Method for preparing lithium-rich manganese-based material with layered / rock salt symbiotic structure, lithium-rich manganese-based material, positive electrode and lithium ion battery
By preparing lithium-rich manganese-based materials with layered/rock-salt symbiotic structures, the problems of its cyclic properties and lithium ion diffusion are solved, high rate performance and good cyclic stability are achieved, and the energy density and life of the battery are improved.
Patent Information
- Application Number
- CN202510211769.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-25
- Publication Date
- 2025-05-16
AI Technical Summary
The layered structure of lithium-rich manganese-based materials leads to poor circulation performance and the diffusion of lithium ions is hindered, which cannot meet the requirements of large-scale charge and discharge.
By preparing a lithium-rich manganese-based material with a layered/rock-salt symbiotic structure, the precursor of the transition metal element is mixed with a specific molar ratio of the lithium source, calcination and composite treatment are carried out, and combined with rapid Joule heat treatment, a material with excellent cycle stability and high rate performance is obtained.
The high-rate performance and good cycle stability of the material are achieved, which extends the cycle life of the battery and increases the energy density of the battery.
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Figure CN120004332A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of lithium-ion batteries, and in particular to a method for preparing a lithium-rich manganese-based material with a layered / rock salt symbiotic structure, and the lithium-rich manganese-based material, a positive electrode and a lithium-ion battery. Background Art
[0002] Lithium-ion batteries have high mass energy density and volume energy density, and can store more electrical energy in a smaller volume and weight. For example, the energy density of common lithium-ion batteries can reach 200-300Wh / kg, which is a significant improvement over traditional lead-acid batteries. This makes them an ideal choice for portable electronic devices, electric vehicles and other fields, meeting people's needs for long battery life, miniaturization and lightweight.
[0003] At present, the positive electrode of lithium-ion batteries generally uses lithium iron phosphate and high nickel ternary materials, but the specific capacity of lithium iron phosphate is low, and the cost of high nickel ternary materials is generally high due to the expensive Ni element. Therefore, these two types of materials cannot meet the needs of the next generation of new energy vehicles. The discharge specific capacity of lithium-rich manganese-based materials can reach more than 300mAh / g, which is far higher than the positive electrode materials such as lithium iron phosphate and high nickel ternary materials currently used in commercial applications. It can greatly improve the energy density of the battery and meet the needs of long-range electric vehicles and other fields. At the same time, the material has a wide voltage window, generally between 2.0-4.8V, combined with high specific capacity, it has more advantages in energy density, can further increase the output voltage and energy of the battery, thereby improving the overall performance of the battery, and because the price of the Mn element is relatively low, the lithium-rich manganese-based positive electrode material has a great cost advantage.
[0004] However, lithium-rich manganese-based materials also have a series of problems. As a typical layered structure material, lithium-rich manganese-based materials are prone to structural deformation and collapse during repeated lithium ion insertion and deinsertion due to the relatively weak interaction between the layers of the layered structure during the cycle process, which ultimately manifests as poor cycle performance. At the same time, the layered structure of lithium-rich manganese-based materials has a certain hindering effect on the diffusion of lithium ions, making the migration rate of lithium ions unable to meet the requirements of high-rate charging and discharging, which seriously restricts the use of lithium-rich manganese-based materials in application scenarios with high rate performance requirements. Summary of the invention
[0005] The purpose of the present invention is to overcome the problem of poor cycle performance caused by the layered structure of existing lithium-rich manganese-based materials, and to provide a method for preparing a lithium-rich manganese-based material with a layered / rock salt symbiotic structure, a lithium-rich manganese-based material, a positive electrode and a lithium-ion battery. The lithium-rich manganese-based material prepared by the method has excellent cycle stability.
[0006] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a layered / rock salt intergrowth structured lithium-rich manganese-based material, wherein the method comprises:
[0007] Mixing a precursor containing a transition metal element and a lithium source to obtain a mixture, wherein the ratio of the total molar amount of the transition metal element in the precursor to the molar amount of the lithium element in the lithium source is 1:1.57-1.7;
[0008] The mixture is subjected to a first calcination and a second calcination in sequence to obtain material II, and then a conductive material is compounded with the material II to obtain a conductive composite. After power is applied, the conductive composite is reacted at 400-600° C. for 2-3 seconds, and subjected to rapid Joule heat treatment to obtain a lithium-rich manganese-based material.
