Metallic boron-doped spinel type high-entropy oxide electrode material and preparation method thereof

Abstract

The invention discloses a metalloid boron doped spinel type high-entropy oxide electrode material and a preparation method thereof. Transition metal salt and a metalloid boron source serve as raw materials, polydentate organic acid serves as a complexing agent, uniform mixing is achieved through the complexing effect of the polydentate organic acid and metal ions, gel is formed through esterification polymerization and then calcined, and the metalloid boron doped spinel type high-entropy oxide electrode material is prepared. The chemical formula of the material is (BxM1-x) 3O4 (M is at least five elements of Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zn or Ti), and the value range of x is 0.05-0.15. Through the synergistic effect of doping of metalloid boron and the high-entropy effect and lattice distortion effect of the high-entropy oxide, the lithium ion adsorption and diffusion capability is improved, the structural stability is enhanced, and the lithium ion battery negative electrode material with excellent performance is obtained. The preparation method is easy to operate, high in controllability, capable of accurately regulating and controlling the boron doping concentration and the material microstructure and suitable for large-scale preparation.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a boron-doped spinel-type high-entropy oxide electrode material and its preparation method. Background Technology

[0002] Lithium-ion batteries, as core energy storage devices in new energy vehicles, energy storage systems, and consumer electronics, rely heavily on technological breakthroughs in electrode materials for performance improvement. Traditional graphite anodes have a theoretical capacity of only 372 mAh / g, insufficient to meet the demands of next-generation high-energy-density batteries. High-entropy oxides (HEOs), as novel multi-component materials, are formed by solid-solution of five or more elements in a 5%–35% ratio to create a single-phase structure. Their unique high-entropy effect, lattice distortion effect, and hysteresis diffusion effect give them significant advantages in electrochemical energy storage. The high-entropy effect maintains material structural stability and suppresses phase transitions and pulverization during cycling; lattice distortion optimizes the electronic structure of active sites, improving ion transport efficiency. Currently, spinel-type high-entropy oxides have become a research hotspot for lithium-ion battery anode materials due to their open three-dimensional ion transport channels and good structural stability. Hou et al. reported a spinel-type (CoMnVFeZn)3O4 anode that maintained a specific capacity of 500 mAh / g after 2000 cycles at a current density of 3 A / g, exhibiting a reversible phase transition and minimal volume expansion during cycling (S. Hou, L. Su, S. Wang, et al. Unlocking the Origins of Highly Reversible Lithium Storage and Stable Cycling in a Spinel High-Entropy Oxide Anode for Lithium-Ion Batteries. Adv. Funct. Mater. 2024, 34: 2307923). However, high-entropy oxides still suffer from problems such as low intrinsic conductivity and sluggish ion diffusion kinetics.

[0003] Heteroatom doping is an effective method for optimizing the electrochemical performance of oxide materials. In particular, metalloid elements located at the metal-nonmetal boundary can significantly alter the electronic structure of transition metals by inducing ionic bonds, covalent bonds, or the unique unconventional bonding characteristics of metalloids. Boron, as a unique element possessing both metallic conductivity and nonmetallic bonding properties, exhibits enhanced electronegativity that prompts transition metals to transfer electrons to metalloid doping sites, resulting in a space charge redistribution where electrons are depleted near boron and enriched near the metal. Furthermore, boron doping enhances lattice mechanical-chemical stability, allowing it to form metalloid-metal (BM) bonds with surrounding transition metals. nMulticenter covalent bonds (such as BMB three-center two-electron bonds) or boride-like networks effectively suppress particle pulverization during long-term cycling.

[0004] However, there are currently no reports on optimizing the lithium storage performance of high-entropy oxide anodes through boron doping. Summary of the Invention

[0005] To address the issues of low conductivity and insufficient cycle stability in existing spinel-type high-entropy oxide electrodes, this invention provides a boron-doped spinel-type high-entropy oxide electrode material. The material has a cubic spinel crystal structure containing B–O–M bonds, a space group of Fd-3m, and a chemical formula of (B… x M 1-x )3O4, and M is at least five elements selected from Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zn or Ti, wherein 0.05≤x≤0.15.

