W-doped ternary precursor, preparation method thereof, positive electrode material, positive electrode and battery

Abstract

The application relates to the technical field of battery materials, and discloses a W-doped ternary precursor, a preparation method of the W-doped ternary precursor, a positive electrode material, a positive electrode and a battery. The preparation method of the disclosed W-doped ternary precursor comprises the following steps: heating a plasma equipment with a built-in conventional ternary precursor to 450-500 DEG C to perform plasma element doping; the plasma element doping mode comprises the following steps: introducing a gas tungsten source into the plasma equipment, starting an arc discharge device, setting the voltage to 660-740 V, and fully reacting to obtain a W element-doped ternary precursor. The preparation method provided by the application is simple and convenient to operate, can realize atomic-level uniform distribution of the doped elements, and has good electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to W-doped ternary precursors and their preparation methods, cathode materials, cathodes, and batteries. Background Technology

[0002] To improve the electrochemical performance of ternary cathode materials, common modification methods include doping and coating with various metallic or non-metallic elements. Currently, the most commonly used methods in industry are wet chemical doping and dry doping. Wet chemical doping involves adding a soluble dopant salt (such as a solution of Mg, Al, Zr, Ti, etc.) along with a main salt (Ni, Co, Mn) solution to a reaction vessel during the co-precipitation process of preparing the ternary precursor (such as NCM or NCA hydroxide / carbonate), achieving doping through co-precipitation. However, because the entire process depends on reaction kinetics, it is easily affected by stirring rate, concentration gradient, and pH fluctuations, and may segregate at grain boundaries or surfaces due to different crystallization rates, easily leading to localized enrichment. Dry doping, on the other hand, involves directly mixing the ternary precursor (such as NCM hydroxide / carbonate), the dopant source (oxides, salts, such as Al2O3, MgO, ZrO2, and Y2O3, etc.), and the lithium salt, driving ions into the crystal lattice or segregating at grain boundaries through calcination. However, due to limitations in mixing equipment, it is difficult to achieve atomic-level uniform distribution, and local fluctuations in doping concentration are likely to occur.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a W-doped ternary precursor and its preparation method, a cathode material, a cathode, and a battery, aiming to improve at least one of the problems mentioned in the background art.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a W-doped ternary precursor, comprising: The plasma equipment containing a conventional ternary precursor is heated to 450~500℃ to perform plasma element doping. The plasma element doping method includes: introducing a gaseous tungsten source into the plasma device, starting the arc discharge device, setting the voltage to 660~740V, and fully reacting to obtain a W-doped ternary precursor.

[0006] In an optional implementation, the flow rate of the gaseous tungsten source is 0.6~2.1 L / min.

[0007] In an optional implementation, plasma element doping is divided into multi-stage doping. As the doping reaction proceeds, the flow rate of the gas tungsten source gradually decreases and the voltage gradually increases in each stage. In an optional implementation, plasma element doping can be performed in three stages: First stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.9~2.1) L / min, the voltage is set to 660~680V, ​​and the reaction time is 10~15min; Second stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.2~1.5) L / min, the voltage is set to 690~710V, and the reaction time is 10~15min; Third stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (0.6~0.9) L / min, the voltage is set to 720~740V, and the reaction time is 10~15min.

[0008] In an optional embodiment, the plasma device is heated to 450~500°C and held at that temperature for at least 2 hours before plasma element doping is performed. Optionally, the heat preservation time is 2.5~3.5 hours.

[0009] In an optional implementation, the chemical formula for the conventional ternary precursor is Ni. 0.6 Co 0.1 Mn 0.3 (OH)2.

[0010] In an optional embodiment, the gaseous tungsten source is at least one of WF6, WCl6, and W(CO)6.

[0011] Secondly, the present invention provides a W-doped ternary precursor, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0012] Thirdly, the present invention provides a ternary cathode material, which is obtained by mixing and sintering a lithium source and a W-doped ternary precursor as described in the aforementioned embodiments.

[0013] Fourthly, the present invention provides a positive electrode, wherein the active layer comprises a ternary positive electrode material as described in the foregoing embodiments.