[0009] The second aspect of the present invention provides a lithium-rich manganese-based material prepared by the preparation method described in the first aspect of the present invention, wherein the lithium-rich manganese-based material has a layered rock salt symbiotic structure, wherein the rock salt structure accounts for 5-15wt% based on the total amount of the lithium-rich manganese-based material.
[0010] The third aspect of the present invention provides a positive electrode, which includes the lithium-rich manganese-based material described in the second aspect of the present invention.
[0011] A fourth aspect of the present invention provides a lithium-ion battery, comprising the positive electrode described in the third aspect of the present invention.
[0012] The preparation method provided by the present invention controls the ratio of the total molar amount of transition metal elements to the molar amount of lithium elements, and simultaneously combines rapid Joule heating to perform treatment at a preset temperature, so that the prepared material can achieve large charge and discharge capacity, high rate performance, and good cycle performance and stability.
[0013] The method provided by the invention has the advantages of simple operation, low energy consumption, high synthesis efficiency, short time and rapidity, etc., is conducive to large-scale production, and has less harm to the environment. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 are the X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Example 1, respectively;
[0015] Figure 2 is the TEM spectrum of the material prepared in Example 1;
[0016] Figure 3 is the pressure drop spectrum of the material prepared in Example 1;
[0017] Figure 4 It is a rate comparison chart of batteries composed of materials prepared in Examples 1-3 and Comparative Example 1 respectively;
[0018] Figure 5 The voltage-capacity curves of batteries composed of materials prepared in Examples 1-3 and Comparative Example 1 at different cycle numbers at a 1C rate;
[0019] Figure 6 It is the first week charge and discharge curve of the battery assembled with the materials prepared in Examples 1-3 and Comparative Example 1 respectively. DETAILED DESCRIPTION
[0020] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.
[0021] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.
[0022] The endpoints and any values of the ranges disclosed in this article 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 each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.
[0023] In addition, the term "and / or" in the specification and claims is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.
[0024] In the description of the present application, unless otherwise specified, “plurality” means two or more.
[0025] A first aspect of the present invention provides a method for preparing a lithium-rich manganese-based material using rapid Joule heat, wherein the method comprises:
[0026] Mixing a precursor containing a transition metal element and a lithium source to obtain a mixture, wherein the ratio of the total molar amount of the transition metal element in the precursor to the molar amount of the lithium element in the lithium source is 1:1.57-1.7;
[0027] The mixture is subjected to a first calcination and a second calcination in sequence to obtain material II, and then a conductive material is compounded with the material II to obtain a conductive composite. After power is applied, the conductive composite is reacted at 400-600° C. for 2-3 seconds, and subjected to rapid Joule heat treatment to obtain a lithium-rich manganese-based material.
[0028] The molar ratio of the total amount of transition metal elements and the lithium element is directly related to the proportion of layered structure and rock salt structure in the obtained material. Too much or too little proportion of rock salt structure is not conducive to improving the cycle stability of the prepared material. The molar ratio of the total amount of transition metal elements and the Li element can be 1:1.57, 1:1.6, 1:1.62, 1:1.65, 1:1.68, 1:1.7, etc., and can also be any value within the numerical range composed of any two numbers therein.
[0029] During the power-on process, the crystals will grow faster and change their orientation, thereby changing the electrochemical properties of the obtained material and enhancing the material's cycle stability. Therefore, the temperature of the Joule heat generated after power-on needs to be reasonably controlled to make the proportion of defective rock salt structures within a suitable range, thereby improving the material's cycle stability. The reaction temperature after power-on can be any value within the numerical range composed of any two numbers among 400°C, 450°C, 500°C, 550°C, and 600°C.
[0030] When the power is turned on, the reaction atmosphere can be any one of air, pure argon or inert gas, and there is no particular limitation on this.
[0031] In some embodiments, preferably, the temperature of the second calcination is greater than the temperature of the first calcination, and the temperature difference between the two is not less than 300°C. The purpose of the first calcination is to remove impurities and volatiles, initially form a crystal structure, and improve the uniformity of the material. The purpose of the second calcination is to further optimize the crystal structure, increase the density of the material, and enhance the stability of the material. Therefore, the specific execution temperature of both calcinations needs to be reasonably controlled.
