CN116230923A - Carbon-coated sodium ferric pyrophosphate cathode material and preparation method and application thereof - Google Patents
Carbon-coated sodium ferric pyrophosphate cathode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a carbon-coated sodium ferric pyrophosphate anode material, and a preparation method and application thereof. The molecular formula of the positive electrode material is Na a Fe b (PO 4 ) c (P 2 O 7 ) Wherein 3 is<a<4；a＝c+2；b＝c+1；1<c<2. The preparation method comprises the following steps: grinding the raw materials of the positive electrode material and the dispersing solvent, drying to obtain a precursor of the sodium iron phosphate positive electrode material, and sintering the precursor of the sodium iron phosphate positive electrode material in an inert atmosphere to obtain the carbon-coated sodium iron phosphate positive electrode material. According to the invention, commercial ferric phosphate or ferric phosphate slag obtained after lithium extraction from waste lithium powder of the positive electrode of the lithium iron phosphate battery is used as a raw material for the first time, and a series of sodium-rich ferric sodium pyrophosphate positive electrode materials are successfully prepared by adopting a simple mechanical ball milling method to assist high-temperature sintering. And the ferric sodium phosphate positive electrodes with different compositions have highPure phase and exhibits excellent rate performance and cycle stability.
Description
Technical Field
The invention relates to the field of sodium ion batteries, and relates to a carbon-coated sodium ferric pyrophosphate positive electrode material, a preparation method and application thereof.
Background
In recent years, along with the increasing severity of two international problems of energy crisis and environmental pollution, the world actively conforms to the global green low-carbon development trend, and clean energy (such as solar energy, wind energy, tidal energy and the like) is unprecedented. The problem of how to store energy is involved while developing these new forms of energy. Batteries have received much attention as an energy storage medium because of their green and convenience advantages. Secondary rechargeable lithium ion batteries are widely studied as an energy storage device because of higher conversion efficiency and energy density. However, the future development of lithium resources is limited by the problems of lack of lithium resources, uneven distribution and the like. With the rise of large-scale energy storage and the consideration of the characteristics of high crust abundance, low price and the like of sodium resources, the sodium ion battery becomes an important supplementary part of the lithium ion battery.
In sodium ion batteries, iron-based polyanion positive electrode materials are receiving extensive attention because of the characteristics of low price, environmental friendliness, excellent cycle performance, good safety and the like. Sodium iron phosphate (Na) with monoclinic phase 3 Fe 2 (PO 4 ) 3 ) Since the valence of iron is positive trivalent, capacity cannot be obtained in the first charge, and thus it is not suitable as a positive electrode material for practical use. Ferrous sodium phosphate (NaFePO) with olivine structure 4 ) Although good electrochemical performance can be achieved, the olivine phase is a non-thermodynamically stable phase and usually requires a complex synthesis process to achieve this. While thermodynamically stable ferrous sodium phosphate (NaFePO) 4 ) The structure of typical sodium-manganese ore is simple and easy to obtain, but the structure has no effective sodium ion diffusion channel and no electrochemical activity. In recent years, sodium iron pyrophosphate has been demonstrated as an electrochemically active positive electrode material, having a specific composition of Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 And Na (Na) 3 Fe 2 PO 4 P 2 O 7 Positive electrodes, their theoretical capacities respectively reach 128mA h g -1 And 119mA h g -1 Has a wide application prospect. Particularly, the sodium ferric pyrophosphate with higher sodium content has high initial capacity, low raw material cost and good cycle performance, and is suitable for a large-scale energy storage system. But now make sodium-rich Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 The positive electrode typically contains electrochemically inert NaFePO 4 And heterogeneous phase, thereby reducing its initial capacity. The sodium content is controlled to be between 3 and 4, not only has higher theoretical capacity (120 to 128mA h g -1 ) And is also beneficial to preparing high-purity ferric sodium phosphate cathode material.
