High-safety lithium metal battery and preparation method thereof

Abstract

The high-safety lithium metal battery comprises a polymer modified lithium metal negative electrode with an artificial protection layer on the surface, a positive electrode plate, a ceramic diaphragm with a high-temperature-resistant coating on the surface and an electrolyte for in-situ solidification of the electrolyte, and the safety of the lithium metal battery can be efficiently improved by utilizing the synergistic effect of all battery components; meanwhile, the method is suitable for an existing lithium battery production line, can meet the mass production requirement of the high-safety lithium metal battery, is used for the preparation method of the battery, specifically comprises six steps and conditions, and has the advantages that the safety of the lithium metal battery can be effectively improved, the method is suitable for the existing lithium battery production line, and the mass production requirement of the high-safety lithium metal battery can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a high-safety lithium metal battery and a preparation method thereof. Background Art

[0002] To address climate change and reduce carbon emissions, the global energy structure is shifting towards renewable energy, significantly increasing the demand for power batteries and energy storage systems. However, the energy density of traditional lithium-ion batteries has reached its theoretical limit, making it difficult to meet the needs of emerging fields such as electric aviation, bionic machines, and electric vehicles. Lithium metal has an ultra-high specific capacity (3860mAh / g), the lowest redox potential (-3.04V VS H + / H2) and a lighter bulk density (0.534g / cm 3 ), so it is considered to be an ideal negative electrode for high-energy-density battery systems, and lithium metal batteries are also regarded as the core of the next generation of high-energy-density batteries.

[0003] Despite the numerous theoretical advantages of lithium metal batteries, their commercialization has been hampered by safety concerns. Specifically, the uneven deposition of lithium on the lithium metal anode during cycling can lead to the formation of dendrites, which can cause internal short circuits when dendrites penetrate the separator. The continuous side reactions between lithium metal and the liquid electrolyte cause repeated rupture and reconstruction of the solid electrolyte interface, consuming active lithium and producing gaseous byproducts. Under abuse conditions, the exothermic reaction enthalpy of lithium metal and the electrolyte can reach as high as 3500 J / g, easily initiating chain reactions and leading to thermal runaway.

[0004] To address the above problems, researchers have proposed a number of improvement strategies. First, they optimize various types of electrolytes, such as copolymers, cross-linked polymers, and polymer / nanoparticle composites. These materials can ensure high ionic conductivity and have a sufficiently strong shear modulus to prevent the formation of lithium dendrites. Second, they optimize the electrode-electrolyte interface structure to reduce the risk of thermal runaway, fire, and explosion within the battery. Third, they construct a three-dimensional framework structure to increase the specific surface area of ​​the negative electrode and promote the uniform distribution of lithium ions.

[0005] To address the above-mentioned issues, several patents have been published: CN 119725707 A, “Preparation method and application of in-situ polymerized high thermal conductivity gel polymer electrolyte”. This invention discloses a method for preparing an in-situ polymerized high thermal conductivity gel polymer electrolyte, which solves the problems of the prior art, such as the easy growth of lithium dendrites on the surface of the lithium negative electrode, poor safety performance, poor electrolyte-electrode interface compatibility, and low ionic conductivity. At high temperatures, the electrolyte has good thermal conductivity. However, this solution cannot significantly improve the safety performance of lithium metal batteries by using only the gel electrolyte. At high temperatures, the inevitable decomposition of the gel electrolyte can also cause thermal runaway of the battery. A "High-safety solid-state lithium metal battery and preparation method" is an invention that introduces a heterogeneous interface layer between the lithium metal negative electrode and the solid electrolyte, effectively improving the physical contact between the lithium metal negative electrode and the solid electrolyte, preventing the growth of lithium dendrites, and at the same time reducing the interfacial reaction between the lithium metal and the solid electrolyte, thereby enhancing the stability and safety performance of the solid-state lithium metal battery at room temperature and high temperature. However, this invention is only applicable to oxide solid-state battery systems. The oxide electrolyte material is relatively brittle and difficult to mass-produce. In addition, the heterogeneous interface layer described in this invention only improves the battery interface contact performance. The electrolyte phase is still prone to lithium dendrite penetration, which can easily cause short circuit and thermal runaway risks.

