Secondary battery and electronic device

Abstract

The present application provides a secondary battery and an electronic device. An electrolyte comprises a salt consisting of an anion and a cation as shown in formula I and a compound of formula II. M1 is selected from element B or element Al. R1, R2, R3, and R4 are each independently selected from C1-C8 alkyl in which at least some hydrogen atoms are substituted by fluorine, C6-C20 aryl in which at least some hydrogen atoms are substituted by fluorine, C7-C22 aralkyl in which at least some hydrogen atoms are substituted by fluorine, C7-C20 alkaryl in which at least some hydrogen atoms are substituted by fluorine, C7-C20 ether bond-containing alkaryl in which at least some hydrogen atoms are substituted by fluorine, or C2-C10 ether bond-containing alkyl in which at least some hydrogen atoms are substituted by fluorine. R is selected from fluorine-substituted or unsubstituted C1-C5 alkyl, or amino substituted by C1-C5 alkyl. Rf is selected from a fluorine atom or trifluoromethyl. The cation comprises one of Li+, Na+, K+, Mg2+, Ca2+, and Zn2+. The electrolyte satisfies the described features, and can improve the cycle performance and the low-temperature discharge performance of the secondary battery.

Description

A secondary battery and electronic device Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] Lithium-ion batteries have significant advantages such as high energy density, miniaturization, and lightweight design, and are widely used in mobile phones, laptops, tablets, drones, electric vehicles, power tools, and energy storage systems. A typical lithium-ion battery consists of a positive electrode, a negative electrode, and an electrolyte. The electrolyte is responsible for maintaining ion transport between the positive and negative electrodes and for maintaining a stable interface, ensuring stable operation of the lithium-ion battery.

[0003] To form a stable interface in lithium-ion batteries, film-forming additives are usually added to the electrolyte. However, these additives often form a high-resistivity interfacial film on the surface of the positive or negative electrode. Although the resulting interfacial film is beneficial for the stable operation of lithium-ion batteries, it makes ion conduction more difficult, which limits the low-temperature discharge performance of lithium-ion batteries.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a secondary battery and electronic device to improve the cycle performance and low-temperature discharge performance of the secondary battery. The specific technical solution is as follows:

[0006] A first aspect of this application provides a secondary battery comprising an electrolyte comprising a salt of anions and cations represented by Formula I and a compound of Formula II.

[0007] Wherein, M1 is selected from element B or element Al; R1, R2, R3, and R4 are each independently selected from C1 to C8 alkyl groups with at least partially fluorinated hydrogen atoms, C6 to C20 aryl groups with at least partially fluorinated hydrogen atoms, C7 to C22 aralkyl groups with at least partially fluorinated hydrogen atoms, C7 to C20 alkylaryl groups with at least partially fluorinated hydrogen atoms, C7 to C20 ether-bonded alkylaryl groups with at least partially fluorinated hydrogen atoms, or C2 to C10 ether-bonded alkyl groups with at least partially fluorinated hydrogen atoms. R is selected from C1 to C5 alkyl groups with or without fluorinated substitution, and amino groups substituted with C1 to C5 alkyl groups; Rf is selected from fluorine atoms or trifluoromethyl groups. The cation includes Li. + Na + K + Mg 2+ Ca 2+ or Zn 2+One of them. By adjusting the electrolyte, which includes a salt composed of anions and cations as shown in Formula I and a compound of Formula II, a secondary battery can simultaneously possess good cycle performance and low-temperature discharge performance.

[0008] In one embodiment of this application, the anion represented by Formula I includes at least one of the following anions:

[0009] Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation shown in Formula I is A, where 0.05% ≤ A ≤ 10%. By selecting the salt composed of the anion and the cation shown in Formula I and adjusting the mass percentage of the salt composed of the anion and the cation shown in Formula I within the scope of this application, the amount of active lithium consumed during the formation stage of the secondary battery can be appropriately controlled, resulting in a suitable thickness of the interface layer. This not only better protects the electrode materials but also facilitates lithium-ion transport, thereby enabling the secondary battery to have higher initial efficiency and better low-temperature discharge performance.

[0010] In one embodiment of this application, the compound of formula II includes at least one of the following compounds:

[0011] Based on the mass of the electrolyte, the mass percentage of the compound of formula II is B, where 1% ≤ B ≤ 50%. By selecting the above-mentioned compound of formula II and adjusting its mass percentage within the scope of this application, the compound of formula II, having a suitable mass percentage, enables the electrolyte to have a suitable viscosity and high ionic conductivity, which is beneficial for lithium-ion transport, thereby improving the cycle performance of the secondary battery while further improving its low-temperature discharge performance.

