A -80 ℃ ultra-low temperature resistant zinc ion battery electrode material and a preparation method thereof

Abstract

The application relates to an 80 DEG C super-low-temperature-resistant zinc ion battery electrode material and a preparation method thereof, and belongs to the technical field of electrochemical energy storage. The 80 DEG C super-low-temperature-resistant zinc ion battery electrode material provided by the application is a monoclinic polycrystalline nano-molybdenum oxide powder, which is composed of secondary particles composed of primary particles. In the application, ammonium molybdate tetrahydrate is used as a molybdenum source, and a mixture of propylene glycol and deionized water is subjected to a hydrothermal reaction at a set temperature. The product is subjected to solid-liquid separation, washing and drying to obtain the electrode material. After the battery material provided by the application is applied to a zinc ion battery, the battery has excellent super-low-temperature electrochemical activity and stable super-low-temperature cycle characteristics. The application avoids the use of a template agent and a complex pretreatment process, and has the advantages of simple process, low cost, easy scale-up preparation and good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to an electrode material for zinc-ion batteries that can withstand ultra-low temperatures of -80℃ and its preparation method. Background Technology

[0002] Rechargeable aqueous zinc-ion batteries are considered a key candidate technology for next-generation large-scale energy storage systems due to the combined advantages of high theoretical specific capacity, suitable redox potential, intrinsic safety, and low cost of the zinc anode. However, when operating temperatures drop below freezing or into extreme low-temperature environments, the battery's electrochemical performance deteriorates drastically, severely limiting its application in polar scientific expeditions, energy storage systems in frigid regions, and deep space exploration. Current research generally agrees that the root causes of low-temperature performance degradation lie primarily in two aspects: the deterioration of electrolyte properties and the sluggish reaction kinetics of electrode materials. Regarding the electrolyte, at low temperatures, the hydrogen bonding between water molecules significantly intensifies, easily inducing freezing or a sharp increase in viscosity, leading to a sharp drop in ionic conductivity and severe obstruction of bulk ion transport. To address this, researchers have developed modification strategies such as high-concentration "salt-in-water," organic co-solvent doping, and gel electrolytes. By controlling the hydrogen bond network and ion solvation structure, they have successfully lowered the electrolyte freezing point to below -70°C. However, electrolyte optimization alone is insufficient to completely solve the battery failure problem at ultra-low temperatures. Another key bottleneck lies in the inherent limitations of the electrode materials themselves. Existing research indicates that mainstream cathode materials, represented by vanadium-based and manganese-based oxides, face multiple challenges at low temperatures: First, the desolvation barrier of hydrated zinc ions at the interface is significantly raised, leading to a surge in charge transfer impedance and extremely sluggish interfacial reaction kinetics; second, the solid-state diffusion coefficient of zinc ions within the crystal lattice decreases exponentially with decreasing temperature, and the shrinkage or distortion of the crystal framework in some materials at low temperatures further narrows the zinc ion migration channels, intensifying electrochemical polarization; third, the structural instability of the cathode material and the dissolution of active materials during cycling are more pronounced at low temperatures, accelerating capacity decay and end-of-life. In summary, the single electrolyte modification approach has approached the limit of low-temperature performance improvement.

