A dual-element layered doped ternary layered cathode material, a preparation method thereof and application thereof

Abstract

The application provides a kind of double-element layered doped ternary layered positive electrode material and its preparation method.The ternary layered positive electrode material provided in the application realizes Mo, B double-element co-doping, the significant difference of Mo element and B element outer electron arrangement and ion radius promotes it to form different coordination space configuration, finally forms Mo body phase uniform doping and B surface enrichment layered doping;High oxidation state Mo 6+ Highly oriented, elongated grain microstructure and Li / TM cation ordered superlattice atomic arrangement can be produced, Li / Ni interlayer mixing energy is reduced, the enrichment of B on the surface and O form high-energy B-O bond, which can effectively stabilize the lattice oxygen framework and inhibit the precipitation of oxygen atoms. Through this double-element collaborative layered doping strategy, the application effectively overcomes the problems such as capacity attenuation caused by lattice collapse and surface reconstruction during the cycle process of existing high-nickel ternary positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material technology, and in particular to a ternary layered cathode material with dual-element synergistic layered doping, its preparation method and its application. Background Technology

[0002] Rechargeable lithium-ion batteries (LiBs), as high-performance electrochemical energy storage devices, have demonstrated broad application prospects and significant economic benefits in portable electronic devices, the automotive industry, the defense industry, and grid energy storage, becoming one of the optimal solutions for achieving efficient energy conversion and storage. Considering the dominant role of cathode materials in the overall weight and cost of LiBs, developing cathode materials that can achieve excellent comprehensive performance, including high capacity, long cycle life, high power, and high safety, is of great significance for the development of next-generation LiBs.

[0003] Among various cathode material systems, the high-nickel layered ternary cathode material LiNi stands out. x Co y Mn(Al) 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 high nickel content, it is considered one of the most promising high-energy battery materials. However, while increasing the nickel content in high-nickel ternary cathode materials significantly increases capacity, it also faces the challenge of gradually deteriorating cycle performance and thermal stability. Research indicates that the main reason for the worsening cycle and thermal stability of high-nickel ternary cathode materials lies in the volume shrinkage caused by the H2-H3 phase transition under deep delithiation conditions and the high activity of Ni. 4+ →Ni 3+ The reaction leads to the release of lattice oxygen. Currently, commercially available high-nickel ternary cathode materials are typically composed of secondary spherical nanoparticles. During cyclic charging and discharging, the material undergoes an H2-H3 phase transition accompanied by oxygen release, causing changes in the lattice constant / cell volume, generating stress, and accelerating the formation of microcracks and particle fragmentation. The electrolyte penetrates along the cracks into the secondary particles and reacts with Ni... 4+ Ions react to form a non-electrochemically active NiO-like rock salt phase, which obstructs lithium-ion transport channels and degrades performance. Therefore, suppressing microcrack formation and structural collapse is a key focus in the research and application of high-nickel ternary cathode materials.

[0004] Currently, elemental doping is one of the most effective methods to improve the stability of high-nickel ternary cathode materials. By doping the ternary material lattice with metal or non-metal ions, not only can electronic conductivity and particle conductivity be improved, but the bulk crystal structure and surface chemical structure of the high-nickel ternary cathode material can also be stabilized, thereby improving the cycle stability and thermal stability of the high-nickel cathode material. In addition, the doping sites and depths of different dopants, as well as the chemical interactions between dopants and between dopants and the matrix material, all have a significant impact on the overall performance of the cathode material. Currently, elemental doping technology mainly focuses on stabilizing the bulk structure of the cathode. However, this excessive elemental co-doping, while stabilizing the bulk lattice structure, also occupies lithium intercalation sites in the bulk lattice, thus sacrificing the high specific capacity advantage of high-nickel cathode materials. Furthermore, existing modification technologies, in addition to improving crystal structure stability through elemental doping, also employ surface coating technology to stabilize the surface chemical structure of the material. This typically requires three sintering processes, increasing process complexity and production costs. 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 by using a simplified calcination process while ensuring the high specific capacity of the materials. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a ternary layered cathode material with dual-element layered doping and its preparation method. The preparation method provided in this application can achieve layered doping of Mo and B elements by only one sintering.

