Electrochemical device and electronic device

Abstract

The present application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector; the positive electrode material layer comprises a positive electrode material; the positive electrode material comprises lithium cobalt oxide of a P63mc structure; in an XRD pattern of the positive electrode material layer, the characteristic peak of a (002) crystal plane of the lithium cobalt oxide of a P63mc structure is between 17° and 19°; the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector; the negative electrode material layer comprises a negative electrode material; and the negative electrode material comprises hard carbon and graphite. By means of the described configuration, the electrochemical device has high energy density and also has good rate performance and high-temperature cycle performance.

Description

An electrochemical device and an electronic device TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and in particular to an electrochemical device and an electronic device. BACKGROUND

[0002] An electrochemical device, such as a lithium ion battery, is widely used in wearable devices, smart phones, unmanned aerial vehicles, notebook computers, electric vehicles and other fields due to its high working voltage, high energy density, environmental friendliness, cycle stability and other advantages.

[0003] In recent years, with the rapid development of electric vehicles and mobile electronic devices, the market has put forward higher requirements for the energy density, service life and charging speed of lithium ion batteries. Generally, in order to make the lithium ion battery have higher energy density, the charging voltage of the lithium ion battery can be increased, but when the charging voltage of the lithium ion battery is increased, the structural stability of the positive electrode material will be reduced, thereby affecting the high-temperature cycle performance and rate performance of the lithium ion battery.

[0004] SUMMARY

[0005] The purpose of the present application is to provide an electrochemical device and an electronic device to improve the energy density, high-temperature cycle performance and rate performance of the electrochemical device. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides an electrochemical device, which comprises a positive electrode sheet, a negative electrode sheet and a separator film, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode material, the positive electrode material comprises a lithium cobalt oxide with a P63mc structure, and in the XRD pattern of the positive electrode material layer, the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with the P63mc structure is located between 17° and 19°; the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode material, and the negative electrode material comprises hard carbon and graphite. The positive electrode material comprises a lithium cobalt oxide with a P63mc structure, and the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with the P63mc structure is controlled to be located between 17° and 19°. The Li-O octahedron of the lithium cobalt oxide with the P63mc structure is connected with the Co-O octahedron on both sides in a common edge and common plane manner, the Co is difficult to migrate to the Li site, the structure can be maintained stable at a high charging voltage, the electrochemical device can have a high energy density while maintaining good high-temperature cycle performance; in addition, the interlayer spacing of the Co-O octahedron layer of the lithium cobalt oxide with the P63mc structure is large, which is beneficial to the embedding and de-embedding of Li + + ​The insertion and extraction of lithium ions can be achieved, and a SEI film of appropriate thickness can be formed during the first cycle of charging, reducing the consumption of active lithium. By matching the positive and negative electrode materials, the high-temperature cycling performance of the electrochemical device can be further improved.

[0007] In some embodiments of the present application, the characteristic peak of the (002) crystal plane of the P63mc lithium cobalt oxide is located between 18.3° and 18.7°. By regulating the position of the characteristic peak of the (002) crystal plane of the P63mc lithium cobalt oxide within the scope of the present application, the structural stability of the positive electrode material can be improved, thereby enabling the electrochemical device to have a higher energy density while further improving the high-temperature cycling performance of the electrochemical device.

[0008] In some embodiments of the present application, the mass percentage of hard carbon is w%, based on the mass of the negative electrode material, 1≤w≤10. By adjusting the mass percentage of hard carbon w%, within the scope of the present application, hard carbon can meet the requirements of Na + It can also form a SEI film of appropriate thickness during the first cycle of charging, reduce the consumption of active lithium, and enable the electrochemical device to have a higher energy density while further improving the high-temperature cycle performance of the electrochemical device.

[0009] In some embodiments of the present application, the lithium cobalt oxide of P63mc structure includes Li x Na y Co 1-a-b A a B b O2, wherein A includes at least one of Mn, Fe, or Ni, B includes at least one of Al, Mg, Ti, La, Y, Zr, Zn, Cu, Cr, Ca, Ce, or Lu, 0.779≤x≤0.95, 0<y≤0.001, 0<a≤0.2, and 0≤b≤0.02. The above arrangement can further improve the structural stability of the positive electrode material, enable the electrochemical device to have higher energy density and rate performance, and further improve the high-temperature cycling performance of the electrochemical device.

[0010] In some embodiments of the present application, the positive electrode material further comprises a lithium cobalt oxide with an R-3m structure, a (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure is located between 18° and 20° in an XRD spectrum of the positive electrode material layer; an intensity of the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure is I1, an intensity of a (002) crystal face characteristic peak of a lithium cobalt oxide with a P63mc structure is I2, and 0≤I1 / I2≤20. The positive electrode material comprises the lithium cobalt oxide with the R-3m structure, and the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure and the value of I1 / I2 are regulated within the range of the present application, so that the energy density of the electrochemical device can be improved while the high-temperature cycle performance of the electrochemical device is taken into account.

[0011] In some embodiments of the present application, the lithium cobalt oxide with the R-3m structure comprises LiCo 1-m-n Al m C n O2, wherein C comprises at least one of Mg, Ti, La, Y, Zr or Lu, 0

[0012] In some embodiments of the present application, the positive electrode material layer further comprises a positive electrode binder and a positive electrode conductive agent, a mass percentage content of the positive electrode binder is m1% and a mass percentage content of the positive electrode conductive agent is m2% based on the mass of the positive electrode material layer, and 0

[0013] In some embodiments of the present application, the negative electrode material layer further comprises a negative electrode binder, a thickening agent and a negative electrode conductive agent, a mass percentage content of the negative electrode binder is m3%, a mass percentage content of the thickening agent is m4%, and a mass percentage content of the negative electrode conductive agent is m5% based on the mass of the negative electrode material layer, and 0

[0014] In some embodiments of the present application, the capacity of the positive electrode tab in the potential range of 3.0V to 4.6V with lithium metal as the counter electrode is d, the capacity of the negative electrode tab in the potential range of 0.005V to 0.8V with lithium metal as the counter electrode is c, and 1.00 < c / d ≤ 1.05. By adjusting the value of c / d within the range of the present application, the negative electrode capacity is slightly greater than the positive electrode capacity, which can make the electrochemical device have higher energy density and good high-temperature cycle performance, while also having good safety performance.

[0015] In some embodiments of the present application, the adhesion between the separator film and the positive electrode tab is F N / m, and 1 ≤ F ≤ 50. The adhesion between the separator film and the positive electrode tab within the range of the present application indicates that the separator film has high adhesion with the positive electrode tab, which is beneficial to improve the safety performance of the electrochemical device.

[0016] In some embodiments of the present application, the upper limit charging voltage of the electrochemical device is 4.5V to 4.75V. This indicates that the upper limit charging voltage of the electrochemical device of the present application is high, and the application scenarios are wide.

[0017] The second aspect of the present application provides an electronic device comprising the electrochemical device in any of the above embodiments. Thus, the electrochemical device provided by the present application has good use performance.

[0018] The beneficial effects of the present application are:

[0019] The present application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode tab, a negative electrode tab, and a separator film. The positive electrode tab comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector. The positive electrode material layer comprises a positive electrode material, and the positive electrode material comprises a lithium cobalt oxide with a P63mc structure. In the XRD pattern of the positive electrode material layer, the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with the P63mc structure is located between 17° and 19°. The negative electrode tab comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The negative electrode material layer comprises a negative electrode material, and the negative electrode material comprises hard carbon and graphite. Through the above arrangement, the electrochemical device has higher energy density, while also having good rate performance and high-temperature cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application.

[0021] FIG. 1 is a high-temperature cycle performance test result graph of the embodiments and comparative examples of the present application;

[0022] Figure 2 is a graph of the rate performance test results of the examples and the comparative examples of the present application;

[0023] Figure 3 is an X-ray diffraction pattern of the positive electrode of Example 1-1 of the present application;

[0024] Figure 4 is an X-ray diffraction pattern of the positive electrode of Example 2-2 of the present application;

[0025] Figure 5 is an X-ray diffraction pattern of the positive electrode of Comparative Example 2-1 of the present application;

[0026] Figure 6 is a scanning electron microscope image of the negative electrode of Example 1-1 of the present application. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions, and superiorities of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. All other examples obtained by those skilled in the art based on the present application shall fall within the scope of protection of the present application.

[0028] It should be noted that in the specific embodiments of the present application, the present application is explained by taking lithium-ion batteries as examples of electrochemical devices, but the electrochemical devices of the present application are not limited to lithium-ion batteries.

[0029] The first aspect of the present application provides an electrochemical device, which comprises a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode material, the positive electrode material comprises a lithium cobalt oxide with a P63mc structure, and the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with the P63mc structure is located between 17° and 19° in the XRD pattern of the positive electrode material layer. For example, the position of the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with the P63mc structure can be 17°, 17.3°, 17.5°, 17.8°, 18°, 18.3°, 18.5°, 18.8°, 19°, or a range composed of any two of the above values. Figure 3 is an XRD pattern of the lithium cobalt oxide with the P63mc structure in one embodiment of the present application, and the position of the characteristic peak of the (002) crystal plane thereof is 18.5°. The negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode material, the negative electrode material comprises hard carbon and graphite. The graphite comprises at least one of natural graphite or artificial graphite.

