A Ta-Ti dual-gradient doped lithium-ion battery high-nickel positive electrode material, battery and preparation method

Abstract

The present invention discloses a Ta-Ti dual gradient doped lithium ion battery high nickel cathode material, a battery and a preparation method thereof, wherein the cathode material is designed by surface-bulk phase partitioning functionalization, Ta 5+ A Li-Ta-O protective layer is formed on the surface of the material to inhibit electrolyte corrosion. 4+ Uniform doping in the bulk phase forms strong Ti-O bonds with the oxygen framework, synergistically stabilizing the lattice structure and reducing Li / Ni mixing, expanding the lattice constant, and optimizing lithium-ion diffusion channels. This cathode material combines high specific capacity, long cycle life, and excellent rate performance, resolving the technical bottleneck of traditional high-nickel materials, which suffer from structural instability and single-element doping, leading to rapid cycling decay and significant capacity loss.

Description

Technical Field

[0001] The present invention relates to battery technology, in particular to a Ta-Ti dual gradient doped lithium ion battery high nickel positive electrode material, a battery and a preparation method. Background Art

[0002] With the rapid popularization of high energy density lithium-ion batteries in electric vehicles and energy storage, high nickel cathode materials (LiMn 0.1 Ni 0.8 Co 0.1 O2) has become the focus of the industry due to its low cost and high specific capacity. However, in the existing technology, the intrinsic instability of the layered structure of high nickel materials (Ni≥80%) (such as drastic H2-H3 phase transition, lattice oxygen escape), high cation mixing degree (Ni 2+ With Li + Problems such as similar radii leading to Li layer occupancy and insufficient cycle life (capacity decay ≥25% after 200 cycles) seriously hinder their large-scale application. One of the key technologies for optimizing the performance of high-nickel materials is the coordinated regulation of multi-scale structural defect repair and interface stability. This is due to the bottlenecks of traditional single-element doping (such as Al, Mg, and Ta), such as the single modification dimension (which only inhibits phase transitions or reduces mixing) and the lack of synergy between doping elements (such as excessive doping blocking lithium channels). Breakthrough solutions are urgently needed to address these bottlenecks.

[0003] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0004] The main purpose of the present invention is to overcome the defects existing in the above-mentioned background technology and provide a Ta-Ti dual gradient doped lithium ion battery high nickel positive electrode material, a battery and a preparation method.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A Ta-Ti dual gradient doped high nickel positive electrode material for lithium ion batteries, wherein the positive electrode material is LiMn 0.1 Ta 0.0 1Ti 0.01 Ni 0.78 Co 0.1 O2, of which Ta 5+ Gradient enrichment forms a Li-Ta-O protective layer on the surface of the material, and Ti 4+ It is uniformly doped in the bulk phase and forms strong Ti-O bonds with the oxygen framework.

[0007] A method for preparing a Ta-Ti dual-gradient doped high-nickel positive electrode material for lithium-ion batteries comprises the following steps:

[0008] S1, mixing Li2CO3 and high nickel ternary precursor material uniformly according to the stoichiometric ratio;

[0009] S2, add Ta2O5 and TiO2 to the mixture of step S1, control the molar ratio of Li:Mn:Ta:Ti:Ni:Co to be 1:0.1:0.01:0.01:0.78:0.1, and mix well;

[0010] S3, in an oxygen atmosphere, the mixed material is pre-calcined, and then the temperature is raised and calcined to obtain a Ta-Ti dual gradient doped high nickel cathode material LiMn 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2.

[0011] Furthermore, in step S1, the high nickel ternary precursor material is Mn 0.1 Ni 0.8 Co 0.1 (OH)2.

[0012] Furthermore, in step S3, the pre-calcination temperature is 450°C to 550°C, and the calcination time is 3 hours to 5 hours; the heating calcination temperature is 750°C to 800°C, and the calcination time is 10 hours to 12 hours.

[0013] A lithium ion battery comprises a positive electrode using the positive electrode material, a negative electrode and an electrolyte.

[0014] Furthermore, the lithium-ion battery includes a metallic lithium negative electrode and an electrolyte containing LiPF6, and the electrolyte is prepared by mixing EMC, DEC and FEC in a volume ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2).

[0015] The present invention has the following beneficial effects:

[0016] The present invention provides a method for modifying a high nickel cathode material with Ta-Ti dual gradient doping, and designs functionalization of the surface-body partitioning to modify LiMn 0.1 Ni 0.8 Co 0.1 O2 material is site selectively doped, and the gradient sintering method is used to utilize Ta 5+ The surface passivation effect of Ti (forming a Li-Ta-O protective layer to inhibit electrolyte corrosion) 4+ The bulk lattice anchoring effect (stabilizing the oxygen framework through strong Ti-O bonds and inhibiting Ni 2+migration), achieving a synergistic improvement in high specific capacity (≥226mAh / g@0.2C) and ultra-long cycle stability (capacity retention rate ≥811% after 250 cycles), overcoming the core defects of high-nickel materials in existing technologies, such as fast cycle attenuation and functional conflicts of doped elements.

