Different crystal direction double-element co-doped high-nickel single-crystal layered positive electrode material and preparation method thereof

Abstract

This invention provides a high-nickel single-crystal layered cathode material with dual elemental co-doping in different crystal orientations and its preparation method. The cathode material has the general formula I: Li w Ni x Co y Mn z Ti m Zr n O2. In cathode materials, by competitively layering Ti and Zr elements into high-nickel ternary cathode materials, uniform doping of Ti and Zr elements in the bulk phase of high-nickel cathode materials is achieved. This results in the synergistic effect of suppressing bulk phase transitions and surface reconstruction during cycling, thereby improving the cycling stability of high-nickel cathode materials.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, and particularly relates to a high-nickel single-crystal layered cathode material with dual element co-doping in different crystal orientations and its preparation method. Background Technology

[0002] Rechargeable lithium-ion batteries (LIBs) are increasingly widely used in consumer electronics, automotive industry and grid energy storage as a high-performance electrochemical energy storage device. Therefore, the development of cathode materials that can achieve excellent comprehensive performance such as high capacity, long cycle life, high power and high safety is of great significance to the development of the next generation of LIBs.

[0003] Among various cathode material systems, the high-nickel layered ternary cathode material Li0 stands out. w Ni x Co y Mn(Ti) 1-x-y O2 (x≥0.8) has a high reversible specific capacity (over 200mAh g). -1 High operating voltage (3.8V vs. Li / Li) + With its advantages such as [missing information], high-nickel ternary cathode materials are considered the most promising high-energy electrode materials. Commercially available high-nickel ternary cathode materials are typically composed of irregularly shaped nanoparticles, which can lead to internal structural collapse during cyclic charge-discharge cycles. Simultaneously, during the harmful H2-H3 phase transition, the randomly oriented single-crystal primary particle crystal faces exacerbate volume anisotropy, leading to the formation and fragmentation of cracks between particles. Therefore, suppressing the formation of microcracks and structural collapse is a necessary condition for the practical application of high-nickel ternary single-crystal small-particle cathode materials.

[0004] Elemental doping is an effective method to improve the stability of high-nickel cathode materials. Multi-element doping can stabilize the bulk crystal structure and surface chemical structure of high-nickel ternary cathode materials, thereby improving their cycle stability and thermal stability. Therefore, it is of great research significance to find a way to improve both the crystal structure and surface chemical structure of high-nickel ternary cathode materials through a simplified calcination process without reducing their specific capacity. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a high-nickel single-crystal layered cathode material with dual element co-doping in different crystal orientations and a method for preparing the same. The cathode material is co-doped with Ti and Zr, and the uniform bulk phase distribution of Ti and the surface enrichment of Zr synergistically improve the crystal structure and surface chemical structure of the material.

[0006] This invention provides a high-nickel single-crystal layered cathode material with dual-element co-doping in different crystal orientations, having the general formula I:

[0007] Li w Ni x Co y Mn z Ti m Zr n O2 type I;

[0008] 0.98≤w≤1.15, 0.8≤x<0.96, 0≤y<0.2, 0.001≤m≤0.05, 0.001≤n≤0.05 and x+y+z+m+n=1;

[0009] The high-nickel single-crystal layered cathode material is in space group R-3m, and under a full charge state of 4.3V, the range of cell parameter c / cell parameter a is 4.88-5.02.

[0010] In this invention, the peak intensity ratio of the XRD diffraction peak (003) / (104) of the high-nickel single-crystal layered cathode material is greater than 1.4.

[0011] In the high-nickel single-crystal layered ternary cathode material of this invention, Ti and Zr elements are competitively layered and doped into the high-nickel ternary cathode material. This achieves Ti doping in the bulk lattice of the high-nickel ternary cathode material, while Zr is enriched on the surface layer. This synergistic effect of suppressing bulk phase transitions and surface reconstruction during cycling improves the cycling stability of the high-nickel cathode material. The significant differences in the extranuclear electron configuration and ionic radius of Ti and Zr elements lead to different coordination space configurations, exhibiting different diffusion barriers during doping. The migration barrier of Ti in the bulk phase is higher than that of Zr, resulting in slower diffusion kinetics. During co-doping, Ti bonds with lattice oxygen to form TiO4 octahedra, and Ti… 4+ The ionic radius of Ti is close to that of transition metal cations in high-nickel cathode materials, and it has a smaller diffusion barrier, making it easier to dope into the transition metal layers in the bulk lattice of layered cathode materials. In summary, through this competitive doping, a layered co-doping effect of uniform bulk doping of Ti and Zr can be achieved in one step, which can synergistically stabilize the bulk chemistry and surface chemistry of layered cathode materials.