[0003] To fundamentally achieve reliable operation of zinc-ion batteries in ultra-low temperature environments, developing novel low-temperature resistant electrode materials that combine excellent intrinsic low-temperature reactivity, a stable crystal framework, and efficient zinc-ion transport pathways has become the key to overcoming current technological bottlenecks. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention aims to provide an electrode material for zinc-ion batteries resistant to ultra-low temperatures of -80℃ and its green and simple preparation method. The battery electrode material provided by this invention is a polycrystalline nano-molybdenum oxide with a monoclinic tunnel structure, exhibiting high specific capacity and excellent cycle stability even at extreme low temperatures of -80℃. In terms of preparation, this invention uses ammonium molybdate tetrahydrate as the molybdenum source precursor and a mixture of propylene glycol and deionized water as the reaction medium, preparing the material through a one-step hydrothermal reaction. The preparation process is simple and efficient, with mild and controllable reaction conditions. The entire preparation process does not use toxic organic solvents, making it green and environmentally friendly, easy to operate, low in cost, and exhibiting excellent product consistency. It is easy to scale up production and shows promising prospects for industrial applications.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides an electrode material for a zinc-ion battery that can withstand ultra-low temperatures of -80°C. The electrode material is a polycrystalline molybdenum nano-oxide with a monoclinic tunnel structure, containing Mo and O elements. The polycrystalline molybdenum nano-oxide is formed by the aggregation of primary particles to form secondary particles. The primary particles have a particle size of 3 nm to 7 nm, and the secondary particles have a particle size of 50 nm to 200 nm.

[0007] A second aspect of the present invention provides a method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material, comprising the following steps:

[0008] Prepare a mixture of propylene glycol and deionized water according to the set volume ratio; then add ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) was dissolved in the above mixture as a molybdenum source precursor. The resulting mixture was magnetically stirred until a clear and homogeneous precursor solution was formed. Subsequently, the precursor solution was subjected to a hydrothermal reaction to complete the crystallization reaction under set temperature and holding time conditions. After the reaction system was naturally cooled to room temperature, liquid-solid separation was performed. The obtained solid product was washed alternately with deionized water and anhydrous ethanol until no impurities remained. The washed product was dried for 10-12 hours until no anhydrous or ethanol residue remained, thus obtaining polycrystalline nano-molybdenum oxide powder. The volume ratio of propylene glycol to deionized water was (1:30) to (3:4); the mass-volume ratio of propylene glycol to ammonium molybdate tetrahydrate was propylene glycol:ammonium molybdate tetrahydrate = (1-60) mL:1 g; the hydrothermal reaction temperature was 160℃-220℃, and the reaction time was 6-48 hours.

[0009] Compared with the prior art, the present invention has the following significant advantages:

[0010] 1. Excellent ultra-low temperature electrochemical activity: Even at extreme low temperatures of -80℃, this material still exhibits considerable zinc storage capacity (maximum discharge / charge specific capacity reaches 88.6 / 88.4 mAh·g). -1 Currently, there are few reports on the zinc storage performance of other inorganic zinc storage materials in such ultra-low temperature environments (around -80℃) (Adv. Energy Mater. 2024, 14, 2304010; Batteries Supercaps 2026, 9, e202500863).

[0011] 2. Stable ultra-low temperature cycling characteristics: The material can maintain stable cycling performance (at least 898 cycles) at -80℃, and its cycling stability is far superior to the performance level of existing zinc-ion battery ultra-low temperature (around -80℃) electrode materials (Adv. Funct. Mater. 2023, 33, 2214546).

[0012] 3. Simple and controllable synthesis route and intrinsic advantages of inorganic materials: Polycrystalline nano-molybdate oxide powder can be prepared in one step via a hydrothermal method using ammonium molybdate tetrahydrate as the molybdenum source and propylene glycol as the solvent. Compared with organic zinc storage materials currently used in ultra-low temperature environments (around -80℃), this inorganic synthesis route eliminates the need for polymerization or molecular design steps, avoids the use of template agents and complex pretreatment processes, and is simpler, lower in cost, and easier to scale up. Attached Figure Description

[0013] Figure 1 XRD pattern of the polycrystalline molybdenum oxide nanoparticles prepared in Example 1.

[0014] Figure 2 SEM image of the polycrystalline molybdenum oxide nanoparticles prepared in Example 1.

[0015] Figure 3 TEM image of the polycrystalline molybdenum oxide nanoparticles prepared in Example 1.

[0016] Figure 4 XPS full spectrum of the polycrystalline molybdenum oxide nanoparticles prepared in Example 1.

