Method for preparing layered lithium manganate from salt lake brine, layered lithium manganate and application

Abstract

The invention discloses a method for preparing layered lithium manganate from salt lake brine, layered lithium manganate and application, and relates to the technical field of lithium batteries. The preparation method comprises the following steps: adsorbing lithium in salt lake brine by using gamma-type MnOOH with a high specific surface area to obtain a MnOOH-Li material, and sintering the MnOOH-Li material to prepare the layered lithium manganate material LiMnO2. The novel adsorption material is adopted, the dosage of chemical reagents can be reduced, the process energy consumption is reduced, the recovery rate and purity of lithium in the salt lake lithium extraction waste liquid are improved, meanwhile, the synthesis process and control conditions of the LiMnO2 material are shortened, and the prepared layered lithium manganate material LiMnO2 is good in electrochemical performance and has remarkable superiority.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, and in particular to a method for preparing layered lithium manganate using salt lake brine, the layered lithium manganate and applications. Background Art

[0002] Lithium-ion batteries have become an indispensable energy storage method in mobile electronic devices, electric vehicles, and large-scale energy storage systems due to their high energy density, long life, and good charge and discharge performance. With the increasing demand for lithium-ion batteries, the extraction and purification technology of lithium resources has also been widely researched and developed. Salt lake brine contains rich lithium resources and is an important source of raw materials for new energy industries such as lithium-ion batteries. However, the lithium ion concentration in salt lake brine is usually low, and is accompanied by a large number of other impurity ions, making the extraction and purification of lithium a technical problem.

[0003] Traditional lithium extraction methods such as precipitation, carbonization, and solvent extraction have problems such as large footprint, high energy consumption, and low yield. At the same time, layered lithium manganese oxide, as a positive electrode material for lithium-ion batteries, has attracted much attention due to its high theoretical specific capacity, low price, abundant raw materials, and no pollution to the environment, but its electrochemical performance is significantly affected by the preparation method. However, layered LiMnO 2 +3 valence Mn 3+ It is easy to form +4-valent Mn during lithium ion insertion and extraction 4+ This transformation will affect the electrochemical properties of the material. At the same time, +3-valent manganese is very sensitive to oxygen and is very easy to contact oxygen to form other lithium manganese oxides, requiring strict oxygen control during the synthesis process.

[0004] The existing salt lake lithium extraction process usually includes: pretreatment, extraction, precipitation, adsorption and ion exchange steps. In the adsorption and ion exchange steps, some materials with high specific surface area, such as activated carbon, zeolite molecular sieve, etc., are usually used to adsorb and exchange lithium ions in the waste liquid to obtain lithium compounds. The synthesis methods of layered lithium manganese oxide include: high temperature solid phase synthesis method, coprecipitation method, sol-gel method, etc.

[0005] Although the existing salt lake lithium extraction process can already achieve lithium extraction and purification, there are still some problems, mainly manifested in:

[0006] (1) Although existing adsorption materials, such as activated carbon and zeolite molecular sieves, have certain adsorption effects, their specific surface area and adsorption capacity are limited, which restricts their application in the treatment of lithium waste liquid from salt lakes.

[0007] (2) Existing ion exchange processes usually require the use of a large amount of chemical reagents, which not only increases the complexity and cost of the process, but also may cause environmental pollution problems.

[0008] (3) The existing sintering process of layered lithium manganese oxide materials usually requires high temperature and high pressure conditions, which not only increases the energy consumption of the process, but also can obtain layered LiMnO by different synthesis methods. 2 , but they all have their own limitations. For example, the high-temperature solid-phase synthesis method is simple and suitable for industrial mass production, but the contact between the reactants is uneven, the reaction is not sufficient, the lithium loss is serious, the stoichiometric ratio is difficult to control, the particle size of the synthesized product is difficult to control, the distribution is uneven, and the morphology is irregular, which leads to poor electrochemical performance of the material; the sol-gel method has a low reaction temperature and a short reaction time, but the raw material price is expensive; the co-precipitation method requires more complex operating steps and condition control, and may also affect the electrochemical performance of the obtained layered lithium manganate material.

