A static self-assembly preparation method of high-nickel ternary material nano-barium titanate core-shell structure

Abstract

The application discloses a static self-assembly preparation method of a high-nickel ternary material nano-barium titanate core-shell structure. The technology realizes uniform coating of nano-particles on the surface of a base through electrostatic attraction by means of surface charge regulation and layer-by-layer self-assembly mechanism, that is, by immersing positively charged high-nickel ternary material into negatively charged nano-barium titanate slurry liquid. The application can obtain core-shell materials with strong binding force and controllable structure. The process is simple in operation and low in energy consumption. The barium titanate coating layer based on the coordination of the physical barrier and electric field modulation dual mechanisms effectively improves the interface stability and the electrochemical kinetic performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion cathode material technology, and in particular to a method for preparing a high-nickel ternary material@nano barium titanate core-shell structure by electrostatic self-assembly. Background Technology

[0002] High-nickel ternary materials (such as NCM and NCA) are key cathode materials for improving the range of electric vehicles, but their high nickel content also brings a series of electrochemical problems, which seriously restricts their full performance.

[0003] The core challenge facing high-nickel ternary materials lies in the severe interfacial side reactions triggered by their highly active surfaces. Under high voltage, the material surface not only catalyzes the oxidative decomposition of the electrolyte, forming a high-impedance CEI film and consuming active lithium, but also undergoes an exothermic reaction with the electrolyte due to lattice oxygen evolution, inducing a vicious cycle of "reaction-gas generation-cracking," which seriously threatens the safety and lifespan of the battery.

[0004] Surface coating technology is considered the most effective solution to this problem. By constructing a dense physical barrier (such as Al2O3, TiO2, ZrO2, Li3PO4, etc.), the coating layer can effectively isolate the positive electrode from direct contact with the electrolyte, block side reaction pathways, and suppress lattice oxygen release. However, most of these coatings exhibit low lithium-ion conductivity or insulating properties, which limits their effectiveness under high-rate conditions.

[0005] As a high-nickel ternary material coating alternative, barium titanate (BaTiO3) possesses excellent thermal stability. It acts as a physical barrier, preventing direct contact between the electrolyte and the NCM surface, reducing Ni / Co / Mn dissolution, and suppressing SEI decomposition at the negative electrode. Secondly, as a ferroelectric material with a high dielectric constant, it induces a local electric field at the interface, thereby promoting lithium-ion migration and suppressing side reactions with the electrolyte, as well as inhibiting oxygen release and surface oxidation reactions at high temperatures. Simultaneously, as a typical ferroelectric ceramic material, barium titanate exhibits a significant positive temperature coefficient (PTC): below its Curie temperature, the material displays low resistivity, exhibiting semiconductor or conductor-like behavior; when the temperature rises to near the Curie point, the crystal structure transforms from a ferroelectric phase to a paraelectric phase, causing a sharp decrease in carrier mobility and an instantaneous shift in resistivity to a high-resistivity insulating state, thus achieving a strong current suppression effect.

[0006] The barium titanate coating, which combines physical barriers and electric field modulation, enhances interfacial stability while improving electrochemical kinetic performance.

[0007] Electrostatic self-assembly (ESA) is an advanced materials synthesis technique based on interfacial electrostatic interactions. Its core lies in utilizing Coulomb attraction to drive the ordered assembly of charged materials at the molecular or nanoscale.

[0008] High-nickel ternary materials are extremely sensitive to water, and a series of complex side reactions (such as surface chemical reactions and bulk structure destruction) occur upon contact with water, severely affecting the material's performance and battery safety. Therefore, surface modification of high-nickel ternary materials should be carried out in non-aqueous solvents. Common modifiers include aminosilane coupling agents (covalent bonding and protonation), quaternary ammonium salt surfactants (electrostatic adsorption and ion pairing), and cationic polymers (coordination, hydrogen bonding, and electrostatic interactions).

