CN115498268A - Lithium ion battery - Google Patents
Lithium ion battery Download PDFInfo
- Publication number
- CN115498268A CN115498268A CN202211432760.0A CN202211432760A CN115498268A CN 115498268 A CN115498268 A CN 115498268A CN 202211432760 A CN202211432760 A CN 202211432760A CN 115498268 A CN115498268 A CN 115498268A
- Authority
- CN
- China
- Prior art keywords
- negative electrode
- lithium ion
- equal
- ion battery
- material layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- 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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
-
- 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
Abstract
In order to solve the problems that the additive of the existing lithium ion battery has unstable film forming quality and affects the cycle performance of the battery, the invention provides a lithium ion battery, which comprises a positive plate, a negative plate and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, lithium salt and the additive, and the additive comprises FEC; the negative plate comprises a negative electrode material layer and an interface film formed by the non-aqueous electrolyte on the surface of the negative electrode material layer, and when a 1s peak of carbon is obtained at 284.5eV, a characteristic peak of LiF appears in a region from 682 to 687 eV through detection of the negative plate by an X-ray photoelectron spectroscopy; the lithium ion battery meets the following conditions: n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, and m is more than or equal to 0.01 and less than or equal to 20.
Description
Technical Field
The invention belongs to the technical field of energy storage devices, and particularly relates to a lithium ion battery.
Background
Compared with lead-acid batteries, nickel-metal hydride batteries and nickel-cadmium batteries, lithium ion batteries have the advantages of high energy density, long cycle life and the like, and are widely applied to various fields at present. For Hybrid Electric Vehicle (HEV) applications, batteries are required to have low internal resistance, long storage life, and cycle life. The lower internal resistance is beneficial to the automobile to have larger charge-discharge power, better acceleration performance and power performance, and can recover energy to a greater extent and improve the fuel efficiency; the long cycle life is for the battery to have long term reliability, maintaining good performance over the normal life of the vehicle.
In a common power battery, graphite and a silicon-containing material are mostly used as negative active materials. The graphite has stable structure and low activity, can provide high safety and long cycle life, but has low specific energy and energy density which cannot meet the increasing requirement of the endurance mileage of the electric automobile. The silicon-containing material combines the advantages of graphite and silicon, and has obvious energy density advantage, but the silicon-containing material has very serious volume expansion in the battery charging and discharging process, and the SEI is continuously damaged to cause pulverization or crack of alloy, so that the silicon material structure collapses and the electrode material peels off, the electrode material loses electric contact, and the cycle performance of the silicon cathode lithium ion battery is sharply reduced. Vinylene Carbonate (VC) is an excellent cathode film-forming additive, is widely applied to various battery systems, such as lithium iron phosphate, lithium manganate, lithium manganese oxide and other systems, and can obviously improve the high-temperature cycle performance of the battery, but the impedance of the formed film on the cathode is large, the power and low-temperature performance are difficult to guarantee, and the normal-temperature cycle water-skipping failure is easily caused by large impedance due to excessive addition amount. By carrying out certain fluorine substitution on vinylene carbonate, such as fluoroethylene carbonate (FEC), the film forming property of the vinylene carbonate can be changed to a certain degree, and a stable and thin interfacial film is formed on a negative electrode interface; however, the interfacial film formed by the ethylene carbonate substituted by fluorine has large quality difference, and is greatly influenced by other factors in the lithium ion battery, so that the interfacial film cannot have stable improvement performance for various batteries.
Disclosure of Invention
The invention provides a lithium ion battery, aiming at the problems that the existing lithium ion battery additive has unstable film forming quality and influences the cycle performance of the battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a lithium ion battery, which comprises a positive plate, a negative plate and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, a lithium salt and an additive, and the additive comprises FEC;
the negative plate comprises a negative electrode material layer and an interface film formed by the non-aqueous electrolyte on the surface of the negative electrode material layer, and when a 1s peak of carbon is obtained at 284.5eV, a characteristic peak of LiF appears in a region from 682 to 687 eV through detection of the negative plate by an X-ray photoelectron spectroscopy;
the lithium ion battery meets the following conditions:
n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, m is more than or equal to 0.01 and less than or equal to 20;
wherein n is the porosity of the negative electrode material layer and has a unit of percent;
p is the thickness of the interfacial film on the surface of the negative electrode material layer, and the unit is nm;
m is the mass percentage content of FEC in the non-aqueous electrolyte, and the unit is;
the negative plate is placed in an environment at 60 ℃ for 72 hours, and has a weight loss ratio of 1-30%.
Optionally, the lithium ion battery satisfies the following conditions:
0.5≤n/p+m≤10。
optionally, the porosity n of the negative electrode material layer is 15% -30%.
Optionally, the thickness p of the interface film on the surface of the negative electrode material layer is 10nm to 100nm.
Optionally, the mass percentage content m of the FEC in the non-aqueous electrolyte is 0.1% -10%.
Optionally, the lithium salt is selected from LiPF 6 、LiBOB、LiDFOB、LiPO 2 F 2 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 F) 2 、LiClO 4 、LiAlCl 4 、LiCF 3 SO 3 、Li 2 B 10 Cl 10 、LiSO 3 F. At least one of lipo (lithium tris oxalate phosphate), lipodfp (lithium difluorooxalate phosphate), liOTFP (lithium tetrafluorooxalate phosphate), and a lower aliphatic carboxylic acid lithium salt.
Optionally, the non-aqueous organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, γ -butyrolactone, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, fluoro ethyl acetate, and fluoro ether.
Optionally, the additive further comprises at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds;
the additive is added in an amount of 0.01-30% based on 100% of the total mass of the nonaqueous electrolyte.
Optionally, the cyclic sulfate compound is selected from vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
At least one of;
the sultone compounds are selected from 1, 3-propane sultone, 1, 4-butane sultone, 1, 3-propylene sultone,
At least one of;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate or a compound shown in a structural formula 1,
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom and C1-C5 group;
the phosphate compound is at least one of tris (trimethylsilane) phosphate, tris (trimethylsilane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated alkyl, unsaturated alkyl, halogenated alkyl, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
the borate compound is at least one selected from tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
Optionally, the negative electrode material layer includes a negative electrode active material selected from at least one of a silicon-based negative electrode, a carbon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.
