Lithium battery positive electrode material with one-dimensional nanostructure and preparation method of lithium battery positive electrode material

Abstract

The invention relates to a one-dimensional nano-structure lithium battery positive electrode material and a preparation method thereof. The one-dimensional nano-structure lithium battery positive electrode material is suitable for various positive electrode material systems such as nickel cobalt lithium manganate, lithium iron phosphate, lithium iron manganese phosphate and a lithium-rich manganese base. According to the method, one-dimensional directional assembly of a precursor on the nanoscale is realized by regulating and controlling coprecipitation conditions, regulating pH and adding a structure-directing agent, and a nanowire or nanorod structure with a high length-diameter ratio is constructed. Meanwhile, a basalt wire drawing method is introduced as a matrix construction means, and large-scale continuous preparation of the one-dimensional structure material is achieved. The obtained positive electrode material has excellent structural stability, conductivity and ion diffusivity, the rate capability is remarkably improved, and the cycle life is remarkably prolonged. The process has good adaptability and expansibility, and is suitable for industrially preparing the high-performance lithium battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the preparation technology of lithium-ion batteries and their key materials, and in particular to a method for preparing a one-dimensional nanostructured lithium battery cathode material, belonging to the field of new energy materials and energy storage technology. Background Technology

[0002] LiNi nickel cobalt manganese oxide cathode material x Co y Mn l-x-y O2 (NCM) is widely used in lithium-ion batteries due to its high theoretical capacity, high energy density, and excellent rate performance. This type of cathode material typically has high initial specific capacity and low internal resistance, while exhibiting good cycle stability, making it highly valuable for applications in new energy vehicles, portable electronic products, and energy storage systems.

[0003] However, traditional lithium nickel cobalt manganese oxide cathode materials are mostly in the form of spherical particles, with particle sizes generally between 3 and 12 micrometers. Although this spherical structure can meet the ion conduction requirements in liquid batteries, with the development of lithium-ion battery technology, liquid lithium batteries are gradually transitioning to semi-solid and solid lithium batteries. Semi-solid batteries use polymer electrolytes or composite solid electrolytes to replace liquid electrolytes. The interface between spherical cathode materials and polymer electrolytes or composite solid electrolytes often has problems such as random dispersion, easy aggregation, and insufficient interface contact, which leads to discontinuous ion transport channels, high interface impedance, and is prone to mechanical damage and lithium dendrite growth risk under high rate or long cycle conditions.

[0004] Currently, lithium nickel cobalt manganese oxide (LCO) cathode materials are typically prepared commercially using a precipitation method. The process involves complexing a NCO sulfate solution with ammonia, adding sodium hydroxide to precipitate spherical NCO precursors with diameters ranging from 3 to 12 micrometers, and then mixing this precursor with a lithium source (such as lithium hydroxide or lithium carbonate) followed by high-temperature sintering to form lithium NCO. A representative patent for this method, such as CN103400973B, discloses a method for preparing spherical NCO cathode materials. While the cathode materials obtained by this method meet the requirements for energy density and cycle life to some extent, the spherical particles often exhibit random dispersion after mixing with the polymer electrolyte, resulting in insufficient interfacial contact between particles. This leads to discontinuous ion transport channels, high interfacial impedance, and a tendency for particle agglomeration, thus affecting the rate performance and cycle stability of the cathode.

[0005] To address the aforementioned issues, this invention proposes fabricating the cathode material as a one-dimensional nanostructure. Compared to traditional spherical particles, one-dimensional nanostructures possess high aspect ratios and continuous orientation, enabling the construction of a continuous ion transport network spanning the entire electrode film within the polymer electrolyte. This significantly shortens the lithium-ion diffusion path, reduces interfacial impedance, and enhances the interfacial bonding between the electrode and the electrolyte. Furthermore, one-dimensional nanostructures can improve the material's mechanical toughness and tear resistance, suppress lithium dendrite growth, and enhance the stability and safety of semi-solid or solid-state batteries under high-rate and high-temperature conditions. Summary of the Invention

[0006] This invention provides a novel one-dimensional nanostructured lithium-ion battery cathode material and its preparation method. By controlling reaction conditions and preparation processes, a novel cathode material preparation method is developed that induces the directional growth of crystals into a one-dimensional nanostructure. This one-dimensional nanostructured cathode material can form a continuous ion transport network throughout the entire electrode sheet in the cathode slurry, thereby significantly improving the overall ionic conductivity, reducing interfacial impedance, and enhancing the mechanical toughness and cycle stability of the electrode film. Lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LFMP), spinel lithium manganese oxide (LMO), and lithium-rich manganese-based cathode materials can all be prepared into one-dimensional nanostructures using this method, thus providing diversified and high-performance cathode material technology solutions for semi-solid-state batteries.

