CN115986086A - Sodium anode active material, preparation method thereof, sodium ion battery and power utilization device - Google Patents
Sodium anode active material, preparation method thereof, sodium ion battery and power utilization device Download PDFInfo
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Abstract
The invention provides a sodium cathode active material, a preparation method thereof, a sodium ion battery and an electric device. The sodium cathode active material of the present invention satisfies the following conditions: pH value 1 ‑pH 2 Less than or equal to 1.0 and pH 1 And pH 2 Are all less than or equal to 13.0; wherein the pH is 1 The pH value obtained by testing the dissolution of the sodium cathode active material in water; pH value 2 The pH value obtained by testing the dissolution of the sodium positive electrode active material in an alcohol organic solvent. The invention selects the pH difference value of the sodium anode active material in water and alcohol organic solvent to carry out sievingAnd (3) selecting, more accurately screening to obtain the positive active material which has stable laminated structure, less reaction with water and is beneficial to battery processing, and preparing the sodium ion battery material with better cycle performance and initial discharge specific capacity.
Description
Technical Field
The invention relates to the technical field of battery materials, in particular to a sodium anode active material, a preparation method thereof, a sodium ion battery and an electric device.
Background
With the rapid development of new energy vehicles and power grid energy storage, the consumption of lithium resources is continuously increasing, and under the background, the sodium ion battery which has the same working principle and similar battery components as the lithium ion battery is paid attention again. The sodium ion battery not only has the advantages of abundant sodium resource reserves, wide distribution, low cost, environmental friendliness and compatibility with the existing production equipment of the lithium ion battery, but also has the advantages of better power characteristic, wide temperature range adaptability, safety performance, no over-discharge problem and the like. Meanwhile, by means of the characteristic that the anode and the cathode can adopt aluminum foil current collectors to construct a bipolar battery, the energy density of the sodium ion battery can be further improved, and the sodium ion battery is advanced towards the directions of low cost, long service life, high specific energy and high safety, so that the sodium ion battery is an ideal energy technology for replacing the lithium ion battery in partial fields, and is a research hotspot in both academic circles and industrial circles in recent years.
In the positive active material of the sodium ion battery, the layered material has a two-dimensional transmission channel, the sodium ion transmission is faster, and the compaction density of the layered material is higher, so that the sodium ion battery has higher energy density and wider application range, and is an ideal positive material.
However, the sodium ion battery layered material has some problems, the stability of the synthesized material in the air is poor, especially the influence in the humid air is further aggravated, mainly, the unstable layered material and water have Na-H exchange reaction to generate more NaOH, the pH of the material is obviously increased and the water absorption is serious due to more generated alkaline impurities, so that the slurry is difficult to coat due to the gel generated in the processing process, the gas generation is increased due to the reaction of the impurities and the electrolyte in the subsequent electrochemical reaction process, and the cycle performance and the safety performance are seriously influenced.
Therefore, it is required to provide a sodium cathode active material having a stable structure and not easily absorbing water to improve the processability and electrochemical properties of a battery.
Disclosure of Invention
The invention aims to overcome the defects that the prior sodium cathode active material is unstable in layered structure, is easy to absorb water and difficult to coat, and is easy to generate gas during the charge and discharge process to influence the cycle performance and the safety performance of a battery, and provides the sodium cathode active material which is stable in structure and difficult to absorb water. According to the sodium cathode active material, the difference value between the pH value measured by dissolving the sodium cathode active material in water and the pH value measured by dissolving the sodium cathode active material in an alcohol organic solvent is within 1.0, and the pH value measured by dissolving the sodium cathode active material in the alcohol organic solvent and the pH value measured by dissolving the sodium cathode active material in water is less than 13, so that the cathode material meeting the conditions is stable in layered structure, less in reaction with water, beneficial to battery processing, capable of improving the cycle stability, reducing the safety risk and further capable of improving the initial specific discharge capacity of the battery prepared by the sodium cathode active material.
Another object of the present invention is to provide a method for preparing the sodium cathode active material.
Another object of the present invention is to provide a sodium ion battery prepared from the sodium cathode active material.
