Lithium-rich manganese oxide positive electrode material, preparation method thereof, positive electrode sheet and lithium ion battery
By introducing Li4Mn5O12 spinel phase and MnO2 phase into lithium-rich manganese oxide cathode material, the problems of low cycle stability and low initial coulombic efficiency were solved, and the performance of high energy density lithium-ion batteries was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU HIGHSTAR BATTERY MFG CO LTD
- Filing Date
- 2020-07-21
- Publication Date
- 2026-06-12
AI Technical Summary
Existing lithium-rich manganese oxide cathode materials suffer from poor cycle stability and low initial coulombic efficiency, which limits their application in lithium-ion batteries.
By controlling the content of Mn and Li in lithium-rich manganese oxide cathode materials, Li4Mn5O12 spinel phase and MnO2 phase are introduced to form cathode materials with layered structures. The preparation method is spray pyrolysis and calcination.
It improves the structural stability and initial coulombic efficiency of the material, enhances cycle performance and rate performance, and meets the requirements of high energy density lithium-ion batteries.
Smart Images
Figure CN111710858B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion batteries, specifically to a lithium-rich manganese oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery. Background Technology
[0002] Lithium-ion batteries, due to their high energy density and other characteristics, have been widely used in portable electronic products, electric vehicles, and energy storage power stations. However, the performance requirements for lithium-ion batteries are constantly increasing. While needing higher energy density, lithium-ion batteries also require high power and long cycle life. The key to achieving high-performance lithium-ion batteries lies in the development of high-performance cathode materials.
[0003] Currently, commercially available cathode materials include layered lithium cobalt oxide (LiCoO2), ternary lithium nickel cobalt manganese oxide (LiMO2, M = Ni, Co, Mn / Al), spinel lithium manganese oxide (LiMn2O4), and lithium iron phosphate (LiFePO4). However, the specific capacity of layered LiCoO2 cathode materials is consistently limited to below 160 mAh / g, and its high Co content leads to high cost and is environmentally unfriendly. Ternary materials have relatively higher capacities, reaching 210–250 mAh / g depending on their discharge voltage, but their rate performance is poor, and their structure is unstable at high temperatures, easily leading to safety accidents. The theoretical specific capacities of spinel-structured lithium manganese oxide (LiMn2O4) cathode materials and polyanionic lithium iron phosphate (LiFePO4) cathode materials are only 148 mAh / g and 170 mAh / g, respectively, with actual capacities even lower, far from meeting the performance requirements of high-energy-density lithium-ion batteries for cathode materials.
[0004] Therefore, the performance of cathode materials has become a bottleneck for further improving the performance of lithium-ion batteries. Lithium-rich manganese-based cathode materials have received increasing attention due to their high specific capacity (greater than 250 mAh / g), low cost, and high safety.
[0005] However, the poor cycle stability and rate performance, as well as the low initial coulombic efficiency, of lithium-rich manganese oxide cathode materials severely restrict their practical application. During cycling, the dissolution of transition metals (TM) in the electrolyte and the migration and rearrangement of TM ions lead to the formation of spinel structures, causing capacity and voltage decay. Methods such as surface coating and ion doping / substitution can typically be used to improve the composition and structural stability of lithium-rich manganese oxide cathode materials, thereby improving their cycle performance, suppressing voltage decay during cycling, and increasing their initial coulombic efficiency.
[0006] However, the contradiction between high capacity and low cycle stability in lithium-rich manganese oxide cathode materials remains unresolved, and their extremely low initial coulombic efficiency hinders their large-scale application. Therefore, further development of lithium-rich manganese oxide cathode materials with high capacity, excellent cycle performance, and high initial coulombic efficiency, along with their efficient preparation methods, is of paramount importance for their application in lithium-ion batteries. Summary of the Invention
[0007] The purpose of this invention is to overcome the contradiction between high capacity and low cycle performance in existing lithium-rich manganese oxide cathode materials, as well as the defect of low initial coulombic efficiency, and to provide a lithium-rich manganese oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery. This cathode material possesses both excellent cycle performance and high initial coulombic efficiency.
[0008] To achieve the above objectives, a first aspect of the present invention provides a lithium-rich manganese oxide cathode material, wherein the cathode material is Li x Ni 0.13 Co 0.13 Mn y O2, where x = 1.2-1.5, y = 0.55-0.95; and the layered structure of the cathode material is doped with Li4Mn5O. 12 Spinel phase and MnO2 phase.
[0009] A second aspect of the present invention provides a method for preparing the aforementioned cathode material, wherein the method includes:
[0010] (1) Mix the acetates of Li, Ni, Co and Mn with water to obtain a reaction solution;
[0011] (2) The reaction solution is subjected to spray pyrolysis to obtain the precursor;
[0012] (3) The precursor is subjected to calcination treatment.
[0013] A third aspect of the present invention provides a positive electrode sheet, characterized in that the positive electrode sheet comprises the aforementioned positive electrode material.
[0014] A fourth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the aforementioned positive electrode.
