Solid-state electrolyte-cathode integrated component, method for manufacturing the same, and lithium metal solid-state battery

Abstract

The application discloses a kind of solid electrolyte-cathode integrated components and its preparation method and lithium metal solid-state battery, first Li3InCl6 is adsorbed on cathode active material, then two-stage calcination is carried out, and composite powder I is obtained;Sucrose is directly coated on composite powder I and calcined to form pores to obtain composite powder II;Composite powder II, conductive agent and binder are mixed and coated on aluminum foil to obtain cathode sheet;Finally, precursor liquid is obtained by vacuum infiltration and hot-pressing molding to obtain solid electrolyte-cathode integrated component.The application forms uneven porous structure by two-stage co-firing of Li3InCl6@Cathode active material and sucrose pore forming, provides multiple ion transport paths, thereby improving ion transport efficiency;Further, by vacuum infiltration and hot-pressing molding, the polymer precursor liquid is infiltrated into the uneven pore structure, tightly fitted to the electrode, and the solid electrolyte-cathode integrated component is prepared, which has excellent electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium metal batteries, and particularly relates to a solid-state electrolyte-cathode integrated component, a preparation method thereof and a lithium metal solid-state battery. BACKGROUND

[0002] With the rapid development of portable electronic devices and electric vehicles, there is an increasing demand for high-energy density and high-safety energy storage systems. Traditional lithium ion batteries use organic liquid electrolytes, which have high ionic conductivity, but have problems such as easy leakage, poor thermal stability and interface side reactions, which seriously restrict their application in extreme environments. Solid-state batteries can solve the problems of leakage and thermal runaway by using non-flammable solid-state electrolytes instead of liquid electrolytes, and can also improve the energy density to more than 500 Wh / kg by matching high-voltage cathodes (such as lithium-rich manganese-based and high-nickel NCM) with lithium metal anodes, thus becoming the most promising next-generation energy storage technology. However, the practical application of solid-state batteries still faces many challenges. On the one hand, the interface between the solid-state electrolyte (such as oxide and sulfide) and the high-voltage cathode has high impedance and chemical / electrochemical instability, which leads to slow ion transport dynamics and limited rate performance and cycle life; on the other hand, the solid-solid contact of the solid-state electrolyte can cause physical contact failure of the electrode-electrolyte interface, further exacerbating the interface impedance problem. SUMMARY

[0003] To solve the interface problem of solid-state batteries, the application aims to provide a solid-state electrolyte-cathode integrated component, a preparation method thereof and a lithium metal solid-state battery. The Li3InCl6 and the cathode active material are co-fired in two stages, and the sucrose is used to form a non-uniform porous structure, thereby providing multiple ion transport paths to improve the ion transport efficiency. Further, the polymer precursor liquid is infiltrated into the non-uniform pore structure by vacuum infiltration and hot pressing to tightly fit the electrode, thereby obtaining the solid-state electrolyte-cathode integrated component with excellent electrochemical performance.

[0004] To achieve the above technical purposes, the application adopts the following technical solutions:

[0005] A preparation method of a solid-state electrolyte-cathode integrated component, comprising the following steps:

[0006] (1) immersing the cathode active material in an ethanol solution containing InCl3 and LiCl, and drying to obtain Li3InCl6@ cathode active material;

[0007] (2) under an inert atmosphere, first calcining the Li3InCl6@ cathode active material at 250-350 ℃, then calcining at 550-650 ℃ to obtain a composite powder I;

[0008] (3) directly coating sucrose on the composite powder I, calcining at 450~550 ℃ under inert atmosphere to obtain composite powder II;

[0009] (4) mixing the composite powder II, conductive agent and binder uniformly, coating on the aluminum foil, and drying to obtain the positive electrode sheet;

[0010] (5) dispersing the olefin polymer and lithium salt in the polar solvent, adding the LLZO nanowire, and fully mixing to obtain a precursor liquid; then, the precursor liquid is added dropwise on the positive electrode sheet, vacuum infiltration and hot pressing are performed to obtain a solid electrolyte-positive electrode integrated component.

[0011] In the present application, the positive active material is a conventional commercial lithium battery positive electrode material, such as NCM811, Ni90, LiCoO2, etc., which is not specially required here.

[0012] Preferably, in step (1), the mass fraction of Li3InCl6 to the positive active material is 2~6 wt%.

