Topological ion-exchange lithium battery ternary positive electrode material, preparation method, application and battery

Abstract

The application discloses a topological ion exchange lithium battery ternary positive electrode material and a preparation method, application and battery, and belongs to the technical field of lithium ion batteries. In the preparation, a sodium salt intermediate is prepared first: a ternary precursor containing nickel, cobalt and manganese is mixed with a sodium source, first-stage high-temperature heat treatment is carried out in an oxygen-containing atmosphere, and a sodium salt ternary oxide intermediate with a layered structure is obtained; then, topological ion exchange is carried out: the intermediate is mixed with a lithium source, second-stage medium-temperature heat treatment is carried out in an oxygen-containing atmosphere, lithium ions replace sodium ions in the intermediate through a topological exchange mechanism, a lithium / sodium mixed crude product is obtained; subsequently, washing and drying are carried out to remove soluble sodium salt and obtain a lithium battery ternary crude product; finally, the lithium battery ternary crude product is mixed with a supplementary lithium source, third-stage heat treatment is carried out in an oxygen-containing atmosphere, and final lithiation and crystal structure optimization are completed. The topological ion exchange lithium battery ternary positive electrode material prepared by the application has high crystallinity, small Li / Ni mixing and good rate and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a ternary cathode material based on topological ion exchange and its preparation method, a battery containing the cathode material and its application. Background Technology

[0002] In fields such as new energy vehicles and high-end consumer electronics, the core performance of lithium-ion batteries largely depends on their cathode materials. Layered ternary cathode materials (mainly lithium nickel cobalt manganese oxide NCM or lithium nickel cobalt aluminum oxide NCA) have become one of the most promising cathode material systems due to their combination of high energy density, high operating voltage, and relatively ideal overall cost.

[0003] Currently, the industrial synthesis of ternary materials mainly employs a co-precipitation method to prepare precursors, followed by high-temperature solid-state sintering for lithium replenishment and crystallization. However, this process is extremely sensitive to sintering conditions, presenting a fundamental technical challenge: if the sintering temperature is too high, lithium ions (Li... + ) and nickel ions (Ni 2+ When Li / Ni sites have similar radii, they are prone to mixing, leading to a reduction in active sites, decreased usable capacity, and compromised structural stability. Conversely, if the sintering temperature is lowered to suppress mixing, insufficient thermal energy will drive the crystal growth and maturation, resulting in poor crystallinity, which will also weaken structural stability and electrochemical performance. This trade-off between mixing and crystallization severely restricts further improvement in material performance. Therefore, developing a novel synthesis method that can fundamentally optimize the crystal growth process and simultaneously improve structural order and stability has significant scientific and engineering value. Summary of the Invention

[0004] This invention aims to overcome the inherent contradiction between Li / Ni mixing and insufficient crystal growth, which is difficult to avoid in existing high-temperature solid-state sintering technologies. It provides a topological ion-exchange-based ternary cathode material for lithium-ion batteries, its preparation method, applications, and batteries. The ternary cathode material prepared by this invention exhibits significantly improved rate performance and cycle stability. Furthermore, the preparation method is highly versatile and applicable to various layered oxide cathode material systems.

[0005] The core of this invention lies in providing a controlled topological ion exchange synthesis strategy. This method abandons the traditional crystallization path that relies entirely on high temperatures, instead achieving mild and controllable crystal reconstruction and defect engineering through precise and coordinated control of the thermodynamic and kinetic conditions of the ion exchange process (including but not limited to reaction temperature, time, atmosphere, and precursor state). Specifically, the inventive concept utilizes chemical potential difference as a driving force to allow target alkali metal ions (such as lithium ions) to be orderly embedded into a pre-formed precursor framework with a specific framework structure through a topological exchange mechanism under suitable conditions. This process can be carried out at relatively low temperatures, effectively suppressing Li / Ni mixing caused by high temperatures and ensuring the cation order of the layered structure. Furthermore, it provides a controllable environment for the gradual and complete growth of crystals, contributing to the formation of structures with good crystallinity and sufficient stress release. Simultaneously, this method can directionally introduce stable defects beneficial to lithium ion transport and structural buffering, thereby constructing a cathode material with high structural stability, low cation mixing, and excellent interfacial properties at the material synthesis source. Therefore, this invention provides a new approach to material preparation that breaks through the limitations of traditional sintering, consumes less energy, and has better performance.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0007] This invention provides a method for preparing a topological ion-exchange lithium-ion battery ternary cathode material, which includes the following steps:

