WO2022237327A1

WO2022237327A1 - Ternary positive electrode material doping and coating method, ternary positive electrode material, and lithium ion battery

Info

Publication number: WO2022237327A1
Application number: PCT/CN2022/082373
Authority: WO
Inventors: 万江涛; 张宁; 张勇杰; 刘满库; 李子郯
Original assignee: 蜂巢能源科技股份有限公司
Priority date: 2021-05-12
Filing date: 2022-03-23
Publication date: 2022-11-17
Also published as: CN112993258A; CN112993258B

Abstract

The present invention provides a ternary positive electrode material doping and coating method, a ternary positive electrode material, and a lithium ion battery. The method comprises: preparing a ternary positive electrode material precursor by means of a one-step co-precipitation method, cleaning a sintered product by using a saturated solution of silicate as a base solution after performing primary sintering, adding metal salt in a cleaning process to perform precipitation coating, and performing secondary sintering after dehydration. The method is simple in operation, the doping and coating uniformity is guaranteed, and meanwhile, costs are properly reduced.

Description

Doping and coating method of ternary positive electrode material, ternary positive electrode material and lithium ion battery

technical field

The present disclosure relates to the technical field of new energy, and relates to a doping and coating method of a ternary positive electrode material, a ternary positive electrode material and a lithium ion battery.

Background technique

High-nickel ternary cathode materials with high specific capacity, high cycle stability and high safety have been a research hotspot in recent years. Doping and coating modification are necessary means to realize the above-mentioned properties of high-nickel ternary cathode materials. The best doping method is to add nano-metal oxides or hydroxides and mix them uniformly before calcining, which requires additional abrasives, mixing and other processes, the operation is complicated, and the mixing effect is average; while coating is also adding nano-metal element materials to mix and sinter , the operation is equally complicated; it is difficult to guarantee the uniformity of all batches.

Existing high-nickel materials are generally doped with zirconium, titanium, aluminum, tungsten, magnesium, scandium, vanadium, calcium, strontium, barium, gallium, indium, etc., which improves the structural stability and conductivity of the material to a certain extent. By coating metal oxides such as zirconium, titanium, aluminum, tungsten, magnesium, scandium, vanadium, calcium, strontium, barium, gallium, indium and other metal oxides, most of the material and electrolyte are isolated, which greatly reduces the gas production.

However, the existing coating and doping methods still need to be further improved in terms of improving safety, reducing gas production, and improving cycle performance. Industrial production.

public content

In one embodiment, the present disclosure provides a method for doping and coating a ternary positive electrode material, the method comprising the following steps:

(1) Using silicate, doped metal source, nickel source, cobalt source and manganese source, a one-step co-precipitation method is used to prepare the ternary cathode material precursor, and one-time sintering to obtain a ternary material co-doped with silicon and doped metal elements Positive material core;

(2) Use a saturated solution of silicate as the bottom liquid to clean the inner core of the ternary positive electrode material, add metal salts during the cleaning process for precipitation coating, and perform secondary sintering after dehydration to obtain the doped and coated Ternary cathode material; the amount of the silicate accounts for 0.05% to 0.5% of the total mass of the inner core of the ternary cathode material.

Wherein, the amount of silicate used in step (1) accounts for 0.05% to 0.5% of the total mass of the inner core of the ternary positive electrode material, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35% , 0.4% or 0.5%, etc.

In an embodiment provided by the present disclosure, the final doping effect can be regulated by adjusting the amount of doping metal source and silicate used in step (1). By adjusting (2) various parameters in the cleaning process, the final coating effect can be regulated.

In an embodiment provided by the present disclosure, by doping non-metal element silicon and other metal elements (for example, at least one of calcium, magnesium, aluminum, titanium, tungsten, zirconium, scandium, etc.) , by preparing the corresponding solution for one-step co-precipitation and one-time sintering to obtain the core of the ternary cathode material co-doped with silicon and doped metal elements. Then wash and dealkalize in a saturated silicate solution and at the same time carry out precipitation of various metal elements to achieve coating, to achieve the double effect of dealkalization and coating. The whole doping and coating process is carried out in the solution by wet precipitation The finished method saves cumbersome grinding and mixing operations, the method is simple to operate, the uniformity of doping and coating is guaranteed, and at the same time, it is beneficial to appropriately reduce the cost. The prepared positive electrode material has a good doping and coating effect, which can effectively solve the problem of gas production, improve cycle performance, and have no abnormalities in electrical performance testing.