[0032] In some embodiments, preferably, the transition metal element includes Ni element, Mn element and Co element, and the molar ratio of them is 0.16-0.25:0.6-0.7:0.1-0.2.
[0033] The precursor containing transition metal elements can be purchased through commercial channels, or prepared according to references, materials or prior art, and can be prepared by co-precipitation method. The present invention does not impose any special restrictions on this, as long as the molar ratio of Ni, Mn and Co meets the requirements. The molar ratio of Ni element, Mn element and Co element can be 0.16:0.6:0.1, 0.2:0.6:0.1, 0.25:0.6:0.1, 0.2:0.65:0.1, 0.2:0.7:0.1, 0.2:0.65:0.15, 0.2:0.65:0.2, etc., and can also be any value within the numerical range composed of any two numbers therein.
[0034] In some embodiments, preferably, a direct current or alternating current power supply is used for the power-on, the power-on current is 20-80A, and the duration is 2-3s.
[0035] In some embodiments, preferably, a capacitor power supply is used when the power is turned on, and its open circuit voltage is 40-80V, the number of power-on times is 1-5 times, and the total power-on time is 2-3s.
[0036] The present invention does not make any special requirements on the type of power supply, which can be direct current, alternating current or a capacitor power supply. By setting parameters such as voltage, current, time and number of power-on times, the energy and temperature changes of the composite material during power-on treatment can be regulated.
[0037] When a DC or AC power supply is used, the power-on current can be any value within the numerical range composed of any two numbers among 20A, 30A, 40A, 50A, 60A, 70A, and 80A, and the total power-on time can be 2s, 3s, etc.; when a capacitor power supply is used for instantaneous discharge for calcination, the open circuit voltage can be 40V, 50V, 60V, 70V, 80V, etc., or any value within the numerical range composed of any two numbers therein, and the number of power-on times can be 1 time, 2 times, 3 times, 4 times, 5 times, etc., as long as the total power-on time is 2-3s.
[0038] In some embodiments, preferably, the first calcination is carried out at a temperature of 400-500° C. and for a time of 4-5 h.
[0039] In some embodiments, preferably, the second calcination is carried out at a temperature of 800-900° C. and for a time of 12-14 h.
[0040] Through two calcinations, impurities in the material can be removed as much as possible, the uniformity of the material can be improved, the density of the material can be increased, the crystal structure can be optimized, and the stability of the material can be enhanced.
[0041] The temperature of the first calcination can be 400°C, 420°C, 450°C, 470°C, 500°C, etc., or any value within the numerical range formed by any two of them; the time can be 4h, 5h, etc. The temperature of the second calcination can be 800°C, 830°C, 850°C, 870°C, 900°C, etc., or any value within the numerical range formed by any two of them; the time can be 12h, 13h, 14h, etc., or any value within the numerical range formed by any two of them.
[0042] In some embodiments, preferably, the precursor is a carbonate and / or a hydroxide.
[0043] In some embodiments, preferably, the lithium source is lithium carbonate and / or lithium hydroxide.
[0044] In some embodiments, preferably, the conductive material includes any one of a conductive metal, a conductive inorganic non-metal, and a conductive high molecular polymer.
[0045] In some embodiments, preferably, the conductive object is in a plate shape, and the composite is to load the material II on the conductive object.
[0046] In some embodiments, preferably, the conductive material may also be in a granular form, or other shapes, as long as it can conduct electricity after being mixed with material II.
[0047] Conductive metals can be copper, nickel, titanium, aluminum, iron, cobalt, nickel-chromium alloy, iron-chromium-aluminum alloy, stainless steel, etc. Conductive inorganic non-metals can be carbonaceous materials such as carbon fiber, carbon nanotubes, graphene, and molybdenum disilicide, silicon carbide, indium tin oxide, etc. Conductive polymers can be polyacetylene, polypyrrole, polythiophene, polyimide, etc. Of course, composite conductive materials can also be used. They can all be purchased commercially and will not be described in detail here.
[0048] The conductive carrier can be in the form of cloth, paper, felt, strips, mesh, foam, etching and composite layers, etc.
[0049] In some embodiments, preferably, the size of the conductive carrier is 1-20 cm 2 , thickness is 4μm-2mm.
[0050] In some embodiments, preferably, the loading amount of the material II on the conductive carrier is 0.5-400 mg.
