TWI781427B - Preparation method of nickel-rich hydroxide precursor and nickel-rich cathode composite material using continuous Taylor flow reactor - Google Patents

Abstract

The invention utilizes a novel continuous Taylor flow reactor (TFR) to prepare nickel-rich lithium-nickel-cobalt-manganese oxide and lithium-nickel-cobalt-manganese-aluminum oxide for lithium-ion secondary batteries with high gram capacity and high cycle stability. Positive electrode composite material, its secondary particles have an elliptical shape, and the primary particles have a nano-scale petal-like structure on the crystal face group {010} plane; in addition, by in-situ synthesis of lithium molybdate (Li ₂ MoO ₄ ) coated nickel-rich lithium-nickel-cobalt-manganese oxide positive electrode composite material can exhibit lower Li ⁺ /Ni ²⁺ cation mixing degree, higher material structural stability and improved its Electrochemical performance of the battery. Accordingly, the electrochemical performance of the battery composed of the nickel-rich lithium-nickel-cobalt-manganese oxide cathode composite material of the present invention is obviously better than that of commercially available nickel-rich lithium-nickel-cobalt-manganese oxide batteries.

Description

Preparation method of nickel-rich hydroxide precursor and nickel-rich cathode composite material using continuous Taylor flow reactor

The present invention relates to a preparation method of a nickel-rich hydroxide precursor and a nickel-rich positive electrode composite material, in particular to a method for preparing nickel-cobalt-manganese, nickel-cobalt-manganese-aluminum hydroxide precursors and nickel-rich positive electrodes using a continuous Taylor flow reactor Preparation method of composite material.

0.4)為最具前景之下世代正極材料，惟其仍具部分缺點，如較差之循環壽命等，而限制其等在鋰離子電池中之應用。 Nickel-rich ternary or quaternary cathode materials have high gram capacity (Specific capacity>170mAh/g) and low cost, so they are gradually being used in lithium-ion batteries; among them, nickel-rich LiNi _1-xy Co _x Al _y O ₂ (LNCA) and LiNi _1-xy Co _x Mn _y O ₂ (LNCM)(x+y

0.4) is the most promising cathode material of the next generation, but it still has some shortcomings, such as poor cycle life, which limits its application in lithium-ion batteries.

In order to improve the cycle stability of nickel-rich ternary or quaternary materials, many scholars have made various attempts. Although element doping (such as: Al, Nb or Zr) and surface modification (such as: Y ₃ O ₃ , CeO ₂ or silyl functional groups) can improve the electrochemical performance of Ni-rich ternary or quaternary cathode materials, but their The oxide cladding material will also be an insulator for Li ⁺ ions. An ideal cladding layer should play a unique role while ensuring high Li ⁺ ion conductivity. Recently, some researchers have turned their attention to the internal structure of cathode materials, mainly by changing the shape of precursors and adjusting their preparation methods, such as the preparation of NCM cathode composite materials with a three-dimensional dumbbell-like structure, which shows Excellent first discharge gram capacity and current rate performance; or the synthesis of porous NCM cathode composite material with layered nanosheet structure and a gram capacity of 137.7mAh/g at a high rate of 20C; In addition, there is also a team that adjusts the distribution of Al on the outer surface of spherical particles by co-precipitation in a continuous stirred reactor (CSTR) to prepare an NCA cathode composite material with a concentration gradient structure. After 100 cycles, 93.6% of the capacity retention rate (Capacity retention, CR) can still be maintained. In addition, it is also reported in the literature that the high-nickel NCM cathode composite material with a full gradient structure formed by coprecipitation in CSTR is used to improve the cycle stability and cycle life of the battery.

However, the preparation technology of nickel-rich ternary and quaternary cathode composite materials with high discharge capacity, high capacity retention rate, excellent cycle stability and cycle life still needs to be improved.

[Prior technical literature] Chinese publication CN108511709A bulletin

In view of this, the main purpose of the present invention is to provide a method for preparing positive electrode composite materials. Firstly, a novel continuous Taylor flow reactor is used to prepare nickel-rich hydroxide precursor materials, and different experimental parameters are used to prepare better crystals. Structure the precursor material, and then further prepare the prepared precursor material into a positive electrode composite material; in addition, in the step of preparing the positive electrode composite material, a layer of coating material is synthesized in situ on the precursor material to prepare A cathode composite material with enhanced crystal structure stability and improved electrochemical performance has been developed, which has significantly excellent charge/discharge cycle stability when applied to lithium-ion batteries, especially at high charge voltages (greater than 4.3V).

The present invention firstly provides a preparation method of a nickel-rich hydroxide (M(OH) ₂ , M=Ni, Co, Mn and/or Al) precursor material, which is used in a novel continuous Taylor flow reactor coprecipitation method. In a Taylor vortex, when the inner cylinder rotates, the gap between two coaxial cylinders with different radii will generate axial periodic fluid motion, and the Taylor flow is above a certain rotational speed of the inner cylinder (above the Taylor number ) and produces strong and uniform radial mixing with small axial dispersion; therefore, the products prepared in the new continuous Taylor flow reactor will have better performance than those prepared in the traditional continuous stirred tank reactor Surface type. In addition, the present invention synthesizes a nickel-rich hydroxide precursor material with a better crystal structure by optimizing the preparation parameters.

Accordingly, the present invention provides a method for preparing a nickel-rich hydroxide (M(OH) ₂ , M=Ni, Co, Mn and/or Al) precursor material, which comprises the following steps:

(a) Add the metal ion source, sodium hydroxide and ammonia water to the reaction chamber of the continuous Taylor flow reactor at the same time under the heating condition of 50°C to 80°C, control the pH value to 10 to 12, and the reactor speed to 500rpm to 1000rpm, the feed rate is 2.23ml/min, the reaction time is 5 hours to 50 hours, and the continuous production and preparation of coprecipitation method is carried out;

(b) filter the precipitate after step (a) reaction, and wash with ethanol and deionized water;

(c) drying the precipitate washed in step (b) in an oven, the drying temperature is 80°C to 120°C, and the time is 12 hours to 36 hours;

Wherein, the metal ion source in step (a) includes nickel source, cobalt source, manganese source and/or aluminum source.

Further, the nickel source in step (a) is at least one selected from the group consisting of nickel sulfate, nickel oxalate, nickel acetate, nickel nitrate, nickel chloride and nickel hydroxide.

Further, the cobalt source in step (a) is at least one selected from the group consisting of cobalt sulfate, cobalt oxalate, cobalt carbonate, cobalt acetate, cobalt nitrate, cobalt chloride and cobalt hydroxide.

Further, the source of manganese in step (a) is selected from manganese oxalate, manganese carbonate, manganese citrate, manganese sulfate, manganese acetate, manganese nitrate, manganese phosphate, electrolytic manganese dioxide and manganese oxide (α-MnO ₂ , β- At least one of the group consisting of MnO ₂ , γ-MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O ₄ ).

Further, the aluminum source in step (a) is at least one selected from the group consisting of aluminum oxalate, aluminum carbonate, aluminum sulfate, aluminum acetate, aluminum nitrate and aluminum phosphate.

Further, the concentration of the metal ion source in step (a) ranges from 1.0M to 2.2M metal sulfate salt solution, preferably 2.0M metal sulfate salt solution.

Further, in step (a), the concentration range of ammonia water is 2.0M to 8.0M, preferably 2.5M or 7.2M, so as to be used as a chelating agent; the heating condition is 60°C, the pH value is 11, and the reactor speed is 600rpm.

Further, in step (a), the reaction time is 20 hours to 45 hours.

Further, in step (c), the drying temperature is 100° C. and the drying time is 24 hours.