[0009] Therefore, there is an urgent need to improve the salt lake lithium extraction process and the preparation process of layered lithium manganese oxide materials, so as to improve the lithium recovery rate and purity in the salt lake lithium extraction waste liquid while reducing energy consumption, and at the same time provide a simple and easy process for preparing layered lithium manganese oxide materials.

[0010] In view of this, the present invention is proposed. Summary of the invention

[0011] The purpose of the present invention is to provide a method for preparing layered lithium manganate using salt lake brine, layered lithium manganate and application, aiming to achieve the improvement of lithium recovery rate and product purity in salt lake lithium extraction waste liquid under the premise of reducing energy consumption, and at the same time provide a simple and easy process for preparing layered lithium manganate material.

[0012] The present invention is achieved in that:

[0013] In a first aspect, the present invention provides a method for preparing layered lithium manganate using salt lake brine, comprising: using a layered lithium manganate having a specific surface area of ​​150 m 2 / g-180m 2 / g of γ-type MnOOH was mixed with salt lake brine for reaction, and then the MnOOH-Li material was obtained by solid-liquid separation;

[0014] The MnOOH-Li material is sintered.

[0015] In an optional embodiment, the process of preparing the MnOOH-Li material includes: mixing γ-type MnOOH with salt lake brine and stirring for 20 min-60 min, then standing for 0.5 h-3.0 h, and then performing solid-liquid separation.

[0016] In an optional embodiment, the concentration of lithium in the salt lake brine is 25 mg / L-35 mg / L, and the amount of γ-type MnOOH corresponding to 100 mL of the salt lake brine is 0.02 g-0.10 g, preferably 0.03 g-0.06 g.

[0017] In an optional embodiment, the solid-liquid separation is performed by centrifugation, and the centrifugal speed is controlled to be 2000rpm-4000rpm, and the centrifugal time is 5min-20min.

[0018] In an optional embodiment, the collected salt lake brine is first pretreated to remove suspended matter and organic matter therein, and then mixed with γ-type MnOOH.

[0019] In an optional embodiment, the pretreatment process includes: filtering the salt lake brine and then evaporating and concentrating it.

[0020] In an optional embodiment, the MnOOH-Li material is sintered at 330° C.-380° C. for 1 h-3 h.

[0021] In a second aspect, the present invention provides a layered lithium manganate prepared by any of the methods described in the foregoing embodiments.

[0022] In a third aspect, the present invention provides a lithium battery positive electrode sheet, comprising the layered lithium manganese oxide of the aforementioned embodiment.

[0023] In a fourth aspect, the present invention provides a lithium battery, comprising the lithium battery positive electrode sheet of the aforementioned embodiment.

[0024] The present invention has the following beneficial effects: the present invention uses high specific surface area γ-type MnOOH to absorb lithium in salt lake brine to obtain MnOOH-Li material, and then sintering the MnOOH-Li material can prepare layered lithium manganate material LiMnO 2 The present invention adopts a new adsorption material, which can reduce the amount of chemical reagents and process energy consumption, not only improving the recovery rate and purity of lithium in the salt lake lithium extraction waste liquid, but also shortening the LiMnO 2 The synthesis process and control conditions of the material, the prepared layered lithium manganese oxide material LiMnO 2 The electrochemical performance is good and has significant advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 This is the XRD pattern of γ-type MnOOH;

[0027] Figure 2 Example 1 LiMnO 2-XRD pattern, corresponding PDF card: 35-0749;

[0028] Figure 3 Example 1 LiMnO 2 -SEM images. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0030] In view of the problems existing in the salt lake lithium extraction process and the layered lithium manganese oxide preparation process in the prior art, the inventor creatively uses the large specific surface area of ​​γ-type MnOOH for adsorption and prepares layered lithium manganese oxide by sintering. In general, the present invention not only improves the recovery rate and purity of lithium in the salt lake lithium extraction waste liquid, but also shortens the LiMnO 2 The synthesis process and control conditions of the material have significant advantages.

