High-efficiency lithium extraction electrode material for salt lake and lithium extraction electrode

Abstract

This invention discloses a high-efficiency lithium extraction electrode material from salt lakes and an electrode prepared using this material. The preparation method of the electrode material is as follows: S1, coating a titanium source onto the surface of iron phosphate to obtain iron phosphate FePO4@titanium oxide coated with titanium oxide; S2, adding FePO4@titanium oxide, lithium source, and carbon source to ethanol, mixing evenly, and drying to form a powder; S3, calcining the powder at 600-900℃ for 6-14 hours under a protective atmosphere to obtain Li 1‑2x Fe 1‑x Ti x The target electrode material is a PO4@lithium titanium oxide composite electrode powder. The obtained electrode material is coated onto a current collector and then delithiated to obtain a rapid and efficient lithium extraction electrode. In the electrode material of this invention, lithium titanium oxide coats LiFePO4 as a dedicated medium for conducting lithium ions, thus acting as an ion sieving agent. Partial Ti doping of LiFePO4 expands the one-dimensional channels of LiFePO4, thereby increasing the Li-ion conductivity of LiFePO4. + The selectivity also improves lithium extraction kinetics.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from salt lake brine, and in particular to a method for preparing a high-efficiency lithium extraction electrode material from salt lakes and an electrode prepared using the electrode material. Background Technology

[0002] Lithium, as the lightest alkali metal, plays an increasingly important role in ceramics, artificial glass, thermonuclear fusion, oils and greases, refrigerants, and especially rechargeable batteries. The booming development of lithium-ion batteries in electronic devices and electric vehicles has spurred strong demand for lithium. Therefore, lithium extraction from salt lake brines and seawater is attracting increasing attention.

[0003] Currently, several technologies have been developed for recovering lithium from salt lake brines and seawater, such as solar evaporation, co-precipitation, electrochemical techniques, solvent extraction, and ion exchange. However, these methods all have their own limitations and complex preparation processes, restricting their widespread application. Electrochemical adsorption lithium extraction is a highly attractive method with advantages such as high selectivity, fast adsorption rate, low energy consumption, no pollution, and low cost. This method can utilize renewable energy to power the electrochemical process. During electrochemical lithium extraction, lithium can be driven into the electrode material by an electric current and then released in the recovery liquid. LiFePO4 electrode material has high electrochemical reversibility, low loss, and good stability with lithium insertion / extraction potentials between H2 and O2 deposition potentials. However, its performance in Na+... + High-concentration aqueous solutions have lower lithium intercalation capacity and contain more Na. + With Li + Since lithium is co-intercalated, increasing the lithium intercalation content of LiFePO4 electrode materials is particularly important. Summary of the Invention

[0004] To solve the problem in Na + Na+ in high-concentration aqueous solutions of traditional LiFePO4 electrodes during lithium extraction + To address the issues of high insertion ratio and slow kinetics, this invention provides a high-efficiency lithium extraction electrode material from salt lakes and an electrode prepared using this material.

[0005] The high-efficiency lithium extraction electrode material provided by this invention is Li 1-2x Fe 1-x Ti x PO4@lithium titanium oxide composite electrode material; wherein the lithium titanium oxide is Li2TiO3 or Li4Ti5O 12 or Li2TiO3 / Li4Ti5O 12 A type of heterojunction.

[0006] The high-efficiency lithium extraction electrode material from salt lakes, namely Li 1-2x Fe1-x Ti x The PO4@lithium titanium oxide composite electrode material is prepared by the following method:

[0007] Step S1: Coat the surface of iron phosphate with a titanium source to obtain iron phosphate FePO4@titanium oxide coated with titanium oxide. The titanium source is one or more of titanium dioxide, metatitanic acid, tetrabutyl titanate, and tetra(dimethylamino)titanium.

[0008] Step S2: Add FePO4@titanium oxide, lithium source, and carbon source to ethanol, mix evenly, and then dry to form powder.

