Preparation method of modified nano functional material

Abstract

The invention discloses a preparation method of a modified nano functional material, and particularly relates to a preparation method of carbon-coated rare earth doped nano barium titanate which integrates a barium titanate PTC (Positive Temperature Coefficient) function and takes electrochemical compatibility and thermal response accuracy into consideration and is a modified functional material in a battery, and the carbon-coated rare earth doped nano barium titanate is suitable for being doped into an electrode material. Therefore, the thermal-electric self-adjusting function of the electrode layer is realized, and the battery is endowed with intrinsic thermosensitive self-protection capability.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a modified nanofunctional material, which is suitable for a functional filler for improving the safety of lithium batteries. BACKGROUND

[0002] With the rapid development of new energy vehicles, large-scale energy storage systems and various portable electronic devices, lithium ion batteries have become the core power source in the current electrochemical energy storage field due to their high energy density, long cycle life and good charge-discharge performance. However, as the application scale continues to expand, the safety risks of lithium batteries in the whole life cycle such as production, transportation, use and recycling have become increasingly prominent. Safety accidents such as fire and explosion caused by thermal runaway occur from time to time, which seriously threatens personal and property safety and has become a key bottleneck restricting the further development of the industry. Therefore, the relevant departments of the state have included the safety of lithium batteries into the key supervision category and have successively introduced a number of mandatory safety standards and technical specifications to promote the construction of a safety management system covering the whole process of design, manufacturing, application and recycling.

[0003] Lithium battery thermal runaway is usually induced by factors such as overcharge, overdischarge, external short circuit, internal micro-short circuit, mechanical damage or high temperature environment, which leads to uncontrollable exothermic chain reaction in the battery, and then causes severe temperature rise, electrolyte decomposition, gas release and even combustion and explosion. The traditional safety protection means mainly rely on the external battery management system (Battery Management System, BMS) for voltage, current and temperature monitoring, and are supplemented by fuses, pressure relief valves and other passive protection elements. However, such external protection mechanism has limitations such as response lag, local failure unable to intervene in time, one-time action not recoverable, etc., and it is difficult to realize precise, fast and reversible control of the thermal evolution process in the battery.

[0004] Under this background, the development of intelligent battery material system with intrinsic safety characteristics has become an important direction of current research. Among them, the functional materials based on the positive temperature coefficient (Positive Temperature Coefficient, PTC) effect show significant potential in the application of lithium battery thermal safety protection. Barium titanate (BaTiO3) as a typical ferroelectric ceramic material has significant PTC characteristics: below its Curie temperature, the material has a low resistivity, showing semiconductor or conductor-like behavior; when the temperature rises to the Curie point, the crystal structure changes from ferroelectric phase to paraelectric phase, which leads to a sharp decrease in carrier mobility and a jump in resistivity by several orders of magnitude (up to 10 4 ~10 8 times) within milliseconds to seconds, instantly changing to a high resistance insulating state, thereby achieving strong inhibition of current.

[0005] By means of element doping, etc., the Curie temperature of barium titanate can be accurately controlled to match the typical trigger temperature range (e.g., 60°C ~ 120°C) of lithium battery thermal runaway, thereby constructing a temperature-sensitive "self-triggering-self-response" safety mechanism. Currently, the application of barium titanate in lithium batteries mainly embodies two technical paths:

[0006] First, as an independent PTC thermistor element, it is connected in series in the external circuit of the battery for overcurrent protection. Under normal working conditions, the element presents a low resistance on state, which has negligible effect on the system; when the temperature of the battery rises due to abnormal working conditions and triggers the PTC effect, the resistance of the element rises sharply, effectively limiting the circuit current and blocking the heat accumulation path. When the temperature decreases, the resistance automatically returns to normal, realizing the reversible protection function. This technology is relatively mature, but it is limited to system-level protection and cannot respond to local thermal runaway in the battery.

[0007] The second, more advanced and innovative application path is to introduce barium titanate in the form of nanoparticles or nanowires as a functional filler into key components of the battery to construct intelligent electrodes or composite separators with endogenous thermal response capability. For example, in the separator system, barium titanate fillers are compounded. When a local area of the battery generates a hot spot due to micro-short circuit or uneven reaction, the barium titanate in that area rapidly triggers the PTC effect, significantly increasing the ion transport impedance and inhibiting the local electrochemical reaction, achieving "hot spot self-closing"; similarly, by incorporating it into the electrode material, the electronic impedance can be increased and the reaction rate can be reduced when the temperature rises, thereby achieving a thermal-electric self-regulation function at the electrode level. This type of embedded design breaks the passivity of traditional external protection and endows the battery with intrinsic thermal-sensitive self-protection capability, representing an important development direction for the next generation of high-safety lithium batteries.

