Tungsten-doped high-nickel cobalt-free material and preparation method thereof

Abstract

The invention discloses a tungsten-doped high-nickel cobalt-free material and a preparation method thereof, belongs to the technical field of lithium ion battery materials, and solves the problems that an existing high-nickel cobalt-free material is poor in electrochemical performance and poor in effect when serving as a lithium ion battery positive electrode material. The chemical general formula is Li (Ni0. 9Mn0. 1) xW1-xO2, and the preparation method comprises the following production steps: preparing a high-nickel low-manganese mixed salt solution, adding a proper amount of a reaction base solution into a reaction kettle, keeping the internal temperature of the reaction kettle constant, pumping the high-nickel low-manganese mixed salt solution, an ammonia water complexing agent solution and an alkali solution into the reaction kettle, carrying out a co-precipitation reaction, aging the obtained precursor mixed solution, and drying to obtain the nickel-nickel low-manganese composite material. The preparation method comprises the following steps: filtering, washing and drying to obtain precursor powder, mixing the precursor powder with a lithium source and tungsten trioxide powder, putting the mixed powder into a sintering furnace, and preparing the material by adopting a two-stage sintering process. The method saves time and labor, is high in adaptability, improves the electrochemical stability, reduces the production cost, and realizes the performance enhancement of the positive electrode material of the lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a tungsten-doped high-nickel cobalt-free material and a preparation method thereof. Background Art

[0002] With the continuous growth of demand for electric vehicles, the development of low-cost, high-energy-density lithium-ion battery cathode materials has become a key research direction. High-nickel cobalt-free materials have shown great potential due to their layered structure similar to LiCoO2, higher theoretical specific capacity, wide operating voltage range and lower cost. 0.9 Mn 0.1 O2 as Ni-Mn solid solution, due to Mn 4+ It is not electrochemically active and can support the structural skeleton, showing good cycle performance and thermal stability. At the same time, the increase in nickel content significantly improves the energy density of the material.

[0003] However, in practical applications, the preparation of stoichiometric materials is difficult, and phase transitions during charge and discharge, as well as structural degradation during cycling, significantly impact their performance and safety. Consequently, electrochemical performance is often improved through the introduction of doping elements. However, the complexity of preparation methods, high costs, and insufficient material stability remain unresolved, limiting their commercial application. Summary of the Invention

[0004] The present invention provides a tungsten-doped high-nickel cobalt-free material and a preparation method thereof, in order to solve the problem that the existing high-nickel cobalt-free material has poor electrochemical performance and is not effective as a positive electrode material for lithium-ion batteries.

[0005] The technical solution of the present invention is: a high nickel cobalt-free material doped with tungsten, characterized in that: the chemical formula of the material is Li(Ni 0.9 Mn 0.1 ) x W 1-x O2, where 0.95≤x≤0.99.

[0006] A method for preparing a high-nickel cobalt-free material doped with tungsten comprises the following steps: A. Prepare a high-nickel, low-manganese mixed salt solution with a molar ratio of nickel to manganese of 9:1; B. adding deionized water and ammonium bicarbonate as reaction base liquids to the reactor, maintaining a constant temperature inside the reactor by connecting a water bath, pumping a high-nickel, low-manganese mixed salt solution into the reactor at a constant rate, and then pumping an ammonia complexing agent solution and an alkaline solution into the reactor in parallel to perform a coprecipitation reaction. After the reaction is completed, a mixed solution of a high-nickel, cobalt-free precursor is obtained; C. The high-nickel-cobalt-free precursor mixed solution is aged, and then filtered, washed, and dried to obtain a high-nickel-cobalt-free precursor powder, which is then mixed with a lithium source and tungsten trioxide powder, and uniformly ground in a mortar to obtain a mixed powder; D. The mixed powder is placed in a sintering furnace, oxygen is passed throughout the process, and a two-stage sintering process is used to prepare a tungsten-doped layered oxide high-nickel cobalt-free material.

[0007] As a further improvement of the present invention, in step A, the total concentration of nickel and manganese in the nickel-manganese mixed salt solution is 2.0-2.5 mol / L.

[0008] As a further improvement of the present invention, in step B, the concentration of ammonia water as the complexing agent is 0.2 to 0.5 mol / L.

[0009] As a further improvement of the present invention, in step B, the reaction temperature is 55-65° C., and the pH of the solution is adjusted to 8.1-8.5.

[0010] As a further improvement of the present invention, in step C, anhydrous ethanol is added as a dispersant to ensure mixing uniformity.

[0011] As a further improvement of the present invention, in step C, the molar ratio of the high-nickel cobalt-free precursor powder to the lithium source is 0.9-1:1.01-1.10.

[0012] As a further improvement of the present invention, in step C, the molar ratio of the high-nickel cobalt-free precursor powder to tungsten trioxide is 0.9-1:0.01-0.05.

