Lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

This invention provides a lithium-rich manganese-based cathode material with the chemical formula Li. 1.2‑y A y Ni 0.4x Mn 0.8‑0.4x O2, A is Na, K, Ti or a combination thereof, wherein 0.375 ≤ x ≤ 0.5 and 0.03 ≤ y ≤ 0.07. This invention also provides a method for preparing a lithium-rich manganese-based cathode material. The lithium-rich manganese-based cathode material of this invention exhibits good electrochemical stability. This lithium-rich manganese-based cathode material can further improve the electrochemical stability of LMR.

Description

Technical Field

[0001] This invention relates to a lithium-rich manganese-based cathode material and a method for preparing the lithium-rich manganese-based cathode material. Background Technology

[0002] In recent years, with the increasing demand for battery energy density, lithium-rich manganese-based cathode materials (LMR) have attracted more and more attention due to their high energy density. LMR can be described as xLi₂MnO₃·(1-x)LiMO₂, especially with its cobalt-free, low-nickel, and high-manganese metering design, which offers cost advantages and features high reversible capacity (>250 mAh / g) and high voltage (>4.5 V).

[0003] The LMR structure consists of two parts: a layered LiMO2 structure and a lithium-rich Li2MnO3 phase. The former contributes capacity at voltages <4.5V, while the latter has an activation voltage ≥4.5V for delithiation. Besides being difficult to pair with electrolytes that can withstand high voltages, the lithium-rich Li2MnO3 phase also readily removes Li2O and releases oxygen (gas production), resulting in a significant irreversible capacity. Therefore, when the Mn content is high, LMR produces a correspondingly high proportion of the lithium-rich Li2MnO3 phase, and LMR as a whole can achieve a high reversible capacity (reversible capacity ~250mAh / g when charged to 4.6V). When the Ni content is high, the layered LiMO2 structure contributes a higher capacity. This layered structure is more stable than the lithium-rich Li2MnO3 phase, thus reducing irreversible capacity, but the overall reversible capacity of LMR is lower (reversible capacity approximately 220mAh / g when charged to 4.6V).

[0004] In view of the above, there is a need to provide a lithium-rich manganese-based cathode material with high electrochemical stability. Summary of the Invention

[0005] This invention provides a lithium-rich manganese-based cathode material. The chemical formula of the lithium-rich manganese-based cathode material is Li. 1.2- y A y Ni 0.4x Mn 0.8-0.4x O2, A is Na, K, Ti or a combination thereof, where 0.375≤x≤0.5 and 0.03≤y≤0.07.

[0006] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material is Li. 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2.

[0007] In some embodiments, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.8 m². 2 / g to 2.5m 2 / g.

[0008] In some embodiments, the porosity of the lithium-rich manganese-based cathode material is between 22.6 vol% and 28.4 vol%.

[0009] This invention also provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps: Adding a weakly alkaline manganese salt to an aqueous nickel salt solution to form a first precipitate solution. Adding a lithium salt and a metal salt to an aqueous manganese salt solution to form a second precipitate solution, wherein the metal salt comprises metal ions, and the metal ions include Na+. + K + Ti 3+ Or a combination thereof, wherein the manganese salt aqueous solution is acidic. The first and second precipitate solutions are mixed to form a precursor solution, and the liquid in the precursor solution is removed to form a precursor dry powder. The precursor dry powder is heat-treated to form a lithium-rich manganese-based cathode material.

[0010] In some implementations, the pH of the first precipitation solution is between 6 and 7.

[0011] In some implementations, the pH of the second precipitate solution is greater than 9.

[0012] In some embodiments, the metal salts include metal carbonates, metal hydroxides, metal oxides, metal nitrates, metal acetates, metal oxalates, or combinations thereof.

[0013] In some embodiments, the heat treatment temperature is between about 800°C and about 1100°C during the heat treatment process.

[0014] In some implementations, the heat treatment time is between 8 and 16 hours during the heat treatment process.

[0015] In some embodiments, the heat treatment atmosphere during the heat treatment includes air, pure oxygen, or a mixture thereof.

