A sulfide solid electrolyte composite oxide positive electrode material and a preparation method and application thereof
By constructing a core-shell structure with a conductive oxide material layer between the oxide cathode particles and the sulfide-based solid electrolyte, the problem of oxidation decomposition when the layered oxide cathode material comes into contact with the sulfide-based solid electrolyte is solved, thereby improving the electrochemical performance and cycle stability of the all-solid-state battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF TECH
- Filing Date
- 2022-11-16
- Publication Date
- 2026-06-23
AI Technical Summary
In the prior art, when layered oxide cathode materials come into direct contact with sulfide-based solid electrolytes, lattice oxygen is released during charging and discharging, leading to the oxidative decomposition of the sulfide-based solid electrolyte and severely reducing the electrochemical performance of all-solid-state batteries.
The core-shell structured sulfide-based solid electrolyte composite oxide cathode material prevents lattice oxygen from reacting with the sulfide-based solid electrolyte by constructing a conductive oxide material layer as a barrier between the oxide cathode particles and the sulfide-based solid electrolyte. The conductive oxide material is selected as a good electronic conductor to form an electron transport channel and improve interface stability.
It effectively prevents the oxidative decomposition of lattice oxygen and sulfur-based solid electrolytes, improves the rate performance and cycle performance of lithium-ion batteries, enhances interfacial chemical stability, and reduces battery impedance.
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Figure CN116230860B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a sulfur-based solid electrolyte composite oxide cathode material, its preparation method, and its application, belonging to the field of lithium-ion battery technology. Background Technology
[0002] Lithium-ion batteries boast advantages such as high energy density, long cycle life, and environmental friendliness, leading to their widespread use in portable electronic products like mobile phones and laptops, as well as in new energy vehicles. High-energy-density batteries enable products to operate for longer periods, giving them a greater competitive edge in the market. However, the excessive pursuit of energy density has resulted in a series of safety incidents, posing a serious challenge to the safety of lithium-ion batteries.
[0003] Currently, all-solid-state batteries, which use solid-state electrolytes instead of organic liquid electrolytes, enable lithium-ion batteries to achieve both high capacity and high safety, and are considered the best method to address safety issues. In all-solid-state batteries, battery performance is primarily determined by the cathode material and the solid-state electrolyte. Among various cathode materials, LiNi0 offers high voltage and high capacity. x Co y Mn 1-x-y O2 (x>0.5, x+y<1) oxide cathode active materials have become a current research hotspot in this field. Among them, layered oxide cathode active materials have attracted more attention due to their better cycle stability and the ability to achieve high energy density by charging to high voltage. Among various solid electrolytes, sulfide-based solid electrolytes have become the preferred choice for matching various cathode materials due to their high ionic conductivity at room temperature, low cost, and stability against lithium metal.
[0004] Currently, oxide cathode materials are often mechanically mixed and pressed into shape when matched with sulfide-based solid electrolytes, as described in CN 113948764 A. However, it has been found that when layered oxide cathode materials come into direct contact with sulfide-based solid electrolytes, especially under high voltage, lattice oxygen in the layered oxide cathode material is released during battery charging and discharging, forming active oxygen and causing severe oxidative decomposition of the sulfide-based solid electrolyte. This significantly reduces the electrochemical performance of this series of solid-state batteries at high rates and high currents. Therefore, how to reduce or eliminate this oxidative decomposition reaction to extend the cycle life of solid-state electrolytes is one of the key scientific issues in the development of solid-state batteries. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of the prior art and provide a sulfur-based solid electrolyte composite oxide cathode material, its preparation method and application.
[0006] The technical solution adopted by this invention to solve its technical problem is:
[0007] One of the objectives of the present invention is to provide a chalcogenide solid electrolyte composite oxide cathode material. The cathode material includes oxide cathode particles, a first coating layer coated on the outer side of the oxide cathode particles, and a second coating layer coated on the outer side of the first coating layer. Among them, the oxide cathode particles are oxide cathode materials, the first coating layer is a conductive oxide material, and the second coating layer is a chalcogenide solid electrolyte material.
