Nanostmctured electrolyte additive containing metal monatomic sites and use thereof for stabilizing metal negative electrodes

Abstract

The application belongs to the technical field of metal battery electrolyte, and particularly discloses a nano-structured electrolyte additive containing metal monatomic sites and application thereof in stabilizing metal negative electrodes. The nano-structured electrolyte additive containing metal monatomic sites is a nano-structured carbon material, and the metal monatomic sites in the nano-structured electrolyte additive are one or more of Co, Zn, Cu, Mn, Ni, Bi, Fe and Sn, which are uniformly dispersed at an atomic level in the nano-structured carbon material. The additive can be selectively adsorbed on the metal surface during metal deposition, wherein the metal monatomic sites have good metal affinity and electron enrichment capacity, can improve the interface environment between the electrolyte and the electrode, promote the uniform distribution of the space electric field and the ion concentration field, make the deposition process more uniform, and effectively solve the problems of dendrite growth and competitive side reactions. The adsorbed nano additive during metal deposition in the application can be dispersed into the electrolyte during stripping, and the dynamic adjustment process can realize the long-term cycle stability and safety of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal battery electrolytes, and more specifically, relates to a nanostructured electrolyte additive containing metal single atom sites and a user-stable metal negative electrode thereof. Background Art

[0002] The rapid development of electronic technology and the active construction of new energy systems have put forward higher performance requirements for energy storage devices. The current commercial lithium-ion batteries have already approached their theoretical capacity and cannot meet the rapidly growing energy storage needs. Thanks to the high theoretical capacity of metal anodes (for example, lithium: 3860 mAh g -1 , zinc: 820 mAh g -1 ), rechargeable metal batteries are expected to achieve capacity breakthroughs. However, problems such as dendrite growth and competing side reactions faced by metal anodes have become major obstacles to their large-scale application. Currently, the technical routes adopted for stabilizing metal anodes include electrode structure design, surface coating construction, multifunctional separator design, and electrolyte composition optimization. Among them, the use of electrolyte additives has shown great practical application potential due to its simplicity and efficiency. In existing technologies, the regulation of metal deposition by electrolyte additives is mostly based on continuous consumption, which reduces the reliability of additives in long-term cycles. Therefore, there is an urgent need to develop electrochemically inert electrolyte additives to achieve sustainable regulation of metal deposition and improve the safety of metal batteries throughout their life cycle. Metal single-atom active sites have good metal affinity, and atomic-scale dispersion maximizes their utilization. At present, metal surface coatings constructed with metal single-atom active sites promote the uniform distribution of nucleation dynamics, ion fields, and spatial electric fields, and have achieved good results in stabilizing metal anodes. At the same time, these metal single-atom materials exhibit electrochemical inertness in the process of stabilizing metal anodes. Therefore, metal single-atom materials have great potential for constructing efficient and sustainable electrolyte additives, but there are currently few related reports. Summary of the Invention

[0003] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a nanostructured electrolyte additive containing metal single-atom sites for stabilizing metal negative electrodes. The present invention directly adds carbon nanomaterials containing metal single-atom sites to the electrolyte of a metal battery, and utilizes the good affinity of metal single-atom carbon nanomaterials to the metal negative electrode to achieve preferential adsorption on the surface of the metal negative electrode. Furthermore, the atomically dispersed metal single-atom active sites exhibit strong metal affinity and electron enrichment capabilities, improve the interface environment between the electrode and the electrolyte, and promote the uniform distribution of the spatial electric field and ion concentration field, so as to achieve the excellent effect of inhibiting dendrite growth and the occurrence of side reactions.

[0004] To achieve the above objectives, according to one aspect of the present invention, a nanostructured electrolyte additive containing metal single atom active sites is proposed, wherein the nanostructured additive is a nanocarbon material, and the metal single atom sites in the nanocarbon material are one or more of Co, Zn, Cu, Mn, Ni, Bi, Fe, and Sn, which are uniformly dispersed at the atomic level in the nanocarbon material.