[0015] Compared with the prior art, the present invention has the following beneficial effects through the above technical solution:
[0016] (1) This invention introduces lithium-rich Li4Mn5O into the layered lithium-rich manganese oxide cathode material by controlling the content of Mn and Li in the lithium-rich manganese oxide cathode material. 12 Spinel phase and trace amounts of MnO2 phase. Li4Mn5O 12 The spinel phase and layered structure of lithium-rich manganese oxide cathode materials exhibit good structural compatibility, increasing their structural stability during cycling. MnO2 compensates for the irreversible capacity loss caused by the activation of the Li2MnO3 component, and the LiMn2O4 formed after lithium intercalation continuously enhances the activity of the lithium-rich manganese oxide cathode material during cycling. Furthermore, Li4Mn5O... 12 It exhibits high resistance to electrolyte corrosion. The lithium-rich manganese oxide cathode material of this invention possesses high initial coulombic efficiency and good cycle performance.
[0017] (2) The preparation method of the lithium-rich manganese oxide cathode material of the present invention is simple. It is only necessary to adjust the content ratio of raw materials when preparing the precursor of the lithium-rich manganese oxide material to achieve the control of the composition and structure of the lithium-rich manganese oxide cathode material without adding other preparation steps. Attached Figure Description
[0018] Figure 1-1 The XRD pattern of the cathode material prepared in Example 1 is shown below.
[0019] Figure 1-2 A schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 1 at a current density of 20 mA / g.
[0020] Figure 1-3 A schematic diagram of the cycling performance curve of the cathode material prepared in Example 1 at a current density of 200 mA / g.
[0021] Figure 1-4 This is a schematic diagram of the midpoint voltage decay curve of the cathode material prepared in Example 1 at a current density of 200 mA / g.
[0022] Figure 1-5 A schematic diagram of the rate performance curve of the cathode material prepared in Example 1;
[0023] Figure 2-1 The image shows the XRD pattern of the cathode material prepared in Example 2.
[0024] Figure 2-2 This is a schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 2 at a current density of 20 mA / g.
[0025] Figure 2-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared in Example 2 at a current density of 200 mA / g.
[0026] Figure 2-4 This is a schematic diagram of the midpoint voltage decay curve of the cathode material prepared in Example 2 at a current density of 200 mA / g.
[0027] Figure 2-5 This is a schematic diagram of the rate performance curve of the cathode material prepared in Example 2;
[0028] Figure 3-1 XRD pattern of the cathode material prepared in Example 3;
[0029] Figure 3-2 This is a schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 3 at a current density of 20 mA / g.
[0030] Figure 3-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared in Example 3 at a current density of 200 mA / g.
[0031] Figure 4-1 The image shows the XRD pattern of the cathode material prepared in Example 4.
[0032] Figure 4-2 This is a schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 4 at a current density of 20 mA / g.
[0033] Figure 4-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared in Example 4 at a current density of 200 mA / g.
[0034] Figure 4-4 This is a schematic diagram of the midpoint voltage decay curve of the cathode material prepared in Example 4 at a current density of 200 mA / g.
[0035] Figure 4-5 The rate performance curve of the cathode material prepared in Example 4;
[0036] Figure 5-1 The image shows the XRD pattern of the cathode material prepared in Example 5.
[0037] Figure 5-2 This is a schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 5 at a current density of 20 mA / g.
[0038] Figure 5-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared in Example 5 at a current density of 200 mA / g.
[0039] Figure 5-4 This is a schematic diagram of the midpoint voltage decay curve of the cathode material prepared in Example 5 at a current density of 200 mA / g.
[0040] Figure 5-5This is a schematic diagram of the rate performance curve of the cathode material prepared in Example 5;
[0041] Figure 5-6 This is a schematic diagram of the differential curve of capacity versus voltage for the first cycle of the cathode material prepared in Example 5 at a current density of 20 mA / g.
[0042] Figure 6-1 The image shows the XRD pattern of the cathode material prepared in Example 6.
[0043] Figure 6-2 This is a schematic diagram of the first charge-discharge curve of the cathode material prepared in Example 6 at a current density of 20 mA / g.
[0044] Figure 6-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared in Example 6 at a current density of 200 mA / g.
[0045] Figure 6-4 A schematic diagram of the midpoint voltage decay curve of the cathode material prepared in Example 6 at a current density of 200 mA / g;
[0046] Figure 6-5 A schematic diagram of the capacity versus voltage differential curves of the cathode material prepared in Example 6 at a current density of 200 mA / g for the 2nd and 100th cycles.
[0047] Figure 7-1 The XRD pattern of the cathode material prepared in Comparative Example 1;
[0048] Figure 7-2 A schematic diagram of the first charge-discharge curve of the cathode material prepared for Comparative Example 1 at a current density of 20 mA / g;
[0049] Figure 7-3 A schematic diagram of the cycling performance curve of the cathode material prepared in Example 1 at a current density of 200 mA / g;
[0050] Figure 7-4 A schematic diagram of the capacity versus voltage differential curve of the cathode material prepared in Comparative Example 1 at a current density of 20 mA / g.
[0051] Figure 7-5 A schematic diagram of the capacity versus voltage differential curves of the cathode material prepared in Comparative Example 1 at a current density of 200 mA / g for the 2nd and 100th cycles.
