CN115799636B - Lithium secondary battery electrolyte, lithium secondary battery and electric equipment - Google Patents
Lithium secondary battery electrolyte, lithium secondary battery and electric equipment Download PDFInfo
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Abstract
The application provides lithium secondary battery electrolyte, a lithium secondary battery and electric equipment, and belongs to the field of lithium secondary battery manufacturing. The additive in the lithium secondary battery electrolyte comprises tetra cyano alkoxy aliphatic linear alkane with the structural formula as shown in the formula I and/or the formula II and tri (trimethylsilane) borate and/or tri (trimethylsilane) phosphite, and the electrolyte can solve the problem that the electrolyte causes poor multiplying power performance, cycle performance, storage performance and the like of the battery at high temperature and high pressure to a certain extent.
Description
Technical Field
The application relates to the field of manufacturing of lithium secondary batteries, in particular to lithium secondary battery electrolyte, a lithium secondary battery and electric equipment.
Background
In the prior art, the electrolyte is taken as an important component of the battery, the performance of the electrolyte determines the performance of the battery, and the electrolyte of the prior component has better comprehensive electrical performance at low temperature, but the battery using the prior electrolyte component has the problem of poor multiplying power performance, cycle performance, storage performance and the like at high temperature and high pressure.
Disclosure of Invention
The application aims to provide lithium secondary battery electrolyte, a lithium secondary battery and electric equipment, which can solve the problem that the electrolyte causes poor multiplying power performance, cycle performance, storage performance and the like of the battery at high temperature and high pressure to a certain extent.
Embodiments of the present application are implemented as follows:
in a first aspect, an embodiment of the present application provides a lithium secondary battery electrolyte, wherein an additive in the lithium secondary battery electrolyte includes: tetracyanoalkoxy aliphatic linear alkanes having the structural formula I and/or II; and tris (trimethylsilyl) borate and/or tris (trimethylsilyl) phosphite;
formula I is shown below:
formula II is shown below:
in the technical scheme, on one hand: the tetracyanoalkoxy aliphatic linear alkane with the structure has higher oxidation potential, is not easy to oxidize at high temperature and high pressure, and has a cyano group with stronger complexing capability, and can coordinate with lithium ions so as to reduce desolvation energy of a battery, thereby improving the rate performance of the battery; meanwhile, the compound has a relatively high elastic ether bond, and can effectively cope with the stress change caused by the expansion of the electrode in the charge and discharge process of the cathode, thereby being beneficial to improving the rate capability of the battery; in addition, oxygen atoms in the alkoxy groups are easy to combine with lithium ions, so that the enrichment degree of the lithium ions on the surface of the positive electrode can be improved, and the impedance of the battery can be effectively reduced. On the other hand, the oxidation potential of the tri (trimethylsilane) borate and the tri (trimethylsilane) phosphite is lower, and silicon-containing clusters are easily lost at the interface of the positive electrode to form a CEI film, so that the damage to the positive electrode structure caused by the intercalation and deintercalation of lithium ions can be effectively reduced, and the reaction between the positive electrode and other materials can be reduced, thereby improving the cycle performance of the battery at high temperature and high pressure; meanwhile, the silicon-containing groups can also effectively remove hydrofluoric acid (generated by decomposition of the electrolyte) in the electrolyte, thereby playing a role in protecting the electrode and being beneficial to improving the cycle performance of the battery; in addition, the boron atoms and the phosphorus atoms in the tri (trimethylsilane) borate and the tri (trimethylsilane) phosphite can also adsorb active oxygen, so that the excessive oxidative decomposition of the electrolyte can be effectively avoided, and the storage performance of the battery is further improved. Through the combined action of the two components, the stability of the battery under high temperature and high pressure conditions can be obviously improved, so that the rate performance, the cycle performance and the storage performance of the battery are obviously improved.
In some alternative embodiments, the mass percent of the additive in the electrolyte of the lithium secondary battery is 0.6 to 7%.
