CN117276548A

CN117276548A - Lithium-rich positive electrode material, preparation method thereof, positive electrode plate and secondary battery

Info

Publication number: CN117276548A
Application number: CN202311286517.7A
Authority: CN
Inventors: 谭旗清; 万远鑫; 孔令涌; 裴现一男; 林律欢
Original assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Current assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2023-12-22

Abstract

The application provides a lithium-rich positive electrode material, a preparation method thereof, a positive electrode plate and a secondary battery. The lithium-rich cathode material includes a lithium-rich core material and nanowires. At least part of the nano wires are wound and distributed on the outer surface of the lithium-rich core material. In the application, the nanowire can play a good protection supporting role on the lithium-rich core material, and the residual alkali number of the lithium-rich cathode material is reduced, so that the formed lithium-rich cathode material has higher structural stability and longer service life. In addition, the winding of the nano wire can play a certain buffering role on the lithium-rich core material, so that the problem of volume expansion of the lithium-rich core material is relieved, and internal cracks are prevented. And the winding layer formed by the nanowires can also play an isolating role, so that the interface stability of the lithium-rich anode material is improved.

Description

Lithium-rich positive electrode material, preparation method thereof, positive electrode plate and secondary battery

Technical Field

The application relates to the technical field of batteries, in particular to a lithium-rich positive electrode material, a preparation method thereof, a positive electrode plate and a secondary battery.

Background

The positive electrode material of the battery is an important component of the battery, determines the indexes of the battery such as energy density, service life, safety and the like, and occupies a core position in the battery. Since a solid electrolyte interface film (SEI film) formed by an electrode in a lithium ion secondary battery during the first charge and discharge process consumes limited lithium ions in the battery, a lithium supplementing material is generally added to a positive electrode material to offset irreversible lithium loss caused by formation of the SEI film. However, the structures of the existing positive electrode material and lithium supplementing material are easy to be damaged in the processes of assembly, transportation and the like, and the atomic lattices of the positive electrode material and the lithium supplementing material deform and expand in the process of charging/discharging the battery, so that the battery pole piece is pulverized and falls off, and the electrochemical performance and the service life of the lithium ion battery are low.

Disclosure of Invention

The application provides a lithium-rich positive electrode material, a preparation method thereof, a positive electrode plate and a secondary battery.

In a first aspect, the present application provides a lithium-rich cathode material comprising a lithium-rich core material and nanowires. At least part of the nano wires are wound and distributed on the outer surface of the lithium-rich core material.

In this application, through twining the surface to rich lithium kernel material with the nanowire, the nanowire can play good protection supporting role to rich lithium kernel material. On one hand, the winding of the nano wire can play a certain buffering role on the lithium-rich core material, so that the problem of volume expansion of the lithium-rich core material is relieved, and internal cracks are prevented. On the other hand, the winding layer formed by the nanowires can also play an isolating role, so that the corrosion of external water vapor to the lithium-rich core material can be prevented, the lithium-rich core material can be isolated from electrolyte, the occurrence of side reaction on the surface of the lithium-rich core material is reduced, and the interface stability of the lithium-rich cathode material is improved.

In one embodiment, the lithium-rich core material is a secondary particle, the secondary particle is composed of a plurality of primary particles, and a part of the nanowire is wound and filled in the gaps of the primary particles; and/or, part of the nano wires are also wound and distributed on the outer surface of the primary particles.

In one embodiment, a portion of the nanowire is wrapped around the outer surface of the primary particle to form a first wrapped coating layer, a portion of the nanowire is wrapped around the outer surface of the secondary particle to form a second wrapped coating layer, and the first wrapped coating layer is connected inside and outside the second wrapped coating layer.

In one embodiment, the primary particles have a porous structure, a portion of the nanowire wrap being contained within the porous structure; and/or, part of the nanowire penetrates through the porous structure

In one embodiment, the thickness of the first winding coating layer is 1nm to 10 μm.

In one embodiment, the second winding coating layer has a thickness of 2-nm to 30 μm.

In one embodiment, the primary particles have a particle size D50 of 50nm to 4 μm.

In one embodiment, the secondary particles have a particle size D50 of 5 μm to 70 μm.

In one embodiment, the nanowires comprise 0.1% -30% of the mass percent of the lithium-rich cathode material.

In one embodiment, the nanowires have a diameter of 1nm to 100nm.

In one embodiment, the nanowires have an aspect ratio of 300-1000.

In one embodiment, the nanowires comprise at least one of a reducing material, a carbon material, a metal oxide.

In one embodiment, the lithium-rich core material includes Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 Wherein a1 is more than or equal to 5 and less than or equal to 8, b1 is more than or equal to 0 and less than or equal to 8, c1 is more than 0 and less than or equal to 13, a2 is more than or equal to 1 and less than or equal to 2.2,0, b2 is more than or equal to 3, c2 is more than or equal to 0 and less than or equal to 5, and A and M are respectively selected from at least one of Fe, ni, mn, cu, zn, co, cr, zr, sb, ti, V, mo, sn, al.

In one embodiment, when the lithium-rich core material includes Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 When Li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 The mass ratio of (1-15) to (85-99.9).

In one embodiment, the lithium-rich core material includes a lithium-rich metal oxide and a positive electrode active material.

In one embodiment, when the lithium-rich core material includes a lithium-rich metal oxide and a positive electrode active material, the mass ratio of the lithium-rich metal oxide to the positive electrode active material is (0.1-15) to (85-99.9).

In a second aspect, the present application provides a method for preparing a lithium-rich cathode material, where the method for preparing a lithium-rich cathode material includes: and mixing the lithium-rich core material with the nanowire, and sintering under an inert atmosphere to obtain the lithium-rich anode material.