[0030] The inventors have found that the Li-O octahedron of lithium cobalt oxide with P63mc structure is connected with the Co-O octahedron on both sides in a co-edge and co-plane manner, and Co is extremely difficult to migrate to the Li site. When applied to the positive electrode material of electrochemical devices, the lithium cobalt oxide with P63mc structure can still maintain good structural stability under high charging voltage conditions, which can make the electrochemical device have a high energy density while maintaining good high-temperature cycle performance. In addition, the interlayer spacing of the Co-O octahedron layer of lithium cobalt oxide with P63mc structure is large, which is conducive to the Li + The insertion and extraction of Na can improve the rate performance of electrochemical devices. However, the lithium cobalt oxide layer of the P63mc structure contains a small amount of Na + , doped in the Li layer, during the cycling of the electrochemical device, a small amount of Na + As the charge and discharge proceed, it will be released from the Li site and + Migrate to the negative electrode together. If graphite is used as the negative electrode material, due to Na + Radius Much larger than Li + Na migrated to the negative electrode + It cannot be embedded in the graphite layers, but is deposited on the surface of the negative electrode, blocking the Li + Migration channel affects the high temperature cycle performance of electrochemical devices. The negative electrode materials of this application include hard carbon and graphite. Hard carbon can meet the Na + This allows for the insertion and removal of lithium ions, and allows for the formation of an appropriately thick SEI film during the first cycle of charging, reducing active lithium consumption. By matching the positive and negative electrode materials, the high-temperature cycling performance of electrochemical devices can be further improved. In this application, "high charging voltage" refers to a maximum charging voltage greater than or equal to 4.5V.

[0031] In some embodiments of the present application, the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with a P63mc structure is located between 18.3° and 18.7°. For example, the position of the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with a P63mc structure can be 18.3°, 18.4°, 18.5°, 18.6°, 18.7°, or a range consisting of any two of these values. By regulating the position of the characteristic peak of the (002) crystal plane of the lithium cobalt oxide with a P63mc structure within the scope of the present application, the structural stability of the positive electrode material can be improved, the electrochemical device can have a higher energy density, and the high-temperature cycling performance of the electrochemical device can be further improved.

[0032] In some embodiments of the present application, the mass percentage of hard carbon is w%, based on the mass of the negative electrode material, 1≤w≤10. For example, the mass percentage of hard carbon can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of these values. The negative electrode material includes hard carbon, and the hard carbon can meet the Na + The hard carbon content (w%) can be adjusted to maintain a high energy density and improve the high-temperature cycling performance of the electrochemical device.

[0033] In some embodiments of the present application, the lithium cobalt oxide of P63mc structure includes Li x Na y Co 1-a-b A a B b O2, wherein A includes at least one of Mn, Fe or Ni, B includes at least one of Al, Mg, Ti, La, Y, Zr, Zn, Cu, Cr, Ca, Ce or Lu, 0.779≤x≤0.95, 0<y≤0.001, 0<a≤0.2, 0≤b≤0.02. For example, the value of x can be 0.779, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, or a range consisting of any two of these values; the value of y can be 0.00001, 0.0001, 0.0003, 0.0005, 0.0008, 0.001, or a range consisting of any two of these values; the value of a can be 0.001, 0.01, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, 0.2, or a range consisting of any two of these values; the value of b can be 0, 0.001, 0.01, 0.013, 0.015, 0.018, 0.02, or a range consisting of any two of these values. Through the above settings, the structural stability of the positive electrode material can be further improved, the electrochemical device can have a higher energy density and rate performance, and the high temperature cycle performance of the electrochemical device can be further improved.

[0034] In some embodiments of the present application, lithium cobalt oxides of P63mc structure may include but are not limited to Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2、Li 0.9495 Na 0.0005 Co 0.95 Fe0.04 Al 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Ni 0.02 Mn 0.02 Al 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.03 Mn 0.01 Cu 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.03 Ni 0.01 Ti 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2, Li 0.937 Na 0.0005 Co 0.9375 Fe 0.03 Ni 0.01 Mn 0.01 Al 0.0125 O2, Li 0.9245 Na 0.0005 Co 0.925 Fe 0.04 Ni 0.01 Mn 0.01 Al 0.015 O2, Li 0.8 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2, Li 0.7895 Na 0.0005 Co 0.79 Fe 0.1 Ni 0.05 Mn 0.05 Al 0.01 O2, Li 0.9395 Na 0.0005 Co 0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02 O2, Li 0.949 Na 0.001 Co 0.95Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2, Li 0.7795 Na 0.0005 Co 0.78 Fe 0.1 Ni 0.05 Mn 0.05 Al 0.02 O2, Li 0.9495 Na 0.0005 Co 0.96 Fe 0.03 Al 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 La 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Lu 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Y 0.01 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Mg 0.005 Ti 0.005 O2, Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Zn 0.005 Ce 0.005 O2, etc.

[0035] In some embodiments of the present application, the positive electrode material further comprises a lithium cobalt oxide with a R-3m structure, and in the XRD pattern of the positive electrode material layer, the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure is located between 18° and 20°; the intensity of the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure is I1, the intensity of the (002) crystal face characteristic peak of the lithium cobalt oxide with the P63mc structure is I2, and 0≤I1 / I2≤20. For example, the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure can be located at 18°, 18.1°, 18.2°, 18.3°, 18.4°, 18.5°, 18.6°, 18.7°, 18.8°, 18.9°, 19°, 19.1°, 19.2°, 19.3°, 19.4°, 19.5°, 19.6°, 19.7°, 19.8°, 19.9°, 20°, or a range defined by any two of the above values. The value of I1 / I2 can be 0, 1, 3, 5, 8, 10, 13, 15, 18, 20, or a range defined by any two of the above values. The positive electrode material comprises the lithium cobalt oxide with the R-3m structure, and the (003) crystal face characteristic peak of the lithium cobalt oxide with the R-3m structure and the value of I1 / I2 are regulated within the range of the present application, which can significantly improve the first discharge specific capacity of the electrochemical device, i.e., the energy density of the electrochemical device can be improved while the high-temperature cycle performance of the electrochemical device is taken into account.

[0036] In some embodiments of the present application, the lithium cobalt oxide with the R-3m structure comprises LiCo 1-m-n Al m C n O2, wherein C comprises at least one of Mg, Ti, La, Y, Zr or Lu, 0

[0037] In some embodiments of the present application, the lithium cobalt oxide with the R-3m structure can comprise, but is not limited to, LiCo 0.97 Al 0.03 O2, LiCo 0.965 Al 0.03 Mg 0.005 O2, LiCo 0.96 Al 0.03 Mg 0.005 Ti 0.005 O2, LiCo0.9 Al 0.1 O2, LiCo 0.92 Al 0.03 Mg 0.01 Ti 0.01 La 0.01 Y 0.01 Zr 0.01 O2, LiCo 0.999 Al 0.001 O2, LiCo 0.99 Al 0.01 O2, LiCo 0.95 Co 0.05 O2, LiCo 0.969 Al 0.03 Y 0.001 O2, LiCo 0.93 Al 0.03 Mg 0.01 Ti 0.01 La 0.01 Y 0.01 O2, LiCo 0.9 Al 0.08 Mg 0.005 Ti 0.005 La 0.005 Y 0.005 O2, etc.

[0038] In some embodiments of the present application, the positive electrode material layer further comprises a positive electrode binder and a positive electrode conductive agent, the mass percentage of the positive electrode binder is m1%, and the mass percentage of the positive electrode conductive agent is m2%, based on the mass of the positive electrode material layer, and 0 < m1≤ 10, 0 < m2≤ 10 are satisfied. For example, the value of the mass percentage m1% of the positive electrode binder can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of them; the value of the mass percentage m2% of the positive electrode conductive agent can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of them. By adjusting the mass percentages of the positive electrode binder and the positive electrode conductive agent within the scope of the present application, the positive electrode sheet can have appropriate conductivity and good stability.

[0039] In some embodiments of the present application, the negative electrode material layer further comprises a negative electrode binder, a thickening agent and a negative electrode conductive agent, the mass percentage of the negative electrode binder is m3%, the mass percentage of the thickening agent is m4%, and the mass percentage of the conductive agent is m5%, based on the mass of the negative electrode material layer, and 0 < m3≤ 5, 0 < m4≤ 5, and 0 < m5≤ 5 are satisfied. For example, the value of the mass percentage m3% of the negative electrode binder can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range formed by any two of the above values; the value of the mass percentage m4% of the thickening agent can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range formed by any two of the above values; and the value of the mass percentage m5% of the negative electrode conductive agent can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range formed by any two of the above values. By adjusting the mass percentages of the negative electrode binder, the thickening agent and the negative electrode conductive agent in the negative electrode material layer within the range of the present application, the negative electrode sheet can have appropriate conductivity and good stability.

