CN115411251A - Negative electrode material and preparation method and application thereof - Google Patents
Negative electrode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a negative electrode material, which comprises a porous framework and metal sodium filled in the porous framework; the porous skeleton comprises doped porous carbon fibers; the doping element of the doped porous carbon fiber comprises any one or at least two of O, S, N, P or F. According to the invention, metal sodium is limited in a porous framework, especially in doped porous carbon fibers, so that the growth of sodium dendrite is inhibited, the volume expansion is limited, the sodium affinity of the material can be improved by doping, the nucleation overpotential is reduced, the uniform deposition of sodium metal is induced, the component of a solid electrolyte interface film is further modified, and meanwhile, the effects of providing space for sodium metal deposition, reducing the nucleation barrier of sodium deposition and reducing local current density are achieved, and the cycle stability and cycle life of the obtained cathode material are obviously improved.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and relates to a negative electrode material, and a preparation method and application thereof
Background
Lithium ion batteries, as a representative of secondary batteries, have already led to markets of portable electronic products and Electric Vehicles (EVs), and have also begun to enter the energy storage field in recent years. However, the lithium resource is limited, and the abundance of Li in the crust is 0.0065%, which is far lower than the storage capacity of Na (2.74%), which is not enough to support the rapid expansion of large energy storage stations. The principles of Sodium Ion Batteries (SIBs) are similar to those of lithium ion batteries, and the development experience of the lithium ion batteries can be used as reference for the sodium ion batteries, so that the sodium ion batteries are regarded as a promising energy storage source choice based on the abundance of materials and the availability of production equipment and processes.
At present, in the material selection of a specific sodium ion battery, the commercialized graphite anode material of the lithium ion battery cannot be directly applied to the sodium ion anode, and only a few anode materials such as hard carbon have the performance capable of being applied to the sodium ion battery. Therefore, the development of the negative electrode material of the sodium-ion battery is the focus of research, and for the research and the application of the sodium metal negative electrode, the advantages of very high theoretical capacity (1166 mAh/g) and lower oxidation-reduction potential are shown; when the metal sodium is used as the negative electrode, and the sulfur, the oxygen and the like are used as the positive electrode, the battery energy storage system has higher theoretical energy density, and is very hopeful to be developed into a next-generation battery energy storage system.
Although sodium metal cathodes have many advantages, the development of sodium metal cathodes still faces many challenges. The reason is that the sodium ions are easy to form dendritic crystals at the interface position due to uneven deposition in the battery circulation process, on one hand, the dendritic crystals penetrate through a diaphragm along with the growth of the dendritic crystals to cause short circuit so as to cause explosion, on the other hand, a solid electrolyte interface film (SEI film) on the surface of a negative electrode is damaged, so that the bare sodium metal reacts with the electrolyte, the utilization rate of the electrode is reduced while the electrolyte is consumed, and due to the structural characteristic that the sodium metal negative electrode has no framework, the volume expansion is infinite under the condition of 100% charging and discharging, and the stability of the electrode is seriously damaged.
In order to solve the problems, CN110400963A proposes a secondary battery of a metal sodium or sodium-potassium alloy negative electrode/polyacrylonitrile sulfide positive electrode, which comprises a polyacrylonitrile sulfide positive electrode, a metal sodium or sodium-potassium alloy negative electrode, a potassium-containing organic electrolyte and a diaphragmThe novel battery system adopts a high-cycle-performance polyacrylonitrile sulfide positive electrode to replace a sulfur-carbon positive electrode with poor cycle performance, adopts a sodium-potassium alloy negative electrode or a metal sodium negative electrode surface to alloy with potassium ions in electrolyte in the battery charging and discharging process, utilizes the eutectic liquidization effect of the sodium-potassium alloy on the negative electrode surface to inhibit the growth of dendrites on the negative electrode surface, and manufactures a sodium or sodium-potassium negative electrode/polyacrylonitrile sulfide positive electrode secondary battery with high specific capacity and high cycle performance; CN111430660A discloses an ion-electron mixed conductive metallic sodium cathode, which is formed by melting and mixing solid electrolyte powder and metallic sodium, wherein the metallic sodium forms a matrix of the metallic sodium cathode, and Na is constructed in the metallic sodium matrix by the solid electrolyte + A conductive network in which the solid electrolyte is coated with SnO 2 NZSP particles of (1), wherein NZSP means Na 3+x Zr 2 Si 2+x P 1-x O 12 (ii) a The metal sodium cathode obtained by the invention has excellent cycling stability and lower electrochemical impedance, and shows high cycling stability and lower capacity fading in a full battery test. The solid electrolyte is directly fused into the cathode, the preparation and operation methods are complex, and the coating effect and coated SnO of NZSP particles need to be ensured 2 The NZSP particles have a good dispersion effect in the electrode, and thus there is a certain obstacle in mass production.