On the other hand, commercial ferric phosphate is used as a precursor of lithium iron phosphate, has stable property, low price and mass production, can simultaneously provide a phosphorus source and an iron source, has the characteristic of high atomic utilization rate when being used for preparing sodium ferric phosphate, and can reduce the generation of byproducts or other gas and liquid phases. In addition, the current widely used lithium iron phosphate batteries tend to lead to a large number of scrapped lithium iron phosphate batteries due to the service life of the lithium iron phosphate batteries, and the positive electrode powder of the waste batteries contains valuable element Li, so that the lithium iron phosphate batteries have great recovery value, and the current situation is that the residual iron phosphate slag is produced after the positive electrode powder of the waste lithium iron phosphate batteries selectively recovers lithium, and the recovery value is low, the residual iron phosphate slag is either piled up or the iron phosphate slag is subjected to acid dissolution and then is subjected to impurity removal, and then the waste iron phosphate batteries are further prepared into ferric phosphate, so that the process is complex, and the recovery and reuse cost is high. If the iron phosphate slag can be directly regenerated into valuable materials, the sustainable recycling of the waste lithium iron phosphate battery can be realized.
CN113104828A discloses a preparation method of porous carbon modified ferric sodium phosphate positive electrode material, ferric nitrate nonahydrate is used as an iron source, ammonium dihydrogen phosphate and sodium pyrophosphate are used as a phosphorus source and a sodium source, citric acid and PVP are used as carbon sources, naCl is used as a template, and porous carbon coated ferric sodium phosphate positive electrode material can be obtained after high-temperature sintering. Although the overall conductivity of the positive electrode material can be improved by introducing porous carbon coating, in the preparation method, the iron content of the ferric nitrate nonahydrate is low, the atomic utilization rate is low, the price is high, and NO is released in the calcination process x And the gas is equal, so that the environment is not protected. The NaCl is used as a template, which means that the product needs to be washed by a large amount of clean water, the process flow is long, and the large-scale production is not facilitated.
CN110061233a discloses a fluorocarbon-doped coated sodium ferric pyrophosphate@mesoporous carbon composite material, which is prepared by taking ferric nitrate nonahydrate, ferrous acetate, ferric oxalate or iron powder as an iron source, adding a phosphorus source, a sodium source, a fluorine-containing polymer and mesoporous carbon as a carbon source, ball-milling and mixing, and sintering at high temperature. The iron source of the preparation method adopts ferric nitrate nonahydrate, ferrous acetate, ferric oxalate and the like, has low atomic utilization rate and high price, is produced along with other gases or products in the calcination process, and is not environment-friendly. The iron powder is used as an iron source, an acidic reagent is required to be added, the corrosiveness is strong, and the requirement on equipment is high. In addition, the polymer and the mesoporous carbon are expensive, which is not beneficial to mass production.
CN112563484a discloses a positive electrode material of a sodium ion battery, a preparation method thereof and the sodium ion battery. The positive electrode material of the sodium ion battery is prepared into a material with a layered structure, and the preparation method is to control the precursor mixed solution to react under the conditions of high temperature and high pressure. The preparation process is simple, but the high-temperature and high-pressure environment has a certain danger, and the high-pressure environment has higher requirements on equipment.
How to prepare a high-rate long-cycle positive electrode material which is simple to operate and suitable for large-scale production with low cost is an important research direction in the field.