[0040] In some embodiments of the present application, the capacity of the positive electrode sheet in the potential range of 3.0V to 4.6V with lithium metal as the counter electrode is d, and the capacity of the negative electrode sheet in the potential range of 0.005V to 0.8V with lithium metal as the counter electrode is c, and 1.00 < c / d ≤ 1.05. For example, the value of c / d can be 1.01, 1.02, 1.03, 1.04, 1.05, or a range formed by any two of the above values. By adjusting the value of c / d within the range of the present application, the negative electrode capacity is slightly greater than the positive electrode capacity, which can make the electrochemical device have higher energy density and good high-temperature cycle performance, while also having good safety performance.

[0041] In some embodiments of the present application, the adhesion between the separator film and the positive electrode sheet is F N / m, and 1 ≤ F ≤ 50. For example, the value of the adhesion F between the separator film and the positive electrode sheet can be 1 N / m, 10 N / m, 20 N / m, 30 N / m, 40 N / m, 50 N / m, or a range formed by any two of the above values. The adhesion between the separator film and the positive electrode sheet within the range of the present application indicates that the separator film and the positive electrode sheet have high adhesion, which is beneficial to improving the energy density and safety performance of the electrochemical device.

[0042] In some embodiments of the present application, the upper limit charging voltage of the electrochemical device is 4.5V to 4.75V. For example, the upper limit charging voltage can be 4.5V, 4.55V, 4.6V, 4.65V, 4.7V, 4.75V, or a range formed by any two of the above values. The upper limit charging voltage of the electrochemical device is 4.5V to 4.75V, which indicates that the upper limit charging voltage of the electrochemical device of the present application is high, and the application scenarios are wide.

[0043] The preparation method of the lithium cobalt oxide of P63mc structure is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the lithium cobalt oxide of P63mc structure Li x Na y Co 1-a-b A a B b The preparation method of O2may include but is not limited to the following steps: taking a cobalt source material, an A source material, and a B source material as raw materials, according to the stoichiometric ratio of the lithium cobalt oxide of P63mc structure Li x Na y Co 1-a-b A a B b O2, dissolving the above raw materials in water in a reaction kettle, stirring under a nitrogen atmosphere, and adding an alkali source solution to the reaction kettle during stirring to control the pH value of the solution in the reaction kettle to 10 to 12. Continue stirring for 10 to 14 hours, filter to obtain a precipitate, wash with deionized water for 3 times, vacuum dry at 60 to 100°C for 20 to 26 hours to obtain a precursor powder. Ball mill the precursor with a sodium source material, mix uniformly, then place the ball-milled mixture in a muffle furnace, heat treat at 700 to 900°C under an air atmosphere for 20 to 24 hours, take out the sample, crush, grind, sieve, and according to the stoichiometric ratio of the lithium cobalt oxide of P63mc structure Li x Na y Co 1-a-b A a B b O2, combined with the addition amount of the cobalt source material, the A source material, and the B source material, add a corresponding amount of lithium bromide-containing n-hexanol solution, and perform a solvothermal reaction at 90 to 110°C for 20 to 26 hours, then perform suction filtration to obtain a precipitate, wash with methanol, vacuum dry at 80 to 100°C for 6 to 10 hours to obtain the lithium cobalt oxide of P63mc structure Li x Na y Co 1-a-b A a B b O2.

[0044] The cobalt source material, the A source material, the B source material, the alkali source, and the sodium source material described above are not particularly limited in the present application, and can be selected as appropriate, as long as the object of the present application is achieved. For example, the cobalt source material can include, but is not limited to, at least one of cobalt sulfate, cobalt carbonate, cobalt chloride, or cobalt nitrate; the A source material can include, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, iron chloride, iron sulfate, iron nitrate, nickel chloride, nickel nitrate, or nickel sulfate; the B source material can include, but is not limited to, at least one of aluminum nitrate, magnesium sulfate, copper sulfate, or titanium dioxide; the alkali source can include, but is not limited to, at least one of sodium hydroxide or aqueous ammonia; and the sodium source can include, but is not limited to, at least one of sodium carbonate, sodium nitrate, or sodium chloride.

[0045] The method for producing the lithium cobalt oxide of R-3m structure is not particularly limited in the present application, and can be selected as appropriate, as long as the object of the present application is achieved. For example, the lithium cobalt oxide of R-3m structure LiCo 1-m-n Al m C n The method for producing the lithium cobalt oxide of R-3m structure LiCo 1-m-n Al m C n O2.

[0046] The aluminum source material and the C source material described above are not particularly limited in the present application, and can be selected as appropriate, as long as the object of the present application is achieved. For example, the aluminum source material can include, but is not limited to, aluminum trioxide; and the C source material can include, but is not limited to, at least one of magnesium sulfate, titanium dioxide, or lanthanum trioxide.

[0047] The positive electrode tab of the present application includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector of the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the positive electrode current collector can include an aluminum foil, an aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector), etc. In the present application, the thickness of the positive electrode current collector and the positive electrode material layer is not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm. The thickness of the single-sided positive electrode material layer is 30 μm to 120 μm. In the present application, the positive electrode material layer can be disposed on one surface in the thickness direction of the positive electrode current collector, or can be disposed on both surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" herein can be the entire area of the positive electrode current collector, or can be a partial area of the positive electrode current collector, and the present application is not particularly limited as long as the purpose of the present application can be achieved.

[0048] The present application does not particularly limit the types of the positive electrode conductive agent and the binder as long as the purpose of the present application can be achieved. For example, the conductive agent can include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, a metal material, or a conductive polymer. The above-mentioned carbon nanotubes can include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers can include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanocarbon fibers. The above-mentioned metal material can include, but is not limited to, metal powder and / or metal fibers, and specifically, the metal can include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above-mentioned conductive polymer can include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder can include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene butadiene rubber, or polyvinylidene fluoride.

[0049] The negative electrode tab of the present application includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. In the present application, the negative electrode material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or on both surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the negative electrode current collector, or a partial area of the negative electrode current collector, which is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The negative electrode current collector is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the negative electrode current collector can include, but is not limited to, a copper foil, a copper alloy foil, a nickel foil, a titanium foil, a foamed nickel, a foamed copper, or a composite current collector, etc. In the present application, the thickness of the negative electrode current collector and the negative electrode material layer is not particularly limited, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm, and the thickness of the single-sided negative electrode material layer is 30 μm to 130 μm. The type of the negative electrode binder, thickening agent, and negative electrode conductive agent in the negative electrode material layer is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the conductive agent and the binder can be at least one of the above-mentioned conductive agents and the above-mentioned binders. The thickening agent can include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0050] The separator film is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the material of the separator film can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (such as polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the separator film can include at least one of a woven film, a non-woven film (non-woven fabric), a microporous film, a composite film, a calendered film, or a spunlaid film. The separator film of the present application can have a porous structure, a porous layer is disposed on at least one surface of the separator film, the porous layer includes inorganic particles and a binder, the inorganic particles can include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder can include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, poly(methyl acrylate), poly(ethyl acrylate), poly(butyl acrylate), polyacrylic acid, polyacrylic acid salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, poly(methyl methacrylate), polytetrafluoroethylene, or polyhexafluoropropylene. The size of the pore diameter of the porous structure is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example, the size of the pore diameter can be 0.01 μm to 1 μm. In the present application, the thickness of the separator film is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness can be 3 μm to 30 μm.

[0051] The electrochemical device of the present application further includes an electrolyte including a lithium salt and a nonaqueous solvent.

[0052] The lithium salt of the present application is not particularly limited as long as the object of the present application can be achieved. For example, the lithium salt can include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. The content of the lithium salt in the electrolyte is not particularly limited as long as the object of the present application can be achieved.

[0053] The non-aqueous solvent is not particularly limited in the present application, as long as the object of the present application can be achieved, for example, the non-aqueous solvent can include, but is not limited to, at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, or other organic solvents. The above-mentioned carbonate compound can include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorinated carbonate compound. The above-mentioned chain carbonate compound can include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The above-mentioned cyclic carbonate can include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound can include, but is not limited to, at least one of fluorinated ethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, or trifluoromethyl ethylene carbonate. The above-mentioned carboxylic acid ester compound can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, or caprolactone. The above-mentioned ether compound can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents can include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The content of the non-aqueous solvent in the electrolyte is not particularly limited in the present application, as long as the object of the present application can be achieved.

[0054] The electrochemical device of the present application further includes a case for accommodating the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte, and other components known in the art of electrochemical devices, which are not limited in the present application. The case is not particularly limited in the present application, and can be a case known in the art, as long as the object of the present application can be achieved. For example, the case can be a hard case or a flexible case. The material of the hard case can be a metal, and the type of the metal is not limited in the present application, and a metal hard case known in the art can be used, as long as the object of the present application can be achieved. The flexible case can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, or the like.