In the technical scheme, the mass percent of the additive is limited in a specific range, so that the electrolyte has the additive with proper dosage, and the battery using the electrolyte has better multiplying power performance, cycle performance and storage performance at high temperature.
In some alternative embodiments, the lithium secondary battery electrolyte has a tetracyanoalkoxy aliphatic linear alkane of 0.5-4% by mass and a tris (trimethylsilane) borate and/or tris (trimethylsilane) phosphite of 0.1-3% by mass.
In the technical scheme, the mass percentage of the tetra cyano alkoxy aliphatic linear alkane in the electrolyte is limited in a specific range, so that the tetra cyano alkoxy aliphatic linear alkane with proper dosage in the electrolyte can be avoided, the excessive dosage (the excessive dosage can cause the excessive impedance of the electrolyte), the electrolyte has the impedance with proper size, and meanwhile, the excessive dosage (the excessive dosage can not effectively improve the multiplying power performance of the battery) can be effectively avoided, and the multiplying power performance of the battery is effectively improved; the mass percent of the borate in the electrolyte is limited in a specific range, so that the borate with proper dosage in the electrolyte can be avoided, the excessive dosage (the excessive dosage can cause the excessive impedance of the electrolyte) can be avoided, the electrolyte has the impedance with proper size, and meanwhile, the excessive dosage (the excessive dosage can not effectively improve the cycle performance and the storage performance of the battery) can be effectively avoided, so that the cycle performance and the storage performance of the battery are effectively improved.
In some alternative embodiments, the organic solvent in the lithium secondary battery electrolyte includes at least one of a cyclic carbonate, a chain carbonate, and a carboxylate.
The additive provided by the embodiment of the application is suitable for various organic solvent systems, and can provide more practical embodiments, so that the additive provided by the embodiment of the application is convenient to popularize and apply.
In some alternative embodiments, the lithium secondary battery electrolyte satisfies at least one of the following conditions a-C:
the cyclic carbonate comprises at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate;
b, the chain carbonic ester comprises at least one of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate;
and C, carboxylic acid esters comprise at least one of propyl acetate, ethyl acetate and propyl propionate.
The additive provided by the embodiment of the application is suitable for the cyclic carbonate system, the chain carbonate system and the carboxylate system, and can provide more practical embodiments, thereby being convenient for popularization and application of the additive provided by the embodiment of the application.
In some alternative embodiments, the lithium salt in the lithium secondary battery electrolyte comprises LiPF 6 、LiBF 4 、LiB(C 2 O 4 ) 2 、LiBF 2 C 2 O 4 、LiN(SO 2 F) 2 And LiN (SO) 2 CF 3 ) 2 At least one of them.
The additive provided by the embodiment of the application is suitable for various lithium salt systems, and can provide more practical embodiments, so that the additive provided by the embodiment of the application is convenient to popularize and apply.
In some alternative embodiments, the mass percentage of lithium salt in the lithium secondary battery electrolyte is 0.5 to 20%.
In the technical scheme, the mass percentage of the lithium salt in the electrolyte of the lithium secondary battery is limited in a specific range, so that the electrolyte has the lithium salt with proper dosage, and the battery can be ensured to have better comprehensive electrical performance.
In a second aspect, embodiments of the present application provide a lithium secondary battery comprising a case, an electrode assembly, and a lithium secondary battery electrolyte as provided in the embodiments of the first aspect. The electrode assembly is accommodated in the case; the lithium secondary battery electrolyte is contained in the case.
In the above technical solution, the lithium secondary battery includes the lithium secondary battery electrolyte provided in the embodiment of the first aspect, so that the lithium secondary battery has better storage and cycle performance at high temperature and high pressure.
In some alternative embodiments, the positive electrode active material in the electrode assembly includes LiNi x Co y Mn z O 2 Wherein x+y+z=1.
