CN115172721A - Hollow high-conductivity lithium cathode material and preparation method thereof - Google Patents

Abstract

The invention provides a hollow high-conductivity lithium positive electrode material and a preparation method thereof. The hollow high-conductivity lithium positive electrode material has more lithium ion diffusion channels, shortens the lithium diffusion path, greatly improves the high-rate charge-discharge performance of the material, and increases the power of assembly. The battery has better power performance; at the same time, the hollow high-conductivity lithium cathode material adopts a spherical shell formed by agglomeration of nano-primary particles, which has space for volume expansion and improves the toughness of the particles, so that the power battery has a longer cycle. The invention has developed a core-shell structure precursor by controlling the crystal growth process of the precursor co-precipitation, combined with the step-by-step high-temperature solid-phase reaction, so that the internal loose precursor crystal core is formed in the process of generating the positive electrode material. The dense outer wall of the isocrystalline phase diffuses to form an internal hollow structure; the dense outer layer of the precursor is reacted at a high temperature to form a shell structure of nano-primary particles and assembled into a shell structure.

Description

Hollow high-conductivity lithium cathode material and preparation method thereof

technical field

The invention relates to the field of positive electrode materials for lithium ion secondary batteries, in particular to a hollow high-conductivity lithium positive electrode material and a preparation method thereof.

Background technique

With the continuous promotion and popularization of new energy vehicles, lithium-ion batteries have become the most mainstream power batteries used in new energy vehicles. The high-rate charge-discharge performance of the battery determines the response sensitivity of the electric vehicle, and the cycle life of the battery directly affects the service life of the electric vehicle. Therefore, the rate performance and cycle life are one of the key indicators to measure the power battery cathode material products.

At present, the commercialized lithium-ion battery cathode materials are mostly solid primary particles or secondary agglomerated particles. The lithium ion conduction path is long, and the de-intercalation efficiency of active materials under high current charge-discharge density is greatly reduced, resulting in a decrease in high-rate specific capacity; On the one hand, the stress caused by the volume change of the active material during the repeated charge and discharge process leads to cracks or even pulverization inside the particles, and the cycle life of the battery declines rapidly.

Therefore, it is necessary to propose a new cathode material and its preparation method to solve the above-mentioned technical problems.

SUMMARY OF THE INVENTION

In view of the technical problems raised by the above background technology, the present invention provides a hollow high-conductivity lithium positive electrode material with excellent rate performance or cycle performance and a preparation method thereof. On the one hand, the hollow high-conductivity lithium positive electrode material has sufficient lithium-conducting channels, which can improve the material On the other hand, the toughness of the particles is improved, and the reversibility of the volume change of the material during the charging and discharging process is maintained, so that the power battery has a longer cycle life.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A hollow high-conductivity lithium positive electrode material has a hollow interior and a spherical-like shell, wherein the spherical-like shell is formed by agglomeration of nano-primary particles.

Further, the spherical shell is formed by agglomeration of 1-2 layers of nano-primary particles.

Further, the D50 of the hollow high-conductivity lithium cathode material is 2-15 μm.

Further, the thickness of the spherical shell is 0.1-2 μm.

Further, the size of the nano-primary particles is 10-900 nm.

Further, the pore size of the hollow interior is 0.5-13 μm.

Further, the specific surface area BET of the hollow high-conductivity lithium cathode material is 0.6-2 m ² /g.

Further, the chemical formula of the hollow high-conductivity lithium cathode material is LiNi _x Co _y M _(1-xy) O ₂ , wherein x=0~1, y=0~1, and M is selected from Mn or Al or a combination thereof .

In order to solve the above-mentioned technical problem, the technical scheme that the present invention also adopts is:

The preparation method of the above-mentioned hollow high-conductivity lithium positive electrode material comprises the following steps:

1) Preparation of precursor crystal nucleus

The alkali solution, the salt solution and the complexing agent solution are subjected to a co-precipitation reaction to obtain a precursor crystal nucleus;

2) Preparation of core-shell structure precursors

The conditions of the co-precipitation reaction are adjusted, and the co-precipitation reaction is continued on the precursor crystal core obtained in the above step 1), so as to continue to grow the precursor shell layer on the surface of the precursor to obtain a core-shell structure precursor, wherein, The density of the precursor shell layer is greater than the density of the precursor seed crystal;

3) Preparation of hollow high-conductivity lithium cathode material

The core-shell structure precursor is mixed with a lithium salt and then subjected to a high-temperature solid-phase reaction to obtain a hollow high-conductivity lithium positive electrode material.