[0008] S1. Preparation of sodium salt intermediate: A ternary precursor containing nickel, cobalt and manganese elements is mixed with a sodium source and subjected to a first stage of high-temperature heat treatment in an oxygen-containing atmosphere to obtain a sodium salt ternary oxide cathode material intermediate with a layered structure.

[0009] S2, Topological ion exchange: The sodium salt ternary oxide cathode material intermediate obtained in step S1 is mixed with a lithium source and subjected to a second stage of medium-temperature heat treatment in an oxygen-containing atmosphere, so that lithium ions partially replace sodium ions in the intermediate through a topological exchange mechanism to obtain a crude lithium / sodium mixed product; then washing and drying are performed to remove soluble sodium salts and obtain a crude lithium battery ternary product.

[0010] S3. Supplementary lithiation and crystallization: The crude lithium-ion battery ternary cathode material obtained in step S2 is mixed with a supplementary lithium source and subjected to a third stage of heat treatment in an oxygen-containing atmosphere to complete the final lithiation and crystal structure optimization, thereby obtaining the topological ion exchange lithium-ion battery ternary cathode material.

[0011] In step S1, the ternary precursor is nickel-cobalt-manganese hydroxide (Ni). x Co y Mn 1-x-y (OH)2, where 0 <x<1,0<y<1。

[0012] In step S1, the sodium source can be one or more of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate, preferably sodium carbonate. Existing technologies also claim to use layered hydroxide precursors for topological transformation, but these require strict sintering temperatures; too low a temperature prevents lithiation, while too high a temperature causes dehydration and oxide formation, which is not a topological transformation. This invention first synthesizes layered sodium batteries and then performs a topological transformation to obtain layered lithium batteries (i.e., first inserting Na and then performing a topological transformation). This method is highly operable, has a wide sintering temperature range, and further modulates the layered lithium structure through the Na battery microstructure, which is more conducive to optimizing the performance of layered lithium batteries. Furthermore, adjusting the sodium source to oxides, hydroxides, or borates, niobates, phosphates, silicates, and tungstates of Ta, W, Mg, H, Mo, Nb, Al, NH4, Co, Mn, Ti, Zr, Sr, Si, B, etc., does not achieve the purpose of this invention.

[0013] In step S1, the molar ratio (Na:TM) of sodium element (Na) in the sodium source to the total amount of transition metal (TM, i.e., Ni+Co+Mn) in the ternary precursor can be (0.5-1.5):1, preferably 0.7:1 to 1.15:1, for example 0.75:1.

[0014] In step S1, the temperature of the first high-temperature heat treatment can be from 500°C to 1000°C, for example, 650°C or 700°C; the heat treatment time can be from 10 hours to 30 hours, for example, 15 hours, 20 hours or 25 hours. Preferably, it is from 650°C to 900°C. The heating rate can be from 1°C / min to 10°C / min, for example, 5°C / min.

[0015] In step S1, the oxygen-containing atmosphere can be pure oxygen or a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen is not less than 20%. The oxygen flow rate can be 20-200 mL / min, for example, 80 mL / min or 100 mL / min.

[0016] In some specific embodiments, the sodium source in step S1 is sodium carbonate, Li:TM = 0.75:1, the sintering temperature is 650℃, the heat treatment time is 20h, and the atmosphere used is a pure oxygen flow of 80 mL / min.

