Method for producing lithium manganese oxide as cathode material for lithium battery by dry mixing

Abstract

The application discloses a method for producing lithium manganese oxide as a positive material of lithium battery by dry mixing, which comprises the following steps: step one, uniformly mixing LiMnO4, manganese dioxide, nano niobium pentoxide, nano aluminum oxide, LiOH powder and boron trioxide at room temperature, and grinding to obtain a mixture; step two, stirring and mixing the mixture in step one and polyvinyl alcohol to obtain a powder mixture; step three, preparing an acidic solution by heating H2O and adding a mixture of prepared anhydrous ethanol and concentrated hydrochloric acid, and stirring to obtain the acidic solution; step four, taking part of the acidic solution and adding to the powder mixture in step two to obtain a suspension; step five, adding the remaining acidic solution into the suspension in step four, and heating to react in a sealed environment; after the reaction is completed, cooling the reaction product to obtain a crystal coated with emulsified glue; step six, sintering and screening the crystal in step five; and step seven, removing iron from the screened material to obtain a product.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and specifically to a method for producing lithium manganese oxide, a cathode material for lithium batteries, using a dry mixing process. Background Technology

[0002] Currently, the main production process for lithium manganese oxide both domestically and internationally is the solid-phase mixing high-temperature synthesis method. The manganese source used is primarily electrolytic MnO2, while lithium sources include Li2CO3, LiOH·H2O, and LiNO3. In traditional solid-phase mixing processes, differences in particle size, hardness, and specific gravity of the raw materials can lead to uneven mixing, thus affecting the quality of the prepared lithium manganese oxide. Summary of the Invention

[0003] The purpose of this invention is to provide a dry mixing method for producing lithium manganese oxide, a cathode material for lithium batteries, to solve the problem of uneven mixing in existing technologies. To achieve the above objective, this invention adopts the following technical solution:

[0004] This invention provides a method for dry mixing to produce lithium manganese oxide, a cathode material for lithium batteries, comprising the following specific steps:

[0005] Step 1: Mix LiMnO4, manganese dioxide, nano niobium pentoxide, nano alumina, LiOH powder, and boron trioxide evenly at room temperature, then grind to obtain a mixture;

[0006] Step 2: Powder mixing: Mix the mixture from Step 1 with polyvinyl alcohol;

[0007] Step 3: Prepare an acidic solution: Heat H2O while adding the prepared mixture of anhydrous ethanol and concentrated hydrochloric acid, and stir to prepare an acidic solution;

[0008] Step 4: Take out a portion of the acidic solution and add it to the powder from Step 2 to mix, thus obtaining a suspension;

[0009] Step 5: Add the remaining acidic solution to the suspension from Step 4, heat in a sealed environment to carry out the reaction, and cool the reactants after the reaction is complete to obtain crystals coated with emulsion gel.

[0010] Step Six: Sinter and sieve the crystals from Step Five;

[0011] Step 7: Remove iron from the screened material to obtain the product.

[0012] Furthermore, in step one, a planetary ball mill is used for grinding, and the grinding time is 30-60 minutes; the ground powder is cooled to room temperature and then mixed with polyvinyl alcohol.

[0013] Furthermore, in step three, the weight ratio of anhydrous ethanol to concentrated hydrochloric acid is (1-2):(98-99); the mass fraction of the concentrated hydrochloric acid is 35-37%; and the pH value of the acidic solution in step three is 3 to 5.

[0014] Furthermore, the ratio of the acidic solution added in step four to the acidic solution added in step four is 1:1.

[0015] Furthermore, the reaction conditions in step five are: reaction temperature 120-300℃, reaction pressure 0.5-0.9Mpa, and reaction time 1-48h.

[0016] Furthermore, the sintering and sieving method in step six is ​​as follows: first, a first sintering is performed, the sintered product is cooled and crushed and sieved; then, the undersize material is taken out, a second sintering is performed, the material after the second sintering is cooled and crushed and sieved to obtain the undersize material.

[0017] Further, the first sintering involves heating to 680–850°C at a heating rate of 1–3°C / min and holding at that temperature for 8–24 hours, then cooling to 80–250°C at a cooling rate of 1–3°C / min, followed by natural cooling; the material after the first sintering is sieved using a double-layer 100–200 mesh screen. The second sintering involves heating to 680–900°C at a heating rate of 1–3°C / min and holding at that temperature for 8–24 hours, then cooling to 80–250°C at a cooling rate of 1–3°C / min, followed by natural cooling; the material after the second sintering is sieved using a double-layer 100–200 mesh screen.

