A nickel hydroxide material with high conductivity and a preparation method and application thereof

Abstract

This invention relates to the field of electrochemical energy storage materials technology, providing a highly conductive nickel hydroxide material, its preparation method, and its applications. The preparation method includes the following steps: preparing a layered α-nickel hydroxide precursor; heat-treating the layered α-nickel hydroxide precursor in air or an inert atmosphere at 150-200°C for 0.5-5 hours; and cooling the heat-treated product to room temperature to obtain a nickel hydroxide material with enhanced conductivity, rich in oxygen vacancies and maintaining its α-phase layered structure. This invention heat-treats the layered α-nickel hydroxide precursor at a low temperature of 150-200°C. Without introducing external conductivity or doping elements, it induces the formation of oxygen vacancies within the material, thereby improving intrinsic electronic conductivity while maintaining its α-phase layered structure. This material can be used as a positive electrode active material in electrode sheets and batteries, significantly reducing electrode polarization and improving battery rate performance and long-cycle stability. The process is simple, low-cost, and highly reproducible.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, and particularly relates to a nickel hydroxide material with high conductivity, its preparation method and application. Background Technology

[0002] Nickel-based alkaline secondary batteries (such as nickel-iron and nickel-zinc batteries) have broad application prospects in energy storage and power supply fields due to their advantages such as high safety, low cost, and environmental friendliness. Nickel hydroxide, as a typical positive electrode active material in this type of battery, has a high theoretical capacity, but its poor electronic conductivity (typically 10) -5 ~10 -7 S cm -1 ( ) is a key bottleneck limiting battery rate performance, energy efficiency and cycle life.

[0003] Currently, conventional strategies for improving the conductivity of nickel hydroxide mainly fall into two categories: one is physical mixing, which involves adding a large amount of conductive agent (such as carbon materials) during electrode fabrication; the other is material composite / doping, such as composite with graphene or doping with elements like Co and Mn. However, these methods have significant limitations: adding a large amount of conductive agent dilutes the proportion of active material, reducing the volumetric energy density of the battery; the interfacial contact between the foreign conductive phase and the active material is unstable and prone to degradation during cycling; elemental doping or high-temperature treatment can easily lead to a transformation of the nickel hydroxide crystal structure (such as the transformation from α phase to β phase, or transformation to NiO), sacrificing its theoretical capacity and structural stability.

[0004] Therefore, there is an urgent need to develop a technical solution that can fundamentally improve the electronic conductivity of nickel hydroxide while maximizing its high-capacity layered structure, and that is simple to process and suitable for large-scale production. Based on this material innovation, it is necessary to develop a set of electrode design and battery construction schemes that are compatible with it, so as to achieve synergistic optimization of performance from materials to devices, thereby breaking the dilemma of energy density, power density and cycle life that are difficult to balance in traditional technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a nickel hydroxide material with high conductivity, thereby addressing the problems mentioned in the background section.

[0006] The present invention is implemented as follows: a method for preparing a highly conductive nickel hydroxide material includes the following steps:

[0007] (1) Preparation of layered α-nickel hydroxide precursor;

[0008] (2) The layered α-nickel hydroxide precursor is heat-treated in air or an inert atmosphere at 150~200℃ for 0.5~5h;

[0009] (3) Cool the heat-treated product to room temperature to obtain a nickel hydroxide material with enhanced conductivity that is rich in oxygen vacancies and maintains the α-phase layered structure.

[0010] Another objective of this invention is to provide a nickel hydroxide material with high conductivity, which is prepared by the above-described preparation method.

[0011] Another objective of this invention is to provide an alkaline secondary battery positive electrode sheet, which includes an active material, a conductive agent, and a binder;

[0012] The active material is the nickel hydroxide material with high conductivity as described in claim 4;

[0013] The mass ratio of the active material, conductive agent, and binder is (85~90):(7.5~5):(7.5~5).

[0014] Another objective of this invention is to provide an alkaline secondary battery, the battery comprising a negative electrode, an alkaline electrolyte, and the aforementioned alkaline secondary battery positive electrode.

