CN111916817B - Lithium ion battery with high capacity and cycle performance - Google Patents

Lithium ion battery with high capacity and cycle performance Download PDF

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CN111916817B
CN111916817B CN202010626121.2A CN202010626121A CN111916817B CN 111916817 B CN111916817 B CN 111916817B CN 202010626121 A CN202010626121 A CN 202010626121A CN 111916817 B CN111916817 B CN 111916817B
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polydimethylsiloxane
silicone oil
lithium ion
ion battery
negative electrode
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CN111916817A (en
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李国华
杜小红
励铠鸿
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Zhejiang University of Technology ZJUT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • 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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
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    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention belongs to the field of batteries, and particularly relates to a lithium ion battery with high capacity and cycle performance. The anode comprises an anode, a cathode and a diaphragm, wherein the anode comprises the following components in percentage by weight: a ternary positive electrode material, carbon nanotubes and conductive carbon black; the negative electrode formula comprises: a negative electrode material and a negative electrode conductive agent; the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps: preparing a mixed solution of polyoxyethylene-b-polydimethylsiloxane and mesitylene, adding silicone oil, carboxyl silicone oil, amino silicone oil, vinyl-terminated silicone oil and a photoinitiator into the mixed solution, uniformly mixing, coating a plate, drying, irradiating for crosslinking, performing heat treatment after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles into an organic solution containing a carbon source to obtain a dispersion liquid, and coking, sintering and curing the dispersion liquid to obtain the cathode material. The lithium ion battery obtained by the invention has good capacity which can reach more than 510 mAh/g; has excellent cycle performance.

Description

Lithium ion battery with high capacity and cycle performance
Technical Field
The invention belongs to the field of batteries, and particularly relates to a lithium ion battery with high capacity and cycle performance.
Background
With the gradual enhancement of the awareness of energy environmental protection, new energy automobiles have been developed greatly in recent years. Among them, the electric vehicle is one of the main directions. Among the power batteries of electric vehicles, lithium ion batteries occupy a very important position.
At present, the negative electrode material of the lithium ion power battery on the market is mainly graphite.
For example, chinese patent application No. 201210092946.6 discloses a method for preparing a negative electrode material for a lithium ion battery, which is obtained by disposing a graphite carbon material in a plasma processing apparatus. The invention also provides a lithium ion battery cathode and a lithium ion battery. The obtained lithium ion battery cathode material has good wettability to electrolyte. The wettability of the lithium ion battery cathode prepared from the lithium ion battery cathode material is also improved correspondingly. Therefore, the infiltration degree of the negative electrode to the electrolyte under the condition that the compaction density of the negative electrode of the lithium ion battery is higher is ensured, and the purposes of improving the unit volume filling amount of the graphite carbon material of the negative electrode of the lithium ion battery and further improving the energy density of the lithium ion battery are achieved.
However, graphite is adopted as a main negative electrode material, so that the problem of low capacity exists, silicon is a material with extremely high theoretical capacitance, the theoretical specific capacity can reach 4200 mAh/g, and the silicon has the characteristic of low lithium clamping potential, so that silicon also occupies an important position in the development of lithium ion batteries. In the existing silicon-carbon composite negative electrode material, the problems of easy pulverization, falling-off and the like of the negative electrode material are caused due to the extremely high volume expansion rate of silicon, so that the capacity and the cycle performance of the negative electrode material can be rapidly reduced in the using process.
Disclosure of Invention
The invention provides a lithium ion battery with high capacity and cycle performance, aiming at solving the problems that the capacity of a cathode material in the existing lithium ion battery is low, the cycle performance is poor when silicon is used as a main component, the cathode material is easy to pulverize and fall off, and the like.
The invention aims to:
firstly, a lithium ion battery with high capacity is provided;
secondly, the cycle performance of the lithium ion battery is improved;
and thirdly, overcoming the problem of volume expansion of silicon in the lithium ion battery cathode material.
In order to achieve the purpose, the invention adopts the following technical scheme.
