WO2018095052A1 - Lithium cobalt oxide positive-electrode material and method for fabrication thereof and lithium-ion rechargeable battery - Google Patents

Abstract

Provided is a lithium cobalt oxide positive-electrode material, said material being a composite structure having a doped lithium-cobalt-oxide substrate and surface coating; the general formula of said doped lithium-cobalt-oxide substrate is Li _1+zCo _1-x-yMa _xMb _yO ₂, wherein 0≤x≤0.01, 0≤y≤0.01 and -0.05≤z≤0.08; said Ma is a doped invariable-valence element, at least one of Al, Ga, Hf, Mg, Sn, Zn, and Zr; said Mb is a doped variable-valence element, at least one of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, and Cr; the surface coating layer is a high-voltage (>4.5 V) positive-electrode material. By means of substitution doping of the variable-valence element, distortion resulting from delithiation of the layered structure is reduced by the maximum extent; the variable-valence element is doped by means of gaps, and during the process of charging, the oxidation of Co ³⁺is reconciled and delayed. The surface coating layer of the high-voltage positive-electrode material has a stable structure at voltages of 4.5 V or higher, and is capable of isolating an electrolyte solution and a lithium-cobalt-oxide substrate, thus reducing side reactions between the two and inhibiting the dissolution of transition metals; it also provides electrochemical energy.

Description

Lithium cobaltate cathode material, preparation method thereof and lithium ion secondary battery Technical field

The present invention relates to the field of materials, and in particular to a lithium cobaltate cathode material, a method for preparing the lithium cobaltate cathode material, and a lithium ion secondary battery.

Background technique

At present, lithium-ion batteries have been widely used in various electronic devices (such as mobile phones and tablet computers). As people's performance requirements for electronic devices continue to increase, the energy density of lithium-ion batteries has also been raised. The volumetric energy density of the battery = discharge capacity × discharge voltage platform × compaction density. Increasing the charge cut-off voltage of the positive electrode material can increase the discharge capacity and the discharge voltage platform, thereby increasing the energy density thereof. However, when the lithium ion battery is charged to 4.2V, lithium ions in LiCoO ₂ are decomposed to form Li _1-x CoO ₂ ( _{0 ≤ x ≤} 0.5), and when the charging voltage is increased to 4.4 V or more, LiCoO ₂ is present. More lithium ion liberation leads to the conversion of LiCoO ₂ from hexagonal to monoclinic and no longer has the function of reversible intercalation and deintercalation of lithium ions; at the same time, the process is accompanied by the dissolution of cobalt ions in the electrolyte, so The actual capacity of lithium cobalt battery cathode material lithium cobaltate (150 mAh·g ^-1 ) is much lower than its theoretical capacity (274 mAh·g ^-1 ).

In order to improve the cycle stability of lithium cobaltate LiCoO ₂ at a high voltage, it may be modified by doping or surface coating, as disclosed in the prior art, a doping and surface coating co-modified lithium The anode material of the ion battery, the cathode material comprises a doped lithium cobaltate matrix and a surface coating thereof, wherein the doped lithium cobaltate matrix has the formula LiCo _1-x M _x O ₂ and M is selected from the group consisting of Mg, Al, Ni, Ca, Zr, Cr, Ti, Cu, Zn, Y, Ce, MO, Nb, V; the coating may be Co ₃ (PO ₄ ) ₂ , AlPO ₄ , Mn ₃ (PO ₄ ) ₂ , phosphates such as FePO ₄ , Ni ₃ (PO ₄ ) ₂ , Mg ₃ (PO ₄ ) ₂ . Compared with unmodified lithium cobaltate, the positive electrode material has higher specific capacity and good cycle stability under high voltage conditions.

However, it should be noted that the positive electrode material doped with the element described above can stabilize the role of the lithium cobaltate layer structure in a high voltage use environment, but has a limited effect on the stable structure because the positive electrode material cannot be excellent. Buffering or releasing stress caused by changes in lattice constant during charge and discharge;

Therefore, there is an urgent need to develop a lithium ion battery positive electrode material which has good cycle performance at high voltage, high capacitance, and can well buffer or release stress caused by changes in lattice constant during charge and discharge.

Summary of the invention

In view of this, the first aspect of the embodiments of the present invention provides a positive electrode of a lithium ion battery having good cycle performance, high capacitance, and good buffering or releasing stress caused by changes in lattice constant during charge and discharge. material.

In a first aspect, the present invention discloses a lithium cobaltate cathode material, the lithium cobaltate cathode material comprising a doped lithium cobaltate substrate and a surface coating layer; wherein the surface coating layer is coated on the a surface of the doped lithium cobaltate substrate;

Wherein the substance constituting the doped lithium cobaltate matrix has a general formula of Li _1+z Co _1-xy Ma _x Mb _y O ₂ ; wherein 0≤x≤0.01, 0≤y≤0.01, -0.05≤ z ≤ 0.08; wherein, said Ma is a doped constant valence element; said Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr; wherein said Mb is a doped variable price An element; the Mb is at least one of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr.

In combination with the first aspect, it is to be noted that the substance constituting the surface coating layer has a general formula of Li _γ1 Mc _γ2 O _γ3 ; wherein, Mc is at least one of Cr, Co, Ni, Cu, Mn, and P. Wherein γ1, γ2, and γ3 may be any positive number but need to satisfy the following formula, γ1+A*γ2=2*γ3, and the A is a valence of Mc.

In combination with the lithium cobaltate cathode material disclosed above, it is further noted that 0.0005 ≤ x ≤ 0.005. For example x can It is 0.004 or 0.003 or 0.005 or 0.0001.

In combination with the lithium cobaltate cathode material disclosed above, it is further noted that 0.0005 ≤ y ≤ 0.005. For example, y can be 0.005 or 0.008 or 0.001.

In combination with the lithium cobaltate cathode material disclosed above, it is further noted that -0.01 ≤ z ≤ 0.03. z can be 0.01 or 0.02;

In combination with the lithium cobaltate cathode material disclosed above, it should be noted that during the charging process of the lithium cobaltate cathode material, the constant valence element will replace the cobalt ion by substitution doping, and the valence element passes. The gap is doped to fill the gap between lithium, cobalt, and oxygen ions.

A second aspect of the invention discloses a method for preparing a lithium cobaltate cathode material, the method comprising:

The cobalt source and the compound containing the constant valence element Ma are disposed as an aqueous solution, and the aqueous solution is mixed with the complex solution and the precipitant solution to cause the aqueous solution to react with the complex solution and the precipitant solution to obtain a solution. a potassium or hydroxide of a cobalt-doped cobalt; wherein the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr;

Mixing the obtained cobalt or hydroxide of the doped cobalt with the compound containing the valence element Mb, and sintering the mixed compound at a temperature of 800 to 1000 ° C for 4-10 hours to obtain the An oxide precursor of Co co-doped with Ma; wherein the Mb is at least one of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr;

The obtained oxide precursor of Co co-doped with Ma and Mb is mixed with a lithium source, and the mixture of the oxide precursor and the lithium source is sintered at a temperature of 950 to 1100 ° C for 8 to 16 hours. Obtaining a high voltage lithium cobaltate matrix co-doped with the Ma and Mb;

The lithium source, the compound containing the element Mc, and the obtained high-voltage lithium cobaltate co-doped with Ma and Mb are mixed and sintered at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain the lithium cobaltate positive electrode. a material, wherein the Mc is at least one of Cr, Co, Ni, Cu, Mn, and P.

Among them, it should be pointed out that the last step of the second aspect is to be treated by solid phase coating.

It should be noted that the last step of the second aspect can be replaced by a high-voltage lithium cobaltate matrix co-doped with a lithium source and a compound containing the element Mc and the obtained Ma and Mb by a liquid phase coating method. After mixing and drying in a liquid phase, sintering at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain a lithium cobaltate cathode material (also referred to as doped and surface-coated co-modified structure-stabilized high-voltage cobalt Lithium acid cathode material).

