CN111969179A - Pre-lithiation method, high-energy-density lithium ion battery and preparation method of high-energy-density lithium ion battery - Google Patents

Pre-lithiation method, high-energy-density lithium ion battery and preparation method of high-energy-density lithium ion battery Download PDF

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CN111969179A
CN111969179A CN202010757935.XA CN202010757935A CN111969179A CN 111969179 A CN111969179 A CN 111969179A CN 202010757935 A CN202010757935 A CN 202010757935A CN 111969179 A CN111969179 A CN 111969179A
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lithium
standing
battery
lithium ion
negative plate
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云亮
彭小强
游江枫
刘兆平
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • 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
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract

The invention provides a prelithiation method, which comprises the following steps: pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil; and assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at a high temperature. Compared with the prior art, the invention does not need to adopt ultrathin lithium foil, can reduce the N/P ratio, can accurately control the pre-lithium amount, and further greatly improves the median voltage of the battery, thereby improving the energy density; in addition, the negative electrode stores a small amount of lithium, and irreversible consumption for supplementing the positive electrode lithium can be released in the later cycle process, so that the battery system has active lithium supplementation, and lithium lost by SEI (solid electrolyte interphase) cracking and reconstruction and other irreversible consumption lithium are offset, and the cycle performance of the lithium battery is improved.

Description

Pre-lithiation method, high-energy-density lithium ion battery and preparation method of high-energy-density lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a prelithiation method, a high-energy density lithium ion battery and a preparation method thereof.
Background
Lithium ion batteries have received much attention due to their advantages such as high energy density and good cycle performance. Along with the popularization of mobile internet equipment, the popularization of electric automobiles and other electric vehicles, and the development of aerospace technologies such as unmanned aerial vehicles and space detectors, the performance of lithium ion batteries is facing higher development requirements, and how to improve the volume energy density and the mass energy density of lithium batteries becomes the key breakthrough direction of high-performance lithium ion batteries.
In the technical scheme of the key field of 2025 manufactured by China, namely in the power battery of a new energy automobile, the energy density of the power battery in 2025 years is required to reach 400Wh/kg, and in order to achieve the aim, researchers mostly adopt a high-gram-capacity positive electrode (a lithium-rich manganese-based material with the capacity of NCM811, NCA or higher gram) and a high-gram-capacity silicon-based negative electrode material with the capacity of negative electrode. However, the high-gram-capacity silicon-based negative electrode material has low initial efficiency, and the energy density of 400Wh/kg is difficult to achieve under the design condition of a limit process, so that the method for solving the problem only carries out pre-lithiation on the negative electrode material or the battery cell, and the initial efficiency is improved. In addition, the appropriate pre-lithiation amount can not only improve the gram capacity of the anode and improve the energy density of the battery, but also weaken the early sharp attenuation in the cycle process of the silicon cathode and improve the overall cycle performance of the battery, and simultaneously can improve the discharge medium voltage and further improve the energy density.
However, the influence of different prelithiation depths on battery cycle by some existing prelithiation technologies has no systematic research, so that most of the prelithiation technologies only promote first effect, and the cycle is not promoted because the positive irreversible lithium is continuously consumed by the fracture and regeneration of SEI in the charging and discharging processes. China with publication number CN109888274A specially uses positive lithium salt as additive to release lithium ion for pre-lithiation in the first circle, the positive electrode obtained by the method has low gram capacity and limited lithium, and substances added according to the mass conservation principle account for certain mass and can not improve the energy density; the method mentioned in the chinese patent publication No. CN109103496 is a method of adjusting the N/P of the negative electrode and the positive electrode, but this method also increases the mass of the negative electrode (1.3: 1-2: 1), which not only does not improve the overall mass energy density of the battery, but also has a large excess, and the capacities of the positive electrode and the negative electrode are not equal, so that it is difficult to achieve the purposes of high initial efficiency, high energy density, and high medium voltage, and also increases the cost of the battery, and loses the meaning of pre-lithiation.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a prelithiation method, a high energy density lithium ion battery and a preparation method thereof, which can not only improve the first efficiency but also improve the cycle performance.