[0052] Figure 8-1 The XRD pattern of the cathode material prepared in Comparative Example 2;
[0053] Figure 8-2 A schematic diagram of the first charge-discharge curve of the cathode material prepared for Comparative Example 2 at a current density of 20 mA / g;
[0054] Figure 8-3 A schematic diagram of the cycling performance curve of the cathode material prepared for Comparative Example 2 at a current density of 200 mA / g;
[0055] Figure 9-1 The XRD pattern of the cathode material prepared in Comparative Example 3;
[0056] Figure 9-2 A schematic diagram of the first charge-discharge curve of the cathode material prepared for Comparative Example 3 at a current density of 20 mA / g;
[0057] Figure 9-3 This is a schematic diagram of the cycling performance curve of the cathode material prepared for Comparative Example 3 at a current density of 200 mA / g. Detailed Implementation
[0058] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0059] The first aspect of this invention provides a lithium-rich manganese oxide cathode material, wherein the cathode material is Li x Ni 0.13 Co 0.13 Mn y O2, where x = 1.2-1.5, y = 0.55-0.95; and the layered structure of the cathode material is doped with Li4Mn5O. 12 Spinel phase and MnO2 phase.
[0060] In this invention, on one hand, the chemical composition (stoichiometry) of the positive electrode material is Li. x Ni 0.13 Co 0.13 Mn y O2, where x = 1.2-1.5, y = 0.55-0.95. That is, relative to Li2MnO3 and ternary Li(Ni) with a molar ratio of 1:1. 1 / 3 Co 1 / 3 Mn 1 / 3 The present invention relates to a basic layered lithium-rich manganese oxide cathode material composed of O2 components. This layered lithium-rich manganese oxide cathode material has an excess of Mn, or a simultaneous excess of Mn and Li. The inventors of this invention discovered that by controlling the Mn and Li content, a Li4Mn5O3 compound can be introduced into the layered lithium-rich manganese oxide cathode material. 12The spinel phase exhibits good structural compatibility with the layered structure of lithium-rich manganese oxide cathode materials, demonstrating high structural stability during electrochemical cycling. It stabilizes the crystal structure of the lithium-rich manganese oxide cathode material and moderates the oxygen evolution reaction (O2) caused by the activation of the Li2MnO3 component during the first charge (i.e., the extraction of Li2O from Li2MnO3), thus increasing the structural stability of the lithium-rich manganese oxide cathode material during cycling. Furthermore, due to the high Mn content, trace amounts of MnO2 are generated, compensating for the irreversible capacity loss caused by the activation of the Li2MnO3 component. The LiMn2O4 formed after lithium intercalation continuously enhances the activity of the lithium-rich manganese oxide cathode material during cycling. In addition, Li4Mn5O... 12 It exhibits high resistance to electrolyte corrosion. The lithium-rich manganese oxide cathode material of this invention possesses high initial coulombic efficiency and excellent cycle performance.
[0061] According to the present invention, in a preferred embodiment, x = 1.25-1.3 and y = 0.55-0.75. Due to the excess Li and Mn, lithium-rich Li4Mn5O is formed in the material. 12 Spinel phase and trace amounts of MnO2 phase are doped into the layered structure of lithium-rich manganese oxide.
[0062] A second aspect of the present invention provides a method for preparing the aforementioned cathode material, wherein the method includes:
[0063] (1) Mix the acetates of Li, Ni, Co and Mn with water to obtain a reaction solution;
[0064] (2) The reaction solution is subjected to spray pyrolysis to obtain the precursor;
[0065] (3) The precursor is subjected to calcination treatment.
[0066] According to the present invention, in step (1), the concentration of the reaction solution is 0.3-0.5 mol / L; preferably 0.4 mol / L; in the present invention, the mixing conditions include: a temperature of 50-80°C and a time of 1-2 hours, preferably a temperature of 60-80°C and a time of 1 hour.
[0067] According to the present invention, in step (2), the conditions for spray pyrolysis include: an inlet temperature of 150-200°C, preferably 200°C; and an outlet temperature of 80-120°C, preferably 100°C.
[0068] According to the present invention, in step (3), the calcination conditions include: a temperature of 800-1100℃ and a time of 8-10h; preferably, a temperature of 50-950℃ and a time of 8-10h.
[0069] According to the present invention, the method further includes: in step (1), mixing in the presence of a complexing agent; preferably, the complexing agent is citric acid, wherein the concentration of citric acid is 0.4 mol / L. The solution is mechanically stirred at 50–80°C for 1 h to obtain a reaction solution. The reaction is carried out under high temperature and high pressure.
[0070] According to a preferred embodiment of the present invention, a method for preparing the above-mentioned layered lithium-rich manganese oxide cathode material comprises adding acetates of Li, Ni, Co, and Mn in a molar ratio of (1.20-1.50):0.13:0.13:(0.55-0.95) to deionized water, adjusting the concentration to 0.3-0.5 mol / L. Citric acid is added as a complexing agent to prevent hydrolysis of the metal salts and the formation of hydroxide precipitates. The citric acid concentration is 0.4 mol / L. The solution is mechanically stirred at 50-80°C for 1 h to obtain a reaction solution. A precursor is obtained by spray pyrolysis under high temperature and high pressure. The precursor is calcined in air at 800-1100°C for 8-10 h.