[0006] In view of this, this application provides a ternary layered cathode material with dual-element layered doping, comprising:

[0007] LiNi x Co y Mn z Mo a B b O2 (Ⅰ);

[0008] Among them, 0.3≤x<0.96, 0<y<0.3, 0<z<0.3, 0.001≤a≤0.05, 0.001≤b≤0.05 and x+y+z+a+b=1;

[0009] Mo is distributed in the bulk lattice of the ternary layered cathode material, while B is enriched on the surface of the ternary layered cathode material.

[0010] Preferably, the peak intensity ratio of the diffraction peak (003) / (104) of the high-nickel ternary cathode material is greater than 1.6.

[0011] This application also provides a method for preparing the aforementioned ternary layered cathode material, comprising the following steps:

[0012] A) Using Li source and precursor Ni m Co n Mn 1-m-n (OH)2, Mo source and B source are mixed to obtain a mixed precursor, wherein 0.3≤m≤0.96 and 0≤n<0.3;

[0013] B) The mixture precursor is sintered and cooled to obtain a ternary layered cathode material.

[0014] Preferably, the sintering includes segmented sintering at 450–600°C and 650–900°C, performed sequentially.

[0015] Preferably, the Li source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium acetate, and the Li source and the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)₂ is (1.01–1.10):1; the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)₂ to Mo in the Mo source is 1:(0.005~0.02); the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)2 to B element in the B source is 1:(0.01~0.05).

[0016] Preferably, the mixing is carried out in a high-speed mixer with a rotation speed of 200-1000 rpm / min and a mixing time of 20-60 min.

[0017] Preferably, the segmented sintering is carried out in an oxygen-containing atmosphere, wherein the oxygen content of the oxygen-containing atmosphere is ≥98 vol%.

[0018] Preferably, the heating rate for sintering at 450–600°C is 1–5°C / min, and the time is 2–10 h; the heating rate for sintering at 650–900°C is 1–5°C / min, and the time is 10–20 h.

[0019] Preferably, after cooling, the process further includes sequential roller crushing, air jet milling, and sieving, wherein the sieving mesh size is 200 to 400 mesh.

[0020] This application also provides a lithium-ion battery, including a positive electrode and a negative electrode, wherein the material of the positive electrode includes the ternary layered positive electrode material with dual-element layered doping or the ternary layered positive electrode material with dual-element layered doping prepared by the preparation method.

[0021] This application provides a ternary layered cathode material with dual-element layered doping, wherein Mo is uniformly doped in the bulk lattice of the high-nickel ternary cathode material, and B is enriched on the surface of the high-nickel ternary cathode material, thereby achieving the synergistic effect of suppressing the bulk phase transition and surface reconstruction of the high-nickel ternary cathode material during cycling, and improving the cycling stability of the high-nickel ternary cathode material.

[0022] Meanwhile, this application also provides a method for preparing a ternary layered cathode material with dual-element layered doping, wherein during the sintering process, Mo... 6+ With B 3+ They exhibit different diffusion barriers. The migration barrier of B in the bulk phase is higher than that of Mo, therefore B diffusion kinetics are slow, and it tends to accumulate on the surface; while Mo atoms doped into the bulk phase bond with lattice oxygen to form MoO6 octahedra, and Mo... 6+ ionic radius The radius of transition metal cations in high-nickel cathode materials It is close to and has a smaller diffusion barrier, so it is easier to dop into the transition metal layer in the bulk lattice of the layered cathode material, thereby achieving two-element layered doping. Attached Figure Description

[0023] Figure 1 The image is a SEM image of the NCM-AB sample prepared in Example 1 of this invention at a magnification of 10,000.

[0024] Figure 2 The image shown is a SEM image of the NCM sample prepared in Comparative Example 1 of this invention at a magnification of 10,000.

[0025] Figure 3 The image shows a SEM cross-section of the NCM-AB sample prepared in Example 1 of this invention at a magnification of 10,000.

[0026] Figure 4 This is a SEM cross-sectional image of the NCM sample prepared in Comparative Example 1 of this invention at a magnification of 10,000.