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a diaphragm, and further comprises:
the positive electrode formula comprises:
a ternary positive electrode material, carbon nanotubes and conductive carbon black;
the negative electrode formula comprises:
a negative electrode material and a negative electrode conductive agent;
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
preparing a mixed solution of polyoxyethylene-b-polydimethylsiloxane and mesitylene, adding silicone oil, carboxyl silicone oil, amino silicone oil, vinyl-terminated silicone oil and a photoinitiator into the mixed solution, uniformly mixing, coating a plate, drying, irradiating for crosslinking, performing heat treatment after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles into an organic solution containing a carbon source to obtain a dispersion liquid, and coking, sintering and curing the dispersion liquid to obtain the cathode material.
In the technical scheme of the invention, the key point is selection and preparation of the cathode material. The negative electrode material adopts a double-network interpenetrating mode to construct a silicon carrier, namely polyoxyethylene-b-polydimethylsiloxane and mesitylene are used as a first group of raw materials, the silicon carrier can be firstly self-assembled to construct a first network structure when a coating plate is thermally dried, the network structure has rich and uniform pore structures, the pore diameter can reach 80-110 nm, then a photoinitiator is added, the construction of a second network is excited under the ultraviolet irradiation condition, the second network is formed by silicone oil, carboxyl silicone oil, amino silicone oil and terminal vinyl silicone oil, the second network matched with the first network is constructed in the irradiation crosslinking process, finally, silicon-carbon composite particles with the double-network interpenetrating structure are obtained through heat treatment, the first network mainly takes carbon as the main component and is a network structure with good structural stability and rigidity, and the second network has certain elasticity, and contains a higher amount of silicon, which is the main source of silicon. After the silicon and the silicon are matched, the silicon can be relatively and uniformly loaded in the framework pores of the double carbon network, the volume expansion allowance of the silicon is provided by the pore space, and the silicon is stably loaded and is not easy to fall off. And coating the silicon-carbon composite particles in an organic solution by using liquid drops, coking, sintering and curing to obtain the amorphous carbon coated double-network structure silicon-carbon composite particle core-shell structure cathode material.
As a preference, the first and second liquid crystal compositions are,
the silicone oil is polydimethylsiloxane;
the carboxyl silicone oil is carboxyl polydimethylsiloxane;
the amino silicone oil is amino polydimethylsiloxane;
the vinyl-terminated silicone oil is vinyl-terminated polydimethylsiloxane.
Tests prove that the silicone oil has a good preparation effect, the generated cross-linked network is more stable, and carboxyl polydimethylsiloxane, amino polydimethylsiloxane and vinyl-terminated polydimethylsiloxane are matched to form a more stable second network structure, so that the density of the negative electrode material is improved.
As a preference, the first and second liquid crystal compositions are,
the preparation method of the polyoxyethylene-b-polydimethylsiloxane comprises the following steps:
in a molar amount of 1: (0.8-1.1) adding the norborene-terminated polydimethylsiloxane and the norborene-terminated polyethylene oxide into dichloromethane to prepare a 0.03-0.06 mol/L pre-solution, adding a third-generation Grignard catalyst into the pre-solution for catalytic reaction, adding the norborene-terminated polydimethylsiloxane after reacting for 12-18 min, and continuously stirring for reacting for 2-3 h to obtain the polyoxyethylene-b-polydimethylsiloxane.
The first heavy network structure formed by matching the special polyoxyethylene-b-polydimethylsiloxane and the mesitylene prepared by the method has stronger pore diameter controllability and higher structural stability, and can provide abundant pore structures to meet the requirements of interpenetrating of a second heavy network and expansion allowance space required by silicon expansion.
As a preference, the first and second liquid crystal compositions are,
in the mixed solution, the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene is 1: (1.3-1.6), wherein the total mass concentration of the polyoxyethylene-b-polydimethylsiloxane and the mesitylene in the mixed solution is 90-105 g/L.
The preparation method can produce better preparation effect under the condition of the proportion, and the utilization rate of the materials is high.
As a preference, the first and second liquid crystal compositions are,
the molar ratio of the silicone oil to the carboxyl silicone oil to the amino silicone oil to the vinyl-terminated silicone oil is 1: (0.2-0.25): (1.1-1.3): (0.3-0.6).