[0014] Fifthly, the present invention provides a battery comprising a positive electrode as described in the foregoing embodiments.

[0015] The present invention has the following beneficial effects: The preparation method provided by this invention is independent of reaction kinetics compared to wet doping, and is simple and convenient to operate; compared to dry doping, it can achieve atomic-level uniform distribution, resulting in products with better electrochemical performance. Due to tungsten doping, the precursor and lithium source are sintered to form a cathode material containing tungsten oxide. 6+ With O 2-Very strong chemical bonds are formed between them, which can firmly lock the oxygen framework and greatly suppress oxygen evolution during deep delithiation (high-voltage charging), thereby improving the thermal and structural stability of the material. In addition, plasma doping can precisely control the doping dosage and implantation depth by adjusting the flow rate and voltage of the gas tungsten source, so as to obtain precursors with the target doping element distribution. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 Cross-sectional EDS energy dispersive spectroscopy analysis of Example 1; Figure 2 The cross-sectional EDS energy spectrum analysis is for Comparative Example 1. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] This invention provides a method for preparing a W-doped ternary precursor, comprising: The plasma equipment containing a conventional ternary precursor is heated to 450~500℃ to perform plasma element doping. Plasma element doping methods include: introducing a gaseous tungsten source into the plasma device, starting the arc discharge device, setting the voltage to 660~740V, and fully reacting to obtain a W-doped ternary precursor.

[0020] The preparation method provided by this invention utilizes arc discharge to generate plasma, thereby ionizing dopant atoms into ions W. 6+ These ions are accelerated under a high-voltage electric field, gaining high kinetic energy, and directly bombard and implant into the surface and near-surface lattice of the precursor particles to achieve elemental doping. Compared with wet doping, this doping method does not depend on reaction kinetics and is simple and convenient to operate; compared with dry doping, it can achieve atomic-level uniform distribution, resulting in products with better electrochemical performance. Due to tungsten doping, the precursor and lithium source are sintered to form a cathode material containing tungsten oxide. 6+ With O 2-Very strong chemical bonds are formed between them, which can firmly lock the oxygen framework and greatly suppress oxygen evolution during deep delithiation (high-voltage charging), thereby improving the thermal and structural stability of the material. In addition, plasma doping can precisely control the doping dosage and implantation depth by adjusting the flow rate and voltage of the gas tungsten source, so as to obtain precursors with the target doping element distribution.

[0021] Optionally, in order to make the prepared precursor have better electrochemical performance, the flow rate of the gaseous tungsten source is a (0.6~2.1) L / min.

[0022] Specifically, the preparation method is as follows: S1, Heating A conventional ternary precursor is placed in a plasma device, and the device cavity is evacuated to a vacuum level below 5 × 10⁻⁶. -3 Pa is heated at 3℃ / min to 450~500℃ (e.g. 450℃, 480℃ or 500℃) to activate the lattice and construct ion diffusion channels.

[0023] Optionally, in order to fully activate the lattice of the conventional precursor, the temperature is raised to 450~500℃ and held for at least 2 hours, preferably 2.5~3.5 hours (e.g. 2.5 hours, 3 hours or 3.5 hours).

[0024] Alternatively, the chemical formula for a conventional ternary precursor is, for example, Ni. 0.6 Co 0.1 Mn 0.3 (OH)2 (It should be noted that this is only one example; generally, the chemical expression satisfies "Ni a Co b Mn c (OH)2, a+b+c=1, where a is 0.6~0.7 and b is 0.07~0.12” are all applicable precursors).

[0025] S2, plasma element doping A gaseous tungsten source is introduced into the plasma device to start the arc discharge device for plasma element doping.

[0026] To ensure that the doped W element forms a structure with decreasing doping concentration from the outside of the precursor particle to the core, plasma element doping is divided into multi-stage doping. As the doping reaction proceeds, the flow rate of the gas tungsten source gradually decreases and the voltage gradually increases in each stage.

[0027] Optionally, the doping stage is divided into three stages, and the specific doping method is as follows: First stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.9~2.1) L / min (e.g. 1.9 L / min, 2 L / min or 2.1 L / min), the voltage is set to 660~680V (e.g. 660V, 670V or 680V), and the reaction time is 10~15 min (e.g. 10 min, 13 min or 15 min).