[0017] Figure 5 The 1 prepared in Example 1 # The battery's ultra-low temperature (-80℃) long-cycle characteristics (0.1 A·g) -1 ).

[0018] Figure 6 The 1 prepared in Example 1 # The battery's ultra-low temperature (-80℃) charge-discharge curve (0.1 A·g)-1 ).

[0019] Figure 7 The 2 prepared in Example 1 # Battery room temperature (25°C) long cycle characteristics (20 A·g) -1 ).

[0020] Figure 8 The 2 prepared in Example 1 # Battery charge-discharge curve at room temperature (25°C) (20 A·g) -1 ).

[0021] Figure 9 The 2 prepared in Example 1 # Battery charge-discharge curve at room temperature (25°C) (5A·g) -1 ).

[0022] Figure 10 The 2 prepared in Example 1 # Rate characteristics of the battery at room temperature (25°C).

[0023] Figure 11 XRD pattern of the polycrystalline molybdenum oxide nanoparticles prepared in Example 2.

[0024] Figure 12 SEM image of the polycrystalline molybdenum oxide nanoparticles prepared in Example 2.

[0025] Figure 13 The 3 prepared in Example 2 # The battery's ultra-low temperature (-80℃) long-cycle characteristics (0.1 A·g) -1 ).

[0026] Figure 14 XRD pattern of the polycrystalline molybdenum oxide nanoparticles prepared in Example 3.

[0027] Figure 15 SEM image of the polycrystalline molybdenum oxide nanoparticles prepared in Example 3.

[0028] Figure 16 The 4 prepared in Example 3 # The battery's ultra-low temperature (-80℃) long-cycle characteristics (0.1 A·g) -1 ).

[0029] Figure 17 The XRD pattern of commercial monoclinic MoO2 powder used in Comparative Example 1.

[0030] Figure 18 SEM images of commercial monoclinic MoO2 powder used in Comparative Example 1.

[0031] Figure 19 TEM image of commercial monoclinic MoO2 powder used in Comparative Example 1.

[0032] Figure 20 XPS full spectrum of commercial monoclinic MoO2 powder used in Comparative Example 1.

[0033] Figure 21 The 5 prepared in Comparative Example 1 # The battery's ultra-low temperature (-80℃) long-cycle characteristics (0.1 A·g) -1 ).

[0034] Figure 22 The 4 prepared in Comparative Example 1 # The battery's ultra-low temperature (-80℃) charge-discharge curve (0.1 A·g) -1 ). Detailed Implementation

[0035] This invention provides an electrode material for zinc-ion batteries that can withstand ultra-low temperatures of -80℃. The electrode material is a polycrystalline molybdenum nano-oxide with a monoclinic tunnel structure, containing Mo and O elements. The polycrystalline molybdenum nano-oxide is formed by the aggregation of primary particles into secondary particles, and there are a large number of grain boundaries between the primary particles.

[0036] In some preferred embodiments of the present invention, the primary particle size is 3nm~7nm, and the secondary particle size is 50nm~200nm.

[0037] The preparation method of the -80℃ ultra-low temperature zinc-ion battery electrode material in this invention includes the following steps:

[0038] Propylene glycol was mixed with deionized water to obtain a mixture, followed by the addition of ammonium molybdate tetrahydrate ((NH4)6Mo7O). 24 Molybdenum oxide (Mo₄H₂O) was dissolved in a mixed solution as a molybdenum source precursor and magnetically stirred until a clear and homogeneous precursor solution was formed. This solution was then transferred to a hydrothermal reactor and sealed for a hydrothermal reaction to complete the crystallization process. After the reaction system cooled naturally to room temperature, liquid-solid separation was achieved by vacuum filtration or centrifugation. The resulting solid product was washed alternately with deionized water and anhydrous ethanol until no ions or organic components remained. The washed product was then placed in an electric drying oven and dried continuously at a suitable temperature until no anhydrous or ethanol residue remained, thus obtaining polycrystalline nano-molybdenum oxide powder.

