Preparation method and application of low-cost monocrystal lithium manganate positive electrode material

Abstract

The invention provides a preparation method and application of a low-cost single-crystal lithium manganate positive electrode material, and belongs to the technical field of lithium ion battery positive electrode materials, preferably, low-cost manganese carbonate is adopted as a raw material, firstly, manganese carbonate and a cracking agent are mixed and then pyrolyzed to prepare high-activity manganese dioxide, and the high-activity manganese dioxide is prepared into a single-crystal lithium manganate positive electrode material. Then manganese dioxide is mixed with lithium salt and a lattice stabilizer and then subjected to high-temperature heat treatment, the single-crystal lithium manganate positive electrode material is prepared, when manganese dioxide is prepared, manganese carbonate is decomposed and can release gas to be pulverized, meanwhile, PVP is used in a combined mode, a self-heating, soft and porous decomposition environment is formed, decomposition of manganese carbonate is promoted, and the manganese granularity is refined; manganese dioxide particles obtained by decomposition are uniform and fine and have high activity; the preparation method provided by the scheme is easy to industrialize, and the product has the characteristics of low cost, low manganese dissolution and excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery positive electrode materials, and in particular relates to a preparation method and application of a low-cost single-crystal lithium manganate positive electrode material. Background Art

[0002] With the rapid development of modern electronic devices and electric vehicles, the demand for high-performance, low-cost lithium-ion battery cathode materials is growing. Lithium manganese oxide has become one of the most promising cathode materials due to its abundant resources, low cost, and environmental friendliness. However, there are some problems with the traditional synthesis method of lithium manganese oxide. For example, the price of electrolytic manganese dioxide is relatively high, the synthesized lithium manganese oxide has large particle size and unsatisfactory crystal morphology, which makes it difficult to balance its capacity, compaction density and high-temperature performance. At the same time, manganese dissolution is prone to occur during use, affecting the cycle life and stability of the battery. Manganese carbonate is an inexpensive manganese source. It is of great significance to use manganese carbonate as a raw material for lithium manganese oxide and develop a low-cost method for synthesizing lithium manganese oxide with small particle size, single crystal form and good comprehensive performance. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing a low-cost single-crystal lithium manganese oxide positive electrode material and its application, which solves the problems of high price of lithium manganese oxide in the prior art, large particle size and poor crystal morphology in synthesis, difficulty in balancing comprehensive performance, and manganese dissolution.

[0004] To achieve the above objectives, this solution first provides a method for preparing a low-cost single-crystal lithium manganese oxide positive electrode material, comprising the following steps: S1, after manganese carbonate and polyvinyl polypyrrolidone are uniformly mixed, placing them in an atmosphere furnace and introducing air or oxygen to perform a heat treatment at elevated temperature to obtain highly active manganese dioxide; S2: After uniformly mixing the manganese dioxide prepared in S1 with a lithium salt and a lattice stabilizer, the mixture is placed in an atmosphere furnace and air or oxygen is introduced to perform a temperature-raising sintering treatment to obtain a single-crystal lithium manganate positive electrode material.

[0005] Preferably, the mass ratio of manganese carbonate to polyvinylpolypyrrolidone (PVP) in S1 is 1:0.002-0.05.

[0006] Preferably, the heating rate in S1 is 5°C / min, the heat treatment temperature is 300-600°C, and the heat treatment time is 4-8h.

[0007] Preferably, the lithium salt in S2 is selected from at least one of lithium carbonate, lithium hydroxide, and lithium acetate, and the lattice stabilizer is selected from at least one of magnesium carbonate and magnesium oxide.

[0008] Preferably, the manganese dioxide and the lithium salt in S2 are in a stoichiometric ratio of Mn:Li of 1.8 to 2.0:1, and the amount of the lattice stabilizer added is 0.1% to 1% of the mass of the manganese dioxide.

[0009] Preferably, the heating rate in S2 is 5° C. / min, the sintering temperature is 700-1000° C., and the sintering time is 8-15 h.

