Lithium-potassium hybrid ion battery and method of making the same

Abstract

The application discloses a lithium-potassium hybrid ion battery and a preparation method thereof. The lithium-potassium hybrid ion battery comprises a negative electrode material composed of a carbon composite sulfide, a counter electrode composed of a potassium sheet, a lithium salt modified diaphragm and a potassium ion organic electrolyte. The lithium salt loaded on the diaphragm is slowly released in the electrolyte to provide lithium carriers, lithium and potassium intercalation and conversion reactions are simultaneously realized in the sulfide charging and discharging process, lithium-potassium collaborative energy storage is realized, and the lithium-potassium hybrid system can be stably cycled in the sulfide negative electrode. Compared with a single potassium ion battery, the lithium-potassium hybrid system has obvious improvement in cycle and capacity.

Description

TECHNICAL FIELD

[0001] The application relates to a lithium-potassium hybrid ion battery and a preparation method thereof, and belongs to the technical field of new energy batteries. BACKGROUND

[0002] In recent years, with the growth of energy demand and the depletion of fossil energy, new clean energy related industries have developed rapidly, and researches including smart grid, large-scale energy storage, new energy vehicles and high energy density portable energy storage devices have become research hotspots in the field of new energy. Among them, lithium ion batteries (LIB) have become one of the most widely used and most mature electrochemical energy storage devices due to their high energy density and long cycle life. However, the crustal abundance of lithium is only 0.0065%, and the price is relatively high. How to reduce the cost of lithium has become a bottleneck problem for the further development of lithium ion batteries. The crustal abundance of potassium is 1.68%, which is abundant in reserves, low in price, and has a similar low standard electrode potential to lithium (Li: -3.04 vs. SHE; K: -2.93 vs. SHE), and is considered to be a battery system with great development potential.

[0003] However, although potassium ions have faster ion transport kinetics in electrolyte (Stokes radius: Through molecular dynamics simulation, the diffusion coefficient is about three times that of Li + The larger atomic radius (K: Li: ) makes it show poor ion diffusion and reaction kinetics on the surface of the solid electrode. Pure potassium ion battery still has many problems to be solved, such as poor cycle performance, low capacity, and low first cycle coulombic efficiency of the battery. In view of the above problems, Mingjun et al. proposed a design idea for potassium ion electrolyte through simulation and electronegativity calculation of the solvation structure of the electrolyte (ACS Energy Lett. 2020, 5, 3124-3131); Yiying Wu team developed a potassium bisfluorosulfonylimide (KFSI)-dimethyl ether (DME) electrolyte, and realized long-time and highly reversible potassium deposition / exfoliation through interface regulation (J. Am. Chem. Soc. 2017, 139, 9475-9478). SUMMARY

[0004] In view of the deficiencies of the existing electrochemical energy storage devices, the application provides a high-performance lithium-potassium hybrid ion battery and a preparation method thereof. The lithium-potassium hybrid ion battery of the application makes lithium and potassium compatible carriers in the same system, realizes lithium-potassium ion collaborative energy storage, and has significant cycle and capacity improvement compared with single potassium ion battery.

[0005] The lithium-potassium hybrid ion battery comprises a negative electrode of carbon composite sulfide, a counter electrode of potassium sheet, a lithium salt modified separator and a potassium ion organic electrolyte; the lithium salt modified separator is prepared by soaking a glass fiber separator in a lithium salt solution and drying; the carbon composite sulfide has a general formula of M x S@C, M is Fe or Mo, and 0

[0006] The preparation method of the lithium-potassium hybrid ion battery comprises the following steps:

[0007] (1) mixing, coating and drying the carbon composite sulfide, a conductive agent and a binder to prepare a negative electrode sheet;

[0008] (2) soaking a glass fiber separator in a lithium salt solution and drying to prepare a lithium salt modified separator;

[0009] (3) assembling the negative electrode sheet, the lithium salt modified separator, the potassium ion organic electrolyte, the potassium metal sheet and a button cell module into a lithium-potassium hybrid ion battery.

[0010] In step (1), the carbon composite sulfide is prepared by the following method: citric acid (C6H8O7), thiourea (CH4N2S) and a metal salt are dissolved in a mixed solvent of water and ethanol, and then a sol-gel and sintering are performed to prepare M x S@C; wherein the mass ratio of citric acid, thiourea and the metal salt is (1-2):(5-10):(1-2), preferably 1:10:1.5; and the metal salt is a chloride, sulfate, nitrate, acetate or ammonium salt of Fe or Mo.

