CN115548444A - Electrolyte for silicon preparation and battery containing same - Google Patents

Electrolyte for silicon preparation and battery containing same Download PDF

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Publication number
CN115548444A
CN115548444A CN202211505929.0A CN202211505929A CN115548444A CN 115548444 A CN115548444 A CN 115548444A CN 202211505929 A CN202211505929 A CN 202211505929A CN 115548444 A CN115548444 A CN 115548444A
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electrolyte
silicon
fec
active material
secondary battery
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孙语蔚
郑银坤
连爽
王金钻
刘婵
侯敏
曹辉
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Rept Battero Energy Co Ltd
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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
    • 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
    • H01M10/05—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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • 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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  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses an electrolyte for preparing silicon and a battery containing the same; the negative electrode active material of the battery contains silicon element, the electrolyte contains fluoroethylene carbonate FEC, and the following requirements are met: 0.3W Si +4.5%≤W FEC ≤0.3*W Si +9%; wherein, W FEC W is the mass ratio of FEC in the electrolyte Si The mass ratio of silicon element in the negative electrode active material is shown. The invention designs the FEC addition scheme aiming at the high-silicon-content secondary battery, avoids severe cycle expansion and gas generation caused by overhigh FEC, and also avoids cycle later stage water jumping caused by too little FEC.

Description

Electrolyte for silicon preparation and battery containing same
Technical Field
The invention belongs to the technical field of secondary battery preparation, and relates to an electrolyte for silicon preparation and a battery containing the same; in particular to an electrolyte adaptive to a secondary battery with high silicon content and a battery containing the same.
Background
Silicon-containing batteries are commonly used to meet the increasing energy density requirements of the battery market. Batteries with silicon contents below 10% have been widely used. The high silicon content battery with more than 10 percent of silicon has more technical difficulties, such as poor circulation, large expansion and the like. The electrolyte for low silicon content cannot be adapted to the high silicon content battery. The most common problems are the design of the addition amount of fluoroethylene carbonate (FEC), too high FEC cycle expansion and large gas production, and too low FEC cycle later stage water jump easily occur.
Disclosure of Invention
The invention aims to provide an electrolyte adaptive to a high-silicon-content battery and a battery containing the same. The invention finds the calculation relationship between the FEC content and the silicon addition amount in the electrolyte of the secondary battery with high silicon content.
The purpose of the invention is realized by the following technical scheme:
the invention relates to an electrolyte adaptive to a high-silicon-content secondary battery, wherein a negative electrode active material of the battery contains a silicon element, and the electrolyte contains fluoroethylene carbonate, so that the following conditions are met:
0.3*W Si +4.5%≤ W FEC ≤0.3*W Si +9%；
wherein, W FEC W is the mass ratio of FEC in the electrolyte Si W is the mass ratio of silicon element in the negative electrode active material Si ＞10%。
As an embodiment, W Si 11 to 50 wt.%, preferably W Si 11wt% -25 wt%.
In the system of the invention, if W FEC Less than 0.3W Si +4.5%, FEC depletion in the late cycle, resulting in cycle skipping. If W FEC Greater than 0.3W Si +9%, excessive FEC, easy risk of gassing and easy SEI thickening.
As an embodiment, W FEC 7.8 to 24 wt.%, preferably W FEC 7.8wt% -16.5 wt％。
As one embodiment, the electrolyte solution retention coefficient in the high-silicon content secondary battery is 2.5 to 3.5, preferably 2.7 to 3.2. Liquid retention coefficient = (injected electrolyte mass-extracted electrolyte mass)/first discharge capacity. If the liquid retention coefficient is too small, the electrolyte is dried in the later circulation stage, and the battery core is easy to cause circulation diving. If the liquid retention coefficient is too large, the electrolyte is injected too much, and the energy density of the battery cell is reduced.
As one embodiment, the anode active material contains a first anode active material that is graphite and a second anode active material selected from one or more of Si, siO n (0-n-2), and SiC.
As an embodiment, the negative active material is a silicon-carbon negative material compounded by graphite and one or more of nano-silicon, a silicon-carbon composite material, silicon nanowires and SiOx (0 < x < 2).
As one embodiment, the electrolyte consists of an organic solvent, an electrolytic lithium salt and a functional additive; the weight of the organic solvent accounts for 60-85% of the total weight of the electrolyte, such as 60%, 62%, 65%, 67%, 70%, 73%, 75%, 78%, 80%, 83% or 85%, and the like: the electrolyte lithium salt accounts for 10-17% of the total weight of the electrolyte, such as 10%, 11%, 12%, 13%, 14%, 15%, 16% or 17% and the like; the functional additive accounts for 4% -25% of the total weight of the electrolyte, such as 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24% or 25%; at least one of the organic solvent and the functional additive contains fluoroethylene carbonate.
