Active material and preparation method thereof, electrode and secondary battery

Abstract

The invention discloses an active material and a preparation method thereof, an electrode and a secondary battery, and the active material comprises porous particles which are provided with particle inner holes; the hole filling particles are filled in the particle inner holes; the coating layer at least coats the outer sides of the porous particles; wherein the pore-filling particles comprise metal particles, and the coating layer comprises a solid electrolyte layer; wherein the value range of the ratio of the mass of the pore-filling particles to the mass of the coating layer is 0.02 to 40. The active material and the preparation method thereof have the beneficial effects that the direct contact between metal lithium in the porous particles and electrolyte is effectively reduced through coating of the coating layer, so that the battery performance is improved. The invention further provides the preparation method of the active material, the electrode and the secondary battery.

Description

Technical Field

[0001] The present application belongs to the field of new energy technology, and in particular relates to an active material and a preparation method thereof, an electrode, and a secondary battery. Background Art

[0002] The lithium metal anode is an important component of lithium-ion batteries, responsible for storing and releasing electrical energy. The performance of the lithium metal anode directly affects the performance of the entire battery, so the research and development of lithium metal anodes has received a lot of attention in recent years. However, when lithium metal is used as the anode, the cycle life of lithium secondary batteries is limited by the lithium metal anode. During the cycle, dendrites will form on the surface of the lithium metal anode. The formation of lithium metal dendrites will, on the one hand, come into contact with the electrolyte, forming SEI, consuming the electrolyte, reducing the Coulombic efficiency, and thus shortening the battery cycle life and causing rapid battery failure. On the other hand, when lithium metal is directly used as the anode, the deposition of lithium metal during the charge and discharge process will cause huge volume expansion, seriously affecting the stability of the battery cycle and further posing safety risks.

[0003] In some related technologies, porous materials are used for lithium metal negative electrodes. Through customized design of porous materials and lithium-philic substances in the pores, metallic lithium can be induced to enter the pores and deposit, thereby reducing the huge volume expansion effect caused by the direct deposition of metallic lithium, thereby enhancing stability and improving cycle life.

[0004] However, when the structure of porous materials and lithium-philic substances in the pores is directly used as the substrate for metallic lithium deposition, the metallic lithium deposited in the pores will still directly contact the electrolyte outside the pores, thereby causing side reactions, resulting in low coulombic efficiency in the first week, short cycle life, and ultimately rapid battery failure; on the other hand, the porous materials used in the existing technical solutions have a relatively large specific surface area. Such a large specific surface area will cause a large amount of SEI to be formed during the first cycle of lithium deposition, resulting in a large amount of active lithium loss and low coulombic efficiency in the first week, which also seriously affects the cycle life of the battery. Summary of the Invention

[0005] In view of this, the present application provides an active material and a preparation method thereof, an electrode, and a secondary battery, aiming to solve the aforementioned technical problems.

[0006] As a first aspect of the present application, an embodiment of the present application provides an active material comprising: porous particles having intragranular pores; pore-filling particles filling the intragranular pores; and a coating layer at least coating the outside of the porous particles; wherein the pore-filling particles comprise metal particles, and the coating layer comprises a solid electrolyte layer; wherein the ratio of the mass of the pore-filling particles to the mass of the coating layer ranges from 0.02 to 40.

[0007] Optionally, in some embodiments of the present application, the porous particles include: one or more of activated carbon particles, carbon fiber particles, carbon nanotube particles, porous copper particles, porous titanium particles, and porous silver particles; and / or, the metal particles include: one or more of gold, silver, magnesium, tin, and lithium particles; and / or, the solid electrolyte layer includes: one or more of LATP layer, LAGP layer, and LLTO layer.

[0008] Optionally, in some embodiments of the present application, the specific surface area of the porous particles is in the range of 10m 2 / g to 2000m 2 / g; and / or, the particle size of the porous particles ranges from 1 μm to 50 μm; and / or, the pore size of the pores within the particles ranges from 1 nm to 100 nm; and / or, the pore volume of the pores within the particles ranges from 0.80 cm 3 / g to 2.0cm 3 / g; and / or, the particle size of the pore-filling particles ranges from 1 nm to 80 nm; and / or, the thickness of the solid electrolyte layer ranges from 1 nm to 80 nm; and / or, the particle size of the active material ranges from 2 μm to 55 μm.

[0009] Optionally, in some embodiments of the present application, the ratio of the mass of the pore-filling particles to the mass of the porous particles ranges from 0.01 to 0.8.

[0010] Optionally, the ratio of the mass of the coating layer to the mass of the porous particles ranges from 0.02 to 0.2.

[0011] Optionally, in some embodiments of the present application, the active material further includes: an intermediate layer formed between the porous particles and the coating layer; wherein the intermediate layer is a carbon layer.

[0012] Optionally, in some embodiments of the present application, the ratio of the mass of the pore-filling particles to the mass of the intermediate layer is in the range of 0.1 to 10; the carbon layer is one or more of soft carbon, hard carbon, amorphous carbon, and onion carbon; and / or the thickness of the carbon layer is in the range of 1 nm to 1000 nm.

[0013] As a second aspect of the present application, an embodiment of the present application provides a method for preparing an active material, which includes: providing porous particles with intragranular pores; filling pore-filling particles in the intragranular pores of the porous particles; and coating the porous particles filled with the pore-filling particles with a coating layer; wherein the porous particles include: one or more of activated carbon particles, carbon fiber particles, carbon nanotube particles, porous copper particles, porous titanium particles and porous silver particles; the pore-filling particles include metal particles, and the coating layer includes a solid electrolyte layer; wherein the ratio of the mass of the pore-filling particles to the mass of the coating layer ranges from 0.02 to 40.