According to the lithium ion battery provided by the invention, FEC is added into the non-aqueous electrolyte as an additive, the FEC can be decomposed on the surface of the negative electrode material layer under formation conditions to form an interface film rich in LiF, and through a large number of experiments, the inventor finds that when the porosity n of the negative electrode material layer, the thickness p of the interface film on the surface of the negative electrode material layer and the mass percentage content m of the FEC in the non-aqueous electrolyte meet the conditions that n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, and m is more than or equal to 0.01 and less than or equal to 20, the film forming quality of the interface film rich in LiF is favorably improved.
Drawings
FIG. 1 is a detection spectrum of the negative electrode sheet provided by the invention by X-ray photoelectron spectroscopy.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clear, the present invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The embodiment of the invention provides a lithium ion battery, which comprises a positive plate, a negative plate and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, a lithium salt and an additive, and the additive comprises FEC;
the negative plate comprises a negative electrode material layer and an interface film formed by the non-aqueous electrolyte on the surface of the negative electrode material layer, and when a 1s peak of carbon is obtained at 284.5eV, a characteristic peak of LiF appears in a region from 682 to 687 eV through detection of the negative plate by an X-ray photoelectron spectroscopy;
the lithium ion battery meets the following conditions:
n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, m is more than or equal to 0.01 and less than or equal to 20;
wherein n is the porosity of the negative electrode material layer and has a unit of percent;
p is the thickness of the interfacial film on the surface of the negative electrode material layer, and the unit is nm;
m is the mass percentage content of FEC in the non-aqueous electrolyte, and the unit is%;
the negative plate is placed in an environment at 60 ℃ for 72 hours, and has a weight loss ratio of 1-30%.
The FEC is added into the non-aqueous electrolyte and can be decomposed on the surface of the negative electrode material layer under formation conditions to form an interface film rich in LiF, and the inventor finds that the film forming quality of the interface film rich in LiF is improved when the porosity n of the negative electrode material layer, the thickness p of the interface film on the surface of the negative electrode material layer and the mass percentage content m of the FEC in the non-aqueous electrolyte meet the conditions that n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, and m is more than or equal to 0.01 and less than or equal to 20.
The weight loss rate of the negative electrode sheet can reflect the residual amount of the non-aqueous electrolyte in the negative electrode sheet, and can be controlled by the porosity of the negative electrode material layer or the content of FEC in the non-aqueous electrolyte, wherein the larger the porosity of the negative electrode material layer is, the better the liquid retention capability of the electrode sheet is; the more the content of FEC in the non-aqueous electrolyte is, the more the wettability of the electrolyte is improved, and the impregnation depth and the liquid retention capability of the pole piece are enhanced. When the porosity of the negative electrode, the FEC content in the non-aqueous electrolyte and the thickness of the interfacial film on the surface of the negative electrode material layer meet n/p + m which is more than or equal to 0.3 and less than or equal to 25, the weight loss rate of the negative electrode piece can be in the range, and the lithium ion battery can be ensured to have good cycle performance on the premise of not sacrificing the energy density of the battery. If the weight loss rate is more than 30%, the energy density of the battery can be reduced, and the commercial application is not facilitated; if the weight loss ratio is less than 1%, the battery performance is deteriorated.
In a preferred embodiment, the lithium ion battery satisfies the following condition:
0.5≤n/p+m≤10。
when the value of n/p + m is too low, the lithium ion battery has the following problems: the retention amount of electrolyte in the negative electrode material layer is limited, so that the liquid phase conduction resistance of lithium ions in the pore channels of the negative electrode material layer is increased, the initial impedance of the battery is increased, the irreversible capacity loss of the battery is increased in the repeated charge and discharge process of the battery, and the cycle performance of the battery is deteriorated; or the improvement effect on the cycle performance of the battery is limited, and the current use requirements on the energy density and the cycle life of the battery cannot be met. When the value of n/p + m is too high, the energy density of the battery is reduced, and the commercial application is not facilitated; or the viscosity of the nonaqueous electrolyte increases, resulting in an increase in the initial resistance of the battery to deteriorate the cycle performance of the battery.
In particular embodiments, the porosity n of the layer of negative electrode material may be 10%, 13%, 15%, 28%, 30%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, or 40%.
In a preferred embodiment, the porosity n of the negative electrode material layer is 15% -30%.
The internal resistance and the cycle performance of the battery are related to the porosity n of the negative electrode material layer, and the porosity n of the negative electrode material layer can influence the residual amount of the electrolyte in the negative electrode material layer, so that the liquid phase conductivity of lithium ions in the pore channels of the negative electrode porous electrode is influenced. Generally, the larger the porosity n of the negative electrode material layer, the more developed the pore structure of the negative electrode material layer, the more the content of the nonaqueous electrolytic solution in the negative electrode material layer, the better the wettability of the nonaqueous electrolytic solution to the negative electrode material layer, and the higher the liquid phase conduction speed of lithium ions inside the pores of the negative electrode material layer, the more easily active ions are embedded into the negative electrode active material during battery charging, thereby reducing the initial impedance of the battery, and thus the less irreversible capacity loss during repeated charging and discharging of the battery. In addition, the battery may cause consumption of the nonaqueous electrolytic solution during repeated charge and discharge, and sufficient nonaqueous electrolytic solution is retained in the negative electrode material layer so that the cycle life of the battery is longer. But as the porosity n of the negative electrode material layer increases, the energy density loss of the battery becomes more and more severe. Therefore, the porosity n of the negative electrode material layer is too large or too small, which has a great influence on the cycle life, initial internal resistance, and energy density of the battery. When the porosity n of the negative electrode material layer is within the preferable range, the negative electrode sheet is ensured to have the advantage of high energy density and simultaneously have good electrolyte wettability, the capacity of the negative electrode sheet for retaining electrolyte is better, the interface charge transfer impedance between the negative electrode active material and the non-aqueous electrolyte is lower, and the internal resistance and the cycle life of the battery can be better improved.
In a specific embodiment, the thickness p of the interface film on the surface of the negative electrode material layer may be 5nm, 10nm, 20nm, 30nm, 40 nm, 50nm, 60 nm, 70 nm, 80 nm, 90 nm, 100nm, 110 nm, 120nm, 130nm, 140 nm, or 150nm.
