CN116779806A

CN116779806A - Lithium supplementing material and preparation method and application thereof

Info

Publication number: CN116779806A
Application number: CN202310740094.5A
Authority: CN
Inventors: 林律欢; 万远鑫; 孔令涌; 裴现一男; 谭旗清
Original assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Current assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Priority date: 2023-06-20
Filing date: 2023-06-20
Publication date: 2023-09-19

Abstract

The application discloses a lithium supplementing material, a preparation method and application thereof, and relates to the technical field of electrode active materials. The lithium supplementing material provided by the application is of a hierarchical porous structure, the core of the lithium supplementing material is distributed with first holes, the surface layer of the lithium supplementing material is distributed with second holes, and the aperture of the second holes is larger than that of the first holes. The lithium supplementing material can facilitate the electrolyte to infiltrate from outside to inside, improve or solve the negative influence of ion diffusion, is beneficial to the release of lithium ions, the infiltration of the electrolyte, the material transmission at the interface and the like, is beneficial to the exertion of the lithium supplementing capacity, can also reduce the residual base number of the surface interface of the lithium supplementing material, and improves the utilization rate of the lithium supplementing material.

Description

Lithium supplementing material and preparation method and application thereof

Technical Field

The application belongs to the technical field of electrode materials, and particularly relates to a lithium supplementing material, and a preparation method and application thereof.

Background

Lithium ion batteries are one of the most widely used secondary batteries because of their advantages such as high voltage, high energy density, long cycle life, etc. However, since the lithium ion battery generates a large amount of solid electrolyte interface film (Solid Electrolyte Interphase, SEI) on the surface of the negative electrode during the first charge and discharge process, it consumes limited lithium ions and electrolyte in the battery, resulting in irreversible capacity loss, and reduces the energy density of the lithium ion battery, reduces the charge and discharge efficiency of the electrode material, limits the application of the lithium ion battery, and the like. Therefore, a suitable lithium supplementing method is particularly important for improving the performance of the lithium ion battery.

In recent years, some lithium supplementing methods have been proposed, for example, adding a lithium supplementing material to the positive electrode of a lithium ion battery. However, in research and practical application, the existing lithium supplementing materials are mostly secondary particles tightly packed by primary particles, and the problems that the existing lithium supplementing materials cannot be fully infiltrated by electrolyte exist, so that the capacity utilization rate of the existing lithium supplementing materials is low. Meanwhile, the free lithium content on the surface of the lithium supplementing materials is extremely high, slurry gel is easy to cause in the slurry mixing process, the processing performance is seriously affected, the high-temperature storage performance of the lithium ion battery is possibly deteriorated, and the problems of storage flatulence, performance attenuation and the like of the lithium ion battery are caused. And is subjected to atmospheric water and oxygen (O) ₂ ) Carbon dioxide (CO) ₂ ) The effect of the lithium supplementing material on the positive electrode of the lithium ion battery is affected by the influence of the poor stability of the existing lithium supplementing material in the air and easy deterioration, so that the lithium supplementing effect of the lithium supplementing material is obviously reduced or even completely destroyed, the lithium supplementing effect of the lithium supplementing material on the positive electrode of the lithium ion battery is affected, and the lithium supplementing material can also be usedImpurity components can be introduced into the positive electrode, and the capacity of the lithium ion battery is reduced.

Therefore, how to effectively improve various problems caused by the use of the lithium supplementing material without affecting other performances of the lithium ion battery is a problem to be solved at present, which has a great influence on the performance improvement of the lithium ion battery.

Disclosure of Invention

The application aims to overcome the defects in the prior art, and provides a lithium supplementing material, a preparation method and application thereof, so as to solve the technical problems that the existing lithium supplementing material cannot be fully soaked by electrolyte, and lithium ions are diffused and released.

The application further aims to provide a positive plate and a secondary battery containing the positive plate, so as to solve the technical problems of poor lithium supplementing effect, low charge and discharge efficiency and the like of the existing secondary battery, such as non-ideal electrochemical performance.

In order to achieve the above object, according to a first aspect of the present application, a lithium supplementing material is provided, the lithium supplementing material has a hierarchical porous structure, a core of the lithium supplementing material is distributed with first holes, a surface layer of the lithium supplementing material is distributed with second holes, and a pore diameter of the second holes is larger than a pore diameter of the first holes.

Further, the first pores comprise micropores and/or mesopores, and the second pores comprise macropores;

alternatively, the first pores comprise micropores and the second pores comprise mesopores and/or macropores.

Further, the value range of the aperture of the micropore is smaller than 2nm, and the value range of the quantitative ratio of the micropore in all the micropores is 5-95%;

And/or the value range of the aperture of the mesoporous is 2-50nm, and the value range of the quantitative ratio of the mesoporous in all the holes is 4-95%;

and/or the value range of the pore diameter of the macropores is larger than 50nm, and the value range of the number ratio of the macropores in all the pores is 1-40%.

Further, the value range of the number ratio of the micropores, the mesopores and the macropores is as follows: (20-80%) and (10-70%) and (3-70%).

Further, the lithium supplementing material comprises a lithium-rich metal oxide, wherein the chemical formula of the lithium-rich metal oxide is Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is selected from at least one metal element from IB group to VIIIB group, IVA group and VA group, x is more than 1 and less than 10, y is more than 0, and z is more than 0 and less than 13.

Further, the lithium supplementing material is in a core-shell structure, and the chemical formula of the core of the lithium supplementing material is different from the M element in the chemical formula of the surface layer of the lithium supplementing material.

Further, the core of the lithium supplementing material is distributed with a carbon material, and the carbon material is filled in the first holes.

Further, the value range of the ratio of the thickness of the surface layer to the radius of the lithium supplementing material is 30-50%;

and/or the thickness of the surface layer is in the range of 4-30000nm.

Further, the porosity of the lithium supplementing material is in the range of 5-80%;

and/or the specific surface area of the lithium supplementing material is in the range of 3-300m ² /g；

And/or the value range of the tap density of the lithium supplementing material is 2-3.5g/cm ³ ；

And/or the residual alkalinity of the lithium supplementing material is less than 5 percent.

In a second aspect of the present application, a method of preparing the lithium-supplementing material of the present application is provided. The preparation method of the lithium supplementing material comprises the following steps:

mixing the first M source with a pore-forming agent to obtain a second M source with a hierarchical porous structure; the core of the second M source is provided with first holes, the surface layer of the second M source is provided with second holes, and the aperture of the second holes is larger than that of the first holes;

mixing the second M source with a lithium source to obtain the lithium supplementing material with a hierarchical porous structure; the core of the lithium supplementing material is distributed with the first holes, and the surface layer of the lithium supplementing material is distributed with the second holes.

In a third aspect of the present application, a positive electrode sheet is provided. The positive plate comprises a positive current collector and a positive active layer combined on the surface of the positive current collector, wherein the positive active layer comprises the lithium supplementing material or the lithium supplementing material prepared by the preparation method of the lithium supplementing material.

In a fourth aspect of the present application, a secondary battery is provided. The application comprises a positive plate and a negative plate, wherein the positive plate is the positive plate of the application.