[0008] Although barium titanate-based PTC materials have great potential in improving the safety of lithium batteries, their actual application still faces several key technical challenges: such as the accurate control and batch consistency guarantee of the Curie temperature, the uniform dispersion and interface stability of the nanofiller in the electrode / separation matrix, the chemical compatibility with the electrolyte, and the impact of the introduction of non-active substances on the overall energy density and cost of the battery.

[0009] Therefore, the development of a battery internal modification functional material that can effectively integrate barium titanate PTC function, take into account electrochemical compatibility and thermal response accuracy, is of great significance for realizing the leap of lithium batteries from "passive protection" to "active defense" and "self-healing recovery". SUMMARY

[0010] The application aims to provide a preparation method of modified nanofunctional materials, and particularly relates to a preparation of carbon-coated rare earth doped nanobarium titanate with integrated barium titanate PTC function, and considering electrochemical compatibility and thermal response accuracy of internal modified functional materials of a battery, which is suitable for being incorporated into electrode materials to realize thermal-electric self-regulation function at the electrode level and endow the battery with intrinsic thermal sensitive self-protection capability.

[0011] To achieve the above object, the application provides the following technical scheme.

[0012] The application discloses a preparation method of modified nanofunctional materials, which sequentially comprises the following steps:

[0013] Step S01, rare earth doped nanobarium titanate Ba 1-x Re x TiO3 is prepared by one-step hydrothermal crystallization reaction. 99.9% titanium tetrachloride solution, 99.5% BaCl2·2H2O, 99.9% rare earth dopant ReCl3 and sodium hydroxide solution are continuously mixed in a mixer according to a proportion, the precursor slurry is delivered into a hydrothermal reaction crystallizer, the reactor is closed after reaching a suitable filling amount, stirring and temperature rising programs are started, and maturation is performed at a constant temperature, wherein x is 0.005-0.025;

[0014] Step S02, crystal slurry cooling, pH adjustment, solid-liquid separation and washing, the slurry discharged from the hydrothermal crystallization reaction of step S01 is discharged to a crystal slurry cooler, delivered to a crystal slurry buffer tank after continuously adjusting pH on the pipeline, and then enters a separation and washing device to obtain rare earth doped nanobarium titanate Ba 1-x Re x TiO3 wet product;

[0015] Step S03, carbon source mixing, drying, carbonization coating, airflow crushing and finished product packaging, the Ba 1- x Re x TiO3 wet product obtained in step S02 is uniformly mixed with a carbon source, and then enters a spray drying system, the dried product is further subjected to high-temperature carbonization coating, the carbonized product is subjected to airflow crushing and packaging to obtain carbon-coated rare earth doped nanobarium titanate Ba 1-x Re x TiO3 / C finished product;

[0016] Step S04, purification and recycling of the mother liquor: The mother liquor from step S02 is subjected to deep purification treatment. First, a precision filter is used to remove deeply insoluble impurities from the mother liquor. Then, an ion exchange resin is used to deeply purify trace high-valence ions. The purified mother liquor is a pure sodium chloride aqueous solution. A dilute sodium hydroxide solution and a dilute hydrochloric acid solution are obtained by bipolar membrane electrodialysis. The dilute sodium hydroxide solution is returned to the system for recycling after being concentrated by MVR evaporation. The dilute hydrochloric acid is recycled as a pH adjuster.

[0017] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the rare earth dopant in step S01 is one or more of LaCl3, NdCl3, PrCl3, CeCl3, and SmCl3.

[0018] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the loading amount of hydrothermal reaction crystallization in step S01 is 70-75%, the hydrothermal reaction temperature is 200-250℃, the constant temperature aging time is 12-24h, and the concentration of sodium hydroxide solution is 15.0-32.0%.

[0019] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the pH in step S02 is 6.0 to 7.0, and the separation device is one or a combination of a horizontal spiral sedimentation centrifuge, a fixed ceramic membrane filter, and a dynamic ceramic membrane filter.