[0027] Figure 5 Comparison of X-ray diffraction patterns of the NCM-AB sample prepared in Example 1 of the present invention and the NCM sample prepared in Comparative Example 1;

[0028] Figure 6 Comparison of X-ray diffraction patterns of the NCM-AB sample prepared in Example 1 of the present invention and the NCM sample prepared in Comparative Example 1;

[0029] Figure 7 A comparison of the high-temperature cycling performance curves of the coin cell of the NCM-AB sample prepared in Example 1 of this invention and the NCM sample prepared in Comparative Example 1.

[0030] Figure 8 A comparison of the high-temperature cycling performance curves of the coin cells of the NCM-AB sample prepared in Example 1 and the NCM-C sample prepared in Example 4 of this invention. Detailed Implementation

[0031] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0032] In view of the problem that the calcination process, crystal structure, and surface chemical structure cannot be simultaneously achieved in the prior art, this application provides a ternary layered cathode material with dual-element layered doping and its preparation method. The preparation method provided in this application can prepare the ternary layered cathode material in only one sintering process, and achieves layered co-doping of bulk Mo and surface enrichment of B, synergistically stabilizing the bulk phase and surface structure of the layered cathode material. Specifically, the embodiments of this invention disclose a ternary layered cathode material with dual-element layered doping, including:

[0033] LiNi x Co y Mn z Mo a B b O2 (Ⅰ);

[0034] Among them, 0.3≤x<0.96, 0<y<0.3, 0<z<0.3, 0.001≤a≤0.05, 0.001≤b≤0.05 and x+y+z+a+b=1;

[0035] Mo is distributed in the bulk lattice of the ternary layered cathode material, while B is enriched on the surface of the ternary layered cathode material.

[0036] In this application, the peak intensity ratio of the diffraction peak (003) / (104) of the high-nickel ternary cathode material is greater than 1.6. More specifically, the peak intensity ratio of the diffraction peak (003) / (104) of the high-nickel ternary cathode material is 1.71. The co-doping of Mo and B has a certain inhibitory effect on the mixing of Li / Ni.

[0037] This application also provides a method for preparing a ternary layered cathode material, comprising the following steps:

[0038] A) Using Li source and precursor Ni m Co n Mn 1-m-n (OH)2, Mo source and B source are mixed to obtain a mixed precursor, wherein 0.3≤m≤0.96, 0<n<0.3;

[0039] B) The mixture precursor is sintered in stages at 450–600°C and 650–900°C, and after cooling, a ternary layered cathode material is obtained.

[0040] In this application, the Li source (calculated as Li) and Ni m Co n Mn 1-m-n The molar ratio of the (OH)₂ precursor is (1.01–1.10):1. Specifically, the Li source (calculated as Li) and Ni m Co n Mn 1-m-n The molar ratio of the (OH)₂ precursor is (1.01–1.05):1, and the Li source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium acetate; the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)2 to Mo in the Mo source is 1:(0.005~0.02). Specifically, the precursor Ni... m Co n Mn 1-m-n The molar ratio of (OH)₂ to Mo in the Mo source is 1:(0.01~0.015); the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)2 to B element in the B source is 1:(0.01~0.05). Specifically, the precursor Ni... m Co n Mn 1-m-n The molar ratio of (OH)₂ to the B element in the B source is 1:(0.02~0.04). The Mo source and B source include, but are not limited to, compounds containing both Mo and B (such as oxides, carbonates, hydroxides, acetates, etc.), and mixtures composed of compounds containing at least one of Mo and B. The mixtures composed of compounds containing at least one of Mo and B include mixtures composed of compounds containing Mo and compounds containing B, or mixtures composed of compounds containing either Mo or B and compounds containing both Mo and B, or mixtures composed of compounds containing both Mo and B.

[0041] In this application, a high-speed mixer is used as the mixing equipment, and the speed of the high-speed mixer is 200-1000 rpm / min, and the time is 20-60 min; specifically, the speed of the high-speed mixer is 400-800 rpm / min, and the time is 30-50 min.

