CN113428907A

CN113428907A - Method for preparing cathode composition of lithium ion battery and lithium ion battery using same

Info

Publication number: CN113428907A
Application number: CN202010207368.0A
Authority: CN
Inventors: 任东
Original assignee: Feiyi New Energy Co
Current assignee: Feiyi New Energy Co
Priority date: 2020-03-23
Filing date: 2020-03-23
Publication date: 2021-09-24

Abstract

The invention relates to a preparation method of a lithium ion battery cathode composition and a lithium ion battery using the same, wherein the preparation method of the lithium ion battery cathode composition comprises the following steps: adding a doping material M3 to prepare a nuclear precursor; adding a doping material M4 to prepare a shell precursor; adding a lithium source for sintering; then adding the sintered product into a coating material M6 for sintering to obtain a target product [ Li_a(Ni_1‑x‑y‑ _zCo_xM1_yM3_z)O₂]_d·[Li_s(Ni_{1‑m‑n‑t}Co_mM2_nM4_t)_1‑ _rM6_rO₂]_1‑d. The lithium ion battery cathode composition with the core-shell structure, which is synthesized by the preparation method, has excellent cycle performance. The preparation method has simple process and controllable process, and is easy for industrial mass production.

Description

Method for preparing cathode composition of lithium ion battery and lithium ion battery using same

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a preparation method of a lithium ion battery cathode composition and a lithium ion battery using the same.

Background

With the popularization of new energy automobiles, the power type lithium ion battery is greatly developed, and meanwhile, the high requirements of the new energy automobiles on the endurance mileage and the energy density, the high cycle performance and the high safety performance of the new energy automobiles are also high. The lithium ion battery cathode composition is one of the key materials of the lithium ion battery and is also a key factor for hindering the energy density of the lithium ion battery.

At present, most of materials produced by anode material manufacturers at home and abroad are secondary particles formed by agglomeration of fine grains. However, secondary spherical particles present some problems to be solved: (1) the structure of the secondary ball is poor in structural firmness, and the secondary ball is easy to break when being pressed by high pressure in the electrode preparation process, so that particles in the material are exposed, side reaction with electrolyte is intensified, metal ions are dissolved out, and the electrochemical performance is reduced; (2) the primary particles forming the secondary spheres have small particle size and many structural defects, and are easy to collapse under the condition of high voltage and sufficiency; (3) the interior of the secondary spherical particles is difficult to modify in structure, and interface side reaction is difficult to inhibit in the charging and discharging process; (4) the secondary spherical particles easily cause problems such as air expansion.

Researches find that the single-crystal-morphology cathode material not only has higher specific capacity and cycling stability under high voltage, but also can effectively improve the problems of the material in the aspects of high-temperature performance, gas expansion and the like compared with the traditional ternary cathode material with a secondary sphere structure, and meanwhile, the single-crystal cathode material also has the following advantages: (1) high mechanical strength, not easy to be broken in the electrode compacting process, and the compacted density can reach 3.8g/cm³～4.0g/cm³The higher compaction density can reduce the internal resistance of the material, reduce the polarization loss, prolong the cycle life of the battery and improve the energy density of the battery; (2) the special shape of primary single crystal particles has low specific surface area, and the side reaction between the material and the electrolyte is effectively reduced; (3) the surface of the single crystal particles is smooth, the single crystal particles are more fully contacted with the conductive agent, and the lithium ion transmission is facilitated. Therefore, the research on the single crystal cathode material will become a new direction for the research on the lithium ion battery material.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a method for preparing a cathode composition for a lithium ion battery and a lithium ion battery using the same.

The invention provides a lithium ion battery cathode composition, which has a core-shell structure and a chemical formula shown in formula (I):

[Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d(I)

Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂is the chemical formula of the core of the lithium ion battery cathode composition, Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂Is the chemical formula of the shell of the lithium ion battery cathode composition; the M1 and M2 are respectively and independently selected from Mn and/or Al; the M3, M4 and M6 are respectively and independently selected from one or more of alkali metal elements, alkaline earth metal elements, IIIA group elements, IVA group elements, transition metals and rare earth elements;

wherein x, y, z, m, n, t, r, a, s and d are mole fractions, x is greater than 0, y is greater than or equal to 0.01 and less than or equal to 0.10, z is greater than or equal to 0 and less than or equal to 0.02, m is greater than or equal to 0.2 and less than or equal to 0.4, t is greater than or equal to 0 and less than or equal to 0.02, a is greater than or equal to 1.01 and less than or equal to 1.07, s is greater than or equal to 1.01 and less than or equal to 1.07, 1-x-y-z is greater than or equal to 0.80 and less than or equal to 0.96, 1-m-n-t is greater than or equal to 0.30 and less than or equal to 0.70, and d is greater than or equal to 0.70 and less than or equal to 1.

In a second aspect, the present invention provides a method for preparing the lithium ion battery cathode composition, comprising the steps of:

step 1, nuclear precursor preparation: preparing a first mixed aqueous solution of a Ni source compound, a Co source compound, a M1 source compound and a M3 source compound, mixing the first mixed aqueous solution, a carbonate solution and ammonia water, and reacting under an alkaline condition to obtain a nuclear precursor Ni_1-x-y-zCo_xM1_yM3_zCO₃(ii) a Wherein M1 is selected from Mn and/or Al; m3 is selected from Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm, MoAt least one of; x, y and z are mole fractions, x>0，0.01≤y≤0.10，0≤z≤0.02，0.60≤1-x-y-z≤0.96；

Step 2, preparing a shell precursor: preparing a second mixed aqueous solution of a Ni source compound, a Co source compound, a M2 source compound and a M4 source compound, and mixing the second mixed aqueous solution with the nuclear precursor Ni_1-x-y-zCo_xM1_yM3_zCO₃Mixing with ammonia water and NaOH solution, and precipitating a shell precursor Ni on the surface of the core precursor_1-m-n-tCo_mM2_nM4_t(OH)₂Obtaining a precursor with a core-shell structure; wherein M2 is selected from Mn and/or Al; m4 is at least one selected from Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm and Mo; wherein m, n and t are mole fractions, m>0，0.2≤n≤0.4，0≤t≤0.02，0.30≤1-m-n-t≤0.70。

Step 3, first sintering: and (3) mixing and grinding the precursor with the core-shell structure obtained in the step (2), a lithium source and a water-soluble sintering aid, uniformly grinding, sintering, and cooling to room temperature after sintering.

And 4, sintering for the second time: and (3) adding a coating material M6 into the product obtained by sintering in the step (3) for sintering, and after sintering is finished, performing cooling annealing treatment to obtain a target product, wherein the chemical formula of the target product is as follows:

[Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d

Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂is the chemical formula of the core of the lithium ion battery cathode composition, Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂Is the chemical formula of the shell of the lithium ion battery cathode composition; the M2 is selected from Mn and/or Al; m6 is selected from alkali metal element, alkaline earth metal element, IIIA group element, IVA group element, transition elementOne or more of metals and rare earth elements; wherein m, n, t, r, s and d are mole fractions, m>0，0.2≤n≤0.4，0≤t≤0.02，0≤r≤0.02，0.30≤1-m-n-t≤0.70，1.01≤s≤1.07，0.70≤d≤1。

The invention provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode comprises the lithium ion battery cathode composition.

In order to make the aforementioned and other objects, features and advantages of the invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.

In one aspect, the present invention provides a lithium ion battery cathode composition, wherein the chemical formula of the lithium ion battery cathode composition is represented by formula (I):

[Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d (I)

in some embodiments, the chemical formula of the core of the lithium ion battery cathode composition is Li_a(Ni_1-x-y- _zCo_xM1_yM3_z)O₂The chemical formula of the shell of the lithium ion battery cathode composition is Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂. Wherein M1 and M2 are each independently selected from Mn and/or Al; the M3, M4 and M6 are respectively and independently selected from one or more of alkali metal elements, alkaline earth metal elements, IIIA group elements, IVA group elements, transition metals and rare earth elements.