[0071] According to another preferred embodiment of the present invention, a method for preparing the above-mentioned layered lithium-rich manganese oxide cathode material comprises adding Li, Ni, Co, and Mn acetates in a molar ratio of (1.20-1.30):0.13:0.13:(0.55-0.75) to deionized water and adjusting the concentration to 0.4 mol / L. Citric acid is added as a complexing agent to prevent hydrolysis of the metal salts and the formation of hydroxide precipitates. The citric acid concentration is 0.4 mol / L. The solution is mechanically stirred at 60-80°C for 1 h to obtain a reaction solution. The reaction solution is then subjected to spray pyrolysis to obtain a precursor. The precursor is calcined in air at 850-950°C for 8-10 h.
[0072] A third aspect of the present invention provides a positive electrode sheet, wherein the positive electrode sheet comprises the aforementioned positive electrode material.
[0073] In this invention, the aforementioned positive electrode material is used as the positive electrode material for lithium-ion batteries and a conductive agent are ball-milled and mixed. The mixed material is then mixed with a binder to form a slurry. The slurry is coated onto an aluminum foil and dried to obtain the positive electrode for lithium-ion batteries.
[0074] According to the present invention, preferably, the conductive agent is selected from one or more of graphite, acetylene black, Super P, carbon nanotubes, graphene and Ketjen black.
[0075] According to the present invention, preferably, the conductive agent content is 5-20% by mass.
[0076] According to the present invention, preferably, the ball-to-material mass percentage is (50-200):1; the ball milling speed is 300-500 rpm; the ball milling time is 2-12 h; and the ball milling atmosphere is one or more of air, oxygen, argon and nitrogen.
[0077] According to the present invention, preferably, the adhesive is an aqueous adhesive or a non-aqueous adhesive, such as polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, or sodium alginate; the mass percentage is 3-20%.
[0078] A fourth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the aforementioned positive electrode.
[0079] According to the present invention, specifically, the aforementioned positive electrode sheet is used as the positive electrode, and it is assembled with a negative electrode, an electrolyte and a separator paper between the positive and negative electrodes to form a lithium-ion battery.
[0080] In the lithium-ion battery of the present invention, the negative electrode material is selected from graphite, silicon and various silicon alloys, iron oxides, tin oxides and various tin alloys, titanium oxides and other negative electrode materials.
[0081] In the lithium-ion battery of the present invention, the electrolyte is a non-aqueous electrolyte, wherein the lithium salt in the electrolyte can be one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, and lithium fluorohydroxysulfonate. The non-aqueous solvent can be one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and vinylene carbonate.
[0082] The present invention will be described in detail below through embodiments.
[0083] Example 1
[0084] This embodiment focuses on preparing a Li-based component. 1.25 Ni 0.13 Co 0.13 Mn 0.64 O2 layered lithium-rich manganese oxide cathode material and cathode sheet, as well as lithium-ion batteries.
[0085] (1) The acetates of Li, Ni, Co and Mn were added to a certain amount of deionized water in a molar ratio of 1.25:0.13:0.13:0.64, with a concentration of 0.4 mol / L. The reaction solution was obtained by mechanical stirring. The reaction solution was spray-pyrolyzed to obtain the precursor. The inlet and outlet temperatures during the spray-pyrolysis process were 200℃ and 100℃, respectively.
[0086] (2) The obtained precursor was heat-treated at 900℃ for 10 h to obtain Li1.25 Ni 0.13 Co 0.13 Mn 0.64 O2 cathode material.
[0087] (3) Li 1.25 Ni 0.13 Co 0.13 Mn 0.64 O2 cathode material, conductive agent Super P, and binder sodium alginate were mixed at a mass percentage of 9.2:1:0.8 and stirred evenly to obtain a slurry. The slurry was then uniformly coated onto aluminum foil, dried, and compacted to obtain the electrode. The electrochemical performance of the electrode material was characterized using a 2025 coin cell in a glove box filled with Ar, with water and oxygen contents both less than 0.1 ppm.
[0088] (4) The positive electrode is the prepared electrode sheet; the reference electrode and the counter electrode are metal Li sheets; the separator is Celgard-2400; the electrolyte is LiPF6 (1mol / L) / EC+DEC+EMC (1:1:1). The assembled battery is placed for testing.
[0089] Figure 1-1 The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 1-1 As shown, the diffraction peak positions correspond to the hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and the monoclinic Li2MnO3 (C / 2m)(PDF#84-1634). The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase, resulting from the ordered superstructure of LiTM2 within the transition metal (TM) layer. Figure 1-1 In the diffraction index, "R" and "M" represent the hexagonal LiMO2 and monoclinic Li2MnO3, respectively. Compared to Comparative Example 1, the characteristic peak (110)M of the Li2MnO3 phase in the XRD pattern is relatively enhanced, indicating that the content of the Li2MnO3 phase is increased compared to Comparative Example 1. In addition, spinel-structured Li4Mn5O is formed in the material. 12 Mutually.
[0090] Figure 1-2 This is a schematic diagram of the first charge-discharge curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. From... Figure 1-2 It can be seen that the initial discharge specific capacity of this cathode material is 269 mAh / g, its initial irreversible capacity is 39 mAh / g, and its initial coulombic efficiency is 87.4%. Compared with Comparative Example 1, the lithium-rich manganese oxide cathode material of the present invention introduces a spinel structure Li4Mn5O 12In this phase, the initial irreversible capacity of the cathode material is significantly reduced, while the initial coulombic efficiency is significantly improved.