[0039] In some preferred embodiments of the present invention, the volume ratio of propylene glycol to deionized water is (1:30) to (3:4).

[0040] In some preferred embodiments of the present invention, the mass-volume ratio of propylene glycol:ammonium molybdate tetrahydrate is (1~60) mL:1 g.

[0041] In some preferred embodiments of the present invention, the hydrothermal reaction temperature is 160°C to 220°C, and the reaction time is 6h to 48h.

[0042] In some preferred embodiments of the present invention, the drying temperature is 65℃~80℃ and the drying time is 10h~12h.

[0043] In this invention, to further illustrate the performance of the polycrystalline molybdenum oxide nanoparticles described herein, electrodes were prepared using them as raw materials, and zinc-ion batteries were constructed by matching the prepared electrodes with zinc foil. The battery performance was tested at room temperature (25°C) and ultra-low temperature (-80°C), respectively.

[0044] The electrode preparation method of this invention includes the following steps: using the polycrystalline nano-molybdenum oxide powder provided by this invention as the active component, weighing it with a conductive agent and a binder according to a certain ratio, adding it to a solvent, and mixing it thoroughly to obtain an electrode slurry with uniform dispersion and suitable rheological properties. The obtained electrode slurry is uniformly coated onto the surface of a stainless steel current collector, and after drying to completely remove the solvent, the resulting electrode sheet is the electrode.

[0045] In some preferred embodiments of the present invention, the mass ratio of polycrystalline molybdenum oxide nanoparticles to conductive agent and binder is 6:3:1, 7:2:1, or 8:1:1.

[0046] In some preferred embodiments of the present invention, the conductive agent is one of acetylene black, Super P, and multi-walled carbon nanotubes.

[0047] In some preferred embodiments of the present invention, the adhesive is polyvinylidene fluoride.

[0048] In some preferred embodiments of the present invention, the solvent is N-methylpyrrolidone (NMP).

[0049] The zinc-ion battery is assembled with the electrode as the working electrode, the zinc foil as the counter electrode, and a glass fiber membrane or cellulose nonwoven fabric as the separator.

[0050] In some preferred embodiments of the present invention, different electrolyte systems are used at room temperature and ultra-low temperature: at an ultra-low temperature of -80°C, with a electrolyte of 7.5 mol·kg⁻¹ -1 ZnCl2 aqueous solution was used as the electrolyte system; at room temperature (25℃), 2 mol·L⁻¹ -1 Zn(CF3SO3)2 aqueous solution is the electrolyte system.

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] Example 1:

[0053] Prepare a mixture of propylene glycol and deionized water at a volume ratio of 1:6. Take 35 mL of the mixture and add 0.44 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O). 24 ·4H2O) was dissolved in it and magnetically stirred until a clear and homogeneous precursor solution was formed; the precursor solution was transferred to a 50mL hydrothermal reactor and hydrothermally reacted at 180℃ for 12 hours; after the reaction was completed, solid-liquid separation was performed by vacuum filtration, and the obtained solid product was washed repeatedly with deionized water and anhydrous ethanol to remove residual ions and organic components; the washed product was placed in an electric drying oven and dried at 80℃ for 12 hours until no water or ethanol residue remained, to obtain polycrystalline nano molybdenum oxide powder.

[0054] The XRD pattern of the product obtained in this embodiment is as follows: Figure 1 As shown, the results indicate that the sample structure is basically consistent with the monoclinic MoO2 (belonging to space group P21 / c) corresponding to card number 644064 in the Inorganic Crystal Structure Database (ICSD). However, the half-width at half-maximum and peak position of the diffraction peak of the (0 1 1) crystal plane of the sample shift towards a lower angle (2θ decreases), and their relative intensity changes; at the same time, the relative intensity of the characteristic diffraction peaks of the (-2 -1 1) crystal plane and the (0 2 2) crystal plane increases.