As an embodiment, M1 is selected from Mn and Al, M2 is selected from Mn; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xAl_1- _yMn_yM3_z)O₂(ii) a The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mMn_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Mn and Al, M2 is selected from Al; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xAl_1- _yMn_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Mn and Al, M2 is selected from Mn and Al; the chemical formula of the core is Li_a(Ni_1-x-y- _zCo_xAl_1-yMn_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_1-nMn_nM4_t)_1-rM6_rO₂；

In one embodiment, M1 is selected from Al, M2 is selected from Mn; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xAl_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mMn_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Al, M2 is selected from Al; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xAl_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Al, M2 is selected from Mn and Al; the chemical formula of the core is Li_a(Ni_1-x-y- _zCo_xAl_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_1-nMn_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Mn, M2 is selected from Mn; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xMn_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mMn_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Mn, M2 is selected from Al; the chemical formula of the core is Li_a(Ni_1-x-y-zCo_xMn_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_nM4_t)_1-rM6_rO₂；

As an embodiment, M1 is selected from Mn, M2 is selected from Al and Mn; the chemical formula of the core is Li_a(Ni_1-x-y- _zCo_xMn_yM3_z)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_1-nMn_nM4_t)_1-rM6_rO₂。

In some embodiments, the Mn may be derived from one or more of manganese sulfate, manganese acetate, manganese chloride, manganese nitrate; the Al may be derived from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum trichloride, aluminum acetate, aluminum isopropoxide, aluminum n-propoxide, aluminum sulfate, aluminum nitrate.

In some embodiments, the shell of the lithium ion battery cathode composition has a layered or spinel structure. In one embodiment, the layered lithium ion battery cathode composition comprises one or more of lithium nickel cobalt manganese oxide, lithium rich lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium cobaltate, lithium nickel cobalt oxide, and lithium manganese oxide. In one embodiment, a spinel lithium ion battery cathode composition includes lithium manganate and/or lithium nickel manganate.

In the embodiment of the invention, x, y, z, m, n, t, r, a, s and d are mole fractions, x is more than 0, y is more than or equal to 0.01 and less than or equal to 0.10, z is more than or equal to 0 and less than or equal to 0.02, m is more than or equal to 0.2 and less than or equal to 0.4, t is more than or equal to 0 and less than or equal to 0.02, r is more than or equal to 0 and less than or equal to 0.02, a is more than or equal to 1.01 and less than or equal to 1.07, s is more than or equal to 1.01 and less than or equal to 1.07, 1-x-y-z is more than or equal to 0.96, 1-m-n-t is more than or equal to 0.30 and less than or equal to 0.70 and d is more than or equal to 1.

In some embodiments, x is greater than 0, 0.01. ltoreq. y.ltoreq.0.05, 0< z.ltoreq.0.02, m >0, 0.2. ltoreq. n.ltoreq.0.3, 0< t.ltoreq.0.02, 0< r.ltoreq.0.02, 1.015. ltoreq. a.ltoreq.1.06, 1.015. ltoreq. s.ltoreq.1.06, 0.83. ltoreq.1-x-y-z.ltoreq.0.92, 0.34. ltoreq.1-m-n-t.ltoreq.0.60, 0.70. ltoreq. d.ltoreq.0.85.

In some embodiments, the mole fraction of Ni content in the lithium ion battery cathode composition (e.g., as in formula Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂1-x-y-z) of (a) may be at least 0.60, at least 0.61, at least 0.62, at least 0.63, at least 0.64, at least 0.65, at least 0.66, at least 0.67, at least 0.68, at least 0.69, at least 0.70, at least 0.71, at least 0.75, at least 0.80, at least 0.81, at least 0.82, at least 0.83, at least 0.85, at least 0.86, at least 0.88, at least 0.89, at least 0.90, at least 0.91, at least 0.92, at least 0.93, at least 0.94, at least 0.95, at least 0.951, at least 0.953, at least 0.955, at least 0.957, at least 0.96, and/or not more than 0.96, not more than 0.957, not more than 0.955, not more than 0.953, not more than 0.951, not more than 0.95, not more than 0.94, not more than 0.93, not more than 0.85, not more than 0.82, not more than 0.81, not more than 0.82, not more than 0.96, not more than 0.80, not more than, A mole fraction of no greater than 0.71, no greater than 0.70, no greater than 0.69, no greater than 0.68, no greater than 0.67, no greater than 0.66, no greater than 0.65, no greater than 0.64, no greater than 0.63, no greater than 0.62, no greater than 0.61, no greater than 0.60, and the like.

In some embodiments, the mole fraction of Li content in the lithium ion battery cathode composition core (e.g., such as formula Li)_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂A) of (a) can be present in a mole fraction of at least 1.01, at least 1.02, at least 1.03, at least 1.035, at least 1.04, at least 1.045, at least 1.05, at least 1.055, at least 1.06, at least 1.065, at least 1.07, and/or not more than 1.07, not more than 1.065, not more than 1.06, not more than 1.055, not more than 1.05, not more than 1.045, not more than 1.04, not more than 1.035, not more than 1.03, not more than 1.02, not more than 1.01, and the like.

Here, when a is less than 1, the content of Li is insufficient, which may affect Li⁺So that lithium ion is reducedThe charge and discharge capacity of the cathode composition of the sub-battery is too high, the content of Li is too high, more byproducts are generated in the preparation process, and the obtained cathode composition of the lithium ion battery contains LiOH and Li₂CO₃When alkaline substances are left, the alkaline substances on the surface are easy to attack the binder in the positive electrode glue solution, the binder forms double bonds to generate adhesion, slurry jelly is caused, the coating effect is influenced, and the performance of the battery cell is influenced. According to the embodiment of the invention, the molar fraction of the Li content is 1.01-1.07, the charge and discharge capacity is high, the byproducts are few, the improvement of the battery cell performance is facilitated, and the unexpected effect is achieved.

In some embodiments, the lithium ion battery cathode composition structure has an average particle size D50 of 3 to 5 μm, and an average particle size D50 of 2.5 to 4 μm; the tap density of the lithium ion battery cathode composition is 1.8-2.3g/cm³. In some embodiments, the lithium ion battery cathode composition is a primary particle. In some cases, the lithium ion battery cathode composition can also be a secondary particle. The lithium ion battery cathode composition has a core-shell structure, and can effectively inhibit the corrosion of electrolyte on a body material and the dissolution of metal ions, so that more lithium vacancies of active materials are kept, and the cycling stability of the material is improved.

In some embodiments, the tap density of the lithium ion battery cathode composition may be at least 1.5g/cm³At least 1.6g/cm³At least 1.7g/cm³At least 1.8g/cm³At least 1.9g/cm³At least 2.0g/cm³At least 2.1g/cm³At least 2.2g/cm³At least 2.3g/cm³And/or not more than 2.3g/cm³Not more than 2.2g/cm³Not more than 2.1g/cm³Not more than 2.0g/cm³Not more than 1.9g/cm³Not more than 1.8g/cm³Not more than 1.7g/cm³Not more than 1.6g/cm³Not more than 1.5g/cm³Etc. are present.

In some cases, the shell of the lithium ion battery cathode composition has a thickness of 0.05 to 1.1 μm; in some cases, the shell thickness is less than 1.1 μm, less than 1.05 μm, less than 1.0 μm, less than 0.95 μm, less than 0.9 μm, less than 0.8 μm, less than 0.7 μm, less than 0.6 μm, less than 0.5 μm, less than 0.4 μm, less than 0.3 μm, less than 0.2 μm, less than 0.1 μm, less than 0.08 μm, less than 0.06 μm, less than 0.05 μm; in some cases, the shell thickness can be at least 0.05 μm, at least 0.06 μm, at least 0.08 μm, at least 0.1 μm, at least 0.2 μm, at least 0.3 μm, at least 0.4 μm, at least 0.5 μm, at least 0.6 μm, at least 0.7 μm, at least 0.8 μm, at least 0.9 μm, at least 0.95 μm, at least 1.0 μm, at least 1.05 μm, at least 1.1 μm, and the like. In various embodiments, any combination of these is also possible; for example: the shell thickness may be between 0.05 μm and 1.1 μm. In addition, it should be understood that the shell may be uniformly or non-uniformly distributed around the core.