[0013] Preferably, in step (2), the heating rate of the first calcination is 2~10 ℃ / min, and the calcination time is 1~3 h; the heating rate of the second calcination is 2~10 ℃ / min, and the calcination time is 0.5~1 h. In the present application, Li3InCl6 is adsorbed on the positive active material, and is first crystallized by the first calcination to form a uniform crystal structure; and then the surface of the positive active material is reconstructed by the second calcination to form more active sites.

[0014] Preferably, in step (3), the mass fraction of sucrose to the composite powder I is 8~12 wt%, and the calcination time is 0.5~2 h. In the present application, sucrose is used as a pore-forming agent, and is directly coated on the composite powder I without other mixing methods such as stirring and ball milling. The sucrose is only distributed on the surface of the active material, but not uniformly distributed in the entire active material. During the calcination process, the gas generated by the decomposition of sucrose diffuses from top to bottom, and the concentration of the gas gradually decreases along the depth direction when the gas diffuses in the active material, resulting in a gradient change in the pore size and number along the depth direction, forming a non-uniform porous structure. The area close to the sucrose layer has a high gas concentration and many pores, forming large and medium pores, and the area far from the sucrose layer has a low gas concentration and few pores, forming small pores. Such a non-uniform porous structure can provide multiple ion transmission paths, thereby improving the ion transmission efficiency. The large and medium pores can provide a fast ion transmission channel, while the small pores can increase the surface area of ion transmission and improve the contact area between ions and electrolyte, thereby improving the ion transmission efficiency between the electrode and the electrolyte through the design of the non-uniform porous structure.

[0015] Preferably, in step (4), the mass ratio of the composite powder II, the conductive agent and the binder is 8:1:1, the conductive agent is one or more combinations of acetylene black, conductive carbon black, carbon fiber, graphene and carbon nanotube, and the binder is one or more combinations of polyvinylidene fluoride, polytetrafluoroethylene and butadiene-styrene rubber.

[0016] Preferably, in step (5), the olefin polymer is one or more combinations of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene) copolymer, poly(vinylidene fluoride-trifluoroethylene) copolymer, poly(vinylidene fluoride-tetrafluoroethylene) copolymer and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer.

[0017] The lithium salt is one or more combinations of LiCl, LiF, LiBr, LiI, Li2SO4, LiNO3, LiPF6, LiTFSI, LiFSI and LiDFOB.

[0018] The polar solvent is one or more combinations of acetone, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and 2,2,2-trifluoro-N,N-dimethylacetamide.

[0019] Preferably, in step (5), the mass ratio of the olefin polymer and the lithium salt is 1-1.5:1, the mass fraction of the LLZO nanowire is 8-15 wt% based on the olefin polymer, the pressure for vacuum infiltration is-0.15--0.05 MPa, the time is 20-40 min, the pressure for hot-pressing is 0.8-1.5 MPa, the temperature is 40-50 ℃, and the time is 5-8 min. The vacuum infiltration combined with the hot-pressing process adopted in the present application allows the polymer electrolyte to penetrate into the uneven pore structure and tightly adhere to the electrode, forming a good contact and a mechanically stable interface. The good contact can reduce the interface resistance and improve the ion transmission efficiency, and the mechanically stable interface can reduce the volume change of the electrode during the charging and discharging process and improve the cycle stability of the electrode.

[0020] The present application also provides a solid-state electrolyte-cathode integrated component prepared by the above preparation method.

[0021] The solid-state electrolyte-cathode integrated component of the present application first adsorbs Li3InCl6 on the cathode active material, and then realizes the crystallization of Li3InCl6 and the surface reconstruction of the cathode active material through two-stage calcination, thereby realizing the integration of Li3InCl6 and the cathode active material. Then, sucrose is directly coated on the integrated composite powder of Li3InCl6 and the cathode active material, without any mixing such as stirring or ball milling, and the sucrose is only distributed on the surface of the active material, but not uniformly distributed in the entire active material. During the calcination process, the gas generated by the decomposition of sucrose diffuses from top to bottom, and the concentration gradually decreases with the depth when the gas diffuses in the active material, resulting in a gradient change in pore size and number along the depth direction, forming a non-uniform porous structure. The area close to the sucrose layer has high gas concentration and many pores, forming large and medium pores, and the area far from the sucrose layer has low gas concentration and few pores, forming small pores. This non-uniform porous structure can provide multiple ion transmission paths, thereby improving the ion transmission efficiency. Large and medium pores can provide fast ion transmission channels, while small pores can increase the surface area of ion transmission and improve the contact area between ions and electrolyte. Through the design of non-uniform porous structure, the ion transmission efficiency between the electrode and the electrolyte is improved. Finally, the polymer precursor liquid is infiltrated into the non-uniform porous structure through vacuum infiltration and hot pressing, and tightly adheres to the electrode to obtain a solid-state electrolyte-cathode integrated component, which has a good contact and mechanically stable interface. Good contact can reduce the interface resistance and improve the ion transmission efficiency, and the mechanically stable interface can reduce the volume change of the electrode during charging and discharging, thereby improving the cycle stability of the electrode.