As one embodiment, the organic solvent is a carbonate-based solvent or a fluorinated solvent. Further, the organic solvent is one or more of fluoroethylene carbonate (FEC), ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC).
As an embodiment, the functional additive is one or more of Vinylene Carbonate (VC), vinyl sulfate (DTD), vinyl carbonate (VEC), fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), methylene Methanedisulfonate (MMDS), succinonitrile (SN), adiponitrile (ADN), hexanetrinitrile (HTCN), tris (trimethylsilyl) borate (TMSB), tris (trimethylsilyl) phosphate (TMSP).
In one embodiment, the electrolyte lithium salt in the electrolyte is one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium bis (fluorosulfonyl) imide and lithium difluorophosphate.
The invention also relates to a high-silicon-content secondary battery which adopts the electrolyte adaptive to the high-silicon-content secondary battery.
As an embodiment, the negative electrode material of the battery is mainly composed of a negative electrode active material containing a silicon element and graphite, and a conductive agent, a binder;
the negative active material contains 11-50 wt% of silicon element;
the negative electrode material contains 0.5-2 wt% of conductive agent and 3-7 wt% of binder.
As one embodiment, the binder in the negative electrode is at least one selected from polyvinylidene fluoride (PVDF), polyaniline (PAN), polyacrylic acid (PAA), sodium alginate, styrene Butadiene Rubber (SBR), sodium carboxymethylcellulose (CMC), phenolic resin, epoxy resin, and other high molecular polymers.
As an embodiment, the conductive agent in the negative electrode is selected from at least one of Carbon Nanotubes (CNTs), carbon fibers (VGCF), mesocarbon microbeads (MCMB), graphene, ketjen black, super P, acetylene black, conductive carbon black, and hard carbon.
As an embodiment, the positive active material of the battery positive electrode is selected from LiCoO 2 、LiNiO 2 、LiFePO 4 、Li x Ni y M 1-y O 2 Wherein x is more than or equal to 0.9 and less than or equal to 1.2, y is more than or equal to 0.5 and less than or equal to 1<1,M is selected from one or more of Co, mn, al, mg, ti, fe, cr, mo and Ca.
As an embodiment, the positive electrode material further includes a binder and a conductive agent.
As an embodiment, the mass percentage of each component in the cathode material is as follows: 80-99wt% of positive electrode active substance, 0.1-10wt% of binder and 0.1-10wt% of conductive agent.
As one embodiment, the binder in the positive electrode is at least one selected from among polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyaniline (PAN), polyacrylic acid (PAA), sodium alginate, styrene Butadiene Rubber (SBR), sodium carboxymethylcellulose (CMC), phenol resin, epoxy resin, and other high molecular polymers.
As an embodiment, the conductive agent in the positive electrode is selected from at least one of Carbon Nanotubes (CNTs), carbon fibers (VGCF), graphene, ketjen black, super P (SP), acetylene black, conductive carbon black, and hard carbon.
Compared with the prior art, the invention has the following beneficial effects:
the invention designs the FEC addition scheme aiming at the high-silicon-content secondary battery, avoids severe cycle expansion and gas generation caused by overhigh FEC, and also avoids cycle later stage water jumping caused by too little FEC.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will aid those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any manner. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. All falling within the scope of the present invention.
