A co-doped layered oxide cathode material and sulfide all-solid-state battery

Abstract

The present invention discloses a co-doped layered oxide positive electrode material and sulfide all-solid-state battery, which belongs to the field of battery technology. The modified layered oxide is a layered oxide co-doped with anions and cations, and the chemical formula is Li 1‑a Ni x Co y Mn 1‑x‑y M a O 2‑b F b , where 0

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a co-doped layered oxide positive electrode material and a sulfide all-solid-state battery. Background Art

[0002] With the rapid rise of electric vehicles and large-scale energy storage, lithium-ion batteries, as the most critical energy storage devices, have attracted widespread attention, and the demand for their energy density, power density, service life and safety performance is growing. Currently, commercial lithium-ion batteries have safety hazards such as flammability and leakage due to the liquid electrolyte they use. Batteries can overheat due to overcharging, internal short circuits, etc., causing the electrolyte to overheat and lead to fire or explosion accidents. In addition, the energy density of liquid lithium-ion batteries has reached 300 Wh kg −1 bottleneck, and cannot meet the higher energy density requirements of electric vehicles and large-scale energy storage equipment.

[0003] All-solid-state lithium-ion batteries (ALLS) are considered the most promising next-generation secondary battery system due to their non-flammable, high-temperature-resistant, and non-volatile solid electrolytes, which offer higher safety and energy density than liquid lithium-ion batteries. ALLS-ion batteries, which combine high-ionic conductivity and thermally stable sulfide solid electrolytes with high-voltage, high-capacity layered oxide cathodes, have attracted considerable attention from both industry and academia.

[0004] However, the power density and service life of sulfide-based all-solid-state lithium batteries assembled with layered oxide materials as positive electrodes are not ideal. There are mainly the following problems: (1) Mechanical instability of layered oxide positive electrodes. During the charge and discharge process, layered oxide positive electrode materials are prone to cracking due to lattice change stress under high voltage, high current and long cycle conditions, which can easily break through the material surface fracture energy limit, leading to inactivation of active materials, increased interface impedance and a sharp drop in capacity. (2) Layered oxides and sulfide solid electrolytes are (electro)chemically unstable. During the electrochemical process, the high-valent cations (Ni 4+ ,Co 3+ , Mn 4+Sulfide solid electrolytes such as (etc.) and oxygen free radicals or oxygen are prone to oxidize sulfide solid electrolytes, and sulfide electrolytes with a narrow electrochemical window decompose under high pressure to generate interfacial by-products that are electron and ion insulating. The residual lithium compounds on the surface of the positive electrode further promote the interfacial side reaction, resulting in the accumulation of insulating by-products at the interface, increasing the lithium ion transport barrier at the interface, and weakening the rate performance and cycle performance of the solid-state battery. (3) The internal structure of the layered oxide material is unstable. During the charge and discharge process of the layered oxide positive electrode material, in order to relieve the stress related to the lithium ion concentration gradient inside the particles, transition metal ions migrate to the lithium layer and lattice oxygen is lost, and the formed spinel and rock salt phase structures further hinder the lithium ion transport in the lithium layer, ultimately leading to the collapse of the layered oxide positive electrode structure and severe capacity decay. Therefore, it is necessary to improve the layered oxide positive electrode material and the sulfide all-solid-state battery. Summary of the Invention

[0005] The purpose of the present invention is to provide a co-doped layered oxide positive electrode material and a sulfide all-solid-state battery, which construct a uniform lithium ion transport, a stable bulk phase structure, and a high mechanical strength and stable interface surface, greatly improving the rate performance and cycle performance of the all-solid-state battery.

[0006] The technical solutions adopted by the present invention to achieve the above purposes are as follows:

[0007] A modified layered oxide, the modified layered oxide is a layered oxide co-doped with cations and anions, and its chemical general formula is Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b , where 0 < a ≤ 0.08, 0 ≤ x ≤ 1, and 0 ≤ y ≤ 1, x and y are not both 0 at the same time, 0 < b ≤ 0.2; M is selected from at least one of Al, Si, Zr, Ti, Sn, Sb, Ta, and comes from a fluorine-containing weak acid material;

[0008] In the layered oxide co-doped with cations and anions, due to the different solubilities of the doped cations and anions in the layered oxide lattice structure, the doped M cations with lower solubility tend to be enriched in the depth of about 3 to 100 nm near the surface, and the ion concentration decreases from the surface to the bulk phase, and the fluorine anions are uniformly distributed inside the bulk phase.

[0009] According to one aspect of the present invention, a preparation method of the above modified layered oxide is provided, including the following steps:

[0010] [[ID=3']]S1. Add the powder of the layered oxide and the weak acid solution to deionized water, stir and mix, and carry out an acid-base reaction; LiOH and / or Li2CO3 exist on the surface of the layered oxide powder,

[0011] S2. Vacuum dry the mixed solution obtained in step S1 to obtain a powder coated with an inorganic layer containing elements M and F; after calcining the obtained powder coated with an inorganic layer containing elements M and F, a modified layered oxide is obtained.

[0012] In step S1, the weak acid is H c MF d , where 0 < c ≤ 2, 0 < d ≤ 6, and M is a metal cation or a non-metal cation. Further, M is at least one of Al, Si, Zr, Ti, Sn, Sb, and Ta;

[0013] In step S1, the molar ratio of the amount of substance of M cations in the weak acid to the total amount of substance of transition metal elements in the layered oxide is 0.02 - 0.08:1;

[0014] In step S1, the mass ratio of the layered oxide to deionized water is 1:1 - 10.

[0015] In step S1, the layered oxide, the weak acid solution and deionized water are stirred and mixed, the stirring speed is 200 - 500 rpm, the temperature of the acid-base reaction is 20 - 30 °C, and the time is 5 - 3 h;

[0016] In step S1, the coating principle is that the weak acid solution can selectively etch the residual lithium compounds LiOH and Li2CO3 on the surface of the layered oxide to form a uniform inorganic coating layer containing elements M and F on the material surface.

[0017] In step S2, the temperature of vacuum drying is 80 - 130 °C, and the drying time is 8 - 24 h;

[0018] In step S2, the calcination atmosphere is one of oxygen, air and pure argon, the calcination temperature is 200 - 700 °C, the heating rate is 1 - 30 °C / min, and the calcination time is 1 - 20 h.