[0031] The embodiment of the present invention provides a method for preparing layered lithium manganate using salt lake brine, the steps are as follows:

[0032] S1. Preprocessing

[0033] The collected salt lake brine is first pre-treated to remove suspended matter, organic matter and other impurities therein, and then enters step S2 to be mixed with γ-type MnOOH.

[0034] Pretreatment or no pretreatment is selected according to the impurity situation of the salt lake brine. If the salt lake brine has been pretreated frequently, no pretreatment operation is required. The pretreatment means are not limited, and conventional pretreatment means for lithium extraction from salt lakes can be used.

[0035] In some embodiments, the pretreatment process includes: filtering the salt lake brine, and then evaporating and concentrating it. The filtration can be performed using a precision filter to remove impurities such as suspended matter and particulate matter in the brine; the filtered brine can be evaporated using energy such as solar energy or thermal energy, so that the water in the brine gradually evaporates and the salts gradually concentrate. While evaporating and concentrating the brine, some sodium and potassium ions are removed (sodium and potassium are easy to crystallize during the evaporation and concentration process), while lithium is relatively enriched in the remaining brine.

[0036] S2. Lithium Extraction from Salt Lake

[0037] The specific surface area is 150m2 / g-180m 2 / g of γ-type MnOOH is mixed with salt lake brine for reaction, and then the solid-liquid separation is performed to obtain MnOOH-Li material. The present invention adopts a γ-type MnOOH adsorption material with a high specific surface area, and its specific surface area and adsorption capacity are significantly higher than those of existing adsorption materials, such as activated carbon, zeolite molecular sieves, etc., so it can more effectively adsorb lithium in the salt lake lithium extraction waste liquid, thereby improving the recovery rate and purity of lithium. In addition, the adsorbent used in the embodiment of the present invention also has an ion exchange effect, does not require a large amount of chemical reagents, and thus can reduce the amount of chemical reagents used, reduce the complexity and cost of the process, and also reduce pollution to the environment.

[0038] In some embodiments, the process of preparing MnOOH-Li material includes: mixing γ-type MnOOH with salt lake brine for 20min-60min, then standing for 0.5h-3.0h, and then performing solid-liquid separation. In the actual operation process, γ-type MnOOH and salt lake brine can be mixed and contacted at room temperature (such as about 20°C), and the stirring time can be 20min, 30min, 40min, 50min, 60min, etc.; after stirring, lithium ions are fully contacted with γ-type MnOOH by standing, and the specific standing time can be 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, etc.

[0039] In some embodiments, the concentration of lithium in the salt lake brine is 25 mg / L-35 mg / L, and the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.02 g-0.10 g, preferably 0.03 g-0.06 g. The utilization rate of lithium is further improved by regulating the amount of γ-type MnOOH. Specifically, the concentration of lithium in the salt lake brine after pretreatment can be 25 mg / L, 28 mg / L, 30 mg / L, 32 mg / L, 35 mg / L, etc., and the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine can be 0.02 g, 0.03 g, 0.04 g, 0.05 g, 0.06 g, 0.07 g, 0.08 g, 0.09 g, 0.10 g, etc.

[0040] In some embodiments, solid-liquid separation is performed by centrifugation, and the centrifugal speed is controlled to be 2000rpm-4000rpm, such as 2000rpm, 2500rpm, 3000rpm, 3500rpm, 4000rpm, etc.; the centrifugal time is 5min-20min, such as 5min, 10min, 15min, 20min, etc. Specifically, the mixed solution is poured into a centrifuge, and the speed is set for centrifugation, and the MnOOH-Li material powder is obtained after the centrifugation is completed.