In a preferred embodiment, the thickness p of the interfacial film on the surface of the negative electrode material layer is 10nm to 100nm.
The interface film rich in LiF is formed on the negative electrode material layer, so that the excessive increase of the thickness of the interface film in the charging and discharging process of the battery can be inhibited, the impedance increase of the battery in the circulating process can be improved by the interface film rich in LiF, and the circulating life of the battery is prolonged. The thickness p of the interface film rich in LiF is related to the porosity n of the anode material layer and the content m of FEC in the nonaqueous electrolytic solution by mass percentage, and is also affected by the formation conditions. If the interface film rich in LiF is too thick, the resistance of the battery is increased, the embedding and extracting efficiency of lithium ions on the negative electrode material layer is influenced, the conductivity of lithium ions is reduced, and the rate capability of the lithium battery is reduced; if the interface film containing LiF is too thin, the conduction rate of lithium ions in the interface film on the negative electrode active material layer increases, but it is not favorable for improving the cycle life of the battery.
In specific embodiments, the content m of FEC in the nonaqueous electrolytic solution may be 0.01%, 0.03%, 0.05%, 0.1%, 0.3%, 0.5%, 1%, 2%, 5%, 10%, 15%, or 20% by mass.
In a preferred embodiment, the content m of the FEC in the nonaqueous electrolytic solution is 0.1% to 10% by mass.
The FEC can form a stable interface film on the interface of the negative electrode material layer; in addition, the FEC contains an electron-donating group F-, and can remarkably reduce the surface tension and the contact angle of the non-aqueous electrolyte on the surface of the negative electrode material layer, thereby improving the wettability of the non-aqueous electrolyte in the negative electrode material layer, improving the compatibility of the negative electrode active material and the non-aqueous electrolyte, and obviously improving the initial impedance and the cycle performance of a graphite negative electrode battery system. Meanwhile, the F element can also increase the oxidation resistance of the non-aqueous electrolyte under high voltage, so that the electrochemical stability window of the non-aqueous electrolyte is widened, and the non-aqueous electrolyte is more difficult to be oxidized in the using process, thereby reducing the side reaction on the surface of the negative electrode material layer and being beneficial to forming an interface film rich in LiF. In the silicon-containing negative electrode system, the interfacial film with the polymer structure formed on the surface of the silicon-containing negative electrode material after FEC formation can inhibit the volume expansion of the silicon-containing material, and the cracked interfacial film in the circulating process is continuously repaired, so that the circulating performance of the battery is finally improved. If the content of FEC in the non-aqueous electrolyte is too much, the viscosity of the non-aqueous electrolyte is increased, the dissociation degree of lithium ions is influenced, and the internal resistance of the battery is increased; if the content of FEC in the nonaqueous electrolyte is too low, the passivation and wetting effects on the negative electrode material layer are insufficient, which affects the retention amount of the nonaqueous electrolyte on the negative electrode sheet and limits the improvement of the cycle life of the battery.
The thickness of the interface film rich in LiF is not only related to the porosity of the negative electrode material layer and the components of the electrolyte, but also can be adjusted through different formation conditions, in the formation process, the thickness of the interface film rich in LiF formed by the battery at different formation potentials is different, the growth of the film layer tends to be complete along with the increase of the formation potential, and meanwhile, the thickness of the interface film can be influenced by formation current, formation time, formation temperature and the like. In some embodiments, the formation conditions of the lithium ion battery comprise the following operation steps:
performing constant-current charging on a lithium ion battery to form a lithium ion battery, charging the lithium ion battery at a rate of 0.03 to 0.1C, stopping charging when the potential reaches 3.0 to 3.5V, and then aging the lithium ion battery at 30 to 50 ℃ for 5 to 30min; and continuously charging the lithium ion battery at a rate of 0.1-0.3C for formation, stopping charging when the formation potential reaches 3.5-3.9V, then aging the lithium ion battery at a temperature of 30-50 ℃ for 30-60min, and continuously charging the lithium ion battery at a rate of 0.3-0.5C for formation until the SOC reaches 100 percent, so as to form the interface film on the surface of the negative electrode material layer.
The thickness p of the interfacial film can be effectively controlled to be not less than 5 and not more than 150 by the formation method, and the film forming quality is ensured.
In some embodiments, the lithium ion battery is a pouch battery or a hard shell battery.
In a preferred embodiment, the lithium salt is selected from LiPF 6 、LiBOB、LiDFOB、LiPO 2 F 2 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 F) 2 、LiClO 4 、LiAlCl 4 、LiCF 3 SO 3 、Li 2 B 10 Cl 10 、LiSO 3 F. At least one of LiTOP (lithium Trioxalato phosphate), liDODFP (lithium difluorooxalato phosphate), liOTFP (lithium tetrafluorooxalato phosphate), and a lower aliphatic carboxylic acid lithium salt.
In some embodiments, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.1-8 mol/L. In a preferred embodiment, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.5mol/L to 2.5mol/L. Specifically, the concentration of the lithium salt in the nonaqueous electrolytic solution may be 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, or 2.5mol/L.
In some embodiments, the non-aqueous organic solvent includes one or more of an ether solvent, a nitrile solvent, a carbonate solvent, and a carboxylate solvent.
In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms, and the cyclic ether may specifically be, but is not limited to, 1, 3-Dioxolane (DOL), 1, 4-Dioxan (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH) 3 -THF), 2-trifluoromethyltetrahydrofuran (2-CF) 3 -THF); the chain ether may specifically but not exclusively be dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol di-n-butyl etherMethyl ether. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferable because chain ethers have high solvating ability with lithium ions and can improve ion dissociation properties. The ether compound may be used alone, or two or more thereof may be used in combination in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-compacted lithium ion battery of the present invention, and is usually 1% by volume or more, preferably 2% by volume or more, and more preferably 3% by volume or more, and is usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less, based on 100% by volume of the nonaqueous solvent. When two or more ether compounds are used in combination, the total amount of the ether compounds may be within the above range. When the amount of the ether compound added is within the above-mentioned preferable range, the effect of improving the ionic conductivity by increasing the degree of dissociation of lithium ions and lowering the viscosity of the chain ether can be easily secured. In addition, when the negative electrode active material is a carbon-based material, the co-intercalation phenomenon of the chain ether and the lithium ion can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be set to appropriate ranges.