The thickness of the shell has a great influence on the performance of the core-shell structure composition, and if the thickness of the shell is too thin, the shell is easily corroded by electrolyte to expose the core, so that the stability of the composition is influenced; conversely, if the shell is too thick, the capacity of the composition will be reduced. The composition provided by the embodiment of the invention has proper shell thickness, can balance the stability of the composition and the capacity of the composition, and has optimal stability and capacity.

On the other hand, the embodiment of the invention also provides a preparation method of the lithium ion battery cathode composition, which comprises the following steps:

step 1, nuclear precursor preparation: preparing a first mixed aqueous solution of a Ni source compound, a Co source compound, a M1 source compound and a M3 source compound, mixing the first mixed aqueous solution, a carbonate solution and ammonia water, and reacting under an alkaline condition to obtain a nuclear precursor Ni_1-x-y-zCo_xM1_yM3_zCO₃(ii) a Wherein x, y and z are mole fractions, and x is>0，0.01≤y≤0.10，0≤z≤0.02，0.60≤1-x-y-z≤0.96；

In the embodiment of the invention, M1 is selected from Mn and/or Al; m3 is at least one selected from Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm and Mo; the reaction conditions include: the pH value is 9-12, the reaction temperature is 60-90 ℃, the reaction time is 3-12h under the constant temperature, and the cooling temperature is 25-30 ℃.

In one embodiment, when z is 0, the product obtained in the step 1 reaction is Li_aNi_1-x-yCo_xM1_yO₂。

Step 2, preparing a shell precursor: preparing a second mixed aqueous solution of a Ni source compound, a Co source compound, a M2 source compound and a M4 source compound, and mixing the second mixed aqueous solution with the nuclear precursor Ni_1-x-y-zCo_xM1_yM3_zCO₃Mixing with ammonia water and NaOH solution, and precipitating a shell precursor Ni on the surface of the core precursor_1-m-n-tCo_mM2_nM4_t(OH)₂Obtaining a precursor with a core-shell structure; wherein m, n and t are mole fractions, m>0，0.2≤n≤0.4，0≤t≤0.02，0.30≤1-m-n-t≤0.70。

In the embodiment of the invention, the M2 is selected from Mn and/or Al; m4 is at least one selected from Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm and Mo; the reaction conditions include: the pH value is 10-12, and the reaction temperature is 60-65 ℃.

In some embodiments, in steps 1 and 2, the reaction may be carried out in the presence of a dispersant, which may use one or more mixtures of surfactants, polyvinyl alcohols, polyglycerols. In some cases, the surfactant may be exemplified by cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG-400), Span-80 (Span-80), and polyoxyethylene octylphenol ether-10 (op-10), and the like.

In the present invention, the above-mentioned surfactants may be used alone or in combination of two or more, and may be used in combination with other dispersants. In the embodiment of the invention, the addition of the surfactant realizes the effect that a common surfactant such as Cetyl Trimethyl Ammonium Bromide (CTAB) is beneficial to particle dispersion and uniform particle distribution, and can regulate and control the growth direction and the dispersibility of crystals, regulate the crystal morphology, influence the layered structure of the material and enable the crystal structure to grow and have uniform particle size.

The mixed salt solution and the alkali liquor are added into the reaction kettle dispersed with the surfactant in a parallel flow manner, so that a large number of crystal nuclei are formed, when metal ions and the precipitant are continuously added, the metal ions and the precipitant are rapidly dispersed in the solution containing the surfactant under the stirring action, the concentrations of the precipitant and the metal ions in the reaction system are low, the supersaturation degree in the solution is low, new crystal nuclei are formed, the crystal particles grow gradually and the particle morphology is regulated, and the particle size of the lithium ion battery cathode composition obtained by metal ion parallel flow feeding is relatively uniformly distributed.

In some embodiments, the Ni source compound is derived from one or more mixtures of nickel chloride, nickel sulfate, nickel acetate, nickel nitrate, or crystalline water compounds thereof; in some embodiments, the Co source compound is derived from one or more mixtures of cobalt sulfate, cobalt acetate, cobalt chloride, cobalt nitrate, or crystalline water compounds thereof.

According to the invention, a Ni source compound, a Co source compound, a Mn source compound and/or an Al source compound are prepared into a solution, a nickel salt, a cobalt salt, an aluminum salt and a manganese salt can be uniformly distributed in the solution, and the lithium ion battery cathode composition is prepared by adopting the solution in which the nickel salt, the cobalt salt, the aluminum salt and the manganese salt are uniformly distributed. Because the precipitation equilibrium constants Ksp of Ni, Co, Al and Mn are different, the order of Ni, Co, Al and Mn forming precipitates in the solution can be influenced, the reaction temperature, pH, solution concentration and stirring speed are optimized, the process is creatively improved, the Ni, Co, Al and Mn precipitation order is consistent, uniform precipitates are formed, the lithium ion battery cathode composition prepared by the method has the advantages that the nickel, cobalt, aluminum and manganese are uniformly distributed in particles, the lithium ion battery cathode composition is mixed with lithium salt, and the lithium ion battery cathode composition is obtained by sintering, so that the crystal structure is more uniform, the framework structure is firmer, the material performance can be favorably exerted, and the capacity and the rate capability of the lithium ion battery cathode composition can be effectively improved.

In the embodiment of the invention, the sintering is carried out for 8-20 hours by adding a lithium source and a water-soluble auxiliary agent at 780-900 ℃ in the air or oxygen atmosphere.

When the sintering temperature is less than 700 ℃, lithiation is insufficient, whereas when the sintering temperature exceeds 1000 ℃, oxidation of metal ions is inhibited, and charge-discharge cycle durability and initial capacity are reduced. The sintering temperature is preferably 780 to 900 ℃. Sintering may be performed in multiple stages.

As the lithium source, one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate can be used. When lithium carbonate is used as the lithium source, for example, the cost is lower than when lithium hydroxide is used. One or more of water-soluble sulfate and water-soluble chloride can be used as the water-soluble sintering aid, and the addition of the water-soluble sintering aid can further reduce the sintering temperature and avoid the influence of high-temperature sintering on the particle morphology and the performance of the high-nickel material.

And 4, sintering for the second time: and (3) adding a coating material M4 into the product obtained by sintering in the step (3) for sintering, and then performing cooling and annealing treatment after sintering to obtain the lithium ion battery cathode composition, wherein the chemical formula of the lithium ion battery cathode composition is shown as the formula (I):

[Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d (I)

Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂is the chemical formula of the core of the lithium ion battery cathode composition, Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂Is the chemical formula of the shell of the lithium ion battery cathode composition; the M4 is selected from one or more of alkali metal elements, alkaline earth metal elements, IIIA group elements, IVA group elements, transition metals and rare earth elements; wherein s, r and d are mole fractions, s is more than or equal to 1.01 and less than or equal to 1.07, and r is more than or equal to 0 and less than or equal to 0.02，0.70≤d≤1。

In one embodiment, when t is 0, the product obtained in the step 4 reaction is [ Li ═ Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]_d·[Li_sNi_1-m-nCo_mM2_n)_1-rM6_rO₂]_1-d。

As an embodiment, when z is 0 and t is 0, the product obtained from the reaction of step 4 is [ Li ═ 0_a(Ni_1-x- _yCo_xM1_y)O₂]_d·[Li_sNi_1-m-nCo_mM2_n)_1-rM6_rO₂]_1-d。

In one embodiment, when z is 0, t is 0, and r is 0, the reaction of step 4 yields a product of [ Li ═ 0_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_sNi_1-m-nCo_mM2_nO₂]_1-d。

In one embodiment, when z is 0, t is 0, r is 0, and d is 1, the product obtained in the step 4 reaction is Li_a(Ni_1-x-yCo_xM1_y)O₂。

In the embodiment of the invention, the sintering is carried out by adding a lithium source and a water-soluble auxiliary agent at the high temperature of 1000 ℃ and 500 ℃ in the air or oxygen atmosphere for 1-12 hours.

