Positive electrode composite material and preparation method therefor, positive electrode layer, and all-solid-state lithium battery

Abstract

A positive electrode composite material and a preparation method therefor, a positive electrode layer, and an all-solid-state lithium battery. The positive electrode composite material comprises positive electrode active particles, an inner coating layer and an outer coating layer, wherein the inner coating layer and the outer coating layer are sequentially attached to the surface of the positive electrode active particles. The inner coating layer and the outer coating layer each contain a fast ion conductor material. The inner coating layer has a standard electrode potential of 3.6-3.9 V, an elastic modulus of 20 GPa or less, and an ionic conductivity of 10-3 S / cm or above. The outer coating layer has a standard electrode potential of 2.6-3 V and an ionic conductivity of 10-4 S / cm or above.

Description

A positive electrode composite material and a preparation method thereof, a positive electrode layer and a full solid-state lithium battery TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of solid-state batteries, in particular, to a positive electrode composite material and a preparation method thereof, a positive electrode layer and a full solid-state lithium battery. BACKGROUND

[0002] The existing full solid-state lithium battery based on inorganic solid-state electrolyte adopts a traditional positive electrode material. Due to the easy occurrence of side reactions between the high-voltage positive electrode and the solid-state electrolyte material, the capacity of the battery rapidly decays, and thus the surface of the positive electrode material needs to be coated. The coating is mostly an oxide, a transition metal oxide containing lithium, etc., such as LiNbO3, LiTaO3, Li4Ti5O 12 , Al2O3, etc. Among them, the positive electrode material coated with LiNbO3 is most widely used. The coating reduces the occurrence of side reactions between the positive electrode material and the solid-state electrolyte which is not resistant to oxidation, so as to improve the overall performance of the battery. The existing technology generally selects one or more materials to coat the positive electrode active material. The performance of the coating material itself will have a certain degree of influence on the coating effect.

[0003] In the related art, the positive electrode material includes a positive electrode active material and a coating layer coated on the surface of the positive electrode active material. The coating layer includes a transition metal sulfide and a transition metal oxide, and the transition metal oxide is generated in situ from part of the transition metal sulfide. The transition metal sulfide has good electronic conductivity, and the transition metal oxide has good ionic conductivity. In the related art, the double-coated positive electrode material includes a first coating layer and a second coating layer which are sequentially coated on the positive electrode material. The first coating layer and the second coating layer are different. The first coating layer is a LATP layer or a LNTO layer, and the second coating layer is a LNTO layer or a LATP layer. The two coating materials produce a synergistic effect, so that the coating layer is well covered on the surface of the positive electrode material. In the charging and discharging process, the coating layer and the surface of the positive electrode material are difficult to produce an interlayer, thereby relieving the interface side reaction. However, the surface coating layer of the above-mentioned positive electrode material still cracks or even falls off, causing the electrolyte particles to contact the positive electrode material particles and be oxidized, the interface impedance increases, and the battery performance continuously decays. In addition, the interface impedance between the positive electrode material and the solid-state electrolyte layer is still large, which affects the electrochemical performance of the battery. Based on the current coating conditions, the uniformity of the coating and the coating temperature cannot achieve perfect coating effect, and the related electrochemical performance of the full solid-state lithium battery is still seriously affected by the space charge layer, such as large battery impedance, serious polarization in the charging and discharging process, low capacity development, poor cycle stability, poor battery performance under high rate, etc. SUMMARY

[0004] The purpose of the present disclosure is to provide a positive electrode composite material and a preparation method, a positive electrode layer and a full solid-state lithium battery, which can effectively block the side reaction between the positive electrode active particles and the solid-state electrolyte, reduce the interface impedance, improve the capacity release degree of the positive electrode active particles, slow down the capacity decay, and improve the cycle performance of the solid-state battery.

[0005] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides a positive electrode composite material, which comprises positive electrode active particles, an inner coating layer and an outer coating layer; the inner coating layer and the outer coating layer are sequentially attached to the surface of the positive electrode active particles; the inner coating layer and the outer coating layer each independently contain a fast ion conductor material;

[0006] The standard electrode potential of the inner coating layer is 3.6-3.9 V, the elastic modulus of the inner coating layer is 20 GPa or less, and the ionic conductivity of the inner coating layer is 10 -3 S / cm or more;

[0007] The standard electrode potential of the outer coating layer is 2.6-3 V, and the ionic conductivity of the outer coating layer is 10 -4 S / cm or more.

[0008] Optionally, the difference between the standard electrode potentials of the inner coating layer and the outer coating layer is 0.6-1.3 V, preferably 0.8-1.2 V.

[0009] Optionally, the weight content of the inner coating layer is 0.2-5 wt% and the weight content of the outer coating layer is 0.05-2 wt% based on the weight of the positive electrode composite material.

[0010] Optionally, the weight content of the inner coating layer is 0.2-2 wt% and the weight content of the outer coating layer is 0.1-1 wt% based on the weight of the positive electrode composite material.

[0011] Optionally, the fast ion conductor material of the inner coating layer comprises zirconium-containing nanoparticles, the zirconium-containing nanoparticles have the chemical formula of Li y ZrCl y+ 3O 0.5 , y is any number between 1 and 4; the fast ion conductor material of the outer coating layer comprises anti-perovskite electrolyte particles, the anti-perovskite electrolyte particles have the chemical formula of Li3OX, X is one or more of Cl, Br and I.

[0012] Optionally, the D 50 particle size of the fast ion conductor material in the inner coating layer is 10-200 nm; the D 50The particle size of the fast ion conductor material in the inner coating layer is 10-150 nm.