In some embodiments, the nitrile solvent may specifically be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.
In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), γ -butyrolactone (GBL), butylene Carbonate (BC); the chain carbonate may be specifically, but not limited to, one or more of dimethyl carbonate (DMC), ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited and may be any within a range not significantly impairing the effect of the lithium ion battery of the present invention, but when one is used alone, the lower limit of the content is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of the solvent of the nonaqueous electrolytic solution. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte solution, and it is easy to achieve a favorable range of the large current discharge characteristic, stability with respect to the negative electrode sheet, and cycle characteristic of the nonaqueous electrolyte battery. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. Setting this range can improve the oxidation/reduction resistance of the nonaqueous electrolytic solution, and contributes to improvement of stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, based on the total amount of the solvent of the nonaqueous electrolytic solution. The volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. When the content of the chain carbonate is in the above range, the viscosity of the nonaqueous electrolytic solution is easily brought to an appropriate range, the decrease in the ionic conductivity is suppressed, and the content contributes to bringing the output characteristics of the nonaqueous electrolyte battery to a good range. When two or more kinds of chain carbonates are used in combination, the total amount of the chain carbonates may be set to satisfy the above range.
In some embodiments, chain carbonates having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonate") may also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, the fluorine atoms may be bonded to the same carbon atom or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.
The carboxylic ester solvent includes cyclic carboxylic ester and/or chain carbonate. Examples of the cyclic carboxylic acid ester include: one or more of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include: one or more of Methyl Acetate (MA), ethyl Acetate (EA), propyl acetate (EP), butyl acetate, propyl Propionate (PP), and butyl propionate.
In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone, and preferably, in the case of the cyclic sulfone, the sulfone is a compound having usually 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of the chain sulfone, the sulfone is a compound having usually 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The amount of the sulfone solvent to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the lithium ion battery of the present invention, and is usually 0.3% by volume or more, preferably 0.5% by volume or more, and more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, and more preferably 30% by volume or less, relative to the total amount of the solvent of the nonaqueous electrolytic solution. In the case where two or more sulfone solvents are used in combination, the total amount of the sulfone solvents may be set to satisfy the above range. When the amount of the sulfone solvent added is within the above range, an electrolyte excellent in high-temperature storage stability tends to be obtained.
In a preferred embodiment, the organic solvent is a mixture of cyclic carbonates and chain carbonates.
In some embodiments, the additive further comprises at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a nitrile-based compound;
preferably, the additive is added in an amount of 0.01 to 30% based on 100% by mass of the total nonaqueous electrolyte.
Preferably, the cyclic sulfate compound includes vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
At least one of (1).
The sultone compounds are selected fromFrom 1, 3-propane sultone, 1, 4-butane sultone, 1, 3-propene sultone,
At least one of;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate or a compound shown in a structural formula 1,
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom, C1-C5 group. Specifically, the compound shown in the structural formula 1 comprises
At least one of (a).
The phosphate ester compound is at least one of tris (trimethyl silane) phosphate, tris (trimethyl silane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the structural formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, unsaturated hydrocarbon group, halogenated hydrocarbon group, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
in a preferred embodiment, the phosphate ester compound may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2, 2-trifluoroethyl phosphate, dipropargyl-3, 3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2, 2-trifluoroethyl phosphate, diallyl-3, 3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate;
the borate compound is at least one selected from tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
In other embodiments, the additives may also include other additives that improve the performance of the battery: for example, the additives for improving the safety performance of the battery include flame retardant additives such as fluorophosphate ester and cyclophosphazene, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.
Unless otherwise specified, in general, the addition amount of any optional substance in the additive in the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, and more preferably 0.1 to 2%. Specifically, the additive amount of any optional substance in the additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.
In some embodiments, the positive electrode sheet includes a positive electrode material layer and a positive electrode current collector, and the positive electrode material layer is formed on a surface of the positive electrode current collector.
The positive electrode current collector is selected from metal materials capable of conducting electrons, preferably, the positive electrode current collector comprises one or more of Al, ni, tin, copper and stainless steel, and in a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.
The positive electrode material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.
The positive binder comprises thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether, copolymers of ethylene and tetrafluoroethylene, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and trichloroethylene, copolymers of vinylidene fluoride and fluoroethylene, copolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, polyethylene, polypropylene and the like; an acrylic resin; sodium carboxymethylcellulose; and styrene butadiene rubber.
The positive electrode conductive agent comprises one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.
In some embodiments, the positive electrode sheet includes a positive electrode material layer containing a positive electrode active material, the kind of the positive electrode active material is not particularly limited and may be selected according to actual needs as long as it is a positive electrode active material or a conversion-type positive electrode material capable of reversibly intercalating/deintercalating lithium ions.
In a preferred embodiment, the positive active material may be selected from LiFe 1-x’ M’ x’ PO 4 、LiMn 2-y’ M y’ O 4 And LiNi x Co y Mn z M 1-x-y-z O 2 Wherein M' is selected from one or more of Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V or Ti, M is selected from Fe, co, ni, mn, mg, cu, zn, al, sn, B,Ga. One or more of Cr, sr, V or Ti, wherein x 'is more than or equal to 0 and less than 1, y' is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is less than or equal to 1, and the anode active material can also be selected from one or more of sulfide, selenide and halide. More preferably, the positive active material may be selected from LiCoO 2 、LiNiO 2 、LiMnO 2 、LiFePO 4 、LiFe 0.7 Mn 0.3 PO 4 、LiFe 0.8 Mn 0.2 PO 4 、LiNi 1/3 Co 1/3 Mn 1/3 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.8 Co 0.15 Mn 0.05 O 2 、LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O 2 、LiMn 2 O 4 、LiNi 0.5 Co 0.2 Al 0.3 O 2 One or more of (a).
In some embodiments, the negative electrode material layer includes a negative electrode active material.