[0012] This invention provides a method for preparing high-nickel single-crystal layered cathode materials with different crystal orientations co-doped by two elements as described in the above-mentioned technical solution, comprising the following steps:

[0013] Li source, precursor Ni a Co b Mn 1-a-b (OH)2, Ti source and Zr source are mixed to obtain a mixture, wherein 0.8≤a<0.96, 0≤b<0.2;

[0014] The mixture was calcined at 550–900°C in an oxygen atmosphere to obtain the high-nickel single-crystal layered cathode material with different crystal orientations and dual element co-doped.

[0015] This invention uses a Li source and a Ni precursor a Co b Mn 1-a-b (OH)₂, a Ti source, and a Zr source are mixed to obtain a mixture. In this invention, the Li source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate; the Ti source is selected from one or more of titanium oxide, titanium carbonate, titanium hydroxide, and titanium acetate; and the Zr source is selected from one or more of zirconium oxide, zirconium carbonate, zirconium hydroxide, and zirconium acetate. It is understood that the Ti source and Zr source include compounds containing both Ti and Zr elements. Precursor Ni a Co b Mn 1-a-b (OH)₂, where 0.8 ≤ a < 0.96, 0 ≤ b < 0.2, it can be understood that the precursor can be Ni. 0.915 Co 0.035 Mn 0.05 (OH)2.

[0016] In this invention, the Li source contains Li and Ni a Co b Mn 1-a-b The molar ratio of (OH)2 precursor is (0.98~1.15):1.

[0017] In this invention, the Ti element in the Ti source accounts for a certain percentage of the Ni content. a Co b Mn 1-a-b The molar concentration of the (OH)₂ precursor is 0.2–0.6%, and the Zr element in the Zr source accounts for a significant portion of the Ni content. a Co b Mn 1-a-b The molar concentration of the (OH)2 precursor is 0.4%–1.0%.

[0018] In a specific embodiment, the

[0019] Ni 0.915 Co 0.035 Mn 0.05 (OH)₂:LiOH:ZrO₂:Ti₂O₅ = 1:1.04:0.005:0.005; or

[0020] Ni 0.915 Co 0.035 Mn 0.05 (OH)₂:LiOH:ZrO₂:Ti₂O₅ = 1:1.04:0.005:0.004; or

[0021] Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH:ZrO2:Ti2O5=1:1.04:0.005:0.003.

[0022] In this invention, the Li source and the precursor Ni a Co b Mn 1-a-b The mixing method for (OH)2, Ti source and Zr source is high-speed mechanical dry mixing; the airflow mixing speed during mixing is 1000-1500 rpm, and the time is 20-90 min.

[0023] This invention involves calcining the mixture under an oxygen atmosphere at 550–750°C to obtain a high-nickel single-crystal layered cathode material with dual-element co-doping in different crystal orientations. In this invention, the calcination at 550–750°C specifically includes:

[0024] The temperature is increased to 550-650℃ at a heating rate of 0.5-5℃ / min and calcined for 4-8 hours, then increased to 650-900℃ at a heating rate of 1-5℃ / min and calcined for 10-20 hours.

[0025] This invention involves cooling the calcined product to below 60°C, crushing, and sieving to obtain high-nickel single-crystal layered cathode materials with dual-element co-doping in different crystal orientations. The calcined product is then subjected to roller crushing followed by ultracentrifugal grinding. After crushing, it is sieved through a 200-mesh sieve.

[0026] This invention co-dops Ti and Zr elements into a single-crystal nickel-cobalt-manganese ternary cathode matrix. By utilizing the differences in coordination space configuration and migration barrier between Ti and Zr elements, different doping effects are achieved. This further realizes the substitution of Ti and Zr elements and the filling of lattice gaps, which improves the interionic interaction and bond energy of the high-nickel cathode material while suppressing surface reconstruction during the cycling process of the high-nickel ternary cathode material, thereby improving the cycling performance of the material.

[0027] The method employed in this invention is simple and low-cost, allowing for the preparation of high-nickel ternary cathode materials with dual-element competitive co-doping in a single sintering step. Currently, only high-nickel ternary cathode materials prepared by this invention achieve comparable high-temperature cycle retention rates through three sintering processes and are coated with nanoscale metal oxides. The high high-temperature cycle retention rate of the three-sintering material is due to the additional step of surface coating with nanoscale oxides. The high stability of this nanoscale oxide coating layer contributes to the improved high-temperature cycle retention rate. This invention, while achieving the same effect, eliminates two sintering steps compared to the three-sintering process, offering significant advantages in both process and cost. Attached Figure Description

[0028] Figure 1 This is a SEM image of the NCM-AB-1 sample prepared in Example 1 of the present invention at a magnification of 10,000.

[0029] Figure 2 This is a SEM image of the NCM sample prepared in Comparative Example 1 of the present invention at a magnification of 10,000.

[0030] Figure 3 A comparison of the X-ray diffraction patterns of the NCM-AB-1 sample prepared in Example 1 of the present invention and the NCM sample prepared in Comparative Example 1.

[0031] Figure 4 This is a comparison of the high-temperature cycling performance curves of the coin cell of the NCM-AB-1 sample prepared in Example 1 of the present invention and the NCM sample prepared in Comparative Example 1.

[0032] Figure 5 The results show the charge / discharge specific capacity and cycle stability test results of the coin cells prepared in the embodiments and comparative examples of this invention. Detailed Implementation

[0033] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a high-nickel single-crystal layered cathode material with dual element co-doping in different crystal orientations and its preparation method, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05 (OH)2, LiOH·H2O, ZrO2 and Ti2O5, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05(OH)2:LiOH·H2O:ZrO2:Ti2O5=1:1.04:0.005:0.003, the above four compounds were placed in an air jet mixer and mixed at a speed of 1200 rpm for 40 min. After thorough mixing, mixture A1 was obtained.

[0036] (2) The mixture A1 was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550℃ for 5.5h with a heating rate of 2.5℃ / min, and in the calcination stage at 815℃ for 14h with a heating rate of 2.5℃ / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B1.

[0037] (3) The high-nickel cathode material B1 was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain high-nickel single crystal layered cathode material NCM-AB-1 with different crystal orientations and dual element co-doping.

[0038] Example 2

[0039] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05 (OH)2, LiOH·H2O, ZrO2 and Ti2O5, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH·H2O:ZrO2:Ti2O5=1:1.04:0.005:0.004, the above four compounds were placed in an air jet mixer at a speed of 1200 rpm for 40 min, and after thorough mixing, mixture A2 was obtained;

[0040] (2) The mixture A2 was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550°C for 5.5 h with a heating rate of 2.5°C / min, and in the calcination stage at 815°C for 14 h with a heating rate of 2.5°C / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B2.

[0041] (3) The high-nickel cathode material B2 was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain high-nickel single crystal layered cathode material NCM-AB-2 with different crystal orientations and dual element co-doping.

[0042] Example 3

[0043] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05(OH)2, LiOH·H2O, ZrO2 and Ti2O5, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH:ZrO2:Ti2O5=1:1.04:0.005:0.005, the above four compounds were placed in an air jet mixer and mixed at a speed of 1200 rpm for 40 min. After thorough mixing, mixture A3 was obtained.

[0044] (2) The mixture A3 was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550°C for 5.5 h at a heating rate of 2.5°C / min, and in the 815°C calcination stage for 14 h at a heating rate of 2.5°C / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B3.

[0045] (3) The high-nickel cathode material B3 was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain high-nickel single crystal layered cathode material NCM-AB-3 with different crystal orientations and dual element co-doping.

[0046] Comparative Example 1

[0047] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05 (OH)2, LiOH·H2O, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH·H2O=1:1.04, the above two compounds were placed in an air jet mixer and mixed at a speed of 1200 rpm for 40 min. After thorough mixing, mixture A1' was obtained.

[0048] (2) The mixture A1' was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550°C for 5.5 h with a heating rate of 2.5°C / min, and in the 815°C calcination stage for 14 h with a heating rate of 2.5°C / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain the high-nickel cathode material B1'.

[0049] (3) The high-nickel cathode material B1' was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain undoped high-nickel ternary cathode material NCM.

[0050] Comparative Example 2

[0051] This comparative example provides a high-nickel ternary cathode material doped only with Ti, and its preparation method specifically includes the following steps:

[0052] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05 (OH)₂, LiOH·H₂O, Ti₂O₅, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH:Ti2O5=1:1.04:0.005, the above three compounds were placed in an air jet mixer and mixed at a speed of 1200 rpm for 40 min. After thorough mixing, mixture A2' was obtained.

[0053] (2) The mixture A2' was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550°C for 5.5 h with a heating rate of 2.5°C / min, and in the calcination stage at 815°C for 14 h with a heating rate of 2.5°C / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B2'.

[0054] (3) The high-nickel cathode material B2' was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain high-nickel single crystal layered cathode material NCM-A with different crystal orientations and dual element co-doping.

[0055] Comparative Example 3

[0056] This comparative example provides a high-nickel ternary cathode material doped only by Zr, and its preparation method specifically includes the following steps:

[0057] (1) Weigh the ternary precursor Ni 0.915 Co 0.035 Mn 0.05 (OH)₂, LiOH·H₂O, ZrO₂, calculated by molar ratio, Ni 0.915 Co 0.035 Mn 0.05 (OH)2:LiOH:ZrO2=1:1.04:0.01, the above four compounds were placed in an air jet mixer and mixed at a speed of 1200 rpm for 40 min. After thorough mixing, mixture A3' was obtained.

[0058] (2) The mixture A3' was transferred to an atmosphere furnace for two-stage high-temperature sintering, in which it was calcined at 550°C for 5.5 h with a heating rate of 2.5°C / min, and in the 815°C calcination stage for 14 h with a heating rate of 2.5°C / min. The oxygen content in the atmosphere was 99 vol%. Then it was cooled with the furnace to obtain the high-nickel cathode material B3'.

[0059] (3) The high-nickel cathode material B3' was crushed by roller crushing, ultracentrifugal grinding and crushing and sieved through 200 mesh in sequence and then packaged to obtain high-nickel single crystal layered cathode material NCM-B with different crystal orientations and dual element co-doping.

[0060] The NCM-AB-1 sample prepared in Example 1 and the NCM sample prepared in Comparative Example 1 were characterized. Figure 1 This is a SEM image of the NCM-AB-1 sample prepared in Example 1 of the present invention at a magnification of 10000x. Figure 2 This is a SEM image of the NCM sample prepared in Comparative Example 1 of the present invention at a magnification of 10,000.

[0061] from Figure 1 and Figure 2 As can be seen, all the prepared samples are composed of primary nanoparticles, with an average particle size of approximately 1.5 μm; furthermore, compared with... Figure 1 and Figure 2 It can be observed that, compared with the NCM sample prepared in Comparative Example 1, the primary particle surface of the NCM-AB-1 sample prepared in Example 1 after dual-element co-doping has a stronger particle texture and the primary particle surface of the NCM sample is smoother. This is mainly because Zr element is difficult to replace or occupy interstitial sites in the bulk lattice during the doping process.

[0062] Figure 3 This is the X-ray diffraction pattern of the NCM-AB-1 sample prepared in Example 1 of this invention. From... Figure 3 As can be seen from the data, the NCM-AB-1 samples all have a layered structure and an α-NaFeO2 rhombic structure with R-3m space group. After Ti and Zr co-doping, the NCM-AB-1 samples have high crystallinity and no extra impurity peaks; in addition, the peak intensity ratio of the (003) / (104) diffraction peaks of the NCM-AB-1 samples is greater than 1.4, which proves that the Li / Ni mixing is weak.

[0063] Figure 4This is a comparison of the cycle stability of coin cells using NCM-AB-1 and NCM samples from Example 1 and Comparative Example 1 as positive electrode sheets for lithium-ion batteries after 50 cycles at 0.3C current density and 45°C. The retention rates after 50 cycles at 0.3C current density and high temperature are 92.84% (NCM-AB-1) and 91.71% (NCM), respectively.

[0064] Figure 5 The battery underwent cycle testing at a voltage of 2.5–4.3V and a cycle life of 0.5CC / 0.5CD. The results are shown in Table 1.

[0065] Table 1. Cyclic test results of batteries prepared in Example 1 and Comparative Examples 1-3

[0066] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial discharge specific capacity (mAh / g) 225.2 224.5 224.8 225.7 Retention rate after 50 cycles 92.84％ 91.71％ 92.04％ 92.78％

[0067] Compared to the NCM sample without any doping, the NCM-AB-1 sample with competitive co-doping of Ti and Zr showed a significant improvement in cycle stability. This is mainly due to the synergistic improvement of the material's crystal structure and surface chemistry caused by the uniform bulk distribution of Ti and the surface enrichment of Zr.

[0068] The high-nickel single-crystal layered cathode material belongs to the R-3m space group, and the cell parameter a ranges from 1 to 3. The range of the unit cell parameter c is Competitive layered doping in different crystal orientations enables Ti to undergo uniform bulk doping while Zr enriches on the material surface during the dual-element co-doping process. Uniform bulk lattice doping of Ti effectively mitigates the sudden contraction of the lattice parameter in the c-direction, reducing the collapse of the lithium atom interlayer spacing at the end of charging. This reduces the anisotropy of the layered structure and lattice collapse in the c-direction, resulting in a cell parameter c / cell parameter a range of 4.88-5.02 at full charge (4.3V). The surface-enriched Zr layer helps form a stable surface / interface layer during cycling, suppressing surface reconstruction. In summary, competitive layered doping significantly improves the cycle stability of high-nickel ternary cathode materials through synergistic improvement of crystal structure and surface chemistry, effectively overcoming the problems of severe capacity and voltage decay during cycling inherent in existing cathode materials.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-nickel single-crystal layered cathode material with dual element co-doping of different crystal orientations, characterized in that, Includes the following steps: mixing a Li source, a precursor Ni a Co b Mn 1-a-b (OH)2, a Ti source and a Zr source, to obtain a mixture, wherein 0.8≤a<0.96, 0≤b<0.2; the Ti source is Ti2O5; The mixture was calcined at 550~900℃ in an oxygen atmosphere to obtain the high-nickel single-crystal layered cathode material with different crystal orientations and dual element co-doped. The roasting at 550~900℃ specifically includes: The temperature is increased to 550-650℃ at a heating rate of 0.5-5℃ / min and calcined for 4-8 hours, then increased to 650-900℃ at a heating rate of 1-5℃ / min and calcined for 10-20 hours. The high-nickel single-crystal layered cathode material with different crystal orientations and dual-element co-doping has the general formula I: Li w Ni x Co y Mn z Ti m Zr n O₂ of formula I; 0.98≤w≤1.15, 0.8≤x<0.96, 0≤y<0.2, 0.001≤m≤0.05, 0.001≤n≤0.05 and x+y+z+m+n=1; The high-nickel single-crystal layered cathode material has a space group of R-3m, and under a full charge state of 4.3V, the ratio of cell parameter c to cell parameter a ranges from 4.88 to 5.

02. The peak intensity ratio of the XRD diffraction peak (003) / (104) of the high-nickel single-crystal layered cathode material is greater than 1.

4.

2. The preparation method according to claim 1, characterized in that, The mixing is carried out at a stirring rate of 1000~1500 rpm; the mixing time is 20~90 min.

3. The preparation method according to claim 1, characterized in that, The Li source and the precursor Ni a Co b Mn 1-a-b The molar ratio of (OH)2 is (0.98~1.15):

1.

4. The preparation method according to claim 1, characterized in that, One of the following conditions must be met: The Li source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate; The Zr source is selected from one or more of zirconium oxide, zirconium carbonate, zirconium hydroxide, and zirconium acetate.

5. The preparation method according to claim 1, characterized in that, After roasting, the process also includes cooling the high-nickel single-crystal layered cathode material with different crystal orientations and dual element co-doping to below 60°C, crushing, and sieving.

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