An all-solid-state lithium-ion battery and its preparation method

Abstract

This invention belongs to the field of lithium-ion battery technology, and provides an all-solid-state lithium-ion battery and its preparation method. The preparation method includes the following steps: activating positive and negative electrode active materials; after activation, immersing the positive and negative electrode active materials in a conductive mixture solution for coating; after coating, sequentially drying and curing the positive and negative electrode active materials to obtain positive and negative electrode materials respectively; mixing lithium salt, organic polymer, ceramic filler, and organic solvent to obtain an electrolyte mixture; coating the electrolyte mixture onto the positive and negative electrode materials and hot-pressing them to obtain positive and negative electrodes respectively; assembling the positive electrode, negative electrode, and solid electrolyte to obtain the all-solid-state lithium-ion battery. This invention not only effectively solves the interface problem of current all-solid-state batteries, but also provides a feasible technical path for the industrial application of solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to an all-solid-state lithium-ion battery and its preparation method. Background Technology

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

[0003] Traditional lithium-ion batteries struggle to utilize high-energy-density metallic lithium as the negative electrode material. During charging and discharging, uneven lithium deposition on the negative electrode side, along with the formation of lithium dendrites due to factors such as the rupture of the solid electrolyte interface film, can puncture the separator, causing a short circuit and leading to safety issues. All-solid-state lithium-ion batteries are considered one of the key technologies for breakthroughs in battery technology. Their core advantages lie in higher safety and energy density. All-solid-state batteries use a solid electrolyte instead of a flammable liquid electrolyte, thereby reducing the risk of spontaneous combustion and explosion.

[0004] Compared with traditional batteries, most all-solid-state lithium-ion batteries exhibit lower capacity, power density, and worse cycle performance in practical applications. These disadvantages are closely related to the interface problems of the electrode / electrolyte. The interface problems of all-solid-state lithium batteries mainly include the following aspects: (1) High interface impedance: Solid electrolytes (such as oxides and sulfides) lack the fluidity of liquid electrolytes, making it difficult to completely fill the pores and surface defects of electrode materials, resulting in a small actual contact area, which leads to an increase in interface impedance, affecting the lithium-ion transport efficiency, 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 the diffusion of interface elements or side reactions, forming a mixed conductive phase interface layer, further deteriorating the interface stability. (3) Lithium dendrite formation: Some solid electrolytes (such as garnet-type LLZO) have a 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, leading to rapid dendrite growth and eventually causing a short circuit. (4) Interfacial side reactions: Chemical reactions between electrode materials and electrolytes may lead to the loss of active sites, thereby affecting battery capacity and lifespan. For example, sulfide electrolytes (such as LPS and LGPS) have a narrow electrochemical window (typically <4.5V), and are prone to oxidative decomposition when matched with LiCoO2 (4.2V) or high-nickel ternary materials (>4.3V). Therefore, how to effectively solve the interfacial problems of current all-solid-state batteries has become an important research direction for researchers in this field. Summary of the Invention

[0005] In view of this, the present invention provides an all-solid-state lithium-ion battery and its preparation method, the purpose of which is to solve the interface problem existing in current all-solid-state batteries.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing 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 is completed, the positive electrode active material and the negative electrode active material are immersed in a conductive mixture solution for coating treatment.

[0010] S3. After the coating process is completed, the positive electrode active material and the negative electrode active material are dried and cured in sequence to obtain the positive electrode material and the negative electrode material respectively.

[0011] S4. Lithium salt, organic polymer, ceramic filler and organic solvent are mixed to obtain an electrolyte mixture. The electrolyte mixture is coated on positive electrode material and negative electrode material and then hot-pressed to obtain positive electrode and negative electrode respectively.

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

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

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

[0015] Furthermore, in step S2, the conductive mixture solution includes an electronically conductive material, an ionicly conductive material, and a solvent; the electronically conductive material accounts for 5-30% of the solvent mass, and the ionicly conductive material accounts for 70-90% of the solvent mass.

[0016] Furthermore, in step S2, the coating treatment uses an immersion method, and the immersion time is 10 to 120 minutes.

[0017] Furthermore, in 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] Furthermore, 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 dioxide, alumina, or silicon dioxide; and the organic solvent includes acetonitrile, dimethyl sulfoxide, or N-methylpyrrolidone.