In some embodiments, different temperature-reducing annealing treatments may also produce different effects. Furnace cooling, staged rate cooling or rate cooling can be adopted, as an implementation mode, the cooling rate of the rate cooling is 0.01-3.0 ℃/min; as an embodiment, the cooling rate is 0.02-2.5 ℃/min; as an embodiment, the cooling rate is 0.02-1.0 deg.C/min. The composition is of a core-shell structure, and in the cooling process, if the temperature is rapidly reduced and the temperature difference change is too large, the crystallization stress of the core and the shell is inconsistent, and the stress is distorted, the shell is cracked, and the core-shell structure cannot be formed; the core-shell structure is formed by adopting rate cooling, staged rate cooling or furnace cooling, the cooling rate is slow, and the contraction ratio of the core and the shell can be effectively prevented from being inconsistent; meanwhile, the annealing process eliminates oxygen defects formed by local overburning of the material in the sintering process, so that the obtained material has higher crystallinity and better structural stability. Therefore, the high-nickel core-shell structure cathode material obtained by the preparation method has high structural stability and long cycle life.

In one embodiment, the method further includes washing the first sintering product, mixing the washed first sintering product with a water-soluble sintering aid and a coating material M6, grinding the mixture, and sintering the mixture.

In some embodiments, the cleaning means is flushed with a stream of carbon dioxide gas; in some embodiments, the washing means is washing with carbonated water. The residual alkali on the surface of the positive electrode material cleaned by carbon dioxide airflow or carbonated water is effectively reduced, the attack of alkaline substances on the surface of the positive electrode material on a binder in a positive electrode glue solution in the configuration process of the positive electrode material is reduced, double bonds formed by the binder are avoided, the coating effect is improved, and the performance of a battery cell is improved.

In some embodiments, M3, M4, and M6 are each independently selected from one or more of alkali metal elements, alkaline earth metal elements, group IIIA elements, group IVA elements, transition metals, and rare earth elements.

In one embodiment, M3, M4, and M6 are each independently selected from at least one of Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm, and Mo. In some cases, M3 is derived from one or more of an oxide of metal M3, a hydroxide of metal M3, a chloride of metal M3, a sulfate of metal M3, a nitrate of metal M3, a fluoride of metal M3, a sulfide of metal M3, a telluride of metal M3, a selenide of metal M3, an antimonide of metal M3, a phosphide of metal M3, and a complex oxide of metal M3. In some cases, M4 is derived from one or more of an oxide of metal M4, a hydroxide of metal M4, a chloride of metal M4, a sulfate of metal M4, a nitrate of metal M4, a fluoride of metal M4, a sulfide of metal M4, a telluride of metal M4, a selenide of metal M4, an antimonide of metal M4, a phosphide of metal M4, and a complex oxide of metal M4. In some cases, M6 is derived from one or more of an oxide of metal M6, a hydroxide of metal M6, a chloride of metal M6, a sulfate of metal M6, a nitrate of metal M6, a fluoride of metal M6, a sulfide of metal M6, a telluride of metal M6, a selenide of metal M6, an antimonide of metal M6, a phosphide of metal M6, and a complex oxide of metal M6. In one embodiment, Mg is derived from one or more of magnesium hydroxide, magnesium chloride, magnesium sulfate, magnesium carbonate, and magnesium nitrate.

According to the technical scheme, different metal elements are coated on the surface of the core and/or the shell of the lithium ion battery cathode composition, and the influence on the structure and the size of the unit cell is different, so that the influence on the multiplying power and the specific capacity of the material is different, and the alkali metal elements and the alkaline earth metal elements have certain structures, so that the stability of a laminated structure is facilitated, the crystal structure is smoother, the unit cell collapse in the circulating process is prevented, the capacity density is facilitated to be improved, and the capacity and the multiplying power performance of the lithium ion battery cathode composition are facilitated to be improved.

According to the method, a metal source compound and a dispersing agent are used for coprecipitation to obtain a single crystal precursor, then the single crystal precursor is mixed with a lithium source and a water-soluble auxiliary agent, the mixture is ground and sintered to obtain a single crystal anode material, wherein the single crystal precursor is of a core-shell structure, and the finally prepared anode material is single-crystal in shape and has a core-shell structure.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

Fig. 2 is a schematic diagram of a process for forming a cathode composition for a lithium ion battery according to one embodiment of the present invention.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the embodiments, structures, features and effects according to the present invention will be made with reference to the accompanying drawings and preferred embodiments.

The lithium ion battery cathode composition of the present invention will be described in detail with reference to examples.

Example 1

A cathode composition of a lithium ion battery is a primary particle, and the structural formula of the cathode composition is as follows:

[Li_1.06(Ni_0.83Co_0.07Al_0.05Mn_0.05)O₂]_0.95·[Li_1.02(Ni_0.55Co_0.05Al_0.4)O₂]_0.05

Li_1.06(Ni_0.83Co_0.07Al_0.05Mn_0.05)O₂is the chemical formula of the core of the lithium ion battery cathode composition, Li_1.02(Ni_0.55Co_0.05Al_0.4)CO₃The chemical formula of the shell of the lithium ion battery cathode composition comprises the following steps:

step 1, preparation of Nuclear precursor

According to the molar ratio of the elements Ni: co: al: mn 0.83:0.07:0.05

Calculating and weighing soluble nickel salt, soluble cobalt salt, soluble aluminum salt and soluble manganese salt; adding the two into deionized water together to mix and prepare a first mixed aqueous solution A with the concentration of 1 mol/L;

mixing the first mixed aqueous solution A, ammonia water, carbonate solution and a dispersing agent, controlling the pH to be 9, reacting at the constant temperature of 60 ℃ for 3 hours, cooling to 30 ℃, filtering, washing and drying precipitates to obtain Ni_0.83Co_0.07Al_0.05Mn_0.05CO₃；

Step 2, preparation of shell precursor

Dissolving Ni source, Co source and Al source in deionized water in proportion to obtain a second mixed aqueous solution, mixing with Ni_0.83Co_0.07Al_0.05Mn_0.05CO₃Mixing ammonia water and NaOH solution, controlling the reaction temperature of the system at 60 ℃, controlling the stirring speed at 750 rpm, adjusting the pH of the mixed solution to 10, and carrying out coprecipitationAfter 3 hours of precipitation reaction, the precipitate is filtered, washed and dried to obtain the composition with the core-shell structure.

Step 3, preparation of lithium ion battery cathode composition with core-shell structure

And (2) mixing the precursor obtained in the step (2), dried lithium carbonate and a water-soluble auxiliary agent in proportion, wherein the use amount of the lithium carbonate is that the molar ratio of Li in the lithium carbonate to (Ni + Co + Al) in the lithium ion battery cathode composition is 0.86, the addition amount of the water-soluble sintering auxiliary agent is that the mass ratio of the lithium ion battery cathode composition is 10%, uniformly mixing and grinding, sintering in an oxygen atmosphere, heating to 850 ℃ for reaction for 12 hours, and then cooling to room temperature along with the furnace to obtain a target product with a core-shell structure.