Example 1
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
the positive electrode formulation is 97.2wt% NCM811+1.1wt% of the SP +0.6wt% carbon nanotubes +1.1wt% PVDF,
the negative electrode formulation was 17.8 wt% SiO +76.5wt% graphite +4wt% PAA binder +0.7wt% SBR binder +0.9wt% SP +0.1wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 3.5, the FEC content in the selected electrolyte is 8.1wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 2
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
the positive electrode formulation was 97.2wt% NCM811+1.1wt% as follows, the% SP +0.6wt% carbon nanotubes +1.1wt% PVDF,
anode formulation 17.8 wt% SiO +76.5wt% graphite +4wt% PAA binder +0.7wt% SBR binder +0.9wt% single-walled carbon nanotubes,
preparing a square battery, wherein the electrolyte retention coefficient is 3.0, the FEC content of the selected electrolyte is 10wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 3
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
anode formulation 17.8 wt% SiO +76.5wt% graphite +4wt% PAA binder +0.7wt% SBR binder +0.9wt% single-walled carbon nanotubes,
the prepared winding soft package battery has the electrolyte retention coefficient of 2.5, the selected electrolyte FEC content of 12.6wt%, and the rest components: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 4
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
the positive electrode formulation was 97.2wt% NCM811+1.1wt% as follows, the% SP +0.6wt% carbon nanotubes +1.1wt% PVDF,
the negative electrode formulation is 26.5 wt% silicon carbide +66.2wt% graphite +5wt% PAA binder +1wt% SBR binder +1wt% SP +0.3wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 3.5, the FEC content of the selected electrolyte is 10.5wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 5
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
the negative electrode formulation is 26.5 wt% silicon carbide +66.2wt% graphite +5wt% PAA binder +1wt% SBR binder +1wt% SP +0.3wt% single-walled carbon nanotubes,
preparing a square battery, wherein the electrolyte retention coefficient is 2.9, the FEC content of the selected electrolyte is 12wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 6
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
the positive electrode formulation was 97.2wt% NCM811+1.1wt% SP +0.6wt% carbon nanotubes +1.1wt% PVDF,
negative electrode formulation 26.5 wt% silicon carbide +66.2wt% graphite +5wt% PAA binder +1wt% SBR binder +1wt% SP +0.3wt% single-walled carbon nanotubes,
the prepared winding soft package battery has the electrolyte retention coefficient of 2.5, the FEC content of the selected electrolyte is 15wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 7
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
anode formulation 36.7wt% sio +56.8wt% graphite +4.5wt% paa bonding +0.8wt% SBR bonding +1wt% sp +0.2wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 3.4, the FEC content of the selected electrolyte is 13.5wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 8
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
the anode formulation 36.7wt% SiO +56.8wt% graphite +4.5wt% PAA binding +0.8 wt%% weight% SBR binding +1wt% SP +0.2wt% single-walled carbon nanotubes,
the prepared square battery has the electrolyte retention coefficient of 3.1, the selected electrolyte FEC content of 16.5wt%, and the rest components: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Example 9
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
the positive electrode formulation was 97.2wt% NCM811+1.1wt% SP +0.6wt% carbon nanotubes +1.1wt% PVDF,
the anode formulation 36.7wt% SiO +56.8wt% graphite +4.5wt% PAA binding +0.8 wt%% weight% SBR binding +1wt% SP +0.2wt% single-walled carbon nanotubes,
the prepared winding soft package battery has the electrolyte retention coefficient of 2.6, the FEC content of the selected electrolyte is 12wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Comparative example 1
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
the anode formulation 36.7wt% SiO +56.8wt% graphite +4.5wt% PAA binding +0.8 wt%% weight% SBR binding +1wt% SP +0.2wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 3.4, the FEC content of the selected electrolyte is 10wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Comparative example 2
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
the anode formulation 36.7wt% SiO +56.8wt% graphite +4.5wt% PAA binding +0.8 wt%% weight% SBR binding +1wt% SP +0.2wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 2, the FEC content of the selected electrolyte is 13.5wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
Comparative example 3
The battery is manufactured according to a conventional battery core manufacturing process, wherein,
NCM811+1.1wt% of the positive electrode formulation, SP +0.6wt% of carbon nanotubes +1.1wt% of PVDF,
the anode formulation 36.7wt% SiO +56.8wt% graphite +4.5wt% PAA binder +0.8 wt%% weight% SBR binder +1wt% SP +0.2wt% single-walled carbon nanotubes,
the laminated soft package battery is prepared, the liquid retention coefficient of the electrolyte is 3.4, the FEC content of the selected electrolyte is 19wt%, and the rest components are as follows: 10wt% of lithium hexafluorophosphate, 5wt% of lithium bis (fluorosulfonyl) imide, 0.5wt% of vinylene carbonate, 0.8wt% of lithium difluorophosphate and the balance of an organic solvent; the organic solvent is prepared from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate according to the mass ratio of 20:70:5:5, mixing to obtain the product.
The laminated cells prepared in the examples and comparative examples were subjected to a hanging test at a normal temperature of 25 + -2 deg.C: 1.1CC to 4.2V, CV to 0.05C, 2. Rest 5min, 3, 1DC to 2.8V, 4. Rest 5min, 5. Step 1 to step 4 cycle until the discharge capacity decayed to 80% of the first discharge capacity.
TABLE 1 summary of electrical property data for various examples and comparative examples
Wsi Liquid retention coefficient WFEC Cycle life/number of turns Expansion rate of negative plate after circulation Remarks for note
Example 1 12% 3.5 8.1% 1532 57.2% Non-circulation diving
Example 2 12% 3.0 10% 1548 60.1% Non-circulation diving
Example 3 12% 2.5 12.6% 1529 58.9% Non-circulation diving
Example 4 20% 3.5 10.5% 1198 65.5% Non-circulation diving
Example 5 20% 2.9 12% 1167 68.2% Non-circulation diving
Example 6 20% 2.5 15% 1149 69.3% Non-circulation diving
Example 7 25% 3.4 13.5% 1023 78.8% Non-circulation diving
Example 8 25% 3.1 16.5% 1036 72.6% Non-circulation diving
Example 9 25% 2.6 12% 1009 75.4% Non-circulation diving
Comparative example 1 25% 3.4 10% 772 83.3% 761 Ring starting diving
Comparative example 2 25% 2 13.5% 661 81.5% 649 circles jump water
Comparative example 3 25% 3.4 19% 986 100.3% Non-circulation diving
Note: the cycle life refers to the number of cycles at which the discharge capacity decayed to 80% of the first discharge capacity.
