CN107611371A - A kind of high circulation and constitutionally stable ternary material preparation method - Google Patents

Abstract

The present invention is applicable to the field of lithium battery cathode materials, and provides a high-cycle and structurally stable ternary material preparation method, comprising: using nickel-cobalt-manganese ternary material precursors with different particle sizes and mixing them with lithium sources respectively, and doping F salt, Co salt, and Si oxides to obtain ternary materials with different median particle sizes, and then mix the ternary materials with the same median particle size in proportion, and the material is coated with lithium silicate to obtain the final high cycle and Structurally stable nickel-cobalt-manganese ternary material. The use of precursors with different particle sizes can achieve high material density and high capacity; use different ion doping to reduce the characteristics of cation mixing, stabilize the structure of the material, increase the electrical conductivity of the material, and improve the cycle performance of the material. Finally, coating the material with lithium silicate can form a lithium silicate protective film on the surface of the material, increasing the electrical conductivity of the material and stabilizing the structure of the material.

Description

A preparation method of ternary material with high cycle and stable structure

technical field

The invention belongs to the technical field of cathode materials for lithium batteries, and in particular relates to a preparation method of a ternary material with high cycle and stable structure.

Background technique

NCM nickel-cobalt-manganese ternary material has the advantages of large discharge capacity, good cycle performance, and low manufacturing cost. It is currently a widely used cathode material for lithium-ion batteries, especially in power batteries, and has a broad market and application prospects.

In order to further meet the market's requirements for ternary materials, ternary materials are developing in the direction of high capacity, high cycle, high safety performance and stable structure. Studies have shown that the performance of NCM ternary materials will decay faster and faster as the number of cycles increases. In order to overcome this problem, the method of doping and covering ternary materials is widely used to stabilize the structure of the material, thereby improving the stability and cycle performance of the material.

The main NCM523 ternary material on the market today has a first discharge capacity of 168mAh/g at a charge rate of 1.2C and a discharge rate of 0.25C under the normal 4.3V condition of 25°C. Cycle at 1.0C discharge rate, the capacity of the 50th cycle is 153mAh/g, and the capacity retention rate is about 95%, which still has a certain gap with the market demand.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a high-cycle and structurally stable ternary material preparation method, aiming to solve the technical problems of the existing NCM523 ternary material with poor capacity, cycle performance, and high-temperature storage performance.

The present invention adopts following technical scheme:

The preparation method of the ternary material with high circulation and stable structure comprises the following steps:

S1. Prepare nickel-cobalt-manganese ternary material precursors with different median particle sizes, mix and ball-mill the nickel-cobalt-manganese ternary material precursors with each median particle size with lithium source and doping compound, and then sinter and crush , sieving, and finally obtain a variety of ternary materials with different median particle sizes;

S2, mixing the obtained ternary materials with different median particle sizes in proportion to obtain a mixed ternary material;

S3. Add the mixed ternary material into deionized water and stir, then dropwise add lithium silicate aqueous solution and continue to stir, after the reaction is completed, filter the obtained slurry, evaporate to dryness, dry, and finally sinter, crush, and sieve Get the target ternary material.

Further, in step S1, the lithium source, the doping compound and the nickel-cobalt-manganese ternary material precursor with a median particle size of Mμm are mixed and ball-milled, and then ternary material B1 is obtained through sintering, crushing, and sieving; the lithium Source, doping compound and nickel-cobalt-manganese ternary material precursor with median particle size Nμm are mixed and ball-milled, and then ternary material B2 is obtained through sintering, crushing, and sieving, where M is greater than N; in step S2, the three The primary materials B1 and B2 are mixed according to the ratio of 5:5 to 8:2 to obtain the mixed ternary material B3.

