CN113428908A

CN113428908A - Lithium composite compound particle powder, preparation method thereof and lithium ion battery

Info

Publication number: CN113428908A
Application number: CN202010207391.XA
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 lithium composite compound particle powder, a preparation method thereof and a lithium ion battery, wherein the preparation method of the lithium composite compound particle powder comprises the following steps: preparing a nuclear precursor; preparing 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‑yCo_xM1_y)O₂]_d·[Li_s(Ni_{1‑m‑n‑t}Co_mM2_nM4_t)_1‑ _rM6_rO₂]_1‑d. The lithium composite compound particle powder with the core-shell structure 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

Lithium composite compound particle powder, preparation method thereof and lithium ion battery

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to lithium composite compound particle powder, a preparation method thereof and a lithium ion battery.

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 composite compound particle powder 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 this, embodiments of the present invention provide a lithium composite compound particle powder, a preparation method thereof, and a lithium ion battery.

The first aspect of the present invention provides a lithium composite compound, wherein the lithium composite compound particle powder has a core-shell structure, and the chemical formula of the lithium composite compound particle powder is represented by formula (I):

[Li_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d (I)

Li_a(Ni_1-x-yCo_xM1_y)O₂is a chemical formula of a core of the lithium composite compound particle powder, Li_s(Ni_1-m-n- _tCo_mM2_nM4_t)_1-rM6_rO₂A chemical formula of a shell that is the lithium composite compound particle powder; the M1 and M2 are respectively and independently selected from Mn and/or Al; the M4 and the 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, m, n, t, a, s, r 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, m is more than 0, n 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, 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, 1-x-y is more than or equal to 0.80 and less 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 less than or equal to 1.

The second aspect of the present invention provides a method for preparing the lithium composite compound particle powder, comprising the steps of:

step 1, nuclear precursor preparation: preparing a first mixed aqueous solution of a Ni source compound, a Co source compound and an M1 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-yCo_xM1_yCO₃(ii) a Wherein M1 is selected from Mn and/or Al; x and y are mole fractions, x>0，0.01≤y≤0.10，0.60≤1-x-y≤0.96；

Step 2, preparing a shell precursor: preparing a second mixed aqueous solution of Ni source compound, Co source compound, M2 source compound and M4 source compound, and mixing the second mixed aqueous solution with the corePrecursor Ni_1-x-yCo_xM1_yCO₃Mixing 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; 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-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d

Li_a(Ni_1-x-yCo_xM1_y)O₂is a chemical formula of a core of the lithium composite compound particle powder, Li_s(Ni_1-m-n- _tCo_mM2_nM4_t)_1-rM6_rO₂A chemical formula of a shell that is the lithium composite compound particle powder; the M2 is selected from Mn and/or Al; the M4 and the 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 m, n, t, s, r and d are mole fractions, m>0，0.2≤n≤0.4，0≤t≤0.02，0.30≤1-m-n-t≤0.70，1.01≤s≤1.07，0≤r≤0.02，0.70≤d≤1。

A third aspect of the invention provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, the positive electrode containing the lithium composite compound particle powder as described above.

In one aspect, the present invention provides a lithium composite compound particle powder having a chemical formula as shown in formula (I):

in some embodiments, the core of the lithium composite compound particle powder has the chemical formula Li_a(Ni_1-x-yCo_xM1_y)O₂The chemical formula of the shell of the lithium composite compound particle powder 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 and the M4 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-yCo_xAl_1- _yMn_y)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-yCo_xAl_1- _yMn_y)O₂The chemical formula of the shell is Li_s(Ni_1-m-n-tCo_mAl_nM4_t)_1-rM6_r O₂；

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- _yCo_xAl_1-yMn_y)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-yCo_xAl_y)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-yCo_xAl_y)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-yCo_xAl_y)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-yCo_xMn_y)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-yCo_xMn_y)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-yCo_xMn_y)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 composite compound particle powder has a layered or spinel structure. In one embodiment, the layered lithium composite compound particle powder includes 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. As one embodiment, the spinel lithium composite compound particle powder includes lithium manganate and/or lithium nickel manganate.