[0007] This invention provides a one-dimensional nanostructured lithium-ion battery cathode material, the preparation method of which includes the following steps:

[0008] (a) Dissolve nickel, cobalt, manganese salts or aluminum-containing nickel cobalt manganese / nickel cobalt aluminum salts in deionized water, and add an appropriate amount of complexing agent and 1-3 wt% of surfactant, selected from polyvinylpyrrolidone (PVPK30), polyethylene glycol (PEG-400), hexadecyl ammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), sodium polyacrylate, ethylene glycol, etc., alone or in combination, to form a precursor solution;

[0009] (b) Under preheating conditions to 60°C, the precursor solution is slowly added dropwise to NaOH solution with a molar concentration of 1.0–5.0 mol / L. Under the conditions of pH 12.0–13.5, thorough stirring, and stirring linear speed of 5–15 m / s, hydroxide precipitate is generated with a particle size D50 of approximately 0.5–1.5 μm and exhibits a preliminary one-dimensional directional growth trend.

[0010] (c) After the precursor described in step (b) is thoroughly washed and dried at 80°C, it is uniformly mixed with a lithium source, such as LiOH·H2O, at a molar ratio of 1:1.0 to 1.05, preferably 1:1.02, and pre-sintered at 600 to 700°C for 2 hours and sintered at 700 to 750°C, preferably 720°C for 10 hours, with a heating rate of 2 to 5°C / min. The precursor is then converted into a cathode material with a stable crystalline phase and a continuous one-dimensional structure.

[0011] Preferably, the surfactant is any combination of polyvinylpyrrolidone (PVPK30) and sodium polyacrylate.

[0012] Preferably, the metal salt is selected from nickel cobalt manganese sulfate or aluminum-containing nickel cobalt manganese / nickel cobalt aluminum sulfate, and the lithium source is selected from one or more combinations of LiOH, LiNO3 and Li2CO3.

[0013] Preferably, in step (b), the molar concentration of the NaOH solution is 2.0–7.0 mol / L, the reaction temperature is 80°C, the pH is controlled at 12.0–13.5, and the stirring linear speed is 5–15 m / s, so as to promote the formation of hydroxide seed crystals and make them exhibit a one-dimensional directional growth trend.

[0014] Preferably, in step (c), the ammonia concentration and pH value are gradually adjusted. First, the ammonia concentration is increased to 1-2 mol / L and the pH is increased to 12.0-13.0, and then decreased to 0.1-0.3 mol / L and the pH is decreased to 10.0-11.0, which further promotes the directional growth of crystals, so that the final particle size D50 of the slurry reaches 0.5-1.5 μm, and forms a fiber or needle-like precursor with a high aspect ratio.

[0015] Preferably, the sintering process in step (d) includes pre-sintering and high-temperature sintering. The pre-sintering temperature is 600-700°C and the holding time is 2 hours. The high-temperature sintering temperature is 700-750°C, preferably 720°C, and the holding time is 10 hours. The heating rate is 2-5°C / min to compensate for the volatilization of lithium during the sintering process and to ensure that the precursor is transformed into a stable positive electrode material crystal phase.

[0016] As a preferred embodiment, the method also includes preparing one-dimensional nanostructures using a basalt-like wire drawing method, which includes:

[0017] (a) According to the target stoichiometric ratio, preferably Li:Ni:Co:Mn=1.1:0.90:0.05:0.05, accurately weigh high-purity raw materials, wherein each element provides multiple candidate compounds. The raw materials include: lithium source selected from Li2CO3 and lithium hydroxide (LiOH); nickel source selected from NiO and nickel hydroxide (Ni(OH)2); cobalt source selected from Co3O4 and cobalt hydroxide (Co(OH)2); manganese source selected from manganese dioxide (MnO2), manganese oxide (Mn2O3 or Mn3O4), and manganese hydroxide (Mn(OH)2).

