CN116364854A - Positive pole piece and sodium ion battery - Google Patents

Positive pole piece and sodium ion battery Download PDF

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Publication number
CN116364854A
CN116364854A CN202310420119.3A CN202310420119A CN116364854A CN 116364854 A CN116364854 A CN 116364854A CN 202310420119 A CN202310420119 A CN 202310420119A CN 116364854 A CN116364854 A CN 116364854A
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sodium
positive electrode
sodium borohydride
active material
electrode active
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陈明峰
刘鑫
袁旭婷
刘瑞
王尊志
马树灯
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Ningbo Ronbay Lithium Battery Material Co Ltd
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Ningbo Ronbay Lithium Battery Material Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a positive pole piece and a sodium ion battery. The invention provides a positive electrode plate, which comprises a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a sodium supplementing agent, and the sodium supplementing agent comprises sodium borohydride and a carbon layer coated on the surface of the sodium borohydride. The sodium supplementing agent provided by the invention has a core-shell structure, sodium borohydride is used as an inner core, and sodium element can be irreversibly decomposed and released in the charging process, so that the sodium supplementing effect is realized, and the first coulomb efficiency and the energy density of the sodium ion battery are improved; in addition, because the conductivity and the stability of sodium borohydride in air are poor, the carbon layer is coated on the surface of the sodium borohydride, so that the conductivity and the stability of the sodium borohydride are effectively improved, and the sodium supplementing effect of the sodium borohydride is improved.

Description

Positive pole piece and sodium ion battery
Technical Field
The invention relates to a positive pole piece and a sodium ion battery, and relates to the technical field of sodium ion batteries.
Background
Lithium ion batteries, which are energy storage devices with high energy density and long service life, are widely used in electronic devices such as mobile phones and notebook computers, however, the lithium ion batteries have limited reserves of lithium resources and are expensive, and the lithium ion batteries are difficult to meet the increasing demands of mobile electronic products and automobile industry. Compared with lithium element, the sodium element has more abundant reserves, can obviously reduce the cost of the battery, and has wide application prospect.
Because the sodium element and the lithium element have similar electrochemical properties, in the first charge and discharge process of the sodium ion battery, a part of sodium ions react on the surface of the negative electrode to form a solid electrolyte membrane (SEI), so that irreversible sodium loss is caused, the first coulomb efficiency and the energy density of the sodium ion battery are reduced, and the sodium ion loss in the first circulation process can be supplemented by adding a sodium supplementing agent into the positive electrode active material layer, so that the first coulomb efficiency and the energy density of the sodium ion battery are improved. Therefore, developing a sodium supplement that effectively compensates for this portion of the sodium ion loss is one of the continuing concerns of those skilled in the art.
Disclosure of Invention
The invention provides a positive pole piece and a sodium ion battery, which comprise sodium supplementing agents for improving the first coulombic efficiency and the energy density of the sodium ion battery.
The first aspect of the invention provides a positive electrode plate, which comprises a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a sodium supplementing agent, and the sodium supplementing agent comprises sodium borohydride and a carbon layer coated on the surface of the sodium borohydride;
the granularity of the sodium borohydride is 0.5-6 mu m, and the thickness of the carbon layer is 10-100 nm.
The positive electrode plate is prepared by the following preparation method:
reacting boric acid with methanol to obtain trimethyl borate, and reacting metallic sodium with hydrogen to obtain sodium hydride;
the trimethyl borate reacts with sodium hydride to prepare sodium borohydride;
and carrying out heat treatment on the sodium borohydride and a gaseous carbon source to obtain the sodium supplement.
As described above, the positive electrode sheet is prepared by reacting metallic sodium with hydrogen to obtain sodium hydride, and specifically comprises:
dispersing metallic sodium in an oily medium, introducing hydrogen into the oily medium, and reacting for 4-12 h at 200-500 ℃ to prepare sodium hydride.
The positive electrode piece is prepared by heat treatment of sodium borohydride and a gaseous carbon source, and specifically comprises the following steps:
and dispersing the sodium borohydride in an oily medium under an inert atmosphere, and introducing a gaseous carbon source to deposit a carbon simple substance on the surface of the sodium borohydride to form a carbon layer, so as to obtain the sodium supplement.
