A high-entropy doped lithium battery high-nickel ternary positive electrode material, a preparation method and application thereof

Abstract

The application discloses a high-entropy doped lithium battery high-nickel ternary positive electrode material and a preparation method and application thereof, and relates to the technical field of lithium battery materials. The application discloses a high-entropy doped lithium battery high-nickel ternary positive electrode material and a preparation method and application thereof, and relates to the technical field of lithium battery materials. The application adopts a high-entropy doping strategy, utilizes the synergistic effect of multiple elements in a crystal lattice, significantly improves the crystal structure stability and interface stability of the material, and effectively inhibits phase transition and micro-crack generation of the high-nickel material in a long cycle process. The capacity retention rate of the obtained positive electrode material can reach 80% after 300 cycles, and the discharge specific capacity can still reach 146 mAh / g under 8 C high rate, and the positive electrode material exhibits excellent cycle stability and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery cathode material technology, specifically relating to a high-entropy doped high-nickel ternary cathode material for lithium batteries, its preparation method, and its application. Background Technology

[0002] With the rapid development of industries such as new energy vehicles and energy storage systems, higher requirements have been placed on the energy density, cycle life and safety of lithium-ion batteries. Compared with other lithium battery cathode materials, high-nickel ternary cathode materials have high energy density, excellent rate performance and low-temperature performance, and are key materials for building the next generation of high-energy-density lithium-ion batteries. However, high-nickel materials have poor thermal stability and suffer from serious structural degradation, interfacial side reactions, microcrack generation and rapid capacity decay during charging and discharging, especially under high voltage conditions, these problems are more prominent [Journal of The Electrochemical Society, 2020, 167(9): 090514.].

[0003] To improve the electrochemical performance of high-nickel ternary cathode materials, researchers have conducted extensive modification studies, mainly including strategies such as elemental doping, surface coating, and structural design. Among these, elemental doping has been proven to be a key means of stabilizing the crystal structure. The effects of ion doping are mainly reflected in the following aspects: (1) increasing the bonding ability between transition metals and oxygen; (2) stabilizing the valence state of Ni and reducing Li / Ni mixing; (3) widening the octahedral interlayer spacing of LiO6 and improving the Li... +Migration efficiency; (4) Regulating the microstructure of materials and optimizing interface properties, etc. Therefore, although traditional single-element doping can improve material performance to a certain extent, its improvement effect is limited and it is difficult to simultaneously meet multiple performance requirements such as structural stability, ionic conductivity and interface stability [Nature Energy, 2020, 5(7): 527-534.]. In recent years, high-entropy doping strategy has received widespread attention due to the synergistic effect of multiple elements in the lattice. By introducing multiple elements into the transition metal layer or lithium layer, the material configuration entropy is significantly increased. High configuration entropy makes the material more thermodynamically stable, which can effectively suppress phase transition, alleviate lattice stress and improve the structural stability of the material [Advance Energy Materials, 2023, 13(12): 2203924.]. For example, patent CN118173737A discloses a method for modifying ternary cathode materials by using medium and high valence trace element doping in conjunction with La4NiLiO8 coating layer, but its preparation process is complicated and not conducive to large-scale application. Patent CN116230940A proposes a one-step solid-state method for synthesizing multi-element high-entropy doped high-nickel cathode materials. By simultaneously introducing multiple doping elements and optimizing the sintering process, the preparation process is simplified while significantly improving the material's cycle stability and rate performance under high voltage. However, it is worth noting that current high-entropy doping strategies are mostly based on experience or trial and error, lacking a unified theoretical framework to guide the optimization of multi-element combinations. The synergistic effects and mutual constraints between different elements are complex, making it difficult to quickly determine the optimal doping scheme, thus increasing the research and development cycle and cost.

