A high-voltage solid-state lithium battery and a preparation method thereof

Abstract

This application relates to a high-voltage solid-state lithium battery and a preparation method thereof. The high-voltage solid-state lithium battery includes a positive electrode, a negative electrode, and a solid electrolyte. Among them, the positive electrode active material is a lithium nickel cobalt manganese oxide ternary material, and the solid electrolyte includes a polymer, a BaTiO3 / LLZO composite material, and a lithium salt. The structure of BaTiO3 / LLZO is that nanosheets of LLZO are formed on the surface of BaTiO3 nanorods with a high aspect ratio. On the one hand, this structure can act as a rigid skeleton to improve the mechanical properties of the composite solid electrolyte and can form a high-speed lithium-ion shuttle network. On the other hand, it can increase the working voltage range of the battery and expand the electrochemical window to 4.9V. Finally, LLZO has excellent lithium-ion conductivity. Combining it with BaTiO3 nanorods is beneficial to further improving the ion conduction rate of the composite solid electrolyte.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and specifically relates to a high-voltage solid-state lithium battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries play a huge role in promoting social development, and their application fields include consumer electronics, power batteries, etc. However, the current commercial batteries can no longer meet the needs under the rapid social development. Now, the development of batteries requires higher energy density, longer cycle life, and being safer and cheaper. Traditional liquid lithium-ion batteries have high conductivity and excellent wettability on the electrode surface, but their electrochemical performance and thermal stability are not good, and the ion selectivity is low, facing many risks such as short circuit, flammability, leakage, and explosion. Using solid electrolytes to replace traditional liquid electrolytes is an effective way to control and solve the above problems. Compared with liquid electrolytes, solid electrolytes have the advantages of high safety, wide electrochemical window, and high energy density. Solid electrolytes are mainly divided into inorganic solid electrolytes, organic solid electrolytes, and composite solid electrolytes according to their composition. Inorganic solid electrolytes have significant advantages in terms of safety, electrochemical stability, and ionic conductivity, but still face challenges in terms of interfacial impedance, cost, and thermal stability. Organic solid electrolytes are mainly composed of organic polymer matrices and lithium salts or sodium salts, and have the advantages of good flexibility, easy processing and molding, and good electrode interface compatibility, but there are problems such as low room-temperature ionic conductivity and poor mechanical strength, making it difficult to be applied alone. Composite solid electrolytes are generally prepared by compounding inorganic solid electrolytes and organic solid electrolytes, and simultaneously possess the excellent properties of inorganic and organic solid electrolytes, having good interface compatibility, high ionic conductivity, and excellent electrochemical stability, and are one of the important materials to replace liquid electrolytes at present. However, the existing composite solid electrolytes still face the problems of low lithium-ion conductivity and limited high-voltage resistance. Summary of the Invention

[0003] Aiming at the problems existing in the background art, the purpose of the present invention is to provide a preparation method and application of a composite solid electrolyte. By preparing a composite material of BaTiO3-LLZO and polymer and lithium salt, the lithium-ion conductivity of the solid electrolyte is improved, and the stability of its electrochemical window is also improved.

[0004] In order to achieve the above purpose, the present application proposes the following technical solutions:

[0005] A preparation method of a high-voltage solid-state lithium battery, characterized by comprising a positive electrode, a negative electrode, and a solid electrolyte, wherein the positive electrode active material is a ternary material of lithium nickel cobalt manganate, and the solid electrolyte includes a polymer, a BaTiO3 / LLZO composite material, and a lithium salt. The preparation steps of the solid electrolyte are as follows:

[0006] Step 1: Weigh a titanium source, a barium source, and urea in a molar ratio of 1:1:(2 - 3), dissolve them in 80 - 100 mL of ethanol, and stir evenly.

[0007] Step 2: Add cetyltrimethylammonium chloride to the solution obtained in Step 1, stir evenly to obtain a precursor mixture.

[0008] Step 3: Transfer the precursor mixture of Step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 200 - 250 °C, and react for 20 - 60 min; after the reaction, perform suction filtration, wash with deionized water, and dry to obtain BaTiO3.

[0009] Step 4: Weigh a certain molar ratio of a lithium salt, a lanthanum salt, and a zirconium salt, dissolve them in deionized water, and stir evenly; continue to add a chelating agent and polyethylene glycol PEG2000, stir evenly, then add the BaTiO3 prepared in Step 3, continue to stir evenly, place it in an oven at 60 - 70 °C to evaporate the solvent to obtain a gel, and calcine it at 600 - 900 °C for 2 - 3 h to obtain a BaTiO3 - LLZO composite material.

