A manganese phosphate modified lithium manganate composite electrode for electrochemical lithium extraction and a preparation method and application thereof

Abstract

The application discloses a kind of for electrochemical lithium extraction manganese phosphate modified lithium manganate composite electrode and its preparation method and application, including lithium manganate matrix material, and the manganese phosphate that is loaded on the surface of lithium manganate matrix material;The phosphate modified lithium manganate composite electrode, the manganese phosphate in the present application is amorphous surface coating.The amorphous phosphate can uniformly coat lithium manganate matrix material, and the manganese phosphate can effectively improve the hydrophilicity of lithium manganate base material, promote lithium ion diffusion, enhance the cycle stability of lithium manganate, and can effectively extract lithium ions in simulated brine and high sodium / lithium ratio containing alkaline zabuye real brine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium extraction from salt lakes, and particularly relates to a manganese phosphate modified lithium manganate composite electrode for electrochemical lithium extraction and a preparation method and application thereof. BACKGROUND

[0002] Lithium and its compounds have important significance in civilian and high-tech military fields due to their high transmission efficiency and electrochemical activity, and they have gradually become a strategic resource. Due to the continuous use of lithium ion batteries in portable electronic products, energy vehicles and energy storage fields, the demand for lithium resources has increased. Lithium resources in salt lake brine account for 87% of global lithium resource reserves, so it is imperative to find a method for efficiently and selectively extracting lithium from salt lake brine.

[0003] The lithium manganate electrochemical lithium ion pump can extract lithium ions from salt lake brine with low energy consumption, high selectivity and high efficiency. The principle is based on the lithium de-embedding and removal in the charging and discharging process of lithium ion batteries, thereby selectively extracting and releasing lithium. Due to the unique lithium ion vacancy formed by the Mn-O framework, the spinel lithium manganate will be affected by the Jahn-Teller effect in the process of electrochemical lithium extraction, which irreversibly destroys the structural integrity of the spinel framework from the cubic phase to the tetragonal phase, resulting in permanent capacity loss. The dissolution of manganese leads to continuous loss of active material, which hinders the three-dimensional diffusion path of lithium, and further reduces the overall performance of lithium manganate. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a low-cost, high-adsorption-capacity and high-cycle-stability manganese phosphate modified lithium manganate composite electrode for lithium extraction from salt lakes to effectively improve the hydrophilicity, cycle stability and lithium ion extraction and release capacity of lithium manganate.

[0005] In order to achieve the above-mentioned application purpose, the technical solutions adopted by the present application are as follows:

[0006] A manganese phosphate modified lithium manganate composite electrode for electrochemical lithium extraction, comprising a lithium manganate base material and manganese phosphate loaded on the surface of the lithium manganate base material.

[0007] In the present application, the manganese phosphate in the manganese phosphate modified lithium manganate composite electrode is amorphous surface coated. The amorphous manganese phosphate can uniformly coat the lithium manganate base material, and the manganese phosphate can effectively improve the hydrophilicity of the lithium manganate base material, promote lithium ion diffusion and enhance the cycle stability of lithium manganate.

[0008] Further, the loading amount of the manganese phosphate is 0.25-2wt% of the base material, preferably 0.25-1wt%, and most preferably 0.5wt%.

[0009] Further, the application also provides a preparation method of the above-mentioned lithium manganese phosphate modified lithium manganate composite electrode for electrochemical lithium extraction, comprising the following steps:

[0010] (1) dissolving a soluble manganese salt in deionized water to obtain solution A;

[0011] (2) dissolving a phosphate salt in deionized water to obtain solution B;

[0012] (3) under stirring, adding lithium manganate into the solution A obtained in step (1) to obtain solution C;

[0013] (4) under stirring, adding the solution B obtained in step (2) into the solution C obtained in step (3) and mixing uniformly to obtain black gel;

[0014] (5) drying the black gel obtained in step (4), grinding into powder, and then calcining under air atmosphere to obtain the lithium manganese phosphate modified lithium manganate composite electrode.

