Metal oxide composite material (at) SA electrode material and preparation method and application thereof

Abstract

The invention discloses a metal oxide composite material (at) SA electrode material and a preparation method and application thereof. The preparation method comprises the following steps: S1, preparing a sodium alginate solution and a metal ion solution; s2, mixing the sodium alginate solution and the metal ion solution, standing, and centrifuging to obtain an intermediate product; s3, calcining the intermediate product to obtain a metal oxide composite material; and S4, immersing the metal oxide composite material into a sodium alginate solution until the surface of the metal oxide composite material is coated with sodium alginate, and after immersion is completed, drying to obtain the metal oxide composite material (at) SA electrode material. According to the invention, metal ions are recovered by using a cross-linking mechanism of functional groups in sodium alginate and complex multivalent metal ions, then the electrode material with a unique core-shell structure is synthesized through calcination and a sodium alginate coating process, and the obtained electrode material shows excellent reversible capacity and excellent cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and particularly to a metal oxide composite @SA electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, due to their high energy density, long cycle life, and relatively mature technical route, lithium-ion batteries (LIBs) have become a research and application hotspot and are widely used in fields such as electric vehicles, portable electronic devices, and grid energy storage. However, the popularization of lithium-ion batteries still faces many challenges. In particular, their manufacturing cost is relatively high, mainly due to the price fluctuations of key materials (such as lithium, cobalt, nickel, etc.) and the uneven global distribution and limited reserves of resources, and long-term large-scale application may lead to resource shortage problems. In addition, lithium-ion batteries also have certain limitations in terms of safety, environmental friendliness, and recycling. Therefore, scientific researchers are actively exploring and developing new technologies to overcome the bottlenecks of lithium-ion batteries, promote the sustainable development of energy storage technologies, and provide more reliable support for the large-scale application of clean energy.

[0003] Meanwhile, with the development of industry, a large amount of industrial wastewater containing complex metal ions has been discharged. These wastewaters mainly come from highly polluting industries such as metallurgy, electroplating, chemical engineering, and battery manufacturing, and often contain heavy metal ions such as cadmium, mercury, chromium, copper, nickel, and toxic elements such as cobalt. These metal ions have high toxicity, are difficult to degrade, and have bioaccumulation. Once they enter water bodies, soil, or the atmosphere, they will cause serious harm to the ecosystem and human health. In addition, the metal ions contained in these wastewaters are resources with high economic value. Direct discharge not only wastes precious resources but also increases the cost of environmental governance. To address this issue, scientific researchers have conducted extensive research to explore efficient and low-cost wastewater treatment technologies. For example, methods such as chemical precipitation, electrocoagulation, chemical adsorption, and membrane filtration are used to remove metal ions from wastewater, but such methods all have deficiencies such as high initial investment, high maintenance cost, and issues related to sludge volume and toxicity. However, the biological adsorption method using algal adsorbents has the ability to biosorb heavy metals. Biological adsorption is formed based on ionic interactions and complex reactions between metal ions and functional groups of the biosorbent. Its advantages are low operating cost, selectivity for specific metals, relatively high efficiency, and minimizing the volume of chemical and biological sludge, making up for the deficiencies of traditional physicochemical methods for removing heavy metals from industrial wastewater. At the same time, resource recovery technologies have also received extensive attention. For example, extracting valuable metals from wastewater to achieve the reuse of waste can contribute to the sustainable development of China in the environmental and energy fields while alleviating environmental and resource pressures.

