CN118231638A

CN118231638A - Lithium manganate material, secondary battery and electricity utilization device

Info

Publication number: CN118231638A
Application number: CN202410316246.3A
Authority: CN
Inventors: 陈海涛; 尹翔; 李双福; 倪欢; 柳娜
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Filing date: 2023-11-03
Publication date: 2024-06-21

Abstract

The application relates to a lithium manganate material, a preparation method thereof, a secondary battery and an electric device, wherein in a differential scanning calorimeter spectrogram of the lithium manganate material, the integral area T of an endothermic peak meets the following conditions: t is less than or equal to 50J/g; the test process of the differential scanning calorimeter spectrogram is as follows: under the atmosphere of protective gas, the temperature is raised to 20 ℃ at the rate of 5 ℃/min at-20 ℃. The concentration of Ovs in the lithium manganate material is maintained at a lower level, so that the stability of the structure of the lithium manganate material is improved, and the cycle performance of the secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

Description

Lithium manganate material, secondary battery and electricity utilization device

The application relates to a lithium manganate material and a preparation method thereof, a secondary battery and an electric device thereof, which are filed by the applicant in 2023, 11 and 3, and the divisional application of Chinese application patent application with the application number 202311452306.6.

Technical Field

The invention relates to the technical field of batteries, in particular to a lithium manganate material, a preparation method thereof, a secondary battery and an electric device.

Background

Secondary batteries are increasingly used because of their clean and renewable characteristics, and mainly rely on the movement of active ions, such as lithium ions, between a positive electrode and a negative electrode to generate electrical energy.

The lithium manganate anode material is considered as one of ideal materials for preparing the power battery because of the characteristics of abundant resources, low price, environmental friendliness, high safety and the like. However, the structural stability of the conventional lithium manganate positive electrode material is low, so that the capacity decay of the battery is accelerated during repeated charge and discharge, and the cycle life of the secondary battery is reduced.

Along with the improvement of the requirements of people on secondary batteries, the traditional lithium manganate anode material is more and more difficult to meet the requirements of people, and needs to be further improved.

Disclosure of Invention

Based on this, it is necessary to provide a lithium manganate material, a method for producing the same, a secondary battery, and an electric device, in order to improve the cycle performance of the secondary battery.

In a first aspect of the present application, there is provided a lithium manganate material, wherein in a differential scanning calorimeter spectrogram of the lithium manganate material, an integral area T of an endothermic peak satisfies: t is more than 0 and less than or equal to 50J/g;

the test process of the differential scanning calorimeter spectrogram is as follows:

under the atmosphere of protective gas, the temperature is raised to 20 ℃ at the rate of 5 ℃/min at-20 ℃.

In a large number of developments and actual production, it is found that: even if the macroscopic composition of the lithium manganate material is the same, the stability of the structure of the lithium manganate material is different, and the cycle performance of the secondary battery is obviously different when the lithium manganate material is especially applied to the preparation of the secondary battery, the lithium manganate material is discovered after a great deal of experimental investigation on the composition, crystal phase and microstructure of the lithium manganate material: when the macroscopic composition of the lithium manganate material is the same, the lower the oxygen vacancy defect (Ovs for short) content in the lithium manganate material, the smaller the endothermic peak area in the differential scanning calorimeter spectrogram is, and the higher the cycle performance of the secondary battery is.

Therefore, the upper limit of the integral area T of the endothermic peak in the differential scanning calorimeter spectrogram of the lithium manganate material is controlled, so that the concentration of Ovs in the lithium manganate material is maintained at a lower level, the stability of the structure of the lithium manganate material is improved, and the cycle performance of the secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

In some embodiments, 5J/g.ltoreq.T.ltoreq.50J/g.

In some of these embodiments, the temperature region of the endothermic peak is: 1-20 ℃.

The temperature region where the endothermic peak of the lithium manganate material appears is as follows: when integrating the endothermic peak at 1-20 ℃, the integrated temperature area is 1-20 ℃.

In some of these embodiments, the composition of the lithium manganate material satisfies: li _(1+a)Mn_(2-x)M_xO_(4-δ);

Wherein M comprises one or more of Mg, al, fe, ca, zr, Y, nb, mo, cr, W, V, tc, co and Ni, a is more than or equal to 0.3 and less than or equal to 0.2, x is more than or equal to 0 and less than or equal to 0.05, and delta is more than or equal to 0 and less than or equal to 0.005.

In some of these embodiments, the lithium manganate material has a spinel phase.

In a second aspect of the present application, there is provided a method for preparing a lithium manganate material, comprising the steps of:

Providing preparation raw materials according to the stoichiometric ratio of corresponding components in the lithium manganate material, wherein the preparation raw materials comprise: lithium source and other ingredient materials;

performing primary sintering treatment on part of the lithium source and the other component raw materials in an oxygen-containing atmosphere to prepare a precursor;

Performing secondary sintering treatment on the precursor and the rest lithium sources in an oxygen-containing atmosphere to prepare the lithium manganate material;

the first sintering treatment condition comprises a constant temperature heat preservation program, the second sintering treatment is carried out under a variable temperature condition, and the variable temperature condition comprises a heating program and a cooling program which are sequentially and continuously carried out.

In the preparation method of the lithium manganate material, the lithium source is added twice, the temperature during sintering is controlled after the lithium source is added each time, a constant-temperature heat preservation program is adopted during the first sintering treatment, so that cells and crystal grains are fully grown, a precursor with a complete crystal structure and stable lattice oxygen is prepared, then the rest lithium source is added, the secondary sintering treatment is carried out under a specific temperature changing condition, the probability of separating lattice oxygen is reduced while the crystal structure is further perfected, and all aspects cooperate, so that the concentration of Ovs in the prepared lithium manganate material is maintained at a lower level, the stability of the structure of the lithium manganate material is improved, and the cycle performance of a secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

In some of these embodiments, the first sintering treatment satisfies at least one of the following conditions (a) - (b):

(a) The temperature of the constant temperature and heat preservation program in the first sintering treatment is 500-850 DEG C

(B) The time of the constant temperature and heat preservation procedure in the first sintering treatment is 5-20 h.

The temperature of the medium constant temperature heat preservation program of the first sintering treatment is regulated and controlled, and the structural integrity of the precursor is further improved.

In some of these embodiments, the temperature increase program is as follows:

Firstly, heating from room temperature to 300-550 ℃ at a first heating rate, and then heating to 600-850 ℃ at a second heating rate;

Wherein the first heating rate is greater than the second heating rate.