[0022] The present application also provides a lithium metal solid-state battery, which comprises the solid-state electrolyte-cathode integrated component and a lithium metal anode.

[0023] In the present application, the lithium metal anode can be a lithium metal, a lithium-copper composite tape or other alloyed lithium metal anode, without special requirements.

[0024] The present application has the following beneficial technical effects:

[0025] (1) The solid-state electrolyte-cathode integrated component of the present application first adsorbs Li3InCl6 on the cathode active material, and then realizes the crystallization of Li3InCl6 and the surface reconstruction of the cathode active material through two-stage calcination, thereby realizing the integration of Li3InCl6 and the cathode active material. Then, sucrose is directly coated on the integrated composite powder of Li3InCl6 and the cathode active material, without any mixing such as stirring or ball milling, and the sucrose is only distributed on the surface of the active material, but not uniformly distributed in the entire active material. During the calcination process, the gas generated by the decomposition of sucrose diffuses from top to bottom, and the concentration gradually decreases with the depth when the gas diffuses in the active material, resulting in a gradient change in pore size and number along the depth direction, forming a non-uniform porous structure. The area close to the sucrose layer has high gas concentration and many pores, forming large and medium pores, and the area far from the sucrose layer has low gas concentration and few pores, forming small pores. This non-uniform porous structure can provide multiple ion transmission paths, thereby improving the ion transmission efficiency. Large and medium pores can provide fast ion transmission channels, while small pores can increase the surface area of ion transmission and improve the contact area between ions and electrolyte. Through the design of non-uniform porous structure, the ion transmission efficiency between the electrode and the electrolyte is improved. Finally, the polymer precursor liquid is infiltrated into the non-uniform porous structure through vacuum infiltration and hot pressing, and tightly adheres to the electrode to obtain a solid-state electrolyte-cathode integrated component, which has a good contact and mechanically stable interface. Good contact can reduce the interface resistance and improve the ion transmission efficiency, and the mechanically stable interface can reduce the volume change of the electrode during charging and discharging, thereby improving the cycle stability of the electrode.

[0026] (2) The solid electrolyte-cathode integrated component of the present application penetrates the polymer precursor liquid into the non-uniform pore structure through vacuum infiltration and hot pressing, and because of the good flexibility and adhesion of the polymer, the electrolyte and the cathode material are tightly combined during the infiltration process, further optimizing the ion transmission path, forming a uniform composite electrolyte network, enhancing the ion transmission and the stability of the interface. In addition, the hot pressing process solves the problem of solvent residue in the traditional preparation process, and the solvent can be completely volatilized during the vacuum infiltration and hot pressing process, avoiding the safety hazards caused by solvent residue.

[0027] (3) The lithium metal solid-state battery comprising the solid electrolyte-cathode integrated component of the present application has low interface impedance, high capacity release, high rate performance and excellent cycle stability. For example, the LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811)-CPE||Li full battery can still release a discharge capacity of 127.3 mAh / g at a 5 C rate, and can stably cycle 1000 times at a room temperature 0.5 C rate, with a capacity retention rate of 90.7%, and can stably cycle 1500 times at a 3 C rate, showing excellent compatibility for high-voltage cathodes, and having great industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 EIS impedance plots of the coin cells assembled for Example 1 and Comparative Examples 1-4 of the present application at room temperature.

[0029] Figure 2 Rate performance plots of the coin cells assembled for Example 1 and Comparative Examples 1-4 of the present application at room temperature 0.1-5 C.

[0030] Figure 3 Cycle performance plots of the coin cells assembled for Example 1 and Comparative Examples 1-4 of the present application at room temperature 0.5 C rate.