Disclosure of Invention
The invention aims to provide a carbon-coated sodium ferric pyrophosphate anode material, and a preparation method and application thereof.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
the first aspect of the invention provides a carbon-coated sodium ferric pyrophosphate positive electrode material, the molecular formula of the positive electrode material is Na a Fe b (PO 4 ) c (P 2 O 7 ) Wherein 3 is<a<4；a＝c+2；b＝c+1；1<c<2。
The value of a may be 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8 or 3.9, etc., and the value of c may be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, etc., but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
The inventionCommercial ferric phosphate (or ferric phosphate slag after lithium extraction from waste lithium phosphate battery anode waste powder), an additional phosphorus source, a sodium source and a carbon source are directly prepared into a series of sodium ferric pyrophosphate anode materials Na with excellent electrochemical performance by regulating and controlling the proportion of Na, P and Fe a Fe b (PO 4 ) c (P 2 O 7 )(3<a<4；a＝c+2；b＝c+1；1<c<2) Has great significance for the application of the sodium ion battery in a large-scale energy storage system in the future. At 3<a<4；a＝c+2；b＝c+1；1<c<2, na in the present invention a Fe b (PO 4 ) c (P 2 O 7 ) Unlike the reported Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 And Na (Na) 3 Fe 2 PO 4 P 2 O 7 When a increases gradually from 3 to 4, the larger a is, the higher the capacity of the material is, because the sodium ion content is high, but when a reaches 4 or more, naFePO is easily generated 4 Leading to a reduced cyclic stability of the material and limited capacity exertion of the material; the smaller a is, the lower the capacity of the material is, because the sodium ion content is lower, but the circulation stability of the material is enhanced, and the capacity is easy to exert; distinguished from the two end compounds Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 And Na (Na) 3 Fe 2 PO 4 P 2 O 7 The corresponding theoretical capacities are 128mA h g respectively -1 And 119mA h g -1 Thus when 3<a<At 4, na a Fe b (PO 4 ) c (P 2 O 7 ) Is between 128mA hg -1 And 119mA h g -1 Therefore, the series of compounds can regulate and control the capacity and the cycle stability of the material by regulating and controlling the content of Na, and the comprehensive performance of the material is necessarily optimal at a certain balance point. Because the materials with different sodium contents belong to mutually-soluble phases, the cathode material of the sodium ferrous pyrophosphate with higher cycling stability and higher capacity can be synthesized without strict control conditions.
As a preferable technical scheme of the invention, the raw materials of the positive electrode material comprise ferric phosphate, an additional phosphorus source, a sodium source and an organic carbon source.
Preferably, the iron phosphate comprises any one or a combination of at least two of anhydrous iron phosphate, ferric phosphate dihydrate, ferric phosphate tetrahydrate or iron phosphate slag after lithium extraction from lithium iron phosphate battery positive electrode waste powder, typical but non-limiting examples of which are: a combination of anhydrous iron phosphate and ferric phosphate dihydrate, a combination of ferric phosphate dihydrate and ferric phosphate tetrahydrate, a combination of ferric phosphate dihydrate and ferric phosphate slag after lithium extraction from lithium iron phosphate battery positive electrode waste powder, or a combination of anhydrous iron phosphate and ferric phosphate dihydrate and ferric phosphate slag after lithium extraction from lithium iron phosphate battery positive electrode waste powder, and the like.
Preferably, the additional phosphorus source comprises any one or a combination of at least two of monoammonium phosphate, monoammonium sodium phosphate, ammonium sodium phosphate, diammonium sodium phosphate, or phosphoric acid, wherein typical but non-limiting examples of such combinations are: a combination of monoammonium phosphate and monoammonium sodium phosphate, a combination of monoammonium sodium phosphate and ammonium phosphate, a combination of ammonium phosphate and ammonium sodium phosphate, a combination of ammonium sodium phosphate and diammonium phosphate, a combination of diammonium phosphate and diammonium sodium phosphate, or a combination of diammonium sodium phosphate and phosphoric acid, and the like.
The invention adopts the leaching slag taking the ferric phosphate as the main component after the lithium is recovered by the lithium iron phosphate anode powder as the raw material, which provides a valuable path for the treatment and the reutilization of the slag after the valuable metal lithium is recovered by the lithium iron phosphate, and can realize the comprehensive reutilization of the waste lithium iron phosphate.
As a preferred embodiment of the present invention, the sodium source comprises any one or a combination of at least two of sodium carbonate, sodium acetate, sodium nitrate, sodium hydroxide or sodium oxalate, wherein typical but non-limiting examples of the combination are: a combination of sodium carbonate and sodium acetate, a combination of sodium acetate and sodium nitrate, a combination of sodium nitrate and sodium hydroxide, or a combination of sodium hydroxide and sodium oxalate, and the like.