[0051] Controlling the size and thickness of the conductive carrier can adjust the resistance, optimize the heat generation and transmission efficiency, enhance the material performance and stability, so as to meet different application requirements and reduce costs. There is no special requirement for the thickness of the material II loaded on the conductive carrier, as long as the thickness is as uniform as possible after flattening. When the conductive material is in block shape, its size can be 1-20cm 2 The thickness can be 4μm-2mm, and the amount of material II loaded thereon can be 0.5mg, 1mg, 5mg, 10mg, 50mg, 100mg, 200mg, 300mg, 400mg, etc.
[0052] The second aspect of the present invention provides a lithium-rich manganese-based material prepared by the preparation method described in the first aspect of the present invention, wherein the lithium-rich manganese-based material has a layered rock salt symbiotic structure, wherein the rock salt structure accounts for 5-15wt% based on the total amount of the lithium-rich manganese-based material.
[0053] The material prepared by the present invention is a secondary particle composed of primary particles, and its average diameter is 8-12 μm. Based on the total amount of lithium-rich manganese-based material, the proportion of rock salt structure can be 5wt%, 8wt%, 10wt%, 13wt%, 15wt%, etc., and can also be any value within the numerical range composed of any two numbers therein.
[0054] When the prepared lithium-rich manganese-based material is used, it can be poured off the conductive carrier and collected before use, or used together with a conductive material. When used together with a conductive carrier, the composite can be crushed together if necessary.
[0055] The third aspect of the present invention provides a positive electrode, which includes the lithium-rich manganese-based material described in the second aspect of the present invention.
[0056] A fourth aspect of the present invention provides a lithium-ion battery, comprising the positive electrode described in the third aspect of the present invention.
[0057] The lithium-rich manganese-based material prepared by the method provided by the present invention has a certain amount of defective rock salt phase, wherein the layered rock salt intergrowth structure can optimize the crystal structure, improve the lithium ion diffusion kinetics, accelerate the charge and discharge process, and at the same time enhance the structural stability, extend the battery cycle life, and increase the material specific capacity, thereby improving the battery energy density.
[0058] The layered rock salt symbiotic structure in the present invention refers to the existence of a rock salt structure in a layered structure, and the two coexist randomly without obvious differences in distribution areas.
[0059] The lithium-rich manganese-based material prepared by the method provided by the present invention has a rock salt structure accounting for 10-14wt% of the total amount of the lithium-rich manganese-based material. After being assembled into a battery, its first-week discharge capacity is not less than 290mAh g -1The first coulombic efficiency is not less than 89%, especially its capacity retention rate is not less than 79% after 100 cycles at 5C, and even the capacity retention rate is not less than 60% after 100 cycles at 10C.
[0060] According to a particularly preferred embodiment of the present invention, the method comprises:
[0061] Mixing a precursor containing a transition metal element and a lithium source to obtain a mixture, wherein the ratio of the total molar amount of the transition metal element in the precursor to the molar amount of the lithium element in the lithium source is 1:1.57-1.6;
[0062] The mixture is subjected to a first calcination and a second calcination in sequence to obtain material II, and then a conductive material is compounded with the material II to obtain a conductive composite. After power is applied, the conductive composite is reacted at 450-550°C for 2-3s. The transition metal elements include Ni, Mn and Co, and the molar ratio of the elements is 0.16-0.2:0.6-0.7:0.1-0.15.
[0063] In the following examples and comparative examples, unless otherwise specified, the reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased from the market. If no specific conditions are indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed.
[0064] Contains a precursor containing transition metal elements, the chemical formula is: Mn 0.69 Ni 0.19 Co 0.12 CO3, the specific preparation process is as follows:
[0065] ① Prepare 1000 mL of metal salt solution: weigh MnSO4·H2O, NiSO4·6H2O and CoSO4·7H2O in a molar ratio of 6.9:1.9:1.2, and prepare a metal salt solution with a concentration of 2 mol / L;
[0066] ② Prepare 1000mL of 4mol / L NH3·H2O and 1000mL of 2mol / L Na2CO3 solution;
[0067] ③ The precursor was prepared in a reactor, the temperature of the thermostatic water bath was set to 55°C, argon was introduced, and 1000ml of deionized water was added as the base liquid, and then the metal salt solution and 2mol / L Na2CO3 solution were added, and the average feed rate of both was 1500ml / h. At the same time, 4mol / L NH3·H2O was introduced, and the feed rate of ammonia water was controlled so that the pH of the reaction system in the reactor was 11, and it was stirred at 350r / min. After the metal salt solution was fed, it was aged for 6h, then filtered and washed, and then placed in a vacuum oven at 80°C for drying. After 24h, a dry precursor powder was obtained, and its chemical formula was: Mn 0.69 Ni 0.19 Co 0.12 CO3.