In the embodiment of the invention, x, y, m, n, t, a, s, r 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, m is more than or equal to 0, n 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, 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, 1-x-y is more than or equal to 0.60 and less 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 0.70 and less than or equal to 1.

In some embodiments, x >0, 0.01. ltoreq. y.ltoreq.0.05, m >0, 0.2. ltoreq. n.ltoreq.0.3, 0< t.ltoreq.0.02, 1.015. ltoreq. a.ltoreq.1.06, 1.015. ltoreq. s.ltoreq.1.06, 0< r.ltoreq.0.02, 0.80. ltoreq.1-x-y.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 composite compound particle powder (e.g., as in formula Li)_a(Ni_1-x-yCo_xM1_y)O₂1-x-y) 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 0.60, at least 0.61, at least 0.66, at least 0.68, or not more than 0.80A mole fraction of 0.96, no more than 0.957, no more than 0.955, no more than 0.953, no more than 0.951, no more than 0.95, no more than 0.94, no more than 0.93, no more than 0.92, no more than 0.91, no more than 0.90, no more than 0.89, no more than 0.88, no more than 0.86, no more than 0.85, no more than 0.83, no more than 0.82, no more than 0.81, no more than 0.80, no more than 0.75, no more than 0.71, no more than 0.70, no more than 0.69, no more than 0.68, no more than 0.67, no more than 0.66, no more than 0.65, no more than 0.64, no more than 0.63, no more than 0.62, no more than 0.61, no more than 0.60, and the like.

In some embodiments, the mole fraction of Li content in the lithium composite compound particle core (e.g., as in formula Li)_a(Ni_1-x-yCo_xM1_y)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⁺The lithium removal or lithium insertion can reduce the charge and discharge capacity of the lithium composite compound particle powder, the content of Li is too high, more byproducts are generated in the preparation process, and the obtained lithium composite compound particle powder 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 composite compound particle structure has an average particle diameter D50 of 3 to 5 μm, and a core average particle diameter D50 of 2.5 to 4 μm; the tap density of the lithium composite compound particle powder is 1.8-2.3g/cm³. In some embodiments, the lithium composite compound particle powder is a primary particle. In some cases, secondary particles as the lithium composite compound particle powder may also be present. The lithium composite compound particle powder has a core-shell structure, and can effectively inhibit the corrosion of electrolyte to 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 composite compound particle powder 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 composite compound particle powder 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.

In another aspect, an embodiment of the present invention further provides a method for preparing a lithium composite compound particle powder, including the steps of:

step 1, nuclear precursor preparation: preparing a first mixed aqueous solution of a Ni source compound, a Co source compound and an M1 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-yCo_xM1_yCO₃(ii) a Wherein x and y are mole fractions, and x>0，0.01≤y≤0.10，0.60≤1-x-y≤0.96；

In the embodiment of the invention, M1 is selected from Mn and/or Al; 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 ℃.

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-yCo_xM1_yCO₃Mixing 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 can be one or more of alkali metal element, alkaline earth metal element, IIIA group element, IVA group element, transition metal and rare earth element; 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; the 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 into 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 lithium composite compound particle powder 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.

The invention prepares Ni source compound, Co source compound, Mn source compound and/or Al source compound into solution, nickel salt, cobalt salt, aluminum salt and manganese salt can be uniformly distributed in the solution, and lithium composite compound particle powder are prepared by adopting the solution in which the nickel salt, cobalt salt, aluminum salt and manganese salt are uniformly distributed. The precipitation equilibrium constants Ksp of Ni, Co, Al and Mn are different and can influence the precipitation sequence of Ni, Co, Al and Mn in the solution, the reaction temperature, pH, solution concentration and stirring speed are optimized, the process is creatively improved, the Ni, Co, Al and Mn precipitation sequence is consistent, uniform precipitation is formed, the nickel, cobalt, aluminum and manganese are uniformly distributed in particles, the lithium composite compound particle powder prepared by the method is mixed with lithium salt, and the lithium composite compound particle powder is obtained by sintering, so that the crystal structure is more uniform, the framework structure is firmer, the material performance is favorably exerted, and the capacity and the rate performance of the lithium composite compound particle powder are 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 M6 into the product obtained by sintering in the step (3) for sintering, and after sintering is finished, performing cooling annealing treatment to obtain lithium composite compound particle powder, wherein the chemical formula of the lithium composite compound particle powder is shown as the formula (I):