In the above technical scheme, the positive electrode active material is limited to the system, because the positive electrode active material of the system has the excellent performances of a plurality of metal materials, and has more excellent electrical performances compared with the positive electrode active material of a single system.
In a third aspect, an embodiment of the present application provides an electric device, where the electric device includes a lithium secondary battery as provided in the embodiment of the second aspect.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In the present application, "and/or" such as "feature 1 and/or feature 2" means that "feature 1" alone, and "feature 2" alone, and "feature 1" plus "feature 2" alone, are all possible.
In addition, in the description of the present application, unless otherwise indicated, "one or more" means "a plurality of" means two or more; the range of "value a to value b" includes both ends "a" and "b", and "unit of measure" in "value a to value b+ unit of measure" represents "unit of measure" of both "value a" and "value b".
The lithium secondary battery electrolyte, the lithium secondary battery and the electric equipment according to the embodiment of the application are specifically described below.
In a first aspect, an embodiment of the present application provides a lithium secondary battery electrolyte, wherein an additive in the lithium secondary battery electrolyte includes: tetracyanoalkoxy aliphatic linear alkanes having the structural formula I and/or II; and tris (trimethylsilyl) borate and/or tris (trimethylsilyl) phosphite;
formula I is shown below:
formula II is shown below:
the electrolyte provided by the embodiment of the application can be prepared according to a conventional composition except for the additive. As an example, the electrolyte may include, in addition to additives, for example, but not limited to, organic solvents and lithium salts.
In the application, on one hand: the tetracyanoalkoxy aliphatic linear alkane with the structure has higher oxidation potential, is not easy to oxidize at high temperature and high pressure, and has a cyano group with stronger complexing capability, and can coordinate with lithium ions so as to reduce desolvation energy of a battery, thereby improving the rate performance of the battery; meanwhile, the compound has a relatively high elastic ether bond, and can effectively cope with the stress change caused by the expansion of the electrode in the charge and discharge process of the cathode, thereby being beneficial to improving the rate capability of the battery; in addition, oxygen atoms in the alkoxy groups are easy to combine with lithium ions, so that the enrichment degree of the lithium ions on the surface of the positive electrode can be improved, and the impedance of the battery can be effectively reduced. On the other hand, the oxidation potential of the tri (trimethylsilane) borate and the tri (trimethylsilane) phosphite is lower, and silicon-containing clusters are easily lost at the interface of the positive electrode to form a CEI film, so that the damage to the positive electrode structure caused by the intercalation and deintercalation of lithium ions can be effectively reduced, and the reaction between the positive electrode and other materials can be reduced, thereby improving the cycle performance of the battery at high temperature and high pressure; meanwhile, the silicon-containing groups can also effectively remove hydrofluoric acid (generated by decomposition of the electrolyte) in the electrolyte, thereby playing a role in protecting the electrode and being beneficial to improving the cycle performance of the battery; in addition, the boron atoms and the phosphorus atoms in the tri (trimethylsilane) borate and the tri (trimethylsilane) phosphite can also adsorb active oxygen, so that the excessive oxidative decomposition of the electrolyte can be effectively avoided, and the storage performance of the battery is further improved. Through the combined action of the two components, the stability of the battery under high temperature and high pressure conditions can be obviously improved, so that the rate performance, the cycle performance and the storage performance of the battery are obviously improved.
It is understood that the electrical properties of the electrolyte are related to the amount of additives, and that the amount of additives in the electrolyte may be defined in consideration of the electrical properties of the electrolyte.
As an example, the mass percentage of the additive in the lithium secondary battery electrolyte is 0.6 to 7%, such as, but not limited to, any one point value or a range value between any two of 0.6%, 1%, 2%, 3%, 4%, 5%, 6% and 7% by mass.
In the embodiment, the mass percent of the additive is limited to a specific range, so that the electrolyte can be provided with the additive with proper dosage, and the battery using the electrolyte has better rate performance, cycle performance and storage performance at high temperature and high temperature.