[0019] Adopting the above technical solution, through the pickling and sintering process, while eliminating the harmful residual alkali compounds on the surface of the layered oxide material, co-doping modification of cations and anions is achieved. During the sintering process, the different diffusion abilities of M cations and fluoride anions in the layered oxide material are utilized to achieve the enrichment of M cations near the surface and the uniform distribution of fluoride ions inside the bulk phase.

[0020] Introducing M cation-oxygen with stronger bonding than transition metal-oxygen in the near-surface lithium layer to improve the surface mechanical strength of the layered oxide cathode material to enhance the surface fracture energy, inhibit the failure of lithium ion transport caused by mechanical cracking of particles, and at the same time use the strong oxygen-fixing effect of the M cation to effectively prevent the degradation of the near-surface structure of the positive electrode and the occurrence of interfacial side reactions, and reduce the interfacial lithium ion transport energy barrier.

[0021] The highly electronegative fluoride ions introduced into the bulk-structured oxygen layer have a shorter bond length with transition metals than oxygen ions, which helps to expand the lithium layer spacing and alleviate the structural disorder caused by the migration of transition metals to the lithium layer, realizing uniform and rapid lithium-ion transport in the lithium layer inside the particles.

[0022] The synergistic effect of strong M-O bonding near the surface and highly electronegative fluoride ions in the bulk enables fast lithium-ion transport kinetics in the bulk and at the interface of the layered oxide material, effectively suppressing problems such as particle cracking, structural degradation, and interfacial side reactions occurring under high current and high voltage, and significantly improving the rate performance and cycling performance of all-solid-state lithium batteries.

[0023] According to one aspect of the present invention, there is provided an all-solid-state lithium battery, comprising a positive electrode, a negative electrode, and an intermediate layer electrolyte; the positive electrode includes a positive electrode material, the positive electrode material includes a positive electrode main material, the positive electrode main material includes one or more of Li6PS5Cl, Li 10 GeP2S 12 、Li 10 SnP2S 12 and a modified layered oxide, the modified layered oxide is a layered oxide co-doped with cations and anions, and its chemical general formula is Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b ,where 0 < a ≤ 0.08, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, x and y are not both 0, 0 < b ≤ 0.2; M is selected from at least one of Al, Si, Zr, Ti, Sn, Sb, Ta, and comes from a fluorine-containing weak acid material; the negative electrode is a lithium-indium alloy; the intermediate layer electrolyte is one of Li6PS5Cl, Li 10 GeP2S 12 、Li 10 SnP2S 12 .

[0024] Preferably, the intermediate layer electrolyte used in the all-solid-state lithium metal battery is Li6PS5Cl.

[0025] Preferably, the positive electrode material further includes a conductive agent and a binder, and the mass ratio of the positive electrode main material, the conductive agent, and the binder is 85-95:3-10:2-5.

[0026] Preferably, the binder is one or more of polyvinylidene fluoride, polyimide, carboxymethyl cellulose, and sodium alginate;

[0027] Preferably, the conductive agent is one or more of Super P, acetylene black, Ketjen black, conductive carbon black, carbon nanotubes, graphene, and modified graphene; the modified graphene is obtained by carbonizing amino-modified graphene oxide, and the amino-modified graphene oxide is obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bithiazole and / or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine.

[0028] By adopting the above technical solution, the conductive agent using modified graphene in the positive electrode material helps to improve the electrochemical performance of the resulting battery, and can significantly improve the first coulombic efficiency of the obtained sodium ion, the positive electrode energy density and the cycle performance.

[0029] This may be because the modified graphene obtained by carbonizing amino-modified graphene oxide helps to form a good conductive network in the resulting positive electrode material, reduce internal resistance and is not easy to polarize, thereby improving the performance of the resulting battery. In particular, the graphene oxide is modified with 2,2'-diamino-4,4'-bithiazole and / or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine. After carbonization, the microstructure of the modified graphene changes, making it more conducive to serving as a sulfur host. At the same time, it has an adsorption effect on lithium polysulfide during the electrochemical process, which can effectively promote the redox reaction kinetics of lithium-sulfur batteries and help reduce the loss of sulfur active material mass.

[0030] According to one aspect of the present invention, there is provided a method for preparing modified graphene, comprising the following steps:

[0031] Graphene oxide (GO) is mixed with NHS (N-hydroxysuccinimide) and EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride), and anhydrous DMF is added under a nitrogen atmosphere and stirred for activation; then, 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are added, and the mixture is stirred for 8-24 hours under a nitrogen atmosphere. After the reaction is completed, the solid product is collected by centrifugation, washed with deionized water, and dried to obtain amino-modified graphene oxide; the obtained amino-modified graphene oxide is carbonized to obtain modified graphene.

[0032] Preferably, the mass ratio of GO to NHS is 1:1-3;

[0033] Preferably, the mass ratio of NHS (N-hydroxysuccinimide) to EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) is 1:0.5-2;

[0034] Preferably, the mass volume ratio of GO to anhydrous DMF is 5-15 mg:3 mL;

[0035] Preferably, the mass ratio of 2,2'-diamino-4,4'-bisthiazole to benzothieno[3,2-d:4,5-d']bisthiazole-2,6-diamine is 0.5-2:0.5-2;

[0036] Preferably, the mass ratio of GO to 2,2'-diamino-4,4'-bisthiazole is 1:2-20.

[0037] Preferably, the temperature of carbonization treatment is 1000-2000 °C, and the carbonization time is 1-4 h.

[0038] According to one aspect of the present invention, the positive electrode material includes a positive electrode main material, a conductive agent, and a binder. The positive electrode main material includes a modified layered oxide, which is a layered oxide co-doped with cations and anions, and its chemical general formula is Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b , where 0 < a ≤ 0.08, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, x and y are not both 0, 0 < b ≤ 0.2; M is selected from at least one of Al, Si, Zr, Ti, Sn, Sb, Ta, and comes from a fluorine-containing weak acid material; the conductive agent includes nitrogen-doped porous carbon nanosheets and one or more of Super P, acetylene black, Ketjen black, conductive carbon black, carbon nanotubes, graphene, and modified graphene. The modified graphene is obtained by carbonizing amino-modified graphene oxide, and the amino-modified graphene oxide is obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bisthiazole and / or benzothieno[3,2-d:4,5-d']bisthiazole-2,6-diamine; the nitrogen-doped porous carbon nanosheets are obtained by carbonizing melamine, melamine diamide, or melamine cyanurate with arbutin.