In a third aspect, the present application provides a positive electrode sheet, where the positive electrode sheet includes the lithium-rich positive electrode material described above, or includes the lithium-rich positive electrode material prepared by the preparation method of the lithium-rich positive electrode material described above.

In a fourth aspect, the present application provides a secondary battery comprising a negative electrode tab, a separator, and a positive electrode tab as described above.

Drawings

In order to more clearly describe the technical solutions in the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be described below.

FIG. 1 is a schematic diagram (one) of a lithium-rich positive electrode material according to an embodiment of the present application;

fig. 2 is a schematic diagram (ii) of a lithium-rich cathode material according to an embodiment of the present application.

Detailed Description

The following description of the technical solutions in the embodiments of the present application will be made with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments.

The terms "first," "second," and the like herein are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

Furthermore, herein, the terms "upper," "lower," and the like, are defined with respect to the orientation in which the structure is schematically disposed in the drawings, and it should be understood that these directional terms are relative concepts, which are used for descriptive and clarity with respect thereto and which may be varied accordingly with respect to the orientation in which the structure is disposed.

For convenience of understanding, the following description will explain and describe english abbreviations and related technical terms related to the embodiments of the present application.

SEI film: solid Electrolyte Interface, i.e., a solid electrolyte interface film.

Batteries, such as lithium ion secondary batteries, typically include a positive electrode, a negative electrode, and a separator. The positive electrode is used for providing active lithium ions for the battery, and the negative electrode can be used as a carrier of the active lithium ions and electrons in the charging and discharging process of the battery. The diaphragm is arranged between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode, and is used for passing active lithium ions and blocking electrons. The positive electrode comprises a positive electrode active material, the positive electrode active material is used for providing active lithium ions for the lithium ion battery, and the active lithium ions migrate between the positive electrode and the negative electrode of the battery, so that the battery is charged and discharged. Because the surface of the electrode can generate a large amount of solid electrolyte interface film (SEI film) in the first charge and discharge process of the battery, the limited lithium ions in the battery are consumed, so that the capacity of the lithium ions is greatly reduced, and irreversible capacity loss is caused. Typically, the positive electrode further includes a lithium-supplementing material capable of providing lithium ions to counteract irreversible lithium loss due to the formation of an SEI film, thereby improving the overall capacity and energy density of the battery. However, the existing positive electrode active material and lithium supplementing material have poor structural stability, are easy to pulverize and fall off, and reduce the electrochemical performance and the service life of the lithium ion battery.

Referring to fig. 1, the present application provides a lithium-rich cathode material 1, where the lithium-rich cathode material 1 includes a lithium-rich core material 10 and nanowires 20, and at least a portion of the nanowires 20 are wound around and distributed on an outer surface of the lithium-rich core material 10.

The lithium-rich cathode material 1 is in the form of particles, and the structure shown in fig. 1 is a structure of one of the particles in the lithium-rich cathode material 1. The lithium-rich positive electrode material 1 can be used for preparing a positive electrode of a battery. The lithium-rich core material 10 is rich in lithium elements, and the lithium-rich core material 10 includes at least one of a positive electrode active material and a lithium supplementing material.

In one embodiment, the lithium-rich core material 10 includes a lithium-replenishing material, and the nanowires 20 are wound around the outer surface of the core formed from the lithium-replenishing material. At this time, the lithium-rich cathode material 1 may be used for lithium supplementation, i.e., lithium (Li) in the lithium-rich cathode material 1 can be released and transferred to the negative electrode of the battery in the first charging process, so as to offset irreversible lithium loss caused by formation of the SEI film, and improve the total capacity and energy density of the battery.

In one embodiment, the lithium-rich core material 10 includes a positive electrode active material, and the nanowires 20 are wound around the outer surface of the core formed by the positive electrode active material. At this time, the lithium-rich cathode material 1 provides active lithium ions to the battery, and the cathode active material can reversibly deintercalate the active lithium ions, which migrate between the cathode and the anode of the battery, to achieve battery charging and discharging.

In one embodiment, the lithium-rich core material 10 includes a positive electrode active material and a lithium-supplementing material, and the nanowire 20 is wound around an outer surface of the core formed of the positive electrode active material and the lithium-supplementing material. At this time, the lithium-rich cathode material 1 can not only provide active lithium ions for the battery to achieve charging and discharging of the battery, but also provide additional lithium ions for counteracting irreversible lithium loss caused by formation of the SEI film.

In this application, nanowires 20 are wrapped around the outer surface of lithium-rich core material 10. The nanowires 20 may be wound around a local outer surface of the lithium-rich core material 10, or the nanowires 20 may be discontinuously wound around and coated on the outer surface of the lithium-rich core material 10, or the nanowires 20 may be continuously wound around and coated on the outer surface of the lithium-rich core material 10. In an embodiment, the nanowires 20 may be wound onto a portion of the outer surface of the lithium-rich core material 10 such that the wound layer formed by the nanowires 20 does not completely cover the entire outer surface of the lithium-rich core material 10. In an embodiment, the nanowires 20 may also be wound to the entire outer surface of the lithium-rich core material 10 such that the nanowires 20 form a dense wound layer on the outer surface of the lithium-rich core material 10, which covers the entire outer surface of the lithium-rich core material 10.

If the nanowire 20 is not wound on the outer surface of the lithium-rich core material 10, when the lithium-rich core material 10 is lithiated or delithiated in the charging or discharging process of the battery, the atomic lattice of the lithium-rich core material 10 is easily deformed and expanded, so that the battery pole piece is pulverized and falls off, and the electrochemical performance and the service life of the lithium ion battery are reduced. Meanwhile, during the process of assembling, storing and transporting the lithium ion battery, the pole piece is easy to be extruded, and the extrusion of the pole piece may cause the damage of the structure of the lithium-rich core material 10 on the pole piece, thereby affecting the performance of the battery.

