Positive electrode active material and preparation method thereof, positive electrode plate, battery and electric equipment

Abstract

The positive electrode active material comprises LiaNixCoyM1zM2bM3cO2, 0.98 < = a < = 1.1, 0.6 < = x < = 1, 0 < = y < = 0.4, 0 < = z < = 0.4, 0 < = b < = 0.05, 0 < = c < = 0.05, M1 comprises one or more of Mn and Al, and M2 and M3 respectively comprise one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr and Ti; 0.2 < = FOM < = 0.5 of the positive electrode active material after 80 cycles at 4.3 V and 45 DEG C; fOM is equal to [delta] d104 / [delta] d003, [delta] d003 is equal to (d00380-d0030) / d0030, and [delta] d104 is equal to (d10480-d1040) / d1040; d00380 is the interplanar spacing of the 003 crystal face of the positive electrode active material after 80 cycles of the battery containing the positive electrode active material; d0030 is the interplanar spacing of the initial 003 crystal face of the positive electrode active material; d10480 is the interplanar spacing of the 104 crystal face of the positive electrode active material after 80 cycles of the battery containing the positive electrode active material; and d1040 is the interplanar spacing of the initial 104 crystal face of the positive electrode active material. And the battery has excellent rate capability and cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular, to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery, and an electric device. BACKGROUND

[0002] The positive electrode material of a lithium ion battery is a core component of the lithium ion battery, mainly including lithium cobaltate, lithium manganate, lithium iron phosphate, and four technical systems of multi-element materials. The performance of the positive electrode material directly affects the energy density, cycle life, and safety of the battery, and accounts for 30-45% of the total cost of battery materials.

[0003] Among them, the positive electrode active material with high nickel content is widely concerned due to its high energy density. However, with the increase of the nickel content, the structural stability of the positive electrode active material decreases. The positive electrode active material adopts a single crystal material, which can improve the structural stability of the material. However, the lithium ion transmission path of the single crystal material is long, and the rate and cycle performance are slightly poor. In particular, the internal structure collapse during the cycle process will block the lithium ion transmission channel of the positive electrode active material, and the rate and cycle performance of the positive electrode active material will be further deteriorated. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art to some extent. The present application provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery, and an electric device. The positive electrode active material provided by the present application can make the lithium ion battery have excellent energy density, rate performance, and cycle performance.

[0005] The first aspect of the present application provides a positive electrode active material, the positive electrode active material comprising single crystal particles, the positive electrode active material comprising: Li a Ni x Co y M1 z M2 b M3 c O2, wherein 0.98≤a≤1.1, 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, 0≤b≤0.05, 0≤c≤0.05, M1 comprises one or more of Mn, Al, M2 and M3 each independently comprises one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ti; the structure merit factor of the positive electrode active material after 80 cycles is FOM, 0.2≤FOM≤0.5; wherein FOM=|Δd 104 | / |Δd 003 |, Δd 003 =(d 003 80 -d003 0 ) / d 003 0 , Ad 104 =(d 104 80 -d 104 0 ) / d 104 0 ; d 003 80 is a d-spacing of a 003 crystal plane of the positive electrode active material after the battery containing the positive electrode active material is cycled for 80 cycles, in Å; d 003 0 is a d-spacing of an initial 003 crystal plane of the positive electrode active material, in Å; d 104 80 is a d-spacing of a 104 crystal plane of the positive electrode active material after the coin battery containing the positive electrode active material is cycled for 80 cycles, in Å; d 104 0 is a d-spacing of an initial 104 crystal plane of the positive electrode active material, in Å.

[0006] The positive electrode active material provided in the present application has a high content of nickel element (0.6≤x≤1), which can improve the energy density of the battery, control the structure figure of merit (FOM) of the positive electrode active material, and the FOM represents a stable framework of metals and oxygen in the positive electrode material, and the anti-interference ability and stability in the cycle process relative to the relatively active lithium ion layer. The FOM satisfies 0.2≤FOM≤0.5, which indicates that the structure of the positive electrode active material is stable in the cycle process, and the lithium ion intercalation and deintercalation effect is good, which means that the positive electrode active material has excellent ionic conductivity, and the kinetic performance of the positive electrode active material is better. At the same time, the positive electrode active material has the largest reversible capacity, which indicates that the thermodynamic performance of the positive electrode active material is better, which can not only ensure that the cycle performance of the positive electrode active material is good, but also ensure that the positive electrode active material has excellent lithium ion conductivity, and improve the rate performance and low temperature performance of the material. In summary, the positive electrode active material provided in the present application can improve the energy density, rate performance and cycle performance of the battery containing the same.

[0007] According to some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions: 0.2≤FOM≤0.4; M2 includes one or more of Mg, La, Y, Ce, Er, Nb, W, Mo, Zr; M3 includes one or more of Co, B, Ca, Si, Al, Mg, Ti, Sr, W.

[0008] According to some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions: 0.002≤|Ad 104 |≤0.01, preferably 0.002≤|Ad104 ≤0.007; 0.005≤Δd 003 ≤0.018; 2.025 Å≤d 104 80 ≤2.035 Å; 4.760 Å≤d 003 80 ≤4.800 Å.

[0009] According to some embodiments of the present application, the positive electrode active material comprises a body and a first coating layer and a second coating layer sequentially formed on at least part of the surface of the body, and the first coating layer and the second coating layer each independently comprise one or more of Co element, B element, Ca element, Si element, Al element, Mg element, Ti element, Sr element, W element.

[0010] According to some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions: the average particle size d 50 is 0.8 μm-5.0 μm, preferably 1.0 μm-2.5 μm; the volume average particle size D 50 is 1.5 μm-8.0 μm, preferably 2.0 μm-5.0 μm; the mass fraction of residual lithium on the surface of the single-crystal particle of the positive electrode active material is ≤2000 ppm, preferably ≤1700 ppm.

[0011] The second aspect of the present application provides a method for preparing the positive electrode active material provided in the first aspect of the present application, and the method comprises: mixing a precursor with a first lithium source and optionally a M2 source, performing first sintering to obtain a process product 1, wherein the precursor comprises Ni element, optionally Co element, and optionally M1 element, and the 101 layer number of the precursor is 60-100; mixing the process product 1 with a second lithium source, and performing second sintering to obtain the positive electrode active material.

[0012] The positive electrode active material prepared in the present application has FOM satisfying 0.2≤FOM≤0.5, which can not only ensure good cycle performance of the positive electrode active material, but also ensure excellent lithium ion conductivity of the positive electrode active material, improve the rate performance and low-temperature performance of the material, and improve the energy density, rate performance and cycle performance of the battery containing the same.

[0013] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the first lithium source comprises one or more of lithium hydroxide, lithium oxide; the ratio of the amount of substance of Li element in the first lithium source to the sum of the amounts of substance of Ni element, Co element, M1 element in the precursor, n(Li1) / [n(Ni)+n(Co)+n(M1)]=0.8-1.02, preferably, n(Li1) / [n(Ni)+n(Co)+n(M1)]=0.9-1.0; the ratio of the amount of substance of M2 element in the M2 source to the sum of the amounts of substance of Ni element, Co element, M1 element in the precursor, n(M2) / [n(Ni)+n(Co)+n(M1)]=0-0.05, preferably, n(M2) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.03; the temperature of the first sintering is 600-1000°C, the time is 5-15h, and the sintering atmosphere is an oxygen-containing gas.

