Solid-liquid battery

Abstract

A solid-liquid battery comprises a positive electrode and a negative electrode, the negative electrode is made of metal lithium, a solid electrolyte is provided between the positive electrode and the negative electrode, an ester electrolyte solution is filled between the solid electrolyte and the positive electrode, and an ether electrolyte solution is filled between the solid electrolyte and the negative electrode. On one hand, the ether electrolyte solution is filled between the lithium metal and the solid electrolyte, which is beneficial to improve the cycle life of the lithium metal; and on the other hand, the ester electrolyte solution is filled between the positive electrode and the solid electrolyte, which is beneficial to increase the selection space of the positive electrode, thereby increasing the energy density of the battery; in addition, by filling the electrolyte solution, the amount of the solid electrolyte used can be reduced, and the interface impedance of the battery can be reduced on the basis of ensuring that the safety is improved by using the solid electrolyte; furthermore, the existence of a solid electrolyte can prevent the influence of metal ions dissolved from the electrolyte on the performance of the negative electrode after migrating to the surface of lithium metal.

Claims

1. Solid-liquid battery comprising a positive electrode and a negative electrode, wherein the negative electrode is made of lithium metal, characterized in that: a solid electrolyte is provided between the positive electrode and the negative electrode, an ester electrolyte solution is filled between the solid electrolyte and the positive electrode, and an ether electrolyte solution is filled between the solid electrolyte and the negative electrode.

2. Solid-liquid battery according to claim 1, wherein the positive electrode comprises one of a high-nickel ternary or manganese-based lithium-rich positive electrode material.

3. Solid-liquid battery according to claim 1, wherein the ester electrolyte solution comprises carbonate, a lithium salt and an additive I with a mass ratio of (4-7):(2-5):1.

4. Solid-liquid battery according to claim 3, wherein the carbonate is selected from the group consisting of methyl ethyl carbonate, dimethyl carbonate and ethylene carbonate.

5. Solid-liquid battery according to claim 3, wherein the lithium salt is selected from the group consisting of LiBOB, LiODFB, LiFSI and LiTFSI.

6. Solid-liquid battery according to claim 3, wherein the additive I is a mixture of cyclohexylbenzene and (β-chloromethyl) phosphate, and the molar ratio of the two is 1:1.

7. Solid-liquid battery according to claim 1, wherein the ester electrolyte solution comprises a fluoroether, a lithium salt and an additive 11 with a mass ratio of (3-6):(3-6):1.

8. Solid-liquid battery according to claim 7, wherein the fluoroether is selected from the group consisting of methyl nonafluoro n-butyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and octafluoropentyl-tetrafluoroethyl ether.

9. Solid-liquid battery according to claim 7, wherein the additive II selected from the group consisting of fluoroethylene carbonate, trifluoroethylene carbonate and trifluoroethyl acrylate.

10. Solid-liquid battery according to claim 1, wherein the metal lithium surface of the negative electrode is provided with a layer of lithium nitride.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

Example I

[0027] A method for preparing a solid-liquid battery with a lithium metal negative electrode and a high-voltage positive electrode, comprising the following steps:

[0028] Step I. Coating lithium metal on a copper foil, and then placing the copper foil with lithium metal in a nitrogen atmosphere for 7 hours to form lithium nitride on the surface of the lithium metal, wherein the temperature of the nitrogen is 45° C. and the flow rate is 4 m/s, so as to finally obtain the negative electrode plate.

[0029] Step II. Adding a LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 material, conductive carbon black and polyethylene oxide—polyvinylidene fluoride at a mass ratio of 90:4:6 to tetrahydrofuran and mixing same thoroughly to prepare a positive electrode slurry with a solid content of 0.5 g/L.

[0030] Step III. Coating the positive electrode slurry uniformly on an aluminum foil with a coating thickness of 25 μm, drying same at a temperature of 110° C.-150° C. until the water content is less than 100 ppm, and then rolling and cutting same to prepare the positive electrode plate.

[0031] Step IV: melting lithium lanthanum zirconium oxide, polyvinylidene fluoride and bistrifluoromethanesulfonimide at a mass ratio of 90:5:5 and mixing same uniformly, and then coating same on both sides of the PP film with a coating thickness of 2.5 μm on both sides; and curing same after cooling and cutting same to obtain a solid electrolyte.

[0032] Step V. laminating the positive electrode plate and the negative electrode plate on the two sides of the solid electrolyte, respectively, and then filling the ether electrolyte solution between the positive electrode plate and the solid electrolyte, and filling the ester electrolyte solution between the negative electrode plate and the solid electrolyte to obtain a battery cell.

[0033] Step VI. Packing the battery cell to obtain the finished solid-liquid battery.

[0034] wherein the ether electrolyte solution is prepared by mixing methyl ethyl carbonate, LiBOB and the additive I at a mass ratio of 4:2:1, and the additive I is prepared by mixing cyclohexylbenzene with (β-chloromethyl) phosphate at a molar ratio of 1:1. The ester electrolyte solution is prepared by mixing methyl nonafluoro n-butyl ether, LiDFOB and fluoroethylene carbonate at a mass ratio of 3:3:1.

Example II

[0035] The method for preparing a solid-liquid battery with a lithium metal negative electrode and a high voltage positive electrode, which is different from the example I only in that the positive electrode slurry in step II is prepared by adding LiNi.sub.0.5Mn.sub.1.5O.sub.4, conductive carbon black and polyethylene oxide—polyvinylidene fluoride at a mass ratio of 45:2:3 and mixing same, wherein the solid content thereof is 0.5 g/L.