[0031] Figure 4 Cycle performance plots of the coin cells assembled for Example 1 and Comparative Examples 1-4 of the present application at room temperature 3 C rate. DETAILED DESCRIPTION

[0032] In order to make the present application more easily understood, the present application is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved in the present application can be purchased from the market or prepared by known methods.

[0033] Example 1

[0034] (1) 10 g of NCM811 (LiNi0.80Co0.10Mn0.10O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120 ℃ for 8 h to obtain Li3InCl6@NCM811; 0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120 ℃ for 8 h to obtain Li3InCl6@NCM811;

[0035] (2) Under an argon atmosphere, Li3InCl6@NCM811 was first calcined at 300 ℃ for 2 h, and then the temperature was raised to 550 ℃ for calcination for 30 min to obtain composite powder I;

[0036] (3) 10 wt% sucrose was directly coated on the composite powder I, and the composite powder I was calcined at 500 ℃ for 1 h under an argon atmosphere to obtain composite powder II;

[0037] (4) The composite powder II, a conductive agent (acetylene black), and a binder [polyvinylidene fluoride (PVDF)] were mixed uniformly at a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80 ℃ for 24 h to obtain a positive electrode sheet;

[0038] (5) 0.5 g of a PVDF polymer matrix and 0.4 g of a lithium salt (LiTFSI + LiODFB, molar ratio of 4:1) were dissolved in 6 mL of acetone, and then 0.05 g of LLZO nanowires was added and mixed thoroughly to obtain a precursor solution; the precursor solution was then added dropwise to the positive electrode sheet, and was infiltrated at a vacuum of -0.1 MPa for 30 min, and then was formed by hot pressing at a pressure of 1 MPa at 45 ℃ for 5 min to obtain a solid electrolyte-positive electrode integrated component.

[0039] (6) Selection of the negative electrode: a 450 μm lithium metal sheet was used as the negative electrode.

[0040] (7) Assembly of lithium metal solid-state battery: Assemble the battery in the order of positive shell, solid-state electrolyte-positive electrode integrated component, lithium sheet (15.6 mm x 0.45 mm), and negative shell, and conduct room temperature impedance, charge-discharge performance test.

[0041] It is detected that the solid-state battery assembled using the solid-state electrolyte-positive electrode integrated component exhibits low interface impedance (28.1 Ω), high capacity, high rate performance, and excellent cycle stability. The NCM811-CPE||Li full battery (where NCM811-CPE represents the solid-state electrolyte-positive electrode integrated component) still exhibits a discharge capacity of 127.3 mAh / g at a 5 C rate, and is stably cycled for 1000 cycles at a room temperature 0.5 C rate with a capacity retention rate of 90.7%, and is stably cycled for more than 1500 cycles at a 3 C rate.

[0042] Example 2

[0043] (1) 10 g of Ni90(LiNi 0.9 Co 0.05 Mn 0.05 O2) powder is immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120°C for 8 h to obtain Li3InCl6@Ni90;

[0044] (2) Under an argon atmosphere, Li3InCl6@Ni90 is first calcined at 350°C for 2 h, and then heated to 600°C for calcination for 30 min to obtain composite powder I;

[0045] (3) 8 wt% sucrose is directly coated on the composite powder I, which is calcined at 500°C for 1 h under an argon atmosphere to obtain composite powder II;

[0046] (4) The composite powder II, conductive agent (acetylene black), and binder [polyvinylidene fluoride (PVDF)] are uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80°C for 24 h to obtain a positive electrode sheet;

[0047] (5) 0.5 g of a PVDF polymer matrix and 0.4 g of a lithium salt (LiTFSI + LiODFB, molar ratio of 4:1) are dissolved in 6 mL of acetone, and then 0.05 g of LLZO nanowires is added and mixed thoroughly to obtain a precursor liquid; the precursor liquid is then added dropwise to the positive electrode sheet, and is infiltrated under vacuum-0.1 MPa for 30 min, and then is formed using a pressure of 1 MPa at 45°C for 5 min to obtain a solid-state electrolyte-positive electrode integrated component.

[0048] The subsequent steps are the same as in Example 1.