[0014] Optionally, in some embodiments of the present application, the provision of porous particles with intragranular pores comprises: dehydrating the mixed raw material particles and the active agent to obtain dehydrated particles; calcining the dehydrated particles under an inert atmosphere to obtain calcined particles; washing and drying the cooled calcined particles to obtain the porous particles; and / or, filling the intragranular pores of the porous particles with pore-filling particles comprises: placing the porous particles into a solution containing metal elements and performing a reduction reaction to obtain a reduction product; washing and drying the reduction product to obtain porous particles filled with the pore-filling particles; and / or, coating the porous particles filled with the pore-filling particles with a coating layer comprises: dispersing the porous particles filled with the pore-filling particles into a slurry of a solid electrolyte material for mixing and drying to obtain the material to be annealed; annealing the material to be annealed to obtain the active material.

[0015] Optionally, in some embodiments of the present application, the raw material particles include one or more of charcoal, fruit shell charcoal, synthetic resin charcoal, petroleum coke, and bamboo charcoal; and / or the activator is one or more of potassium hydroxide, sodium hydroxide, zinc chloride, phosphoric acid, sulfuric acid, potassium carbonate, polyphosphoric acid, and phosphate ester; and / or the ratio of the mass of the raw material particles to the mass of the activator is in the range of 0.03 to 0.5; and / or the dehydration temperature of the dehydration treatment is in the range of 250°C to 500°C; and / or the dehydration time of the dehydration treatment is in the range of 1h to 5h; and / or the calcination temperature of the calcination treatment is in the range of 600°C to 850°C; and / or the calcination time of the calcination treatment is in the range of 1h to 5h; and / or the inert atmosphere includes one or more of nitrogen, argon, and helium; and / or the solution containing metal elements is silver. ammonia solution; the molar concentration of the silver ammonia solution ranges from 0.01 mol / L to 10.0 mol / L; and / or, the reducing agent is one or more of anhydrous ethanol, ethylene glycol, glucose, formaldehyde, acetaldehyde, and acetone; the molar concentration of the reducing agent ranges from 0.01 mol / L to 1.0 mol / L; and / or, the reaction temperature of the reduction reaction ranges from 60°C to 100°C, and the reaction time of the reduction reaction ranges from 1h to 48h; and / or, the solid content of the slurry of the solid electrolyte material ranges from 1% to 30%; and / or, the annealing temperature of the annealing treatment ranges from 600°C to 1000°C, the annealing time of the annealing treatment ranges from 1h to 10h, the heating rate of the annealing treatment ranges from 1°C / min to 5°C / min, and the cooling rate of the annealing treatment ranges from 5°C / min to 10°C / min.

[0016] Optionally, in some embodiments of the present application, the preparation method further includes: before using the coating layer to coat the porous particles filled with the pore-filling particles, using an intermediate layer to coat the porous particles filled with the pore-filling particles; wherein the intermediate layer is a carbon layer; and the ratio of the mass of the pore-filling particles to the mass of the intermediate layer is in the range of 0.1 to 10.

[0017] Optionally, in some embodiments of the present application, the coating method used to coat the porous particles filled with the pore-filling particles with an intermediate layer includes one or more of: solid-phase sintering method, liquid-phase coating method, chemical vapor deposition method, and physical vapor deposition method.

[0018] Optionally, in some embodiments of the present application, the use of an intermediate layer to coat the porous particles filled with the pore-filling particles includes: sintering the mixed precursor and the porous particles filled with the pore-filling particles; wherein the precursor includes: one or more of glucose, sucrose, fructose, phenolic resin, urea-formaldehyde resin, asphalt, and petroleum coke; and / or, the sintering temperature of the sintering treatment is in the range of 600°C to 1000°C; and / or, the sintering time of the sintering treatment is in the range of 1h to 48h.

[0019] As a third aspect of the present application, an embodiment of the present application provides an electrode, comprising the active material as described above or the active material prepared by the above preparation method.

[0020] As a fourth aspect of the present application, an embodiment of the present application provides a battery comprising the electrode as described above.

[0021] The beneficial effects of the present application are: providing an active material, a preparation method thereof, an electrode, and a secondary battery that effectively reduces direct contact between metallic lithium in porous particles and an electrolyte by coating with a coating layer, thereby improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 is a schematic structural diagram of the active material provided in some embodiments of the present application;

[0024] Figure 2 It is a schematic diagram of the main steps of the preparation method provided in some embodiments of the present application;

[0025] Figure 3 is a SEM image of the porous particles prepared in Example 4 of the present application;

[0026] Figure 4 is a SEM image of the active material prepared in Example 4 of the present application;

[0027] Figure 5 1 is a schematic diagram of a curve showing the cycle number and retention rate of a full battery assembled in Example 1 of the present application;

[0028] Figure 6 1 is a schematic diagram of a curve showing the cycle number and retention rate of a full battery assembled in Example 4 of the present application;

[0029] Figure 7 1 is a schematic diagram of a curve showing the cycle number and retention rate of a full battery assembled in Example 6 of the present application;

[0030] Figure 8 is an EDS (energy dispersive X-ray spectroscopy) graph of the active material of Example 10 of the present application;

[0031] Figure 9 1 is a graph showing the C value and the first cycle coulombic efficiency of the half-cell in Examples 1 to 14 of the present application;

[0032] Figure 10 1 is a graph showing the C value and the number of cycles for 80% capacity retention of the full battery in Examples 1 to 14 of the present application;

[0033] Figure 11 is a schematic diagram of a curve showing the C value and the specific surface area of the active material in Examples 1 to 14 of the present application;

[0034] Figure 12 Schematic diagram of the curves of C value and first cycle coulombic efficiency of half-cell in Examples 15 to 24 of the present application;

[0035] Figure 13 It is a graph showing the C value and the number of cycles for 80% capacity retention of the full battery in Examples 15 to 24 of the present application.

[0036] Meaning of the reference numerals in the figure:

[0037] 100, active material; 101, porous particle; 101a, intrapore of particle; 102, pore-filling particle; 103, coating layer; 104, intermediate layer. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as labels and do not impose numerical requirements or establish a sequence.