In combination with the second aspect, in a first possible implementation of the second aspect, the aqueous solution is mixed with a complex solution and a precipitant solution, such that the aqueous solution and the complex solution and the precipitant solution Reaction crystallization, obtaining the carbonate or hydroxide of the cobalt-doped cobalt comprises: mixing the aqueous solution containing the Co ion and the constant-valent element Ma ion with the precipitant solution by using a parallel flow control flow; wherein, the cocurrent flow The flow rate of the control flow does not exceed 200 L/h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100 °C.

In combination with the second aspect or the first possible implementation of the second aspect, it should be noted that

The cobalt source is at least one of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride; the compound containing a constant valence element Ma is a nitrate, oxalate, acetate containing Ma. At least one of fluoride, chloride, and sulfate; the concentration of Co ion in the aqueous solution containing Co ion and the constant-valent element Ma ion is 0.5-2.0 mol/L; the precipitant solution is a strong alkali solution, carbonate a solution, an oxalic acid or an oxalate solution; the complexing agent solution is an ammonia water or an aminohydroxy acid salt solution; the compound containing the variable element Mb is selected from the group consisting of oxides, hydroxides, carbonates, nitric acids containing Mb At least one of a salt, an oxalate, and an acetate; the lithium source is lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, At least one of lithium oxide and lithium citrate; or the compound containing the element Mc is at least one of an oxide, a hydroxide, a carbonate, a nitrate, an oxalate, and an acetate containing Mc. Kind.

A third aspect of the invention discloses a method for preparing another lithium cobaltate cathode material, the method comprising:

The cobalt source and the compound containing the constant valence element Ma are disposed as an aqueous solution, and the aqueous solution is mixed with the complex solution and the precipitant solution to cause the aqueous solution to react with the complex solution and the precipitant solution to obtain a solution. a potassium or hydroxide of a cobalt-doped cobalt; wherein the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr;

The obtained cobalt-doped cobalt carbonate or hydroxide is sintered at a temperature of 900 to 1000 ° C to obtain a Ma-doped precursor Co ₃ O ₄ , wherein the sintering time is 4 to 10 h. ;

The lithium source, the Mb-containing compound and the Ma-doped precursor Co ₃ O ₄ are sintered at a temperature of 950 to 1100 ° C for 8 to 16 hours to obtain a high-voltage lithium cobaltate matrix co-doped with Ma and Mb. ;

The lithium source, the compound containing the element Mc, and the obtained high-voltage lithium cobaltate co-doped with Ma and Mb are mixed and sintered at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain the lithium cobaltate positive electrode. a material, wherein the Mc is at least one of Cr, Co, Ni, Cu, Mn, and P.

It should be noted that the last step of the third aspect can be replaced by a high-voltage lithium cobaltate matrix co-doped with a lithium source and a compound containing element Mc and a obtained Ma and Mb by a liquid phase coating method. After mixing and drying in the liquid phase, the mixture is sintered at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain a lithium cobaltate cathode material doped with surface coating and co-modified (also referred to as doping and surface coating). Co-modified structurally stable high voltage lithium cobaltate cathode material).

In combination with the third aspect, in a first possible implementation manner of the third aspect, the aqueous solution is mixed with the complex solution and the precipitant solution, so that the aqueous solution and the complex solution and the precipitant solution are Reaction crystallization to obtain the carbonate or hydroxide of the Ma-doped cobalt includes:

The aqueous solution containing Co ions and the constant-valent element Ma ions is mixed with the precipitating agent solution by means of cocurrent flow control; wherein the flow rate of the parallel flow control does not exceed 200 L/h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100. °C.

In combination with the third aspect or the first possible implementation of the third aspect, the cobalt source is at least one of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride; The compound is at least one of nitrate, oxalate, acetate, fluoride, chloride, and sulfate containing Ma; the concentration of Co ion in the aqueous solution containing Co ion and the constant-valent element Ma ion is 0.5 to 2.0. Mol/L; the precipitant solution is a strong alkali solution, a carbonate solution, an oxalic acid or an oxalate solution; the complexing agent solution is an ammonia water or an aminohydroxy acid salt solution; and the compound containing the variable element Mb is At least one selected from the group consisting of oxides, hydroxides, carbonates, nitrates, oxalates, and acetates containing Mb; the lithium source is lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, At least one of lithium acetate, lithium oxide, and lithium citrate; or the compound containing the element Mc is an oxide, hydroxide, carbonate, nitrate, oxalate, or acetate containing Mc At least one of them.

A fourth aspect of the invention discloses a lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte solution and a separator disposed between the positive and negative electrode sheets, wherein the positive electrode sheet includes a positive electrode current collector and a distribution The positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer uses the lithium cobaltate positive electrode material according to any one of the first aspect or the first aspect of the first aspect as the positive electrode active material.

Further, it should be noted that the active capacity of the lithium cobaltate cathode material is greater than 190 mAh/g.

A fifth aspect of the invention discloses an electronic device comprising the lithium ion battery of the fourth aspect.

As can be seen from the above, an embodiment of the present invention discloses a lithium cobaltate cathode material, the lithium cobaltate cathode material comprising a doped lithium cobaltate substrate and a surface coating layer; wherein the doped lithium cobaltate matrix The general formula is Li _1+z Co _1-xy Ma _x Mb _y O ₂ ; wherein 0≤x≤0.01, 0≤y≤0.01, -0.05≤z≤0.08; wherein the Ma is doped a valence element; the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr; wherein the Mb is a doped valence element; and the Mb is Ni, Mn, V, Mo, At least one of Nb, Cu, Fe, In, W, Cr; wherein the substance constituting the surface coating layer has a general formula of Li _γ1 Mc _γ2 O _γ3 ; the Mc is Cr, Co, Ni, Cu At least one of Mn, P, γ1, γ2 and γ3 is any positive number satisfying the formula γ1+A*γ2=2*γ3, and the valence of A is Mc according to the above description, the present invention provides The lithium cobaltate cathode material is doped with a variable-valent element and doped with a constant-valent element. Among them, the constant valence element replaces the cobalt site by substitution doping, and replaces the cobalt ion to ensure that the skeleton-cobalt site of the layered structure is not distorted by oxidation, and can stabilize the layered structure of the lithium cobaltate positive electrode material under high voltage use. Stability; in addition, the variable element is doped through the gap and filled into the gap between lithium, cobalt and oxygen ions. In the charging process, not only the oxidation in the oxidizing atmosphere takes precedence over Co ³⁺ , but also the Co ³⁺ oxidation can be delayed. Occurs, and when Co ³⁺ changes the ionic radius due to oxidation, the valence ions also occur or have ionic radius changes to relieve or release the stress caused by the skeletal structure of the layered structure, and stabilize the lithium cobaltate layer structure. Further, the surface coating layer serves as a stable cathode material/electrolyte interface on the one hand, and isolates the lithium cobaltate matrix from the electrolyte, reduces the reaction area, increases the interface stability, and ensures lithium cobaltate at high voltage. The matrix does not dissolve in the electrolyte, thereby stabilizing the structure of the lithium cobaltate, increasing the activation energy to suppress the phase transition; on the other hand, as the coating itself Storage effects, while the effect of stabilizing the structure, without sacrificing the capacity of the cathode material g, it will not sacrifice the energy density. In summary, the present invention combines the principle and process of phase transition of a lithium cobaltate layer structure in a high voltage scene, fully exerts the advantages of each doping element, and significantly improves the overall performance of the cathode material.

The advantages of the embodiments of the present invention will be set forth in part in the description which follows.

DRAWINGS

1 is a schematic view showing a lattice structure of a layered lithium cobalt oxide provided by an embodiment of the present invention;

2 is a schematic diagram of phase transition of lithium cobaltate during charging;

3 is a schematic diagram of phase transition of lithium cobaltate during charging;

4 is an X-ray diffraction spectrum of a lithium cobaltate cathode material according to an embodiment of the present invention;

5a is a SEM (scanning electron microscope) diagram of a lithium cobaltate cathode material according to an embodiment of the present invention;

Figure 5b is a cross-sectional view of a lithium cobaltate positive electrode material particle;

6 is a particle size distribution of a lithium cobaltate cathode material according to an embodiment of the present invention;

7 is a first charge and discharge curve of a lithium cobaltate cathode material according to an embodiment of the present invention;

8 is a cycle curve of a lithium cobaltate cathode material according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a lithium ion battery including a lithium cobaltate cathode material according to an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be described below in conjunction with the accompanying drawings in the embodiments of the present invention.

