Lithium ion secondary battery and electric equipment

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a lithium ion secondary battery and electric equipment. The dinitrile and the trinitrile are matched with the compound A and the content is specially regulated and controlled, so that the high-temperature capacity fading of the high-voltage lithium ion battery can be effectively inhibited, and the first coulombic efficiency is improved. Specifically, the dinitrile and the trinitrile HTCN are matched for use, so that the dissolution of metal elements of the positive electrode can be improved; the compound A has specific reducing capacity and reaction activity in the electrolyte, so that a stable solid electrolyte interface can be formed on the surface of the negative electrode, a relatively good protection layer is formed, direct contact between the electrolyte and the negative electrode is effectively isolated, and further damage to the negative electrode is prevented; the capacity loss of the battery is effectively inhibited, and the first efficiency of the battery is improved.

Description

Technical Field

[0001] This application belongs to the technical field of secondary batteries, and particularly relates to a lithium-ion secondary battery and an electrical device. Background Art

[0002] With the wide application of energy storage products such as communication, household appliances, power tools, electric bicycles, electric vehicles, solar energy, and wind power generation, lithium-ion batteries, as a new type of green energy, have shown broad development prospects. Among them, the rapid development of the new energy vehicle industry, especially the rapid growth of the electric vehicle market, has put forward higher requirements for the performance of lithium batteries, including higher energy density, higher voltage, longer cycle life, and better safety performance, etc.

[0003] Among them, silicon anodes are regarded as one of the key materials to improve the energy density of lithium batteries due to their high theoretical specific capacity. However, silicon anodes will undergo significant volume expansion during charge and discharge, resulting in problems such as anode structure failure and reduced cycle life. In addition, under high voltage conditions (≥4.55V), the crystal structure of the cathode material is prone to phase transformation, resulting in cracks, fragmentation, and metal ion dissolution in the material. This structural damage will seriously affect the electrochemical performance of the cathode material, such as capacity decline and internal resistance increase, leading to cathode material failure and affecting the cycle performance.

[0004] These requirements have promoted the innovative research on key materials of lithium batteries. Among them, as an important component of lithium batteries, the optimization of the performance of the electrolyte has become a research hotspot. Summary of the Invention

[0005] Therefore, the technical problem to be solved by this application is to overcome the defects in the prior art that the cathode material is prone to metal ion dissolution and failure under high voltage, and the silicon-based material will affect the cycle performance due to volume expansion, etc., so as to provide a lithium-ion secondary battery and an electrical device.

[0006] For this purpose, this application provides the following technical solutions:

[0007] According to one aspect of this application, a lithium-ion secondary battery is provided, including a positive electrode sheet, a negative electrode sheet, and an electrolyte;

[0008] Wherein, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes a silicon-based material;

[0009] The electrolyte includes a polynitrile compound and Compound A. The polynitrile compound includes a dinitrile and a trinitrile, and the trinitrile includes 1,3,6-hexanetricarbonitrile (HTCN);

[0010] The general formula composition of Compound A is as follows:

[0011]

[0012] Wherein, L is O or a linking group; R is selected from an unsubstituted or Ra-substituted C2-C6 alkyl group, an unsubstituted or Ra-substituted C2-C6 alkenyl group, an unsubstituted or Ra-substituted C2-C6 alkynyl group, an unsubstituted or Ra-substituted C2-C6 nitrogen-containing heteroaryl group, and an unsubstituted or Ra-substituted C6-C 12 aryl group, and the substituents Ra of each group are each independently selected from fluorine or a C1-C6 fluoroalkyl group; R1 is selected from one of fluorine or a C1-C6 fluoroalkyl group;

[0013] Based on the total mass of the electrolyte, the mass percentage content of the polynitrile compound is W1%, 1 ≤ W1 ≤ 12; the mass percentage content of the compound A is W2%, 0.1 ≤ W2 ≤ 10;

[0014] The content of the compound A and the polynitrile compound satisfies: 0.05 ≤ W2 / W1 ≤ 5.

[0015] In some optional embodiments, the content of the compound A and the polynitrile compound satisfies: 2 ≤ W1 + W2 ≤ 20;

[0016] And / or, the content of the compound A and the polynitrile compound satisfies: 0.5 ≤ W2 / W1 ≤ 3.

[0017] In some optional embodiments, the mass ratio of the trinitrile to the dinitrile is 1:0.16 - 2;

[0018] And / or, the dinitrile includes at least one of succinonitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, tetramethylsuccinonitrile, 2-methylglutaronitrile, glutarodinitrile, 2,2'-azobisisovaleronitrile, pimelonitrile (646-20-8), 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanedinitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene, and 1,6-dicyano-2-methyl-5-methyl-3-hexene;

[0019] And / or, the trinitrile also includes at least one of triglyceronitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, 1,2,5-tris(cyanoethoxy)pentane, and organophosphorus compounds containing three cyano groups.

[0020] In some alternative embodiments, the electrolyte further includes an organophosphorus compound containing three cyano groups, and the organophosphorus compound containing three cyano groups has a structure represented by any of the following general formulas:

[0021]

[0022] Wherein, m1, m2, m3, n1, n2, and n3 are each independently selected from integers greater than or equal to 1, preferably integers between 1 and 30;

[0023] Preferably, the organophosphorus compound containing three cyano groups has a structure represented by any of the following:

[0024]

[0025] In some alternative embodiments, based on the mass of the electrolyte, the mass percentage content of the organophosphorus compound containing three cyano groups is W3%, and 0.1 ≤ W3 ≤ 6;

[0026] Preferably, the contents of the compound A and the organophosphorus compound containing three cyano groups satisfy: 0.1 ≤ W2 / W3 ≤ 3, and more preferably 0.5 ≤ W2 / W3 ≤ 1.