[0018] Furthermore, the molar ratio of LiOH powder to MnO2 in step one is (0.7:2)~

[0019] (1.2:2); The mass ratio between polyvinyl alcohol in step two and LiOH powder in step one is 1:(4-6).

[0020] Furthermore, during the secondary sintering, oxygen is introduced as a combustion aid.

[0021] Furthermore, when the acidic solution is mixed with the powder in step four, the temperature of the acidic solution is 45℃~60℃; when the acidic solution is mixed with the suspension in step five, the temperature of the acidic solution is 60℃~80℃.

[0022] The beneficial effects of this invention are:

[0023] (1) The method for preparing lithium manganese oxide of the present invention first obtains a lithium source mixture in a ball mill, and then coats the mixture with PVA to form crystal nuclei. The powder is mixed first to avoid the influence of the adhesive force of PVA binder and the resistance of water on the mixing when mixing in solution. Then, the pH value of the acidic solution is adjusted to a range of 6-8. The material is strongly alkaline, and stirring and neutralizing with the acidic solution can prevent the material from absorbing water in the later stage. Moreover, since the pH value is adjusted first, the material does not need to be washed again afterward, thus omitting a step. Furthermore, the use of acidic solution for emulsification and coating reduces the adverse reactions caused by strong alkalinity in subsequent stirring and sintering. The process is stirred at a constant temperature, which overcomes the phenomenon of uneven mixing of solid phase mixtures and improves the uniformity of raw material mixing, thereby improving the quality of lithium manganese oxide products.

[0024] (2) The lithium manganese oxide prepared by this method has a specific capacity of more than 128 mAh / g, which is higher than that of lithium manganese oxide obtained by ordinary solid-phase mixing high-temperature synthesis method. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0026] The following will be combined with the appendix Figure 1 The technical solutions of the present invention will be further described in conjunction with the embodiments, so that those skilled in the art can more clearly understand the content of the technical solutions.

[0027] Example 1:

[0028] The present invention discloses a method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing, comprising the following specific steps:

[0029] Step 1: Mix LiMnO4, manganese dioxide, nano niobium pentoxide, nano alumina, LiOH powder, and boron trioxide evenly at room temperature, and grind them using a planetary ball mill for 30-60 minutes. Cool the ground powder to room temperature to obtain a mixture. The molar ratio of LiOH powder to MnO2 is 0.7:2. The mass ratio of polyvinyl alcohol in Step 2 to LiOH powder in Step 1 is 1:4.

[0030] Step 2: Mix the mixture from Step 1 with polyvinyl alcohol at low speed;

[0031] Step 3: Prepare an acidic solution: Prepare a mixture of anhydrous ethanol and concentrated hydrochloric acid, wherein the weight ratio of anhydrous ethanol to concentrated hydrochloric acid is 2:98; the mass fraction of the concentrated hydrochloric acid is 35%; add the mixture to heated water and stir to prepare an acidic solution with a pH value of 3.

[0032] Step 4: Take out a portion of the acidic solution, heat the acid solution to 45°C, add it to the powder from Step 2 and mix to obtain a suspension;

[0033] Step 5: Heat the remaining acidic solution to 60°C and add it to the suspension in Step 4. Heat the solution in a sealed environment to carry out the reaction at a temperature of 120°C, a pressure of 0.5 MPa, and a reaction time of 48 hours. After the reaction is completed, cool the reactants to obtain crystals coated with emulsion gel.

[0034] In this embodiment, the acidic solution is added in two steps, with the ratio of acidic solution added in steps four and five being 1:1. First, the acidic solution is maintained at 45°C to allow the powder from step one to rapidly emulsify and mix with PVA to form a colloid. Then, the remaining solution is heated to 60°C to improve the consistency of the reaction.

[0035] Step Six: Sinter and sieve the crystals from Step Five. The sintering and sieving method in Step Six is ​​as follows: First, perform a primary sintering, then cool and crush the sintered product; then, remove the undersize material and perform a secondary sintering, cooling and crushing the material after the secondary sintering to obtain the undersize material; the primary sintering involves heating to 680℃ at a heating rate of 1-3℃ / min and holding for 8 hours, then cooling to 80℃ at a cooling rate of 1-3℃ / min, followed by natural cooling; the material after the primary sintering is sieved using a double-layer 100-200 mesh screen; the secondary sintering involves heating to 680℃ at a heating rate of 1-3℃ / min and holding for 8 hours, then cooling to 80℃ at a cooling rate of 1-3℃ / min, followed by natural cooling; the material after the secondary sintering is sieved using a double-layer 100-200 mesh screen.