And the specific temperature control program is regulated, so that the probability of lattice oxygen separation is further reduced.

In some of these embodiments, the temperature increase program satisfies at least one of the following conditions (a) to (b):

(a) The first heating rate is 1-10 ℃/min;

(b) The second heating rate is 0.15 ℃/min-2.5 ℃/min.

In some of these embodiments, the cooling procedure is as follows:

Firstly, cooling to 300-550 ℃ at a first cooling rate, and then cooling to room temperature at a second cooling rate;

Wherein, the first cooling rate is less than the second cooling rate.

In some embodiments, the cooling program satisfies at least one of the following conditions (a) - (b):

(a) The first cooling rate is 0.15-2.5 ℃/min;

(b) The second cooling rate is 1-10 ℃/min.

In some of these embodiments, the molar ratio of the lithium element contained in a portion of the lithium source to the lithium element contained in the remaining lithium source is (3 to 11): 1.

In some of these embodiments, the molar ratio of the lithium element contained in a portion of the lithium source to the lithium element contained in the remaining lithium source is (3 to 9): 1.

The molar quantity of the lithium source added for two times is regulated so as to better cooperate with a specific sintering temperature control program, and the probability of lattice oxygen separation is further reduced while the crystal structure is further perfected.

In some of these embodiments, the other constituent raw materials include a manganese source and an M source, where M includes one or more of Li, mg, al, fe, ca, zr, Y, nb, mo, cr, li, W, V, tc, co and Ni.

In a third aspect of the present application, there is provided a lithium manganate material prepared by the preparation method of the lithium manganate material of the second aspect.

According to a fourth aspect of the present application, there is provided a positive electrode sheet, the positive electrode sheet comprising a current collector and a positive electrode active layer provided on the surface of the current collector, the composition of the positive electrode active layer comprising the lithium manganate material of the first aspect or the lithium manganate material of the third aspect.

In a fifth aspect of the present application, there is provided a secondary battery comprising the lithium manganate material of the first aspect or the positive electrode sheet of the third aspect or the fourth aspect.

In a sixth aspect of the present application, there is provided an electric device including the secondary battery of the fifth aspect.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the accompanying drawings. In the drawings:

FIG. 1 is a schematic diagram of one embodiment of a battery cell;

FIG. 2 is an exploded view of FIG. 1;

FIG. 3 is a schematic diagram of an embodiment of a battery pack;

FIG. 4 is an exploded view of FIG. 3;

FIG. 5 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source;

FIG. 6 is an X-ray diffraction pattern of the lithium manganate material prepared in example 1 and comparative example 1, (A) an X-ray diffraction pattern of the lithium manganate material prepared in example 1, and (B) an X-ray diffraction pattern of the lithium manganate material prepared in comparative example 1;

FIG. 7 is a comparative graph of differential scanning calorimetry patterns of the lithium manganate material prepared in example 1 and comparative example 1, (a) a differential scanning calorimetry pattern of the lithium manganate material prepared in example 1, and (b) a differential scanning calorimetry pattern of the lithium manganate material prepared in comparative example 1;

Fig. 8 shows the charge and discharge curves, (c) and (d) of the button cell prepared in example 1;

fig. 9 is a graph of capacity retention rate of cyclic charge and discharge of the batteries manufactured in example 1 and comparative example 1.

Reference numerals illustrate:

1. A battery pack; 2. an upper case; 3. a lower box body; 4. a battery cell; 41. a housing; 42. an electrode assembly; 43. a cover plate; 5. and (5) an electric device.

Detailed Description

The following detailed description of the present application will provide further details in order to make the above-mentioned objects, features and advantages of the present application more comprehensible. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present application, unless otherwise specified, "room temperature" generally means 4℃to 30℃and preferably means 20.+ -. 5 ℃.

In a large number of developments and actual production, it is found that: even if the macroscopic composition of the lithium manganate material is the same, the stability of the structure of the lithium manganate material is different, and the cycle performance of the secondary battery is obviously different when the lithium manganate material is especially applied to the preparation of the secondary battery, the lithium manganate material is discovered after a great deal of experimental investigation on the composition, crystal phase and microstructure of the lithium manganate material: when the macroscopic composition of the lithium manganate material is the same, the lower the oxygen vacancy defect (Ovs for short) content in the lithium manganate material is, the smaller the endothermic peak area in the differential scanning calorimeter spectrogram is, and the higher the cycle performance of the secondary battery is.

In the traditional technology, a high-temperature solid-phase sintering method is often adopted to prepare a lithium manganate material, and the method is realized by mixing and grinding raw materials such as a manganese source, a lithium source and the like according to the component proportion of the lithium manganate material, and then sintering the mixture at a high temperature.

The high-temperature solid phase method has the advantages of simple operation, easily available raw materials, easy realization of industrialization and the like, but the sintering process has the problems of excessive lattice oxygen separation reduction, high oxygen vacancy (Ovs) content of the product and the like. Those skilled in the art have attempted to improve the stability of lithium manganate materials by doping elements, but the substantial improvement is limited, and industrialization is not easy to realize.

It is accidentally found in long-term actual production process and exploration: in the high-temperature solid-phase sintering process, the separation of lattice oxygen is related to the adding mode of a lithium salt source and the sintering method.

Therefore, after a great deal of exploration, the lithium manganate material and the preparation method thereof are obtained.

In one embodiment of the present application, a lithium manganate material is provided, wherein in a differential scanning calorimeter spectrogram of the lithium manganate material, an integral area T of an endothermic peak satisfies: t is more than 0 and less than or equal to 50J/g; the test process of the differential scanning calorimeter spectrogram is as follows:

By controlling the upper limit of the integral area T of the endothermic peak in the differential scanning calorimeter spectrogram of the lithium manganate material, the concentration of Ovs in the lithium manganate material is maintained at a lower level, so that the stability of the structure of the lithium manganate material is improved, and the cycle performance of the secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

It is understood that the differential scanning calorimeter is obtained using a differential scanning calorimeter analysis (DIFFERENTIAL SCANNING Calorimetry, abbreviated as DSC) test. The temperature control program in computer software is used for controlling the temperature condition in the test process, the relation between the power difference and the temperature of a sample to be tested and a reference object in an input instrument is measured, the data obtained by the test are directly fed back into the computer software, a differential scanning calorimetric spectrogram can be obtained through program processing, the peak in the differential scanning calorimetric spectrogram is upward and represents an endothermic peak, and the peak is downward and represents an exothermic peak; the integration of the endothermic peak can be performed directly by a computer program.