The structural formula of the target product is as follows:

ICP element analysis test results show that the mole percentages of Ni, Co, Al and Mn are as follows:

example 2

Embodiment 2 of the present invention provides a lithium ion battery cathode composition doped with Si core, having a structural formula:

[Li_1.05(Ni_0.85Co_0.08Al_0.03Mn_0.03Si_0.01)O₂]_0.93·[Li_1.03(Ni_0.58Co_0.07Mn_0.35)O₂]_0.07

the preparation process is similar to example 1, except that:

step 1, preparation of Nuclear precursor

According to the molar ratio of the elements Ni: co: al: mn: si is 0.85:0.08:0.03:0.03:0.01

Calculating and weighing soluble nickel salt, soluble cobalt salt, soluble aluminum salt, soluble manganese salt and doping agent SiO₂(ii) a The first mixed aqueous solution A and the second mixed aqueous solution A are added into deionized water together and mixed to prepare 1mol/L first mixed aqueous solution A.

The structural formula of the target product in this example 2 is:

the ICP element analysis test result shows that the mole percentages of the metals of Ni, Co, Al, Mn and Si are as follows:

example 3

Embodiment 3 of the present invention provides a Ta core-doped and Nb shell-doped lithium ion battery cathode composition, which has a structural formula:

[Li_1.07(Ni_0.86Co_0.08Al_0.03Mn_0.02Ta_0.01)O₂]_0.9·[Li_1.05(Ni_0.53Co_0.15Al_0.1Mn_0.2Nb_0.02)O₂]_0.1

the preparation method is similar to that of example 2, except that:

step 1, preparation of Nuclear precursor

According to the molar ratio of the elements Ni: co: al: mn: ta 0.86:0.08:0.03:0.02:0.01

Calculating and weighing soluble nickel salt, soluble cobalt salt, soluble aluminum salt, soluble manganese salt and dopant Ta₂O₅(ii) a The first mixed aqueous solution A and the second mixed aqueous solution A are added into deionized water together and mixed to prepare 1mol/L first mixed aqueous solution A.

Step 2, preparation of shell precursor

Ni source, Co source, Al source,Dissolving Mn source and Nb source in deionized water in proportion to obtain a second mixed aqueous solution, mixing with Ni_0.86Co_0.08Al_0.03Mn_0.02Ta_0.01CO₃Mixing ammonia water and NaOH solution, controlling the reaction temperature of the system at 60 ℃, controlling the stirring speed at 750 rpm, adjusting the pH of the mixed solution to 10, carrying out coprecipitation reaction for 3 hours, and filtering, washing and drying the precipitate to obtain a precursor with a core-shell structure.

The target product of this example 3 has the formula:

ICP element analysis test results show that the mole percentages of Ni, Co, Al, Mn, Ta and Nb are as follows:

example 4

This example 4 provides a lithium ion battery cathode composition doped with a Y shell, having the structural formula:

[Li_1.035(Ni_0.88Co_0.08Al_0.04)O₂]_0.88·[Li_1.01(Ni_0.52Co_0.15Al_0.3Y_0.03)O₂]_0.12

ICP element analysis test results show that the mole percentages of Ni, Co, Al and Y are as follows:

example 5

Example 5 provides Mg Nuclear doped, Ga₂O₃Shell-coated lithium ion battery cathode assemblyThe compound has a structural formula:

[Li_1.02(Ni_0.90Co_0.08Al_0.01Mg_0.01)O₂]_0.85·[Li_1.015(Ni_0.34Co_0.26Mn_0.4)_0.98Ga_0.02O₂]_0.15

ICP element analysis test results show that the mole percentages of Ni, Co, Al, Mn, Mg and Ga are as follows:

example 6

Example 6 provides a cathode composition for a lithium ion battery with Er core doped, W shell doped, and SrO shell coated, the structural formula of which is:

[Li_1.025(Ni_0.91Co_0.05Al_0.03Er_0.01)O₂]_0.82·[Li_1.03(Ni_0.45Co_0.13Al_0.1Mn_0.3W_0.02)_0.98Sr_0.02O₂]_0.18

the ICP element analysis test result shows that the mole percentage of each metal of Ni, Co, Al, Mn, Er, W and Sr is as follows:

example 7

Example 7 provides Mo Nuclear doped, La₂O₃The shell-coated lithium ion battery cathode composition has the structural formula:

[Li_1.055(Ni_0.92Co_0.03Mn_0.04Mo_0.01)O₂]_0.8·[Li_1.02(Ni_0.5Co_0.15Al_0.35)_0.999La_0.001O₂]_0.2

ICP element analysis test results show that the mole percentages of the metals of Ni, Co, Al, Mn, Mo and La are as follows:

example 8

This example 8 provides a Sr-doped, MgO shell coated lithium ion battery cathode composition having the structural formula:

[Li_1.04(Ni_0.93Co_0.02Mn_0.04Sr_0.02)O₂]_0.75·[Li_1.05(Ni_0.6Co_0.1Mn_0.3)_0.998Mg_0.002O₂]_0.25

the ICP element analysis test result shows that the mole percentage of each metal of Ni, Co, Mn, Mg and Sr is as follows:

example 9

This example 9 provides Ce core-doped, Sm shell-doped, Al₂O₃The shell-coated lithium ion battery cathode composition has the structural formula:

[Li_1.01(Ni_0.95Co_0.02Mn_0.02Ce_0.01)O₂]_0.7·[Li_1.03(Ni_0.7Co_0.09Al_0.1Mn_0.1Sm_0.01)_0.98Al_0.02O₂]_0.3

the ICP element analysis test result shows that the molar percentages of the metals of Ni, Co, Al, Mn, Ce and Sm are as follows:

example 10

The structural formula of the cathode composition of the lithium ion battery provided in this example 10 is:

[Li_1.06(Ni_0.62Co_0.28Al_0.05Mn_0.05)O₂]_0.95·[Li_1.02(Ni_0.34Co_0.33Mn_0.33)O₂]_0.05

example 11

The target product of the cathode composition for lithium ion batteries provided in this example 11 has the structural formula:

[Li_1.06(Ni_0.65Co_0.25Al_0.05Mn_0.05)O₂]_0.95·[Li_1.02(Ni_0.34Co_0.33Mn_0.33)O₂]_0.05

examples 4 to 14 are similar to the preparation methods of examples 1 to 3, except that: the reaction conditions, raw material ratios and products of each step are shown in tables 1 and 2.

Example 15

A lithium ion battery cathode composition is a primary particle, and has a structural formula as follows:

Li_1.06(Ni_0.65Co_0.25Al_0.05Mn_0.05)O₂the preparation method comprises the following steps:

step 1, precursor Ni_0.65Co_0.25Al_0.05Mn_0.05CO₃Preparation of

According to the molar ratio of the elements of Ni, Co, Al and Mn being 0.65, 0.25, 0.05 and 0.05

mixing the first mixed aqueous solution A, ammonia water, carbonate solution and a dispersing agent, controlling the pH to be 9, reacting at the constant temperature of 60 ℃ for 3 hours, cooling to 30 ℃, filtering, washing and drying precipitates to obtain Ni_0.65Co_0.25Al_0.05Mn_0.05CO₃；

Step 2, preparation of cathode composition of lithium ion battery

And (3) sintering: drying lithium carbonate until crystal water is completely lost, and mixing with the Ni prepared in the step 1_0.65Co_0.25Al_0.05Mn_0.05CO₃Mixing the water-soluble sintering aid in proportion, wherein the use amount of lithium carbonate is that the molar ratio of Li in lithium carbonate to (Ni + Co + Al + Mn) in the composition is 0.86, the addition amount of the water-soluble sintering aid is that the mass ratio of the composition is 10%, uniformly mixing and grinding, sintering in an oxygen atmosphere, heating to 820 ℃, reacting for 16 hours, and then cooling to room temperature at a cooling rate of 0.3 ℃/min; the structural formula of the target product is as follows: li_1.06(Ni_0.65Co_0.25Al_0.05Mn_0.05)O₂。

Example 16

A lithium ion battery cathode composition is a primary particle, and has a structural formula as follows: li_1.03(Ni_0.71Co_0.19Al_0.10)O₂The preparation process is analogous to example 15.