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

[0020] Furthermore, in step S4, an ion-conducting mixture is coated on at least one of the positive and negative electrodes, the ion-conducting mixture comprising an ion-conducting agent, an organic solvent, and additives.

[0021] This invention provides an all-solid-state lithium-ion battery prepared by the above-described method for preparing all-solid-state lithium-ion batteries.

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

[0023] The technical solution of this invention can effectively solve the interface problem of current all-solid-state batteries. At the same time, without solvents, the positive and negative electrode active materials will not oxidize, and unlike lithium metal anodes, they will not produce cavities, poor contact, or local lithium plating. Moreover, the battery energy density is one to several times higher than that of existing lithium batteries, and the cycle performance is also significantly better than that of existing lithium batteries. Attached Figure Description

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

[0025] Figure 2 The graph shows the electrochemical cycling performance of the all-solid-state lithium-ion battery prepared in Example 1.

[0026] Figure 3 This is a graph showing the elemental analysis data of the cathode material obtained in Example 1. Detailed Implementation

[0027] This 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 is completed, the positive electrode active material and the negative electrode active material are immersed in a conductive mixture solution for coating treatment.

[0030] S3. After the coating process is completed, the positive electrode active material and the negative electrode active material are dried and cured in sequence to obtain the positive electrode material and the negative electrode material respectively.

[0031] S4. Lithium salt, organic polymer, ceramic filler and organic solvent are mixed to obtain an electrolyte mixture. The electrolyte mixture is coated on positive electrode material and negative electrode material and then hot-pressed to obtain positive electrode and negative electrode respectively.

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

[0033] In this invention, in step S1, the positive electrode active material includes lithium metal oxide, which is preferably lithium cobalt oxide, lithium nickel oxide or lithium manganese oxide; the negative electrode active material includes graphite or silicon-based material, which is preferably pure silicon, silicon-aluminum alloy or silicon-magnesium alloy.

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

[0035] In this invention, in step S2, the conductive mixture solution includes an electronically conductive material, an ionicly conductive material, and a solvent. The electronically conductive material is preferably carbon nanotubes or graphene, and the ionicly conductive material is preferably Li3PS4 or Li7P3S. 11 Alternatively, Na3PS4 may be used, wherein the solvent is preferably water or ethanol; the electronically conductive material comprises 5-30% of the solvent mass, preferably 10-25%, more preferably 15-20%; and the ionically conductive material comprises 70-90% of the solvent mass, preferably 75-85%, more preferably 80%.

[0036] In this invention, in step S2, the coating treatment uses an immersion method, and the immersion 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 this invention, in step S3, the drying temperature is 60-120°C, preferably 80-100°C, and more preferably 90°C; the drying time is 1-24 hours, preferably 5-20 hours, and more preferably 10-15 hours; the curing temperature is 150-300°C, preferably 180-260°C, and more preferably 200-240°C; and the curing time is 1-12 hours, preferably 3-10 hours, and more preferably 5-8 hours.

[0038] In this invention, 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 dioxide, alumina, or silicon dioxide; and the organic solvent includes acetonitrile, dimethyl sulfoxide, or N-methylpyrrolidone. The preferred mass ratio of the lithium salt, organic polymer, ceramic filler, and organic solvent is 5–15:20–40:10–30:30–50, and more preferably 10:30:20:40.

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

[0040] In this invention, in 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 electronic conductivity and ionic conductivity. The 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 this invention, in step S4, an ion-conducting mixture is coated onto at least one of the positive and negative electrodes. The ion-conducting mixture comprises an ion-conducting agent, an organic solvent, and an additive. The ion-conducting 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 vinyl sulfite. The mass ratio of the ion-conducting agent, organic solvent, and additive is preferably 5–20:60–90:2–10, more preferably 10:70:5. This ion-conducting mixture can form good ion conductivity with the electrolyte mixture.

[0042] In this invention, in step S5, the solid electrolyte is preferably LiLa3Zr2O. 12 Li 10 GeP2S 12 Any one of Li6PS5Cl and polyethylene oxide.

[0043] This invention provides an all-solid-state lithium-ion battery prepared by the above-described method for preparing all-solid-state lithium-ion batteries.

[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 scope of protection of the present invention.