In some embodiments, 5J/g.ltoreq.T.ltoreq.50J/g.

In the above "5J/g.ltoreq.T.ltoreq.50J/g", the value of T includes the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the examples and the point values below: 5J/g, 10J/g, 15J/g, 20J/g, 25J/g, 30J/g, 35J/g, 40J/g, 45J/g, 50J/g; or any two values, for example, may be 5J/g to 50J/g, 5J/g to 45J/g, 5J/g to 40J/g, 5J/g to 35J/g, 5J/g to 30J/g, 5J/g to 25J/g, 5J/g to 20J/g, 5J/g to 10J/g.

In some embodiments, the button cell is made from a positive plate, a lithium plate, a separator and an electrolyte;

the positive electrode active layer in the positive electrode plate comprises the lithium manganate material, carbon black SP, carbon nano tubes and polyvinylidene fluoride in a mass ratio of 94:1.5:0.5:3.

The electrolyte comprises LiPF ₆ and a solvent, wherein the solvent is a mixed solution of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1.

The separator adopts polyolefin separator.

And (3) carrying out charge and discharge test on the button cell by adopting 0.1C to obtain a charge and discharge curve.

In the charge-discharge curve, the total discharge gram capacity in the potential interval of 3.0V-3.4V is DC1, and the total discharge gram capacity in the potential interval of 2.8V-4.3V is DC2,0.001< DC1/DC2<0.02.

Specifically, a charge-discharge test is performed with a constant current of 0.1C (1 c=0.1a·g ^-1 is set), a charge-discharge curve is obtained, wherein the ordinate of the discharge curve is voltage, the abscissa is discharge gram capacity, DC2 is the difference between the abscissa value corresponding to voltage 4.3V and the abscissa value corresponding to voltage 2.8V, and DC1 is the difference between the abscissa value corresponding to voltage 3.4V and the abscissa value corresponding to voltage 3.0V.

Further researches show that the oxygen vacancy defect (Ovs) content in the lithium manganate material has a positive correlation trend with the DC1 and DC2 ratio obtained by testing under specific conditions, namely the upper limit of DC1/DC2 is controlled, namely the Ovs concentration in the lithium manganate material is maintained at a lower level, so that the structural stability of the lithium manganate material is improved, and the cycle performance of the secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

In some of these embodiments, 0.002< DC1/DC2<0.02.

In some of these embodiments, the composition of the lithium manganate material satisfies: li _(1+a)Mn_(2-x)M_xO_(4-δ).

In the above "0.ltoreq.x.ltoreq.0.05", the value of x includes the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the following point values: 0. 0.01, 0.02, 0.03, 0.04, 0.05; or a range of any two values, for example: 0 to 0.04, 0.01 to 0.02, 0.03 to 0.04 and 0.03 to 0.05.

In the above "0 < δ+.0.005", the value of δ includes the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the point values below: 0.001, 0.002, 0.003, 0.004, 0.005; or a range of any two values, for example: 0.001-0.002, 0.001-0.003, 0.001-0.004, 0.001-0.005, 0.002-0.005, 0.003-0.005.

In the above "-0.3+.a+.0.2", the value of a includes the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values in the examples and the point values below: -0.3, -0.25, -0.2, -0.15, -0.1, -0.05, 0, 0.1, 0.15, 0.2; or a range of any two values, e.g. ：-0.3～-0.1、-0.3～0、-0.3～-0.1、-0.3～0.15、-0.3～0.2、-0.2～-0.1、-0.2～0、-0.2～-0.1、-0.2～0.15、0～0.1、0～0.15、0～0.2.

According to an embodiment of the application, a preparation method of a lithium manganate material is provided, and the preparation method comprises the following steps S10-S20.

Step S10: providing preparation raw materials according to the stoichiometric ratio of corresponding components in the lithium manganate material, wherein the preparation raw materials comprise: lithium source and other ingredient materials.

In some of these embodiments, the stoichiometric ratio of the respective components in the lithium manganate material is such that: li _(1+a)Mn_(2-x)M_xO₄.

The values of M and x are the same as above, and are not described here again.

It can be understood that the stoichiometric ratio of Li _(1+a)Mn_(2-x)M_xO₄ is adopted when the material is fed in step S10, and the oxygen atom is changed due to the presence of oxygen defects in the preparation process, specifically, the values of Li _(1+a)Mn_(2-x)M_xO_(4-δ), a, x and δ are the same in the ranges and are not described herein.

Step S20: and (3) carrying out primary sintering treatment on part of the lithium source and other component raw materials in an oxygen-containing atmosphere to obtain the precursor.

In some of these embodiments, the other constituent raw materials include a manganese source and an M source.

M includes one or more of Li, mg, al, fe, ca, zr, Y, nb, mo, cr, W, V, tc, co and Ni.

In some of these embodiments, the molar ratio of the lithium source, the manganese source, and the M source is (0.6-0.95): 1.95-1.99): 0.01-0.05.

In the present application, the lithium source, the manganese source and the M source may employ lithium source compounds, manganese source compounds and M source compounds commonly used in the art, and the lithium source, the manganese source and the M source are exemplified as follows, but are not limited to the following species.

The lithium source may be at least one of a lithium-containing salt compound, a lithium-containing oxide, and a lithium-containing hydroxide; further, it may include: at least one of a lithium-containing oxide, a lithium-containing hydroxide, a lithium-containing carbonate, a lithium-containing oxalate, a lithium-containing nitrate, and a lithium-containing borate; specifically, at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium borate may be included.

The manganese source can be at least one of manganese-containing salt compounds, manganese-containing oxides and manganese-containing hydroxides; further, it may include: at least one of a manganese-containing oxide, a manganese-containing hydroxide, a manganese-containing carbonate, a manganese-containing oxalate, and a manganese-containing nitrate; specifically, at least one of manganese hydroxide, manganese carbonate, manganese nitrate, and manganese oxide may be included.

The M source can be at least one of M-containing salt compound, M-containing oxide and M-containing hydroxide; further, at least one of an oxide containing M, an hydroxide containing M, a carbonate containing M, an oxalate containing M, a nitrate containing M, and the like may be included; such as at least one of magnesium acetate, calcium carbonate, aluminum nitrate, hydrogen oxide, and zirconium oxide.

