CN117080361A - Secondary battery with silicon-based negative electrode - Google Patents

Secondary battery with silicon-based negative electrode Download PDF

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Publication number
CN117080361A
CN117080361A CN202311324000.2A CN202311324000A CN117080361A CN 117080361 A CN117080361 A CN 117080361A CN 202311324000 A CN202311324000 A CN 202311324000A CN 117080361 A CN117080361 A CN 117080361A
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silicon
content
secondary battery
negative electrode
battery
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金飘
崔屹
刘婵
侯敏
曹辉
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Shanghai Ruipu Energy Co Ltd
Rept Battero Energy Co Ltd
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Shanghai Ruipu Energy Co Ltd
Rept Battero Energy 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention relates to a secondary battery with a silicon-based negative electrode, wherein the silicon content in the secondary battery with the silicon-based negative electrode is x%; the secondary battery of the silicon-based negative electrode comprises an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate with a content of a%; the cut-off state of charge (SOC) of the secondary battery of the silicon-containing anode after being formed is w; the above parameters satisfy: 1.0 < a/(x w) 2.2, the silicon content x% is: the mass percentage of silicon in the silicon-based material in the anode active material layer is as follows: the mass percent of fluoroethylene carbonate in the electrolyte. By regulating and controlling the silicon content of the negative electrode in the battery, the cut-off SOC in formation and the fluoroethylene carbonate content in the electrolyte, the full charge interface, high-temperature storage and hot box performance of the battery are obviously improved, the cruising ability of the battery is ensured, and the safety of the battery is improved.

Description

Secondary battery with silicon-based negative electrode
Technical Field
The invention belongs to the field of batteries with silicon-based cathodes, and relates to a secondary battery with a silicon-based cathode.
Background
The silicon-based negative electrode has the advantages that huge volume change can occur in the charging and discharging process and the self conductivity is low, so that the battery capacity is fast attenuated, the silicon-based negative electrode material is unstable in structure and easy to react with electrolyte chemically and electrochemically, and as the silicon content is increased, the silicon-based negative electrode is more obvious in expansion, the damage to the electrode material and the decomposition of electrolyte are aggravated, so that the battery performance attenuation is accelerated, fluoroethylene carbonate (FEC) is added into the electrolyte to form a stable SEI film, protect the electrode, reduce the electrode to react with the electrolyte, improve the cycle performance of an electrochemical device, but the viscosity is larger, the conductivity of the electrolyte is reduced due to the addition of a large amount of FEC, the FEC reduction potential is higher, and the electrolyte is easy to expand when stored at high temperature, so that the high-temperature storage performance of the battery is reduced.
Disclosure of Invention
In order to solve the technical problems, the invention provides a secondary battery with a silicon-based negative electrode, wherein the silicon content of the negative electrode in the battery, the cut-off SOC in formation and the fluoroethylene carbonate content in electrolyte are regulated to satisfy the relation of 1.0-a/(x w) 2.2, so that the full charge interface, high-temperature storage and hot box performance of the battery are obviously improved, the cruising ability of the battery is ensured, and the safety of the battery is improved.
To achieve the purpose, the invention adopts the following technical scheme:
the invention provides a secondary battery with a silicon-based negative electrode, wherein the silicon content in the secondary battery with the silicon-based negative electrode is x%; the secondary battery of the silicon-containing negative electrode comprises an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate (FEC) with a content of a%;
the cut-off state of charge (SOC) of the secondary battery of the silicon-containing anode after being formed is w;
the above parameters satisfy: 1.0.ltoreq.a/(x.w). Ltoreq.2.2, which may be 1, 1.2, 1.5, 1.8, 2 or 2.2, for example, but is not limited to the values recited, other values not recited in the numerical ranges are equally applicable.
The silicon content refers to the mass percentage of silicon in the silicon-based material in the anode active material layer, and the composition of the anode active material layer is not particularly limited herein, and may further include other anode active materials, such as a carbon material, which may be one or more of graphite, hard carbon, soft carbon, and the like, and may further include a binder, and the like, on the basis of including the silicon-based material. The content of the FEC refers to the mass percentage of the FEC in the electrolyte.