[0041] Specifically, the high specific surface area γ-type MnOOH can be a commercially available material or can be independently prepared. This γ-type high specific surface area MnOOH not only has a large specific surface area and a strong adsorption capacity, but can also exchange hydrogen ions with lithium ions, which can significantly improve the utilization rate of lithium in salt lake brine.

[0042] S3, Sintering

[0043] The MnOOH-Li material is sintered to prepare the layered lithium manganate material LiMnO 2 .

[0044] In some embodiments, the MnOOH-Li material is sintered at 330°C-380°C for 1h-3h. Compared with the existing high-temperature air-oxygen sintering process, the method provided by the embodiment of the present invention significantly reduces energy consumption, which is beneficial to saving energy and reducing production costs. In addition, the layered lithium manganese oxide material LiMnO prepared by the embodiment of the present invention 2 , it has good electrochemical properties and can be used as the positive electrode material of lithium-ion batteries, with broad application prospects.

[0045] Specifically, the sintering temperature may be 330° C., 340° C., 350° C., 360° C., 370° C., 380° C., etc.; the sintering time may be 1 h, 2 h, 3 h, etc.

[0046] If γ-type MnOOH is prepared by self-preparation, the following preparation method can be used: mix manganese powder and water to make pulp and grind to obtain manganese slurry; mix manganese slurry and ammonium acetate to react and age to obtain aged slurry; separate the aged slurry into solid and liquid to obtain manganese tetraoxide material; use manganese tetraoxide material and oxidant to mix and react to prepare MnOOH material. The specific steps are as follows:

[0047] (1) Preparation of manganese slurry

[0048] Manganese powder and water are mixed to form a slurry with a certain solid content, and then ground to obtain manganese slurry. Grinding reduces the particle size of particles in the manganese slurry, which is conducive to the subsequent acquisition of manganese tetraoxide materials with a larger specific surface area.

[0049] Specifically, manganese powder is a commercially available material, such as that purchased from Sinosteel Tianyuan, and most of the manganese powder is converted into manganese hydroxide after mixing with water. The grinding method is not limited, such as using a ball mill to grind, so that the particle size D50 of the particles in the slurry after grinding meets the requirements.

[0050] In some embodiments, the amount of water is adjusted to make the solid content of the manganese slurry 55%-65%, such as 55%, 58%, 60%, 63%, 65%, etc. By adjusting the ball milling parameters, the particle size D50 of the particles in the manganese slurry after grinding is controlled to be 0.8μm-2.0μm, such as 0.8μm, 1.0μm, 1.2μm, 1.5μm, 1.8μm, 2.0μm, etc.

[0051] (2) Reaction with ammonium acetate

[0052] The ground manganese slurry is poured into a reactor, and ammonium acetate is added to the reactor to cause an exothermic reaction. After the reaction is completed, it is aged to obtain an aged slurry. The role of ammonium acetate in the reaction process is equivalent to a catalyst. 3 COO - It is a weak acid ion that can buffer the pH value of the solution, making the reaction milder and avoiding too fast or too slow reaction. It can also produce carbon dioxide, making the specific surface area larger and the product purer.

[0053] In order to increase the specific surface area of ​​manganese tetraoxide, the inventor optimized the dosage of ammonium acetate: ammonium acetate can be added in an amount of 0.8g / L-1.2g / L, and the pH value of the system can be adjusted to 6.4-7.6 at this dosage to promote the reaction. If the catalyst concentration is too low, the reaction rate is too slow, the reaction time is prolonged, and the product specific surface area is high, but if the concentration is too low, the reaction will be incomplete, the product will be impure, the yield will be low, the economy will be poor, and the synthesized MnOOH will have low crystallinity; if the catalyst concentration is too high: the reaction rate is too fast, the product particles are large, the specific surface area is reduced, and the crystallinity is poor.

[0054] Specifically, the amount of ammonium acetate added can be 0.8 g / L, 0.9 g / L, 1.0 g / L, 1.1 g / L, 1.2 g / L, etc.; by adjusting the amount of ammonium acetate added, the pH value of the system can be 6.4, 6.5, 6.8, 7.0, 7.2, 7.4, 7.6, etc.

[0055] In some embodiments, during the reaction of manganese slurry and ammonium acetate, the reaction temperature is controlled to be less than or equal to 70°C. Since the reaction is an exothermic reaction, the maximum temperature is controlled to be ≤70°C during the reaction to prevent excessive temperature from affecting the morphology of manganese tetraoxide. Specifically, the reaction temperature can be 70°C, 60°C, 50°C, 40°C, etc. The reaction time is controlled to be 4h-6h so that the reaction is fully carried out, specifically 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, etc.

[0056] In some embodiments, during the reaction of manganese slurry and ammonium acetate, the stirring rate is 200r / min-300r / min, such as 200r / min, 230r / min, 250r / min, 280r / min, 300r / min, etc. The reaction rate is preferably within the above range. If the stirring speed is too high, high shear force will cause product particles to break, and the specific surface area may be higher, but high shear force will also make the reaction rate too fast, resulting in local supersaturation and generating uneven products, and too high stirring speed may cause crystal breakage and reduce crystallinity; if the stirring speed is too low, precipitation or agglomeration will occur, the surface area is low, and the reaction rate is slow, the product particles may be larger, and the production efficiency will also decrease.

[0057] In some embodiments, when the mass fraction of manganese in the manganese particles in the manganese slurry after the reaction is measured to be between 71% and 72%, that is, approximately equal to the manganese content in manganese tetraoxide, the manganese slurry after the reaction is aged for 20 minutes to 60 minutes. Specifically, the aging process can be carried out in an aging tank, and the aging time can be controlled to be 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0058] (3) Solid-liquid separation

[0059] The aged slurry is subjected to solid-liquid separation, and water and ammonium acetate are removed to obtain the manganese tetraoxide material. The specific surface area of ​​the manganese tetraoxide prepared in the embodiment of the present invention is 30-35 m 2 / g.

[0060] In some embodiments, the aged slurry may be separated into solid and liquid by filter pressing, but the present invention is not limited thereto. The water content of the solid material after filter pressing may be controlled to be 2%-5% to meet the requirement of water content of the product.

[0061] (4) Oxidation reaction

[0062] The obtained manganese tetraoxide material with high specific surface area is mixed with an oxidant for reaction to obtain a MnOOH material with high specific surface area.

[0063] In some embodiments, the oxidant is hydrogen peroxide, and the molar ratio of manganese tetraoxide material to hydrogen peroxide is controlled to be 2:(2-5), such as 2:2, 2:3, 2:4, 2:5, etc. The reaction formula is as follows:

[0064] 2Mn 3 O 4 +3H 2 O 2 →6MnOOH+O 2 ;

[0065] In some embodiments, the reaction temperature of the manganese tetraoxide material and the oxidant is controlled to be 180° C.-220° C., and the reaction time is 2 h-4 h, so that the manganese tetraoxide is fully converted into MnOOH. Specifically, the reaction temperature can be 180° C., 190° C., 200° C., 210° C., 220° C., etc., and the reaction time can be 2 h, 3 h, 4 h, etc.

[0066] It should be noted that the present invention simplifies the synthesis steps, reduces the reaction temperature and time, and can also accurately control the specific surface area and crystal form of the MnOOH material, thereby improving the synthesis efficiency and facilitating large-scale production.

[0067] The embodiment of the present invention also provides a layered lithium manganate, which is prepared by the above method and has the advantages of low preparation cost and good electrochemical performance.

[0068] The embodiment of the present invention further provides a lithium battery positive electrode sheet, comprising the above-mentioned layered lithium manganese oxide, using the layered lithium manganese oxide material as a positive electrode active material, and forming a positive electrode active coating on the surface of a current collector.

[0069] The embodiment of the present invention provides a lithium battery, including the above-mentioned lithium battery positive electrode sheet, and may also include a negative electrode sheet, a separator, an electrolyte, etc. Due to the improvement of the preparation process of layered lithium manganese oxide, the preparation cost of the lithium battery is reduced.

[0070] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0071] It should be noted that the preparation process of the γ-type high specific surface area MnOOH material used in the following examples is as follows: (1) Mix metal manganese powder with a particle size D50 of 6-15 μm and water to prepare a manganese slurry with a solid content of 60% (mass fraction, the same below), grind the manganese slurry on a ball mill, and grind the particle size D50 to about 1.2-3 μm. (2) Introduce the ground manganese slurry into a reactor, and at the same time add ammonium acetate to the reactor at 1.0 g / L, adjust the pH value of the solution to about 7.0, the reaction process itself is an exothermic reaction, control the highest temperature during the reaction process ≤ 70°C (the reaction temperature is within the range of 40°C-60°C), control the stirring speed to between 250 r / min, and the reaction time is 5h. When the manganese content in the manganese slurry is measured to be between 71-72%, the manganese slurry is introduced into an aging tank and aged for 30 minutes. (3) The manganese slurry aged in the aging tank is filtered in a filter press, and the water content of the filter press is controlled at 2%-5% to obtain a manganese tetraoxide material. (4) The obtained manganese tetraoxide material with a high specific surface area is mixed with 30% hydrogen peroxide by mass, and the molar ratio of the manganese tetraoxide material to the hydrogen peroxide is 2:3, and the reaction is carried out at 200°C for 3h to obtain a γ-type MnOOH material with a high specific surface area. After testing, the specific surface area of ​​the manganese tetraoxide material obtained in step (3) is 35.11m 2 / g, the specific surface area of ​​the MnOOH material obtained in step (4) is 160.67 m 2 / g, the crystallinity of the material is: 98%.

[0072] The XRD pattern of the prepared MnOOH material is shown in Figure 1 As shown, it can be seen that the corresponding PDF card of this material is: 18-0805. It can be seen that the MnOOH material is γ-type and has a large specific surface area because ammonium acetate dissociates into NH 4 + and CH 3 COO - , CH 3 COO - It is a weak acid ion and can form a relatively stable complex with metallic manganese to avoid excessive reaction. In addition, the acetate ion produces gas when it decomposes, which is beneficial to increase the pH value of the product.

[0073] It should be noted that the salt lake brine used in the following examples and comparative examples was collected from the Chaerhan Salt Lake brine provided by Qinghai Salt Lake Industry Group Co., Ltd.

[0074] Example 1

[0075] This embodiment provides a method for preparing layered lithium manganate using salt lake brine, the steps are as follows:

[0076] (1) Collect brine containing lithium from the salt lake and pre-treat it by first using a precision filter to remove impurities such as suspended matter and particulate matter in the brine. Then, heat it to 65±5°C and evaporate and concentrate it to a lithium concentration of 30 mg / L.

[0077] (2) Add the γ-type high specific surface area MnOOH material to the above-mentioned pretreated salt lake brine, the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.04 g, stir for 30 minutes, and then stand for 1 hour. Pour the obtained mixed solution into a centrifuge, set the speed to 3000 rpm, the centrifugation time to 10 minutes, and obtain MnOOH-Li material powder after centrifugal separation.

[0078] (3) The MnOOH-Li material obtained in step (2) is placed in a muffle furnace, the temperature is set to 350° C., the heat preservation time is 2 hours, and then naturally cooled to room temperature to obtain a layered lithium manganate material LiMnO 2 .

[0079] The layered lithium manganate material LiMnO 2 The XRD pattern of Figure 2 As shown, it can be seen that the diffraction peak position and PDF 35-0749LiMnO 2 The characteristic peaks coincide with each other.

[0080] The layered lithium manganate material LiMnO 2 The SEM images are as follows Figure 3 As shown, it can be seen that the particle size is at the micron or submicron level and exhibits a certain porosity and layered structure, which helps to increase the diffusion rate of lithium ions and improve the capacity and rate performance of the electrode.

[0081] Example 2

[0082] The only difference from Example 1 is that in step (2), the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.02 g.

[0083] Example 3

[0084] The only difference from Example 1 is that in step (2), the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.10 g.

[0085] Example 4

[0086] The only difference from Example 1 is that in step (2), the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.005 g.

[0087] Example 5

[0088] The only difference from Example 1 is that in step (2), the amount of γ-type MnOOH corresponding to 100 mL of salt lake brine is 0.30 g.

[0089] Example 6

[0090] The only difference from Example 1 is that the sintering temperature in step (3) is 330°C.

[0091] Example 7

[0092] The only difference from Example 1 is that the sintering temperature in step (3) is 380°C.

[0093] Example 8

[0094] The only difference from Example 1 is that the sintering temperature in step (3) is 300°C.

[0095] Example 9

[0096] The only difference from Example 1 is that the sintering temperature in step (3) is 400°C.

[0097] Comparative Example 1

[0098] The only difference from Example 1 is that step (2) uses commercially available MnOOH material with a β-type crystal form and a specific surface area of ​​48.31, which was purchased from the official website of Sigma-Aldrich.

[0099] Comparative Example 2

[0100] The only difference from Example 1 is that step (2) uses commercially available MnOOH material with an α-type crystal form and a specific surface area of ​​54.59, which was purchased from the official website of Sigma-Aldrich.

[0101] Comparative Example 3

[0102] This comparative example provides a traditional layered lithium manganese oxide material LiMnO 2 The preparation method comprises the following steps: a lithium source (LiOH*H 2 O) and manganese source (Mn 2 O 3 ) are mixed evenly according to the molar ratio of lithium and manganese of 1:1, and then placed in a high-temperature furnace at a temperature of 850°C for calcination for 12 hours, and then cooled to room temperature in an inert atmosphere to obtain a layered lithium manganate material LiMnO 2 .

[0103] Test Example 1

[0104] The lithium concentration of the salt lake brine before and after adsorption in the test examples and comparative examples was calculated to determine the lithium recovery rate; adsorption amount (Qe):

[0105] Qe=[(C0-Ce)×V] / m

[0106] in:

[0107] C0 represents: initial lithium concentration (mg / L)

[0108] Ce means: lithium concentration after adsorption equilibrium (mg / L)

[0109] V: Brine volume (L)

[0110] m: adsorbent mass (g)

[0111] Lithium recovery rate (R):

[0112] R(%)=[(C0-Ce) / C0]×100

[0113] The results are shown in Table 1.

[0114] Table 1 Comparison of lithium extraction effects from salt lakes in the examples and comparative examples

[0115]

[0116]

[0117] It can be seen from Table 1 that the method provided in the embodiment of the present invention can improve the effect of lithium extraction from salt lakes compared with the comparative example, and the lithium recovery rate is higher.

[0118] Comparing Examples 1-3, it can be seen that as the mass of the adsorbent increases, the adsorption capacity decreases because the utilization rate of the unit mass of the adsorbent decreases. When the mass of the adsorbent is 0.02g, the adsorption capacity is the highest (60mg / g), but the recovery rate is low (40%). The optimal adsorbent mass: 0.04g (adsorption capacity 45mg / g, recovery rate 90%), a balance is achieved between the recovery rate and the utilization rate of the adsorbent.