[0020] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the carbon source in step S03 is one or more of glucose, sucrose, citric acid, and phenolic resin, and the proportion of carbon source added is 6-12% of rare earth-doped nano barium titanate.

[0021] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the carbonization coating temperature in step S03 is 600-900℃.

[0022] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the precision filter in step S04 is one or more of a microfiltration filter, a hollow fiber ultrafiltration membrane filter, and a tubular ceramic membrane filter.

[0023] Preferably, in the above-mentioned method for preparing modified nanofunctional materials, the concentration of dilute hydrochloric acid in step S04 is 1.5-2.0 mol / L, the concentration of dilute sodium hydroxide is 1.5-2.0 mol / L, and the concentration of sodium hydroxide in the MVR evaporation concentrate is 15.0-20.0%, which is then mixed with 32.0-42.0% ion-exchange membrane liquid alkali and recycled.

[0024] Compared with existing technologies, the advantage of this technical solution lies in achieving precise control of the Curie temperature of rare-earth-doped barium titanate nanomaterials, enabling it to be highly matched with the safe operating temperature window of specific battery systems, thereby providing intrinsic safety assurance at the thermal management level. By introducing rare-earth elements, the local structure and charge distribution of the barium titanate lattice are effectively controlled, not only achieving directional adjustment of the Curie temperature but also significantly improving the intrinsic conductivity of the material in the ferroelectric phase (i.e., below the Curie temperature).

[0025] Furthermore, by coating barium titanate nanoparticles with a carbon layer, a core-shell composite material was constructed. This design not only synergistically improves the overall conductivity of the material and enhances the electron transport dynamics within the electrode, but also, as a protective interface, the carbon layer effectively inhibits the aggregation of nanoparticles during electrode preparation and cycling, ensuring their uniform dispersion within the electrode. Simultaneously, the carbon coating imparts excellent chemical and electrochemical stability to the material, effectively blocking side reactions between the active material and the electrolyte, and improving interfacial compatibility.

[0026] In addition, the preparation process is designed to be environmentally friendly, enabling the recycling of acid and alkali reagents, which is in line with the development trend of green manufacturing. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The diagram shows a flowchart of the preparation method of the modified nanofunctional materials in an embodiment of the present invention;

[0029] Figure 2 The image shown is an example of rare earth-doped barium titanate nanoparticles (Ba) from Embodiment 1 of the present invention. 0.985 Nd 0.015 XRD pattern of TiO3;

[0030] Figure 3 The image shown is an example of rare earth-doped barium titanate nanoparticles (Ba) from Embodiment 1 of the present invention. 0.985 Nd 0.015 SEM image of TiO3;

[0031] Figure 4 The image shown is an example of rare earth-doped barium titanate nanoparticles (Ba) from Embodiment 1 of the present invention. 0.985 Nd 0.015 Temperature spectrum of dielectric constant of TiO3. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, a method for preparing a novel internally modified nanomaterial for high-safety lithium batteries: rare earth-doped barium titanate nanomaterials (Ba... 1-x Re x A one-step hydrothermal crystallization reaction system for TiO3; a crystal slurry cooling, pH adjustment, solid-liquid separation and washing system; a carbon source mixing, drying, carbonization coating, air jet milling and finished product packaging system; and a purification and circulation system for the mother liquor.

[0034] Example 1

[0035] (1) Rare earth doped nano barium titanate Ba 0.985 Nd 0.015 One-step hydrothermal crystallization reaction system for TiO3: rare earth-doped nano-barium titanate Ba 0.985 Nd 0.015 The one-step hydrothermal crystallization reaction of TiO3 involves continuously mixing 99.9% titanium tetrachloride solution, 99.5% BaCl2·2H2O, 99.9% NdCl3 rare earth dopant, and sodium hydroxide solution in a molar ratio of Ba:Nd:Ti = 0.985:0.015:1 in a high-efficiency mixer. The precursor slurry is then transferred to the hydrothermal reactor. Once 75% of the reactor is filled, the reactor is sealed, and the stirring and heating programs are initiated. The temperature is then increased to 220°C. The rare earth neodymium-doped nano-barium titanate was prepared by hydrothermal crystallization by constant temperature aging at ℃ for 20 hours.