The silicon-based material is any silicon-containing material that can be used as a negative electrode, for example, a silicon oxygen compound such as SiO 2 The silicon-carbon compound such as SiC and silicon simple substance are all conventional choices, and the invention is not particularly limited. The secondary battery of the silicon-containing anode can be a sodium ion battery or a lithium ion battery, and the positive electrode material of the secondary battery can be any positive electrode material, such as a lithium nickel manganese cobalt ternary material (NCM) and lithium cobalt oxide (LiCoO) 2 ) Lithium iron phosphate (LiFePO) 4 ) And one or more of the respective doping and/or cladding modifying compounds thereof are selected conventionally, and are not particularly limited in the present invention.
According to the invention, through regulating and controlling the relation between the silicon content of the negative electrode in the battery and the cut-off SOC in formation and the fluoroethylene carbonate content in the electrolyte to be less than or equal to 1.0/(x w) less than or equal to 2.2, the full charge interface, high-temperature storage and hot box performance of the battery are remarkably improved, the cruising ability of the battery is ensured, and the safety of the battery is improved.
For a negative electrode silicon-containing system, FEC plays an important role in electrolyte, not only participates in forming a stable SEI film during formation, but also plays an important role in maintaining the stability of the SEI film in a long cycle process of a battery, and more FEC is consumed due to the instability of the SEI film caused by expansion and contraction in the cycle process of silicon with the increase of the silicon content. However, high levels of FEC tend to produce gas during storage and cycling, resulting in battery swelling. In addition, after unstable SEI is formed after the battery is formed incompletely, FEC can continue to react to produce gas when the battery is divided into capacity, so that interface black spots are formed, and the storage and cycle performance of the battery are not facilitated. Therefore, in order to reduce the reaction gas production of the battery in capacity division and even later performance test, a good full charge interface is formed and long-term circulation and storage performance of the battery are ensured, and a method for properly improving the SOC is adopted, so that stable SEI is formed when the FEC is formed under certain silicon content. If the SOC is excessively increased, for example, the battery is fully charged during formation, during which the FEC is excessively reacted and other additives are fully reacted together, so that the formed SEI has a thick and high impedance, consumes more lithium ions, and causes a significant decrease in battery capacity, and during full charge aging, the self-discharge of the battery is increased, and in addition, excessive reaction of the FEC and other additives also causes a large amount of gas generation, gas hinders lithium ion transmission, causes interface black spots, and is unfavorable for battery storage and cycle performance.
Preferably, the method of the formation is segmentation formation.
Preferably, the method of segmentation includes: the charge state is formed to be the cut-off state of charge SOC by 0.01-0.05C to 2.5-3.0V, 0.06-0.1C to 3.1-3.4V and 0.05-0.3C.
Preferably, the cut-off state of charge SOC is 0.45.ltoreq.w.ltoreq.1, and may be, for example, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.
When the SOC is too small, the battery can form an unstable SEI film, and the SEI film can continue to react in the subsequent capacity division process, so that the performance of the battery is reduced due to gas production.
Preferably, the silicon content of the silicon-based anode is 0 < x.ltoreq.50, and may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50, but not limited to the values listed, other values not listed in the range of values are equally applicable, and more preferably 0 < x.ltoreq.30.
The silicon content cannot be defined to exceed a certain range in the present invention, because when the silicon content is too large, the FEC alone is insufficient to form a stable SEI film.
Preferably, in the secondary battery of the silicon-containing anode, the relationship between the silicon content and the FEC content is: 0.65. Ltoreq.a/x.ltoreq.1.2, which may be, for example, 0.65, 0.7, 0.8, 0.9, 1 or 1.2, but is not limited to the values recited, other values not recited in the numerical range being equally applicable.
