Method for regulating and controlling stability of high-load positive electrode material by hydrated nano-domain electrolyte

Abstract

The invention discloses a zinc sulfate-based hydrated nano-domain electrolyte regulated and controlled high-load positive electrode material. According to the electrolyte, ZnSO4 serves as electrolyte salt, sulfolane (SL) is introduced to construct a hydrated nano-domain system, and the nano-confinement effect of the system remarkably inhibits the molecular movement and proton delocalization phenomena. Meanwhile, an amphiphilic structure (hydrophilic-SO2-and hydrophobic carbocyclic rings) of SL is coordinated with Zn < 2 + > to form an SL-[Zn (H2O) 5] < 2 + > compound, the water activity is inhibited, side reactions are prevented, the wettability of the electrode material is improved, and Jahn-Teller distortion of high-load delta-MnO2 is effectively inhibited by a dynamically limited cathode interface. The electrolyte is prepared from environment-friendly and low-cost raw materials through a simple and large-scale process. The high-load water-based zinc ion soft package battery prepared on the basis of the zinc sulfate-based hydrated nano-domain electrolyte can still keep the specific discharge capacity of 100100mAh. G <-1 > after circulating for 2000 times under the harsh large current density of 2.5 A.g <-1 >, and successfully drives an LED lamp to operate, so that the excellent circulating stability and practical potential of the battery are fully verified. The invention provides an efficient and reliable electrolyte technical path for developing a high-load aqueous zinc ion battery which is high in performance, long in service life, low in cost and easy for large-scale production, and has a remarkable industrial application value.

Description

Technical Field

[0001] This invention relates to the field of battery electrolyte technology, and more particularly to an additive for functional electrolytes of aqueous zinc-ion batteries and a method for regulating the interface stability of high-load cathode materials using the additive. Background Technology

[0002] With the global emphasis on developing green and low-carbon energy, significant efforts have been made in exploring and utilizing advanced energy storage and conversion technologies. Aqueous zinc-ion batteries, due to their high safety, low cost, environmental friendliness, high energy density, and ideal redox potential, have demonstrated enormous application potential and have become a promising candidate material for next-generation energy storage systems. However, the commercialization of zinc-ion batteries still faces major obstacles: on the negative electrode side, interfacial instability leads to side reactions (such as self-corrosion, hydrogen evolution, and dendrite growth of the zinc negative electrode); on the positive electrode side, traditional weakly acidic electrolytes often dissolve the positive electrode material, especially for high-load positive electrode materials, resulting in more severe damage to their cycle stability. It is noteworthy that existing strategies often focus on negative electrode protection, while effective solutions for the stability problems of positive electrode materials (especially high-load positive electrodes) are relatively lacking. Therefore, it is urgent to formulate effective strategies and develop protection methods for high-load positive electrode materials to improve the overall performance of the battery.

[0003] Aqueous zinc-ion batteries (AZIBs) commonly use zinc salt solutions as electrolytes, such as ZnSO4, ZnCl2, Zn(CF3SO3)2, and Zn(CH3COO)2. Among these, ZnSO4 is the most widely used system due to its low cost, environmental friendliness, wide electrochemical window, and ease of preparation. However, ZnSO4 itself cannot completely suppress dendrite growth, hydrogen evolution corrosion, and dissolution and structural degradation of the high-load cathode in a weakly acidic environment. Electrolyte additive strategies have become a research hotspot. The main methods include adding heavy metal ions, which utilize a more negative potential in the ZnSO4 electrolyte to form an electrostatic shielding layer at the tip of the cathode to suppress dendrites. However, heavy metals pose risks of environmental pollution and high cost. Adding organic additives can adsorb onto the cathode surface, regulate zinc deposition and solvation structures, and suppress side reactions. However, these strategies have limited effectiveness against the severe interfacial side reactions, structural collapse, and ion transport limitations faced by high-load cathodes.

[0004] Amphiphilic additive molecules can interact simultaneously with hydrophilic components in the electrolyte and hydrophobic regions on the electrode surface. This promises to synergistically achieve multiple functions: while maintaining or even improving ionic conductivity, it can more effectively regulate zinc deposition and suppress negative electrode side reactions; more importantly, through directional adsorption or interface modification, it can provide a direct and robust protective barrier for high-load positive electrodes, thereby simultaneously stabilizing the battery electrode interface and providing a new strategy for solving key bottlenecks in ZnSO4-based AZIBs (especially high-load systems).