[0012] In one embodiment of this application, the secondary battery satisfies at least one of the following characteristics: (1) based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, 0.1% ≤ A ≤ 5%; (2) based on the mass of the electrolyte, the mass percentage of the compound of Formula II is B, 3% ≤ B ≤ 30%; (3) based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, and the mass percentage of the compound of Formula II is B, 0.5 ≤ B / A ≤ 60.

[0013] In one embodiment of this application, the electrolyte further includes a compound of formula III.

[0014] In this electrolyte, R5, R6, R7, R8, and R9 are each independently selected from hydrogen atoms, fluorine atoms, alkyl groups of C1 to C5 (substituted or unsubstituted), alkenyl groups of C2 to C5, alkynyl groups of C2 to C5, carbonyl groups, ester groups, aldehyde groups, or carboxylic acid groups. Adjacent groups in R5, R6, R7, R8, and R9 can be covalently linked to form a ring. X is selected from methylene or oxygen atoms. The electrolyte also includes the compound of Formula III, which is an inner salt molecule. The compound of Formula III can synergistically interact with the anion shown in Formula I to promote the decomposition reaction of the anion shown in Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also giving the secondary battery better low-temperature discharge performance.

[0015] In one embodiment of this application, the compound of formula III includes at least one of the following compounds:

[0016] The above-mentioned compound III can synergistically interact with the anion shown in Formula I to promote the decomposition reaction of the anion shown in Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0017] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage content of the compound of formula III is C, where 0.1% ≤ C ≤ 1%. By adjusting the mass percentage content of the compound of formula III within the scope of this application, a suitable mass percentage content of the compound of formula III can be achieved. The compound of formula III can synergistically interact with the anion represented by formula I to promote the decomposition reaction of the anion represented by formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0018] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, where 0.5 ≤ A / C ≤ 5. By adjusting the value of A / C within the range of this application, the mass percentage of the salt composed of the anion and the cation represented by Formula I is matched with the mass percentage of the compound of Formula III. The compound of Formula III can synergistically act with the anion represented by Formula I to promote the decomposition reaction of the anion represented by Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0019] In one embodiment of this application, the electrolyte further includes a linear ester, which comprises at least one of ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl tert-butyrate, ethyl tert-butyrate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate. Using the above-mentioned linear esters allows the electrolyte to have a suitable overall viscosity and high ionic conductivity, which is beneficial for lithium-ion transport and can further improve the cycle performance and low-temperature discharge performance of the secondary battery.

[0020] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the linear ester is D, where 10% ≤ D ≤ 90%, preferably 20% ≤ D ≤ 70%. By adjusting the value of D within the range of this application, the linear ester can have a suitable mass percentage, resulting in a suitable viscosity of the electrolyte as a whole, high ionic conductivity, which is beneficial for lithium-ion transport and can further improve the cycle performance and low-temperature discharge performance of the secondary battery.

[0021] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, where 0.005 ≤ A / D ≤ 0.1. By adjusting the value of A / D within the range of this application, the mass percentage of the salt composed of the anion and the cation represented by Formula I is matched with the mass percentage of the linear ester. The linear ester enables the electrolyte to have a suitable overall viscosity and high ionic conductivity, which is beneficial for lithium-ion transport. At the same time, the linear ester can synergistically interact with the anion represented by Formula I. The linear ester decomposes to generate an interface layer containing lithium carboxylate, further enhancing the interfacial ion conductivity and further improving the cycle performance and low-temperature discharge performance of the secondary battery.

[0022] A second aspect of this application provides an electronic device that includes a secondary battery as described in any of the foregoing embodiments. Therefore, the electronic device provided by this application has good performance characteristics.

[0023] The beneficial effects of this application are:

[0024] This application provides a secondary battery and an electronic device. The secondary battery includes an electrolyte comprising a salt of an anion and a cation as shown in Formula I and a compound of Formula II. M1 is selected from element B or element Al; R1, R2, R3, and R4 are each independently selected from C1 to C8 alkyl groups with at least partially fluorinated hydrogen atoms, C6 to C20 aryl groups with at least partially fluorinated hydrogen atoms, C7 to C22 aralkyl groups with at least partially fluorinated hydrogen atoms, C7 to C20 alkylaryl groups with at least partially fluorinated hydrogen atoms, C7 to C20 ether-bonded alkylaryl groups with at least partially fluorinated hydrogen atoms, or C2 to C10 ether-bonded alkyl groups with at least partially fluorinated hydrogen atoms; R is selected from C1 to C5 alkyl groups with or without fluorinated hydrogen atoms, and amino groups substituted with C1 to C5 alkyl groups; Rf is selected from fluorine atoms or trifluoromethyl groups; the cation includes Li. + Na + K + Mg 2+ Ca 2+ or Zn 2+ One of them. By adjusting the electrolyte, which includes a salt composed of anions and cations as shown in Formula I and a compound of Formula II, the cycle performance and low-temperature discharge performance of the secondary battery can be improved. Attached Figure Description

[0025] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0026] Figure 1 is a schematic cross-sectional structure of the negative electrode sheet in one embodiment of this application;

[0027] Figure 2 is a schematic cross-sectional view of the negative electrode sheet in another embodiment of this application;

[0028] Figure 3 is a schematic cross-sectional view of the negative electrode sheet in another embodiment of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0030] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0031] This application provides a secondary battery comprising an electrolyte, the electrolyte comprising a salt composed of anion and cation as shown in Formula I and a compound of Formula II.