Another object of the present invention is to provide an electric device including the sodium ion battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
a sodium positive electrode active material comprising a layered metal oxide, the sodium positive electrode active material satisfying the following conditions:
pH 1 -pH 2 less than or equal to 1.0 and pH 1 And pH 2 Are all less than or equal to 13.0;
wherein the pH is 1 The pH value measured for the dissolution of the sodium positive electrode active material in water; pH value 2 The pH value obtained by the test was measured for the dissolution of the positive electrode active material in an alcohol organic solvent.
According to the invention, a great deal of research shows that if the difference value of the pH value obtained by dissolving the prepared positive active material in water and testing the positive active material in an alcohol organic solvent meets the above condition, the layered structure of the positive active material is relatively stable; the present inventors have also found that the pH of the positive electrode active material, such as in the above two solvents, is too high (e.g., greater than 13), the pH at which water is inserted into the molecule can be changed is limited, and that highly basic materials have a particularly large influence on the battery performance, gas evolution is accelerated, and cycle stability is drastically reduced. Therefore, within the appropriate pH range, the difference between the pH values of the two solvents is small, and the structure of the positive active material meeting the condition is more stable, so that the sodium-ion battery prepared from the positive active material has better cycle performance and initial discharge specific capacity.
The sodium positive electrode active material inevitably contains a certain amount of free sodium elements, and these free metal ions react with OH in water - In addition to the formation of alkali to increase the alkalinity of the material in aqueous solution, undoped metal oxides (including sodium oxide, doped element oxides, etc.) also absorb water and react to form alkali, further increasing the pH of the material in water; the sodium anode active material is stable in the alcohol organic solvent, does not generate alkali to influence the pH value of the solution, and can reflect the property of the active material. Therefore, the pH value obtained by testing the sodium cathode active material in water in the invention can reflect the content of water-absorbable impurities (such as free sodium ions and metal oxides) in the cathode active material to a certain extent, and when the pH difference value of the active material in two solvents is smaller, the content of water-absorbable impurities in the active material is smaller, and the material reacts with water less, so that the layered structure of the cathode active material is more stable.
The pH difference value of the active material in water and an alcohol organic solvent is selected for characterization, so that the water absorption performance of the anode active material can be more accurately reflected. The alcohol organic solvent does not react with water-absorbable impurities such as free sodium or sodium oxide, metal oxide, etc. to generate alkali, and does not ionize H + Affecting the pH of the sodium cathode active material in its solution.
Methods for pH testing of the solution include, but are not limited to, titration, pH meter testing.
Preferably, the positive electrode active material is dissolved in water to test the resulting pH 1 11.5 to 12.5, pH measured in an alcoholic organic solvent 2 Is 11.0 to 12.5. If the pH value is larger, the content of residual alkali (such as NaOH) in the positive active material is higher, water is easy to absorb, and in the preparation process of the electrode active slurry, the binder PVDF and the positive active material can be mixedResidual alkali (namely free sodium) on the surface of the material undergoes defluorination reaction, namely OH in the residual alkali - Nucleophilic reaction with PVDF, rearrangement to generate conjugated polyene, and the conjugated double bond in polyene is further reacted with OH - Further nucleophilic reactions take place, the double bonds are oxidized to carbonyl and hydroxyl groups and finally the PVDF is degraded, during which water is also formed, causing the PVDF to coagulate and gel in water. Slurry gelation can cause the active slurry to form an uneven surface during the coating process; the pH value is small, so that the free sodium is less, the alkalinity of the material is weaker, the water absorption is weaker, the reaction of the active material and the PVDF binder can be greatly reduced when the slurry is stirred, uniform pole pieces can be formed by stirring and coating, and the cycling stability of the battery is improved.
Preferably, the alcohol organic solvent comprises at least one of absolute methanol and absolute ethanol, and is further preferably absolute ethanol.
Preferably, the content of moisture in the positive electrode active material is <1000ppm. The size of solid moisture reflects the water absorption degree of the material, the structure of the material can be damaged when the water absorption is excessive, and meanwhile, the preparation process of the battery can be interfered, so that the cycle performance and the safety performance are seriously influenced. In the invention, the moisture content is tested by referring to a Karl Fischer titration method in GB/T243358-2019, a Karl Fischer titrator is adopted as equipment, 1g of powder sample is taken, the heating temperature is 200 ℃, the heating time is 5min, the air flow rate is 50mL/min, and the moisture content is obtained through data displayed by the titrator.