[0009] Aminosilane coupling agent (H2N-R-Si(OR')3) is the most mature non-aqueous positive charge modifier in industrial and laboratory applications. Its mechanism of action is described below:

[0010] Aminosilane coupling agents possess a bifunctional structure, with an amino terminus of H2N-CH2CH2CH2- and a siloxane terminus of -Si(OCH3)3. The amino terminus can react / coordinate with organic matter, protonate to acquire a positive charge, and engage in hydrogen bonding. The siloxane terminus hydrolyzes to form silanols, which condense with hydroxyl groups on the surface of inorganic metal oxides to form Si-OM covalent bonds. On the surface of the activated high-nickel ternary material, metallic hydroxyl groups M-OH condense with the hydrolyzed silanol groups of the aminosilane coupling agent to form stable Si-OM covalent bonds. In an ethanol / trace water mixed solvent, trace water molecules or ethanol self-ionize to provide protons, and the amino group partially protonates under weakly acidic to neutral conditions, resulting in a positive charge on the surface of the high-nickel ternary material. The hydrolysis and surface modification reaction mechanism of the aminosilane coupling agent is as follows:

[0011] Hydrolysis: H₂N-R-Si(OR')₃ + H₂O → HO-Si(OH)₂-R-NH₂ + 3ROH

[0012] Surface modification: M-OH + HO-Si(OH)2-R-NH2 + H+ → MO-Si(OH)2-R-NH3 + + H2O

[0013] The isoelectric point (IEP) of nano-barium titanate in aqueous solution is pH = 2.5-3.5. Stable dispersion can be achieved by adjusting the pH to >10, moving it away from the isoelectric point and enhancing electrostatic repulsion. However, alkaline conditions also significantly reduce the protonation of the surface of high-nickel ternary materials modified with aminosilane coupling agents, thereby reducing the density of positive charge on their surface. In non-aqueous solvents such as ethanol, carboxyl groups (-COO⁻), sulfonic acid groups (-SO3⁻), and phosphate groups can be introduced.

[0014] Citric acid forms chelate coordination with Ba²⁺ on the surface of nano-BaTiO3 through three carboxyl groups, releasing protons to make the surface negatively charged, thus achieving electrostatic repulsion stabilization. Phosphate ester R-OPO(OH)₂ dissolves in the solvent, and the phosphate groups dissociate to become negatively charged R-OPO(OH)O⁻. It then forms strong coordination adsorption with Ba²⁺ on the nano-BaTiO3 surface through PO bonds, creating a negatively charged layer on the surface, achieving a combination of electrostatic repulsion and steric hindrance stabilization.

[0015] In this invention Summary of the Invention

[0016] The purpose of this invention is to provide an electrostatic self-assembly method for preparing a high-nickel ternary material@barium titanate core-shell structure. This method involves controlling and stabilizing the surface charge of the high-nickel ternary material and the barium titanate nanoparticles, utilizing electrostatic attraction to achieve spontaneous adsorption and deposition of the barium titanate nanoparticles, and finally forming a dense coating layer through heat treatment. The core of the method lies in the targeted control of the surface charge of the two components: First, in a non-aqueous solvent system, the surface of the high-nickel ternary material is modified to impart a stable positive charge; simultaneously, the surface of the barium titanate nanoparticles is modified to impart a stable negative charge. Subsequently, using the Coulomb attraction between opposite charges, the negatively charged barium titanate nanoparticles are driven to undergo directional adsorption and self-assembly on the positively charged high-nickel ternary material surface, thereby forming a uniform core-shell structure coating layer.

[0017] This barium titanate coating functions through a synergistic mechanism of "physical barrier" and "electric field modulation." On the one hand, as a physical isolation layer, it effectively suppresses side reactions between the high-nickel cathode and the electrolyte, reducing the dissolution of transition metal ions and thus significantly improving the interfacial stability of the electrode material. On the other hand, by utilizing the ferroelectric / piezoelectric properties of barium titanate, the local electric field at the electrode / electrolyte interface is modulated during charging and discharging, optimizing the lithium-ion transport path and kinetic behavior, thereby improving the rate performance and overall electrochemical kinetic performance of the material.

[0018] To achieve the above objectives, the present invention provides the following technical solution.

[0019] This application discloses a method for electrostatic self-assembly of a high-nickel ternary material@barium titanate core-shell structure, which includes the following steps:

[0020] Step S01: Neutralization of residual alkali and surface hydroxylation pretreatment of high-nickel ternary material surface. Dilute acid ultrasonic treatment is used to neutralize residual alkali on the surface of high-nickel ternary material, increase surface hydroxyl density, and perform solid-liquid separation and washing.

[0021] In step S02, the aminosilane coupling agent is hydrolyzed, condensed, and protonated to modify the surface of the high-nickel ternary material, giving it a stable positive charge. The aminosilane coupling agent is slowly added dropwise to a non-aqueous / aqueous mixed solvent, the pH value is adjusted appropriately, the mixture is vigorously stirred and allowed to stand to ensure that the siloxane end of the aminosilane coupling agent is fully hydrolyzed into silanol. The pretreated high-nickel ternary material is efficiently mixed with the aminosilane coupling agent hydrolysate and refluxed for reaction, followed by solid-liquid separation and washing.

