Lithium-rich manganese-based positive electrode material and preparation method and application thereof
By adjusting the lithium-manganese-nickel ratio through co-precipitation and precisely controlling the superlattice structure, lithium-rich manganese-based cathode materials with high specific energy and high specific capacity were prepared, solving the problems of voltage and capacity decay and realizing simple, low-cost, large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-03
- Publication Date
- 2026-04-10
AI Technical Summary
Existing lithium-rich manganese-based cathode materials suffer from severe voltage and capacity decay during cycling, and traditional modification methods are complex, costly, and difficult to mass-produce.
A co-precipitation method was used to prepare lithium-rich manganese-based cathode materials. By adjusting the ratio of lithium, nickel, and manganese in the chemical formula of the material, the proportion of the Li2MnO3 superlattice phase was reduced. Oxalic acid or oxalate was used as a precipitant to precisely control the superlattice structure and the stoichiometry of nickel, manganese, and lithium, thus avoiding complexation and simplifying the preparation process.
It effectively suppresses stress accumulation during charge-discharge cycles, reduces transition metal migration and oxygen release, maintains high specific energy and high specific capacity, has excellent cycle performance, low cost, and is suitable for large-scale production.
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Figure CN121839670A_ABST
Abstract
Description
[0001] This application is a divisional application of the invention patent application with application number 202410006164.9, application date January 3, 2024, entitled "A lithium-rich manganese-based cathode material and its preparation method and application". Technical Field
[0002] This invention belongs to the field of energy storage materials technology, specifically relating to a lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology
[0003] In recent years, global warming and environmental pollution have been severe challenges facing human development. Meanwhile, the gradual depletion of fossil fuels cannot meet the energy demands of the economy and society. Developing sustainable and clean energy has become an urgent issue. Electric vehicles can effectively reduce carbon dioxide emissions and alleviate the environmental pressure caused by transportation. Therefore, lithium-ion batteries, the core energy component of electric vehicles, have become a field of close attention for researchers. Lithium-ion batteries are widely used in electric vehicles, rail transportation, large-scale energy storage, and aerospace due to their advantages such as high energy density, high output power, long lifespan, wide operating temperature range, no memory effect, and environmental friendliness. The cathode material is the heart of a lithium-ion battery, being the most expensive and having the greatest impact on performance. Currently, the most widely used cathode materials for lithium-ion batteries are ternary lithium and lithium iron phosphate. However, the low energy density of ternary lithium and lithium iron phosphate contributes to range anxiety in current electric vehicles. Furthermore, ternary lithium also poses certain safety risks, and its cobalt content leads to high costs and significant environmental pollution. Lithium iron phosphate is relatively stable, but its lower energy density makes it more difficult to meet the demands of battery energy storage. Therefore, researching lithium-ion batteries with higher energy density and higher operating voltage is of great significance.
[0004] Lithium-rich manganese-based cathode materials have emerged as a focal point of attention in recent years due to their higher specific capacity, higher operating voltage, and lower cost. However, traditional lithium-rich materials suffer from severe voltage and capacity decay, resulting in significant capacity and voltage losses after only a few dozen cycles, making them unusable for multiple cycles. Furthermore, they exhibit poor rate performance, with high-rate capacity loss and even worse low-rate cycling performance. Current technologies employ doping, coating, and surface treatment to mitigate voltage and capacity decay to some extent, but the effects are limited. Moreover, complex modification methods and the incorporation of precious metals further complicate large-scale production.
[0005] Therefore, there is an urgent need to provide a novel lithium-rich manganese-based cathode material that can reduce voltage and capacity decay and facilitate large-scale production. Summary of the Invention
[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a lithium-rich manganese-based cathode material, its preparation method, and its applications. The lithium-rich manganese-based cathode material provided by this invention has high specific energy and high specific capacity, effectively reduces voltage and capacity decay, and has low material cost, does not contain any other doped elements, and is beneficial for large-scale production.
[0007] This invention provides a lithium-rich manganese-based cathode material.
[0008] Specifically, a lithium-rich manganese-based cathode material with the chemical formula Li 1.20-1.40 Ni x Mn y O 2.0-2.5 , where x = 0.35 - 0.40, y = 0.60 - 0.65, and x + y = 1.
[0009] Preferably, the lithium-rich manganese-based cathode material has the chemical formula Li. 1.20-1.35 Ni x Mn y O 2.0-2.4 Where x = 0.35-0.39, y = 0.61-0.65, and x + y = 1. More preferably, the lithium-rich manganese-based cathode material has the chemical formula Li. 1.22-1.35 Ni x Mn y O 2.1-2.4 Where x = 0.35 - 0.39, y = 0.61 - 0.65, and x + y = 1 The present invention also provides a method for preparing the above-mentioned novel lithium-rich manganese-based cathode material.
