A modified ternary positive electrode material and preparation method thereof

Abstract

The present invention relates to a modified ternary positive electrode material and a preparation method thereof, belonging to the technical field of lithium batteries. The present invention simultaneously applies Mg and B2O3 for dual doping modification. After the second stage heating in the preparation method of the present invention, the dual doping modification of Mg and B2O3 produces a coupling effect. The doping of B2O3 makes the morphology of the positive electrode material similar to a pompom, which is divergent outwards, for Li + The transmission of Mg provides a good channel, which alleviates the gradual decrease in the discharge capacity of the positive electrode material and the decrease in the cycle performance. It is also found that the presence of Mg partially destroys the doped radial arrangement structure of B2O3, which inhibits the Li + In addition, during the second stage heating, B2O3 can convert the impurity Li2CO3 into Li3BO3, which has good room temperature ionic conductivity, much higher than the ionic conductivity of the Li2CO3 impurity, thus improving the ionic conductivity of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular, relates to a modified ternary positive electrode material and a preparation method thereof. Background Art

[0002] In recent years, lithium-ion batteries have become a rapidly developing electrochemical energy storage device due to their high voltage platform, long cycle life, high energy density and wide range of usage scenarios. With the rapid development of new energy vehicles and other industries, lithium-ion batteries have become the main energy device for new energy vehicles as power batteries. Ternary materials represented by lithium nickel cobalt manganese oxide have become the focus of researchers due to their high specific capacity and low cost.

[0003] In nickel-cobalt-manganese-oxide lithium ternary materials, nickel is mainly used to provide capacity. In order to achieve higher energy density of batteries, ternary materials with high nickel content have gradually become the development direction of ternary materials. However, the oxidation barrier of divalent nickel is relatively high, so the increase in nickel content will lead to an increase in the degree of cation mixing, hindering the transmission of lithium ions; in addition, highly active nickel ions are prone to interfacial side reactions with the electrolyte, resulting in a transition from a layered structure to a rock salt phase, resulting in a decrease in the thermal stability and cycle stability of the ternary material. Therefore, it is urgent to improve the structure and electrochemical lithium storage performance of high-nickel ternary materials and enhance the performance of high-nickel ternary materials. Summary of the invention

[0004] The purpose of the present invention is to provide a modified ternary positive electrode material, which can alleviate the problem in the prior art that the degree of cation mixing is aggravated due to the increase in nickel content, thereby hindering the transmission of lithium ions.

[0005] The second object of the present invention is to provide a method for preparing the above-mentioned modified ternary positive electrode material.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for preparing a modified ternary positive electrode material, characterized by comprising the following operations:

[0008] Preparation of ternary precursor materials: Prepare a mixed metal sulfate solution, wherein the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05; 2 O 3 Dissolve in deionized water to prepare a modifier, wherein the molar ratio of the B element to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.02-0.03; mix the mixed metal sulfate solution, the complexing agent, the precipitant and the modifier under an inert gas atmosphere to react, and obtain a ternary precursor material after the reaction is completed;

[0009] Preparation of modified ternary cathode material: Take a certain amount of ternary cathode precursor material, LiOH·H 2 O and MgO are mixed as raw materials, heated at 480-520°C for 1.5-2h in an oxygen atmosphere, and then heated to 650-700°C for a second heating for 10-12h to obtain a modified ternary positive electrode material.

[0010] As a preferred embodiment of the present invention, in the preparation of the ternary precursor material, the concentration of the mixed metal sulfate solution is 1.5 mol / L.

[0011] As a preferred embodiment of the present invention, in the preparation of the ternary precursor material, the precipitant is a 5 mol / L sodium hydroxide solution.

[0012] As a preferred embodiment of the present invention, in the preparation of the ternary precursor material, the complexing agent is a 9 mol / L ammonia solution.

[0013] As a preferred embodiment of the present invention, in the preparation of the ternary precursor material, before the mixed metal sulfate solution, the complexing agent, the precipitant and the modifier are mixed and reacted, deionized water, the complexing agent and the precipitant are first added, and the pH after the addition is controlled to be 12±0.3 and the ammonia value is 4±0.2g·L -1 .

[0014] As a preferred embodiment of the present invention, in the preparation of the ternary precursor material, the reaction is terminated by waiting for D 50 The reaction was stopped when the thickness reached 7±0.3μm.

[0015] As a preferred embodiment of the present invention, in the preparation of the modified ternary positive electrode material, the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03.

[0016] The modified ternary positive electrode material is prepared by the above preparation method.

