Secondary battery and electric device

Abstract

Disclosed in the present application are a secondary battery and an electric device, relating to the field of batteries. By controlling mVC, mFEC, mBP, PD, and mn to satisfy formula (I), the present application ensures that the secondary battery using natural graphite as a negative electrode active material has good high-temperature cycling and storage performance and a higher cost performance.

Description

Secondary battery and electrical equipment

[0001] Cross-references

[0002] This application is related to the Chinese application filed on December 28, 2023, whose invention name is "A secondary battery and electrical equipment", application number is 202311853057.1, and the entire contents of the application are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of batteries, and in particular to a secondary battery and an electrical device. Background Art

[0004] As secondary battery technology matures, it's widely used in power and energy storage applications. While they offer advantages like high energy density and environmental friendliness, they come at a high cost. Optimizing secondary battery costs has become a necessity for battery manufacturers.

[0005] Compared to artificial graphite, natural graphite offers a simpler manufacturing process, lower cost, and higher specific capacity. Using natural graphite instead of artificial graphite as the negative electrode active material for secondary batteries can reduce costs. However, natural graphite suffers from numerous surface defects, poor electrolyte compatibility, and numerous side reactions, resulting in poor high-temperature cycling and storage performance. Therefore, there is an urgent need to develop a technology that effectively addresses these issues with natural graphite. Summary of the Invention

[0006] Based on the defects of the existing technology, the purpose of this application is to provide a secondary battery and electrical equipment. The secondary battery uses natural graphite as the negative electrode active material of the secondary battery, which not only has low cost but also has good high-temperature cycle performance and high-temperature storage performance.

[0007] In a first aspect, the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises natural graphite;

[0008] The electrolyte comprises a first additive and a second additive, the first additive comprising vinylene carbonate (VC), and the second additive comprising at least two of fluoroethylene carbonate (FEC), a phosphorus-containing additive, and a boron-containing additive;

[0009] The secondary battery satisfies the following relationship:

[0010] Among them, m VC % is the mass percentage of vinylene carbonate in the electrolyte;

[0011] m FEC % is the mass percentage of fluoroethylene carbonate in the electrolyte;

[0012] m BP % is the sum of the mass percentages of the phosphorus-containing additive and the boron-containing additive in the electrolyte,

[0013] PD g / cm 3 is the compaction density of the negative electrode active material layer;

[0014] m n It is the ratio of the mass of the natural graphite to the total mass of the negative electrode active material.

[0015] In some embodiments, 1≤m VC ≤5.

[0016] In some embodiments, 0≤m FEC ≤5.

[0017] In some embodiments, m VC +m FEC ≥3.

[0018] In some embodiments, 0 <m BP ≤4.

[0019] In some embodiments, 0≤m B <2.5 or 0≤m p <2.5; where m B %, m p % respectively represent the mass percentage of the boron-containing additive and the phosphorus-containing additive in the electrolyte.

[0020] In some embodiments, 1.2≤PD≤2.0.

[0021] In some embodiments, 0.05≤m n ≤1.

[0022] In some embodiments, the phosphorus-containing additive includes at least one of lithium tetrafluorooxalophosphate, trimethyl phosphate, diethyl fluorophosphate, and tris(2,2,2-trifluoroethyl) phosphate.

[0023] In some embodiments, the boron-containing additive includes at least one of lithium difluorooxalatoborate, lithium dioxalatoborate, trimethyl borate, and triallyl borate.

[0024] In some embodiments, the electrolyte further comprises an organic solvent, and the organic solvent comprises a cyclic carbonate and a chain carbonate.

[0025] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0026] In some embodiments, the electrolyte further comprises an organic solvent, and the mass percentage of the organic solvent in the electrolyte is 70% to 85%.

[0027] In some embodiments, the electrolyte further comprises a sulfur-containing additive, wherein the sulfur-containing additive includes at least one of vinyl sulfate, methylene methanedisulfonate, ethylene sulfite, and 1,3-propanedisulfonic anhydride.

[0028] In some embodiments, the mass percentage of the sulfur-containing additive in the electrolyte is 0.1% to 1%.

[0029] In some embodiments, the electrolyte further comprises a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.8 to 1.5 mol / L.

[0030] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises Li a Fe 1-y Mn y PO4, where 0.9≤a≤1.1, 0≤y<1.

[0031] In a second aspect, the present application provides an electric device, comprising the secondary battery, wherein the secondary battery is used as a power supply for the electric device.

[0032] The beneficial effects of this application are:

[0033] (1) This application is controlled by m VC 、m FEC 、m BP , PD and m n Satisfying the above relationship can improve the high-temperature performance of the secondary battery, ensuring that it has good high-temperature cycle performance and high-temperature storage performance.