Step S30: and (3) in an oxygen-containing atmosphere, carrying out secondary sintering treatment on the precursor and the rest lithium source to prepare the lithium manganate material.

The first sintering treatment condition comprises a constant temperature heat preservation program, and the second sintering treatment is performed under a variable temperature condition which comprises a temperature raising program and a temperature lowering program which are sequentially and continuously performed.

What is required is: the heating program and the cooling program which are sequentially and continuously performed are that the heat preservation program is not arranged in the middle process; in other words, the heating program process has no heat preservation program, the cooling program process has no heat preservation program, and the connection process from the heating program to the cooling program has no heat preservation program.

In some of these embodiments, the temperature of the constant temperature soak procedure in the first sintering process is 500 ℃ to 850 ℃.

In some of these embodiments, the time for the constant temperature incubation procedure in the first sintering process is from 5 hours to 20 hours.

In the above-mentioned "500 ℃ to 850 ℃, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the examples and the following point values: 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃; or a range of any two values, for example: 500-550 ℃, 500-650 ℃, 500-750 ℃, 600-650 ℃, 600-750 ℃, 600-850 ℃.

In the above "5h to 20h", the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the following point values: 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h; or a range of any two values, for example: 5 to 20 hours, 10 to 20 hours, 5 to 15 hours and 10 to 15 hours.

In some of these embodiments, the temperature ramp up procedure is as follows: the temperature is raised from room temperature to 300-550 ℃ at a first temperature raising rate, and then is raised to 600-850 ℃ at a second temperature raising rate.

Wherein the first heating rate is greater than the second heating rate.

In some of these embodiments, the first ramp rate is from 1 ℃/min to 10 ℃/min.

In some of these embodiments, the second ramp rate is from 0.15 ℃/min to 2.5 ℃/min.

In the above "1 ℃/min to 10 ℃/min", the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the following point values: 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min; or a range of any two values, e.g. ：1℃/min～10℃/min、1℃/min～9℃/min、1℃/min～8℃/min、1℃/min～5℃/min、3℃/min～10℃/min、5℃/min～10℃/min、5℃/min～8℃/min、3℃/min～6℃/min.

In the above "0.15 ℃/min to 2.5 ℃/min", the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the point values below: 0.15 ℃/min, 0.5 ℃/min, 1 ℃/min, 1.15 ℃/min, 1.5 ℃/min, 2 ℃/min, 2.5 ℃/min; or a range of any two values, e.g. ：0.5℃/min～2.5℃/min、1℃/min～2.5℃/min、1℃/min～2℃/min、0.15℃/min～2℃/min、0.15℃/min～1.5℃/min、0.15℃/min～1℃/min.

In some of these embodiments, the cooling procedure is as follows: firstly, cooling to 300-550 ℃ at a first cooling rate, and then cooling to room temperature at a second cooling rate.

Wherein, the first cooling rate is smaller than the second cooling rate.

In some of these embodiments, the room temperature is 4 ℃ to 30 ℃; further, the room temperature was 20.+ -. 5 ℃.

In some of these embodiments, the first cooling rate is from 0.15 ℃/min to 2.5 ℃/min.

In some of these embodiments, the second cooling rate is from 1 ℃/min to 10 ℃/min.

In some of these embodiments, the molar ratio of the lithium element contained in a portion of the lithium source to the lithium element contained in the remaining lithium source is (3-11): 1.

In some of these embodiments, the molar ratio of the lithium element contained in a portion of the lithium source to the lithium element contained in the remaining lithium source is (3-9): 1.

The above "(3 to 11): 1", the values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values in the embodiments and the following point values: 11: 1. 10: 1. 9: 1. 8: 1. 7: 1. 6: 1. 5: 1. 4: 1. 3:1, a step of; or a range of any two values, e.g. ：(3～8)：1、(3～7)：1、(3～6)：1、(3～5)：1、(3～4)：1、(4～9)：1、(4～8)：1、(4～7)：1、(4～6)：1、(5～9)：1、(5～8)：1、(5～7)：1、(5～6)：1、(6～9)：1、(6～8)：1、(6～7)：1.

In some of these embodiments, prior to the first sintering process, a step of subjecting a portion of the lithium source and other constituent raw materials to a first mixing process is also included; further, the first mixing treatment is performed in a solvent.

In some of these embodiments, the solvent comprises an alcoholic organic solvent having 1 to 4 carbon atoms; may include at least one of methanol, ethanol, and propanol.

In some of these embodiments, the volume ratio of solvent to solid component in the first mixing process is (5-15): 1.

In some of these embodiments, the time of the first mixing process is 500min to 700min.

In some of these embodiments, the first mixing process is performed using a ball mill.

After the step of the first mixing treatment and before the step of performing the first sintering treatment, a step of performing a drying treatment on the mixture after the first mixing treatment to remove the solvent is further included.

Further, the drying treatment adopts vacuum drying; specifically, the drying temperature is 100-150 ℃ and the pressure is 100pa.

In some of these embodiments, prior to the second sintering process, a step of subjecting the precursor to a second mixing process with the remaining lithium source is further included; further, the second mixing treatment is performed in a solvent.

In some of these embodiments, the volume ratio of solvent to solid component in the second mixing process is (5-15): 1.

In some of these embodiments, the second mixing process takes 500min to 700min.

In some of these embodiments, the second mixing process is performed using a ball mill.

After the step of the second mixing treatment and before the step of performing the second sintering treatment, a step of performing a drying treatment on the mixture after the mixing treatment to remove the solvent is further included.

In some of these embodiments, the "oxygen-containing atmosphere" described above may be air, oxygen-enriched air, or a pure oxygen atmosphere.

In some embodiments, the "oxygen-containing atmosphere" described above has an oxygen content of greater than or equal to 50% by volume.

In some embodiments, the "oxygen-containing atmosphere" described above has an oxygen content of greater than or equal to 60% by volume.

In some embodiments, the "oxygen-containing atmosphere" has an oxygen content of 60% to 99.9% by volume.

In another embodiment of the present application, a lithium manganate material is provided, and the lithium manganate material is prepared by the preparation method of the lithium manganate material.

The concentration of Ovs in the lithium manganate material prepared by the preparation method of the lithium manganate material is maintained at a lower level, so that the stability of the structure of the lithium manganate material is improved, and the cycle performance of the secondary battery can be improved when the lithium manganate material is applied to the preparation of the secondary battery.