[0004] In lithium-ion battery materials, transition metal oxides (TMOs) have become promising candidates for anode materials due to their high theoretical specific capacity and energy density. Compared with traditional graphite anodes, TMOs (such as CuO, Co3O4, NiO, etc.) can provide a higher specific capacity, usually 2-3 times that of graphite, which makes them have great application potential in high-energy density batteries. However, TMOs face a key challenge in practical applications. Their lithium storage mechanism is mainly based on conversion reactions, that is, during charge and discharge, TMOs react with lithium ions to form metal nanoparticles and Li2O. Although this process can store a large amount of lithium ions, it also causes a significant expansion of the material volume, leading to serious structural deformation. This repeated volume change will cause cracks or even fragmentation inside the TMOs particles, resulting in poor contact between the electrode material and the current collector, and a rapid decay of the electrochemical performance. In addition, the volume expansion will also destroy the stability of the solid electrolyte interface (SEI) film, causing continuous decomposition of the electrolyte, further reducing the cycle life and Coulomb efficiency of the battery. These problems severely limit the application of TMOs in actual batteries. To solve this problem, researchers have proposed a series of solutions, such as designing TMOs with different nanostructures and recombining them with carbonaceous materials, or constructing eggshell structures to slow down the volume change. However, the experimental process is complex and it is still difficult to achieve large-scale commercialization. Summary of the Invention

[0005] The purpose of the present invention is to provide a metal oxide composite material @SA electrode material, its preparation method and application, so as to solve the problems that the wastewater containing metal ions cannot be resourcefully treated and the volume expansion of transition metal oxides as battery materials leads to a reduction in the battery cycle life.

[0006] To achieve the above purpose, the first aspect of the present invention provides a preparation method of a metal oxide composite material @SA electrode material, including the following steps:

[0007] S1: Prepare a sodium alginate solution and a metal ion solution;

[0008] S2: Mix the sodium alginate solution and the metal ion solution and let it stand, then centrifuge to obtain an intermediate product;

[0009] S3: Calcinate the intermediate product to obtain a metal oxide composite material;

[0010] S4: Immerse the metal oxide composite material in the sodium alginate solution until the sodium alginate coats the surface of the metal oxide composite material. After soaking, dry to obtain the metal oxide composite material @SA electrode material.

[0011] The metal ions in the present invention include transition metal ions and heavy metal ions. The metal ion solution can be prepared by oneself or the metal ions from industrial wastewater can be selected. If industrial wastewater is selected as the metal ion solution, the cheap and easily available algal extract sodium alginate is used as the capturer. By using the crosslinking reaction between sodium alginate and polyvalent metal ions in industrial wastewater, the efficient capture of metal ions in industrial wastewater can be realized, which provides a new idea for the recovery and resource utilization of a large amount of industrial wastewater containing complex metal ions.

[0012] Preferably, in step S1, the concentration of the sodium alginate solution is 15 - 30 g / L.

[0013] Preferably, in step S1, the concentration of the metal ion solution is 0.01 - 0.2 mol / L.

[0014] Preferably, in step S2, the standing time is 18 - 30 h.

[0015] Preferably, in step S3, the calcination temperature is 400 - 700 °C and the calcination time is 2 - 5 h.

[0016] Preferably, in step S4, the concentration of the sodium alginate solution is 1 - 10 g / L, and the mass ratio of the metal oxide composite material to the sodium alginate solution is 1:90 - 110.

[0017] Preferably, in step S4, the soaking time is 3 - 5 h, the drying temperature is 60 - 80 °C, and the drying time is 8 - 12 h.

[0018] In the second aspect of the present invention, a metal oxide composite material@sA electrode material is provided, which is prepared by the above preparation method.

[0019] In the third aspect of the present invention, an application of the metal oxide composite material@SA electrode material is provided, that is, the application of the metal oxide composite material@SA electrode material in the preparation of the cathode material of a lithium-ion battery.

[0020] Preferably, the assembly process of the lithium-ion battery is as follows:

[0021] Using a lithium metal foil as the counter electrode and reference electrode, using the metal oxide composite material@SA electrode material as the working electrode, and using LiPF6 as the electrolyte, a lithium-ion battery is assembled.

[0022] Therefore, the present invention adopts the above-mentioned metal oxide composite material@SA electrode material, its preparation method and application, and has the following beneficial effects:

[0023] (1) The present invention uses sodium alginate extracted from seaweed as a capturing agent, and utilizes the cross-linking reaction between the functional groups in sodium alginate and heavy metal ions to achieve efficient capture of heavy metal ions in industrial wastewater, which provides a new idea for the treatment of industrial wastewater containing metal ions and realizes the resource utilization of industrial wastewater.

