All-solid-state lithium ion battery and preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and provides an all-solid-state lithium ion battery and a preparation method thereof. The preparation method comprises the following steps: activating a positive electrode active material and a negative electrode active material; after the activation treatment is finished, immersing the positive electrode active material and the negative electrode active material into a conductive mixture solution for coating treatment; after the coating treatment is finished, sequentially drying and curing the positive electrode active material and the negative electrode active material to respectively obtain a positive electrode material and a negative electrode material; mixing a lithium salt, an organic polymer, a ceramic filler and an organic solvent to obtain an electrolyte mixture, coating a positive electrode material and a negative electrode material with the electrolyte mixture, and performing hot pressing treatment to obtain a positive electrode and a negative electrode respectively; and assembling the positive electrode, the negative electrode and the solid electrolyte to obtain the all-solid-state lithium ion battery. The invention not only effectively solves the interface problem of the current all-solid-state battery, but also provides a feasible technical path for industrial application of the solid-state battery.

Description

Technical Field

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

[0002] With the continuous consumption of energy and the increasing shortage of resources, energy storage and conversion have become increasingly important. As one of the main energy storage and conversion devices at present, secondary batteries have attracted much attention and research. Among them, lithium-ion batteries exhibit advantages such as high working voltage, large energy density, long cycle life, low self-discharge, and no memory effect, and are now widely used in fields such as mobile phones, computers, drones, aerospace, and new energy vehicles.

[0003] Traditional lithium-ion batteries are difficult to use high-energy-density metallic lithium as the negative electrode material. During the charge and discharge process, lithium dendrites formed by factors such as uneven lithium deposition on the negative electrode side and rupture of the solid electrolyte interphase film will pierce the separator, causing battery short circuit and triggering safety problems. All-solid-state lithium-ion batteries are considered to be one of the key technologies for breakthroughs in battery technology. Their core advantage lies in higher safety and energy density. All-solid-state batteries use solid electrolytes to replace flammable liquid electrolytes, thereby reducing the risk of battery spontaneous combustion and explosion.

[0004] Compared with traditional batteries, most all-solid-state lithium-ion batteries exhibit lower capacity, power density, and poorer cycling performance in practical applications. These disadvantages are closely related to the interface problems between the electrode and the electrolyte. The interface problems of all-solid-state lithium batteries mainly include the following aspects: (1) High interface impedance: Solid electrolytes (such as oxides, sulfides) lack the fluidity of liquid electrolytes and are difficult to completely fill the pores and surface defects of electrode materials, resulting in a small actual contact area, increased interface impedance, and affecting the transport efficiency of lithium ions, thereby reducing the rate performance and cycle life of the battery. (2) Poor interface stability: There is a significant potential difference between sulfide electrolytes (such as LPS, LLS, etc.) and high-voltage cathode materials (such as LCO, NCM, LFP), which easily leads to interface element diffusion or side reactions, forming a mixed-conducting phase interface layer and further deteriorating the interface stability. (3) Lithium dendrite formation: Some solid electrolytes (such as garnet-type LLZO) have certain electronic conductivity. When the current density exceeds the critical value, electrons will migrate inside the electrolyte and combine with lithium ions to form metallic lithium, resulting in rapid dendrite growth and ultimately causing a short circuit. (4) Interface side reactions: Chemical reactions between electrode materials and electrolytes may lead to the loss of active sites, thereby affecting the battery capacity and life. For example, the electrochemical window of sulfide electrolytes (such as LPS, LGPS) is relatively narrow (usually <4.5V), and when matched with LiCoO2 (4.2V), high-nickel ternary materials (>4.3V), oxidation decomposition is likely to occur. Therefore, how to effectively solve the current interface problems of all-solid-state batteries has become an important research direction for those in this field. Summary of the Invention

[0005] In view of this, the present invention provides an all-solid-state lithium-ion battery and a preparation method thereof, aiming to solve the interface problems existing in current all-solid-state batteries.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method for an all-solid-state lithium-ion battery, comprising the following steps:

[0008] S1. Activate the positive electrode active material and the negative electrode active material;

[0009] S2. After the activation treatment, immerse the positive electrode active material and the negative electrode active material in a conductive mixture solution for coating treatment;

[0010] S3. After the coating treatment, sequentially dry and cure the positive electrode active material and the negative electrode active material to obtain a positive electrode material and a negative electrode material respectively;

[0011] S4. Mix a lithium salt, an organic polymer, a ceramic filler, and an organic solvent to obtain an electrolyte mixture, and coat the electrolyte mixture on the positive electrode material and the negative electrode material, followed by hot pressing to obtain the positive electrode and the negative electrode respectively;

[0012] S5. Assemble the positive electrode, the negative electrode, and the solid electrolyte to obtain a all-solid-state lithium-ion battery.