When the silicon content and the FEC content are less than 0.65, the film forming additive is continuously consumed in the silicon circulation process, the additive is completely consumed in the early period of circulation, the film forming additive is not repaired after the expansion and rupture in the later period of the silicon circulation, the circulation is fast attenuated, and when the FEC content is more than 1.2, the FEC content is too high, and the high-temperature storage and the high-temperature circulation are poor due to the instability of the high-temperature FEC content.
Preferably, the electrolyte further comprises a lithium salt, wherein the lithium salt comprises LiPF 6 And LiFSI.
Preferably, the lithium salt LiPF 6 The content b% and the content c% of LiFSI satisfy the following conditions: b+c is more than or equal to 0 and less than or equal to 14.5, and c is less than b; b+c may be, for example, 1, 2, 3, 4, 5, 6, 7.5, 9.5, 11.5, 13.5 or 14.5, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.
The LiPF is 6 The content b% of (B) refers to LiPF 6 The mass percentage of the mass in the electrolyte; the content c% of LiFSI refers to the mass percentage of LiFSI in the electrolyte.
LiFSI is not higher than LiPF in the present invention 6 To avoid LiFSI corrosion of aluminum foil, liPF 6 The high content of the aluminum foil can effectively inhibit the aluminum foil from being corroded by LiFSI.
Preferably, the electrolyte further comprises at least one of ethylene carbonate and propylene carbonate.
Preferably, the content of the ethylene carbonate is w1%, and the condition is satisfied: w1 is 0.ltoreq.w1.ltoreq.20, w1 may be, for example, 2, 4, 6, 8, 10, 12, 16, 18, 20, but is not limited to the values recited, and other values not recited in the numerical range are equally applicable.
Preferably, the propylene carbonate content is w2%, and the conditions are satisfied: w2 is 0.ltoreq.w2.ltoreq.20, w2 may be, for example, 2, 4, 6, 8, 10, 12, 16, 18, 20, but is not limited to the values recited, and other values not recited in the numerical range are equally applicable.
The content of ethylene carbonate and the content of propylene carbonate refer to the mass percentage of ethylene carbonate in the electrolyte and the mass percentage of propylene carbonate in the electrolyte, respectively.
According to the invention, the Ethylene Carbonate (EC) is added, so that the high-temperature storage and high-temperature circulation are not facilitated, a proper amount of EC is favorable for film formation, the Propylene Carbonate (PC) is stable at the high temperature of the silicon system, the high-temperature performance of the battery is facilitated, and the PC and graphite are co-embedded due to the too high PC, so that the battery performance is reduced.
Preferably, the negative electrode active material layer of the secondary battery including a silicon-based negative electrode further includes a carbon material.
Compared with the prior art, the invention has at least the following beneficial effects:
according to the invention, through regulating and controlling the relation between the silicon content of the negative electrode in the battery and the cut-off SOC in formation and the fluoroethylene carbonate content in the electrolyte to be less than or equal to 1.0/(x w) less than or equal to 2.2, the full charge interface, high-temperature storage and hot box performance of the battery are remarkably improved, the cruising ability of the battery is ensured, and the safety of the battery is improved.
Detailed Description
According to an aspect of the present invention, there is provided a secondary battery including a silicon-based negative electrode, in which the silicon content is x%; the secondary battery of the silicon-based negative electrode comprises an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate with a content of a%;
the cut-off state of charge (SOC) of the secondary battery of the silicon-containing anode after being formed is w;
the above parameters satisfy: a/(x w) is less than or equal to 1.0 and less than or equal to 2.2.
In one embodiment, the formation is a segmentation formation.
In one embodiment, the segmentation method includes: the charge state is formed to be the cut-off state of charge SOC by 0.01-0.05C to 2.5-3.0V, 0.06-0.1C to 3.1-3.4V and 0.05-0.3C.
In one embodiment, the off state of charge SOC is 0.45.ltoreq.w.ltoreq.1.
In one embodiment, the silicon content in the silicon-based anode is 0 < x.ltoreq.50.
In one embodiment, the silicon content in the silicon-based anode is 0 < x.ltoreq.30.