[0024] (2) The present invention recovers mixed metal oxides from the cross-linked gel through simple calcination treatment. In order to improve the cycle life of the metal oxides as anode materials, an SA layer is further coated on the surface of the metal oxide composite material to form a metal oxide composite material@SA electrode material. The peripheral SA can cross-link with the metal ions escaping from the core to form a viscous gel, significantly inhibiting the further dissolution of the metal oxide composite material as an electrode and maintaining the capacity of the electrode material. At the same time, SA is a material with strong elasticity, and the core-shell structure formed by the metal oxide composite material and the SA layer can relieve the volume change during repeated cycling, thereby inhibiting the rupture of the metal oxides in the core.

[0025] (3) The present invention can recover resources such as metal ions from industrial wastewater, and through annealing and coating processes, synthesize a metal oxide composite material@SA anode material with a unique core-shell structure and apply it to lithium-ion batteries. The results show that the synthesized electrode material has a high reversible capacity of 400 mAh g -1 at 0.125 A g -1 and exhibits excellent reversible capacity and cycle stability.

[0026] (4) The preparation method of the present invention conforms to the development concept of green environmental protection and comprehensively realizes the unity of economic benefits, social benefits and environmental benefits.

[0027] The technical solutions of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0028] Figure 1 In the figure, a is the schematic diagram of the preparation of the CuO / NiO@SA electrode material in Example 1; b is the X-ray diffraction pattern of CuO / NiO; c is the enlarged transmission electron microscope characterization diagram of the CuO / NiO@SA electrode material in Example 1; d is the transmission electron microscope characterization diagram of the CuO / NiO@SA electrode material in Example 1; e-i are the Mapping diagrams of C element, Cu element, Ni element, Na element and O element in the CuO / NiO@SA electrode material in Example 1 respectively;

[0029] Figure 2 is the CV curve diagram of the CuO / NiO@SA electrode material in Example 1 in the first four cycles at 0.01 - 3.0 V and 0.2 mV s -1 ;

[0030] Figure 3 The CV curves of the CuO / NiO electrode material of Comparative Example 1 in the first four cycles at 0.01 - 3.0 V and 0.2 mV s -1 are shown below;

[0031] Figure 4 The CV curves of the CuO / NiO electrode of Comparative Example 1 and the CuO / NiO@SA electrode of Example 1 at a scanning rate of 0.2 mV -1 are shown below;

[0032] Figure 5 The galvanostatic charge - discharge curves of the CuO / NiO@SA electrode material of Example 1 in the first four cycles at a current density of 0.125 A g -1 are shown below;

[0033] Figure 6 The galvanostatic charge - discharge curves of the CuO / NiO electrode material of Comparative Example 1 in the first four cycles at a current density of 0.125 A g -1 are shown below;

[0034] Figure 7 The charge / discharge capacity diagrams of the CuO / NiO electrode of Comparative Example 1 and the CuO / NiO@SA electrode material of Example 1 at different current densities are shown below;

[0035] Figure 8 The cycling stability test diagrams of the CuO / NiO electrode of Comparative Example 1 and the CuO / NiO@SA electrode material of Example 1 at 0.25 A g -1 are shown below;

[0036] Figure 9 In the figure, a and b are the Nyquist diagrams of the CuO / NiO electrode of Comparative Example 1 and the CuO / NiO@SA electrode material of Example 1 at a frequency of 10 mHz - 100 kHz; c and d are the inherent resistance (R I ) and charge transfer resistance (R CT ) of the two electrodes before and after cycling of the CuO / NiO and CuO / NiO@SA electrodes. Detailed Embodiments

[0037] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and gives detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0038] Example 1

[0039] As Figure 1 shown in a, a preparation method of a CuO / NiO@SA electrode material includes the following steps:

[0040] S1: Prepare sodium alginate solution: Dissolve 1 g of sodium alginate in 50 mL of deionized water to obtain a sodium alginate solution, which serves as the capture agent solution;