[0042] According to the present invention, the obtained mixture is then sintered and cooled to obtain a ternary layered cathode material. The sintering temperature is 450–730°C; to further improve the cycle stability of the cathode material, the sintering in this application preferably employs segmented sintering at 450–600°C and 650–900°C. During the sintering process at 450–600°C, Ni first… m Co n Mn 1-m-n Both (OH)₂ and LiOH undergo thermal decomposition reactions to produce Ni. x Co y Mn 1-x-y O and Li₂O; secondly, Ni m Co n Mn 1-m-n O and Li₂O first undergo a combination reaction in the presence of oxygen to form LiNi. m Co n Mn z O2 and B2O3 are in a molten state within this temperature range, which is beneficial for the formation of LiNi. m Co n Mn z O2 achieves surface coating and initially diffuses from the surface into the particle interior. Ion diffusion rates in the solid phase are relatively slow; therefore, during sintering at 650–900℃, Li… + B 3+ And Mo 6+ Ions at high temperature towards LiNi m Co n Mn z The diffusion rate of O2 inside the body is accelerated, but due to Mo 6+ It has more than B 3+ A smaller diffusion barrier, therefore Mo 6+ It is easier to dope into the bulk lattice of the cathode material, thereby achieving layered doping of Mo and B elements.

[0043] The sintering is carried out in an oxygen-containing atmosphere with an oxygen content ≥98 vol%. The sintering time for the 450–600℃ sintering section is 2–10 h with a heating rate of 1–5℃ / min; the sintering time for the 650–900℃ sintering section is 10–20 h with a heating rate of 1–5℃ / min; specifically, the sintering time for the 450–600℃ sintering section is 4–8 h with a heating rate of 2.5–4.5℃ / min; the sintering time for the 650–900℃ sintering section is 13–18 h with a heating rate of 2.5–4.5℃ / min.

[0044] The cooling process includes sequential roller crushing, air jet milling, and sieving, with the sieving mesh size being 200-400 mesh.

[0045] Compared with existing technologies, the present invention has the following advantages:

[0046] ① This invention co-dops Mo and B elements in a nickel-cobalt-manganese layered ternary cathode matrix. By utilizing the differences in coordination space configuration and migration barrier between Mo and B elements, synergistic layered doping is achieved. This realizes the substitution of Mo element and the filling of lattice gaps, as well as the enrichment of B element on the matrix surface. This 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. It takes into account the dual effects of doping and surface coating, and synergistically improves the crystal structure stability and surface chemical stability of the high-nickel ternary cathode material, thereby improving the cycling performance of the material.

[0047] ② The synergistic layered doping strategy of the present invention can achieve the substitution of Mo and the filling of lattice gaps without reducing the proportion of Ni in the high-nickel ternary cathode material, i.e. without reducing its discharge specific capacity. This avoids the lattice distortion and the obstruction of bulk diffusion caused by the doping of B element with a small ionic radius into the interstitial position. At the same time, since the price of Ni element is much lower than that of Co element, the present invention has a high proportion of Ni element and a low proportion of Co element, which takes into account the advantage of reducing raw material costs.

[0048] ③ The method of this invention is simple and low-cost, and a high-nickel ternary cathode material with dual-element synergistic layered doping can be prepared in one sintering step. Currently, the only high-nickel ternary cathode material that can match the high-temperature cycle retention rate of the material prepared in this application is the high-nickel ternary cathode material that has undergone three sinterings and is coated with nano-scale metal oxides. The reason why the high-temperature cycle retention rate of the three-sintering material is that it adds an extra step of coating the surface with nano-oxides. The high stability of the nano-oxide coating layer is what improves its high-temperature cycle retention rate. Under the premise of achieving the same effect, this application has two fewer sintering steps than the three-sintering process, which has a significant advantage in terms of process and cost.

[0049] To further understand the present invention, the following detailed description of the dual-element layered doped ternary layered cathode material and its preparation method is provided in conjunction with the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0050] Unless otherwise specified, the test reagents used in the following examples are all conventional biochemical reagents; and the experimental methods described are all conventional methods unless otherwise specified.

[0051] Example 1

[0052] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11(OH)2, LiOH·H2O, MoO3 and B2O3, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH:MoO3:B2O3=1:1.04:0.01:0.01. The above four compounds were placed in a high-speed mixer at a speed of 450 rpm / min and a mixing time of 40 min. After thorough mixing, mixture A was obtained.

[0053] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein the temperature was raised to 560°C at a rate of 2.5°C / min and calcined for 5.5h, and then raised to 730°C at a rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. The furnace was then cooled to obtain high-nickel cathode material B.

[0054] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain dual-element synergistic layered doped LiNi. 0.83 Co 0.05 Mn 0.09 Mo 0.01 B 0.02 O2 ternary cathode material NCM-AB1.

