Ti / W counter-gradient doped high-nickel ternary positive electrode material, preparation method, application, positive electrode material, positive electrode and lithium secondary battery

Abstract

The application relates to a positive electrode material, in particular to a Ti / W counter-gradient doped high-nickel ternary positive electrode material and a preparation method, application and positive electrode material and positive electrode and lithium secondary battery thereof, wherein the Ti / W counter-gradient doped high-nickel ternary positive electrode material is a layered structure oxide with a chemical formula of Li 1+ x Ni y Co z Mn a Ti β w γ O 2+δ ; the Ti / W counter-gradient doped high-nickel ternary positive electrode material is secondary particles formed by aggregation of primary particles; wherein the primary particles in the secondary particles have spinel phases on the surfaces, the primary particles on the surface layer of the secondary particles have rock salt phases; in the primary particles, the amount of Ti / W elements on the surface layer of the primary particles is greater than that in the primary particles, and a Li-Ti-W-O composite phase protective layer is formed on the surface; in the secondary particles, the Ti / W doping content has a concentration gradient distribution continuously decreasing from the inside of the secondary particles to the surface of the secondary particles. The material with a novel physical and chemical structure has excellent high-voltage cycle stability and rate performance.​

Description

Technical Field

[0001] This invention relates to the field of cathode materials, specifically to Ti / W reverse gradient doped high-nickel ternary cathode materials, their preparation methods, applications, and battery technology. Background Technology

[0002] With the rapid development of electric vehicles and high-end electronic products, the demand for high-energy-density and high-safety lithium-ion batteries is expanding. Currently, widely used low-nickel ternary and lithium iron phosphate cathode materials offer good safety, but their capacity does not meet the requirements of high-energy-density lithium-ion batteries. While lithium-rich manganese-based and disordered rock salt phase materials have high theoretical specific capacities, their capacity cannot be fully utilized, and they pose serious safety risks, hindering large-scale application. High-nickel ternary cathode materials have higher discharge specific capacity and voltage plateaus, and their safety and cycle stability are also superior to lithium-rich manganese-based and disordered rock salt phase materials. Increasing their nickel content and charge / discharge voltage can further improve their specific capacity, making them one of the ideal cathode materials for future high-energy-density batteries. However, high-voltage environments and further increases in nickel content can exacerbate the intrinsic instability of the layered structure, increase cation mixing, cause drastic volume changes, and lead to transition metal dissolution, severely hindering their large-scale application. Currently, one of the key technologies for performance optimization is phase structure strengthening, achieved through doping to reinforce or stabilize the layered phase. Traditional single-element doping has limited functionality, only building stable structures on the surface and failing to address the complex problems inside the material, thus necessitating alternative solutions.

[0003] Gradient doping is a solution that can construct stable phase structures at multiple scales. For example, patent document CN120261561A discloses a Ta-Ti dual-gradient doped high-nickel cathode material for lithium-ion batteries, a battery, and a preparation method. 5+ Ti is enriched in a gradient on the material surface. 4+ The gradient structure design formed by uniform doping in the bulk phase solves the problems of rapid cycle decay and significant capacity loss in traditional high-nickel materials due to structural instability and single-element doping.

[0004] Patent document CN121063595A discloses a fluorine-tungsten co-doped full-concentration gradient high-nickel cathode material and its preparation method and application, including a tungsten-doped gradient high-nickel cathode substrate and a rock salt phase fluorine-doped layer formed in situ on the surface of the tungsten-doped gradient high-nickel cathode substrate, achieving simultaneous improvement in discharge specific capacity and cycle life.

[0005] Patent document CN117263262A discloses a dual-dimensional gradient-doped cathode material, its preparation method, and its application. The cathode material consists of micron-sized secondary spherical particles formed by the aggregation of nanoscale primary particles. The doped metal element exhibits a gradient distribution within both the primary and secondary particles, with the doped metal element content gradually increasing from the core to the surface in both types of particles. The doped metal element is enriched on the surface of the secondary spherical particles. The dual-dimensional gradient-doped cathode material exhibits improved crystal structure and compressive strength, enhancing its overall electrochemical performance.

[0006] Patent document CN121292541A discloses a tungsten gradient-doped precursor, its preparation method, a cathode material, and a battery. The precursor core comprises uniformly doped tungsten, while the outer shell comprises gradient-doped tungsten, wherein the tungsten content in the outer shell gradually decreases from the core surface to the outer shell surface. Furthermore, the tungsten gradient-doped precursor comprises radially distributed primary particles. This preparation method improves the specific capacity and long-term cycle performance of the cathode material.