[0049] Example 3

[0050] (1) 10 g LCO (LiCoO2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120°C for 8 h to obtain Li3InCl6@LCO;

[0051] (2) Under an argon atmosphere, Li3InCl6@LCO was first calcined at 250°C for 2 h, and then the temperature was raised to 500°C for calcination for 30 min to obtain composite powder I;

[0052] (3) 12 wt% sucrose was directly coated on composite powder I, and under an argon atmosphere, calcination was performed at 500°C for 1 h to obtain composite powder II;

[0053] (4) Composite powder II, conductive agent (acetylene black), and binder [polyvinylidene fluoride (PVDF)] were mixed uniformly in a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80°C for 24 h to obtain a positive electrode sheet;

[0054] (5) 0.5 g of a PVDF polymer matrix and 0.4 g of a lithium salt (LiTFSI + LiODFB, molar ratio of 4:1) were dissolved in 6 mL of acetone, and then 0.05 g of LLZO nanowires was added and mixed thoroughly to obtain a precursor solution; the precursor solution was then added dropwise to the positive electrode sheet, and under vacuum-0.1 MPa, it was infiltrated for 30 min, and then using a pressure of 1 MPa, it was hot-pressed at 45°C for 5 min to form a solid-state electrolyte-positive electrode integrated component.

[0055] The subsequent steps are the same as in Example 1.

[0056] Comparative Example 1

[0057] (1) 10 g of NCM811 (LiNi0.6Co0.2Mn0.2O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120°C for 8 h to obtain Li3InCl6@NCM811; 0.8 Co 0.1 Mn 0.1 (2) 10 wt% sucrose was directly coated on Li3InCl6@NCM811, and under an argon atmosphere, calcination was performed at 500°C for 1 h to obtain a composite powder;

[0058] (3) 10 wt% sucrose was directly coated on Li3InCl6@NCM811, and under an argon atmosphere, calcination was performed at 500°C for 1 h to obtain a composite powder;

[0059] (4) The composite powder, conductive agent (acetylene black) and binder [polyvinylidene fluoride (PVDF)] were mixed uniformly at a mass ratio of 8:1:1, coated on an aluminum foil, dried in a vacuum drying oven at 80 °C for 24 h, and an anode sheet was obtained;

[0060] (5) 0.5 g of a PVDF polymer matrix and 0.4 g of a lithium salt (LiTFSI + LiODFB, molar ratio 4:1) were dissolved in 6 mL of acetone, 0.05 g of LLZO nanowires was added, and the mixture was uniformly mixed to obtain a precursor solution; the precursor solution was then added dropwise to the anode sheet, and the anode sheet was infiltrated under vacuum-0.1 MPa for 30 min, and then molded by hot pressing at 1 MPa and 45 °C for 5 min to obtain a solid-state electrolyte-anode integrated component.

[0061] The subsequent steps are the same as in Example 1.

[0062] Comparative Example 2

[0063] (1) 10 g of NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120 °C for 8 h to obtain Li3InCl6@NCM811;

[0064] (2) Under an argon atmosphere, Li3InCl6@NCM811 was first calcined at 300 °C for 2 h, and then the temperature was increased to 550 °C and calcined for 30 min to obtain a composite powder;

[0065] (3) The composite powder, conductive agent (acetylene black) and binder [polyvinylidene fluoride (PVDF)] were mixed uniformly at a mass ratio of 8:1:1, coated on an aluminum foil, dried in a vacuum drying oven at 80 °C for 24 h, and an anode sheet was obtained;

[0066] (4) 0.5 g of a PVDF polymer matrix and 0.4 g of a lithium salt (LiTFSI + LiODFB, molar ratio 4:1) were dissolved in 6 mL of acetone, 0.05 g of LLZO nanowires was added, and the mixture was uniformly mixed to obtain a precursor solution; the precursor solution was then added dropwise to the anode sheet, and the anode sheet was infiltrated under vacuum-0.1 MPa for 30 min, and then molded by hot pressing at 1 MPa and 45 °C for 5 min to obtain a solid-state electrolyte-anode integrated component.

[0067] The subsequent steps are the same as in Example 1.