[0017] In step S2, the lithium source may be one or more of lithium chloride, lithium nitrate, and lithium acetate, preferably lithium chloride.

[0018] In step S2, the molar ratio (Li:TM) of lithium element (Li) in the lithium source to the total amount of transition metal (TM) in the intermediate of step S1 can be (0.5-10):1, preferably 0.7:1 to 1.0:1, for example 0.85:1.

[0019] In step S2, the temperature of the second stage of medium-temperature heat treatment can be from 100°C to 800°C, for example, 550°C, 600°C or 650°C; the heat treatment time can be from 2 hours to 10 hours, for example, 3 hours, 4 hours or 6 hours.

[0020] In step S2, the solvent used for the washing process is deionized water or an alcohol solvent, and the number of washing cycles can be 2-5 times to ensure that residual sodium ions are fully removed.

[0021] In step S2, the drying temperature can be from 50°C to 100°C, for example, 60°C or 80°C; the drying time can be from 6 hours to 24 hours.

[0022] In some specific embodiments, the lithium source in step (2) is lithium chloride, Li:TM = 0.85:1, the exchange temperature is 600℃, the heat treatment time is 4h, and the product is washed with deionized water and dried overnight in an oven at 60℃.

[0023] In step S3, the supplementary lithium source is one or more of lithium hydroxide, lithium carbonate, and lithium nitrate, preferably lithium hydroxide. The molar ratio (Li:TM) of lithium element (Li) in the supplementary lithium source to the total amount of transition metal (TM) in the crude product of step (2) can be (0-1):1, preferably 0.7:1 to 0.8:1, for example 0.75:1.

[0024] In step S3, the third stage of heat treatment can employ either a one-step isothermal process or a segmented heating process. When using a one-step isothermal process, the heat treatment temperature can be 600℃ to 1000℃, for example, 750℃, 760℃, or 780℃; the time can be 5 hours to 15 hours. When using a segmented heating process, the temperature can be first held at a first temperature, then raised to a second temperature and held thereafter; the first temperature can be 450℃ to 550℃, for example, 500℃; the holding time can be 1 hour to 10 hours, for example, 2 hours; the second temperature can be 600℃ to 1000℃, for example, 750℃ or 760℃; the holding time can be 2 hours to 10 hours, for example, 3 hours. The heating rate can be 1℃ / min to 10℃ / min, for example, 5℃ / min.

[0025] In some specific embodiments, the segmented heat treatment conditions in step (3) are: first, heat at 500°C for 2 hours, then heat up to 750-780°C and heat for 3-12 hours.

[0026] In some specific embodiments, the ternary precursor is Ni. 0.8 Co 0.1 Mn 0.1 (OH)2.

[0027] In steps S1 and S2, the mixing method can be either dry mixing or wet mixing. When wet mixing is used, the solvent used is anhydrous ethanol, deionized water, etc., and a drying pretreatment is required after mixing.

[0028] This invention also provides a topological ion-exchange lithium-ion ternary cathode material prepared by the aforementioned method, with the general chemical formula LiNi. x Co y Mn1- x - y O2 has an α-NaFeO2 type layered crystal structure (R-3m space group). The intensity ratio of the (003) crystal plane diffraction peak to the (104) crystal plane diffraction peak in its X-ray diffraction pattern is I. (003) / I (104) A value greater than 1.5, preferably greater than 1.8, indicates that the material has a low Li / Ni cation mixing degree.

[0029] The present invention also provides the application of the aforementioned topological ion-exchange lithium-ion ternary cathode material as an active material in the cathode of a lithium-ion battery.

[0030] The present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises the aforementioned topological ion-exchange lithium-ion ternary positive electrode material.

[0031] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0032] The reagents and raw materials used in this invention are all commercially available.