[0055] The SEM images of the products obtained in this embodiment are as follows: Figure 2 As shown, the grains are uniformly distributed, and the secondary particles have a diameter range of approximately 50 nm to 200 nm.

[0056] The TEM image of the product obtained in this embodiment is as follows: Figure 3 As shown, the secondary particles are composed of primary particles with a particle size of 3 nm to 7 nm, and a large number of grain boundaries can be observed, which are beneficial to the rapid diffusion of ions.

[0057] The XPS full spectrum of the product obtained in this embodiment is as follows: Figure 4 As shown, this confirms that both Mo and O elements coexist in polycrystalline molybdenum oxide nanoparticles.

[0058] The polycrystalline molybdenum oxide nanoparticles prepared in this embodiment were mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 7:2:1. An appropriate amount of NMP was added and the mixture was ground into a slurry. This slurry was then coated onto a stainless steel current collector and dried for 10-12 hours until all NMP was released, thus obtaining a polycrystalline molybdenum oxide nanoparticle-based electrode sheet. To illustrate the excellent performance of the polycrystalline molybdenum oxide nanoparticles prepared in this embodiment when applied to batteries in ultra-low temperature environments (-80°C), this embodiment used the prepared polycrystalline molybdenum oxide nanoparticle-based electrode sheet as the working electrode, zinc foil as the counter electrode, and a glass fiber membrane as the separator. (7.5 mol·kg⁻¹) -1ZnCl2 aqueous solution is used as the electrolyte system to form a battery, denoted as 1. # Battery.

[0059] The 1 obtained in this embodiment # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical cyclic characteristics of time, such as Figure 5 As shown, the highest discharge / charge specific capacity (79.6 / 79.5 mAh·g) -1 The highest specific capacity was observed on the 109th cycle; after 1006 cycles, the battery retained 96.1% of its charge capacity (based on the highest specific capacity during the cycle).

[0060] The 1 obtained in this embodiment # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical charge-discharge curves at this time are as follows: Figure 6 As shown, the highest specific capacity during the 109th discharge / charge cycle was 79.6 / 79.5 mAh·g. -1 The specific capacity after the 720th discharge / charge cycle was 74.9 / 74.6 mAh·g. -1 The specific capacity during the 1006th discharge / charge cycle was 76.5 / 76.6 mAh·g. -1 .

[0061] To further illustrate that the polycrystalline molybdenum oxide nanoparticles prepared in this embodiment still exhibit excellent performance at room temperature (25°C) when applied to a battery, this embodiment uses the prepared polycrystalline molybdenum oxide nanoparticle-based electrode sheet as the working electrode, zinc foil as the counter electrode, and a glass fiber membrane as the separator, with 2 mol·L⁻¹... -1 Zn(CF3SO3)2 aqueous solution is used as the electrolyte system to form a battery, denoted as 2. # Battery.

[0062] The 2 prepared in this embodiment # The battery operates at 25°C and a current density of 20 A·g. -1 Typical cyclic characteristics of time, such as Figure 7 As shown, the highest discharge / charge specific capacity (59.4 / 61.7 mAh·g) -1 The highest specific capacity was achieved at the 2088th cycle; after 21,000 cycles, the battery retained 70.2% of its charge capacity (based on the highest specific capacity during the cycle).

[0063] The 2 prepared in this embodiment # The battery operates at 25°C and a current density of 20 A·g. -1 Typical charge-discharge curves at this time are as follows: Figure 8 As shown, the highest specific capacity during the 2088th discharge / charge cycle was 59.4 / 61.7 mAh·g. -1The specific capacity after 21,000 discharge / charge cycles was 43.3 / 43.3 mAh·g. -1 .

[0064] The battery constructed from the electrode sheet and zinc foil obtained in this embodiment operates at 25°C and a current density of 5 A·g. -1 Typical charge-discharge curves at this time are as follows: Figure 9 As shown, the specific capacity during the second discharge / charge cycle is 112.1 / 109.5 mAh·g. -1 The specific capacity after 500 discharge / charge cycles is 87.1 / 87.0 mAh·g. -1 .

