CN115172746A - Composite negative electrode material, preparation method thereof and lithium ion battery - Google Patents
Composite negative electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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- CN115172746A CN115172746A CN202110363721.9A CN202110363721A CN115172746A CN 115172746 A CN115172746 A CN 115172746A CN 202110363721 A CN202110363721 A CN 202110363721A CN 115172746 A CN115172746 A CN 115172746A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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Abstract
The application relates to the field of negative electrode materials, and provides a composite negative electrode material, a preparation method thereof and a lithium ion battery, wherein the composite negative electrode material comprises a core and a coating layer positioned on the surface of the core; wherein the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the primary particle comprises a skeleton comprising a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to a surface of the primary particle; the nanoparticle layer is formed with micropores and/or mesopores. The composite negative electrode material, the preparation method of the composite negative electrode material and the lithium ion battery can effectively inhibit the volume expansion of the negative electrode material and improve the cycle performance of the battery.
Description
Technical Field
The application relates to the technical field of negative electrode materials, in particular to a composite negative electrode material, a preparation method thereof and a lithium ion battery.
Background
Lithium ion batteries are widely used in electric vehicles and consumer electronics because of their advantages of high energy density, high output power, long cycle life, and low environmental pollution. In order to improve the energy density of the battery, research and development of silicon negative electrode materials are becoming mature. However, the volume expansion of the silicon negative electrode material is large (> 300%) in the lithium desorption process, the silicon negative electrode material can be pulverized and fall off the current collector in the charging and discharging processes, and the electric touch between the active material and the current collector is lost, so that the electrochemical performance is poor, the capacity is attenuated, the cycling stability is reduced, and the silicon negative electrode material is difficult to be commercially applied.
Based on this, it is urgently needed to develop a silicon negative electrode material with low expansion rate and high cycle stability and a preparation method thereof.
Disclosure of Invention
In view of this, the application provides a composite negative electrode material, a preparation method thereof, and a lithium ion battery, which can reduce the expansion rate of the negative electrode material, improve the charge-discharge cycle performance of the negative electrode material, and the preparation method can reduce the preparation cost.
In a first aspect, the present application provides a composite anode material, including an inner core and a coating layer located on the surface of the inner core; wherein the content of the first and second substances,
the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the primary particle comprises a skeleton comprising a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to a surface of the primary particle; the nanoparticle layer is formed with micropores and/or mesopores.
In above-mentioned scheme, the material pulverization can effectively be avoided to the nano-particle layer, can alleviate the volume expansion of material, guarantees the structural stability of the inside primary particle of cathode material. After the coating layer is adopted for coating, the composite negative electrode material has better conductivity and stability, can effectively avoid the inner pores of the carbon filling material, improves the first effect of the material, and enables the composite negative electrode material to show the characteristics of high capacity, long cycle life, high rate performance, low expansion and the like.
In one embodiment, the composite anode material includes at least one of the following features a-d:
a. the nanoparticle layer comprises a plurality of stacked nanoparticles;
b. the nano particles are selected from at least one of nano silicon particles, nano germanium particles, nano antimony particles, nano tin particles and nano boron particles;
c. the nanoparticle layer comprises a plurality of nanoparticles, and the median particle size of the nanoparticles is 20 nm-200 nm;
d. the thickness of the nanoparticle layer is 20nm to 2000nm.
In one embodiment, the composite anode material includes at least one of the following features a-e:
a. the main framework is of a three-dimensional net structure;
b. the individual ones of the branches are individual die,
c. the single branch is an individual crystal grain, and the size of the crystal grain is 30nm-100nm;
d. the maximum width of the cross section of the branch is 20nm-250nm, and the maximum length of the cross section of the branch is 100nm-1500nm;
e. the branch is selected from at least one of a rod-shaped nanoparticle, a nano sheet, a nano wire and a nano tube.
In a second aspect, the present application provides a composite anode material, including an inner core and a coating layer located on the surface of the inner core; wherein the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the nanoparticle layer is formed with micropores and/or mesopores;
the primary particles are of a macroporous structure, pore channels are formed inside the primary particles, and the pore channels extend to the surfaces of the primary particles.
The pore channel structure of the cathode material extending to the surface of the primary particles has the following advantages: 1. the expansion of the lithium battery can be reduced while the lithium storage performance is improved. The volume expansion in the lithium intercalation process can be relieved, and an internal expansion space is provided for lithiation, so that the electrode material is expanded inwards after lithiation to reduce the thickness of the whole electrode film, and the safety of the lithium ion battery is greatly improved. 2. And a channel for flowing the electrolyte is provided, so that the contact of the electrolyte is facilitated. The pore structure can also bring higher tap density, and can increase the volume energy density of the battery.
In one embodiment, the diameter of the pore channel is 20nm to 250nm; the depth of the pore channel is 50 nm-1000 nm; and/or
The volume of the pore canal in all pore structures accounts for 35-90%, the volume of the mesopores in all pore structures accounts for 5-45%, and the volume of the micropores in all pore structures accounts for 5-20%.
In one embodiment, the composite anode material includes at least one of the following features a-d:
a. the porosity of the composite negative electrode material is 30-70%, wherein the porosity of the primary particles is 15-75%, and the porosity of the nanoparticle layer is 5-35%;
b. the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is (2-10): 1;
c. the proportion of open pore volume in all pore structures of the composite negative electrode material is 60-95%, and the proportion of closed pore volume is 5-40%;
d. in the open pores of all pore structures, the volume ratio of the cross-linked pores to all open pores is 79-95%, the volume ratio of the through pores to all open pores is 4-20%, and the volume ratio of the blind pores to all open pores is 1-10%.
In one embodiment, the composite anode material includes at least one of the following features a-g:
a. the primary particles are selected from at least one of silicon, germanium, antimony, tin and boron;
b. the median particle diameter of the primary particles is 0.1-10 μm;
c. the median particle diameter of the composite negative electrode material is 0.1-15 mu m;
d. the specific surface area of the composite negative electrode material is 1m 2 /g～100m 2 /g；
e. The cladding layer includes a carbon layer;
f. the coating layer comprises a carbon layer, and the thickness of the carbon layer is 5 nm-100nm;
g. the mass percentage content of carbon in the composite negative electrode material is 5-50%.
In a third aspect, the present application provides a method for preparing a composite anode material, comprising the steps of:
forming a coating layer on the surface of the N-M alloy to obtain the N-M alloy containing the coating layer;
adding the N-M alloy containing the coating layer into an ammonium salt solution for oxidation-reduction reaction to obtain an intermediate;
and carrying out dealloying heat treatment on the intermediate in a protective atmosphere, and carrying out acid washing on a reaction product to obtain the composite cathode material, wherein N in the N-M alloy comprises at least one of silicon, germanium, antimony, tin and boron, and M in the N-M alloy comprises at least one of magnesium, aluminum, calcium and zinc.
In the scheme, the composite cathode material with two pore structures can be prepared in one step through simple in-situ reaction, the coated N-M alloy and the ammonium salt solution react and then are heated in a protective atmosphere, so that the composite cathode material can be obtained, the appearance and the pore structure of the composite cathode material are easy to regulate and control, the alloy components can be controlled to change the size and the porosity of pores, and the depth of the pores can be controlled by the reaction time and the reaction temperature. The prepared holes in the negative electrode material can provide an internal expansion space in the lithium desorption process of the negative electrode material, and can be used as a flow channel of electrolyte, so that the expansion of the lithium battery is reduced while the lithium storage performance is improved, the negative electrode material is favorable for inward expansion after lithiation so as to reduce the thickness of the whole electrode film, and the safety of the lithium ion battery is greatly improved. The outer nano particle layer can effectively avoid material pulverization, can relieve volume expansion of the material and ensure the structural stability of primary particles in the negative electrode material. After the coating material is adopted for coating, the composite negative electrode material has better conductivity and stability, can effectively avoid carbon from filling three-dimensional pore channels of primary particles, improves the first effect of the material, and can show the characteristics of high capacity, long cycle life, high rate performance, low expansion and the like.