In the embodiment of the application, the nanowire 20 can play a good role in protecting and supporting the lithium-rich core material 10 by arranging the nanowire 20 and winding the nanowire 20 on the outer surface of the lithium-rich core material 10. On the one hand, the winding of the nano wires 20 can also play a certain role in buffering the lithium-rich core material 10, so that the problem of volume expansion of the lithium-rich core material 10 is relieved, and internal cracks are prevented from being generated. On the other hand, the winding layer formed by the nano wire 20 can also play an isolating role, so that the corrosion of external water vapor to the lithium-rich core material 10 can be prevented, the lithium-rich core material 10 can be isolated from electrolyte, the occurrence of side reaction on the surface of the lithium-rich core material 10 is reduced, and the interface stability of the lithium-rich cathode material 1 is improved.

In general, the lithium-rich cathode material 1 provided by the embodiment of the application has higher structural stability, ensures that the lithium-rich cathode material 1 normally plays a role in supplementing lithium or providing active lithium ions, and improves the electrochemical performance and the service life of a lithium ion battery.

Referring to fig. 2, in one embodiment, the lithium-rich core material 10 is a secondary particle, the secondary particle is composed of a plurality of primary particles, a portion of the nanowires 20 are entangled and filled in the gaps of the primary particles, and/or a portion of the nanowires 20 are entangled to the outer surface of the primary particles. The lithium-rich core material 10 may include primary particles therein, and a portion of the primary particles may be agglomerated to form secondary particles. In the lithium-rich cathode material 1, the lithium-rich cathode material 1 is in a core-shell structure, the inner core of the lithium-rich cathode material 1 can be secondary particles formed by the lithium-rich inner core material 10, and part of the nanowires 20 are wound on the outer surfaces of the secondary particles of the lithium-rich inner core material 10 to form a winding layer. For a plurality of primary particles in the secondary particles, another portion of the nanowires 20 may also be entangled to the outer surface of the primary particles and/or filled between the primary particles. I.e. in the lithium-rich cathode material 1, the nanowires 20 are also provided inside.

It can be understood that, in the lithium-rich cathode material 1, the lithium-rich cathode material 1 has a core-shell structure, and the core of the lithium-rich cathode material 1 may be a primary particle of the lithium-rich core material 10, and the shell of the lithium-rich cathode material 1, that is, the nanowire 20 is wound around the outer surface of the primary particle.

In this embodiment, in the surface or the clearance of the primary particle of rich lithium kernel material 10 and the surface of secondary particle all are equipped with nano wire 20, the structural stability of primary particle and the compactness of connecting between the primary particle have been promoted, and make secondary particle's overall structure inseparabler, nano wire 20's setting makes the rich lithium positive electrode material 1 granule that forms inseparabler, the tap density of rich lithium positive electrode material 1 has been improved, and the deformation and the inflation of the atomic lattice of rich lithium kernel material 10 have been restrained, the emergence of the problem of rich lithium positive electrode material 1 pulverization, droing has been reduced, further the stability of rich lithium positive electrode material 1 has been promoted, thereby the electrochemical performance and the life of lithium ion battery have been improved.

In one embodiment, a portion of the nanowires 20 is wrapped around the outer surface of the primary particles to form a first wrapping layer, a portion of the nanowires 20 is wrapped around the outer surface of the secondary particles to form a second wrapping layer, and the first wrapping layer is connected to the inner and outer sides of the second wrapping layer. Illustratively, a portion of the nanowires 20 are simultaneously wound around the outer surfaces of the primary particles and the secondary particles so that the first wound coating layer is connected to the inside and outside of the second wound coating layer.

In this embodiment of the application, first winding coating is connected with the inside and outside of second winding coating makes rich lithium positive electrode material 1 granule inseparabler, has improved rich lithium positive electrode material 1's tap density, and has restrained the deformation and the inflation of rich lithium kernel material 10's atomic lattice, has reduced the emergence of rich lithium positive electrode material 1 pulverization, the problem of coming off, has further promoted the stability of rich lithium positive electrode material 1 to lithium ion battery's electrochemical performance and life have been improved.

In one embodiment, the first winding cladding and the second winding cladding may not be connected.

In one embodiment, the primary particles have a porous structure with a portion of the nanowire material 20 entangled within the porous structure. The nanowire material 20 is accommodated in the porous structure, which is beneficial to increasing the tap density of primary particles, thereby being beneficial to increasing the energy density of the lithium-rich cathode material 1.

In one embodiment, a portion of the nanowire material 20 is disposed through the porous structure. The nanowire material 20 is arranged in the porous structure in a penetrating manner, so that the bonding strength of the nanowire 20 and primary particles is improved, the nanowire 20 is not easy to fall off from the primary particles, the nanowire 20 can better play a good role in protecting and supporting the lithium-rich core material 10, the volume expansion problem of the lithium-rich core material 10 is relieved, and internal cracks are prevented.

In an embodiment, the nanowire 20 forms a dense winding layer on the outer surface of the lithium-rich core material 10, and the dense winding layer can better protect and buffer the lithium-rich core material 10, so that the particles of the lithium-rich cathode material 1 are more compact, the deformation and expansion of the atomic lattice of the lithium-rich core material 10 are inhibited, and the problems of pulverization and falling of the lithium-rich cathode material 1 are reduced. The lithium-rich cathode material 1 has higher structural stability, and improves the electrochemical performance and the service life of the lithium ion battery.

In one embodiment, the thickness of the first winding cladding is 1nm to 10 μm. The thickness of the first winding coating layer formed on the outer surface of the primary particles of the nanowire 20 affects the performance of the lithium-rich cathode material 1. If the thickness of the first winding clad layer is too small, the winding layer has a weak effect of protecting and buffering the lithium-rich core material 10. If the thickness of the first winding coating layer is too large, the thicker first winding coating layer may hinder the diffusion of lithium ions in the lithium-rich core material 10, affecting the transmission rate of lithium ions, thereby reducing the cycle performance of the lithium-rich cathode material 1. In addition, the thicker first winding coating layer also affects the energy density of the lithium-rich cathode material 1 to reduce the 1 g capacity of the lithium-rich cathode material.