[0013] Further, in the step S1, the positive electrode active material includes a lithium metal oxide; the negative electrode active material includes graphite or a silicon-based material.

[0014] Further, in the step S1, the activation treatment temperature is 100 - 200 °C, and the activation treatment time is 5 - 30 min.

[0015] Further, in the step S2, the conductive mixture solution includes an electron conductive material, an ion conductive material, and a solvent; the electron conductive material is 5 - 30% of the mass of the solvent, and the ion conductive material is 70 - 90% of the mass of the solvent.

[0016] Further, in the step S2, the coating treatment uses an impregnation method, and the impregnation time is 10 - 120 min.

[0017] Further, in the step S3, the drying temperature is 60 - 120 °C, and the drying time is 1 - 24 h; the curing temperature is 150 - 300 °C, and the curing time is 1 - 12 h.

[0018] Further, in the step S4, the lithium salt includes lithium iodide, lithium sulfate, or lithium hexafluorophosphate; the organic polymer includes polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride; the ceramic filler includes titanium oxide, aluminum oxide, or silicon dioxide; the organic solvent includes acetonitrile, dimethyl sulfoxide, or N-methylpyrrolidone.

[0019] Further, in the step S4, the hot pressing treatment temperature is 120 - 180 °C, the hot pressing treatment time is 10 - 30 min, and the hot pressing treatment pressure is 5 - 15 MPa.

[0020] Further, in the step S4, an ion conductive mixture is coated on at least one of the positive electrode and the negative electrode, and the ion conductive mixture includes an ion conductive agent, an organic solvent, and an additive.

[0021] The present invention provides a all-solid-state lithium-ion battery prepared by the above preparation method of the all-solid-state lithium-ion battery.

[0022] As can be seen from the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The technical solution of the present invention can effectively solve the interface problems of current all-solid-state batteries. At the same time, without solvents, the positive and negative active materials will not be oxidized, and there will be no problems such as cavity contact failure and local lithium precipitation as in the case of lithium metal anodes. Moreover, the energy density of the battery is doubled or even several times that of existing lithium batteries, and the cycling performance is also significantly better than that of existing lithium batteries. Description of the Drawings

[0024] Figure 1 Comparison chart of the mass energy density of all-solid-state lithium-ion batteries prepared in Examples 1 to 3;

[0025] Figure 2 Electrochemical cycling performance chart of the all-solid-state lithium-ion battery prepared in Example 1;

[0026] Figure 3 Elemental analysis data chart of the positive electrode material obtained in Example 1. Detailed Embodiments

[0027] The present invention provides a method for preparing an all-solid-state lithium-ion battery, comprising the following steps:

[0028] S1. Activate the positive electrode active material and the negative electrode active material;

[0029] S2. After the activation treatment, immerse the positive electrode active material and the negative electrode active material in a conductive mixture solution for coating treatment;

[0030] S3. After the coating treatment, sequentially dry and cure the positive electrode active material and the negative electrode active material to obtain the positive electrode material and the negative electrode material respectively;

[0031] S4. Mix a lithium salt, an organic polymer, a ceramic filler and an organic solvent to obtain an electrolyte mixture, and coat the electrolyte mixture on the positive electrode material and the negative electrode material for hot pressing treatment to obtain the positive electrode and the negative electrode respectively;

[0032] S5. Assemble the positive electrode, the negative electrode and the solid electrolyte to obtain the all-solid-state lithium-ion battery.

[0033] In the present invention, in the step S1, the positive electrode active material includes a lithium metal oxide, and the lithium metal oxide is preferably lithium cobaltate, lithium nickelate or lithium manganate; the negative electrode active material includes graphite or a silicon-based material, and the silicon-based material is preferably pure silicon, a silicon-aluminum alloy or a silicon-magnesium alloy.

[0034] In the present invention, in the step S1, the temperature of the activation treatment is 100 - 200 °C, preferably 120 - 180 °C, and more preferably 140 - 160 °C; the time of the activation treatment is 5 - 30 min, preferably 10 - 25 min, and more preferably 15 - 20 min.