[0032] Wherein, M1 is selected from element B or element Al; R1, R2, R3, and R4 are each independently selected from C1 to C8 alkyl groups with at least some hydrogen atoms substituted by fluorine, C6 to C20 aryl groups with at least some hydrogen atoms substituted by fluorine, C7 to C22 aralkyl groups with at least some hydrogen atoms substituted by fluorine, C7 to C20 alkylaryl groups with at least some hydrogen atoms substituted by fluorine, C7 to C20 ether-bonded alkylaryl groups with at least some hydrogen atoms substituted by fluorine, or C2 to C10 ether-bonded alkyl groups with at least some hydrogen atoms substituted by fluorine. R is selected from C1 to C5 alkyl groups substituted by fluorine or not, and amino groups substituted by C1 to C5 alkyl groups; Rf is selected from fluorine atoms or trifluoromethyl groups. Cations include Li. + Na + K + Mg 2+ Ca 2+ or Zn 2+ One of them.

[0033] The inventors discovered that the anion represented by Formula I has a high reduction potential, allowing it to preferentially undergo reduction reactions at the negative electrode during the secondary battery formation stage, compared to most solvent molecules. Due to its aluminum center and highly fluorinated groups, it forms an interface layer rich in inert lithium fluoride and highly ion-conducting lithium fluoroaluminate, thus providing excellent interface passivation and protection. This effectively protects the electrode materials, thereby improving the cycle capacity retention and cycle performance of the secondary battery. However, the high fluorination of the anion represented by Formula I can easily lead to the formation of excessive lithium fluoride at the positive and / or negative electrode interfaces, affecting interfacial ion transport. Adding a compound of Formula II introduces a sulfur-containing interface through decomposition, resulting in better interface stability and improved interfacial ion transport performance. This allows for the simultaneous achievement of good cycle performance and low-temperature discharge performance. Therefore, by controlling the electrolyte to include a salt composed of the anion and cation represented by Formula I and a compound of Formula II, the secondary battery can simultaneously possess good cycle performance and low-temperature discharge performance.

[0034] In one embodiment of this application, the anion represented by Formula I includes at least one of the following anions:

[0035] Based on the mass of the electrolyte, the mass percentage of the salt composed of anions and cations as shown in Formula I is A, where 0.05% ≤ A ≤ 10%, preferably 0.1% ≤ A ≤ 5%. Exemplarily, the value of A can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any two of the above values. By selecting the salt composed of anions and cations as shown in Formula I and adjusting the mass percentage of the salt composed of anions and cations as shown in Formula I within the scope of this application, the amount of active lithium consumed during the formation stage of the secondary battery can be appropriately controlled, resulting in a suitable thickness of the interface layer. This not only better protects the electrode material but also facilitates lithium-ion transport, thereby enabling the secondary battery to have higher initial efficiency and better low-temperature discharge performance.

[0036] In one embodiment of this application, the compound of formula II includes at least one of the following compounds:

[0037] Based on the mass of the electrolyte, the mass percentage of compound II is B, where 1% ≤ B ≤ 50%, preferably 3% ≤ B ≤ 30%. Exemplarily, the value of B can be 1%, 3%, 5%, 7%, 9%, 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, or a range of any two of the above values. By selecting the above-mentioned compound II and adjusting the mass percentage of compound II within the scope of this application, compound II, having a suitable mass percentage, enables the electrolyte to have a suitable viscosity and high ionic conductivity, which is beneficial for lithium-ion transport, improving both the cycle performance of the secondary battery and the low-temperature discharge performance.

[0038] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the salt composed of anion and cation shown in Formula I is A, and the mass percentage of the compound in Formula II is B, with 0.5 ≤ B / A ≤ 60. Exemplarily, the value of B / A can be 0.5, 1, 3, 5, 7, 9, 10, 13, 15, 17, 19, 20, 23, 25, 27, 29, 30, 33, 35, 37, 39, 40, 43, 45, 47, 49, 50, 53, 55, 57, 59, 60, or a range of any two of the above values. By adjusting the value of B / A within the range of this application, the mass percentage of the salt composed of anion and cation shown in Formula I is matched with the mass percentage of the compound in Formula II, which can form a more stable and highly ion-conductive interface layer, better protect the electrode material, and better facilitate lithium-ion transport, further improving the cycle performance and low-temperature discharge performance of the secondary battery.