[0013] Optionally, the D50 of the fast ion conductor material in the inner coating layer is 10-150 nm. 50 The particle size of the fast ion conductor material in the outer coating layer is 15-150 nm. 50 The particle size of the fast ion conductor material in the outer coating layer is 15-100 nm.

[0014] Optionally, the mass content of the zirconium element is 0.065-1.6 wt%, preferably 0.065-0.65 wt%, based on the weight of the positive electrode composite material; and the mass content of the X element is 0.05-2 wt%, preferably 0.1-1 wt%.

[0015] Optionally, the positive electrode active particles include one or more of lithium cobaltate, lithium manganate, nickel cobalt manganese, and nickel cobalt aluminum.

[0016] The second aspect of the present disclosure provides a method for preparing the positive electrode composite material of the first aspect of the present disclosure, the method comprising the following steps:

[0017] The inner layer particles are first mixed with the positive electrode active particles to obtain positive electrode active particles with an inner coating layer; the positive electrode active particles with the inner coating layer are second mixed with the outer layer particles to obtain the positive electrode composite material with the inner coating layer and the outer coating layer; the inner layer particles and the outer layer particles each independently include a fast ion conductor material;

[0018] The standard electrode potential of the inner coating layer is 3.6-3.9 V, the elastic modulus of the inner coating layer is 20 GPa or less, and the ionic conductivity of the inner coating layer is 10 -3 S / cm or more;

[0019] The standard electrode potential of the outer coating layer is 2.6-3 V, and the ionic conductivity of the outer coating layer is 10 -4 S / cm or more.

[0020] Optionally, the D50 of the positive electrode active particles is 3-10 μm. 50 The particle size of the fast ion conductor material in the inner coating layer is 10-150 nm.

[0021] Optionally, the mass ratio of the positive electrode active particles to the inner layer particles is 100:0.2-5; and the mass ratio of the positive electrode active particles with the inner coating layer to the outer layer particles is 100:0.05-2.

[0022] Optionally, the mass ratio of the positive electrode active particles to the inner layer particles is 100:0.2-2; and the mass ratio of the positive electrode active particles with the inner coating layer to the outer layer particles is 100:0.1-1.

[0023] Optionally, the conditions of the first mixing include that the first mixing is performed in a fusion modifier machine, the mixing time is 10-40 min, preferably 15-35 min; the rotation speed is 2000-6000 rpm, preferably 3000-5000 rpm.

[0024] The conditions of the second mixing include that the temperature is 300-500℃, preferably 350-450℃; the time is 15-25 h, preferably 18-22 h.

[0025] The third aspect of the present disclosure provides a positive electrode layer, which comprises a positive electrode composite, a conductive agent and a sulfur-based solid electrolyte particle; the positive electrode composite is the positive electrode composite according to the first aspect of the present disclosure.

[0026] The fourth aspect of the present disclosure provides a full solid-state lithium battery comprising the positive electrode layer according to the fourth aspect of the present disclosure.

[0027] Through the above technical solution, the present disclosure coats the positive electrode active particles with a double-layer coating, the standard electrode potential of the double-layer coating decreases in turn, and the inner coating layer in contact with the positive electrode active particles has a certain elastic modulus, so that the surface potential of the positive electrode active particles to the solid electrolyte layer decreases slowly in turn, avoiding sharp drop, reducing the potential difference of the interface layer, and reducing the interface impedance; at the same time, the inner coating layer has good deformation ability and ionic conductivity, which can adapt to the volume change of the positive electrode active particles in the process of deintercalating lithium, absorb the stress generated in the charging and discharging process, relieve the generation of cracks in the positive electrode material, improve the mechanical strength of the positive electrode material, and further improve the cycle performance of the solid-state battery. The positive electrode composite of the present disclosure can effectively block the side reaction between the positive electrode active particles and the solid electrolyte, reduce the interface impedance, improve the capacity of the positive electrode active particles, slow down the capacity decay, and improve the cycle performance of the solid-state battery.

[0028] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation on the present disclosure. In the drawings:

[0030] FIG. 1 is a TEM image of the positive electrode composite prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0031] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and do not limit the present disclosure.

[0032] The first aspect of the present disclosure provides a positive electrode composite material, which comprises positive electrode active particles, an inner coating layer and an outer coating layer; the inner coating layer and the outer coating layer are sequentially attached to the surface of the positive electrode active particles; the inner coating layer and the outer coating layer each independently contain a fast ion conductor material;

[0033] The standard electrode potential of the inner coating layer is 3.6-3.9 V, the elastic modulus of the inner coating layer is 20 GPa or less, and the ionic conductivity of the inner coating layer is 10 -3 S / cm or more;

[0034] The standard electrode potential of the outer coating layer is 2.6-3 V, and the ionic conductivity of the outer coating layer is 10 -4 S / cm or more.

[0035] The present disclosure coats the positive electrode active particles with a double layer. The inner coating layer in contact with the positive electrode active particles has a certain elastic modulus and a standard electrode potential lower than that of the positive electrode active particles. The standard electrode potential of the outer coating layer away from the positive electrode active particles is higher than that of the solid-state electrolyte layer, so that the surface potential of the positive electrode active particles to the solid-state electrolyte layer gradually decreases in turn, avoiding a sharp drop, reducing the potential difference of the interface layer, and reducing the interface impedance. At the same time, the inner coating layer has good deformation ability and ionic conductivity, which can adapt to the volume change of the positive electrode active particles during lithium deintercalation, absorb the stress generated during charging and discharging, relieve the generation of positive electrode material cracks, improve the mechanical strength of the positive electrode material, and further improve the cycle performance of the solid-state battery. The positive electrode composite material of the present disclosure can effectively block the side reaction between the positive electrode active particles and the solid-state electrolyte, reduce the interface impedance, improve the capacity of the positive electrode active particles, slow down the capacity decay, and improve the cycle performance of the solid-state battery.