[0017] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the material synthesis technology roadmap of the present invention.

[0019] Figure 2 The XRD pattern of the sample of the embodiment of the present invention is shown in FIG.

[0020] Figure 3 This is the XRD refined pattern of the sample in the embodiment of the present invention.

[0021] Figure 4 This is the scanning electron microscopy image of NCM.

[0022] Figure 5 This is a scanning electron microscope image of TaTi-NCM according to an embodiment of the present invention.

[0023] Figure 6 This is the EDS spectrum of TaTi-NCM according to the embodiment of the present invention.

[0024] Figure 7 This is the TEM spectrum of TaTi-NCM in the embodiment of the present invention.

[0025] Figure 8 This is the charge and discharge diagram of the sample of the embodiment of the present invention.

[0026] Figure 9 This is a long cycle life graph of the sample of the embodiment of the present invention.

[0027] Figure 10 This is a magnification diagram of the sample of the embodiment of the present invention.

[0028] Figure 11 This is the impedance diagram of the sample of the embodiment of the present invention.

[0029] Figure 12 This is a graph of the lithium ion diffusion coefficient of the sample according to the embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0031] The embodiment of the present invention provides a Ta-Ti double gradient doped lithium ion battery high nickel positive electrode material, the positive electrode material is LiMn 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2, through surface-bulk partitioning functionalization design, where Ta 5+ Gradient enrichment forms a Li-Ta-O protective layer on the surface of the material, and Ti 4+ It is uniformly doped in the bulk phase and forms strong Ti-O bonds with the oxygen framework, thereby synergistically inhibiting electrolyte corrosion, stabilizing the lattice structure and reducing Li / Ni mixing.

[0032] The present invention also provides a method for preparing a Ta-Ti dual-gradient doped high-nickel cathode material for lithium-ion batteries, comprising the following steps:

[0033] Step S1, mixing Li2CO3 and high nickel ternary precursor material uniformly according to the stoichiometric ratio;

[0034] Step S2, adding Ta2O5 and TiO2 to the mixture of step S1, controlling the molar ratio of Li:Mn:Ta:Ti:Ni:Co to be 1:0.1:0.01:0.01:0.78:0.1, and mixing uniformly;

[0035] Step S3: pre-calcining the mixture in an oxygen atmosphere and then heating and calcining to obtain a Ta-Ti dual gradient doped high nickel cathode material LiMn 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2.

[0036] In some embodiments, in step S1, the high nickel ternary precursor material is Mn 0.1 Ni 0.8 Co 0.1 (OH)2.

[0037] In some embodiments, in step S3, under an oxygen atmosphere, the mixed material is pre-calcined at 450°C to 550°C for 3 to 5 hours, and then heated to 750°C to 800°C and calcined for 10 to 12 hours to obtain a Ta-Ti dual gradient doped high nickel positive electrode material.

[0038] An embodiment of the present invention further provides a lithium-ion battery, comprising a positive electrode using the positive electrode material, a negative electrode, and an electrolyte.

[0039] In some embodiments, the lithium-ion battery includes a metallic lithium negative electrode and an electrolyte containing LiPF6, and the electrolyte is prepared by mixing EMC, DEC and FEC in a volume ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2).

[0040] The present invention adopts Ta 5+ Gradient enrichment forms a Li-Ta-O protective layer on the surface of the material to inhibit electrolyte corrosion. 4+ The uniform doping into the bulk phase stabilizes the lattice oxygen framework through strong Ti-O bonds and reduces Li / Ni mixing, and the high nickel positive electrode material LiMn is achieved by utilizing the synergistic effect of Ta-Ti double gradient doping. 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2 has high specific capacity, long cycle life and excellent rate performance, and optimizes lithium ion diffusion channels by expanding the interlayer spacing, solving the technical bottlenecks of traditional high-nickel materials such as fast cycle attenuation and significant capacity loss due to structural instability and single function of doping elements.

[0041] The following further describes specific embodiments of the present invention and experimental verification.

[0042] Three cathode materials with different doping strategies were designed and synthesized using a high-temperature solid-phase calcination method, as follows:

[0043] Sample 1 (control group): Li2CO3 and Mn 0.1 Ni 0.8 Co 0.1 (OH)2 is used as raw material, mixed and calcined in appropriate proportions to synthesize the benchmark material LiMn 0.1 Ni 0.8 Co 0.1 O2 (abbreviated as NCM).

