Graphene composite solid electrolyte and all-solid-state lithium metal battery
By coating the surface of the sulfide solid electrolyte with a multilayer graphene oxide coating, the interfacial compatibility problem between the sulfide electrolyte and the positive and negative electrode materials is solved, improving the cycle performance and safety performance of the lithium-ion battery and inhibiting the growth of lithium dendrites.
Patent Information
- Application Number
- CN202511308140.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-15
- Publication Date
- 2025-12-12
AI Technical Summary
Existing sulfide solid electrolytes have poor interfacial compatibility with positive and negative electrode materials, high interfacial impedance, and are prone to lithium dendrite formation. Polymer electrolytes have low ionic conductivity and insufficient mechanical strength, and cannot effectively suppress lithium dendrite formation.
A multilayer graphene oxide coating is applied to the surface of a sulfide solid electrolyte to construct ion transport channels, improve the lithium-ion diffusion coefficient, enhance mechanical strength, provide high lithium affinity, and inhibit lithium dendrite growth.
The cycle performance and safety performance of lithium-ion batteries are improved by using a multi-layer graphene oxide coating to improve the interfacial compatibility between sulfides and lithium metal anodes, enhance the mechanical strength of the battery, and suppress the growth of lithium dendrites.
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Figure CN121123376A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of secondary battery solid electrolyte, and particularly relates to a graphene composite solid electrolyte and a full-solid-state lithium metal battery. BACKGROUND
[0002] Lithium ion batteries are widely used in communication devices, energy storage systems and electric vehicles due to their high energy density and long cycle life. However, in the context of life safety such as vehicles, battery safety is crucial. The conventional liquid electrolyte lithium battery uses flammable organic solvents, which have low flash point and strong volatility, and are extremely easy to cause thermal runaway under thermal abuse, mechanical abuse or electrical abuse, resulting in battery fire or explosion.
[0003] Solid-state batteries use solid electrolytes to replace liquid electrolytes, which fundamentally eliminate the risk of solvent flammability and significantly improve safety. Among them, sulfide solid electrolytes are considered as the ideal choice for full-solid-state batteries due to their high ionic conductivity and good mechanical flexibility. However, sulfide electrolytes still face severe challenges in practical applications: the physical contact between sulfide electrolytes and positive and negative electrode materials is poor, the interface impedance is high, and lithium dendrites are easily formed between sulfide and metal lithium negative electrode during charging and discharging. To improve the interface compatibility, the conventional solution is to coat a polymer layer on the surface of the sulfide electrolyte. However, this strategy has significant defects: the ionic conductivity of the polymer electrolyte is low, the mechanical strength of the composite electrolyte layer is insufficient, and lithium dendrites cannot be effectively inhibited. SUMMARY
[0004] To solve the problems of the prior art, the application provides a graphene composite solid electrolyte and a full-solid-state lithium metal battery. The application provides a multi-layer graphene oxide coating to improve the lithium affinity, improve the interface compatibility between sulfide and lithium metal negative electrode, enhance the mechanical strength, and improve the cycle stability, thereby improving the safety performance and cycle performance of the secondary battery.
[0005] To achieve the above purpose, the application adopts the following technical solutions:
[0006] A graphene composite solid electrolyte, comprising a sulfide solid electrolyte and a graphene coating, wherein the graphene coating is a multi-layer graphene oxide coating, and the interlayer spacing of the graphene oxide is 5-20 angstroms.
[0007] The thickness of the multi-layer graphene oxide coating is 3-10 microns.
[0008] The solid electrolyte material layer is selected from Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12Li6PS5Cl, Li6PS5Br, Li6PS5I, Li6PS5ClBr, Li 10 SnP2S 12 Li7GePS8.
[0009] The multilayer graphene oxide coating is disposed on the negative side surface of the sulfide solid electrolyte material layer.
[0010] The multilayer graphene oxide coating is prepared by coating a multilayer graphene oxide slurry, wherein the mass ratio of multilayer graphene oxide to binder is 80-90:10-20.
[0011] The graphene composite solid electrolyte, wherein the preparation method of the multilayer graphene oxide slurry comprises the following steps:
[0012] S1, stirring and mixing graphene oxide, dispersant and deionized water, ultrasonic dispersion to obtain a first mixture;
[0013] S2, coating the first mixture in S1 on a polymer substrate film, and then drying and peeling to obtain a multilayer graphene oxide film;
[0014] S3, crushing the multilayer graphene oxide film obtained in S2, and dispersing in NMP with a binder to obtain a multilayer graphene oxide slurry.