[0008] By adopting the above technical solution, the chalcogenide solid electrolyte composite oxide cathode material of the present invention has an overall core-shell structure, and a barrier composed of a conductive oxide material is constructed between the oxide cathode particles and the chalcogenide solid electrolyte material, which can effectively prevent lattice oxygen from reacting with the chalcogenide solid electrolyte after escaping from the oxide cathode particles, effectively avoid the oxidation decomposition of the chalcogenide solid electrolyte, and further enhance the stability of the interface structure. At the same time, selecting a conductive oxide material as the component of the barrier can serve as a good electronic conductor, forming a good electronic transport channel, which is beneficial to reducing the impedance of the lithium-ion battery and improving the rate performance of the lithium-ion battery. And the conductive oxide material and the material of the oxide cathode particles belong to the oxide system, having better grain boundary compatibility, which is more conducive to the transport of electrons and ions. The chalcogenide solid electrolyte composite oxide cathode material of the above technical solution of the present invention also has excellent interfacial chemical stability, which is beneficial to improving the cycle performance of the lithium-ion battery.
[0009] Preferably, the oxide cathode material includes one or more materials conforming to the characteristics of LiNi x Co y Mn 1-x-y O2 (0.5 < x < 1, x + y < 1). More preferably, the oxide cathode material includes LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiCoO2, etc. More preferably, the particle size of the oxide cathode material is 6 - 20 μm.
[0010] Preferably, the conductive oxide material in the first coating layer is a material with high electronic conductivity and capable of forming high-energy chemical bonds with oxygen elements. The high-energy chemical bond refers to a chemical bond whose bond energy is not lower than the bond energy of chemical bonds formed by non-metallic elements in sulfide electrolytes such as S, P, etc. More preferably, the conductive oxide material includes one or more of indium tin oxide (ITO, Sn / In = 1 / 9 - 1 / 6), indium oxide, and tin dioxide.
[0011] More preferably, the conductive oxide material is a nanoscale material, and even more preferably, the particle size of the conductive oxide material is 2-3 nm. By using nanoscale materials and combining them with the amount of conductive oxide material, an extremely thin conductive oxide material layer can be obtained, thereby preventing lattice oxygen precipitation without affecting the ionic conductivity between solid interfaces.
[0012] Preferably, the sulfide solid electrolyte material in the second coating layer includes materials conforming to xLi₂S-yP₂S₅ (x+y=100), β-Li₃PS₄, Li₆PS₅X (LPSX, X=Cl, Br or I), and Li 5.5 PS 4.5 Cl 1.5 Li 10±1 MP2S 12 (M = Ge, Si, Sn, Al or P) and one or more of their corresponding doped and modified materials. More preferably, the particle size of the sulfide-based solid electrolyte is 1-2 μm. By adopting the above technical solution, the lithium-ion conductivity in the composite cathode material can be further improved.
[0013] Preferably, the oxide cathode particles have a particle size of 6–20 μm, the first coating layer thickness is 5–10 nm, and the second coating layer thickness is 2–8 μm. More preferably, the sulfide-based solid electrolyte composite oxide cathode material has a particle size of 10–36 μm.
[0014] The second objective of this invention is to provide a method for preparing any of the aforementioned sulfide-based solid electrolyte composite oxide cathode materials, comprising the following steps:
[0015] S1. Conductive oxide material is pre-coated onto the surface of oxide cathode particles using a mechanical coating process to obtain a pre-coated material;
[0016] S2. The pre-coated material obtained in step S1 is sintered at low temperature to obtain composite positive electrode particles coated with conductive oxide;
[0017] Furthermore, the sintering temperature is 180–400℃, and the sintering time is 30–150 min;
[0018] Furthermore, the heating rate of the low-temperature sintering in step S2 is 1-5℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0019] S3. The sulfur-based solid electrolyte material is coated onto the surface of the composite cathode particles obtained in step S2 by a mechanical coating process to obtain a sulfur-based solid electrolyte composite oxide cathode material.
[0020] Preferably, the mechanical coating process in step S1 includes the following steps:
[0021] (S1.1) Weigh out the oxide cathode material and the conductive oxide material;
[0022] Furthermore, the mass of the oxide cathode material accounts for 97% to 99% of the total mass of the oxide cathode material and the conductive oxide material; the thickness of the first coating layer can be adjusted by adjusting the ratio of the two materials.