The powder resistivity of the positive active material under 20kN can meet the use requirement of the battery within the range of 3000-1000000 omega-cm, but the powder resistivity of the positive active material can reflect the dynamic performance of the material, has important significance for the process stability of the material and the resistance estimation of a finished battery, and the multiplying power performance is influenced by the overlarge powder resistance, so that the capacity is low. Therefore, the powder resistivity of the positive electrode active material at 20kN is preferably 8000 to 35000 Ω · cm. In the invention, the powder resistivity is tested by referring to a four-probe method in GB/T30835-2014, a resistivity tester is adopted as equipment, 10g of powder sample is taken and introduced into a die, and then 20KN pressure is applied to read the powder resistance through the tester.
Preferably, the positive active material has a true density of 4.2 to 4.4g/cm 3 . For example, the true density may be 4.2g/cm 3 、4.3g/cm 3 、4.4g/cm 3 Or a range consisting of any two of them, and the true density is more preferably 4.3 to 4.4g/cm 3 The true density is equal to the ratio of the mass of the positive active material to the true volume of the positive active material, where the true volume is the actual volume of the solid material and affects the compaction density of the material, which in turn affects the electrochemical properties of the battery, such as energy density, initial discharge energy, etc. In the invention, the true density is tested by referring to a method in GB/T24332019, the equipment adopts a true density tester, wherein the volume of a sample pool is 10cm 3 And (3) filling a sample amount of not less than 2/3 into the sample pool, and reading the value by using a true density instrument.
Optionally, the layered metal oxide comprises sodium nickel iron manganese oxide containing an element Me comprising at least one of Zr, mo, al, sr, mg, W, Y, nb, ru, ti, or Ca elements. The doping elements can effectively enhance the structural stability of the material and improve the cycle performance and the safety performance. Ni, fe, mn are main elements constituting the layered metal oxide.
Preferably, the layered metal oxide comprises a compound of formula Na q Ni x Fe y Mn z Me p O 2 Wherein 0.67<q≤1.1，0<x≤0.5，0<y≤0.5，0<z≤0.5，0≤p≤0.05，x+y+z+p＝1。
Preferably, the Na q Ni x Fe y Mn z Me p O 2 In the formula, q is more than or equal to 0.95 and less than or equal to 1.1. The sodium anode active material contains a large amount of Na element, and the increase of the Na element content is beneficial to improving the energy density of the battery, so that the performances of the battery such as initial discharge capacity and the like are improved.
The preparation method of the sodium cathode active material comprises the following steps:
s1, preparing a sodium anode active material precursor
Mixing a main element metal salt solution, a precipitator and a complexing agent to obtain a mixed solution, controlling the pH of the mixed solution to be 11.0-12.0 under an inert atmosphere, reacting for 12-48 h at 50-60 ℃, and drying to obtain a sodium anode active material precursor;
s2, after uniformly mixing the sodium anode active material precursor obtained in the step S1, sodium salt and doped element oxide, pre-calcining for 2-3 hours at 450-500 ℃, and then calcining for 10-14 hours at 800-900 ℃ to obtain the sodium anode active material.
In the invention, a proper process is selected to prepare a precursor material, and then the prepared precursor material, sodium salt and doping elements are calcined: on one hand, more sodium elements can be doped, and can generate a sodium-rich phase, so that more disintercalable sodium ions can be provided for electrochemical reaction, the capacity is higher, and the energy density of the battery is improved; on the other hand, the precursor elements are more uniformly distributed, the morphology is more regular, the reaction activity is higher, the generated sodium oxide can be more firmly fixed in the precursor material, the content of free sodium and free sodium oxide in the sodium anode active material is reduced, and the stability of the material is improved.
Preferably, the base metal salt in the base metal salt solution is at least one of a sulfate, nitrate, acetate, oxalate or chloride of the base metal.