[0027] In some alternative embodiments, the compound A has a structure represented by any of the following:

[0028]

[0029]

[0030] In some alternative embodiments, the electrolyte further includes a fluorinated carboxylic acid ester compound. Based on the total mass of the electrolyte, the mass percentage content of the fluorinated carboxylic acid ester compound is W4%, and 5 ≤ W4 ≤ 40;

[0031] Preferably, the sum of the contents of the compound A and the fluorinated carboxylic acid ester compound satisfies: 10 ≤ W2 + W4 ≤ 20;

[0032] Preferably, the fluorinated carboxylate compound includes at least one of ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, and propyl fluoropropionate.

[0033] In some alternative embodiments, the electrolyte further includes a boron-containing additive. Based on the total mass of the electrolyte, the mass percentage of the boron-containing additive is W5%, where 0.5 ≤ W5 ≤ 5;

[0034] Preferably, the boron-containing additive includes at least one of lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)borate, and lithium bis(oxalato)borate.

[0035] In some alternative embodiments, the particle size Dv50 of the silicon-based material is 5 - 20 μm, and the sphericity is above 0.8;

[0036] And / or, based on the mass of the negative electrode active material, the mass percentage of silicon element is P1%, where 3 ≤ P1 ≤ 30.

[0037] According to another aspect of the present application, there is also provided an electrical device including the above lithium ion secondary battery.

[0038] The technical solution of the present application has the following advantages:

[0039] A lithium-ion secondary battery provided by the present application includes a positive electrode sheet, a negative electrode sheet, and an electrolyte; wherein, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; the electrolyte includes a polynitrile compound and a compound A with a specific structure, the polynitrile compound includes a dinitrile and a trinitrile, and the trinitrile includes 1,3,6-hexanetricarbonitrile; based on the total mass of the electrolyte, the mass percentage content of the polynitrile compound is W1%, 1 ≤ W1 ≤ 12; the mass percentage content of the compound A is W2%, 0.1 ≤ W2 ≤ 10; the contents of the compound A and the polynitrile compound satisfy: 0.05 ≤ W2 / W1 ≤ 5. Through the cooperation and content limitation of the dinitrile and the trinitrile HTCN and the compound A, the present application can effectively inhibit the capacity attenuation caused by the volume expansion of the silicon-based negative electrode and the dissolution of metal ions in the positive electrode material under high voltage, and improve the cycle performance and the first Coulomb efficiency of the battery. Specifically, when the dinitrile and the trinitrile HTCN are used in combination, they can preferentially adsorb on the surface of the positive electrode material, occupy the active sites of metal elements, and improve the dissolution of positive electrode metal elements. However, the compatibility between the polynitrile compound and the silicon-based negative electrode material is not very good, and nitrile substances are embedded in the silicon-based material, forming a SEI film with poor quality, which prevents the deintercalation of lithium ions and cannot effectively relieve the volume expansion of the silicon-based material; while the compound A has specific reduction ability and reactivity in the electrolyte, so that it can form a stable solid electrolyte interface on the surface of the negative electrode, forming a better protective layer, effectively isolating the direct contact between the electrolyte and the negative electrode, preventing nitrile substances from being embedded in the silicon-based material, preventing further damage to the negative electrode, and effectively relieving the volume expansion of the silicon-based material, thereby improving the inhibition of the capacity loss of the battery and the first efficiency of the battery.

[0040] Additional aspects and advantages of the embodiments of the present application will be described and shown in part in the following description, or will be explained through the implementation of the embodiments of the present application. Detailed implementation manners

[0041] The following embodiments are provided to better further understand the present application, which are not limited to the best implementation manners, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior art features falls within the protection scope of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the text of the present application are intended to cover non-exclusive inclusion.

[0043] References to "embodiments" in this specification mean that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment each time, nor are they independent or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0044] The "scope" disclosed in this application is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular scope. The scope defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, in this text, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0046] In the description of the embodiments of this application, the term "at least one" refers to one or more than two (including two).

[0047] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained commercially.

[0048] As described in the background art, in order to overcome the defects of the prior art such as the rapid attenuation of the high - voltage lithium - ion battery capacity at high temperatures, poor initial Coulomb efficiency and stability performance, the present application provides the following technical solutions:

[0049] According to one aspect of the present application, there is provided a lithium - ion secondary battery, including a positive electrode sheet, a negative electrode sheet, and an electrolyte;

[0050] Wherein, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes a silicon - based material;

[0051] The electrolyte includes a polynitrile compound and Compound A. The polynitrile compound includes dinitrile and trinitrile, and the trinitrile includes 1,3,6 - hexanetricarbonitrile;

[0052] The general formula composition of Compound A is as follows:

[0053]

[0054] Wherein, L is O or a linking bond; R is selected from an unsubstituted or Ra - substituted C2 - C6 alkyl group, an unsubstituted or Ra - substituted C2 - C6 alkenyl group, an unsubstituted or Ra - substituted C2 - C6 alkynyl group, an unsubstituted or Ra - substituted C2 - C6 nitrogen - containing heteroaryl group, an unsubstituted or Ra - substituted C6 - C 12 aryl group, and the substituent Ra of each group is independently selected from fluorine or a C1 - C6 fluoroalkyl group; R1 is selected from one of fluorine or a C1 - C6 fluoroalkyl group;

[0055] Based on the total mass of the electrolyte, the mass percentage content of the polynitrile compound is W1%, 1 ≤ W1 ≤ 12; the mass percentage content of Compound A is W2%, 0.1 ≤ W2 ≤ 10;

[0056] The content of Compound A and the polynitrile compound satisfies: 0.05 ≤ W2 / W1 ≤ 5.