From the above, it is still necessary to develop a new sodium metal negative electrode and a related technical solution of the manufacturing method thereof, which can solve the problem of suppressing the growth of dendrites by a simpler and more convenient process, thereby improving the stability of the negative electrode and further improving the performance of the battery.
Disclosure of Invention
In view of the problems in the prior art, the present invention aims to provide an anode material comprising a porous skeleton and metallic sodium filled in the porous skeleton; the porous skeleton comprises doped porous carbon fibers; the doping element of the doped porous carbon fiber comprises any one or at least two of O, S, N, P or F. According to the invention, metal sodium is limited in the porous framework, especially in the doped porous carbon fiber, so that the growth of sodium dendrite can be inhibited, and the components of the solid electrolyte interface membrane can be modified, and meanwhile, the method has the functions of providing space for sodium metal deposition, reducing the nucleation barrier of sodium deposition and reducing local current density, and the cycle stability and the cycle life of the obtained cathode material are obviously improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an anode material, which includes a porous skeleton and metallic sodium filled in the porous skeleton; the porous skeleton comprises doped porous carbon fibers; the doping element of the doped porous carbon fiber comprises any one or at least two of O, S, N, P or F.
According to the invention, metal sodium is limited in a porous framework, particularly in doped porous carbon fibers, and a gap structure is used as a framework for supporting the metal sodium, so that the growth of sodium dendrite can be inhibited, the volume expansion can be limited, the sodium affinity of the material can be improved by doping, the nucleation overpotential is reduced, the uniform deposition of sodium metal is induced, the effect of modifying the components of a solid electrolyte interface film is further achieved, and meanwhile, the effects of providing space for sodium metal deposition, reducing the nucleation barrier of sodium deposition and reducing the local current density are achieved, and the cycle stability and the cycle life of the obtained cathode material are obviously improved.
It should be noted that the doping element of the doped porous carbon fiber of the present invention includes any one or at least two of O, S, N, P or F, and typical but non-limiting examples of the combination include a combination of O and S, a combination of O and N, a combination of O and P, a combination of O and F, a combination of S and N, a combination of S and P, a combination of S and F, a combination of N and P, a combination of N and F or a combination of P and F.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
In a preferred embodiment of the present invention, the mass of the porous skeleton accounts for 3wt% to 30wt% of the total mass of the negative electrode material, for example, 3wt%, 6wt%, 9wt%, 12wt%, 15wt%, 18wt%, 21wt%, 24wt%, 27wt%, or 30wt%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.
Preferably, the mass of the metallic sodium is 70wt% to 97wt% of the total mass of the anode material, such as 70wt%, 73wt%, 76wt%, 79wt%, 82wt%, 85wt%, 88wt%, 91wt%, 94wt%, or 97wt%, and the like, but is not limited to the recited values, and other values not recited in the above-mentioned numerical range are also applicable.
Preferably, the mass of the porous skeleton accounts for 23wt% to 28wt%, such as 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, or 28wt%, etc., of the total mass of the anode material, but is not limited to the enumerated values, and other unrecited values within the above-mentioned range of values are also applicable.
Preferably, the mass of the metal sodium is 2.5 to 3.3 times, for example, 2.5 times, 2.6 times, 2.7 times, 2.8 times, 2.9 times, 3 times, 3.1 times, 3.2 times, or 3.3 times, the mass of the porous skeleton, and the like, but is not limited to the enumerated values, and other unrecited values within the above numerical range are also applicable.
In a preferred embodiment of the present invention, the mass of the doping element is 0.005wt% to 1wt%, for example, 0.005wt%, 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt% of the total mass of the doped porous carbon fiber, but is not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.