In a preferred embodiment, the anode active material comprises at least one of a carbon-based anode, a silicon-based anode, a tin-based anode, a lithium anode. The carbon-based negative electrode can comprise graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads and the like; the silicon-based negative electrode can comprise silicon materials, silicon oxides, silicon-carbon composite materials, silicon alloy materials and the like; the tin-based negative electrode may include tin, tin carbon, tin oxide, tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.
In some embodiments, the graphite includes, but is not limited to, one or more of natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, resin-coated graphite. The natural graphite may be scale graphite, flake graphite, soil graphite, and/or graphite particles obtained by spheroidizing, densifying, or the like, using these graphites as a raw material. The artificial graphite can be obtained by graphitizing organic matters such as coal tar pitch, coal heavy crude oil, atmospheric residual oil, petroleum heavy crude oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenyl, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenolic resin, imide resin and the like at high temperature. The amorphous carbon may be one obtained by heat-treating a graphitizable carbon precursor such as tar or pitch at a temperature range (400 to 2200 ℃) where graphitization does not occur for 1 or more times, or one obtained by heat-treating a graphitizable carbon precursor such as a resin. The carbon-coated graphite may be obtained by mixing natural graphite and/or artificial graphite with a carbon precursor which is an organic compound such as tar, pitch, or resin, and heat-treating the mixture at 400 to 2300 ℃ for 1 or more times. The obtained natural graphite and/or artificial graphite is used as core graphite, and the core graphite is coated with amorphous carbon to obtain a carbon graphite composite. The carbon graphite composite may be in a form in which the entire or partial surface of the core graphite is coated with amorphous carbon, or in a form in which a plurality of primary particles are compounded with carbon derived from the above-described carbon precursor as a binder. Further, a carbon-graphite composite can be obtained by reacting a hydrocarbon gas such as benzene, toluene, methane, propane, or an aromatic volatile component with natural graphite and/or artificial graphite at a high temperature to deposit carbon on the graphite surface. The graphite-coated graphite may be natural graphite and/or artificial graphite mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch, resin, etc., and subjected to heat treatment at 2400 to 3200 ℃ or more for 1 time. The obtained natural graphite and/or artificial graphite is used as core graphite, and the whole or part of the surface of the core graphite is coated with a graphitized substance, whereby graphite-coated graphite can be obtained. The resin-coated graphite may be obtained by mixing natural graphite and/or artificial graphite with a resin or the like, drying the mixture at a temperature of less than 400 ℃, and coating the mixture with a resin or the like using the natural graphite and/or artificial graphite obtained as core graphite. Examples of the organic compound such as the tar and the pitch resin include carbonizable organic compounds selected from coal-based heavy crude oil, direct-current-based heavy crude oil, decomposed petroleum-based heavy crude oil, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenyl, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins.
In a preferred embodiment, the addition amount of the silicon-based material is more than 0 and less than 30%. Preferably, the upper limit value of the addition amount of the silicon-based material is 10%, 15%, 20%, or 25%; the lower limit of the addition amount of the silicon-based material is 5%, 10% or 15%.
In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon, and hollow porous silicon.
In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
The selectable ranges of the negative electrode binder and the negative electrode conductive agent are respectively the same as those of the positive electrode binder and the positive electrode conductive agent, and are not described again.
In some embodiments, the negative electrode sheet further includes a negative electrode current collector, and the negative electrode material layer is formed on a surface of the negative electrode current collector.
The negative electrode current collector is selected from metal materials capable of conducting electrons, preferably, the negative electrode current collector comprises at least one of Al, ni, tin, copper and stainless steel, and in a more preferred embodiment, the negative electrode current collector is selected from copper foil.
In some embodiments, the lithium ion battery further comprises a separator, and the separator is located between the positive plate and the negative plate.
The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, and the like, including but not limited to a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP, and the like.
The present invention will be further illustrated by the following examples.
TABLE 1 design of parameters of examples and comparative examples
Example 1
This embodiment is used to illustrate a lithium ion battery and a method for manufacturing the same disclosed in the present invention, and includes the following operation steps:
1) Preparation of positive plate
Step 1: adding PVDF as a binder into an NMP solvent, and fully and uniformly stirring to obtain a PVDF glue solution.
Step 2: the PVDF glue solution is added with a conductive agent (super P + CNT), and the mixture is fully and uniformly stirred.
And 3, step 3: the positive electrode active materials shown in table 1 were continuously added, and sufficiently and uniformly stirred to finally obtain the desired positive electrode slurry.
And 4, step 4: and uniformly coating the prepared positive electrode slurry on a positive electrode current collector, and drying, rolling, die cutting or stripping to obtain the positive electrode plate.
2) Preparation of negative plate
Step 1: the following materials are weighed according to the following ratio of graphite (sequoia jezoensis, FSN-1), conductive carbon (super P), sodium carboxymethylcellulose (CMC), styrene Butadiene Rubber (SBR) = 96.3.
Step 2: firstly, adding CMC with the solid content of 1.5 percent into pure water, and fully and uniformly stirring (for example, stirring for 120 min) to prepare transparent CMC glue solution.
And 3, step 3: adding conductive carbon (super P) into the CMC glue solution, and fully and uniformly stirring (for example, stirring for 90 min) to prepare the conductive glue.
And 4, step 4: and continuously adding the negative electrode active material shown in the table 1, and fully and uniformly stirring to finally obtain the required negative electrode slurry.
And 5, step 5: the prepared negative electrode slurry is uniformly coated on a copper foil, a negative electrode sheet is obtained through drying, rolling, die cutting or strip dividing, the porosity of a negative electrode material layer is controlled as shown in table 1, the porosity n of the negative electrode material layer can be obtained through a gas replacement method, the porosity n = (V1-V2)/V1 x 100%, V1 represents an apparent volume, and V2 represents a real volume.
3) Preparation of non-aqueous electrolyte
Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) were mixed at a mass ratio of EC: DEC: EMC =1 6 ) To a molar concentration of 1mol/L.
4) Preparation of lithium ion cell
And assembling the prepared positive plate and the prepared negative plate into a laminated soft package battery cell.