[0028] Under the above-mentioned flow rate and voltage conditions, the ion range is greater than 500-600 nm. W elements are mainly injected and accumulated in the surface and subsurface regions of the precursor particles. After 10-15 min of reaction, a W-rich shell with a thickness of about 500 nm is formed, and the W atom concentration is the highest in this region.

[0029] Second stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.2~1.5) L / min (e.g. 1.2L / min, 1.3L / min, 1.4L / min or 1.5L / min), the voltage is set to 690~710V (e.g. 690V, 700V or 710V), and the reaction time is 10~15 min (e.g. 10 min, 13 min or 15 min).

[0030] Under the aforementioned flow rate and voltage conditions, the ion energy is moderate, which allows the dopant element to penetrate further into the particle, forming a gradient transition zone with gradually decreasing W concentration between the shell and the core. The thickness of the gradient transition zone formed after 10-15 minutes of reaction is approximately 1-2 μm.

[0031] The third stage: the flow rate of the gaseous tungsten source introduced into the plasma device is a (0.6~0.9) L / min (e.g. 0.6 L / min, 0.7 L / min, 0.8 L / min or 0.9 L / min), the voltage is set to 720~740V (e.g. 720V, 730V or 740V), and the reaction time is 10~15 min (e.g. 10 min, 13 min or 15 min).

[0032] Under the aforementioned flow rate and voltage conditions, the ion energy is relatively high. Higher energy ions can allow W to penetrate into the core region of the particle, achieving an overall distribution of W within the particle and forming a lower W doping concentration at the core.

[0033] It should be noted that dividing it into three stages is only one implementation of the present invention. In other implementations, it may be divided into four stages, five stages, or even more than five stages.

[0034] Optionally, the gaseous tungsten source is at least one of WF6, WCl6, and W(CO)6.

[0035] The W-doped ternary precursor provided in this embodiment of the invention is prepared using the preparation method provided in this embodiment of the invention.

[0036] The present invention provides a ternary cathode material, which is obtained by sintering a lithium source and a W-doped ternary precursor provided in the present invention.

[0037] An embodiment of the present invention provides a positive electrode whose active layer includes a ternary positive electrode material provided in the embodiment of the present invention.

[0038] An embodiment of the present invention provides a battery, including a positive electrode provided in the embodiment of the present invention.

[0039] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0040] Example 1 500g of precursor Ni 0.60 Co 0.1 Mn 0.3 (HO)2 is evenly spread on the sample stage of the plasma injection equipment. The sample stage is then moved into the vacuum chamber, sealed, and evacuated until the background vacuum level is below 5 × 10⁻⁶. -3 Pa is heated to 470℃ at a rate of 3℃ / min and held for 3 hours. A doped gas, WF6, with a purity ≥99.99%, is then introduced into the vacuum chamber. An arc discharge device is activated to excite a W-containing gas within the chamber. 6+ Highly reactive plasma of ions. Under the guidance of a high-voltage electric field, W 6+ Ions are accelerated and directed to bombard precursor particles. The ion implantation process is carried out in three energy phases sequentially: Outer layer injection stage (first stage): control the WF6 gas flow rate to 2L / min, the accelerating voltage to 670V, and the reaction time to 13min.

[0041] Intermediate layer injection stage (second stage): Adjust the WF6 gas flow rate to 1.3 L / min, the accelerating voltage to 700 V, and react for 13 min.

[0042] Inner layer injection stage (third stage): WF6 gas flow rate is adjusted to 0.7 L / min, acceleration voltage is 730 V, and reaction time is 13 min.

[0043] After ion implantation was completed, the WF6 gas supply was stopped, and the arc discharge and high-voltage power supply were turned off. The sample was cooled to room temperature under vacuum, and then removed to obtain a W-gradient-doped ternary precursor. The tungsten doping content was found to be 1000 ppm.