Further, in the step 1), the salt solution is a soluble salt solution of Ni, a soluble salt solution of Co, and a soluble salt solution of M; the alkali solution is a NaOH solution; the complexing agent is an ammonia solution;

Further, in the step 1), a magnetic field perpendicular to the direction of the liquid eddy current is applied during the co-precipitation reaction, and the intensity of the magnetic field is 5000-20000 Gauss.

Further, in the step 1), the pH value of the co-precipitation reaction is controlled to be 12-13, and the D50 of the precursor crystal nucleus is ≤5 μm.

Further, in the step 2), adjusting the conditions of the co-precipitation reaction includes adjusting the pH value of the reaction to be 10-11.

Further, in the step 3), the high-temperature solid-phase reaction includes a low-temperature step and a high-temperature step that are performed in sequence, the temperature of the low-temperature step is 400-800 ° C, the holding time is 4-48 h, and the temperature of the high-temperature step is 700~1050℃, the holding time is 4~48h.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The hollow high-conductivity lithium cathode material of the present invention has more lithium ion diffusion channels, shortens the lithium diffusion path, greatly improves the high-rate charge and discharge performance of the material, and the assembled power battery has better power performance; The high-conductivity lithium cathode material adopts a spherical shell formed by agglomeration of nano-primary particles, which has space for volume expansion and improves the toughness of the particles, so that the power battery has a longer cycle life.

(2) The present invention develops a precursor with a core-shell structure by controlling the crystal growth process of the precursor co-precipitation, combined with a step-by-step high-temperature solid-phase reaction, so that the internal loose precursor crystal core is formed in the process of generating the positive electrode material. It diffuses to the dense outer wall of the isocrystalline phase to form an internal hollow structure; the dense outer layer of the precursor is reacted at a high temperature to form a shell structure of nano-primary particles and assembled into a shell structure.

Description of drawings

1 is a SEM image of a hollow high-conductivity lithium positive electrode material in Example 1 of the present invention;

2 is a cross-sectional CP-SEM image of a hollow high-conductivity lithium positive electrode material in Example 1 of the present invention;

3 is a cross-sectional hard-section-SEM image of a hollow high-conductivity lithium positive electrode material in Example 1 of the present invention;

4 is a cross-sectional SEM image of the core-shell structure precursor in Example 1 of the present invention.

Detailed ways

All raw materials involved in the present invention are not particularly limited in their sources, and can be purchased from the market or prepared according to conventional preparation methods well known to those skilled in the art.

The invention provides a hollow high-conductivity lithium positive electrode material, which has a hollow interior and a spherical-like shell, and the spherical-like shell is formed by agglomeration of nano-primary particles. That is to say, the hollow high-conductivity lithium cathode material is hollow quasi-spherical particles, that is, the nano-primary particles are agglomerated to form a quasi-spherical shell, and the spherical casing has a hollow interior. For the specific structure, please refer to Figure 2 and Figure 3 .

The hollow high-conductivity lithium positive electrode material of the present invention has more lithium ion diffusion channels, shortens the lithium diffusion path, greatly improves the high-rate charge and discharge performance of the material, and the assembled power battery has better power performance; at the same time, the hollow high-conductivity lithium The positive electrode material adopts a spherical shell formed by agglomeration of nano-primary particles, which has the space for volume expansion, which improves the toughness of the particles, so that the power battery has a longer cycle life.

In the present invention, the spherical shell is formed by agglomeration of 1-2 layers of nano-primary particles, which not only ensures that the particles have a certain skeleton strength, but also provides a buffer space for the volume change of the material during the charging and discharging process. It also has a good lithium conduction channel, so that Li ⁺ in the electrolyte has a faster solid-liquid interface diffusion rate.