As shown in FIG. 1, this FIG. 1 is a lattice structure of layered lithium cobaltate. In the lattice structure of the layered lithium cobaltate, the oxygen ions form a close-packed layer; the cobalt layer and the lithium layer are alternately distributed on both sides of the oxygen layer, and the lithium octahedron and the cobalt octahedron pile are shared by the boundary. Stacked, in ABCABC cubic close packing structure. Due to the pursuit of high energy density, the charging cut-off voltage of lithium cobaltate operation has been continuously improved, from 4.2V, 4.35V, to today's 4.4V. For every 0.1V increase in operating voltage, the lithium cobalt oxide discharge capacity can be increased by about 10%, and the discharge voltage platform is increased by about 0.02V. However, after the cut-off voltage is increased (especially above 4.3V), the structure of the layered lithium cobaltate is unstable (the change in lithium concentration causes a structural change, causing stress to cause microcracks) and surface instability (and The electrolyte reacts to cause dissolution of the cobalt), causing collapse of the lattice structure and irreversible phase transition.

During the charging process, the lithium ions on the surface of the lithium cobaltate particles are first removed to form an empty octahedron, so that adjacent lithium ions can be sequentially diffused and extracted; in the different layers inside the particles, the main conduction path of the lithium ions is the grain boundary; In the interlayer, lithium ions are mainly conducted between the octahedrons between the layers.

Figure 2 depicts the specific phase change process, which is described below:

For Li _x CoO ₂ , when x=1～0.9, lithium cobaltate maintains the initial layered structure and is hexagonal (Fig. 3(a)); when x=0.9~0.78, the initial hexagonal system changes to twice Hexagonal system, this region is a two-phase coexistence zone. The reason for this transformation is that as the lithium ions are removed, a Mott insulator is produced. The voltage platform corresponding to this phase change is 3.97V; when x<0.78 The initial hexagonal system disappears and becomes a single secondary hexagonal system; in this process, as the lithium ions continue to escape, the negatively charged oxygen-oxygen electrostatic repulsion between adjacent CoO ₂ layers increases, causing c Continue to increase, this process until x is close to 0.5; when x < 0.5, the secondary hexagonal system begins to transform into a monoclinic system; in the region of x = 0.5 ~ 0.46, lithium cobaltate is monoclinic; When x is close to 0.46, the monoclinic system is again transformed into a hexagonal system. This transformation is caused by the realignment of lithium ions in the lithium layer, which corresponds to the voltage platform of 4.08V and 4.15V. The original layered structure in 3(b) is twisted, causing the c-axis index to change; when x<0.46, the voltage exceeds 4.2V, The continuation, the c of the hexagonal system begins to decrease sharply; when x=0.22, the hexagonal system begins to transform into a secondary monoclinic system; after that, when x=0.22~0.18, it is a hexagonal system and a second order. The two-phase coexistence zone of the slant system, the corresponding voltage platform is 4.55V; the transition of these two phases reaches the pole at x=0.148, and as the lithium ions continue to move out, the hexagonal system continues to the second monoclinic Crystalline transformation; subsequently, LixCoO ₂ undergoes frequent phase transitions, a secondary monoclinic phase region appears, and transforms into a hexagonal system as x decreases until the lithium ions are completely removed, and the structure becomes a single layer of CoO ₂ The CoO ₂ structure produced by the phase change can be seen in Figure 3(c). After multiple charge and discharge, the LixCoO ₂ layer begins to crack (Fig. 3(d)), and many broken crystal particles appear on the side close to the electrolyte (Fig. 3(e)), which is due to the cobalt layer in contact with the electrolyte. Decomposition, caused by the collapse of the crystal lattice.

The key to the development of high-voltage lithium cobaltate cathode material is to solve the frequent phase transition process of the layered structure of lithium cobalt oxide and the damage of the stress generated during the phase transition process in the high voltage and deep delithiation state; And in the deep delithiation state, the strong oxidizing property of the tetravalent cobalt ion in the lithium cobaltate to the carbonate solvent and the dissolution of the cobalt ion in the electrolyte are solved. Therefore, the development of high-voltage lithium cobaltate cathode materials has become one of the development trends of current batteries.

In view of the above problems, the present invention proposes element doping of two forms of coexistence of lithium cobaltate: one is to substitute a constant-valent element by substitution, instead of cobalt ion, to ensure the skeleton-cobalt position of the layered structure- Oxidation and distortion; the other is to dope the valence element through the gap, filling the gap between lithium, cobalt and oxygen ions. On the one hand, in the oxidizing atmosphere, the valence element ions oxidize preferentially over Co ³⁺ , thereby delaying Co ³⁺ oxidation occurs, on the other hand, when Co ³⁺ changes in ionic radius due to oxidation, the valence ion also undergoes or has an ionic radius change, which improves lattice fit to alleviate or release the skeletal structure of the layered structure. The stress generated.

Whether it is substitution doping or gap doping, it is to stabilize the layered structure of lithium cobaltate itself and avoid the frequent transition of lithium cobaltate between layered hexagonal system and spinel monoclinic system. And coating, can reduce the occurrence of electrolyte and lithium cobalt oxide side effects. The side reaction occurs because ions or electrons are concentrated at the interface of the electrolyte/active material, and the electrolyte directly contacts the high concentration of tetravalent cobalt ions on the surface of the positive electrode to initiate decomposition reaction and cause dissolution of cobalt ions in the electrolyte. Release the gas. In the present invention, it is proposed to coat the surface of the lithium cobaltate particles with a high-voltage positive electrode active material, and the material itself can maintain a stable structure in a high voltage scene, and as a coating, the lithium cobaltate substrate is separated from the electrolyte. It can form a stable cathode material/electrolyte interface, delay the oxidation and dissolution of Co, and stabilize the lithium cobaltate structure; these materials have the function of energy storage, without sacrificing the gram capacity of the cathode material, nor sacrificing Its energy density.

Combined with the above analysis, in order to stabilize the lithium cobaltate layered structure and improve the cycle performance under high voltage environment, the present invention modifies lithium cobaltate from the aspects of doping and coating, thereby making the modified lithium cobaltate material. It can be cycled at 4.45V and above to meet battery requirements.

For the doping of lithium cobaltate crystals, we consider both the ionic radius and the valence state. When the doping is substituted, the closer the doping ions are to the substituted ions, the smaller the lattice distortion caused by the substitution; the substitution doping is dominated by the constant valence ions. In the case of gap doping, the radius of the doping ions is also close to the size of the cobalt ions in principle, and the valence state changes earlier than the trivalent cobalt ions, especially in the high de-lithium state; the gap doping is based on the valence ions. the Lord. In the lithium cobaltate system, the ionic radius of Co ³⁺ is 0.0685 nm, the ionic radius of Li ⁺ is 0.090 nm, and the ionic radius of O ²⁻ is 0.126 nm.

Considering the above information, in the present invention, in order to stabilize the bulk structure, the doped constant valence element Ma can be selected from the following elements: Al (Al ³⁺ , 0.0675 nm), Ga (Ga ³⁺ , 0.076 nm) , Hf (Hf ⁴⁺ , 0.085 nm), Mg (Mg ²⁺ , 0.086 nm), Sn (Sn ⁴⁺ , 0.083 nm), Zn (Zn ²⁺ , 0.088 nm), Zr (Zr ⁴⁺ , 0.086 nm) Wait. The ionic radius and valence state of these doping elements are close to Co ³⁺ , which can replace Co in the positive electrode material to improve the stability of the layered structure of the positive electrode material.