The proportion can produce better preparation effect, the material utilization rate is high, and the silicon content in the silicon-carbon composite particles can be ensured to be at a higher level.
As a preference, the first and second liquid crystal compositions are,
the drying temperature of the hot drying of the coated plate is set to be 140-150 ℃, and the drying lasts for 1.5-2 h.
Under the temperature condition, the drying can promote the construction and formation of a first heavy network, and the self-assembly behavior of the polyoxyethylene-b-polydimethylsiloxane and the mesitylene can be stimulated to progress.
As a preference, the first and second liquid crystal compositions are,
the irradiation power of the irradiation crosslinking is set to be 40-50 mW/cm2Irradiating for 3-5 min;
the heat treatment is carried out in a protective atmosphere, the set temperature is 620-650 ℃, and the heat treatment is carried out for 45-70 min.
Under the irradiation condition, the construction and formation of the second heavy network can be excited, but the construction and formation rate is slow, so that the damage of the first heavy network structure caused by the problem of uneven concentration and the like in the formation process of the second heavy network is avoided. Meanwhile, under the heat treatment conditions, the carbonization and final molding of the silicon-carbon composite particles can be realized, and the granular silicon-carbon composite particles are obtained.
As a preference, the first and second liquid crystal compositions are,
the organic carbon solution is a glucose solution, wherein the concentration of glucose is 25-30 wt%.
The glucose can be coated on the outer surface of the silicon-carbon composite particle to form a compact and smooth amorphous carbon coating layer, and the amorphous carbon coating layer shows better reversible specific capacity and first coulombic efficiency.
As a preference, the first and second liquid crystal compositions are,
the coking set temperature is 160-180 ℃, and the coking lasts for 2-4 hours;
the sintering and curing set temperature is 960-990 ℃, and the sintering and curing process lasts for 2-3 hours.
The heat treatment can generate a good treatment effect, realize cross-linking coating under the coking condition, form a complete gel structure, and finally realize carbonization coating of the gel in the sintering and curing process to form a shell layer of a core-shell structure.
As a preference, the first and second liquid crystal compositions are,
the positive electrode formula is as follows:
90-98 parts by weight of a ternary positive electrode material, 0.1-4.0 parts by weight of a carbon nano tube, 1.0-3.0 parts by weight of conductive carbon black and 1.0-3.0 parts by weight of a positive electrode binder;
the cathode formula is as follows:
90-97 parts by weight of a negative electrode material, 0.2-3.0 parts by weight of a negative electrode conductive agent and 1.0-6.0 parts by weight of a negative electrode binder.
The formula has better actual use effect through tests.
The invention has the beneficial effects that:
1) the lithium ion battery obtained by the invention has good capacity which can reach more than 600 mAh/g;
2) the cycle performance is very excellent;
3) the problems of pulverization of the negative electrode material and the like can be effectively avoided.
Drawings
FIG. 1 is a comparative graph of a test of battery capacity;
fig. 2 is a comparative graph of the test of the cycle performance of the battery.
Detailed Description
The invention is described in further detail below with reference to specific embodiments and the attached drawing figures. Those skilled in the art will be able to implement the invention based on these teachings. Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.
Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all those known to those skilled in the art.