[0018] (b) The raw materials are ball-milled for a long time (preferably 10 hours) using a high-energy ball mill to ensure that the components are fully mixed and refined;

[0019] (c) The mixed powder is placed in a high-temperature resistant crucible and pre-sintered at 700°C for 6 hours to form a uniform cathode material precursor;

[0020] (d) Under the protection of an inert gas, the precursor powder obtained in step (c) is placed into a high-temperature platinum crucible and heated to 1300–1400°C, preferably 1300°C, to completely melt it into a glassy melt.

[0021] (e) Using a melt drawing device, the glassy melt is extruded through a fine hole under a protective atmosphere, and the drawing parameters, including drawing rate, tension and cooling rate, are controlled so that the diameter of the formed continuous fiber is controlled within 50 nm, 40–50 nm.

[0022] (f) After collecting the amorphous fibers obtained by drawing, heat them in air or inert gas at 3℃ / min to 750℃ or 900℃ and keep them at that temperature for 3 hours to anneal the amorphous fibers into crystalline one-dimensional nanostructure cathode materials.

[0023] Preferably, an annealing temperature of 750°C is mainly suitable for the conversion of precipitation precursors; when the annealing temperature is 900°C, it is suitable for the crystallization of amorphous fibers after drawing.

[0024] Preferably, the cathode material prepared by the method exhibits a continuous one-dimensional nanostructure with an aspect ratio of not less than 10, and can construct a continuous ion transport network that runs through the entire electrode sheet in the cathode slurry, thereby significantly improving the lithium-ion conduction rate, reducing interfacial impedance, and improving the mechanical stability and cycle life of the electrode.

[0025] Preferably, the positive electrode of the lithium-ion battery comprises the one-dimensional nanostructured lithium battery positive electrode material as described in claim 9.

[0026] Beneficial effects:

[0027] (1) The one-dimensional nano cathode material prepared by this invention has a continuous linear structure and a high aspect ratio. After being dispersed in the cathode slurry, it can construct a continuous ion transport network that runs through the entire electrode sheet. This structure not only shortens the diffusion path of lithium ions and improves the ion conduction rate, but also improves the contact between particles and electrolyte through directional arrangement, thereby significantly reducing interfacial impedance and optimizing battery charge and discharge performance.

[0028] (2) Using one-dimensional nano-anode materials as active components can effectively improve the mechanical stability and interfacial compatibility of the electrode. The continuous fibrous structure forms a skeleton-like support in the cathode, which not only provides a continuous transport channel for ions, but also enhances the overall tear resistance of the electrode sheet and reduces local stress concentration caused by particle aggregation or uneven dispersion, thereby significantly improving the cycle life and safety of the battery.

[0029] (3) In this invention, the one-dimensional nano-anode material is dispersed in situ in the cathode slurry, and the electrode sheet formed after coating, drying and curing exhibits excellent performance in terms of ionic conductivity, rate performance and thermal stability. Compared with the use of traditional spherical cathode materials, the one-dimensional nanostructure of this invention, due to its directional continuity advantage, can construct a more complete ion transport network, thereby comprehensively improving the charging and discharging efficiency and safety performance of the battery.

[0030] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This invention relates to one-dimensional LiNi 0.90 Co 0.05 Mn 0.05 XRD pattern of O2 cathode material;

[0033] Figure 2 This invention relates to one-dimensional LiNi 0.90 Co 0.05 Mn 0.05 SEM image of O2 cathode material;

[0034] Figure 3The above are the charge-discharge performance waveforms under high and low temperature environments of Embodiment 1 and the comparative example of the present invention.

[0035] Figure 4 The figures show the gram capacity at different magnifications of Embodiment 1 and the comparative example of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0038] Please see Figures 1-4 This invention discloses two preparation techniques: precipitation method (self-templating method) and basalt-like filament drawing method. Detailed parameters and optimal conditions are provided for each process, as follows:

[0039] I. Precipitation method

[0040] Step 1: Raw material preparation and precursor solution preparation

[0041] 1.1 Raw material selection

[0042] Nickel cobalt manganese sulfate (or aluminum-containing nickel cobalt manganese / nickel cobalt aluminum sulfate) was selected as the main source of metal ions, and its molar concentration was controlled at 0.5–3.0 mol / L; at the same time, an appropriate amount of lithium source (such as LiOH, LiNO3 or Li2CO3) was prepared for subsequent replenishment of lithium content.