[0055] Example 2

[0056] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)2, LiOH·H2O, Mo2O3 and B2O3, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH:MoO3:B2O3=1:1.04:0.005:0.005. The above four compounds were placed in a high-speed mixer at a speed of 450 rpm / min and a mixing time of 40 min. After thorough mixing, mixture A was obtained.

[0057] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein it was heated to 560°C at a heating rate of 2.5°C / min and calcined for 5.5h, and then heated to 730°C at a heating rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B.

[0058] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain dual-element synergistic layered doped LiNi. 0.83 Co 0.06 Mn 0.095 Mo 0.005 B 0.01 O2 ternary cathode material NCM-AB2.

[0059] Example 3

[0060] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)2, LiOH·H2O, Mo2O3 and B2O3, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH:MoO3:B2O3=1:1.04:0.015:0.015. The above four compounds were placed in a high-speed mixer at a speed of 450 rpm / min and a mixing time of 40 min. After thorough mixing, mixture A was obtained.

[0061] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein it was heated to 560°C at a heating rate of 2.5°C / min and calcined for 5.5h, and then heated to 730°C at a heating rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B.

[0062] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain dual-element synergistic layered doped LiNi. 0.83 Co 0.04 Mn 0.085 Mo 0.015 B 0.03 O2 ternary cathode material NCM-AB3.

[0063] Example 4

[0064] This embodiment provides a segmentless sintering, Mo and B dual-element doped high-nickel ternary cathode material, the preparation method of which specifically includes the following steps:

[0065] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)2, LiOH·H2O, MoO3 and B2O3, calculated by molar ratio, Ni 0.83 Co 0.06 Mn0.11 (OH)2:LiOH:MoO3:B2O3=1:1.04:0.01:0.01. The above four compounds were placed in a high-speed mixer at a speed of 450 rpm / min and a mixing time of 40 min. After thorough mixing, mixture A was obtained.

[0066] (2) The mixture A was transferred to an atmosphere furnace for a high-temperature sintering process. The temperature was increased to 730°C at a rate of 2.5°C / min and calcined for 16.5 hours. The oxygen content in the atmosphere furnace was 99 vol%. The mixture was then cooled in the furnace to obtain the high-nickel cathode material B.

[0067] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain Mo and B dual-element co-doped LiNi. 0.83 Co 0.05 Mn 0.09 Mo 0.01 B 0.02 O2 ternary cathode material NCM-C.

[0068] Comparative Example 1

[0069] This comparative example provides a high-nickel ternary cathode material without elemental doping, and its preparation method specifically includes the following steps:

[0070] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)2, LiOH·H2O, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH = 1:1.04. The two compounds were mixed in a high-speed mixer at a speed of 450 rpm / min for 40 min. After thorough mixing, mixture A was obtained.

[0071] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein it was heated to 560°C at a heating rate of 2.5°C / min and calcined for 5.5h, and then heated to 730°C at a heating rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B.

[0072] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain undoped LiNi. 0.83 Co 0.06 Mn 0.11 O2 high-nickel ternary cathode material NCM.

[0073] Comparative Example 2

[0074] This comparative example provides a high-nickel ternary cathode material doped only with Mo, and its preparation method specifically includes the following steps:

[0075] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)₂, LiOH·H₂O, Mo₂O₃, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH:MoO3 = 1:1.04:0.01. The above three compounds were placed in a high-speed mixer and mixed at a speed of 450 rpm / min for 40 min. After thorough mixing, mixture A was obtained.

[0076] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein it was heated to 560°C at a heating rate of 2.5°C / min and calcined for 5.5h, and then heated to 730°C at a heating rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. Then it was cooled with the furnace to obtain high-nickel ternary cathode material B.

[0077] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain Mo-doped LiNi. 0.83 Co 0.06 Mn 0.10 Mo 0.01 O2 high-nickel ternary cathode material NCM-A.

[0078] Comparative Example 3

[0079] This comparative example provides a high-nickel ternary cathode material doped only with boron (B) element, and its preparation method specifically includes the following steps:

[0080] (1) Weigh the ternary precursor Ni 0.83 Co 0.06 Mn 0.11 (OH)₂, LiOH·H₂O, B₂O₃, calculated by molar ratio, Ni 0.83 Co 0.06 Mn 0.11 (OH)2:LiOH:B2O3 = 1:1.04:0.01. The above four compounds were placed in a high-speed mixer and mixed at a speed of 450 rpm / min for 40 min. After thorough mixing, mixture A was obtained.