The positive electrode sheet as described above, wherein the gaseous carbon source comprises one or more of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.
As described above, the molar ratio of the sodium borohydride to the gaseous carbon source is 50-200:1.
As described above, the heat treatment temperature of the sodium borohydride and the gaseous carbon source is 250-280 ℃ and the time is 2-12 h.
The positive electrode plate, wherein the positive electrode active material layer further comprises a positive electrode active material, a conductive agent and a binder, and the mass of the sodium supplement agent is 5-20% of the total mass of the positive electrode active material, the conductive agent and the binder.
The positive electrode sheet comprises 8-9 mass ratio of positive electrode active material, conductive agent and binder: 1:1.
the second aspect of the invention provides a sodium ion battery comprising any one of the positive electrode sheets described above.
The implementation of the invention has at least the following advantages:
1. the positive electrode plate provided by the invention comprises a sodium supplementing agent with a core-shell structure, sodium borohydride is used as an inner core, sodium ions can be irreversibly decomposed and released in the charging process of the sodium ion battery, the sodium supplementing effect is realized, and the specific capacity and the coulomb efficiency of the sodium ion battery are improved; in addition, because the conductivity and the stability of sodium borohydride in air are poor, the carbon layer is coated on the surface of the sodium borohydride, so that the conductivity and the stability of the sodium borohydride are effectively improved, and the sodium supplementing effect of the sodium borohydride is improved.
2. The invention is beneficial to further improving the sodium supplementing effect of sodium borohydride and improving the specific capacity and coulombic efficiency of the sodium ion battery by limiting the granularity of the sodium borohydride and the thickness of the carbon coating layer.
3. The sodium supplement provided by the invention has the advantages of simple preparation method, readily available raw materials, small pollution and simple post-treatment, can be compatible with the existing sodium ion battery manufacturing process, and is beneficial to large-scale production and application.
4. The sodium ion battery provided by the invention comprises the sodium supplementing agent, and can effectively improve the specific capacity and coulombic efficiency of the sodium ion battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it will be obvious that the drawings in the following description are some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a sodium supplement agent according to an embodiment of the present invention.
Reference numerals illustrate:
1-positive electrode current collector;
2-a positive electrode active material layer;
31-sodium borohydride;
32-carbon layer.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present invention, and as shown in fig. 1, the positive electrode sheet includes a positive electrode current collector 1 and a positive electrode active material layer 2 disposed on a surface of the positive electrode current collector, it is understood that the upper and lower surfaces of the positive electrode current collector in fig. 1 are both provided with positive electrode active material layers, and in addition, the positive electrode active material layers may be separately disposed on an upper surface or a lower surface of the positive electrode current collector.
The positive electrode current collector 1 is a base metal for attaching an active material to a positive electrode of a battery, and may be, for example, a conventional material such as aluminum foil.
The positive electrode active material layer 2 includes a sodium supplementing agent, and fig. 2 is a schematic structural diagram of the sodium supplementing agent according to an embodiment of the present invention, and as shown in fig. 2, the sodium supplementing agent includes sodium borohydride 31 and a carbon layer 32 coated on the surface of the sodium borohydride, and the inventor of the present application research finds that the sodium borohydride has a sodium ion transmission capability and a capability of dissociating sodium ions, so that the sodium borohydride is used as the sodium supplementing agent; in order to improve the conductivity and stability of sodium borohydride, elemental carbon is deposited in a very fine powder state on the surface of sodium borohydride 31 by van der waals forces to form a coated carbon layer 32.
Specifically, the granularity of sodium borohydride is 0.5-6 mu m, and the granularity refers to the size of sodium borohydride particles and can be obtained through a granularity meter test.
The thickness of the carbon layer 32 is 10 to 100nm, the thickness of the carbon layer 32 refers to the distance between the outermost layer of the carbon layer 32 and the surface of the sodium borohydride 31, the distance range is 10 to 100nm, and the thickness of the carbon layer 32 and the thickness thereof can be determined by various modes such as SEM, EDS, TEM, XPS.