[0044] 500 g of W-doped ternary precursor was uniformly mixed with 473 g of lithium hydroxide using a high-speed mixer. The mixture was then heated to 960 °C in a box furnace at a heating rate of 3 °C / min and sintered for 10 h. After cooling, W-doped single-crystal LiNi was obtained. 0.60 Co 0.1 Mn 0.3 O2 cathode material is fed into the sample after being pulverized by a jaw crusher and airflow.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is that the gaseous tungsten source is WCl6.

[0046] Example 3 The difference between this embodiment and Embodiment 1 is that the gaseous tungsten source is W(CO)6.

[0047] Example 4 The difference between this embodiment and Embodiment 1 is that the WF6 gas flow rate is kept constant at 2 L / min throughout the doping process, and the reaction time is 39 min.

[0048] Example 5 The difference between this embodiment and Embodiment 1 is that the control voltage remains unchanged at 700V, and the reaction time is 30~45min.

[0049] Example 6 The difference between this embodiment and Embodiment 1 is that the reaction time for each stage is 8 minutes.

[0050] Comparative Example 1 The difference between this comparative example and Example 4 is that a wet doping method (co-precipitation method) was used to prepare the W-doped ternary precursor. The specific doping method is as follows: a Ni:Co:Mn=6:1:3 main metal salt solution was prepared and thoroughly mixed with a precisely measured sodium tungstate solution (doping amount 0.1 mol%); a bottom solution was prepared in a reactor, the pH was adjusted to 11.0, the temperature was raised to 68°C, and N2 was purged for protection; the mixed salt solution, NaOH precipitant, and ammonia complexing agent were fed simultaneously, and the co-precipitation reaction was carried out under constant temperature and pH, followed by aging; the product was washed with hot water to remove impurities, vacuum dried, and demagnetized to obtain the W-doped NCM613 precursor.

[0051] The resulting precursor was then calcined together with lithium hydroxide in the manner described in Example 1.

[0052] Comparative Example 2 The difference between this comparative example and Example 4 is that the W-doped ternary precursor was prepared using dry doping. The specific doping method is as follows: Take the same undoped conventional precursor as in Example 1 and mix it with 0.67g of tungsten oxide, then calcine it at 970°C for 10h.

[0053] The resulting precursor was then calcined together with lithium hydroxide in the manner described in Example 1.

[0054] Comparative Example 3 The difference between this comparative example and Example 4 is that: the undoped precursor and lithium hydroxide were directly mixed and sintered in the manner described in Example 1.

[0055] Experimental Example (1) Taking Example 1 and Comparative Example 1 as examples, the obtained precursor was subjected to ion milling, and the cross-section was analyzed by EDS energy dispersive spectroscopy, as shown below. Figures 1 to 2 As shown.

[0056] from Figure 1 and Figure 2 It can be seen that the precursor prepared by plasma regulation exhibits a W-shaped gradient transition zone between the surface and the core, with the concentration gradually decreasing, while the precursor prepared by wet chemical method does not have this trend.

[0057] (2) The ternary cathode materials obtained in Examples 1-6 and Comparative Examples 1-3 were used to make 2025 coin cells and their electrochemical performance was tested. The preparation and testing methods are as follows: Preparation method of coin cell: In an argon-protected glove box (H2O and O2 content both <0.1ppm), CR2025 coin cell half-cells were assembled, with lithium metal sheet as counter electrode, polypropylene membrane as separator, and 1 M LiPF6 / EC:EMC:DMC (volume ratio 1:1:1) electrolyte. The positive electrode sheet was prepared by mixing active material (NCM), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a mass ratio of 90:5:5, coating it onto an aluminum foil current collector, drying it at 105℃, and then punching it into an electrode sheet with a diameter of 14 mm.

[0058] The conditions for the button battery test included: using the CT3002A battery testing system (LAND), with a charging voltage range of 2.8V to 4.4V, and conducting charge and discharge tests at 0.1C, 0.2C, 0.5C, and 1C respectively. Finally, its cycle performance was tested at a high temperature of 45°C. The test results were recorded in Table 1.

[0059] Table 1. Test results for each embodiment and comparative example.