[0057] As an example, based on the total mass of the electrolyte, the mass percentage content of the polynitrile compound can be 1%, 3%, 5%, 7%, 9%, 10%, 11%, 12%, or within the range composed of any of the above values; the mass percentage content of Compound A can be 0.1%, 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, or within the range composed of any of the above values; the content ratio W2 / W1 of Compound A and the polynitrile compound can be 0.05, 0.1, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, 4, 5, or within the range composed of any of the above values.

[0058] Through the combination of dinitrile and trinitrile HTCN, the combination of polynitrile compounds and compound A, and the special regulation of the content, the present application can effectively inhibit the high-temperature capacity decay of high-voltage lithium-ion batteries and improve the initial Coulombic efficiency. Specifically, when dinitrile and trinitrile are used in combination, the trinitrile compound preferably includes HTCN because the antioxidant property of HTCN is stronger than that of other nitriles. It can remain undecomposed in a voltage system above 4.58V, can preferentially adsorb on the surface of the positive electrode material, occupy the active sites of metal elements, and improve the dissolution of metal elements in the positive electrode. However, its compatibility with the negative electrode silicon-based material is not very good. Nitrile substances are embedded in the silicon-based material to form a SEI film with poor quality, which blocks the deintercalation of lithium ions and cannot effectively relieve the volume expansion of the silicon-based material, damaging the interface of the negative electrode and reducing the capacity performance and initial efficiency; compared with other nitrile substances, in addition to improving the dissolution of metal ions, HTCN can also form an oxide film on the surface of the positive electrode to wrap the surface of the positive electrode, further preventing the occurrence of side reactions with the electrolyte. Due to the presence of fluorine elements and sulfonate groups / sulfonyl groups in compound A, the electronic structure and chemical properties of the molecule are changed, which makes compound A have specific reduction ability and reactivity in the electrolyte: it can be preferentially reduced compared with traditional film-forming additives to form a relatively dense interface film, and can also form a fixed target binding with the silicon-based material, stabilizing the interface of the silicon-based material and preventing the silicon-based material from cracking and the volume from expanding, so as to form a stable solid electrolyte interface on the surface of the negative electrode; compound A preferentially forms a denser and more stable SEI film on the surface of the negative electrode than the polynitrile compound. This SEI film is mainly composed of substances such as lithium alkyl carbonate, ethers, and LiF, forming a better protective layer, effectively isolating the direct contact between nitrile substances in the electrolyte and the negative electrode, thereby preventing further damage to the negative electrode by nitrile substances; effectively inhibiting the capacity loss of the battery and improving the initial efficiency of the battery. If the content of the polynitrile compound is higher than 12%, it will lead to a large internal resistance and polarization of the battery, resulting in an accelerated decline in the cyclic capacity retention rate. If it is lower than 1%, the dissolution of metal ions in the material on the positive electrode side under high voltage is obvious and the cycle life is poor; if the content of compound A is higher than 20%, it will lead to over-reduction at the negative electrode, forming a relatively thick SEI film with a large internal resistance and difficult lithium-ion insertion. If it is lower than 2%, a stable interface protection cannot be formed at the negative electrode; when the content ratio W2 / W1 of compound A to the polynitrile compound is higher than 5, the attenuation of the high-temperature cyclic capacity retention rate is relatively fast, the Coulombic efficiency is too low, and the capacity loss is large. When W2 / W1 is lower than 0.05, a relatively stable interface cannot be formed at the negative electrode, the solvent is reduced, resulting in a serious deterioration of the high-temperature storage performance.

[0059] In some optional embodiments, the contents of compound A and the polynitrile compound satisfy: 2 ≤ W1 + W2 ≤ 20; as an example, the sum W1 + W2 of the contents of compound A and the polynitrile compound can be 2, 4, 6, 8, 10, 12, 15, 18, 20, or within the range composed of any of the above values. By limiting the sum of their dosages in this application, the fluorophenyl ester compound preferentially forms a denser and more stable SEI film on the negative electrode surface than the polynitrile compound. This SEI film is mainly composed of substances such as lithium alkyl carbonate, ethers, LiF, etc., covering the negative electrode surface, forming a good protective layer, effectively isolating the direct contact between nitrile substances in the electrolyte and the negative electrode, thereby preventing further damage to the negative electrode by nitrile substances; effectively inhibiting capacity loss and improving the initial efficiency of the battery. If the total amount of compound A and the polynitrile compound is too high, it will lead to a large battery impedance, attenuation of the cycle life and high-temperature cycle capacity retention rate. If it is too low, a stable interfacial protection cannot be formed on the positive electrode side, resulting in insufficient protection, the solvent will be oxidized, resulting in poor high-temperature performance of the battery and gas generation, etc.