Example III

[0036] The method for preparing a solid-liquid battery with a lithium metal negative electrode and a high voltage positive electrode is different from the example I only in that the ether electrolyte solution is prepared by mixing dimethyl carbonate, LiFSI and the additive I at a mass ratio of 7:5:1, and the ester electrolyte solution is prepared by mixing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, LiTFSI and trifluoroethylene carbonate at a mass ratio of 6:6:1.

Example IV

[0037] The method for preparing a new solid-liquid battery with a lithium metal negative electrode and a high voltage positive electrode is different from the example I only in that the ether electrolyte solution is prepared by mixing ethylene carbonate, LiODFB and the additive I at a mass ratio of 5:3:1, and the ester electrolyte solution is prepared by mixing octafluoropentyl-tetrafluoroethyl ether, LiBOB and trifluoroethyl acrylate at a mass ratio of 4:4:1.

Example V

[0038] The method for preparing a solid-liquid battery with a lithium metal negative electrode and a high voltage positive electrode is different from the example I only in that the ether electrolyte solution is prepared by mixing dimethyl carbonate, LiTFSI and the additive I at a mass ratio of 4:5:1, and the ester electrolyte solution is prepared by mixing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, LiTFSI and fluoroethylene carbonate at a mass ratio of 4:4:1.

Example VI

[0039] A method for preparing a solid-liquid battery with a lithium metal negative electrode and a high-voltage positive electrode, which is different from the example I only in that the solid electrolyte is a pure inorganic ceramic sheet with a chemical formula of Li.sub.6.4La.sub.3Zr.sub.1.4Ta.sub.0.6O.sub.12.

Comparative Example I

[0040] Compared to example I, the difference only lies in that the surface of the lithium metal is not treated in a nitrogen atmosphere.

Comparative Example II

[0041] Compared to example I, the difference only lies in that the additive I only contains cyclohexylbenzene.

Comparative Example III

[0042] Compared to example I, the difference only lies in that the additive I only contains (β-chloromethyl) phosphate.

Comparative Example IV

[0043] Compared to example I, the difference only lies in that fluoroethylene carbonate (additive II) is not added to the ester electrolyte solution.

Comparative Example V

[0044] Compared to example I, the difference only lies in that there is no ester electrolyte solution.

Comparative Example VI

[0045] Compared to example I, the difference only lies in that there is no ether electrolyte solution.

[0046] [Use Test]

[0047] LiNi.sub.0.5Mn.sub.1.5O.sub.4 or LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 ternary materials are used as the positive matching assembly, and lithium metal is used as the negative electrode, then stainless steel current collectors are arranged on the positive and negative electrodes, and leads are attached to the current collectors. Finally, an insulation sleeve is used to isolate and seal the inner part of an insulation outer cylinder from the outer gas atmosphere, thereby fabricating a test battery. Test run is performed on the test battery.

[0048] [Impedance and Cycle Performance Test]

[0049] The battery is placed at a constant temperature of 25° C., charged at a constant current value of 0.05 C (20 h, 1 C=1 mA, which is calculated on the positive electrode) relative to the theoretical capacity of the battery, and the charging is finished at a voltage of 4.3 V (LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 is used as the positive electrode) or 5 V (LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 is used as the positive electrode). Then, discharge is performed at a current of the same 0.05 C multiplying power, and the discharge is finished when the voltage is 3.0 V. In this way, the coulombic efficiency and discharge capacity of the battery are obtained, and the impedance is characterized by testing the EIS of the battery.

[0050] Starting from the second cycle, charge and discharge cycles are carried out for 200 times at 0.2 C. The higher the capacity retention rate of the calculator, the better the cycle performance.

[0051] The test results are shown in table 1:

TABLE-US-00001 TABLE I Percentage of 3 C discharge capacity First charge- 100 cycles accounting for Battery resistance Battery resistance discharge retention 0.1 C discharge before cycling after 100 cycles Test items efficiency % rate % capacity % Ω cm.sup.−2 Ω cm.sup.−2 Example 1 82.3 69.8 69.5 652.1 700.2 Example 2 97.6 98.6 88.7 375.3 396.5 Example 3 87.4 87.7 73.5 522.9 542.6 Example 4 96.2 92.3 80.4 456.5 485.2 Example 5 87.8 89.4 80.5 400.9 440 Example 6 87.4 87.9 80.1 412.6 456.3 Comparative 80 64.8 65 709.8 886.5 example 1 Comparative 81.9 67.2 67.0 673.4 715.3 example 2 Comparative 80.7 66.9 67.6 679.5 719.4 example 3 Comparative 81.6 66.4 62.2 697.5 759.5 example 4 Comparative 80.9 65.1 64.3 693.4 763.9 example 5 Comparative 81.3 64.2 60 700.8 786.4 example 6

[0052] It can be seen from the above battery test results that compared with the comparative examples, on one hand, the ether electrolyte solution is filled between the lithium metal and the solid electrolyte, which is beneficial to improve the cycle life of the lithium metal; and on the other hand, the specific ester electrolyte solution is filled between the positive electrode and the solid electrolyte, which has a high voltage resistance, which is beneficial to improve the selection space of the positive electrode, especially the material with a high potential voltage can be used as the positive electrode, which is beneficial to improve the energy density of the battery; in addition, by filling a high-temperature resistant electrolyte solution additive, on the basis of ensuring that the safety is improved by using solid electrolyte, the solid-liquid interface with a better compatibility is used instead of the solid-solid interface, which reduces the interface impedance of the battery, and finally enables the battery to obtain high cycle life, energy density and overcharge resistance.

[0053] The specific examples of the present invention are only explanations of the present invention, and are not intended to limit the present invention. A person skilled in the art, after reading this description, would have made modifications to the specific examples as needed without inventive contribution, and they are all protected by the Patent Law as long as they fall within the scope of the claims of the present invention.