As a preferred embodiment of the present invention, the organic carbon source includes any one or a combination of at least two of citric acid, sodium citrate, oleic acid, sodium oleate, polyvinylpyrrolidone, glucose, sucrose, dopamine hydrochloride, starch, graphene, carbon nanotubes or ketjen black, wherein typical but non-limiting examples of the combination are: a combination of citric acid and sodium citrate, a combination of sodium citrate and oleic acid, a combination of oleic acid and sodium oleate, a combination of sodium oleate and polyvinylpyrrolidone, a combination of polyvinylpyrrolidone and glucose, a combination of glucose and sucrose, a combination of sucrose and dopamine hydrochloride, a combination of dopamine hydrochloride and starch, a combination of starch and graphene or a combination of carbon nanotubes and ketjen black, and the like.
As a preferable technical scheme of the invention, the molar ratio of the organic carbon source to the ferric phosphate is (0.5-10): 1, wherein the molar ratio may be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
A second aspect of the present invention is to provide a method for preparing the carbon-coated sodium iron pyrophosphate cathode material according to the first aspect, comprising:
grinding the raw materials of the positive electrode material and the dispersing solvent, drying to obtain a precursor of the sodium iron phosphate positive electrode material, and sintering the precursor of the sodium iron phosphate positive electrode material in an inert atmosphere to obtain the carbon-coated sodium iron phosphate positive electrode material.
According to the invention, commercial ferric phosphate or ferric phosphate slag obtained after lithium extraction from waste lithium powder of the positive electrode of the lithium iron phosphate battery is used as a raw material for the first time, and a series of sodium-rich ferric sodium pyrophosphate positive electrode materials are successfully prepared by adopting a simple mechanical ball milling method to assist high-temperature sintering. And the ferric sodium phosphate positive electrodes with different compositions have high purity phases and show excellent multiplying power performance and cycle stability.
As a preferred embodiment of the present invention, the dispersing solvent includes any one or a combination of at least two of deionized water, ethanol or acetone, wherein typical but non-limiting examples of the combination are: a combination of deionized water and ethanol, a combination of ethanol and acetone, or a combination of deionized water and acetone, etc.
Preferably, the mass ratio of the dispersant in the dispersion solution to the raw materials of the positive electrode material is (3 to 5): 1, wherein the mass ratio may be 3:1, 4:1, 5:1, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
As a preferred embodiment of the present invention, the milling comprises ball milling.
Preferably, the rotation speed of the ball mill is 200-1200 r/min, wherein the rotation speed can be 200r/min, 300r/min, 400r/min, 500r/min, 600r/min, 700r/min, 800r/min, 900r/min, 1000r/min, 1100r/min or 1200r/min, and the like, but the ball mill is not limited to the listed values, and other non-listed values in the range of the values are also applicable.
Preferably, the ball milling time is 0.5-24 h, wherein the time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, etc., but not limited to the recited values, other non-recited values within the range of values are equally applicable.
The grinding equipment in the ball milling comprises a ball mill and/or a sand mill, wherein the mass ratio of the ball mill to the reaction materials is (2-3): 1, and the mass ratio can be 2:1, 2.1:1 and 2.2:1. 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1, etc., but are not limited to the recited values, other non-recited values within the range of values are equally applicable, preferably 2.5:1.
The drying treatment is preferably performed at a temperature of 60 to 130 ℃, wherein the temperature may be 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable.
As a preferred embodiment of the present invention, the inert atmosphere comprises any one or a combination of at least two of argon, nitrogen or neon, wherein typical but non-limiting examples of the combination are: a combination of argon and nitrogen, a combination of nitrogen and neon, or a combination of neon and argon, etc.
Preferably, the sintering temperature of the sintering treatment is 400 to 700 ℃, wherein the sintering temperature may be 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable, and further preferably 500 to 600 ℃;
preferably, the sintering time of the sintering treatment is 2 to 20 hours, wherein the sintering time may be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, etc., but not limited to the recited values, and other non-recited values within the range of the values are equally applicable.