It is understood that the amounts of the different types of additives may be respectively defined in consideration of the overall electrical properties of the battery due to the technical effects corresponding to the different types of additives.
As an example, in the lithium secondary battery electrolyte, the mass percentage of the tetracyanoalkoxy aliphatic linear alkane is 0.5-4%, such as, but not limited to, any one point value or a range value between any two of 0.5%, 1%, 2%, 3% and 4% by mass; the mass percent of the tris (trimethylsilyl) borate and/or tris (trimethylsilyl) phosphite is 0.1-3%, such as, but not limited to, any one point value or range value between any two of 0.1%, 0.5%, 1%, 2% and 3% by mass.
In the embodiment, the mass percentage of the tetra cyano alkoxy aliphatic linear alkane in the electrolyte is limited in a specific range, so that the tetra cyano alkoxy aliphatic linear alkane with proper dosage in the electrolyte can be avoided, the excessive dosage (the excessive dosage can cause the excessive impedance of the electrolyte), the electrolyte with proper impedance can be avoided, and meanwhile, the excessive dosage (the excessive dosage can not effectively improve the multiplying power performance of the battery) can be effectively avoided, so that the multiplying power performance of the battery can be effectively improved; the mass percent of the borate in the electrolyte is limited in a specific range, so that the borate with proper dosage in the electrolyte can be avoided, the excessive dosage (the excessive dosage can cause the excessive impedance of the electrolyte) can be avoided, the electrolyte has the impedance with proper size, and meanwhile, the excessive dosage (the excessive dosage can not effectively improve the cycle performance and the storage performance of the battery) can be effectively avoided, so that the cycle performance and the storage performance of the battery are effectively improved.
It should be noted that the type of the organic solvent in the electrolyte is not limited, and may be adjusted according to actual needs.
As one example, the organic solvent in the lithium secondary battery electrolyte includes at least one of cyclic carbonate, chain carbonate, and carboxylate.
In this embodiment, the additive provided by the embodiment of the present application is suitable for the above-mentioned various organic solvent systems, and can provide more possible embodiments, so that the popularization and application of the additive provided by the embodiment of the present application are facilitated.
It should be noted that the type of each organic solvent is not particularly limited, and may be adjusted according to actual needs.
As one example, the lithium secondary battery electrolyte satisfies at least one of the following conditions a to C:
the cyclic carbonate includes at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate.
And B, the chain carbonic ester comprises at least one of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.
And C, carboxylic acid esters comprise at least one of propyl acetate, ethyl acetate and propyl propionate.
In this embodiment, the additive provided in the present embodiment is suitable for the above-mentioned various cyclic carbonate systems, chain carbonate systems and carboxylate systems, and can provide more possible embodiments, so that the popularization and application of the additive provided in the present embodiment are facilitated.
It should be noted that the type of lithium salt in the electrolyte is not limited, and may be adjusted according to actual needs.
As an example, the lithium salt in the electrolyte of the lithium secondary battery includes LiPF 6 、LiBF 4 、LiB(C 2 O 4 ) 2 、LiBF 2 C 2 O 4 、LiN(SO 2 F) 2 And LiN (SO) 2 CF 3 ) 2 At least one of them.
In this embodiment, the additive provided by the embodiment of the present application is suitable for the above-mentioned various lithium salt systems, and can provide more possible embodiments, so that the popularization and application of the additive provided by the embodiment of the present application are facilitated.
It is understood that the electrical properties of the electrolyte are related to the amount of lithium salt, and that the amount of lithium salt in the electrolyte may be defined in consideration of the electrical properties of the electrolyte.
As an example, the mass percentage of lithium salt in the lithium secondary battery electrolyte is 0.5 to 20%, such as, but not limited to, any one point value or a range value between any two of 0.5%, 1%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% and 20% by mass.