[0022] Step S03: Surface modification of barium titanate nanoparticles to impart a stable negative charge. Barium titanate nanoparticles are ultrasonically dispersed in a non-aqueous solvent and efficiently mixed with surface modifiers such as carboxylic acids to modify the surface of the barium titanate nanoparticles and impart a stable negative charge.

[0023] Step S04, electrostatic self-assembly coating and heat treatment: High-nickel ternary material with positive surface charge is added to nano-barium titanate slurry with negative surface charge. Using the Coulomb attraction between opposite charges, the negatively charged nano-barium titanate is driven to perform directional adsorption and self-assembly on the surface of the positively charged high-nickel ternary material, thereby forming a uniform core-shell structure coating layer. After solid-liquid separation and washing, heat treatment is performed at a certain temperature to realize the preparation of high-nickel ternary cathode material@nano-barium titanate core-shell structure composite material.

[0024] Preferably, in the above-mentioned method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly, the dilute acid in step S01 is one or more of nitric acid, citric acid, and acetic acid, with a concentration of 0.5-2.0%, and the ultrasonic treatment time is 5-60 min.

[0025] Preferably, in the above-mentioned method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly, the aminosilane coupling agent in step S02 is one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and diethylenetriaminopropyltrimethoxysilane; the non-aqueous / water mixed solvent is one of methanol / water, ethanol / water, and isopropanol / water; the volume ratio of the non-aqueous / water mixed solvent is 90:10 to 99:1; the suitable pH varies depending on the type of aminosilane coupling agent, and the pH range is 3 to 8; the reflux reaction temperature is 40 to 80°C, and the reflux reaction time is 4 to 12 hours.

[0026] Preferably, in the above-mentioned electrostatic self-assembly preparation method of high-nickel ternary material@barium titanate core-shell structure, the particle size of the barium titanate nanoparticles in step S03 is 50-100 nm; the non-aqueous solvent is one or a combination of methanol, ethanol, and isopropanol; the surface modifier is one of citric acid, BYK111, and carboxysilane; the concentration of the surface modifier is 0.5-2.0%; and the volume ratio of the barium titanate nanoparticle dispersion to the surface modifier is 2:1 to 1:2.

[0027] Preferably, in the above-mentioned electrostatic self-assembly preparation method of high-nickel ternary material@barium titanate core-shell structure, the solid-liquid ratio of the high-nickel ternary material with positive surface charge to the barium titanate slurry with negative surface charge in step S04 is 1:5 to 1:20; the heat treatment temperature is 400 to 600°C, and the heat treatment time is 0.5 to 4 hours.

[0028] Compared with existing technologies, the advantages of this technical solution are:

[0029] 1. Strong interfacial bonding: The core and shell are tightly bonded together by chemical bonds or electrostatic interactions, forming a highly dense protective layer.

[0030] 2. Simple process: It operates at normal temperature and pressure, has low energy consumption, and is widely applicable.

[0031] 3. When applied to the NCM@BaTiO3 system, this technology can not only suppress interfacial side reactions, but also optimize the interfacial electric field distribution by utilizing the high dielectric constant of BaTiO3, thereby improving the cycle stability and rate performance of the battery. Attached Figure Description

[0032] 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.

[0033] Figure 1 The diagram shows a flowchart of the electrostatic self-assembly preparation method of high-nickel ternary material@barium titanate core-shell structure in an embodiment of the present invention;

[0034] Figure 2 The image shown is a scanning electron microscope (SEM) image of nano-barium titanate from Example 1.

[0035] Figure 3 The image shown is a transmission electron microscope (TEM) image of nano-barium titanate from Example 1.

[0036] Figure 4The image shown is a scanning electron microscope (SEM) image of the high-nickel ternary material coated with barium titanate nanoparticles prepared in Example 1.

[0037] Figure 5 The image shown is a transmission electron microscope (TEM) image of the high-nickel ternary material coated with barium titanate nanoparticles prepared in Example 1.

[0038] Figure 6-8 The figure shown is a discharge performance test diagram of the high-nickel ternary material coated with barium titanate nanoparticles prepared in Example 1;

[0039] Figure 9 The figure shown is a test graph of the cycle performance of a button battery made of barium titanate nano-coated high-nickel ternary material prepared in Example 1.

[0040] Figure 10 The figure shown is a full-cell cycle performance test diagram of the high-nickel ternary material coated with barium titanate nanoparticles prepared in Example 1. Detailed Implementation

[0041] 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.