[0043] 1.2 Preparation of precursor solution

[0044] The selected metal salt is dissolved in deionized water, and an appropriate amount of ammonia (0.1–2 mol / L) is added to complex the metal ions and improve their coordination environment. To induce directional crystal growth, 1–3 wt% of a surfactant (such as polyvinylpyrrolidone (PVPK30), polyethylene glycol (PEG-400), hexadecyl ammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), sodium polyacrylate, ethylene glycol, or any combination thereof) is added to the solution. This surfactant selectively adsorbs onto the high-energy crystal surface of the crystal nucleus, inhibiting growth in that direction and promoting crystal extension in other directions, thus initially forming a one-dimensional growth tendency.

[0045] Step 2: Precipitation reaction and seed formation

[0046] 2.1 Precipitation reaction conditions

[0047] In a preheated reactor (30–80°C), the precursor solution is slowly added dropwise to a pre-prepared NaOH solution (NaOH molar concentration of 1.0–5.0 mol / L), while the pH of the reaction system is controlled at 12.0–13.5.

[0048] 2.2 Directional crystal growth and precursor formation

[0049] Under thorough stirring conditions (stirring speed 5–15 m / s), after reacting for 30–80 minutes, preliminary hydroxide seed crystals are generated, with a diameter of approximately 20 nm and a particle size D50 of approximately 0.5–1.5 μm. Due to the action of the surfactant, the crystals begin to grow directionally along the non-inhibitory direction during the formation process, tending to form fibrous or needle-like structures rather than traditional isotropic spherical particles.

[0050] Step 3: Post-treatment and high-temperature sintering

[0051] 3.1 Washing and Drying

[0052] After the reaction is complete, the precursor slurry is thoroughly washed to remove residual ions and surfactants, and then dried at 80°C for 12 hours to obtain dry cathode material precursor powder.

[0053] 3.2 Heat Treatment and Sintering

[0054] The dried precursor powder is mixed uniformly with a lithium source (such as LiOH·H2O) at a set molar ratio (1:1.0 to 1.05, more preferably 1:1.02 to compensate for lithium volatilization during sintering). Pre-sintering is first performed in a tube furnace (600–700°C, held for 2 hours) to form an intermediate state; subsequently, after ball milling (e.g., 650 rpm, 5 hours), sintering is performed at 700–750°C (preferably 720°C, held for 10 hours, heating rate 2–5°C / min) to transform the precursor into a cathode material with a stable crystalline phase and a continuous one-dimensional structure.

[0055] II. Basalt-like wire drawing method

[0056] This process uses a method that mimics natural basalt to draw fibers, transforming precursor powder into continuous fibers to achieve a one-dimensional nanostructure.

[0057] (1) Raw material mixing: Accurately weigh high-purity raw materials Li2CO3, lithium hydroxide (LiOH), NiO, nickel hydroxide (Ni(OH)2), Co3O4, cobalt hydroxide (Co(OH)2), manganese dioxide (MnO2), manganese oxide (Mn2O3 or Mn3O4), and manganese hydroxide (Mn(OH)2) according to the target stoichiometric ratio (preferably Li:Ni:Co:Mn=1.1:0.90:0.05:0.05). Perform long-term ball milling (preferably 10 hours) using a high-energy ball mill to ensure thorough mixing and refinement of all components, guaranteeing reaction uniformity.

[0058] (2) Pre-sintering: The uniformly mixed powder is placed in a high-temperature resistant crucible and pre-sintered in oxygen at 700°C for 6 hours to promote partial reaction of the raw materials to form the target cathode material precursor. This step helps to eliminate local compositional differences and provides a uniform solid-phase raw material for subsequent high-temperature melting.

[0059] (3) High-temperature melting: The pre-sintered precursor powder is placed in a high-temperature resistant platinum crucible and heated under the protection of an inert gas (such as nitrogen or argon) to ensure that oxidation loss is avoided. The temperature is raised to 1300–1400℃ (preferably 1300℃) to completely melt the precursor and form a homogeneous glassy melt. The high temperature and liquid-phase mixing during the melting process ensure that all metal ions (including Ni, Co, Mn and lithium) diffuse fully, thereby ensuring the uniform distribution of each element in the material.

[0060] (4) Fiber drawing: Using precision melt drawing equipment, the glassy melt is extruded through fine orifices under a protective atmosphere. By precisely controlling the drawing rate, tensile tension, and cooling rate, the melt is formed into continuous fibers under high-speed stretching. The fiber diameter is controlled within 50 nm (e.g., 40–50 nm), which can be achieved by real-time monitoring of the drawing process and adjustment of stretching parameters. High draw ratio and rapid cooling enable the fiber to solidify rapidly, thereby fixing the one-dimensional structure.