Example 1
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a PE diaphragm;
the positive electrode formula is as follows:
95 parts by weight of NCA (5: 2: 3), 3.0 parts by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
95 parts by weight of a negative electrode material, 3.0 parts by weight of a negative electrode conductive agent (SP), and 2.0 parts by weight of a negative electrode binder (CMC);
the positive electrode formula and the negative electrode formula are uniformly mixed and then coated on the surface of a current collector to respectively obtain a positive electrode and a negative electrode, and the electrolyte is 1.0 mol/L lithium hexafluorophosphate/EC-DMC solution (EC-DMC volume ratio is 1: 1);
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
in a molar amount of 1: 1, adding the norborene-terminated polyethylene oxide into dichloromethane to prepare a 0.05 mol/L pre-solution, adding a third generation Grignard catalyst into the pre-solution for catalytic reaction, adding the norborene-terminated polydimethylsiloxane after reacting for 15 min, and continuously stirring for reacting for 2.5 h to obtain polyoxyethylene-b-polydimethylsiloxane;
with tetrahydroAnd (2) taking furan as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.5, the concentration of the mixed solution is 100 g/L, polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane, vinyl-terminated-polydimethylsiloxane and Basfurdarocur 1173 are added to the mixed solution, and the molar ratio of the polydimethylsiloxane, the carboxyl-polydimethylsiloxane, the amino-polydimethylsiloxane and the vinyl-terminated-polydimethylsiloxane is 1: 0.2: 1.2: 0.5, adding 35 g of the total amount of the solution per liter of the mixed solution, adding 3 g of the solution per liter of the mixed solution into the Basfurdarocur 1173, uniformly mixing, coating the mixture on a plate, drying the plate for 1.5 hours at the temperature of 150 ℃, and drying the plate with the total amount of 45 mW/cm2Carrying out irradiation crosslinking for 5 min, carrying out heat treatment at 650 ℃ for 50 min after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles in 26 wt% glucose aqueous solution to obtain dispersion, and carrying out 170 ℃ coking for 3 h and 980 ℃ sintering curing for 2.5 h on the dispersion to obtain the cathode material.
Example 2
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a PE diaphragm;
the positive electrode formula is as follows:
95 parts by weight of NCA (5: 2: 3), 3.0 parts by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
95 parts by weight of a negative electrode material, 3.0 parts by weight of a negative electrode conductive agent (SP), and 2.0 parts by weight of a negative electrode binder (CMC);
the positive electrode formula and the negative electrode formula are uniformly mixed and then coated on the surface of a current collector to respectively obtain a positive electrode and a negative electrode, and the electrolyte is 1.0 mol/L lithium hexafluorophosphate/EC-DMC solution (EC-DMC volume ratio is 1: 1);
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
in a molar amount of 1: 0.8 of norborene-terminated polydimethylsiloxane and norborene-terminated polyethylene oxide are used as raw materials, the norborene-terminated polyethylene oxide is added into dichloromethane to prepare a 0.03 mol/L pre-solution, a third generation Grignard catalyst is added into the pre-solution for catalytic reaction, the norborene-terminated polydimethylsiloxane is added after the reaction is carried out for 12 min, and the stirring reaction is continued for 2 h, so that the polyethylene oxide-b-polydimethylsiloxane is obtained;
taking tetrahydrofuran as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.6, the concentration of the mixed solution is 105 g/L, polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane, vinyl-terminated-polydimethylsiloxane and Basfurdarocur 1173 are added to the mixed solution, and the molar ratio of polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane and vinyl-terminated-polydimethylsiloxane is 1: 0.2: 1.1: 0.3, adding 30 g of the total addition amount of the mixed solution per liter, adding 3 g of the Basfurdaurocur 1173 per liter of the mixed solution, uniformly mixing, coating a plate, performing thermal drying at 140 ℃ for 2 h, and drying with 40 mW/cm2Carrying out irradiation crosslinking for 5 min, carrying out heat treatment at 620 ℃ for 70 min after crosslinking to obtain silicon-carbon composite particles, putting the silicon-carbon composite particles into 25 wt% glucose aqueous solution to obtain dispersion, carrying out coking at 160 ℃ for 4 h and sintering and curing at 960 ℃ for 3 h on the dispersion to obtain the cathode material.