[0007] In summary, existing technologies have disclosed some gradient doping designs to enhance phase structures. However, current gradient doping mainly focuses on structural designs where the doping element has a high content on the surface and a low content in the interior. This distribution provides weak enhancement to the internal structure, which makes it impossible to solve the problems of stability of the internal layered structure and large volume change of high-nickel materials under high voltage conditions. This results in poor battery cycle stability, and a more suitable doping structure design is needed. Summary of the Invention

[0008] To address the problems existing in the prior art, the primary objective of this invention is to provide a Ti / W reverse gradient doped high-nickel ternary cathode material, which aims to provide a cathode material with a special physicochemical structure that also possesses excellent electrochemical performance, such as structural stability and high-voltage long-cycle performance.

[0009] The second objective of this invention is to provide a method for preparing and applying the aforementioned Ti / W reverse gradient doped high-nickel ternary cathode material.

[0010] A third objective of this invention is to provide a lithium secondary battery comprising the aforementioned Ti / W reverse gradient doped high-nickel ternary cathode material.

[0011] A Ti / W reverse gradient doped high-nickel ternary cathode material, with the chemical formula Li 1+x Ni y Co z Mn a Ti β W γ O 2+δ Layered oxide structure;

[0012] Ti / W reverse gradient doped high-nickel ternary cathode material is a secondary particle formed by the aggregation of primary particles; wherein, the surface of the primary particles inside the secondary particles has a spinel phase, and the primary particles on the surface of the secondary particles have a rock salt phase.

[0013] In the primary particles, the amount of Ti / W elements on the surface of the primary particles is greater than that inside the primary particles, and a Li-Ti-WO composite phase protective layer is formed on the surface;

[0014] In the secondary particles, the Ti / W doping content has a concentration gradient distribution that continuously decreases from the interior of the secondary particles to the surface of the secondary particles;

[0015] x is 0~0.05, y is 0.75~0.85, z is 0.08~0.13, α is 0.08~0.13, β is 0.008~0.012, γ is 0.008~0.012, δ is -0.05~0.05; and y+z+α=1;

[0016] The primary particles exhibit a needle-like structure, and are arranged radially.

[0017] This invention provides a novel material with an inner spinel surface rock salt phase and Ti / W dual doping, exhibiting a decreasing concentration distribution from the inside out. Research in this invention shows that the material with this novel physicochemical structure possesses excellent structural stability and resistance to volume expansion. Furthermore, it also exhibits excellent high-voltage cycling stability and rate performance.

[0018] Furthermore, the Ti / W reverse gradient doped high-nickel ternary cathode material of the present invention is a material in which Ti / W is used to double-dopate a high-nickel cobalt-manganese material, wherein the chemical formula of the high-nickel cobalt-manganese material can be Li 1+x Ni y Co z Mn a O2. Where y is 0.75~0.85, z is 0.08~0.13, and α is 0.08~0.13. Further, the molar ratio of Ti / W is 0.7~1.5:1; further, it can be 0.95~1.05:1. The ratio of the total molar amount of Ti / W to the total molar amount of nickel, cobalt, and manganese (γ+δ) / (x+y+z) can be 0.018~0.022.

[0019] This invention also provides a method for preparing a Ti / W reverse gradient doped high-nickel ternary cathode material, wherein stoichiometric amounts of metal raw materials containing Li, Ni, Co, Mn, Ti, and W are pre-calcined in an oxygen-containing atmosphere, followed by calcination at a higher temperature to obtain the Ti / W reverse gradient doped high-nickel ternary cathode material.

[0020] This invention demonstrates that by innovatively employing Ti / W as synergistic doping elements, and through combined control of the doping amount and concentration, a synergistic effect can be unexpectedly achieved. Based on the preferential diffusion principle of Ti and W elements in interstitial spaces and grain boundaries, high-concentration doping is achieved at high-density interstitial sites internally, while low-concentration doping occurs at low-density interstitial sites on the surface. This results in a novel material with an inner spinel and an outer rock salt phase, exhibiting high-concentration Ti / W doping on the primary particle surface with a decreasing concentration distribution from the inside out. This invention also demonstrates that the special material prepared by this method possesses excellent structural stability, can withstand high-pressure cycling requirements, and exhibits superior high-pressure cycling stability.