Li_a(Ni_1-x-yCo_xM1_y)O₂is a chemical formula of a core of the lithium composite compound particle powder, Li_s(Ni_1-m-n- _tCo_mM2_nM4_t)_1-rM6_rO₂A chemical formula of a shell that is the lithium composite compound particle powder; the M4 and the 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 s, r and d are mole fractions, 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.

In one embodiment, when t is 0, the product obtained in the step 4 reaction is [ Li ═ Li_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-nCo_mM2_n)_1-rM6_rO₂]_1-d。

In one embodiment, when t is 0 and r is 0, the product obtained from the step 4 reaction is [ Li ═ 0_a(Ni_1-x- _yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-nCo_mM2_n)O₂]_1-d。

In one embodiment, when t is 0, r is 0, and d is 1, the product obtained from the reaction in step 4 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 lithium composite compound particle powder cleaned by carbon dioxide airflow or carbonated water is effectively reduced, the attack of alkaline substances on the surface of the lithium composite compound particle powder on a binder in the positive glue solution in the preparation process of the lithium composite compound particle powder 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, M4 and M6 are each independently selected from one or more of an alkali metal element, an alkaline earth metal element, a group IIIA element, a group IVA element, a transition metal, and a rare earth element.

In one embodiment, 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, 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 one embodiment, Mg is derived from one or more of magnesium hydroxide, magnesium chloride, magnesium sulfate, magnesium carbonate, and magnesium nitrate. 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.

According to the technical scheme, different metal elements are coated on the surfaces of the core and/or the shell of the lithium composite compound particle powder, 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 structures which are beneficial to the stability of a laminated structure, so that the crystal structure is smoother, the unit cell collapse in the circulation process is prevented, the capacity density is improved, and the capacity and the multiplying power of the lithium composite compound particle powder are 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 view of a process of forming a lithium composite compound particle powder 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 composite compound particle powder of the present invention will be described in detail with reference to examples.

Example 1

A lithium composite compound particle powder, which is a primary particle, having a structural formula of:

[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)O₂a chemical formula of a core of the lithium composite compound particle powder, Li_1.02(Ni_0.55Co_0.05Al_0.4)CO₃The preparation method, which is a chemical formula of the shell of the lithium composite compound particle powder, includes:

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, carrying out coprecipitation reaction for 3 hours, and filtering, washing and drying precipitates to obtain the composition with the core-shell structure.

Step 3, preparation of lithium composite compound particle powder with core-shell structure

And (2) mixing the composition 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 lithium composite compound particle powder is 0.86, the addition amount of the water-soluble sintering auxiliary agent is that the mass ratio of the lithium composite compound particle powder 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 a 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 composite compound particle powder doped with a Si shell, having a structural formula:

[Li_1.05(Ni_0.85Co_0.07Al_0.04Mn_0.04)O₂]_0.93·[Li_1.03(Ni_0.58Co_0.06Mn_0.35Si_0.01)O₂]_0.07

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

step 2, preparation of shell precursor

Dissolving a Ni source, a Co source, an Al source and a Si source in deionized water according to a ratio (Ni: Co: Mn: Si: 0.58:0.06:0.35:0.01) to obtain a second mixed aqueous solution, mixing the second mixed aqueous solution with a core precursor, ammonia water and a NaOH solution, and reacting to obtain a precursor with a core-shell structure.