[0010] Based on a general inventive concept, this solution also provides a low-cost single-crystal lithium manganese oxide positive electrode material.

[0011] Based on a general inventive concept, the present invention also provides an application of a low-cost single-crystal lithium manganese oxide positive electrode material in the preparation of a lithium secondary battery.

[0012] The mechanism of this scheme's low-cost single-crystal lithium manganese oxide positive electrode material: During the preparation of manganese dioxide, manganese carbonate decomposes, releasing gas and pulverizing. Combined with PVP, this creates a self-heating, soft, porous decomposition environment, promoting the decomposition of manganese carbonate and refining the manganese particle size. The resulting manganese dioxide particles are uniform, fine, and highly active. The lithium manganate obtained by sintering this mixture of manganese dioxide and lithium carbonate has a small particle size and a single crystal form, offering an excellent balance between capacity, compactness, and high-temperature performance.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This scheme is based on low-cost manganese carbonate raw materials and combines the use of cracking agent PVP to greatly reduce the cost of synthesizing single crystal lithium manganate.

[0014] 2. Since lithium manganese oxide is in single crystal form and is combined with the lattice stabilizer magnesium carbonate to stabilize the lattice, it can effectively inhibit manganese dissolution, reduce interface side reactions, and improve the cycle life and stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 This is the particle form of the single crystal lithium manganate positive electrode material prepared in Example 1.

[0017] Figure 2 This is the particle morphology of the single crystal lithium manganate positive electrode material prepared in Comparative Example 4. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0019] The following examples are provided to illustrate the present invention but are not intended to limit the scope of the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0020] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art; unless otherwise specified, the reagents used in the examples are commercially available.

[0021] Example 1 Preparation of low-cost single-crystal lithium manganate positive electrode material.

[0022] S1 produces highly active manganese dioxide: Weigh 100g of manganese carbonate and 3g of PVP and mix them thoroughly. Place the mixture in a sagger and place it in an atmosphere furnace. Raise the temperature to 500°C at a rate of 5°C / min in an air atmosphere and sinter at this temperature for 6 hours. This produces uniform, highly active manganese dioxide.

[0023] S2 produces single crystal lithium manganese oxide positive electrode material: According to the stoichiometric ratio of Mn:Li = 1.83:1, the high-activity manganese dioxide and lithium carbonate prepared in S1 were weighed, and 0.3% of the mass of manganese dioxide magnesium carbonate was added as an additive. After being put into a high-speed mixer and thoroughly mixed, the mixed materials were placed in a sagger and placed in an atmosphere furnace. Under an air atmosphere, the temperature was increased at a rate of 5°C / min to 980°C, and the reaction was carried out for 10 hours to obtain a single-crystal lithium manganate positive electrode material.

[0024] The particle morphology of the prepared single crystal lithium manganese oxide positive electrode material is as follows Figure 1 shown.

[0025] Example 2 Preparation of low-cost single-crystal lithium manganate positive electrode material.

[0026] S1 produces highly active manganese dioxide: Weigh 200g of manganese carbonate and 5g of PVP and mix them thoroughly. Place the mixture in a sagger and place it in an atmosphere furnace. Heat the mixture to 600°C at a rate of 5°C / min in an air atmosphere and sinter at this temperature for 5 hours. This produces uniform, highly active manganese dioxide.

[0027] S2 produces single crystal lithium manganese oxide positive electrode material: According to the stoichiometric ratio of Mn:Li = 1.85:1, the high-activity manganese dioxide and lithium carbonate prepared in S1 were weighed, and 0.5% of the mass of manganese dioxide magnesium carbonate was added as an additive. After being put into a high-speed mixer and thoroughly mixed, the mixed materials were placed in a sagger and placed in an atmosphere furnace. Under an air atmosphere, the temperature was raised to 950°C at a rate of 5°C / min and the reaction was carried out for 12 hours to obtain a single-crystal lithium manganate positive electrode material.

[0028] Example 3 Preparation of low-cost single-crystal lithium manganate positive electrode material.