[0039] In one embodiment of this application, the electrolyte further includes a compound of formula III.

[0040] In this electrolyte, R5, R6, R7, R8, and R9 are each independently selected from hydrogen atoms, fluorine atoms, fluorine-substituted or unsubstituted C1-C5 alkyl groups, C2-C5 alkenyl groups, C2-C5 alkynyl groups, carbonyl groups, ester groups, aldehyde groups, or carboxylic acid groups. Adjacent groups in R5, R6, R7, R8, and R9 can be covalently linked to form a ring; X is selected from methylene or oxygen atoms. The electrolyte also includes the compound of Formula III, which is an inner salt molecule. The compound of Formula III can synergistically interact with the anion shown in Formula I to promote the decomposition reaction of the anion shown in Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also giving the secondary battery better low-temperature discharge performance. In this application, the above-mentioned "covalent bond" can be a single bond.

[0041] In one embodiment of this application, the compound of formula III includes at least one of the following compounds:

[0042] The above-mentioned compound III can synergistically interact with the anion shown in Formula I to promote the decomposition reaction of the anion shown in Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0043] In one embodiment of this application, the mass percentage of compound III is C, 0.1% ≤ C ≤ 1%, based on the mass of the electrolyte. Exemplarily, the value of C can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range of any two of the above values. By adjusting the mass percentage of compound III within the scope of this application, a suitable mass percentage of compound III can be achieved. Compound III can synergistically interact with the anion represented by formula I to promote the decomposition reaction of the anion represented by formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0044] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the salt composed of anion and cation shown in Formula I is A, and 0.5 ≤ A / C ≤ 5. Exemplarily, the value of A / C can be 0.5, 0.7, 0.9, 1, 1.3, 1.5, 1.7, 1.9, 2, 2.3, 2.5, 2.7, 2.9, 3, 3.3, 3.5, 3.7, 3.9, 4, 4.3, 4.5, 4.7, 4.9, 5, or a range of any two of the above values. By adjusting the value of A / C within the range of this application, the mass percentage of the salt composed of anion and cation shown in Formula I is matched with the mass percentage of the compound in Formula III. The compound in Formula III can synergistically act with the anion shown in Formula I, promoting the decomposition reaction of the anion shown in Formula I, forming an interface layer with better passivation and protection functions, better protecting the electrode material, further improving the cycle performance of the secondary battery, and also enabling the secondary battery to have better low-temperature discharge performance.

[0045] In one embodiment of this application, the electrolyte further includes a linear ester, which includes at least one selected from ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl tert-butyrate, ethyl tert-butyrate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate. Using the above-mentioned linear esters allows the electrolyte to have a suitable overall viscosity and high ionic conductivity, which is beneficial for lithium-ion transport and can further improve the cycle performance and low-temperature discharge performance of the secondary battery.

[0046] In one embodiment of this application, the mass percentage of the linear ester, D, is based on the mass of the electrolyte, where 10% ≤ D ≤ 90%, preferably 20% ≤ D ≤ 70%. Exemplarily, the value of D can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or a range of any two of the above values. By adjusting the value of D within the range specified in this application, the linear ester can have a suitable mass percentage, resulting in a suitable overall viscosity of the electrolyte, high ionic conductivity, which is beneficial for lithium-ion transport and can further improve the cycle performance and low-temperature discharge performance of the secondary battery.

[0047] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the salt composed of anion and cation shown in Formula I is A, where 0.005 ≤ A / D ≤ 0.1. Exemplarily, the value of A / D can be 0.005, 0.007, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a range of any two of the above values. By adjusting the value of A / D within the range of this application, the mass percentage of the salt composed of anion and cation shown in Formula I is matched with the mass percentage of the linear ester. The linear ester enables the electrolyte to have a suitable overall viscosity and high ionic conductivity, which is beneficial for lithium-ion transport. Simultaneously, the linear ester can synergistically interact with the anion shown in Formula I, and the decomposition of the linear ester generates an interface layer containing lithium carboxylate, further enhancing the interfacial ion conductivity and further improving the cycle performance and low-temperature discharge performance of the secondary battery.

[0048] In this application, the characteristics of the different components contained in the electrolyte can be combined, and the implementation methods covered by the above combinations are all within the protection scope of this application.

[0049] In this application, the electrolyte also includes lithium salts and non-aqueous organic solvents. This application does not particularly limit the type of lithium salt; lithium salts known in the art can be used. Exemplarily, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO2F)2), LiFSI), lithium difluorophosphate (LiPO2F2), lithium bis(oxalatoborate) (LiB(C2O4)2, LiBOB), or lithium difluorooxalatoborate (LiBF2(C2O4), LiDFOB). This application does not particularly limit the non-aqueous organic solvent, as long as it achieves the purpose of this application. For example, the non-aqueous organic solvent may contain at least one of carbonate compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). The aforementioned fluorinated carbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the mass percentage of lithium salt and non-aqueous organic solvent in the electrolyte, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage E of the lithium salt is 8% to 15%, and the mass percentage F of the non-aqueous organic solvent is 0.8% to 90%.