[0004] Therefore, there is an urgent need to develop a high-entropy doping method that is simple to process and can significantly improve the cycle stability and rate performance of high-nickel materials, so as to further promote the industrial application prospects of the next generation of high-nickel cathodes [Nano Energy, 2021, 89:106456., ACS Energy Letters, 2022, 7(4): 1324-1333.]. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a high-entropy doped lithium-ion battery high-nickel ternary cathode material.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a high-entropy doped high-nickel ternary cathode material for lithium batteries, comprising,

[0009] The NCM9055 ternary precursor was mixed with a lithium source, and a high-entropy dopant was added to obtain a mixture. The high-entropy dopant was composed of oxides of any four elements selected from Mg, Zn, Cu, Fe, Cr, Al, Ca, Sr, Ba, Ti, Zr, Ta, Nb, Y, Yb, Si, V, Bi, Te, In, Sn, Mo, Sb, Ga, Ge, La, Ce, Nd, and W, mixed in an equimolar ratio of 0.2~1:0.2~1:0.2~1:0.2~1. The molar ratio of the NCM9055 precursor to the high-entropy dopant was 1:0.0015~0.02. The mixture was then subjected to high-temperature solid-state sintering under a protective atmosphere at a temperature of 700-950℃ for 10-20 hours. After natural cooling, a high-entropy doped high-nickel ternary cathode material was obtained.

[0010] The general chemical formula of the NCM ternary precursor is Ni. 1-x-y CoxMny(OH)2 (wherein Ni≥0.8), wherein the lithium source is lithium carbonate or lithium hydroxide.

[0011] In a preferred embodiment of the preparation method described in this invention, the oxides of Mg, Zn, Cu, Fe, Cr, Al, and Ca are: MgO, ZnO, CuO, Fe2O3, Cr2O3, Al, and CaO; SrO, BaO, TiO2, ZrO2, Ta2O5, Nb2O5, Y2O3, Yb2O3, SiO2, V2O5, and Bi2O3.

[0012] In a preferred embodiment of the preparation method described in this invention, the oxide of Te is TeO2, the oxide of In is In2O5, the oxide of Sn is SnO2, the oxide of Mo is MoO3, the oxide of Sb is Sb2O3 or Sb2O5, the oxide of Ga is Ga2O3, the oxide of Ge is GeO2, the oxide of La is La2O3, the oxide of Ce is CeO2, the oxide of Nd is Nd2O3, and the oxide of W is WO3.

[0013] In a preferred embodiment of the preparation method described in this invention, the molar ratio of the lithium source to the NCM precursor is (1.02-1.10):1.

[0014] In a preferred embodiment of the preparation method described in this invention, the protective atmosphere is oxygen or air.

[0015] As a preferred embodiment of the preparation method described in this invention, the high-temperature solid-state sintering is carried out at a heating rate of 2-10℃ / min.

[0016] In a preferred embodiment of the preparation method described in this invention, the sintering temperature is 700-900℃ and the sintering time is 10-15h.

[0017] Another objective of this invention is to overcome the shortcomings of the prior art and provide a high-entropy doped lithium-ion battery high-nickel ternary cathode material.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a high-entropy doped high-nickel ternary cathode material in the preparation of lithium-ion batteries.

[0019] Beneficial effects of this invention:

[0020] (1) This invention uses a high-entropy dopant composed of four elements, Nb, Mo, W, and Sb, in an equimolar ratio to dope NCM9055 high-nickel ternary material. By utilizing the synergistic effect of multiple elements, the crystal structure of the material is effectively stabilized, the occurrence of harmful phase transitions under high voltage is suppressed, and the long-cycle stability of the material is significantly improved, with a capacity retention rate of up to 80% after 300 cycles. (2) The high-entropy doping strategy of this invention introduces multiple elements with high valence states to adjust the electronic structure of the material surface and improve the lithium-ion diffusion dynamics, so that the material can still maintain a discharge specific capacity of 146 mAh / g at a high rate of 8C, showing excellent rate performance. (3) The preparation process of this invention is simple, compatible with existing industrial solid-state sintering processes, requires no complex equipment or post-processing, has low cost, and is easy to scale up for production. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0022] Figure 1 This is a scanning electron microscope (SEM) image of the undoped NCM-1 cathode material obtained in Comparative Example 1 of this invention.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the high-entropy doped HE-NCM-2 cathode material obtained in Comparative Example 2 of this invention.

[0024] Figure 3This is a scanning electron microscope (SEM) image of the high-entropy doped HE-NCM-3 cathode material obtained in Example 1 of the present invention.

[0025] Figure 4 The images show transmission electron microscopy (TEM) images and HR-TEM mapping spectra of the high-entropy doped HE-NCM-3 cathode material obtained in Example 1 of this invention.