[0034] (2) The present application reduces costs by adding inexpensive natural graphite to the negative electrode active material layer.

[0035] (3) The secondary battery of the present application is low in price, has excellent high-temperature performance, and is cost-effective. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present application, the present application will be further described below in conjunction with specific embodiments and comparative examples. Its purpose is to understand the content of the present application in detail, rather than to limit the present application. All other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present application. The experimental reagents and instruments involved in the implementation of this application are all commonly used ordinary reagents and instruments unless otherwise specified.

[0037] In a first aspect, the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises natural graphite;

[0038] The electrolyte comprises a first additive and a second additive, the first additive comprising vinylene carbonate (VC), and the second additive comprising at least two of fluoroethylene carbonate (FEC), a phosphorus-containing additive, and a boron-containing additive;

[0039] The secondary battery satisfies the following relationship: 2.47≤I≤5.84,

[0040] in,

[0041] m VC % is the mass percentage of vinylene carbonate in the electrolyte;

[0042] m FEC % is the mass percentage of fluoroethylene carbonate in the electrolyte;

[0043] m BP % is the sum of the mass percentages of phosphorus-containing additives and boron-containing additives in the electrolyte,

[0044] PD g / cm 3 is the compaction density of the negative electrode active material layer;

[0045] m n It is the ratio of the mass of natural graphite in the negative electrode active material layer to the total mass of the negative electrode active material.

[0046] The above secondary battery reduces its cost by adding relatively low-priced natural graphite in the negative electrode active material layer; and by controlling m VC 、m FEC 、m BP , PD and m nSatisfying the above relationship ensures that it has good high temperature performance, such as high temperature cycle performance and high temperature storage performance, thus making it more cost-effective and more competitive. In addition, the proportion of natural graphite in the negative electrode active material will affect the selection of additives and their content. By controlling m VC 、m FEC 、m BP , PD and m n By satisfying the above relationship, a battery with excellent performance can be designed through early formula calculations during the research and development process, greatly shortening the research and development cycle and reducing research and development costs.

[0047] In the present application, I is in the range of 2.47 to 5.84, such as I is 2.47, 2.60, 2.80, 3.00, 3.20, 3.50, 3.70, 4.00, 4.30, 4.50, 4.80, 5.00, 5.20, 5.50, 5.84 or a range formed by any two of the above values.

[0048] Vinylene carbonate (VC) is a negative electrode film-forming additive and overcharge protection additive with good high-temperature performance, which can extend the high-temperature cycle life of secondary batteries and improve their high-temperature storage performance. In some embodiments, 1≤m VC ≤5, such as m VC is 1, 2, 3, 4, 5 or any two of the above values ​​to improve the high temperature cycle and storage performance of the secondary battery. In one embodiment, 2≤m VC ≤5, such as m VC The range is 2, 3, 4, 5 or any two of the above values ​​to better improve the high temperature cycle and storage performance of the secondary battery. VC Can be measured by GC-MS.

[0049] Fluoroethylene carbonate (FEC) is a negative electrode film-forming additive that causes the formed SEI film to contain more inorganic component LiF, which can increase ion conductivity and stabilize the solid-liquid interface, thereby improving the high-temperature cycle and storage performance of the battery. In some embodiments, 0≤m FEC ≤5, such as m FEC is 0, 1, 2, 3, 4, 5 or a range formed by any two of the above values. In one embodiment, 1≤m FEC ≤4, such as m FEC It is 1, 2, 3, 4 or any two values ​​above to better improve the high temperature cycle and storage performance of the battery and avoid DCR deterioration. FEC Can be measured by GC-MS.

[0050] In this application, m VC +m FEC >0, such as mVC +m FEC is 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any two of the above values ​​to improve the high temperature cycle and storage performance of the battery by using VC and / or FEC. In some embodiments, m VC +m FEC ≥3, such as m VC +m FEC The range is 3, 4, 5, 6, 7, 8, 9, 10 or any two of the above values ​​to better improve the high temperature cycle and storage performance of the battery.

[0051] Phosphorus-containing additives and boron-containing additives are beneficial for forming a more stable SEI film, reducing the occurrence of side reactions, reducing the consumption of active lithium, and improving the high-temperature cycle and storage performance of the battery. In some embodiments, <m BP ≤4, such as m BP is 0.2, 0.5, 1, 2, 3, 4 or a range formed by any two of the above values. In one embodiment, 0.4≤m BP ≤1.9, such as m BP It is 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 1.9 or a range formed by any two of the above values ​​to better improve the high temperature cycle and storage performance of the battery.