[0021] In this invention, the metal raw material is at least one of the oxides, hydroxides, carbonates, and organic acid salts of various metal elements.

[0022] Further, the lithium source, Ti source, W source and NCM precursor are mixed to obtain the metal raw material.

[0023] This invention explores how, with Ti / W synergistic dual doping, and further by specifically controlling the ratio and dosage of the two, synergy can be achieved, enabling the construction of materials with the aforementioned special structure, thereby significantly improving the stability of the materials under high pressure.

[0024] Furthermore, the molar ratio of Ti / W is 0.7~1.5:1; further, it can be 0.95~1.05:1. The ratio of the total molar amount of Ti / W to the total molar amount of nickel, cobalt and manganese (γ+δ) / (x+y+z) can be 0.018~0.022.

[0025] The NCM precursor is a nickel-cobalt-manganese hydroxide, with a chemical formula such as Ni y Co z Mn a (OH)2; y is 0.75~0.85, and can be further 0.8±0.05; z is 0.08~0.13, and can be further 0.1±0.01; α is 0.08~0.13, and can be further 0.1±0.01;

[0026] The mixing method can be grinding or ball milling in PET bottles. Studies have shown that ball milling in PET jars helps to further facilitate the synergistic doping of Ti / W, helps to further enhance the special physicochemical structure of the material, and thus significantly improves the stability of the material under high pressure.

[0027] In this invention, a PET bottle is used as a ball milling jar to ball mill and mix the above-mentioned metal raw materials. The ball milling time is 20-40 minutes and the rotation speed is 200-400 r / min.

[0028] In this invention, the pre-calcination temperature is 450~550℃; the heating rate is 2~10℃ / min;

[0029] Preferably, the pre-calcination time is 4 to 6 hours.

[0030] In this invention, the calcination temperature is 750~850℃; the heating rate is 2~10℃ / min;

[0031] Preferably, the calcination time is 9-11 hours.

[0032] The present invention also provides an application of the aforementioned Ti / W reverse gradient doped high-nickel ternary cathode material, using it as a cathode active material for the preparation of lithium secondary batteries.

[0033] The present invention also includes a cathode material, comprising a cathode active material, wherein the cathode active material comprises the Ti / W reverse gradient doped high-nickel ternary cathode material described in the present invention.

[0034] Preferably, the positive electrode material further includes a binder and / or a conductive agent.

[0035] The present invention also provides a positive electrode, comprising a current collector and a positive electrode material composited thereon, wherein the positive electrode material is the positive electrode material containing the Ti / W reverse gradient doped high-nickel ternary positive electrode material described in the present invention.

[0036] The present invention also provides a lithium secondary battery, wherein the positive electrode comprises the aforementioned Ti / W reverse gradient doped high-nickel ternary positive electrode material.

[0037] The lithium secondary battery of the present invention, except for the Ti / W reverse gradient doped high-nickel ternary cathode material described in the present invention, can have conventional components and structural relationships.

[0038] The lithium secondary battery of the present invention has a lithium metal negative electrode; or it may contain at least one of silicon material, carbon material, and silicon-carbon composite material.

[0039] The electrolyte is a LiPF6-containing electrolyte, which is prepared by mixing FEC and FEMC in a volume ratio of (0.1~0.3):(0.7~0.9).

[0040] Beneficial effects

[0041] This invention provides a material with a novel physical structure, and the material has excellent structural stability and excellent high-pressure cycle stability.

[0042] This invention demonstrates that by innovatively employing TI / W co-doping, based on the synergistic combination of doped elements and the joint control of their ratio and doping amount, it is possible to unexpectedly construct the aforementioned special physical and chemical structure while maintaining excellent mechanical stability and high-temperature cycling stability.