[0011] In step (1), the conductive agent is a conventional conductive agent used in the field, including but not limited to carbon nanotubes, graphene, Super P, acetylene black and Ketjen black.

[0012] In step (1), the binder is a conventional binder used in the field, including but not limited to polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE) and carboxymethyl cellulose (CMC).

[0013] In step (2), the concentration of the lithium salt solution is 0.5-2 mol / L, the lithium salt is a conventional lithium salt used in electrolyte in the field, including but not limited to lithium trifluoromethanesulfonate (LiCF3SO3), lithium hexafluorophosphate (LiPF6), lithium nitrate (LiNO3), lithium perchlorate (LiClO4), lithium phosphate (Li3PO4) and lithium bis-trifluoromethanesulfonimide (LiTFSI); and the solvent of the lithium salt solution is a conventional solvent used in electrolyte in the field, including but not limited to ethanol, dimethyl ether (DME) and dimethyl sulfoxide (DMSO).

[0014] In step (2), the soaking time is 2-24 h.

[0015] In step (2), the drying temperature is 30-80 DEG C, and the drying time is 2-24 h.

[0016] In step (3), the potassium ion organic electrolyte contains a soluble potassium salt, including but not limited to potassium hexafluorophosphate (KPF6), potassium bisfluorosulfonylimide (KFSI) or potassium bis(trifluoromethylsulfonyl)imide (KTFSI), a solvent including but not limited to dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), methyl ethyl carbonate (EMC), dimethyl ether (DME), diethylene glycol dimethyl ether (DGLME) and tetraethylene glycol dimethyl ether (TEGDME), and an additive including but not limited to vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0017] In step (3), the concentration of the soluble potassium salt in the potassium ion organic electrolyte is 0.5-2.5 mol / L.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The present application provides lithium carriers through slow release of the separator-loaded lithium salt in the electrolyte, simultaneously realizes lithium and potassium intercalation and conversion reactions in the sulfide charge-discharge process, realizes lithium-potassium collaborative energy storage, has significant cycle and capacity improvement compared with single potassium ion batteries, has the characteristics of fast kinetics and high capacity of lithium ions and low cost of potassium ions, and the anion of the added lithium salt also has the function of SEI film forming additive, further improves the cycle stability of the mixed ion battery system, and has the characteristics of low cost, simple preparation process, strong universality and excellent electrochemical behavior. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the XRD pattern of FeS@C prepared in Example 1.

[0021] Figure 2 is the specific capacity-voltage graph of the first cycle charge-discharge of the battery prepared in Example 1 and Comparative Example 1.

[0022] Figure 3 is the charge-discharge cycle graph of the battery prepared in Example 1 and Comparative Example 1.

[0023] Figure 4 is the XRD pattern of MoS2@C prepared in Example 2.

[0024] Figure 5is the specific capacity-voltage graph of the first cycle charge-discharge of the battery prepared in Example 2 and Comparative Example 2.

[0025] Figure 6 is the charge-discharge cycle graph of the battery prepared in Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in conjunction with the examples and the accompanying drawings, but the content of the present application is not limited thereto.

[0027] The M x The preparation of S@C is described in the reference

ACS Nano 2017, 11, 12658-12667

[0028] Example 1

[0029] (1) Citric acid, thiourea and ferric nitrate were dissolved in a mixed solvent of water and ethanol in a volume ratio of 1:3 in a mass ratio of 1:10:1.5, and a sol was formed by stirring in a water bath at 75°C and aging to obtain a gel. The gel was sintered in an argon tube furnace at 350°C for 3h and at 750°C for 8h to obtain FeS@C powder. The obtained FeS@C powder was uniformly ground with conductive agent Super P and binder PVDF in a mass ratio of 8:1:1, and then an appropriate amount of N-methyl pyrrolidone was added and stirred for 12h to obtain a uniform slurry. The slurry was coated on a copper foil using a wet film preparation device, and the thickness of the coated wet film was 50μm. Then the coated copper foil was placed in a vacuum oven at 80°C and vacuum dried for 12h to obtain a negative electrode sheet for a hybrid ion battery, and was punched into a circular electrode sheet with a diameter of 12mm for assembling a button cell.