[0060] In some optional embodiments, the contents of compound A and the polynitrile compound satisfy: 0.5 ≤ W2 / W1 ≤ 3; by limiting the proportional relationship between the contents of compound A and the polynitrile compound in this application, the initial Coulomb efficiency and cycle capacity retention rate of the lithium-ion secondary battery can be further improved.

[0061] In some optional embodiments, the mass ratio of the trinitrile to the dinitrile is 1:0.16 - 2; as an example, the mass ratio of the trinitrile to the dinitrile can be 1:0.16, 1:0.2, 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, or within the range composed of any of the above values. By regulating the mass ratio of the trinitrile to the dinitrile in this application, the battery cycle performance can be further improved. If the above range is not satisfied, nitrile substances are more likely to embed in the silicon-based negative electrode, forming a SEI film with poor quality, unable to effectively relieve the volume expansion of the silicon-based negative electrode, damaging the interface of the negative electrode, and causing attenuation of the battery cycle performance.

[0062] And / or, the dinitrile includes at least one of succinonitrile (SN), adiponitrile (ADN), 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, tetramethylsuccinonitrile, 2-methylglutaronitrile, glutaronitrile, azodiisobutyronitrile, pimelonitrile, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxo-heptanedinitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene, and 1,6-dicyano-2-methyl-5-methyl-3-hexene;

[0063] And / or, the trinitrile further includes at least one of glycerol trinitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, 1,2,5-tris(cyanoethoxy)pentane, and organophosphorus compounds containing three cyano groups.

[0064] In some alternative embodiments, the electrolyte further includes an organophosphorus compound containing three cyano groups, and the organophosphorus compound containing three cyano groups has any one of the following general formula structures:

[0065]

[0066] Wherein, m1, m2, m3, n1, n2, and n3 are each independently selected from integers greater than or equal to 1, preferably integers between 1 and 30;

[0067] Preferably, the organophosphorus compound containing three cyano groups has any one of the following structures:

[0068]

[0069] In this application, compared with ordinary polynitrile compounds, the organophosphorus compound containing three cyano groups can form a stable passivation film on the surface of the SEI film on the basis of the film formation of compound A, further inhibiting the volume change of the silicon-based material and not damaging the structure of the silicon-based material. The organophosphorus compound containing three cyano groups can replace part of the content of ordinary dinitrile and trinitrile compounds in the electrolyte. On the basis of maintaining the positive electrode protection effect, it can further reduce the damage to the silicon-based negative electrode material, improve the capacity retention rate of the battery, especially the high-temperature capacity retention rate, and improve the initial efficiency.

[0070] In some alternative embodiments, based on the mass of the electrolyte, the mass percentage content of the organophosphorus compound containing three cyano groups is W3%, and 0.1 ≤ W3 ≤ 6; as an example, based on the mass of the electrolyte, the mass percentage content of the organophosphorus compound containing three cyano groups can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, or within the range composed of any of the above values. In this application, when the content of the organophosphorus compound containing three cyano groups is higher than 6%, it will cause a large internal resistance and polarization of the battery, resulting in an accelerated decline in the cycle capacity retention rate. When it is lower than 0.1%, it will not be able to further improve the problem of metal ion dissolution and increase the cycle life. Limiting the content of the organophosphorus compound containing three cyano groups to the above range can achieve further optimization of the cycle performance.

[0071] Preferably, the contents of compound A and the organophosphorus compound containing three cyano groups satisfy: 0.1 ≤ W2 / W3 ≤ 3, and more preferably 0.5 ≤ W2 / W3 ≤ 1. The ratio W2 / W3 of compound A to the organophosphorus compound containing three cyano groups can be 0.1, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, or within the range composed of any of the above values. In this application, when the content ratio W2 / W3 of compound A to the organophosphorus compound containing three cyano groups is higher than 1, it will affect the high-temperature cycle capacity retention rate and Coulomb efficiency, causing a certain capacity loss. When W2 / W3 is lower than 0.5, the interface stability formed on the negative electrode becomes poor, and the high-temperature storage performance cannot be further improved. By limiting the ratio of the contents of compound A and the organophosphorus compound containing three cyano groups to the above range in this application, the balance between various battery performances can be achieved.

[0072] In some alternative embodiments, compound A has any of the following structures:

[0073]

[0074]

[0075] In some alternative embodiments, the electrolyte further includes a fluorinated carboxylate compound. Based on the total mass of the electrolyte, the mass percentage content of the fluorinated carboxylate compound is W4%, where 5 ≤ W4 ≤ 40; as an example, based on the total mass of the electrolyte, the mass percentage content of the fluorinated carboxylate compound can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or within the range composed of any of the above values.

[0076] In this application, under high-temperature conditions, compound A may react with other components in the electrolyte such as lithium salts, resulting in a decrease in the stability of the electrolyte, which easily causes the SEI film to rupture or reorganize during the cycling process, reducing the stability of the SEI film. The fluorinated carboxylate compound helps to reduce the volatilization and decomposition of the electrolyte at high temperatures, reduces the internal resistance of the battery, and can improve the stability of compound A, participate in the formation of a stable and dense SEI film, improve the stability of the SEI film at high temperatures, and reduce the polarization degree and internal resistance of the battery. At the same time, the fluorinated carboxylate compound can also promote the rapid diffusion of lithium ions in the SEI film and improve the high-temperature cycling performance. If the content of the fluorinated carboxylate compound is higher than 40%, the viscosity of the electrolyte will increase, resulting in insufficient kinetics. If it is lower than 5%, it cannot stabilize the interface of the electrolyte at the positive electrode, is easily oxidized, and causes poor high-temperature cycling capacity retention.