In order to coordinate the change in the radius of the Co ³⁺ ion, the stress caused by the change in the lattice constant is released, and the gap doping of the variable element is performed. The amount of interstitial doping is small, and it is necessary to find a site with the lowest formation energy and the most stable energy level which can be lattice matched with lithium cobaltate. The doped variable element Mb can be selected from the following elements: Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr, and the like. These elements, in the valence state change, produce a change in ionic radius that matches the change in the radius of the cobalt ion, thereby releasing or mitigating the stress caused by the change in lattice size.

By doping these two types of elements, a positive electrode material Li _1+z Co _1-xy Ma _x Mb _y O _{2 of a} lithium cobaltate bulk phase is obtained (generally, 0≤x≤0.01, 0≤y≤0.01, - 0.05≤z≤0.08; preferably, 0.0005≤x≤0.005, 0.0005≤y≤0.005, -0.01≤z≤0.03), Ma is a doped constant element Al, Ga, Hf, Mg One or more of these, the doping is the substitution doping of the above element instead of the cobalt site; Mb is the doped variable element Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr One or more of such doping is doped with a gap into which the above element enters the lithium cobaltate lattice gap.

After the synthesis of the bulk material of lithium cobaltate, it is also necessary to surface coat the lithium cobaltate particles to obtain the final high-voltage lithium cobaltate product. The surface coating can be coated by dry or wet method: the coating itself has excellent high-voltage structural stability, can form a stable cathode material/electrolyte interface, and isolate the lithium cobaltate matrix from the electrolyte. , reducing the reaction area, increasing the stability of the interface, ensuring that the lithium cobaltate matrix does not dissolve in the electrolyte under high voltage, thereby stabilizing the structure of the lithium cobaltate, increasing the activation energy to suppress the phase transition; As a coating layer itself, it has the function of energy storage, and does not sacrifice the energy capacity of the positive electrode material without sacrificing its energy density while functioning as a stable structure. In the present invention, in order to achieve the above object, the coating material used is a high voltage positive active material Li _γ1 Mc _γ2 O _γ3 , wherein Mc is one or more of Cr, Co, Ni, Cu, Mn, P. , γ1, γ2, and γ3 may be any positive number, but need to satisfy the distribution of valence, and Mc may have various options.

Through the above-mentioned bulk phase doping and surface coating, a structurally stable high-voltage lithium cobaltate cathode material αLi _γ1 Mc _γ2 O _γ3 ·βLi _1+z Co _{1- which is} bulk-doped and surface-coated co-modified is finally obtained. _Xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1, 0≤x≤0.01, 0≤y≤0.01, -0.05≤z≤0.08; preferably, 0<α≤0.05 , 0.95 ≤ β ≤ 1, 0.0005 ≤ x ≤ 0.005, 0.0005 ≤ y ≤ 0.005, -0.01 ≤ z ≤ 0.03).

The following table lists several possibilities for bulk-doped high-voltage lithium cobaltate matrix and cladding materials (but this patent is not limited to the possibilities shown in the table below), where the bulk phase is doped with a lithium cobaltate matrix and The coating material can be arbitrarily used by different processing processes to obtain a structurally stable high-voltage lithium cobaltate cathode material with bulk phase doping and surface coating co-modification.

In another embodiment of the present invention, there is also provided a method for preparing a structurally stable high voltage lithium cobaltate cathode material doped with a surface coating and co-modified, the method comprising:

Step (1): using a controlled crystallization method, a molar ratio, an appropriate amount of a cobalt source and a compound containing a constant valence element Ma, and an aqueous solution containing a Co ion and a constant valence element Ma ion, mixed with a complexing agent solution and a precipitating agent solution The reaction is crystallized while stirring, and the pH of the reaction system is controlled to 6 to 12, and after crystallization, centrifugal filtration is performed to obtain a carbonate or hydroxide of a cobalt doped with a constant valence element Ma;

Step (2): molar ratio, taking an appropriate amount of the compound containing the variable element Mb and the cobalt carbonate or hydroxide doped with the constant-valent element Ma obtained after the step (1), and uniformly mixed, and placed in a horse boiling furnace or Temperature sintering is performed in a sintering furnace, and then the product is pulverized to obtain an oxide precursor of Co co-doped with Ma and Mb;

Step (3): molar ratio, the oxide precursor of Co co-doped with Ma and Mb obtained in step (2) is mixed with a lithium source and ground uniformly, and placed in a horse boiling furnace or a sintering furnace for temperature sintering, and then The product is subjected to pulverization treatment to obtain a matrix of lithium cobaltate cathode material Li _1+z Co _1-xy Ma _x Mb _y O ₂ co-doped with Ma and Mb (generally, 0 _{≤ x ≤} 0.01, 0 _{≤ y ≤} 0.01, - 0.05≤z≤0.08; preferably, 0.0005≤x≤0.005, 0.0005≤y≤0.005, -0.01≤z≤0.03);

Step (4): using a solid phase coating synthesis method, a molar ratio, a lithium source and a compound containing the element Mc, and a lithium cobaltate positive electrode material substrate Li _1+z Co _1-xy Ma _x obtained after the step (3) Mb _y O _{2 is} stirred and mixed uniformly, and is sintered in a horse boiling furnace or a sintering furnace, and then the product is pulverized to obtain a structurally stable high-voltage lithium cobaltate cathode material αLi _{γ1 which is} co-modified by bulk phase coating and surface coating. Mc _γ2 O _γ3 ·βLi _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1; preferably, 0<α≤0.05, 0.95≤β≤1) .

In addition, the step (4) may be replaced by: using a liquid phase coating synthesis method, a molar ratio, a lithium source and a compound containing the element Mc, and a lithium cobaltate positive electrode material substrate Li _1+z Co obtained after the step (3). _1-xy Ma _x Mb _y O _{2 is} stirred and mixed uniformly. After the powder is dried, it is placed in a horse boiling furnace or a sintering furnace for temperature sintering, and then the product is pulverized to obtain a structural stability of bulk phase doping and surface coating co-modification. High-voltage lithium cobaltate cathode material αLi _γ1 Mc _γ2 O _γ3 ·βLi _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1; preferably, 0< α ≤ 0.05, 0.95 ≤ β ≤ 1).

Optionally, in the step (1), the cobalt source is one or more of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride;

Optionally, in the step (1), the constant valence element Ma is one or more of Al, Ga, Hf, Mg, Sn, Zn, and Zr;

Optionally, in the step (1), the compound containing the constant valence element Ma is one selected from the group consisting of nitrates, oxalates, acetates, fluorides, chlorides, sulfates, and the like containing Ma or a plurality of; more preferably one or more selected from the group consisting of sulfates, nitrates, and acetates of Ma, such as: aluminum oxalate, aluminum nitrate, magnesium oxalate, magnesium nitrate, zirconium oxalate, zirconium nitrate, zinc oxalate , zinc nitrate, gallium nitrate, gallium fluoride, tin sulfide, etc.;

Optionally, in the step (1), the Co ion concentration in the aqueous solution containing the Co ion and the constant valence element Ma ion is 0.5-2.0 mol/L; more optionally, the Co ion and the constant-valent element Ma ion are included. The concentration of Co ions in the aqueous solution is 0.8 to 1.5 mol/L.

Optionally, in the step (1), the precipitant solution is a strong alkali solution, a carbonate solution, an oxalic acid or an oxalate solution.

Optionally, in the step (1), the complexing agent solution is an ammonia water or an aminohydroxy acid salt solution.

Optionally, in the step (1), when the aqueous solution containing the Co ion and the constant valence element Ma ion is mixed with the precipitant solution, the flow is controlled by the cocurrent flow control method; and the flow rate of the parallel flow control does not exceed 200 L/ h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100 °C.

Optionally, in the step (1), the crystallization is repeated for 4 to 8 times in a continuous reaction.