In the present invention, the D50 of the hollow high-conductivity lithium cathode material is 2 to 15 μm, which can be 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc., and other values within the above numerical range can be selected, which will not be omitted here. Repeat them one by one.

In the present invention, the thickness of the spherical shell is 0.1-2 μm. When the thickness exceeds 2 μm, the solid-phase diffusion paths of lithium ions increase, and the grain boundaries increase, which reduces the rate capability of the material.

In the present invention, the size of the nano primary particles is 10 to 900 nm. When the size of the nano-primary particle is less than 10nm, the activity of the material is too high; when the size is greater than 900nm, the solid-phase diffusion of lithium ions will deteriorate, reducing the rate performance of the material.

In the present invention, the pore size of the hollow interior is 0.5 to 13 μm, which can be 0.5 μm, 2.5 μm, 5 μm, 7 μm, 10 μm, 13 μm, etc. Other values within the above numerical range can be selected, which are not omitted here. Repeat them one by one.

In the present invention, the specific surface area BET of the hollow high-conductivity lithium positive electrode material is 0.6-2 m ² /g. The positive electrode material in this specific surface area range can take into account both the electrochemical performance and the processing performance of the pole piece.

In the present invention, the chemical formula of the hollow high-conductivity lithium cathode material is LiNi _x Co _y M _(1-xy) O ₂ , wherein M is selected from Mn or Al or a combination thereof, x=0~1, y=0~1 . The above chemical formula can also be doped with one or more elements in Al, Na, K, Rb, Cs, Sc, Nb, Bi, Fe, Mo, Ti, Mg, Zn, V, Zr, Ru, to Improve material chemical properties.

The present invention also provides a method for preparing a hollow high-conductivity lithium positive electrode material, comprising the following steps:

1) Preparation of precursor crystal nucleus

The alkali solution, the salt solution and the complexing agent solution are subjected to a co-precipitation reaction to obtain a precursor crystal nucleus;

2) Preparation of core-shell structure precursors

The conditions of the co-precipitation reaction are adjusted, and the co-precipitation reaction is continued on the precursor crystal core obtained in the above step 1), so as to continue to grow the precursor shell layer on the surface of the precursor to obtain a core-shell structure precursor, wherein, The density of the precursor shell layer is greater than the density of the precursor seed crystal;

3) Preparation of hollow high-conductivity lithium cathode material

The core-shell structure precursor is mixed with a lithium salt and then subjected to a high-temperature solid-phase reaction to obtain a hollow high-conductivity lithium positive electrode material.

The present invention develops a precursor with a core-shell structure by controlling the crystal growth process of the precursor co-precipitation, combined with a high-temperature solid-phase reaction, so that the internal loose precursor crystal nucleus is transformed into the isocrystalline phase in the process of generating the positive electrode material. The dense outer wall diffuses to form an inner hollow structure; the dense outer layer of the precursor is reacted at high temperature to form nano-primary particles and assemble into a shell structure.

In the present invention, the salt solution in step 1) is a soluble salt solution of Ni, a soluble salt solution of Co, and a soluble salt solution of M. For example, nickel sulfate solution, cobalt sulfate solution, sulfuric acid M solution (when M is selected from Al, it is aluminum sulfate solution; when M is Mn, it is manganese sulfate solution; when M is selected from Al and Mn, it is a mixture of aluminum sulfate and manganese sulfate solution); also can be nickel nitrate solution, cobalt nitrate solution, M nitrate solution (when M is selected from Al, it is aluminum nitrate solution; when M is Mn, it is manganese nitrate solution; when M is selected from Al and Mn, it is aluminum nitrate solution and manganese nitrate).

In the present invention, in step 1), the alkaline solution is preferably a NaOH solution; the complexing agent is preferably an ammonia solution.

In the present invention, a magnetic field perpendicular to the direction of the liquid eddy current is applied during the co-precipitation reaction, and the intensity of the magnetic field is 5000-20000 Gauss, which can be

5,000 Gauss, 8,000 Gauss, 10,000 Gauss, 15,000 Gauss, 20,000 Gauss, etc., other point values within the above numerical range can be selected, and will not be repeated here.