[0006] Furthermore, the particle size of the material is 10~30 nm.

[0007] This invention also provides a method for preparing a boron-doped spinel-type high-entropy oxide electrode material, comprising the following steps: S1. Preparation of precursor solution: Dissolve at least five transition metal salts and metalloid boron sources in water, use multidentate organic acid as a complexing agent, and carry out a complexation reaction at room temperature to obtain the precursor solution; S2, Sol-gel conversion: Add polyol to the precursor solution, heat and stir to form an elastic transparent gel; S3. Heat treatment crystallization: After drying the gel, place it in a drying oven to dehydrate and dry it to obtain a dry gel. Then, calcine the dry gel in an air or oxygen atmosphere to obtain a powdered boron-doped spinel-type high-entropy oxide electrode material.

[0008] Further, the transition metal salt is one of nitrate, acetate, or chloride; the transition metal includes at least five of Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zn, or Ti; the metalloid boron source is one of boric acid, sodium metaborate, or triethylborane; the polydentate organic acid is one of citric acid, tartaric acid, or EDTA; and the polyol is one of ethylene glycol, glycerol, or polyethylene glycol.

[0009] Further, the transition metal salt is preferably Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cr(NO3)3·9H2O, and Mn(NO3)2; the metalloid boron source is preferably boric acid; the multidentate organic acid is preferably citric acid; and the polyol is preferably ethylene glycol.

[0010] Furthermore, the molar ratio of the metalloid boron source to the metal ions is 0.05~0.15:1, corresponding to the metalloid element accounting for 5%~15% of the total cation molar fraction in the resulting oxide.

[0011] Furthermore, the total molar ratio of the multidentate organic acid to the metal ion is 1.5~4:1.

[0012] Furthermore, the molar ratio of polyol to polydentate organic acid is 1~3:1.

[0013] Furthermore, the heating and stirring temperature in step S2 is 70℃~120℃.

[0014] Furthermore, the calcination temperature in step S3 is 450℃~800℃, and the time is 0.5h~3h.

[0015] The application of the boron-doped spinel-type high-entropy oxide electrode material provided by this invention in lithium-ion batteries.

[0016] The present invention has the following beneficial effects: 1. This invention achieves uniform doping of metal-like boron in spinel-type high-entropy oxides through the sol-gel method. The complexation effect of citric acid with each ion ensures elemental molecular-level mixing, avoiding local enrichment and phase separation of boron. The preparation process is simple, highly controllable, and suitable for large-scale production. 2. Synergistic optimization of material performance by boron doping and high entropy effect: The high electronegativity of boron induces charge rearrangement, reduces the lithium ion adsorption energy barrier, and improves intrinsic conductivity; the strong covalent bond formed by boron and transition metals enhances lattice stability and inhibits pulverization and structural degradation during cycling; the lattice distortion and hysteresis diffusion effect of the high entropy system further improves ion transport dynamics, achieving a balance between high capacity and long cycling. 3. The prepared (B) 0.1 M 0.9 The 3O4 electrode material has a specific capacity of approximately 1100 mAh / g after 1000 cycles at a current density of 1 A / g, which is superior to traditional spinel oxide and undoped high-entropy oxide materials. Attached Figure Description

[0017] Figure 1 In Embodiment 1 of the present invention (B) 0.1 M 0.9 XRD pattern of 3O4 powder; Figure 2 In Embodiment 1 of the present invention (B) 0.1 M 0.9 EDS surface scan image of 3O4 powder; Figure 3 In Embodiment 1 of the present invention (B) 0.1 M0.9 TEM image of 3O4 powder; Figure 4 In Embodiment 1 of the present invention (B) 0.1 M 0.9 Long-cycle performance curves of M3O4 electrode and M3O4 electrode in the comparative example at a current density of 1A / g. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments, but these descriptions do not limit the scope of protection of the present invention.

[0019] This invention achieves uniform boron doping through the sol-gel method, and leverages the synergistic effect of boron's electronic structure regulation and the intrinsic advantages of high-entropy oxides to improve the electrochemical performance of the material.