[0065] The 2 prepared in this embodiment # Typical rate performance of the battery at 25°C is as follows Figure 10 As shown, when the current density gradually increases from 0.1 A·g -1 Increased to 20 A·g -1 At that time, the electrode exhibited stable cycling; however, when the current density was directly reduced to 0.1 A·g, the electrode showed stable cycling. -1 The electrode still exhibits stable cycling performance and 145.0 / 144.3 mAh·g. -1 Discharge / charge ratio capacity.

[0066] Example 2:

[0067] Prepare a mixture of propylene glycol and deionized water at a volume ratio of 1:30. Take 150 mL of the mixture and add 2.14 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O). 24 ·4H2O) was dissolved in it and magnetically stirred until a clear and homogeneous precursor solution was formed; the precursor solution was transferred to a 200mL hydrothermal reactor and hydrothermally reacted at 220℃ for 6 hours; after the reaction was completed, solid-liquid separation was performed using a centrifuge, and the obtained solid product was washed repeatedly with deionized water and anhydrous ethanol to remove residual ions and organic components; the washed product was placed in an electric drying oven and dried at 70℃ for 12 hours until no water or ethanol residue remained, to obtain polycrystalline nano-molybdenum oxide powder.

[0068] The XRD pattern of the product obtained in this embodiment is as follows: Figure 11 As shown, the results indicate that the sample structure is consistent with the monoclinic MoO2 (belonging to space group P21 / c) corresponding to card number 644064 in the Inorganic Crystal Structure Database (ICSD).

[0069] The SEM images of the products obtained in this embodiment are as follows: Figure 12 As shown, the grains are uniformly distributed, and the secondary particles have a diameter range of approximately 50 nm to 200 nm.

[0070] The above powder was mixed with Super P and polyvinylidene fluoride in a mass ratio of 6:3:1, and an appropriate amount of NMP was added to grind it into a slurry. This slurry was then coated onto a stainless steel current collector and dried for 10-12 hours until all NMP was released, thus obtaining a polycrystalline nano-molybdenum oxide-based electrode sheet. Using the prepared polycrystalline nano-molybdenum oxide-based electrode sheet as the working electrode, zinc foil as the counter electrode, and a glass fiber membrane as the diaphragm, 7.5 mol·kg⁻¹... -1 ZnCl2 aqueous solution is used as the electrolyte system to form a battery, denoted as 3. # Battery.

[0071] The 3 obtained in this embodiment # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical cyclic characteristics of time, such as Figure 13 As shown, its highest discharge / charge specific capacity (81.3 / 81.5 mAh·g) -1 The specific capacity was observed on the 103rd cycle; after 968 cycles, the battery exhibited a discharge / charge specific capacity of 78.9 / 79.3 mAh·g. -1 The charge specific capacity retention rate was 97.3% (based on the highest specific capacity during the cycle).

[0072] Example 3:

[0073] Prepare a mixture of propylene glycol and deionized water at a volume ratio of 3:4. Take 70 mL of the mixture and add 0.88 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O). 24 ·4H2O) was dissolved in it and magnetically stirred until a clear and homogeneous precursor solution was formed; the precursor solution was transferred to a 100mL hydrothermal reactor and hydrothermally reacted at 160℃ for 48 hours; after the reaction was completed, solid-liquid separation was performed using a centrifuge, and the obtained solid product was washed repeatedly with deionized water and anhydrous ethanol to remove residual ions and organic components; the washed product was placed in an electric drying oven and dried at 65℃ for 12 hours until no water or ethanol residue remained, to obtain polycrystalline nano-molybdenum oxide powder.