The method provided by an embodiment of the present disclosure is especially suitable for a high specific capacity, high cycle stability, high safety and high nickel ternary positive electrode material system.

In related technologies, ternary materials, especially high-nickel ternary materials, are unstable at the grain boundaries of the secondary particles after preparation and sintering. After multiple cycles, cracks first appear at the grain boundaries, and the electrolyte enters the interior of the crystal through the continuously generated cracks. Oxidation-reduction reactions occur rapidly in a short period of time, a large amount of gas is produced and new cracks continue to be generated in large quantities, and the performance of the battery also drops sharply, causing safety hazards. How to stabilize the crystal interface of polycrystalline high-nickel and delay the formation of cracks The process is also a problem that must be solved to ensure the high specific capacity, high cycle stability and high safety of high-nickel ternary cathode materials.

In an embodiment provided by the present disclosure, the silicate is used to stabilize the grain boundary between the primary particles of the positive electrode by co-doping with the silicate and the metal source, and after the dealkalization coating process is completed, the dehydrated silicate (such as lithium silicate) can automatically generate a better protective film during the drying process; saturated silicate solution can inhibit the reverse dissolution of silicate in the material, so the introduction of silicate doping and coating It further plays a role in stabilizing the material structure and enhancing the coating effect, and improves the safety performance and cycle performance of the material.

In one embodiment, the doping metal in the doping metal source in step (1) includes at least one of calcium, magnesium, aluminum, titanium, tungsten, zirconium and scandium, and the doping metal in step (1) The amount of the source accounts for 0.05%-0.5% of the total mass of the core of the ternary cathode material, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.5%.

In the present disclosure, the anion of the doping metal source is not limited, for example, it may be sulfate, nitrate or chloride.

In one embodiment, the silicate in step (1) includes at least one of sodium silicate and lithium silicate.

In the present disclosure, the co-precipitation method can be carried out with reference to related technologies, and is not specifically limited. Exemplarily, the one-step co-precipitation method described in step (1) to prepare the ternary cathode material precursor includes:

preparing a mixed solution comprising nickel source, cobalt source, manganese source, doping metal source and silicate, mixing the mixed solution with lye and ammonia water for precipitation reaction to obtain a ternary cathode material precursor;

The lye includes sodium hydroxide solution and/or potassium hydroxide solution.

In one embodiment, it can be carried out according to the following scheme:

(I) The preparation concentration is 0.1mol/L～1mol/L (such as 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.5mol/L, 0.7mol/L, 0.8mol/L or 1mol/L, etc. ) soluble nickel salt, cobalt salt, manganese salt mixed solution, the concentration described here is the total metal cation concentration in the mixed solution;

The molar ratio of nickel-cobalt-manganese is not particularly limited. When the molar content of nickel in the precursor is greater than or equal to 80%, it is called a high-nickel ternary positive electrode material precursor, and the prepared ternary positive electrode material is a high-nickel ternary positive electrode material. The method of an embodiment of the present disclosure has a better effect on improving the electrochemical performance of the high-nickel ternary positive electrode material.