[0033] The positive and progressive effects of this invention are as follows: the topological ion exchange lithium-ion ternary cathode material prepared by this invention has high crystallinity, small Li / Ni mixing, and excellent rate capability and cycle stability; moreover, the preparation method is highly practical and can be applied to various cathode material systems. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 SEM results for topological ion-exchange ternary cathode materials;

[0036] Figure 2 EDS results after topological ion exchange followed by water washing;

[0037] Figure 3 XRD results for ternary cathode materials with topological ion exchange;

[0038] Figure 4XRD results for the topological ion-exchange precursor layered sodium cathode. Detailed Implementation

[0039] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0040] Ternary precursor Ni in Examples and Comparative Examples 0.8 Co 0.1 Mn 0.1 All (OH)2 was purchased from Shenzhen Youyan Technology, the tubular furnace was manufactured by Hefei Kejing, and the high-purity oxygen (99.999%) was produced by Shanghai Haoqi Gas Co., Ltd. The oxygen flow rate during the sintering process was 80 mL / min.

[0041] Example 1

[0042] Step (1): Solid-phase preparation of sodium salt intermediate. Weigh the precursor Ni at a molar ratio of Na:TM = 0.75:1. 0.8 Co 0.1 Mn 0.1 (OH)2 and sodium carbonate Na2CO3 (Grate, 99.9%) were added to a mortar, and about 5 mL of anhydrous ethanol (Guoyao, 99.9%) was added. After being wet-ground evenly, the mixture was kept at 650℃ for 20 h in a tube furnace under a pure oxygen atmosphere with a heating rate of 5℃ / min. After the heating was maintained, the mixture was allowed to cool naturally to room temperature to obtain the Na-based ternary cathode intermediate.

[0043] Step (2): Preparation of crude ternary lithium-ion battery product. Take the sodium salt intermediate from Step 1 and mix it with lithium chloride (Aladdin, 99%) at a ratio of Li:TM = 0.85:1. Maintain the temperature at 600℃ for 4 hours under a pure oxygen atmosphere with a heating rate of 5℃ / min. After maintaining the temperature, allow it to cool naturally to room temperature to obtain the Li / Na exchanged material. Wash it three times with 200 mL of deionized water and then dry it overnight in a vacuum oven at 60℃ to obtain the crude ternary lithium-ion battery product.

[0044] Step (3): Preparation of ternary lithium-ion battery product. Take the crude product from step (2) and mix it with lithium hydroxide monohydrate LiOH·H2O (Sigma-Aldrich, AR) at a ratio of Li:TM = 0.75:1. Hold the mixture at 500℃ for 2 hours in a pure oxygen atmosphere, then at 760℃ for 3 hours. The heating rate is 5℃ / min. After holding the mixture at this temperature, allow it to cool naturally to room temperature to obtain the topological ion exchange ternary lithium-ion battery product.

[0045] Example 2

[0046] Compared with Example 1, step (1) involves weighing the precursor Ni at a molar ratio of Na:TM = 0.90:1. 0.8 Co 0.1 Mn 0.1 (OH)2 and sodium hydroxide NaOH (Shanghai test, 99.7%); Step (2) Lithium chloride LiCl is mixed according to Li:TM = 1.10:1; Step (3) Lithium hydroxide monohydrate LiOH·H2O is mixed according to Li:TM = 0.20:1, and the other conditions are the same.

[0047] Comparative Example 1

[0048] Weigh the precursor Ni at a molar ratio of Li:TM = 1.02:1. 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide monohydrate LiOH·H2O (Sigma-Aldrich, AR) were mixed with about 5 mL of anhydrous ethanol (Guoyao, 99.9%) and wet-ground until homogeneous. The mixture was then heated at 500℃ for 2 h and 780℃ for 12 h in a tube furnace under a pure oxygen atmosphere, with a heating rate of 5℃ / min. After heating, the mixture was allowed to cool naturally to room temperature to obtain a lithium battery ternary cathode.

[0049] Effect Example

[0050] (1) Scanning electron microscopy (SEM) characterization

[0051] like Figure 1 As shown, the prepared topological ion-exchange ternary cathode material exhibits a polycrystalline secondary morphology with a particle size of approximately 10 μm. Figure 2 As shown, the energy dispersive spectroscopy (EDS) spectrum of the crude product after water washing indicates that the Na ions have been largely washed away.