[0015] The sheet diameter D50 of graphene in the multilayer graphene oxide slurry is 0.5-30 μm.
[0016] The graphene composite solid electrolyte, wherein the preparation method of the graphene composite solid electrolyte comprises the following steps:
[0017] S1, pressing sulfide powder to obtain a sulfide solid electrolyte film;
[0018] S2, coating the multilayer graphene oxide slurry on the surface of the sulfide electrolyte film in S1, and vacuum drying to obtain a composite solid electrolyte.
[0019] A full solid-state lithium metal battery comprising the composite solid electrolyte of claim 1.
[0020] Compared with the prior art, the beneficial effects of the application are: (1) the multilayer graphene oxide coating prepared by the application adopts a multilayer graphene oxide coating to construct an ion transmission channel, improve the lithium ion diffusion coefficient, inhibit dendrite growth and isolate the sulfide electrolyte from contact with metal lithium, and improve the cycle performance.
[0021] (2) The multilayer graphene oxide coating prepared by the method has a large number of oxygen-containing functional groups on the surface of the multilayer graphene oxide coating, can form strong binding sites with lithium ions through electrostatic action, provides high lithium affinity, reduces the lithium nucleation energy barrier, guides uniform deposition of lithium ions, reduces dendrite growth, and improves the cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS
[0022] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings.
[0023] Figure 1 SEM image of the multilayer graphene oxide film prepared for Example 1.
[0024] Figure 2 XRD patterns of graphene oxides with different layer spacings. DETAILED DESCRIPTION
[0025] The embodiments of the application will be described in detail below with reference to the accompanying drawings, but those skilled in the art will understand that the following embodiments are only used to illustrate the application and should not be regarded as limiting the scope of the application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are conventional products that can be purchased on the market.
[0026] The application provides a graphene coating sulfide solid electrolyte and a preparation method thereof, to reduce the generation of lithium dendrites, thereby effectively improving the cycle stability of the all-solid-state lithium metal battery at high rate.
[0027] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:
[0028] The application provides a preparation method of a multilayer graphene oxide coating, comprising the following steps:
[0029] S1, coating the graphene oxide slurry on a polymer substrate film, drying at 50 DEG C for 24 hours to obtain a multilayer graphene oxide film; wherein the polymer substrate film comprises at least one of PET film, PP film, PE film, PE film, PEN film, PEEK film, PI film, PPS film, preferably the polymer substrate film is PET film.
[0030] The drying process parameters are: drying at 45-60 DEG C for 12-36 hours, preferably drying at 45-55 DEG C for 18-30 hours.
[0031] The interlayer spacing of the multi-layer graphene oxide film is 5-20 angstroms, preferably, the interlayer spacing is 6-18 angstroms, for example, can be 7 angstroms, 8 angstroms, 10 angstroms, 12 angstroms, 15 angstroms, etc.
[0032] S2, crushing the multi-layer graphene oxide film in S1, mixing with the binder and NMP uniformly to obtain a multi-layer graphene oxide slurry.
[0033] Further, the fragment size D50 of the multi-layer graphene oxide film after crushing is 0.5-30 μm, preferably 1-25 μm, and more preferably 5-20 μm.
[0034] Further, the mass ratio between the multi-layer graphene oxide film after crushing and the binder is 80-90:10-20.
[0035] In another aspect, the application provides a preparation method of a composite sulfide solid-state electrolyte, comprising the following steps:
[0036] S1, pressing the sulfide solid-state electrolyte into a solid-state electrolyte film;
[0037] S2, coating the multi-layer graphene oxide-NMP slurry on the surface of the solid-state electrolyte negative electrode side in S1, and vacuum drying to obtain a composite sulfide solid-state electrolyte.
[0038] The specific embodiments of the application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the application, and are not used to limit the application.
[0039] Example 1:
[0040] Preparation of multi-layer graphene oxide coating:
[0041] (1) 15 g of graphene oxide was weighed and dispersed in water to obtain a graphene oxide dispersion;
[0042] (2) The graphene oxide dispersion and 0.15 g of PVP were added to 50 ml of deionized water and stirred for 4 h, and then ultrasonic dispersed for 2 h. After standing, a coating slurry (solid content of 2.5 wt%) was obtained;
[0043] (3) The coating slurry was coated onto a PET film using a coating machine, and then dried at 50°C for 12 h to obtain a multi-layer graphene oxide film with a thickness of about 2.5 μm (as shown in Figure 1 ), and the interlayer spacing of the multi-layer graphene oxide was 7.7 angstroms (as shown in Figure 2 );
[0044] (4) The multi-layer graphene oxide film is crushed into fragments with a particle size D50 of 15 μm, and then mixed and dispersed in NMP at a mass ratio of multi-layer graphene oxide to PVDF of 90:10 to obtain a multi-layer graphene oxide slurry.