[0035] In the present invention, in the step S2, the conductive mixture solution includes an electron conductive material, an ion conductive material, and a solvent. The electron conductive material is preferably carbon nanotubes or graphene, and the ion conductive material is preferably Li3PS4, Li7P3S 11 or Na3PS4, and the solvent is preferably water or ethanol; the electron conductive material is 5-30% by mass of the solvent, preferably 10-25%, and more preferably 15-20%; the ion conductive material is 70-90% by mass of the solvent, preferably 75-85%, and more preferably 80%.

[0036] In the present invention, in the step S2, the coating treatment uses an impregnation method, and the impregnation time is 10-120 min, preferably 30-100 min, and more preferably 40-80 min; the coating thickness is preferably 5-500 nm, and more preferably 100-300 nm.

[0037] In the present invention, in the step S3, the drying temperature is 60-120 °C, preferably 80-100 °C, and more preferably 90 °C; the drying time is 1-24 h, preferably 5-20 h, and more preferably 10-15 h; the curing temperature is 150-300 °C, preferably 180-260 °C, and more preferably 200-240 °C; the curing time is 1-12 h, preferably 3-10 h, and more preferably 5-8 h.

[0038] In the present invention, in the step S4, the lithium salt includes lithium iodide, lithium sulfate, or lithium hexafluorophosphate; the organic polymer includes polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride; the ceramic filler includes titanium oxide, aluminum oxide, or silicon dioxide; the organic solvent includes acetonitrile, dimethyl sulfoxide, or N-methylpyrrolidone; the mass ratio of the lithium salt, organic polymer, ceramic filler, and organic solvent is preferably 5-15:20-40:10-30:30-50, and more preferably 10:30:20:40.

[0039] In the present invention, in the step S4, the hot pressing treatment temperature is 120-180 °C, preferably 130-160 °C, and more preferably 140-150 °C; the hot pressing treatment time is 10-30 min, preferably 15-25 min, and more preferably 20 min; the hot pressing treatment pressure is 5-15 MPa, preferably 10 MPa.

[0040] In the present invention, in the step S4, the electrolyte mixture can fill the pores inside the electrode to form a diffusion layer. The electrolyte mixture inside the positive and negative electrodes has electron conductivity and ion conductivity. This electrolyte mixture can form effective contact with the conductive mixture coated on the surface of the active material and can form an effective diffusion layer.

[0041] In the present invention, in step S4, an ion-conductive mixture is coated on at least one of the positive electrode and the negative electrode. The ion-conductive mixture includes an ion-conductive agent, an organic solvent, and an additive; the ion-conductive agent is preferably LiPF6 or NaF, the organic solvent is preferably ethylene carbonate, dimethyl carbonate, or diethyl carbonate, and the additive is preferably vinyl carbonate or vinylene sulfite; the mass ratio of the ion-conductive agent, the organic solvent, and the additive is preferably 5-20:60-90:2-10, more preferably 10:70:5; this ion-conductive mixture can form good ion conductivity with the electrolyte mixture.

[0042] In the present invention, in step S5, the solid electrolyte is preferably LiLa3Zr2O 12 、Li 10 GeP2S 12 、Li6PS5Cl or polyethylene oxide.

[0043] The present invention provides a all-solid-state lithium-ion battery prepared by the preparation method of the above all-solid-state lithium-ion battery.

[0044] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0045] Example 1

[0046] Take lithium cobaltate as the positive electrode active material and graphite as the negative electrode active material. Activate the positive and negative electrode active materials at 150°C for 20 min. Disperse graphene (20%) and Li3PS4 (80%) in ethanol to form a uniform conductive mixture solution, and then immerse the activated positive and negative electrode active materials in the conductive mixture solution for 60 min to uniformly coat a layer of conductive mixture with a thickness of 200 nm on their surfaces. Dry the coated materials at 100°C for 10 h, and then cure them at 200°C for 8 h to obtain the positive electrode material and the negative electrode material.

[0047] Take LiPF6, polyvinylidene fluoride, Al2O3, and N-methylpyrrolidone with a mass ratio of 10:30:20:40, and mix them by ultrasonic dispersion method to ensure uniform dispersion of each component and form a stable electrolyte mixture. Uniformly coat the electrolyte mixture on the surfaces of the positive electrode material and the negative electrode material with a coating thickness of 100 μm, and then perform hot pressing treatment at 150°C and 10 MPa for 20 min to closely combine the electrolyte mixture with the positive electrode material and the negative electrode material to form a stable electrode structure.