In the present invention, step 1) controls the pH value of the co-precipitation reaction to be 12-13, and the precursor crystal nucleus D50 is less than or equal to 5 μm.

In the present invention, step 2) adjusting the conditions of the co-precipitation reaction includes adjusting the pH value of the reaction to be 10-11.

In the present invention, step 3) high-temperature solid-phase reaction includes a low-temperature step and a high-temperature step that are performed in sequence, the temperature of the low-temperature step is 400-800°C, the holding time is 4-48h, and the temperature of the high-temperature step is 700-800°C 1050℃, the holding time is 4~48h.

The temperature of the low temperature step can be 400°C, 500°C, 600°C, 700°C, 800°C, etc., and the holding time can be 4h, 8h, 12h, 16h, 20h, 26h, 30h, 34h, 40h, 48h, etc.

The temperature of the high temperature step can be 700°C, 800°C, 900°C, 1000°C, 1050°C, etc., and the holding time can be 4h, 8h, 12h, 16h, 20h, 26h, 30h, 34h, 40h, 48h, etc.

Other point values within the above-mentioned numerical range can be selected, which will not be repeated here.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In order to further illustrate the present invention, the following examples are used for detailed description. The sources of the raw materials used in the following examples of the present invention are not particularly limited, and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

Example 1

This embodiment provides a hollow high-conductivity lithium cathode material LiNi _0.5 Co _0.3 Mn _0.2 O ₂ , and a preparation method thereof includes the following steps:

1) Preparation of precursor crystal nucleus

Prepare 1mol/L NaOH solution and 2mol/L ammonia solution; prepare _NiSO4 solution, CoSO4 solution, MnSO4 solution with a molar ratio of ₅ :3:2 in terms of Ni, Co, and Mn, mix NaOH solution, _NiSO4 solution ₄ solution, CoSO ₄ solution, MnSO ₄ solution, and ammonia solution are placed in the reactor to carry out co-precipitation reaction, and a magnetic field perpendicular to the direction of liquid eddy current is applied during the reaction, and the intensity of the magnetic field is 7000 Gauss, and the pH value of the control reaction is 12~13, The precursor crystal nucleus with D50=1.5μm was obtained;

2) Preparation of precursor shell layer

By adding deionized water, the pH value of the reaction is adjusted to 10-11, and on the precursor crystal nucleus obtained in the above step 1), the co-precipitation reaction is continued for 12 hours to obtain a densely grown precursor shell;

3) Preparation of core-shell structure precursors

The slurry after the reaction in step 2) was subjected to solid-liquid separation, washed three times with deionized water, dried in an oven at 150°C, and sieved.

Then the core-shell structure precursor is obtained;

4) Preparation of hollow high-conductivity lithium cathode material

Weigh lithium carbonate and the above precursors according to the molar ratio of Li/(Ni+Co+Mn)=1.04:1, mix them well in a high-speed mixer, place them in a high-temperature reaction furnace, roast in an air atmosphere, and set the roasting system It is as follows: heating at a rate of 2°C/min, holding at 800°C for 4 hours, and holding at 950°C for 24 hours; after cooling, the reaction product is crushed, sieved, and demagnetized to obtain a hollow high-conductivity lithium cathode material LiNi _0.5 Co _0.3 Mn _0.2 O ₂ .

Example 2

This embodiment provides a hollow high-conductivity lithium cathode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , and a preparation method thereof includes the following steps:

1) Preparation of precursor crystal nucleus

Prepare 1mol/L NaOH solution and 2mol/L ammonia solution; prepare _NiSO4 solution, CoSO4 solution and MnSO4 solution with a molar ratio of ₆ :2:2 in terms of Ni, Co and Mn, mix NaOH solution, _NiSO4 solution ₄ solution, CoSO ₄ solution, MnSO ₄ solution, and ammonia solution are placed in the reactor to carry out co-precipitation reaction, and a magnetic field perpendicular to the direction of liquid eddy current is applied during the reaction, and the intensity of the magnetic field is 5000 Gauss, and the pH value of the control reaction is 12~13, The precursor crystal nucleus with D50=3μm was obtained;

2) Preparation of precursor shell layer

By adding deionized water, the pH value of the reaction is adjusted to 10-11, and the co-precipitation reaction is continued on the precursor crystal nucleus obtained in the above step 1) for 8 hours to obtain a densely grown precursor shell;

3) Preparation of core-shell structure precursors

The slurry after the reaction in step 2) was subjected to solid-liquid separation, washed three times with deionized water, dried in an oven at 120°C, and sieved.