[0015] Specifically, in step (1), the metal salt is any one or more than two kinds of mixture of manganese nitrate, manganese chloride and manganese acetate. The manganese ion concentration in the solution A is 0.27-2.16 g / L.

[0016] Specifically, in step (2), the phosphate salt is any one or mixture of two of diammonium hydrogen phosphate and ammonium dihydrogen phosphate. The phosphate concentration in the solution B is 0.98-7.84 g / L.

[0017] Specifically, in step (3), the content of lithium manganate in the solution C is 80-120 g / L.

[0018] Specifically, in step (4), the solution B and the solution C are mixed at a volume ratio of 0.8-1.2:1, and are mixed uniformly at a stirring speed of 400-800 r / min to obtain black gel. The formed gel is black and has Tyndall effect.

[0019] Specifically, in step (5), the drying temperature is 60-90℃, the drying time is 6-9 h, the calcining temperature is 450-750℃, and the calcining time is 4-9 h.

[0020] Further, the application also claims the application of the above-mentioned lithium manganese phosphate modified lithium manganate composite electrode in liquid lithium-containing solution as an electrode material for extracting lithium ions.

[0021] Specifically, the concentration of lithium ions in the liquid lithium-containing solution is 200-1500 mg / L.

[0022] Beneficial effects:

[0023] (1) The protection ability of manganese phosphate to electrode active material in the application comes from the high electronegativity of PO4 3- , PO4 3- has a strong P-O covalent bond to maintain the phase stability between the electrode and the electrolyte, and the inert manganese ion can be replaced with the surface elements of lithium manganate during the calcination process to achieve the surface doping of metal ions, thereby improving the cycle stability of lithium manganate. In addition, the strong polarity of manganese phosphate can effectively improve the interface hydrophilicity of lithium manganate, increase the contact opportunity of lithium manganate and lithium ions, and further improve the lithium ion extraction and release capacity of the material. Therefore, manganese phosphate can not only optimize the stability of lithium manganate, but also improve the lithium ion extraction and release performance.

[0024] (2) The application first uses manganese phosphate to improve the hydrophilicity of lithium manganate matrix material, further improves the hydrophilicity of the composite electrode, and further improves the lithium ion diffusion performance, cycle stability, and lithium extraction capacity of salt lake brine of the electrode material.

[0025] (3) The manganese phosphate modified lithium manganate composite electrode prepared by the sol-gel method adopted in the application has the advantages of simple operation, short preparation period, green process, and uniform loading of manganese phosphate.

[0026] (4) The manganese phosphate modified lithium manganate material prepared in the application can effectively extract and release lithium ions in simulated brine and real Zhabuye alkaline brine containing high sodium / lithium ratio.

[0027] (5) The electrochemical lithium ion pump driving method adopted in the application does not need to use organic reagents throughout the process, is simple to operate, green and environmentally friendly, and has good industrial prospects. BRIEF DESCRIPTION OF DRAWINGS

[0028] The above and / or other aspects of the application will become more apparent by describing in detail the application with reference to the accompanying drawings, as follows:

[0029] Figure 1 is a transmission electron microscope picture of 0.5% manganese phosphate-lithium manganate.

[0030] Figure 2 is a contact angle picture of 0.5% manganese phosphate-lithium manganate and other samples.

[0031] Figure 3 is a cycle performance picture of 0.5% manganese phosphate-lithium manganate and other samples.

[0032] Figure 4 is a manganese dissolution loss picture of 0.5% manganese phosphate-lithium manganate and other samples after 20 cycles.

[0033] Figure 5 is an electrochemical lithium extraction performance graph of 0.5% manganese phosphate-lithium manganate and other samples in simulated brine.

[0034] Figure 6 is a plot of the electrochemical lithium extraction performance of 0.5% manganese phosphate - lithium manganate in simulated lithium setting mother liquor.