In one embodiment, in the secondary battery of the silicon-based negative electrode, the relationship between the silicon content and the fluoroethylene carbonate content is satisfied: a/x is more than or equal to 0.65 and less than or equal to 1.2.
In one embodiment, the electrolyte further comprises a lithium salt comprising LiPF 6 And LiFSI.
In one embodiment, the lithium salt LiPF 6 The content b% and the content c% of LiFSI satisfy the following conditions: b+c is more than or equal to 0 and less than or equal to 14.5, and c is less than b.
In one embodiment, the electrolyte further includes at least one of ethylene carbonate and propylene carbonate.
In one embodiment, the content of the ethylene carbonate is w1%, the content of the propylene carbonate is w2%, and the condition is satisfied: w1 is more than or equal to 0 and less than or equal to 20, and w2 is more than or equal to 0 and less than or equal to 20.
In one embodiment, the negative electrode active material layer of the secondary battery including a silicon-based negative electrode further includes a carbon material.
To facilitate understanding of the present invention, examples are set forth below. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The present embodiment provides a secondary battery comprising a silicon-based negative electrode, the positive electrode of which is NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ）。
The anode of the secondary battery is SiO 2 And graphite, wherein the silicon content is 5%.
The electrolyte of the secondary battery comprises fluoroethylene carbonate with the content of 4%, ethylene carbonate with the content of 12% and propylene carbonate with the content of 12%, and lithium salt LiPF 6 And LiFSI, liPF 6 The content of LiFSI was 9.5%, and the content of LiFSI was 5%.
The secondary battery of the silicon-based negative electrode is formed by sectioning, namely, firstly, 0.05C is used for forming to 3.0V, then 0.1C is used for forming to 3.4V, and finally, 0.2C is used for forming to the state of charge (SOC) of 0.45.
Example 2
The present embodiment provides a secondary battery comprising a silicon-based negative electrode, the positive electrode of which is NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ）。
The anode of the secondary battery is SiO 2 And graphite, wherein the silicon content is 10%.
The electrolyte of the secondary battery comprises 8% fluoroethylene carbonate, 12% ethylene carbonate and 12% propylene carbonate, and lithium salt LiPF 6 And LiFSI, liPF 6 The content of LiFSI was 9.5%, and the content of LiFSI was 5%.
The secondary battery of the silicon-based negative electrode is formed by sectioning, namely, firstly, 0.05C is used for forming to 3.0V, then 0.1C is used for forming to 3.4V, and finally, 0.2C is used for forming to the state of charge (SOC) of 0.5.
Example 3
The embodiment provides a secondary battery with a silicon-based negative electrode, wherein the positive electrode of the secondary battery is as follows: NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O 2 ）。
The anode of the secondary battery is SiO 2 And graphite, wherein the silicon content is 15%.
The electrolyte of the secondary battery comprises fluoroethylene carbonate with the content of 12%, ethylene carbonate with the content of 12% and propylene carbonate with the content of 12%, and lithium salt LiPF 6 And LiFSI, liPF 6 The content of LiFSI was 9.5%, and the content of LiFSI was 5%.
The secondary battery of the silicon-based negative electrode is formed by sectioning, namely, firstly, 0.05C is used for forming to 3.0V, then 0.1C is used for forming to 3.4V, and finally, 0.2C is used for forming to the state of charge (SOC) of 0.55.
Example 4
The embodiment provides a secondary battery with a silicon-based negative electrode, wherein the positive electrode of the secondary battery is as follows: NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O 2 ）。
The anode of the secondary battery is SiO 2 And graphite, wherein the silicon content is 20%.
The electrolyte of the secondary battery comprises fluoroethylene carbonate with the content of 15 percent and ethylene carbonate with the content of 12 percent, and lithium salt LiPF 6 And LiFSI, liPF 6 The content of LiFSI was 9.5%, and the content of LiFSI was 5%.
The secondary battery of the silicon-based negative electrode is formed by sectioning, namely, firstly, 0.05C is used for forming to 3.0V, then 0.1C is used for forming to 3.4V, and finally, 0.2C is used for forming to the state of charge (SOC) of 0.6.
