CN113097451A - Pre-lithiation method, pre-lithiation negative plate and lithium ion battery - Google Patents

Pre-lithiation method, pre-lithiation negative plate and lithium ion battery Download PDF

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CN113097451A
CN113097451A CN202110355735.6A CN202110355735A CN113097451A CN 113097451 A CN113097451 A CN 113097451A CN 202110355735 A CN202110355735 A CN 202110355735A CN 113097451 A CN113097451 A CN 113097451A
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lithiation
stirring
prelithiation
treatment
negative plate
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邱昭政
李文龙
赵育松
梁世硕
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Kunshan Bao Innovative Energy Technology Co Ltd
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Kunshan Bao Innovative Energy Technology Co Ltd
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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Abstract

The invention provides a pre-lithiation method, a pre-lithiation negative plate and a lithium ion battery. The prelithiation method of the present invention comprises: 1) stirring and pre-lithiating the to-be-pre-lithiated negative plate by using a pre-lithiation reagent to obtain an intermediate pre-lithiated negative plate; 2) sequentially carrying out stirring cleaning treatment and drying treatment on the intermediate pre-lithiation negative plate to obtain a pre-lithiation negative plate; the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, and the pre-lithiation reagent comprises a Li-polycyclic aromatic hydrocarbon methyl derivative. In the pre-lithiation method, the stirring pre-lithiation treatment can accelerate the pre-lithiation process, the stirring cleaning treatment is beneficial to removing the residual pre-lithiation reagent on the pole piece, and the stirring pre-lithiation treatment and the stirring cleaning treatment can enable the silica-alumina negative pole piece with high surface density and high compaction density to finish the pre-lithiation process under the condition of shortening the pre-lithiation time and can inhibit the volume expansion of the negative pole piece to be pre-lithiated in the pre-lithiation process.

Description

Pre-lithiation method, pre-lithiation negative plate and lithium ion battery
Technical Field
The invention relates to a prelithiation method, a prelithiation negative plate and a lithium ion battery, and belongs to the field of lithium ion batteries.
Background
In order to improve the mileage problem of the electric vehicle, the research and development of the power battery are gradually developing towards a long endurance direction. In the prior art, the silicon-based material and the graphite particles are compounded as the negative active material, so that the energy density of the battery can be improved, the battery can be ensured to have good rate capability, and the electric automobile is endowed with good long-term endurance. Since pure silicon carbon material has a severe volume effect during charging and discharging, which may cause a rapid reduction in the cycle life of the battery, the industry is more inclined to use silicon oxygen material as the negative active material of the power battery. Since the silicon monoxide material contains a large amount of O element, a large amount of Li source is consumed by materials forming an SEI film and lithium silicate/lithium oxide during the formation process, which results in low first efficiency of the battery.
In the prior art, the first effect of a silicon-oxygen negative electrode sheet is improved by performing pre-lithiation on the silicon-oxygen negative electrode sheet, so that the first effect of a lithium ion battery is improved. Prelithiation refers to the introduction of exogenous lithium into the battery system in a suitable manner and morphology to ameliorate the first coulombic efficiency reduction due to the depletion of available lithium by the silicon oxygen cathode. Currently, the prelithiation is mainly divided into positive prelithiation and negative prelithiation, and the negative prelithiation is divided into direct addition of exogenous lithium, active additive prelithiation, electrochemical prelithiation and chemical prelithiation according to a prelithiation mode. The chemical prelithiation is simple to operate and has low requirements on a drying environment, so that researchers pay attention to the prelithiation technical research in recent years.
However, when the pre-lithiated target is a negative electrode sheet with high areal density, high compaction density and thickness, it takes a very long time for the electrode sheet to be completely infiltrated by the chemical pre-lithiation reagent during the pre-lithiation, and the reaction time of the pre-lithiation after infiltration is longer. Moreover, soaking the negative electrode plate in a liquid chemical pre-lithiation reagent for a long time can cause the negative electrode plate to expand greatly in volume, so that the thickness of the finished battery is increased, and the battery is deformed and difficult to group.
Disclosure of Invention
The invention provides a prelithiation method, which can be used for prelithiating a thick negative plate with high surface density and high compaction density, and has short prelithiation time and small volume expansion of the negative plate after prelithiation.