[0005] The structure and type of cathode material have a significant impact on the overall performance of the battery. Manganese oxides have attracted much attention due to their high capacity, high redox properties, and low toxicity. Among the various crystal forms of MnO2 (α-MnO2, β-MnO2, γ-MnO2, and δ-MnO2), layered δ-MnO2 is a highly attractive cathode material due to its open framework facilitating rapid ion insertion / extraction, high theoretical capacity, and abundant resources. However, meeting the high-load requirements of industrial applications still faces significant challenges: in weakly acidic ZnSO4 electrolytes, H... + Cooperative embedding triggers Mn 3+ Disproportionation dissolution leads to loss of active material and structural collapse. Simultaneously, the large electrode / electrolyte interface under high load exacerbates side reactions such as Mn dissolution, while the slow ion transport within the thickened electrode limits rate performance and capacity. Addressing the core challenges of structural collapse, interface deterioration, and limited transport in high-load δ-MnO2, this study introduces sulfolane (SL) based on amphiphilic molecular design to modulate the microenvironment of the ZnSO4 electrolyte, forming a unique hydrated nanodomain that demonstrates the potential to synergistically solve these problems. The hydrated nanodomain operates through multiple mechanisms: reducing free water contact with the δ-MnO2 surface, inhibiting H+ ion exchange, and reducing free water contact with the electrolyte. + It inhibits corrosion and Mn dissolution, protecting the framework stability; amphiphilic molecules are directionally adsorbed on the cathode surface to form an ordered interface layer, constructing a barrier to block corrosion and passivate side reactions; in addition, this structure may optimize ion channels or Zn 2+ Solvation structures (e.g., lowering the desolvation energy barrier) enhance Zn 2+ Improve the transport efficiency of the electrolyte body and the interface, and alleviate the transport bottleneck. Summary of the Invention

[0006] To address the key technical challenges of the aforementioned high-load cathode materials, this invention innovatively introduces SL additives to construct a hydrated nanodomain electrolyte system with a significant nano-confinement effect. The core of this system lies in achieving efficient regulation and protection of the high-load cathode material / electrolyte interface: (1) Suppressing interfacial side reactions and structural degradation: The hydrophilic -SO2- group of SL preferentially interacts with Zn. 2+ Coordination occurs, forming SL-[Zn(H2O)5] 2+ The complex structure significantly reduces the overall water activity of the electrolyte, and the confinement effect of the nanodomains strongly inhibits the movement of water molecules and protons (H+). + The delocalization phenomenon effectively suppresses side reactions such as dissolution caused by active water molecules at the interface of the high-load δ-MnO2 cathode, and significantly alleviates the Jahn-Teller distortion exacerbated by factors such as proton co-intercalation, thereby preventing the structural collapse of the high-load cathode material. (2) Improved interfacial compatibility and ion transport: The amphiphilic structure of SL significantly improves the wettability of the electrolyte to the highly loaded δ-MnO2 cathode material, optimizing the electrode / electrolyte contact. The optimized interfacial bonding with nanodomain characteristics is beneficial for ion (ZnO2) transport. 2+ H + Transport dynamics within and at the interface of high-load cathode materials. This invention prepares a hydrated nanodomain electrolyte by means of the following steps:

[0007] S1: Dissolve ZnSO4·7H2O in water to form a solution with a concentration of 2.0 mol·L⁻¹. -1 Solution A;

[0008] S2: Add 0.01–1.0 mol·L⁻¹ to the solution obtained in step S1. -1 SL;

[0009] S3: Stir at 25°C until the solution is clear and transparent.

[0010] According to the present invention, preferably, the concentration of ZnSO4 in the hydrated nanodomain electrolyte is 2.0 mol·L⁻¹. -1 The concentration of SL is 0.01–1.0 mol·L⁻¹. -1 .

[0011] The hydrated nanodomain electrolyte is used to regulate the high-load cathode material in an aqueous zinc-ion battery. The battery system comprises: a zinc foil as the negative electrode and δ-MnO2 as the positive electrode, with a loading of 10–40 mg·cm³. -2 The electrolyte consists of a separator and a hydrated nanodomain electrolyte. The battery configuration can be a coin cell or a pouch cell. A high-load pouch cell using this electrolyte achieves a capacity of 0.2 A·g. -1 The capacity is 913mAh·g -1 The cycle life exceeds 5000 cycles. Furthermore, the pouch battery exhibits a high CE (cycle efficiency) of 88% after 48 hours of self-discharge from a fully charged state, and maintains a cycle life of 2.5 A·g. -1 Achieving a long cycle life of 2000 continuous cycles, sufficient to power LED lights, fully demonstrates its excellent cycle stability and reliability in practical devices. Furthermore, the symmetrical cell with SL exhibits excellent cycle life at a current density of 1.0 mA·cm⁻¹. -2 / 1.0mAh·cm -2 At that time, it exhibited 5000h cycle stability compared to the battery without SL (690h). Attached Figure Description

[0012] Figure 1 The SAXS test spectrum and Guinier analysis fitting curve are shown for Example 1.

[0013] Figure 2 These are MD simulation snapshots and partially magnified snapshots of Example 1.

[0014] Figure 3 This is a radial distribution function graph for Example 1.

[0015] Figure 4 This is a SEM image of the δ-MnO2 cathode material.

[0016] Figure 5 The XRD patterns of δ-MnO2 in Example 1 and Comparative Example 1 are compared.

[0017] Figure 6 The contact angles of Example 1 and Comparative Example 1 on the δ-MnO2 electrode are shown.

[0018] Figure 7 The image shows the in-situ XRD pattern of the Zn||δ-MnO2 full cell during the charge and discharge process of Example 1.

[0019] Figure 8 The image shows the quasi-in-situ XPS Zn 2p spectrum of the Zn||δ-MnO2 full cell of Example 1.

[0020] Figure 9 The image shows the quasi-in-situ XPS Mn 3p spectrum of the Zn||δ-MnO2 full cell of Example 1.

[0021] Figure 10 The diagram shows the long-cycle performance of the Zn||δ-MnO2 pouch cell and the Zn||Zn symmetric cell in Example 1.

[0022] Figure 11 This is a photograph of an LED light powered by a Zn||δ-MnO2 soft-pack battery as shown in Example 1. Detailed Implementation

[0023] The technical solution and effects of the present invention will be further described below with reference to the embodiments. However, the specific methods, formulas and descriptions used are not intended to limit the present invention.

[0024] Example 1: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 0.3 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 20 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 100mg.

[0025] Comparative Example 1: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 0.0 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 20 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 100mg.

[0026] Example 2: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 0.01 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 10 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 50mg.

[0027] Example 3: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 0.1 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 15 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 75mg.

[0028] Example 4: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 0.5 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 30 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 150mg.

[0029] Example 5: A high-load zinc-ion battery based on zinc sulfate-based hydrated nanodomain electrolyte, comprising the following components: 2 mol·L⁻¹ -1 ZnSO4, 1.0 mol·L -1 The electrolyte was prepared using 50 ml of deionized water and 1 ml of zinc sheet. A 0.15 mm thick zinc sheet was used as the negative electrode, and glass fiber was used as the diaphragm. The loading was 40 mg / cm³. -2 δ-MnO2 is used as the positive electrode material. The assembled soft-pack zinc-ion battery has a total size of 10cm×8cm, the size of the positive electrode material is 2.0cm×2.5cm, and the total mass is 200mg.

[0030] Experimental Example 1: SAXS test performed on Example 1 ( Figure 1 The results showed that in the range of q = 0.10–0.15 nm -1 Characteristic scattering peaks exist within the range, and are present in the range of q = 0.18–0.25 nm. -1 Secondary scattering peaks are present, with a primary-to-secondary peak intensity ratio ≥ 1.5. Furthermore, SAXS analysis agrees with Guinier analysis, confirming the presence of hydrated nanodomains in the solution.

[0031] Experimental Example 2: Theoretical calculations were performed for Example 1, such as... Figure 2 As shown, the S=O group in SL partially replaces Zn. 2+ Radial distribution function (RDF) analysis of neighboring water atoms in the solvated shell ( Figure 3 This indicates that the addition of SL reduced the water coordination number from 5.0 to 4.1, and... The introduction of a new peak indicates that the reduction of solvated water effectively suppressed water-induced side reactions. This inhibitory effect is attributed to SL-[Zn(H2O)5]. 2+ The formation of complexes. This improved solvation structure not only lowers the dehydration energy barrier but also promotes improved interfacial mass transfer efficiency, ultimately enabling the material to exhibit stable cycling performance.

[0032] Experimental Example 3: Morphological Characterization of High-Load Electron Material - Scanning Electron Microscopy Images (as shown) Figure 4 As shown, spherical manganese dioxide typically has a large specific surface area, and due to its regular shape, it can reduce the non-uniformity of particle packing, which helps to improve the conductivity of the material.

[0033] Experimental Example 4: XRD pattern analysis of δ-MnO2 cathode material showed significant differences in stability in different electrolytes. Figure 5Comparative Example 1 exhibits significant peak broadening and intensity reduction, typical characteristics of structural degradation caused by manganese dissolution. In stark contrast, the δ-MnO2 in the electrolyte of Example 1 maintains almost the same diffraction pattern, indicating exceptionally excellent structural stability. This stabilizing effect stems from the steric barrier formed by the hydrophobic framework in the hydrated nanodomain structure, effectively preventing H... + / H2O penetration into vulnerable manganese-oxygen bonds. Contact angle measurements showed a sharp drop from 103.6° in Comparative Example 1 to 54.3° in Example 1. Figure 6 This directly demonstrates the significant improvement in electrolyte wettability. This transformation stems from the preferential adsorption of hydrophilic -SO2- groups on the δ-MnO2 surface, forming an ordered monolayer structure that both reduces the solid-liquid interfacial energy and promotes ion transport.

[0034] Experimental Example 5: In-situ XRD and quasi-in-situ XPS analyses reveal the role of hydrated nanodomain structures in regulating Zn in δ-MnO2 cathodes. 2+ The crucial role of embedding in chemical reactions. For example... Figure 7 As shown, the (001) diffraction peak undergoes a completely reversible shift from 12.6° to 12.3° during discharge, corresponding to an increase in interlayer spacing, and returns to its initial position during charging. This significant structural reversibility indicates that the hydrated nanodomain structure has an effective stress buffering capacity during electrochemical cycling. Zn 2p XPS spectrum ( Figure 8 This directly proves that Zn is reversible. 2+ The intensity change of the (de)intercalation process is related to Mn 4+ / Mn 3+ Dynamic redox transitions between states ( Figure 9 This aligns with the results. The ordered interface layer and the confined aquatic environment effectively suppressed H... + Erosion and Mn dissolution ensure the structural integrity and electrochemical reversibility of the cathode material, ultimately achieving stable cycle performance.

[0035] Experimental Example 6: Assembly of a soft-pack full cell Zn||δ-MnO2 in Example 1 at 2.5 A·g -1 Long-term cycling tests were conducted under these conditions, and the Zn||δ-MnO2 pouch cell performed at 2.5 A·g -1 It can still maintain 100 mAh·g after undergoing 2000 charge-discharge cycles at high current density. -1 The discharge capacity is such that its cycle efficiency (CE) still reaches 100%. Figure 10 Symmetric cells at 1.0 mA·cm -2 / 1.0mAh·cm -2 At that time, it exhibited 5000h cycle stability compared to the battery without SL (690h).

[0036] Experimental Example 7: Using two Zn||δ-MnO2 cells assembled in Example 1 to light an LED ( Figure 11 This provides strong technical verification for the practical application of hydrated nanodomain electrolytes in real-world scenarios.

[0037] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for regulating the stability of highly loaded cathode materials using a hydrated nanodomain electrolyte, characterized in that, Includes: concentration of 2.0 mol·L -1 ZnSO4, with a concentration of 0.01–0.1 mol·L⁻¹. -1 SL, deionized water.

2. The hydrated nanodomain electrolyte according to claim 1, characterized in that, Includes the following steps: (1) Dissolve ZnSO4·7H2O in water to form a solution with a concentration of 2.0 mol·L⁻¹. -1 The solution; (2) Add SL to the solution obtained in step (1) at a concentration of 0.01–0.1 mol·L⁻¹. -1 ; (3) Stir at 25°C until the solution is clear and transparent.

3. A regulation mechanism for a stable high-load cathode material electrolyte, characterized in that, The cathode material / electrolyte interface is controlled using the hydrated nanodomain electrolyte as described in claim 1 or 2, including: through SL and Zn 2+ Coordination to form SL-[Zn(H 2 O) 5 ] 2+ The complex reduces the water activity of the electrolyte; it forms nano-confined domains at the positive electrode interface to inhibit H2O. + Erosion and Mn dissolution; improve the wettability of the electrolyte to the cathode material and optimize ion transport kinetics.

4. An aqueous zinc-ion battery, comprising a negative electrode, a positive electrode, a separator, and an electrolyte, characterized in that: The electrolyte is the hydrated nanodomain electrolyte as described in claim 1 or 2, the negative electrode is a zinc sheet with a thickness of 0.15 mm, the diaphragm is glass fiber, and the positive electrode has a loading of 10–40 mg·cm³. -2 The battery is a soft-pack battery with a positive electrode material size of 2.0cm×2.5cm, a total mass of 50~200mg, and an overall size of 10cm×8cm.

5. The aqueous zinc-ion battery according to claim 4, characterized in that, At 2.5A·g -1 After 2000 cycles at current density, the discharge specific capacity reaches 100 mAh·g. -1 .

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