[0041] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0042] In this application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0043] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0044] Reference Figure 1 As shown in FIG. 1 , as a first aspect, the active material 100 of the present application includes: porous particles 101, pore-filling particles 102, and a coating layer 103. The porous particles 101 are formed with intraparticle pores 101a; the pore-filling particles 102 fill the intraparticle pores 101a; and the coating layer 103 at least coats the outside of the porous particles 101. The pore-filling particles 102 include metal particles, and the coating layer 103 includes a solid electrolyte layer. The ratio of the mass of the pore-filling particles 102 to the mass of the coating layer 103 ranges from 0.02 to 40.

[0045] By adopting the above scheme, by controlling the ratio of the mass of the pore-filling particles 102 to the mass of the coating layer 103, a reasonable thickness of the coating layer 103 is controlled. On the one hand, the coating layer 103 is prevented from being too thin, which causes the coating layer 103 to rupture due to expansion after the metal lithium is deposited in the pores, and the metal lithium directly reacts with the electrolyte, resulting in continuous side reactions, causing active lithium loss, thereby shortening the cycle life. On the other hand, the coating layer 103 is prevented from being too thick, which makes it difficult for the metal lithium to pass through the coating layer 103 and enter the pores for deposition, resulting in the metal lithium being deposited directly outside the pores, which also causes direct side reactions between the metal lithium and the electrolyte, shortening the cycle life. By controlling the mass ratio of the pore-filling particles 102 to the coating layer 103, the lithium affinity of the pore-filling particles 102 in the pores is maintained, and lithium ions can effectively and quickly enter the pores for deposition. At the same time, it can also ensure that the coating layer 103 can well isolate the metal lithium deposited in the pores from side reactions with the electrolyte outside the pores, ultimately achieving the beneficial effect of both kinetics and cycle life.

[0046] Figures 3 and 4 The SEM image of the porous particles 101 and the active material 100 prepared according to the specific embodiment of the present application is shown. The intra-particle pores 101a and the specific coating structure of the present application are all in terms of microstructure.

[0047] In some embodiments of the present application, the porous particles 101 include: one or more of activated carbon particles, carbon fiber particles, carbon nanotube particles, porous copper particles, porous titanium particles, and porous silver particles;

[0048] In some embodiments of the present application, the metal particles include: one or more particles of gold, silver, magnesium, tin, and lithium;

[0049] In some embodiments of the present application, the solid electrolyte layer includes: one or more of a LATP layer, a LAGP layer, and a LLTO layer.

[0050] In some embodiments of the present application, the specific surface area of the porous particles 101 ranges from 10 m2 / g to 2000 m2 / g;

[0051] In some embodiments of the present application, the particle size of the porous particles 101 ranges from 1 μm to 50 μm;

[0052] In some embodiments of the present application, the pore size of the particle pore 101a ranges from 1 nm to 100 nm;

[0053] In some embodiments of the present application, the pore volume of the particle pore 101a ranges from 0.80 cm 3 / g to 2.0cm 3 / g;

[0054] In some embodiments of the present application, the particle size of the pore-filling particles 102 ranges from 1 nm to 80 nm;

[0055] In some embodiments of the present application, the particle size of the active material 100 ranges from 2 μm to 55 μm.

[0056] In some embodiments of the present application, in some embodiments of the present application, the ratio of the mass of the pore-filling particles 102 to the mass of the porous particles 101 ranges from 0.01 to 0.8; specifically, it can be from 0.01 to 0.2.

[0057] In some embodiments of the present application, the ratio of the mass of the coating layer 103 to the mass of the porous particles 101 ranges from 0.02 to 0.2.

[0058] In some embodiments of the present application, the ratio of the mass of the coating layer 103 to the mass of the porous particles 101 ranges from 0.02 to 0.1.

[0059] In some embodiments of the present application, the active material 100 further includes an intermediate layer 104 formed between the porous particles 101 and the coating layer 103; the intermediate layer is a carbon layer; and the ratio of the mass of the pore-filling particles 102 to the mass of the intermediate layer ranges from 0.1 to 10.

[0060] In some embodiments of the present application, the carbon layer includes one or more of a soft carbon layer, a hard carbon layer, amorphous carbon, and onion carbon.

[0061] In some embodiments of the present application, the thickness of the carbon layer ranges from 1 nm to 1000 nm. Preferably, the thickness is 1 nm, 5 nm, 10 nm, 50 nm, 300 nm, 500 nm, or 1000 nm.

[0062] Reference Figure 2 As shown, as a second aspect, the preparation method of the active material 100 of the present application includes the following steps:

[0063] S100: Providing a porous particle 101 having intra-particle pores 101 a formed therein.

[0064] S200 : filling the pores 101 a of the porous particles 101 with pore-filling particles 102 .

[0065] S300: using an intermediate layer to coat the porous particles 101 filled with the pore-filling particles 102 .

[0066] S400 : coating the porous particles 101 filled with the pore-filling particles 102 with a coating layer 103 .

[0067] The step S300 may be omitted, and only the coating layer 103 is used for coating.

[0068] In some embodiments of the present application, step S100 includes:

[0069] Dehydrating the mixed raw material particles and the active agent to obtain dehydrated particles;

[0070] calcining the dehydrated particles under an inert atmosphere to obtain calcined particles;

[0071] The cooled calcined particles are washed with water and dried to obtain the porous particles 101 .

[0072] In some embodiments of the present application, step S200 includes:

[0073] The porous particles 101 are placed in a solution containing a metal element and subjected to a reduction reaction to obtain a reduction product;

[0074] The reduction product is washed and dried to obtain porous particles 101 filled with the pore-filling particles 102 .

[0075] In some embodiments of the present application, step S400 includes:

[0076] Dispersing the porous particles 101 filled with the pore-filling particles 102 into a slurry of a solid electrolyte material, mixing and drying the mixture to obtain a material to be annealed;

[0077] The material to be annealed is annealed to obtain the active material 100 .

[0078] In some embodiments of the present application, the raw material particles include one or more of charcoal, fruit shell charcoal, synthetic resin charcoal, petroleum coke, and bamboo charcoal.