[0015] This invention, through heat treatment of the layered α-nickel hydroxide precursor within a temperature range of 150-200°C, induces abundant oxygen vacancies within the material's crystal lattice without introducing any external elements or disrupting its α-phase layered structure. These oxygen vacancies act as electron donors, significantly increasing the carrier concentration within the material, thereby resulting in a leapfrog increase in its electronic conductivity (by 2-3 orders of magnitude). This highly intrinsically conductive material can be applied in alkaline secondary batteries to construct a positive electrode with low dependence on conductive agents and a high proportion of active material (≥85%). This not only significantly improves the active material loading and volumetric energy density of the electrode but also reduces the risk of performance degradation due to instability at the conductive agent interface, effectively transferring and amplifying the advantages of material modification at the battery device level.

[0016] Specifically, it has the following beneficial effects:

[0017] (1) Breakthrough improvement in intrinsic conductivity: conductivity can be improved by one-step low-temperature heat treatment, with conductivity increasing by 2 to 3 orders of magnitude, which solves its shortcomings as an electrode material;

[0018] (2) Stable structure and strong applicability: The layered structure of α-Ni(OH)2 is maintained during heat treatment, avoiding capacity decay caused by high temperature phase transformation, and the material has good electrochemical stability;

[0019] (3) Electrode design innovation: High intrinsic conductivity enables the optimization of electrode formulation, which can significantly reduce the amount of conductive agent, significantly increase the loading of active material and electrode energy density, and at the same time reduce the performance degradation caused by the instability of the conductive agent interface.

[0020] (4) Significant performance improvement: The battery assembled with the obtained material has significantly reduced polarization and excellent rate performance, especially in high-rate long-cycle tests;

[0021] (5) Environmentally friendly and easy to scale up: raw materials are readily available, the process is green, it is highly versatile, suitable for large-scale preparation, and has good industrial application prospects. Attached Figure Description

[0022] Figure 1 Comparison of X-ray diffraction patterns of materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention;

[0023] Figure 2 Comparison of electron paramagnetic resonance images of the materials prepared in Example 1 and Comparative Example 1 of this invention;

[0024] Figure 3 This is a comparison chart of the electrical conductivity of the materials prepared in Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 4 This is a comparison chart of the rate performance of nickel-iron batteries assembled using the materials prepared in Example 1 and Comparative Example 1 of this invention;

[0026] Figure 5 Nickel-iron batteries assembled using the materials prepared in Example 1 and Comparative Example 1 of this invention were tested at 8 A g. -1 Cyclic performance diagram under current. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0029] Example 1: A nickel hydroxide material with high conductivity, the preparation method of which includes the following steps:

[0030] (1) Preparation of α-Ni(OH)2 precursor by hydrothermal method: 2.42g of Ni(NO3)2·6H2O and 2.78g of urea were added to 23.15g of deionized water and stirred at 90℃ for 12h. Then, the mixture was allowed to stand at the same temperature for 12h. After filtration, washing and drying, α-Ni(OH)2 precursor was obtained.

[0031] (2) The obtained α-Ni(OH)2 precursor powder was placed in a magnetic boat and placed in a tube furnace. Under air conditions, the temperature was increased to 170°C at a rate of 5°C / min, then held for 0.5 hours and then naturally cooled to room temperature. The nickel hydroxide with enhanced conductivity was collected.

[0032] Example 2: Compared with Example 1, the only difference is that the heat treatment temperature in step (2) is adjusted to 180°C and the holding time is 1 hour.

[0033] Example 3: Compared with Example 1, the only difference is that the air conditions in step (2) are adjusted to argon atmosphere, the heat treatment temperature is adjusted to 150°C, and the heat treatment time is 5 hours.

[0034] Comparative Example 1 differs from Example 1 in that step (2) is omitted.

[0035] Comparative Example 2, compared with Example 1, differs only in that the heat treatment temperature in step (2) is adjusted to 280°C and the holding time is 2 hours.