In the embodiment, the mass percentage of the lithium salt in the electrolyte of the lithium secondary battery is limited to a specific range, so that the electrolyte has a proper amount of the lithium salt, and the battery can be ensured to have better comprehensive electrical performance.
In a second aspect, embodiments of the present application provide a lithium secondary battery comprising a case, an electrode assembly, and a lithium secondary battery electrolyte as provided in the embodiments of the first aspect. The electrode assembly is accommodated in the case; the lithium secondary battery electrolyte is contained in the case.
In the application, the lithium secondary battery comprises the lithium secondary battery electrolyte provided by the embodiment of the first aspect, so that the lithium secondary battery has better storage and cycle performance at high temperature and high pressure.
It should be noted that the electrode assembly is also called as a battery cell and comprises a positive electrode plate, an isolating film and a negative electrode plate which are sequentially arranged.
Note that the kind of the positive electrode active material in the electrode assembly is not limited, and may be adjusted according to actual needs.
As one example, in the electrode assembly, the positive electrode active material includes LiNi x Co y Mn z O 2 Wherein x+y+z=1.
In this embodiment, the positive electrode active material is limited to the above-described system because the positive electrode active material of the system has excellent properties of a plurality of metal materials, and has more excellent electrical properties than the positive electrode active material of a single system.
The configuration of the lithium secondary battery, which is not specifically described, may be selected and set according to the conventional manner in the art.
In a third aspect, an embodiment of the present application provides an electric device, where the electric device includes a lithium secondary battery as provided in the embodiment of the second aspect.
It should be noted that the type of the electric equipment is not limited, and is, for example, a mobile phone, a portable device, a notebook computer, a battery car, an electric automobile, a ship, a spacecraft, an electric toy, an energy storage device, an electric tool, and the like.
The features and capabilities of the present application are described in further detail below in connection with the examples.
Example 1
The embodiment of the application provides a preparation method of battery electrolyte, which comprises the following steps:
mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) according to a mass ratio of 3:2:5 to obtain a mixed organic solvent; then, lithium hexafluorophosphate (LiPF) was added to the mixed organic solvent 6 ) Tris (trimethylsilane) borate (TMSB for short) and a compound of formula I (BTTN); wherein, the organic solvent and the LiPF are mixed 6 The mass percentage of TMSB and BTTN is 88.5:10:0.5:1.
example 2
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the BTTN content of the electrolyte was changed to 1% of the compound of formula II (CTTN).
Example 3
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: TMSB accounting for 0.5 percent of the electrolyte is replaced by tris (trimethylsilane) phosphite (TMSP for short) accounting for 0.5 percent of the electrolyte.
Example 4
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the BTTN content of the electrolyte was changed to 0.5% BTTN and 0.5% CTTN.
Example 5
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the electrolyte mass ratio is changed from 0.5% TMSB to 0.25% TMSB and 0.25% TMSP.
Example 6
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the electrolyte was replaced with 1% by mass of BTTN by 0.8% by mass of BTTN and 0.2% by mass of 1,2, 3-tris (2-cyanooxy) propane.
Example 7
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the electrolyte was replaced with 1% by mass of BTTN by 0.8% by mass of BTTN and 0.2% by mass of 1, 2-penta (2-cyanooxy) ethane.
Example 8
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: TMSB accounting for 0.5 percent of the electrolyte by mass is replaced by TMSB accounting for 0.25 percent and tributyl phosphate accounting for 0.25 percent.
Example 9
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: TMSB accounting for 0.5 percent of the electrolyte by mass is replaced by TMSB accounting for 0.25 percent and triethyl borate accounting for 0.25 percent.
Example 10
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the mass percent of BTTN is 4%, the mass percent of TMSB is 3%, and the mass percent change of the BTTN and the TMSB is regulated by the mass percent of the organic solvent.