[0017] Beneficial effects of the present invention:

[0018] In the modified ternary positive electrode material provided by the present invention, Mg and B are used 2 O 3 The double doping modification effectively alleviates the problem of increased cation mixing and hindering lithium ion transmission caused by increased nickel content, as follows:

[0019] In high-nickel lithium-ion batteries, the oxidation barrier of divalent nickel is relatively high, so the increase in nickel content will lead to an increase in the degree of cation mixing, hindering the transmission of lithium ions. After doping with Mg, Mg occupies the Li site, showing a good layered structure support effect. However, after Mg occupies the Li site, the content of reversibly deintercalated lithium ions decreases, and some of the deintercalated lithium ions are blocked by Mg at the Li site during the process of inserting into the Li interlayer, and cannot enter the Li site, resulting in a decrease in both specific capacity and cycle performance.

[0020] The present invention simultaneously applies Mg and B 2 O 3 In the preparation method of the present invention, after the second stage heating, Mg and B 2 O 3 The double doping modification produces a coupling effect, B 2 O 3 The doping of Li makes the morphology of the positive electrode material similar to a pompom, which is divergent outward. + The transmission of B provides a good channel, which alleviates the gradual decrease in the discharge capacity of the positive electrode material caused by Mg incorporation and the decrease in cycle performance; and it is found that the presence of Mg partially destroys the 2 O 3 The doped radial arrangement structure inhibits the Li + Rapid removal / embedding process. And, B 2 O 3 In the second stage heating, the impurities Li that are inevitably introduced into the positive electrode material can be removed. 2 CO 3 Converted to Li 3 BO 3 , Li 3 BO 3 It has good room temperature ionic conductivity, much higher than Li 2 CO 3 The ionic conductivity of the impurities improves the ionic conductivity of the prepared positive electrode material. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific implementation methods.

[0022] Example 1

[0023] A modified ternary positive electrode material is prepared by the following preparation method:

[0024] Prepare a 1.5 mol / L mixed metal sulfate solution, in which the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05. 2 O 3Dissolve in deionized water to prepare a modifier, wherein the molar ratio of element B to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.02. Pass 80% deionized water by volume into the reactor, pass N 2 After 30 minutes, stirring was started, and complexing agent and precipitant were added to control the pH in the reactor to 12±0.3 and the ammonia value to 4±0.2 g·L -1 Then, the mixed metal sulfate solution, precipitant (5 mol / L sodium hydroxide solution), complexing agent (9 mol / L ammonia solution) and modifier were added into the reactor for co-precipitation reaction. 50 When the particle size reaches 7±0.3μm, the machine is stopped and the material is discharged. After aging for 2h, the material is centrifuged, washed, dried and iron removed to obtain the ternary precursor material for use;

[0025] Take a certain amount of ternary cathode precursor material, LiOH·H 2 O and MgO are fully mixed as raw materials in a high-speed mixer, wherein the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03. All the raw materials are transferred to a box furnace, heated at 480°C for 1.5 hours in an oxygen atmosphere, then heated to 720°C for a second stage of 10 hours, cooled naturally to room temperature after heating, ground and pulverized to obtain a modified ternary positive electrode material.

[0026] Example 2

[0027] A modified ternary positive electrode material is prepared by the following preparation method:

[0028] Prepare a 1.5 mol / L mixed metal sulfate solution, in which the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05. 2 O 3 Dissolve in deionized water to prepare a modifier, wherein the molar ratio of element B to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.022. 80% deionized water by volume is introduced into the reactor, and N 2 After 30 minutes, stirring was started, and complexing agent and precipitant were added to control the pH in the reactor to 12±0.3 and the ammonia value to 4±0.2 g·L -1 Then, the mixed metal sulfate solution, precipitant (5 mol / L sodium hydroxide solution), complexing agent (9 mol / L ammonia solution) and modifier were added into the reactor for co-precipitation reaction. 50 When the particle size reaches 7±0.3μm, the machine is stopped and the material is discharged. After aging for 2h, the material is centrifuged, washed, dried and iron removed to obtain the ternary precursor material for use;

[0029] Take a certain amount of ternary cathode precursor material, LiOH·H 2O and MgO are fully mixed as raw materials in a high-speed mixer, wherein the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03. All the raw materials are transferred to a box furnace, heated at 490°C for 1.5 hours in an oxygen atmosphere, then heated to 730°C for a second stage of 10.5 hours, and naturally cooled to room temperature after heating, ground and crushed to obtain a modified ternary positive electrode material.

[0030] Example 3

[0031] A modified ternary positive electrode material is prepared by the following preparation method:

[0032] Prepare a 1.5 mol / L mixed metal sulfate solution, in which the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05. 2 O 3 Dissolve in deionized water to prepare a modifier, wherein the molar ratio of element B to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.025. Pass 80% deionized water by volume into the reactor, pass N 2 After 30 minutes, stirring was started, and complexing agent and precipitant were added to control the pH in the reactor to 12±0.3 and the ammonia value to 4±0.2 g·L -1 Then, the mixed metal sulfate solution, precipitant (5 mol / L sodium hydroxide solution), complexing agent (9 mol / L ammonia solution) and modifier were added into the reactor for co-precipitation reaction. 50 When the particle size reaches 7±0.3μm, the machine is stopped and the material is discharged. After aging for 2h, the material is centrifuged, washed, dried and iron removed to obtain the ternary precursor material for use;

[0033] Take a certain amount of ternary cathode precursor material, LiOH·H 2 O and MgO as raw materials are fully mixed in a high-speed mixer, wherein the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03. All the raw materials are transferred to a box furnace, heated at 500°C for 2 hours in an oxygen atmosphere, then heated to 740°C for 11 hours in a second stage, cooled naturally to room temperature after heating, ground and pulverized to obtain a modified ternary positive electrode material.

[0034] Example 4

[0035] A modified ternary positive electrode material is prepared by the following preparation method:

[0036] Prepare a 1.5 mol / L mixed metal sulfate solution, in which the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05. 2 O 3Dissolve in deionized water to prepare a modifier, wherein the molar ratio of element B to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.028. Pass 80% deionized water by volume into the reactor, pass N 2 After 30 minutes, stirring was started, and complexing agent and precipitant were added to control the pH in the reactor to 12±0.3 and the ammonia value to 4±0.2 g·L -1 Then, the mixed metal sulfate solution, precipitant (5 mol / L sodium hydroxide solution), complexing agent (9 mol / L ammonia solution) and modifier were added into the reactor for co-precipitation reaction. 50 When the particle size reaches 7±0.3μm, the machine is stopped and the material is discharged. After aging for 2h, the material is centrifuged, washed, dried and iron removed to obtain the ternary precursor material for use;

[0037] Take a certain amount of ternary cathode precursor material, LiOH·H 2 O and MgO are fully mixed as raw materials in a high-speed mixer, wherein the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary cathode precursor material is 1:1.03. The raw materials are transferred to a box furnace, heated at 510°C for 2 hours in an oxygen atmosphere, and then heated to 750°C for a second stage of 11.5 hours. After heating, they are naturally cooled to room temperature, ground and pulverized to obtain a modified ternary cathode material.

[0038] Example 5

[0039] A modified ternary positive electrode material is prepared by the following preparation method:

[0040] Prepare a 1.5 mol / L mixed metal sulfate solution, in which the molar ratio of Ni:Co:Mn is 0.83:0.12:0.05. 2 O 3 Dissolve in deionized water to prepare a modifier, wherein the molar ratio of element B to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.03. Pass 80% deionized water by volume into the reactor, pass N 2 After 30 minutes, stirring was started, and complexing agent and precipitant were added to control the pH in the reactor to 12±0.3 and the ammonia value to 4±0.2 g·L -1 Then, the mixed metal sulfate solution, precipitant (5 mol / L sodium hydroxide solution), complexing agent (9 mol / L ammonia solution) and modifier were added into the reactor for co-precipitation reaction. 50 When the particle size reaches 7±0.3μm, the machine is stopped and the material is discharged. After aging for 2h, the material is centrifuged, washed, dried and iron removed to obtain the ternary precursor material for use;

[0041] Take a certain amount of ternary cathode precursor material, LiOH·H 2O and MgO are fully mixed as raw materials in a high-speed mixer, wherein the molar ratio of Mg to the total amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03. All the raw materials are transferred to a box furnace, heated at 520°C for 2 hours in an oxygen atmosphere, and then heated to 760°C for a second stage of 12 hours. After heating, it is naturally cooled to room temperature, ground and pulverized to obtain a modified ternary positive electrode material.

[0042] Comparative Example 1

[0043] A modified ternary positive electrode material, which differs from Example 3 in that B is not used 2 O 3 Modifier: only Mg doping modification is performed, and the rest of the operations are the same as in Example 3.

[0044] Comparative Example 2

[0045] A modified ternary positive electrode material, which is different from Example 3 in that a heating temperature is 200° C., and the remaining operations are the same as Example 3.

[0046] Comparative Example 3

[0047] A modified ternary positive electrode material, which is different from Example 3 in that the second stage heating temperature is 800°C, and the rest of the operations are the same as Example 3.

[0048] Comparative Example 4

[0049] A modified ternary positive electrode material, which is different from Example 3 in that a heating time is 3 hours, and the rest of the operations are the same as Example 3.

[0050] Comparative Example 5

[0051] A modified ternary positive electrode material, which is different from Example 3 in that the second stage heating time is 6 hours, and the other operations are the same as Example 3.

[0052] The modified ternary positive electrode materials prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were made into batteries, and the preparation method was as follows:

[0053] The modified ternary cathode material, polyvinylidene fluoride and carbon black were mixed in a mass ratio of 8:1:1, and then an appropriate amount of N-methylpyrrolidone was added. The slurry was fully mixed and evenly applied on the aluminum foil. The aluminum foil was then dried at 110°C in a vacuum for 12 hours, and then cut into small discs with a diameter of 12 mm as the cathode sheet. The active material loading was about 2 mg / cm 2 Metal lithium was used as the negative electrode, porous polypropylene membrane (Celgard 2500) was used as the separator, and 1.15 mol / L LiPF 6A solution (the solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 1:2:2) is used as an electrolyte and assembled into a battery with a positive electrode sheet.

[0054] Test Example 1

[0055] The assembled battery was charged and discharged on the Blue Electric Battery Test System with a voltage range of 2.8 to 4.3 V. Electrochemical impedance and cyclic voltammetry tests were performed. During the test, the current of 1C was set to 180 mA / g, and the discharge capacity of the sample at a current rate of 5C was tested and recorded; the impedance value of the sample after 100 cycles and the cycle retention rate after 300 cycles were tested and recorded. The results are shown in Table 1.

[0056] Table 1

[0057]

[0058] As shown in Table 1, the discharge capacity of the batteries prepared in Examples 1 to 5 at a current rate of 5C is above 162 mA·h / g, the impedance value is 150Ω, and the cycle retention rate is greater than 93%, which is excellent. 2 O 3 Modifier, only Mg doping modification is performed. After Mg element occupies Li site, the content of reversibly deintercalated lithium ions is reduced. Some of the deintercalated lithium ions are blocked by Mg at Li site during the process of inserting into Li interlayer, and cannot enter Li site, resulting in a decrease in specific capacity. 2 O 3 The modifier can effectively improve the cycle performance. Comparative Examples 2 to 5 respectively adjusted the temperature and time of the first and second heating stages, which had a significant impact on the comparative capacity, cycle performance and impedance value.

[0059] The above is only an implementation method of the invention, and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the invention, which still fall within the scope of patent protection.

Claims

1. A method for preparing a modified ternary positive electrode material, characterized in that: The following operations are included: Preparation of ternary precursor materials: Prepare mixed metal sulfate solution, The molar ratio of Ni:Co:Mn is 0.83:0.12:0.05; B2O3 is dissolved in deionized water to prepare a modifier, wherein the molar ratio of the B element to the total amount of nickel, cobalt and manganese in the mixed metal sulfate solution is 1:0.02-0.03; the mixed metal sulfate solution, the complexing agent, the precipitant and the modifier are mixed and reacted under an inert gas atmosphere, and D 50 When the reaction reaches 7±0.3μm, the reaction is stopped and the ternary precursor material is obtained at the end of the reaction; Preparation of modified ternary positive electrode material: taking a certain amount of ternary positive electrode precursor material, LiOH·H2O and MgO as raw materials and mixing them, wherein the ratio of the total molar amount of Mg to the total molar amount of nickel, cobalt and manganese in the ternary positive electrode precursor material is 1:1.03, heating at 480-520°C for 1.5-2h in an oxygen atmosphere, then heating to 650-700°C for a second stage of heating for 10-12h, to obtain a modified ternary positive electrode material.

2. The preparation method according to claim 1, characterized in that: In the preparation of the ternary precursor material, the concentration of the mixed metal sulfate solution is 1.5 mol / L.

3. The preparation method according to claim 1, characterized in that: In the preparation of the ternary precursor material, the precipitant is a 5 mol / L sodium hydroxide solution.

4. The preparation method according to claim 1, characterized in that: In the preparation of the ternary precursor material, the complexing agent is a 9 mol / L ammonia solution.

5. The preparation method according to claim 1, characterized in that: In the preparation of the ternary precursor material, before the mixed metal sulfate solution, complexing agent, precipitant and modifier are mixed for reaction, deionized water, complexing agent and precipitant are added, and the pH after addition is controlled to be 12±0.3 and the ammonia value is 4±0.2g·L -1 .

6. A modified ternary positive electrode material obtained by the preparation method according to any one of claims 1 to 5.

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