Solid-state battery and preparation method thereof

Abstract

The invention discloses a solid-state battery, relates to the technical field of lithium ion battery preparation, and aims to solve the technical problems that the current solid-state battery is generally short in cycle life and poor in rate capability, the solid-state battery comprises a positive electrode, a negative electrode and a solid-state electrolyte layer, and the solid-state battery is prepared by adopting a hot-pressing melting method; wherein the positive electrode is a composite positive electrode film composed of an active material Li < 1.75 > Ti < 2 > (Mo < 0.25 > P < 0.75 > S < 3.8 > Se < 0.2 >) < 3 > and a binder, the negative electrode is a composite negative electrode film composed of a C3N3 carbon nitride material and a binder, and the solid electrolyte layer is a composite solid electrolyte film composed of LiWS2 and a binder; the binder is lithium lipoate or lipoic acid. The invention further discloses a preparation method of the solid-state battery and application of the solid-state battery in a new energy automobile. The solid-state battery disclosed by the invention is good in cycle performance and rate capability, simple in preparation process, low in synthesis temperature, relatively wide in electrochemical window and relatively good in electrochemical stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery preparation, and more specifically, to a solid-state battery and a preparation method thereof. Background Art

[0002] As a core component product of pure electric vehicles and hybrid electric vehicles, developing new lithium-ion batteries and new system batteries with high performance, low cost, and high reliability is the main direction of the development of power batteries for new energy vehicles, and also indicates the necessity of the technological innovation and progress of power batteries. However, at present, the ternary high-nickel material - liquid electrolyte - graphite chemical system is already the power cell chemical system with the highest known energy density in the market, and its monomer capacity density of 350 Wh / kg has approached the limit design of the material system itself. Although some domestic manufacturers want to further improve the energy density of monomer batteries by reducing the amount of electrolyte, thinning the thickness of the current collector, and reducing the mass of the battery case, these measures can only be improved in a piecemeal manner and cannot fundamentally solve the problem. At the same time, due to the existence of contradictions between energy density, power density, and safety issues themselves, these limit designs will bring more problems.

[0003] Therefore, in the development of next-generation power batteries, solid-state batteries have emerged. Many researchers and enterprises believe that compared with lithium-sulfur, lithium-air, aluminum, magnesium batteries, and non-existent graphene batteries, solid-state batteries are the most promising candidate technologies to replace existing high-energy-density lithium-ion batteries. Their energy density is expected to increase exponentially, with better cycle performance, longer service life, higher rate performance, and may fundamentally solve the safety problems of existing liquid electrolyte lithium-ion batteries. However, the solid-state battery technology is currently not yet mature, with defects such as low ionic conductivity, poor solid / solid interface contact and stability; especially in terms of fast charging performance, there is a large gap between solid-state batteries and liquid batteries. The rate performance of liquid batteries can generally reach the commercial level of 4C - 5C, while the rate performance of solid-state batteries is generally below 1C. Therefore, it is necessary to develop a solid-state battery with fast charging performance, which can promote the practical application of solid-state batteries in new energy vehicles. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, one of the purposes of the present invention is to provide a solid-state battery to solve the technical problems that the current solid-state batteries generally have low cycle life and poor rate performance.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A solid-state battery, comprising a positive electrode, a negative electrode, and a solid electrolyte layer, and the solid-state battery is prepared by a hot pressing and melting method; wherein, the positive electrode is an active material Li 1.75Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and a binder to form a composite positive electrode film, the negative electrode is a composite negative electrode film composed of C3N3 carbon nitride material and a binder, and the solid electrolyte layer is a composite solid electrolyte film composed of LiWS2 and a binder; the binder is lithium thioacetate or thioacetic acid.

[0007] The solid-state battery of the present invention has good cycling performance and rate performance, and moreover, the preparation process is simple, the synthesis temperature is low, it has a wide electrochemical window and good electrochemical stability, and can be applied to large-scale production.