[0026] Figure 5 This is a comparison chart of the cycle performance of Embodiment 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0027] Figure 6 This is a comparison chart of the rate performance of Embodiment 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0029] Example 1

[0030] This embodiment provides a method for preparing a high-entropy-doped high-nickel ternary cathode material for lithium batteries. The specific steps are as follows:

[0031] (1) Ni, the precursor of NCM9055 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH·H2O are mixed in a molar ratio of 1:1.05, and a high-entropy dopant is added. The high-entropy dopant is composed of Nb2O5, MoO3, WO3 and Sb2O5 in an equimolar ratio (1:1:1:1). The molar ratio of NCM9055 precursor to high-entropy dopant is 1:0.01. The mixture is then homogenized in a high-speed mixer.

[0032] (2) The mixture was placed in a corundum boat and put into a tube furnace. The temperature was raised to 780°C at a heating rate of 2°C / min under an oxygen atmosphere and held for 10 hours. The mixture was then naturally cooled to room temperature, ground and sieved to obtain a high-entropy doped high-nickel ternary cathode material, denoted as HE-NCM-3.

[0033] (3) The obtained positive electrode material is mixed with conductive carbon black and PVDF at a mass ratio of 8:1:1, and an appropriate amount of NMP is added to grind it into a slurry. The slurry is then coated onto aluminum foil (the mass concentration of the slurry is 60%, and the coating amount on the aluminum foil is 1.299 g / cm). 2 After drying, the electrode is punched into a diameter of 12mm, and lithium metal is used as the counter electrode. The CR2032 button cell is assembled in an argon glove box.

[0034] Electrochemical performance was tested within a voltage range of 2.7–4.35 V.

[0035] Examples 2-11

[0036] The ternary lithium-ion battery cathodes in Examples 2-11 were all prepared according to the method in Example 1 and their performance was tested and analyzed. The differences are as follows:

[0037] The content of high-entropy oxidant and the preparation process conditions are different, as shown in Table 1.

[0038] Table 1

[0039]

[0040] Comparative Example 1

[0041] The difference between this comparative example and Example 1 is that no high-entropy dopant was added. Instead, the NCM9055 precursor and the lithium source were mixed in the same proportion and sintered under the same conditions to obtain undoped NCM-1 cathode material.

[0042] Comparative Example 2

[0043] The difference between this comparative example and Example 1 is that the molar ratio of NCM9055 precursor to high-entropy dopant is 1:0.005, while the remaining steps are the same as in Example 1, to obtain the doped HE-NCM-2 cathode material.

[0044] Comparative Example 3

[0045] The difference between this comparative example and Example 1 is that no high-entropy dopant was added, and the pyrolysis temperature was 800℃, resulting in a doped NCM-4 cathode material.

[0046] Performance testing:

[0047] The cathode materials obtained in Example 1 and Comparative Examples 1 and 2 were assembled into coin cells, and their electrochemical performance was tested within a voltage window of 2.7-4.35V.

[0048] Electrochemical performance testing conditions: The test was conducted in a constant temperature chamber at 25℃. First, the device was allowed to stand for 6 hours. The first cycle of activation was performed with a current of approximately 20 mA / g (0.1C). Then, a long charge-discharge cycle test was conducted at 200 mA / g (1C). The charging process adopted a constant current charging mode. When the voltage reached 4.35V, the charging mode was switched to a constant voltage charging mode until the current dropped to 10 mA / g (or 0.05C) and then the charging was stopped.

[0049] The discharge process uses a constant current discharge mode until the voltage drops to 2.7V;

[0050] During the test, the system automatically records data such as voltage, current, and capacity, and uses this data to calculate key electrochemical performance indicators such as specific capacity, coulombic efficiency, and cycle life.

[0051] After activation at a current density of 0.1C, cycle performance was tested at a current density of 1C, and the results are as follows. Figure 6 As shown.

[0052] The high-entropy doped material in Example 1 retained 80% of its capacity after 300 cycles, significantly higher than Comparative Example 1 (undoped, approximately 60%) and Comparative Example 2 (0.5% doped, approximately 66%). Rate performance testing is as follows. Figure 5 As shown, Example 1 still achieves a discharge specific capacity of 146 mAh / g at a high rate of 8C, while Comparative Examples 1 and 2 only achieve 110 mAh / g and 125 mAh / g, respectively, at 8C. These results demonstrate that the high-entropy doping strategy employed in this invention effectively improves the cycle stability and rate performance of the NCM9055 high-nickel material.