[0016] In some embodiments, the heating temperature is between about 40°C and about 80°C during the mixing of the first precipitate solution and the second precipitate solution.

[0017] In some embodiments, the first precipitation solution comprises nickel hydroxide precipitate.

[0018] In some embodiments, the second precipitation solution includes manganese hydroxide precipitate.

[0019] In some embodiments, the molar ratio of nickel salt to weakly alkaline manganese salt in the nickel salt aqueous solution is between (0.2-0.3):(0.265-0.3).

[0020] In some embodiments, the molar ratio of manganese salt, lithium salt and metal salt in the manganese salt aqueous solution is between (0.265-0.3):(1.14-1.20):(0.02-0.06).

[0021] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material is Li. 1.2-y A y Ni 0.4x Mn 0.8-0.4x O2, A is Na, K, Ti or a combination thereof, where 0.375≤x≤0.5 and 0.03≤y≤0.07.

[0022] In some embodiments, the ratio of the molar number of the weakly basic manganese salt to the molar number of manganese in the lithium-rich manganese-based cathode material is (0.25 to 0.5):1.

[0023] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material is Li. 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2.

[0024] In some implementations, the specific surface area of ​​the lithium-rich manganese-based cathode material is less than 2.5 m². 2 / g.

[0025] It should be understood that the foregoing general description and the following specific description are merely exemplary and explanatory, and are intended to provide further illustration of the claimed invention. Attached Figure Description

[0026] The above and other aspects, features, and advantages of the present invention will be more clearly understood with reference to the description and accompanying drawings, wherein:

[0027] Figure 1 This is the LMR polycrystalline powder of Comparative Example 1 of the present invention.

[0028] Figure 2 This is the LMR polycrystalline powder of Embodiment 1 of the present invention.

[0029] Figure 3 This is the LMR polycrystalline powder of Comparative Example 2 of the present invention.

[0030] Figure 4 This invention uses Comparative Example 1 to produce the charge-discharge curve of a button cell.

[0031] Figure 5This is the charge-discharge curve of a button cell produced using Example 1 of the present invention.

[0032] Figure 6 The present invention uses Comparative Example 2 to prepare the charge-discharge curve of a button cell.

[0033] Figure 7 This is a schematic diagram of the cycle test performed on coin cells made from polycrystalline powders of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0034] To make the description of the present invention more detailed and complete, reference can be made to the accompanying drawings and the various embodiments described below, in which the same numbers represent the same or similar elements.

[0035] The following describes several embodiments of the present invention with reference to the accompanying drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and elements will be shown in the drawings in a simple schematic manner.

[0036] Although the methods disclosed herein are illustrated using a series of operations or steps, the order in which these operations or steps are shown should not be construed as a limitation of the invention. For example, some operations or steps may be performed in a different order and / or simultaneously with other steps. Furthermore, not all illustrated operations, steps, and / or features are required to achieve embodiments of the invention. Additionally, each operation or step described herein may comprise several sub-steps or actions.

[0037] This invention provides a method for preparing a lithium-rich manganese-based cathode material. This method primarily utilizes two different manganese sources to control the surface area of ​​the lithium-metal chromatograph (LMR). Furthermore, to reduce the release of large amounts of gas (e.g., carbon dioxide) during high-temperature synthesis, the two manganese sources are reacted separately.

[0038] In detail, the preparation method of lithium-rich manganese-based cathode material includes the following steps: A weakly basic manganese salt is added to an aqueous nickel salt solution to form a first precipitate solution. More specifically, the aqueous nickel salt solution can be placed in a high-energy mill for cyclic grinding, and the weakly basic manganese salt is added during grinding to form the first precipitate solution. In some embodiments, the weakly basic manganese salt includes manganese carbonate (MnCO3), manganese(III) hydroxide (Mn(OH)3), or other suitable weakly basic manganese salts. In some embodiments, the pH value of the weakly basic manganese salt is greater than 7, for example, between 7.5 and 10. In some embodiments, the nickel salt includes nickel nitrate, nickel chloride, nickel acetate, nickel oxalate, or other organic nickel salts. More specifically, in this step, some of the weakly basic manganese salt decomposes, releasing carbon dioxide and precipitating nickel hydroxide precipitate.

[0039] In some embodiments, the pH of the first precipitation solution is between 6 and 7. That is, the first precipitation solution is weakly acidic. In some embodiments, the first precipitation solution comprises nickel hydroxide precipitate (Ni(OH)₂). n(s) In some embodiments, the molar ratio of nickel salt to weakly basic manganese salt in the nickel salt aqueous solution is between (0.2–0.3):(0.265–0.3). In some embodiments, when the molar ratio of nickel salt to weakly basic manganese salt in the nickel salt aqueous solution is less than a certain value, for example, 0.2:0.3, the acidity provided by the nickel salt is insufficient, resulting in insufficient CO2 removal capacity of manganese carbonate, thus leading to a higher specific surface area value of the final LMR. Conversely, when the molar ratio of nickel salt to weakly basic manganese salt in the nickel salt aqueous solution is greater than a certain value, for example, 0.3:0.265, the acidity provided by the nickel salt is sufficient, resulting in complete CO2 removal of manganese carbonate, thus leading to a lower specific surface area value of the final LMR.

[0040] Lithium salt and a metal salt are added to an aqueous solution of manganese salt to form a second precipitate solution, wherein the metal salt includes metal ions, and the metal ions are Na+. + K + Ti 3+ Or a combination thereof, and the manganese salt aqueous solution is acidic. More specifically, the manganese salt aqueous solution can be placed in a high-energy grinder for circulating grinding, and lithium salt and metal salts are added sequentially or simultaneously for grinding to form a second precipitate solution. In some embodiments, the lithium salt includes lithium carbonate, lithium hydroxide, lithium acetate, or lithium nitrate. In some embodiments, the manganese salt includes manganese nitrate (Mn(NO3)2). More specifically, in this step, the lithium salt and metal salt are decomposed, releasing carbon dioxide and precipitating manganese hydroxide precipitate. In some embodiments, the pH of the manganese salt aqueous solution is less than 7, for example, 4 to 6.5.

[0041] In some embodiments, the pH of the second precipitation solution is greater than 9. That is, the second precipitation solution is alkaline. In some embodiments, the second precipitation solution comprises manganese hydroxide precipitate (Mn(OH)₂). n(s) In some embodiments, the metal salt includes metal carbonates, metal hydroxides, metal oxides, metal nitrates, metal acetates, metal oxalates, or combinations thereof. For example, the metal salt may include sodium carbonate, potassium carbonate, titanium carbonate, sodium hydroxide, potassium hydroxide, titanium hydroxide, sodium oxide, potassium oxide, titanium oxide, sodium nitrate, potassium nitrate, titanium nitrate, sodium acetate, potassium acetate, titanium acetate, sodium oxalate, potassium oxalate, titanium oxalate, or combinations thereof.

[0042] In some embodiments, the molar ratio of manganese salt, lithium salt, and metal salt in the manganese salt aqueous solution is between (0.265–0.3):(1.14–1.20):(0.02–0.06). In this embodiment, the manganese salt and metal salt are designed to be acidic metal salts, while lithium salt is lithium carbonate. This aims to remove as much CO2 as possible from carbonate ions during the acid-base reaction; therefore, the molar amounts of manganese salt and metal salt are summed to (manganese salt + metal salt):(lithium salt) = (0.267–0.36):(1.14–1.20). In some embodiments, when the molar ratio of (manganese salt + metal salt) to (lithium salt) in the manganese salt aqueous solution is less than a certain value, for example, 0.267:1.20, the provided acidity is insufficient, resulting in insufficient CO2 removal capacity from lithium carbonate, thus leading to a higher specific surface area value of the final LMR. Conversely, when the molar ratio of (manganese salt + metal salt) to (lithium salt) in the manganese salt aqueous solution is greater than a certain value, such as 0.36:1.14, the acidity provided is sufficient, resulting in a complete CO2 reaction to remove lithium carbonate, which in turn leads to a lower specific surface area value of the final LMR.

[0043] It should be noted that the first and second precipitation solutions need to be prepared separately to reduce the release of large amounts of carbon dioxide gas during the reaction, thereby reducing the specific surface area of ​​the subsequent LMR powder formation. However, the first and second precipitation solutions can be prepared simultaneously or sequentially.

[0044] Next, the first and second precipitate solutions are mixed to form a precursor solution, and the liquid in the precursor solution is removed to form a precursor powder. More specifically, the first and second precipitate solutions are nano-milled at a heating temperature for approximately 3 hours to form the precursor solution. In some embodiments, the pH value of the precursor solution is greater than 7.5. The precursor solution is then spray-dried to obtain the precursor powder. In some embodiments, the average particle size of the precursor powder is less than 10 micrometers.

[0045] In some embodiments, the heating temperature during mixing of the first and second precipitate solutions is between about 40°C and about 80°C. In some embodiments, when the heating temperature is below a certain value, such as 40°C, during mixing of the first and second precipitate solutions, the chemical reaction rate and integrity of the solution cannot be promoted, thus failing to achieve the desired effect. Conversely, when the heating temperature is above a certain value, such as 80°C, during mixing of the first and second precipitate solutions, it indicates that the reaction rate of the solution is too fast, and after the partial reaction is completed, new products are easily coated on the original reactants, resulting in incomplete reaction. Therefore, the heating temperature during mixing of the first and second precipitate solutions can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or 75°C.

[0046] The precursor dry powder is then heat-treated to form the lithium-rich manganese-based cathode material. More specifically, the precursor dry powder is placed in a high-temperature furnace and a treatment atmosphere is introduced. The temperature is raised to the heat treatment temperature at a rate of 5°C / min, and after holding at that temperature for the specified time, it is allowed to cool naturally to obtain the lithium-rich manganese-based cathode material (LMR). This lithium-rich manganese-based cathode material (LMR) is in the form of a polycrystalline powder.

[0047] In some embodiments, the heat treatment temperature is between about 800°C and about 1100°C during the heat treatment process. In some embodiments, when the heat treatment temperature is below a certain value, such as 800°C, the LMR layered structure is incomplete, and the Li... + The ions do not easily detach from the structure and can be activated Li + Fewer ions mean a lower capacity contribution. Conversely, when the heat treatment temperature exceeds a certain value, such as 1100°C, excessively high temperatures can easily lead to severe agglomeration of the LMR powder, resulting in lower capacity utilization. Therefore, the heat treatment temperature can be 850°C, 900°C, 950°C, 1000°C, or 1050°C. In some embodiments, the heat treatment time is between 8 and 16 hours. In some embodiments, when the heat treatment time is less than a certain value, such as 8 hours, the LMR layered structure is incomplete, especially in the superlattice Li₂MnO₃, which exhibits an upward-sloping delithiation plateau at 4.6V, indicating that Li + The ions are not easily detached from the structure, and the activated Li +Fewer ions contribute to a lower capacity. Conversely, when the heat treatment time exceeds a certain value, such as 16 hours, the LMR structure is fully formed, and excessively long times are not productive. Therefore, the heat treatment time can be 9, 10, 11, 12, 13, 14, or 15 hours. In some embodiments, the heat treatment atmosphere during the heat treatment includes air, pure oxygen, or a mixture thereof.

[0048] Another embodiment of the present invention is a lithium-rich manganese-based cathode material prepared by the above-described preparation method. The chemical formula of the lithium-rich manganese-based cathode material is: Li 1.2-y A y Ni 0.4x Mn 0.8-0.4x O2, A is Na, K, Ti or a combination thereof, wherein 0.375 ≤ x ≤ 0.75 and 0.03 ≤ y ≤ 0.07. In some embodiments, the molar ratio of the weakly basic manganese salt to the molar ratio of manganese in the lithium-rich manganese-based cathode material is (0.25 to 0.5):1, for example, it can be 0.3:1, 0.35:1, 0.4:1 or 0.45:1.

[0049] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material can be Li 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2. In some embodiments, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.8 m². 2 / g to 2.5m 2 / g. For example, the specific surface area of ​​lithium-rich manganese-based cathode materials can be 1.9m². 2 / g, 2.0m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.3m 2 / g or 2.4m 2 / g. It should be noted that lithium-rich manganese-based cathode materials with low specific surface areas can suppress the rapid degradation characteristic of their structure. In some embodiments, the porosity of the lithium-rich manganese-based cathode material is less than 22.6 vol% to 28.4 vol%. For example, the porosity of the lithium-rich manganese-based cathode material can be 22.8 vol%, 23.0 vol%, 23.5 vol%, 24.0 vol%, 24.5 vol%, 25.0 vol%, 25.5 vol%, 26.0 vol%, 26.5 vol%, 27.0 vol%, 27.5 vol%, or 28.0 vol%.

[0050] The lithium-rich manganese-based cathode material of the present invention has several advantages. For example, the lithium-rich manganese-based cathode material prepared by the above preparation method has a small specific surface area, thus avoiding the rapid degradation of the LMR structure and improving the electrochemical stability of the LMR.

[0051] The following embodiments are provided to detail specific aspects of the present invention and to enable those skilled in the art to implement the invention. However, the following embodiments are not intended to limit the invention. Several comparative examples and embodiments will be listed below to verify the effectiveness of the invention.

[0052] Comparative Example 1: Preparation of Lithium-Rich Manganese-Based Cathode Materials Using a Single Manganese Source

[0053] Figure 1 This is the LMR polycrystalline powder of Comparative Example 1 of the present invention. The experimental steps are as follows: 116.3g of nickel nitrate (Ni(NO3)2·6H2O) was added to 1000mL of deionized water and stirred until completely dissolved. The nickel nitrate aqueous solution was poured into a high-energy mill for circulating grinding. During grinding, 138g of manganese carbonate (MnCO3), 85g of lithium carbonate (Li2CO3), and finally 5.3g of sodium carbonate (Na2CO3) were added and ground together. At this time, the acidic nickel nitrate and the alkaline manganese carbonate, lithium carbonate, and sodium carbonate underwent acid-base neutralization, and a small amount of carbonate ions were dissociated to produce carbon dioxide. After 3 hours of nano-grinding, the precursor slurry was completed. The precursor slurry was spray-dried to obtain a precursor dry powder with an average particle size of <10 micrometers. The precursor dry powder was placed in a high-temperature furnace and air was introduced. The temperature was increased to 950°C at a rate of 5°C / min and held for 12 hours, and then naturally cooled to obtain a stoichiometric amount of Li. 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2-rich lithium manganese-based cathode material polycrystalline powder C1, such as Figure 1 As shown.

[0054] The specific surface area of ​​the lithium-rich manganese-based cathode material polycrystalline powder C1 from Comparative Example 1, measured using the Brunauer-Emmett-Teller (BET) method in monolayer adsorption mode, was 5.6 m². 2 / g. The porosity of the lithium-rich manganese-based cathode material polycrystalline powder C1 in Comparative Example 1 was measured to be 43.2 vol%. using a mercury porosimeter.

[0055] Example 1: Preparation of lithium-rich manganese-based cathode materials using two different manganese sources

[0056] It should be noted that in Example 1, the molar ratio of the two different manganese source reactants (manganese carbonate and manganese nitrate) was 1:1, and the experimental steps are as follows. Figure 2 This is the LMR polycrystalline powder of Example 1 of the present invention. 116.3 g of nickel nitrate (Ni(NO3)2·6H2O) was added to 700 mL of deionized water and stirred until completely dissolved. The nickel nitrate aqueous solution was poured into a high-energy mill for circulating grinding, while 69.2 g of manganese carbonate (MnCO3) was added during grinding. The acidic nickel nitrate caused some of the manganese carbonate to decompose, releasing CO2 and precipitating Ni(OH). n A first precipitate solution with a pH between 6 and 7 was obtained. Separately, 150.6 g of manganese nitrate (Mn(NO3)2·4H2O) was added to 700 mL of deionized water and completely dissolved. During the circulating grinding process using a high-energy grinder, 85 g of lithium carbonate (Li2CO3) and 5.3 g of sodium carbonate (Na2CO3) were added sequentially. The reaction caused some of the lithium carbonate and sodium carbonate to decompose, releasing CO2 and precipitating Mn(OH). n A second precipitate solution with a pH > 9 was obtained. The first and second precipitate solutions prepared above were mixed and nano-milled at 40℃~80℃ for 3 hours to obtain the precursor slurry. The pH of this precursor slurry was > 7.5. After spray drying, the precursor slurry yielded a dry precursor powder with an average particle size < 10 micrometers. This dry precursor powder was placed in a high-temperature furnace and purged with air, heated to 1000℃ at a rate of 5℃ / min, held at that temperature for 10 hours, and then allowed to cool naturally to obtain a Li-stoichiometric concentration. 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2-rich manganese-based cathode material polycrystalline powder E1, such as Figure 2 As shown.

[0057] The specific surface area of ​​the lithium-rich manganese-based cathode material polycrystalline powder E1 from Example 1, measured using the Brunauer-Emmett-Teller (BET) method in monolayer adsorption mode, was 2.4 m². 2 / g. The porosity of the lithium-rich manganese-based cathode material polycrystalline powder E1 in Example 1 was measured to be 28.4 vol%. using a mercury porosimeter.

[0058] Both Comparative Example 1 and Example 1 can synthesize Li in stoichiometric amounts. 1.15 Na 0.05 Ni 0.2 Mn 0.6The lithium-rich manganese-based cathode material of O2 has the same composition and is within the scope of this invention. However, the specific surface area and porosity of the lithium-rich manganese-based cathode material of Example 1 are much smaller than those of the lithium-rich manganese-based cathode material of Comparative Example 1.

[0059] Comparative Example 2: Preparation of Lithium-Rich Manganese-Based Cathode Materials Using Two Different Manganese Sources

[0060] It should be noted that, compared to Example 1, Comparative Example 2 adjusted the molar ratio of the two different manganese source reactants (manganese carbonate and manganese nitrate) to 1:1. The experimental procedure is as follows: 175g of nickel nitrate (Ni(NO3)2·6H2O) was added to 700mL of deionized water and stirred until completely dissolved. The nickel nitrate aqueous solution was poured into a high-energy grinder for circulating grinding, while 115g of manganese carbonate (MnCO3) was added during grinding. The acidic nickel nitrate caused some of the manganese carbonate to decompose, releasing CO2 and precipitating Ni(OH). n A first precipitate solution with a pH between 6 and 7 was obtained. Separately, 133g of manganese nitrate (Mn(NO3)2·4H2O) was added to 700mL of deionized water and completely dissolved. During the circulating grinding process using a high-energy grinder, 85g of lithium carbonate (Li2CO3) and 3.18g of sodium carbonate (Na2CO3) were added sequentially. The reaction caused some of the lithium carbonate and sodium carbonate to decompose, releasing CO2 and precipitating Mn(OH). n A second precipitate solution with a pH > 9 was obtained. The first and second precipitate solutions were mixed and nano-milled at 40℃–80℃ for 3 hours to obtain the precursor slurry. The pH of this precursor slurry was > 7.5. After spray drying, the precursor slurry yielded a dry precursor powder with an average particle size < 10 micrometers. The dry precursor powder was placed in a high-temperature furnace and purged with air, heated to 1000℃ at a rate of 5℃ / min, held at that temperature for 10 hours, and then allowed to cool naturally to obtain a Li-based precursor powder. 1.14 Na 0.03 Ni 0.3 Mn 0.53 O2-rich manganese-based cathode material polycrystalline powder C2, such as Figure 3 As shown.

[0061] The specific surface area of ​​the lithium-rich manganese-based cathode material polycrystalline powder of Comparative Example 2, measured using the Brunauer-Emmett-Teller (BET) method in monolayer adsorption mode, was 2.4 m². 2 / g. The porosity of the lithium-rich manganese-based cathode material polycrystalline powder of Comparative Example 2, measured using a mercury porosimeter, was 28.4 vol%. The difference in synthesis stoichiometry between Comparative Example 2 and Example 1 is that Comparative Example 2 is Li... 1.14 Na0.03 Ni 0.3 Mn 0.53 O2-rich lithium-manganese-based cathode materials, compared with Li 1.2-y A y Ni 0.4x Mn 0.8-0.4x The general formula for O2 structure is x = 0.75 (Ni = 0.3, Mn = 0.53), y = 0.03, and the doped A is Na. + Ions, but the quantification of Ni and Mn is outside the reasonable quantification design (x≤0.5) described in this invention.

[0062] Experiment Example 1: Fabrication of LMR|Li coin cell

[0063] In this experimental example, LMR powders from Comparative Example 1, Example 1, and Comparative Example 2 were mixed with N-methyl-2-pyrrolidone (NMP). A slurry was prepared at a ratio of (NMP and LMR powder mixture):conductor:binder of 86:6:8 (with a solid content of approximately 42 wt% to 45 wt%) and coated onto a 15-micron aluminum current collector layer. After drying, 12-millimeter diameter electrodes were used to fabricate LMR|Li coin cells (R2032). In some embodiments, the conductor included Super P. In some embodiments, the binder included a fluorinated resin, such as PVdF. The cells were formed by charge-discharge at a constant current of 0.1C from 2 volts (V) to 4.7V.

[0064] Figure 4 This is the charge-discharge curve of the coin cell fabricated using LMR powder from Comparative Example 1. Figure 4 As shown, the initial charge capacity is 322 mAh / g, the reversible discharge capacity is 263 mAh / g, and the initial coulombic efficiency (ICE) is 81.7%. It can be understood that the capacity below 4.5V during the initial charge is contributed by the LiMO2 layered structure in the LMR structure, with a capacity of approximately 100 mAh / g. The capacity above and / or equal to 4.5V is contributed by the Li2MnO3 in the LMR structure, with a capacity of 222 mAh / g.

[0065] Figure 5 This is the charge-discharge curve of the coin cell fabricated using the LMR powder from Example 1 of this invention. Figure 5As shown, the initial charge capacity is 320 mAh / g, the reversible discharge capacity is 265 mAh / g, and the initial coulombic efficiency (ICE) is 82.8%. It can be understood that the capacity below 4.5V during the initial charge is contributed by the LiMO2 layered structure in the LMR structure. Due to the low Ni stoichiometry, it contributes only about 100 mAh / g. The high Mn stoichiometry means that the capacity above and / or equal to 4.5V is contributed by Li2MnO3 in the LMR structure, reaching 231 mAh / g.

[0066] from Figure 4 and Figure 5 It can be seen that increasing the Mn element stoichiometry can improve the reversible capacity of LMR.

[0067] Figure 6 This is the charge-discharge curve of the coin cell fabricated using LMR powder from Comparative Example 2. Figure 6 As shown, the initial charge capacity is 330 mAh / g, the reversible discharge capacity is 240 mAh / g, and the initial coulombic efficiency (ICE) is 72.7%. It is understood that the capacity below 4.5V during the initial charge is contributed by the LiMO2 layered structure in the LMR structure. Due to the slightly higher Ni metric, which exceeds the metric range of this invention, the contributed capacity is increased to approximately 120 mAh / g. The capacity above and / or equal to 4.5V is contributed by Li2MnO3 in the LMR structure, with a capacity of 220 mAh / g. Figure 5 and Figure 6 It can be seen that the present invention can control the charge and discharge capacity of the LMR cathode material by designing the metering of the cathode material.

[0068] Experiment Example 2: Loop Testing

[0069] In this experimental example, the LMR|Li coin cell made from the LMR obtained in Example 1 and the LMR|Li coin cell made from the LMR obtained in Comparative Example 1 were subjected to cyclic testing under a constant current of 0.2C and a voltage range of 2V to 4.7V.

[0070] Figure 7 This is a schematic diagram illustrating the cycle testing of coin cells made from polycrystalline powders of Embodiment 1 and Comparative Example 1 of the present invention, where curve A represents the LMR obtained in Embodiment 1, and curve B represents the LMR obtained in Comparative Example 1. Figure 7 It can be seen that the LMR polycrystalline powder prepared in Example 1 has a low specific surface area and low porosity, resulting in better cycling stability. Curve A still has 93.4% capacity retention after 100 cycles, while curve B only has 79.3% capacity retention after 100 cycles.