[0005] As a further preference, the nanostructured electrolyte additive containing metal single atom sites has good electrochemical inertness during the electrolyte and metal deposition process, and the additive can form a suspension when added to the metal battery electrolyte.

[0006] According to another aspect of the present invention, a method for preparing an electrolyte containing a nanostructured additive having metal single atom active sites is provided, comprising the following steps.

[0007] Step 1: Add soluble electrolyte salt to the solvent to prepare a basic electrolyte solution.

[0008] Step 2: After the base electrolyte is stabilized, add a nanostructured additive containing metal single atom active sites and disperse the additive in the electrolyte through ultrasonic and magnetic stirring.

[0009] According to another aspect of the present invention, a metal battery electrolyte is provided, which includes an electrolyte salt, a solvent, and the nanostructured electrolyte additive containing metal single atom active sites according to claim 1.

[0010] As further preferred, the concentration of the nanostructured electrolyte additive containing metal single atom active sites in the electrolyte is 0.1-5.0 mg / mL.

[0011] As further preferred, the electrolyte salt is one or more of ZnSO4, Zn(CH3COO)2, ZnCl2, Zn(NO3)2, ZnF2, Zn(CF3SO3)2, Zn(TFSI)2, Zn(BF4)2, LiTFSI, LiFSI, LiPF6, LiBF4, LiClO4, LiBOB, LiDFOB, NaTFSI, NaFSI, NaClO4, KPF6, KFSI, and FTFSI, and the concentration of the electrolyte salt in the electrolyte is 0.5~5.0 mol / L.

[0012] As further preferred, the solvent is one or more of water, 1,3-dioxolane, ethyl methyl carbonate, fluoroethylene carbonate, methyl fluoroacetate, propyl fluoroacetate, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate.

[0013] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technologies.

[0014] 1. The nanostructured electrolyte additive containing single-atom metal active sites described herein has a strong affinity for metal anodes and preferentially adsorbs onto metal surfaces during metal deposition. Furthermore, the atomically dispersed single-atom active sites in the additive exhibit strong metal ion binding and electron enrichment capabilities, significantly improving the interface between the electrode and electrolyte, inducing a uniform spatial electric field and ion concentration distribution, and promoting uniform metal distribution.

[0015] 2. The nanostructured electrolyte additive containing metal single-atom active sites described in this invention exhibits electrochemical inertness in metal battery electrolytes and during metal deposition. This prevents irreversible consumption of the additive during metal deposition / stripping, ensuring the long-term stability of the additive's regulatory function.

[0016] 3. The nanostructured additive containing metal single-atom active sites in the electrolyte of the present invention can preferentially adsorb onto the metal surface during metal deposition. Furthermore, during metal stripping, the adsorbed additive can be redispersed into the electrolyte, maintaining its concentration in the electrolyte essentially unchanged. This electrolyte additive dynamically adjusts to the complex and ever-changing metal deposition conditions. Therefore, the electrolyte additive provided by the present invention can achieve long-term battery cycling stability and safety.

[0017] 4. The method of the present invention using a nanostructured electrolyte additive containing metal single-atom active sites to stabilize the metal negative electrode has the characteristics of simple process, low cost, high efficiency and long-term performance. It can not only effectively promote the uniform deposition of metals, but also achieve dynamic and sustainable regulation, meeting the requirements of large-scale promotion and practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Graph showing the coulombic efficiency of Zn||Cu asymmetric cells assembled using the electrolytes of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4;

[0019] Figure 2The time-voltage curves of the Zn||Zn symmetric battery assembled using the electrolytes in Example 1 and Comparative Example 2 under the test conditions of 1 mA cm-2 and 1 mAh cm-2;

[0020] Figure 3 Scanning electron microscope images of the Zn electrode of the Zn||Zn symmetric battery assembled using the electrolytes in Example 1 (Figure a) and Comparative Example 2 (Figure b) after cycling for 200 h;

[0021] Figure 4 The time-voltage curves of the Zn||Zn symmetric battery assembled using the electrolytes in Example 1 and Comparative Example 2 under the test conditions of 10 mAcm-2 and 2.5 mAhcm-2. Implementation Method

[0022] In order to more clearly express the purpose, technical solutions and advantages of the present invention, the present 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 only used to explain the present invention, but are not used to limit the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The raw materials and reagents used in this example can be obtained from commercial sources or prepared by known methods.