[0077] Preferably, the sum of the contents of compound A and the fluorinated carboxylate compound satisfies: 10 ≤ W2 + W4 ≤ 20; as an example, the sum of the contents of compound A and the fluorinated carboxylate compound W2 + W4 can be 10, 12, 14, 16, 18, 20, or within the range composed of any of the above values. By limiting the total amount of compound A and the fluorinated carboxylate compound in this application, the balance between high-temperature storage performance and high-temperature cycling performance can be achieved.

[0078] Preferably, the fluorinated carboxylate compound includes at least one of ethyl methyl fluorocarbonate, diethyl fluorocarbonate, dimethyl fluorocarbonate, ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, and propyl fluoropropionate.

[0079] In some alternative embodiments, the electrolyte further includes a boron-containing additive. Based on the total mass of the electrolyte, the mass percentage content of the boron-containing additive is W5%, where 0.5 ≤ W5 ≤ 5; as an example, based on the total mass of the electrolyte, the mass percentage content of the boron-containing additive can be 0.5%, 1%, 2%, 2.5%, 3%, 4%, 5%, or within the range composed of any of the above values.

[0080] Those skilled in the art can understand that the boron-containing additive can participate in film formation at the positive and negative electrodes, reduce the reduction reaction of the solvent, improve the stability of the interface, make the high-temperature interface more firm, improve the high-temperature performance, so that the capacity can be normally exerted. The addition of boron element can also promote the diffusion and intercalation of lithium ions in the positive and negative electrodes, and reduce the interface resistance between the negative electrode and the electrolyte. This helps more lithium ions to migrate smoothly from the positive electrode to the negative electrode during the first charging process, and quickly diffuse and intercalate in the negative electrode, so that more electrical energy can be released during the first discharge, thereby further improving the capacity performance and high-temperature performance of the lithium battery.

[0081] Preferably, the boron-containing additive includes but is not limited to at least one of lithium difluorooxalate borate, lithium tetrafluorooxalate borate, and lithium bis(oxalato)borate.

[0082] In some alternative embodiments, the Dv50 particle size of the silicon-based material is 5-20 μm, and the sphericity is above 0.8; as an example, the Dv50 particle size of the silicon-based material can be 5 μm, 8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or within the range composed of any of the above values, and the sphericity can be 0.8, 0.82, 0.85, 0.88, 0.90, 0.93, 0.95, 0.97, 0.99, or within the range composed of any of the above values.

[0083] Those skilled in the art can understand that too small a particle size of the silicon-based material will lead to an unstable structure of the electrode sheet, a large specific surface area, resulting in severe expansion and contraction; too large a particle size of the silicon-based material will lead to a decrease in the specific surface area and a decrease in the ion migration rate, resulting in a decline in the battery cycle performance; and too small a sphericity will increase the specific surface area, increase the formation area of the SEI film and the consumption of the electrolyte. In this application, the silicon-based material that meets the above sphericity range usually has a smaller specific surface area, which means that under the same volume, the contact area between the spherical particles and the electrolyte is smaller, thereby reducing the formation area of the SEI film, thereby reducing the volume expansion of the silicon-based material, and the particle size of the silicon-based material meets the above range, and the silicon-based material has a larger specific surface area, increasing the contact area with the electrolyte, which is beneficial to the intercalation and deintercalation process of lithium ions, thereby improving the cycle capacity retention rate of the battery.

[0084] And / or, based on the mass of the negative electrode active material, the mass percentage of silicon element is P1%, where 3 ≤ P1 ≤ 30. As an example, based on the mass of the negative electrode active material, the mass percentage of silicon element can be 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, or within the range composed of any of the above values. By limiting the silicon element content in this application, the balance between energy density and safety performance can be achieved. If the silicon content is too high, the thickness of the battery will increase relatively fast, bringing greater potential safety hazards. If the silicon content is too low, the energy density design of the battery will be insufficient.

[0085] Those skilled in the art can understand that during the charge and discharge process of the battery, lithium ions are intercalated and deintercalated between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is arranged between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows lithium ions to pass through.

[0086] As an example, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector. The materials, compositions, and manufacturing methods of the positive electrode plate used in the lithium ion secondary battery of this application can include any technologies disclosed in the prior art. As an example, the positive electrode active material is selected from layered lithium composite oxides, and its chemical general formula is Li (1+x) Ni y Co z M (1-y-z) O2, where -0.1 ≤ x ≤ 1; 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1; M is one or several of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0087] As an example, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector. The materials, compositions, and manufacturing methods of the negative electrode plate used in the lithium ion secondary battery of this application can include any technologies disclosed in the prior art. In this application, the negative electrode active material includes a silicon-based negative electrode material. As an example, the silicon-based material includes at least one of silicon-carbon materials (the mass percentage of silicon element can be 10% - 80%) or silicon-oxygen materials; the negative electrode active material also includes a carbon-based material, and the carbon-based material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon.

[0088] There are no particular limitations on the materials and shapes of the separators used in the lithium-ion secondary batteries of the present application, and they can include any technologies disclosed in the prior art.

[0089] The electrolytes used in the lithium-ion secondary batteries of the present application can include any technologies disclosed in the prior art.

