Layered lithium titanate membrane electrode and preparation method thereof

Abstract

The invention discloses a layered lithium titanate membrane electrode and a preparation method thereof. The preparation method comprises the following steps: S100, placing a lithium source, a titanium source and a carbon source in water, and dispersing to obtain a mixed electrolyte; s200, a three-electrode system is constructed, a current collector serves as a working electrode, a graphite rod serves as a counter electrode, Ag / AgCl serves as a reference electrode, and the three-electrode system is placed in the mixed electrolyte to be stirred; s300, applying a constant voltage for treatment, and distributing the layered lithium titanate on the surface of the current collector to obtain a layered lithium titanate membrane electrode precursor; and S400, washing and drying the layered lithium titanate membrane electrode precursor, and treating the layered lithium titanate membrane electrode precursor in an acid solution to obtain the layered lithium titanate membrane electrode. According to the electrochemical co-deposition method, close contact can be formed between the lithium titanate and the current collector, the structural stability and the mechanical stability are improved, the selective adsorption performance and the adsorption capacity of lithium ions are increased, the agglomeration phenomenon is reduced, the production cost is reduced, and the economic benefit is increased.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical lithium extraction, and in particular to a layered lithium titanate film electrode and a preparation method thereof. Background Art

[0002] In recent years, with the widespread application of lithium-ion batteries in new energy vehicles, energy storage systems, and portable electronic devices, global demand for lithium resources has increased dramatically. Currently, lithium resources are mainly extracted from ores and salt lake brine. Salt lake brine, due to its large lithium reserves and low cost, has become one of the most promising lithium resources for development. However, traditional salt lake lithium extraction technologies, such as evaporation crystallization, adsorption, and solvent extraction, generally suffer from long process flows, high energy consumption, and environmental pollution, making it difficult to meet the demand for efficient and green lithium extraction in production.

[0003] It is worth noting that electrochemical lithium extraction technology has become a research hotspot within the industry due to its high lithium selectivity, low energy consumption, and environmental friendliness. This technology achieves selective lithium extraction by reversibly adsorbing and desorbing lithium ions on electrode materials under an applied electric field, avoiding the use of additional chemical reagents and the resulting secondary pollution. Among various electrode materials, layered lithium titanate (Li2Ti3O7) has attracted considerable attention due to its unique crystal structure and stable electrochemical properties. Its ion channels enable efficient lithium ion insertion and extraction, and the environmentally friendly and low-cost nature of the titanium element facilitates its large-scale application. However, the low intrinsic conductivity of conventional lithium titanate materials leads to slow lithium ion diffusion kinetics, further limiting the rate of lithium extraction. Furthermore, conventional lithium titanate materials lack active sites, especially in brines containing multiple metal ions, such as those with a high sodium ion / lithium ion ratio. This leads to insufficient selective lithium ion adsorption, poor cycling stability, and lattice structure collapse after repeated charge and discharge cycles, resulting in significant capacity decay. Although lithium titanate is modified by carbon coating, element doping and other means in the existing technology, the preparation process is complicated and the modified product cannot take into account both conductivity and selectivity. Summary of the Invention

[0004] One purpose of the present application is to provide a layered lithium titanate membrane electrode and a preparation method thereof, which is conducive to improving the selective adsorption performance of lithium ions, reducing the interference of other ions, and reducing the risk of agglomeration.

[0005] Another object of the present application is to provide a layered lithium titanate film electrode and a preparation method thereof, which are beneficial to improving the structural stability and mechanical stability of the electrode, enhancing the contact performance between the deposited layered lithium titanate and the current collector, and further improving the electron transmission efficiency.

[0006] Another object of the present application is to provide a layered lithium titanate membrane electrode and a preparation method thereof, which is conducive to simplifying the production process and further reducing the production cost consumed during preparation.

[0007] To achieve the above objectives, the technical solution adopted in this application is: a method for preparing a layered lithium titanate film electrode, comprising the steps of: S100, placing a lithium source, a titanium source, and a carbon source in water and dispersing them to obtain a mixed electrolyte; S200, constructing a three-electrode system, wherein the current collector serves as a working electrode, the graphite rod serves as a counter electrode, and the Ag / AgCl serves as a reference electrode, and the three electrodes are placed in the mixed electrolyte and stirred; S300, applying a constant voltage for treatment, so that layered lithium titanate is distributed on the surface of the current collector to obtain a layered lithium titanate membrane electrode precursor; S400 , after washing and drying the layered lithium titanate membrane electrode precursor, placing it in an acid solution for treatment to obtain a layered lithium titanate membrane electrode.