[0006] Therefore, it is of great significance to develop a high-safety lithium metal battery and its preparation method. Summary of the Invention

[0007] The task of the present invention is to overcome the shortcomings of the existing technology and propose a high-safety lithium metal battery and its preparation method. The high-safety lithium metal battery includes a polymer-modified lithium metal negative electrode with an artificial protective layer on the surface, a positive electrode plate, a ceramic diaphragm with a high-temperature resistant coating on the surface, and an electrolyte with an in-situ solidified electrolyte. By utilizing the synergistic effect between the various battery components, the safety of the lithium metal battery can be effectively improved. At the same time, it is suitable for existing lithium battery production lines and can meet the mass production needs of high-safety lithium metal batteries.

[0008] The preparation method for the battery specifically includes the following steps and conditions:

[0009] (1) uniformly coating a multilayered artificial protective layer on one or both sides of a pure lithium metal negative electrode to obtain a polymer-modified lithium metal negative electrode;

[0010] (2) uniformly coating the high-temperature resistant coating on one side or both sides of the diaphragm to obtain a ceramic diaphragm;

[0011] (3) mixing a polymer monomer, an initiator, an organic solvent, a lithium salt, and a functional additive to obtain an in-situ solidified electrolyte;

[0012] (4) laminating, welding and packaging the positive electrode sheet, polymer-modified lithium metal negative electrode and ceramic diaphragm to obtain a dry battery cell;

[0013] (5) Injecting the in-situ solidified electrolyte into the dry cell, placing it in a vacuum state and sealing it, and then hot pressing and solidifying it to obtain a high-safety lithium metal battery.

[0014] Because the coating on the surface of the lithium metal has good structural stability, the present invention can completely prevent the contact between the electrolyte and the lithium metal, and completely eliminate the corrosion of the electrolyte on the lithium metal; at the same time, because the high-temperature resistant coating on the surface of the diaphragm can improve the thermal shrinkage performance of the diaphragm, it can effectively avoid direct contact between the positive and negative electrodes during thermal runaway; in addition, because the polymer skeleton in the in-situ solidified electrolyte restricts the free movement of anions from the lithium salt, it can suppress the exothermic reaction during thermal runaway.

[0015] In summary, the high-safety lithium metal battery and its preparation method of the present invention utilize the synergistic effect between battery components such as polymer-modified lithium metal negative electrode, ceramic diaphragm and in-situ solidified electrolyte to effectively improve the safety of lithium metal batteries. It is suitable for existing lithium battery production lines and can meet the mass production needs of high-safety lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a lithium metal strip with an artificial protective coating is provided for a high-safety lithium metal battery and a preparation method thereof according to the present invention.

[0017] Figure 2 for Figure 1 The high-safety lithium metal battery and the high-safety lithium metal battery prepared by the preparation method shown are compared before and after the needle penetration test.

[0018] Figure 3 for Figure 1 The temperature and voltage curves of the high-safety lithium metal battery and its preparation method during the acupuncture process of the high-safety lithium metal battery are shown.

[0019] Figure 4 Schematic diagram showing the comparison of the conventional lithium metal battery before and after the puncture test in the comparative example.

[0020] Figure 5 Schematic diagram of temperature and voltage curves during the acupuncture process of a conventional lithium metal battery in the comparative example.

[0021] The present invention is described in further detail below with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] like Figures 1 to 5As shown, the high-safety lithium metal battery, the high-safety lithium metal battery, includes a polymer-modified lithium metal negative electrode with an artificial protective layer on the surface, a positive electrode plate, a ceramic diaphragm with a high-temperature resistant coating on the surface and an electrolyte with in-situ solidified electrolyte. It utilizes the synergistic effect between the various battery components to effectively improve the safety of the lithium metal battery. At the same time, it is suitable for existing lithium battery production lines and can meet the mass production needs of high-safety lithium metal batteries.