In a preferred embodiment of the present invention, the porosity of the doped porous carbon fiber is 40% to 98%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 98%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.
Within the preferable range of the porosity, the wettability of the material and sodium can be improved by properly increasing the porosity, the specific surface area of the material can be improved, the effective current density can be reduced, and the volume expansion and the volume change buffering during the deposition of sodium metal can be accommodated.
Preferably, the pore size of the doped porous carbon fibers is 5 to 100 μm, for example, 5 μm, 15 μm, 25 μm, 35 μm, 45 μm, 55 μm, 65 μm, 75 μm, 85 μm, 95 μm, or 100 μm, but is not limited to the recited values, and other values not recited within the above numerical range are also applicable.
Preferably, the length of the doped porous carbon fibers is 3 to 6mm, such as 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, or 6mm, but not limited to the recited values, and other values not recited within the above numerical range are also applicable.
Preferably, the doped porous carbon fibers have an outer diameter of 5 to 20 μm, for example, 5 μm, 8 μm, 11 μm, 14 μm, 17 μm, or 20 μm, but are not limited to the recited values, and other unrecited values within the above-mentioned range of values are also applicable.
In a second aspect, the present invention provides a method for preparing the anode material according to the first aspect, the method comprising: heating and heating metal sodium in an inert atmosphere to melt the metal sodium; and immersing the porous framework into molten metal sodium for filling to obtain the negative electrode material.
As a preferable embodiment of the present invention, the mass ratio of the metallic sodium to the porous skeleton is (2.5 to 3.3) from 1, for example, 2.5.
In order to better inhibit the growth of sodium dendrites and the volume expansion thereof, the mass ratio of the metal sodium to the porous framework needs to be controlled, when the metal sodium is too much, the porous framework cannot effectively act on all the metal sodium, and if the metal sodium is too little and the filling amount of the porous framework is not enough, the energy density of the battery is too low.
Preferably, the temperature for the heat-raising is 100 to 300 ℃, for example, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃ or 300 ℃, but is not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.
The heat preservation temperature for heating and temperature rise used in the invention is to ensure that the metallic sodium can be completely melted, and the porous framework material and the structure thereof can not be damaged, and the technical personnel in the field can select and adjust the temperature according to the actual situation.
Preferably, after the immersion time is over, the negative electrode material is pulled away from the molten metal sodium and is naturally cooled under the protection of inert atmosphere.
Preferably, the inert atmosphere comprises any one of argon, nitrogen or helium or a combination of at least two of these, typical but non-limiting examples of which include argon and nitrogen, argon and helium, nitrogen and helium or argon and nitrogen and helium.
As a preferable technical scheme, the preparation method of the porous skeleton comprises the steps of uniformly mixing the porous carbon fiber and the doping source, and then placing the mixture in an inert atmosphere for heating reaction to obtain the doped porous carbon fiber serving as the porous skeleton.
As a preferred embodiment of the present invention, the doping source includes any one or a combination of at least two of an oxygen source, a sulfur source, a nitrogen source, a phosphorus source, or a fluorine source, and typical but non-limiting examples of the combination include a combination of an oxygen source and a sulfur source, a combination of an oxygen source and a nitrogen source, a combination of an oxygen source and a phosphorus source, a combination of an oxygen source and a fluorine source, a combination of a sulfur source and a nitrogen source, a combination of a sulfur source and a phosphorus source, a combination of a sulfur source and a fluorine source, a combination of a nitrogen source and a phosphorus source, a combination of a nitrogen source and a fluorine source, and a combination of a phosphorus source and a fluorine source.
Preferably, the oxygen source comprises ammonium oxalate and/or ammonium persulfate.
Preferably, the source of sulphur comprises any one or combination of at least two of sulphur, a sulphur-containing organic compound, a polysulphide or a sulphate, typical but non-limiting examples of such combinations include sulphur in combination with a sulphur-containing organic compound, sulphur in combination with a polysulphide, sulphur in combination with a sulphate, a sulphur-containing organic compound in combination with a polysulphide, a sulphur-containing organic compound in combination with a sulphate or a polysulphide in combination with a sulphate.