Optionally, in the step (2), the variable element Mb is one or more of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr; and/or

Optionally, in the step (2), the compound containing the variable-valent element Mb is one selected from the group consisting of oxides, hydroxides, carbonates, nitrates, oxalates, acetates, and the like containing Mb. Or more than one; more optionally selected from one or more of nitrates and acetates containing Mb, such as: nickel nitrate, nickel oxide, nickel hydroxide, nickel oxyhydroxide, nickel carbonate, nickel oxalate, manganese oxide , manganese carbonate, manganese oxalate, manganese nitrate, molybdenum oxide, molybdenum hydroxide, molybdenum carbonate, molybdenum oxalate, molybdenum nitrate, cerium oxide, cerium hydroxide, cerium oxalate, cerium nitrate, copper oxide, copper hydroxide, copper nitrate, acetic acid Copper, copper chloride, iron oxide, iron hydroxide, iron nitrate, iron oxalate, iron chloride, indium oxide, indium hydroxide, indium chloride, tungsten oxide, tungsten fluoride, chromium oxide, chromium hydroxide, chromium carbonate , chromium oxalate, chromium nitrate and the like.

Optionally, in the step (2), the temperature sintering temperature is 800-1000 ° C, the sintering time is 4-10 h; more optionally, the temperature sintering temperature is 900-950 ° C, and the sintering time is 6-8 h.

Optionally, in the step (3), the lithium source is selected from the group consisting of lithium-containing compounds and compositions thereof, and may be selected from the group consisting of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, lithium oxide, and citric acid. One or more of lithium, more preferably selected from lithium carbonate and lithium hydroxide;

Optionally, in the step (3), the temperature sintering temperature is 950 to 1100 ° C, and the sintering time is 8 to 16 h; more optionally, the temperature sintering temperature is 1020 to 1080 ° C, and the sintering time is 10 to 14 h.

Optionally, in the step (4), the element Mc is one or more of Cr, Co, Ni, Cu, Mn, and P;

Optionally, in the step (4), the compound containing the element Mc is one or more of an oxide, a hydroxide, a carbonate, a nitrate, an oxalate, an acetate, etc. containing Mc. ;

Optionally, in the step (4), the temperature sintering temperature is 850 to 1050 ° C, and the sintering time is 8 to 16 hours; more optionally, the temperature sintering temperature is 900 to 1000 ° C, and the sintering time is 10 to 14 hours.

In the above preparation method, by using the controlled crystallization method, the constant-valent element and the cobalt source are uniformly distributed in the liquid system, so that the doping element is uniformly distributed, the reaction is complete, and the formed crystal structure is stable. In the step (2), while the mixture of the precursor and the valence element is sintered at a temperature, the precursor cobalt salt of the loose structure shrinks into a tightly fused and stabilized precursor Co ₃ O ₄ , which is a more stable valence element ion than the cobalt ion. Occupying the cobalt site enhances the structural stability of the precursor Co ₃ O ₄ , and at the same time, the variable element ions have higher energy at the time of temperature sintering, and can enter the gap of the lattice structure to form a gap doping, thereby being high. The function of buffering or releasing stress in the voltage cycle stabilizes the crystal structure. Step (4) provides another alternative processing method, first sintering the precursor carbonate or hydroxide of the cobalt doped with the constant-valent element Ma into a constant-valent element, Ma-doped Co ₃ O ₄ , Thereafter, a compound of the variable element Mb and a lithium source are added, and temperature co-sintering is performed. In this way, when the bulk-doped lithium cobaltate matrix is formed, it is more advantageous for the variable-valent element to enter the gap of the space formed by the lattice lithium ion, the cobalt ion and the oxygen ion, thereby better exerting the function of buffering or releasing stress.

In another embodiment of the present invention, there is also provided a method for preparing a structurally stable high voltage lithium cobaltate cathode material doped with a surface coating and co-modified, the method comprising:

Step (1): using a controlled crystallization method, a molar ratio, an appropriate amount of a cobalt source and a compound containing a constant valence element Ma, and an aqueous solution containing a Co ion and a constant valence element Ma ion, mixed with a complexing agent solution and a precipitating agent solution The reaction is crystallized while stirring, and the pH of the reaction system is controlled to 6 to 12, and after crystallization, centrifugal filtration is performed to obtain a carbonate or hydroxide of a cobalt doped with a constant valence element Ma;

Step (2): temperature-decomposing the cobalt carbonate or hydroxide of the constant-valent element Ma doped after the step (1), and then pulverizing the decomposition product to obtain a precursor of the constant-doped element Ma doping Body Co ₃ O ₄ ; molar ratio, take an appropriate amount of the compound containing the variable element Mb, the constant-content element Ma-doped precursor Co ₃ O ₄ and the lithium source are stirred and mixed uniformly, and placed in a horse boiling furnace or a sintering furnace for temperature sintering. Then, the product is pulverized to obtain a matrix of lithium cobaltate cathode material Li _1+z Co _1-xy Ma _x Mb _y O ₂ co-doped with Ma and Mb (generally, 0≤x≤0.01, 0≤y≤0.01 , -0.05 ≤ z ≤ 0.08; preferably, 0.0005 ≤ x ≤ 0.005, 0.0005 ≤ y ≤ 0.005, -0.01 ≤ z ≤ 0.03);

Step (3): using a solid phase coating synthesis method, a molar ratio, a lithium source and a compound containing the element Mc, and a lithium cobaltate cathode material substrate Li _1+z Co _1-xy Ma _x obtained after the step (2) Mb _y O _{2 is} stirred and mixed uniformly, and is sintered in a horse boiling furnace or a sintering furnace, and then the product is pulverized to obtain a structurally stable high-voltage lithium cobaltate cathode material αLi _{γ1 which is} co-modified by bulk phase coating and surface coating. Mc _γ2 O _γ3 ·βLi _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1; preferably, 0<α≤0.05, 0.95≤β≤1) .

It should be noted that the step (3) can be replaced by: using a liquid phase coating synthesis method, a molar ratio, a lithium source and a compound containing the element Mc, and a lithium cobaltate positive electrode material substrate obtained after the step (2). Li _1+z Co _1-xy Ma _x Mb _y O _{2 is} stirred and mixed uniformly. After the powder is dried, it is sintered in a horse boiling furnace or a sintering furnace, and then the product is pulverized to obtain bulk phase doping and surface coating. Modified structurally stable high voltage lithium cobaltate cathode material αLi _γ1 Mc _γ2 O _γ3 ·βLi _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1; Alternatively, 0 < α ≤ 0.05, 0.95 ≤ β ≤ 1).

Optionally, in the step (1), the cobalt source is one or more of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride;

Optionally, in the step (1), the constant valence element Ma is one or more of Al, Ga, Hf, Mg, Sn, Zn, and Zr;

Optionally, in the step (1), the compound containing the constant valence element Ma is one selected from the group consisting of nitrates, oxalates, acetates, fluorides, chlorides, sulfates, and the like containing Ma or a plurality of; more preferably one or more selected from the group consisting of sulfates, nitrates, and acetates of Ma, such as: aluminum oxalate, aluminum nitrate, magnesium oxalate, magnesium nitrate, zirconium oxalate, zirconium nitrate, zinc oxalate , zinc nitrate, gallium nitrate, gallium fluoride, tin sulfide, etc.;

Optionally, in the step (1), the Co ion concentration in the aqueous solution containing the Co ion and the constant valence element Ma ion is 0.5-2.0 mol/L; more optionally, the Co ion and the constant-valent element Ma ion are included. The concentration of Co ions in the aqueous solution is 0.8 to 1.5 mol/L.

Optionally, in the step (1), the precipitant solution is a strong alkali solution, a carbonate solution, an oxalic acid or an oxalate solution.

Optionally, in the step (1), the complexing agent solution is an ammonia water or an aminohydroxy acid salt solution.

Optionally, in the step (1), when the aqueous solution containing the Co ion and the constant valence element Ma ion is mixed with the precipitant solution, the flow is controlled by the cocurrent flow control method; and the flow rate of the parallel flow control does not exceed 200 L/ h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100 °C.

Optionally, in the step (1), the crystallization is repeated for 4 to 8 times in a continuous reaction.