Compared with the prior art, the application has the following technical effects:

the lithium supplementing material is of a hierarchical porous structure, the core of the hierarchical porous structure is provided with the first holes, the surface layer is provided with the second holes, and the aperture of the second holes is larger than that of the first holes, so that the aperture of the holes is enlarged along the direction from the core to the surface layer of the lithium supplementing material, and electrolyte is conveniently infiltrated from the surface layer to the core, namely, electrolyte is conveniently infiltrated from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, is beneficial to playing of lithium supplementing capacity, and can also reduce the residual base number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved.

According to the preparation method of the lithium supplementing material, the first M source forms a hierarchical porous structure through the pore-forming agent, and then the first M source is combined with the lithium source to obtain the lithium supplementing material with the hierarchical porous structure, and the unique hierarchical pore structure of the lithium supplementing material can facilitate infiltration of electrolyte from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, is beneficial to exertion of lithium supplementing capacity, and can also reduce the residual base number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved; in addition, the second M source with the hierarchical porous structure has abundant surface holes, increases active sites which react with the lithium source, can fully react with the lithium source, and reduces the residual lithium amount, thereby reducing the residual alkali number of the surface interface of the lithium supplementing material, improving the utilization rate of the lithium supplementing material, and the preparation method has the advantages of simple process, low synthesis cost, easy popularization and application and the like.

The positive plate of the application contains the lithium supplementing material, so the positive plate of the application has high energy density, high cycle performance and long service life, and can effectively improve the slurry coagulation phenomenon of the lithium supplementing material, improve the environmental stability, the cycle stability, the structural stability and the like of the lithium supplementing material, and prolong the use and the storage life of the lithium supplementing material, thereby prolonging the use and the storage life of the positive plate.

The secondary battery of the application has excellent first coulombic efficiency, high energy density, high cycle performance, high capacity retention rate, long service life and stable electrochemical performance because of the electrode plate.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a first lithium supplementing material according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a second lithium supplementing material according to an embodiment of the present application;

fig. 3 is a process flow chart of a preparation method of a first lithium supplementing material according to an embodiment of the present application;

fig. 4 is a process flow chart of a preparation method of a second lithium supplementing material according to an embodiment of the present application.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

In the present application, the term "and/or" describes an association relationship of an association object, which means that three relationships may exist, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c" may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c or a-b-c, wherein a, b, c may be single or multiple, respectively.

It should be understood that, in various embodiments of the present application, the sequence number of each process described above does not mean that the execution sequence of some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The weights of the relevant components mentioned in the description of the embodiments of the present application may refer not only to the specific contents of the components, but also to the proportional relationship between the weights of the components, so long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down within the scope of the disclosure of the embodiments of the present application. Specifically, the mass described in the specification of the embodiment of the application can be mass units known in the chemical industry field such as mu g, mg, g, kg.

The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

In a first aspect, as shown in fig. 1 and fig. 2, the embodiment of the present application provides a lithium supplementing material, where the lithium supplementing material has a hierarchical porous structure, a core of the lithium supplementing material is distributed with a first hole, a surface layer of the lithium supplementing material is distributed with a second hole, and a pore diameter of the second hole is larger than that of the first hole.

The lithium supplementing material may be a core-shell structure as shown in fig. 2, where the core-shell structure may be a shell layer 11 wrapping an inner core 12, and in this case, the shell layer 11 of the core-shell structure is the surface layer, the inner core 12 of the core-shell structure is the core, and the materials of the inner core 12 and the shell layer 11 are different; of course, the lithium supplementing material may not have a core-shell structure, and for example, as shown in fig. 1, the lithium supplementing material may be a uniform material, which is not particularly limited herein.

The core of the lithium supplementing material is provided with a plurality of first holes, and the first holes can be arranged at intervals (independently) or communicated with each other. The shape of the first hole is not particularly limited herein, and the shape of the first hole may be circular, rectangular, etc. as shown in fig. 1 and 2, for example, depending on the actual process.

The surface layer of the lithium supplementing material is provided with a plurality of second holes which can be arranged at intervals (independently) or communicated with each other. The shape of the second hole is not particularly limited herein, and illustratively, the shape of the second hole may be circular, rectangular, etc. as shown in fig. 1 and 2, particularly, based on actual processes.

It should be noted that fig. 1 and 2 illustrate the shape of the lithium supplementing material as a sphere, and of course, the lithium supplementing material may also have other shapes, which are specific to practical applications.

Meanwhile, the first hole and the second hole only need to ensure that the hole diameters are different, and other parameters, such as shapes and the like, of the first hole and the second hole can be the same, but can also be different, and the method is not particularly limited.

The lithium supplementing capacity of the lithium supplementing material can be in the range of 200-900mAh/g, and the lithium supplementing capacity of the lithium supplementing material can be 200mAh/g, 400mAh/g, 500mAh/g, 700mAh/g, 800mAh/g, 900mAh/g or the like. The lithium supplementing material can release more lithium ions, thereby being beneficial to the exertion of the lithium supplementing capacity.

The lithium supplementing material provided by the embodiment of the application is of a hierarchical porous structure, wherein the core of the hierarchical porous structure is provided with the first holes, the surface layer is provided with the second holes, and the pore diameter of the second holes is larger than that of the first holes, so that the pore diameter of the holes is enlarged along the direction from the core to the surface layer of the lithium supplementing material, and electrolyte is conveniently infiltrated from the surface layer to the core, namely, electrolyte is conveniently infiltrated from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, thereby being beneficial to playing of lithium supplementing capacity, and can also reduce the residual alkali number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved.

Further, as shown in fig. 1 and 2, the first pores comprise micropores 1 and/or mesopores 2, and the second pores comprise macropores 3; alternatively, the first pores comprise micropores 1 and the second pores comprise mesopores 2 and/or macropores 3.

The pore diameter of the micropores can be smaller than 2nm, and the numerical value range of the quantitative ratio of the micropores in all the micropores can be 5-95%, preferably 20-80%. Illustratively, the pore size of the micropores may be 0.1nm, 0.2nm, 0.8nm, 1nm, 1.4nm, or 1.9nm, etc.; the ratio of the number of micropores in all the micropores may be 20%, 40%, 50%, 60%, 70% or 80%, etc. The purity of the lithium supplementing material is higher and the structure is stable by limiting the quantity of micropores to the ratio; meanwhile, the lithium supplementing material can be fully infiltrated by the electrolyte.

It should be noted that, in this case, the pore diameters of the plurality of micropores may be partially the same; alternatively, the pore diameters of the plurality of micropores may all be the same; alternatively, the pore sizes of the plurality of micropores may all be different, particularly based on the actual process.

And/or the pore diameter of the mesopores can be 2-50nm, and the numerical value range of the numerical ratio of the mesopores in all the pores can be 4-95%, preferably 10-80%. Illustratively, the mesoporous pore size may be 2nm, 10nm, 20nm, 30nm, 40nm, or 50nm, etc.; the ratio of the number of mesopores in all the pores can be 10%, 30%, 40%, 50%, 60% or 80%, etc. The purity of the lithium supplementing material is higher and the structure is stable by limiting the number of mesoporous to the ratio; meanwhile, the lithium supplementing material can be fully soaked by the electrolyte.