[0068] Comparative Example 3

[0069] (1) 10 g of NCM811 (LiNi0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of ethanol solution containing InCl3 and LiCl (total amount 0.5 g, molar ratio 1:3) and dried at 120 °C for 8 h to obtain Li3InCl6@NCM811;

[0070] (2) Under argon atmosphere, Li3InCl6@NCM811 was first calcined at 300 °C for 2 h, and then heated to 550 °C for 30 min to obtain composite powder I;

[0071] (3) Based on composite powder I, 10 wt% sucrose and composite powder I were thoroughly mixed by ball milling (wherein the ball milling speed was 450 rpm, the ball-to-material ratio was 1.2:1, and the ball milling time was 2 h), and calcined at 500 °C for 1 h under argon atmosphere to obtain composite powder II;

[0072] (4) The composite powder II, conductive agent (acetylene black) and binder [polyvinylidene fluoride (PVDF)] were mixed uniformly in a mass ratio of 8:1:1, coated on aluminum foil, and dried in a vacuum drying oven at 80 °C for 24 h to obtain a positive electrode sheet;

[0073] (5) Dissolve 0.5 g of PVDF polymer matrix and 0.4 g of lithium salt (LiTFSI + LiODFB, molar ratio 4:1) in 6 mL of acetone, then add 0.05 g of LLZO nanowires and mix thoroughly to obtain a precursor liquid; then drop the precursor liquid onto the positive electrode sheet, infiltrate under vacuum -0.1 MPa for 30 min, and then use 1 MPa pressure at 45 °C for 5 min to form a solid electrolyte-positive electrode integrated component.

[0074] The subsequent steps are the same as those in Example 1.

[0075] Comparative Example 4

[0076] (1) 10 g NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of ethanol solution containing InCl3 and LiCl (total amount 0.5 g, molar ratio 1:3) and dried at 120 °C for 8 h to obtain Li3InCl6@NCM811;

[0077] (2) Under argon atmosphere, Li3InCl6@NCM811 was first calcined at 300 °C for 2 h, and then heated to 550 °C for 30 min to obtain composite powder I;

[0078] (3) 10 wt% sucrose was directly coated on the composite powder I, and calcined at 500 ℃ for 1 h under argon atmosphere, to obtain composite powder II;

[0079] (4) The composite powder II, conductive agent (acetylene black) and binder [polyvinylidene fluoride (PVDF)] were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80 ℃ for 24 h to obtain a positive electrode sheet;

[0080] (5) 0.5 g of PVDF polymer matrix and 0.4 g of lithium salt (LiTFSI + LiODFB, molar ratio 4:1) were dissolved in 6 mL of acetone, and then 0.05 g of LLZO nanowires was added and mixed thoroughly to obtain a precursor liquid; the precursor liquid was then cast on the positive electrode sheet, and a 500 μm doctor blade was used for coating, and the residual solvent was removed by drying in a vacuum oven at 45 ℃ for 8 h to obtain a solid-state electrolyte-positive electrode integrated component.

[0081] The following is the same as Example 1.

[0082] Comparative Example 5

[0083] (1) 10 g of NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120 ℃ for 8 h to obtain Li3InCl6@NCM811;

[0084] (2) Li3InCl6@NCM811 was first calcined at 300 ℃ for 2 h, and then heated to 550 ℃ for 30 min under argon atmosphere, to obtain composite powder I;

[0085] (3) 10 wt% sucrose was directly coated on the composite powder I, and calcined at 500 ℃ for 1 h under argon atmosphere, to obtain composite powder II;

[0086] (4) The composite powder II, conductive agent (acetylene black) and binder [polyvinylidene fluoride (PVDF)] were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80 ℃ for 24 h to obtain a positive electrode sheet;

[0087] (5) 0.5 g PVDF polymer matrix and 0.4 g lithium salt (LiTFSI + LiODFB, molar ratio 4:1) were dissolved in 6 mL of acetone, 0.01 g of poly(ethylene glycol) diacrylate (PEGDA) monomer and 0.5 wt% of photoinitiator 4-methylbenzophenone (MBP) were added, and then 0.05 g of LLZO nanowires were added, and the mixture was thoroughly mixed to obtain a precursor solution; the precursor solution was then cast on the positive electrode sheet, and the solid-state electrolyte-positive electrode integrated component was obtained by irradiating with 365 nm UV light at an intensity of 10 mW / cm 2 for 3 min.

[0088] The subsequent steps were the same as in Example 1.

[0089] Comparative Example 6

[0090] (1) 10 g of NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) powder was immersed in 20 mL of an ethanol solution containing InCl3 and LiCl (total amount of 0.5 g, molar ratio of 1:3), and dried at 120 °C for 8 h to obtain Li3InCl6@NCM811.

[0091] (2) Under an argon atmosphere, Li3InCl6@NCM811 was first calcined at 300 °C for 2 h, and then the temperature was increased to 550 °C and calcined for 30 min to obtain composite powder I.

