A hybrid ionic conductor layer for a lithium metal negative electrode, a preparation method thereof, and a full solid-state battery

Abstract

The application discloses a kind of mixed ionic conductor layer for lithium metal negative electrode and its preparation method and full solid battery, belong to sulfide full solid battery technical field.By liquid phase synthesis sulfide electrolyte 70 (0.75Li2S-0.25P2S5) -30LiI, in the process of preparing electrolyte, introduce graphene oxide and lithium salt precursor 2,5-dihydroxy-1,4-lithium benzene diphosphate, after heat treatment and pressing can obtain mixed ionic conductor layer;Wherein graphene oxide can isolate sulfide electrolyte layer and lithium metal negative electrode, avoids interface reaction, and the unique porous and interlayer structure provides lateral growth space for lithium metal deposition.Graphene interlayer lithium diphosphate-based MOF ensures the fast movement of lithium ion, enhances the lithium body diffusion of negative electrode end, reduces local current density and plays the role of dredging lithium ion distribution, significantly the cycle life of sulfide full solid battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sulfide all-solid-state batteries, and particularly relates to a mixed ion conductor layer for a lithium metal negative electrode, a preparation method thereof and an all-solid-state battery. BACKGROUND

[0002] There is an urgent need for secondary batteries with high safety and higher energy density in large-scale energy storage devices and electric vehicle applications. All-solid-state batteries using non-flammable solid-state electrolytes are expected to fundamentally solve the safety problem and improve the energy density, and are one of the ideal next-generation energy storage devices.

[0003] For example, the invention with the publication number CN118156593A discloses a sulfide solid-state electrolyte film, a preparation method and application thereof. The sulfide solid-state electrolyte film is composed of an ion-conducting polymer binder and a sulfide solid-state electrolyte, and the sulfide solid-state electrolyte is uniformly wrapped by the ion-conducting polymer binder. Organic polymer A, lithium salt B and ionic liquid C are added to organic solvent D for mixing to obtain a uniform solution, and then the organic solvent is dried to remove the organic solvent to obtain the ion-conducting polymer binder. The organic polymer A is a thermoplastic polymer electrolyte with a melting range of 40-140 DEG C. The chemical structure of the organic polymer A has a polar group. The sulfide solid-state electrolyte powder and the ion-conducting polymer binder are mixed and then a dry process is used to obtain the sulfide solid-state electrolyte film.

[0004] For another example, the invention with the publication number CN114914422A also discloses a composite negative electrode suitable for sulfide all-solid-state batteries, a preparation method and a lithium battery. The composite negative electrode includes a mixture of a sulfide solid-state electrolyte and an inert protective layer type core-shell lithium alloying negative electrode. The preparation method includes: first sintering lithium-storing metal and metal lithium at a proper ratio to obtain a pre-lithiated lithium alloying negative electrode material; ball milling the pre-lithiated lithium alloying negative electrode for granulation treatment; uniformly mixing and dispersing the granulated pre-lithiated lithium alloying negative electrode and the sulfide solid-state electrolyte at a proper ratio to obtain a composite negative electrode precursor; and placing the composite negative electrode precursor in an oxygen atmosphere for second sintering to obtain the required composite negative electrode.

[0005] However, there are still some challenges in using sulfide solid-state electrolytes, mainly including: (1) the electrolyte reacts with lithium metal, and the production of interface products increases the interface resistance and leads to low storage efficiency; (2) lithium dendrites can grow along the pores, cracks and grain boundaries inside the sulfide solid-state electrolyte, and eventually penetrate the entire electrolyte, leading to battery failure. Therefore, developing a new type of lithium metal negative electrode protective layer has become the current research focus. SUMMARY