[0010] Step 5: Dissolve the BaTiO3 - LLZO composite material, a polymer, and a lithium salt in an organic solvent, stir and mix evenly, and dry to obtain a solid electrolyte.

[0011] Further, the lithium source is one or more of lithium nitrate and lithium hydroxide.

[0012] Further, the lanthanum source is one or more of lanthanum nitrate and lanthanum oxide.

[0013] Further, the zirconium source is zirconium nitrate.

[0014] Further, the molar ratio of the lithium source, the lanthanum source, and the zirconium source is (7 - 7.1):3:2.

[0015] Further, the BaTiO3 - LLZO material has a nano - sheet structure of LLZO formed on the surface of BaTiO3 nanorods.

[0016] Further, the chelating agent is citric acid or tartaric acid.

[0017] Further, the mass ratio of the BaTiO3 - LLZO inorganic material, the polymer, and the lithium salt is (1 - 3):(5 - 7):(1 - 2);

[0018] Further, the polymer is PEO or PVDF;

[0019] Further, the addition amount of polyethylene glycol PEG200 is 1 - 5 g;

[0020] Furthermore, the addition amount of cetyltrimethylammonium chloride is 2 - 5 g;

[0021] Adopting the above technical solution, the present invention can achieve the following technical effects:

[0022] In this application, BaTiO3-LLZO is combined with a polymer and a lithium salt to form a composite solid electrolyte. The BaTiO3-LLZO material has a nano-sheet structure of LLZO formed on the surface of BaTiO3 nanorods with a high aspect ratio. On the one hand, this structure can serve as a rigid skeleton to improve the mechanical properties of the composite solid electrolyte and form a high-speed lithium-ion shuttle network, effectively improving the lithium-ion conductivity; on the other hand, this composite solid electrolyte can increase the working voltage range of the battery and expand the electrochemical window to 4.9 V. In addition, LLZO itself has excellent lithium-ion conductivity, and combining it with BaTiO3 nanorods is beneficial to further improving the ion conduction rate of the composite solid electrolyte. Brief Description of the Drawings

[0023] Figure 1 It is the SEM image of the BaTiO3-LLZO composite material of this application. Detailed Embodiments

[0024] The present invention will be further described below through the description of specific embodiments. However, this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements according to the basic idea of the present invention, but as long as they do not depart from the basic idea of the present invention, they are within the scope of the present invention.

[0025] Example 1

[0026] Step 1: Weigh tetrabutyl titanate, barium nitrate, and urea in a molar ratio of 1:1:2, and dissolve them in 85 mL of ethanol. Among them, tetrabutyl titanate is 3.4 g, barium nitrate is 2.6 g, and urea is 1.2 g, and stir evenly;

[0027] Step 2: Add 3.2 g of cetyltrimethylammonium chloride to the solution obtained in Step 1, and stir evenly to obtain a precursor mixture;

[0028] Step 3: Transfer the precursor mixture in Step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 200 °C, and react for 30 min; after the reaction, filter by suction, wash with deionized water, and dry to obtain BaTiO3;

[0029] Step 4: Weigh 4.76 g of lithium nitrate, 9.72 g of lanthanum nitrate, and 27.6 g of zirconium acetate and dissolve them in 40 mL of deionized water, and stir evenly; continue to add the chelating agent citric acid and 4 g of polyethylene glycol PEG2000, stir evenly, then add the BaTiO3 prepared in Step 3, stir evenly, place it in an oven at 60 °C to evaporate the solvent to obtain a gel, and calcine it at 800 °C for 2 h to obtain the inorganic composite material BaTiO3-LLZO;

[0030] Step 5: Dissolve 0.2 g of the inorganic composite material BaTiO3-LLZO, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in 10 mL of the organic solvent DMF, stir and mix evenly, and dry to obtain a solid electrolyte.