[0013] As a further improvement of the present invention, in step D, the sintering temperature of the first stage of the two-stage sintering process is 450-550°C, the heating rate is 15-18°C / min, and the holding time is 10-15 h; the sintering temperature of the second stage of the two-stage sintering process is 650-870°C, the heating rate is 5-8°C / min, and the holding time is 10-20 h.

[0014] The beneficial effects of the present invention are: 1. The present invention optimizes the preparation process and obtains a high-quality cobalt-free, high-nickel precursor mixed solution through a coprecipitation reaction, which significantly simplifies the operation process and reduces production costs. By regulating the nuclear barrier and critical nuclear size, the particles exhibit a high degree of orientation.

[0015] 2. The present invention dopes tungsten into the crystal lattice through high-temperature solid-phase sintering, and finally prepares a tungsten-doped layered oxide high-nickel cobalt-free positive electrode material, which provides more free electrons, enhances the directional migration rate of lithium ions, improves the ability of rapid energy transfer, and effectively inhibits the formation and expansion of microcracks under high charge state, effectively controls capacity attenuation, structural phase transition and lattice distortion, and realizes performance improvement of lithium-ion battery positive electrode materials.

[0016] 3. The material obtained by the present invention does not contain cobalt, which reduces the cost of the positive electrode material and minimizes the high oxidation state and unstable Ni 4+ , enhancing the structural stability of the material.

[0017] The present invention saves time and labor, has strong adaptability, realizes the use of high-nickel cobalt-free materials as positive electrode materials for lithium-ion batteries, improves electrochemical stability, reduces production costs, and realizes the performance enhancement of positive electrode materials for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The electrochemical performance data of the 1% tungsten-doped high-nickel-cobalt-free material prepared in Example 1 and the undoped high-nickel-cobalt-free material prepared in Comparative Example 1 are shown.

[0019] Figure 2 This is an SEM image of the tungsten-doped high-nickel cobalt-free material prepared in Example 1. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 Prepare a salt solution with a total concentration of 2.0 mol / L of nickel and manganese in a ratio of Ni:Mn=0.9:0.1, a 2.5 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia complexing agent solution.

[0022] The reactor temperature was set at 55 °C, and a certain volume of deionized water and ammonium bicarbonate were added to the reactor as reaction base liquids. The concentration of the ammonium bicarbonate solution was 0.05 mol / L. All the salt solution was placed in the intermediate reactor, and the speed of the reactor stirring paddle was controlled to 600 rpm. At the same time, the solution in the intermediate reactor was continuously pumped into the reactor. At the same time, the intermediate reactor pumped the evenly stirred salt solution into the reaction, and ammonia solution and alkaline solution also flowed into the reactor in parallel to carry out a co-precipitation reaction. At the same time, the pH of the solution in the reactor was controlled to be stable at 8.5. After 25 minutes of reaction, the liquid was stopped and the stirring was turned off to obtain a cobalt-free high-nickel precursor mixed solution.

[0023] After aging the cobalt-free, high-nickel precursor solution for 12 hours, the designed cobalt-free, high-nickel precursor powder was obtained after filtration, drying, and washing. The precipitate was washed multiple times with deionized water until neutral and then dried in a constant temperature vacuum drying oven at 80°C to obtain a cobalt-free, high-nickel precursor with an average composition.

[0024] The dried cobalt-free, high-nickel precursor powder was mixed with LiOH at a ratio of Li:TM=1:1.03, and 1% WO3 was added. 15 ml of anhydrous ethanol was added as a dispersant during the grinding process. Excess LiOH was added to compensate for the loss of lithium during high-temperature sintering. After grinding evenly, the powder was placed in a sintering furnace for two-stage sintering in an O2 atmosphere. The specific sintering procedure was: heating from room temperature to 450°C over 0.5 h and holding for 15 h, then heating to 650°C over 2 h, then holding for 20 h, and finally cooling to room temperature to prepare a tungsten-doped layered oxide high-nickel cobalt-free lithium material.

[0025] The high-nickel cathode material obtained in Example 1 was mixed with acetylene black and PVDF in a ratio of 80:10:10, coated on Al foil, and assembled into a 2032 button cell. The electrochemical performance test showed that under a constant voltage window of 2.7-4.3 V, the first cycle capacity at a discharge rate of 0.2 C was 218.16 mAh·g -1 The first cycle capacity at 0.5 C is 155.76 mAh g -1 , the capacity retention rate after 100 cycles at 0.5 C was 86.20%.

[0026] Comparative Example 1 Prepare a salt solution with a total concentration of 2.0 mol / L of nickel and manganese in a ratio of Ni:Mn=0.9:0.1, a 2.5 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia complexing agent solution.