Further, when preparing the ternary materials B1 and B2, the molar ratio Ni:Co:Mn=0.5:0.2:0.3 in the nickel-cobalt-manganese ternary material precursor, the lithium source and the nickel-cobalt-manganese ternary material precursor The molar ratio Li/(Ni+Co+Mn)=1.01～1.05, the lithium source, the doping compound and the nickel-cobalt-manganese ternary material precursor are carried out in a planetary ball mill at a rotation speed of 300r/min and a revolution speed of 10r/min Mix the materials for 1-3 hours to obtain blended powder. During sintering, heat the blended powder to T1 at a rate of 1.5-5°C/min and keep the temperature constant for 1-3 hours, then continue to heat up to T2 at a rate of 1.5-5°C/min and keep the temperature at 8-8 15h, then crushed and sieved to obtain ternary materials; the median particle size of the obtained ternary material B1 was 12-16 μm, and the median particle size of the obtained ternary material B2 was 5-9 μm.

Further, M is 12-16 μm, N is 5-9 μm, and the dopant compound is a nanoscale material with a median particle size <50 nm.

Further, the doping compound is a mixture of F salt, Co salt, and Si oxide, wherein the F salt is one or more of NaF, LiF, MgF ₂ , CaF ₂ , and the Co salt is Co3O4, CoC2O4 , CoCO3, Co (OH) 3 in one or more, the oxide of Si is α-SiO2, β-SiO2 in one or both.

Further, the temperature T1 is 180-250°C, and the temperature T2 is 890-950°C.

Further, the preparation process of the lithium silicate aqueous solution added dropwise in step S3 is as follows:

Pass the silicate through a cation exchange resin to obtain a SiO2 solution, react the SiO2 solution with an aqueous lithium hydroxide solution, stir for 20-60 minutes to obtain a dilute lithium silicate solution, and then place the obtained dilute lithium silicate solution at a temperature of 50-90°C Evaporating and concentrating at the bottom to obtain a lithium silicate aqueous solution with a concentration of 10% to 50%.

Further, the silicate is one or more of MgSiO3, K2SiO3, Na2SiO3, the concentration of the SiO2 solution is 2%-5%, and the particle size of SiO2 in the SiO2 solution is 1-4nm.

Further, step S3 is specifically:

Add the mixed ternary material into deionized water and stir in a magnetic stirrer for 5-20 minutes, add the lithium silicate solution evenly and slowly with a dropper within 3-5 minutes, and then continue magnetic stirring while heating for 20-20 minutes. 60min, control the water temperature at 60-90°C, then pour the heated and stirred material into the Buchner funnel for suction filtration, transfer the material into a rotary evaporator to evaporate the material after suction filtration, and control the water temperature at 70-85°C , and then take out the evaporated material and place it in a vacuum drying oven for 6-12 hours at 100-180°C. During sintering, the vacuum-dried material is heated to T3 at a rate of 1.5-3.5°C/min and kept at a constant temperature for 1-3 hours. Continue to raise the temperature to T4 at a rate of 1.5-3.5°C/min and keep the temperature constant for 4-8 hours, and finally obtain the target ternary material after crushing and sieving.

Further, the evaporation water temperature of the rotary evaporator is 70-85°C, the temperature T3 is 180-250°C, and the temperature T4 is 550-650°C.

The beneficial effects of the present invention are: the present invention uses nickel-cobalt-manganese ternary material precursors of different particle sizes to be mixed with lithium sources respectively, and doped with F salt, Co salt, and Si oxides to achieve high density and high capacity use of different ion doping to reduce the characteristics of cation mixing, stabilize the structure of the material, increase the conductivity of the material, and improve the cycle performance of the material, and the slurry will not form a jelly shape during coating, which improves the coating Process and material performance; finally, coating the material with lithium silicate can form a lithium silicate protective film on the surface of the material, increasing the conductivity of the material and stabilizing the structure of the material. After modification, the capacity, cycle performance, and high-temperature storage performance of the ternary material are greatly improved, and the manufacturing process is simple and easy to process.