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 invention provides a method for doping and cladding Ta shell with Nb material₂O₅A shell-coated lithium composite compound particle powder having a structural formula:

[Li_1.07(Ni_0.86Co_0.08Al_0.03Mn_0.03)O₂]_0.9·[Li_1.05(Ni_0.53Co_0.15Al_0.1Mn_0.2Ta_0.02)_0.998Nb_0.002O₂]_0.1

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

further comprises the following steps of 4, secondary sintering: mixing and grinding the product obtained by sintering in the step 3 and a water-soluble sintering aid, and adding the mixture and a coating materialMaterial Nb₂O₅Mixed of Nb₂O₅Is added in an amount of Nb₂O₅The molar ratio of Nb in (Nb) to (Ni + Co + Al + Mn) in the lithium composite compound particle powder was 0.002: 0.998, heating to 650 ℃, sintering for 6.5 hours, and cooling to room temperature to obtain the target product.

The target product of this example 3 has the formula:

[Li_1.07(Ni_0.86Co_0.08Al_0.03Mn_0.03O₂]_0.9·[Li_1.05(Ni_0.53Co_0.15Al_0.1Mn_0.2Ta_0.02)_0.998Nb_0.002O₂]_0.1

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

example 4

Example 4 provides the use of a coating material Y₂O₅A shell-coated lithium composite compound particle powder having a structural formula:

[Li_1.035(Ni_0.88Co_0.08Al_0.04)O₂]_0.88·[Li_1.01(Ni_0.52Co_0.18Al_0.3)_0.9985Y_0.0015O₂]_0.12

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

example 5

This example 5 provides Ga shell doped lithium composite particle powder having the structural formula:

[Li_1.02(Ni_0.90Co_0.08Al_0.02)O₂]_0.85·[Li_1.015(Ni_0.34Co_0.25Mn_0.4Ga_0.01)O₂]_0.15

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

example 6

Example 6 provides Er shell doped lithium composite compound particle powder coated with a coating material, SrO shell, having the structural formula:

[Li_1.025(Ni_0.91Co_0.05Al_0.04)O₂]_0.82·[Li_1.03(Ni_0.45Co_0.14Al_0.1Mn_0.3Er_0.01)_0.998Sr_0.002O₂]_0.18

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

example 7

Example 7 provides Mo Shell doping with La cladding Material₂O₃A shell-coated lithium composite compound particle powder having a structural formula:

[Li_1.055(Ni_0.92Co_0.04Mn_0.04)O₂]_0.8·[Li_1.02(Ni_0.5Co_0.12Al_0.35Mo_0.03)_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 shell doped, MgO shell coated lithium composite particle powder with the structural formula:

[Li_1.04(Ni_0.93Co_0.02Mn_0.05)O₂]_0.75·[Li_1.05(Ni_0.6Co_0.13Mn_0.25Sr_0.02)_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 shell doped, clad with Al₂O₃A shell-coated lithium composite compound particle powder having a structural formula:

[Li_1.01(Ni_0.95Co_0.02Mn_0.03)O₂]_0.7·[Li_1.03(Ni_0.7Co_0.09Al_0.1Mn_0.1Ce_0.01)_0.998Al_0.002O₂]_0.3

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

example 10

The structural formula of the lithium composite compound particle powder provided in this example 10 is:

[Li_1.06(Ni_0.60Co_0.30Al_0.05Mn_0.05)O₂]_0.95·[Li_1.02(Ni_0.34Co_0.33Mn_0.33)O₂]_0.05

example 11

[Li_1.06(Ni_0.63Co_0.27Al_0.05Mn_0.05)O₂]_0.95·[Li_1.02(Ni_0.34Co_0.33Mn_0.33)O₂]_0.05

examples 4 to 13 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 14

A lithium composite compound particle powder which is a primary particle and has a structure of:

Li_1.06(Ni_0.61Co_0.29Al_0.05Mn_0.05)O₂the preparation method comprises the following steps:

step 1, precursor Ni_0.61Co_0.29Al_0.05Mn_0.05CO₃Preparation of

According to the molar ratio of the elements of Ni to Co to Al to Mn of 0.61 to 0.29 to 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_0.61Co_0.29Al_0.05Mn_0.05CO₃；

Step 2, preparation of lithium composite compound particle powder

And (3) sintering: drying lithium carbonate until crystal water is completely lost, and mixing with the Ni prepared in the step 1_0.64Co_0.26Al_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; obtaining a target product Li_1.06(Ni_0.64Co_0.26Al_0.05Mn_0.05)O₂。

Example 15

A lithium composite compound particle powder, which is a primary particle, having a structural formula: li_1.03(Ni_0.75Co_0.15Mn_0.10)O₂The preparation process is similar to that of example 14.

Example 16

A lithium composite compound particle powder, which is a primary particle, having a structural formula: li_1.01(Ni_0.80Co_0.10Al_0.10)O₂The preparation process is similar to that of example 14.

Example 17

A lithium composite compound particle powder, which is a primary particle, having a structural formula: li_1.05(Ni_0.92Co_0.04Al_0.02Mn_0.02)O₂The preparation process is similar to that of example 14.

Comparative example 1

Comparative example 1 provides a ternary cathode material,the chemical formula is 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 17 and comparative example 1 reaction conditions in the respective steps

Table 2, examples 1 to 17 and comparative example 1 reaction conditions and products of the respective steps

Assembling a CR2032 button battery:

the lithium composite compound particle powder prepared in the embodiments 1 to 17 and the ternary positive electrode material prepared in the comparative example 1 are used as active materials of a positive electrode, a metal lithium sheet is used as a negative electrode, a Celgard 2500 diaphragm is used as the diaphragm, the electrolyte is fosai LB-002 electrolyte of Suzhou Buddhist New Material Co., Ltd, a CR2032 type button cell 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 lithium composite compound particle powder was weighed with an accuracy of 0.0001 g. The lithium composite compound particle powder was put into a measuring cylinder, and then the measuring cylinder was fixed on a holder. The lithium composite compound particle powder was repeatedly tapped (i.e., automatically lifted and dropped into a measuring cylinder) 3000 times, 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) Preparation of lithium composite compound particle powder clear solution: w was weighed with an accuracy of 0.0001g₁(30.0000. + -. 0.0040g) of lithium composite Compound particle powder, and W was weighed with an accuracy of 0.01g₂(100 +/-0.1 g) deionized water, mixing lithium composite compound particle powder with the deionized water, replacing air in the mixed solution with argon, stirring, filtering to obtain a filtrate, transferring 50mL of the filtrate, putting the filtrate into a 100mL beaker, and preparing 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: li in g equivalent to hydrochloric acid standard solution (2.000mol/L)₂CO₃The mass of (c);

residual alkali content on the surface of lithium composite compound particle powder is omega₁+ω₂。

Table 3, examples 1 to 17 and comparative example 1

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

example 1 compared with comparative example 1, example 1 is a lithium composite compound with a core-shell structure, the capacity retention rate after 100 cycles is 95.2%, the surface residual alkali weight percentage is 0.32%, and the lithium composite compound of comparative example 1 has the capacity retention rate after 100 cycles is 79.7%, the surface residual alkali weight percentage is 0.83%.

Example 2 compared with comparative example 1, example 2 is a lithium composite compound doped with an Si shell, the capacity retention rate after 100 cycles is 101.2%, the weight percentage of surface residual alkali is 0.38%, and the lithium composite compound of comparative example 1 has the capacity retention rate after 100 cycles is 79.7%, the weight percentage of surface residual alkali is 0.83%.