[0061] (5) Annealing process: Collect the amorphous nanofibers obtained by drawing and place them in an annealing furnace for heat treatment. In air or inert gas, raise the temperature to 750°C and hold for 3 hours to promote the transformation of the amorphous state inside the fiber into the crystalline cathode material phase, while maintaining the ultrafine one-dimensional morphology.

[0062] The cathode materials involved in this invention include not only lithium nickel cobalt manganese oxide, but also lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LFMP), spinel lithium manganese oxide (LMO), lithium-rich manganese-based materials, etc.

[0063] Example 1: Preparation of one-dimensional LiNi nanoparticles by precipitation method 0.90 Co 0.05 Mn0.05 O2 cathode material

[0064] (1) Preparation of mixed solution:

[0065] a. Prepare 1.5 mol / L Ni 0.90 Co 0.05 Mn 0.05 A mixed sulfate solution (Ni:Co:Mn molar ratio of 0.90:0.05:0.05);

[0066] b. Dissolve the solution in 100 mL of deionized water and add 10.0 mol / L ammonia solution to form a complex;

[0067] c. Add 1.5 wt% sodium polyacrylate to the solution and stir thoroughly to form a precursor solution, inducing preliminary directional growth of crystals.

[0068] (2) Crystal precipitation:

[0069] a. In a preheated reactor at 60°C, the precursor solution from step 1 is slowly added dropwise to a 6.0 mol / L NaOH solution at a rate of 0.5 mL / min;

[0070] b. Maintain the pH of the system at approximately 12.8, react for 1 hour, and generate Ni under thorough stirring (approximately 10 m / s). 0.90 Co 0.05 Mn 0.05 (OH)2 seed crystals with a particle size D50 of approximately 1 μm exhibit a tendency to grow along a specific direction.

[0071] (3) Post-treatment and sintering: a. After the reaction, the precursor slurry was filtered, thoroughly washed (to remove residual ions and surfactants), and dried at 80°C for 12 hours to obtain dried Ni. 0.90 Co 0.05 Mn 0.05 (OH)2 precursor powder;

[0072] b. Mix the dry precursor powder with LiOH·H2O at a molar ratio of 1:1.02 until homogeneous (i.e., 1.02 moles of LiOH are required for every 1 mole of precursor to compensate for lithium volatilization during sintering).

[0073] c. Place the mixture in a tube furnace, heat it to 500°C at a rate of 5°C / min, and hold it at that temperature for 6 hours for pre-sintering;

[0074] d. After ball milling at 650 rpm for 5 hours and pressing into tablets, the temperature was increased to 720℃ at 3℃ / min and held for 10 hours to finally obtain LiNi with a continuous one-dimensional nanostructure. 0.90 Co 0.05Mn 0.05 O2 cathode material.

[0075] (5) Cathode preparation and battery assembly:

[0076] a. After washing and coating the sintered cathode material, prepare a cathode slurry (add appropriate amounts of PVDF and NMP solution), uniformly coat it on aluminum foil and dry it to form a cathode film.

[0077] b. Using this positive electrode film, a CR2032 coin cell was assembled, and electrochemical tests were performed. The test results showed:

[0078] - The initial coulomb efficiency is approximately 95%;

[0079] - Under 0.1C discharge conditions, the cycle capacity reaches 228mAh / g;

[0080] Example 2: Preparation of one-dimensional nano-Li1.2Mn0.6Ni0.2O2 lithium-rich manganese-based cathode material by precipitation method

[0081] (1) Preparation of precursor solution:

[0082] a. Prepare a 1.5 mol / L mixed solution of MnSO4 and NiSO4, with a Mn:Ni molar ratio of 0.6:0.2;

[0083] b. Dissolve the solution in 100 mL of deionized water and add 10.0 mol / L ammonia water to complex it, thereby improving the coordination environment of the metal ions;

[0084] c. Add 1.5 wt% sodium polyacrylate (PAA) to the solution and stir until homogeneous to form a precursor solution to induce preliminary directional crystal growth.