Example 11
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the mass percent of BTTN is 0.5%, the mass percent of TMSB is 0.1%, and the mass percent change of the two is regulated by the mass percent of the organic solvent.
Example 12
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the mass percentage of BTTN is 5%, and the mass percentage change is adjusted by the mass percentage of the organic solvent.
Example 13
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the mass percentage of BTTN was 0.1%, and the mass percentage change was adjusted by the mass percentage of the organic solvent.
Example 14
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the TMSB has a mass percentage of 4%, and the mass percentage change is adjusted by the mass percentage of the organic solvent.
Example 15
The embodiment of the application provides a preparation method of a battery electrolyte, which is different from embodiment 1 only in that: the TMSB has a mass percentage of 0.05%, and the mass percentage change is adjusted by the mass percentage of the organic solvent.
Comparative example 1
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the electrolyte does not contain BTTN and TMSB, and the mass percent change of the BTTN and TMSB is adjusted by the mass percent of the organic solvent.
Comparative example 2
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the electrolyte does not contain BTTN, and the mass percent change is adjusted by the mass percent of the organic solvent.
Comparative example 3
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the electrolyte does not contain TMSB, and the mass percent change is adjusted by the mass percent of the organic solvent.
Comparative example 4
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the electrolyte does not contain TMSB, the BTTN accounting for 1% of the mass of the electrolyte is replaced by CTTN accounting for 1%, and the mass percentage change is regulated by the mass percentage of the organic solvent.
Comparative example 5
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the electrolyte does not contain BTTN, TMSB accounting for 0.5 percent of the mass of the electrolyte is replaced by TMSP accounting for 0.5 percent of the mass of the electrolyte, and the mass percent change is regulated by the mass percent of the organic solvent.
Comparative example 6
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: TMSB accounting for 0.5 percent of the electrolyte is replaced by tributyl phosphate accounting for 0.5 percent of the electrolyte.
Comparative example 7
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: TMSB accounting for 0.5 percent of the electrolyte is replaced by triethyl borate accounting for 0.5 percent of the electrolyte.
Comparative example 8
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: 1% of BTTN in the electrolyte is replaced by 1% of 1,2, 3-tri (2-cyanooxy) propane.
Comparative example 9
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: 1% of BTTN in the electrolyte is replaced by 1% of 1, 2-penta (2-cyanooxy) ethane.
Comparative example 10
The comparative example of the present application provides a method for preparing a battery electrolyte, which is different from example 1 only in that: the BTTN accounting for 1% of the electrolyte is replaced by 1% of tetra (2-cyanoethyl) methane.
To facilitate understanding of the components and ratios of the respective battery electrolytes, a concentrated arrangement was performed by the following table 1.
The amount of the organic solvent used was the balance excluding the contents shown in table 1 below.
Table 1 battery electrolyte composition tables of examples and comparative examples
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EC means abbreviation of ethylene carbonate, DEC means abbreviation of diethyl carbonate, and EMC means abbreviation of ethylmethyl carbonate.
Test example 1
Electrical property test
The testing method comprises the following steps:
the electrolytes prepared in examples 1 to 15 and comparative examples 1 to 10 were assembled into lithium secondary batteries, respectively, and numbered correspondingly, and then, the lithium secondary batteries were tested for capacity retention at 25 ℃ (2C/1C current density), 45 ℃ (2C/1C current density) for 1000 weeks, capacity retention at 60 ℃ for 15 days, capacity recovery and expansion, and rate performance (including rate discharge performance and rate charge performance), respectively.
Wherein, the liquid crystal display device comprises a liquid crystal display device,
the lithium secondary battery was assembled as follows:
s1, according to 97:1:1:1 mass ratio of LiNi 0.6 Co 0.1 Mn 0.3 O 2 (positive electrode active material), super P, carbon nano tube (conductive agent) and polyvinylidene fluoride (binder) are dispersed in N-methyl-2-pyrrolidone to obtain positive electrode slurry; the positive electrode slurry was then uniformly coated on both sides of an aluminum foil (coating amount 250g/m 2 ) Drying at 85 ℃ and then cold pressing; then trimming, cutting pieces and slitting, and drying at 85 ℃ for 4 hours under vacuum condition after slitting; and then welding the tab to prepare the positive plate.