[0020] Example 1 A boron-doped spinel-type high-entropy oxide electrode material with the chemical formula (B 0.1 M 0.9 The preparation method of 3O4 includes the following steps: S1. Weigh out 2 mmol Fe(NO3)3·9H2O, 2 mmol Co(NO3)2·6H2O, 2 mmol Ni(NO3)2·6H2O, 2 mmol Cr(NO3)3·9H2O, 2 mmol Mn(NO3)2, and 1 mmol H3BO3 in a molar ratio of Fe:Co:Ni:Cr:Mn:B = 1:1:1:1:1:0.5, dissolve them in 20 mL of deionized water, add 20 mmol citric acid monohydrate, and stir at room temperature for 30 min to form a homogeneous complex solution. S2. Add 40 mmol of ethylene glycol to the complex solution, heat to 100°C, and stir continuously for 1 hour until a transparent elastic gel is formed. S3. Place the gel in a 120℃ drying oven for 12 hours to dehydrate, removing residual moisture and volatile organic compounds, and prevent violent expansion or splashing during rapid heating to obtain a dry gel; calcine the dry gel at 550℃ for 1 hour in an air or oxygen atmosphere to decompose organic matter (citric acid, ethylene glycol) and nitrates into oxides, inducing crystal nucleation and crystal growth, and then cool it to room temperature with the furnace to obtain (B) 0.1 M 0.9 )3O4 powder.

[0021] Example 2 A boron-doped spinel-type high-entropy oxide electrode material with the chemical formula (B 0.1 M 0.9 The preparation method of 3O4 includes the following steps: S1. Weigh out 1.25 mmol Fe(NO3)3·9H2O, 1.25 mmol Co(NO3)2·6H2O, 1.25 mmol Ni(NO3)2·6H2O, 1.25 mmol Cr(NO3)3·9H2O, 1.25 mmol Mn(NO3)2, and 0.63 mmol H3BO3 in a molar ratio of Fe:Co:Ni:Cr:Mn:B = 1:1:1:1:1:0.5, dissolve them in 20 mL of deionized water, add 25 mmol citric acid monohydrate, and stir at room temperature for 30 min to form a homogeneous complex solution. S2. Add 50 mmol of ethylene glycol to the complex solution, heat to 80°C, and stir continuously for 2 hours until a transparent elastic gel is formed. S3. Place the gel in a 120℃ drying oven for 12 hours to dehydrate, removing residual moisture and volatile organic compounds, and prevent violent expansion or splashing during rapid heating to obtain a dry gel; calcine the dry gel at 550℃ for 1 hour in an air or oxygen atmosphere to decompose organic matter (citric acid, ethylene glycol) and nitrates into oxides, inducing crystal nucleation and crystal growth, and then cool it to room temperature with the furnace to obtain (B) 0.1 M 0.9 )3O4 powder.

[0022] Example 3 A boron-doped spinel-type high-entropy oxide electrode material with the chemical formula (B 0.15 M 0.85 The preparation method of 3O4 includes the following steps: S1. With a molar ratio of Fe:Co:Ni:Cr:Mn:B = 1:1:1:1:1:0.75, weigh out 1.25 mmol Fe(NO3)3·9H2O, 1.25 mmol Co(NO3)2·6H2O, 1.25 mmol Ni(NO3)2·6H2O, 1.25 mmol Cr(NO3)3·9H2O, 1.25 mmol Mn(NO3)2, and 0.94 mmol H3BO3, dissolve them in 20 mL of deionized water, add 25 mmol citric acid monohydrate, and stir at room temperature for 30 min to form a homogeneous complex solution. S2. Add 50 mmol of ethylene glycol to the complex solution, heat to 80°C, and stir continuously for 2 hours until a transparent elastic gel is formed. S3. Place the gel in a 120℃ drying oven for 12 hours to dehydrate, removing residual moisture and volatile organic compounds, and prevent violent expansion or splashing during rapid heating to obtain a dry gel; calcine the dry gel at 550℃ for 1 hour in an air or oxygen atmosphere to decompose organic matter (citric acid, ethylene glycol) and nitrates into oxides, inducing crystal nucleation and crystal growth, and then cool it to room temperature with the furnace to obtain (B)0.15 M 0.85 )3O4 powder.