Example 5
The embodiment provides a secondary battery with a silicon-based negative electrode, wherein the positive electrode of the secondary battery is as follows: NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O 2 ）。
The anode of the secondary battery is SiO 2 And graphite, wherein the silicon content is 30%.
The electrolyte of the secondary battery comprises fluoroethylene carbonate with the content of 25%, ethylene carbonate with the content of 12% and propylene carbonate with the content of 12%, and lithium salt LiPF 6 And LiFSI, liPF 6 The content of LiFSI was 9.5%, and the content of LiFSI was 5%.
The secondary battery of the silicon-based negative electrode is formed by sectioning, namely, firstly, 0.05C is used for forming to 3.0V, then 0.1C is used for forming to 3.4V, and finally, 0.2C is used for forming to the state of charge (SOC) of 0.7.
Example 6
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the off state of charge SOC is 0.4.
Example 7
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the relation between the silicon content and the fluoroethylene carbonate content is as follows: a/x=0.6.
Example 8
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the relation between the silicon content and the fluoroethylene carbonate content is as follows: a/x=1.25.
Example 9
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the content of LiFeSI is 8%, liPF 6 The content of (2) was 6.5%.
Example 10
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the content of the ethylene carbonate was 2%, and the content of the propylene carbonate was 22%.
Example 11
This example provides a secondary battery comprising a silicon-based negative electrode, which differs from example 4 in that: the content of the ethylene carbonate was 22%, and the content of the propylene carbonate was 2%.
Comparative example 1
This comparative example provides a secondary battery comprising a silicon-based negative electrode, which is different from example 4 in that: the fluoroethylene carbonate content was 28%.
Comparative example 2
This comparative example provides a secondary battery comprising a silicon-based negative electrode, which is different from example 4 in that: the state of charge SOC after the formation is 1.
The contents of the components of the secondary battery including a silicon-based negative electrode are shown in table 1.
TABLE 1
The secondary battery obtained above was tested under the following conditions and methods:
(1) Disassembling a full charge interface: charging the battery 1C to 4.2V, disassembling the battery in a disassembling room, separating the anode and the cathode from the diaphragm, and observing the interface condition of the anode.
(2) Storage test at 60 ℃): the secondary battery is charged to 4.2V at 25 ℃ with constant current of 1C, is charged to 0.05C at constant voltage of 4.2V, is discharged to 2.8V with constant current of 1C, which is recorded as a charge-discharge cycle process, the initial discharge capacity C0 is recorded, the secondary battery is placed in a 60 ℃ oven after full charge again, after 30 days of storage, the secondary battery is kept stand for 2 hours at normal temperature, the residual discharge capacity of the battery is recorded at this time and the final battery capacity retention rate is calculated. Battery capacity retention = remaining discharge capacity/initial discharge capacity x 100%.
(3) And (3) 25 ℃ cycle test: the secondary battery was charged to 4.2V at a constant current of 1C in a 25 ℃ incubator, charged to 0.05C at a constant voltage of 4.2V, and discharged to 2.8V at a constant current of 1C, which was recorded as a charge-discharge cycle, and the initial discharge capacity was recorded. Capacity retention = remaining discharge capacity/initial discharge capacity x 100%. The number of battery cycles at 80% capacity retention was recorded.
(4) And (3) hot box test: the secondary battery was charged to 4.2V at 25 ℃ with a constant current of 1C and charged to 0.05C at a constant voltage of 4.2V. The temperature of the oven is regulated to 80 ℃, the battery is put into the oven at room temperature, the battery is stabilized for 3 hours, and then the battery is preserved for 30 minutes at the temperature rising rate of 5 ℃ per minute and the temperature rising rate of 5 ℃ per liter. Reaching 130 ℃, and preserving the heat for 60min at 130 ℃. Then, the temperature is continuously raised from 130 at the speed of 5 ℃ per minute, and the temperature is kept at 5 ℃ for 30 minutes per liter. One of the following determination conditions is reached: the temperature reaches 200 ℃ or the valve is opened, the battery is observed for 60min, and the test is finished.