[0119] Comparison of Examples 4-5 shows that the adsorption sites of 0.02g-0.10g and 0.005g are far from enough to adsorb lithium ions in brine, resulting in an extremely low recovery rate (10%). Although the adsorption amount is 60mg / g, the actual total amount of lithium recovered is extremely small due to the small amount of adsorbent, which cannot meet the needs of industrialization; the adsorbent dosage is too high (0.3g) and the adsorbent utilization rate is low: the adsorbent dosage is too high, and the adsorption amount per unit mass of the adsorbent is significantly reduced, resulting in waste of adsorbent, poor economic efficiency, increased adsorbent cost, but limited recovery rate improvement (from 80% to 90%), and low cost performance. Moreover, excessive adsorbent dosage may cause adsorbent particles to aggregate, increasing the difficulty of subsequent separation and purification.

[0120] Test Example 2

[0121] The layered lithium manganate material LiMnO was prepared by testing the examples and comparative examples. 2 The performance results are shown in Table 2.

[0122] Test method: At a voltage of 2.5-4.5V, charge to 4.5V at 0.1C constant current, let stand for 15 minutes, then discharge to 2.5V at 0.1C constant current, record the discharge capacity, then charge to 4.5V at 1C, then charge to 0.05C at constant voltage, let stand for 15 minutes, then discharge to 2.5V at 1C, record the discharge capacity, repeat the 1C step for 100 cycles, and record the 100-cycle 1C cycle retention rate.

[0123] Table 2 Layered lithium manganate material LiMnO prepared in Examples and Comparative Examples 2 Performance test results

[0124]

[0125] It can be seen from Table 2 that the layered lithium manganate material LiMnO prepared in the embodiment of the present invention 2 Excellent electrochemical performance.

[0126] Comparative Example 1 and Examples 6-9 show that:

[0127] Low-temperature sintering leads to insufficient crystallinity of the material and unstable structure, which affects the insertion and extraction of lithium ions, resulting in decreased capacity and cycle performance. Insufficient crystallinity also leads to reduced conductivity of the material, affecting the rate performance and cycle stability of the battery. High-temperature sintering leads to overburning of the material, excessive grain growth, reduced grain boundaries, and longer lithium ion diffusion paths, affecting the rate performance and cycle stability of the battery. Overburning may also cause material structure damage and form inactive phases, further reducing battery performance. LiMnO in Example 1 2 The material exhibits the best electrochemical performance, including the highest first charge, first discharge capacity, first efficiency, 1C capacity and 100-cycle 1C cycle retention rate.

[0128] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing layered lithium manganate using salt lake brine, characterized in that: include: The specific surface area is 150m 2 / g-180m 2 / g of γ-type MnOOH was mixed with salt lake brine for reaction, and then the MnOOH-Li material was obtained by solid-liquid separation; The MnOOH-Li material is sintered.

2. The method according to claim 1, characterized in that The process of preparing the MnOOH-Li material includes: mixing the γ-type MnOOH with the salt lake brine and stirring for 20 minutes to 60 minutes, then standing for 0.5 hours to 3.0 hours, and then performing solid-liquid separation.

3. The method according to claim 1 or 2, characterized in that: The concentration of lithium in the salt lake brine is 25 mg / L-35 mg / L, and the amount of the γ-type MnOOH corresponding to 100 mL of the salt lake brine is 0.02 g-0.10 g, preferably 0.03 g-0.06 g.

4. The method according to claim 1 or 2, characterized in that: Solid-liquid separation is performed by centrifugation, the centrifugal speed is controlled to be 2000rpm-4000rpm, and the centrifugal time is 5min-20min.

5. The method according to claim 1 or 2, characterized in that: The collected salt lake brine is first pre-treated to remove suspended matter and organic matter therein, and then mixed with the γ-type MnOOH.

6. The method according to claim 5, characterized in that The pretreatment process includes: filtering the salt lake brine and then evaporating and concentrating it.

7. The method according to claim 1, characterized in that The MnOOH-Li material is sintered at 330° C.-380° C. for 1 h-3 h.

8. A layered lithium manganate, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. A lithium battery positive electrode plate, characterized in that: Including the layered lithium manganate as described in claim 8.

10. A lithium battery, characterized in that: Including the lithium battery positive electrode sheet as described in claim 9.

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