Bulk reconstituted metal foil negative electrode and preparation and use thereof

Abstract

The application belongs to the field of battery materials, and specifically discloses a method for phase reconstruction of a metal foil negative electrode, which comprises the following steps: heat treating a metal foil under the assistance of plasma to obtain a metal foil negative electrode with phase reconstruction; the metal elements of the metal foil include at least one of Cu, Sn, Al, Zn, Mg and Ca; the temperature of the heat treatment is greater than or equal to 0.65T and less than 1T, wherein T is the melting point temperature of the metal foil; and the atmosphere in the heat treatment stage contains at least one of CH4, O2, N2, NH3, CO, CO2 and H2 functional gases. The application also includes the material prepared by the preparation method and the application of the material in batteries. The process can realize the phase modification of the metal foil and improve the performance of the prepared material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of battery materials, and particularly relates to the technical field of modification of metal foil negative electrodes. BACKGROUND

[0002] In order to avoid the energy and environmental crisis caused by the over-consumption of traditional fossil resources, it is urgent to supply renewable clean energy from sources such as solar, wind, biomass, waterfalls, and geothermal energy. However, due to the limitations of time and space and geographical conditions, the electrical energy generated from these sources is usually intermittent, and a high-efficiency and stable energy storage system is needed to store it for grid applications. Compared with traditional mechanical energy storage systems (pumped storage, gravity storage and compressed air storage systems, etc.), electrochemical energy storage has the advantages of flexible assembly, not restricted by terrain and climate, high energy density, large power, rapid response, etc., and can meet the future needs of a wide range of energy storage applications from wearable / portable electronic devices to large-scale stationary energy storage systems.

[0003] Water-based metal-ion batteries have been found to fully meet the requirements of large-scale energy storage systems. Due to the non-flammable characteristics of using aqueous electrolyte, and the ion transmission speed of water-based electrolyte is faster than that of organic electrolyte, water-based metal-ion batteries have become a research hotspot for large-scale energy storage systems. Although there have been a large number of related research works dedicated to the development of high-performance water-based metal-ion batteries, it is still far from realizing the commercial application of water-based metal-ion batteries, and there are still some important scientific problems to be solved. The dendrites caused by the non-uniform deposition and stripping of the metal negative electrode surface will directly induce internal short circuit of the battery, thereby causing the battery to fail. In addition, the non-uniform dissolution of the surface in the first stripping step of the metal negative electrode will cause the formation of holes or cracks. Due to the exposure of the inner surface with high local activity, the uncontrollable dendrite growth and side reactions are intensified on this non-uniform surface. At present, the main optimization strategy for the metal negative electrode is the traditional surface modification, which makes the electric field and ion field uniform, such as constructing an electron guiding layer and an ion guiding layer. Due to the huge volume change and irreversible zinc loss in the solid-liquid conversion process, the gap formed between the protective layer and the zinc surface is inevitable. Therefore, the protective layer will be split and separated from the surface after repeated stripping, resulting in the loss of the protective effect of the protective layer on the negative electrode. Since the working mechanism of the intercalation electrode of lithium ion battery is the solid-solid conversion insertion / desorption process, the construction of the solid electrolyte interphase on the electrode surface can effectively improve the reversibility of the lithium ion battery. However, due to the inevitable solid-liquid separation in the repeated stripping / deposition process, the introduction of the interface layer on the metal surface may not be suitable for the long-term protection of the negative electrode. In addition, due to the polarization and weak corrosion in the water electrolyte, the coulombic efficiency in the deposition / stripping reaction is always less than 100%, which leads to the formation of a "fresh" surface after each stripping process. After deep stripping, the fresh surface without a protective layer cannot hinder the growth of dendrites and side reactions due to the serious damage to the surface. Therefore, only optimizing the surface should not be enough to provide long-term protection for the metal negative electrode. It is necessary to establish a surface with strong resistance to dendrites and side reactions in the negative electrode interior / surface through a bulk modification strategy. SUMMARY

[0004] In view of the problem that the electrochemical performance of the metal foil negative electrode is not ideal, the first object of the present application is to provide a method for bulk reconstruction of a metal foil negative electrode, which aims to prepare a metal foil negative electrode with excellent electrochemical performance.