In this embodiment of the present application, the thickness of the first winding coating layer formed on the outer surface of the primary particle by the nanowire 20 is controlled within the range of 1nm-10 μm, so that on one hand, the first winding coating layer formed by the nanowire 20 can better protect and buffer the primary particle of the lithium-rich core material 10, inhibit the deformation and expansion of the atomic lattice of the primary particle of the lithium-rich core material 10, and reduce the pulverization and shedding problems of the lithium-rich cathode material 1. The lithium-rich cathode material 1 has higher structural stability, and improves the electrochemical performance and the service life of the lithium ion battery. On the other hand, the influence of the first winding coating layer on the release and the intercalation of lithium ions is reduced, and the transmission rate of the lithium ions is improved. Meanwhile, the quality of the lithium-rich cathode material 1 is not excessively increased by the first winding coating layer, and the influence on the energy density of the battery caused by the overlarge quality of the first winding coating layer is avoided, so that the battery capacity is reduced.

In one embodiment, the thickness of the first winding cladding may be 1nm, 5nm, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

In one embodiment, the thickness of the second winding cladding is 2nm to 30 μm. The thickness of the second winding coating layer affects the performance of the lithium-rich cathode material 1. If the thickness of the first winding coating layer is too small, it is difficult to tightly agglomerate the primary particles. If the thickness of the first winding coating layer is too large, the thicker first winding coating layer may affect the transmission rate of lithium ions and the energy density of the lithium-rich cathode material 1.

In the embodiment of the application, the thickness of the second winding coating layer formed by the nanowire 20 on the outer surface of the secondary particle is regulated and controlled within the range of 2nm-30 μm, so that on one hand, the overall structure of the secondary particle is more compact, the tap density of the lithium-rich cathode material 1 is improved, the deformation and expansion of the atomic lattice of the lithium-rich core material 10 are restrained, the pulverization and falling problems of the lithium-rich cathode material 1 are reduced, the stability of the lithium-rich cathode material 1 is further improved, and the electrochemical performance and the service life of a lithium ion battery are further improved. On the other hand, the influence of the second winding coating layer on the release and intercalation of lithium ions is reduced, and the transmission rate of the lithium ions is improved. Meanwhile, the quality of the lithium-rich positive electrode material 1 is not excessively increased by the second winding coating layer, and the influence on the energy density of the battery caused by the overlarge quality of the second winding coating layer is avoided, so that the battery capacity is reduced.

In one embodiment, the thickness of the second winding cladding may be 2nm, 5nm, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

In one embodiment, the primary particles have a particle size D50 of 50nm to 4 μm. The particle diameter D50 of the primary particles is the particle diameter corresponding to the case where the cumulative particle size distribution percentage in the primary particles reaches 50%. The particle size of the primary particles affects the performance of the lithium-rich cathode material 1. If the particle diameter of the primary particles is too small, agglomeration is easy, lithium ion deintercalation is not facilitated, and dispersion of the primary particles in the positive electrode slurry is also not facilitated. If the primary particles have a larger particle diameter, the internal electron conduction and ion conduction are not facilitated, and thus the electrical performance of the lithium ion secondary battery is affected.

In the embodiment of the application, the particle diameter D50 of the primary particles is in the range of 50nm-4 mu m, so that the dispersibility of the lithium-rich positive electrode material 1 can be improved while the rapid release of lithium ions is ensured.

In one embodiment, the primary particles may have a particle size D50 of 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 μm, 2 μm, 3 μm or 4 μm.

In one embodiment, the secondary particles have a particle size D50 of 5 μm to 70 μm. The particle diameter D50 of the secondary particles is the particle diameter corresponding to the case where the cumulative particle size distribution percentage in the secondary particles reaches 50%. The particle size of the secondary particles affects the performance of the lithium-rich cathode material 1. If the particle size of the secondary particles is too small, the preparation difficulty of the secondary particles is increased, and the secondary particles are easy to agglomerate to form larger particles, which is not beneficial to the deintercalation of lithium ions. If the secondary particles have a larger particle diameter, the internal electron conduction and ion conduction are not facilitated, and the electrical performance of the lithium ion secondary battery is affected.

In the embodiment of the application, the particle diameter D50 of the secondary particles is in the range of 5-70 μm, so that the dispersibility and the processability of the lithium-rich positive electrode material 1 can be improved while the rapid release of lithium ions is ensured.

In one embodiment, the secondary particles may have a particle size D50 of 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm or 70 μm.

In one embodiment, the nanowires 20 comprise 0.1% -30% of the mass percent of the lithium-rich cathode material 1. Namely, the mass ratio of the nanowire 20 to the lithium-rich cathode material 1 is (0.1-30) to 100. The relative content of the nanowires 20 affects the performance of the lithium-rich cathode material 1. If the mass of the nanowire 20 is relatively low, the nanowire 20 has a weak effect of protecting and buffering the lithium-rich core material 10. If the mass ratio of the nanowire 20 is too large, the nanowire 20 may obstruct the diffusion of lithium ions in the lithium-rich core material 10, affecting the transmission rate of lithium ions, thereby reducing the cycle performance of the lithium-rich cathode material 1. In addition, the relatively large amount of nanowires 20 also affects the energy density of the lithium-rich cathode material 1, reducing the 1 g capacity of the lithium-rich cathode material.