[0048] Take LiPF6, ethylene carbonate, and vinyl carbonate with a mass ratio of 10:70:5 and place them in a mixing container. Stir at a speed of 200 rpm for 60 min at room temperature to ensure that all components are fully and evenly mixed. After mixing, let the mixture stand for 24 h to remove bubbles and impurities, ensuring the purity and stability of the ion-conductive mixture. Coat the ion-conductive mixture on the positive and negative electrodes with a coating thickness of 100 μm, using LiLa3Zr2O 12 as the solid electrolyte for assembling a all-solid-state lithium-ion battery.

[0049] Example 2

[0050] Take lithium nickelate as the positive electrode active material and graphite as the negative electrode active material. Activate the positive and negative electrode active materials at 180 °C for 10 min. Disperse graphene (25%) and Li7P3S 11 (75%) in ethanol to form a uniform conductive mixture solution. Then immerse the activated positive and negative electrode active materials in the conductive mixture solution for 60 min to uniformly coat their surfaces with a conductive mixture layer with a thickness of 300 nm. Dry the coated materials at 100 °C for 10 h, and then cure them at 250 °C for 6 h to obtain the positive electrode material and the negative electrode material.

[0051] Take LiI, polyethylene oxide, TiO2, and acetonitrile with a mass ratio of 5:25:30:40, and mix them using ultrasonic dispersion to ensure that all components are evenly dispersed, forming a stable electrolyte mixture. Uniformly coat the electrolyte mixture on the surfaces of the positive electrode material and the negative electrode material with a coating thickness of 100 μm, and then perform hot pressing treatment at 160 °C and 15 MPa for 15 min to tightly bond the electrolyte mixture with the positive electrode material and the negative electrode material, forming a stable electrode structure.

[0052] Take LiPF6, dimethyl carbonate, and vinyl carbonate with a mass ratio of 15:80:4 and place them in a mixing container. Stir at a speed of 200 rpm for 60 min at room temperature to ensure that all components are fully and evenly mixed. After mixing, let the mixture stand for 24 h to remove bubbles and impurities, ensuring the purity and stability of the ion-conductive mixture. Coat the ion-conductive mixture on the positive and negative electrodes with a coating thickness of 100 μm, using Li 10 GeP2S 12 as the solid electrolyte for assembling a all-solid-state lithium-ion battery.

[0053] Example 3

[0054] Lithium manganate is used as the positive electrode active material, and pure silicon is used as the negative electrode active material. The positive and negative electrode active materials are activated at 120 °C for 30 min. Carbon nanotubes (20%) and Na3PS4 (80%) are dispersed in ethanol to form a uniform conductive mixture solution. Then, the activated positive and negative electrode active materials are impregnated in the conductive mixture solution for 60 min to uniformly coat a layer of conductive mixture with a thickness of 150 nm on their surfaces. The coated materials are dried at 100 °C for 10 h and then cured at 200 °C for 8 h to obtain the positive electrode material and the negative electrode material.

[0055] Take Li2S, polyacrylonitrile, SiO2, and dimethyl sulfoxide with a mass ratio of 10:40:10:40, and mix them using the ultrasonic dispersion method to ensure that each component is uniformly dispersed to form a stable electrolyte mixture. The electrolyte mixture is uniformly coated on the surfaces of the positive electrode material and the negative electrode material with a coating thickness of 100 μm, and then heat-pressed at 120 °C and 15 MPa for 20 min to tightly combine the electrolyte mixture with the positive electrode material and the negative electrode material to form a stable electrode structure.

[0056] Take NaF, diethyl carbonate, and vinylene sulfite with a mass ratio of 16:75:9 and place them in a mixing container. Stir at a speed of 200 rpm at room temperature for 60 min to ensure that each component is fully and uniformly mixed. After mixing, let the mixture stand for 24 h to remove bubbles and impurities to ensure the purity and stability of the ionic conductive mixture. The ionic conductive mixture is coated on the positive and negative electrodes with a coating thickness of 100 μm, and a solid-state lithium-ion battery is assembled using polyethylene oxide as the solid electrolyte.

[0057] Using the direct measurement method, the mass energy density of the all-solid-state lithium-ion batteries prepared in Examples 1 to 3 was tested, and the test results are shown in Figure 1 . The energy density of existing ternary lithium batteries (NCM / NCA) is generally 200 - 300 Wh / kg, the energy density of lithium iron phosphate batteries (LFP) is generally 160 - 190 Wh / kg, and the energy density of lithium cobalt oxide batteries (LCO) is generally 200 - 250 Wh / kg. Therefore, the energy density of the all-solid-state lithium-ion batteries prepared in the present invention is doubled or even several times higher than that of existing lithium batteries.