The present invention further prepares the synthesized nickel-rich hydroxide precursor material into a nickel-rich oxide cathode composite material, which includes the following steps:

(a) Grinding and mixing the nickel-rich hydroxide precursor material and lithium in a methanol solvent by means of a ball mill; wherein,

The grinding and mixing conditions of the ball mill are 100rpm to 200rpm, and the grinding time is 5 hours to 10 hours, the weight ratio of sample and ball is 1:1 to 1:10;

(b) The mixture after step (a) is subjected to a three-stage calcining heat treatment in a high-temperature furnace in an air or pure oxygen atmosphere.

Further, the lithium source is at least one selected from the group consisting of lithium hydroxide, lithium nitrate, lithium acetate, lithium chloride, lithium hydrogen phosphate, lithium phosphate and lithium carbonate.

Further, the lithium source is LiOH. H ₂ O, and nickel-rich hydroxide precursor material and LiOH. The molar ratio of H ₂ O is 1:1.05 to 1:1.25, preferably 1:1.05.

Further, in step (a), the grinding and mixing conditions of the ball mill are 100 rpm, the grinding time is 5 hours, and the weight ratio of the sample to the ball is 1:1.

Further, in step (b), the conditions of calcining heat treatment are: the first stage is at 150°C for 2 hours; the second stage is at 400°C to 600°C for 6 hours, preferably 450°C to 550°C for 6 hours ; The third stage is at 750°C to 900°C, 10 hours to 25 hours, preferably 800°C to 850°C, 12 hours to 20 hours; calcining heat treatment is carried out separately, and the heating rate of the above three stages is 1°C/ min to 10°C/min, preferably 2°C/min.

In addition, the present invention can also in-situ synthesize a layer of coating material on the prepared nickel-rich hydroxide precursor, for example, it can be an ion-conducting layer of Li ₂ MoO ₄ , and synthesize it into a positive electrode composite material with a coated surface. . The uniform distribution of Mo ⁶⁺ ions makes it expand along the c-axis of the crystal, and after high-temperature calcination, a strong bond is formed between the synthesized lithium nickel cobalt manganese oxide and the Li ₂ MoO ₄ cladding layer. The electrode material shows enhanced crystal structure stability and improved electrochemical performance, especially at high charging voltages (greater than 4.3 V).

Accordingly, the present invention further provides a method for preparing a nickel-rich oxide cathode composite material whose surface has been coated, which comprises the following steps:

(a) Fully mix the coating material with the nickel-rich hydroxide precursor material; wherein, the coating material is at least one of the group consisting of Li-Nafion, Li ₂ MoO ₄ , Li ₄ SiO ₄ and 3D-porous carbon material One, and the coating amount of the coating material is 0.1wt.% to 5wt.% of the aforementioned nickel-rich hydroxide precursor material, preferably 0.5wt.% to 2wt.%;

(b) Grinding and mixing the mixed mixture in step (a) in a ball mill;

(c) The ground mixture in step (b) is subjected to a three-stage calcining heat treatment in a high-temperature furnace in an air or pure oxygen atmosphere.

Further, in step (a), the cladding material is Li ₂ MoO ₄ , by combining the nickel-rich hydroxide precursor material, 2wt.% ammonium molybdate and LiOH relative to the nickel-rich hydroxide precursor material ． The _H2O was mixed well to complete step (a).

Further, in step (c), the conditions of calcining heat treatment are: the first stage is at 150°C for 2 hours; the second stage is at 400°C to 600°C for 6 hours, preferably 450°C to 550°C for 6 hours ; The third stage is at 750°C to 900°C, 10 hours to 25 hours, preferably 800°C to 850°C, 12 hours to 20 hours; calcining heat treatment is carried out separately, and the heating rate of the above three stages is 1°C/ min to 10°C/min, preferably 2°C/min.

The present invention also provides a lithium ion battery, which uses lithium metal as the negative electrode, and the active material, the conductive agent and the composition of the binder are used as the positive electrode on the current collecting layer (aluminum foil); wherein,

The active material is prepared by the method for preparing the nickel-rich oxide cathode composite material provided by the present invention.

With the preparation method of the nickel-rich hydroxide (M(OH) ₂ , M=Ni, Co, Mn and/or Al) precursor material of the present invention, the material preparation parameters are highly controlled at the same time, and the nickel-rich Oxide (LiMO ₂ , M=Ni, Co, Mn and/or Al) positive electrode composite material, the primary particle has a nano-scale petal-like structure on the crystal face group {010} plane, and the secondary particle has an elliptical shape In terms of appearance, the battery composed of it has a relatively high gram capacity and long-term charge/discharge cycle stability.

In addition, the present invention also coats the nickel-rich cathode composite material by in-situ synthesis of Li ₂ MoO ₄ . Due to the ion conductor effect of Li ₂ MoO ₄ , the in-situ synthesis of Li ₂ MoO ₄ coats the nickel-rich cathode composite material at 2.5 Under the condition of V to 4.3V or even 4.5V high voltage, it can show lower Li ⁺ /Ni ²⁺ cation mixing degree, higher material structure stability and improve the electrochemical performance of its battery. The performance is significantly better than that of commercially available nickel-rich oxide batteries.

[Figure 1] Batch #1 of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was reacted after the reaction time was (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours SEM image of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles produced.

[Figure 2] Batch #2 of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was reacted after reaction times of (a) 16 hours, (b) 20 hours, (c) 30 hours and (d) 40 hours SEM image of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles produced.

[Figure 3] Batch #1 synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was reacted after reaction times of (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours XRD analysis results of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ powder.

[Figure 4] Batch #2 synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ reacted after reaction times of (a) 16 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours XRD analysis results of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ powder.

[Figure 5] Batch #1 synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was reacted after reaction times of (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours Laser particle size analysis diagram of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles.

[Figure 6] Batch #2 synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ reacted after reaction times of (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours Laser particle size analysis diagram of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles.

[Figure 7] Comparison of the laser particle size analysis results of batches #1 and #2Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursors synthesized from Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , the reaction times were respectively For: (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours.

[Figure 8] Batch #1 (Figure 8(a), (b)) and Batch #2 (Figure 8(c), (d)) synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ after calcining SEM image of the rear LNCM622.

[Fig. 9] XRD analysis results of LNCM622 after calcination of batch #1 (Fig. 9(a)) and batch #2 (Fig. 9(b)) synthesized by Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ .

[Figure 10] The preparation equipment of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor and the surface morphology of the product.

[Figure 11] (a) is the particle size distribution of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ at different speeds of 900, 800 and 600 rpm; (b)-(d) are Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ SEM images at (b) 900, (c) 800 and (d) 600 rpm at different speeds.

[Figure 12] (a) is the particle size distribution of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ at 600rpm and different reaction times; (b)-(d) is Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ at 600rpm The SEM images of (b) 5 hours, (c) 10 hours, (d) 15 hours, (e) 20 hours and (f) 40 hours respectively under the rotating speed.

[Figure 13] (a) is the XRD pattern of self-made Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ and commercially available Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ at different speeds of 900, 800 and 600rpm respectively; (b ) is the relative intensity comparison histogram of each peak of the two samples; (c) is the SEM image of commercially available Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ ; (d) is the self-made Ni _0.8 Co _0.1 prepared at 600rpm SEM image of Mn _0.1 (OH) ₂ .

[Figure 14] (a) is the SEM surface morphology of the LNCM811 product prepared by traditional CSTR before and after calcination; (b) is the SEM surface morphology of the self-made LNCM811 product before and after calcination.