[0023] (S1.2) The mixture of S1.1 is pre-coated by low-speed ball milling;
[0024] Furthermore, the ball milling time is 1–3 hours, and the rotation speed is 100–300 rpm; at this speed, the mixture can be more uniform, achieving uniform coating.
[0025] Furthermore, the ball-to-material ratio is 10-20:1, and even further, the number of grinding balls with diameters of 20, 10, and 5 mm in a single grinding jar is in a ratio of 2:6:20. By adopting the above technical solution, the macroscopic structure of the oxide cathode particles can be further prevented from being damaged due to the ball milling process.
[0026] Preferably, the mechanical coating process in step S3 includes the following steps:
[0027] (S3.1) Weigh the composite cathode particles and sulfur-based solid electrolyte material obtained in step S2 under an environment where the moisture and oxygen content are both no higher than 0.5 ppm.
[0028] Furthermore, the mass of the composite cathode particles accounts for 85% to 95% of the total mass of the composite cathode particles and the sulfur-based solid electrolyte material; by adjusting the ratio between the substances, the thickness of the second coating layer can be adjusted.
[0029] (S3.2) Place the sample from S3.1 into a well-sealed ball mill jar and ball mill it at -0.05 to -0.1 MPa;
[0030] Furthermore, the ball milling time is 2-5 hours, and the ball milling speed is 100-300 rpm.
[0031] Furthermore, the ball-to-material ratio is 10:1 to 15:1, and even further, the number of grinding balls with diameters of 20, 10, and 5 mm in a single grinding jar is in a ratio of 2:6:20; thereby preventing the macroscopic structure of the composite cathode particles and sulfur-based solid electrolyte materials from being damaged by the ball milling process.
[0032] The third objective of this invention is to provide an application of any of the above-mentioned sulfide-based solid electrolyte composite oxide cathode materials or sulfide-based solid electrolyte composite oxide cathode materials prepared by any of the above-mentioned methods in lithium-ion batteries and their preparation.
[0033] Compared with the prior art, the beneficial effects of the sulfur-based solid electrolyte composite oxide cathode material provided by the present invention are:
[0034] (1) The present invention constructs a barrier composed of conductive oxide material between the oxide cathode particles and the sulfur-based solid electrolyte material, which effectively prevents lattice oxygen from reacting with the sulfur-based solid electrolyte after being released from the cathode material, thus avoiding the oxidative decomposition of the sulfur-based solid electrolyte.
[0035] (2) In this invention, the conductive oxide material acts as a good electronic conductor, forming a good electronic transport channel, which is beneficial to reducing the impedance of the lithium-ion battery and improving the rate performance of the lithium-ion battery.
[0036] (3) In this invention, the conductive oxide material and the oxide cathode particles belong to the same oxide system, which has better grain boundary compatibility and is more conducive to the transport of electrons and ions.
[0037] (4) The sulfur-based solid electrolyte composite oxide cathode material described in this invention has excellent interfacial chemical stability, which is beneficial to improving the cycle performance of lithium-ion batteries.
[0038] (5) The sulfur-based solid electrolyte composite oxide cathode material of the present invention has excellent electrical properties and broad market application prospects. Attached Figure Description
[0039] Figure 1 This is a schematic diagram of the sulfur-based solid electrolyte composite oxide cathode material of the present invention;
[0040] In the figure, 1. Oxide cathode particles; 2. First coating layer; 3. Second coating layer;
[0041] Figure 2 The image shows the scanning electron microscope (SEM) morphology of the sulfur-based solid electrolyte composite oxide cathode material obtained in Example 1.
[0042] Figure 3 The X-ray diffraction pattern of the sulfur-based solid electrolyte composite oxide cathode material obtained in Example 1 is shown below.
[0043] Figure 4 The AC impedance spectra of the sulfur-based solid electrolyte composite oxide cathode material obtained in Example 1 before and after cycling with the sulfide solid electrolyte are shown.
[0044] Figure 5The graph shows the cycle performance of the sulfur-based solid electrolyte composite oxide cathode material obtained in Example 1 when matched with a sulfide solid electrolyte.
[0045] Figure 6 The charge / discharge voltage-capacity curves are shown for the sulfur-based solid electrolyte composite oxide cathode material obtained in Example 1 when matched with a sulfide solid electrolyte. Detailed Implementation
[0046] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.