[0010] Specifically, the preparation method of the above-mentioned lithium-rich manganese-based cathode material includes the following steps: Nickel and manganese salts are dissolved in a solvent, and then a precipitant is added and stirred. The precipitate is obtained by solid-liquid separation. Finally, the precipitate is mixed with a lithium source and sintered to obtain a lithium-rich manganese-based cathode material. The precipitant includes at least one of oxalic acid, oxalate, and carbonate.
[0011] Preferably, the molar ratio of nickel to manganese in the nickel salt and the manganese salt is (6-9):(11-14).
[0012] Preferably, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium chloride, and lithium nitrate; more preferably, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium oxide.
[0013] Preferably, the nickel salt is a soluble divalent nickel salt; more preferably, the nickel salt is selected from at least one of nickel sulfate, nickel chloride, nickel bromide, nickel iodide, and nickel aminosulfonate.
[0014] Preferably, the manganese salt is a soluble divalent manganese salt; more preferably, the manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese bromide, manganese iodide, and manganese aminosulfonate.
[0015] Preferably, the solvent is deionized water. That is, the nickel salt and the manganese salt are dissolved in water to form a mixed solution.
[0016] Preferably, the precipitant is oxalic acid and / or oxalate, such as sodium oxalate, potassium oxalate, or ammonium oxalate.
[0017] Preferably, the amount of precipitant added is 1-1.2 times the sum of the amounts of the nickel salt and the manganese salt; more preferably, the amount of precipitant added is 1-1.05 times the sum of the amounts of the nickel salt and the manganese salt.
[0018] Preferably, the precipitant is added in the form of a precipitant solution, wherein the solvent of the precipitant solution is water and / or ethanol; more preferably, the solvent of the precipitant solution is water and ethanol.
[0019] Preferably, the process of adding the precipitant solution involves adding the precipitant solution dropwise to a mixed solution of nickel salt and manganese salt.
[0020] Preferably, the stirring process is as follows: stirring at a speed of 400-1000 rpm for 24-72 hours under sealed conditions.
[0021] Preferably, the precipitate is washed and dried before being mixed with the lithium source. The washing process involves first washing the precipitate with water, and then washing it with ethanol.
[0022] Preferably, the amount of lithium in the lithium source is 1.1-1.5 times the amount of the precipitate; more preferably, the amount of lithium in the lithium source is 1.2-1.43 times the amount of the precipitate.
[0023] Preferably, the sintering process is as follows: heating to 400-700℃ at a heating rate of 1-3℃ / min, holding at that temperature for 3-6 hours, and then heating to 800-1000℃ at a heating rate of 4-8℃ / min, holding at that temperature for 8-16 hours. More preferably, the sintering process is as follows: heating to 420-620℃ at a heating rate of 1.5-2.5℃ / min, holding at that temperature for 5-6 hours, and then heating to 800-1000℃ at a heating rate of 4-6℃ / min, holding at that temperature for 12-14 hours.
[0024] This invention provides applications of the above-mentioned lithium-rich manganese-based cathode material.
[0025] Specifically, the application of the aforementioned lithium-rich manganese-based cathode material in battery fabrication.
[0026] This invention provides a lithium battery.
[0027] Specifically, a lithium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material.
[0028] Preferably, the electrolyte is LB-012 electrolyte or LB-301 electrolyte.
[0029] Preferably, the membrane is a polypropylene microporous membrane or a glass fiber membrane, such as a polypropylene microporous membrane manufactured by Celgard or a glass fiber membrane manufactured by Whatman.
[0030] Traditional lithium-rich manganese-based cathode materials have the chemical formula Li 1.2 Ni 0.2 Mn 0.6 O2, and some materials also contain cobalt, such as Li. 1.2 Ni 0.16 Mn 0.56 Co 0.08 O2 or Li 1.2 Ni 0.12 Mn 0.56 Co 0.12 O2, cobalt-containing lithium-rich materials are expensive and environmentally unfriendly. The chemical formula of traditional lithium-rich manganese-based cathode materials can also be written as 0.5LiNi. 0.5 Mn 0.5 O2·0.5 Li2MnO3, wherein the Li2MnO3 superlattice phase accounts for approximately 50%. This structure of lithium-rich manganese-based cathode material exhibits high discharge specific capacity, but suffers from severe voltage and capacity decay. This is due to the initial driving force of harmful stress accumulation, leading to transition metal migration and oxygen release, ultimately resulting in structural failure. This invention obtains a novel lithium-rich manganese-based cathode material through the modulation and control of the superlattice phase, with the chemical formula Li2MnO3. 1.20-1.40 Ni x Mn y O 2.0-2.5The stoichiometric coefficient of O cannot be directly measured and is generally obtained by balancing. The sum of the stoichiometric coefficients of Ni and Mn is 1. This invention reduces the proportion of the Li2MnO3 superlattice phase to between 22% and 28% by introducing more Ni. At the same time, the two phases themselves have a certain degree of Ni, Mn, and Li mixing. This allows the lithium-rich manganese-based cathode material with this structure to greatly reduce stress accumulation during charge-discharge cycles, thereby suppressing transition metal migration and oxygen release, and inhibiting voltage and capacity decay from the original driving force.
