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CN113809330B - Silicon-based composite anode material, preparation method thereof and all-solid-state lithium battery - Google Patents

Silicon-based composite anode material, preparation method thereof and all-solid-state lithium battery Download PDF

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CN113809330B
CN113809330B CN202010539828.XA CN202010539828A CN113809330B CN 113809330 B CN113809330 B CN 113809330B CN 202010539828 A CN202010539828 A CN 202010539828A CN 113809330 B CN113809330 B CN 113809330B
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silicon
negative electrode
based composite
lithium
anode material
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CN113809330A (en
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历彪
郭姿珠
王国帅
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BYD Co Ltd
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • C01B21/0607—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with alkali metals
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/40—Alloys based on alkali metals
    • H01M4/405—Alloys based on lithium
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Abstract

The application provides a silicon-based composite anode material, which has a nano porous structure, wherein the components of the silicon-based composite anode material comprise Li 3 N and Li 3 At least one of P and lithium silicon alloy. The silicon-based composite anode material has high energy density, low volume effect in the charge and discharge process of the battery and strong cycling stability. The application also provides a preparation method of the silicon-based composite anode material and an all-solid-state lithium battery.

Description

Silicon-based composite anode material, preparation method thereof and all-solid-state lithium battery
Technical Field
The application relates to the technical field of batteries, in particular to a silicon-based composite anode material, a preparation method thereof and an all-solid-state lithium battery.
Background
The traditional lithium ion battery adopts liquid electrolyte, and a series of potential safety hazards such as battery short circuit, thermal runaway, ignition explosion and the like are easy to generate in the use process. All-solid-state lithium batteries are believed to essentially solve the potential safety hazards of conventional lithium ion batteries due to the use of solid electrolytes. As an important component of an all-solid-state lithium battery, the performance of the negative electrode material of the all-solid-state lithium battery directly influences various performance indexes of the negative electrode material. The existing silicon-based anode materials are widely paid attention to because of having very high theoretical specific capacity. However, the existing silicon-based anode material often has the defects that the capacity decay is too fast in the practical application process, and the volume change is easy to occur when lithium is inserted or extracted, so that the whole cycle performance of the all-solid-state lithium battery is poor, and the further development of the battery is severely limited.
Disclosure of Invention
In view of the above, the application provides a silicon-based composite anode material, a preparation method thereof and an all-solid-state lithium battery, wherein the silicon-based composite anode material has high energy density, low volume effect in the charge and discharge processes of the battery and high cycle stability. The application also provides a preparation method of the silicon-based composite anode material and an all-solid-state lithium battery.
Specifically, in a first aspect, the present application provides a silicon-based composite anode material, the silicon-based composite anode material has a nano-porous structure, and the composition components of the silicon-based composite anode material include Li 3 N and Li 3 At least one of P and lithium silicon alloy.
In embodiments of the present application, the porosity of the nanoporous structure is from 10 to 70%.
In the embodiment of the application, the pore diameter of the nano porous structure is 5-100nm, and the pore wall thickness is 5-200nm.
In the embodiment, the density of the silicon-based composite anode material is 0.7-2.1g cm -3 。
In an embodiment of the present application, the nano-porous structure is formed by in situ reaction of lithium powder and at least one of silicon nitride and silicon phosphide.
In a second aspect, the present application further provides a method for preparing a silicon-based composite anode material, including the following steps:
Uniformly mixing at least one of silicon nitride and silicon phosphide, lithium powder and a solvent in a protective atmosphere to obtain mixed slurry;
coating the mixed slurry on a negative electrode current collector, and dryingAfter drying and pressing treatment, a silicon-based composite anode material with a nano porous structure is formed on the anode current collector; the silicon-based composite anode material comprises the following components in percentage by weight 3 N and Li 3 At least one of P and lithium silicon alloy.
In the embodiment of the application, the particle sizes of the silicon nitride and the silicon phosphide are 0.03-1 mu m, and the particle size of the lithium powder is 0.01-50 mu m.
In a third aspect, the present application further provides an all-solid-state lithium battery, including a positive electrode sheet, a negative electrode sheet, and a solid electrolyte layer, where the solid electrolyte layer is located between the positive electrode sheet and the negative electrode sheet; the negative electrode sheet comprises the silicon-based composite negative electrode material as claimed in any one of claims 1 to 5 or the silicon-based composite negative electrode material prepared by the preparation method as claimed in any one of claims 6 to 7.
In this application embodiment, the negative electrode sheet includes negative electrode current collector and set up negative electrode material layer on the negative electrode current collector, negative electrode material layer contains silicon-based composite negative electrode material, just negative electrode material layer does not contain conductive agent and solid electrolyte material.
In an embodiment of the present application, the negative electrode material layer further contains a binder; the mass percentage of the binder in the negative electrode material layer is 0.5-5%
The beneficial effects of this application include:
(1) The silicon-based composite anode material has a certain nano porous structure, and the composition components of the silicon-based composite anode material comprise Li 3 N and Li 3 At least one of P and lithium silicon alloy, li in the silicon-based composite anode material 3 N and Li 3 P has very high room temperature ion conductivity; the nano porous structure can also effectively inhibit or eliminate the influence of volume change generated in the charge and discharge process of the lithium-silicon alloy, ensure the stability and the integrity of the nano porous structure, maintain the channels for transmitting electrons and ions, greatly improve the cycling stability of the silicon-based composite anode material, and simultaneously have high specific capacity and energy density.
(2) The preparation method of the silicon-based composite anode material has the advantages of simple process and low cost, and is suitable for large-scale industrial production; the prepared silicon-based composite anode material has good electron and ion conduction network, excellent electrochemical performance in the charge and discharge process and strong cycling stability.
(3) The all-solid-state lithium battery comprises the silicon-based composite anode material with the nano porous structure, and is high in energy density, long in cycle life and good in safety performance.
Additional features and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the application.
Drawings
For a clearer description of the present application, reference will be made to the following detailed description of specific embodiments taken in conjunction with the accompanying drawings.
FIG. 1 is a scanning electron microscope image of a silicon-based composite anode material according to an embodiment of the present application;
FIG. 2 is a schematic diagram of Li 3 N and Li 3 Scanning electron microscope pictures of cathode materials directly mixed by P lithium silicon alloy;
fig. 3 is a schematic cross-sectional structure of an all-solid-state lithium battery 100 according to an embodiment of the present application.
Detailed Description
The following description is of the preferred embodiments of the present application, and it should be noted that it will be apparent to those skilled in the art that modifications and adaptations can be made without departing from the principles of the present application, and such modifications and adaptations are intended to be comprehended within the scope of the present application.
Unless otherwise specified, the chemical reagents used in the preparation methods are all commercially available reagents.
An embodiment of the present application provides a silicon-based composite anode material, where the silicon-based composite anode material has a nano porous structure, and the composition components of the silicon-based composite anode material include Li 3 N and Li 3 At least one of P and lithium silicon alloy.