[0050] In one embodiment of this application, the electrolyte may include a salt composed of anions and cations as shown in Formula I, a compound of Formula II, a lithium salt, and a non-aqueous organic solvent. The mass percentages of the salt composed of anions and cations as shown in Formula I, the compound of Formula II, and the lithium salt are as described above, and the mass percentage F of the non-aqueous organic solvent is 25% to 90%. The secondary battery including the above electrolyte exhibits both good cycle performance and low-temperature discharge performance.

[0051] In one embodiment of this application, the electrolyte may include a salt composed of anions and cations as shown in Formula I, a compound of Formula II, a lithium salt, a compound of Formula III, and a non-aqueous organic solvent. The mass percentages of the salt composed of anions and cations as shown in Formula I, the compound of Formula II, the lithium salt, and the compound of Formula III are as described above, and the mass percentage F of the non-aqueous organic solvent is 24% to 90%. The secondary battery including the above electrolyte exhibits both good cycle performance and low-temperature discharge performance.

[0052] In one embodiment of this application, the electrolyte may include a salt composed of anions and cations as shown in Formula I, a compound of Formula II, a lithium salt, a linear ester, and a non-aqueous organic solvent. The mass percentages of the salt composed of anions and cations as shown in Formula I, the compound of Formula II, the lithium salt, and the linear ester are as described above, and the mass percentage F of the non-aqueous organic solvent is 0.9% to 15%. The secondary battery including the above electrolyte exhibits both good cycle performance and low-temperature discharge performance.

[0053] In one embodiment of this application, the electrolyte may include a salt composed of anions and cations as shown in Formula I, a compound of Formula II, a lithium salt, a compound of Formula III, a linear ester, and a non-aqueous organic solvent. The mass percentages of the salt composed of anions and cations as shown in Formula I, the compound of Formula II, the lithium salt, the compound of Formula III, and the linear ester are as described above, and the mass percentage F of the non-aqueous organic solvent is 0.8% to 14%. The secondary battery including the above electrolyte exhibits both good cycle performance and low-temperature discharge performance.

[0054] In this application, the secondary battery further includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The aforementioned "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive current collector or only a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the positive current collector, as long as the purpose of this application is achieved; for example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector).

[0055] The cathode material layer of this application includes a cathode active material, which comprises a substance capable of reversibly inserting and de-intercalating active ions such as lithium ions. The cathode material layer can be one or more layers, and each layer in a multilayer cathode material layer can contain the same or different cathode active materials. This application does not impose any particular limitation on the cathode active material, as long as it can achieve the purpose of this application. For example, the cathode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. The cathode material layer of this application also includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the cathode material layer, as long as it can achieve the purpose of this application. For example, the conductive agent can include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned conductive carbon black may include, but is not limited to, Super P, acetylene black, or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application can be achieved.

[0056] This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. This application also does not impose any particular limitation on the thickness of the positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided positive electrode material layer is 30 μm to 120 μm.

[0057] Optionally, the positive electrode may further include a conductive layer, which is located between the positive current collector and the positive electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0058] In this application, the secondary battery further includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The aforementioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a part of it; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved, for example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, or composite current collectors, etc.

[0059] The negative electrode material layer of this application includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO₂, etc. x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 The negative electrode material layer of this application includes at least one of the following: Li-Al alloy or metallic lithium. The negative electrode material layer of this application also includes a binder. This application does not impose any particular limitation on the binder in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the binder can be at least one of the aforementioned binders. The negative electrode material layer of this application also includes a conductive agent. This application does not impose any particular limitation on the conductive agent in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the conductive agent can be at least one of the aforementioned conductive agents. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, binder, and conductive agent in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0060] This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector can be from 5 μm to 16 μm. This application also does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of the single-sided negative electrode material layer can be from 30 μm to 120 μm.

[0061] Optionally, the negative electrode sheet may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, which can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent and binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved. This application does not impose any particular limitation on the thickness of the conductive layer, as long as the purpose of this application can be achieved; for example, the thickness of the conductive layer is 1 μm to 10 μm. Exemplarily, FIG1 shows a schematic cross-sectional structure of a negative electrode sheet according to one embodiment of this application. The negative electrode sheet 10 includes a negative electrode current collector 11, a conductive layer 12, and a negative electrode material layer 13. The conductive layer 12 is disposed between the negative electrode current collector 11 and the negative electrode material layer 13, and the conductive layer 12 and the negative electrode material layer 13 are sequentially disposed on the A surface of the negative electrode current collector 11. In one embodiment, as shown in FIG2, the conductive layer 12 and the negative electrode material layer 13 are sequentially disposed on the B surface of the negative electrode current collector 11. In another embodiment, as shown in FIG3, the conductive layer 12 and the negative electrode material layer 13 are disposed on the A surface and the B surface of the negative electrode current collector 11, respectively.