Example 3
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a PE diaphragm;
the positive electrode formula is as follows:
95 parts by weight of NCA (5: 2: 3), 3.0 parts by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
95 parts by weight of a negative electrode material, 3.0 parts by weight of a negative electrode conductive agent (SP), and 2.0 parts by weight of a negative electrode binder (CMC);
the positive electrode formula and the negative electrode formula are uniformly mixed and then coated on the surface of a current collector to respectively obtain a positive electrode and a negative electrode, and the electrolyte is 1.0 mol/L lithium hexafluorophosphate/EC-DMC solution (EC-DMC volume ratio is 1: 1);
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
in a molar amount of 1: 1.1, adding the norborene-terminated polydimethylsiloxane and the norborene-terminated polyethylene oxide into dichloromethane to prepare a 0.06 mol/L pre-solution, adding a third generation Grignard catalyst into the pre-solution for catalytic reaction, adding the norborene-terminated polydimethylsiloxane after reacting for 18 min, and continuously stirring for reacting for 3 h to obtain polyoxyethylene-b-polydimethylsiloxane;
taking tetrahydrofuran as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.3, the concentration of the mixed solution is 90 g/L, polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane, vinyl-terminated-polydimethylsiloxane and Basfurdarocur 1173 are added to the mixed solution, and the molar ratio of the polydimethylsiloxane, the carboxyl-polydimethylsiloxane, the amino-polydimethylsiloxane and the vinyl-terminated-polydimethylsiloxane is 1: 0.25: 1.3: 0.6, the total addition amount is that 40 g is added into each liter of mixed solution, 5 g is added into each liter of mixed solution by the Basofur darocur 1173, the mixture is uniformly mixed and coated on a plate to be dried for 1.5 h under 150 ℃, and the dried mixture is 50 mW/cm2Irradiating and crosslinking for 3 min, performing heat treatment at 650 ℃ for 45 min after crosslinking to obtain silicon-carbon composite particles, putting the silicon-carbon composite particles into 30 wt% glucose aqueous solution to obtain dispersion, and performing 180 ℃ coking and 990 ℃ sintering and curing on the dispersion for 2 h to obtain the cathode material.
Example 4
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a PE diaphragm;
the positive electrode formula is as follows:
95 parts by weight of NCA (5: 2: 3), 3.0 parts by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
95 parts by weight of a negative electrode material, 3.0 parts by weight of a negative electrode conductive agent (SP), and 2.0 parts by weight of a negative electrode binder (CMC);
the positive electrode formula and the negative electrode formula are uniformly mixed and then coated on the surface of a current collector to respectively obtain a positive electrode and a negative electrode, and the electrolyte is 1.0 mol/L lithium hexafluorophosphate/EC-DMC solution (EC-DMC volume ratio is 1: 1);
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
in a molar amount of 1: 0.95 of norborene-terminated polydimethylsiloxane and norborene-terminated polyethylene oxide are used as raw materials, the norborene-terminated polyethylene oxide is added into dichloromethane to prepare a 0.05 mol/L pre-solution, a third generation Grignard catalyst is added into the pre-solution for catalytic reaction, the norborene-terminated polydimethylsiloxane is added after the reaction is carried out for 15 min, and the stirring reaction is continued for 3 h, so that the polyethylene oxide-b-polydimethylsiloxane is obtained;
taking tetrahydrofuran as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.5, the concentration of the mixed solution is 95 g/L, polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane, vinyl-terminated-polydimethylsiloxane and Basfurdarocur 1173 are added to the mixed solution, and the molar ratio of polydimethylsiloxane, carboxyl-polydimethylsiloxane, amino-polydimethylsiloxane and vinyl-terminated-polydimethylsiloxane is 1: 0.2: 1.3: 0.5, adding 40 g of the total addition amount of the mixed solution per liter, adding 5 g of the Basfurdarocur 1173 per liter of the mixed solution, uniformly mixing, coating a plate, performing thermal drying at 150 ℃ for 1.5 h, and performing drying 50 timesmW/cm2Carrying out irradiation crosslinking for 3 min, carrying out heat treatment at 650 ℃ for 60 min after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles in 28 wt% glucose aqueous solution to obtain dispersion, carrying out coking at 180 ℃ for 3 h and sintering and curing at 980 ℃ for 3 h on the dispersion to obtain the cathode material.