Description of drawings

Fig. 1 is the flow chart of the present invention is the ternary material preparation method of high circulation and stable structure;

Fig. 2 is the electron micrograph figure of embodiment one gained ternary material;

Fig. 3 is a graph showing the relationship between the number of cycles and the discharge capacity of button batteries made of ternary materials prepared in Example 1, Example 2 and Comparative Example 1 at a voltage of 4.3V.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1, the high cycle and structurally stable ternary material preparation method provided by the present invention comprises the following steps:

S1. Prepare nickel-cobalt-manganese ternary material precursors with different median particle sizes, mix and ball-mill the nickel-cobalt-manganese ternary material precursors with each median particle size with lithium source and doping compound, and then sinter and crush , sieving, and finally obtain a variety of ternary materials with different median particle sizes;

S2, mixing the obtained ternary materials with different median particle sizes in proportion to obtain a mixed ternary material;

S3. Add the mixed ternary material into deionized water and stir, then dropwise add lithium silicate aqueous solution and continue to stir, after the reaction is completed, filter the obtained slurry, evaporate to dryness, dry, and finally sinter, crush, and sieve Get the target ternary material.

The present invention firstly prepares a variety of nickel-cobalt-manganese ternary material precursors with different median particle sizes, and then adds lithium source and doping compound to these ternary material precursors, and obtains them through ball milling, sintering, crushing and sieving A variety of ternary materials with different median particle sizes. Then these ternary materials with different median particle sizes are mixed according to a certain ratio to obtain a mixed ternary material, and finally the mixed ternary material is wet-coated with lithium silicate to obtain NCM523 cathode material with superior performance.

Since the mixed ternary material is obtained by mixing nickel-cobalt-manganese ternary materials with different median particle sizes, the gaps of the large-grained ternary materials can be filled with small-grained ternary materials, making the mixed ternary materials more dense, and the final quilt Lithium batteries have a higher capacity. Moreover, the precursor is doped with F salt, Co salt, and Si oxide to form Me-F bond and Si-O bond to reduce the characteristics of cation mixing, stabilize the structure of the material, increase the conductivity of the material, and improve the cycle performance. Finally, the material is coated with lithium silicate, which can form a lithium silicate protective film on the surface of the material, increase the electrical conductivity of the material and stabilize the structure of the material.

Generally, two kinds of nickel-cobalt-manganese ternary material precursors with median particle size can be selected and mixed with lithium source and doping compound to obtain two kinds of ternary material B1 and B2 with median particle size. In fact, it is also possible to select three or more nickel-cobalt-manganese ternary material precursors with a median particle size according to needs to obtain three or more ternary materials with a median particle size, which are all within the protection scope of the present invention within.

In step S1, when mixing lithium source, nickel-cobalt-manganese ternary material precursor and doping compound, Li/Me=1.01～1.05, namely Li/(Ni+Co+Mn)=1.01～1.05, nickel-cobalt-manganese Ni:Co:Mn=0.5:0.2:0.3 in the element material precursor. Among the two nickel-cobalt-manganese ternary material precursors with median particle sizes, one has a median particle size of 12-16 μm, and the other has a median particle size of 5-9 μm. The median particle size of the finally obtained ternary material B1 is 12-16 μm, and the median particle size of the obtained ternary material B2 is 5-9 μm.

In order to illustrate the technical solutions of the present invention, specific examples are used below to illustrate.

Embodiment one:

Select Ni _0.5 Co _{0.2 Mn 0.3 (OH) 2 with a median particle size of 15 μm, and weigh Ni 0.5 Co 0.2 Mn 0.3 ( OH ) 2 ,} Li ₂ CO ₃ and doping compound according to Li/Me=1.03, and dope The doping amount of F element in the compound is 1500ppm, the doping amount of Si element is 1500ppm, and the doping amount of Co element is 12000ppm. They were ball milled and mixed for 2 hours, then placed in a roasting furnace, and roasted at 910°C for 10 hours in an air atmosphere. After the roasted product was crushed and sieved, an NCM523 ternary material with a D ₅₀ of 14.0 μm was obtained.