[0036] (2) Crystal slurry cooling, pH adjustment, solid-liquid separation and washing system: The slurry liquid after the hydrothermal crystallization reaction is discharged to a high-efficiency wound crystal slurry cooler and the pH is continuously adjusted to 6.5 by 2.0 mol / L dilute hydrochloric acid in the pipeline before being transported to the crystal slurry buffer tank and then into the dynamic ceramic membrane separation and washing device to obtain rare earth doped nano-barium titanate Ba. 0.985 Nd 0.015 The wet TiO3 product has an average particle size of approximately 60–80 nm and a Curie temperature of 88.0–90.0 °C at 1 kHz. ℃;

[0037] (3) Carbon source mixing, drying, carbonization coating, airflow pulverization and finished product packaging system: The obtained Ba 0.985 Nd 0.015TiO3 wet product is uniformly mixed with glucose at a ratio of 8.0%, and then enters a spray drying system. The dried product undergoes further high-temperature carbonization coating. The carbonized product is then subjected to airflow pulverization and packaging to obtain carbon-coated rare earth-doped nano-barium titanate (Ba). 0.985 Nd 0.015 TiO3 / C finished product, carbonization coating temperature is 750℃ ℃;

[0038] (4) Purification and Circulation System of Separation Mother Liquor: The separation mother liquor from hydrothermal crystallization is subjected to deep purification treatment. First, microfiltration and ultrafiltration membranes are used to deeply purify the separation mother liquor to remove insoluble impurities. Then, ion exchange resin is used to deeply purify trace amounts of high-valence ions. The purified separation mother liquor is basically a pure sodium chloride aqueous solution. A 2.0 mol / L dilute sodium hydroxide solution and a 2.0 mol / L dilute hydrochloric acid solution are obtained by bipolar membrane electrodialysis. The dilute sodium hydroxide solution is concentrated to 18.3% by MVR evaporation and then returned to the system for recycling. The dilute hydrochloric acid is recycled as a pH adjuster.

[0039] Figure 2 The image shown is the XRD pattern of rare earth-doped barium titanate nanoparticles Ba0.985Nd0.015TiO3 prepared in Example 1 of this invention; Figure 3 The image shown is a SEM image of rare earth-doped barium titanate nanoparticles Ba0.985Nd0.015TiO3 prepared in Example 1 of this invention. Figure 4 The figure shows the dielectric constant temperature spectrum of rare earth-doped barium titanate nanoparticles Ba0.985Nd0.015TiO3 prepared in Example 1 of this invention.

[0040] Example 2

[0041] (1) Rare earth doped nano barium titanate Ba 0.995 La 0.005 One-step hydrothermal crystallization reaction system for TiO3: rare earth-doped nano-barium titanate Ba 0.995 La 0.005 The one-step hydrothermal crystallization reaction of TiO3 involves continuously mixing 99.9% titanium tetrachloride solution, 99.5% BaCl2·2H2O, 99.9% LaCl3 rare earth dopant, and sodium hydroxide solution in a molar ratio of Ba:Nd:Ti = 0.995:0.005:1 in a high-efficiency mixer. The precursor slurry is then transferred to the hydrothermal crystallizer. Once 75% of the fill volume is reached, the reactor is sealed, and the stirring and heating programs are initiated. The temperature is then increased to 240°C. The rare earth lanthanum-doped nano-barium titanate was prepared by hydrothermal crystallization by constant temperature aging at ℃ for 12 hours.

[0042] (2) Crystal slurry cooling, pH adjustment, solid-liquid separation and washing system: The slurry liquid after the hydrothermal crystallization reaction is discharged to a high-efficiency wound crystal slurry cooler and the pH is continuously adjusted to 6.2 by 2.0 mol / L dilute hydrochloric acid on the pipeline before being transported to the crystal slurry buffer tank and then into the dynamic ceramic membrane separation and washing device to obtain rare earth doped nano-barium titanate Ba. 0.995 La 0.005 The average particle size of wet TiO3 product is approximately 80–100 nm.