[0039] According to an embodiment of the present invention, the positive electrode material includes a positive electrode main material, a conductive agent, and a binder. The positive electrode main material includes a modified layered oxide, which is a layered oxide co-doped with cations and anions, and its chemical general formula is Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b, where \(0 < a\leq0.08\), \(0\leq x\leq1\), \(0\leq y\leq1\), \(x\) and \(y\) are not both \(0\), and \(0 < b\leq0.2\); \(M\) is selected from at least one of \(Al\), \(Si\), \(Zr\), \(Ti\), \(Sn\), \(Sb\), \(Ta\), and comes from a fluorine-containing weak acid material; the conductive agent includes nitrogen-doped porous carbon nanosheets and modified graphene, and the modified graphene is obtained by carbonizing amino-modified graphene oxide, and the amino-modified graphene oxide is obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bisthiazole and / or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine; the nitrogen-doped porous carbon nanosheets are obtained by carbonizing melamine, melamine diamide or melamine cyanurate and arbutin.

[0040] Preferably, in the conductive agent, the mass ratio of the modified graphene to the nitrogen-doped porous carbon nanosheets is 1:0.15 - 1.

[0041] The preparation method of the nitrogen-doped porous carbon nanosheets is as follows:

[0042] Disperse melamine, melamine diamide or melamine cyanurate and arbutin in an aqueous solution of ethanol to obtain a dispersion. Dry the above dispersion at a temperature of 60 - 85 °C, grind the obtained solid, heat it to 350 - 500 °C in a nitrogen atmosphere, and keep it for 1 - 3 h; then heat it to 600 - 750 °C and keep it for 1 - 3 h; then heat it to 950 - 1200 °C and keep it for 1 - 3 h. Then naturally cool it to 25 °C to obtain the nitrogen-doped porous carbon nanosheets.

[0043] Among them, ethanol and water in the aqueous ethanol solution are mixed according to a volume ratio of 1:0.5 - 1.5; the mass ratio of melamine, melamine diamide or melamine cyanurate to arbutin is 10 - 30:1; the mass-volume ratio of melamine, melamine diamide or melamine cyanurate to the aqueous ethanol solution is 0.5 - 3 g:10 mL.

[0044] Adopting the above technical solution, in the positive electrode material, adding nitrogen-doped porous carbon nanosheets to the conductive agent can further improve the electrochemical performance of the obtained sulfide all-solid-state battery. Especially when the modified graphene and the nitrogen-doped porous carbon nanosheets are used in combination, the initial Coulomb efficiency, positive electrode energy density and cycle performance of the obtained battery are further improved.

[0045] This may be because, in the nitrogen-doped porous carbon nanosheets, the doping of nitrogen atoms can effectively regulate the charge distribution and increase the electron transfer rate. Moreover, the nitrogen-doped porous carbon nanosheets can provide more active sites and promote electron transfer, thus contributing to improving the electrochemical performance of the obtained battery.

[0046] According to one aspect of the present invention, there is provided the application of the above all-solid-state lithium battery in an electric vehicle.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. A modified layered oxide and a method for preparing the modified layered oxide are provided. Based on the elimination of residual lithium compounds and the co-doping of anions and cations, a bulk phase with uniform lithium ion transport and structural stability is constructed, along with a surface with high mechanical strength and interfacial stability, significantly improving the rate capability and cycling performance of all-solid-state batteries. Strong MO bonding introduced near the surface enhances the surface's mechanical strength and chemical stability, effectively mitigating the high interfacial impedance caused by mechanical cracking and accumulation of insulating side reaction products at high currents and voltages in the layered oxide cathode, thereby enhancing interfacial lithium ion transport kinetics. Highly electronegative fluoride anions introduced into the layered oxide bulk form stronger bonds with transition metal ions, inhibiting transition metal migration into the lithium layer, resulting in a disordered phase with low ion transport, and expanding the interlayer spacing, alleviating the internal and external lithium concentration gradients in the cathode particles during charge and discharge. This synergistic effect, combined with the strong MO bonding near the surface, enhances the structural stability and lithium ion transport kinetics of the layered oxide cathode.

[0049] 2. The all-solid-state lithium battery assembled with the above-mentioned layered oxide positive electrode has the advantages of large charge and discharge capacity, rate performance and excellent cycle performance under high current.

[0050] 3. The acid-washing and sintering process simultaneously achieves the elimination of residual alkali on the surface and the co-doping of anions and cations. The preparation process is simple, efficient, and low-cost, meeting the requirements of industrial production and is expected to greatly promote the large-scale commercialization of layered oxide cathode materials.

[0051] 4. In the preparation of the positive electrode for an all-solid-state lithium battery, the use of a composite positive electrode material I containing a modified peroxide, combined with conductive-modified graphene, significantly improves the initial coulombic efficiency, positive electrode energy density, and capacity retention of the resulting battery. Modified graphene, obtained by carbonizing amino-modified graphene oxide, helps form a good conductive network in the resulting positive electrode material, reducing internal resistance and resisting polarization, thereby improving the performance of the resulting battery.

[0052] 5. In the preparation of the positive electrode for all-solid-state lithium batteries, the combination of modified graphene and nitrogen-doped porous carbon nanosheets in the conductive agent can further enhance the electrochemical performance of the resulting sulfide all-solid-state battery, further improving the initial coulombic efficiency, positive electrode energy density, and cycling performance. This is likely because the nitrogen-doped porous carbon nanosheets can provide more active sites and promote electron transfer, thereby improving the electrochemical performance of the resulting battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1This is the XRD test result of the positive electrode main material obtained in Example 1;

[0054] Figure 2 This is the XRD test result of the positive electrode material obtained in Comparative Example 1;

[0055] Figure 3 HRTEM image of a particle slice of the layered oxide obtained in Example 1;

[0056] Figure 4 HRTEM spectrum element information results of the layered oxide particle slice obtained in Example 1;

[0057] Figure 5 This is a scanning electron microscope image of the positive electrode sheet of the battery obtained in Example 1 after 150 cycles;

[0058] Figure 6 This is a scanning electron microscope morphology of the positive electrode sheet of the battery obtained in Comparative Example 1 after 150 cycles. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0060] Example 1

[0061] Preparation of modified layered oxides

[0062] S1. Layered oxide LiNi 0.83 Co 0.12 Mn 0.05 O2 powder and weak acid solution are added to deionized water, stirred and mixed to carry out acid-base reaction; LiOH and Li2CO3 are present on the surface of the layered oxide powder, the weak acid is H2SiF6 aqueous solution, and the mass percentage of H2SiF6 is 30wt%.

[0063] S2. The mixed solution obtained in step S1 is vacuum dried to obtain a powder coated with an inorganic layer containing Si and F elements; the obtained powder coated with an inorganic layer containing Si and F elements is calcined to obtain a modified layered oxide.