[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The lithium-rich manganese-based cathode material provided by the present invention has the chemical formula Li 1.20-1.40 Ni x Mn y O 2.0-2.5 By introducing more Ni, reducing the proportion of the Li₂MnO₃ superlattice phase, and coordinating the mixing of Ni, Mn, and Li in the molecule, this invention significantly reduces stress accumulation during charge-discharge cycles, inhibits transition metal migration and oxygen release, thereby suppressing voltage and capacity decay. The lithium-rich manganese-based cathode material provided by this invention, while possessing high specific energy and high specific capacity, effectively eliminates voltage decay, maintaining essentially no capacity voltage decay after 500 cycles, and exhibits excellent cycling performance under both high and low rate conditions.
[0032] (2) In the preparation of lithium-rich manganese-based cathode materials in this invention, a precursor is prepared by co-precipitation, using oxalic acid or oxalate as a precipitant to precisely control the ratio of superlattice structure to nickel, manganese, and lithium; then, it is obtained by sintering. Using oxalic acid or oxalate as a precipitant not only makes precipitation more complete and avoids complexation, but also allows for more precise control of the stoichiometry of superlattice structure and nickel, manganese, and lithium. Compared with the sol-gel method and the nickel-manganese hydroxide method, the lithium-rich manganese-based cathode materials prepared in this invention have superior cycle performance.
[0033] (3) The method for preparing lithium-rich manganese-based cathode material provided by the present invention has a simple synthesis process. It can obtain lithium-rich manganese-based cathode material with excellent cycle performance by simply adjusting the ratio of lithium, nickel and manganese in the chemical formula of the material and the ratio of the two phases. It does not contain any other elements, does not contain cobalt, has low cost, is environmentally friendly, and is conducive to large-scale production and application. Attached Figure Description
[0034] Figure 1 A comparison diagram of stress accumulation between the lithium-rich manganese-based cathode material (LRN-1) provided in Example 1 and the conventional lithium-rich cathode material (LR); Figure 2 The XRD diffraction pattern of the lithium-rich manganese-based cathode material provided in Example 1; Figure 3 A comparison of voltage and oxygen release during charging and discharging between the lithium-rich manganese-based cathode material (LRN-1) provided in Example 1 and the conventional lithium-rich cathode material (LR); Figure 4 The lithium-rich manganese-based cathode material provided in Example 1; Figure 5 This is a graph showing the change in the coordination of Ni and Mn elements in traditional lithium-rich cathode materials over one charge-discharge cycle. Figure 6 The graph shows the capacity change of the lithium-rich manganese-based cathode material provided in Example 1 during charge-discharge cycles. Figure 7 The voltage variation diagram of the lithium-rich manganese-based cathode material provided in Example 1 during charge-discharge cycles; Figure 8 The graph shows the capacity change of the lithium-rich manganese-based cathode material provided in Example 2 during charge-discharge cycles. Figure 9 The voltage variation diagram of the lithium-rich manganese-based cathode material provided in Example 2 during charge-discharge cycles is shown. Figure 10 The graph shows the capacity change of the lithium-rich manganese-based cathode material provided in Example 3 during charge-discharge cycles. Figure 11 The voltage variation diagram of the lithium-rich manganese-based cathode material provided in Example 3 during charge-discharge cycles; Figure 12 The graph shows the capacity change of the lithium-rich manganese-based cathode material provided in Example 4 during charge-discharge cycles. Figure 13 The voltage variation diagram of the lithium-rich manganese-based cathode material provided in Example 4 during charge-discharge cycles is shown. Detailed Implementation
[0035] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.
[0036] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.
[0037] Example 1 This embodiment provides a novel lithium-rich manganese-based cathode material with the chemical formula Li. 1.27 Ni 0.372 Mn 0.628 O 2.27 .