[0036] The coating of the present disclosure refers to that the inner layer particles are attached to the surface of the active particles, and the outer layer particles are attached to the surface of the inner layer particles. The inner coating layer and the outer coating layer of the present disclosure can coat the entire surface of the positive electrode active particles, or coat part of the surface of the positive electrode active particles.

[0037] According to an embodiment of the present disclosure, the difference between the standard electrode potentials of the inner coating layer and the outer coating layer is 0.6-1.3 V, preferably 0.8-1.2 V. The above embodiment is beneficial to gradually reduce the surface potential of the positive electrode composite material particles from the inside to the outside, avoid a sharp drop, reduce the potential difference of the interface layer, and further reduce the interface impedance, which is beneficial to optimize the space charge layer between the positive electrode active particles and the solid-state electrolyte interface.

[0038] According to an embodiment of the present disclosure, the weight content of the inner coating layer is 0.2-5 wt%, preferably 0.2-2 wt%, based on the weight of the positive electrode composite material; the weight content of the outer coating layer is 0.05-2 wt%, preferably 0.1-1 wt%. In the present disclosure, the weight content of the inner coating layer and the outer coating layer is calculated based on the feeding amount of the inner layer particles and the outer layer particles in the preparation process. In the above embodiment, the inner coating layer and the outer coating layer are coated with appropriate weights, which is beneficial to alleviate the generation of cracks in the positive electrode composite material, improve the mechanical strength of the positive electrode composite material, and better improve the cycle performance of the solid-state lithium battery.

[0039] According to an embodiment of the present disclosure, the fast ion conductor material can be in the form of particles.

[0040] According to an embodiment of the present disclosure, the fast ion conductor material of the inner coating layer comprises zirconium-containing nanoparticles, the zirconium-containing nanoparticles have a chemical formula of Li y ZrCl y+3 O 0.5 , wherein y is any number between 1 and 4; the D 50 particle size of the zirconium-containing nanoparticles is 10-200 nm, preferably 15-150 nm. In the above embodiment, the inner coating layer is coated with an appropriate thickness, which is beneficial to the inner coating layer having good ion conductivity and better deformation ability, and the inner coating layer is not easy to break, so that the inner coating layer can absorb the volume change of the positive electrode composite material during the charging and discharging process while providing higher lithium ion conductivity, alleviate the generation of cracks in the positive electrode composite material, improve the mechanical strength of the positive electrode composite material, and further improve the cycle performance of the solid-state lithium battery.

[0041] According to an embodiment of the present disclosure, the fast ion conductor material of the outer coating layer comprises anti-perovskite electrolyte particles, the anti-perovskite electrolyte particles have a chemical formula of Li3OX, X is one or more of Cl, Br and I; the anti-perovskite electrolyte particles comprise one or more of Li3OCl, Li3OBr, Li3OCl 0.5 Br 0.5 , and Li3OI; the D 50 particle size of the anti-perovskite electrolyte particles is 10-150 nm, preferably 15-100 nm. In the above embodiment, the outer coating layer is coated with an appropriate thickness, which is beneficial to slowly reduce the potential of the positive electrode composite material particles from the inside to the outside, avoid sharp drop, optimize the space charge layer between the positive electrode active particles and the solid-state electrolyte interface, reduce the interface impedance, maximize the capacity of the positive electrode composite material, alleviate the rapid capacity decay of the battery, and improve the cycle performance of the solid-state lithium battery.

[0042] In the present disclosure, the particle size of the inner layer of the particles of the fast ion conductor material in the positive electrode composite material and the particle size of the outer layer of the particles of the fast ion conductor material can be tested by the following method: a certain amount of the composite positive electrode sheet is taken, the composite positive electrode sheet is cross-sectionally cut using a focused ion beam, and then observed using a scanning electron microscope, and the D 50 particle size of the inner layer particles and the outer layer particles on the surface of the positive electrode active particles is counted.

[0043] According to an embodiment of the present disclosure, the mass content of the zirconium element is 0.065-1.6 wt%, preferably 0.065-0.65 wt%, and the mass content of the X element is 0.025-1.0 wt%, preferably 0.05-0.5 wt%, and the X is one or more of Cl, Br and I, based on the weight of the positive electrode composite material. In this embodiment, the mass content of the X element refers to the mass content of the X element from the anti-perovskite electrolyte particles of the outer coating layer in the positive electrode composite material. It can be understood in the art that in the embodiment in which the X element includes Cl, the mass content of the Cl element measured in the positive electrode composite material includes the Cl (X element) of the anti-perovskite electrolyte particles of the outer coating layer, and also includes the Cl from the zirconium-containing nanoparticles of the inner coating layer. The above embodiment is advantageous for coating the inner coating layer and the outer coating layer with a suitable thickness, so that the inner coating layer can absorb the volume change of the positive electrode composite material during the charging and discharging process while providing a higher lithium ion conductivity, relieve the generation of cracks in the positive electrode composite material, and improve the mechanical strength of the positive electrode composite material; it is also advantageous for the potential of the positive electrode composite material particles to decrease slowly from the inside to the outside, avoiding a sharp drop, and for optimizing the space charge layer between the positive electrode active particles and the solid-state electrolyte interface, reducing the interface impedance, and maximizing the capacity of the positive electrode composite material, relieving the rapid capacity decay of the battery, and improving the cycle performance of the all-solid-state lithium battery.