5) Liquid injection and formation of battery core
And (3) in a glove box with the dew point controlled below-40 ℃, injecting the prepared electrolyte into the battery cell, carrying out vacuum packaging, and standing for 72h. Then, carrying out primary constant current charging according to the following steps: charging the lithium ion battery at a multiplying power of 0.03 to 0.1C, stopping charging when the potential reaches 3.0 to 3.5V, and then aging the lithium ion battery at a temperature of 30 to 50 ℃ for 5 to 30min; and continuously charging the lithium ion battery at a rate of 0.1-0.3C for formation, stopping charging when the formation potential reaches 3.5-3.9V, then aging the lithium ion battery at a temperature of 30-50 ℃ for 30-60min, and continuously charging the lithium ion battery at a rate of 0.3-0.5C for formation until the SOC reaches 100 percent, so as to form an interface film rich in LiF on the surface of the negative electrode material layer.
The composition of the interfacial film on the surface of the negative electrode active material layer was tested using an X-ray photoelectron spectroscopy (XPS) apparatus. The method comprises the steps of disassembling a battery in a glove box with the dew point controlled below-40 ℃, taking out a negative plate, cleaning the surface of the negative plate by DMC, putting the negative plate into a glove box transition bin, vacuumizing (-0.1 MPa) for storage for 72h to ensure that no electrolyte residue exists in the plate, cutting the negative plate into blocks of 1cm X1cm by scissors, sticking the blocks on a conductive adhesive of an aluminum sample table by using tweezers, transferring the sample to an inert test chamber of XPS equipment in a vacuum environment, testing the components of an interface film according to an ESCLAB 250X-ray photoelectron spectrometer operation instruction to obtain an X-ray photoelectron spectroscopy detection map as shown in figure 1, wherein when a peak of 1s of carbon is obtained at 284.5eV, a characteristic peak of LiF appears in a region of 682-687 eV, and the interface film contains LiF.
The thickness of the LiF rich interfacial film was measured and filled in table 1, as follows: the thickness of the interfacial film containing LiF on the surface of the anode active material layer was tested using a Transmission Electron Microscope (TEM). The method comprises the steps of disassembling a battery in a glove box with the dew point controlled below-40 ℃, taking out a negative plate, cleaning the surface of the negative plate by DMC, then placing the negative plate in a glove box transition bin, vacuumizing (-0.1 MPa) for storage for 72h to ensure that no electrolyte remains in the plate, cutting the negative plate into blocks of 1cm x 1cm by scissors, then pasting the blocks on a conductive adhesive of an aluminum sample table by tweezers, transferring the sample to an inert test chamber of TEM equipment in a vacuum environment, and then testing the thickness of an interface film containing LiF according to the FEI Tecnai G2F 30 transmission electron microscope operation instruction.
Examples 2 to 25
Examples 2 to 25 are used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operation steps in example 1, except that:
the positive electrode active material, the negative electrode active material, the interfacial film thickness of the surface of the negative electrode material layer, and the additives and the mass percentage content of the nonaqueous electrolytic solution used in examples 2 to 25 are shown in table 1, and the formation conditions used for the first constant current charging formation in each example are also different.
Comparative examples 1 to 18
Comparative examples 1 to 18 are used for comparative explanation of the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operation steps in example 1, except that:
the positive electrode active material, the negative electrode active material, the interfacial film thickness of the surface of the negative electrode material layer, and the additive and the mass percentage content of the nonaqueous electrolytic solution used in comparative examples 1 to 18 are shown in table 1, and the formation conditions used for the first constant current charging formation in each comparative example are also different.
By using a nonaqueous electrolytic solution to which FEC is added at a predetermined ratio and adjusting the current level, formation temperature, formation time, and the like used in the formation of the battery, an interface film having a predetermined thickness is formed on the surface of the negative electrode material layer.
Performance testing
The lithium ion battery prepared above was subjected to the following performance tests:
1. high-temperature cycle performance test:
the lithium ion batteries prepared in examples and comparative examples were charged at 1C rate, discharged at 1C rate, recorded for initial capacity, and full charge discharge cycle test was performed within the charge and discharge cut-off voltage range until the capacity of the lithium ion battery decayed to 80% of the initial capacity, and the number of cycles was recorded.
2. And (3) testing the weight loss rate of the negative plate:
discharging the battery at 0.2C to the lower limit and cutting to 3.0V, then disassembling and taking out the negative plate, then cutting the negative plate into a wafer with the diameter of 14 +/-0.2 mm, weighing the weight (m 1) of the wafer, and placing the wafer at the temperature of 60 ℃ for standing for 72h. After the standing, the wafer was taken out, and after the wafer was cooled to room temperature, the weight (m 2) of the wafer was measured. The weight loss rate of the negative plate is calculated by the following formula:
the weight loss ratio of the negative electrode sheet = (m 1-m 2)/m 1 × 100%.
(1) The test results obtained in examples 1 to 17 and comparative examples 1 and 5 to 16 are filled in Table 2.
TABLE 2
From the test results of examples 1 to 17 and comparative examples 1, 5 to 16, it can be seen that in a battery system using FEC as an electrolyte additive, by controlling formation conditions and FEC content, an interface film rich in LiF is formed on the surface of a negative electrode material layer of a non-aqueous electrolyte, and adjusting a porosity n of the negative electrode material layer, a thickness p of the interface film on the surface of the negative electrode material layer, and a mass percentage content m of FEC in the non-aqueous electrolyte to satisfy the conditions that n/p + m is greater than or equal to 0.3 and less than or equal to 25, n is greater than or equal to 10 and less than or equal to 40, p is greater than or equal to 5 and less than or equal to 150, and m is greater than or equal to 20, the obtained lithium ion battery has a higher energy density, and a cycle life under a high temperature condition is prolonged, which indicates that the FEC content in the non-aqueous electrolyte has an influence on material affinity of the negative electrode material layer, and the adjustment of the porosity n of the negative electrode material layer affects the infiltration degree of the non-aqueous electrolyte to the negative electrode material layer, so that a suitable non-aqueous electrolyte is retained in the negative electrode material layer, and the interface film-containing lithium ion battery has improved interface film volume stability under a high temperature condition, and the interface film containing lithium ion battery has improved interface film stability.