Optionally, in the step (2), the variable element Mb is one or more of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr;

Optionally, in the step (2), the compound containing the variable-valent element Mb is one selected from the group consisting of oxides, hydroxides, carbonates, nitrates, oxalates, acetates, and the like containing Mb. Or more than one; more optionally selected from one or more of nitrates and acetates containing Mb, such as: nickel nitrate, nickel oxide, nickel hydroxide, nickel oxyhydroxide, nickel carbonate, nickel oxalate, manganese oxide , manganese carbonate, manganese oxalate, manganese nitrate, molybdenum oxide, molybdenum hydroxide, molybdenum carbonate, molybdenum oxalate, molybdenum nitrate, cerium oxide, cerium hydroxide, cerium oxalate, cerium nitrate, copper oxide, copper hydroxide, copper nitrate, acetic acid Copper, copper chloride, iron oxide, iron hydroxide, iron nitrate, iron oxalate, iron chloride, indium oxide, indium hydroxide, indium chloride, tungsten oxide, tungsten fluoride, chromium oxide, chromium hydroxide, chromium carbonate , chromium oxalate, chromium nitrate and the like.

Optionally, in the step (2), the temperature sintering temperature is 800-1000 ° C, the sintering time is 4-10 h; more optionally, the temperature sintering temperature is 900-950 ° C, and the sintering time is 6-8 h.

Optionally, in the step (3), the element Mc is one or more of Cr, Co, Ni, Cu, Mn, and P;

Optionally, in the step (3), the compound containing the element Mc is one or more of an oxide, a hydroxide, a carbonate, a nitrate, an oxalate, an acetate, etc. containing Mc. ;

Optionally, in the step (3), the temperature sintering temperature is 850 to 1050 ° C, and the sintering time is 8 to 16 hours; more optionally, the temperature sintering temperature is 900 to 1000 ° C, and the sintering time is 10 to 14 hours.

The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

Example 1:

A structurally stable high-voltage lithium cobaltate cathode material formed by doping Al, Ni and coating LiCo _0.5 Ni _0.5 O ₂ with lithium cobaltate, and having a molecular formula of 0.005LiCo _0.5 Ni _0.5 O ₂ ·0.995LiCo _0.996 Al _0.003 Ni _0.001 O ₂ , the preparation method comprises the following steps:

(1) Dissolve CoSO ₄ and Al ₂ (SO ₄ ) _{3 in} deionized water, and arrange a mixed salt solution having a molar ratio of Co:Al=99.6:0.3, and the concentration of Co ²⁺ in the mixed salt solution is 1.25 mol/ L; using concentrated ammonia water and distilled water to form a complexing agent solution at a volume ratio of 1:10; using 1.2 mol/L sodium carbonate solution as a precipitating agent solution; injecting a solvent solution of 1/3 of the solvent into the reaction kettle, Under the action of strong agitation and inert gas protection, the above mixed salt solution, complexing agent solution and precipitant solution are simultaneously injected into the reaction vessel by cocurrently controlling the flow rate, and the flow rate of the flow control is not more than 200 L/ h, stirring at the same time, the stirring speed does not exceed 200 rpm, and control the pH value of the reaction system is 6-12, and the temperature of the reaction kettle is controlled at 70-80 ° C during the reaction; the doping element Al in the reaction system is monitored in real time during the reaction. And the liquid phase ion concentration of Co; the continuous reaction is repeated 4 times and then subjected to centrifugal filtration to obtain a precursor cobalt salt doped with Al;

(2) molar ratio Co:Ni=99.6:0.1 Weigh a certain amount of nickel acetate, and mix and mix the Al-doped precursor cobalt salt obtained in step (1), and place it in a horse-boiling furnace at 900 ° C for sintering. The time is 8h, and then the sintered product is pulverized to obtain an Al, Ni co-doped Co ₃ O ₄ precursor with uniform particle distribution;

(3) The molar ratio Li:Co=100:99.6 weighs a certain amount of lithium carbonate, and the Al and Ni co-doped Co ₃ O ₄ precursor obtained after the step (2) is stirred and uniformly mixed, and placed in a horse boiling furnace. At 1050 ° C, the sintering time is 12h, and then the sintered product is pulverized to obtain Al and Ni co-doped lithium cobaltate matrix LiCo _0.996 Al _0.003 Ni _0.001 O _{2 with} uniform particle distribution;

(4) molar ratio Li:Co:Ni:LiCo _0.996 Al _0.003 Ni _0.001 O ₂ =0.5:0.25:0.25:99.5 Weigh a certain amount of lithium carbonate, cobalt carbonate, nickel acetate and the step (3) LiCo _0.996 Al _0.003 Ni _0.001 O _{2 was} stirred and mixed uniformly, placed in a horse boiling furnace at 950 ° C, and the sintering time was 12 h, and then the sintered product was pulverized to obtain a structurally stable high volume of body phase doping and surface coating co-modification. Voltage lithium cobaltate cathode material 0.005LiCo _0.5 Ni _0.5 O ₂ ·0.995LiCo _0.996 Al _0.003 Ni _0.001 O ₂ .

Please refer to Figure 4 to Figure 8. The constant-current charge-discharge test is performed on the prepared structurally stable high-voltage lithium cobaltate cathode material 0.005LiCo _0.5 Ni _0.5 O ₂ ·0.995LiCo _0.996 Al _0.003 Ni _0.001 O ₂ . The positive electrode material has a high discharge specific capacity and excellent cycle stability. At room temperature, the initial charge and discharge efficiency of the lithium cobaltate cathode material was 98.2% at a voltage range of 3.0 to 4.6 V, and the capacity retention rate was 93.75% after 70 cycles.

Example 2:

A structurally stable high-voltage lithium cobaltate cathode material formed by doping Al, Cr and coated with LiNiPO ₄ with lithium cobaltate, and having a molecular formula of 0.005LiNiPO ₄ ·0.995Li _1.03 Co _0.995 Al _0.004 Cr _0.001 O ₂ The preparation method comprises the following steps:

(1) Dissolve CoSO ₄ and Al ₂ (SO ₄ ) _{3 in} deionized water, and arrange a mixed salt solution having a molar ratio of Co:Al=99.5:0.4, and the concentration of Co ²⁺ in the mixed salt solution is 1.25 mol/ L; using concentrated ammonia water and distilled water to form a complexing agent solution at a volume ratio of 1:10; using 1.2 mol/L sodium carbonate solution as a precipitating agent solution; injecting a solvent solution of 1/3 of the solvent into the reaction kettle, Under the action of strong agitation and inert gas protection, the above mixed salt solution, complexing agent solution and precipitant solution are simultaneously injected into the reaction vessel by cocurrently controlling the flow rate, and the flow rate of the flow control is not more than 200 L/ h, stirring at the same time, the stirring speed does not exceed 200 rpm, and control the pH value of the reaction system is 6-12, and the temperature of the reaction kettle is controlled at 70-80 ° C during the reaction; the doping element Al in the reaction system is monitored in real time during the reaction. And the liquid phase ion concentration of Co; the continuous reaction is repeated 4 times and then subjected to centrifugal filtration to obtain a precursor cobalt salt doped with Al;

(2) molar ratio Co:Cr=99.5:0.1 Weigh a certain amount of chromium oxide, and mix and mix the Al-doped precursor cobalt salt obtained in step (1), and place it in a horse-boiling furnace at 900 ° C for sintering. The time is 8h, and then the sintered product is pulverized to obtain an Al, Cr co-doped Co ₃ O ₄ precursor with uniform particle distribution;

(3) The molar ratio Li:Co=103:99.5 weighs a certain amount of lithium carbonate, and the Al and Cr co-doped Co ₃ O ₄ precursor obtained after the step (2) is stirred and uniformly mixed, and placed in a horse boiling furnace. At 1050 ° C, the sintering time is 12h, and then the sintered product is pulverized to obtain Al and Cr co-doped lithium cobaltate matrix Li _1.03 Co _0.995 Al _0.004 Cr _0.001 O _{2 with} uniform particle distribution;

(4) molar ratio Li: Ni: P: Li _1.03 Co _0.995 Al _0.004 Cr _0.001 O ₂ = 0.5: 0.5: 0.5: 99.5 Weigh a certain amount of lithium carbonate, nickel acetate, ammonium dihydrogen phosphate and step (3) The prepared Li _1.03 Co _0.995 Al _0.004 Cr _0.001 O _{2 was} stirred and mixed uniformly, placed in a horse boiling furnace at 950 ° C, and the sintering time was 12 h, and then the sintered product was pulverized to obtain bulk phase doping and surface coating. Sexually stable high voltage lithium cobaltate cathode material 0.005LiNiPO ₄ ·0.995Li _1.03 Co _0.995 Al _0.004 Cr _0.001 O ₂ .