Wherein the lithium silicon alloyHas the molecular general formula of Li x Si，0<x is less than or equal to 4.4. The alloy phase of the lithium silicon alloy can specifically comprise LiSi, li 12 Si 7 (or is Li 1.71 Si)、Li 7 Si 3 (or is Li 2.33 Si)、Li 13 Si 4 (or is Li 3.25 Si)、Li 15 Si 4 (or is Li 3.75 Si)、Li 21 Si 5 (or is Li 4.2 Si) and Li 22 Si 5 (or is Li 4.4 Si). In one embodiment, the lithium silicon alloy has a molecular formula of Li x Si，2<x is less than or equal to 4.4. In a second embodiment, the lithium silicon alloy has a molecular formula of Li x Si，4<x is less than or equal to 4.4. In a third embodiment, the lithium silicon alloy is Li alone 4.4 Si alloy. The larger the lithium intercalation amount in the lithium silicon alloy is, the larger the corresponding capacity is, wherein Li is 4.4 Si alloys have a very high specific capacity. Alternatively, the lithium silicon alloy may be, but is not limited to, a lithium silicon alloy including one or more crystal lattices. Alternatively, the crystal lattice in the lithium silicon alloy may include one or more of tetragonal, orthorhombic, rhombohedral Fang Jingji, body-centered cubic, and face-centered cubic.
In an embodiment of the present application, the composition component of the silicon-based composite anode material may be Li 3 N、Li 3 P and lithium silicon alloy. Alternatively, the silicon-based composite anode material may have a composition of Li 3 N and lithium silicon alloy. Alternatively, the silicon-based composite anode material may have a composition of Li 3 P and lithium silicon alloy. The final composition of the silicon-based composite anode material does not contain independent metallic lithium and silicon simple substance, and the silicon-based composite anode material has excellent electrochemical performance.
In an embodiment of the present application, the nano-porous structure is formed of silicon nitride (Si 3 N 4 ) And silicon phosphide (Si) 3 P 4 ) Is formed by in situ reaction with lithium powder. Wherein silicon nitride and lithium powder can react to generate Li 3 N and lithium silicon alloys; silicon phosphide and lithium powder can react to generate Li 3 P and lithium silicon alloy. In silicon nitride and silicon phosphideAfter being uniformly mixed with lithium powder, at least one of the particles can be subjected to in-situ reaction, external force pressing is properly added to enable the particles to be in close contact with each other, so that the in-situ reaction is promoted, and the particles disappear or contact with each other due to the reaction, so that the integrated silicon-based composite anode material with the nano porous structure is formed in situ. The nano porous structure can also effectively inhibit or eliminate the influence of volume change generated in the charge-discharge process of the lithium-silicon alloy, ensure the stability and the integrity of the nano porous structure, maintain the channels for transmitting electrons and ions, and enhance the circulation stability of the silicon-based composite anode material.
In the embodiment of the application, the silicon-based composite anode material has higher ion conductivity and electron conductivity and excellent electrochemical performance. Wherein Li in the silicon-based composite anode material 3 N and Li 3 P has very high room temperature ionic conductivity, and can greatly improve the electrochemical performance of the silicon-based composite anode material. Wherein Li is 3 The ion conductivity of N at room temperature can reach 10 -3 S·cm -1 ，Li 3 The room temperature ion conductivity of P can reach 10 -4 S·cm -1 The above. Optionally, the ionic conductivity of the silicon-based composite anode material at room temperature is 10 -6 -10 -3 S·cm -1 。
In embodiments of the present application, the porosity of the nanoporous structure is from 10 to 70%. Optionally, the porosity of the nanoporous structure is 30-70%. Further optionally, the porosity of the nanoporous structure is 50-70%. For example, the porosity of the nanoporous structure may be in particular 10%, 20%, 30%, 35%, 40%, 45%, 50%, 60% or 70%. The nano porous structure with proper porosity can effectively inhibit or eliminate the influence of volume change generated in the charge and discharge process of the lithium silicon alloy, and improve the structural stability and the cycle stability of the silicon-based composite anode material.
In the embodiment of the application, the pore diameter of the nano porous structure is 5-100nm, and the pore wall thickness is 5-200nm. The pore walls may be the spacing between adjacent pores in the nanoporous structure. The nano porous structure of the silicon-based composite anode material is stable, is not easy to collapse and has long service life. Optionally, the pore size of the nano-porous structure is 10-100nm. Further optionally, the pore size of the nano-porous structure is 30-60nm, or 50-100nm. Optionally, the thickness of the hole wall is 20-150nm. Further alternatively, the pore wall thickness is 20-100nm, or 100-200nm.
In the embodiment, the density of the silicon-based composite anode material is 0.7-2.1g cm -3 . Further optionally, the density of the silicon-based composite anode material is 1.0-2.1g cm -3 . When the porosity of the nano-porous silicon-based composite anode material is large, the density of the silicon-based composite anode material is small. The silicon-based composite anode material with the density and the nano porous structure has higher specific capacity on the premise of effectively improving the influence of the volume change of the lithium silicon alloy material.
In the embodiment of the application, the silicon-based composite anode material further comprises a binder, wherein the mass percentage of the binder in the silicon-based composite anode material is 0.5-5%. In one embodiment, the mass percentage of the binder in the silicon-based composite anode material is 1-5%. In another embodiment, the mass percentage of the binder in the silicon-based composite anode material is 2-4%.
Optionally, the binder includes one or more of Polythiophene (PT), polypyrrole (PPy), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyacrylamide (PAM), ethylene-propylene-diene copolymer, styrene-butadiene rubber, polybutadiene, fluororubber (FPM), polyvinylpyrrolidone (PVP), polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol (PVA), carboxypropylcellulose (HPC), ethylcellulose (EC), polyethylene oxide (PEO), sodium carboxymethyl cellulose (CMC), and styrene-butadiene latex (SBR). The binder with the content range is favorable for ensuring that the silicon-based composite anode material has a firmer structure and better integrity, and can avoid the influence on electrochemical performance caused by the transmission of lithium ions and electrons in the barrier material due to the excessively high content of the binder. The adhesive can also stably fix the silicon-based composite anode material on the anode current collector.
The silicon-based composite anode material has a certain nano porous structure, and the composition components of the silicon-based composite anode material comprise Li 3 N and Li 3 At least one of P and lithium silicon alloy, li in the silicon-based composite anode material 3 N and Li 3 P has very high room temperature ion conductivity; the nano porous structure can also effectively inhibit or eliminate the influence of volume change generated in the charge and discharge process of the lithium-silicon alloy, ensure the stability and the integrity of the nano porous structure, maintain the channels for transmitting electrons and ions, greatly improve the cycling stability of the silicon-based composite anode material, and simultaneously have high specific capacity and energy density.
The silicon-based composite anode material can be used in the field of solid-state lithium batteries, and particularly can be used as an anode material of an all-solid-state lithium battery.