[0047] Example 1:
[0048] NCM811 (LiNi) with particle sizes of 6μm, 1μm, and 2nm were used. 0.8 Mn 0.1 Co 0.1 O2), Li6PS5Cl, and nano ITO were weighed at a mass ratio of 92.15:5:2.85. NCM811 and ITO were first mixed by ball milling at a low speed of 100 rpm for 3 hours. The mixture was then placed in a tube furnace and heated to 180°C at 1°C / min. After sintering for 150 minutes, it was ultrasonically cleaned with ethanol. The resulting composite cathode particles and solid electrolyte material Li6PS5Cl were then placed in a ball mill jar in a glove box and sealed for ball milling at a low speed of 100 rpm for 5 hours.
[0049] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 16 μm was obtained, wherein the thickness of the conductive oxide material layer is 10 nm and the thickness of the sulfur-based solid electrolyte layer is 5 μm.
[0050] The cathode material described above has the following properties: Figure 1 The three-layer core-shell structure shown has an oxide cathode material particle 1 at the center, a first coating layer 2 made of conductive oxide material, and a second coating layer 3 made of sulfide solid electrolyte material. By setting the first coating layer of conductive oxide material, it is possible to effectively prevent lattice oxygen from being released from the oxide cathode material particle and reacting with the sulfide solid electrolyte, thereby effectively avoiding the oxidation and decomposition of the sulfide solid electrolyte and further improving the rate performance and cycle performance of the lithium-ion battery.
[0051] The SEM image of the chalcogenide solid electrolyte composite oxide cathode material prepared in this embodiment is shown below. Figure 2 As shown, the surface of the NCM811 secondary particles is coated with a layer of ITO, and the outermost layer is coated with the solid electrolyte Li6PS5Cl.
[0052] The XRD pattern of the sulfur-based solid electrolyte composite oxide cathode material in this embodiment is as follows: Figure 3As shown, the diffraction peaks correspond to NCM811 and the solid electrolyte Li6PS5Cl.
[0053] The sulfur-based solid electrolyte composite oxide cathode material prepared in this embodiment was cold-pressed into a sheet with a thickness of approximately 80 μm under a pressure of 300 MPa in a glove box. This yielded a cathode sheet composed of the sulfur-based solid electrolyte composite oxide cathode material.
[0054] The positive electrode sheet prepared in this embodiment is used to assemble a solid-state lithium battery. The solid electrolyte is Li6PS5Cl, the negative electrode is lithium metal, and the thickness is about 280μm.
[0055] In this embodiment, the AC impedance of the solid-state battery assembled from the chalcogenide solid electrolyte composite oxide cathode material is as follows: Figure 4 As shown, the starting position in the high-frequency region corresponds to the bulk resistance of the solid electrolyte, while the low-frequency resistance is the interfacial impedance between the positive and negative electrodes and the solid electrolyte.
[0056] The assembled solid-state lithium battery was subjected to cycle testing at 30°C, such as... Figure 5 As shown, at 0.05C (1C = 200mA g) -1 The initial discharge specific capacity at high rate is 181.7 mAh g. -1 The initial coulombic efficiency was 65.78%. It maintained relatively stable cycling performance for the first 50 cycles, with a specific capacity of 159.8 mAh g on the 50th cycle. -1 The capacity retention rate was 88.28%.
[0057] The charge-discharge curves of the solid-state lithium battery assembled using the sulfide-based solid electrolyte composite oxide cathode material in this embodiment are as follows: Figure 6 As shown, the charge / discharge voltage-capacity curves of the high-nickel ternary cathode material are displayed. The median discharge voltage in the first cycle is 3.79V, and the average median discharge voltages in the 25th and 50th cycles are 3.71V and 3.68V, respectively.
[0058] Example 2:
[0059] NCM811 and Li with particle sizes of 6μm, 1μm, and 3nm were used. 5.5 PS 4.5 Cl 1.5 Nano-ITO was weighed at a mass ratio of 94.05:5:0.95. NCM811 and ITO were first mixed using a low-speed ball mill at 300 rpm for 1 hour. The mixture was then placed in a tube furnace and heated to 400°C at 5°C / min, and sintered for 30 minutes. Afterward, it was ultrasonically cleaned with ethanol. Finally, the resulting positive electrode structure material was mixed with the solid electrolyte Li in a glove box. 5.5 PS 4.5 Cl 1.5 After mixing, the mixture is ball-milled at a low speed of 300 rpm for 2 hours.