S2, according to the proportion of 95:1.5:1:2.5, mixing graphite (anode active material), super P (conductive agent), CMC (thickener) and styrene butadiene rubber emulsion (binder) according to the mass ratio, and dispersing the mixture in deionized water to obtain anode slurry; then, coating the negative electrode slurry on two sides of the copper foil; then, drying, calendaring and vacuum drying are sequentially carried out, and an outgoing line made of nickel is welded by an ultrasonic welder, so that the negative plate is obtained.
And S3, sequentially stacking the prepared positive electrode sheet, the prepared diaphragm (PE ceramic coated diaphragm and the prepared negative electrode sheet with the thickness of 20 mu m) and the prepared negative electrode sheet, winding to prepare a bare cell, then injecting the bare cell, a shell and the battery electrolyte groups prepared in examples 1-15 and comparative examples 1-10 into a dried battery, and carrying out packaging, standing, formation, shaping and capacity testing to obtain the lithium secondary battery.
The test of the corresponding electrical parameters of the lithium secondary battery and the corresponding calculation formula are as follows:
capacity retention test of the cell at 25 ℃ cycle 1000 weeks: charging at 25deg.C under constant current of 2.0C to 4.5V, charging at constant voltage of 4.5V to cutoff current of 0.05C, discharging the battery with constant current of 1.0C, and recording the first discharge capacity as C 0 Repeating the charge and discharge for 1000 weeks to obtain discharge capacity C at 1000 weeks 1000 。
Capacity retention test of the battery at 45 ℃ cycle 1000 weeks: charging at 45deg.C with constant current of 2.0C to 4.5V, charging at constant voltage of 4.5V to cutoff current of 0.05C, discharging the battery with constant current of 1.0C, and recording the first discharge capacity as C 0 Repeating the charge and discharge for 1000 weeks to obtain discharge capacity C at 1000 weeks 1000 。
Thickness expansion rate, capacity retention rate and capacity recovery rate test of the battery stored at 60 ℃ for 15 days: the initial thickness and initial capacity of the battery were tested and recorded, charged to 4.5V at a constant current of 1.0C at 60℃, charged to 0.05C at a constant voltage of 4.5V, and then discharged at a constant current of 1.0C, then the battery was placed in an explosion-proof oven at 60℃, and after 15 days of storage, the battery was tested for thermal thickness in the oven, and then taken out and cooled to room temperature, and then its discharge holding capacity and recovery capacity discharged to 2.75V were tested using a current of 1C.
Testing the multiplying power performance of the battery: multiplying power discharge test, charging to 4.5V at 25deg.C constant current, charging to 0.05C constant voltage 4.5V, discharging the battery with 1.0C constant current, and recording the first discharge capacity as C 0 Then repeating the above charging steps, discharging to 2.75V with constant current of 4.0C, and discharging to C for the second time 2 The method comprises the steps of carrying out a first treatment on the surface of the Multiplying power charge test, charging to 4.5V at 25deg.C constant current of 1.0C, recording charge capacity as C 3 Then discharging to 2.75V at 1.0C constant current, then charging to 4.5V at 4.0C constant current, recording charge capacity as C 4 。
It should be noted that the process parameters and steps not involved in the testing process can be set according to conventional requirements in the art.
The calculation formula is as follows:
1000-cycle capacity retention (%) = (1000-th discharge retention capacity/1-th cycle discharge capacity) ×100%;
capacity recovery rate (%) =recovery capacity/initial capacity×100%;
storage capacity retention (%) =retention capacity/initial capacity×100%;
thickness expansion ratio (%) = (hot measured thickness-initial thickness)/initial thickness×100%;
rate charge capacity retention (%) = (4.0C charge capacity)/1.0C charge capacity×100%;
rate discharge capacity retention (%) = (4.0C discharge capacity)/1.0C discharge capacity×100%.