[0006] Based on the deficiencies in the prior art, the application provides a mixed ion conductor layer for a lithium metal negative electrode, a preparation method thereof and a full solid-state battery, a sulfide electrolyte 70 (0.75Li2S-0.25P2S5)-30LiI is synthesized by a liquid phase, in the process of preparing the electrolyte, graphene oxide (GO) and a lithium salt precursor 2,5-dihydroxy-1,4-benzenediol lithium phosphate are introduced, and after heat treatment and pressing, the mixed ion conductor layer can be obtained; the GO can isolate the sulfide electrolyte layer from the lithium metal negative electrode, and the interface reaction is avoided, and the unique porous and interlayer structure provides a horizontal growth space for lithium metal deposition. At the same time, the lithium phosphate-based MOF between the graphene layers ensures the rapid movement of lithium ions, enhances the lithium body diffusion at the negative electrode end, reduces the local current density and plays a role of dredging the distribution of lithium ions, and the cycle life of the sulfide full solid-state battery is significantly improved.

[0007] The object of the application can be achieved by the following technical solutions:

[0008] The application provides a preparation method of a mixed ion conductor layer for a lithium metal negative electrode, comprising the following steps:

[0009] (1) preparing graphene oxide powder;

[0010] (2) mixing the graphene oxide powder, an organic solvent, a 2,5-dihydroxy-1,4-benzenediol lithium phosphate precursor, Li2S, P2S5 and LiI to form a slurry, and performing reaction to obtain a precursor;

[0011] (3) performing annealing treatment on the precursor of step (2) to obtain the mixed ion conductor layer;

[0012] Preferably, the preparation method of the GO adopts an improved Hummer method, and specifically comprises the following steps:

[0013] Preferably, the preparation method of the GO adopts an improved Hummer method, and specifically comprises the following steps:

[0014] The preparation of the graphene oxide powder in step (1) comprises the following steps:

[0015] (1.1) pre-oxidation treatment: adding sodium nitrate and graphite into a concentrated sulfuric acid system and performing constant temperature reaction;

[0016] (1.2) step-by-step oxidation: adding potassium permanganate into the system of step (1.1) in multiple times, and after the addition is completed, continuing to react by increasing the temperature;

[0017] (1.3) high-temperature hydrolysis:

[0018] (1.3.1) adding water into the system of step (1.2), and then continuing to react by increasing the temperature;

[0019] (1.3.2) adding water and hydrogen peroxide into the system of step (1.3.1) to terminate the reaction, and filtering the system while hot to obtain a filter cake;

[0020] (1.4) purification treatment: washing the filter cake with dilute hydrochloric acid and water in sequence, then dispersing the filter cake in water for dialysis, and drying to obtain the graphene oxide powder.

[0021] In some embodiments of the present application, in step (1.1), the molar ratio of the concentrated sulfuric acid, the sodium nitrate and the graphite is 4-5:0.05-0.06:0.4-0.5;

[0022] The temperature of the constant-temperature reaction is -5-30℃, and the time is 20-40 min;

[0023] In step (1.2), the potassium permanganate is added for 10-30 times, and the total mass of the potassium permanganate added is 1:2.5-3.5 times the mass of the graphite in step (1.1);

[0024] In the temperature-increasing continuous reaction, the temperature is increased to 30-50℃, and the reaction is continued for 20-40 min.

[0025] In some embodiments of the present application, in step (1.3), in step (1.3.1), the mass ratio of the water added to the concentrated sulfuric acid system in step (1.1) is 1:0.5-1, and the temperature is increased to 95-100℃ for 50-70 min;

[0026] In step (1.3.2), when the reaction is terminated, the amount of water added is 500-1000 ml, and the amount of 5wt% hydrogen peroxide added is determined according to the actual reaction phenomenon (slowly adding hydrogen peroxide until no bubbles are generated, and the residual potassium permanganate is completely reacted, and the reaction liquid finally becomes a golden yellow transparent dispersion liquid);

[0027] In step (1.4), the concentration of the dilute hydrochloric acid is 5wt%, and the mass ratio of the dilute hydrochloric acid to water in a single washing is 10-20:20-30, and the washing is repeated for 3-5 times;

[0028] The washed filter cake is dispersed in 1000-2000 parts by mass of water, and dialyzed for 5-10 days after stirring at room temperature for 1-2 days;

[0029] The drying temperature is 120℃.