The invention provides a prelithiation method, which comprises the following steps:
pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil;
and assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at a high temperature.
Preferably, the thickness of the lithium foil is 2 to 50 μm.
Preferably, the thickness of the lithium foil is 20 to 50 μm.
Preferably, the roller gap for pressing is 50-300 μm.
Preferably, the pressing pressure is 1-20 kg.
Preferably, the high-temperature standing temperature is 35-75 ℃; the high-temperature standing time is 20-48 h.
Preferably, the high-temperature standing temperature is 50-75 ℃; the high-temperature standing time is 24-48 h.
The invention also provides a high-energy-density lithium ion battery which comprises the negative plate treated by the pre-lithiation method.
The invention also provides a preparation method of the high-energy density lithium ion battery, which comprises the following steps:
s1) pressing lithium foil on two sides of the negative plate to obtain a negative plate of the composite lithium foil;
s2) assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at high temperature;
s3) forming the battery after high-temperature standing into components and capacity, and obtaining the high-energy density lithium ion battery.
Preferably, the formation and capacity grading process specifically comprises the following steps:
standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then charging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components;
t1 is 12-24 h, U1 is 3.5-4.3V, U2 is 4.6V, U3 is 2-2.5V, and t2 is 1-5 min.
The invention provides a prelithiation method, which comprises the following steps: pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil; and assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at a high temperature. Compared with the prior art, the invention does not need to adopt ultrathin lithium foil, can reduce the N/P ratio, and can accurately control the pre-lithium amount, so that the surface of the negative electrode is provided with a thin yarn-shaped lithium deposition layer after full charge, thus the median voltage of the battery is greatly improved because the positive electrode is provided with a thin lithium layer, and the energy density is improved; in addition, the negative electrode stores a small amount of lithium which can be released in the later cycle process to supplement the irreversible consumption of the positive electrode lithium, so that the battery system can supplement active lithium, and the lithium lost by SEI (solid electrolyte interphase) rupture and reconstruction and other irreversible consumption lithium are offset, thereby improving the cycle performance of the lithium battery; the prelithiation method provided by the invention is simple to operate, only needs simple calculation and verification, is low in cost, can be realized only by a common roller press without a precise prelithiation machine, and can be practically applied in large-scale industrialization.
Drawings
FIG. 1 is a graph of the first efficiency of the lithium ion batteries prepared in example 1 and comparative example 1;
FIG. 2 is a graph comparing the cycle curves of the lithium ion batteries prepared in example 1 and comparative example 1;
FIG. 3 is a graph comparing the cycle efficiencies of the lithium ion batteries obtained in example 1 and comparative example 1;
FIG. 4 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 1 and comparative example 1;
FIG. 5 is a graph showing data on charge and discharge cycles at 0.5C of the lithium ion battery obtained in example 1;
fig. 6 is a graph of cycle efficiency of the lithium ion battery obtained in example 2;
FIG. 7 is a graph showing cycle voltages of the lithium ion batteries obtained in example 2 and comparative example 2;
FIG. 8 is a graph showing cycle voltages of the lithium ion batteries obtained in example 2 and comparative example 2;
fig. 9 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 2 and comparative example 2;
fig. 10 is a graph showing charge and discharge cycle data at 0.5C for the lithium ion battery obtained in example 2;
FIG. 11 is a process diagram of the formation of lithium ion batteries prepared in example 3 and comparative example 3;
FIG. 12 is a graph comparing the cycling curves of the lithium ion batteries prepared in example 3 and comparative example 3;
FIG. 13 is a graph comparing the cycle efficiencies of the lithium ion batteries obtained in example 3 and comparative example 3;
FIG. 14 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 3 and comparative example 3;
fig. 15 is a graph showing charge/discharge cycle data at 0.5C for the lithium ion battery obtained in example 3.