Preferably, the nitrogen source comprises any one of urea, melamine, cyanamide, dicyandiamide, polyaniline or polypyrrole, or a combination of at least two of the combinations, typical but non-limiting examples of which include urea and melamine, urea and cyanamide, urea and dicyandiamide, urea and polyaniline, urea and polypyrrole, melamine and cyanamide, melamine and dicyandiamide, melamine and polyaniline, melamine and polypyrrole, or polyaniline and polypyrrole.
Preferably, the source of phosphorus comprises any one of or a combination of at least two of monosodium phosphate, sodium monohydrogen phosphate, phosphoric acid, ammonium dihydrogen phosphate, triammonium phosphate, pyrophosphoric acid, sodium pyrophosphate, or sodium dihydrogen pyrophosphate, typical but non-limiting examples of which include a combination of sodium dihydrogen phosphate and sodium phosphate, a combination of sodium dihydrogen phosphate and sodium monohydrogen phosphate, a combination of sodium dihydrogen phosphate and phosphoric acid, a combination of sodium dihydrogen phosphate and ammonium dihydrogen phosphate, a combination of sodium dihydrogen phosphate and pyrophosphoric acid, a combination of sodium dihydrogen phosphate and sodium dihydrogen pyrophosphate, a combination of phosphoric acid and pyrophosphoric acid, a combination of triammonium phosphate and sodium pyrophosphate, or a combination of pyrophosphoric acid and sodium dihydrogen pyrophosphate.
Preferably, the fluorine source comprises ammonium fluoride and/or polyvinylidene fluoride.
As a preferred embodiment of the present invention, the mass ratio of the porous carbon fiber to the dopant source is 1 (1 to 10), for example, 1.
Preferably, the temperature of the heating reaction is 400 to 800 ℃, for example 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃ or 800 ℃, but is not limited to the recited values, and other values not recited in the above numerical range are also applicable.
Preferably, the heating reaction time is 5 to 12 hours, such as 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, but is not limited to the recited values, and other values not recited within the above-mentioned range of values are also applicable.
In a third aspect, the invention provides an application of the negative electrode material of the first aspect or the negative electrode material obtained by the preparation method of the second aspect in a sodium-ion battery.
Compared with the prior art, the invention at least has the following beneficial effects: by limiting the metal sodium in the porous framework, particularly in the doped porous carbon fiber, and using the void structure as the framework for supporting the metal sodium, the growth of sodium dendrite can be inhibited, the volume expansion can be limited, the effect of modifying the membrane component of the solid electrolyte interface can be achieved, and meanwhile, the method has the effects of providing space for sodium metal deposition, reducing the nucleation barrier of sodium deposition and reducing the local current density, and the cycle stability and the cycle life of the obtained cathode material are obviously improved.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides an anode material, which comprises a porous skeleton and metal sodium filled in the porous skeleton; the porous skeleton is oxygen-doped porous carbon fiber, and the preparation method of the cathode material comprises the following steps:
preparing porous carbon fibers with the porosity of 80%, the pore size of 5-100 microns, the length of 3-6 mm and the outer diameter of 5-20 microns, weighing the porous carbon fibers and ammonium oxalate according to the mass ratio of 1; heating metal sodium to 200 ℃ in an argon atmosphere to completely melt the metal sodium, completely immersing the oxygen-doped porous carbon fiber into the molten metal sodium, controlling the residence time, then lifting the oxygen-doped porous carbon fiber to separate from the molten metal sodium, and naturally cooling the oxygen-doped porous carbon fiber to room temperature to obtain the cathode material, wherein the mass of the metal sodium in the obtained cathode material accounts for 75wt%, and the mass of the oxygen-doped porous carbon fiber accounts for 25wt%.
Example 2
The embodiment provides an anode material, which comprises a porous skeleton and metal sodium filled in the porous skeleton; the porous skeleton is sulfur-doped porous carbon fiber, and the preparation method of the negative electrode material comprises the following steps:
preparing porous carbon fiber with porosity of 40%, pore size of 5-100 μm, length of 3-6 mm and outer diameter of 5-20 μm, weighing the porous carbon fiber and sulfur according to a mass ratio of 1; heating metal sodium to 100 ℃ in an argon atmosphere to completely melt the metal sodium, completely immersing the sulfur-doped porous carbon fiber into the molten metal sodium, controlling the retention time, then pulling the molten metal sodium away, and naturally cooling the molten metal sodium to room temperature to obtain the cathode material, wherein the mass of the metal sodium in the obtained cathode material accounts for 97wt%, and the mass of the sulfur-doped porous carbon fiber accounts for 3wt%.