[Figure 15] (a)-(e) is the EDS Mapping spectrum analysis of LNCM811 cathode composite material: (a) Ni, (b) Co, (c) Mn, (d) O, (e) C; (f) It is the EDS spectrum and atomic percentage of Ni, Co and Mn elements of LNCM811 cathode composite material.

[Figure 16] (a) is the XRD patterns of commercially available LNCM811 and LNCM811 produced by the present invention; (b) is the FT-IR spectrum analysis results of commercially available LNCM811 and LNCM811 produced by the present invention.

[Figure 17] (a) is the SEM surface morphology of Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursor; (b)-(d) are prepared under different third-stage calcination conditions SEM surface morphology of LNCMA: (b) 750°C, 15 hours, (c) 800°C, 15 hours and (d) 800°C, 20 hours.

[Figure 18] XRD analysis results of LNCMA prepared from Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursors under different third-stage calcination conditions.

[Figure 19] Charge/discharge curves of batteries composed of LNCM622 electrodes of batch #1 at (a) 2.8-4.3V and (b) 2.8-4.5V respectively, when the current rate is 17mA/g (0.1C) picture.

[Figure 20] Charge/discharge curves of batteries composed of LNCM622 electrodes of batch #2 at (a) 2.8-4.3V and (b) 2.8-4.5V respectively, when the current rate is 17mA/g (0.1C) picture.

[Figure 21] The battery composed of the LNCM622 electrodes of batches #1 and #2, at a current rate of 17 Under mA/g (0.1C), 5 cycles, compare the discharge gram capacity of 5 cycles between (a) 2.8 to 4.3V and 2.8 to 4.5V.

[Fig. 22] Charge/discharge curves of the battery composed of LNCM622 electrodes of batch #1 at (a) 2.8-4.3V and (b) 2.8-4.5V, and the current rate is 0.2C-10C.

[Fig. 23] The charging/discharging curves of batteries composed of LNCM622 electrodes of batch #2 at (a) 2.8-4.3V and (b) 2.8-4.5V, and the current rate is 0.2C-10C.

[Figure 24] Comparison of the current rate capabilities of batteries composed of batches #1 and #2 of LNCM622 electrodes at (a) 2.8-4.3V and (b) 2.8-4.5V, when the current rate is 0.2C-10C picture.

[Fig. 25] The cycle performance diagram of the battery composed of the LNCM622 electrodes of batches #1 and #2 at a rate of 1C and a range of 2.8-4.3V.

[Fig. 26] The cycle performance diagram of the battery composed of the LNCM622 electrodes of batches #1 and #2 at a rate of 1C and a range of 2.8-4.5V.

[Figure 27] (a)-(b) is a battery composed of commercially available LNCM811 at (a) 0.1C, (b) 1C current rate and the self-made LNCM811 positive electrode composite material of the present invention, in the voltage range of 2.5-4.3V The cycle performance comparison below; (c)-(d) is the battery composed of (c) commercially available LNCM811 and (d) the self-made LNCM811 positive electrode composite material of the present invention, charged and discharged at 1C rate and 2.5-4.3V voltage range / Electric cycle curve comparison.

[Figure 28] (a)-(b) are the charge/discharge curves of the battery composed of (a) self-made LNCM811 and (b) self-made Li ₂ MoO ₄ coated LNCM811 cathode composite material at 1C rate and 100 cycles Figure; (c) compares the stability of batteries composed of commercially available LNCM811, self-made LNCM811 and self-made Li ₂ MoO ₄ coated LNCM811 cathode composite materials at 1C rate and 100 cycles; (d) compares the stability of commercially available LNCM811 , self-made LNCM811 and self-made Li ₂ MoO ₄ coated LNCM811 positive electrode composite materials for the comparison of current rate capability.

[Figure 29] (a) is a comparison of the Nyquist graphs of batteries composed of LNCM811 and Li ₂ MoO ₄ coated LNCM811 cathode composite materials after 100 cycles at 1C rate; (b) is the corresponding ω ^{- 1/2} vs Z' diagram.

[Fig. 30] Charge/discharge curves of 3 cycles at 2.8-4.3V, 0.1C rate, for a battery composed of LNCMA cathode composite material calcined at 800°C for 20 hours.

[Figure 31] Comparison of the current rate capability of 0.2C-10C at 2.8-4.3V for batteries composed of LNCMA positive electrode composite materials calcined at 800°C for 20 hours.

[Figure 32] Batteries composed of LNCMA positive electrode composite materials with a calcination temperature of 800°C and a firing time of 15 hours and 20 hours respectively, at 2.8-4.3V, (a) Comparison of different current rate capabilities; (b) 1C/ 1C rate, cycle performance comparison under 100 cycles.

The preparation steps, product identification methods and results of the present invention, and the performance test of the prepared battery are described below by means of exemplary embodiments. It should be noted that the following exemplary embodiments are only used to illustrate the present invention, but not to limit the scope of the present invention.

First, a nickel-rich hydroxide precursor (M(OH) ₂ , M=Ni, Co, Mn and/or Al) is prepared. In the following embodiments, the present invention prepares nickel cobalt manganese hydroxide Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ , and nickel cobalt manganese aluminum hydroxide Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ .

【Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ 】

A continuous Taylor flow reactor (Taylor flow reactor, TFR; LCTR ^® -tera 3100, Laminar Co., Ltd, Korea) was used to prepare the Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor by coprecipitation. With 2M metal sulfate solution, nickel sulfate (NiSO ₄ .6H ₂ O, 98%, Alfa Aesar), cobalt sulfate (CoSO ₄ .7H ₂ O, 99%, Vetec ^TM ) and manganese sulfate (MnSO ₄ .H ₂ O, 98%, JTBaker ^® ) as a source of metal ions, and its ratio is Ni ²⁺ : Co ²⁺ : Mn ²⁺ =6:2:2. In addition, 4M sodium hydroxide solution (NaOH, 98%, UR) was used as a precipitating agent, and ammonia water (NH ₃ .H ₂ O, 28-30%, JTBaker ^® ) was used as a chelating agent; among them, as shown in Table 1, In this embodiment, two different concentrations of ammonia water of 7.5M and 2.5M are used to synthesize different batches of products. Batch #1 uses 7.5M ammonia water, batch #2 uses 2.5M ammonia water, and In the subsequent identification and analysis steps, the performance of the synthesized products with these two different ammonia concentrations will be compared. Add the aforementioned reactants into the reaction chamber at the same time at 60°C, and the doses of the precipitating agent and the chelating agent can be properly configured according to the doses of different raw material ratios. Then the pH value was maintained at 11.0 by the pH control system, and the rotational speed of the reactor was controlled to be fixed at 600 rpm. The continuously produced brown precipitated product was washed several times with deionized water and 99% ethanol to remove residual ions (Na ⁺ , SO ₄ ^2- and other ions). Finally, after filtering and drying at 100° C. for 24 hours, the Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor can be obtained.

【Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ 】

Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursors were prepared by co-precipitation method using continuous Taylor flow reactor (TFR). First, mix 2M NiSO ₄ stoichiometrically. 6H ₂ O, CoSO ₄ . 7H ₂ O and MnSO ₄ . The H ₂ O aqueous solution is injected continuously into the TFR by a pump. At the same time, 4M NaOH precipitation agent and the required NH ₃ . The amount of _H2O chelator solution was added to the reactor. Table 2 lists the detailed parameters of this coprecipitation process. After the reaction was completed, the precipitate was filtered and washed several times with deionized water and 99% ethanol to remove residual ions. Finally, the precipitate was dried in an oven at 100° C. for 24 hours.

【Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ 】

Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursors were prepared by co-precipitation calcination in a continuous Taylor flow reactor (TFR). First, mix 2M NiSO ₄ stoichiometrically. 6H ₂ O, CoSO ₄ . 7H ₂ O, MnSO ₄ . H ₂ O and Al ₂ (SO ₄ ) ₃ . The 6H ₂ O aqueous solution is injected into the TFR continuously by a pump. At the same time, 4M NaOH precipitation agent and the required NH ₃ . The amount of _H2O chelator solution was added to the reactor. Table 3 lists the detailed parameters of this coprecipitation process. After the reaction was completed, the precipitate was filtered and washed several times with deionized water and 99% ethanol to remove residual ions. Finally, the precipitate was dried in an oven at 100° C. for 24 hours.

Next, the prepared nickel-rich hydroxide precursor was further synthesized into a positive electrode composite material; among them, the positive electrode composite material synthesized from the Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor was named LNCM622 powder, and the Ni _0.8 The positive electrode composite material synthesized by Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor is named LNCM811 powder, and the positive electrode composite material synthesized by Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursor is named LNCMA powder . The synthesis steps and parameters are described in detail below.

【LNCM622 powder preparation】

The Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor was used in a ball mill (Planetary Mill PULVERISETTE 5 classic line, Fritsch, Germany) using polyurethane (Polyurethane, PU) balls and 5% excess LiOH. Grinding and mixing H ₂ O in 99% methanol solvent, among them, Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ and LiOH. The ratio of H ₂ O is 1:1.05, the speed of the ball mill is 100rpm, the grinding time is 5 hours, and the weight ratio of the sample to the ball is 1:1; here, 5% excess lithium is used to compensate for the lithium in the subsequent calcination process Losses due to high temperature evaporation. Next, the mixture is dried. Next, heat the mixture at 150° C. for 2 hours, 450° C. for 6 hours, and 850° C. for 15 hours in a tubular furnace in a pure oxygen atmosphere for calcination heat treatment; the parameters of the calcination process are as follows in Table 4. The calcined product is named LNCM622 powder.

【LNCM811 powder preparation】

The Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor using a ball mill using agate (Agate) balls and 5% excess LiOH. H ₂ O was thoroughly ground in 99% methanol solvent, among them, Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ and LiOH. The ratio of H ₂ O is 1:1.05, the rotational speed of the ball mill is 100 rpm, the grinding time is 5 hours, and the weight ratio of the sample to the ball is 1:1. Next, the mixture was calcined and heat-treated in a pure oxygen tubular furnace at 150°C for 2 hours, 500°C for 6 hours and 830°C for 12 hours; the parameters of the calcining process are shown in Table 5. The calcined product was named LNCM811 powder.

In addition, in order to synthesize in-situ coated positive electrode composite materials, the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor is coated, and ammonium molybdate (ammonium molybdate, (NH ₄ ) ₆ Mo ₇ O ₂₄ ) and the required LiOH. The amount of H ₂ O is first mixed to form Li ₂ MoO ₄ , then the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor and Li ₂ MoO ₄ are ground and mixed in a ball mill with agate balls, and the ball mill speed is 100rpm. The grinding time is 5 hours, the weight ratio of the sample to the ball is 1:1, and Li ₂ MoO ₄ is 2wt.% relative to Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ ; and the calcination is carried out under the aforementioned calcination conditions. The synthesized product is Li ₂ MoO ₄ coated LNCM811 whose surface has been modified.

【LNCMA powder preparation】

The Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursor was ground and mixed with polyurethane balls and 5% excess LiOH in a methanol 99% solvent using a ball mill. The ball mill speed was 100 rpm and the milling time was 5 hours. The weight ratio of sample and ball is 1:1, among them, Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ and LiOH. The ratio of H ₂ O is 1:1.05; here, 5% excess lithium is used to compensate the loss of lithium due to high temperature evaporation during the subsequent calcination process. The mixture is dried. Next, the mixture was heated in a tubular furnace in a pure oxygen atmosphere at 150° C. for 2 hours, 550° C. for 6 hours, and 800° C. for 20 hours for calcination heat treatment; the parameters of the calcination process are as follows in Table 6. The calcined product is named as LNCMA powder.

Table 6: Calcination parameters for the synthesis of LNCMA powders

Next, material analysis and identification were performed on the prepared hydroxide precursors and cathode composite materials. Use CuKα5 X-ray powder diffractometer (XRD, Bruker D2 PHASER, Germany, λ=0.1534753nm, 30kV, 10mA) to identify the crystal structure of the material, and at a rate of 0.02°/sec between 2θ of 10° to 70° Collect the signal within the range. Rietveld refinement of lattice parameters of powder materials was performed using TOPAS software (version 4.2).

In addition, the surface morphology and microstructure of powder materials were also measured and analyzed by field emission scanning electron microscopy (FE-SEM, JEOL JSM-7610F Plus, Japan); and X-ray energy scattering spectrometer (EDS, Oxford X-MaxN, UK) analyzes the composition and proportion of material elements.

【Materials Analysis】

【Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor】

Firstly, for the Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor, two batches of products were synthesized at different concentrations of ammonia water, namely batch #1 (the concentration of ammonia water was 7.5M) and batch #2 ( The concentration of ammonia water is 2.5M), and the material analysis is carried out separately to examine its surface morphology and crystal structure.

【Surface Morphology of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ Hydroxide Precursor - Batch #1】

Figure 1 shows the reaction time of batch #1 to form Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles after reaction time of (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours SEM images. During the reaction process, the primary particles of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ will gradually agglomerate into secondary particles. It can be seen from Figure 1 that when the reaction time is increased, the original small and irregular secondary particles (about 5 μm in diameter) become large spherical particles (about 7 μm in diameter). Figure 1(a) From the beginning to 20 hours, the shape of the particles showed an agglomerated appearance; and after 30 hours, the shape of the particles began to transform into spherical and elliptical.

【Surface Morphology of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ Hydroxide Precursor - Batch #2】

Figure 2 shows that batch #2 reacted to form Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles after reaction times of (a) 16 hours, (b) 20 hours, (c) 30 hours, and (d) 40 hours SEM image of . As shown in Figure 2, when the ammonia concentration is reduced to 2.5M, secondary particles are formed earlier compared to 7.5M ammonia concentration; for example, after 16 hours, the secondary particles of the precursor have formed The spherical shape increases the particle size (diameter is about 7 μm), and when the reaction time is continued to be extended to 40 hours, the particle size will continue to grow to about 9 μm. The main reason may be due to the combination of ammonium ions and metal ions to form metal-ammonium complexes, which then generate metal hydroxides. Therefore, when the chelation reaction of ammonia water is reduced, metal ions are more likely to provide space for crystal growth, thereby promoting the agglomeration of crystals. Accordingly, when the ammonia water fed into the reactor increases with time, its particles also become larger.

【Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor crystal structure (batch #1)】

Figure 3 shows that batch #1 reacted to form Ni _0.6 Co _0.2 Mn ₀ . ₂ (OH) ₂ after the reaction time was (a) 20 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours. XRD analysis result of powder. In Figure 3, the XRD pattern of Batch #1 shows that the XRD pattern of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ powder is almost consistent with the crystal structure of typical M(OH) ₂ (M=Ni,Co,Mn), Indicates the success of the preparation.

In addition, by increasing the reaction time, the 2θ in Fig. 3(b)-(d) is about 19 compared with Fig. 3(a). Here the first (003) peak is shifted to a smaller angle and has a higher intensity, which may be due to the formation of a more complete layered structure.

【Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor crystal structure (batch #2)】

Fig. 4 shows that the reaction time of batch #2 is respectively (a) 16 hours, (b) 30 hours, (c) 40 hours and (d) 45 hours and then reacts to generate Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ powder XRD analysis results. In Figure 4, the XRD pattern of Batch #2 shows that the XRD pattern of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ powder is also almost consistent with the crystal structure of typical M(OH) ₂ (M=Ni,Co,Mn) . In addition, by increasing the reaction time, the first (003) peak in Figure 4(a)-(d) is quite consistent at a position around 2θ of about 19°, and the intensity of this peak becomes higher as the reaction time increases. Compared with Fig. 3, the positions of all peaks in Fig. 4 hardly shifted, which means that the crystal structure of the hydroxide precursor has been very stable since 16 hours.

[Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursor particle size]

5 and 6 are the laser particle size analysis diagrams of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ particles produced by the reaction of batch #1 and batch #2 after different reaction times, respectively. The results show that when the concentration of the ammonia chelating agent is reduced from 7.5M to 2.5M, compared with the average particle diameter of the secondary particles of the two products ( _D50 , _D50 is defined as the particle diameter greater than 50% of the total particle diameter number size) increased from about 6 μm to 8 μm. The results are also shown in Table 7 and Table 8 below.

Table 8: Particle Sizes of Batch #2 Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ Hydroxide Precursor

[Comparison of particles of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ hydroxide precursors]

The relationship between the secondary particle size and the reaction time of batch #1 and batch #2 hydroxide precursors is shown in Figure 7. Among them, batch #1 just started to increase with time, and its particle size also increased, until the particle size stabilized after 40 hours of reaction time; however, the particle size of batch #2 changed from 20 hours to 45 hours not big.

【Surface Morphology of LNCM622 Powder】

Next, the analysis of LNCM622 was carried out. Fig. 8 is the SEM image of LNCM622 synthesized from batch #1 (Fig. 8(a), (b)) and batch #2 (Fig. 8(c), (d)) after calcination. As shown in Fig. 8, the product of LNCM622 is almost elliptical and has no cracks. However, it can also be observed that the particle size of the primary particles of batch #2 is smaller than that of batch #1, and the particle size of the secondary particles is larger than that of batch #1. It can be understood that the primary particle size of the precursor material is smaller and the secondary particle size is larger, which means that the precursor material is agglomerated from more and smaller primary particles into secondary particles, and it will have more More closely arranged pores, the porous and closely arranged micropore structure can promote more and faster diffusion of lithium ions in/out during the electrochemical charge/discharge process, thereby promoting better electrical performance. That is, in this embodiment, the structure of batch #2 is better than that of batch #1.

【LNCM622 powder crystal structure】

Figure 9 shows the XRD patterns of two samples of batch #1 and batch #2, all peaks are consistent with the results of the layered α-NaFeO ₂ structure, and no diffraction peaks of other phases or impurities appear. And it is observed from Figure 9 and Table 9 below that the crystal plane (108/110) has a clear peak splitting effect, and the c/a values are higher than 4.9, which means that both samples have a clear layered structure.

Then analyze the surface morphology and crystal structure of the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor and the further synthesized LNCM811; in this embodiment, further control and comparison under different experimental parameters, such as the reactor Speed, grinding and mixing with agate balls in the ball mill, pH range and calcination temperature, etc., the shape and structure of the synthesized product are good or bad, so as to obtain the best reaction conditions. In addition, further compare the commercially available Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ , LNCM811, and the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ , LNCM811 prepared by the present invention, and the traditional continuous stirred tank reaction LNCM811 prepared by the device, the morphology and structure of each product are good or bad.

【Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor surface morphology and grain size】

First, Figure 10 is the surface morphology of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor; as shown in Figure 10, Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursors, enabling successful scale-up of the co-precipitation-calcination two-step synthesis, i.e. to 0.5 kg per batch (approximately 3 liters of metal salt aqueous solution).

Figure 11(a) shows the particle size distribution of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor powder at different reactor rotation speeds (600, 800, 900 rpm). This rotational speed increases the collisions between particles (particle/particle interaction) and within particles (particles interacting with Taylor flow walls), a mechanism that enables the formation of homogeneous particles and the control of particle size. For example, increasing the rotation speed from 600, 800 to 900 rpm, the particle size will decrease to 8.3 μm, 5.2 μm and 3.2 μm, respectively. Fig. 11(b) shows that the secondary particles of the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor powder are irregularly agglomerated after being treated at 900 rpm. Fig. 11(c) shows that at a rotation speed of 800 rpm, the secondary particles aggregated into asymmetric elliptical particles. In addition, Fig. 11(d) shows that at a rotation speed of 600rpm, the powder is uniformly and densely aggregated into regular elliptical secondary particles from the primary particles. Therefore, regular-shaped secondary particles can be obtained using a rotational speed of 600 rpm, which is also the best result for the co-precipitation preparation of hydroxide precursors.

In addition, in order to understand the crystal growth mechanism of the hydroxide precursor at 600rpm in the continuous Taylor flow reactor, the growth morphology of different co-precipitation reaction stages was analyzed by SEM, and the results are shown in Figure 12; among them, Particle size is calculated by _D50 . Figure 12(a) shows the particle size change of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursors during different coprecipitation reaction times; At the beginning (5 hours), many irregular aggregates were produced, with a particle size of 4.5 μm; Figure 12(c) shows that when the reaction time was about 10 hours, the aggregates began to break down, and at the same time, some hexagonal aggregates were formed. The primary particles consisted of small secondary particles (approximately 6.5 μm in size); the estimated duration of the reaction was 15 hours for a particle size of 7.03 μm ( FIG. 12( d )). During the 20-hour reaction stage, the primary particles formed a close arrangement, and the particles uniformly aggregated into regular elliptical secondary particles, as shown in Figure 12(e), with a particle size of 8.35 μm. When the reaction time reaches 40 hours, the particle size is about 8.39 μm (as shown in Figure 12(f)).

【Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor crystal structure】

The crystal phase and purity of the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor powder were identified by XRD technology. Among them, the main peaks of the XRD pattern of the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor are in good agreement with the layered crystal structure of pure β-Ni(OH) ₂ with a hexagonal structure (a = 3.207 Å, c = 4.688 Å).

As shown in Figure 13(a), comparing the commercially available Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ (ternary material precursor, Ubike Technology Co., Ltd., Taiwan) and the prepared Ni _0.8 Co _0.1 Mn _0.1 The XRD pattern of (OH) ₂ at different rotational speeds (900, 800, 600rpm) shows that there is no heterophase peak, which means that the above-mentioned hydroxide precursors belong to the pure phase Ni _0.8 Co _0.1 Mn _0.1 (OH ) ₂ layered crystal structure. It is worth noting that the intensity of the (101) peak of the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor produced by the present invention is stronger than that of the (001) peak; in addition, as shown in Figure 13(b) As shown, the intensity of the (101) peak of commercially available Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ is lower than that of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ prepared by the present invention. The precursor crystal structure grows favorably along the c-axis direction, resulting in high exposure of the {010} facets. The SEM image of Figure 13(c) shows that the commercially available hydroxide precursor powder looks like spherical secondary particles with large size differences, and the smaller particles are about 2~3μm; while Figure 13(d ) in the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ hydroxide precursor prepared by the present invention has elliptical secondary particles with relatively uniform size distribution, showing that its structure is relatively stable.

【Surface morphology of LNCM811 powder】

Compare the surface morphology of LNCM811 prepared by a traditional continuous stirring tank reactor (CSTR) and the LNCM811 prepared by the present invention, as shown in FIG. 14 . The surface morphology of the LNCM811 particles prepared by CSTR before and after calcination is shown in Figure 14(a), the primary particles are smaller and the pore structure is less; in contrast, the LNCM811 powder material prepared by the present invention has petals (petal) shaped primary particles, the pore structure is relatively densely arranged (the surface area and pore size are estimated to be 0.27m ² /g and 11.33nm from the BET measurement results, respectively), as shown in Figure 14(b), the porous densely arranged micro-pore structure is in During the electrochemical charge/discharge process, it can promote more and faster lithium ion in/out diffusion effect.