Select Ni _{0.5 Co 0.2 Mn 0.3 (OH) 2 with a median particle size of 6 μm, and weigh Ni 0.5 Co 0.2 Mn 0.3 ( OH ) 2 ,} Li ₂ CO ₃ and doping compound according to Li/Me=1.03, doping The doping amount of F element in the compound is 1500ppm; the doping amount of Si element is 1500ppm, and the doping amount of Co element is 12000ppm. They were ball milled and mixed for 2 hours, and then calcined at 900°C for 10 hours in an air atmosphere; after the calcined product was crushed and sieved, an NCM523 ternary material with a D ₅₀ of 8.0 μm was obtained.

Weigh two ternary materials with D ₅₀ =14.0 μm and D ₅₀ =8.0 μm according to the mass ratio of 7:3 and mix them evenly. Take 300 g of the mixture and add it to 200 g of deionized water, place it on a magnetic stirrer and stir for 15 minutes Then use a dropper to uniformly add the prepared lithium silicate solution with a concentration of 25% into it within 3 minutes, and then start heating while magnetically stirring. The stirring time is 30 minutes, and the water temperature is 70°C.

Pour the material on the magnetic stirrer into a Buchner funnel for suction filtration for 20 minutes, then import the filtered material into a rotary evaporator and evaporate to dryness at 80°C, and place the evaporated material in a vacuum drying oven at 120°C Dry for 10h. Then put the vacuum-dried material into a box-type furnace, and finally raise the temperature of the vacuum-dried material to 220°C at a constant temperature of 2 hours at 3°C/min, and then heat it to 600°C at a constant temperature of 2°C/min for 5 hours for calcination. 1. After sieving, the NCM523 ternary material with a D ₅₀ of 12.2 μm was obtained. Its electron micrograph is shown in Fig. 2.

Embodiment two:

Select Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ with a median particle size of 15 μm, and weigh Ni _0.5 Co _0.2 Mn _0.3 O ₂ , Li ₂ CO ₃ and the doping compound according to Li/Me=1.03, and the doping compound The doping amount of F element is 2000ppm; the doping amount of Si element is 2000ppm. They were ball milled and mixed for 3 hours, then placed in a roaster, and roasted at 930°C for 10 hours in an air atmosphere; after the roasted product was crushed and sieved, an NCM523 ternary material with a D ₅₀ of 14.0 μm was obtained.

Select Ni _{0.5 Co 0.2 Mn 0.3 (OH) 2 with a median particle size of 6 μm, and weigh the source of Ni 0.5 Co 0.2 Mn 0.3 ( OH ) 2 ,} Li ₂ CO ₃ and each doping element according to Li/Me=1.03 compound, wherein the doping amount of F element is 2000ppm; the doping amount of Si element is 2000ppm, and the doping amount of Co element is 12000ppm. They were ball milled and mixed for 3 hours, then placed in a roasting furnace, and roasted at 920°C for 10 hours in an air atmosphere; after the roasted product was crushed and sieved, an NCM523 ternary material with a D ₅₀ of 8.0 μm was obtained.

Mix the materials with D ₅₀ = 14.0 μm and D ₅₀ = 8.0 μm evenly according to the mass ratio of 6:4, take 300g of the mixture, add 200g of deionized water, put it on a magnetic stirrer and stir for 15min, then use a dropper to prepare the mixture Lithium silicate solution with a concentration of 25% was uniformly added therein within 3 minutes, and then heated while magnetic stirring was started, the stirring time was 20 minutes, and the water temperature was 80°C.

Pour the material on the magnetic stirrer into the Buchner funnel and suction filter for 20 minutes, then import the filtered material into a rotary evaporator and evaporate it to dryness at 80°C, and place the evaporated material in a vacuum drying oven at 150°C under vacuum Dry for 6h. Then put the vacuum-dried material into a box-type furnace and heat up to 220°C for 2 hours at 3°C/min, then heat up to 700°C for 5 hours at 2°C/min for calcination. After crushing and sieving, the D ₅₀ is 11.6μm NCM523 ternary material.

Comparative example one:

Select 15 μm Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ and 6 μm Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ at a mass ratio of 7:3, and mix with Li ₂ CO ₃ according to Li/Me=1.03 ball milling for 3 hours . Place in a roasting furnace and roast at 920°C for 10 h in a dry air atmosphere; crush and sieve the roasted product to obtain NCM523 ternary material with a D ₅₀ of 12.2 μm.