[0060] As can be seen from Table 1, the precursor-supported cathode materials prepared in each embodiment have better electrochemical performance after being assembled into batteries. The coin cell capacity is significantly improved when doped with W compared to undoped W (Comparative Example 3).

[0061] Comparing Example 4 with Comparative Example 1, Comparative Example 1 uses wet doping, and its coin cell capacity, first-cycle efficiency and cycle retention rate are all worse than those of Example 1. This shows that wet doping is not only more troublesome to operate than the present application, but also produces a precursor with worse performance. Comparing Example 4 with Comparative Example 2, Comparative Example 2 uses dry doping, and its coin cell capacity and cycle retention rate are worse than those of Example 4, indicating that the performance of the precursor prepared by dry doping is worse than that of the precursor prepared in this application. Comparing Example 1 with Example 4, Example 4 has poorer coin cell capacity and first-cycle efficiency. Comparing Example 1 with Example 5, Example 5 has worse coin cell capacity, first-cycle efficiency, and cycle retention rate than Example 1. The comparison results show that if the plasma doping process is carried out in stages and the appropriate operating parameters are adjusted in each stage, a precursor with better performance can be obtained. Comparing Example 1 and Example 6, Example 6 showed that the coin charge capacity, first-cycle efficiency, and cycle retention rate were all worse than those of Example 1. This indicates that sufficient reaction time at each stage is necessary to ensure a more suitable doping amount and element distribution, which can ensure better electrochemical performance of the precursor.

[0062] In summary, the preparation method provided in this invention utilizes arc discharge to generate plasma, thereby ionizing dopant atoms into ions W. 6+ These ions are accelerated under a high-voltage electric field, gaining high kinetic energy, and directly bombard and implant into the surface and near-surface lattice of the precursor particles to achieve elemental doping. Compared with wet doping, this doping method does not rely on reaction kinetics and is simple and convenient to operate; compared with dry doping, it can achieve atomic-level uniform distribution, and the resulting product has better electrochemical performance. In addition, plasma doping can precisely control the doping dosage and implantation depth by adjusting the flow rate and voltage of the gas tungsten source, thus obtaining a precursor with the target doping element distribution.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a W-doped ternary precursor, characterized in that, include: The plasma equipment containing a conventional ternary precursor is heated to 450~500℃ to perform plasma element doping. The plasma element doping method includes: introducing a gaseous tungsten source into the plasma device, starting the arc discharge device, setting the voltage to 660~740V, and fully reacting to obtain a W-doped ternary precursor.

2. The preparation method according to claim 1, characterized in that, The flow rate of the gaseous tungsten source is 0.6~2.1 L / min.

3. The preparation method according to claim 2, characterized in that, The plasma element doping is divided into multi-stage doping. As the doping reaction proceeds, the flow rate of the gas tungsten source gradually decreases and the voltage gradually increases in each stage. Optionally, the plasma element doping method includes three-stage doping: First stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.9~2.1) L / min, the voltage is set to 660~680V, ​​and the reaction time is 10~15min; Second stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (1.2~1.5) L / min, the voltage is set to 690~710V, and the reaction time is 10~15min; Third stage: The flow rate of the gaseous tungsten source introduced into the plasma device is a (0.6~0.9) L / min, the voltage is set to 720~740V, and the reaction time is 10~15min.

4. The preparation method according to claim 1, characterized in that, After heating the plasma device to 450-500°C, hold it at that temperature for at least 2 hours before performing plasma element doping. Optionally, the heat preservation time is 2.5~3.5 hours.

5. The preparation method according to claim 1, characterized in that, The chemical formula for the conventional ternary precursor is Ni. 0.6 Co 0.1 Mn 0.3 (OH)2.

6. The preparation method according to claim 1, characterized in that, The gaseous tungsten source is at least one of WF6, WCl6, and W(CO)6.

7. A W-doped ternary precursor, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. A ternary cathode material, characterized in that, It is obtained by mixing and sintering a lithium source and a W-doped ternary precursor as described in claim 7.

9. A positive electrode, characterized in that, Its active layer includes the ternary cathode material as described in claim 8.

10. A battery, characterized in that, Includes the positive electrode as described in claim 9.

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