The application also provides a positive plate, which comprises a current collector and a positive active layer arranged on the surface of the current collector, wherein the components of the positive active layer comprise the lithium manganate material or the lithium manganate material prepared by the preparation method of the lithium manganate material.

In some of these embodiments, the weight ratio of the lithium manganate material in the positive electrode active layer is 80wt% to 100wt% based on the total weight of the positive electrode active layer.

In any embodiment of the present application, the components of the positive electrode active layer further include a positive electrode conductive agent and a positive electrode binder.

The positive electrode conductive agent may be a conductive agent commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, at least one of conductive carbon black (Super-P, abbreviated as SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, superconducting carbon black with branched structure (ECP), vapor Grown Carbon Fiber (VGCF), carbon Nanotubes (CNTs), and graphene and a composite conductive agent thereof may be included.

The weight ratio of the positive electrode conductive agent in the positive electrode active layer is 0 to 20wt% based on the total weight of the positive electrode active layer.

In any embodiment of the present application, the binder of the positive electrode binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and a fluoroacrylate resin.

The weight ratio of the positive electrode binder in the positive electrode active layer is 0 to 30wt% based on the total weight of the positive electrode active layer.

In any embodiment of the present application, the positive electrode sheet may be prepared by: dispersing the components for preparing the positive plate in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry; and (3) coating the positive electrode slurry on a current collector, and drying, cold pressing and other working procedures to obtain the positive electrode plate. The solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000 mPa.s

Coating positive electrode slurry on the surface of a positive electrode current collector, drying, and cold pressing by a cold rolling mill to form a positive electrode plate; the positive pole piece has a compacted density of 3.0g/cm ³～3.6g/cm³, optionally 3.3g/cm ³～3.5g/cm³. The calculation formula of the compaction density is as follows:

compacted density = areal density of the single-sided positive electrode active material layer/(positive electrode sheet thickness of the single-sided positive electrode active material layer-current collector thickness).

In one embodiment of the present application, a secondary battery is provided that includes the above lithium manganate material or positive electrode tab.

The secondary battery further includes a negative electrode sheet, a separator, and an electrolyte, examples of which are described below, including but not limited to the following.

Electrolyte solution: generally, the electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from electrolyte salts commonly used in the art, such as lithium ion electrolyte salts.

As examples, lithium ion electrolyte salts include, but are not limited to: one or more of lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium perchlorate (LiClO ₄), lithium hexafluoroarsenate (LiAsF ₆), lithium bis-fluoro-sulfonimide (LiFSI), lithium bis-trifluoro-methanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro-oxalato-borate (lidaob), lithium difluoro-oxalato-borate (LiBOB), lithium difluoro-phosphate (LiPO ₂F₂), lithium difluoro-oxalato-phosphate (LiDFOP) and lithium tetrafluorooxalato-phosphate (LiTFOP).

In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene Carbonate (EC), propylene Carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), butylene Carbonate (BC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

In some embodiments, the concentration of electrolyte salt in the electrolyte is typically 0.5mol/L to 15mol/L.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

Isolation film: the isolating film is arranged between the positive plate and the negative plate.

The type of the isolating membrane can be any known porous isolating membrane with good chemical stability and mechanical stability.

In some embodiments, the material of the isolation film may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different.

The thickness of the diaphragm is controlled between 2 and 15 mu m; alternatively, the thickness of the separator is controlled to be 2 μm to 13 μm.

Negative electrode plate: the negative electrode plate can be a negative electrode plate for various secondary battery systems in the field.

In some of these embodiments, the battery is a lithium metal secondary battery and the negative electrode sheet may be a negative electrode sheet that is well known in the art to be used in lithium metal batteries.

In some embodiments, the negative electrode sheet is directly a lithium-containing metal sheet.

In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer that are stacked.

Further, the lithium-containing technique in the lithium-containing metal sheet and the lithium-containing metal layer may be lithium metal, or may be an alloy of lithium metal and other metal or nonmetal elements.

Further, the other metal includes at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and foil (Pt); the nonmetallic element includes at least one of boron (B), carbon (C) and silicon (Si).

In some of these embodiments, the conductive layer may be a copper foil.

In any embodiment of the present application, the above-described negative electrode sheet may be prepared by: the lithium-containing metal sheet is directly pressed to obtain the negative electrode sheet, or the lithium-containing metal layer and the conductive layer are laminated and pressed to obtain the negative electrode sheet.

In some of these embodiments, the battery is a lithium ion secondary battery and the negative electrode sheet may be a negative electrode sheet that is well known in the art and can be used in a lithium ion battery.

In some of these embodiments, the negative electrode sheet includes a current collector and a negative electrode active layer supported on the surface of the current collector.

The composition of the anode active layer includes an anode active material.

The negative electrode active material may be a negative electrode active material commonly used in the present application.

In any embodiment of the present application, the negative electrode active material includes at least one of mesophase carbon microspheres, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials, and iron-based materials.

Alternatively, specific examples of the above-described anode active material include, but are not limited to: at least one of mesophase carbon microspheres, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon carbon composites, lithium metal and lithium metal alloys.

In any embodiment of the present application, the mass ratio of the negative electrode active material in the negative electrode active layer is 70% to 100%.

In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

In any embodiment of the present application, the above-mentioned negative electrode conductive agent may use conductive materials commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, at least one of conductive carbon black (SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, superconducting carbon black with branched structure (ECP), vapor Grown Carbon Fiber (VGCF), carbon Nanotubes (CNTs), and graphene and its composite conductive agent may be included.

The weight ratio of the anode conductive agent in the anode active layer is 0 to 20wt% based on the total weight of the anode active layer.

The negative electrode binder may be at least one binder commonly used in the art, and may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

The weight ratio of the anode binder in the anode active layer is 0 to 30wt% based on the total weight of the anode active layer.

In any embodiment of the present application, the anode active layer may further optionally include other auxiliary agents, for example, a thickener such as sodium carboxymethyl cellulose (CMC-Na) or the like. The weight ratio of the other auxiliary agent in the anode active layer is 0 to 15wt% based on the total weight of the anode active layer.

In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used.

The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material on a polymeric material substrate.

In some of these embodiments, the metallic material is selected from any one of aluminum, aluminum alloy, nickel alloy, titanium alloy, silver, and silver alloy.