[0053] Table 2

[0054]

[0055] Table 3

[0056]

[0057] Material characterization:

[0058] Figure 1 This is a scanning electron microscope (SEM) image of the undoped NCM-1 cathode material obtained in Comparative Example 1 of this invention. Figure 1 It can be seen that the undoped NCM-1 material consists of secondary spherical particles formed by the agglomeration of primary particles. The particle surface is relatively smooth, but the particle size distribution is relatively wide (about 5~15 μm). Some particles have irregular morphology and slight agglomeration, indicating that the grain growth of the undoped high-nickel material is disordered.

[0059] Figure 2 This is a scanning electron microscope (SEM) image of the high-entropy doped HE-NCM-2 cathode material obtained in Comparative Example 2 of this invention. It can be seen that, compared with... Figure 1 In comparison, the particle morphology of HE-NCM-2 material is improved, but the particle surface is still relatively rough, the particle size distribution is uneven (about 6~14 μm), and some areas have obvious sharp edges and irregular protrusions, indicating that the optimization effect of low doping content on material morphology is limited.

[0060] Figure 3 This is a scanning electron microscope (SEM) image of the high-entropy-doped HE-NCM-3 cathode material obtained in Example 1 of this invention. From... Figure 3It can be seen that after high-entropy doping under the optimal conditions of this invention (equal molar ratio of Nb, Mo, W, and Sb, doping amount of 1%), the material particle clusters are the most dense and uniform, with smooth surfaces, concentrated particle size distribution, and obvious consistency in grain growth direction. This is beneficial to improving the structural stability and electrochemical cycling performance of the material.

[0061] Figure 4 The images show transmission electron microscopy (TEM) images and HR-TEM mapping spectra of the high-entropy doped HE-NCM-3 cathode material obtained in Example 1 of this invention. The mapping spectra show that the four doping elements Nb, Mo, W, and Sb are uniformly distributed within the particles, with no elemental segregation. Specifically: the TEM image on the left shows that the material has clear lattice fringes with a lattice spacing of approximately 0.47 nm, corresponding to the (003) crystal plane of the layered structure, indicating good crystallinity and no obvious lattice defects or impurities observed; the HR-TEM mapping spectra on the right show the elemental distribution of Ni, Co, Mn, and high-entropy doping elements (Nb, Mo, W, Sb) within a single particle; it can be seen from the figures that all doping elements are uniformly distributed within the particles, with no elemental segregation or enrichment, proving that the high-entropy doping of this invention achieves uniform solid solution at the elemental level, which is beneficial for stabilizing the layered structure and improving electrochemical performance.

[0062] In summary, this invention successfully stabilizes the structure and improves the electrochemical performance of NCM9055 high-nickel ternary cathode material through high-entropy doping with Nb, Mo, W, and Sb in equal molar ratios. This method is simple, effective, and has excellent prospects for industrial application.

[0063] Comparative Example 4

[0064] To further investigate the synergistic effect among the four elements Nb, Mo, W, and Sb, the following experiment was designed:

[0065] Experiment 1: Based on Example 1, without adding Nb and Mo, and with all other conditions the same as in Example 1, a cathode material was prepared;

[0066] Experiment 2: Based on Example 1, without adding W and Nb, and with all other conditions the same as in Example 1, a positive electrode material was prepared;

[0067] Experiment 3: Based on Example 1, without adding W and Mo, and with all other conditions the same as in Example 1, a positive electrode material was prepared;

[0068] Experiment 4: Based on Example 1, without adding W, and with all other conditions the same as in Example 1, a positive electrode material was prepared.

[0069] Experiment 5: Based on Example 1, without adding Mo, and with all other conditions the same as in Example 1, a positive electrode material was prepared;

[0070] Experiment 6: Based on Example 1, without adding Nb, and with all other conditions the same as in Example 1, a positive electrode material was prepared;

[0071] Experiment 7: Based on Example 1, without adding Sb, and with all other conditions the same as in Example 1, a positive electrode material was prepared.