An embodiment of the application provides a preparation method of a silicon-based composite anode material, which comprises the following steps:
uniformly mixing at least one of silicon nitride and silicon phosphide, lithium powder and a solvent in a protective atmosphere to obtain mixed slurry;
coating the mixed slurry on a negative current collector, and drying and pressing to form a silicon-based composite negative electrode material with a nano porous structure on the negative current collector; the silicon-based composite anode material comprises the following components in percentage by weight 3 N and Li 3 At least one of P and lithium silicon alloy.
In the present embodiment, the protective atmosphere may be, but is not limited to, a rare gas atmosphere. In one embodiment, the protective atmosphere is an argon (Ar) atmosphere. In the application, the protective atmosphere can prevent the lithium powder with active chemical property from being oxidized or reacting with other raw materials which do not participate in the preparation of the silicon-based composite anode material.
In the embodiment of the application, the particle sizes of the silicon nitride and the silicon phosphide are 0.03-1 mu m. In one embodiment, the silicon nitride and silicon phosphide both have a particle size of 0.05-0.5 μm. In another embodiment, the silicon nitride and silicon phosphide both have a particle size of 0.1-0.3 μm. The particle sizes of the silicon nitride and the silicon phosphide can be the same or different. For example, the particle size of the silicon nitride or silicon phosphide may be specifically 0.03 μm, 0.05 μm, 0.1 μm, 0.5 μm, 0.8 μm or 1 μm.
In an embodiment of the present application, the particle size of the lithium powder is 0.01 to 50 μm. In one embodiment, the lithium powder has a particle size of 0.1 to 10 μm. In another embodiment, the lithium powder has a particle size of 0.01 to 5 μm. For example, the particle size of the lithium powder may be specifically 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm or 50 μm.
In the present embodiment, the solvent may be selected from at least one of toluene, xylene, anisole, heptane, decane, ethyl acetate, ethyl propionate, butyl butyrate, N-methylpyrrolidone (NMP) and acetone. In the preparation method, the solvent does not chemically react with lithium powder. Alternatively, the solvent may be used in an amount of 0.5 to 4 times the total mass of the solid raw materials in the mixed slurry. The solid raw materials in the mixed slurry refer to solid raw materials participating in the preparation of the silicon-based composite anode material, such as lithium powder and at least one of silicon nitride and silicon phosphide.
In the embodiment of the application, after at least one of silicon nitride and silicon phosphide is mixed and pressed with lithium powder, the silicon nitride and the lithium powder can react to generate lithium nitride and lithium silicon alloy, and the silicon phosphide and the lithium powder react to generate lithium phosphide and silicon nitride. In the mixed slurry, the dosage of lithium powder is controlled in a proper range, so that the prepared silicon-based composite anode material has better electrochemical performance. On one hand, the added lithium powder can completely react, so that the phenomenon that the lithium powder remains after full in-situ reaction, which causes the excessive lithium powder in the components of a final product, is avoided, the excessive lithium powder is prevented from participating in the charge and discharge process of the battery, and the cycle stability of the battery is reduced; on the other hand, the amount of the added lithium powder is not too small, so that the generated lithium nitride or lithium phosphide is insufficient, and the situation of short circuit in the lithium intercalation process and the performance of an electronic and ion conduction network are reduced is caused.
Optionally, the molar amount of the lithium powder is more than 4 times of the sum of the molar amounts of silicon elements of the silicon nitride and the silicon phosphide. In one embodiment, the molar amount of the lithium powder is 4 to 9 times the sum of the molar amounts of silicon elements of the silicon nitride and the silicon phosphide.
In the present embodiment, the drying temperature of the drying process may be, but is not limited to, 80 to 120 ℃. In one embodiment, the drying temperature of the drying process is 90-110 ℃. For example, the drying temperature of the drying process is 100 ℃.
In the embodiment of the application, the pressing can be achieved through rolling, calendaring and other modes, and can be achieved through equipment such as a roll press, a roll grinder, a calendaring machine, a belt press, a flat press, an isostatic press and the like. Optionally, the pressure applied during the pressing is above 50MPa, for example between 50 and 800MPa. Preferably 300-800MPa. The greater pressure facilitates more rapid formation of the nanoporous structures described above. The pressing process may be performed after the mixed slurry is cooled after being dried.
In an embodiment of the present application, the mixed slurry further includes a binder. The binder includes one or more of polythiophene, polypyrrole, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polystyrene, polyacrylamide, ethylene-propylene-diene copolymer, styrene-butadiene rubber, polybutadiene, fluororubber, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxypropyl cellulose, ethyl cellulose, polyethylene oxide, sodium carboxymethyl cellulose, and styrene-butadiene latex. The mass percentage of the binder in the mixed slurry is 0.5-5%. In one embodiment, the mass percentage of the binder in the mixed slurry is 1-5%. In another embodiment, the mass percentage of the binder in the mixed slurry is 2-4%.
The preparation method of the silicon-based composite anode material has the advantages of simple process and low cost, and is suitable for large-scale industrial production; the prepared silicon-based composite anode material has good electron and ion conduction network, excellent electrochemical performance in the charge and discharge process and strong cycling stability. The relevant limitation of the silicon-based composite anode material prepared by the preparation method is consistent with the specific limitation of the silicon-based composite anode material, and is not repeated in the embodiment.
According to the specific steps of the preparation method described in the above embodiment, a silicon-based composite anode material sample is prepared, and then is subjected to detection under a scanning electron microscope, and the result is shown in fig. 1. As can be seen from FIG. 1, the silicon-based composite anode material has high integration degree, li 3 N、Li 3 The components such as P, lithium silicon alloy and the like are uniformly distributed in the silicon-based composite anode material and are well contacted, and the silicon-based composite anode material basically has no granular feel and has a fine nano-scale porous structure. And in FIG. 2 is directly composed of Li 3 N、Li 3 P and lithium silicon alloy are mixed and pressed to form the cathode material. As can be seen from fig. 2, the particles of each component of the negative electrode material formed by the ex-situ reaction are sparse, many gaps exist, and the overall morphology of the negative electrode material is full of the particle feeling. The nano porous structure of the silicon-based composite anode material sample prepared by the preparation method is formed by the steps of preparing a silicon-based composite anode material sample from Si 3 N 4 、Si 3 P 4 Mixing with lithium powder, pressing, and in-situ reacting to obtain Li 3 N、Li 3 The P or lithium silicon alloy components are generated in situ, compared with the negative electrode material formed by an ex-situ method, the silicon-based composite negative electrode material sample particles are smaller, the components are mixed more uniformly, the contact degree between the particles is far higher than that of the negative electrode material formed by the ex-situ method, and the nano porous structure is more beneficial to the transmission of lithium ions.
Referring to fig. 3, the present application also provides an all-solid-state lithium battery 100, including a solid electrolyte layer 10, a positive electrode sheet 20, and a negative electrode sheet 30, wherein the solid electrolyte layer 10 is disposed between the positive electrode sheet 20 and the negative electrode sheet 30.