The invention provides a pre-lithiated negative plate which is high in surface density and compaction density, has sufficient lithium ions and can improve the energy density and cycle performance of a lithium ion battery when being used for the lithium ion battery.
The invention provides a lithium ion battery which has higher energy density and cycle performance.
The invention provides a prelithiation method, which comprises the following steps:
1) stirring and pre-lithiating the to-be-pre-lithiated negative plate by using a pre-lithiation reagent to obtain an intermediate pre-lithiated negative plate;
2) sequentially carrying out stirring cleaning treatment and drying treatment on the intermediate pre-lithiation negative plate to obtain a pre-lithiation negative plate;
the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, and the pre-lithiation reagent comprises a Li-polycyclic aromatic hydrocarbon methyl derivative.
The prelithiation method described above, wherein the molar ratio of metallic lithium to polycyclic aromatic hydrocarbon methyl derivative in the Li-polycyclic aromatic hydrocarbon methyl derivative is (1.5-10): 1.
The prelithiation process as described above, wherein the polycyclic aromatic hydrocarbon methyl derivative has an oxidation-reduction potential of less than 0.2V.
The prelithiation method as described above, wherein the polycyclic arylmethyl derivative is selected from at least one of a methyl substituent of biphenyl, a methyl substituent of terphenyl, a methyl substituent of diphenylmethane, a methyl substituent of fluorene, and a methyl substituent of anthracene.
The prelithiation method as described above, wherein the concentration of the prelithiation agent is 0.5-3 mol/L.
In the prelithiation method described above, in step 2), the stirring and washing treatment is performed on the intermediate prelithiation negative electrode sheet using a washing reagent;
the cleaning reagent is at least one selected from carbonates, ethers and furans.
The pre-lithiation method described above, wherein the temperature of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 25 to 80 ℃; and/or the presence of a gas in the gas,
the time of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 5-40 min.
The invention also provides a pre-lithiation negative electrode sheet, wherein the pre-lithiation negative electrode sheet is obtained by pre-lithiation through the pre-lithiation method.
The prelithiation negative electrode sheet as described above, wherein the areal density of the prelithiation negative electrode sheet is 2-16mg/cm2The compacted density is 1.0-1.7g/cm3。
The invention also provides a lithium ion battery, wherein the lithium ion battery comprises the pre-lithiation negative electrode sheet.
The prelithiation method of the present invention comprises: 1) stirring and pre-lithiating the to-be-pre-lithiated negative plate by using a pre-lithiation reagent to obtain an intermediate pre-lithiated negative plate; 2) sequentially carrying out stirring cleaning treatment and drying treatment on the intermediate pre-lithiation negative plate to obtain a pre-lithiation negative plate; the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, and the pre-lithiation reagent comprises a Li-polycyclic aromatic hydrocarbon methyl derivative. In the pre-lithiation method, the stirring speed of stirring pre-lithiation treatment is 5-200r/min, so that the pre-lithiation process can be accelerated, the stirring speed of stirring cleaning treatment is 5-200r/min, so that the residual pre-lithiation reagent on a pole piece can be removed, the stirring pre-lithiation treatment and the stirring cleaning treatment can enable a silicon-oxygen negative pole piece with high surface density and high compaction density to complete the pre-lithiation process under the condition of shortening the pre-lithiation time, and the volume expansion of the negative pole piece to be pre-lithiated in the pre-lithiation process can be inhibited.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A first aspect of the invention provides a prelithiation method comprising the steps of:
1) stirring and pre-lithiating the to-be-pre-lithiated negative plate by using a pre-lithiation reagent to obtain an intermediate pre-lithiated negative plate;
2) sequentially carrying out stirring cleaning treatment and drying treatment on the intermediate pre-lithiation negative plate to obtain a pre-lithiation negative plate;
the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, and the pre-lithiation reagent comprises a Li-polycyclic aromatic hydrocarbon methyl derivative.
The negative plate to be pre-lithiated refers to a negative plate containing a silicon-based negative material. In a specific embodiment, the mass ratio of the silicon monoxide to the graphite in the negative electrode sheet to be pre-lithiated can be 1 (1-10).