The preparation concentration is 5g/L～50g/L (such as 5g/L, 6g/L, 8g/L, 10g/L, 15g/L, 20g/L, 25g/L, 30g/L, 35g/L, 40g/L L, 45g/L or 50g/L, etc.) doped metal source solution, the doped metal source can be a single type, also can be a combination of two or more, the type can be at least one of titanium, aluminum, magnesium, for example Sulphate, the concentration described here is the total metal cation concentration in the mixed solution;

The preparation concentration is 0.1mol/L～1mol/L (such as 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.5mol/L, 0.7mol/L, 0.8mol/L or 1.0mol/L, etc.) Silicate solution, a single type of silicate, or a combination of two or more, the concentration described here is the total metal cation concentration in the mixed solution;

Prepare a strong base solution with a concentration of 5 mol/L to 10 mol/L (such as 5 mol/L, 6 mol/L, 7 mol/L, 8 mol/L, 9 mol/L or 10 mol/L, etc.), the strong base solution includes Sodium solution and/or potassium hydroxide solution;

Prepare an ammonia solution with a concentration of 8mol/L to 12mol/L (such as 8mol/L, 9mol/L, 10mol/L, 11mol/L or 12mol/L, etc.);

There is no sequence in the preparation of the above solutions;

(II) mix soluble nickel salt, cobalt salt, manganese salt mixed solution with doping metal source solution and silicate solution to obtain mixed solution A, then add above-mentioned strong alkali solution and ammoniacal liquor to mixed solution A synchronously, carry out Co-precipitation reaction to obtain the precursor of the ternary cathode material.

In one embodiment, the primary sintering temperature in step (1) is 650°C to 850°C, such as 650°C, 680°C, 700°C, 725°C, 750°C, 775°C, 800°C, 820°C, 840°C Or 850°C, etc.; the time for the primary sintering is 10h-20h, such as 10h, 12h, 13h, 15h, 16h, 18h, 19h or 20h.

In one embodiment, the lithium source is used in an appropriate excess.

In one embodiment, the molar ratio of the lithium source and the precursor of the ternary cathode material is 1.02˜1.06, such as 1.02, 1.03, 1.04, 1.05 or 1.06.

In one embodiment, the product obtained by the first sintering is crushed after the first sintering.

In one embodiment, in the cleaning step described in step (2), the metal elements in the metal salt include at least one of zirconium, titanium, aluminum, tungsten, magnesium, scandium, vanadium, calcium, strontium, barium, gallium and indium. One, in the cleaning step described in step (2), the amount of metal salt used accounts for 0.05% to 0.5% of the total mass of the inner core of the ternary positive electrode material, such as 0.05%, 0.08%, 0.1%, 0.15%, 0.2% %, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%, etc.

In one embodiment, the step of cleaning in step (2) includes: using a silicate saturated solution as the bottom liquid, mixing the inner core of the ternary positive electrode material with the bottom liquid, and the liquid-solid ratio is 1: 1～5:1 (such as 1:1, 2:1, 3:1, 3.5:1, 4:1 or 5:1, etc.), the mixing time is 20min～60min (such as 20min, 25min, 30min, 35min, 40min , 45min, 50min, 55min or 60min, etc.), in the mixing process, the concentration of 10g/L～50g/L (such as 10g/L, 15g/L, 20g/L, 25g/L, 30g/L, 35g/L, 40g/L, 45g/L or 50g/L, etc., where the concentration is the total metal cation concentration in the metal salt solution) for precipitation coating.

In one embodiment, the water content after dehydration in step (2) is less than 5wt%, such as 4.5wt%, 4wt%, 3wt%, 2.5wt%, 2wt%, 1wt% or 0.5wt%.

In one embodiment, the water content after the dehydration in step (2) is 1wt%-5wt%.

In one embodiment, the dehydration in step (2) is achieved by feeding nitrogen gas into the dehydration process.

In one embodiment, a step of pre-drying is carried out after dehydration in step (2) and before secondary sintering, the temperature of the pre-drying is 150°C-220°C, such as 150°C, 160°C, 170°C, 180°C , 200°C, 210°C or 220°C, etc.; the pre-drying time is 3h to 12h, such as 3h, 4h, 5h, 6h, 8h, 9h, 10h, 11h or 12h; the pre-drying time is up to the moisture content of the material Less than 0.05wt%, such as 0.04wt%, 0.03wt% or 0.02wt%, etc.

The dehydrated silicate (such as lithium silicate) can automatically form a better protective film during the drying process, and a more stable protective film can be obtained by pre-drying under the above conditions.

The present disclosure does not specifically limit the equipment used for pre-drying, for example, a double-cone dryer may be used.