[0008] In some embodiments, the molar number of lithium element in the mixed electrolyte is n1, and the molar number of titanium element is n2, wherein the ratio of n1 / n2 is (1.90-2.10):3.

[0009] In some embodiments, the mass of the carbon source is m1, and the mass of the layered lithium titanate prepared in step S200 is m2, wherein 0.005≤m1 / m2≤0.03.

[0010] In some embodiments, the concentration of lithium ions in the mixed electrolyte is 0.05 mol / L to 0.2 mol / L, and the lithium source is one or more of lithium carbonate, lithium chloride, and lithium hydroxide.

[0011] In some embodiments, the titanium source is one or more of titanium dioxide, titanium chloride, and metatitanic acid.

[0012] In some embodiments, the carbon source is one or more of glucose, acetylene black, and graphene oxide.

[0013] In some embodiments, in step S300, the constant voltage is -1V to -0.5V, and the time for applying the constant voltage is 10 minutes to 60 minutes.

[0014] In some embodiments, in step S400, the acid solution is one or more of dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid, acetic acid, and citric acid; the time of the acid solution treatment is t1, where 0s≤t1≤30s, and the concentration of the acid solution is 0.05mol / L~0.2mol / L.

[0015] In some embodiments, in step S200, the current collector is one or more of aluminum foil, nickel foam, titanium mesh, and carbon paper.

[0016] To achieve the above objectives, the technical solution adopted in this application is: a layered lithium titanate film electrode is prepared by any of the preparation methods described above.

[0017] Compared with the prior art, the present invention has the following advantages: (1) This application uses electrochemical co-deposition to directly grow a layered lithium titanate film on the current collector, forming a close physical and electrochemical contact between the deposited layered lithium titanate and the current collector, further improving the structural and mechanical stability of the electrode. Acid etching then forms oxygen vacancies that can serve as active sites, increasing the selective adsorption performance and adsorption capacity for lithium ions, reducing the risk of interference from other ions, especially sodium ions, and reducing the occurrence of agglomeration.

[0018] (2) The layered lithium titanate film electrode and its preparation method provided in this application use an electrochemical co-deposition method to replace the high-temperature sintering and subsequent coating steps, which is beneficial to reducing energy consumption in the production process, further reducing production costs, and increasing economic benefits.

[0019] (3) The layered lithium titanate film electrode and its preparation method provided by this application have the advantages of simple preparation process, easy operation, environmental friendliness, and the potential for large-scale production. DETAILED DESCRIPTION

[0020] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0021] As used herein, the term "prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0022] When an amount, concentration or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose the range formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range includes its end values ​​and all integers and fractions within the range.

[0023] Approximating terms in the specification and claims are used to modify a quantity to indicate that the invention is not limited to that specific quantity and includes acceptable modifications close to that quantity that do not result in a change in the relevant basic function. Accordingly, the use of "about," "approximately," or the like to modify a numerical value indicates that the invention is not limited to that exact numerical value. In some instances, approximating terms may correspond to the precision of the instrument used to measure the value. In the specification and claims of this application, range definitions may be combined and / or interchanged, and unless otherwise indicated, such ranges include all subranges contained therein.

[0024] To achieve the above objectives, the technical solution adopted in this application is: a method for preparing a layered lithium titanate film electrode, comprising the steps of: S100, placing a lithium source, a titanium source, and a carbon source in water and dispersing them to obtain a mixed electrolyte; S200, constructing a three-electrode system, with the current collector as the working electrode, the graphite rod as the counter electrode, and the Ag / AgCl as the reference electrode, and placing them in a mixed electrolyte for stirring; S300, applying a constant voltage for treatment, so that the layered lithium titanate is distributed on the surface of the current collector to obtain a layered lithium titanate membrane electrode precursor; S400, after washing and drying the layered lithium titanate membrane electrode precursor, placing it in an acid solution for treatment to obtain a layered lithium titanate membrane electrode.

[0025] This application uses electrochemical co-deposition to directly grow a layered lithium titanate film on the current collector, forming a close physical and electrochemical contact between the deposited layered lithium titanate and the current collector, further improving the structural and mechanical stability of the electrode. Acid etching then creates oxygen vacancies that serve as active sites, increasing the selective adsorption performance and adsorption capacity for lithium ions, reducing the risk of interference from other ions, and reducing the occurrence of agglomeration.