[0009] The lithium source is one or more of lithium hydroxide, lithium chloride, lithium carbonate, lithium acetate dihydrate, and lithium oxalate.

[0010] The carbon source is one or more of the following: carbon powder, glucose, sucrose, and starch.

[0011] Step S3: Calcine the powder obtained in step S2 at 600-900℃ for 6-14 hours under a protective atmosphere to obtain Li. 1- 2x Fe 1-x Ti x PO4@lithium titanium oxide composite electrode material powder, i.e., high-efficiency lithium extraction electrode material from salt lakes; wherein 0 <x<0.5。

[0012] Preferably, in step S1, the molar ratio of the titanium source to iron phosphate is 0.05 to 0.3:1.

[0013] Preferably, in step S2, the ratio of the lithium source to FePO4@TiO2 is required to ensure that the molar ratio of Li:Fe:Ti is 1.06-1.62:1:0.05-0.2.

[0014] Preferably, in step S2, the molar ratio of the carbon source to iron phosphate is 0.25 to 0.3:1. For carbon sources whose molar ratio cannot be calculated, the amount of carbon source added is 8% to 15% of the mass of iron phosphate.

[0015] Using the above-mentioned Li 1-2x Fe 1-x Ti x The method for preparing electrodes using PO4@lithium titanium oxide composite electrode material is as follows:

[0016] (1) Li 1-2x Fe 1-x Ti x After mixing PO4@lithium titanium oxide composite electrode powder, conductive agent, binder and dispersant, the mixture is coated onto the surface of the current collector and dried to produce Li 1-2x Fe1-x Ti x PO4@lithium titanium oxide composite electrode.

[0017] (2) Li 1-2x Fe 1-x Ti x The PO4@lithium titanium oxide composite electrode is connected to the positive electrode, and the nickel foam electrode is connected to the negative electrode. Delithiation occurs in the electrolyte to obtain Fe. 1-x Ti x PO4@lithium titanium oxide composite electrode.

[0018] Preferably, in step (1), the conductive agent is one of acetylene black, carbon black, Ketjen black, vapor-grown carbon fiber, KS-6, SFG-6, carbon nanotubes, activated carbon, graphite, graphene, or SuperP; the binder is one of polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, or polytetrafluoroethylene; and the dispersant is N-methylpyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide.

[0019] Preferably, in step (1), the Li 1-2x Fe 1-x Ti x The mass ratio of PO4@lithium titanium oxide composite electrode powder, conductive agent, and binder is 7-8:1-2:1.

[0020] Preferably, the current collector is one of titanium foil, titanium mesh, titanium plate, stainless steel sheet, graphite sheet, graphite plate, carbon paper, carbon cloth, or carbon felt.

[0021] Preferably, in step (1), the drying conditions are: forced air drying at 60-80°C for 8-16 hours, followed by vacuum drying at 80-120°C for 8-16 hours.

[0022] Preferably, in step (2), delithiation is performed using a constant voltage of 1V until the current density is less than 0.05mA / cm. 2 At the specified time, the electrolyte is one or more of NaCl, KCl, and MgCl2.

[0023] Li 1-2x Fe 1-x Ti x PO4@lithium titanium oxide composite electrode with Fe 1-x Ti x The PO4@lithium titanium oxide composite electrode was placed in the recovery solution and lithium extraction solution of an electrolytic cell with anion exchange membrane, respectively, and connected to the positive and negative electrodes for electrochemical lithium extraction. Then, the two electrodes were exchanged to allow Li to... + It is enriched in the recovery liquid.

[0024] The recovery solution is a dilute NaCl solution or a dilute LiCl solution; the lithium extraction method can be one of the following:

[0025] (1) Maintain a constant voltage of 0.2V until the current density is less than 0.05mA / cm. 2 Deadline;

[0026] (2) 1.5 mA / cm 2 The constant current continues until the voltage reaches 0.35V and then cuts off.