In addition, the LNCM811 powder material was further analyzed by EDS Mapping, and the results are shown in Figure 15, in which (a) Ni, (b) Co, (c) Mn, (d) O and some (e) C elements EDS Mapping is evenly distributed throughout the sphere, again showing the integrity of its structure; in addition, Figure 15(f) is an EDS spectrum analysis diagram, which can preliminarily confirm the composition ratio of the main elements of nickel, cobalt and manganese, and its value is close to 80:10: 10.

【Crystal structure of LNCM811 powder】

After calcination, both commercially available and prepared LNCM811 powders in the present invention have a hexagonal α-NaFeO ₂ layered structure, and the space group (space group) is R-3m, as shown in Figure 16 (a), and there is no The pure crystal structure of the heterogeneous phase; among them, the two peaks of 006/012 and 018/110 are clearly separated, indicating that it is an ordered layered structure. In addition, Rietveld actuarial calculations are used to obtain more accurate structural details, and the relevant analysis results are shown in Table 10 below. The table shows that the LNCM811 cathode composite material prepared by the present invention has a higher peak intensity than the commercially available LNCM811 product (LiNiCoMnO ₂ lithium nickel cobalt manganese oxide ternary material, Youbike Technology Co., Ltd., Taiwan) Ratio (ie R value, R =I003/I104), this result may be derived from a lower degree of cation mixing (ie Li ⁺ /Ni ²⁺ ).

【FT-IR identification of LNCM811 powder】

In order to understand the generation of impurities on the surface of the material after storage, the commercially available and prepared LNCM811 material of the present invention was stored in the air for 30 days, and then FT-IR identification was carried out; as shown in Figure 16(b), Obviously, for commercially available materials, there are strong absorption peaks at 1754cm ^-1 , 2836-2935cm ^-1 and ^{3200-3600cm -1} respectively; however, the LNCM811 material prepared by the present invention has is a weak absorption peak. According to literature reports, the band at 3200-3600 cm ^-1 is considered to be the stretching vibration of LiOH to OH in the cathode composite. The absorption peak at 1754 cm- ₁ of the symmetric stretching vibration of CO in Li2CO3 is attributed to the _CH formed from the residue of commercially available ^LNCM811 at 2836-2935 cm ^-1 . Compared to the commercial product, the LNCM811 material prepared by the present invention showed less impurity formation on its surface even after 30 days of storage.

Then, the surface morphology and crystal structure of LNCMA under different calcination conditions were also analyzed to examine the pros and cons of the synthesized products under different calcination conditions.

【Surface Topography of LNCMA】

Figure 17(a) shows the surface morphology of the Ni _0.9 Co _0.04 Mn _0.03 Al _0.03 (OH) ₂ hydroxide precursor, which is a secondary particle similar to the needle-like structure of the primary particle agglomerated into a sphere; in addition, at different temperatures Morphology of LNCMA calcined under the conditions of time and time, it can be observed that the particles of LNCMA after calcining at 750°C (Fig. Granular form. In contrast, as shown in Figure 17(c) and Figure 17(d), as the calcination temperature increases, the grains of the primary particles constituting the micron secondary particles tend to increase. This result is consistent with the subsequent XRD analysis The results were consistent.

【Crystal structure of LNCMA】

Figure 18 shows the XRD patterns of LNCMA prepared at different calcination temperatures (750°C and 800°C); among them, the peaks of all samples can correspond to the hexagonal α-NaFeO ₂ layered structure of the R-3m space group , without any other impurity. In the XRD pattern of the sample calcined at 800 °C by LNCMA, in addition to the higher peak of (003), it can be observed that the peaks of (006)/(102) and (108)/(110) are clearly separated, while LNCMA The spectrum of the sample after calcination at 750°C is not obvious, showing that the relatively low calcination temperature of 750°C is not conducive to the high crystallinity of the LNCMA layered structure. In addition, the calcination time is another important factor affecting the performance of LNCMA (for example: LNCMA is calcined at 800°C, the calcination time is 15 hours and 20 hours comparison), both samples belong to LiNiO ₂ layered structure, and no other impurity phases could be found. Furthermore, the obvious peak separation of (006)/(102) and (108)/(110) in the two samples can indicate that the layered structure of the LNCMA material is well developed.

Next, each positive electrode composite material powder prepared above was prepared into an electrode and assembled into a battery, and various performances were further evaluated.

【Preparation of positive electrode sheet】

Use LNCM622, LCNM811 or LNCMA as the active material, and super P conductive carbon black as the conductive agent and polyvinylidene fluoride (PVDF) as the binder in a weight ratio of 8:1:1 (wt.%) to N - Dispersing and mixing in a methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry, and coat the mixed slurry on an aluminum foil (collector layer) to form an electrode sheet; then wrap the coated Dry the electrode sheet in an oven at 60°C for 12 hours to remove the NMP solvent, and dry it in an oven at 120°C for 1 hour to remove moisture and moisture; finally cut the dried electrode sheet into 1.3 cm in diameter A circular sheet, wherein the area of the electrode disk is about 1.33cm ² .

【Production of button battery】

The dried positive electrode (working electrode) pole piece is assembled into a CR2032 button cell in an argon-filled glove box (1TS100-1, Germany MBRAUN UniLab-B, H ₂ O and O ₂ <0.5ppm); , with lithium metal foil as the negative electrode, commercially available polyethylene microporous membrane (PE, Hipore ^TM , thickness about 16 μm, Japan Asahi Kasei Corp., Ltd.) as the separator (Separator), 1M LiPF ₆ was dissolved in ethylene carbonate (EC) and diethylene carbonate (DEC) (v/v=1:1) as electrolyte. In addition, in the present invention, the assembled battery is expressed as "positive electrode//negative electrode"; for example, when LNCM622 is used as the positive electrode and lithium metal foil is used as the negative electrode, the assembled battery is expressed as "LNCM622//Li battery" .

【Electrochemical test】

Let the assembled battery stand for 24 hours to fully wet the separator and electrodes with the electrolyte, and then at room temperature (25°C), according to the required current rate (1C is 170mA/g (LNCM622) and 200mA respectively) /g (LNCM811 and LNCMA)), the constant current charge/discharge cycle test was performed between the cut-off voltages of 2.8-4.3V and/or 2.8-4.5V (vs. Li/Li ⁺ ), respectively.

Using PGSTAT-302N potentiostatic/constant current workstation (Metrohm Autolab BV, Netherlands), within the frequency range of 10 ^-2 -10 ⁶ Hz, the electrochemical impedance spectroscopy (EIS) of the battery was measured with an AC amplitude of 5mV .

In the following, similarly, each product synthesized under different synthesis conditions will be analyzed after being assembled into a battery to examine the performance difference of the synthesized products under different synthesis conditions, including whether the LNCM811 electrode is coated with Li ₂ MoO ₄ or not. Analysis of differences in performance results, and comparison with commercially available batteries.

【LNCM622//Li battery electrical analysis】

【Charge/discharge at 0.1C/0.1C】

【Lot #1 of LNCM622】

Figure 19 shows the charging/charging rate at a current rate of 0.1C (17mA/g) for batteries composed of LNCM622 electrodes of batch #1 under the cut-off voltage ranges of (a) 2.8-4.3V and (b) 2.8-4.5V, respectively. Discharge curve; In addition, its performance is shown in Table 11 and Table 12 below.

Table 12. The electrochemical performance of the battery composed of LNCM622 electrodes of batch #1 at 2.8-4.5V at a rate of 0.1C.