[0026] In some embodiments, the molar number of lithium element in the mixed electrolyte is n1, and the molar number of titanium element is n2, wherein the ratio of n1 / n2 is (1.90~2.10):3, specifically, the ratio of n1 / n2 is 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05, further preferably, the ratio of n1 / n2 is (1.90~2.05):3, more preferably, the ratio of n1 / n2 is (1.95~2.00):3, more preferably, the ratio of n1 / n2 is 1.95:3. It is worth noting that, because the layered lithium titanate (Li2Ti3O7) grown directly on the current collector via electrochemical co-deposition has a molar ratio of Li to Ti of 2:3, the n1 / n2 ratio is set to (1.90-2.10):3, ensuring that the compound formed during the electrochemical co-deposition process is primarily composed of layered lithium titanate. The layered structure of lithium titanate facilitates rapid lithium ion intercalation and deintercalation, allowing lithium ions to diffuse rapidly through the two-dimensional interlayer channels within the layered lithium titanate, thereby enhancing the electrode's adsorption and desorption performance. Furthermore, the Ti-O bonds in the layered lithium titanate form negatively charged adsorption sites, allowing for the specific capture of lithium ions through electrostatic interactions, further enhancing the selective adsorption of lithium ions. This makes it suitable for lithium ion extraction from salt lake brines containing a variety of impurities. Furthermore, the high strength of the Ti-O bonds in the layered lithium titanate ensures excellent structural stability in a variety of operating environments, particularly acidic and neutral environments, further enhancing the operational stability of the layered lithium titanate membrane electrode.

[0027] In some embodiments, the mass of the carbon source is m1, and the mass of the layered lithium titanate prepared in step S200 is m2, wherein 0.005≤m1 / m2≤0.03, specifically, the ratio of m1 to m2 is in the range of 0.005, 0.007, 0.009, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.025, 0.03, further preferably, the ratio of m1 to m2 is in the range of 0.005≤m1 / m2≤0.02, more preferably, the ratio of m1 to m2 is in the range of 0.02. It can be understood that by introducing a carbon source and compounding with the layered lithium titanate during the electrochemical deposition process, a continuous conductive network is formed throughout the layered lithium titanate film electrode, which is beneficial to enhancing conductivity to increase charge conduction. On the other hand, the carbon source can serve as a physical isolation layer, inserted between the layers of layered lithium titanate to prevent the face-to-face stacking of two-dimensional sheets during the deposition process, which is beneficial to enhance the diffusion of lithium ions, further reduce the risk of agglomeration of lithium titanate particles, and increase the stability of the layered lithium titanate membrane electrode.

[0028] In some embodiments, the concentration of lithium ions in the mixed electrolyte is 0.05mol / L~0.2mol / L, specifically, the concentration of lithium ions in the mixed electrolyte is 0.05mol / L, 0.07mol / L, 0.09mol / L, 0.1mol / L, 0.12mol / L, 0.14mol / L, 0.16mol / L, 0.18mol / L, 0.2mol / L, further preferably, the concentration of lithium ions in the mixed electrolyte is 0.1mol / L~0.2mol / L, more preferably, the concentration of lithium ions in the mixed electrolyte is 0.1mol / L. It can be understood that when preparing a layered lithium titanate film electrode, selecting an appropriate lithium ion concentration is conducive to forming a uniform layered lithium titanate structure, optimizing the conductivity of the layered lithium titanate film electrode, and thereby enhancing the performance and stability of the prepared layered lithium titanate film electrode. On the other hand, selecting an appropriate lithium ion concentration is beneficial to improving the uniformity of the dispersion of lithium source, titanium source and carbon source in water, thereby forming a uniform mixed electrolyte, and also helps to form uniform layered lithium titanate in subsequent steps.

[0029] In some embodiments, the lithium source is one or more of lithium carbonate, lithium chloride and lithium hydroxide. Among them, lithium carbonate, as a commonly used lithium source, has high purity and good chemical stability. Therefore, in the preparation process of the layered lithium titanate film electrode, lithium carbonate can stably provide lithium ions, which helps to form a uniform layered lithium titanate structure in subsequent reactions, thereby improving the electrochemical performance of the electrode. Lithium chloride has a high solubility in water, which allows lithium ions to be evenly dispersed in the mixed electrolyte, further improving the uniformity of the mixed electrolyte, thereby improving the uniformity and consistency of the prepared layered lithium titanate film electrode. On the other hand, lithium hydroxide has a high alkalinity and can provide a good pH environment during the preparation process, further promoting the formation of layered lithium titanate, and the high solubility of lithium hydroxide also helps to form a uniformly distributed mixed electrolyte.

