Solid-state lithium ion battery and negative electrode manufacturing method thereof

Abstract

The invention discloses a solid-state lithium ion battery and a negative electrode manufacturing method thereof. The solid-state lithium ion battery comprises a solid-state electrolyte and a negative electrode, the negative electrode is on a surface of the solid electrolyte and contains a lithium metal chloride. The negative electrode is provided with an alloy and an artificial solid electrolyte interface layer at the same time, so that the junction between the solid electrolyte and the negative electrode has better wettability.

Description

Technical Field

[0001] The present invention relates to a solid-state lithium-ion battery, and particularly to a solid-state lithium-ion battery for improving wettability and a method for manufacturing a negative electrode thereof. Background Art

[0002] With the rise of the electric vehicle and drone industries, the battery endurance has received increasing attention. Lithium-ion batteries are the mainstream of current storage batteries. However, traditional lithium-ion batteries use organic electrolytes, so they are bulky and have risks such as explosion and leakage.

[0003] To solve the above problems, solid-state lithium-ion batteries using solid electrolytes have been proposed. The solid electrolyte is mainly a garnet-type solid electrolyte. However, the wettability between the garnet-type solid state electrolyte and lithium metal used as the negative electrode (or anode) is poor, resulting in a very large interfacial impedance at the interface between the garnet-type solid electrolyte and lithium metal. In addition, voids will form in the garnet-type solid electrolyte during long-term charge and discharge, causing polarization problems in the reduction of lithium ions. Over long-term use, lithium dendrites grow at the grain boundaries of the garnet-type solid electrolyte, rendering the garnet-type solid electrolyte ineffective and causing the solid-state lithium-ion battery to short-circuit. As Figure 1 shown, there are multiple gaps 16 at the interface between the solid electrolyte 12 and the negative electrode 14, resulting in a very large interfacial impedance, and voids 18 will form in the solid electrolyte 12. For ease of explanation, Figure 1 only the solid electrolyte 12 and the negative electrode 14 of the solid-state lithium-ion battery 10 are shown, and the remaining parts (such as the positive electrode) are not shown.

[0004] The most direct way to solve wettability is to use an artificial solid electrolyte interphase (SEI) layer or an alloy of lithium metal and different metal elements. Current solid-state lithium-ion batteries can only use an artificial SEI layer or an alloy to improve wettability, and do not use an artificial SEI layer or an alloy simultaneously to improve wettability. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a solid-state lithium-ion battery for improving wettability and a method for manufacturing a negative electrode thereof.

[0006] The present invention provides a solid-state lithium-ion battery including a solid electrolyte and a negative electrode. The negative electrode is on a surface of the solid electrolyte and contains lithium metal chloride. The negative electrode has both an alloy and an artificial solid electrolyte interface layer, so that the interface between the solid electrolyte and the negative electrode has better wettability.

[0007] The present invention also provides a method for fabricating a negative electrode of a solid-state lithium-ion battery, comprising: coating a metal ion chloride solvent on a surface of a solid electrolyte; drying the metal ion chloride solvent coated on the solid electrolyte to obtain a metal ion chloride; forming lithium metal on the metal ion chloride; and subjecting the metal ion chloride and the lithium metal to an alloying process to form an interface layer having an alloy and an artificial solid electrolyte interface layer between the solid electrolyte and the lithium metal, wherein the lithium metal and the interface layer form the negative electrode of the solid-state lithium-ion battery. Since the negative electrode has both an alloy and an artificial solid electrolyte interface layer, the interface between the solid electrolyte and the negative electrode has better wettability. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Showing a cross-sectional view of a conventional solid-state lithium-ion battery.

[0009] Figure 2 Showing the solid-state lithium-ion battery of the present invention.

[0010] Figure 3 Showing Figure 2 a method for fabricating a negative electrode of a solid-state lithium-ion battery of

[0011] Figure 4 Showing the voltage change of the solid-state lithium-ion battery of the present invention under actual operation.

[0012] Figure 5 Showing the capacity and potential curves of the solid-state lithium-ion battery of the present invention after charge and discharge.

[0013] Description of Reference Numerals: 10 - solid-state lithium-ion battery; 12 - solid electrolyte; 14 - negative electrode; 16 - gap; 18 - void; 20 - solid-state lithium-ion battery; 22 - solid electrolyte; 24 - negative electrode; 242 - lithium metal; 244 - interface layer; 30 - curve; 32 - curve; 34 - curve; 36 - curve; R1 - voltage change range; R2 - voltage change range; S10 - step; S12 - step; S14 - step; S16 - step. DETAILED DESCRIPTION OF THE INVENTION