Example 3

A structurally stable high-voltage lithium cobaltate cathode material, which is doped with Al, Mn by lithium cobaltate and coated with Li _1.06 (Ni _0.425 Co _0.15 Mn _0.425 ) _0.94 O ₂ , and has a molecular formula of 0.005Li _1.06 (Ni _0.425 Co _0.15 Mn _0.425 ) _0.94 O2·0.995Li _1.02 Co _0.994 Al _0.004 Mn _0.002 O ₂ , the preparation method thereof comprises the following steps:

(1) Dissolving CoSO ₄ and Al ₂ (SO ₄ ) _{3 in} deionized water, and configuring a mixed salt solution having a molar ratio of Co:Al=99.4:0.4, and the concentration of Co ²⁺ in the mixed salt solution is 1.25 mol/ L; using concentrated ammonia water and distilled water to form a complexing agent solution at a volume ratio of 1:10; using 1.2 mol/L sodium carbonate solution as a precipitating agent solution; injecting a solvent solution of 1/3 of the solvent into the reaction kettle, Under the action of strong agitation and inert gas protection, the above mixed salt solution, complexing agent solution and precipitant solution are simultaneously injected into the reaction vessel by cocurrently controlling the flow rate, and the flow rate of the flow control is not more than 200 L/ h, stirring at the same time, the stirring speed does not exceed 200 rpm, and control the pH value of the reaction system is 6-12, and the temperature of the reaction kettle is controlled at 70-80 ° C during the reaction; the doping element Al in the reaction system is monitored in real time during the reaction. And the liquid phase ion concentration of Co; the continuous reaction is repeated 4 times and then subjected to centrifugal filtration to obtain a precursor cobalt salt doped with Al;

(2) The Al-doped precursor cobalt salt obtained in the step (1) is subjected to pyrolysis at 900 ° C in a horse-boiling furnace, and the decomposition time is 6 h, and then the decomposition product is pulverized to obtain Al having uniform particle distribution. a doped Co ₃ O ₄ precursor;

(3) molar ratio Li:Co:Mn=102:99.4:0.2 Weigh a certain amount of lithium carbonate and manganese acetate, and the Al-doped Co ₃ O ₄ precursor obtained after the step (2) is stirred and mixed uniformly. It was placed in a horse-boiling furnace at 1050 ° C for 12 h, and then the sintered product was pulverized to obtain Al and Mn co-doped lithium cobaltate matrix Li _1.02 Co _0.994 Al _0.004 Mn _0.002 O _{2 with} uniform particle distribution;

(4) molar ratio Li: Ni: Co: Mn: Li _1.02 Co _0.994 Al _0.004 Mn _0.002 O ₂ = 0.53: 0.2125: 0.075: 0.2125: 99.5 Weigh a certain amount of lithium carbonate, nickel acetate, cobalt carbonate, manganese acetate Li _1.02 Co _0.994 Al _0.004 Mn _0.002 O ₂ prepared after the step (3) is stirred and uniformly mixed, placed in a horse boiling furnace at 950 ° C, and the sintering time is 12 h, and then the sintered product is pulverized to obtain bulk phase doping and The surface-coated co-modified structurally stabilized high-voltage lithium cobaltate cathode material 0.005Li _1.06 (Ni _0.425 Co _0.15 Mn _0.425 ) _0.94 O ₂ ·0.995Li _1.02 Co _0.994 Al _0.004 Mn _0.002 O ₂ .

It can be seen from the above that the present invention combines the practical application of academia and industry to carry out intensive research, and proposes a structure-stabilized high-voltage lithium cobaltate cathode material doped and coated and modified by process improvement and preparation thereof. method. Wherein, the variable valence elements doped in the lithium cobaltate cathode material are Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr, and the immutable valence elements are Al, Ga, Hf, Mg, Sn, Zn, Zr. On the one hand, the non-variable valence element replaces the cobalt site by substitution doping, instead of cobalt ion, to ensure that the skeleton-cobalt site of the layered structure is not distorted by oxidation, and the layered structure of the lithium cobaltate positive electrode material can be stabilized under high voltage use. On the other hand, the variable valence element is doped through the gap and filled into the gap between lithium, cobalt and oxygen ions. In the charging process, not only in the oxidizing atmosphere, oxidation occurs in preference to Co ³⁺ , but Co ³⁺ can be delayed. Oxidation occurs, and while Co ³⁺ changes in ionic radius due to oxidation, the valence ions also undergo or have undergone ionic radius changes to relieve or release the stress generated by the skeletal structure of the layered structure, achieving a stable lithium cobaltate layer. The purpose of the structure. The invention combines the principle and process of phase transformation of a lithium cobaltate layer structure in a high voltage scene, fully exerts the advantages of each doping element, and significantly improves the comprehensive performance of the cathode material.

Further, the surface of the doped lithium cobaltate substrate coated with the high voltage positive electrode active material is provided by the invention, and the coating layer itself has the advantages of stable structure and excellent cycle performance under high voltage, and after forming the cladding layer, on the one hand As a stable cathode material/electrolyte interface, the lithium cobaltate matrix is separated from the electrolyte to reduce the reaction area, increase the interface stability, and ensure that the lithium cobaltate matrix does not dissolve in the electrolyte under high voltage. Stabilizing the structure of lithium cobaltate, so that the activation energy is increased to suppress the phase transition; on the other hand, as a coating layer itself, it has the function of energy storage, and does not sacrifice the gram capacity of the positive electrode material while functioning as a stable structure. It will not sacrifice its energy density. The structurally stabilized lithium cobaltate cathode material prepared by the method of doping and surface coating co-modification by the method can significantly improve the cycle performance of the lithium cobaltate cathode material in a high voltage environment of 4.6V or higher, and is made of the cathode material. Lithium-ion batteries have a wider range of applicability and increase the life of lithium-ion batteries.

Further, the present invention is prepared by a liquid phase-solid phase method, combining the advantages of the two methods, uniformly dispersing doping elements in the material during the reaction, and the surface of the doped lithium cobaltate cathode material is subjected to high voltage positive electrode activity. The material is evenly coated, which greatly increases the stability of the interface and stabilizes the lithium cobaltate layer structure. The product prepared by the process has excellent crystal quality, high tap density, good processing performance, chemical composition close to the theoretical value, and excellent layered structure.

Further, the present invention comprehensively considers the controlled crystallization method for preparing a substituted doped precursor and solid phase sintering to synthesize a high voltage lithium cobaltate product; the existing equipment can be used for large scale industrial production.

In another embodiment of the present invention, a structurally stable high voltage lithium cobaltate cathode material doped with a surface coating and a surface coating is provided, the cathode material comprising a doped lithium cobaltate substrate and a surface coating Layer, its general chemical composition such as αLi _γ1 Mc _γ2 O _γ3 ·βLi _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0<α≤0.08, 0.92≤β≤1; 0≤x≤0.01 , 0 ≤ y ≤ 0.01, -0.05 ≤ z ≤ 0.08; γ1, γ2, and γ3 may be any positive number, but need to satisfy the distribution of valence).

Wherein, the doped lithium cobaltate matrix has the formula Li _1+z Co _1-xy Ma _x Mb _y O ₂ (generally, 0≤x≤0.01, 0≤y≤0.01, -0.05≤z≤0.08; Preferably, 0.0005≤x≤0.005, 0.0005≤y≤0.005, -0.01≤z≤0.03), Ma is one or more of the doped constant-valent elements Al, Ga, Hf, Mg, Sn, Zn, Zr Mb is one or more of the doped variable elements Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr.

Wherein, the chemical composition of the surface coating layer is Li _γ1 Mc _γ2 O _γ3 , wherein Mc is generally one or more of Cr, Co, Ni, Cu, Mn, P, and γ1, γ2 and γ3 may be any positive number. , but need to meet the distribution of valence.