The NCM523 ternary material finally prepared by the above-mentioned Example 1, Example 2 and Comparative Example 1 was tested for electrochemical performance of the obtained material according to the following method: the NCM523 ternary material was used as the positive electrode active material, and the lithium sheet was used as the negative electrode. Assemble the button battery. In the positive electrode sheet, m (active material): m (acetylene black): m (PVDF) = 8:1:1, using the blue electric test system for testing, the charge and discharge voltage is 2.7 ~ 4.3V, and the cycle is carried out at 25 ° C Performance Testing. Figure 3 shows the relationship between the number of cycles and the discharge capacity of the button batteries made of ternary materials prepared in Example 1, Example 2 and Comparative Example 1 at a voltage of 4.3V.

In Example 1, the first discharge capacity of the battery at 1.2C charge rate and 0.25C discharge rate can reach 171.1mAh/g, and the first charge and discharge efficiency can reach 87%. The discharge capacity of the ring is 156.8mAh/g, the capacity retention rate is 96.9%, and the cycle performance has been significantly improved.

In Example 1, the first discharge capacity of the battery at 1.2C charge rate and 0.25C discharge rate can reach 170.8mAh/g, and the first charge and discharge efficiency can reach 87.1%. Cycle at 1.2C charge rate and 1.0C discharge rate, the 50th The discharge capacity of the ring is 156.6mAh/g, the capacity retention rate is 97.0%, and the cycle performance has been significantly improved.

In Comparative Example 1, the first discharge capacity of the battery at 1.2C charge rate and 0.25C discharge rate can reach 168.3mAh/g, and the first charge and discharge efficiency can reach 86.2%. Cycle at 1.2C charge rate and 1.0C discharge rate, the 50th The discharge capacity of the ring was 152.2mAh/g, the capacity retention rate was 94.6%, and the cycle performance was poor.

From the accompanying drawings 3 and the test results of Example 1, Example 2, and Comparative Example 1, the precursors of the two examples are doped with F salt, Co salt, and Si oxides, while the comparative examples are combined Undoped, the cycle performance of the material can be significantly improved after doping. In addition, Example 1, Example 2, and Comparative Example 1 all used two kinds of nickel-cobalt-manganese ternary material precursors with median particle sizes to prepare ternary materials, and the first discharge capacity and first charge-discharge capacity of the finally obtained NCM523 ternary material The efficiency is very high, which is conducive to improving the battery capacity.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (10)

