Cobaltosic oxide for O2-phase lithium cobalt oxide as well as preparation method and application of cobaltosic oxide

Abstract

The invention discloses cobaltosic oxide for O2-phase lithium cobalt oxide as well as a preparation method and application of the cobaltosic oxide. The porosity of the cobaltosic oxide is increased along the direction from inside to outside. The porosity of the cobaltosic oxide is increased from inside to outside, so that when the cobaltosic oxide is applied to the preparation of O2-phase lithium cobalt oxide, the ion exchange process of sodium cobalt oxide can be improved, the preparation of O2-phase lithium cobalt oxide is facilitated, and the performance of a lithium ion battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to cobalt tetroxide for O2-phase lithium cobaltate, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries, with their advantages of high specific energy and excellent cycle performance, are widely used in a variety of fields, including aerospace, automotive, and portable consumer electronics. Common cathode materials for lithium-ion batteries include lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and nickel-cobalt-manganese ternary cathode materials. Lithium cobalt oxide is widely used due to its stable structure, high specific capacity, and high operating voltage.

[0003] O3-phase lithium cobalt oxide (LCO) materials, with their high density and high capacity, have become the preferred cathode material for lithium-ion batteries used in portable consumer electronics. Increasing voltage is the primary method for increasing the energy density of LCO batteries. However, increasing the voltage of LCO to above 4.55V for O3-phase LCO materials faces significant challenges. The O2-type structure offers superior electrochemical performance at high voltages.

[0004] The cobalt tetroxide currently on the market matches the O3 phase lithium cobaltate, which requires a uniform distribution of doping elements and a high tap density. O2 phase lithium cobaltate requires the preparation of sodium cobaltate first, and then ion exchange to obtain O2 phase lithium cobaltate. For example, CN119153664A discloses a lithium cobalt oxide positive electrode material with an O2 phase structure and its preparation method and application. The preparation method comprises: step S1, uniformly mixing a cobalt source material, a sodium source material, an M element-containing material, and an M' element-containing material in proportion to obtain a mixed material; step S2, calcining the mixed material at a high temperature to obtain an intermediate product; step S3, weighing a certain amount of lithium compound and dissolving it in pure water to obtain a lithium compound aqueous solution; step S4, weighing the intermediate product according to a certain Li / Na molar ratio, adding it to the lithium compound aqueous solution for ion exchange to obtain an ion exchanged product; step S5, washing and drying the ion exchanged product to obtain a lithium cobalt oxide positive electrode material. Therefore, in order to improve the ion exchange efficiency, it is particularly important to increase the porosity of the precursor. The cobalt tetroxide currently on the market is no longer suitable for the preparation of O2 phase lithium cobalt oxide.

[0005] Therefore, providing a cobalt trioxide for O2 phase lithium cobaltate that can facilitate ion exchange and thus improve the performance of O2 phase lithium cobaltate is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In view of the above technical problems existing in the prior art, the purpose of the present invention is to provide a cobalt trioxide for O2 phase lithium cobaltate and its preparation method and application.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a cobalt trioxide for O2-phase lithium cobaltate, wherein the porosity of the cobalt trioxide increases from the inside to the outside.

[0009] Since the porosity of the cobalt trioxide of the present invention increases from the inside to the outside, when it is used to prepare O2 phase lithium cobalt oxide, the ion exchange process of sodium cobalt oxide can be improved, thereby facilitating the preparation of O2 phase lithium cobalt oxide and further improving the performance of lithium ion batteries.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0011] Preferably, the porosity increases in a gradient, or the porosity increases continuously.

[0012] In the cobalt oxide of the present invention, the porosity gradient increases, which means that there are multiple layers with different porosities along the direction away from the center, and the porosity of each layer is the same within the thickness range.

[0013] In the cobalt oxide of the present invention, the continuous increase in porosity means that there are no multiple layer structures in the material in the direction away from the center, and the increase in porosity is continuous rather than a step-by-step change.

[0014] Preferably, the porosity of the cobalt trioxide is 25% to 35%, for example, it can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%.

[0015] In a second aspect, the present invention provides a method for preparing cobalt trioxide for O2-phase lithium cobaltate as described in the first aspect, the preparation method comprising the following steps:

[0016] (1) injecting a cobalt salt solution and a precipitant solution into a reactor at a certain flow rate, wherein as time goes by, the flow rate v1 of the cobalt salt solution and the flow rate v2 of the precipitant solution both increase, and the reaction produces cobalt carbonate;

[0017] The pH of the reaction is 7.0 to 7.1; the temperature of the reaction is 50° C. to 60° C.;

[0018] (2) calcining the cobalt carbonate to obtain the cobalt trioxide.

[0019] In the method of the present invention, the reaction temperature is 50°C to 60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C.