【Lot #2 of LNCM622】

Figure 20 is the battery composed of LNCM622 electrodes of batch #2, at (a) 2.8-4.3V and (b) 2.8-4.5V respectively, the charge/discharge curve at the current rate of 17mA/g (0.1C) ; In addition, its performance is shown in Table 13 and 14 below respectively.

Table 14. The electrochemical performance of the battery composed of LNCM622 electrodes of batch #2 at 2.8-4.5V at a rate of 0.1C.

Figure 21 shows the battery composed of LNCM622 electrodes of batches #1 and #2. Under the current rate of 17mA/g (0.1C) and 5 cycles, the voltages of (a) 2.8 to 4.3V and (b) 2.8 to 4.5V respectively Between V, compare the gram capacitance of 5 cycles. Compared with the battery composed of batch #1, the battery of batch #2 has a higher and more stable gram capacity value for 5 cycles under two different cut-off voltages.

In the comparison of the performance of batteries composed of LNCM622 electrodes, the electrode material of batch #2 has a higher capacity to maintain the capacity than the material of batch #1, and has a higher cut-off voltage of 2.8-4.3V and 2.8-4.5V, respectively. High gram capacitance and better current rate capability, this result is in line with the aforementioned material identification results, including the analysis of primary and secondary particle size.

【Charge/discharge at 0.2C-10C】

【Lot #1 LNCM622 electrodes】

Fig. 22 is the charging/discharging curves of batteries composed of LNCM622 electrodes of batch #1 at (a) 2.8-4.3V and (b) 2.8-4.5V respectively, when the current rate is 0.2C-10C; in addition, Tables 15 and 16 below compare their current rate capabilities.

【Lot #2 LNCM622 electrodes】

Fig. 23 is the charging/discharging curves of batteries composed of LNCM622 electrodes of batch #2 at (a) 2.8-4.3V and (b) 2.8-4.5V respectively, when the current rate is 0.2C-10C; in addition, Tables 17 and 18 below compare their current rate capabilities.

Figure 24 is a comparison chart of the current rate capability when the current rate is 0.2C-10C under the conditions of (a) 2.8-4.3V and (b) 2.8-4.5V respectively, which are composed of LNCM622 electrodes of batches #1 and #2 ; In addition, the following tables 19 and 20 are comparison tables of capacitance maintenance ratios.

【Charge/discharge at 1C/1C】

Batch #2 had higher cut-off voltages, 1C/1C charge/discharge rates, and capacity retention after 100 charge/discharge cycles of 84.4% and 88.0%, respectively, which were higher than those of batch #1 (75.6% and 81.2 %), to verify again the consistency of the aforementioned analysis results for material identification. Figures 25 and 26 are the charge/discharge cycle performance diagrams of batteries composed of LNCM622 electrodes of batch #1 and #2 at a charge/discharge rate of 1C/1C; in addition, the following tables 21 and 22 are the charge/discharge of the same Comparison of cycle performance indicators.

【LNCM811//Li battery electrical analysis】

[Commercially available LNCM811 and LNCM811 prepared by the present invention]

Figure 27(a) compares the cycle performance of batteries made of commercially available LNCM811 and LNCM811 prepared by the present invention after 30 charge/discharge cycles at a charge/discharge rate of 0.1C/0.1C. Among them, the battery capacity retention rate of the LNCM811 prepared by the present invention is 91.25%, and the average Coulombic efficiency is 94.62%. However, the capacity retention rate of the commercially available LNCM811 battery is only 87.70%, while the average Coulombic efficiency is 92.04%. In addition, Figure 27(b) compares the commercially available LNCM811 and the battery composed of LNCM811 prepared by the present invention. The stability test of 100 long-term cycles is carried out at 1C/1C charge/discharge rate and 2.5-4.3V voltage range. The results It shows that the capacity retention rate of the LNCM811 battery prepared by the present invention is about 85.48%, and the average Coulombic efficiency is about 98.79%; however, the commercially available LNCM811 only shows a capacity retention rate of 68.70% after 100 cycles, while the average Coulombic efficiency is about 98.78%. Figure 27 (c) and (d) show commercially available LNCM811 and the prepared LNCM811 of the present invention respectively Charge/discharge curves of LNCM811 at 1C/1C charge/discharge rate from the first to 100th charge/discharge cycle. The first and 100th discharge gram capacities of commercially available LNCM811 electrodes are 165.4mAh/g and 123.7mAh/g respectively (Fig. 27(c)); The first and 100th discharge gram capacities are 162.4mAh/g and 138.9mAh/g respectively (Fig. 27(d)). Although the first gram capacity of the commercially available LNCM811 battery is slightly higher than that of the battery prepared by the present invention, after After the 100th cycle, the LNCM811 prepared by the present invention showed a higher discharge gram capacity (12.3% more than the battery composed of commercially available LNCM811 electrodes=((138.9-123.7)/123.7)× 100%).

[LNCM811 prepared by the present invention and Li ₂ MoO ₄ coated LNCM811]

The present invention also coats a layer of Li ₂ MoO ₄ (i.e. LMO@LNCM811) on the LNCM811 positive electrode composite prepared in situ (in-situ), and this Li ₂ MoO ₄ layer acts as an ion conductor (Ionic conductor), making More Li ⁺ ions diffuse to the LNCM811 host material to react, as shown in Figure 28(a) and (b), comparing the battery composed of self-made LNCM811 and 2wt.% Li ₂ MoO ₄ coated LNCM811 cathode composite material at 1C rate , 2.5 to 4.3V voltage range, 100 charge / discharge cycle curves. In addition, the capacity retention rate of three batteries composed of commercially available LNCM811, self-made LNCM811 and self-made 2wt.% Li ₂ MoO ₄ coated LNCM811 were compared at 1C rate, voltage range from 2.5 to 4.3V, and 100 charge/discharge cycles. The values are 68.7%, 85.5% and 94.0%, respectively, as shown in Figure 28(c). In the voltage range of 2.5 to 4.3V, the current rate capabilities of the above three batteries were tested and compared at current rates of 0.2C, 0.5C, 1C, 3C, 5C and 10C, as shown in Figure 28(d). Compared with the self-made LNCM811 cathode composite material without coating and modification, the battery composed of 2wt.% Li ₂ MoO ₄ coated LNCM811 showed the best discharge gram capacity. In order to clearly compare the current rate capabilities of the three batteries, the capacity retention rate at the 0.2C rate at different rates is also compared, as shown in Table 23. It is worth noting that the battery composed of 2wt.% Li ₂ MoO ₄ coated LNCM811 has the best capacity retention rate compared with the other two batteries, especially at a high rate of 10C, its discharge capacity is 151.6mAh/g , The capacitance retention rate at this rate is 77.6%, which is much higher than that of the commercially available LNCM811 (the discharge gram capacity is 121.1mAh/g, and the capacitance retention rate is 62.7%).