[0030] Preferably, in step (2), the mass ratio of the graphene oxide powder, 2,5-dihydroxy-1,4-benzenediol lithium phosphate, lithium sulfide Li2S, phosphorus pentasulfide P2S5 and lithium iodide LiI is 0.1-0.4:0.01-0.03:0.1-0.25:0.2-0.6:0.1-0.31;

[0031] In the embodiments of the present invention, the mass ratio of graphene oxide powder, lithium 2,5-dihydroxy-1,4-phenylenediphosphate, lithium sulfide Li2S, phosphorus pentasulfide P2S5, and lithium iodide LiI is 0.1~0.3∶0.03∶0.21~0.27∶0.22~0.29∶0.24~0.31.

[0032] The organic solvent is anhydrous n-hexane, accounting for 40% to 80% of the total mass of the slurry;

[0033] The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is as follows:

[0034] 2,5-Dihydroxy-1,4-phenylenediphosphate, lithium nitrate, and 200-300 ml of water were reacted at 35°C for 60 min. The water was removed by vacuum distillation to obtain the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor. The molar ratio of 2,5-dihydroxy-1,4-phenylenediphosphate to lithium nitrate was 0.5-1:1, and the mass ratio was 1.96-3.92:1.

[0035] In this embodiment of the invention, a preferred molar ratio of 2,5-dihydroxy-1,4-phenylenediphosphoric acid to lithium nitrate is 1:1 as an example.

[0036] Furthermore, in step (2), the reaction temperature is 30-60℃ and the reaction time is 60-84 hours;

[0037] After the reaction, a suspension is obtained. The suspension is then evaporated to dryness to obtain the precursor. The evaporation temperature is 50-100℃ and the time is 10-14 hours.

[0038] The reaction mechanism of this invention is as follows:

[0039] Self-assembly of MOF structures: In this process, metal ions and organic ligands self-assemble to form MOF structures through coordination bonding. The key to this process is controlling the reaction conditions to ensure the regularity and uniformity of MOFs, which has a decisive impact on the functional properties of the final material.

[0040] The role of graphene oxide: As a substrate material, graphene oxide not only provides a reaction site, but its abundant functional groups may also participate in the reaction, enhancing the overall functionality of the material, such as providing additional chemically active sites or enhancing electron transport capabilities. Its porous and interlayer structure provides lateral space for the growth of lithium metal.

[0041] The role of the hybrid conductor GO-MOF-LPSI: The hybrid ionic conductor has a good affinity with lithium metal and can react with lithium to form a stable interface, blocking the growth of lithium dendrites. The lithium diphosphate-based MOF can selectively induce the deposition of lithium ions, reduce local current density, and prevent local interface fluctuations.

[0042] Preferably, in step (3), the annealing temperature is 200-300℃ and the time is 0.5-2 hours.

[0043] The present invention also provides a mixed ion conductor layer prepared by the aforementioned preparation method.

[0044] The present invention also provides a lithium metal composite anode, comprising: a lithium metal substrate and the aforementioned mixed ion conductor layer covering the surface of the lithium metal substrate.

[0045] The present invention also provides an all-solid-state battery, the all-solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte, wherein the positive electrode is NCM811, the solid electrolyte is a sulfide electrolyte lithium phosphorus sulfur chloride, and the negative electrode is the lithium metal composite negative electrode described above.

[0046] The beneficial effects of this invention are:

[0047] (1) Due to the high structural strength of GO, it can suppress the side reaction between the sulfide electrolyte layer LPSC and the negative electrode Li metal and the uneven deposition of lithium at the negative electrode. At the same time, the layered structure and porous structure provide sufficient space for the volume expansion caused by lithium ion deposition, preventing the unrestricted longitudinal growth of lithium dendrites.