[0036] Material characterization and performance testing:

[0037] 1. Structural characterization: The materials prepared in Example 1 and Comparative Examples 1-2 were analyzed, and the XRD patterns were obtained as follows: Figure 1 As shown, the electron paramagnetic resonance image is as follows: Figure 2 As shown, the XRD patterns of Example 1 and Comparative Example 1 both show characteristic peaks of the α-Ni(OH)2 structure, indicating that the heat treatment at 170℃ did not destroy its main crystal structure. However, the XRD patterns of Comparative Example 2 at 280℃ show characteristic peaks of NiO, indicating a structural change. Meanwhile, the electron paramagnetic resonance (EPR) images show that the oxygen vacancy intensity of the material after heat treatment at 170℃ in Example 1 is stronger than that of the untreated sample in Comparative Example 1.

[0038] 2. Conductivity Test: The materials prepared in Example 1 and Comparative Example 1 were tested using the four-probe method. The results are as follows: Figure 3 As shown, the electrical conductivity of the material prepared in Example 1 is significantly higher than that of Comparative Example 1;

[0039] 3. Battery assembly and electrochemical testing:

[0040] The material prepared in Example 1 was mixed with Super P conductive agent and binder (PVDF) at a mass ratio of 90:5:5, NMP solvent was added and stirred evenly to form a slurry, which was coated on carbon paper and vacuum dried at 60°C for 12 hours. The slurry was then cut into 1cm*1.5cm positive electrode sheets. The negative electrode was made of iron-based material and the negative electrode sheet was prepared in the same way. The electrolyte was 2M KOH aqueous solution, and the mixture was assembled into a simulated battery.

[0041] The materials prepared in Comparative Example 1 were assembled into a simulated battery using the same method described above;

[0042] The material prepared in Comparative Example 1 was mixed with Super P conductive agent and binder (PVDF) at a mass ratio of 70:20:10, and then a simulated battery was assembled as Comparative Example 3 in the same manner as described above.

[0043] Electrochemical performance testing was conducted;

[0044] like Figure 4 As shown, at different current densities, the battery assembled using the material of Example 1 exhibits a higher discharge capacity than the battery assembled using the material of Comparative Example 1.

[0045] like Figure 5 As shown, in 8A g -1 At the specified current density, after 500 cycles, the battery using the material of Example 1 retained 91.5% of its capacity, while the battery using Comparative Example 1 retained only 72.3% of its capacity. The battery using the high-conductivity agent formulation of Comparative Example 3 had a lower initial capacity and faster cycle decay, with a retention rate of approximately 68% after 500 cycles.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nickel hydroxide material with high conductivity, characterized in that, Includes the following steps: (1) Preparation of layered α-nickel hydroxide precursor; (2) The layered α-nickel hydroxide precursor is heat-treated in air or an inert atmosphere at 150~200℃ for 0.5~5h. (3) Cool the heat-treated product to room temperature to obtain a nickel hydroxide material with enhanced conductivity that is rich in oxygen vacancies and maintains the α-phase layered structure.

2. The method for preparing the highly conductive nickel hydroxide material according to claim 1, characterized in that, In step (1), the layered α-nickel hydroxide precursor is prepared by any one of the following methods: hydrothermal method, chemical precipitation method, and electrochemical deposition method.

3. The method for preparing the highly conductive nickel hydroxide material according to claim 1, characterized in that, In step (2), the heat treatment temperature is 160~180℃ and the holding time is 0.2~2 hours.

4. A nickel hydroxide material with high conductivity, characterized in that, It is prepared using the preparation method described in any one of claims 1-3.

5. A positive electrode sheet for an alkaline secondary battery, characterized in that, It includes active materials, conductive agents, and adhesives; The active material is the nickel hydroxide material with high conductivity as described in claim 4; The mass ratio of the active material, conductive agent, and binder is (85~90):(7.5~5):(7.5~5).

6. The alkaline secondary battery positive electrode sheet according to claim 5, characterized in that, The conductive agent is at least one of Super P, Ketgen Black, and carbon nanotubes; The adhesive is at least one of PVDF, PTFE, and PVA.

7. An alkaline secondary battery, characterized in that, The battery includes a negative electrode, an alkaline electrolyte, and a positive electrode as described in claim 5 or 6 for an alkaline secondary battery.

8. The alkaline secondary battery according to claim 7, characterized in that, The electrolyte is an aqueous solution of KOH or NaOH with a concentration of 1~6 mol / L.

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