In a third aspect, the present invention provides an application of the carbon-coated sodium ferric pyrophosphate cathode material according to the first aspect, wherein the carbon-coated sodium ferric pyrophosphate cathode material is applied to the field of sodium ion batteries.
Compared with the prior art, the invention has the following beneficial effects:
(1) The ferric phosphate can be used as a phosphorus source and an iron source simultaneously, so that the atomic utilization rate is high, the source is wide, the price is low, the whole process flow is short, the operation is simple, and the method is suitable for large-scale production.
(2) The invention provides a commercial ferric phosphate to prepare sodium ferric phosphate series anode materials, which adopts leaching slag taking ferric phosphate as a main component after lithium is recovered from the prior ferric phosphate anode powder as a raw material, thereby providing a valuable path for the treatment and reuse of slag after valuable metal lithium is recovered from the ferric phosphate, and realizing the comprehensive recycling of waste ferric phosphate lithium.
(3) The preparation method provided by the invention obtains a series of sodium-enriched ferric sodium pyrophosphate positive electrode materials with different compositions, the assembled button cell can realize charge and discharge test under 0.1C, the initial discharge specific capacity can reach more than 95% of the theoretical capacity, the specific capacity retention rate of 20C is about 82% (compared with 0.1C), and the capacity retention rate can reach more than 95% after being circulated for 200 weeks under 1C. The sodium-rich ferric sodium pyrophosphate has the advantages of low cost, high multiplying power and long cycle. The preparation method is simple to operate, obvious in improvement effect, easy to industrialize and suitable for popularization and use in the field.
Drawings
FIG. 1 is an XRD pattern of sodium ferric pyrophosphate phosphate positive electrode in example 1 of the present invention.
FIG. 2 is a graph showing charge and discharge of the sodium iron pyrophosphate positive electrode of example 1 of the present invention at 0.1C.
FIG. 3 is a graph showing charge and discharge at 20C of the sodium iron pyrophosphate positive electrode of example 1 of the present invention.
FIG. 4 is a graph showing the cycle performance of the sodium ferric pyrophosphate positive electrode of example 1 of the present invention at 1C.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
in the present embodiment Na is provided 3.5 Fe 2.5 (PO 4 ) 1.5 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: the molar ratio was 1.75:2.5:1, ferric phosphate dihydrate (CAS: 13463-10-0), ammonium dihydrogen phosphate and glucose are placed into a ball milling tank, and ethanol is added as a dispersing agent, wherein the mass ratio of the substances of the glucose and the ferric phosphate is 2:1. the ball milling rotating speed is 1200r/min, and the ball milling time is 0.5 hour. The mixture was then dried overnight in a vacuum oven at 80 degrees celsius. Grinding the obtained precursor to powder state, and sintering in a tubular furnace in argon atmosphere at 550 ℃ for 10 hours to obtain Na 3.5 Fe 2.5 (PO 4 ) 1.5 P 2 O 7 And a positive electrode material.
The XRD pattern of the sodium iron phosphate cathode prepared in this example is shown in fig. 1, the charge-discharge curve of the sodium iron phosphate cathode prepared at 0.1C is shown in fig. 2, and the charge-discharge curve of the sodium iron phosphate cathode prepared at 20C is shown in fig. 3. The cycling performance of the prepared ferric sodium pyrophosphate positive electrode at 1C is shown in figure 4.
Example 2
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
the present embodiment provides Na 3.6 Fe 2.6 (PO 4 ) 1.6 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: the composition ratio was 1.8:2.6:1, ferric phosphate dihydrate (CAS: 13463-10-0), diammonium phosphate and glucose are placed in a ball mill pot, and acetone is added as a dispersing agent, the mass ratio of glucose to ferric phosphate is 1.5:1. the ball milling rotating speed is 200r/min, and the ball milling time is 24 hours. The mixture was then dried overnight in a vacuum oven at 70 degrees celsius. Grinding the obtained precursor to powder state, and sintering in a tubular furnace in argon atmosphere at 600 ℃ for 2 hours to obtain Na 3.6 Fe 2.6 (PO 4 ) 1.6 P 2 O 7 And a positive electrode material.