Example 3
The embodiment provides an anode material, which comprises a porous skeleton and metal sodium filled in the porous skeleton; the porous skeleton is nitrogen-doped porous carbon fiber, and the preparation method of the cathode material comprises the following steps:
preparing porous carbon fibers with the porosity of 60%, the pore size of 5-100 microns, the length of 3-6 mm and the outer diameter of 5-20 microns, weighing the porous carbon fibers and melamine according to the mass ratio of 1; heating metal sodium to 150 ℃ in an argon atmosphere to completely melt the metal sodium, completely immersing the nitrogen-doped porous carbon fiber into the molten metal sodium, controlling the residence time, then lifting the molten metal sodium away, and naturally cooling to room temperature to obtain the cathode material, wherein the mass of the metal sodium in the obtained cathode material accounts for 85wt%, and the mass of the nitrogen-doped porous carbon fiber accounts for 15wt%.
Example 4
The embodiment provides an anode material, which comprises a porous skeleton and metal sodium filled in the porous skeleton; the porous skeleton is phosphorus-doped porous carbon fiber, and the preparation method of the cathode material comprises the following steps:
preparing porous carbon fibers with porosity of 88%, pore size of 5-100 microns, length of 3-6 mm and outer diameter of 5-20 microns, weighing the porous carbon fibers and sodium dihydrogen phosphate according to a mass ratio of 1; heating metal sodium to 250 ℃ in an argon atmosphere to completely melt the metal sodium, completely immersing the phosphorus-doped porous carbon fiber into the molten metal sodium, controlling the retention time, then pulling the molten metal sodium away, and naturally cooling the molten metal sodium to room temperature to obtain the cathode material, wherein the mass of the metal sodium in the obtained cathode material accounts for 76wt%, and the mass of the phosphorus-doped porous carbon fiber accounts for 24wt%.
Example 5
The embodiment provides an anode material, which comprises a porous skeleton and metal sodium filled in the porous skeleton; the porous skeleton is fluorine-doped porous carbon fiber, and the preparation method of the cathode material comprises the following steps:
preparing porous carbon fiber with the porosity of 98%, the pore size of 5-100 microns, the length of 3-6 mm and the outer diameter of 5-20 microns, weighing the porous carbon fiber and ammonium fluoride according to the mass ratio of 1; heating metal sodium to 300 ℃ in an argon atmosphere to completely melt the metal sodium, completely immersing the fluorine-doped porous carbon fiber into the molten metal sodium, controlling the residence time, then lifting the fluorine-doped porous carbon fiber to separate from the molten metal sodium, and naturally cooling the fluorine-doped porous carbon fiber to room temperature to obtain the cathode material, wherein the mass of the metal sodium in the obtained cathode material accounts for 70wt%, and the mass of the nitrogen-doped porous carbon fiber accounts for 30wt%.
Example 6
This example provides an anode material which is identical to example 1 except that the porosity of the porous carbon fiber is adjusted from 80% to 30%.
Example 7
This example provides an anode material which is identical to example 1 except that the porosity of the porous carbon fiber is adjusted from 80% to 40%.
Example 8
This example provides an anode material which is identical to that of example 1 except that the porosity of the porous carbon fiber is adjusted from 80% to 60%.
Example 9
This example provides an anode material which is identical to example 1 except that the porosity of the porous carbon fiber is adjusted from 80% to 90%.
Example 10
This example provides an anode material which is identical to example 1 except that the porosity of the porous carbon fiber is adjusted from 80% to 98%.
Example 11
The present example provides a negative electrode material, which is completely the same as in example 1 except that the porous carbon fibers and ammonium oxalate are weighed according to a mass ratio of 1.3, and the mass of oxygen element in the obtained oxygen-doped porous carbon fibers is adjusted from 0.45wt% to 0.001 wt%.