The prelithiation method of the invention specifically comprises the following steps: stirring and pre-lithiating the negative plate of the silicon-based negative material by using a pre-lithiation reagent, wherein the negative plate of the silicon-based negative material subjected to stirring and pre-lithiation treatment is called an intermediate pre-lithiation negative plate; and then, sequentially stirring and cleaning the intermediate pre-lithiation negative plate, cleaning the pre-lithiation reagent remained on the intermediate pre-lithiation negative plate, and drying the cleaned intermediate pre-lithiation negative plate to obtain the pre-lithiation negative plate.
According to the invention, the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, wherein the stirring speed of the stirring pre-lithiation treatment is 5-200r/min, so that the pre-lithiation process can be accelerated, the stirring speed of the stirring cleaning treatment is 5-200r/min, the removal of the residual pre-lithiation reagent on a pole piece is facilitated, and the stirring pre-lithiation treatment and the stirring cleaning treatment can enable a silica-oxygen negative pole piece with high surface density and high compaction density to complete the pre-lithiation process under the condition of shortening the pre-lithiation time, so that the volume expansion of the negative pole piece to be pre-lithiated in the pre-lithiation process can be inhibited.
Further, the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 10-150 r/min.
In some embodiments of the invention, the molar ratio of lithium metal to the polycyclic aromatic hydrocarbon methyl derivative in the Li-polycyclic aromatic hydrocarbon methyl derivative is (1.5-10): 1.
In a specific embodiment, the Li-polycyclic aromatic hydrocarbon methyl derivative can be prepared by adding metallic lithium to a mixture of the polycyclic aromatic hydrocarbon methyl derivative and an organic solvent. The organic solvent may be ethers or furans as the solvent. The lithium metal may be at least one of lithium powder, lithium foil, lithium sheet or lithium block.
In the Li-polycyclic aromatic hydrocarbon methyl derivative of the present invention, if the content of the metallic lithium is too small, the too small metallic lithium is insufficient to achieve sufficient prelithiation of the negative electrode sheet, and if the content of the metallic lithium is too large, the content of the polycyclic aromatic hydrocarbon methyl derivative is small, and the SEI film can be formed only on the surface of the silicon-based negative electrode material, and the lithium intercalation can not be performed on the bulk phase of the silicon-based negative electrode material, and the SEI film can not be formed on the bulk phase. In the invention, the molar ratio of the metal lithium to the polycyclic aromatic hydrocarbon methyl derivative is (1.5-10):1, and in the range, enough metal lithium is available for carrying out sufficient prelithiation on the negative plate, and enough polycyclic aromatic hydrocarbon methyl derivative is also available, so that an SEI film can be formed on the surface of the silicon-based negative material, and an SEI film can also be formed on the bulk phase of the silicon-based negative material.
In some embodiments of the invention, the polycyclic aromatic hydrocarbon methyl derivative has an oxidation-reduction potential of less than 0.2V.
In the invention, the relationship between the oxidation-reduction potential of the chemical prelithiation reagent and the oxidation-reduction potential of the silicon-based negative electrode material can greatly influence the prelithiation effect. The oxidation-reduction potential of the silicon-based negative electrode material is usually 0.2V, when the oxidation-reduction potential of the pre-lithiation reagent is higher than that of the silicon-based negative electrode material, the pre-lithiation reagent can only form an SEI film on the surface of the silicon-based negative electrode material, but can not embed lithium in a bulk phase of the silicon-based negative electrode material, and can not form the SEI film in the bulk phase. The oxidation-reduction potential of the polycyclic aromatic hydrocarbon methyl derivative is limited to be less than 0.2V, so that an SEI film can be formed on the surface of the silicon-based negative electrode material, and the SEI film can be formed on the bulk phase of the silicon-based negative electrode material.
In some embodiments of the invention, the polycyclic arylmethyl derivative is selected from at least one of a methyl substituent of biphenyl, a methyl substituent of terphenyl, a methyl substituent of diphenylmethane, a methyl substituent of fluorene, and a methyl substituent of anthracene.
In a particular embodiment, the polycyclic aromatic hydrocarbon methyl derivative is selected from the group consisting of 3,3 ' -dimethylbiphenyl, 4,4 ' -dimethylbiphenyl (4,4 ' -DMBP), 2-methylbiphenyl, 3 ', 4,4 ' -tetramethylbiphenyl, 9-dimethyl-9H-fluorene.