[0045] Example 1

[0046] Lithium cobalt oxide was used as the positive electrode active material, and graphite as the negative electrode active material. The positive and negative electrode active materials were activated at 150℃ for 20 min. Graphene (20%) and Li3PS4 (80%) were dispersed in ethanol to form a homogeneous conductive mixture solution. The activated positive and negative electrode active materials were then immersed in the conductive mixture solution for 60 min to uniformly coat their surfaces with a 200 nm thick conductive mixture layer. The coated materials were dried at 100℃ for 10 h, and then cured at 200℃ for 8 h to obtain the positive and negative electrode materials.

[0047] LiPF6, polyvinylidene fluoride, Al2O3, and N-methylpyrrolidone were mixed in a mass ratio of 10:30:20:40 using ultrasonic dispersion to ensure uniform dispersion of all components and form a stable electrolyte mixture. The electrolyte mixture was then uniformly coated onto the surfaces of both the positive and negative electrode materials to a thickness of 100 μm. Finally, the mixture was hot-pressed at 150 °C and 10 MPa for 20 min to ensure tight bonding between the electrolyte mixture and the positive and negative electrode materials, forming a stable electrode structure.

[0048] LiPF6, ethylene carbonate, and vinyl carbonate in a mass ratio of 10:70:5 were placed in a mixing container and stirred at 200 rpm for 60 min at room temperature to ensure thorough and uniform mixing. After mixing, the mixture was allowed to stand for 24 h to remove air bubbles and impurities, ensuring the purity and stability of the ion-conducting mixture. The ion-conducting mixture was then coated onto the positive and negative electrodes to a thickness of 100 μm, and then coated with LiLa3Zr2O4. 12 Assemble all-solid-state lithium-ion batteries using solid-state electrolytes.

[0049] Example 2

[0050] Lithium nickelate was used as the positive electrode active material, and graphite as the negative electrode active material. The positive and negative electrode active materials were activated at 180℃ for 10 min. Graphene (25%) and Li7P3S were then used... 11 (75%) is dispersed in ethanol to form a uniform conductive mixture solution. Then, the activated positive and negative electrode active materials are immersed in the conductive mixture solution for 60 min to uniformly coat the surface with a conductive mixture with a thickness of 300 nm. The coated material is dried at 100 °C for 10 h and then cured at 250 °C for 6 h to obtain the positive electrode material and the negative electrode material.

[0051] LiI, polyethylene oxide, TiO2, and acetonitrile were mixed in a mass ratio of 5:25:30:40 using ultrasonic dispersion to ensure uniform dispersion of all components and form a stable electrolyte mixture. The electrolyte mixture was then uniformly coated onto the surfaces of both the positive and negative electrode materials to a thickness of 100 μm. Finally, the mixture was hot-pressed at 160 °C and 15 MPa for 15 min to ensure tight bonding between the electrolyte mixture and the positive and negative electrode materials, forming a stable electrode structure.

[0052] LiPF6, dimethyl carbonate, and vinyl carbonate in a mass ratio of 15:80:4 were placed in a mixing container and stirred at 200 rpm for 60 min at room temperature to ensure thorough and uniform mixing. After mixing, the mixture was allowed to stand for 24 h to remove air bubbles and impurities, ensuring the purity and stability of the ion-conducting mixture. The ion-conducting mixture was then coated onto the positive and negative electrodes to a thickness of 100 μm, using Li... 10 GeP2S 12 Assemble all-solid-state lithium-ion batteries using solid-state electrolytes.

[0053] Example 3

[0054] Lithium manganese oxide was used as the positive electrode active material, and pure silicon was used as the negative electrode active material. The positive and negative electrode active materials were activated at 120℃ for 30 min. Carbon nanotubes (20%) and Na3PS4 (80%) were dispersed in ethanol to form a homogeneous conductive mixture solution. The activated positive and negative electrode active materials were then immersed in the conductive mixture solution for 60 min to uniformly coat their surfaces with a conductive mixture layer of 150 nm thickness. The coated materials were dried at 100℃ for 10 h, and then cured at 200℃ for 8 h to obtain the positive and negative electrode materials.

[0055] Li₂S, polyacrylonitrile, SiO₂, and dimethyl sulfoxide were mixed in a mass ratio of 10:40:10:40 using ultrasonic dispersion to ensure uniform dispersion of all components and form a stable electrolyte mixture. The electrolyte mixture was then uniformly coated onto the surfaces of both the positive and negative electrode materials to a thickness of 100 μm. Finally, the mixture was hot-pressed at 120 °C and 15 MPa for 20 min to ensure tight bonding between the electrolyte mixture and the positive and negative electrode materials, forming a stable electrode structure.