[0064] In step S1, the molar ratio of the amount of the non-metallic cation Si in the weak acid to the total amount of the transition metal elements in the layered oxide is 0.02:1;

[0065] In step S1, the mass ratio of the layered oxide to deionized water is 1:10.

[0066] In step S1, the layered oxide, the weak acid solution and the deionized water are stirred and mixed at a stirring speed of 300 rpm, the acid-base reaction temperature is 30°C, and the time is 10 h;

[0067] In step S2, the vacuum drying temperature is 100°C and the drying time is 12 hours;

[0068] In step S2, the calcination atmosphere is air, the calcination temperature is 500°C, the heating rate is 5°C / min, and the calcination time is 10 h.

[0069] The modified layered oxide was prepared according to the above method, and the general chemical formula is Li 0.996 N i0.83 Co 0.12 Mn 0.05 Si 0.00 4F 0.024 O 1.976 , Si comes from H2SiF6; the above-mentioned modified layered oxide is a layered oxide co-doped with anions and cations, the non-metallic cation Si is enriched at a depth of about 3~100 nm near the surface, the ion concentration decreases from the surface to the bulk phase, and the fluoride anions are uniformly distributed inside the bulk phase.

[0070] Preparation of all-solid-state lithium batteries

[0071] The all-solid-state lithium battery includes a positive electrode, a negative electrode and an intermediate layer electrolyte; the positive electrode includes a positive electrode material, and the positive electrode material includes a positive electrode main material.

[0072] In this embodiment, the modified layered oxide obtained above and Li6PS5Cl were mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I. The composite positive electrode main material I was roll-pressed to obtain a positive electrode film, which was used as a positive electrode material to prepare a positive electrode;

[0073] Li6PS5Cl was placed in a polyetheretherketone (PEEK) mold and pressed at 380 MPA for 5 minutes to form a solid electrolyte sheet. A cathode film was then laminated onto one side of the solid electrolyte sheet and pressed at 380 MPA for 10 minutes. The mass ratio of the solid electrolyte sheet to the cathode material was 10:1. Finally, a lithium-indium alloy anode with 60 wt% indium was placed on the other side and pressed at 20 MPA for 1 minute to create an all-solid-state lithium battery.

[0074] Example 2

[0075] The difference between this embodiment and embodiment 1 is that:

[0076] In the preparation of the modified layered oxide, in step S1, the molar ratio of the amount of the non-metallic cation Si in the weak acid to the total amount of the transition metal elements in the layered oxide is 0.04: 1; the prepared modified layered oxide has the general chemical formula Li 0.992 N i0.83 Co 0.12 Mn 0.05 Si 0.008 F 0.048 O 1.952 .

[0077] Other conditions and steps are the same.

[0078] Example 3

[0079] The difference between this embodiment and embodiment 1 is that:

[0080] In the preparation of the modified layered oxide, in step S1, the layered oxide is LiNi 0.6 Co 0.2 Mn 0.2 O2; the molar ratio of the amount of non-metallic cation Si in the weak acid to the total amount of transition metal elements in the layered oxide is 0.02:1; the modified layered oxide obtained has the general chemical formula Li 0.996 N i0.6 Co 0. 2 Mn 0.2 Si 0.004 F 0.024 O 1.976 .

[0081] Other conditions and steps are the same.

[0082] Example 4

[0083] The difference between this embodiment and embodiment 1 is that:

[0084] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0085] In this example, a modified layered oxide and Li6PS5Cl were mixed in a mass ratio of 7:3 to form a composite positive electrode material I. The conductive agent was modified graphene, and the binder was polyvinylidene fluoride. The mass ratio of the positive electrode material, conductive agent, and binder was 90:3:3. The composite positive electrode material I, conductive agent, and binder were mixed, ball-milled at 200 rpm for 1 hour, and then roller-pressed to obtain a positive electrode film, which served as the positive electrode material for preparing the positive electrode. The solid electrolyte sheet, negative electrode, and other conditions and procedures were the same as in Example 1.

[0086] The preparation method of the modified layered oxide is the same as that in Example 1.

[0087] The preparation method of modified graphene is as follows:

[0088] GO was prepared by the Hummer method; GO was then mixed with NHS and EDC, and anhydrous DMF was added under a nitrogen atmosphere, and the mixture was stirred for activation; then, 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine were added, and the mixture was stirred for 12 hours under a nitrogen atmosphere. After the reaction, the solid product was collected by centrifugation, washed with deionized water, and dried to obtain amino-modified graphene oxide; the obtained amino-modified graphene oxide was carbonized to obtain modified graphene.

[0089] The mass ratio of GO to NHS is 1:2;

[0090] The mass ratio of NHS to EDC was 1:1;

[0091] The mass volume ratio of GO to anhydrous DMF was 10 mg:3 mL;

[0092] The mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 1:1;

[0093] The mass ratio of GO to 2,2'-diamino-4,4'-bithiazole was 1:8.

[0094] The temperature of the carbonization treatment is 1400°C and the carbonization time is 2 h.

[0095] Example 5

[0096] The difference between this embodiment and embodiment 1 is that:

[0097] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0098] In this embodiment, modified layered oxide and Li6PS5Cl are mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent is modified graphene, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:5:3.

[0099] The preparation method of the modified layered oxide is the same as that of Example 1;

[0100] The preparation method of modified graphene is the same as that of Example 4.

[0101] Other conditions and steps are the same.

[0102] Example 6

[0103] The difference between this embodiment and embodiment 1 is that:

[0104] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0105] In this embodiment, modified layered oxide and Li6PS5Cl are mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent is modified graphene, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:7:3.

[0106] The preparation method of the modified layered oxide is the same as that of Example 1;

[0107] The preparation method of modified graphene is the same as that of Example 4.

[0108] Other conditions and steps are the same.

[0109] Example 7

[0110] The difference between this embodiment and embodiment 1 is that:

[0111] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0112] In this embodiment, modified layered oxide and Li6PS5Cl are mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent is modified graphene, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:5:3.

[0113] The preparation method of the modified layered oxide is the same as that of Example 1;

[0114] Preparation method of modified graphene Compared with Example 4, the mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 1.5:0.5; the mass ratio of GO to 2,2'-diamino-4,4'-bithiazole is 1:12.

[0115] Other conditions and steps are the same.

[0116] Example 8

[0117] The difference between this embodiment and embodiment 1 is that:

[0118] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0119] In this embodiment, modified layered oxide and Li6PS5Cl are mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent is modified graphene, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:5:3.