[0020] In the method of the present invention, as time goes by, the flow rates of the cobalt salt solution and the precipitant solution both increase, and by maintaining a relatively low pH and a relatively high reaction temperature, the growth rate can be increased, thereby increasing the porosity of the cobalt trioxide from the inside out.

[0021] The method of the invention is simple, easy to operate and suitable for industrial production.

[0022] Preferably, the concentration of the cobalt salt solution is 1 mol / L to 2.5 mol / L, for example, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.7 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L or 2.5 mol / L.

[0023] Preferably, the precipitant solution is an aqueous solution of ammonium bicarbonate.

[0024] Preferably, the concentration of the precipitant solution is 150 g / L to 250 g / L, for example, it can be 150 g / L, 155 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L or 250 g / L, etc.

[0025] Preferably, v1 is 50L / h to 150L / h, for example, it can be 50L / h, 55L / h, 60L / h, 65L / h, 70L / h, 75L / h, 80L / h, 85L / h, 90L / h, 95L / h, 100L / h, 105L / h, 110L / h, 115L / h, 120L / h, 125L / h, 130L / h, 135L / h, 140L / h, 145L / h or 150L / h, etc. v2 is 150L / h to 250L / h, for example, it can be 150L / h, 160L / h, 170L / h, 180L / h, 190L / h, 200L / h, 210L / h, 220L / h, 230L / h, 240L / h or 250L / h.

[0026] Preferably, v1 and v2 increase gradually; or, v1 and v2 increase continuously.

[0027] In the method of the present invention, the gradient increase of v1 and v2 means that after the two increase, they remain unchanged for a period of time, so that the porosity of the obtained layer is fixed.

[0028] In the method of the present invention, the continuous increase of v1 and v2 means that the two continue to increase until the end of the reaction without remaining unchanged.

[0029] Preferably, v1 and v2 continue to rise, and v1 increases by 0.01L / min to 0.08L / min (for example, 0.01L / min, 0.02L / min, 0.03L / min, 0.04L / min, 0.05L / min, 0.06L / min, 0.07L / min or 0.08L / min, etc.), and v2 increases by 0.01L / min to 0.05L / min (for example, 0.01L / min, 0.02L / min, 0.03L / min, 0.04L / min or 0.05L / min, etc.). This scheme can obtain a suitable porosity distribution, maintain structural stability and excellent ion exchangeability, and is conducive to the preparation of O3 phase lithium cobalt oxide.

[0030] Preferably, the reaction is accompanied by stirring, and the stirring rate is 200 rpm to 500 rpm, for example, it can be 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 325 rpm, 350 rpm, 375 rpm, 400 rpm, 420 rpm, 450 rpm, 470 rpm or 500 rpm.

[0031] Preferably, the reaction is stopped when the particle size D50 of the cobalt carbonate reaches 6 μm to 12 μm. For example, D50 can be 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm.

[0032] Preferably, after the reaction in step (1) is completed, the product is washed with hot water and dried to obtain the cobalt carbonate.

[0033] Preferably, the temperature of the hot water is 70°C to 80°C, for example, 70°C, 72°C, 74°C, 75°C, 77°C, 78°C or 80°C.

[0034] Preferably, the drying method is oven drying, and the oven drying temperature is 100°C to 180°C, for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C, etc.

[0035] Preferably, the calcination temperature is 350°C to 450°C, for example, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C or 450°C.

[0036] Preferably, the calcination time is 8 h to 10 h, for example, 8 h, 8.5 h, 9 h, 9.5 h or 10 h.

[0037] In a third aspect, the present invention provides an O2-phase lithium cobaltate, wherein the O2-phase lithium cobaltate is prepared using the cobalt trioxide described in the first aspect.

[0038] In a fourth aspect, the present invention provides a lithium-ion battery, comprising the O2-phase lithium cobalt oxide described in the third aspect.

[0039] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention provides a cobalt trioxide for O2-phase lithium cobalt oxide. Since the porosity increases from the inside to the outside, when it is used in the preparation of O2-phase lithium cobalt oxide, the ion exchange process of sodium cobalt oxide can be improved, thereby facilitating the preparation of O2-phase lithium cobalt oxide and further improving the performance of lithium-ion batteries.

[0042] (2) The cobalt oxide of the present invention is used to prepare O2-phase lithium cobalt oxide, which can improve its electrochemical performance. The battery prepared by using the cobalt oxide of the present invention to prepare O2-phase lithium cobalt oxide and assembled has high discharge capacity and good cycle performance. Its 0.1C discharge capacity is above 210.9 mAh / g, preferably above 213.6 mAh / g; the capacity retention rate after 100 cycles of 0.2C / 0.2C is above 82.3%, preferably above 91.2%. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0044] Example 1

[0045] This embodiment provides a cobalt oxide for O2-phase lithium cobaltate, wherein the porosity of the cobalt oxide is 25%.

[0046] This embodiment also provides a method for preparing the above-mentioned cobalt trioxide, comprising the following steps:

[0047] Step 1, preparing 2 mol / L cobalt sulfate solution as cobalt salt solution A and 200 g / L ammonium bicarbonate solution as precipitant solution B;

[0048] Step 2: Cobalt salt solution A and precipitant solution B were injected into the reactor at a rate of 100 L / h and 200 L / h, respectively. The flow rate of solution A was increased by 0.01 L / min, and the flow rate of solution B was increased by 0.02 L / min. During the reaction, the pH was maintained at 7.0, the reaction temperature was 55° C., and the stirring rate was 300 rpm. Feeding was stopped when D50 grew to 8 μm.

[0049] Step 3, washing the material with 70°C hot water;

[0050] Step 4, drying the washed material at 120° C. to obtain cobalt carbonate;

[0051] Step 5: calcining the obtained cobalt carbonate at 400° C. for 10 h to obtain cobalt trioxide with high porosity.

[0052] Example 2

[0053] This embodiment provides a cobalt oxide for O2-phase lithium cobaltate, wherein the porosity of the cobalt oxide is 30%.

[0054] This embodiment also provides a method for preparing the above-mentioned cobalt trioxide, comprising the following steps:

[0055] Step 1, preparing 2.5 mol / L cobalt sulfate solution as cobalt salt solution A, and 250 g / L ammonium bicarbonate solution as precipitant solution B;

[0056] Step 2: Cobalt salt solution A and precipitant solution B were injected into the reactor at a rate of 80 L / h and 175 L / h, respectively. The flow rate of solution A was increased by 0.02 L / min, and the flow rate of solution B was increased by 0.04 L / min. During the reaction, the pH was maintained at 7.0, the reaction temperature was 50°C, and the stirring rate was 200 rpm. Feeding was stopped when D50 grew to 7 μm.

[0057] Step 3, washing the material with 80°C hot water;

[0058] Step 4, drying the washed material at 100° C. to obtain cobalt carbonate;

[0059] Step 5: calcining the obtained cobalt carbonate at 370° C. for 10 h to obtain cobalt trioxide with high porosity.

[0060] Example 3

[0061] This embodiment provides a cobalt oxide for O2-phase lithium cobaltate, wherein the porosity of the cobalt oxide is 35%.

[0062] This embodiment also provides a method for preparing the above-mentioned cobalt trioxide, comprising the following steps:

[0063] Step 1, preparing 1 mol / L cobalt sulfate solution as cobalt salt solution A and 150 g / L ammonium bicarbonate solution as precipitant solution B;

[0064] Step 2: Cobalt salt solution A and precipitant solution B were injected into the reactor at a rate of 125 L / h and 180 L / h, respectively. The flow rate of solution A was increased by 0.03 L / min, and the flow rate of solution B was increased by 0.04 L / min. During the reaction, the pH was maintained at 7.1, the reaction temperature was 60°C, and the stirring rate was 500 rpm. Feeding was stopped when D50 grew to 12 μm.

[0065] Step 3, washing the material with 75°C hot water;

[0066] Step 4, drying the washed material at 160° C. to obtain cobalt carbonate;

[0067] Step 5: calcining the obtained cobalt carbonate at 450° C. for 8 h to obtain cobalt trioxide with high porosity.

[0068] Example 4

[0069] The only difference between this embodiment and embodiment 1 is that the flow rate of solution A is increased by 0.2 L / min, and the flow rate of solution B is increased by 0.4 L / min.

[0070] The porosity of the cobalt trioxide prepared in this embodiment is 48%.

[0071] Example 5

[0072] The difference between this embodiment and embodiment 1 is that the flow rate of solution A is increased by 0.02 L / min, the flow rate of solution B is increased by 0.04 L / min, and after increasing for 1 hour, the flow rates of each are maintained unchanged for 1 hour, and then the flow rate of solution A is increased by 0.02 L / min, the flow rate of solution B is increased by 0.4 L / min, and after increasing for 1 hour, the flow rates of each are maintained unchanged until D50 grows to 8 μm, and the feeding is stopped.

[0073] The porosity of the cobalt trioxide prepared in this embodiment is 25%.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that v1 and v2 remain unchanged throughout the reaction process.

[0076] The porosity of the cobalt trioxide prepared in this comparative example is 6%.

[0077] Application Examples

[0078] The cobalt trioxide of Examples 1 to 5 and Comparative Example 1 was used to prepare O2-phase lithium cobaltate, respectively, and the preparation method was as follows:

[0079] 1. Cobalt trioxide and sodium carbonate were mixed evenly at a molar ratio of Na / Co=0.7, sintered at 400°C for 2 hours, and then sintered at 800°C for 10 hours to obtain P2 phase sodium cobaltate.