In one embodiment, the atmosphere of the secondary sintering in step (2) is an oxygen-containing atmosphere, and the temperature of the secondary sintering is 400°C to 700°C, such as 400°C, 450°C, 500°C, 550°C, 600°C °C, 650 °C or 700 °C, etc.; the time for the secondary sintering is 2h to 15h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 10h, 12h, or 15h. Wherein, the volume content of oxygen in the oxygen-containing atmosphere is greater than 80%, such as 82%, 85%, 90%, 95%, 98%, 99% or 100%.

In one embodiment, the present disclosure provides a ternary positive electrode material prepared by the above method, the ternary positive electrode material includes a core of the ternary positive electrode material co-doped with silicon and doped metal elements, and is coated on the Metal oxides on the surface of the inner core.

In one embodiment, in the core of the ternary positive electrode material co-doped with silicon and doping metal elements, the silicon element exists in the form of silicate.

In one embodiment, the metal oxide coated on the surface of the inner core includes at least one of oxides of zirconium, titanium, aluminum, tungsten, magnesium, scandium, vanadium, calcium, strontium, barium, gallium and indium.

In one embodiment, taking the core as a whole, the total mass concentration of the doped element silicon and the doped metal element is 500ppm-5000ppm, such as 500ppm, 600ppm, 650ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1250ppm, 1500ppm , 1600ppm, 1800ppm, 2000ppm, 2300ppm, 2600ppm, 2800ppm, 3000ppm, 3500ppm, 3700ppm, 4000ppm, 4200ppm, 4500ppm or 5000ppm, etc.; 900ppm, 1000ppm, 1250ppm, 1500ppm, 1600ppm, 1800ppm, 2000ppm, 2300ppm, 2600ppm, 2800ppm, 3000ppm, 3500ppm, 3700ppm, 4000ppm, 4200ppm, 4500ppm or 5000ppm etc.

In one embodiment, taking the inner core as a whole, the mass concentration of the metal oxide coated on the surface of the inner core is 500ppm-5000ppm, such as 500ppm, 600ppm, 650ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1250ppm, 1500ppm、1600ppm、1800ppm、2000ppm、2300ppm、2600ppm、2800ppm、3000ppm、3500ppm、3700ppm、4000ppm、4200ppm、4500ppm或5000ppm等；包覆层的质量浓度为500ppm～5000ppm，例如500ppm、600ppm、650ppm、700ppm、800ppm , 900ppm, 1000ppm, 1250ppm, 1500ppm, 1600ppm, 1800ppm, 2000ppm, 2300ppm, 2600ppm, 2800ppm, 3000ppm, 3500ppm, 3700ppm, 4000ppm, 4200ppm, 4500ppm or 5000ppm, etc.

In one embodiment, the present disclosure provides a lithium ion battery, including a positive electrode, a negative electrode and a separator, and the positive electrode adopts the above-mentioned ternary positive electrode material.

specific embodiment

The technical solutions of the present disclosure will be further described below through specific embodiments. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present disclosure, and should not be regarded as specific limitations on the present disclosure.

Example 1

This embodiment provides a method for doping and covering a ternary positive electrode material, including the following steps:

① Precursor synthesis: first weigh soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the molar ratio of 8:1:1 to prepare nickel-cobalt-manganese ternary mixed solution A (the total metal cation concentration in mixed solution A is 0.6mol /L); the zirconium chloride solution B of preparation 10g/L, the zirconium chloride in this solution B accounts for 0.2% of the gross mass of a sintered material H; the sodium silicate solution C of preparation 0.5mol/L, this solution C The sodium silicate in accounts for 0.2% of the total mass of one-fired material H;

Then prepare the ammonia solution E of 5mol/L lye D (being specifically sodium hydroxide solution) and 8mol/L,

Mix the mixed solution A, solution B and solution C to obtain a mixed system, then add lye D and solution E to the mixed system simultaneously, and react to synthesize the ternary 811 precursor. After the synthesis is completed, wash, dehydrate, and dry to obtain the precursor Finished product F, particle size 9.8um.