[0043] (3) Carbon source mixing, drying, carbonization coating, airflow pulverization and finished product packaging system: The obtained Ba 0.995 La 0.005 TiO3 wet product is uniformly mixed with glucose at a ratio of 8.0%, and then enters a spray drying system. The dried product undergoes further high-temperature carbonization coating. The carbonized product is then subjected to airflow pulverization and packaging to obtain carbon-coated rare earth-doped nano-barium titanate (Ba). 0.995 La 0.005 TiO3 / C finished product, carbonization coating temperature is 700℃ ℃;

[0044] (4) Purification and Circulation System of Separation Mother Liquor: The separation mother liquor from hydrothermal crystallization is subjected to deep purification treatment. First, microfiltration and ultrafiltration membranes are used to deeply purify the separation mother liquor to remove insoluble impurities. Then, ion exchange resin is used to deeply purify trace amounts of high-valence ions. The purified separation mother liquor is basically a pure sodium chloride aqueous solution. A 2.0 mol / L dilute sodium hydroxide solution and a 2.0 mol / L dilute hydrochloric acid solution are obtained by bipolar membrane electrodialysis. The dilute sodium hydroxide solution is concentrated to 18.6% by MVR evaporation and then returned to the system for recycling. The dilute hydrochloric acid is recycled as a pH adjuster.

[0045] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing modified nanomaterials, characterized in that, The steps are as follows: Step S01, rare earth-doped nano-barium titanate Ba 1-x Re x The one-step hydrothermal crystallization reaction of TiO3 involves continuously mixing 99.9% titanium tetrachloride solution, 99.5% BaCl2•2H2O, 99.9% ReCl3 rare earth dopant, and sodium hydroxide solution in a mixer according to a certain ratio. The precursor slurry is then transported to the hydrothermal reaction crystallizer. Once the appropriate loading amount is reached, the reactor is sealed, and the stirring and heating program is started. The mixture is then aged at a constant temperature under a certain temperature, where x is 0.005 to 0.

025. Step S02 involves slurry cooling, pH adjustment, solid-liquid separation, and washing. The slurry from the hydrothermal crystallization reaction in step S01 is discharged to a slurry cooler and continuously adjusted at pH via pipeline before being transported to a slurry buffer tank. It then enters a separation and washing device to obtain rare-earth-doped nano-barium titanate (Ba). 1-x Re x TiO3 wet products; Step S03 involves mixing, drying, carbonizing, coating, airflow pulverizing, and packaging the Ba obtained in step S02. 1- x Re x After being uniformly mixed with a carbon source, the wet TiO3 product enters a spray drying system. The dried product is then subjected to high-temperature carbonization coating. The carbonized product is then pulverized and packaged to obtain carbon-coated rare-earth-doped nano-barium titanate (Ba). 1-x Re x TiO3 / C finished product; Step S04, purification and recycling of the mother liquor: The mother liquor from step S02 is subjected to deep purification treatment. First, a precision filter is used to remove deeply insoluble impurities from the mother liquor. Then, an ion exchange resin is used to deeply purify trace high-valence ions. The purified mother liquor is a pure sodium chloride aqueous solution. A dilute sodium hydroxide solution and a dilute hydrochloric acid solution are obtained by bipolar membrane electrodialysis. The dilute sodium hydroxide solution is returned to the system for recycling after being concentrated by MVR evaporation. The dilute hydrochloric acid is recycled as a pH adjuster.

2. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S01, the rare earth dopant is one or more of LaCl3, NdCl3, PrCl3, CeCl3, and SmCl3.

3. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S01, the amount of hydrothermal crystallization is 70-75%, the hydrothermal reaction temperature is 200-250℃, the constant temperature aging time is 12-24h, and the concentration of sodium hydroxide solution is 15.0-32.0%.

4. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S02, the pH is 6.0 to 7.0, and the separation device is one or a combination of a horizontal spiral sedimentation centrifuge, a fixed ceramic membrane filter, and a dynamic ceramic membrane filter.

5. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S03, the carbon source is one or more of glucose, sucrose, citric acid, and phenolic resin, and the proportion of carbon source added is 6-12% of rare earth-doped nano barium titanate.

6. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, The carbonization coating temperature in step S03 is 600-900℃.

7. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S04, the precision filter is one or more of the following: microfiltration filter, hollow fiber ultrafiltration membrane filter, and tubular ceramic membrane filter.

8. The method for preparing modified nanofunctional materials according to claim 1, characterized in that, In step S04, the concentration of dilute hydrochloric acid is 1.5–2.0 mol / L, the concentration of dilute sodium hydroxide is 1.5–2.0 mol / L, and the concentration of sodium hydroxide in the MVR evaporation concentrate is 15.0–20.0%, which is then mixed with 32.0–42.0% ion-exchange membrane liquid alkali and recycled.

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