[0090] The organic solvents in the electrolytes of the present application are selected from one or more of carbonate solvents, unsubstituted carboxylate solvents, or fluoroethers and fluorobenzenes;

[0091] Preferably, the carbonate solvents are selected from one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethyl methyl carbonate, fluoroethyl diethyl carbonate, and fluorodimethyl carbonate;

[0092] Preferably, the unsubstituted carboxylate solvents are selected from one or more of the following solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, ethyl propionate, n-propyl propionate (PP), methyl butyrate, ethyl butyrate, and n-ethyl butyrate.

[0093] Preferably, the fluoroethers include at least one of bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, tris(trifluoroethoxy)methane, and ethyl nonafluorobutyl ether; the fluorobenzenes include at least one of fluorobenzene, 1,3-difluorobenzene, and 1,4-difluorobenzene.

[0094] The lithium salts in the electrolytes of the present application are selected from one or more of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiODFB), lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyl, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium hexafluorozirconate (Li2ZrF6). Based on the total mass of the electrolyte, the mass concentration of the lithium salt is 12-20%.

[0095] The electrolytes also include other additives, and the other additives are selected from one or more of fluoroethylene carbonate (FEC), fluoropropylene carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1,3-propane sultone (PS), and allyl-1,3-sultone.

[0096] In the present application, the method for preparing the lithium-ion secondary battery is conventional in the art. As an example, the preparation method may include:

[0097] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, ensuring that the separator is between the positive and negative electrode sheets to play an isolation role, and then obtain an un-injected bare battery cell by winding; place the bare battery cell in an outer packaging foil, inject the prepared electrolyte into the dried bare battery cell, and obtain the required lithium-ion secondary battery through processes such as vacuum packaging, standing, forming, shaping, and sorting.

[0098] According to another aspect of the present application, there is also provided an electrical device including the above lithium-ion secondary battery.

[0099] As an example, the lithium-ion secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0100] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0101] Example 1

[0102] This example provides a lithium-ion secondary battery, and its specific composition and preparation method are as follows:

[0103] (1) Preparation of the electrolyte

[0104] In a glove box filled with an inert gas (xenon) (H2O < 0.1 ppm, O2 < 0.1 ppm), mix ethylene carbonate, propylene carbonate, diethyl carbonate, and propyl propionate evenly according to a mass ratio of 15:10:10:65. Then, based on the total mass of the electrolyte, quickly add 13% of fully dried lithium hexafluorophosphate LiPF6 thereto, stir evenly, and finally add 5.5% of unsubstituted trinitrile and unsubstituted dinitrile (mass ratio of 1,3,6-hexanetricarbonitrile: adiponitrile: succinonitrile is 2.5:2:1), 6% of the fluorobenzenesulfonate of formula 1, 12% of FEC, 4% of 1,3-propane sultone, 1% of an organic phosphorus compound containing three cyano groups (formula c), and 0.5% of the boron-containing additive lithium difluorooxalate borate. After passing the moisture and free acid tests, the required electrolyte is obtained.

[0105] (2) Preparation of the positive electrode sheet

[0106] Mix the cathode active material lithium cobalt oxide (LiCoO₂), polyvinylidene fluoride (number-average molecular weight 20,000 - 100,000), conductive carbon black, and carbon nanotubes in a mass ratio of 96:2:1.5:0.5. Add N-methylpyrrolidone (NMP) and stir under a vacuum mixer until the mixed system becomes a homogeneous and flowable cathode active paste; uniformly coat the two surfaces of the aluminum foil with the cathode active paste; dry the coated aluminum foil, and obtain the required cathode sheet through rolling and slitting, with a surface density of 16 mg / cm 2 .

[0107] (3) Prepare the anode sheet

[0108] Mix the anode active material (composed of 88 wt% graphite + 12 wt% silicon-carbon material, and the mass percentage of silicon element in the silicon-carbon material is 25%), styrene-butadiene rubber (SBR), lithium polyacrylate (number-average molecular weight 20,000 - 100,000), conductive carbon black (SP), and carbon nanotubes (CNTs) evenly in a mass ratio of 96.5:1.5:0.5:1.0:0.5. Subsequently, add deionized water step by step and make it fully mixed under a vacuum mixer to finally form a homogeneous and good-flowing anode paste, with a solid content of 45 wt%; uniformly coat the above anode paste on a copper foil with a thickness of 6 μm, dry, roll, and die-cut to obtain an anode sheet with a surface density of 10 mg / cm 2 . The particle size Dv50 of the silicon-carbon material is 12 μm, and the sphericity is 0.92.

[0109] (4) Separator: Select an 8-μm-thick polyethylene separator (provided by Asahi Kasei Corporation).

[0110] (5) Battery assembly:

[0111] Stack the above-prepared cathode sheet, separator, and anode sheet in sequence, ensuring that the separator is between the cathode and anode sheets to play an isolation role, and then obtain an un-injected bare battery cell through winding; place the bare battery cell in the outer packaging foil, inject the above-prepared electrolyte into the dried bare battery cell, and obtain the required lithium-ion secondary battery through processes such as vacuum packaging, standing, formation, shaping, and sorting. The total capacity of the battery is 3600 mAh, the thickness is 3.8 mm, the width is 62 mm, and the length is 80 mm.