In this embodiment, through setting up nanowire 20 and accounting for 0.1% -30% of the mass percent of rich lithium positive electrode material 1, on the one hand, make nanowire 20 play better protection, the cushioning effect to rich lithium kernel material 10, the winding of nanowire 20 has improved rich lithium positive electrode material 1 granule's compactness, has restrained the deformation and the inflation of rich lithium kernel material 10's atomic lattice, has reduced the emergence of rich lithium positive electrode material 1 chalking, the problem that drops. The lithium-rich cathode material 1 has higher structural stability, and improves the electrochemical performance and the service life of the lithium ion battery. On the other hand, the influence of the nanowire 20 on the extraction and intercalation of lithium ions is reduced, and the transmission rate of the lithium ions is improved. Meanwhile, the quality of the lithium-rich cathode material 1 is not excessively increased by the nano wires 20, and the influence on the energy density of the battery caused by the excessively high content of the nano wires 20 is avoided, so that the capacity of the battery is reduced.

Preferably, the nanowire 20 accounts for 0.5-15% of the mass percent of the lithium-rich cathode material 1. Within this range, the lithium-rich cathode material 1 has more excellent properties.

In one embodiment, the nanowires 20 comprise 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30% of the mass percent of the lithium-rich cathode material 1.

In one embodiment, the nanowires 20 have a diameter of 1nm to 100nm. The diameter size of the nanowires 20 affects the performance of the lithium-rich cathode material 1. If the diameter of the nanowire 20 is too small, the nanowire 20 is easily broken and easily agglomerated, and it is difficult to well protect and buffer the lithium-rich core material 10. If the diameter of the nanowire 20 is too large, the gap between the nanowire 20 and the nanowire 20 is large, so that not only is a compact winding layer difficult to form, but also the thickness of the lithium-rich cathode material 1 is easily and excessively increased, and the energy density of the lithium-rich cathode material 1 is affected.

In the embodiment of the application, the diameter of the nanowire 20 is regulated and controlled within the range of 1nm-100nm, so that the nanowire 20 has larger strength and toughness, is not easy to break and agglomerate, and can form a compact winding layer on the outer surface of the lithium-rich core material 10, so that the nanowire 20 can better protect and buffer the lithium-rich core material 10.

In one embodiment, the diameter of the nanowire 20 may be 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm.

In one embodiment, the aspect ratio of the nanowires 20 is 300-1000. I.e., the ratio of the length to the diameter of the nanowire 20 is 300-1000. The aspect ratio of the nanowires 20 affects the performance of the lithium-rich cathode material 1. If the aspect ratio of the nanowire 20 is too small and the length of the nanowire 20 is too short, the nanowire 20 cannot be wound around the outer surface of the lithium-rich core material 10. If the aspect ratio of the nanowire 20 is too large, the length of the nanowire 20 is too long, which may affect the transmission rate of lithium ions in the lithium-rich core material 10.

In the embodiment of the application, the length-diameter ratio of the nanowire 20 is set in the range of 300-1000, so that the influence of the nanowire 20 on the removal and intercalation of lithium ions can be reduced while the nanowire 20 is ensured to be smoothly wound on the outer surface of the lithium-rich core material 10, and the transmission rate of the lithium ions is improved, so that the lithium-rich cathode material 1 has higher structural stability and more excellent electrochemical performance.

In one embodiment, the aspect ratio of the nanowire 20 is 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000.

In one embodiment, the nanowires 20 comprise at least one of a reducing material, a carbon material, a metal oxide. It is understood that the nanowire 20 is made of at least one of a reducing material, a carbon material, and a metal oxide, and that the nanowire 20 is doped with at least one of a reducing material, a carbon material, and a metal oxide.

The reducing material is a substance having a reducing property that is capable of consuming oxygen, and illustratively, the reducing material is capable of reacting with oxygen, the reaction of the reducing material with oxygen including, but not limited to, redox reactions. The lithium-rich core material 10 may generate active oxygen during charge and discharge, which may generate oxygen. The reducing material can be combined with active oxygen to inhibit the gas generating reaction caused by the active oxygen, and the reducing agent can also be combined with oxygen to reduce the gas generating amount of the battery, so that the safety performance, the electrochemical performance and the stability of the battery are effectively improved.

In one embodiment, the reducing material includes at least one of sulfide, sulfite, a low-valence metal ion-containing compound, ascorbic acid, and the like.

The carbon material has conductivity and the nanowires 20 may be carbon nanowires. The carbon material included in the nanowire 20 can improve the conductivity of the lithium-rich cathode material 1 and accelerate the transfer of electrons, reduce the polarizability of the lithium-rich cathode material 1, and is beneficial to improving the rate capability and the cycle performance of the lithium-rich cathode material 1.

The metal oxide comprises at least one of titanium dioxide, aluminum oxide, silicon monoxide, silicon dioxide, magnesium oxide, manganese oxide, niobium oxide and molybdenum oxide. The metal oxide contributes to increase the moisture resistance of the lithium-rich cathode material 1.

In the embodiment of the present application, the nanowire 20 includes at least one of a reducing material, a carbon material, and a metal oxide, and the performance of the lithium-rich cathode material 1 can be improved according to the requirements.

In one embodiment, the nanowire 20 includes one of a reducing material, a carbon material, and a metal oxide, which reduces the manufacturing cost and difficulty of the manufacturing process of the nanowire 20. Illustratively, in one embodiment, the nanowires 20 comprise a reducing material, and the lithium-rich cathode material 1 has a lower gas yield, which improves the safety performance of the battery. In one embodiment, the nanowires 20 comprise a carbon material to enhance the electrical conductivity of the lithium-rich cathode material 1. In one embodiment, the nanowires 20 comprise a metal oxide, which increases the moisture resistance of the lithium-rich cathode material 1.

In one embodiment, the nanowires 20 comprise two or three of a reducing material, a carbon material, and a metal oxide, which helps to improve the performance of the lithium-rich cathode material 1 in combination. Illustratively, the nanowire 20 comprises a reducing material and a carbon material, and the lithium-rich cathode material 1 has a lower gas yield and a higher electrical conductivity.