[0043] This invention provides a method for modifying high-nickel cathode materials for lithium-ion batteries using gradient doping-induced composite structures, specifically for LiNi... 0.8 Co0.1Mn 0.1 The material employs a differentiated structural and functional design, utilizing solid-state sintering. High-concentration doping of Ti and W within the secondary particles creates a spinel phase on the surface of the primary particles, suppressing volume changes during high-lithiation states and reducing stress concentration caused by volume changes during cycling. Low-concentration doping of Ti and W on the surface of the secondary particles creates a thin rock salt phase on the surface of the primary particles, suppressing surface side reactions and transition metal dissolution. The dopant elements accumulate on the surface of the primary particles, forming a Li-Ti-WO composite protective layer, further enhancing chemical stability. High-valence metal doping across the entire particle scale creates a more stable oxygen framework structure, further improving the overall layered structure stability of the material. This structure enables the high-nickel cathode material to exhibit high specific capacity (≥224 mAh / g@0.1C) and excellent cycling stability (capacity retention ≥80% after 500 cycles) in a high-cutoff-voltage (4.5V) operating environment, overcoming the problem of rapid capacity decay in existing high-nickel materials under high-voltage cycling. Attached Figure Description

[0044] Figure 1 The XRD patterns are those of Sample 1 and Comparative Examples 1-3.

[0045] Figure 2 The XRD patterns are those of Sample 1 and Comparative Examples 4-5.

[0046] Figure 3 The XRD patterns of the samples from Example 1 and Comparative Example 1 are shown.

[0047] Figure 4 The images are scanning electron microscope (SEM) images of the samples from Example 1 and Comparative Example 1.

[0048] Figure 5 The image shows the EDS spectrum of the sample from Example 1.

[0049] Figure 6 The images are FIB-SEM images of the samples from Example 1 and Comparative Example 1.

[0050] Figure 7 The image shows the cross-sectional EDS spectrum of sample 2 in Comparative Example 2.

[0051] Figure 8 The image shows the cross-sectional EDS spectrum of sample 3 in Comparative Example 3.

[0052] Figure 9 The image shows the cross-sectional EDS spectrum of the sample from Example 1.

[0053] Figure 10 The image shows the cross-sectional EDS spectrum of sample 6 in Comparative Example 6.

[0054] Figure 11 The FIB-TEM spectra of the samples from Example 1 and Comparative Example 1 are shown.

[0055] Figure 12 The charge-discharge diagrams are for the samples of Example 1 and Comparative Example 1.

[0056] Figure 13 This is a comparison chart of the long cycle life of the samples in Example 1 and Comparative Example 1.

[0057] Figure 14 This is a comparison chart of the long cycle life of samples from Example 1 and Comparative Examples 2-5.

[0058] Figure 15 The diagram shows the long cycle life at 4.6V and 4.7V for the samples of Example 1 and Comparative Example 1.

[0059] Figure 16 The images are post-cycle scanning electron microscope (SEM) images of the samples from Example 1 and Comparative Example 1.

[0060] Figure 17 The ICP results of the negative electrode Li sheet after cycling are shown for the samples of Example 1 and Comparative Example 1.

[0061] Figure 18 The graph shows the cycling performance of the samples from Examples 2, 3, and Comparative Example 6. Detailed Implementation

[0062] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0063] The following further describes specific embodiments and experimental verifications of the present invention.

[0064] Four cathode materials with different doping strategies were designed and synthesized using a high-temperature solid-state calcination method, as follows:

[0065] Example 1

[0066] According to the molar ratio of Li:Ni:Co:Mn:Ti:W = 1:0.8:0.1:0.1:0.01:0.01, LiOH·H2O and Ni 0.8 Co 0.1 Mn 0.1(OH)2 precursor, TiO2 titanium source, and WO3 tungsten source were added to a PET bottle, and then zirconium beads were added for solid-phase ball milling (ball-to-material ratio of 6:1) for mixing. The ball milling rate was 300 rpm and the ball milling time was 30 min.

[0067] The metal mixture was pre-calcined at 500℃ (labeled T1) for 5 hours in an oxygen atmosphere, followed by high-temperature calcination at 800℃ (labeled T2) for 10 hours to obtain the Ti / W co-doped material Li. 1.04 Ni 0.77 Co 0.12 Mn 0.05 Ti 0.008 W 0.01 O2 (Example 1; also labeled 1T1W-811; also called TW811).

[0068] Example 2

[0069] Compared with Example 1, the only difference is that the temperature T2 is 780℃ and the high-temperature calcination time is 6 hours. All other operations and parameters are the same as in Example 1 (the obtained product is labeled TW811-6h).

[0070] Example 3

[0071] Compared with Example 1, the only difference is that the precursor is mixed with LiOH·H2O, titanium source and tungsten source by dry grinding in an agate mortar for 30 minutes. All other operations and parameters are the same as in Example 1 (the product obtained is labeled TW811-Dry).

[0072] Comparative Example 1

[0073] Compared with Example 1, the only difference is that TiO2 titanium source and WO3 tungsten source were not added, and all other operations and parameters are the same as in Example 1 (the product obtained is labeled R811).