[0041] Prepare metal ion solution: Mix 0.1 M metal ion solutions (nickel chloride solution and copper chloride solution) in the same volume ratio to 40 mL, that is, mix 20 mL of 0.1 M nickel chloride aqueous solution and 20 mL of 0.1 M copper chloride aqueous solution to obtain 40 mL of metal ion solution;

[0042] S2: Mix the sodium alginate solution and the metal ion solution and let it stand at room temperature for 24 h. During this process, use the self-crosslinking mechanism of sodium alginate to synthesize a gel crosslinked product. Then, centrifuge at 8000 rpm for 5 min and filter off the supernatant to obtain an intermediate product;

[0043] S3: Calcinate the intermediate product in a muffle furnace at 600 °C for 3 h to obtain the metal oxide composite CuO / NiO;

[0044] S4: Immerse 1 g of CuO / NiO in 100 mL of sodium alginate solution. The sodium alginate solution is prepared by dissolving 0.5 g of sodium alginate in 100 mL of deionized water, and soak for 4 h until the sodium alginate coats the surface of the metal oxide composite. After soaking, place it in a vacuum drying oven for drying. The drying temperature is 60 °C and the drying time is 10 h to obtain the CuO / NiO@SA electrode material.

[0045] Example 2

[0046] A preparation method of Co3O4 / CdO@SA electrode material, comprising the following steps:

[0047] S1: Prepare sodium alginate solution: Dissolve 1 g of sodium alginate in 50 mL of deionized water to obtain a sodium alginate solution, which serves as the capture agent solution;

[0048] Prepare metal ion solution: Mix 0.1 M metal ion solutions (cobalt chloride solution and cadmium chloride solution) in the same volume ratio to 40 mL, that is, mix 20 mL of 0.1 M cobalt chloride aqueous solution and 20 mL of 0.1 M cadmium chloride aqueous solution to obtain 40 mL of metal ion solution;

[0049] S2: Mix the sodium alginate solution and the metal ion solution and let it stand at room temperature for 24 h. During this process, use the self-crosslinking mechanism of sodium alginate to synthesize a gel crosslinked product. Then, centrifuge at 8000 rpm for 5 min and filter off the supernatant to obtain an intermediate product;

[0050] S3: Calcinate the intermediate product in a muffle furnace at 600 °C for 3 h to obtain the metal oxide composite Co3O4 / CdO:

[0051] S4: Immerse 1 g of Co3O4 / CdO into 100 mL of sodium alginate solution. The sodium alginate solution is prepared by dissolving 0.5 g of sodium alginate in 100 mL of deionized water. Soak for 4 h until the sodium alginate coats the surface of the metal oxide composite. After soaking, place it in a vacuum drying oven for drying. The drying temperature is 60 °C and the drying time is 10 h to obtain the Co3O4 / CdO@SA electrode material.

[0052] Example 3

[0053] A preparation method of a CuO / NiO / Co3O4 / CdO@SA electrode material includes the following steps:

[0054] S1: Prepare sodium alginate solution: Dissolve 1 g of sodium alginate in 50 mL of deionized water to obtain the sodium alginate solution, which is used as the capture agent solution;

[0055] Prepare metal ion solution: Mix 0.1 M metal ion solutions (nickel chloride solution, copper chloride solution, cobalt chloride solution, and cadmium chloride solution) in the same volume ratio to 40 mL, that is, mix 10 mL of 0.1 M nickel chloride aqueous solution, 10 mL of 0.1 M copper chloride aqueous solution, 10 mL of 0.1 M cobalt chloride aqueous solution, and 10 mL of 0.1 M cadmium chloride aqueous solution to obtain 40 mL of metal ion solution, and measure the pH of the metal ion solution to be 3.35;

[0056] S2: Mix the sodium alginate solution and the metal ion solution and let it stand at room temperature for 24 h. During this process, use the self-crosslinking mechanism of sodium alginate to synthesize a gel crosslinked product, and then centrifuge at 8000 rpm for 5 min, and filter off the supernatant to obtain the intermediate product;