[0062] In this application, the secondary battery also includes a separator, which separates the positive electrode and the negative electrode to prevent internal short circuits, allow electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process. This application does not impose any particular limitations on the separator, as long as it achieves the purpose of this application. For example, the separator material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the separator type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0063] In this application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. This application does not have any particular limitation on the aforementioned inorganic particles, and may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not have any particular limitation on the aforementioned binders, and may include at least one of the aforementioned binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0064] The secondary battery of this application also includes a packaging bag for containing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the art for secondary batteries. This application does not limit the aforementioned other components. This application does not have any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0065] This application does not impose any particular limitation on the type of secondary battery, which may include any device in which an electrochemical reaction occurs. In this application, the secondary battery may include, but is not limited to: lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries (lithium-ion polymer batteries), etc.

[0066] The preparation process of the secondary battery described in this application is well known to those skilled in the art, and this application has no particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, overcurrent protection components, conductive plates, etc., may be placed in the packaging bag as needed to prevent the internal pressure of the secondary battery from rising and overcharging / discharging.

[0067] A second aspect of this application provides an electronic device that includes a secondary battery as described in any of the foregoing embodiments. Therefore, the electronic device provided by this application has good performance characteristics.

[0068] This application does not specifically limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0069] Example

[0070] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0071] Test methods and equipment:

[0072] Cyclic performance test:

[0073] The lithium-ion battery was placed in a constant temperature environment of 25°C and left to stand for 30 minutes to allow it to reach the constant temperature state of 25°C. It was then charged at a constant current of 0.5C to 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.025C. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 3.0V. The initial discharge capacity was recorded as C0. This charge-discharge cycle was repeated 500 times, and the discharge capacity after 500 cycles was recorded as C1.

[0074] Cyclic capacity retention rate = C1 / C0 × 100%.

[0075] Low-temperature discharge performance test:

[0076] The lithium-ion battery was placed in a constant temperature environment of 25℃ and left to stand for 30 minutes to reach the constant temperature state of 25℃. It was then charged at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V to a current of 0.025C, and discharged at a constant current of 0.2C to 3.0V. The discharge capacity at 25℃ was recorded as C2. The battery was then charged again at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V to a current of 0.025C, and transferred to a constant temperature test chamber of -10℃. It was left to stand for 60 minutes to reach the constant temperature state of -10℃, and then discharged at a constant current of 0.2C to 3.0V. The discharge capacity at -10℃ was recorded as C3.

[0077] -10℃ low-temperature discharge capacity retention rate = C3 / C2 × 100%.

[0078] Example 1-1

[0079] <Preparation of Negative Electrode Sheets>

[0080] The negative electrode active materials, artificial graphite, SBR, and CMC-Na, were mixed in a mass ratio of 98.5:1:0.5, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 54 wt%. The slurry was then stirred evenly in a vacuum mixer. The conductive agent Super P and the binder SBR were mixed in a mass ratio of 9:1, and then deionized water was added as a solvent to prepare a conductive layer slurry with a solid content of 10 wt%. The conductive layer slurry was uniformly coated onto one surface of an 8 μm thick copper foil used as a negative electrode current collector and dried at 85°C, forming a 2 μm thick conductive layer on one surface of the copper foil. Then, the negative electrode slurry was coated onto the surface of the conductive layer away from the copper foil and dried at 85°C, forming a 100 μm thick negative electrode material layer on the same surface. This yielded a negative electrode sheet with a single-sided conductive layer and a negative electrode material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided conductive layer and a negative electrode material layer. After coating, the negative electrode sheet is cold-pressed and cut into 76mm × 851mm dimensions for later use. The compaction density of the negative electrode material layer after cold pressing is 1.70 g / cm³. 3 .

[0081] <Preparation of the positive electrode>

[0082] Lithium cobalt oxide (LiCoO2), a positive electrode active material, Super P, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. The mixture was stirred evenly in a vacuum mixer to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector and dried at 85°C to obtain a single-sided coated positive electrode sheet with a coating thickness of 110 μm. The above steps were then repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After coating, the positive electrode sheet was cold-pressed and cut into 74 mm × 867 mm dimensions for later use. The compaction density of the positive electrode layer after cold pressing was 4.15 g / cm³. 3 .