[0074] Comparative Example 2

[0075] Compared with Example 1, the only difference is that no TiO2 titanium source was added, and all other operations and parameters are the same as in Example 1 (the product obtained is labeled as 1W-811).

[0076] Comparative Example 3

[0077] Compared with Example 1, the only difference is that no WO3 tungsten source was added, and all other operations and parameters are the same as in Example 1 (the product obtained is labeled as 1Ti-811).

[0078] Comparative Example 4

[0079] Compared with Example 1, the only difference is that Na is used to replace Ti in Ti-W, and the doping amount of Na is the same as the Ti doping amount in Example 1. All other operations and parameters are the same as in Example 1 (the product obtained is labeled as 1Na1W-811).

[0080] Comparative Example 5

[0081] Compared with Example 1, the only difference is that Al is used to replace W in Ti-W, and the doping amount of Al is the same as that of W in Example 1. All other operations and parameters are the same as in Example 1 (the product obtained is labeled as 1Al1Ti-811).

[0082] Comparative Example 6

[0083] Compared with Example 1, the only difference is that the amount of TiO2 titanium source and WO3 tungsten source is increased, and the molar ratio of Li:Ni:Co:Mn:Ti:W is controlled to be 1:0.8:0.1:0.1:0.02:0.02. All other operations and parameters are the same as in Example 1 (the product obtained is labeled as 2T2W-811).

[0084] The crystal structure of the samples was characterized by X-ray diffraction (XRD) using a Rigaku Smartlab SE diffractometer (Japan). The radiation source was Cu Kα rays (λ = 0.15406 nm), and the operating conditions were a tube voltage of 45 kV and a tube current of 40 mA. The scan rate was 5° / min within the 2θ range of 10°–80°. The XRD patterns of the three samples are shown below. Figure 1 As shown, the results indicate that all samples exhibit a layered structure characteristic of the R-3m space group, and no heterophase formation was observed. Meanwhile, single doping negatively impacted the layered structure, but the 003 / 104 plane intensity ratio exhibited by the TiW dual-doped Example 1 was only slightly different from the plane intensity ratio of the undoped Comparative Example 1 sample. Figure 2 As shown, the intensity of the 003 / 104 surface of samples 4 and 5 is greater than that of samples 2 and 3, indicating that the synergistic effect of TiW dual doping can alleviate the negative impact of single doping on lithium-nickel mixing.

[0085] Detailed crystal structure information was obtained through refinement using GSAS II software, such as... Figure 3 As shown. The increased c-axis length of the unit cell in Example 1 indicates a wider interlayer spacing, which is advantageous for lithium-ion diffusion.

[0086] The morphology of Comparative Example 1 and Example 1 was characterized by scanning electron microscopy (TESCAN MIRA4 LMH) and equipped with an energy dispersive spectroscopy (EDS, Ultim Max 40). The relevant results are as follows: Figure 4 , Figure 5As shown, the synthesized material of Example 1 has a uniformly distributed spherical secondary particle structure and refined primary particles. EDS also shows that elements such as Ni, Co, Mn, Ti, W, and O are uniformly distributed on the surface of the secondary particles, indicating that the doping elements are well dispersed.

[0087] The cross-sectional morphologies of Comparative Examples 1, 2, 3, 6, and Example 1 were characterized by scanning electron microscopy (TESCAN MIRA4 LMH) and energy dispersive spectroscopy (EDS, Ultim Max 40) after sample preparation by focused ion beam (FIB). Figures 6-10 As shown. Example 1 has needle-shaped primary particles arranged radially, while Comparative Example 1 has blocky primary particle morphology. The doping element distribution in Example 1 shows a gradient distribution that gradually decreases from the center to the surface, while Comparative Examples 2 and 3, with less doping, show a uniform distribution, and Comparative Example 6, with more doping, shows a gradient distribution that gradually increases from the center to the surface.

[0088] The primary particle microstructures of Comparative Example 1 and Example 1 were characterized by transmission electron microscopy (FEI Titan G2 60-300), as shown below. Figure 11 As shown. In Comparative Example 1, a thicker rock salt phase was observed on the surface of the primary particles, while in Example 1, the primary particles on the surface of the secondary particles had only a very thin rock salt phase at the interface, while the primary particles inside the secondary particles had a spinel phase formed on their surface.