The sodium salt includes, but is not limited to, at least one of sodium carbonate, sodium nitrate, sodium sulfate, sodium acetate, or sodium oxalate.
Conventional precipitating and complexing agents may be used in the present invention. The precipitating agents include, but are not limited to, sodium hydroxide; the complexing agent includes, but is not limited to, ammonia.
The inert atmosphere is an atmosphere formed by mixing at least one of nitrogen, argon or helium.
Preferably, in the step S2, the calcination is carried out in an oxygen-containing atmosphere, the calcination temperature is 800-900 ℃, the calcination time is 10-14 h, and the temperature rise rate of the calcination is 3-5 ℃/min.
The invention also provides a sodium ion battery prepared from the sodium cathode active material. The sodium ion battery comprises a positive pole piece, wherein the positive pole piece comprises a positive current collector and a sodium positive active material layer arranged on the positive current collector, and the sodium positive active material layer comprises the sodium positive active material.
An electric device comprising the sodium-ion battery is also within the scope of the present invention.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the pH difference value of the sodium anode active material in water and an alcohol organic solvent is selected for screening, so that the anode active material which has a stable layered structure, has less reaction with water and is beneficial to battery processing can be screened more accurately, and the sodium ion battery material with better cycle performance and initial discharge specific capacity can be prepared.
Drawings
Fig. 1 is an SEM image of a sodium cathode active material prepared in example 1;
fig. 2 is an SEM image of the sodium cathode active material prepared in comparative example 4.
Detailed Description
To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples and drawings, but the examples are not intended to limit the present invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated. Unless otherwise indicated, reagents and materials used in the present invention are commercially available.
Example 1
This example provides a sodium cathode active material of the formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation method comprises the following steps:
s1, preparing a sodium anode active material precursor
Preparing nickel nitrate, ferrous nitrate and manganese nitrate into a mixed metal salt solution with a molar ratio of 0.33; preparing a sodium hydroxide solution with the concentration of 4 mol/L; preparing 6mol/L ammonia water solution;
synchronously adding a mixed metal salt solution, a precipitator sodium hydroxide solution and a complexing agent ammonia water solution which are equal in volume into a reaction kettle, controlling the stirring speed at 300rpm, the temperature at 55 ℃, maintaining the pH at 11.5, reacting for 36 hours, continuously introducing nitrogen as a protective gas to prevent metal oxidation in the reaction process, wherein the nitrogen flow is 15m 3 H, washing and drying after the reaction to prepare a precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 ；
S2, the sodium anode active material precursor obtained in the step S1, sodium carbonate and ZrO 2 Uniformly mixed at a molar ratio of 0.998 3 H, preheating from room temperature (25 ℃) to 450 ℃ at a heating rate of 3 ℃/min, preserving heat for 3h, then continuously heating to 800 ℃, calcining at the temperature for 12h, naturally cooling to room temperature after the calcination is finished, and then crushing and classifying to obtain the Na (Ni) positive electrode active material 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 。
Example 2
This example provides a sodium cathode active material having the chemical formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation method is different from the example 1 in that the reaction time in the step S1. Is 24h, and the temperature rise rate in the step S2. Is 5 ℃/min.
Example 3
This example provides a sodium cathode active material of the formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation process differs from example 1 in that the reaction time described in step S1. Is 48h.
Example 4
This example provides a sodium cathode active material having the formulaNa(Ni 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation process differs from example 1 in that the temperature of the reaction described in step S1. Is 50 ℃.
Example 5
This example provides a sodium cathode active material having the chemical formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation process differs from example 1 in that the temperature of the reaction described in step S1. Is 60 ℃.
Example 6
This example provides a sodium cathode active material having the chemical formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation method is different from example 1 in that the pH of the mixed solution in step s1. Is 11.0.
Example 7
This example provides a sodium cathode active material having the chemical formula Na (Ni) 0.33 Fe 0.33 Mn 0.33 ) 0.998 Zr 0.002 O 2 The preparation method is different from example 1 in that the pH of the mixed solution in step s1. Is 12.0.