Example 3
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
the present embodiment provides Na 3.7 Fe 2.7 (PO 4 ) 1.7 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: the composition ratio was 3.7:2.7:1, ferric phosphate tetrahydrate (CAS: 31096-47-6), phosphoric acid and glucose are placed in a ball mill pot, and a proper amount of ethanol is added as a dispersing agent, wherein the mass ratio of the glucose to the ferric phosphate is 1:1. the ball milling rotating speed is 1000r/min, and the ball milling time is 2 hours. The mixture was then dried overnight in a vacuum oven at 90 degrees celsius. Grinding the obtained precursor to powder state, placing into a tube furnace in argon atmosphere, sintering at 620 ℃ for 8 hours to obtain Na 3.7 Fe 2.7 (PO 4 ) 1.7 P 2 O 7 And a positive electrode material.
Example 4
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
the present embodiment provides Na 3.8 Fe 2.8 (PO 4 ) 1.8 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: the molar ratio was 3.8:2.8:1.8 sodium acetate, anhydrous ferric phosphate (CAS: 10045-86-0), ammonium phosphate and sucrose are placed in a ball mill tank, and a proper amount of deionized water is added as a dispersant, wherein the mass ratio of sucrose to ferric phosphate is 1:1. the ball milling rotating speed is 350r/min, and the ball milling time is 20 hours. The mixture was then dried overnight in a vacuum oven at 120 degrees celsius. Grinding the obtained precursor to powder state, and sintering in a tubular furnace in argon atmosphere at 550 ℃ for 5 hours to obtain Na 3.8 Fe 2.8 (PO 4 ) 1.8 P 2 O 7 And a positive electrode material.
Example 5
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
the present embodiment provides Na 3.2 Fe 2.2 (PO 4 ) 1.2 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: the molar ratio was 3.2:2.2:1.2 sodium hydroxide, ferric phosphate dihydrate (CAS: 13463-10-0), phosphoric acid and glucose are placed in a ball mill pot and an appropriate amount of ethanol is added as dispersant, wherein the mass ratio of glucose to ferric phosphate is 1:1. the ball milling rotating speed is 1000r/min, and the ball milling time is 2 hours. The mixture was then dried overnight in a vacuum oven at 90 degrees celsius. Grinding the obtained precursor to powder state, placing into a tubular furnace in argon atmosphere, sintering at 600 deg.C for 8 hr to obtain Na 3.2 Fe 2.2 (PO 4 ) 1.2 P 2 O 7 And a positive electrode material.
Example 6
The embodiment provides a carbon-coated sodium ferric pyrophosphate cathode material and a preparation method thereof:
in this embodiment, na is provided 3.5 Fe 2.5 (PO 4 ) 1.5 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps: preparation of Na by using leached slag of positive electrode powder of waste lithium iron phosphate battery after selective recovery of lithium as raw material 3.5 Fe 2.5 (PO 4 ) 1.5 P 2 O 7 The slag contains a small amount of residual Li, al, carbon, conductive adhesive and other organic matters, and according to the contents of Fe and P in the iron phosphate leaching slag, the slag comprises the following components: the molar ratio of P is 3.5:2.5:3.5, a certain amount of sodium carbonate, diammonium hydrogen phosphate and glucose are added, the mixture is placed in a ball milling tank, ethanol is added as a dispersing agent, and the mass ratio of glucose to ferric phosphate is 2:1. the ball milling rotating speed is 500r/min, and the ball milling time is 12 hours. The mixture was then dried overnight in a vacuum oven at 90 degrees celsius. Grinding the obtained precursor to powder state, placing into a tube furnace in argon atmosphere, sintering at 55deg.C for 8 hr to obtain Na 3.5 Fe 2.5 (PO 4 ) 1.5 P 2 O 7 And a positive electrode material.
Example 7
The mass ratio of glucose to iron phosphate was 2:1 with glucose and ferric phosphate at a mass ratio of 0.5:1, the other conditions were the same as in example 1.