[0089] Combining the characterization results of XRD, SEM and TEM, we can conclude that this technology is based on phase structure enhancement and adopts an anti-gradient doping strategy, including: (1) Ti 4+ and W 6+ High-concentration doping inside the secondary particles causes the formation of a spinel phase on the surface of the primary particles, improving the stability of the crystal structure and alleviating the volume change problem during deep charge and discharge; (2) Ti 4+ and W 6+ Low-concentration doping of the secondary particles' surface layer forms a rock salt phase on the surface of the primary particles, which improves the stability of the crystal structure while reducing interfacial side reactions and the dissolution of transition metal ions.

[0090] To prepare the electrode slurry, the positive electrode active material, Super P, and polyvinylidene fluoride (PVDF, HSV900) were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 in an argon-atmospheric glove box and stirred until homogeneous. The resulting slurry was then uniformly coated onto an aluminum foil current collector, with an active material mass loading of 1.5–2.5 mg·cm³. -2 The coated electrodes were dried on a heating plate at 80°C for 12 hours in an Ar atmosphere, and then cut into circular electrode sheets with a diameter of 10 mm.

[0091] The battery assembly adopts a CR2025 coin cell structure, with the prepared positive electrode as the positive electrode sheet (Al foil as the current collector, PVDF as the binder, and Super P as the conductive agent; the mass ratio of active material, binder, and conductive agent is 8:1:1; and the electrode surface load is 1.5 mg / cm²). 2 The negative electrode is lithium metal, and the separator is a Celgard PP2320 membrane. Each battery is injected with 160 μL of electrolyte, which is 1M LiPF6 dissolved in a solvent prepared by mixing fluoroethylene carbonate (FEC) and methyl trifluoroethyl carbonate (FEMC) in a volume ratio of 2:8.

[0092] The electrochemical performance of the coin cells was tested on a multi-channel battery testing system, with a voltage range of 2.8–4.5 V (vs Li). + / Li), such as Figure 12 As shown. Example 1 had a first-cycle discharge specific capacity of 224.6 mAh / g at 0.1C, while Comparative Example 1 had 222.4 mAh / g. After 500 cycles at 1C with a cutoff voltage of 4.5V, the capacity retention was 80.3% (161.5 mAh / g), while Comparative Example 1 only retained 50.7% (103.2 mAh / g). Figure 13 As shown, this illustrates that the reverse gradient doping strategy has significant advantages in improving structural stability and cycle life. The cycle performance of Example 1 is compared with that of Comparative Examples 4 and 5, which have different element combinations, at a cutoff voltage of 4.5V. Figure 14 As shown, the embodiment exhibits the best overall performance in terms of specific capacity and capacity retention.

[0093] Under high-voltage charge-discharge conditions with cutoff voltages of 4.6V and 4.7V, the cycle performance of Example 1 and Comparative Example 1 is as follows: Figure 15 As shown. At a cutoff voltage of 4.6V, the first-cycle discharge specific capacity of Example 1 was 251.8 mAh / g, and the capacity retention rate after 300 cycles was 81.6% (172.4 mAh / g); at a cutoff voltage of 4.7V, the first-cycle discharge specific capacity of Example 1 was 262.6 mAh / g, and the capacity retention rate after 300 cycles was 80.1% (174.0 mAh / g), both of which were stronger than Comparative Example 1. This is attributed to the better stability of the layered structure of Example 1 at higher voltages, which enabled it to maintain a higher active lithium content.

[0094] The particle morphology of Comparative Example 1 and Example 1 after cycling was characterized by scanning electron microscopy (TESCAN MIRA4 LMH), as follows: Figure 16As shown. After 200 cycles, the secondary particles of the material in Comparative Example 1 developed obvious cracks, which expanded into fragmentation of the secondary particles, disintegrating into smaller particles. In contrast, the particles in Example 1 appeared as complete secondary spherical particles without obvious cracks, indicating higher crystal structure stability. Figure 16 (See the upper part of the attached diagram).

[0095] After cycling, the negative electrode Li sheets of Comparative Example 1 and Example 1 were characterized by ICP (Spectro Blue). Figure 17 As shown, the results indicate that the dissolution of transition metals in Example 1 was significantly reduced.