[0045] Preparation of the positive electrode sheet:
[0046] NCM811 is used as the active material, LATP is used as the solid-state electrolyte, Super P is used as the conductive agent, and PVDF is used as the binder. The mass ratio of the active material, LATP, Super P, and PVDF is 92:2:3:3. The active material, Super P, and 5% PVDF@NMP solution are fully mixed and stirred in proportion to obtain a positive electrode slurry. Finally, the positive electrode slurry is uniformly coated on an aluminum foil, and after drying and cold pressing processes, a positive electrode sheet is obtained.
[0047] Preparation of the solid-state electrolyte:
[0048] The sulfide solid-state electrolyte is used as the main material, the sulfide powder is pressed to obtain a sulfide electrolyte film, and then the multi-layer graphene oxide slurry is uniformly coated on the solid-state electrolyte. After drying treatment, a composite solid-state electrolyte is obtained, and the thickness of the multi-layer graphene oxide coating in the obtained composite electrode sheet is 4.5 μm.
[0049] Preparation of the lithium metal battery:
[0050] The above positive electrode sheet, sulfide solid-state electrolyte, and metal lithium sheet are stacked in sequence, so that the composite sulfide solid-state electrolyte is located between the positive electrode sheet and the negative electrode sheet (metal lithium sheet) to play a role of isolation. Then, the aluminum plastic film is wrapped, transferred to a vacuum oven for drying at 60°C, and then sealed. The soft package battery is obtained by formation at 0.1C current under a pressure of 2.0 MPa at 60°C.
[0051] Example 2:
[0052] Similar to Example 1, except that the sulfide solid-state electrolyte LPSC is adjusted to LGPS.
[0053] Example 3:
[0054] Similar to Example 1, except that NCM811 is adjusted to lithium iron phosphate.
[0055] Example 4:
[0056] Similar to Example 1, except that the thickness of the multi-layer graphene oxide coating is adjusted to 2 μm.
[0057] Example 5:
[0058] Similar to Example 1, except that the thickness of the multi-layer graphene oxide coating is adjusted to 10 μm.
[0059] Example 6:
[0060] Similar to Example 1, except that the particle size D50 of the multi-layer graphene oxide film was controlled at ~10 pm.
[0061] Example 7:
[0062] Similar to Example 1, except that the interlayer spacing of the multi-layer graphene oxide film was adjusted to 12.2 angstroms by adding 10% diethylene triamine to the graphene oxide dispersion.
[0063] Example 8:
[0064] Similar to Example 1, except that the interlayer spacing of the multi-layer graphene oxide film was adjusted to 18.3 angstroms by adding 10% hexadecyl trimethyl ammonium bromide to the graphene oxide dispersion.
[0065] Comparative Example 1:
[0066] Similar to Example 1, except that there was no multi-layer graphene oxide coating.
[0067] Comparative Example 2:
[0068] Similar to Example 1, except that the multi-layer graphene oxide in the coating was heat treated at high temperature, and the interlayer spacing was changed to 3.35 angstroms.
[0069] Performance Test
[0070] Electrochemical performance tests were performed on the lithium metal batteries obtained by the preparation methods of Examples 1-8 and Comparative Examples 1-2. Each group of tests was tested in parallel for 3 cells, and the average of the test results of the 3 cells was taken as the final result, which is recorded in Table 1.
[0071] 1. Capacity test: In a 25°C constant temperature box, first use a current of 0.33C to charge the battery to the upper limit voltage (NCM811 full charge to 4.4V, lithium iron phosphate full charge to 3.65V), then constant voltage charge to 0.05C cut-off, then discharge the battery to 2.8V with a current of 0.33C, record the cumulative charge output during the discharge process, which is the initial 0.33C discharge capacity, and calculate the specific capacity C1 based on the positive active material C1(mAh / g)=(0.33C discharge capacity / positive active material mass) x 100%;
[0072] 2. Rate discharge test: in a 25℃ constant temperature box, using 0.33C current to charge to the upper limit voltage (NCM811 full charge to 4.4V, lithium iron phosphate full charge to 3.65V), then constant voltage charge to 0.05C cut-off, then discharge to 2.8V with 1.5C current, and calculate the specific capacity C2 based on the positive active material, specific capacity C2(mAh / g)=(1.5C discharge capacity / positive active material mass) x 100%, then calculate the 1.5C discharge capacity retention rate, retention rate=(1.5C discharge specific capacity C2 / 0.33C discharge specific capacity C1) x 100%;
[0073] 3. Cycle test: in a 25℃ constant temperature box, repeat using 0.33C current to charge to the upper limit voltage, then constant voltage charge to 0.05C, 0.33C current discharge to 2.8V, cycle, record the discharge capacity of the 1st cycle as Q1 and the discharge capacity of the n th cycle as Qn, calculate the discharge capacity retention rate of the n th cycle (%)=(Qn / Q1) x 100%, record the cycle number n when the cycle capacity retention rate is 80%; Table 1 is the electrochemical performance of lithium metal batteries of examples and comparative examples. n n , calculate the discharge capacity retention rate of the n th cycle (%)=(Qn / Q1) x 100%, record the cycle number n when the cycle capacity retention rate is 80%; Table 1 is the electrochemical performance of lithium metal batteries of examples and comparative examples.