[0036] During the secondary sintering, oxygen is introduced as a combustion aid. Adding a combustion aid during the second calcination can prevent excessive combustion from causing irregularities in the morphology and pore size consistency of the mixture, and can also prevent it from affecting the subsequent material compaction, charge and discharge properties.

[0037] Step 7: Remove iron from the screened material using an iron remover to obtain the product.

[0038] Example 2:

[0039] The present invention discloses a method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing, comprising the following specific steps:

[0040] Step 1: Mix LiMnO4, manganese dioxide, nano niobium pentoxide, nano alumina, LiOH powder, and boron trioxide evenly at room temperature, and grind them using a planetary ball mill for 30-60 minutes. Cool the ground powder to room temperature to obtain a mixture. The molar ratio of LiOH powder to MnO2 is 1.2:2. The mass ratio of polyvinyl alcohol in Step 2 to LiOH powder in Step 1 is 1:6.

[0041] Step 2: Mix the mixture from Step 1 with polyvinyl alcohol at low speed;

[0042] Step 3: Prepare an acidic solution: Prepare a mixture of anhydrous ethanol and concentrated hydrochloric acid, wherein the weight ratio of anhydrous ethanol to concentrated hydrochloric acid is 1:99; the mass fraction of the concentrated hydrochloric acid is 37%; add the mixture to heated water and stir to prepare an acidic solution with a pH value of 5.

[0043] Step 4: Take out half of the acidic solution, heat the acid solution to 60°C, add it to the powder from Step 2 and mix to obtain a suspension;

[0044] Step 5: Heat the remaining half of the acidic solution to 80°C and add it to the suspension in Step 4. Heat the solution in a sealed environment to carry out the reaction at a temperature of 300°C, a pressure of 0.9 MPa, and a reaction time of 1 hour. After the reaction is completed, cool the reactants to obtain crystals coated with emulsion gel.

[0045] Step Six: Sinter and sieve the crystals from Step Five. The sintering and sieving method in Step Six is ​​as follows: First, perform a primary sintering, then cool and crush the sintered product; then, remove the undersize material and perform a secondary sintering, cooling and crushing the material after the secondary sintering to obtain the undersize material; the primary sintering involves heating to 850℃ at a heating rate of 1–3℃ / min and holding for 24 hours, then cooling to 250℃ at a cooling rate of 1–3℃ / min, followed by natural cooling; the material after the primary sintering is sieved using a double-layer 100–200 mesh screen. The secondary sintering involves heating to 900℃ at a heating rate of 1–3℃ / min and holding for 24 hours, then cooling to 250℃ at a cooling rate of 1–3℃ / min, followed by natural cooling; the material after the secondary sintering is sieved using a double-layer 100–200 mesh screen. Oxygen is introduced as a combustion aid during the secondary sintering.

[0046] Step 7: Remove iron from the screened material using an iron remover to obtain the product.

[0047] Example 3:

[0048] The present invention discloses a method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing, comprising the following specific steps:

[0049] Step 1: Mix LiMnO4, manganese dioxide, nano niobium pentoxide, nano alumina, LiOH powder, and boron trioxide evenly at room temperature, and grind them using a planetary ball mill for 30-60 minutes. Cool the ground powder to room temperature to obtain a mixture. The molar ratio of LiOH powder to MnO2 is 1:2. The mass ratio of polyvinyl alcohol in Step 2 to LiOH powder in Step 1 is 1:5.

[0050] Step 2: Mix the mixture from Step 1 with polyvinyl alcohol at low speed;

[0051] Step 3: Prepare an acidic solution: Prepare a mixture of anhydrous ethanol and concentrated hydrochloric acid, wherein the weight ratio of anhydrous ethanol to concentrated hydrochloric acid is 2:99; the mass fraction of the concentrated hydrochloric acid is 35%; add the mixture to heated water and stir to prepare an acidic solution with a pH value of 4.

[0052] Step 4: Take out half of the acidic solution, heat the acid solution to 50°C, add it to the powder from Step 2 and mix to obtain a suspension;

[0053] Step 5: Heat the remaining half of the acidic solution to 70°C and add it to the suspension from Step 4. Heat the solution in a sealed environment to carry out the reaction at a temperature of 200°C, a pressure of 0.7 MPa, and a time of 20 hours. After the reaction is complete, cool the reactants to obtain crystals coated with emulsion gel.