[0091] Figure 1-3 This is a schematic diagram of the cycling performance curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. From... Figure 1-3 It can be seen that the initial discharge specific capacity of this cathode material is 208 mAh / g, and the discharge specific capacity after 150 cycles is 184 mAh / g, with a discharge capacity retention rate of 88.5%. This cathode material exhibits good cycle stability.
[0092] Figure 1-4 This is a schematic diagram of the midpoint voltage decay curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. Figure 1-4 It can be seen that the cathode material has a good discharge midpoint voltage retention rate.
[0093] Figure 1-5 This is a schematic diagram of the rate performance curve of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 1-5 It can be seen that the cathode material exhibits high electrochemical capacity at 0.1C, 0.5C, 1C, 2C, 5C, and up to 10C. At a high rate of 10C, its discharge capacity is still 120mAh / g, and it retains 45% of the reversible capacity relative to 0.5C; this cathode material has excellent rate performance.
[0094] The lithium-rich manganese oxide cathode material of this invention incorporates a spinel-structured Li4Mn5O 12 This phase significantly improves the cycling performance and rate performance of the material.
[0095] Example 2
[0096] This embodiment focuses on preparing a Li-based component. 1.3 Ni 0.13 Co 0.13 Mn 0.74 O2 layered lithium-rich manganese oxide cathode materials and cathode sheets, as well as lithium-ion batteries.
[0097] The cathode material, cathode sheet, and lithium-ion battery were prepared using the same preparation method as in Example 1, except that Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.3:0.13:0.13:0.74, with a molar concentration of 0.5 mol / L.
[0098] In addition, the electrochemical performance testing method for the cathode material is the same as in Example 1.
[0099] Figure 2-1The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 2-1 As shown, the diffraction peaks correspond to the hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and the monoclinic Li2MnO3 (C / 2m)(PDF#84-1634). Figure 2-1 In the diffraction index, "R" and "M" represent the hexagonal structure of LiMO2 and the monoclinic structure of Li2MnO3, respectively. This material is a composite structure of LiMO2 and Li2MnO. Furthermore, a spinel-structured Li4Mn5O3 is formed within the material. 12 In contrast to Example 1, the Li4Mn5O in this example... 12 The content of the phase and Li2MO3 phase increased.
[0100] Figure 2-2 This is a schematic diagram of the first charge-discharge curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. Figure 2-2 It can be seen that the initial discharge specific capacity of this cathode material is 243 mAh / g, the initial irreversible capacity is 30 mAh / g, and the initial coulombic efficiency is 89.0%. In this embodiment, the cathode material is produced by increasing the content of Li and Mn, introducing Li4Mn5O. 12 This phase effectively reduces the initial irreversible capacity of lithium-rich manganese oxide cathode materials and improves their initial coulombic efficiency.
[0101] Figure 2-3 This is a schematic diagram of the cycling performance curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. From... Figure 2-3 It can be seen that the initial discharge specific capacity of this cathode material is 160 mAh / g, and the discharge specific capacity after 150 cycles is 154 mAh / g, with a discharge capacity retention rate of 96.3%, demonstrating excellent cycle stability.
[0102] Figure 2-4 This is a schematic diagram of the discharge midpoint voltage retention rate curve of the lithium-rich manganese oxide cathode material prepared in this embodiment during a 200 mA / g cycle. Figure 2-4 This demonstrates that the cathode material exhibits good voltage retention. This embodiment utilizes the introduction of Li4Mn5O... 12 This phase effectively suppresses voltage decay of lithium-rich manganese materials during cycling.
[0103] Figure 2-5 This is a schematic diagram of the rate performance curve of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 2-5 It can be seen that the cathode material has high electrochemical capacity at 0.1C, 0.5C, 1C, 2C, 5C and 10C.
[0104] Example 3
[0105] This embodiment focuses on preparing a Li-based component. 1.4 Ni 0.13 Co 0.13 Mn 0.94 O2 cathode materials, cathode plates, and lithium-ion batteries.
[0106] The cathode material, cathode sheet, and lithium-ion battery were prepared using the same preparation method as in Example 1, except that Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.4:0.13:0.13:0.94, with a molar concentration of 0.4 mol / L.
[0107] In addition, the electrochemical performance testing method for the cathode material is the same as in Example 1.
[0108] Figure 3-1 The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 3-1 As shown, the diffraction peaks indicate the coexistence of hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m)(PDF#84-1634) in the material. The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. Figure 3-1 In the diffraction index, "R" and "M" represent the hexagonal LiMO2 and monoclinic Li2MnO3, respectively. In this embodiment, by increasing the Li and Mn content, a higher content of Li2MnO3 and Li4Mn5O phases were formed in the material. 12 Mutually.
[0109] Figure 3-2 This is a schematic diagram of the first charge-discharge curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. Figure 3-2 It can be seen that the initial discharge specific capacity of this cathode material is 177 mAh / g, its initial irreversible capacity is 3 mAh / g, and its initial coulombic efficiency is as high as 98.3%.
[0110] Figure 3-3 This is a schematic diagram of the cycling performance curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. From... Figure 3-3 It can be seen that the initial discharge specific capacity of the cathode material is 115 mAh / g. During the cycling process, as the activity of the material continuously increases, the capacity of the material continuously increases, and the discharge specific capacity increases to 162 mAh / g after 150 cycles.