It should be noted that the pore diameters of the plurality of mesopores may be partially the same at this time; alternatively, the pore diameters of the plurality of mesopores may all be the same; alternatively, the pore diameters of the plurality of mesopores may all be different, particularly based on actual processes.

And/or the pore diameter of the macropores can be larger than 50nm, and the numerical value range of the number ratio of the macropores in all the pores can be 1-40%, preferably 3-35%. Illustratively, the pore size of the macropores may be 51nm, 55nm, 60nm, 70nm, 80nm, 90nm, or the like; the ratio of the number of macropores in all the pores may be 3%, 10%, 20%, 30%, 31% or 35%, etc. Therefore, on the premise that the electrolyte can fully infiltrate the lithium supplementing material, the lithium supplementing material can be effectively prevented from being corroded by harmful substances in the external environment by limiting the quantity of macropores within a smaller range.

It should be noted that, in this case, the pore diameters of the plurality of macropores may be partially the same; alternatively, the pore diameters of the plurality of macropores may all be the same; alternatively, the pore sizes of the plurality of macropores may all be different, particularly based on actual processes.

The pore diameters of the plurality of pores of the lithium supplementing material will be specifically described below taking the shape of the lithium supplementing material as a sphere. Wherein, the spherical lithium supplementing material shown in fig. 1 is uniform in material; the spherical lithium supplementing material shown in fig. 2 has a core-shell structure.

As shown in fig. 1, the core of the lithium supplementing material includes a plurality of micropores 1 and a plurality of mesopores 2, and the surface layer of the lithium supplementing material includes a plurality of mesopores 2 and a plurality of macropores 3.

As shown in fig. 2, the core of the lithium supplementing material includes a plurality of micropores 1 and a plurality of mesopores 2, and the shell of the lithium supplementing material includes a plurality of mesopores 2 and a plurality of macropores 3.

It should be understood that the shape, size, etc. of the plurality of micropores located in the core/core may be at least partially the same, or may be different, of course, the shape, size, etc. of the plurality of mesopores located in the core/core may be at least partially the same, or may be different, of course; similarly, the shapes, sizes, etc. of the plurality of mesopores located in the surface layer/the shell may be at least partially the same, or may be different, or the shapes, sizes, etc. of the plurality of macropores located in the surface layer/the shell may be at least partially the same, or may be different; the shape, size, etc. of the plurality of mesopores located in the core/core and the plurality of mesopores located in the surface layer/shell may be at least partially the same, or may be different, and are not particularly limited herein.

In the lithium supplementing material provided by the embodiment of the application, micropores and/or mesopores are distributed in the core of the hierarchical porous structure, macropores are distributed in the surface layer of the hierarchical porous structure, or micropores are distributed in the core of the hierarchical porous structure, and mesopores and/or macropores are distributed in the surface layer of the hierarchical porous structure, so that the pore diameter of the pore is enlarged along the direction from the core to the surface layer of the lithium supplementing material, and electrolyte is conveniently infiltrated from the surface layer to the core, namely, electrolyte is conveniently infiltrated from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, thereby being beneficial to playing of lithium supplementing capacity, and can also reduce the residual alkali number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved.

Further, the value range of the number ratio of micropores, mesopores and macropores is as follows: (20-80%) and (10-70%) and (3-70%).

Illustratively, the number ratio of microwells in all wells may be 20%, 30%, 40%, 50%, 60%, 80%, or the like.

Illustratively, the number ratio of mesopores in all the pores can be 10%, 20%, 30%, 50%, 60% or 70%, etc.

Illustratively, the ratio of the number of macropores in all the pores may be 3%, 30%, 40%, 50%, 60%, or 70%, etc.

In the lithium supplementing material provided by the embodiment of the application, the hierarchical porous structure is provided with micropores, mesopores and macropores, and the numerical range of the number ratio of the micropores, the mesopores and the macropores is as follows: (20-80%):

(10-70 percent) of the lithium ion supplementing material, namely (3-70 percent), which is favorable for the release of lithium ions in the lithium supplementing material, the infiltration of electrolyte, the material transmission at the interface and the like, and simultaneously can ensure that the lithium supplementing material has good structural stability.

Further, the lithium supplementing material comprises a lithium-rich metal oxide, and the chemical formula of the lithium-rich metal oxide is Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is selected from at least one metal element from IB group to VIIIB group, IVA group and VA group, x is more than 1 and less than 10, y is more than 0, and z is more than 0 and less than 13.

Further, li _x M _y O _z M is at least one element selected from iron, nickel, manganese, copper, zinc, cobalt, chromium, zirconium, antimony, titanium, vanadium, molybdenum and tin, x is more than or equal to 2 and less than or equal to 8, y is more than 0, and z is more than 0 and less than 13. In particular embodiments, the lithium-rich metal oxide may be Li ₅ FeO ₄ 、Li ₆ MnO ₄ 、Li ₆ CoO ₄ 、Li ₆ ZnO ₄ 、Li ₂ NiO ₂ 、Li ₂ CuO ₂ 、Li ₂ CoO ₂ 、Li ₂ MnO ₂ 、Li ₂ Ni _0.5 Mn _1.5 O ₄ 、Li ₂ Ni _0.5 Cu _0.5 O ₂ At least one of the following. It should be noted that some of the above lithium-rich metal oxides can be directly used as lithium-rich positive electrode materials, such as Li ₂ NiO ₂ 、Li ₂ CuO ₂ 、Li ₂ CoO ₂ 、Li ₂ MnO ₂ 、Li ₂ Ni _0.5 Mn _1.5 O ₄ 。

Further, the lithium supplementing material is in a core-shell structure, and the chemical formula of the core of the lithium supplementing material is different from the M element in the chemical formula of the surface layer of the lithium supplementing material. The core and the surface layer of the lithium supplementing material are composed of different lithium-rich metal oxides, so that the advantages of the different lithium-rich metal oxides can be combined, and the comprehensive performance of the lithium supplementing material is improved. Of course, the core and the surface layer of the lithium supplementing material may be composed of the same lithium-rich metal oxide.

In the core-shell structure, the shell of the core-shell structure is the surface layer of the lithium supplementing material, and the inner core of the core-shell structure is the core of the lithium supplementing material.

The ratio of the mass of the inner core to the mass of the outer shell of the lithium supplementing material can be in the range of 70-50:30-50. Further, the ratio of the mass of the core to the mass of the shell of the lithium supplementing material may be in the range of 60-50:40-50. Illustratively, the ratio of the mass of the inner core to the mass of the outer shell of the lithium-compensating material may be 70-50:30-50, 60-50:40-50, 50-50:50-50, etc. Because the shell of the lithium supplementing material is provided with the second hole with larger hole diameter, the shell mass of the lithium supplementing material is preferably smaller than or equal to the core mass, so that the electrolyte can be ensured to be quickly infiltrated with the surface of the lithium supplementing material, and meanwhile, harmful substances in the external environment can be prevented from corroding the lithium supplementing material.