In one specific embodiment, the sodium supplement is prepared by the following preparation method:
step 1, reacting boric acid with methanol to prepare trimethyl borate, and reacting metallic sodium with hydrogen to prepare sodium hydride;
firstly, boric acid and methanol are used as raw materials to react, trimethyl borate is prepared, and the reaction formula is as follows: b (OH) 3 +3CH 3 OH＝B(OCH 3 ) 3 +3H 2 The molar ratio of O, boric acid and methanol is 1:3, the reaction temperature is 25-100 ℃ and the reaction time is 1-2 h.
Meanwhile, sodium hydride is prepared by taking metal sodium and hydrogen as raw materials to react. Because the activity of the metal sodium is extremely high and the metal sodium is extremely easy to react with air and water, the metal sodium is dispersed in an oily medium, and hydrogen is introduced into the oily medium, and specifically, the molar ratio of the metal sodium to the hydrogen is 1:1, the reaction temperature is 200-500 ℃, the reaction time is 4-12 h, and the sodium hydride is prepared.
Further, the oily medium is paraffin oil.
Step 2, reacting the trimethyl borate with sodium hydride to prepare sodium borohydride;
and secondly, reacting trimethyl borate and sodium hydride prepared in the step 1, wherein the molar ratio of the trimethyl borate to the sodium hydride is 1:4, the reaction temperature is 200-400 ℃, the reaction time is 2-12 h, and collecting a solid product after the reaction is finished to obtain sodium borohydride.
Crushing the sodium borohydride prepared and controlling the granularity of the sodium borohydride to be 0.5-6 mu m.
And step 3, carrying out heat treatment on the sodium borohydride and a gaseous carbon source to obtain the sodium supplement agent.
And (3) dispersing the sodium borohydride obtained in the step (2) in an oily medium in an inert atmosphere, introducing a gaseous carbon source for reaction, and preparing the sodium supplement after the reaction is finished.
Further, the gaseous carbon source comprises one or more of methane, ethane, propane, ethylene, propylene, acetylene, propyne.
Further, the molar ratio of the sodium borohydride to the gaseous carbon source is 50-200:1.
Further, the heat treatment temperature of the sodium borohydride and the gaseous carbon source is 250-280 ℃ and the time is 2-12 h, so that the carbon element is deposited on the surface of the sodium borohydride to form a coating layer.
It is understood that the positive electrode active material layer 2 includes a positive electrode active material, a conductive agent, and a binder in addition to the sodium supplementing agent, wherein the mass of the sodium supplementing agent is 5 to 20% of the total mass of the positive electrode active material, the conductive agent, and the binder.
Further, the mass ratio of the positive electrode active material, the conductive agent and the binder is 8-9: 1:1.
the choice of the positive electrode active material, the conductive agent and the binder is not particularly limited and may be conventionally selected in the art. For example, the positive electrode active material may be a sodium-containing layered oxide material, a prussian white material, a sodium-containing polyanion material, or the like; for example, the positive electrode active material may be NaNi containing nickel 0.3 Fe 0.25 Mn 0.45 O 2 Copper-containing NaCu 0.20 Fe 0.40 Mn 0.40 O 2 Polyanionic NaV 2 (PO 4 ) 3 One or more of the following; the conductive agent is selected from one or more of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, single-walled carbon nanotube, multi-arm carbon nanotube, and carbon fiber, and the binder is selected from polyvinylidene fluorideOne or more of alkene (PVDF), polytetrafluoroethylene (PTFE), lithium Polyacrylate (PAALi).
In the preparation process, dispersing an anode active material, a sodium supplementing agent, a conductive agent and a binder in a solvent, and uniformly stirring to obtain anode slurry; and then, uniformly coating the positive electrode slurry on the positive electrode current collector 1 to obtain a positive electrode active material layer 2, and drying and cutting to obtain the positive electrode plate.
The second aspect of the invention provides a sodium ion battery comprising any one of the positive electrode sheets.
The sodium ion battery comprising the positive electrode plate provided by the invention has better specific capacity and coulombic efficiency.