In some of these embodiments, the polymeric material substrate comprises at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE).

In any embodiment of the present application, the negative electrode sheet may be prepared by: dispersing the above components for preparing a negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, in a solvent to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining the negative electrode plate after the procedures of drying, cold pressing and the like.

In some of these embodiments, the above solvents include, but are not limited to: and (3) water.

In some of these embodiments, the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at 25 ℃ is adjusted to 2000mpa·s to 10000mpa·s.

In some of these embodiments, the surface density of the anode active material layer contained in the anode sheet is 0.005g/cm ²～0.03g/cm².

Areal density of the anode active material layer = mass of the anode active material layer/area of the anode active material layer in the anode sheet.

The shape of the secondary battery of the present application may be a cylindrical shape, a square shape, or any other shape. For example, fig. 1 is a square-structured battery cell 4 as one example.

In some embodiments, referring to fig. 2, the housing may include a shell 41 and a cover plate 43. The housing 41 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 41 has an opening communicating with the accommodation chamber, and the cover plate 43 can be provided to cover the opening to close the accommodation chamber.

The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 42 through a winding process or a lamination process. The electrode assembly 42 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 42. The number of electrode assemblies 42 included in the battery cell 4 may be one or more, and may be adjusted according to the need.

The application also provides an electric device which comprises the secondary battery.

Further, in the above-described power consumption device, the secondary battery may exist in the form of a battery cell or may exist in the form of a battery pack further assembled.

Fig. 3 and 4 are battery packs 1 as an example. The battery pack 1 includes a battery case and one or more battery cells 4 provided in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3, and a closed space for the battery cells 4 is formed.

The plurality of battery cells 4 may be arranged in the battery box in any manner.

The battery or the battery pack assembled by the battery can be used as a power source of an electric device and also can be used as an energy storage unit of the electric device.

The above-mentioned electric device may be, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, or the like.

In some of these embodiments, the mobile device may be a cell phone or a notebook computer, or the like.

In some of these embodiments, the electric vehicle includes, but is not limited to: pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, and the like.

Fig. 5 is an electric device 5 as an example. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the battery of the power consumer 5, a battery pack may be used.

As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. The device is generally required to be light and thin, and a battery can be used as a power source.

The application will be described in connection with specific embodiments, but the application is not limited thereto, and it will be appreciated that the appended claims outline the scope of the application, and those skilled in the art, guided by the inventive concept, will appreciate that certain changes made to the embodiments of the application will be covered by the spirit and scope of the appended claims.

The following are specific examples.

Example 1

S1: preparation of lithium manganate material

(1) Weighing preparation raw materials, specifically as follows:

5.036g of lithium hydroxide monohydrate, 26.286g of manganese hydroxide and 0.641g of magnesium acetate are weighed respectively, mixed, ethanol with the total volume of 10 times of the solid is added, wet-milled and mixed for 600 minutes by a super-energy ball mill, and then vacuum-dried at 120 ℃ and 100pa to obtain a mixture.

(2) Heating the mixture to 600 ℃ in an atmosphere furnace, preserving heat, performing primary sintering treatment for 10h, controlling the oxygen volume content in the sintering atmosphere to be 66% in the sintering process, cooling and crushing after sintering to obtain a precursor.

(3) Adding 1.259g of lithium hydroxide monohydrate into the precursor, wet-milling and uniformly mixing by using a super-energy ball mill, vacuum-drying, and then placing into an oxygen-enriched air atmosphere furnace with 66% of oxygen volume content for secondary sintering treatment, wherein the process is as follows: heating from room temperature to 450 ℃ at a first heating rate of 5 ℃/min, continuously heating to 700 ℃ at a second heating rate of 0.3 ℃/min, cooling the sintering temperature to 450 ℃ at a first cooling rate of 0.3 ℃/min, and cooling to room temperature at a second cooling rate of 5 ℃/min to obtain the lithium manganate material.

Wherein the molar ratio of the lithium element in the lithium hydroxide monohydrate added in the step (1) to the lithium element in the lithium hydroxide monohydrate added in the step (3) is recorded as H, and the specific application is shown in Table 1.

S2: preparation of positive plate

The lithium manganate material, the conductive agent, the carbon nano tube and the polyvinylidene fluoride are prepared into positive electrode slurry according to the formula of 94:1.5:0.5:3, the positive electrode slurry is coated on an Al foil with the thickness of 13 mu m, and the positive electrode plate is obtained after vacuum drying, cold pressing and cutting and slitting at the temperature of 120 ℃, wherein the surface density of the positive electrode plate is 15mg/cm ².

S3: preparation of electrolyte

Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed according to the volume ratio EC: EMC: dec=1:1:1 to obtain an organic solvent, and then a fully dried lithium source LiPF ₆ is dissolved in the organic solvent to prepare an electrolyte with the concentration of 1 mol/L.

S4: polyethylene film was chosen as the separator for lithium ion batteries.

S5: and (3) a negative electrode: graphite, conductive agent carbon black, binder styrene butadiene rubber SBR and thickener sodium carboxymethylcellulose CMC are mixed according to the weight ratio of 97:0.5:1.25:1.25, adding the mixture into deionized water, mixing and stirring for 6 hours to obtain negative electrode slurry; and uniformly coating the cathode current collector on a cathode current collector, and drying to obtain a cathode sheet, wherein the surface density of the cathode sheet is 8mg/cm ².

S6: assembling a lithium ion battery: and stacking the positive plate, the isolating film and the negative plate in sequence, enabling the isolating film to be positioned in the middle of the anode and the cathode to play a role of isolation, winding to obtain a bare cell, placing the bare cell in an outer package, injecting 10g of prepared electrolyte, packaging, injecting the electrolyte, forming, exhausting and other working procedures to obtain the lithium ion battery.

S7: testing

Characterization test of lithium manganate material:

(1) X-ray diffraction test

Carrying out X-ray diffraction test on the prepared lithium manganate material, wherein the equipment model Bruker D8Discover is as follows: the Cu target has a tube pressure of 40V, a tube current of 40mA, a scanning speed of 2 DEG/min, a2 theta scanning range of 15 DEG-70 DEG, a step length of 0.02 DEG, an emission slit (DS) of 1mm, an anti-Scattering Slit (SS) of 8mm, and a graphite monochromator.

The X-ray diffraction pattern of the lithium manganate material prepared above is shown in fig. 6 (a), and shows spinel phase characteristics.