[0112] Examples 2 - 30

[0113] Examples 2 - 30 are different from Example 1 in that the composition of the electrolyte is different. See the specific table below. Among them, the change in the content W1% of the polynitrile compound in Examples 5 - 11 is achieved by adjusting the total amount of unsubstituted trinitrile and unsubstituted dinitrile. The types and mass ratios of unsubstituted trinitrile and unsubstituted dinitrile remain unchanged, and the content W3% of the organophosphorus compound containing three cyano groups is also unchanged. In Examples 12 - 13, the change in the mass ratio of trinitrile to dinitrile is achieved by adjusting the mass ratio of unsubstituted trinitrile and unsubstituted dinitrile. The type and ratio of unsubstituted dinitrile and the content W3% of the organophosphorus compound containing three cyano groups are also unchanged.

[0114] Table 1

[0115]

[0116]

[0117] Examples 31 - 36

[0118] Examples 31 - 36 are different from Example 1 in that the composition of the negative electrode active material is different. Among them, in Example 35, the silicon content in the silicon-carbon material remains unchanged compared with Example 1, and the percentage content of silicon-carbon in the negative electrode active material is 60%. In Example 36, the silicon element content in the silicon-carbon material is adjusted to 75%, and the percentage content of silicon-carbon in the negative electrode active material is 40%. See the specific table below.

[0119] Table 2

[0120]

[0121] Comparative Example 1

[0122] This comparative example is different from Example 25 only in that it does not contain Compound A.

[0123] Comparative Example 2

[0124] This comparative example is different from Example 25 only in that it uses difluorobenzene instead of Compound A shown in Formula 2.

[0125] Comparative Example 3

[0126] This comparative example is different from Example 25 only in that it uses an equal amount of 1,3,6 - hexanetricarbonitrile to replace ADN and adiponitrile, that is, the electrolyte does not contain dinitrile.

[0127] Comparative Example 4

[0128] This comparative example is different from Example 25 only in that it uses an equal amount of adiponitrile to replace 1,3,6 - hexanetricarbonitrile, that is, the electrolyte does not contain trinitrile.

[0129] Comparative Example 5

[0130] The only difference between this comparative example and Example 25 is that the total amount of polynitrile compounds is 0.8% and W2 / W1 is 7.5.

[0131] Comparative Example 6

[0132] The only difference between this comparative example and Example 25 is that the total amount of the polynitrile compound is 1% and W2 / W1 is 6.

[0133] Comparative Example 7

[0134] The only difference between this comparative example and Example 25 is that an equal mass of glycerol trinitrile is used instead of HTCN.

[0135] Test Case

[0136] The lithium ion secondary batteries prepared in the examples and comparative examples were subjected to performance tests, and the specific test methods are as follows:

[0137] 1. High temperature cycle performance test

[0138] The batteries prepared in the examples and comparative examples were subjected to a 45°C cycle test. The specific test method is as follows:

[0139] The test sample was allowed to stand for 10 min at 45°C; discharged at 1C to a lower limit voltage of 3.0V, and allowed to stand for 10 min; charged at 1C to an upper limit voltage of 4.55V at 45°C, with a cutoff current of 0.025C, and allowed to stand for 10 min; discharged at a rate of 1.2C to a cutoff voltage of 3.0V in a 45°C constant temperature box environment, and allowed to stand for 10 min. This was one cycle. After 600 cycles, the discharge capacity Q1 after 600 cycles of high-temperature cycling and the initial discharge capacity Q0 were recorded. The high-temperature cycle capacity retention rate (%) = Q1 / Q0×100%.

[0140] 2. First Coulomb efficiency

[0141] Charge the lithium battery at a constant current density of 0.2C until it reaches a predetermined charging voltage of 4.55V, and record the amount of electricity during the charging process, i.e., the first charging capacity. Shelf treatment: After charging is completed, the lithium battery is shelved for a period of time (e.g., 5 minutes) so that the internal state of the battery can stabilize again. First discharge: Discharge the lithium battery at a constant current density (0.2C) until the battery voltage drops to a predetermined discharge cut-off voltage (e.g., 3V), and record the amount of electricity during the discharge process. First coulomb efficiency = first charging capacity / first discharge capacity × 100%.

[0142] 3. High temperature storage performance

[0143] The batteries prepared in the examples and comparative examples were subjected to high-temperature storage, and the specific test method was as follows:

[0144] Under the environment of 25°C ± 3°C, discharge at 0.5C to the lower limit voltage, stand still for 10 min, place the battery cell in a constant temperature oven at 25°C, charge it fully at a constant current of 0.5C, with a cut-off current of 0.02C. After being fully charged, store the battery cell in an 85°C environment. After storing for 6 h, measure the thickness of the battery cell body and record the thickness expansion rate of the battery cell.

[0145] 4. Room-temperature cycling performance

[0146] The batteries prepared in the examples and comparative examples were subjected to a 25°C cycling test, and the specific test method was as follows:

[0147] Test the incoming sample and let it stand still for 10 min at 25°C; discharge at 1C to the lower limit voltage of 3.0V and stand still for 10 min; charge at 1C to the upper limit voltage of 4.55V at 25°C, with a cut-off current of 0.025C, and stand still for 10 min; in a constant temperature oven environment at 25°C, discharge at a rate of 1.2C to the cut-off voltage of 3.0V and stand still for 10 min; cycle 1000 times, record the capacity Q1 after 1000 room-temperature cycles and the initial discharge capacity Q0, then the room-temperature cycling capacity retention rate (%) = Q1 / Q0 × 100%.