Then the core-shell structure precursor is obtained;

4) Preparation of hollow high-conductivity lithium cathode material

Weigh lithium hydroxide and the above precursors according to the molar ratio of Li/(Ni+Co+Mn)=1.02:1, mix them well in a high-speed mixer, place them in a high-temperature reaction furnace, and roast them in an oxygen atmosphere. The setting is as follows: heating at a rate of 2°C/min, holding at 700°C for 8 hours, and holding at 880°C for 10 hours. After cooling, the reaction product is crushed, sieved, and demagnetized to obtain a hollow high-conductivity lithium cathode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ .

Example 3

This embodiment provides a hollow high-conductivity lithium positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , and a preparation method thereof includes the following steps:

1) Preparation of precursor crystal nucleus

Prepare 1mol/L NaOH solution and 2mol/L ammonia solution; prepare _NiSO4 solution, CoSO4 solution, MnSO4 solution with a molar ratio of ₈ :1:1 in terms of Ni, Co, and Mn, mix NaOH solution, _NiSO4 solution ₄ solution, CoSO ₄ solution, MnSO ₄ solution, and aqueous ammonia solution are placed in the reactor for co-precipitation reaction, and a magnetic field perpendicular to the direction of liquid eddy current is applied during the reaction, and the intensity of the magnetic field is 8000 Gauss, and the pH value of the control reaction is 12~13, The precursor crystal nucleus with D50=0.5μm was obtained;

2) Preparation of precursor shell layer

By adding deionized water, the pH value of the reaction is adjusted to 10~11, and on the precursor crystal nucleus obtained in the above step 1), the co-precipitation reaction is continued for 15 hours to obtain a densely grown precursor shell;

3) Preparation of core-shell structure precursors

The slurry after the reaction in step 2) was subjected to solid-liquid separation, washed three times with deionized water, dried in an oven at 100°C, and sieved.

Then the core-shell structure precursor is obtained;

4) Preparation of hollow high-conductivity lithium cathode material

Weigh lithium carbonate and the above precursors according to the molar ratio of Li/(Ni+Co+Mn)=1.02:1, mix them well in a high-speed mixer, place them in a high-temperature reaction furnace, roast in an oxygen atmosphere, and set the roasting system The steps are: heating at a rate of 2°C/min, holding at 400°C for 10 hours, and holding at 700°C for 4 hours. After cooling, the reaction product is crushed, sieved, and demagnetized to obtain a hollow high-conductivity lithium cathode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ .

Comparative Example 1

This comparative example provides a positive electrode material LiNi _0.5 Co _0.3 Mn _0.2 O ₂ . The difference between the preparation method and the preparation method of Example 1 is that during the reaction in step 1), no magnetic field perpendicular to the direction of the liquid eddy current is applied.

Comparative Example 2

This comparative example provides a positive electrode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , the preparation method of which differs from the preparation method of Example 2 only in that step 1) prolongs the reaction time to obtain a precursor crystal nucleus with D50=15 μm.

Comparative Example 3

This comparative example provides a positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , the preparation method of which is different from the preparation method of Example 3 only in that the baking formula in step 4) is set as: the rate of heating at 2°C/min, 700°C Incubate for 14h.

SEM test was carried out on the hollow high-conductivity lithium positive electrode material prepared in Example 1. Figure 2 is a cross-sectional CP-SEM image of the hollow high-conductivity lithium positive electrode material in Example 1 of the present invention; Figure 3 is a hollow high-conductivity lithium positive electrode in Example 1 of the present invention. Hard cross-section-SEM image of the material (cross-sectional view after freezing the positive electrode material with liquid nitrogen); it can be seen from Figures 2 and 3 that the hollow high-conductivity lithium positive electrode material synthesized in Example 1 of the present invention has a hollow The inner part and the spherical shell, the spherical shell is formed by the agglomeration of nano-primary particles. The spherical shell is formed by the agglomeration of 1-2 layers of nano-primary particles.

Experimental situation:

Table 1 lists the reversible specific capacity and the first coulombic efficiency under the condition of 0.1C by using the cathode materials prepared in the above-mentioned Examples 1-3 and Comparative Examples 1-3 to assemble a lithium-ion button battery. The test conditions for the coin cell are LR 2032, 0.1C 3.0~4.25V, vs. Li ⁺ /Li. The charging and discharging equipment used is a blue electricity charging and discharging instrument.

Table 1

It can be seen from the data in the table that the reversible specific capacity and the first coulombic efficiency of the hollow high-conductivity lithium cathode materials prepared in Examples 1 to 3 of the present invention are respectively better than those of the cathode materials prepared in Comparative Examples 1 to 3. This is because the hollow high-conductivity lithium cathode material prepared by the stepwise high-temperature solid-phase reaction by applying a magnetic field perpendicular to the direction of the liquid eddy current in Example 1 has better crystallinity. The size of the internal crystal nucleus prepared in Example 2 is more suitable for pore formation than that in Comparative Example 2, and the positive electrode material prepared after high-temperature solid-phase reaction has higher porosity. Compared with Comparative Example 3, the step-by-step roasting in Example 3 can improve the crystallinity of the hollow high-conductivity lithium cathode material. The improvement of crystallinity and the increase of material porosity enable the reversible capacity of the material to be fully exerted.

Table 2 lists the rate performance of lithium ion button batteries assembled with the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3. The test conditions of the battery are, LR 2032, 3.0~4.25V vs. Li ⁺ /Li: 0.1C/0.1C charge and discharge for one cycle; 0.1C/1C charge and discharge for one cycle; 0.1C/5C charge and discharge for one cycle. The charging and discharging equipment is a blue electricity charging and discharging instrument.

Table 2

It can be seen from the data in Table 2 that the rate performance of the hollow high-conductivity lithium cathode materials prepared in Examples 1 to 3 is significantly better than that of Comparative Examples 1 to 3, respectively. This is because the hollow high-conductivity lithium cathode material prepared by the step-by-step high-temperature solid-phase reaction by applying a magnetic field perpendicular to the liquid eddy current direction in Example 1 has better crystallinity, reduces cation mixing, and improves the diffusion channel of lithium ions The high long-range order makes it easier for lithium ions to expand into the active material particles, and the lithium ions immersed in the pore electrolyte can contact more reaction sites, which improves the material reaction rate at high current rates. The size of the internal crystal nucleus prepared in Example 2 is more suitable for pore formation than that in Comparative Example 2. The positive electrode material prepared after high-temperature solid-phase reaction has higher porosity, and it is easier for lithium ions to expand into the interior of the active material particles. Lithium ions can access more reaction sites, increasing the reaction rate of materials at high current rates. Compared with Comparative Example 3, the step-by-step calcination in Example 3 can improve the crystallinity of the hollow high-conductivity lithium cathode material, reduce the mixing of cations, and improve the long-range order of the diffusion channels of lithium ions.

Table 3 lists the capacity retention rates of the reversible capacity of lithium-ion button batteries assembled with the positive electrode materials prepared in the above Examples 1 to 3 and Comparative Examples 1 to 3 for 50 weeks. The test conditions of the battery are, LR 2032, 45℃, 1C, 3.0~4.25V, vs. Li ⁺ /Li. The charging and discharging equipment used is a blue electricity charging and discharging instrument.