[0038] A novel method for preparing lithium-rich manganese-based cathode material includes the following steps: (1) Precursor synthesis. Nickel sulfate (NiSO4·6H2O) and manganese sulfate (MnSO4·H2O) were mixed in a specific ratio to prepare approximately 0.05 mol. 4.94 g of nickel sulfate and 5.281 g of manganese sulfate were added, followed by 25 mL of water, and the mixture was stirred with a magnetic stir bar. Sodium oxalate (NaC2O4) was used as a precipitant, with an addition of 6.905 g. 25 mL of water and 25 mL of ethanol were added to the sodium oxalate powder, and the mixture was stirred and sonicated until homogeneous to obtain the precipitant solution. The precipitant solution was added dropwise to the nickel-manganese mixed solution, and then 50 mL of water was added to wash the precipitant beaker before being added dropwise. The mixture was stirred at 600 rpm in a sealed container for 48 h. The precipitate was then obtained by centrifugation, washed three times with water and three times with ethanol, dried at 80 °C for 24 h, and then stored.
[0039] (2) Sintering. 2g of precipitate (i.e., precursor) was mixed with 0.537g of lithium hydroxide (LiOH·H2O). After uniform mixing and grinding, the mixture was placed in a muffle furnace for sintering. The heating program was as follows: the temperature was increased to 500℃ at a heating rate of 2℃ / min, held for 5 hours, then increased to 900℃ at a heating rate of 5℃ / min, held for 12 hours, and then cooled to room temperature to obtain lithium-rich manganese-based cathode material.
[0040] This embodiment also provides a lithium battery, including a positive electrode, a negative electrode, a separator, and an LB-012 electrolyte. The positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material. The specific preparation and assembly methods are as follows: (1) Coating. Take the lithium-rich manganese-based cathode material prepared by sintering, conductive carbon black and PVDF (polyvinylidene fluoride), mix them in a ratio of 80mg:10mg:10mg, grind them evenly, and then add 0.2mL of NMP (dimethylpyrrolidone) solvent. After standing for a few minutes, stir with a planetary stirrer for 25 minutes, coat it on aluminum foil with a thickness of 15mm, dry it in a drying oven, and then dry it in a vacuum oven at 110℃ for 12 hours.
[0041] (2) Slicing, weighing, and assembling the battery. The cut electrode sheet has a diameter of 10 mm. A CR2025 battery case, a 15 mm diameter lithium sheet, and a glass fiber membrane produced by Whatman are used. 0.08 mL of LB-012 electrolyte is added. The LB-012 electrolyte and glass fiber membrane are used in combination with the lithium-rich manganese-based cathode material provided by this invention to prepare a battery with better performance.
[0042] The composition of the prepared lithium-rich manganese-based cathode material was accurately determined using ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry), and the stoichiometric ratio was found to be Li:Ni:Mn = 1.27:0.372:0.628. Therefore, the chemical formula of the sample is Li. 1.27 Ni 0.372 Mn 0.628 O2.27 .
[0043] Studies have shown that irreversible stress accumulation during charge-discharge cycles in lithium-rich manganese-based cathode materials is the primary driving force behind structural damage and voltage / capacity decay. Therefore, suppressing this stress accumulation is crucial for controlling voltage and capacity degradation. The stress accumulation of lithium-rich manganese-based cathode materials during charge-discharge cycles was investigated using characterization techniques such as X-ray diffraction, X-ray absorption spectroscopy, and Bragg coherence diffraction. Batteries were first assembled using the cathode material according to the cycle testing method, and then tested at a 0.1C rate. Figure 1 The charging and discharging potentials are shown. The battery is then disassembled inside the glove box, and the corresponding positive electrode is removed and cleaned in dimethyl carbonate to remove the electrolyte. Finally, the electrode is dried. X-ray diffraction patterns are obtained using an Ultima IV X-ray diffractometer at a step size of 0.02° and a scan rate of 10° / min. Based on the full width at half maximum (FWHM) and peak position of the characteristic peaks in the patterns calculated using Origin software, the stress magnitude is calculated using the Scherer formula and the definition of FWHM. The stress accumulation results after charging at various voltages, compared to the uncharged initial state, are as follows: Figure 1 As shown, Figure 1 The medium bar diagrams represent the lithium-rich manganese-based cathode material (LRN-1) provided in this embodiment and the conventional lithium-rich manganese-based cathode material 0.5LiNi, respectively. 0.5 Mn 0.5 O2·0.5Li2MnO3 (LR). Comparison shows that the novel lithium-rich manganese-based cathode material provided by this invention exhibits significantly reduced stress during charge-discharge cycles.
[0044] The lithium-rich manganese-based cathode material prepared in this embodiment was analyzed by X-ray diffraction, and the XRD diffraction pattern is shown below. Figure 2 As shown. Figure 2 The two curves represent the lithium-rich manganese-based cathode material (LRN-1) provided in this embodiment and the traditional lithium-rich manganese-based cathode material 0.5LiNi, respectively. 0.5 Mn 0.5 O2·0.5Li2MnO3 (LR). From Figure 2 It can be seen that several superlattice characteristic peaks of the lithium-rich manganese-based cathode material (LRN-1) provided in this embodiment have changed significantly, representing changes in the structure and content of the superlattice structure.