[0120] The preparation method of the modified layered oxide is the same as that of Example 1;

[0121] Preparation method of modified graphene Compared with Example 4, the mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 0.5:1.5; the mass ratio of GO to 2,2'-diamino-4,4'-bithiazole is 1:4.

[0122] Other conditions and steps are the same.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 1 is that:

[0125] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0126] In this embodiment, a modified layered oxide and Li6PS5Cl are uniformly mixed in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent includes modified graphene and nitrogen-doped porous carbon nanosheets, the mass ratio of modified graphene and nitrogen-doped porous carbon nanosheets is 1:0.2, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:3.6:3.

[0127] The preparation method of the modified layered oxide is the same as that of Example 1;

[0128] The preparation method of modified graphene is the same as that of Example 4.

[0129] The preparation method of nitrogen-doped porous carbon nanosheets is as follows:

[0130] Melamine cyanurate and arbutin were dispersed in an ethanol-water solution and sonicated for 10 minutes to obtain a uniform dispersion. The ethanol-water solution contained a 1:1 volume ratio of ethanol to water, a 20:1 mass ratio of melamine cyanurate to arbutin, and a mass-to-volume ratio of 1 g cyanurate to 10 mL ethanol-water solution. The dispersion was dried at 75°C. The resulting solid was ground and heated to 450°C at a rate of 5°C / min under a nitrogen atmosphere for 2 hours, followed by heating to 650°C at a rate of 5°C / min for 3 hours, and then to 1000°C at a rate of 5°C / min for 3 hours. The solution was then cooled to 25°C to obtain nitrogen-doped porous carbon nanosheets.

[0131] Other conditions and steps are the same.

[0132] Example 10

[0133] The difference between this embodiment and embodiment 1 is that:

[0134] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0135] In this embodiment, a modified layered oxide and Li6PS5Cl are uniformly mixed in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent includes modified graphene and nitrogen-doped porous carbon nanosheets, the mass ratio of modified graphene and nitrogen-doped porous carbon nanosheets is 1:0.4, and the binder is polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder is 90:4.2:3.

[0136] The preparation method of the modified layered oxide is the same as that of Example 1;

[0137] The preparation method of modified graphene is the same as that of Example 4;

[0138] The preparation method of nitrogen-doped porous carbon nanosheets is the same as that in Example 9.

[0139] Other conditions and steps are the same.

[0140] Comparative Example 1

[0141] The difference between this comparative example and Example 1 is that:

[0142] The preparation of modified layered oxides was omitted and unmodified layered oxide LiNi was directly used. 0.83 Co 0.12 Mn 0.05 O2 preparation of all-solid-state lithium batteries.

[0143] Other conditions and steps are the same.

[0144] Comparative Example 2

[0145] The difference between this comparative example and Example 1 is that:

[0146] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0147] The modified layered oxide and Li6PS5Cl were mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent was modified graphene, and the binder was polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder was 90:3:3.

[0148] The preparation method of the modified layered oxide is the same as that in Example 1.

[0149] The preparation method of modified graphene is compared with Example 4, in which benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is replaced with an equal mass of 2,2'-diamino-4,4'-bithiazole.

[0150] Other conditions and steps are the same.

[0151] Comparative Example 3

[0152] The difference between this comparative example and Example 1 is that:

[0153] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0154] The modified layered oxide and Li6PS5Cl were mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent was modified graphene, and the binder was polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder was 90:3:3.

[0155] The preparation method of the modified layered oxide is the same as that in Example 1.

[0156] The preparation method of modified graphene is compared with Example 4, in which 2,2'-diamino-4,4'-bithiazole is replaced by an equal mass of benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine.

[0157] Other conditions and steps are the same.

[0158] Comparative Example 4

[0159] The difference between this comparative example and Example 1 is that:

[0160] In the preparation of all-solid-state lithium batteries, the positive electrode materials include positive electrode main material, conductive agent and binder.

[0161] The modified layered oxide and Li6PS5Cl were mixed uniformly in a mass ratio of 7:3 to obtain a composite positive electrode main material I; the conductive agent was graphene and the binder was polyvinylidene fluoride; the mass ratio of the composite positive electrode main material I, the conductive agent, and the binder was 90:3:3.

[0162] The preparation method of the modified layered oxide is the same as that in Example 1.

[0163] Other conditions and steps are the same.

[0164] Test example

[0165] XRD test

[0166] The powder X-ray diffraction (XRD) test was performed on the positive electrode main materials obtained in Example 1 and Comparative Example 1. The results are shown in Figure 1 and Figure 2 ; The XRD refinement results of the obtained layered oxide positive electrode are shown in Table 1.

[0167] Table 1 XRD refinement results of the positive electrode main materials obtained in Example 1 and Comparative Example 1

[0168]

[0169] Combine Figure 1 and Figure 2 The XRD characteristic peaks of the composite positive electrode material I containing the modified layered oxide obtained in Example 1 are consistent with those of the positive electrode material obtained in Comparative Example 1, with no obvious impurity peaks observed. Furthermore, the diffraction peaks at (006) / (102) and (018) / (110) show significant splitting, indicating that the modification does not affect the layered structure of the layered oxide.

[0170] The refined data in Table 1 show that the a-axis value of the composite positive electrode main material I containing modified layered oxides decreases and the c-axis value increases, proving that the doped F ions effectively bond strongly with the transition metal to shorten the a-axis and expand the lithium interlayer spacing.

[0171] HRTEM characterization

[0172] The modified layered oxide material particles obtained in Example 1 were cut and thinned using a focused ion beam. The thinned particle pieces were transferred to a high-resolution transmission electron microscope for observation, and the Ni, Co, Mn, O, F, and Si elemental information of the particle pieces were collected using energy dispersive X-ray spectroscopy to intuitively characterize the distribution of doping elements within the layered oxide positive electrode particles. The results are shown in Figure 3 and Figure 4 .Depend on Figure 3 and Figure 4 The HRTEM images and energy spectrum analysis of the particle slices show that the Li 0.996Ni 0.83 Co 0.12 Mn 0.05 Si 0.004 F 0.024 O 1.976 The Si element is enriched near the surface of the particle slice, and the concentration decreases from the surface to the bulk. The F element is evenly distributed throughout the entire particle, which proves the element distribution characteristics of the modified material.

[0173] Electrochemical testing

[0174] Electrochemical tests were performed on the batteries prepared in Examples 1-10 and Comparative Examples 1-4.