Example 3 in comparison to comparative example 1, example 3 was Nb doped with a Ta shell₂O₅The lithium composite compound obtained by coating the shell and cleaning by carbon dioxide gas flow has the capacity retention rate of 106 percent and the surface residual alkali weight percent of 0.04 percent after 100 cycles, the lithium composite compound of comparative example 1 has the capacity retention rate of 79.7 percent and the surface residual alkali weight percent of 0.83 percent after 100 cycles, and compared with the comparative example 1, the lithium composite compound of example 3 adopts Ta shell doping and Nb shell doping and has the advantages of high content of sodium hydroxide, sodium hydroxide and sodium hydroxide₂O₅The shell-coated lithium composite compound 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 lithium composite compound obtained by coating the shell and washing the shell with carbonated water has a capacity retention rate of 103.5% and a surface residual alkali weight percentage of 0.07% after 100 cycles, and the lithium composite compound 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 lithium composite compound 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 lithium composite compound obtained by doping with Ga shell and purging with carbon dioxide gas flow, the capacity retention rate after 100 cycles is 96.7%, the weight percentage of surface residual alkali is 0.11%, the capacity retention rate after 100 cycles is 79.7%, the weight percentage of surface residual alkali is 0.83% for the lithium composite compound of comparative example 1, and compared with comparative example 1, the lithium composite compound doped with Ga shell 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 lithium composite compound obtained by doping with an Er shell, coating with an SrO shell and washing with a carbon dioxide gas stream, the capacity retention rate after 100 cycles is 102%, the weight percentage of the surface residual alkali is 0.12%, the capacity retention rate after 100 cycles is 79.7%, the weight percentage of the surface residual alkali is 0.83% of the lithium composite compound of comparative example 1, and compared with comparative example 1, the lithium composite compound of example 6, which is coated with an Er shell and an SrO shell, 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 7 compared with comparative example 1, example 7 was a Mo shell doped La₂O₃The lithium compound obtained by coating the shell and cleaning with carbonated water has capacity retention rate of 100 cycles102.6% by weight of surface residual alkali, 0.14% by weight of the lithium composite compound of comparative example 1, having a capacity retention rate of 79.7% by weight after 100 cycles and a surface residual alkali content of 0.83% by weight of the lithium composite compound of example 7, compared with comparative example 1, in which Mo shell doping and La shell doping are used, the lithium composite compound of example 7₂O₃The shell-coated lithium composite compound 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 Sr shell doping, Mg (OH)₂The shell-coated lithium composite compound had a capacity retention of 101.5% and a surface residual alkali content of 0.24% after 100 cycles, and the lithium composite compound of comparative example 1 had a capacity retention of 79.7% and a surface residual alkali content of 0.83% after 100 cycles, and example 8, which was prepared by doping with SrO shell and Mg (OH) as compared with comparative example 1₂The shell-coated lithium composite compound has more stable cycle performance and reduced surface residual alkali.

Example 9 in comparison with comparative example 1, example 9 was carried out using Ce shell doping and Al₂O₃The lithium composite compound obtained by coating the shell and cleaning with carbonated water has a capacity retention rate of 101.8% and a surface residual alkali weight percentage of 0.13% after 100 cycles, the lithium composite compound 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,

example 9 doping with Ce shell, Al₂O₃The shell-coated lithium composite compound has more stable cycle performance; the residual alkali on the surface is effectively reduced by adopting carbonated water for cleaning.

Examples 10 to 13 compare example 3, which is a Ta shell doped, Nb₂O₅The lithium composite compound obtained by coating the shell and cleaning by adopting carbon dioxide gas flow has the capacity retention rate of 106 percent after being circulated for 100 circles, the weight percentage of the surface residual alkali is 0.04 percent, and the capacity retention rates of 99.8 percent, 99.45 percent, 98.3 percent and 96.65 percent after being circulated for 100 circles in examples 10 to 13 respectively; example 3 is Nb doping with Ta shell, compare with examples 10-13₂O₅Core-shell coated lithium composite compound inThe nickel content is increased, and the stable capacity retention rate can be achieved.