[0056] NaF, diethyl carbonate, and vinyl sulfite in a mass ratio of 16:75:9 were placed in a mixing container and stirred at 200 rpm for 60 minutes at room temperature to ensure thorough and uniform mixing of all components. After mixing, the mixture was allowed to stand for 24 hours to remove air bubbles and impurities, ensuring the purity and stability of the ion-conducting mixture. The ion-conducting mixture was then coated onto the positive and negative electrodes to a thickness of 100 μm, and an all-solid-state lithium-ion battery was assembled using polyethylene oxide as the solid electrolyte.

[0057] The mass energy density of the all-solid-state lithium-ion batteries prepared in Examples 1-3 was measured using a direct measurement method. The test results are shown in [Figure number missing]. Figure 1 Existing ternary lithium batteries (NCM / NCA) typically have an energy density of 200–300 Wh / kg, lithium iron phosphate batteries (LFP) typically have an energy density of 160–190 Wh / kg, and lithium cobalt oxide batteries (LCO) typically have an energy density of 200–250 Wh / kg. Therefore, the all-solid-state lithium-ion battery prepared in this invention has an energy density that is one to several times higher than that of existing lithium batteries.

[0058] The all-solid-state lithium-ion battery prepared in Example 1 was selected and operated for three cycles at a current of 0.1 mA / cm. Then, the current was increased to 0.3 mA / cm for long-cycle charge-discharge curve testing. The electrochemical cycle performance test results of the all-solid-state lithium-ion battery are shown in the figure. Figure 2 ).

[0059] Figure 3 This is an elemental analysis data graph of the cathode material obtained in Example 1, from... Figure 3Sulfur (S) and carbon (C) are predominant, accounting for 34% and 2% respectively. The high proportion of sulfur, derived from the solid electrolyte Li3PS4 (containing 4 S atoms), confirms the dominant role of the electrolyte. Carbon, derived from graphene (20% by mass), provides electron transport channels for the coating layer due to its high conductivity. The ratio of lithium (25%) and phosphorus (9%) is consistent with the stoichiometry of Li3PS4 (Li3PS4→3Li:1P:4S), indicating that the electrolyte structure remains stable after mixing. No significant amounts of oxygen (O) and hydrogen (H) were detected, indicating that the ethanol solvent completely evaporated during drying and did not remain in the coating layer.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an all-solid-state lithium-ion battery, characterized in that, Includes the following steps: S1. Activate the positive electrode active material and the negative electrode active material; S2. After the activation treatment is completed, the positive electrode active material and the negative electrode active material are immersed in a conductive mixture solution for coating treatment. S3. After the coating process is completed, the positive electrode active material and the negative electrode active material are dried and cured in sequence to obtain the positive electrode material and the negative electrode material respectively. S4. Lithium salt, organic polymer, ceramic filler and organic solvent are mixed to obtain an electrolyte mixture. The electrolyte mixture is coated on positive electrode material and negative electrode material and then hot-pressed to obtain positive electrode and negative electrode respectively. S5. Assemble the positive electrode, negative electrode and solid electrolyte to obtain an all-solid-state lithium-ion battery. 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 dioxide, alumina, or silicon dioxide; and the organic solvent includes acetonitrile, dimethyl sulfoxide, or N-methylpyrrolidone. In step S4, the hot pressing temperature is 120–180°C, the hot pressing time is 10–30 min, and the hot pressing pressure is 5–15 MPa.

2. The method for preparing an all-solid-state lithium-ion battery according to claim 1, characterized in that, In 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 step S1, the activation temperature is 100–200°C and the activation time is 5–30 min.

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 an electronically conductive material, an ionicly conductive material, and a solvent; the electronically conductive material accounts for 5-30% of the solvent mass, and the ionicly conductive material accounts for 70-90% of the solvent mass.

5. The method for preparing an all-solid-state lithium-ion battery according to claim 1 or 3, characterized in that, In step S2, the coating process uses an immersion method, 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 h; the curing temperature is 150–300°C and the curing time is 1–12 h.

7. The method for preparing an all-solid-state lithium-ion battery according to claim 1, characterized in that, In step S4, an ion-conducting mixture is coated on at least one of the positive and negative electrodes, the ion-conducting mixture comprising an ion-conducting agent, an organic solvent, and additives.

8. An all-solid-state lithium-ion battery prepared by the method of any one of claims 1 to 7.

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