[0044] According to an embodiment of the present disclosure, the positive electrode active particles include one or more of lithium cobaltate, lithium manganate, nickel cobalt manganese and nickel cobalt aluminum. In the present disclosure, lithium cobaltate, lithium manganate, nickel cobalt manganese and nickel cobalt aluminum are conventional positive electrode active materials in the art.

[0045] The second aspect of the present disclosure provides a method for preparing the positive electrode composite material of the first aspect of the present disclosure, which comprises the following steps:

[0046] The inner layer particles are first mixed with the positive electrode active particles to obtain positive electrode active particles with an inner coating layer; the positive electrode active particles with the inner coating layer are second mixed with the outer layer particles to obtain positive electrode composite material with an inner coating layer and an outer coating layer; the inner layer particles and the outer layer particles each independently comprise a fast ion conductor material;

[0047] The standard electrode potential of the inner coating layer is 3.6-3.9 V, the elastic modulus of the inner coating layer is 20 GPa or less, and the ionic conductivity of the inner coating layer is 10 -3 S / cm or more;

[0048] The standard electrode potential of the outer coating layer is 2.6-3 V, and the ionic conductivity of the outer coating layer is 10 -4 S / cm or more.

[0049] The method of the present disclosure sequentially attaches an inner coating layer and an outer coating layer to the surface of the positive electrode active particles, the standard electrode potential of the double-layer coating layer sequentially decreases, and the inner coating layer in contact with the positive electrode active particles has a certain elastic modulus, which gradually reduces the surface potential of the positive electrode active particles to the solid-state electrolyte layer, avoids sharp drops, reduces the potential difference of the interface layer, and reduces the interface impedance; at the same time, the inner coating layer has good deformation ability and ionic conductivity, which can adapt to the volume change of the positive electrode active particles during lithium extraction, absorb the stress generated during charging and discharging, relieve the generation of positive electrode material cracks, improve the mechanical strength of the positive electrode material, and improve the cycle performance of the solid-state battery.

[0050] According to an embodiment of the present disclosure, the inner layer particles include zirconium-containing nanoparticles, the zirconium-containing nanoparticles have a chemical formula of Li y ZrCl y+3 O 0.5 , wherein y is any number between 1 and 4; the D 50 particle size of the zirconium-containing nanoparticles is 10-200 nm. The above embodiment is beneficial for coating an inner coating layer with a suitable thickness, is beneficial for the inner coating layer to have good ionic conductivity and better deformation ability, is not easy to break, and enables the inner coating layer to absorb the volume change of the positive electrode composite material during charging and discharging while providing higher lithium ion conductivity, relieve the generation of positive electrode composite material cracks, improve the mechanical strength of the positive electrode composite material, and further improve the cycle performance of the solid-state lithium battery.

[0051] According to an embodiment of the present disclosure, the outer layer particles include anti-perovskite electrolyte particles, the anti-perovskite electrolyte particles have a chemical formula of Li3OX, X is one or more of Cl, Br, and I; the D 50 particle size of the outer layer particles is 10-150 nm. The above embodiment is beneficial for coating an outer coating layer with a suitable thickness, is beneficial for the potential of the positive electrode composite material particles to gradually decrease from the inside to the outside, avoid sharp drops, is beneficial for optimizing the space charge layer between the positive electrode active particles and the solid-state electrolyte interface, reducing the interface impedance, is beneficial for the capacity of the positive electrode composite material to be maximized, relieving the phenomenon of rapid capacity decay of the battery, and improving the cycle performance of the all-solid-state lithium battery.

[0052] According to an embodiment of the present disclosure, the mass ratio of the positive electrode active particles to the inner layer particles is 100:0.2-5, preferably 100:0.2-2; the mass ratio of the positive electrode active particles with the inner coating layer to the outer layer particles is 100:0.05-2, preferably 100:0.1-1; the D50 of the positive electrode active particles is 3-10 μm. 50 The particle size is 3-10 μm. The above embodiment is advantageous for coating the inner coating layer and the outer coating layer with a suitable thickness, so that the inner coating layer can absorb the volume change of the positive electrode composite material during the charging and discharging process while providing a higher lithium ion conductivity, relieve the generation of cracks of the positive electrode composite material, and improve the mechanical strength of the positive electrode composite material; it is advantageous for the potential of the positive electrode composite material particles to slowly decrease from the inside to the outside, avoiding sharp drop, and it is advantageous for optimizing the space charge layer between the positive electrode active particles and the solid-state electrolyte interface, reducing the interface impedance, and it is advantageous for the capacity of the positive electrode composite material to be maximized, relieving the phenomenon of rapid capacity decay of the battery, and improving the cycle performance of the full solid-state lithium battery.

[0053] According to an embodiment of the present disclosure, the conditions of the first mixing include that the first mixing is carried out in a fusion modifier, the mixing time is 10-40 min, preferably 15-35 min; the rotation speed is 2000-6000 rpm, preferably 3000-5000 rpm. The conditions of the first mixing include that the temperature is 300-500℃, preferably 350-450℃; the time is 15-25 h, preferably 18-22 h. The above embodiment is advantageous for the inner coating layer and the outer coating layer to better adhere to the surface of the positive electrode active particles.