[0014] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the second lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium oxide, lithium acetate; the ratio of the amount of substance of Li element in the second lithium source to the sum of the amounts of substance of Ni element, Co element, M1 element in the precursor, n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.01-0.3, preferably, n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.05-0.2; the temperature of the second sintering is 700-1200°C, the time is 10-30h, and the sintering atmosphere is an oxygen-containing gas; the second sintering further comprises: reducing the temperature of the second sintering by 20-100°C and continuing sintering for 1-5h.

[0015] According to some embodiments of the present application, after the second sintering, the method further comprises: mixing the process product 2 obtained by the second sintering with a first coating agent to perform third sintering to obtain a process product 3, wherein the first coating agent comprises a M3 source; mixing the process product 3 with a second coating agent to perform fourth sintering to obtain the positive electrode active material, and the second coating agent comprises a M3 source.

[0016] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the temperature of the third sintering calcination is 500-800°C, the time is 5-20h, and the calcination atmosphere is an oxygen-containing gas; the ratio of the sum of the amounts of substance of B elements and W elements in the second coating agent to the sum of the amounts of substance of Ni elements, Co elements, and M1 elements in the precursor is n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.02, preferably n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.01; the temperature of the fourth sintering is 200-500°C, the time is 5-20h, and the calcination atmosphere is an oxygen-containing gas; the ratio of the sum of the amounts of substance of M3 elements in the first coating agent and the second coating agent to the sum of the amounts of substance of Ni elements, Co elements, and M1 elements in the precursor is n(M3) / [n(Ni)+n(Co)+n(M1)]=0-0.05, preferably n(M3) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.03.

[0017] The third aspect of the present application provides a positive electrode tab, comprising the positive electrode active material provided in the first aspect of the present application or the positive electrode active material prepared by the method provided in the second aspect of the present application.

[0018] The fourth aspect of the present application provides a battery, comprising the positive electrode tab provided in the third aspect of the present application.

[0019] The fifth aspect of the present application provides a power consumption device, comprising the battery provided in the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the references to the figures, in which: Figure 1 FIG. 1 shows the SEM image of the positive electrode active material prepared in Example 1 of the present application.

[0021] Figure 2 FIG. 2 shows the XRD image of the positive electrode active material prepared in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0022] The embodiments of the present application are described in detail below. The embodiments described below are exemplary only, and are intended to explain the present application, but are not to be understood as limiting the present application. In the embodiments, the specific techniques or conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained by purchase on the market.

[0023] The first aspect of the present application provides a positive electrode active material, the positive electrode active material comprising single crystal particles, the positive electrode active material comprising: Li a Ni x Co y M1 z M2 b M3 c O2, wherein 0.98≤a≤1.1, 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, 0≤b≤0.05, 0≤c≤0.05, M1 comprises one or more of Mn, Al, M2 and M3 each independently comprises one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ti; the structure figure of merit of the positive electrode active material after 80 cycles is FOM, 0.2≤FOM≤0.5; wherein FOM=|Δd 104 | / |Δd 003 |, Δd 003 =(d 003 80 -d 003 0 ) / d 003 0 , Δd 104 =(d 104 80 -d 104 0 ) / d 104 0 ; d 003 80 is the interplanar spacing of the 003 crystal plane of the positive electrode active material after 80 cycles of the battery containing the positive electrode active material, in Å; d 003 0 is the interplanar spacing of the initial 003 crystal plane of the positive electrode active material, in Å; d 104 80 is the interplanar spacing of the 104 crystal plane of the positive electrode active material after 80 cycles of the battery containing the positive electrode active material, in Å; d 104 0 is the interplanar spacing of the initial 104 crystal plane of the positive electrode active material, in Å.

[0024] It can be understood that in the embodiments of the present application, "initial" refers to the corresponding state before use after formation of the positive electrode active material, and the number of formation cycles is ≤20 times.

[0025] As an example, a can be 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc.; x can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc.; y can be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, etc.; z can be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, etc.; b can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, etc.; c can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, etc.

[0026] The positive electrode active material proposed in the present application has a high content of nickel element (0.6≤x≤1), which can improve the energy density of the battery; the single crystal particles can improve the cycle performance of the battery; the structure merit factor FOM of the positive electrode active material is controlled, FOM represents the stable framework of metals and oxygen in the positive electrode material, and the anti-interference ability and stability in the cycle process relative to the relatively active lithium ion layer. FOM satisfies 0.2≤FOM≤0.5, which indicates that the structure of the positive electrode active material is stable in the cycle process, and the lithium ion intercalation and deintercalation effect is good, which means that the positive electrode active material has excellent ionic conductivity, and the positive electrode active material has excellent kinetic performance; at the same time, the positive electrode active material has the largest reversible capacity, which indicates that the positive electrode active material has excellent thermodynamic performance, which can not only ensure that the positive electrode active material has good cycle performance, but also ensure that the positive electrode active material has excellent lithium ion conductivity, thereby improving the rate performance and low temperature performance of the material. In summary, the positive electrode active material of the present application can improve the energy density, rate performance and cycle performance of the battery containing the same.

[0027] It can be understood that the 003 crystal face is a vertical layer direction crystal face, d 003 is half of the distance between adjacent transition metal layers, that is, the thickness of one lithium layer plus one transition metal layer. When lithium ions are deintercalated, lithium layer vacancies are caused, the electrostatic repulsion of O-O bonds increases, and the interlayer expands, so Δd 003 > 0 and changes greatly, and because of lithium ion deintercalation, d 003 changes. The structural change formed in the normal cycle state is inevitable and acceptable within a reasonable range. The 104 crystal face is an oblique cut surface, d 104 reflects the Li-O and TM-O bond lengths. After charging, the transition metal is oxidized, the valence state is increased, and the lithium ion radius is reduced, so the TM-O bond is shortened, and Δd 104 < 0 and changes little, d 104 The change is irreversible and harmful to the distortion and destruction of the structure framework of the positive electrode active material. The smaller the change is, the more stable the structure is.

[0028] FOM represents the anti-interference ability and stability of the stable framework composed of multi-metal and oxygen in the positive electrode active material relative to the lithium ion layer in the cycle process. The FOM conforming to 0.2≤FOM≤0.5 indicates that the material is stable in the cycle process, and the lithium ion intercalation and deintercalation effect is good. The particularity of the crystal structure of the positive electrode active material requires that the change of the 003 crystal face or the 104 crystal face cannot be considered alone, because the 003 crystal face will inevitably expand or shrink with the intercalation and deintercalation of lithium ions, which will inevitably affect the change of the 104 crystal face. If only the change rate of a single crystal face is considered, the overall lattice structure state of the positive electrode active material cannot be explained. FOM is too small, which means that the absolute value |Δd 104 | is much smaller than the absolute value |Δd 003 |, that is, the transition metal layer has extremely high stability and almost no irreversible phase change occurs, while the lithium ion layer has changed significantly, and the large |Δd 003 | change may cause severe anisotropic expansion and shrinkage, and even because the TM-O layer is too rigid, the bond length and bond angle cannot be adjusted adaptively, hindering the continuous diffusion of lithium ions, and even causing micro-cracks. The huge lattice strain will also cause surface defects of the positive electrode active material, and intensify the interface reaction with the electrolyte. FOM is too small, which represents a rigid positive electrode active material with slow kinetics and low actual utilization rate, and the positive electrode active material has poor rate performance and low temperature performance. FOM is too large, which means that |Δd 104 | is too large relative to |Δd 003 |, the crystal structure has undergone irreversible degradation, or the structure in the layer and between the layers does not match, the TM-O bond length and TM-O-TM bond angle are distorted, the internal stress is large, the structure is easy to change from layered to spinel or rock salt phase, hindering the lithium ion migration channel, and the rate performance of the positive electrode active material decreases, and the cycle life also decreases sharply.