[0081] (2) The mixture A was transferred to an atmosphere furnace for two-stage high-temperature sintering, wherein it was heated to 560°C at a heating rate of 2.5°C / min and calcined for 5.5h, and then heated to 730°C at a heating rate of 2.5°C / min and calcined for 16.5h. The oxygen content in the atmosphere furnace was 99 vol%. Then it was cooled with the furnace to obtain high-nickel cathode material B.

[0082] (3) The high-nickel cathode material B was sequentially subjected to roller crushing, air jet milling, and 325-mesh sieve before being packaged to obtain B-doped LiNi. 0.83 Co 0.06 Mn 0.10 B 0.01 O2 high-nickel ternary cathode material NCM-B.

[0083] The NCM-AB 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 sample prepared in Example 1 of this invention at a magnification of 10000x. Figure 2 This is a SEM image of the NCM sample prepared for Comparative Example 1 of this invention at a magnification of 10,000.

[0084] from Figure 1 and Figure 2 As can be seen, all prepared samples consist of secondary microspheres assembled from primary nanoparticles, with an average size of approximately 4 μm; furthermore, compared to... Figure 1 and Figure 2 It can be observed that, compared with the NCM sample prepared in Comparative Example 1, the NCM-AB sample prepared in Example 1 after dual-element synergistic layered doping has a stronger grainy texture on the primary particle surface, while the primary particle surface of the NCM sample is smoother. This is mainly because the B element is difficult to replace or occupy interstitial sites in the bulk lattice during the co-doping process and thus becomes enriched on the surface.

[0085] Figure 3 and Figure 4 The images show particle SEM cross-sections of Example 1 (NCM-AB sample) and Comparative Example 1 (NCM sample), respectively. The comparison shows that the secondary particles of the sample synergistically doped with Mo and B are more compact, which helps to eliminate the harmful strain caused by sudden lattice contraction and thus improves the cycle stability of the cathode material.

[0086] Figure 5 and Figure 6 This is the X-ray diffraction pattern of the NCM-AB sample prepared in Example 1 of this invention. From... Figure 5As can be seen, the NCM-AB samples all have a layered structure with an α-NaFeO2 rhombic structure in the R-3m space group. After Mo and B co-doping, the NCM-AB samples have high crystallinity and no extra impurity peaks. In addition, the peak intensity ratio of the diffraction peak (003) / (104) of the NCM-AB samples is 1.71, which is much greater than 1.2, indicating that the Li / Ni mixing is weak. It is also greater than the peak intensity ratio of (003) / (104) of the NCM samples (which is 1.56), indicating that the co-doping of Mo and B has a certain inhibitory effect on the Li / Ni mixing. Local observation of the XRD patterns revealed that the (018) and (110) diffraction peaks of the NCM-AB sample prepared in Example 1 of this invention exhibited similar splitting degrees to the diffraction peaks of the NCM sample prepared in Comparative Example 1. This indicates that the sample, after Mo and B co-doping, did not alter its original crystal structure due to elemental doping and maintained a good layered structure, which is beneficial for lithium ion insertion / extraction during charging and discharging. Furthermore, analysis of the (003) and (104) diffraction peaks revealed that ( Figure 6 The FWHM of the (003) and (104) diffraction peaks of the NCM-AB sample are larger than those of the NCM sample, indicating that the grain size of the NCM-AB sample co-doped with Mo and B is smaller than that of the undoped NCM sample. This is beneficial to eliminating the harmful strain caused by the sudden contraction of the lattice, thereby improving the cycling performance of the material.

[0087] Figure 7 This is a comparison of the cycle stability of coin cells using NCM-AB and NCM samples from Example 1 and Comparative Example 1 as positive electrode sheets for lithium-ion batteries after 50 cycles at a current density of 0.5C and a temperature of 45°C. The retention rates after 50 cycles at 0.5C are 93.56% (NCM-AB) and 90.69% (NCM), respectively. Compared to the undoped NCM sample, the NCM-AB sample, which undergoes Mo and B synergistic layered doping, shows a significant improvement in cycle stability. This is mainly attributed to the synergistic improvement in the material's crystal structure and surface chemistry resulting from the uniform bulk distribution of Mo and the surface enrichment of B.