[0054] According to an embodiment of the present disclosure, the Li y ZrCl y+3 O 0.5 The preparation method of the particles includes: under an inert atmosphere, LiCl, ZrCl4 and Li2O are weighed according to the stoichiometric ratio, mixed and then ball milled; optionally, the rotation speed of the ball milling can be 300-800 rpm, preferably 500-700 rpm; the ball milling time can be 4-16 h, preferably 6-12 h. The above embodiment is advantageous for better preparing the Li y ZrCl y+3 O 0.5 particles. In this embodiment, the D50 of the Li y ZrCl y+3 O 0.5 particles can be measured by using a laser particle size analyzer. 50 particle size.

[0055] According to an embodiment of the present disclosure, the outer layer particles comprise Li3OCl particles; and a preparation method of the Li3OCl particles comprises: mixing LiOH and LiCl in a stoichiometric ratio, and then placing the mixture in a vacuum tube furnace for calcination after ball milling, wherein the calcination conditions comprise: a heating rate of 1-5 ℃ / min, a calcination temperature of 270-350 ℃, and a calcination time of 3-7 h. The above embodiment is advantageous for obtaining Li3OCl particles. In this embodiment, the particle size of the Li3OCl particles can be measured by using a laser particle size analyzer. y ZrCl y+3 O 0.5 D 50 particle size.

[0056] The third aspect of the present disclosure provides a positive electrode layer, which comprises a positive electrode composite material, a conductive agent, and a sulfide solid-state electrolyte particle; the positive electrode composite material is the positive electrode composite material according to the first aspect of the present disclosure.

[0057] According to an embodiment of the present disclosure, the conductive agent can be selected from one or more of carbon black, conductive graphite, carbon nanotubes, and nano-carbon fiber (VGCF).

[0058] The fourth aspect of the present disclosure provides an all-solid-state lithium battery comprising the positive electrode layer according to the third aspect of the present disclosure.

[0059] According to an embodiment of the present disclosure, the all-solid-state lithium battery further comprises a negative electrode layer and a solid-state electrolyte layer located between the positive electrode layer and the negative electrode layer; the solid-state electrolyte layer is a sulfide solid-state electrolyte selected from one or more of lithium phosphorus sulfur chloride solid-state electrolyte (LPSC), lithium germanium phosphorus sulfur solid-state electrolyte (LGPS), and lithium phosphorus sulfur solid-state electrolyte (LPS); wherein the chemical formula of the LPSC is Li 6-x PS 5-x Cl 1+x , x is any value between 0 and 0.8; the chemical formula of the LGPS is Li 11-y M 2-y P 1+y S 12 , M is selected from Ge or S, and y is any value between 0.5 and 1.5; and the chemical formula of the LPS is 75Li2S-25P2S5; the negative electrode layer comprises a negative electrode active material, and the negative electrode active material comprises one or more of a silicon-based material, a silicon-oxygen-based material, a silicon-carbon-based material, graphite, metallic lithium, lithium titanate, and lithium-indium alloy material.

[0060] The fifth aspect of the present disclosure provides a method for preparing the all-solid-state lithium battery according to the fourth aspect of the present disclosure, which comprises the following steps: sequentially performing pressing treatment on the positive electrode layer, the solid-state electrolyte layer, and the negative electrode layer.

[0061] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited in any way by the examples.

[0062] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure are all purchased through commercial channels. The positive electrode active particles used in the present disclosure are NCM811, purchased from BASF Sunsheng Battery Materials (Ningxiang) Co., Ltd., with a particle size of 3.7 μm and a product number of T85RS.

[0063] Example 1

[0064] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 1.17 g of LiCl, 6.42 g of ZrCl4 and 0.42 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball-milled in a ball mill at a speed of 600 rpm for 10 hours to obtain Li2ZrCl5O 0.5 , with a particle size of 10 nm; 50

[0065] (2) The prepared Li2ZrCl5O 0.5 was weighed according to a mass ratio of 1:100 with NCM811 and added to a fusion modifier, and mixed at a speed of 4000 rpm for 20 min to prepare NCM811 with an inner coating layer of Li2ZrCl5O 0.5 attached to the surface;

[0066] (3) 2.4 g of LiOH and 2.1 g of LiCl were mixed and ball-milled to make them uniformly mixed, and the mixture was placed in a vacuum tube furnace and heated to 300℃ at a rate of 2℃ / min, and kept at 300℃ for 5h to obtain Li3OCl particles, with a particle size of 15 nm; 50

[0067] (4) The prepared Li3OCl particles were mixed with the NCM811 coated with Li2ZrCl5O 0.5 in step (2) according to a mass ratio of 0.5:100, and heated to 400℃ and kept for 20h; then cooled to room temperature to obtain a positive electrode composite material S1 with NCM811 being sequentially attached and coated with Li2ZrCl5O 0.5 and Li3OCl.

[0068] The positive electrode composite material S1 obtained in Example 1 was characterized by TEM, as shown in Figure 1, it can be seen that there are obvious heterophase particles stacked in sequence on the surface of the positive electrode active particles, indicating that there are inner coating layers (LZCO) and outer coating layers (LOC) attached to the surface of the positive electrode active particles (NCM).

[0069] Example 2 ​​

[0070] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 1.17 g of LiCl, 6.42 g of ZrCl4 and 0.42 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball milled in a ball mill at 600 rpm for 10 hours to obtain Li2ZrCl5O 0.5 , the particle size D 50 was 12 nm;

[0071] (2) The prepared Li2ZrCl5O 0.5 was weighed according to a mass ratio of 1:100 with NCM811 and added to a fusion modifier, mixed at a speed of 4000 rpm for 20 min to prepare NCM811 with a Li2ZrCl5O 0.5 coating layer attached to the surface;

[0072] (3) 2.4 g of LiOH and 4.3 g of LiBr were mixed and ball milled to mix them uniformly, and the mixture was placed in a vacuum tube furnace, which was raised to 300°C at a rate of 2°C / min, and kept at 300°C for 5 h to obtain Li3OBr particles, the particle size D 50 was 18 nm;

[0073] (4) The prepared Li3OBr particles were mixed uniformly with the Li2ZrCl5O 0.5 coated NCM811 in step (2) according to a mass ratio of 0.5:100, and heated to 400°C for 20 h; then cooled to room temperature to obtain the positive electrode composite material S2 with NCM811 sequentially coated with Li2ZrCl5O 0.5 and Li3OBr.