[0074] Table 1
[0075]
[0076] From Table 1, it can be seen that:
[0077] The full solid-state batteries assembled based on the graphene composite solid-state electrolyte provided by examples 1-8 all show better charge and discharge performance, realizing high specific capacity and long cycle life.
[0078] From examples 1, 2, 3 and comparative example 1, it can be seen that the surface of the sulfide solid-state electrolyte coated with a graphene coating can significantly improve the rapid charge and discharge performance of the battery, and improve the long cycle life, which benefits from the rapid ion transmission channel provided by the multi-layer graphene oxide coating, significantly reducing polarization, avoiding lithium precipitation, and reducing side reactions.
[0079] From examples 1, 4, 5, it can be seen that the thickness of the multi-layer graphene oxide coating has a significant effect on the performance, too thick coating will reduce the specific capacity, and also has an adverse effect on the charge and discharge performance, and too thin coating is difficult to realize in the processing process.
[0080] From examples 1, 7, 8 and comparative example 2, it can be seen that the interlayer spacing of the multi-layer graphene oxide has a significant effect on the performance, and a suitable interlayer spacing can construct an ion rapid channel, which is beneficial to ion transmission, and without interlayer structure or too small interlayer spacing, the ion channel cannot be constructed, and the existence of the coating hinders ion transmission.
[0081] The embodiments are only illustrative of the present application, and are not intended to limit the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.
Claims
1. A graphene composite solid-state electrolyte, characterized by, The sulfide solid electrolyte comprises a graphene coating, and the graphene coating is a multilayer graphene oxide coating, and the interlayer spacing of the graphene oxide is 5-20 angstroms.
2. The graphene composite solid-state electrolyte of claim 1, wherein, The thickness of the multilayer graphene oxide coating is 3-10 microns.
3. The graphene composite solid-state electrolyte of claim 1, wherein, The solid-state electrolyte material layer is selected from Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , Li6PS5CI, Li6PS5Br, Li6PS5I, Li6PS5CI Br, Li 10 SnP2S 12 , Li7GePS8 or a mixture of one or several of these.
4. The graphene composite solid-state electrolyte of claim 1, wherein, The multilayer graphene oxide coating is arranged on the negative side surface of the sulfide solid electrolyte material layer.
5. The graphene composite solid-state electrolyte of claim 1, wherein, The multilayer graphene oxide coating is prepared by coating a multilayer graphene oxide slurry, and the mass ratio of multilayer graphene oxide to binder is 80-90:10-20.
6. The graphene composite solid-state electrolyte of claim 5, wherein, A preparation method of a multilayer graphene oxide slurry comprises the following steps: S1, stirring and mixing graphene oxide, a dispersing agent and deionized water, and ultrasonic dispersion to obtain a first mixture; S2, coating the first mixture in S1 on a polymer substrate film, and then drying and peeling to obtain a multilayer graphene oxide film; S3, crushing the multilayer graphene oxide film obtained in S2, and dispersing in NMP with a binder to obtain a multilayer graphene oxide slurry.
7. The graphene composite solid-state electrolyte of claim 6, wherein, The flake diameter D50 of graphene in the multilayer graphene oxide slurry is 0.5-30 microns.
8. The graphene composite solid-state electrolyte of claim 1, wherein, A preparation method of a graphene composite solid electrolyte comprises the following steps: S1, pressing sulfide powder to obtain a sulfide solid electrolyte film; S2, coating a multilayer graphene oxide slurry on the surface of the sulfide electrolyte film in S1, and vacuum drying to obtain a composite solid electrolyte.
9. An all-solid-state lithium metal battery, characterized by, The composite solid electrolyte comprises the graphene composite solid electrolyte.