A controllable preparation method of non-stoichiometric Cu2-xS for zinc-ion battery anodes

Abstract

The application discloses a controllable preparation method of non-metering ratio Cu 2‑x S of a zinc ion battery negative electrode, and belongs to the field of electrode material preparation and electrochemical energy storage technology. In view of the problem that existing technologies are difficult to controllably prepare specific non-metering ratio copper sulfide in the same system, the application realizes the controllable preparation of various metering ratio Cu 2‑x S from CuS to Cu2S by constructing a weak reduction atmosphere, under a solvent thermal condition, and by accurately adjusting a reaction temperature and a solvent composition. When the obtained material is used as a zinc ion battery negative electrode material, the material exhibits high specific capacity and excellent cycle stability. The application has simple process and strong controllability, and provides an ideal negative electrode material for the development of a high-performance "rocking chair type" zinc ion battery.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation and electrochemical energy storage technology, specifically relating to a non-stoichiometric Cu anode for zinc-ion batteries. 2-x S is a controllable preparation method. Background Technology

[0002] Aqueous zinc-ion batteries (AZIBs) have shown great potential in large-scale energy storage due to their low cost, high safety, and environmental friendliness. Their performance largely depends on the electrode materials, especially the anode material. Currently, zinc metal is widely used as the anode due to its high theoretical capacity and suitable potential. However, problems such as dendrite growth, hydrogen evolution reaction, corrosion, and passivation during cycling are unavoidable and severely affect the cycle life and reliability of the battery. Furthermore, to mitigate the adverse effects of the zinc anode on overall battery performance, excessive zinc metal is often used, leading to a decrease in zinc anode utilization and actual energy density. Therefore, researchers have begun exploring the development of novel "rocking chair" zinc-ion batteries, namely, searching for batteries capable of reversibly inserting, deinserting, or storing Zn. 2+ The negative electrode material is used to replace zinc metal, because Zn 2+ The hydration radius (4.3 Å) is significantly larger than that of Li. + (0.76 Å) Many anode materials that exhibit excellent electrochemical performance in lithium-ion batteries are not suitable for zinc-ion batteries. Developing reversible Zn insertion / extraction / deintercalation technologies is crucial. 2+ Furthermore, negative electrode materials with lower potentials have become an important research direction.

[0003] Among numerous candidate materials, copper sulfides (mainly CuS and Cu2S) have attracted attention due to their high theoretical specific capacity and reversible zinc storage mechanism based on conversion reactions, especially their non-stoichiometric form (general formula Cu2S). 2-x S, such as Cu 1.8 S, Cu 1.75 S, etc., are believed to be beneficial for reducing Zn content due to the natural presence of copper vacancies in the crystal lattice. 2+ The activation energy for insertion / extraction can potentially lead to better electrochemical performance. However, the controllable synthesis of such non-stoichiometric copper sulfide materials faces significant challenges. In traditional synthetic routes, Cu... 2+ In aqueous solution, it tends to react with S² - Direct reaction forms stable CuS; however, under strong reducing conditions, Cu₂S is mainly formed. Various non-stoichiometric Cu ratios exist between these two conditions. 2-x S (such as Cu) 1.8 S, Cu 1.75S) Although occasionally reported in the literature, its synthesis is usually highly random, depending heavily on specific reaction conditions and precursor states. There is a lack of a universal, controllable method to precisely and reproducibly prepare Cu with different specific stoichiometric ratios in a single reaction system by systematically adjusting parameters. 2-x The uncontrollable nature of the synthesis of copper sulfide materials severely hinders systematic research on their structure-property relationships and limits their development and optimization as high-performance zinc-ion battery anode materials. In existing technologies, the synthesis of copper sulfide materials largely relies on complex multi-step processes. Precise control of intermediate states is difficult, typically resulting in only one or a few pre-defined products. Furthermore, existing methods often focus on controlling the macroscopic morphology of the material (e.g., nanosheets, nanospheres) or introducing defects through drastic post-processing, but often lack the ability to directly and precisely control the basic building blocks of the crystal (i.e., stoichiometry) and the crystal phase they determine in the early stages of synthesis, thus failing to achieve synergistic control of stoichiometry and crystal phase. Based on this, most synthesis methods aim to obtain the material itself, and their process design does not fully consider the unique requirements of end-use applications for material properties. For example, in battery applications, materials with larger Zn... 2+ Storage behavior and Li + / Na + They are quite different, but conventional methods do not have the ability to design materials for specific charge carrier ions.