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.
The invention provides a prelithiation method, which comprises the following steps: pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil; and assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at a high temperature.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
Pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil; the thickness of the lithium foil is preferably 2-50 μm, more preferably 10-50 μm, and further preferably 20-50 μm; the thickness of the negative plate is preferably 90-120 μm, and more preferably 110 μm; the negative plate is formed by a negative current collector and negative slurry coated on the negative current collector; the thickness of the negative current collector is preferably 5-10 μm, more preferably 5-8 μm, and still more preferably 6 μm; the negative electrode slurry is preferably silicon-carbon negative electrode slurry, graphite negative electrode slurry or tin-based negative electrode slurry; the roller gap for pressing is preferably 50-300 μm, more preferably 50-200 μm, and still more preferably 80-160 μm; the pressing pressure is preferably 1-20 kg, more preferably 1-15 kg, and still more preferably 1.5-10 kg.
Assembling the negative plate, the positive plate, the diaphragm and the electrode solution of the composite lithium foil into a soft package battery, and standing at a high temperature; the thickness of the positive plate is preferably 180-280 μm, more preferably 200-260 μm, and further preferably 240 μm; the positive plate is formed by a positive current collector and positive slurry coated on the positive current collector; the thickness of the positive electrode current collector is preferably 5-20 μm, more preferably 8-15 μm, still more preferably 10-15 μm, and most preferably 12 μm; the positive electrode slurry is preferably a lithium-rich manganese-based positive electrode slurry, an NCM ternary positive electrode slurry or a lithium cobaltate positive electrode slurry; the electrolyte is preferably Tantai Huarong LB4750 FB; the positive electrode slurry is preferably NCM111, NCM532, NCM622, NCM811, NCM92, LRM or NCA; the high-temperature standing temperature is preferably 35-75 ℃, more preferably 45-75 ℃, and further preferably 50-75 ℃; the high-temperature standing time is preferably 20-48 h, and more preferably 24-48 h.
According to the invention, an ultrathin lithium foil is not needed, the N/P ratio can be reduced, the pre-lithium amount can be accurately controlled, and a thin yarn-shaped lithium deposition layer is arranged on the surface of the negative electrode after full charge, so that the median voltage of the battery is greatly improved due to the fact that the positive electrode is a thin layer of lithium, and the energy density is improved; in addition, the negative electrode stores a small amount of lithium which can be released in the later cycle process to supplement the irreversible consumption of the positive electrode lithium, so that the battery system can supplement active lithium, and the lithium lost by SEI (solid electrolyte interphase) rupture and reconstruction and other irreversible consumption lithium are offset, thereby improving the cycle performance of the lithium battery; the prelithiation method provided by the invention is simple to operate, only needs simple calculation and verification, is low in cost, can be realized only by a common roller press without a precise prelithiation machine, and can be practically applied in large-scale industrialization.
The invention also provides a high-energy-density lithium ion battery which comprises the negative plate treated by the pre-lithiation method.
The invention also provides a preparation method of the high-energy density lithium ion battery, which comprises the following steps: s1) pressing lithium foil on two sides of the negative plate to obtain a negative plate of the composite lithium foil; s2) assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at high temperature; s3) forming the battery after high-temperature standing into components and capacity, and obtaining the high-energy density lithium ion battery.
Wherein the step S1) is the same as the step S2), and is not described herein again.
According to the invention, the high-energy density lithium ion battery can be obtained by forming the battery after standing at high temperature into partial capacity; the method of the component content is not particularly limited, and is preferably a method known to those skilled in the art, specifically: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then charging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12-24 h, preferably 12-20 h, more preferably 12-15 h, U1 is 3.5-4.3V, preferably 3.5-4V, U2 is 4.6V, U3 is 2-2.5V, t2 is 1-5 min, preferably 2-5 min, and more preferably 3-5 min.