The lithium supplementing material provided by the embodiment of the application has a core-shell structure, and the chemical formulas of the inner core and the outer shell of the core-shell structure are different, so that the lithium supplementing material with multiple element types can be obtained. Under the action of voltage and current, chemical bonds of the lithium supplementing material can be changed, so that the structural stability, the conductivity and the like of the lithium supplementing material can be enhanced, and the energy density and the like of the lithium ion battery can be improved.

In the preparation process of the lithium supplementing material provided by the embodiment of the application, the first holes are formed by using the organic pore-forming agent, and the carbon material can be formed by sintering the organic pore-forming agent at high temperature, so that the conductivity of the lithium supplementing material is improved.

Further, the value range of the ratio of the thickness of the surface layer to the radius of the lithium supplementing material is 30-50%; and/or the thickness of the surface layer is in the range of 4-30000nm.

Illustratively, the ratio of the thickness of the surface layer of the lithium-compensating material to the radius of the lithium-compensating material may be 30%, 35%, 40%, 45%, 47%, 50%, or the like.

Illustratively, the thickness of the surface layer of the lithium supplementing material may be 4nm, 100nm, 500nm, 1000nm, 2000nm, 30000nm, or the like.

The lithium supplementing material provided by the embodiment of the application is beneficial to the release of lithium ions, the infiltration of electrolyte, the material transmission at the interface and the like, and meanwhile, the lithium supplementing material can be ensured to have good structural stability.

Further, the particle diameter D50 of the lithium supplementing material satisfies: d50 is more than or equal to 0.5 μm and less than or equal to 100 μm.

Illustratively, the particle size D50 of the lithium-compensating material may be 0.5 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, or the like.

If the particle size of the lithium supplementing material provided by the embodiment of the application is too small, the dispersion of the lithium supplementing material particles in the slurry of the positive plate is not facilitated; if the particle size is too large, electron conduction, ion conduction, and the like of the positive electrode sheet may be affected, and thus the electrical performance of the lithium ion battery may be affected. Therefore, the particle size of the lithium supplementing material provided by the embodiment of the application is set in a proper range, so that the dispersion of the lithium supplementing material particles in the slurry of the positive plate is facilitated, the influence on the electronic conduction, the ion conduction and the like of the positive plate can be reduced/eliminated, and the conductivity, the stability and the like of the lithium supplementing material can be better.

Further, the porosity of the lithium supplementing material is in the range of 5-80%; and/or the specific surface area of the lithium supplementing material is in the range of 3-300m ² /g; and/or the tap density of the lithium supplementing material is 2-3.5g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the And/or the residual alkalinity of the lithium supplementing material is less than 5 percent.

Illustratively, the porosity of the lithium-compensating material may be 5%, 20%, 45%, 55%, 60%, 80%, or the like. Thereby not only facilitating the transmission of lithium ions, but also not increasing the preparation difficulty, being beneficial to the storage of the lithium supplementing material, simultaneously, reducing/isolating the contact of the lithium supplementing material and air, avoiding the corrosion of water, oxygen, carbon dioxide and the like in the air to the lithium supplementing material, thereby improving the stability of the lithium supplementing material.

And/or, exemplary, the specific surface area of the lithium supplementing material may be 3m ² /g、50m ² /g、100m ² /g、200m ² /g、250m ² /g or 300m ² /g, etc. The specific surface area of the preferred lithium supplementing material is in the range of 5-150m ² Per gram, the specific surface area of the lithium supplementing material may be 5m ² /g、30m ² /g、50m ² /g、80m ² /g、100m ² /g or 150m ² /g, etc. The lithium supplementing material is of a hierarchical porous structure, namely, the inside is of a small-aperture structure, and the outside is of a larger-aperture structure, so that the specific surface area of the lithium supplementing material is increased, the lithium supplementing capacity of the lithium supplementing material, the transmission rate of lithium ions and the like are improved; the lithium supplementing material has larger specific surface area, so that the purity of the lithium supplementing material is higher, and the high specific surface area provides a larger reaction surface for the intercalation and deintercalation of lithium ions in the charge and discharge process, thereby improving the charge and discharge activity of the lithium supplementing material.

And/or, exemplary, the tap density of the lithium-supplementing material may be 1g/cm ³ 、1.3g/cm ³ 、1.5g/cm ³ 、2g/cm ³ 、2.4g/cm ³ Or 2.9g/cm ³ Etc. The higher the tap density of the lithium supplementing material is, the higher the energy density of the lithium supplementing material is, and the particles of the lithium supplementing material are not easy to agglomerate in the slurry of the positive plateThereby making the lithium supplementing material more stable.

And/or, illustratively, the residual alkalinity of the lithium-compensating material may be 0.5%, 1%, 2%, 3%, 3.5%, or 4%, etc. The lower the residual alkalinity of the lithium supplementing material is, the more stable the residual alkali interface is, and the higher the purity of the lithium supplementing material is, so that the utilization rate of the lithium supplementing material can be improved.

Further, the lithium supplementing material further comprises a coating layer for coating the surface layer, and the material of the coating layer is at least one of carbon (C), oxide, carbide, phosphate and nitride.

The oxide may be, for example, silicon oxide (SiO ₂ ) Zinc oxide (ZnO), zirconium oxide (ZrO ₂ ) Any of the following; the carbide may be any one of tungsten carbide (WC), molybdenum carbide (MoC), and the like; the phosphate may be lithium phosphate (Li) ₃ PO ₄ ) Aluminum phosphate (AlPO) ₄ ) Or the like, the nitride may be carbon nitride (C ₃ N ₄ ) Molybdenum nitride (MoN), and the like.

The present application will be described only in connection with the point of the application, and the remaining structure may be obtained by referring to the related art, which will not be described in detail herein.

In a second aspect, embodiments of the present application also provide a method of preparing the above lithium-supplementing material.

The preparation method of the lithium supplementing material provided by the embodiment of the application has the technical flow shown in the figure 3, and comprises the following steps:

s1, mixing the first M source with a pore-forming agent to obtain a second M source with a hierarchical porous structure.

The core of the second M source is provided with first holes, the surface layer of the second M source is provided with second holes, and the aperture of the second holes is larger than that of the first holes.

The first M source may be at least one metal oxide, metal hydroxide, metal carbonate, metal nitrate, metal sulfate, metal acetate, metal chloride, etc., wherein M may be at least one metal element selected from group IB to group VIIIB, group IVA, and group VA. By way of example, M may be at least one element selected from iron, nickel, manganese, copper, zinc, cobalt, chromium, zirconium, antimony, titanium, vanadium, molybdenum, tin.

S2, mixing the second M source with a lithium source to obtain the lithium supplementing material with the hierarchical porous structure.

The core of the lithium supplementing material is provided with first holes, and the surface layer of the lithium supplementing material is provided with second holes.

The lithium source may be at least one of lithium hydroxide, lithium oxide, lithium carbonate, lithium sulfate, lithium oxalate, and the like. These lithium sources are sintered at high temperatures and lithium ions can migrate into the lithium-replenishing material to react with metal ions to form a lithium-rich positive electrode active material in situ within the lithium-replenishing material.