Examples 8 to 13
Sodium positive electrode active materials were prepared according to the method of example 1, with the kind and ratio of doping elements changed, and the chemical formulas of the sodium positive electrode active materials of examples 8 to 13 are shown in table 1, in terms of the element molar ratio:
table 1 chemical composition of sodium positive electrode active materials of examples 8 to 13
| Examples | Doping element | Chemical formula (II) |
| Example 8 | ZrO 2 ,SrO 2 | Na(Ni 0.33 Fe 0.33 Mn 0.33 ) 0.998 Sr 0.001 Zr 0.001 O 2 |
| Example 9 | ZrO 2 ,MoO 3 ,CeO 2 | Na(Ni 0.33 Fe 0.33 Mn 0.33 ) 0.996 Zr 0.002 Mo 0.001 Ce 0.001 O 2 |
| Example 10 | WO 3 ,SrO 2 ,Nb 2 O 3 | Na(Ni 0.33 Fe 0.33 Mn 0.33 ) 0.992 W 0.004 Sr 0.002 Nb 0.002 O 2 |
| Example 11 | ZrO 2 ,MgO,Al 2 O 3 | Na(Ni 0.33 Fe 0.33 Mn 0.33 ) 0.990 Zr 0.003 Mg 0.004 Al 0.003 O 2 |
| Example 12 | CaO 2 ,RuO 2 | Na(Ni 0.6 Fe 0.2 Mn 0.2 ) 0.996 Ca 0.002 Ru 0.002 O 2 |
| Example 13 | ZrO 2 ,YO 2 ,MgO | Na(Ni 0.6 Fe 0.2 Mn 0.2 ) 0.996 Zr 0.002 Y 0.001 Mg 0.001 O 2 |
Comparative example 1
This comparative example provides a sodium positive electrode active material prepared according to the method of example 1, except that: and S1, the pH value of the mixed solution is 13.0.
Comparative example 2
This comparative example provides a sodium positive electrode active material prepared according to the method of example 1, differing from example 1 in that: and S2, calcining for 8 hours at 800 ℃.
Comparative example 3
This comparative example provides a sodium positive electrode active material prepared according to the method of example 1, differing from example 1 in that: the calcination temperature in step S2 is 700 ℃.
Comparative example 4
This comparative example provides a sodium positive electrode active material prepared according to the method of example 1, differing from example 1 in that: in the step S2, the pre-calcination is not carried out, but the calcination is carried out for 15 hours by directly heating to 800 ℃.
Comparative example 5
This comparative example provides a sodium positive electrode active material prepared according to the method of example 1, differing from example 1 in that: in the step S2, the pre-calcination temperature is 400 ℃.
Performance testing
The sodium cathode active materials obtained in the above examples and comparative examples and the sodium ion batteries prepared therefrom were tested for their performance, and the specific test items, test methods and results were as follows:
1. characterization of physical parameters of the sodium cathode active material:
1) Dissolving a sodium cathode active material into deionized water to prepare a solution with the concentration of 0.1g/mL, and testing the pH of the solution by using a pH meter, wherein the pH is recorded as pH 1 (ii) a The sodium positive electrode active material was dissolved in absolute ethanol to prepare a solution having a concentration of 0.1g/mL, and the pH of the solution was measured with a pH meter and was recorded as pH 2 ；
2) Powder resistivity (Ω. Cm): testing by a four-probe method in GB/T30835-2014, wherein the equipment adopts a resistivity tester, 10g of powder sample is introduced into a die, and then 20KN pressure is applied to read the resistivity of the powder through the tester;
3) True density (denoted as ρ True ，g/cm 3 ): the method is characterized in that the method is tested according to the method in the GB/T24332019 standard, the equipment adopts a true density tester, wherein the volume of a sample pool is 10cm 3 The sample amount of not less than 2/3 is filled in the sample pool, and the value is read by a true density instrument;
4) Solid moisture content (ppm): the method is characterized by comprising the following steps of (1) testing by referring to a Karl Fischer titration method in GB/T24332019, wherein a Karl Fischer titrator is adopted as equipment, 1g of powder sample is taken, the heating temperature is 200 ℃, the heating time is 5min, the air flow rate is 50mL/min, and the water content is obtained through data displayed by the titrator;
5) And (3) morphology characterization: the surface morphology of the obtained positive active material is characterized by adopting a Scanning Electron Microscope (SEM), and the test result is shown in figures 1 and 2; as can be seen from the figure, when the pH value is lower, the obtained cathode material is dispersed more uniformly and has less fine powder (as the active material of example 1 shown in fig. 1), which is beneficial to improving the cycle stability of the material.