②Primary mixing and sintering: Weigh a certain amount of the precursor product F and lithium hydroxide G for high-mixer mixing. The precursor product F and lithium hydroxide are fully mixed at a molar ratio of 1:1.05. , calcined at a temperature of 750°C for 15h to obtain a calcined material H.

③ Dealkalization coating: put the one-calcined material H in a three-in-one washing machine, add an appropriate amount of pure water to prepare a saturated lithium silicate solution, the liquid-solid ratio is 2:1, stir and wash for 30 minutes, and continuously add 10g dropwise during the process /L of zirconium sulfate solution for precipitation coating, the zirconium sulfate in the zirconium sulfate solution accounts for 0.1% of the total mass of the first-fired material H, and then nitrogen gas is fed into it for rapid dehydration, and after dehydration, it is confirmed that the moisture content is less than 5wt%.

④ Pre-drying: Use a double-cone dryer to pre-dry at 150°C for 5 hours. After drying, put it into a sagger for secondary sintering.

⑤ Coating secondary sintering: Weigh a certain amount of the pre-dried sample and calcinate at 700° C. for 8 hours in an oxygen atmosphere to obtain secondary sintering material I.

Example 2

① Precursor synthesis: first weigh soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the molar ratio of 83:11:6 to prepare nickel-cobalt-manganese ternary mixed solution A (the total metal cation concentration in mixed solution A is 0.5mol /L); prepare 20g/L titanium nitrate solution B, the titanium nitrate in the solution B accounts for 0.15% of the total mass of the material H; prepare the sodium silicate solution C of 0.8mol/L, the silicic acid in the solution C Sodium accounts for 0.25% of the total mass of the first-fired material H;

Then prepare the ammonia solution E of 7mol/L lye D (being specifically sodium hydroxide solution) and 10mol/L,

Mix the mixed solution A, solution B and solution C to obtain a mixed system, then add alkali solution D and solution E to the mixed system simultaneously, and react to synthesize the ternary 83 precursor. After the synthesis is completed, wash, dehydrate, and dry to obtain the precursor Finished product F, the particle size is about 9.5um.

②Primary mixing and sintering: Weigh a certain amount of the precursor product F and lithium hydroxide G for high-mixer mixing. The precursor and lithium hydroxide are fully mixed at a molar ratio of 1:1.04. Under an oxygen atmosphere, the Calcined at a temperature of 730°C for 12 hours to obtain a calcined material H.

③ Dealkalization coating: put the one-calcined material H in a three-in-one washing machine, add an appropriate amount of pure water to prepare a saturated lithium silicate solution, the liquid-solid ratio is 2:1, stir and wash for 40 minutes, and continuously add 20g dropwise during the process /L zirconium nitrate solution for precipitation coating. The zirconium nitrate in the zirconium nitrate solution accounts for 0.2% of the total mass of the first-fired material H, and then nitrogen gas is passed into it for rapid dehydration. After dehydration, it is confirmed that the moisture content is less than 5wt%.

④ Pre-drying: Use a double-cone dryer to pre-dry at 180°C for 5 hours. After drying, put it into a sagger for secondary sintering.

⑤ Coating secondary sintering: Weigh a certain amount of the pre-dried sample and calcinate at 550° C. for 9 hours in an oxygen atmosphere to obtain secondary sintering material I.

Example 3

① Precursor synthesis: first weigh soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the molar ratio of 88:9:3 to prepare nickel-cobalt-manganese ternary mixed solution A (the total metal cation concentration in mixed solution A is 0.8mol /L); prepare 30g/L aluminum sulfate solution B, the aluminum sulfate in this solution B accounts for 0.15% of the gross mass of one-fired material H; prepare the lithium silicate solution C of 0.1mol/L, the silicon in this solution C Lithium acid accounts for 0.1% of the total mass of the first-fired material H;

Then prepare the ammonia solution E of 4mol/L lye D (being specifically sodium hydroxide solution) and 8mol/L,

Mix the mixed solution A, solution B and solution C to obtain a mixed system, then add alkali solution D and solution E to the mixed system simultaneously, and react to synthesize the precursor of ternary 88, after the synthesis is completed, wash, dehydrate, and dry to obtain the precursor Finished product F, the particle size is about 9.5um.