[0148] 5. Metal ion dissolution

[0149] Take the battery after 600 high-temperature cycles, disassemble it in a drying room, gently scrape off the negative electrode active layer with a ceramic knife, and then completely dissolve the sample with acid to ensure that metal ions enter the solution. Calibrate the ICP instrument with a standard solution to ensure accuracy. Convert the digested sample into an aerosol through an atomizer. In a high-temperature plasma, metal ions are excited to a high-energy state, and a spectrometer is used to separate light of different wavelengths, and the concentration of each metal ion in the sample is calculated according to the standard curve.

[0150] The specific test results are shown in the following table:

[0151] Table 3

[0152]

[0153]

[0154] From the comparison of the data of the above examples and comparative examples, it can be seen that through the combination of dinitrile and trinitrile HTCN with compound A and the special regulation of the content, the present application can effectively inhibit the high-temperature capacity attenuation of high-voltage lithium-ion batteries, improve the first Coulomb efficiency, and reduce the dissolution of positive electrode metal ions under high voltage.

[0155] Obviously, the above embodiments are merely examples given for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A lithium ion secondary battery, characterized in that: Including positive electrode sheet, negative electrode sheet and electrolyte; Wherein, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; The electrolyte includes a polynitrile compound and a compound A, wherein the polynitrile compound includes a dinitrile and a trinitrile, and the trinitrile includes 1,3,6-hexane trinitrile; The general formula of the compound A is as follows: Wherein, L is O or a connecting bond; R is selected from C2-C6 alkyl which is unsubstituted or substituted by Ra, C2-C6 alkenyl which is unsubstituted or substituted by Ra, C2-C6 alkynyl which is unsubstituted or substituted by Ra, C2-C6 nitrogen-containing heteroaryl which is unsubstituted or substituted by Ra, C6-C 12 One of the aryl groups, the substituents Ra of each group are independently selected from fluorine or C1-C6 fluoroalkyl; R1 is selected from one of fluorine or C1-C6 fluoroalkyl; Based on the total mass of the electrolyte, the mass percentage of the polynitrile compound is W1%, 1≤W1≤12; the mass percentage of the compound A is W2%, 0.1≤W2≤10; The contents of the compound A and the polynitrile compound satisfy: 0.05≤W2 / W1≤5.

2. The lithium ion secondary battery according to claim 1, characterized in that: The contents of the compound A and the polynitrile compound satisfy: 2≤W1+W2≤20; And / or, the contents of the compound A and the polynitrile compound satisfy: 0.5≤W2 / W1≤3.

3. The lithium ion secondary battery according to claim 1, characterized in that: The mass ratio of the trinitrile to the dinitrile is 1:0.16-2; and / or, the dinitrile comprises succinonitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, tetramethylsuccinonitrile, 2-methylglutaronitrile, glutaronitrile, azobisisoheptanenitrile, heptanenitrile, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanenitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol di(2-cyanoethyl) ether, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 1,3 - at least one of bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, ethylene glycol di(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene and 1,6-dicyano-2-methyl-5-methyl-3-hexene; And / or, the trinitrile also includes at least one of glycerol trinitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, 1,2,5-tris(cyanoethoxy)pentane, and an organic phosphorus compound containing three cyano groups.

4. The lithium ion secondary battery according to claim 3, characterized in that: The trinitriles include an organic phosphorus compound containing three cyano groups, and the organic phosphorus compound containing three cyano groups has a structure shown in any of the following general formulas: wherein m1, m2, m3, n1, n2 and n3 are each independently selected from an integer greater than or equal to 1, preferably an integer between 1 and 30; Preferably, the organophosphorus compound containing three cyano groups has any of the following structures:

5. The lithium ion secondary battery according to claim 4, characterized in that: The mass percentage of the organic phosphorus compound containing three cyano groups is W3% based on the mass of the electrolyte, 0.1≤W3≤6; Preferably, the contents of the compound A and the organic phosphorus compound containing three cyano groups satisfy: 0.1≤W2 / W3≤3, more preferably 0.5≤W2 / W3≤1.

6. The lithium ion secondary battery according to claim 1, characterized in that: The compound A has any of the following structures:

7. The lithium ion secondary battery according to claim 1, characterized in that: The electrolyte further comprises a fluorinated carboxylate compound, and the mass percentage of the fluorinated carboxylate compound is W4% based on the total mass of the electrolyte, 5≤W4≤40; Preferably, the sum of the contents of the compound A and the fluorocarboxylic acid ester compound satisfies: 10≤W2+W4≤20; Preferably, the fluorocarboxylate compound includes at least one of ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate and propyl fluoropropionate.

8. The lithium ion secondary battery according to claim 1, characterized in that: The electrolyte further includes a boron-containing additive, and the mass percentage of the boron-containing additive is W5% based on the total mass of the electrolyte, 0.5≤W5≤5; Preferably, the boron-containing additive includes at least one of lithium difluorooxalatoborate, lithium tetrafluorooxalatoborate, and lithium dioxalatoborate.

9. The lithium ion secondary battery according to any one of claims 1 to 8, characterized in that: The particle size Dv50 of the silicon-based material is 5-20 μm, and the sphericity is above 0.8; And / or, based on the mass of the negative electrode active material, the mass percentage of silicon element is P1%, 3≤P1≤30.

10. An electrical device, characterized in that: A lithium ion secondary battery comprising any one of claims 1 to 9.

Images