Illustratively, substitution of the ortho position of biphenyl with 1 methyl group gives 2-methylbiphenyl having an oxidation-reduction potential of 0.131V, substitution of the meta position of biphenyl with 2 methyl groups gives 3,3 '-dimethylbiphenyl having an oxidation-reduction potential of 0.294V, substitution of the para position of biphenyl with 2 methyl groups gives 4, 4' -dimethylbiphenyl having an oxidation-reduction potential of 0.186V, and substitution of the meta and para positions of biphenyl with 4 methyl groups gives 3,3 ', 4, 4' -tetramethylbiphenyl having an oxidation-reduction potential of 0.129V. When the polycyclic aromatic hydrocarbon methyl derivative is used as a prelithiation reagent, the silicon-based part to be prelithiated can be subjected to more effective prelithiation treatment.
In some embodiments of the invention, the concentration of the prelithiation agent is 0.5 to 3 mol/L.
In the present invention, prelithiation reagent concentration refers to the concentration of polycyclic aromatic hydrocarbon methyl derivative in solution. When the concentration of the prelithiation reagent is too low, the sufficient prelithiation of the negative plate is not enough, and when the concentration of the prelithiation reagent is too high, the content of the polycyclic aromatic methyl derivative is high, and the excessive polycyclic aromatic methyl derivative pollutes the environment and damages the health of human bodies. The concentration of the prelithiation reagent is selected to be 0.5-3mol/L, and the sufficient prelithiation can be carried out on the negative plate on the premise of not causing excessive pollution.
In some embodiments of the invention, in step 2), the intermediate pre-lithiated negative electrode sheet is subjected to stirring cleaning treatment by using a cleaning reagent;
the cleaning agent is at least one selected from carbonates, ethers and furans.
In particular embodiments, the cleaning agent may be at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dimethyl ether, diethyl ether, and tetrahydrofuran. The invention extracts the pre-lithiation reagent by cleaning the reagent, can more thoroughly remove the pre-lithiation reagent on the surface and in pores of the pre-lithiation part to be pre-lithiated, and reduces the influence of the residual pre-lithiation reagent on the battery performance.
In some embodiments of the invention, the temperature of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 25-80 ℃; and/or the presence of a gas in the gas,
the time of stirring pre-lithiation treatment and/or stirring cleaning treatment is 5-40 min.
When the temperature of the stirring pre-lithiation treatment is too low, the speed of the pre-lithiation is slow, and when the temperature of the stirring pre-lithiation treatment is too high, the pre-lithiation reagent volatilizes and the energy consumption of the stirring pre-lithiation treatment is increased; when the temperature of the agitation cleaning process is too low, the cleaning speed is slow, and when the temperature of the agitation cleaning process is too high, the cleaning agent is volatilized, and the energy consumption of the agitation cleaning process is increased. The temperature of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 25-80 ℃, and the pre-lithiation process and the cleaning process can be accelerated under the conditions that excessive energy consumption is not generated, and the pre-lithiation reagent and the cleaning reagent are not volatilized.
When the stirring pre-lithiation treatment time is too long, the pre-lithiation negative plate to be pre-lithiated can expand after being soaked in the pre-lithiation reagent for a long time, so that the cycle performance of the lithium ion battery is influenced, and when the stirring pre-lithiation treatment time is too short, the pre-lithiation of the pre-lithiation negative plate is insufficient; when the time of the stirring and cleaning treatment is too long, the intermediate pre-lithiation negative plate is soaked in the cleaning reagent for a long time and can expand, so that the cycle performance of the lithium ion battery is influenced, and when the time of the stirring and cleaning treatment is too short, the cleaning of the pre-lithiation reagent remained on the intermediate pre-lithiation negative plate is insufficient. The stirring pre-lithiation treatment and/or the stirring cleaning treatment are/is selected for 5-40min, so that the pre-lithiation of the negative plate to be pre-lithiated can be fully performed on the premise of not causing the expansion of the negative plate to be pre-lithiated and the expansion of the intermediate pre-lithiation negative plate, and the residual pre-lithiation reagent of the intermediate pre-lithiation negative plate can be fully cleaned.