[0030] In some embodiments, the titanium source is one or more of titanium dioxide, titanium chloride and metatitanic acid. By using a suitable titanium source in the re-preparation, the stability of the layered lithium titanate is improved. It is worth mentioning that titanium dioxide can serve as a heterogeneous nucleation site, which is beneficial to guide the orderly epitaxial growth of layered lithium titanate and reduce the standard deviation of the interlayer spacing. Titanium chloride can quickly release active titanium and increase the reaction rate of subsequent preparation reactions. The hydroxyl groups and layered structure contained in metatitanic acid can induce the oriented growth of the lithium titanate crystal plane, which is beneficial to the preparation of uniformly distributed layered lithium titanate.

[0031] In some embodiments, the carbon source is one or more of glucose, acetylene black, and graphene oxide. It is understood that by introducing a carbon source and compounding it with the layered lithium titanate during the electrochemical deposition process, a continuous conductive network is formed throughout the layered lithium titanate film electrode, which is beneficial to enhancing the electrical conductivity to increase the charge conduction rate. On the other hand, the carbon source can serve as a physical isolation layer, inserted between the layers of the layered lithium titanate, to prevent the face-to-face stacking phenomenon of the two-dimensional sheets during the deposition process, which is beneficial to the diffusion of lithium ions, further reducing the risk of agglomeration of lithium titanate particles, and improving the stability of the layered lithium titanate film electrode.

[0032] In some embodiments, in step S300, the constant voltage is between -1V and -0.5V, specifically, -1V, -0.9V, -0.8V, -0.7V, -0.6V, and -0.5V. More preferably, the constant voltage is between -1V and -0.8V, and more preferably, -1V. The constant voltage is applied for a period of 10 to 60 minutes, specifically, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 minutes. More preferably, the constant voltage is applied for a period of 10 to 30 minutes, and more preferably, for 30 minutes. It is understood that setting the current collector voltage between (-1.2 and -0.8V) vs. Ag / AgCl facilitates driving cations, such as lithium ions and titanium ions, to undergo reduction reactions on the working electrode surface, further forming a lithium titanate deposition layer. While selecting a suitable potential window for depositing layered lithium titanate, a constant voltage is beneficial for accurately maintaining the window and driving the lithium titanate nuclei to align along the lowest surface energy crystal plane, thereby stably generating layered lithium titanate.

[0033] It is worth mentioning that when the constant voltage is too negative, it may trigger the water reduction hydrogen evolution reaction, and the bubbles generated will destroy the layered lithium titanate deposition on the current collector surface, reducing the continuity of the film during formation. When the constant voltage is too positive, the deposition driving force of lithium titanate is insufficient, resulting in a loose and porous film.

[0034] Among them, the use of electrochemical co-deposition to replace high-temperature sintering and subsequent coating steps is conducive to reducing energy consumption in the production process, further reducing production costs, increasing economic benefits, and is easy to operate, environmentally friendly, and has the potential to be put into large-scale production.

[0035] In some embodiments, in step S400, the acid solution is one or more of dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid, acetic acid, and citric acid; the time for the acid treatment is t1, wherein 0s≤t1≤30s, specifically, the time for the acid treatment is 0s, 0.5s, 1s, 2s, 3s, 4s, 5s, 10s, 15s, 20s, 25s, 30s, further preferably, the time for the acid treatment is 10s~20s, more preferably, the time for the acid treatment is 10s. It can be understood that the etching effect produced by the acid treatment is conducive to the formation of oxygen vacancy active sites on the surface of the layered lithium titanate, increasing the selective adsorption performance and adsorption capacity of lithium ions, reducing the interference risk of other ions, especially sodium ions, and reducing the occurrence of agglomeration. Therefore, this layered lithium titanate membrane electrode driven by defect engineering has good performance and stability.

[0036] In some embodiments, the concentration of the acid solution is 0.05 mol / L to 0.2 mol / L, specifically, the concentration of the acid solution is 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, or 0.2 mol / L. More preferably, the concentration of the acid solution is 0.1 mol / L. Selecting appropriate acid treatment conditions is beneficial for forming oxygen vacancy active sites on the surface of the layered lithium titanate, increasing the adsorption performance of lithium ions and reducing interference from impurity ions, especially sodium ions.