[0042] The following is in conjunction with the appendix Figure 1-10 The present invention will be further described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] Weigh 100g of high-nickel ternary material and mix it in 400ml of 1% citric acid solution. Sonicate the mixture for 30min, then separate the solid and liquid phases and wash the contents for later use. Using a pipette, slowly add 3-aminopropyltriethoxysilane (KH-550) dropwise to an ethanol / water mixture (ethanol:water volume ratio must be 95:5). Adjust the pH to 4.5 using glacial acetic acid. The concentration of the KH-550 hydrolysate should be 1.5%. Stir vigorously for 60min and let stand for 2h to ensure complete hydrolysis of the siloxane end of the KH-550 into silanol. The pretreated high-nickel ternary material and KH-550 hydrolysate are efficiently mixed in a high-speed homogenizer and refluxed at 60℃ for 6h. Separate the solid and liquid phases and wash the contents for later use.

[0045] Weigh 2g of barium titanate nanoparticles with an average particle size of 80nm, ultrasonically disperse them in ethanol to prepare a dispersion slurry of 1g / 100ml, and mix them thoroughly with a 1.0% citric acid aqueous solution with pH=7.0. The volume ratio of the barium titanate nanoparticle dispersion to the citric acid aqueous solution is 1:1.

[0046] High-nickel ternary materials modified with KH-550 were added to a modified nano-barium titanate dispersion and efficiently mixed in a high-speed homogenizer. Utilizing the Coulomb attraction between opposite charges, the negatively charged nano-barium titanate was driven to undergo directional adsorption and self-assembly on the positively charged high-nickel ternary material surface, forming a uniform core-shell structure coating layer. After solid-liquid separation and washing, the mixture was heat-treated at 500℃ for 3 hours to achieve the preparation of a high-nickel ternary cathode material@nano-barium titanate core-shell composite material.

[0047] Combination Figure 2-10 As shown, scanning electron microscopy, transmission electron microscopy, and electrochemical tests indicate that the high-nickel ternary cathode material@barium titanate core-shell structure material constructed based on electrostatic self-assembly technology has a uniform coating layer, and its rate performance and cycle performance are significantly better than those of the uncoated high-nickel ternary material.

[0048] Example 2

[0049] Weigh 100g of high-nickel ternary material and mix it in 0.5% nitric acid solution. Sonicate the mixture for 30 min, then separate the solid and liquid phases and wash the mixture for later use. Using a pipette, slowly add 3-aminopropyltrimethoxysilane (KH-540) dropwise to an ethanol / water mixture (ethanol:water volume ratio must be 95:5). Adjust the pH to 6.5 using glacial acetic acid. The concentration of the KH-540 hydrolysate should be 1.5%. Stir vigorously for 30 min and let stand for 1 h to ensure complete hydrolysis of the siloxane end of the KH-540 into silanol. The pretreated high-nickel ternary material and KH-540 hydrolysate are efficiently mixed in a high-speed homogenizer and refluxed at 80 °C for 4 h. Separate the solid and liquid phases and wash the mixture for later use.

[0050] Weigh 4g of barium titanate nanoparticles with an average particle size of 80nm, ultrasonically disperse them in ethanol to prepare a dispersion slurry of 0.5g / 100ml, and mix thoroughly with 10ml of 2.5% BYK111 ethanol solution.

[0051] High-nickel ternary materials modified with KH-540 were added to a modified nano-barium titanate dispersion and efficiently mixed in a high-speed homogenizer. Utilizing the Coulomb attraction between opposite charges, the negatively charged nano-barium titanate was driven to directionally adsorb and self-assemble on the positively charged surface of the high-nickel ternary material, forming a uniform core-shell structure coating layer. After solid-liquid separation and washing, the mixture was heat-treated at 550℃ for 2 hours to achieve the preparation of a high-nickel ternary cathode material@nano-barium titanate core-shell composite material.

[0052] Example 3

[0053] Weigh 100g of high-nickel ternary material and mix it in a 1.5% acetic acid solution. Sonicate the mixture for 30 min, then separate the solid and liquid phases and wash the residue for later use. Using a pipette, slowly add 3-aminopropyltrimethoxysilane (KH-540) dropwise to an ethanol / water mixture (ethanol:water volume ratio must be 95:5). Adjust the pH to 7.0 using glacial acetic acid. The concentration of the KH-540 hydrolysate should be 2.0%. Stir vigorously for 30 min and let stand for 1 h to ensure complete hydrolysis of the siloxane end of the KH-540 into silanol. The pretreated high-nickel ternary material and the KH-540 hydrolysate are efficiently mixed in a high-speed homogenizer and refluxed at 70 °C for 8 h. Separate the solid and liquid phases and wash the residue for later use.