From the test results of examples 1 to 7, it can be seen that as the value of n/p + m increases, the initial capacity and the high-temperature cycle performance of the lithium ion secondary battery increase first and then decrease, which indicates that the porosity of the negative electrode material layer, the thickness of the LiF-containing interface film, and the FEC content are related to the electrochemical performance of the lithium ion secondary battery, and in particular, when n/p + m is greater than or equal to 0.5 and less than or equal to 10, the lithium ion secondary battery has the best initial capacity and high-temperature cycle performance.
From the test results of comparative examples 5 to 10, it can be seen that even if the porosity n of the negative electrode material layer, the thickness p of the interfacial film on the surface of the negative electrode material layer, and the mass percentage content m of the FEC in the nonaqueous electrolyte satisfy the condition that n/p + m is not less than 25 and n, p, or m does not satisfy the range limitation, the lithium ion battery still has good initial capacity exertion and high-temperature cycle performance, which indicates that the n, p, or m has a strong relationship in improving the energy density and high-temperature performance of the lithium ion battery. Similarly, it is understood from comparative examples 11 to 16 that when n, p, or m satisfy the range limits, but n/p + m does not satisfy the predetermined conditions, the battery performance is deteriorated and the weight loss ratio of the negative electrode sheet is unbalanced.
From the test results of examples 8 to 17 and comparative examples 7 to 12, it can be seen that lithium ion batteries with excellent initial capacity and high-temperature cycle life can be obtained for different types of positive electrode active materials when the positive electrode active materials meet the conditions defined in the present invention.
(2) The test results obtained in examples 1, 18 to 22 and comparative examples 6 to 7 and 9 are shown in Table 3.
TABLE 3
From the test results of example 1 and comparative examples 6 to 7 and 9, it is known that silicon oxide is added to a negative electrode active material of graphite to prepare a silicon-based material, and it is found that the silicon-based negative electrode can improve the energy density of the battery but deteriorate the cycle performance of the battery to some extent compared with a carbon-based negative electrode material. From examples 18 to 22 and comparative examples 6 to 7 and 9, it can be seen that when the parameters n, p and m satisfy the predetermined relationship of 0.3. Ltoreq. N/p + m. Ltoreq.25, the weight loss ratio of the negative electrode sheet is within the range of 1 to 30%, and the battery can still have high energy density and long cycle life, which indicates that the battery system provided by the invention can reduce the influence of the silicon-based negative electrode material on the cycle life of the battery to a certain extent.
(3) The test results obtained in example 1 and comparative examples 2 to 4 are filled in Table 4.
TABLE 4
As is clear from the test results of example 1 and comparative examples 2 to 4, liNi was used 0.5 Co 0.2 Mn 0.3 O 2 And graphite as positive and negative active materials, respectively, and additive VC (ethylene carbonate) is used in the electrolyte solution although the porosity of the negative material layer and the thickness of the interfacial film containing LiF satisfy the requirementsWhen the FEC is replaced by ester), DTD (vinyl sulfate) or TMSB (tris (trimethylsilyl) borate), the improvement degree of the battery is far less than that of the FEC added into the electrolyte, which shows that the relational expression provided by the invention is not suitable for other additives except the FEC, and the FEC is more favorable for the film forming reaction on the surface of the negative electrode material, and the formed interface film is firmer and more stable, so that the protection effect on the negative electrode material is better, and the cycle improvement degree of the battery is larger.
(4) The test results obtained in example 1 and examples 23 to 25 are shown in Table 5.
TABLE 5
From the test results of example 1 and examples 23 to 25, it is assumed that when an additive VC (vinylene carbonate), DTD (vinyl sulfate), or TMSB (tris (trimethylsilyl) borate) is additionally added to the non-aqueous electrolyte containing FEC in the battery system provided by the present invention, the cycle performance and the initial capacity performance of the battery can be further improved, and it is assumed that a passivation film with more excellent stability is obtained because FEC and the additive participate in the molding of the passivation film on the surface of the negative electrode active material, and further, the reaction of the electrolyte on the surface of the electrode is effectively reduced, and the electrochemical performance of the battery is improved. More preferably, among the above additives, it can be seen that the cycle performance of the battery is most remarkably improved when the TMSB additive is compounded with FEC in the electrolyte.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A lithium ion battery is characterized by comprising a positive plate, a negative plate and a nonaqueous electrolyte, wherein the nonaqueous electrolyte comprises a nonaqueous organic solvent, a lithium salt and an additive, and the additive comprises FEC;
the negative plate comprises a negative electrode material layer and an interface film formed by the non-aqueous electrolyte on the surface of the negative electrode material layer, and when a 1s peak of carbon is obtained at 284.5eV, a characteristic peak of LiF appears in a region from 682 to 687 eV through detection of the negative plate by an X-ray photoelectron spectroscopy;
the lithium ion battery meets the following conditions:
n/p + m is more than or equal to 0.3 and less than or equal to 25, n is more than or equal to 10 and less than or equal to 40, p is more than or equal to 5 and less than or equal to 150, m is more than or equal to 0.01 and less than or equal to 20;
wherein n is the porosity of the negative electrode material layer and has a unit of percent;
p is the thickness of the interfacial film on the surface of the negative electrode material layer, and the unit is nm;
m is the mass percentage content of FEC in the non-aqueous electrolyte, and the unit is%;
the negative plate is placed in an environment at 60 ℃ for 72 hours, and has a weight loss ratio of 1-30%.
2. The lithium ion battery of claim 1, wherein the lithium ion battery satisfies the following condition:
0.5≤n/p+m≤10。
3. the lithium ion battery of claim 1, wherein the porosity n of the negative electrode material layer is 15% to 30%.
4. The lithium ion battery of claim 1, wherein the thickness p of the interfacial film on the surface of the negative electrode material layer is 10nm to 100nm.
5. The lithium ion battery of claim 1, wherein the content m of the FEC in the non-aqueous electrolyte is 0.1% to 10% by mass.
6. The lithium ion battery of claim 1, wherein the lithium salt is selected from LiPF 6 、LiBOB、LiDFOB、LiPO 2 F 2 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 F) 2 、LiClO 4 、LiAlCl 4 、LiCF 3 SO 3 、Li 2 B 10 Cl 10 、LiSO 3 F. At least one of LiTOP (lithium Trioxalato phosphate), liDODFP (lithium difluorooxalato phosphate), liOTFP (lithium tetrafluorooxalato phosphate), and a lower aliphatic carboxylic acid lithium salt.