[0029] S1 produces highly active manganese dioxide: Weigh 200g of manganese carbonate and 5g of PVP and mix them thoroughly. Then, place the mixture in a sagger and heat it to 450°C at a rate of 5°C / min. Sinter at this temperature for 5.5 hours to obtain uniform, highly active manganese dioxide.

[0030] S2 produces single crystal lithium manganese oxide positive electrode material: According to the stoichiometric ratio of Mn:Li = 1.88:1, the high-activity manganese dioxide and lithium carbonate prepared in S1 were weighed, and 0.8% of the mass of manganese dioxide magnesium oxide was added as an additive. After being put into a high-speed mixer and thoroughly mixed, the mixed materials were placed in a sagger and placed in an atmosphere furnace. Under an air atmosphere, the temperature was increased at a rate of 5°C / min to 860°C, and the reaction was carried out for 9 hours to obtain a single-crystal lithium manganate positive electrode material.

[0031] Example 4 Preparation of low-cost single-crystal lithium manganate positive electrode material.

[0032] S1 produces highly active manganese dioxide: Weigh 200g of manganese carbonate and 8g of PVP and mix them thoroughly. Place the mixture in a sagger and place it in an atmosphere furnace. Raise the temperature to 450°C at a rate of 5°C / min in an air atmosphere and sinter at this temperature for 5.5 hours. This yields uniform, highly active manganese dioxide.

[0033] S2 produces single crystal lithium manganese oxide positive electrode material: According to the stoichiometric ratio of Mn:Li = 1.90:1, the high-activity manganese dioxide and lithium carbonate prepared in S1 were weighed, and 0.3% of the mass of manganese dioxide magnesium oxide was added as an additive. After being put into a high-speed mixer and thoroughly mixed, the mixed materials were placed in a sagger and placed in an atmosphere furnace. Under an air atmosphere, the temperature was raised to 800°C at a rate of 5°C / min and the reaction was carried out for 8 hours to obtain a single-crystal lithium manganate positive electrode material.

[0034] Comparative Example 1 A single-crystal lithium manganate positive electrode material without PVP was prepared.

[0035] Compared with Example 1, the only difference is that PVP is not added to S1, and other operations and parameters are the same as Example 1.

[0036] Comparative Example 2 A single-crystal lithium manganate positive electrode material without the lattice stabilizer PVP was prepared.

[0037] Compared with Example 1, the only difference is that magnesium carbonate is not added to S2, and other operations and parameters are the same as those in Example 1.

[0038] Comparative Example 3: Single crystal lithium manganese oxide positive electrode materials containing different lattice stabilizers PVP were prepared.

[0039] A: Compared with Example 1, the only difference is that the magnesium carbonate in S2 is replaced by an equal amount of calcium carbonate. Other operations and parameters are the same as in Example 1.

[0040] B: Compared with Example 1, the only difference is that the magnesium carbonate in S2 is replaced by an equal amount of titanium oxide, and the other operations and parameters are the same as Example 1.

[0041] C: Compared with Example 1, the only difference is that the magnesium carbonate in S2 is replaced by an equal amount of zirconium oxide, and the other operations and parameters are the same as Example 1.

[0042] Comparative Example 4: Single crystal lithium manganese oxide positive electrode material was prepared using ordinary manganese dioxide.

[0043] Compared with Example 1, the only difference is that the step of preparing highly active manganese dioxide in S1 is omitted, commercial electrolytic manganese dioxide is used as the manganese source in S2, and the other operations and parameters are the same as in Example 1.

[0044] The particle morphology of the prepared lithium manganate cathode material is as follows Figure 2 As shown, the particle morphology of the lithium manganate positive electrode material prepared in Example 1 is Figure 1 In comparison, the single crystals of the lithium manganate material obtained in this comparative example are uneven in size, poor in consistency, have a large amount of surface fine powder, and suffer from severe agglomeration and adhesion between particles, which is not conducive to dispersion.

[0045] Experimental Example 1 The chemical properties of the positive electrode materials prepared in Examples 1-4 and Comparative Examples 1-4 were examined.

[0046] (1) Sample electrical performance test S1. Preparation of positive electrode sheet: The positive electrode materials prepared by the above method in Examples 1 to 4 and Comparative Examples 1 to 4 were used as positive electrode active materials. The positive electrode active materials: SP (superconducting carbon black): PVDF (polyvinylidene fluoride) were homogenized in a mass ratio of 90:5:5 and coated on a 20 μm thick aluminum foil to produce a positive electrode sheet with an area density of 8 mg / cm2 , and then through drying, rolling, die cutting, punching into positive electrode sheets.

[0047] S2. Battery Preparation: A button cell battery was assembled using an R2032 button cell shell, with a lithium sheet as the negative electrode and a PE separator. 80 μmL of electrolyte was added. The test temperature was 25°C, the test voltage range was 3.0V to 4.3V, and the battery was charged to 4.3V using a constant current and constant voltage charging method, and discharged to 3.0V using a constant current and constant voltage discharge method. The first three cycles were charged and discharged at currents of 0.1C, 0.5C, and 1C, respectively. The battery was then charged and discharged at a current of 1C for 100 cycles. The test temperature was 55°C, the test voltage range was 3.0V to 4.3V, and the battery was charged to 4.3V using a constant current and constant voltage charging method, and discharged to 3.0V using a constant current and constant voltage discharge method. The first three cycles were charged and discharged at currents of 0.1C, 0.5C, and 1C, respectively. The battery was then charged and discharged at a current of 1C for 100 cycles. The test results are shown in Table 1 below.

[0048] (2) Sample manganese dissolution test 1 g of the samples prepared in the examples and comparative examples were weighed, immersed in 50 mL of electrolyte, and allowed to stand at room temperature for 24 hours. The electrolyte was then filtered three times, and the Mn content in the filtrate was tested. The results are listed in Table 1 below.

[0049]

[0050] From the above test results, it can be seen that the single-crystal lithium manganate positive electrode material prepared by the preparation method provided in this scheme can effectively inhibit the dissolution of manganese, improve the structural stability of the material, and thus effectively improve the normal high temperature cycle performance of the material.

[0051] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a low-cost single-crystal lithium manganate positive electrode material, characterized in that: The following steps are involved: S1, after manganese carbonate and polyvinyl polypyrrolidone are uniformly mixed, placing them in an atmosphere furnace and introducing air or oxygen to perform a heat treatment at elevated temperature to obtain highly active manganese dioxide; S2. After uniformly mixing the manganese dioxide prepared in S1 with a lithium salt and a lattice stabilizer, the mixture is placed in an atmosphere furnace and air or oxygen is introduced to perform a temperature-raising sintering treatment to obtain a single-crystal lithium manganate positive electrode material.

2. The preparation method according to claim 1, characterized in that The mass ratio of manganese carbonate to polyvinylpolypyrrolidone in S1 is 1:0.002-0.

05.

3. The preparation method according to claim 1, characterized in that The heating rate in S1 is 5°C / min, the heat treatment temperature is 300-600°C, and the heat treatment time is 4-8 hours.

4. The preparation method according to claim 1, characterized in that The lithium salt in S2 is selected from at least one of lithium carbonate, lithium hydroxide, and lithium acetate, and the lattice stabilizer is selected from at least one of magnesium carbonate and magnesium oxide.

5. The preparation method according to claim 1, characterized in that The manganese dioxide and lithium salt in the S2 are in a stoichiometric ratio of Mn:Li of 1.8 to 2.0:1, and the amount of the lattice stabilizer added is 0.1% to 1% of the mass of the manganese dioxide.

6. The preparation method according to claim 1, characterized in that The heating rate in S2 is 5° C. / min, the sintering temperature is 700-1000° C., and the sintering time is 8-15 hours.

7. A low-cost single-crystal lithium manganate positive electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of a low-cost single-crystal lithium manganate positive electrode material prepared by the preparation method according to any one of claims 1 to 6 in the preparation of a lithium secondary battery.

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