[0054] Weigh 6g of barium titanate nanoparticles with an average particle size of 80nm, ultrasonically disperse them in ethanol to prepare a dispersion slurry of 1g / 100ml, and mix them thoroughly with a 1.0% citric acid aqueous solution with pH=6.5. The volume ratio of the barium titanate nanoparticle dispersion to the citric acid aqueous solution is 1:1.

[0055] High-nickel ternary materials modified with KH-540 were added to a modified nano-barium titanate dispersion and efficiently mixed in a high-speed homogenizer. Utilizing the Coulomb attraction between opposite charges, the negatively charged nano-barium titanate was driven to undergo directional adsorption and self-assembly on the positively charged high-nickel ternary material surface, forming a uniform core-shell structure coating layer. After solid-liquid separation and washing, the mixture was heat-treated at 600℃ for 1 hour to achieve the preparation of a high-nickel ternary cathode material@nano-barium titanate core-shell composite material.

[0056] 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 a high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly, characterized in that, The steps are as follows: Step S01: Neutralization of residual alkali and surface hydroxylation pretreatment of high-nickel ternary material surface. Dilute acid ultrasonic treatment is used to neutralize residual alkali on the surface of high-nickel ternary material, increase surface hydroxyl density, and perform solid-liquid separation and washing. In step S02, the aminosilane coupling agent is hydrolyzed, condensed, and protonated to modify the surface of the high-nickel ternary material, giving it a stable positive charge. The aminosilane coupling agent is slowly added dropwise to a non-aqueous / aqueous mixed solvent, the pH value is adjusted appropriately, the mixture is vigorously stirred and allowed to stand to ensure that the siloxane end of the aminosilane coupling agent is fully hydrolyzed into silanol. The pretreated high-nickel ternary material is efficiently mixed with the aminosilane coupling agent hydrolysate and refluxed for reaction, followed by solid-liquid separation and washing. Step S03: Surface modification of barium titanate nanoparticles to impart a stable negative charge. Barium titanate nanoparticles are ultrasonically dispersed in a non-aqueous solvent and efficiently mixed with surface modifiers such as carboxylic acids to modify the surface of the barium titanate nanoparticles and impart a stable negative charge. Step S04, electrostatic self-assembly coating and heat treatment: High-nickel ternary material with positive surface charge is added to nano-barium titanate slurry with negative surface charge. Using the Coulomb attraction between opposite charges, the negatively charged nano-barium titanate is driven to perform directional adsorption and self-assembly on the surface of the positively charged high-nickel ternary material, thereby forming a uniform core-shell structure coating layer. After solid-liquid separation and washing, heat treatment is performed at a certain temperature to realize the preparation of high-nickel ternary cathode material@nano-barium titanate core-shell structure composite material.

2. The method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly according to claim 1, characterized in that, The dilute acid in step S01 is one or more of nitric acid, citric acid, and acetic acid, with a concentration of 0.5-2.0%, and the ultrasonic treatment time is 5-60 min.

3. The method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly according to claim 1, characterized in that, The aminosilane coupling agent in step S02 is one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and diethylenetriaminopropyltrimethoxysilane. The non-aqueous / water mixed solvent is one of methanol / water, ethanol / water, and isopropanol / water. The volume ratio of the non-aqueous / water mixed solvent is 90:10 to 99:

1. The suitable pH varies depending on the type of aminosilane coupling agent and ranges from 3 to 8. The reflux reaction temperature is 40 to 80°C, and the reflux reaction time is 4 to 12 hours.

4. The method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly according to claim 1, characterized in that, In step S03, the particle size of the nano-barium titanate is 50-100 nm; the non-aqueous solvent is one or a combination of methanol, ethanol, and isopropanol; the surface modifier is one of citric acid, BYK111, and carboxysilane; the concentration of the surface modifier is 0.5-2.0%; and the volume ratio of the nano-barium titanate dispersion to the surface modifier is 2:1 to 1:

2.

5. The method for preparing high-nickel ternary material@barium titanate core-shell structure by electrostatic self-assembly according to claim 1, characterized in that, In step S04, the solid-liquid ratio of the high-nickel ternary material with positive surface charge added to the nano-barium titanate slurry with negative surface charge is 1:5 to 1:20; the heat treatment temperature is 400 to 600℃, and the heat treatment time is 0.5 to 4h.

Images