The test results are shown in Table 2.
TABLE 2
As can be seen from examples 1 to 11 and comparative examples 1 to 2, the formulation in the battery was controlled so as to satisfy the relationship of 1.0 a/(x×w) < 2.2, and it was possible to ensure good cycle performance of the battery, and at the same time, remarkably improve the full charge interface, high temperature storage and hot box performance of the battery, and achieve improvement of the battery endurance and improvement of the battery safety.
In example 6, the off state of charge SOC was less than 0.45, and the battery formed an unstable SEI film, and the battery performance was degraded. In examples 7 and 8, when the silicon content and fluoroethylene carbonate content are less than 0.65, the film forming additive is continuously consumed in the silicon circulation process, the additive is completely consumed in the early circulation period, the expansion and rupture in the later period of the silicon circulation is not repaired by the film forming additive, the circulation is rapidly attenuated, and when the FEC content is more than 1.2, the FEC content is too high, and the high temperature of the FEC content is unstable, so that the high temperature storage and the high temperature circulation are poor.
In example 9, the content of LiFSI was too high, which easily corroded the current collector, resulting in deterioration of cycle. In example 10, the high EC in the formed battery had high reactivity due to the high EC content, deteriorating storage and cycle performance. In example 11, since the content of PC is high, co-intercalation occurs on the graphite surface at a high content of PC in the battery, resulting in deterioration of cycle performance.
The detailed process equipment and process flow of the present invention are described by the above embodiments, but the present invention is not limited to, i.e., it does not mean that the present invention must be practiced depending on the detailed process equipment and process flow. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims (10)

1. A secondary battery comprising a silicon-based anode, characterized in that an anode active material layer of the secondary battery comprising a silicon-based material and having a silicon content of x%; the secondary battery of the silicon-based negative electrode comprises an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate with a content of a%;
the cut-off state of charge (SOC) of the secondary battery of the silicon-containing anode after being formed is w;
the above parameters satisfy: a/(x w) is less than or equal to 1.0 and less than or equal to 2.2;
the silicon content x% is: the mass percentage of silicon in the silicon-based material in the anode active material layer is as follows: the mass percent of fluoroethylene carbonate in the electrolyte.
2. The secondary battery of claim 1, wherein the state of charge SOCw satisfies 0.45+.w+.1.
3. The secondary battery of claim 1, wherein x% of silicon content in the silicon-based negative electrode satisfies 0 < x.ltoreq.50.
4. The secondary battery of claim 3, wherein x% of silicon content in the silicon-based negative electrode satisfies 0 < x.ltoreq.30.
5. The secondary battery of a silicon-based negative electrode according to claim 1, wherein in the secondary battery of a silicon-based negative electrode, the relationship between the silicon content and the fluoroethylene carbonate content is satisfied: a/x is more than or equal to 0.65 and less than or equal to 1.2.
6. The secondary battery of claim 1, wherein the electrolyte further comprises a lithium salt, the lithium salt comprising LiPF 6 And LiFSI.
7. The secondary battery of claim 6, wherein the lithium salt LiPF 6 The content b% and the content c% of LiFSI satisfy the following conditions: b+c is more than or equal to 0 and less than or equal to 14.5, and c is less than b.
8. The secondary battery of any one of claims 1 to 7, wherein the electrolyte further comprises at least one of ethylene carbonate and propylene carbonate.
9. The secondary battery of a silicon-based anode according to claim 8, wherein the content of the ethylene carbonate is w1% and the content of the propylene carbonate is w2%, satisfying: w1 is more than or equal to 0 and less than or equal to 20, and w2 is more than or equal to 0 and less than or equal to 20.
10. The secondary battery of claim 1, wherein the negative electrode active material layer of the secondary battery further comprises a carbon material.
CN202311324000.2A 2023-10-13 2023-10-13 Secondary battery with silicon-based negative electrode Pending CN117080361A (en)

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