[0027] (3) 0.6A constant current until the voltage reaches 0.35V, and work at this voltage until the current is 0.1A and then cut off.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] (1) Lithium titanium oxide coated on LiFePO4 acts as a medium for conducting lithium ions, enhancing the performance of LiFePO4 in low Li-level environments. + High Na concentration + Li concentration in solution + The selectivity is enhanced. Simultaneously, during lithium intercalation into the titanium-coated iron phosphate precursor, both the internal iron phosphate and the external titanium oxide achieve lithium intercalation. A small amount of titanium also enters the lithium iron phosphate lattice at high temperatures, achieving doping. Metal ion doping helps expand the internal lithium ion diffusion channels, increasing the internal diffusion rate of the electrode, thereby enhancing the kinetic characteristics of the lithium extraction electrode.

[0030] (2) The lithium extraction electrode prepared by this invention has a simple process, is environmentally friendly, and improves lithium selectivity and lithium extraction rate, making it an excellent electrochemical lithium extraction material.

[0031] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0032] Figure 1 The graph shows the adsorption capacity of the electrodes prepared in Examples 1-3 and the comparative examples in LiCl solution at different times.

[0033] Figure 2 Li adsorbed in simulated brine by electrodes prepared in Examples 1-3 and the comparative example. + Zhan Li + +Na + The proportion. Detailed Implementation

[0034] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0035] Example 1

[0036] A high-efficiency lithium extraction electrode material from salt lakes (Li 0.98 Fe 0.99 Ti 0.01 Preparation method of PO4@Li2TiO3 composite material:

[0037] (1) Add 8g of tetrabutyl titanate to 1L of ethanol and stir evenly. Add ferric phosphate at a molar ratio of tetrabutyl titanate to ferric phosphate of 0.2:1 while stirring. Continue stirring until a slurry is formed. Then dry it in an oven at 70℃. Then calcine the dried powder at 700℃ for 2h to obtain titanium dioxide-coated ferric phosphate FePO4@TiO2.

[0038] (2) The FePO4@TiO2, Li2CO3 and carbon powder obtained in step (1) are mixed evenly in ethanol at a Li:Fe:Ti:C molar ratio of 1.42:1:0.2:0.25, and then dried in an oven at 60°C to make powder.

[0039] (3) The dried powder was heated at 700℃ for 12 hours under argon atmosphere to obtain Li. 0.98 Fe 0.99 Ti 0.01 PO4@Li2TiO3 composite electrode powder.

[0040] Using Li 0.98 Fe 0.99 Ti 0.01 The electrode was prepared from PO4@Li2TiO3 composite electrode powder using the following method:

[0041] Step 1: Place Li 0.98 Fe 0.99 Ti 0.01 PO4@Li2TiO3 composite electrode powder, SuperP, and polyvinylidene fluoride were mixed evenly in N-methylpyrrolidone at a mass ratio of 7:2:1 (the mass of N-methylpyrrolidone was 20 times the mass of polyvinylidene fluoride). The mixture was then coated onto a carbon felt, dried first at 60℃ for 12 hours by forced air drying, and then vacuum dried at 120℃ for 12 hours to prepare Li2TiO3 composite electrode powder. 0.98 Fe 0.99 Ti 0.01 PO4@Li2TiO3 composite electrode.

[0042] Step 2: Li 0.98 Fe 0.99 Ti 0.01A PO4@Li2TiO3 composite electrode was connected to the positive electrode, and a nickel foam electrode was connected to the negative electrode. Lithium was removed in a 0.5M NaCl solution to obtain Fe. 0.99 Ti 0.01 For the PO4@Li2TiO3 composite electrode, delithiation was performed using a constant voltage of 1V until the current density was less than 0.05mA / cm. 2 Deadline.