[0004] The patent with publication number CN116741943A, entitled "A Defect-Rich Copper Sulfide / Carbon Composite Anode Material for Sodium-Ion Batteries and its Preparation Method," specifically discloses a method using ethylene glycol as a solvent to mix copper salt and thiourea, adding polyvinylpyrrolidone (PVP), and then carrying out a solvothermal reaction. The resulting precursor is then calcined at high temperature under an inert atmosphere to finally obtain defect-rich copper sulfide (Cu) with an amorphous carbon layer loaded on its surface. x S, x being 1.81, 1.96, or 2) composite anode materials, which are then used in sodium-ion batteries. However, the above scheme requires a subsequent high-temperature calcination step to stabilize the defects and introduce a carbon layer when preparing non-stoichiometric copper-sulfur compounds with specific defects. It is difficult to actively control the selective synthesis of different stoichiometric ratios and specific crystalline phase products in the same reaction system by gently and continuously adjusting the precursor reaction conditions. Summary of the Invention

[0005] To address the shortcomings of existing copper sulfide synthesis methods, such as difficulty in achieving controllable product stoichiometry and crystal phase, complex processes, and unsuitability of the prepared materials for aqueous zinc-ion batteries, this invention provides a non-stoichiometric Cu for zinc-ion battery anodes. 2-x A controllable preparation method for S aims to achieve the preparation of a series of non-stoichiometric, cubic Cu phases under mild conditions. 2-xThe selective preparation of S and its application to the negative electrode of zinc-ion batteries yielded excellent electrochemical performance.

[0006] To achieve this objective, the following solution is provided: This invention provides a non-stoichiometric Cu anode for a zinc-ion battery. 2-x A controllable preparation method for S: Solution A is obtained by placing a copper source in an organic amine solvent that provides a weak reducing atmosphere; Solution B is obtained by placing a sulfur source in an organic amine solvent that provides a weak reducing atmosphere; Solution A and Solution B are mixed and subjected to a solvothermal reaction. By controlling the type and composition of the organic amine solvent and the reaction temperature, the strength of the weak reducing atmosphere can be controlled, thereby selectively synthesizing cubic Cu phases with different stoichiometric ratios x. 2-x S product; of which 0 <x<1。

[0007] Furthermore, the organic amine solvent is one of N,N-dimethylformamide and ethylenediamine; the composition of the organic amine solvent is to add distilled water to the organic amine solvent to reduce its reducing properties.

[0008] Furthermore, the reaction temperature is 100-120°C, and the reaction time is 12 h.

[0009] Furthermore, the copper source is copper nitrate, and the sulfur source is thiourea; the molar ratio of the copper source to the sulfur source is 1:1.

[0010] Furthermore, the solution A also contains a dispersant, which is polyvinylpyrrolidone, and its mass is 60% of the mass of the copper source.

[0011] This invention provides a non-stoichiometric Cu anode for a zinc-ion battery. 2-x S.

[0012] This invention also provides a non-stoichiometric Cu anode for a zinc-ion battery. 2-x Application of S in the preparation of zinc-ion batteries.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention abandons the complex path of existing technologies that rely on strong reducing agents or introduce defects through subsequent high-temperature calcination and other harsh conditions. Instead, it constructs a controllable reducing environment in a one-step solvothermal process simply by selecting and adjusting an organic solvent with moderate reducing properties (such as DMF or ethylenediamine) or by adding distilled water to regulate the reducing power and reaction temperature. This method is simple, mild, and energy-efficient. Furthermore, through precise control of the key variable of "reducing atmosphere strength," it achieves effective intervention in the thermodynamics and kinetics of the reaction.

[0014] 2. By continuously controlling the weak reducing atmosphere, this invention enables the predictable and selective synthesis of a series of CuS with different stoichiometric ratios, ranging from CuS (x=1) to Cu2S (x=0), within a unified reaction system. 2-x S products (such as Cu) 1.8 S, Cu 1.75 S) not only enabled the direct and controllable introduction of intrinsic defect (copper vacancy) concentration into the material, but also achieved effective regulation of the material's multi-level nanostructures. It also specifically guided the generation of cubic Cu phase. 2-x Compared to the common hexagonal phase structure, the cubic phase may provide more isotropic ion diffusion channels and higher structural reversibility, which lays a key microstructural foundation for improving the reaction kinetics and cycle stability of electrode materials.