In one embodiment, the method of preparation includes at least one of the following features a-d:
a. the forming method of the clad layer comprises the following steps: coating the surface of the N-M alloy by adopting a carbon source to form a carbon layer;
b. the forming method of the clad layer comprises the following steps: coating the surface of the N-M alloy by adopting a carbon source to form a carbon layer; the carbon source comprises at least one of a gas phase carbon source and a solid phase carbon source, the gas phase carbon source comprises at least one of methane, acetylene, acetone and alcohol; the solid-phase carbon source comprises at least one of calcium carbonate, lithium carbonate, iron carbonate, zinc carbonate and magnesium carbonate;
c. the thickness of a coating layer formed on the surface of the N-M alloy is 5 nm-100nm;
d. the median particle diameter of the N-M alloy is 0.1-15 mu M.
In one embodiment, the method of preparation includes at least one of the following features a-f:
a. the median particle diameter of the N-M alloy containing the coating layer is 0.1-15 mu M;
b. the ammonium salt comprises at least one of ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium carbonate, ammonium perchlorate, ammonium sulfate and ammonium sulfide;
c. the mass concentration of the ammonium salt solution is 0.1-5 mol/L;
d. the mol ratio of the N-M alloy containing the coating layer to the ammonium salt is 1: (0.1 to 2);
e. the redox reaction time of the N-M alloy containing the coating layer and the ammonium salt solution is 0.5-12 h;
f. the redox reaction temperature of the N-M alloy containing the coating layer and the ammonium salt solution is 20-80 ℃.
In one embodiment, the method of preparation includes at least one of the following features a-g:
a. the temperature of the dealloying heat treatment is 200-950 ℃;
b. the heat preservation time of the dealloying heat treatment is 2-18 h;
c. the temperature rise rate of the dealloying heat treatment is 1 ℃/min to 20 ℃/min;
d. the protective atmosphere comprises at least one of helium, neon, argon, krypton and xenon;
e. the acid solution adopted by the acid cleaning comprises at least one of hydrochloric acid, nitric acid and sulfuric acid;
f. the mass concentration of the acid solution is 1-5 mol/L;
g. the pickling time is 1-10 h.
In a fourth aspect, the present application provides a lithium ion battery, where the lithium ion battery includes the composite anode material or the anode material prepared by the preparation method of the composite anode material.
Drawings
Fig. 1a is a schematic structural diagram of a composite anode material provided in an embodiment of the present application;
fig. 1b is a schematic structural diagram of primary particles in a composite anode material provided in an embodiment of the present application;
fig. 1c is a schematic structural diagram of a nanoparticle layer in a composite anode material provided in an embodiment of the present application;
fig. 2 is a flowchart of a method for preparing a composite anode material provided in an embodiment of the present application;
fig. 3 is a scanning electron microscope picture of the silicon-carbon composite anode material provided in the embodiment of the present application;
fig. 4 is an XRD pattern of the silicon-carbon composite anode material provided in the examples of the present application;
fig. 5 is a graph of cycle performance of the silicon-carbon composite anode material provided in the example of the present application.
Detailed Description
While the following is a preferred embodiment of the embodiments of the present application, it should be noted that various modifications and adaptations can be made by those skilled in the art without departing from the principles of the embodiments of the present application, and are intended to be within the scope of the embodiments of the present application.
At present, in a lithium ion battery, a negative electrode material is one of key materials influencing the charge and discharge performance of the lithium ion battery, the existing negative electrode material is a graphite carbon material, the theoretical lithium storage capacity of the carbon material is only 372mA h/g, and the requirement of people for a high-energy density material cannot be met. Silicon as a lithium ion battery negative electrode material has very high theoretical capacity (about 4200mA h/g), but the silicon negative electrode material has large volume expansion (> 300%) in the lithium releasing and embedding process, and is easy to be pulverized and fall off a current collector in the charging and discharging process, so that the electric touch between an active substance and the current collector is lost, and the electrochemical performance is poor. Therefore, the large volume change effect easily causes poor cycle stability and is difficult to be commercially applied.
In order to improve the cycle stability of the lithium ion battery, the embodiment of the application provides a composite negative electrode material.
Specifically, as shown in fig. 1a, the composite negative electrode material includes a core and a coating layer 30 located on the surface of the core; wherein, the inner core comprises primary particles 10 and a nano particle layer 20 positioned on the surface of the primary particles 10; the primary particle 10 includes a skeleton including a main skeleton 11 located inside the primary particle and a plurality of branches 12 extending from the main skeleton 11 to a surface of the primary particle 10; the nanoparticle layer 20 is formed with micropores and/or mesopores.
Referring further to fig. 1b, the primary particle 10 has a macroporous structure, wherein a pore channel 13 is formed inside the primary particle, and the pore channel 13 extends to the surface of the primary particle. Among them, those having a pore diameter of more than 50nm are called macropores according to the definition of the International Union of Pure and Applied Chemistry (IUPAC).
The main framework 11 and the branches 12 extending from the main framework to the surface of the primary particle are integrated, so that the electron transfer and ion diffusion of the whole framework structure reinforcing material can effectively release the stress after lithiation, and the material fracture and pulverization caused by the concentration of the stress at the grain boundary can be avoided.
The pore channel structure of the composite anode material, which has the pore channel extending to the surface of the primary particles, has the following advantages: 1. the expansion of the lithium battery can be reduced while the lithium storage performance is improved. The lithium ion battery electrode can relieve the volume expansion in the lithium intercalation process, is favorable for providing an internal expansion space for lithiation, enables the electrode material to expand inwards after lithiation so as to reduce the thickness of the whole electrode film, and greatly improves the safety of the lithium ion battery. 2. And a channel for flowing the electrolyte is provided, so that the contact of the electrolyte is facilitated.
The nano particle layer is composed of nano particles, and the nano particles can effectively avoid pulverization of materials; the nano particle layer is provided with micropores and/or mesopores, so that the volume expansion of the material can be effectively relieved, the infiltration of electrolyte and the contact surface are promoted, the lithium ion transmission is accelerated, the multiplying power performance of the whole material is improved, and the structural stability of primary particles in the negative electrode material is ensured. After the coating layer is adopted for coating, the composite negative electrode material has better conductivity and stability, can effectively avoid the inner pores of the carbon filling material, improves the first effect of the material, and enables the composite negative electrode material to show the characteristics of high capacity, long cycle life, high rate performance, low expansion and the like.
In some embodiments, the backbone is a three-dimensional network structure;
in some embodiments, a single said branch is an individual grain; compared with the structure, the branch on the primary particle in the embodiment is a single large crystal grain without excessive crystal boundaries, so that the stress can be well dispersed after lithiation, and the damage of the material caused by stress concentration is avoided; meanwhile, the curve of the crystal face of a single crystal grain is the same, so that the relative volume expansion of the material in a certain direction is reduced, the volume expansion of a structure formed by a plurality of small crystal grains is relatively large, and meanwhile, the structural stability is relatively poor, so that the circulation stability is poor.
Specifically, the size of the crystal grains is 30nm-100nm; illustratively, the size of the grains may be 30nm, 45nm, 50nm, 60nm, 75nm, 100nm.
With continued reference to FIG. 1b, the maximum width 12W of the cross section of the branch 12 is 20nm to 250nm, and the maximum length 12L of the cross section of the branch 12 is 100nm to 1500nm.
Illustratively, the maximum width 12W of the cross section of the branch 12 may be 20nm, 40nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm or 250nm, and the maximum length 12L of the cross section of the branch 12 may be 100nm, 200nm, 300nm, 400nm, 500nm, 800nm, 1000nm, 1200nm or 1500nm, without limitation.