In one embodiment, the lithium-rich core material 10 includes Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 Wherein a1 is more than or equal to 5 and less than or equal to 8, b1 is more than or equal to 0 and less than or equal to 8, c1 is more than 0 and less than or equal to 13, a2 is more than or equal to 1 and less than or equal to 2.2,0, b2 is more than or equal to 3, c2 is more than or equal to 0 and less than or equal to 5, and A and M are respectively selected from at least one of Fe, ni, mn, cu, zn, co, cr, zr, sb, ti, V, mo, sn, al. Wherein Li is _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 The lithium-rich positive electrode material 1 can be used as a lithium supplementing material, and lithium (Li) in the lithium-rich positive electrode material 1 can be released and transferred to a battery negative electrode in the first charging process so as to offset irreversible lithium loss caused by formation of an SEI film and improve the total capacity and energy density of the battery. In one embodiment, li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 At least one of them may be used as a positive electrode active material.

Illustratively, li _a1 A _b1 O _c1 Comprises Li ₅ FeO ₄ 、Li ₆ MnO ₄ 、Li ₆ CoO ₄ 、Li ₆ ZnO ₄ Etc.

Illustratively, li _a2 M _b2 O _c2 Comprises Li ₂ NiO ₂ 、Li ₂ MnO ₂ 、Li ₂ CuO ₂ 、Li ₂ CoO ₂ 、Li ₂ Ni _x Cu _(1-x) O ₂ (0 < x < 1), etc.

When Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 When all are used as lithium supplementing materials, li _a1 A _b1 O _c1 High lithium supplementing capacity, but Li _a1 A _b1 O _c1 The gas yield is high in the charging process, the impedance of the battery is increased, and the safety performance and the electrochemical performance of the battery are reduced. While Li is _a2 M _b2 O _c2 Low gas production during charging, but Li _a2 M _b2 O _c2 The lithium supplementing capacity is low, the lithium supplementing effect is poor, and the improvement of the battery performance is limited.

In the present embodiment, the lithium-rich core material 10 includes Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 The lithium supplementing capacity of the lithium-rich core material 10 can be improved, so that the battery capacity is higher, the gas production of the lithium-rich core material 10 can be reduced, and the safety performance of the battery is improved.

In one embodiment, li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 The mass ratio of (1-15) to (85-99.9). Li (Li) _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 The relative content of (2) affects the performance of the lithium-rich core material 10. If Li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 If the mass ratio of (c) is too large, the gas yield of the lithium-rich core material 10 may be increased. If Li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 If the mass ratio is too small, the capacity of the lithium-rich core material 10 may be reduced.

In the examples of the present application, li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 The mass ratio of (1-15) to (85-99.9) is set to be (0.1-15), so that the capacity of the lithium-rich core material 10 is improved, the gas production of the lithium-rich core material 10 is reduced, and the lithium-rich core material 10 has more excellent electrochemical performance.

In one embodiment, the lithium-rich core material 10 includes a lithium-rich metal oxide and a positive electrode active material. Wherein the positive electrode active material may be a phosphate-based positive electrode active material. The lithium-rich metal oxide can be a lithium supplementing material or can be used as a positive electrode active material according to different types of the selected lithium-rich metal oxide. The lithium supplementing material is used for counteracting irreversible lithium loss caused by forming the SEI film, and the positive electrode active material is used for providing active lithium ions required in the charge and discharge processes of the battery.

In one embodiment, where the lithium-rich core material 10 includes a lithium-rich metal oxide and a positive electrode active material, the mass ratio of the lithium-rich metal oxide to the positive electrode active material is (0.1-15) to (85-99.9). The lithium-rich core material 10 has a relatively large proportion of the positive electrode active material, which is beneficial to improving the electrochemical performance of the lithium-rich core material 10.

In some embodiments, the gas production attenuation rate of the lithium-rich cathode material 1 is greater than 3%. The lithium-rich anode material 1 has a gas production attenuation rate of more than 3% at normal temperature and high temperature. The larger the gas production attenuation rate of the lithium-rich cathode material 1 is, the more effective the gas production problem of the battery can be restrained, and the higher the safety performance of the battery is. In this embodiment of the application, through setting up the surface of the primary particle and the secondary particle at the lithium-rich positive electrode material 1 and all twining the nanowire and forming the coating for the coating is porous structure, can effectively adsorb the produced oxygen of lithium-rich kernel material 10. Further, the nanowire 20 comprises a reducing material, and the reducing material can react with oxygen, so that gas released by the lithium-rich cathode material 1 in the charge and discharge processes of the battery can be effectively inhibited, and the gas generation phenomenon of the battery can be further reduced.

In some embodiments, the lithium-rich positive electrode material 1 has a compacted density in the range of 3.5g/cm ³ -5g/cm ³ . In the embodiment of the application, the nanowire 20 is used for winding the lithium-rich core material 10, so that the compaction density of the lithium-rich cathode material 1 is improved. The compaction density of the lithium-rich cathode material 1 is maintained at a higher level, so that the energy density of the lithium-rich cathode material 1 is improved, the deformation and expansion of the atomic lattice of the lithium-rich core material 10 are inhibited, the pulverization and falling problems of the lithium-rich cathode material 1 are reduced, the stability of the lithium-rich cathode material 1 is further improved, and the electrochemical performance and the service life of a lithium ion battery are improved.

The application provides a preparation method of a lithium-rich cathode material 1, wherein the preparation method of the lithium-rich cathode material 1 comprises the following steps: the lithium-rich core material 10 is mixed with the nanowires 20 and sintered in an inert atmosphere to obtain the lithium-rich cathode material 1.