[0031] Example 2

[0032] Step 1: Weigh tetrabutyl titanate, barium nitrate, and urea in a molar ratio of 1:1:2, and dissolve them in 85 mL of ethanol. Among them, tetrabutyl titanate is 3.4 g, barium nitrate is 2.6 g, and urea is 1.2 g, and stir evenly;

[0033] Step 2: Add 2.1 g of cetyltrimethylammonium chloride to the solution obtained in Step (1), stir evenly to obtain a precursor mixture;

[0034] Step 3: Transfer the mixture in Step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 200 °C, and react for 30 min; after the reaction, filter by suction, wash with deionized water, and dry to obtain BaTiO3;

[0035] Step 4: Weigh 2.38 g of lithium nitrate, 4.86 g of lanthanum nitrate, and 13.3 g of zirconium acetate and dissolve them in 40 mL of deionized water, and stir evenly; continue to add the chelating agent tartaric acid and 2 g of polyethylene glycol PEG2000, stir evenly, then add the BaTiO3 prepared in Step 3, stir evenly, place it in an oven at 60 °C to evaporate the solvent to obtain a gel, and calcine it at 800 °C for 2 h to obtain the inorganic composite material BaTiO3-LLZO;

[0036] Step 5: Dissolve 0.2 g of the inorganic composite material BaTiO3-LLZO, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in 10 mL of the organic solvent DMF, stir and mix evenly, and dry to obtain a solid electrolyte.

[0037] Example 3

[0038] Step 1: Weigh tetrabutyl titanate, barium nitrate, and urea in a molar ratio of 1:1:2, and dissolve them in 85 mL of ethanol. Among them, tetrabutyl titanate is 3.4 g, barium nitrate is 2.6 g, and urea is 1.2 g, and stir evenly;

[0039] Step 2: Add 3.2 g of cetyltrimethylammonium chloride to the solution obtained in step (1), stir evenly to obtain a precursor mixture.

[0040] Step 3: Transfer the mixture in step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 230 °C, and react for 25 min; after the reaction, filter by suction, wash with deionized water, and dry to obtain BaTiO₃.

[0041] Step 4: Weigh 2.38 g of lithium nitrate, 4.86 g of lanthanum nitrate, and 13.3 g of zirconium acetate and dissolve them in 40 mL of deionized water, stir evenly; continue to add the chelating agent citric acid and 2 g of polyethylene glycol PEG2000, stir evenly and then add the BaTiO₃ prepared in step 3, continue to stir evenly, place it in an oven at 60 °C to evaporate the solvent to obtain a gel, and calcine it at 900 °C for 2 h to obtain an inorganic composite material of BaTiO₃-LLZO.

[0042] Step 5: Dissolve 0.2 g of the inorganic composite material of BaTiO₃-LLZO, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in 10 mL of the organic solvent DMF, stir and mix evenly, and dry to obtain a solid electrolyte.

[0043] Example 4

[0044] Step 1: Weigh tetrabutyl titanate, barium nitrate, and urea in a molar ratio of 1:1:3, and dissolve them in 85 mL of ethanol, where tetrabutyl titanate is 3.4 g, barium nitrate is 2.6 g, and urea is 1.3 g, and stir evenly.

[0045] Step 2: Add 3.2 g of cetyltrimethylammonium chloride to the solution obtained in step 1, stir evenly to obtain a precursor mixture.

[0046] Step 3: Transfer the mixture in step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 230 °C, and react for 25 min; after the reaction, filter by suction, wash with deionized water, and dry to obtain BaTiO₃.

[0047] Step 4: Weigh 2.38 g of lithium nitrate, 4.86 g of lanthanum nitrate, and 13.3 g of zirconium acetate and dissolve them in 40 mL of deionized water, stir evenly; continue to add the chelating agent citric acid and 2 g of polyethylene glycol PEG2000, stir evenly and then add the BaTiO₃ prepared in step 3, continue to stir evenly, place it in an oven at 60 °C to evaporate the solvent to obtain a gel, and calcine it at 900 °C for 2 h to obtain an inorganic composite material of BaTiO₃-LLZO.

[0048] Step 5: Dissolve 0.2 g of the inorganic composite material of BaTiO3-LLZO, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in 10 mL of the organic solvent DMF, stir and mix evenly, and dry to obtain the solid electrolyte.

[0049] Comparative Example 1

[0050] Step 1: Weigh tetrabutyl titanate, barium nitrate, and urea with a molar ratio of 1:1:2, and dissolve them in 85 mL of ethanol. Among them, tetrabutyl titanate is 3.4 g, barium nitrate is 2.6 g, and urea is 1.2 g. Stir evenly.

[0051] Step 2: Add 3.2 g of cetyltrimethylammonium chloride to the solution obtained in Step 1, stir evenly to obtain the precursor mixture.

[0052] Step 3: Transfer the mixture in Step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 200 °C, and react for 30 min; after the reaction, filter by suction, wash with deionized water, and dry to obtain BaTiO3.

[0053] Step 4: Dissolve 0.2 g of the inorganic material of BaTiO3, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in an organic solvent, stir and mix evenly, and dry to obtain the solid electrolyte.