Further, the temperature of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 30-80 ℃.
In a specific embodiment, when the stirring speed of the stirring pre-lithiation treatment is 15-120 r/min, the temperature of the stirring pre-lithiation treatment is 30-75 ℃, the stirring speed of the stirring cleaning treatment is 15-120 r/min, and the temperature of the stirring cleaning treatment is 30-75 ℃, a better pre-lithiation effect and cleaning effect are achieved.
A second aspect of the present invention provides a prelithiated negative electrode sheet obtained by prelithiation by the prelithiation method described above. The prelithiation negative plate has high surface density, high compaction density and sufficient lithium ions, and when the prelithiation negative plate is used for a lithium ion battery, the energy density of the lithium ion battery can be improved, and the cycle performance of the lithium ion battery can be improved.
Specifically, the area density of the prelithiation negative plate is 2-16mg/cm2The compacted density is 1.0-1.7g/cm3。
A third aspect of the invention provides a lithium ion battery comprising the pre-lithiated negative electrode sheet described above.
The lithium ion battery of the invention has high energy density and high cycle performance due to the pre-lithiated negative electrode sheet.
The invention is further illustrated by the following specific examples in which all parts, percentages, and ratios recited in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used as such without further treatment, and the equipment used in the examples is commercially available.
Example 1
The preparation method of the lithium ion battery of the embodiment comprises the following steps:
1) preparation of negative plate
Mixing silicon monoxide and graphite according to the mass ratio of 1:10 to prepare a negative electrode active material with the specific capacity of 464mAh/g, mixing the negative electrode active material, conductive carbon black (SP) serving as a conductive agent and a binder (the mass ratio of CMC to SBR is 1:1) according to the mass ratio of 80:12:8, adding a proper amount of deionized water to obtain negative electrode active slurry, coating the negative electrode active slurry on two functional surfaces of a Cu foil, and drying to obtain a negative electrode sheet. The surface density of the negative plate is 4mg/cm2Compacted density of 1.1g/cm3。
2) Preparation of prelithiation reagent
Adding lithium foil into a methyl butyl ether solution dissolved with Li-4,4 '-dimethyl biphenyl (Li-4, 4' -DMBP) in a glove box, and stirring to obtain a Li-4,4 '-DMBP compound solution with the concentration of 0.5mol/L, wherein the Li-4, 4' -DMBP compound solution is used as a prelithiation reagent;
wherein the molar ratio of Li to 4, 4' -DMBP is 4.0: 1.
3) Prelithiation
Stirring and pre-lithiating the negative plate in the step 1) by using the pre-lithiation reagent in the step 2) to obtain an intermediate pre-lithiated negative plate;
stirring and cleaning the intermediate pre-lithiation negative plate by using a cleaning reagent, and then drying to obtain a pre-lithiation negative plate;
wherein the cleaning reagent is propylene carbonate, the stirring speed of the stirring pre-lithiation treatment is 20r/min, the temperature of the stirring pre-lithiation treatment is 35 ℃, and the time of the stirring pre-lithiation treatment is 30 min; the stirring speed of the stirring cleaning treatment is 30r/min, the time of the stirring cleaning treatment is 10min, and the temperature of the stirring cleaning treatment is 40 ℃.
4) Preparation of Positive plate
Mixing Li (Ni)0.5Co0.2Mn0.3)O2Mixing the positive electrode active material, SP and PVDF binder at a mass ratio of 84:8:8, adding N-methylpyrrolidone (NMP) to obtain positive electrode active slurry, and coating the positive electrode active slurry on the functional surface of the carbon-coated Al foil to obtain a positive electrode sheet.
5) Preparation of lithium ion battery
Assembling the pre-lithiated negative plate obtained in the step 3), the positive plate obtained in the step 4) and the diaphragm into a battery, and injecting electrolyte to prepare the full battery.
Example 2
The preparation steps of the lithium ion battery of the embodiment are basically the same as those of the embodiment 1, and the only difference is that in the step 1), the silicon monoxide and the graphite are mixed according to the mass ratio of 1:5 to prepare the negative electrode active material with the specific capacity of 550 mAh/g.