Example 17

A lithium ion battery cathode composition is a primary particle, and has a structural formula as follows: li_1.07(Ni_0.86Co_0.09Mn_0.05)O₂The preparation process is analogous to example 15.

Example 18

A lithium ion battery cathode composition is a primary particle, and has a structural formula as follows: li_1.04(Ni_0.93Co_0.02Al_0.025Mn_0.025)O₂The preparation process is analogous to example 15.

Comparative example 1

Comparative example 1 provides a ternary cathode material of the formula Li_1.035Ni_0.815Co_0.15Al_0.035O₂The preparation method comprises the following steps:

step (1), primary sintering: precursor Ni of ternary positive electrode material_1-x-yCo_xAl_y(OH)_2+ySintering, heating to 500 ℃ and reacting for 10 hours;

step (2), sintering for the second time: and (2) drying the lithium hydroxide monohydrate until crystal water is completely lost, and mixing the lithium hydroxide monohydrate with the sintered product obtained in the step (1), wherein the dosage of the lithium hydroxide monohydrate is that the molar ratio of Li in the lithium hydroxide monohydrate to (Ni + Co + Al) in the precursor of the ternary cathode material is 1.035: 1, uniformly mixing and grinding, sintering in an oxygen atmosphere, heating to 715 ℃, reacting for 16.5 hours, and then cooling to room temperature at a cooling rate of 0.3 ℃/min;

step (3), sintering for the third time: heating the sintered product obtained in the step (2) to 650 ℃, sintering for 3.5 hours, and cooling to room temperature to obtain the comparative material Li_1.035Ni_0.815Co_0.15Al_0.035O₂。

Table 1, examples 1 to 18 and comparative example 1 reaction conditions in the respective steps

Table 2, examples 1 to 18 and comparative example 1 Each step reaction conditions and products

Assembling a CR2032 button battery:

the cathode composition of the lithium ion battery prepared in the embodiment 1-18 and the anode material prepared in the comparative example 1 are used as active substances of an anode, a metal lithium sheet is used as a cathode, a Celgard 2500 diaphragm is used as a diaphragm, electrolyte is fosai LB-002 electrolyte of Suzhou Buddhist New Material Co., Ltd, a CR2032 type button battery is assembled according to the prior art, and the assembling sequence is as follows: the positive cover is flatly placed, the spring piece is placed, the stainless steel sheet is placed, the positive plate is placed, the electrolyte is injected, the diaphragm sheet is placed, the lithium sheet is placed, the negative cap is covered, the sealing is carried out, and the assembly is completed. The cell was assembled in a dry glove box filled with argon. After the assembly was completed, the cell was subjected to performance testing, the test results of which are shown in table 3.

1. ICP elemental detection

The test method comprises the following steps: inductively coupled plasma mass spectrometry test method

Inductively coupled plasma mass spectrometer

The model is as follows: prodigy DC Arc

Test instrument manufacturers: leisha Leibos company, Rieman

2. Resistivity of powder

The test method comprises the following steps: four-probe method

The instrument name: powder resistance tester

The instrument model is as follows: MCP-T700

The instrument manufacturer: mitsubishi chemical

3. Cycle performance

Name of the test instrument: xinwei battery detection system, model: BTS-5V10mA

Test instrument manufacturers: shenzhen, New Wille electronics, Inc.;

the test method comprises the following steps: charging to 4.3V at a constant current of 1C at 25 ℃, keeping the constant voltage of 4.3V to 0.05C, then discharging to 3V at 1C, repeatedly carrying out 100 times of the charge-discharge cycles, measuring the discharge capacity at the first cycle and the discharge capacity at the 100 th cycle, and calculating the capacity retention rate after 100 cycles, wherein the formula is as follows: capacity retention after cycling ═ 100% of (discharge capacity at 100 th cycle)/(discharge capacity at first cycle).

4. Tap density

Name of the test instrument: tap density instrument

The instrument model is as follows: JZ-1

The instrument manufacturer: chengdu refined powder test equipment Co Ltd

The test method comprises the following steps: about 10 to 20g of the positive electrode material was weighed with an accuracy of 0.0001 g. And (3) putting the positive electrode material into the measuring cylinder, and then fixing the measuring cylinder on the bracket. The positive electrode material was repeated 3000 times tapping (i.e., automatically lifting and dropping the cylinder), and then the corresponding volume was measured. Tap density is the mass after tapping/volume after tapping. Three replicates were performed and the results listed in table 2 represent the average of the three experiments.

5. The surface residual alkali amount test method comprises the following steps: acid-base titration method

(1) Preparing a positive electrode material clear solution: w was weighed with an accuracy of 0.0001g₁(30.0000. + -. 0.0040g) of a positive electrode material, and W was weighed with an accuracy of 0.01g₂(100 +/-0.1 g) deionized water, mixing the cathode material with the deionized water, replacing air in the mixed solution with argon, stirring, filtering to obtain a filtrate, transferring 50mL of the filtrate, and putting the filtrate into a 100mL beaker for titration;

(2) measurement of LiOH content: using phenolphthalein as an indicator, titrating with 0.05mol/L hydrochloric acid standard solution, and measuring the volume V of the consumed hydrochloric acid standard solution at the end point₁；

(3) Measurement of Li₂CO₃The content is as follows: replacing CO in the titrated clear liquid in the step (2) by argon₂Then titrating with 0.05mol/L hydrochloric acid standard solution by using methyl red indicator, and measuring the volume V of the consumed hydrochloric acid standard solution at the end point₂；

LiOH content (wt%) calculation formula: omega₁＝(2V₁-V₂)*0.05*2.395*W₂/W₁/50；

Li₂CO₃Content (wt%) calculation formula: omega₂＝(V₂-V₁)*0.05*7.389*W₂/W₁/50；

2.395: the mass of LiOH in g corresponding to the hydrochloric acid standard solution (1.000 mol/L);

7.389: with hydrochloric acid standard solution (2)000mol/L) of Li in g₂CO₃The mass of (c);

surface residual alkali content of positive electrode material omega₁+ω₂。

Table 3, examples 1-18 and comparative example 1 Performance test results

Referring to tables 1 to 3 together, it can be seen that:

example 1 compared with comparative example 1, in the cathode composition for a lithium ion battery of the core-shell structure of example 1, the capacity retention rate after 100 cycles is 95.2%, the surface residual alkali amount is 0.32% by weight, in the cathode material of the comparative example 1, the capacity retention rate after 100 cycles is 79.7%, the surface residual alkali amount is 0.83% by weight, and compared with comparative example 1, the cathode composition for a lithium ion battery of the core-shell structure of example 1 has more stable cycle performance and reduced surface residual alkali.

Example 2 compared to comparative example 1, example 2 is a cathode composition for a lithium ion battery doped with an Si core, the capacity retention ratio after 100 cycles is 101.2%, the weight percentage of surface residual alkali is 0.38%, the cathode material of comparative example 1 has a capacity retention ratio after 100 cycles is 79.7%, the weight percentage of surface residual alkali is 0.83%, and compared to comparative example 1, the cathode composition for a lithium ion battery doped with an Si core of example 2 has more stable cycle performance with reduced surface residual alkali.

Example 3 in comparison with comparative example 1, example 3 was prepared by doping with Ta nuclei and Nb₂O₅The cathode composition for the lithium ion battery, which is obtained by coating the shell and cleaning the shell by using carbon dioxide airflow, has the capacity retention rate of 106 percent after being circulated for 100 circles, the weight percentage of the surface residual alkali of 0.14 percent, the anode material of the comparative example 1 and the capacity after being circulated for 100 circlesThe retention ratio was 79.7%, the surface residual alkali content was 0.83% by weight, and in comparison with comparative example 1, Ta core doping and Nb core doping were used in example 3₂O₅The shell-coated cathode composition for a lithium ion battery has more stable cycle performance; and the carbon dioxide airflow is adopted for cleaning, so that the residual alkali on the surface is effectively reduced.