[0035] Figure 7 is a plot of the electrochemical lithium extraction performance of 0.5% manganese phosphate - lithium manganate in real Zhabuye brine. DETAILED DESCRIPTION

[0036] The present application can be better understood in accordance with the following examples.

[0037] Comparative Example 1

[0038] 1 g of lithium manganate (LiMn204) was added to the solution to form a black solution, the black solution was dried at 60°C for 7 hours, ground uniformly with a mortar into a black powder, and calcined at 550°C for 4 hours in an air atmosphere to obtain pure LiMn204, which was marked as lithium manganate.

[0039] 1 g of lithium manganate, 0.125 g of polyvinylidene fluoride (PVDF), and 0.125 g of conductive carbon black were mixed and ground uniformly, and dissolved in 10 ml of N-methyl pyrrolidone (NMP) to form an electrode slurry after stirring at a rate of 500 r / min for 24 hours. The electrode slurry was uniformly coated on a graphite plate of 1 cm x 2 cm to form a working electrode after drying at 60°C for 10 hours, and the loading amount was 10 mg. The contact angle of the lithium manganate working electrode was 57.43°. With a platinum sheet as a counter electrode and a mercury-tungsten electrode as a reference electrode, the discharge capacity retention rate after 20 charge-discharge cycles was 50.6%, and the manganese dissolution loss in the electrolyte after 20 charge-discharge cycles was 0.187%. With lithium manganate as a working electrode and an Ag sheet as a counter electrode, an electrochemical lithium ion extraction and release experiment was completed in an electric field driving 30 mmol / L simulated salt lake brine (in which the lithium, sodium, potassium, magnesium, and calcium ion concentrations were about 210, 690, 1180, 730, and 1200 mg / L), respectively. After 5 extraction and release cycles, the average lithium release capacity was 13.05 mg / g each time.

[0040] Example 1

[0041] Take 0.0065 g of manganese nitrate (Mn(NO3)2) dissolved in 10 ml of deionized water to form solution A, take 0.0024 g of ammonium dihydrogen phosphate (NH4H2PO4) dissolved in 10 ml of deionized water to form solution B, under the stirring rate of 500 r / min, 1 g of LiMn2O4 is added to the solution to form solution C, and finally under the stirring rate of 500 r / min, solution B is slowly dropped into solution C to form a black gel, and there is obvious Tyndall effect; the black gel is dried at 60°C for 7 hours, ground uniformly with a mortar to a black powder, and calcined at 550°C in an air atmosphere for 4 hours to obtain 0.25wt% phosphate modified LiMn2O4, marked as 0.25MP-lithium manganate.

[0042] 1 g of 0.25MP-lithium manganate, 0.125 g of PVDF, and 0.125 g of conductive carbon black are mixed and ground uniformly, and dissolved in 10 ml of NMP to form an electrode slurry after stirring at a rate of 500 r / min for 24 hours. The electrode slurry is uniformly coated on a 1 cm×2 cm graphite plate to form a working electrode after drying at 60°C for 10 hours, with a loading of 10 mg. The contact angle of the 0.25MP-lithium manganate working electrode is 53.76°. With a platinum sheet as the counter electrode and a mercury-tungsten electrode as the reference electrode, the discharge capacity retention rate after 20 charge-discharge cycles is 73.86%, and the manganese dissolution loss in the electrolyte after 20 charge-discharge cycles is 0.165%. With 0.25MP-lithium manganate as the working electrode and an Ag sheet as the counter electrode, an electrochemical lithium ion extraction and release experiment is carried out in a 30 mmol / L simulated salt lake brine (where the lithium, sodium, potassium, magnesium, and calcium ion concentrations are about 210, 690, 1180, 730, and 1200 mg / L, respectively) under the action of an electric field. After 5 extraction and release cycles, the average lithium release capacity is 15.51 mg / g.