Wherein the negative electrode sheet 30 comprises a negative electrode current collector 31 and a negative electrode material layer 32 arranged on the negative electrode current collector 31, and the negative electrode material layer 32 contains the silicon-based composite negative electrode material. Alternatively, the negative electrode material layer has a thickness of 5 to 50 μm. When the negative electrode material layer is thicker, the negative electrode sheet still has good and stable electrochemical performance.
Further, the anode material layer 32 does not contain a conductive agent and a solid electrolyte material. The negative electrode material layer 32 without conductive agent and solid electrolyte material can comprise a larger content of the silicon-based composite negative electrode material, so that the capacity of the negative electrode sheet 30 is larger, and the energy density of the all-solid lithium battery 100 is greatly improved. The silicon-based composite anode material has good electron and ion conduction network, so that excellent electrochemical performance is exerted in the charge and discharge process, and the cycling stability is strong; the conductive agent and the solid electrolyte material also have little influence on the lithium ion transporting property of the anode material layer 32.
In the present embodiment, the negative electrode material layer 32 may further contain the above binder. The binder helps to firmly fix the silicon-based composite anode material to the anode current collector and to give the anode material layer 32 a certain elasticity. Further, the mass percentage of the binder in the negative electrode material layer is 0.5-5%. For example 1-5%, or 2-4%.
In the present embodiment, the positive electrode sheet 20 includes a positive electrode current collector 21 and a positive electrode material layer 22 provided on the positive electrode current collector 21. The positive electrode material layer 22 may include a positive electrode active material, a conductive agent, a solid electrolyte material for a positive electrode, and a binder for a positive electrode.
Alternatively, the solid electrolyte layer 10 may be formed by coating and drying a slurry containing a solid electrolyte material and a solvent, and the components of the solid electrolyte layer 10 include the solid electrolyte material. In other embodiments of the present application, the solid electrolyte layer 10 may further contain a binder, and the material thereof may be the same as or different from the binder in the anode material layer 32. In an embodiment of the present application, the solid electrolyte layer 10 may be bonded to the negative electrode material layer 32 by coating, and further the solid electrolyte layer 10 may be bonded to the positive electrode sheet 20 with the positive electrode material layer 22 by pressing.
In an embodiment of the present application, there is also provided a method for preparing an all-solid-state lithium battery shown in fig. 3, including the steps of:
s101, preparing a negative electrode sheet 30: uniformly mixing at least one of silicon nitride and silicon phosphide, lithium powder and a first solvent in a protective atmosphere to obtain negative electrode mixed slurry;
the negative electrode mixed slurry is coated on a negative electrode current collector 31, and after drying and pressing treatment, the negative electrode mixed slurry reacts on the negative electrode current collector 31 in situ to form a negative electrode material layer 32 which comprises a silicon-based composite negative electrode material with a nano porous structure, so as to obtain a negative electrode plate 32; wherein the silicon-based composite anode material comprises the following components in percentage by weight 3 N and Li 3 At least one of P and lithium silicon alloy;
s102, preparing the solid electrolyte layer 10: uniformly mixing a solid electrolyte material and a second solvent in a protective atmosphere to obtain solid electrolyte mixed slurry, continuously coating the solid electrolyte mixed slurry on a negative electrode plate 30, and forming a solid electrolyte layer 10 on the negative electrode plate 30 after drying;
s103, preparing a positive plate 20: uniformly mixing an anode active material, an anode solid electrolyte, a conductive agent, an anode binder and a third solvent to obtain anode mixed slurry; coating the positive electrode mixed slurry on a positive electrode current collector 21, and drying and tabletting to obtain a positive electrode plate 20;
And S104, aligning the negative electrode sheet 30 with the solid electrolyte layer 10 with the positive electrode sheet 20 obtained in the step S103 under a protective atmosphere, attaching the tab, and performing hot pressing treatment, vacuum sealing and isostatic pressing treatment to obtain the all-solid-state lithium battery 100.
Wherein the second solvent and the third solvent are independently selected from at least one of water, ethanol, toluene, xylene, anisole, heptane, decane, ethyl acetate, ethyl propionate, butyl butyrate, N-methylpyrrolidone and acetone. The first solvent is not water or an alcohol solvent, and is at least one of toluene, xylene, anisole, heptane, decane, ethyl acetate, ethyl propionate, butyl butyrate, N-methylpyrrolidone and acetone, for example. The amount of each solvent may be generally 0.5 to 4 times the total mass of the solid raw materials in the formulation of the corresponding mixed slurry.
In S104, the temperature of the hot pressing treatment may be, but not limited to, about 100 ℃, and the hot pressing treatment time is 0.5-3 hours. The isostatic pressing pressure is more than 100MPa, for example, the pressure is 100-300MP; the isostatic pressing treatment time is 3-10min.
In the present embodiment, the solid electrolyte material for the positive electrode and the solid electrolyte material in the solid electrolyte layer 10 are independently selected from one or more of sodium super ion conductor (NASICON) solid electrolyte, garnet-type solid electrolyte, perovskite-type solid electrolyte, and sulfide-type solid electrolyte. The solid electrolyte layer is made of the same material as or different from the solid electrolyte material for the positive electrode. For example, the components of the solid electrolyte layer are selected from reduction-resistant solid electrolyte materials so as to protect the silicon-based composite anode material of the anode piece and further improve the cycle stability of the silicon-based composite anode material; the positive electrode solid electrolyte is a solid electrolyte material with higher ion conductivity. Further, in preparing the solid electrolyte layer and the positive electrode material layer, the solid electrolyte material used may have a particle diameter of 20nm to 5 μm.
Specifically, the NASICON type solid electrolyte may be LiM 2 (PO 4 ) 3 And one or more of its dopants, wherein M is Ti, zr, ge, sn or Pb, the dopant employing a doping element selected from one or more of Mg, ca, sr, ba, sc, al, ga, in, nb, ta and V.
Alternatively, the garnet-type solid electrolyte has the chemical formula of Li 7+a-b-3c Al c La 3-a X a Zr 2-b Y b O 12 Wherein a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, X is selected from one or more of La, ca, sr, ba and K, and Y is selected from one or more of Ta, nb, W and Hf.
Alternatively, the perovskite solid electrolyte has the chemical formula A 1 x1 B 1 y1 TiO 3 、A 1 x2 B 2 y2 Ta 2 O 6 、A 3 x3 B 3 y3 Nb 2 O 6 Or A c E d D e Ti f O 3 Wherein x1+3y1=2, 0 < x1 < 2,0 < y1 < 2/3; x2+3y2=2, 0 < x2 < 2,0 < y2 < 2/3; x3+3y3=2, 0 < x3 < 2,0 < y3 < 2/3; c+2d+5e+4f=6, c, d, e, f are all greater than 0; a is that 1 、A 2 、A 3 Independently selected from at least one of Li and Na, B 1 、B 2 、B 3 Independently selected from at least one of La, ce, pr, Y, sc, nd, sm, eu and Gd, E is selected from at least one of Sr, ca, ba, ir and Pt, and D is selected from at least one of Nb and Ta.
Optionally, the sulfur-based solid state electrolyte comprises crystalline Li g Q h P i S r Glassy Li 2 S-P 2 S 5 And glass-ceramic state Li 2 S-P 2 S 5 And one or more of its dopants. Wherein the crystalline Li g Q h P i S p Wherein Q is one or more of Si, ge and Sn, g+4h+5i=2p, and h is more than or equal to 0 and less than or equal to 1.5. The glassy Li 2 S-P 2 S 5 Comprises Li 2 S and P 2 S 5 Different products of composition, e.g. comprising Li 7 P 3 S 11 Or 70Li 2 S-30P 2 S 5 Etc.
In an embodiment of the present application, the positive electrode active material includes one or more of an oxide type, a sulfide type, a polyanion type, and a composite of the above materials.
Specifically, the oxide type positive electrode active material may include TiO 2 、Cr 3 O 8 、V 2 O 5 、MnO 2 、NiO、WO 3 、LiMn 2 O 4 (lithium manganate), li 2 CuO 2 、LiCo q Ni 1-q O 2 (0≤q≤1)、LiCo r Ni 1-r-s Al s O 2 、LiFe t Mn u G v O 4 、Li 1+ w L 1－y－z H y R z O 2 At least one of the following. Wherein the LiCo r Ni 1-r-s Al s O 2 Wherein r is more than or equal to 0 and less than or equal to 1, s is more than or equal to 0 and less than or equal to 1. The LiFe is t Mn u G v O 4 Wherein G is at least one selected from Al, mg, ga, cr, co, ni, cu, zn and Mo, and t is more than or equal to 0 and less than or equal to 1, u is more than or equal to 0 and less than or equal to 1, v is more than or equal to 0 and less than or equal to 1, and t+u+v=1. The Li is 1+w L 1－y－z H y R z O 2 Wherein L, H and R are respectively and independently selected from at least one of Li, co, mn, ni, fe, al, mg, ga, ti, cr, cu, zn, mo, F, I, S and B, L, H and R are mutually different elements, w is more than or equal to-0.1 and less than or equal to 0.2, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y+z is more than or equal to 0 and less than or equal to 1.
The sulfide-type positive electrode active material may include TiS 2 、V 2 S 3 、FeS、FeS 2 、WS 2 、LiJS o (J is at least one selected from Ti, fe, ni, cu and Mo, and 1.ltoreq.o.ltoreq.2.5), etc.
The polyanionic positive electrode active material may specifically include LiFePO 4 (lithium iron phosphate), li 3 V 2 (PO 4 ) 3 (lithium vanadium phosphate), liVPO 4 F.
Alternatively, the particle size of the positive electrode active material is 0.1 to 500 μm. In one embodiment, the particle size of the positive electrode active material is 0.5 to 200 μm, or 0.5 to 100 μm, or 0.5 to 10 μm.
In this embodiment, the surface of the positive electrode active material may further have a coating layer, so as to optimize the interface between the positive electrode material layer and the solid electrolyte, reduce interface impedance, and improve cycle stability. Specifically, the coating layer on the surface of the positive electrode active material may be LiNbO 3 、LiTaO 3 、Li 3 PO 4 、Li 4 Ti 5 O 12 Etc.
In the present application, the binder for the positive electrode in the positive electrode material layer is not particularly limited, and the material may be the same as or different from that of the binder in the negative electrode layer. For example, one or more of the group consisting of fluorine-containing resins, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol, polyolefin, and the like may be used. The conductive agent in the positive electrode material layer is not particularly limited, and conventional materials existing in the art may be used, such as one or more of conductive carbon black (e.g., acetylene black, ketjen black), carbon nanotubes, carbon fibers, graphite, and furnace black.
Optionally, the mass percentage content of the binder for the positive electrode in the positive electrode material layer is 0.1-10%. Further, optionally, the binder for positive electrode is contained in the positive electrode material layer in an amount of 0.2 to 5% by mass. Optionally, the mass percentage content of the conductive agent in the positive electrode material layer is 0.1-20%. Further may be 1 to 10%.
In the present embodiment, the negative electrode current collector 31 and the positive electrode current collector 21 are independently selected from metal foil or alloy foil. Wherein the metal foil comprises copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold or silver foil, and the alloy foil comprises stainless steel or an alloy containing at least one element of copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold and silver. For example, negative electrode current collector 31 may be specifically an aluminum foil, and positive electrode current collector 21 may be specifically a copper foil. The thickness and the surface roughness of the negative current collector and the positive current collector can be adjusted according to actual requirements.
In this embodiment, the negative electrode plate of the all-solid lithium battery contains the silicon-based composite negative electrode material with the nano porous structure, and the all-solid lithium battery has high energy density, long cycle life and good safety performance.
The embodiments of the present application are further described below in terms of a number of examples.
Example 1
A method of making an all-solid-state lithium battery comprising the steps of:
(1) Manufacturing of negative plate
1000g of Si under an argon atmosphere 3 N 4 The materials, 841g of lithium powder, 30g of binder SBR and 1500mL of toluene are placed in a dispersing machine together for 30min to form stable and uniform cathode mixed slurry. The negative electrode mixed slurry was uniformly and intermittently coated on a copper foil (width 160mm, thickness 16 μm), then dried at 100℃and pressed into tablets by a roll press Obtaining a negative plate comprising a copper foil and a negative electrode material precursor layer thereon; wherein, during tabletting, si in the precursor layer of the anode material on the copper foil 3 N 4 The reaction with lithium powder already started.
(2) Fabrication of solid electrolyte layer
600g of 70Li 2 S·30P 2 S 5 Putting a glassy solid electrolyte material into 1200g of toluene solution containing 30g of butadiene rubber binder, and heating and stirring to obtain stable and uniform slurry; and (3) continuously coating the slurry on the negative plate obtained in the step (1), and then drying at 100 ℃ to form a solid electrolyte layer on the negative plate.
(3) Manufacturing of positive plate
1000g LiCoO 2 Fully mixing 51mL of niobium ethoxide, 12g of lithium ethoxide, 1000mL of deionized water and 1000mL of ethanol, dropwise adding ammonia water to pH 10 under continuous stirring, evaporating the solution to dryness, and heating the obtained powder at 400 ℃ for 8h to obtain LiNbO coated on the surface 3 LiCoO of (C) 2 A positive electrode active material;
the 930g of LiNbO is taken 3 Coated LiCoO 2 Positive electrode active material, 150g of Li 10 GeP 2 S 12 Adding solid electrolyte material, 30g of adhesive butadiene rubber, 20g of acetylene black and 20g of carbon fiber into 1500g of toluene solvent, and stirring in a vacuum stirrer to form stable and uniform anode mixed slurry; the positive electrode mixed slurry is uniformly and intermittently coated on aluminum foil (width 160mm, thickness 16 μm), then dried at 120 ℃, pressed by a roller press, and then a positive electrode material layer is formed on the aluminum foil, thus obtaining the positive electrode plate.
(4) Manufacture of all-solid-state lithium battery
And (3) under the protective atmosphere, aligning the positive plate with the negative plate with the solid electrolyte layer in the step (2), placing in a tablet press, attaching the electrode lug, hot-pressing for 1h at 100 ℃, vacuumizing and sealing by using an aluminum plastic film, and finally pressing for 300s at 200MPa in an isostatic press, so that the in-situ reaction of the silicon-based composite negative electrode material is finished, and converting the precursor layer of the negative electrode material into the negative electrode material layer to obtain the all-solid-state lithium battery.
In the obtained all-solid-state lithium battery, the negative electrode material layer consists of a binder SBR and a silicon-based composite negative electrode material with a nano porous structure, wherein the components of the silicon-based composite negative electrode material comprise Li 3 N and lithium silicon alloys; wherein, the porosity of the nano porous structure is 45%, the aperture is 50nm, the thickness of the pore wall is 40nm, and the density of the silicon-based composite anode material is 1.0 g.cm -3 。
Example 2
(1) Manufacturing of negative plate
1000g of Si under an argon atmosphere 3 P 4 The materials, 566g of lithium powder, 30g of binder SBR and 1500mL of toluene solvent are placed in a dispersing machine together for 30min to form stable and uniform cathode mixed slurry. Uniformly and intermittently coating the negative electrode mixed slurry on a copper foil (with the width of 160mm and the thickness of 16 mu m), drying at 100 ℃, and tabletting by a roll squeezer to obtain a negative electrode plate, wherein the negative electrode plate comprises the copper foil and a negative electrode material precursor layer thereon; wherein, during tabletting, si in the precursor layer of the anode material on the copper foil 3 P 4 The reaction with lithium powder already started.
(2) Fabrication of solid electrolyte layer
600g of 70Li 2 S·30P 2 S 5 Putting a glassy solid electrolyte material into 1200g of toluene solution containing 30g of butadiene rubber binder, and heating and stirring to obtain stable and uniform slurry; and (3) continuously coating the slurry on the negative plate obtained in the step (1), and then drying at 100 ℃ to form a solid electrolyte layer on the negative plate.
(3) Manufacturing of positive plate
1000g LiCoO 2 Fully mixing 51mL of niobium ethoxide, 12g of lithium ethoxide, 1000mL of deionized water and 1000mL of ethanol, dropwise adding ammonia water to pH 10 under continuous stirring, evaporating the solution to dryness, and heating the obtained powder at 400 ℃ for 8h to obtain LiNbO coated on the surface 3 LiCoO of (C) 2 A positive electrode active material;
the 930g of LiNbO is taken 3 Coated LiCoO 2 Positive electrode active material, 150g of Li 10 GeP 2 S 12 Adding solid electrolyte material, 30g of adhesive butadiene rubber, 20g of acetylene black and 20g of carbon fiber into 1500g of toluene solvent, and stirring in a vacuum stirrer to form stable and uniform anode mixed slurry; the positive electrode mixed slurry is uniformly and intermittently coated on aluminum foil (width 160mm, thickness 16 μm), then dried at 120 ℃, pressed by a roller press, and then a positive electrode material layer is formed on the aluminum foil, thus obtaining the positive electrode plate.
(4) Manufacture of all-solid-state lithium battery
And (3) under the protective atmosphere, aligning the positive plate with the negative plate with the solid electrolyte layer in the step (2), placing in a tablet press, attaching the electrode lug, hot-pressing for 1h at 100 ℃, vacuumizing and sealing by using an aluminum plastic film, and finally pressing for 300s at 200MPa in an isostatic press, so that the in-situ reaction of the silicon-based composite negative electrode material is finished, and converting the precursor layer of the negative electrode material into the negative electrode material layer to obtain the all-solid-state lithium battery.
In the obtained all-solid-state lithium battery, the negative electrode material layer consists of a binder SBR and a silicon-based composite negative electrode material with a nano porous structure, wherein the components of the silicon-based composite negative electrode material comprise Li 3 P and lithium silicon alloys; wherein, the porosity of the nano porous structure is 45%, the aperture is 50nm, the thickness of the pore wall is 40nm, and the density of the silicon-based composite anode material is 1.3 g.cm -3 。
Example 3
(1) Manufacturing of negative plate
1000g of Si under an argon atmosphere 3 N 4 The materials, 1247g of lithium powder, 30g of binder SBR and 1500mL of toluene solvent are placed into a dispersing machine together, and the dispersing time is 30min, so that stable and uniform cathode mixed slurry is formed. Uniformly and intermittently coating the negative electrode mixed slurry on a copper foil (with the width of 160mm and the thickness of 16 mu m), drying at 100 ℃, and tabletting by a roll squeezer to obtain a negative electrode plate, wherein the negative electrode plate comprises the copper foil and a negative electrode material precursor layer thereon; wherein, during tabletting, si in the precursor layer of the anode material on the copper foil 3 N 4 The reaction with lithium powder already started.
(2) Fabrication of solid electrolyte layer
600g of 70Li 2 S·30P 2 S 5 Putting a glassy solid electrolyte material into 1200g of toluene solution containing 30g of butadiene rubber binder, and heating and stirring to obtain stable and uniform slurry; and (3) continuously coating the slurry on the negative plate obtained in the step (1), and then drying at 100 ℃ to form a solid electrolyte layer on the negative plate.
(3) Manufacturing of positive plate
930g of TiS is taken 2 Positive electrode active material, 150gLi 10 GeP 2 S 12 Adding solid electrolyte material, 30g of adhesive butadiene rubber, 20g of acetylene black and 20g of carbon fiber into 1500g of toluene solvent, and stirring in a vacuum stirrer to form stable and uniform anode mixed slurry; the positive electrode mixed slurry is uniformly and intermittently coated on aluminum foil (width 160mm, thickness 16 μm), then dried at 120 ℃, pressed by a roller press, and then a positive electrode material layer is formed on the aluminum foil, thus obtaining the positive electrode plate.
(4) Manufacture of all-solid-state lithium battery
And (3) under the protective atmosphere, aligning the positive plate with the negative plate with the solid electrolyte layer in the step (2), placing in a tablet press, attaching the electrode lug, hot-pressing for 1h at 100 ℃, vacuumizing and sealing by using an aluminum plastic film, and finally pressing for 300s at 200MPa in an isostatic press, so that the in-situ reaction of the silicon-based composite negative electrode material is finished, and converting the precursor layer of the negative electrode material into the negative electrode material layer to obtain the all-solid-state lithium battery.
In the obtained all-solid-state lithium battery, the negative electrode material layer consists of a binder SBR and a silicon-based composite negative electrode material with a nano porous structure, wherein the components of the silicon-based composite negative electrode material comprise Li 3 N and lithium silicon alloys; wherein, the porosity of the nano porous structure is 45%, the aperture is 50nm, the thickness of the pore wall is 40nm, and the density of the silicon-based composite anode material is 1.1 g.cm -3 。
Example 4
(1) Manufacturing of negative plate
1000g of Si under an argon atmosphere 3 P 4 The materials, 840g of lithium powder, 30g of binder SBR and 1500mL of toluene solvent are placed in a dispersing machine together for 30min to form stable and uniform cathode mixed slurry. Uniformly and intermittently coating the negative electrode mixed slurry on a copper foil (with the width of 160mm and the thickness of 16 mu m), drying at 100 ℃, and tabletting by a roll squeezer to obtain a negative electrode plate, wherein the negative electrode plate comprises the copper foil and a negative electrode material precursor layer thereon; wherein, during tabletting, si in the precursor layer of the anode material on the copper foil 3 P 4 The reaction with lithium powder already started.
(2) Fabrication of solid electrolyte layer
600g of 70Li 2 S·30P 2 S 5 Putting a glassy solid electrolyte material into 1200g of toluene solution containing 30g of butadiene rubber binder, and heating and stirring to obtain stable and uniform slurry; and (3) continuously coating the slurry on the negative plate obtained in the step (1), and then drying at 100 ℃ to form a solid electrolyte layer on the negative plate.
(3) Manufacturing of positive plate
930g of TiS is taken 2 Positive electrode active material, 150gLi 10 GeP 2 S 12 Adding solid electrolyte material, 30g of adhesive butadiene rubber, 20g of acetylene black and 20g of carbon fiber into 1500g of toluene solvent, and stirring in a vacuum stirrer to form stable and uniform anode mixed slurry; the positive electrode mixed slurry is uniformly and intermittently coated on aluminum foil (width 160mm, thickness 16 μm), then dried at 120 ℃, pressed by a roller press, and then a positive electrode material layer is formed on the aluminum foil, thus obtaining the positive electrode plate.
(4) Manufacture of all-solid-state lithium battery
And (3) under the protective atmosphere, aligning the positive plate with the negative plate with the solid electrolyte layer in the step (2), placing in a tablet press, attaching the electrode lug, hot-pressing for 1h at 100 ℃, vacuumizing and sealing by using an aluminum plastic film, and finally pressing for 300s at 200MPa in an isostatic press, so that the in-situ reaction of the silicon-based composite negative electrode material is finished, and converting the precursor layer of the negative electrode material into the negative electrode material layer to obtain the all-solid-state lithium battery.
Wherein the method comprises the steps ofIn the obtained all-solid-state lithium battery, the negative electrode material layer consists of a binder SBR and a silicon-based composite negative electrode material with a nano porous structure, wherein the components of the silicon-based composite negative electrode material comprise Li 3 N and lithium silicon alloys; wherein, the porosity of the nano porous structure is 45%, the aperture is 50nm, the thickness of the pore wall is 40nm, and the density of the silicon-based composite anode material is 1.4 g.cm -3 。
To highlight the benefits of the examples of the present application, the following comparative examples are provided:
comparative example 1
An all solid-state lithium battery was prepared, which was different from the procedure of example 1 in that carbon-coated Si was used as a negative electrode material: in the step (1), 1000gSi g and 240g of sucrose are placed in 1000mL of deionized water together and stirred uniformly, then the mixture is heated to 100 ℃ in the stirring process, the product is taken out after water evaporation and is placed in an inert atmosphere and heated to 300 ℃, so that the carbon-coated silicon negative electrode material can be obtained, 1500g of carbon-coated silicon negative electrode material, 30g of binder SBR and 1500mL of toluene are prepared into mixed slurry, the mixed slurry is coated on copper foil, and the negative electrode sheet is prepared through drying and tabletting, and the rest steps and operation are unchanged.
Comparative example 2
An all solid-state lithium battery was prepared, which was different from the procedure of example 1 in that carbon-coated Si was used as a negative electrode material, and a solid electrolyte material and a conductive agent were added in the procedure (1):
in the step (1), 1000gSi g and 240g of sucrose are placed in 1000mL of deionized water together and stirred uniformly, then heated to 100 ℃ in the stirring process, the product is taken out after water evaporation and is placed in an inert atmosphere and heated to 300 ℃, thus obtaining a carbon-coated silicon anode material, and then 1500g of carbon-coated silicon anode material and 400g of 70Li are added 2 S·30P 2 S 5 Preparing a mixed slurry from a glassy electrolyte material, 100g of acetylene black, 30g of binder SBR and 1500mL of toluene, coating the mixed slurry on a copper foil, drying and tabletting to prepare a negative plate, and preparing the negative plate; the rest steps and operations are unchanged.
Comparative example 3
An all solid state lithium battery was prepared which differed from the procedure of example 1 in that: in the step (1), lithium powder is not added in the preparation of the negative electrode sheet, but a metal lithium foil is used:
in step (1), 1000g of Si was reacted under an argon atmosphere 3 N 4 The material, 30g of binder SBR and 1500mL of toluene solution are placed together in a dispersing machine, and the dispersing time is 30min, so that stable and uniform cathode slurry is formed. The negative electrode slurry is uniformly and intermittently coated on a copper foil (width 160mm, thickness 10 μm of lithium foil, usable tape Kong Libo, thickness 16 μm of copper foil) with lithium foil on the surface, then 373K dried, pressed by a roll press to obtain a negative electrode sheet A, si in the negative electrode sheet A 3 P 4 The lithium battery anode material has no nano porous structure because the lithium battery anode material is not fully mixed, and the rest steps and operations are unchanged
The negative electrode material layer of the all-solid lithium battery obtained in comparative example 3 had no nanoporous structure, and the negative electrode material had a porosity of 8% and a density of 1.2 g.cm -3 。
Comparative example 4
An all solid state lithium battery was prepared which differed from the procedure of example 1 in that: in the step (1), 1000g of Si was used in the preparation of the negative electrode sheet 3 P 4 Materials other than 1000g Si 3 N 4 Material, and not lithium powder, but metallic lithium foil used:
in step (1), 1000g of Si was reacted under an argon atmosphere 3 P 4 The material, 30g of binder SBR and 1500mL of toluene solution are placed together in a dispersing machine, and the dispersing time is 30min, so that stable and uniform cathode slurry is formed. The negative electrode slurry is uniformly and intermittently coated on a copper foil (width 160mm, thickness 10 μm of lithium foil, usable tape Kong Libo, thickness 16 μm of copper foil) with lithium foil on the surface, then 373K dried, pressed by a roll press to obtain a negative electrode sheet A, si in the negative electrode sheet A 3 P 4 The lithium battery anode material has no nano porous structure because the lithium battery anode material is not fully mixed, and the rest steps are unchanged.
The full solid prepared in comparative example 4The anode material layer of the lithium battery does not have a nano porous structure, the porosity of the anode material is 8 percent, and the density is 1.5g cm -3 。
Comparative example 5
An all solid state lithium battery was prepared which differed from the procedure of example 1 in that: in the step (1), 848g Li was directly used in the preparation of the negative electrode sheet 1.71 Si material, 993g Li 3 N material, not 1000g Si 3 N 4 Material and 841g lithium powder, the remaining steps are unchanged.
In the negative electrode material layer of the all-solid lithium battery prepared in comparative example 5, the negative electrode material layer was lithium silicon alloy and Li 3 Simple mixing of N layers, rather than in situ generation; its porosity is 3%, density is 1.2g cm -3 。
Comparative example 6
An all solid state lithium battery was prepared which differed from the procedure of example 3 in that: in the step (1), 1254g Li was directly used in the preparation of the negative electrode sheet 4.4 Si material, 993g Li 3 N, not 1000g Si 3 N 4 Material and 1247g lithium powder, the remaining steps being unchanged.
In the negative electrode material layer of the all-solid lithium battery prepared in comparative example 6, the negative electrode material layer was lithium silicon alloy and Li 3 Simple mixing of N layers, rather than in situ generation; its porosity is 3%, density is 1.3g cm -3 。
Comparative example 7
An all solid state lithium battery was prepared which differed from the procedure of example 1 in that: in the step (1), 1000g of Si was used in the preparation of the negative electrode sheet 3 N 4 Material and 200g lithium powder, instead of 1000g Si 3 N 4 Material and 841g lithium powder, the remaining steps are unchanged.
In the negative electrode material layer of the all-solid lithium battery prepared in comparative example 7, the negative electrode material layer was Li 3 N, si and unreacted complete Si 3 N 4 Does not have a nanoporous morphology; its porosity is 8%, density is 2.9g cm -3 。
Effect examples
The all solid-state lithium batteries obtained in examples 1 to 4 and comparative examples 1 to 7 were subjected to cycle life test of the batteries by the following test methods: all solid-state lithium battery samples prepared in each example and comparative example were taken 20 for each, and the battery was subjected to charge-discharge cycle test at a rate of 0.1C on a LAND CT 2001C secondary battery performance detection device under 298±1k.
The testing steps are as follows: standing for 10min; constant voltage charging to 4.25V/0.05C cut-off; standing for 10min; constant current discharge to 3V, 1 cycle, was recorded, and the first cycle discharge capacity (TiS as positive electrode active material used in examples 3-4, comparative example 6 2 The upper and lower voltage limits are 3V/0.05C and 1V, respectively, with the remaining conditions being the same). This procedure was repeated, and when the battery capacity was lower than 80% of the first discharge capacity during the cycle, the cycle was terminated, the number of cycles was the cycle life of the battery, and each group was averaged, and the obtained results were shown in table 1.
Table 1: cycle life test data sheet for each set of samples
As can be seen from the results in table 1, the negative electrode material layers in the negative electrode sheets of all-solid-state lithium batteries in examples 1 to 4 of the present application are silicon-based composite negative electrode materials with nano-porous structures, which are formed by in-situ reaction, and the negative electrode discharge capacities in examples 1 to 4 are higher, and the cycle lives are excellent, in particular, examples 3 and 4; while comparative example 1, in which the silicon-based composite anode material of the present application was not used, was poor in both discharge capacity and cycle life; and the cycle life in comparative examples 2-7 is very low.
Wherein, the comparative example 1 adopting the silicon cathode material coated by carbon has extremely poor battery performance, very low discharge capacity and cycle life; in comparative example 2, in which a solid electrolyte material and a conductive agent were added to a negative electrode material, the performance of the battery was improved as compared with comparative example 1, but still far from that of all-solid lithium batteries of examples 1 to 4 of the present application. In comparative examples 3 to 4, si was directly used 3 N 4 、Si 3 P 4 Preparing a negative plate with a lithium foil to obtain an all-solid-state lithium battery, wherein the discharge capacity and the cycle life of the all-solid-state lithium battery are very poor; in comparative examples 5 to 6, the negative electrode sheet of the all-solid lithium battery was directly prepared with Li 3 N/Li 3 P, and lithium silicon alloy, the discharge capacity and the cycle life of the lithium silicon alloy are lower than those of the examples 3-4; in comparative example 7, the negative electrode sheet of the all-solid lithium battery was also prepared from SiC and lithium powder, but the lithium powder was used in a low amount, and the product electron conductivity and ion conductivity were poor, resulting in degradation of the negative electrode sheet electron and ion conductive network properties, and both the discharge capacity and cycle life of the battery were poor.
The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims (9)

1. The silicon-based composite anode material is characterized by having a nano porous structure, wherein the nano porous structure is formed by at least one of silicon nitride and silicon phosphide and lithium powder through in-situ pressing reaction; the silicon-based composite anode material comprises the following components in percentage by weight 3 N and Li 3 At least one of P and lithium silicon alloy; the silicon-based composite anode material does not contain a simple substance of lithium and a simple substance of silicon.
2. The silicon-based composite anode material of claim 1, wherein the nanoporous structure has a porosity of 10-70%.
3. The silicon-based composite anode material according to claim 1 or 2, wherein the pore diameter of the nano-porous structure is 5-100nm, and the pore wall thickness is 5-200nm.
4. The silicon-based composite anode material according to claim 1, wherein the density of the silicon-based composite anode material is 0.7-2.1 g-cm -3 。
5. The preparation method of the silicon-based composite anode material is characterized by comprising the following steps of:
uniformly mixing the first raw material, lithium powder and a solvent in a protective atmosphere to obtain mixed slurry; wherein the first raw material is at least one of silicon nitride and silicon phosphide; the molar weight of the lithium powder is 4-9 times of the sum of the molar weight of silicon elements in the first raw material;
The mixed slurry is coated on a negative electrode current collector, and after drying and pressing treatment, the first raw material and the lithium powder undergo an in-situ pressing reaction to form a nano porous structure so as to form a silicon-based composite negative electrode material on the negative electrode current collector; the silicon-based composite anode material comprises the following components in percentage by weight 3 N and Li 3 At least one of P and lithium silicon alloy; the silicon-based composite anode material does not contain a simple substance of lithium and a simple substance of silicon.
6. The method for producing a silicon-based composite anode material according to claim 5, wherein the particle diameters of the silicon nitride and the silicon phosphide are each 0.03 to 1 μm, and the particle diameter of the lithium powder is 0.01 to 50 μm.
7. An all-solid-state lithium battery is characterized by comprising a positive plate, a negative plate and a solid electrolyte layer, wherein the solid electrolyte layer is positioned between the positive plate and the negative plate; the negative electrode sheet comprises the silicon-based composite negative electrode material according to any one of claims 1 to 4 or the silicon-based composite negative electrode material prepared by the preparation method according to any one of claims 5 to 6.
8. The all-solid lithium battery of claim 7, wherein the negative electrode tab comprises a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector, the negative electrode material layer containing the silicon-based composite negative electrode material and the negative electrode material layer being free of conductive agent and solid electrolyte material.
9. The all-solid lithium battery of claim 8, wherein the negative electrode material layer further comprises a binder; the mass percentage of the binder in the negative electrode material layer is 0.5-5%.
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