[0083] <Preparation of Electrolyte>

[0084] In an argon atmosphere glove box with a water content of less than 10 ppm, the anion shown in Formula I-1 is reacted with Li + The salts of Formula II and Compound II-1 are mixed, then lithium hexafluorophosphate is added, followed by diethyl carbonate (DEC), and the mixture is stirred until homogeneous to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage E of the lithium salt is 12.5%, and the anion represented by Formula I-1 reacts with Li... + The salt composition A has a mass percentage of 0.5%, the compound of formula II has a mass percentage of 30%, and the diethyl carbonate has a mass percentage of 57%.

[0085] <Septum>

[0086] A 5μm thick polyethylene (PE) porous membrane (supplied by Celgard) was used.

[0087] <Preparation of Lithium-ion Batteries>

[0088] The prepared positive electrode, separator, negative electrode, and separator are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrodes are then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation (0.02C constant current charging to 3.5V, then 0.1C constant current charging to 3.9V), shaping, and capacity testing.

[0089] Examples 1-2 to Examples 1-36

[0090] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0091] Examples 2-1 to 2-16

[0092] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Example 1-1. Specifically, when the anion shown in Formula I-1 reacts with Li... + When the mass percentage of the salt or compound of formula II changes, the mass percentage of diethyl carbonate changes accordingly, while the mass percentage of lithium salt remains unchanged.

[0093] Examples 3-1 to 3-22

[0094] Except for the addition of compound III in the <Preparation of Electrolyte> section and the adjustment of relevant preparation parameters according to Table 3, the rest is the same as in Example 1-1. Specifically, when the anion represented by Formula I-1 reacts with Li... + When the mass percentage of the salts and compounds of formula III changes, the mass percentage of diethyl carbonate changes accordingly, while the mass percentage of lithium salts and compounds of formula II remains unchanged.

[0095] Examples 4-1 to 4-25

[0096] Except for the addition of a linear ester and adjustment of the relevant preparation parameters according to Table 4 in the <Preparation of Electrolyte> section, the rest is the same as in Examples 2-11. Specifically, when the anion represented by Formula I-1 reacts with Li... + When the mass percentage of the salt, Formula II compound, or linear ester changes, the mass percentage of diethyl carbonate changes accordingly, while the mass percentage of lithium salt remains unchanged.

[0097] Example 4-26

[0098] Except for the addition of compound III-1 of formula III in the <Preparation of Electrolyte> section, the rest is the same as in Examples 4-6. Specifically, based on the mass of the electrolyte, the mass percentage E of the lithium salt is 12.5%, the mass percentage A of the salt composed of the anion and Li+ shown in formula I-1 is 0.5%, the mass percentage B of the compound of formula II is 30%, the mass percentage D of the linear ester is 30%, the mass percentage C of the compound of formula III is 0.5%, and the mass percentage F of diethyl carbonate is 26.5%.

[0099] Comparative Examples 1 to 3

[0100] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1. Specifically, when the anion shown in Formula I-1 reacts with Li... + When the mass percentage of the salt or compound of formula II changes, the mass percentage of diethyl carbonate changes accordingly, while the mass percentage of lithium salt remains unchanged.

[0101] The preparation and performance parameters of each embodiment and comparative example are shown in Tables 1 to 4.

[0102] Table 1

[0103] Note: In Table 1, " / " indicates that there are no relevant preparation parameters.

[0104] Referring to Table 1, and from Examples 1-1 to 1-36 and Comparative Examples 1 to 3, it can be seen that by adjusting the electrolyte to include a salt composed of anions and cations as shown in Formula I and a compound of Formula II, the lithium-ion battery exhibits higher cycle capacity retention and higher low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance. In contrast, in Comparative Examples 1 to 3, the lithium-ion battery exhibits lower cycle capacity retention and lower low-temperature discharge capacity retention at -10°C, indicating poorer cycle performance and low-temperature discharge performance.

[0105] Table 2

[0106] The mass percentage of the salt composed of anions and cations as shown in Formula I typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 2-1 to 2-9, when the mass percentage of the salt composed of anions and cations as shown in Formula I is within the range of this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0107] The mass percentage of compound II typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 2-1, 2-10 to 2-16, when the mass percentage of compound II is within the range of this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0108] The B / A ratio typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 2-1 to 2-9, when the B / A ratio is within the range specified in this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0109] Table 3 Note: In Table 3, " / " indicates that there are no relevant preparation parameters.

[0110] The electrolyte also includes compounds of formula III, the types of which typically affect the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 3-4, 3-8 to 3-22, when the electrolyte also includes compounds of formula III (within the scope of this application), the lithium-ion battery exhibits higher cycle capacity retention and higher low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0111] The mass percentage of Formula III compound typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 3-1 to 3-6, when the mass percentage of Formula III compound is within the range of this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0112] The A / C ratio typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 3-1 to 3-7, when the A / C value is within the range specified in this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0113] Table 4 Note: In Table 4, " / " indicates that there are no relevant preparation parameters.