[0074] Example 3

[0075] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 1.17 g of LiCl, 6.42 g of ZrCl4 and 0.42 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball milled in a ball mill at 600 rpm for 10 hours to obtain Li2ZrCl5O 2.25 ZrCl 5.25 O 0.5 , the particle size D 50 was 12 nm;

[0076] (2) The prepared Li 2.25 ZrCl 5.25 O 0.5 was weighed according to a mass ratio of 1:100 with NCM811 and added to a fusion modifier, mixed at a speed of 4000 rpm for 20 min to prepare NCM811 with a Li2ZrCl5O 2.25ZrCl 5.25 O 0.5 NCM811 with inner coating layer;

[0077] (3) 2.4 g of LiOH, 1.0 g of LiCl and 2.2 g of LiBr were mixed and ball-milled to mix them uniformly, the mixture was placed in a vacuum tube furnace, and was raised to 300℃ at a rate of 2℃ / min, and was kept at 300℃ for 5 h to obtain Li3OCl 0.5 Br 0.5 particles, particles D 50 with a particle size of 20 nm;

[0078] (4) The prepared Li3OCl 0.5 Br 0.5 particles were mixed with Li2ZrCl5O 0.5 coated NCM811 obtained in step (2) uniformly at a mass ratio of 0.5:100, and was heated to 400℃ and kept for 20 h; then cooled to room temperature to obtain NCM811 coated with Li 2.25 ZrCl 5.25 O 0.5 and Li3OCl 0.5 Br 0.5 coated positive electrode composite material S3 in turn.

[0079] Example 4

[0080] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 2.0 g of LiCl, 5.60 g of ZrCl4 and 0.36 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball-milled in a ball mill at 600 rpm for 10 hours to obtain Li3ZrCl6O 0.5 , particles D 50 with a particle size of 20 nm;

[0081] (2) The prepared Li3ZrCl6O0.5 was weighed and mixed with NCM811 at a mass ratio of 0.5:100 and added to a fusion modifier, and mixed at a speed of 4000 rpm for 20 min to prepare NCM811 with Li3ZrCl6O 0.5 inner coating layer;

[0082] (3) 2.4 g of LiOH and 2.1 g of LiCl were mixed and ball-milled to mix them uniformly, the mixture was placed in a vacuum tube furnace, and was raised to 300℃ at a rate of 2℃ / min, and was kept at 300℃ for 5 h to obtain Li3OCl particles, particles D 50 with a particle size of 50 nm;

[0083] (4) The prepared Li3OCl particles were mixed with the Li3ZrCl6O 0.5 The coated NCM811 was mixed uniformly at a mass ratio of 0.5:100 and heated to 400°C for 20h; then cooled to room temperature to obtain NCM811 coated with Li3ZrCl6O 0.5 and Li3OCl in sequence.

[0084] Example 5

[0085] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 0.91g of LiCl, 6.66g of ZrCl4 and 0.43g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball milled in a ball mill at 600rpm for 10 hours to obtain Li 1.75 ZrCl 4.75 O 0.5 , particle D 50 with a particle size of 30nm;

[0086] (2) The prepared Li 1.75 ZrCl 4.75 O 0.5 was weighed and added to a fusion modifier at a mass ratio of 1:100 with NCM811, and mixed at a speed of 4000rpm for 20min to prepare NCM811 coated with Li 1.75 ZrCl 4.75 O 0.5 inner coating layer;

[0087] (3) 2.4g of LiOH and 2.1g of LiCl were mixed and ball milled to mix them uniformly, and the mixture was placed in a vacuum tube furnace, heated to 300°C at a rate of 2°C / min, and kept at 300°C for 5h to obtain Li3OCl particles, particle D 50 with a particle size of 60nm;

[0088] (4) The prepared Li3OCl particles were mixed with the Li 1.75 ZrCl 4.75 O 0.5 coated NCM811 obtained in step (2) at a mass ratio of 1:100 and heated to 400°C for 20h; then cooled to room temperature to obtain NCM811 coated with Li 1.75 ZrCl 4.75 O 0.5 and Li3OCl in sequence.

[0089] Example 6

[0090] (1) In an argon-protected glove box (water and oxygen content <0.01 ppm), 1.17 g of LiCl, 6.42 g of ZrCl4 and 0.42 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconium oxide ball mill jar, which was sealed and ball milled in a ball mill at 500 rpm for 12 hours to obtain Li2ZrCl5O 0.5 , particle D 50 with a particle size of 32 nm;

[0091] (2) The prepared Li2ZrCl5O 0.5 and NCM811 were weighed in a mass ratio of 1.5:100 and added to a fusion modifier, mixed at a speed of 3000 rpm for 40 min to obtain NCM811 coated with a Li2ZrCl5O 0.5 inner coating layer;

[0092] (3) 2.4 g of LiOH and 2.1 g of LiCl were mixed and ball milled to mix them uniformly, and the mixture was placed in a vacuum tube furnace, which was raised to 300°C at a rate of 2°C / min, and kept at 300°C for 5h to obtain Li3OCl particles, particle D 50 with a particle size of 80 nm;

[0093] (4) The prepared Li3OCl particles and NCM811 coated with a Li2ZrCl5O 0.5 inner coating layer obtained in step (2) were mixed uniformly in a mass ratio of 1:100, and heated to 400°C and kept for 20h; then cooled to room temperature to obtain NCM811 coated with Li2ZrCl5O 0.5 and Li3OCl in turn, which was positive electrode composite material S6.