[0045] Oxygen release during charging poses a safety hazard. Differential electrochemical mass spectrometry (DEMS) was used to detect oxygen release. First, a mold battery was assembled using a DEMS mold equipped with a glass microfiber filter. Then, the mold battery was charged and discharged once at a rate of 0.1C. Simultaneously, Ar carrier gas was passed through the mold at a constant rate (0.2 mL / min) and flowed into a quadrupole mass spectrometer (OmniStar GSD 320) equipped with a Pfeiffer Vacuum. This allowed the mass spectrometer to capture and test the oxygen released during the charging and discharging process in real time. The test results are as follows: Figure 3 As shown. In Figure 3 The two upper curves represent the charge-discharge curves, corresponding to the left ordinate; the two lower curves represent the oxygen release, corresponding to the right ordinate. Figure 3 It is known that the lithium-rich manganese-based cathode material (LRN-1) provided in this embodiment does not release any oxygen.
[0046] Hard X-ray absorption spectroscopy (H-XAS) can characterize the coordination of elements, and thus the migration of transition metals. H-XAS was used to study the lithium-rich manganese-based cathode material (LRN-1) provided in this embodiment and the conventional lithium-rich manganese-based cathode material 0.5LiNi. 0.5 Mn 0.5 O2·0.5Li2MnO3(LR). The test structure is shown below. Figure 4 and Figure 5 , Figure 4 and Figure 5 The curve represents the result of a Fourier transform of the hard X-ray absorption spectrum, illustrating the coordination of different elements within the material. By comparing the changes in coordination before and after charging and discharging, it can be determined whether metal migration has occurred. The test was conducted by disassembling the battery after one cycle at 0.1C (consistent with the stress test method). Figure 4 and Figure 5 In the diagram, A represents Ni and B represents Mn. Focusing on the first two peaks, taking the Ni curve as an example, the first two peaks represent the Ni-O and Ni-Ni coordination, respectively; the Mn curve follows the same logic. It can be seen that after one charge-discharge cycle, the Ni-O and Mn-O coordination in the traditional lithium-rich manganese-based material (LR) differs significantly, indicating severe migration of both Ni and Mn, accompanied by significant oxygen loss. However, the Ni and Mn coordination in the lithium-rich manganese-based cathode material (LRN-1) provided by this invention remains essentially unchanged, indicating that metal migration and loss are greatly suppressed. This also confirms that the lithium-rich manganese-based cathode material provided by this invention eliminates voltage and capacity decay.
[0047] Based on the above characterization results, this invention addresses the root cause of voltage and capacity decay—stress accumulation—by essentially solving the two major structural factors leading to voltage decay: oxygen release and transition metal migration. This results in a truly virtually decay-free lithium-rich manganese-based lithium battery cathode material.
[0048] The assembled battery was cycled 200 times at a low rate of 0.2C to test its performance. First, the mass of the active material was calculated by subtracting the mass of the aluminum foil, conductive carbon black, and PVDF binder from the mass of the electrode sheet. A 1C rate represents the time required to complete charging or discharging at the nominal specific capacity in one hour. The nominal specific capacity of the lithium-rich manganese-based cathode material is 250 mAh / g, so the discharge current can be calculated by multiplying the mass of the active material by the nominal specific capacity and the required rate. Then, using the Xinwei testing system, the battery was charged to 4.8V per cycle and then discharged to 2.0V. After two cycles of activation at 0.1C, a constant current charge-discharge test of 200 cycles was performed. The test results are as follows: Figure 6 , Figure 7 As shown. In Figure 6 , Figure 7 In the diagram, curve LRN-1 represents the battery provided in this embodiment, and LR represents the 0.5LiNi cathode material, which is a traditional lithium-rich manganese-based cathode material. 0.5 Mn 0.5 A battery prepared from O2·0.5Li2MnO3 (LR). Figure 6 , Figure 7 It can be seen that, at low rates, the battery provided in this embodiment does not decrease in voltage and capacity after 200 charge-discharge cycles (total cycle time of about half a year), which is a qualitative leap compared to traditional lithium-rich materials.
[0049] Example 2 This embodiment provides a novel lithium-rich manganese-based cathode material with the chemical formula Li. 1.23 Ni 0.389 Mn 0.611 O 2.1 .