[0096] In summary, by constructing a Ti / W reverse gradient doping system, a high capacity retention of 80.3% (161.5 mAh / g) was achieved after 500 cycles at a cutoff voltage of 4.5V and a rate of 1C, significantly outperforming the undoped system. This invention, through the different functionalized structures of the bulk and surface layers resulting from gradient doping, achieves high structural stability of high-nickel ternary materials across the entire particle scale at high voltage. This effectively overcomes the technical bottleneck of the single-dimensional modification of traditional doping strategies, establishing a new material design paradigm with significant competitive advantages and possessing important technological value and application prospects.

Claims

1. A Ti / W reverse gradient doped high-nickel ternary cathode material, characterized in that, Its chemical formula is Li 1+ x Ni y Co z Mn a Ti β W γ O 2+δ Layered oxide structure; Ti / W reverse gradient doped high-nickel ternary cathode material is a secondary particle formed by the aggregation of primary particles; wherein, the surface of the primary particles inside the secondary particles has a spinel phase, and the primary particles on the surface of the secondary particles have a rock salt phase. In the primary particles, the amount of Ti / W elements on the surface of the primary particles is greater than that inside the primary particles, and a Li-Ti-WO composite phase protective layer is formed on the surface; In the secondary particles, the Ti / W doping content has a concentration gradient distribution that continuously decreases from the interior of the secondary particles to the surface of the secondary particles; x is 0~0.05, y is 0.75~0.85, z is 0.08~0.13, α is 0.08~0.13, β is 0.008~0.012, γ is 0.008~0.012, δ is -0.05~0.05; and y+z+α=1; The primary particles exhibit a needle-like structure, and are arranged radially.

2. A method for preparing a Ti / W reverse gradient doped high-nickel ternary cathode material, characterized in that, The Ti / W reverse gradient doped high-nickel ternary cathode material is prepared by pre-calcining stoichiometric amounts of metal raw materials containing Li, Ni, Co, Mn, Ti, and W in an oxygen-containing atmosphere, followed by calcination at a higher temperature.

3. The method for preparing Ti / W reverse gradient doped high-nickel ternary cathode material as described in claim 2, characterized in that, The metallic raw materials are at least one of the oxides, hydroxides, carbonates, and organic acid salts of various metallic elements; Preferably, a PET bottle is used as the ball milling jar to ball mill and mix the above-mentioned metal raw materials. The ball milling time is 20-40 minutes and the rotation speed is 200-400 r / min. Preferably, the molar ratio of Ti / W is 0.7~1.5:1; more preferably, it can be 0.95~1.05:

1. The ratio of the total molar amount of Ti / W to the total molar amount of nickel, cobalt, and manganese is 0.018~0.

022.

4. The method for preparing Ti / W reverse gradient doped high-nickel ternary cathode material as described in claim 2, characterized in that, The pre-calcination temperature is 450~550℃; Preferably, the heating rate is 2~10℃ / min; Preferably, the pre-calcination time is 4 to 6 hours.

5. The method for preparing Ti / W reverse gradient doped high-nickel ternary cathode material as described in claim 2, characterized in that, The calcination temperature is 750~850℃; Preferably, the heating rate is 2~10℃ / min; Preferably, the calcination time is 9-11 hours.

6. The application of the Ti / W reverse gradient doped high-nickel ternary cathode material according to claim 1 or the Ti / W reverse gradient doped high-nickel ternary cathode material prepared by the preparation method according to any one of claims 2 to 5, characterized in that, It is used as a positive electrode active material in the preparation of lithium secondary batteries.

7. A positive electrode material, comprising a positive electrode active material, characterized in that, The positive electrode active material comprises the Ti / W reverse gradient doped high nickel ternary positive electrode material according to claim 1 or the Ti / W reverse gradient doped high nickel ternary positive electrode material prepared by the preparation method according to any one of claims 2 to 5; Preferably, the positive electrode material further includes a binder and / or a conductive agent.

8. A positive electrode, comprising a current collector and a positive electrode material composited thereon, characterized in that, The cathode material is the cathode material as described in claim 7.

9. A lithium secondary battery, characterized in that, Its positive electrode comprises the Ti / W reverse gradient doped high nickel ternary positive electrode material as described in claim 1 or the Ti / W reverse gradient doped high nickel ternary positive electrode material prepared by the preparation method described in any one of claims 2 to 5; Preferably, the positive electrode is the positive electrode as described in claim 8.

10. The lithium secondary battery as described in claim 9, characterized in that, Its negative electrode is a lithium metal negative electrode; or it may be at least one of silicon material, carbon material, or silicon-carbon composite material.

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