[0005] The second object of the present application is to provide a bulk-reconstructed metal foil negative electrode prepared by the method and its application in metal batteries.

[0006] The third object of the present application is to provide a battery comprising the bulk-reconstructed metal foil negative electrode.

[0007] Repeated peeling of the surface damage caused by solid-liquid transformation is the main problem leading to dendritic growth and side reactions, affecting the electrochemical performance of metal foil negative electrode. In view of this industry problem, some improvement ideas of metal foil are provided in the industry, but mainly stay at the surface treatment level of metal foil, so it is still difficult to adapt to the use demand of negative electrode, and cannot resist the interface damage caused by repeated cycling of negative electrode. In view of this industry problem, the present application first proposes a body phase reconstruction idea in the industry, however, early research found that inappropriate body phase reconstruction process not only is difficult to construct suitable body phase sites and interface adaptability, but also easily damages the original structure of metal foil, affecting the performance of negative electrode. Based on this, the present application provides the following improvement scheme:

[0008] A method for body phase reconstruction of metal foil negative electrode, the metal foil is heat treated under plasma assistance to obtain a body phase reconstructed metal foil negative electrode;

[0009] The metal elements of the metal foil include at least one of Cu, Sn, Al, Zn, Mg and Ca;

[0010] The temperature of the heat treatment is greater than or equal to 0.7T and less than 1T, and T is the melting point temperature of the metal foil;

[0011] The atmosphere in the heat treatment stage contains at least one of CH4, O2, N2, NH3, CO, CO2 and H2.

[0012] The present application innovatively performs heat treatment under plasma assistance, based on the combination of plasma treatment and heat treatment, further cooperates with the joint control of the conditions such as temperature and atmosphere of the treatment, cooperatively reconstructs the body phase of the metal foil, in-situ constructs the body phase active sites, improves the adaptability between the interfaces, and then effectively relieves the interface damage in the repeated cycling process, and improves the electrochemical performance of the prepared metal foil negative electrode.

[0013] In the present application, the metal foil can be a commercial metal foil material, which can be a metal plane material.

[0014] In the present application, the thickness of the metal foil has no special requirement, which can meet the application demand of metal foil negative electrode, for example, the thickness of the metal foil is greater than or equal to 35 microns, preferably greater than or equal to 50 microns, further preferably 50-200 microns, and more preferably 50-100 microns.

[0015] In the present application, before the plasma-assisted heat treatment, the metal foil can be pretreated by existing conventional means, including polishing and / or cleaning.

[0016] In the present application, the plasma treatment and the heat treatment are innovatively combined, which can improve the lattice vibration, improve the body phase reconstruction effect, construct the body phase active site, and improve the interface adaptation uniformity, thereby improving the electrochemical performance of the metal foil.

[0017] In the present application, the plasma-assisted heat treatment process can be carried out in a reaction furnace with a plasma device.

[0018] In the present application, the plasma conditions and the temperature of the plasma-assisted heat treatment stage are controlled, which helps to further improve the body phase reconstruction effect and the electrochemical performance of the metal foil after treatment.

[0019] In the heat treatment stage, the plasma power is less than or equal to 300W, preferably less than or equal to 250W, further preferably 50-220W, and more preferably 100-200W.

[0020] The flow rate of the plasma atmosphere is greater than or equal to 5sccm, preferably greater than or equal to 20sccm, further preferably 25-60sccm, and more preferably 25-40sccm.