[0071] Although the invention has been described in considerable detail with reference to certain embodiments, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

[0072] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from its scope or spirit. In view of the foregoing, this invention is intended to cover any modifications and variations falling within the scope of the appended claims.

[0073] [Symbol Explanation]

[0074] C1: Lithium-rich manganese-based cathode material polycrystalline powder

[0075] E1: Lithium-rich manganese-based cathode material polycrystalline powder

[0076] C2: Lithium-rich manganese-based cathode material polycrystalline powder

[0077] A: Curve

[0078] B: Curve.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, The chemical formula of the lithium-rich manganese-based cathode material is: Li 1.2-y A y Ni 0.4x Mn 0.8-0.4x O2, A is Na, K, Ti or a combination thereof, where 0.375≤x≤0.5 and 0.03≤y≤0.

07.

2. The lithium-rich manganese-based cathode material according to claim 1, wherein the chemical formula of the lithium-rich manganese-based cathode material is Li 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2.

3. The lithium-rich manganese-based cathode material according to claim 1, wherein the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.8 m². 2 / g to 2.5m 2 / g.

4. The lithium-rich manganese-based cathode material according to claim 1, wherein the porosity of the lithium-rich manganese-based cathode material is from 22.6 vol% to 28.4 vol%.

5. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, include: A weakly alkaline manganese salt is added to an aqueous solution of nickel salt to form a first precipitate solution; Lithium salt and a metal salt are added to an aqueous manganese salt solution to form a second precipitate solution, wherein the metal salt comprises metal ions, including Na+. + K + Ti 3+ Or a combination thereof, and the aqueous solution of the manganese salt is acidic; The first precipitation solution and the second precipitation solution are mixed to form a precursor solution and the liquid in the precursor solution is removed to form a precursor dry powder. as well as The precursor dry powder was heat-treated to form the lithium-rich manganese-based cathode material.

6. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the pH value of the first precipitate solution is between 6 and 7.

7. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the pH value of the second precipitate solution is greater than 9.

8. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the metal salt includes metal carbonate, metal hydroxide, metal oxide, metal nitrate, metal acetate, metal oxalate, or a combination thereof.

9. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the heat treatment temperature is between 800°C and 1100°C during the heat treatment.

10. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the heat treatment time is between 8 hours and 16 hours during the heat treatment.

11. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the heat treatment atmosphere during the heat treatment includes air, pure oxygen, or a mixture thereof.

12. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the heating temperature is between 40°C and 80°C during the mixing of the first precipitate solution and the second precipitate solution.

13. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the first precipitation solution comprises nickel hydroxide precipitate.

14. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the second precipitation solution comprises manganese hydroxide precipitate.

15. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the molar ratio of nickel salt to weakly alkaline manganese salt in the nickel salt aqueous solution is between 0.2 and 0.3: 0.265 and 0.

3.

16. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the molar ratio of manganese salt, lithium salt and metal salt in the manganese salt aqueous solution is between 0.265-0.3:1.14-1.20:0.02-0.

06.

17. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the chemical formula of the lithium-rich manganese-based cathode material is: Li 1.2-y A y Ni 0.4x Mn 0.8-0.4x O2, A is Na, K, Ti or a combination thereof, where 0.375≤x≤0.5 and 0.03≤y≤0.

07.

18. The method for preparing lithium-rich manganese-based cathode material according to claim 17, wherein the ratio of the molar number of the weakly basic manganese salt to the molar number of manganese in the lithium-rich manganese-based cathode material is 0.25 to 0.5:

1.

19. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the chemical formula of the lithium-rich manganese-based cathode material is Li 1.15 Na 0.05 Ni 0.2 Mn 0.6 O2.

20. The method for preparing lithium-rich manganese-based cathode material according to claim 5, wherein the specific surface area of ​​the lithium-rich manganese-based cathode material is less than 2.5 m². 2 / g.

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