[0057] S3: Calcinate the intermediate product in a muffle furnace at 600 °C for 3 h to obtain the metal oxide composite CuO / NiO / Co3O4 / CdO:

[0058] S4: Immerse 1 g of CuO / NiO / Co3O4 / CdO into 100 mL of sodium alginate solution. The sodium alginate solution is prepared by dissolving 0.5 g of sodium alginate in 100 mL of deionized water. Soak for 4 h until the sodium alginate coats the surface of the metal oxide composite. After soaking, place it in a vacuum drying oven for drying. The drying temperature is 60 °C and the drying time is 10 h to obtain the CuO / NiO / Co3O4 / CdO@SA electrode material.

[0059] Example 4

[0060] A preparation method of a CuO / NiO / Co3O4 / CdO@SA electrode material, comprising the following steps:

[0061] S1: Prepare a sodium alginate solution: Dissolve 1 g of sodium alginate in 50 mL of deionized water to obtain a sodium alginate solution, which serves as a capture agent solution;

[0062] Prepare a metal ion solution: 0.1 M various metal ion solutions (nickel chloride solution, copper chloride solution, cobalt chloride solution, and cadmium chloride solution) are mixed in the same volume ratio to 40 mL, that is, 10 mL of 0.1 M nickel chloride aqueous solution, 10 mL of 0.1 M copper chloride aqueous solution, 10 mL of 0.1 M cobalt chloride aqueous solution, and 10 mL of 0.1 M cadmium chloride aqueous solution are mixed to obtain 40 mL of a metal ion solution, and the pH of the metal ion solution is adjusted to 4.59 with 1 M sodium hydroxide solution;

[0063] S2: Mix the sodium alginate solution and the metal ion solution and let it stand at room temperature for 24 h. During this process, use the cross-linking mechanism of sodium alginate itself to synthesize a gel cross-linked product, and then centrifuge at 8000 rpm for 5 min, and filter off the supernatant to obtain an intermediate product;

[0064] S3: Calcinate the intermediate product in a muffle furnace at 600 °C for 3 h to obtain a metal oxide composite material CuO / NiO / Co3O4 / CdO;

[0065] S4: Immerse 1 g of CuO / NiO / Co3O4 / CdO in 100 mL of a sodium alginate solution, where the sodium alginate solution is prepared by dissolving 0.5 g of sodium alginate in 100 mL of deionized water, and soak for 4 h until the sodium alginate coats the surface of the metal oxide composite material. After the soaking is completed, place it in a vacuum drying oven for drying, with a drying temperature of 60 °C and a drying time of 10 h to obtain a CuO / NiO / Co3O4 / CdO@SA electrode material.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that the metal oxide composite material CuO / NiO in step S3 is directly used as the electrode material.

[0068] Test Example

[0069] (1) Characterize the electrode materials prepared in Example 1 and Comparative Example 1

[0070] Figure 1b is the XRD image of the CuO / NiO@SA electrode material of Example 1. There are obvious diffraction peaks at 2θ = 35.5, 38.7, 46.2, 48.7, 53.5, 58.3, 61.5, 65.8, 66.2, 67.9, 72.4, 75.0, corresponding to (002), (111), (020), (202), (022), (113), (311), (004) crystal planes, belonging to monoclinic copper oxide (JCPDS 45-0937). The diffraction peaks are at 2θ = 37.2, 43.3, 62.9, 79.4, corresponding to (111), (200), (220), (311) crystal planes, belonging to cubic nickel monoxide (JCPDS 47-1049). Therefore, after calcining the cross-linked gel, metal ions can be recovered from the wastewater to obtain a metal oxide composite material, realizing the reuse of resources.

[0071] Figure 1 c and d are the TEM images of the CuO / NiO@SA electrode of Example 1. The lattice fringes of the metal oxide core with a spacing of 0.17 nm can be observed in the transmission electron microscope, and the SA with a thickness of ~1 nm is coated on the periphery of the metal oxide. Since the amorphous SA has no lattice fringes, a core-shell structure can be observed. This core-shell structure can alleviate the volume expansion degree of CuO / NiO during the charge / discharge process.