Example 4 in comparison with comparative example 1, example 4 was carried out using Y₂O₃The cathode composition for a lithium ion battery obtained by coating the shell and washing the cathode composition with carbonated water has a capacity retention rate of 103.5% and a surface residual alkali weight percentage of 0.12% after 100 cycles, and the cathode material of comparative example 1 has a capacity retention rate of 79.7% and a surface residual alkali weight percentage of 0.83% after 100 cycles, compared with comparative example 1, in example 4 using Y₂O₃The shell-coated cathode composition for a lithium ion battery has more stable cycle performance; the residual alkali on the surface is effectively reduced by adopting carbonated water for cleaning.

Example 5 compared with comparative example 1, example 5 is a cathode composition for a lithium ion battery obtained by Mg core doping, Ga core doping and carbon dioxide gas stream cleaning, the capacity retention ratio after 100 cycles is 96.7%, the weight percentage of surface residual alkali is 0.11%, the cathode material of comparative example 1 has a capacity retention ratio after 100 cycles of 79.7%, the weight percentage of surface residual alkali is 0.83%, and compared with comparative example 1, the cathode composition for a lithium ion battery obtained by Mg core doping and Ga core doping of example 5 has more stable cycle performance; and the carbon dioxide airflow is adopted for cleaning, so that the residual alkali on the surface is effectively reduced.

Example 6 compared with comparative example 1, example 6 is a cathode composition for a lithium ion battery obtained by Er core doping, W shell doping, SrO shell coating and carbon dioxide gas stream cleaning, the capacity retention rate after 100 cycles is 102%, the weight percentage of surface residual alkali is 0.12%, the capacity retention rate after 100 cycles is 79.7%, the weight percentage of surface residual alkali is 0.83% of the cathode material of comparative example 1, and the cathode composition for a lithium ion battery obtained by Er core doping and SrO shell coating in example 6 has more stable cycle performance compared with comparative example 1; and the carbon dioxide airflow is adopted for cleaning, so that the residual alkali on the surface is effectively reduced.

Example 7 in comparison with comparative example 1, example 7 was carried out by doping with Mo nuclei and La₂O₃The cathode composition for the lithium ion battery obtained by coating the shell and cleaning the shell with carbonated water has the capacity retention rate of 102.6 percent and the surface residual alkali weight percentage of 0.08 percent after 100 cycles, and the cathode material of the comparative example 1 has the capacity retention rate of 79.7 percent and the surface residual alkali weight percentage of 0.83 percent after 100 cycles, compared with the comparative example 1, the cathode composition for the lithium ion battery obtained by coating the shell and cleaning the cathode composition with carbonated water adopts Mo core doping and La core doping, and the cathode composition for the lithium ion battery obtained by coating the shell and cleaning the cathode material with carbonated water₂O₃The shell-coated cathode composition for a lithium ion battery has more stable cycle performance; the residual alkali on the surface is effectively reduced by adopting carbonated water for cleaning.

Example 8 in comparison to comparative example 1, example 8 was prepared using SrO nuclear doping, Mg (OH)₂The cathode composition for a lithium ion battery coated with a shell has a capacity retention rate of 101.5% and a surface residual alkali content of 0.22% after 100 cycles, and the cathode material of comparative example 1 has a capacity retention rate of 79.7% and a surface residual alkali content of 0.83% after 100 cycles, compared to comparative example 1, in example 8 in which SrO core doping, Mg (OH)₂The cathode composition for a lithium ion battery coated with the shell has more stable cycle performance and reduced surface alkali residue.

Example 9 in comparison with comparative example 1, example 9 was carried out using Ce core doping, Sm shell doping, Al₂O₃The cathode composition for a lithium ion battery obtained by coating the shell and cleaning the cathode composition with carbonated water has a capacity retention rate of 101.8% and a surface residual alkali weight percentage of 0.03% after 100 cycles, and the cathode material of comparative example 1 has a capacity retention rate of 79.7% and a surface residual alkali weight percentage of 0.83% after 100 cycles, and compared with comparative example 1, example 9 adopts Ce core doping, Sm shell doping, Al core doping and Al core doping₂O₃The shell-coated cathode composition for a lithium ion battery has more stable cycle performance; the residual alkali on the surface is effectively reduced by adopting carbonated water for cleaning.

Examples 10 to 14 compare example 3, in which Ta core doping and Nb are used as example 3₂O₅The cathode composition for the lithium ion battery obtained by coating the shell and cleaning the cathode composition by using carbon dioxide airflow has the capacity retention rate of 106% after being circulated for 100 circles, the weight percentage of the surface residual alkali is 0.14%, and the capacity retention rates of 99.5%, 99.2%, 99.1%, 96.65% and 96.98% after being circulated for 100 circles in examples 10 to 14 respectively; in comparison with examples 10 to 14, example 3 is a Ta-core doped, Nb₂O₅The cathode composition for the lithium ion battery, which is coated with the shell-coated core shell, can improve the nickel content and also has stable capacity retention rate.

In summary, the cathode composition for lithium ion batteries with a core-shell structure of the present invention has at least the following advantages:

(1) the cathode composition for the lithium ion battery with the core-shell structure has more stable cycle performance: compared with the comparative example 1, after the cycles of the examples 1 to 9 are 100 times, the capacity retention rate of the cathode composition of the core-shell structure for the lithium ion battery prepared by the embodiment of the invention is higher than that of the traditional ternary cathode material of the comparative example 1; compared with the traditional ternary cathode material, the cathode composition for the lithium ion battery has a core-shell structure, and can effectively inhibit the corrosion of electrolyte on the body material and the dissolution of metal ions, so that more lithium vacancies of the active material are kept, and the cycling stability of the material is improved.

(2) The cathode composition for the lithium ion battery prepared by core doping, shell coating and core-shell coating has more stable cycle performance: compared with the embodiment 1, the embodiments 2 and 5 are nuclear doping, and the capacity retention rates of the embodiments 2 and 5 after 100 cycles are respectively 101.2% and 96.7%, which are higher than those of the embodiment 1: the nuclear doping can improve the cycle stability;

in example 4, the shell is doped, and the capacity retention rate after 100 cycles is 103.5%, which is obviously higher than that in example 1: shell doping is shown to improve cycling stability; similarly, in example 4, compared with examples 2 and 5, the capacity retention ratio of example 4 was 103.5% higher than that of examples 2 and 5, i.e., 101.2% and 96.7%: the shell doping is superior to the core doping in the core-shell structure for improving the cycle stability;

examples 3 and 6 to 9 are core-shell doping, and the capacity retention rates of examples 3 and 6 to 9 after 100 cycles are 106%, 102%, 102.6%, 101.5% and 101.8%, respectively, which are higher than those of example 1: the core-shell doping can improve the cycling stability.

(3) The anode material cleaned by carbon dioxide gas flow or carbonic water effectively reduces the surface residual alkali: compared with the unwashed positive electrode materials in the embodiments 1, 2 and 8 and the comparative example 1, the positive electrode materials in the embodiments 3 to 7 and 9 are washed by carbon dioxide airflow or carbonated water, and the residual alkali amount on the surface of the positive electrode material washed by the carbon dioxide airflow or the carbonated water is effectively reduced, so that the attack of alkaline substances on the surface of the positive electrode material on the binder in the positive electrode glue solution is reduced in the configuration process of the positive electrode material, the double bonds formed by the binder are avoided, the coating effect is improved, and the cell performance is improved.