[0030] (2) A Whatman glass fiber separator was punched into a circular sheet with a diameter of 16mm, soaked in a fully dissolved LiNO3 / DME solution of 1mol / L for 12h, and then taken out and vacuum dried in a vacuum oven at 60°C for 12h to obtain a LiNO3 modified separator.

[0031] (3) In an argon protected environment in a glove box, potassium metal was rolled into a thin sheet and punched into a circular potassium sheet with a diameter of 12mm as a counter electrode. 0.8M KPF6 / (EC / DEC+5% FEC) was used as the electrolyte, and the LiNO3 modified separator with a diameter of 16mm was used as the separator. The prepared electrode sheet, separator and potassium sheet were assembled into a button cell in the glove box, and then the charge-discharge cycle test was carried out on a LAND battery test system, and the working voltage was 0.01-3V (vs. K / K + ).

[0032] Example 2

[0033] (1) Citric acid, thiourea, and ammonium molybdate were dissolved in a mixed solvent of water and ethanol in a mass ratio of 1:10:1.5 and stirred in a water bath at 75°C to form a sol. The sol was then aged to obtain a gel. The gel was sintered in an argon tube furnace at 350°C for 3 hours and 750°C for 8 hours to obtain MoS2@C powder. The obtained MoS2@C powder was ground uniformly with conductive agent Super P and binder PVDF in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone was added and stirred for 12 hours to obtain a uniform slurry. The slurry was coated onto copper foil using a wet film preparation device. The thickness of the wet film was 50 μm. The coated copper foil was then placed in a vacuum oven at 80°C and vacuum dried for 12 hours to obtain the negative electrode sheet of the hybrid ion battery. The negative electrode sheet was then cut into circular electrode sheets with a diameter of 12 mm for assembling button batteries.

[0034] (2) The Whatman glass fiber membrane was punched into a circular piece with a diameter of 16 mm, soaked in a fully dissolved LiNO3 / DME solution of 1 mol / L for 12 h, and then placed in a vacuum oven at 60 °C for vacuum drying for 12 h to obtain the LiNO3 modified membrane.

[0035] (3) Under argon protection in a glove box, potassium metal was rolled into a thin sheet and punched into a circular potassium sheet with a diameter of 12 mm as the counter electrode. Using 0.8 M KPF6 / (EC / DEC+5% FEC) as the electrolyte and a 16 mm LiNO3-modified membrane as the separator, the prepared electrode, separator, and potassium sheet were assembled into a button cell in a glove box. Charge-discharge cycle tests were then performed on a LAND battery testing system with a working voltage of 0.01-3 V (vs. K / K). + ).

[0036] Comparative Example 1

[0037] A lithium-potassium hybrid ion battery was prepared according to the method of Example 1, except that a blank Whatman glass fiber separator was used.

[0038] Comparative Example 2

[0039] A lithium-potassium hybrid ion battery was prepared according to the method of Example 2, except that a blank Whatman glass fiber separator was used.

[0040] like Figure 1 As shown in the XRD pattern of FeS@C synthesized in Example 1, all main diffraction peaks belong to the FeS structure in space group P63mc. The sharp peak shapes and high intensities indicate good crystal development. Furthermore, the peak around 26° belongs to partially graphitized amorphous carbon, indicating good recombination between the prepared sulfide and amorphous carbon, which positively influences the electrochemical behavior of the sulfide.

[0041] As shown in Figure 2 , the first cycle reversible capacity of the lithium-potassium hybrid ion battery with the lithium nitrate modified separator prepared in Example 1 reached 267.9 mAh g -1 at a current density of 500 mA g -1 , which was significantly improved compared with the 105.4 mAh g -1 of the reversible capacity of the battery with the blank separator prepared in Comparative Example 1, and there was a clear lithium ion reaction platform around 1.8 V, and the conversion reaction platform below 0.6 V was also extended, indicating that the synergistic reaction of lithium ions and potassium ions with FeS@C could improve the battery capacity.

[0042] Figure 3 The cycle performance of the batteries prepared in Example 1 and Comparative Example 1 in the voltage range of 0.01-3 V showed that the synergistic reaction of lithium and potassium exhibited good stability, and the capacity retention rate was as high as 94% after 50 cycles at a current density of 500 mA g -1 , and the high reversible capacity of 253.0 mAh g -1 was still maintained, while the capacity retention rate of Comparative Example 1 was only 74%, and the reversible capacity was only 78.2 mAh g -1 .