In some embodiments, the branches are selected from at least one of rod-like nanoparticles, nanoplates, nanowires, and nanotubes.
In some embodiments, the diameter of the channels 13 is from 10nm to 150nm as measured by mercury intrusion test methods; the depth of the pore channel is 50nm-1500nm. Illustratively, the diameter of the pore channel may be 10nm, 50nm, 60nm, 80nm, 100nm or 150nm, but is not limited thereto. The depth of the pore channel 13 may be 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 800nm or 1000nm, but is not limited thereto. The reaction time and reaction temperature can be controlled to vary the depth of the pores (generally, the longer the reaction time and the higher the reaction temperature, the deeper the depth of the pores.)
In some embodiments, the primary particles are selected from at least one of silicon, germanium, tin, boron, and antimony; the framework can be a silicon framework, a germanium framework, a tin framework, a boron framework, an antimony framework and the like; if the primary particle is selected from the silicon material, the primary particle comprises a silicon skeleton, a main skeleton positioned in the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle. The framework structures of germanium, boron, tin and antimony are similar to the silicon framework structure described above.
As shown in fig. 1c, the nanoparticle layer 20 includes a plurality of nanoparticles 21, and the plurality of nanoparticles 21 are stacked on one another. The shape of the nanoparticles 21 may be spherical, spheroidal, flat or any other shape, and is not limited herein. The nano-particles 21 are formed with micropores 22 and/or mesopores 23, the pore diameter of the micropores is smaller than 2nm, and the pore diameter of the mesopores is larger than 2nm and smaller than 50nm.
In some embodiments, the nanoparticles are selected from at least one of nano-silicon particles, nano-germanium particles, nano-antimony particles, nano-tin particles, nano-boron particles.
In some embodiments, the porosity of the composite anode material is 30% to 70%, specifically 30%, 40%, 50%, 60% or 70%, and is not limited herein, and the porosity of the composite anode material is preferably 40% to 60%.
In some embodiments, the porosity of the primary particle 10 is 15% to 75%, and specifically may be 15%, 20%, 35%, 40%, 50%, 60%, or 75%, which is not limited herein.
In some embodiments, the nanoparticle layer has a porosity of 5% to 35%, specifically 5%, 10%, 15%, 20%, 25%, 30%, or 35%; in this example, the ratio of the total porosity of the mesopores to the total porosity of the micropores of the nanoparticle layer was (2 to 10): 1. it is understood that the number of mesopores in the nanoparticle layer is greater than the number of micropores. The number of the mesopores is more than that of the micropores, so that the circulation of electrolyte is facilitated.
It is understood that the nanoparticles 21 are formed on the surface of the primary particles 10 and are tightly combined with the primary particles 10 to form the nanoparticle layer 20, the nanoparticle layer 20 has a distinct grain boundary with the primary particles 10, and is not van der waals bonded, the bonding force is higher, the primary particles 10 are more stably connected with the nanoparticle layer 20, and the overall structure is more stable.
More specifically, the volume proportion of the pore channel in all pore structures is 35-90%, the volume proportion of the mesopores in all pore structures is 5-45%, and the volume proportion of the micropores in all pore structures is 5-20%.
The proportion of the open pore volume in all pore structures is 60-95%, and the proportion of the closed pore volume is 5-40%, wherein the open pores can be divided into cross-linked pores, through pores and blind pores according to the pore structure types, in the open pores of all pore structures, the proportion of the cross-linked pores in the open pores is 79-95%, the proportion of the through pores in the open pores is 4-20%, and the proportion of the blind pores in the open pores is 1-10%.
The blind hole is a through hole connecting the surface layer and the inner layer of the primary particle without penetrating the primary particle, and the cross-linked hole is formed by intersecting a plurality of pore channels. It can be understood that the cross-linked holes with a larger proportion can provide a channel for the electrolyte to flow through, the electrolyte can flow in the primary particles along the cross-linked holes, the expansion of the lithium battery is reduced while the lithium storage performance of the silicon is improved, the through holes can also provide a flow channel for the electrolyte, but the flow rate of the electrolyte is reduced, so the volume proportion of the through holes is less than that of the cross-linked holes. Furthermore, the blind hole is not beneficial to electrolyte circulation, electrolyte flowing into the blind hole can only flow out in the original path, and the generation of the blind hole is reduced as much as possible in the preparation process.
In some embodiments, the nanoparticles 21 have a median particle size of 20nm to 200nm; the median diameter of the nanoparticles 21 may be 20nm, 40nm, 50nm, 60nm, 80nm, 100nm, 150nm or 200nm, but it is needless to say that the median diameter of the nanoparticles 21 may be set according to the actual situation, and is not limited herein. The nano particles 21 with small particle size are wrapped on the surface of the primary particles, so that the carbon layer can be prevented from filling and blocking pore channels, and channels for flowing electrolyte are increased, thereby improving the lithium storage performance of silicon and reducing the expansion of the lithium battery.
In some embodiments, the thickness of the nanoparticle layer 20 is 20nm to 2000nm, and specifically, may be 20nm, 50nm, 100nm, 200nm, 300nm, 500nm, 800nm, 1000nm, 2000nm, or the like, and the thickness of the nanoparticle layer 20 may be set according to actual circumstances, which is not limited herein.
It can be understood that the nano-particle layer 20 with a suitable thickness can effectively avoid material pulverization, can relieve volume expansion of the material, and ensures structural stability of primary particles in the silicon material.
In some embodiments, the median particle diameter of the primary particles 10 is 0.1 μm to 10 μm, and specifically may be 0.1 μm, 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 5 μm, or 10 μm, and preferably, the median particle diameter of the primary particles 10 is 0.3 μm to 5 μm, which is not limited herein.
In some embodiments, the median particle diameter of the composite negative electrode material is 0.1 μm to 15 μm, and may be, specifically, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or 15 μm, or the like, which is not limited herein. The median particle diameter of the composite negative electrode material is preferably 0.5 to 10 μm, more preferably 1 to 8 μm.
In some embodiments, the composite anode material has a specific surface area ratio of 1m 2 /g～100m 2 (ii) in terms of/g. Alternatively, the specific surface area of the composite anode material may be 1m 2 /g、5m 2 /g、10m 2 /g、15m 2 /g、20m 2 /g、25m 2 /g、30m 2 /g、35m 2 /g、40m 2 /g、45m 2 /g、50m 2 /g、60m 2 /g、80m 2 In g or 100m 2 (iv)/g, etc., without limitation; the specific surface area of the composite anode material is preferably 10m 2 /g～50m 2 (ii) in terms of/g. Understandably, the excessive specific surface area easily causes SEI film formation, consumes excessive irreversible lithium salt, reduces the first efficiency of the battery, and comprehensively considers the cost of the preparation process to control the specific surface area to be 10m 2 /g～50m 2 /g。
In some embodiments, the coating layer in the composite negative electrode material is a carbon layer, and has a thickness of 5nm to 100nm, specifically, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, or 100nm, and the like, the carbon layer is too thick, the lithium ion transmission efficiency is reduced, large-rate charge and discharge of the material is not facilitated, the comprehensive performance of the negative electrode material is reduced, the carbon layer is too thin, the conductivity of the negative electrode material is not facilitated to be increased, and the volume expansion inhibition performance of the material is weak, resulting in a long cycle performance price difference.
In some embodiments, the content of carbon in the composite anode material is 5% to 50% by mass, and specifically may be 5%, 8%, 10%, 15%, 20%, 25%, 30%, 40%, or 50%, which is not limited herein. Optionally, the carbon content is 10% to 30% by mass.
As used herein, "dealloying" refers to a process in which one or more components of an alloy are selectively removed by a chemical or electrochemical corrosion process. The dealloying process involves the removal of old lattice sites and the formation of new lattice sites, and also involves the nucleation and growth of new crystals, wherein the formation of a nanoporous structure in the dealloying process is closely related to the recombination of atomic levels on an alloy/solution interface, the recombination process is completed through the surface diffusion of undissolved metal atoms and vacancies, and the speed of the surface diffusion has an important influence on the size of ligaments/channels in the finally formed nanoporous metal.