In the preparation method of the lithium supplementing material provided by the embodiment of the application, the first M source forms a hierarchical porous structure through the pore-forming agent, and then the first M source is combined with the lithium source to obtain the lithium supplementing material with the hierarchical porous structure, and the unique hierarchical pore channel structure of the lithium supplementing material can facilitate the infiltration of electrolyte from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, is beneficial to exertion of lithium supplementing capacity, and can also reduce the residual base number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved; in addition, the second M source with the hierarchical porous structure has abundant surface holes, increases active sites which react with the lithium source, can fully react with the lithium source, and reduces the residual lithium amount, thereby reducing the residual alkali number of the surface interface of the lithium supplementing material, improving the utilization rate of the lithium supplementing material, and the preparation method has the advantages of simple process, low synthesis cost, easy popularization and application and the like.

Further, in the step S1, the first M source is mixed with the porogen to obtain a second M source with a hierarchical porous structure, which includes the following steps:

and S10, sintering the first M source and the first pore-forming agent in a protective atmosphere at 100-600 ℃ to obtain a third M source with a porous structure.

The first pore-forming agent may be an organic substance. The present application is not particularly limited to the first pore-forming agent, and the first pore-forming agent may be at least one of various synthetic fibers, natural fibers, modified fibers, and the like, by way of example. Specifically, the first pore-forming agent may be at least one of polyvinyl alcohol (PVA), urea, polyvinyl chloride (PVC), polystyrene (PS), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyvinyl butyral Ding Quanzhi (PVB), and the like.

The porous structure of the third M source may have a plurality of pores having the same pore size; alternatively, the porous structure of the third M source may have a porous structure having pore diameter portions different from each other, and is not particularly limited herein.

The protective atmosphere is not particularly limited, and may include at least one of inert gases such as nitrogen, argon, helium, neon, and the like. The third M source is more active and therefore needs to be reacted in an inert atmosphere.

The present application is not particularly limited to the above sintering temperature, and the sintering temperature may be, for example, 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, or the like. The sintering time is not particularly limited, and the value range of the sintering time can be 1-15h by way of example. Specifically, the sintering time may be 1h, 3h, 5h, 8h, 10h, 15h, or the like. Thus, the reaction is more sufficient, the crystal grain is reduced/avoided from becoming larger, the multiplying power performance, the compaction density and the like of the third M source are reduced/avoided from being reduced, and the generated third M source product is more uniform.

And S11, sintering the third M source and the second pore-forming agent in a protective atmosphere at 100-600 ℃ to obtain the second M source with the hierarchical porous structure.

The first pore-forming agent may be an inorganic substance. The second pore-forming agent is not particularly limited, and may be, for example, ammonium carbonate ((NH 4) ₂ CO ₃ ) Ammonium bicarbonate (NH) ₄ HCO ₃ ) Ammonium Nitrate (NH) ₄ NO ₃ ) Magnesium bicarbonate (Mg (HCO) ₃ ) ₂ ) Calcium bicarbonate (Ca (HCO) ₃ ) ₂ ) Sodium bicarbonate (NaHCO) ₃ ) Potassium bicarbonate (KHCO) ₃ )、Ammonium chloride (NH) ₄ Cl), and the like.

The protective atmosphere is not particularly limited, and may include at least one of inert gases such as nitrogen, argon, helium, neon, and the like. The second M source is more active and therefore needs to be reacted in an inert atmosphere.

In the above step, the sum of the masses of the first porogen and the second porogen may have a value in the range of 10-40wt% of the mass percentage of the first M source. Specifically, the mass percent of the porogen in the first M source may be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 40wt%, or the like. Thereby not only facilitating the preparation of the hierarchical porous structure of the lithium supplementing material, but also avoiding the increase of cost; in addition, the porosity, specific surface area and the like of the lithium supplementing material are not excessively high, and the storage of the lithium supplementing material is facilitated.

In the above steps, the first pore-forming agent: the mass percentage of the second pore-forming agent is 50-90:10-50. Illustratively, the first pore-conforming agent: the mass percent of the second porogen may be 50-90:10-50, 40-90:20-50, or 30-90:30-50, etc. By setting the ratio of the mass of the first porogen to the mass of the second porogen within a suitable range, a hierarchical porous structure can be better achieved.

The present application is not particularly limited to the above sintering temperature, and the sintering temperature may be, for example, 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, or the like. The sintering time is not particularly limited, and the value range of the sintering time can be 1-10h by way of example. Specifically, the sintering time may be 1h, 3h, 5h, 8h, 9h, 10h, or the like. Thus, the reaction is more sufficient, the crystal grain is reduced/avoided from becoming larger, the multiplying power performance, the compaction density and the like of the second M source are reduced/avoided from being reduced, and the generated second M source product is more uniform.

Further, in the step S2, the second M source and the lithium source are mixed to obtain the lithium supplementing material with the hierarchical porous structure, which includes the following steps:

s21, mixing the second M source with the lithium source, and sintering at 500-900 ℃ in a protective atmosphere to obtain the lithium supplementing material with the hierarchical porous structure.

The protective atmosphere is not particularly limited, and may include at least one of inert gases such as nitrogen, argon, helium, neon, and the like. The lithium-supplementing material has high activity and thus needs to be reacted in an inert atmosphere.

The present application is not particularly limited to the above-mentioned range of sintering temperature, and the range of sintering temperature may be 500-900 ℃. Specifically, the sintering temperature may be 500 ℃, 600 ℃, 700 ℃, 750 ℃, 800 ℃, 900 ℃, or the like. Therefore, the reaction is more sufficient, the crystal grains are reduced/avoided from becoming larger, the rate capability, compaction density and the like of the lithium supplementing material are reduced/avoided from being reduced, and the generated lithium supplementing material is more uniform.

According to the preparation method of the lithium supplementing material, firstly, the first M source and the first consistent pore agent are sintered for a period of time at high temperature, and the first consistent pore agent with stronger alkalinity can enable the first M source to be porous, so that the third M source with a porous structure is obtained; then sintering the third M source and the second pore-forming agent for a period of time at a high temperature, wherein the second pore-forming agent with weaker alkalinity can further increase the pore diameters of a plurality of pores positioned close to the surface of the third M source without influencing the pore diameters of a plurality of pores positioned far away from the surface of the third M source, so that the second M source with a hierarchical porous structure is obtained; and then sintering the second M source and the lithium source for a period of time at high temperature to obtain the lithium supplementing material.