[0043] Example 2

[0044] Take 0.013 g of Mn(NO3)2 dissolved in 10 ml of deionized water to form solution A, take 0.0048 g of NH4H2PO4 dissolved in 10 ml of deionized water to form solution B, under the stirring rate of 500 r / min, 1 g of LiMn2O4 is added to the solution to form solution C, and finally under the stirring rate of 500 r / min, solution B is slowly dropped into solution C to form a black gel, and there is obvious Tyndall effect; the black gel is dried at 60°C for 7 hours, ground uniformly with a mortar to a black powder, and calcined at 550°C in an air atmosphere for 4 hours to obtain 0.5wt% phosphate modified LiMn2O4, marked as 0.5MP-lithium manganate.

[0045] 1 g of 0.5MP-lithium manganese oxide, 0.125 g of PVDF, 0.125 g of conductive carbon black were mixed and ground uniformly, and dissolved in 10 ml of NMP to form an electrode slurry after stirring at a rate of 500 r / min for 24 hours. The electrode slurry was uniformly coated on a 1 cm x 2 cm graphite plate to form a working electrode after drying at 60°C for 10 hours, with a loading of 10 mg. The contact angle of the 0.5MP-lithium manganese oxide working electrode was 51.18°. With a platinum sheet as the counter electrode and a mercury-tungsten electrode as the reference electrode, the discharge capacity retention rate after 20 charge-discharge cycles was 93.64%, and the manganese dissolution loss in the electrolyte after 20 charge-discharge cycles was 0.154%. With 0.5MP-lithium manganese oxide as the working electrode and Ag sheet as the counter electrode, an electrochemical lithium ion extraction and release experiment was carried out in 30 mmol / L simulated salt lake brine (wherein the lithium, sodium, potassium, magnesium, calcium lithium ion concentrations were about 210, 690, 1180, 730, 1200 mg / L) under the action of an electric field. After 5 extraction and release cycles, the average lithium release capacity was 16.52 mg / g.

[0046] Example 3

[0047] 0.026 g of Mn(NO3)2 was dissolved in 10 ml of deionized water to form solution A, and 0.0096 g of NH4H2PO4 was dissolved in 10 ml of deionized water to form solution B. 1 g of LiMn2O4 was added to the solution to form solution C under stirring at a rate of 500 r / min, and finally solution B was slowly dropped into solution C to form a black gel with obvious Tyndall effect under stirring at a rate of 500 r / min. The black gel was dried at 60°C for 7 hours, ground uniformly with a mortar to form a black powder, and calcined at 550°C for 4 hours in an air atmosphere to obtain 1 wt% phosphate modified LiMn2O4, marked as 1MP-lithium manganese oxide.

[0048] 1 g of 1MP-lithium manganate, 0.125 g of PVDF, 0.125 g of conductive carbon black were mixed and ground uniformly, and dissolved in 10 ml of NMP to form an electrode slurry after stirring at a rate of 500 r / min for 24 hours. The electrode slurry was uniformly coated on a 1 cm x 2 cm graphite plate to form a working electrode after drying at 60°C for 10 hours, with a loading of 10 mg. The contact angle of the 1MP-lithium manganate working electrode was 46.29°. With a platinum sheet as the counter electrode and a mercury-tungsten electrode as the reference electrode, the discharge capacity retention rate after 20 charge-discharge cycles was 81.77%, and the manganese dissolution loss in the electrolyte after 20 charge-discharge cycles was 0.162%. With 1MP-lithium manganate as the working electrode and an Ag sheet as the counter electrode, an electrochemical lithium ion extraction and release experiment was performed in 30 mmol / L simulated salt lake brine (with lithium, sodium, potassium, magnesium, and calcium ion concentrations of about 210, 690, 1180, 730, and 1200 mg / L) under the action of an electric field. After 5 extraction and release cycles, the average lithium release capacity was 13.85 mg / g.