The preparation method of the lithium-rich cathode material 1 provided by the embodiment of the application is simpler, the lithium-rich cathode material 1 with the nanowire 20 wound on the outer surface of the lithium-rich core material 10 can be prepared, and the prepared lithium-rich cathode material 1 has higher structural stability.

In one embodiment, where the lithium-rich core material 10 comprises a plurality of materials, the lithium-rich core material 10 comprises a lithium-rich metal oxide and a positive electrode active material. The preparation method of the lithium-rich cathode material 1 comprises the following steps: mixing the lithium-rich metal oxide with the positive electrode active material, mixing with the nanowire, and sintering under inert atmosphere to obtain the lithium-rich positive electrode material 1.

In one embodiment, the lithium-rich core material 10 and the nanowires 20 are mixed in a ball-to-material ratio of 10:1 at 30Hz for 1-10 hours, sintered in an inert atmosphere, and then ball-milled in a ball-to-material ratio of 10:1 at 10-25Hz for 1-5 hours.

In one embodiment, the inert atmosphere comprises at least one of nitrogen, argon, helium, neon.

In one embodiment, the sintering temperature of the lithium-rich core material 10 and the nanowire 20 is 650-900 ℃ and the heat preservation time is 2-15 h.

The application provides a positive electrode plate, which comprises the lithium-rich positive electrode material 1 or comprises the lithium-rich positive electrode material 1 prepared by the preparation method of the lithium-rich positive electrode material 1.

The application provides a secondary battery, which comprises a negative electrode plate, a diaphragm and a positive electrode plate.

In order to illustrate the beneficial effects of the methods of the present application, the present application also provides the following examples and comparative examples:

example 1

Example 1 provides a lithium-rich cathode material, wherein the lithium-rich core material is Li ₂ NiO ₂ The nanowire is stannous sulfide nanowire. The nanowires are wound around the outer surfaces of the primary particles and the secondary particles of the lithium-rich core material. Wherein the nanowireThe length of (2) was 5. Mu.m, the thickness of the first winding coat was 15nm, and the thickness of the second winding coat was 30nm.

The preparation method of the lithium-rich positive electrode material comprises the following steps:

Li ₂ NiO ₂ mixing the lithium-rich metal oxide with stannous sulfide nanowire according to the mass ratio of = 100:2, and sintering in nitrogen atmosphere to obtain the lithium-rich anode material.

Example 2

Example 2 provides a lithium-rich cathode material, which is different from the lithium-rich cathode material in example 1 in that in example 2, the nanowires are wound around and coated on the outer surface of the secondary particles of the lithium-rich core material, and no nanowires are present on the outer surface of the primary particles and in the gaps between the primary particles.

Example 3

Example 3 provides a lithium-rich cathode material, which is different from the lithium-rich cathode material in example 1 in that the nanowires in example 3 are discontinuously coated on the outer surface of the lithium-rich core material.

Example 4

Example 4 provides a lithium-rich cathode material, which is different from the lithium-rich cathode material of example 1 in that in example 4, the thickness of the first winding coating layer is 1 μm and the thickness of the second winding coating layer is 2 μm.

Example 5

Example 5 provides a lithium-rich cathode material, which is different from that in example 1 in that in example 5, the length of the nanowire is 10 μm.

Example 6

Embodiment 6 provides a lithium-rich cathode material, which is different from the lithium-rich cathode material in embodiment 1 in that in embodiment 6, the nanowires are carbon nanowires.

Example 7

Example 7 provides a lithium-rich cathode material, which is different from the lithium-rich cathode material of example 1 in that in example 7, the lithium-rich core material is Li ₂ NiO ₂ And Li (lithium) ₅ FeO ₄ And Li (lithium) ₂ NiO ₂ And Li (lithium) ₅ FeO ₄ The mass ratio of (2) is 95:5.

Comparative example 1

Comparative example 1 provides a lithium-rich cathode material, which is different from that in example 1 in that comparative example 1 provides a lithium-rich cathode material that does not include nanowires.

Comparative example 2

Comparative example 2 provides a lithium-rich cathode material, which is different from that of example 5 in that the nanowires of comparative example 2 are not wound to the outer surface of the lithium-rich core material, but are coated in a granular shape to the outer surface of the lithium-rich core material.

The lithium-rich positive electrode materials provided in the above examples and comparative examples were assembled into a positive electrode sheet and a lithium ion battery, respectively, according to the following methods:

and (3) a positive electrode: mixing the lithium-rich positive electrode material with polyvinylidene fluoride and SP-Li in a mass ratio of 80:8:12, 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 a positive electrode plate;

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

electrolyte solution: mixing ethylene carbonate and ethylmethyl carbonate in a volume ratio of 3:7, and adding LiPF6 to form an electrolyte, wherein the concentration of the LiPF6 is 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.

Correlation performance test

Electrochemical performance test:

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, first-turn charging and discharging voltage is 2.0-4.3V, current is 0.1C, and cut-off current is 0.01C.

And (3) gas production test:

when the battery is charged and discharged for the first time, a battery gas production testing device is adopted to detect the gas production after the battery is charged and discharged for the first time.

The test results are shown in table 1 below:

TABLE 1 Performance test results

From the test results of example 1 and comparative example 1 in table 1, it can be seen that the capacity retention rate and the first-cycle gas production attenuation rate of the lithium-rich cathode material containing the embodiment of the application after 50 cycles are both greater than those of comparative example 1, so that the peripheries of the primary particles and the secondary particles of the lithium-rich cathode material are completely wrapped and coated by the nano wires, on one hand, the insulation effect is achieved, on the other hand, a certain buffering effect can be achieved, the volume expansion problem of the lithium-rich material is relieved, the generation of internal cracks is prevented, and meanwhile, the nano wires with reducibility can inhibit the gas released by the lithium-rich cathode material in the charging and discharging processes of the battery because the nano wires can also contain reducibility substances, so that the gas production phenomenon of the battery is reduced.