[0021] In the present application, the heat treatment is assisted by plasma, and the temperature is controlled at 0.8-0.99 times (preferably 0.9-0.98 times) of the melting point of the metal foil, which helps to construct the body phase structure and interface suitable for the metal foil negative electrode, and further improves the performance of the metal foil after treatment.

[0022] In the preferred embodiment of the present application, the metal foil is a zinc foil, and the temperature in the heat treatment stage is 350-410℃, further preferably 370-410℃. The metal foil is an aluminum foil, and the preferred heat treatment temperature is 600-650℃.

[0023] In the present application, based on the innovative plasma-assisted heat treatment process and the joint control of functional gas, the active site suitable for the metal foil body phase can be constructed. For example, when the functional gas is nitrogen, the nitride active site of the metal can be constructed in the body phase based on the joint process.

[0024] In the present application, dilution gas such as Ar can also be added to the atmosphere in the heat treatment stage.

[0025] In the present application, the heat treatment time under the assistance of plasma is 0.5-10h, further preferably 1-8h, and more preferably 3-5h.

[0026] The present application also provides a body phase reconstructed metal foil negative electrode prepared by the method.

[0027] In the present application, the active sites, such as metal nitrides, carbides, etc., are dispersed in-situ in the restructured metal foil. Preferably, the depth of the bulk phase restructuring can be 10-40% of the thickness of the metal foil.

[0028] The present application also provides an application of the bulk phase restructured metal foil negative electrode prepared by the method, which is used as a negative electrode for preparing a metal battery, preferably for preparing a metal aqueous battery.

[0029] The present application also provides a metal battery using the bulk phase restructured metal foil negative electrode prepared by the method as a negative electrode.

[0030] In the present application, the metal foil negative electrode treated by the method can be assembled into a desired metal battery based on existing means.

[0031] In the present application, the bulk phase restructured metal foil provided by the present application can significantly improve the metal deposition / stripping reversibility and alleviate the side reactions when used as a negative electrode material for an aqueous metal ion battery. For example, the metal negative electrode with abundant high metal affinity sites in the bulk phase can still provide a uniform and high metal affinity surface after repeated cycles or deep stripping, solving the problem of surface damage caused by solid-liquid transformation after the cycle of the conventional surface optimized metal negative electrode, and providing persistent dendrite inhibition protection for the metal negative electrode.

[0032] Compared with the prior art, the present application has at least the following advantages:

[0033] (1) The present application innovatively performs heat treatment under plasma assistance, and based on the combination of plasma treatment and heat treatment and the joint control of parameters such as temperature, atmosphere, etc., the synergy can be improved, the bulk phase restructuring of the metal foil can be realized, the abundant high affinity active sites can be constructed in-situ in the bulk phase, the interface adaptability can be improved, and the metal foil negative electrode after treatment can be adapted to the needs of the metal foil negative electrode application, and the electrochemical performance of the metal foil negative electrode after treatment can be improved.

[0034] (2) The bulk phase restructured metal foil material obtained by the present application is applied to the negative electrode material of an aqueous metal ion battery, and excellent electrochemical performance is obtained. The defects of the short-term metal negative electrode protection of the conventional metal negative electrode surface optimization strategy are alleviated.

[0035] (3) The process of the present application is simple and easy to realize industrial large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 XRD pattern of the zinc foil processed by plasma and heat treatment at different temperatures and times.

[0037] Figure 2 XPS etching curve of the bulk phase restructured zinc foil in Example 1.

[0038] Figure 3 XRD, XPS and Raman plots of bulk restructured zinc foil in Example 1 at different electro-polishing depths.

[0039] Figure 4 Cycle charge-discharge plots of bulk restructured zinc foil anodes in Example 1.

[0040] Figure 5 XPS and Raman plots of bulk and surface restructured zinc foil after 50 cycles.

[0041] Figure 6 XRD plots of surface optimized zinc foils in Comparative Examples 1, 2 and 3.

[0042] Figure 7 XPS etching plots of surface optimized zinc foils in Comparative Examples 1, 2 and 3.