[0068] Material characterization analysis methods:
[0069] ① X-ray diffraction (XRD) test: X-ray diffractometer, instrument model: Rigaku Ultima IV-185, Japan.
[0070] ②Battery cycle performance test: LAND CT 2001A tester.
[0071] ③ Transmission electron microscopy (TEM) test: Transmission electron microscope, instrument model: G2 F20, FEI Company, USA.
[0072] ④Rock salt structure ratio, tested by X-ray diffraction (XRD), instrument model: Rigaku Ultima IV-185, Japan, importing XRD test data into GSAS or MDI Jade, and obtained through software analysis;
[0073] ⑤ The particle size of the material was tested by scanning electron microscopy (SEM), instrument model: QUANTA, FEI Company, USA.
[0074] Example 1
[0075] Step (1): Add Mn 0.69 Ni 0.19 Co 0.12 CO3 and lithium carbonate were weighed and mixed evenly in a ratio of 1:1.575 between the total molar amount of Ni, Mn, and Co elements and the molar ratio of lithium element. Then, the mixture was placed in a muffle furnace and calcined at 500°C for 5 hours at a heating rate of 5°C / min. After the material was cooled to room temperature, it was taken out and ground for 5 minutes to obtain material I.
[0076] Step (2): placing the material I in a muffle furnace and sintering at 850°C for 12 hours at a heating rate of 5°C / min; after the material is cooled to room temperature, taking out the material and grinding it for 5 minutes to obtain material II.
[0077] Step (3): Load the material II on a 10 cm 2 , on a copper plate with a thickness of 1 mm, adjust the AC power supply, control the current to 20 A, the power-on time to 2 s, control the reaction temperature to 400 ° C for calcination for 2 s, and perform rapid Joule heat treatment to obtain lithium-rich manganese-based materials.
[0078] Example 2
[0079] The process was carried out in the same manner as in Example 1, except that the current was controlled to be 50 A, the power-on time was 2 s, the reaction temperature was controlled to be 500° C. and the calcination was performed for 2 s to obtain a lithium-rich manganese-based material.
[0080] Example 3
[0081] The process was carried out in the same manner as in Example 1, except that the current was controlled to be 80 A, the power-on time was 2 s, the reaction temperature was controlled to be 600° C. and the calcination was performed for 2 s to obtain a lithium-rich manganese-based material.
[0082] Example 4
[0083] The method of Example 1 is followed, except that the molar ratio of the total molar amount of the three elements Ni, Mn and Co to the lithium element is 1:1.695.
[0084] Comparative Example 1
[0085] The only difference from Example 1 is that no rapid Joule heat treatment is performed, specifically as follows:
[0086] Step (1): Add Mn 0.69 Ni 0.19 Co 0.12 CO3 and lithium carbonate were weighed and mixed evenly in a ratio of 1:1.575 between the total molar amount of Ni, Mn, and Co and the molar ratio of lithium element, and then pre-calcined in a muffle furnace at 500°C for 5h with a heating rate of 5°C / min. After the material was cooled to room temperature, it was taken out and ground to obtain material I.
[0087] Step (2): placing the material I in a muffle furnace and sintering at 850°C for 12 hours at a heating rate of 5°C / min. After the material is cooled to room temperature, taking out the material and grinding it to obtain the desired material, which is named bulk material.
[0088] Comparative Example 2
[0089] The method of Example 1 was followed, except that the power supply parameters were adjusted and the reaction temperature was controlled to be 900° C. for calcination for 2 seconds.
[0090] Comparative Example 3
[0091] The method of Example 1 is followed, except that the molar ratio of the total molar amount of Ni, Mn and Co to the lithium element in lithium carbonate is 1:1.8.
[0092] Comparative Example 4
[0093] The method of Example 1 is followed, except that the molar ratio of the total molar amount of Ni, Mn and Co to the lithium element in lithium carbonate is 1:1.4.