[0094] Example 7

[0095] The method was the same as that of Example 1, except that the mass ratio of Li2ZrCl5O 0.5 to NCM811 in step (2) was 3:100, and positive electrode composite material S7 was obtained.

[0096] Example 8

[0097] The method was the same as that of Example 1, except that the mass ratio of Li3OCl particles to Li2ZrCl5O 0.5 coated NCM811 in step (4) was 1.5:100, and positive electrode composite material S8 was obtained.

[0098] Example 9

[0099] The method was the same as that of Example 1, except that Li2ZrCl5O 50 with a particle size of 230 nm was prepared in step (1).0.5 ; D was prepared in step (3) 50 Li3OCl particles with a particle size of 200 nm were obtained, and a positive electrode composite S9 was obtained.

[0100] Comparative Example 1

[0101] (1) In an argon glove box (water and oxygen content <0.01 ppm), 1.17 g of LiCl, 6.42 g of ZrCl4 and 0.83 g of Li2O were weighed according to the stoichiometric ratio and placed in a zirconia ball mill jar, which was sealed and ball milled in a ball mill at 600 rpm for 10 hours to obtain Li2ZrCl5O 0.5 , particles D 50 with a particle size of 15 nm;

[0102] (2) The prepared Li2ZrCl5O 0.5 was weighed according to a mass ratio of 1:100 with NCM811 and added to a fusion modifier, mixed at a speed of 4000 rpm for 20 min to prepare NCM811 with a Li2ZrCl5O 0.5 coating layer attached to the surface, denoted as positive electrode composite D1.

[0103] Comparative Example 2

[0104] 2.4 g of LiOH and 2.1 g of LiCl were mixed and ball milled to mix them uniformly, and the mixture was placed in a vacuum tube furnace, raised to 300°C at a rate of 2°C / min, and kept at 300°C for 5 h to obtain Li3OCl particles with a particle size of 20 nm;

[0105] The prepared Li3OCl particles were mixed with uncoated NCM811 according to a mass ratio of 0.5:100 and uniformly mixed, and then heated to 400°C and kept for 20 h; then cooled to room temperature to obtain NCM811 with Li3OCl attached to the surface, denoted as positive electrode composite D2.

[0106] Comparative Example 3

[0107] The uncoated NCM811 was used as a positive electrode material D3.

[0108] Test Example

[0109] The element content of the positive electrode composite material obtained in Examples 1-9 and Comparative Examples 1-3 was tested, and the weight content of the elements was tested by an inductively coupled plasma instrument of model iCAP 7400DUO; at the same time, the ionic conductivity of the inner coating layer and the ionic conductivity of the outer coating layer were tested by an alternating current impedance test instrument; the elastic modulus of the inner coating layer was tested by a universal testing machine instrument; the particle size of the inner layer particles and the outer layer particles was tested by a scanning electron microscope instrument of Pharos G2 model; the particle size of the positive electrode composite material was tested by a laser particle size instrument of LT3600Plus model; and the transmission electron microscope was tested on an instrument of model TH7800, and the test results are shown in Table 1. 50 The particle size was tested by a laser particle size instrument of LT3600Plus model; the transmission electron microscope was tested on an instrument of model TH7800, and the test results are shown in Table 1.

[0110] In an argon-filled glove box, the coated positive electrode material obtained in Examples 1-9 and Comparative Examples 1-3, and the conductive agent VGCF, Li6PS5Cl were mixed uniformly as the positive electrode layer, the solid electrolyte layer used Li6PS5Cl, the standard electrode potential was 2.5V, and the negative electrode layer used lithium-indium alloy to assemble solid-state mold batteries (SP-1 to SP-9 and DP-1 to DP-3) each 3 pieces; the test equipment was a LAND CT 2001C secondary battery performance detection device, and the charge-discharge cycle test was performed.

[0111] The cycle test conditions were that the above-mentioned batteries were placed at room temperature (25°C) for 10 min; charged to 3.7V at a constant current of 0.1C and stopped; placed for 10 min; discharged to 2V at a constant current of 0.1C, which was 1 cycle. The step was repeated, the discharge capacity was recorded, the cycle number was set to 100 times, the cycle was terminated and the capacity retention rate was calculated, the finally determined capacity retention rate was the average value of the capacity retention rates of 3 test batteries, and the average test results are shown in Table 1.

[0112] Among them, the cycle 100 times capacity maintenance rate = (cycle 100 times discharge specific capacity ÷ first discharge specific capacity) x 100%.

[0113] The test results are shown in Table 2.

[0114] Table 1

[0115] Table 2

[0116] According to the data in Table 2, compared with Comparative Examples 1-3, the positive electrode composite material of the present disclosure can effectively improve the initial discharge specific capacity and cycle performance of the solid-state lithium battery when used in the solid-state lithium battery. According to the comparison between Example 1 and Example 7, within the preferred weight ratio range of the inner layer particles and the positive electrode active particles, the performance of the prepared positive electrode composite material is better, and when used in the solid-state lithium battery, the initial discharge specific capacity and cycle performance are better. According to the comparison between Example 1 and Example 8, within the preferred weight ratio range of the outer layer particles and the positive electrode active particles with the inner coating layer, the performance of the prepared positive electrode composite material is better, and when used in the solid-state lithium battery, the initial discharge specific capacity and cycle performance are better. According to the comparison between Example 1 and Example 9, within the preferred D 50 range of the inner layer particles and the outer layer particles, the performance of the prepared positive electrode composite material is better, and when used in the solid-state lithium battery, the initial discharge specific capacity and cycle performance are better.