[0055] The preparation process of the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited, for example, can include but is not limited to the following steps: stacking the positive electrode sheet, the separator film and the negative electrode sheet in order, and winding, folding, etc. as needed to obtain a wound structure of the electrode assembly, placing the electrode assembly into the case, injecting the electrolyte into the case and sealing to obtain the electrochemical device. Alternatively, the positive electrode sheet, the separator film and the negative electrode sheet are stacked in order, and then the four corners of the entire stack structure are fixed with adhesive tape to obtain an electrode assembly of the stack structure, the electrode assembly is placed into the case, the electrolyte is injected into the case and sealed to obtain the electrochemical device. In addition, a current protection element, a guide plate, etc. can also be placed in the case as needed, thereby preventing the pressure inside the electrochemical device from rising, overcharging and discharging.

[0056] The second aspect of the present application provides an electronic device comprising the electrochemical device of any of the above embodiments. Thus, the electrochemical device provided by the present application has good use performance.

[0057] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the art. In some embodiments of the present application, the electronic device can include but is not limited to a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a household large storage battery and a lithium ion capacitor, etc.

[0058] Examples

[0059] Hereinafter, examples and comparative examples are given to more specifically explain the embodiments of the present application. Various tests and evaluations were carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0060] Test methods and apparatus:

[0061] X-ray diffraction pattern test

[0062] After the lithium ion battery is completely discharged at 0.2C constant current to 3.0V, the positive electrode sheet is obtained by disassembly, soaked in ethylene carbonate (EC) for 30min, then washed with ethylene carbonate for 3 times, and naturally dried under argon atmosphere to obtain the treated positive electrode sheet. The treated positive electrode sheet with a size of 3cmx3cm is taken for XRD (X-ray diffraction) test. The positive electrode sheet is placed on the sample table of the XRD tester (model: Bruker, D8), Cu target Kα ray is used, the scanning rate is 10° / min, the scanning angle range is 10° to 71°, and the XRD diffraction pattern is obtained. The corresponding diffraction peak is read, and the position of the diffraction peak is recorded.

[0063] Mass percentage content test of hard carbon

[0064] After the lithium ion battery is completely discharged at 0.2C constant current to 3.0V, the negative electrode sheet is obtained by disassembly, soaked in ethylene carbonate (EC) for 30min, then washed with ethylene carbonate for 3 times, and naturally dried under argon atmosphere to obtain the treated negative electrode sheet. The treated negative electrode sheet is cut by ion beam to obtain a cross section along the thickness direction thereof. The cross section is observed by scanning electron microscope (SEM), the magnification is limited to 1000X, and the shooting area is 125μm x 85μm. In the SEM backscattering mode, the morphology of the hard carbon particles is angular block particles, and the morphology of the graphite particles is lamellar particles. ImageJ image analysis software is used to calculate the area of the hard carbon particles and the area of the graphite particles in at least 50 pictures respectively, the area of the hard carbon particles is divided by the area of the hard carbon and graphite particles, and the arithmetic mean is taken as the mass percentage content of the hard carbon.

[0065] Adhesion test between separator and positive electrode sheet

[0066] After the lithium ion battery is completely discharged at 0.2C constant current to 3.0V, the positive electrode sheet with a separator adhered to one side is obtained by disassembly. The positive electrode sheet is adhered to a steel plate with double-sided adhesive tape on the side without the separator, and a tensile testing machine is used for 180° peeling test. The steel plate is fixed in the lower clamp, the upper clamp clamps the separator, and the separator is stretched by 50mm at a constant rate of 50mm / min to tear off the separator from the positive electrode sheet to 180° to obtain stress and displacement data. The adhesion between the separator and the positive electrode sheet = stress / displacement.

[0067] Calculation of the mass of positive electrode active material

[0068] For the positive electrode sheet and aluminum foil taken out from the lithium ion battery, a circular sheet with a diameter of 44mm is taken respectively, and the weight is obtained.

[0069] The mass of the positive electrode active material = (the weight of the positive electrode sheet circular sheet - the weight of the aluminum foil) / (π x 22 x 22) x the length of the positive electrode sheet x the width of the positive electrode sheet x (1 - the mass fraction of conductive carbon black - the mass fraction of binder).

[0070] Calculation of the mass of the negative active material

[0071] For the negative electrode sheet and copper foil taken out from the lithium ion battery, a disc with a diameter of 44 mm was taken, and the weight was measured;

[0072] The mass of the negative active material = (the weight of the negative electrode sheet disc - the weight of the copper foil) / (π x 22 x 22) x the length of the negative electrode sheet x the width of the negative electrode sheet x (1 - the mass fraction of the conductive carbon - the mass fraction of the binder - the mass fraction of the dispersing agent).

[0073] Test of the positive electrode sheet capacity d and the negative electrode sheet capacity c

[0074] A disc with a diameter of 14 mm was taken from the positive electrode sheet and the negative electrode sheet respectively, and a lithium sheet was used as the counter electrode to make a coin cell to test the initial discharge specific capacity of the positive electrode and the negative electrode material respectively;

[0075] The positive electrode sheet capacity d = the specific capacity of the positive electrode material x the mass of the positive active material;

[0076] The negative electrode sheet capacity c = the specific capacity of the negative electrode material x the mass of the negative active material;

[0077] The value of c / d was calculated again.

[0078] Test of the initial specific capacity

[0079] The lithium ion battery was placed in an environment at 25°C, and was charged at a constant current of 0.2C to 4.55V, then was charged at a constant voltage of 4.55V until the current was less than 0.05C, and then was discharged at a constant current of 0.2C to 3.0V, and the initial discharge capacity was recorded. The model of the lithium ion battery test equipment was Land CT2001A.

[0080] When the lithium ion batteries of Examples 1-13 were tested for the initial specific capacity, the upper limit voltage 4.55V in the above step was adjusted to 4.75V, and the remaining examples and comparative examples were tested according to the upper limit voltage of 4.55V.

[0081] The initial specific capacity = the initial discharge capacity / the mass of the positive active material. The energy density of the lithium ion battery was evaluated by the initial specific capacity of the lithium ion battery, the greater the initial specific capacity, the higher the energy density, and the smaller the initial specific capacity, the lower the energy density.

[0082] Test of the rate performance

[0083] The lithium ion battery was placed in a 25℃ environment, first, discharged to 3.0V at a constant current of 0.2C, then charged to 4.55V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 0.2C, and the discharge capacity at this time was recorded as C1. Charged to 4.55V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 0.5C. Charged to 4.55V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 1.0C. Charged to 4.55V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 2.0C, and the discharge capacity at this time was recorded as C2. The model of the lithium ion battery test equipment was Land CT2001A.

[0084] The upper limit voltage 4.55V in the above steps was adjusted to 4.75V when the lithium ion batteries of Examples 1-13 were subjected to rate performance tests, and the rest of the examples and comparative examples were tested according to an upper limit voltage of 4.55V.

[0085] The capacity retention rate R = C2 / C1 x 100%, and the rate performance was represented by R, the larger the R value, the better the rate performance.

[0086] Test of high temperature cycle performance

[0087] The lithium ion battery was placed in a 45℃ constant temperature oven, first, discharged to 3.0V at a constant current of 0.2C.

[0088] Then charged to 4.25V at a constant current of 1.0C, then charged to a current less than 0.5C at a constant voltage of 4.25V, then charged to 4.55V at a constant current of 0.5C, then charged to a current less than 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 0.7C, and the discharge capacity C1 at this time was recorded as a first charge-discharge cycle.

[0089] After 49 cycles of the above process, a small current charge-discharge cycle was performed once, i.e. charged to 4.55V at a constant current of 0.2C, then charged to a current less than 0.05C at a constant voltage of 4.55V, then discharged to 3.0V at a constant current of 0.2C. After n cycles, the discharge capacity was recorded as C n .

[0090] The upper limit voltage 4.55V in the above steps was adjusted to 4.75V when the lithium ion batteries of Examples 1-13 were subjected to high temperature cycle performance tests, and the rest of the examples and comparative examples were tested according to an upper limit voltage of 4.55V.

[0091] 45℃ capacity retention rate = C n / C1 x 100%, record the cycle number n when the 45℃ capacity retention rate is 80%.

[0092] Example 1-1

[0093] Preparation of the positive active material

[0094] (1) In a reaction kettle, 274.99 g of CoSO4·7H2O, 5.73 g of FeSO4·7H2O, 2.71 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 3.86 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and during stirring, a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was obtained by filtration, washed with deionized water 3 times, and vacuum dried at 80℃ for 24 h to obtain a Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 (OH)3 precursor.

[0095] (2) 112.79 g of Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 (OH)3 precursor was uniformly mixed with 60.03 g of Na2CO3 by ball milling. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850℃ for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide solution in n-hexanol was added, and the solvothermal reaction was carried out at 100℃ for 24 h. After filtration, the precipitate was washed with methanol 3 times and vacuum dried at 90℃ for 8 h to obtain a P63mc-structured lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2 powder.

[0096] Preparation of the positive electrode sheet

[0097] The positive electrode active material prepared above, conductive agent conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:1.5:1.5, N-methyl pyrrolidone (NMP) was added as a solvent, and the mixture was stirred uniformly in a vacuum stirrer to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and was dried at 120°C to obtain a positive electrode sheet with a single-sided positive electrode material layer, and the coating weight of the positive electrode material layer was Y g / 1540.25 mm 2 , Y was 0.198 g / 1540.25 mm 2 . The above steps were repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. Then, after drying at 120°C, the positive electrode sheet was subjected to cold pressing, sheet cutting, slitting, and tab welding to obtain a positive electrode sheet with a size of 74 mm x 867 mm. The thickness of the single-sided positive electrode material layer was 42 μm. The mass percentage content m1% of the positive electrode binder was 1.5% and the mass percentage content m2% of the positive electrode conductive agent was 1.5% based on the mass of the positive electrode material layer.

[0098] <Preparation of negative electrode active material>

[0099] 190 g of natural graphite and 10 g of hard carbon material were mixed in a container, and the mixture was uniformly obtained as a negative electrode active material.

[0100] <Preparation of negative electrode sheet>

[0101] The negative electrode active material prepared above, binder styrene-butadiene rubber, thickening agent sodium carboxymethyl cellulose, and conductive agent conductive carbon black (Super P) were mixed in a mass ratio of 97:1.5:0.75:0.75, deionized water was added as a solvent, and the mixture was adjusted to a slurry with a solid content of 45 wt% to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 10 μm, and was dried at 120°C to obtain a negative electrode sheet with a single-sided negative electrode material layer, and the coating weight of the negative electrode material layer was 6.87 mg / cm 2 . Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer. After drying at 120°C, the negative electrode sheet was subjected to cold pressing, sheet cutting, slitting, and tab welding to obtain a negative electrode sheet with a size of 78 mm x 875 mm. The thickness of the single-sided negative electrode material layer was 40.4 μm. The mass percentage content m3% of the negative electrode binder was 1.5%, the mass percentage content m4% of the thickening agent was 0.75%, and the mass percentage content m5% of the negative electrode conductive agent was 0.75% based on the mass of the negative electrode material layer.

[0102] Preparation of the separator

[0103] First, α-Al2O3 particles were added to water as a solvent, mixed uniformly, and then a binder, polyvinylidene fluoride (PVDF), was added and stirred to prepare a slurry with a solid content of 60%, in which the mass ratio of α-Al2O3 to polyvinylidene fluoride was 95:5. The slurry was coated on one surface of a 5-μm-thick polyethylene (PE) porous substrate, and after drying at 90°C, a separator with a 2-μm-thick ceramic layer of aluminum oxide coated on one surface was obtained. Then, the slurry was coated on the other surface of the polyethylene (PE) porous substrate, and after drying at 90°C, a separator with a ceramic layer of aluminum oxide coated on both surfaces was obtained.

[0104] Preparation of the electrolyte

[0105] In an environment with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1 to obtain an organic solvent, and then electrolyte salt LiPF6 was added to the organic solvent and mixed uniformly to obtain an electrolyte. The mass percentage of electrolyte salt LiPF6 in the electrolyte was 12.5% based on the mass of the electrolyte, and the rest was the organic solvent.

[0106] Preparation of the lithium ion battery

[0107] The positive electrode sheet, the separator, and the negative electrode sheet prepared above were stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a role of separation, and then wound to obtain an electrode assembly. The electrode assembly was placed in an aluminum plastic film packaging bag, and water was removed at 80°C. The electrolyte prepared above was injected, and the lithium ion battery was obtained after vacuum packaging, standing, formation, degassing, and edge cutting processes. The upper limit voltage of the formation was 4.15V, the formation temperature was 70°C, and the standing time of the formation was 2h.

[0108] Example 1-2

[0109] Preparation of the positive active material

[0110] (1) In a reaction kettle, 275.04 g of CoSO4·7H2O, 11.45 g of FeSO4·7H2O, and 3.86 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered and washed with deionized water 3 times. After vacuum drying at 80°C for 24 h, a Co 0.95 Fe 0.04 Al 0.01 (OH)3 precursor was obtained.

[0111] (2) 112.79 g of Co (NO3)2·6H2O, 0.48 g of Ni(NO3)2·6H2O, 0.48 g of Mn(NO3)2·6H2O, and 0.48 g of Al(NO3)3·9H2O were mixed with 60.04 g of Na2CO3 and ball-milled until uniform. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide n-hexanol solution was added, and a solvothermal reaction was performed at 100°C for 24 h. After extraction, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.95 Fe 0.04 Al 0.01 (OH)3 precursor was ball-milled with 60.04 g of Na2CO3 until uniform. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide n-hexanol solution was added, and a solvothermal reaction was performed at 100°C for 24 h. After extraction, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Fe 0.04 Al 0.01 O2 powder.

[0112] Except that the <preparation of a positive electrode active material> was prepared according to the above procedure, the rest was the same as in Example 1-1.

[0113] Example 1-3

[0114] <Preparation of a positive electrode active material>

[0115] (1) In a reaction kettle, 274.93 g of CoSO4·7H2O, 5.41 g of NiSO4·6H2O, 3.48 g of MnSO4·H2O, and 3.86 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered, washed three times with deionized water, and vacuum dried at 80°C for 24 h to obtain a Co 0.95 Ni 0.02 Mn 0.02 Al 0.01 (OH)3 precursor.

[0116] (2) 112.79 g of Co (NO3)2·6H2O, 0.48 g of Ni(NO3)2·6H2O, 0.48 g of Mn(NO3)2·6H2O, and 0.48 g of Al(NO3)3·9H2O were mixed with 60.04 g of Na2CO3 and ball-milled until uniform. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide n-hexanol solution was added, and a solvothermal reaction was performed at 100°C for 24 h. After extraction, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.95 Ni 0.02 Mn 0.02 Al 0.01The (OH)3 precursor was mixed with 60.02 g of Na2CO3 in a ball mill. The mixture after ball milling was placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide n-hexanol solution was added, and a solvothermal reaction was performed at 100°C for 24 h. After filtration, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Ni 0.02 Mn 0.02 Al 0.01 O2 powder.

[0117] Except that the positive electrode active material was prepared according to the above steps, the rest was the same as in Example 1-1.

[0118] Example 1-4

[0119] Preparation of a positive electrode active material

[0120] (1) In a reaction kettle, 274.04 g of CoSO4·7H2O, 8.56 g of FeSO4·7H2O, 1.73 g of MnSO4·H2O, and 2.56 g of CuSO4·5H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered and washed three times with deionized water. The precipitate was vacuum dried at 80°C for 24 h to obtain a Co 0.95 Fe 0.03 Mn 0.01 Cu 0.01 (OH)3 precursor.

[0121] (2) 112.75 g of Co 0.95 Fe 0.03 Mn 0.01 Cu 0.01 (OH)3 precursor was mixed with 59.89 g of Na2CO3 in a ball mill. The mixture after ball milling was placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.08 mol / L lithium bromide n-hexanol solution was added, and a solvothermal reaction was performed at 100°C for 24 h. After filtration, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Fe0.03 Mn 0.01 Cu 0.01 O2 powder.

[0122] The rest is the same as Example 1-1 except that the <preparation of positive active material> is prepared according to the above steps.

[0123] Example 1-5

[0124] <Preparation of positive active material>

[0125] (1) In a reaction kettle, 274.37 g of CoSO4·7H2O, 8.57 g of FeSO4·7H2O, 2.70 g of NiSO4·6H2O, and 0.82 g of TiO2 were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was obtained by filtration, washed with deionized water 3 times, and vacuum dried at 80°C for 24 h to obtain Co 0.95 Fe 0.03 Ni 0.01 Ti 0.01 (OH)3 precursor.

[0126] (2) 112.75 g of Co 0.95 Fe 0.03 Ni 0.01 Ti 0.01 (OH)3 precursor was uniformly mixed with 59.89 g of Na2CO3 by ball milling. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850°C for 24 h under an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.08 mol / L lithium bromide solution in n-hexanol was added, and the solvothermal reaction was carried out at 100°C for 24 h. After that, the precipitate was obtained by suction filtration, washed with methanol 3 times, and vacuum dried at 90°C for 8 h to obtain lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Fe 0.03 Ni 0.01 Ti 0.01 O2 powder.

[0127] The rest is the same as Example 1-1 except that the <preparation of positive active material> is prepared according to the above steps.

[0128] Example 1-6

[0129] <Preparation of negative active material>

[0130] 180 g of natural graphite and 20 g of hard carbon material were mixed in a container, and after uniform mixing, a negative electrode active material was obtained.

[0131] In addition to the <preparation of the negative electrode active material> being prepared according to the above steps, the <preparation of the positive electrode sheet> adjusts the coating weight Y of the positive electrode material layer according to Table 1, and the rest is the same as Example 1-1.

[0132] Example 1-7

[0133] <Preparation of the negative electrode active material>

[0134] 198 g of natural graphite and 2 g of hard carbon material were mixed in a container, and after uniform mixing, a negative electrode active material was obtained.

[0135] In addition to the <preparation of the negative electrode active material> being prepared according to the above steps, the <preparation of the positive electrode sheet> adjusts the coating weight Y of the positive electrode material layer according to Table 1, and the rest is the same as Example 1-1.

[0136] Example 1-8

[0137] <Preparation of the positive electrode active material>

[0138] (1) In a reaction kettle, 271.92 g of CoSO4·7H2O, 8.61 g of FeSO4·7H2O, 2.71 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 4.84 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and during stirring, a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle, so that the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered and washed with deionized water 3 times, and vacuum dried at 80°C for 24 h to obtain a Co 0.9375 Fe 0.03 Ni 0.01 Mn 0.01 Al 0.0125 (OH)3precursor.

[0139] (2) 112.91 g of Co 0.9375 Fe 0.03 Ni 0.01 Mn 0.01 Al 0.0125The (OH)3 precursor was mixed with 60.15 g of Na2CO3 in a ball mill. The mixed sample was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.10 mol / L lithium bromide n-hexanol solution was added, and the sample was solvothermal-reacted at 100°C for 24 h. After filtration, the precipitate was washed with methanol three times and vacuum-dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.937 Na 0.0005 Co 0.9375 Fe 0.03 Ni 0.01 Mn 0.01 Al 0.0125 O2 powder.

[0140] In addition to the preparation of the <positive active material> being prepared according to the above steps, the <preparation of the positive electrode sheet> adjusts the coating weight Y of the positive electrode material layer according to Table 1, and the rest is the same as Example 1-1.

[0141] Example 1-9

[0142] Preparation of the <positive active material>

[0143] (1) In a reaction kettle, 268.85 g of CoSO4·7H2O, 11.50 g of FeSO4·7H2O, 2.72 g of NiSO4·6H2O, 1.75 g of MnSO4·H2O, and 5.82 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was obtained by filtration and then washed with deionized water three times. The sample was vacuum-dried at 80°C for 24 h to obtain a Co 0.925 Fe 0.04 Ni 0.01 Mn 0.01 Al 0.015 (OH)3 precursor.

[0144] (2) 113.02 g of Co 0.925 Fe 0.04 Ni 0.01 Mn 0.01 Al 0.015The (OH)3 precursor was mixed with 60.27 g of Na2CO3 in a ball mill. The mixture after ball milling was placed in a muffle furnace and heat treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, broken, ground, and sieved, 500 mL of a 3.10 mol / L lithium bromide n-hexanol solution was added, and the mixture was solvothermal reacted at 100°C for 24 h. After filtration, the precipitate was washed with methanol three times and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.9245 Na 0.0005 Co 0.925 Fe 0.04 Ni 0.01 Mn 0.01 Al 0.015 O2 powder.

[0145] In addition to the preparation of the <positive active material> being prepared according to the above steps, the <preparation of the positive electrode sheet> adjusts the coating weight Y of the positive electrode material layer according to Table 1, and the rest is the same as Example 1-1.

[0146] Example 1-10

[0147] Preparation of the <positive active material>

[0148] (1) In a reaction kettle, 271.49 g of CoSO4·7H2O, 5.71 g of FeSO4·7H2O, 2.70 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 7.71 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was obtained by filtration and then washed with deionized water three times. The mixture was vacuum dried at 80°C for 24 h to obtain a Co 0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02 (OH)3 precursor.

[0149] (2) 112.91 g of Co 0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02The (OH)3 precursor was mixed with 60.27 g of Na2CO3 in a ball mill. The mixture after ball milling was placed in a muffle furnace and heat treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, broken, ground, and sieved, 500 mL of a 3.10 mol / L lithium bromide n-hexanol solution was added, and the mixture was solvothermal reacted at 100°C for 24 h. After filtration, the precipitate was washed with methanol three times and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.9395 Na 0.0005 Co 0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02 O2 powder.

[0150] In addition to the preparation of the positive active material being prepared according to the above steps, the preparation of the positive electrode sheet is adjusted to the coating weight Y of the positive electrode material layer according to Table 1.

[0151] Example 1-11

[0152] Preparation of the positive active material

[0153] (1) In a reaction kettle, 274.37 g of CoSO4·7H2O, 5.71 g of FeSO4·7H2O, 2.70 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 7.71 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was obtained by filtration and washed with deionized water three times. The mixture was vacuum dried at 80°C for 24 h to obtain a Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 (OH)3 precursor.

[0154] (2) 112.79 g of Co 0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02The (OH)3 precursor was mixed with 60.03 g of Na2CO3 in a ball mill. The mixture after ball milling was placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, broken, ground, and sieved, 500 mL of a 3.08 mol / L lithium bromide n-hexanol solution was added, and the mixture was subjected to a solvothermal reaction at 100°C for 12 h. After filtration, the precipitate was washed with methanol three times and vacuum dried at 90°C for 8 h to obtain a lithium cobalt oxide Li 0.949 Na 0.001 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2 powder.

[0155] The rest was the same as in Example 1-1, except that the <preparation of a positive electrode active material> was prepared according to the above procedure.

[0156] Example 1-12

[0157] <Preparation of a negative electrode active material>

[0158] 180 g of natural graphite and 20 g of a hard carbon material were mixed in a container. After uniform mixing, a negative electrode active material was obtained.

[0159] The rest was the same as in Example 1-11, except that the <preparation of a negative electrode active material> was prepared according to the above procedure, and the <preparation of a positive electrode sheet> was adjusted to the coating weight Y of the positive electrode material layer according to Table 1.

[0160] Example 1-13

[0161] <Preparation of a positive electrode active material>

[0162] (1) In a reaction kettle, 271.49 g of CoSO4·7H2O, 5.71 g of FeSO4·7H2O, 2.70 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 7.71 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered and washed with deionized water three times. The mixture was vacuum dried at 80°C for 24 h to obtain a Co 0.78 Fe 0.1 Ni 0.05 Mn 0.05 Al 0.02 (OH)3 precursor.

[0163] (2) 114.29 g of Co0.94 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.02 The (OH)3 precursor was uniformly mixed with 61.24 g of Na2CO3 by ball milling. The ball-milled mixture was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was removed, crushed, ground, and sieved, 500 mL of a 3.15 mol / L lithium bromide n-hexanol solution was added, and the mixture was subjected to a solvothermal reaction at 100°C for 24 h. After filtration, the precipitate was washed three times with methanol and vacuum dried at 90°C for 8 h to obtain the lithium cobalt oxide Li 0.7795 Na 0.0005 Co 0.78 Fe 0.1 Ni 0.05 Mn 0.05 Al 0.02 O2 powder.

[0164] Except that the <preparation of the positive active material> was prepared according to the above steps, and the <preparation of the positive electrode sheet> adjusted the coating weight Y of the positive electrode material layer according to Table 1, the rest was the same as Example 1-1.

[0165] Comparative Example 1-1

[0166] <Preparation of the positive active material>

[0167] After 100 g of LiCoO2, 0.16 g of Al2O3, and 0.11 g of Li2CO3 were uniformly mixed, they were transferred to a corundum crucible and sintered at 1030°C for 10 h in an O2 atmosphere. The sintered product was crushed into powder using a jaw crusher and a roll crusher, further crushed using an air jet pulverizer, and finally sieved using a 400-mesh sieve to obtain the lithium cobalt oxide Li 0.997 Al 0.003 O2 powder.

[0168] Except that the <preparation of the positive active material> was prepared according to the above steps, and the <preparation of the positive electrode sheet> adjusted the coating weight Y of the positive electrode material layer according to Table 1, the rest was the same as Example 1-1.

[0169] Comparative Example 1-2

[0170] <Preparation of the positive active material>

[0171] LiCoO2, 0.16 g of Al2O3, and 0.11 g of Li2CO3 were mixed uniformly, transferred to a corundum crucible, sintered at 1030°C for 10 h under an O2 atmosphere, put into a jaw crusher and a roll crusher to make a powder, further crushed by an air jet pulverizer, and finally sieved by a 400-mesh screen to obtain a lithium cobalt oxide LiCoO2 powder having an R-3m structure. 0.997 Al 0.003 O2 powder.

[0172] Except that the <preparation of a positive active material> was prepared according to the above procedure, and the <preparation of a positive electrode sheet> adjusted the coating weight Y of the positive electrode material layer according to Table 1, the rest was the same as Example 1-1.

[0173] Comparative Example 1-3

[0174] Except that the negative active material was adjusted to natural graphite, and no hard carbon was added, and the <preparation of a positive electrode sheet> adjusted the coating weight Y of the positive electrode material layer according to Table 1, the rest was the same as Example 1-1.

[0175] Comparative Example 1-4

[0176] Except that the negative active material was adjusted to hard carbon, and no natural graphite was added, and the <preparation of a positive electrode sheet> adjusted the coating weight Y of the positive electrode material layer according to Table 1, the rest was the same as Example 1-1.

[0177] Example 2-1

[0178] <Preparation of a positive active material>

[0179] Preparation of a lithium cobalt oxide having a P63mc structure:

[0180] (1) In a reaction kettle, 274.99 g of CoSO4·7H2O, 5.73 g of FeSO4·7H2O, 2.71 g of NiSO4·6H2O, 1.74 g of MnSO4·H2O, and 3.86 g of Al(NO3)3·9H2O were dissolved in water, stirred under a nitrogen atmosphere, and a solution containing 2 mol / L of NaOH and 2 mol / L of NH3·H2O was added to the reaction kettle during stirring to make the solution pH = 11. Stirring was continued for 12 h, and the precipitate was filtered and washed with deionized water 3 times, and vacuum dried at 80°C for 24 h to obtain a Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 (OH)3 precursor.

[0181] (2) 112.79 g of Co 0.95 Fe 0.02 Ni 0.01Mn 0.01 Al 0.01 The (OH)3 precursor was mixed with 60.03 g of Na2CO3 in a ball mill. The mixed powder was then placed in a muffle furnace and heat-treated at 850°C for 24 h in an air atmosphere. After the sample was taken out, crushed, ground, and sieved, 500 mL of a 3.09 mol / L lithium bromide n-hexanol solution was added, and the mixture was subjected to a solvothermal reaction at 100°C for 24 h. After filtration, the precipitate was washed with methanol three times and vacuum dried at 90°C for 8 h to obtain the P63mc-structured lithium cobalt oxide Li 0.9495 Na 0.0005 Co 0.95 Fe 0.02 Ni 0.01 Mn 0.01 Al 0.01 O2 powder.

[0182] Preparation of the R-3m-structured lithium cobalt oxide:

[0183] After 100 g of LiCoO2, 1.56 g of Al2O3, and 1.13 g of Li2CO3 were mixed, the mixture was transferred to a corundum crucible and sintered at 1030°C for 10 h in an O2 atmosphere. The sintered product was crushed into powder using a jaw crusher and a roll crusher, further crushed using an air jet pulverizer, and finally sieved using a 400-mesh sieve to obtain the R-3m-structured lithium cobalt oxide LiCo 0.97 Al 0.03 O2 powder.

[0184] The R-3m-structured lithium cobalt oxide powder and the P63mc-structured lithium cobalt oxide powder prepared above were mixed in a mass ratio M of 4 to obtain the positive electrode active material.

[0185] <Preparation of a negative electrode active material>

[0186] After 198 g of natural graphite and 2 g of hard carbon material were mixed in a container, the mixture was uniformly mixed to obtain the negative electrode active material.

[0187] In addition to the <Preparation of a positive electrode active material> and the <Preparation of a negative electrode active material> being prepared according to the above procedure, the <Preparation of a positive electrode tab> was prepared according to Table 2, with the exception that the coating weight Y of the positive electrode material layer was adjusted.

[0188] Example 2-2

[0189] <Preparation of a negative electrode active material>

[0190] After 195 g of natural graphite and 5 g of hard carbon material were mixed in a container, the mixture was uniformly mixed to obtain the negative electrode active material.

[0191] Example 2-1 except that the value of M in the preparation of the positive active material was adjusted to 1 in the above-described procedure.

[0192] Example 2-3, Example 2-4

[0193] Example 2-1 except that the value of M in the preparation of the positive active material was adjusted to 1 in the above-described procedure.

[0194] Example 2-5

[0195] Preparation of lithium cobalt oxide of R-3m structure: 100 g of LiCoO2, 1.56 g of Al2O3, 1.13 g of Li2CO3, 0.21 g of MgO were mixed uniformly and transferred to a corundum crucible, sintered at 1030°C for 10 h under O2atmosphere, put into a jaw crusher, a pair of rollers to make powder, further broken by an air jet pulverizer, and finally sieved by a 400 mesh screen to obtain lithium cobalt oxide of R-3m structure LiCo 0.965 Al 0.03 Mg 0.005 O2powder. Example 2-2 except that the lithium cobalt oxide of R-3m structure was prepared in the above-described procedure in the preparation of the positive active material.

[0196] Example 2-6

[0197] Preparation of lithium cobalt oxide of R-3m structure: 100 g of LiCoO2, 1.56 g of Al2O3, 1.13 g of Li2CO3, 0.21 g of MgO, 0.41 g of TiO2were mixed uniformly and transferred to a corundum crucible, sintered at 1030°C for 10 h under O2atmosphere, put into a jaw crusher, a pair of rollers to make powder, further broken by an air jet pulverizer, and finally sieved by a 400 mesh screen to obtain lithium cobalt oxide of R-3m structure LiCo 0.96 Al 0.03 Mg 0.005 Ti 0.005 O2powder. Example 2-2 except that the lithium cobalt oxide of R-3m structure was prepared in the above-described procedure in the preparation of the positive active material.

[0198] Example 2-7

[0199] Preparation of lithium cobalt oxide of R-3m structure: 100 g of LiCoO2, 1.56 g of Al2O3, 1.13 g of Li2CO3, 0.21 g of MgO were mixed uniformly and transferred to a corundum crucible, sintered at 1030°C for 10 h under O2atmosphere, put into a jaw crusher, a pair of rollers to make powder, further broken by an air jet pulverizer, and finally sieved by a 400 mesh screen to obtain lithium cobalt oxide of R-3m structure LiCo0.9 Al 0.1 O2 powder. Except for the preparation of the positive active material, the lithium cobalt oxide of R-3m structure was prepared by the above method, and the preparation of the positive electrode sheet was adjusted for the coating weight Y of the positive material layer according to Table 2, and the rest was the same as Example 2-2.

[0200] Example 2-8

[0201] Preparation of lithium cobalt oxide of R-3m structure: 100 g of LiCoO2, 1.56 g of Al2O3, 1.13 g of Li2CO3, 0.41 g of MgO, 0.82 g of TiO2, 1.66 g of La2O3, 1.15 g of Y2O3, 1.26 g of ZrO2 were mixed uniformly and then transferred to a corundum crucible, sintered at 1030°C for 10 h under O2 atmosphere, put into a jaw crusher and a roll mill to make powder, further crushed by an air jet pulverizer, and finally sieved by a 400 mesh screen to obtain lithium cobalt oxide LiCo 0.92 Al 0.03 Mg 0.01 Ti 0.01 La 0.01 Y 0.01 Zr 0.01 O2 powder. Except for the preparation of the positive active material, the lithium cobalt oxide of R-3m structure was prepared by the above method, and the preparation of the positive electrode sheet was adjusted for the coating weight Y of the positive material layer according to Table 2, and the rest was the same as Example 2-2.

[0202] Comparative Example 2-1

[0203] Preparation of positive active material

[0204] Preparation of lithium cobalt oxide of R-3m structure: 100 g of LiCoO2, 1.56 g of Al2O3, 1.13 g of Li2CO3 were mixed uniformly and then transferred to a corundum crucible, sintered at 1030°C for 10 h under O2 atmosphere, put into a jaw crusher and a roll mill to make powder, further crushed by an air jet pulverizer, and finally sieved by a 400 mesh screen to obtain lithium cobalt oxide LiCo 0.97 Al 0.03 O2 powder.

[0205] Except for the preparation of the positive active material, which was prepared according to the above steps, the negative active material was natural graphite without the addition of hard carbon, and the preparation of the positive electrode sheet was adjusted for the coating weight Y of the positive material layer according to Table 2, and the rest was the same as Example 2-1.

[0206] Comparative Example 2-2

[0207] Preparation of positive active material

[0208] LiCoO2, 1.56 g of Al2O3, and 1.13 g of Li2CO3 were mixed uniformly and then transferred to a corundum crucible. The mixture was sintered at 1030°C for 10 h under an O2 atmosphere, and then crushed by a jaw crusher and a roll crusher to obtain a powder. The powder was further crushed by an air jet pulverizer, and then sieved with a 400-mesh screen to obtain a lithium cobalt oxide LiCoO2 powder having an R-3m structure. 0.97 Al 0.03 O2 powder.

[0209] <Preparation of a positive active material>

[0210] A container was prepared by mixing 195 g of natural graphite and 5 g of a hard carbon material. After mixing, a negative active material was obtained.

[0211] Except that the <Preparation of a positive active material> and the <Preparation of a negative active material> were prepared according to the above steps, and the <Preparation of a positive electrode sheet> was adjusted according to Table 2 for the coating weight Y of the positive material layer, the rest was the same as Example 2-1.

[0212] Comparative Example 2-3

[0213] Except that the <Preparation of a positive active material> and the <Preparation of a negative active material> were prepared according to the above steps, and the <Preparation of a positive electrode sheet> was adjusted according to Table 2 for the coating weight Y of the positive material layer, the rest was the same as Example 2-1. 0.9 Al 0.1 O2, the <Preparation of a positive electrode sheet> was adjusted according to Table 2 for the coating weight Y of the positive material layer, the rest was the same as Example 2-7.