[0074] The XRD pattern of the product obtained in this embodiment is as follows: Figure 14 As shown, the results indicate that the sample structure is basically consistent with the monoclinic MoO2 (belonging to space group P21 / c) corresponding to card number 644064 in the Inorganic Crystal Structure Database (ICSD). However, the full width at half maximum (FWHM) and peak position of the diffraction peak of the (0 1 1) crystal plane in the sample are more significantly shifted to the lower 2θ direction (compared to Example 1), and their relative intensities have changed; at the same time, the relative intensities of the characteristic diffraction peaks of the (-2 -1 1) crystal plane and the (0 2 2) crystal plane are also enhanced.

[0075] The SEM images of the products obtained in this embodiment are as follows: Figure 15 As shown, the grains are uniformly distributed, and the secondary particles have a diameter range of 50nm to 200nm.

[0076] The above powder was mixed with multi-walled carbon nanotubes and polyvinylidene fluoride in a mass ratio of 8:1:1, and an appropriate amount of NMP was added to grind it into a slurry. This slurry was then coated onto a stainless steel current collector and dried for 10-12 hours until all NMP was released, thus obtaining a polycrystalline molybdenum oxide nano-based electrode sheet. Using the prepared polycrystalline molybdenum oxide nano-based electrode sheet as the working electrode, zinc foil as the counter electrode, and a glass fiber membrane as the diaphragm, a 7.5 mol·kg⁻¹ solution was applied. -1 ZnCl2 aqueous solution is used as the electrolyte system to form a battery, denoted as 4. # Battery.

[0077] The 4 prepared in this embodiment # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical cyclic characteristics of time, such as Figure 16 As shown, its highest discharge / charge specific capacity (88.6 / 88.4 mAh·g) -1 The specific capacity was observed at the 95th cycle; after 898 cycles, the battery exhibited a discharge / charge specific capacity of (85.5 / 85.7 mAh·g). -1 The charge specific capacity retention rate was 97.0% (based on the highest specific capacity during the cycle).

[0078] Comparative Example 1:

[0079] This comparative example uses commercial monoclinic MoO2 as raw material to demonstrate that the excellent ultra-low temperature properties of the material of this invention cannot be directly provided by ordinary commercial monoclinic MoO2.

[0080] XRD characterization of commercial monoclinic MoO2 yielded the following results: Figure 17 As shown, analysis revealed that its crystal structure is consistent with the monoclinic MoO2 (belonging to space group P21 / c) corresponding to card number 644064 in the Inorganic Crystal Structure Database (ICSD).

[0081] The microstructure of the commercial monoclinic MoO2 used in this comparative example was characterized, and the results are as follows: Figure 18 , 19 As shown in the figure, the particle size range is approximately 1μm to 5μm. The internal region of the grains is significantly different from that of the example, and no obvious grain boundaries can be observed.

[0082] The XPS full spectrum of commercial monoclinic MoO2 used in this comparative example is as follows: Figure 20 As shown, this confirms that both Mo and O elements coexist in the material of this comparative example.

[0083] Using commercial monoclinic MoO2 as the raw material, it was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 7:2:1. An appropriate amount of NMP was added and the mixture was ground into a slurry. This slurry was coated onto a stainless steel current collector and then dried for 10-12 hours until all NMP was released, thus obtaining an electrode sheet based on commercial monoclinic MoO2. The obtained electrode sheet was used as the working electrode, zinc foil as the counter electrode, and a glass fiber membrane as the diaphragm. (7.5 mol·kg⁻¹) -1 ZnCl2 aqueous solution is used as the electrolyte system to form a battery, denoted as 5. # Battery.

[0084] The 5 prepared in this comparative example # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical cyclic characteristics of time, such as Figure 21 As shown, the highest discharge / charge specific capacity is only 2.9 / 2.5 mAh·g. -1 (First cycle).

[0085] The 5 samples prepared in this comparative example # The battery operates at -80℃ and a current density of 0.1 A·g. -1 Typical charge-discharge curves at this time are as follows: Figure 22 As shown, the specific capacity after 300 discharge / charge cycles is only 0.7 / 0.7 mAh·g. -1 .