It can be understood that the sodium ion battery provided by the invention further comprises a negative electrode plate, a diaphragm and electrolyte, which are all conventional choices in the field.
The sodium supplement, the positive electrode sheet and the sodium ion battery provided by the invention are described below with reference to specific examples.
Example 1
The embodiment provides a preparation method of a sodium supplementing agent, which specifically comprises the following steps:
step 1, boric acid and methanol are mixed according to the following formula 1:3, adding the mixture into a reaction kettle according to the molar ratio, and heating to 80 ℃ for reaction for 2 hours to prepare trimethyl borate;
step 2, dispersing metal sodium in paraffin oil, heating to 300 ℃, introducing hydrogen according to the molar ratio of metal sodium to hydrogen=1:1, and reacting for 6 hours at 400 ℃ to prepare sodium hydride;
step 3, mixing trimethyl borate and sodium hydride according to a molar ratio of 1:4, and reacting for 5 hours at 350 ℃ to obtain sodium borohydride;
step 4, grinding the sodium borohydride in a mortar for 20min to obtain sodium borohydride with the granularity of 3.79 mu m;
step 5, placing trimethyl borate and sodium hydride in paraffin oil, continuously introducing nitrogen as a protective gas, heating to 250 ℃, and introducing methane under the protection of nitrogen to react for 2 hours to obtain a sodium supplement NaBH 4 And @ C, the thickness of the carbon layer was 16nm.
Example 2
The preparation method of the sodium supplement provided in this embodiment can refer to embodiment 1, and is different in that in step 3, the reaction time of introducing methane is 5 hours, and the thickness of the carbon layer is 43nm.
Example 3
The preparation method of the sodium supplement provided in this embodiment can refer to embodiment 1, and is different in that in step 3, the reaction time of introducing methane is 8 hours, and the thickness of the carbon layer is 68nm.
Example 4
The preparation method of the sodium supplement provided in this embodiment can refer to embodiment 1, and is different in that in step 3, the reaction time of introducing methane is 11h, and the thickness of the carbon layer is 95nm.
Example 5
The preparation method of the sodium supplement provided in this embodiment can refer to embodiment 1, and is different in that in step 3, the introduced carbon source is replaced by ethylene by methane, and the thickness of the carbon layer is 21nm.
Example 6
The preparation method of the sodium supplement provided in this embodiment can refer to embodiment 1, and is different in that in step 3, the introduced carbon source is replaced by acetylene by methane, and the thickness of the carbon layer is 19nm.
Comparative example 1
The preparation method of the sodium supplement provided in this comparative example can be referred to in example 1, and is different in that in step 3, the reaction time of methane is 20 hours, and the thickness of the carbon layer is 200nm.
Comparative example 2
The comparative example provides a method for preparing a sodium supplement with reference to example 1, except that the sodium borohydride has a particle size of 8.06 μm.
Example 7
The present embodiment provides a positive electrode sheet comprising a positive electrode current collector aluminum foil and a positive electrode active material layer provided on the surface of the positive electrode current collector aluminum foil, the positive electrode active material layer comprising 8 parts by mass of a positive electrode active material (NaNi 0.3 Fe 0.25 Mn 0.45 O 2 ) 1 part by mass of the sodium supplement agent provided in example 1, 1 part by mass of the conductive agent acetylene black, and 1 part by mass of polyvinylidene fluoride (PVDF))。
Positive electrode active material (NaNi) 0.3 Fe 0.25 Mn 0.45 O 2 ) The preparation method of (2) comprises the following steps:
step 1, uniformly mixing a precursor and lithium hydroxide in a coulter mixer, and then sintering for 20 hours at 900 ℃;
step 2, crushing, sieving, washing and drying the materials after primary sintering, transferring the materials into a rotary kiln, and sintering for 16 hours at 600 ℃;
step 3, sieving the material after secondary sintering to remove iron, thus obtaining the polycrystalline ternary anode active material (NaNi) 0.3 Fe 0.25 Mn 0.45 O 2 )。
The preparation method of the positive electrode plate comprises the following steps:
step 1, dispersing an anode active material, a sodium supplementing agent, acetylene black and polyvinylidene fluoride (PVDF) in an N-methyl pyrrolidone (NMP) solution, and uniformly stirring to obtain anode slurry;
and step 2, uniformly coating the anode slurry on an aluminum foil, drying for 24 hours in a vacuum drying oven, and cutting to obtain an anode plate.