[0024] Example 1

[0025] 1. Preparation of additives.

[0026] The preparation method of the additive in this embodiment includes the following steps.

[0027] Step 1: Dissolve a certain amount of ammonium citrate and metal cobalt salt in deionized water to form a uniform solution; then, remove excess water using vacuum freeze-drying technology to obtain a precursor powder.

[0028] Step 2: The precursor obtained in step 1 is carbonized under a N2 atmosphere, and then the carbonized product is acid-washed and dried for later use.

[0029] Step 3: The carbonized product obtained in step 2 is annealed in an NH3 atmosphere to obtain a nanocarbon material containing a Co single atom site.

[0030] 2. Preparation of electrolyte.

[0031] ZnSO₄·7H₂O was dissolved in deionized water to prepare a 2 mol / L ZnSO₄ electrolyte. Once the electrolyte stabilized, the aforementioned nanostructured additive containing Co single-atom active sites was added at a concentration of 0.5 mg / mL. Ultrasonic dispersion was performed for 2 hours, followed by magnetic stirring overnight to obtain the desired electrolyte (labeled as ZSO-CoSA / C-0.50 electrolyte).

[0032] Example 2

[0033] In this example, a similar parallel experiment was conducted as in Example 1, wherein the metal Co salt was replaced with a metal Mn salt. Other preparation methods were identical to those in Example 1, and an electrolyte containing a nanostructured additive with Mn single-atom active sites was obtained.

[0034] Example 3

[0035] In this example, a similar parallel experiment was conducted as in Example 1, wherein the metal Co salt was replaced with a metal Fe salt. The other preparation methods were exactly the same as in Example 1, and an electrolyte containing a nanostructured additive with Fe single-atom active sites was obtained.

[0036] Example 4

[0037] 1. Preparation of additives.

[0038] The preparation method of the additive in this embodiment is the same as that in Example 1.

[0039] 2. Preparation of electrolyte.

[0040] LiTFSI and LiNO₃ were dissolved in a 1:1 volume ratio of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) to create an electrolyte solution containing 1 mol / L LiTFS and 2 wt% LiNO₃. Once the electrolyte stabilized, the aforementioned nanostructured additive containing Co single-atom active sites was added at a concentration of 0.5 mg / mL. Ultrasonic dispersion was performed for 2 hours, followed by magnetic stirring overnight to obtain the desired electrolyte.

[0041] Example 5

[0042] 1. Preparation of additives.

[0043] The preparation method of the additive in this embodiment is the same as that in Example 2.

[0044] 2. Preparation of electrolyte.

[0045] LiPF6 and fluoroethylene carbonate (FEC) were dissolved in a mixed solvent of EC, EMC, and dimethyl carbonate (DMC) (mass ratio 4:3:3) to create an electrolyte solution containing 1 mol / L LiPF6 and 2 wt% FEC. Once the electrolyte stabilized, the aforementioned nanostructured additive containing single-atom Mn active sites was added at a concentration of 0.5 mg / mL. Ultrasonic dispersion was performed for 2 hours, followed by magnetic stirring overnight to obtain the desired electrolyte.

[0046] Example 6

[0047] 1. Preparation of additives.

[0048] The preparation method of the additive used in this embodiment is the same as that in Example 3.

[0049] 2. Preparation of electrolyte.

[0050] NaClO₄ was dissolved in a 1:1 volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) to create a 1 mol / L NaClO₄ electrolyte. Once the electrolyte stabilized, the aforementioned nanostructured additive containing single-atom Mn active sites was added at a concentration of 0.5 mg / mL. Ultrasonic dispersion was performed for 2 hours, followed by magnetic stirring overnight to obtain the desired electrolyte.

[0051] Comparative Example 1

[0052] This comparative example was subjected to a similar parallel experiment as Example 1.

[0053] 1. Preparation of additives.

[0054] The additive used in this comparative example is the additive of Example 1 after acid treatment (concentrated HCl and concentrated HNO3 are mixed in a volume ratio of 3:1), and the following steps are included.

[0055] Step 1: Mix concentrated HCl and concentrated HNO3 in a volume ratio of 3:1 to prepare a mixed acid.

[0056] Step 2: Add the additive containing Co single-atom active sites in Example 1 to the mixed acid obtained in Step 1, stir magnetically for 24 h, wash with deionized water several times, and vacuum dry to obtain.

[0057] 2. Preparation of electrolyte.

[0058] The preparation method of the electrolyte was the same as that of Example 1 (labeled as ZSO-C-0.50 electrolyte).

[0059] Comparative Example 2

[0060] In this comparative example, ZnSO4·7H2O was dissolved in deionized water to prepare a 2 mol / L ZnSO4 electrolyte, thereby obtaining the desired comparative electrolyte (labeled as ZSO electrolyte).

[0061] Comparative Example 3

[0062] This comparative example was subjected to a similar parallel experiment as Example 1, wherein the concentration of the nanostructured additive containing Co single-atom active sites was 0.25 mol / L, and the other preparation methods were exactly the same as in Example 1 to obtain an electrolyte containing a nanostructured additive containing Co single-atom active sites (labeled as ZSO-CoSA / C-0.25 electrolyte).

[0063] Comparative Example 4

[0064] This comparative example was subjected to a similar parallel experiment as Example 1, wherein the concentration of the nanostructured additive containing Co single-atom active sites was 1.00 mol / L, and the other preparation methods were exactly the same as in Example 1 to obtain an electrolyte containing the nanostructured additive containing Co single-atom active sites (labeled as ZSO-CoSA / C-1.00 electrolyte).

[0065] Electrochemical performance tests were conducted on CR2032 button-type batteries at 25°C. Commercial zinc foil (purity >99.99%, thickness 0.1 mm) and copper foil (purity >99.99%, thickness 0.2 mm) were cut into discs as zinc and copper electrodes, respectively. Commercial glass fiber was used as the separator. Zn||Cu asymmetric cells were assembled using the electrolytes obtained in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. The electrolyte addition amount was 80 μL. At 1 mA cm -2 The cycling stability was tested by discharging at a current density of 100V for 1 h and then charging to 0.5V. Figure 1 As shown in the figure, the Zn||Cu asymmetric battery can be stably cycled for 800 times in the electrolyte of Example 1 and exhibit a coulombic efficiency of up to 99.42%. In contrast, the Zn||Cu asymmetric battery can only be stably cycled for 112 times and 342 times in the electrolyte of Comparative Example 1 and Comparative Example 2. In addition, compared with Comparative Example 1 (38.4 mV) and Comparative Example 2 (65.8 mV), the Zn||Cu asymmetric battery can be stably cycled for 800 times and exhibit a coulombic efficiency of up to 99.42%. 2+The electrolyte deposited in Example 1 exhibits the lowest nucleation voltage (28.5 mV). This shows that the addition of the additives of the present invention can effectively reduce the nucleation voltage and improve the cycle life of the battery. At the same time, comparing the performance of the Zn||Cu asymmetric battery in the electrolytes of Example 1, Comparative Example 3, and Comparative Example 4, it can be seen that the cycle stability of the asymmetric battery using the electrolytes of Comparative Example 3 and Comparative Example 4 has significantly decreased. This is because the use of too little additive reduces the coverage of the Co single-atom active site on the electrode surface, while the excessive use of additives reduces the deposition kinetics of the metal.