(4) By using Al₂O₃The shell coating can effectively reduce the surface residual alkali amount of the anode material: example 9 compared with example 6, example 6 adopted Er core doping, W shell doping and SrO shell coating, and the weight percentage of the surface residual alkali was 0.12%; example 9 core doping with Ce, shell doping with Sm and Al₂O₃The shell is coated, the weight percentage of the surface residual alkali is 0.03 percent, and the surface residual alkali is obviously reduced. Active lithium on the surface of the anode material and CO in the air₂、H₂O reaction to produce LiOH and Li₂CO₃Using Al₂O₃Is coated with Al₂O₃Can react with active lithium on the surface of the anode material to generate LiAlO₂The active lithium content on the surface of the anode material is reduced, so that LiOH and Li on the surface of the anode material are reduced₂CO₃The content of the residual alkali on the surface of the positive electrode material is effectively reduced, so that the attack of alkaline substances on the surface of the positive electrode material on the binder in the positive electrode glue solution can be reduced in the preparation process of the positive electrode material, the binder is prevented from forming double bonds to generate adhesion, the slurry jelly is prevented from being caused, the coating effect is improved, and the performance of a battery cell is improved.

(5) With Mg (OH)₂The shell coating has more stable cycle performance, and the surface residual alkali amount is effectively reduced: example 8 compared to example 1Using Sr nucleus doped, Mg (OH)₂The shell is coated, the capacity retention rate is 95.2 percent and the weight percentage of the surface residual alkali is 0.32 percent after the cycle of 100 circles in the embodiment 1; the capacity retention rate is 103.5% after the cycle of the embodiment 4 is cycled for 100 circles, the weight percentage of the surface residual alkali is 0.12%, the cycle performance is more stable, and the surface residual alkali is effectively reduced. The addition of the metal element Mg effectively improves the structural stability of the anode material, reduces the strong side reaction of the anode material and the organic electrolyte, and reduces the impedance of the battery in the charging and discharging processes, thereby improving the electrochemical performance of the anode material, and Mg (OH)₂The shell-coated modified cathode material has higher capacity retention rate and more stable cycle performance.

(6) The powder resistivity of the anode material can be effectively reduced by adopting Al shell coating: example 2 is Si core doping with a powder resistivity of 181 Ω · cm; example 4 is Y shell doping with a powder resistivity of 192 Ω cm; in comparison with examples 2 and 4, example 9 was Ce core-doped, Sm shell-doped, and Al shell-coated, and the powder resistivity was 162 Ω · cm. By using Al₂O₃Is coated with Al₂O₃Can react with active lithium on the surface of the anode material to generate LiAlO₂，LiAlO₂The high-speed ion conductor can reduce the resistance of electron migration, thereby effectively reducing the powder resistivity of the positive electrode material.

(7) The appropriate shell thickness in the core-shell structure can improve the stability and capacity of the lithium ion battery cathode composition: the thickness of the lithium ion battery cathode composition shell of the embodiment of the invention is 0.05-1.1 μm; if the thickness of the shell is too thin, the shell is easily corroded by the electrolyte to expose the core, which affects the stability of the cathode composition of the lithium ion battery; conversely, if the shell is too thick, the capacity of the lithium ion battery cathode composition may be reduced. The lithium ion battery cathode composition provided by the embodiment of the invention has proper shell thickness, can balance the stability of the lithium ion battery cathode composition and the capacity of the lithium ion battery cathode composition, and has optimal stability and capacity.

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A preparation method of a cathode composition of a lithium ion battery is characterized by comprising the following steps:

step 1, nuclear precursor preparation: preparing a first mixed aqueous solution of a Ni source compound, a Co source compound, a M1 source compound and a M3 source compound, mixing the first mixed aqueous solution, a carbonate solution and ammonia water, and reacting under an alkaline condition to obtain a nuclear precursor Ni_1-x-y-zCo_xM1_yM3_zCO₃(ii) a Wherein M1 is selected from Mn and/or Al; m3 is at least one selected from Mg, Zr, Al, Sc, Ti, W, Sr, Nb, Si, Y, La, Ta, Cs, Ce, Ga, Sn, Er, V, Sm and Mo; x, y and z are mole fractions, x>0，0.01≤y≤0.10，0≤z≤0.02，0.60≤1-x-y-z≤0.96；

Step 3, first sintering: and (3) mixing and grinding the product obtained in the step (2), a lithium source and a water-soluble sintering aid, sintering, and cooling to room temperature after sintering is completed.

And 4, sintering for the second time: and (3) adding a coating material M6 into the product obtained by sintering in the step (3) for sintering, and then performing cooling and annealing treatment after sintering to obtain the target property right with a core-shell structure, wherein the chemical formula is as follows:

Li_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂is the chemical formula of the core of the lithium ion battery cathode composition, Li_s(Ni_1-m-n- _tCo_mM2_nM4_t)_1-rM6_rO₂Is the chemical formula of the shell of the lithium ion battery cathode composition; the M6 is selected from one or more of alkali metal elements, alkaline earth metal elements, IIIA group elements, IVA group elements, transition metals and rare earth elements; wherein a, s, r and d are mole fractions, a is more than or equal to 1.01 and less than or equal to 1.07, s is more than or equal to 1.01 and less than or equal to 1.07, r is more than or equal to 0 and less than or equal to 0.02, and d is more than or equal to 0.70 and less than or equal to 1.

2. The method for preparing the cathode composition of the lithium ion battery according to claim 1, wherein the step 4 further comprises cleaning the secondary sintering product obtained in the above step, mixing the cleaned secondary sintering product with a water-soluble sintering aid and a coating material, grinding the mixture, and sintering the mixture.

3. The method for preparing the cathode composition of the lithium ion battery according to claim 1, wherein in the step 1, the reaction is carried out in the presence of a dispersant, and the dispersant is one or more of a surfactant, polyvinyl alcohol and polyglycerol.

4. The method of claim 3, wherein the surfactant is polyoxyethylene octylphenol ether-10.

5. The method for preparing the cathode composition of the lithium ion battery according to claim 1, wherein the M3, M4 and M6 are each independently selected from at least one of Si, Ta, Nb, Y, Mg, Ga, Er, W, Sr, Mo, La, Ce, Sm and Al.

6. The method of claim 1, wherein r is 0, and wherein the lithium ion battery cathode composition has a chemical formula of [ Li ═ 0 [_a(Ni_1-x-y-zCo_xM1_yM3_z)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)O₂]_1-dX, y, z, m, n, t, a, s, d are mole fractions, x>0，0.01≤y≤0.10，0≤z≤0.02，0.80≤1-x-y-z≤0.96，m>0，0.2≤n≤0.4，0≤t≤0.02，0.30≤1-m-n-t≤0.70，1.01≤a≤1.07，1.01≤s≤1.07，0.70≤d≤1。

7. The method of preparing the lithium ion battery cathode composition of claim 6, wherein: z is 0, t is 0, and the chemical formula of the lithium ion battery cathode composition is [ Li-_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-nCo_mM2_n)O₂]_1-dX, y, m, n, a, s, d are mole fractions, x>0，0.01≤y≤0.10，0.80≤1-x-y≤0.96，m>0，0.2≤n≤0.4，0.30≤1-m-n≤0.70，1.01≤a≤1.07，1.01≤s≤1.07，0.70≤d≤1。

8. The method of preparing the lithium ion battery cathode composition of claim 7, wherein: d is 1, and the chemical formula of the lithium ion battery cathode composition is Li_a(Ni_1-x-yCo_xM1_y)O₂X, y, a are mole fractions, x>0，0.01≤y≤0.10，0.80≤1-x-y≤0.96，1.01≤a≤1.07。

9. The method of preparing the lithium ion battery cathode composition of claim 1, wherein: the surface residual alkali content of the lithium ion battery cathode composition is 0.03-0.38 wt%.

10. The method of preparing the lithium ion battery cathode composition of claim 1, wherein: the capacity retention rate of a battery prepared by the lithium ion battery cathode composition after 100 cycles is 94-106% under the 1C rate.