Example 12
This example provides a negative electrode material, which is prepared under the same conditions as in example 1, except that the porous carbon fibers and ammonium oxalate are weighed at a mass ratio of 1.
Example 13
This example provides a negative electrode material, which is identical to example 1 except that the porous carbon fiber and ammonium oxalate are weighed according to a mass ratio of 1.
Example 14
This example provides a negative electrode material, which is identical to example 1 except that the porous carbon fiber and ammonium oxalate are weighed according to a mass ratio of 1.
Example 15
This example provides a negative electrode material, which is identical to example 1 except that the porous carbon fiber and ammonium oxalate are weighed according to a mass ratio of 1.
Example 16
This example provides a negative electrode material, which is identical to example 1 except that the porous carbon fiber and ammonium oxalate are weighed according to a mass ratio of 1.
Example 17
This example provides an anode material in which the mass of metallic sodium is 65wt%, and the mass of oxygen-doped porous carbon fiber is 35wt%, and the other conditions are exactly the same as in example 1.
Example 18
The embodiment provides a negative electrode material, wherein the mass of the metal sodium in the negative electrode material accounts for 70wt%, the mass of the oxygen-doped porous carbon fiber accounts for 30wt%, and other conditions are completely the same as those in embodiment 1.
Example 19
This example provides an anode material in which the mass of metallic sodium is 77wt%, and the mass of oxygen-doped porous carbon fiber is 23wt%, and the other conditions are exactly the same as in example 1.
Example 20
This example provides an anode material in which the mass of metallic sodium is 72wt%, and the mass of oxygen-doped porous carbon fiber is 28wt%, and the other conditions are exactly the same as in example 1.
Example 21
This example provides an anode material in which the mass of metallic sodium is 85wt%, and the mass of oxygen-doped porous carbon fiber is 15wt%, and the other conditions are exactly the same as in example 1.
Example 22
This example provides an anode material, wherein the mass of the metal sodium in the anode material accounts for 97wt%, the mass of the oxygen-doped porous carbon fiber accounts for 3wt%, and other conditions are exactly the same as those in example 1.
Example 23
The embodiment provides a negative electrode material, wherein the mass of metal sodium in the negative electrode material accounts for 65wt%, the mass of the oxygen-doped porous carbon fiber accounts for 99wt%, and other conditions are completely the same as those in embodiment 1.
Comparative example 1
This comparative example used a commercially available sodium metal negative electrode as a negative electrode material and was subjected to subsequent testing.
The negative electrode materials obtained in the examples and the comparative examples are respectively prepared into conventional button batteries, wherein the positive electrode adopts sodium vanadium phosphate, the obtained batteries are cycled for 500 circles under the multiplying power of 0.5C, 1C and 2C, the capacity retention rate is obtained, and the obtained data are recorded in table 1.
TABLE 1
As can be seen from table 1:
(1) In comparison with the commercially available sodium metal negative electrode used in comparative example 1, it was found that: in embodiments 1 to 5, the negative electrode material provided by the invention after being compounded is adopted, so that the local current density can be effectively reduced, more nucleation sites can be provided, the uniform deposition and growth of sodium metal can be promoted, and the volume change of the sodium metal in the circulation process can be buffered by a three-dimensional structure, so that the circulation performance of a battery cell can be improved;
(2) Comparing example 1 with examples 6-10, it was found that: by controlling the porosity of the porous framework to select a higher value in a preferred range, the wettability of the porous framework to the metal sodium can be improved, the specific surface area of the material can be increased, the effective current density can be reduced, the volume expansion during the deposition of the metal sodium can be limited, and the volume change can be buffered, so that the cycle performance of the battery cell can be improved;
(3) Comparing example 1 with examples 11-16, it was found that: the sodium affinity of the material can be effectively improved by properly increasing the doping amount of elements in the porous framework, so that the nucleation overpotential is reduced, the uniform deposition of sodium metal is induced, and the cycle performance of the battery cell is improved;
(4) Comparing example 1 with examples 17-23, it was found that: the mass ratio of the porous framework to the metal sodium is adjusted, so that the overall deposition uniformity of the obtained cathode material is reduced when the metal content of the sodium is too high, and the porous framework cannot effectively adjust the excessive metal sodium, so that the buffer volume change capability of the metal sodium is poor, and the cycle performance is influenced;
from the analysis, the invention can obviously improve the cycle stability and the cycle life of the obtained cathode material by limiting the metal sodium in the porous framework, particularly in the doped porous carbon fiber and utilizing the void structure as the framework for supporting the metal sodium.