As can be seen from example 1, comparative example 1 and comparative example 2, although the addition of the granular nanowires to the outer surface of the lithium-rich core material can alleviate the gassing of the lithium-rich cathode material and improve the capacity retention after 50 cycles of the cycle, in example 1, the nanowires are distributed around the peripheries of the primary particles and the secondary particles of the lithium-rich core material in a wound form, and remarkably improve the capacity retention after 50 cycles of the lithium-rich cathode material and the first cycle gassing attenuation.

The nanowires in example 1 have the best combination properties because they are wound around the outer surfaces of the primary particles and the secondary particles of the lithium-rich core material and the coating thickness is within a certain preferred range.

The gaps between the primary particles of the lithium-rich core material in example 2 do not include nanowires, and the outer surface of the part of the lithium-rich core material in example 3 is not wrapped by the nanowires, so that the capacity retention rate and the first-turn gas-generating attenuation rate of the lithium-rich cathode materials in examples 2 and 3 after 50 circles of circulation are reduced, and the comprehensive performance of the lithium-rich cathode materials in examples 2 and 3 is lower than that of example 1.

The thicker coating thickness of the nanowires in example 4 compared to example 1 resulted in difficulty in extraction of lithium ions, which eventually reduced the capacity retention rate of the battery.

The longer length of the nanowires in example 5 results in weaker contact of the nanowires with the lithium-rich cathode material, and thus lower overall performance than in example 1.

In example 6, the first-turn gas attenuation rate was lower than in example 1 because the nanowire material had no reducibility.

Example 7 since the lithium-rich cathode material formed by combining two materials is provided, the contact between the nanowire and the lithium-rich cathode material is also affected, and thus the overall performance is slightly lower than that of example 1

The lithium-rich positive electrode material, the preparation method thereof, the positive electrode plate and the secondary battery provided by the embodiment of the application are described in detail, and specific examples are applied to illustrate the principle and the embodiment of the application, and the description of the embodiment is only used for helping to understand the method and the core idea of the application; meanwhile, as those skilled in the art will have modifications in specific embodiments and application scope in accordance with the ideas of the present application, the present disclosure should not be construed as limiting the present application in view of the above description.

Claims

1. A lithium-rich cathode material, characterized in that the lithium-rich cathode material comprises:

a lithium-rich core material;

and the nanowire is at least partially wound and distributed on the outer surface of the lithium-rich core material.

2. The lithium-rich cathode material according to claim 1, wherein the lithium-rich core material is a secondary particle composed of a plurality of primary particles, and a part of the nanowire is wound and filled in a gap of the primary particles; and/or the number of the groups of groups,

part of the nano wires are wound and distributed on the outer surface of the primary particles.

3. The lithium-rich cathode material of claim 2, wherein a portion of the nanowire is wrapped around the outer surface of the primary particle to form a first wrapped coating, a portion of the nanowire is wrapped around the outer surface of the secondary particle to form a second wrapped coating, and the first wrapped coating is connected inside and outside the second wrapped coating.

4. The lithium-rich cathode material of claim 2, wherein the primary particles have a porous structure, a portion of the nanowire being wound and contained within the porous structure; and/or the number of the groups of groups,

and part of the nanowire penetrates through the porous structure.

5. The lithium-rich cathode material according to claim 3, wherein the thickness of the first winding coating layer is 1nm to 10 μm; and/or the number of the groups of groups,

the thickness of the second winding coating layer is 2nm-30 mu m; and/or the number of the groups of groups,

the particle diameter D50 of the primary particles is 50nm-4 mu m; and/or the number of the groups of groups,

the secondary particles have a particle diameter D50 of 5 μm to 70 μm.

6. The lithium-rich cathode material according to claim 3, wherein the nanowires account for 0.1% -30% by mass of the lithium-rich cathode material; and/or the number of the groups of groups,

the diameter of the nanowire is 1nm-100nm; and/or the number of the groups of groups,

the aspect ratio of the nanowire is 300-1000.

7. The lithium-rich cathode material of claim 1, wherein the nanowires comprise at least one of a reducing material, a carbon material, a metal oxide.

8. The lithium-rich cathode material of claim 1, wherein the lithium-rich core material comprises Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 Wherein a1 is more than or equal to 5 and less than or equal to 8, b1 is more than or equal to 0 and less than or equal to 8, c1 is more than or equal to 0 and less than or equal to 13, a2 is more than or equal to 1 and less than or equal to 2.2,0, b2 is more than or equal to 3, c2 is more than or equal to 0 and less than or equal to 5, and A and M are respectively selected from at least one of Fe, ni, mn, cu, zn, co, cr, zr, sb, ti, V, mo, sn, al; and/or the number of the groups of groups,

the lithium-rich core material includes a lithium-rich metal oxide and a positive electrode active material.

9. The lithium-rich cathode material of claim 6, wherein when the lithium-rich core material comprises Li _a1 A _b1 O _c1 And Li (lithium) _a2 M _b2 O _c2 When Li _a1 A _b1 O _c1 With Li _a2 M _b2 O _c2 The mass ratio of (1-15) to (85-99.9); and/or the number of the groups of groups,

when the lithium-rich core material comprises a lithium-rich metal oxide and a positive electrode active material, the mass ratio of the lithium-rich metal oxide to the positive electrode active material is (0.1-15) to (85-99.9).

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

and mixing the lithium-rich core material with the nanowire, and sintering under an inert atmosphere to obtain the lithium-rich anode material.

11. The positive electrode plate is characterized by comprising the lithium-rich positive electrode material according to any one of claims 1 to 9 or the lithium-rich positive electrode material prepared by the preparation method of the lithium-rich positive electrode material according to claim 10.

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