The test results are shown in Table 2.
2. And (3) testing the battery performance:
the method comprises the following steps of mixing a sodium positive electrode active material, a conductive agent, conductive carbon black and a binder polyvinylidene fluoride (PVDF) according to a mass ratio of 95:3:2, mixing, adding solvent N-methyl pyrrolidone (NMP), stirring in a vacuum stirrer, and preparing uniform anode slurry after stirring; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 16 mu m, drying in a drying oven at 100 ℃ after coating, and then rolling, slitting and cutting into pieces to obtain a positive electrode piece;
the stability of the positive electrode slurry is also tested, and the discharge viscosity and the viscosity after standing for 24 hours are compared for evaluation, wherein the viscosity (mPa.s) test method comprises the following steps: testing the viscosity by adopting a viscosity tester, putting 500mL of positive slurry into a beaker, putting a corresponding rotor into the beaker, setting parameters for testing, and reading the viscosity value by reading a reading on the tester;
resistivity (Ω. Cm) test of the positive electrode sheet: testing the diaphragm resistance by adopting a diaphragm resistance tester, taking a pole piece and placing the pole piece on a workbench, wherein the testing area is 1540mm 2 Taking the point sampling time as 15s, taking the test times as 20 times, reading the data through a tester, and then taking an average value to obtain the resistivity (omega. Cm) of the positive pole piece;
mixing hard carbon, sodium carboxymethyl cellulose, conductive carbon black and styrene butadiene rubber according to a mass ratio of 96.5:1.5:1.5:0.5, adding the mixture into water, uniformly mixing to prepare negative electrode slurry, and coating the negative electrode slurry on the surface of a negative electrode current collector to obtain a negative electrode plate.
And (2) stacking the prepared positive pole piece, the diaphragm (PP film) and the negative pole piece in sequence to ensure that the diaphragm is just positioned between the positive pole and the negative pole to play a role of isolating the two electrodes, then winding the positive pole piece, the diaphragm (PP film) and the negative pole piece into a bare cell, putting the bare cell into an aluminum plastic film, baking the bare cell at 80 ℃ to remove moisture, injecting electrolyte (1 mol/L sodium hexafluorophosphate is dissolved in an organic solvent (volume ratio EC: DMC: DEC = 1).
When the performance of the battery is tested, the first charging is carried out by adopting 0.1C constant current charging to 3.9V, and the first discharging is carried out by adopting 0.1C constant current discharging to 1.5V: 1) The cycle performance test is that the cycle number (the capacity retention rate can keep 80% of the maximum number) is constant at 25 ℃/45 ℃, the voltage interval is 1.5-3.8V, and 1C constant current and constant voltage charging (the cut-off current is 0.05C in constant voltage) and constant current discharging are adopted; 2) Initial specific discharge capacity (mAh/g) test: and (3) carrying out constant-current constant-voltage charging (the cut-off current is 0.02C at constant voltage) on the soft-packaged cell at room temperature by using 0.1C, wherein the upper limit of the voltage is 3.9V, and carrying out constant-current discharging by using 0.1C after standing for 5min, wherein the lower limit of the voltage is 1.5V. The test results are shown in Table 2.