In summary, the lithium composite compound with the core-shell structure of the present invention has at least the following advantages:

(1) the lithium composite compound with the core-shell structure has more stable cycle performance: compared with the comparative example 1, after the examples 1-9 are cycled for 100 times, the capacity retention rate of the core-shell structure lithium composite compound prepared by the embodiment of the invention is higher than that of the traditional ternary lithium composite compound of the comparative example 1; compared with the traditional ternary lithium composite compound, the lithium composite compound has a core-shell structure, and can effectively inhibit the corrosion of the 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 lithium composite compound prepared by shell doping and shell coating has more stable cycle performance: compared with example 1, examples 2 and 5 are shell doped, and the capacity retention rates after 100 cycles of examples 2 and 5 are 101.2% and 96.7%, respectively, which are higher than those of example 1: shell doping is shown to improve cycling stability;

the embodiment 4 is shell coating, and the capacity retention rate after 100 times of circulation is 103.5 percent, which is obviously higher than that of the embodiment 1: the shell coating can improve the circulation 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 coating is superior to shell doping in the core-shell structure for improving the circulation stability;

examples 3 and 6 to 9 are shell-doped coatings, 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: indicating that shell doping and cladding can improve cycling stability.

(3) The lithium compound cleaned by carbon dioxide gas flow or carbonated water effectively reduces the surface residual alkali: compared with the unwashed lithium composite compounds of the embodiments 1 and 2 and the comparative example 1, the carbon dioxide airflow or the carbonated water is adopted for cleaning in the embodiments 3 to 7 and 9, and the residual alkali amount on the surface of the lithium composite compound cleaned by the carbon dioxide airflow or the carbonated water is effectively reduced, so that the attack of alkaline substances on the surface of the lithium composite compound on the binder in the positive glue solution in the preparation process of the lithium composite compound is reduced, 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 lithium composite compound: example 9 compared with example 6, example 6 was doped with Er shell and coated with SrO shell, and the weight percentage of the surface residual alkali was 0.32%; example 9 doping with Ce shell, Al₂O₃And (3) coating the shell, wherein the weight percentage of the surface residual alkali is 0.17%, and the surface residual alkali is obviously reduced. Active lithium on the surface of lithium composite compound and CO in air₂、H₂O reaction to produce LiOH and Li₂CO₃Using Al₂O₃Is coated with Al₂O₃Can react with active lithium on the surface of the lithium composite compound to generate LiAlO₂The active lithium content on the surface of the lithium composite compound is reduced, so that LiOH and Li on the surface of the lithium composite compound are reduced₂CO₃The content of the alkaline residue on the surface of the lithium composite compound is effectively reduced, so that the attack of alkaline substances on the surface of the lithium composite compound on a binder in the positive glue solution in the preparation process of the lithium composite compound can be reduced, 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 with example 1, using 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 100 circles, the weight percentage of the surface residual alkali is 0.07%, the more stable cycle performance is realized, and the surface residual alkali is effectively reduced. The addition of the metal element Mg effectively improves the structural stability of the lithium composite compound, reduces the strong side reaction of the lithium composite compound and the organic electrolyte, reduces the impedance of the battery in the charging and discharging processes, and improves the lithium compositeElectrochemical Properties of the Compounds via Mg (OH)₂The shell-coated modified lithium composite compound 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 5 Ga shell doping with a powder resistivity of 218 Ω · cm; in comparison with example 5, example 9 was Ce shell doped, Al shell coated, and the powder resistivity was 158 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 composite compound particle powder: the thickness of the powder shell of the lithium composite compound particles in 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 may affect the stability of the lithium composite compound particle powder; on the contrary, if the shell is too thick, the capacity of the lithium composite compound particle powder is reduced. The lithium composite compound particle powder provided by the embodiment of the invention has proper shell thickness, can balance the stability of the lithium composite compound particle powder and the capacity of the lithium composite compound particle powder, 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 method for producing a lithium composite compound particle powder, characterized by comprising the steps of:

step 1, nuclear precursor preparation: first preparation of Ni Source Compound, Co Source Compound and M1 Source CompoundMixing the first mixed aqueous solution, carbonate solution and ammonia water, and reacting under alkaline condition to obtain a nuclear precursor Ni_1-x-yCo_xM1_yCO₃(ii) a Wherein M1 is selected from Mn and/or Al; x and y are mole fractions, x>0，0.01≤y≤0.10，0.60≤1-x-y≤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-yCo_xM1_yCO₃Mixing 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; 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 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-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-n-tCo_mM2_nM4_t)_1-rM6_rO₂]_1-d