[0043] Figure 4 The XRD pattern of MoS2@C prepared in Example 2 is shown, all the main diffraction peaks belong to the MoS2 structure in the P63mc space group, and the main diffraction peak is sharp, and the overall shows a trend of amorphization, indicating that the prepared sulfide and amorphous carbon have good composite, which has a positive effect on the electrochemical behavior of the sulfide.

[0044] As shown in Figure 5 , the first cycle reversible capacity of the lithium-potassium hybrid ion battery with the lithium nitrate modified separator prepared in Example 2 reached 527.9 mAh g -1 at a current density of 500 mA g -1 , while the reversible capacity of the battery with the blank separator prepared in Comparative Example 2 was only 53.2 mAh g -1 , indicating that the synergistic reaction of lithium ions and potassium ions with FeS@C3N4 improved the capacity of the battery.

[0045] Figure 6 The cycle performance of the batteries prepared in Example 2 and Comparative Example 2 in the voltage range of 0.01-3 V showed that the synergistic reaction of lithium and potassium exhibited good stability, and the capacity retention rate was as high as 94% after 50 cycles at a current density of 500 mA g -1 , and the high reversible capacity of 253.0 mAh g -1high capacity of 89%, while Comparative Example 2 only remained 11.8 mAh g -1 a reversible capacity of 22%.

Claims

1. Lithium-potassium hybrid ion battery, characterized in that The negative electrode is composed of carbon composite sulfide, the counter electrode is composed of potassium sheet, the lithium salt modified diaphragm and the potassium ion organic electrolyte; the lithium salt modified diaphragm is prepared by soaking the glass fiber diaphragm in a lithium salt solution and then drying; the general formula of the carbon composite sulfide is M x S@C, M is Fe or Mo, and 0 < x ≤ 1.

2. The method for producing a lithium-potassium hybrid ionic battery according to claim 1, characterized by, The method comprises the following steps: (1) mixing, coating and drying the carbon composite sulfide with a conductive agent and a binder to form a negative electrode sheet; (2) soaking a glass fiber separator in a lithium salt solution and drying to form a lithium salt modified separator; (3) assembling a lithium-potassium hybrid ion battery by combining the negative electrode sheet, the lithium salt modified separator, a potassium ion organic electrolyte, a potassium metal sheet and a button cell module.

3. The production method according to claim 2, characterized by, In step (1), the carbon composite sulfide is prepared by the following method: citric acid, thiourea and metal salt are dissolved in a mixed solvent of water and ethanol, and then M x S@C; wherein the mass ratio of citric acid, thiourea and metal salt is (1-2):(5-10):(1-2); the metal salt is chloride, sulfate, nitrate, acetate or ammonium salt of Fe or Mo.

4. The production method according to claim 3, characterized by, The mass ratio of citric acid, thiourea and metal salt is 1:10:1.

5.

5. The production method according to claim 2, characterized by, In step (1), the conductive agent is selected from carbon nanotubes, graphene, Super P, acetylene black or Ketjen black.

6. The preparation method according to claim 2, characterized in that, In step (1), the binder is selected from polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene or carboxymethyl cellulose.

7. The preparation method according to claim 2, characterized in that, In step (2), the concentration of the lithium salt solution is 0.5-2 mol / L, the lithium salt is selected from lithium triflate, lithium hexafluorophosphate, lithium nitrate, lithium perchlorate, lithium phosphate or lithium bis-trifluoromethanesulfonimide, and the solvent of the lithium salt solution is selected from ethanol, dimethyl ether or dimethyl sulfoxide.

8. The preparation method according to claim 2, characterized in that, In step (2), the soaking time is 2-24 h.

9. The preparation method according to claim 2, characterized in that, In step (2), the drying temperature is 30-80℃ and the drying time is 2-24 h.

10. The method of claim 2, wherein, In step (3), the potassium ion organic electrolyte contains a soluble potassium salt, the soluble potassium salt is selected from potassium hexafluorophosphate, potassium bis-fluorosulfonimide or potassium bis(trifluoromethylsulfonyl)imide, the solvent is selected from dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl ether, diethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether, and the additive is selected from vinylene carbonate or fluoroethylene carbonate.

11. The production method according to claim 2, characterized by, In step (3), the concentration of the soluble potassium salt in the potassium ion organic electrolyte is 0.5-2.5 mol / L.

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