[0029] According to some embodiments of the present application, 0.2≤FOM≤0.5, for example, FOM can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc., and according to other embodiments of the present application, 0.2≤FOM≤0.4.

[0030] It can be understood that the chemical formula of the positive electrode active material can be measured by ICP method (inductively coupled plasma technology): the instrument used is PE Optima 7000DV, and the test conditions are that 0.1 g of sample is completely dissolved in a mixed acid solution of 3 mL of HNO3+9 mL of HCl, and diluted to 250 mL for testing.

[0031] The d 003 80 , d 104 80 , d 003 0d 104 0 The positive electrode active material can be made into a positive electrode sheet, and the positive electrode sheet before and after cycling can be directly placed on a glass slide for XRD testing. The interplanar spacing can be obtained by refining the whole powder pattern fitting method.

[0032] It can be understood that the positive electrode sheet of a commercial battery is removed and then cut to the required size to prepare a battery, and when 0.2≤FOM≤0.5 is tested, it is also within the protection scope of the present application; or the positive electrode active material on the positive electrode sheet of the commercial battery is scraped off, other substances (such as conductive agents, binders) are removed, and only the positive electrode active material is retained, and then the battery is made again according to the same method, and when 0.2≤FOM≤0.5 is tested, it is also within the protection scope of the present application.

[0033] It can be understood that d 104 80 and d 003 80 When testing, the present application does not limit the type of battery and the conditions of cycling. As an example, the type of battery can be a button cell, the temperature of cycling can be 45°C, and the upper limit voltage of cycling can be 4.3V.

[0034] According to some embodiments of the present application, M2 includes one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ti. According to other embodiments of the present application, M2 includes one or more of Mg, La, Y, Ce, Er, Nb, W, Mo, Zr. The above-mentioned M2 elements can stabilize the crystal structure of the positive electrode active material, reduce structural collapse, and improve the rate performance and cycle performance of the positive electrode active material. In addition, the above-mentioned elements have a large ionic radius, can support the layer structure, are beneficial to lithium ion deintercalation, and the M2-O bond formed by M2 and O has a strong bond strength, can fix oxygen atoms, prevent oxygen release, and the host layer structure is more stable.

[0035] According to some embodiments of the present application, M3 includes one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ti. According to other embodiments of the present application, M3 includes one or more of Co, B, Ca, Si, Al, Mg, Ti, Sr, W. Thus, the crystal structure of the positive electrode active material can be further stabilized, the structural collapse can be reduced, and the rate performance and cycle performance of the positive electrode active material can be further improved.

[0036] It can be understood that in the positive electrode active material, the M2 element can be doped in the bulk phase of the positive electrode active material, and the M3 element can be doped as a coating layer and doped in the surface layer to form a concentration gradient.

[0037] According to some embodiments of the present application, 0.002≤|Δd 104 ≤0.01, for example, Δd 104 The absolute value |Δd 104 | can be 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, etc. According to other embodiments of the present application, 0.002≤|Δd 104 ≤0.007, so that |Δd 104 | is the distortion and damage of the positive electrode active material structure framework, which is irreversible and harmful, the change is small, the structure of the positive electrode active material is stable, and the cycle performance of the positive electrode active material can be improved.

[0038] According to some embodiments of the present application, 0.005≤Δd 003 ≤0.01, for example, Δd 003 | can be 0.005, 0.006, 0.007, 0.008, 0.009, 0.1, etc., so that d 003 The change is too small to cause the interlayer breathing of the lithium intercalation and deintercalation of the positive electrode active material to be poor, resulting in the lithium ion transmission in the positive electrode active material being blocked, d 103 The change is too large to cause the collapse of the layer structure, and the cycle life of the positive electrode active material is reduced.

[0039] According to some embodiments of the present application, 2.025Å≤d 104 80 ≤2.035Å, for example, d 104 80 | can be 2.025Å, 2.026Å, 2.027Å, 2.028Å, 2.029Å, 2.030Å, 2.031Å, 2.032Å, 2.033Å, 2.034Å, 2.035Å, etc. The interplanar spacing of the 104 crystal plane after 80 cycles of the positive electrode active material is controlled within the above range, the structure stress in the positive electrode active material is small, the structure stability of the positive electrode active material after the cycle is still good, long cycle can be realized, and the kinetic performance of the positive electrode active material after the cycle remains excellent.

[0040] According to some embodiments of the present application, 4.760Å≤d 003 80 ≤4.800Å, for example, d 003 804.760 Å, 4.765 Å, 4.770 Å, 4.775 Å, 4.780 Å, 4.785 Å, 4.790 Å, 4.795 Å, 4.800 Å, etc. The interplanar spacing of the 003 crystal plane of the positive electrode active material after 80 cycles is controlled within the above range. After the positive electrode active material is cycled, the interlayer spacing is within the appropriate range, the lithium ion transmission channel is maintained, the structure is stable, the material kinetics is good, and the rate capability and low-temperature performance are better.

[0041] According to some embodiments of the present application, the positive electrode active material comprises a body and a first coating layer and a second coating layer sequentially formed on at least part of the surface of the body, and the first coating layer and the second coating layer each independently comprises one or more of Co element, B element, Ca element, Si element, Al element, Mg element, Ti element, Sr element, and W element. Thus, the above-mentioned element coating can effectively reduce the surface residual alkali of the positive electrode active material, reduce the side reaction of the positive electrode active material and the electrolyte, form a concentration gradient, reduce the surface Ni content, reduce lithium-nickel mixing and metal elution, and improve the cycle performance of the positive electrode active material. Some elements such as B element, W element, and Sr element also have fluxing effect, which can effectively improve the surface morphology of the positive electrode active material, make the surface smooth, and make the coating layer and the substrate more stable, thereby further improving the cycle performance of the positive electrode active material.

[0042] It can be understood that the coating structure of the positive electrode active material can be measured by transmission electron microscopy, and the material of the coating layer can be measured by XPS, EDS, etc.

[0043] According to some embodiments of the present application, the average particle size d 50 of the positive electrode active material is 0.8 μm-5.0 μm. For example, the average particle size d 50 of the positive electrode active material can be 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. According to some other embodiments of the present application, the average particle size d 50 of the positive electrode active material is 1.0 μm-2.5 μm. The average particle size d 50 of the positive electrode active material is controlled within the above range. The single crystal particle size of the positive electrode active material is moderate, which can shorten the transmission distance of lithium ions, and also can not be too small to cause too much side reaction between the positive electrode active material and the electrolyte, so that the excellent rate capability and cycle performance of the battery can be further achieved.

[0044] It can be understood that the average particle size d 50The average particle size d of the positive electrode active material can be measured by a scanning electron microscope, specifically, a scanning electron microscope of model ERA-9200 of ELIONIX, Japan, randomly selecting at least 500 particles in a field of view, respectively measuring the particle size of the 500 particles, and calculating the average value of the particle sizes of the 500 particles, i.e., the average particle size d of the positive electrode active material 50 .

[0045] According to some embodiments of the present application, the volume average particle size D 50 of the positive electrode active material is 1.5 μm-8.0 μm. For example, D 50 may be 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, etc. According to other embodiments of the present application, the volume average particle size D 50 of the positive electrode active material is 2.0 μm-5.0 μm. Controlling the volume average particle size D 50 of the positive electrode active material within the above range, the positive electrode active material single crystal particle size is moderate, reducing the unevenness of the electrode sheet caused by particle adhesion and cracking during the cycle process, and also not generating excess fine powder, which can further achieve excellent rate performance and cycle performance of the battery.

[0046] It can be understood that the volume average particle size D 50 indicates that the particles less than the particle size account for 50% of the total volume of the particles, and the particles greater than the particle size also account for 50% of the total volume of the particles. The laser particle size analyzer can be used for convenient measurement, such as referring to the standard GB / T19077-2016 “Particle Size Distribution-Laser Diffraction Method”, and using a laser particle size analyzer of model Mastersizer3000 of Malvern Instruments Ltd., UK.

[0047] It can be understood that D 50 is the volume average particle size, and d 50 may be biased towards the number average particle size.

[0048] According to some embodiments of the present application, the mass fraction of residual lithium on the surface of the positive electrode active material single crystal particle is ≤2000 ppm. For example, it can be 0, 100 ppm, 300 ppm, 500 ppm, 700 ppm, 900 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1700 ppm, 1900 ppm, 2000 ppm, etc. The residual lithium usually exists in the form of Li2CO3 and LiOH. Controlling the content of residual lithium on the surface of the positive electrode active material within the above range can reduce the impedance of the positive electrode active material, reduce gas production, and improve the rate performance and cycle performance of the battery.

[0049] It can be understood that the mass percentage of residual lithium on the surface of the positive electrode active material single crystal particle can be obtained by a potential titrator. Specifically, 5 g of the positive electrode active material sample can be mixed with 95 g of water and stirred for 5 min, filtered, and the entire filtrate is obtained by 0.1 M hydrochloric acid potential titration. The residual lithium amount is the proportion of lithium in lithium hydroxide and lithium carbonate in the total amount of the positive electrode active material sample.

[0050] In a second aspect of the present application, a method for preparing the positive electrode active material is provided. According to an embodiment of the present application, the method comprises: S1: mixing the precursor with a first lithium source and optionally a M2 source, and performing a first sintering to obtain a process product 1, wherein the precursor comprises Ni elements, optionally Co elements, and optionally M1 elements, and the 101 sheet number of the precursor is 60-100.

[0051] According to some embodiments of the present application, the 101 sheet number of the precursor is 60-100, for example, it can be 60, 65, 70, 75, 80, 85, 90, 95, 100, etc. Controlling the 101 sheet number of the precursor within the above range, the 101 crystal surface of the precursor corresponds to the direction of the positive electrode material layer, and a high 101 sheet number of the precursor indicates that the precursor has good crystallinity and higher internal structure order, which can form a positive electrode active material with fewer defects, and is beneficial to the structural stability of the positive electrode active material and better cycle performance.

[0052] It can be understood that the 101 sheet number of the precursor can be measured by XRD, and the 101 sheet number of the precursor = 101 crystal surface size of the precursor / crystal surface spacing. If the precursor is an oxide, the sheet number cannot be tested due to different phases, and the sheet number is the 101 sheet number of the corresponding hydroxide before forming the oxide.

[0053] According to some embodiments of the present application, the first lithium source comprises one or more of lithium hydroxide and lithium oxide. Compared with lithium carbonate and lithium acetate, lithium oxide and lithium hydroxide do not produce carbon dioxide gas during sintering, and the carbon dioxide gas will have a side reaction and affect the crystal structure.

[0054] According to some embodiments of the present application, the ratio of the amount of substance of Li element in the first lithium source n(Li1) to the sum of the amount of substance of Ni element, Co element, M1 element in the precursor [n(Ni)+n(Co)+n(M1)], n(Li1) / [n(Ni)+n(Co)+n(M1)] = 0.8-1.02, for example, n(Li1) / [n(Ni)+n(Co)+n(M1)] can be 0.8, 0.85, 0.9, 0.95, 1.0, 1.02, etc., according to other embodiments of the present application, n(Li1) / [n(Ni)+n(Co)+n(M1)] = 0.9-1.0. Controlling the ratio of lithium in the first sintering in the above range is beneficial to fully lithiate the process product 1, complete the internal chemical reaction, and uniformly distribute the dopant.

[0055] According to some embodiments of the present application, the ratio of the amount of substance of M2 element in the M2 source n(M2) to the sum of the amount of substance of Ni element, Co element, M1 element in the precursor [n(Ni)+n(Co)+n(M1)], n(M2) / [n(Ni)+n(Co)+n(M1)] = 0-0.05, for example, can be 0, 0.0001, 0.0005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, etc., according to other embodiments of the present application, n(M2) / [n(Ni)+n(Co)+n(M1)] = 0.0001-0.03; thereby, the doping amount of the doping element M2 is controlled in the above range, the above element ion radius is larger, which can support the layer structure, is beneficial to lithium ion deintercalation, and the M2-O bond formed by M2 and O has a strong bond strength, which can fix oxygen atoms, prevent oxygen release, and make the host layer structure more stable.

[0056] It can be understood that the M2 source can be one or more of carbonates, hydroxides, oxides, and acetates containing M2 elements. The precursor can be a self-produced or commercially available precursor, and the phase of the precursor is an oxide or a hydroxide.

[0057] According to some embodiments of the present application, the temperature of the first sintering is 600-1000°C, the time is 5-15h, and the sintering atmosphere is an oxygen-containing gas. As an example, the temperature of the first sintering can be 600°C, 700°C, 800°C, 900°C, 1000°C, etc., the time of the first sintering can be 5h, 7h, 9h, 10h, 12h, 14h, 15h, etc., and the sintering atmosphere can be an oxygen atmosphere or an air atmosphere, thereby, it is beneficial to fully lithiate the process product 1, complete the internal chemical reaction, and uniformly distribute the dopant.

[0058] S2: mixing the process product 1 with a second lithium source, performing a second sintering to obtain a positive electrode active material.

[0059] Thus, the twice addition of lithium source (the first lithium source and the second lithium source) is beneficial to the uniform distribution of lithium ions, and a material with better morphology and fewer internal defects is obtained. The first lithium source is added for sintering, so that the material is fully lithiated, the internal chemical reaction is complete, and the dopant is uniformly distributed. The second lithium source is added to fully monocrystallize the material, and the fluxing effect of lithium is used to make the material have a higher degree of monocrystallization and a more rounded morphology.

[0060] According to some embodiments of the present application, the second lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium oxide, and lithium acetate. According to other embodiments of the present application, the second lithium source includes one or more of lithium hydroxide and lithium oxide. Compared with lithium carbonate and lithium acetate, lithium oxide and lithium hydroxide do not produce carbon dioxide gas during sintering, and the carbon dioxide gas can cause side reactions and affect the crystal structure.

[0061] According to some embodiments of the present application, the ratio of the amount of substance of Li element in the second lithium source n(Li2) to the sum of the amounts of substance of Ni element, Co element, and M1 element in the precursor [n(Ni)+n(Co)+n(M1)] n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.01-0.3. As an example, n(Li2) / [n(Ni)+n(Co)+n(M1)] can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc. According to other embodiments of the present application, n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.05-0.2. Thus, the content of the second lithium source is controlled within the above range, the second lithium source can fully play a fluxing role to promote the monocrystallization of the positive electrode active material, so that the material has a higher degree of monocrystallization and a more rounded morphology.

[0062] According to some embodiments of the present application, the temperature of the second sintering is 700-1200°C, the time is 10-30h, and the sintering atmosphere is an oxygen-containing gas. As an example, the temperature of the first sintering can be 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc. The time of the first sintering can be 10h, 15h, 20h, 25h, 30h, etc. The sintering atmosphere can be an oxygen atmosphere or an air atmosphere. Thus, it is beneficial to promote the monocrystallization of the positive electrode active material, so that the material has a higher degree of monocrystallization and a more rounded morphology.

[0063] According to some embodiments of the present application, the second sintering further comprises: reducing the temperature of the second sintering by 20-100°C, and continuing sintering for 1-5h. For example, the second sintering temperature can be reduced by 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., and the sintering can be continued for 1h, 2h, 3h, 4h, 5h, etc., that is, the second sintering has a temperature reduction platform, which can further repair internal defects, make the internal stress smaller, and make the positive active material structure more stable.

[0064] According to some embodiments of the present application, after the second sintering, the method further comprises: S3: mixing the process product 2 obtained by the second sintering with a first coating agent to perform a third sintering to obtain a process product 3, wherein the first coating agent comprises a M3 source.

[0065] S4: mixing the process product 3 with a second coating agent to perform a fourth sintering to obtain a positive active material, wherein the second coating agent comprises a M3 source.

[0066] According to some embodiments of the present application, the third sintering is performed at a temperature of 500-800°C for 5-20h in an oxygen-containing atmosphere. For example, the third sintering can be performed at a temperature of 500°C, 600°C, 700°C, 800°C, etc., for 5h, 10h, 15h, 20h, etc., so as to make the first coating layer and the body tightly combined. And effectively improve the surface morphology of the positive active material, make the surface smooth, the coating layer and the substrate more stably combined, and further improve the cycle performance of the positive active material.

[0067] According to some embodiments of the present application, the ratio of the sum of the amounts of substance of B and W in the second coating agent n(B / W) to the sum of the amounts of substance of Ni, Co and M1 in the precursor [n(Ni)+n(Co)+n(M1)] is n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.02, for example, it can be 0.0001, 0.0005, 0.01, 0.015, 0.02, etc. According to some other embodiments of the present application, n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.01; thereby, the surface residual alkali of the positive active material can be effectively reduced, the lithium-nickel mixing and the metal elution can be reduced, the surface morphology of the positive active material can be effectively improved, the surface can be smooth, the coating layer and the substrate can be more stably combined, and the cycle performance of the positive active material can be further improved.

[0068] B\W can be added in a small amount to have fluxing effect, low-temperature resintering can improve surface coating uniformity, make the substrate and the coating layer more closely combined, not easy to fall off in the cycle process, inhibit the reaction of electrolyte and positive material. And B\W coating can activate the surface lithium, improve the material capacity.

[0069] According to some embodiments of the present application, the temperature of the fourth sintering is 200-500℃, and the time is 5-20h, and the calcination atmosphere is an oxygen-containing gas; for example, the temperature of the fourth sintering can be 200℃, 300℃, 400℃, 500℃, etc., and the time can be 5h, 10h, 15h, 20h, etc., thereby the electrochemical activity of the elements can be maximized, and the material capacity can be improved.

[0070] According to some embodiments of the present application, the ratio of the amount of substance of M3 element in the first coating agent and the second coating agent n(M3) to the sum of the amount of substance of Ni element, Co element and M1 element in the precursor [n(Ni)+n(Co)+n(M1)] is n(M3) / [n(Ni)+n(Co)+n(M1)]=0-0.05, for example, it can be 0, 0.0001, 0.0005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, etc., according to other embodiments of the present application, n(M3) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.03. Thus, the surface residual alkali of the positive active material can be effectively reduced, the lithium-nickel mixing and the metal dissolution can be reduced, and the M3 element can act as a consumption layer, preferentially react with the electrolyte to generate a stable CEI film, inhibit the further reaction of the electrolyte with the positive active material, and the cycle performance and rate performance of the battery can be further improved.

[0071] According to some embodiments of the present application, the M3 source can be one or more of hydroxide, oxide, carbonate, cobalt trioxide, hydroxyl oxide, and acetate containing M3 element.

[0072] In the third aspect of the present application, the present application provides a positive electrode sheet. According to embodiments of the present application, the positive electrode sheet comprises the positive active material of the first aspect of the present application or the positive active material obtained by the method of the second aspect of the present application.

[0073] According to embodiments of the present application, the positive electrode sheet comprises a positive current collector and a positive active material layer disposed on the positive current collector, and the positive active material layer comprises the positive active material described above, wherein the positive current collector can be a metal foil or a composite current collector (a metal material can be disposed on a polymer substrate to form a composite current collector), for example, the positive current collector can be an aluminum foil.

[0074] According to some embodiments of the present application, the positive electrode active material layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0075] According to some embodiments of the present application, the positive electrode active material layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0076] According to some embodiments of the present application, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and then drying, cold-pressing, and the like to obtain the positive electrode tab.

[0077] It should be noted that the features and advantages described above for the positive electrode active material and the method of preparing the same also apply to the positive electrode tab, which will not be described again here.

[0078] In a fourth aspect of the present application, a battery is provided. According to embodiments of the present application, the battery includes the above-mentioned positive electrode tab.

[0079] As an example, the battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator film between the positive electrode tab and the negative electrode tab. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode tab and the negative electrode tab. The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab. The separator film is arranged between the positive electrode tab and the negative electrode tab, mainly to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0080] According to embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. The negative electrode current collector can be a metal foil or a composite current collector (a metal material can be disposed on a polymer substrate to form a composite current collector), for example, the positive electrode current collector can be a copper foil.

[0081] According to some embodiments of the present application, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.

[0082] According to some embodiments of the present application, the negative active material layer can optionally further include a conductive agent. The conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0083] According to some embodiments of the present application, the negative active material layer can optionally further include other additives, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0084] According to some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, and the binder, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and then performing drying, cold pressing, etc., to obtain the negative electrode sheet.

[0085] According to some embodiments of the present application, the type of the separator film is not particularly limited, and any known porous structure separator film with good chemical stability and mechanical stability can be used. As an example, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0086] According to some embodiments of the present application, the type of the electrolyte is not particularly limited, and can be selected according to the needs. For example, the electrolyte can be in a gel state or a full solid state. According to some specific embodiments of the present application, the electrolyte uses an electrolyte solution, which includes a lithium salt and a solvent.

[0087] According to some specific embodiments of the present application, the lithium salt can include at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonate, or lithium bis(trifluoromethylsulfonyl)imide.

[0088] According to some specific embodiments of the present application, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, glycol dimethyl ether, methyl ethyl sulfone, or diethyl sulfone.

[0089] In some embodiments of the application, the electrolyte can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, etc.

[0090] It should be noted that the features and advantages described above in relation to the positive electrode sheet also apply to the battery, which will not be described again here.

[0091] In a fifth aspect, the present application provides a power consuming device. According to embodiments of the present application, the power consuming device includes the battery described above. According to embodiments of the present application, the power consuming device can include, but is not limited to, a mobile phone, a notebook computer, an electric vehicle, etc.

[0092] It should be noted that the features and advantages described above in relation to the battery also apply to the power consuming device, which will not be described again here.

[0093] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are intended to explain the present application, and should not be understood as limiting the present application. In the embodiments, specific techniques or conditions not described are performed according to techniques or conditions described in the literature in the art or according to product instructions. The reagents or instruments not described by the manufacturer are all conventional products that can be obtained on the market.

[0094] Example 1 S1, a precursor with a nickel-cobalt-manganese molar ratio of 95:3:2 and a number of sheets of 82 0.98 Co 0.01 Mn 0.01 (OH)2, lithium hydroxide (first lithium source), magnesium oxide (M2 source) are uniformly mixed in a high-speed mixer at a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li1):n(M2)=1:0.9:0.005 to obtain a mixture. Subsequently, the mixture is subjected to a first sintering treatment under an oxygen atmosphere, specifically including: 3h to 700℃, and 6h at 700℃, and then broken and sieved to obtain a positive electrode active material process product 1.

[0095] S2, the positive electrode active material process product 1, lithium hydroxide (second lithium source) are uniformly mixed in a high-speed mixer at a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li2)=1:0.16 to obtain a mixture. Subsequently, the mixture is subjected to a second sintering treatment under an oxygen atmosphere, specifically including: 8h to 820℃, and 10h at 820℃, and then cooled to 750℃, and 3h at 750℃, and then broken and sieved to obtain a positive electrode active material process product 2.

[0096] S3, the positive electrode active material process product 2, titanium oxide (M3 source) are uniformly mixed in a high-speed mixer according to the molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Ti)=1:0.03, to obtain a mixture. Then the mixture is subjected to a third sintering treatment under an oxygen atmosphere, specifically including: 8h at 720℃, and then naturally cooled to room temperature. After crushing and sieving, the positive electrode active material process product 3 is obtained.

[0097] S4, the positive electrode active material process product 3, boric acid (B source) are uniformly mixed in a high-speed mixer according to the molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(B)=1:0.0002, to obtain a mixture. Then the mixture is subjected to a fourth sintering treatment under an oxygen atmosphere, specifically including: 8h at 400℃, and then naturally cooled to room temperature. After crushing and sieving, the single-crystal positive electrode active material A is obtained.

[0098] The composition of Li 1.05 Ni 0.95 Co 0.03 Mn 0.02 Mg 0.005 Ti 0.03 B 0.0002 O2. Among them, the first coating layer includes Ti element, and the second coating layer includes B element.

[0099] Compared with Example 1, the ratio of the first lithium source to the second lithium source in Example 2 is slightly higher, and the temperature of the second sintering is adjusted, see the following table.

[0100] Compared with Example 1, the first lithium source in Example 3 is changed to lithium oxide, the number of 101 layers of the precursor is adjusted, and the temperature of the second sintering is adjusted accordingly, see the following table.

[0101] The difference between the remaining examples and Example 1 is shown in the following table. Among them, the precursor of Example 9 is replaced by Ni 0.98 Co 0.01 Al 0.01 (OH)2; Example 13 does not perform the third sintering and the fourth sintering of steps S3 and S4.

[0102] Compared with Example 1, the number of 101 layers of the precursor in Comparative Example 1 is reduced, the first lithium source is adjusted to lithium oxide, there is no B / W coating, and the temperature is adjusted accordingly, see the following table.

[0103] Compared with Example 1, the number of 101 layers of the precursor in Comparative Example 2 is reduced, the first lithium source is adjusted to lithium carbonate, there is no first coating layer (i.e. no third sintering) and B / W coating (fourth sintering is performed, and the B element is adjusted to Al element), and the temperature is adjusted accordingly, see the following table.

[0104] Compared with Example 1, the number of 101 layers of the precursor of Comparative Example 3 is reduced, the first lithium source is adjusted to lithium carbonate, the second sintering has no temperature reduction platform (the temperature reduction platform is to reduce the temperature to 750°C and keep for 3h), there is no first coating layer (i.e. no third sintering) and B / W coating (fourth sintering is performed, and the element B is adjusted to the element Al), and the temperature is adjusted accordingly, see the following table.

[0105] Table 1

[0106] Performance test 1. Morphology test: the positive electrode active material prepared in Example 1 is subjected to SEM scanning electron microscope test, and the following results are obtained Figure 1 , wherein Figure 1 It can be seen that the positive electrode active material prepared in Example 1 is a single crystal particle, and the average particle size d 50 is 1.6 μm.

[0107] 2. XRD test: the positive electrode active material prepared in the examples and comparative examples, and the positive electrode active material prepared in each example and comparative example is subjected to XRD test according to the following method, the equipment is SmartLab 9KW model, the test target is Cu and the analysis is carried out under Cu Kα radiation, the tube voltage of the equipment is set to 40 kV, the tube current is set to 200 mA, the test angle range of the sample is 10° to 80°, the scanning rate is 2° / min, and the scanning step is 0.02°.

[0108] The XRD patterns of the positive electrode active materials of Example 1 and Comparative Example 1 are shown in Figure 2 , and the FOM data can be obtained by data refinement.

[0109] From the XRD patterns of the positive electrode active materials obtained from each example and comparative example, the interplanar spacing d 003 80 , d 104 80 , d 003 0 , d 104 0 , wherein d 003 80 , d 104 80 is measured after the positive electrode active material is prepared into a button cell according to the following method, and after 80 cycles at 4.3V and 45°C, the positive electrode active material is obtained by disassembling the battery, and according to the formula FOM=|Δd 104 | / |Δd 003 |, Δd003 = (d 003 80 -d 003 0 ) / d 003 0 , Δd 104 = (d 104 80 -d 104 0 ) / d 104 0 , FOM is calculated.

[0110] The average particle size d 50 of the positive electrode active material is tested as follows: using a scanning electron microscope of model ERA-9200 of Japan ELIONIX Co., Ltd., at least 500 particles in a visual field are randomly taken, the particle sizes are respectively measured, and the average value of the particle sizes of the 500 particles is calculated, that is, the average particle size d 50 of the positive electrode active material.

[0111] The volume average particle size D 50 of the positive electrode active material is tested as follows: referring to the standard GB / T 19077-2016 “Particle Size Distribution-Laser Diffraction Method”, a laser particle size analyzer of model Mastersizer3000 of Malvern Instruments Co., Ltd. of the United Kingdom is used for measurement.

[0112] The mass proportion of residual lithium of the positive electrode active material is tested by a potential titrator.

[0113] The parameters of the positive electrode active materials of the examples and the comparative examples are shown in Table 2.

[0114] Table 2

[0115] The preparation process of the battery is as follows: Preparation of the positive electrode sheet: the positive electrode active material, acetylene black and polyvinylidene fluoride (PVDF) prepared above are mixed with N-methyl pyrrolidone (NMP) in a mass ratio of 95:3:2 to form a uniform slurry, the slurry is coated on an aluminum foil and dried at 120°C for 12 h, and then the slurry is punched and formed into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm using a pressure of 100 MPa, wherein the loading amount of the multi-element positive electrode material is 15-16 mg / cm 2 .

[0116] Battery assembly: In an argon-filled glove box with water content and oxygen content less than 5 ppm, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte were assembled into a 2025 button cell, and then the button cell was left to stand for 6 h. The negative electrode sheet was a metal lithium sheet with a diameter of 17 mm and a thickness of 1 mm; the separator was a polyethylene porous film (Celgard 2325) with a thickness of 25 μm; and the electrolyte was an equal mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / L LiPF6.

[0117] Electrochemical performance test: In the following examples and comparative examples, the electrochemical performance of the 2025 button cell was tested by using a Shenzhen Xinwei battery test system, and the charge-discharge current density of 0.1C was 200 mA / g.

[0118] The charge-discharge voltage range was controlled to be 3.0-4.3 V, and the button cell was charged and discharged at 0.1C at room temperature to evaluate the initial charge-discharge specific capacity and the initial charge-discharge efficiency of the multi-element positive electrode material.

[0119] Cycle performance test: The charge-discharge voltage range was controlled to be 3.0-4.3 V, and the button cell was charged and discharged at 0.1C at a constant temperature of 45℃ for 2 cycles, and then at 1C for 80 cycles to evaluate the high-temperature capacity retention rate of the multi-element positive electrode material.

[0120] Rate performance test: The charge-discharge voltage range was controlled to be 3.0-4.3 V, and the button cell was charged and discharged at 0.1C at room temperature for 2 cycles, and then at 0.2C, 0.33C, 0.5C and 1C for 1 cycle respectively, and the ratio of the initial discharge specific capacity at 0.1C to the discharge specific capacity at 1C was used to evaluate the rate performance of the multi-element positive electrode material. The initial discharge specific capacity at 0.1C was the discharge specific capacity of the first week cycle of the button cell, and the discharge specific capacity at 1C was the discharge specific capacity of the sixth week cycle of the button cell.

[0121] The test results of the batteries in the examples and comparative examples are shown in Table 3.

[0122] Table 3

[0123] As can be seen from Tables 2 and 3, in Examples 1-13 of the present application, the structure of the positive electrode active material is stable during the positive electrode active material cycle, and the lithium ion insertion and extraction effect is good, and the battery containing the positive electrode active material has excellent energy density, rate performance and cycle performance.

[0124] Compared with Example 1, the number of 101 layers of the precursor of Comparative Example 1 is reduced, the first lithium source is changed to lithium oxide, there is no B / W coating, and the temperature is adjusted accordingly; the total alkali (residual lithium mass fraction) of the obtained positive electrode active material is higher, |Δd 003 |, |Δd 104 | and FOM are larger, and the capacity, rate and cycle of the positive electrode active material are significantly reduced. It is shown that the change of the 003 crystal face of the positive electrode active material before and after cycling is within a certain range, but the shrinkage of the 104 crystal face is obvious, the structure distortion is obvious, the material cycle performance is poor, and the change of the 104 crystal face is larger than that of the 003 crystal face, indicating that the reversible shrinkage and expansion performance of the positive electrode active material is poor, and the rate performance is poor.

[0125] Compared with Example 1, the number of 101 layers of the precursor of Comparative Example 2 is reduced, the first lithium source is changed to lithium carbonate, there is no B / W coating, and the temperature is adjusted accordingly; the total alkali of the obtained positive electrode active material is high, |Δd 003 |, |Δd 104 | and FOM are larger, and the capacity, rate and cycle of the positive electrode active material are more significantly reduced. It is shown that the shrinkage of the 104 crystal face of the positive electrode active material is obvious, the structure distortion is obvious, the internal stress is large, the material cycle performance is poor, and the change of the 104 crystal face is larger than that of the 003, the lattice structure is not matched, the reversible shrinkage and expansion performance of the positive electrode active material is poor, and the rate performance is poor.

[0126] Compared with Example 1, the number of 101 layers of the precursor of Comparative Example 3 is reduced, the first lithium source is changed to lithium carbonate, there is no B / W coating, and the temperature is adjusted accordingly, and the particle size is the same; the total alkali of the obtained positive electrode active material is the highest, Δd 003 |, d 003 80 | and FOM are larger, and the capacity, rate and cycle of the positive electrode active material are more significantly reduced. It is shown that the expansion of the 003 crystal face of the positive electrode active material is obvious, the structure distortion is obvious, the internal stress is large, and the change of the 104 crystal face is smaller than that of the 003 crystal face, the lattice structure is not matched, the irreversible phase change of the positive electrode active material is obvious, and the rate performance is worse.

[0127] Compared with Example 1, the number of 101 layers of the precursor of Comparative Example 4 is reduced, the first lithium source is changed to lithium carbonate, and the total alkali of the obtained positive electrode active material is increased, FOM is larger, and the capacity, rate and cycle of the positive electrode active material are significantly reduced. It is shown that the change of the 003 crystal face of the positive electrode active material before and after cycling is within a certain range, but the shrinkage of the 104 crystal face is obvious, the structure distortion is obvious, the material cycle performance is poor, and the change of the 104 crystal face is larger than that of the 003 crystal face, indicating that the reversible shrinkage and expansion performance of the positive electrode active material is poor, and the rate performance is poor.

[0128] Compared to Example 1, Example 2 has a slightly higher proportion of the first lithium source than the second lithium source, the temperature is adjusted accordingly, the particle size is the same, and the total alkali is higher than in Example 1. 003 80 and Δd 003 The capacity, rate capability, and cycle life of the positive electrode active material are relatively large, indicating that the 003 crystal facet of the positive electrode active material undergoes slightly greater changes during cycling. However, the 104 crystal facet does not show significant structural degradation, resulting in a slight deterioration in material performance. In Example 3, the first lithium source was changed to lithium oxide, the temperature was adjusted accordingly, the particle size remained the same, and the total alkali was higher than in Example 2. 003 80 and Δd 003 Larger, and Δd 104 The larger value indicates that the capacity, rate, and cycle life are slightly reduced, but the FOM is within a reasonable range. This suggests that the 003 crystal plane widens during the cycle process, while the 104 crystal plane shrinks, resulting in a deterioration in the performance of the positive electrode active material. However, the fact that the FOM is within a reasonable range indicates that the unit cell of the positive electrode active material has undergone bond length and bond angle adjustments, resulting in a rebalancing of the structure and controllable internal stress.

[0129] Compared to Example 1, Example 4 shows a significantly higher proportion of the first lithium source compared to the second lithium source, a lower number of 101 layers in the precursor, a lower second sintering temperature, and a significantly higher total alkali content. 003 80 、|Δd 104 |、|Δd 003 |larger, and FOM increases,|Δd 104 |For|Δd 003 If the TM-O bond length and TM-O-TM bond angle are too large, the crystal structure will undergo partial irreversible degradation, the internal stress will be large, and the structure will easily transform from layered to spinel or rock salt phase, which will hinder the lithium ion migration channel, reduce the rate performance of the positive electrode active material, and also reduce the cycle life.

[0130] Similarly, compared to Example 1, |Δd| in Example 6 is different. 104 If the FOM value is too large, the FOM value increases. However, if the FOM is within the range of 0.2-0.5, the crystal structure of the positive electrode active material undergoes partial irreversible degradation during cycling. The structure easily transforms from layered to spinel or rock salt phase, hindering lithium-ion migration channels. This leads to a decrease in the rate performance and a reduction in cycle life of the positive electrode active material. Compared to Example 1, the positive electrode active material in Example 7 has a higher FOM value. 003 If the value is too small, the FOM value will increase. However, if the FOM is in the range of 0.2-0.5, the crystal structure of the positive electrode active material will undergo partial irreversible degradation during cycling. The structure is prone to transform from layered to spinel or rock salt phase, which hinders the lithium ion migration channel, reduces the rate performance of the positive electrode active material, and also reduces the cycle life.

[0131] Compared with Example 1, d 104 80 is too large, however, due to the change of preparation conditions, d 104 0 is also increased, |Ad 003 is reduced, so that the FOM is in the range of 0.2-0.5, and the rate performance and cycle performance of the positive active material are slightly reduced compared with Example 1.

[0132] Compared with Example 1, Example 11 does not contain the doping element M1, and Example 12 does not contain the elements M1 and Co, which causes the stability of the positive active material to be reduced, the polarization of the positive active material to be increased, and the cycle performance and rate performance of the battery to be also reduced.

[0133] Compared with Example 1, Example 13 does not perform the third and fourth sintering, and the surface does not have a coating layer, the total alkali content of the positive active material surface is increased, the side reaction between the positive active material and the electrolyte is increased, the lithium-nickel mixing and the metal dissolution are more, and the cycle performance and rate performance of the battery are also reduced.

[0134] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. The illustrative expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0135] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material comprises single crystal particles, and the positive electrode active material includes: Li a Ni x Co y M1 z M2 b M3 c O2 Wherein, 0.98≤a≤1.1, 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, 0≤b≤0.05, 0≤c≤0.05, M1 includes one or more of Mn and Al, and M2 and M3 each independently include one or more of Ba, Ra, Co, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, and Ti; The positive electrode active material has a structural figure of merit (FOM) of 0.2 ≤ FOM ≤ 0.5 after 80 cycles. Among them, FOM = |Δd 104 | / |Δd 003 |, Δd 003 = (d 003 80 - d 003 0 ) / d 003 0 , Δd 104 = (d 104 80 - d 104 0 ) / d 104 0 ; d 003 80 The interplanar spacing of the 003 crystal plane of the positive electrode active material after 80 cycles is given in Å. d 003 0 The interplanar spacing of the initial 003 crystal plane of the positive electrode active material is expressed in Å. d 104 80 The interplanar spacing of the 104 crystal plane of the positive electrode active material after 80 cycles is given in Å. d 104 0 Å represents the interplanar spacing of the initial 104 crystal plane of the positive electrode active material.

2. The positive electrode active material according to claim 1, characterized in that, The positive electrode active material satisfies at least one of the following conditions: 0.2 ≤ FOM ≤ 0.4; M2 includes one or more of Mg, La, Y, Ce, Er, Nb, W, Mo, and Zr; M3 includes one or more of Co, B, Ca, Si, Al, Mg, Ti, Sr, and W.

3. The positive electrode active material according to claim 1, characterized in that, The positive electrode active material satisfies at least one of the following conditions: 0.002≤|Δd 104 |≤0.01, preferably 0.002≤|Δd 104 |≤0.007; 0.005≤Δd 003 ≤0.018; 2.025Å≤d 104 80 ≤2.035Å； 4.760Å≤d 003 80 ≤4.800Å。 4. The positive electrode active material according to any one of claims 1-3, characterized in that, The positive electrode active material includes a body and a first coating layer and a second coating layer sequentially formed on at least a portion of the surface of the body. The first coating layer and the second coating layer each independently include one or more of the following elements: Co, B, Ca, Si, Al, Mg, Ti, Sr, and W.

5. The positive electrode active material according to any one of claims 1-3, characterized in that, The positive electrode active material satisfies at least one of the following conditions: The average particle size d of the positive electrode active material 50 The micrometer size is 0.8μm-5.0μm, preferably 1.0μm-2.5μm; The volume average particle size D of the positive electrode active material 50 The micrometer size is 1.5μm-8.0μm, preferably 2.0μm-5.0μm; The residual lithium mass percentage on the surface of the single crystal particles of the positive electrode active material is ≤2000ppm, preferably ≤1700ppm.

6. A method for preparing the positive electrode active material according to any one of claims 1-5, characterized in that, include: The precursor is mixed with a first lithium source and optionally an M2 source, and subjected to a first sintering to obtain process product 1. The precursor includes Ni element, optionally Co element, and optionally M1 element, and the number of 101 layers of the precursor is 60-100. The process product 1 is mixed with a second lithium source and subjected to a second sintering to obtain a positive electrode active material.

7. The method according to claim 6, characterized in that, The method satisfies at least one of the following conditions: The first lithium source includes one or more of lithium hydroxide and lithium oxide; The ratio of the amount of Li in the first lithium source to the sum of the amounts of Ni, Co, and M1 in the precursor is n(Li1) / [n(Ni)+n(Co)+n(M1)]=0.8-1.02, preferably n(Li1) / [n(Ni)+n(Co)+n(M1)]=0.9-1.0; The ratio of the amount of M2 element in the M2 source to the sum of the amounts of Ni, Co, and M1 elements in the precursor, n(M2) / [n(Ni)+n(Co)+n(M1)]=0-0.05, preferably n(M2) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.03; The first sintering temperature is 600℃-1000℃, the time is 5h-15h, and the sintering atmosphere is oxygen-containing gas.

8. The method according to claim 6, characterized in that, The method satisfies at least one of the following conditions: The second lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium oxide, and lithium acetate; The ratio of the amount of Li in the second lithium source to the sum of the amounts of Ni, Co, and M1 in the precursor is n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.01-0.3, preferably n(Li2) / [n(Ni)+n(Co)+n(M1)]=0.05-0.2; The second sintering temperature is 700℃-1200℃, the time is 10h-30h, and the sintering atmosphere is oxygen-containing gas; The second sintering process also includes: reducing the temperature of the second sintering process by 20°C to 100°C and continuing sintering for 1 hour to 5 hours.

9. The method according to any one of claims 6-8, characterized in that, After the second sintering, the method further includes: The process product 2 obtained by the second sintering is mixed with the first coating agent and then sintered in the third sintering process to obtain the process product 3, wherein the first coating agent includes source M3; The process product 3 is mixed with the second coating agent and subjected to a fourth sintering to obtain a positive electrode active material. The second coating agent includes source M3.

10. The method according to claim 9, characterized in that, The method satisfies at least one of the following conditions: The third sintering and calcination temperature is 500℃-800℃, the time is 5h-20h, and the calcination atmosphere is oxygen-containing gas; The ratio of the sum of the amounts of B and W elements in the second coating agent to the sum of the amounts of Ni, Co, and M1 elements in the precursor is n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.02, preferably n(B / W) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.01; The fourth sintering temperature is 200℃-500℃, the time is 5h-20h, and the calcination atmosphere is oxygen-containing gas; The ratio of the sum of the amounts of M3 elements in the first and second coating agents to the sum of the amounts of Ni, Co, and M1 elements in the precursor is n(M3) / [n(Ni)+n(Co)+n(M1)]=0-0.05, preferably n(M3) / [n(Ni)+n(Co)+n(M1)]=0.0001-0.

03.

11. A positive electrode plate, characterized in that, The positive electrode active material includes any one of claims 1-5 or any one of claims 6-10 prepared by the method thereof.

12. A battery, characterized in that, Includes the positive electrode sheet as described in claim 11.

13. An electrical appliance, characterized in that, Includes the battery as described in claim 12.

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