[0049] Example 4

[0050] 0.052 g of Mn(NO3)2 was dissolved in 10 ml of deionized water to form solution A, and 0.0192 g of NH4H2PO4 was dissolved in 10 ml of deionized water to form solution B. 1 g of LiMn2O4 was added to the solution to form solution C under stirring at a rate of 500 r / min, and finally solution B was slowly added dropwise to solution C to form a black gel with obvious Tyndall effect. The black gel was dried at 60°C for 7 hours, ground uniformly with a mortar to form a black powder, and calcined at 550°C for 4 hours in an air atmosphere to obtain 2wt% phosphate-modified LiMn2O4, labeled as 2MP-lithium manganate.

[0051] 1 g of 2MP-lithium manganese oxide, 0.125 g of PVDF, and 0.125 g of conductive carbon black were mixed and ground evenly, and then dissolved in 10 ml of NMP. The mixture was stirred at 500 rpm for 24 hours to form an electrode slurry. The electrode slurry was uniformly coated onto a 1 cm × 2 cm graphite plate and dried at 60 °C for 10 hours to form a working electrode with a loading of 10 mg. The contact angle of the 2MP-lithium manganese oxide working electrode was 41.02°. Using a platinum sheet as the counter electrode and a calomel electrode as the reference electrode, the discharge capacity retention rate after 20 charge-discharge cycles was 69.76%, and the manganese loss in the electrolyte after 20 charge-discharge cycles was 0.159%. Using 2MP-lithium manganese oxide as the working electrode and an Ag sheet as the counter electrode, an electrochemical lithium-ion extraction and release experiment was conducted in 30 mmol / L simulated salt lake brine (where the lithium, sodium, potassium, magnesium, and calcium lithium ion concentrations were approximately 210, 690, 1180, 730, and 1200 mg / L, respectively) under an electric field drive. After 5 extraction and release cycles, the average lithium release capacity per cycle was 13.58 mg / g.

[0052] Example 5

[0053] The preparation method of 0.5MP-lithium manganese oxide is the same as that in Example 3.

[0054] Using 0.5 MPa lithium manganese oxide as the working electrode and an Ag sheet as the counter electrode, an electrochemical lithium ion extraction and release experiment was conducted in a simulated lithium precipitation mother liquor (where the lithium, sodium, potassium, magnesium, and calcium lithium ion concentrations were approximately 1236, 71447, 787, 84, and 37 mg / L, respectively) under an electric field drive. After 5 extraction and release cycles, the average lithium release capacity per cycle was 21.64 mg / g.

[0055] Example 6

[0056] The preparation method of 0.5MP-lithium manganese oxide is the same as that in Example 3.

[0057] Using 0.5 MPa lithium manganese oxide as the working electrode and an Ag sheet as the counter electrode, an electrochemical lithium ion extraction and release experiment was conducted in the brine of the real Zabuye Salt Lake (where the lithium, sodium, potassium, magnesium, and calcium lithium ion concentrations were approximately 471, 72577, 171, 18072, and 225 mg / L, respectively) under an electric field drive. After 5 extraction and release cycles, the average lithium release capacity per cycle was 16.56 mg / g.

[0058] like Figure 1 As shown, in 0.5 MP-lithium manganese oxide, phosphate exhibits an amorphous and uniformly loaded structure.

[0059] Contact angle experiments were conducted on Comparative Example 1, Example 1, Example 2, Example 3, and Example 4, and the results are as follows: Figure 2As shown, it is illustrated that the loading of phosphate can effectively improve the hydrophilicity of lithium manganate.

[0060] The constant current charge and discharge experiments were carried out on the real comparative example 1, example 1, example 2, example 3, example 4, and the results are as follows Figure 3 As shown, the capacity retention rates of lithium manganate, 0.25MP-lithium manganate, 0.5MP-lithium manganate, 1MP-lithium manganate and 2MP-lithium manganate after 20 cycles are 50.6%, 73.86%, 93.63%, 81.87% and 70.76% respectively, as shown in Figure 4 As shown, the manganese dissolution losses in the solution are 0.187%, 0.165%, 0.154%, 0.162% and 0.159% respectively, which illustrates that a small amount of phosphate coating can effectively improve the cycle stability of lithium manganate, and 0.5MP-lithium manganate has the best cycle stability.