[0043] The obtained Fe 0.99 Ti 0.01 PO4@Li2TiO3 composite electrode and Li 0.98 Fe 0.99 Ti 0.01 The PO4@Li2TiO3 composite electrode was placed in the lithium extraction solution and the recovery solution in an electrolytic cell with anion exchange membrane, respectively, and connected to the negative and positive electrodes for electrochemical lithium extraction. Then, the two electrodes were exchanged to allow Li to be extracted. + The lithium is enriched in the recovery solution. The lithium extraction solution is a 0.15M LiCl solution or simulated brine, and the recovery solution is a 0.1M NaCl solution. The lithium extraction is carried out using a constant current of 0.6A until the voltage reaches 0.35V, and then operates at this voltage until the current drops to 0.1A to cut off.

[0044] Example 2

[0045] This embodiment is basically the same as Embodiment 1, except that the proportion of Li2CO3 is different in step (2). The molar ratio of FePO4@TiO2, Li2CO3, and carbon powder is 1.18:1:0.2:0.25, and the prepared electrode material powder is Li 0.98 Fe 0.99 Ti 0.01 PO4@Li4Ti5O 12 The complex, and the rest are set up the same way.

[0046] Example 3

[0047] This embodiment is basically the same as Embodiment 1, except that the proportion of Li2CO3 is different in step (2). The molar ratio of FePO4@TiO2, Li2CO3, and carbon powder is 1.27:1:0.2:0.25, and the prepared electrode material powder is Li 0.98 Fe 0.99 Ti 0.01 PO4@Li2TiO3 / Li4Ti5O 12 The complex, and the rest are set up the same way.

[0048] Comparative Example

[0049] This comparative example of lithium extraction from salt lakes is directly produced by sintering using the same lithium source, carbon source, and iron phosphate as in the above examples, i.e., without lithium titanium oxide coating. Specifically, the comparative example of lithium extraction from salt lakes is prepared through the following steps:

[0050] (1) FePO4, Li2CO3 and carbon powder were mixed evenly in ethanol at a Li:Fe:C molar ratio of 1.01:1:0.25, and then dried in an oven at 60°C. The dried powder was then heated at 700°C for 12 hours under a protective atmosphere to obtain LiFePO4 electrode powder.

[0051] (2) The LiFePO4 composite electrode powder obtained in step (1), SuperP, and polyvinylidene fluoride are mixed evenly in N-methylpyrrolidone at a mass ratio of 7:2:1 (the mass of N-methylpyrrolidone is 20 times the mass of polyvinylidene fluoride). The mixture is then coated on a carbon felt, dried at 60°C for 12 hours and then vacuum dried at 120°C for 12 hours to produce a LiFePO4 electrode.

[0052] (3) Connect the LiFePO4 electrode obtained in step (2) to the positive electrode and the nickel foam electrode to the negative electrode, and delithigate in a 0.5M NaCl solution to obtain the FePO4 electrode. The delithiation is performed using a constant voltage of 1V until the current density is less than 0.05mA / cm. 2 Deadline.

[0053] The obtained FePO4 electrode and LiFePO4 electrode were placed in the lithium extraction solution and recovery solution of an electrolytic cell equipped with anion exchange membrane, respectively, and connected as negative and positive electrodes for electrochemical lithium extraction. Then, the two electrodes were exchanged to allow Li... + The lithium is enriched in the recovery solution. The lithium extraction solution is a 0.15M LiCl solution or simulated brine, and the recovery solution is a 0.1M NaCl solution. The lithium extraction is carried out using a constant current of 0.6A until the voltage reaches 0.35V, and then operates at this voltage until the current drops to 0.1A to cut off.

[0054] The performance of the lithium extraction electrodes from salt lakes obtained in Examples 1-3 and the comparative example was tested experimentally. The recovered solution was then diluted with deionized water, and the concentration was measured to simulate the equilibrium adsorption capacity and adsorption kinetics during the adsorption process. The experimental results are shown in [Figure number missing]. Figure 1 and Figure 2 .

[0055] from Figure 1 and Figure 2 As can be seen, compared with the electrode materials prepared by conventional methods in the comparative example, the lithium extraction electrode material prepared by this invention has a larger adsorption capacity, better lithium-ion selectivity, and still maintains high selectivity after multiple cycles. That is, the electrode material of this invention can effectively improve lithium-ion selectivity while ensuring a large adsorption capacity.