[0048] (2) The sulfide LPSI in the mixed ionic conductor layer acts as a sacrificial phase, reacting with lithium metal to further form a stable interface and block the growth of lithium dendrites;

[0049] (3) The lithium diphosphate-based MOF uses the functional groups on the surface of graphene oxide as anchors, which further enhances the interlayer strength of graphene oxide; and has a certain lithium-ion conduction ability, which improves the lithium-ion transfer rate and local current density; at the same time, the lithium diphosphate-based MOF has a lower interface energy with lithium metal, and has better wettability on the surface of lithium metal, which can improve the critical current density during charging, so that the all-solid-state lithium metal battery can achieve a higher charging rate.

[0050] In summary, graphene oxide modified with lithium diphosphate MOF not only enhances the overall performance of batteries through its unique chemical and physical properties, but also significantly improves the cycle performance of battery systems using sulfur-based solid electrolytes by increasing conductivity, enhancing structural stability, and optimizing interface properties. These characteristics make this material highly promising for high-performance batteries, and it is expected to play a significant role in electric vehicles and other high-demand battery applications in the future. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the all-solid-state battery of the present invention. Detailed Implementation

[0052] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific implementation methods and effects of the present invention will be described in detail below with reference to the embodiments.

[0053] Example 1

[0054] A method for preparing a hybrid ion conductor layer GO-MOF-LPSI for use in lithium metal anodes of sulfide all-solid-state batteries includes the following steps:

[0055] (1) Preparation of graphene oxide (GO): The preparation method of GO is the modified Hummer method. The specific preparation method is carried out according to the following steps.

[0056] 1) Pour 230 mL of concentrated sulfuric acid into a three-necked glass flask and stir at 0 °C.

[0057] 2) Add 5g of sodium nitrate and 5g of graphite to the system in step 1) one by one, and react at 0℃ for 30 minutes.

[0058] 3) In the system of step 2), add 15g of potassium permanganate slowly in 15 portions. After the potassium permanganate is completely added, raise the temperature of the system by 40°C and continue the reaction for 30 minutes.

[0059] 4) Slowly add 500 mL of deionized water to the system in 3), and then raise the temperature of the system to 98 °C and continue the reaction for 60 min.

[0060] 5) Add 1200 mL of deionized water and 500 mL of 5 wt% hydrogen peroxide solution to the system in 4), filter at high temperature to obtain a solid filter cake.

[0061] 6) The obtained solid was washed four times with 15 mL of 5% dilute hydrochloric acid solution and 25 mL of deionized water respectively to obtain filter cake.

[0062] 7) Redisperse the filter cake from step 6) in 1500 mL of deionized water and stir at room temperature for 1 day. Then, transfer the suspension into dialysis bags and dialyze in water for 5 days. After dialysis, the suspension in the dialysis bags is the GO suspension.

[0063] 8) Collect the suspension obtained in 7) into a container and dry it at 120°C to obtain graphene oxide (GO) powder.

[0064] (2) Preparation of ionic conductor mixture GO-MOF-LPSI:

[0065] The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is as follows:

[0066] 27g of 2,5-dihydroxy-1,4-phenyl diphosphate, 6.9g of lithium nitrate, and 250ml of water were reacted at 35℃ for 60min. The water was removed by vacuum distillation to obtain the lithium 2,5-dihydroxy-1,4-phenyl diphosphate precursor.

[0067] The graphene oxide (GO) was prepared in a mass ratio of 0.15:0.03:0.25:0.27:0.3: lithium 2,5-dihydroxy-1,4-phenylenediphosphate (Li2S): lithium sulfide: phosphorus pentasulfide: lithium iodide. Specifically, 4.5 g of GO was dispersed in 100 mL of anhydrous n-hexane and stirred. Then, 7.5 g of lithium sulfide (Li2S), 0.9 g of the Li2S precursor, 9 g of lithium iodide (LiI), and 8.1 g of phosphorus pentasulfide (P2S5) were thoroughly ground and added to the graphene oxide dispersion. The mixture was stirred at 50 °C for 72 h until the reaction was complete. The solvent was then evaporated at 80 °C for 12 h to obtain the electrolyte precursor. The resulting powder was ground uniformly and annealed at 250 °C for 1 h to finally obtain the ionic conductor mixture GO-MOF-LPSI. All preparation processes were carried out in an argon-filled glove box.