[0111] Example 4
[0112] This embodiment focuses on preparing a Li-based component. 1.2 Ni 0.13 Co 0.13 Mn 0.57 O2 layered lithium-rich manganese oxide cathode materials and cathode sheets, as well as lithium-ion batteries.
[0113] The cathode material, cathode sheet, and lithium-ion battery were prepared using the same preparation method as in Example 1, except that Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.2:0.13:0.13:0.57, with a molar concentration of 0.4 mol / L.
[0114] In addition, the electrochemical performance testing method for the cathode material is the same as in Example 1.
[0115] Figure 4-1 The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 4-1 As shown, the diffraction peaks indicate the coexistence of hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m)(PDF#84-1634) in the material. The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. Figure 4-1 In the diffraction index, "R" and "M" represent the hexagonal structure of LiMO2 and the monoclinic structure of Li2MnO3, respectively. XRD was used, but Li4Mn5O was not detected. 12 The phase may be present in relatively small amounts. However, a high Mn content is beneficial to Li4Mn5O. 12 Phase formation.
[0116] Figure 4-2 This is a schematic diagram of the first charge-discharge curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. From... Figure 4-2 It can be seen that the initial discharge specific capacity of this cathode material is 278 mAh / g, its initial irreversible capacity is 53 mAh / g, and its initial coulombic efficiency is 84.0%. This is comparable to the relatively low Mn content of 0.5Li₂MnO₃-0.5LiNi. 0.33 Co 0.33 Mn 0.33 The coulombic efficiency of the O2 cathode material (Comparative Example 1) was improved for the first time.
[0117] Figure 4-3 This is a schematic diagram of the cycling performance curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. From... Figure 4-3It can be seen that the initial discharge specific capacity of this cathode material is 214 mAh / g, and the discharge specific capacity after 150 cycles is 185 mAh / g, with a discharge capacity retention rate of 86.5%. This cathode material exhibits good cycle stability.
[0118] Figure 4-4 This is a schematic diagram of the discharge midpoint voltage retention rate curve of the lithium-rich manganese oxide cathode material prepared in this embodiment during cycling at 200 mA / g. Figure 4-4 This demonstrates that the cathode material has a good voltage retention rate.
[0119] Figure 4-5 The rate performance curve of the lithium-rich manganese oxide cathode material prepared in this embodiment is shown below. Figure 2-5 It can be seen that this cathode material exhibits high electrochemical capacity at 0.1C, 0.5C, 1C, 2C, 5C, and 10C. At a high rate of 10C, its discharge capacity is still 130mAh / g, and it retains 45% of the reversible capacity relative to 0.5C.
[0120] Example 5
[0121] This embodiment focuses on preparing a Li-based component. 1.2 Ni 0.13 Co 0.13 Mn 0.59 O2 layered lithium-rich manganese oxide cathode materials and cathode sheets, as well as lithium-ion batteries.
[0122] The cathode material, cathode electrode, and lithium-ion battery were prepared using the same preparation method as in Example 1, except that Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.2:0.13:0.13:0.59, with a molar concentration of 0.4 mol / L. The cathode material and cathode were prepared using the same spray and heat treatment methods as in Example 1, and the electrochemical performance of the electrode materials was tested.
[0123] Figure 5-1 The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 5-1 As shown, the diffraction peaks indicate that hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m)(PDF#84-1634) coexist in the material, forming Li4Mn5O 12 The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. Figure 5-1 In the diffraction index, "R" and "M" represent the hexagonal structure of LiMO2 and the monoclinic structure of Li2MnO3, respectively.
[0124] Figure 5-2 This is a schematic diagram of the first charge-discharge curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. Figure 5-2 It can be seen that the initial discharge specific capacity of this cathode material is 264 mAh / g, its initial irreversible capacity is 50 mAh / g, and its initial coulombic efficiency is 84.1%.
[0125] Figure 5-3 This is a schematic diagram of the cycling performance curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. From... Figure 5-3 It can be seen that the initial discharge specific capacity of this cathode material is 188 mAh / g, and the discharge specific capacity after 150 cycles is 181 mAh / g, with a discharge capacity retention rate of 96.2%, demonstrating excellent cycle performance.
[0126] Figure 5-4 This is a schematic diagram of the discharge midpoint voltage retention rate curve of the lithium-rich manganese oxide cathode material prepared in this embodiment during a 200 mA / g cycle. Figure 5-4 The discharge midpoint voltage retention rate during material cycling indicates that this cathode material has good resistance to voltage decay during cycling.
[0127] Figure 5-5 This is a schematic diagram of the rate performance curve of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 5-5 It can be seen that the cathode material has a high electrochemical capacity at different rates.
[0128] Figure 5-6 The first capacity-voltage differential (dQ / dV) curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g shows that during the first lithium delithiation (charging) process, in addition to the lithium delithiation reduction reaction of conventional lithium-rich manganese materials, a reduction peak also exists at approximately 2.6 V relative to the lithium potential. This reduction peak is Li4Mn5O 12 The spinel phase insertion / extraction peaks also indicate that Li4Mn5O 12 The presence of the spinel phase. However, this reduction peak was not present during the first delithiation process in Comparative Example 1.