[0085] (2) Crystal precipitation:

[0086] a. In a preheated reactor at 80°C, the precursor solution from step 1 is slowly added dropwise to a pre-prepared 6.0 mol / L NaOH solution at a rate of 0.5 mL / min;

[0087] b. The pH of the system was controlled at around 12.8, and the reaction was carried out for 1 hour. Mn0.6Ni0.2(OH)2 seed crystals were generated under the condition of full stirring (stirring rate of about 10m / s). The particle size D50 was about 1μm, and they showed a tendency to grow along a specific direction.

[0088] (3) Post-treatment and sintering:

[0089] a. After the reaction is complete, the precursor slurry is filtered, washed thoroughly (to remove residual ions and surfactants), and dried at 80°C for 12 hours to obtain dry Mn0.6Ni0.2(OH)2 precursor powder;

[0090] b. Mix the dried precursor powder with LiOH·H2O at a molar ratio of 1:1.25 until homogeneous (i.e., 1.25 moles of LiOH are needed for every 1 mole of precursor to compensate for lithium volatilization during sintering).

[0091] c. Place the mixture in a tube furnace, heat it to 500°C at a rate of 5°C / min, and hold it at that temperature for 6 hours for pre-sintering;

[0092] d. After ball milling at 650 rpm for 5 hours and pressing into tablets, the temperature is increased to 800 ℃ at 3 ℃ / min and held for 10 hours to finally obtain Li1.2Mn0.6Ni0.2O2 cathode material with continuous one-dimensional nanostructure.

[0093] (4) Cathode preparation and battery assembly:

[0094] a. After washing and coating the sintered cathode material, prepare a cathode slurry (add appropriate amounts of PVDF and NMP solution), uniformly coat it on aluminum foil and dry it to form a cathode film.

[0095] b. Using this positive electrode film, a CR2032 coin cell was assembled, and electrochemical tests were performed. The test results showed:

[0096] - The initial Coulomb efficiency is approximately 91%;

[0097] - Under 0.1C discharge conditions, the cycle capacity reaches 270mAh / g;

[0098] Example 3: Preparation of one-dimensional nano-Li1.2Mn0.6Ni0.2O2 cathode material by basalt-like wire drawing method

[0099] (1) Accurately weigh Li2CO3, NiO, and MnO2, and prepare a mixed powder according to the corresponding element molar ratio of 1.25:0.6:0.2. Ball mill the powder for 12 hours to ensure uniform dispersion of each component. Place the mixed powder in a platinum crucible and pre-sinter at 700℃ for 6 hours to generate a uniform positive electrode precursor.

[0100] (2) The pre-sintered precursor powder is placed into a platinum crucible and heated to 1350°C under nitrogen protection to completely melt the material into a homogeneous glassy melt. The molten state is maintained for a certain period of time to ensure that the metal ions in the liquid phase diffuse fully and to guarantee homogeneity.

[0101] (3) The glassy melt is extruded through a precision drawing die in a protective atmosphere and then stretched at high speed using a mechanical drawing device. The drawing parameters (e.g., drawing rate, tension, and cooling rate) are adjusted to keep the continuous fiber diameter at approximately 45 nm (target ≤ 50 nm). The fiber morphology is monitored in real time during the drawing process to ensure that the fibers are continuous, uniform, and without breakage.

[0102] (4) After collecting the amorphous fibers obtained by drawing, place them in an annealing furnace and heat them to 800℃ in air at 3℃ / min, and hold them for 3 hours. After annealing, the fiber interior changes from amorphous to crystalline Li1.2Mn0.6Ni0.2O2 positive electrode phase, while the fiber diameter remains in the range of 45–50 nm, maintaining a one-dimensional morphology.

[0103] (5) After washing and coating modification of the sintered cathode material, a cathode slurry (with appropriate amounts of PVDF and NMP solution added) is prepared, uniformly coated on aluminum foil, and dried to form a cathode film; this cathode film is used to assemble a CR2032 coin cell, and electrochemical tests are performed. The test results show:

[0104] - The initial Coulomb efficiency is approximately 91%;

[0105] - Under 0.1C discharge conditions, the cycle capacity reaches 265mAh / g;

[0106] Example 4: Preparation of one-dimensional lithium iron phosphate nanomaterials using a basalt-like wire drawing method

[0107] (1) Take iron phosphate (FePO4) and lithium carbonate (Li2CO3) and mix them at a Li:Fe molar ratio of 1:1.04. Add 70% deionized water as the medium and ball mill for 6 hours to obtain a precursor slurry with a particle size of 500 nanometers.

[0108] (2) The ball-milled slurry was vacuum dried for 12 hours to obtain precursor powder.