Example 8
The mass ratio of glucose to iron phosphate was 2:1 with glucose and ferric phosphate at a mass ratio of 10:1, the other conditions were the same as in example 1.
Comparative example 1
Comparative example provides Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 As a positive electrode material, the preparation method comprises the following steps:
the molar ratio was set to 2:3:1, ferric phosphate dihydrate (CAS: 13463-10-0), ammonium dihydrogen phosphate and glucose are placed into a ball milling tank, and ethanol is added as a dispersing agent, wherein the mass ratio of the substances of the glucose and the ferric phosphate is 2:1. the ball milling rotating speed is 400r/min, and the ball milling time is 15 hours. The mixture is then placedDrying in a vacuum oven at 90 degrees celsius for one night. Grinding the obtained precursor to powder state, and sintering in a tubular furnace in argon atmosphere at 550 ℃ for 10 hours to obtain Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 And a positive electrode material.
Comparative example 2:
comparative example provides Na 3 Fe 2 PO 4 (P 2 O 7 ) As a positive electrode material, the preparation method comprises the following steps:
the molar ratio was 1.5:2:1, ferric phosphate dihydrate (CAS: 13463-10-0), ammonium dihydrogen phosphate and glucose are placed into a ball milling tank, and ethanol is added as a dispersing agent, wherein the mass ratio of the substances of the glucose and the ferric phosphate is 1:1. the ball milling rotating speed is 500r/min, and the ball milling time is 12 hours. The mixture was then dried overnight in a vacuum oven at 80 degrees celsius. Grinding the obtained precursor to powder state, placing into a tubular furnace in argon atmosphere, sintering at 580 deg.C for 8 hr to obtain Na 3 Fe 2 PO 4 (P 2 O 7 ) And a positive electrode material.
The carbon-coated sodium ferric pyrophosphate cathode materials prepared in examples 1-8 and comparative examples 1-2 were assembled into a battery, and the assembly process included the following steps:
(1) Preparation of a battery positive plate: and grinding and uniformly mixing the prepared ferric sodium phosphate cathode material, ketjen black and polytetrafluoroethylene binder according to the mass ratio of 7:2:1, and then fully rolling by a pair roller to form a film with uniform thickness. And (3) drying the positive electrode film in a vacuum drying oven at 120 ℃ for 5 hours, cutting the obtained positive electrode film into square pole pieces with the side length of about 6mm, accurately weighing the mass of the square pole pieces, and calculating the mass of active substances in the positive electrode pieces according to the composition of a formula.
(2) And (3) battery assembly:
the square positive electrode plate, the diaphragm with the diameter of 16mm, the sodium plate with the diameter of 15mm, the elastic sheet, the gasket and the like are assembled into a 2032 type testable button cell in a glove box (the oxygen content is less than 0.01ppm and the water content is less than 0.01 ppm).
The assembled batteries of examples 1 to 8 and comparative examples 1 to 2 were subjected to charge and discharge tests at various rates using the wuhan-blue electric high-performance battery test system, and the test results are shown in table 1, with the first-turn discharge specific capacity at 0.1C, the first-turn discharge specific capacity at 20C, and the first-turn discharge specific capacity at 1C and the capacity retention rate at 200 turns at 1C.
TABLE 1
As can be seen from comparative examples 1 to 6, a series of ferric sodium pyrophosphate prepared from ferric phosphate exhibited good electrochemical properties, the specific capacity for initial discharge was 95% or more of the theoretical capacity, the specific capacity retention rate of 20C was 82% or so (compared to 0.1C), and the capacity retention rate was 95% or more after 200 weeks of cycling at 1C. As can be seen from comparing example 1 with example 7, a small amount of carbon coating has correspondingly deteriorated electrochemical performance due to poor electron conductivity; as can be seen from comparing example 1 with example 8, excessive carbon coating increases the interface resistance of the positive electrode material, and has more side reactions, which are also detrimental to the electrochemical performance of the material. It can be seen from example 1, comparative example 1 and comparative example 2 that as the sodium content is more, the capacity of the material is higher, but the capacity exertion of the material is deteriorated, and the cycle stability of the material is also lowered; the lower the sodium content, the lower the capacity of the material, but the actual capacity of the material is closer to the theoretical capacity, i.e. the capacity of the material performs better and the cycling stability is better. Thus, a moderate sodium content can simultaneously achieve a good combination of properties of the material.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.