[0088] Figure 8 This is a comparison of the cycle stability of coin cells using NCM-AB and NCM-C samples from Examples 1 and 4 as positive electrode sheets for lithium-ion batteries after 50 cycles at a current density of 0.5C and a temperature of 45°C. The retention rates after 50 cycles at 0.5C are 93.56% (NCM-AB) and 91.89% (NCM-C), respectively. Compared to the NCM-C sample without segmented sintering, the NCM-AB sample with segmented sintering exhibits superior cycle stability. This is mainly attributed to the effect of B2O3 on the generated LiNi during the low-temperature calcination reaction. x Coy Mn z O2 achieves a relatively uniform surface coating and initially diffuses from the surface into the particle interior, which is beneficial to improving the surface chemical structure of the cathode material and enhancing cycle stability.

[0089] In summary, by simultaneously doping high-nickel ternary cathode materials with Mo and B, a synergistic layered doping effect is achieved, where Mo is uniformly doped in the bulk structure while B is enriched on the material surface. The bulk lattice-doped Mo acts as an "ion pillar," effectively mitigating the sudden contraction of lattice parameters in the c-direction and reducing the collapse of lithium atom interlayer spacing during charging, thereby reducing the anisotropy of the layered structure and lattice collapse in the c-direction. The surface-enriched B forms high-energy BO bonds with lattice oxygen, suppressing oxygen atom precipitation, stabilizing the lattice oxygen framework, and contributing to the formation of a stable surface / interface layer during cycling, thus suppressing surface reconstruction during cycling. In conclusion, synergistic layered doping significantly improves the cycle stability of high-nickel ternary cathode materials through synergistic improvements in crystal structure and surface chemistry, effectively overcoming the problems of severe capacity and voltage decay during cycling inherent in existing cathode materials.

[0090] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a ternary layered cathode material with dual-element layered doping, comprising the following steps: A) Using Li source and precursor Ni m Co n Mn 1-m-n (OH)2, Mo source and B source are mixed to obtain a mixed precursor, wherein 0.3≤m<0.96, 0<n<0.3; B) The mixture precursor is sintered and cooled to obtain a ternary layered cathode material. The sintering includes segmented sintering at 450-600℃ and 650-900℃ sequentially. The heating rate for the sintering at 450-600℃ is 1-5℃ / min, and the time is 2-10h. The heating rate for the sintering at 650-900℃ is 1-5℃ / min, and the time is 10-20h. The segmented sintering is carried out in an oxygen-containing atmosphere with an oxygen content ≥98% vol%. The dual-element layered doped ternary layered cathode material includes: LiNi x Co y Mr z Mo a B b O2 (Ⅰ); Among them, 0.3≤x<0.96, 0<y<0.3, 0<z<0.3, 0.001≤a≤0.05, 0.001≤b≤0.05 and x+y+z+a+b=1; Mo is distributed in the bulk lattice of the ternary layered cathode material, while B is enriched on the surface of the ternary layered cathode material.

2. The preparation method according to claim 1, characterized in that, The peak intensity ratio of the diffraction peaks (003) / (104) of the ternary layered cathode material is greater than 1.

6.

3. The preparation method according to claim 1, characterized in that, The Li source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium acetate, and the Li source and the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)₂ is (1.01~1.10):1; the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)₂ to Mo in the Mo source is 1:(0.005~0.02); the precursor Ni m Co n Mn 1-m-n The molar ratio of (OH)2 to the B element in the B source is 1:(0.01~0.05).

4. The preparation method according to claim 1, characterized in that, The mixing is carried out in a high-speed mixer with a rotation speed of 200~1000 rpm / min and a mixing time of 20~60 min.

5. The preparation method according to claim 1, characterized in that, After cooling, the process includes sequential roller crushing, air jet milling, and sieving, with the sieve mesh size being 200-400 mesh.

6. A lithium-ion battery, comprising a positive electrode and a negative electrode, characterized in that, The cathode material includes the ternary layered cathode material with dual-element layered doping prepared by the preparation method according to any one of claims 1 to 5.

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