[0079] In some embodiments of the present application, the synthetic resin carbon includes one or more of phenolic resin carbon, furfuryl alcohol resin carbon, polyimide resin carbon, asphalt resin carbon, and epoxy resin carbon.

[0080] In some embodiments of the present application, the activator is one or more of potassium hydroxide, sodium hydroxide, zinc chloride, phosphoric acid, sulfuric acid, potassium carbonate, polyphosphoric acid, and phosphate ester.

[0081] In some embodiments of the present application, the ratio of the mass of the raw material particles to the mass of the activator ranges from 0.03 to 0.5.

[0082] In some embodiments of the present application, the dehydration temperature of the dehydration treatment ranges from 250°C to 500°C.

[0083] In some embodiments of the present application, the dehydration time of the dehydration treatment ranges from 1 hour to 5 hours.

[0084] In some embodiments of the present application, the calcination temperature of the calcination treatment ranges from 600°C to 850°C.

[0085] In some embodiments of the present application, the calcination time of the calcination treatment ranges from 1 hour to 5 hours.

[0086] In some embodiments of the present application, the inert atmosphere includes one or more of nitrogen, argon, and helium.

[0087] In some embodiments of the present application, the solution containing metal elements is a silver ammonia solution; the molar concentration of the silver ammonia solution ranges from 0.01 mol / L to 10.0 mol / L.

[0088] In some embodiments of the present application, the reducing agent is one or more of anhydrous ethanol, ethylene glycol, glucose, formaldehyde, acetaldehyde, and acetone; and the molar concentration of the reducing agent ranges from 0.01 mol / L to 1.0 mol / L.

[0089] In some embodiments of the present application, the reaction temperature of the reduction reaction ranges from 60° C. to 100° C., and the reaction time of the reduction reaction ranges from 1 h to 48 h.

[0090] In some embodiments of the present application, the solid content of the slurry of the solid electrolyte material ranges from 1% to 30%.

[0091] In some embodiments of the present application, the annealing temperature of the annealing treatment ranges from 600°C to 1000°C, the annealing time of the annealing treatment ranges from 1h to 10h, the heating rate of the annealing treatment is 1°C / min to 5°C / min, and the cooling rate of the annealing treatment is 5°C / min to 10°C / min.

[0092] In some embodiments of the present application, step S300 may adopt one or more of solid phase sintering, liquid phase coating, chemical vapor deposition, and physical vapor deposition.

[0093] In some embodiments of the present application, step S300 includes:

[0094] Sintering the mixed precursor and the porous particles 101 filled with the pore-filling particles 102;

[0095] The precursor includes one or more of glucose, sucrose, fructose, phenolic resin, urea-formaldehyde resin, asphalt, and petroleum coke.

[0096] In some embodiments of the present application, the sintering temperature of the sintering treatment ranges from 600°C to 1000°C.

[0097] Optionally, in some embodiments of the present application, the sintering time of the sintering treatment ranges from 1 hour to 48 hours.

[0098] In a third aspect, an embodiment of the present application provides an electrode, comprising the aforementioned active material 100 or the active material 100 prepared by the aforementioned preparation method.

[0099] In a fourth aspect, an embodiment of the present application provides a secondary battery comprising the aforementioned electrode.

[0100] Based on the above solution, the problems of lithium metal volume expansion, interface stability, and lithium dendrite growth can be solved simultaneously. By coating the metal particles in the particle pores 101a with the coating layer 103, on the one hand, it can induce metallic lithium to enter the pores and deposit. On the other hand, the metal particles are more active, have higher conductivity, and have a stronger induction effect. The use of solid electrolyte for coating can further enhance the lithium ion transfer kinetics, while reducing direct contact between the electrolyte and metallic lithium, reducing side reactions, and improving interface stability. At the same time, the coated solid electrolyte such as LATP is reduced during the reaction with metallic lithium to form an inorganic-rich SEI, which further improves interface stability.

[0101] The present application is further described below through specific implementation methods.

[0102] Examples 1 to 14

[0103] Examples 1 to 14 of the present application all adopt the following preparation process, differing in the specific values of parameters A, B, and C. A% represents the percentage of the mass of the pore-filling particles to the mass of the porous material (the mass of the porous material is 100%), B% represents the percentage of the mass of the coating layer to the mass of the porous material (the mass of the porous material is 100%), and C represents the mass ratio of the pore-filling particles to the coating layer.

[0104] 200g coconut shell and 1000g potassium hydroxide were thoroughly mixed, dehydrated at 450°C for 1 hour under a nitrogen atmosphere, and then calcined at 800°C for 2 hours under a nitrogen atmosphere. The product was fully washed to neutrality to obtain a porous carbon skeleton (porous particles).

[0105] The specific surface area of the porous carbon skeleton was 1300 m 2 / g, pore volume is 1.1cm 3 / g, 1L of deionized water was added to a beaker, followed by the addition of 25g of silver sulfate, and the mixture was stirred until completely dissolved. 10mL of ammonia water was then slowly added while continuing to stir, and the solution became clear from turbidity. 2g of porous carbon skeleton was added to the clear solution, and the mixture was fully stirred and mixed. 20mL of anhydrous ethanol was then added, and the reaction temperature was controlled at 80°C for 24 hours. The mixture was then filtered, washed, and dried to obtain a porous carbon skeleton (a complex of porous particles and pore-filling particles) with pores filled with nanosilver particles (pore-filling particles).

[0106] The mass ratio of the silver nanoparticles to the porous carbon skeleton can be controlled to be A% by controlling the type of silver salt, the concentration of silver ions, the reaction time and other conditions during the reaction.

[0107] The porous carbon skeleton filled with nano-silver particles in the pores was uniformly dispersed (by ultrasound and stirring) into LATP slurry (used to form a coating layer, the solid content of LATP slurry was 17.1%), and then dried.

[0108] The dried product is annealed and sintered in a nitrogen atmosphere, heated to a target temperature of 800°C at a heating rate of 5°C / min in a high-temperature sintering furnace, kept at that temperature for 1 hour, and then cooled to obtain the final active material; the active material can be used as a lithium metal negative electrode material.

[0109] By controlling the amount of the porous carbon skeleton and the LATP slurry, the mass percentage of LATP to the porous carbon skeleton (i.e., the mass percentage of the coating layer to the porous material) in the active material of this embodiment is B%, and the mass ratio of the nanosilver particles to the LATP (the mass ratio of the pore-filling particles to the coating layer) is C.

[0110] The specific values of parameters A, B, and C in Examples 1 to 14 can be referred to as shown in Table 1.

[0111] Comparative Example 1

[0112] 200g coconut shell was mixed with 1000g potassium hydroxide, and dehydrated at 450℃ for 1 hour under nitrogen atmosphere, and then calcined at 800℃ for 2 hours under nitrogen atmosphere. The product was washed thoroughly to neutrality to obtain a porous carbon skeleton. The BET test showed that its specific surface area was 1300m 2 / g, pore volume is 1.1cm 3 / g, add 1L of deionized water to the beaker, then add 25g of silver sulfate, stir until completely dissolved, then continue to stir while slowly adding 10mL of ammonia water, the solution changes from turbid to clear, add 2g of porous carbon skeleton to the above clear solution, stir and mix thoroughly, then add 20mL of anhydrous ethanol, control the reaction temperature at 80℃, the reaction time is 24 hours, then filter, wash and dry to obtain a porous carbon skeleton with nanosilver particles filled in the pores. The mass ratio of nanosilver particles to porous carbon skeleton in TG test is 1:100, and the specific surface area in BET test is 889m 2 / g.

[0113] Comparative Example 2

[0114] 200g coconut shell was mixed with 1000g potassium hydroxide, and dehydrated at 450℃ for 1 hour under nitrogen atmosphere, and then calcined at 800℃ for 2 hours under nitrogen atmosphere. The product was washed thoroughly to neutrality to obtain a porous carbon skeleton. The BET test showed that its specific surface area was 1300m 2 / g, pore volume is 1.1cm 3 / g, add 1L of deionized water to the beaker, then add 185g of silver sulfate, stir until completely dissolved, then continue to stir while slowly adding 10mL of ammonia water, the solution changes from turbid to clear, add 2g of porous carbon skeleton to the above clear solution, stir and mix thoroughly, then add 20mL of anhydrous ethanol, control the reaction temperature at 80℃, the reaction time is 24 hours, then filter, wash and dry to obtain a porous carbon skeleton filled with nanosilver particles in the pores. The mass ratio of nanosilver particles to porous carbon skeleton in TG test is 91:100, and the specific surface area in BET test is 341m 2 / g.

[0115] It can be understood that Comparative Examples 1 and 2 do not use a coating layer composed of a solid electrolyte.

[0116] Comparative Example 3

[0117] 200g coconut shell was mixed with 1000g potassium hydroxide, and dehydrated at 450℃ for 1 hour under nitrogen atmosphere, and then calcined at 800℃ for 2 hours under nitrogen atmosphere. The product was washed thoroughly to neutrality to obtain a porous carbon skeleton. The BET test showed that its specific surface area was 1300m 2 / g, then, a certain amount of porous carbon skeleton was dispersed into LATP slurry, wherein the solid content of LATP slurry was 17.1%. By controlling the amount of LATP slurry, ultrasonication, uniform stirring, and drying, the dried sample was annealed and sintered in a nitrogen atmosphere, and the temperature was raised to the target temperature of 800°C in a high-temperature sintering furnace at a heating rate of 5°C / min, kept at this temperature for 1h, and then cooled to obtain the final active material. The product had a particle size D50 of 12μm and a specific surface area of 952m 2 / g, the final mass ratio of porous carbon skeleton to LATP is 100:5, and the mass ratio of nanosilver particles to LATP in the product active material is 1.

[0118] It can be understood that in Comparative Example 3, the porous particles are not filled with pore-filling particles.

[0119] Comparative Example 4

[0120] 200g coconut shell was mixed with 1000g potassium hydroxide, and dehydrated at 350℃ for 1 hour under nitrogen atmosphere, and then calcined at 600℃ for 2 hours under nitrogen atmosphere. The product was washed thoroughly to neutrality to obtain a porous carbon skeleton. The BET test showed that its specific surface area was 1490m 2 / g, pore volume 1cm 3 / g, aluminum nitride (AlN) was filled in the above-mentioned pores by magnetron sputtering, and the mass ratio of AlN to the porous carbon skeleton was 5:100 in TG test. The porous carbon skeleton coated with aluminum nitride was then dispersed into the LATP slurry, wherein the solid content of the LATP slurry was 17.1%, and the mass ratio of the porous carbon skeleton to LATP was 100:5. Ultrasonication, stirring and drying were performed, and then the dried sample was annealed and sintered in a nitrogen atmosphere. The temperature was raised to the target temperature of 800°C at a heating rate of 5°C / min in a high-temperature sintering furnace, kept warm for 1h, and then cooled to obtain the final active material. The product particle size D50 was 12.4μm and the specific surface area was 651m 2 / g.

[0121] It can be understood that the main difference between Comparative Example 4 and Examples 1 to 14 is that the pore-filling particles are replaced with aluminum nitride particles.

[0122] In Comparative Examples 1 to 4, A% still represents the percentage of the mass of the pore-filling particles to the mass of the porous material, B% still represents the percentage of the mass of the coating layer to the mass of the porous material (the mass of the porous material is 100%), and C still represents the mass ratio of the pore-filling particles to the coating layer.

[0123] The specific values of parameters A, B, and C in Comparative Examples 1 to 4 can also be referred to as shown in Table 1.

[0124] Examples 15 to 24

[0125] Examples 15 to 24 of the present application all adopt the following preparation process, differing in the specific values of parameters A, B, and C. A% represents the percentage of the mass of the pore-filling particles to the mass of the porous material (the mass of the porous material is 100%), B% represents the percentage of the mass of the coating layer to the mass of the porous material (the mass of the porous material is 100%), and C represents the mass ratio of the pore-filling particles to the coating layer.

[0126] 200g coconut shell and 1000g potassium hydroxide were thoroughly mixed, dehydrated at 450°C for 1 hour under a nitrogen atmosphere, and then calcined at 800°C for 2 hours under a nitrogen atmosphere. The product was fully washed to neutrality to obtain a porous carbon skeleton (porous particles).

[0127] The specific surface area of the material was 1300 m 2 / g, pore volume is 1.1cm 3 / g, 1L of deionized water was added to a beaker, followed by the addition of 25g of silver sulfate, and the mixture was stirred until completely dissolved. 10mL of ammonia water was then slowly added while continuing to stir, and the solution became clear from turbidity. 2g of porous carbon skeleton was added to the clear solution, and the mixture was fully stirred and mixed. 20mL of anhydrous ethanol was then added, and the reaction temperature was controlled at 80°C for 24 hours. The mixture was then filtered, washed, and dried to obtain a porous carbon skeleton (a complex of porous particles and pore-filling particles) with pores filled with nanosilver particles (pore-filling particles).

[0128] The mass ratio of the silver nanoparticles to the porous carbon skeleton can be controlled to be A% by controlling the type of silver salt, the concentration of silver ions, the reaction time and other conditions during the reaction.

[0129] The porous carbon filled with nanosilver particles in the pores was dissolved in a phenolic resin solution, fully stirred, dried, and sintered at 800°C for 1 hour to prepare a skeleton material coated with a first carbon layer (middle layer), wherein the mass ratio of the first carbon layer to the porous skeleton was 1:10.

[0130] Then, the previously prepared skeleton material coated with the first carbon layer (a complex of the intermediate layer, porous particles and pore-filling particles) was uniformly dispersed (by ultrasound and stirring) into the LATP slurry (used to form a coating layer, the solid content of the LATP slurry was 17.1%) and then dried.

[0131] The dried sample was annealed and sintered in a nitrogen atmosphere, and the temperature was raised to the target temperature of 800°C in a high-temperature sintering furnace at a heating rate of 5°C / min, kept at that temperature for 1 hour, and then cooled to obtain the final active material.

[0132] By controlling the amount of LATP slurry, the mass ratio of LATP to the porous carbon skeleton (i.e., the mass ratio of the coating layer to the porous material) in the active material of this embodiment is B%, where the mass ratio of the nanosilver particles (pore-filling particles) to the LATP (coating layer) is defined as C.

[0133] The specific values of parameters A, B, and C in Examples 15 to 24 can be referred to as shown in Table 2.

[0134] The difference between Examples 15 to 24 and Examples 1 to 14 is that an intermediate layer is added.

[0135] After the active materials of the above examples and comparative examples are prepared, the specific surface areas of the active materials prepared in Examples 1 to 24 and Comparative Examples 1 to 4 can be tested.

[0136] The active materials prepared in Examples 1 to 24 and Comparative Examples 1 to 4 were used to prepare button-type full batteries using the following process:

[0137] The active materials, SP, and 5% LA133 were mixed in a mass ratio of 80:10:10, and an appropriate amount of water was added to prepare a slurry in a degassing machine. The slurry was then coated onto copper foil with a spatula. The electrode was cut into 12mm diameter discs as the negative electrode, and then assembled into a button-type half-cell with a 500μm thick metal sheet.

[0138] In addition, the negative electrode sheet was roll-combined with 20μm metal lithium foil to prepare a composite negative electrode, and NCM with a diameter of 8.4mm was used as the positive electrode, 1MLiTFSI+DOL / DME (DOL volume / DME volume = 1:1)+2wt%LiNO3 was used as the electrolyte, Celgard2400 was used as the separator, and the shell was a 2016 button battery shell. The full battery was assembled and subjected to charge and discharge tests.

[0139] Among them, SP is super carbon black, LA133 is a fluorine-free binder, NCM is a nickel-cobalt-manganese ternary positive electrode material, MLiTFSI is lithium bis(trifluoromethanesulfonyl)imide (which is a commonly used raw material component in the preparation of electrolyte), DOL is the abbreviation of 1,3-dioxolane, DME is the abbreviation of 1,2-dimethoxyethane, DOL and DME are both commonly used solvents in the preparation of electrolyte, LiNO3 is lithium nitrate (which is a commonly used additive in the preparation of electrolyte). The above materials are all commonly used materials in the field of lithium-ion batteries, and you can freely choose the manufacturer and model according to your needs.

[0140] The following describes the experimental equipment, test methods, test conditions, etc. of this application.

[0141] The materials obtained in the above examples and comparative examples were used to test the specific surface area and pore size distribution of the samples using a Gaobo BK300C specific surface area analyzer and an American Micromeritics TriStar-3030 pore size analyzer.

[0142] The particle size range of the samples was tested using a Malvern 3000 laser particle size analyzer, and the surface and cross-section SEM and element distribution of the samples were tested using a Zeiss SEM460 thermal field emission scanning electron microscope and an Oxford UltimMax170 energy dispersive spectrometer.

[0143] The electrochemical performance tests of the samples were carried out using a Blue Power M340A test cabinet, and the battery assembly was carried out in a German Braun glove box.

[0144] The specific test conditions are as follows:

[0145] Half-cell test: At room temperature (25°C), the prepared material electrode is used as the half-cell negative electrode, and a 500μm thick metal lithium sheet is used as the counter electrode. The discharge capacity is set to 2000mAh / g. The half-cell is first discharged and then charged to 0.8V with a charging current of 0.1C. The weekly coulombic efficiency is calculated by dividing the weekly charge capacity by the discharge capacity.

[0146] Full battery test: At room temperature (25°C), the battery was first charged and discharged at a constant rate of 0.05C for two weeks with a voltage range of 2.75V to 4.2V, and then cycled at a charge and discharge rate of 1C / 5C. The designed gram capacity of the active material electrodes with a combination of large and small particle sizes in all embodiments and comparative examples was >2000mAh / g.

[0147] Refer to Table 3 and Table 4 and Figure 10 and 11 As shown, the battery performance analysis corresponding to Examples 1 to 14 and Comparative Examples 1 to 4 is as follows:

[0148] Compared with Comparative Examples 1 and 2, Examples 1 to 14 show that since Examples 1 to 14 all use a coating layer, the negative electrodes made from their corresponding active materials reduce the specific surface area of the porous carbon skeleton, and the coating layer covers the metallic lithium deposited in the pores of the porous particles, thereby avoiding direct contact between the metallic lithium and the electrolyte and reducing the occurrence of side reactions.

[0149] By comparing Example 8 with Comparative Example 1, it can be seen that even though the proportion of the coating layer is low, both the coulombic efficiency and the capacity retention capacity are improved compared with Comparative Example 1, which verifies that the presence of the coating layer can improve the performance of the battery when the active material is used as an electrode material.

[0150] With reference to Comparative Examples 1 and 2, it can be seen that in the absence of a coating layer, even if the mass of the pore-filling particles is increased, the improvement in performance is relatively limited.

[0151] Referring to Comparative Example 3, it can be seen that when there is only a coating layer but no pore-filling particles, the expected performance cannot be achieved.

[0152] Referring to Comparative Example 4, it can be seen that when non-conductive particles such as aluminum nitride are selected as the pore-filling particles, the expected performance cannot be achieved.

[0153] From the above comparison, it can be seen that both a coating layer and conductive pore-filling particles are required to achieve performance improvement.

[0154] Referring to Examples 1 to 14, it can be seen that with appropriate quality of the coating layer (representing appropriate coating thickness) and the quality of the pore-filling particles, metallic lithium can quickly pass through the outer surface layer. At the same time, the outer coating layer of the solid electrolyte can also effectively coat the inner deposited metallic lithium to avoid direct contact with the electrolyte and reduce side reactions; therefore, the coating layer needs to be compatible with the pore-filling particles.

[0155] Referring to Examples 1 to 8, it can be seen that when the content of the pore-filling particles (relative to the porous material) remains unchanged, changes in the mass of the coating layer will cause changes in performance. In general, as the amount of the coating layer increases (Examples 5 to 8), the coulombic efficiency and capacity retention rate are improved, but then as the amount of the coating layer increases (Examples 1 to 4), the coulombic efficiency and capacity retention rate begin to decline. This shows that the coating layer cannot be too little or too much. Too little will not achieve the barrier effect, and too much will affect the carrier transmission efficiency.

[0156] Referring to Examples 7, 9, 10 and 12 to 14, it can be seen that when the mass of the coating layer is fixed, changes in the content of the pore-filling particles will also cause changes in performance, but this change does not mean that the more or less the content of the pore-filling particles, the better or worse the corresponding performance will be; that is, from another perspective, it is proved that the coating layer needs to be compatible with the pore-filling particles to achieve an improvement effect.

[0157] With reference to Examples 1 to 14, it can be seen that controlling the amount of the coating layer and the pore-filling particles alone is not sufficient to obtain the desired performance. Therefore, it is necessary to control their ratio in order to obtain better performance.

[0158] Similarly, refer to Table 2 and Table 4 and Figure 12 and 13As shown, in addition to the results of the above analysis (the intermediate layer and coating layer of Examples 15 to 24 as a whole can be considered as the coating layer in Examples 1 to 14), Examples 15 to 24, on the basis of the above, add an intermediate carbon layer of appropriate proportion and an intermediate carbon layer of appropriate thickness, which can further reduce the specific surface area of the active material and improve the first effect. At the same time, the intermediate carbon layer can not only protect the metallic lithium deposited in the pore together with the external solid electrolyte coating layer, and avoid the metallic lithium from directly contacting the electrolyte and causing side reactions after being deposited in the pore, but also avoid the deposited metallic lithium from directly contacting the external solid electrolyte coating layer, thereby avoiding the deposited metallic lithium from causing side reactions with the external solid electrolyte coating layer. Moreover, due to the good ion transport properties of the carbon layer, it can be ensured that the metallic lithium can effectively pass through the layer, enter the pores for deposition and dissolution, thereby ensuring good kinetic performance. In short, a suitable intermediate carbon layer can play a role in synergistically protecting the interface and jointly conducting ions with the outer solid electrolyte coating layer, thereby obtaining better performance indicators.

[0159] Table 1 shows the specific values of A, B, and C in Examples 1 to 14 and Comparative Examples 1 to 4.

[0160] Table 1

[0161]

[0162]

[0163] Table 2 shows the specific values of A, B, and C in Examples 15 to 24.

[0164] Table 2

[0165]

[0166] Table 3 shows the relevant performance test results of button-type full batteries made from the active materials prepared in Examples 1 to 14 and Comparative Examples 1 to 4.

[0167] Table 3

[0168]

[0169]

[0170] Table 4 shows the relevant performance test results of button-type full batteries made from the active materials prepared in Examples 15 to 24.

[0171] Table 4

[0172]

[0173] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An active material, characterized in that: The active material includes: Porous particles are formed with intraparticle pores; Pore-filling particles, filling the pores in the particles; A coating layer, at least coating the outside of the porous particles; wherein the pore-filling particles include metal particles, and the coating layer includes a solid electrolyte layer; The ratio of the mass of the pore-filling particles to the mass of the coating layer ranges from 0.02 to 40.

2. The active material according to claim 1, Its characteristics are: in, The porous particles include: one or more of activated carbon particles, carbon fiber particles, carbon nanotube particles, porous copper particles, porous titanium particles, and porous silver particles; and / or, the metal particles include: one or more of particles of gold, silver, magnesium, tin, and lithium; And / or, the solid electrolyte layer includes: one or more of a LATP layer, a LAGP layer, and a LLTO layer.

3. The active material according to claim 1, characterized in that: in, The specific surface area of the porous particles ranges from 10m 2 / g to 2000m 2 / g; And / or, the particle size of the porous particles ranges from 1 μm to 50 μm; And / or, the pore size of the particle is in the range of 1 nm to 100 nm; And / or, the pore volume of the particles is in the range of 0.80 cm 3 / g to 2.0cm 3 / g; And / or, the particle size of the pore-filling particles ranges from 1 nm to 80 nm; And / or, the thickness of the solid electrolyte layer ranges from 1 nm to 80 nm; And / or, the particle size of the active material ranges from 2 μm to 55 μm.

4. The active material according to claim 1, characterized in that: in, The ratio of the mass of the pore-filling particles to the mass of the porous particles ranges from 0.01 to 0.8; And / or, the ratio of the mass of the coating layer to the mass of the porous particles is in a range of 0.02 to 0.

2.

5. The active material according to any one of claims 1 to 4, characterized in that: The active material also includes: an intermediate layer formed between the porous particles and the coating layer; Wherein, the middle layer is a carbon layer.

6. The active material according to claim 5, characterized in that: in, The ratio of the mass of the pore-filling particles to the mass of the intermediate layer ranges from 0.1 to 10; the carbon layer is one or more of soft carbon, hard carbon, amorphous carbon, and onion carbon; and / or the thickness of the carbon layer ranges from 1 nm to 1000 nm.

7. A method for preparing an active material, characterized in that: The preparation method comprises: providing porous particles having intraparticle pores; Filling pore-filling particles in the pores of the porous particles; coating the porous particles filled with the pore-filling particles with a coating layer; The porous particles include one or more of activated carbon particles, carbon fiber particles, carbon nanotube particles, porous copper particles, porous titanium particles, and porous silver particles; the pore-filling particles include metal particles, and the coating layer includes a solid electrolyte layer; The ratio of the mass of the pore-filling particles to the mass of the coating layer ranges from 0.02 to 40.

8. The preparation method according to claim 7, Its characteristics are: Wherein, providing porous particles with intragranular pores comprises: Dehydrating the mixed raw material particles and the active agent to obtain dehydrated particles; calcining the dehydrated particles under an inert atmosphere to obtain calcined particles; washing and drying the cooled calcined particles to obtain the porous particles; And / or, filling the pores of the porous particles with pore-filling particles comprises: The porous particles are placed in a solution containing a metal element and then subjected to a reduction reaction to obtain a reduction product; washing and drying the reduction product to obtain porous particles filled with the pore-filling particles; And / or, coating the porous particles filled with the pore-filling particles with a coating layer, comprising: Dispersing the porous particles filled with the pore-filling particles into a slurry of a solid electrolyte material, mixing and drying the mixture to obtain a material to be annealed; The material to be annealed is subjected to an annealing treatment to obtain the active material.

9. The preparation method according to claim 8, characterized in that: in, The raw material particles include one or more of charcoal, fruit shell charcoal, synthetic resin charcoal, petroleum coke, and bamboo charcoal; And / or, the activator is one or more of potassium hydroxide, sodium hydroxide, zinc chloride, phosphoric acid, sulfuric acid, potassium carbonate, polyphosphoric acid, and phosphate ester; and / or, the ratio of the mass of the raw material particles to the mass of the activator is in the range of 0.03 to 0.5; And / or, the dehydration temperature of the dehydration treatment ranges from 250° C. to 500° C.; And / or, the dehydration time of the dehydration treatment ranges from 1 hour to 5 hours; And / or, the calcination temperature of the calcination treatment ranges from 600° C. to 850° C.; And / or, the calcination time of the calcination treatment ranges from 1 h to 5 h; and / or, the inert atmosphere comprises one or more of nitrogen, argon, and helium; And / or, the solution containing metal elements is a silver ammonia solution; the molar concentration of the silver ammonia solution ranges from 0.01 mol / L to 10.0 mol / L; And / or, the reducing agent is one or more of anhydrous ethanol, ethylene glycol, glucose, formaldehyde, acetaldehyde, and acetone; the molar concentration of the reducing agent ranges from 0.01 mol / L to 1.0 mol / L; And / or, the reaction temperature of the reduction reaction ranges from 60° C. to 100° C., and the reaction time of the reduction reaction ranges from 1 h to 48 h; And / or, the solid content of the slurry of the solid electrolyte material ranges from 1% to 30%; And / or, the annealing temperature of the annealing treatment ranges from 600°C to 1000°C, the annealing time of the annealing treatment ranges from 1h to 10h, the heating rate of the annealing treatment is from 1°C / min to 5°C / min, and the cooling rate of the annealing treatment is from 5°C / min to 10°C / min.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The preparation method further comprises: Before coating the porous particles filled with the pore-filling particles with the coating layer, coating the porous particles filled with the pore-filling particles with the intermediate layer; The intermediate layer is a carbon layer; and the ratio of the mass of the pore-filling particles to the mass of the intermediate layer ranges from 0.1 to 10.

11. The preparation method according to claim 10, characterized in that: in, The coating method used to coat the porous particles filled with the pore-filling particles with the intermediate layer includes: one or more of a solid-phase sintering method, a liquid-phase coating method, a chemical vapor deposition method, and a physical vapor deposition method.

12. The preparation method according to claim 11, Its characteristics are: in, The method of coating the porous particles filled with the pore-filling particles with an intermediate layer includes: sintering the mixed precursor and the porous particles filled with the pore-filling particles; Wherein, the precursor includes: one or more of glucose, sucrose, fructose, phenolic resin, urea-formaldehyde resin, asphalt, and petroleum coke; And / or, the sintering temperature of the sintering treatment ranges from 600° C. to 1000° C.; And / or, the sintering time of the sintering treatment ranges from 1 hour to 48 hours.

13. An electrode comprising the active material according to any one of claims 1 to 6 or the active material prepared by the preparation method according to any one of claims 7 to 12. 14 . A secondary battery comprising the electrode according to claim 13 .

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