Example 8
The positive electrode sheet provided in this example can refer to example 7, except that the sodium supplement agent provided in example 2 is included in the positive electrode active material layer.
Example 9
The positive electrode sheet provided in this example can refer to example 7, except that the sodium supplement agent provided in example 3 is included in the positive electrode active material layer.
Example 10
The positive electrode sheet provided in this example can refer to example 7, except that the sodium supplement agent provided in example 4 is included in the positive electrode active material layer.
Example 11
The positive electrode sheet provided in this example can refer to example 7, except that the sodium supplement agent provided in example 5 is included in the positive electrode active material layer.
Example 12
The positive electrode sheet provided in this example can refer to example 7, except that the sodium supplement agent provided in example 6 is included in the positive electrode active material layer.
Comparative example 3
The positive electrode sheet provided in this comparative example can be referred to example 7, except that the sodium supplement agent is not included in the positive electrode sheet.
Comparative example 4
The positive electrode sheet provided in this comparative example can be referred to example 7, except that the sodium supplementing agent is sodium borohydride coated with a carbon-free layer.
The preparation method of the sodium borohydride coated by the carbon-free layer comprises the following steps:
step 1, boric acid and methanol are mixed according to the following formula 1:3, adding the mixture into a reaction kettle according to the molar ratio, and heating to 80 ℃ for reaction for 2 hours to prepare trimethyl borate;
step 2, dispersing metal sodium in paraffin oil, heating to 300 ℃, introducing hydrogen according to the molar ratio of metal sodium to hydrogen=1:1, and reacting for 6 hours at 400 ℃ to prepare sodium hydride;
and step 3, mixing trimethyl borate and sodium hydride according to a molar ratio of 1:4, and reacting for 5 hours at 350 ℃ to obtain sodium borohydride.
Comparative example 5
The positive electrode sheet provided in this comparative example can be referred to example 7, except that the sodium supplement agent provided in comparative example 1 is included in the positive electrode active material layer.
Comparative example 6
The positive electrode sheet provided in this comparative example can be referred to example 7, except that the sodium supplement agent provided in comparative example 2 is included in the positive electrode active material layer.
Comparative example 7
The positive electrode sheet provided in this comparative example can be referred to example 7, except that the sodium supplementing agent is Na 2 O。
The positive electrode sheets and the hard carbon negative electrodes provided in examples 7 to 12 and comparative examples 3 to 7 were placed on both sides of a separator, respectively, and a proper amount of sodium ion battery electrolyte (sodium hexafluorophosphate as a solute, ethylene Carbonate (EC) and dimethyl carbonate (DMC) as a solvent, and the volume ratio thereof was EC: dmc=1:1) was added to assemble a soft pack battery. The specific discharge capacity and the first coulombic efficiency of the cells were then tested as follows, and the test results are shown in table 1.
The method for testing the specific discharge capacity and the first coulombic efficiency comprises the following steps: at 25 ℃, 1.5-4.2V is charged at 0.1C/discharged at 0.1C to test the charge-discharge performance, and then according to the formula: first discharge efficiency = first-turn discharge specific capacity/first-turn charge specific capacity 100%, first coulombic efficiency is calculated.
Table 1 results of performance test of the batteries provided in examples 7 to 12 and comparative examples 3 to 7
Specific discharge capacity (mAh/g) First coulombic efficiency (%)
Example 7 117.7 86.2％
Example 8 120.3 87.3％
Example 9 121.9 88.6％
Example 10 119.6 87.1％
Example 11 118.2 85.9％
Example 12 117.0 86.0％
Comparative example 3 105.9 75.6％
Comparative example 4 111.3 81.4％
Comparative example 5 112.7 81.9％
Comparative example 6 114.1 82.6％
Comparative example 7 108.9 79.5％
According to the data provided in the comparative example 3, the addition of the sodium supplement agent to the positive electrode sheet is helpful to improve the discharge specific capacity and the first coulombic efficiency of the battery; according to comparative example 4, the carbon layer is coated on the surface of sodium borohydride, which is helpful for improving the discharge specific capacity and the first coulombic efficiency of the sodium ion battery; according to the data provided in comparative examples 5 to 6, it is found that the sodium borohydride particle size and the carbon coating thickness are controlled to further improve the specific discharge capacity and the first coulombic efficiency of the sodium ion battery; as is clear from comparative example 7, borohydrideSodium supplementing effect of sodium is superior to Na 2 O; according to the embodiments 7 to 10, as the gas carbon source is introduced for a longer time, the thickness of the carbon layer is increased, but the specific discharge capacity and the first coulomb efficiency of the sodium ion battery are increased and then reduced, so that the gas carbon source is introduced for 5 to 8 hours, and the carbon layer is controlled for a longer time than 40 to 70nm, which is beneficial to further increasing the specific discharge capacity and the first coulomb efficiency of the sodium ion battery; according to examples 11 to 12, the type of the gaseous carbon source has little influence on the performance of the sodium ion battery, and is beneficial to mass production and application.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. The positive electrode plate is characterized by comprising a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a sodium supplementing agent, and the sodium supplementing agent comprises sodium borohydride and a carbon layer coated on the surface of the sodium borohydride;
the granularity of the sodium borohydride is 0.5-6 mu m, and the thickness of the carbon layer is 10-100 nm.
2. The positive electrode sheet according to claim 1, wherein the sodium supplementing agent is prepared by the following preparation method:
reacting boric acid with methanol to obtain trimethyl borate, and reacting metallic sodium with hydrogen to obtain sodium hydride;
the trimethyl borate reacts with sodium hydride to prepare sodium borohydride;
and carrying out heat treatment on the sodium borohydride and a gaseous carbon source to obtain the sodium supplement.
3. The positive electrode sheet according to claim 2, wherein sodium hydride is prepared by reacting metallic sodium with hydrogen gas, and specifically comprises:
dispersing metallic sodium in an oily medium, introducing hydrogen into the oily medium, and reacting for 4-12 h at 200-500 ℃ to prepare sodium hydride.
4. The positive electrode sheet according to claim 2, wherein the sodium borohydride is heat-treated with a gaseous carbon source to obtain the sodium supplement, specifically comprising:
and dispersing the sodium borohydride in an oily medium under an inert atmosphere, and introducing a gaseous carbon source to deposit a carbon simple substance on the surface of the sodium borohydride to form a carbon layer, so as to obtain the sodium supplement.
5. The positive electrode sheet of claim 2 or 4, wherein the gaseous carbon source comprises one or more of methane, ethane, propane, ethylene, propylene, acetylene, propyne.
6. The positive electrode sheet according to claim 2 or 4, characterized in that the molar ratio of sodium borohydride to gaseous carbon source is 50-200:1.
7. The positive electrode sheet according to claim 2 or 4, wherein the heat treatment temperature of the sodium borohydride and the gaseous carbon source is 250-280 ℃ for 2-12 hours.
8. The positive electrode sheet according to claim 1, wherein the positive electrode active material layer further comprises a positive electrode active material, a conductive agent and a binder, and the mass of the sodium supplement agent is 5 to 20% of the total mass of the positive electrode active material, the conductive agent and the binder.
9. The positive electrode sheet according to claim 8, wherein the mass ratio of the positive electrode active material, the conductive agent, and the binder is 8 to 9:1:1.
10. a sodium ion battery, characterized in that it comprises the positive electrode sheet according to any one of claims 1 to 9.
CN202310420119.3A 2023-04-17 2023-04-17 Positive pole piece and sodium ion battery Pending CN116364854A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117352870A (en) * 2023-10-19 2024-01-05 重庆中润新材料股份有限公司 Modified sodium supplement agent and CNT compound conductive slurry for sodium ion battery

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117352870A (en) * 2023-10-19 2024-01-05 重庆中润新材料股份有限公司 Modified sodium supplement agent and CNT compound conductive slurry for sodium ion battery

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