[0072] As Figure 1 shown in e-1i, it can be clearly observed from the mapping diagram of the CuO / NiO@SA electrode that the Cu element and Ni element are concentrated in the central core, and the Na element and C element stored in sodium alginate are dispersed around CuNi, confirming the successful coating of sodium alginate.

[0073] (2) Electrochemical performance tests were carried out on the electrode materials prepared in Example 1 and Comparative Example 1

[0074] Battery assembly:

[0075] The CuO / NiO@SA electrode material of Example 1 and the CuO / NiO electrode material of Comparative Example 1 were mixed with polyvinylidene fluoride (PVDF) and acetylene black at a mass ratio of 1:1:8, and then an appropriate amount of N-methylpyrrolidone (NMP) was added. After stirring for 6 hours, the mixture was evenly coated on a copper foil. After drying in an oven for 15 h, the copper foil was cut into pieces with a size of 0.5 cm × 0.5 cm. In a glove box filled with argon (O2 and H2O < 1 ppm), a lithium metal foil was used as the counter electrode and reference electrode, and LiPF6 (ethylene carbonate EC: dimethyl carbonate DMC: ethyl methyl carbonate EMC = 1:1:1 v01.) was used as the electrolyte to assemble a CR2025 coin cell. Electrochemical tests were carried out on the battery. When performing cyclic voltammetry scanning, the range of the cyclic voltammetry characteristic curve was set to 0.01 V to 3.0 V, and the scanning rate was 0.2 mVs -1 ~1 mVs -1 . When performing constant current charge-discharge tests, the voltage range was set to 0.01 V to 3.0 V, and the current intensity was 10 μA to 640 μA. When performing impedance tests, the frequency range was set to 100 kHz to 10 mHz, and the voltage amplitude was 10 mV. When performing cyclic stability tests using constant current charge-discharge, the voltage range was set to 0.01 V to 3.0 V, and the current density was set to 0.125 A g -1 , and the number of cycles was 70 times.

[0076] Performance determination:

[0077] By assembling coin-type lithium-ion batteries with CuO / NiO and CuO / NiO@SA electrode materials as the working electrodes, lithium foil as the counter electrode and reference electrode, the electrochemical performance of CuO / NiO and CuO / NiO@SA electrode materials was studied. The cyclic voltammetry (CV) curves of the first four cycles of the electrode material at 0.2 mV s -1 are as shown in Figure 2 , 3 . During the discharge cycle process, three obvious reduction peaks appeared at ~0.83 V, ~1.06 V, and ~1.28 V. The reduction peaks at ~0.83 V and ~1.06 V correspond to a series of reduction reactions from CuO to Cu2O and then to Cu (2CuO + 2Li + + 2e - →Cu2O + Li2O, Cu2O + 2Li + + 2e-→2Cu + Li2O). The reduction peak at 1.28 V is attributed to the reduction reaction from NiO to Ni (NiO + 2Li + + 2e -→Ni + Li2O). In the anodic scanning region, there are two oxidation peaks at ~2.5 V and ~1.42 V. The oxidation peak at ~2.5 V is related to the de-lithiation and formation of CuO, while the oxidation peak at 1.42 V is attributed to the de-lithiation and formation of NiO. It is also obvious that the CV curve of the first cycle is significantly different from that of the subsequent cycles, which is due to the irreversible reaction between the electrode surface and the electrolyte, forming a solid electrolyte phase (SE). At the same time, there is a wide shoulder-shaped plateau near the low potential, which may benefit from the coating of external SA.

[0078] As Figure 4 shown, the CV curves of CuO / NiO and CuO / NiO@SA electrodes at a scanning rate of 0.2 mV s -1 are compared. It can be judged from the intensity of the redox peaks that the CuO / NiO@SA electrode has a larger integral area, indicating its higher capacity storage performance.