[0052] (2) X-ray diffraction (XRD) characterization

[0053] like Figure 3 As shown, the prepared topological ion-exchange ternary cathode material exhibits a typical α-NaFeO2 type structure with no impurity phases. Furthermore, the intensity ratio of the (003) peak to the (104) peak is approximately 1.84, indicating that Li / Ni mixing is significantly suppressed.

[0054] Figure 4 XRD results for the topological ion-exchange precursor layered sodium cathode, from Figure 4 It is known that lithium ions are orderly embedded in a pre-formed precursor backbone with a specific framework structure through a topological exchange mechanism.

[0055] (3) Electrochemical performance testing

[0056] 1. Preparation of lithium battery positive electrode sheet

[0057] The modified layered oxide cathode material prepared according to this invention, conductive carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were weighed and mixed evenly at a mass ratio of 80:10:10. Subsequently, N-methylpyrrolidone (NMP) solvent, which is 2.5 times its total mass, was added to the mixed powder, and the resulting mixture was placed in a vortex mixer and stirred continuously at room temperature for 2 hours to form a uniform slurry.

[0058] The above slurry was uniformly coated onto a carbon-coated aluminum foil current collector. After drying in a forced-air oven at 110°C for 30 minutes, the electrode sheet was rolled and cut using a punching machine to obtain a circular positive electrode sheet with a diameter of 12 mm. This electrode sheet was then placed in a vacuum oven and dried at 110°C for 12 hours to completely remove residual solvent. The areal density of the active material on the resulting electrode sheet was approximately 2.0 mg / cm². After drying, the prepared electrode sheet was immediately transferred to an argon-filled glove box for battery assembly.

[0059] 2. Assembly of button-type lithium-ion batteries

[0060] CR2032 button cells were assembled in an argon atmosphere glove box with both moisture and oxygen concentrations below 0.1 ppm. All cell components (including cell casings, separators, and electrode plates) were ultrasonically cleaned and dried with ethanol before being transferred to the glove box.

[0061] The battery uses the aforementioned positive electrode as the positive electrode, a lithium metal sheet as the negative electrode, a ceramic separator (2ccs+12pe+2ccs), and an electrolyte solution of 1 M lithium hexafluorophosphate (LiPF6) in a mixture of dimethyl carbonate (DMC) / ethylene carbonate (EC) / ethyl methyl carbonate (EMC) + 5 wt% fluoroethylene carbonate (FEC) (the volume ratio of solvent DMC:EC:EMC is 1:1:1).

[0062] The assembly sequence is as follows: place the negative electrode shell, lithium negative electrode, appropriate amount of electrolyte, separator, appropriate amount of electrolyte, positive electrode sheet, and positive electrode shell in sequence. Ensure that the separator is fully wetted by the electrolyte and completely covers the electrode sheet for effective isolation. After aligning the positive and negative electrode sheets, seal them using an electric button battery sealing machine under a constant pressure of 700 kg.

[0063] The assembled battery needs to be allowed to mature for 6 hours before testing. The electrochemical performance test results are shown in Table 1. 1C is 200 mA g. -1 .

[0064] Table 1

[0065]

[0066] Based on the above experimental results, it can be seen that the topological ion-exchange ternary cathode material prepared by the present invention has superior rate capability and cycle performance.