1. A high cycle and structurally stable ternary material preparation method, characterized in that said method may further comprise the steps: S1. Prepare nickel-cobalt-manganese ternary material precursors with different median particle sizes, mix and ball-mill the nickel-cobalt-manganese ternary material precursors with each median particle size with lithium source and doping compound, and then sinter and crush , sieving, and finally obtain a variety of ternary materials with different median particle sizes; S2, mixing the obtained ternary materials with different median particle sizes in proportion to obtain a mixed ternary material; S3. Add the mixed ternary material into deionized water and stir, then dropwise add lithium silicate aqueous solution and continue to stir, after the reaction is completed, filter the obtained slurry, evaporate to dryness, dry, and finally sinter, crush, and sieve Get the target ternary material. 2. The ternary material preparation method with high circulation and stable structure as claimed in claim 1, characterized in that, in step S1, the lithium source, the doping compound and the nickel-cobalt-manganese ternary material precursor with a median particle size of M μm Mix and ball mill the body, then sinter, crush, and sieve to obtain the ternary material B1; mix and ball-mill the lithium source, doping compound, and nickel-cobalt-manganese ternary material precursor with a median particle size of Nμm, and then sinter and crush and sieving to obtain the ternary material B2, where M is greater than N; in step S2, mix the ternary materials B1 and B2 according to the ratio of 5:5 to 8:2 to obtain the mixed ternary material B3. 3. The ternary material preparation method with high circulation and stable structure as claimed in claim 2, characterized in that, when preparing ternary materials B1 and B2, the molar ratio Ni in the nickel-cobalt-manganese ternary material precursor: Co : Mn=0.5:0.2:0.3, the molar ratio Li/(Ni+Co+Mn)=1.01～1.05 between the lithium source and the nickel-cobalt-manganese ternary material precursor, the lithium source, the doping compound and the nickel-cobalt-manganese ternary material The material precursor is mixed in a planetary ball mill at a rotation speed of 300r/min and a revolution speed of 10r/min for 1-3 hours to obtain a blended powder. During sintering, the blended powder is heated to T1 at a rate of 1.5-5°C/min and kept at a constant temperature for 1 ~3h, then continue to heat up to T2 at a rate of 1.5~5°C/min and keep the temperature constant for 8~15h, then crush and sieve to obtain the ternary material; the median particle size of the obtained ternary material B1 is 12~16μm, The median particle size of the obtained ternary material B2 is 5-9 μm. 4. The method for preparing a ternary material with high circulation and stable structure as claimed in claim 3, characterized in that M is 12-16 μm, N is 5-9 μm, the doping compound is a nano-scale material, and the median particle size <50nm. 5. the ternary material preparation method of high cycle and structural stability as claimed in claim 4, is characterized in that, is the mixing of the oxide compound of F salt, Co salt, Si in the described doping compound, and wherein F salt is NaF, One or more of LiF, MgF ₂ , CaF ₂ , Co salt is one or more of Co ₃ O ₄ , CoC ₂ O ₄ , CoCO ₃ , Co(OH) ₃ , Si oxide is α One or both of -SiO ₂ and β-SiO ₂ . 6 . The method for preparing a high-cycle and structurally stable ternary material according to claim 3 , wherein the temperature T1 is 180-250° C., and the temperature T2 is 890-950° C. 7. The ternary material preparation method with high circulation and stable structure as claimed in claim 1, wherein the preparation process of the aqueous solution of lithium silicate added dropwise in step S3 is as follows: Pass the silicate through a cation exchange resin to obtain a _SiO2 solution, react the _SiO2 solution with an aqueous solution of lithium hydroxide, stir for 20-60 minutes to obtain a dilute lithium silicate solution, and then place the dilute lithium silicate solution at 50-90 Evaporating and concentrating at a temperature of °C to obtain a lithium silicate aqueous solution with a concentration of 10% to 50%. 8. The method for preparing a high cycle and structurally stable ternary material according to claim 7, wherein the silicate is one or more of MgSiO ₃ , K ₂ SiO ₃ , Na ₂ SiO ₃ , The concentration of the SiO ₂ solution is 2%-5%, and the SiO ₂ particle diameter in the SiO ₂ solution is 1-4nm. 9. The method for preparing a high cycle and structurally stable ternary material according to claim 1, wherein step S3 is specifically: Add the mixed ternary material into deionized water and stir in a magnetic stirrer for 5-20 minutes, add the lithium silicate solution evenly and slowly with a dropper within 3-5 minutes, and then continue magnetic stirring while heating for 20-20 minutes. 60min, control the water temperature at 60-90°C, then pour the heated and stirred material into the Buchner funnel for suction filtration, transfer the material into a rotary evaporator to evaporate the material after suction filtration, and control the water temperature at 70-85°C , and then take out the evaporated material and place it in a vacuum drying oven for 6-12 hours at 100-180°C. During sintering, the vacuum-dried material is heated to T3 at a rate of 1.5-3.5°C/min and kept at a constant temperature for 1-3 hours. Continue to raise the temperature to T4 at a rate of 1.5-3.5°C/min and keep the temperature constant for 4-8 hours, and finally obtain the target ternary material after crushing and sieving. 10. The method for preparing ternary materials with high circulation and stable structure according to claim 9, characterized in that the evaporation water temperature of the rotary evaporator is 70-85°C, the temperature T3 is 180-250°C, and the temperature T4 is 550-650°C.