(2) Differential Scanning Calorimeter (DSC) test

The lithium manganate material prepared above was tested by Differential Scanning Calorimetry (DSC): in the test process, protective gas nitrogen is introduced, the ventilation amount is 50mL/min, the temperature is raised to 20 ℃ at the speed of 5 ℃/min at the temperature of minus 20 ℃, then the temperature is naturally cooled, a differential scanning calorimeter (DSC spectrogram) is obtained, specifically, as shown by a curve (a) in fig. 7, the abscissa is temperature (Temp), the ordinate is power (DSC and Mw/mg) which indicates the flow direction of each gram of sample, the endothermic peak is smaller in fig. 7, the endothermic peak is not obvious due to the compression of the ordinate, after the actual stretching of the ordinate, the endothermic peak appears in the range of 1-20 ℃, the area scanning integration is carried out on the endothermic peak, and the integral temperature range is: the integral area is recorded as T at 1-20 ℃, and is shown in Table 1.

The endothermic peak area on the DSC spectrogram has positive correlation with the oxygen vacancy content of the lithium manganate material, and the smaller the numerical value of the integral area is, the lower the oxygen vacancy content of the lithium manganate material is.

Cell performance test:

1. Gram capacity test: the positive electrode sheet is used as a positive electrode, the lithium sheet is used as a negative electrode, the button cell is assembled, and in the test process, a charge and discharge test is performed by adopting a current with the multiplying power of 0.1C (1 C=0.1 A.g ^-1 is set), a charge and discharge curve is shown in fig. 8, wherein (d) is a discharge curve, and (C) is a charge curve: testing the charge-discharge capacity of the battery in a 2.8-4.3V interval, wherein the total discharge gram capacity of a discharge platform in a 3.0-3.4V potential interval is recorded as DC1, namely, the difference between an abscissa value corresponding to 3.4V voltage and an abscissa value corresponding to 3.0V voltage in a discharge curve; the total discharge gram capacity of the discharge plateau in the potential interval of 4.3V-2.8V is recorded as DC2, namely the difference between the abscissa value corresponding to the voltage of 4.3V and the abscissa value corresponding to the voltage of 2.8V in the discharge curve. The numerical value of DC1/DC2 has positive correlation with the oxygen vacancy content of the lithium manganate material, and the smaller the numerical value of DC1/DC2 is, the lower the oxygen vacancy content of the lithium manganate material is. DC1/DC2 is designated as γ, and Table 1 is specifically referred to.

2. And (3) testing the cycle performance: at 25 ℃, the lithium ion battery prepared in the step S6 is subjected to cyclic test according to the following procedures: the charge and discharge test was performed at a 1C rate (1 c=0.1 a·g ^-1) and the voltage interval was set to 2.8V to 4.3V, charge-discharge was once considered as one cycle, the initial capacity at this time was recorded, the cycle was thus performed for 100 cycles, the capacity of the cell was recorded for 100 cycles, and the percentage value of the capacity of the cycle 100 cycles to the initial capacity was recorded as P ₁₀₀. See Table 1 for details.

The capacity retention rate curve of the lithium ion battery prepared in example 1 for cyclic charge and discharge at 2.8V to 4.3V is shown in fig. 9, and the abscissa is the number of cycles, and the unit is: circles, ordinate are capacity retention.

Examples 2 to 4

Examples 2 to 4 are substantially identical to example 1, except that: in step S1, in the case where the total amount of the lithium hydroxide monohydrate added in step (1) and the lithium hydroxide monohydrate added in step (3) is the same as in example 1, the mass of the lithium hydroxide monohydrate added in step (1) and the lithium hydroxide monohydrate added in step (3) is changed, thereby changing H.

Other steps are the same as in example 1, and specific parameters are shown in Table 1.

Example 5

Example 5 is substantially the same as example 1, except that: in the step S1, the mass of the lithium hydroxide monohydrate added in the step (1) and the step (3) is 5.099g and 1.825g respectively, and magnesium acetate is not added in the step (1), so that the lithium manganate material is prepared.

Example 6

Example 6 is substantially the same as example 1, except that: in step S1, in step (1), 0.641g of magnesium acetate was replaced with 1.688g of aluminum nitrate.

Example 7

Example 7 is substantially the same as example 1, except that: in step S1, in step (1), 0.641g of magnesium acetate was replaced with 0.555g of zirconia.

Examples 8 to 13

Examples 8 to 13 are substantially identical to example 1, except that: in step S1, the constant temperature or time of the first sintering treatment in step (2) is changed.

Examples 14 to 17

Examples 14 to 17 are substantially identical to example 1, except that: in step S1, the cutoff temperature at the time of the temperature increase at the first temperature increase rate or the cutoff temperature at the time of the second temperature increase rate in the second sintering treatment in step (4) is changed. Wherein the temperature was increased from room temperature to 350deg.C at a first rate of 5 deg.C/min in example 14, from room temperature to 550deg.C at a first rate of 5 deg.C/min in example 15, and further increased to 650deg.C at a second rate of 0.3 deg.C/min in example 16, and further increased to 800deg.C at a second rate of 0.3 deg.C/min in example 17.

Examples 18 to 22

Examples 18 to 22 are basically the same as example 1, except that: in step S1, the first temperature rise rate or the second temperature rise rate is changed in the second sintering treatment in step (4).

Examples 23 to 26

Examples 23 to 26 are basically the same as example 1, except that: in step S1, the first cooling rate or the second cooling rate is changed during the second sintering treatment in step (4).

Comparative example 1

Comparative example 1 is substantially the same as example 1 except that: step S1 is as follows:

(1) The 6.295 lithium hydroxide monohydrate, 26.286g of manganese hydroxide and 0.641g of magnesium acetate were weighed separately, mixed, added with ethanol 10 times the total volume of the solid, wet-milled and mixed for 600 minutes by a super-energy ball mill, and then vacuum-dried at 120 ℃ and 100pa to obtain a mixture.

(3) The precursor is placed in an oxygen-enriched air atmosphere furnace with 66% of oxygen volume content for secondary sintering treatment, and the process is as follows: heating from room temperature to 450 ℃ at a first heating rate of 5 ℃/min, continuously heating to 700 ℃ at a second heating rate of 0.3 ℃/min, cooling the sintering temperature to 450 ℃ at a first cooling rate of 0.3 ℃/min, and cooling to room temperature at a second cooling rate of 5 ℃/min to obtain the lithium manganate material.