[0060] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 10 μm was obtained, wherein the thickness of the conductive oxide material layer is 5 nm and the thickness of the sulfur-based solid electrolyte layer is 2 μm.
[0061] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 75 μm.
[0062] Assemble solid-state lithium batteries, with Li as the solid electrolyte. 5.5 PS 4.5 Cl 1.5 The negative electrode is lithium metal, with a thickness of approximately 280 μm.
[0063] Solid-state lithium batteries were tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at the given current is 190.4 mAh g. -1 The initial coulombic efficiency was 70.41%, and the discharge specific capacity after 50 cycles was 171.5 mAh g. -1 The capacity retention rate was 90.07%. The median discharge voltage in the first cycle was 3.79V, and the average discharge voltages in the 25th and 50th cycles were 3.75V and 3.69V, respectively.
[0064] Example 3:
[0065] NCM811, Li6PS5I, and nano-In2O3 with particle sizes of 20μm, 1.5μm, and 2.5nm were weighed at a mass ratio of 87.3:10:2.7. NCM811 and In2O3 were first mixed by ball milling at a low speed of 220rpm for 2h. Then, the mixture was placed in a tube furnace and heated to 320℃ at 5℃ / min. After sintering for 120min, it was ultrasonically cleaned with ethanol. Then, the obtained positive electrode structure material and solid electrolyte Li6PS5I were ball milled at a low speed of 250rpm for 3h in a glove box.
[0066] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 36 μm was obtained, wherein the thickness of the conductive oxide material layer is 9 nm and the thickness of the sulfur-based solid electrolyte layer is 8 μm.
[0067] The sheets are cold-pressed under 300MPa pressure inside the glove box, with a thickness of approximately 80μm.
[0068] Assemble a solid-state lithium battery with Li6PS5I as the solid electrolyte and lithium-indium alloy as the negative electrode.
[0069] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at the given current is 175.4 mAh g. -1The initial coulombic efficiency was 69.40%, and the specific capacity after 50 cycles was 158.2 mAh g. -1 The capacity retention rate was 90.19%. The median discharge voltage in the first cycle was 3.30V, and the average discharge voltages in the 25th and 50th cycles were 3.26V and 3.21V, respectively (for lithium-indium alloy potential).
[0070] Example 4:
[0071] NCM622, Li6PS5Cl, and nano-In2O3 with particle sizes of 14μm, 1.7μm, and 2.4nm were weighed at a mass ratio of 89.1:10:0.9. NCM622 and In2O3 were first mixed by low-speed ball milling at 200 rpm for 2 hours. The mixture was then placed in a tube furnace and heated to 300℃ at 5℃ / min, and sintered for 130 minutes to obtain a 5nm layer of positive electrode material coated with In2O3. The material was ultrasonically cleaned with ethanol, and then mixed with solid electrolyte Li6PS5Cl in a glove box and ball-milled at 270 rpm for 3 hours.
[0072] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 28 μm was obtained, wherein the thickness of the conductive oxide material layer is 5 nm and the thickness of the sulfur-based solid electrolyte layer is 7 μm.
[0073] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 80 μm.
[0074] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0075] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at the given current is 184.3 mAh g. -1 The initial coulombic efficiency was 79.19%, and the discharge specific capacity after 50 cycles was 167.5 mAh g. -1 The capacity retention rate was 90.88%. The median discharge voltage in the first cycle was 3.80V, and the average discharge voltages in the 25th and 50th cycles were 3.75V and 3.72V, respectively.
[0076] Example 5:
[0077] NCM523, Li6PS5Cl, and nano-In2O3 with particle sizes of 18μm, 1μm, and 2nm were weighed at a mass ratio of 93:5.5:1.5. NCM523 and In2O3 were first mixed by low-speed ball milling at 150 rpm for 2 hours. The mixture was then placed in a tube furnace and heated to 290℃ at 5℃ / min, and sintered for 135 minutes to obtain a 6nm layer of positive electrode material coated with In2O3. The material was ultrasonically cleaned with ethanol, and then mixed with solid electrolyte Li6PS5Cl in a glove box and ball-milled at 110 rpm for 3 hours.
[0078] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 26 μm was obtained, wherein the thickness of the conductive oxide material layer is 8 nm and the thickness of the sulfur-based solid electrolyte layer is 4 μm.
[0079] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 75 μm.
[0080] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0081] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at specific current is 173.3 mAh g. -1 The initial coulombic efficiency was 83.40%, and the discharge specific capacity after 50 cycles was 158.5 mAh g. -1 The capacity retention rate was 91.62%. The median discharge voltage in the first cycle was 3.78V, and the average median discharge voltages in cycles 25 and 50 were 3.70V and 3.68V, respectively.
[0082] Example 6
[0083] NCM811 and Li with particle sizes of 12 μm, 2 μm, and 2.5 nm were used. 10 GeP2S 12 Nano-In₂O₃ was weighed at a mass ratio of 87.3:10:2.7. NCM811 and In₂O₃ were first mixed using a low-speed ball mill at 220 rpm for 2 hours. The mixture was then placed in a tube furnace and heated to 300°C at 5°C / min, and sintered for 120 minutes. Afterward, it was ultrasonically cleaned with ethanol. Finally, the resulting positive electrode structure material was mixed with the solid electrolyte Li₂O₃ in a glove box. 10 GeP2S 12 Perform low-speed ball milling at 250 rpm for 3 hours.
[0084] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 24 μm was obtained, wherein the thickness of the conductive oxide material layer is 9 nm and the thickness of the sulfur-based solid electrolyte layer is 6 μm.
[0085] The sheets are cold-pressed under 300MPa pressure inside the glove box, with a thickness of approximately 80μm.
[0086] Assemble solid-state lithium batteries, with Li as the solid electrolyte. 10 GeP2S 12 The negative electrode is a lithium-indium alloy.
[0087] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at the given current is 182.4 mAh g. -1 The initial coulombic efficiency was 70.60%, and the specific capacity after 50 cycles was 168.2 mAh g. -1 The capacity retention rate was 92.21%. The median discharge voltage in the first cycle was 3.31V, and the average discharge voltages in the 25th and 50th cycles were 3.29V and 3.25V, respectively (for lithium-indium alloy potential).
[0088] Example 7
[0089] NCM811, β-Li3PS4, and nano-ITO with particle sizes of 12μm, 1μm, and 3nm were weighed at a mass ratio of 94.05:5:0.95. NCM811 and ITO were first mixed by ball milling at a low speed of 280 rpm for 1 h. The mixture was then placed in a tube furnace and heated to 400℃ at 5℃ / min. After sintering for 30 min, it was ultrasonically cleaned with ethanol. The resulting positive electrode structure material was then mixed with the solid electrolyte β-Li3PS4 in a glove box and ball milled at a low speed of 300 rpm for 2 h.
[0090] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 16 μm was obtained, wherein the thickness of the conductive oxide material layer is 5 nm and the thickness of the sulfur-based solid electrolyte layer is 2 μm.
[0091] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 75 μm.
[0092] Assemble a solid-state lithium battery with β-Li3PS4 as the solid electrolyte and lithium metal as the negative electrode, with a thickness of approximately 280 μm.
[0093] Solid-state lithium batteries were tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at the given current is 168.4 mAh g. -1 The initial coulombic efficiency was 67.41%, and the discharge specific capacity after 50 cycles was 148.5 mAh g.-1 The capacity retention rate was 88.18%. The median discharge voltage in the first cycle was 3.74V, and the average discharge voltages in the 25th and 50th cycles were 3.71V and 3.68V, respectively.
[0094] Comparative Example 1:
[0095] NCM811 and Li6PS5Cl with particle sizes of 6μm and 1μm respectively were weighed in a glove box at a mass ratio of 90:10, preliminarily mixed evenly, and then placed in a sealed ball mill jar for low-speed ball milling at 110rpm for 3 hours.
[0096] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 16 μm was obtained, wherein the thickness of the sulfur-based solid electrolyte layer is 5 μm.