The present invention also provides a lithium ion battery, as shown in FIG. 9, comprising a positive electrode sheet, a negative electrode sheet and a separator disposed between the positive and negative electrode sheets, and an electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a distribution The positive electrode active material on the positive electrode current collector is made of the lithium cobaltate positive electrode material described above as a positive electrode active material. The active capacity of such a lithium cobaltate material is greater than 190 mAh/g. The present invention also provides an electronic device using the above lithium ion battery.

Claims (13)

1. A lithium cobaltate cathode material, characterized in that the lithium cobaltate cathode material comprises a doped lithium cobaltate substrate and a surface coating layer; wherein the surface coating layer is coated on the doped cobalt The surface of the lithium acid substrate;

   Wherein the substance constituting the doped lithium cobaltate matrix has the general formula Li _1+z Co _1-xy Ma _x Mb _y O ₂ ;

   Wherein, 0≤x≤0.01, 0≤y≤0.01, -0.05≤z≤0.08;

   Wherein, the Ma is a doped constant valence element; and the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, and Zr;

   Wherein, the Mb is a doped variable element; the Mb is at least one of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, Cr;

   Wherein, the general composition constituting the surface coating layer is Li _γ1 Mc _γ2 O _γ3 ; the Mc is at least one of Cr, Co, Ni, Cu, Mn, P, and the γ1, γ2, and γ3 are Any positive number satisfying the formula γ1+A*γ2=2*γ3, which is the valence of Mc, is satisfied.
2. The lithium cobaltate cathode material according to claim 1, wherein in the charging process, the constant valence element replaces cobalt ions by substitution doping, and the valence element The gap between lithium, cobalt, and oxygen ions is filled by gap doping.
3. The lithium cobaltate cathode material according to claim 1 or 2, wherein 0.0005 ≤ x ≤ 0.005.
4. The lithium cobaltate cathode material according to any one of claims 1 to 3, wherein 0.0005 ≤ y ≤ 0.005.
5. The lithium cobaltate cathode material according to any one of claims 1 to 4, wherein -0.01 ? z ? 0.03.
6. A method for producing the lithium cobaltate cathode material according to any one of claims 1 to 5, characterized in that the method comprises:

   The cobalt source, the compound containing the constant valence element Ma is configured as an aqueous solution; wherein the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr;

   Mixing the aqueous solution with the complex solution and the precipitant solution to cause the aqueous solution, the complex solution and the precipitant solution to react and crystallize to obtain the carbonate or hydroxide of the Ma-doped cobalt;

   Mixing the obtained cobalt or hydroxide of the doped cobalt with a compound containing a valence element Mb; wherein the Mb is Ni, Mn, V, Mo, Nb, Cu, Fe, In, W At least one of Cr;

   The mixture obtained by mixing is sintered at a temperature of 800 to 1000 ° C for 4-10 hours to obtain an oxide precursor of Co co-doped with Ma and Mb;

   The obtained oxide precursor of Co co-doped with Ma and Mb is mixed with a lithium source;

   The mixture of the oxide precursor and the lithium source is sintered at a temperature of 950 to 1100 ° C for 8 to 16 hours to obtain the high voltage lithium cobaltate matrix co-doped with the Ma and Mb;

   The lithium source, the compound containing the element Mc, and the obtained high-voltage lithium cobaltate co-doped with Ma and Mb are mixed and sintered at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain the lithium cobaltate positive electrode. a material, wherein the Mc is at least one of Cr, Co, Ni, Cu, Mn, and P.
7. The method according to claim 6, wherein the aqueous solution is mixed with a complex solution and a precipitant solution to cause the aqueous solution to react with the complex solution and the precipitant solution to obtain the Ma-doped cobalt carbonates or hydroxides include:

   Mixing an aqueous solution containing Co ions and a constant-valent element Ma ion with a precipitant solution by using a flow-controlled flow rate; Wherein, the flow rate of the parallel flow control does not exceed 200 L/h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100 °C.
8. Method according to claim 6 or 7, characterized in that

   The cobalt source is at least one of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride;

   The compound containing a constant valence element Ma is at least one of nitrate, oxalate, acetate, fluoride, chloride, and sulfate containing Ma;

   The concentration of Co ions in the aqueous solution containing Co ions and the constant-valent element Ma ions is 0.5-2.0 mol/L;

   The precipitant solution is a strong alkali solution, a carbonate solution, an oxalic acid or an oxalate solution;

   The complexing agent solution is an ammonia water or an aminohydroxy acid salt solution;

   The compound containing a variable-valent element Mb is at least one selected from the group consisting of oxides, hydroxides, carbonates, nitrates, oxalates, and acetates containing Mb;

   The lithium source is at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, lithium oxide, and lithium citrate; or

   The compound containing the element Mc is at least one of an oxide, a hydroxide, a carbonate, a nitrate, an oxalate, and an acetate containing Mc.
9. A method for producing the lithium cobaltate cathode material according to any one of claims 1 to 5, characterized in that the method comprises:

   The cobalt source, the compound containing the constant valence element Ma is configured as an aqueous solution; wherein the Ma is at least one of Al, Ga, Hf, Mg, Sn, Zn, Zr;

   Mixing the aqueous solution, the complex solution and the precipitant solution to cause the aqueous solution to react with the complex solution and the precipitant solution to obtain a carbonate or hydroxide of the Ma-doped cobalt;

   The obtained cobalt-doped cobalt carbonate or hydroxide is sintered at a temperature of 900 to 1000 ° C to obtain a Ma-doped precursor Co ₃ O ₄ , wherein the sintering time is 4 ～ 10h;

   The lithium source, the Mb-containing compound and the Ma-doped precursor Co ₃ O ₄ are sintered at a temperature of 950 to 1100 ° C for 8 to 16 hours to obtain a high-voltage lithium cobaltate matrix co-doped with Ma and Mb. ;

   The lithium source, the compound containing the element Mc, and the obtained high-voltage lithium cobaltate co-doped with Ma and Mb are mixed and sintered at a temperature of 850 to 1050 ° C for 8 to 16 hours to obtain the lithium cobaltate positive electrode. a material, wherein the Mc is at least one of Cr, Co, Ni, Cu, Mn, and P.
10. The method according to claim 9, wherein the aqueous solution is mixed with a complex solution and a precipitant solution to cause the aqueous solution to react with the complex solution and the precipitant solution to obtain the Ma-doped cobalt carbonates or hydroxides include:

    The aqueous solution containing Co ions and the constant-valent element Ma ions is mixed with the precipitating agent solution by means of cocurrent flow control; wherein the flow rate of the parallel flow control does not exceed 200 L/h, the stirring speed does not exceed 200 rpm, and the crystallization temperature does not exceed 100. °C.
11. Method according to claim 9 or 10, characterized in that

    The cobalt source is at least one of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride;

    The compound containing a constant valence element Ma is at least one of nitrate, oxalate, acetate, fluoride, chloride, and sulfate containing Ma;

    The concentration of Co ions in the aqueous solution containing Co ions and the constant-valent element Ma ions is 0.5-2.0 mol/L;

    The precipitant solution is a strong alkali solution, a carbonate solution, an oxalic acid or an oxalate solution;

    The complexing agent solution is an ammonia water or an aminohydroxy acid salt solution;

    The compound containing a variable-valent element Mb is at least one selected from the group consisting of oxides, hydroxides, carbonates, nitrates, oxalates, and acetates containing Mb;

    The lithium source is at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, lithium oxide, and lithium citrate; or

    The compound containing the element Mc is at least one of an oxide, a hydroxide, a carbonate, a nitrate, an oxalate, and an acetate containing Mc.
12. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte solution, and a separator disposed between the positive and negative electrode sheets, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode distributed on the positive electrode current collector The active material layer is characterized in that the positive electrode active material layer is a lithium cobaltate positive electrode material according to any one of claims 1 to 5 as a positive electrode active material.
13. An electronic device comprising the lithium ion battery of claim 12.

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