Example 5
A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a PE diaphragm;
the positive electrode formula is as follows:
95 parts by weight of NCA (5: 2: 3), 3.0 parts by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
95 parts by weight of a negative electrode material, 3.0 parts by weight of a negative electrode conductive agent (SP), and 2.0 parts by weight of a negative electrode binder (CMC);
the positive electrode formula and the negative electrode formula are uniformly mixed and then coated on the surface of a current collector to respectively obtain a positive electrode and a negative electrode, and the electrolyte is 1.0 mol/L lithium hexafluorophosphate/EC-DMC solution (EC-DMC volume ratio is 1: 1);
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
in a molar amount of 1: 1, adding the norborene-terminated polydimethylsiloxane and the norborene-terminated polyethylene oxide into dichloromethane to prepare a 0.05 mol/L pre-solution, adding a third generation Grignard catalyst into the pre-solution for catalytic reaction, adding the norborene-terminated polydimethylsiloxane after reacting for 15 min, and continuously stirring for reacting for 2 h to obtain polyoxyethylene-b-polydimethylsiloxane;
taking tetrahydrofuran as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.5, the concentration of the mixed solution is 100 g/L, and polydimethylsiloxane and carboxyl-polydimethylsiloxane are added into the mixed solutionSiloxane, amino-polydimethylsiloxane, vinyl-terminated polydimethylsiloxane and pasteur furan darocur 1173, the molar ratio of polydimethylsiloxane, carboxy-polydimethylsiloxane, amino-polydimethylsiloxane and vinyl-terminated polydimethylsiloxane being 1: 0.25: 1.15: 0.4, adding 40 g of the total addition amount of the mixed solution per liter, adding 3 g of the Basfurdarocur 1173 per liter of the mixed solution, uniformly mixing, coating a plate, performing thermal drying at 140 ℃ for 2 h, and performing drying at 45 mW/cm2Carrying out irradiation crosslinking for 3 min, carrying out heat treatment at 620 ℃ for 70 min after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles in 28 wt% glucose aqueous solution to obtain dispersion, carrying out coking at 160 ℃ for 3 h and sintering and curing at 960 ℃ for 3 h on the dispersion to obtain the cathode material.
Example 6
The specific procedure was the same as in example 1, except that:
the positive electrode formula is as follows:
90 parts by weight of NCA (5: 2: 3), 4.0 parts by weight of carbon nanotubes, 3.0 parts by weight of conductive carbon black and 3.0 parts by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
90 parts by weight of the negative electrode material, 3.0 parts by weight of the negative electrode conductive agent (SP), and 6.0 parts by weight of the negative electrode binder (CMC).
Example 7
The specific procedure was the same as in example 1, except that:
the positive electrode formula is as follows:
97.9 parts by weight of NCA (5: 2: 3), 0.1 part by weight of carbon nanotubes, 1.0 part by weight of conductive carbon black and 1.0 part by weight of a positive electrode binder (PVDF);
the cathode formula is as follows:
97 parts by weight of a negative electrode material, 0.2 parts by weight of a negative electrode conductive agent (SP), and 1.0 part by weight of a negative electrode binder (CMC).
Comparative example
The following lithium ion battery control groups were set for comparison, respectively:
control group 1: the technical scheme of embodiment 1 disclosed in CN 108346799A;
control group 2: the specific procedure was the same as in example 1, except that: the negative electrode material adopts the silicon-carbon composite particles prepared in CN101931076A example 1;
control group 3: the specific procedure was the same as in example 1, except that: the anode material adopts 1: 0.4 mass ratio of mixed graphite and needle coke;
control group 4: the specific operation was the same as in example 1, except that the negative electrode material was prepared by the following method:
taking tetrahydrofuran as a solvent, respectively preparing 20 g/L polyoxyethylene-b-polydimethylsiloxane solution and 20 g/L mesitylene solution, mixing the two solutions to obtain a mixed solution, wherein the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene in the mixed solution is 1: 1.5, uniformly mixing the mixed solution with the concentration of 100 g/L, coating a plate, carrying out thermal drying at 150 ℃ for 1.5 h, carrying out thermal treatment at 650 ℃ for 50 min after crosslinking to obtain silicon-carbon composite particles, putting the silicon-carbon composite particles into 26 wt% glucose aqueous solution to obtain dispersion, carrying out coking at 170 ℃ for 3 h and sintering and curing at 980 ℃ for 2.5 h on the dispersion to obtain the cathode material.