[0175] The constant current charge and discharge test and cycle life test of the battery are achieved by Xinwei CT4000, and the voltage and electrochemical impedance test of the cyclic voltammetry test are achieved by Chenhua CHI760D electrochemical workstation.

[0176] The batteries obtained in Examples 1-10 and Comparative Examples 1-4 were tested for their initial charge and discharge capacities at a rate of 50C and their initial coulombic efficiencies were calculated. The results of the initial coulombic efficiency tests are shown in Table 2.

[0177] Table 2 First coulombic efficiency test results of each embodiment and comparative example

[0178]

[0179] Referring to the data in Table 2, the first coulombic efficiency of the batteries obtained in Examples 1-3 is not much different, which shows that when preparing the modified layered oxide, LiNi 0.83 Co 0.12 Mn 0.05 O2 or LiNi 0.6 Co 0.2 Mn 0.2 O2 has little effect on the first coulombic efficiency of the obtained all-solid-state lithium battery. Compared with Example 1, the first coulombic efficiency of the battery obtained in Example 2 is improved. It can be seen that when the composite positive electrode main material I containing the modified layered oxide is used to prepare the positive electrode of the all-solid-state lithium battery, the increase in the content of the modified layered oxide in the composite positive electrode main material I helps to improve the first coulombic efficiency of the obtained all-solid-state lithium battery.

[0180] Compared with Comparative Example 1, the first coulombic efficiency of the battery obtained in Example 1 is increased by 6.7%. It can be seen that, compared with the unmodified layered oxide, the use of the composite positive electrode main material I containing the modified layered oxide to prepare the positive electrode of the all-solid-state lithium battery can greatly improve the first coulombic efficiency of the obtained battery.

[0181] Compared with Example 1, the first coulombic efficiency of the batteries obtained in Examples 4-10 and Comparative Examples 2-4 increased by 8.1%, 9.6%, 11.0%, 5.8%, 6.8%, 13.6%, 14.6%, 5.3%, 6.4%, and 2.8%, respectively. Compared with Comparative Example 4, the first coulombic efficiency of the batteries obtained in Examples 4-10 and Comparative Examples 2-3 increased by 5.2%, 6.5%, 7.9%, 2.9%, 3.9%, 10.4%, 11.5%, 2.4%, and 3.4%, respectively. It can be seen that in the process of preparing the positive electrode of an all-solid-state lithium battery, the use of a composite positive electrode main material I containing a modified peroxide and combined with a conductive agent modified graphene can improve the first coulombic efficiency of the resulting battery. In particular, in the preparation process of the modified graphene, when the mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 1:1, the first coulombic efficiency of the resulting battery can be significantly improved. The first coulombic efficiency of the batteries obtained in Examples 4-6 is on an upward trend. It can be seen that in the process of preparing the positive electrode of an all-solid-state lithium battery, increasing the amount of modified graphene as a conductive agent within a certain range helps to improve the first coulombic efficiency of the resulting battery.

[0182] Combined with the data of Example 4 and Examples 7-8, it can be seen that the use of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine in combination to modify graphene oxide, and the obtained modified graphene is used to prepare an all-solid-state lithium battery, the usage ratio of the two has an impact on the first coulombic efficiency of the obtained all-solid-state lithium battery. When the two are used together, the amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are equivalent, and the first coulombic efficiency of the resulting all-solid-state lithium battery is more significantly improved than that of using graphene as a conductive agent. When the amount of 2,2'-diamino-4,4'-bithiazole or the amount of benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is relatively high, the first coulombic efficiency of the resulting all-solid-state lithium battery is also improved compared to that of using graphene as a conductive agent. However, compared to using equivalent amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine when modifying graphene oxide, the first coulombic efficiency of the resulting all-solid-state lithium battery is relatively lower.

[0183] Combined with the data of Comparative Examples 2-3, it can be seen that compared with the modified graphene obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bithiazole alone or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine alone; 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are used in combination to modify graphene oxide, and the obtained modified graphene is used for the composite positive electrode main material I and to prepare the positive electrode of the all-solid-state lithium battery, and the first coulombic efficiency of the obtained all-solid-state lithium battery is significantly improved.

[0184] Compared to Example 4, the first coulombic efficiency of the batteries obtained in Examples 9 and 10 increased by 5.0% and 6.0%, respectively. This indicates that, in the preparation of all-solid-state lithium batteries, the use of a composite cathode material I containing a modified peroxide and the use of a composite of modified graphene and nitrogen-doped porous carbon nanosheets as a conductive agent can further improve the first coulombic efficiency of the resulting battery. Furthermore, within a certain range, the first coulombic efficiency of the resulting all-solid-state lithium battery is positively correlated with the amount of nitrogen-doped porous carbon nanosheets used.

[0185] For the batteries prepared in Examples 1-10 and Comparative Examples 1-4, the battery capacity was obtained by charging to 4.0 V at a constant current and constant voltage of 0.5 C and discharging to 1.5 V at 0.5 C. The weight of the battery cell was measured with a balance, and the energy density of the battery cell was calculated. The positive electrode energy density test results are shown in Table 3.

[0186] Table 3 Test results of positive electrode energy density of various embodiments and comparative examples

[0187]

[0188] Referring to the data in Table 3, the positive electrode energy densities of the batteries obtained in Examples 1-3 are not much different, which shows that when preparing the modified layered oxide, LiNi 0.83 Co 0.12 Mn 0.05 O2 or LiNi 0.6 Co 0.2 Mn 0.2 O2 has little effect on the positive electrode energy density of the obtained all-solid-state lithium battery. Compared with Example 1, the positive electrode energy density of the battery obtained in Example 2 is improved. It can be seen that when the composite positive electrode main material I containing the modified layered oxide is used to prepare the positive electrode of the all-solid-state lithium battery, the increase in the content of the modified layered oxide in the composite positive electrode main material I helps to improve the positive electrode energy density of the obtained all-solid-state lithium battery.

[0189] Compared with Comparative Example 1, the first coulombic efficiency of the battery obtained in Example 1 is increased by 18.7%. It can be seen that, compared with the unmodified layered oxide, the positive electrode energy density of the battery can be greatly improved by using the composite positive electrode main material I containing the modified layered oxide to prepare the positive electrode of the all-solid-state lithium battery.