[0067] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing a topological ion-exchange lithium-ion battery ternary cathode material, characterized in that, The method includes the following steps: S1. Preparation of sodium salt intermediate: A ternary precursor containing nickel, cobalt and manganese is mixed with a sodium source and subjected to a first-stage high-temperature heat treatment in an oxygen-containing atmosphere to obtain a sodium salt ternary oxide cathode material intermediate with a layered structure; the temperature of the first-stage high-temperature heat treatment is 500℃ to 900℃. The ternary precursor is nickel cobalt manganese hydroxide Ni x Co y Mn 1-x-y (OH)2, where 0 < x < 1, 0 < y < 1; the molar ratio of sodium element in the sodium source to the total amount of transition metal TM in the ternary precursor is Na:TM = (0.5 - 1.5):1; TM is Ni + Co + Mn; S2, Topological Ion Exchange: The sodium salt ternary oxide cathode material intermediate obtained in step S1 is mixed with a lithium source and subjected to a second-stage medium-temperature heat treatment in an oxygen-containing atmosphere. This allows lithium ions to partially replace sodium ions in the intermediate through a topological exchange mechanism, yielding a crude lithium / sodium mixed product. Subsequently, washing and drying are performed to remove soluble sodium salts and obtain a crude lithium-ion battery ternary product. The lithium source is lithium chloride. The temperature of the second-stage medium-temperature heat treatment is 550°C to 800°C. The molar ratio of lithium element in the lithium source to the total amount of transition metal in the intermediate of step S1 is (0.7-1.1):

1. S3. Supplementary Lithification and Crystallization: The crude lithium-ion battery product obtained in step S2 is mixed with a supplementary lithium source, and a third-stage heat treatment is performed in an oxygen-containing atmosphere to complete the final lithiation and crystal structure optimization, thereby obtaining the topological ion-exchange lithium-ion battery ternary cathode material; the molar ratio of lithium element in the supplementary lithium source to the total amount of transition metal in the crude product of step S2 is 0.2:1 to 0.8:1; the third-stage heat treatment adopts a one-step isothermal or segmented heating process; when using a one-step isothermal process, the heat treatment temperature is 600℃ to 1000℃; when using a segmented heating process, the temperature is first held at a first temperature of 500℃ to 550℃, and then raised to a second temperature of 750℃ to 780℃ and held. The chemical formula of the prepared topological ion-exchange lithium-ion ternary cathode material is LiNi. x Co y Mn1- x - y O2 has an α-NaFeO2 type layered crystal structure. In its X-ray diffraction pattern, the intensity ratio of the (003) crystal plane diffraction peak to the (104) crystal plane diffraction peak is I. (003) / I (104) Greater than 1.

5.

2. The method for preparing the topological ion-exchange lithium-ion ternary cathode material according to claim 1, characterized in that, In step S1, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate.

3. The method for preparing the topological ion-exchange lithium-ion ternary cathode material according to claim 1, characterized in that, In step S1, the heat treatment time of the first high-temperature heat treatment is 10 to 30 hours. And / or, the heating rate is from 1℃ / min to 10℃ / min; And / or, the oxygen-containing atmosphere is pure oxygen or a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen in the mixture is not less than 20%; And / or, the flow rate of the oxygen-containing atmosphere is 20-200 mL / min.

4. The method for preparing the topological ion-exchange lithium-ion ternary cathode material according to claim 1, characterized in that, In step S3, the supplementary lithium source is one or more of lithium hydroxide, lithium carbonate, and lithium nitrate.

5. The method for preparing the topological ion-exchange lithium-ion ternary cathode material according to claim 1, characterized in that, In step S2, the heat treatment time for the second stage of medium-temperature heat treatment is 2 to 10 hours; And / or, the solvent used for washing is deionized water or an alcohol solvent, and the number of washing cycles is 2-5; And / or, the drying process is carried out at a temperature of 50°C to 100°C for a drying time of 6 hours to 24 hours.

6. The method for preparing the topological ion-exchange lithium-ion ternary cathode material according to claim 1, characterized in that, In step S3, the heating rate in the third stage of heat treatment is from 1℃ / min to 10℃ / min.

7. A topological ion-exchange lithium-ion ternary cathode material prepared by the method according to any one of claims 1-6.

8. The application of the topological ion exchange lithium-ion ternary cathode material according to claim 7 as an active material in the cathode of a lithium-ion battery.

9. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The cathode comprises the topological ion-exchange lithium-ion ternary cathode material as described in claim 7.

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