[0037] In some embodiments, in step S200, the current collector is one or more of aluminum foil, nickel foam, titanium mesh, and carbon paper. It is worth mentioning that the (111) crystal plane in the aluminum foil forms a semi-coherent interface with the (001) plane of lithium titanate, which promotes the vertical arrangement of layered lithium titanate. On the other hand, the cost of aluminum foil is low, which is conducive to large-scale production. Nickel foam has a high porosity and a large specific surface area, which in turn increases the deposition amount of layered lithium titanate. Titanium mesh has corrosion resistance, with a corrosion rate of less than 0.01 mm / year in an acidic deposition solution with a pH value of 2 to 4, and good high-temperature stability. Carbon paper has a low density, which is conducive to reducing the mass of the electrode and further reducing energy consumption.

[0038] To achieve the above objectives, the present application also provides a layered lithium titanate film electrode prepared by the aforementioned preparation method.

[0039] This application uses electrochemical co-deposition to directly grow a layered lithium titanate film on a current collector, creating close physical and electrochemical contact between the deposited lithium titanate and the current collector, further enhancing the structural and mechanical stability of the electrode. Acid etching then creates oxygen vacancies that serve as active sites, increasing the selective adsorption performance and adsorption capacity for lithium ions, reducing the risk of interference from other ions, and minimizing agglomeration, thereby producing a layered lithium titanate film electrode with excellent lithium ion adsorption performance and easy preparation.

[0040] Example 1 A method for preparing a layered lithium titanate film electrode comprises the following steps: S100, dissolving 8 g of lithium chloride, 46.3 g of titanium trichloride, and 0.08 g of graphene oxide in 3.8 L of water, and ultrasonically dispersing the mixture for 10 min to obtain a mixed electrolyte, wherein the molar ratio of lithium ions to titanium ions in the mixed electrolyte is 1.90:3, the concentration of lithium ions is 0.05 mol / L, and the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.005; S200, construct a three-electrode system, with carbon paper as the working electrode, graphite rod as the counter electrode, and Ag / AgCl as the reference electrode, and place them in a mixed electrolyte for stirring; S300, applying a constant voltage of -0.5 V for 30 minutes, so that the layered lithium titanate is distributed on the surface of the current collector to obtain a layered lithium titanate membrane electrode precursor; S400, after washing and drying the lithium titanate membrane electrode at 60°C, placing it in 0.05 mol / L citric acid for 20 seconds to obtain a layered lithium titanate membrane electrode.

[0041] Example 2 The difference between Example 2 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, and the mass of lithium chloride is 8.3 g.

[0042] Example 3 The difference between Example 3 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 2.05:3, and the mass of lithium chloride is 8.7 g.

[0043] Example 4 The difference between Example 4 and Example 1 is that in step S100, the molar ratio of lithium ions to titanium ions in the mixed electrolyte is 1.95:3, the concentration of lithium ions is 0.1 mol / L, and the amount of water used is 1.95 L.

[0044] Example 5 The difference between Example 5 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.02, and the mass of graphene oxide is 0.54 g.

[0045] Example 6 The difference between Example 6 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.02, and the constant voltage in step S300 is -0.8 V.

[0046] Example 7 The difference between Example 7 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.02, and the constant voltage in step S300 is -1 V.

[0047] Example 8 The difference between Example 8 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.02, and the acid treatment etching time in step S400 is 10 s.

[0048] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, and graphene oxide is not used.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the molar ratio of lithium ions to titanium ions in the mixed electrolyte in step S100 is 1.95:3, the concentration of lithium ions is 0.1 mol / L, the mass ratio of graphene oxide to the prepared layered lithium titanate is 0.02, and citric acid etching is not used.

[0050] Performance evaluation An electrochemical lithium extraction system was constructed using the layered lithium titanate membrane electrodes described in Examples 1-8 and Comparative Examples 1-2, and electrochemical lithium extraction performance testing was performed. The construction and testing methods were as follows: the layered lithium titanate membrane electrode and the counter electrode were placed parallel to each other with a spacing of 1 cm, with the reference electrode close to the layered lithium titanate membrane electrode. A simulated brine mixture of 0.1 mol / L LiCl and 1 mol / L NaCl at a pH of 6 was injected until the electrodes were submerged. The constant voltage was set to -0.5 V (vs. Ag / AgCl) and the system was operated for 30 minutes. Magnetic stirring was activated at a speed of 200 rpm to promote mass transfer. After the electrochemical desorption of lithium ions was completed, the working electrode was removed and quickly transferred to an enrichment tank containing a 0.1 mol / L LiCl solution. The counter electrode was replaced with a platinum sheet to reduce side reactions. After applying a constant voltage of +0.9 V (vs. Ag / AgCl) for 20 minutes, the lithium ion concentration was measured using inductively coupled plasma mass spectrometry, and a cycle test was performed 100 times to detect the capacity retention rate of the layered lithium titanate film electrode. The test results are shown in Table 1.