Table 2 battery performance test results of examples and comparative examples
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Referring to tables 1 and 2, it is understood from the test results of examples 1 to 5 and examples 6 to 9 that when BTTN/CTTN is used in combination with TMSB/TMSP, most of the rate performance, cycle performance and storage performance of the corresponding battery at high temperature and high pressure are better than when BTTN/CTTN and TMSB/TMSP are partially replaced with the same type of material.
From the test results of examples 1 to 5 and comparative examples 6 to 10, it is understood that when BTTN/CTTN and TMSB/TMSP are used in combination, most of the performance of the corresponding battery at high temperature and high pressure, cycle performance and storage performance are better than when BTTN/CTTN and TMSB/TMSP are replaced with the same type of material.
From the test results of examples 1 to 5 and comparative examples 1 to 5, it is understood that when BTTN/CTTN and TMSB/TMSP are used in combination, most of the rate performance, cycle performance and storage performance of the battery corresponding to the above are better at high temperature and high pressure than when BTTN/CTTN or TMSB/TMSP are used alone.
From the test results of examples 1 to 5 and examples 11 to 15, it is understood that when the amounts of BTTN/CTTN and TMSB/TMSP are within the range, most of the rate performance, cycle performance and storage performance of the corresponding battery at high temperature and high pressure are better than when the amounts of BTTN/CTTN and TMSB/TMSP are out of the range.
The embodiments described above are some, but not all embodiments of the application. The detailed description of the embodiments of the application is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Claims (8)
1. A lithium secondary battery electrolyte, characterized in that an additive in the lithium secondary battery electrolyte comprises: tetracyanoalkoxy aliphatic linear alkanes having the structural formula I and/or II; tris (trimethylsilyl) phosphite;
the formula I is shown as follows:
a formula I;
the formula II is shown as follows:
a formula II;
the mass percentage of the additive in the lithium secondary battery electrolyte is 0.6-7%;
in the lithium secondary battery electrolyte, the mass percentage of the tetra cyano alkoxy aliphatic linear alkane is 0.5-4%, and the mass percentage of the tri (trimethylsilane) phosphite is 0.1-3%.
2. The lithium secondary battery electrolyte according to claim 1, wherein the organic solvent in the lithium secondary battery electrolyte comprises at least one of a cyclic carbonate, a chain carbonate, and a carboxylic acid ester.
3. The lithium secondary battery electrolyte according to claim 2, wherein at least one of the following conditions a to C is satisfied:
a, the cyclic carbonate comprises at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate;
b, the chain carbonic ester comprises at least one of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate;
and C, the carboxylic acid ester comprises at least one of propyl acetate, ethyl acetate and propyl propionate.
4. The lithium secondary battery electrolyte according to claim 1, wherein the lithium salt in the lithium secondary battery electrolyte comprises LiPF 6 、LiBF 4 、LiB(C 2 O 4 ) 2 、LiBF 2 C 2 O 4 、LiN(SO 2 F) 2 And LiN (SO) 2 CF 3 ) 2 At least one of them.
5. The lithium secondary battery electrolyte according to claim 4, wherein the mass percentage of the lithium salt in the lithium secondary battery electrolyte is 0.5-20%.
6. A lithium secondary battery, characterized by comprising;
a housing;
an electrode assembly accommodated within the case; and
the lithium secondary battery electrolyte according to any one of claims 1 to 5, which is contained in the case.
7. The lithium secondary battery according to claim 6, wherein in the electrode assembly, the positive electrode active material includes LiNi x Co y Mn z O 2 Wherein x+y+z=1.
8. An electric device comprising the lithium secondary battery according to claim 6 or 7.
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