[0050] A novel method for preparing lithium-rich manganese-based cathode material includes the following steps: (1) Precursor synthesis. Nickel sulfate (NiSO4·6H2O) and manganese sulfate (MnSO4·H2O) were mixed in a specific ratio to prepare approximately 0.1 mol. 10.48 g of nickel sulfate and 10.26 g of manganese sulfate were added, followed by 50 mL of water and stirred with a magnetic stir bar. Oxalic acid (HC2O4) was used as a precipitant, with 9.45 g added. 50 mL of water and 50 mL of ethanol were added to sodium oxalate powder, stirred, and sonicated until homogeneous to obtain a precipitant solution. The precipitant solution was added dropwise to the nickel-manganese mixed solution, and then 100 mL of water was added to wash the precipitant beaker before adding it dropwise. The mixture was stirred at 600 rpm in a sealed container for 24 h. The precipitate was then obtained by centrifugation, washed three times with water and three times with ethanol, dried at 80 °C for 24 h, and then stored.
[0051] (2) Sintering. 1g of precipitate (i.e., precursor) was mixed with 0.268g of lithium hydroxide (LiOH·H2O), and after being mixed and ground evenly, it was placed in a muffle furnace for sintering. The heating program was as follows: heating to 500℃ at a heating rate of 2℃ / min, holding at that temperature for 6 hours, then heating to 1000℃ at a heating rate of 4.5℃ / min, holding at that temperature for 10 hours, and then cooling to room temperature to obtain lithium-rich manganese-based cathode material.
[0052] This embodiment also provides a lithium battery, including a positive electrode, a negative electrode, a separator, and an LB-012 electrolyte. The positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material. The specific preparation and assembly methods are as follows: (1) Coating. Take the lithium-rich manganese-based cathode material prepared by sintering, conductive carbon black and PVDF (polyvinylidene fluoride), mix them in a ratio of 160mg:20mg:20mg, grind them evenly, and then add 0.5mL of NMP (dimethylpyrrolidone) solvent. After standing for a few minutes, stir with a planetary stirrer for 20 minutes, coat it on aluminum foil with a thickness of 15mm, dry it in a drying oven, and then dry it in a vacuum oven at 100℃ for 10 hours.
[0053] (2) Slicing, weighing, and assembling the battery. The cut electrode sheet is 10 mm in diameter. Use a CR2016 battery case, a 10 mm diameter lithium sheet, a polypropylene microporous membrane produced by Celgard, and add 0.04 mL of LB-012 electrolyte.
[0054] The composition of the prepared lithium-rich manganese-based cathode material was accurately determined using ICP-OES (Inductively Coupled Plasma Emission Spectrometry). The determined stoichiometric ratio was Li:Ni:Mn = 1.23:0.389:0.611. Therefore, the chemical formula of the prepared lithium-rich manganese-based cathode material was determined to be Li... 1.23 Ni 0.389 Mn 0.611 O2.1 .
[0055] The assembled battery was cycled 400 times at a 1C rate to test its performance. The test results are as follows: Figure 8 , Figure 9 As shown. In Figure 8 , Figure 9 In the diagram, curve LRN-2 represents the battery provided in this embodiment, and LR represents the 0.5LiNi cathode material, which is a traditional lithium-rich manganese-based cathode material. 0.5 Mn 0.5 A battery prepared from O2.0.5Li2MnO3. Figure 8 , Figure 9 It can be seen that, at a 1C medium rate, the battery provided in this embodiment exhibits almost no voltage or capacity degradation after 400 charge-discharge cycles (total cycle time of approximately two months).
[0056] Example 3 This embodiment provides a novel lithium-rich manganese-based cathode material with the chemical formula Li. 1.3 Ni 0.353 Mn 0.647 O 2.4 .
[0057] A novel method for preparing lithium-rich manganese-based cathode material includes the following steps: (1) Precursor synthesis. Nickel sulfate (NiSO4·6H2O) and manganese sulfate (MnSO4·H2O) were mixed in a specific ratio to prepare approximately 0.2 mol of solution. 18.81 g of nickel sulfate and 21.87 g of manganese sulfate were added, followed by 100 mL of water, and the mixture was stirred with a magnetic stir bar. Sodium oxalate (NaC2O4) was used as a precipitant, with an addition amount of 27.62 g. 100 mL of water and 100 mL of ethanol were added to the sodium oxalate powder, and the mixture was stirred and sonicated until homogeneous to obtain the precipitant solution. The precipitant solution was added dropwise to the nickel-manganese mixed solution, and then 200 mL of water was added to wash the precipitant beaker before adding it dropwise. The mixture was stirred under sealed conditions at 600 rpm for 36 h. The precipitate was then obtained by centrifugation, washed three times with water and three times with ethanol, dried at 90 °C for 15 h, and then stored.