②Primary mixing and sintering: Weigh a certain amount of the precursor product F and lithium hydroxide G for high-mixer mixing. The precursor and lithium hydroxide are fully mixed at a molar ratio of 1:1.03. Calcined at a temperature of 700°C for 12 hours to obtain a calcined material H.

③Dealkalization coating: put the one-calcined material H in a three-in-one washing machine, add an appropriate amount of pure water to prepare a saturated lithium silicate solution, the liquid-solid ratio is 3:1, stir and wash for 50 minutes, and add 30g dropwise during the process /L zirconium chloride solution for precipitation coating, the zirconium chloride in the zirconium chloride solution accounts for 0.15% of the total mass of the first-fired material H, and then nitrogen gas is fed into it for rapid dehydration, and after dehydration, it is confirmed that the moisture content is less than 5wt%.

④ Pre-drying: Use a double-cone dryer to pre-dry at 170°C for 6 hours. After drying, put it into a sagger for secondary sintering.

⑤ Coating secondary sintering: Weigh a certain amount of the pre-dried sample and calcinate at 600° C. for 6 hours in an oxygen atmosphere to obtain secondary sintering material I.

Example 4

① Precursor synthesis: first weigh soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the molar ratio of 8:1:1 to prepare nickel-cobalt-manganese ternary mixed solution A (the total metal cation concentration in mixed solution A is 0.6mol /L); the zirconium chloride solution B of preparation 20g/L, the zirconium chloride in this solution B accounts for 0.1% of the gross mass of a sintered material H; the lithium silicate solution C of preparation 0.5mol/L, this solution C Lithium silicate in accounts for 0.3% of the gross mass of one-fired material H;

Then prepare the ammonia solution E of 7mol/L lye D (being specifically sodium hydroxide solution) and 9mol/L,

Mix the mixed solution A, solution B and solution C to obtain a mixed system, then add lye D and solution E to the mixed system simultaneously, and react to synthesize the ternary 811 precursor. After the synthesis is completed, wash, dehydrate, and dry to obtain the precursor Finished product F, particle size 10um.

②Primary mixing and sintering: Weigh a certain amount of the precursor product F and lithium hydroxide G for high-mixer mixing. The precursor product F and lithium hydroxide are fully mixed at a molar ratio of 1:1.03. , calcined at a temperature of 800°C for 10 h to obtain a fired material H.

③ Dealkalization coating: put the one-calcined material H in a three-in-one washing machine, add an appropriate amount of pure water to prepare a saturated lithium silicate solution, the liquid-solid ratio is 2:1, stir and wash for 30 minutes, and continuously add 25g dropwise during the process /L of magnesium sulfate solution for precipitation coating, the zirconium sulfate in the magnesium sulfate solution accounts for 0.25% of the total mass of the one-fired material H, and then feeds nitrogen gas for rapid dehydration, and confirms that the moisture content is less than 5wt% after dehydration.

④ Pre-drying: use a double-cone dryer to pre-dry at 165°C for 8 hours. After drying, put it into a sagger for secondary sintering.

⑤ Coating secondary sintering: Weigh a certain amount of the pre-dried sample and calcinate at 500° C. for 10 h in an oxygen atmosphere to obtain secondary sintering material I.

Example 5

The difference from Example 1 is that the sodium silicate in the solution C in step 1 accounts for 0.02% of the total mass of the first-fired material H.

Example 6

The difference from Example 1 is that the sodium silicate in the solution C in step ① accounts for 1% of the total mass of the first-fired material H.

Comparative example 1

The difference with Example 1 is that step 1. does not add sodium silicate.

Comparative example 2

The difference from Example 1 is that the step ③ dealkalization coating is not carried out, but only water washing is carried out.

Test section:

The positive electrode materials prepared in various examples and comparative examples were used to prepare positive electrode sheets, and assembled into all-electric soft packs for electrochemical performance testing, wherein the negative electrode active material was graphite, and the results are shown in Table 1. specific:

Discharge capacity test: at 25°C, the charge rate is 0.33C, and the discharge rate is 0.33C.