[0068] (3) Preparation of lithium metal anode coated with mixed ion conductor layer

[0069] 1) The ionic mixture GO-MOF-LPSI obtained in (2) was added to a container containing anhydrous acetonitrile and homogenized by a vacuum stirrer;

[0070] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0071] To investigate the impact of the hybrid ionic conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-MOF-LPSI / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-MOF-LPSI / Li battery achieved an initial discharge capacity of 160.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate was still 82.7%.

[0072] Example 2

[0073] A method for preparing a hybrid ion conductor layer GO-MOF-LPSI for use in lithium metal anodes of sulfide all-solid-state batteries includes the following steps:

[0074] (1) Preparation of graphene oxide (GO): The preparation method of GO is the modified Hummer method. The specific preparation method is carried out according to the following steps.

[0075] 1) Pour 230 mL of concentrated sulfuric acid into a three-necked glass flask and stir at 0 °C.

[0076] 2) Add 5g of sodium nitrate and 5g of graphite to the system in step 1) one by one, and react at 0℃ for 30 minutes.

[0077] 3) In the system of step 2), add 15g of potassium permanganate slowly in 15 portions. After the potassium permanganate is completely added, raise the temperature of the system by 40°C and continue the reaction for 30 minutes.

[0078] 4) Slowly add 500 mL of deionized water to the system in 3), and then raise the temperature of the system to 98 °C and continue the reaction for 60 min.

[0079] 5) Add 1200 mL of deionized water and 500 mL of 5 wt% hydrogen peroxide solution to the system in 4), filter at high temperature to obtain a solid filter cake.

[0080] 6) The obtained solid was washed four times with 15 mL of 5% dilute hydrochloric acid solution and 25 mL of deionized water respectively to obtain filter cake.

[0081] 7) Redisperse the filter cake from step 6) in 1500 mL of deionized water and stir at room temperature for 1 day. Then, transfer the suspension into dialysis bags and dialyze in water for 5 days. After dialysis, the suspension in the dialysis bags is the GO suspension.

[0082] 8) Collect the suspension obtained in 7) into a container and dry it at 120°C to obtain graphene oxide (GO) powder.

[0083] (2) Preparation of ionic conductor mixture GO-MOF-LPSI:

[0084] The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is as follows:

[0085] 27g of 2,5-dihydroxy-1,4-phenyl diphosphate, 6.9g of lithium nitrate, and 250ml of water were reacted at 35℃ for 60min. The water was removed by vacuum distillation to obtain the lithium 2,5-dihydroxy-1,4-phenyl diphosphate precursor.

[0086] The graphene oxide (GO) was dissolved in 20 mL of anhydrous n-hexane at a mass ratio of 0.3:0.03:0.21:0.22:0.24. The mixture was prepared by stirring 3.15 g of lithium sulfide, 0.45 g of the 2,5-dihydroxy-1,4-phenylenediphosphate precursor, 3.6 g of lithium iodide, and 3.3 g of phosphorus pentasulfide, which were then thoroughly ground and added to the GO solution. The mixture was stirred at 40 °C for 60 h until the reaction was complete. The solvent was then evaporated at 50 °C for 10 h to obtain the electrolyte precursor. The resulting powder was ground uniformly and annealed at 200 °C for 0.5 h to finally obtain the ionic conductor mixture GO-MOF-LPS. All of the above processes were carried out in an argon-filled glove box.