Control group 5: the specific operation was the same as in example 1, except that the negative electrode material was prepared by the following method:
adding polydimethylsiloxane, carboxy-polydimethylsiloxane, amino-polydimethylsiloxane, vinyl-terminated polydimethylsiloxane, and basfurrocur 1173 to tetrahydrofuran in a molar ratio of 1: 0.2: 1.2: 0.5, the total addition amount is 35 g of tetrahydrofuran per liter, the Basofur darocur 1173 g of tetrahydrofuran per liter is added, the mixture is evenly mixed and coated on a plate with the concentration of 45 mW/cm2Carrying out irradiation crosslinking for 5 min, carrying out heat treatment at 650 ℃ for 50 min after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles in 26 wt% glucose aqueous solution to obtain dispersion, and carrying out 170 ℃ coking for 3 h and 980 ℃ sintering curing for 2.5 h on the dispersion to obtain the cathode material.
Testing
The capacity and cycle performance (20 ℃) of the battery were tested. The cycle performance test was performed at 1C rate.
The test results are shown in fig. 1 to 2.
In the figure, A1-A7 sequentially indicate embodiment 1-embodiment 7, and B1-B5 sequentially indicate control group 1-control group 5.
And (3) capacity testing: the capacity test is carried out ten times of effective measurement, and 500 mA/g constant current charging and discharging is adopted. The result is shown in fig. 1, it is obvious from the figure that the lithium ion batteries of examples 1 to 7 prepared by the technical scheme of the invention can reach high capacity of more than about 600 mAh/g, and the reference of the control groups 1 to 3 as the prior art shows that the capacity of the lithium ion battery obtained by the technical scheme of the invention is obviously superior to that of the three groups, especially compared with the control group 2, the control group 2 can measure higher capacity under the low constant current charging and discharging condition of 50 mA/g, but after the current is increased to 500 mA/g, the capacity is reduced in a cliff-type manner, and when the lithium ion battery is used in actual life, the lithium ion battery cannot be charged and discharged by adopting the ultra-low current of 50 mA/g, so the constant current test of 500 mA/g is more practical, and compared with the technical scheme of the invention, the control group 4, the formed first heavy network structure only has low silicon content, the capacity is remarkably reduced, but is still slightly better than that of the comparison group 1, and the comparison group 5 only has the second heavy network structure, so that the capacity retention rate is higher, but still lower than that of the lithium ion battery obtained by the technical scheme of the embodiment 1-7. It can be clearly seen by comparison that in the technical scheme of the invention, the dual-network structure in the silicon-carbon composite particles with the dual-network interpenetrating structure can affect the battery capacity, but the effect of the second network is larger.
And (3) testing the cycle performance: the test results are shown in fig. 2. As is apparent from fig. 2, after 1600 cycles, the capacity retention rate of the lithium ion battery prepared in embodiments 1 to 7 of the present invention can still reach more than 96.5%, the capacity retention rate of the comparative group 1 rapidly decreases for the first time during 100 to 200 cycles, rapidly decreases for the second time during 500 to 1200 cycles, and the second time is very serious, after the second time decreases, a plateau phase occurs and a small amount of fluctuation exists on the plateau phase, the total stability is about 65%, the comparative group 2 rapidly decreases continuously during 800 to 1500 cycles, the plateau phase occurs after about 1600 cycles, and is higher, and the main decrease of the comparative group 3 is during 500 to 1200 cycles, the capacity rapidly decreases during the plateau phase, the capacity retention rate of the comparative group 4 can substantially reach more than 92%, but also significantly decreases, the plateau phase has a capacity retention rate of about 93%, the capacity retention of the control group 5 was significantly reduced, and the plateau period was about 70%. The main reason for the rapid decrease of the capacitance generated by the control group 1 and the control group 5 is that the volume expansion of silicon causes partial pulverization of the negative electrode, and the like, and the active material is reduced, wherein the control group 5 has higher capacitance, but the structural stability of the silicon-carbon composite particles is poor under the condition that only the second network structure exists, so the collapse and pulverization are easy to generate, the control group 2 can reduce the influence of the decrease of the cycle performance caused by the volume expansion of the silicon to a certain extent due to the regulation and control of the microstructure of the silicon-containing negative electrode material, but the obvious capacity decrease is still generated after a large amount of cycles, the decrease of the capacitance of the control group 3 is aging decrease, the whole is stable, and the capacity retention rate in the plateau period is slightly higher than that of the control group 1.