[0092] (3) 10 wt% sucrose was directly coated on the composite powder I, which was calcined at 500 °C for 1 h under an argon atmosphere to obtain composite powder II.

[0093] (4) The composite powder II, conductive agent (acetylene black), and binder [polyvinylidene fluoride (PVDF)] were mixed uniformly in a mass ratio of 8:1:1, coated on an aluminum foil, and dried in a vacuum drying oven at 80 °C for 24 h to obtain a positive electrode sheet.

[0094] (5) 0.5 g of PVDF polymer matrix and 0.4 g of lithium salt (LiTFSI + LiODFB, molar ratio 4:1) were dissolved in 6 mL of acetone, 0.05 g of LLZO nanowires was added, and the mixture was stirred at 50 °C for 8 h until it was completely dissolved. The obtained solution was uniformly cast into a film and placed in a vacuum drying oven at 60 °C for 24 h to dry, obtaining a polymer solid-state electrolyte.

[0095] (6) Selection of the negative electrode: a 450 μm metal lithium sheet was used as the negative electrode.

[0096] (7) Assembly of lithium metal solid-state battery: Assemble the battery in the order of positive shell, positive sheet, polymer solid-state electrolyte, lithium sheet (15.6 mm x 0.45 mm), and negative shell, and conduct room temperature impedance, charge-discharge performance test.

[0097] Table 1 Performance test results of each example and comparative example

[0098] Group Full cell impedance value at the first circle at room temperature (Ω) Discharge capacity at 5C rate (mAh / g) 0.5C cycle first circle capacity (mAh / g) 0.5C cycle capacity retention rate at 1000 cycles (%) 3C cycle first circle capacity (mAh / g) Stable cycle number of 3C cycle Example 1 28.1 127.3 175.2 90.7 142.3 1500 Example 2 37.2 113.4 161.5 81.4 127.2 1240 Example 3 24.1 134.7 179.2 86.7 150.6 1375 Comparative Example 1 149.1 74.8 150.8 31.3 98.8 569 Comparative Example 2 87.7 93.4 155.2 51.78 105.9 793 Comparative Example 3 42.7 111.7 160.7 75.13 117.4 1091 Comparative Example 4 165.9 54.18 148.9 19.4 92.7 360 Comparative Example 5 53.9 102.5 159.1 68.73 110.5 953 Comparative Example 6 135.8 87.2 152.7 39.62 101.3 618

[0099] From Table 1, when Li3InCl6@NCM811 in Comparative Example 1 is not subjected to two-stage calcination, the first circle full resistance impedance at room temperature is 149.1 Ω, the discharge capacity at 5 C rate is only 74.8 mAh / g, the capacity retention rate is only 31.3 % after 1000 cycles at 0.5 C, and the discharge capacity drops at 3 C rate after only 569 cycles. This shows that Li3InCl6 is difficult to form a stable interface layer by adsorbing on the surface of the positive electrode, and the structure is unstable during charging and discharging.

[0100] From Comparative Example 2, the solid-state electrolyte-positive electrode integrated component without sucrose carbonization pore forming treatment shows a discharge capacity of 93.4 mAh / g at 5 C and poor cycle stability, indicating that the solid-state electrolyte-positive electrode integrated component without pore forming, the polymer cannot effectively fill the pores, resulting in large interface impedance and poor cycle stability.

[0101] The solid-state electrolyte-positive electrode integrated component with uniform pore structure formed by uniform dispersion of sucrose carbonization in Comparative Example 3 shows an interface impedance of 42.7 Ω and stable cycles of 1091 at 3 C rate, indicating that the structure with uniform pore distribution can improve the interface to a certain extent, but cannot provide multiple ion transmission channels.

[0102] From Comparative Examples 4 and 5, the solid-state electrolyte-positive electrode integrated components formed by traditional solution casting and ultraviolet polymerization show interface impedances of 165.9 Ω and 53.9 Ω, respectively, and only 19.4 % and 68.73 % capacity retention after 1000 cycles at 0.5 C, which shows that the traditional process cannot effectively penetrate into the uneven voids, and cannot form good interface contact, and the inevitable solvent residue in the preparation process will affect the stability of long cycle.

[0103] From Comparative Example 6, the non-integrated component shows an interface impedance of 135.8 Ω, a discharge capacity of only 87.2 mAh / g at 5 C rate, a capacity retention rate of only 39.62 % after 1000 cycles at 0.5 C, and a discharge capacity drop after only 618 cycles at 3 C rate, indicating that the surface solid-solid contact is small, the interface void is large, and the ion transmission path is tortuous.