Li_a(Ni_1-x-yCo_xM1_y)O₂is a chemical formula of a core of the lithium composite compound particle powder, Li_s(Ni_1-m-n- _tCo_mM2_nM4_t)_1-rM6_rO₂A chemical formula of a shell that is the lithium composite compound particle powder; said M2 is selected fromMn and/or Al; the M4 and the 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 m, n, t, a, s, r and d are mole fractions, m>0，0.2≤n≤0.4，0≤t≤0.02，0.30≤1-m-n-t≤0.70，1.015≤a≤1.06，1.01≤s≤1.07，0≤r≤0.02，0.70≤d≤1。

2. The method for producing a lithium composite compound particle powder according to claim 1, wherein the step 4 further comprises cleaning the sintered product obtained in the step 3, mixing the cleaned product with a water-soluble sintering aid and a coating material, grinding the mixture, and sintering the mixture.

3. The method for preparing the lithium composite compound particle powder according to claim 1, wherein the reaction is carried out in the presence of a dispersant in step 1, wherein the dispersant is one or more selected from the group consisting of a surfactant, polyvinyl alcohol, and polyglycerin.

4. The method for producing a positive electrode active material powder for a lithium secondary battery according to claim 3, wherein the surfactant is polyvinylpyrrolidone.

5. The method for producing a lithium composite compound particle powder according to claim 3, wherein M4 and M6 are each independently at least one selected from the group consisting of Si, Ta, Nb, Ga, Y, Er, Sr, Mo, La, Mg, Ce, and Al.

6. The method for producing a lithium composite compound particle powder according to claim 1, wherein t is 0, and the chemical formula of the lithium composite compound particle powder is [ Li ═ Li_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-nCo_mM2_n)_1-rM6_rO₂]_1-dA, x, y, s, m, n, r and d are mole fractions, and a is more than or equal to 1.015 and less than or equal to 1.06，x>0，0.01≤y≤0.10，0.60≤1-x-y≤0.96，1.01≤s≤1.07，m>0，0.2≤n≤0.4，0.30≤1-m-n≤0.70，0≤r≤0.02，0.70≤d≤1。

7. The method for producing a lithium composite compound particle powder according to claim 6, characterized in that: r is 0, and the chemical formula of the lithium composite compound particle powder is [ Li [ ]_a(Ni_1-x-yCo_xM1_y)O₂]_d·[Li_s(Ni_1-m-nCo_mM2_n)O₂]_1-dA, x, y, s, m, n and d are mole fractions, a is more than or equal to 1.015 and less than or equal to 1.06, x>0，0.01≤y≤0.10，0.60≤1-x-y≤0.96，1.01≤s≤1.07，m>0，0.2≤n≤0.4，0.30≤1-m-n≤0.70，0.70≤d≤1。

8. The method for producing a lithium composite compound particle powder according to claim 7, characterized in that: d is 1, and the chemical formula of the lithium composite compound particle powder is Li_a(Ni_1-x-yCo_xM1_y)O₂A, x and y are mole fractions, a is more than or equal to 1.015 and less than or equal to 1.06, x>0，0.01≤y≤0.10，0.60≤1-x-y≤0.96。

9. The method for producing a lithium composite compound particle powder according to claim 1, characterized in that: the amount of residual alkali on the surface of the lithium composite compound particle powder is 0.04 to 0.38 wt%.

10. The method for producing a lithium composite compound particle powder according to claim 1, characterized in that: the capacity retention rate of a battery prepared from the lithium composite compound particle powder is 95.2% -106% after 100 cycles under the rate of 1C.