[0027] The reactor temperature was set to 55°C, and a certain volume of deionized water and ammonium bicarbonate was added to the reactor as a reaction base liquid. The concentration of the ammonium bicarbonate solution was 0.05 mol / L. The salt solution was placed entirely in the intermediate reactor. The speed of the reactor stirring paddle was controlled to 600 rpm, and the solution in the intermediate reactor was continuously pumped into the reactor. At the same time, while the salt solution after uniform stirring was pumped into the intermediate reactor for reaction, ammonia solution and alkaline solution were also flowed into the reactor in parallel to perform a co-precipitation reaction. At the same time, the pH of the solution in the reactor was controlled to be stable at 8.5. After 25 minutes of reaction, the liquid was stopped and the stirring was turned off to obtain a cobalt-free high-nickel precursor mixed solution. The resulting cobalt-free, high-nickel precursor solution was aged for 12 hours before being filtered, dried, and washed to obtain the designed cobalt-free, high-nickel precursor powder. The precipitate was washed multiple times with deionized water until neutral and then dried in a constant-temperature vacuum drying oven at 80°C to obtain a cobalt-free, high-nickel material with an average composition free of tungsten.

[0028] The high-nickel cathode material obtained in Comparative Example 1 was mixed with acetylene black and PVDF in a ratio of 80:10:10, coated on Al foil, and assembled into a 2032 button cell. The electrochemical performance test showed that under a constant voltage window of 2.7-4.3 V, the first cycle capacity at a discharge rate of 0.2 C was 227.24 mAh·g -1 The first cycle capacity at 0.5 C is 171.2 mAh g -1 , the capacity retention rate after 100 cycles at 0.5 C is 41.12%.

[0029] like Figure 1-2 As shown, by comparing Example 1 with Comparative Example 1, it can be found that the tungsten-doped layered oxide high-nickel cobalt-free lithium material has better electrochemical performance. By doping tungsten as a high-valent ion, more free electrons are provided, the directional migration rate of lithium ions is improved, and energy is transferred quickly. It also effectively inhibits the formation and expansion of microcracks in a high-charge state. As a positive electrode material for lithium batteries, the unstable Ni with high oxidation valence on the surface of the material in a high-delithiation state is minimized. 4+ , which enhances the structural stability of the material, has the potential to achieve industrial mass production, and has broad application prospects.

Claims

1. A high-nickel, cobalt-free material doped with tungsten, characterized by: The general chemical formula of the material is Li(Ni 0.9 Mn 0.1 ) x W 1-x O2, where 0.95≤x≤0.

99.

2. A method for preparing a high-nickel cobalt-free material doped with tungsten according to claim 1, characterized in that: The steps include: A. Prepare a high-nickel, low-manganese mixed salt solution with a molar ratio of nickel to manganese of 9:1; B. adding deionized water and ammonium bicarbonate as reaction base liquids to a reactor, maintaining a constant temperature inside the reactor, pumping a high-nickel, low-manganese mixed salt solution into the reactor at a constant rate, and then pumping an ammonia complexing agent solution and an alkaline solution into the reactor in parallel to carry out a coprecipitation reaction. After the reaction is completed, a mixed solution of a high-nickel, cobalt-free precursor is obtained; C. Aging the high-nickel-cobalt-free precursor mixed solution, followed by filtering, washing, and drying to obtain a high-nickel-cobalt-free precursor powder, adding a lithium source and tungsten trioxide powder to the high-nickel-cobalt-free precursor powder, and uniformly grinding to obtain a mixed powder; D. The mixed powder is placed in a sintering furnace, oxygen is passed throughout the process, and a two-stage sintering process is used to prepare a high-nickel cobalt-free material doped with tungsten.

3. The method for preparing a high-nickel cobalt-free material doped with tungsten according to claim 2, characterized in that: In step A, the total concentration of nickel and manganese in the nickel-manganese mixed salt solution is 2.0-2.5 mol / L.

4. The method for preparing a tungsten-doped high-nickel cobalt-free material according to claim 2, characterized in that: In step B, the reaction temperature in the reactor is 55-65°C.

5. The method for preparing a tungsten-doped high-nickel cobalt-free material according to claim 4, characterized in that: In step B, the pH of the mixed solution in the reactor is 8.1-8.

5.

6. The method for preparing a tungsten-doped high-nickel cobalt-free material according to claim 2, characterized in that: In step C, the molar ratio of the high-nickel cobalt-free precursor powder to the lithium source is 0.9-1:1.01-1.

10.

7. The method for preparing a tungsten-doped high-nickel cobalt-free material according to claim 6, characterized in that: In step C, the molar ratio of the high-nickel cobalt-free precursor powder to tungsten trioxide is 0.9-1:0.01-0.

05.

8. The method for preparing a tungsten-doped high-nickel cobalt-free material according to claim 2, characterized in that: In step D, the first stage of the two-stage sintering process has a sintering temperature of 450-550°C, a heating rate of 15-18°C / min, and a holding time of 10-15 h; the second stage of the two-stage sintering process has a sintering temperature of 650-870°C, a heating rate of 5-8°C / min, and a holding time of 10-20 h.

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