[0023] Example 4 A boron-doped spinel-type high-entropy oxide electrode material with the chemical formula (B 0.1 M 0.9 The preparation method of 3O4 includes the following steps: S1. Weigh out 2 mmol Fe(NO3)3·9H2O, 2 mmol Co(NO3)2·6H2O, 2 mmol Ni(NO3)2·6H2O, 2 mmol Cr(NO3)3·9H2O, 2 mmol Mn(NO3)2, and 1 mmol H3BO3 in a molar ratio of Fe:Co:Ni:Cr:Mn:B = 1:1:1:1:1:0.5, dissolve them in 20 mL of deionized water, add 20 mmol citric acid monohydrate, and stir at room temperature for 30 min to form a homogeneous complex solution. S2. Add 40 mmol of ethylene glycol to the complex solution, heat to 80°C, and stir continuously for 2 hours until a transparent elastic gel is formed. S3. Place the gel in a 120℃ drying oven for 12 hours to dehydrate, removing residual moisture and volatile organic compounds, and preventing violent expansion or splashing during rapid heating at high temperatures, to obtain a dry gel; calcine the dry gel at 700℃ for 2 hours in an air or oxygen atmosphere to decompose organic matter (citric acid, ethylene glycol) and nitrates into oxides, inducing crystal nucleation and crystal growth, and then cool it to room temperature with the furnace to obtain (B) 0.1 M 0.9 )3O4 powder.

[0024] In the above embodiments, nitrate [M(NO3)] x Provides a source of metal cations (Fe) 3+ Co 2+ / 3+ Ni 2+ Cr 3+ Mn 2 + After high-temperature treatment, elements such as Fe, Co, Ni, Cr, and Mn form a high-entropy solid solution; boric acid serves as a boron source, providing boron doping, and boron atoms selectively replace metal ions at tetrahedral sites to form BO4. 5-Units, or those existing in interstitial spaces of the lattice, fine-tune the d-band center of the transition metal through electronic coupling effects, enhancing electronic conductivity and interfacial reaction kinetics. Simultaneously, the lattice distortion and high-entropy effect introduced by boron doping synergistically stabilize the material structure and suppress volume expansion during cycling. Citric acid, as a complexing agent, forms stable carboxylic acid complexes with metal ions, preventing precipitation or excessively high local concentrations. It also acts as a fuel, participating in combustion reactions to release energy during subsequent heating, which aids in oxide crystallization. Ethylene glycol, as an esterification reaction promoter, undergoes esterification and polycondensation with citric acid to form a three-dimensional network structure (polyester), thereby promoting the transformation of the sol into a gel.

[0025] Comparative Example 1: Boric acid was not added, and other experimental steps and conditions were the same as in Example 1.

[0026] Since Examples 1 to 4 have the same structure and similar performance, Example 1 will be used as an example for subsequent structural and performance tests.

[0027] Figure 1 In Embodiment 1 of the present invention (B) 0.1 M 0.9 XRD pattern of 3O4 powder. Figure 1 It can be seen that (B) 0.1 M 0.9 )3O4 is a pure phase, with the same structure as Co3O4.

[0028] Figure 2 In Embodiment 1 of the present invention (B) 0.1 M 0.9 EDS surface scan image of 3O4 powder. (Source: [Insert source here]) Figure 2 It can be seen that all elements are uniformly distributed in the sample, with no obvious segregation or aggregation.