The present invention is described in detail by the above embodiments, but the present invention is not limited to the above detailed structural features, which means that the present invention must not be implemented by the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (10)
1. The negative electrode material is characterized by comprising a porous skeleton and metallic sodium filled in the porous skeleton; the porous skeleton comprises doped porous carbon fibers; the doping element of the doped porous carbon fiber comprises any one or the combination of at least two of O, S, N, P or F.
2. The negative electrode material of claim 1, wherein the mass of the porous skeleton accounts for 3-33 wt% of the total mass of the negative electrode material;
preferably, the mass of the metal sodium accounts for 70-97 wt% of the total mass of the negative electrode material;
preferably, the mass of the porous framework accounts for 23-28 wt% of the total mass of the negative electrode material;
preferably, the mass of the metal sodium is 2.5 to 3.3 times of the mass of the porous skeleton.
3. The anode material according to claim 1 or 2, characterized in that the mass of the doping element is 0.005-1 wt% of the total mass of the doped porous carbon fibers.
4. The negative electrode material of any one of claims 1 to 3, wherein the doped porous carbon fibers have a porosity of 40% to 98%;
preferably, the pore size of the doped porous carbon fiber is 5-100 μm;
preferably, the length of the doped porous carbon fiber is 3-6 mm;
preferably, the doped porous carbon fiber has an outer diameter of 5 to 20 μm.
5. A method for preparing the anode material of any one of claims 1 to 4, wherein the method comprises: heating and heating metal sodium in an inert atmosphere to melt the metal sodium; and immersing the porous framework into molten metal sodium for filling to obtain the negative electrode material.
6. The method for preparing the anode material according to claim 5, wherein the holding temperature for heating is 100 to 300 ℃;
preferably, after the immersion time is over, the negative electrode material is pulled away from the molten metal sodium and is naturally cooled under the protection of inert atmosphere;
preferably, the inert atmosphere comprises any one of argon, nitrogen or helium or a combination of at least two thereof.
7. The preparation method of the anode material according to claim 5 or 6, wherein the preparation method of the porous framework comprises the steps of uniformly mixing porous carbon fibers and a doping source, and then placing the mixture in an inert atmosphere for heating reaction to obtain doped porous carbon fibers as the porous framework.
8. The method for preparing the anode material according to claim 7, wherein the doping source includes any one of or a combination of at least two of an oxygen source, a sulfur source, a nitrogen source, a phosphorus source, or a fluorine source;
preferably, the oxygen source comprises ammonium oxalate and/or ammonium persulfate;
preferably, the sulphur source comprises any one or a combination of at least two of sulphur, a sulphur-containing organic compound, a polysulphide or a sulphate;
preferably, the nitrogen source comprises any one of urea, melamine, cyanamide, dicyandiamide, polyaniline or polypyrrole or a combination of at least two of the two;
preferably, the source of phosphorus comprises any one of, or a combination of at least two of, sodium dihydrogen phosphate, sodium monohydrogen phosphate, phosphoric acid, ammonium dihydrogen phosphate, triammonium phosphate, pyrophosphoric acid, sodium pyrophosphate, or sodium dihydrogen pyrophosphate;
preferably, the fluorine source comprises ammonium fluoride and/or polyvinylidene fluoride.
9. The method for preparing the negative electrode material according to claim 7 or 8, wherein the mass ratio of the porous carbon fiber to the doping source is 1 (1-10);
preferably, the temperature of the heating reaction is 400-800 ℃;
preferably, the heating reaction time is 5-12 h.
10. Use of the negative electrode material according to any one of claims 1 to 4 or the negative electrode material obtained by the preparation method according to any one of claims 5 to 9 in a sodium ion battery.
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| CN115893371A (en) * | 2022-12-28 | 2023-04-04 | 蜂巢能源科技(马鞍山)有限公司 | Sulfur, nitrogen and phosphorus doped porous carbon material and preparation and application thereof |
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