[0052] In some embodiments, 0≤m B <2.5 or 0≤m p <2.5; where m B 、m p Respectively represent the mass percentage of the boron-containing additive and the phosphorus-containing additive in the electrolyte. B 0, 0.1, 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.4 or any two of the above values. p 0, 0.1, 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.4 or the range formed by any two of the above values. B and m p Can be measured by GC-MS.

[0053] In some embodiments, the phosphorus-containing additive includes at least one of lithium tetrafluorooxalophosphate, trimethyl phosphate, diethyl fluorophosphate, and tris(2,2,2-trifluoroethyl)phosphate.

[0054] In some embodiments, the phosphorus-containing additive includes lithium tetrafluorooxalophosphate.

[0055] In some embodiments, the boron-containing additive includes at least one of lithium difluorooxalatoborate, lithium dioxalatoborate, trimethyl borate, and triallyl borate.

[0056] In some embodiments, the boron-containing additive includes lithium difluorooxalatoborate.

[0057] In some embodiments, the electrolyte further includes a third additive comprising a sulfur-containing additive. Optionally, the sulfur-containing additive includes at least one of vinyl sulfate, methylene methanedisulfonate, ethylene sulfite, and 1,3-propanedisulfonic anhydride. Optionally, the mass percentage of the sulfur-containing additive in the electrolyte is 0.1% to 1%, such as 0.1%, 0.3%, 0.5%, 0.7%, 1%, or a range formed by any two of the above values.

[0058] In the present application, the electrolyte also includes an organic solvent. Cyclic carbonates have high dielectric constants and ionic conductivity, enabling the formation of a stable SEI film on the negative electrode surface, but they have relatively high viscosity; chain carbonates, on the other hand, have lower viscosity. In some embodiments, the organic solvent includes both cyclic carbonates and chain carbonates, leveraging the properties of both to produce a solvent with suitable viscosity, high dielectric constant, and high ionic conductivity. As an example, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate. As an example, the chain carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Optionally, the mass percentage of the cyclic carbonate in the organic solvent is greater than 20%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range formed by any two of these values. Optionally, the mass percentage of the chain carbonate in the organic solvent is greater than 50%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range formed by any two of these values. Optionally, the mass percentage of the organic solvent in the electrolyte is 70% to 85%, such as 70%, 75%, 80%, 85% or a range formed by any two of the above values.

[0059] In some embodiments, the electrolyte further includes a lithium salt. As an example, the lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Optionally, the concentration of the lithium salt in the electrolyte is 0.8 to 1.5 mol / L, such as 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, or a range formed by any two of the above values.

[0060] The compaction density (PD) of the negative electrode active material layer affects the high-temperature cycle and storage performance of the battery, and also affects the energy density of the battery. In some embodiments, in order to obtain better high-temperature cycle and storage performance and higher energy density at the same time, 1.2≤PD≤2.0 is selected, such as PD is 1.2, 1.4, 1.6, 1.8, 2.0 or the range formed by any two of the above values. In some embodiments, 1.3≤PD≤1.8, such as PD is 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or the range formed by any two of the above values, to obtain better high-temperature cycle and storage performance and higher energy density. PD can be measured by the following method: take a pole piece of a certain area, measure its area S, then weigh its weight W, and then use a vernier caliper to measure the thickness d of the pole piece, then PD=W / (S×d), where W is in g and S is in cm 2 , d is in cm, PD is in g / cm 3 .

[0061] In some embodiments, 0.05≤m n ≤1, such as m n is 0.05, 0.1, 0.3, 0.5, 0.7, 1 or any two of the above values ​​to ensure a low cost of the secondary battery. In one embodiment, 0.3≤m n ≤0.7, such as m n The range formed by 0.3, 0.4, 0.5, 0.6, 0.7 or any two of the above values ​​not only has lower cost, but also has better high-temperature cycle and storage performance of the battery.

[0062] In some embodiments, the negative electrode active material further comprises artificial graphite. Optionally, the mass percentage of the artificial graphite in the negative electrode active material is 0-95%, such as 0, 1%, 5%, 10%, 30%, 50%, 70%, 90%, 95%, or a range formed by any two of the above values.

[0063] In some embodiments, the mass percentage of the negative electrode active material in the negative electrode active material layer is 94% to 97%.