[0190] Compared with Example 1, the positive electrode energy density of the batteries obtained in Examples 4-10 and Comparative Examples 2-4 increased by 10.8%, 13.2%, 15.1%, 6.6%, 9.6%, 16.9%, 19.3%, 5.4%, 7.8%, and 4.2%, respectively. Compared with Comparative Example 4, the positive electrode energy density of the batteries obtained in Examples 4-10 and Comparative Examples 2-3 increased by 6.4%, 8.7%, 10.4%, 2.3%, 5.2%, 12.1%, 14.4%, 1.2%, and 3.5%, respectively. It can be seen that in the process of preparing the positive electrode of an all-solid-state lithium battery, the use of a composite positive electrode main material I containing a modified peroxide and combined with a conductive agent modified graphene can improve the positive electrode energy density of the resulting battery. In particular, in the preparation process of the modified graphene, when the mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 1:1, the positive electrode energy density of the resulting battery can be significantly improved. The positive electrode energy density of the batteries obtained in Examples 4-6 is on an upward trend. It can be seen that in the process of preparing the positive electrode of an all-solid-state lithium battery, increasing the amount of modified graphene as a conductive agent within a certain range helps to improve the positive electrode energy density of the resulting battery.

[0191] Combined with the data of Example 4 and Examples 7-8, it can be seen that the use of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine in combination to modify graphene oxide, and the obtained modified graphene is used to prepare an all-solid-state lithium battery, the usage ratio of the two has an impact on the positive electrode energy density of the obtained all-solid-state lithium battery. When the two are used together, the amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are equivalent, and the positive electrode energy density of the resulting all-solid-state lithium battery is more significantly improved than that of using graphene as a conductive agent. When the amount of 2,2'-diamino-4,4'-bithiazole or the amount of benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is relatively high, the positive electrode energy density of the resulting all-solid-state lithium battery is also improved compared to that of using graphene as a conductive agent. However, compared to using equivalent amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine when modifying graphene oxide, the positive electrode energy density of the resulting all-solid-state lithium battery is relatively reduced.

[0192] Combined with the data of Comparative Examples 2-3, it can be seen that compared with the modified graphene obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bithiazole alone or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine alone; 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are used in combination to modify graphene oxide, and the obtained modified graphene is used for the composite positive electrode main material I and to prepare the positive electrode of the all-solid-state lithium battery, and the energy density of the positive electrode of the obtained all-solid-state lithium battery is significantly improved.

[0193] Compared to Example 4, the positive electrode energy density of the batteries obtained in Examples 9 and 10 increased by 5.4% and 7.6%, respectively. This indicates that, in the preparation of all-solid-state lithium batteries, the use of a composite positive electrode material I containing a modified peroxide and the use of a composite of modified graphene and nitrogen-doped porous carbon nanosheets as a conductive agent can further improve the positive electrode energy density of the resulting battery. Furthermore, within a certain range, the positive electrode energy density of the resulting all-solid-state lithium battery is positively correlated with the amount of nitrogen-doped porous carbon nanosheets used.

[0194] For the batteries prepared in Examples 1-10 and Comparative Examples 1-4, the cycle performance was tested for 150 cycles using a 1C rate charge / discharge test. The SEM morphology results of the positive electrode sheets obtained in Example 1 and Comparative Example 1 after the cycles are shown in Table 1. Figure 5 and Figure 6 ;contrast Figure 5 and Figure 6 As can be seen from the scanning electron microscope morphology of the positive electrode sheet containing the modified layered oxide after cycling in Example 1, it exhibits lower interfacial impedance, fewer interfacial side reactions, and less particle cracking, demonstrating that the modified layered oxide improves mechanical stability, interfacial stability, structural stability, and lithium-ion transport kinetics. Capacity retention test results are shown in Table 4.

[0195] Table 4 Capacity retention test results of each embodiment and comparative example after 150 cycles

[0196]

[0197] Referring to the data in Table 4, the capacity retention rates of the batteries obtained in Examples 1-3 after 150 cycles are similar, which shows that when preparing the modified layered oxide, LiNi 0.83 Co 0.12 Mn 0.05 O2 or LiNi 0.6 Co 0.2 Mn 0.2O2 has little effect on the capacity retention rate of the obtained all-solid-state lithium battery. Compared with Example 1, the capacity retention rate of the battery obtained in Example 2 is improved. It can be seen that when the composite positive electrode main material I containing the modified layered oxide is used to prepare the positive electrode of the all-solid-state lithium battery, the increase in the content of the modified layered oxide in the composite positive electrode main material I helps to improve the capacity retention rate of the obtained all-solid-state lithium battery.

[0198] Compared with Comparative Example 1, the capacity retention rate of the battery obtained in Example 1 after 150 cycles is increased by 11.2%. It can be seen that, compared with the unmodified layered oxide, the use of the composite positive electrode main material I containing the modified layered oxide to prepare the positive electrode of the all-solid-state lithium battery can greatly improve the capacity retention rate of the obtained battery.

[0199] Compared to Example 1, the capacity retention rates of the batteries obtained in Examples 4-10 and Comparative Examples 2-4 after 150 cycles increased by 9.8%, 11.2%, 13.2%, 5.8%, 7.4%, 15.4%, 16.7%, 5.9%, 7.3%, and 3.8%, respectively. Compared to Comparative Example 4, the capacity retention rates of the batteries obtained in Examples 4-10 and Comparative Examples 2-3 after 150 cycles increased by 5.8%, 7.1%, 9.1%, 2.0%, 3.5%, 11.2%, 12.5%, 2.1%, and 3.4%, respectively. This indicates that, in the preparation of the positive electrode for an all-solid-state lithium battery, the use of a composite positive electrode material I containing a modified peroxide in combination with conductive agent-modified graphene can significantly improve the capacity retention rate of the resulting battery. The capacity retention rates of the batteries obtained in Examples 4-6 are on an upward trend. It can be seen that in the process of preparing the positive electrode of the all-solid-state lithium battery, increasing the amount of modified graphene as a conductive agent within a certain range is helpful to improve the capacity retention rate of the obtained battery.

[0200] Combined with the data of Example 4 and Examples 7-8, it can be seen that the use of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine in combination to modify graphene oxide, and the obtained modified graphene is used to prepare an all-solid-state lithium battery, the usage ratio of the two has an impact on the capacity retention rate of the obtained all-solid-state lithium battery after 150 cycles. When the two are used together, the amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are equivalent, and the capacity retention rate of the resulting all-solid-state lithium battery is more significantly improved than that of using graphene as a conductive agent. When the amount of 2,2'-diamino-4,4'-bithiazole or the amount of benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is relatively high, the capacity retention rate of the resulting all-solid-state lithium battery is also improved compared to that of using graphene as a conductive agent. However, compared to the use of equivalent amounts of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine when modifying graphene oxide, the capacity retention rate of the resulting all-solid-state lithium battery is relatively lower.