In order to further illustrate the present invention, a prelithiation method, a high energy density lithium ion battery and a method for manufacturing the same according to the present invention are described in detail below with reference to examples.
The reagents used in the following examples are all commercially available.
Example 1
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was LRM: SP: SWCNT, PVDF 97.5%, 0.8%, 0.2%, 1.5%; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the negative electrode slurry was composed of SiO, SP, SWCNT, PAA, 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 1000mAh/g)
Pressing 20-micron-thick lithium foils on two sides of the negative plate, wherein the roller gap for pressing is 140 microns; the pressure is 5kg, and the negative plate of the composite lithium foil is obtained.
And assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (the electrolyte is 4750FB) of the composite lithium foil into a soft-package battery, and standing at the high temperature of 45 ℃ for 24 hours.
After standing at high temperature, the first efficiency and the medium pressure are recorded by carrying out chemical composition volume operation. The method comprises the following specific steps: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then discharging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a voltage constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12h, U1 is 3.5V, U2 is 4.6V, U3 is 2.5V, and t2 is 3 min.
And performing 0.5C circulation after the component capacity.
Comparative example 1
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was LRM: SP: KS-6, 97.5 percent of PVDF, 0.8 percent of PVDF, 0.2 percent of PVDF and 1.5 percent of PVDF; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the negative electrode slurry was composed of SiO, SP, SWCNT, PAA, 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 1000mAh/g)
And (3) assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (Chinese Thailand Huarong 4750FB) into a soft-package battery, and standing at a high temperature of 45 ℃ for 24 hours.
After standing at high temperature, the first efficiency and the medium pressure are recorded by carrying out chemical composition volume operation. The method comprises the following specific steps: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then discharging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a voltage constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12h, U1 is 3.5V, U2 is 4.6V, U3 is 2.5V, and t2 is 3 min.
And performing 0.5C circulation after the component capacity.
Fig. 1 is a graph showing the first efficiency of the lithium ion batteries prepared in example 1 and comparative example 1.
Fig. 2 is a graph comparing the cycle curves of the lithium ion batteries prepared in example 1 and comparative example 1.
Fig. 3 is a graph comparing the cycle efficiencies of the lithium ion batteries obtained in example 1 and comparative example 1.
Fig. 4 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 1 and comparative example 1.
FIG. 5 is a graph showing data on charge and discharge cycles at 0.5C of the lithium ion battery obtained in example 1; it can be seen from the charge-discharge cycle data of fig. 5 that the charge capacity of the next cycle is always larger than the discharge capacity of the previous cycle, thereby embodying the idea of micro-lithiation.
Example 2
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was NCM 811: SP: SWCNT: 97.5 percent of PVDF, 0.8 percent of PVDF, 0.2 percent of PVDF and 1.5 percent of PVDF; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the anode slurry was SIO: SP: SWCNT: PAA ═ 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 900mAh/g)
Pressing 10-micron-thick lithium foils on two sides of the negative plate, wherein the roller gap for pressing is 140 microns; the pressure is 5kg, and the negative plate of the composite lithium foil is obtained.
And assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (the national Thailand Huarong LB4753-74) of the composite lithium foil into a soft-package battery, and standing at a high temperature of 45 ℃ for 30 hours.
After standing at high temperature, the first efficiency and the medium pressure are recorded by carrying out chemical composition volume operation. The method comprises the following specific steps: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then discharging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a voltage constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12h, U1 is 3.75V, U2 is 4.35V, U3 is 2.5V, and t2 is 5 min.
And performing 0.5C circulation after the component capacity.
Comparative example 2
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was NCM 811: SP: KS-6, 97.5 percent of PVDF, 0.8 percent of PVDF, 0.2 percent of PVDF and 1.5 percent of PVDF; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the negative electrode slurry was composed of SiO, SP, SWCNT, PAA, 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 1000mAh/g)
And (3) assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (China's Huarong 4753-74) into a soft-package battery, and standing at a high temperature of 45 ℃ for 24 hours.
After standing at high temperature, the first efficiency and the medium pressure are recorded by carrying out chemical composition volume operation. The method comprises the following specific steps: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then discharging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a voltage constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12h, U1 is 3.75V, U2 is 4.35V, U3 is 2.5V, and t2 is 3 min.
And performing 0.5C circulation after the component capacity.
Fig. 6 is a graph showing the cycle efficiency of the lithium ion battery obtained in example 2.
Fig. 7 is a graph showing cycle voltages of the lithium ion batteries obtained in example 2 and comparative example 2.
Fig. 8 is a graph showing cycle voltages of the lithium ion batteries obtained in example 2 and comparative example 2.
FIG. 9 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 2 and comparative example 2
Fig. 10 is a graph showing charge and discharge cycle data at 0.5C for the lithium ion battery obtained in example 2; it can be seen from the charge-discharge cycle data of fig. 10 that the charge capacity of the next cycle is always larger than the discharge capacity of the previous cycle, thereby embodying the idea of micro-lithiation.
Example 3
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was NCM 92: SP: KS-6, 97.5 percent of PVDF, 0.8 percent of PVDF, 0.2 percent of PVDF and 1.5 percent of PVDF; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the anode slurry was SIO: SP: SWCNT: PAA ═ 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 850mAh/g)
Pressing 15-micron-thick lithium foils on two sides of the negative plate, wherein the roller gap for pressing is 140 microns; the pressure is 5kg, and the negative plate of the composite lithium foil is obtained.
And assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (LB 4750-72) (pp) of the composite lithium foil into a soft package battery, and standing at a high temperature of 45 ℃ for 48 hours.
Comparative example 3
Coating the positive electrode slurry on an aluminum foil with the thickness of 12 microns, coating the aluminum foil with the thickness of 240 microns, and tabletting to obtain a positive plate with the thickness of 200 microns; the positive electrode slurry was NCM 92: SP: KS-6, 97.5 percent of PVDF, 0.8 percent of PVDF, 0.2 percent of PVDF and 1.5 percent of PVDF; the slurry viscosity was 4500 with a solids content of 63%.
Coating the negative electrode slurry on a copper foil with the thickness of 6 microns, coating the copper foil with the thickness of 125 microns, and tabletting to obtain a negative electrode plate with the thickness of 110 microns; the negative electrode slurry was composed of SiO, SP, SWCNT, PAA, 95.8%: 1.04%, 0.06% and 3.1%. (the gram volume of the mixture of the silicon monoxide and the graphite is 1000mAh/g)
And (3) assembling the negative plate, the positive plate, the diaphragm celgard16+4 and electrolyte (the China capacity LB4750-72) into a soft-package battery, and standing at a high temperature of 45 ℃ for 24 hours.
After standing at high temperature, the first efficiency and the medium pressure are recorded by carrying out chemical composition volume operation. The method comprises the following specific steps: standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then discharging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a voltage constant current of 0.1C, decompressing, exhausting and sealing, and completing the capacity of chemical components; t1 is 12h, U1 is 3.75V, U2 is 4.4V, U3 is 2.5V, and t2 is 3 min.
And performing 0.5C circulation after the component capacity.
Fig. 11 is a process diagram of the formation of lithium ion batteries prepared in example 3 and comparative example 3.
Fig. 12 is a graph comparing the cycle curves of the lithium ion batteries prepared in example 3 and comparative example 3.
Fig. 13 is a graph comparing the cycle efficiencies of the lithium ion batteries obtained in example 3 and comparative example 3.
Fig. 14 is a graph comparing the medium-voltage primary efficiency and capacity of the lithium ion batteries obtained in example 3 and comparative example 3.