[0087] (3) Preparation of lithium metal anode coated with mixed ion conductor layer

[0088] 1) The ionic mixture GO-MOF-LPSI obtained in (2) was added to a container containing anhydrous acetonitrile and homogenized by a vacuum stirrer;

[0089] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0090] To investigate the impact of the hybrid ionic conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-MOF-LPSI / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-MOF-LPSI / Li battery achieved an initial discharge capacity of 158.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate was still 72.7%.

[0091] Example 3

[0092] In Example 3, the preparation method of graphene oxide (GO) and lithium 2,5-dihydroxy-1,4-phenyl diphosphate precursor was the same as in Example 1.

[0093] The difference lies in adjusting the mass ratio of graphene oxide:lithium 2,5-dihydroxy-1,4-phenylenediphosphate:lithium sulfide:phosphorus pentasulfide:lithium iodide in the mixed ionic conductor mixture to 0.1:0.03:0.27:0.29:0.31. Specifically, 4.5 g of GO was dissolved in 100 mL of anhydrous n-hexane and stirred. Then, 12.15 g of lithium sulfide, 1.35 g of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor, 13.95 g of lithium iodide, and 13.05 g of phosphorus pentasulfide were thoroughly ground and added to the graphene oxide solution. The mixture was stirred at 40°C for 60 h until the reaction was complete. The solvent was then evaporated at 50°C for 10 hours to obtain an electrolyte precursor. The obtained powder was then ground evenly and annealed at 200°C for 0.5 hours to finally obtain the ionic conductor mixture GO-MOF-LPS. All of the above processes were carried out in an argon-filled glove box.

[0094] (3) Preparation of lithium metal anode coated with mixed ion conductor layer

[0095] 1) The ionic mixture GO-MOF-LPSI obtained in (2) was added to a container containing anhydrous acetonitrile and homogenized by a vacuum stirrer;

[0096] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0097] To investigate the impact of the hybrid ionic conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-MOF-LPSI / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-MOF-LPSI / Li battery achieved an initial discharge capacity of 155.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate is still 70.7%.

[0098] Comparative Example 1

[0099] An ionic conductor mixture GO-Li7P3S 11 The preparation method includes the following steps:

[0100] (1) Preparation of graphene oxide (GO):

[0101] The steps are the same as in Example 1.

[0102] (2) Preparation of the ionic conductor mixture GO-LPSI: The mass ratio of graphene oxide:lithium sulfide:phosphorus pentasulfide:lithium iodide was 0.4:0.19:0.2:0.21. 1.86 g of lithium sulfide, 1.98 g of phosphorus pentasulfide and 2.16 g of lithium iodide were thoroughly ground and added to the 4 g graphene oxide-dehydrated n-hexane dispersion of Example 1. The above mixture was stirred at 50 °C for 72 h until the reaction was complete. Then the solvent was evaporated at 80 °C for 12 h to obtain the electrolyte precursor. The obtained powder was ground evenly and annealed at 250 °C for 1 h to finally obtain the ionic conductor mixture GO-LPSI. All preparation processes were carried out in an argon-filled glove box.

[0103] (3) Preparation of lithium metal anode coated with mixed ion conductor layer:

[0104] 1) The obtained ionic mixture GO-LPSI was added to a container containing anhydrous acetonitrile and homogenized using a vacuum stirrer;

[0105] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0106] To investigate the impact of the hybrid ion conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-LPSI / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-LPSI / Li battery achieved an initial discharge capacity as high as 105.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate was still 63.7%.

[0107] Comparative Example 2

[0108] A method for preparing an ionic conductor mixture GO-MOF includes the following steps:

[0109] (1) Preparation of graphene oxide (GO):

[0110] The steps are the same as in Example 1.

[0111] (2) Preparation of ionic conductor mixture GO-MOF:

[0112] The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is as follows:

[0113] 27g of 2,5-dihydroxy-1,4-phenyl diphosphate, 6.9g of lithium nitrate, and 250ml of water were reacted at 35℃ for 60min. The water was removed by vacuum distillation to obtain the lithium 2,5-dihydroxy-1,4-phenyl diphosphate precursor.