[0044] Sample 2 (Ta single doping group): Based on sample 1, Ta2O5 was introduced as a tantalum source, and mixed and calcined in the ratio of Li:Mn:Ni:Co:Ta=1:0.1:0.78:0.1:0.02 to obtain the doping material LiMn 0.1 Ta 0.02 Ni 0.78 Co 0.1 O2 (abbreviated as Ta-NCM).

[0045] Sample 3 (Ta-Ti dual-doping group): TiO2 was further introduced as a titanium source based on Sample 2, and the mixture was calcined in the ratio of Li:Mn:Ta:Ti:Ni:Co=1:0.1:0.01:0.01:0.78:0.1 to obtain the final material LiMn of the present invention. 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2 (abbreviated as TaTi-NCM).

[0046] All three samples were prepared by a two-step calcination method: the uniformly mixed raw materials were first pre-calcined at 500 ° C in an oxygen atmosphere for 4 hours, and then calcined at 780 ° C for 11 hours to obtain the target product. Figure 1 As shown:

[0047] The crystal structures of the samples were characterized by X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer with a Cu Kα radiation source (λ = 0.15406 nm) at a tube voltage of 45 kV and a tube current of 40 mA. The measurements were performed over a 2θ range of 10°-90° at a scan rate of 10° / min. The XRD patterns of the three samples are shown in Figure 2. Figure 2 As shown in the figure, the results show that all samples exhibit layered structural characteristics of the R-3m space group, and no heterogeneous phase formation was found.

[0048] The detailed crystal structure information was obtained by using GSAS II software for refinement. Figure 3 The relevant refinement results are summarized in Table 1. XRD refinement results show that after Ta / Ti dual doping, Li + / Ni 2+ The degree of intermixing was reduced from 4.4% in the original material to 2.4%, significantly suppressing the Li / Ni intermixing phenomenon. Furthermore, the increase in the c-axis lattice constant indicates that the interlayer spacing has been expanded, which is conducive to optimizing the lithium ion diffusion channel and thus improving the electrochemical performance of the material.

[0049] Table 1. Summary of XRD refinement data

[0050]

[0051] The morphologies of NCM and TaTi-NCM were characterized by field emission scanning electron microscopy (HITACHI S-4800, SU 8010) equipped with energy dispersive spectrometer (EDS, IXRF SYSTEM, 550i). Figure 4 and Figure 5As shown in the scanning electron micrograph, the synthesized TaTi-NCM material has a uniformly distributed spherical particle structure. Figure 6 As shown, the EDS element distribution map further shows that Mn, Ni, Co, Ta, Ti and O elements are evenly distributed in TaTi-NCM particles, indicating that the doping elements are successfully introduced and well dispersed.

[0052] Transmission electron microscopy (TEM) images were acquired using FEI Tecnai T12 and FEI Tecnai G2 F30 instruments, and the samples were prepared using a focused ion beam system (FIB, Scios, FEI). Figure 7 As shown in Figure 2, a clear Li-Ta-O protective layer is formed on the surface of TaTi-NCM. Combining the characterization results of XRD, SEM and TEM, it can be concluded that this technology is based on the theory of lattice defect repair of high nickel materials and adopts a dual-path design strategy, including: (1) Ta 5+ Gradient enrichment on the surface of the material forms a Li-Ta-O protective layer, which effectively inhibits the corrosion of the electrolyte on the positive electrode material; (2) Ta 5+ With Ti4 + Uniform doping in the bulk phase enhances the stability of the crystal structure with the help of strong Ta-O and Ti-O bonds, thereby improving the structural integrity and electrochemical performance of the material.

[0053] To prepare the electrode slurry, the cathode active material, acetylene black, and polyvinylidene fluoride (PVDF, Solef 5130) were mixed in an N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 and stirred until uniform. The resulting slurry was evenly coated onto an aluminum foil current collector, with an active material mass loading of 2-3 mg cm. -2 The coated electrodes were dried in a vacuum oven at 120 °C for 12 h, then punched into circular electrode pieces with a diameter of 12 mm and transferred to an argon-filled glove box.

[0054] The battery was assembled using a CR2032 button cell structure, with the prepared positive electrode as the positive electrode, metallic lithium as the negative electrode, and Celgard PP2400 membrane as the separator. Each cell was injected with 60 μL of electrolyte: 1 M LiPF₆ dissolved in a solvent mixture of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) in a 1:1:1 volume ratio.