When the coating layer is a carbon layer, a method for preparing a composite anode material according to an embodiment, as shown in fig. 2, includes the following steps S100 to S400:
s100, preparing an N-M alloy;
s200, forming a coating layer on the surface of the N-M alloy to obtain the N-M alloy containing the coating layer;
s300, adding the N-M alloy containing the coating layer into an ammonium salt solution for oxidation-reduction reaction to obtain an intermediate;
s400, carrying out dealloying heat treatment on the intermediate in a protective atmosphere, and carrying out acid washing on a reaction product to obtain the composite negative electrode material, wherein N in the N-M alloy comprises at least one of silicon, germanium, antimony, tin and boron, and M in the N-M alloy comprises at least one of magnesium, aluminum, calcium and zinc.
According to the scheme, the composite cathode material with two pore structures can be prepared in one step through simple in-situ reaction, the N-M alloy coated with carbon reacts with a cheap common ammonium salt solution to obtain an intermediate, then high-temperature dealloying treatment is carried out in a protective atmosphere, active metal in the N-M alloy is reacted in the dealloying treatment process, so that a nanoparticle layer is formed on the surface of the N-M alloy, and finally the composite cathode material is obtained.
The primary particles obtained by dealloying the inner layer N-M alloy have continuous through pore passages, the continuous pore passages can provide internally expanded pore diameters for the lithiation process, and can also provide a circulating channel for electrolyte, so that the expansion of the lithium battery is reduced while the lithium storage performance of the negative electrode material is improved. The generated nano particle layer is provided with mesopores and micropores, so that the pulverization of the material can be avoided, the volume expansion of the material can be relieved, and the structural stability of the cathode material is ensured. The carbon-coated N-M alloy is used as a raw material, so that the pore channel structure can be prevented from being blocked by carbon coating in the later period, and the first effect of the battery is improved.
The composite negative electrode material obtained by the method comprises a kernel and a coating layer positioned on the surface of the kernel; wherein the content of the first and second substances,
the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the primary particle comprises a skeleton comprising a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to a surface of the primary particle; the nanoparticle layer is formed with micropores and/or mesopores.
The preparation process is explained in detail below:
s100, preparing an N-M alloy;
in some embodiments, N in the N-M alloy comprises at least one of Si, ge, sn, B, and Sb; m in the N-M alloy includes at least one of Mg, al, zn, and Ca. In specific examples, the N-M alloy may be a Si-Mg alloy, a Si-Al alloy, a Ge-Mg alloy, a Ge-Al alloy, or the like. Different types of alloys can obtain branches with different shapes, including at least one of rod-shaped nano particles, nano sheets, nano wires and nano tubes.
In some embodiments, the N-M alloy is prepared by mixing N powder and an active metal M and then heating the mixture to react under a protective gas to prepare the N-M alloy.
The powder particle size of the N powder is 0.1 to 15 μm, and specifically may be 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, or 15 μm, and the like, which is not limited herein.
The particle size of the active metal M powder is 0.1 μ M to 80 μ M, and specifically, it may be 0.1 μ M, 5 μ M, 10 μ M, 20 μ M, 40 μ M, 50 μ M or 80 μ M, and the like, and is not limited herein.
The molar ratio of the N powder to the active metal M is 1: (1 to 3), specifically 1:1, 1.5, 1:2, 1.5 or 1:3, but not limited thereto.
The heating reaction temperature is 400-900 deg.C, specifically 400 deg.C, 500 deg.C, 600 deg.C, 700 deg.C, 800 deg.C or 900 deg.C.
The heat preservation time of the heating reaction is 2 h-8 h, specifically 2h, 4h, 6h or 8h, which is not limited herein.
The heating rate of the heating reaction is 1 ℃/min to 10 ℃/min, and specifically can be 1 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min or 10 ℃/min, which is not limited herein.
In the application, parameters such as the particle size of silicon powder, the particle size of active metal, reaction temperature, reaction time and the like are controlled, so that the generation of the N-M alloy is facilitated, and the doping uniformity of metal elements of the N-M alloy is improved.
Of course, the N-M alloy may also be prepared by other preparation methods, in particular: high-energy ball milling, vacuum smelting, hot-pressing sintering and the like. It is understood that the N-M alloy may be commercially available, and step S100 may be omitted.
In some embodiments, the content of N in the N-M alloy is 15% to 60% by mass, and optionally, the content of N may be 15%, 20%, 30%, 40%, 50% or 60% by mass, which is not limited herein. In a specific embodiment, the N-M alloy may specifically be at least one of a silicon-magnesium alloy, a silicon-aluminum alloy, a silicon-calcium alloy, and a silicon-zinc alloy. It is understood that the pore size and porosity of the channels of the N material can be varied by controlling the composition of the N-M alloy, and in general, the higher the N content in the N-M alloy, the smaller the pore size. The heating reaction time and reaction temperature can be controlled to vary the depth of the pores, and generally, the longer the reaction time and the higher the reaction temperature, the deeper the depth of the pores.
In a specific embodiment, the method further comprises:
the obtained N-M alloy is pulverized to adjust the particle size of the N-M alloy powder to 0.1 to 15 μ M, specifically, 0.1, 0.5, 1, 2, 5, 10 or 15 μ M, but not limited thereto.
Specifically, the crushing treatment equipment comprises at least one of a planetary ball mill, a sand mill and an air flow crusher. It is understood that the smaller the grain size of the N-M alloy is, the larger the specific surface area thereof is, and the more sufficient the reaction can be made at the time of the dealloying heat treatment.
Of course, the N-M alloy may also be prepared by other preparation methods, specifically: high-energy ball milling, vacuum smelting, hot-pressing sintering and the like.
It is understood that the N-M alloy may be commercially available, and step S100 may be omitted.
Step S200, forming a coating layer on the surface of the N-M alloy to obtain the N-M alloy containing the coating layer;
in this embodiment, a carbon layer is vapor-deposited on the surface of the N-M alloy using a carbon source gas including at least one of methane, acetylene, acetone, and alcohol under a protective gas. In another embodiment, a carbon layer may be formed on the surface of the N — M alloy by liquid phase coating, solid phase coating, or the like. Wherein the solid-phase carbon source comprises at least one of calcium carbonate, lithium carbonate, iron carbonate, zinc carbonate and magnesium carbonate;
when the vapor deposition is adopted, the protective gas adopted in the vapor deposition process includes at least one of helium, neon, argon, krypton and xenon.
The volume ratio of the carbon source gas to the protective gas is 1: (0.1 to 100), specifically, 1.
The carbon source gas is introduced for 5min to 60min, specifically 5min, 15min, 25min, 35min, 45min or 60min, and may be set according to actual conditions, which is not limited herein.
The flow rate of the carbon source gas is 0.1L/min to 2L/min, and specifically may be 0.1L/min, 0.5L/min, 0.8L/min, 1.5L/min, or 2L/min, which may be set according to actual conditions, and is not limited herein.
The vapor deposition temperature is 400 ℃ to 950 ℃, and specifically, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ or 950 ℃, which can be set according to the actual situation, and is not limited herein.
The heating rate is 1-20 deg.C/min, specifically 1 deg.C/min, 5 deg.C/min, 10 deg.C/min, 15 deg.C/min or 20 deg.C/min, so as to effectively improve the reaction efficiency.
It should be noted that, within the above-mentioned suitable ranges of the carbon source introduction time or flow rate, vapor deposition temperature, and temperature increase rate, it is helpful to improve the ability of the carbon layer to be uniformly deposited on the surface of the N — M alloy.
When a solid phase coating mode is adopted, the molar mass ratio of the solid phase carbon source to the N-M alloy is 2: (1-10), specifically, it may be 2: 1. 2: 3. 2: 5. 2: 7. 2: 8. 2:9 or 2:10 may be set according to actual conditions, and is not limited herein.
The reaction temperature of the solid-phase carbon source and the N-M alloy is 500-1000 ℃, specifically 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ or 1000 ℃, and can be set according to the actual situation, and is not limited herein.
In this embodiment, the carbon layer formed on the surface of the N — M alloy may have a thickness of 5nm to 100nm, specifically, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, or 100nm, and the deposition thickness of the carbon layer may be controlled according to the deposition time.
The carbon-coated N-M alloy may have a median particle diameter of 0.1 to 15 μ M, specifically, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 15 μ M, and is not limited thereto.
And step S300, adding the N-M alloy containing the coating layer into an ammonium salt solution for oxidation-reduction reaction to obtain an intermediate.
In this embodiment, the ammonium salt includes at least one of ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium carbonate, ammonium perchlorate, ammonium sulfate, and ammonium sulfide. The mass concentration of the ammonium salt solution may be 0.1mol/L to 5mol/L, specifically 0.1mol/L, 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 4mol/L or 5mol/L, and may be set according to the actual situation.
Optionally, the molar ratio of the N-M alloy containing the coating layer to the ammonium salt is 1: specifically, (0.1 to 2) may be 1.1, 1.5, 1.
The time of the oxidation-reduction reaction of the N-M alloy and the ammonium salt solution is 0.5h to 12h, specifically 0.5h, 1h, 2h, 3h, 6h, 9h, 10h or 12h, and the temperature of the oxidation-reduction reaction is 20 ℃ to 80 ℃, specifically 20 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃ or 80 ℃.
For example, when the N-M alloy is a Si-M alloy, the carbon-coated Si-M alloy is immersed in an ammonium salt solution, and the Si-M alloy reacts with the ammonium salt solution to form a layer of silicic acid on the surface of the Si-M alloy, wherein the reaction chemical formula is shown as follows:
MSi+NH 4 Y+H 2 O→H 2 SiO 3 +MY+NH 3 +H 2
for example, the silicon magnesium alloy is put into ammonium chloride solution, silicic acid, magnesium chloride, ammonia gas and hydrogen gas are generated on the surface of the silicon magnesium alloy, and the silicic acid is adhered to the surface of the silicon magnesium alloy in the form of colloidal particles, precipitates or gels, and the silicon magnesium alloy is further dried to enable silicic acid nano colloidal particles to be attached to the surface of the silicon magnesium alloy.
And S400, performing dealloying heat treatment on the intermediate under a protective atmosphere, and performing post-treatment on a reaction product to obtain the composite negative electrode material.
It can be understood that, for example, when the N-M alloy is a Si-M alloy, active metal vapor evaporated from the Si-M alloy reacts with silicic acid during a de-alloying process, so that the silicic acid reduces nano-silicon particles in situ at a high temperature, the nano-silicon particles are stacked to form a nano-particle layer, so that the nano-particle layer has micropores and/or mesopores, that is, the silicic acid nano-particle particles react with the active metal vapor to form an oxide, and the nano-particle layer can form micropores or mesopores after the oxide is removed.
The reaction chemical formula is shown as the following formula:
M+H 2 SiO 3 →Si+MO+H 2 O，
in order to allow the mixture to react sufficiently, the temperature of the dealloying heat treatment is 200-950 ℃, specifically 200 ℃, 300 ℃, 400 ℃, 600 ℃, 800 ℃ or 950 ℃, and the heat preservation time is 2-18 h, specifically 2h, 3h, 6h, 9h, 12h, 15h or 18h, which is not limited herein.
The heating rate of the dealloying heat treatment is 1 ℃/min-20 ℃/min, and specifically can be 1 ℃/min, 5 ℃/min, 10 ℃/min, 15 ℃/min or 20 ℃/min, so that the reaction efficiency is effectively improved.
In order to improve the safety of the reaction, the dealloying heat treatment is performed under the protection of inert gas, wherein the inert gas comprises at least one of helium, neon, argon, krypton and hernia. The flow rate of the inert gas can be controlled between 1L/min and 10L/min.
It can be understood that within the temperature, time and heating rate range of the above-mentioned suitable heat treatment, the Si-M alloy is helped to form a skeleton structure in the dealloying process, and a nano particle layer is helped to form on the surface of the Si-M alloy.
In one embodiment, the acid washing is performed by washing the reaction product with an acid solution to remove the metal oxide from the reaction product.
The mass concentration of the acid solution is 1mol/L to 5mol/L, and specifically may be 1mol/L, 2mol/L, 3mol/L, 4mol/L or 5mol/L. It is needless to say that the mass concentration of the acid solution may be adjusted according to actual requirements, and is not limited herein.
The acid washing time is 1 h-10 h, specifically 1h, 3h, 5h, 7h or 10h. In this example, the acid-washed product can still be recovered for recycling.
It is understood that the concentration of the acid solution and the pickling time range described above are suitable to contribute to the improvement of the pickling efficiency and the reduction of impurities in the negative electrode material.
In the embodiment, a silicic acid layer is formed on the surface of the Si-M alloy after the Si-M alloy reacts with the ammonium salt solution, and in the high-temperature dealloying process, metal vapor of active metal in the Si-M alloy reacts with silicic acid, so that the silicic acid is reduced in situ to form nano-silicon particles at high temperature, and the nano-silicon particles form a nano-particle layer with micropores and/or mesopores. The finally prepared cathode material has a pore structure with various pore diameters, and the pore diameter of the surface layer of the silicon material is smaller than that of the inner layer, so that the volume expansion of silicon is relieved, the pulverization of the material is effectively inhibited, and the structural stability is enhanced. The prepared composite negative electrode material can also effectively improve the stability of the charge-discharge cycle of the lithium battery, and has the advantages of high capacity, long cycle life, high rate performance, low expansion and the like.
The embodiment of the application also provides a lithium ion secondary battery cathode pole piece and a lithium ion secondary battery, and the composite cathode material provided by the embodiment of the application or the cathode material prepared by the preparation method of the composite cathode material provided by the embodiment of the application is adopted.
The examples of the present application are further illustrated below in various examples. The present embodiments are not limited to the following specific examples. The present invention can be modified and implemented as appropriate within the scope of the main claim.
Example 1
A preparation method of the composite anode material comprises the following steps:
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to fully react the mixture to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 micron silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 1h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into argon atmosphere, heating to 700 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the median particle diameter of the obtained composite negative electrode material is 1.2 mu m, the mass percent content of carbon is 15 percent, and the specific surface area is 45m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite anode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 25%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 4:1, the open pore volume in all pore structures accounts for about 80%, and the closed pore volume accounts for about 20%; the maximum width of the cross-section of the branches is about 40nm and the thickness of the nanoparticle layer is 100nm.
Fig. 3 is a scanning electron microscope picture of the composite anode material, and fig. 4 is an XRD pattern of the composite anode material provided in this example; fig. 5 is a cycle performance curve of the porous silicon negative electrode material in the present example, and the charge and discharge current is 0.5C. As can be seen from the scanning electron microscope image in fig. 3, the prepared porous silicon has an obvious porous structure, and the surface of the porous silicon is coated with a carbon layer. From the XRD pattern of FIG. 4, it can be seen that the three intensity peaks at 28.4 °, 47.3 ° and 56.1 ° correspond to the three intensity peaks of silicon (JCPDS No. 27-1402), with substantially no impurity phases; as can be seen in FIG. 5, the material has high cycle performance, and has a capacity of 997mAh/g after being cycled for 1000 weeks under a high current of 0.5C.
Example 2
(1) Uniformly mixing silicon powder with the particle size of 2 microns and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 650 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 5 hours to enable the mixture to fully react to obtain silicon-magnesium alloy; ball-milling the silicon-magnesium alloy to obtain 1.5 mu m silicon-magnesium alloy powder;
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/mind acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 2h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into argon atmosphere, heating to 650 ℃ at a heating rate of 1 ℃/min, and then preserving heat for 6 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the median particle diameter of the obtained composite negative electrode material is 1.8 mu m, the mass percent content of carbon is 16 percent, and the specific surface area is 55m 2 The carbon layer thickness is 53nm. The porosity of the obtained composite anode material is 55%, the porosity of the primary particles is 35%, the porosity of the nanoparticle layer is 23%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 5:1, the open pore volume in all pore structures accounts for about 83%, and the closed pore volume accounts for about 17%; the cross-sectional maximum width of the branches is about 35nm and the thickness of the nanoparticle layer is 150nm.
Example 3
(1) Uniformly mixing silicon powder with the particle size of 2 micrometers and aluminum powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 650 ℃ at the heating rate of 5 ℃/min under the protection of argon inert gas, and then preserving heat for 5 hours to ensure that the mixture fully reacts to obtain silicon-aluminum alloy; ball-milling the silicon-magnesium alloy to obtain 3 mu m silicon-magnesium alloy powder;
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/mind acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 1h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate, wherein the concentration of the ammonium chloride solution is 0.5 mol/L;
(4) Putting the intermediate into an argon atmosphere, heating to 650 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 6 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the obtained composite negative electrode material has the median particle diameter of 3.5 mu m, the carbon content of 15 percent by mass and the specific surface area of 40m 2 The carbon layer thickness is 80nm. The porosity of the obtained composite anode material is 45%, the porosity of the primary particles is 36%, the porosity of the nanoparticle layer is 27%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 5:1, the open pore volume in all pore structures accounts for about 83%, and the closed pore volume accounts for about 17%; the cross-sectional maximum width of the branches is about 50nm and the thickness of the nanoparticle layer is 50nm.
Example 4
(1) Uniformly mixing 2 mu m silicon powder and aluminum powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 650 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 5 hours to ensure that the mixture fully reacts to obtain silicon-magnesium alloy; ball milling the silicon-magnesium alloy to obtain 1 micron silicon-aluminum alloy powder;
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 650 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/mind acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 2h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate, wherein the concentration of the ammonium chloride solution is 5mol/L;
(4) Putting the intermediate into an argon atmosphere, heating to 650 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 6 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the median particle diameter of the obtained composite negative electrode material is 1.5 mu m, the mass percent content of carbon is 18 percent, and the specific surface area is 90m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite anode material is 45%, the porosity of the primary particles is 30%, the porosity of the nanoparticle layer is 15%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 8:1, the open pore volume in all pore structures accounts for about 81%, and the closed pore volume accounts for about 19%; the maximum width of the cross-section of the branches is about 30nm and the thickness of the nanoparticle layer is 500nm.
Example 5
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to fully react the mixture to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 micron silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 60min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 1h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into argon atmosphere, heating to 700 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests show that the median particle diameter of the obtained composite negative electrode material is 1.2 mu m, the mass percentage content of carbon is 20 percent, and the specific surface area is 50m 2 The carbon layer thickness is 100nm. The porosity of the obtained composite anode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 25%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 4:1, the open pore volume in all pore structures accounts for about 80%, and the closed pore volume accounts for about 20%; the maximum width of the cross-section of the branches is about 40nm and the thickness of the nanoparticle layer is 100nm.
Example 6
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the mol ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to ensure that the mixture is fully reacted to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 micron silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 12h under the water bath condition of 90 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into argon atmosphere, heating to 800 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the median particle diameter of the obtained composite negative electrode material is 1.6 mu m, the mass percentage content of carbon is 20 percent, and the specific surface area is 30m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite anode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 32%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 4:1, the open pore volume in all pore structures accounts for about 80%, and the closed pore volume accounts for about 20%; the cross-sectional maximum width of the branches is about 40nm and the thickness of the nanoparticle layer is 100nm.
Example 7
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to fully react the mixture to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 mu m silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotating atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotating atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 1h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into an argon atmosphere, heating to 1000 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests show that the median particle diameter of the obtained composite negative electrode material is 1.3 mu m, the mass percentage content of carbon is 20 percent, and the specific surface area is 30m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite anode material is 50%, and the pores of the primary particlesThe porosity is 65%, the porosity of the nanoparticle layer is 22%, the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 4:1, the open pore volume in all pore structures accounts for about 80%, and the closed pore volume accounts for about 20%; the maximum width of the cross-section of the branches is about 60nm and the thickness of the nanoparticle layer is 70nm.
Example 8
(1) Uniformly mixing germanium powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 650 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and preserving heat for 8 hours to ensure that the mixture fully reacts to obtain germanium-magnesium alloy; and ball-milling the germanium-magnesium alloy to obtain 1 micron germanium-magnesium alloy powder.
(2) Putting the germanium-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated germanium-magnesium alloy powder.
(3) Adding 1mol of carbon-coated germanium-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 2h under the water bath condition of 60 ℃, filtering and drying to obtain an intermediate;
(4) Putting the intermediate into an argon atmosphere, heating to 1000 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests prove that the median particle diameter of the obtained composite negative electrode material is 1.3 mu m, the mass percent content of carbon is 21 percent, and the specific surface area is 31m 2 The carbon layer thickness is 40nm. The porosity of the obtained composite anode material is 52%, the porosity of the primary particles is 64%, the porosity of the nanoparticle layer is 23%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 4:1, the open pore volume in all pore structures accounts for about 81%, and the closed pore volume accounts for about 19%; maximum width of cross-section of branchThe degree is about 62nm and the thickness of the nanoparticle layer is 73nm.
Comparative example 1
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to fully react the mixture to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 micron silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Putting the carbon-coated silicon-magnesium alloy powder into an argon atmosphere, heating to 700 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the carbon-coated silicon-magnesium alloy powder to fully react to obtain a reaction product;
(4) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests show that the median particle diameter of the obtained composite negative electrode material is 1.4 mu m, the mass percentage content of carbon is 20 percent, and the specific surface area is 15m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite anode material is 70%, the open pore volume in all pore structures accounts for about 70%, and the closed pore volume accounts for about 30%; the maximum diameter of the skeleton of the nano silicon skeleton unit is about 65nm.
Comparative example 2
(1) Uniformly mixing silicon powder with the particle size of 1 mu m and magnesium powder according to the molar ratio of 1:2, putting the mixture into an atmosphere furnace, heating the mixture to 600 ℃ at the heating rate of 3 ℃/min under the protection of argon inert gas, and then preserving heat for 6 hours to fully react the mixture to obtain silicon-magnesium alloy; and ball-milling the silicon-magnesium alloy to obtain 1 micron silicon-magnesium alloy powder.
(2) Putting the silicon-magnesium alloy powder into a rotary atmosphere furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under the protection of argon atmosphere, introducing 0.5L/min of acetylene gas to ensure that the volume ratio of the argon to the acetylene in the rotary atmosphere furnace is 9:1, keeping the temperature for 30min, then closing the acetylene gas, and cooling to obtain the carbon-coated silicon-magnesium alloy powder.
(3) Adding 1mol of carbon-coated silicon-magnesium alloy powder into 1L of ammonium chloride solution, reacting for 12h under the water bath condition of 100 ℃, filtering and drying to obtain an intermediate, wherein the concentration of the ammonium chloride solution is 10 mol/L;
(4) Putting the intermediate into argon atmosphere, heating to 700 ℃ at a heating rate of 3 ℃/min, and then preserving heat for 8 hours to enable the intermediate to fully react to obtain a reaction product;
(5) And mechanically stirring and pickling the reaction product in 1mol/L hydrochloric acid solution for 2 hours, and performing suction filtration, washing and drying to obtain the composite negative electrode material.
Tests show that the median particle diameter of the obtained composite negative electrode material is 1.8 mu m, the mass percentage content of carbon is 25 percent, and the specific surface area is 45m 2 The carbon layer thickness is 50nm. The porosity of the obtained composite negative electrode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 7%, the ratio of the total porosity of mesopores in the nanoparticle layer to the total porosity of micropores is 1.8, the open pore volume proportion in all pore structures is about 58%, and the closed pore volume proportion is about 42%; the maximum width of the cross-section of the branches is about 40nm and the thickness of the nanoparticle layer is 200nm.
Comparative example 3
The composite anode material Si/C is adopted, the median particle size of the composite anode material is 1.5 mu m, the inner core of the composite material is a porous silicon structure accumulated by nano silicon particles, and the shell of the composite material is wrapped by a carbon layer; wherein the carbon content is 22 percent by mass and the specific surface area is 38m 2 The carbon layer thickness is 50nm, and the porosity of the composite negative electrode material is 67%. I.e. the process is repeated.
And (3) performance testing:
(1) And (3) observing the microscopic morphology of the composite negative electrode material powder particles:
observing and characterizing the surface condition of the material by using a scanning electron microscope to perform powder micro-morphology, wherein the selected test instrument is as follows: the focal length is adjusted by adopting an OxFORD EDS (X-max-20 mm < 2 >), the accelerating voltage is 10KV, the observation times are from 50K for high-power observation, and the agglomeration condition of particles is mainly observed at low power of 500-2000.
(2) And (3) particle size testing:
about 0.02g of the powder sample was added to a 50ml clean beaker, about 2 ml of deionized water was added, a few drops of 1% surfactant were added dropwise to completely disperse the powder in water, and the mixture was ultrasonically cleaned in a 120W ultrasonic cleaner for 5min and tested for particle size distribution using a MasterSizer 2000.
(3) The diameter test method of the framework comprises the following steps:
the core of 20 negative electrode materials was randomly selected using SEM, and the diameter and length of the backbone and the size of the branches were tested.
(4) The method for testing the carbon content in the negative electrode material comprises the following steps:
the sample is heated and combusted at high temperature by a high-frequency furnace under the condition of oxygen enrichment to oxidize carbon and sulfur into carbon dioxide and sulfur dioxide, the gas enters a corresponding absorption cell after being treated, corresponding infrared radiation is absorbed, and then the infrared radiation is converted into corresponding signals by a detector. The signal is sampled by a computer, is converted into a numerical value in direct proportion to the concentration of carbon dioxide and sulfur dioxide after linear correction, then the value of the whole analysis process is accumulated, after the analysis is finished, the accumulated value is divided by a weight value in the computer, and then multiplied by a correction coefficient, and blank is deducted, so that the carbon percentage content in the sample can be obtained. The sample was tested using a high frequency infrared carbon sulfur analyzer (Shanghai DE Ky HCS-140).
(5) The method for testing the specific surface area of the negative electrode material comprises the following steps:
after the adsorption amount of the gas on the solid surface at different relative pressures is measured at constant temperature and low temperature, the adsorption amount of the monolayer of the sample is obtained based on the Bronuore-Eltt-Taylor adsorption theory and the formula (BET formula) thereof, and the specific surface area of the solid is calculated.
(6) And (3) porosity testing:
and testing the porosity of the negative electrode material and the negative electrode plate by adopting a gas displacement method. The calculation method comprises the following steps: sample pore volume as a percentage of total area, P = (V-V0)/V100%, V0: true volume, V: apparent volume.
(7) Cross section test of the anode material:
the section polishing instrument ionizes inert gas by adopting an ion source to generate inert ions, and after acceleration and focusing, the atoms or molecules on the surface of a sample are impacted by the high-speed inert ions to realize ion polishing. After CP cutting, the sample is placed on a special sample stage for SEM test. The instrument model IB-09010CP, the ion acceleration voltage is 2-6kV, and the used gas is argon. After the silicon-carbon negative electrode material is cut through a cross section test, the thickness of the nanoparticle layer and the thickness of the carbon layer on the cross section can be tested.
The negative electrode materials prepared in examples 1 to 8 and comparative examples 1 to 3 were used, and the sample numbers were S1 to S8 and R1 to R3; preparing slurry from a negative electrode material, sodium carboxymethylcellulose, styrene-butadiene rubber, conductive graphite (KS-6) and carbon black (SP) according to a ratio of 92.
And (3) carrying out a discharge specific capacity test on the 11 groups of batteries on a blue CT2001A battery test system, wherein the ratio of the discharge capacity in 1 hour to the battery capacity is the discharge specific capacity.
And (3) carrying out a first coulombic efficiency test on the 11 groups of batteries on a blue CT2001A battery test system, wherein the charge-discharge current is 0.05C, and measuring the first coulombic efficiency.
And (3) performing a cycle test on the 11 groups of batteries for 100 weeks on a blue CT2001A battery test system, wherein the charge and discharge current is 0.2C, and the test after 100 cycles is performed to calculate the battery capacity and the capacity retention rate after cycles.
The capacity retention rate after 100 cycles at 0.2C cycles = 100 th cycle discharge capacity/100% first cycle discharge capacity, and the results are shown in table 1.
TABLE 1 comparison table of parameter and performance of each anode material
TABLE 2 parameter performance comparison table of each battery
As can be seen from the above tables 1 and 2, the main difference between the embodiment 4 and the embodiment 1 is that the ammonium chloride concentration is higher, and the soaking time is longer, so that the silicic acid particles generated on the surface of the carbon-coated silicon-magnesium alloy are more, the thickness of the nano silicon particle layer of the final product is larger, the mesopores and micropores of the nano silicon particle layer are reduced, the electrolyte is not easy to flow into the primary particles of the inner layer, and thus the expansion rate of the pole piece is improved and the cycle stability is poor in the charging and discharging process of the battery.
Compared with the embodiment 1, the negative electrode material of the comparative example 1 is prepared without soaking in ammonium chloride solution, silicic acid particles are not generated on the surface of the silicon-magnesium alloy, and further the final product only comprises a carbon layer and primary particles, and the carbon particles of the carbon layer easily block the pore structure of the primary particles, so that the expansion rate of a pole piece is improved and the cycle stability is poor in the charging and discharging processes of the battery.
The main difference between the comparative example 2 and the embodiment 1 is that the concentration of ammonium chloride is higher, the soaking temperature is higher, the duration is longer, the silicic acid particles generated on the surface of the carbon-coated silicon-magnesium alloy are more, the thickness of the nano silicon particle layer of the final product is larger, the mesopores and micropores of the nano silicon particle layer are reduced, the electrolyte is not easy to flow into primary particles of the inner layer, and therefore the expansion rate of the pole piece is improved and the cycling stability is poor in the charging and discharging process of the battery.
Comparative example 3 is a carbon-coated porous silicon negative electrode material, and the capacity and capacity retention rate of the battery made of the material are reduced after 100 cycles of 0.2C cycle, and the electrode film expansion rate of comparative example 3 is also higher than that of example 1.
According to the embodiment and the comparative example, the nano particle layer on the surface of the primary particle of the negative electrode material has excellent mesopores and micropores, so that material pulverization can be effectively avoided, a rigid silicon-lithium alloy layer is formed after lithiation, the volume expansion of the primary particle is further inhibited, and the structural stability of porous silicon is ensured. In the lithiation process, the silicon-intercalated lithium expands to fill the mesoporous pores, so that the side reaction caused by the contact of electrolyte solvent molecules and primary particles can be further avoided, more SEI is generated, and the first effect is low. Moreover, the pore structure on the primary particles is different from the mesoporous and microporous structures of the nanoparticle layer, so that the stress generated by the volume expansion of the porous silicon can be further relieved, the expansion of the electrode film is reduced, and the safety is improved; avoid the structural damage of material, guarantee the structural stability of material, bring long cycle life. After the carbon layer is coated with the silicon material, the carbon layer has better conductivity and stability, and the porous structure is prepared by adopting the sequence of coating carbon firstly and then reacting, so that the carbon filling or the closed pore structure can be effectively avoided, the first effect of the material is reduced, and even side reaction is caused. Therefore, the composite cathode material is beneficial to meeting the requirements of long cycle life, high capacity and low expansion of the battery, and can be widely applied to the field of cathode materials of lithium ion batteries.
In conclusion, the preparation method of the composite anode material is simple and easy to operate, and the preparation process is safe and efficient; the manufacturing cost is effectively reduced, and the method is suitable for quantitative production; the prepared product is used as a battery pole piece and has better charge-discharge cycle performance.
Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.
Claims (12)
1. The composite negative electrode material is characterized by comprising a core and a coating layer positioned on the surface of the core; wherein the content of the first and second substances,
the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the primary particle comprises a skeleton comprising a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to a surface of the primary particle; the nanoparticle layer is formed with micropores and/or mesopores.
2. The composite anode material according to claim 1, wherein the composite anode material comprises at least one of the following features a to d:
a. the nanoparticle layer comprises a plurality of stacked nanoparticles;
b. the nano particles are selected from at least one of nano silicon particles, nano germanium particles, nano antimony particles, nano tin particles and nano boron particles;
c. the nanoparticle layer comprises a plurality of nanoparticles, and the median particle size of the nanoparticles is 20 nm-200 nm;
d. the thickness of the nanoparticle layer is 20nm to 2000nm.
3. The composite anode material according to claim 1 or 2, characterized in that the composite anode material comprises at least one of the following features a to e:
a. the main framework is a three-dimensional net structure;
b. a single said branch is an individual die;
c. the single branch is an independent crystal grain, and the size of the crystal grain is 30nm-100nm;
d. the maximum width of the cross section of the branch is 20nm-250nm, and the maximum length of the cross section of the branch is 100nm-1500nm;
e. the branch is selected from at least one of a rod-shaped nanoparticle, a nano sheet, a nano wire and a nano tube.
4. The composite negative electrode material is characterized by comprising an inner core and a coating layer positioned on the surface of the inner core; wherein the inner core comprises primary particles and a nano particle layer positioned on the surface of the primary particles; the nanoparticle layer is formed with micropores and/or mesopores;
the primary particles are of a macroporous structure, pore channels are formed inside the primary particles, and the pore channels extend to the surfaces of the primary particles.
5. The anode material according to claim 4, wherein the diameter of the pore channel is 20nm to 250nm; the depth of the pore channel is 50 nm-1000 nm; and/or
The volume of the pore canal in all pore structures accounts for 35-90%, the volume of the mesopores in all pore structures accounts for 5-45%, and the volume of the micropores in all pore structures accounts for 5-20%.
6. The composite anode material according to any one of claims 1 to 5, characterized in that the composite anode material comprises at least one of the following features a to d:
a. the porosity of the composite negative electrode material is 30-70%, wherein the porosity of the primary particles is 15-75%, and the porosity of the nanoparticle layer is 5-35%;
b. the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is (2-10): 1;
c. the proportion of open pore volume in all pore structures of the composite negative electrode material is 60-95%, and the proportion of closed pore volume is 5-40%;
d. in the open pores of all pore structures, the volume ratio of the cross-linked pores to all open pores is 79-95%, the volume ratio of the through pores to all open pores is 4-20%, and the volume ratio of the blind pores to all open pores is 1-10%.
7. The composite anode material according to any one of claims 1 to 6, characterized in that the composite anode material comprises at least one of the following features a to g:
a. the primary particles are selected from at least one of silicon, germanium, antimony, tin and boron;
b. the median particle diameter of the primary particles is 0.1-10 μm;
c. the median particle size of the composite negative electrode material is 0.1-15 mu m;
d. the compoundThe specific surface area of the composite cathode material is 1m 2 /g～100m 2 /g；
e. The cladding layer includes a carbon layer;
f. the coating layer comprises a carbon layer, and the thickness of the carbon layer is 5 nm-100nm;
g. the mass percentage content of carbon in the composite negative electrode material is 5-50%.
8. The preparation method of the composite anode material is characterized by comprising the following steps of:
forming a coating layer on the surface of the N-M alloy to obtain the N-M alloy containing the coating layer;
adding the N-M alloy containing the coating layer into an ammonium salt solution for oxidation-reduction reaction to obtain an intermediate;
and carrying out dealloying heat treatment on the intermediate in a protective atmosphere, and carrying out acid washing on a reaction product to obtain the composite cathode material, wherein N in the N-M alloy comprises at least one of silicon, germanium, antimony, tin and boron, and M in the N-M alloy comprises at least one of magnesium, aluminum, calcium and zinc.
9. The method according to claim 8, characterized by comprising at least one of the following features a-d:
a. the forming method of the coating layer comprises the following steps: coating the surface of the N-M alloy by adopting a carbon source to form a carbon layer;
b. the forming method of the clad layer comprises the following steps: coating the surface of the N-M alloy by adopting a carbon source to form a carbon layer; the carbon source comprises at least one of a gas phase carbon source and a solid phase carbon source, the gas phase carbon source comprises at least one of methane, acetylene, acetone and alcohol; the solid-phase carbon source comprises at least one of calcium carbonate, lithium carbonate, iron carbonate, zinc carbonate and magnesium carbonate;
c. the thickness of a coating layer formed on the surface of the N-M alloy is 5 nm-100nm;
d. the median particle diameter of the N-M alloy is 0.1-15 mu M.
10. The production method according to any one of claims 8 or 9, characterized by comprising at least one of the following features a to f:
a. the median particle diameter of the N-M alloy containing the coating layer is 0.1-15 mu M;
b. the ammonium salt comprises at least one of ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium carbonate, ammonium perchlorate, ammonium sulfate and ammonium sulfide;
c. the mass concentration of the ammonium salt solution is 0.1-5 mol/L;
d. the molar ratio of the N-M alloy containing the coating layer to the ammonium salt is 1: (0.1 to 2);
e. the redox reaction time of the N-M alloy containing the coating layer and the ammonium salt solution is 0.5-12 h;
f. the redox reaction temperature of the N-M alloy containing the coating layer and the ammonium salt solution is 20-80 ℃.
11. The production method according to any one of claims 8 to 10, characterized by comprising at least one of the following features a to g:
a. the temperature of the dealloying heat treatment is 200-950 ℃;
b. the heat preservation time of the dealloying heat treatment is 2-18 h;
c. the temperature rise rate of the dealloying heat treatment is 1 ℃/min to 20 ℃/min;
d. the protective atmosphere comprises at least one of helium, neon, argon, krypton and xenon;
e. the acid solution adopted by the acid cleaning comprises at least one of hydrochloric acid, nitric acid and sulfuric acid;
f. the mass concentration of the acid solution is 1-5 mol/L;
g. the pickling time is 1-10 h.
12. A lithium ion battery comprising the composite anode material according to any one of claims 1 to 7 or the anode material produced by the method for producing the composite anode material according to any one of claims 8 to 11.
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| CN202110363721.9A CN115172746A (en) | 2021-04-02 | 2021-04-02 | Composite negative electrode material, preparation method thereof and lithium ion battery |
| KR1020227013073A KR20220104683A (en) | 2020-12-11 | 2021-07-29 | Anode material and manufacturing method thereof, lithium ion battery |
| EP21895928.6A EP4053944A4 (en) | 2020-12-11 | 2021-07-29 | Negative electrode material and preparation method therefor, and lithium ion battery |
| PCT/CN2021/109137 WO2022121334A1 (en) | 2020-12-11 | 2021-07-29 | Negative electrode material and preparation method therefor, and lithium ion battery |
| US17/781,920 US20230261177A1 (en) | 2020-12-11 | 2021-07-29 | Anode material, preparation method thereof, and lithium ion battery |
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