In conclusion, the test results show that the lithium ion battery prepared by the invention has very high specific capacity and excellent cycle performance, can effectively reduce the adverse effect of the volume expansion of silicon on the battery, and has very excellent performance.

Claims (9)

1. A lithium ion battery with high capacity and cycle performance comprises a positive electrode, a negative electrode and a diaphragm, and is characterized by further comprising:
the positive electrode formula comprises:
90-98 parts by weight of a ternary positive electrode material, 0.1-4.0 parts by weight of a carbon nano tube, 1.0-3.0 parts by weight of conductive carbon black and 1.0-3.0 parts by weight of a positive electrode binder;
the negative electrode formula comprises:
90-97 parts by weight of a negative electrode material, 0.2-3.0 parts by weight of a negative electrode conductive agent and 1.0-6.0 parts by weight of a negative electrode binder;
the cathode material is a core-shell structure formed by carbon-coated silicon-carbon composite particles, and the preparation method comprises the following steps:
preparing a mixed solution of polyoxyethylene-b-polydimethylsiloxane and mesitylene, adding silicone oil, carboxyl silicone oil, amino silicone oil, vinyl-terminated silicone oil and a photoinitiator into the mixed solution, uniformly mixing, coating a plate, drying, irradiating for crosslinking, performing heat treatment after crosslinking to obtain silicon-carbon composite particles, placing the silicon-carbon composite particles into an organic solution containing a carbon source to obtain a dispersion liquid, and coking, sintering and curing the dispersion liquid to obtain the cathode material.
2. The lithium ion battery with high capacity and cycle performance according to claim 1,
the silicone oil is polydimethylsiloxane;
the carboxyl silicone oil is carboxyl polydimethylsiloxane;
the amino silicone oil is amino polydimethylsiloxane;
the vinyl-terminated silicone oil is vinyl-terminated polydimethylsiloxane.
3. The lithium ion battery with high capacity and cycle performance according to claim 1,
the preparation method of the polyoxyethylene-b-polydimethylsiloxane comprises the following steps:
in a molar amount of 1: (0.8-1.1) adding the norborene-terminated polydimethylsiloxane and the norborene-terminated polyethylene oxide into dichloromethane to prepare a 0.03-0.06 mol/L pre-solution, adding a third-generation Grignard catalyst into the pre-solution for catalytic reaction, adding the norborene-terminated polydimethylsiloxane after reacting for 12-18 min, and continuously stirring for reacting for 2-3 h to obtain the polyoxyethylene-b-polydimethylsiloxane.
4. The lithium ion battery with high capacity and cycle performance according to claim 1,
in the mixed solution, the mass ratio of polyoxyethylene-b-polydimethylsiloxane to mesitylene is 1: (1.3-1.6), wherein the total mass concentration of the polyoxyethylene-b-polydimethylsiloxane and the mesitylene in the mixed solution is 90-105 g/L.
5. The lithium ion battery with high capacity and cycle performance according to claim 1,
the molar ratio of the silicone oil to the carboxyl silicone oil to the amino silicone oil to the vinyl-terminated silicone oil is 1: (0.2-0.25): (1.1-1.3): (0.3-0.6), and the total addition amount is 30-40 g per liter of the mixed solution.
6. The lithium ion battery with high capacity and cycle performance according to claim 1,
the drying temperature of the hot drying of the coated plate is set to be 140-150 ℃, and the drying lasts for 1.5-2 h.
7. The lithium ion battery with high capacity and cycle performance according to claim 1,
the irradiation power of the irradiation crosslinking is set to be 40-50 mW/cm2Irradiating for 3-5 min;
the heat treatment is carried out in a protective atmosphere, the set temperature is 620-650 ℃, and the heat treatment is carried out for 45-70 min.
8. The lithium ion battery with high capacity and cycle performance according to claim 1,
the organic carbon solution is a glucose solution, wherein the concentration of glucose is 25-30 wt%.
9. The lithium ion battery with high capacity and cycle performance according to claim 1,
the coking set temperature is 160-180 ℃, and the coking lasts for 2-4 hours;
the sintering and curing set temperature is 960-990 ℃, and the sintering and curing process lasts for 2-3 hours.
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