[0023] The lithium metal battery of the present invention may further be

[0024] The artificial protective layer has a multi-layer structure, wherein the surface layer is a fluorinated polymer enriched layer, and the inner layer is a lithium-philic layer dominated by a polyether polymer.

[0025] The artificial protective layer is located on one side or both sides of the lithium metal negative electrode, and the thickness of one side is 0.5 to 10 μm.

[0026] The high-temperature resistant coating is one or more of boehmite (γ-AlOOH), aluminum oxide (Al2O3), titanium oxide (TiO2), lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), and lithium lanthanum tantalum oxide (LLTO).

[0027] The high temperature resistant coating is located on one side or both sides of the diaphragm, and the thickness of one side is 0.1 to 3 μm.

[0028] The polymer monomer, initiator, organic solvent, lithium salt and functional additive are mixed to obtain an in-situ solidified electrolyte.

[0029] The polymer monomers are chain monomers containing unsaturated carbon-carbon double bonds, cyclic monomers capable of ring-opening polymerization, and monomers having polymerizable active functional groups.

[0030] The preparation method for the lithium metal battery specifically includes the following steps and conditions:

[0031] (1) uniformly coating a multilayered artificial protective layer on one or both sides of a pure lithium metal negative electrode to obtain a polymer-modified lithium metal negative electrode;

[0032] (2) uniformly coating the high-temperature resistant coating on one side or both sides of the diaphragm to obtain a ceramic diaphragm;

[0033] (3) mixing a polymer monomer, an initiator, an organic solvent, a lithium salt, and a functional additive to obtain an in-situ solidified electrolyte;

[0034] (4) laminating, welding and packaging the positive electrode sheet, polymer-modified lithium metal negative electrode and ceramic diaphragm to obtain a dry battery cell;

[0035] (5) Injecting the in-situ solidified electrolyte into the dry cell, placing it in a vacuum state and sealing it, and then hot pressing and solidifying it to obtain a high-safety lithium metal battery.

[0036] This method can further be

[0037] The pressure of the hot pressing curing in step (5) is 0.01 to 10 kg / cm 2 , temperature is 40-100℃, and time is 10-500min.

[0038] Example 1

[0039] S1. Apply an artificial protective layer to both sides of the lithium metal strip by gap coating, with a single-side coating thickness of 0.5 μm to obtain a polymer-modified lithium metal negative electrode.

[0040] S2. Apply an Al2O3 high-temperature resistant coating on both sides of the diaphragm by gravure coating, with a single-side coating thickness of 1 μm to obtain a ceramic diaphragm.

[0041] S3. Mixing a polymer monomer, an initiator, an organic solvent, a lithium salt, and a functional additive to obtain an in-situ solidified electrolyte, wherein the polymer monomer is a chain monomer having an unsaturated double bond.

[0042] S4. The positive electrode sheet, polymer-modified lithium metal negative electrode and ceramic diaphragm are stacked, the tabs are welded and packaged to obtain a dry battery cell.

[0043] S5. In situ solidification of electrolyte is injected into the dry cell, vacuum-stabilized and sealed, and then hot-pressed to obtain a high-safety lithium metal battery. The hot-pressing pressure is 3.6 kg / cm 2 , temperature is 65℃, and time is 120min.

[0044] Example 2

[0045] S1. Apply an artificial protective layer to one side of a lithium metal strip by gap coating, with a coating thickness of 4 μm on one side, to obtain a polymer-modified lithium metal negative electrode.

[0046] S2. Apply the LATP high-temperature resistant coating to both sides of the diaphragm by gravure coating, with a single-side coating thickness of 0.5 μm to obtain a ceramic diaphragm.

[0047] S3. Mixing a polymer monomer, an initiator, an organic solvent, a lithium salt, and a functional additive to obtain an in-situ solidified electrolyte, wherein the polymer monomer is a cyclic monomer that can be ring-opening polymerized.