[0064] In some embodiments, the negative electrode active material layer further includes a conductive agent, a thickener, and a binder. As an example, the conductive agent in the negative electrode active material layer includes at least one of conductive agent SP (conductive carbon black), graphene, and carbon nanotubes. As an example, the thickener in the negative electrode active material layer includes sodium carboxymethyl cellulose (CMC). As an example, the binder in the negative electrode active material layer includes styrene-butadiene rubber (SBR). Optionally, the mass percentage of the conductive agent in the negative electrode active material layer is 1% to 3%. Optionally, the mass percentage of the thickener in the negative electrode active material layer is 0.5% to 2.5%. Optionally, the mass percentage of the binder in the negative electrode active material layer is 0.5% to 2.5%.

[0065] In some embodiments, the negative electrode current collector includes copper foil.

[0066] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises Li a Fe 1-y Mn y PO4, wherein 0.9≤a≤1.1, 0≤y<1. Optionally, a is 0.9, 0.95, 1.0, 1.05, 1.1 or a range formed by any two of the above values. Optionally, y is 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 0.99 or a range formed by any two of the above values. Optionally, Li a Fe 1-y Mn y The mass percentage of PO4 in the positive electrode active material layer is 94% to 98%.

[0067] In some embodiments, the positive electrode active material layer further includes a conductive agent and a binder. As an example, the conductive agent in the positive electrode active material layer includes at least one of conductive agent SP (conductive carbon black), acetylene black, Ketjen black, graphene, and carbon nanotubes. As an example, the binder in the positive electrode active material layer includes polyvinylidene fluoride (PVDF). Optionally, the mass percentage of the conductive agent in the positive electrode active material layer is 1% to 3%. Optionally, the mass percentage of the binder in the positive electrode active material layer is 0.5% to 2.5%.

[0068] In some embodiments, the positive electrode current collector comprises aluminum foil.

[0069] In the present application, the secondary battery further comprises a separator. In some embodiments, the separator comprises at least one of a polyolefin separator, a non-woven fabric separator, and a polyimide separator. Alternatively, the polyolefin separator comprises at least one of a polyethylene separator and a polypropylene separator.

[0070] In a second aspect, the present application provides an electrical device comprising the aforementioned secondary battery, wherein the secondary battery serves as a power supply for the electrical device. As an example, the electrical device comprises at least one of an electric car, an electric motorcycle, an electric tool, and a household appliance.

[0071] In order to clearly understand the technical solution of the present application, the present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be understood as limiting the scope of protection claimed in the present application.

[0072] Example 1

[0073] This embodiment provides a method for preparing a lithium-ion secondary battery, which includes the following steps:

[0074] The positive electrode active material LiFePO4, the conductive agent SP, and the binder PVDF were mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) was added and stirred under vacuum to obtain a positive electrode slurry. The obtained positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil, and then dried and cold pressed to obtain a positive electrode sheet;

[0075] Natural graphite, artificial graphite, conductive agent SP, thickener CMC, and binder SBR were mixed in a mass ratio of 28.9:67.3:1.2:1.2:1.4, deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet provided with a negative electrode active material layer, wherein the compaction density PD of the negative electrode active material layer was 1.6 g / cm 3 , the ratio of the mass of natural graphite to the total mass of the negative electrode active material is 0.3;

[0076] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed in a mass ratio of 30:40:30 to obtain an organic solvent, LiPF6 is added to the organic solvent, and the mixture is stirred and dispersed, followed by adding vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfate, and lithium tetrafluorooxalate phosphate, and stirring and dispersing to obtain an electrolyte, wherein the mass percentage of LiPF6 in the electrolyte is 12.5%, the mass percentage of vinylene carbonate (VC) is 3%, the mass percentage of fluoroethylene carbonate (FEC) is 2%, the mass percentage of lithium tetrafluorooxalate phosphate is 1%, and the mass percentage of vinyl sulfate is 0.5%;

[0077] The positive electrode sheet, separator (made of polypropylene, 16 μm thick, referred to as 16PP) and negative electrode sheet are stacked in sequence with the separator placed between the positive electrode sheet and the negative electrode sheet. The core is wound to obtain a roll, which is then encapsulated in an aluminum-plastic film, dried, and injected with electrolyte. After encapsulation, standing, formation, and hot pressing, a secondary battery (pouch-type soft-pack battery) is obtained.

[0078] Examples 2 to 21

[0079] The differences from Example 1 are the compacted density PD of the negative electrode active material layer, the composition of the electrolyte, and / or the ratio of the mass of natural graphite in the negative electrode active material layer to the total mass of the negative electrode active material. Specific differences are shown in Table 1. The compacted density PD is obtained by controlling the cold pressing pressure. The boron-containing additive used in Examples 12-19, Example 21, and Comparative Examples 2 and 4-6 is lithium difluorooxalatoborate.