The unique hierarchical pore structure of the lithium supplementing material can facilitate the electrolyte to infiltrate from outside to inside; meanwhile, the aperture of the first hole of the core is smaller, so that the stability of the whole structure of the lithium supplementing material is guaranteed; in addition, the unique hierarchical pore structure of the lithium supplementing material can improve or solve the negative influence of ion diffusion, is beneficial to release of lithium ions, infiltration of electrolyte, substance transmission at an interface and the like, is beneficial to exertion of lithium supplementing capacity, and can also reduce the residual base number of the surface interface of the lithium supplementing material, so that the utilization rate of the lithium supplementing material is improved; in addition, the second M source with the hierarchical porous structure has abundant surface holes, increases active sites which react with the lithium source, can fully react with the lithium source, and reduces the residual lithium amount, thereby reducing the residual alkali number of the surface interface of the lithium supplementing material, improving the utilization rate of the lithium supplementing material, and the preparation method has the advantages of simple process, low synthesis cost, easy popularization and application and the like.

In a third aspect, an embodiment of the present application further provides a positive electrode sheet. The positive plate comprises a positive current collector and a positive active layer combined on the surface of the positive current collector, wherein the positive active layer comprises the lithium supplementing material or the lithium supplementing material prepared by the preparation method of the lithium supplementing material.

The positive electrode active layer may include other materials in addition to the lithium supplementing material, for example: positive electrode active material, binder, conductive agent, etc.

Wherein the positive electrode active material may include lithium cobaltate (LiCoO) ₂ ) Lithium manganate (LiMn) ₂ O ₄ ) Lithium iron phosphate (LiFePO) ₄ ) Lithium manganese phosphate, lithium vanadium phosphate (Li) ₃ V ₂ (PO4) ₃ ) Lithium vanadyl phosphate (LiVOPO) ₄ ) Lithium vanadium fluorophosphate (LiVOPO) ₄ F) Lithium titanate (Li) ₄ Ti ₅ O), lithium nickel cobalt manganate (LiNiCoMnO) ₂ ) Lithium nickel cobalt aluminate (LiNiAlCoO) ₂ ) One or more of the following.

The binder may be a conventional electrode binder such as one or more including polyvinylidene chloride (PVDC), soluble Polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), acrylonitrile (AN) copolymer, sodium Alginate (SA), chitosan (CTS), and chitosan derivatives.

The conductive agent may be a conventional conductive agent such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotube.

In an embodiment, the preparation process of the positive electrode sheet may be: the lithium supplementing material, the conductive agent and the binder or the positive electrode active material are further mixed to obtain electrode slurry, the positive electrode slurry is coated on a positive electrode current collector, and the positive electrode plate is prepared through the steps of drying, rolling, die cutting and the like.

The positive plate of the embodiment of the application contains the lithium supplementing material of the embodiment of the application, so that the positive plate of the embodiment of the application has high energy density, lithium supplementing effect, high cycle performance and long service life; moreover, the lithium supplementing material can effectively improve the slurry coagulation phenomenon of the lithium supplementing material, improve the environmental stability, the circulation stability, the structural stability and the like of the lithium supplementing material, and prolong the use and the storage life of the lithium supplementing material, thereby prolonging the use and the storage life of the positive plate.

In a fourth aspect of the present application, a secondary battery is provided. The application comprises a positive plate and a negative plate, wherein the positive plate comprises the positive plate.

The secondary battery according to the embodiment of the present application may include necessary components such as a separator and an electrolyte, and may include other necessary or auxiliary components. The positive plate is the positive plate of the embodiment of the application, namely, the positive active layer contained in the positive plate contains the lithium supplementing material of the embodiment of the application.

The secondary battery provided by the embodiment of the application contains the lithium supplementing material of the embodiment of the application, and the lithium supplementing material of the embodiment of the application based on the above text has high energy density, lithium supplementing effect and the like, so that the secondary battery provided by the application has excellent first coulombic efficiency, high energy density, high cycle performance, high capacity retention rate, long service life and stable electrochemical performance.

The lithium supplementing material, the preparation method and the application thereof and the like of the embodiment of the application are illustrated by specific examples.

1. Lithium supplementing material and preparation method thereof are as follows:

example 1

The embodiment provides a lithium supplementing material. The lithium supplementing material comprises Li with a hierarchical porous structure ₅ FeO ₄ The core of the lithium supplementing material is provided with micropores, the surface layer of the lithium supplementing material is provided with mesopores and macropores from inside to outside, the pore diameter of the micropores is about 1.3nm, the pore diameter of the mesopores is about 35.4nm, the pore diameter of the macropores is about 60.3nm, and the number ratio of the micropores, the mesopores and the macropores is 70 percent to 10 percent to 20 percent.

The preparation method of the lithium supplementing material comprises the following steps:

s011, preparation of a third M source:

uniformly mixing ferric chloride and polyvinyl alcohol according to the mass ratio of 100:6, sintering for 5 hours at the temperature of 500 ℃ under nitrogen, and washing residual carbon materials with ethanol to obtain the porous third M source.

S012, preparation of a second M source:

mixing a third M source with sodium bicarbonate according to the mass ratio of 100:4, sintering for 10 hours at the temperature of 600 ℃ under nitrogen, and washing residual impurities with deionized water to obtain the ferric oxide with the hierarchical porous structure.

S013, preparing a lithium supplementing material:

mixing ferric oxide with a hierarchical porous structure and lithium hydroxide according to the molar ratio of 0.5:5, and sintering at the temperature of 900 ℃ under nitrogen to obtain Li with the hierarchical porous structure ₅ FeO ₄ And (3) a lithium supplementing material.

In the above step, the mass ratio of ferric chloride to porogen=100:10, wherein the polyvinyl alcohol: sodium bicarbonate mass ratio = 6:4.

Example 2

The present embodiment provides a lithium supplementing material comprising Li of a hierarchical porous structure ₅ FeO ₄ The core of the lithium supplementing material is distributed with micropores, the surface layer of the lithium supplementing material is distributed with mesopores, the pore diameter of the micropores is about 1.4nm, the pore diameter of the mesopores is about 45.8nm, and the quantity ratio of the micropores to the mesopores is 70 percent to 30 percent.

s021 preparation of a third M source: s011 as in example 1, except that ferric chloride and polyvinyl chloride were mixed at a mass ratio of 100:8.

S022, preparation of a second M source: s012 in example 1, except that the third M source was mixed with ammonium carbonate at a mass ratio of 100:2.

S023, preparation of lithium supplementing materials: s013 in example 1.

In the above steps, the mass ratio of ferric chloride to porogen=100:10, wherein the mass ratio of polyvinyl chloride to ammonium carbonate=8:2.

Example 3

The present embodiment provides a lithium supplementing material comprising Li of a hierarchical porous structure ₅ FeO ₄ The core of the lithium supplementing material is distributed with micropores, the surface layer of the lithium supplementing material is distributed with macropores, the aperture of the micropores is about 1.7nm, the aperture of the macropores is about 126.3nm, and the number ratio of the micropores to the macropores is 70 percent to 30 percent.

s031, preparation of a third M source: s011 as in example 1, except that iron chloride and polyvinyl alcohol were mixed in a mass ratio of 100:10.5 mixing.

S032, preparation of a second M source: s012 in example 1 is the same except that the third M source is mixed with ammonium bicarbonate at a mass ratio of 100:4.5.

S033, preparation of lithium supplementing materials: s013 in example 1.

In the above steps, the mass ratio of ferric chloride to pore-forming agent is=100:15, wherein the mass ratio of polyvinyl alcohol to ammonium bicarbonate is=10.5:4.5.

Example 4

This example provides a lithium supplementing material that differs from the lithium supplementing material provided in example 1 only in that: the lithium supplementing material of this example includes a hierarchical porous structure of Li ₆ MnO ₄ 。

s041, preparation of a third M source: s011 as in example 1, except that ferric chloride is replaced with manganese chloride.

S042, preparation of a second M source: s012 in example 1.

S043, preparation of a lithium supplementing material:

mixing manganese oxide with a hierarchical porous structure and lithium hydroxide according to a molar ratio of 1:6, and sintering at 900 ℃ under nitrogen to obtain Li with the hierarchical porous structure ₆ MnO ₄ And (3) a lithium supplementing agent.

In the above steps, the mass ratio of manganese chloride to porogen=100:10, wherein the mass ratio of polyvinyl alcohol to sodium bicarbonate=6:4.

Example 5

The present embodiment provides a lithium supplementing material comprising Li of a hierarchical porous structure ₅ FeO ₄ The core of the lithium supplementing material is provided with micropores, mesopores and macropores, the micropores, mesopores and macropores are distributed on the surface layer from inside to outside, the pore diameter of the micropores is about 1.3nm, the pore diameter of the mesopores is about 35.4nm, the pore diameter of the macropores is about 60.3nm, and the quantity ratio of the micropores, mesopores and macropores is 95 percent to 4 percent to 1 percent.

preparation of S051, third M source:

uniformly mixing ferric chloride and polymethyl methacrylate according to the mass ratio of 100:21, sintering for 5 hours at the temperature of 500 ℃ under nitrogen, and washing residual carbon materials with methanol to obtain a porous third M source.

S052, preparation of a second M source:

mixing a third M source with ammonium nitrate according to the mass ratio of 100:9, sintering for 10 hours at the temperature of 600 ℃ under nitrogen, and washing residual impurities by adopting deionized water to obtain the ferric oxide with the hierarchical porous structure.

S053, preparation of a lithium supplementing material:

mixing ferric oxide with a hierarchical porous structure and lithium hydroxide according to the molar ratio of 0.5:5, and sintering at the temperature of 900 ℃ under nitrogen to obtain Li with the hierarchical porous structure ₅ FeO ₄ And (3) a lithium supplementing agent.

In the above step, the mass ratio of ferric chloride to porogen is=100:30, wherein the mass ratio of polymethyl methacrylate to ammonium nitrate is=21:9.

Example 6

This example provides a lithium supplementing material that differs from the lithium supplementing material provided in example 5 only in that: in the lithium supplementing material of the embodiment, the quantity ratio of micropores to mesopores to macropores is 40 percent to 20 percent.

s061, preparation of a third M source:

uniformly mixing ferric chloride and polymethyl methacrylate according to the mass ratio of 100:22.2, sintering for 10 hours at the temperature of 500 ℃ under nitrogen, and washing residual carbon materials with methanol to obtain the porous third M source.

S062, preparation of a second M source:

mixing a third M source with ammonium nitrate according to the mass ratio of 100:14.8, sintering for 10 hours at the temperature of 600 ℃ under nitrogen, and washing residual impurities by adopting deionized water to obtain the ferric oxide with the hierarchical porous structure.

S063, preparation of lithium supplementing materials:

In the above step, the mass ratio of ferric chloride to porogen=100:37, wherein the mass ratio of polymethyl methacrylate to ammonium nitrate=18.5:18.5.

Example 7

This example provides a lithium supplementing material that differs from the lithium supplementing material provided in example 4 only in that: the lithium supplementing material of this embodiment has a core-shell structure, wherein the core is Li ₂ NiO ₂ The shell is Li ₆ MnO ₄ 。

s071 preparation of a third M source:

and (3) uniformly mixing nickel oxide and polyvinyl alcohol according to the mass ratio of 100:6, sintering for 5 hours at the temperature of 500 ℃ under nitrogen, and washing residual carbon materials with ethanol to obtain the porous third M source.

S072, preparation of a second M source:

and (3) uniformly mixing manganese chloride and sodium bicarbonate according to the mass ratio of 100:4, sintering for 5 hours at the temperature of 500 ℃ under nitrogen, and washing residual impurities by adopting deionized water to obtain the porous second M source.

S073, preparing a core lithium supplementing material:

and mixing the porous third M source with lithium hydroxide according to a molar ratio of 1:2, and sintering for 8 hours at the temperature of 700 ℃ under nitrogen to obtain the lithium supplementing material (core) with the porous structure.

S074, preparing a shell lithium supplementing material:

mixing the porous second M source and lithium hydroxide according to a molar ratio of 1:6, and sintering for 10 hours at 780 ℃ under nitrogen to obtain the lithium supplementing material (shell) with the porous structure.

S075 preparation of a lithium supplementing material:

mixing the lithium supplementing material (inner core) and the lithium supplementing material (outer shell) according to the mass ratio of 70:30, and sintering for 5 hours at the temperature of 600 ℃ under nitrogen to obtain the lithium supplementing material with the core-shell structure.

In the above steps, the mass ratio of nickel oxide to porogen=100:10, wherein the mass ratio of polyvinyl alcohol to sodium bicarbonate=6:4.

Example 8

This example provides a lithium supplementing material that differs from the lithium supplementing material provided in example 7 only in that: the lithium supplementing material of this example contains 3wt% of carbon material.

s081. preparation of third M source:

mixing nickel oxide and polyvinyl alcohol uniformly according to the mass ratio of 100:6, sintering for 5 hours at the temperature of 500 ℃ under nitrogen, and washing the residual part of carbon material by adopting ethanol to obtain a porous third M source.

S082. preparation of a second M2 source: same as S072 in example 7.

S083, preparing a core lithium supplementing material: same as S073 in example 7.

S084, preparing a shell lithium supplementing material: same as S074 in example 7.

S085, preparation of a lithium supplementing material: s075 in example 7.

Comparative example 1

This comparative example provides a lithium supplementing material which is commercially availablePure Li ₅ FeO ₄ And the lithium supplementing material does not have a pore structure.

Comparative example 2

This comparative example provides a lithium supplementing material that is pure Li purchased in the market ₆ MnO ₄ And the lithium supplementing material does not have a pore structure.

Comparative example 3

This comparative example provides a lithium supplementing material that is pure Li purchased in the market ₂ NiO ₂ And the lithium supplementing material does not have a pore structure.

Comparative example 4

The comparative example provides a lithium supplementing material and a preparation method thereof, and the chemical formula of the lithium supplementing material is Li ₅ FeO ₄ The lithium supplementing material only has a micropore structure.

The preparation method of the lithium supplementing material of the comparative example comprises the following steps:

s041, mixing ferric oxide and lithium hydroxide according to a molar ratio of 0.5:5, and sintering at 900 ℃ under nitrogen to obtain Li ₅ FeO ₄ And (3) a lithium supplementing material.

S042, mixing the lithium supplementing material obtained in the step S041 with pore-forming agent ammonium carbonate according to the mass ratio of = 100:1.5, and sintering at 400 ℃ for 3 hours to obtain the lithium supplementing material with a micropore structure.