[0015] 3. This invention specifically solves the key technical challenges of zinc-ion battery anodes by synthesizing Cu with specific defects and a cubic phase structure through controllable synthesis. 2-x The S material was applied to the anode of an aqueous zinc-ion battery. Experiments have shown that it can effectively suppress the uncontrollable growth of zinc dendrites and reduce capacity decay caused by side reactions (such as hydrogen evolution and corrosion). As an anode, this material exhibits high reversible specific capacity and ultra-long cycle life. In particular, it can maintain stable capacity output even at high current density, thus meeting the requirements of "rocking chair" zinc-ion batteries for high-capacity and high-stability anode materials.

[0016] 4. This invention innovatively combines three aspects: “controllable preparation method in a weak reducing atmosphere”, “non-stoichiometric material design” and “application in aqueous zinc-ion batteries”, forming a complete and efficient technical loop. It provides a universal and precise preparation strategy, which not only solves the long-standing problem of controllable preparation of copper sulfide series materials, but also has important implications for the synthesis of other multivalent metal compounds through the core idea of ​​controlling the metal valence state through solvent engineering. Attached Figure Description

[0017] Figure 1 Cu, the negative electrode of the zinc-ion battery in Example 1 1.8 Scanning electron microscope (SEM) image of S; Figure 2 The image shows a scanning electron microscope (SEM) image of CuS in the negative electrode of the zinc-ion battery in Example 3. Figure 3 Cu for zinc-ion battery anodes prepared with different temperatures and solvent compositions in this invention 2-x X-ray diffraction (XRD) pattern of S material; Figure 4 Cu for zinc-ion battery anodes prepared at different temperatures in Example 5 2-xThe initial charge-discharge curve and cycle performance graph of S; Figure 5 This is a comparison chart of the cycle performance of stoichiometric copper sulfide and non-stoichiometric copper sulfide as negative electrodes of zinc-ion batteries in Example 5. Figure 6 Cu, which is the zinc-ion battery negative electrode with good electrochemical performance in Example 5. 2-x Long-cycle stability test curve of material S at a current density of 0.5 A / g. Detailed Implementation

[0018] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0019] In this invention, the control of the type and composition of the organic amine solvent includes, but is not limited to, selecting solvents with different reducing abilities (such as ethylenediamine or DMF), or introducing components such as distilled water to continuously adjust its reducing power. Through this fine control, the intensity of the reducing atmosphere in the reaction system can be continuously varied within a wide range, thereby achieving continuous and precise control of the stoichiometric ratio x of the product, and not only obtaining the endpoint product (CuS or Cu2S).

[0020] Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0021] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0022] Example 1 This embodiment provides a non-stoichiometric Cu-type zinc-ion battery negative electrode. 2-xA controllable preparation method for S, characterized by comprising the following steps: Weighing 0.4832 g Cu(NO3)2·3H2O, adding it to 10 mL N,N-dimethylformamide, and stirring magnetically until dissolved; then adding 0.29 g polyvinylpyrrolidone (PVP K30), and continuing to stir until completely dissolved to obtain a homogeneous solution, which is designated as solution A; weighing 0.1523 g thiourea, adding it to 20 mL DMF, and stirring for 5 min until dissolved to obtain solution B; slowly adding solution B to solution A, stirring for 3 min to mix evenly; transferring the mixture to a reaction vessel and sealing it; placing the reaction vessel in an oven and reacting at 100°C for 12 h; after the reaction is complete, removing the reaction solution, and washing it three times by alternating centrifugation with deionized water and ethanol to obtain Cu. 1.8 S.

[0023] Cu 1.8 S scanning electron microscope (SEM) image as follows Figure 1 As shown, when observed at different magnifications, the product is a microsphere structure composed of nanoparticles with nanofibers as the basic unit.