[0051] Table 1: Performance test of layered lithium titanate film electrode

[0052] It can be seen from Examples 1, 2 and 3 that when the molar ratio of lithium ions to titanium ions in the mixed electrolyte is 1.95:3, the adsorption capacity for lithium ions is the highest. Therefore, selecting an appropriate molar ratio of lithium ions to titanium ions is beneficial to improving the adsorption capacity of the layered lithium titanate membrane electrode for lithium ions.

[0053] It can be known from Example 2 and Example 4 that the adsorption capacity of the lithium ion of the layered lithium titanate film electrode increases with the increase of the lithium ion concentration. On the other hand, it can be known from Example 4 and Example 5 that the cycle stability of the layered lithium titanate film electrode can be significantly improved with the increase of the amount of the carbon source.

[0054] It can be known from the analysis of Example 5, Example 6 and Example 7 that the thickness of the layered lithium titanate film deposited on the current collector increases with the increase of the constant voltage, which further improves the adsorption capacity and cycle stability of the layered lithium titanate film electrode.

[0055] It can be found from the analysis of Example 5, Example 7 and Comparative Example 1 that the stability of the layered lithium titanate film electrode after multiple cycles is significantly reduced without the addition of graphene oxide. This is because the carbon source can be inserted into the interlayer of the layered lithium titanate as a physical isolation layer, preventing the face-to-face stacking phenomenon of the two-dimensional sheet layer generated during the deposition process, facilitating the diffusion of lithium ions, further reducing the risk of agglomeration of lithium titanate particles, and increasing the use stability of the layered lithium titanate film electrode.

[0056] It can be found from the analysis of Example 7, Example 8 and Comparative Example 2 that the selective adsorption of the lithium titanate film electrode without citric acid etching to lithium ions is poor, and a shorter etching time will also damage the lattice structure, which is not conducive to enhancing the selective adsorption of lithium ions.

[0057] The above describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a layered lithium titanate film electrode, characterized in that: Including steps: S100, placing a lithium source, a titanium source, and a carbon source in water and dispersing them to obtain a mixed electrolyte; S200, constructing a three-electrode system, with the current collector serving as the working electrode, the graphite rod serving as the counter electrode, and the Ag / AgCl serving as the reference electrode, and placing the mixed electrolyte for stirring; S300, applying a constant voltage for treatment, so that layered lithium titanate is distributed on the surface of the current collector to obtain a layered lithium titanate membrane electrode precursor; S400 , after washing and drying the layered lithium titanate membrane electrode precursor, placing it in an acid solution for treatment to obtain a layered lithium titanate membrane electrode.

2. The preparation method according to claim 1, characterized in that The molar number of lithium element in the mixed electrolyte is n1, and the molar number of titanium element is n2, wherein the ratio of n1 / n2 is (1.90-2.10):

3.

3. The preparation method according to claim 1, characterized in that The mass of the carbon source is m1, and the mass of the layered lithium titanate prepared in step S200 is m2, wherein 0.005≤m1 / m2≤0.

03.

4. The preparation method according to claim 1, characterized in that The concentration of lithium ions in the mixed electrolyte is 0.05 mol / L to 0.2 mol / L, and the lithium source is one or more of lithium carbonate, lithium chloride and lithium hydroxide.

5. The preparation method according to claim 1, characterized in that The titanium source is one or more of titanium dioxide, titanium chloride and metatitanic acid.

6. The preparation method according to claim 1, characterized in that The carbon source is one or more of glucose, acetylene black and graphene oxide.

7. The preparation method according to claim 1, characterized in that In step S300, the constant voltage is -1V to -0.5V, and the time for applying the constant voltage is 10 minutes to 60 minutes.

8. The preparation method according to claim 1, characterized in that In step S400, the acid solution is one or more of dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid, acetic acid, and citric acid; the time of the acid solution treatment is t1, where 0s≤t1≤30s, and the concentration of the acid solution is 0.05mol / L~0.2mol / L.

9. The preparation method according to claim 1, characterized in that In step S200, the current collector is one or more of aluminum foil, nickel foam, titanium mesh and carbon paper.

10. A layered lithium titanate film electrode, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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