[0201] Combined with the data of Comparative Examples 2-3, it can be seen that compared with the modified graphene obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bithiazole alone or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine alone; 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are used in combination to modify graphene oxide, and the obtained modified graphene is used for the composite positive electrode main material I and to prepare the positive electrode of the all-solid-state lithium battery, and the capacity retention rate of the obtained all-solid-state lithium battery is significantly improved.

[0202] Compared to Example 4, the capacity retention rates of the batteries obtained in Examples 9 and 10 after 150 cycles increased by 5.1% and 6.3%, respectively. This indicates that, in the preparation of all-solid-state lithium batteries, the use of a composite cathode material I containing a modified peroxide and the use of a composite of modified graphene and nitrogen-doped porous carbon nanosheets as a conductive agent can further improve the initial coulombic efficiency of the resulting battery. Furthermore, within a certain range, the capacity retention rate of the resulting all-solid-state lithium battery is positively correlated with the amount of nitrogen-doped porous carbon nanosheets used.

[0203] The conventional operations in the operating steps of the present invention are well known to those skilled in the art and will not be described in detail here.

[0204] The embodiments described above provide a detailed description of the technical solutions of the present invention. However, it should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications or substitutions that a person skilled in the art could readily conceive within the technical scope disclosed herein are intended to fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A modified layered oxide, wherein the modified layered oxide is a layered oxide co-doped with anions and cations, and its general chemical formula is Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b ,in, 0 < a ≤ 0.08, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, x and y are not simultaneously 0, and 0 < b ≤ 0.2; M is selected from Si and is derived from a fluorine-containing weak acid material; in the anion-cation co-doped layered oxide, due to different solubilities of the doped anions and cations in the layered oxide lattice structure, the doped M cations with lower solubility tend to be enriched at a depth of 3 to 100 nm near the surface, the ion concentration decreases from the surface to the bulk, and the fluoride anions are uniformly distributed within the bulk; The method for preparing the modified layered oxide comprises: S1. The layered oxide powder and a weak acid solution are added to deionized water, stirred and mixed, and an acid-base reaction is performed; the surface of the layered oxide powder is LiOH and / or Li2CO3; the weak acid is H c MF d , where 0< c ≤2, 0 < d ≤6, and M is Si; S2. The mixed solution obtained in step S1 is vacuum dried to obtain a powder containing an inorganic layer of M and F elements; the obtained powder containing an inorganic layer of M and F elements is calcined to obtain a modified layered oxide.

2. A method for preparing a modified layered oxide, characterized in that: The following steps are involved: S1. The layered oxide powder and a weak acid solution were added to deionized water, stirred and mixed, and an acid-base reaction was performed; the surface of the layered oxide powder was LiOH and / or Li2CO3, S2. The mixed solution obtained in step S1 is vacuum dried to obtain a powder containing M and F elements coated with an inorganic layer; the obtained powder containing M and F elements coated with an inorganic layer is calcined to obtain a modified layered oxide; In step S1, the weak acid is H c MF d , wherein 0< c ≤ 2, 0 < d ≤ 6, M is Si; the molar ratio of the amount of substance of the M cation in the weak acid to the total amount of substance of the transition metal element in the layered oxide is 0.02 to 0.08: 1; In step S2, the modified layered oxide has a chemical formula of Li 1-a Ni x Co y Mn 1-x-y M a O 2-b F b , where 0< a≤0.08, 0 ≤ x≤ 1, 0 ≤ y≤ 1, x and y are not 0 at the same time, and 0 < b≤ 0.

2.

3. The method for preparing a modified layered oxide according to claim 2, wherein: In step S2, the vacuum drying temperature is 80-130°C and the drying time is 8-24 hours; In step S2, the calcination atmosphere is one of oxygen, air and pure argon, the calcination temperature is 200-700°C, the heating rate is 1-30°C / min, and the calcination time is 1-20 h.

4. An all-solid-state lithium battery comprising a positive electrode, a negative electrode and an intermediate layer electrolyte; characterized in that: The positive electrode includes a positive electrode material, the positive electrode material includes a positive electrode main material, the positive electrode main material includes a modified layered oxide prepared by the preparation method according to claim 2 or 3; the negative electrode is a lithium indium alloy; the intermediate layer electrolyte is Li6PS5Cl, Li 10 GeP2S 12 、Li 10 SnP2S 12 One of them.

5. The all-solid-state lithium battery according to claim 4, characterized in that: The positive electrode material also includes a conductive agent and a binder, and the mass ratio of the positive electrode main material, the conductive agent, and the binder is 85-95:3-10:2-5; The binder is one or more of polyvinylidene fluoride, polyimide, carboxymethyl cellulose, and sodium alginate; the conductive agent is one or more of Super P, acetylene black, Ketjen black, conductive carbon black, carbon nanotubes, graphene, and modified graphene; the modified graphene is obtained by carbonizing amino-modified graphene oxide, and the amino-modified graphene oxide is obtained by modifying graphene oxide with 2,2'-diamino-4,4'-bithiazole and / or benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine.

6. The all-solid-state lithium battery according to claim 5, characterized in that: The preparation method of the modified graphene comprises the following steps: Graphene oxide is mixed with N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and anhydrous DMF is added under a nitrogen atmosphere, and the mixture is stirred for activation; then, 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine are added, and the mixture is stirred for reaction for 8-24 hours under a nitrogen atmosphere. After the reaction is completed, the solid product is collected by centrifugation, washed with deionized water, and then dried to obtain amino-modified graphene oxide; the obtained amino-modified graphene oxide is carbonized to obtain modified graphene.

7. The all-solid-state lithium battery according to claim 6, characterized in that: The mass ratio of graphene oxide to N-hydroxysuccinimide is 1:1-3; The mass ratio of N-hydroxysuccinimide to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1:0.5-2; The mass volume ratio of graphene oxide to anhydrous DMF is 5-15 mg:3 mL.

8. The all-solid-state lithium battery according to claim 6, characterized in that The mass ratio of 2,2'-diamino-4,4'-bithiazole and benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diamine is 0.5-2:0.5-2; The mass ratio of graphene oxide to 2,2'-diamino-4,4'-bithiazole is 1:2-20.

9. An electric vehicle, characterized in that: An all-solid-state lithium battery comprising any one of claims 4 to 8.

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