[0080] Comparative Examples 1 to 6

[0081] The difference from Example 1 is that the compaction density PD of the negative electrode active material layer and / or the composition of the electrolyte are different. The specific differences are shown in Table 1.

[0082] The cycle performance and storage performance of the lithium-ion secondary batteries obtained in the examples and comparative examples were tested at 60° C., with the test voltage ranging from 2.5 V to 3.65 V. The test results are shown in Table 1.

[0083] Table 1

[0084] From the above data, it can be seen that after the secondary batteries of each embodiment of the present application are cycled for 1000 weeks at 60°C, the capacity retention rate is still above 72%, and the DC internal resistance (DCR) growth rate is below 43%; after being stored at 60°C for 180 days, the capacity retention rate is still above 65%, and the DC internal resistance (DCR) growth rate is below 106%; and when the secondary battery meets At the same time, it is conducive to coordinating the relationship between the high-temperature cycle capacity retention rate, the high-temperature cycle DC internal resistance (DCR) growth rate, the high-temperature storage capacity retention rate and the high-temperature storage DC internal resistance (DCR) growth rate, ensuring its better high-temperature comprehensive performance and better meeting the requirements of electric vehicles, electric motorcycles, power tools, home appliances and other products for secondary batteries.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A secondary battery, comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material contains natural graphite; the electrolyte contains a first additive and a second additive, the first additive contains vinylene carbonate, and the second additive contains at least two of fluoroethylene carbonate, a phosphorus-containing additive, and a boron-containing additive; The secondary battery satisfies the following relationship: Among them, m VC % is the mass percentage of vinylene carbonate in the electrolyte; m FEC % is the mass percentage of vinylene carbonate fluoride in the electrolyte solution; m BP % is the sum of the mass percentages of the phosphorus-containing additive and the boron-containing additive in the electrolyte; PD g / cm 3 is the tap density of the negative electrode active material layer; m n It is the ratio of the mass of the natural graphite to the total mass of the negative electrode active material.

2. The secondary battery according to claim 1, wherein, 1≤m VC ≤5。 3. The secondary battery according to claim 1, wherein, 0≤m FEC ≤5。 4. The secondary battery according to claim 1, wherein, m VC +m FEC ≥ 3.

5. The secondary battery according to claim 1, wherein, 0<m BP ≤4。 6. The secondary battery according to claim 1, wherein the secondary battery further satisfies 0 ≤ m B < 2.5 or 0 ≤ m p < 2.5; wherein, m B %, m p % respectively represent the mass percentages of the boron-containing additive and the phosphorus-containing additive in the electrolyte solution.

7. The secondary battery according to claim 1, wherein, 1.2 ≤ PD ≤ 2.

0.

8. The secondary battery according to claim 1, wherein, 0.05≤m n ≤1。 9. The secondary battery according to claim 1, wherein the phosphorus-containing additive includes at least one of lithium tetrafluorophosphate, trimethyl phosphate, diethyl fluorophosphate, and tris(2,2,2-trifluoroethyl) phosphate.

10. The secondary battery according to claim 1, wherein the boron-containing additive includes at least one of lithium difluorooxalate borate, lithium bis(oxalato)borate, trimethyl borate, and triallyl borate.

11. The secondary battery according to claim 1, wherein the electrolyte further contains an organic solvent, and the organic solvent includes a cyclic carbonate and a chain carbonate.

12. The secondary battery according to claim 11, wherein the mass percentage of the cyclic carbonate in the organic solvent is more than 20%.

13. The secondary battery according to claim 11, wherein the mass percentage of the chain carbonate in the organic solvent is more than 50%.

14. The secondary battery according to claim 1, wherein the electrolyte further contains a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

15. The secondary battery according to claim 1, wherein the electrolyte further contains an organic solvent, and the mass percentage of the organic solvent in the electrolyte is 70% - 85%.

16. The secondary battery according to claim 1, wherein the electrolyte further contains a sulfur-containing additive, and the sulfur-containing additive includes at least one of ethylene sulfate, methylene methane disulfonate, ethylene sulfite, and 1,3-propanedisulfonic anhydride.

17. The secondary battery according to claim 1, wherein the electrolyte further contains a sulfur-containing additive, and the mass percentage of the sulfur-containing additive in the electrolyte is 0.1% - 1%.

18. The secondary battery according to claim 1, wherein the electrolyte further contains a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.8 - 1.5 mol / L; 19. The secondary battery according to claim 1, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer contains Li a Fe 1-y Mn y PO4, wherein, 0.9 ≤ a ≤ 1.1, 0 ≤ y < 1.

20. An electrical device, comprising the secondary battery according to any one of claims 1 - 19, and the secondary battery is used as a power supply for the electrical device.

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