The lithium-supplementing materials provided in examples 1 to 8 and the lithium-supplementing materials provided in comparative examples 1 to 4 were assembled into a positive electrode and a lithium ion battery, respectively, according to the following methods:

positive electrode: mixing the lithium supplementing material with lithium iron phosphate according to the mass ratio of 4:96 to obtain a mixture, mixing the mixture with polyvinylidene fluoride and SP-Li according to the mass ratio of 93:3:4, ball milling and stirring to obtain positive electrode slurry, coating the positive electrode slurry on the surface of an aluminum foil, vacuum drying overnight at 110 ℃, and rolling to obtain the positive electrode plate.

And (3) a negative electrode: mixing graphite, CMC, SBR and SP according to the mass ratio of 95.8:1.2:2:1, ball milling and stirring to obtain negative electrode slurry, coating the negative electrode slurry on the surface of copper foil, and vacuum drying overnight at 110 ℃ to obtain the negative electrode plate.

Electrolyte solution: ethylene carbonate and ethylmethyl carbonate in a 3:7 volume ratioMixing in proportion, and adding LiPF ₆ Electrolyte is formed, liPF ₆ The concentration of (C) was 1mol/L.

A diaphragm: a polypropylene microporous separator.

And (3) assembling a lithium ion battery: and assembling the button type lithium ion full battery in an inert atmosphere glove box according to the assembling sequence of the graphite negative electrode plate, the diaphragm, the electrolyte and the positive electrode plate.

The electrochemical properties of each lithium ion battery assembled in the above lithium ion battery examples were respectively subjected to the performance test as in table 1, and the test conditions were as follows: constant-current constant-voltage charging, the first-circle charging and discharging voltage is 2.5-4.3V, the current is 0.1C, the cut-off current is 0.01C, and 300 circles of circulation are carried out by the current of 2C, and the cut-off current is 0.01C.

The test results are shown in table 1 below:

TABLE 1

As can be seen from the test results of examples 1-8 and comparative examples 1-4 of Table 1, the electrochemical properties of the lithium batteries prepared with the lithium supplementing material provided by the present application were higher than those of comparative examples 1-4.

This is because: the multi-stage porous lithium supplementing material with the microporous mesoporous and/or macroporous structure with a certain quantity ratio is beneficial to the release of lithium ions, the infiltration of electrolyte, the material transmission at the interface and the like, so that the exertion of the lithium supplementing capacity is facilitated, and meanwhile, in the process of preparing the multi-stage porous lithium supplementing material, the M source has abundant surface holes and more active sites which react with the lithium source, so that the multi-stage porous lithium supplementing material can fully react with the lithium source, the residual lithium quantity is reduced, and the residual base number of the surface interface of the lithium supplementing material is further reduced.

It can be seen from examples 1 to 3 that when the pore size contained in the lithium supplementing material is not uniform, the first charge capacity of the lithium battery is improved to be fluctuated, wherein the electrochemical performance of example 1 is more excellent due to the gradient distribution of micropores, mesopores and macropores.

As can be seen from examples 1-4, when the pore size and the number of the lithium supplementing materials are the same and the types of the lithium supplementing materials are different, the electrochemical properties of the prepared lithium supplementing materials are basically consistent, thereby demonstrating that the lithium supplementing materials have universality.

It can be seen from examples 1 and 5-6 that when the pore sizes of the lithium-compensating materials are the same and the numbers are different, the electrochemical performance of the battery is reduced when the numbers of mesopores and macropores on the outer surface layer are reduced, which indicates that the pore structure of the outer surface layer of the lithium-compensating material is smaller, so that the lithium-compensating material is difficult to fully contact with the electrolyte, and the ion transmission rate at the interface of the lithium-compensating material is further reduced.

As can be seen from examples 1 and 7 to 8, when the lithium supplementing material has a core-shell structure, i.e., the lithium supplementing material of the core is different from the lithium supplementing material of the shell layer, the chemical bond of the lithium supplementing material at the interface of the core and the shell is changed under the action of voltage and current due to the multi-element lithium supplementing material, so that the structural stability, the conductivity and the like of the lithium supplementing material are enhanced, the energy density of the battery is improved, and the electrochemical performance of example 8 is superior to that of example 7 because the carbon containing material is also contained.

The lithium-supplementing materials of comparative examples 1 to 3 were not provided with a pore structure, so that the residual alkali rate was high, and the initial charge capacity, the cycle capacity retention rate, and the like of the corresponding batteries were low. The lithium supplementing material in comparative example 4 has a microporous structure, so that the first charge capacity and the cycle capacity retention rate of the corresponding battery are superior to those of comparative examples 1 to 3. However, the pore structure in comparative example 4 is microporous, which is unfavorable for the infiltration of electrolyte, and the residual alkali on the surface is more, so the electrochemical performance is obviously inferior to that of examples 1-8.

The foregoing examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. The lithium supplementing material is characterized in that the lithium supplementing material is of a hierarchical porous structure, a first hole is distributed in the core of the lithium supplementing material, a second hole is distributed in the surface layer of the lithium supplementing material, and the aperture of the second hole is larger than that of the first hole.

2. The lithium-supplementing material of claim 1, wherein the first pores comprise micropores and/or mesopores and the second pores comprise macropores;

3. The lithium supplementing material according to claim 2, wherein the range of pore diameters of the micropores is smaller than 2nm, and the range of the numerical ratio of the micropores in all the micropores is 5-95%;

4. The lithium-supplementing material according to claim 2 or 3, wherein the numerical range of the number ratio of the micropores, the mesopores, and the macropores is: (20-80%) and (10-70%) and (3-70%).

5. The lithium-supplementing material of claim 4, wherein the lithium-supplementing material comprises a lithium-rich metal oxide having a chemical formula of Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is selected from at least one metal element from IB group to VIIIB group, IVA group and VA group, x is more than 1 and less than 10, y is more than 0, and z is more than 0 and less than 13.

6. The lithium-compensating material of claim 5, wherein the lithium-compensating material is of core-shell structure, the core of the lithium-compensating material having a chemical formula different from the M element in the chemical formula of the surface layer of the lithium-compensating material.

7. The lithium-compensating material of claim 6, wherein the core of the lithium-compensating material is distributed with a carbon material and the carbon material fills the first pores.

8. The lithium-compensating material of claim 7, wherein the ratio of the thickness of the surface layer to the radius of the lithium-compensating material is in the range of 30-50%;

and/or the thickness of the surface layer is in the range of 4-30000nm.

9. The lithium-compensating material of claim 8, wherein the porosity of the lithium-compensating material has a value in the range of 5-80%;

10. The preparation method of the lithium supplementing material is characterized by comprising the following steps of:

11. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer bonded to the surface of the positive electrode current collector, wherein the positive electrode active layer comprises the lithium supplementing material according to any one of claims 1 to 9 or the lithium supplementing material prepared by the preparation method according to claim 10.

12. A secondary battery comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprising the positive electrode sheet of claim 11.