[0024] Example 2 This embodiment provides a non-stoichiometric Cu-type zinc-ion battery negative electrode. 2-x A controllable preparation method for S, characterized by comprising the following steps: Weighing 0.4832 g Cu(NO3)2·3H2O, adding it to 10 mL N,N-dimethylformamide, stirring magnetically until dissolved, then adding 0.29 g polyvinylpyrrolidone (PVP K30), and continuing to stir until completely dissolved to obtain a homogeneous solution, designated as solution A; Weighing 0.1523 g thiourea, adding it to 20 mL DMF, and stirring for 5 min until dissolved to obtain solution B; Slowly adding solution B to solution A, stirring for 3 min to mix evenly; Transferring the mixture to a reaction vessel and sealing it; Placing the reaction vessel in an oven and reacting at 120°C for 12 h; After the reaction is complete, removing the reaction solution and washing it three times by alternating centrifugation with deionized water and ethanol to obtain Cu. 1.75 S.

[0025] Example 3 This embodiment also provides a controllable preparation method of CuS for the negative electrode of a zinc-ion battery, characterized by the following steps: Weigh 0.4832 g Cu(NO3)2·3H2O, add it to 10 mL N,N-dimethylformamide, stir magnetically until dissolved, then add 0.29 g polyvinylpyrrolidone (PVP K30), and continue stirring until completely dissolved to obtain a homogeneous solution, which is solution A; Weigh 0.1523 g thiourea, add it to a mixed solution of 10 mL DMF and 10 mL distilled water, stir for 5 min until dissolved, which is solution B; Slowly add solution B to solution A, stir for 3 min to mix evenly, transfer the mixture to a reaction vessel and seal it, place the reaction vessel in an oven, and react at 120°C for 12 h; After the reaction is completed, take out the reaction solution, and wash it three times by alternating centrifugation with deionized water and ethanol to obtain CuS.

[0026] Scanning electron microscope (SEM) images of CuS are as follows: Figure 2 As shown, when observed at different magnifications, the product is a flower-like microsphere structure composed of aggregated nanoparticles.

[0027] Example 4 This embodiment also provides a controllable preparation method of Cu2S for the negative electrode of a zinc-ion battery, characterized by the following steps: Weigh 0.4832 g Cu(NO3)2·3H2O, add it to 10 mL ethylenediamine, stir magnetically until dissolved, then add 0.29 g polyvinylpyrrolidone (PVP K30), and continue stirring until completely dissolved to obtain a homogeneous solution, which is solution A; Weigh 0.1523 g thiourea, add it to 20 mL ethylenediamine, stir for 5 min until dissolved to obtain solution B; Slowly add solution B to solution A, stir for 3 min to mix evenly, transfer the mixture to a reaction vessel and seal it, place the reaction vessel in an oven, and react at 120°C for 12 h; After the reaction is completed, take out the reaction solution, and wash it three times by alternating centrifugation with deionized water and ethanol to obtain Cu2S.

[0028] The results showed that different types of Cu were synthesized via a solvothermal method. 2-x S, where the diffraction peaks obtained at 100°C are similar to those of the cubic phase Cu. 1.8 S standard card consistent, such as Figure 3 As shown in Figure a, increasing the temperature increases the reducing power of DMF, leading to further reduction of Cu ions to Cu₂S, which causes the diffraction peak to shift to the left. However, at lower reaction temperatures, the reducing power of DMF weakens, potentially generating Cu₇S₄, a higher valence state of Cu. This is due to the non-stoichiometric Cu produced. 2-x S mainly exists in the cubic phase, and it stores zinc with Cu having an insertion-extraction mechanism. 2- xThe uniformity of the Se crystal phase may make Se doping at the S site more effective and feasible; for example Figure 3 As shown in b, by changing the composition of the solvent (i.e., introducing water to form a mixed solvent), the diffraction peaks shift significantly to the right, with CuS as the main component, and the crystal phase tends to transform into the hexagonal phase of the stable CuS phase.

[0029] Example 5 This embodiment provides a zinc-ion battery, whose negative electrode active material is a non-stoichiometric Cu prepared in Examples 1, 2, and 4. 2-x S.

[0030] Active material (Cu) 1.8 S, CuS), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added to the mixture to adjust the slurry. The slurry was then coated onto a stainless steel mesh, dried, rolled, and cut to obtain a working electrode with a diameter of 14 mm. A coin cell was assembled using 2 mol / L zinc sulfate and 0.2 mol / L manganese sulfate as electrolytes, and zinc sheets as counter and reference electrodes for electrochemical performance testing.