[0072] Experiment 8: Based on Example 1, an equimolar amount of Ta (corresponding oxide is Ta2O5) was added to the four elements Nb, Mo, W and Sb, and all other conditions were the same as in Example 1 to prepare the cathode material.

[0073] The measured electrochemical performance indicators are shown in Table 4.

[0074] Table 4

[0075]

[0076] According to the data in Table 4, compared with the Nb, Mo, W, and Sb quaternary equimolar ratio high-entropy doping of Example 1 (capacity retention of 80.03% after 300 cycles), the absence of one or more doping elements (Experiments 1-7) and the addition of Ta (Experiment 8) both led to a significant decrease in cycle stability (retention rate dropped to 65.3%~72.6%), indicating that there is a strong synergistic effect among the four elements. Among them, the performance degradation was most severe when W and Mo were absent simultaneously (Experiment 3, retention rate of only 65.3%), indicating that W and Mo play the most critical role in suppressing phase transition and microcrack formation. The effects of the absence of W alone (Experiment 4) or Mo alone (Experiment 5) were also quite significant. The effects of the absence of Nb and Sb were relatively small but still not negligible. The addition of Ta (Experiment 8) caused the lattice balance to be disrupted due to ionic radius mismatch, which in turn reduced the retention rate to 64.6% and the specific capacity to a significant degree.

[0077] In summary, the specific combination of the quaternary elements Nb, Mo, W, and Sb is a necessary guarantee for achieving high cyclic stability. The absence of any element or the blind addition of other elements will destroy the high-entropy synergistic effect.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a high-entropy doped high-nickel ternary cathode material for lithium batteries, characterized in that: include, The NCM9055 ternary precursor was mixed with a lithium source, and a high-entropy dopant was added to obtain a mixture. The high-entropy dopant was composed of oxides of any four elements selected from Mg, Zn, Cu, Fe, Cr, Al, Ca, Sr, Ba, Ti, Zr, Ta, Nb, Y, Yb, Si, V, Bi, Te, In, Sn, Mo, Sb, Ga, Ge, La, Ce, Nd, and W, mixed in an equimolar ratio of 0.2~1:0.2~1:0.2~1:0.2~1. The molar ratio of the NCM9055 precursor to the high-entropy dopant was 1:0.0015~0.

02. The mixture was then subjected to high-temperature solid-state sintering under a protective atmosphere at a temperature of 700-950℃ for 10-20 hours. After natural cooling, a high-entropy doped high-nickel ternary cathode material was obtained. The general chemical formula of the NCM ternary precursor is Ni. 1-x-y CoxMny(OH)2 (wherein Ni≥0.8), wherein the lithium source is lithium carbonate or lithium hydroxide.

2. The preparation method according to claim 1, characterized in that: The oxides of Mg, Zn, Cu, Fe, Cr, Al, and Ca are MgO, ZnO, CuO, Fe2O3, Cr, and Al, respectively. The oxides of Sr, Ba, Ti, ZrO2, Ta, Nb, Y2O3, Yb, Si, V, and Bi are Bi2O3.

3. The preparation method according to claim 1 or 2, characterized in that: The oxide of Te is TeO2, the oxide of In is In2O5, the oxide of Sn is SnO2, the oxide of Mo is MoO3, the oxide of Sb is Sb2O3 or Sb2O5, the oxide of Ga is Ga2O3, the oxide of Ge is GeO2, the oxide of La is La2O3, the oxide of Ce is CeO2, the oxide of Nd is Nd2O3, and the oxide of W is WO3.

4. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the lithium source to the NCM precursor is (1.02-1.10):

1.

5. The preparation method according to claim 4, characterized in that: The protective atmosphere is oxygen or air.

6. The preparation method according to claim 5, characterized in that: The high-temperature solid-state sintering is carried out at a heating rate of 2-10℃ / min.

7. The preparation method according to claim 1 or 6, characterized in that: The sintering temperature is 700-900℃, and the sintering time is 10-15h.

8. The high-entropy doped high-nickel ternary cathode material for lithium batteries prepared by any of the preparation methods described in claims 1 to 7.

9. The application of the high-entropy doped high-nickel ternary cathode material as described in claim 8 in the preparation of lithium-ion batteries.

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