[0097] The sheets are cold-pressed under 300MPa pressure inside the glove box, with a thickness of approximately 80μm.
[0098] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0099] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at specific current is 178.5 mAh g. -1 The initial coulombic efficiency was 62.3%, and the discharge specific capacity after 50 cycles was 132.89 mAh g. -1 The capacity retention rate was 74.45%. The median discharge voltage in the first cycle was 3.75V, and the average median discharge voltages in the 25th and 50th cycles were 3.72V and 3.66V, respectively.
[0100] Comparative Example 2:
[0101] NCM811, Li6PS5Cl, and conductive carbon black with particle sizes of 6μm, 1μm, and 2.4nm were weighed at a mass ratio of 92.15:5:2.85. First, NCM523 and conductive carbon black were mixed by low-speed ball milling at 100 rpm for 3 hours. Then, the resulting positive electrode structure material was mixed with solid electrolyte in a glove box and ball milled at 100 rpm for 3 hours.
[0102] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 16 μm was obtained, wherein the thickness of the conductive carbon black layer is 7 nm and the thickness of the sulfur-based solid electrolyte layer is 2 μm.
[0103] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 75 μm.
[0104] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0105] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at specific current is 177.8 mAh g. -1 The initial coulombic efficiency was 68.9%, and the discharge specific capacity after 50 cycles was 139.85 mAh g. -1 The capacity retention rate was 78.66%. The median discharge voltage in the first cycle was 3.77V, and the average median discharge voltages in the 25th and 50th cycles were 3.71V and 3.64V, respectively. Because the carbon layer material, when applied to sulfide-based solid electrolytes, catalyzes additional decomposition of the sulfide-based solid electrolyte, it does not achieve the goal of tightly binding the cathode material to the electrolyte interface and further consumes the solid electrolyte.
[0106] Comparative Example 3:
[0107] NCM811, Li6PS5Cl, and nano-ITO with particle sizes of 12μm, 1μm, and 2nm were weighed at a mass ratio of 88:5:7. NCM811 and nano-ITO were first mixed by ball milling at a low speed of 110 rpm for 3 hours. The mixture was then placed in a tube furnace and heated to 300℃ at 1℃ / min. After sintering for 120 minutes, it was ultrasonically cleaned with ethanol. The resulting positive electrode structure material was then mixed with the solid electrolyte in a glove box and ball milled at a low speed of 100 rpm for 3 hours.
[0108] A sulfur-based solid electrolyte composite oxide cathode material with a particle size of 16 μm was obtained, wherein the thickness of the conductive oxide material layer is 15 nm and the thickness of the sulfur-based solid electrolyte layer is 2 μm.
[0109] The sheets are cold-pressed under 350 MPa pressure inside the glove box, with a thickness of approximately 75 μm.
[0110] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0111] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at specific current is 85.67 mAh g. -1 The initial coulombic efficiency was 58.42%. However, due to the excessively high mass ratio of the conductive oxide material, lithium-ion transport between the solid cathode material and the solid electrolyte was affected, thus Comparative Example 3 could not complete 50 cycles.
[0112] Comparative Example 4:
[0113] NCM811, Li6PS5Cl, and nano-ITO with particle sizes of 12 μm, 1 μm, and 2 nm were weighed at a mass ratio of 92.15:5:2.85. The three materials were then simultaneously placed in a ball mill jar and sealed inside a glove box. Afterward, the mixture was removed from the glove box and ball-milled at a low speed of 100 rpm for 5 hours. The mixture was then heated to 180 °C at a rate of 1 °C / min, sintered for 150 min, and then ultrasonically cleaned with ethanol.
[0114] The cathode material is cold-pressed into a sheet with a thickness of about 80 μm under a pressure of 300 MPa inside a glove box, resulting in a cathode sheet composed of a composite multilayer cathode material.
[0115] Assemble a solid-state lithium battery with Li6PS5Cl as the solid electrolyte and a lithium metal anode with a thickness of approximately 280 μm.
[0116] The assembled solid-state battery was tested at 30°C and at 0.05C (1C = 200 mAg). -1 The initial discharge specific capacity at specific current is 24.68 mAh g. -1 The initial coulombic efficiency was 42.63%. However, due to the decomposition of the solid electrolyte at high temperatures, lithium-ion transport within the battery system was paralyzed, resulting in extremely poor electrochemical performance in Comparative Example 4.