[0094] Figure 3-Figure 6 The 400, 500 and 600 correspond to the rapid Joule heat treatment temperatures of 400° C., 500° C. and 600° C., respectively, which correspond to the materials prepared in Examples 1-4.
[0095] The materials of Example 1 and Comparative Example 1 were subjected to X-ray diffraction scanning, and the materials of Example 1 were further subjected to transmission electron microscopy testing. The results obtained were as follows: Figure 1 and Figure 2 shown.
[0096] Figure 1 In the figure, (a) is the XRD refinement diagram of comparative example 1, and (b) is the XRD refinement diagram of embodiment 1. By comparing the two figures, it can be seen that only the layered phase exists in comparative example 1, while the layered phase and the rock salt phase exist simultaneously in embodiment 1. It can be seen that the layered rock salt intergrowth structure is generated by the material after Joule heat treatment, and the layered rock salt intergrowth structure is conducive to the material maintaining good structural stability and cycle stability in long-term circulation.
[0097] Figure 2 In the figure, (a) is the TEM image of comparative example 1, and (b) is the TEM image of embodiment 1. By comparing the two figures, it can be seen that Figure 2 (a) only has layered structures, while Figure 2 (b) There is a layered salt rock symbiotic structure, which shows that the material prepared in Example 1 successfully achieved the symbiosis of layered and salt rock structures.
[0098] The materials prepared in Examples 1-3 and Comparative Example 1 were assembled into batteries, and their rate performance and voltage-capacity curves at different cycle numbers were tested. The results are as follows: Figure 3-6 shown.
[0099] Figure 3It is the voltage drop spectrum of the materials prepared in Example 2 and Comparative Example 1 after the first cycle (Voltage in the figure is voltage, and the test conditions are: temperature 30°C, window voltage 2.0-4.8V, 0.1C. The black curve is the material of Comparative Example 1, and the blue curve is the material of Example 1). It can be seen from the figure that compared with the material prepared in Comparative Example 1, the voltage drop of the material prepared in Example 1 is significantly reduced, the oxygen release of lattice oxygen is reduced, and the lattice structure is more stable.
[0100] Figure 4 The comparison chart of the rate of the battery composed of the materials prepared in Examples 1, 2, 3 and Comparative Example 1 (the horizontal axis Cycle number in the figure is the number of cycles, and the vertical axis Specific Capacity is the specific capacity). The test conditions are: temperature 30°C, window voltage 2.0-4.8V, 1C = 250mAg -1 It can be seen that compared with the bulk material (Pristine) prepared in Comparative Example 1, the rate performance of the lithium-rich manganese-based materials prepared in Examples 1-3 is significantly improved, among which the rate performance of the lithium-rich manganese-based materials prepared at 500° C. is the best.
[0101] Figure 5 The voltage-capacity curves of batteries composed of materials prepared in Examples 1-3 and Comparative Example 1 at different cycle numbers at 1C rate are tested under the following conditions: temperature 30°C, window voltage 2.0-4.8V, 1C. As can be seen from the figure, compared with the material prepared in Comparative Example 1, the cycle performance of the lithium-rich manganese-based material prepared by the method provided by the present invention is significantly better than that of the material prepared in Comparative Example 1, and in the late cycle (after 100 cycles), the discharge specific capacity of the materials prepared in Examples 1-3 shows an upward trend, which may be due to the combined effect of multiple factors such as sufficient activation of the electrode material in the late cycle, formation of new phases or structural domains, reduced diffusion impedance, improved electrochemical reaction kinetics, sufficient electrolyte infiltration and decomposition product action. This increase is beneficial to improving the energy density of the battery, extending the service life of the battery, reducing the cost of use, and improving the performance and competitiveness of the battery in different application scenarios.
[0102] Figure 6The first-week charge-discharge curves of the batteries composed of the materials prepared in Examples 1-3 and Comparative Example 1, respectively (Specific Capacity on the horizontal axis is the specific capacity, and Voltage on the vertical axis is the voltage), and the test conditions are: temperature 30°C, window voltage 2.0-4.8V, 0.1C. As can be seen from the figure, the first-week discharge specific capacity of the lithium-rich manganese-based materials prepared by Examples 1-3 is very close to that of the material prepared in Comparative Example 1, which shows that the material prepared by the method provided by the present invention successfully introduces a defective rock salt phase and improves the cycle performance of the material while having a negligible effect on the charge specific capacity of the material, that is, while improving the cycle performance of the material, especially the charge-discharge cycle performance at a high rate, the first-week charge specific capacity of the material is basically not affected.