[0117] The above describes the preferred embodiments of the present disclosure, but the present disclosure is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0118] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

Claims

1. A positive electrode composite material, characterized in that, The positive electrode composite material includes positive electrode active particles, an inner coating layer, and an outer coating layer; the inner coating layer and the outer coating layer are sequentially attached to the surface of the positive electrode active particles; the inner coating layer and the outer coating layer each independently contain a fast ion conductor material; The standard electrode potential of the inner coating layer is 3.6–3.9 V, the elastic modulus of the inner coating layer is below 20 GPa, and the ionic conductivity of the inner coating layer is 10. -3 S / cm or higher; The standard electrode potential of the outer coating layer is 2.6–3V, and the ionic conductivity of the outer coating layer is 10. -4 S / cm or higher.

2. The positive electrode composite material according to claim 1, wherein, The difference between the standard electrode potential of the inner coating layer and the outer coating layer is 0.6 to 1.3 V, preferably 0.8 to 1.2 V.

3. The positive electrode composite material according to claim 1 or 2, wherein, Based on the weight of the positive electrode composite material, the inner coating layer has a weight content of 0.2 to 5 wt%, and the outer coating layer has a weight content of 0.05 to 2 wt%.

4. The positive electrode composite material according to any one of claims 1 to 3, wherein, Based on the weight of the positive electrode composite material, the weight content of the inner coating layer is 0.2-2 wt%, and the weight content of the outer coating layer is 0.1-1 wt%.

5. The positive electrode composite material according to any one of claims 1 to 4, wherein, The fast ion conductor material of the inner cladding layer includes zirconium-containing nanoparticles, which have Li... y ZrCl y+3 O 0.5 The chemical formula of , where y is any value between 1 and 4; the fast ion conductor material of the outer coating layer includes anti-perovskite electrolyte particles, which have the chemical formula Li3OX, where X is one or more of Cl, Br and I.

6. The positive electrode composite material according to any one of claims 1 to 5, wherein, The fast ion conductor material in the inner cladding layer D 50 The particle size is 10–200 nm; the D of the fast ion conductor material in the outer coating layer 50 The particle size is 10–150 nm; the particle size of the positive electrode composite material is 3.2–5.6 μm.

7. The positive electrode composite material according to any one of claims 1 to 6, wherein, The fast ion conductor material in the inner cladding layer D 50 The particle size is 15-150 nm; the D of the fast ion conductor material in the outer coating layer 50 The particle size is 15–100 nm.

8. The positive electrode composite material according to claim 5, wherein, Based on the weight of the positive electrode composite material, the zirconium content is 0.065–1.6 wt%, preferably 0.065–0.65 wt%; the X content is 0.05–2 wt%, preferably 0.1–1 wt%.

9. The positive electrode composite material according to any one of claims 1 to 8, wherein, The positive electrode active particles include one or more of lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese, and nickel cobalt aluminum.

10. A method for preparing a positive electrode composite material as described in any one of claims 1 to 9, characterized in that, The method includes the following steps: The inner layer particles and the positive electrode active particles are first mixed to obtain positive electrode active particles with an inner coating layer; the positive electrode active particles with an inner coating layer are second mixed with the outer layer particles to obtain a positive electrode composite material with an inner coating layer and an outer coating layer; the inner layer particles and the outer layer particles each independently include fast ion conductor materials; The standard electrode potential of the inner coating layer is 3.6–3.9 V, the elastic modulus of the inner coating layer is below 20 GPa, and the ionic conductivity of the inner coating layer is 10. -3 S / cm or higher; The standard electrode potential of the outer coating layer is 2.6–3V, and the ionic conductivity of the outer coating layer is 10. -4 S / cm or higher.

11. The method according to claim 10, wherein, The positive electrode active particles have D 50 The particle size is 3–10 μm.

12. The method according to claim 10 or 11, wherein, The mass ratio of the positive electrode active particles to the inner layer particles is 100:0.2-5; the mass ratio of the positive electrode active particles with the inner coating layer to the outer layer particles is 100:0.05-2.

13. The method according to claim 10 or 11, wherein, The mass ratio of the positive electrode active particles to the inner layer particles is 100:0.2 to 2; the mass ratio of the positive electrode active particles with the inner coating layer to the outer layer particles is 100:0.1 to 1.

14. The method according to any one of claims 10 to 13, wherein, The conditions for the first mixing include: the first mixing is carried out in a fusion modifier, the mixing time is 10 to 40 minutes, preferably 15 to 35 minutes; the rotation speed is 2000 to 6000 rpm, preferably 3000 to 5000 rpm; The conditions for the second mixing include: a temperature of 300–500°C, preferably 350–450°C; and a time of 15–25 h, preferably 18–22 h.

15. A positive electrode layer, characterized in that, The positive electrode layer comprises a positive electrode composite material, a conductive agent, and sulfur-based solid electrolyte particles; the positive electrode composite material is the positive electrode composite material according to any one of claims 1 to 9.

16. An all-solid-state lithium battery, characterized in that, It includes the positive electrode layer as described in claim 15.

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