[0043] Figure 8 XPS and Raman plots of surface optimized zinc foils in Comparative Examples 1 and 2 at different electro-polishing depths.

[0044] Figure 9 Cycle charge-discharge plots of surface optimized zinc foil anodes in Comparative Examples 1 and 2.

[0045] Figure 10 XPS etching plots of surface optimized aluminum foil in Comparative Example 4

[0046] Figure 11 Cycle charge-discharge plots of optimized aluminum foil anodes in Example 4 and Comparative Example 4. DETAILED DESCRIPTION

[0047] Example 1

[0048] Step (1): A 50 pm commercial zinc foil was polished several times by sandpaper and cleaned several times with alcohol and deionized water, and then cut into a zinc sheet of 10 x 3 cm in size after natural air drying.

[0049] Step (2): The zinc sheet obtained in step (1) was placed in a tube furnace equipped with a plasma device, and the tube furnace was cleaned three times with nitrogen gas at a flow rate of 200 seem.

[0050] Step (3): After step (2) was completed, the tube furnace heating and plasma were turned on at the same time, the plasma atmosphere was N2, the flow rate was controlled at 30 seem, and the power was set at 200 W; the tube furnace was heated at a rate of 5 °C / min -1 , and after the furnace temperature was raised to 410 °C (marked as T1), it was kept for 4 h, and the plasma was turned off.

[0051] Step (4): The phase of the treated zinc foil was analyzed by XRD, from which Figure 1 It can be seen that the treated zinc foil produces a new Zn3N2 characteristic peak in addition to the Zn phase, indicating that the structure of the zinc foil has changed. The change in N element on the zinc surface was analyzed by XPS etching, as shown in Figure 2 The N1s spectrum is clearly visible after etching for 500 s in Ar plasma. The treated zinc foil was polished to different depths by an electrochemical polishing technique, Figure 3 XRD, Raman, and XPS in -2 N-related characteristic peaks were still observed on the surface polished at 5 mAh cm -2 , indicating that N active sites were successfully introduced into the bulk phase of the zinc foil, with a depth of more than 8.5 μm.

[0052] Step (5): A symmetric battery was assembled using a 2M ZnSO4 solution as the electrolyte, glass fiber as the separator, and the zinc foil obtained in step (3) (the plasma-assisted heat-treated surface was close to the separator) as the negative electrode. The electrochemical performance was tested using a Neware battery test system, with a current density of 5 mA cm -2 , a surface capacity of 1 mAh cm -2 , and a temperature of 30°C.

[0053] Step (6): As Figure 4 , the symmetric battery in step (5) can be cycled for 1970 h. This indicates that the bulk-restructured zinc foil negative electrode can effectively guide uniform zinc deposition. After repeated stripping, there are still high-zincophilic N active sites on the surface, as Figure 5 N signals detected by XPS and Raman on the surface of the bulk-restructured zinc foil after cycling.

[0054] Example 2

[0055] Compared with Example 1, the only difference is that T1 is changed, and the experimental groups are as follows:

[0056] Group A: T1 is 390°C;

[0057] Group B: T1 is 370°C;

[0058] Group C: T1 is 350°C.

[0059] From Figure 1 It can be seen that the treated A, B, and C samples produce a new Zn3N2 characteristic peak in addition to the Zn phase, indicating that the structure of the zinc foil has changed. The electrochemical performance was determined by the method of Example 1, and the results are as follows: Group A: 1750 h, Group B: 1521 h, and Group C: 983 h.

[0060] Example 3

[0061] The difference compared with Example 1 is only that the holding time under T1 is changed, and the experimental groups are respectively:

[0062] Group A: 1 h;

[0063] Group B: 8 h;

[0064] From Figure 1 It can be seen that the treated A and B groups of samples produce new Zn3N2 characteristic peaks in addition to the Zn phase, indicating that the structure of the zinc foil has changed. The electrochemical performance is determined by the method of Example 1, and the results are respectively: Group A: 1450 h, Group B: 1651 h.