[0104] In Example 1, Li3InCl6 is first adsorbed on NCM811, and then the crystallization of Li3InCl6 and the surface reconstruction of NCM811 are achieved through two-stage calcination, thereby realizing the integration of Li3InCl6 and NCM811. Sucrose is then directly coated on the integrated composite powder of Li3InCl6 and NCM811 and sintered to form a non-uniform pore distribution. Finally, vacuum infiltration and hot pressing are used to fill the powder, providing a variety of ion transmission paths, forming a dense interface contact and excellent interface stability, effectively reducing the interface impedance, improving the ion transmission efficiency, and achieving low interface impedance, high rate and long cycle performance. For example, the NCM811-CPE||Li full battery in Example 1 exerts a high discharge capacity of 127.3 mAh / g at a rate of 5 C, and still has a capacity retention rate of 90.7% after 1000 cycles at room temperature and 0.5C, and achieves stable cycling for more than 1500 cycles at a rate of 3 C. In addition, it can be seen from Examples 2 and 3 that the use of Ni90 and LCO positive electrode materials can both exhibit excellent capacity development and electrochemical performance.

Claims

1. A method for preparing a solid electrolyte-positive electrode integrated component, characterized in that: The steps include: (1) Immersing the cathode active material in an ethanol solution containing InCl3 and LiCl, and obtaining Li3InCl6@ cathode active material after drying; (2) Under an inert atmosphere, the Li3InCl6@ cathode active material was first calcined at 250-350 °C and then heated to 550-650 °C for a second calcination to obtain composite powder I; (3) directly coating the composite powder I with sucrose and calcining the composite powder at 450-550 °C under an inert atmosphere to obtain composite powder II; (4) Mix the composite powder II, conductive agent and binder evenly, apply them on aluminum foil, and dry them to obtain the positive electrode sheet; (5) Dispersing the vinyl polymer and lithium salt in a polar solvent, adding LLZO nanowires, and mixing thoroughly to obtain a precursor liquid; The precursor liquid is then added dropwise to the cathode sheet, and a solid electrolyte-cathode integrated component is obtained through vacuum infiltration and hot pressing. In step (2), the heating rate of the first calcination is 2~10 ℃ / min, and the calcination time is 1~3 h; the heating rate of the first calcination is 2~10 ℃ / min, and the calcination time is 0.5~1 h; In step (3), based on the composite powder I, the mass proportion of sucrose is 8-12 wt%, and the calcination time is 0.5-2 h.

2. The preparation method according to claim 1, characterized in that In step (1), based on the positive electrode active material, the mass proportion of Li3InCl6 is 2~6 wt%.

3. The preparation method according to claim 1, characterized in that In step (4), the mass ratio of the composite powder II, the conductive agent and the binder is 8:1:1, the conductive agent is one or more combinations of acetylene black, conductive carbon black, carbon fiber, graphene and carbon nanotubes, and the binder is one or more combinations of polyvinylidene fluoride, polytetrafluoroethylene and styrene-butadiene rubber.

4. The preparation method according to claim 1, characterized in that In step (5), the olefinic polymer is one or more combinations of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene) copolymer, poly(vinylidene fluoride-trifluoroethylene) copolymer, poly(vinylidene fluoride-tetrafluoroethylene) copolymer and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) copolymer; The lithium salt is one or more combinations of LiCl, LiF, LiBr, LiI, Li2SO4, LiNO3, LiPF6, LiTFSI, LiFSI, and LiDFOB; The polar solvent is one or more of acetone, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and 2,2,2-trifluoro-N,N-dimethylacetamide.

5. The preparation method according to claim 1, characterized in that In step (5), the mass ratio of the olefin polymer to the lithium salt is 1-1.5:1; the mass ratio of the LLZO nanowires based on the olefin polymer is 8-15 wt%; the pressure of vacuum infiltration is -0.15-0.05 MPa, and the time is 20-40 min; the pressure of hot pressing is 0.8-1.5 MPa, the temperature is 40-50 °C, and the time is 5-8 min.

6. A solid electrolyte-positive electrode integrated component obtained by the preparation method according to any one of claims 1 to 5.

7. A lithium metal solid-state battery, characterized in that: It comprises the solid electrolyte-positive electrode integrated component according to claim 6 and a lithium metal negative electrode.

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