[0058] (2) Sintering. The precipitate (i.e., the precursor) was mixed with lithium carbonate (Li2CO3). 2g of the precursor was taken out and 0.163g of lithium carbonate was added. After mixing and grinding evenly, the mixture was placed in a muffle furnace for sintering. The heating program was to raise the temperature to 600℃ at a heating rate of 2℃ / min, hold for 6 hours, then raise the temperature to 860℃ at a heating rate of 6℃ / min, hold for 16 hours, and then cool to room temperature to obtain the lithium-rich manganese-based cathode material.
[0059] This embodiment also provides a lithium battery, including a positive electrode, a negative electrode, a separator, and an LB-301 electrolyte. The positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material. The specific preparation and assembly methods are as follows: (1) Coating. The lithium-rich manganese-based cathode material prepared by sintering, conductive carbon black and PVDF (polyvinylidene fluoride) were mixed in a ratio of 84mg:8mg:8mg, ground evenly, and then 0.15mL of NMP (dimethylpyrrolidone) solvent was added dropwise. After standing for a few minutes, the mixture was stirred for 30 minutes with a planetary stirrer to remove bubbles, and coated onto aluminum foil with a thickness of 12.5mm. After drying in a drying oven, it was dried in a vacuum oven at 110℃ for 12 hours.
[0060] (2) Slicing, weighing, and assembling the battery. The cut electrode sheet is 10 mm in diameter. Use a CR2025 battery case, a 20 mm diameter lithium sheet, a glass fiber membrane produced by Whatman, and add 0.1 mL of LB-301 electrolyte.
[0061] The composition of the prepared lithium-rich manganese-based cathode material was accurately determined using ICP-OES (Inductively Coupled Plasma Emission Spectrometry), and the stoichiometric ratio was found to be Li:Ni:Mn = 1.3:0.353:0.647. Therefore, the chemical formula of the prepared lithium-rich manganese-based cathode material, determined using ICP-OES, is Li... 1.3 Ni 0.353 Mn 0.647 O 2.4 .
[0062] The assembled battery was tested for performance by cycling 800 times at a high rate of 5C. The test results are as follows: Figure 10 , Figure 11 As shown. In Figure 10 , Figure 11 In the diagram, curve LRN-3 represents the battery provided in this embodiment, and LR represents the 0.5LiNi cathode material, which is a traditional lithium-rich manganese-based cathode material. 0.5 Mn 0.5 A battery prepared from O2·0.5Li2MnO3. Figure 10 , Figure 11 It can be seen that, at a 5C rate, the battery provided in this embodiment, after 800 charge-discharge cycles (total cycle time of about one month), shows a significant improvement in voltage and capacity decay compared to traditional lithium-rich manganese-based cathode material batteries.
[0063] It should be noted that the cycle performance of the batteries assembled in Examples 1-3 of this invention at other rates is similar to the test results of other examples. In summary, the batteries assembled in Examples 1-3 of this invention, after 200 cycles at a low rate of 0.2C, show no voltage or capacity decay, with a capacity of approximately 220 mAh / g.-1 (100% capacity retention after cycling), voltage approximately 3.68V (voltage retention over 99% after cycling); after 400 cycles at 1C medium rate, its voltage and capacity show almost no decay, with a capacity of approximately 180mAhg. -1 (100% capacity retention after cycling), voltage approximately 3.66V (voltage retention over 98% after cycling); after 800 cycles at a high rate of 5C, both voltage and capacity decay are significantly improved, with a capacity of approximately 140mAhg. -1 (Capacity retention after cycling is greater than 91.5%), voltage is approximately 3.55V (voltage retention after cycling is greater than 97.5%).
[0064] Example 4 This embodiment provides a novel method for preparing lithium-rich manganese-based cathode materials, including the following steps: (1) Precursor synthesis. Nickel sulfate (NiSO4·6H2O) and manganese sulfate (MnSO4·H2O) were mixed in a specific ratio to prepare approximately 0.05 mol. Approximately 4.94 g of nickel sulfate and 5.281 g of manganese sulfate were added, followed by 25 mL of water and stirred with a magnetic stir bar. Sodium carbonate (NaCO3·H2O) was used as a precipitant, with an addition of 5.512 g. 25 mL of water and 25 mL of ethanol were added to sodium oxalate powder, stirred, and sonicated until homogeneous to obtain a precipitant solution. The precipitant solution was added dropwise to the nickel-manganese mixed solution, and then 50 mL of water was added to wash the precipitant beaker before adding it dropwise. The mixture was stirred at 600 rpm in a sealed container for 48 h. The precipitate was then obtained by centrifugation, washed three times with water and three times with ethanol, dried at 80 °C for 24 h, and then stored.