[0054] Step Six: Sinter and sieve the crystals from Step Five. The sintering and sieving method in Step Six is ​​as follows: First, perform a primary sintering, then cool and crush the sintered product; then, remove the undersize material and perform a secondary sintering, cooling and crushing the material after the secondary sintering to obtain the undersize material; the primary sintering involves heating to 750℃ at a heating rate of 1–3℃ / min and holding for 24 hours, then cooling to 100℃ at a cooling rate of 1–3℃ / min, followed by natural cooling; the material after the primary sintering is sieved using a double-layer 100–200 mesh screen; the secondary sintering involves heating to 750℃ at a heating rate of 1–3℃ / min and holding for 24 hours, then cooling to 150℃ at a cooling rate of 1–3℃ / min, followed by natural cooling; the material after the secondary sintering is sieved using a double-layer 100–200 mesh screen. Oxygen is introduced as a combustion aid during the secondary sintering.

[0055] Step 7: Remove iron from the screened material using an iron remover to obtain the product.

[0056] Comparative example:

[0057] Lithium manganese oxide, a cathode material for lithium batteries, was synthesized using a solid-phase mixing high-temperature synthesis method based on existing technology, with MnO2 as the manganese source and LiOH as the lithium source.

[0058] The products obtained in the above embodiments and comparative examples were subjected to relevant tests, and the test results are as follows:

[0059]

Claims

1. A method for producing lithium manganese oxide, a cathode material for lithium batteries, using a dry mixing process, characterized in that... The specific steps include the following: Step 1: Mix LiMnO4, manganese dioxide, nano niobium pentoxide, nano aluminum oxide, LiOH powder, and boron trioxide evenly at room temperature, then grind to obtain a mixture; Step 2: Mix the mixture from Step 1 with polyvinyl alcohol; Step 3: Prepare an acidic solution: Heat H2O while adding the prepared mixture of anhydrous ethanol and concentrated hydrochloric acid, and stir to prepare an acidic solution with a pH value of 3 to 5. Step 4: Take out a portion of the acidic solution and add it to the powder from Step 2 to mix, thus obtaining a suspension; Step 5: Add the remaining acidic solution to the suspension from Step 4, heat in a sealed environment to carry out the reaction, and cool the reactants after the reaction is complete to obtain crystals coated with emulsion gel. Step Six: Sinter and sieve the crystals from Step Five; Step 7: Remove iron from the screened material to obtain the product; The reaction conditions in step five are: reaction temperature 120-300℃, reaction pressure 0.5-0.9Mpa, and reaction time 1-48h; When the acidic solution is mixed with the powder in step four, the temperature of the acidic solution is 45℃~60℃; when the acidic solution is mixed with the suspension in step five, the temperature of the acidic solution is 60℃~80℃.

2. The method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing as described in claim 1, is characterized in that... In step one, a planetary ball mill is used for grinding, and the grinding time is 30-60 minutes; the ground powder is cooled to room temperature and then mixed with polyvinyl alcohol.

3. The method for producing lithium manganese oxide, a cathode material for lithium batteries, using dry mixing as described in claim 1, is characterized in that... In step three, the weight ratio of anhydrous ethanol to concentrated hydrochloric acid is (1~2):(98~99); the mass fraction of the concentrated hydrochloric acid is 35~37%.

4. The method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing as described in claim 1, characterized in that... The ratio of the acidic solution added in step four to the acidic solution added in step five is 1:

1.

5. The method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing as described in claim 1, characterized in that... The sintering and sieving method in step six is ​​as follows: First, sintering is performed once, the sintered product is cooled and crushed and sieved; then the undersize material is taken out, sintered a second time, the material after the second sintering is cooled and crushed and sieved to obtain the undersize material.

6. The method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing as described in claim 5, is characterized in that... The first sintering process involves heating the material to 680-850℃ at a heating rate of 1-3℃ / min and holding it at that temperature for 8-24 hours, then cooling it down to 80-250℃ at a cooling rate of 1-3℃ / min, followed by natural cooling. The material after the first sintering is sieved using a double-layer 100-200 mesh screen. The second sintering process involves heating the material to 680-900℃ at a heating rate of 1-3℃ / min and holding it at that temperature for 8-24 hours, then cooling it down to 80-250℃ at a cooling rate of 1-3℃ / min, followed by natural cooling. The material after the second sintering is sieved using a double-layer 100-200 mesh screen.

7. The method for producing lithium manganese oxide, a cathode material for lithium batteries, by dry mixing as described in claim 1, characterized in that, The molar ratio between LiOH powder and MnO2 in step one is (0.7:2) to (1.2:2); the mass ratio between polyvinyl alcohol and LiOH powder in step two is 1:(4~6).

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