the heating and stirring temperature is 60-200 ℃, the stirring speed is 300-1000 rpm, and the time is 1-6 h.
9. The preparation method of the anion-cation functionalized doped modified high-entropy polyanionic positive electrode material according to claim 6, which is characterized in that: in the step (2), the sintering temperature is 400-600 ℃, and the time is 6-12 h; the protective gas is nitrogen or inert gas.
10. A sodium ion battery, characterized by: the positive electrode material of the battery adopts the anion-cation functionalized doping modified high-entropy polyanion-type positive electrode material as claimed in any one of claims 1 to 3.
CN202211167558.XA 2022-09-23 2022-09-23 Anion-cation functionalized doped modified high-entropy polyanion type positive electrode material, preparation method and application thereof Pending CN115360340A (en)

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