Wherein, the X-ray diffraction pattern of the lithium manganate material prepared in comparative example 1 is shown in (B) of FIG. 6, and also shows spinel phase characteristics; the differential scanning calorimetric spectrum (DSC spectrum) of the lithium manganate material prepared in comparative example 1 is specifically shown in a curve (b) in fig. 7, and the capacity retention rate curve of the lithium ion battery prepared in comparative example 1 for cyclic charge and discharge at 2.8V to 4.3V is shown in fig. 9.

Comparative example 2

Comparative example 2 is substantially the same as example 1 except that: step S1 is as follows:

(1) 5.036g of lithium hydroxide monohydrate, 26.286g of manganese hydroxide and 0.641g of magnesium acetate are weighed respectively, mixed, ethanol with the total volume of 10 times of the solid is added, wet-milled and mixed for 600 minutes by a super-energy ball mill, and then vacuum-dried at 120 ℃ and 100pa to obtain a mixture.

(2) Then adding 1.259g of lithium hydroxide monohydrate into the mixture, wet-grinding and uniformly mixing by using a super-energy ball mill, and placing the mixture into an oxygen-enriched air atmosphere furnace with 66% of oxygen volume content for sintering treatment after vacuum drying, wherein the process is as follows: and heating from room temperature to 800 ℃ at a heating rate of 5 ℃/min, and performing heat preservation and sintering for 10 hours to obtain the lithium manganate material.

Comparative example 3

Comparative example 3 is substantially the same as example 1 except that: step S1 is as follows:

(2) The mixture was subjected to a first sintering treatment in an atmosphere furnace as follows: heating from room temperature to 450 ℃ at a first heating rate of 5 ℃/min, continuously heating to 700 ℃ at a second heating rate of 0.3 ℃/min, cooling the sintering temperature to 450 ℃ at a first cooling rate of 0.3 ℃/min, cooling to room temperature at a second cooling rate of 5 ℃/min, crushing to obtain a precursor, and controlling the oxygen volume content in the sintering atmosphere to be 66% in the sintering process.

(3) Adding 1.259g of lithium hydroxide monohydrate into the precursor, wet-milling and uniformly mixing by using a super-energy ball mill, vacuum-drying, and then placing into an oxygen-enriched air atmosphere furnace with 66% of oxygen volume content for secondary sintering treatment: heating to 600 ℃, and preserving heat and sintering for 10 hours to obtain the lithium manganate material.

The relevant parameters and performance test results of each example and comparative example are shown in Table 1. Wherein the molar ratio of the lithium element in the lithium hydroxide monohydrate added in the step (1) to the lithium element in the lithium hydroxide monohydrate added in the step (3) is recorded as H; in the step (3), the first heating rate, the second heating rate, the first cooling rate and the second cooling rate are respectively denoted as Y1, Y2, Y3 and Y1, the cut-off temperature when the temperature is raised at the first heating rate is denoted as X1, and the cut-off temperature when the temperature is raised at the second heating rate is denoted as X2.

TABLE 1

From the data analysis in table 1, it can be seen that: in the application, the following components are added: the lithium manganate material with the integral area of the endothermic peak in the differential scanning calorimeter spectrogram in a specific range or the lithium manganate material prepared by the preparation method of the lithium manganate material can improve the cycle performance of the secondary battery.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. The scope of the application is therefore intended to be covered by the appended claims, and the description and drawings may be interpreted in accordance with the contents of the claims.

Claims

1. The lithium manganate material is characterized in that in a differential scanning calorimeter spectrogram of the lithium manganate material, the integral area T of an endothermic peak meets the following conditions: t is more than 0 and less than or equal to 50J/g;

Heating to 20 ℃ at a rate of 5 ℃/min at-20 ℃ under the atmosphere of protective gas;

the components of the lithium manganate material meet the following conditions: li _(1+a)Mn_(2-x)M_xO_(4-δ);

2. The lithium manganate material of claim 1, wherein 5J/g.ltoreq.t.ltoreq.50J/g.

3. The lithium manganate material of claim 1, wherein 5J/g.ltoreq.t.ltoreq.30J/g.

4. The lithium manganate material of claim 1, wherein 5J/g.ltoreq.t.ltoreq.10J/g.

5. The lithium manganate material of any one of claims 1-4, wherein M comprises one or more of Mg, al, zr.

6. The lithium manganate material of any one of claims 1-4, wherein M is Mg.

7. The lithium manganate material of any one of claims 1-4, wherein 0.ltoreq.a.ltoreq.0.2, 0.01.ltoreq.x.ltoreq. 0.05,0.001 < δ.ltoreq.0.003.

8. The lithium manganate material of any one of claims 1-4, wherein the temperature region of the endothermic peak is: 1-20 ℃.

9. The lithium manganate material of any one of claims 1-4, wherein the lithium manganate material has a spinel phase.

10. The lithium manganate material according to any one of claims 1-4, wherein the lithium manganate material satisfies the following condition:

the button cell is manufactured by adopting a positive plate, a lithium plate, a diaphragm and electrolyte;

the positive electrode active layer in the positive electrode plate comprises the components of the lithium manganate material, carbon black SP, carbon nano tubes and polyvinylidene fluoride in a mass ratio of 94:1.5:0.5:3;

The electrolyte comprises the components of LiPF ₆ and a solvent, wherein the concentration of LiPF ₆ is 1mol/L; the solvent is a mixed solution of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate with the volume ratio of 1:1:1,

The separator is a polyolefin separator,

Performing charge and discharge test on the button cell by adopting 0.1C to obtain a charge and discharge curve, wherein 1C=0.1A.g ^-1;

In the charge-discharge curve, the total discharge gram capacity in the potential interval of 3.0V-3.4V is DC1, and the total discharge gram capacity in the potential interval of 2.8V-4.3V is DC2, and 0.001< DC1/DC2<0.02.

11. The lithium manganate material of claim 10, wherein 0.002< dc1/DC2<0.02.

12. A positive electrode sheet, wherein the positive electrode sheet comprises a current collector and a positive electrode active layer arranged on the surface of the current collector, and the composition of the positive electrode active layer comprises the lithium manganate material as set forth in any one of claims 1 to 11.

13. A secondary battery comprising the lithium manganate material according to any one of claims 1 to 11 or the positive electrode sheet according to claim 12.

14. An electric device, characterized in that the electric device comprises the secondary battery according to claim 13.