[0129] This embodiment increases the Mn content in the material, thereby generating a higher content of Li4Mn5O in the cathode material. 12 This phase improves the initial coulombic efficiency and cycle performance of the cathode material.
[0130] Example 6
[0131] This embodiment focuses on preparing a Li-based component. 1.2 Ni 0.13Co 0.13 Mn 0.64 O2 layered lithium-rich manganese oxide cathode materials and cathode sheets, as well as lithium-ion batteries.
[0132] The cathode material, cathode electrode, and lithium-ion battery were prepared using the same preparation method as in Example 1, except that Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.2:0.13:0.13:0.64, with a molar concentration of 0.4 mol / L. The cathode material and cathode were prepared using the same spray and heat treatment methods as in Example 1, and the electrochemical performance of the electrode materials was tested.
[0133] Figure 6-1 The image shows the XRD pattern of the lithium-rich manganese oxide cathode material prepared in this embodiment. Figure 6-1 As shown, the diffraction peaks reveal the coexistence of hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m)(PDF#84-1634) on the surface material. The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. Figure 6-1 In the diffraction index, "R" and "M" represent the hexagonal structure of LiMO2 and the monoclinic structure of Li2MnO3, respectively. This embodiment increases the Mn content in the material to generate a higher content of Li4Mn5O3. 12 Mutually.
[0134] Figure 6-2 This is a schematic diagram of the first charge-discharge curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 20 mA / g. Figure 6-2 It can be seen that the initial discharge specific capacity of this cathode material is 238 mAh / g, its initial irreversible capacity is 38 mAh / g, and its initial coulombic efficiency is 86.2%, which is high.
[0135] Figure 6-3 This is a schematic diagram of the cycling performance curve of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g. The initial discharge specific capacity of this cathode material is 165 mAh / g, and the discharge specific capacity after 150 cycles is 161 mAh / g, with a capacity retention of 97.6%, demonstrating excellent cycling performance.
[0136] Figure 6-4 The diagram shows the discharge midpoint voltage retention rate curve of the lithium-rich manganese oxide cathode material prepared in this embodiment during cycling at a current density of 200 mA / g, demonstrating the good resistance to voltage decay during cycling.
[0137] Figure 6-5This is a schematic diagram of the capacity versus voltage differential (dQ / dV) curves of the lithium-rich manganese oxide cathode material prepared in this embodiment at a current density of 200 mA / g during the second and 100th cycles. Besides the delithiation reduction reaction of conventional lithium-rich manganese materials, a reduction peak also exists at approximately 2.6 V relative to the lithium potential. This reduction peak is Li4Mn5O 12 The spinel phase insertion / extraction peaks were present in both the 2nd and 100th cycles, which not only clarified the presence of Li4Mn5O 12 The presence of the spinel phase also indicates that Li4Mn5O is in a recyclable process. 12 The phase exhibits good stability and high reversibility. In contrast, Comparative Example 1 did not show this delithiation reaction during cycling. Figure 7-5 ).
[0138] This embodiment increases the Mn content in the material, thereby generating a higher content of Li4Mn5O in the cathode material. 12 This phase further improves the initial coulombic efficiency and cycle performance of the cathode material.
[0139] Comparative Example 1
[0140] This comparative example is prepared with Li as the component. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 cathode material, namely the conventional 0.5Li2MnO3-0.5LiNi 0.33 Co 0.33 Mn 0.33 O2-rich lithium manganese oxide cathode material.
[0141] Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.2:0.13:0.13:0.54, resulting in a molar concentration of 0.4 mol / L. The cathode material and cathode were prepared using the same spray and heat treatment methods as in Example 1, and the electrochemical performance of the electrode material was tested.
[0142] Figure 7-1 The image shows the XRD pattern of the cathode material prepared in this comparative example. Figure 7-1 As shown, all diffraction peaks correspond to the hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and the monoclinic Li2MnO3 (C / 2m) (PDF#84-1634). The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. In the figure, “R” and “M” under the diffraction indices represent the hexagonal LiMO2 and the monoclinic Li2MnO3, respectively.
[0143] Figure 7-2This is a schematic diagram of the initial charge-discharge curve of the cathode material prepared for this comparative example at a current density of 20 mA / g. From... Figure 7-2 It can be seen that the initial discharge specific capacity of this cathode material is 289 mAh / g, its initial irreversible capacity is 63 mAh / g, and its initial coulombic efficiency is 82.1%. The initial irreversible capacity is high, while the initial coulombic efficiency is relatively low.
[0144] Figure 7-3 This is a schematic diagram of the cycling performance curves of the cathode material prepared for this comparative example at a current density of 200 mA / g. From... Figure 7-3 It can be seen that the initial discharge specific capacity of this cathode material is 224 mAh g. -1 After 150 cycles, the discharge specific capacity was 190 mAh / g, the discharge capacity retention rate was 84.1%, and the cycle stability was poor.
[0145] Figure 7-4 A schematic diagram of the capacity versus voltage differential curve of the cathode material prepared for this comparative example at a current density of 20 mA / g; Figure 7-5 The capacity versus voltage differential curves of the cathode material prepared for this comparative example at a current density of 200 mA / g for the 2nd and 100th cycles.
[0146] Comparative Example 2
[0147] This comparative example is prepared with Li as the component. 1.2 Ni 0.13 Co 0.13 Mn 0.69 O2 cathode material.