[0066] The electrolytes obtained in Example 1 and Comparative Example 1 were used to further assemble Zn||Zn symmetrical batteries for cycle performance testing. Figure 2 As shown, at 1 mA cm -2 Under the test conditions of continuous charge and discharge at a current density of 1 h each, the symmetrical battery using the electrolyte of Example 1 can stably cycle for 2000 h, which far exceeds that of the comparative example 1. The scanning electron microscope images of the zinc electrode after cycling in different electrolytes are shown in FIG. Figure 3 As shown, Figure 3 a is the zinc electrode after circulating in the electrolyte containing additives for 200 h. Figure 3 b is a zinc electrode cycled in an electrolyte without additives. The results show that after cycling in an electrolyte with additives, the surface of the zinc electrode is flat and uniform, with no obvious dendrites. In an electrolyte without additives, the zinc electrode presents an uneven surface, indicating that it has experienced severe dendrite growth during the cycling process. Figure 4 As shown, at 10 mA cm -2 The deposition capacity is 2.5 mAh cm at a current density of -2 The stable cycle time of the symmetric cell using the electrolyte of Example 1 was 1600 h, more than 20 times that of the asymmetric cell using the electrolyte of Comparative Example 1. This demonstrates the reliability of the additive in regulating high current density and large capacity. Precisely because the nanostructured additive of the present invention preferentially adsorbs on the surface of the metal negative electrode during deposition, the metal single-atom active sites with strong metal affinity and electron-enrichment capacity can improve the interface environment between the electrode and the electrolyte, promoting the uniform distribution of the spatial electric field and ion concentration field, thereby suppressing dendrite growth and side reactions and achieving uniform metal deposition.

[0067] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present invention, but the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An electrolyte additive containing a nanostructure of metal single atom sites, characterized in that: The nanostructured additive is a nanocarbon material, which contains metal single-atom active sites. The metal single-atom sites are one or more of Co, Zn, Cu, Mn, Ni, Bi, Fe, and Sn, which are uniformly dispersed at the atomic level in the nanocarbon material. The concentration of the additive in the electrolyte is 0.1-5.0 mg / mL.

2. The electrolyte additive comprising a nanostructure containing metal single atom sites according to claim 1, wherein: The electrolyte additive containing a nanostructure of a metal single atom site is electrochemically inert in both the electrolyte and the metal deposition process, and the additive is directly added to the metal battery electrolyte to form a suspension.

3. An electrolyte for a secondary rechargeable metal battery, characterized in that: The electrolyte comprises an electrolyte salt, a solvent, and an electrolyte additive having a nanostructure containing metal single atom sites according to any one of claims 1 to 2.

4. The electrolyte according to claim 3, characterized in that The preparation method comprises the following steps: Step 1: Add a soluble electrolyte salt to a solvent to prepare a basic electrolyte solution; Step 2: After the base electrolyte is stabilized, add a nanostructured additive containing metal single atom active sites and disperse the additive in the electrolyte through ultrasonic and magnetic stirring.

5. The electrolyte according to claim 3, characterized in that The electrolyte salt is one or more of ZnSO4, Zn(CH3COO)2, ZnCl2, Zn(NO3)2, ZnF2, Zn(CF3SO3)2, Zn(TFSI)2, Zn(BF4)2, LiTFSI, LiFSI, LiPF6, LiBF4, LiClO4, LiBOB, LiDFOB, NaTFSI, NaFSI, NaClO4, KPF6, KFSI, and FTFSI, and the concentration of the electrolyte salt in the electrolyte is 0.5~5.0 mol / L.

6. The electrolyte according to claim 3, characterized in that The solvent is one or more of deionized water, 1,3-dioxolane, ethyl methyl carbonate, fluoroethylene carbonate, methyl fluoroacetate, propyl fluoroacetate, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate.

Images