[0086] The polycrystalline nano-molybdenum oxide powder provided by this invention has the following characteristics:

[0087] 1. X-ray photoelectron spectroscopy (XPS) full-spectrum analysis of the sample obtained according to Example 1 of the present invention confirmed that the polycrystalline molybdenum nanoparticles contain two elements, Mo and O.

[0088] 2. X-ray diffraction (XRD) analysis of samples obtained according to different embodiments of the present invention shows that the prepared samples are basically consistent with the monoclinic MoO2 crystal structure corresponding to ICSD #644064, but the characteristic diffraction peak positions, full width at half maximum (FWHM), and relative intensities of some sample examples show significant changes. With the change of the volume ratio of propylene glycol to deionized water, the FWHM and peak positions of the diffraction peaks of the (0 1 1) crystal plane in the sample change, and their relative intensities also change; at the same time, the relative intensities of the characteristic diffraction peaks of the (-2 -1 1) crystal plane and the (0 22) crystal plane also change.

[0089] 3. Transmission electron microscopy (TEM) results of samples obtained according to different embodiments of the present invention show that the primary particle size of the polycrystalline molybdenum nanoparticles prepared by the present invention is 3nm~7nm, and secondary particles are formed by the aggregation of primary particles. There are a large number of grain boundaries between the primary particles, which facilitate the rapid diffusion of ions.

[0090] 4. Scanning electron microscopy (SEM) results of samples obtained according to different embodiments of the present invention show that the amount of propylene glycol used in the preparation of polycrystalline molybdenum oxide nanoparticles has no significant effect on the secondary particle size of the series of polycrystalline molybdenum oxide nanoparticles, and the particle size is 50 nm to 200 nm.

[0091] The scope of protection of this invention is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its scope and spirit. If these modifications and variations fall within the scope of this invention and its equivalents, then the intent of this invention also includes these modifications and variations.

Claims

1. A zinc-ion battery electrode material resistant to ultra-low temperature (-80℃), characterized in that, The electrode material is a monoclinic tunnel structure polycrystalline molybdenum nano-oxide containing Mo and O elements; The polycrystalline molybdenum nano-oxide is formed by the aggregation of primary particles into secondary particles.

2. The zinc-ion battery electrode material resistant to -80℃ ultra-low temperature according to claim 1, characterized in that, The primary particle size is 3nm~7nm, and the secondary particle size is 50nm~200nm.

3. A method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material as described in claim 1 or 2, characterized in that, Includes the following steps: Ammonium molybdate tetrahydrate was added to a mixture of propylene glycol and deionized water and stirred until a clear and homogeneous precursor solution was formed. The precursor solution was subjected to a hydrothermal reaction, and the crystallization reaction was completed by maintaining the temperature at a set temperature. After the reaction system was naturally cooled to room temperature, it was separated into solid and liquid phases, washed, and dried to obtain polycrystalline nano-molybdenum oxide powder, which is the electrode material for zinc-ion batteries resistant to ultra-low temperatures of -80℃.

4. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 3, characterized in that, By mass percentage, propylene glycol: ammonium molybdate tetrahydrate = (1~60) mL: 1 g.

5. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 4, characterized in that, By volume ratio, propylene glycol:deionized water = (1:30) ~ (3:4).

6. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 4, characterized in that, The hydrothermal reaction temperature is 160℃~220℃, and the reaction time is 6h~48h.

7. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 4, characterized in that, The washing process involves washing the solid product obtained from solid-liquid separation with deionized water and anhydrous ethanol alternately until no impurities remain.

8. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 4, characterized in that, The drying process involves continuously drying the washed product for 10 to 12 hours until no deionized water or ethanol residue remains.

9. The method for preparing the -80℃ ultra-low temperature zinc-ion battery electrode material according to claim 4, characterized in that, Stirring is performed using magnetic stirring.

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