[0117] Table 1 shows the performance test results of the batteries prepared with the sulfide-based solid electrolyte composite oxide cathode materials of Examples 1-6 and Comparative Examples 1-4, as detailed below:
[0118] Table 1. Battery performance test results for each embodiment and comparative example.
[0119]
[0120]
[0121] The results above demonstrate that the advantage of this invention lies in the ability of the prepared multilayer composite cathode material to effectively prevent the side reactions between lattice oxygen released from the layered oxide cathode material and the sulfide solid electrolyte during cycling, significantly reducing the additional consumption of the sulfide solid electrolyte during cycling and further improving interface stability. Furthermore, the use of conductive oxides (such as nano-ITO) to construct rapid electron conduction channels further ensures the capacity utilization and cycling stability of the cathode material.
[0122] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, it is not intended to limit the invention in any way. Modifications or improvements can be made to the present invention, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A sulfur-based solid electrolyte composite oxide cathode material, characterized in that, It includes oxide cathode particles, a first coating layer covering the outside of the oxide cathode particles, and a second coating layer covering the outside of the first coating layer. The oxide cathode particles are oxide cathode materials, the first coating layer is a conductive oxide material, and the second coating layer is a sulfide solid electrolyte material. The conductive oxide material includes one or more of indium tin oxide, indium oxide, and tin dioxide. The thickness of the first coating layer is 5-10 nm, and the thickness of the second coating layer is 2-8 μm.
2. The sulfur-based solid electrolyte composite oxide cathode material according to claim 1, characterized in that, The described oxide cathode material includes one or more materials that conform to LiNi x Co y Mn 1-x-y O2, where 0.5 < x < 1 and x + y < 1.
3. The sulfur-based solid electrolyte composite oxide cathode material according to claim 1, characterized in that, The sulfide-based solid electrolyte material includes materials conforming to xLi₂S-yP₂S₅, where x+y=100; β-Li₃PS₄; Li₆PS₅X, where X=Cl,Br or I; Li 5.5 PS 4.5 Cl 1.5 Li 10±1 MP2S 12 M = Ge, Si, Sn, Al or P and one or more of their corresponding doped and modified materials.
4. The sulfur-based solid electrolyte composite oxide cathode material according to claim 1, characterized in that, The oxide cathode particles have a particle size of 6–20 μm.
5. A method for preparing the sulfide-based solid electrolyte composite oxide cathode material according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Conductive oxide material is pre-coated onto the surface of oxide cathode particles using a mechanical coating process to obtain a pre-coated material; S2. The pre-coated material obtained in step S1 is sintered at low temperature to obtain composite positive electrode particles coated with conductive oxide material; S3. The sulfur-based solid electrolyte material is coated onto the surface of the composite cathode particles obtained in step S2 by a mechanical coating process to obtain a sulfur-based solid electrolyte composite oxide cathode material.
6. The method for preparing the sulfide-based solid electrolyte composite oxide cathode material according to claim 5, characterized in that, In step S1, the mechanical coating process includes the following steps: S1.
1. Weigh the oxide cathode material and the conductive oxide material; wherein the oxide cathode material accounts for 97% to 99% of the total mass; S1.
2. The mixture of S1.1 is pre-coated by low-speed ball milling.
7. The method for preparing the sulfide-based solid electrolyte composite oxide cathode material according to claim 5, characterized in that, In step S2, the heating rate is 1-5℃ / min, the sintering temperature is 180-400℃, and the sintering time is 30-150min.
8. The method for preparing the sulfide-based solid electrolyte composite oxide cathode material according to claim 5, characterized in that, In step S3, the mechanical coating process includes the following steps: S3.
1. Under an environment where the moisture and oxygen content are both no higher than 0.5 ppm, weigh the composite cathode particles and sulfur-based solid electrolyte material obtained in step S2; wherein, the mass of the composite cathode particles accounts for 85% to 95% of the total mass. S3.
2. The sample from S3.1 is ball-milled at -0.05 to -0.1 MPa.
9. The application of the sulfide-based solid electrolyte composite oxide cathode material according to any one of claims 1-4 in lithium-ion batteries and their preparation.