[0054] Comparative Example 2

[0055] Step 1: Weigh 4.76 g of lithium nitrate, 9.72 g of lanthanum nitrate, and 27.6 g of zirconium acetate, dissolve them in 40 mL of deionized water, and stir evenly; continue to add the chelating agent citric acid and 4 g of polyethylene glycol PEG2000, mix evenly, place it in an oven at 60 °C to evaporate the solvent to obtain a gel, and calcine it at 800 °C for 2 h to obtain the inorganic material of LLZO.

[0056] Step 2: Dissolve 0.2 g of the inorganic composite material of LLZO, 0.6 g of the polymer PVDF, and 0.2 g of lithium hexafluorophosphate in an organic solvent, stir and mix evenly, and dry to obtain the solid electrolyte.

[0057] Comparative Example 3

[0058] The difference from Comparative Example 1 is that the BaTiO3-LLZO composite material is not added to the solid electrolyte.

[0059] Test Example

[0060] Select LiNi 0.8 Co 0.1 Mn 0.1O2 is used as the positive electrode active material, and the lithium metal sheet is used as the negative electrode. The thickness of the solid electrolyte in Examples 1-4 and Comparative Examples 1-3 is 50 microns. The battery is assembled and its performance is tested. The results are shown in Table 1 below.

[0061] Table 1: Test Results

[0062]

[0063] As can be seen from the above figure, after the PVDF polymer is modified with the BaTiO3-LLZO composite material, compared with pure PVDF and PVDF modified with BaTiO3 and LLZO respectively, its voltage window is further improved, and the ionic conductivity, the first reversible capacity of the battery, and the cycle efficiency are all improved. This fully shows that BaTiO3-LLZO can effectively improve the ionic conductivity and electrochemical stability of the solid electrolyte.

[0064] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural or equivalent process transformations made using the description of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. A preparation method of a high-voltage solid-state lithium battery, characterized in that, It includes a positive electrode, a negative electrode and a solid electrolyte. Among them, the positive electrode active material is a lithium nickel cobalt manganese ternary material, and the solid electrolyte includes a polymer, a BaTiO3 / LLZO composite material and a lithium salt. Among them, the preparation steps of the solid electrolyte are as follows: Step 1: Weigh a titanium source, a barium source and urea in a molar ratio of 1:1:(2 - 3), dissolve them in 80 - 100 mL of ethanol, and stir evenly; Step 2: Add cetyltrimethylammonium chloride to the solution obtained in Step 1, and stir evenly to obtain a precursor mixture; Step 3: Transfer the precursor mixture in Step 2 to a polytetrafluoroethylene reaction kettle, heat it by microwave, control the temperature at 200 - 250 °C, and react for 20 - 60 min; after the reaction, perform suction filtration, wash with deionized water, and dry to obtain BaTiO3; Step 4: Weigh a lithium source, a lanthanum source, and a zirconium source, dissolve them in deionized water, and stir evenly; continue to add a chelating agent and polyethylene glycol PEG2000, stir evenly, then add the BaTiO3 prepared in Step 3, stir evenly, place it in an oven at 60 - 70 °C to evaporate the solvent to obtain a gel, and calcine it at 600 - 900 °C for 2 - 3 h to obtain an inorganic composite material of BaTiO3 - LLZO; Step 5: Dissolve the BaTiO3 - LLZO composite material, the polymer and the lithium salt in an organic solvent, stir and mix evenly, and dry to remove the solvent to obtain the solid electrolyte.

2. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the lithium source is lithium nitrate or lithium hydroxide.

3. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the lanthanum source is lanthanum nitrate or lanthanum oxide.

4. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the zirconium source is zirconium nitrate.

5. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the molar ratio of the lithium source, the lanthanum source, and the zirconium source is (7 - 7.1):3:

2.

6. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the BaTiO3 - LLZO material is a nano - sheet structure with LLZO formed on the surface of BaTiO3 nanorods.

7. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the chelating agent is citric acid or tartaric acid.

8. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the titanium source is one or more of tetrabutyl titanate, fluotitanic acid, and titanium tetrachloride; the barium source is one or more of barium chloride, barium hydroxide, barium acetate, and barium nitrate.

9. According to the method for preparing a high - voltage solid - state lithium battery described in claim 1, the polymer is PVDF or PEO.

10. A high-voltage solid-state lithium battery, characterized in that, Prepared by using the method according to any one of claims 1 - 9.

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