[0114] The electrolyte also includes linear esters, and the type of linear ester typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 4-8, 4-13 to 4-25, when the electrolyte also includes linear esters (within the scope of this application), the lithium-ion battery exhibits higher cycle capacity retention and higher low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0115] The mass percentage of linear esters typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 4-1 to 4-12, when the mass percentage of linear esters is within the range specified in this application, the lithium-ion batteries exhibit high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion batteries possess both good cycle performance and low-temperature discharge performance.

[0116] The A / D ratio typically affects the cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 4-1 to 4-12, when the A / C value is within the range specified in this application, the lithium-ion battery exhibits high cycle capacity retention and high low-temperature discharge capacity retention at -10°C, indicating that the lithium-ion battery simultaneously possesses good cycle performance and low-temperature discharge performance.

[0117] As can be seen from Examples 1-1, 3-4, 4-6, and 4-26, when the electrolyte also includes a compound of Formula III and a linear ester, the lithium-ion battery exhibits a high cycle capacity retention rate and a high low-temperature discharge capacity retention rate at -10℃, indicating that the lithium-ion battery has both good cycle performance and low-temperature discharge performance.

[0118] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0119] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0120] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A secondary battery comprising an electrolyte, said electrolyte comprising a salt of anions and cations of Formula I and a compound of Formula II. in, M1 is selected from element B or element Al; R1, R2, R3, and R4 are each independently selected from C1 to C8 alkyl groups with at least some hydrogen atoms substituted by fluorine, C6 to C20 aryl groups with at least some hydrogen atoms substituted by fluorine, C7 to C22 aralkyl groups with at least some hydrogen atoms substituted by fluorine, C7 to C20 alkylaryl groups with at least some hydrogen atoms substituted by fluorine, C7 to C20 ether-bonded alkylaryl groups with at least some hydrogen atoms substituted by fluorine, or C2 to C10 ether-bonded alkyl groups with at least some hydrogen atoms substituted by fluorine. R is selected from C1 to C5 alkyl groups that are fluorinated or unsubstituted, or amino groups that are substituted with C1 to C5 alkyl groups; Rf is selected from fluorine atoms or trifluoromethyl groups; The cation includes Li + Na + K + Mg 2+ Ca 2+ or Zn 2+ One of them.

2. The secondary battery according to claim 1, wherein, The anion represented by Formula I includes at least one of the following anions: Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, where 0.05% ≤ A ≤ 10%.

3. The secondary battery according to claim 1, wherein, The compound of formula II includes at least one of the following compounds: Based on the mass of the electrolyte, the mass percentage of the compound of formula II is B, where 1% ≤ B ≤ 50%.

4. The secondary battery according to claim 1, wherein, The secondary battery satisfies at least one of the following characteristics: (1) Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, 0.1% ≤ A ≤ 5%; (2) Based on the mass of the electrolyte, the mass percentage of the compound of formula II is B, 3% ≤ B ≤ 30%; (3) Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, the mass percentage of the compound represented by Formula II is B, and 0.5≤B / A≤60.

5. The secondary battery according to claim 1, wherein, The electrolyte also includes a compound of formula III. R5, R6, R7, R8, and R9 are each independently selected from hydrogen atoms, fluorine atoms, alkyl groups of C1 to C5 that are substituted with fluorine or not, alkenyl groups of C2 to C5, alkynyl groups of C2 to C5, carbonyl groups, ester groups, aldehyde groups, or carboxylic acid groups. Adjacent groups in R5, R6, R7, R8, and R9 can be connected to form a ring by covalent bonds; X is selected from methylene or oxygen atoms.

6. The secondary battery according to claim 5, wherein, The compound of formula III includes at least one of the following compounds:

7. The secondary battery according to claim 5, wherein, Based on the mass of the electrolyte, the mass percentage of the compound of formula III is C, where 0.1% ≤ C ≤ 1%.

8. The secondary battery according to claim 7, wherein, Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, where 0.5 ≤ A / C ≤ 5.

9. The secondary battery according to claim 1, wherein, The electrolyte further includes linear esters, which include at least one of ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl tert-butyrate, ethyl tert-butyrate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate.

10. The secondary battery according to claim 9, wherein, Based on the mass of the electrolyte, the mass percentage of the linear ester is D, where 10% ≤ D ≤ 90%.

11. The secondary battery according to claim 10, wherein, 20％≤D≤70％。 12. The secondary battery according to claim 10, wherein, Based on the mass of the electrolyte, the mass percentage of the salt composed of the anion and the cation represented by Formula I is A, where 0.005 ≤ A / D ≤ 0.

1.

13. An electronic device comprising a secondary battery according to any one of claims 1 to 12.

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