[0065] Comparative Example 1

[0066] Compared with Example 1, the difference is only that the plasma device is turned on in the T1 holding stage, but not heated, that is, T1 is room temperature (25-35°C), and other operations and parameters are the same as Example 1.

[0067] The phase of the treated zinc foil is analyzed by XRD, and from Figure 6 It can be seen that the treated zinc foil does not appear new characteristic peaks in addition to the Zn phase. As Figure 7 shown, XPS etching shows that N active sites are introduced to the surface of the zinc foil, indicating that the surface optimization of the zinc foil is realized by plasma treatment at room temperature. By electrochemical polishing technology, the treated zinc foil is polished to different depths, Figure 8 showing that the Raman, XPS spectrum of the polished surface at 0.5 mAh cm -2 capacity, no N-related characteristic peaks are found, indicating that the N active site is destroyed in the stripping process due to the solid-liquid transformation reaction.

[0068] The electrochemical performance is determined by the method of Example 1, and as Figure 9 shown, the symmetrical battery can be cycled for 259 h. The active N sites on the surface of the zinc foil negative electrode are destroyed after repeated cycles, resulting in serious dendrite growth and side reactions. Figure 5 No N-related information is detected in the zinc foil after cycling, indicating that the N sites on the surface of the zinc foil are destroyed after repeated cycles.

[0069] Comparative Example 2

[0070] Compared with Example 1, the difference is only that the plasma device is not turned on in the T1 holding stage, and no holding heat treatment is assisted by plasma, and other operations and parameters are the same as Example 1.

[0071] The phase of the treated zinc foil is analyzed by XRD, and from Figure 6 It can be seen that the treated zinc foil does not appear new characteristic peaks in addition to the Zn phase. As Figure 7XPS etching shows N active sites are introduced to the surface of zinc foil, indicating that the surface of zinc foil is optimized by T1 treatment. The treated zinc foil is polished by electrochemical polishing technology to different depths, Figure 8 The XRD, Raman, XPS spectra of the polished surface at 0.5 mAh cm -2 Capacity show that no N-related characteristic peaks are found, indicating that the N active sites are destroyed during the stripping process due to the solid-liquid transformation reaction. The electrochemical performance is measured by the method of Example 1, and the symmetrical battery can be cycled for 137 h as shown. Figure 9 The active N sites on the surface of the zinc foil negative electrode are destroyed after repeated cycles, leading to serious dendrite growth and side reactions. Figure 5 No N-related information is detected on the zinc foil after cycling, indicating that the N sites on the surface of the zinc foil are destroyed after repeated cycles.

[0072] Comparative Example 3

[0073] Compared with Example 1, the only difference is that the zinc foil is treated by the plasma under the conditions, but without heating, and the treatment time is 4 h, followed by a T1 holding treatment for 4 h. The plasma and heat treatment are not synchronized, and other operations and parameters are the same as in Example 1. The phase of the treated zinc foil is analyzed by XRD, and from Figure 6 It can be seen that no new characteristic peaks appear in the treated zinc foil except for the Zn phase. As shown in Figure 7 XPS etching shows that N active sites are introduced to the surface of the zinc foil, indicating that the surface of the zinc foil is optimized by further heat annealing after plasma treatment. The electrochemical performance is measured by the method of Example 1, and the symmetrical battery can be cycled for 230 h.

[0074] Example 4

[0075] Compared with Example 1, the only difference is that the type of metal foil is changed, and the experimental group is aluminum foil, and the T1 temperature is 635°C. The change of N element on the surface of zinc is analyzed by XPS etching, as shown in Figure 10 The N1s spectrum is clearly visible after Ar plasma etching for 500 s, indicating that the phase structure of the aluminum foil has changed.