[0058] Select the all-solid-state lithium-ion battery prepared in Example 1, operate it at a current of 0.1 mA / cm for three cycles, and then increase the current to 0.3 mA / cm to perform a long-cycle charge-discharge curve test to obtain the test result graph of the electrochemical cycle performance of the all-solid-state lithium-ion battery ( Figure 2 ).

[0059] Figure 3 It is the elemental analysis data graph of the positive electrode material obtained in Example 1. From Figure 3It can be seen that sulfur (S) and carbon (C) are dominant, accounting for 34% and 2% respectively. Sulfur comes from the solid electrolyte Li3PS4 (containing 4 S atoms), and its high proportion confirms the main role of the electrolyte. Carbon comes from graphene (20% mass ratio), and its high conductivity provides an electron transport channel for the coating layer. The proportions of lithium (25%) and phosphorus (9%) are consistent with the stoichiometric ratio of Li3PS4 (Li3PS4 → 3Li: 1P: 4S), indicating that the structure of the electrolyte remains stable after mixing. No significant content of oxygen (O) and hydrogen (H) was detected, indicating that the ethanol solvent has completely evaporated during the drying process and has not remained in the coating layer.

[0060] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an all-solid-state lithium-ion battery, characterized in that: The following steps are involved: S1, activating the positive electrode active material and the negative electrode active material; S2, after the activation treatment is completed, immersing the positive electrode active material and the negative electrode active material in a conductive mixture solution for coating treatment; S3, after the coating treatment is completed, the positive electrode active material and the negative electrode active material are dried and cured in sequence to obtain a positive electrode material and a negative electrode material respectively; S4, mixing a lithium salt, an organic polymer, a ceramic filler and an organic solvent to obtain an electrolyte mixture, coating the electrolyte mixture on a positive electrode material and a negative electrode material, and performing a hot pressing treatment to obtain a positive electrode and a negative electrode respectively; S5. Assemble the positive electrode, the negative electrode and the solid electrolyte to obtain an all-solid-state lithium-ion battery.

2. The method for preparing an all-solid-state lithium-ion battery according to claim 1, characterized in that: In the step S1, the positive electrode active material includes lithium metal oxide; the negative electrode active material includes graphite or silicon-based material.

3. The method for preparing an all-solid-state lithium-ion battery according to claim 2, characterized in that: In the step S1, the temperature of the activation treatment is 100-200° C., and the time of the activation treatment is 5-30 minutes.

4. The method for preparing an all-solid-state lithium-ion battery according to claim 3, characterized in that: In step S2, the conductive mixture solution includes electronic conductive material, ion conductive material and solvent; the electronic conductive material accounts for 5-30% of the mass of the solvent, and the ion conductive material accounts for 70-90% of the mass of the solvent.

5. The method for preparing an all-solid-state lithium-ion battery according to claim 1 or 3, characterized in that: In the step S2, the coating treatment is carried out by immersion, and the immersion time is 10 to 120 minutes.

6. The method for preparing an all-solid-state lithium-ion battery according to claim 5, characterized in that: In step S3, the drying temperature is 60-120° C., and the drying time is 1-24 hours; the curing temperature is 150-300° C., and the curing time is 1-12 hours.

7. The method for preparing an all-solid-state lithium-ion battery according to claim 3 or 6, characterized in that: In step S4, the lithium salt includes lithium iodide, lithium sulfate or lithium hexafluorophosphate; the organic polymer includes polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride; the ceramic filler includes titanium oxide, aluminum oxide or silicon dioxide; and the organic solvent includes acetonitrile, dimethyl sulfoxide or N-methylpyrrolidone.

8. The method for preparing an all-solid-state lithium-ion battery according to claim 7, characterized in that: In step S4, the temperature of the hot pressing treatment is 120-180° C., the time of the hot pressing treatment is 10-30 min, and the pressure of the hot pressing treatment is 5-15 MPa.

9. The method for preparing an all-solid-state lithium-ion battery according to claim 8, characterized in that: In the step S4, an ion conductive mixture is coated on at least one of the positive electrode and the negative electrode, wherein the ion conductive mixture includes an ion conductive agent, an organic solvent and an additive.

10. An all-solid-state lithium-ion battery prepared by the method for preparing an all-solid-state lithium-ion battery according to any one of claims 1 to 9.

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