[0109] (3) The pretreated precursor is fed into the high-temperature melting zone of the basalt wire drawing equipment. The temperature is controlled at 1400℃ to completely melt the material into a homogeneous glassy melt. The molten state is maintained for a certain period of time to ensure that the metal ions in the liquid phase diffuse fully and to guarantee uniformity.

[0110] (4) The glassy melt is extruded through a precision drawing die in a protective atmosphere and then stretched at high speed using a mechanical drawing device. The drawing parameters (e.g., drawing rate, tension, and cooling rate) are adjusted to keep the continuous fiber diameter at approximately 45 nm (target ≤ 50 nm). The fiber morphology is monitored in real time during the drawing process to ensure that the fibers are continuous, uniform, and without breakage.

[0111] (5) The obtained one-dimensional lithium iron phosphate was sintered for 6 hours in a tube furnace at 400°C with 5% glucose as a carbon source under a reducing atmosphere (nitrogen) to obtain LiFePO4 nanofiber material with good crystallinity and continuous conductive network structure.

[0112] (6) Add appropriate amounts of PVDF and NMP solutions to the sintered cathode material to prepare a cathode slurry, uniformly coat it onto aluminum foil, and dry it to form a cathode film; use this cathode film to assemble a CR2032 coin cell and perform electrochemical tests. The test results show:

[0113] - The initial coulomb efficiency is approximately 99.9%;

[0114] - Under 0.1C discharge conditions, the cycle capacity reaches 165mAh / g.

[0115] Comparative example: Spherical large-particle LiNi 0.90 Co 0.05 Mn 0.05 O2 cathode material

[0116] (1) LiNi with a D50 of 10 micrometers 0.90 Co 0.05 Mn 0.05 O2 precursor and LiOH·H2O were mixed evenly, and then heated to 470℃ at 3℃ / min under an oxygen atmosphere, held at that temperature for 5 hours, and then heated to 735℃ at 5℃ / min and held for 10 hours to obtain LiNi. 0.90 Co 0.05 Mn 0.05 O2 cathode material.

[0117] (2) Cathode preparation and battery assembly:

[0118] a. After washing and coating the sintered cathode material, prepare a cathode slurry (add appropriate amounts of PVDF and NMP solution), uniformly coat it on aluminum foil and dry it to form a cathode film.

[0119] b. Using this positive electrode film, a CR2032 coin cell was assembled, and electrochemical tests were performed. The test results showed:

[0120] - The initial coulomb efficiency is approximately 90%;

[0121] - Under 0.1C discharge conditions, the cycle capacity reaches 220mAh / g;

[0122]

[0123] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A one-dimensional nanostructured lithium-ion battery cathode material, characterized in that, The one-dimensional nanostructured lithium-ion battery cathode material includes the following preparation steps: (a) Dissolve nickel, cobalt, manganese salts or aluminum-containing nickel cobalt manganese / nickel cobalt aluminum salts in deionized water, and add an appropriate amount of complexing agent and 1-3 wt% of surfactant, selected from polyvinylpyrrolidone (PVPK30), polyethylene glycol (PEG-400), hexadecyl ammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), sodium polyacrylate, ethylene glycol, etc., alone or in combination, to form a precursor solution; (b) Under preheating conditions to 60°C, the precursor solution is slowly added dropwise to NaOH solution with a molar concentration of 1.0–5.0 mol / L. Under the conditions of pH 12.0–13.5, thorough stirring, and stirring linear speed of 5–15 m / s, hydroxide precipitate is generated with a particle size D50 of approximately 0.5–1.5 μm and exhibits a preliminary one-dimensional directional growth trend. (c) After the precursor described in step (b) is thoroughly washed and dried at 80°C, it is uniformly mixed with a lithium source, such as LiOH·H2O, at a molar ratio of 1:1.0 to 1.05, preferably 1:1.02, and pre-sintered at 600 to 700°C for 2 hours and sintered at 700 to 750°C, preferably 720°C for 10 hours, with a heating rate of 2 to 5°C / min. The precursor is then converted into a cathode material with a stable crystalline phase and a continuous one-dimensional structure.

2. The one-dimensional nanostructured lithium-ion battery cathode material according to claim 1, characterized in that, The surfactant is any combination of polyvinylpyrrolidone (PVPK30) and sodium polyacrylate.