[0061] The simulated brine electrochemical lithium extraction experiments were carried out on the real comparative example 1, example 1, example 2, example 3, example 4, and the results are as follows Figure 5 As shown, the lithium ion release capacities of lithium manganate, 0.25MP-lithium manganate, 0.5MP-lithium manganate, 1MP-lithium manganate and 2MP-lithium manganate are 13.51, 15.51, 16.52, 13.85 and 13.58mg / g respectively, which illustrates that a small amount of phosphate coating can effectively improve the electrochemical lithium extraction performance of lithium manganate, and 0.5MP-lithium manganate has the best lithium extraction performance.

[0062] The simulated lithium precipitation mother liquor electrochemical lithium extraction experiment was carried out on example 5, and the results are as follows Figure 6 As shown, the simulated lithium precipitation mother liquor has a high sodium ion concentration (71447mg / L), and the lithium ion release capacity of 0.5MP-lithium manganate reaches 21.64mg / g.

[0063] The real Zhabuye brine electrochemical lithium extraction experiment was carried out on example 6, and the results are as follows Figure 7 As shown, the Zhabuye salt lake brine has a high sodium ion concentration (72577mg / L) and potassium ion concentration (18072mg / L), and the lithium ion release capacity of 0.5MP-lithium manganate reaches 16.56mg / g.

[0064] The present application provides a kind of for electrochemical lithium extraction phosphorus manganese modified lithium manganate composite electrode and its preparation method and application idea and method, the method and approach for specifically realizing this technical scheme are many, above-mentioned only preferred embodiment of the present application, it should be pointed out, for the ordinary skilled person in the art, without departing from the principle of the present application, can make a number of improvements and refinements, these improvements and refinements also should be considered as the protection scope of the present application. Each component not specified in the embodiment can be realized by prior art.

Claims

1. A manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction, characterized in that, This includes lithium manganese oxide matrix materials and manganese phosphate loaded on the surface of lithium manganese oxide matrix materials; The manganese phosphate loading is 0.25-2 wt% of the matrix material. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction is prepared by the following steps: (1) Dissolve the soluble manganese salt in deionized water to obtain solution A; (2) Dissolve the phosphate in deionized water to obtain solution B; (3) While stirring, lithium manganese oxide is added to solution A obtained in step (1) to obtain solution C; (4) While stirring, add the B solution obtained in step (2) to the C solution obtained in step (3) and mix evenly to obtain a black gel; (5) Dry the black gel obtained in step (4), grind it into powder, and then calcine it in air atmosphere to obtain the final product.

2. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction according to claim 1, characterized in that, In step (1), the soluble manganese salt is any one or a mixture of two or more of manganese nitrate, manganese chloride, and manganese acetate; the concentration of manganese ions in solution A is 0.27-2.16 g / L.

3. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction according to claim 1, characterized in that, In step (2), the phosphate is any one of diammonium hydrogen phosphate or diammonium dihydrogen phosphate or a mixture of both, and the phosphate concentration in solution B is 0.98-7.84 g / L.

4. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction according to claim 1, characterized in that, In step (3), the lithium manganese oxide content in solution C is 80-120 g / L.

5. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction according to claim 1, characterized in that, In step (4), the B solution and the C solution are mixed at a volume ratio of 0.8-1.2:1 and stirred at a stirring rate of 400-800 r / min to obtain a black gel.

6. The manganese phosphate-modified lithium manganese oxide composite electrode for electrochemical lithium extraction according to claim 1, characterized in that, In step (5), the drying temperature is 60-90℃ and the drying time is 6-9h. The calcination temperature is 450-750℃ and the calcination time is 4-9h.

7. The application of the manganese phosphate modified lithium manganese oxide composite electrode according to claim 1 as an electrode material for extracting lithium ions in a liquid lithium-containing solution.

8. The application according to claim 7, characterized in that, The concentration of lithium ions in the liquid lithium-containing solution is 200~1500 mg / L.

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