[0079] As Figure 5 shown, as an SA-coated anode, the specific discharge capacity of the CuO / NiO@SA electrode material can reach 628 mAh g -1 in the first cycle, and the capacity in subsequent cycles can be maintained at ~400 mAh g -1 . The high specific capacity in the first cycle comes from the formation of SEI.

[0080] As Figure 6 shown, the discharge and charge capacities of the CuO / NiO electrode material in the first cycle reach 429 mAh g -1 and 355 mAh g -1 respectively, which are much lower than those of the CuO / NiO@SA anode. This may be because the outer SA coating can cross-link with the corresponding metal ions, thus promoting the release of Li + .

[0081] As Figure 7 shown, due to the SA layer on the periphery of the metal oxide, the CuO / NiO@SA negative electrode has more stable charge-discharge performance at different current densities. When the current density increases to 2 A g -1 , the capacity retention rate reaches 17.71%, which is comparable to that of the CuO / NiO negative electrode without SA coating (18.46%). However, when there is an external SA coating, it not only does not reduce the capacity of the CuO / NiO@SA electrode, but also improves its lithium storage performance.

[0082] As Figure 8As shown, the CuO / NiO@SA anode maintains ~85.7% after 1120 cycles, much higher than the CuO / NiO anode without SA coating (30.9%), demonstrating its excellent cycling stability. The excellent cycling stability of the CuO / NiO@SA anode is mainly due to the fact that the peripheral SA layer can crosslink with the metal ions escaping from the core, significantly inhibiting the further dissolution of the CuO / NiO core and maintaining the capacity. It is worth mentioning that SA is a material with strong elasticity, and the core-shell structure formed with metal oxides can relieve the volume change during repeated cycling, thereby inhibiting the cracking of the CuO / NiO core.

[0083] As Figure 9 shown, since SA is a non-conductive organic material, coating SA on the electrode will increase the inherent resistance of the electrode. Therefore, numerically, the R of CuO / NiO@SA CT is greater than the R of the CuO / NiO electrode CT . And the R of the CuO / NiO@SA electrode slightly decreases (26.51%) after cycling, while the RCT of the CuO / NiO counterpart increases significantly (71.63%), proving the stability of the CuO / NiO@SA electrode. CT

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a metal oxide composite material @SA electrode material, characterized in that: The following steps are involved: S1: preparing sodium alginate solution and metal ion solution; S2: mixing the sodium alginate solution and the metal ion solution and allowing them to stand, and centrifuging to obtain an intermediate product; S3: calcining the intermediate product to obtain a metal oxide composite material; S4: immersing the metal oxide composite material into a sodium alginate solution until the sodium alginate is coated on the surface of the metal oxide composite material. After the immersion is completed, drying is performed to obtain a metal oxide composite material@SA electrode material.

2. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S1, the concentration of the sodium alginate solution is 15-30 g / L.

3. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S1, the concentration of the metal ion solution is 0.01-0.2 mol / L.

4. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S2, the standing time is 18 to 30 hours.

5. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S3, the calcination temperature is 400-700° C., and the calcination time is 2-5 hours.

6. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S4, the concentration of the sodium alginate solution is 1-10 g / L, and the mass ratio of the metal oxide composite material to the sodium alginate solution is 1:90-110.

7. The method for preparing a metal oxide composite material@SA electrode material according to claim 1, characterized in that: In step S4, the soaking time is 3 to 5 hours, the drying temperature is 60 to 80° C., and the drying time is 8 to 12 hours.

8. A metal oxide composite material @SA electrode material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. The use of a metal oxide composite material @SA electrode material according to claim 8, characterized in that: Application of metal oxide composites @SA electrode materials in the preparation of lithium-ion battery cathode materials.

10. The use of a metal oxide composite material @SA electrode material according to claim 9, characterized in that: The assembly process of lithium-ion batteries is as follows: A lithium-ion battery was assembled using metallic lithium foil as the counter electrode and reference electrode, metal oxide composite material @SA electrode material as the working electrode, and LiPF6 as the electrolyte.

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