[0114] 4.5 g of GO was dispersed in 20 mL of anhydrous n-hexane and stirred. 0.45 g of lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor was added to the graphene oxide dispersion. The mixture was stirred at 40 °C for 60 h until the reaction was complete. The solvent was then evaporated to dryness at 50 °C for 10 h to obtain the electrolyte precursor. The obtained powder was ground uniformly and annealed at 300 °C for 2 h to finally obtain the ionic conductor mixture GO-MOF. All the above processes were carried out in an argon-filled glove box.

[0115] (3) Preparation of lithium metal anode coated with mixed ion conductor layer:

[0116] 1) The obtained ionic mixture GO-MOF was added to a container containing anhydrous acetonitrile and homogenized using a vacuum stirrer;

[0117] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0118] To investigate the impact of the hybrid ion conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-MOF / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-MOF / Li battery achieved an initial discharge capacity of 145.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate was 50.7%.

[0119] Comparative Example 3

[0120] The difference from Example 1 is that the sulfide electrolyte type LPSI is replaced with LPSC;

[0121] (1) Preparation of graphene oxide (GO):

[0122] The preparation method is the same as in Example 1;

[0123] (2) Preparation of ionic conductor mixture GO-MOF-LPSC:

[0124] The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is the same as in Example 1;

[0125] 4.5 g of GO was dispersed in 100 mL of anhydrous n-hexane and stirred. 36.76 g of Li₂S, 8.1 g of lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor, 17 g of lithium chloride (LiCl), and 177.8 g of phosphorus pentasulfide (P₂S₅) were thoroughly ground and added to the graphene oxide dispersion. The mixture was stirred at 40 °C for 60 h until the reaction was complete. The solvent was then evaporated at 50 °C for 10 h to obtain the electrolyte precursor. The resulting powder was ground uniformly and annealed at 300 °C for 2 h to finally obtain the ionic conductor mixture GO-MOF-LPSC. All of the above processes were carried out in an argon-filled glove box.

[0126] (3) Preparation of lithium metal anode coated with mixed ion conductor layer:

[0127] 1) The ionic mixture GO-MOF-LPSC obtained in (2) was added to a container containing anhydrous acetonitrile and homogenized by a vacuum stirrer;

[0128] 2) Spread the mixture slurry from 1) evenly on the lithium-copper composite sheet, and use a four-sided film forming device to evenly coat the slurry onto the lithium metal surface. Place the electrode sheet in a vacuum oven to dry and remove the solvent, and a lithium metal anode coated with a mixed ion conductor layer can be obtained. All preparation processes are carried out in a glove box filled with argon gas.

[0129] To investigate the impact of the hybrid ionic conductor layer on the cycle performance of lithium metal all-solid-state batteries, an NCM811 / LPSC / GO-MOF-LPSC / Li all-solid-state battery was assembled using NCM811 as the positive electrode and lithium phosphorus-sulfur-chloride LPSC as the sulfide solid electrolyte layer. At a current density of 0.1C, the NCM811 / LPSC / GO-MOF-LPSC / Li battery achieved an initial discharge capacity of 145.0 mAh g⁻¹. -1 After 100 cycles, the capacity retention rate was still 65.4%.

Claims

1. A method for preparing a mixed ionic conductor layer for lithium metal anodes, characterized in that, Includes the following steps: (1) Preparation of graphene oxide powder; (2) The graphene oxide powder, organic solvent, lithium 2,5-dihydroxy-1,4-phenyl diphosphate precursor, Li2S, P2S5 and LiI are mixed to form a slurry, and the mixture is reacted to obtain the precursor. The preparation method of the lithium 2,5-dihydroxy-1,4-phenylenediphosphate precursor is as follows: 2,5-Dihydroxy-1,4-phenylenediphosphoric acid, lithium nitrate, and 200-300 ml of water were reacted at 35°C for 60 min. The water was removed by vacuum distillation to obtain a lithium 2,5-dihydroxy-1,4-phenylenediphosphoric acid precursor. The molar ratio of 2,5-dihydroxy-1,4-phenylenediphosphoric acid to lithium nitrate was 0.5-1:

1. (3) Anneal the precursor from step (2) to obtain the mixed ion conductor layer; Steps (2) and (3) are carried out under an inert atmosphere.