[0103] The materials of Examples 1-4 and Comparative Examples 1-4 were used as active materials to assemble batteries, as follows:
[0104] Battery assembly method:
[0105] The material prepared in the embodiment or comparative example is used as the active material, the active material, the conductive agent (Super P), and the binder (PVDF-polyvinylidene fluoride) are uniformly mixed in a mortar at a mass ratio of 8:1:1, and an appropriate amount of clear and transparent NMP is added as a dispersant to grind into a slurry with uniform composition, which is coated on an aluminum foil with a scraper, and dried and cut into pieces to prepare the positive electrode sheet required for a button battery; then, the slurry is assembled into a button-type half-cell in an argon atmosphere glove box with a water and oxygen content of less than 0.01ppm, wherein the positive electrode is the positive electrode sheet prepared above, the negative electrode is a lithium sheet, the separator is Celgard 2500, and the main component of the electrolyte is a solution made of 1 mol / L LiPF6 as a solute and a mixed liquid of dimethyl carbonate, diethyl carbonate, and ethylene carbonate in a volume ratio of 1:1:1 as a solvent.
[0106] The electrochemical performance of the battery assembled above was tested. The test results are shown in Table 1, where the proportion of rock salt structure is based on the total amount of prepared materials, and the secondary particle size is the average particle size D 50 The first week of charge and discharge was tested at 30°C, 2.0-4.8V window voltage, and 0.1C (1C = 250mAh / g). The temperature and window voltage of the cycle performance test at other currents were the same as those of the first week of charge and discharge. The difference was that the battery was first activated at 0.1C for two cycles, and then the cycle performance was tested at the corresponding current.
[0107] Table 1
[0108]
[0109] Table 1 continued
[0110]
[0111] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any appropriate manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.
Claims
1. A method for preparing a layered / rock salt intergrowth structured lithium-rich manganese-based material, characterized in that: The method comprises: Mixing a precursor containing a transition metal element and a lithium source to obtain a mixture, wherein the ratio of the total molar amount of the transition metal element in the precursor to the molar amount of the lithium element in the lithium source is 1:1.57-1.7; The mixture is subjected to a first calcination and a second calcination in sequence to obtain material II, and then a conductive material is compounded with the material II to obtain a conductive composite. After power is applied, the conductive composite is reacted at 400-600° C. for 2-3 seconds, and subjected to rapid Joule heat treatment to obtain a lithium-rich manganese-based material.
2. The method according to claim 1, wherein: The temperature of the second calcination is greater than the temperature of the first calcination, and the temperature difference between the two is not less than 300° C.; And / or, the transition metal elements include Ni, Mn and Co, and the molar ratio of them is 0.16-0.25:0.6-0.7:0.1-0.
2.
3. The method according to claim 1 or 2, wherein: The power supply is a direct current or alternating current, the current is 20-80A, and the duration is 2-3s; Alternatively, a capacitor power supply is used when powering on, the open circuit voltage is 40-80V, the number of power-on times is 1-5 times, and the total power-on time is 2-3s.
4. The method according to any one of claims 1 to 3, wherein: The first calcination is carried out at a temperature of 400-500° C. and for a time of 4-5 hours.
5. The method according to any one of claims 1 to 4, wherein: The second calcination temperature is 800-900° C. and the time is 12-14 hours.
6. The method according to any one of claims 1 to 5, wherein: The conductive material includes any one of conductive metal, conductive inorganic non-metal, and conductive high molecular polymer; And / or, the conductive object is in a plate shape, and the composite is to load the material II on the conductive object.
7. The method according to any one of claims 1 to 6, wherein: The precursor is a carbonate and / or a hydroxide; And / or, the lithium source is lithium carbonate and / or lithium hydroxide.
8. A lithium-rich manganese-based material prepared according to the method according to any one of claims 1 to 7, characterized in that: The lithium-rich manganese-based material has a layered rock salt symbiotic structure, wherein the rock salt structure accounts for 5-15wt% based on the total amount of the lithium-rich manganese-based material.
9. A positive electrode, characterized in that: Including the lithium-rich manganese-based material as described in claim 8.
10. A lithium ion battery, characterized in that: Comprising the positive electrode as claimed in claim 9.