[0031] like Figure 4 Cu prepared at different temperatures 2-x S (in Cu) 1.8 As shown in the charge-discharge curves (taking S as an example), the reaction temperature directly affects the reduction conditions of the synthesis system, leading to certain differences in the crystallinity and Cu / S ratio of the products. Specifically, the materials synthesized at 80℃, 100℃, and 120℃ have initial discharge specific capacities of approximately 182.3 mAh / g, 170.4 mAh / g, and a relatively low value, respectively. Among these, the material synthesized at 120℃ exhibits the best crystallinity and the lowest initial discharge capacity; while the materials synthesized at 80℃ and 100℃ show higher initial discharge capacities. Figure 4 b shows Cu prepared at different temperatures 2-x The cycling stability of S was assessed, and the results showed that Cu synthesized at 100℃ was the most stable. 2-x The S material exhibits the best cycle stability, and its specific capacity does not show significant decay even after 100 charge-discharge cycles.

[0032] Figure 5 The comparison shown highlights the stoichiometric hexagonal CuS and the non-stoichiometric cubic CuS phases. 2-x S (in Cu) 1.8 Taking CuS as an example, the cycling performance of the negative electrode in a zinc-ion battery is shown. Hexagonal CuS exhibits a higher initial discharge capacity, but its cycling stability is weaker; after 100 cycles at a current density of 0.1 A / g, its specific capacity decreases to approximately 50 mAh / g. CuS in the cubic phase...1.8 Although S has a slightly lower initial capacity, it exhibits extremely excellent cycling stability. After the same number of cycles, its capacity retention rate is much higher than that of CuS, highlighting the substantial progress made by this invention in material design and performance optimization.

[0033] Figure 6 It shows the non-stoichiometric cubic phase Cu 2-x S (in Cu) 1.8 (Taking S as an example) The long-term cycling stability at a current density of 0.5 A / g was studied. The results show that the cycling curve of this material exhibits a typical activation and stabilization process: in the initial cycling stage, its reversible capacity underwent an activation and adjustment process of first increasing and then slightly decreasing; subsequently, the capacity entered a slow and stable plateau period. After 500 cycles, its specific capacity remained at approximately 105.2 mAh / g, demonstrating excellent long-term cycling stability and capacity retention. This further confirms that the cubic phase Cu prepared by the method of this invention... 1.8 The S-type anode material possesses long-term and stable zinc storage capacity even at high current densities, meeting the key requirements for battery cycle life in practical applications.

[0034] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A non-stoichiometric Cu anode for a zinc-ion battery 2-x The controllable preparation method of S is characterized by, Solution A is obtained by placing a copper source in an organic amine solvent that provides a weak reducing atmosphere; solution B is obtained by placing a sulfur source in an organic amine solvent that provides a weak reducing atmosphere; solutions A and B are mixed and subjected to a solvothermal reaction. By controlling the type and composition of the organic amine solvent and the reaction temperature, the strength of the weak reducing atmosphere can be controlled, thereby selectively synthesizing cubic Cu phases with different stoichiometric ratios x. 2-x S product; of which 0 <x<1。 2. The non-stoichiometric Cu of a zinc-ion battery negative electrode according to claim 1 2-x The controllable preparation method of S is characterized by, The organic amine solvent is one of N,N-dimethylformamide and ethylenediamine; the composition of the organic amine solvent is to add distilled water to the organic amine solvent to reduce its reducing properties.

3. The non-stoichiometric Cu of a zinc-ion battery negative electrode according to claim 1 2-x The controllable preparation method of S is characterized by, The solvothermal reaction temperature is 100-120°C, and the reaction time is 12 h.

4. The non-stoichiometric Cu of a zinc-ion battery negative electrode according to claim 1 2-x The controllable preparation method of S is characterized by, The copper source is copper nitrate, and the sulfur source is thiourea; the molar ratio of the copper source to the sulfur source is 1:

1.

5. The non-stoichiometric Cu of a zinc-ion battery negative electrode according to claim 1 2-x The controllable preparation method of S is characterized by, The solution A also contains a dispersant, which is polyvinylpyrrolidone, and its mass is 60% of the mass of the copper source.

6. A non-stoichiometric Cu anode for a zinc-ion battery 2-x S, characterized in that, It is prepared by any one of the preparation methods described in claims 1-5.

7. A non-stoichiometric Cu anode for a zinc-ion battery as described in claim 6 2-x Application of S in the preparation of zinc-ion batteries.

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