[0014] Figure 2 Showing the solid-state lithium-ion battery of the present invention. For convenience of description, Figure 2Twenty solid-state lithium-ion batteries 20 show a solid electrolyte 22 and a negative electrode 24. Other parts of the solid-state lithium-ion battery 20 are not shown, such as the positive electrode (or cathode) of the solid-state lithium-ion battery 20. The solid electrolyte 22 can be, but is not limited to, a garnet-type solid electrolyte. For example, the solid electrolyte 22 can be lithium lanthanum zirconium tantalum oxide (LLZTO). The negative electrode 24 is on the solid electrolyte 22, and the negative electrode 24 contains a lithium metal 242 and an interface layer 244. The interface layer 244 includes an alloy and a solid electrolyte interphase (SEI) layer. Since the interface layer 244 has the functions of both an alloy and an artificial SEI layer, the negative electrode 24 of the present invention has better wettability with the solid electrolyte 22. The alloy in the interface layer 244 includes, but is not limited to, lithium calcium alloy, lithium indium alloy, lithium tin alloy, or lithium silicon alloy. The artificial SEI layer in the interface layer 244 includes lithium chloride. There is no gap at the interface between the lithium metal chloride 244 and the solid electrolyte 22, so the interface impedance can be reduced. In addition, the lithium metal chloride 244 can also fill the voids 18 on the surface of the solid electrolyte 22 to prevent the growth of lithium dendrites at the grain boundaries of the solid electrolyte.

[0015] Figure 3 show Figure 2 Method for manufacturing a negative electrode of a solid-state lithium-ion battery. Figure 3 The method for manufacturing the negative electrode includes performing step S10 to coat a metal ion chloride solvent on a surface (such as the upper surface) of the solid electrolyte 22. In one embodiment, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, or 0.07 grams of calcium chloride (CaCl2) can be added to a sample bottle together with 1 milliliter of isopropanol, 1 milliliter of ethanol, and 1 milliliter of acetone and mixed for 1 hour to obtain the metal ion chloride solvent, but the present invention is not limited thereto. In one embodiment, 5, 10, or 15 microliters of the metal ion chloride solvent can be coated on the upper surface of the solid electrolyte 22 by drop coating, but the present invention is not limited thereto. In one embodiment, the metal ion chloride solvent can be coated on the upper surface of the solid electrolyte 22 by spin coating. The spin coating method includes first coating at a speed of 500 rpm for 20 seconds and then coating at a speed of 2000 rpm for 5 seconds, first coating at a speed of 1000 rpm for 30 seconds and then coating at a speed of 3000 rpm for 10 seconds, or first coating at a speed of 1500 rpm for 40 seconds and then coating at a speed of 4000 rpm for 15 seconds, but the present invention is not limited thereto.

[0016] After applying a metal ion chloride solvent onto the surface of the solid electrolyte 22, the solvent of the metal ion chloride solvent applied on the solid electrolyte 22 is dried to obtain a metal ion chloride, as shown in step S12. In one embodiment, the way of solvent drying includes heating the solid electrolyte 22 coated with the metal ion chloride solvent to 40, 50 or 60 °C in a glove box filled with an argon atmosphere for solvent drying. The metal ion chloride can be a conductor, a semiconductor or a non-conductor. The metal ion chloride has lithiophilicity. The metal ion chloride can be, but is not limited to, calcium chloride, silicon chloride, indium chloride or tin chloride.

[0017] After completing the solvent drying, step S14 is carried out to form lithium metal 242 on the metal ion chloride. Finally, step S16 is carried out to perform an alloying process on the metal ion chloride and the lithium metal 242 to form an interface layer 244 having an alloy and an artificial solid electrolyte interface layer between the solid electrolyte 22 and the lithium metal 242, wherein the lithium metal 242 and the interface layer 244 form the negative electrode 24 of the solid state lithium ion battery 20. In one embodiment, the alloying process includes continuously heating the lithium metal 242, the interface layer 244 and the solid electrolyte at 400 °C for 2 minutes and then cooling to room temperature, but the present invention is not limited thereto. In one embodiment, the alloying process includes continuously heating the lithium metal 242, the interface layer 244 and the solid electrolyte at 460 °C for 3 minutes and then cooling to room temperature, but the present invention is not limited thereto. In one embodiment, the alloying process includes continuously heating the lithium metal 242, the interface layer 244 and the solid electrolyte at 540 °C for 5 minutes and then cooling to room temperature, but the present invention is not limited thereto. In one embodiment, the reaction temperature of the alloying process is 460 - 540 °C, preferably 480 - 540 °C, but the present invention is not limited thereto.