[0056] In summary, the method for preparing a high-efficiency lithium extraction electrode from salt lakes provided by this invention is simple and convenient to operate, and the resulting adsorbent material product has excellent performance and is environmentally friendly. The prepared high-efficiency lithium extraction electrode from salt lakes involves coating an iron phosphate precursor with a titanium source, then mixing it uniformly with a lithium source, and finally subjecting this material to high-temperature sintering for lithium intercalation. During this process, both the internal iron phosphate and the external titanium oxide simultaneously achieve lithium intercalation. Simultaneously, a small amount of titanium enters the lithium iron phosphate lattice at high temperature, achieving doping, which improves the LiFePO4 Li-… + The selectivity also improves lithium extraction kinetics, and the process is simple yet powerful.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-efficiency lithium extraction electrode material from salt lakes, characterized in that, The preparation method is as follows: S1. Coating the surface of iron phosphate with titanium source to obtain iron phosphate FePO4@titanium oxide coated with titanium oxide; S2. Add FePO4@titanium oxide, lithium source, and carbon source to ethanol, mix evenly, and then dry to form powder; S3. Calcine the powder obtained in step S2 at 600-900℃ for 6-14 hours under a protective atmosphere to obtain Li. 1-2x Fe 1-x Ti x PO4@lithium titanium oxide composite electrode material powder, i.e., high-efficiency lithium extraction electrode material from salt lakes; wherein 0 <x<0.5; The lithium titanium oxide is Li2TiO3 or Li4Ti5O. 12 or Li2TiO3 / Li4Ti5O 12 A type of heterojunction.

2. The high-efficiency lithium extraction electrode material from salt lakes as described in claim 1, characterized in that, The titanium source is one or more of titanium dioxide, metatitanic acid, tetrabutyl titanate, and tetra(dimethylamino)titanium.

3. The high-efficiency lithium extraction electrode material from salt lakes as described in claim 2, characterized in that, The molar ratio of the titanium source to iron phosphate is 0.05 to 0.3:

1.

4. The high-efficiency lithium extraction electrode material from salt lakes as described in claim 1, characterized in that, The lithium source is one or more of lithium hydroxide, lithium chloride, lithium carbonate, lithium acetate dihydrate, and lithium oxalate.

5. The high-efficiency lithium extraction electrode material from salt lakes as described in claim 1, characterized in that, The carbon source is one or more of the following: carbon powder, glucose, sucrose, and starch.

6. A high-efficiency lithium extraction electrode from salt lakes, characterized in that, It is prepared using the high-efficiency lithium extraction electrode material from salt lakes as described in any one of claims 1-5.

7. The high-efficiency lithium extraction electrode from salt lakes as described in claim 6, characterized in that, The preparation method is as follows: (1) Li 1-2x Fe 1-x Ti x After mixing PO4@lithium titanium oxide composite electrode powder, conductive agent, binder and dispersant, the mixture is coated onto the surface of the current collector and dried to produce Li 1-2x Fe 1-x Ti x PO4@lithium titanium oxide composite electrode; (2) Li 1-2x Fe 1-x Ti x The PO4@lithium titanium oxide composite electrode underwent delithiation in the electrolyte to obtain Fe. 1-x Ti x PO4@lithium titanium oxide composite electrode.

8. The high-efficiency lithium extraction electrode from salt lakes as described in claim 7, characterized in that, The conductive agent is one of acetylene black, carbon black, Ketjen black, vapor-grown carbon fiber VGCF, KS-6, SFG-6, carbon nanotubes, activated carbon, graphite, graphene, or Super P; the binder is one of polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, or polytetrafluoroethylene; the dispersant is N-methylpyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide.

9. The high-efficiency lithium extraction electrode from salt lakes as described in claim 7, characterized in that, In step (1), the drying conditions are: forced air drying at 60-80°C for 8-16 hours, followed by vacuum drying at 80-120°C for 8-16 hours.

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