Expansion ratio of negative plate after cycle = thickness of negative plate in full charge state when cycle life is reached/thickness of negative plate after rolling-1
As can be seen from table 1, in comparative example 1, compared with example 7, the FEC content in the electrolyte is too low, which results in too low FEC total amount in the cell, FEC depletion at the end of the cycle, and cycle water-skipping occurs in the cell.
Compared with example 7, the electrolyte solution retention coefficient is too low, so that the total FEC amount in the cell is too low, FEC exhaustion at the end of circulation is caused, and circulation water-skipping occurs in the cell.
Comparative example 3 compared to example 7, the FEC content in the electrolyte was too high, resulting in too high a total amount of FEC in the cell,
leading to over-thick SEI film formation at the later cycle stage and over-large battery core expansion rate.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims (10)

1. An electrolyte adapted to a high-silicon-content secondary battery, a negative active material of the battery contains silicon, and the electrolyte contains fluoroethylene carbonate, so that:
0.3*W Si +4.5%≤ W FEC ≤0.3*W Si +9%；
wherein, W FEC W is the mass ratio of fluoroethylene carbonate in the electrolyte Si W is the mass ratio of silicon element in the negative electrode active material Si ＞10%。
2. The electrolyte for adapting a high-silicon-content secondary battery according to claim 1, wherein W is W Si 11wt% -50 wt%.
3. The electrolyte for adapting a high-silicon-content secondary battery according to claim 1, wherein W is W FEC 7.8wt% -24 wt%.
4. The electrolyte for adapting a high-silicon-content secondary battery according to claim 1, wherein the electrolyte solution retention coefficient in the high-silicon-content secondary battery is 2.5-3.5, and the retention coefficient = (injected electrolyte solution mass-extracted electrolyte solution mass)/first discharge capacity.
5. The electrolyte for a secondary battery with a high silicon content according to claim 1, wherein the negative electrode active material comprises a first negative electrodeThe negative electrode comprises an active material and a second negative electrode active material, wherein the first negative electrode active material is graphite, and the second negative electrode active material is selected from Si and SiO n (0<n<2) And SiC.
6. The electrolyte for adapting a high-silicon-content secondary battery according to claim 1, wherein the electrolyte is composed of an organic solvent, an electrolytic lithium salt, and a functional additive; the weight of the organic solvent accounts for 60-85% of the total weight of the electrolyte, the weight of the electrolyte lithium salt accounts for 10-17% of the total weight of the electrolyte, and the weight of the functional additive accounts for 4-25% of the total weight of the electrolyte; at least one of the organic solvent and the functional additive contains fluoroethylene carbonate.
7. The electrolyte solution for a secondary battery with high silicon content according to claim 6, wherein the organic solvent is a carbonate-based solvent or a fluorinated solvent; the functional additive is one or more of vinylene carbonate, vinyl sulfate, vinyl ethylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, methylene methanedisulfonate, succinonitrile, adiponitrile, hexanetrinitrile, tri (trimethylsilyl) borate and tri (trimethylsilyl) phosphate; the electrolyte lithium salt is one or more of lithium hexafluorophosphate, lithium difluoro oxalate borate, lithium bis (fluorosulfonyl) imide and lithium difluorophosphate.
8. A high silicon content secondary battery, characterized in that the battery employs the electrolyte as claimed in any one of claims 1 to 7.
9. The high-silicon-content secondary battery according to claim 8, wherein the negative electrode material of the battery is mainly composed of a negative electrode active material containing a silicon element and graphite, and a conductive agent, a binder;
the negative active material contains 11-50 wt% of silicon element;
the negative electrode material contains 0.5-2 wt% of conductive agent and 3-7 wt% of binder.
10. The secondary battery of claim 8, wherein the positive electrode active material of the battery positive electrode is selected from LiCoO 2 、LiNiO 2 、LiFePO 4 、Li x Ni y M 1-y O 2 Wherein x is more than or equal to 0.9 and less than or equal to 1.2, and y is more than or equal to 0.5 and less than or equal to 1.2<1,M is selected from one or more of Co, mn, al, mg, ti, fe, cr, mo and Ca.
CN202211505929.0A 2022-11-29 2022-11-29 Electrolyte for silicon preparation and battery containing same Pending CN115548444A (en)

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