【Electrochemical Impedance Analysis】

The electrochemical reaction process at the electrode/electrolyte interface was analyzed by electrochemical impedance spectroscopy (EIS). Figure 29(a) shows the Nyquist diagram of the battery composed of LNCM811 and 2wt.% Li ₂ MoO ₄ coated LNCM811 cathode composite material at 1C, after 100 cycles, and Figure 29(b) shows the corresponding ω ^{-1/ 2} vs Z'(Ω) relationship diagram; where the semicircle in the intermediate frequency region is related to the charge transfer impedance and interface capacitance of the electrode/electrolyte interface. The sloped line in the low frequency region (Warburg impedance) is related to the lithium ion diffusion impedance through the solid electrode. The equivalent circuit shown in the inset of Fig. 29(a) was used to simulate and analyze various impedance values. In addition, R _s represents the impedance of the electrolyte solution, R _ct is the charge transfer impedance, CPE is the capacitance value of the electrode/electrolyte double layer, R _t is the overall impedance, and Zw is the Warburg impedance. Table 24 lists the fitting values of the corresponding parameters, among which the R _ct value of the battery composed of the LNCM811 positive electrode coated with 2wt.% Li ₂ MoO ₄ is lower than that of the battery composed of the non-coated LNCM811 positive electrode (ie 816.5<988.9Ω) . This result proves that the coated modified Li ₂ MoO ₄ can effectively reduce the charge transfer resistance at the electrode-electrolyte interface. Similarly, the Li ⁺ ion diffusion coefficient of the 2wt.% Li ₂ MoO ₄ coated LNCM811 battery is about D _Li+ : 1.30×10 ^-10 cm ² /s, which is much higher than that of the uncoated modified LNCM811 battery (D _Li+ : 2.69×10 ^-11 cm ² /s), this result proves that the Li ₂ MoO ₄ ionic conductor layer not only improves the ionic conductivity of the LNCM811 electrode, but also isolates the contact between the electrode and the electrolyte to reduce the probability of side reactions.

【LNCMA//Li battery electrical analysis】

The following is a comparison of the current rate capability and cycle performance test of the battery composed of the LNCMA cathode composite material under different calcination conditions. In general, the sample LNCMA has better gram capacitance and cycle stability among all samples under the calcination conditions of 800°C and 20 hours, and its first charge/discharge gram capacitance at 0.1C is 225.8mAh/g and 197.1mAh/g (first coulombic efficiency = 87.29%), as shown in Figure 30. In the 0.2C-10C different discharge current rate capability test, as shown in Figure 31, the capacitance retention rate of 1C relative to 0.2C is about 77.03% (that is, the ratio of the gram capacitance at the second cycle, Q _{sp@ 1C} : 142.5mAh/g/Q _sp@0.2C : 184.9mAh/g). Figure 32 shows that under the same calcination temperature (800°C), the gram capacity of the LNCMA battery with a calcination time of 20 hours at 1C for the first time and 100 charge/discharge cycles is higher than that of an LNCMA battery with a calcination time of 15 hours The battery is high, and the results show that the calcination conditions at a temperature of 800°C and a time of 20 hours are the most suitable conditions for the synthesis and preparation of LNCMA.

Table 26. Comparison of rate capability at 0.2-10C at 2.8-4.3V for batteries composed of LNCMA cathode composite materials calcined at 800°C for 20 hours.

Accordingly, the nickel-rich hydroxide precursor and the nickel-rich oxide cathode composite material prepared by the preparation method of the present invention have better electrical performance than the nickel-rich oxide cathode materials prepared by traditional CSTR and commercially available. Retention rate and significantly excellent electrical performance; at the same time, the present invention also coats the Li ⁺ ion conductive layer on the surface of the hydroxide precursor in situ to improve the conductivity of lithium ions while also isolating the direct contact between the positive electrode and the electrolyte And reduce the probability of side reactions, thereby improving its electrical performance. In addition, the present invention also finds and verifies the best synthesis and preparation conditions by optimizing the preparation parameters.

Claims (5)

A method for preparing a nickel-rich oxide cathode composite material is characterized by the following steps: (a) the nickel-rich hydroxide precursor material and LiOH. H ₂ O is ground and mixed in a methanol solvent with a molar ratio of 1:1.05 to 1:1.25 by a ball mill; wherein, the grinding and mixing conditions of the aforementioned ball mill are 100 rpm to 200 rpm, and the grinding time is 5 hours to 10 hours. Samples and balls The weight ratio is 1:1 to 1:10; (b) The mixture mixed in step (a) is subjected to three-stage calcination heat treatment in a high-temperature furnace with air or pure oxygen atmosphere; wherein, in the aforementioned step (b) The conditions of calcining heat treatment are: the first stage is at 150°C for 2 hours, the second stage is at 400°C to 600°C for 6 hours, and the third stage is at 750°C to 900°C for 10 hours to 25 hours. For heat treatment, the heating rate of the above three stages is 1°C/min to 10°C/min; wherein, the preparation method of the nickel-rich hydroxide precursor material includes the following steps: (i) metal ion source, hydrogen Sodium oxide and ammonia water are simultaneously added to the reaction chamber of the continuous Taylor flow reactor under the heating condition of 50°C to 80°C, the pH value is controlled to be 10 to 12, the reactor speed is 500rpm to 1000rpm, and the feed rate is 2.23ml/ min, the reaction time is 5 hours to 50 hours, and not 5 hours, the continuous production and preparation of coprecipitation method; (ii) filter the precipitate after the reaction of step (i), and ethanol and deionized water Washing; (iii) placing the precipitate after washing in step (ii) in an oven to dry, the temperature of the aforementioned drying is 80°C to 120°C, and the time is 12 hours to 36 hours; wherein, the metal ion source of the aforementioned step (i) is Nickel sulfate, cobalt sulfate and manganese sulfate. A method for preparing a nickel-rich oxide cathode composite material whose surface has been coated, which is characterized by comprising the following steps: (a) fully mixing the coating material with the nickel-rich hydroxide precursor material; wherein the coating material Li ₂ MoO ₄ , the coating amount of the coating material is 0.1wt.% to 5wt.% of the aforementioned nickel-rich hydroxide precursor material; (b) Grinding the mixed mixture in step (a) in a ball mill Mixing; wherein, the grinding and mixing conditions of the aforementioned ball mill are 100 rpm to 200 rpm, the grinding time is 5 hours to 10 hours, and the weight ratio of the mixed mixture and the balls in the aforementioned step (a) is 1:1 to 1:10; (c) The ground mixture in step (b) is subjected to a three-stage calcination heat treatment in a high-temperature furnace in an air or pure oxygen atmosphere; wherein, in the aforementioned step (c), the conditions for calcination heat treatment are: the first stage is at 150°C, 2 hours, the second stage is at 400°C to 600°C, 6 hours, the third stage is at 750°C to 900°C, 10 hours to 25 hours, respectively, for calcination heat treatment, the heating rate of the above three stages is 1°C/ min to 10°C/min; wherein, the preparation method of the aforementioned nickel-rich hydroxide precursor material comprises the following steps: (i) simultaneously heating the metal ion source, sodium hydroxide and ammonia water at 50°C to 80°C Add to the reaction chamber of the continuous Taylor flow reactor, control the pH value of 10 to 12, the reactor speed is 500rpm to 1000rpm, the feed rate is 2.23ml/min, the reaction time is 5 hours to 50 hours, and not 5 hours, carry out the continuous production preparation of co-precipitation method; (ii) filter the precipitate after step (i) reaction, and wash with ethanol and deionized water; (iii) place the precipitate after step (ii) washing Drying in an oven, the aforementioned drying temperature is 80 ° C to 120 ° C, and the time is 12 hours to 36 hours; wherein, the metal ion source of the aforementioned step (i) is nickel sulfate, cobalt sulfate and manganese sulfate. The preparation method of the nickel-rich oxide positive electrode composite material as described in item 1 of the scope of the patent application, wherein the concentration range of the aforementioned metal ion source is an aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate in the range of 1.0M to 2.2M. The preparation method of the nickel-rich oxide cathode composite material as described in item 1 of the scope of the patent application, wherein, in the aforementioned step (i), the concentration of ammonia water is in the range of 2.0M to 8.0M. A lithium ion battery, which uses lithium metal as the negative electrode, and the composition of the active material, the conductive agent and the binder is used as the positive electrode on the current collecting layer. It is prepared by the preparation method of the nickel-rich oxide cathode composite material.

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