Claims (10)
1. Carbon bagThe phosphoric acid coated sodium iron pyrophosphate positive electrode material is characterized in that the molecular formula of the positive electrode material is Na a Fe b (PO 4 ) c (P 2 O 7 ) Wherein 3 is<a<4；a＝c+2；b＝c+1；1<c<2。
2. The positive electrode material according to claim 1, wherein the raw materials of the positive electrode material include iron phosphate, an additional phosphorus source, a sodium source, and an organic carbon source;
preferably, the ferric phosphate comprises any one or a combination of at least two of anhydrous ferric phosphate, ferric phosphate dihydrate, ferric phosphate tetrahydrate or ferric phosphate slag after lithium extraction from lithium iron phosphate battery positive electrode waste powder;
preferably, the additional phosphorus source comprises any one or a combination of at least two of monoammonium phosphate, monoammonium sodium phosphate, ammonium sodium phosphate, diammonium sodium phosphate, or phosphoric acid.
3. The positive electrode material of claim 2, wherein the sodium source comprises any one or a combination of at least two of sodium carbonate, sodium acetate, sodium nitrate, sodium hydroxide, or sodium oxalate.
4. The positive electrode material according to claim 2 or 3, wherein the organic carbon source comprises any one or a combination of at least two of citric acid, sodium citrate, oleic acid, sodium oleate, polyvinylpyrrolidone, glucose, sucrose, dopamine hydrochloride, starch, graphene, carbon nanotubes, or ketjen black.
5. The positive electrode material according to any one of claims 2 to 4, wherein the molar ratio of the organic carbon source to the iron phosphate is (0.5 to 10): 1.
6. a method for preparing the carbon-coated sodium ferric pyrophosphate cathode material according to any one of claims 1 to 5, comprising:
grinding the raw materials of the positive electrode material and the dispersing solvent, drying to obtain a precursor of the sodium iron phosphate positive electrode material, and sintering the precursor of the sodium iron phosphate positive electrode material in an inert atmosphere to obtain the carbon-coated sodium iron phosphate positive electrode material.
7. The method of claim 6, wherein the dispersing solvent comprises any one or a combination of at least two of deionized water, ethanol, or acetone;
preferably, the mass ratio of the dispersant in the dispersion solution to the raw materials of the positive electrode material is (3 to 5): 1.
8. the method of preparation according to claim 6 or 7, wherein the milling comprises ball milling;
preferably, the rotation speed of the ball milling is 200-1200 r/min;
preferably, the ball milling time is 0.5-24 hours;
preferably, the temperature of the drying treatment is 60 to 130 ℃.
9. The method of any one of claims 6-8, wherein the inert atmosphere comprises any one or a combination of at least two of argon, nitrogen, or neon;
preferably, the sintering temperature of the sintering treatment is 400-700 ℃, and more preferably 500-600 ℃;
preferably, the sintering time of the sintering treatment is 2 to 20 hours.
10. Use of a carbon-coated sodium iron pyrophosphate cathode material according to any of the claims 1-5, characterized in that said carbon-coated sodium iron pyrophosphate cathode material is applied in the field of sodium ion batteries.
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| CN116495716A (en) * | 2023-06-26 | 2023-07-28 | 南昌大学 | Method for preparing sodium ion battery anode material by using waste lithium iron phosphate |
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| CN116495716A (en) * | 2023-06-26 | 2023-07-28 | 南昌大学 | Method for preparing sodium ion battery anode material by using waste lithium iron phosphate |
| CN116741944A (en) * | 2023-08-11 | 2023-09-12 | 深圳海辰储能控制技术有限公司 | Positive electrode plate, preparation method thereof, energy storage device and power utilization device |
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