Table 2 performance test results of sodium positive active material battery
From the above results, it can be seen that:
when the pH value is low and the difference value of the tested pH value is small by using different testing methods, the structural stability of the material is favorably improved, and the cycle performance of the battery is further improved; however, when the pH value is large to a certain extent (for example, the pH values of comparative examples 1 to 3 are all larger than 13), even if the difference value of different solvent tests is small, the cycle performance of the obtained battery is still poor, mainly because the residual alkali on the surface of the material is too much, the structure is unstable, the solvent is more alkali dissolved by water or ethanol, the gas generation is accelerated, and the cycle stability is also seriously deteriorated.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (11)
1. A sodium positive electrode active material comprising a layered metal oxide, characterized in that the sodium positive electrode active material satisfies the following condition:
pH 1 -pH 2 less than or equal to 1.0 and pH 1 And pH 2 Are all less than or equal to 13.0;
wherein the pH is 1 The pH value measured for the dissolution of the sodium positive electrode active material in water; pH value 2 The pH value obtained by the test was measured for the sodium positive electrode active material dissolved in an alcohol organic solvent.
2. The sodium positive electrode active material according to claim 1, wherein the sodium positive electrode active material is dissolved in water to measure a pH 1 Is 11.5 to 12.5.
3. The sodium positive electrode active material according to claim 1, wherein the sodium positive electrode active material is dissolved in an alcohol organic solvent to measure a pH 2 Is 11.0 to 12.5.
4. The sodium cathode active material according to claim 1, wherein the layered metal oxide comprises sodium nickel iron manganese oxide containing an element Me comprising at least one of Zr, mo, al, sr, mg, W, Y, nb, ru, ti, or Ca elements.
5. The sodium cathode active material according to claim 4, wherein the layered metal oxide comprises Na having a formula q Ni x Fe y Mn z Me p O 2 Compound (1), wherein 0.67<q≤1.1，0<x≤0.5，0<y≤0.5，0<z≤0.5，0≤p≤0.05，x+y+z+p＝1。
6. The sodium positive electrode active material according to claim 1, wherein the content of moisture in the sodium positive electrode active material is <1000ppm.
7. The sodium positive electrode active material according to claim 1, wherein a powder resistivity of the sodium positive electrode active material at 20kN is 8000 to 35000 Ω -cm.
8. The sodium positive electrode active material according to claim 1, wherein the sodium positive electrode active material has a true density of 4.3 to 4.4g/cm 3 。
9. The method for producing a sodium positive electrode active material according to any one of claims 1 to 8, characterized by comprising the steps of:
s1, preparing a sodium anode active material precursor
Mixing a main element metal salt solution, a precipitator and a complexing agent to obtain a mixed solution, controlling the pH of the mixed solution to be 11.0-12.0 under an inert atmosphere, reacting for 12-48 h at 50-60 ℃, and drying to obtain a sodium anode active material precursor;
s2, after the precursor of the sodium anode active material obtained in the step S1, sodium salt and the doped element oxide are uniformly mixed, precalcining is carried out for 2-3 h at the temperature of 450-500 ℃, and then calcining is carried out for 10-14 h at the temperature of 800-900 ℃, so as to obtain the sodium anode active material.
10. A sodium ion battery comprising a positive electrode plate, wherein the positive electrode plate comprises a positive current collector and a sodium positive active material layer disposed on the positive current collector, and the sodium positive active material layer comprises the sodium positive active material according to any one of claims 1 to 8.
11. An electric device comprising the sodium-ion battery according to claim 10.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116314728A (en) * | 2023-05-15 | 2023-06-23 | 宁德时代新能源科技股份有限公司 | Sodium layered metal oxide, method for producing same, secondary battery, and electricity-using device |
| CN116404117A (en) * | 2023-06-07 | 2023-07-07 | 四川富临新能源科技有限公司 | Method for improving capacity of sodium ion positive electrode material |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116314728A (en) * | 2023-05-15 | 2023-06-23 | 宁德时代新能源科技股份有限公司 | Sodium layered metal oxide, method for producing same, secondary battery, and electricity-using device |
| CN116314728B (en) * | 2023-05-15 | 2023-10-27 | 宁德时代新能源科技股份有限公司 | Sodium layered metal oxide, method for producing same, secondary battery, and electricity-using device |
| CN116404117A (en) * | 2023-06-07 | 2023-07-07 | 四川富临新能源科技有限公司 | Method for improving capacity of sodium ion positive electrode material |
| CN116404117B (en) * | 2023-06-07 | 2023-08-11 | 四川富临新能源科技有限公司 | Method for improving capacity of sodium ion positive electrode material |
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