[0008] Preferably, the positive electrode of the solid-state battery is an active material Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and lithium thioacetate to form a composite positive electrode film, the mass ratio of lithium thioacetate in the composite positive electrode film is 1-50%, and the thickness of the composite positive electrode film is 10 μm-10 cm. Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 has a homogenized structure and high ionic conductivity and electronic conductivity. Therefore, no additional conductive agent needs to be introduced during the manufacturing process, and lithium thioacetate is a self-healing binder with high ionic conductivity. A composite positive electrode film with good performance can be obtained by simply melting and mixing with the positive electrode.

[0009] Preferably, the negative electrode of the solid-state battery is a composite negative electrode film composed of the active material C3N3 and thioacetic acid, the mass ratio of thioacetic acid in the composite negative electrode film is 1-50%, and the thickness of the composite negative electrode film is 10 μm-10 cm.

[0010] Preferably, the C3N3 carbon nitride material has a specific capacity of 2800 mAh / g, can replace the lithium metal negative electrode material in the application of solid-state batteries, and compared with lithium metal, the volume expansion rate of C3N3 during charge and discharge is extremely low, thus having better cycling performance and rate performance.

[0011] Preferably, the solid electrolyte layer of the solid-state battery is a composite solid electrolyte membrane composed of LiWS2 and lithium thioacetate. The mass ratio of lithium thioacetate in the composite solid electrolyte membrane is 1-50%, and the thickness of the composite solid electrolyte membrane is 10 μm-10 cm. LiWS2 has high ionic conductivity, and since lithium thioacetate has high ionic conductivity, the ionic conduction performance of LiWS2 will not be reduced after compounding. Instead, due to the introduction of lithium thioacetate, the encapsulation of the flexible solid electrolyte membrane can be realized.

[0012] The second object of the present invention is to provide a method for preparing the above-mentioned solid-state battery, comprising the following steps:

[0013] (1) Mix Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and a binder, and then obtain a composite positive electrode membrane by high-energy ball milling and pressing;

[0014] (2) Mix LiWS2 and a binder, and then obtain a composite solid electrolyte membrane by high-energy ball milling and pressing;

[0015] (3) Mix C3N3 and a binder, and then obtain a composite negative electrode membrane by high-energy ball milling and pressing;

[0016] (4) Stack the composite positive electrode membrane, the composite solid electrolyte membrane, and the composite negative electrode membrane of the same size after cutting in sequence from top to bottom, and then obtain a solid-state battery monomer by hot pressing and melting.

[0017] Further, the ball milling conditions in step (1), step (2), and step (3) are the same. The rotation speed of ball milling is 100-500 rpm, and the ball milling time is 1-12 h.

[0018] Further, in step (4), the hot pressing and melting temperature is 50-200 °C, the hot pressing time is 10-120 min, and the hot pressing pressure is 1-100 MPa.

[0019] The third object of the present invention is to provide an application of the above-mentioned solid-state battery in new energy vehicles.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The solid-state battery of the present invention has good cycle performance and rate performance, and the preparation process is simple, the synthesis temperature is low, it has a wide electrochemical window, good electrochemical stability, and can be applied to large-scale production. Specific Embodiments

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] The test materials and reagents used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels. For those not specifying specific techniques or conditions in the embodiments, they can all be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications.

[0023] Example 1

[0024] This embodiment provides a preparation method of a solid-state battery, including the following steps:

[0025] (1) According to the mass ratio, 80% of Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and 20% of lithium thioacetate are mixed, and after high-energy ball milling, they are pressed to obtain a composite positive electrode film with a thickness of 150 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h;

[0026] (2) According to the mass ratio, 80% of LiWS2 and 20% of lithium thioacetate are mixed, and after high-energy ball milling, they are pressed to obtain a composite solid electrolyte film with a thickness of 20 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h;

[0027] (3) According to the mass ratio, 80% of C3N3 and 20% of thioacetic acid are mixed, and after high-energy ball milling, they are pressed to obtain a composite negative electrode film with a thickness of 50 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h;

[0028] (4) The positive electrode film, solid electrolyte film and negative electrode film with the same size after cutting are stacked together in the up-and-down order, and are pressed at a hot melting condition of 100 °C for 60 min to prepare a solid-state battery.