Example 3
The preparation steps of the lithium ion battery of the embodiment are basically the same as those of the embodiment 1, and the only difference is that in the step 1), the silicon monoxide and the graphite are mixed according to the mass ratio of 1:1 to prepare the negative electrode active material with the specific capacity of 930 mAh/g.
Example 4
The lithium ion battery of this example was prepared by substantially the same procedure as in example 1, except that the areal density of the negative electrode sheet in step 1) was 2mg/cm2。
Example 5
The lithium ion battery of this example was prepared by substantially the same procedure as in example 1, except that the areal density of the negative electrode sheet in step 1) was 8mg/cm2。
Example 6
Of the present embodimentThe preparation steps of the lithium ion battery are basically the same as those of the example 1, except that the surface density of the negative electrode sheet in the step 1) is 12mg/cm2。
Example 7
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the compacted density of the negative electrode sheet in step 1) was 1.0mg/cm3。
Example 8
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the compacted density of the negative electrode sheet in step 1) was 1.2mg/cm3。
Example 9
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the compacted density of the negative electrode sheet in step 1) was 1.3mg/cm3。
Example 10
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the compacted density of the negative electrode sheet in step 1) was 1.4mg/cm3。
Example 11
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the compacted density of the negative electrode sheet in step 1) was 1.5mg/cm3。
Example 12
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the prelithiation agent concentration in step 2) was 1.0mol/L and the molar ratio of Li to 4, 4' -DMBP was 2.0: 1.
Example 13
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 12, except that the concentration of the prelithiation agent in step 2) was 2.0 mol/L.
Example 14
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 12, except that the concentration of the prelithiation agent in step 2) was 3.0 mol/L.
Example 15
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the concentration of the prelithiation agent in step 2) was 3.0 mol/L.
Example 16
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 13, except that the molar ratio of Li to 4, 4' -DMBP in step 2) was 8.0: 1.
Example 17
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 12, except that the molar ratio of Li to 4, 4' -DMBP in step 2) was 10.0: 1.
Example 18
The lithium ion battery of this example was prepared by essentially the same procedure as in example 1, except for step 2):
adding a lithium foil into a tetrahydrofuran solution dissolved with Li-9.9-dimethyl-9H-fluorene, and stirring to obtain a Li-9.9-dimethyl-9H-fluorene compound solution with the concentration of 1.0mol/L, wherein the Li-9.9-dimethyl-9H-fluorene compound solution is used as a pre-lithiation reagent;
wherein the molar ratio of Li to 9.9-dimethyl-9H-fluorene is 4.0: 1.
Example 19
The procedure for the preparation of the lithium ion battery of this example was substantially the same as in example 18, except that the molar ratio of Li to 9.9-dimethyl-9H-fluorene in step 2) was 6.0: 1.
Example 20
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the stirring speed of the stirring prelithiation treatment in step 3) was 50 r/min.
Example 21
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the stirring speed of the stirring prelithiation treatment in step 3) was 120 r/min.
Example 22
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the stirring speed of the stirring prelithiation treatment in step 3) was 15 r/min.
Example 23
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the temperature of the agitation prelithiation treatment in step 3) was 50 ℃.
Example 24
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the temperature of the agitation prelithiation treatment in step 3) was 75 ℃.
Example 25
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the stirring prelithiation treatment time in step 3) was 10 min.
Example 26
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the time for the agitation prelithiation treatment in step 3) was 40 min.
Example 27
The procedure for preparing the lithium ion battery of this example is substantially the same as that of example 1, except that the washing reagent in step 3) is tetrahydrofuran.
Example 28
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the prelithiation agent in step 2) was a 0.5mol/L Li-biphenyl (Li-BP) complex.
Example 29
The procedure for preparing the lithium ion battery of this example was substantially the same as in example 1, except that the areal density of the negative electrode sheet in step 1) was 14mg/cm2The compacted density is 1.6mg/cm3。
Comparative example 1
The preparation steps of the lithium ion battery of the comparative example are basically the same as those of the example 2, and the only difference is that the negative electrode sheet obtained in the step 1), the positive electrode sheet obtained in the step 4) and the diaphragm are assembled into a battery in the step 5), and electrolyte is injected to prepare the full battery.