[0029] Figure 3 In Embodiment 1 of the present invention (B) 0.1 M 0.9 TEM image of 3O4 powder. (Source: [Insert source here]) Figure 3 It can be seen that the product is a nanocluster composed of crystals with a size of 10~30nm, and there are many mesopores and micropores in the clusters; Electrochemical performance tests were conducted on the materials by assembling CR2025 coin cells. First, the active material, Super P, and polyvinylidene fluoride were mixed and dispersed in N-methylpyrrolidone at a mass ratio of 7:2:1. After stirring at 40 °C for 6 h, the resulting slurry was uniformly coated onto carbon-coated copper foil using a doctor blade with a coating thickness of 120 μm, and then vacuum dried at 60 °C for 12 h. Afterwards, the electrodes were pressed into circular electrodes with a diameter of 12 mm using a roller press, with an active material loading of approximately 1 mg / cm³. 2Inside the glove box, lay the positive electrode shell flat with the opening facing upwards. Using insulated tweezers, sequentially cover the electrode sheet, electrolyte (20 μL at a time), separator, electrolyte, lithium sheet, nickel foam, and negative electrode shell. Then, use a sealing machine at 50 kg / cm². 2 The battery was encapsulated under pressure. After being left to stand for 12 hours, the battery was placed in a constant temperature chamber at 30 ℃ and cycle performance was tested using a battery tester (voltage range 0.01-3 V).

[0030] Figure 4 In Embodiment 1 of the present invention (B) 0.1 M 0.9 The long-cycle performance of the M3O4 electrode and the comparative M3O4 electrode at a current density of 1 A / g. Figure 4 It can be seen that after 1000 cycles (B) 0.1 M 0.9 The specific capacity of the M3O4 electrode is approximately 1100 mAh / g, which is significantly higher than that of M3O4, and it has a good cycle life.

[0031] Although the above embodiments have described the present invention and its implementation in detail, it should be noted that for those skilled in the art, any changes, modifications, substitutions, combinations, simplifications, etc., made to the corresponding conditions without departing from the technical principles of the present invention should be considered as equivalent substitutions, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A metalloid boron-doped spinel high-entropy oxide electrode material, characterized in that, The crystal structure of the material is a cubic spinel structure and contains B-O-M bonds, the space group of the material is Fd-3m, the chemical formula of the material is (B x M 1-x )3O4, and M is at least five elements of Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zn or Ti, wherein 0.05≤x≤0.

15.

2. The electrode material of claim 1, wherein, The particle size of the material is 10-30 nm.

3. A method for preparing a metalloid boron-doped spinel high-entropy oxide electrode material, characterized in that, The method comprises the following steps: S1, precursor solution preparation: at least five transition metal salts and metalloid boron sources are dissolved in water, a polydentate organic acid is used as a complexing agent, and a complexing reaction is carried out at room temperature to obtain a precursor solution; S2, sol-gel conversion: polyhydric alcohol is added to the precursor solution, and heating and stirring are performed to form an elastic transparent gel; S3, heat treatment crystallization: the gel is placed in a drying oven for dehydration and drying to obtain a dry gel, and then the dry gel is calcined in an air or oxygen atmosphere to obtain a powder-like metalloid boron-doped spinel high-entropy oxide electrode material; The transition metal salt is one of a nitrate, an acetate or a chloride; the transition metal includes at least five of Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zn or Ti; the metalloid boron source is one of boric acid, sodium metaborate or triethylborane; the polydentate organic acid is one of citric acid, tartaric acid or EDTA; and the polyhydric alcohol is one of ethylene glycol, glycerol or polyethylene glycol.

4. The production method according to claim 3, characterized by, Preferably, the transition metal salt is Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cr(NO3)3·9H2O and Mn(NO3)2; the metalloid boron source is boric acid; the polydentate organic acid is citric acid; and the polyhydric alcohol is ethylene glycol.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the metalloid boron source to metal ions is 0.05-0.15:1, corresponding to 5%-15% of the metalloid element in the total cation molar fraction of the obtained oxide.

6. The preparation method according to claim 3, characterized in that, The total molar ratio of the polydentate organic acid to metal ions is 1.5-4:

1.

7. The preparation method according to claim 3, characterized in that, The molar ratio of the polyhydric alcohol to the polydentate organic acid is 1-3:

1.

8. The preparation method according to claim 3, characterized in that, The heating and stirring temperature in step S2 is 70-120°C.

9. The preparation method according to claim 3, characterized in that, The calcination temperature in step S3 is 450-800°C, and the time is 0.5-3h.

10. The metalloid boron-doped spinel high-entropy oxide electrode material according to any one of claims 1-9 is applied in a lithium ion battery.

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