Cycle test: Under the condition of 25°C, the charge rate is 0.5C, the discharge rate is 1C, and the capacity retention rate after 600 cycles is tested.

Table 1

From the comparison between Example 1 and Examples 5-6, it can be seen that the amount of silicate added in the doping stage will affect the doping effect, and then affect the electrochemical performance of the ternary positive electrode material. If the amount of silicate used is too small, it will This will lead to a decrease in cycle performance, an increase in gas production, and a decrease in the first effect; if the amount of silicate is used too much, it will lead to a decrease in capacity and a decrease in the first effect.

From the comparison of Example 1 and Comparative Example 1, it can be seen that if only metal is used for doping but no silicate is used for doping, the cycle will be deteriorated, the gas production will be increased, and the first effect will be reduced.

From the comparison of Example 1 and Comparative Example 2, it can be seen that the present disclosure replaces conventional water washing by dealkalization coating, which is beneficial to improve cycle stability and reduce gas production.

Claims

A method for doping and coating a ternary positive electrode material, the method comprising the following steps:

(1) Using silicate, doped metal source, nickel source, cobalt source and manganese source, a one-step co-precipitation method is used to prepare the ternary cathode material precursor, and one-time sintering to obtain a ternary material co-doped with silicon and doped metal elements Positive material core;

(2) Use a saturated solution of silicate as the bottom liquid to clean the inner core of the ternary positive electrode material, add metal salts during the cleaning process for precipitation coating, and perform secondary sintering after dehydration to obtain the doped and coated Ternary cathode material;

The amount of silicate used in step (1) accounts for 0.05% to 0.5% of the total mass of the inner core of the ternary positive electrode material, and the doping metal in the doping metal source in step (1) is selected from calcium, magnesium, At least one of aluminum, titanium, tungsten, zirconium and scandium.
The method according to claim 1, wherein the amount of the doping metal source in step (1) accounts for 0.05% to 0.5% of the total mass of the core of the ternary positive electrode material.
The method according to claim 1, wherein the silicate in step (1) comprises at least one of sodium silicate and lithium silicate.
The method according to claim 1, wherein the temperature of the primary sintering in step (1) is 650°C-850°C, and the time of the primary sintering is 10h-20h.
The method according to claim 1, wherein, in the cleaning step described in step (2), the metal elements in the metal salt include zirconium, titanium, aluminum, tungsten, magnesium, scandium, vanadium, calcium, strontium, barium, gallium and at least one of indium, in the step of cleaning in step (2), the amount of metal salt used is 0.05% to 0.5% of the total mass of the inner core of the ternary positive electrode material.
The method according to claim 1, wherein the step of cleaning in step (2) comprises: using a silicate saturated solution as the bottom liquid, mixing the inner core of the ternary positive electrode material with the bottom liquid, and the liquid The solid ratio is 1:1-5:1, and the mixing time is 20-60 minutes. During the mixing process, a metal salt solution with a concentration of 10g/L-50g/L is continuously added dropwise to the bottom liquid for precipitation coating.
The method according to claim 1, wherein, the step of pre-drying is carried out before the secondary sintering after the dehydration in step (2), the temperature of the pre-drying is 150° C. to 220° C., and the time of the pre-drying is 3h to 12h, the pre-drying until the water content of the material is less than 0.05wt%.
The method according to claim 1, wherein the atmosphere of the secondary sintering in step (2) is an oxygen-containing atmosphere, the temperature of the secondary sintering is 400°C to 700°C, and the time of the secondary sintering is 2h ~15h.
A ternary positive electrode material prepared by the method according to any one of claims 1-8, the ternary positive electrode material comprising a ternary positive electrode material core co-doped with silicon and doped metal elements, and coated with metal oxide on the surface of the inner core.
A lithium ion battery comprising a positive electrode, a negative electrode and a diaphragm, the positive electrode adopts the ternary positive electrode material according to claim 9.