Performance testing
1) First effect
a. Specific discharge capacity: the manufactured negative plate is cut into a circular plate with the diameter of 14mm, the circular plate is assembled into a 2032 type button cell, the button cell is discharged to the cutoff voltage of 0.005V by the current of 0.2C, the discharge capacity is recorded, and the first discharge specific capacity is calculated according to the load capacity of the negative active material.
b. Charging specific capacity: and C, charging the button battery which is completely discharged in the step a to 2.0V by 0.2C current, recording the charging capacity, and calculating the first charging specific capacity according to the loading capacity of the active material of the negative electrode material.
c. First efficiency of button cell: specific capacity of button cell for first charge/first discharge. The test results are shown in Table 1.
2) Energy density
Energy density of the whole battery: and manufacturing the positive plate, the negative plate and the diaphragm into an 8Ah battery core in a lamination mode, injecting electrolyte (the liquid retention coefficient is 2.7g/Ah), forming the electrolyte at a rate of 0.2C under the condition that a voltage window is 2.7-4.25V, wherein the discharge rate is 0.5C, and calculating the energy density of the whole battery according to the 3 rd discharge capacity, the discharge platform and the weight of the battery. The test results are shown in Table 1.
3) Capacity retention after 200 weeks of cycling
Capacity retention rate at 200 weeks: the discharge capacity at the 201 th cycle was recorded and the capacity retention rate was calculated by performing charge-discharge cycles at room temperature (23 ℃) for 200 weeks on a 0.5C/0.5C cycle system. The test results are shown in Table 1.
TABLE 1
Figure BDA0003003728810000131
Figure BDA0003003728810000141
As can be seen from table 1, the prelithiation device of the present invention can prelithiate a negative electrode sheet with high areal density and high compaction density, and the lithium ion battery prepared from the prelithiated negative electrode sheet has high first efficiency, high energy density and high capacity retention rate.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A prelithiation method comprising the steps of:
1) stirring and pre-lithiating the to-be-pre-lithiated negative plate by using a pre-lithiation reagent to obtain an intermediate pre-lithiated negative plate;
2) sequentially carrying out stirring cleaning treatment and drying treatment on the intermediate pre-lithiation negative plate to obtain a pre-lithiation negative plate;
the stirring speed of the stirring pre-lithiation treatment and the stirring cleaning treatment is 5-200r/min, and the pre-lithiation reagent comprises a Li-polycyclic aromatic hydrocarbon methyl derivative.
2. The prelithiation process according to claim 1, wherein the molar ratio of metallic lithium to polycyclic aromatic hydrocarbon methyl derivative in the Li-polycyclic aromatic hydrocarbon methyl derivative is (1.5-10): 1.
3. The prelithiation process according to claim 2, wherein the polycyclic aromatic hydrocarbon methyl derivative has an oxidation-reduction potential of less than 0.2V.
4. The prelithiation method of claim 2 or 3, wherein the polycyclic arylmethyl derivative is selected from at least one of a methyl substituent of biphenyl, a methyl substituent of terphenyl, a methyl substituent of diphenylmethane, a methyl substituent of fluorene, and a methyl substituent of anthracene.
5. The prelithiation method according to any one of claims 1 to 4, wherein the concentration of the prelithiation agent is 0.5 to 3 mol/L.
6. The prelithiation method according to any of claims 1-5, wherein in step 2), the intermediate prelithiation negative electrode sheet is subjected to the agitation washing treatment using a washing reagent;
the cleaning reagent is at least one selected from carbonates, ethers and furans.
7. The prelithiation method according to any one of claims 1 to 6, wherein the temperature of the stirring prelithiation treatment and/or the stirring cleaning treatment is 25 to 80 ℃; and/or the presence of a gas in the gas,
the time of the stirring pre-lithiation treatment and/or the stirring cleaning treatment is 5-40 min.
8. A prelithiated negative electrode sheet, characterized in that it is prelithiated by the prelithiation method of any one of claims 1 to 7.
9. The prelithiated negative electrode sheet of claim 8, wherein the areal density of the prelithiated negative electrode sheet is from 2 to 16mg/cm2The compacted density is 1.0-1.7g/cm3。
10. A lithium ion battery comprising the prelithiated negative electrode sheet of claim 8 or 9.
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