[0055] The electrochemical performance test of button cells was carried out on a multi-channel battery test system with a voltage range of 2.8-4.3V (relative to Li + / Li). Figure 8As shown in the figure, the first discharge specific capacity of TaTi-NCM material at 0.2C current density reaches 226 mAh / g, which is significantly higher than that of undoped NCM material (194 mAh / g), indicating that the dual-doping strategy effectively improves the reversible capacity and lithium ion storage capacity of the material. Figure 9 As shown in the figure, after three activation cycles at a current density of C / 5, the battery was subjected to a long cycle test at 1C. The results showed that the TaTi-NCM material still maintained a capacity retention rate of 81% after 250 cycles, which was significantly better than the 71% of the undoped NCM sample, indicating that the dual-doping strategy has significant advantages in improving structural stability and cycle life. In addition, as Figure 10 As shown in the figure, the TaTi-NCM sample exhibited excellent rate performance under different rate (C-rate) conditions, further verifying its good electrochemical kinetics and lithium ion diffusion ability.

[0056] Electrochemical impedance spectroscopy (EIS) tests were performed on a multi-channel electrochemical workstation with a test frequency range of 100 kHz to 10 mHz. Figure 11 As shown in the figure, the impedance of the TaTi-NCM sample is significantly reduced compared with the undoped NCM material, indicating that the dual-doping strategy effectively reduces the interfacial resistance and enhances the mobility of lithium ions in the electrode material, thereby helping to improve the electrochemical reaction kinetics of the material.

[0057] The lithium ion diffusion coefficient (D) was measured by the constant current intermittent titration technique (GITT) at a current density of 0.1C and a voltage range of 2.8–4.3V. During the test, the battery was charged at a constant current for 20 minutes and then left to stand for 3 hours to achieve a quasi-equilibrium state. Figure 12 As shown in the figure, compared with the undoped NCM material, the TaTi-NCM sample exhibits a higher lithium ion diffusion coefficient, indicating that the dual-doping strategy effectively optimizes the crystal structure of the material, broadens the lithium ion migration channel and reduces the diffusion resistance, thereby helping to improve the material's rate performance and kinetic reaction activity.

[0058] In summary, by constructing a Ta-Ti dual-gradient doping system, a specific capacity of up to 226 mAh / g (0.2C) and a capacity retention of ≥81% over 250 cycles were achieved, significantly outperforming existing high-nickel single-doping systems. This invention, through the synergistic enhancement mechanism of "surface passivation + bulk strengthening," effectively overcomes the technical bottleneck of traditional doping strategies, which restrict modification to a single dimension. This establishes a new paradigm for material design with significant technical value and application prospects.

[0059] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A Ta-Ti dual gradient doped high nickel cathode material for lithium ion batteries, characterized in that: The positive electrode material is LiMn 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2, of which Ta 5+ The Li-Ta-O protective layer is formed by gradient enrichment on the surface of the material. 5+ With Ti 4 + It is uniformly doped in the bulk phase and forms strong Ta-O and strong Ti-O bonds with the oxygen framework. The strong Ta-O and Ti-O bonds enhance the stability of the crystal structure and synergize with the Li-Ta-O protective layer to inhibit electrolyte corrosion, stabilize the lattice structure and reduce Li / Ni mixing.

2. A method for preparing the Ta-Ti dual gradient doped high nickel cathode material for lithium ion batteries according to claim 1, characterized in that: The steps include: S1, mixing Li2CO3 and high nickel ternary precursor material uniformly according to the stoichiometric ratio; S2, add Ta2O5 and TiO2 to the mixture of step S1, control the molar ratio of Li:Mn:Ta:Ti:Ni:Co to be 1:0.1:0.01:0.01:0.78:0.1, and mix well; S3, in an oxygen atmosphere, the mixed material is pre-calcined, and then the temperature is raised and calcined to obtain a Ta-Ti dual gradient doped high nickel cathode material LiMn 0.1 Ta 0.01 Ti 0.01 Ni 0.78 Co 0.1 O2.

3. The preparation method according to claim 2, wherein The high nickel ternary precursor material is Mn 0.1 Ni 0.8 Co 0.1 (OH)2.

4. The preparation method according to claim 2 or 3, wherein In step S3, the pre-calcination temperature is 450° C. to 550° C., and the calcination time is 3 to 5 hours; the heating calcination temperature is 750° C. to 800° C., and the calcination time is 10 to 12 hours.

5. A lithium-ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and an electrolyte using the positive electrode material as claimed in claim 1.

6. The lithium ion battery according to claim 5, wherein The invention comprises a metal lithium negative electrode and an electrolyte containing LiPF6, wherein the electrolyte is prepared by mixing EMC, DEC and FEC in a volume ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2).

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