[0029] The prepared solid-state battery is subjected to a discharge cycle performance test, and the cycle life under 3C conditions is measured to be 2500 times.

[0030] Example 2

[0031] This embodiment provides a preparation method of a solid-state battery, including the following steps:

[0032] (1) According to the mass ratio, 70% of Li1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 is mixed with 30% lithium thioacetate, and after high-energy ball milling, it is pressed to obtain a composite positive electrode film with a thickness of 150 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0033] (2) According to the mass ratio, 80% of LiWS2 and 20% of lithium thioacetate are mixed, and after high-energy ball milling, it is pressed to obtain a composite solid electrolyte film with a thickness of 20 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0034] (3) According to the mass ratio, 80% of C3N3 and 20% of thioacetic acid are mixed, and after high-energy ball milling, it is pressed to obtain a composite negative electrode film with a thickness of 50 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0035] (4) The positive electrode film, solid electrolyte film and negative electrode film of the same size after cutting are stacked together in the up and down order, and pressed at a hot melting condition of 100 °C for 60 min to prepare a solid-state battery.

[0036] The prepared solid-state battery is subjected to a discharge cycle performance test, and the cycle life under 3C conditions is measured to be 2200 times.

[0037] Example 3

[0038] This example provides a method for preparing a solid-state battery, including the following steps:

[0039] (1) According to the mass ratio, 60% of Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 is mixed with 40% lithium thioacetate, and after high-energy ball milling, it is pressed to obtain a composite positive electrode film with a thickness of 150 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0040] (2) According to the mass ratio, 90% of LiWS2 and 10% of lithium thioacetate are mixed, and after high-energy ball milling, it is pressed to obtain a composite solid electrolyte film with a thickness of 20 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0041] (3) According to the mass ratio, 80% of C3N3 and 20% of thioacetic acid are mixed, and after high-energy ball milling, it is pressed to obtain a composite negative electrode film with a thickness of 50 μm; wherein, the rotation speed of the ball milling is 200 rpm and the ball milling time is 10 h;

[0042] (4) Stack the positive electrode film, solid electrolyte film, and negative electrode film of the same size after cutting together in the up-and-down order, and press them for 60 minutes under the hot-melt condition at 100 °C to prepare a solid-state battery.

[0043] Perform a discharge cycle performance test on the prepared solid-state battery, and the cycle life under the condition of 3C is measured to be 2000 times.

[0044] Example 4

[0045] This example provides a method for preparing a solid-state battery, including the following steps:

[0046] (1) According to the mass ratio, mix 80% of Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and 20% of lithium thioacetate, and press them after high-energy ball milling to obtain a composite positive electrode film with a thickness of 150 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h.

[0047] (2) According to the mass ratio, mix 80% of LiWS2 and 20% of lithium thioacetate, and press them after high-energy ball milling to obtain a composite solid electrolyte film with a thickness of 20 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h.

[0048] (3) According to the mass ratio, mix 80% of C3N3 and 20% of thioacetic acid, and press them after high-energy ball milling to obtain a composite negative electrode film with a thickness of 50 μm; among them, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 10 h.

[0049] (4) Stack the positive electrode film, solid electrolyte film, and negative electrode film of the same size after cutting together in the up-and-down order, and press them for 60 minutes under the hot-melt condition at 150 °C to prepare a solid-state battery.

[0050] Perform a discharge cycle performance test on the prepared solid-state battery, and the cycle life under the condition of 3C is measured to be 1500 times.

[0051] In the present invention, the size and thickness of the positive electrode film, solid electrolyte film, and negative electrode film can be cut according to needs, and the preparation of the solid-state battery can also adopt an in-series type.

[0052] The solid-state battery prepared by the present invention can also be applied to 3C fields such as mobile phones, laptops, and tablet computers.