[0048] S4. The positive electrode sheet, polymer-modified lithium metal negative electrode and ceramic diaphragm are stacked, the tabs are welded and packaged to obtain a dry battery cell.

[0049] S5. In situ solidification of electrolyte is injected into the dry cell, vacuum-stood and sealed, and hot-pressed to obtain a high-safety lithium metal battery. The hot-pressing pressure is 3kg / cm 2 , temperature is 55℃, and time is 240min.

[0050] Comparative Example 1

[0051] A battery is assembled by assembling a pure lithium metal strip without an artificial protective layer, a conventional separator without a high-temperature resistant coating, and a prepared positive electrode sheet, and then injecting the liquid electrolyte. After completing the steps of sealing, formation, secondary sealing, and capacity separation, a comparative lithium metal battery is obtained.

[0052] As described above, the present invention can be better implemented. The above embodiments are only the best implementation methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Other changes, modifications, replacements, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. High-safety lithium metal battery, characterized by It includes a polymer-modified lithium metal negative electrode with an artificial protective layer on the surface, a positive electrode, a ceramic diaphragm with a high-temperature resistant coating on the surface, and an electrolyte with in-situ solidified electrolyte. It utilizes the synergistic effect between the various battery components to effectively improve the safety of lithium metal batteries. At the same time, it is suitable for existing lithium battery production lines and can meet the mass production needs of high-safety lithium metal batteries.

2. The lithium metal battery according to claim 1, characterized in that The artificial protective layer has a multi-layer structure, wherein the surface layer is a fluorinated polymer enriched layer, and the inner layer is a lithium-philic layer dominated by a polyether polymer.

3. The lithium metal battery according to claim 1, characterized in that The artificial protective layer is located on one side or both sides of the lithium metal negative electrode, and the thickness of one side is 0.5 to 10 μm.

4. The lithium metal battery according to claim 1, characterized in that The high-temperature resistant coating is one or more of boehmite (γ-AlOOH), aluminum oxide (Al2O3), titanium oxide (TiO2), lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), and lithium lanthanum tantalum oxide (LLTO).

5. The lithium metal battery according to claim 1, characterized in that The high temperature resistant coating is located on one side or both sides of the diaphragm, and the thickness of one side is 0.1 to 3 μm.

6. A method for preparing the in-situ solidified electrolyte for lithium metal batteries according to claim 1, characterized in that The polymer monomer, initiator, organic solvent, lithium salt and functional additive are mixed to obtain an in-situ solidified electrolyte.

7. The method for preparing an in-situ solidified electrolyte for a lithium metal battery according to claim 6, wherein The polymer monomers are chain monomers containing unsaturated carbon-carbon double bonds, cyclic monomers capable of ring-opening polymerization, and monomers having polymerizable active functional groups.

8. A method for preparing a battery according to any one of claims 1 to 5, characterized in that The specific steps and conditions are as follows: (1) uniformly coating a multilayered artificial protective layer on one or both sides of a pure lithium metal negative electrode to obtain a polymer-modified lithium metal negative electrode; (2) uniformly applying the high temperature resistant coating on one side or both sides of the diaphragm to obtain a ceramic diaphragm; (3) mixing a polymer monomer, an initiator, an organic solvent, a lithium salt, and a functional additive to obtain an in-situ solidified electrolyte; (4) laminating, welding and packaging the positive electrode sheet, polymer-modified lithium metal negative electrode and ceramic diaphragm to obtain a dry battery cell; (5) Injecting the in-situ solidified electrolyte into the dry cell, placing it in a vacuum state and sealing it, and then hot pressing and solidifying it to obtain a high-safety lithium metal battery.

9. The preparation method according to claim 8, wherein The pressure of the hot pressing curing in step (5) is 0.01 to 10 kg / cm 2 , temperature is 40-100℃, and time is 10-500min.

Images