2. The method for preparing the mixed ion conductor layer according to claim 1, characterized in that, The preparation of graphene oxide powder in step (1) includes the following steps: (1.1) Pre-oxidation treatment: Sodium nitrate and graphite are added to a concentrated sulfuric acid system and reacted at a constant temperature; (1.2) Stepwise oxidation: Potassium permanganate was added to the system of step (1.1) in multiple portions, and the temperature was raised to continue the reaction after the addition was completed; (1.3) High-temperature hydrolysis: (1.3.1) Add water to the system of step (1.2), and then raise the temperature to continue the reaction; (1.3.2) Add water and hydrogen peroxide to the system in step (1.3.1) to terminate the reaction, and filter the mixture while it is hot to obtain a filter cake; (1.4) Purification treatment: The filter cake was washed with dilute hydrochloric acid and water in sequence, then dispersed in water for dialyzing, and dried to obtain the graphene oxide powder.

3. The method for preparing the mixed ion conductor layer according to claim 2, characterized in that, In step (1.1), the molar ratio of concentrated sulfuric acid, sodium nitrate and graphite is 4-5:0.05-0.06:0.4-0.5; The isothermal reaction is carried out at a temperature of -5 to 30°C for 20 to 40 minutes. In step (1.2), the potassium permanganate is added 10-30 times, and the total mass added is in a mass ratio of 1:2.5 to 3.5 with the mass of graphite in step (1.1). The reaction continues at 30-50℃ for 20-40 minutes.

4. The method for preparing the mixed ion conductor layer according to claim 2, characterized in that, In step (1.3), the mass ratio of water added in step (1.3.1) to the mass ratio of concentrated sulfuric acid added in step (1.1) is 1:0.5~1, and the temperature is raised to 95-100℃ and the reaction is carried out for 50-70 min. In step (1.4), the concentration of the dilute hydrochloric acid is 5 wt%, the mass ratio of dilute hydrochloric acid to water in a single wash is 10-20:20-30, and the washing is repeated 3-5 times. Disperse the washed filter cake in 1000-2000 parts by weight of water, stir at room temperature for 1-2 days, and then dialyze for 5-10 days; The drying temperature is 120℃.

5. The method for preparing the mixed ion conductor layer according to claim 1, characterized in that, In step (2), the mass ratio of the graphene oxide powder, lithium 2,5-dihydroxy-1,4-phenylenediphosphate, Li2S, P2S5, and LiI is 0.1~0.4∶0.01~0.03∶0.1~0.25∶0.2~0.6∶0.1~0.31; The organic solvent is anhydrous n-hexane, accounting for 40% to 80% of the total mass of the slurry.

6. The method for preparing the mixed ion conductor layer according to claim 1 or 5, characterized in that, In step (2), the reaction temperature is 30-60℃ and the reaction time is 60-84 hours; After the reaction, a suspension is obtained. The suspension is then evaporated to dryness to obtain the precursor. The evaporation temperature is 50-100℃ and the time is 10-14 hours.

7. The method for preparing the mixed ion conductor layer according to claim 1, characterized in that, In step (3), the annealing temperature is 200-300℃ and the time is 0.5-2 hours.

8. The mixed ion conductor layer prepared by the preparation method according to any one of claims 1-7.

9. A lithium metal composite anode, characterized in that, include: The lithium metal substrate and the mixed ion conductor layer of claim 8 covering the surface of the lithium metal substrate.

10. An all-solid-state battery, the all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte, characterized in that, The positive electrode is NCM811, the solid electrolyte is a sulfide electrolyte lithium-phosphorus-sulfur-chlorine, and the negative electrode is the lithium metal composite negative electrode as described in claim 9.

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