[0076] A 2M Al(OTF)3 solution is used as the electrolyte, glass fiber is used as the separator, and the aluminum foil (the treated surface of the plasma-assisted heat treatment is close to the separator) is used as the negative electrode to assemble a symmetrical battery. The electrochemical performance is tested by a new battery test system, and the test conditions are a current density of 0.5 mA cm -2 , a temperature of 30°C, and a surface capacity of 0.25 mAh cm -2 . As shown in Figure 11 , the symmetrical battery assembled with the bulk-modified aluminum foil negative electrode can be cycled for 135 h.

[0077] Comparative Example 4

[0078] Compared with Example 4, the difference is that the plasma device is turned on in the T1 holding stage, but is not heated, that is, T1 is room temperature (25-35℃), and other operations and parameters are the same as those in Example 4.

[0079] The change of N element on the zinc surface was analyzed by XPS etching analysis, as shown in Table 1. Figure 10 After Ar plasma etching for 500 s, the N1s spectrum is clearly visible, indicating that the structure of the aluminum foil surface is changed.

[0080] The electrochemical performance was determined by using the method of Example 1, Figure 11 It is shown that the symmetrical battery can be cycled for 58 h.

[0081] The specific parameters and electrochemical performance of the comparative example corresponding to the example

[0082] Plasma Heat treatment Temperature / °C Time / h Cycling life / h Example 1 √ √ 410 4 1970 Example 2A √ √ 390 4 1750 Example 2B √ √ 370 4 1521 Example 2C √ √ 350 4 983 Example 3A √ √ 410 1 1450 Example 3B √ √ 410 8 1651 Example 4 √ √ 635 4 135 Comparative Example 1 √ 25 4 259 Comparative Example 2 √ 410 4 137 Comparative Example 3 √ alone √ alone 25+410 4+ 230 Comparative Example 4 √ 25 4 58

[0083] It can be seen that the plasma-thermal treatment of the system is further combined with the joint control of parameters, so that the bulk phase controllable modification of the metal foil can be achieved, and the performance of the material can be significantly improved.

Claims

1. A method of metal foil negative body phase reconstitution of a metal- water battery, characterized by, The metal foil is heat-treated under plasma assistance to obtain a bulk restructured metal foil negative electrode; The metal element of the metal foil is Al or Zn; The atmosphere of the heat treatment stage is N2; The metal foil is a zinc foil, and the temperature of the heat treatment stage is 370-410℃; The metal foil is an aluminum foil, and the preferred temperature of the heat treatment is 635℃; The heat treatment time under plasma assistance is 3-5h.

2. The method of phase reconstitution of a metal foil negative body according to claim 1, wherein, The thickness of the metal foil is greater than or equal to 35μm.

3. The method of phase reconstitution of a metal foil negative body according to claim 1, wherein The thickness of the metal foil is greater than or equal to 50μm.

4. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The thickness of the metal foil is 50-200μm.

5. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The metal foil is pretreated in advance, including polishing and / or cleaning.

6. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The plasma power in the heat treatment stage is less than or equal to 300W.

7. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The plasma power in the heat treatment stage is less than or equal to 250W.

8. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The plasma power in the heat treatment stage is 50-220W.

9. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The flow rate of the plasma atmosphere in the heat treatment stage is greater than or equal to 5sccm.

10. The method of phase reconstitution of a metal foil negative body of claim 1, wherein, The flow rate of the plasma atmosphere in the heat treatment stage is 25-60sccm.

11. A bulk restructured metal foil negative electrode prepared by the method of any one of claims 1-10.

12. Use of a bulk reconstituted metal foil negative electrode produced by the method of any one of claims 1 to 10, characterized in that, The bulk restructured metal foil negative electrode is used as a negative electrode to prepare a metal aqueous battery.

13. A metal-aqueous battery, characterized by, The bulk restructured metal foil negative electrode prepared by the method of any one of claims 1-10 is used as a negative electrode.

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