3. The one-dimensional nanostructured lithium-ion battery cathode material according to claim 1, characterized in that, The metal salt is selected from nickel cobalt manganese sulfate or aluminum-containing nickel cobalt manganese / nickel cobalt aluminum sulfate, and the lithium source is selected from one or more combinations of LiOH, LiNO3 and Li2CO3.

4. The one-dimensional nanostructured lithium-ion battery cathode material according to claim 1, characterized in that, In step (b), the molar concentration of NaOH solution is 2.0–7.0 mol / L, the reaction temperature is 80℃, the pH is controlled at 12.0–13.5, and the stirring linear speed is 5–15 m / s, in order to promote the formation of hydroxide seed crystals and make them exhibit a one-dimensional directional growth trend.

5. The one-dimensional nanostructured lithium-ion battery cathode material according to claim 1, characterized in that, In step (c), the ammonia concentration and pH value are gradually adjusted. First, the ammonia concentration is increased to 1-2 mol / L and the pH is increased to 12.0-13.0, and then decreased to 0.1-0.3 mol / L and the pH is decreased to 10.0-11.

0. This further promotes the directional growth of crystals, so that the final particle size D50 of the slurry reaches 0.5-1.5 μm, and forms fiber or needle-like precursors with a high aspect ratio.

6. The one-dimensional nanostructured lithium-ion battery cathode material according to claim 1, characterized in that, The sintering process in step (d) includes pre-sintering and high-temperature sintering. The pre-sintering temperature is 600-700℃ and the holding time is 2 hours. The high-temperature sintering temperature is 700-750℃, preferably 720℃, and the holding time is 10 hours. The heating rate is 2-5℃ / min to compensate for the volatilization of lithium during the sintering process and to ensure that the precursor is transformed into a stable positive electrode material crystal phase.

7. A method for preparing a one-dimensional nanostructured lithium-ion battery cathode material according to any one of claims 1-6, characterized in that, It also includes the preparation of one-dimensional nanostructures using a basalt-like filament drawing method, which includes: (a) According to the target stoichiometric ratio, preferably Li:Ni:Co:Mn=1.1:0.90:0.05:0.05, accurately weigh high-purity raw materials, wherein each element provides multiple candidate compounds. The raw materials include: lithium source selected from Li2CO3 and lithium hydroxide (LiOH); nickel source selected from NiO and nickel hydroxide (Ni(OH)2); cobalt source selected from Co3O4 and cobalt hydroxide (Co(OH)2); manganese source selected from manganese dioxide (MnO2), manganese oxide (Mn2O3 or Mn3O4), and manganese hydroxide (Mn(OH)2). (b) The raw materials are ball-milled for a long time (preferably 10 hours) using a high-energy ball mill to ensure that the components are fully mixed and refined; (c) The mixed powder is placed in a high-temperature resistant crucible and pre-sintered at 700°C for 6 hours to form a uniform cathode material precursor; (d) Under the protection of an inert gas, the precursor powder obtained in step (c) is placed into a high-temperature platinum crucible and heated to 1300–1400°C, preferably 1300°C, to completely melt it into a glassy melt. (e) Using a melt drawing device, the glassy melt is extruded through a fine hole under a protective atmosphere, and the drawing parameters, including drawing rate, tension and cooling rate, are controlled so that the diameter of the formed continuous fiber is controlled within 50 nm, 40–50 nm. (f) After collecting the amorphous fibers obtained by drawing, heat them in air or inert gas at 3℃ / min to 750℃ or 900℃ and keep them at that temperature for 3 hours to anneal the amorphous fibers into crystalline one-dimensional nanostructure cathode materials.

8. The method for preparing a one-dimensional nanostructured lithium-ion battery cathode material according to claim 7, characterized in that, When the annealing temperature is 750℃, it is mainly suitable for the conversion of precipitation precursors; when the annealing temperature is 900℃, it is suitable for the crystallization of amorphous fibers after drawing.

9. A method for preparing a one-dimensional nanostructured lithium-ion battery cathode material according to any one of claims 1 to 8, characterized in that, The cathode material prepared by the method exhibits a continuous one-dimensional nanostructure with an aspect ratio of not less than 10. It can also construct a continuous ion transport network that runs through the entire electrode sheet in the cathode slurry, thereby significantly improving the lithium-ion conduction rate, reducing interfacial impedance, and improving the mechanical stability and cycle life of the electrode.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery comprises the one-dimensional nanostructured lithium battery positive electrode material as described in claim 9.

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