Fig. 15 is a graph showing data on charge and discharge cycles at 0.5C of the lithium ion battery obtained in example 3; it can be seen from the charge-discharge cycle data of fig. 15 that the charge capacity of the next cycle is always larger than the discharge capacity of the previous cycle, thereby embodying the idea of micro-lithiation.
The detection test standard is as follows: efficiency 0.1C charge/0.1C discharge; and (3) circulation: 0.5C charging/0.5C discharging; medium pressure: 0.5C charge/0.5C discharge.
Comparison results
After the pre-lithiated pole pieces form a battery, the first efficiency is improved by more than 20%, the capacity is improved by more than 20%, the highest energy density can reach 402Wh/kg, and the energy density is highest in the lithium ion battery disclosed at present.

Claims (10)

1. A prelithiation method, comprising:
pressing lithium foils on two sides of the negative plate to obtain a negative plate of the composite lithium foil;
and assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at a high temperature.
2. The prelithiation method of claim 1, wherein the lithium foil has a thickness of 2 to 50 μm.
3. The prelithiation method of claim 1, wherein the lithium foil has a thickness of 20 to 50 μm.
4. The prelithiation method according to claim 1, wherein the roll gap for pressing is 50 to 300 μm.
5. The prelithiation method according to claim 1, wherein the pressure of the pressing is 1 to 20 kg.
6. The prelithiation method according to claim 1, wherein the high temperature resting temperature is 35 ℃ to 75 ℃; the high-temperature standing time is 20-48 h.
7. The prelithiation method according to claim 1, wherein the high temperature resting temperature is 50 ℃ to 75 ℃; the high-temperature standing time is 24-48 h.
8. A high-energy-density lithium ion battery is characterized by comprising a negative plate treated by the prelithiation method according to any one of claims 1 to 7.
9. A preparation method of a high energy density lithium ion battery is characterized by comprising the following steps:
s1) pressing lithium foil on two sides of the negative plate to obtain a negative plate of the composite lithium foil;
s2) assembling the negative plate, the positive plate, the diaphragm and the electrolyte of the composite lithium foil into a soft package battery, and standing at high temperature;
s3) forming the battery after high-temperature standing into components and capacity, and obtaining the high-energy density lithium ion battery.
10. The preparation method according to claim 9, wherein the process of component capacity is specifically as follows:
standing the battery after standing at high temperature for t1, then charging to U1 with a current constant current of 0.02C, then charging to U2 with a current constant current of 0.1C, then charging to a current of 0.02C with a voltage constant voltage of U2, standing for t2, discharging to U3 with a constant current of 0.1C, decompressing, exhausting and sealing, and completing the volume of the components;
t1 is 12-24 h, U1 is 3.5-4.3V, U2 is 4.6V, U3 is 2-2.5V, and t2 is 1-5 min.
CN202010757935.XA 2020-07-31 2020-07-31 Pre-lithiation method, high-energy-density lithium ion battery and preparation method of high-energy-density lithium ion battery Pending CN111969179A (en)

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CN112701253A (en) * 2020-12-29 2021-04-23 惠州亿纬锂能股份有限公司 Pre-lithiation composite negative plate and preparation method and application thereof
CN112786971A (en) * 2021-02-04 2021-05-11 湖南立方新能源科技有限责任公司 Preparation method of negative electrode pre-lithiation lithium ion battery and negative electrode pre-lithiation lithium ion battery
CN113078367A (en) * 2021-03-29 2021-07-06 中南大学 Manufacturing method of high-energy-density flexible package lithium ion battery
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CN112701253A (en) * 2020-12-29 2021-04-23 惠州亿纬锂能股份有限公司 Pre-lithiation composite negative plate and preparation method and application thereof
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CN113078367A (en) * 2021-03-29 2021-07-06 中南大学 Manufacturing method of high-energy-density flexible package lithium ion battery
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CN113097567B (en) * 2021-03-29 2022-04-12 湖南高远电池有限公司 Manufacturing method of high-energy-density soft package battery
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