[0080] 2. P2 phase sodium cobaltate and lithium salt are ion exchanged in a liquid phase at a molar ratio of Li / Na = 10:1 at 60°C for 10 hours, and then washed, dried, and post-treated to obtain O2 phase lithium cobaltate.

[0081] Preparation of lithium-ion batteries:

[0082] Using the O2-phase lithium cobalt oxide prepared in the application example as the active material, the active material was mixed with carbon black and PVDF in a 90:5:5 mass ratio to form a slurry. The slurry was evenly coated on aluminum foil to form the positive electrode. A button cell was assembled using the lithium negative electrode as the counter electrode.

[0083] Performance testing:

[0084] (1) Discharge capacity test: the test temperature is 25℃, the test voltage is 4.60V, and the discharge rate is 0.1C.

[0085] (II) Cycle performance test: the test temperature is 25℃, the test voltage is 4.60V, the charge and discharge capacity are both 0.2C, and the cycle is 100 cycles. According to the first discharge capacity C1 and the 100th cycle discharge capacity C 100 Calculate the capacity retention rate, capacity retention rate = C 100 / C1×100%.

[0086] See Table 1 for the results.

[0087] Table 1

[0088]

[0089] In summary, since the porosity of the cobalt oxide of the present invention increases from the inside to the outside, when it is applied to the preparation of O2 phase lithium cobalt oxide, the ion exchange process of sodium cobalt oxide can be improved, thereby facilitating the preparation of O2 phase lithium cobalt oxide, and further improving the performance of lithium-ion batteries.

[0090] At the same time, by comparing Example 1 with Example 4, it can be seen that if the porosity is too high, although the discharge capacity is slightly improved, it will have a negative impact on the cycle performance.

[0091] By comparing Example 1 with Example 5, it can be seen that the discontinuous increase in pores has a certain negative impact on the discharge capacity and cycle performance.

[0092] By comparing Example 1 with Comparative Example 1, it can be seen that the O2 phase lithium cobalt oxide prepared using ordinary cobalt tetroxide as raw material may lead to insufficient ion exchange due to its low porosity, resulting in poor capacity and cycle performance.

[0093] The applicant states that the present invention is intended to illustrate the detailed methods of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed methods, that is, it does not mean that the present invention must rely on the above-described detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A cobalt trioxide for O2 phase lithium cobaltate, characterized in that: The porosity of the cobalt trioxide increases from the inside to the outside.

2. The cobalt trioxide for O2-phase lithium cobaltate according to claim 1, characterized in that The porosity increases in a gradient, or the porosity increases continuously; Preferably, the porosity of the cobalt trioxide is 25% to 35%.

3. A method for preparing cobalt trioxide for O2-phase lithium cobaltate according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) injecting a cobalt salt solution and a precipitant solution into a reactor at a certain flow rate, wherein as time goes by, the flow rate v1 of the cobalt salt solution and the flow rate v2 of the precipitant solution both increase, and the reaction produces cobalt carbonate; The pH of the reaction is 7.0 to 7.1; the temperature of the reaction is 50° C. to 60° C.; (2) calcining the cobalt carbonate to obtain the cobalt trioxide.

4. The preparation method according to claim 3, characterized in that The concentration of the cobalt salt solution is 1 mol / L to 2.5 mol / L; Preferably, the precipitant solution is an aqueous solution of ammonium bicarbonate; Preferably, the concentration of the precipitant solution is 150 g / L to 250 g / L.

5. The preparation method according to claim 3 or 4, characterized in that v1 is 50L / h~150L / h, v2 is 150L / h~250L / h; Preferably, v1 and v2 increase gradually; or, v1 and v2 increase continuously; Preferably, v1 and v2 continue to rise, with v1 increasing at 0.01 L / min to 0.08 L / min and v2 increasing at 0.01 L / min to 0.05 L / min.

6. The preparation method according to any one of claims 3 to 5, characterized in that The reaction is accompanied by stirring at a rate of 200 rpm to 500 rpm; Preferably, the reaction is stopped when the particle size D50 of the cobalt carbonate reaches 6 μm to 12 μm.

7. The preparation method according to any one of claims 3 to 6, characterized in that After the reaction in step (1) is completed, the product is washed with hot water and dried to obtain the cobalt carbonate; Preferably, the temperature of the hot water is 70°C to 80°C; Preferably, the drying method is oven drying, and the oven drying temperature is 100°C to 180°C.

8. The preparation method according to any one of claims 3 to 7, characterized in that The calcination temperature is 350°C to 450°C; Preferably, the calcination time is 8 hours to 10 hours.

9. An O2-phase lithium cobalt oxide, characterized in that The O2 phase lithium cobaltate is prepared by using the cobalt trioxide according to claim 1 or 2.

10. A lithium ion battery, characterized in that: The lithium-ion battery includes the O2-phase lithium cobalt oxide according to claim 9.

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