[0214] Table 1 Note: " / " in Table 1 indicates that the corresponding parameter or substance does not exist.

[0215] As can be seen from Example 1-1 to Example 13 and Comparative Example 1-1 to Comparative Example 1-4, the positive material includes a lithium cobalt oxide having a P63mc structure, and the characteristic peak position of the (002) crystal plane of the lithium cobalt oxide having a P63mc structure is within the scope of the present application. The negative material includes a hard carbon and a graphite. The lithium ion battery has a high initial discharge mass specific capacity, a high capacity retention rate R, and a high cycle number at 80% of the capacity at 45°C, indicating that the lithium ion battery has a high energy density, and also has good rate performance and high-temperature cycle performance.

[0216] Figure 1 is a graph of the high-temperature cycle performance test results of Example 1-1, Example 1-5 to Example 1-7, Example 1-9, Comparative Example 1-1, Comparative Example 1-3, and Comparative Example 2-1. As can be seen from Figure 1, when the cycle capacity retention rate is 80%, the cycle number of Example 1-1, Example 1-5 to Example 1-7, and Example 1-9 is significantly greater than that of Comparative Example 1-1 and Comparative Example 1-3, indicating that the lithium ion battery of the present application has good high-temperature cycle performance.

[0217] Figure 2 is a graph of the rate performance test results of Example 1-1, Example 1-5 to Example 1-7, Example 1-9, Comparative Example 1-1, Comparative Example 1-3, and Comparative Example 2-1. As can be seen from Figure 2, under the discharge rates of 0.5C, 1C, and 2C, the capacity retention rates of Example 1-1, Example 1-5 to Example 1-7, and Example 1-9 are all greater than those of Comparative Example 1-1 and Comparative Example 2-1, indicating that the lithium ion battery of the present application has good rate performance.

[0218] Figure 3 is an XRD pattern of P63mc structured lithium cobalt oxide in the positive electrode material layer of Example 1-1. The characteristic peak position of the (002) crystal plane of P63mc structured lithium cobalt oxide is 18.50°.

[0219] Figure 6 is an SEM image of the negative electrode sheet of Example 1-1. The particles with angular blocky morphology are hard carbon, and the particles with lamellar morphology are graphite.

[0220] The mass percentage content of hard carbon generally affects the energy density and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-6, Example 1-7, Comparative Example 1-3, and Comparative Example 1-4, when the negative electrode active material includes hard carbon and the mass percentage content of hard carbon is controlled within the range of the present application, the lithium ion battery has a higher initial discharge mass specific capacity, a higher cycle number at a 45°C capacity retention rate of 80%, and a higher energy density and good high-temperature cycle performance.

[0221] The type of A element in P63mc structured lithium cobalt oxide generally affects the energy density, rate performance, and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 1-1 to Example 1-3, when the type of A element in P63mc structured lithium cobalt oxide is within the range of the present application, the lithium ion battery has a higher initial discharge mass specific capacity, a higher capacity retention rate R, and a higher cycle number at a 45°C capacity retention rate of 80%, indicating that the lithium ion battery has a higher energy density, as well as good rate performance and high-temperature cycle performance.

[0222] The B element species in the lithium cobalt oxide with P63mc structure generally affects the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-4 and Example 1-5, the B element species in the lithium cobalt oxide with P63mc structure is within the scope of the present application, which can make the lithium ion battery have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the capacity retention rate at 45°C, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0223] The values of x, y, a and b in the lithium cobalt oxide with P63mc structure generally affect the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 1-1 to Example 1-12, by adjusting the values of x, y, a and b in the lithium cobalt oxide with P63mc structure within the scope of the present application, the lithium ion battery can have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the capacity retention rate at 45°C, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0224] The value of the adhesion F between the separator film and the positive electrode sheet generally affects the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 1-1 to Example 1-13, the value of the adhesion F between the separator film and the positive electrode sheet is within the scope of the present application, which can make the lithium ion battery have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the capacity retention rate at 45°C, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0225] Table 2 Note: " / " in Table 2 indicates the absence of the corresponding parameter or substance.

[0226] The value of I1 / I2 generally affects the high-temperature cycle performance of the lithium ion battery. As can be seen from Example 2-1 to Example 2-4 and Comparative Example 2-1 to Comparative Example 2-3, by adjusting the value of I1 / I2 within the scope of the present application, the lithium ion battery can have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the capacity retention rate at 45°C, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0227] Figure 4 is an XRD pattern of the lithium cobalt oxide with P63mc structure and the lithium cobalt oxide with R-3m structure in the positive electrode material layer of Example 2-2, and the ratio of the intensity of the (003) crystal face characteristic peak of the lithium cobalt oxide with R-3m structure I1 to the intensity of the (002) crystal face characteristic peak of the lithium cobalt oxide with P63mc structure I2 is 0.15.

[0228] The (003) crystal face characteristic peak position of the lithium cobalt oxide with R-3m structure generally affects the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 2-1 to Example 2-8, the (003) crystal face characteristic peak position of the lithium cobalt oxide with R-3m structure is within the range of the application, which can make the lithium ion battery have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the 45℃ capacity retention rate, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0229] Figure 5 is an XRD pattern of the lithium cobalt oxide with R-3m structure in the positive electrode material layer of Comparative Example 2-1, and the (003) crystal face characteristic peak position of the lithium cobalt oxide with R-3m structure is 18.93°.

[0230] The type of C element in the lithium cobalt oxide with R-3m structure generally affects the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 2-5 to Example 2-6, the type of C element in the lithium cobalt oxide with R-3m structure is within the range of the application, which can make the lithium ion battery have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the 45℃ capacity retention rate, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0231] The values of m and n in the lithium cobalt oxide with R-3m structure generally affect the energy density, rate performance and high-temperature cycle performance of the lithium ion battery. As can be seen from Example 2-1 to Example 2-8, by adjusting the values of m and n in the lithium cobalt oxide with R-3m structure within the range of the application, the lithium ion battery can have a higher initial discharge mass specific capacity, a higher capacity retention rate R and a higher cycle number at 80% of the 45℃ capacity retention rate, indicating that the lithium ion battery has a higher energy density, and also has good rate performance and high-temperature cycle performance.

[0232] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. An electrochemical device, comprising a positive electrode sheet, a negative electrode sheet, and a separator film, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer comprising a positive electrode material, the positive electrode material comprising a lithium cobalt oxide of a P63mc structure, a characteristic peak of a (002) crystal plane of the lithium cobalt oxide of the P63mc structure being located between 17° and 19° in an XRD pattern of the positive electrode material layer; the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer comprising a negative electrode material, the negative electrode material comprising hard carbon and graphite.

2. The electrochemical device of claim 1, wherein, the characteristic peak of the (002) crystal plane of the lithium cobalt oxide of the P63mc structure is located between 18.3° and 18.7°.

3. The electrochemical device of claim 1, wherein, a mass percentage content of the hard carbon is w% based on a mass of the negative electrode material, 1≤w≤10.

4. The electrochemical device of claim 1, wherein, The lithium cobalt oxide of the P63mc structure includes Li x Na y Co 1-a-b A a B b O2, wherein A includes at least one of Mn, Fe, or Ni, B includes at least one of Al, Mg, Ti, La, Y, Zr, Zn, Cu, Cr, Ca, Ce, or Lu, 0.779≤x≤0.95, 0 y≤0.001, 0 5.The electrochemical device of claim 1, wherein the positive electrode material further comprises a lithium cobalt oxide of an R-3m structure, a characteristic peak of a (003) crystal plane of the lithium cobalt oxide of the R-3m structure being located between 18° and 20° in the XRD pattern of the positive electrode material layer; an intensity of the characteristic peak of the (003) crystal plane of the lithium cobalt oxide of the R-3m structure is I1, an intensity of the characteristic peak of the (002) crystal plane of the lithium cobalt oxide of the P63mc structure is I2, and 0≤I1 / I2≤20.

6. The electrochemical device of claim 5, wherein, The lithium cobalt oxide of the R-3m structure includes LiCo 1-m-n Al m C n O2, wherein C includes at least one of Mg, Ti, La, Y, Zr, or Lu, 0 < m < 0.1, and 0 < n < 0.

05.

7. The electrochemical device according to any one of claims 1 to 6, wherein, a capacity of the positive electrode sheet with lithium metal as a counter electrode in a potential range of 3.0 V to 4.6 V is d, a capacity of the negative electrode sheet with lithium metal as a counter electrode in a potential range of 0.005 V to 0.8 V is c, and 1.00 8. The electrochemical device according to any one of claims 1 to 6, wherein, an adhesion between the separator film and the positive electrode sheet is F N / m, and 1≤F≤50. 9.The electrochemical device of any one of claims 1 to 6, wherein a charge upper limit voltage is 4.5 V to 4.75 V. 10.An electronic device comprising the electrochemical device of any one of claims 1 to 9.

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