[0065] (2) Sintering. 2g of precipitate (i.e., precursor) was mixed with 0.537g of lithium hydroxide (LiOH·H2O). After uniform mixing and grinding, the mixture was placed in a muffle furnace for sintering. The heating program was as follows: the temperature was increased to 500℃ at a heating rate of 2℃ / min, held for 5 hours, then increased to 900℃ at a heating rate of 5℃ / min, held for 12 hours, and then cooled to room temperature to obtain lithium-rich manganese-based cathode material.
[0066] This embodiment also provides a lithium battery, including a positive electrode, a negative electrode, a separator, and an LB-012 electrolyte. The positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material. The specific preparation and assembly methods are as follows: (1) Coating. Take the lithium-rich manganese-based cathode material prepared by sintering, conductive carbon black and PVDF (polyvinylidene fluoride), mix them in a ratio of 80mg:10mg:10mg, grind them evenly, and then add 0.2mL of NMP (dimethylpyrrolidone) solvent. After standing for a few minutes, stir with a planetary stirrer for 25 minutes, coat it on aluminum foil with a thickness of 15mm, dry it in a drying oven, and then dry it in a vacuum oven at 110℃ for 12 hours.
[0067] (2) Slicing, weighing, and assembling the battery. The cut electrode sheet is 10 mm in diameter. Use a CR2025 battery case, a 15 mm diameter lithium sheet, a glass fiber membrane produced by Whatman, and add 0.08 mL of LB-012 electrolyte.
[0068] The assembled battery was cycled 300 times at a 1C rate to test its performance. The test results are as follows: Figure 12 , Figure 13 As shown. In Figure 12 , Figure 13 In the diagram, curve LRN-4 represents the battery provided in this embodiment, and LR represents the 0.5LiNi cathode material, which is a traditional lithium-rich manganese-based cathode material. 0.5 Mn 0.5 A battery prepared from O2.0.5Li2MnO3. Figure 12 , Figure 13 It can be seen that, at a 1C medium rate, the battery provided in this embodiment exhibits a slight decrease in voltage and capacity after 300 charge-discharge cycles, but it is significantly superior to the traditional lithium-rich manganese-based cathode material 0.5LiNi. 0.5 Mn 0.5 A battery prepared from O2.0.5Li2MnO3.
[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. A method for preparing a lithium battery positive electrode sheet, characterized in that, include: (1) Precursor synthesis: Nickel salt and manganese salt are dissolved in a solvent, and then a precipitant is added dropwise while stirring; then the precipitate is obtained by solid-liquid separation; finally, the precipitate is mixed with a lithium source compound and sintered to obtain the cathode material; Wherein, the precipitant is oxalic acid or oxalate, and the molar ratio of nickel to manganese in the nickel salt and the manganese salt is (6-9):(11-14); the lithium source compound is selected from at least one of lithium hydroxide, lithium carbonate, and lithium oxide; the nickel salt is selected from at least one of nickel sulfate, nickel chloride, nickel bromide, nickel iodide, and nickel aminosulfonate; and the manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese bromide, manganese iodide, and manganese aminosulfonate. During the sintering process, the temperature is increased to 420-620℃ at a heating rate of 1.5-2.5℃ / min and held for 5-6 hours. Then, the temperature is increased to 800-1000℃ at a heating rate of 4-6℃ / min and held for 12-14 hours to obtain the cathode material. (2) Coating: Take the positive electrode material, conductive carbon black and polyvinylidene fluoride prepared by sintering, grind them evenly, add dimethylpyrrolidone solvent, coat them on aluminum foil, and dry them; (3) Slicing and assembling the battery.
2. The preparation method according to claim 1, characterized in that, The amount of precipitant added is 1-1.2 times the sum of the amounts of the nickel salt and the manganese salt.
3. The preparation method according to claim 1, characterized in that, The amount of lithium in the lithium source is 1.1-1.5 times the amount of the precipitate.
4. The preparation method according to claim 1, characterized in that, The precipitant is an ethanol solution of sodium oxalate.
5. A lithium battery positive electrode sheet, characterized in that, It is prepared by any one of the preparation methods according to claims 1-4.
6. The lithium battery positive electrode sheet according to claim 5, characterized in that, The positive electrode material in the positive electrode sheet has the chemical formula Li. 1.20-1.35 Ni x Mn y O 2.0-2.4 Where x = 0.35-0.39, y = 0.61-0.65, x+y = 1, and the proportion of the Li2MnO3 superlattice phase is 22%-28%.
7. A lithium battery, characterized in that, It includes the positive electrode, negative electrode, separator, and electrolyte of a lithium battery according to claim 5 or 6, wherein the separator is a glass fiber membrane.