[0018] There are many methods for manufacturing the solid electrolyte 22. Here, a method for manufacturing a garnet-type solid electrolyte of LLZTO is provided as an example. Assuming the formula of lithium lanthanum zirconium tantalum oxide is Li 6.75 La3Zr 1.75 Ta 0.25 O 12, materials such as lithium hydroxide, lanthanum oxide, zirconium oxide, and tantalum oxide are weighed according to the atomic molar ratio of lithium:lanthanum:zirconium:tantalum = 7.425:3:1.75:0.25 (since lithium is prone to evaporation during sintering, an additional 10% by weight is taken for compensation). Then, isopropyl alcohol is added and ball-milled at 300 revolutions per minute for 12 hours to uniformly mix the materials into a suspension. The suspension is placed in an alumina crucible and dried at a temperature of 70 °C for 12 hours, and then sintered at a temperature of 900 °C for 12 hours to obtain cubic-phase LLZTO. After sintering, ball-milling is carried out at a speed of 300 revolutions per minute for 12 hours to homogenize the powder. The powder is placed in a mold with a diameter of 12 mm and a force of 20 metric tons is applied for 1 minute and then demolded to obtain a precursor ingot with a diameter of 12 mm and a thickness of 3 mm. The precursor ingot is placed in an alumina crucible and covered with twice the weight of the parent powder to prevent lithium evaporation. Then, it is sintered in air at a temperature of 900 °C for 4 hours, and then sintered at a temperature of 1100 °C for 12 hours. After sintering is completed, the parent powder on the precursor ingot is removed and polished to obtain the solid electrolyte 22 of LLZTO.

[0019] Figure 4 Shows the voltage change of the solid-state lithium-ion battery of the present invention under actual operation. Figure 4 Shows the voltage change ranges R1 and R2 of the solid-state lithium-ion batteries fabricated by the drop-casting method and the spin-coating method, respectively. From Figure 4 It can be seen that for the solid-state lithium-ion batteries fabricated by either the drop-casting method or the spin-coating method, the voltage change ranges R1 and R2 are both within the range of ±20 mV, and the voltage change range R2 of the spin-coating method is smaller than the voltage change range R1 of the drop-casting method.

[0020] Figure 5 Shows the capacity and potential curves of the solid-state lithium-ion battery of the present invention after charge and discharge. In Figure 5 , the rightmost curves 30 and 32 are the capacity and potential curves of the first charge and discharge, and the leftmost curves 34 and 36 are the capacity and potential curves of the 100th charge and discharge.

[0021] From Figure 4 and Figure 5 It can be seen that the solid-state lithium-ion battery of the present invention is superior to the traditional solid-state lithium-ion battery.

[0022] The above are only embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the present invention has been provided above in the form of embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field to which the present invention pertains, without departing from the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments by using the technical content disclosed above. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A solid-state lithium-ion battery, characterized in that, Comprising: A solid electrolyte; And A negative electrode, on a surface of the solid electrolyte and containing a lithium metal chloride.

2. The solid-state lithium battery according to claim 1, characterized in that, The negative electrode comprises a lithium metal and an interfacial layer having an alloy and an artificial solid electrolyte interface layer.

3. The solid-state lithium battery according to claim 2, wherein The alloy includes a lithium-calcium alloy, a lithium-indium alloy, a lithium-tin alloy or a lithium-silicon alloy.

4. The solid-state lithium battery according to claim 2, wherein The artificial solid electrolyte interface layer includes lithium chloride.

5. The solid-state lithium battery according to claim 1, wherein The solid electrolyte includes lithium lanthanum zirconium tantalum oxide.

6. A method for manufacturing a negative electrode of a solid-state lithium-ion battery, characterized in that, Including the following steps: A. Coating a metal ion chloride solvent on a surface of a solid electrolyte; B. Drying the solvent of the metal ion chloride solvent coated on the solid electrolyte to obtain a metal ion chloride; C. Forming a lithium metal on the metal ion chloride; and D. Performing an alloying process on the metal ion chloride and the lithium metal to form an interfacial layer having an alloy and an artificial solid electrolyte interface layer between the solid electrolyte and the lithium metal, wherein the lithium metal and the interfacial layer form the negative electrode of the solid lithium ion battery.

7. The method for manufacturing the negative electrode according to claim 6, characterized in that Step A includes coating the metal ion chloride solvent on the surface by a drop coating method or a spin coating method.

8. The method for manufacturing the negative electrode according to claim 6, wherein The metal ion chloride includes conductors, semiconductors and non-conductors.

9. The method for manufacturing the negative electrode according to claim 6, wherein, The metal ion chloride has lithiophilicity.

10. The method for manufacturing a negative electrode according to claim 6, characterized in that, The metal ion chloride includes calcium chloride, silicon chloride, indium chloride or tin chloride.

11. The method for manufacturing the negative electrode according to claim 6, wherein The alloy includes a lithium-calcium alloy, a lithium-indium alloy, a lithium-tin alloy or a lithium-silicon alloy.

12. The method for manufacturing a negative electrode according to claim 6, characterized in that, The artificial solid electrolyte interface layer includes lithium chloride.

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