table 3

It can be seen from the data in Table 3 that the high-conductivity lithium cathode materials prepared in Examples 1 to 3 have better capacity retention rates than those of Comparative Examples 1 to 3, respectively. It can be seen that the structure design of the spherical shell formed by the hollow interior and the agglomeration of nano-primary particles plays a role in inhibiting the cyclic decay of the material; the improvement of the crystallinity of the material is beneficial to improve the lithium ion extraction/insertion during the charging and discharging process of the material. Reversibility, reducing the loss of active material during cycling, thereby improving the cycling performance of the material. The hollow high-conductivity lithium cathode material adopts a spherical shell formed by agglomeration of nano-primary particles, which has the space for volume expansion and improves the toughness of the particles, so that the power battery has a longer cycle life. The reason why the capacity retention rates of Example 2 and Example 3 are lower than that of Comparative Example 1 is that the material systems are different, and the higher the Ni content, the lower the cycle performance.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A hollow high-conductivity lithium positive electrode material, characterized in that it has a hollow interior and a spherical shell, wherein the spherical shell is formed by agglomeration of nano-primary particles. 2 . The hollow high-conductivity lithium positive electrode material according to claim 1 , wherein the spherical shell is formed by agglomerating 1-2 layers of nano-primary particles. 3 . 3. The hollow high-conductivity lithium positive electrode material according to claim 1, wherein at least one of the following conditions is satisfied: The D50 of the hollow high-conductivity lithium positive electrode material is 2-15 μm; The thickness of the spherical shell is 0.1-2 μm; The size of the nano-primary particles is 10-900 nm; The inside of the hollow has a pore size of 0.5-13 μm; The specific surface area BET of the hollow high-conductivity lithium positive electrode material is 0.6-2 m ² /g. 4. The hollow high-conductivity lithium positive electrode material according to claim 1, wherein the chemical formula is LiNi _x Co _y M _(1-xy) O ₂ , wherein x=0~1, y=0~1, M is selected from Mn or Al or a combination thereof. 5. the preparation method of the hollow high-conductivity lithium positive electrode material as described in any one of claim 1～4, is characterized in that, comprises the following steps: 1) Preparation of precursor crystal nucleus The alkali solution, the salt solution and the complexing agent solution are subjected to a co-precipitation reaction to obtain a precursor crystal nucleus; 2) Preparation of core-shell structure precursors The conditions of the co-precipitation reaction are adjusted, and the co-precipitation reaction is continued on the precursor crystal core obtained in the above step 1), so as to continue to grow the precursor shell layer on the surface of the precursor to obtain a core-shell structure precursor, wherein, The density of the precursor shell layer is greater than the density of the precursor seed crystal; 3) Preparation of hollow high-conductivity lithium cathode material The core-shell structure precursor is mixed with a lithium salt and then subjected to a high-temperature solid-phase reaction to obtain a hollow high-conductivity lithium positive electrode material. 6. The method for preparing a hollow high-conductivity lithium positive electrode material according to claim 5, wherein in the step 1), the salt solution is a soluble salt solution of Ni, a soluble salt solution of Co, and a soluble salt solution of M; The alkali solution is NaOH solution; the complexing agent is ammonia solution. 7 . The method for preparing a hollow high-conductivity lithium cathode material according to claim 5 , wherein in the step 1), a magnetic field perpendicular to the direction of the liquid eddy current is applied during the co-precipitation reaction, and the intensity of the magnetic field is 5000-20000 Gauss. 8 . 8 . The method for preparing a hollow high-conductivity lithium cathode material according to claim 5 , wherein, in the step 1), the pH value of the co-precipitation reaction is controlled to be 12-13, and the precursor crystal nucleus D50 is less than or equal to 5 μm. 9 . 9 . The method for preparing a hollow high-conductivity lithium positive electrode material according to claim 5 , wherein in the step 2), adjusting the conditions of the co-precipitation reaction comprises adjusting the pH value of the reaction to be 10-11. 10 . 10 . The method for preparing a hollow high-conductivity lithium positive electrode material according to claim 5 , wherein, in the step 3), the high-temperature solid-phase reaction comprises a low-temperature step and a high-temperature step that are performed in sequence, and the temperature of the low-temperature step is 10 . 400~800°C, the holding time is 4~48h, the temperature of the high temperature step is 700~1050°C, and the holding time is 4~48h.

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