[0148] Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.2:0.13:0.13:0.69, resulting in a molar concentration of 0.4 mol / L. The cathode material and cathode were prepared using the same spray and heat treatment methods as in Example 1, and the electrochemical performance of the electrode material was tested.
[0149] Figure 8-1 The image shows the XRD pattern of the cathode material prepared in this comparative example. Figure 8-1 As shown, the diffraction peaks indicate the coexistence of hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m) (PDF#84-1634) in the material. The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. Figure 8-1 In the diffraction index, "R" and "M" represent the hexagonal structure of LiMO2 and the monoclinic structure of Li2MnO3, respectively. Due to the high Mn content in the material, a large amount of Li4Mn5O is formed within it. 12 Mutually.
[0150] Figure 8-2 This is a schematic diagram of the initial charge-discharge curve of the cathode material prepared for this comparative example at a current density of 20 mA / g. From... Figure 8-2 It can be seen that the initial discharge specific capacity of this cathode material is 206 mAh / g, its initial irreversible capacity is 23 mAh / g, and its initial coulombic efficiency is 90.0%. The initial coulombic efficiency is high.
[0151] Figure 8-3 The cycling performance curves of the cathode material prepared for this comparative example are shown at a current density of 200 mA / g. The initial discharge specific capacity of the electrode is 138 mAh / g, and the discharge specific capacity after 150 cycles is 135 mAh / g, with a capacity retention of 98%.
[0152] The high amount of Mn in the material results in a high amount of Li4Mn5O. 12 While this further improves the initial coulombic efficiency and cycle performance of the material, it also significantly reduces the capacity.
[0153] Comparative Example 3
[0154] This comparative example is prepared with Li as the component. 1.6 Ni 0.13 Co 0.13 Mn 1.34 O2 cathode material, which means simultaneously increasing the Li and Mn content in the material.
[0155] Li, Ni, Co, and Mn acetates were added to deionized water in a molar ratio of 1.6:0.13:0.13:1.34, resulting in a molar concentration of 0.4 mol / L. The cathode material and cathode were prepared using the same spray and heat treatment methods as in Example 1, and the electrochemical performance of the electrode material was tested.
[0156] Figure 9-1 The image shows the XRD pattern of the cathode material prepared in this comparative example. Figure 9-1 As shown, the diffraction peaks indicate the coexistence of hexagonal LiMO2 (M=Ni,Co,Mn)(R-3m)(PDF#85-1966) and monoclinic Li2MnO3 (C / 2m) (PDF#84-1634) in the material. The diffraction peaks between 20° and 25° (2θ) are characteristic peaks of the Li2MnO3 phase. In the figure, "R" and "M" under the diffraction index represent hexagonal LiMO2 and monoclinic Li2MnO3, respectively. The material also contains a high content of Li4Mn5O. 12 Mutually.
[0157] Figure 9-2This is a schematic diagram of the initial charge-discharge curve of the cathode material prepared for this comparative example at a current density of 20 mA / g. From... Figure 9-2 It can be seen that the initial discharge specific capacity of this cathode material is 143 mAh / g, and the charging capacity is slightly larger than the discharge capacity, at 150 mAh / g. However, its capacity is too low.
[0158] Figure 9-3 This is a schematic diagram of the cycling performance curves of the cathode material prepared for this comparative example at a current density of 200 mA / g. From... Figure 9-3 It can be seen that the initial discharge specific capacity of this cathode material is only 96 mAh / g, which is too low. Although the capacity increases during cycling, and the discharge specific capacity is 166 mAh / g after 150 cycles, the capacity is still too low.
[0159] Excessive Li and Mn content in the material is detrimental to the electrochemical performance of lithium-rich manganese oxide cathode materials.
[0160] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A positive electrode material, characterized in that, The cathode material is Li. x Ni 0.13 Co 0.13 Mn y O2, where, x =1.25-1.3, y =0.55-0.75, wherein the positive electrode material comprises a layered lithium-rich manganese oxide positive electrode material; and Li4Mn5O is doped into the structure of the layered lithium-rich manganese oxide positive electrode material. 12 Spinel phase and MnO2 phase; The method for preparing the cathode material includes: (1) The acetates of Li, Ni, Co and Mn are mixed with water in a molar ratio to obtain a reaction solution; (2) The reaction solution is subjected to spray pyrolysis to obtain the precursor; the conditions for spray pyrolysis include: inlet temperature of 150-200℃ and outlet temperature of 80-120℃; (3) The precursor is subjected to calcination treatment, wherein the calcination conditions include: temperature of 800-1100℃ and time of 8-10h.
2. The cathode material according to claim 1, wherein, In step (1), the concentration of the reaction solution is 0.3-0.5 mol / L.
3. The cathode material according to claim 1, wherein, The mixing conditions include a temperature of 50-80℃ and a time of 1-2 hours.
4. The cathode material according to any one of claims 1-3, wherein, The method further includes: in step (1), mixing is performed in the presence of a complexing agent.
5. The cathode material according to claim 4, wherein, The complexing agent is citric acid.
6. A positive electrode sheet, characterized in that, The positive electrode sheet comprises the positive electrode material according to any one of claims 1-5.
7. A lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The positive electrode is the positive electrode as described in claim 6.