[0053] Comparative Example 1

[0054] According to the mass ratio, mix 80% of Li 1.75 Ti2(Mo 0.25 P0.75 S 3.8 Se 0.2 )3 and 20% polyvinylidene fluoride (PVDF) are used to form a composite positive electrode, 80% LiWS2 and 20% PVDF are used to form a composite solid electrolyte, and 80% C3N3 and 20% PVDF are used to form a composite negative electrode. They are hot-pressed at 100 °C for 60 min to prepare a solid-state battery. The prepared solid-state battery is subjected to a discharge cycle performance test, and the cycle life under 3C conditions is less than 500 times.

[0055] Comparative Example 2

[0056] According to the mass ratio, 80% Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and 20% polyethylene oxide (PEO) are used to form a composite positive electrode, 80% LiWS2 and 20% PEO are used to form a composite solid electrolyte, and 80% C3N3 and 20% PEO are used to form a composite negative electrode. They are hot-pressed at 100 °C for 60 min to prepare a solid-state battery. The prepared solid-state battery is subjected to a discharge cycle performance test, and the cycle life under 3C conditions is less than 500 times.

[0057] The solid-state battery of the present invention has good cycle performance and rate performance, simple preparation process, low synthesis temperature, a wide electrochemical window, and good electrochemical stability, and can be applied to large-scale production.

[0058] The embodiments disclosed in the present invention are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not depart from the spirit of the present invention, they are within the protection scope of the present invention.

Claims

1. A solid-state battery, characterized in that: It includes a positive electrode, a negative electrode and a solid electrolyte layer, and the solid-state battery is prepared by a hot pressing and melting method; wherein, the positive electrode is a composite positive electrode film composed of an active material Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and a binder, the negative electrode is a composite negative electrode film composed of a C3N3 carbon nitride material and a binder, and the solid electrolyte layer is a composite solid electrolyte film composed of LiWS2 and a binder; the binder is lithium thioacetate or thioacetic acid.

2. The solid-state battery according to claim 1, wherein: The positive electrode of the solid-state battery is a composite positive electrode film composed of the active material Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 and lithium thioacetate, and the mass ratio of lithium thioacetate in the composite positive electrode film is 1 to 50%, and the thickness of the composite positive electrode film is 10 μm to 10 cm.

3. The solid-state battery according to claim 1, wherein: The negative electrode of the solid-state battery is a composite negative electrode film composed of active material C3N3 and lipoic acid. The mass ratio of lipoic acid in the composite negative electrode film is 1-50%, and the thickness of the composite negative electrode film is 10 μm to 10 cm.

4. The solid-state battery according to claim 3, wherein: The C3N3 carbon nitride material has a specific capacity of 2800 mAh / g.

5. The solid-state battery according to claim 1, characterized in that: The solid electrolyte layer of the solid-state battery is a composite solid electrolyte film composed of LiWS2 and lithium lipoate. The mass ratio of lithium lipoate in the composite solid electrolyte film is 1-50%, and the thickness of the composite solid electrolyte film is 10 μm to 10 cm.

6. A method for preparing a solid-state battery as claimed in claim 1, characterized in that, It includes the following steps: (1) Mix Li 1.75 Ti2(Mo 0.25 P 0.75 S 3.8 Se 0.2 )3 with a binder, and then obtain a composite cathode film after high-energy ball milling and lamination; (2) After mixing LiWS2 and a binder, subject them to high-energy ball milling and then press them to obtain a composite solid electrolyte film; (3) Mix C3N3 and a binder, subject them to high-energy ball milling and then press them to obtain a composite negative electrode film; (4) Stack the composite positive electrode film, composite solid electrolyte film, and composite negative electrode film of the same size after cutting in order from top to bottom, and obtain a solid-state battery monomer through hot pressing and melting.

7. The manufacturing method of the solid-state battery according to claim 6, wherein: The ball milling conditions in step (1), step (2), and step (3) are the same. The rotation speed of ball milling is 100-500 rpm, and the ball milling time is 1-12 h.

8. The method for preparing a solid-state battery according to claim 6, wherein: In step (4), the hot pressing and melting temperature is 50-200 °C, the hot pressing time is 10-120 min, and the hot pressing pressure is 1-100 MPa.

9. Application of a solid-state battery as described in claim 1 in a new energy vehicle.