7. The lithium ion battery of claim 1, wherein the non-aqueous organic solvent comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, gamma-butyrolactone, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, fluoroethyl acetate, and fluoroether.
8. The lithium ion battery of claim 1, wherein the additive further comprises at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a nitrile-based compound;
the additive is added in an amount of 0.01-30% based on 100% of the total mass of the nonaqueous electrolyte.
9. The lithium ion battery according to claim 8, the cyclic sulfate compound is selected from vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
At least one of;
the sultone compound is selected from 1, 3-propane sultone and 14-butane sultone, 1, 3-propene sultone,
At least one of;
the cyclic carbonate compound is at least one selected from vinylene carbonate, ethylene carbonate, methylene ethylene carbonate or a compound shown in a structural formula 1;
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom and C1-C5 group;
the phosphate compound is at least one of tris (trimethylsilane) phosphate, tris (trimethylsilane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, unsaturated hydrocarbon group, halogenated hydrocarbon group, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
the borate compound is at least one selected from tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, nonanedionitrile and decanedionitrile.
10. The lithium ion battery of claim 1, wherein the negative electrode material layer comprises a negative electrode active material selected from at least one of a silicon-based negative electrode, a carbon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211432760.0A CN115498268A (en) | 2022-11-16 | 2022-11-16 | Lithium ion battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211432760.0A CN115498268A (en) | 2022-11-16 | 2022-11-16 | Lithium ion battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115498268A true CN115498268A (en) | 2022-12-20 |
Family
ID=85115832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211432760.0A Pending CN115498268A (en) | 2022-11-16 | 2022-11-16 | Lithium ion battery |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115498268A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116454393A (en) * | 2023-06-16 | 2023-07-18 | 蔚来电池科技(安徽)有限公司 | Secondary battery and device |
| CN117175015A (en) * | 2023-11-02 | 2023-12-05 | 深圳新宙邦科技股份有限公司 | Nonaqueous electrolyte and battery |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008103148A (en) * | 2006-10-18 | 2008-05-01 | Sony Corp | Negative electrode and battery |
| CN103378349A (en) * | 2012-04-30 | 2013-10-30 | 三星Sdi株式会社 | Negative electrode, rechargeable lithium battery including same and method of preparing rechargeable lithium battery |
| WO2017126337A1 (en) * | 2016-01-22 | 2017-07-27 | Ｊｆｅケミカル株式会社 | Negative-electrode material for li-ion secondary cell, method for manufacturing said material, li-ion-secondary-cell negative electrode, and li-ion secondary cell |
| CN110190253A (en) * | 2019-05-10 | 2019-08-30 | 华南理工大学 | A kind of high-voltage lithium ion batteries |
| CN115117347A (en) * | 2022-06-20 | 2022-09-27 | 深圳新宙邦科技股份有限公司 | Negative plate and secondary battery |
| CN115189029A (en) * | 2022-09-13 | 2022-10-14 | 深圳新宙邦科技股份有限公司 | Lithium ion battery |
-
2022
- 2022-11-16 CN CN202211432760.0A patent/CN115498268A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008103148A (en) * | 2006-10-18 | 2008-05-01 | Sony Corp | Negative electrode and battery |
| CN103378349A (en) * | 2012-04-30 | 2013-10-30 | 三星Sdi株式会社 | Negative electrode, rechargeable lithium battery including same and method of preparing rechargeable lithium battery |
| WO2017126337A1 (en) * | 2016-01-22 | 2017-07-27 | Ｊｆｅケミカル株式会社 | Negative-electrode material for li-ion secondary cell, method for manufacturing said material, li-ion-secondary-cell negative electrode, and li-ion secondary cell |
| CN110190253A (en) * | 2019-05-10 | 2019-08-30 | 华南理工大学 | A kind of high-voltage lithium ion batteries |
| CN115117347A (en) * | 2022-06-20 | 2022-09-27 | 深圳新宙邦科技股份有限公司 | Negative plate and secondary battery |
| CN115189029A (en) * | 2022-09-13 | 2022-10-14 | 深圳新宙邦科技股份有限公司 | Lithium ion battery |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116454393A (en) * | 2023-06-16 | 2023-07-18 | 蔚来电池科技(安徽)有限公司 | Secondary battery and device |
| CN116454393B (en) * | 2023-06-16 | 2023-09-05 | 蔚来电池科技(安徽)有限公司 | Secondary battery and device |
| CN117175015A (en) * | 2023-11-02 | 2023-12-05 | 深圳新宙邦科技股份有限公司 | Nonaqueous electrolyte and battery |
| CN117175015B (en) * | 2023-11-02 | 2024-04-05 | 深圳新宙邦科技股份有限公司 | Nonaqueous electrolyte and battery |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN114068936B (en) | Lithium ion battery | |
| CN108428940A (en) | Electrolyte for lithium secondary battery and the lithium secondary battery including it | |
| CN114024028A (en) | Secondary battery | |
| CN114639872B (en) | Lithium ion battery | |
| CN114094109A (en) | Lithium ion battery | |
| CN115498268A (en) | Lithium ion battery | |
| CN113972366A (en) | Secondary battery positive plate and secondary battery | |
| CN115020813B (en) | Lithium ion battery | |
| CN115117452B (en) | Lithium ion battery | |
| WO2023246554A1 (en) | Negative electrode sheet and secondary battery | |
| CN114447295A (en) | Lithium ion battery | |
| CN115064770B (en) | Lithium ion battery | |
| CN115020815B (en) | Lithium ion battery | |
| CN114497692A (en) | Secondary battery | |
| CN115189029B (en) | Lithium ion battery | |
| CN115036572A (en) | Lithium secondary battery | |
| CN116435595A (en) | Lithium ion battery | |
| CN114373980B (en) | Secondary battery | |
| CN115692825A (en) | Lithium ion battery | |
| CN116093428A (en) | Lithium ion battery | |
| CN114975873A (en) | Positive plate and lithium ion battery | |
| EP4239745A1 (en) | Lithium ion battery | |
| CN115882043A (en) | Lithium ion battery | |
| CN117096440A (en) | Lithium ion battery | |
| CN116404253A (en) | Lithium ion battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |